Utilization of waste cooking oil to synthesis of trimethylolpropane ester as hydraulic biolubricant

Abstract

Waste cooking oil is the remaining cooking oil after being used repeatedly and has undergone a heating process. As one of the largest palm oils producing countries in the world, most of the cooking oil products in Indonesia come from palm oil. Despite being a derivative of food products, disposing the waste cooking oil carelessly can potentially contaminate water and soil, as well as putting the river biota at risk. The best way to recycle waste cooking oil is by utilizing it as the basic material for vegetable lubricants or biolubricant. Transesterification process requires alcohol for the reaction. The alcohol type used in the methyl esters transesterification reaction is the trimethylolpropane which does not contain hydrogen atoms in beta carbon and prevents the formation of free fatty acids. In addition, trimethylolpropane also has good stability and flexibility for the product, so it is considered suitable for the synthesis of biolubricant. In the industrial sector, lubricants are useful for hydraulic machines to transfer and control power using liquid media. The expected hydraulic lubricant should have a high viscosity index. Before synthesis process, pretreatment is needed purify the oil. The pretreatment process with adsorption method use activated carbon can make the good-oil quality. The optimum temperature of adsorption process is 75°C. This temperature has the smallest FFA content (0.59%), smallest peroxide value (74.24 (Meq peroxide / Kg), and has absorbance value of 0.236 that closest to pure palm oil (0.097). In the transesterification process, time of reaction variation was carried out, and have the best time at 6 hours of reaction with 91% of conversion and 14.25 c.St of kinematic viscosity at 40°C. To make sure the reaction has occurred, FTIR spectrum has been test. Result of the test describe the reaction of TMP ester transesterification was considerably close to completion. TMP ester has lubricant specifications from the test. From the result, only the value of flash point and pour point are still classified as poor, in compared with SNI 7069.9:2016 and Maxoline Hydra ISO VG 15. Furthermore, value of flash point is still close to the commercial value in hydraulic lubricants, and value of pour point still can be used as a lubricant if using it in tropical climates.