Abstract:
In this work, biodiesel was produced from esterification of oleic acid and short chain alcohols (methanol, ethanol, propanol, and butanol) catalyzed by Novozym 435 in a batch system at conditions: 45°C, oleic to alcohol molar ratio of 1:2, Novozym 435 loading at 5% (w/w of oleic acid), 250 rpm and 8 h of reaction time. Novozym 435 exhibited the best catalytic activity in the production of methyl oleate (FFA conversion of 94.82%). At 45°C, the rate constants (k values) for the production of methyl oleate, ethyl oleate, propyl oleate, and butyl oleate by Novozym 435 were 0.78, 0.52, 0.69 and 0.17 m3∙h-1∙kmol-1, respectively. The activation energies for the production of methyl oleate and ethyl oleate over the temperature range of 40 °C to 55 °C were 4.7 and 39.1 kJ/mol, respectively. The effect of thermal deactivation on the reusability of Novozym 435 in the esterification of oleic acid with ethanol at 50°C was greater than that with methanol. Novozym 435 could be reused in the production of methyl oleate and ethyl oleate for 13 cycles with FFA conversions of > 90%. When 96.0% ethanol and 95.0% ethanol were used, the numbers of Novozym 435 reuse cycles were not greater than 10 cycles and 8 cycles, respectively. The effective development of esterification from FFAs (oleic acids and PFAD) and methanol catalyzed by Novozym 435 was studied. The optimal operating condition was obtained in the single expanded bed circulation reactor at; FFA to methanol molar ratio of 1:2, 45oC, rotation speed of 600 rpm, feed volumetric flow rate of 5 mL/min, the bed to catalyst volumetric ratio of 2:1, Novozym 435 of 10% w/w of FFA and 5h. Novozym 435 could be reused 22 cycles with FFA conversion>90%. The continuous process in four expanded bed reactors in series was also investigated. FAME yields of esterification from FFAs (oleic acid and PFAD) and methanol were 93.46% and 88.50%, respectively. The productivity of biodiesel production using oleic acid and PFAD were 5.24 and 4.68 g FAME•h-1•g enzyme-1, respectively.
