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，以有效地将废物塑料转化为有价值的建筑块化学物质和燃料。 将获得基本的见解，以开发持续的模块化化学转化过程，这将使当地市政当局能够利用废物塑料（以及其他类型的市政废物）来获得经济利益。该项目的重点是与市政废物处理厂的规模兼容的技术，从而避免了在大型集中化学加工厂的长距离运输以进行处理。 除了促进美国在环保和环保化学过程中的竞争力之外，该项目还将包括教育和外展工作，以培训下一代科学家和工程师，同时还提高了社会对塑料污染问题的认识以及解决该问题的努力。研究人员的实验室中的努力限制了迫切型号的迫切反应和效应的效率，使得效应限制了效率，并确定聚烯烯类到高价值培养基和长链烷烃和烷烃。此外，先前的工作揭示了催化与热量和质量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。该项目将研究针对高粘性聚合物熔体混合的高级反应器几何形状的设计和使用，以了解和限制聚芬蛋白催化裂解中质量转运的影响。将采用一种直接向催化剂颗粒传递热能的新的微波能量输送机制，以避免或大大减少未催化的热根部反应机制的作用。 将研究呈现酸和金属反应位点的双功能催化剂的基本表面反应能量，以便可以平衡且优化的聚烯烃脱氢，C-C裂解和氢化的组成反应动力学。机械和化学刺激的微波头受感受器硅碳化物（SIC）将用于同时提供可调的固体酸反应位点，淬灭热自由基，并将微波能量转换为局部热能。 SIC酸催化剂将与定义明确的非金属金属间的化合物纳米颗粒催化剂结合使用，该纳米粒子催化剂将提供金属样表面化学，以实现有效的氢化。此外，将研究通过微波吸收而产生的热声子的作用，以加速动力学反应步骤。为了得出大量和表面催化之间的明确连接，将使用前和原位X射线衍射和高分辨率的能量分散性X射线，X射线光电链球以及高敏感性低能量的低能离子离子散射光谱进行研究。利用一套反应条件，这些反应条件提供了一系列热量和质量传输环境，对未催化的反应机制的作用有明确的见解，中等化的化学势以及催化剂表面附近的组成极化。还将确定链动力学和分支点在催化裂解机制中的作用，以便可以开发出更坚固，更一般的催化过程来对实用的混合聚烯烃废物进行操作。水含量在激励最佳催化剂制剂中的作用也将确定，以确保将科学应用于现实世界中聚烯二合作的努力。除了循环循环之外，该项目还将产生与热，大众传输和反应堆设计相关的可转移理解，从而可以大大改善催化型在上周期循环顽固，固体或高粘性材料的努力。该教育组成部分将增强田纳西大学诺克斯维尔大学的化学工程和材料科学计划，并提高对当地社区中塑料污染问题的认识。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来通过评估来支持的。