Thermal Kinetic Analysis Of Co/Al-LDH And Effects Of Ce Doping On Catalytic Efficiency Of Co-based LDO

With the development of a variety of advanced oxidation technologies,the requirement for innovative,efficient and environment-friendly catalysts is constantly increasing.Countless investigators are dedicated to the development of various catalytic materials for decades.LDH and LDO have been the topic of investigation because of their unique layered structure and interlayer ion and metal ion exchangeability,etc.In this paper,the process preparation,analytical characterization,performance testing and catalytic mechanism of binary and ternary Co-LDO-based ozone catalysts are systematically discussed as follows.（1）Firstly,the Co/LDO ozone catalysts prepared by Co/Al-LDH precursors were characterized and evaluated in detail.The Co/Al-LDH calcination products obtained in a certain temperature program were studied systematically and thoroughly by applying a series of modern instrumental test characterization methods.Four key nodes were selected according to the TG curves,and the morphology,elemental distribution,crystalline shape,functional groups and free radicals of the products obtained at different temperature were systematically investigated.It was found that calcination products with Co₃O₄ and CoAl₂O4 crystalline phases as the main crystalline phases could be obtained at all temperatures,and the content of crystalline phases increased gradually with the increase of calcination temperature.Although calcination products with mostly Co₃O₄ crystalline phases could be obtained at 500°C,the growth and refinement process of crystals continued during the further increase of temperature.Meanwhile,XPS tests also proved that the substance corresponding to the cobalt element in calcination products was mainly Co₃O₄,and the variation of Co₃O₄ content reflected a trend similar to that of XRD.The results of FTIR-Raman analysis further verified the theoretical reaction of Co/Al-LDH in each temperature region during the thermal treatment process.According to the TEM inspection,the layer spacing of the calcined products at four temperature points were 0.324 nm、0.212 nm、0.149 nm、0.166 nm,respectively.With the increase of temperature,the layer spacing gradually decreases and the layer structure starts to be less homogeneous,and the boundary between layers also starts to be unclear.The catalytic operation proves that the best COD and TOC removal can be obtained by calcination at500℃.（2）Subsequently,thermal kinetic modeling were constructed for the formation process of Co/Al-LDO.The exploratory study of thermo-kinetic modeling was conducted based on thermodynamic analysis and mathematical deconvolution analysis（symmetric deconvolution and asymmetric deconvolution）.The activation energy of each peak fitted was obtained by integral isoconversion rate method KAS method and evaluated.Moreover,the model parameters were further obtained and preliminary thermo-kinetic models were constructed.（3）Furthermore,various ratios of Ce doping were applied in the preparation of two different Co-LDO catalysts,i.e.,Ce@Co/Fe-LDO and Ce@Co/Al-LDO,and their catalytic efficiency as well as crystal structure was evaluated.The results showed the ratio value of Co:[Fe（or Al）+Ce]=3:1 of the Ce-doping Co-LDO catalysts,i.e.Ce@Co/Fe-LDO and Ce@Co/Al-LDO,can enhance the crystallinity and improve the catalytic efficiency,while in the case of the Ce-doping was carried out under the constant ratio of Co:Fe（or Al）=3:1,an inhibitory effect would emerged both on the crystallinity and efficiency of LDO catalysts.