Synthesis of carbonaceous solid acid magnetic catalyst from empty fruit bunch for esterification of palm fatty acid distillate (PFAD)

Abstract

A biomass-based magnetic catalyst was synthesised by way of a chemical activation-doping-sulphonation process using empty fruit bunch (EFB) char as a precursor for conversion of palm fatty acid distillate (PFAD) to biodiesel. The magnetic heterogeneous acid catalyst AC-Fe(x)-SO3Cl, with x = 2, 5, 10 and 15 (%) was prepared, to synthesise the optimised magnetic catalyst. The optimised magnetic catalyst was identified by applying TPD-NH3, BET, XRD, XPS, VSM, TGA and FESEM. The prepared magnetic catalyst had a higher surface area (20.42 m2/g), high acidity (29,520 μmol/g), and high magnetic properties (HC = 344.14G). The esterification activity of the AC-Fe(10)-SO3Cl catalyst showed high free fatty acid conversion (98.6%) with optimal reaction conditions of 4 wt% catalyst, 3 h reaction time, 16:1 methanol/PFAD ratio and 100 °C reaction temperature. In addition, AC-Fe(10)-SO3Cl showed the capability of maintaining esterification activity for six continuous cycles with no further treatment and gave a ∼79% biodiesel conversion. The produced catalysts showed characteristics such as high durability during esterification, with metal leaching containing low activity after several cycles. The EFB waste-based acidic magnetic catalysts are potentially efficient, economical, and eco-friendly for the esterification of waste oils and fats for biodiesel production.