First-principles based catalyst and solvent design for the selective conversion of biomass to platform chemicals

加拿大拥有巨大的木质纤维素生物质资源，可以作为碳的替代来源，而不会给人口的营养需求带来任何压力。为了将生物质转化为增值燃料和化学品，需要将其转化为可集成到现有工业基础设施中的理想平台中间体。液相催化处理生物质是其选择性转化的唯一非生物、热化学途径。然而，溶剂系统的筛选和选择是一个挑战，因为溶剂不仅是良性的溶剂化介质，而且会改变转化率和选择性。此外，作为生物质反应中不溶性缩合和聚合副产物的人类素的形成需要最小化，以减少碳损失和催化剂失活。因此，拟议的项目旨在发展对溶剂在生物质反应中的作用以及人类及其前体形成的化学作用的基本理解。具体目标包括研究溶剂的作用(1)改变催化剂上生物质部分的吸附构型和能量，(2)由于反应物和过渡态的不同相对稳定性以及溶剂动力学和非平衡溶剂化而改变反应动力学。此外，还将确定人素及其前体形成的催化反应机理，揭示促进人素形成的溶剂体系和催化剂功能。在此基础上，提出溶剂、催化剂和操作条件的最佳组合。该项目将是第一个结合溶剂效应、反应机制和人源物质形成的液相生物质转化协同研究。基于第一原理的坚实基础的多尺度分子建模方法将在项目中实施，并与实验协同。初步筛选将使用密度泛函理论中的隐式溶剂化模型进行，选定的计算将在显式溶剂分子中进行，并进行量子力学处理。从头算分子动力学和偏置方法，如元动力学将被实施来研究溶剂的影响。首席研究员具有相关的专业知识和跟踪记录，以确保项目的成功。本项目将培养3名博士生和5名本科生。

Canada has huge lignocellulosic biomass resources that can be utilized as an alternate source of carbon, without putting any stress on the nutritional needs of the population. To convert the biomass to value-added fuels and chemicals, it needs to be transformed into desired platform intermediates that can be integrated into the existing industrial infrastructure. Liquid phase catalytic processing of biomass is the only non-biological, thermochemical pathway for its selective conversion. However, screening and selection of solvent systems is a challenge, since solvents are not only benign solvation media but they alter the conversion and selectivity. Additionally, the formation of humins, which are insoluble condensation and polymerization by-products in biomass reactions, needs to be minimized to reduce carbon loss and catalyst deactivation. Hence, the proposed project aims to develop fundamental understanding of the role of solvent in biomass reactions and of the chemistry of the formation of humins and their precursors. Specific objectives include investigating the role of solvents (I) in modifying the adsorption configuration and energies of biomass moieties on the catalyst, (II) in altering reaction kinetics due to different relative stabilization of reactants and transition states and due to solvent dynamics and non-equilibrium solvation. Additionally, catalytic reaction mechanisms of the formation of humins and their precursors will be identified and solvent systems and catalyst functionalities promoting humins formation will be revealed. Based on the fundamental understanding developed in the project, optimum combination of solvent, catalysts and operating conditions will be proposed. The proposed project will be the first synergistic investigation in liquid phase biomass conversion, combining solvent effects, reaction mechanisms and humins formation. A multiscale molecular modeling approach, based on the solid foundations of first principles, will be implemented in the project, in synergy with experiments. Preliminary screening will be done using implicit solvation model in density functional theory and selected calculations will be performed in explicit solvent molecules, treated quantum mechanically. Ab initio molecular dynamics along with biasing methods like metadynamics will be implemented to investigate solvent effects. The principal investigator has the relevant expertise and track record to ensure the success of the project. Three PhD students and five undergraduate students will be trained in the project.