Removal Of Low Concentration Of Methane With Catalytic Oxidation Technology

Catalytic oxidation technology was a better purification technology for low concentration methane,which was suitable for the treatment of the high flow and low concentration vetilation air methane?VAM?of coal mine.In this paper,the removal of low concentration methane was investigated with catalytic oxidation technology in a self-made reverse flow reactor,which provided theoretical and experimental basis for the optimization of the system performance and design of the reaction device.Catalytic activity over bimetallic Pd-M/?-Al₂O₃?M=Pt?Ce?La?Co and Ni?catalysts prepared by impregnation method for low concentration methane combustion was investigated.Structures and chemical properties of catalysts were characterized by Scanning electron microscopy?SEM?,N₂ adsorption/desorption isotherms,H₂-temperature programmed reduction?H₂-TPR?and X-ray diffraction?XRD?.At the same time,the effects of different calcination temperature and different loadings on the catalytic activities were studied,and the circular test was carried out.The results showed that the optimal calcination temperature was 550?for the bimetallic catalyst,and the optimal capacity was 1.25%Pd/?-Al₂O₃?0.75%Pd-0.25%Pt/?-Al₂O₃?0.75%Pd-1.5%Ce/?-Al₂O₃?0.75%Pd-0.1%La/?-Al₂O₃?0.75%Pd-0.1%Co/?-Al₂O₃?0.75%Pd-3%Ni/?-Al₂O₃ for the Pd-M/?-Al₂O₃ catalyst,respectively.At the same time,the catalytic activity improved significantly by several times catalytic reaction.The optimal preparation conditions for the monolith catalyst were determined by active experiment of the powder catalyst:cordierite was the first supporter,the transfer coating was Silica sol,?-A1₂O₃ was the second supporter and the active component was noble metal elements of Pd and Pt.And the catalytic activity was investigated by the experimental evaluation platform.The results showed that the loading times of active component could influent the catalytic activity of methane and Pt could improve the activity of catalyst effectively.A bench-scale reverse flow reactor was built up and the catalyst performance of which was studied.The variation of activity of methane catalytic combustion and axial temperature distribution of bed reaction system by different preheating temperature were studied with the conditions of the initial concentration of methane being 0.2%,the gas volume being 30 L·min^-1 and the commutation period being 10min.At the same time,the characteristics of the heat wave formation and the dynamic change of the reactor bed after the stabilization of the catalytic converter were analyzed.The results showed that with temperature increasing,the methane catalytic combustion activity showed a trend of increasing.Furthermore,Pt could improve the activity of the catalysts.The preheating temperature of the catalyst had a great influence on the temperature distribution of the reactor bed,especially the catalytic section of the reaction system.When the system tended to steady state,the temperature distribution of the whole bed was high and the two sides were low,the axial temperature profile for continuous periods of operation was basically in a coincidence state.