Catalytic Conversion of Epoxidized Palm Fatty Acids through Oxirane Ring Opening Combined with Esterification and the Properties of Palm Oil-Based Biolubricants
Jeerati Ob-eye, Kanokwan Chaiendoo, Vorranutch Itthibenchapong
Abstract
In this work, biolubricants were produced by a two-step catalytic conversion of a palm-based fatty acid mixture. First, the epoxidation of fatty acids with H2O2 solution was performed at 45 °C for 4 h; it was catalyzed by performic acid generated in situ, and the reaction produced epoxidized fatty acids in >98% yield. Subsequently, the ester-based biolubricant product was obtained through a dual process of oxirane ring opening and esterification with 2-ethyl-1-hexanol in a temperature range of 70–130 °C and a reaction time of 2–6 h, with tetrafluoroboric acid used as a catalyst. The optimal synthesis temperature was 110 °C at a reaction time of at least 4 h, as these conditions resulted in 100% conversion. The highest yield of monoesters, one of the main products, was 70.5%. The catalytic performance remained consistent for 6 h, with a total ester-based biolubricant yield of 97.6%. The mono- and di-esters, the main components of the biolubricant, exhibited kinematic viscosities of 46.6 cSt (40 °C) and 7.6 cSt (100 °C), a viscosity index (VI) of 128, and a pour point (PP) of −43 °C. Ketone esters became the main components of the biolubricant products when high-temperature synthesis conditions were used. The viscosity and flow properties of ketone esters were strongly modified: they had an excellent VI of 159 and a PP of 3 °C. Biolubricants with these desirable and tunable properties can potentially be used as a base stock for wide temperature range utilization and as biodegradable-grade lubricants for industrial applications such as hydraulic fluids, turbine oils, and compressor oils.