CAREER: Revealing Kinetic Pathways by Pulsed-Film Pyrolysis of Cellulosic Biomass

通过燃烧、热解或气化对木质纤维素、非食品生物质的转化，为生产第二代生物燃料提供了一套可持续的技术，这将对能源独立、经济增长、全球排放和我们的社会产生重大影响。然而，尽管在过去的几十年里进行了深入的研究，但仍然缺乏有关这些系统的基本知识，包括反应途径、中间体和详细的动力学。正是这种信息导致了过去一个世纪炼油工业的成功发展，而这也是生物质利用所迫切需要的。对这些转化技术的基本理解缺乏进展，部分原因在于原料的多相和多尺度性质，以及与传输效应错综复杂的大型反应网络的相关复杂性。智力优势：我们在这项研究中的目标是通过开发和利用一种新的实验技术，开发纤维素热解的单个分子反应的第一个动力学描述，称为？pulsed-film热解,?或者亲。提出的PFP技术旨在将纤维素的微尺度薄膜快速加热到400-600°C，然后在规定的时间增量（例如10 ms）内进行等温热解，然后进行快速热猝灭。通过描述每个连续热脉冲产生的化学物质的数量和类型，可以获得反应速率的动力学信息。研究计划发展脉冲膜热解技术：三个任务将集中于设计、构建和测试用于纤维素热解的脉冲膜技术。利用多物理场设计模型和新型反应堆结构将使第一个能够在高温下进行无输运动力学实验的实验系统成为可能。分为两个具体目的：测量纤维素热解动力学：三个任务将测量初级产物（例如左旋葡聚糖和呋喃）的形成速率，左旋葡聚糖的二次反应，以及将纤维素还原为活性低聚物的缩合反应。在完成这两个目标后，预计将首次测量纤维素热解主要途径的动力学。智力优势：建议的研究将改变我们对固体和凝聚相生物质化学的反应机制和动力学的理解。这项研究的一个引人注目的方面是，它提供了第一个实验测量与关键热解产物形成相关的活化能的策略，可以将其与正在进行的计算进行比较，首次阐明生物质热解的机制。更广泛的影响：生物质反应途径和动力学的科学发现将为构建第一性原理动力学模型提供关键数据，这些模型可用于优化热解反应器。改进的生物质过程通过生产成本更低、质量更高的生物燃料和减少对环境的影响，对该国产生了广泛影响。此外，从生物质热解研究中获得的发现和基本见解将为开发指导性材料提供大量机会，以教育未来的本科生、高中生和公众关于生物质转化为燃料和化学品的价值和环境影响。我们建议制定一项具有广泛影响的综合战略，将高中教师的教育和本科生的指导结合起来，就生物质技术、环境影响和政策的主题在公共研讨会上发表演讲。提出了举办专题讨论会的逐年发展计划，并将与教育资料一起在互联网上播出，以便广泛传播。与研讨会相结合的是一门以可再生能源为重点的本科课程，以及一项NSF-RET提案，该提案旨在为少数族裔高度集中的学校（马萨诸塞州斯普林菲尔德和威斯康星州密尔沃基）的K-12学生提供科学教师和开发学习模块。我们的教育方法将有助于确保来自经济困难背景和代表性不足的少数民族的学生有机会获得工程科学和技术的鼓舞人心的例子，并确保公众充分了解生物质转化的重要性，作为实现不依赖进口石油的国家目标的可持续和环保手段。

The conversion of lignocellulosic, non-food biomass by combustion, pyrolysis, or gasification provides a sustainable set of technologies for the production of second generation biofuels that can have significant impact on energy independence, economic growth, global emissions, and our society. However, despite intensive research for the past several decades, there is still a lack of fundamental knowledge pertaining to these systems including reaction pathways, intermediates, and detailed kinetics. It is this kind of information that has led to the successful development of the refinery industry in the past century and which is critically needed for biomass utilization. The lack of progress on fundamental understanding of these conversion technologies is partially rooted in the multiphase and multi-scale nature of the raw material and the associated complexity of a large reaction network convoluted with transport effects.Intellectual Merit: Our objective in this research is to develop the first kinetic description of the individual molecular reactions of cellulose pyrolysis by developing and utilizing a novel experimental technique referred to as ?pulsed-film pyrolysis,? or PFP. The proposed PFP technique aims to rapidly heat micro-scale films of cellulose to 400-600 °C, whereupon isothermal pyrolysis occurs for a defined increment of time (e.g. 10 ms), followed by rapid thermal quench. Kinetic information on the rate of reaction will then be obtained from characterizing the quantity and type of chemical species produced for each consecutive thermal pulse. The research plan1.) Develop the technique of pulsed-film pyrolysis: Three tasks will focus on designing, constructing, and testing the pulsed-film technique for cellulose pyrolysis. Utilization of multi-physics design models and novel reactor construction will allow for the first experimental system capable of transport-free kinetic experiments at high temperature. is divided into two specific aims:2.) Measure the kinetics of cellulose pyrolysis: Three tasks will measure rates of formation of primary products (e.g. levoglucosan and furans), secondary reactions of levoglucosan, and condensed-phase reactions to reduce cellulose to reactive oligomers.At the completion of these two aims, it is anticipated that the kinetics of the major pathways of cellulose pyrolysis will be measured for the first time. Intellectual merit: The proposed research will transformour understanding of the reaction mechanisms and kinetics of solid and condensed-phase biomass chemistry. A compelling aspect of this research is that it provides the first strategy for experimentally measuring the activation energies associated with the formation of key pyrolysis products, which can be compared with ongoing computations to elucidate for the first time the mechanisms of biomass pyrolysis.Broader Impact: The scientific discoveries of biomass reaction pathways and kinetics will provide the critical data for constructing first-principles kinetic models which can be used to optimize pyrolysis reactors. Improved biomass processes broadly impact the country by producing higher quality biofuels with lower cost and reduced environmental impact. Additionally, the discoveries and fundamental insights from the proposed research on the pyrolysis of biomass will provide a plethora of opportunities for developing instructive material to educate prospective undergraduates, high school students and the general public on the value and environmental impact of biomass conversion to fuels and chemicals. We propose to develop an integrated strategy with broad impact which combines the education of high school teachers and the instruction of undergraduates to develop presentations for public symposia on the topic of biomass technology, environmental impact and policy. A year-to-year development plan has been proposed for conducting public symposia, which will be broadcast on the internet along with educational materials for broad dissemination. Integrated with the symposia will be an undergraduate course focused on renewable energy as well as an NSF-RET proposal for hosting science teachers and developing learning modules for K-12 students in schools with high concentration of underrepresented minorities (Springfield, MA, & Milwaukee, WI). Our approach to education will contribute to ensuring that students from economically depressed backgrounds and underrepresented minorities have access to inspiring examples of engineering science and technology and that the general public is well-informed on the importance of biomass conversion as a sustainable and environmentally-friendly means of achieving the national goal of independence from imported oil.