Browsing by Author "Mrema, Godwill D."

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    High Free Fatty Acid (FFA) Feedstock Pre-Treatment Method for Biodiesel Production
    (Trans Tech Publications, Switzerland, 2011) Kombe, Godlisten G.; Temu, Abraham K.; Rajabu, Hassan; Mrema, Godwill D.
    Biodiesel is an alternative fuel for engine and other appliances that is obtained by transesterifying vegetable oils or other materials largely comprised of triacylglycerols with monohydric alcohols to give the corresponding mono-alkyl esters. The quality of feedstocks for the biodiesel production dictates the method of its production and quality. Based on the initial amount of minor components in feedstocks, a process comparison of acid pre-treatment and caustic pretreatment of feedstock for alkali transesterification was done. Acid pre-treatment was carried out with 0.60 w/w methanol-to-oil ratios in the presence of 2% w/w H 2 SO 4 as an acid catalyst in 2 h reaction at 60 °C. In caustic pretreatment process, the same amount of oil was neutralized with the required amount of sodium hydroxide based on the initial amount of free fatty acid and gums in the oil. The acid pretreatment process gives a 4% loss in feedstock compared to 20% from the neutralization process. The yields 96% and 94% of biodiesel from acid pretreated and caustic pretreatment feedstock were obtained respectively. The oxidation stabilities of biodiesel from acid pretreatment and neutralized feedstock were 1.12h and 3h respectively. The biodiesel from acid pretreatment oil could not pass the ASTM standard.
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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 catalyzed 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℃, 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.