Influence of Catalyst Type on Biodiesel Production Using Seed Oil of Jatropha Curcas

The use of biodiesel has grown dramatically during the last few years and is becoming a key component in the motor diesel pool because of its attractive features. In the present thesis, a comparison is made of catalysts (homogeneous basic - sodium hydroxide, potassium hydroxide; homogeneous acidic catalyst – sulphuric acid and heterogeneous catalyst – calcium oxide, magnesium oxide and zeolite) for methanolysis of indigenous Jatropha curcas seed oil. The variables studied were temperature, the types and the catalyst concentration by weight of jatropha curcas seed oil, the reaction time and the methanol: vegetable oil molar ratio, while the response was biodiesel yield. In addition, the Jatropha curcas seed oil as well as the biodiesels produced were evaluated for quality characteristics. These were conducted using standard analytical methods. The physicochemical properties recorded for the Jatropha curcas seed oil were: saponification value 195.3mg/g, iodine value 104.13mg/g, acid value 3.86mgKOH/g, density 918kg/m3 @ 28oC, kinematic viscosity 42.6mm2/s, refractive index 1.465 and % free fatty acids 1.92%. Nearly 80% yields were obtained for the basic homogeneous base catalyst – NaOH, KOH and NaOH/KOH mixture (78%) when the reaction was conducted at 60oC, 6:1 methanol-oil molar ratio and 2%w/w catalyst concentration for 30minutes. The maximum biodiesel yield of nearly 30% were achieved for the heterogeneous catalyst – CaO, MgO and zeolite at 60oC, 25: 1 methanol-oil molar ratio and 0.5%w/w catalyst concentration for 48hrs. The homogeneous acidic catalyst produced a 25.2% biodiesel yield at 60oC, 35:1 methanol-oil molar ratio and 1% w/w catalyst concentration for 48hrs. The fuel properties of the biodiesel produced from the indigenous Jatropha curcas seed oil were density 881.4 - 886kg/m3, total sulphur 0.02-0.05ppm, kinematic viscosity 4.2 - 6.5mm2/s, pour point -3 to 2oC, carbon residue 0.11 - 0.0.2%wt, total acid 0.14 - 0.37mmKOH/g, total ash 0.001 - 0.023%wt, cetane index 54.55 - 56.30, basic water and sediment 0.10%vol and sodium metal content 0.78 – 6.33ppm. From the results it was found that the biodiesel fuel produced, whether by homogeneous basic catalyst or homogeneous acid catalyst, was within the recommended standards of biodiesel fuel except for the kinematic viscosity of 6.5mm2/s, density of 886kg/m3 and sodium metal content of 6.33ppm which deviated marginally from the ASTM recommended limits.
A Thesis Submitted to the School of GRADUATE STUDIES, Kwame Nkrumah University of Science and Technology, Kumasi, in Partial Fulfilment of the Award of MSc. Degree in Analytical Chemistry, .