Kinetics, Mechanism, and Active Site Requirements for Hydrodeoxygenation over Reducible Metal Oxides

生物油是从生物质的快速热解中获得的，它们转化为燃料和化学品代表了煤炭，天然气和石油资源的可持续替代品。 生物油升级的关键步骤是在氢气的环境压力下和在催化剂的存在下从木质素衍生的级分中选择性去除氧原子（也称为“加氢脱氧”）。 理想的加氢脱氧催化剂应该是丰富的、廉价的和易于处理的，同时也是活性的、选择性的、氢效率高的、稳定的和可再生的。该研究项目的目标是在分子水平上了解生物质衍生模型化合物在一类称为可还原金属氧化物的催化剂上加氢脱氧过程中发生的化学和物理过程。 首先，研究将集中在氧化铈（二氧化铈），一种广泛用于商业的材料，作为汽车排气系统中的储氧成分。 该研究项目作为研究生和本科生进行尖端研究的培训基地。 研究人员还将参加休斯顿地区的外展活动，包括能源日和雪佛龙女孩工程未来日，作为ACS SEED项目的一部分，他们将在实验室接待高中生，并为他们提供实践研究经验。衍生的模型化合物提出了关于可还原金属氧化物中氧空位的性质和密度的有趣的基本问题。 本论文将通过四个实验步骤来研究氧化铈上碳氧键断裂的精确机理：（1）本体氧化铈作为加氢脱氧催化剂的潜力的论证;（2）在本体氧化铈上苯甲醚加氢脱氧的机理的阐明;（3）在氧化铈上加氢脱氧的活性位要求的建立;（4）在本体氧化铈上催化苯甲醚加氢脱氧的机理。以及（4）了解掺杂对活性位点特性、密度和功效的影响。 该研究项目旨在通过指导加氢脱氧催化剂的设计和澄清Mars-van Krevelen/反向Mars-van Krevelen氧化还原循环中涉及的机械步骤的身份，优化生物质转化过程的能量，成本和原子效率，该奖项反映了NSF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。

Bio-oils are obtained from the fast pyrolysis of biomass, and their conversion into fuels and chemicals represents a sustainable alternative to coal, natural gas, and petroleum sources. The critical step in upgrading bio-oil is the selective removal of oxygen atoms from the lignin-derived fraction under ambient pressures of hydrogen and in the presence of a catalyst (otherwise known as "hydrodeoxygenation"). The ideal catalyst for hydrodeoxygenation would be abundant, inexpensive and easy to handle, while also being active, selective, hydrogen efficient, stable, and regenerable. The goal of this research project is to develop a molecular-level understanding of the chemical and physical processes occurring during the hydrodeoxygenation of biomass-derived model compounds over a class of catalysts called reducible metal oxides. Primarily, the studies will focus on cerium oxide (ceria), a material widely used commercially as an oxygen storage component in automotive exhaust systems. The research project serves as a training ground for graduate and undergraduate students to perform cutting edge research. The researchers also will participate in outreach activities in the Houston area, including Energy Day and Chevron Girls Engineering the Future Day, and they will host high school students in the laboratory and provide them with hands-on research experience as part of Project ACS SEED.The fact that bulk ceria selectively cleaves carbon-oxygen bonds in biomass-derived model compounds raises interesting fundamental questions regarding the nature and density of oxygen vacancies in reducible metal oxides. The precise mechanism through which carbon-oxygen bond cleavage over ceria occurs will be studied via four experimental steps: (1) demonstration of the potential of bulk ceria as a hydrodeoxygenation catalyst; (2) elucidation of the mechanism of anisole hydrodeoxygenation over bulk ceria; (3) establishing the active site requirements for hydrodeoxygenation over cerium oxide; and (4) understanding the effect of doping on active site identity, density, and efficacy. This research project aims to optimize energy, cost, and atom-efficiency of biomass conversion processes by guiding the design of hydrodeoxygenation catalysts and clarifying the identity of the mechanistic steps involved in Mars-van Krevelen/reverse Mars-van Krevelen redox cycles, ubiquitous in the realm of bulk oxide catalysis.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.