(522f) Synthesis of Green Diesel Fuel From Fatty Acid Feedstocks Via Electrochemical Hofer-Moest Decarboxylation

Production of biodiesel by esterification or transesterification of long-chain fatty acids is a well known process, but the fuel product has characteristics making it not fully compatible with petroleum diesel engines.  A better option is to convert fatty acid molecules to hydrocarbons by removing their carboxyl group.  Decarboxylation of fatty acid feedstocks was performed by electrolysis using graphite electrodes, which selectively causes a Hofer-Moest (or non-Kolbe)-type reaction.  Methanol was used as a solvent for a robust selection of fatty acid feedstocks. 

The liquid product created by the electrochemical reaction was composed of mainly alkenes with at least one double bond, ethers, and methyl esters.  This fuel product has advantageous cold-flow properties, no sulfur content, heating values close to those of diesel fuels, and is capable of running in current diesel engines as a drop-in replacement for petroleum diesel, unlike biodiesel.  The temperature, pH, concentrations of ions, and type of base used were all varied to optimized the current density, which limits the production rate.  A separation method was tested for removal of the fuel product from the electrolyte.  An efficiency was then calculated for several varieties of fatty acid feedstocks, comparing the electrical energy input to the product generated from the electrolysis.  Overall first-law thermodynamics and economics were also evaluated, examining production rates and the large-scale viability of the process.