Analysis of carbon deposition behavior in methane reforming in order to evaluate the catalyst life

在甲烷重整过程中，最严重的问题之一是反应过程中的积碳。然而，对碳的形成途径和形成碳的结构的研究还不够。特别是在长寿命催化剂的研制中，这些信息是非常重要的。研究的目的是阐明催化剂寿命与积碳行为之间的关系。研究了不同催化剂下CO_2、蒸汽和CO_2+蒸汽对甲烷重整的影响。考察了活性测试、反应温度依赖性、空速依赖性和总压依赖性。结果表明，NiO-MgO固溶体催化剂表现出优异的性能。特别是，低比表面积固溶体催化剂比高比表面积固溶体催化剂表现出更高的抗积碳能力。通过对催化剂床层各位置积碳情况的分析，发现催化剂床层入口积碳受到抑制。这表明甲烷分解生成的碳被抑制了。此外，还研究了其他金属的加入对其性能的影响。目前，Sn的加入抑制了碳的沉积。该催化剂还应用于甲烷重整用重整剂引入氧进行内供热的流化反应器系统。流态化反应体系提高了甲烷的转化率，并且发现在高压条件下根本没有碳沉积。这是由于反应器中活性催化剂的原位再生造成的。

In methane reforming, one of the most serious problems is carbon deposition during the reaction. However the investigation of the route of carbon formation and the structure of formed carbon is not enough. Especially, in the development for the long-life catalyst, the information is very important. The research of the purpose is the elucidation of the relation between the catalyst life and carbon deposition behavior.I investigated the methane reforming with CO_2, steam and CO_2+steam over various catalysts. The activity test, reaction temperature dependence, space velocity dependence, and total pressure dependence have been investigated. As a result, NiO-MgO solid solution catalysts showed excellent performance. Especially, the solid solution catalyst with low surface area exhibited much higher resistance to carbon deposition that that with high surface area. From the analysis ol the carbon deposition at various position of the catalyst bed, it is found that the carbon deposition at the inlet of the catalyst bed was inhibited. This indicates that the carbon formation from the methane decomposition is inhibited. Furthermore, the effect of other metal addition is also investigated. At present, the addition of Sn inhibited the carbon deposition.The excellent catalyst is also applied to the fluidized reactor system for the methane reforming with internal heat supply using oxygen introduction with the reforming agents. Fluidization reaction system enhanced the methane conversion and it is found that the carbon deposition is not observed at all under highly pressurized condition. This is caused by the in-situ reproduction ol the active catalyst in the reactor.