流化床反应器中不同Ni/Al2O3催化剂上CH4-CO2重整反应性能的比较研究

Using incipient impregnation, solgel method and conventional drying, and solgel and supercritical drying techniques, three kinds of 20% Ni/Al2O3 catalysts have been prepared, the catalyst samples were characterized by means of BET, XRD, H2-TPR and H2-TPD. Catalytic performances of the different catalysts for CH4-CO2 reforming reaction were investigated in a micro fluidized bed reactor. Strong interaction between Ni species and support Al2O3 is found and NiO and spinel NiAl2O4 were formed in the aerogel catalyst, but weaker interaction is observed in the impregnation catalyst and xerogel catalyst. Among the catalysts examined, the aerogel catalyst exhibits high specific surface area, low bulk density, high Ni reduction degree and Ni dispersion degree. Excellent catalytic activity and stability were achieved via the combination of aerogel catalyst and fluidized bed reactor. The fluidization of aerogel porous agglomerates provides high bed expansion and long gas residence time, which remarkably improves the mass transfer. Thus the deposited carbon was quickly gasified and only a limited amount of carbon was formed on aerogel catalyst. For the impregnation catalyst and xerogel catalysts, low bed expansion and little particles circulation result worse efficiency of mass transfer and short gas residence time, which decrease the rate of carbon gasification, and thus result in the carbon deposition. The characterization revealed that massive graphite carbon deposition is the most important reason resulting in the deactivation of the impregnation catalyst and xerogel catalysts.