Production of Renewable Diesel Fuel via Hofer-Moest Decarboxylation of Free Fatty Acids
AuthorWagner, Cody James
AdvisorCoronella, Charles J
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The industrialization and modernization of some of the world's poorest, densely populated countries, coupled with the limited supply of petroleum globally, has created an escalating energy problem. Advanced biofuels, derived from biologically grown feedstocks, are renewable fuels which provide a drop-in replacement for petroleum. One potential conversion pathway to turn lipid-based biomass feedstocks into a renewable diesel fuel is through non-Kolbe electrolysis. When performed on a graphite surface, electrolysis of free fatty acid (FFA) salts in an alcoholic electrolyte at potentials of at least 2.5 V/cell causes a two-electron Hofer-Moest decarboxylation. This reaction produces several hydrocarbons, ethers, and esters at a current efficiency of approximately 73.9%. Using 2011 electricity statistics, an average electrical energy cost to produce one gallon of the fuel from pure oleic acid is $0.383. From analysis of a full factorial design of experiment, higher ion concentrations and lower temperatures optimize the production rate and current efficiency of the reaction, while a maximal percentage of hydrocarbons are produced in neutral solutions. In comparison to biodiesel, this fuel product has better heating values and cold flow properties but demonstrates worse oxidative stability. An advantage of this electrochemical process is the robustness of feedstocks that can be used, which includes algae oils, high FFA wastes such as brown and yellow grease, and biodiesel waste FFA salts.