Zeolite-Catalyzed Isomerization of Oleic Acid to Branched-Chain Isomers

Authors: Ngo, Helen; Nunez, Alberto; LIN, WENBIN - UNIV OF NORTH CAROLINA; Foglia, Thomas

Submitted to: European Journal of Lipid Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2007
Publication Date: 3/1/2007
Citation: Ngo, H., Nunez, A., Lin, W., Foglia, T.A. 2007. Zeolite-Catalyzed Isomerization of Oleic Acid to Branched-Chain Isomers. European Journal of Lipid Science and Technology. 108:214-224.

Interpretive Summary: Branched-chain saturated fatty acids are oxidatively more stable than common naturally abundant unsaturated fatty acids and have better low-temperature properties than common naturally abundant straight-chain saturated fatty acids. Hence they are ideally suited in such uses as lubricants and functional fluids. Several chemical approaches, including clay and metal-catalyzed reactions have been examined for the conversion of linear unsaturated fatty acids to branched-chain isomers but all suffer from poor yields. In this paper, we describe the production of branched-chain fatty acids from unsaturated linear chain fatty acids in high yields using modified zeolite catalysts, which can be recycled at least three times. The branched products obtained are liquids at room temperature and remain liquid at temperatures significantly lower than that of oleic acid and its esters. This new route to saturated branched-chain fatty acids represents a viable alternative to this important class of compounds, which are now obtained primarily as minor co-products from the industrial production of dimer acids.

Technical Abstract: Branched-chain saturated fatty acids have potential as oleochemical intermediates since they have better oxidative stability than linear unsaturated fatty acids and have better low-temperature properties than linear saturated fatty acids. Previous studies in converting unsaturated fatty acids to branched-chain fatty acids (bc-FA) using clay catalysts have resulted in only modest yields and conversions. Recent reports, however, have suggested that certain zeolites can be effective catalysts for converting unsaturated fatty acids to branched-chain fatty acids in higher yields and conversions. In this work, we examined the scope and potential of the zeolite-catalyzed synthesis of branched-chain fatty acids starting from readily available monounsaturated linear fatty acids. Our results show that common unsaturated fatty acids such as oleic acid can be converted to branched-chain isomers using modified Ferrierite zeolite catalysts in high conversions (98%) and high selectivity (85%) and that the zeolite catalysts are reusable for at least three cycles. The positions of branching (methyl) on the fatty acid chain were determined from the GC-MS spectra of the picolinyl esters of the bc-FA.