Studies on catalytic and conductive properties of LaNiO_3 for oxidation of C_2H_5OH, CH_3CHO, and CH_4

摘要

The oxidation of C_2H_5OH, CH_3CHO, and CH_4 on perovskite-type mixed metal oxide LaNiO_3 was conducted in flowing air. The conductivity change of the oxide during oxidation was also measured to ascertain the adaptability of using it as a sensing material. It was demonstrated that the oxidation reaction was accompanied by a loss of oxygen from the lattice and hence a change in conductance of the oxide. The degree of the conductance change depended on the nature and concentration of the gases as well as the oxidizing conditions. These phenomena were more obvious for alcohol and aldehyde than for methane. The temperature was an important factor affecting the sensitivity. The presence of water vapor (the products of hydrocarbon combustion) depressed the oxidation rate, probably owing to the formation of OH species on the oxide and its acting as an electron donor to reduce conductivity. The catalysts were characterized by TPR and TPD techniques. A comparison of oxidation rate and conductance as a function of reactant concentration is discussed.