Superior pillared clay catalysts for selective catalytic reduction of nitrogen oxides for power plant emission control

Fe3+-, Cr3+-, Cu2+-, Mn2+-, Co2+-, and Ni2+-exchanged Al2O3- pillared interlayer clay (PILC) or TiO2-PILC catalysts are investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of excess oxygen. Fe3+-exchanged pillared clay is found to be the most active. The catalytic activity of Fe-TiO2-PILC could be further improved by the addition of a small amount of cerium ions or cerium oxide. H2O and SO2 increase both the activity and the product selectivity to N-2. The maximum activity on the Ce-Fe-TiO2-PILC is more than 3 times as active as that on a vanadium catalyst. Moreover, compared to the V2O5-WO3/TiO2 catalyst, the Fe-TiO2-PILC catalysts show higher N-2/N2O product selectivities and substantially lower activities (by similar to 85%) for SO2 oxidation to SO3 under the same reaction conditions. A 100-hr run in the presence of H2O and SO2 for the CeO2/Fe-TiO2-PILC catalyst showed no decrease in activity.