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 SiO 2 /Al 2 O 3 ratios were prepared and evaluated for ethylene oxidation at 25 °C. Ethylene can be completely oxidized into CO 2 by all the Ag/ZSM-5 catalysts at 25 °C. It is found that SiO 2 /Al 2 O 3 ratio of ZSM-5 has a significant effect on catalytic stability. Ag/ZSM-5 with SiO 2 /Al 2 O 3 ratio of 38 exhibits enhanced catalytic stability compared with other Ag/ZSM-5 catalysts. The conversion of ethylene with Ag/ZSM-5 (SiO 2 /Al 2 O 3  = 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 C 2 H 4 adsorption sites and the inhibition of C 2 H 4 adsorption sites by H 2 O vapor is one of the crucial reasons of the activity loss for ethylene oxidation. H 2 O adsorption-desorption kinetics results demonstrate that slow adsorption and fast desorption characters of H 2 O on Ag/ZSM-5 with SiO 2 /Al 2 O 3 ratio of 38 contribute to its good catalytic stability for ethylene oxidation. Taking into account the elucidation of the negative effect of H 2 O 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.