We recently developed a method to separate a mixture of fatty acids into their individual components by passing them through a membrane. The significance of this work is that although vegetable oils and their fatty acids represent the largest source of biorenewable feedstock for the chemical industry, the impurity of fatty acids limits their applications. Fatty acids are readily cleaved from glycerol to yield a mixture of five or more fatty acids depending on the original oil, but the purification of the fatty acids is very expensive. For instance, soybean oil is composed of a mixture of 5 different fatty acids, and separating these fatty acids from each other is expensive and not possible on an industrial scale. We developed a method to separate this mixture of five fatty acids into pure fatty acids by passing them through a membrane. An amine is added to the fatty acids to form a salt, these salts have different sizes and shapes and can be separated by a nanoporous membrane based on polydicylopentadiene.  These membranes are easy and inexpensive to fabricate from commercially available starting materials, and they possess pores on the subnanometer to nanometer size scale. The salts of the fatty acids have sizes that are similar to the size of the pores, so the salts have different flux through the membranes. When pressure was applied, the value for the flux was similar to that desired for industrial applications. One critical aspect of this work is that the separation is based on the size of the salts and these sizes can be adjusted by the choice of amine. Thus, the separation to retain a fatty acid can be readily optimized by testing different amines.

Simple separation of fatty acids using an organic nanofiltration membrane

246th National Meeting (2013)

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