Probing support-solvent-solute interactions in heterogeneous catalysts by surface-sensitive magnetic resonance tools

通过表面敏感磁共振工具探测多相催化剂中载体-溶剂-溶质的相互作用

基本信息

批准号：
1800596
负责人：
Song-I Han
金额：
$ 64.5万
依托单位：
University of California-Santa Barbara
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-01 至 2023-01-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1800596&HistoricalAwards=false
关键词：
Probing support solvent solute interactions

项目摘要

The manufacturing of chemicals from renewable biomass is an important, long term alternative to petroleum. Co-production of higher-value chemicals can also help to make these processes more economical. However, biomass has a high oxygen content. To make useful chemicals, this oxygen must first be removed. Dehydration is one important route to reducing oxygen content. With this funding from the NSF Division of Chemistry, Drs. Han and Scott of the University of California Santa Barbara are investigating these dehydration reactions. The role of solvents and catalysts are being studied to aid in the design of more effective catalysts for these reactions. At the same time, powerful new measurement methods for probing the fundamental chemistry are being developed. The graduate students on the project are acquiring advanced research skills, and learning to integrate their findings with collaborators. They are also gaining international and industrial perspectives of their research. The PIs and their students are mentoring younger, at-risk students, who are also experiencing first-hand experimental problem-solving.The efficient conversion of biomass-derived polyols to value-added renewable chemicals by dehydration is an important challenge for heterogeneous catalysis. Conducting such reactions selectively in semi-aqueous solvent systems, under mild reaction conditions, requires the development of highly active, hydrothermally stable catalysts. Their activity can be enhanced by tuning the solvent composition and the catalyst support to promote the partitioning of dissolved reactant molecules to the catalytically active solid, and adsorbed product molecules back into solution. This project elucidates and quantifies the interdependent solid-solvent-solute interactions that control activity and selectivity in catalytic dehydration reactions. In the presence of solid catalysts for acid-catalyzed alcohol dehydration reactions, the dynamics of adsorbed reactants and products, the surface-coupled solvent dynamics, and the partitioning of (co-)solutes to the surface relative to bulk, are being characterized with molecular precision. The measurements are made possible by state-of-the-art, surface-sensitive magnetic resonance tools, including solid-state magic-angle spinning (MAS) dynamic nuclear polarization (DNP) NMR to characterize catalyst supports and active sites with dramatically enhanced sensitivity, and Overhauser DNP to measure the surface diffusivity of solvent molecules which is correlated with the solvation barrier to adsorption. The key questions being addressed are: (1) How can catalytic activity and selectivity in polyol dehydration be controlled, by varying the solvation barrier for solute adsorption to the catalyst surface? (2) How can the solvation barrier for solute approach be modulated, by tuning the hydrophobicity of the catalyst surface and the composition of the solvent mixture? The study generates a basis for new structure-property-function relationships in liquid-phase heterogeneous catalysis, exploring their validity in an important family of reactions for the upgrading of biomass-derived polyols, and advancing the development of surface-sensitive magnetic resonance-based tools to characterize heterogeneous catalysts. The graduate students involved with the project are learning advanced research techniques, and learning to integrate their findings with collaborators. They are also gaining international and industrial perspectives of their research. The PIs and their students are mentoring younger, at-risk students, who themselves are experiencing first-hand experimental problem-solving.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.

利用可再生生物质制造化学品是石油的重要、长期替代品。联合生产更高价值的化学品也有助于使这些过程更加经济。然而，生物质的氧含量很高。为了制造有用的化学品，必须首先除去氧气。脱水是降低氧含量的重要途径之一。借助 NSF 化学部的资助，博士。加州大学圣巴巴拉分校的汉和斯科特正在研究这些脱水反应。正在研究溶剂和催化剂的作用，以帮助设计用于这些反应的更有效的催化剂。与此同时，用于探测基础化学的强大的新测量方法正在开发中。该项目的研究生正在获得先进的研究技能，并学习将他们的发现与合作者结合起来。他们的研究也获得了国际和工业视角。 PI 和他们的学生正在指导年轻的高危学生，他们也正在体验解决第一手实验问题的经验。通过脱水将生物质衍生的多元醇有效转化为增值的可再生化学品是多相催化的一个重要挑战。在温和的反应条件下，在半水溶剂体系中选择性地进行此类反应需要开发高活性、水热稳定的催化剂。它们的活性可以通过调整溶剂组成和催化剂载体来增强，以促进溶解的反应物分子分配到催化活性固体，并将吸附的产物分子返回到溶液中。该项目阐明并量化了控制催化脱水反应活性和选择性的相互依赖的固-溶剂-溶质相互作用。在酸催化醇脱水反应的固体催化剂存在下，吸附反应物和产物的动力学、表面耦合溶剂动力学以及（共）溶质相对于本体在表面的分配，可以用分子表征精确。这些测量是通过最先进的表面敏感磁共振工具实现的，包括固态魔角旋转 (MAS) 动态核极化 (DNP) NMR，以显着提高的灵敏度来表征催化剂载体和活性位点和 Overhauser DNP 来测量溶剂分子的表面扩散率，该扩散率与吸附的溶剂化势垒相关。需要解决的关键问题是：（1）如何通过改变催化剂表面溶质吸附的溶剂化势垒来控制多元醇脱水中的催化活性和选择性？ (2) 如何通过调节催化剂表面的疏水性和溶剂混合物的组成来调节溶质方法的溶剂化势垒？该研究为液相多相催化中新的结构-性能-功能关系奠定了基础，探索了它们在生物质衍生多元醇升级的重要反应家族中的有效性，并推动了基于表面敏感磁共振的发展表征多相催化剂的工具。参与该项目的研究生正在学习先进的研究技术，并学习将他们的发现与合作者结合起来。他们的研究也获得了国际和工业视角。 PI 及其学生正在指导年轻的高危学生，他们自己正在经历第一手的实验问题解决。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查进行评估，被认为值得支持标准。