KINETIKA PRA-PENCUCIAN DENGAN CaO PADA PENCUCIAN KERING (DRY WASHING) BIODIESEL

Biodiesel is the most promising alternative fuel to substitute petroleum diesel because of its environmentally advantageous and renewability. The main chemical process to produce biodiesel is transesterification of triglyceride and methanol with alkaline as catalyst which produce glycerin as side product. After glycerin removals, biodiesel still contains the impurities including remaining reactants, alkaline catalyst, and glycerin. Therefore further process is needed to meet biodiesel standard ASTM D8526, EN 14048, or SNI 04-7182-2006. Several studies have found that rice husk ash (RHA) as byproduct of the rice processing has a promising capacity for biodiesel dry washing removing FFA, soap, remaining methanol, and glycerin due to its high content of silica. However it was still unsatisfactory for removing non-polar component such as the remaining triglyceride. To enhance the performance of triglyceride removal, CaO was added in pre-washing step for biodiesel dry washing using RHA. The objective of this work was to study the purification of biodiesel from refined palm oil using rice husk ash (RHA) at concentrations of 5% (w/w) with pre-washing using CaO at concentrations of 0.1%, 0.5%, 1%, 2% and 5% (w/w). The result was compared with non-pre-washed biodiesel. The effect of prewashing temperature at 30, 45, 65, 75oC, and stirring speed at 150, 300, 600 rpm were also examined. In a concentration of 1% CaO at 65oC and 300 rpm, pre-washing step using CaO showed optimum results enhancing the triglyceride removal capacity of dry washing biodiesel using 5% RHA. The remaining free and total gliserol contents in biodiesel were 0.0138% and 0.3760% respectively. Three simultaneous processes: glycerin adsorption over CaO, glycerides adsorption over CaO, and conversion of remaining non-polar glycerides into polar component by transesterification reaction were included into mathematical model proposed in the present study.The proposed model was apparently close to the experimental data