Cu-Ag/mordenite catalysts for NO reduction: Effect of silver on catalytic activity and hydrothermal stability

Abstract

Mordenite-supported bimetallic (Cu-Ag) catalysts were prepared for NO reduction. The effect of silver concentration on catalytic activity and hydrothermal stability was analyzed. The synthesis of monometallic catalyst was achieved by ion exchange of Cu+2. Bimetallic catalysts were obtained adding Ag+ by ion exchange. Hydrothermal stability was proved by exposing catalysts to a water vapor stream at high temperature during several hours. Bimetallic catalysts exhibit higher catalytic activity than monometallic Cu catalyst. FTIR and UV–vis studies show catalysts to contain Cu+ and Cu+2 species. Copper cationic species can be in a configuration similar to bis(μ-oxo)dicopper cores linked to catalytic activity by completing copper cationic red-ox cycle, which is promoted by silver. XPS studies suggest that copper migrates to form CuO in hydrotreated monometallic Cu diminishing its catalytic activity. In hydrotreated bimetallic catalysts copper cationic species remain and the lower catalytic activity was due to a weaker copper-silver interaction.