不同预处理下氧化石墨烯负载铁催化剂的结构及费托反应性能研究

Due to the low price and wide operation conditions, iron-based catalysts have been widely applied in Fischer-Tropsch synthesis (FTS) to produce liquid fuels. The improvement of FTS performances is dependent on the establishment of structure-activity relationship, among which the active phase of iron catalysts is the key. However, owing to the complexities of iron phase transformation and phase structure, the active phase and role of each phase in iron catalysts are in great dispute. In our previous work, it was found the tunable metal-support interaction in graphene oxide not only guaranteed the homogeneous and stable dispersion of iron nanoparticles (NPs), but also benefited the study of the intrinsic catalytic characteristics of active components. This is hopeful to solve the problems of active phases and structure-activity relationship in iron catalysts. In this project, based on the previous study, the graphene oxide supported iron NPs (Fe/GO) as model catalysts will be synthesized, and the structure-activity relationship and active phase of Fe/GO will be studied in the aim of enhancing FTS performances. Through the various ex situ and in situ characterizations, the phase transformation, active phase, role of each phase and structure-activity relationship in Fe/GO under different pretreatments and FTS conditions will be investigated. Finally, it will be expected to get a deep understanding of the interaction mechanism between graphene oxide and iron NPs, which will provide guidance for the design of industrial catalysts.

铁基催化剂应用于费托合成制液体燃料，具有价格低廉、操作范围广等优点。其反应性能的改善依赖于构效关系的建立，其中最关键的是确定催化剂的活性相。然而，铁基催化剂的物相转变多样和相结构复杂，导致目前对其活性相及各相态的作用存在较大争议。前期工作发现，利用氧化石墨烯可调的金属-载体相互作用，实现纳米粒子的均匀稳定分散，又能观察活性组分的本征催化特性，有望解决铁基催化剂活性相难确定及构效关系难建立的问题。本项目拟在前期工作的基础上，以氧化石墨烯负载铁纳米粒子为模型催化剂，研究不同预处理条件下催化剂的构效关系和物相转变，优化其费托反应性能。通过对催化剂进行一系列离线和原位表征，掌握不同预处理和反应条件下催化剂物相结构转变规律，研究催化剂中活性相及各相态的作用，阐明催化剂结构、性质和性能之间的构效关系，深化氧化石墨烯与铁纳米粒子相互作用机制的认识，为铁基催化剂的工业设计和开发提供指导。

铁基催化剂应用于费托合成制液体燃料，具有价格低廉、操作范围广等优点。其反应性能的改善依赖于构效关系的建立，其中最关键的是确定催化剂的活性相。然而，铁基催化剂的相结构复杂，物相转变多样，导致目前对其活性相及各相态的作用存在较大争议。本项目以氧化石墨烯负载铁纳米粒子催化剂（Fe/GO）为研究对象，利用氧化石墨烯可调的金属-载体相互作用，可实现纳米粒子的均匀稳定分散，并研究活性组分的本征催化特性。通过水热溶剂热法实现了尺寸介于3~50 nm，相态单一，分布均匀的Fe/GO催化剂的可控制备，并探明反应温度、沉淀剂、有机物修饰等合成条件对催化剂形貌、尺寸、孔结构、相态等的影响；结合第一性原理计算分析氧化石墨烯与铁纳米粒子之间的相互作用机制及调控规律，从实验和理论两方面深入认识催化剂结构；利用多种离线、原位表征手段，揭示了Fe/GO催化剂在不同活化和反应条件下的物相结构转变规律，证明θ-Fe3C是费托合成反应的活性相，具有高C5+选择性和低CH4选择性；揭示了活化气氛对催化剂表面碳缺陷的影响机制，提出具有适度碳势的乙烯气氛能够产生较多的碳缺陷，有助于反应物的吸附和活性相的稳定，初步建立催化剂表面、体相与化学环境之间的关系，掌握了费托合成铁基催化剂活性相调控和稳定技术，为进一步优化设计和可控制备高效稳定的铁基费托合成催化剂提供了实验基础和理论依据。