生物质基呋喃化合物选择加氢脱氧制备烯烃催化体系构筑及催化行为研究

The hydrodeoxygenation (HDO) reactions are widely used in transforming biomass and their derivates into chemicals, due to the high ratio of O/C in these materials. The high-valued chemicals consist of unsaturated bonds could be obtained from selective hydrodeoxygenation (SHDO) of biomass with lower hydrogen consumption. In this project, the efficient SHDO of biomass-based furans into olefins will be conducted over transition-metal sulfides and metal oxides catalysts by modulating the composition, structure, surface properties of these catalysts and the reaction pathway in the SHDO. The effect of catalyst composition, preparation methods, pretreatment and reaction conditions on the catalyst structure and catalytic performance will be investigated to illustrate the structure-performance relationship in the SHDO reactions. The catalysts properties will be measured by in situ or operando characterization techniques to predict the mode of substrate adsorption, activation and products desorption on potential active sites over catalyst surface. Based on the experimental results and theoretical basis, the effective means for adjusting catalyst properties and reaction performance is established gradually. Combining with the results on catalyst characterization, reaction mechanism and DFT calculation, the more suitable catalytic system would be designed at the level of atom or molecule, which will provide theoretical guidance for establishing the novel catalytic systems of the synthesis of high-valued chemicals by selective hydrodeoxygenation of platform molecule derived from biomass resource in nature.

由于生物质及其衍生物中O/C比高，加氢脱氧是转化生物质资源制备化工产品的重要途径，选择加氢脱氧可保留重要不饱和键，降低氢耗。本申请主要采用过渡金属硫化物和金属氧化物为催化剂，通过调变催化剂的组成、结构和表面性质，调控催化反应路径，将生物质基呋喃化合物高效选择加氢脱氧制备烯烃；研究催化剂的组成、制备方法、前处理条件以及反应条件等因素对催化剂结构和反应性能的影响，阐述催化剂结构与活性、选择性之间的构效关系。借助多类（原位）表征技术，认识催化剂活性相，揭示催化剂中可能活性位点对底物的吸附活化及产物脱附方式，推断呋喃化合物选择加氢脱氧的反应路径，逐步建立调控催化剂结构及其反应性能的有效方法。根据对催化剂结构及反应路径的认识，结合密度泛函理论，从分子/原子水平上设计合成更为合理的催化体系，为生物质平台分子选择加氢脱氧新型催化体系的构建提供理论依据。

加氢脱氧是转化生物质平台化合物制备化学品的有效途径，呋喃环类化合物的加氢脱氧研究较少。本项目以2-甲基呋喃为模型化合物，构建了不同硫化钼结构的硫化物催化体系，实现了2-甲基呋喃制备戊稀。研究发现硫化钼结构影响反应物转化率和产物选择性，低堆积层数的硫化钼暴露更多活性位点有利于加氢脱氧反应；钴助剂显著提高2-甲基呋喃转化率但对烯烃选择性影响不大，而镍助剂不利于烯烃选择性。基于氧化钼活性组分构建了氧化物催化体系，实现了加氢脱氧和异构功能耦合，成功由2-甲基呋喃制备了环戊烯，研究发现催化剂表面钼物种产生的B酸有利于加氢脱氧活性，而载体的L酸能增加环戊烯的选择性，但强酸位点因烯烃聚合不利于催化剂稳定性。此外，助剂调变载体表面的酸碱性可提高催化剂的稳定性。利用生物质基的2-甲基呋喃加氢脱氧制备环戊烯可减少对化石资源的依赖，同时为糠醛转化过程中副产物2-甲基呋喃的利用提供新途径。