Catalytic Oxidation Of Propane By MPt/Ti_xAlO_y Catalyst

Since most low carbon alkanes are carcinogenic and mutagenic,the atmospheric pollution caused by their emission into the air seriously endangers human health and ecological sustainability.Therefore,effective control of low carbon alkane emissions is of great significance to alleviate environmental pollution in China.Catalytic oxidation is considered to be the most effective and complete method to eliminate low carbon alkanes because of its high catalytic efficiency and low energy consumption,and the most critical step of catalytic oxidation is the development of catalysts with high efficiency performance.Propane is a highly representative of low-carbon alkanes,which is chemically stable and has C-C bonds that are not easily broken,so removal of propane usually requires high temperatures.Pt-based catalysts are the catalysts of choice for catalytic oxidation of propane,and Pt nanoparticles play a key role in the catalytic reaction,but their high price and scarce supply limit their application.How to achieve the best efficiency of propane elimination with less Pt,and to reduce the temperature of catalytic oxidation as much as possible to break the C-C bond of propane to produce non-toxic CO₂ and H₂O,and to solve the problem of catalytic oxidation of propane with water,and to improve the problem of sulfur poisoning in catalytic oxidation of propane are the current scientific challenges for researchers.These are the challenges for researchers.To address these issues,catalysts with different structural and physicochemical properties were prepared for the catalytic oxidation of propane by one-step volatilization-induced self-assembly,in situ vacuum impregnation and restricted domain encapsulation,respectively.The main components are as follows:1.Synthesis of catalysts Pt/Ti_0.1Al O_y-400,Pt/Ti_0.1Al O_y-500,Pt/Ti_0.1Al O_y-600 by one-step evaporation induced self-assembly（EISA）method for application in catalytic oxidation of propane.After screening the best roasting temperature for the preparation of catalytic oxidation of propane catalyst activity,the effect of different Ti/Al contents on the catalyst activity was investigated.The higher specific surface area,larger pore size,good thermal stability and suitable surface acidity of ordered mesoporous Al₂O₃ were utilized to facilitate the dispersion of the active metal,as well as the high chemical stability of Ti O₂ and the easy decomposition of sulfate on the Ti O₂ surface.Ti O₂ was doped on ordered mesoporous Al₂O₃ carrier,and the surface acidity was adjusted to promote the interaction between SO₂ and ordered mesoporous Al₂O₃,and a series of Ti/Al loaded precious metal Pt catalysts with water and sulfur resistance were prepared for propane catalytic oxidation.The activity test analysis revealed that Pt/Ti_0.1Al O_y catalysts with high specific surface area,high Pt²⁺content and lattice oxygen content,and abundant acid sites have good redox performance,good water resistance and sulfur resistance.These works provide new ideas and experimental accumulation for the ordered mesoporous Pt/Ti_xAl O_y catalysts to cope with complex working conditions.2.Three skeleton-limited catalysts 0.2%Pt/Ti_0.1Al O_y-EISA,0.3%Pt/Ti_0.1Al O_y-EISA,0.5%Pt/Ti_0.1Al O_y-EISA were successfully prepared by one-step evaporation-induced self-assembly method.it was found that the skeleton-limited effect promoted the dispersion of noble metal Pt nanoparticles.All catalysts showed ordered mesoporous structures with the order of activity:0.2%Pt/Ti_0.1Al O_y-EISA<0.3%Pt/Ti_0.1Al O_y-EISA<0.5%Pt/Ti_0.1Al O_y-EISA.Among them,the 0.3%Pt/Ti_0.1Al O_y-EISA catalyst was found to be highly dispersed due to the Pt nanoparticles and abundant.The 0.3%Pt/Ti_0.1Al O_y-EISA catalyst exhibited excellent catalytic activity for propane oxidation due to the dual effect of highly dispersed Pt nanoparticles and abundant surface adsorbed oxygen(O_ads).All three catalysts exhibited good thermal stability and water and sulfur resistance due to the good immobilization of Pt nanoparticles by the skeleton domain-limiting effect,which prevented their high-temperature agglomeration effect to a certain extent.3.The skeleton-limited 0.3%Pt/Ti_0.1Al O_y-EISA catalysts were prepared by one-step evaporation-induced self-assembly technique,while the pore-limited 0.3%Pt/Ti_0.1Al O_y-VI catalysts were prepared by in situ vacuum impregnation.The experimental results demonstrated that the ordered mesoporous structure of the pore-limited0.3%Pt/Ti_0.1Al O_y-VI catalyst was destroyed,but with better water and sulfur resistance.This is because the pore channel protects the active site from sulfate coverage to some extent,while the introduction of SO₂ increases the acidity of the catalyst,giving it good sulfur resistance.However,the catalytic oxidation activity of the skeleton-limited0.3%Pt/Ti_0.1Al O_y-EISA catalyst was superior to that of the pore-channel-limited0.3%Pt/Ti_0.1Al O_y-VI catalyst due to the suitable particle size,larger pores（favorable charge transfer and mass transfer effects）,more active adsorbed oxygen(O_ads),and more Pt²⁺active site species.The anchoring effect of the skeleton-limited and pore-limited domains on the noble metal Pt nanoparticles resulted in good thermal stability of both catalysts.In addition,the possible reaction pathways were obtained by in situ DRIFTS experiments（propane→isopropanol→propylene→acetone→carboxylate→...→CO₂+H₂O）.