Activity of carbon-based solid acid catalyst derived from palm empty fruit bunch for esterification of palmitic acid

Abstract

The activity of a heterogeneous solid acid catalyst derived from palm empty fruit bunch, synthesized through the direct in-situ H2SO4 impregnation was investigated for the esterification of palmitic acid. The prepared catalyst was characterized by scanning electron microscopy (SEM), Nitrogen adsorption and desorption isotherm, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). It was also analyzed for acid density and elemental composition. The results revealed that the esterification efficiency increases with increasing reaction time, temperature, and methanol loading up to an optimum value. The catalyst showed an excellent activity resulting in >98% esterification efficiency using 5 wt% catalyst, a 6:1 methanol to palmitic acid molar ratio, at 80°C for 5 h in an open reflux reactor, for the reaction conditions. The catalyst was employed in three consecutive runs without considerable loss of the activity. The obtained high catalytic activity is attributed to the high acid density due to the presence of strong (SO3H) and weak (COOH, OH) acid sites in the hydrophobic carbon structure.