Study On Methane Chemical-looping Reforming Over Cerium-based Oxygen Carrier

Methane chemical-looping reforming?CLR?technology can convert natural gas to syngas,which not only efficiently use natural gas resources,but also effectively relieve Greenhouse.Therefore,substantial researchers have focused on this technology.In this study,the preparation of oxygen support,reaction conditions,reaction mechanism were investigated systematically in terms of the production of syngas deriving from methane.Firstly,CeO₂ and Fe₂O₃ were selected as complex oxygen carriers for methane chemical looping reforming.The composite oxygen carriers,x Ce?1-x?Fe,?x=0,0.3,0.4,0.5,0.6,0.7?were prepared by co-precipitation method,and the effect of calcination temperature on the preparation of oxygen carrier was studied in detail.Experimental results indicated that there was a strong interaction between Fe and Ce,and the oxygen support,0.7Ce0.3Fe,with calcination temperature of 900? performed better performance.No change in methane conversion,carbon dioxide selectivity,carbon monoxide selectivity as well as hydrogen selectivity was observed after five circular reaction of methane with carbon dioxide,which manifested that 0.7Ce0.3Fe oxygen carrier possessed excellent recyclable stability and thermal stability.Subsequently,the performance of oxygen carriers was improved by supporting metal C u,La?1%?2%?3%?6%?9%?12%?and Co?3%?6%?9%?12%?on 0.7Ce0.3Fe,which were prepared by an impregnation method.And the effect of calcination temperature on metal-supported oxygen carriers was investigated.Results revealed that the performance of oxygen carriers was changed by supporting metal.As for 0.7Ce0.3Fe with Cu loading of 1%,calcination temperature of 700 ?,carbon monoxide selectivity increased by about 15%;concerning 0.7Ce0.3Fe with La loading of 2%,calcination temperature of 700 ?,carbon monoxide selectivity reached to the peak value with maximum increasing by 20%;for 0.7Ce0.3Fe with Co loading of 9%,calcination temperature of 900 ?,the amount of carbon dioxide increased,the carbon monoxide,methane selectivity and conversion decreased.The oxygen carriers were characterized by H₂-TPR,XRD,TG.C haracterization results indicated that the oxygen transfer ability and oxygen release ability of the oxygen carriers with C u and Co obviously increased,and the amount of carbon monoxide produced correspondingly increased;on the other hand,the CH₄ pyrolysis performance of oxygen carriers with La enhanced remarkablely.The thermogravimetric reaction and carbon deposition determination results showed that the effective oxygen content of the oxygen carrier with metal obviously increased,and the amount of carbon deposition after reaction obviously reduced.