Metal Oxide Gasification of Lignocellulosic Biomass: Tar Cracking Mechanism

PI：范良石提案编号：1236467机构：俄亥俄州立大学木质纤维素生物质金属氧化物气化：焦油裂解机理生物质化学循环(BCL)是近年来公认的一种有效利用生物质的方法。BCL过程可以将生物质转化为有价值的生物燃料及其前体，如氢气，同时以较低的能源成本捕获二氧化碳。本项目旨在探索木质纤维生物质在金属氧化物(氧载体)气化过程中的反应机理。生物质热解过程中产生的焦油使这一过程变得复杂。因此，对焦油的高效脱除提出了更高的要求。本项目的目标是在分子水平上确定焦油的分解途径，并合成高性能的氧载体。实验装置包括热重分析仪(TGA)、微型固定/沸腾床(MFB)以及各种气体和固体分析仪器。TGA将作为焦油发生器，在那里生物质热解以受控的方式进行。生成的焦油随后将进入MFB与氧气载体反应。气态物质将通过气相色谱(GC)、傅里叶变换红外光谱(FTIR)和质谱仪进行采样和分析，以确定其组成和重要的中间体。还将对氧载体进行实验后分析，以揭示金属与载体的相互作用。此外，萘、苯酚和苯也将分别作为典型的伯级、二级和烷基三级焦油物种直接进入MFB。此外，还将测试不同组成的氧载体，以揭示不同的初级金属-载体相互作用对反应机理的影响。这些结果将结合解释复杂的非催化气固反应BCL系统。焦油转化是阻碍生物质原料、清洁能源和碳负燃料来源利用的障碍之一。催化裂解是目前应用最广泛的焦油脱除方法。然而，这种方法需要大量的资金和物质资源，因为在气化炉之后需要单独的焦油分解反应器才能达到理想的脱除效果。在BCL工艺中，以往的实验表明，合成的复合氧载体具有在单一还原反应器中转化所有生物质热解产物的潜力，例如挥发油、焦油和焦炭。在这些热解产物中，焦油分解被认为是一个复杂的反应网络。为了避免氧载体开发中既费力又费时的反复试验，了解焦油分解机理是关键。早期的研究人员已经以一些芳香族物种作为焦油模型分子，如萘、苯和苯酚，研究了焦油催化分解过程的机理。在BCL工艺中，氧载体作为晶格供氧体而不是催化剂(其组成基本保持不变)。氧载体氧化焦油，从而改变组成，使得初级金属和载体之间的固-固相互作用更加复杂。将结合多种实验方法，通过确定重要的中间体来研究反应机理。通过在分子水平上对焦油分解机理的了解，可以合理地合成高效的氧载体。通过突出金属氧化物氧载体热解生物质的基本机理，本研究有助于清洁和经济的能源转化过程的不断发展。这项研究将为新出现的BCL系统奠定科学基础，该系统可以为生物质丰富的社区提供负担得起的能源。MFB的发展为热化学反应分析提供了一种新的基础工具。除了潜在地改变生物质能源的面貌，这项拟议的研究将为学生提供丰富的机会。通过这项研究完成的结果将被纳入本科生和研究生班的课程材料。本科生和研究生将参与这项研究。拟议的K-12外联计划将促进未来科学家和工程师的科学研究。这项研究将能够增强BCL的商业化潜力，BCL是一种关键的创新技术，用于热化学生物质转化。

PI: Fan, Liang-ShihProposal Number: 1236467Institution: Ohio State UniversityTitle: Metal Oxide Gasification of Lignocellulosic Biomass: Tar Cracking MechanismBiomass Chemical Looping (BCL) has been recognized as a promising way to utilize biomass efficiently in recent years. The BCL process can convert biomass to valuable biofuels and its precursors such as H2, while capturing CO2 at a low energy cost. This proposed project seeks to explore the reaction mechanisms during the gasification of lignocellulosic biomass by metal oxides (the oxygen carriers). Tar, generated during biomass pyrolysis, complicates the process. Thus, the removal of tar with high efficiency is greatly desired. The target of this project is to identify the decomposition pathway of tar at a molecular level and to synthesize an oxygen carrier with high performance. The experiment assembly consists of using a thermo gravimetric analyzer (TGA), a micro fixed/fluidized bed (MFB), and various gas and solid analysis instruments. The TGA will act as a tar generator where biomass pyrolysis takes place in a controlled manner. The generated tar will subsequently go into the MFB to react with the oxygen carrier. The gaseous species will be sampled and analyzed by gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), and mass spectroscopy to identify the composition as well as important intermediates. Post-experiment analyses will also be carried out on the oxygen carrier to reveal the metal-support interactions. In addition, naphthalene, phenol, and benzene will also be directly fed into MFB as typical primary, secondary, and alkyl tertiary tar species, respectively. Furthermore, oxygen carriers of various compositions will be tested to reveal the effect that different primary metal-support interactions could have on the reaction mechanism. These results will be combined to interpret the complex non-catalytic gas-solid reaction BCL system.Tar conversion is one of the obstacles that impedes the utilization of biomass materials, clean energy and carbon-negative fuel sources. Currently, catalytic decomposition is the most widely used method to remove tar. However, this method requires extensive capital and material resources as a separate tar decomposition reactor is necessary after the gasifier in order to achieve desirable removal results. In the BCL process, previous experiments have indicated that the synthesized composite oxygen carriers have the potential to convert all biomass pyrolysis products, e.g., volatile, tar, and char, in a single reducer reactor. Among these pyrolysis products, tar decomposition is considered to be a complex reaction network. In order to avoid a both labor and time intensive trial-and-error method in oxygen carrier development, understanding the tar decomposition mechanism is key. Early researchers have investigated the mechanism of tar catalytic decomposition process with some aromatic species as tar model molecules, such as naphthalene, benzene, and phenol. In the BCL process, the oxygen carrier acts as a lattice oxygen donor rather than as a catalyst (that largely remains unchanged in composition). The oxygen carrier oxidizes the tar, thereby, changing the composition such that the solid-solid interactions between the primary metal and the supports are more complex. Multiple experimental methods will be combined to investigate the reaction mechanism by identifying the important intermediates. With the knowledge on the tar decomposition mechanism at molecular level, the rational to synthesize an efficient oxygen carrier can be developed.By highlighting the fundamental mechanisms behind biomass pyrolysis with metal oxide oxygen carriers, this proposed research aids the continuous development of clean and economical energy conversion processes. This research would lay the scientific groundwork for the emerging BCL system, which could provide affordable energy sources for biomass-rich communities. The MFB development provides a novel fundamental tool for thermochemical reaction analysis. Beyond potentially transforming the biomass energy landscape, this proposed study will present enriching opportunities for students. The results completed through this study will be incorporated as curriculum material of undergraduate and graduate classes. Undergraduate and graduate students will participate in this research. The proposed K-12 outreach programs will promote the scientific research for future scientists and engineers. This research will be able to enhance the potential commercialization of BCL, a crucial and innovative technology for thermochemical biomass conversion.