The Preparation And Kinetic Study Of Biodiesel From Jatropha Oil Under Subcritical Condition

With the rapid development of country's economy, the demand for fuel consumption has increased dramatically. As a future prospective fuel, biodiesel is made from renewable sources,consists of the simple alkyl esters of fatty acids.Biodiesel as an alternative fuel for diesel engines is becoming increasingly important due to dim inishing petroleum reserves and the rising awareness of environmental protection. Bio-diesel produced will be of great significance for improving the economic efficiency and reducing environmental pollution. However, the expensive cost of biodiesel restricts its usage and comercialized. Using cheaper feedstock is a major way to reduce the cost of the biodiesel. To develop biodiesel productions with non-food oil crops,which accords with the situation of our country.The production of biodiesel can be divided into one-step process and two-step process. Compared with the two-step process,one-step process has fewer steps, short reaction time, etc.,but the acid value of the feedstock is required to be lower than 1mgKOH / g。This study made an experiment on the transesterification of Jatropha Curcas Oil and subcritical methanol with p-toluene sulphonic acid as catalyst to prepare methyl esters (biodiesel). By measuring the acid-value of raw materials, acid-catalyzed to produce biodiesel.was used .The effects of reaction temperature,reaction time,amount of catalyst and alcohol to oil molar ratio for reaction were stuided. Experimental data of single-factor showed that the best single factor in all experimental conditions were as follows: temperature 170℃, oil-alcohol molar ratio of 35:1, reaction time 30 minutes, catalyst amount 0.75% (representing the mass fraction of heavy oil). According to the results of single-factor, the cross-testing was designed. The results of orthogonal test showed that the best bio-diesel preparation conditions were as follows: the reaction temperature 170℃, oil-alcohol molar ratio 40:1, reaction time 30 minutes, the amount of catalyst of 0.75% (representing the mass fraction of heavy oil), under the conditions bio-diesel conversion rate was 93%. The biodiesel fuel obtained from this technology had a similar specification with diesel fuel. Main properties of the biodiesel were comparable with that of ASTMPS121-99(USA) and No.0 diesel oil.The kinetics of biodiesel's one-step production process from Jatropha oil in subcritical methanol was discussed. By measuring the conversion rate of free fatty acid (FFA) and triglycerides (TG) under different temperatures, the macro kinetic equations of FFA esterification and triglycerides transesterification with subcritical methanol respectively, was obtained based on the simplified kinetic model. The result showed that, within the range of the experimental condition, the kinetic equations of esterification and transesterification could describe these two reaction processes very well respectively.The esterification reaction order was 0.5, the reaction activation energy was 16.21 kJ·mol-1, and the pre exponential faction was 5.61 L·mol-1·min-1. The transesterification reaction order was 1, the reaction activation energy was 25.32 kJ·mol-1, and the pre exponential faction was 29.69 L·mol-1·min-1.