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

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 NH x species. As a result, the NO x from acetonitrile overoxidation would be eliminated through internal selectivity catalytic reduction over the Cu–Ce/ZSM-5 core.

Simultaneous Generation of Ammonia during Nitrile Waste Gas Purification over a Silver Single-Atom-Doped Ceria Catalyst

“…Simultaneously, the negative bands as a result of the consumption of surface OH (at 3600 cm –1 ) could also be observed . At 100 °C, the new band located at 1601 cm –1 was assigned to NH 3 , as verified by comparison to DRIFTS patterns of NH 3 adsorption (Figure S16 of the Supporting Information), indicating the occurrence of further hydrolysis from CH 3 CONH 2 species to form NH 3 and CH 3 COOH . New bands at 2933 and 2843 cm –1 assigned to adsorbed −CH 3 appeared, which might have originated from CH 3 CONH 2 or CH 3 COOH species .…”

“…17 At 100 °C, the new band located at 1601 cm −1 was assigned to NH 3 , as verified by comparison to DRIFTS patterns of NH 3 adsorption (Figure S16 of the Supporting Information), 39 indicating the occurrence of further hydrolysis from CH 3 CONH 2 species to form NH 3 and CH 3 COOH. 5 New bands at 2933 and 2843 cm −1 assigned to adsorbed −CH 3 appeared, which might have originated from CH 3 CONH 2 or CH 3 COOH species. 40 Further DFT calculations (Figure S17 of the Supporting Information) indicated that the most probable pathway of −CH 3 formation was from the C−C bond cracking of CH 3 COOH molecules because of its lower energy consumption than that of CH 3 CONH 2 .…”

“…Therefore, effective purification of nitrile exhaust gas is an urgent demand. Selective catalytic combustion (SCC) for converting nitriles to N 2 , CO 2 , and H 2 O has become one of the most promising technologies as a result of its high purification efficiency and less secondary pollution. ,− …”

“…Ceria (CeO 2 ) has been considered as one of the most active hydrolysis catalysts. , Activation and dissociation of water was the crucial process in the catalytic hydrolysis reactions, depending upon the concentrations of oxygen vacancies and low-coordinated Ce cations in CeO 2 (active sites). , As such, ceria was widely studied in the nitrile hydration reaction in water. , In our previous study, it was observed that the addition of Ce promoted the hydrolysis of acetonitrile . Furthermore, Ce-based catalysts also exhibited superior catalytic activities in catalytic removal of volatile organic compounds (VOCs) with the advantages of excellent redox property and high oxygen storage capacity. , In addition, the basic feature of ceria could promote NH 3 desorption and, thereby, inhibit NH 3 further oxidation on the surface of the catalyst.…”

“…17,18 In our previous study, it was observed that the addition of Ce promoted the hydrolysis of acetonitrile. 5 Furthermore, Ce-based catalysts also exhibited superior catalytic activities in catalytic removal of volatile organic compounds (VOCs) with the advantages of excellent redox property and high oxygen storage capacity. 19,20 In addition, the basic feature of ceria could promote NH 3 desorption and, thereby, inhibit NH 3 further oxidation on the surface of the catalyst.…”