In-situ synthesis of hierarchical lamellar ZSM-5 zeolite with enhanced MTP catalytic performance by a facile seed-assist
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In‑situ synthesis of hierarchical lamellar ZSM‑5 zeolite with enhanced MTP catalytic performance by a facile seed‑assisted method Yan‑Hong Chen1 · Dong‑Min Han1 · Qiang Zhang2 · Hong‑Xia Cui1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A seed-assisted route has been applied to prepare the hierarchical lamellar ZSM-5 zeolite with good porosity and catalytic performance in methanol to propylene (MTP) reaction. In this method, ZSM-5 crystal seeds instead of organic quaternary ammonium were used to direct the formation of ZSM-5 nuclei and conventional surfactant cetyltrimethylammonium bromide (CTAB) employed as the mesoporogen. The process for the formation of hierarchical lamellar ZSM-5, including the effect of the ratio of CTAB/SiO2, initial gel aging temperature, synthesis temperature and synthesis time were discussed in detail. The results suggested that mesoporous structure was first obtained and then transformed into MFI structure in-situ during the hydrothermal synthesis process. The obtained hierarchical lamellar ZSM-5 zeolite displays an organized flack-like nanosheet stacks morphology with regular intercrystal mesopores of 3–7 nm, possessing large surface area and mesopore volume. Moreover, the synthesized hierarchical ZSM-5 zeolite has perfect catalyst lifetime in methanol to propylene (MTP) reaction than conventional microporous ZSM-5 zeolite, which could be ascribed to the hierarchical mesoporous structure accommodating more bulky molecules and accessible acid sites in the catalytic reaction. Keywords Hierarchical ZSM-5 · CTAB · Seeds · Nanosheets
1 Introduction Zeolites with well-defined pores have been extensively used in the fields of petroleum and petrochemistry for its shape selectivity, high acidity and good thermal/hydrothermal stability [1–3]. However, the dimensions of micropores limit the diffusion rate of large molecules, which leaves a large part of acid sites within a zeolite crystals can not be utilized leading to the low catalytic efficiencies and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10934-020-00898-w) contains supplementary material, which is available to authorized users. * Yan‑Hong Chen [email protected] * Qiang Zhang [email protected] 1
Department of Chemical Engineering, Shengli College China University of Petroleum, Dongying 257100, Shandong Province, China
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong Province, China
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undesired secondary reactions such as coke deposition. In order to solve these problems, a lot of measures have been made, such as the synthesis of nanozeolites and ordered mesoporous materials [4–6]. A variety of synthetic methods for the preparation of nanozeolites have been reported in recent years. The reduced crystal size of zeolite nanocrystals can increase the external surface area and reduce the diffusion path, thus improving the catalytic activity [7]. But the difficulty of separation nanozeolites
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