SYNTHESIS OF HIGH SILICA MCM-22 ZEOLITE WITH DUAL ORGANIC STRUCTURE-DIRECTING AGENTS AND ITS CATALYTIC PERFORMANCE

Abstract

Abstract: MCM-22 zeolite with high crystallinities was synthesized under optimized the crystallization time, amount of TMAdaOH and SiO2/Al2O3 molar ratio conditions by using hexamethyleneimine (HMI) and N,N,N-trimethyl-1-ammonium adamantine (TMAdaOH) as dual organic structure-directing agents. The zeolite was characterized by X-ray diffraction, scanning electron microscopy, N₂ adsorption-desorption, NH₃-TPD and TG analysis. The catalytic performance of H-type MCM-22 zeolite for the pyrolysis of triisopropylbenzene (TiPB) was investigated. The results showed that with the addition of a small amount of TMAdaOH, MCM-22 zeolite could be synthesized under a wide range of n(SiO₂)/n(Al₂O₃), and MCM-22 zeolite had the advantages of crystal purity, high solid yield and adjustable acidity. The high silica MCM-22 with n(SiO₂)/n(Al₂O₃) of 60-100 displayed better cracking performance for TiPB than that of conventional MCM-22 with n(SiO₂)/n(Al₂O₃) of 30.

Key words: MCM-22 zeolite, high silica, dual organic structure-directing agent, TiPB, cracking

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