Development of Magnesium Oxide–Zeolite Catalysts for Isomerization of Fatty Acids

Three zeolites were treated with magnesium nitrate hexahydrate (Mg(NO3)2⋅6H2O) salt to generate active magnesium oxide (MgO)–zeolite catalysts for the isomerization of oleic acid to give the iso-oleic acid (precursor of isostearic acid). Isostearic acid is a crucial component used in the formulation of bio-lubricants including cosmetic and personal care products. The treatment step is intended to poison (or neutralize) the external acid sites of the zeolites, thus inhibiting the formation of by-products (i.e., dimer fatty acids). The acid sites, crystallinity, thermal property, morphology and elemental composition of the zeolites before and after treatments were investigated by scanning electron microscopy, fourier-transform spectroscopy, thermogravimetric analysis, and x-ray powder diffraction. In addition, the effect of a calcination step after treatment was examined to determine if this step was necessary to obtain an active and stable catalyst. As expected, the higher the concentration of MgO on the zeolites, the less dimer was detected in the isomerization products, while the conversion of oleic acid and selectivity of iso-oleic acid remained at a relatively high level. This is promising because the MgO has deprotonated the external acids of the zeolites to generate a high purity isostearic acid that is potentially suitable for personal care products.