Study On The Morphology Regulation Of Cobalt-based Oxide And Its Effect On The Performance Of Propane Oxidation

Volatile organic compounds（VOCs）emitted from industrial production,transportation and interior decoration are one of the main air pollutions.They not only have obvious toxic effects on the human body,but also are important precursors for the formation of PM_2.5and O₃.Propane（C₃H₈）in VOCs is a kind of short-chain alkanes.The total C-H bond energy is 4016 k J/mol,which is difficult to be degradated and destroyed.Catalytic oxidation technology is an economical and efficient technology without secondary pollution.Its core is the development of high activity and good stability catalysts.Co₃O₄shows high catalytic activity and anti-poisoning ability,becoming the focus of many researches.However,Co₃O₄particles are sintered and agglomerated easily in high temperature environment and mobility of its oxygen species is insufficient,which limits the further improvement of catalytic oxidation performance.In this work,we take the strategies of biomass template and doping of met al elements to regulate the morphology and structure of cobalt-based oxides,enhance the dispersibility of cobalt-based oxide and the mobility of oxygen species,and thereby improving the C₃H₈catalytic oxidation ability.A series of cobalt-based oxides were prepared by impregnation method,hydrothermal method and inverse co-precipitation method respectively.XRD,N₂adsorption-desorption,SEM,TEM,Raman,H₂-TPR,O₂-TPD,C₃H₈-TPSR,NH₃-TPD,XPS,XANES,EXAFS,in situ DRIFTS and other technologies are carried to systematically characterize and analyze the physicochemical properties of the catalyst,therefore the structure-effect relationship is revealed.The specific research content is as follows:（1）Co₃O₄was prepared by impregnation method using rice husk powder Si-C template with a large specific surface area as carrier and the its catalytic oxidation performance was explored.The results show that Co₃O₄with fine grain size and high dispersion was synthesized,benefiting from the restriction of the pore structure from rice husk powder,the inhibit agglomeration of biomass carbon and the reduction of calcination temperature.This contributes to the enrichment of surface Co³⁺species and the enhancement of low-temperature reduction ability,thereby showing better catalytic oxidation activity for C₃H₈.（2）The layered Co Al composite oxide with large specific surface area and good thermal stability from the layered double hydroxide was prepared,and the modification effect of the NH₃treatment strategy on the Co Al composite oxide was discussed.The results show that the Co Al oxide treated with NH₃for 4 hours has a higher nitrogen doping amount,which cooperates with the reduction of part of Co³⁺to promote the generation of oxygen vacancies.On the other hand,the active oxygen species,Co²⁺and Co³⁺enriched on the surface of Co Al oxide contribute to the adsorption and oxidation of C₃H₈molecules.Thus,the nitrogen-doped layered Co Al composite oxide exhibits better C₃H₈catalytic oxidation performance.（3）A series of porous core-shell Mn-Co-O catalysts were prepared by the inverse co-precipitation method.The results show that the porous core-shell structure composed of Co-Mn solid solution effectively improves the mass transfer and deep oxidation capabilities of the Mn-Co-O catalyst,optimizes the distribution of surface Co valence,improves surface acidity and increases the content of surface adsorbed oxygen species.This is beneficial to the adsorption of C₃H₈and the cracking of C-H,thereby showing excellent catalytic performance,thermal stability,resistance to H₂O and resistance to CO₂.