Browsing by Author "Temu, A. K."
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Item The effects of pre-treatment and refining of high free fatty acid oil on the oxidation stability of biodiesel(Taylor & Francis, 2017) Kombe, G. G.; Temu, A. K.Although non-edible oil feedstocks with high free fatty acid (FFA) are potential feedstocks for biodiesel production, their utilization may require refining or pre-treatment prior to the production of biodiesel by alkali catalyzed transesterification. In this study, the crude Jatropha curcas oil with 4.54% FFA was either refined (neutralized, deodorized, and fully refining) or pre-treated (acid esterifying and glycolysis) to lower the FFA to less than 1% prior to biodiesel production by homogeneous base catalyzed transesterification. The study revealed that the oxidation stability of the biodiesel varies significantly with the method of either refining or pre-treating the FFA in oil. It was further observed that the biodiesel from re-esterified oil presented the greatest stability, followed by the biodiesel from neutralized, deodorized, acid pre-treated, and fully refined oil in that order. Biodiesel produced from fully refined and acid esterified oil showed the poorest oxidation stability and fail to meet the minimum required induction time of 6 h and 3 h as recommended by the EN 14214 and ASTM D6751 standards, respectively. Both neutralized and re-esterified oil present superior biodiesel oxidation stability with oxidation induction time 8.18 h and 8.24 h, respectively. Although pre-treatment and refining process lowers the FFA in the oil to less than 1% and produces biodiesel with more than 96.5% fatty acid methyl ester content content, the addition of antioxidants in the biodiesel from deodorized, acid esterified, and fully refined oil is inevitable due to poor oxidation stability of the produced biodiesel.Item Physico-chemical properties of biodiesel from jatropha and castor oils(Gazi University, 2012) Okullo, Aldo; Temu, A. K.; Ogwok, P.; Ntalikwa, J. W.Biodiesel is becoming prominent among the alternatives to conventional petro-diesel due to economic, environmental and social factors. The quality of biodiesel is influenced by the nature of feedstock and the production processes employed. High amounts of free fatty acids (FFA) in the feedstock are known to be detrimental to the quality of biodiesel. In addition, oils with compounds containing hydroxyl groups possess high viscosity due to hydrogen bonding. American Standards and Testing Materials, (ASTM D 6751) recommends FFA content of not more than 0.5% in biodiesel and a viscosity of less than 6 mm2/s. The physico-chemical properties of jatropha and castor oils were assessed for their potential in biodiesel. The properties of jatropha and castor oils were compared with those of palm from literature while that of biodiesel were compared with petro-diesel, ASTM and European Standards (EN14214). Results showed that high amounts of FFA in oils produced low quality biodiesel while neutralized oils with low amounts of FFA produced high quality biodiesel. The quality of biodiesel from jatropha and castor oils was improved greatly by neutralising the crude oilsItem Steam deacidification of high free fatty acid in jatropha oil for biodiesel production(American Chemical Society, 2017) Kombe, G. G.; Temu, A. K.Although non-edible oil feedstocks are available at a lower price than edible oil feedstocks, their high free fatty acid (FFA) content hinders their direct utilization in the production of biodiesel by alkali-catalyzed transesterification. In this study, the steam deacidification process has been employed in reducing the FFA of crude Jatropha oil before alkali-catalyzed transesterification. The response surface methodology (RSM) established on the central composite design (CCD) was used to model and optimize the steam deacidification efficiency under two process variables, namely, temperature and amount of steam. The optimum conditions for deacidification efficiency of 98.74% were found to be the temperature of 235 °C and the amount of steam of 3.4% (w/w) of the feedstock. These conditions reduce the high FFA of crude Jatropha oil from 4.54 to 0.09%, which is below 1% recommended for base-catalyzed transesterification. The deacidified crude Jatropha oil was then transesterified using a homogeneous base catalyst and gave a conversion of 97.45%. The tested fuel properties of biodiesel, such as viscosity at 40 °C, acid value, gross calorific value, iodine value, fatty acid methyl ester (FAME) content, and density at 15 °C, were found to be comparable to those of ASTM D6751 and EN 14214 standards.Item Transesterification reaction kinetics of jatropha oil for biodiesel production(2011) Okullo, A.; Temu, A. K.; Ntalikwa, J. W.Biodiesel, defined as the monoalkyl esters of vegetable oils and animal fats, is becoming prominent among alternatives to conventional petro-diesel due to economic, environmental and social factors. Transesterification is the most preferred method of biodiesel production. Knowledge of transesterification reaction kinetic enables prediction of the extent of the chemical reaction (or the conversion) at any time under particular conditions. It is also essential in the optimization of operating conditions in industrial applications and in the design of reactors for biodiesel production. In this study, transesterification of jatropha oil with methanol was carried out in a well mixed reactor at different agitation speeds (600-900 rpm) and temperatures (35-65 oC) using sodium hydroxide as a catalyst. The methanol to oil molar ratio of 6:1 was used and catalyst loading was 0.5% weight of oil. Mass transfer controlled state was assumed to be minimal using the above agitation speeds. A second order kinetic model was used to determine the reaction rate constants. The goodness of fit predicting the moles of methyl ester in the reaction products was determined by correlation coefficient (R2) and least square curve fit. The forward reactions were the most important as revealed by the rate constants.