Energy consumption of biodiesel production from microalgae oil using homogeneous and heterogeneous catalyst

Abstract

Transesterification reaction of the new generating biofuel resource, microalgae was conducted. In order to evaluate the effects of reaction variables such as catalyst type (KOH, NaOH), catalyst amount (1-1.5 % w/w), oil:methanol molar ratio (1:6-1:10), and time (5-20 min) on the methyl ester content of biodiesel. Suitable transesterification reaction conditions were determined as 65 C, 1 wt % catalyst amount, 5 min, 1:8 microalgae oil:methanol molar ratio using microwave heating system for both homogeneous catalysts. At these conditions fatty acid methyl ester content was determined as 96.54 and 96.82 % for KOH and NaOH, respectively. The results show that microwave heating has effectively reduced the reaction time from 210 min (for conventional heating) to 5 min. Electric energy consumption for microwave heating in this accelerated transesterification reaction was only 28.22 % of estimated minimum heat energy demand. Heterogeneous base catalyst, KOH/Al2O3, was also used to investigate the reaction activity due to growing interest in transesterification. According to slow reaction rate of heterogeneously catalyzed reactions, time, oil:methanol molar ratio and catalyst amount were increased as 35 min, 1:12 and 3 % w/w, respectively. Biodiesel conversion was found to be 97.79 % at these conditions