The Oxygen Carrier Design And Study On Reaction Mechanism Of Hydrogen-rich Syngas Produced By In-situ Catalytic Reforming Of Methane

Chemical looping reforming of methane（CLRM）,combining in-situ catalytic reforming of methane with carbon capture technology,is a new type of hydrogen production process.The key of it is to obtain oxygen carriers with suitable reactivity,oxygen supply capacity and redox ability.Sol-gel method was used to prepare CeO₂/LaFeO₃,a metal composite oxide oxygen carrier which contains two active components,aiming to comprehensively utilize the reactivity,thermal stability of perovskite and the partial oxidation ability of CeO₂ to solve carbon deposits problem in the CLRM.The effects of component ratio,ion doping,reaction temperature on the structure,oxygen supply capacity and reaction performance of the oxygen carrier CeO₂/LaFeO₃were investigated in detail through XRD,H₂-TPR,XPS and fixed bed reaction experiments.Finally,reaction mechanism about migration and transformation of oxygen species and evolution of hydrocarbon elements was discussed.The experimental results indicated:CeO₂acted as an auxiliary agent to regulate oxygen vacancies on the surface of the oxygen carrier and disperse active sites without changing crystal structure of the perovskite;doping Sr²⁺and Ni²⁺at the A site and B site（optimal doping ratio was 0.1 and 0.2,respectively）,respectively,increased the crystal defects of the oxygen carrier and surface adsorbed oxygen content and lattice oxygen migration rate,thus,performance of the oxygen carrier was improved significantly.At 850℃,the optimal reactive temperature,the oxygen carrier10%CeO₂/La_0.9Sr_0.1Fe_0.8Ni_0.2O₃ had optimal performance which could maintain stable structure and performance in the redox cycles,and reacted continuously with methane for 20 min without obvious carbon deposits.In the methane reforming reaction,methane conversion rate remained85-90%,CO selectivity was 71-80%,and H₂ selectivity was 78-83%;in the steam oxidation stage,yield of H₂ could reach 23 mL/min,and its relative content remained above 95%.In the CLRM,surface adsorbed oxygen and reducing metal ions constituted the active sites together which changed dynamically with consumption of oxygen species,therefore actual products distribution depended on whether lattice oxygen migration rate matched carbon-hydrogen bond breaking rate.