Browsing by Author "Temu, Abraham K."

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    The effects of pre-treatment and refining of high free fatty acid oil on the oxidation stability of biodiesel
    (Taylor & Francis, 2017) Temu, Abraham K.; Kombe, Godlisten G.
    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, 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.
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    Gas chromatographic determination of glycerol and triglycerides in biodiesel from jatropha and castor vegetable oils
    (Trans Tech Publications Ltd., 2013) Okullo, Apita, Aldo; Ogwok, P; Temu, Abraham K.; Ntalikwa, J.W.
    Monoacylglycerols and diacylglycerols are intermediate compounds in biodiesel which result from incomplete transesterification reaction during biodiesel production. Traces of free glycerine and partially reacted triacylglycerols are also found in biodiesel. These contaminants cause serious operational problems in engines, such as engine deposits, filter plugging, and emissions of hazardous gasses. Increased levels of these contaminants in biodiesel compromise quality which is vital for commercialisation of this product. In this work, levels of free glycerine and total glycerine in jatropha methyl ester (JME) and castor methyl ester (CME) were determined using gas chromatography (GC) equipment. Amounts of free and total glycerine in JME and CME were generally high compared to the ASTM D6751 and EN14214 recommended values. Free glycerine from JME was 0.1% wt compared to 0.02% wt (ASTM D6751) and 0.01% wt (EN14214) values whereas the total glycerine from JME was 2.96% wt compared to 0.24 %wt (ASTM D6751) and 0.21% wt (EN14214). These discrepancies could have resulted from insufficient purification of the product and incomplete conversion or due to the high temperature associated with GC analysis that might have caused pyrolysis or thermal degradation of certain lipid components. Castor methyl ester free glycerine was 0.14% wt while total glycerine was 13.21% wt. This can still be explained by the same reasons given for JME. Thermal decomposition of lipid components in a GC could have interfered with the summative mass closure calculations that were done to determine the total composition of the biomass.
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    Low temperature glycerolysis as a high FFA pre-treatment method for biodiesel production
    (Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Lee, Keat Teong
    A novel low temperature glycerolysis process for lowering free fatty acid (FFA) in crude jatropha oil for alkali cata-lyzed transesterification has been developed. The response surface methodology (RSM) based on central composite design was used to model and optimize the glycerolysis efficiency under three reaction variables namely; reaction time, temperature and glycerol to oil mass ratio. The optimum conditions for highest glycerolysis efficiency of 98.67% were found to be temperature of 65°C, reaction time of 73 minutes and 2.24 g/g glycerol to oil mass ratio. These conditions lower the high free fatty acid of crude jatropha oil from 4.54% to 0.0654% which is below 3% recommended for alkali catalyzed transesterification. The pre-treated crude jatropha oil was then transesterified by using homogeneous base transesterification resulting to a conversion of 97.87%. The fuel properties of jatropha biodiesel obtained were found to be comparable to those of ASTM D6751 and EN 14214 standards. The process can also utilize the crude glycerol from the transesterification reaction, hence lowering the cost of biodiesel. The glycerolysis is easier implemented than acid esterification thereby avoiding the need for neutralization and alcohol removal step.
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    Pre-treatment of high free fatty acids oils by chemical re-esterification for biodiesel production—a review
    (Scientific Research, 2013) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan M.; Mrema, Godwill D.; Kansedo, Jibrail; Lee, Keat Teong
    Non edible oil sources have the potential to lower the cost of biodiesel. However, they usually contain significant high amounts of free fatty acids (FFA) that make them inadequate for direct base catalyzed transesterification reaction (where the FFA content should be lower than 3%). The present work reviews chemical re-esterification as a possible method for the pre-treatment of high FFA feedstock for biodiesel production. The effects of temperature, amount of glycerol, type and amount of catalyst have been discussed. Chemical re-esterification lowers FFA to acceptable levels for transesterification at the same time utilizing the glycerol by product from the same process. Further researches have been proposed as a way forward to improve the process kinetics and optimization so as to make it more economical.
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    Steam deacidification of high free fatty acid in Jatropha oil for biodiesel production
    (ACS Publications, 2017) Temu, Abraham K.; Kombe, Godlisten G.
    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.