介孔氮杂碳促进非贵金属高效催化甲酸氢转移加氢乙酰丙酸衍生物及反应机理研究

Presently, catalytic hydrogenation of biomass-derived levulinic acid derivatives into fuel and organic chemicals is one of the most effective ways to solve the energy crisis. Traditionally, noble metal catalysts and fossil-derived hydrogen are commonly used in this transformation, in which the acidic reaction system often leads to the loss or the deactivation of catalysts. In this project, high-surface-area and mesopore-dominanted nitrogen-doped carbons can be synthesized by “one-pot” pyrolysis of renewable biomass, cheap organic nitrogen compounds and chloride salts, which will realize the high dispersion and stabilization of non-noble metal nanoparticles by their rich N-groups and pore structure; the strong hetero-junction due to the enhanced interaction between metal and N-groups makes nitrogen-doped carbon supported non-noble metal as a bifunctional catalyst for transferring hydrogen of formic acid to hydrogenate levulinic acid. A controllable synthesis strategy will be adopted to reveal the inherent relation of the structural, component characteristics of catalysts to the catalytic activity and selectivity, enabling high-efficiency control synthesis of high performance catalysts. Simultaneously, systematical studies on catalytic reactions and processes will provide useful information to disclose the mechanism of hydrogen-transfer hydrogenation of levulinic acid with formic acid. The success of the project will help the establishment of new catalytic technology for converting biomass source into high-value products efficiently.

乙酰丙酸是一种重要的平台化合物, 将乙酰丙酸及其衍生物加氢合成燃料和化工产品具有重要的意义和应用前景。传统工艺采用贵金属催化剂和化石来源的氢气，且反应体系为酸性, 催化剂易流失。本项目拟以可再生生物质、廉价含氮有机物和氯化盐为原料，设计合成高比表面积、富含介孔的氮杂碳材料，希望借助其表面丰富的氮物种和孔结构进一步负载非贵金属（Cu或Co）活性中心；利用氮杂碳与金属之间的强相互作用克服催化剂流失，同时将副产物甲酸的解离制氢反应与乙酰丙酸加氢过程相偶联，从而实现乙酰丙酸及其衍生物的绿色、原子经济转化。通过高效催化剂的制备和表征，探索催化剂材料活性源与材料组成、结构的内在关系。通过反应条件和工艺的深入探索，揭示该催化剂对甲酸解离和乙酰丙酸加氢的协同作用机制和催化机理。经过本项目的研究不仅可以为乙酰丙酸及其衍生物的高效、绿色转化提供依据，而且可以为其它生物质原料的高效转化提供理论依据。

工业催化加氢多以化石来源的纯氢做氢源，存在储运不便、易燃爆等不足。将可再生的甲酸作为氢源，偶联生物质平台化合物的催化加氢，在环保及碳排放等方面具有显著优势。本项目对甲酸转移加氢过程与催化剂设计进行了创新，杜绝使用贵金属和碱添加剂，利用氮杂碳热解过程自发还原、包覆非金属纳米粒子的特性，设计合成氮杂碳包覆非金属核壳结构催化剂，实现了香草醛、糠醛、5-羟甲基糠醛、木糖、喹啉等分子的转移加氢。主要结论及成绩有：1）在Fe、Co、Ni、Cu等非贵金属中，Co具有最佳的转移加氢活性；2）包覆型核壳结构显著抑制非贵金属核的流失，提高催化剂在甲酸中的稳定性；3）氮杂碳表面丰富的吡啶氮物种可充当碱性位，显著促进甲酸的催化脱氢，提高转移加氢的反应速率；4）除作为氢源外，甲酸还可作为Bronsted酸，催化生物质糖的一步脱水-转移加氢反应；5）相较于氢气做氢源，甲酸显著加速催化速率，抑制中间产物过度加氢，提高目标产物的选择性，显示出完全迥异的加氢机理。该课题的研究结果，对多功能催化材料的合成及甲酸利用具有指导意义。在本课题的资助下，已经发表标注论文15篇（其中SCI论文15篇），申请国家发明专利9项（4项已经获得授权），培养研究生3名，本科生9名。项目组成员参加国际会议1人次、国内学术会议5人次。