Study On Catalytic Combustion And Performance Of Composite Spinel Catalysts For Ventilation Air Methane

Environmental pollution and energy shortages have become global challenges.Natural gas has attracted much attention because of its clean,environmentally friendly and high thermal efficiency.However,since the main component of natural gas is methane,the methane structure is relatively stable,especially when the concentration is low(when the methane concentration is less than or equal to 2%,it is called gas ventilation gas),the energy obtained by the traditional combustion method has the disadvantages of high combustion light-off temperature,low effic iency and high pollutant emission.The catalytic combustion method is currently one of the ways to effectively solve such problems,however,in order to achieve catalytic combustion of methane,especially catalytic combustion of low concentration methane,it is critical to research and develop catalysts with excellent performance.In this paper,the spinel catalyst CoCr2O4,ZnCr2O4 and composite spine l catalysts CoCr2O4-Al2O3,CoCr2O4-Si O2,CoCr2O4-Zr O2,CoCr2O4-Sn O2,ZnCr2O4-Si O2,ZnCr2O4-Zr O2,ZnCr2O4-Sn O2 were prepared by sol-gel method.After selecting the best performance composite oxide corresponding to different A sites,the effect of the composite ratio of each active component and oxide on the catalytic combustion performance of the ventilation air methane.The above catalyst was calcined at 700? and 900? in an air atmosphere,and was applied to a ventilation air methane catalytic combustion reaction to investigate the difference in catalytic performance.A variety of physicochemical analyses were used to characterize the phase,composite,and surface ion valence of the catalyst.Here are the results:1.Spinel-type catalyst CoCr2O4,ZnCr2O4 and composite spinel catalystCoCr2O4-BxOy(B=Al,Si,Zr,Sn),ZnCr2O4-BxOy(B=Si,Zr,Sn)are applied to ventilation air methane catalytic combustion,CoCr2O4-Al2O3 and ZnCr2O4-Si O2 in the series of composite catalysts show good activity in catalytic performance of ventilation air methane.The T10 of CoCr2O4-Al2O3 is 310.8?,the T50 is 388.0?,the T90 is 467.5?,the T10 of ZnCr2O4-Si O2 is 334.7?,the T50 is 409.0?,and the T90 is 491.5?.2.Studying the effect of the composite ratio of active components and oxides on the reactivity of ventilation air methane catalytic combustion,preparing CoCr2O4(X)-Al2O3 series catalysts(where X is the mass percentage of spinel CoCr2O4: 30%,50%,70%,90%),ZnCr2O4(X)-Si O2 series catalyst(where X is the mass percentage of spinel CoCr2O4: 30%,50% 70%,80%,90%).The composite spinel catalyst 70% CoCr2O4-Al2O3 exhibits good catalytic activity in this series of catalysts and is completely converted at a temperature of 435.2?.The large specific surface area of the composite spinel catalyst 70% CoCr2O4-Al2O3(67.994)m2/g is beneficial for promoting the catalytic combustion reaction of ventilation air methane.The composite spinel catalyst 70% CoCr2O4-Al2O3 was prepared at a calcination temperature of 900?,and the T90 of the catalyst was basically unchanged,showing good high temperature stability.After the Al2O3 particles are combined with the pure phase CoCr2O4 at a 30% oxide amount,the small size and good dispersibility of the composite spinel catalyst is the reason for its good activity.3.80% ZnCr2O4-SiO2 has good catalytic activity in a series of composite spine l catalysts,starting to burn at 225.0?,and completely converting at a temperature of 334.0 ?.The composite spinel catalyst 80% ZnCr2O4-Si O2 was prepared at a calcination temperature of 900?,and T90 of the catalyst was basically unchanged,showing good high temperature stability.After Si O2 partic les are combined with pure phase ZnCr2O4 at a ratio of 20% oxide,the uniform sphericity and good dispersibility of the composite spinel catalyst are responsible for its excellent activity.4.After the introduction of different oxides,it is found that a suitable interactionbetween the oxide and the spinel can produce significant interactions,which can affect the surface morphology of the catalyst to a different extent,increase the specific surface area,and the catalytic combustion performance of the ventilation air methane of the composite catalyst is remarkably improved.