•Hierarchical nano-ferrierite aggregates were synthesized using pyrrolidine as the sole OSDA.•Hierarchical nano-ferrierite aggregates consisted of mainly intercrystalline mesopore due to the stacking and assembly of nano-particles.•The size of nano-ferrierite was in the range of 40–180 nm depending on the crystallization temperature and initial gel compositions.•Excellent catalytic stability and product selectivity in 1-butene skeletal isomerization reaction were observed.Nano-ferrierite zeolite aggregates with hierarchical porosity were successfully prepared by using pyrrolidine as sole organic structure-directing agent. SEM and TEM images revealed that nano-sized crystals (40–60 nm) stacked together loosely to form irregular clusters. Influence of crystallization temperature and initial gel compositions (pyrrolidine content, alkalinity, water content) on the synthesis of ferrierite zeolite were investigated in detail. Low crystallization temperature and high alkalinity were beneficial to form nano-ferrierite zeolite aggregates with high hierarchical porosity (total pore volume: 0.461 cm3/g). Compared with commercialized ferrierite zeolite, hierarchical nano-ferrierite aggregates showed better catalytic stability and product selectivity in the 1-butene skeletal isomerization reaction.Download high-res image (196KB)Download full-size image

The atomically economic and green chemical reaction of direct amination of isobutylene to tert-butylamine, particularly under the relative mild reaction conditions available for future industrial use, was carried out over zeolite catalysts possessing different topological structures, from one dimensional to three dimensional pore system, and from small 8-member ring pore (MRP) to medium 10 MRP and further to large 12 MRP zeolites, to disclose the relationship between the zeolite properties/topologies and their amination performance systematically under the mild reaction conditions. It was discovered that the pore structure and the acidities of zeolite catalysts played crucial roles in the isobutylene amination process, and suitable pore diameter (larger than 0.5 nm or with large side pockets/cups in the outside surface) and a certain number of mid-strong acid sites are indispensable to catalyze the amination reaction, while too strong acid strength was not conducive to the process of isobutylene amination. Among them, zeolites with topologies of BEA, MFI, MEL, MWW and EUO exhibited good amination performance, with which the isobutylene conversion was higher than 12.61% (>46.42% of the equilibrium conversion) under the studied mild reaction conditions. Due to the good amination performance and the large adjustable Si/Al2 ratio range, ZSM-5 was selected to further study the effect of acidity on the amination performance systematically under the mild reaction conditions, and the activity-acidity relationship in the amination process was disclosed: the amination activity (isobutylene conversion) had a linear correlation with the amount of mid-strong B acidity under the studied conditions over ZSM-5 catalyst, which can provide guidance for further developing high-efficient amination catalyst under mild reaction conditions available for future industrial use.Direct amination of isobutylene over zeolite catalysts with various topologies and acidities was studied under mild reaction conditions and the activity-acidity linear correlation provided good guidance for developing high-efficient amination catalyst available for industrial use.Download high-res image (107KB)Download full-size image

On basis of thermodynamic empirical equations, the thermodynamic parameters for the direct amination of isobutylene to tert-butylamine, an atomically economic and green chemical reaction, were calculated. In particular, the equilibrium conversion of isobutylene under various reaction conditions close to those used in industry was calculated and discussed. Isobutylene amination is a temperature sensitive reaction due to its exothermic nature and isobutylene equilibrium conversion decreases with temperature. However, kinetically, the amination reaction will be faster at a higher temperature. Thus, there must be an optimum temperature for the reaction. A high pressure and n(NH3)/n(i-C4H8) molar ratio promote the transformation of isobutylene to tert-butylamine. Developing a highly efficient catalyst under mild reaction conditions is preferred for the amination process. The reaction was investigated over a series of acidic zeolites. ZSM-11 zeolite exhibited the best performance with 14.2% isobutylene conversion (52.2% of the equilibrium conversion) and > 99.0% tert-butylamine selectivity. The effect of reaction conditions on the performance of the ZSM-11 catalyst agreed with the thermodynamic results, which provides guidance for further catalyst development and reaction condition optimization.Thermodynamic study of direct amination of isobutylene to tert-butylamine Shangyao Gao, Xiangxue Zhu *, Xiujie Li, Yuzhong Wang, Ye Zhang, Sujuan Xie, Jie An, Fucun Chen, Shenglin Liu, Longya Xu * Dalian Institute of Chemical Physics, Chinese Academy of Sciences Thermodynamic calculation of the direct amination of isobutylene to tert-butylamine, an atomically economic and green chemical process, provide guidance for developing a highly efficient catalyst and reaction condition optimization.Download high-res image (79KB)Download full-size image

A facile alkaline treatment with the addition of surfactant cetyltrimethylammonium bromide (CTAB) to prepare hierarchical ZSM-11 zeolite (Z-xat-yCTAB) is presented. The textural and structural properties of Z-xat-yCTAB were characterized by XRD and adsorption and desorption of N2 and benzene. By virtue of CTAB addition, uniform intracrystalline mesopore distribution centered at ca. 4.2 nm was introduced accompanied by well-protected microporosity. Based on characterization results such as TEM images and BJH curves as well as 29Si and 27Al MAS NMR spectra, the composite effects of NaOH and CTAB on mesoporosity production were proposed. Acidity was characterized thoroughly by FTIR of adsorbed pyridine (Py-IR) and pivalonitrile. Accordingly, the ratio and accessibility factor of Brønsted and Lewis acid sites are discussed systematically. In the alkylation of benzene with dimethyl ether, Z-xat-yCTAB series samples exhibited better reaction stability than ZSM-11 samples treated with NaOH solution. The catalytic promotion could be attributed to the dual effects of NaOH and CTAB on the porosity and acidity regulation. Moreover, based on the correlation between the reaction stability and the ratio of Brønsted to Lewis acid concentration with weak–medium strength, measured by Py-IR, it was revealed that the regulation of acidity could play a more important role for better reaction stability. In addition, the physicochemical properties and reaction activity were compared between ZSM-11 samples derived from alkaline treatment with CTAB addition and with tetrapropylammonium bromide (TPABr) addition under the same conditions.

•Uniform intracrystalline mesopores were introduced in MCM-49 zeolite.•A CTAB micelle directed desilication mechanism was proposed.•The extra-framework aluminum of MCM-49 could be selectively removed.•The prepared hierarchical MCM-49 zeolite showed improved alkylation stability.Hierarchical MCM-49 zeolite with intracrystalline mesopores was prepared through post-treating the conventional MCM-49 zeolite in hexadecyltrimethylammonium bromide (CTAB) and NaOH mixed solution. N2 adsorption and desorption, XRD, TEM, XRF, ICP and Py-IR techniques were applied to characterize the obtained samples. It was found that uniform intracrystalline mesopores were distributed in the MCM-49 crystals, and the intracrystalline meso-porosity could be modified by changing the post-treatment conditions such as CTAB concentration, NaOH concentration, temperature and time. Based on the characterization results upon the hierarchical MCM-49 zeolite samples obtained by post-treating different time, the formation of intracrystalline mesopores in MCM-49 zeolite was proposed, which followed a CTAB micelle directed desilication mechanism. By virtue of the intracrystalline mesopores, the hierarchical MCM-49 zeolite prepared under proper post-treatment condition exhibited superior stability than the conventional MCM-49 zeolite in liquid alkylation of benzene with ethylene.

Hierarchical ZSM-11 zeolites (Z-xat) were prepared by treating the pristine ZSM-11 zeolite in a solution of NaOH with different concentrations (CNaOH). It was found the porosity and acidity (concentration, strength, distribution and accessibility factor of Brønsted and Lewis acid sites) of modified ZSM-11 zeolite changed obviously with CNaOH. When used for alkylation of benzene with dimethyl ether, the modified Z-xat exhibited better reaction stability than the unmodified HZSM-11 zeolite. Typically, the reaction stability of Z-xat zeolite catalysts was directly related to the mesopore volume, besides the weak-medium acid concentrations determined by Py-IR technique.

•Cofeeding n-butane with methanol suppresses the dry gas formation.•The improvement effect depends on cofeeding composition and reaction conditions.•Only under suitable conditions, the selectivity of aromatics can be improved.The aromatization of cofeeding n-butane with methanol was investigated in a fixed bed reactor over the Zn loaded ZSM-5/ZSM-11 zeolite catalyst. Compared with the methanol and n-butane aromatizations, individually, the introduction of methanol in n-butane effectively suppresses the formation of dry gas and promotes that of LPG, since water produced from methanol dehydration may adsorb on the active sites of the catalyst and therefore inhibits the cracking reaction. The improvement effect of cofeeding n-butane with methanol in the integrated process is mainly discussed in terms of the concept of product improvement coefficient. It is found that the synergy between aromatization of methanol and that of n-butane is closely related to the reaction conditions, such as the cofeeding composition, pressure, temperature, and space velocity. Under the selected reaction conditions of 480 °C, 0.4 MPa, WHSV (CH2) = 0.6 h− 1 with an n-butane/methanol ratio of 60/40 over the catalyst, the selectivity of aromatics can be effectively improved.

The silicon/aluminum ratio is proved to be a key parameter for mesoporosity tuning in the synthesis of hierarchical MFI zeolites by organosilane surfactant. At the fixed synthesis temperature, the mesopore size distribution evolves from a bimodal type to a uniform mode with the increase of Si/Al ratios. Moreover, different Si/Al ratios result in opposite responses of mesopore distributions to the elevation of synthesis temperature. With the elevated temperature from 140 to 150 °C, the mesopore distribution of low-silica MFI zeolites (Si/Algel = 20) evolves from a bimodal type (centered at 4 and 10 nm) to a relatively uniform mode (centered at 8 nm), whereas the high-silica samples (Si/Algel = 40) exhibit a reverse transformation from a uniform mesopore distribution (centered at 3 nm) to a bimodal mode (centered at 4 and 20 nm). This work demonstrates alternative methods for the mesoporosity tuning of organosilane-directed hierarchical zeolites.

The interzeolite conversion of zeolite MCM-49 into zeolite ZSM-35 in “cyclohexylamine (CHA)–hexamethyleneimine (HMI)–Na2O–H2O” systems, consisting of “CHA–Na2O–H2O”, “HMI–Na2O–H2O” and “Na2O–H2O”, was investigated in detail using X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) characterization techniques. Both CHA and HMI play important roles in directing the interzeolite conversion of MCM-49 into ZSM-35, and the conversion speed is much faster in systems containing CHA than those containing HMI. Even in the Na2O–H2O system without any organic amine, MCM-49 can still transform into some other zeolites with more stable topological structures than itself, such as ZSM-35, ZSM-5, and mordenite, but the product of the interzeolite conversion is more complicated than that in the systems containing organic amines (CHA and/or HMI). In the Na2O–H2O system, alkalinity has been proved to be a crucial factor influencing the conversion trend of MCM-49. Zeolites ZSM-5 and mordenite will appear in the products besides ZSM-35 with the increase of the alkalinity. The conversion process of zeolite MCM-49 in the systems investigated accords well with the solution-mediated transformation mechanism.

•Sequential steaming-acid leaching-alkaline treatment on Al-rich mordenite.•Intra-crystalline mesopores are introduced by this sequential method.•Elevated steaming temperature enhances the final mesoporosity.•An extraction-realumination is observed for Al sites with Si(2Al) configuration.A three-step method consisting of steaming-acid leaching-alkaline treatment is used to introduce mesoporosity in a commercially available Al-rich mordenite zeolite (Si/Al = 4.8). It has been found that the three-step sequential treatment results in the intra-crystalline mesoporosity with a pore size distribution centered at around 20 nm. Single step or binary combination among steaming, acid leaching (treated in 3.0 M HNO3 solution at 80 °C for 1 h) and alkaline treatment (treated in 0.1 M NaOH aqueous solution at 85 °C for 2 h) hardly induces the mesoporosity with a controlled mesopore size distribution. Among the involved three steps, the impact of steaming temperature on the mesoporosity development is studied. The elevation of steaming temperature in the range of 300–600 °C improves the susceptibility to the successive alkaline treatment and thus enhances the mesoporosity formation. Moreover, transitions of 29Si NMR spectra demonstrate an extraction-realumination of framework Al species with Si(2Al) configuration during the synthesis of hierarchical mordenite zeolite.Graphical abstract

A mechanism of the realumination process was proposed when MCM-22 was post-treated in Al(NO3)3 solution. Al atoms would deposit into zeolite with the amorphous alumina form, or insert into the framework by substituting Si atoms on certain T sites near the surface. The realumination process increased the amount of acid sites on the surface of MCM-22, significantly improved the catalytic activity and stability for olefins conversions in the alkylation of benzene with diluted olefins.

Liquid-phase transalkylation of phenol with cumene was studied over various zeolites. Among the evaluated catalysts, ZSM-5 zeolites showed higher activities (ca. 50% phenol conversion) and usage efficiencies of isopropyl groups (ca. 80%) at 200 °C and 1.5 MPa. The higher catalytic performances of ZSM-5 zeolites are closely related to their channel structure and moderate cumene uptake capacities. It has been shown that the activities are related to the strong acidity of ZSM-5 zeolites. The passivation of external acid sites on ZSM-5 zeolite enhances the selectivity for para-isopropylphenol.

A series of ZSM-35 zeolites with different alkaline treatment degrees were prepared. The precise effects of alkaline treatment on composition, morphology, porosity, transportation and acidity of the samples were characterized by means of multiple techniques including N2 sorption, transmission electron microscopy (TEM), intelligent gravimetric analyzer (IGA) and Fourier transform infrared spectroscopy (FTIR). ZSM-35 after moderate alkaline treatment exhibited enhanced carbonylation activity compared with the parent sample. As revealed by the N2 adsorption and TEM results, alkaline treatment could induce the deaggregation of ZSM-35 clusters and remove the amorphous debris on the surface of ZSM-35 platelets. Furthermore, an improved diffusion behavior of the dimethyl ether reactant molecule was observed on the alkali-treated sample from IGA experiments which directly led to the better catalytic performance for the carbonylation of the dimethyl ether with carbon monoxide. Mesoporosity created by severe alkaline leaching does not enhance the catalytic properties of ZSM-35 in dimethyl ether carbonylation reaction. Especially, a decrease in reaction stability was observed due to the limitation effect of carbonaceous deposit formation.

A series of Mo/mordenite-alumina catalysts with progressive sodium exchange degrees in mordenite were prepared and their performance in 1-butene metathesis reaction was evaluated. Significant variations in product distribution and catalytic activity were observed when the exchange degree of mordenite changed. As revealed by NH3-TPD and 1H MAS NMR results, the acid site density and distribution over the catalysts were directly related to the degree of ion-exchange of sodium in mordenite. The change of support acidity led to different anchoring modes and dispersion of Mo species on the support which further resulted in the different reduction behavior of Mo species under olefin atmosphere. A good correlation between product distribution and properties of the catalysts was proposed.Graphical abstractHighlights► 1-Butene metathesis product distribution could be tuned through changing the sodium exchange degree of mordenite. ► 1-Butene self-metathesis dominates on the catalyst with low sodium exchange degree due to the limitation of 1-butene isomerization. ► High propene yield of 27.4 mol% is obtained on 6Mo/HMOR–Al2O3. ► Anchoring modes and dispersion of Mo species are closely related to the sodium exchange degrees of the support.

One-step transformation of isobutyl alcohol to aromatics (benzene, toluene, and xylene) has been studied in a gas phase, fixed-bed reactor system over several purely acidic zeolites and zeolite-supported metal catalysts. ZSM-5 zeolites give higher aromatics yields (∼42 wt %) among the evaluated zeolites, and the Si/Al ratios (Si/Al = 13–43) of ZSM-5 slightly influence their catalytic performances. During the transformation of isobutyl alcohol, large amounts of short alkanes (mainly propane and butane isomers) are also generated on the acidic ZSM-5. To improve the conversion to aromatics, several metal species (Zn, Ga, Mo, La, Ni, Ag, and Pt) are supported on the ZSM-5. The enhancements in aromatics yields (∼60 wt %) are observed only on the Zn/ZSM-5 catalysts. The incorporation of Zn species preferentially decreases the strong-strength Brønsted acidity and, thus, suppresses the cracking to C3 fragments. Moreover, mainly the Zn species at the exchange sites facilitate the recombinative desorption of H2 and, hence, enhance the reactions toward aromatics. Through these effects, Zn/ZSM-5 catalysts exhibit the remarkably promoted formation of toluene and xylene and inhibit the generation of undesired alkanes products.Keywords: aromatization; isobutyl alcohol; zeolites; zinc species;

A series of ZSM-5/ZSM-11 co-crystalline zeolites with various compositions and morphologies were successfully synthesized via an organic template-free hydrothermal route and characterized by XRD, XRF, SEM, NMR and N2 adsorption/desorption technologies. The effects of raw materials and batch composition were investigated systematically. Various silicon sources can be employed in the organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite, however only a few types of aluminum sources are available. This organic template-free system is favorable to the aluminum-rich zeolite. With the increase of initial SiO2/Al2O3 ratio, the ZSM-5 percentage in the ZSM-5/ZSM-11 co-crystalline zeolite increases as well as the crystal size, and especially the morphology of ZSM-5/ZSM-11 co-crystalline zeolite prepared from the colloidal silica–NaAlO2 solution system changes gradually from nano-rod aggregation, micro-spindle to single hexagon and then to twinned hexagon crystals. Moreover, Na+ and OH− in the initial materials can promote the nucleation of the ZSM-5/ZSM-11 co-crystalline zeolite significantly and are beneficial to the formation of crystals with relatively low length/width ratio, while K+ postpones the crystallization process seriously.Graphical abstractHighlights► ZSM-5/ZSM-11 co-crystalline zeolite was organic template-free synthesized. ► The crystal phase was more sensitive to the aluminum source than the silicon source. ► The ZSM-5 percentage and crystal size increased with the initial SiO2/Al2O3 ratio. ► Na+ and OH− promoted the nucleation of ZSM-5/ZSM-11 co-crystalline zeolite. ► K+ postponed the crystallization process of ZSM-5/ZSM-11 co-crystalline zeolite.

Influences of alkaline treatment on the structural properties and catalytic performances of ZSM-5/ZSM-11 composite zeolites with alumina as binder at different preparation steps were studied in the present investigation. Temperature-programmed desorption of ammonium (NH3-TPD) and pyridine infrared (Py-IR) spectra revealed that alkaline treatment sequences changed both the distribution and amount of the acidities in the ZSM-5/ZSM-11-Al2O3 samples. The mesopores created by alkaline treatment were found beneficial for the diffusion of aromatic molecules, as determined by the xylene-uptake experiments using a tapered element oscillating microbalance (TEOM). In 1-hexene isomerization and aromatization reactions, the sample after extrusion followed by alkaline treatment exhibited excellent aromatization activity and stability compared with other samples undergoing different treatment sequences. The enhanced catalytic performance could be attributed to the redistribution of acid sites and introduction of more mesopores.Graphical abstractS2 sample prepared by ZSM-5/ZSM-11 extrudate with successive alkaline treatment showed enhanced mass transfer performance for aromatic molecules as verified by the m-xylene uptake experiments.Research highlights▶ Influences of alkaline treatment on the structural properties and catalytic performances of ZSM-5/ZSM-11 composite zeolites with alumina as binder at different preparation steps were studied. ▶ ZSM-5/ZSM-11-Al2O3 catalyst for 1-hexene isomerization and aromatization reaction. ▶ ZSM-5/ZSM-11 after extrusion followed by alkaline treatment exhibited best catalytic performance among four samples. ▶ Better mass transfer performance for aromatic molecules in sample S2 was verified by the m-xylene uptake experiments using tapered element oscillating microbalance (TEOM).

Effects of Zn and Mg addition on the catalytic performances of ZSM-5 in 1-hexene aromatization and isomerization were investigated. NH3-TPD and Pyridine-IR spectra revealed that the addition of Zn could increase the Lewis acidity amount of the support. And the catalytic aromatization activity was improved. Introduction of Mg resulted in a decrease of total acidity, especially for Brϕnsted acid sites which was beneficial for the high iso-paraffin and liquid product yield. The optimal modification way on ZSM-5 was obtained as addition of Mg with successive Zn introduction which may lead to the presence of Zn species inside of the zeolite channel evidenced by XPS results. The close proximity of Zn species to Brϕnsted acid sites may enhance the synergy effect between them in the aromatization reaction. The optimized Zn–Mg/HZSM-5 sample also exhibited good catalytic performance when using FCC gasoline as reactant.

ZSM-5 and ZSM-11 zeolites with high crystallinity are synthesized and tested in the aromatization and isomerization reactions of 1-hexene at 370 °C in a continuous flow fixed bed. The results indicate that ZSM-5 and ZSM-11 zeolites possess similar acid site amount and strength, and most of the acid sites belong to Brønsted acid. When the ZSM-5 and ZSM-11 zeolites were used as catalysts, the aromatics selectivity over ZSM-11 catalyst was higher than that over ZSM-5 catalyst in contrast to i-paraffins selectivity, maybe attributed to that the C7 and C8 aromatics have an easier exit from the ZSM-11 zeolite. Moreover, the decrease of particle size can present superior aromatics selectivity and less i-paraffins selectivity in the aromatization and isomerization of 1-hexene over the ZSM-11 catalyst.

Pure silica ITQ-13 (ITH) zeolite was successfully synthesized using fumed silica as silica source. Compared with the conventionally used tetraethyl orthosilicate (TEOS), application of fumed silica facilitated the gel-making process as the hydrolysis procedure was omitted. On basis of that, influences of reactant H2O/Si ratios and crystallization temperatures on the synthesis of ITQ-13, as well as the properties of the as-synthesized and calcined samples, were investigated. As evidenced by XRD, SEM, XRF, N2 adsorption, TGA and TPO-MS results, well crystallized ITQ-13 zeolites were obtained at low H2O/Si ratios (7∼8). The primary crystals of the ITQ-13 zeolites were in plate-like shape, and the plate thickness increased upon the increasing crystallization temperature. ITQ-13 samples exhibited excellent thermal stability, especially for those synthesized at high temperatures.

MCM-22 zeolites with high SiO2/Al2O3 (Si/Al2) ratios were synthesized by a one-pot procedure with the assisting of boron. Based on this boron-containing method, the Si/Al2 ratios of the MCM-22 zeolites could be greatly extended from 30 to 600 in control by tuning the Si/Al2 ratios of the starting gels. ICP-AES and 11B MAS NMR results demonstrated that a small part of the boron still existed in the framework of the MCM-22 after calcination and ammonium exchange. However, the residual boron species had little influence on the physicochemical properties of the MCM-22 samples evidenced by XRD, BET, TG–DTA, NH3–TPD, and Py-IR determinations. The reaction of catalytic cracking of 1-butene to propene was carried out to study the performances of the high silica MCM-22 catalysts. Increasing of the Si/Al2 ratios in the MCM-22 zeolites suppressed the formation of byproducts such as propane and aromatics effectively, and the optimal selectivity towards propene was obtained on the sample with a Si/Al2 ratio of 158.

A novel route for synthesis of MCM-49/ZSM-35 composite zeolites with different compositions in a mixed amine system containing hexamethyleneimine (HMI) and cyclohexamine (CHA) has been developed. Furthermore, both MCM-49 zeolite and ZSM-35 zeolite can be successfully synthesized by adjusting the synthesis conditions in the same system. Especially, the MCM-49/ZSM-35 composites with more content of ZSM-35 zeolite can be produced under conditions of larger CHA/HMI molar ratio, higher Na2O/Al2O3 molar ratio and longer crystallization time. The structure characterization, acid distribution and morphology of the MCM-49/ZSM-35 composite zeolites are characterized by X-ray diffraction, N2 adsorption isotherms, NH3-TPD, scanning electron microscopy as well as HP-129Xe NMR technology. These characterizations give obvious different pore structure of the MCM-49/ZSM-35 composite zeolites from the mechanical mixing counterpart.

The combined alkali-steam treatment was employed to prepare the ZSM-5 zeolite possessing the micro-mesopore hierarchical structure and proper acidity simultaneously. The tailored zeolite displayed superior catalytic performance in the aromatization and isomerization of 1-hexene.

A brief review of the work carried out at Dalian Institute of Chemical Physics, Chinese Academy of Sciences for development of two new on-purpose processes enhancing propene production is presented. This includes the processes of catalytic cracking of C4 alkenes to propene and metathesis of ethene and 2-butene to propene, by which the large amounts of the C4 recourses from the petrochemical can be upgraded and the severity of demand for propene can be lessened.

By modifying the Hβ zeolite with proper amount HF, the catalytic performance of fluorinated Hβ was obviously improved for the olefin alkylation thiophenic sulfur process. Particularly, the acid sites of the fluorinated Hβ catalysts were increased, especially its distribution of medium and stronger Lewis and Brönsted acid sites was optimized, and its thiophene alkylation activity and stability are thus promoted as well as its coking behavior is suppressed during OATS process.

The efficiency of the catalytic alkylation, the first step of the olefins alkylation thiophenic sulfur (OATS) process was investigated in three typical gasoline samples with different olefins contents over a fluorinated Hβ zeolite catalyst. Under the reaction conditions of 120 °C, 1.5 MPa and WHSV 0.5 h− 1, over 95% light sulfur compounds in the feeds could be transformed to be heavier than the heptyl-thiophenes within a period of time-on-stream. The lifetime of the catalyst could prolong from 10 h to 26 h when the olefins content in the gasoline feed decreased from 40.87 wt.% to 9.20 wt.%. It was also found that the olefins content decrease was favorable for keeping and promoting the octane number by redistributing the components of the treated gasoline. In addition, the influence of the reaction conditions such as the temperature and WHSV on the efficiency of the catalytic alkylation was investigated.

Since the commercialization of ethylbenzene production via alkylation of benzene with the dilute ethene in FCC off-gas over a ZSM-5/ZSM-11 co-crystallized zeolite catalyst in China, the catalyst has been regenerated several times and showed good regeneration performance. During the alkylation process, the catalytic activity decreases, some of the catalyst pores are blocked and the acid centers are partly covered by coke deposition. Influence of the factors such as catalyst particle size, temperature, etc. on the burning rate of the coke was investigated by the TG technique, and a rate equation for coke burning on the ZSM-5/ZSM-11 co-crystallized catalyst was established.

Catalysts containing 10 wt.% W were prepared using Al2O3–HY mixed supports with various HY contents. The catalytic performance of these catalysts for the metathesis of ethene and 2-butene to propene was determined in a fixed-bed flow reactor at 180 °C under 0.1 MPa. The 2-butene conversion of these catalysts increases remarkably with the HY content in the range of 0–30 wt.%. Between 30 and 70 wt.% of HY content, the conversion reaches a plateau of 60–63%, which is very close to the thermodynamic equilibrium value of ∼64%. After that, the 2-butene conversion decreases substantially. The propene selectivity shows the similar trends. The maximum propene selectivity goes up to 88%. By the studies of NH3-TPD, H2-TPR and UV–vis, the role of HY zeolite in the 10W/Al2O3–xHY is explained in two following aspects: (i) changing the Brönsted acidity of catalysts, which may affect the formation of initial carbene species; (ii) modifying the interaction between W species and support for the formation of active centers with intermediate oxidation number (W4+, W5+, W(6−y)+ (0 < y <1)). Based on this information, the optimal HY content for 10W/Al2O3–xHY catalysts is about 50–70%.CH2CH2+CH3CHCHCH3⟶180 °C, 0.1 MPa10 wt.% W/Al2O3–xHY2CH3CHCH2Metathesis between ethene and 2-butene to propene is catalyzed by 10 wt.%W/Al2O3–xHY with various HY content at temperature 180 °C and pressure 0.1 MPa. Reaction and characterization results reveal that Brönsted acidity of catalysts and the interaction between W species and support simultaneously play their important roles in the reaction.

Direct synthesis of alcohols from CO and H2O was investigated using TiO2 catalyst. MeOH (about 24 mg g−1 h−1) and EtOH (about 8 mg g−1 h−1) could be produced under the reaction conditions of T=573 K, P=0.5 MPa, CO flow rate of 30 ml min−1 and CO/H2O=3/2 during the period of 12 to 44 h time-on-stream. Compared with PbO, TiO2 could preserve stable catalytic activity during a long time of reaction. For the same catalyst TiO2, the reaction performance of alkali carbonates increased with their solubility (K2CO3>Na2CO3>Li2CO3). The corresponding catalytic activity was found to increase with the alkalescence of solvent. The formation mechanism of alcohols was proposed as well.

HZSM-11 zeolite supported Zn catalysts with different Zn contents (xZn/HZSM-11A) were prepared. In the alkylation of benzene with dimethyl ether (DME) in a fixed bed reactor, the catalyst with Zn content of 6 wt% (6Zn/HZSM-11A) showed appropriate performance. Focus was put on the comparison between 6Zn/HZSM-5 and 6Zn/HZSM-11 with the same crystal size of 600–800 nm, and also with the similar BET surface area, micropore volume, Si/Al2 molar ratio, and acidity. In the alkylation of benzene with DME, the 6Zn/HZSM-11 showed better activity and stability, and especially enhanced the conversion of benzene and selectivities to xylene and trimethylbenzene, compared with the 6Zn/HZSM-5. This was mainly related to the higher adsorption capacity and adsorption-desorption rates to the three adsorbates (benzene, m-xylene and 1,3,5-trimethylbenzene) over the 6Zn/HZSM-11 in comparison with the 6Zn/HZSM-5.Zn/HZSM-11 zeolite catalyst presents better activity and stability in the alkylation of benzene with dimethyl ether compared with Zn/HZSM-5, in spite of similar physicochemical properties for the two catalysts.Download full-size image

A series of 3.0Mo/MCM-22-Al2O3 catalysts with γ-Al2O3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al2O3 did not affect the structure of MCM-22 zeolite as evidenced by XRD and N2 adsorption measurements. It was deduced from TPR experiments that γ-Al2O3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al2(MoO4)3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence (Mo6+ or Mo5+) contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/(MCM-22-30%Al2O3) under the reaction condition of 1.0 MPa and 125 γC using N2 as the pretreatment gas.

A new propene production route from 1-butene metathesis has been developed on heterogeneous 10WO3/Al2O3-HY catalysts with different HY contents. It is found that the catalysts play bi-functionally first for the isomerization of 1-butene to 2-butene and then for the cross-metathesis between 1-butene and 2-butene to propene and 2-pentene. The combination of HY zeolite and Al2O3 is prerequisite for the production of propene. The propene yield keeps increasing with the HY content in the range of 10–70 wt%, where 10WO3/Al2O3-70HY exhibits the highest propene yield. The MS-H2-TPR and MS-O2-TPO characterizations indicate that the increase of HY content in the catalysts weakens the interaction between W species and supports, whereas enhance the probability of coking on the metal species and acid sites.

•We studied the acylation of anisole with acetic anhydride over Beta zeolite.•The Brönsted/Lewis acid concentration of poisoned Beta samples was determined.•Strong acid sites played the predominant role in the anisole acylation.•The contribution of external surface acid sites to the reaction can be ignored.•The relation between Brönsted acid sites and anisole conversion was calculated.Catalytic roles of the acid sites in Beta zeolite for the acylation of anisole (AN) with acetic anhydride were investigated. There existed obvious difference between the Beta zeolite acidity modified with inorganic alkali cation (K+) and that modified with organic base (2,4-dimethylquinoline, 2,4-DMQ). With the increase in K+ loadings, the Beta zeolite showed decreases in both total acid strength and acylation performance. Strong acid sites played the predominant role in the AN acylation. Whereas the modifier of 2,4-DMQ mainly poisoned the Brönsted acid sites and kept the Lewis acid sites almost intact. Over the Beta zeolite poisoned by 2,4-DMQ, the AN conversion (XAN) versus the concentration of Brönsted acid sites (CB) could be represented by two linear expressions, namely XAN = 37.53CB − 0.20 (when 0.0053 ⩽ CB ⩽ 0.0167 mmol/g) and XAN = 2.68CB + 0.38 (when 0.0167 < CB ⩽ 0.0857 mmol/g).Over Beta-N samples with similar concentrations of Lewis acid sites, the relationship between anisole conversion (XAN) and the concentration of Brönsted acid sites (CB) could be represented by two linear expressions: XAN = 37.53CB − 0.20 (when 0.0053 ⩽ CB ⩽ 0.0167 mmol/g); XAN = 2.68CB + 0.38 (when 0.0167 < CB ⩽ 0.0857 mmol/g).Download high-res image (39KB)Download full-size image

A novel industrial process was designed for the highly selective production of ethylbenzene. It comprised of a reactor vessel, vapor phase ethylene feed stream, benzene and transalkylation feed stream. Especially the product stream containing ethylbenzene was used to heat the reactor vessel, which consisted of an alkylation section, an upper heat exchange section, and a bottom heat exchange section. In such a novel reactor, vapor phase benzene and liquid phase benzene were coexisted due to the heat produced by isothermal reaction between the upper heat exchange section and the bottom heat exchange section. The process was demonstrated by the thermodynamic analysis and experimental results. In fact, during the 1010 hour-life-test of gas phase ethene with gas phase-liquid phase benzene alkylation reaction, the ethene conversion was above 95%, and the ethylbenzene selectivity was above 83% (only benzene feed) and even higher than 99% (benzene plus transalkylation feed). At the same time, the xylene content in the ethylbenzene was less than 100 ppm when the reaction was carried out under the reaction conditions of 140–185 °C of temperature, 1.6–2.1 MPa of pressure, 3.0–5.5 of benzene/ethylene mole ratio, 4–6 v% of transalkylation feed/(benzene+transalkylation feed), 0.19–0.27 h−1 of ethene space velocity, and 1000 g of 3998 catalyst loaded. Thus, compared with the conventional ethylbenzene synthesis route, the transalkylation reactor could be omitted in this novel industrial process.

HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD characterization techniques. Compared to the unmodified zeolite, the thermal and hydrothermal stabilities of the alkali-treated ZSM-5 zeolites were slightly deteriorated because of the introduction of mesopores caused by the desilication. Nevertheless, the alkali-treated zeolite framework could be maintained until the temperature increased to 1175 °C.

Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 °C, 1.5 MPa, WHSV 3.0 h−1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.

Effects of space velocity, reaction temperature and support acidity on product distribution and induction period in 1-butene isomerization and metathesis over Mo/mordenite-alumina were investigated. As revealed by the catalytic performance results, induction period and objective product were closely related to the reaction conditions. Lower space velocity led to longer induction period and higher propene yield. The optimal reaction temperature for propene production is around 150 °C and it shifted to 100 °C for ethene production. 1-Butene auto-metathesis predominated in the reaction network if the support with lower degree of sodium exchanged. And propene gradually became the dominant product upon increasing the support sodium exchange degree. 6Mo/H100Na0M-30Al catalyst with a support of full sodium exchange degree exhibited the highest propene yield.

The properties of three types of pore systems in MCM-49 zeolite have been investigated by precoking to block the supercages and poisoning the surface pockets. Most Lewis acid sites (ca. 73%) are located within the supercages, while 38% of Brönsted acid sites are located in the surface pockets, 28% in the sinusoidal pores and only 34% in the supercages, respectively. Alkylation of benzene with ethylene mainly occurs in the surface pockets, and the contribution from the sinusoidal pores is limited. The generation of heavy aromatics in supercages results in the deactivation of MCM-49 at the early reaction stage. A moderate alkali-treatment process has been demonstrated to enlarge the opening of supercages without affecting the sinusoidal pores, resulting in improved diffusion of big molecules and hence better catalytic performance for liquid alkylation of benzene with ethylene.Graphical abstractSurface pockets of MCM-49 are the main place for the liquid alkylation of benzene with ethylene. The generation of heavy aromatics within the supercage system is the main reason for the deactivation of MCM-49 catalyst at the early reaction stage.Download high-res image (81KB)Download full-size imageHighlights► Liquid alkylation of benzene with ethylene over MCM-49 zeolite was studied. ► Ethylbenzene was mainly produced in the surface pockets. ► Distributions of acidic sites within different pore system were determined. ► Possible reactions within different pores were proposed. ► Effects of alkali-treatment on catalytic performances of MCM-49 were studied.

•Ion exchange method is beneficial for the formation of ZnOZn bridging species inside the micropore channel.•ZnOZn bridging species increase the promoting effect of cofeeding n-butane with methanol on aromatics selectivity.•Bulk ZnO particles promote the formation of C2 C4 light alkane in cofeeding reaction.Combination of the exothermic methanol aromatization with the endothermic n-butane aromatization provides a good way to meet the increasing demand for aromatics. Here, a series of Zn-ZSM-5/ZSM-11 catalysts were prepared with different introduction methods. The influence of location and state of Zn species on the coupling effects of cofeeding n-butane with methanol were investigated in detail. UV–vis, H2-TPR and XPS spectra were applied to reveal the state of the Zn species on different catalysts. Quantitative results of NH3-TPD and Pyridine-FTIR were provided to compare the acidity changes of the catalyst after Zn loading. Physical mixing method led to high portion of bulk ZnO particles outside the channel which could promote the formation of C2 C4 light alkane in cofeeding reaction. Ion exchange and impregnation modes were beneficial for the formation of ZnOZn bridging species in the micropore channel. ZnOZn bridging species was found to increase the promoting effect of cofeeding n-butane with methanol on aromatics selectivity.Download high-res image (196KB)Download full-size image

A facile alkaline treatment with the addition of surfactant cetyltrimethylammonium bromide (CTAB) to prepare hierarchical ZSM-11 zeolite (Z-xat-yCTAB) is presented. The textural and structural properties of Z-xat-yCTAB were characterized by XRD and adsorption and desorption of N2 and benzene. By virtue of CTAB addition, uniform intracrystalline mesopore distribution centered at ca. 4.2 nm was introduced accompanied by well-protected microporosity. Based on characterization results such as TEM images and BJH curves as well as 29Si and 27Al MAS NMR spectra, the composite effects of NaOH and CTAB on mesoporosity production were proposed. Acidity was characterized thoroughly by FTIR of adsorbed pyridine (Py-IR) and pivalonitrile. Accordingly, the ratio and accessibility factor of Brønsted and Lewis acid sites are discussed systematically. In the alkylation of benzene with dimethyl ether, Z-xat-yCTAB series samples exhibited better reaction stability than ZSM-11 samples treated with NaOH solution. The catalytic promotion could be attributed to the dual effects of NaOH and CTAB on the porosity and acidity regulation. Moreover, based on the correlation between the reaction stability and the ratio of Brønsted to Lewis acid concentration with weak–medium strength, measured by Py-IR, it was revealed that the regulation of acidity could play a more important role for better reaction stability. In addition, the physicochemical properties and reaction activity were compared between ZSM-11 samples derived from alkaline treatment with CTAB addition and with tetrapropylammonium bromide (TPABr) addition under the same conditions.