Preparation of wax esters from palmitic acid for superhydrophobic coating

Abstract

Based on the desire for value-added palm oil products, the conversion of palm oil to wax esters consisting of between 38 and 44 carbon atoms has gained in attention. These important wax compounds are derived from the esterification of long-chain alcohols and fatty acids. This work focused on the synthesis of wax esters via reduction and esterification. Palmitic wax was prepared from palmitic acid (PA) and cetyl alcohol (CA), the latter produced from reduction of PA using lithium aluminium hydride, via esterification using dicyclohexylcarbodiimide and 4-dimethylaminopyridine catalysts. Extraction of the CA product was evaluated using various solvents (methanol, ethanol, isopropyl alcohol, and methyl ethyl ketone). For the palmitic wax extracted at a CA: solvent (v/v) ratio of 1:2 with methanol, ethanol (W-CA-EtOH2), and methyl ethyl ketone, the esterification gave a sufficiently high wax yield of 48.1, 71.0, and 56.7 %, respectively. The palmitic wax was characterized by Fourier transformed infrared spectroscopy, X-ray diffractometry, and ¹³C nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. When applied as a paper coating, the palmitic wax W-CA-EtOH2 exhibited superhydrophobic behavior with high water contact angle (161.4°) and possessed a high degree of water resistance with a low water absorption of 0.43.