Preparation And Catalytic Activity Of Chlorine-doped Catalysts Ni（Clx）/CeO₂ For Selective Methanation Of CO

CO in H2-rich gas must be decreased to less than 10 ppm for proton exchange membrane fuel cell(PEMFC) to generate electric power stably. However, the H2-rich gas produced by steam reforming reaction of hydrocarbons and the following water-gas shift reaction contains 1% CO and 18% CO2. Selective methanation of CO in H2-rich gas(CO-SMET) is an effective way to reduce CO to a safe level. In this thesis, Ni/CeO2 catalysts were prepared and used for CO-SMET reaction. Effects of preparation methods and chlorine ion doping were investigated. The main results are as follows.(1) Four methods were adopted to prepare samples 20%NiO/CeO2, which were then reduced at 500 oC for 2h and used for CO-SMET reaction. It is found that the catalyst20%Ni/CeO2 prepared from the precipitation method using aqueous ammonia as precipitant had the largest specific surface area and exhibited the highest conversions of CO and CO2.(2) Chlorine-doped catalysts Ni(Clx)/CeO2 were prepared with the precipitation method using aqueous ammonia as precipitant and used for CO-SMET reaction. It is found that chlorine ion dopping decreased adsorption amounts of CO and CO2 and suppressed CO2 conversion greatly. At x = 0.2, CO conversion of 100% could be achieved in 240 ~ 270 o C(by TCD detector). Furthermore, effect of atomic ratio of Ni/Ce was investigated. It is confirmed that the catalyst 40%Ni(Cl0.2)/CeO2 could reduce CO concentration to several ppm and with selectivity higher than 50%.(3) Impregnation method was used to prepare catalysts Ni(Clx)/CeO2. It is found that size of Ni crystallites increased with chlorine ion doping. And, chlorine ions suppressed CO2 conversion. At reaction temperatures 230 ~ 250 oC, 20%Ni(Cl0.2)/CeO2 could also decrease CO concentration to a few ppm, with selectivity higher than 50%.