Specific surface area - Key factor determining the catalytic activity of Pd/SnO<inf>2</inf> catalyst in nitrate hydrogenation

Abstract

Mesoporous nanocrystalline SnO2 supports were synthesized by modified sol gel method in different pH environment (pH=2 and pH=8) both starting from SnCI2·2H2O and citric acid. Equal amount of palladium was introduced via wet impregnation of obtained supports using PdCl2 solution as active phase precursor. Lower pH value during the support synthesis results in final material characterized with more developed porosity and higher surface area. Corresponding catalyst samples showed affirmative activity in nitrate removal reaction from water, performed in semi-batch conditions under hydrogen flow. The mild basic conditions of SnO2 support synthesis result in unfavorable material by means of very low surface area and corresponding catalyst samples with equally low activity regardless of their other characteristics. Presented activity results speak in favor of nitrate hydrogenation as a specific structure sensitive reaction performing a maximum activity for an optimal SnO2 crystalline size.