Preparation,Modification And Catalytic Combustion Of Dimethyl Ether By Manganese Oxide Octahedral Molecular Sieves

Industrial waste gas is one of the main sources of volatile organic compounds?VOCs?in the atmosphere.Catalytic combustion is one of the main methods to remove VOCs in industry.Manganese oxide octahedral molecular sieve?hereinafter referred to as OMS-2?has been widely studied in the field of catalytic oxidation due to its special skeleton structure,many mixed metal valence states,excellent hydrophobic performance and redox performance.In this paper,the influence of preparation method and preparation conditions on the crystal structure,size,morphology and catalytic combustion performance of OMS-2 catalyst and v-OMS-2 catalyst was studied,and the activity performance of the two kinds of catalysts under different working conditions was investigated.Using solid phase method,reflux method and of OMS-2 catalyst prepared by sol gel,examine reductant?manganese sulfate,manganese carbonate,manganese nitrate,manganese acetate?,roasting temperature?350?-550??,unburned,surfactant?PEG,CTAB,SDBS?on the activity of catalytic combustion,grain appearance,size,specific surface area,etc.The results show that the solid phase method of OMS-2 specific surface area of the biggest?120.15m²/g?,catalytic activity is the highest,under the condition of the airspeed of 10000 h^-1,concentration of 1000 ppm CH₃OCH₃ T_90%temperature is 148?only;PEG can improve the specific surface area?135.81 m²/g?,pore volume?0.992 cm³/g?and average pore diameter?28.99 nm?of OMS-2.CTAB and SDBS can significantly improve the crystallinity and grain size of OMS-2 and significantly reduce the specific surface area?31.13 m²/g,45.06 m²/g?.In addition,with the addition of CTAB,the morphology of OMS-2 grains changed significantly from nanorods to columns.With manganese carbonate and manganese nitrate as reducing agents,the degree of crystallinity and grain size of OMS-2 prepared by reflux method decreased,but its catalytic activity was higher.The appropriate calcination temperature was beneficial to the improvement of the catalyst activity,through the test of 450?baking conditions,the catalytic combustion of dimethyl ether activity fared best.Out by doping method and impregnation method before V-OMS-2 catalyst,different precursors,roasting temperature?350?-550??,vanadium load?1%-10%?and other preparation conditions on the catalytic activity and grain morphology,size and the influence of catalytic combustion performance.The results show that 1%of the doped prepared prior to the V-R-OMS-2 specific surface area increased?129.75 m²/g?,catalytic oxidation activity of dimethyl ether has also improved,T_90%temperature is 157?;The solid phase preparation of OMS-2 as the precursor doped with vanadium,the specific surface area decreased,the catalytic activity decreased;A small amount of vanadium doping can improve the catalytic activity of the catalyst,but with the increase of vanadium content to 5%and 10%,the grain size of V-OMS-2 increases and the specific surface area decreases,but the catalytic activity decreases.With the increase of calcination temperature,catalyst crystallinity and crystal grain size increases,the performance test under the condition of 450?roasting catalyst activity is best.The effects of five factors,such as gas component?CH₃OCH₃,CO?,concentration?500ppm-1500 ppm?,air speed(10000 h^-1-25000 h^-1),oxygen content?10%-40%?and relative humidity?0-80%?on the catalytic combustion performance of four catalysts prepared by solid phase method,reflux method,sol-gel method and predoping method were investigated.The results showed that the catalytic combustion activities of the four catalysts were negatively correlated with VOCs concentration,air velocity and relative humidity,and positively correlated with oxygen content.Water vapor can reversibly inhibit the catalytic combustion activities of the four catalysts.With the increase of reaction temperature,the competitive adsorption ability between H₂O molecules and VOCs molecules is weakened,and the degree of influence on the catalyst activity is reduced.The antiwater activity of OMS-2 prepared by reflux method was the best.In the mixed gas component,CO can reduce the ignition temperature of catalyst.