Study On Performance And Mechanism Of Sorption-enhanced Steam Reforming Multifunctional Catalyst

With the development of society,humanity is facing increasingly serious energy and environmental problems.Hydrogen production from steam reforming of renewable and carbonneutral bio-ethanol can mitigate the energy strain and adverse environmental effect during the fossil fuel utilization.Furthermore,the combination of sorption-enhanced steam reforming technology can effectively improve the purity of hydrogen and ruduce the cost of hydrogen production.However,conventional Ni-based catalysts suffer from deactivation due to sintering or coke deposition,CaO-based sorbents have poor stability are still great challenges.The development of high stability multifunctional catalysts is critical for the scaleup of this system.First,this dissertation describes the design and preparation of a novel Ni/MgO-CaO catalyst for sorption-enhanced ethanol steam reforming process.The morphological characterization of the catalyst confirmed that a unique structure where metallic Ni exists around MgO supported on CaO formed.Thus,MgO interacting with both Ni and CaO can effectively suppress the sintering of both and improve the stability.The test results with the multifunctional catalyst shows stable performance over 10cycles,100%ethanol conversion and>96%hydrogen purity.Reaction pathway studies have indicated that the formation of CaCO₃ hinders the activation of H₂O on the catalyst surface,and thus inhibits the conversion of the reaction intermediates.MgO can dissociates H₂O to form hydroxyl groups which participate in the reaction,thereby improving the catalytic activity and carbon deposition resistance.Secondly,the feasibility of NiO-Fe₂O₃-CaO for sorption-enhanced chemical looping steam reforming of ethanol reaction was investigated.After thermodynamic analysis and experimental investigation,the catalyst with the ratio of NiO:Fe₂O₃:CaO=1:2:2 showed the best performance.Hydrogen with a purity of 95.7%was obtained at500°C,1 atm and S/C=2.Furthermore,the introduction of the H₂O oxidation step in the reaction can increase the total hydrogen production of the system by effectively utilizing the FeNi₃ alloy produced by reforming reduction to produce hydrogen compared to traditional O₂ regeneration step.