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The chemical liquid deposition modification can decorate the pore aperture size by external surface deposition, which is a very efficient way to further improve the shape‐selective performance of zeolites. Here, SAPO‐34 zeolite was modified with silica by chemical liquid deposition, and then was applied in MTO reaction. It was found the Brønsted acid of SiO2‐modified SAPO‐34 zeolite increased, mainly due to the transformation from Al‐OH to Si‐OH‐Al, which can promote the selectivity to light olefins in MTO reaction. After the chemical liquid deposition, the silica located on the external surface of SAPO‐34 zeolite, reduces the apparent diffusion coefficient of propylene, which will restrain the formation and diffusion of propylene. So the selectivity to ethylene and the ratio of ethylene to propylene were significantly increased over the SiO2‐modified SAPO‐34 in the MTO reaction. Furthermore, the increase of the reactive sites can prolong the lifetime of catalyst effectively. [ABSTRACT FROM AUTHOR]

SAPO‐34 is an important member in the family of zeolites, which shows excellent catalytic activity in MTO reaction, but suffers from the diffusion bottleneck. To overcome the diffusion problem, porogen was added to generate meso/macro pores in SAPO‐34 zeolite. In this work, amphipathic molecules were designed as CSDA to synthesize a tri‐level hierarchically porous SAPO‐34, and the introduction of CSDA could promote the Si atoms incorporating into the AlPO4 framework, change the morphology of particles and decrease the acidity of prepared SAPO‐34 zeolite. The prepared SAPO‐34 catalyst exhibits higher selectivity of C2H4 and C3H6 in the MTO reaction than the conventional SAPO‐34 zeolite. The morphology and the microstructure of the prepared samples vary with the carbon chain of the amphipathic molecules due to the matching between amphipathic molecules and topological structure of CHA. [ABSTRACT FROM AUTHOR]

The kaleidoscopic applications of zeolite catalysts (zeo-catalysts) in petrochemical processes has been considered as one of the major accomplishments in recent decades. About twenty types of zeolite have been industrially applied so far, and their versatile porous architectures have contributed their most essential features to affect the catalytic efficiency. This review depicts the evolution of pore models in zeolite catalysts accompanied by the increase in industrial and environmental demands. The indispensable roles of modulating pore models are outlined for zeo-catalysts for the enhancement of their catalytic performances in various industrial processes. The zeolites and related industrial processes discussed range from the uni-modal micropore system of zeolite Y (12-ring micropore, 12-R) in fluid catalytic cracking (FCC), zeolite ZSM-5 (10-R) in xylene isomerization and SAPO-34 (8-R) in olefin production to the multi-modal micropore system of MCM-22 (10-R and 12-R pocket) in aromatic alkylation and the hierarchical pores in FCC and catalytic cracking of C4 olefins. The rational construction of pore models, especially hierarchical features, is highlighted with a careful classification from an industrial perspective accompanied by a detailed analysis of the theoretical mechanisms. [ABSTRACT FROM AUTHOR]

The flow fluidized bed reactor was applied to methanol-to-olefins research after some necessary improvements of traditional fixed flow bed reactor. Methanol decomposition probability before contacting the catalysts could be decreased to the lowest level by adjusting the pre-heater temperature and changing the material of descending feed pipe. The results of device repeatability and material balance investigation showed this reactor had good data repeatability and could achieve 97% of mass balance. The experiments about the effect of reaction temperature and water/methanol mass ratio on main products distribution were carried out based on the SA-PO-34 molecular sieve catalysts. The results of temperature experiments showed the temperature increase improved the ethylene selectivity greatly. As well as speed up the coke formation, the methanol conversion was almost 100%, and the C2= ~C4= selectivity could be over 90%. For ethylene as main product, the reaction temperature was suggested to choose 500 °C with C2= / C3= molar ratio of 1. 5. For propylene as main product, the reaction temperature of 450~470 °C should be chosen with C2= / C3= molar ratio of 0. 9~1. 1. The results of water/methanol mass ratio experiment showed that increasing the water content could not only delay the coke formation rate, but also increase the ethylene selectivity remarkably, which could put the C2= / C3= molar ratio up to more than 2. 0. Too much water would increase the energy consume and the load of reactor and products separator unavoidably no matter for ethylene or propylene as main products. Therefore, water/methanol mass ratio of 0. 25~0. 5 was advocated. [ABSTRACT FROM AUTHOR]

The unsupported Mo–Co–K sulfide catalysts promoted by La were prepared through ultrasonic technology in non-aqueous medium and its performances for the synthesis of mixed alcohols from syngas were also investigated. The results showed that the catalysts promoted by La exhibited higher CO conversion and selectivity to ethanol than the unsupported Mo–Co–K sulfide catalyst without addition of La did under identical reaction conditions. The catalysts were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Raman, and X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

Both γ-Al2O3 and MgAl2O4 spinel used as support for the palladium–lanthanum catalyst in the preparation of 2,6-diisopripylaniline (2,6-DIPA) by the gas-phase amination of 2,6-diisopropyl phenol (2,6-DIPP) were studied. The bulk and surface properties of Pd–La/Al2O3 and Pd–La/MgAl2O4 catalysts were characterized by XRD, BET, NH3-TPD, pyridine-IR, and XPS techniques. The replacement of Al2O3 with MgAl2O4 spinel in the palladium–lanthanum supported catalyst not only neutralized some strong acid sites, but also transformed them into relatively weaker acid sites according to the NH3-TPD and pyridine-IR results. The XPS analysis showed that the MgAl2O4 spinel support improved the reduction of PdO. All these factors increased the catalytic performance for gas-phase amination of 2,6-DIPP. On the Pd–La/MgAl2O4 catalyst, under the LHSV 0.3 h-1, the highest conversion of 2,6-DIPP was 98.5%, the highest selectivity and the highest yield of 2,6-DIPA was 88.9% and 87.5%, respectively. The whole run time of Pd–La/MgAl2O4 catalyst was up to 400 h, and the yield of 2,6-DIPA after 200 h reaction was still more than 80%. [Copyright &y& Elsevier]

Abstract: A series of HZSM-5 catalysts with various phosphorus (P) loadings (0–2.1 wt%) were prepared by impregnation of phosphoric acid. The effect of phosphorus on the structure and acidity of HZSM-5 catalyst and its catalytic performance for C4-olefin cracking reactions were studied by XRD, N2 adsorption, NMR, NH3-TPD, FTIR spectra of adsorbed pyridine, TGA, and catalytic tests. The results revealed that the structure of HZSM-5 samples was scarcely damaged with increasing P loadings, whereas strong acidity of them was weakened mainly due to the dealumination of tetrahedral framework aluminum (TFAL) after P modification. The results of C4-olefin cracking reactions showed a great increment of the propylene selectivity for the P-modified HZSM-5 with the optimal propylene yield at a P-loading of 1.5 wt%. It was found that both coke deposition and dealumination were the crucial factors in the deactivation of HZSM-5. Due to the dealumination and thus elimination of part of the strong acid sites, P-modified HZSM-5 showed excellent anticoking ability. TFAL of P-modified HZSM-5 changed mainly to distorted tetrahedral aluminum (DTAL) or pentacoordinated aluminum (PAL) species in the process of C4-olefin cracking reaction, which can still act as stable active centers for C4-olefin cracking to produce propylene. Thus, P-modified HZSM-5 shows excellent stability. A possible reaction pathway for C4-olefin cracking reactions has been proposed based on the reaction results. [Copyright &y& Elsevier]

Abstract: A series of MCM-41-supported vanadia catalysts (VO x /MCM-41) with the vanadium loading of 0.5–3.0mmol/g were studied with respect to their performance in the dehydrogenation of ethylbenzene to styrene in the presence of CO2. Structural and textural characterizations of the catalysts were performed by means of N2 adsorption, X-ray diffraction (XRD), UV–vis and Raman spectroscopy, and temperature-programmed reduction (TPR). These catalysts were found to be effective for the dehydrogenation reaction. The dispersity and the nature of the vanadium species depend strongly on the V loading, so does the catalyst activity. It was confirmed that, during the dehydrogenation of ethylbenzene with CO2 over VO x /MCM-41, two reaction pathways, i.e., direct oxidative dehydrogenation of ethylbenzene with CO2 (one-step pathway) and reaction coupling of simple dehydrogenation of ethylbenzene with the reverse water–gas shift (two-step pathway) occurred. Forty-one percent of styrene could be produced by the one-step pathway. The promoting effect of CO2 in ethylbenzene dehydrogenation has been attributed to different reaction pathways in the presence and in the absence of CO2 as well as a higher concentration of active V5+ species on the catalyst surface under CO2 atmosphere. The MCM-41-supported vanadia is more active than the vanadia catalyst supported on conventional amorphous SiO2. [Copyright &y& Elsevier]

The mesoporosity development in high silica HZSM-5 was carried out by alkaline desilication treatment and soft template method, and its relationship with the catalytic performance of the modified catalysts in methanol-to-propylene reaction was studied. High propylene selectivity (42.2%) and propylene/ethylene ratio (10.1) were observed on the high silica HZSM-5 catalyst modified by alkaline desilication. The enhanced catalytic performance can be attributed to the newly created open mesopores on the surface of the zeolite crystals together with the low Brønsted acidity. A greater amount of mesoporosity could be readily formed in HZSM-5 crystals via the soft template route. However, the mesopores formed in this method are randomly distributed in the zeolite crystals and play a minor role in the molecular transport of the reaction, so the improvement in propylene selectivity and propylene/ethylene ratio of the catalyst is less evident. The higher propylene selectivity and propylene/ethylene ratio on modified HZSM-5 (especially by alkaline treatment) than unmodified HZSM-5 could be also related to different contributions of the methylaromatics route and olefins methylation/cracking route in MTP reaction. [Copyright &y& Elsevier]

Abstract: Enhanced catalytic performance for C4 olefin cracking to propene and ethene was observed on phosphorus-modified HZSM-5 treated in steam at 1073 K. Combining the results of 31P and 27Al MAS NMR, D2/OH exchange, NH3-TPD, and catalytic performance of the catalysts, it seems reasonable to conclude that new and hydrothermally stable acid sites are formed during the steam treatment through the interaction of phosphorus species with silanol nests exposed on the zeolite due to dealumination. It is tentatively suggested that the incorporated phosphorous species stabilized by some nonframework aluminum species are responsible for both the enhanced acid stability and the significantly improved catalytic performance for the cracking of C4 olefin. [Copyright &y& Elsevier]

Abstract: The effect of tin on the structure, acidity, and water adsorption property of Nb2O5/α-Al2O3 catalyst and on this catalyst''s performance for ethylene oxide (EO) hydration were studied by XRD, Raman spectroscopy, NH3-TPD, IR of pyridine and of H2O adsorption, and catalytic tests. Characterization results revealed that the density of acidic sites decreased with the addition of tin and with increasing Sn/Nb ratio in the cases studied, whereas the acidity exhibited minimum strength at . The IR of water adsorption indicated that addition of tin significantly enhanced the water adsorption property of the catalyst. The catalytic tests revealed that monoethylene glycol (MEG) selectivity increased from 89.8% of the Nb2O5/α-Al2O3 catalyst to 94.0% of the tin-promoted catalyst maintaining the EO conversion at 99.7%, and the catalyst exhibited excellent stability. The enhanced water adsorption property of the tin-promoted catalyst is proposed to be responsible for the significant improvement in MEG selectivity. [Copyright &y& Elsevier]