Kinetics of hydrogenation of conjugated triene and diene with nickel, palladium, platinum and copper‐chromite catalysts

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Abstract
A mixture of methyl linoleate and alkali‐conjugated methyl linoleate was reduced with nickel, palladium, platinum and copper‐chromite catalysts. The course of hydrogenation was followed by gas liquid chromatography of samples withdrawn at intervals. Relative rate constants of reactants and inermediates were calculated by a computer. Conjugated linoleate was 10–18 times more reactive than methyl linoleate with all catalysts except platinum, which showed no selectivity at 60 C. At 150 C conjugated diene reacted four times faster than methyl linoleate with platinum catalyst. A conjugated diene‐to‐stearate shunt was observed with palladium and platinum catalysts. When β‐eleostearate was hydrogenated with the same catalysts, 50–97% of the triene was reduced directly to monoene with all catalysts except copper chromite, which selectively reduced conjugated triene to conjugated diene. On the basis of present kinetic data and previous knowledge about the mode of hydrogen addition to conjugated systems, a scheme has been proposed to account for the products formed during hydrogenation of methyl linolenate.