Catalytic Decomposition of H2O2 for NO Oxidation-Removal over Hierarchical Fe-ZSM-5: Effect of Ethanol on Zeolite Performance

Hierarchical Fe-ZSM-5 zeolite catalysts hydrothermally prepared using tetrapropylammonium hydroxide (TPAOH) and [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride (TPOAC) as micropore structure-directing agent and mesoporogen, respectively, were investigated for oxidation-removal of NO via catalytic decomposition of gas-phase H2O2 into hydroxyl free radicals ((OH)-O-center dot). The effects of ethanol in synthesis gel on the structure, porosity, Fe species state, and catalytic performance of zeolite catalysts were explored. And the function mechanism of ethanol was speculated. Appropriate ethanol dosage in synthesis gel probably stabilized TPOAC micelles during MFI crystallization, facilitated mesopores integration in zeolite crystals, benefited oxygen vacancy formation, accelerated (OH)-O-center dot radicals generation, and thereby enhanced NO oxidation-removal efficiency. The hierarchical Fe-ZSM-5 prepared with ethanol/H2O ratio of 1 in synthesis gel displayed an excellent catalytic activity with the optimal NO conversion up to 35.9% enhancement compared to the microporous Fe-ZSM-5. The SO2 resistance and (OH)-O-center dot scavenger test during catalytic reaction, as well as the reaction condition influence on the catalytic performance of hierarchical Fe-ZSM-5 were explored, and then the oxidation-removal mechanism of NO over hierarchical Fe-ZSM-5 was preliminarily proposed.