Enhanced Catalytic Performance of Zn‐containing HZSM‐5 upon Selective Desilication in Ethane Dehydroaromatization Process

Abstract

The effect of introducing mesoporosity on the catalytic stability and selectivity of Zn‐containing ZSM‐5 catalysts was investigated for direct conversion of ethane to high‐value aromatics. Voids and mesopores were created in the zeolite (Si/Al=40) by selective desilication (recrystallization) using ammonium hydroxide and cetyltrimethylammonium bromide. Zinc was incorporated in the samples by incipient wetness impregnation to achieve different concentrations of 0.5, 1 and 5 wt %. The samples were characterized by XRD, N2 physisorption, TGA, NH3‐TPD, ICP‐OES, FTIR, 1H, 27Al and 29Si solid‐state MAS NMR. The desilicated samples were compared to their parent analogues for ethane conversion to aromatics such as benzene, toluene and xylenes (BTX). All of the desilicated samples showed an improvement in BTX yield and catalytic stability. Thus, the presence of mesoporosity increases the accessibility to the active sites and facilitates the mass transfer of aromatic compounds, which result in higher performance and catalytic stability of the desilicated ZSM‐5 samples containing zinc.

Biomass Catalytic Pyrolysis over Zeolite Catalysts with an Emphasis on Porosity and Acidity: A State-of-the-Art Review

“…In addition, although ZSM-5 zeolites modified by the bottom-up approach bring in higher interior acid and lower exterior acid, more stringent conditions in the post-treatment strategy resulted in an increasing at excess for exterior acid sites and mesopore volume, which reduced acid sites and increased the selectivity of some BTXs. The result of it is similar to that of Goodarzi et al’s experiment on ethane . On these materials, both the polymerization reaction and the condensation reaction are supported, thereby increasing the formation of coke and polyaromatic hydrocarbons, which cannot count against the formation of monoaromatic hydrocarbons.…”

“…The result of it is similar to that of Goodarzi et al's experiment on ethane. 84 On these materials, both the polymerization reaction and the condensation reaction are supported, thereby increasing the formation of coke and polyaromatic hydrocarbons, which cannot count against the formation of monoaromatic hydrocarbons. And its desilication process is not easy to control, and it is easy to destroy the original structure of zeolite.…”

The catalytic effects of sulfur in ethane dehydroaromatization

“…Since ethylene selectivity is dependent on aromatization rate, the decrease of ethylene selectivity for sulfided catalyst over time is due to increase of ethylene conversion to aromatics. Based on our previous results 31 , we propose that ZnOH + species, which are weak acid sites 32 , is responsible for dehydrogenation of ethane to ethylene. Notably, the NH3-TPD of the sulfided and non-sulfided catalysts show a similar density of weak acid sites.…”

“…The most studied catalyst, which has shown high catalytic performance in this process, is zinc-containing ZSM-5, providing both dehydrogenating and acidic sites. [3][4][5][6][7] However, the two most important challenges for this catalyst deactivation are coke deposition and zinc leaching under the reducing conditions of the process. Based on previous studies, 8,9 the dissociation energy of C−C bonds is lower than that of C−H bonds; therefore, cracking reactions and rapid coke formation occur as a result.…”

Interzeolite conversion of a micronsized FAU to a nanosized CHA zeolite free of organic structure directing agent with a high CO2 capacity

“…1 Zeolites have pores, and cages of molecular dimensions and can be used for molecular sieving. Molecular sieving is a very useful property in both catalysis [2][3][4][5][6] and molecules separation in gas and liquid phases. [7][8][9] With more than 240 10 different zeolite framework structures, a key parameter is nding the zeolite structure that ts the right needs for the desired application.…”