Heterogeneous Emulsion Catalysis: Transesterification using Amphiphilic Catalysts in Nanoemulsion Environments

Texas A&M Agrilife Research, College Station TX

Investigators

Abstract

CBET-0827514 Fernando Transesterification (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.