Durable and selective activity of Pd loaded on WO3/ZrO2 for NOCH4O2 in the presence of water vapor

Pd loaded on WO3/ZrO2 was applied for the selective reduction of NO by methane in the presence of O2. The catalyst exhibited the highest NO and methane conversion when WO3 monolayer covered over ZrO2 surface. NO reduction activity was observed when Pd loading was lower than 0.17 wt.%. However, further increase in the Pd concentration lowered the NO conversion due to the occurrence of direct oxidation of methane. The Pd loaded on monolayer-WO3/ZrO2 catalyst exhibited durable and selective activity for the NOCH4O2 reaction. The selectivity was considerably improved in an atmosphere of 10% water vapor. The durability of the catalysis was responsible for the stability and enhanced concentration of Brønsted acidity in WO3/ZrO2 as proved by NH3 temperature programmed desorption (TPD) and measurement of adsorbed pyridine.