Heat-Modeling of Microwave Assisted Epoxidation of Palm Acid Oil

Saifuddin Saifuddin

doi:10.3844/ajassp.2011.217.229

Abstract

Problem statement: While microwave chemistry could well be the most convenient, rapid and energy-saving way to initiate a chemical reaction, the issues of thermal versus microwave specific effect remain unaddressed. Approach: A three-dimensional Finite Element Model (FEM) was developed to predict temperature profile during the enzymatic epoxidation of palm acid oil using microwave heating. Three-dimensional partial differential equations are formulated for the electromagnetic field and heat and mass transfer processes. The temperature profile of the FEM generated from the commercial software (ANSYS Emag) was verified using experimental data from microwave oven heated samples containing palm acid oil and reactants in cylindrical bottles and has compared favorably with real time data. An Infra Red thermometer was used to measure temperature of the reactants during the real time experiment to ensure less contact with the reaction vessel. Results: Apart from ascertaining the temperature profile of the epoxidation process in the cylindrical bottle, the heat-modeling of this reaction can predict the Energy required during the reaction and provide insights to non-thermal microwave effects. It has shown the possibility of Microwave Non-Thermal Effects and Microwave Selectivity in Substrate Specificity. The energy used by the microwave irradiated reaction is by far much lesser than the energy used in conventional heating. This study has also improved the epoxidation process of Palm Acid Oil by incorporating enzyme as a catalyst and using microwave heating. Epoxidation can be done rapidly and at a lower level of activation energy of 27.767 kJ mol−1. It is a green process with increased efficiency as it reduced a typically 5-hour reaction to less than an hour. Conclusion: In this study, a quantitative view of a microwave assisted process of enzymatic epoxidation has been established. We have successfully developed and experimentally validated a 3D electromagnetic heat transfer model. This model can thus be used to predict the energy of the epoxidation and other future microwave reactions. the study also have shown the existence of microwave non-thermal effects and microwave selectivity in substrate specificity.

Highlights

Microwave chemistry has been gaining attention in recent years as it provides rapid reaction rates and higher yield of pure products
The selective absorption of microwave energy by polar molecules or polar transition state intermediates formed during the course of the reaction has shown significant increase in reaction rates (Saifuddin and Fazlili, 2009; Caddick and Fitzmaurice, 2009; Jumbe and Nandini, 2009)
Apart from organic synthesis, MW heating has been applied in fields such as organometallic synthesis, homogeneous and heterogeneous catalysis, phase transfer catalysis, organocatalysis and biocatalysis (Jumbe and Nandini, 2009)

Summary

Introduction

Microwave chemistry has been gaining attention in recent years as it provides rapid reaction rates and higher yield of pure products. The containment materials for a chemical reaction may be chosen in such a way that the microwave energy passes

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