Collaborative Research: SusChEM: Designing Catalytic Interfaces to Promote Selective Lignin Depolymerization

木质素是木本植物和草本植物细胞壁的三大组分之一，其化学组成不仅富含碳，而且与许多以石油为基础的化学前体相似。该项目解决了木质素催化分解成其组成单元所带来的挑战，以努力生产可再生和低成本的芳香化学品。具体地说，目的是了解催化剂如何与木质素中容易发生裂解的部分相互作用。该催化剂含有分散在多孔固体载体上的铜纳米颗粒，在超临界甲醇(sc-MeOH)中，它催化固体木质素裂解成高能量的有机液体，而不形成焦炭。两个关键问题是笨重、难于溶解的聚合物的移动和催化剂内表面的接触。通过调整反应条件和催化材料的性质，催化剂与木质素的相互作用将得到优化，以促进解聚，并能够经济地生产可再生的芳香族化学品。我们的目标是开发创新、可持续和可扩展的转化工艺，使用由地球上丰富的材料制成的多孔固体催化剂，经济地从木质素中产生平台可再生化学品。本项目将测试两个最重要的假设：1)木素在多孔催化剂上的吸附及其在催化剂表面的吸附引起构象变化，从而增加木质素与催化剂之间的相互作用；以及2)具有适当内部结构和组成的多孔催化剂使关键的芳基醚与催化活性中心的相互作用最大化。研究内容包括：1)具有可控和系统变化的孔结构和表面官能度(即疏水性)的有序介孔催化剂；2)具有可控制和系统变化的链长、芳醚键比例和芳醚键之间间隔基的木素二聚体和低聚物模型体系；以及3)吸附模式和反应动力学的现场评估。实现这些目标和检验这些假设的计划包括合成木质素模型体系和具有可控和系统变化的结构和组成的模板化介孔催化剂，以探测溶剂-木质素、溶剂-催化剂和木质素-催化剂的相互作用；并使用先进的光谱方法，探索木质素和催化剂之间的界面相互作用，以了解它们如何通过芳醚键的氢解来促进木质素的选择性解聚。研究小组将与学校伙伴研究所合作，为圣路易斯社区中代表性不足和贫困的八年级学生开展外联和教育活动。具体地说，外展工作将包括每年一次的研究人员日计划，通过校园访问、校园参观和实验室演示，为当地代表不足的少数族裔学生提供服务。类似的活动将通过加州大学圣巴巴拉分校的SciTrek外联计划提供。

Lignin is one of the three major components of woody and grassy plant cell walls, and its chemical make-up is not only carbon-rich but also resembles many petroleum-based chemical precursors. This project addresses challenges presented by the catalytic deconstruction of lignin into its constituent units in an effort to generate renewable and low-cost aromatic chemicals. Specifically, the aims are to understand how the catalyst interacts with portions of lignin that are susceptible to cleavage. The catalyst contains copper nanoparticles dispersed on a porous solid support, and in supercritical methanol (sc-MeOH) it catalyzes the cleavage of solid lignin to energy-rich organic liquids without forming char. Two key problems are movement of the bulky, poorly soluble polymer and access to the internal surfaces of the catalyst. By tuning the reaction conditions and the properties of the catalytic material, the interactions of the catalyst with lignin will be optimized to enhance depolymerization and enable economical production of renewable aromatic chemicals. The goal is to develop innovative, sustainable, and scalable conversion processes that generate platform renewable chemicals from lignin economically using porous solid catalysts made with Earth-abundant materials. This project will test two overarching hypotheses: 1) that lignin absorption into a porous catalyst and its adsorption onto catalyst surfaces induce conformational changes that increase interactions between the lignin and the catalyst; and 2) that porous catalysts with appropriate internal structure and composition maximize interactions of the key aryl ether linkages with catalytically active sites. The research will involve: 1) ordered mesoporous catalysts with controlled and systematically varied pore architecture and surface functionality (i.e., hydrophobicity); 2) lignin dimer and oligomer model systems that have controlled and systematically varied chain length, proportion of linkages that are aryl ethers, and spacers between aryl ether linkages, and 3) in-situ assessment of adsorption modes and reaction kinetics. The plan to achieve these objectives and test these hypotheses involves synthesizing both lignin model systems and templated mesoporous catalysts with controlled and systematically varied structures and compositions to probe solvent-lignin, solvent-catalyst, and lignin-catalyst interactions; and using advanced spectroscopic methods, to probe interfacial interactions between lignin and catalyst to understand how they promote selective lignin depolymerization by hydrogenolysis of aryl ether linkages. The research team will collaborate with the Institute for School Partnership to develop outreach and education activities for underrepresented and underprivileged eighth grade students in the St. Louis community. Specifically, the outreach efforts will include an annual Researcher for a Day program for local underrepresented minority students through a campus visit, a campus tour, and lab demonstrations. A similar activity will be offered through the SciTrek outreach program at UC Santa Barbara.