A highly active intra-zeolite iron site for the selective catalytic reduction of NO by isobutane

Abstract

A novel preparation for Fe-ZSM-5, which involves intense grinding of FeCl 3 with H-ZSM-5, with subsequent rapid dissolution of remaining iron chloride, leads to materials that catalyse the selective reduction of NO by isobutane at high reaction rates with very low amounts of iron (0.5 wt%): NO conversions of 80% (NO and isobutane – 1000 ppm each, 2% O 2) are achieved at 673 K with a GHSV of 30 000 h −1. The influence of water on the NO conversion is small below 623 K. Above 673 K, both reversible poisoning and irreversible deactivation occur. XPS data imply that the iron is not enriched in the external zeolite region. An EXAFS investigation of the catalyst shows that there are no bulk iron phases; instead, iron is present as an isolated ion (i.e. not in dimeric or oligomeric forms).