Biolubricant synthesis from waste cooking oil via enzymatic hydrolysis followed by chemical esterification

BACKGROUND: Lubricants manufactured conventionally from non-renewable mineral oil resources are not biodegradable and are liable to cause adverse environmental impacts. Biodegradable vegetable oils present a promising lubricant feedstock alternative. Waste cooking oil (WCO), which otherwise finds no immediate potential utilization can be successfully used to synthesize bio-lubricant. A novel synthetic method was developed by using the two-step process of C. rugosa lipase-mediated hydrolysis of WCO to free fatty acids (FFA) followed by Amberlyst 15H esterification of FFA with octanol. The octyl esters produced was the desired biolubricant. RESULTS: The effect of different physico-chemical parameters like temperature, catalyst loading, agitation speed, molar ratio of octanol : FFA and the presence of different desiccants on the esterification reaction was examined. The optimum conditions to get maximum yield of biolubricant in minimum time were, octanol : FFA molar ratio = 3 : 1, temperature = 80 degrees C, catalyst = 2 g and desiccant (preferably silica gel powder) = 50% weight of FFA. Fourier transform infrared spectroscopy confirmed that the product formed was ester. CONCLUSION: Biolubricant (octyl esters) was prepared efficiently from WCO by the two-step process developed. This novel approach represents a viable means of producing lubricants from wastes which are renewable in nature and can be an alternative to non-renewable mineral oil feedstocks. (C) 2012 Society of Chemical Industry