低温乾式同時脱硫・脱硝触媒の開発 Ｃｒ２Ｏ３‐ＴｉＯ２共沈酸化物

Abstract

Catalysts for the low-temperature dry-type simultaneous removal of sulfur oxides (SOx) and nitrogen oxides (NOx) were investigated, and Cr2O3-TiO2 prepared by the coprecipitation method was found as a superior catalyst.In this process, SO2 was catalytically oxidized to SO3, then deposited onto catalyst surface as ammonium sulfates by the reaction with H2O and NH3, and NOx were reduced to N2 with NH3 over the same catalyst at low temperature (ca. 130°C).The experiments were carried out using a flow type packed bed reactor under atmospheric pressure at 110-150°C. Inlet gases were SO2 (mainly 250ppm), NO (250ppm), NH3 (500-750ppm), O2 (5%), H2O (10%) and N2 (balance gas).The main results obtained are as follows:1) 10-30mol%Cr2O3-90-70mol%TiO2 gave the higer activity than the other composition oxides for the simultaneous removal of SOx, and NOx.2) The salts deposited on Cr2O3-TiO2 were amorphous form of NH4HSO4 and (NH4) 2SO4.3) The used catalyst could be regenerated by heating at 500°C in N2 stream, and then treating with O2 (5%)-N2 mixture at 500°C.4) The active oxygen of Cr2O3-TiO2 gave the high activity for not only the denitrification (NOx removal), but the oxidation of NO to NO2. When the active oxygen was consumed, the addition rate of the oxygen from the gas phase was promoted by the coexistence of SO2.5) The almost complete removal of SOx, and NOx without the leak of NH3 could be done by controling the quantity of NH3 supplied over Cr2O3-TiO2.