Simultaneous esterification and transesterification of microbial oil from Chlorella minutissima by acid catalysis route: A comparison between homogeneous and heterogeneous catalysts

•The built photo-bioreactor was found to be suitable for Chlorella minutissima cultivation.•The function desirability was used to simultaneously analyze the process variables.•Microalgal oil revealed as main fatty acids: C16:0 (57.1%) and C18:1 (26.3%).•Microbial oil can be considered a good candidate for biofuel synthesis using (H2SO4) and (Nb2O5/SO4).•Higher biodiesel yield was attained by heterogeneous catalyst.

Using low cost materials, tubular photo-bioreactors type bubble column were built for microalgae cultivation. Six factors/two levels Taguchi orthogonal array (L8) was adopted to identify the input variables with the greatest influence on oil accumulation by Chlorella minutissima. The function desirability was used to simultaneously analyze the process variables to attain maximum biomass concentration and lipid content. The microalgal oil was submitted to acid simultaneous esterification and transesterification reactions using homogeneous (H2SO4) and heterogeneous (Nb2O5/SO4) catalysts. Both catalysts afforded high biodiesel yield (>96%), although heterogeneous catalyst showed better yield (98%) and low residual glycerides at 4 h reaction.

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