| dc.description.abstract | Croton oil was extracted from dry Croton megalocarpus seeds by a mechanical pressing machine then filtered. The optimum conditions for preparation of biodiesel from the oil through a two-stage chemical process in reactor were determined by varying parameters such as temperature, oil: alcohol mole ratio and amount of catalysts. The optimum conditions established were temperatures of 50 and 60 oC for esterification and transesterification, respectively, methanol: oil mole ratio of 3:1 and 6:1 for esterification and transesterification, correspondingly and a base catalyst mass of 1% (w/w) of the Croton oil for transesterification. The optimum reaction times established were 1 and 2 hours for transesterification and esterification correspondingly. A maximum yield of 88% biodiesel which had an acid value of 0.336 mg KOH/g, a density of 0.8858 g/cm3 and viscosity of 4.51 cs at 40 oC was obtained. The flash point of the biodiesel was greater than 200 oC, which made it safer to store and transport as compared to diesel which had a flash point of 65 oC. Both the cloud and pour points of the biodiesel were lower than that of petrodiesel, thus making its blends more suitable for lower temperature operations.
An enzymatic procedure for transesterification of Croton oil was also investigated. Croton biodiesel was prepared using commercial lipase from Thermomyces lanuginosus. The enzymatic transesterification of Croton oil produced a high yield of 93% biodiesel at optimum conditions of 35 oC, oil: alcohol molar ratio of 1:6, catalyst volume of 8% of croton oil and reaction time of 1 hour. All the physico-chemical properties of Croton biodiesel prepared using the two-stage chemical and commercial enzyme were found to be similar. Thin layer chromatography (TLC) analysis showed distinct differences between chromatograms of Croton oil and that of biodiesel while Gas chromatograph – Mass spectrometer (GC – MS) analysis showed that the Croton
biodiesel was composed of both saturated and unsaturated methyl esters with carbon atom chain lengths ranging from C-9 to C-19.
Extracellular lipase producing microorganisms were enriched by separately incubating 100 ml portions of sterile salt media (pH 8) containing 4% Croton oil inoculated with selected water and soil samples in a reciprocating shaker at 37 oC and 100 rpm for 10 days. The lipase producing microorganisms were then grown on agar plates containing minimum salt media and 4% Croton oil in an incubator. The lipase activities were screened by monitoring orange halos formed around the colonies on Rhodamine B/agar plates under ultraviolet (UV) light at 350 nm after 12 hours in an incubator. Pure colonies of lipase producing microorganisms were produced through submerged fermentation (SmF) in LB media for 48 hours in a reciprocating shaker at 37oC and 100 rpm. Aqueous solutions of lipase enzymes were obtained from fermentation mixture by collecting the supernatant liquid after centrifugation of the LB media solutions. TLC and GC-MS analysis showed that the extracted lipase solutions poorly catalysed transesterification of the Croton oil using methanol under the optimum conditions established for T. lanuginosus.
Emission, performance and combustion characteristics of Croton biodiesel blends were tested in a computerized direct injection single cylinder four stroke diesel engine test rig. The use of biodiesel blends led to a reduction in exhaust smoke emissions ranging from 10 to 41% at maximum engine load of 10 Kg as compared to petrodiesel, while a slight increase in NOx emissions was observed with increase in concentration of biodiesel in the blends. Similar general increase in brake thermal efficiency (BTE), temperature of exhaust gas emissions and fuel flow rate for both petrodiesel and biodiesel blends were observed with increasing engine load. The difference between BTE for petrodiesel and biodiesel blends ranged from 2 to 5%. The brake specific energy consumption (BSEC) decreased with increasing engine load for both petrodiesel
and biodiesel blends. Both engine pressure and heat released increased with increase in concentration of biodiesel in the blends. The difference in maximum engine pressure ranged from 1.05 bars at 0 Kg to 3.77 bars at 10 Kg load. The greatest difference in maximum engine pressure was recorded between petrodiesel and B50 blend.
The effects of antioxidants and storage on oxidation stability of Croton biodiesel and its blends were determined using PetroOxy equipment. The biodiesel and blends with and without antioxidants were stored in a metallic locker at room temperature for 8 weeks. The oxidation stability indices of the biodiesel and blends were monitored after every 2 weeks. The oxidation stability index for neat biodiesel depreciated at a very fast rate of 45% while that for biodiesel with 1000 ppm antioxidants depreciated by 16, 12 and 21% for pyrogallol (PYG), propyl gallate (PRG) and butylhydroxyanisole (BHA) correspondingly during the 8 weeks storage period. A more rapid decline in oxidation stability was therefore noted in biodiesel and blends without antioxidants than those with antioxidants and the oxidation stability rose with increase in concentration of the antioxidants. The use of appropriate concentrations of suitable antioxidants can therefore improve oxidation stability of biodiesel by preventing extensive and deleterious oxidative deterioration on storage. | en_US |
