Transesterification Reaction

3.2 Catalytic Activity for Transesterification Reaction

The catalytic activity of the hydrated-calcined seashell catalysts has been evaluated in the transesterification of refined palm oil with methanol as model reaction. As mentioned above, the hydrated-calcined seashell was predominantly Ca(OH)2. The initial tests were conducted in a conventional reactor type, i.e. batch stirred tank reactor operated at 95oC with heat supplied from hot oil through the reactor wall. The reactor was pressurized with nitrogen up to 5 barg to allow the reaction taking place at increased temperature (95oC) while maintaining methanol in liquid phase. Fig. 6 shows biodiesel yields at various catalyst loadings for the transeterification of palm oil with methanol at

[10], even better for some cases. Buasri et al. [14] prepared CaO catalyst derived from oyster and Pyramidella shells, and was used as biodiesel production catalysts under microwave assisted transesterification of Jatropha curcas oil with methanol. The optimum conditions, which gave an oil conversion nearly 93% for both waste shell-derived catalysts, were reaction time 5 min, methanol to oil molar ratio 15, and catalyst loading 4 wt%. Ye at al. [27] prepared potassium sodium tartrate on alumina/silica support by a sol-gel process for transesterification of soybean oil. When the transesterification was carried out in a microwave reactor with a molar ratio of methanol to oil of 13 and a catalyst concentration of 8.0wt% at 65°C for 45 min, the highest biodiesel yield reached 96.5%. Hsiao et al. [28] found for transesterification of soybean oil over nano CaO assisted by microwave irradiation, the optimal reaction took place at a methanol to oil molar ratio of 7, amount of catalyst of 3.0 wt.% and temperature 60oC, achieving a conversion of 96.6% at 60 min. Interestingly, they observed effect of water in methanol on the catalyst and revealed that water adsorbed dissociatively on CaO surface to form hydroxyl groups and then produced more reactive methoxy anions. Similarly with the present work, water adsorption occurred during air exposure to form Ca(OH)2 as the main component in the hydrated-calcined seashell. Methoxide anion is strong basic and has high catalytic activity in transesterification reactions [1]. By this mechanism, therefore, the hydrated-calcined seashell effectively catalysed the palm oil conversion to biodiesel under microwave irradiation with yield of biodiesel close to equillibrium at a very short reaction time 5-10 minutes regardless catalyst