Study On Y₂O₃-M_xO_y Supported Ni For Ethanol Steam Reforming To Generate Hydrogen

Hydrogen energy is attracted more attention as clean and highly efficient. Ethanol, which can be produced from fermentation of biomass, is a renewable resource. Therefore, ethanol steam reforming for hydrogen production is got lots of research. In this thesis, different series of composite supports Y2O3-MxOy(M=Nb, Al) were prepared by co-precipitation method, and Ni-base catalyst were prepared by impregnation method. Effect of temperature on the catalytic properties was studied. The catalysts were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), thermogravimetry (TG) hydrogen chemisorptions and temperature programmed desorption (H2-TPD).In the first part, effect of different reduction time at550℃, different H2O/EtOH molar rate and feed flow rate on the Ni/Y2O3catalytic properties were evaluted in ethanol steam reforming reaction (SRE). The result showed that catalyst Ni/Y2O3performed the best activity affter H2reduced at550℃for3h. Hhigher H2O/EtOH molar rate and feed flow rate could prompt methane reforming which is benefit to hydrogen yield. Therefore, the subsequent experiment conditions are fixed as follow: the catalyst reduced at550℃for3h, H2O/EtOH molar rate is13:1, feed flow rate is0.05ml/min.In the second part, composite supports Y2O3-Nb2O5with different mole ratio of Y:Nb were prepared by co-precipitation method. We found that catalyst NY and NNb performed poor for SRE reaction at low temperature, as too weak interaction between NiO and Y2O3and too strong between NiO and Nb2O5. This situation was improved after using composite support, and the acid-base property of catalyst is also changed. Catalyst NYNb11was exhibited the best, ethanol translate completely at400℃, and the selectivity of CO was only0.1%.In the third part, composite supports Y2O3-Al2O3with different mole ratio of Y:Al were prepared by co-precipitation method. Compare with catalyst NY, NiO can be reduced easily which loaded on composite supports, that lead to catalysts exhibited high activity at low temperture. H2can be desorbed easily from the composite support, which result in relative high H2yeild over the composite support catalyst. Catalyst with1:1mole ratio of Y:Al in the support performed better for SRE reaction, and have no inactivation after60h continuous reaction at500℃over NYA11.In the last part, over catalyst Ni/Y2O3-Al2O3, effect of the addition of a small amount of Pt on the propertis of ethanol steam reforming were investigated. The result showed that the ability of Pt for rupture of C-C bond was quite strong at low temperture, and it increase with the load of Pt. Meanwhile, the ability of resist carbon deposition is enhanced by Pt addition, after60h SRE reaction, the amount of carbon deposition over15PNYA only0.017g of per gram catalyst.