Insight into the Role of Cerium in the Enhanced Performances during Catalytic Combustion of Acetonitrile over Core–Shell-like Cu–Ce/ZSM-5 Catalysts
Yaoyu Zhang, Yu-Xiong Wang, Yue Liu, Huimin Xu, Qingji Ying, Zhongbiao Wu
Abstract
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.