Mesoporous ZSM-5 Research Articles

A facile route to synthesize mesoporous ZSM-5 with hexagonal arrays using P123 triblock copolymer

Mesoporous ZSM-5 samples were synthesized using Pluronic P123 triblock copolymer (EO20PO70EO20) as a supramolecular template through a pH adjusting method. The resulting materials were characterized using X-ray diffraction, transmission electron microscopy (TEM), nitrogen adsorption/desorption, scanning electron microscopy (SEM), solid-state nuclear magnetic resonance (MAS-NMR) and ammonia temperature programmed desorption (TPD) analyses. Adjusting the synthesis pH allowed obtaining a well-crystallized ZSM-5 material with meso-channels of size of 8–10 nm as calculated from non-local density functional theory (NLDFT) and also supported by TEM images. This strategy performs the growth of zeolite crystals with a mesostructured pore lattice in a cooperative manner, avoiding both a phase separation between the surfactant and zeolite units during crystallization and the formation of a separate amorphous mesoporous material. In addition, ammonia TPD studies revealed that the acidity of the mesoporous ZSM-5 material is comparable with the microporous conventional one. It was found from NH3-TPD profiles that in the case of the mesoporous ZSM-5 samples some of the strong acid sites have been transformed into weak acid sites which might be attributed to the acid sites present on the crystal external surface in mesopores.

Catalytic upgrading of coal pyrolysis volatiles by Ga-substituted mesoporous ZSM-5

Five MFI-type zeolite catalysts, which were aluminosilicate ZSM-5 (Z5), gallium-substituted silicalite-1 (Ga-S1), mesoporous ZSM-5 (MZ5), gallium-substituted mesoporous silicalite-1 (Ga-MS1) and gallium-substituted mesoporous ZSM-5 (Ga-MZ5), were hydrothermally synthesized with combined using of TPAOH and TPOAC as micropore and mesopore structure-directing agents respectively, followed by the application in the catalytic upgrading of volatiles from low-rank coal fast pyrolysis. The obtained results indicated that significant improvements with the yield of high value-added products of BTEXN (benzene, toluene, ethylbenzene, xylene and naphthalene) increased from 5.4 mg.g−1 to 11.9–26.4 mg.g−1, as well as the content of light fractions (<300 °C) in coal tars increased from 51% to 65–88% were realized by using the representative MFI-type zeolite catalysts in contrast to non-catalyst pyrolysis. Moreover, the possible mechanism for catalytic upgrading over the best-performing catalyst of gallium-substituted mesoporous ZSM-5 (Ga-MZ5) with the highest yield of aromatics and effective reduction of phenols was proposed on the basis of systematic comparison of structural features and catalytic performances of various MFI-type zeolite catalysts and fundamental study of the synergetic effects dominated by acidity, ratio of Brønsted/Lewis acid sites, intra-/extra-framework gallium species and hierarchical meso-/microporosity.

One-pot Synthesis of Hierarchical Mesoporous ZSM-5 from the Assembly of Nanocrystals Using Urea as Additive

A hierarchical mesoporous ZSM-5 catalyst with aggregated nanocrystals structure was one-pot hydrothermally synthesized by using urea as the additive. The crystalline phase, morphology and hierarchical architectures were characterized by the XRD, SEM, TEM and N2 adsorption/desorption analyses. The nano-aggregates showed MFI crystalline phase and were composed of connected nanoparticles. The samples had the high surface area and the pore volume from intercrystalline among the nanoparticles due to spontaneously stacking of nanocrystals. The pyridine-adsorbed FTIR and the catalytic performances in the alkylation of phenol and tert-butyl alcohol were applied to evaluate the accessibility of acid sites and the catalytic activities for the hierarchical mesoporous ZSM-5 samples. The samples possessed high accessibility of acid sites which resulted from their large amount of mesopores, and its catalytic activity was improved dramatically. The phenol conversion could reach up to 95.6%, and the corresponding selectivity of 4-TBP and 2,4-DTBP was 44% and 51.5%, respectively.

Effect of mesoporous ZSM-5 morphology on the catalytic performance of cobalt catalyst for Fischer-Tropsch synthesis

Mesoporous ZSM-5 with various morphologies loading cobalt were prepared and applied in Fischer-Tropsch synthesis. Smaller ZSM-5 particles showed higher intensity of strong acid sites resulting in higher cobalt-support interaction. The activity and CH4 selectivity were remarkably related with cobalt-support interaction over such acidic supports. Cobalt loaded on spindle mesoporous ZSM-5 exhibited the lowest activity and the highest CH4 selectivity due to the strongest cobalt-support interaction, but the highest activity was obtained over cubic mesoporous ZSM-5 with the lowest cobalt-support interaction originating from weaker acid sites. In addition, adjusting acid intensity and mesopore volumes could successfully tuned hydrocarbon distribution. Spherical ZSM-5 with hierarchical structure containing larger mesopore volumes and moderate acid intensity effectively promoted the production of C12-18 hydrocarbons. The highest C5-11 selectivity was observed over cobalt supported on hexagonal meso-ZSM-5 due to the enhancement in diffusion limitation over lower mesopore volumes and hydrocracking of primary hydrocarbons over higher Brønsted acid sites.

Synthesis of CuCe co-modified mesoporous ZSM-5 zeolite for the selective catalytic reduction of NO by NH3.

Mesoporous ZSM-5 zeolite (MZ) was used as support for Cu and Ce species, and the effects of structure and physical-chemical properties on selective catalytic reduction of NO with NH3 (NH3-SCR) were investigated. The characterization and experimental results show that the high activity of the Cu-Ce/MZ catalyst could be due to its high surface area, more and uniformly distributed active sites, and abundant oxidative species. Compared with the conventional ZSM-5 and SBA-15, the Cu-Ce/MZ possesses large amount of mesopores, and more accessible active sites, which are beneficial to accelerate the diffusion and improve the internal mass transfer in the denitration process. The Cu-Ce/MZ catalyst shows higher activity than Cu-Ce/ZSM-5 and Cu-Ce/SBA-15 at 200°C.

The Application of Mesoporous ZSM-5 Zeolite in the ULSD Catalysts

The mesoporous ZSM-5 zeolite containing MoCoP/Al2O3 catalyst (C12-ZSM5) with the mixture of Al2O3 and mesoporous ZSM- 5 zeolite as carrier was synthesized. The catalytic performance of C12-ZSM5 catalyst was evaluated by the hydrodesulfurization (HDS) of different diesel feedstock. The carriers and catalysts were characterized by N2 adsorption-desorption, pyridine-FTIR, X-ray diffraction (XRD) and CO in-situ FTIR (CO-FTIR) techniques. Results showed that mesoporous ZSM-5 can improve the acidity of the catalyst and increase the number of MoCoS active phases. The C12-ZSM5 catalyst had low HDS and HDN activity, because the acidic sites of mesoporous ZSM-5 were easily occupied by nitrogen compounds. The HDS activity of C12-ZSM5 catalyst was fully exploited by using graded packing technology, the sulfur content of product oil was 5.9 ng/μL. The relative HDS activity of C12-ZSM5 catalyst is 1.47 times that of FHUDS-8 catalyst.

The effect of steam on maximizing light olefin production by cracking of ethanol and oleic acid over mesoporous ZSM-5 catalysts

Steam cracking significantly improved light olefin selectivity: mainly ethylene was obtained from ethanol and propylene from oleic acid.

Synthesis of micro-mesoporous ZSM-5 zeolite with microcrystalline cellulose as co-template and catalytic cracking of polyolefin plastics.

Micro–mesoporous ZSM-5 with different Si/Al ratios (MZ-X, X = 27, 80, 150) were synthesized by adding microcrystalline cellulose (MCC) as co-template into the hydrothermal synthesis process of zeolites. The resultant ZSM-5 were used for catalytic cracking of high density polyethylene (HPDE) and polypropylene. It was found that introduction of MCC significantly enhanced the formation of mesopores and strong acid sites. MZ-27 achieved the highest oil yield: 21.5% for HPDE and 32.1% for polypropylene, and the light aromatics (BTEX) selectivity therein were 87.6% and 79.7%, respectively. HZ-150 (MCC-free ZSM-5, Si/Al = 150) achieved the highest gas yield: 85.4% for HDPE and 76.7% for polypropylene, and the light olefins (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> 2–4) selectivity therein were 44% and 48.3%, respectively. The dense acidic sites and mesoporous structure of MZ-27 were responsible for its better activity for producing aromatic products. The moderate acidity and microporous structure of HZ-150 were helpful for producing light olefins from catalytic cracking of polyolefin plastics.

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Facile synthesis of hydrothermally stable mesoporous ZSM-5 zeolite from Al- SBA-16 via steam assisted crystallization

In this work, Al grafted SBA-16 (Al-SBA-16) is converted into a fully crystalline hierarchical mesoporous ZSM-5 zeolite with hydrothermal stability by steam assisted crystallization under controlled conditions. The secondary mesoporosity is due to reorganization and recrystallization events happening upon steaming the precursor. Two mesoporous aluminosilicates (Al-SBA-16s) are used as the precursors of zeolites. The precursors are obtained by post-synthetic Al grafting on the silica walls of SBA-16 with aluminium isopropoxide and sodium aluminate. Mesoporous ZSM-5 zeolites obtained from the Al-SBA-16 precursors and commercial ZSM-5 are characterized using XRD, XRF, FT-IR, TEM, N2 adsorption, 27Al and 29Si MAS NMR, and TPD of NH3. The results indicated the presence of intraparticle mesoporosity in the prepared mesoporous zeolites and they have comparable crystallinity with commercial ZSM-5. Catalytic activity of the synthesized mesoporous zeolites in benzylation of mesitylene is found to be comparatively more than commercial ZSM-5, which shows existence of micro/meso hierarchical structure in the mesoporous ZSM-5 zeolites. The aluminium sources, aluminium isopropoxide and sodium aluminate have a remarkable influence on the textural, acidity, and hydrothermal stability characteristics of the synthesized mesoporous ZSM-5 zeolites.

Controlled fabrication of mesoporous ZSM-5 zeolite-supported PdCu alloy nanoparticles for complete oxidation of toluene

Mesoporous ZSM-5 zeolite-supported PdCu alloy nanoparticle catalysts are synthesized via a facile and environmentally friendly method. The mesoporous structure is formed through the loss of carbon black particles encapsulated by zeolite crystals during calcination. The ZSM-5-supported PdCu nanoparticles are shown to possess mesoporous structure, evenly distributed PdCu alloy nanoparticles, and excellent catalytic performance in toluene oxidation. The mesoporous structure of the ZSM-5-supported PdCu nanoparticles provides a large specific surface area and pore size, resulting in numerous accessible active sites. The alloying of Pd with Cu both increases the catalytic performance of the catalyst and lowers its cost. Overall, the catalyst with a Pd/Cu ratio of 8:2 showed the highest catalytic activity of the fabricated materials, achieving 100 % toluene conversion at 160 °C. The mechanism of toluene oxidation over these catalysts can be explained by the Mars–van Krevelen model.

Адсорбция СО2 в различных мезопористых цеолитах ZSM-5 приготовленных с биомассой

Адсорбция СО2 в различных мезопористых цеолитах ZSM-5 приготовленных с биомассой

One-pot synthesis of layered mesoporous ZSM-5 plus Cu ion-exchange: Enhanced NH3-SCR performance on Cu-ZSM-5 with hierarchical pore structures

Hierarchical ZSM-5 zeolite with meso- and micro-pore structures was successfully prepared through a facile one-pot hydrothermal synthesis method using bifunctional template. After copper ion-exchange, it was applied for the selective catalytic reduction of NO with NH3 (NH3-SCR). Compared with conventional Cu-ZSM-5 catalyst containing only micropores, the hierarchical catalyst with ca. 2 wt.% Cu loading displayed significantly improved catalytic performance. Particularly, the hierarchical zeolite catalyst also displayed excellent hydrothermal stability and sulfur resistance that exhibited great potential in practical application. Characterization techniques such as XRD, N2 physisorption, temperature programmed desorption/reduction (TPD/TPR) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were comprehensively used to reveal the relationship between zeolite structure and catalytic properties. It was concluded that the hierarchically porous structure could not only improve the mass transfer of reactant/product but also provide larger specific surface area, higher surface acidity, larger NO adsorption capacity. And we found that bidentate nitrate species was more active in Cu-ZSM-5-meso than Cu-ZSM-5-C, which were all beneficial to the NH3-SCR reaction. This work can provide a guideline to design other high performance hierarchical zeolites with different crystalline structures (such as CHA, LTA) for efficient catalytic NOx removal processes.

π-π Interactions Between Aromatic Groups in Amphiphilic Molecules: Directing Hierarchical Growth of Porous Zeolites.

The development of hierarchical macro- or mesoporous zeolites is essential in zeolite synthesis because the size of the micropores limits mass transport and their use as industrial catalysts for bulky molecules. Although major breakthroughs have been achieved, fabricating crystallographically ordered mesoporous zeolites using a templating strategy is still an unsolved challenge. This minireview highlights our recent efforts on the self-assembly of amphiphilic molecules to obtain ordered hierarchical MFI zeolites by introducing aromatic groups into the hydrophobic tail of the amphiphilic molecules. Owing to the geometric matching between the self-assembled aromatic tails and the MFI framework, a) single-crystalline mesostructured zeolite nanosheets (SCZNs), b) SCZNs with a 90° rotational intergrowth structure, c) a hierarchical MFI zeolite with a two-dimensional square P4mm mesostructure, and d) a single-crystalline mesoporous ZSM-5 with three-dimensional pores and sheetlike mesopores layered along the a-axis were successfully synthesized.

Improved catalytic performance of mesoporous ZSM-5 nanocrystalline zeolite prepared by the cationic surfactant-ammonium salt mixed agent method in the methanol to gasoline reaction

A mixed organic agent system was employed to achieve mesoporous highly crystalline ZSM-5 zeolite. Decyltrimethylammonium bromide (DeTAB) and tetramethyl ammonium hydroxide (TMAOH) were used as the mesogenous and molecular templates respectively in the synthesis gel with a composition of 60SiO2: 1Al2O3:12Na2O:3150H2O:xDeTAB:8TMAOH. The sole presence of DeTAB as the mesogenous template in the synthesis gel led to the high degrees of mesoporosity in the ZSM-5/xD samples but negatively affected the intrinsic properties of zeolites. At the high concentration of DeTAB (x = 0.7), the mesopore volume dramatically increased while the relative crystallinity and the total acid sites critically decreased. By adding the TMA+ ions as a microporous template to the ZSM-5/0.7D synthesis gel, not only a zeolite with well-developed mesoporosity was obtained but also its crystal structure and the intrinsic acidity were preserved. The catalyst samples were characterized by FESEM, TEM, XRD, FT-IR, nitrogen adsorption–desorption isotherms, NH3-TPD and TGA techniques. The ZSM-5/0.7D/T exhibited higher surface area, higher mesopore volume, higher crystallinity and more acid sites than the ZSM-5/0.7D. The catalytic conversion of methanol to gasoline was conducted in a fixed bed reactor at T = 390 °C and WHSV = 4.74 h−1. In ZSM-5/0.7D/T catalyst the mesoporosity formation without severely damaging the crystal structure and the acidity of the zeolite led to the best catalytic performance including the highest liquid hydrocarbon yield, most stable catalytic performance and longest catalytic lifetime.

Influence of mesoporous structure ZSM-5 zeolite on the degradation of Urban plastics waste

In the present work, mesoporous ZSM-5 zeolite structures were developed by means of post-synthesis modification and direct synthesis and the materials were applied as pyrolysis catalysts of different sources of plastic waste. The plastic wastes were purchased from a cooperative of selective collection, classified as polyethylene, polypropylene and polystyrene, which were used in plastic mixtures with quantities consistent with the Brazilian Association of the Plastic Industry (ABIPLAST) in order to simulate urban plastic waste in Brazil. Previously, these plastic waste mixtures were extruded with 10% m/m of catalyst and thermogravimetric analysis was performed. It was possible to observe the decrease in degradation temperatures, as well as additional degradation steps in catalytic pyrolysis compared to thermal pyrolysis. The synthesized mesoporous ZSM-5 zeolite was the catalyst with higher performance in the pyrolysis of plastic waste mixtures due to the higher proportion of strong to weak acid sites.

Theoretical study on the influence of ZSM-5 zeolite with different structures for methanol to aromatics

Abstract The influence of hierarchical structure and SiO2 modification of ZSM-5 on the mechanism of methanol to aromatics was studied. The formation of benzene and toluene through reaction pathways of carbenium ions with high carbon number was discussed over ZSM-5 and modified ZSM-5, respectively. The results demonstrated that the energy barriers for the formation of aromatics over hierarchical ZSM-5 were higher than that over ZSM-5, indicating that aromatics were easier to form in micropores thermodynamically. Moreover, higher activation energy was observed over mesoporous ZSM-5 with SiO2 modification indicating greater difficulty in the reaction. A decrease in the acid strength by desilication then SiO2 modification was benefit to suppressing the production of aromatics. In addition, the reactions related to hydride transfer needed overcome higher barriers and thus were the rate-determining steps for aromatization compared with those in deprotonation and cyclization steps. Meanwhile, the length of C–O bond for alkoxy groups increased obviously from ZSM-5 to modified ZSM-5 zeolite in such step, which was ascribed to the reduction of acidic site strength of modified ZSM-5.

The role of catalyst acidity and shape selectivity on products from the catalytic fast pyrolysis of beech wood

The catalytic fast pyrolysis (CFP) of biomass represents an efficient integrated process to produce deoxygenated stable liquid fuels and valuable chemical products from lignocellulosic biomass. The zeolite ZSM-5 is a widely studied catalyst for the CFP process. However, its microporous structure may limit the diffusion of high molecular weight pyrolysis intermediates to its active sites. Mesoporous aluminosilicates such as Al-SBA-15 are promising materials with larger pore sizes that can overcome these diffusional limitations. Previous comparisons between mesoporous aluminosilicates and ZSM-5 for the CFP process have neglected the disproportionately high acidity of ZSM-5. In this study, an Al-SBA-15 catalyst has been synthesised with high acidity, comparable to that of a ZSM-5 catalyst with a Si:Al ratio of 15:1. The synthesised Al-SBA-15 catalyst was characterised by N2 physisorption, XRD and propylamine-TPD, and was compared to a ZSM-5 catalyst and a typical industrial equilibrium fluid catalytic cracking catalyst (e-FCC). All three catalysts were used at three different catalyst to biomass (C/B) ratios, to investigate the effect of varying concentrations of acid sites on the product distribution from the catalytic fast pyrolysis of beech wood. Interestingly, despite their dissimilar structural architectures, all three solid acid catalysts displayed similar reaction pathways towards the cracking of high molecular weight products such as levoglucosan and formation of intermediates including phenolics and furans. However, the selectivity towards the final catalytic products was dictated mainly by the structure of the catalysts. Despite their very similar surface area and acidity, the ZSM-5 exhibited high selectivity for the formation of desirable aromatic hydrocarbon products due to its shape-selective micropore structure, while Al-SBA-15 instead shifted the selectivity towards the formation of undesirable coke. The results highlighted the importance of catalyst shape-selectivity in the catalytic fast pyrolysis of biomass for the conversion of pyrolysis vapours into desirable products and the suppression of undesirable solid byproduct formation.

Designing of Hollow ZSM-5 with Controlled Mesopore Sizes To Boost Gasoline Production from Syngas

Hollow mesoporous ZSM-5 zeolite is synthesized through a method of alkaline treatment with the TPAOH/NaOH mixed solution. The amount and pore size distribution of mesopores in the shell of hollow z...

Sorption of Heavy Metal Cations on Mesoporous ZSM-5 and Mordenite Zeolites.

Desilication and dealumination techniques were used to obtain mesoporous ZSM-5 and mordenite zeolites. The study provides insight into specific structural, textural, and sorption properties of obtained materials with different Si/Al ratios. Subsequent dealumination and desilication procedures were found to be efficient methods of generating a secondary system of mesopores in mordenite and ZSM-5 crystals while preserving their microporous character. The investigated materials were evaluated in terms of their sorption properties of selected heavy metal cations (Cd2+, Cr3+, and Pb2+). Particular emphasis was placed on the structural examination of the materials via infrared spectroscopy (FT-IR). Other research methods included X-ray diffraction (XRD), X-ray fluorescence (XRF), nuclear magnetic resonance (NMR) and atomic absorption spectrometry (AAS).