Direct synthesis of zeolite coatings on cordierite supports by in situ hydrothermal method

摘要

A simple and green in situ hydrothermal method,free of organic templates or zeolite seeds,was examined and introduced by depositing several typical microporous aluminosilicate zeolites(Linde A,Linde Y,mordenite and ZSM-5)on cordierite supports.Such preparative factors as crystallization time,crystallization temperature and basic strength were systematically investigated to discuss their effect on the growth of zeolites on cordierite supports.The as-prepared zeolite/cordierite samples were characterized by various techniques and a supposed in situ growth mechanism of zeolites on supports was given.The aluminium atoms on cordierite supports were activated by OH~-and these activated atoms subsequently built a zeolite framework together with the silicon atoms and aluminium atoms of the synthesis gel.Based on this,the in situ deposition of zeolites can be easily extended to other aluminium-containing supports.With respect to pure zeolite powders,the in situ coated zeolites on supports exhibited much better stability and accessibility,which were thought essential for industrial applications.Copper ion-exchanged ZSM-5/cordierite was studied as catalyst for the direct decomposition of NO and selective catalytic reduction of NO by propane in excess oxygen.Cu-ZSM-5/cordierite was found to exhibit an obviously enhanced turnover frequency compared to Cu-ZSM-5 powders,which made it a potential deNO_x catalyst for future applications.