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A series of Beta zeolite catalysts with controllable particle sizes and similar Si/Al ratios were prepared by introducing imidazole (IMD) into the synthesis system and used for a liquid-phase transalkylation of diethylbenzene (DEB) with benzene (Bz). Beta zeolite catalyst prepared with IMD/SiO2 molar ratio of 0.5 possessed the smallest particle size (mean particle size of 119 nm) and the highest DEB conversion of 79.16%, under the reaction conditions: 260 oC, 4.0 MPa, WHSV (diethylbenzene) of 2.0 h-1, W(benzene)/W(diethylbenzene) of 3/1, time on stream of 5 h. Then, for the purpose of elucidating the catalytic roles of the acid sites with different strength, types and positions in Beta zeolite in the transalkylation reaction, we carried out Na+ loading on the prepared Beta zeolite to eliminate strong acid sites, and poisoned Bronsted acid sites and external acid sites by using 2,4-dimethylquinoline (2,4-DMQ) and triphenylphosphorus (TPP) as toxic reagents, respectively. The results suggested that the moderate and strong Bronsted acid sites of Beta-IMD0.5 were the active sites for the liquid-phase transalkylation of DEB with Bz and their utilization rate showed a trend of increased first and then decreased. Significantly, 31% of the external Bronsted acid sites of Beta-IMD0.5 contributed 81% of DEB conversion. The external acid sites had more contribution to the reaction, due to the short diffusion path and fine accessibility.

Crystallographic sites of Bronsted acids (Si-OH-Al) in zeolites, which are closely associated with the Al sites, play a significant and unique role in the catalytic application, especially when they are distributed in open channel systems or confined in cavities with small pore openings. In this article, we unraveled constrained Al crystallographic sites in FER-type zeolites containing the distinct local environments (10-ring channels and ferrierite cavities) by Rietveld refinement against the powder X-ray diffraction data. Final refinement demonstrates that regardless of the types of structure-directing agents and synthetic medium utilized, T1 and/or T3 are Al-rich positions, which are further confirmed by theoretical calculations. This new finding of constrained Al sites in the FER-type zeolite can well explain its limited catalytic activity in the DME carbonylation reaction.

The organic structure-directing agent (OSDA)-free synthesis of MCM-49 is strongly desired because OSDA makes synthesis cost expensive and environment unfriendly. In this work, an efficient, eco-friendly and simple route to synthesize MCM-49 zeolite is developed, via seed-assistance, without deliberately adding OSDA, with ultraphonic aging treatment. For comparison, the effect of microwave aging, mechanical stirring aging and without any aging processes on the synthesis is investigated. Due to the acoustic cavitation, the ultraphonic aging treatment shows superiority over the others. Ultraphonic aging not only keeps the MCM-49 seed integrity but also promotes both the silica species and aluminum species to the solid phase, which is beneficial for the growth of MCM-49 and the suppression of MOR formation in the absence of OSDA. 27Al MAS NMR data show that the seed-assisted MCM-49 almost has no extra-framework aluminum, but dealumination will happen upon ammonium exchange. 23Na MAS NMR results demonstrate that the interaction between Na ions and framework of the seed-assisted MWW product is strengthened after calcination, which makes the exchange of Na species difficult. Alternatively, ammonium exchange upon the as-made sample is an effective method to remove Na species, which improves the micropore volume, external surface area, and acid amount of the seed-assisted MCM-49.

ZSM-11 zeolite is an important microporous material that has wide application prospects in various petrochemical and chemical processes. Herein, we reported a simple method to significantly reduce the crystallization time of ZSM-11 zeolite by adding N-methyl-2-pyrrolidone (NMP) as the ‘promoter’. The effects of various synthetic parameters on the NMP-assisted synthesis of ZSM-11 zeolite were also investigated. Subsequently, characterization techniques such as SEM, XRD, XRF, FT-IR, TEM-EDS, TG and 13C NMR were used to unveil the acceleration mechanism of NMP. It was revealed that NMP can facilitate the bonding of TBA+ with aluminosilicate by breaking the hydration layer around them, thus reducing the apparent nucleation activation energy and accelerating the nucleation process. Meanwhile, we used N-ethyl-2-pyrrolidone (NEP) instead of NMP as the promoter to verify the acceleration mechanism. In addition, the fast-synthesized ZSM-11 zeolite exhibited comparable composition, hydrothermal stability, and catalytic performance to conventionally synthesized counterparts.

CO2-oxidative dehydrogenation of propane (CO2-ODHP) provides a promising route for propylene production. Sufficient propane conversion and propylene selectivity remain a great challenge due to the difficulty in activating inert propane and CO2 simultaneously. Herein, a Sn doped CeO2 supported Pt (Pt/Sn-CeO2) catalyst in CO2-ODHP reaction is reported. Sn doping appears to kill two birds with one stone for propane and CO2 activation. On the one side, it increases the electron density of Pt species via PtSn alloy formation, promoting propane adsorption and C−H bond cleavage. On the other side, it enhances oxygen vacancy concentrations of CeO2 support, facilitating CO2 dissociation. A higher propylene selectivity (63.9 % vs 22.3 %) was obtained on 0.1 wt % Pt/1.0 wt % Sn-CeO2 than that on 0.1 wt % Pt/CeO2 with a comparable propane conversion (15.1 % vs 14.3 %) at 550 °C after 240 min on stream. This work provides a reference for designing efficient catalysts.

Introduction of mesopore is critical for applications where mass-transport limitations within microporous networks, especially for zeolite with one-dimensional microporous network, hinder their performance. Generally, the creation of mesopore in zeolite through a direct synthesis route is strongly dependent on complex and expensive organic molecules, which limits their commercial application. Here, we successfully developed a facile synthesis route for preparing ZSM-48 zeolite (*MRE topology) with ultralarge mesoporosity in which typical 1,6-hexylenediamine worked as an organic structure-directing agent, innovatively assisted by a simple crystal growth modifier (tetraethylammonium bromide, TEABr). The working mechanism of TEABr during crystallization was revealed and proposed on the basis of TEM, thermal gravimetric mass spectrum, and 13C cross-polarization magic angle spinning NMR characterization results. In the process, TEA+ ions preferentially interacted with the solid during the induction period, which effectively suppressed the aggregation of ZSM-48 primary nanorods. As a result, ultralarge mesoporosity of 0.97 cm3·g-1 was constructed through the stacking of the nanorods. Interestingly, TEA+ ions only took part in the crystallization process and did not occlude in the pores of the final zeolites indicating its potential in recyclability. Moreover, similar synthesis strategy could be applied for the preparation of hierarchical ferrierite zeolites, implying the universality of this strategy. Compared with a conventional sample, ZSM-48 zeolite with ultralarge mesoporosity showed superior catalytic stability in the m-xylene isomerization reaction due to its significantly enhanced diffusion and mass transfer capability, which will greatly promote the practical application of ZSM-48 zeolite.

Ferrierite (FER) zeolite has been successfully synthesized within 2–3 h through microwave assisted crystallization without using organic structure directing agent. Crystallization temperature and seed content were found to be two of the key factors. XRD patterns and SEM images of the samples taken at different periods of time revealed that seeds were only partially dissolved during the crystallization process and silicate (alumino) species in the gel grew upon the surface of the partially dissolved seed. A core-shell zeolite growth model was proposed. Compared with original seed zeolite, as-synthesized FER zeolite had more regular morphology and larger particle size. The FER crystal size could be controlled in the range of 0.4–3.0 μm by adjusting the particle size of the seeds. FER obtained through microwave assisted rapid synthesis showed similar catalytic performance in 1-butene skeletal isomerization with the FER obtained through conventional hydrothermal synthesis.

Hollow zeolites are widely investigated as catalysts and nanoreactors in the petrochemical and fine chemical industries because they offer fast mass transfer along with a hollow core for encapsulation of functional components. However, the synthesis of hollow zeolites still remains a significant challenge due to the complexity and restrictions of currently available synthetic strategies. Herein, a direct and efficient approach for constructing hollow zeolite beta with simultaneously a low Si/Al ratio (∼19) and high yield (above 89 wt%), based on some cost-effective and recyclable pentacyclic lactams, is reported. Meanwhile, a unique formation mechanism involving the selective decomposition of the tetraethylammonium (TEA+) cations locating at internal Al sites, and dissolution and recrystallization of the internal activated aluminosilicate species from the core to outer surface is proposed for the first time. In addition, the hollow beta catalyst exhibits better catalytic performance in the alkylation of benzene with isobutylene compared with the conventional solid beta sample.

The crystal size of zeolites has an enormous effect on zeolite properties and catalytic performance. Herein, a direct hydrothermal synthesis method to control the size of FER zeolites, by using piperidine (PI) as the structure directing agent (SDA) assisted by cetyltrimethyl ammonium bromide (CTAB), is developed. All the resultant FER samples possess high crystallinity, while their crystal sizes range from ∼100 nm to ∼2 μm. The effect of CTAB in the synthesis gel on the physicochemical properties, especially the crystal sizes, and the 1-butene skeletal isomerization performance of FER zeolites was investigated. The addition of CTAB has an obvious effect on the formation of FER zeolites, and the hydrophobic tail of CTAB can restrict the excessive growth of FER leading to the formation of highly crystallized FER with various crystal sizes. The nano-scale FER shows higher initial 1-butene conversion and better catalytic stability than micron-sized FER, which is mainly related to the superior accessibility of acid sites, larger external surface area, and less diffusion limitation due to the decrease of the crystal size. This novel synthesis strategy provides an effective way to regulate the size and performance of FER zeolites, and a new function of CTAB in the synthesis of zeolites is developed.

It may be an important route to improve the alkylation performance of MCM-22 zeolite by regulating the Al siting during the synthesis, as the liquid alkylation of benzene with ethylene mainly occur on the acid sites in the surface pockets and supercages of MCM-22. Here, the Al siting has been successfully adjusted by introducing additional anion in the hydrothermal synthesis of MCM-22 using piperidine as the structure directing agent. The effect of the additional anion in the synthesis precursor on the physiochemical property, especially the Al siting, and alkylation performance of MCM-22 zeolite was investigated. The morphology of products tends to be irregular lamellar structure when Cl−, PO43−, or SO42− are present in the synthesis gel. Although H-MCM-22-PO43− and H-MCM-22-SO42− show less acid site concentration than H-MCM-22, they exhibit obviously higher conversion of ethylene than H-MCM-22. This can be attributed to that more Al species are oriented to T2 sites located in the pockets or supercages by virtue of the presence of PO43− or SO42− in the synthesis gel. The novel synthesis strategy may provide an alternative way to modify the performances of MCM-22 and even other zeolites.

A series of FER/MOR composite zeolites were synthesized through seed-assisted organic template free route. And the FER/MOR composite zeolites exhibited specific catalytic performance in the dimethyl ether carbonylation to methyl acetate reaction. SEM images revealed that the FER circle plates grew along the surface of MOR bundle aggregates. Good pore connectivity and high adsorption capacity were observed on FER/MOR on basis of the hyperpolarized (HP) 129Xe NMR spectra and propane adsorption results, which was different from its corresponding mechanical mixture. Quantitative analysis of 1H MAS NMR spectra using pyridine as probe revealed that the total Brϕnsted acid density in FER/MOR, especially that in 8 MR channel, was higher than that of single zeolites. High Brϕnsted acid density and good pore connectivity guaranteed the superior performance of FER/MOR in DME carbonylation reaction.

A novel route involving self-metathesis of 1-butene under mild conditions that gave high yields of ethene and hexene was proposed. The results of thermodynamic analysis revealed that the Gibbs energy of the target Metathesis I reaction (1-butene → ethene + 3-hexene) was much higher than that of the main side Metathesis II (1-butene + 2-butene → propene + 2-pentene). Suppression of 1-butene double-bond isomerization was the key step to increase the selectivity for the target olefin in the reaction network. The relationship between the catalytic performance and support nature was investigated in detail. On basis of H2-TPR, UV-Vis spectra and HRTEM results, an alumina (Al2O3) support with large surface area was beneficial for the dispersion of molybdenum (Mo) species. Both suitable acidity and sufficient Mo dispersion were important to selectively promote the self-metathesis reaction of 1-butene. On the optimal 6Mo/Al2O3 catalyst, 1-butene conversion reached 47% and ethene selectivity was as high as 42% on the premise of good catalytic stability (80 °C, 1.0 MPa, 3 h−1).

Zeolite beta, an important catalytic material widely applied in the petrochemical field, is typically prepared under hydrothermal conditions. However, it usually suffers from the drawback of relatively long crystallization time. Herein, we show that the crystallization rate of zeolite beta can be accelerated by a factor of as much as about nine via the addition of the low-toxic and cost-effective pentacyclic lactam N-methyl-2-pyrrolidone (NMP) as a ‘promoter’. Using characterization techniques, we demonstrate that the pentacyclic lactam induces the fast formation of secondary building units (SBUs) and enhances the formation rate of the activated TEA+ species responsible for the nucleation of beta crystals. More importantly, the as-synthesized beta exhibited high product yield (above 85 wt%) and good performance in the direct amination of isobutene (i-C4H8) to tert-butylamine reaction.

MCM-49 zeolite with a three-dimensional MWW framework was directly synthesized using low-toxicity and cost-effective cyclohexylamine (CHA) as an organic structure-directing agent under hydrothermal conditions. Compared with the traditional hexamethyleneimine template, the interaction between CHA with the framework was weaker and more CHA molecules occupied the surface pockets and supercages of as-synthesized MCM-49 zeolite. The obtained sample showed good catalytic performance in the liquid phase alkylation reaction of benzene with ethylene.

The synthesis of ferrierite (FER) zeolite using piperidine as an organic structure-directing agent was investigated. X-ray diffraction, X-ray fluorescence, N2-adsorption, and scanning electron microscopy were used to characterize the crystal phases, textural properties, and particle morphologies of the zeolite samples. The crystallization behavior of the FER zeolite was found to be directly related to crystallization temperature. At 150 °C, pure FER phase was observed throughout crystallization. At 160–170 °C, MWW phase appeared first and gradually transformed into FER phase over time, indicating that the FER phase was thermodynamically favored. In the piperidine-Na2O-H2O synthetic system, alkalinity proved to be the crucial factor determining the size and textural properties of FER zeolite. Furthermore, the obtained FER samples exhibited good catalytic performance in the skeletal isomerization of 1-butene.

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.

Shaped binderless ZSM-11 zeolite catalysts were synthesized via a dry-gel conversion technique from 70ZSM-11/30SiO2mix extrudates. 1,6-hexanediamine combined with tetrabutylammonium bromide was proved to be the best structure directing agent for the synthesis of the binderless ZSM-11 catalyst, without adding other alkaline materials. The 70HZSM-11/30SiO2mix serials materials crystallized for different times were detected by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy–energy dispersive spectroscopy (STEM–EDS) techniques, and so on. In order to investigate the possible crystallization mechanism, the textural and structural properties of 70HZSM-11/30SiO2mix serials samples were further characterized by N2 adsorption–desorption. Acid properties were determined by temperature-programed desorption of NH3 (NH3-TPD) and pyridine adsorption-infrared (Py-IR) measurements. In the alkylation of benzene with dimethyl ether, the serials catalysts exhibited different benzene conversions. 70HZSM-11/30SiO2mix showed the lowest benzene conversion while sample 70HZSM-11/30SiO2mix-6.5h synthesized only for 6.5h displayed a higher benzene conversion, even higher than the value over 70HZSM-11/30Al2O3mix. Extending the crystallization time, the obtained samples displayed the increased benzene conversion in general under the same reaction conditions. In the end, the relation of physicochemical properties with the reaction performance was investigated.

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 cm 3 /g). Compared with commercialized ferrierite zeolite, hierarchical nano-ferrierite aggregates showed better catalytic stability and product selectivity in the 1-butene skeletal isomerization reaction.

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 conver-sion 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 (NH 3 )/ n (i-C 4 H 8 ) 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 cata-lyst development and reaction condition optimization.

A shaped binderless and two binder-containing ZSM-11 zeolite catalysts were prepared and char-acterized by powder X-ray diffraction, N 2 adsorption-desorption, and pyridine adsorption-infrared measurements. The binderless catalyst was synthesized using a dry-gel conversion technique, in which 1,6-hexanediamine and tetrabutylammonium bromide were used as structure-directing agents and no other alkaline materials were added. The catalytic performance of the zeolites in the direct amination of isobutene to tert -butylamine was evaluated in a fixed-bed reactor. By virtue of its high crystallinity as well as its good mechanical strength, the shaped binderless ZSM-11 catalyst showed a higher rate of formation of tert -butylamine than did the binder-containing catalysts.

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, H 2 -TPR and XPS spectra were applied to reveal the state of the Zn species on different catalysts. Quantitative results of NH 3 -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 C 2 C 4 light alkane in cofeeding reaction. Ion exchange and impregnation modes were beneficial for the formation of Zn O Zn bridging species in the micropore channel. Zn O Zn bridging species was found to increase the promoting effect of cofeeding n -butane with methanol on aromatics selectivity.

Zeolites are crystalline microporous aluminosilicates with periodic arrangements of cages and well-defined channels, which make them very suitable for separating ions of different sizes, and thus also for use in battery applications. Herein, an ultra-thin ZSM-35 zeolite flake was introduced onto a poly(ether sulfone) based porous membrane. The pore size of the zeolite (ca. 0.5 nm) is intermediary between that of hydrated vanadium ions (0.6 nm) and protons (0.24 nm). The resultant membrane can thus be used to perfectly separate vanadium ions and protons, making this technology useful in vanadium flow batteries (VFB). A VFB with a zeolite-coated membrane exhibits a columbic efficiency of99 % and an energy efficiency of81 % at 200 mA cm(-2), which is by far the highest value ever reported. These convincing results indicate that zeolite-coated membranes are promising in battery applications.

A new synthetic protocol of hollow structured Beta zeolite via interzeolite conversion with the assistance of N-methyl-2-pyrrolidone (NMP) was reported in this work. The synthesis conditions were optimized to obtain the pure and hollow Beta zeolite from the USY zeolite. In comparison, the solid Beta zeolite with low yield was obtained in the absence of NMP. The important factors in successful synthesis of hollow Beta zeolite were the usage of USY zeolite and the addition of NMP. On the basis of the characterization data, such as XRD, SEM, TEM, and 29Si/27Al MAS NMR, a formation mechanism for the synthesis of hollow Beta zeolite from USY was proposed and discussed. The silicon species in the parent USY crystals dissolved firstly, afterwards the primary solid Beta crystals with high SiO2/Al2O3 molar ratio were generated at the earlier stage, finally, the hollow Beta zeolite was formed due to the dissolution-recrystallization of the crystalline nutriments located in the core of the primary solid Beta crystals as well as the consumption of USY. The catalytic performance of alkylation of benzene with isobutylene demonstrated that the obtained hollow Beta catalyst exhibited excellent isobutylene conversion and tert-butylbenzene selectivity against the solid Beta synthesized from an amorphous silica/alumina.

A zeolite composite membrane (ZCM) was designed and fabricated via a simple versatile and scalable method. A thin layer of ZSM-35 flakes with pore size between hydrated protons and vanadium ions was fixed on the poly(ether-sulfone)/sulfonated poly(ether-ether-ketone) (PES/SPEEK) porous substrate by in-situ interfacial polymerization. The ZSM flake layer can perfectly separate hydrated vanadium ions and protons, therefore, show very impressive performance for vanadium flow batteries (VFBs). As a result, a VFB assembled with an optimized ZCM exhibited a columbic efficiency more than 99% and energy efficiency of over 91% at a current density of 80 mA cm-2, which is among the highest performance ever reported. Furthermore, the energy efficiency can reach 81.6% at a very high current density of 200 mA cm-2 and keep stable for 1000 cycles at a current density of 180 mA cm-2. This method opened a door toward the large-scale production of highly selective composite membranes for flow batteries.

A series of Mo-based catalysts for 1-butene metathesis to propene were prepared by supporting Mo species on SBA-15 premodified with alumina. The effects of the method of introduction of the alumina guest to the host SBA-15 on the location of the Mo species and the corresponding metathesis activity were studied. As revealed by N-2 adsorption isotherms and TEM results, well-dispersed alumina was formed on the pore walls of SBA-15 if the ammonia/water vapor induced hydrolysis (NIH) method was employed. The Mo species preferentially interacted with alumina instead of SBA-15, as evidenced by X-ray photoelectron spectroscopy, time-of-flight secondary-ion mass spectrometry, and IR spectroscopy of adsorbed pyridine. Furthermore, new BrOnsted acid sites favorable for the dispersion of the Mo species and low-temperature metathesis activity were generated as a result of the effective synergy between the alumina and SBA-15. The Mo/Al2O3@SBA-15 catalyst prepared by the NIH method showed higher metathesis activity and stability under the conditions of 120 degrees C, 0.1MPa, and 1.5h(-1) than catalysts prepared by other methods.

Micro–mesoporous composites were prepared by post-treatment of MCM-49, and applied to degrade low-density polyethylene (LDPE) and polypropylene. It was found that LDPE degradation mainly occurred on the external surface of MCM-49. The highest activity was achieved over the sample with large external surface area and relatively high acid site concentration. The main products of LDPE degradation were liquefied petroleum gas and gasoline range hydrocarbons, and the product selectivity depended on the acid site concentration.

A series of Mo/Al 2 O 3 catalysts were prepared and evaluated in the consecutive metathesis of 1-butene and isobutene. The correlations between the states of Mo species and Metathesis I (2-C 4 = + 1-C 4 = → C 3 = + 2-C 5 = ), Metathesis II (2-C 4 = + i -C 4 = → C 3 = + i -C 5 = ) were discussed in detail. It was found that Metathesis I and Metathesis II followed different deactivation rate due to the differences in active sites. Metathesis I was more acidity-sensitive and it was suppressed when alumina was calcined at high temperature due to the decrease of acid sites. Metathesis II kept relative good catalytic stability and high calcination temperature was beneficial to increase the ratio of isopentene in pentene fraction. As revealed by the XPS and reductive pretreatment results, different C 4 olefin molecules on the same Mo-based catalyst exhibited different metathesis activity and partially reduced Mo V (or Mo IV ) species from octahedrally coordinated Mo(O) species contributed to the selective promotion of Metathesis II.

The aromatization of light alkenes in liquefied petroleum gas (LPG) with and without dimethyl ether (DME) addition in the feed was investigated on a modified ZSM-5 catalyst. The results showed that under the given reaction conditions the selectivity of alkenes to high-octane gasoline blending components was markedly enhanced and the formation of propane and butanes was greatly suppressed with the addition of DME. It was also found that the distribution of C5+ components was changed a lot with DME addition into the LPG feed. The formation of branched hydrocarbons (mainly C-6-C-8 i-paraffin) and multi-methyl substituted aromatics, which are high octane number gasoline blending components, was promoted significantly, while the content of n-paraffins and olefins in C5+ components was decreased obviously, indicating that in addition to the oligomerization, cracking, hydrogen-transfer and dehydrogenation-cyclization of alkenes, the methylation of the formed aromatics and olefins intermediates also plays an important role in determining the product distribution due to the high reactivity of surface methoxy groups formed by DME. And this process, in combination with the syngas-to-methanol/DME technology, provides an alternative way to the production of high-octane gasoline from coal, natural gas or renewable raw materials.

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 H-1 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. (C) 2013 Elsevier B.V. All rights reserved.

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/H 100 Na 0 M-30Al catalyst with a support of full sodium exchange degree exhibited the highest propene yield.

A novel route with high yields of propene and isopentene on the basis of consecutive metathesis of 1-butene and isobutene is proposed. Two series of Mo-based catalysts supported on gamma-Al2O3 and HMOR-Al2O3 composite materials were prepared and evaluated in a fixed bed reactor. Experimental results revealed that three interesting reactions occurred on the catalysts, i.e. 1-C-4(-) -> 2-C-4(-) (Isomerization I), 2-C-4(-)+1-C-4(-) -> C-3(-)+2-C-5(-) (Metathesis I), 2-C-4(-)+i-C-4(-) -> C-3(-)+i-C-5(-) (Metathesis II). Isomerization I was the prerequisite step of the following two metathesis reactions. Metathesis I was more acidity-sensitive and it could happen at low temperatures provided that the catalyst acidity was sufficient. Metathesis II, as the targeted reaction, was proved to be more temperature-sensitive, and high reaction temperatures were preferable for the metathesis of 2-butene and isobutene. 6Mo/Al2O3 exhibited the best catalytic metathesis performance among the candidate catalysts in the consecutive metathesis of 1-butene and isobutene. Furthermore, isopentene selectivity could be highly enhanced through the steam treatment of gamma-Al2O3 support. The modifications of alumina support led to the different distribution of Mo species and the formation of more Mo species in octahedral state may contribute to the preferential activation of Metathesis II. (C) 2012 Elsevier B.V. All rights reserved.

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. 2Zn–4Mg/AT-Z5 catalyst prepared by Mg addition with successive Zn introduction on modified ZSM-5 support showed optimal product distribution in 1-hexene aromatization reaction.

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 H(2)O/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, N(2) adsorption,TGA and TPO-MS results, well crystallized ITQ-13 zeolites were obtained at low H(2)O/Si ratios (7 similar to 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. (C) 2009 Published by Elsevier Inc.