Production and characterization of cold-flow quality biofuel from soybean oil using different alky and benzyl alcohols

Biodiesel is an alternative fuel that has been used for partial or total substitution of diesel to reduce its environmental impacts. In Brazil, the main industrial technique used to produce biodiesel is via transesterification of soybean oil with methanol under sodium methoxide as a homogenous catalyst. Some studies on this topic have focused on improving the cold properties of biodiesel for use in cold climate countries. This research focused on the comparison of the cold properties of the biofuel produced from the transesterification of soybean oil with different alcohols. The alcohols used vary according to the size of the carbon chain and its nature: methyl, ethyl, isopropyl, isoamyl and benzyl alcohol. The chemical composition of the esters formed were studied by means of 1H NMR, HPLC, FTIR, sodium and sulphur content. The 1H NMR spectra showed that only the methyl and ethyl esters reached the minimum value of ester content established for the international specifications for biodiesel. Despite the greater difficulty in removing the excess of the reactant alcohol at the end of the reaction and having an ester content above requirements, the esters obtained from the alcohol isopropyl and isoamyl presented the best results in terms of their cold properties. However, the presence of the benzyl in the structure of the ester did not show any change in its CFPP, compared to the respective methyl ester. In addition to the cold properties, studies of some other physicochemical properties have also been made to show the maintenance of international specifications.