特定结构复合材料衍生催化剂在甲烷干重整中的研究进展

Research progress of specific structural composites derived catalysts in dry reforming of methane

钙钛矿、尖晶石和水滑石这类特定结构复合材料组成灵活、结构可控、热稳定性较好,在催化应用中吸引了广泛的研究兴趣。甲烷干重整是一项可同时将CH4和CO_(2)转化为低H2/CO摩尔比合成气的极具应用前景技术,常规负载型催化剂在高温重整条件下易面临由积炭和活性组分烧结导致催化剂失活的难题,而由特定结构复合材料衍生的负载型催化剂因在催化活性和稳定性方面表现出一定的优越性而备受关注。本文先简述了甲烷干重整反应特征、面临的挑战以及反应机制研究现状,并阐述钙钛矿、尖晶石和水滑石这3种复合材料的结构特性,作为催化剂前体应用于该反应的优缺点、性能以及催化路径研究现状。文中指出:钙钛矿结构相对更稳定,但高煅烧温度易导致衍生催化剂表面积较低;水滑石衍生催化剂通常具有较高比表面积,且在特定情况下能恢复部分有序层状结构;水滑石与尖晶石对温度相对更敏感一些,存在的反尖晶石结构有利于提高衍生催化剂还原性。此外,还总结了这3种特定结构复合材料衍生催化剂的催化机制,明确CH4是在活性金属位点上活化,因催化剂和操作条件的影响,目前研究人员对于催化剂表面反应机制的细节暂时还没有达成明确共识。最后,本文对特定结构复合材料衍生催化剂在甲烷干重整中的应用提出了建议。

Specific structural composites such as perovskite,spinel and hydrotalcite have attracted widespread research interest in catalytic applications due to their flexible composition,controllable structure,and better thermal stability.Dry reforming of methane is a technology with great application prospect for converting CH4 and CO_(2) into syngas with low H2/CO molar ratio simultaneously.Conventional supported catalysts are susceptible to face the challenge of catalyst deactivation caused by carbon deposition and active component sintering under high-temperature reforming conditions,whereas supported catalysts derived from specific structural composites have attracted much attention owing to their superiority in terms of catalytic activity and stability.In this paper,the characteristics of dry reforming of methane,the challenges faced and the current research status of the reaction mechanism are first briefly outlined,and then elaborates on the structural characteristics of perovskite,spinel and hydrotalcite these three composites,the advantages and disadvantages of applying them as catalyst precursors in this reaction,their performance and the current status of research on the catalytic pathway.Perovskite structure is relatively more stable,but high calcination temperatures may easily lead to a lower surface area of its derived catalyst.Hydrotalcite-derived catalysts usually have a high specific surface area and can restore partially ordered layered structures when calcined under certain circumstances.Hydrotalcite and spinel are relatively more sensitive to temperature,and the presence of inverse spinel structure is beneficial for improving the reducibility of the derived catalysts.Additionally,the catalytic mechanisms of these three specific structural composites derived catalysts are summarized.The clear one is that CH4 is activated at the active metal sites,and due to the influence of catalysts and operating conditions,researchers have not reached a clear consensus on the details of the reaction mechanism at the catalyst surface for the time being.Finally,some advice is put forward on the application of these specific structural composites derived catalysts in dry reforming of methane.