Thermal stability of CeVO4-based catalysts depending on support composition for the selective catalytic reduction of NOx by ammonia

Abstract

The role of SiO2 and WO3 in CeVO4-based catalyst supported on TiO2 support containing silica-tungsten was systematically investigated for selective catalytic reduction (SCR) by hydrothermal aging. It has been found that the CeVO4 with SiO2 and WO3 added to TiO2 (i.e., CeVO4/TWS) is the optimal catalyst to promote N-2 selectivity through improved thermal stability and NH3 oxidation. CeVO4/TWS(HT; hydrothermal aging) had abundant defects and surface adsorbed oxygen species even after thermal aging. The high Vn+ (n = 4, 3) fraction of CeVO4/TWS(HT) is due to the improved thermal stability by adding SiO2 and WO3 to TiO2. The addition of SiO2 and WO3 maintains NH3 adsorption and redox properties, so the TWS support exhibits high thermal stability. As the NH3-SCR reaction mechanism, the pristine catalyst shows an Eley-Rideal and Langmuir-Hinshelwood models as dual model (ER-LH) based on abundant Lewis and Bronsted acid sites below 300 degrees C. On the other hand, the hydrothermal aged catalyst dominates the Eley-Rideal mechanism (reaction of activated ammonia with gaseous NO) based on Lewis acid sites. This study comprehensively shows that CeVO4-based catalysts have improved thermal stability by including SiO2 and WO3 in the TiO2 support.