Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 2009
Publication Date: April 4, 2010
Citation: Ngo, H., Zafiropoulos, N.A., Foglia, T., Samulski, E.T., Lin, W. 2010. Mesoporous Silica-Supported Diarylammonium Catalysts for Esterification of Free Fatty Acids in Greases. Journal of the American Oil Chemists' Society. 87:445-452. Interpretive Summary: Biodiesel (BD) is a viable alternative biofuel that has environmental benefits, including reduction in greenhouse emissions and in the release of harmful environmental pollutants as compared to diesel fuel. Currently the predominant technologies for BD production involve single-use liquid-phase (i.e., ‘homogeneous’) catalysts. Not only is their replacement for each reaction a cost center, but their neutralization before disposal also generates large quantities of salt wastes that must be disposed of. In addition, the large amounts of water required to remove these salts places another burden on the environment. To address these concerns, our group has worked with a university partner to develop catalysts immobilized on silica supports for esterifying the free fatty acids in low value feedstocks to fatty acid methyl esters, the chemical species in BD. These reactions gave high degrees of conversion to produce BD under mild reaction conditions without generating waste materials.
Technical Abstract: Biodiesel, typically fatty acid methyl esters (FAME), has received much attention because it is a renewable biofuel that contributes little to global warming compared to petroleum-based diesel fuel. The most common method used for biodiesel production is based on the alkali-catalyzed transesterification of first-use refined oils and fats with an alcohol (e.g., methanol). These technologies, however, require significant modification when applied to second use materials such as greases because of their higher free fatty acid (FFA) content. Recently, we reported a series of insoluble porous polymer grafted diphenylammonium salts that efficiently esterified the FFA in greases to FAME. In this work, the diphenylammonium salts were supported onto two robust mesoporous silicas. The resulting catalysts had high esterification activity with > 99% of the FFA in greases converted to FAME, and the FFA content in the treated greases was reduced to < 1 wt%. The mesoporous silica-supported catalysts displayed minimal transesterification activity.