木质生物质到烃类的定向转化及催化化学研究

Biomass is a natural energy carrier of solar energy. The efficient conversion of lignocellulosic biomass into liquid fuels is one way to comprehensively utilize the biomass resources and ease the world’s energy crisis. However, the current technologies for lignocellulosic biomass conversion into liquid hydrocabons are typically multi-step and low energy-efficiency processes with long production cycle. Therefore, the direct, simultaneous hydrodeoxygenation of cellulose, hemicellulose and lignin components in raw biomass into liquid hydrocarbon fuels, through the design and preparation of multifunctional catalysts, would be of high significance for efficient biomass utilization. Especially for lignin component which contains plently of aromatic rings in its construction, it is very meaningful to adjust the product distributions to get higher value-added aromatic hydrocarbons by controlling its reaction kinetics. Herein, in this project, we plan to (1) systematically and fundamentally investigate the formation of liquid hydrocarbons from direct conversion of lignocellulosic biomass, by the design and preparation of a series of highly efficient multifunctional catalysts; (2) reveal the catalytic mechanism of the reaction and understand the role of each component in the catalyst and their synergetic effects in hydrodeoxygenation, by a combination of control experiments study, reaction pathways study, isotope tracer study, in-situ characterization and DFT calculations; (3) to reveal the catalysis chemistry of MOx species on C-O bond activation through DFT calculation, and in-situ FTIR, EXAFS and inelastic neutron scattering (INS) studies, especially for the selective lignin conversion into aromatic hydrocarbons; (4) design and invent a set of catalytic technologies with self-owned intellectual property rights for the direct hydrodeoxygenation of lignocellulosic biomass such as wood sawdusts into liquid hydrocarbons, through the design and preparation of the crucial multifunctional catalysts.

木质生物质作为太阳能贮存的自然能量载体，其催化转化为液态燃料是缓解能源危机的最有效途径之一。针对目前转化路线工艺繁杂、周期长、利用效率低等问题，通过多功能催化剂的设计，实现木质生物质中三组分的一步直接脱氧加氢制备液态烃类，特别是针对富含芳环的木质素资源,实现附加值更高的芳烃的选择性制备，对于木质生物质的高效利用具有重要的现实意义。为此，本项目将（1）着眼以基础研究引导的一类高效、多功能催化剂的创制和科学制备，探究烃类生成路线的控制和优化；（2）综合实验表征和量化计算，揭示催化反应机理，理解不同活性中心在脱氧加氢中作用本质和协同机制；（3）揭示C-O键活化与反应的普遍规律，探究活性组分元素、结构、反应条件等对活性及选择性的精细调控和优化，重点建立木质素到芳烃选择性转化的控制方案；（4）针对木质生物质的脱氧加氢制备烷烃、芳烃过程，形成以多功能催化剂为核心的、具有自主知识产权的催化技术与工艺。

本项目创新性地设计并制备了金属-C-O键活化-酸中心协同作用的多功能铌基催化剂，并将其成功应用于木质生物质及其衍生物定向转化制液态烃类燃料的反应中：1）以Pd/NbOPO4为催化剂，将生物质衍生物-糠醛进行Michael加成/Aldol缩合碳链增长后的C13/C10-C15、C26化合物进行脱氧加氢，可高选择性地得到支链烷烃，其中C13支链烃的密度为0.800 g/cm3，凝点低至-50 oC以下，可作为航空煤油组分使用；2）以Ru/Nb2O5为催化剂，首次在温和条件下将水体系中的木质素高效转化到芳烃，木质素单体转化率接近理论值，烃类质量收率为35.5 wt%，其中芳烃选择性高达71 wt%，该过程既保留了芳香官能团，所得芳烃可直接作为高密度航空煤油组分使用，又降低了氢耗；3）以Pt/NbOPO4为催化剂，第一次实现了木质生物质不需经过化学预处理即可到烷烃的直接转化，液相收率高达28%，其中不仅木质生物质中的纤维素，半纤维素可以转化为为己烷、戊烷，而且可把木质素成分转化为取代环己烷，为木质生物质转化为燃料的过程开辟了一条新路径。基于以上反应的催化性能结果，结合多种常规及原位的表征手段（如原位红外、原位XFS、原位非弹性中子散射）和DFT计算，发现正是由于活化H2的贵金属组分（Pd、Ru、Pt）、解离C-O键的Nb以及Nb基氧化物的酸性这三种活性中心进行协同作用，才使得木质生物质定向高效转化为烃类的过程得以实现。.项目进行期间，共发表包括Nature Communication (2篇)， ACS Catalysis (2篇), Journal of Catalysis 在内的SCI论文40篇，申请中国发明专利6项，培养学生10余名；多次参加国际、国内催化学术会议，并组织了一次华东地区催化研讨会；项目人员获得国家自然科学基金委杰出青年基金项目和重点项目各一项。