Catalysts Esters 7 Esterification 6 Fatty acids 5 Palm fatty acid distillate 4 Biodiesel 3 Fatty acid methyl ester 3 Methanol 3 Carbon 2 Fourier transform infrared spectroscopy 2 Heterogeneous catalyst 2 Heterogeneous solid acid catalysts 2 High free fatty acids 2 Reaction temperature 2 Reusability 2 Scanning electron microscopy 2 Solid acid catalysts 2 Supercritical methanol 2 Temperature programmed desorption 2 X ray diffraction 2 Acetic acid 1 Acetone 1 Acid esterification 1 Aldehydes 1 Ammonium ions 1 Article 1 BET surface area 1 Batch reactors 1 Binary alloys 1 Bio-fuels 1