CAREER: Catalytic Membranes for Integrated CO2 Capture and Conversion

从空气中捕获二氧化碳(CO2)被认为是缓解全球变暖的一项重要的负排放技术。目前基于脱硫剂的二氧化碳捕集工艺成本高得令人望而却步，因为脱硫剂必须通过能量密集的步骤进行再生才能释放捕获的二氧化碳。一旦从吸附剂中释放出来，捕获的二氧化碳也必须被压缩并运输到现场进行储存，这进一步降低了效率。理想的二氧化碳捕获技术应该是高容量和高能效的，同时将废旧的二氧化碳流转化为增值产品。该项目将推进利用新设想的双功能催化膜在单一单元过程中将二氧化碳捕获与二氧化碳转化相结合的基础科学。该膜将同时作为二氧化碳分离和转化介质，为基于吸收剂的二氧化碳捕获、压缩、运输和储存提供一种能源和原子效率高的替代方案。这样的薄膜可能会彻底改变燃料和化学品的生产方式，导致化学加工行业的革命性变化，并长期刺激美国经济。该项目支持的学生将接受催化、膜分离和高级光谱表征方面的跨学科培训。该职业项目还将通过印第安纳州南本德市纳瓦拉中学的外展活动，以及为波多黎各的本科生和研究生提供研究机会，扩大未被充分代表的群体在STEM中的参与。该职业项目旨在促进将二氧化碳捕获和转化整合为单一单元、基于膜的过程的基础科学。设想的双功能二氧化碳捕获和转化膜是以聚合物为基础的：(1)连接到聚合物链上的胺基团，以选择性地从空气或浓缩的点源中捕获二氧化碳，并促进二氧化碳在膜上的传输；以及(2)催化基团(例如，胺、卤化物、金属)在膜的渗透侧催化二氧化碳的转化。该项目的研究目标是确定限制整体二氧化碳捕获和转化总体速度的关键因素(质量传输、反应动力学和稳定性)。该项目将研究循环碳酸盐合成作为二氧化碳转化反应的模型。将利用对速率限制因素的知识来制定规避这些性能限制过程的策略。该项目的创新之处在于，它使用了由研究人员开发的独特的操纵面光谱技术，以探测现实操作条件下催化膜的结构、性能和动力学。研究成果将提供催化膜的动力学、机理和稳定性的基础知识，这将为开发实用的膜系统提供框架，将二氧化碳捕获与二氧化碳转化为各种燃料和化学品相结合。这项研究还将推进最先进的操纵膜表征，改进用于二氧化碳分离的膜，并改进用于二氧化碳转化的催化剂。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。

Carbon dioxide (CO2) capture from air is considered an important negative emissions technology to mitigate global warming. Current sorbent-based CO2 capture processes are prohibitively expensive because the sorbent must be regenerated via an energy-intensive step to release the captured CO2. Once released from the sorbent, the captured CO2 must also be compressed and transported to sites for storage, which further reduces efficiency. An ideal CO2 capture technology would be both high-capacity and energy-efficient, while simultaneously converting the waste CO2 stream into a value-added product. This project will advance the fundamental science of integrating CO2 capture with CO2 conversion in a single unit process using a newly-envisioned bifunctional catalytic membrane. The membrane would act as both the CO2 separation and conversion medium, providing an energy- and atom-efficient alternative to sorbent-based CO2 capture, compression, transport, and storage. Such a membrane could revolutionize the way fuels and chemicals are produced, leading to transformative change in the chemical process industries and long-term stimulation of the United States economy. The students supported by this project will receive interdisciplinary training in catalysis, membrane separations, and advanced spectroscopic characterization. This CAREER project will also broaden the participation of underrepresented groups in STEM through outreach activities at Navarre Middle School in South Bend, Indiana, and research opportunities for undergraduate and graduate students from Puerto Rico.This CAREER project aims to advance the fundamental science underlying the integration of CO2 capture and conversion into a single unit, membrane-based process. The envisioned bifunctional CO2 capture and conversion membrane is polymer-based with: (1) amine groups attached to the polymer chain to selectively capture CO2 from air, or concentrated point sources, and facilitate CO2 transport across the membrane; and (2) catalytic groups (e.g. amines, halides, metals) to catalyze conversion of CO2 on the permeate side of the membrane. The research goal of this project is to identify the key factors (mass transport, reaction kinetics, and stability) that limit the overall rate of integrated CO2 capture and conversion. The project will examine cyclic carbonate synthesis as a model CO2 conversion reaction. Knowledge of the rate-limiting factors will be used to develop strategies for circumventing these performance-limiting processes. The project is innovative in its use of unique operando spectroscopy techniques developed by the investigator to probe the structure, performance, and dynamics of the catalytic membranes under realistic operating conditions. The research outcomes will provide foundational knowledge of the kinetics, mechanisms, and stability of the catalytic membrane, which will provide a framework for developing a practical membrane system for integrating CO2 capture with CO2 conversion to a wide range of fuels and chemicals. The research will also advance the state-of-the-art of operando membrane characterization, enhance membranes for CO2 separation, and enhance catalysts for CO2 conversion.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.