Understanding Advanced Heat and Mass Transport Control and Non-Noble Metal Catalyst Designs for Low Temperature Polyolefin Up-Cycling

了解用于低温聚烯烃升级循环的先进传热和传质控制以及非贵金属催化剂设计

• 批准号: 2051231
• 负责人: Siris Laursen
• 金额: $ 30.16万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2051231&HistoricalAwards=false
• 关键词: Understanding; Advanced; Heat; Mass; Transport

The project will investigate inexpensive catalytic materials and new energy delivery mechanisms to efficiently transform waste plastics into valuable building-block chemicals and fuels. Fundamental insights will be obtained to develop continuous and modular chemical transformation processes that will enable local municipalities to utilize waste plastics (as well as other types of municipal waste) for economic gain. The project focuses on technologies compatible with the scale of municipal waste treatment plants, thus avoiding long-distance transport of waste material for processing in large centralized chemical processing plants. Beyond promoting U.S. competitiveness in cyclic and environmentally friendly chemical processes, the project will include education and outreach efforts to train next-generation scientists and engineers, while also increasing societal awareness of the plastics pollution problem and efforts to solve the issue.Preliminary efforts in the investigator's laboratory have determined that uncatalyzed thermal radical reaction mechanisms dramatically limit the efficiency and role of catalytic materials in the catalytic conversion of polyolefins to higher-value medium and long-chain alkanes and alkenes. Additionally, the prior work has revealed linkages between the catalysis and heat and mass transport effects, thus inhibiting the development of fundamental mechanistic insights needed for catalyst and reaction environment design. The project will investigate the design and use of advanced reactor geometries specific for highly viscous polymer melt mixing to understand and limit the effect of mass transport in the catalytic cleavage of polyolefins. A new microwave energy delivery mechanism that delivers heat energy directly to the catalyst particles will be employed to avoid or dramatically reduce the role of uncatalyzed thermal radical reaction mechanisms. The fundamental surface reaction energetics of a bifunctional catalyst that presents both acid and metallic reaction sites will be investigated such that constituent reaction kinetics for polyolefin dehydrogenation, C-C cleavage, and hydrogenation may be balanced and optimized. A mechanically and chemically-robust microwave susceptor, silicon carbide (SiC), will be used to simultaneously provide tunable solid acid reaction sites, quench thermal radicals, and convert microwave energy to localized heat energy. The SiC acid catalyst will be combined with well-defined non-noble metal intermetallic compound nanoparticle catalysts that will provide metal-like surface chemistry to achieve efficient hydrogenation. Additionally, the role of hot phonons, produced through microwave absorption by SiC, will be investigated for accelerating kinetically-difficult reaction steps. To derive clear connections between bulk and surface catalysis, the catalysts will be investigated using ex- and in-situ x-ray diffraction and high-resolution energy-dispersive x-ray, x-ray photoelectron, and high-sensitivity low-energy ion scattering spectroscopies. Utilizing a suite of reaction conditions that provide a range of heat and mass transport environments, clear insights into the role of uncatalyzed reaction mechanisms, intermediate chemical potential, and composition polarization near the catalyst surface will be developed. The role of chain dynamics and branch points in the catalytic cleavage mechanism will also be determined such that a more robust and general catalytic process may be developed to operate on practical mixed polyolefin waste. The role of water content in motivating optimal catalyst formulations will also be determined to ensure the application of the science developed to real-world polyolefin up-cycling efforts. Beyond polyolefin up-cycling, this project will produce transferable understanding associated with heat and mass transport and reactor design that may greatly improve efforts to catalytically up-cycle recalcitrant, solid, or highly viscous materials. The educational component will enhance the chemical engineering and materials science programs of the University of Tennessee, Knoxville, and raise awareness of the plastics pollution problem in the local community.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.

该项目将研究廉价的催化材料和新的能源输送机制，以有效地将废塑料转化为有价值的积木化学品和燃料。将获得基本的见解，以开发连续和模块化的化学转化过程，使地方市政当局能够利用废塑料(以及其他类型的城市废物)来获得经济利益。该项目的重点是与城市垃圾处理厂规模相适应的技术，从而避免长途运输废物材料，以便在大型集中式化学加工厂进行处理。除了提高美国在循环和环境友好的化工过程中的竞争力，该项目还将包括教育和推广工作，以培训下一代科学家和工程师，同时提高社会对塑料污染问题的认识和解决问题的努力。研究人员实验室的初步努力已确定，非催化热自由基反应机理极大地限制了催化材料将聚烯烃催化转化为更高价值的中长链烷烃和烯烃的效率和作用。此外，先前的工作揭示了催化与热质传输效应之间的联系，从而抑制了催化剂和反应环境设计所需的基本机理见解的发展。该项目将研究专门用于高粘度聚合物熔体混合的先进反应器几何结构的设计和使用，以了解和限制聚烯烃催化裂解中的传质效果。一种新的微波能量传递机制，将热能直接传递给催化剂颗粒，将被用来避免或显著减少非催化热自由基反应机制的作用。研究同时存在酸和金属反应中心的双功能催化剂的基本表面反应能，以便平衡和优化聚烯烃脱氢、C-C裂解和加氢的组分反应动力学。一种机械和化学性能都很好的微波感应器，碳化硅(SIC)，将被用来同时提供可调谐的固体酸反应中心，淬灭热自由基，并将微波能量转换为局域热能。碳化硅酸催化剂将与定义良好的非贵金属金属间化合物纳米颗粒催化剂相结合，提供类似金属的表面化学，以实现高效加氢。此外，还将研究碳化硅通过微波吸收产生的热声子的作用，以加速动力学上困难的反应步骤。为了在体相和表面催化之间建立清晰的联系，我们将使用X-射线衍射仪和现场X-射线衍射仪以及高分辨率能量色散X-射线、X-射线光电子能谱和高灵敏度低能离子散射谱对催化剂进行研究。利用一套提供一系列热量和质量传输环境的反应条件，可以清楚地了解催化剂表面附近的非催化反应机理、中间化学势和组成极化的作用。还将确定链动力学和分支点在催化裂解机理中的作用，以便开发出更强大和更通用的催化过程来处理实际的混合聚烯烃废物。还将确定水含量在激励最佳催化剂配方中的作用，以确保将开发的科学应用于现实世界的聚烯烃上循环努力。除了聚烯烃上循环外，该项目将产生与热和质量传输以及反应器设计相关的可转让的理解，这可能会极大地改进催化上循环顽固、固体或高粘性材料的努力。教育部分将加强田纳西大学诺克斯维尔分校的化学工程和材料科学项目，并提高当地社区对塑料污染问题的认识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。