Heterogeneous Emulsion Catalysis: Transesterification using Amphiphilic Catalysts in Nanoemulsion Environments

CBET-0827514亚铁酯交换反应(或酯化反应)是化学工业中广泛使用的化学反应。目前使用的均相(液体)催化剂存在下游产物分离困难的问题，这导致了对多相(固体)催化剂的探索。然而，由于甘油三酯/醇/催化剂相对应的液/液/固(L/L/S)界面的传质限制，使用多相催化仍然是一个挑战。该方案旨在利用多相乳液催化这一新现象来消除L/L/S多相催化反应的传质瓶颈。智力优势：我们的方法是解决L/L不相容体系表现出的传质限制，同时通过开发一种充当乳化剂(两亲性)的多相催化剂来改善下游催化剂分离问题，该催化剂基本上将位于两不相容液体之间的界面。根据我们的概念，两亲性催化剂首先将两个亲水和疏水的液体分子聚集在一起，由于催化剂的乳化性质，稳定了乳液。同时，催化剂将为反应(在本例中为酯交换反应)提供活性中心。当反应后分离催化剂时，乳状液失去稳定性，聚合成现在的产物，即脂肪酸甲酯和甘油，分别是亲水和疏水的液体。这一没有引起我们注意的过程可能会开辟一系列新的催化剂和催化过程，并可能推广到包括生物可再生能源生产在内的许多应用领域。我们已经通过一系列初步研究证明了这一概念是可行的，这些研究已经导致了几份同行评议的出版物。在这些研究中，我们观察到单体、二聚、三聚和四聚形式的异丙醇钛在超声作用下有助于形成稳定的纳米乳液。这些体系的进一步反应生成了脂肪酸乙酯，与传统的混合体系相比，一些体系的产率提高了133%以上。这种非均相两亲-催化杂化无机聚合物的概念是新颖的，在这种催化体系的几乎每一个方面都存在着知识鸿沟。这一概念的优点是能够通过控制溶液中的水量来控制非均相催化剂颗粒的大小，这极大地有助于验证我们的中心假设，即部分聚合的金属醇盐在酯交换反应中充当非均相两亲催化剂。这一假设背后的理论基础是，纳米乳液的大表面积将提供高反应速率。我们计划研究的基本科学问题是两亲性多相催化剂在这样的纳米乳液环境中如何发挥作用。本应用的目的是：1.评价纳米乳液的粒径(金属异丙醇齐聚)、组分浓度和超声参数对纳米乳液形成和稳定性的影响；2.确定金属异丙醇齐聚对脂肪酸甲酯产率的影响。更广泛的影响：这项创新和创造性的工作将产生巨大的经济和环境效益，此外还将促进我们目前对乳液催化相关科学的理解。一个主要的教育目标是通过一种名为“以应用为中心的培训”(ACT)的创新技术将研究整合到教育中，该技术使学生在本科生涯早期就接触到现实世界中的工程问题。这个项目预计将介绍科学、数学和工程之间的联系，并解决当今工程教育面临的几个问题。低成绩学生研究经验(REUAS)是国际学生联合会想要试验的一个概念，在这个概念中，学业上有风险的少数族裔和代表性不足的学生(GPA为2.5分，ACT标准分数为26分)将在本科课程早期获得研究机会。这些学生将在他们的本科生涯中跟踪他们的进步，以评估让他们从事实践研究是否有助于他们重新振作对工程教育和学位课程的热情。

CBET-0827514 FernandoTransesterification (or esterification) is a widely used chemical reaction in the chemical industry. Presently used homogeneous (liquid) catalysis is plagued with downstream product separation difficulties which has led the quest for heterogeneous (solid) catalysts. However, using heterogeneous catalysis is still a challenge due to mass transfer limitations in liquid/liquid/solid (L/L/S) interface corresponding to immiscible triglyceride/alcohol/catalyst phases, respectively. This proposal intends to use a novel phenomenon, heterogeneous emulsion catalysis, to remove the mass transfer bottleneck of L/L/S heterogeneous catalytic reactions. Intellectual Merit: Our approach is to address mass transfer limitations exhibited by immiscible L/L systems while ameliorating downstream catalysts separation issues by developing a heterogeneous catalyst that acts as an emulsifier (amphiphile) which essentially will be positioned at the interface between the two immiscible liquids. According to our concept, the amphiphilic catalyst first brings the two hydrophilic and hydrophobic liquid molecules together and due to the emulsification properties of the catalyst, stabilizes the emulsion. In the mean time, the catalyst will lend its active sites for the reaction (in this case transesterification) to occur. When the catalyst is separated after reaction, the emulsion loses its stability and will coalesce to, now the products, fatty acid methyl esters and glycerol which are hydrophilic and hydrophobic liquids, respectively. This process that has eluded our attention may open up a new line of catalysts and catalytic processes that may be propagated to many applications including biorenewable energy production. We have proven that this concept is feasible via a series of preliminary studies that have already resulted in a couple of peer reviewed publications. During these studies, we observed that titanium isopropoxide in its monomeric, dimeric, trimeric and tetrameric forms helped formation of stable nanoemulsions when subjected to ultrasonication. Further reaction of these systems resulted in fatty acid ethyl esters with some exhibiting above 133% yield increase as compared to conventionally mixed systems. This concept of heterogeneous amphiphilic-catalytic hybrid inorganic polymers is novel and there is a knowledge gap in just about every aspect of such a catalytic system. The beauty of this concept is the ability to control the size of the heterogeneous catalyst particles by controlling the amount of water in the solution which immensely helps testing our central hypothesis, i.e., partially polymerized metal alkoxides acts as heterogeneous amphiphilic catalysts in transesterification reactions. The rationale behind this hypothesis is that the large surface area of the nanoemulsions will provide for high reaction rates. The fundamental scientific question we plan investigate is how an amphiphilic heterogeneous catalyst will function in such a nanoemulsion environment. The objectives of this application are to: 1. Evaluate the effect of particle size (metal isopropoxide oligomerization), component concentration and ultrasonic parameters on formation and stability of nanoemulsions and 2. Determine the effect of oligomerization of metal isopropoxides on fatty acid methyl esters yield. Broader Impacts: This innovative and creative work will generate enormous economical and environmental benefits in addition to advancing our present understanding of science related to emulsion catalysis. A major educational objective is to integrate research into education via an innovative technique named "Application Centered Training" (ACT) which engages students early in their undergraduate career with real world engineering problems. This program is expected to introduce the nexus between science, math and engineering and address several issues engineering education faces today. Research Experience for Under Achieving Students (REUAS) is a concept the PI would like to experiment where minority and under represented students who are academically at risk (2.5 GPA and 26 standard ACT scores) will be provided with research opportunities early in their undergraduate program. The progress of these students will be tracked during the course of their undergraduate career to evaluate whether exposing them into practical research helps them resuscitate their excitement towards engineering education and the degree program.