Catalytic performance of plasma catalysis system with nickel oxide catalysts on different supports for toluene removal: Effect of water vapor

The effect of water vapor on the performance of a combined non-thermal plasma catalysis (CPC) system with nickel oxide catalysts loaded on different supports was investigated. The catalysts NiO/γ-Al2O3, NiO/SBA-15 (Santa Barbara Amorphous-15), and NiO/TiO2 were prepared and their activities were tested in the absence and presence of water vapor. Complete destruction of toluene was achieved in the absence of water vapor at ambient temperature and pressure. The activities of catalysts for the toluene conversion in dry air decreased in the following order: NiO/γ-Al2O3 > NiO/SBA-15 > NiO/TiO2. The presence of water vapor in the feed stream had a significant negative impact on the performance of the CPC systems. This reduction in performance was primarily due to the quenching by water vapor of active species in the plasma and the competitive adsorption of water vapor on the catalyst surfaces. A novel in situ FTIR system was constructed and used to obtain in situ FTIR spectra of the reactive surfaces of the catalysts, revealing that the water molecules that adsorbed on the catalyst surfaces came from both water vapor present in the gas stream and from water vapor formed during the oxidation of toluene. H2O-TPD results indicated that the activation energies of water desorption from the catalysts decreased in the following order: NiO/γ-Al2O3 > NiO/SBA-15 > NiO/TiO2. The catalyst with lower water vapor desorption activation energy had higher resistance to water vapor. Therefore, the durability towards water vapor poisoning of these catalysts followed the order of: NiO/TiO2 > NiO/SBA-15 > NiO/γ-Al2O3.