ECNU‐13: A High‐Silica Zeolite with Three‐Dimensional and High‐Connectivity Multi‐Pore Structures for Selective Alkene Cracking

Abstract

AbstractA high‐silica zeolite ECNU‐13 (Si/Al=23) with a new three‐dimensional (3D) pore system and a nanosized morphology has been developed, consisting of multitudes of 10‐membered ring (10‐R) medium pores and one set of 8‐R small pores. A phase‐discrimination strategy was proposed to synthesize ECNU‐13 by regulating the gel compositions and nucleation processes that were used for preparing 12‐R large‐pore germanosilicate IM‐20 with the known UWY topology. The crystallization was directed towards forming one set of single four‐ring (s4r) composite building units together with one set of double four‐ring (d4r) rather than two different types of d4r units in IM‐20. The electron crystallographic investigations elucidated that the ECNU‐13 structure was composed of two kinds of polymorphs as a result of distinct atomic positionings in s4r units. In catalytic cracking of 1‐butene, ECNU‐13 exhibited high propene selectivity (55.6 %) and propene to ethylene molar ratio (>4.7) superior to well‐studied conventional ZSM‐5 zeolite catalyst.