Study On The Multifunctional Catalysts For Sorption Enhanced Steam Ethanol Reforming

Sorption enhanced ethanol steam reforming（SE-SRE）has attracted wide attention for hydrogen production,which possesses numerous advantages such as clean and renewable biofuel,high purity of hydrogen and controllable CO₂ greenhouse gas emissions.It is quite crucial to select suitable multifunctional catalyst in this technology.At present,most of the package methods are the mechanical mixture of adsorbent and catalyst for reforming hydrogen production,but the complex catalysts integrated sorption-catalysis into body for experimental study are far from enough.Compared to mechanical mixed catalysts,the complex catalysts that are close to in situ sorption-catalytic exhibit faster reaction rate,smaller mass transfer resistance,more uniform heat transfer,and higher sorption performance and catalytic activity for hydrogen production.Therefore,in order to investigate the effect of complex catalyst on sorption enhanced reforming to produce hydrogen,a new complex catalyst combined sorption and catalysis was prepared and the process conditions were studied.In this paper,a thermodynamic equilibrium analysis model for SE-SRE based on Gibbs free energy minimization is carried out,and the effects of operating conditions on the concentration of equilibrium compositions and the thermal efficiency of the system were displayed and analyzed through Matlab numerical calculation.The results show that the atmospheric pressure,higher temperature and higher water-to-alcohol ratio are beneficial to increase the hydrogen mole fraction of the product and energy efficiency.The addition of CaO can play a significant role in sorption enhancement and energy efficiency.It is suggested that the theoretical favorable operating conditions of sorption enhanced ethanol steam reforming for hydrogen production should be atmospheric pressure,temperature 900¹000K,water-ethanol ratio 6¹0,calcium-ethanol ratio>1.5.Then a series of Ni/CaO-Al₂O₃ complex catalysts with different CaO/Al₂O₃ mass ratio were prepared by sol-gel method and their physicochemical structures were characterized in detail,as well as the CO₂ adsorption capacity and reforming hydrogen production performance were also studied.The results show that the optimal mass ratio of the complex catalyst is 81%CaO:9%Al₂O₃:10%Ni,which possesses the largest specific surface area and specific pore volume,the strongest adsorption catalysis,and excellent cycle stability of carbonation.Finally,according to the above conclusions,the process conditions like temperature,water-ethanol ratio and liquid space-time velocity of SE-SRE are studied.Seeing that the hydrogen-producing productivity and energy consumption the appropriate conditions are derived as follow:atmospheric pressure,temperature 650℃,LHSV 0.03ml/min,water-ethanol ratio 6.Under this condition,the prebreakthrough time was more than eighteen minutes,and the hydrogen volume concentration was higher than ninety percent.Compared the mechanical mixed catalyst,complex catalyst had a better sorption enhanced effect and cycle stability.