SELECTIVE REDUCTION OF NOX BY ETHANOL ON CATALYSTS COMPOSED OF AG AL2O3 AND CU/TIO2 WITHOUT FORMATION OF HARMFUL BY-PRODUCTS/

An attempt was made to remove by-products such as NH3, CH3CN, HCN, CO and CH3CHO which are produced from the reduction of lean NOx by ethano l over an alumina-supported silver catalyst. The efficiency of titania -supported noble metals, vanadium oxide, tungsten oxide, and copper su lfate for the removal of these compounds was examined. It was found th at NH3, CH3CN, and HCN were easily oxidized to NOx and that the reduct ion of NOx to N-2 by these nitrogen-compounds did not occur effectivel y on noble metal catalysts. Among the tested catalysts, CuSO4/TiO2 was the most effective for simultaneously removing NH3, CH3CN, and HCN an d reducing NOx to N-2 by using these nitrogen-compounds. Lean NOx were reduced to N-2 by ethanol effectively and the concentration of nitrog en-containing by-products was lowered over the composite catalyst, Ag/ Al2O3 + CuSO4/TiO2. However, in addition to CuSO4/TiO2, Pt/TiO2 was re quired to remove harmful compounds completely. Consequently, a three-c omponent composite catalyst, Ag/Al2O3 + CuSO4/TiO2 + Pt/TiO2, has been employed in reducing lean NOx by ethanol. This composite catalyst has proved to be quite effective even in the presence of water vapor in t hat it can reduce lean NOx to N-2 by ethanol effectively and sufficien tly lower the concentrations of all harmful by-products. (C) 1998 Else vier Science B.V.