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Doctoral Dissertation Announcement
Candidate: Solomon Bera Simiyu
Doctor of Philosophy
Title: Optimization of Biodiesel Production from Free Fatty Acids (FFA) in Trap Grease in the Presence of Different Meta Salts
Dr. John Miller, Chair
Dr. Steve Bertman
Dr. Serine Obare
Dr. Daniel Cassidy
Date: Tuesday, May 15, 2012 2:00 p.m. to 4:00 p.m.
1710 Wood Hall
Fatty acid methyl esters (FAMEs) are used as biodiesel fuel and may be derived from either vegetable or animal fats. Currently, commercial production of biodiesel fuel largely relies on converting triglycerides to FAMEs using base-catalyzed transesterification, but the high cost of virgin-oil feedstock is an impediment to widespread production. One approach to making biodiesel economically competitive with petroleum diesel is to use less-expensive feedstocks, including waste cooking oils (yellow grease) or so called trap grease (brown grease). Unfortunately, the high free fatty acid (FFA) content of waste feedstocks, particularly trap grease, makes base-catalyzed chemistry problematic, so a two-step process, acid-catalyzed esterification of the FFA followed by base-catalyzed transesterification of any remaining glycerides, is often employed. In this study, we examined the use of aluminum salts as alternative catalysts for converting trap grease, a particularly low-value, low-quality lipid, to FAMEs. A comparison of the relative rates of esterification by the aluminum compounds, other metal salts and sulfuric acid an industry standard esterification catalyst are presented.
Some aluminum salts such as AlCl3 are routinely considered to be Lewis acid while other, particularly the hexaaqua cation Al(H2O)63+ may act as Brønsted acids. A mechanistic analysis of the esterification of octadecanoic acid (as a FFA surrogate for trap grease) was carried out by means of comparison kinetic and 27Al NMR measurements. Results of this study suggest that under esterification conditions, the putative Lewis acidic AlCl3 is converted to the Brønsted acid Al(H2O)63+, which can also act as highly-recoverable and reusable esterification catalyst