[Selective reduction of NO over indium catalysts prepared by different methods].

Alumina-supported indium catalysts with different metal loadings were prepared by various methods including impregnation, co-precipitation and sol-gel. Activity tests were carried out on the selective catalytic reduction (SCR) of NO by propene in excess O2 over the catalysts. And the effects of oxygen concentration in reaction gas feed on catalytic activities were examined. The results show that In/Al2O3 catalysts possess high deNO2 activity, and the preparation methods have obvious effects on catalytic activities. The catalysts prepared by co-precipitation or sol-gel method exhibited high NO, conversion to N2 about 90%; the impregnation samples have poor activities, the highest conversion rate not exceeding 60%. The O2 concentration in gas feed has significant effects on the highest conversion rates of NOx reduction and the corresponding reaction temperatures. Along with the increasing of O2 concentration, the temperatures mentioned above declined. The introduction of water into the gas feed depressed greatly the deNO2 activities of In/Al2O3 catalysts. Compared to many other metals as active components of deNOx catalysts, indium has a prominent different behavior that the respective best metal loadings of the catalysts prepared by these three diverse preparation methods have little difference, being all around 1% to approximately 2%.