Process Intensification via Bijels for Simultaneous and Continuous Catalytic Reaction and Separation

在社会对可持续制造需求的驱动下，化学过程的集约化利用了旨在减少能源需求和最小化环境影响的过程。膜反应器可以连续进行同时催化反应和分离，是该技术的一个重要例子。当被膜分离的流体相具有不同极性（例如，油和水）时，油溶性试剂可以与水溶性产物反应并分离（反之亦然），进一步增加了这些系统的灵活性。膜反应器在制药工业中有着重要的影响，因为它能够固定酶作为催化剂来驱动膜内油/水界面的生化反应。由于酶催化反应在温和的条件和pH下进行，因此被认为是药物连续反应分离的绿色处理方法。膜反应器还可以通过去除非活性或有害的化学物质来减少农业肥料和除草剂对环境的影响。这些过程还可能影响植物油的加工，以形成从膳食补充剂、婴儿配方奶粉、药品、化妆品、食品和饮料等消费品的特种产品。然而，在这些系统中，决定反应速率的界面面积仅限于膜反应器孔中的油水界面。本研究计划的目标是通过引入新的高界面面积结构，以负载催化剂的界面区域（称为bijels）作为膜元件，来改变膜基反应分离领域。这种材料可以在薄层中实现多种关键功能，具有非常高的油水界面面积，估计比传统膜大100倍。在本项目中，甘油三酯水解反应生产脂肪酸和甘油等原料将在bijel膜反应器中进行；这是一个具有重要工业意义的过程，美国每年的市场规模超过250亿美元。Bijels（双连续界面堵塞的乳液凝胶）是通过一个临界点淬火可混相体系以诱导相分离而形成的。这种淬火发生在纳米颗粒存在的情况下，纳米颗粒形成了被困在界面上的堵塞层。由于bijel膜中油和水的特殊双连续排列，使得界面面积随着bijel膜厚度的增加而增加，从而实现了高界面面积。此外，bijels具有一个蜿蜒连续的油域，与蜿蜒连续的水域相邻并交织在一起。界面是稳定的，并且用纳米颗粒修饰，纳米颗粒也可以支持固定化酶。该研究团队将在先前成功制造bijels的基础上，通过一种称为溶剂转移诱导相分离（STRIPS）的可扩展方法控制其内部微观结构。研究人员还将在他们与韩国浦项科技大学的合作基础上，展示使用酶催化的批处理模式反应性分离。在此基础上，本项目的目标是开发基于bijel的膜反应器，以促进不同极性的试剂和产物的多相酶催化反应，实现连续反应和分离。膜反应器的性能将通过脂肪酶催化的甘油三酯与水形成甘油和脂肪酸的反应来评估。研究计划的具体目标包括：(1)研究条带加工条件对bijels的影响；(2)通过数学建模和实验证明酯类的连续水解；(3)降低膜传输限制，创造反应速率受限的性能。该项目的成功完成将通过使用新型纳米结构液体膜实现工艺强化。研究团队将学习如何将bijel技术最佳地应用于具有社会重要性的过程，包括选择性对映体生产、特种化学品生产、制药和脂肪分解。纳米结构bijels中的连续酶反应分离可能对对映体药物生产产生变革性影响，这是一类具有重大经济潜力的反应。该奖项反映了美国国家科学基金会的法定使命，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。

Chemical process intensification, driven by societal needs for sustainable manufacturing, exploits processes designed to reduce energy demand and minimize environmental impact. Membrane reactors that continuously perform simultaneous catalytic reaction and separation are an important example of this technology. When fluid phases separated by the membrane are of differing polarity (e.g., oil and water), oil-soluble reagents can be reacted and separated from aqueous-soluble products (and vice versa), further adding to the flexibility of these systems. Membrane reactors have had significant impact in the pharmaceutical industry because of the ability to immobilize enzymes as catalysts to drive biochemical reactions at oil/water interfaces within the membrane. Because enzyme-catalyzed reactions operate under mild conditions and pH, they are considered a green processing approach to the continuous reactive separation of pharmaceuticals. Membrane reactors could also reduce the environmental impact of agricultural fertilizers and herbicides by removing inactive or detrimental chemical species. Such processes could also impact the processing of vegetable oils to form specialty products for consumer products ranging from dietary supplements, infant formulas, pharmaceuticals, cosmetics, food, and beverages. In these systems, however, interfacial area, which determines the rate of reaction, is limited to the oil-water interfaces in the membrane reactor pores. The objective of this research program is to transform the field of membrane-based reactive separations by introducing novel high-interfacial area structures with catalyst-laden interface areas (called bijels) as membrane elements. This material allows multiple key functionalities to occur in a thin layer, with remarkably high oil-water interfacial area estimated to be 100 times larger than conventional membranes. In this project, hydrolysis reactions of triglycerides to produce raw materials such as fatty acids and glycerol will be carried out in a bijel membrane reactor; this is an industrially significant process with an annual U.S. market in excess of $25B.Bijels (bicontinuous interfacially jammed emulsion gels) are formed by quenching a miscible system through a critical point to induce phase separation. This quench occurs in the presence of nanoparticles, which form jammed layers trapped at the interface. High interfacial area is achieved because of the special, bicontinuous arrangement of oil and water in bijel membranes that allows interfacial area to increase with bijel membrane thickness. Furthermore, bijels have a sinuous continuous oil domain adjacent and intertwined with a sinuous, continuous water domain. The interface is stabilized and decorated with nanoparticles that can also support immobilized enzymes. The research team will build on their prior success in fabricating bijels and controlling their internal microstructure via a scalable method termed solvent transfer-induced phase separation (STRIPS). The researchers also will build on their collaboration with Pohang University of Science and Technology in South Korea in which batch mode reactive separation using an enzymatic catalysis was demonstrated. Based on these advances, the project objective is to develop bijel-based membrane reactors to facilitate heterogeneous enzyme-catalyzed reactions of reagents and products of differing polarity for continuous reaction and separation. Membrane reactor performance will be assessed using the lipase-catalyzed reaction of triglycerides with water to form glycerol and fatty acids. Specific aims of the research program include (1) studying the effects of STRIPS processing conditions on bijels; (2) demonstrating the continuous hydrolysis of esters through mathematical modeling and experiments; and (3) reduction of membrane transport limitations to create reaction-rate limited performance. The successful completion of this project will enable process intensification through the use of the novel nanostructured liquid films. The research team will learn how to optimally employ the bijel technology in processes of societal importance, including selective enantiomer production, production of specialty chemicals, pharmaceuticals, and fat splitting. Continuous enzymatic reactive separation in nanostructured bijels could have transformative impact on enantiomeric pharmaceutical production, a class of reactions with significant economic potential.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.