Synthesis of waxes from vegetable oil derived self-metathesized aliphatic esters

Abstract

Five wax ester oligomers of oleyl oleate (monomer to pentamer) produced from the self-metathesis of oleyl oleate derived from soybean oil were separated from the crude metathesis product by column chromatography. The purified compounds contained trans- and cis- configurations with a trans/cis ratio ranging from 3.6 for the monomer to 6.6 for the pentamer. The thermal transition behaviour of the oligomers as revealed by DSC was directly related to their trans- and cis- composition. Although odd/even effects presented predictable deviations, the crystallization and melting characteristics such as temperature and enthalpy scaled predictably with molecular size, and demonstrated a diminishing effect of incremental increases in monomer units. As determined by TGA, and except for the monomer which started to evaporate at ∼200°C, the oligomers presented excellent thermal stability with onsets of degradation higher than 360°C. The thermal transition characteristics of the monoester oligomers are comparable to commercial waxes and show potential for their use in a large range of wax applications ranging from viscous fluids to hard brittle solids. Furthermore, the thermal transitions occurred over narrow temperature spans, a feature that is useful for applications requiring collimated melting and crystallization ranges.