NO reduction by urea under lean conditions over alumina supported catalysts

We prepared Pt on alumina and Au on alumina catalysts using a single step sol-gel process and traditional techniques, such as impregnation and deposition-precipitation. The activity of these catalysts was tested for NOx reduction with aqueous urea solutions under oxidizing conditions. Our results show that when a bubbler was used to feed urea and water, catalysts prepared by the sol-gel process had better performance than the catalysts prepared with impregnation and deposition-precipitation methods. The NOx conversion changed almost linearly over Au on alumina catalysts regardless of preparation techniques but over the single step sol-gel synthesized Pt on alumina catalyst (Pt-SG) a typical dome shape of the conversion versus temperature curve was observed. Oxygen in the feed increased the conversion activity and the presence of SO2 did not have an adverse effect on the activity of Pt-SG and the single step sol-gel Au on alumina (Au-SG) and the impregnation Au on sol-gel alumina (Au-IMP-SG) catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.