The Study On Ni/Ce_0.5Zr_0.5O₂ Catalysts For Ethanol Steam Reforming

Hydrogen is considered to be the energy carrier of the future. Ethanol steam reforming has many advantages over other ways for hydrogen production and will play an important role in producing hydrogen. Ni-based catalysts characterize with high activity and low cost. However, its selectivity towards H2 is relatively low, and catalyst stability is poor as the result of sintering and carbon deposition. In this paper, we used a new method to prepare Ni/Ce-Zr-O catalysts, which showed high activity and good stability for ethanol steam reforming.We investigated the effect of preparation method, calcination temperature, reduction temperature, the molar ratio of metal ion and citric, the content of active component on catalyst performance. We also examined catalyst activity with high space velocity. And the stability test of 20% Ni/Ce_0.5Zr_0.5O₂ catalysts after the reaction 6 hours separately at 350℃and 550℃was carried out. XRD and TPR have been used to investigate the structure and reduction behavior of the samples.TG-DTA has been used to investigate the carbon resistance of catalysts.The main results are as follows:(1)20wt%Ni/Ce_0.5Zr_0.5O₂-700 prepared by sol-gel method showed the best catalytic performance with the reduction temperature at 550℃and the molar ratio of (Ce4++Zr4+: citric acid ) 2:1.(2)The catalysts showed high activity and selectivity even at space velocity of 160,000ml/h.g.cat.(3)The ethanol conversion was 100% at the temperature from 350℃to 700℃over 20wt%Ni/Ce_0.5Zr_0.5O₂-700 catalyst.(4)The stability test is carried out for 6h over 20%Ni/Ce_0.5Zr_0.5O₂ catalyst separately at 350℃and 550℃There is no changes of activity and products selectivities were observed.(5)XRD results indicated that the catalyst include the phase of NiO and Ce0.5Zr0.5O2. Both the distribution of Ni species and the interaction between NiO and CeO2 affected catalysts performance.(6)The active component of Ni0 exists in different forms of catalysts with different preparation conditions. Meanwhile, the interaction between NiO and carrier will affect catalyst performance. (7)TG-DTA results showed no weight loss over 20%Ni/Ce_0.5Zr_0.5O₂ catalyst which is used for 6h at 550℃. So the 20%Ni/Ce_0.5Zr_0.5O₂ catalyst has better anti-carbon deposition property.