Effect of the template on the hydrothermal synthesis of mixed molecular sieves for methanol dehydration

Abstract

In this work, microporous–mesoporous H‐ZSM‐5/MCM‐41 mixed molecular sieves catalyst was successfully synthesized using a hydrothermal synthesis technology. Mesoporous MCM‐41 sieves were obtained by partial alkali treatment of microporous H‐ZSM‐5. The effect of the amount of template (i.e., cetyltrimethyl ammonium bromide, CTAB) on the preparation process of catalyst was investigated. The catalyst was characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and N2 adsorption–desorption. Methanol dehydration to dimethyl ether was selected to evaluate the catalytic performance of H‐ZSM‐5/MCM‐41. The content of mesoporous MCM‐41 in the mixed molecular sieve catalyst as well as its particle and pore sizes increased with the amount of CTAB, thereby enhancing the catalytic activity of the final material while keeping constant the microporous ZSM‐5 loadings. Thus, the amount of mesoporous MCM‐41 in the mixed molecular sieve catalyst reached a maximum at a CTAB loading of 10%, with the resultant material showing a maximum specific surface area of 335 m2/g and a mean pore size of 3.8 nm. Additionally, this material showed optimum catalytic activity (84% methanol conversion at 220°C). © 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901–1907, 2018

Synthesis of micro-mesoporous molecular sieve ZSM-5/SBA-15: tuning aluminium content for tert-butylation of phenol

“…The partial crystallization of mesoporous molecular sieves with suitable acidity and good hydrothermal stability can boost their acid catalytic performance. [19][20][21][22][23][24][25][26][27] Relatively few reports focused on the preparation of micro-mesoporous molecular sieves by mesoporous wall crystallization, mainly due to the small pore wall thickness that is difficult to be completely crystallized. Huang et al, 28 synthesized the ZSM-5/MCM-41 composite molecular sieve by partially crystallizing the amorphous pore wall of MCM-41 through a two-step crystallization process, in which the crystallization time was controlled at the second step.…”