Synthesis, characterization and evaluations of the Ag/ZSM-5 for ethylene oxidation at room temperature: Investigating the effect of water and deactivation

Abstract Ag/ZSM-5 catalysts with different SiO2/Al2O3 ratios were prepared and evaluated for ethylene oxidation at 25 °C. Ethylene can be completely oxidized into CO2 by all the Ag/ZSM-5 catalysts at 25 °C. It is found that SiO2/Al2O3 ratio of ZSM-5 has a significant effect on catalytic stability. Ag/ZSM-5 with SiO2/Al2O3 ratio of 38 exhibits enhanced catalytic stability compared with other Ag/ZSM-5 catalysts. The conversion of ethylene with Ag/ZSM-5 (SiO2/Al2O3 = 38) remained approximately 100% for 405 min at 25 °C, and then the ethylene conversion gradually decreased to zero in the following 450 min. It is revealed that Bronsted acid sites are the C2H4 adsorption sites and the inhibition of C2H4 adsorption sites by H2O vapor is one of the crucial reasons of the activity loss for ethylene oxidation. H2O adsorption-desorption kinetics results demonstrate that slow adsorption and fast desorption characters of H2O on Ag/ZSM-5 with SiO2/Al2O3 ratio of 38 contribute to its good catalytic stability for ethylene oxidation. Taking into account the elucidation of the negative effect of H2O adsorption on Bronsted acid sites on the catalytic stability of Ag/ZSM-5 catalysts for ethylene oxidation, this work will provide new insights into designing high-performance catalysts for ethylene elimination at room temperature.