Studies On The Catalytic Combustion Performance Of Flame Spray Pyrolysis Synthesized Cu-based Nanocatalysts

Catalyst is an important object in the research of energy and materials.The method of catalyst synthesis has great influence on the performance of catalyst.Compared to conventional preparation methods,flame spray pyrolysis exhibits unique advantages and it is a method for synthesizing high-efficient nano catalyst with the prospective of industrialization.Cu-based nanomaterials with different CuO contents and different support were synthesized by flame spray pyrolysis in this work.To examine their performance,the CO catalytic combustion at low temperature and the sintering behavior of Cu-based catalysis at high temperature CH₄ catalytic combustion were studied respectively.All the catalysts possess a high specific surface area,of which the CuO-TiO₂ nanoparticles with 2 wt.%Cu（2CT）is as high as 98 m²/g,and exhibits a spherical structure with a diameter of 15-20 nm.Compared with other methods,the FSP method can significantly improve the loading of CuO without producing large crystalline CuO particles on the catalyst surface.Interestingly,the addition of CuO will essentially change the lattice structure of TiO₂ for all catalysts,including its crystal spacing and XRD diffraction angle.Copper cations are embedded in TiO₂ lattice,to form solid solution structure,and to promote the transformation from anatase to rutile by producing oxygen defect at high flame temperature.The interaction between CuO and TiO₂ has significant influence on its physicochemical properties.A lower reduction temperature on the sample with higher CuO loading is obtained through examining hydrogen spillover effect in H₂-temperature programmed reduction（H₂-TPR）test.Moreover,the loading of CuO increases the content of more stable rutile phase in the materials,so that it reduces the strong metal-support interaction（SMSI）effect of CuO and anatase phase to further improve the catalytic properties of CO catalytic combustion.The synthesized CuO-TiO₂nanoparticles can significantly promote CO combustion conversion at low temperature and achieve complete conversion of CO at lower temperature of 120℃.The catalytic combustion tests of CH₄ with Cu-based nanomaterials supported on TiO₂,SiO₂ and ZrO₂ as catalyzer were carried out at high temperature.The experimental results show that ZrO₂ can effectively avoid the sintering of CuO on the catalyst surface.Under a 20wt.%CuO loading,there is still no large crystal CuO on the surface of the CuO-ZrO₂ catalyst.A series of experiments have found the sintering mechanism of CuO/ZrO₂ which is dominated by surface diffusion and the CuO-TiO₂ sintering mechanism which is dominated by grain boundary diffusion.According to the TEM results of these catalysts,flame synthesized materials appear hollow structure in a high temperature process,which may be attributed to the Kirkendall effect.The CuO-ZrO₂ catalyst exhibits high anti-sintering performance and superior reactivity.It achieves 80%conversion of CH₄ at a temperature of 500℃.