Optimization and lubrication properties of Malaysian crude palm oil fatty acids based neopentyl glycol diester green biolubricant

Abstract

Green biolubricant base stock based on crude palm oil fatty acids (CPOFAs) was produced through acid catalyst esterification of palm oil fatty acids with neopentyl glycol (NPG). The response surface methodology (RSM) of D-optimal design was employed to optimize the esterification process. The resultant polyol ester, crude palm oil fatty acids-NPG diester (CPOFAs-NPGDE) was evaluated its lubrication properties. The optimal condition for the esterification process was obtained at CPOFAs:NPG molar ratio of 2.26:1, 1.12% H2SO4 catalyst, reaction temperature of 138 °C for 4.79 h reaction time, respectively. The optimal CPOFAs-NPGDE produced was 87.6% yield with 100% diester selectivity. The resultant ester showed good lubrication properties with oxidative stability temperature at 184 °C, pour point at 10 °C, flash point at 235 °C and viscosity index of 190. Tribological tests showed that COFAs-NPGDE has shown low coefficient friction of hydrodynamic regime of 0.20 at 40 °C and 0.19 at 100 °C and comparable with some commercial lubricants. Rheological tests show that CPOFAs-NPGDE can be classified as a Newtonian fluid with good lubrication properties within ISO VG 46 lubricant grade. This make it plausible to be used for green industrial lubrication applications such as hydraulic oil, compressor and turbine fluids.