Study On Propane Partial Oxidation And In-situ Sorption Enhanced Hydrogen Production

Hydrogen energy has the advantages of high energy density,zero pollution of combustion products,and extensive distribution of hydrogen resources.It is considered to be the most promising clean and renewable energy carrier.At present,an important scenario for hydrogen energy utilization is hydrogen fuel cells,which have an energy conversion efficiency of up to 50-65%,which is twice as high as direct combustion and conventional thermal cycles.Compared with proton exchange membrane fuel cells,high temperature solid oxide fuel cells(SOFC)have the advantages of stable performance and wide fuel adaptability.Propane is a kind of hydrogen-rich,low-cost,easy-to-liquefy gas material.As the main component of liquefied natural gas,the price is low.The partial oxidation(POx)reaction of propane makes it easy to interact with fuel cells due to its compact process and short response time.Build a more compact and safe hydrogen production-utilization system.However,the CO and CO2 generated in the POx process will not only reduce the purity of hydrogen,but also corrode the electrode and cause the performance and life of the fuel cell to decrease.Enhancing the partial oxidation process through the sorption of CO2 in situ can promote the positive shift of the equilibrium reaction,enhance hydrogen production,increase the purity of hydrogen,and reduce CO2 to a very low concentration.In order to solve the above problems,this paper conducts theoretical and experimental studies on the porous structure modification of the CaObased sorbent,the high temperature resistance to sintering,and the loading of CO priority oxidation active components.First,improve the CaO-based sorbent that has excellent sorption performance and is highly matched to the propane POx temperature.CoxMgyCa(1-x-y)Oz multifunctional sorbent was prepared by using template-step precipitation method on the basis of modifying the porous structure of CaO,doped with high temperature structure stabilizer and loaded with CO preferential oxidation active component.Based on the characterization analysis of BET,SEM and TEM,it is found that the doping of CoO and MgO is beneficial to improve the stability of the porous structure of CaO and the preferential oxidation activity of CO.The cage-like porous structure helps to increase the specific surface area of CaO,effectively increasing the reaction contact area and sorption active sites.Through kinetic analysis,Co0.110Mg0.204Ca0.686Oz reduced the activation energy of CO2 sorption,with the most uniform pore size distribution and the highest CO2 sorption capacity.Through the joint reaction of Ni/Al2O3-SiC catalyst combined with CoxMgyCa(1-x-y)Oz sorbent,the maximum hydrogen production reached 920μmol gcat-1·s-1.The sorption strengthening effect makes the hydrogen production more than catalyzed alone(650 μmol gcat-1·s-1)increased by 41.54 vol.%.The catalyst-sorbent coreaction also showed better hydrogen production stability,and the hydrogen content did not significantly decrease after 60 minutes of reaction.On this basis,the X/CeO2-CaO(X=Fe,Co and Cu)multifunctional CO preferential oxidation-sorbent was further prepared.Among them,Fe/CeO2-CaO and Ni/Al2O3-SiC have the best sorption and enhancement of hydrogen production.In the initial stage of the reaction,the hydrogen production was as high as 1654 μmol gcat-1·s-1,and the sorption enhancement effect increased the hydrogen production by nearly three times.In addition,the sample of Co/CeO2-CaO and Ni/AlO3-SiC has the most obvious preferential oxidation effect on CO,and the CO output at the initial stage of the reaction is reduced to 55.38 μmol gcat-1.s-1,which is better than pure Ni/Al2O3-SiC(438.45μmol gcat-1·s-1)reduced by 87.3 vol.%.The cage structure of the X/CeO2-CaO(X=Fe,Co and Cu)multifunctional sorbent remains stable before and after the reaction,and almost no carbon deposits are formed.A test system for hydrogen production by partial oxidation of propane and a solid oxide fuel cell(SOFC)test system was built on the basis of the determination of high-efficiency multifunctional sorbents.The experimental results show that the sorption-enhanced partial oxidation of propane for hydrogen production has better electrochemical performance.The use of catalyst combined with Co0.110Mg0.204Ca0.686Oz sorbent for sorption and enhanced hydrogen production can make the fuel cell reach the maximum output density of 513 mW/cm2,which is 58.5%higher than the commercial Ni-Co/Al2O3 catalyst(325mW/cm2).For Fe/CeO2-CaO sorbent,the maximum output power density of sorption enhancement is 498mW/cm2.The sorption-enhanced partial oxidation of propane for hydrogen production shows good carbon resistance and hydrogen production stability.The research results can provide new ideas for the development of low-cost hydrogen production processes and their application in external reforming hydrogen fuel cells.