Study On Ni Catalyst For Ethanol Steam Reforming To Generate Hydrogen

The different ways of reforming ethanol to generate hydrogen were reviewed inthe thesis, such as steam reforming, partial oxidation reforming, plasma reforming,photocatalysis induced reforming and separate membrane reaction. Effect of Mo andZrO₂ t on the properties of Ni/ZnO for ethanol reforming to generate hydrogen wasstudied.The structure and size of the catalysts were analyzed by means of X-raydiffraction(XRD). The reductive property of the catalysts was characterized bytemperature programmed reduction(TPR) and the ability of resistance to carbondeposition of the catalysts was tested by temperature programmed oxidization.The results showed that the activity and selectivity to H₂ of Ni/ZnO catalyst arepromoted by addition of Mo at 773K. The activities of the catalysts increase with thetemperature. Ethanol is converted completely at 823K. At 873K, NMZ-2 catalyst, inwhich the content of Mo was 0.83%, has the optimum activity, the highest selectivitytowards hydrogen and the best stability among the catalysts. The ability ofresistance to carbon deposition of NZ can be promoted by addition of Mo,therefore,the stability of the catalyst is improved. TPR and XRD results show that addition ofMo increases the dispersion of nickel oxide over ZnO and weakens the interactionbetween Ni oxide and the support. Therefore, the activity, selectivity and stability ofNi/ZnO catalyst are improved.The Catalyst Ni/ZnO-ZrO₂ used in ethanol steam reforming were prepared by acoprecipitation method using Na₂C₂O₄ as a precipitant. The catalytic properties of thecatalysts with different ratio of ZnO:ZrO₂ between 300 and 650℃were discussed.The catalysts were characterized by means of TPR, TPO and XRD. The resultssuggested that ethanol was conversed compeletely at 400℃. The selectivites tohydrogen over Ni/ ZnO-ZrO₂ were higher than Ni/ ZnO and Ni/ ZrO₂ at lowtemperature. Meanwhile. the amount of carbon deposition on Ni/ZnO-ZrO₂ and Ni/ZrO₂ was less than that on Ni/ ZnO. the cubic ZrO₂ could enhance the surface accumulating ability of lattice oxygen in ZnO-ZrO2, decreasing the amount of carbondeposited.The thesis also studed the effect of hydrogen reduction on the catalytic propertiesof Ni/ZnO, Ni/ZrO₂, Ni/ZnO-ZrO₂ (Zn:Zr=1:1) catalysts which were prepared byCodeposition method for ethanol steam reforming to hydrogen production, theselectivity to hydrogen over the un-reducted catalysts are higher generally than thatover the reduced catalysts. The ability of resistance to carbon deposition of theZnO-ZrO₂ and Ni/ZrO₂ un-reduced is stronger than that of the reduced.but the NZncatalyst is reversed.