SusChEM: Mapping Reaction Pathways of Biomass Pyrolysis and Catalytic Pyrolysis using Isotopically Labeled Plant Cell Culture

植物生物质，如木材、稻草和农业残留物，代表了用于生产液体运输燃料和化学品的丰富、廉价和可再生的原料。 从生物质中制造燃料的一种方法是通过一种称为快速热解的过程，其中固体植物材料在没有空气的情况下快速加热，将其分解为气体，固体炭和称为生物油的液体的混合物，可以升级为液体运输燃料。 植物生物质是三种生物产生的聚合物-纤维素、半纤维素和木质素-排列成复杂的三维网络的混合物。来自这种复杂混合物的热解产物的起源还不清楚，因为所有这些材料在生物质热解过程中彼此相互作用。这种缺乏了解的情况阻碍了从特定植物物种中最大限度地生产生物油的努力。该项目旨在将生物质热解产品的来源映射到真实的生物质材料中的特定生物质成分。 一个关键的创新是使用植物细胞技术来标记纤维素和木质素成分，以便在快速热解过程中跟踪它们的命运。 与该项目相关的教育活动包括一个针对高中生的暑期住宿计划，该计划使用从研究中开发的主题。 学生们将看到植物如何捕获和储存碳和能量，使用化学探针来帮助发现生物过程，并讨论从可再生资源中获得燃料和化学品的机会和挑战。研究的总体目标是确定和映射木质纤维素生物质快速热解到特定纤维素和木质素分子成分的反应途径。 研究计划有两个目标，以追踪快速热解产物的来源。 第一个目标是开发一种方法，使映射的反应途径，通过碳-13标记。 为此，将在未标记和13-C标记的葡萄糖和苯丙氨酸（分别为纤维素和木质素生物合成的前体）的混合物上异养培养模式植物拟南芥的细胞，以分别标记拟南芥细胞壁中的碳水化合物和木质素级分。 然后，在不同温度下使用13 C标记的拟南芥细胞作为探针，在有和没有催化剂的情况下热解拟南芥茎插条。 将结果与未标记细胞与标记的小分子结构单元的简单混合物的产物进行比较。 通过跟踪标记位点的命运，将有可能构建一个反应网络，描述它们在植物物质中的掺入以及形成热解产物的化学事件。第二个目标是将根据目标1制定的方法用于与生物能源生产有关的杨树属和黍属木本植物。 研究成果将导致改进的，基于机理的反应和动力学模型，用于预测从真实的木质纤维素生物质底物的快速热解反应途径的产物产率，而不仅仅是模型化合物。然后，该信息可用于确定反应器设计和操作策略，以稳定和优化生物油的产率及其下游转化为液体运输燃料。

Plant biomass such as wood, grass straw, and agricultural residues represent an abundant, cheap, and renewable feedstock for the production of liquid transportation fuels and chemicals. One way to make fuel out of biomass is through a process called fast pyrolysis, where the solid plant material is rapidly heated in the absence of air to decompose it to a mixture of gas, solid char, and a liquid called bio-oil, which can be upgraded to liquid transportation fuel. Plant biomass is a mixture of three biologically- produced polymers - cellulose, hemicellulose, and lignin - arranged into a complex three-dimensional network. The origin of pyrolysis products from this complex mixture is not well understood, since all these materials interact with one another during biomass pyrolysis. This lack of understanding has hampered efforts to maximize bio-oil production from a given plant species. This project seeks to map the origin of biomass pyrolysis products to specific biomass components within real biomass materials. A key innovation is the use of plant cell technology to label the cellulose and lignin components so that their fate can be tracked during fast pyrolysis. The educational activities associated with this project include a summer residential program for high school students using topics developed from the research. Students will see how plants capture and store carbon and energy, use chemical probes to help discover biological processes, and discuss the opportunities and challenges of obtaining fuels and chemicals form renewable resources.The overall goal of the research is to identify and map reaction pathways for fast pyrolysis of lignocellulosic biomass to specific cellulosic and lignin molecular constituents. The research plan has two objectives to trace the origins of the fast pyrolysis products. The first objective is to develop a methodology to enable mapping of the reaction pathways through carbon-13 labeling. Towards this end, cells of the model plant Arabidopsis thaliana will be heterotrophically cultured on a mixture of unlabeled and 13-C labeled glucose and phenylalanine, precursors for cellulose and lignin biosynthesis respectively, to separately tag the carbohydrate and lignin fractions in the Arabidopsis cell wall. Arabidopsis stem cuttings will then be pyrolyzed, with and without catalyst, using 13C-labeled Arabidopsis cells as probes at different temperatures. The results will be compared to the products of simple mixtures of unlabeled cells with labeled small-molecule building blocks. By tracking the fate of the labeled sites, it will be possible to construct a reaction network that describes both their incorporation in the plant matter, and the chemical events that form the pyrolysis products. The second objective is to use the methodology developed under objective 1 on woody plants within genera Populus and Paniceae that are relevant to bioenergy production. The research outcomes will lead to improved, mechanism-based reaction and kinetic models for predicting product yields from reaction pathways for fast pyrolysis from real lignocellulosic biomass substrates, not just model compounds. This information can then be used to identify reactor design and operation strategies to stabilize and optimize the yield of bio-oil and its downstream conversion into liquid transportation fuel.