Mechanochemical Synthesis Of High Entropy Oxide And Their Performance On Catalytic Combustion Of Propane

With the rapid development of industry,people’s quality of life has been greatly improved,but it also brings increasingly serious challenges to the environment.As an important air pollutant,volatile organic compounds（VOCs）from industrial sources are important precursors of air pollution such as photochemical smog and haze,and pose serious health hazards to humans.Among many VOCs control technologies,catalytic combustion method is widely used due to its low cost,easy operation and good purification effect.With the continuous development of this technology,it is especially urgent to develop more efficient and stable catalysts for catalytic combustion of VOCs.Among them,the high entropy series metal oxides have many active sites and their excellent stability,which makes them one of the most popular catalytic materials today.In this work,the high entropy oxide catalyst was successfully synthesized by a simple mechanized method,and its special elements compatibility,entropy driving force and rare earth metal doping were used to effectively regulate the surface oxygen vacancy content of the catalyst,thus improving its low temperature catalytic activity and showing good stability.The main elements include:1.High entropy oxides with different elemental pairings,namely（Mg Cu Co Ni Mn）O_x,（Mg Cu Co Ni Cr）O_x,and（Mg Cu Co Ni Fe）O_x,were prepared by modulating the elemental composition,and the XRD results showed that the high entropy oxides were successfully synthesized.It was found that（Mg Cu Co Ni Mn）O_x showed optimal activity in the catalytic combustion reaction with the T₉₀ equal to 310°C,which was about 50°C lower than the T₉₀ of the corresponding（Mg Cu Co Ni Fe）O_x.The stability experiment showed that（Mg Cu Co Ni Mn）Ox reaction at 500℃for 50 h,the catalyst activity did not degrade or deactivate.The catalytic activity of the catalyst was maintained at the level of the first use for five consecutive reactions,i.e.,the（Mg Cu Co Ni Mn）O_x catalyst exhibited better long-term stability and cyclic thermal stability.2.The role of entropic driving forces in multi-metal oxide catalysts,especially the role of high entropic properties in stability and tolerance in catalytic reactions,was investigated.（Mg Cu Co Ni Mn）O_x high-entropy metal oxides were prepared,and a series of Mg O,（Mg Cu）O_x,（Mg Cu Co）O_x,and（Mg Cu Co Ni）O_x multiple oxides were synthesized to explore the effect of entropy driving force on the catalytic effect.Propane catalytic combustion experiments showed that the activity of（Mg Cu Co Ni Mn）Ox was the best at 290℃,which was 65℃lower than that of tetrad oxide.After the formation of high entropy structure,the catalyst showed better thermal stability and toxicity resistance than the ternary oxide.3.Cerium-based high entropy oxide catalysts with Ce O₂ lattice were synthesized by introducing cerium oxide species,which can easily form abundant oxygen vacancies,into the high-entropy system and preparing（Ce_nFe Co Ni Mn）O_x（n=0,1,2,4,6）series samples.The effect of oxygen vacancy number on high entropy oxide was studied by changing the content of cerium,and the propane catalytic activity of high entropy oxide catalyst was further improved.The（Ce₂Fe Co Ni Mn）O_x has a high concentration of oxygen vacancies,which effectively enhances its activation ability to O₂ with the T₉₀ of 260°C and good cycling stability even after 5 cycles.