Catalytic reduction of NO sub(x) with H sub(2)/CO/CH sub(4) over PdMOR catalysts

• Published in: Applied catalysis. B, Environmental Environmental, 2007-05, Vol.73 (3-4), p.327-335
• Main Authors: Pieterse, Johannis AZ, Booneveld, Saskia
• Format: Article
• Language: English
• Subjects: Air pollution control; Alcohol; Aldehydes; Carbon dioxide; Catalysis; Catalysts; Cerium; Exhaust emissions; Feeds; Methane; Oxygen; Palladium; Q1; Temperature; zeolites
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2007.01.005

Conversion of NO sub(x) with reducing agents H sub(2), CO and CH sub(4), with and without O sub(2), H sub(2)O, and CO sub(2) were studied with catalysts based on MOR zeolite loaded with palladium and cerium. The catalysts reached high NO sub(x) to N sub(2) conversion with H sub(2) and CO (>90% conversion and N sub(2) selectivity) range under lean conditions. The formation of N sub(2)O is absent in the presence of both H sub(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 sub(2) and CO at 450-500 K. The positive effect of cerium is significant in the case of H sub(2) and CH sub(4) reducing agent but is less obvious with H sub(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 CH sub(4), 500 ppm NO, 5% O sub(2), 10% H sub(2)O (0-1% H sub(2)), N sub(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 sub(x) reduction with H sub(2), CO, hydrocarbons, alcohols and aldehydes under lean conditions at temperatures up to 673 K.