| Summary: | Currently, a majority of the worlds energy needs are met through use of fossil fuels, petroleum, coal and natural gas. The depletion of petroleum reserves, rising and extremely volatile crude oil prices, and environmental concerns have led to search for renewable and environmentally friendly fuels. The ultimate goal of this research was to develop, test and optimize a batch microwave system using traditional and alternate non-food feedstocks.
Microwave assisted extraction (MAE) of oil from conventional feedstocks (soybeans and rice bran) and an alternative feedstock (Chinese tallow tree (CTT) seeds) was carried out. The study concluded that MAE of oil is a rapid, efficient and effective method of extracting oil from the feedstocks as compared to conventional extraction techniques. Maximum yields of 17.3%, 17.2% and 32.5%, representing ~ 95% of total recoverable oil, were obtained for soybean, rice bran and CTT seeds by microwave extraction in 20 mins. This compares extremely favorably to the hours of processing required by conventional methods. The enhanced extraction is due to the specific interaction of the microwave field with the solvent-feedstock matrix, where higher temperature and pressure gradients develop at the microscopic level, leading to enhanced mass transfer coefficients.
Optimization of transesterification reaction parameters was carried out as the second objective of the research. Refined soybean and rice bran oil were used as biodiesel feedstocks. Two alcohols, methanol and ethanol, were tested in this study. Sodium hydroxide was the catalyst and the reactions were carried out in presence of microwaves. By use of microwaves, the reaction times were drastically reduced, and >95% conversions could be achieved for very small catalyst concentration (< 0.2%) which reflected in easier separation of byproducts from the biodiesel phase. The enhanced biodiesel production reaction rates occurred due to two main mechanisms: (1) molecular mixing of the polar alcohol molecules with the oil in the presence of the oscillating electric field component and (2) volumetric heating effect of microwaves, eliminating the time for transient conductive/ convective heat transfer in the mixture. Quality analysis of biodiesel according to ASTM standards was performed and the samples were found to meet the necessary specifications.
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