In this paper, the reaction behaviors of CH 3 CN catalytic combustion over CuCeO x -HZSM-5 catalysts prepared by the physical mixing and wet impregnation methods were investigated. The experimental results had revealed that the composite catalysts exhibited excellent degradation efficiency and high N 2 selectivity: the Cu-Ce oxides ensured the high activity, and the introduction of HZSM-5 limited the formation of NO x . The involved reaction mechanism was then studied by an in situ DRIFT analysis. It could be deduced that different reaction pathways would occur over CuCeO x and HZSM-5. The catalytic reaction over CuCeO x mainly proceeded via an oxidation pathway. The CN group could be converted to isocyanate species [NCO(a)] which would be further oxidized to NO x . Over HZSM-5, CH 3 CN was mainly hydrolyzed into ammonia. For the CuCeO x -HZSM-5 composite catalysts, the over-oxidation of NCO(a) and NH 3 was inhibited, and an internal selective catalytic reduction (SCR) reaction could occur, thereby greatly improving the N 2 selectivity.
A sequence of CuCeO x -HZSM-5 composite catalysts at different Cu-Ce loading synthesized by the citric acid complex impregnation method were evaluated for the catalytic oxidation of acetonitrile. Among which, the 2CuCeO x -HZSM-5 sample exhibited the best degradation efficiency. In the temperature range of 225–350 °C, its activity and mineralization rate were approximately 100%, and the N 2 selectivity remained more than 93%. The characterization results revealed that all the samples showed an existence of isolated Cu 2+ species. And more Cu-Ce mixed oxides covered on HZSM-5 at an elevated Cu-Ce content, leading to the enhanced reducibility. In situ DRIFTS results showed that both oxidation and hydrolysis reaction routes proceeded during the degradation of acetonitrile over the composite catalysts. Their synergism was crucial to guarantee both high activity and N 2 selectivity. The highly dispersed CuO x species ensured the superior activity of the 2CuCeO x -HZSM-5 sample. And Cu 2+ exchanged HZSM-5 zeolite would be beneficial to N 2 selectivity owing to the improved internal SCR (Selective Catalytic Reduction) reaction to reduce NO x from oxidation routes. Additionally, the mineralization rate was lowered with the formation of carbonaceous products like CH 4 and CO for the catalysts at low Cu-Ce loading due to the lack of redox capacity.
危险品化学品经营许可证（带存储）