Adsorbent/catalyst bi-functional Fe-ZSM-5 prepared by a simple CVD process for exhaust gas treatment

In exhaust gas purification systems, the use of an inorganic porous ‘pre-filter’ in combination with a conventional catalytic converter with Pt-group metal nanoparticles is considered to be effective for reducing cold-start emissions. Organic compounds that are difficult to catalytically oxidize at low temperatures can be captured to this ‘pre-filter’ until the Pt-group catalyst has reached its operating temperature. In the present work, a simple chemical vapor deposition (CVD) method was applied to load catalytically active Fe species (Fe(III) ions, Fe(III)_xO_y clusters, and Fe₂O₃ nanoparticles) on a commercial MFI type H-ZSM-5 zeolite. The CVD could maintain the adsorption performance of H-ZSM-5 zeolite, but more importantly enhance the catalytic oxidation activity of acetaldehyde. The adsorbed acetaldehyde was oxidized with high efficiency on Fe ion & oxide loaded H-ZSM-5 (Fe-ZSM-5), which eventually can reduce cold-start emissions and improve the catalytic conversion efficiency of exhaust purification systems. Furthermore, based on in-situ DRIFTS analyses, surface poisoning of H-ZSM-5 that was induced by accumulation of coke could be eliminated by CVD of Fe ion & oxide.