AIR: Towards a CO2-free, Sustainable, Ethylene Oxide Technology

传统的环氧乙烷(EO)工艺在乙烯和环氧乙烷(EO)的燃烧过程中都会排放副产物二氧化碳(约3.4 Mt/年)，消除这种副产物一直是几十年来工业化学中的一大挑战。在美国国家科学基金会资助的一个项目中，堪萨斯大学最近展示了一种对环氧乙烷有99%选择性的替代技术概念，没有检测到二氧化碳的形成。这一替代工艺是基于均相乙烯氧化的基础上，在25-40℃和~50巴的条件下，以甲基三氧基苯(MTO)为催化剂，用H_2O_2氧化。这一建议解决了商业化的关键障碍，即可回收MTO催化剂的设计和演示。多相载体和可溶聚合物(能够通过纳滤膜保留在溶液中)都在考虑之中。通过初步的经济分析，建立了催化剂实际可行性的定量性能指标(活性、选择性和耐久性)，并将指导催化剂设计。项目目标的成功完成将产生用于环氧化反应的新颖、可回收的催化剂配方。连续乙烯膨胀液相催化反应器的演示将是此类反应器中的第一个。ADM(对植物油的环氧化反应感兴趣)、Evonik(主要的过氧化氢生产商)和宝洁(主要的环氧乙烷消费者)人员的项目指导增加了项目成功和最终商业化的可能性。拟议的概念有可能显著节约石油和天然气储量(约1300万桶原油/年)，并减少作为副产品的碳排放(每年340万公吨二氧化碳)。将这项技术应用于含有乙烯和乙烷的混合饲料，也将大大节省能源，因为它们在传统加工中需要分离。这项拟议工作的技术成果将纳入正在进行的题为“可持续化学工艺的发展”的课程，对本科生和研究生课程都有影响。

Conventional ethylene oxide (EO) processes emit CO2 as byproduct (roughly 3.4 MM tons/yr) from the combustion of both the ethylene and EO, the elimination of which has been a major grand challenge in industrial chemistry for decades. In a NSF-funded project, an alternate technology concept that is 99% selective toward EO was recently demonstrated at the University of Kansas with no detectable CO2 formation. This alternate process is based on homogeneous ethylene oxidation with H2O2 at 25-40C and ~50 bars using methyltrioxorhenium (MTO) as catalyst. This proposal addresses the key barrier to commercialization, viz., the design and demonstration of a recyclable MTO catalyst. Both heterogeneous supports and bulky soluble polymers (capable of retention in solution by nanofiltration membranes) are being considered. Quantitative catalyst performance metrics (activity, selectivity and durability) for practical viability have been established through preliminary economic analysis and will guide catalyst design. Successful completion of the project objectives will result in novel, recyclable catalyst formulations for epoxidation reactions in general. The demonstration of a continuous ethylene-expanded liquid phase catalytic reactor will be the first of its kind. The project guidance from ADM (interested in epoxidation of vegetable oils), Evonik (a major H2O2 producer) and P&G (a major EO consumer) personnel increases the probability of project success and eventual commercialization. The proposed concept has the potential to result in significant conservation of oil and gas reserves (~13 million barrels crude oil/year) and reduction of carbon emissions as byproduct (3.4 million metric tons of CO2 each year). The application of this technology to mixed feeds containing ethylene and ethane will also result in significant energy savings associated with their separation required in conventional processing. The technical outcomes from this proposed work will be integrated into an ongoing course titled Development of Sustainable Chemical Processes, impacting both the undergraduate and graduate curricula.