Trimethylolpropane based biolubricant synthesis from sweet almond (Prunusamygdalus dulcis) seed oil for use in automotive applications

Abstract

This paper presents the synthesis of a sweet almond oil-based trimethylolpropane biolubricant and the evaluation of its temperature-dependent viscosity properties. The oil was converted into biodiesel by the transesterification process after extraction, refining, and acid-alkaline transesterification. After, biolubricant was produced by further transesterifying biodiesel with trimethylolpropane at 105 oC at a ratio of 3.9:1 for a 60-minute reaction time with a potassium hydroxide catalyst concentration of 1 wt.%. According to the American Standard Test Methods (ASTM), the biolubricant's pour point and index of viscosity were determined to be -4 oC and 267.50, respectively. The measured viscosities were 42.80, 30.18, 21.39, 12.25, and 8.90 cSt. at 30, 40, 60, 80, and 100 °C, demonstrating an inverse relationship between temperature and lubricant viscosity. The difference between the FTIR spectra of the biodiesel and the biolubricant at 1755.74 versus 1743.96 cm-1 verifies the ester group. Sweet almond oil has a higher iodine content than unsaturated glycerides (9.52 g of iodine per 100 g of oil sample) and contains 53.478% more unsaturated fatty acids than saturated fatty acids and 71.725% unsaturated fatty acids for biolubricant. Linoleic acid made up the majority of the fatty acids in the oil and synthetic biolubricant, with percentages of 31.44 and 45.93%, respectively. The biolubricant and oil from sweet almonds contained palmitic, linoleic, and oleic acids. The biolubricant has the potential to function as light gear oil for automobiles because its characterization results correlate favorably with the ISO VG-32 criteria