Analytical methods Fatty acids composition of the used jatropha oil was determined using gas liquid chromatographic analysis of the oil ethyl esters. Modification of the oil to its ethyl esters was made using 2 % H2SO4 as catalyst in the presence of dry ethyl alcohol in excess. The chromatographic analysis was made using Hewlett Packard Model 6890 Chromatograph. A capillary column 30 m length and 530 μm inner diameter packed with Apiezon®was used. Detector temperature, injection temperature and the column temperature were 280 ºC, 300 ºC and 100 to 240 ºC at 15 ºC/min, respectively. Purity of glycerol was determined using the HPLC Shimadzu LC 10 with a refractive index detector. The used column was Shim- Pack SCR– 10N (7.9 mm × 30 cm) (Shimadzu column). The mobile phase was water with flow rate of 0.5 mL/min at 50 ºC. Biodiesel properties such as viscosity (Knothe and Steidley, 2005), flash point, pour point, cloud point, carbon residue, acid value and calorific value were carried out by Petroleum Institute at Egypt using ASTM standard methods.
Bench scale experiment Biodiesel was produced based on bench scale by transesterification of jatropha oil according to the optimum reaction conditions obtained from laboratory study with maximum yield of 98 % of methyl esters. Transesterification of 2 kg of jatropha oil was carried out in 4 L round flask placed in an adjusted temperature water bath. The reaction was performed using 6:1 molar ratio of alcohol to oil and catalyst concentration of 1 % by weight of the oil at 65 º C under reflux condenser with mechanical stirrer as illustrated in Fig. 1. After one hour reaction time, the reaction mixture was carefully transferred to a suitable separating funnel. Two layers were separated after about 6 h; the upper layer is methyl esters and the lower one is the glycerol containing layer.
Pilot scale process Transesterification of 100 L jatropha oil was carried out on the pilot scale with the same chemical conditions used in the bench scale experiment. The reaction was carried out in an enameled reactor of 150 L capacity equipped with an anchor stirrer and provided with temperature, pressure and stirring speed controllers. Jatropha oil was loaded to the reactor and preheated. The solution of the methanol and sodium hydroxide was prepared and added to the reactor. The reactants