Thesis (M.Sc.)--Chulalongkorn University, 2011

The present thesis investigated the effect of nitrogen bubbles on transesterification of plam oil in a fixed bed reactor. Dolomite, a natural calcium rocks was used as the heterogeneous catalyst. The catalysts were prepared by physical mixing technique. The catalyst was formulated with a size of 2x5 mm. After that, the catalyst was calcined at 800 ℃ for 6 h before used in transesterification. In the non-nitrogen gas feed system, the effect of types of palm oil, effect of molar ratio of methanol to oil, effect of catalyst extrudates size and effect of the addition of methyl ester were investigated. The optimum reaction condition of transesterification with the presence of nitrogen bubbles was studied. The FAME yield of 96.7% was achieved under the optimal conditions. The optimal reaction conditions were, reaction temperature was 60 ℃, nitrogen gas feed rate was 30 mL/min, molar ratio of methanol to oil was 30:1 and total flow rate of reactants was 2.5 mL/min. The stability of transesterification of the nitrogen gas feed system was compared with non-nitrogen gas feed system. The decrease of the FAME yield was observed in case of transesterification in non-nitrogen gas feed system. It should be due to the glyceride derivatives covered on the catalyst surface and resulting to the deactivation of catalyst. The FAME yield of transesterification with the presence of nitrogen bubbles was stable throughout the time on stream of 18 h. It should be due to the feed of nitrogen gas can leach glyceride derivative on the catalyst surface which prevents the deactivation of catalyst. The value of activation energy of transesterification in the presence of nitrogen gas was 38.6 kJ mol⁻¹.