Wei Huang

Name:

Organization: Taiyuan University of Technology

Department: Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province

Title:

Chemicals
References

Diesel Ultradeep Hydrodesulfurization over Trimetallic WMoNi Catalysts by a Liquid-Phase Preparation Method in a Slurry Bed Reactor

Co-reporter:Yong-Jun Liu, Shu-Zheng Song, Xuan Deng, and Wei Huang

Energy & Fuels July 20, 2017 Volume 31(Issue 7) pp:7372-7372

Publication Date(Web):June 5, 2017

DOI:10.1021/acs.energyfuels.7b00122

A series of Ni–Mo–W slurry catalysts were prepared by a novel complete liquid-phase method and tested for diesel ultradeep hydrodesulfurization (HDS) in a slurry bed reactor. Results showed that Ni–Mo–W catalysts prepared by this novel method exhibited a relatively high HDS efficiency, reaching approximately 96%. Characterization results showed that a suitable amount of W was beneficial for the dispersion of MoS2 species and the production of small particles. Meanwhile, the catalysts incorporating a suitable amount of W had a shorter slab length and more stacking number of MS2, which would enhance the HDS activity. It was also found that HDS efficiency was closely related to (Ni + Mo + W)/(Ti + Al) atomic ratios on the catalyst surface. The incorporation of a suitable amount of W was beneficial for the HDS reproduction, and the best catalytic performance was obtained when the Ni/W atomic ratio was 1:0.5.

Catalytic depolymerization of coal char over iron-based catalyst: Potential method for producing high value-added chemicals

Co-reporter:Jianwei Liu, Qian Zhang, Litong Liang, Guoqing Guan, Wei Huang

Fuel 2017 Volume 210(Volume 210) pp:

Publication Date(Web):15 December 2017

DOI:10.1016/j.fuel.2017.08.074

•The liquid yield increases more than 7 times with the adding of Fe-based catalyst.•High-purity liquid could be yielded by catalytic depolymerization process.•Some of the ether bonds can be easily cracked by the iron-based catalyst.This study examined the feasibility of catalytic depolymerization of coal char obtained from the pyrolysis of low-rank coal at low temperature over iron-based catalyst to produce valuable chemicals. The depolymerization with or without the addition of ferric nitrate in a Gray-King assay reactor from 150 to 600 °C was performed. Compared with 0.2% of organic liquid products generated from the depolymerization without catalyst, the liquid yield increased to 1.61% (more than 7 times) when 1 wt% of catalyst was added. The GC×GC–MS analyses of the de-watered liquid products from depolymerization with catalyst showed that nitro-substituted phenols and alkyl-substituted naphthalene occupied the main contents, which were approximately 54.67% and 36.53%, respectively, and the rests were aliphatic hydrocarbons. An obvious DTG peak was observed from depolymerization with catalyst at 150–400 °C interval. The FTIR spectra analysis showed that the percentage of ether bond of the remained char with catalyst decreased compared with that of raw char without catalyst, reflected that the catalyst facilitates the breaking of ether bond of the raw char to produce more smaller fragments so that more liquid organic products were produced. This research provides a novel method for clean and efficient utilization of coal char and a potential way to produce high value-added chemicals.

Higher alcohols synthesis from syngas over P-promoted non-noble metal Cu-based catalyst

Co-reporter:Yongjun Liu, Xuan Deng, Peide Han, Wei Huang

Fuel 2017 Volume 208(Volume 208) pp:

Publication Date(Web):15 November 2017

DOI:10.1016/j.fuel.2017.07.043

•Alkalis and F-T elements were not indispensable for C2+OH synthesis.•P enhanced the performance of CO hydrogenation to C2+OH.•The synergism of Cu0, Cu+ and AlOOH favored to the formation of C2+OH.A series of P-promoted non-noble metal Cu-based catalysts without alkalis and Fischer-Tropsch elements were prepared by a complete liquid-phase method and tested for the synthesis of higher alcohols (C2+OH) from syngas in slurry bed reactor. The catalysts were characterized by XRD, 27Al-MAS-NMR, N2 adsorption, XPS, H2-TPR and NH3-TPD techniques. Results showed that the incorporation of an appropriate amount of phosphorus into the non-noble metal Cu-based catalyst could increase the surface Cu content, the amount of weak acid and improved the Cu+ reducibility, which promoted the synergistic effect between Cu and Al, and thus enhanced both stability and selectivity towards to higher alcohols formation. Activity results showed that the production of alcohols and hydrocarbons over this kind of catalyst followed A-S-F distributions, similar with conventional CuFe and CuCo based catalysts. The catalysts with Cu:Zn:Al:P = 2:1:0.8:0.05 showed the best catalytic performance with long-term stability toward CO conversion and C2+OH selectivity (reaching 55%) during the lifetime test for 120 h. It was speculated that AlOOH favored CO dissociation, and the synergism of Cu0, Cu+ and AlOOH was beneficial to the formation of higher alcohols. This work provided a new sight that alkalis and F-T elements were not indispensable for direct synthesis of higher alcohols from syngas over non-noble metal Cu-based catalysts.Download high-res image (104KB)Download full-size image

Synthesis of hydrophilic acid-resistant Ge-ZSM-5 membranes via secondary growth method using silicalite-1 zeolite as seeds

Co-reporter:Xiaodong Wang;Yujiao Huang;Xiaoxiao Zhang

Chemical Research in Chinese Universities 2017 Volume 33( Issue 1) pp:12-16

Publication Date(Web):2017 February

DOI:10.1007/s40242-017-6198-7

Hydrophilic acid-resistant Ge-ZSM-5 membranes were synthesized via secondary growth method on porous α-Al2O3 substrates with Silicalite-1 zeolite as seeds. The membranes were characterized by means of scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectrometer to look into the microstructures and element contents of the membranes. The separation performance of the membranes was investigated for separating water from acetic acid solution by pervaporation. The results show that membranes fabricated by the conventional secondary growth method have a high flux, but the selectivity of them is rather limited. Preheating the secondary synthesis sol and using the supernatant as the secondary synthesis sol for membrane fabrication were found to be ef-fective to lower the concentration of the nutrient to constrain re-nucleation, at the same time, lower the Al content in the membranes. The membrane obtained exhibited improved separation performance with a separation factor of 83 at a flux of 0.67 kg·m–2·h–1 at 353 K for a feed concentration of 98% acetic acid solution.

Influence of Si on the performance of higher alcohols synthesis from syngas over CuZnSiAl catalysts without alkalis or Fischer-Tropsch elements

Co-reporter:Yong-Jun Liu, Xuan Deng, Pei-De Han, Wei Huang

International Journal of Hydrogen Energy 2017 Volume 42, Issue 39(Volume 42, Issue 39) pp:

Publication Date(Web):28 September 2017

DOI:10.1016/j.ijhydene.2017.08.064

•Si had a significant influence on the catalytic performance.•Larger Cu particles favored to improve the catalysts stability.•C2+OH synthesis required suitable amount of surface Cu content and weak acidity.•Catalyst with Si/Al = 0.5 showed the best catalytic performance.A series of CuZnSiAl catalysts with Si/Al molar ratios from 0 to 1 were prepared by a complete liquid-phase method and tested for syngas to higher alcohols (C2+OH) in slurry bed reactor. The catalysts were characterized by XRD, H2-TPR, NH3-TPD, N2 adsorption, FT-IR and XPS techniques. Activity results showed that the mass fractions of C2+OH in the total alcohols reached approximately 40.8% over CuZnAl catalyst without promoters. With increased Si/Al ratio, the crystallite size of Cu0 first increased until Si/Al = 0.5 and then decreased, However, the total number of weak acid on catalysts surface increased continuously and the surface Cu content gradually decreased. In addition, compared with the acidic Si sol, the catalysts promoted by alkaline Si sol exhibited better performance in terms of both stability and selectivity to C2+OH. It was found that AlOOH functioned for CO dissociation and C2+OH synthesis simultaneously required relative larger Cu particles, more number of weak acid and higher Cu content on catalyst surface. The incorporation of a suitable amount of alkaline Si sol was beneficial for both the stability as well as C2+OH selectivity, and the best catalytic performance was obtained when the Si/Al atomic ratio was 0.5.Download high-res image (165KB)Download full-size image

The formation mechanism of the initial C–C chain in ethanol synthesis on γ-AlOOH(100)

Co-reporter:Lin Zhang;Bing Bai;Hui Bai;Zhi-Hua Gao;Zhi-Jun Zuo;Yong-Kang Lv

Physical Chemistry Chemical Physics 2017 vol. 19(Issue 29) pp:19300-19307

Publication Date(Web):2017/07/26

DOI:10.1039/C7CP03419A

An in-depth understanding of the reaction mechanism at the molecular level is the key to guide the synthesis of ethanol over the CuZnAl catalyst, which is one of the major challenges for ethanol application in energy. Reported herein is a density functional theory study of ethanol synthesis from mixed methanol and syngas on the γ-AlOOH(100) surface. The possible elementary reactions are unambiguously identified and for the first time we confirm the high reactivity of the γ-AlOOH(100) surface for the initial C–C chain formation via CO insertion into CH3, which has a 62.8 kJ mol−1 (0.65 eV) activation barrier that is significantly lower than the barriers previously reported. And its corresponding reaction energy is −288.2 kJ mol−1 (−2.99 eV). Bader charge analyses indicate that it is advantageous for the nucleophilic attack of CO to the neighboring CH3 on the γ-AlOOH(100) surface. Our calculations show that ethanol synthesis starts with CH3OH dissociation, goes through CH3O dissociation to yield CH3, subsequently, CO inserts into CH3 to form CH3CO, which is further hydrogenated to yield CH3CHO and eventually obtain C2H5OH. And the formation of intermediate CH3 is the rate-determining step of the overall reaction. The results not only provide new mechanistic insights into the role of γ-AlOOH but also may be useful for the rational designing and optimizing of the CuZnAl catalyst for ethanol synthesis.

B12Fn0/− (n = 1–6) series: when do boron double chain nanoribbons become global minima?

Co-reporter:Hui Bai;Bing Bai;Lin Zhang;Hua-Jin Zhai;Si-Dian Li

Physical Chemistry Chemical Physics 2017 vol. 19(Issue 47) pp:31655-31665

Publication Date(Web):2017/12/06

DOI:10.1039/C7CP05658C

We present an extensive density-functional and wave function theory study of partially fluorinated B12Fn0/− (n = 1–6) series, which show that the global minima of B12Fn0/− (n = 2–6) are characterized to encompass a central boron double chain (BDC) nanoribbon and form stable BF2 groups at the corresponding BDC corner when n ≥ 3, but the B12F0/− system maintains the structural feature of the well-known quasi-planar C3v B12. When we put the spotlight on B12F60/− species, our single-point CCSD(T) results unveil that albeit with the 3D icosahedral isomers not being their global minima, C2 B12F6 (6.1, 1A) and C1 B12F6− (12.1, 2A) as typical low-lying isomers are 0.60 and 1.95 eV more stable than their 2D planar counterparts D3h B12F6 (6.7, 1A′) and C2v B12F6− (12.7, 2A2), respectively, alike to B12H60/− species in our previous work. Detailed bonding analyses suggest that B12Fn0/− (n = 2–5) possess ribbon aromaticity with σ plus π double conjugation along the BDC nanoribbon on account of their total number of σ and π delocalized electrons conforming the common electron configuration (π2(n+1)σ2n). Furthermore, the simulated PES spectra of the global minima of B12Fn− (n = 1–6) monoanions may facilitate their experimental characterization in the foreseeable future. Our work provides new examples for ribbon aromaticity and powerful support for the F/H/Au/BO analogy.

High-Yielded Side-Chain Alkylation from Toluene and Methanol Over K3PO4/CsX

Co-reporter:Huihui Wang;Bin Wang;Yueli Wen

Catalysis Letters 2017 Volume 147( Issue 1) pp:161-166

Publication Date(Web):2017 January

DOI:10.1007/s10562-016-1911-6

Potassium phosphate supported on ion-exchanged CsX zeolite was prepared by impregnation method, and their performance was investigated for the side-chain alkylation of toluene with methanol. When K3PO4 was more than 5 wt%, the catalyst activity and selectivity of styrene and ethylbenzene were improved significantly. The conversion of methanol and selectivity of styrene and ethylbenzene reached 84.1 and 92.8% with K3PO4 loading of 7 wt%. It was concluded that moderate addition of K3PO4 decreased the amount of weak acid and increased the strength and amount of middle base sites. The base sites at 270–300 °C (CO2-TPD) were favorable for this reaction.

CO hydrogenation to higher alcohols over CuZnAl catalysts without promoters: Effect of pH value in catalyst preparation

Co-reporter:Yongjun Liu, Xuan Deng, Peide Han, Wei Huang

Fuel Processing Technology 2017 Volume 167(Volume 167) pp:

Publication Date(Web):1 December 2017

DOI:10.1016/j.fuproc.2017.08.012

•pH value had significant influence on the catalytic activity.•Catalyst prepared at pH = 8 showed the best catalytic performance.•Larger Cu0 particle size and a suitable amount of acid favored C2 + OH formation.CO hydrogenation to higher alcohols (C2 + OH) was examined in a slurry bed reactor. CuZnAl samples without promoters were prepared by a complete liquid-phase method at different pH value (pH = 7–10), with the aim of studying the influence of pH value on the catalytic performance in this catalytic reaction. The pH value had significantly influence on the Cu0 crystallite size, the amount of reducible Cu+, surface Cu/Zn atomic ratios and the acidity, which led to the diverse activities toward C2 + OH synthesis. Characterization results showed that relatively larger crystallite size of Cu0 and a suitable amount of acid sites was beneficial to the formation of C2 + OH. Activity results indicated that the sample prepared at pH = 8 exhibited the best catalytic performance compared with other samples. In addition, the catalytic performance of pH = 8 sample showed that increasing temperature favored to the formation of C2 + OH.Download high-res image (101KB)Download full-size image

Reaction mechanisms of methanol synthesis from CO/CO2 hydrogenation on Cu2O(111): Comparison with Cu(111)

Co-reporter:Yi-Ming Liu, Jiang-Tao Liu, Shi-Zhong Liu, Jing Li, Zhi-Hua Gao, Zhi-Jun Zuo, Wei Huang

Journal of CO2 Utilization 2017 Volume 20(Volume 20) pp:

Publication Date(Web):1 July 2017

DOI:10.1016/j.jcou.2017.05.005

•Methanol can be synthesized from CO/CO2 hydrogenation which is dependent on Cu valence.•CO is the main carbon source when the surface is predominantly covered by Cu+ species.•CO2 is the primary carbon source when metallic Cu covers the surface.A systematic theoretical study was performed to investigate methanol synthesis from CO/CO2 hydrogenation and the water-gas-shift (WGS) reaction on Cu(111) and Cu2O(111) surfaces using density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations. Specifically, DFT was used to investigate methanol synthesis from CO/CO2 hydrogenation on these surfaces at P = 80 atm, T = 553 K and (CO+ CO2)/H2 = 20/80. The results show that methanol can be synthesized from CO or CO2 hydrogenation and is dependent on the catalyst’s preparation as well as the active site type. Further, CO is the main carbon source when the surface is predominantly covered by Cu+ species. However, CO2 is the primary carbon source when metallic Cu covers the surface. Under the reaction conditions investigated, H2 and CO easily reduce Cu2O to metallic Cu, and the Cu+ species are stabilized by the presence of H2O, CO2, carrier (such as MgO) or alkali metals. For this reason, the scale of methanol produced from CO or CO2 hydrogenation depends on the ratio of Cu+/Cu0.Download high-res image (349KB)Download full-size image

Simulation of pyrolysis in low rank coal particle by using DAEM kinetics model: Reaction behavior and heat transfer

Co-reporter:Junli Wang, Wenhao Lian, Peng Li, Zhonglin Zhang, Jingxuan Yang, Xiaogang Hao, Wei Huang, Guoqing Guan

Fuel 2017 Volume 207(Volume 207) pp:

Publication Date(Web):1 November 2017

DOI:10.1016/j.fuel.2017.06.078

•Kinetic parameters of coal pyrolysis were obtained by DAEM via TG/DTG experiments.•E0 = 186.5 kJ/mol, k0 = 3.96 × 1010 s−1 and σ = 39.5 kJ/mol were obtained.•A coal particle pyrolysis model coupling with reaction and heat transfer was proposed.•Mass fraction and temperature profiles inside the coal particle was well predicted.•ΔT > 300 K from surface to core of a 3 mm particle was predicted at 900 °C pyrolysis.A comprehensive and systematic study on the fundamental pyrolysis behaviors of a single coal particle was performed in this study. The pyrolysis characteristics of coal was investigated by non-isothermal thermo gravimetric analysis whereas the reaction kinetic parameters were obtained by using the distribute activation energy model (DAEM). As three heating rate profiles were applied (10, 20 and 30 °C/min) in TG/DTG experiments with a final pyrolysis temperature of 900 °C, the obtained kinetic parameters, i.e., activation energy (E0), pre-exponential factor (k0) and standard deviation (σ) were 186.5 kJ/mol, 3.96 × 1010 s−1 and 39.5 kJ/mol, respectively. When these calculated kinetic parameters were used to predict devolatilization curves, the simulation results were in well agreement with the experimental data. As such, a one-dimensional, time-dependent particle pyrolysis model was proposed to characterize the detailed chemical and physical phenomena occurred within a pyrolyzing coal particle. It is found that this model successfully predicted the mass fraction residue and temperature profiles inside the coal particle. In addition, the effect of particle size on pyrolysis performance was also investigated through simulation. It is expected that such a model can be integrated with CFD simulation to provide useful insight for the design of a practical coal pyrolysis reactor.Download high-res image (299KB)Download full-size image

Experimental study on co-pyrolysis and gasification of biomass with deoiled asphalt

Co-reporter:Qian Zhang, Qingfeng Li, Linxian Zhang, Zhongliang Yu, Xuliang Jing, Zhiqing Wang, Yitian Fang, Wei Huang

Energy 2017 Volume 134(Volume 134) pp:

Publication Date(Web):1 September 2017

DOI:10.1016/j.energy.2017.05.157

•Co-pyrolysis of biomass and DOA does not show synergetic effect on the char yield.•DOA melt and stuck to biomass surface causes the char an obvious agglomeration.•Synergetic effect is observed during gasification of the co-pyrolysis chars.•Co-gasification of DOA and biomass is a good choice for disposing DOA.The behavior of co-pyrolysis and gasification of biomass and deoiled asphalt (DOA) was investigated. The co-pyrolysis of three biomasses and DOA reflected no obvious synergetic effect on the char yield, but the char's graphite degree reduced greatly. For the DOA was melted and stuck to the biomass surface during pyrolysis, the co-pyrolysis char showed an obvious agglomeration. The gasification rate of the co-pyrolysis chars was greatly increased by the addition of biomass, and the gasification curve were much similar to that of a homogenous char, indicating the blends were quite uniform and the alkali and alkaline earth metals in biomass could catalyze DOA gasification greatly. Sunflower stalk which has the highest potassium content and mineral content promoted the gasification rate best. Kinetic analysis showed that the average E values of the co-pyrolysis chars increased compared with the pure biomass char. The co-gasification of DOA and biomass is a good choice for disposing DOA.

Higher alcohols synthesis via CO hydrogenation on Cu/Zn/Al/Zr catalysts without alkalis and F–T elements

Co-reporter:Yong-Jun Liu, Zhi-Jun Zuo, Chao-Bo Liu, Chao Li, Xuan Deng, Wei Huang

Fuel Processing Technology 2016 Volume 144() pp:186-190

Publication Date(Web):April 2016

DOI:10.1016/j.fuproc.2016.01.005

•The higher alcohols selectivity reached 58.8% over Cu/Zn/Al catalyst.•Al favored the formation of higher alcohols.•Zr was beneficial to improve the stability of catalyst.•The amount of weak acidic sites played a key role in the higher alcohols synthesis.A series of Cu/Zn/Al/Zr catalysts without alkalis and F–T elements, were prepared with various atomic ratios of Al/Zr by complete liquid-phase technology and tested for higher alcohols synthesis from CO hydrogenation. The results showed that the Cu/Zn/Al catalyst exhibited excellent higher alcohols selectivity, reaching approximately 58.8%. With the increase of Zr/Al atomic ratio, the catalytic activity and stability increased, but methanol became the dominant product in the liquid products over Cu/Zn/Zr catalyst. It was concluded that Al favored the formation of higher alcohols and Zr was beneficial to improve the stability of catalysts. Characterization results showed that the addition of Zr improved the dispersion of Cu and made the catalyst easier to be reduced. It also favored the stability of pore structure and decreased the amount of weak acidic sites. It was also found that the amount of the weak acidic sites played a key role in the higher alcohols formation and the amount of weak acidic sites decrease might lead to the deactivation of catalysts.

Theoretical Study on Catalytic Pyrolysis of Benzoic Acid as a Coal-Based Model Compound

Co-reporter:Ming-Fei Wang, Zhi-Jun Zuo, Rui-Peng Ren, Zhi-Hua Gao, and Wei Huang

Energy & Fuels 2016 Volume 30(Issue 4) pp:2833-2840

Publication Date(Web):March 17, 2016

DOI:10.1021/acs.energyfuels.6b00132

Benzoic acid (C6H5COOH) is selected as a coal-based model compound, and its catalytic pyrolysis mechanisms on ZnO, γ-Al2O3, CaO, and MgO catalysts are studied using density functional theory (DFT) compared to the non-catalytic pyrolysis mechanism. DFT calculation shows that the pyrolysis process of C6H5COOH in the gas phase occurs via the direct decarboxylation pathway (C6H5COOH → C6H6 + CO2) or the stepwise decarboxylation pathway (C6H5COOH → C6H6COO → C6H6 + CO2). For C6H5COOH catalytic pyrolysis on the ZnO (101̅0) surface, the preferred reaction pathway is C6H5COOH → C6H5COO + H → C6H6 + CO2, whereas the preferred reaction pathway on γ-Al2O3 (110), CaO (100), and MgO (100) surfaces is C6H5COOH → C6H5COO + H → C6H5 + CO2 + H → C6H6 + CO2, indicating that the presence of catalysts changed the pyrolysis mechanism of C6H5COOH. In addition, dissociative adsorption of C6H5COOH is observed on these surfaces. It is found that ZnO (101̅0), MgO (100), and CaO (100) are beneficial to C6H5COOH decomposition, but γ-Al2O3 (110) is disadvantageous to the C6H5COOH decomposition. At the same reaction temperature, the rate constants show the order: k(ZnO) > k(MgO) > k(CaO) > k(no catalyst) > k(γ-Al2O3).

Initial stages of oxidation for Cu-based catalysts using density functional theory

Co-reporter:Zhi-Jun Zuo, Na Li, Shi-Zhong Liu, Pei-De Han, Wei Huang

Applied Surface Science 2016 Volume 366() pp:85-94

Publication Date(Web):15 March 2016

DOI:10.1016/j.apsusc.2016.01.067

Highlights

•: The dissociation energies of O₂ molecules increase with the coverage increasing.
•: The binding strengths of O₂ molecules decrease with the coverage increasing.
•: The saturated coverage of O atoms on Cu(111), Cu(110) and Cu(100) surfaces are 0.25, 0.75 and 0.375 ML, respectively.
•: O and O₂ co-adsorb on Cu surface at room temperature.

Kinetics Modeling of Low-Rank Coal Pyrolysis Based on a Three-Gaussian Distributed Activation Energy Model (DAEM) Reaction Model

Co-reporter:Junli Wang, Peng Li, Litong Liang, Jingxuan Yang, Xiaogang Hao, Guoqing Guan, and Wei Huang

Energy & Fuels 2016 Volume 30(Issue 11) pp:9693

Publication Date(Web):October 3, 2016

DOI:10.1021/acs.energyfuels.6b01599

A three-Gaussian distributed activation energy model (DAEM) reaction model (3-DAEM) was successfully applied for the kinetics study on the thermal pyrolysis of four types of low-rank coals, based on their nonisothermal thermogravimetric data. It is found that 3-DAEM was feasible for the analysis of coal pyrolysis process, which can be divided into three stages, using the second derivative method for thermogravimetry (TG) curves and the Peakfit software for differential thermogravimetry (DTG) curves. Calculated kinetic parameters, including three mean activation energies (E0), three standard deviations (σE), and two weights (w), were used to predict the pyrolysis process, and the results agreed well with the experimental data. Furthermore, the kinetics parameters were found to have a strong relationship with the DTG curve shape and especially with the coal property. These results indicated that 3-DAEM provided a good way to process thermogravimetric analysis (TGA) data and understand the pyrolysis mechanism for low-rank coals.

Insight into the influence of liquid paraffin for methanol synthesis on Cu(110) surface using continuum and atomistic models

Co-reporter:Wei-Hong Jiao, Shi-Zhong Liu, Zhi-Jun Zuo, Rui-Peng Ren, Zhi-Hua Gao, Wei Huang

Applied Surface Science 2016 Volume 387() pp:58-65

Publication Date(Web):30 November 2016

DOI:10.1016/j.apsusc.2016.06.074

Highlights

•: The influence of liquid paraffin is studied using continuum and atomistic models.
•: Liquid paraffin does not alter the reaction pathways of CO hydrogenation and WGS.
•: Liquid paraffin alters the reaction pathways of CO₂ hydrogenation.

Density Functional Theory (DFT) and Kinetic Monte Carlo (KMC) Study of the Reaction Mechanism of Hydrogen Production from Methanol on ZnCu(111)

Co-reporter:Zhi-Jun Zuo, Xiao-Yu Gao, Pei-De Han, Shi-Zhong Liu, and Wei Huang

The Journal of Physical Chemistry C 2016 Volume 120(Issue 48) pp:27500-27508

Publication Date(Web):November 15, 2016

DOI:10.1021/acs.jpcc.6b10261

Cu/ZnO-based catalysts have been widely used for methanol decomposition (MD), partial oxidation of methanol (POM), steam reforming of methanol (SRM), and oxidative steam reforming of methanol (OSRM). In this work, we systematically studied all possible reaction paths involved in MD, POM, SRM, and OSRM on ZnCu alloys (111) using density functional theory (DFT). On the basis of these results, Kinetic Monte Carlo (KMC) simulations show that the rate-limiting step of the four reactions is CH2O formation from CH3O dehydrogenation. The reaction pathway of MD occurs via the direct decomposition of CH3OH, and the main reaction pathways of POM and SRM occur via CH2OO and CH2OOH, respectively. There are two main reaction pathways of OSRM as follows: one occurs via CH2OO, whereas the other occurs via CH2OOH. Finally, according to the results of sensitivity analysis, some possible modifications to improve the CO2 selectivity and turnover frequency (TOF) of H2 for OSRM on Cu/ZnO-based catalysts are also presented. The results may be useful for designing and optimizing Cu-based catalysts for MD, POM, SRM, and OSRM.

A study on deactivation of Cu–Zn–Al catalyst for higher alcohols synthesis

Co-reporter:Yongjun Liu, Chaobo Liu, Xuan Deng and Wei Huang

RSC Advances 2015 vol. 5(Issue 120) pp:99023-99027

Publication Date(Web):04 Nov 2015

DOI:10.1039/C5RA18731A

A Cu–Zn–Al catalyst without promoters was prepared using a complete liquid-phase method and tested for a deactivation study in higher alcohols synthesis from syngas. Results showed that the selectivity of higher alcohols first increased from 36.0% to 68.6% then gradually decreased to 14.1% with time on stream. Characterization results showed that Cu species and Zn species had little changes whereas the phase of Al species changed after reaction. It was found that the Al species of the Cu–Zn–Al catalyst changed from AlOOH to Al2O3. The phase change weakened CO dissociation and chain growth which led to the decrease of higher alcohols selectivity with time on stream. It was suggested that AlOOH had a function of CO dissociation and chain growth, which favored the formation of higher alcohols, whereas Al2O3 had no function of CO dissociation, which caused the formation of methanol.

Mild catalytic depolymerization of low rank coals: a novel way to increase tar yield

Co-reporter:Litong Liang, Wei Huang, Fuxing Gao, Xiaogang Hao, Zhonglin Zhang, Qian Zhang and Guoqing Guan

RSC Advances 2015 vol. 5(Issue 4) pp:2493-2503

Publication Date(Web):02 Dec 2014

DOI:10.1039/C4RA13029D

Mild catalytic depolymerization of two kinds of low-rank coals named as Neimeng and Xinjiang coals sprayed with Mo- and Fe-based catalysts were performed in a batch reactor. The obtained tar was analyzed by gas chromatography/mass spectrometry (GC/MS), and the coal and char were characterized by Raman and Fourier transform infrared spectroscopy (FTIR). The results indicated that the tar yields for Neimeng coal were increased from 3.6% to 5.0% and 7.8% while those for Xinjiang coal were increased from 8.1% to 11.4% and 10.9% after the addition of Mo- and Fe-based catalysts, respectively. Based on the GC/MS analysis, it is found that the hydroxybenzene content was significantly decreased while naphthalene content was increased in the tar derived from Neimeng coal when the Mo-based catalyst was used. In contrast, the production of light aromatics was enhanced by the addition of Fe-based catalyst. For comparison, the production of aromatics from Xinjiang coal was remarkably inhibited but the content of aliphatic hydrocarbon was significantly increased after the addition of the catalyst. The Raman and FTIR analyses results indicated that the catalyst could improve the reaction of hydrogen free radicals with char, which was beneficial to the depolymerization of coal.

Effect of preparation method on CuZnAl catalysts for ethanol synthesis from syngas

Co-reporter:Yong-Jun Liu, Zhi-Jun Zuo, Chao Li, Xuan Deng, Wei Huang

Applied Surface Science 2015 Volume 356() pp:124-127

Publication Date(Web):30 November 2015

DOI:10.1016/j.apsusc.2015.08.039

Highlights

•: Preparation methods had significant difference towards ethanol formation.
•: The CuZnAl catalysts could directly catalyze syngas to ethanol.
•: The selectivity of ethanol, reaching approximately 30%.
•: Ethanol synthesis requires Cu⁺ as well as the strong weak acid.

Insights into the reaction mechanisms of methanol decomposition, methanol oxidation and steam reforming of methanol on Cu(111): A density functional theory study

Co-reporter:Zhi-Jun Zuo, Le Wang, Pei-De Han, Wei Huang

International Journal of Hydrogen Energy 2014 Volume 39(Issue 4) pp:1664-1679

Publication Date(Web):22 January 2014

DOI:10.1016/j.ijhydene.2013.11.048

•Methanol decomposition, methanol oxidation and MSR are studied using DFT.•CH2O formation is the rate-limiting step for the three reactions.•Methanol oxidation and MSR are faster than that of methanol decomposition.•Preadsorbed O and OH alter the reaction pathway and activation energy.Cu-based catalysts have been widely used for hydrogen production from methanol decomposition, methanol oxidation and steam reforming of methanol (MSR). In this study, we have systematically identified possible reaction paths for the thermodynamics and dynamics involved in the three reactions on a Cu(111) surface at the molecular level. We find that the reaction paths of the three reactions are the same at the beginning, where methanol scission is favourable involving O–H bond scission followed by sequential dehydrogenation to formaldehyde. Formaldehyde is an important intermediate in the three reactions, where direct dehydrogenation of formaldehyde to CO is favourable for methanol decomposition; for methanol oxidation, formaldehyde tends to react with oxygen to form dioxymethylene through C–H bond breaking and finally the end products are mainly CO2 and hydrogen; for MSR, formaldehyde tends to react with hydroxyl to form hydroxymethoxy through formic acid and formate formation, followed by dissociation to CO2. CH2O formation from methoxy dehydrogenation is considered to be the rate-limiting step for the three reactions. In general, the thermodynamic and kinetic preference of the three reactions shows the order methanol oxidation > MSR > methanol decomposition. Methanol oxidation and MSR are faster than methanol decomposition by about 500 and 85 times at typical catalytic conditions (e.g., 523 K), respectively. The result may be useful for computational design and optimization of Cu-based catalysts.

Insight into the size effect on methanol decomposition over Cu-based catalysts based on density functional theory

Co-reporter:Zhi-Jun Zuo, Le Wang, Pei-De Han, Wei Huang

Computational and Theoretical Chemistry 2014 Volume 1033() pp:14-22

Publication Date(Web):1 April 2014

DOI:10.1016/j.comptc.2014.01.029

•Size effect on methanol decomposition over Cu is studied based on DFT.•Methanol is decomposed over Cu through CH3O, CH2O, CHO and CO.•The highest activation energy is the CH2O formation from methoxy dehydrogenation.•Size effect can improve the reaction rate.A study on the size effect on methanol decomposition over metal Cu is investigated based on density functional theory. It is found that the size effect cannot alter the reaction pathway and product of methanol decomposition, such effect can improve the reaction rate as well as inhibit the main by-product of CH2O desorption to a certain extent. The most favorable route for methanol decomposition is described as follows: CH3OH → CH3O → CH2O → CHO → CO. CO desorbs rather than decomposes. The highest activation energy of methanol decomposition is CH2O formation from methoxy dehydrogenation.Graphical abstract

Experimental and Theoretical Studies of Ethanol Synthesis from Syngas over CuZnAl Catalysts without Other Promoters

Co-reporter:Zhi-Jun Zuo ; Le Wang ; Lin-Mei Yu ; Pei-De Han

The Journal of Physical Chemistry C 2014 Volume 118(Issue 24) pp:12890-12898

Publication Date(Web):May 30, 2014

DOI:10.1021/jp502828c

Ethanol synthesis from syngas over CuZnAl catalyst without other promoters is studied using theoretical and experimental methods. The possible reaction paths of the ethanol synthesis in thermodynamic and dynamic over Cu cluster and Cu–O species adsorbed on ZnO surface are systematically identified at the molecular level. Three possible paths involving the formation of CH3 as the key intermediate are proposed, which are COH, CHOH, CH2OH, and CH3; CHO, CH, CH2, and CH3; and CH3OH and CH3. CO insertion into the CH3 intermediate produces CH3CO, which is further hydrogenated to yield CH3CHO and CH3CHOH and finally obtain ethanol. The CuZnAl catalyst, which is prepared by complete liquid-phase technology, has high ethanol selectivity and stability because of the strong interaction between Cu species and ZnO. In summary, the coexistence of both Cu0 and Cu+ is necessary for ethanol synthesis from syngas over CuZnAl catalyst without other promoters.

XPS and DFT Studies on the Autoxidation Process of Cu Sheet at Room Temperature

Co-reporter:Zhi-Jun Zuo ; Jing Li ; Pei-De Han

The Journal of Physical Chemistry C 2014 Volume 118(Issue 35) pp:20332-20345

Publication Date(Web):August 11, 2014

DOI:10.1021/jp504977p

To better understand the autoxidation mechanism of Cu-based catalysts, we studied the oxidation of Cu sheet exposed to ultrahigh vacuum and air at ambient temperature using X-ray photoelectron spectroscopy (XPS) and density functional theory. Six main stages of Cu autoxidation are revealed: (1) dissociative adsorption of O2, (2) coexistence of nondissociative and dissociative H2O adsorption, (3) diffusion of O and OH into Cu bulk, (4) formation of metastable Cu2O layer, (5) further oxidation and formation of metastable Cu(OH)2 and CuO layer, and (6) transformation phase of the metastable Cu(OH)2 to CuO. The formation of Cu(OH)2 depends on the relative humidity of air and the concentration of adsorbed OH of the Cu sheet. On the basis of these results, we propose that the preservation time of the Cu-based catalysts should be decreased or the catalysts should be preserved in a high vacuum and at low relative humidity. Considering the time of the sample preparation before ex situ XPS analysis and other surface characterizations, the Cu-based catalysts need to be etched by ∼10 s using an Ar ion gun. These findings serve as a guide for the preservation and preparation of Cu-based catalysts before actual measurement.

The synthesis of super-hydrophilic and acid-proof Ge–ZSM-5 membranes by simultaneous incorporation of Ge and Al into a Silicalite-1 framework

Co-reporter:Xiaodong Wang, Xuan Deng, Zhongxiang Bai, Xiaoxiao Zhang, Xianshe Feng, Wei Huang

Journal of Membrane Science 2014 468() pp: 202-208

Publication Date(Web):

DOI:10.1016/j.memsci.2014.06.007

A sol–gel dip/spin coating method to prepare titanium oxide films

Co-reporter:Xiaodong Wang, Fang Shi, Xiaoxia Gao, Caimei Fan, Wei Huang, Xianshe Feng

Thin Solid Films 2013 Volume 548() pp:34-39

Publication Date(Web):2 December 2013

DOI:10.1016/j.tsf.2013.08.056

•A dip/spin coating method to prepare titanium oxide films was proposed.•The films were prepared by the lower side of the support contacting the sol.•The crystal grains in the films were tiny and uniform with a unique structure.•The films demonstrated excellent photocatalytic activity.A dip/spin coating method for the preparation of titanium oxide films was proposed. Instead of placing an oxide sol on top of a substrate surface, the dip/spin coating was accomplished on the lower surface of the substrate where gravitational force exerted on the colloidal particles during spreading under a centrifugal force. The resulting TiO2 films were compared to those prepared using the conventional spin-coating and dip-coating methods. All the films were found to be composed primarily of anatase with a small amount of brookite. Compared to the films prepared using the conventional spin-coating and dip-coating methods, the TiO2 films fabricated using the dip/spin method had small and uniform grains with a unique structure, resulting in an increased photocatalytic activity when tested for degradation of methyl orange under UV irradiation.

Synthesis of b-oriented TS-1 zeolite membranes with high performance in the oxyfunctionalization of n-hexane

Co-reporter:Xiaodong Wang, Jing Yan, Wei Huang

Thin Solid Films 2013 Volume 534() pp:40-44

Publication Date(Web):1 May 2013

DOI:10.1016/j.tsf.2013.01.075

The b-oriented TS-1 zeolite membranes were synthesized with higher reproducibility by a simple secondary growth method, in which the membranes grew from b-oriented seed layers obtained by ultrasonication–electrostatic adsorption. The membranes demonstrated excellent catalytic performance in the oxyfunctionalization of n-hexane with a high average reaction rate of 1423 mol m− 3 h− 1.Highlights► b-Oriented TS-1 zeolite membranes were prepared on α-Al2O3 substrate. ► The membranes were prepared by a simple secondary growth method. ► b-Oriented seed layers were obtained by ultrasonication–electrostatic adsorption. ► The membranes demonstrated excellent catalytic performance.

Can methanol be synthesized from CO by direct hydrogenation over Cu/ZnO catalysts?

Co-reporter:Zhi-Jun Zuo, Pei-De Han, Zhe Li, Jian-Shui Hu, Wei Huang

Applied Surface Science 2012 Volume 261() pp:640-646

Publication Date(Web):15 November 2012

DOI:10.1016/j.apsusc.2012.08.074

Abstract

Methanol synthesis from CO by direct hydrogenation has been studied using the density-functional theory (DFT). The charge of Cu has been found to be transferred to the ZnO carrier having low Cu cover. Due to the electron-charge transfer between the metallic Cu and the ZnO carrier, the Cu valency is greater than zero and less than one. Consideration of the water-gas-shift reaction and hydrogenation of CO₂ to CHOO and COOH, the result shows that the active sites for the synthesis of methanol from CO₂ and CO are different. Methanol is synthesized from CO by direct hydrogenation over Cu^δ+ (0 < δ < 1) species through the intermediates CHO, CH₂O, and CH₃O, and the rate-limiting step is the hydrogenation of CHO, indicating that the Cu^δ+ (0 < δ < 1) species comprise the active sites for the synthesis of methanol from CO by direct hydrogenation.

A DFT study the solvent effects of H2 adsorption on Cu(h k l) surface

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han

Applied Surface Science 2012 Volume 258(Issue 8) pp:3364-3367

Publication Date(Web):1 February 2012

DOI:10.1016/j.apsusc.2011.09.024

Abstract

Density functional theory (DFT) combined with conductor-like solvent model (COSMO) have been performed to study the solvent effects of H₂ adsorption on Cu(h k l) surface. The result shows H₂ can not be parallel adsorbed on Cu(h k l) surface in gas phase and only vertical adsorbed. At this moment, the binding energies are small and H₂ orientation with respect to Cu(h k l) surfaces is not a determining parameter. In liquid paraffin, when H₂ adsorbs vertically on Cu(h k l) surface, solvent effects not only influences the adsorptive stability, but also improves the ability of H₂ activation; When H₂ vertical adsorption on Cu(h k l) surface at 1/4 and 1/2 coverage, H–H bond is broken by solvent effects. However, no stable structures at 3/4 and 1 ML coverage are found, indicating that it is impossible to get H₂ parallel adsorption on Cu(h k l) surfaces at 3/4 and 1 ML coverages due to the repulsion between adsorbed H₂ molecules.

Synthesis of high quality TiO2 membranes on alumina supports and their photocatalytic activity

Co-reporter:Xiaodong Wang, Fang Shi, Wei Huang, Caimei Fan

Thin Solid Films 2012 Volume 520(Issue 7) pp:2488-2492

Publication Date(Web):31 January 2012

DOI:10.1016/j.tsf.2011.10.023

This study describes the synthesis of TiO2 membranes on alumina supports by the spin-coating technique using the sol–gel method with water-soluble chitosan (WSC) as an additive. After calcining the sample at 500 °C, the WSC was completely decomposed, and the remaining membrane consisted mainly of anatase. Controlling the amount of WSC in the TiO2 sol to within a range of 0.1 wt.%–0.3 wt.% resulted in TiO2 membranes on alumina supports with enhanced structural and catalytic properties. These properties included a high surface area (164 m2/g–116 m2/g) and porosity (47.3%–52.2%), homogeneity without cracks and pinholes, thinness (0.8 μm), as well as high degradation of methyl orange (61.2%–49.2%).

Synthesis of Cu nanoparticles for large-scale preparation

Co-reporter:Yueli Wen, Wei Huang, Bin Wang, Jinchuan Fan, Zhihua Gao, Lihua Yin

Materials Science and Engineering: B 2012 Volume 177(Issue 8) pp:619-624

Publication Date(Web):15 May 2012

DOI:10.1016/j.mseb.2012.02.026

Cu nanoparticles have been synthesized by a novel method, where diethanolamine (DEA) is used as reductant, solvent, surface modifier and shape controller. As-obtained nano-copper has been characterized by XRD, SEM, TEM, XPS and FT-IR. The results show that the nano-copper particles are cubic. The well-dispersed copper nanocubes are single crystals and antioxidized. Nanocube is not oxidized when exposed to air at room temperature for a year. The precursor concentration has little effect on the size and morphology of the product. In addition, this method is simple; raw materials are cheap that makes it applicable for large-scale preparation of copper nanocubes.Highlights► A novel and simple method for large-scale preparation of nano-copper is proposed. ► As prepared Cu nanoparticles are anti-oxidized even exposed to air for one year. ► Precursor concentration has little effect on the size and morphology of the product.

Effect of surface hydroxyls on DME and methanol adsorption over γ-Al2O3 (hkl) surfaces and solvent effects: a density functional theory study

Co-reporter:Zhi-Jun Zuo;Pei-De Han;Jian-Shui Hu

Journal of Molecular Modeling 2012 Volume 18( Issue 12) pp:5107-5111

Publication Date(Web):2012 December

DOI:10.1007/s00894-012-1495-z

Methanol and dimethyl ether (DME) adsorption over clean and hydrated γ-Al2O3(100) and (110) surfaces was studied by using density functional theory (DFT) combined with conductor-like solvent model (COSMO) in gas phase and liquid paraffin. On clean γ-Al2O3 (100) and (110) surfaces, DME and methanol preferentially interact with Al3 and Al1 of the γ-Al2O3(110) and (100) surfaces, respectively. On hydrated γ-Al2O3(100) and (110) surfaces, the OH group can influence the adsorptive behavior of DME and methanol. The Al3 and Al1 active sites of the hydrated (110) and (100) surfaces are inactivated due to hydroxyl influence, respectively. Compared to the adsorption energies of DME and methanol adsorption over the clean and hydrated (110) and (100) surfaces in gas phase and liquid paraffin, it is found that the solvent effects can slightly reduce adsorptive ability.

Methane reforming reaction with carbon dioxide over SBA-15 supported Ni–Mo bimetallic catalysts

Co-reporter:Tao Huang, Wei Huang, Jian Huang, Peng Ji

Fuel Processing Technology 2011 Volume 92(Issue 10) pp:1868-1875

Publication Date(Web):October 2011

DOI:10.1016/j.fuproc.2011.05.002

A series of mesoporous molecular sieves SBA-15 supported Ni–Mo bimetallic catalysts (xMo1Ni, Ni = 12 wt.%, Mo/Ni atomic ratio = x, x = 0, 0.3, 0.5, 0.7) were prepared using co-impregnation method for carbon dioxide reforming of methane. The catalytic performance of these catalysts was investigated at 800 °C, atmospheric pressure, GHSV of 4000 ml·gcat− 1·h− 1 and a V(CH4)/(CO2) ratio of 1 without dilute gas. The result indicated that the Ni–Mo bimetallic catalysts had a little lower initial activity compared with Ni monometallic catalyst, but it kept very stable performance under the reaction conditions. In addition, the Ni–Mo bimetallic catalyst with Mo/Ni atomic ratio of 0.5 showed high activity, superior stability and the lowest carbon deposition rate (0.00073gc·gcat− 1·h− 1) in 600-h time on stream. The catalysts were characterized by power X-ray diffraction, N2-physisorption, H2-TPR, CO2-TPD, TG and TEM. The results indicate that the Ni–Mo bimetallic catalysts have smaller metal particle, higher metal dispersion, stronger basicity, metal–support interaction and Mo2C species. It is concluded that Mo species in the Ni–Mo bimetallic catalysts play important roles in reducing effectively the amount of carbon deposition, especially the amount of shell-like carbon deposition.► The catalysts prepared using co-impregnation method. ► The Ni–Mo bimetallic catalysts show excellent stability and high activity. ► The metal–support interaction (MSI) changes morphology of carbon deposition. ► The catalytic performances correlate with MSI, basicity, particle size and Mo2C. ► Mo species play important roles in outstanding catalytic performances.

Synthesis of salicylaldehyde Schiff base modified Cu nanocrystals by thermal treatment in liquid paraffin

Co-reporter:Yueli Wen, Wei Huang, Bin Wang, Jinchuan Fan, Zhihua Gao, Lihua Yin

Applied Surface Science 2011 Volume 258(Issue 2) pp:946-949

Publication Date(Web):1 November 2011

DOI:10.1016/j.apsusc.2011.09.033

Abstract

Cuboid copper nanocrystals were synthesized by thermal treatment in liquid paraffin without any inert gas protection with salicylaldehyde Schiff base copper (II) (Cu (II)–Salen) complex as precursor. Liquid paraffin was used as solvent and reductant. The obtained copper nanocrystals are morphology-controlled and stable when exposed to air for one year. The nanocrystals were characterized by X-ray diffraction measurements (XRD), UV–visible spectroscopy (UV–vis), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the stable cuboid copper nanocrystals are synthesized by using Salen as capping agents.

Research on Si–Al based catalysts prepared by complete liquid-phase method for DME synthesis in a slurry reactor

Co-reporter:Zhihong Li, Zhijun Zuo, Wei Huang, Kechang Xie

Applied Surface Science 2011 Volume 257(Issue 6) pp:2180-2183

Publication Date(Web):1 January 2011

DOI:10.1016/j.apsusc.2010.09.069

Abstract

A series of Si–Al based DME synthesis catalysts were prepared by complete liquid-phase method and characterized by in situ XPS, XRD, N₂ adsorption and NH₃-TPD analyses. Based on the results, the addition of Si could adjust the pore structure and surface acidity of catalyst, exhibiting a strong promoting effect on the CO conversion and DME selectivity. However, when Si/Al ratio is higher, Si would cover active sites and increase the amount of strong acidity sites, causing the reduction in catalytic activity. It was found from in situ XPS characterization that Cu⁰ is the active center of methanol synthesis in DME production, and the addition of Si changes the chemical surroundings of active components and weaken the interaction between Cu, Zn and Al, which maybe give rise to the decrease in catalyst stability.

Effect of surfactant on structure and performance of catalysts for DME synthesis in slurry bed

Co-reporter:Jinchuan Fan, Chaoqiu Chen, Jie Zhao, Wei Huang, Kechang Xie

Fuel Processing Technology 2010 Volume 91(Issue 4) pp:414-418

Publication Date(Web):April 2010

DOI:10.1016/j.fuproc.2009.05.005

The Cu–Zn–Al slurry catalysts prepared via modified sol–emulsion–gel method by adding different water-soluble surfactants were studied for CO hydrogenation to produce dimethyl ether (DME) in slurry bed reactor. The results indicated that the catalyst adding Tween80 or PEG600 had higher activity than the catalyst with the PVP additive. All the catalysts had good stability. X-ray diffraction (XRD) results showed that Cu and Cu2O existed in the pre-reduced Cu–Zn–Al catalysts, while ZnO did not appear. Nitrogen adsorption studies showed that the catalyst prepared with the additives of PEG600 or Tween80 was mesoporous structure with higher specific surface area compared with the one prepared with the additive of PVP. X-ray photoelectron spectroscopy (XPS) results indicated that the Cu/Zn ratio on the surface of all catalysts increased after subject to reduction and reaction. The morphology and size of the catalyst particles could be adjusted by adding water-soluble surfactants.

Solvent effects for CO and H2 adsorption on Cu2O (1 1 1) surface: A density functional theory study

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han, Zhihong Li

Applied Surface Science 2010 Volume 256(Issue 8) pp:2357-2362

Publication Date(Web):1 February 2010

DOI:10.1016/j.apsusc.2009.10.067

Abstract

To investigate solvent effects, CO and H₂ adsorption on Cu₂O (1 1 1) surface in vacuum, liquid paraffin, methanol and water are studied by using density functional theory (DFT) combined with the conductor-like solvent model (COSMO). When H₂ and CO adsorb on Cu_cus of Cu₂O (1 1 1) surface, solvent effects can improve CO and H₂ activation. The H–H bond increases with dielectric constant increasing as H₂ adsorption on O_suf of Cu₂O (1 1 1) surface, and the H–H bond breaks in methanol and water. It is also found that both the structural parameters and Mulliken charges are very sensitive to the COSMO solvent model. In summary, the solvent effects have obvious influence on the clean surface of Cu₂O (1 1 1) and the adsorptive behavior.

A density functional theory study of CH4 dehydrogenation on Co(1 1 1)

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han, Zhihong Li

Applied Surface Science 2010 Volume 256(Issue 20) pp:5929-5934

Publication Date(Web):1 August 2010

DOI:10.1016/j.apsusc.2010.03.078

Abstract

The dehydrogenation of CH₄ on the Co(1 1 1) surface is studied using density functional theory calculation (DFT). It is found that CH₄ is favored to dissociate to CH₃ and then transforms to CH₂ and CH by sequential dehydrogenation, and CH₄ activation into CH₃ and H is the rate-determining step on the Co(1 1 1) surface. CH₂ is quite unstable on Co(1 1 1) surface. CH dehydrogenation into C and H is difficult. CH₃ and H prefer to adsorb on 3-fold hollow hcp and fcc sites, and CH₂, CH and C prefer to adsorb on hcp sites.

Synthesis of methanol and ethanol over CuZnAl slurry catalyst prepared by complete liquid-phase technology

Co-reporter:Wei Huang;Linmei Yu;Wenhui Li;Zhili Ma

Frontiers of Chemical Science and Engineering 2010 Volume 4( Issue 4) pp:472-475

Publication Date(Web):2010 December

DOI:10.1007/s11705-010-0525-6

A new method, named the complete liquid-phase technology, has been applied to prepare catalysts for methanol synthesis. Its main innovative thought lies in preparing slurry catalysts directly from raw solution. Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor, while CO conversion reaches 35.9% and ethanol selectivity is more than 20%, with a total alcohol selectivity of more than 87%. No deactivation was found during the 192 h reaction.

Theoretical and experimental investigation of the influence of Co and Pd on the titanium dioxide phase transition by different calcined temperature

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han, Zhihong Li

Journal of Molecular Structure 2009 Volume 936(1–3) pp:118-124

Publication Date(Web):12 November 2009

DOI:10.1016/j.molstruc.2009.07.025

In the paper, we have systematically studied compounds of Co/TiO2 and Co/Pd/TiO2 by sol–gel method. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicate that Co promotes the anatase to rutile phase transition, on the contrary, Pd inhibits the phase transition. In order to study the reason that Co/TiO2 and Co/Pd/TiO2 have the different phase transition temperature, ab initio calculations are used for the study of the Co/TiO2 and Co/Pd/TiO2 system. The calculation results show good agreement with the experiments.

XPS and XRD investigation of Co/Pd/TiO2 catalysts by different preparation methods

Co-reporter:Wei Huang, Zhijun Zuo, Peide Han, Zhihong Li, Tingdong Zhao

Journal of Electron Spectroscopy and Related Phenomena 2009 Volume 173(2–3) pp:88-95

Publication Date(Web):July 2009

DOI:10.1016/j.elspec.2009.05.012

In the article, the Co/Pd/TiO2, Co/TiO2 and Pd/TiO2 catalysts prepared by the impregnation and sol–gel method are studied by using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The result shows that Co2+ and metal Pd may act as the active center for the direct synthesis of acetic acid from CH4 and CO2 by a two-step reaction sequence. When the catalysts are prepared by the sol–gel, Co2+ can enter the crystal lattice of the TiO2, causing the phase transition from anatase to rutile at lower temperature, but existence of Pd2+ can prevent from the phase transition. When the catalysts are prepared by the impregnation, the phase transition is inhibited not only Co2+ but also Pd2+.

Theoretical and experimental investigation of the influence of Co content on the titanium dioxide phase transition

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han, Zhihong Li

Solid State Communications 2009 Volume 149(47–48) pp:2139-2142

Publication Date(Web):December 2009

DOI:10.1016/j.ssc.2009.09.027

We have systematically studied compounds of Co/ TiO2 by the sol–gel method. X-ray diffraction result indicates that Co influences the anatase to rutile phase transition. In addition, the higher the content of Co, the higher the intensity of rutile peaks. In order to study the reason Co promotes phase transition from metastable anatase to rutile, first-principles methods are used to study the Co/ TiO2 system. The calculation results showed good agreement with the experiments.

Adsorption of CO on Cu (110) and (100) surfaces using COSMO-based DFT

Co-reporter:Zhijun Zuo;Peide Han;Zhihong Li

Journal of Molecular Modeling 2009 Volume 15( Issue 9) pp:1079-1083

Publication Date(Web):2009 September

DOI:10.1007/s00894-009-0471-8

Density functional theory (DFT) combined with the conductor-like solvent model (COSMO) can provide valuable atomistic level insights into CO adsorption on Cu surface interactions in liquid paraffin. The objective of this research was to investigate the solvent effect of liquid paraffin. It was found that both structural parameters and relative energies are very sensitive to the COSMO solvent model. Solvent effects can improve the stability of CO adsorption on Cu (110) and (100) surfaces and the extent of CO activation.

The Structure Properties of CuZnAl Slurry Catalysts Prepared by a Complete Liquid-Phase Method and its Catalytic Performance for DME Synthesis from Syngas

Co-reporter:Zhihua Gao;Lihua Yin;Lifeng Hao;Kechang Xie

Catalysis Letters 2009 Volume 127( Issue 3-4) pp:354-359

Publication Date(Web):2009 February

DOI:10.1007/s10562-008-9689-9

Four CuZnAl slurry catalysts with different contents of Al were directly prepared from the solution of these metal salts to catalyst slurry by a complete liquid-phase method. The structure properties of the catalysts were characterized by XRD, BET, XPS, FTIR, and their catalytic performances for the single-step synthesis of Dimethyl ether (DME) from syngas were evaluated in a slurry reactor of 250 mL with a mechanical magnetic agitator. The results indicate the main phase existed in the catalysts are Cu, Cu2O, ZnO and boehmite (AlOOH) and the structures of pore and surface are comparable with those of the commercial methanol synthesis catalysts. Activity tests show that the slurry catalysts are quite effective for the single-step synthesis of DME from syngas. Among them, the catalyst with 2.09 mol% Al is best, whose DME selectivity reaches 93.08%. All of the catalysts prepared by the novel method exhibit good stability during the reaction time investigated for 18 days.

Carbon dioxide reforming of methane over Ni/Mo/SBA-15-La2O3 catalyst: Its characterization and catalytic performance

Co-reporter:Jian Huang, Renxiong Ma, Tao Huang, Anrong Zhang, Wei Huang

Journal of Natural Gas Chemistry (September 2011) Volume 20(Issue 5) pp:465-470

Publication Date(Web):1 September 2011

DOI:10.1016/S1003-9953(10)60226-5

The Ni/Mo/SBA-15 catalyst was modified by La2O3 in order to improve its thermal stability and carbon deposition resistance during the CO2 reforming of methane to syngas. The catalytic performance, thermal stability, structure, dispersion of nickel and carbon deposition of the modified and unmodified catalysts were comparatively investigated by many characterization techniques such as N2 adsorption, H2-TPR, CO2-TPD, XRD, FT-IR and SEM. It was found that the major role of La2O3 additive was to improve the pore structure and inhibit carbon deposition on the catalyst surface. The La2O3 modified Ni/Mo/SBA-15 catalyst possessed a mesoporous structure and high surface area. The high surface area of the La2O3 modified catalysts resulted in strong interaction between Ni and Mo-La, which improved the dispersion of Ni, and retarded the sintering of Ni during the CO2 reforming process. The reaction evaluation results also showed that the La2O3 modified Ni/Mo/SBA-15 catalysts exhibited high stability.

Influence of acidic and alkaline silica sols on the performance of Cu/Zn/Al slurry catalysts

Co-reporter:Kai SUN, Xiao-yu ZHANG, Lin ZHANG, Zhong-kai BIAN, ... Zhi-huan ZHAO

Journal of Fuel Chemistry and Technology (October 2015) Volume 43(Issue 10) pp:1221-1229

Publication Date(Web):1 October 2015

DOI:10.1016/S1872-5813(15)30037-2

A series of Cu/Zn/Al/Si slurry catalysts were prepared using acidic and alkaline silica sols by the complete liquid-phase technology. The samples were characterized with XRD, H2-TPR, FT-IR, BET, NH3-TPD, XPS and TEM techniques. Addition of acidic silica sol to the catalyst gave the highest CO conversion and dimethyl ether (DME) selectivity, being 65.38% and 76.26% respectively. The acidic silica sol weakens the interaction between Cu and other components, resulting in a rapid reduction of Cu species and exposure of more active lattice planes of Cu0. In addition, the acidic/alkaline properties of silica sol also influence the number and the strength of acid sites in the sample. It was found that both the strong and the weak acid sites decreased in the strength. The acidic silica sol significantly increased the weak acid sites, mesopores and specific surface area, consequently promoting the methanol dehydration and increasing the DME selectivity.

Studies on the structure and catalytic performance of Cu-Zn-Al catalyst prepared by liquid-phase preparation technology under different heat treatment atmosphere

Co-reporter:Zhihua Gao, Wei Huang, Lihua Yin, Kechang Xie

Journal of Natural Gas Chemistry (November 2010) Volume 19(Issue 6) pp:611-616

Publication Date(Web):1 November 2010

DOI:10.1016/S1003-9953(09)60131-6

Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscope, and N2 adsorption-desorption. Their application in the single-step synthesis of dimethyl ether from syngas was also investigated. The results indicate that the type of heat treatment atmosphere has an influence on the Cu species and the Cu0/Cu+ ratio on the catalyst surface. Moreover, the final Cu/Zn ratio on the catalyst surface is mainly dependent on the composition and reaction environment of the catalyst and less on the type of heat treatment atmosphere. The prepared catalysts can suppress sintering of active sites at high temperatures, and the type of heat treatment atmosphere mainly affects the capability of the catalyst for methanol synthesis. The catalysts perform best using N2 as the heat treatment atmosphere.

A DFT study on the interaction of Co with an anatase TiO2 (001)-(1×4) surface

Co-reporter:Zhijun Zuo, Wei Huang, Peide Han, Zhihong Li, Jian Huang

Journal of Natural Gas Chemistry (March 2009) Volume 18(Issue 1) pp:78-82

Publication Date(Web):1 March 2009

DOI:10.1016/S1003-9953(08)60086-9

The substitution/adsorption structures of Co on an anatase TiO2 (001)-(1×4) surface are investigated using the DFT/local density approximation (LDA) method. Theoretical calculation shows that the Co ion prefers to be adsorbed on the surface of anatase TiO2. The density of states (DOS) analysis finds that the Co 3dis located mainly in the energy gap region. The Co 3dpartial density of states (PDOS) indicates that there is a substantial degree of hybridization between O 2s and Co3din valence band (VB) regions in the substitution models. The conclusion is that the mode of substitution is more active when the catalyst is a higher-energy surface.

CH4 dissociation on Co(0001): A density functional theory study

Co-reporter:Wei Huang, Lulu Sun, Peide Han, Jinzhen Zhao

Journal of Natural Gas Chemistry (January 2012) Volume 21(Issue 1) pp:98-103

Publication Date(Web):1 January 2012

DOI:10.1016/S1003-9953(11)60339-3

CH4 dissociation on Co(0001) surfaces is an important step, which has been investigated at the level of density functional theory. It is found that CH4 is unfavorable to adsorb on Co(0001), while CH4 favores to dissociate to CH3, CH2 and CH on Co(0001) surface by sequential dehydrogenation. In the whole process of CH4 dehydrogenation, CH4 dissociate to CH3 and H is the rate-determining step. The calculated results show that CH2 and CH exist mainly on Co(0001) surface, while the dehydrogenation of CH into C and H is difficult.

Methanol synthesis by CO and CO2 hydrogenation on Cu/γ-Al2O3 surface in liquid paraffin solution

Co-reporter:Zhi-Jun Zuo, Le Wang, Pei-De Han, Wei Huang

Applied Surface Science (30 January 2014) Volume 290() pp:

Publication Date(Web):30 January 2014

DOI:10.1016/j.apsusc.2013.11.092

•Methanol synthesis in liquid paraffin over Cu-based catalysts has been studied.•The rate-limiting step of CH3OH synthesis from CO2 hydrogenation was CH2OO formation.•The rate-limiting step of CH3OH synthesis from CO hydrogenation was CH2O formation.•The reaction rate of CO2 hydrogenation was faster than that of CO hydrogenation.Methanol synthesis by CO and CO2 hydrogenation over Cu-based γ-Al2O3 catalysts has been extensively studied. However, the reaction mechanism of this synthesis on Cu/γ-Al2O3 in liquid paraffin solution is still unclear at the microscopic level. This work investigated the synthesis of methanol by CO and CO2 hydrogenation and water–gas-shift reaction on Cu/γ-Al2O3 in liquid paraffin solution using density functional theory calculations. In CO hydrogenation, methanol was synthesized through the intermediates CHO, CH2O, and CH3O; the rate-limiting step was CHO hydrogenation. In CO2 hydrogenation, methanol was synthesized through the intermediates CHOO, CH2OO, CH2O, and CH3O; the rate-limiting step was CHOO hydrogenation. A comparison of the activation energies of the rate-limiting steps in CO and CO2 hydrogenation (1.37 and 1.10 eV, respectively) at typical catalytic conditions (e.g., 573 K) revealed that the reaction rate of direct CO2 hydrogenation was faster than that of direct CO hydrogenation. This finding indicated that methanol was mainly produced by CO2 hydrogenation. The calculated results were consistent with the experimental ones.

Theoretical studies on the reaction mechanisms of AlOOH- and γ-Al2O3-catalysed methanol dehydration in the gas and liquid phases

Co-reporter:ZhiJun Zuo, Wei Huang, PeiDe Han, ZhiHua Gao, Zhe Li

Applied Catalysis A: General (28 November 2011) Volume 408(Issues 1–2) pp:130-136

Publication Date(Web):28 November 2011

DOI:10.1016/j.apcata.2011.09.011

Kinetics of selective catalytic reduction of NO by NH3 on Fe-Mo/ZSM-5 catalyst

Co-reporter:Zhe LI, Lin-tao SHEN, Wei HUANG, Ke-chang XIE

Journal of Environmental Sciences (2007) Volume 19(Issue 12) pp:1516-1519

Publication Date(Web):1 January 2007

DOI:10.1016/S1001-0742(07)60247-2

The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction (SCR) of nitric oxide (NO) with NH3. The kinetics of the SCR reaction in the presence of O2 was studied in this work. The results showed that the observed reaction orders were 0.74–0.99, 0.01–0.13, and 0 for NO, O2 and NH3 at 350–450°C, respectively. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst. The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N2 and H2O. Gaseous O2 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process. It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH3.

The formation mechanism of the initial C–C chain in ethanol synthesis on γ-AlOOH(100)

Co-reporter:Lin Zhang, Bing Bai, Hui Bai, Wei Huang, Zhi-Hua Gao, Zhi-Jun Zuo and Yong-Kang Lv

Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 29) pp:NaN19307-19307

Publication Date(Web):2017/06/23

DOI:10.1039/C7CP03419A