Production of biodiesel/biofuel via acylglycerol route

Another approach reported in the literature for the conversion of DD consists in esterification of FFA with glycerol to form acylglycerols as an intermediate step in the production of biodiesel/biofuels.

Synthesis of MAG from DD was mainly studied due to the large number of applications as additives, for enhancing plasticity of fats or as bases in the food, medicine and cosmetic industry. Among synthesized acylglycerols, the monoester has the highest surface activity, and therefore, its concentration is very important for direct usage of the reaction product as an emulsifier.

The esterification of glycerol with fatty acids leads normally to a mixture of MAG, DAG, and TAG and some amount of unreacted substrates. The proportions depend on the presence and type of catalyst, as well as the reaction conditions such as temperature and the molar ratio FFA:glycerol.

Studies showed that enzymes have an enormous potential as catalysts in the processes where high regioselectivity is required (Lo et al., 2005). However, for the large-scale synthesis, the processes are not yet competitive due to the high cost of the enzyme.

Different studies summarized hereafter describe processes for the synthesis of acylglycerols in order to decrease the acidity of the feedstocks. These processes are catalyzed either enzymatically or conducted under non-catalytic conditions. However, the step of transesterification of acylglycerols to FAME was not further described in order to evaluate the final quality of the biodiesel.