Study On Hydrogen Production By Steam Reforming Of Ethanol Oxidation With Metallic Nickel Asymmetric Hollow Fiber Membranes

Hydrogen is an advanced alternative fuel and energy carrier,which is widely used in many industrial fields such as chemistry,petrochemical,metallurgy,food,electronics and energy.At present,hydrogen is mainly obtained from fossil fuels.The hydrogen produced by the natural gas and other hydrocarbons through steam reforming usually contains CO₂,CO,H₂S and other impurities,which needs to be further separated and purified.The preparation and purification of hydrogen is the basis and premise of hydrogen utilization.Compared with the traditional separation technologies,membrane separation technology has become a rapidly developing technology due to its unique advantages.The most studied membrane reactor for hydrogen production is palladium membrane reactor.However,the palladium membrane also has the unavoidable shortcomings such as expensive cost,susceptibility to damage by CO and H₂S,and hydrogen embrittlement caused by repeated transformations between phases during thermal cycling.So it is urgent to develop a low-cost and high-stability membrane material.The nickel-based membrane is a promising substitute due to its lower material cost and excellent chemical stability to withstand the presence of CO and sulfide in the hydrogen-containing atmosphere at high temperatures.In this paper,metallic nickel asymmetric hollow fiber membranes with an inner dense skin on the outer porous layer were fabricated by the dry-wet spinning and sintering technique.And the hydrogen permeation test was carried out.As a result,the prepared nickel hollow fiber membrane exhibited high H₂ permeability and 100%H₂-permselectivity.In the 50%H₂-He mixture gas,the H₂ permeation flux of the hollow fiber can reach（0.83～31.43）mmol?m^-2?s^-1 at 400～1000°C.Compared with the nickel hollow fiber with symmetrical structure under the same condition,the hydrogen permeability increased～84%.The nickel asymmetric hollow fiber membrane was used to produce hydrogen via oxidative steam reforming of ethanol.The operating conditions including temperature,feeding flow rate,sweeping rate,steam-to-carbon molar ratio（S/C）and oxygen-to-carbon ratio（O₂/C）were investigated and optimized.The results have shown that the asymmetric nickel hollow fibers have excellent catalytic activity to EOSR and high hydrogen permeation performance as well.Operated at≥500°C with a steam-to-carbon ratio of 4 and an oxygen-to-carbon molar ratio of 0.8,the ethanol was completely consumed with 81.59%hydrogen yield,and the hydrogen permeation rate reached up to 13.99 mmol·m^-2·s^-1.With the increase of oxygen concentration in feed,the carbon deposition on the membrane surface was remarkably inhibited,while the hydrogen yield and CO selectivity were decreased.