Collaborative Research: Towards a Generalized Microkinetic Description of Lignin Liquefaction

木质素是一种丰富的自然资源，与纤维素和半纤维素相比，其较高的碳含量使其成为生产燃料和化学品的非常有吸引力的可再生原料。木质素液化是一种很有前途的方法，可以将这种未充分利用的资源转化为单体酚，可以很容易地升级为燃料和化学品，但潜在的化学动力学过程尚不清楚。该合作研究项目旨在开发一个合理的框架，集成建模和实验工具，以明确说明木质素及其低聚中间化学结构在相关液化条件下存在或不存在溶剂。木质素液化可以在水环境（水热液化）、有机溶剂（溶剂溶解）、离子液体或无溶剂条件（热解）下进行。合理地描述和控制木质素液化反应是木质素及其低聚中间体的重要挑战之一。溶剂和添加剂影响液化反应的机理也知之甚少。正因为如此，木质素液化仍然是一门艺术而不是一门科学。本项目的主要目标是在详细描述木质素液化过程中解聚和再聚合反应以及中间产物去除机理的微动力学模型的基础上，建立合理的微动力学框架。实际目标是使用该数学模型和实验工具来确定在溶剂和酸碱催化剂存在下合适的木质素液化策略，以最大限度地提高单酚的产量，这将促进现有基础设施的进一步生物油升级。除了培训两名研究生外，主要研究人员还计划通过西北大学和太平洋西北路易斯·斯托克斯少数民族参与联盟的暑期研究机会项目，在他们的实验室中招收女性和代表性不足的少数民族高中生作为暑期研究实习生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Lignin is an abundant natural resource whose higher carbon content, when compared to cellulose and hemicellulose, makes it a very attractive renewable feedstock for producing fuels and chemicals. Lignin liquefaction is a promising process for converting this underutilized resource into monomeric phenols that can be easily upgraded to fuels and chemicals, but the underlying chemical kinetic processes are not well understood. This collaborative research project aims to develop a rational framework that integrates modelling and experimental tools to explicitly account for lignin and its oligomeric intermediate chemical structures at relevant liquefaction conditions in the presence or absence of solvents.Lignin liquefaction can be conducted in aqueous environments (hydrothermal liquefaction), in organic solvents (solvolysis), in ionic liquids or in solvent free conditions (pyrolysis). Assigning a realistic chemical formula to lignin and its oligomeric intermediates is one of the major challenges to rationally describe and control lignin liquefaction reactions. The mechanisms by which solvents and additives impact liquefaction reactions are also poorly understood. Because of this, lignin liquefaction remains an art rather than a science. The main goal of this project is to develop a rational micro-kinetic framework based on detailed micro-kinetic models describing depolymerization and repolymerization reactions and intermediate products removal mechanisms during lignin liquefaction. The practical goal is to use this mathematical model and experimental tools to identify suitable lignin liquefaction strategies in the presence of solvents and acid-base catalysts to maximize mono-phenol production which will facilitate further bio-oil upgrading in existing infrastructure. In addition to training two graduate students the principal investigators plan to host female and underrepresented minority high school students in their laboratories as summer research interns through the Summer Research Opportunity Program at Northwestern University and the Pacific Northwest Louis Stokes Alliance for Minority Participation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.