Regulating the redox of a bimetallic catalyst for synchronous enhancement of acrylonitrile conversion and N2 selectivity

Abstract

A key problem of the catalytic oxidisation of nitrogen-containing volatile organic compounds (NVOCs) is to regulate the redox property of the catalyst. A too low oxidability results in low conversion; however, a too high oxidability produces undesired by-products such as N₂O and NO_x. In this study, Ce, Cu, Mn and V were loaded on TiO₂ and applied in the catalytic oxidisation of acrylonitrile. Results revealed that Ce-doped TiO₂ simultaneously showed better conversion (99 %) and N₂ selectivity (95.3 %) than the other catalysts at 210 °C. However, the high selectivity was swiftly decreased to 74.5 % at 240 °C. After co-doping of Cu, the high selectivity was maintained above 89.8 % within 210 °C–270 °C. Meanwhile, catalytic conversions were close to 100 %. These ensured a stable catalytic performance even when the catalytic temperature was unusually high due to NVOC catalytic burning. Surface chemistry analyses showed that the redox potential of Ce-doped TiO₂ was restrained after Cu doping, thus resulting in stable high N₂ selectivity. This study presents a successful example of redox regulation by combining transition metals with different oxidabilities, which would develop more suitable catalysts for pollutants with unique catalytic requirements.