Selective Catalytic Reduction of Nitric Oxide with Ethylene on Copper Ion-Exchanged Al−MCM-41 Catalyst

Abstract

Selective catalytic reduction (SCR) of NOx by ethylene was investigated on copper and/or cerium ion-exchanged Al−MCM-41 in the presence of excess oxygen. Ce−Al−MCM-41 showed little activity, but Cu−Al−MCM-41 and cerium-promoted Cu−Al−MCM-41 (i.e., Ce−Cu−Al−MCM-41) were found to be active in this reaction. Higher NOx conversions to N2 were obtained on Ce−Cu−Al−MCM-41 as compared with Cu−Al−MCM-41. The maximum activity of Ce−Cu−Al−MCM-41 was close to that of Cu−ZSM-5, but the former had a wider temperature window. TPR results indicated that only isolated Cu2+ and Cu+ ions were detected in the Cu2+-exchanged Al−MCM-41 samples, which may play an important role in the selective catalytic reduction of NOx to N2. After some cerium ions were introduced into Cu−Al−MCM-41, Cu2+ in the molecular sieve became more easily reducible by H2. This may be related to the increase of catalytic activity of NOx reduction by ethylene.