Fe基费托催化剂上低碳烯烃形成机理及动力学特征

Fe基催化剂因能直接转化煤、生物质等来源的合成气经费托合成直接制低碳烯烃（FTO），引起了学术界与工业界的高度关注。然而，催化剂理性设计及产物选择性精细调控受限于复杂催化剂结构特性及反应路径。为此，本项目提出结合DFT计算和SSITKA阐明Fe基催化剂上低碳烯烃形成机理及动力学特征的新思路。采用DFT计算研究有无助剂存在条件下Fe基催化剂主要活性相χ-Fe5C2不同晶面上FTO反应路径，并对其进行微观动力学分析，进一步结合多组分SSITKA方法，以发展用于甄别Fe基催化剂上FTO反应机理的DFT计算与SSITKA耦合技术，从而解析动力学同位素效应及甄别FTO反应机理，最终阐明助剂对Fe基FTO催化剂活性中心结构及动力学特征的影响规律。本项目研究成果不仅可用于指导Fe基FTO催化剂的理性设计，还有助于深入理解DFT计算与SSITKA耦合技术在甄别复杂反应体系反应机理以及活性中心结构的重要性。

Fe-catalyzed Fischer-Tropsch synthesis to lower olefins (FTO) is of prime scientific and industrial importance in enabling direct conversion of CO-rich syngas derived from coal and biomass for the sustainable production of lower olefins. Rational design of the Fe-based catalysts and fine-tuned control of product selectivity are, however, limited by the complex catalyst structural nature and reaction pathways...To this end, this proposal aims to unravel the underlying mechanism and kinetic behavior for the formation of lower olefins on the Fe-based Fischer-Tropsch catalysts by a combination of density functional theory (DFT) calculations with steady-state isotopic transient kinetic analysis (SSITKA). At first, systematic DFT calculations followed by microkinetic analysis will be carried out to understand effects of typical promoters on the mechanism of FTO reaction over different χ-Fe5C2 crystal facets. Subsequently, based on the supported iron-based FTO catalysts in the presence or absence of promoters, the methodology of multicomponent steady-state isotopic transient kinetic analysis and the coupling of DFT calculations with SSITKA studies will be developed to realize the kinetic isotopic effects and discriminate the FTO reaction mechanism. Finally, the promoter effects on the properties of the active sites and the kinetic behaviors will be elucidated. . .This research is valuable not only for rational design of Fe-based FTO catalysts, but also for in-depth understanding of the crucial role of coupling DFT calculations with SSITKA in the discrimination of the reaction mechanism and the properties of the active sites in complex heterogeneous catalytic reactions.