Developing structure-function relationships for CO2-assisted ethane dehydrogenation through zeolite-supported chromium sites

通过沸石负载的铬位点开发二氧化碳辅助乙烷脱氢的结构-功能关系

• 批准号: 2034647
• 负责人: Coleman Kronawitter
• 金额: $ 59.51万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-15 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2034647&HistoricalAwards=false
• 关键词: Developing; structure; function; relationships; CO2

Domestic natural gas is an important contributor to the U.S. energy and chemical manufacturing sectors, with strong effects on the economy and national security. In the context of the chemicals industry, a unique opportunity exists to utilize light alkane components of natural gas, such as ethane, as feedstocks for production of value-added chemicals. Notably, ethane can be catalytically dehydrogenated to produce ethylene, which is a critically important building block feedstock for the manufacture of many types of polymers. Current ethane dehydrogenation process economics are limited by low yields, which result from the prevalence of side reactions and catalyst deactivation. The use of carbon dioxide (CO2) as a co-reactant enhances catalyst activity, facilitates high ethylene selectivity, and extends catalyst lifetimes. Additionally, the CO2 (an industrial waste product and greenhouse gas) is converted to carbon monoxide (CO), which is itself a value-added product used in the chemicals industry. Nevertheless, advances are needed in catalyst technology to assure commercial viability of carbon dioxide-assisted ethane dehydrogenation. The project develops fundamental insights into this conversion process through novel engineering of catalyst structures coupled with systematic investigation of the chemical reactions. Overall, the study will generate critical fundamental information on the mechanistic origins of high single-pass olefin yields, which will translate to improved process economics for combined alkane-CO2 conversion systems. The project is supported by broader efforts to enhance educational and research opportunities for women and underrepresented groups, especially the large Hispanic population served by the investigators’ university.The project focuses on zeolite-supported chromium (Cr) catalysts to develop insights into multiple aspects of the overall catalytic process: ethane activation, CO2 activation, competition and cooperation between co-occurring reactions, and the influence of both metal-support interactions and active site structure. Specifically, heteroatom-substituted zeotype supports (including framework Al, B, and Ga in MFI zeolites) are used to generate Cr active sites with consistent coordination geometry but with varied metal-support interaction (which will be determined by the targeted heteroatom elemental composition). Structural, chemical, and electronic properties of the dispersed Cr sites will be related to catalytic performance via a comprehensive suite of characterization tools, including probe molecule adsorption infrared spectroscopy, ex situ and operando synchrotron-based X-ray absorption spectroscopy, chemisorption and thermogravimetric analysis with mass spectrometry, and Raman spectroscopy. Using well-defined catalysts, the impact of CO2 on reaction kinetics will be isolated and interpreted in the context of the parallel ethane dehydrogenation and reverse water-gas shift (RWGS) reactions. The reaction network will be analyzed through reactor studies, employing varying feed compositions, probe reactions, and isotope labeling experiments. Catalyst structure-function relationships and optimized reaction conditions, obtained at low ethane conversion, will be further investigated in the high conversion regime, relevant to commercial single-pass reactor operation.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.

国内天然气是美国能源和化学制造业的重要贡献者，对经济和国家安全具有重要影响。 在化学工业的背景下，存在利用天然气的轻质烷烃组分（例如乙烷）作为生产增值化学品的原料的独特机会。 值得注意的是，乙烷可以催化脱氢以产生乙烯，乙烯是用于制造许多类型的聚合物的至关重要的结构单元原料。 目前乙烷脱氢工艺的经济性受到低产率的限制，这是由于副反应和催化剂失活的普遍存在。 使用二氧化碳（CO2）作为共反应物增强了催化剂活性，促进了高乙烯选择性，并延长了催化剂寿命。 此外，二氧化碳（一种工业废物和温室气体）被转化为一氧化碳（CO），这本身就是一种用于化学工业的增值产品。 然而，需要在催化剂技术方面取得进展以确保二氧化碳辅助的乙烷脱氢的商业可行性。该项目通过对催化剂结构的新工程设计以及对化学反应的系统研究，开发了对这种转化过程的基本见解。总的来说，这项研究将产生高单程烯烃产率的机理起源的关键基础信息，这将转化为提高工艺经济性的组合烷烃-CO2转化系统。 该项目得到了更广泛的努力的支持，以提高妇女和代表性不足的群体，特别是研究人员大学所服务的大量西班牙裔人口的教育和研究机会。该项目侧重于沸石负载的铬（Cr）催化剂，以深入了解整个催化过程的多个方面：乙烷活化、CO2活化、共发生反应之间的竞争和合作，以及金属-载体相互作用和活性中心结构的影响。 具体地，杂原子取代的沸石型载体（包括MFI沸石中的骨架Al、B和Ga）用于产生具有一致配位几何形状但具有变化的金属-载体相互作用（其将由目标杂原子元素组成确定）的Cr活性位点。分散的铬网站的结构，化学和电子性质将通过一套全面的表征工具，包括探针分子吸附红外光谱，异位和operando同步加速器为基础的X-射线吸收光谱，化学吸附和热重分析与质谱，和拉曼光谱的催化性能。使用定义明确的催化剂，二氧化碳对反应动力学的影响将被隔离和解释的上下文中的并行乙烷脱氢和逆水煤气变换（RWGS）反应。反应网络将通过反应器研究进行分析，采用不同的进料组合物，探针反应和同位素标记实验。 在低乙烷转化率下获得的催化剂结构-功能关系和优化的反应条件将在高转化率范围内进一步研究，与商业单程反应器操作相关。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。