Bifunctional Cu/HZSM5 zeolite with hierarchical porosity for hydrocarbon abatement under coldstart conditions

A key target to reduce current hydrocarbon emissions from vehicular exhaust is to improve their abatement under coldstart conditions. Here, we demonstrate the exceptional properties of a hierarchical Cu/HZSM5 zeolitebased system as a catalytic trap. The largely increased external surface area coupled with the preserved intrinsic properties attainable upon alkaline treatment and subsequent acid washing of a conventional ZSM5 zeolite enable an improved dispersion of copper species in the hierarchical counterpart. The impact of postsynthetic modification on the preparation of coppercontaining ZSM5 is clearly revealed by XRD, N2 sorption, FTIR, NH3TPD, TEM, SEM, and HAADFSTEM. By providing stronger adsorption sites, the introduction of copper species improves the retention of propene and toluene with respect to the protonic zeolites, and enables their further conversion to carbon dioxide and water on reaching its desorption temperature. The equivalent adsorption capacity and improved oxidation activity and lower susceptibility to deactivation exhibited by the hierarchical Cu/HZSM5 catalyst visavis its conventional counterpart yield a superior bifunctional catalyst able of reach full hydrocarbon conversion under realistic operating conditions.