EFRI E3P: Nonthermal Plasma-Assisted Hydrogenolysis of Waste Plastics to Value-added Chemicals and Fuels

难以回收的塑料废物堆积在垃圾填埋场和环境中，因为几乎没有商业上可行的回收技术，这严重恶化了陆地和水生生态系统。该项目将研究一种名为非热等离子体辅助氢解的方法，作为回收塑料废物混合物的潜在方法。低温等离子体辅助氢解为混合塑料(即聚合物)的解聚提供了一条低能量途径，并产生了作为化学原料和运输燃料的单体、C2-C3烯烃和液体石蜡等增值小分子。低温等离子体将提供两个关键功能：(I)引导电能以激活聚合物键断裂过程；(Ii)作为电解液，将聚合物碎片电化学转化为所需的小分子。该项目整合了阿克伦大学和劳伦斯伯克利国家实验室的研究人员的专业知识，目的是(I)开发电催化中的转化概念，使用聚合物中的氢/烃等离子体作为气体电解液，以及(Ii)将这一新概念与传统催化相结合，实现聚合物废物快速和选择性地转化为所需的化学品。非热等离子体辅助氢解概念的成功演示将建立所需的知识基础，以推进气体电解液和等离子体反应工程电催化的科学前沿。建议的技术可以进一步应用于消费产品的上行循环和集约化养殖产生的有机农业废物。塑料废物的非热等离子体辅助氢解在关闭塑料碳循环循环方面具有潜在的变革性作用。本项目的目标是研究一种非热等离子体辅助催化方法，用于选择性地将混合塑料(即聚合物)转化为单体和小分子。非热等离子体放电，即介质阻挡放电产生的电离气体物种，引发C-H和C-C聚合物键的断裂，从而在气相中产生聚合物碎片及其自由基和离子物种。塑料垃圾中的无机污染物不能蒸发，以固体颗粒的形式沉淀。然后，聚合物碎片吸附在催化剂表面，在常温常压下选择性转化为所需的小分子。离子物种可以作为电解质，使吸附在电催化剂表面的物种能够转化，这是一个控制反应速度和选择性的过程。常温电催化具有以下几个吸引人的特点：(1)减少了对热能的需求；(2)减少了副反应(特别是焦油的生成)；(3)提高了对所需产品的选择性。通过全面的动力学研究、反应性吸附中间体的红外光谱研究、催化剂和吸附聚合物碎片结构的原位X射线吸收研究、催化剂表征、催化剂的合理设计和中试反应器的试验，将获得对聚合物废物非热等离子体催化氢解的机理的了解。这一研究结果将促进低温等离子体辅助氢解作为一种聚合物废物回收利用的方法，并对气相等离子体电催化的机理有更深入的了解。此外，以等离子体为电解液的气相电催化的变革性概念为进一步的基础研究和实际应用提供了一种新的电化学范式。最终，该项目将(I)确定适用于塑料垃圾的非热等离子体辅助催化转化的活性、选择性和耐用性催化剂，以及(Ii)为非热等离子体气固催化反应器的设计和运行提供技术基础。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。

Difficult to recycle plastic waste accumulates in landfills and the environment since few commercially viable recycling technologies exist, which severely deteriorates terrestrial and aquatic ecosystems. This project will examine a method called nonthermal plasma-assisted hydrogenolysis as a potential approach for recycling mixtures of plastic waste materials. Nonthermal plasma-assisted hydrogenolysis provides a low-energy pathway for depolymerizing mixed plastics (i.e., polymers) and generating value-added small molecules, such as monomers, C2-C3 olefins, and liquid paraffins, which serve as chemical feedstocks and transportation fuels. Nonthermal plasma will provide two key functions: (i) channeling electric energy to activate polymer bond-breaking processes and (ii) serving as an electrolyte for electrochemical conversion of polymer fragments to desired small molecules. This project integrates the expertise of investigators from The University of Akron and Lawrence Berkley National Laboratory with the objective of (i) developing a transformational concept in electrocatalysis, using plasma of hydrogen/hydrocarbon from polymers as gaseous electrolyte and (ii) coupling this novel concept with conventional catalysis to achieve fast and selective conversion of polymer wastes to desired chemicals. Successful demonstration of the nonthermal plasma-assisted hydrogenolysis concept will establish the knowledge base required to advance the scientific frontiers in electrocatalysis with gaseous electrolyte and plasma reaction engineering. The proposed technology could be further applied to upcycle consumer products and organic agricultural wastes generated by intensive animal farming. The nonthermal plasma-assisted hydrogenolysis of plastic wastes has a potentially transformative role in closing the loop of the plastics carbon cycle. The objective of this project is to investigate a non-thermal plasma-assisted catalysis approach for the selective conversion of mixed plastics (i.e., polymers) to monomers and small molecules. Nonthermal plasma discharge, i.e., electrically ionized gaseous species produced by dielectric barrier discharge, initiates the breaking of C-H and C-C polymer bonds which produces polymer fragments as well as their radicals and ionic species in the gas phase. The inorganic contaminants in the plastic waste, which cannot be vaporized, precipitate in the form of solid particles. Then, polymer fragments adsorb on the catalyst surface for the selective conversion to desirable small molecules at ambient temperature and pressure. Ionic species could serve as electrolytes to enable the conversion of adsorbed species on the electrocatalyst surface, a process that controls the rate and selectivity of the reactions. Ambient temperature electrocatalysis provides several attractive features: (i) decreasing the need for thermal energy, (ii) minimizing the side reactions (in particular, the formation of tar), and (iii) enhancing the selectivity toward desired products. The mechanistic understanding of nonthermal plasma-assisted catalytic hydrogenolysis of polymer wastes will be achieved through comprehensive kinetic studies, operando infrared spectroscopic studies of reactive adsorbed intermediates, in situ X-ray absorption studies of the structure of the catalyst and adsorbed polymer fragments, catalyst characterization, rational design of catalysts, and testing of a pilot-scale reactor. The results of this study will advance nonthermal plasma-assisted hydrogenolysis as a method for polymer waste recycling and yield a mechanistic understanding of gas-phase plasma electrocatalysis. Moreover, the transformative concept of gas-phase electrocatalysis with plasma as an electrolyte offers a new paradigm in electrochemistry for further basic research and practical applications. Ultimately, this project will (i) identify active, selective, and durable catalysts suitable for nonthermal plasma-assisted catalytic conversion of plastic wastes and (ii) provide the technical basis for the design and operation of nonthermal plasma gas-solid catalytic reactors.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.