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

在社会对可持续制造需求的推动下，化工过程强化利用了旨在减少能源需求和最大限度地减少对环境影响的过程。连续进行同时催化反应和分离的膜反应器就是这项技术的一个重要例子。当膜分离的流体相具有不同的极性(例如，油和水)时，油溶试剂可以反应并从水溶产品中分离出来(反之亦然)，进一步增加了这些体系的灵活性。膜反应器在制药工业中产生了重大影响，因为它能够固定酶作为催化剂，在膜内的油/水界面上驱动生化反应。由于酶催化反应在温和的条件和pH条件下进行，它们被认为是药物连续反应分离的一种绿色加工方法。膜反应器还可以通过去除不活跃或有害的化学物质来减少农业化肥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、食品和饮料等消费产品的特殊产品。然而，在这些体系中，决定反应速度的界面面积仅限于膜反应器孔中的油-水界面。本研究的目标是通过引入新型的高界面区域结构(称为双凝胶)作为膜元件来改变基于膜的反应分离领域。这种材料允许在薄层中实现多种关键功能，极高的油水界面面积估计是传统膜的100倍。在这个项目中，甘油三酯的水解反应将在Bijel膜反应器中进行，以生产脂肪酸和甘油等原材料；这是一个具有重要工业意义的过程，美国市场年销售额超过25亿美元。Bijels(双连续界面堵塞的乳胶凝胶)是通过通过临界点冷却可混合体系以诱导相分离而形成的。这种猝灭是在纳米粒子存在的情况下发生的，纳米粒子形成了困在界面上的堵塞层。由于双凝胶膜中油和水的特殊的双连续排列，使得双凝胶膜的界面面积随着双凝胶膜厚度的增加而增加，因此获得了高的界面面积。此外，比耶尔有一个蜿蜒的连续油域，与蜿蜒的连续水域相邻并交织在一起。界面是稳定的，并用纳米颗粒装饰，这些纳米颗粒也可以支持固定化酶。研究小组将在他们之前成功制造双凝胶并通过一种名为溶剂转移诱导相分离(STRIPS)的可扩展方法来控制其内部微结构的基础上再接再厉。研究人员还将在与韩国浦项科技大学合作的基础上，展示使用酶催化的批处理模式反应分离。在这些进展的基础上，该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异相酶催化反应，以实现连续反应和分离。膜反应器的性能将使用脂肪酶催化甘油三酯与水反应生成甘油和脂肪酸进行评估。该研究计划的具体目标包括(1)研究条带加工条件对比凝胶的影响；(2)通过数学建模和实验演示酯的连续水解；以及(3)减少膜传输限制，以创造反应速度限制的性能。该项目的成功完成将通过使用新型纳米结构液体薄膜来实现过程强化。研究小组将学习如何在具有社会重要性的过程中最佳地使用Bijel技术，包括选择性对映体生产、特种化学品生产、药品和脂肪分解。在纳米结构双凝胶中的连续酶反应分离可能会对对映体药物生产产生革命性影响，这是一类具有巨大经济潜力的反应。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。

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.