纳米碳修饰Al2O3构筑高效钴基费-托合成催化剂及其水热稳定性研究

Traditional alumina supported cobalt-based Fischer-Tropsch synthesis (FTS) catalysts have problems including too strong metal-support interaction, low reducibility of active metals and poor hydrothermal stability. In this project, carbon atoms which was in situ produced by high temperature pyrolysis of C-H bond will be applied to modify alumina surface defect sites, in order to regulate metal-support interaction, optimize active metal structure and inhibit the formation of CoxAlyOz compound in corresponded cobalt catalysts, and then their FTS activity and hydro-thermal stability would be improved. Through the structure adjustment of surface carbon species and active metal, the effects of various factors, such as coupling modes of carbon atoms, carbon-based functional groups, carbon thermal reduction properties, active metal geometric structure and electronic properties, on FTS activity, selectivity and stability of catalysts will be systematically studied. The structure evolution of active metal and supports during hydro-thermal deactivation process will be thoroughly investigated by various in-situ and ex-situ characterizations. The deactivation mechanism of cobalt catalyst under high water pressure and high CO conversion will be studied and discussed. The objective of this project is to obtain cobalt-based catalyst with high cobalt utilization efficiency, high activity, high C5+ selectivity and good stability. In addition, this work may provide a scientific basis for the design, preparation and application of FTS catalysts.

传统氧化铝负载的钴基费-托合成催化剂存在金属-载体相互作用强、活性金属还原度低、强水热环境（高CO转化率）下易失活等问题。本项目将通过热解C-H键生成碳原子修饰氧化铝表面缺陷位，调节其负载钴催化剂金属-载体相互作用，优化活性金属结构，抑制CoxAlyOz生成，提高催化剂活性和耐水热性能。制备表界面纳米碳和金属结构调变的系列催化剂，研究催化剂表面碳原子耦合方式、碳基官能团、碳热还原性质及钴晶粒几何结构和电子性质等因素对催化剂费-托合成活性及选择性的影响规律。借助原位X-射线衍射、原位X-射线光电子能谱、原位红外光谱-质谱联用等技术，研究水热失活过程中载体和活性金属的结构演变机制，探明高CO转化率和高水分压下钴催化剂的失活机理。旨在获得金属钴原子利用率高、活性高、C5+产物选择性高和稳定性好的钴基费-托合成催化剂，为高效费-托合成催化剂设计、制备及应用提供科学基础。

项目围绕高活性和高水热稳定性费-托合成催化剂的设计与合成开展研究。通过高分散纳米Al2O3、Si-Al2O3、Al2O3@C及纳米Co3O4颗粒材料合成方法的探究，获得Co/Si-Al2O3、Co/OMC及Co/Al2O3@C催化剂的表界面结构的有效调控方法；研究了Si元素掺杂对Co/Si-Al2O3催化剂性能的影响，研究了介孔碳结构对限域钴基催化剂性能的影响，研究了表界面碳层结构对Co/Al2O3@C催化剂性能的影响。结果表明：适量的Si元素修饰可以有效增加催化剂燃油段产物选择性，介孔碳材料限域的高分散钴催化剂具有良好热稳定性，碳结构修饰Al2O3载体后催化剂水热稳定性显著增强，Al2O3@C负载的钴催化剂在CO转化率70%时，依然具有良好的稳定性。项目通过对载体表面元素、碳基官能团类别以及界面碳性质等结构因素进行调控，优化了活性金属落位、金属-载体相互作用以及活性金属的电子性质，实现催化剂性能提升，为优化催化剂结构设计，制备高反应活性和高水热稳定性费-托合成催化剂提供了实验和理论指导。