Hydrogen Production By Steam Reforming Of Ethanol Over Ni-M/Al₂O₃-SiO₂ Catalysts

Producing hydrogen from ethanol steam reforming reaction is still a current highlight for fuel cell technique, and exploring high active catalysts with high hydrogen selectivity and good stability at low temperature is one of important issues to the utilization of hydrogen energy.The second metal was added into Ni catalyst to improve the activity of the Ni/Al₂O₃-SiO₂ catalyst.the reaction temperature was 350 to 650℃;Cu, Co, La, Y and Zr were added into catalyst to prepare Ni-M/Al₂O₃-SiO₂ catalyst(M= Cu, Co, La, Y and Zr).the result shows that Cu, Co, La and Y can promote the activity of Ni/Al₂O₃-SiO₂ catalyst in steam reforming reaction of ethanol(SRE). The best hydrogen selectivity was gained on 30Ni5Co catalyst, and its selectivity of CO was lower than 30Ni.TPR analysis illuminate Si addition to Al₂O₃ support can low down the reaction between Ni and Al₂O₃. the catalyst should be reduced easier when Cu and Co were added into 30Ni, metal Ni in 30Ni5La catalyst exist as the form of amorphous spinel Ni-aluminate. XPS analysis shows that Co oxides were reduced totally, Cu in 30Ni5Cu catalyst exist as the form of Cu oxides(CuO, CuAl2O4 and CuSiO3 and be reduced into metal Cu or Cu⁺, Y³⁺ and Zr⁴⁺ still exist in 30Ni5Y and 30Ni5Zr after reduction. XRD analysis shows Si addition to Al₂O₃ support can low down the reaction between Ni and Al₂O₃, so decrease the reduction temperature, 30Ni5Co was reduced in site. The size of NiO in 30Ni5La was far smaller than it in 30Ni and 30Ni5Co catalyst, it means La can disperse Ni into support. NH3-TPD shows that the acid of catalyst was lowed at 20% when Co was addedFor 30Ni5La/Al₂O₃·SiO₂, the increasement of water to ethanol molar ratio from 3 to 12 can increase the hydrogen selectivity, low down the selectivity of CH₄, when the molar ratio surpass 5, no CO was gained. When GHSV changed from 2.0 mlh^-1g^-1 to 4.0 mlh^-1g^-1, selectivity of hydrogen decreased. Ethanol could be conversed totally when temperature higher than 300℃, the hydrogen selectivity was increased as the temperature increased, it reached 90% at 600℃(GHSV=8.0mlg^-1h^-1 ,W/E =4).