新型Fe基双金属催化木质素基酚类化合物加氢脱氧的理论研究

Biomass conversion and utilization is an effective approach to sustainable energy development. How to efficiently remove the excess amount of oxygen in the transformation products is one of the important research subjects. Tailoring catalyst composition and proper processing conditions are of critical importance for both fundamental advance and practical applications for enhancing the selective hydrodeoxygenation (HDO) of lignin-derived phenolic compounds to aromatic hydrocarbons. This project focuses on developing mechanistic understanding of key factors affecting the bimetallic catalysts consisiting of oxophilic metal Fe and a small amount of precious metal such as Pd for HDO of phenolic compounds. Using density functional theory (DFT) and microkinetic modeling, the proposed research will investigate the critical factors of HDO catalysis including adsorption and activation of reactants, electronic interactions, reaction pathways, desorption of products, kinetics as well as the important factors affecting catalytic performance such as bimetallic surface structure, adsorbate structure and property of phenolic compounds, surface H2O-like species and support. Based on the computational investigation, the essence of potential synergic catalytic effect and composition-structure-performance relationship of the Fe-based bimetallic catalysts will be clarified. Through the identification of key descriptor and establishment of the computational catalyst screening system, we will elucidate the modulation mechanism of bimetallic composition and structures that can selectively regulate the formation of aromatics via CAr-O bond cleavage and suppress the hydrogenation of aromatic ring and C-C bond cleavage. Based on these computational results, novel M-Fe(M=Pd,Pt,Ru,Rh) bimetallic catalysts will be designed for selective HDO of specific phenolic compounds to aromatic hydrocarbons. The project will pave the way for new idea and new method for the research on HDO of biomass-derived oxygenated compounds, and will provide a theoretical basis of critical importance for the design and applications of novel highly-efficient bimetallic catalysts for HDO.

生物质的转化利用是可持续能源发展的有效途径，其中如何高效地脱除其转化产品中过多的氧是一个重要研究课题。通过调变催化剂组成结构和反应条件对木质素基酚类化合物进行选择加氢脱氧制备芳烃具有重要的研究和应用价值。本项目针对亲氧金属Fe与少量贵金属构成的双金属催化酚类化合物加氢脱氧体系，通过对分子吸附活化、电子作用机制、反应路径、反应动力学以及双金属表面结构、表面H2O物种、载体等重要因素对反应性能的影响进行系统的理论计算研究，阐明双金属协同催化的微观本质及构-效关系。通过关键模拟参数的确立和理论预测系统的构建，阐明能够促进CAr-O键断裂生成芳烃并抑制芳环加氢及C-C键断裂的双金属表面组成与结构；调变并优化设计新型M-Fe(M=Pd,Pt,Ru,Rh)双金属催化剂。本项研究将拓展生物质基含氧化合物催化加氢脱氧理论研究的新思路和新方法，为新型高效双金属加氢脱氧催化剂的设计合成提供重要的理论基础。

本项目基于生物质转化的重要研究课题，采用密度泛函理论方法系统研究了Fe与贵金属构成的双金属Fe-M (M=Pd, Pt, Ru, Rh)催化酚类化合物加氢脱氧的反应机理，通过对分子吸附活化、电子作用机制、反应路径、反应动力学以及双金属表面结构、表面水物种、载体等重要因素对反应性能的影响进行系统的理论计算，阐明双金属协同催化的微观本质及构-效关系。通过关键模拟参数的确立和理论预测系统的构建，阐明能够促进CAr-O键断裂生成芳烃并抑制芳环加氢及C-C键断裂的双金属表面组成与结构，调变并优化设计新型双金属催化剂。计算结果表明，Fe催化剂晶面对酚反应物分子吸附活化和加氢脱氧性能具有重要影响，苯酚在Fe(111)表面上吸附要强于Fe(110)和Fe(211)；Fe(211)对苯酚的加氢脱氧生成苯具有明显优势，而在Fe(111)和Fe(110)表面上苯酚更易发生苯环加氢生成环饱和产物；在Fe(211)表面掺杂贵金属Pd，能够促进苯酚加氢脱氧生成苯；在Fe(211)表面掺杂贵金属Rh，能够促进愈创木酚加氢脱氧生成苯酚。对于Fe-Pt和Fe-Ru双金属催化剂，贵金属的掺杂形式（表面取代和表面吸附）以及掺杂量（单个原子和金属团簇）对酚类加氢脱氧反应活性和产物选择性具有重要影响，不同形式引入的贵金属通过结构效应和电子效应影响酚类反应物的吸附和加氢脱氧反应；此外，不同酚反应物（苯酚、邻甲酚、愈创木酚）由于分子内所含官能团不同，其加氢脱氧路径和反应性能也存在明显差异。加氢脱氧反应中生成的水可以通过氢传递和氢键作用影响芳烃生成动力学。理论计算结果表明，在Fe催化剂中（尤其是带有阶梯的211晶面）掺杂少量贵金属有利于酚类CAr-O键断裂，高选择性生成芳烃。本项研究拓展了生物质基含氧化合物催化加氢脱氧理论研究的新思路和新方法，为新型高效双金属加氢脱氧催化剂的设计合成提供重要的理论基础。