The Preparation And Characterization Of Ce-Cu-O Solid Solution Catalyst And The Study On Oxidative Steam Reforming Of Methanol

In recent years, increasing attention has been focused on producinghydrogen-rich gas as fuel. The oxidative steam reforming of methanol (OSRM)is one of the most promising routes for the hydrogen production frommethanol considering the low reaction temperature, the acceptable hydrogenyield and the possibility to eliminate CO due to the present of H₂O.Furthermore, OSRM has several advantages for transportation applicationsdue to its autothermal process with idealized reaction stoichiometry, Eq. (1).CH₃OH + 3/4H₂O + 1/8O₂ = CO₂ + 11/4H₂ â–³H573K = 0 (1)These advantages are particularly important because: (1) autothermal processallows more rapid response to changing in the power demand and faster starupin engine, (2) less heat exchange between incoming reactants and the hotproducts could simplified the reactor structure.In this thesis, a novel solid solution Ce_1-XCu_XO_Y (X < 0.15) prepared bycomplexation-combustion route was used for oxidative steam reforming ofmethanol. At low Cu content, the incorporation of Cu atoms into CeO₂ latticeleads to the formation of solid solution with the enhancement of oxygenvacancy. A high and stable redox property was observed for the solid solution.XPS results indicated that the synergistic function between Cu²⁺/Cu⁺ andCe⁴⁺/Ce³⁺ occurred in the redox cycle, which is the reason of lower reductiontemperature and improved redox property as shown in TPR profiles. As aresult, a methanol conversion higher than 85% with 90% hydrogen yield wasobtained for Ce_0.95Cu_0.05OY prepared by complexation-combustion from theoxidative steam reforming of methanol reaction at 240℃. However, thecatalysts prepared by co-precipitation and deposition-precipitation routesshowed methanol conversion lower than 30% at 240 C, and less than 60% oeven at 360 C. The high catalytic activity of Ce0.9Cu0.1OY prepared by ocomplexation-combustion is mainly related to the formation of solid solutionand the improved redox property. The mechanism of hydrogen production from methanol was studied byusing TAP (Temporal Analysis of Products) reactor. It was found that thebehaviors of methanol decomposition and oxidation are depended on theoxidation degree of the Ce0.95Cu0.05OY solid solution. The CO response time islonger with the increasing in the oxidation degree of the catalyst. WhenCH3OH/O2/Ne was pulsed on the oxidized catalyst, it was found that the CO2originated and the response time of CO2 is almost same to that of CO, whichindicated that CO2 is coming from the methanol instead of CO oxidation. So, itwas reasonable to suggest that the oxidation degree of the catalyst has a stronginfluence on the methanol reaction route. It was concluded that the Ce1-XCuXOY solid solution is a kind ofpromising catalyst considering the high catalytic activity for the hydrogenproduction and the potential capabilityin the elimination of CO in rich H2.