“Super Hydrocarbon Reformer Trap” for the Complete Oxidation of Toluene Using Iron‐Exchanged β‐Zeolite with a Low Silicon/Aluminum Ratio

Abstract

Abstract This study examines the effects of the Si/Al ratio and metal cation exchange of a zeolite on the ability to adsorb and reform unburned hydrocarbons (HCs) in emissions from gasoline vehicles. Iron ion‐exchanged β‐zeolites with a low Si/Al ratio not only trap but also oxidize HCs efficiently, which spurred on the development of a “super HC reformer trap”. Toluene temperature‐programmed desorption experiments in an O 2 ‐containing stream revealed that >90 % of the adsorbed toluene was converted into CO 2 , and other oxygenates were not observed. This material could be reused and it retained its performance. The strong adsorption of toluene on the zeolites was derived from two synergistic effects: (1) electrostatic interactions between the π orbital of the aromatic ring and the p orbital of the metal cation and (2) interactions between the positively polarized methyl group of toluene and a basic oxygen atom in the zeolite framework. This new material will pave the way for low‐emission, Pt‐free vehicles.