Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate

Abstract

A method of biodiesel production from the freshwater microalgae Chlorella vulgaris based on the conversion of the dewatered algal biomass from a foam column (“foamate”) was investigated. The foam column collected and concentrated the microalgae. The foam was generated by passing air through a pool of algae, to which a collector/surfactant cetyltrimethylammonium bromide (CTAB) had been added. To produce biodiesel, the resultant “foamate” was esterified in situ using sulfuric acid and methanol. The effect of reaction temperature (30–70 °C), reaction time (30–120 min) and methanol/oil molar ratio (100–1000), were examined in a single-stage extraction–transesterification experiment on biodiesel yield at concentration of the catalyst H2SO4/oil molar ratio of (8.5/1). The thermodynamics and kinetics of transesterification of the microalgae oil were also investigated. The maximum biodiesel yield (96 ± 0.2%) was obtained at a reaction temperature of 70 °C, a reaction time of 90 min and methanol/oil molar ratio of 1000/1. Reaction kinetic parameters were determined that fitted the experimental data at all temperatures. A reversible reaction with first order forward and second order backward kinetics were found to be a good match for the experimental results. The kinetic model fitted experiments well under various temperatures and methanol/oil mole ratios. Under the most suitable conditions of reaction temperature, reaction time and methanol/oil molar ratio, the apparent activation energy was found to be 18.7 kJ/mol and pre-exponential factor 51.4 min−1. The activation entropy (ΔS), change in Gibbs free energy (ΔG) and variation in activation enthalpy (ΔH) revealed that the transesterification reaction is endergonic and unspontaneous, while the endothermic nature of the reaction was confirmed by the positive value (16.6 kJ/mol) of the ΔH. The thermodynamic information and kinetic model reported here will provide valuable insight into the understanding of the in situ transesterification process from algae foamate to biodiesel.

Utilization of microalgae for agricultural runoff remediation and sustainable biofuel production through an integrated biorefinery approach

“…The GC–MS result of the current study was higher than the findings of Najjar et al (Najjar et al 2021 ) who reported obtained GC–MS amount of biodiesel from cooking oil was 83.08%. Similarly, it was also higher than the results reported by Al-Humairi et al (Al-Humairi et al 2022 ) who obtained the maximum biodiesel yield (96 ± 0.2%). In the current study, the FAME content of algal biodiesel was methyl palmitate (32.1%), methyl heptadecanoate (11.2%), methyl myristate (8.2%), methyl lineolate (29.8%), methyl stearate (6.2%), methyl 10-heptadecanoate (7.7%) and methyl hexanoate (3%).…”

Sustainable Biotechnology Approaches Using Chlorella vulgaris's Biomass and Lipids as Biofuel Feedstock

“…Supercritical methanol with oxide catalysts, is another heterogenous catalyst, having supercritical methanol in conjunction with oxide catalysts (α-Al2O3) has shown to enhance the yield of fatty acid methyl esters (FAMEs), suggesting that complete dewatering of Chlorella vulgaris biomass may not be necessary. This method promotes higher liquid product and FAME yields, highlighting its potential for one-pot biodiesel production [78]. Table 2 provides a summary of the various catalysts used for biodiesel generation from Chlorella vulgaris, focusing on their reaction conditions and yields.…”

Influence of Molecular Structure on the Physicochemical and Tribological Properties of Biolubricants: A Review

“…The ability to skip the cell disruption and extraction steps is advantageous in terms of both operating cost and energy consumption. Table 1 shows the research that has used this technique for FAME (biodiesel) production in recent years, highlighting the presence of microalgae [44][45][46][47][48][49].…”