Kinetics of Transesterification of Chlorella Protothecoides Microalgal Oil to Biodiesel

Abstract

Biodiesel has been receiving extensive attention in recent years due to its potential as a biodegradable and nontoxic substitute to petroleum diesel. Biodiesel derived from edible, non-edible oil and animal fat cannot satisfy even a small fraction of the existing demands due to low oil content (25–40 %) and slow growth rates (1–2 years) of oil producing plants. Microalgae is considered globally as the most promising third generation feedstocks for biodiesel production, as it requires less time for maturity (24 h–2 days) with oil productivities almost 30 times or more than the terrestrial oil seed crops. Out of various microalgae species, Chlorella protothecoides is selected as the potential feedstocks due to having high oil content (58 %), faster growth rate (24 h) and high biomass productivities (1214 mg/l/day). The present paper covers the optimization of process variables for methyl ester production using Chlorella protothecoides microalgal oil purchased from M/s Soley Institute, Turkey. The kinetics studied yielded the activation energy and reaction rate constant with maximum methyl ester yield. The results indicated that the maximum methyl ester yield of 98 % has been achieved at optimum condition of catalyst conc. of 0.5 % (w/v), methanol to oil molar ratio of 8:1, temperature of 60 °C and reaction time of 60 min. The kinetics study reported that the transesterification reaction is of first order with the reaction rate of 0.034 min−1. The stability and Cold flow property are found very good compared to other biodiesels and would not need any quantity enhancement. This kinetics result may be useful for the design and development of reactors.