Synthesis of fatty acid methyl ester (biodiesel) using environmentally benign catalyst (yam peel)

Abstract

Homogeneous alkali-catalyzed transesterification is the typical process used in biodiesel production, complicating the downstream separation processes and causing oversupply of glycerol as by-product. In this work the synthesis of biodiesel by solid heterogeneous acid catalysts using sulphuric and phosphoric acids functionalized yam peel as catalysts and fried oil as the source of glyceride was investigated. The solid acid catalysts were prepared by carbonization followed by direct sulfonation and phosphoration via reflux. The FTIR Spectra of the catalyst and the XRD confirmed the incorporation of sulphate and phosphate groups on the carbonized yam peels. The amount of catalyst loading was investigated on the biodiesel yield. Sulphuric acid treated catalyst showed highest yield of 62.6 % at 1.0 g catalyst load, with phosphoric acid treated catalyst having slightly lower at 61.2 % and 1.0 g load. The physicochemical analysis of the used oil showed acid value of 27.50 mg KOH/g, free fatty acid (FFA) value of 13.83, density 0.91 g/mL, saponification value 154.28mgKOH/g. The presence of high free fatty acid in the oil feed indicate that the preferred catalyst to be used is heterogeneous catalyst.