Decarboxylation of oleic acid using iridium catalysis to form products of increased aromatic content compared to ruthenium systems

The decarboxylation of 9-cis-octadecenoic (oleic) acid to aromatic and aliphatic hydrocarbons suitable as blend components for aviation fuel applications utilising ruthenium dodecacarbonyl [Ru3(CO)12] with a variety of other catalysts is presented. Due to the different relative rates of decarboxylation and hydrogenation/dehydrogenation, different product distributions are possible when the catalyst is varied. Chloro-1,5-cyclooctadiene iridium (I) dimer [(C8H12IrCl)2] gave a similar conversion to the ruthenium system but provided an altered product distribution. Aromatic contents of up to 35% were achieved in the iridium system, thereby providing a wider range of blending options for fuel producers. Additionally, both catalytic systems were found to decarboxylate high-oleic soybean oil fatty acids, giving a product of similar energy content to that obtained using high grade oleic acid.