Preparation Of Catalysts And Its Catalytic Performance For CO Methanation

Because the present status of energy is"rich coal, poor petrolem, less gas"and the huge demand of energy consumption especially for the clean energy, which makes the coal to SNG (substitute natual gas) could be as a direction of developing clean energy of our country.SNG system includs two steps include coal gasification to hydrogen rich gas and carbon monoxide methanation. The gasification technology was already well proven The research is focus on developing the novel catalyst with high activity and well stability.According to requirements of the economics and energy, it's important to carry out some approachs to make the traditional Nickel catalyst for CO methanation high- efficiency,for example, using mixed oxides as the support, or adding another metal as the promoter to the catalyst.In this paper, we studied Nickel loaded on the aluminum oxide catalyst for CO methanation. Firstly, the appropriate amount of Ni loading on the aluminum oxide was investigated. Then the Al-Ti mixed oxides supports with different percentage of TiO₂ were prepared. On the basis of the appropriate amount of Ni loading, we investigated the effect of TiO₂ contents in the Al-Ti mixed oxides on the catalytic performace of CO methanation, and found the optimum content of TiO₂. Meanwhile, the effect of adding another metal as the promoter such as Ru, La, Co, Fe and Mg to Ni loaded on the Al-Ti mixed oxides catalysts were studied. Finally, the influence of reaction conditions including of temperature and space velocity on the catalytic performace were discussed.It was found that the appropriate amount of Ni loading is 15% (mass percentage). With respective to the 15%Ni/Al₂O₃-TiO₂ catalysts, when the amount of TiO₂ in the support is 40%, the catalyst exhibited excellent catalytic performace. In the range of 340-440℃, the CO conversion was up to 100%, and the selectivity of CH4 was close to 90.73% in the range of 400-440℃. Adding another metal as the promoter such as Ru, La, Co, Fe and Mg to Ni loaded on the Al-Ti mixed oxides catalysts, we found that the addition of Ru could improve the lower temperature activity of the catalyst, while adding La could promote the higher temperature activity of the catalyst. However, the addition of Co, Fe and Mg has less improvement with the catalytic performace of M+15%Ni/Al₂O₃-40%TiO₂. The experiment of reaction condition indicated that between activation temperature and 420℃, the catalytic activity was increased with increasing temperature, however, when the temperature was over 420℃, the selectivity of CH4 was apparently decreased. Additionally, under the condition of low and middle space velocity, the catalytic activity was almost unchanged, while the catalytic activity would be dropped sharply with higher space velocity. With the thermodynamic data of the CO methanation reaction, we found that the CO methanation reaction was a strong exothermic reaction. When the reaction temperature was up to 622.20℃(895.35K), theâ–³_rG^θ_m=0, and K^θ=1, the positive reaction was extreme. When the reaction temperature was over 622.20℃(895.35K), the reverse reaction was enhanced, therefore the temperature of CO methanation reaction should be controlled below 622.20℃(895.35K).