Identification of active structure and catalytic efficiency of MCM-22 zeolite detemplated by two different processes

摘要

This study attempts to identify the active structure and the catalytic efficiency of MCM-22 zeolite after the successful removal of pre-synthesized MCM-22(P) template by two different methods. The MCM-22(P) zeolite was firstly synthesized by hydrothermal process with a SiO2/Al2O3 ratio of 50, and its 2D layered hexamethyleneimine (HMI) precursor template was removed by (i) thermal calcination at high temperature (550 degrees C) to obtain the MCM-22(C), and (ii) oxidation with H2O2 treatment at low temperature (90 degrees C) to obtain the MCM-22(H2O2). The structural characteristics of MCM-22(C) and the MCM-22(H2O2) were identified by XRD, N-2 absorption/desorption, FTIR, NH3-TPD and Al-27 MAS-NMR. The catalytic performance of MCM-22(C) and MCM-22(H2O2) loaded by 20 wt% zinc nanoparticles were examined through a Friedel-Grafts (FC) alkylation of benzene with benzyl chloride in a liquid phase environment. It was found that Zn-MCM-22(H2O2) was more efficient in FC alkylation reaction in comparison with Zn-MCM-22(C) for the formation of intercrystal pores due to the inhibitory influence of silonal group condensation on the external surface of MCM-22 crystals.