Rational Design of a Novel Core–Shell Cu-ZSM-5@Ru/S‑1 Tandem Catalyst for the Catalytic Combustion of Dichloromethane

To achieve a well synergistic effect between dissociative adsorption and deep oxidation during the dichloromethane (DCM) catalytic combustion process, a novel tandem catalyst, Cu-ZSM-5@Ru/S-1, was developed by rationally designing the catalyst structure. Activity experiments revealed that the Cu-ZSM-5@Ru/S-1 catalyst achieved a DCM conversion and mineralization rate of over 90% under a 5% H2O atmosphere at 290 °C with a low Ru loading of 0.2 wt %. The mineralization rate of the Cu-ZSM-5@Ru/S-1 was approximately 78% higher than that of the Cu-ZSM-5 catalyst, and the activity was approximately 55% higher than that of the Ru/HZSM-5 catalyst. Furthermore, the in situ characterizations and simulation results indicated that the DCM catalytic reaction followed a tandem reaction mechanism. The initial dissociative adsorption and conversion of DCM primarily occurred in internal Cu-ZSM-5 active sites, and the deep oxidation of the intermediates was subsequently achieved on the Ru/S-1 shell. The two steps mentioned above acted synergistically to enhance both DCM dechlorination and deep oxidation. In addition, the PCDD/F emission of Cu-ZSM-5@Ru/S-1 catalyst at 350 and 400 °C met the national standard for municipal solid waste incineration (0.1 ng I-TEQ Nm–3). Overall, this study provides new strategies for developing highly active and cost-effective catalysts for CVOC catalytic combustion

Insight into the Role of Cerium in the Enhanced Performances during Catalytic Combustion of Acetonitrile over Core–Shell-like Cu–Ce/ZSM‑5 Catalysts

Cerium-modified Cu/ZSM-5 catalysts were employed for the selective catalytic combustion of acetonitrile. It was obtained that cerium addition effectively improved the mineralization rate of acetonitrile and nitrogen selectivity as well. The optimal Cu5Ce8/ZSM-5 sample exhibited 100% mineralization rate and higher than 95% nitrogen selectivity within 325–500 °C. The strong interaction between Cu and Ce species was induced in a core–shell-like structure of Cu–Ce/ZSM-5 samples, where the Cu–Ce/ZSM-5 core was wrapped with a Cu–Ce mixed oxide layer. The external mixed oxides exhibited enhanced reducibility and increased active oxygen species. In situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory simulations revealed that surface cerium species strengthened the hydrolysis reaction path of acetonitrile as ceria could effectively promote the dissociation of water and the hydrolysis of cyano groups, thereby generating a sufficient amount of NHx species. As a result, the NOx from acetonitrile overoxidation would be eliminated through internal selectivity catalytic reduction over the Cu–Ce/ZSM-5 core