Collaborative Research: Experimental and computational methods to study chemical transformations of solid xylose into useful compounds

我国经济的长期安全需要有一系列国内原料来生产燃料和化学品。生物质是一个很有前途的选择；然而，可靠、可复制和经济的转换技术尚未进入市场。由于其低成本和多功能性，生物质快速热解技术是生产可再生燃料和化学品的理想选择。这项技术的一个限制其实施的问题是，生物质转化的潜在物理和化学性质在很大程度上仍然未知。该项目是明尼苏达大学和华盛顿大学工程小组的一项合作研究。与此同时，这些小组正在使用实验（明尼苏达州）和计算（华盛顿州）方法进行详细的基础调查。这项研究的总体目标是确定木聚糖（可再生生物质的主要成分）化学转化为小分子化合物（燃料和化学品的前体）的机制。这项研究也将有利于类似原料的其他高温转化，以形成广泛的产品板。这个项目的教育效益正在影响研究生和本科生的研究人员。合作项目机制是通过定期互动和共同发表研究成果来丰富实验或理论方法专业学生培养的理想途径。这个研究项目的成果也将通过增加现实世界的问题和源于研究结果的小项目来丰富化学工程课程。本基础研究项目的目的是阐明木聚糖（一种生物聚合物）到产物的所有关键热解反应途径。这项实验是基于一种叫做PHASR（固体反应的脉冲加热分析）的新技术，它能够在完全不受传输限制的情况下测量转化速率。模拟和建模结合了图论、从头算动力学和元动力学方法以及动力学蒙特卡罗建模。该团队首先通过实验和模拟来研究形成液体中间相的物理原理和液体中间相的特性。在确定瞬时中间体的结构和动力学之后，该项目将重点研究生物质转化的动力学和机制。详细的相位分析与图论相结合，以确定中间和最终小分子产品如何形成的建议。在此基础上，从头算分子动力学（MD）和研究人员开发的尖端方法被用于发现单个反应途径并表征其速率。最后一步结合实验和新的机制见解来建立一个详细的整体模型，能够描述这个过程的整体物理和化学。

The long-term security of our economy requires a portfolio of domestic feedstocks to produce fuels and chemicals. Biomass is a promising choice; however, conversion technologies that are reliable, reproducible and economical have yet to come to market. Because of its low cost and versatility, biomass fast pyrolysis technology is an ideal choice for producing a renewable stream of fuels and chemicals. One issue with this technology that limits its implementation is that the underlying physical and chemical properties of the biomass transformations remain largely unknown. This project is a collaborative research study involving engineering groups at the Universities of Minnesota and Washington. In parallel, the teams are carrying out a detailed fundamental investigation using experimental (Minnesota) and computational (Washington) methods. The research has the overall goal of determining the mechanism of the chemical transformation of xylan, a major constituent of renewable biomass, into small molecule compounds that are precursors for fuels and chemicals. The research will also benefit other high temperature conversions of similar feedstocks to form a wide product slate. The educational benefits of this project are impacting graduate and undergraduate researchers. The collaborative project mechanism is an ideal way to enrich the training of students who specialize in experimental or theoretical methods through regular interactions and joint publication of research. The outcomes of this research project will also enrich chemical engineering coursework by the addition of real world problems and mini-projects stemming from the research results. The objective of this fundamental research project is to elucidate all of the key pyrolysis reaction pathways in the evolution of xylan, a biopolymer, to products. The experimental effort is based a new technique called PHASR (Pulsed heated analysis of solid reactions), that is capable of measuring rates of conversion in a regime totally free from transport limitations. The simulations and modeling combine graph theory, ab initio dynamics with the metadynamics method, and kinetic Monte Carlo modeling. The team is first investigating the physics of forming a liquid intermediate phase and the properties of the liquid intermediate with experiments and simulations. After determining the structure and dynamics of the transient intermediate, the project will focus on the kinetics and mechanism of biomass conversion. Detailed PHASR analysis is combined with graph theory to determine suggestions for how intermediate and final small molecule products are formed. Building on this, ab initio molecular dynamics (MD) and cutting edge methods developed by the researchers are used to discover individual reaction pathways and characterize their rates. The final step combines the experiments and new mechanistic insights to build a detailed overall model capable of describing both the overall physics and chemistry of this process.