Layered Double Hydroxides for the Catalytic Isomerization of Linoleic Acid to Conjugated Linoleic Acids (CLAs)

Several hydrotalcite-type compounds with different divalent (Mg 2+, Ni 2+, Cu 2+, Zn 2+) and trivalent (Al 3+, Cr 3+) cations and different ratio compositions were tested for the isomerization of linoleic acid in order to study their role on the obtention of specific conjugated linoleic acids (CLAs) with anticarcinogenic and nutritional properties. This is a complex reaction due to the high number of possible isomers of linoleic acid together with the significant competition of the isomerization reaction with other secondary undesired reactions. All catalysts showed very high conversions of linoleic acid, but condensation products were mainly obtained, especially for the hydrotalcite-type compounds with higher Mg/Al ratios due to their higher Br？nsted basicity and for the catalysts with higher Ni 2+ content or with the presence of Cu 2+, Zn 2+ in the layers because of the influence of the higher acidity of these cations on the Br？nsted basicity of the hydroxides. The best results were achieved for the catalysts with Mg/Al ratio around 2.5–3, resulting in 29–38% of selectivity to the identified CLAs. View Full-Tex