煤基合成气甲烷化用镍基催化剂失活热力学和抗失活预测

摘要

Thermodynamics of sulfur poisoning and coking on nickel-based catalyst for coal-based synthesis gas methanation were systematically analyzed. It was found that the reactions of the active metal Ni,Mo with H2S,COS were spontaneous under the methanation reaction condition. The Ni-based catalysts could be poisoned by H2S,COS at a partial pressure magnitude of 10–10 and 10–14, respectively,and the sulfur content for Mo added catalysts could be no more than 10-6. Different types of coking reactions occurred at different temperature ranges,and the carbon deposition was mainly from the CO disproportionation reaction and the CO reduction reaction when temperature was 633.15—898.15K,while that was mainly from CH4cracking reaction when temperature was 898.15—983.15K. In addition,Ni-based catalysts could avoid carbon deposition at 0.1MPa by adding water vapor with the amount above 11.11%(mole fraction).%利用热力学数据对煤基合成气甲烷化用镍基催化剂硫中毒以及积炭热力学进行了详细的计算。计算发现，活性金属Ni、Mo在甲烷化反应条件下与H2S、COS发生反应是自发进行的过程。10-10数量级分压的H2S含量、10¯14数量级分压的COS含量即可使镍金属活性组分生成硫化镍而使催化剂失活；当Mo作为助剂添加到Ni基催化剂时，硫含量不能超过10–6数量级。不同温度区间发生的积炭反应类型不同，当温度为633.15～898.15K时，积炭反应主要以CO歧化反应、CO还原反应为主；898.15～983.15K时以CH4裂解反应为主。另外，在0.1MPa下，添加摩尔分数为11.11%及以上含量水蒸气可以避免积炭。