Effect Of Alcohol And Polyethylene Glycol As Auxiliary On The Texture And Catalytic Performance Of MCM-22 Zeolite

A series of MCM-22 zeolite samples were synthesized by dynamic hydrothermal crystallization method, using alcohol and PEG-2000 as auxiliary and hexamethyleneimine as the template. The effect of alcohol and PEG-2000 on the textural property of MCM-22 zeolite was characterized by XRD, FT-IR, nitrogen adsorption, NH₃-TPD, SEM and so on. In addition, taking the alkylation of benzene with propylene to form cumene as a model reaction, the catalytic performance of MCM-22 zeolite synthesized here was experimentally evaluated, so as to provide the basic reference for the catalyst development and performance control of this kind of zeolites.The results showed that adding proper amount of alcohol in synthesis could effectively adjust the textural property and acidity of MCM-22 zeolite. The crystallinity of MCM-22 was slightly higher than that synthesized without using alcohol. Moreover, the strength of weak acid gradually decreased while strong acid increased. Total acid and Br(?)nsted acid increased, but Lewis acid decreased. And the lamellas of high crystallization could be seen from the SEM images, and their sizes were smaller than the lamellas synthesized without using alcohol. The BET specific surface area could be controlled from 453.2 m²Â·g^-1 up to 492.7 m²Â·g^-1. The specific volume was decreased from 0.574 cm³Â·g^-1 to 0.440 cm³Â·g^-1, and the average pore diameter was almost a constant. However, excessive alcohol would lead to form ZSM-5 zeolite. Better crystal samples could be obtained if adding proper amount of PEG-2000 when the zeolites were sythesised. Depending on the amount of PEG-2000 as auxiliary, the strength of weak acid of the zeolite decreased gradually while strong acid increased. The BET specific surface area could be controlled from 453.2 m²Â·g^-1 up to 472.2 m²Â·g^-1, and the specific volume could be controlled from 0.574 cm³Â·g^-1 up to 0.648 cm³Â·g^-1, but the average pore diameter had no obvious change.The results of the evaluation of the catalytic performance of MCM-22 zeolite synthesized here showed that when the molar ratio of alcohol to SiO₂ is between 0.5 and 1.0, significant increasing of initial activity of MCM-22 and cumene selectivity could be obtained. However, cumene initial selectivity decreased lightly while using PEG-2000 as auxiliary. But it would increase quickly when the reaction moved on.