Selective production of propylene from methanol: Mesoporosity development in high silica HZSM-5

Programmable synthesis of mesoporous ZSM-5 nanocrystals as selective and stable catalysts for the methanol-to-propylene process

Programmable synthesis of mesoporous ZSM-5 nanocrystals for a highly efficient methanol to propylene reaction.

Oxygen-containing coke species in zeolite-catalyzed conversion of methanol to hydrocarbons

Oxygen-containing coke species are identified during methanol-to-hydrocarbons reactions, and their influence on the deactivation of catalyst is investigated.

Synthesis and evaluation of mesopore structured ZSM-5 and a CuZSM-5 catalyst for NH3-SCR reaction: studies of simulated exhaust and engine bench testing

A modified ZSM-5 zeolite (denoted as ZSM-5-M) was synthesized using tetrapropylammonium hydroxide (TPAOH) and cetyltrimethylammonium bromide (CTAB) as dual templates, using commercial ZSM-5 zeolite (denoted as ZSM-5-C).

The catalytic properties evolution of HZSM-5 in the conversion of methanol to gasoline

Catalytic properties evolution of HZSM-5 in MTG process was demonstrated basing on the analysis of spent catalysts with characteristic reaction.

The formation and degradation of active species during methanol conversion over protonated zeotype catalysts

The methanol to hydrocarbon (MTH) process provides an efficient route for the conversion of carbon-based feedstocks into olefins, aromatics and gasoline. Still, there is room for improvements in product selectivity and catalytic stability. This task calls for a fundamental understanding of the formation, catalytic mechanism and degradation of active sites. The autocatalytic feature of the MTH process implies that hydrocarbons are active species on the one hand and deactivating species on the other hand. The steady-state performance of such species has been thoroughly studied and reviewed. However, the mechanism of formation of the initial hydrocarbon species (i.e.; the first C-C bond) and the evolution of active species into deactivating coke species have received less attention. Therefore, this review focuses on the significant progress recently achieved in these two stages by a combination of theoretical calculations, model studies, operando spectroscopy and catalytic tests.

Phosphorus promotion and poisoning in zeolite-based materials: synthesis, characterisation and catalysis

Complex interactions between phosphorus and zeolites are related to several promotional and poisoning effects in zeolite catalysis.

Phosphorus and microporous aluminosilicates, better known as zeolites, have a unique but poorly understood relationship. For example, phosphatation of the industrially important zeolite H-ZSM-5 is a well-known, relatively inexpensive and seemingly straightforward post-synthetic modification applied by the chemical industry not only to alter its hydrothermal stability and acidity, but also to increase its selectivity towards light olefins in hydrocarbon catalysis. On the other hand, phosphorus poisoning of zeolite-based catalysts, which are used for removing nitrogen oxides from exhaust fuels, poses a problem for their use in diesel engine catalysts. Despite the wide impact of phosphorus–zeolite chemistry, the exact physicochemical processes that take place require a more profound understanding. This review article provides the reader with a comprehensive and state-of-the-art overview of the academic literature, from the first reports in the late 1970s until the most recent studies. In the first part an in-depth analysis is undertaken, which will reveal universal physicochemical and structural effects of phosphorus–zeolite chemistry on the framework structure, accessibility, and strength of acid sites. The second part discusses the hydrothermal stability of zeolites and clarifies the promotional role that phosphorus plays. The third part of the review paper links the structural and physicochemical effects of phosphorus on zeolite materials with their catalytic performance in a variety of catalytic processes, including alkylation of aromatics, catalytic cracking, methanol-to-hydrocarbon processing, dehydration of bioalcohol, and ammonia selective catalytic reduction (SCR) of NO_x. Based on these insights, we discuss potential applications and important directions for further research.

Performance of hierarchical HZSM-5 zeolites prepared by NaOH treatments in the aromatization of glycerol

A study on the aromatization of glycerol over hierarchical ZSM-5 zeolites modified by alkaline treatment.

One-step synthesis, characterization and catalytic performance of hierarchical Zn-ZSM-11 via facile ZnO routes

Hierarchical Zn-ZSM-11 with an olive-shaped intergrowth morphology was synthesized via a novel and facile one-step hydrothermal method.

Tailoring and visualizing the pore architecture of hierarchical zeolites

This review provides an overview of the different synthesis methods and microscopy techniques for tailoring and visualizing the pore architecture of hierarchical zeolites.

Future of nano-/hierarchical zeolites in catalysis: gaseous phase or liquid phase system

This perspective highlights the catalytic characteristics and future prospects of nano-/hierarchical zeolites in gaseous phase and liquid phase reactions.

F-assisted synthesis of a hierarchical ZSM-5 zeolite for methanol to propylene reaction: a b-oriented thinner dimensional morphology

A hierarchical ZSM-5 zeolite with a thinner dimension morphology has been synthesized in fluoride medium, and presents a superior performance in MTP reaction.

Hydrothermal liquefaction of Chlorella pyrenoidosa for bio-oil production over Ce/HZSM-5

This paper investigated a novel hydrothermal liquefaction process of Chlorella pyrenoidosa catalyzed by Ce/HZSM-5. The chemical groups and components of the residues of C. pyrenoidosa were analyzed by Fourier transform infrared spectrometry and Gas Chromatograph-Mass Spectrometer. The crystal structure and micro surface topography of C. pyrenoidosa before and after catalytic liquefaction were characterized by X-ray diffraction and Scanning electron microscopy, respectively. The experimental results showed that the catalytic cracking effects of Ce/HZSM-5 were superior to that of HZSM-5 as a liquefaction catalyst of C. pyrenoidosa. Compared with HZSM-5, Ce/HZSM-5 has a significantly enhanced Lewis acid active center, smaller particle size, larger specific surface, and highly dispersed Ce4O7 with trivalent and tetravalent cerium in the zeolite skeleton channel that accelerate the catalytic liquefaction of C. pyrenoidosa. The rare earth modified zeolite Ce/HZSM-5 exhibits good potential and a beneficial nature for the preparation of bio-oil from microalgae with high efficiency.

Propylene from renewable resources: catalytic conversion of glycerol into propylene

Propylene, one of the most demanded commodity chemicals, is obtained overwhelmingly from fossil resources. In view of the diminishing fossil resources and the ongoing climate change, the identification of new efficient and alternative routes for the large-scale production of propylene from biorenewable resources has become essential. Herein, a new selective route for the synthesis of propylene from bio-derived glycerol is demonstrated. The route consists of the formation of 1-propanol (a versatile bulk chemical) as intermediate through hydrogenolysis of glycerol at a high selectivity. A subsequent dehydration produces propylene.

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

In order to elucidate phosphorus-zeolite H-ZSM-5 interactions, a variety of phosphorus-modified zeolite H-ZSM-5 materials were studied in a multi-spectroscopic manner. By deploying single pulse (27)Al, (31)P MAS NMR, 2D heteronuclear (27)Al-(31)P correlation (HETCOR), (27)Al MQ MAS NMR spectroscopy, TPD of pyridine monitored by FT-IR spectroscopy, and Scanning Transmission X-ray Microscopy (STXM) the interplay and influence of acidity, thermal treatment and phosphorus on the structure and acidity of H-ZSM-5 were established. It was found that while acid treatment did not affect the zeolite structure, thermal treatment leads to the breaking of Si-OH-Al bonds, a decrease in the strong acid site number and the formation of terminal Al-OH groups. No extra-framework aluminium species was observed. Phosphorus precursors interact with the zeolitic framework through hydrogen bonds and physical coordination, as phosphorus species can be simply washed out with hot water. After phosphatation and thermal treatment two effects occur simultaneously, namely (i) phosphorus species transform into water insoluble condensed poly-phosphoric acid and (ii) phosphoric acid binds irreversibly to the terminal Al-OH groups of partially dislodged four-coordinated framework aluminium, forming local silico-aluminophosphate interfaces. These interfaces are potentially the promoters of hydrothermal stability in phosphated zeolite H-ZSM-5.

Kinetics of the catalytic cracking of naphtha over ZSM-5 zeolite: effect of reduced crystal size on the reaction of naphthenes

The catalytic cracking of model naphthenes over ZSM-5 zeolites of different crystal sizes was examined at reaction temperatures ranging from 748 to 923 K under atmospheric pressure, focusing on the associated reaction rate constants and activation energies.

Highly stable boron-modified hierarchical nanocrystalline ZSM-5 zeolite for the methanol to propylene reaction

A highly stable MTP catalyst, boron-modified hierarchical nanocrystalline ZSM-5 zeolite, has been synthesized by a facile salt-aided seed-induced route. It exhibits a long lifetime (about 725 h) even at a high WHSV (4.0 h⁻¹).

Microstructured fiber@HZSM-5 core–shell catalysts with dramatic selectivity and stability improvement for the methanol-to-propylene process

Dramatic selectivity and stability improvement of ZSM-5 zeolite for the methanol-to-propylene process has been achieved by a solely microstructured core–shell catalyst design.

Unraveling the reaction mechanisms governing methanol-to-olefins catalysis by theory and experiment

The conversion of methanol to olefins (MTO) over a heterogeneous nanoporous catalyst material is a highly complex process involving a cascade of elementary reactions. The elucidation of the reaction mechanisms leading to either the desired production of ethene and/or propene or undesired deactivation has challenged researchers for many decades. Clearly, catalyst choice, in particular topology and acidity, as well as the specific process conditions determine the overall MTO activity and selectivity; however, the subtle balances between these factors remain not fully understood. In this review, an overview of proposed reaction mechanisms for the MTO process is given, focusing on the archetypal MTO catalysts, H-ZSM-5 and H-SAPO-34. The presence of organic species, that is, the so-called hydrocarbon pool, in the inorganic framework forms the starting point for the majority of the mechanistic routes. The combination of theory and experiment enables a detailed description of reaction mechanisms and corresponding reaction intermediates. The identification of such intermediates occurs by different spectroscopic techniques, for which theory and experiment also complement each other. Depending on the catalyst topology, reaction mechanisms proposed thus far involve aromatic or aliphatic intermediates. Ab initio simulations taking into account the zeolitic environment can nowadays be used to obtain reliable reaction barriers and chemical kinetics of individual reactions. As a result, computational chemistry and by extension computational spectroscopy have matured to the level at which reliable theoretical data can be obtained, supplying information that is very hard to acquire experimentally. Special emphasis is given to theoretical developments that open new perspectives and possibilities that aid to unravel a process as complex as methanol conversion over an acidic porous material.