Porous ZSM-5 Research Articles

Catalytic conversion of methanol to propylene over high-silica mesoporous ZSM-5 zeolites prepared by different combinations of mesogenous templates

The effects of mesoporosity on catalytic performance of methanol to propylene (MTP) reaction have been investigated by using a series of high-silica nanosized hierarchical ZSM-5 zeolites with different degrees of mesoporosity, which were hydrothermally synthesized in the presence of different mesogenous templates, i.e., TPOAC, CTAB, and their combinations. The results were compared with a conventional microporous ZSM-5 catalyst. The prepared catalysts were characterized by XRD, FE-SEM, BET, NH3-TPD and FT-IR techniques. Meanwhile, their catalytic activities were evaluated in a fixed-bed reactor under atmospheric pressure, 460 °C and WHSV of 1h−1. Compared with conventional catalyst, the nanosized hierarchical porous ZSM-5 templated with a mixture of 75% TPOAC and 25% CTAB displayed reliable MTP catalytic lifetime (76 h) as well as sufficiently high propylene selectivity (43.65%) and propylene to ethylene (P/E) ratio (4.05), which were predominately attributed to its optimal combination of acidity and porosity.

High activity and stability in the cross-coupling of aryl halides with disulfides over Cu-doped hierarchically porous zeolite ZSM-5

A Cu-doped zeolite ZSM-5 (Cu-ZSM-5-M) with a micro-meso-macroporous structure was directly synthesized, and it exhibits excellent catalytic activity and good recyclability in the cross-coupling of aryl halides with diphenyl disulfides. This feature should be attributed to the structural characteristics of meso-macropores and homogeneous dispersion of active Cu(δ+) (δ < 2) species in Cu-ZSM-5-M.

Promoting effects of MgO and Pd modification on the catalytic performance of hierarchical porous ZSM-5 for catalyzing benzene alkylation with methanol

The dual modification catalyst (MgO and Pd) could effectively combine the effect of MgO for suppressing the side reaction of methanol to olefins and the effect of Pd for inhibiting the formation of ethylbenzene and coke.

Alkylation of benzene with methanol over hierarchical porous ZSM-5: synergy effects of hydrogen atmosphere and zinc modification

The introduction of ZnO could improve the activity of ZSM-5 and the hydrogen atmosphere could suppress the dehydrogenation of ZnOH+.

Mercaptosilane-assisted synthesis of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials and their enhanced hydrogenation properties.

A novel catalyst that consists of sub-nanosized Pt particles within hierarchically porous ZSM-5/SBA-15 materials was synthesized. This catalyst exhibited high stability and a hierarchically porous structure of a micro-mesoporous composite and possessed a high density of active sites by confinement of sub-nanosized Pt particles within small-pore zeolites, showing high catalytic properties for the hydrogenation of 1,3-butadiene and cyclooctadiene at room temperature.

Ordered mesoporous ZSM-5 employing an imidazolium-based ionic liquid.

Hierarchically porous ZSM-5 was achieved by using a simple bottom-up strategy combining zeolite seeds with imidazolium-based ionic liquids. The bimodal ZSM-5 with hexagonal arranged mesopores (3 nm) shows important activity in the acid catalysis of bulky compounds relative to conventional ZSM-5.

A defiltration control method of pressurized liquid in zeolite ZSM-5 by silanol introduction

The defiltration performance of the zeolite ZSM-5/liquid system can be effectively modified by sodium hydroxide (NaOH) additive with various concentrations. The infiltration of NaOH aqueous solutions increases the density of silanol (Si-OH) groups on inner surface of the porous ZSM-5, converting the originally hydrophobic surface to hydrophilic and ceasing the liquid outflow. More importantly, the defiltration performance of the system can be adjusted independently without affecting the working pressure of the system. This unique infiltration associated hydrophobic-hydrophilic transition of nanopore surface leads the ZSM-5 based liquid system to an efficient energy absorption system instead of a super-elastic molecular spring.

Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and steam-assisted-crystallization method is used to synthesize hierarchically porous zeolite ZSM-5 with varied Si/Al malar ratios. X-ray diffraction (XRD), N2 physisorption, NH3-temperature programmed desorption (TPD), scanning electronic microscopic (SEM) measurement and Fourier transform infrared (FT-IR) are employed to characterize the structure and acidity of both hierarchically porous zeolites and their conventional counterparts. The method is found to be applicable to ZSM-5 with molar ratios of Si/Al from 20 to 180. The ZSM-5 zeolites are used as catalysts for benzene methylation at 460°C to investigate the effect of additional porosity and Si/Al ratios. At low Si/Al ratios, the benzene conversions over conventional and hierarchical ZSM-5 are close, and selectivity to toluene is high over hierarchical ZSM-5. It is found that hierarchical porosity markedly enhances the utility of zeolite and the selectivity towards xylenes via improved mass transport at higher Si/Al ratios. Under an optimized hierarchical ZSM-5 catalyst, xylene selectivity reaches 34.9% at a Si/Al ratio of 180.

Catalytic activity and stability of porous Co–Cu–Mn mixed oxide modified microfibrous-structured ZSM-5 membrane/PSSF catalyst for VOCs oxidation

Porous microfibrous-structured ZSM-5 membrane catalyst possesses excellent catalytic activity and stability.

Synthesis of hierarchically porous ZSM-5 zeolites by steam-assisted crystallization of dry gels silanized with short-chain organosilanes

Nanounits gradually appear within silanized dry gels and assemble by the same orientation into self-sustaining zeolite aggregates with large mesopores.

Synthesis of highly accessible ZSM-5 coatings on SiC foam support for MTP reaction

Highly accessible porous ZSM-5 coating with high loading and high adherence was successfully grown on SiC foam support using a two-step coating and steam-assisted crystallization process. The zeolite precursor gel pre-coated on the SiC foam surface and existed in the upper mixed coating layer functioned as a binder to firmly bond the SiC support and the pre-coated zeolite crystals with the formation of a dense ZSM-5 transition layer. The high porosity was achieved from the pre-coated zeolite crystals. The ZSM-5/SiC foam composite catalyst prepared by the proposed method showed higher propylene selectivity and propylene to ethylene (P/E) ratio, lower C1–C4 saturated hydrocarbons and aromatics and as well as higher stability in comparison to that prepared by conventional in situ hydrothermal process in methanol to propylene reaction.

A facile synthesis of iron functionalized hierarchically porous ZSM-5 and its visible-light photocatalytic degradation of organic pollutants

The hierarchically porous and iron-functionalized zeolite ZSM-5 has been fabricated as a Fenton photocatalyst by a facile post-treatment process, which exhibits an excellent visible-light catalytic property in the adsorption/degradation of organic pollutants under mild reaction conditions.

Novel Gradient Porous ZSM-5 Zeolite Membrane/PSSF Composite for Enhancing Mass Transfer of Isopropanol Adsorption in a Structured Fixed Bed

A novel gradient porous ZSM-5 membrane/PSSF (paperlike sintered stainless steel fiber) composite was prepared by the wet layup papermaking/sintering technique and a secondary growth process. The effects of crystallization time on the morphology, thickness, and Si/Al ratio of the ZSM-5 membranes were studied. The composites were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and N2 adsorption. Adsorption behaviors of isopropanol in structured fixed beds filled with granular activated carbon (GAC) or ZSM-5 particles in the inlet of the bed and ZSM-5/PSSF composites in the outlet of the bed were investigated. Adsorption breakthrough behaviors of isopropanol in fixed beds containing only GAC or ZSM-5 particles were also studied. Theoretical breakthrough curves were predicted using the Yoon–Nelson model and compared with the experimental results. Satisfactory agreement between the theoretical breakthrough curves and the experimental dat...

Catalytic cracking of C5 raffinate to light olefins over lanthanum-containing phosphorous-modified porous ZSM-5: Effect of lanthanum content

Lanthanum-containing phosphorous-modified porous ZSM-5 catalysts (LaX-P/C-ZSM5) were prepared with a variation of La/Al atomic ratio (X=0.3, 0.7, 0.9, and 1.2) for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of lanthanum content of LaX-P/C-ZSM5 catalysts on their physicochemical properties and catalytic activities for the cracking of C5 raffinate was investigated. It was found that acidity of LaX-P/C-ZSM5 catalysts decreased with increasing lanthanum content, while basicity of LaX-P/C-ZSM5 catalysts increased with increasing lanthanum content. In the catalytic cracking of C5 raffinate, acid and base properties of LaX-P/C-ZSM5 catalysts were closely related to the conversion of C5 raffinate and selectivity for light olefins, respectively. Conversion of C5 raffinate decreased with decreasing acidity of the catalyst and selectivity for light olefins increased with increasing basicity of the catalyst. Among the catalysts tested, La0.7-P/C-ZSM5 catalyst with moderate acidity and basicity exhibited the best catalytic performance in terms of yield for light olefins. It is concluded that an optimal lanthanum content of LaX-P/C-ZSM5 catalysts was required for maximum light olefin production in the catalytic cracking of C5 raffinate.

Fabrication of Large Porous ZSM-5 Bulk Bodies by a One-pot Hydrothermal Method

Abstract The fabrication of large ZSM-5 bulk bodies by a hydrothermal method was investigated. The results reveal that porous ZSM-5 bulk bodies with sizes of the order of centimeters could be prepared by the one-pot hydrothermal method using raw materials for synthesizing ZSM-5 powder. Machinability tests and mechanical strength measurements suggest that the bulk bodies obtained are promising as practical materials.

Preparation and characterization of a novel gradient porous ZSM-5 zeolite membrane/PSSF composite and its application for toluene adsorption

A novel gradient porous ZSM-5 membrane/PSSF composite was prepared by the wet lay-up papermaking process and secondary growth process. Firstly, the paper-like sintered stainless steel fibers (PSSFs) support was prepared by the wet lay-up papermaking process and sintering process, then a ZSM-5 membrane was fabricated on this PSSF support by secondary growth process. The morphology and structure of ZSM-5 membrane/PSSF composite were characterized by SEM, XRD and ASAP 2020, respectively. The experimental results indicated that the junctures of stainless steel fibers were completely sintered together to form a three-dimensional network structure and ZSM-5 membrane was fabricated on the PSSF support. The specific surface area of composite was 145.1m2/g, which was calculated with the BET (Brunauer–Emmett–Teller) method, and the total pore volume was 0.1547cm3/g. The adsorption breakthrough curve of toluene in the structured fixed bed filled with both granular activated carbons (GACs) of 2.4cm in the inlet of bed and NaZSM-5/PSSF composites of 0.6cm in the outlet of bed was also investigated, comparing with that in individual GAC fixed bed with bed height of 3cm. The length of unused bed was calculated according to the breakthrough curve data. The experimental results showed that the length of unused bed in structured fixed bed was obviously decreased.

Vapor assisted “in situ” transformation of mesoporous carbon–silica composite for hierarchically porous zeolites

Ordered mesoporous carbon–silica composite was “in situ” transformed into hierarchically porous zeolites ZSM-5 (H-ZSM-5) under water vapor, which synthesized from evaporation induced “tri-constituent” co-assembly of resin, silica and surfactant. The vapor assisted transformation was realized within 2-D hexagonally mesochannels of carbon–silica composite infused with tetrapropylammonium hydroxide at 130 °C for 72 h. The calcined H-ZSM-5-570 possesses a mesostructure with mean pore sizes of 0.6 and 9.0 nm, BET surface area of 409 cm 2/g, and pore volume of 0.54 cm 3/g. High-resolution TEM images of H-ZSM-5-570 display that mesoporous walls consisted of zeolite nanocrystals of about 6 nm in the same domain. Weak acidity of H-ZSM-5-570 has also been concluded from ammonia desorption measurements.

Synthesis of Hierarchically Porous ZSM-5 by Solvent-Evaporation Route

A hierarchically porous zeolite ZSM-5 is prepared under hydrothermal conditions by using hexadecyltrimethoxysilane as inhibitor and template. The physical and acid properties of the hierarchically porous ZSM-5 are characterized by XRD, SEM, N2 physisorption and NH3-TPD techniques. Benzene alkylation with methanol is carried out with both conventional and hierarchically porous ZSM-5 in a fixed bed reactor. The creation of mesoporosity in zeolite ZSM-5 promotes benzene conversion and xylene selectivity with respect to conventional counterpart.

Solid-State NMR Characterization of the Insertion of Cobalt into Aluminosilicate Materials

The location of cobalt in two porous metal-substituted zeolites, mordenite and ZSM5, and in a reference amorphous silicoalumina material, was investigated by solid-state NMR spectroscopy. The hyperfine shift and pseudoshift effects due to the paramagnetic metal on the NMR spectra of silicon and aluminum were used to estimate the number of aluminum and silicon framework sites in proximity of the cobalt. It was possible to confirm previous IR findings that only a fraction of the SiOHAl sites were involved directly in the bonding of the metal. A semiquantitative solid-state NMR analysis proved that siloxane bridges, and preferentially those close to aluminum locations, played a concurrent marked binding role in zeolites. It was found that for both zeolites the metal penetrates deeply into the structure. Furthermore, analysis of the NMR spectra implies that the cobalt position must be crystallographically well determined.

Hierarchically Porous ZSM-5 Synthesized by Nonionic- and Cationic-Templating Routes and Their Catalytic Activity in Liquid-Phase Esterification

Hierarchically porous MFI zeolites (ZSM-5) have been synthesized by hydrothermal treatment in the presence of trialkoxysilylated-derivatives of nonionic poly(oxyethylene) alkyl ether or alkyl quaternary ammonium cation as mesopore-generating agent, along with tetrapropylammonium cation as zeolite structure-directing agent. Powder X-ray diffraction revealed that zeolites have been crystallized, and scanning electron microscopy showed rugged surface morphology that was quite different from conventional ZSM-5. The mesoporosity was confirmed by nitrogen adsorption-desorption measurement showing type IV isotherms with narrow distribution of mesopore diameters. The catalytic activity of these mesoporous ZSM-5 was tested in liquid-phase esterification of benzyl alcohol with hexanoic acid. The conversion of benzyl alcohol on mesoporous ZSM-5 prepared via cationic-templating route was almost 100%, being much higher than on mesoporous ZSM-5 prepared with silylated nonionic surfactant as well as on conventional ZSM-5 with no mesopores. The presence of Bronsted acid sites, together with the mesopores, was responsible for this catalytic conversion, as confirmed by pyridine adsorption monitored by in situ infrared and 27 Al magic angle spinning nuclear