MCM-41 modified with transition metals by template ion-exchange method as catalysts for selective catalytic oxidation of ammonia to dinitrogen

Abstract

Copper, iron and manganese were deposited on MCM-41 using template ion-exchange (TIE) method. Methanol solutions of CuCl2, FeCl2 and MnCl2 were used as precursors of deposited transition metal species. It was shown that introduction of transition metals into MCM-41 by TIE method resulted in deposition of iron and manganese in the form of highly dispersed species (mainly monomeric cations), while in case of copper also CuO crystallites were formed. Such aggregated copper oxide species were not detected in the samples of MCM-41 containing both copper and iron as well as copper and manganese. MCM-41 modified with transition metals by TIE method were found to be active catalysts for the process of the selective oxidation of NH3 to N2 (NH3-SCO), however catalytic performance of the studied samples strongly depended on the type of deposited metal. The samples modified with iron and manganese effectively catalyzed ammonia oxidation to dinitrogen only in the high temperature range. On the other side MCM-41 modified with copper was catalytically active at significantly lower temperatures, however selectivity to dinitrogen decreased at elevated temperatures. It was shown that simultaneous incorporation of copper and iron as well as copper and manganese resulted in the catalysts for the low-temperature NH3-SCO with significantly increased selectivity to dinitrogen in comparison to the monometallic copper containing catalyst.