Synthesis of ZSM-5/SAPO-34 zeolite composites from LAPONITE® and their catalytic properties in the MTO reaction

Abstract

ZSM-5/SAPO-34 zeolite composites were successfully synthesized by adding ZSM-5 into SAPO-34 synthetic gel under hydrothermal synthesis conditions, and SAPO-34 as a part of the composite zeolite was synthesized from LAPONITE® as the Si source. The presence of ZSM-5 in the synthetic gel affects the nucleation and crystal growth rate, and core–shell structured zeolite composites can be formed by adding an appropriate amount of ZSM-5. LAPONITE® itself contains Li and Mg atoms which were subsequently introduced into the framework of the SAPO-34 part in the composites via depolymerization–reorganization during the process of crystallization. Furthermore, the depolymerized LAPONITE® can be converted in situ into zeolitic precursors and act as crystalline seeds under hydrothermal conditions. Compared with the ZSM-5/SAPO-34 zeolite composites synthesized from tetraethylorthosilicate (TEOS) instead of LAPONITE® as the Si source, the ZSM-5/SAPO-34 composites synthesized from LAPONITE® exhibited higher selectivity to light olefins and longer lifetime in the MTO reaction. This work provides a convenient route to the synthesis of ZSM-5/SAPO-34 zeolite composites with excellent MTO performance.