Catalytic reduction of NO, with H2/CO/CH4 over PdMOR catalysts

Conversion of NOx with reducing agents H-2, CO and CH4, with and without O-2, H2O, and CO2 were studied with catalysts based on MOR zeolite loaded with palladium and cerium. The catalysts reached high NOx to N-2 conversion with H-2 and CO (> 90% conversion and N-2 selectivity) range under lean conditions. The formation of N2O is absent in the presence of both H-2 and CO together with oxygen in the feed, which will be the case in lean engine exhaust. PdMOR shows synergic co-operation between H-2 and CO at 450-500 K. The positive effect of cerium is significant in the case of H-2 and CH4 reducing agent but is less obvious with H-2/CO mixture and under lean conditions. Cerium lowers the reducibility of Pd species in the zeolite micropores. The catalysts showed excellent stability at temperatures up to 673 K in a feed with 2500 ppm CH4, 500 ppm NO, 5% O-2, 10% H2O (0-1 % H-2), N-2 balance but deactivation is noticed at higher temperatures. Combining results of the present study with those of previous studies it shows that the PdMOR-based catalysts are good catalysts for NO, reduction with H2, CO, hydrocarbons, alcohols and aldehydes under lean conditions at temperatures up to 673 K. (c) 2007 Elsevier B.V. All rights reserved.