A Unique Fe/Beta@TiO2 Core–Shell Catalyst by Small-Grain Molecular Sieve as the Core and TiO2 Nanosize Thin Film as the Shell for the Removal of NOx

Abstract

Fe/Beta@TiO2 core–shell catalysts with nanosize TiO2 thin film as the shell and small-grain Beta supporting Fe oxides as the core were controllably synthesized by a self-assembly method, and their catalytic performances were investigated for selective catalytic reduction of NOx with NH3 (NH3–SCR). It was found that TiO2 shells decrease the acid amount and weaken the acid strength of the catalyst, which could be beneficial to inhibiting the adsorption of acrolein species from covering active sites and then improving the ability of NO oxidation to NO2 during NH3–SCR. Moreover, TiO2 shells not only can prevent the deposition of coke and nitrate species from blocking the active iron sites, but also can serve as an effective barrier to suppress the active metal oxide nanoparticles from aggregating at high temperature. Therefore, Fe/Beta@TiO2 exhibits an improved thermal stability, higher propene, and H2O-tolerance.