Catalytic Synthesis of Fatty Acid Methyl Esters from Extremely Low Quality Greases

Biodiesel (BD) is a renewable fuel for compression ignition engines that is composed of the simple alkyl esters, usually methyl-, of fatty acids (FAME). It is typically produced via base-catalyzed transesterification between refined vegetable oil or animal fat (e.g., soybean oil, tallow) and an alcohol (e.g., methanol). This process can, however, be marginally cost-effective due to the high feedstock and processing costs. It is thus desirable to develop new catalytic routes that can efficiently convert less expensive feedstocks to BD. We report here on the application of a series of diarylammonium based homogeneous and heterogeneous catalysts for converting a particularly low value, low quality lipid, trap grease, to FAME. In the course of a 1-h reaction at 125 °C these catalysts simultaneously esterified the free fatty acids (>90 wt% of the substrate) and transesterified the acylglycerols (<10 wt%) of the feedstock to FAME with greater than 95% overall conversion.