Co-reporter:Wenhui Li, Anfeng Zhang, Xiao Jiang, Chen Chen, Zhongmin Liu, Chunshan Song, and Xinwen Guo
ACS Sustainable Chemistry & Engineering September 5, 2017 Volume 5(Issue 9) pp:7824-7824
Publication Date(Web):August 1, 2017
DOI:10.1021/acssuschemeng.7b01306
A Co-based zeolitic imidazolate framework, ZIF-67, has been utilized as a precursor to obtain Co-based porous carbon catalysts. The obtained catalysts display an outstanding catalytic performance toward the CO2 methanation at low temperature. The ZIF-67 crystal morphology can be controlled from cubic to rhombic dodecahedron, and the original particle sizes can be regulated from 150 nm to 1 μm in aqueous solution by cetyltrimethylammonium bromide (CTAB) surfactants. After carbonation in N2 flow, Co-based porous carbon catalysts kept the original ZIF-67 crystal morphology and particle size but differed in the micropore property; the 0.01 wt % CTAB content led to the maximum micropore volume 0.125 cm3/g. The Co nanoparticles inside the carbon matrix range between 7 and 20 nm, and they are separated by the graphite-like carbon avoiding the metal sintering effectively. Furthermore, the catalysts with 0.01% CTAB addition exhibited the highest CO2 conversion (52.5%) and CH4 selectivity (99.2%) under the 72000 mL g–1 h–1 GHSV (gas hourly space velocity) at 270 °C. Noticeably, the Co/PC catalysts performed higher activity and stability than the supported catalysts 20Co/AC. The versatile way offers good prospects for low temperature CO2 methanation and prevents metal sintering effectively.Keywords: CO2 methanation; Cobalt; CTAB; Low-temperature; ZIF-67;
Co-reporter:Xiaowa Nie, Haozhi Wang, Michael J. Janik, Yonggang Chen, Xinwen Guo, and Chunshan Song
The Journal of Physical Chemistry C June 22, 2017 Volume 121(Issue 24) pp:13164-13164
Publication Date(Web):May 25, 2017
DOI:10.1021/acs.jpcc.7b02228
Density functional theory (DFT) calculations were carried out to investigate the mechanism of CO2 hydrogenation in production of C1 and C2 hydrocarbons over Cu–Fe bimetallic catalyst. CH* is found to be the most favorable monomeric species for production of CH4 and C2H4 via C–C coupling of two CH* species and subsequent hydrogenation. On the bimetallic Cu–Fe(100) surface at 4/9 ML Cu coverage, the energetically preferred path for CH* formation goes through CO2* → HCOO* → HCOOH* → HCO* → HCOH* → CH*, in which both the HCOO* → HCOOH* and HCO* → HCOH* steps have substantial barriers. The bimetallic surface suppresses CH4 formation and is more selective to C2H4 due to the higher hydrogenation barrier of CH2* species relative to those for C–C coupling and CH–CH* conversion to C2H4. On monometallic Fe(100) surface, CH* formation goes through a path of CO2* → CO* → HCO* → HCOH* → CH*, different from that identified on Cu–Fe(100). The hydrogenation of HCO* to HCOH* is the rate-limiting step that controls CO2 conversion to CH4 and C2H4. CH4 formation is kinetically more favored, with a 0.3 eV lower energy barrier, than C2H4 formation. The bimetallic combination of Cu and Fe enhances CO2 conversion by reducing the kinetic barriers, and alters the selectivity preference to more valuable C2H4 from CH4 on monometallic Fe surface. C2H6 can be produced from further hydrogenation of C2H4 with moderate barriers.
Co-reporter:Lei Luo, Anfeng Zhang, Michael J. Janik, Keyan Li, Chunshan Song, Xinwen Guo
Applied Surface Science 2017 Volume 396() pp:78-84
Publication Date(Web):28 February 2017
DOI:10.1016/j.apsusc.2016.10.190
Highlights
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Ordered mesoporous graphitic carbon nitrides with SBET = 279.3 m2/g were prepared.
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Enhanced photocatalytic activity and reusability were presented.
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Improved SBET and charge carrier separation efficiency contribute to the activity.
Co-reporter:Lei Luo, Anfeng Zhang, Michael J. Janik, Keyan Li, Chunshan Song, Xinwen Guo
Materials Letters 2017 Volume 188() pp:130-133
Publication Date(Web):1 February 2017
DOI:10.1016/j.matlet.2016.11.043
•g-C3N4 nanosheets were prepared with the assistance of NH4NO3.•Increased SBET and enhanced charge separation efficiency were demonstrated.•The catalytic activity maximizes at an intermediate NH4NO3/melamine ratio at 0.15.With the assistance of inorganic salt, graphitic carbon nitride nanosheets were prepared with increased mesoporous surface area for promoting the photocatalytic performance compared with the one without. Series of photocatalysts with different mass ratio of NH4NO3/melamine were prepared and characterized by XRD, FT-IR, XPS, TEM, SEM, N2 physical adsorption, UV–vis and PL spectrometries. Photocatalytic degradation of RhB under visible light irradiation (λ>420 nm) was applied to evaluate catalytic properties. The catalytic activity maximizes at an intermediate NH4NO3/melamine ratio at 0.15, giving a maximum performance, RhB totally being degraded within 30 min and kinetic constant reaching 0.167 min−1 that is 4.5 times as high as that on BCN. The NH4NO3 assisted procedure is a facile, repeatable, environmental friendly, and efficient method for preparing g-C3N4 nanosheets with high photocatalytic performance.
Co-reporter:Junhui Liu, Anfeng Zhang, Min Liu, Shen Hu, Fanshu Ding, Chunshan Song, Xinwen Guo
Journal of CO2 Utilization 2017 Volume 21(Volume 21) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jcou.2017.06.011
•Fe-MOF-derived catalysts were prepared by one-step pyrolyzing Fe-MIL-88B.•Iron species could variously transform under the reaction conditions, resulting in different catalytic performances.•Fe-MOF-derived catalysts exhibited high selectivity of C5+ hydrocarbons and the addition of K made the ratio of olefins to paraffins increase to 5.5.•The presence of appropriate amount of Fe3O4 and χ-Fe5C2 was beneficial to the reaction. However, metallic iron and/or θ-Fe3C were less active.Fe-based catalysts were acquired by one-step Fe-MIL-88B pyrolyzation and it showed high catalytic performance on hydrogenated conversion of carbon dioxide to valuable hydrocarbons. The iron compositions and catalytic performance of the catalysts were determined by pyrolysis temperatures according to XRD, SEM, TEM, N2-physisorption, Raman and evaluation results. Magnetite was obtained at 773 K while metallic iron was the main phase when the pyrolysis temperature increased to 973 K. Different catalytic performances over these catalysts were attributed to the transformation of iron species under the reaction conditions. Olefin-to-paraffin ratio (O/P) over pyrolyzed and K-doped catalysts was 1.3 and 5.5, respectively, and the two samples exhibited CO2 conversion with 46.0% and 43.1%, respectively. Higher catalytic performance was achieved when certain amount of Fe3O4 and χ-Fe5C2 existed in catalysts whereas metallic iron and/or θ-Fe3C had detrimental effects on lower conversion of CO2 and selectivity of valuable hydrocarbons.
Co-reporter:Shen Hu;Min Liu;Keyan Li;Chunshan Song;Guoliang Zhang;Xinwen Guo
RSC Advances (2011-Present) 2017 vol. 7(Issue 1) pp:581-587
Publication Date(Web):2016/12/20
DOI:10.1039/C6RA25745C
NH2-MIL-125(Ti) is a promising microporous MOF material which has potential applications in photocatalytic and catalytic oxidation reactions. In this work, a facile surfactant assistant synthetic method was employed to obtain hierarchical NH2-MIL-125 with the mesoporosity for photocatalytic degradation of organic dyes. The as-prepared NH2-MIL-125 showed excellent dye removal efficiency due to the combination of improved adsorption and photodegradation. Compared with the microporous NH2-MIL-125, the adsorption capacity of organic dyes increased 28% on hierarchical NH2-MIL-125 and the photodegradation rate approximately increased 2.4 times according to the structure with abundant mesopores and macropores. The morphology of hierarchical NH2-MIL-125 can also be modulated from tetragonal plates to truncated bipyramids and octahedrons, and the obtained catalyst shows similar enhanced photodegradation performance.
Co-reporter:Qiao Sun;Min Liu;Keyan Li;Yitong Han;Yi Zuo;Fanfan Chai;Chunshan Song;Guoliang Zhang;Xinwen Guo
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 1) pp:144-153
Publication Date(Web):2017/01/13
DOI:10.1039/C6QI00441E
Partial isomorphic substitution of iron in an Fe(BDC)(DMF,F) metal organic framework by manganese, cobalt, and nickel has been described for the first time. Specifically, different amounts of Mn, Co and Ni have been incorporated into the Fe-based framework during a solvothermal crystallization procedure. Several characterization techniques, including XRD, FT-IR, SEM, EDS, TG, XPS and ICP-AES, strongly support the effective incorporation of Mn, Ni and Co into material frameworks. The catalytic performance of these materials was examined in liquid-phase degradation of phenol at 35 °C and near neutral pH of 6.2. The results show that the degradation efficiency can be evidently improved by the incorporation of Mn, while it can be inhibited by the incorporation of Ni. The incorporation of Co shows no remarkable influence on the degradation process. Moreover, the ratios of n(Fe)/n(Mn) in the bimetallic MOFs have a strong impact on the degradation process. The stability and reusability of these catalysts under mild conditions were also demonstrated in this study. This work illustrates the potential of bimetallic MOF structures in developing active heterogeneous catalysts for the degradation process of toxic compounds.
Co-reporter:Chengyi Dai, Anfeng Zhang, Lei Luo, Xinbao Zhang, Min Liu, Junhu Wang, Xinwen Guo, Chunshan Song
Catalysis Today 2017 Volume 297(Volume 297) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.cattod.2017.02.001
•Fe-Cu bimetallic oxide nanoparticles were encapsulated in hollow zeolite.•Encapsulated Fe-Cu show excellent dispersion and strong bimetallic interaction.•The short channels in the hollow zeolite wall enhance transport of reactants.•The hollow crystal wall prevents the leaching of metal oxide.•Encapsulated Fe-Cu shows high activity and reusability for phenol degradation.Highly dispersed Fe-Cu bimetallic oxide nanoparticles were successfully encapsulated in hollow Silicalite-1 single crystals (Fe2O3CuO@Hol S-1) by tetrapropylammonium hydroxide (TPAOH) hydrothermal treatment with an “impregnation-dissolution-recrystallization” process. Due to the Fe-Cu bimetallic interaction compared with single iron oxide, Fe-Cu bimetallic oxide exhibits a higher dispersion with the particle size decreasing from ∼11.3 nm to ∼3.7 nm. For aqueous phenol degradation, the Fe2O3CuO@Hol S-1 catalyst exhibits high activity attributed to the enhanced transport of reactants/products in the short microporous channels (20 nm) and the small metal oxide particle size. Interestingly, the particle size of encapsulated Fe2O3CuO (3.7 nm) is larger than that of zeolite micropore (0.53 nm), which helps preventing the leaching of metal oxide that is a significant problem for conventional supported Fe catalyst in this reaction.Download high-res image (146KB)Download full-size image
Co-reporter:Keyan Li, Yongqin Zhao, Chunshan Song, Xinwen Guo
Applied Surface Science 2017 Volume 425(Volume 425) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.apsusc.2017.07.041
•Magnetic Fe3O4/CeO2 composites with ordered mesoporous structure were synthesized.•Fe3O4/CeO2 played a dual-function role as both adsorbent and Fenton-like catalyst.•The superior adsorption ability was attributed to the abundant oxygen vacancies on CeO2 surface.•The good oxidative degradation resulted from the synergistic effect between Fe and Ce.•Fe3O4/CeO2 composite presented very low metal leaching.Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L−1 and cerium 0.63 mg L−1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.Mesoporous Fe3O4/CeO2 plays a dual-function role as both adsorbent and Fenton-like catalyst with low metal leaching.Download high-res image (139KB)Download full-size image
Co-reporter:Chengyi Dai;Junjie Li;Anfeng Zhang;Changhong Nie;Chunshan Song;Xinwen Guo
RSC Advances (2011-Present) 2017 vol. 7(Issue 60) pp:37915-37922
Publication Date(Web):2017/07/28
DOI:10.1039/C6RA28030G
A series of boron-containing ZSM-5 (B-ZSM-5) catalysts with particle sizes from ∼153 nm to ∼14.2 μm are synthesized by regulating the addition of silicalite-1 seeds. The B-ZSM-5 particle size with seed addition (D), the seed addition amount (x), the seed particle size (d) and the B-ZSM-5 particle size without seed addition (D0) are related with by the new function D3 = d3D03/[xD03 + (1 − x)d3], and the particle size of B-ZSM-5 has been precisely controlled and predicted in both micro (TPABr as template) and nano (TPAOH as template) synthesis systems. The function also shows the evolution of B-ZSM-5 particle size versus the seed amount and size, which helps guide the synthetic choice of the seed amount used or decreasing the seed size to decrease the B-ZSM-5 size for a specific synthesis system. Furthermore, the effect of particle size on the catalytic performance of B-ZSM-5 for the methanol to propylene (MTP) reaction is also investigated. The addition of 1 wt% ∼74 nm seeds to the synthesis system improves the resulting catalyst lifetime from 46 h to 794 h.
Co-reporter:Yitong Han;Min Liu;Keyan Li;Qiao Sun;Wensheng Zhang;Chunshan Song;Guoliang Zhang;Z. Conrad Zhang;Xinwen Guo
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 11) pp:1870-1880
Publication Date(Web):2017/11/07
DOI:10.1039/C7QI00437K
Titanium in different amounts has been successfully doped into the zirconium-based metal–organic framework UiO-66 via an in situ synthesis method, resulting in a series of hybrid UiO-66-nTi MOFs. These materials maintain a relatively high crystallinity and excellent structural stability. The addition of titanium has a significant effect on the crystal size and morphology of UiO-66. The UiO-66-nTi MOFs exhibit a sphere-like crystal morphology with a smaller crystal size and a rougher surface compared to the octahedral UiO-66 crystals. The framework order and porosity of the UiO-66-nTi MOFs decrease slightly due to titanium doping. The UiO-66-nTi MOFs were studied as adsorbents for the removal of an organic dye from water. The results demonstrate that these hybrid materials have enhanced adsorption capacity for the organic dye Conge red in comparison with the parent UiO-66. UiO-66-2.7Ti with 2.7% titanium doping shows the highest adsorption capacity of 979 mg g−1, which is three times higher than that of the parent UiO-66. The strong electrostatic attraction between the positively charged surface of UiO-66-2.7Ti and the negatively charged Congo red molecules was identified as the main driving force for the high adsorption capacity.
Co-reporter:Tianze Xie, Jianyang Wang, Fanshu Ding, Anfeng Zhang, Wenhui Li, Xinwen Guo, Chunshan Song
Journal of CO2 Utilization 2017 Volume 19(Volume 19) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.jcou.2017.03.022
•Alumina supports with a wide range of pore size were prepared.•Support pore size controls the size of Fe2O3 particles.•Optimum Fe2O3 particle size will lead to the highest selectivity to C5+ hydrocarbons from CC chain growth.The effect of support pore size of FeK/Al2O3 catalysts on the catalytic performance in CO2 hydrogenation reaction was investigated. A total of 8 iron-based catalysts supported on alumina with different pore size were prepared by incipient wetness impregnation where the amount of Fe and K were fixed at 15 and 10 wt%, respectively. N2 adsorption/desorption, XRD, TPR and PZC were used to characterize the supports and catalysts. The results show that the support pore size impacts the size of Fe2O3 particles formed in the catalyst; increasing pore size of Al2O3 supports led to increased size of Fe2O3 particles formed in the pores. Catalyst pore sizes of 7–10 nm and the corresponding Fe2O3 particle sizes of 5–8 nm were the most active for CO2 hydrogenation to hydrocarbons. Outside this range, larger pore size further decrease the iron dispersion and reduce the number of active sites; smaller pore size is not favorable on account of the too small Fe2O3 particle sizes and lower reducibility of the small particle.
Co-reporter:Yitong HanMin Liu, Keyan Li, Qiao Sun, Chunshan Song, Guoliang Zhang, Zongchao Zhang, Xinwen Guo
Crystal Growth & Design 2017 Volume 17(Issue 2) pp:
Publication Date(Web):December 20, 2016
DOI:10.1021/acs.cgd.6b01533
Controlled synthesis of metal–organic frameworks (MOFs) in nanometer scale is highly desired for the optimization of properties and the extending of applications. In this work, Cu2O was used as additive for the first time in the synthesis of zirconium-based MOF UiO-66. We found that the amount of Cu2O additive had an important impact on downsizing the crystal size of UiO-66. Cu2O additive plays a role of rate controller of crystal growth of UiO-66 crystals by their competitive coordination behavior with the linker H2BDC between the [Zr–O] clusters. This generates a depleted H2BDC concentration for the coordination with the [Zr–O] clusters for constructing the UiO-66 framework, which favors the production of small crystals. As a result, well-dispersed nanometer scale UiO-66 crystals with mean crystal size of 40 nm can be easily synthesized by the addition of Cu2O. The as-synthesized nanometer scale UiO-66 crystals have a pure crystal structure with high crystallinity and superior porosity.
Co-reporter:Keyan Li, Fenfen Shua, Xinwen Guo, Dongfeng Xue
Electrochimica Acta 2016 Volume 188() pp:793-800
Publication Date(Web):10 January 2016
DOI:10.1016/j.electacta.2015.12.047
•Porous MnO@C composite was prepared by sintering the mixture of MnC2O4 and glucose.•MnO@C composite exhibits high specific capacity and excellent rate capability as Li-ion battery anodes.•The excellent electrochemical performance can be ascribed to porous structure, good crystallinity and proper amount of carbon coating.•This facile method can be applied to synthesis of other transition metal oxide@carbon electrode materials.MnC2O4 precursor was prepared by a precipitation method, and then porous MnO@C composites were obtained by mixing MnC2O4 precursor with different amounts of glucose and sintering at different temperatures. The influences of carbon content and crystallinity on the electrochemical performance of MnO@C were investigated. Galvanostatic charge–discharge test results showed that the MnO@C sample “1.2,700” has the largest specific capacity among all samples, which can reach high specific discharge capacity of 1691 mAh g−1 at the current density of 100 mA g−1 after 200 cycles. Even at the high current density of 1600 mA g−1, a remarkable discharge capacity of ∼630 mAh g−1 can still be delivered, demonstrating a good rate capability. The excellent electrochemical performance can be ascribed to porous structure, good crystallinity and proper amount of carbon coating. This facile method can be applied to the large-scale synthesis of high performance transition metal oxide@carbon composite electrode materials.
Co-reporter:Fanfan Chai, Keyan Li, Chunshan Song, Xinwen Guo
Journal of Colloid and Interface Science 2016 Volume 475() pp:119-125
Publication Date(Web):1 August 2016
DOI:10.1016/j.jcis.2016.04.047
Magnetic porous Fe3O4/C/Cu2O composites were prepared by a simple two-step process. Porous Fe3O4/C was synthesized via calcining iron tartrate precursor and then Cu2O was composited with Fe3O4/C by a precipitation-reduction method. The as-prepared samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) elemental mapping. Results show that Fe3O4/C has porous nanorod structure, which is composed of numerous small nanoparticles of about 50 nm. Fe3O4 and carbon are uniformly distributed in the Fe3O4/C/Cu2O composite and Cu2O is dispersed on the surface of Fe3O4/C. Fe3O4/C/Cu2O composite exhibits excellent photo-Fenton catalytic performance for the degradation of methylene blue (MB) under visible light irradiation and neutral pH conditions, and MB (100 mg/L) could be almost completely removed within 60 min. The composite shows good recyclability and could be conveniently separated by an applied magnetic field. These results demonstrate that the Fe3O4/C/Cu2O composite is a powerful Fenton-like catalyst for degradation of organic pollutants from wastewater.Magnetic Fe3O4/C/Cu2O composite exhibits excellent photo-Fenton catalytic performance and reusability under visible light irradiation and neutral pH conditions.
Co-reporter:Qiao Sun, Min Liu, Keyan Li, Yitong Han, Yi Zuo, Junhu Wang, Chunshan Song, Guoliang Zhang and Xinwen Guo
Dalton Transactions 2016 vol. 45(Issue 19) pp:7952-7959
Publication Date(Web):01 Feb 2016
DOI:10.1039/C5DT05002B
A series of MIL-53(Fe)-type materials, Fe(BDC)(DMF,F), were prepared by using different ratios of n(FeCl3)/n(FeCl2), which have varied amounts of Fe2+ in their frameworks. From FeCl3 to FeCl2, the structures of the synthesized samples transform from MIL-53(Fe) to Fe(BDC)(DMF,F). Along with this structure transformation, the crystal morphology goes through a striking change from a small irregular shape to a big triangular prism. This phenomenon indicates that the addition of FeCl2 is beneficial for the formation of a Fe(BDC)(DMF,F) structure. The catalytic activity of these iron-containing MOFs was tested in phenol degradation with hydrogen peroxide as an oxidant at near neutral pH and 35 °C. The degradation efficiency of these samples increases gradually from MIL-53(Fe) to Fe(BDC)(DMF,F). 57Fe Mössbauer spectra reveal that Fe2+ and Fe3+ coexist in the Fe(BDC)(DMF,F) framework, and the highest amount of Fe2+ in the sample prepared with mixed FeCl3 and FeCl2 is 26.0%. The result illustrates that the amount of Fe2+ in the samples can be controlled using varied n(FeCl3)/n(FeCl2) in the feed. The diverse amount of Fe2+ in this series of FeMOF materials exactly explains the distinction of reaction efficiency. The iron leaching tests, structures of the fresh and used catalysts, and the data of the recycling runs show that the Fe-containing MOFs are stable in this liquid-phase reaction.
Co-reporter:Chengyi Dai, Anfeng Zhang, Min Liu, Junjie Li, Fangyu Song, Chunshan Song and Xinwen Guo
RSC Advances 2016 vol. 6(Issue 13) pp:10831-10836
Publication Date(Web):18 Jan 2016
DOI:10.1039/C5RA26009D
A versatile strategy involving one-step desilication of coke-deposited spent zeolite catalyst was successfully developed to prepare hierarchical porous carbon monoliths (HPCMs). Such a strategy avoids the use of hard or soft templates and carbon sources, eliminates high temperature carbonization, simultaneously minimizing the emissions from processing spent catalysts. The resulting carbon exhibits a controlled morphology such as three-dimensional networks, hollow spheres or nanosheets, a high degree of graphitization and a multi-level porous structure. Its mesopore (2–50 nm) surface area can reach 522 m2 g−1 and both mesopore and macropore (50–350 nm) volumes are more than 1.0 cm3 g−1. Such hierarchical porous carbon was found to be a superior support for minimizing the nanoparticle size and enhancing the synergism of the Fe–K catalyst for promoting CO2 hydrogenation. Using such a catalyst results in increased conversion of carbon dioxide and enhanced selectivity of high value olefins (C2–4) and long-chain hydrocarbons (C5+).
Co-reporter:He Han, Min Liu, Xiaowa Nie, Fanshu Ding, Yiren Wang, Junjie Li, Xinwen Guo, Chunshan Song
Microporous and Mesoporous Materials 2016 Volume 234() pp:61-72
Publication Date(Web):1 November 2016
DOI:10.1016/j.micromeso.2016.06.045
•Alkali metal oxides promote the dehydrogenation of methanol to formaldehyde.•The synergistic effects between alkali metal oxide and alkali metal cations exert strong influence on the catalytic pathway.The side-chain alkylation of toluene with methanol was investigated on a series of catalysts which were prepared by ion-exchange or subsequent impregnation of zeolie X with potassium hydroxide or cesium hydroxide aqueous solution. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence, Ar physical adsorption-desorption, NH3 temperature-programmed desorption (TPD), CO2-TPD, pyridine adsorption Fourier-transform infrared (FT-IR) spectroscopy, FT-IR spectroscopy in OH stretch region, thermogravimetric/differential thermal analysis, ultraviolet-Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that alkali metal oxide played extremely important roles in the modification of catalysts and in the catalytic reaction pathway. Strong basic sites were formed by modification of basic zeolite X with alkali metal oxide. These basic sites promoted the dehydrogenation of methanol to formaldehyde which was recognized as the true alkylating agent in side-chain alkylation. Consequently, side-chain alkylation of toluene with formaldehyde was enhanced. As toluene was mainly adsorbed and activated on alkali metal cations bonded on the zeolite framework, the synergistic effects between alkali metal oxide and alkali metal cations were proposed. One of the possible reaction path ways for side-chain alkylation of toluene with methanol over basic zeolite was described. Alkali metal ion-exchanged zeolite X modified with alkali metal oxide demonstrated relatively high side-chain alkylation activity. However, the improvement of styrene selectivity faced with great challenges.
Co-reporter:He Han, Min Liu, Fanshu Ding, Yiren Wang, Xinwen Guo, and Chunshan Song
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 7) pp:1849
Publication Date(Web):January 29, 2016
DOI:10.1021/acs.iecr.5b04174
The side-chain alkylation of toluene with methanol was studied on cesium-modified zeolite X prepared by ion-exchange and impregnation with different cesium precursors. The catalyst was characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence spectroscopy, Ar physical adsorption–desorption, NH3 temperature-programmed desorption (TPD), CO2-TPD, thermogravimetric/differential thermal analysis, ultraviolet-Raman spectroscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy. Cesium hydroxide was found to be the most effective precursor for modifying zeolite X. Cesium ions bonded on the framework and cesium oxide formed in the pore were found to take different roles in this reaction. Cesium ions could adsorb and activate toluene or modify the basicity of framework oxygen, whereas cesium oxide could ensure the effective conversion of methanol to formaldehyde and inhibit the process of coke deposition. A possible reaction pathway for this reaction over cesium-modified samples was described. The synergistic effect of cesium ions and cesium oxide was proven to be important for the formation of styrene and ethylbenzene.
Co-reporter:Anfeng Zhang, Keke Hou, Haiyang Duan, Wei Tan, Chunshan Song and Xinwen Guo
RSC Advances 2016 vol. 6(Issue 6) pp:4343-4353
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5RA19416D
The zirconium-promoted hydrothermal synthesis of hierarchical porous carbons with ordered cubic mesostructures (Im3m) under acidic aqueous conditions was first presented using F127 as a template, pre-synthesized resol as carbon precursor, hydrochloric acid as catalyst and zirconium oxychloride as an assistant agent. The effects of the zirconium oxychloride assistant, acid concentration, hydrothermal treatment time and treatment conditions on the structural properties of the hierarchical porous carbons were investigated. The results indicate that the zirconium polyoxo oligomers in the acid synthesis solution can suppress the condensation of the resols at a moderate rate around the micelles of F127 to form mesosporous carbon. Under hydrothermal conditions, zirconium polyoxo oligomers could interact with the polyethylene (PEO) chains of F127 through hydrogen bonding, increasing the hydrophilic/hydrophobic volume ratio and the interfacial curvature to promote the phase transformation of the mesostructure from 2-D hexagonal to 3-D body-centered cubic. With suitable acid concentration (1.0–3.0 M), hierarchical porous carbons with ordered cubic mesostructures can be synthesized in 8 h on a large scale. After activation with KOH, the equilibrium CO2 adsorption capacities of the resulting materials at 1 atm were in the range of 3.3–4.1 mmol g−1 at 25 °C and 4.8–6.6 mmol g−1 at 0 °C.
Co-reporter:Chengyi Dai, Anfeng Zhang, Min Liu, Lin Gu, Xinwen Guo, and Chunshan Song
ACS Nano 2016 Volume 10(Issue 8) pp:7401
Publication Date(Web):July 18, 2016
DOI:10.1021/acsnano.6b00888
Inspired by the vesicular structure of alveolus which has a porous nanovesicle structure facilitating the transport of oxygen and carbon dioxide, we designed a hollow nanovesicle assembly with metal-encapsulated hollow zeolite that would enhance diffusion of reactants/products and inhibit sintering and leaching of active metals. This zeolitic nanovesicle has been successfully synthesized by a strategy which involves a one-pot hydrothermal synthesis of hollow assembly of metal-containing solid zeolite crystals without a structural template and a selective desilication-recrystallization accompanied by leaching-hydrolysis to convert the metal-containing solid crystals into metal-encapsulated hollow crystals. We demonstrate the strategy in synthesizing a hollow nanovesicle assembly of Fe2O3-encapsulated hollow crystals of ZSM-5 zeolite. This material possesses a microporous (0.4–0.6 nm) wall of hollow crystals and a mesoporous (5–17 nm) shell of nanovesicle with macropores (about 350 nm) in the core. This hierarchical structure enables excellent Fe2O3 dispersion (3–4 nm) and resistance to sintering even at 800 °C; facilitates the transport of reactant/products; and exhibits superior activity and resistance to leaching in phenol degradation. Hollow nanovesicle assembly of Fe-Pt bimetal-encapsulated hollow ZSM-5 crystals was also prepared.Keywords: hollow nanovesicle; metal-encapsulated; multilevel structure; phenol degradation; zeolite
Co-reporter:Xiaowa Nie
The Journal of Physical Chemistry C 2016 Volume 120(Issue 17) pp:9364-9373
Publication Date(Web):April 14, 2016
DOI:10.1021/acs.jpcc.6b03461
Density functional theory (DFT) calculations were carried out to investigate Fe–Cu bimetallic catalysts for the adsorption, activation, and initial hydrogenation of CO2. CO2 adsorption strength decreases monotonically as surface Cu coverage increases. For dissociation of CO2, the reaction energy and activation barrier scale linearly with surface Cu coverage. The reaction energy becomes less exothermic, and the activation barrier increases with increasing surface Cu coverage from 0 to 1 ML. For initial hydrogenation of CO2, formation of a formate (HCOO*) intermediate is kinetically favored over carboxyl (COOH*) at all surface Cu coverages. A substantial decrease of the kinetic barrier for HCOO* formation is observed when surface Cu coverage increases to 4/9 ML. CO* is the preferred intermediate from CO2 dissociation at 2/9 ML surface Cu coverage or below; however, the favorable conversion path changes to CO2 hydrogenation to a HCOO* intermediate when surface Cu coverage increases to 4/9 ML or higher. The composition and structure of the bimetallic catalysts determine the preferred intermediates and dominant reaction paths for CO2 conversion, and thus, both impact the catalytic activity and selectivity.
Co-reporter:Chengyi Dai;Anfeng Zhang;Min Liu;Xinwen Guo;Chunshan Song
Advanced Functional Materials 2015 Volume 25( Issue 48) pp:7479-7487
Publication Date(Web):
DOI:10.1002/adfm.201502980
Hollow ZSM-5 single crystals with silicon-rich exterior surface are prepared by a “dissolution–recrystallization” strategy in tetrapropylammonium hydroxide solution. Selective dissolution and exterior recrystallization cause the silicon components to migrate from the inside to outside, resulting in a regular void in the interior of the crystal, increased Brönsted acid sites and a silicon-rich external surface. The as-prepared hollow ZSM-5 exhibits excellent acid catalysis with enhanced shape selectivity, as shown in biphenyl methylation as a probe reaction, which is attributed to the silicon-rich external surface and thus the inhibition of isomerization on external surface. More interestingly, hollow ZSM-5 single crystals with double shells are successfully prepared by layer-by-layer technique followed with dissolution–recrystallization strategy. Furthermore, hollow ZSM-5 encapsulating iron and carbon nanotubes are successfully synthesized. Furthermore, hollow ZSM-5 nanosized crystals with the interior functionalized as bimetallic (oxide) nanoparticles such as CuO-Pd are also successfully synthesized.
Co-reporter:Xinquan Cheng, Min Liu, Anfeng Zhang, Shen Hu, Chunshan Song, Guoliang Zhang and Xinwen Guo
Nanoscale 2015 vol. 7(Issue 21) pp:9738-9745
Publication Date(Web):24 Apr 2015
DOI:10.1039/C5NR01292A
A postsynthetic modification method was used to prepare thiol-functionalized metal–organic frameworks (MOFs) by the amidation of mercaptoacetic acid with the amine group, which is present in the frameworks of NH2-MIL-53(Al). By doing this, the thiol group has been successfully grafted on the MOF, which perfectly combined the highly developed pore structures of the MOF with the strong coordination ability of the thiol group. The resulting thiol-functionalized MIL-53(Al) showed a significantly high adsorption capacity for heavy metal ions like Ag+ (182.8 mg g−1). Even more importantly, these grafted thiol groups can be used as anchoring groups for stabilizing metal nanoparticles (NPs) with controllable sizes. Taking silver as an example, monodispersed Ag NPs encapsulated in the cages of MIL-53(Al) have been prepared by using a two-step procedure. In addition, the particle size of the Ag NPs was adjustable to some extent by controlling the initial loading amount. The average size of the smallest Ag NPs is 3.9 ± 0.9 nm, which is hard to obtain for Ag NPs because of their strong tendency to aggregate.
Co-reporter:Chengyi Dai, Shaohua Zhang, Anfeng Zhang, Chunshan Song, Chuan Shi and Xinwen Guo
Journal of Materials Chemistry A 2015 vol. 3(Issue 32) pp:16461-16468
Publication Date(Web):29 Jun 2015
DOI:10.1039/C5TA03565A
Highly dispersed Ni–Pt bimetallic nanoparticles encapsulated in hollow silicalite-1 single crystals (1.5Ni–0.5Pt@Hol S-1) were a superior catalyst for sintering and coking resistant dry (CO2) reforming of CH4. Large Ni particles loaded on the surface of solid silicalite-1 crystals triggered coke formation, which simultaneously degraded the catalytic activity of small Ni particles. With Ni encapsulated in hollow crystals, the small Ni particles inhibited coke formation. The encapsulating shell prevented coke formed outside from degrading the activity of nickel on the inside, leading to stable high activity even in the presence of carbon. Compared with single metals (Ni or Pt), 1.5Ni–0.5Pt@Hol S-1 enhanced the dispersion of nickel and platinum. In the dry reforming of methane, the 1.5Ni–0.5Pt@Hol S-1 catalyst operated stably under high gaseous hourly space velocity (GHSV = 72000 ml g−1 h−1) without any inert gas. Only 1.0 wt% carbon deposition was observed by thermogravimetric analysis (TGA) after 6 h of the reaction. Hollow zeolite crystals can reliably support coke resistant catalysts for dry reforming of CH4 and multi-metallic catalysts with well-dispersed nanoparticles.
Co-reporter:Lei Luo, Chengyi Dai, Anfeng Zhang, Junhu Wang, Min Liu, Chunshan Song and Xinwen Guo
Catalysis Science & Technology 2015 vol. 5(Issue 6) pp:3159-3165
Publication Date(Web):31 Mar 2015
DOI:10.1039/C5CY00242G
The mesoporous ZSM-5 zeolite obtained from alkaline treatment was found to be a superior support of bimetallic FeCu, minimizing the nanoparticle size, enhancing the bimetallic interaction, and promoting catalytic oxidation of phenol. The physicochemical characteristics of the as-prepared FexCuy/ZSM-5 samples were evaluated by XRD, TEM, Ar adsorption, H2-TPR, and 57Fe Mossbauer spectroscopy which revealed a strong bimetallic interaction. Meanwhile, phenol oxidation was applied as a probe reaction under mild conditions. By supporting FeCu bimetallic oxides on mesoporous ZSM-5, the obtained Fe5Cu5/ME displayed the highest activity, which can be attributed to both the minimized nanoparticle size and the enhanced bimetallic interaction. The mesoporous ZSM-5 support used in this work was obtained from alkaline treatment, which led to a rough mesoporous surface. This surface sufficiently enhanced the dispersion and prohibited metal migration, therefore preventing nanoparticle aggregation and enhancing the bimetallic interaction. The strategy of using mesoporous ZSM-5 obtained from alkaline treatment as a support is a reliable method for preparing multi-metallic catalysts with well-dispersed nanoparticles.
Co-reporter:Qiao Sun, Min Liu, Keyan Li, Yi Zuo, Yitong Han, Junhu Wang, Chunshan Song, Guoliang Zhang and Xinwen Guo
CrystEngComm 2015 vol. 17(Issue 37) pp:7160-7168
Publication Date(Web):07 Aug 2015
DOI:10.1039/C5CE01375E
In this work, MIL-53(Fe) was synthesized using a solvothermal method under static conditions. However, it was interesting to find that another MIL-53 type material, Fe(BDC)(DMF,F), was obtained when stirring conditions were used while keeping the other conditions fixed. The Fe-containing metal–organic frameworks (MOFs) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), 57Fe Mössbauer spectrometry and thermogravimetric analysis (TGA). By simply increasing the crystallization time under agitation, the morphology of the Fe(BDC)(DMF,F) crystals went through a striking transition from a bulky irregular shape to a rod-like morphology. The catalytic performance of the Fe-MOFs was evaluated in the degradation of phenol solution at near neutral pH at 35 °C. A significantly better catalytic activity was achieved for Fe(BDC)(DMF,F) than for MIL-53(Fe) and NH2-MIL-53(Fe) due to the existence of Fe(II) in its framework. Phenol was almost completely decomposed in 3 hours, and the conversions of hydrogen peroxide and chemical oxygen demand (COD) were 74.1% and 78.7%, respectively.
Co-reporter:Yanli Wang, Min Liu, Keyan Li, Anfeng Zhang and Xinwen Guo
CrystEngComm 2015 vol. 17(Issue 19) pp:3636-3644
Publication Date(Web):24 Mar 2015
DOI:10.1039/C5CE00278H
Homogeneous flower-like OMS-2 particles were successfully prepared in a short time of merely 4 h using a hydrothermal method under a MnSO4–K2S2O8–K2SO4–H2SO4 system. The flower-like OMS-2 particles with a diameter of around 2 μm were composed of uniform slender cryptomelane rods several hundred nanometers in length when the pH of the precursor solution was 0.18 and the solution was treated at 443 K. XRD and SEM characterization techniques demonstrated that formation of flower-like OMS-2 involved three stages including formation of fiber-like OMS-2, flower-like pyrolusite-type MnO2 and flower-like OMS-2 with decreasing pH value from 4.08 to 0.18. In the case of reaction time, the redox reaction between Mn2+ and S2O82− was accomplished within the initial 1 h, and the highly crystallized uniform flower-like particles were obtained at 4 h.
Co-reporter:Yitong Han, Min Liu, Keyan Li, Yi Zuo, Yingxu Wei, Shutao Xu, Guoliang Zhang, Chunshan Song, Zongchao Zhang and Xinwen Guo
CrystEngComm 2015 vol. 17(Issue 33) pp:6434-6440
Publication Date(Web):17 Jul 2015
DOI:10.1039/C5CE00729A
UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with cubic and cuboctahedral morphologies were synthesized. Crystal size and morphology varied with the additive amount of hydrofluoric acid and the concentration of reactants (ZrCl4 and H2BDC) during solvothermal synthesis. According to energy dispersive spectrometry (EDS) and 19F MAS NMR measurements, the fluorine ions directly bonded to Zr in the SBUs (secondary building units) in the MOF framework due to their strongest electronegativity. The bonding of the fluorine ions and Zr not only compensated for the charge imbalance of the framework caused by missing linkers but also competed with the linkers to coordinate with the Zr metal centers, thereby controlling the processes of nucleation and growth of the UiO-66 crystals. The samples were further characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and Ar sorption isotherms, showing that the introduction of fluorine enhanced the thermostability and porosity of UiO-66.
Co-reporter:Keyan Li, Fenfen Shua, Jiawei Zhang, Kunfeng Chen, Dongfeng Xue, Xinwen Guo, Sridhar Komarneni
Ceramics International 2015 Volume 41(Issue 5) pp:6729-6733
Publication Date(Web):June 2015
DOI:10.1016/j.ceramint.2015.01.116
Orthorhombic LiMnO2 (o-LiMnO2) was prepared under hydrothermal conditions using sol–gel derived Mn2O3 and LiOH as precursors and the effects of hydrothermal reaction parameters such as reaction temperature and LiOH and Mn2O3 concentrations on the phase purity of o-LiMnO2 were studied. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and galvanostatic charge−discharge tests. Phase purity of o-LiMnO2 was affected by hydrothermal temperature and LiOH and Mn2O3 concentrations. High LiOH concentration facilitated the synthesis of pure phase o-LiMnO2. Low reaction temperature, lower than 140 °C, did not lead to the formation of pure phase of o-LiMnO2. Galvanostatic charge–discharge test results showed that pure o-LiMnO2 had larger discharge capacity than the mixed phases of o-LiMnO2 and Li2MnO3. However, the cycling performance of the mixed phases of o-LiMnO2 with Li2MnO3 was found to be better than that of pure o-LiMnO2.
Co-reporter:Chengyi Dai, Xinmin Li, Anfeng Zhang, Chun Liu, Chunshan Song and Xinwen Guo
RSC Advances 2015 vol. 5(Issue 50) pp:40297-40302
Publication Date(Web):27 Apr 2015
DOI:10.1039/C5RA05952F
Pd and Pd–CuO nanoparticles were successfully encapsulated in hollow silicalite-1 single crystals by tetrapropylammonium hydroxide (TPAOH) hydrothermal treatment with an “impregnation-dissolution-recrystallization” process. The size and number of particles in the hollow zeolite depended mainly on the nature of the metal. For palladium, the palladium nanoparticles easily aggregated into larger particles in the hydrothermal process, which displays excellent substrate selectivity for the meta- and para-substituted aryl bromides in the Suzuki–Miyaura reaction. For Pd–CuO binary metals (oxide), introducing copper oxide prevents aggregation of palladium, which shows about 3 times higher activity than encapsulated single Pd catalyst for the above reaction. The strategy using a hollow zeolite crystal as a support is a more reliable method for preparing multi-metallic (oxide) catalysts with well-dispersed nanoparticles.
Co-reporter:Yi Zuo, Xiaowa Nie, Min Liu, Ting Zhang, Chengyi Dai, Fanshu Ding, Chunshan Song, and Xinwen Guo
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 30) pp:7364-7372
Publication Date(Web):July 10, 2015
DOI:10.1021/acs.iecr.5b01233
A novel route for the environmentally friendly synthesis of diethyl toluene diamine (DETDA) was developed by the ethylation of 2,4-toluene diamine (2,4-TDA) over acidic zeolites using ethene and ethanol as the alkylation reagents. Different types of zeolites and reaction conditions were examined. Monoethyl toluene diamine (ETDA) was first generated and then DETDA was formed by ethylation of ETDA. Triethyl toluene diamine (TETDA) was the excessive ethylation product. The acidic zeolites were characterized by NH3 temperature-programmed desorption, pyridine adsorption Fourier transform infrared spectroscopy, argon/nitrogen physisorption and scanning/transmission electron microscopy. The acidity, especially the Brønsted acid sites on the external surface of zeolites, plays a more important role in the ethylation than the pore channel does. A small crystal size exposing more acid sites on the external surface is beneficial for the producing of DETDA. The treatment with NaOH generating meso- and macropores and increasing external surface area can also improve the catalytic activity of ZSM-5.
Co-reporter:Keyan Li, Fanfan Chai, Yongqin Zhao and Xinwen Guo
RSC Advances 2015 vol. 5(Issue 114) pp:94397-94404
Publication Date(Web):29 Oct 2015
DOI:10.1039/C5RA19076B
Magnetic Fe3O4/CeCO3OH composites were prepared through a one-step hydrothermal route and their applications as adsorbents for removal of dyes were investigated. The as-prepared Fe3O4/CeCO3OH composites as well as single component Fe3O4 and CeCO3OH were characterized by XRD, TEM, FTIR, TG, XPS, EDX, Ar physisorption, and zeta potential analysis. Results showed that the composite of Fe3O4 with CeCO3OH significantly improved the adsorption ability compared to both Fe3O4 and CeCO3OH, and Fe/Ce dosage ratio was the key to control the adsorption properties of the adsorbents. The adsorption amount of the adsorbent was closely related to the amount of surface carboxylate groups, which exhibited surface negative charge and thus superior ability to adsorb cationic dyes. The weight percentages of surface carboxylate groups for the adsorbents with Fe/Ce dosage ratios of 5:0, 4:1, 1:1, 1:4 and 0:5 were 7.6%, 18.3%, 15.1%, 12.0% and 5.9%, respectively. The maximum adsorption capacity reached 666.2 mg g−1 for methylene blue (MB) at the Fe/Ce dosage ratio of 4:1, much higher than other magnetic adsorbents. The kinetic adsorption data fitted the pseudo-second-order model and the isotherm data followed the Langmuir model. Besides, the magnetic property of the Fe–Ce composite made solid–liquid separation easily achievable. These results demonstrated that this composite material could be used as a good adsorbent for selective removal of small cationic dyes from wastewater, and this facile synthesis method can be used to prepare other high performance adsorbents.
Co-reporter:Yanli Wang, Jinxia Zhou and Xinwen Guo
RSC Advances 2015 vol. 5(Issue 91) pp:74611-74628
Publication Date(Web):14 Aug 2015
DOI:10.1039/C5RA11957J
The catalytic hydrogenolysis of readily available glycerol to 1,2-propanediol (1,2-PD) and 1,3-propanediol (1,3-PD), which provides a new promising synthesis route to produce propanediols, has been extensively studied in the past decades. This study summarizes the most significant reports regarding glycerol hydrogenolysis into propanediols. Three reaction routes, including those working towards 1,2-PD production and the recently proposed one leading to 1,3-PD production, have been summarized. The catalysts used for this reaction have been classified into two categories according to the type of metal components: the transition metal catalysts taking Cu, Ni, and Co as representative metal components and the noble metal catalysts containing Ru, Pt, Ir, and Ag. Some inexpensive transition-metal catalysts exhibit high 1,2-PD selectivity and yield under mild reaction conditions, whereas several noble metal catalysts are promising in synthesizing the more valuable 1,3-PD. Efficient preparation methods and precise modulation techniques have been systematically developed to synthesize functionalized catalysts on the basis of the metal species in combination with acidic or basic compounds. Other technological aspects, such as hydrogen sources, reaction solvents, reactor types and feeding processes, are also summarized in this study. The focus of this review is on summarizing the preparation methods and the performance of various catalysts in glycerol hydrogenolysis.
Co-reporter:Anfeng Zhang, Lin Gu, Keke Hou, Chengyi Dai, Chunshan Song and Xinwen Guo
RSC Advances 2015 vol. 5(Issue 72) pp:58355-58362
Publication Date(Web):29 Jun 2015
DOI:10.1039/C5RA09456A
Mesostructure-fine-tuned and size-controlled hierarchical porous silica nanospheres were synthesized by aldehyde-modified Stöber method in the TEOS–CTAB–NH3·H2O–aldehyde system. The samples were characterized by XRD, N2 adsorption–desorption isotherms, SEM, TEM and TG analysis. The results indicate that the particle size of the micro/mesoporous silica nanospheres synthesized with acetaldehyde as a co-solvent can be controlled from 40 to 850 nm by regulating the molar ratio of acetaldehyde to water and the initial pH of the synthesis solution. When propionaldehyde or butyraldehyde was used as a co-solvent, hierarchical porous silica nanospheres with large cone-like cavities and small mesopores in the cavity wall were synthesized; the diameter of the flower-like nanospheres is less than 130 nm. The hierarchical pore structure of the flower-like silica nanospheres can be fine-tuned by controlling the polymerization of butyraldehyde by the synthesis temperature from 27 to 100 °C, both the depth and opening diameter of the cone-like cavities can be fine-tuned from 40 to 2 nm; simultaneously, the small mesopores templated by CTAB become more ordered.
Co-reporter:Lei Luo, Chengyi Dai, Anfeng Zhang, Junhu Wang, Min Liu, Chunshan Song and Xinwen Guo
RSC Advances 2015 vol. 5(Issue 37) pp:29509-29512
Publication Date(Web):19 Mar 2015
DOI:10.1039/C5RA02194D
Meso-ZSM-5 modified by polyethyleneimine has been found to be an excellent support for iron oxide with improved physicochemical properties of iron oxide particles including size and chemical state. The resulting ZSM-5 encapsulated iron nanoparticles exhibit superior catalytic activity for phenol oxidation.
Co-reporter:Yi Zuo, Min Liu, Luwei Hong, Mengtong Wu, Ting Zhang, Mengtong Ma, Chunshan Song, and Xinwen Guo
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 5) pp:1513
Publication Date(Web):January 21, 2015
DOI:10.1021/ie504531v
Titanium silicalite-1 (TS-1) was extruded with silica and alumina supports, and then the extrudates were treated with dilute tetrapropylammonium hydroxide (TPAOH) solution. The treated TS-1 extrudates were characterized and evaluated in the epoxidation of propene. The two supports exhibited different properties after the treatment. The dissolution of silicon, forming hollows in the TS-1 crystals, preferably occurred when alumina support was used. The inhibition of generation of hollows in the silica supported TS-1 arose from the dissolution and recrystallization of silica support. The crystallization of support also led to the unblocking of inherent micropores, which was beneficial for improving the catalytic performance. Alumina support showed a different result. A very small amount of aluminum was inserted into the framework of TS-1, but the small amount of framework Al caused a sharp increase of the acid amount, and thus a low selectivity of propene oxide and poor catalyst stability in propene epoxidation.
Co-reporter:Dr. Yi Zuo;Dr. Min Liu;Ting Zhang; Changgong Meng; Xinwen Guo; Chunshan Song
ChemCatChem 2015 Volume 7( Issue 17) pp:2660-2668
Publication Date(Web):
DOI:10.1002/cctc.201500440
Abstract
A facile method for the size-controllable synthesis of titanium silicalite-1 (TS-1) is presented. A tetrapropylammonium bromide hydrothermal system was used, and the amount of seeds (silicalite-1 suspension) and crystallization time were tuned to control the crystal size. The crystal size could be adjusted from 200 to 1200 nm by varying the seed amount from 12 to 0.05 wt %. Crystallization time plays a less important role than the seed amount on the crystal size. TS-1 samples with different crystal sizes were characterized and evaluated in propene epoxidation. The catalytic activity and selectivity of propene oxide are enhanced by decreasing the crystal size from 1200 to 200 nm because the diffusion limitation is eliminated gradually. The seed is significant for this system, as a lack of seeds leads to poor crystallization and low catalytic activity. The mechanism of the seed function was studied by simulating the transformation process of the seed in the TS-1 synthesis system.
Co-reporter:Chengyi Dai, Anfeng Zhang, Junjie Li, Keke Hou, Min Liu, Chunshan Song and Xinwen Guo
Chemical Communications 2014 vol. 50(Issue 37) pp:4846-4848
Publication Date(Web):24 Mar 2014
DOI:10.1039/C4CC00693C
HPW@Hollow S-1, a novel solid catalyst which can be reused in the synthesis of ethyl acetate, was successfully prepared by the ship-in-bottle approach. The catalyst simultaneously shows high activity that resembles homogeneous catalysts, and outstanding stability like that of heterogeneous catalysts.
Co-reporter:Shen Hu, Min Liu, Keyan Li, Yi Zuo, Anfeng Zhang, Chunshan Song, Guoliang Zhang and Xinwen Guo
CrystEngComm 2014 vol. 16(Issue 41) pp:9645-9650
Publication Date(Web):08 Sep 2014
DOI:10.1039/C4CE01545B
The MOF material NH2-MIL-125(Ti) was synthesized through the solvothermal method, and the morphology can be controlled by simply modulating the concentration of the reactants during crystallization, which ranges from circular plate through tetragon to octahedron. All samples were characterized by SEM, XRD, FT-IR, UV Raman spectra, TGA, Ar adsorption/desorption and UV-vis spectra. In situ XRD results show that this Ti-incorporated MOF is highly thermostable until 290 °C. It is interesting to find that the light response of NH2-MIL-125(Ti) crystals is closely related to their morphology, and the absorption edges of different morphologies range from 480 nm to 533 nm with band gaps of 2.6 to 2.3 eV, making them potential candidates for photocatalytic applications.
Co-reporter:Fanshu Ding, Anfeng Zhang, Min Liu, Yi Zuo, Keyan Li, Xinwen Guo, and Chunshan Song
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 45) pp:17563-17569
Publication Date(Web):2017-2-22
DOI:10.1021/ie5031166
The effects of surface hydroxyl groups and SiO2 content of alumina supports for FeK/Al2O3 catalysts on their activity and product selectivity for CO2 hydrogenation to hydrocarbons reaction were investigated. A series of iron-based catalysts supported on six commercial Al2O3 supports were prepared and tested for hydrocarbons production in a fixed-bed reactor. Surface acidic–basic hydroxyls distribution of the supports were evaluated by Fourier transform infrared (FT-IR) and point of zero charge (PZC) measurement. It was found that the PZC of Al2O3 supports strongly affects the dispersion as well as particle size of the Fe-based catalysts. Increasing PZC value of Al2O3, the iron dispersion increased and particle size decreased. The highest CO2 conversion (54.4%) and C5+ hydrocarbons selectivity (31.1%) were achieved when the PZC was 8.0. CO2 conversion and the long-chain products selectivity decreased when PZC declined. Moreover, SiO2-doping of alumina strongly affected the surface acidic–basic hydroxyls distribution of the supports, while a desired SiO2 content improved the catalyst activity by adjusting CO adsorption and the reduction behavior of the iron-based catalysts.
Co-reporter:Keyan Li, Hao Chen, Fenfen Shua, Dongfeng Xue and Xinwen Guo
RSC Advances 2014 vol. 4(Issue 69) pp:36507-36512
Publication Date(Web):14 Aug 2014
DOI:10.1039/C4RA06889K
Iron oxide@C composites and lithium ferrites were synthesized by a cotton-template method as anode materials for Li-ion batteries. α-Fe2O3@C composites with 3-D porous hollow secondary structures were prepared by directly burning the cotton containing the iron salt (FeCl3 or Fe(NO3)3) in air, and the Fe3O4@C composites with similar structures were obtained by annealing α-Fe2O3@C under a N2 atmosphere. α-LiFeO2 and α-LiFe5O8 particles with sizes of 100–500 nm were also prepared using a similar method. Electrochemical measurements showed that all these samples demonstrated good electrochemical performances as Li-ion battery anodes, especially α-Fe2O3@C derived from Fe(NO3)3, which delivers a high reversible capacity of 990 mA h g−1 at 100 mA g−1 after 50 cycles. Both the porous hollow secondary structure and the suitable amount of amorphous carbon are significant for the electrochemical performances of the iron oxide@C composites. Such a method is simple, rapid and inexpensive and may facilitate the preparation of other high performance electrode materials with porous hollow structures.
Co-reporter:Fanshu Ding, Anfeng Zhang, Min Liu, Xinwen Guo and Chunshan Song
RSC Advances 2014 vol. 4(Issue 17) pp:8930-8938
Publication Date(Web):17 Jan 2014
DOI:10.1039/C3RA44485F
SiO2-coated FeK/Al2O3 catalysts with different silica content were prepared and examined for the synthesis of hydrocarbons from CO2 hydrogenation. It was found that SiO2 coating affects both the activity for CO2 conversion and the selectivity to higher hydrocarbons, depending on the loading level. The catalyst with 9 wt% SiO2 coating showed both high CO2 conversion (63%) and high selectivity toward C2+ hydrocarbons (74%), while further higher coating led to suppression of catalyst activity. The analytical characterization of SiO2-coated catalysts confirmed the interactions of SiO2–Fe and SiO2–Al2O3, which largely reduced the metal–support interaction and decreased the reduction temperature of iron oxide. In addition, an increase of adsorption capacity for CO was observed with desired SiO2 coating. It is likely that SiO2-coating improved the catalyst hydrophobic property, thereby reducing the negative impact of water by-product and facilitating the reverse water gas shift reaction and subsequent hydrogenation towards higher CO2 conversion to higher hydrocarbons.
Co-reporter:Wei Tan, Min Liu, Yan Zhao, Keke Hou, Hongyu Wu, Anfeng Zhang, Haiou Liu, Yiren Wang, Chunshan Song, Xinwen Guo
Microporous and Mesoporous Materials 2014 Volume 196() pp:18-30
Publication Date(Web):15 September 2014
DOI:10.1016/j.micromeso.2014.04.050
•Nano-ZSM-5 were modified with SiO2, P2O5 and MgO for toluene methylation with methanol.•Combined modifications with a proper sequence gives best p-xylene selectivity.•Synergeistic modifications can passivate external acid sites and narrow pore opening.•Nano-sized 6Si–5P–3Mg/ZSM-5 gives 98% p-xylene selectivity for 1000 h on stream.The nano-sized ZSM-5 catalysts were modified by surface coating with SiO2, P2O5, MgO and their combinations; the catalytic properties were investigated in the shape-selective methylation of toluene with methanol. The catalysts were characterized by XRD, XRF, N2 adsorption–desorption, temperature programmed desorption of ammonia (NH3-TPD), Fourier-transform infrared spectra of adsorbed pyridine/2,6-di-tert-butylpyridine, and adsorption of n-hexane/cyclohexane. The passivation of Lewis acid sites occurs prior to that of the Brönsted acid sites over ZSM-5 modified by SiO2, while P2O5 or MgO preferentially neutralizes the Brönsted acid sites of ZSM-5. The deposition of MgO is more efficient in passivating the acid sites and narrowing the pore openings, compared to SiO2 or P2O5 modification with the same oxide content (<9 wt%). The single modification could not completely passivate the external surface acid sites and simultaneously narrow the pore openings to a proper extent; so the selectivity to para-xylene does not exceed 90% even at the highest oxide loading. The multiple modification by SiO2, P2O5 and MgO, with a suitable sequence can efficiently eliminate external surface acid sites, and simultaneously narrow the pore openings, which led to a higher para-selectivity (∼98%). The combined modification with SiO2, P2O5 and MgO in a proper sequence can lead to a synergistic effect for tailoring the acid property and pore mouth of the catalyst, thus enhancing the para-selectivity to ∼98% and improving catalytic stability, as demonstrated by flow test for 1000 h on stream.Graphical abstract
Co-reporter:Chengyi Dai, Anfeng Zhang, Lingling Li, Keke Hou, Fanshu Ding, Jie Li, Dengyou Mu, Chunshan Song, Min Liu, and Xinwen Guo
Chemistry of Materials 2013 Volume 25(Issue 21) pp:4197
Publication Date(Web):October 7, 2013
DOI:10.1021/cm401739e
A simple strategy involving desilication and recrystallization of silicalite-1 in tetrapropylammonium hydroxide (TPAOH) solution was successfully developed to prepare hollow zeolite nanocubes and three-dimensionally macroporous zeolite monoliths. Large voids were introduced to silicalite-1 crystals by controlled silicon leaching with OH– and thin intact shells were formed by the recrystallization of silicon with TPA+. The size of nanocubes could be easily controlled from ∼150 nm to ∼600 nm by simply adjusting the size of parent silicalite-1. Apart from template function to increase the yield of hollow silicalite-1, TPA+ adsorbed on the zeolite protects the parent crystal surface where the recrystallization occurred. The size of the mesopores and/or macropores in the hollow zeolite shell can be controlled by varying the amount of competitive Na+ adsorbent added to the TPAOH solution. Furthermore, three-dimensional macroporous zeolite monoliths can be formed when an electrolyte, such as NaCl, was added to the TPAOH solution. When the sample was used as the support for iron-based catalyst for hydrogenation of CO2 to hydrocarbons, both the conversion of CO2 and the selectivity of C5+ higher hydrocarbons were improved.Keywords: alkaline treatment; competitive adsorption; desilication; hollow nanocubes; macroporous monoliths; silicalite-1;
Co-reporter:Xinquan Cheng, Anfeng Zhang, Keke Hou, Min Liu, Yingxia Wang, Chunshan Song, Guoliang Zhang and Xinwen Guo
Dalton Transactions 2013 vol. 42(Issue 37) pp:13698-13705
Publication Date(Web):16 Jul 2013
DOI:10.1039/C3DT51322J
We present here a simple solvothermal method to fabricate metal–organic framework NH2-MIL-53(Al) crystals with controllable size and morphology just by altering the ratio of water in the DMF–water mixed solvent system without the addition of any surfactants or capping agents. With increasing the volume ratio of water in the mixed solvents, a series of NH2-MIL-53(Al) crystals with different sizes and morphologies were synthesized. The average size of the smallest crystal is 76 ± 20 nm, which provides us a simple and environmentally friendly way to prepare nanoscale MOFs. The largest BET surface area of these samples is 1882 m2 g−1 that is mainly contributed by its micropore surface area, and its corresponding micropore volume is 0.83 cm3 g−1, which have greatly extended its application in the fields of gas adsorption and postsynthetic modification. All these samples were characterized by SEM, XRD, N2 adsorption/desorption, TGA and FT-IR. Then a mechanism for the impact of the water ratio on the crystal size and morphology is presented and discussed.
Co-reporter:Jinchang Zhang, Gang Wang, Fengying Jin, Xiangchen Fang, Chunshan Song, Xinwen Guo
Journal of Colloid and Interface Science 2013 Volume 396() pp:112-119
Publication Date(Web):15 April 2013
DOI:10.1016/j.jcis.2013.01.032
Hollow spheres were synthesized from MCM-41 solid spheres by dry-gel conversion. It was found that water amount has a major impact on the formation of hollow spheres. Transmission electron microscopy (TEM) images revealed that the hollow spheres are between 500 and 600 nm in size with a dense shell of ca. 100 nm. The synthesized hollow sphere sample was examined as a support for hydrodesulfurization catalyst. The sulfur removal was enhanced while olefin hydrogenation of FCC gasoline was suppressed, and thus, the octane value was preserved when the hollow spheres (Na type) were loaded with Ni and Mo oxides as catalyst.Graphical abstractHighlights► Hollow spheres were synthesized from MCM-41 solid spheres by dry-gel conversion. ► Hollow spheres are between 500 and 600 nm with a dense shell of ca. 100 nm. ► Water amount has a major impact on hollow sphere formation. ► The hollow sphere was effective as support for minimizing the olefin hydrogenation.
Co-reporter:Keke Hou, Anfeng Zhang, Min Liu and Xinwen Guo
RSC Advances 2013 vol. 3(Issue 47) pp:25050-25057
Publication Date(Web):26 Sep 2013
DOI:10.1039/C3RA43055C
The synthesis of ordered mesoporous carbons (OMCs) was carried out under acidic aqueous conditions, by cooperative self-assembly of phenol–formaldehyde resol and surfactant F127. The influence of the acid source on the structural and anti-oxidation properties of the OMCs was investigated. The acids (HCl, HNO3, H3PO4 and H2SO4) used in the synthesis are sufficient to induce the self-assembly of resol and F127 to form the mesophase, while the final products carbonized at 600 °C show different structural properties. This was mainly due to the different decomposition behaviors of the surfactant during the carbonization process, which depends on the nature of the anions from the acids. After oxidization in acidic (NH4)2S2O8 solution, the H3PO4 catalyzed sample undergoes a minimum reduction in surface area and pore volume, and exhibits a larger adsorptive capacity for Co2+, compared with those using HCl and HNO3 as catalyst. This was related to the incorporation of the phosphorus atoms in the sample with H3PO4 as catalyst, which is in favour of increasing the carbonization degree of the sample, and they can also act as adsorptive sites for Co2+.
Co-reporter:Anfeng Zhang, Keke Hou, Lin Gu, Chengyi Dai, Min Liu, Chunshan Song, and Xinwen Guo
Chemistry of Materials 2012 Volume 24(Issue 6) pp:1005
Publication Date(Web):February 24, 2012
DOI:10.1021/cm300242n
Silica nanotubes with mesopores perforating the wall were synthesized on the channel surface of porous anodic alumina (PAA) or polycarbonate membranes via interfacial growth. Transmission and scanning electron microscopy characterizations indicated that the mesopore orientation can be regulated from perpendicular to the wall to circling the axis when the thickness of the silica nanotube wall increases from about 15 to 40–60 nm, without any modification of the channel surface or external forces, just by optimizing the amount of the tetraethoxysilane confined in the channels of PAA. Mesopores in the silica nanotube wall arrange hexagonally when the diameter of the silica nanotubes is larger than 200 nm.Keywords: interfacial growth; mesopore orientation; mesoporous film; perpendicular; silica nanotube;
Co-reporter:Yi Zuo, Xiangsheng Wang, Xinwen Guo
Microporous and Mesoporous Materials 2012 Volume 162() pp:105-114
Publication Date(Web):1 November 2012
DOI:10.1016/j.micromeso.2012.06.016
Titanium silicalite-1 with small crystal size (small-crystal TS-1) was synthesized in a TPABr–ethylamine hydrothermal system by using the mother liquor of nano-sized TS-1 as seeds. The synthesis conditions were systematically studied, including the purification methods of the small-crystal TS-1, Si/Ti molar ratio in TS-1, amount of the added seed and the crystallization period. The as-synthesized TS-1 was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR), Ultraviolet–visible diffuse reflectance (UV–vis), Ultraviolet Raman spectroscopy (UV-Raman), nitrogen sorption, elemental analysis, atomic force microscope (AFM) and scanning electron microscopy (SEM). The size of the TS-1 crystals formed (about 600 nm × 400 nm × 250 nm) was not significantly affected by the synthesis conditions except for the amount of added seed. The catalytic performance of the synthesized small-crystal TS-1 for the epoxidation of propylene was evaluated. The conversion of hydrogen peroxide, the selectivity of propylene oxide and the utilization of hydrogen peroxide reached 92.2%, 98.0% and 97.0%, respectively, when the mother liquor of small-crystal TS-1 was purified three times by precipitation, the Si/Ti molar ratio was 50, the seed/SiO2 weight ratio was 0.06 and the crystallization time was 48 h.Graphical abstractHighlights► Small-crystal TS-1 was synthesized in a TPABr–ethylamine hydrothermal system. ► The three times precipitating separation was effective in purification of crystals. ► The crystal size was only affected by the amount of seeds after the crystal formed. ► Small-crystal TS-1 showed an excellent catalytic performance in propylene epoxidation. ► The amount of Na+ in small-crystal TS-1 affected the catalytic performance obviously.
Co-reporter:Lin Gu, Anfeng Zhang, Keke Hou, Chengyi Dai, Shuguang Zhang, Min Liu, Chunshan Song, Xinwen Guo
Microporous and Mesoporous Materials 2012 Volume 152() pp:9-15
Publication Date(Web):1 April 2012
DOI:10.1016/j.micromeso.2011.11.047
An effective one-pot hydrothermal synthesis method based on suppressed growth strategy was invented to produce mesoporous silica nanoparticles (MSNs). In a TEOS–CTAB–NH4OH–water–formaldehyde system, formaldehyde was used as suppressant which formed a polymer shell on the outer surface of the MSNs to control the particle size to about 30 nm. A nanoporous carbon framework was obtained when precursor was carbonized in N2 followed by a HF leaching of the silica. The pore size of the carbon was about 30 nm. The mechanism for the synthesis process was described.Graphical abstractOne-pot hydrothermal synthesis using formaldehyde as a suppressant based on suppressed growth strategy was invented to produce mesoporous silica nanoparticles.Highlights► One-pot hydrothermal synthesis based on suppressed growth strategy was invented to produce mesoporous silica nanoparticles. ► Formaldehyde was used as a suppressant of the grain growth of the nanoparticles. ► The particle size of MSNs was well controlled at about 30 nm.
Co-reporter:Yi Zuo, Mengli Wang, Wancang Song, Xiangsheng Wang, and Xinwen Guo
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 32) pp:10586-10594
Publication Date(Web):July 26, 2012
DOI:10.1021/ie300581z
TS-1 extrudates that were used for propene epoxidation in a pilot plant for about 1700 h deactivated partly. To study the reason for the deactivation, the deactivated and regenerated catalysts were investigated with X-ray diffraction analysis, Fourier-transform infrared, Ultraviolet–visible diffuse reflectance, thermogravimetry–differential thermogravimetry, N2 sorption, n-hexane adsorption, cyclohexane adsorption, and elemental analysis. The catalytic performance of the deactivated and regenerated TS-1 extrudates in the epoxidation of propene was evaluated in a fixed-bed reactor and in a batch reactor. The activity of the deactivated catalyst from the inlet of the pilot-plant reactor was higher than that from the outlet of the reactor in which more propene oxide oligomers were generated than in the pores of catalyst taken from the inlet of the reactor. External and in situ regeneration could reinstate the activity of the deactivated catalysts, while the in situ regeneration was preferred.
Co-reporter:Xiaowa Nie ; Michael J. Janik ; Xinwen Guo ;Chunshan Song
The Journal of Physical Chemistry C 2012 Volume 116(Issue 6) pp:4071-4082
Publication Date(Web):January 12, 2012
DOI:10.1021/jp209337m
Methylation of 2-methylnaphthalene (2-MN) for synthesis of 2,6-dimethylnaphthalene (2,6-DMN) is an industrially important reaction because 2,6-DMN is a key precursor for the advanced polymer material polyethylenenaphthalate. Shape-selective methylation of 2-MN with methanol in an H-ZSM-5 pore was studied using the ONIOM2 model and density functional theory. Two proposed reaction mechanisms, stepwise and concerted, were considered. Computational results reveal that the stepwise path, with methanol dehydration to produce a methoxide intermediate as the rate-limiting step, is kinetically favored. Both the stepwise and concerted path indicated that methylation at the 6-position is favored over methylation at the 7-position; however, the concerted path shows a greater selectivity. 2-MN isomerization and methylation, which may occur on the catalyst external surface and decrease selectivity to the desired 2,6-DMN product were also examined. Isomerization of 2-MN to 1-MN proceeds faster on external surface sites than 2-MN methylation with methanol. Decreasing the external surface acid site concentration will restrict the extent of 2-MN isomerization, therefore increasing the β,β′-DMN selectivity inside the pore.
Co-reporter:Jinchang Zhang, Min Liu, Chunshan Song, Xinwen Guo
Microporous and Mesoporous Materials 2011 Volume 139(1–3) pp:31-37
Publication Date(Web):March 2011
DOI:10.1016/j.micromeso.2010.10.012
B-MCM-41 nanoparticles with controlled morphologies including nanorods and nanospheres have been synthesized in water–acetone media using cetyltrimethylammonium bromide (CTAB) as the template and boric acid as boron source. It was found that the total boron content in the product increases with reducing both the water-to-acetone molar ratios in the synthesis gel and hydrothermal temperature. The framework boron content rises with the increase in the hydrothermal temperature. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the long axis in major areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these boron-containing mesoporous silicas.Graphical abstractResearch highlights► Adjusting the r value (the water-to-acetone molar ratio in the mixed solvent) leads to different morphology of B-MCM-41. ► The mesoporous parallel channels run along the long axis in major areas in the nanorods. ► The radially arranged mesopore channels are present in the nanospheres.
Co-reporter:Yi Zuo, Xiangsheng Wang, and Xinwen Guo
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 14) pp:8485-8491
Publication Date(Web):June 15, 2011
DOI:10.1021/ie200281v
Titanium silicalite-1 (TS-1) with small crystal size was synthesized in a TPABr-ethylamine system using the mother liquid of nanosized TS-1 as seed. The as-synthesized small-crystal TS-1, the size of which was about 600 nm × 400 nm × 250 nm was characterized with X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), ultraviolet–visible (UV–vis), UV-Raman, N2 sorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Its catalytic performance was evaluated in the epoxidation of propylene and the hydroxylation of phenol. The conversion of hydrogen peroxide and selectivity of propylene oxide (PO) in the propylene epoxidation reached 92 and 98 mol %, respectively. In the hydroxylation of phenol, small-crystal TS-1 also resulted in a high conversion of phenol.
Co-reporter:Shu Shuang Li, An Feng Zhang, Min Liu, Xin Wen Guo
Chinese Chemical Letters 2011 Volume 22(Issue 3) pp:303-305
Publication Date(Web):March 2011
DOI:10.1016/j.cclet.2010.06.036
Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant. The material is characterized with XRD, TEM, N2 adsorption isotherm. The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20–30 nm. The BET surface area increases from 420 to 513 m2/g compared to conventional TS-1 zeolite. The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.
Co-reporter:Jinxue Wang;Min Liu;Xinwen Guo;Hongyu Wu
Reaction Kinetics, Mechanisms and Catalysis 2011 Volume 102( Issue 2) pp:447-457
Publication Date(Web):2011 April
DOI:10.1007/s11144-010-0267-y
Supported Ag/TS-1 catalysts were prepared by the cool plasma sputtering technique and characterized by BET, SEM/EDX, XRD, UV–Vis and TEM techniques. The Ag loading and particle size on TS-1 were tailored by sputtering time. The catalytic performance of the supported catalysts was tested in the gas-phase propene epoxidation reaction using H2 and O2 at a space velocity of 4000 h−1, and atmospheric pressure. Ag/TS-1 with 1.0–19.9 wt% Ag loading and a Ag particle size around 10–40 nm exhibited a selectivity above 90% in the propene epoxidation reaction at a suitable temperature. Catalysts with high Ag loading and large Ag size cause H2 combustion in O2, leading to propene combustion. The heat evolved in the reaction process may lead to over-oxidation of propene to CO2.
Co-reporter:Linping Sun, Xinwen Guo, Min Liu and Xiangsheng Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 2) pp:506-514
Publication Date(Web):November 20, 2009
DOI:10.1021/ie901218j
Ethylation of coking benzene, the product of coke oven gas, with ethanol over nanosized HZSM-5 zeolites poisoned by 2,6-dimethylpyridine has been investigated in a fixed-bed reactor. Pyridine infrared (Py-IR), amonia temperature programmed desorption (NH3-TPD), thermogravimetry (TG), acidity titration with a Hammett indicator, and cyclohexane and n-hexane adsorption were used to characterize the changes in acidity and porosity of the nanosized HZSM-5 zeolites poisoned by 2,6-dimethylpyridine. Conversion and product distribution depend strongly on the degree of catalyst poisoning. The acidity−activity correlation indicates that acid sites with pKa < −3.0 are responsible for the ethylation of coking benzene and sites with pKa < 2.27 are responsibly for the thiophene conversion. The remaining acid sites, which are not active for the ethylation of coking benzene over the poisoned sample, act as active centers for ethanol dehydration to ethylene. 2,6-Dimethylpyridine not only adsorbs on the strong Brönsted acid sites but blocks the zeolite channels over the poisoned sample.
Co-reporter:Jian Gao, Min Liu, Xiangsheng Wang and Xinwen Guo
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 5) pp:2194-2199
Publication Date(Web):February 2, 2010
DOI:10.1021/ie901360y
Ti-ZSM-5 has attracted much attention for its unique catalytic properties in selective oxidation. Isomorphous substitution is an alternative synthesis method to obtain Ti-ZSM-5 with low contents of extraframework Ti. However, the nature of the precursor also has a great influence on the catalytic performance of Ti-ZSM-5. In this work, two Ti-ZSM-5 samples were prepared by isomorphous substitution of precursor B-ZSM-5 zeolites with gaseous TiCl4. The effect of the nature of the B-ZSM-5 precursor obtained by different hydrothermal synthesis procedures on the catalytic performance was investigated through characterization by XRD; FT-IR, UV−vis, and UV−Raman spectroscopies; SEM; N2 adsorption; and phenol hydroxylation. The characterization results show that the two Ti-ZSM-5 samples synthesized by gas−solid isomorphous substitution of the B-ZSM-5 precursor contain very little anatase and have similar amounts of active sites. They consist of cuboidlike crystals with different sizes that are agglomerated into different sizes of spherelike particles. Phenol hydroxylation with dilute H2O2 showed that, because of the smaller crystal size of its cuboid particles, Ti-ZSM-5 synthesized with B-ZSM-5 as the precursor at lower crystallization temperature had better catalytic performance and better recyclability.
Co-reporter:Xiaowa Nie, Xin Liu, Lei Gao, Min Liu, Chunshan Song and Xinwen Guo
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 17) pp:8157-8163
Publication Date(Web):July 26, 2010
DOI:10.1021/ie100800c
Several SO3H-functionalized ionic liquids (FILs) were synthesized and their catalytic performances for catechol (CAT) alkylation with tert-butyl alcohol (TBA) were studied theoretically as well as experimentally. Under optimized reaction conditions, the conversion of CAT was 41.5%, and the selectivity for 4-tert-butyl catechol (4-TBC) could reach 97.1%. This electrophilic reaction exhibits a kinetics-dependent character. The higher frontier electron density at the C4 site, comparatively lower activation energy barrier (Ea), and higher thermodynamic stability all act in concert to make the reaction proceed preferentially toward 4-TBC. The FILs can lead to a much higher CAT conversion and a similar selectivity to 4-TBC compared to a Beta zeolite catalyst. Because the frontier electron density [fr(E)] of CAT was not significantly affected by the solvent, the product selectivity rule would not vary, whereas the addition of a solvent with a higher dielectric constant would slow the reaction by increasing Ea, thus resulting in a lower CAT conversion.
Co-reporter:Jinchang Zhang, Min Liu, Anfeng Zhang, Kaifeng Lin, Chunshan Song, Xinwen Guo
Solid State Sciences 2010 Volume 12(Issue 2) pp:267-273
Publication Date(Web):February 2010
DOI:10.1016/j.solidstatesciences.2009.11.005
Mesoporous silica nanoparticles with controlled morphologies including nanococoons, nanorods and nanospheres have been synthesized in water–acetone media at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained nanoparticles generally show hexagonal-like mesoporous structures with average pore size ranging from 2.7 to 3.3 nm and surface area from 806 to 1055 m2/g, respectively. It was found that the changes in water-to-acetone molar ratios have a dramatic impact on the morphologies of the mesoporous silica with different surface roughness, probably due to the solvent influence on the rate of the hydrolysis of tetraethoxy silane (TEOS) and the polymerization of inorganic species. Interestingly, the morphology of the mesoporous silica products can be controlled in shape from nanococoons to nanorods to nanospheres just by decreasing the water-to-acetone molar ratio from 75 to 30 to 15, respectively. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the short axis in some areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these mesoporous silicas.
Co-reporter:Shushuang Li, Min Liu, Anfeng Zhang, Xinwen Guo
Materials Letters 2010 Volume 64(Issue 5) pp:599-601
Publication Date(Web):15 March 2010
DOI:10.1016/j.matlet.2009.12.013
Spherical mesoporous silica was synthesized using a mixture of 1-methyl-3-octylimidazolium chloride and cetyltrimethylammonium bromide as the structure-directing agent. The obtained silica was characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, and 13C NMR spectroscopic techniques. The results show that the spherical silica possesses worm-like mesopores and larger mesopores, with the sizes about 6–50 nm. It is very interesting that the spherical mesoporous spheres were converted to hollow ones after reflux in boiling water. The treatment results in the generation of the hollow interior by dissolving the silica core. Meanwhile, the silica shell is well retained, which is confirmed by SEM and TEM images.
Co-reporter:Xiaowa Nie, Xin Liu, Chunshan Song, Xinwen Guo
Journal of Molecular Catalysis A: Chemical 2010 Volume 332(1–2) pp:145-151
Publication Date(Web):1 November 2010
DOI:10.1016/j.molcata.2010.09.010
SO3H-functionalized ionic liquids (FILs) have been used to catalyze the alkylation of phenol, o-cresol and catechol with tert-butyl alcohol (TBA), and the catalytic performances are promising. During these Brønsted acid-catalyzed tert-butylations, t-butyl phenol ether (TBPE) and t-butyl o-cresol ether (TBOCE) are found, but no t-butyl catechol ether (TBCE) is detected. With the help of density functional theory (DFT) calculations, the reaction mechanisms of Brønsted acid-catalyzed tert-butylation of phenol, o-cresol and catechol were examined. The steric effect of t-butyl group does not have an apparent impact on the regioselectivity to t-butyl ether. The differences in the stability of O-alkylation intermediates, resulted from different ortho-substituents, account for the regioselectivity to t-butyl ether. For catechol tert-butylation, an intramolecular hydrogen bond is formed within the O-alkylation intermediate, which leads to extra stability of this intermediate and obvious increase of the activation barrier for TBCE formation. The intramolecular hydrogen bond formed within the O-alkylation intermediate facilitates its isomerization, inhibits the TBCE formation, thus making the reaction kinetics for catechol tert-butylation unique.Graphical abstractThe intramolecular hydrogen bond formed within O-alkylation intermediate facilitates its isomerization to C-alkylation intermediates, inhibits the t-butyl catechol ether formation, thus making the reaction kinetics for catechol tert-butylation unique.Research highlights▶ DFT calculations provide new insight into tert-butylation mechanisms. ▶ The differences in the stability of O-alkylation intermediates account for the regioselectivity to tert-butyl ether from phenolics. ▶ The intramolecular H-bond inhibits tert-butyl ether formation from catechol.
Co-reporter:Shaoyun Chen, Yongchun Zhang, Xinwen Guo
Separation and Purification Technology 2009 Volume 69(Issue 3) pp:288-293
Publication Date(Web):15 October 2009
DOI:10.1016/j.seppur.2009.07.020
This study investigates the adsorption performance of a number of absorbents prepared by incipient wetness impregnation of 3.85 wt% Fe, Co, Ni, Mn, Co and Ce oxides on HZSM-5 for the removal of trace NO (150–200 ppm) from a CO2 stream to produce food-grade CO2. The adsorbents were characterized using X-ray diffraction, X-ray fluorescence, and N2 adsorption with their performances evaluated in a fixed-bed flow system. The investigations revealed NO removal of better than 0.1 ppm from the CO2 stream. The breakthrough capacities of the adsorbents for NO removal in the presence of O2 were found to significantly increase. The converse was observed in the case of NO adsorption selectivity. Co/HZSM-5(25) was found to be the best adsorbent under all the conditions tested producing CO2 purities of better than 99.9999%. This is significantly higher than for Fe–Mn mixed oxides, claimed to be the best NO adsorbent reported in the literature for CO2 purification.
Co-reporter:An Feng Zhang, Yong Chun Zhang, Na Xing, Ke Ke Hou, Jing Wang, Xin Wen Guo
Chinese Chemical Letters 2009 Volume 20(Issue 7) pp:852-856
Publication Date(Web):July 2009
DOI:10.1016/j.cclet.2009.03.001
Micron-sized hollow silica spheres whose shells are made up of mesocellular silica foams (MCFs) have been synthesized by one-pot sol–gel method in benzene/water/P123 emulsion. The material is characterized with SEM, TEM, BET and 29Si MAS NMR. The results show that the MCFs of the unique shell of hollow silica spheres were connected by large windows with a narrow distribution of ∼10 nm in diameter, the inner space of the hollow sphere is accessible. And the formation mechanism of the hollow silica spheres is proposed.
Co-reporter:Xiumei Liu, Jinxia Zhou, Xinwen Guo, Min Liu, Xiaoliang Ma, Chunshan Song and Chang Wang
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 15) pp:5298
Publication Date(Web):June 25, 2008
DOI:10.1021/ie070647t
The SO3H-functionalized ionic liquids were synthesized by using pyridine and 1,4-butane or 1,3-propane sulfone as the source and characterized by NMR and time-of-flight mass spectrometry. The acidity of the ionic liquids determined by the Hammett method is almost the same as that of a conventional acid, such as H2SO4. The catalytic performance of ionic liquids for the tert-butylation of p-cresol with tert-butanol was evaluated; by using the ionic liquids as catalysts at the optimum reaction conditions, 79% of the p-cresol conversion and 92% of the selectivity to 2-tert-butyl-p-cresol can be obtained. The spent ionic liquid can be recovered and recycled. The possible mechanism for this reaction system was discussed based on the reaction results and the ab initio calculation results.
Co-reporter:Xiaobo Zhao, Xinwen Guo, Xiangsheng Wang
Fuel Processing Technology 2007 Volume 88(Issue 3) pp:237-241
Publication Date(Web):March 2007
DOI:10.1016/j.fuproc.2006.10.001
Nanoscale HZSM-5 zeolite was hydrothermally treated with ammonia water at different temperatures and then loaded with La2O3 and ZnO. The parent and the modified nanoscale HZSM-5 catalysts were characterized by SEM, NH3-TPD, IR and XRF. The performance of the modified HZSM-5 catalysts for FCC gasoline upgrading was evaluated in a fixed bed reactor in the presence of hydrogen. The results indicated that the modified catalyst which was hydrothermally treated at 400 °C exhibited excellent aromatization activity, isomerization activity and higher ability of reducing olefin content in FCC gasoline. Under the given reaction conditions, the olefin content in FCC gasoline could be decreased from 49.6 to 8.1 vol.%. The catalytic performance of the modified nanoscale ZSM-5 catalyst hardly changed within 300 h time on stream, and the research octane number (RON) of gasoline was preserved.
Co-reporter:Chen Zhang, Xin Wen Guo, Ya Nan Wang, Xiang Sheng Wang, Chun Shan Song
Chinese Chemical Letters 2007 Volume 18(Issue 10) pp:1281-1284
Publication Date(Web):October 2007
DOI:10.1016/j.cclet.2007.07.025
The methylation of 2-methylnaphthalene (2-MN) into 2,6-dimethylnaphthalene (2,6-DMN) was investigated over the solid acid catalysts. The results show that HZSM-5 modified by NH4F has better catalytic performance than parent HZSM-5 due to the decrease in the acidity. When NH4F/HZSM-5 is further modified by SrO, its catalytic activity decreases due to the decrease in the total acid amount and acidic strength. As a result, the comprehensive modification of NH4F and SrO leads to the increase in the 2,6-DMN selectivity (2,6-DMN to DMN), up to 64.8% when 2-MN conversion is 10%. We calculated the ESP charge by density functional theory and the results show that the 6-position in 2-MN has higher ESP charge value than 7-position. The formation of 2,6-DMN is favored energetically as compared to that for 2,7-DMN. This suggests during the alkylation of 2-MN inside the ZSM-5 channel, the formation of 2,6-DMN is favored electronically than that of 2,7-DMN. Hence, lowering the acidity of catalyst is a key factor to obtain high selectivity of 2,6-DMN.
Co-reporter:Shen Hu, Min Liu, Fanshu Ding, Chunshan Song, Guoliang Zhang, Xinwen Guo
Journal of CO2 Utilization (September 2016) Volume 15() pp:89-95
Publication Date(Web):1 September 2016
DOI:10.1016/j.jcou.2016.02.009
•Hydrothermally stable MOFs for CO2 hydrogenation to hydrocarbons.•MOFs show excellent properties compared with traditional supports γ-Al2O3.•The types of MOFs could affect the activity and selectivity.•The particle size could affect the selectivity.Two types of hydrothermally stable MOFs, ZIF-8 and MIL-53(Al) with different size and morphology, were prepared and used as supports for catalysts for synthesis of hydrocarbons from CO2 hydrogenation. XRD patterns proves that all these two types of MOFs materials could be stable under the reaction conditions (P = 3 MPa; T = 573 K) with water as byproduct. MOFs as a novel porous materials show excellent properties on catalysis compared with traditional supports γ-Al2O3 and the type of MOF supports has a significant impact on the activity and selectivity of Fe catalysts for CO2 hydrogenation. Due to the acidity of supports, ZIF-8 supports show different levels of considerable light olefins selectivity, while all MIL-53 supports nearly could not obtain light olefins. The light olefins selectivity of ZIF-8 is also affected by the secondary reaction of hydrogenation during the internal diffusion process. In this article, catalyst with high active and high light olefins selectivity was obtained just by modulating the MOFs supports.Download high-res image (139KB)Download full-size image
Co-reporter:Liang ZHAO, Xinwen GUO, Min LIU, Xiangsheng WANG, Chunshan SONG
Chinese Journal of Chemical Engineering (October 2010) Volume 18(Issue 5) pp:742-749
Publication Date(Web):1 October 2010
DOI:10.1016/S1004-9541(09)60123-3
Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over NH4F and Pt modified HZSM-5 (SiO2/Al2O3 = 83) catalysts in a fixed-bed down-flow reactor using methanol as methylating agent and 1,3,5-trimethylbenzene (1,3,5-TMB) as a solvent. Pt promoted HZSM-5 catalysts showed low concentration of coke-like polycondensed aromatics, NH4F modification decreased non-shape-selective acid sites. After Pt and NH4F co-modification, both conversion of 2-MN and selectivity to 2,6-DMN were improved. 6%NH4F/0.5%Pt/HZSM-5 catalyst exhibited 13.8% of 2-MN conversion with 6.2% of 2,6-DMN yield after 7 h time on stream (TOS), and 2,6-/2,7-DMN ratio of 1.7 after 10 h of TOS.
Co-reporter:Hongyu Wu, Min Liu, Wei Tan, Keke Hou, ... Xinwen Guo
Journal of Energy Chemistry (July 2014) Volume 23(Issue 4) pp:491-497
Publication Date(Web):1 July 2014
DOI:10.1016/S2095-4956(14)60176-5
A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaCl and crystal seed. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and temperature-programmed desorption of ammonia (NH3-TPD) were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified sample showed the best stability among the tested three modified samples.ZSM-5-C sample appeared good stability during the toluene methylation reaction, due to its proper pore structure and abundant intergranular pores.Download full-size image
Co-reporter:Linping Sun, Xinwen Guo, Min Liu, Xiangsheng Wang
Applied Catalysis A: General (28 February 2009) Volume 355(Issues 1–2) pp:184-191
Publication Date(Web):28 February 2009
DOI:10.1016/j.apcata.2008.12.015
Co-reporter:Xiaowa Nie, Michael J. Janik, Xinwen Guo, Xin Liu, Chunshan Song
Catalysis Today (16 May 2011) Volume 165(Issue 1) pp:120-128
Publication Date(Web):16 May 2011
DOI:10.1016/j.cattod.2010.11.070
Tert-butylation of phenol with tert-butyl alcohol (TBA) over H-β zeolite was studied using the ONIOM approach with two proposed reaction paths: stepwise and concerted mechanisms. The results obtained by the ONIOM2 (B3LYP/6-31G(d,p):UFF) method reveals that the tert-butylation of phenol preferentially occurs through a co-adsorbed, concerted mechanism without prior dehydration of tert-butyl alcohol, rather than via a stepwise mechanism through dehydration to form tert-butyl carbenium ion as the first step followed by tert-butyl cation attack on the 2- or 4-position on phenol. The kinetic difference between 2- and 4-tert-butylation is more apparent in the concerted path, where 4-tert-butylation proceeds over a lower activation barrier. Decreasing the acid site strength, via substitution of Ga for Al, reduces the H-bonding interaction between the zeolitic proton and tert-butyl alcohol and increases the apparent activation barriers, which slows the overall reaction, and also lowers the selectivity to 4-tert-butyl phenol.
Co-reporter:Chen Zhang, Xinwen Guo, Chunshan Song, Shuqi Zhao, Xiangsheng Wang
Catalysis Today (15 January 2010) Volume 149(Issues 1–2) pp:196-201
Publication Date(Web):15 January 2010
DOI:10.1016/j.cattod.2009.04.015
Shape-selective methylation of 2-methylnaphthalene (2-MN) over HZSM-5 catalysts modified by steam and tetraethoxysilane (TEOS) treatments was carried out in a fixed-bed reactor. Catalysts were characterized by XRD, NH3-TPD, BET, FT-IR spectra of pyridine adsorbed, and by adsorption of hexane and cyclohexane. The results show that the TEOS treatment can effectively passivate external active site and narrow pore mouth of catalyst, but it has less effect on the internal surface than steam modification. Hydrothermal treatment can effectively reduce both external and internal acid sites, and adjust channel of catalyst. Steam treatment can effectively increase the ratio of 2,6/2,7-DMN, but the ratio has no increasing trend on TEOS modified catalyst. So adjusting acidity property is more useful to increase the selectivity to 2,6-DMN and the ratio of 2,6/2,7-DMN than narrowing catalyst pore mouth. Tailoring acidic characteristics is more important than spatial control for distinguishing between 2,6-DMN and 2,7-DMN.
Co-reporter:Jiandong Bi, Xinwen Guo, Min Liu, Xiangsheng Wang
Catalysis Today (15 January 2010) Volume 149(Issues 1–2) pp:143-147
Publication Date(Web):15 January 2010
DOI:10.1016/j.cattod.2009.04.016
Nanoscale and microscale HZSM-5 zeolite catalysts were prepared and characterized by using SEM, XRD, IR, TPD and modified Hammett indicator method. Their performances in the dehydration of bio-ethanol into ethylene were compared in a fixed-bed reactor at 240 °C under atmospheric pressure. The results show that nanoscale HZSM-5 zeolite catalyst exhibits better stability than microscale HZSM-5 zeolite catalyst. When the 95(v) % bio-ethanol is used as the reactant, over nanoscale HZSM-5 catalyst, the conversion of bio-ethanol and the selectivity for ethylene almost keep constant during 630 h reaction, while over microscale HZSM-5 zeolite catalyst, the conversion of bio-ethanol decreases after 60 h reaction; in the case of the 45(v) % bio-ethanol employed as the feedstock, over nanoscale HZSM-5 catalyst, the conversion of bio-ethanol and the selectivity for ethylene almost keep constant during 320 h reaction, while over microscale HZSM-5 zeolite catalyst, both the conversion of bio-ethanol and the selectivity for ethylene decrease almost at the beginning of the reaction.
Co-reporter:Jinxia Zhou, Xiumei Liu, Shuguang Zhang, Jingbo Mao, Xinwen Guo
Catalysis Today (15 January 2010) Volume 149(Issues 1–2) pp:232-237
Publication Date(Web):15 January 2010
DOI:10.1016/j.cattod.2009.07.089
Our previous work showed that for catalytic alkylation of m-cresol with tert-butanol (TBA) SO3H-functionalized ionic liquids exhibited several characteristic advantages over conventional catalysts. This work investigated the reaction mechanism of the alkylation of m-cresol with tert-butanol catalyzed by the SO3H-functionalized ionic liquid (IL) through quantum chemical calculation in combination with the experimental studies. The experimental results showed that 2-tert-butyl-5-methyl phenol (2-TBC), 4-tert-butyl-3-methyl phenol (4-TBC) and tert-butyl-m-cresol ether (TBMCE) products were all primary products, while 2,6-di-tert-butyl-3-methyl phenol (2,6-DTBC) was a secondary product. The calculation results indicated that the selectivities of the products depended on the fundamental natures of the reactive sites, including the orbital overlap, the Coulomb and the steric effect in the interaction between the tert-butyl ion ([t-C4H9]+) and the m-cresol; the TBMCE was dynamically favored but not thermodynamically stable, while the C-alkylated products, especially 2-TBC, were the thermodynamically preferred products; the IL played an important role in generating the [t-C4H9]+ from the TBA and the final products from the intermediates.
Co-reporter:Ting Zhang, Yi Zuo, Min Liu, Chunshan Song, and Xinwen Guo
ACS Omega Volume 1(Issue 5) pp:1034-1040
Publication Date(Web):November 29, 2016
DOI:10.1021/acsomega.6b00266
Titanium silicalite-1 (TS-1) with little extraframework Ti was hydrothermally synthesized in a tetrapropylammonium hydroxide system using starch as the additive. The influences of the amount of starch added on the coordination states of titanium ions and the functional mechanism of starch were studied by various characterization means. The addition of starch slowed the crystallization rate of TS-1 so that the insertion rate of titanium to the framework matched well with that of silicon. Therefore, the generation of extraframework Ti, including the anatase TiO2 and octahedrally coordinated titanium, was eliminated. The catalytic performances of the TS-1 samples were evaluated in the epoxidation of 1-butene to produce butene oxide. The catalytic activity of TS-1 was improved significantly due to the increasing amount of framework Ti.Topics: Catalysts; Crystal structure; Reaction kinetics; Reaction kinetics; Redox reaction; Redox reaction; Spectra;
Co-reporter:Qiao Sun, Min Liu, Keyan Li, Yitong Han, Yi Zuo, Fanfan Chai, Chunshan Song, Guoliang Zhang and Xinwen Guo
Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 1) pp:NaN153-153
Publication Date(Web):2016/11/17
DOI:10.1039/C6QI00441E
Partial isomorphic substitution of iron in an Fe(BDC)(DMF,F) metal organic framework by manganese, cobalt, and nickel has been described for the first time. Specifically, different amounts of Mn, Co and Ni have been incorporated into the Fe-based framework during a solvothermal crystallization procedure. Several characterization techniques, including XRD, FT-IR, SEM, EDS, TG, XPS and ICP-AES, strongly support the effective incorporation of Mn, Ni and Co into material frameworks. The catalytic performance of these materials was examined in liquid-phase degradation of phenol at 35 °C and near neutral pH of 6.2. The results show that the degradation efficiency can be evidently improved by the incorporation of Mn, while it can be inhibited by the incorporation of Ni. The incorporation of Co shows no remarkable influence on the degradation process. Moreover, the ratios of n(Fe)/n(Mn) in the bimetallic MOFs have a strong impact on the degradation process. The stability and reusability of these catalysts under mild conditions were also demonstrated in this study. This work illustrates the potential of bimetallic MOF structures in developing active heterogeneous catalysts for the degradation process of toxic compounds.
Co-reporter:Lei Luo, Chengyi Dai, Anfeng Zhang, Junhu Wang, Min Liu, Chunshan Song and Xinwen Guo
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 6) pp:NaN3165-3165
Publication Date(Web):2015/03/31
DOI:10.1039/C5CY00242G
The mesoporous ZSM-5 zeolite obtained from alkaline treatment was found to be a superior support of bimetallic FeCu, minimizing the nanoparticle size, enhancing the bimetallic interaction, and promoting catalytic oxidation of phenol. The physicochemical characteristics of the as-prepared FexCuy/ZSM-5 samples were evaluated by XRD, TEM, Ar adsorption, H2-TPR, and 57Fe Mossbauer spectroscopy which revealed a strong bimetallic interaction. Meanwhile, phenol oxidation was applied as a probe reaction under mild conditions. By supporting FeCu bimetallic oxides on mesoporous ZSM-5, the obtained Fe5Cu5/ME displayed the highest activity, which can be attributed to both the minimized nanoparticle size and the enhanced bimetallic interaction. The mesoporous ZSM-5 support used in this work was obtained from alkaline treatment, which led to a rough mesoporous surface. This surface sufficiently enhanced the dispersion and prohibited metal migration, therefore preventing nanoparticle aggregation and enhancing the bimetallic interaction. The strategy of using mesoporous ZSM-5 obtained from alkaline treatment as a support is a reliable method for preparing multi-metallic catalysts with well-dispersed nanoparticles.
Co-reporter:Xinquan Cheng, Anfeng Zhang, Keke Hou, Min Liu, Yingxia Wang, Chunshan Song, Guoliang Zhang and Xinwen Guo
Dalton Transactions 2013 - vol. 42(Issue 37) pp:NaN13705-13705
Publication Date(Web):2013/07/16
DOI:10.1039/C3DT51322J
We present here a simple solvothermal method to fabricate metal–organic framework NH2-MIL-53(Al) crystals with controllable size and morphology just by altering the ratio of water in the DMF–water mixed solvent system without the addition of any surfactants or capping agents. With increasing the volume ratio of water in the mixed solvents, a series of NH2-MIL-53(Al) crystals with different sizes and morphologies were synthesized. The average size of the smallest crystal is 76 ± 20 nm, which provides us a simple and environmentally friendly way to prepare nanoscale MOFs. The largest BET surface area of these samples is 1882 m2 g−1 that is mainly contributed by its micropore surface area, and its corresponding micropore volume is 0.83 cm3 g−1, which have greatly extended its application in the fields of gas adsorption and postsynthetic modification. All these samples were characterized by SEM, XRD, N2 adsorption/desorption, TGA and FT-IR. Then a mechanism for the impact of the water ratio on the crystal size and morphology is presented and discussed.
Co-reporter:Chengyi Dai, Shaohua Zhang, Anfeng Zhang, Chunshan Song, Chuan Shi and Xinwen Guo
Journal of Materials Chemistry A 2015 - vol. 3(Issue 32) pp:NaN16468-16468
Publication Date(Web):2015/06/29
DOI:10.1039/C5TA03565A
Highly dispersed Ni–Pt bimetallic nanoparticles encapsulated in hollow silicalite-1 single crystals (1.5Ni–0.5Pt@Hol S-1) were a superior catalyst for sintering and coking resistant dry (CO2) reforming of CH4. Large Ni particles loaded on the surface of solid silicalite-1 crystals triggered coke formation, which simultaneously degraded the catalytic activity of small Ni particles. With Ni encapsulated in hollow crystals, the small Ni particles inhibited coke formation. The encapsulating shell prevented coke formed outside from degrading the activity of nickel on the inside, leading to stable high activity even in the presence of carbon. Compared with single metals (Ni or Pt), 1.5Ni–0.5Pt@Hol S-1 enhanced the dispersion of nickel and platinum. In the dry reforming of methane, the 1.5Ni–0.5Pt@Hol S-1 catalyst operated stably under high gaseous hourly space velocity (GHSV = 72000 ml g−1 h−1) without any inert gas. Only 1.0 wt% carbon deposition was observed by thermogravimetric analysis (TGA) after 6 h of the reaction. Hollow zeolite crystals can reliably support coke resistant catalysts for dry reforming of CH4 and multi-metallic catalysts with well-dispersed nanoparticles.
Co-reporter:Qiao Sun, Min Liu, Keyan Li, Yitong Han, Yi Zuo, Junhu Wang, Chunshan Song, Guoliang Zhang and Xinwen Guo
Dalton Transactions 2016 - vol. 45(Issue 19) pp:NaN7959-7959
Publication Date(Web):2016/02/01
DOI:10.1039/C5DT05002B
A series of MIL-53(Fe)-type materials, Fe(BDC)(DMF,F), were prepared by using different ratios of n(FeCl3)/n(FeCl2), which have varied amounts of Fe2+ in their frameworks. From FeCl3 to FeCl2, the structures of the synthesized samples transform from MIL-53(Fe) to Fe(BDC)(DMF,F). Along with this structure transformation, the crystal morphology goes through a striking change from a small irregular shape to a big triangular prism. This phenomenon indicates that the addition of FeCl2 is beneficial for the formation of a Fe(BDC)(DMF,F) structure. The catalytic activity of these iron-containing MOFs was tested in phenol degradation with hydrogen peroxide as an oxidant at near neutral pH and 35 °C. The degradation efficiency of these samples increases gradually from MIL-53(Fe) to Fe(BDC)(DMF,F). 57Fe Mössbauer spectra reveal that Fe2+ and Fe3+ coexist in the Fe(BDC)(DMF,F) framework, and the highest amount of Fe2+ in the sample prepared with mixed FeCl3 and FeCl2 is 26.0%. The result illustrates that the amount of Fe2+ in the samples can be controlled using varied n(FeCl3)/n(FeCl2) in the feed. The diverse amount of Fe2+ in this series of FeMOF materials exactly explains the distinction of reaction efficiency. The iron leaching tests, structures of the fresh and used catalysts, and the data of the recycling runs show that the Fe-containing MOFs are stable in this liquid-phase reaction.
Co-reporter:Chengyi Dai, Anfeng Zhang, Junjie Li, Keke Hou, Min Liu, Chunshan Song and Xinwen Guo
Chemical Communications 2014 - vol. 50(Issue 37) pp:NaN4848-4848
Publication Date(Web):2014/03/24
DOI:10.1039/C4CC00693C
HPW@Hollow S-1, a novel solid catalyst which can be reused in the synthesis of ethyl acetate, was successfully prepared by the ship-in-bottle approach. The catalyst simultaneously shows high activity that resembles homogeneous catalysts, and outstanding stability like that of heterogeneous catalysts.
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