Study On The Preparation And Catalytic Performance Of Ni-based Catalysts For Dry Reforming Of Methane Reaction

Dry reforming of methane?DRM?reaction has received an increasing attention as it provide a practical method for the consumption of the green house gases of CH4 and CO2.Furthermore,it can produce synthesis gas with a H₂/CO ratio around 1,which is suitable for the production of methanol and the Fischer-Tropsh synthesis.Supported Ni catalysts are widely studied for dry reforming of methane reaction due to its high reactivity and low cost.However,the catalyst deactivation caused by carbon deposition and sintering of metallic Ni particles limits its industrial applications.In this work,a series of Ni/?-Al₂O₃ were prepared by incipient wetness impregnation method,and fatty acids were adopted as a dispersing agent.The influence of different carbon chain numbers?Nc?and different concentration?Ca,Ca= n?FA?/n?Ni2+??of fatty acids on the properties and catalytic performance of catalysts were investigated.Meanwhile,the effect of Mg and Y as promoters on the properties of catalyst prepared by fatty acid is also investigated,respectively.Main results are given as follows.1.The addition of fatty acid can significantly improve the dispersion of Ni and decrease Ni particle size.The catalyst prepared by fatty acid with a larger carbon chain numbers achieved higher dispersion of Ni species and stronger metal-support interaction,which lead to smaller Ni particles after reduction.The concentration of fatty acid also play an important role on the dispersion of Ni.The catalyst prepared with oleic acid shows best catalytic performance among catalysts prepared by fatty acid with different carbon chain numbers.The smallest Ni particles of 5.0nm were obtained over the Ni/?-Al₂O₃ catalyst prepared by oleic acid with a concentration of 0.5,which shows excellent catalytic activity with a methane conversion of 76% at 700 oC,54,000 ml? h-1? g-1?cat.?.The NiAl-OA catalyst shows good stability with the slight decrease of 8% during the time on stream of 80 h.The characterization for this used catalyst indicates that Ni particles possesses strong anti-sintering capacity,and carbon deposition is the main reason for its deactivation.2.The stability of NiAl-OA catalyst can be enhanced by the addition of Mg and Y,and the dispersion of Ni also can be further improved.The CO2-TPD results shows that the addition of Mg and Y can increase the amount of basic site compared to unpromoted NiAl-OA catalyst.The stability trend of the catalysts is NiYAl-OA>NiMgAl-OA>NiAl-OA.The characterization for used catalyst indicates the least amount of carbon deposition on NiYAl-OA catalyst.The reason for this is that Y2O3 can react with CO2 to generate Y2O2CO3 during reaction,which is beneficial to the elimination of carbon deposition.