Preparation Of Supported Catalysts And Its Catalytic Oxidation Performance Of Propane

With the acceleration of industrialization and economic growth,the volatile organic compounds（VOCs）emissions have increased dramatically in recent years.Low-temperature catalytic oxidation has been demonstrated to be one of the most efficient and economically viable technologies for VOCs oxidation into carbon dioxide,water,and other relatively harmless compounds.And the development and application of high-performance catalysts are the core of this technology.In this work,supported catalysts are selected to be the research object,and the effects of supports morphologies and the modification of supports on the catalytic performances of the prepared catalysts for propane oxidation are extensively investigated:（1）Nb₂O₅ supports with pompom（Nb₂O₅-P）,froth（Nb₂O₅-F）and layer-like（Nb₂O₅-L）morphologies were synthesized for the fabrication of supported Mn O_x catalysts.It has been demonstrated that the obtained catalysts exhibited variable catalytic activities for propane oxidation and notable diversity of physicochemical properties,which was closely related to the interface interaction between Mn O_x nanoparticles and Nb₂O₅ supports.Based on the comparison with a bulk catalyst of Prepared（Mn O_x/Nb₂O₅-B）,it was found that the morphology construction of Nb₂O₅ supports was favorable for boosting the catalytic activities of the catalysts,generally following an order of Mn O_x/Nb₂O₅-L>Mn O_x/Nb₂O₅-F>Mn O_x/Nb₂O₅-P>Mn O_x/Nb₂O₅-B.The optimum catalytic activity of Mn O_x/Nb₂O₅-L was attributed to the good surface dispersion,small dimension of Mn O_x nanoparticles and strong metal-support interaction,leading to significantly high low-temperature reducibility and lattice oxygen mobility,plentiful surface oxygen species and great proportion of Mn⁴⁺/Mn³⁺.However,Mn O_x/Nb₂O₅-L possessed inadequate thermal and catalytic stability with irreversible deactivation after long-term catalytic reactions.Characterization results of the deactivated catalyst revealed that the severe agglomeration and sintering of surface Mn O_xnanoparticles resulted in dramatically poor surface metal dispersion,low redox capacity and serious shortage of surface active oxygen species,which were recognized to be the predominant factors responsible for catalytic deactivation.（2）A series of TiO₂ supported Ru catalysts modified with different rare earth elements（Sm,Pr and Ce）were prepared by an impregnation method.The modification effect of variable rare earth elements on the crystalline phase,surface oxygen mobility,oxygen vacancies and catalytic performance for propane oxidation over the prepared catalysts was studied.It was found that the modification of TiO₂ support by rare earths（Sm,Pr and Ce）had a significant effect on the propane oxidation activity of the supported catalyst,following a descending order of Ru/Ce-TiO₂>Ru/Sm-TiO₂>Ru/Pr-TiO₂>Ru/TiO₂.Beneficially from the modification effect of Ce on the TiO₂ support,Ru/Ce-TiO₂ exhibited relatively better surface metal dispersion,more oxygen vacancies and more abundant surface active oxygen species,thus giving the optimum catalytic activity,good catalytic stability and resistant ability towards H₂O and CO₂.（3）TiO₂ supported Ru catalysts modified with cerium were prepared by an impregnation method,and the modification effect of the cerium addition amount（0%,0.5%,1.0%,1.5%and 2.0%）on the crystalline phase,the surface oxygen mobility,oxygen vacancies and catalytic performances for propane oxidation over the supported catalysts was studied.The variable catalytic activities of the catalysts followed a descending order of Ru/1.5Ce-TiO₂>Ru/1.0Ce-TiO₂>Ru/0.5Ce-TiO₂>Ru/2.0Ce-TiO₂>Ru/TiO₂.Among all,Ru/1.5Ce-TiO₂exhibited the optimum catalytic activity and good catalytic stability,which was closely related to its more surface oxygen vacancies,more abundant active oxygen species and higher redox ability.