CATALYTIC DECOMPOSITION OF NITROUS-OXIDE OVER PEROVSKITE-TYPE SOLID OXIDE SOLUTIONS AND SUPPORTED NOBLE-METAL CATALYSTS

The catalytic decomposition of nitrous oxide to nitrogen and oxygen ha s been investigated over various solid oxide solutions (SOS), La(0.8)S r(0.2)MO(3-delta) (M = Cr, Fe, Mn, Co or Y), La1.8Sr0.2CuO4-delta and supported Pd, Pt catalysts. The reaction was carried out in a gradient less recycle reactor at 1 atm pressure with a feed gas containing abou t 0.5% N2O (in helium). Among the various solid solutions, La0.8Sr0.2C oO3-delta showed a maximum N2O conversion of 90% at 600 degrees C. The order of activity observed for N2O decomposition was La0.8Sr0.2CoO3-d elta .2CuO4-delta>La(0.8)Sr(0.2)CrO(3-delta)approximate to La0.8ST0.2Y O3-delta. The activity of La0.8Sr0.2CoO3-delta was compared with suppo rted Pd, Pt and also with unsubstituted LaCoO3 catalysts under similar reaction conditions. Among all the catalysts tested in this study, Pd /Al2O3 showed the lowest light-off temperature for N2O decomposition. The activity of La0.8Sr0.2CoO3-delta was found to be comparable to Pd/ Al2O3 catalyst at temperatures above 500 degrees C. The influence of a dded oxygen (about 4%) in the feed was examined over La0.8Sr0.2CoO3-de lta and Pd/Al2O3 catalysts and only in the case of cobalt catalyst was the conversion of N2O decreased by similar to 13%. By choosing varied sintering conditions, La0.8Sr0.2CoO3-delta of different BET surface a reas were prepared and the light-off temperature was found to decrease with increase in surface area. The results obtained over solid soluti ons are discussed on the basis of the cation mixed valency and oxygen properties of the catalyst.