CAREER: Tailoring the Synergy between Catalyst Design and Reaction Engineering for Direct Conversion of Methane to Aromatics

职业：定制催化剂设计和反应工程之间的协同作用，将甲烷直接转化为芳烃

• 批准号: 2245190
• 负责人: Sheima Khatib
• 金额: $ 59.31万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-10-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2245190&HistoricalAwards=false
• 关键词: CAREER; Tailoring; Synergy; between; Catalyst

The vast abundance of methane in natural resources makes it an attractive chemical feedstock for conversion into higher hydrocarbon fuels and bulk chemicals of industrial interest. However much of the natural gas is found in stranded locations and is flared due to high transportation and processing costs. Direct transformation routes of methane into liquid chemicals can reduce processing costs but are currently not economically viable due to unanswered scientific challenges. The proposal targets catalytic methane dehydroaromatization (MDA) for the direct conversion of methane to benzene and hydrogen, both mainstays in the chemicals industry. The proposed study seeks to integrate catalysis and reaction engineering to overcome technological challenges arising during MDA. The research results will be integrated with educational and outreach activities.Two major challenges currently prevent the implementation of MDA at an industrial level: (1) thermodynamic limitations leading to low methane equilibrium conversion; (2) rapid catalyst deactivation. While processes involving removal of the hydrogen product from the reaction medium are successful in shifting the equilibrium to the right and increasing methane conversion to benzene, they also accelerate coking. Thus, catalyst deactivation in MDA is a ubiquitous issue that must be addressed. Molybdenum (Mo) oxide supported on HZSM-5 zeolite is the most commonly studied catalyst for the MDA reaction. It is agreed that during an induction period Mo oxide species transform to Mo carbide species that are responsible for the conversion of methane to aromatics. Adding oxidant co-reactants can help the process thermodynamics, however, only low oxidant concentrations can be used since the active Mo carbide phases will otherwise be oxidatively destroyed. At low oxidant concentrations benzene yields are improved but the oxidant distribution in a packed-bed reactor (PBR) is not even, thus kinetic measurements are not representative of the entire catalyst bed. Distributed-feed membrane reactors (DFMR) can overcome the reactor heterogeneity problem and increase benzene yields, but catalyst coking is not fully prevented. The PI has discovered a method to increase catalyst resistance to coking by preparing Mo carbide phases ex situ in the presence of a second metal X (X= Fe, Co, or Ni), but the nature of the Mo-X interaction remains unknown. The proposed project includes studies of stable Mo-X/HZSM-5 catalysts in a DFMR with an oxidant (oxygen or carbon dioxide) as co-reactant to determine the role of Mo-X-C interactions on the reaction and catalyst deactivation pathways. Model catalysts will be prepared by ensuring that the metals (Mo and X) are located inside the zeolite channels by blocking the anchoring sites on the external surface. The structure, location and evolution of the Mo-X phases will be monitored by in situ and Operando experiments using advanced characterization techniques, including X-ray absorption and high-resolution powder diffraction. DFMR operating conditions will be tuned to ensure even axial distribution of the oxidant and maximum enhancement in benzene yield. Kinetic testing will be performed with the DFMR and compared to a PBR as reference. The combination of the kinetic tests, in situ structural characterization and theoretical calculations will result in the determination of the reaction and deactivation pathways of MDA in the presence of oxidants and will provide the basis for the rational design of catalysts tailored for a DFMR. The PI will develop two new graduate courses focused on an integrated interdisciplinary approach to catalysis and an interdisciplinary Science, Technology, Engineering, Art, Mathematics (STEAM) project with the School of Theatre and Dance at Texas Tech University to use storytelling to increase the awareness of the public on the importance of science and engineering and attract students into STEM careers. The stories will be propagated in various formats including theatre performances at local schools, digital stories and podcasts posted on a YouTube channel.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.

自然资源中巨大的甲烷丰富性使其成为一种有吸引力的化学原料，用于转换为更高的碳氢化合物燃料和工业兴趣的散装化学品。但是，许多天然气都在搁浅的位置发现，并且由于高运输和加工成本而被爆发。将甲烷直接转化为液体化学物质可以降低加工成本，但由于未解决的科学挑战，目前在经济上不可行。该提案靶向催化甲烷脱氢芳族化（MDA），用于将甲烷直接转化为苯和氢，这都是化学工业中的主要支柱。拟议的研究旨在整合催化和反应工程，以克服MDA期间引起的技术挑战。研究结果将与教育和外展活动相结合。目前，两个重大挑战可以阻止在工业层面实施MDA：（1）热力学限制导致甲烷平衡转化率低； （2）快速催化剂停用。虽然涉及从反应介质中去除氢产物的过程成功地将平衡转移到右侧并增加甲烷转化为苯，但它们也加速了焦化。因此，在MDA中取消催化剂是必须解决的无处不在的问题。在HZSM-5沸石上支撑的氧化钼（MO）是MDA反应最常见的催化剂。同意，在诱导期间，氧化物物种转化为碳化物物种，这些物种负责将甲烷转化为芳香族。添加氧化剂共反应可以帮助过程热力学，但是，由于活性Mo碳化物相可以氧化销毁，因此只能使用低氧化剂浓度。在低氧化剂浓度下，苯屈服得到改善，但填充床反应器（PBR）中的氧化剂分布甚至没有，因此动力学测量不能代表整个催化剂床。分布式喂养的膜反应器（DFMR）可以克服反应器异质性问题并增加苯屈服，但催化剂的焦化并不能完全预防。 PI通过在存在第二个金属X（X = Fe，Co或Ni）的情况下制备MO碳化物相的原位，发现了一种增加催化剂抗性的方法，但是MO-X相互作用的性质尚不清楚。拟议的项目包括对具有氧化剂（氧或二氧化碳）的DFMR中稳定的MO-X/HZSM-5催化剂的研究，以确定MO-X-C相互作用对反应和催化剂脱氧途径的作用。通过确保金属（MO和X）位于沸石通道内部，可以通过阻止外表面上的锚定位点来制备模型催化剂。 MO-X相的结构，位置和演变将通过原位和Operando实验来监测高级特征技术，包括X射线吸收和高分辨率粉末衍射。 DFMR的工作条件将进行调整，以确保氧化剂的轴向分布和苯产量的最大增强。动力学测试将使用DFMR进行，并与PBR作为参考进行比较。动力学测试的结合，原位结构表征和理论计算将导致在存在氧化剂的情况下确定MDA的反应和失活途径，并将为针对DFMR量身定制的催化剂的合理设计提供基础。 PI将开发两个新的研究生课程，重点是综合跨学科方法进行催化和跨学科科学，技术，工程，工程，艺术，数学，数学（Steam）项目（Steam和舞蹈学院项目），以利用讲故事来提高对公众对科学和工程学的重要性的认识，并吸引学生参与茎。这些故事将以各种格式传播，包括在YouTube频道上发布的数字故事和播客的戏剧表演，该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子和更广泛的影响评估评估标准来通过评估来获得支持的。