Author: Ocholi Ocheje
Department: Chemical Engineering
Affiliation: Nnamdi Azikiwe University Awka
The synthesis of jatropha and sesame oil polyol esters as novel biodegradable base stock for lubricant production was conducted via chemical transesterification of their methyl esters with 2-ethyl-2- (hydroxymethyl)- 1 ,3-propanediol, trimethylolpropane (TMP)using calcium hydroxide (Ca(OH)2) catalyst. Both jatropha and sesame seeds were used as the precursors. The reactions were carried out under different temperatures (80 to 160°C) and methyl esters to TMP mole ratios (3:1 to 7:1). To maintain forward reaction, the ratios of Jatropha Methyl Ester (JME) and Sesame Methyl Ester (SME) to TMP above the stoichiometric ratios were used. Analysis of the reaction products was performed using Gas Chromatographywith a high temperature capillary column, operated at a temperature gradient of 6°C/min starting from 80°C to 340°C. Their physicochemical properties were obtained on the basis of ASTM standard methods in order to determine their suitability for lubricant application. Response surface methodology was used to optimize the process. The optimum conditions for the synthesis of JBL were obtained at 150oC, reactants mole ratio of 5.0 and 200 min while that for SBL were 150oC, mole ratio of 6.0 and 197.27 min. JBL and SBL containing 82.74 wt% and 79.70 wt% triesters were successfully synthesized under these conditions. The reaction was found to follow a second order reaction with an overall rate constant of 1.00E-01 (%wt/wt min ◦C)−1 for JBL and 1.40E-01 (%wt/wt min ◦C)−1 for SBL. The estimated activation energiesfor JBL and SBL were 13.57kJ/mol and 16.22kJ/mol respectively. JBL was found to have the following tribological properties: viscosity of 39.45 and 8.51 cSt at 40 and 100°C, respectively; viscosity index of 204, pour point of -7°C and flash point of 178°C. SBL had the following lubrication properties: viscosities of 35.55 and 7.66 cSt at 40 and 100°C, respectively; viscosity index of 193, pour point of -21°C and flash point of 196°C. Both lubricants complied with ISO VG 46 AND VG 22 standards and are ideally suitable for use in automobiles with minor modifications.The lubrication properties of these oil-based TMP esters indicated good potential as base stock in biodegradable lubricant formulation.
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