The Dimerization of Oleic Acid with a Montmorillonite Catalyst I: Important Process Parameters; Some Main Reactions

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Abstract
Some important process parameters, e. g. amount of catalyst, water content, stirring intensity, reaction time and pH of the catalyst were studied in the dimerization of oleic acid using montmorillonite as catalyst. A yield limit seems to exist at about 60 wt% (dimers and trimers). The remaining 40 wt% of the reaction mixture (monomers) contain only small amounts of cis‐ and trans‐mono‐unsaturated fatty acids, the rest of it being unidentified products, which can hardly be dimerized and can not be hydrogenated with palladium on carbon. Infrared spectra of these monomers reveal also the presence of small amounts of γ‐stearolactone and an increase in the number of methyl groups, which is probably the result of skeletal isomerization, although structures like ‐CH = C (CH3)‐ are absent. The results indicate that a fairly large amount of saturated fatty acids is formed, most likely by hydrogen transfer. According to this assumption, dienoic acids must also be formed, which are readily dimerized to cyclic dimers. Thus the common assumption that the dimers of oleic acid obtained by this process are non‐cyclic, becomes improbable.