Performance of Zeolite-Supported Catalysts for Selective Catalytic Reduction of Nitric Oxide and Oxidation of Methane

Abstract

The selective catalytic reduction of nitric oxide by methane over copper ion-exchanged natural zeolites was investigated in a packed-bed tubular reactor. The catalytic activity of Cu−N and Cu−H−N catalysts was confirmed as NO, CH4, and O2 displayed very little reaction in the absence of any catalyst and zeolite without ion exchange was totally inactive. A maximum NO conversion of 33% at 650 °C for Cu−N-66 was achieved with 2% NO and 1% CH4 and a contact time of 0.9 g s cm-3, but the introduction of 2% O2 reduced the NO conversion to only 12%. Ion exchange for the H-form prior to copper ion exchange was essential for oxygen to promote catalytic activity over the temperature range 250−650 °C, with a maximum conversion of 30% at 450 °C with O2 present. The direct reduction of NO by methane was ruled out as a possible reaction pathway.