| Syngas is important chemical raw materials and used widely.CO2 dry reforming CH4,an effective way to produce syngas,can turn two main greenhouse gases into high added-value products,and it is significant to reduce environmental pollution and carbon emission.Fe-based catalyst is green and environment-friendly,but it is low activity and trend to carbon deposition when applied to dry reforming process.Microwave heating is efficient,timely,and selective and it can emerge coupling effects with strong microwave-absorbing mediums(heating effect,discharging,carbon elimination),making it is possible to be a novel heating type for reforming.On the based of synergistic effect between microwave and Fe-based catalyst,the feasibility of cheap metals replaceing noble metals is discussed.To make reference for the exploitation of CO2 reforming CH4,the reforming progress and influence factors are researched,and the carbon deposition and reaction mechanisms are analyzed.Polyurethane sponge is selected as precursor and foam impregnation method is employed to create Al2O3 and SiC-SiO2 foam ceramics which are acted as catalyst supports.Moreover,the effect of sintering temperature and additives content on catalyst support were carried out.Results show that with the sintering temperature increasing,the compressive capacity is get enhanced and the microwave absorbing ability has reverse change;the compressive capacity and microwave absorbing ability present improvement firstly and then declining with the additives(Al2O3)content increase.The catalyst support has favorable performance under the condition that sintering temperature is 1200? and additives content is 20wt%.The influence factors(catalyst support,active component content,microwave heating power,space velocity)on reforming reactions were implemented on self-made catalysts.The main results as follows.1)The temperature rised to the maximum and decreased to different extent with microwave heating continuing.Fe/Al2O3 catalyst temperature reach the maximum 600 ? in 30min and the Fe/(SiC-SiO2)catalyst achieve 810? in 3min;2)There is weak reforming on the Fe/Al2O3 catalyst,but with the Fe/(SiC-SiO2),the reactants conversion realize maximum about 95%after microwave heating 5-8 min.3)The conversion first increase and then decrease accompanied with the Fe content increasing and the product selectivity change trend is in accordance with reactants.The catalyst has perfect performance when Fe fraction weight is 12wt%,the conversion of CO2 reach 93%and the product selectivity up to 95%.4)The lower microwave heating is,the longer times to reach the stable reforming state are,and the reactants conversion is worse.The time to achieve reforming conversion maximum and stable state is depressed with 80%microwave heating power compared to full heating power(900w).5)An increase in the gas flow rate gives rise to a reduction in conversion and selectivity.The typical reforming process curve is analyzed with the help of MS.The reacants(products)gases change processes are divided into three stages.The reactants conversions exceed 95%when the catalyst bed temperature is 810?,and the products selectivities are about 95%.At last,the conversions decline to 85%with the temperature decrease to 777?.Fresh and spent catalysts are analysed.Results show that the carbon deposition get worse with the reforming continues,causing the decline of pore volume and specific surface area.There is lwt%carbon deposition,belonging to fibrous carbon,when is catalyst spent 50h.However,some carbide may develop into active sites under microwave heating contributing to the reforming reactions.Based on the experimental researches,the reforming reaction mechanism of Fe-based catalyst are raised on the condition of conventional heating,and the microwave can activate the carbon depositon accelerating the reforming progress. |
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