Esterification of palm fatty acid distillate using sulfonated carbon-based catalyst derived from palm kernel shell and bamboo

Abstract

In this work, sulphonated carbon-based solid acid catalysts were synthesized using two types of biomass sources, which were palm kernel shell and bamboo. Both carbon precursor contained different lignocellulosic composition that eventually determined the catalyst backbone structure. The sulfonate (SO3H) group was attached on the surface of catalyst by sulfonation process of carbon source with the chlorosulfonic acid (ClSO3H) under 70 °C for 4 h. The resultant catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), thermogravimetric analysis (TGA), fourier transform infrared (FTIR), temperature programmed desorption of ammonia (TPD-NH3). Both sulfonated PKS (PKS-SO3H) and Bamboo (Bamboo-SO3H) catalysts were found to have high total amount of acidity about 14.4 mmol g−1 and 8.9 mmol g−1 which were expected to have high catalytic activity. Meanwhile, the acid value of palm fatty acid distillate (PFAD) and percentage reduction of FFA were calculated based on standard AOCS method (Cd 3d-63). The catalytic activity of PKS-SO3H and Bamboo-SO3H demonstrated higher conversion of PFAD to biodiesel under the following reaction condition: catalyst loading of 4 wt%, methanol-to-PFAD molar ratio of 15:1, reaction temperature of 65 °C and the reaction time was 1 h. The PKS-SO3H catalyst managed to produce the highest FAME yield and FFA conversion which is 95% and 97%, respectively. Meanwhile Bamboo-SO3H shows slightly lower FAME yield and FFA conversion of 94.2% and 95.8%, respectively. The prepared catalysts showing the ability to recycle up to 4 times. In conclusion, the catalyst-derived palm kernel shell and bamboo had high potentials to esterify high FFA feedstocks and will be a significant finding to lower the biodiesel production’s cost.