Synthesis optimization of phase-singularized UZM-5 zeolite under hydrothermal conditions: The critical control points of its crystalline phase and crystallinity

Abstract

Pure UZM-5 zeolite with either nanosheet or rosette-shaped morphology have been successfully synthesized by a charge density mismatch (CDM) method under a corresponding tumbling or static conditions. The synthesis parameters were fully investigated to abstain from commonly accompanying by-products, including SOD or amorphous phase which greatly interfered with the use of UZM-5. The crystalline phases and relative crystallinity of resultant products were carefully substantiated by using scanning electron microscope and X-ray diffraction. As a result, the molar ratios of water and structure directing agents thereof were deemed to be two vital parameters which had significant effects on the well-defined pure-phase UZM-5 zeolite production. Trace ethanol added in the reagent solution was found to play a role in zeolite purification. There is an urgent need in electrocatalytic reduction of nitrate to ammonia. In this work, pure UZM-5 zeolite with Lewis acid sites served as catalyst matrix for the application to produce this valuable chemical. Excellent ammonia production rate with high faradaic efficiency was achieved by using the obtained novel UZM-5-based catalyst for the reduction reaction, strongly proving the great potential of this young zeolite in catalysis applications.