高稳定性和产物选择性可控的钴基费-托合成催化剂研究

The Fischer-Tropsch synthesis (FTS) is a heterogeneous catalytic process that converts a mixture of carbon monoxide and hydrogen, which typically derived from coal, natural gas, or biomass, into ultra clean liquid hydrocarbons. The development of novel FTS catalysts with high reaction stability and controllable selectivity is the key challenge towards the improvement of FTS technologies. However, there are still some problems in tuning the product selectivity and understanding the nature of catalyst deactivation for conventional catalysts with complicated status, since the interrelations between product selectivity, catalyst deactivation and the character of catalyst such as composition, texture, and the physicochemical properties of support and active components are undefined. In this project, novel cobalt-based FTS catalysts with definite and controllable character will be designed and prepared by in-situ synthesis method using specific ordered materials such as hierarchical porous materials, mesoporous materials with three-dimensional cage-like pore, and mesoporous carbon materials, etc. The individual/collective effects of the character of above catalysts including composition, texture, acidity, promoters, metal-support interaction, confinement, and chemical state, cluster size, dispersion, morphology, location of active phase on the product selectivity and reaction stability will be studied, using in-situ characterization techniques and the evaluation of catalysts' performance in FTS. The mechanism of tuning product selectivity and nature of catalyst deactivation can be clarified by above studies, furthermore, the achievement of this project can make contribution to the development of advanced cobalt-based FTS catalysts with high activity, good stability and controllable selectivity.

费-托合成产物选择性调控和催化剂稳定性控制是费-托合成技术进步面临的两个关键科学难题，传统的费-托合成催化剂体系的结构和性质不明确且无法精确调控，加之缺乏有效的研究手段，无法科学理解影响产物选择性和催化剂稳定性的各种因素的作用机制。本项目将有序多级孔材料、有序介孔碳、三维笼型介孔材料等新材料与催化剂原位合成技术相结合，构建结构规整可控、性质明确的钴基费-托合成催化剂，并将催化剂性能评价与先进的原位表征技术相结合，从机理层面上深入系统地研究催化剂组成、载体酸性、孔结构、助剂、金属-载体相互作用、限域作用、活性金属尺寸、形貌、所处位置等因素对产物选择性和催化剂稳定性的独立/综合的影响规律，确定产物选择性的调控机制，阐明催化剂在不同因素下的失活机理，为活性高、稳定性好、产物选择性可控的可工业化应用的先进钴基费-托合成催化剂的设计开发提供科学指导和理论依据。

费-托合成产物选择性调控和催化剂稳定性控制是费-托合成技术进步面临的两个关键科学难题，传统的费-托合成催化剂体系的结构和性质不明确且无法精确调控，加之缺乏有效的研究手段，无法科学理解影响产物选择性和催化剂稳定性的各种因素的作用机制。本项目采用水热法、固相法、水蒸汽辅助转晶法等制备了纳米尺度多级孔ZSM-5分子筛、SBA-15/ZSM-5介孔-微孔复合分子筛材料、介孔泡沫硅（MCF）/ ZSM-5介孔-微孔复合分子筛材料、多级孔硅铝材料、有序介孔氧化铝、Al掺杂MCF介孔材料、有序介孔碳、C3N4/SBA-15复合材料、碳包裹TiO2复合材料等一系列微孔、介孔及多级孔材料；系统研究了合成条件对多级孔分子筛材料的结构和性质的影响规律，研究表明处理方法（水热法、固相法、水蒸汽辅助转晶法）、晶化温度、有机胺模板剂的种类、Si/Al比、碳凝胶硬模板的加入量、水蒸气处理时间和温度、铝盐前驱体的种类、二次水蒸气处理、不同前驱体混合后固化方式均显著影响多级孔分子筛材料的结构、形貌和酸性；经过条件筛选，发展了结构和性质可有效调控的多级孔分子筛材料的合成方法；进一步以上述材料为载体制备了钴基费-托合成催化剂，系统研究了载体酸性、孔结构、助剂修饰、金属-载体相互作用、限域作用、活性金属尺寸、形貌和落位等因素对催化剂在费-托合成反应中的活性、产物选择性和稳定性的影响规律，发展了一系列有序多级孔材料、有序介孔碳、三维笼型介孔材料为载体制备结构和性质可控的钴基费-托合成催化剂的制备技术，明确了钴基催化剂在费-托合成反应过程中的活性、产物选择性以及稳定性的影响因素和调控机制，确定了具有不同组成和结构的钴基费-托合成催化剂体系的构效关系，并以这些认识为指导开发了活性高、稳定性好的可工业化应用的高效钴基费-托合成催化剂。