Synthesis of EMT Zeolite by a Steam-Assisted Crystallization Method Using Crown Ether as a Structure-Directing Agent

Abstract

A high-silica hexagonal faujasite EMT was crystallized by a steam-assisted crystallization (SAC) method using a crown ether of 1,4,7,10,13,16-hexaoxacyclooctadecane, 18-crown-6, as a structure-directing agent. The growth mechanism of EMT by SAC is quite different from that of EMT by the conventional hydrothermal synthetic method, in which layer-by-layer growth occurs. Another characteristic of SAC is that nanoparticles fuse and the surface of the dry gel is rearranged, resulting in a distinct hexagonal shape for the EMT crystals. Sodium content must be strictly defined when the SAC method is used, and the crystallization temperature must be kept below 408 K to keep the crown ether in the dry gel to obtain a pure phase of EMT.