Continuous transesterification of jatropha oil via microwave irradiation

• Main Author: Lee, Carlo Luis N.
• Format: text
• Language: English
• Published: Animo Repository 2012
• Subjects: Transesterification; Jatropha; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6789
• Institution: De La Salle University

In the production of biodiesel, the most commonly used process is the alkali transesterification process due to its inherent advantages such as the availability of the reactants involved and the speed of the reaction. However, most studies and current methods in employing the alkali catalyzed transesterification makes use batch processes, and in order to bridge the gap between the laboratory and commercialization in a better manner, several researches have been endeavored making use of solid catalysts. However, this is still not feasible and hence, this study has made use of the alkali transesterification in conjuction with continuous flow processes. In this study, a continuous flow reactor had been designed by modifying the reactor design of Lertsathapornsuk et al. (2008). The reactor is made of quartz, and has a length of 200.00 cm, with an inside diameter of 0.25 inches, and a total volume of 63.34 cc. This was coiled 7 times in order to have a small enough coil diameter to keep the whole reactor within the center of the microwave cavity. Relying solely on gravitational force, the setup was able to achieve a maximum constant flow rate of 9.1 ml/min. To maintain stable temperature within the reactor, a thermocouple was placed in the center of the microwave cavity and made use of a PID controller. The basis for the selection of parameters used in the study was taken from preliminary batch experiments. The study made use of two-step acid-alkali transesterification. The parameters being tested were catalyst type, catalyst loading, alcohol to oil ratio, temperature, and time after steady state before sampling was conducted. However, preliminary experiments had shown that a 1.0% w/w of alkali catalyst should be used. The resulting Jatropha Methyl Esters (JME) had % FAME ranging from 98.48% to 99.26%, and % yields ranging from 88.92% to 94.57%. The Jatropha L. Curcas oil was sourced from Philforest Corporation, and had an initial FFA level of about 1.89%, and was pre-esterified using sulfuric acid to below 1%. After esterification, the oil was then run through the continuous flow setup and to iv determine steady-state conditions, the refractive index was measured at intervals. Once steady-state had been achieved, the product was collected. The biodiesel was weighed in order to calculate the % yield, and analyzed via gas chromatography to determine % FAME. All fuel properties were found to conform to ASTM standards for biodiesel but were beyond limits for PNS guidelines for Coco Methyl Esters with regard to kinematic viscosity and acid value. It had also been found out that temperature exhibited a positive correlation with respect to % yield, and that the catalyst type did not affect either % FAME, or % yield. But it was very noticeable that when sodium hydroxide was used, and temperature was increased from 50 to 60 degrees Celsius, the amount of time required to reach steady state was reduced by 50%, but when potassium hydroxide was used, the time to reach steady state was reduced by only about 22%. Moreover, comparisons between batch microwave and continuous microwave transesterification processes have shown that the values for the reaction time in the batch process of 3 and 9 minutes did not affect the % yield, or % conversion much, which could be explained by the continuous flow process. The continuous flow process showed that at three minutes, the reaction had already reached steady state conditions in most runs; hence, there would be no difference between 3 minutes and any value beyond that.