Valorization of waste tires in the synthesis of an effective carbon based catalyst for biodiesel production from a mixture of non-edible oils

Abstract

In this investigation, char derived by the pyrolysis of waste tires was steam activated, to prepare waste tires derived activated carbon (WTAC). The attained WTAC was then impregnated with KOH to synthesize a novel carbon base catalyst (KOH/WTAC). Transesterifcation reaction of a mixture of non-edible oils with methanol and mixed methanol/ethanol was conducted using so-prepared carbon base catalyst. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), thermo-gravimetric analysis (TGA), energy dispersive spectrometer (EDS), and the Hammett indicator method, were applied to characterize the KOH/WTAC catalyst. The obtained outcomes disclosed that the WTAC impregnated with 50 wt% KOH and calcanied at 400 °C (50K400/WTAC) has exhibited the highest catalytic activity and basicity. The highest methyl ester yield of 94.50% was attained when the reaction was conducted under (4 wt%, g cat./g oil), reaction period of 2 h, 60 °C reaction temperature and 8/1 methanol/oil molar ratio, while a catalyst dosage of (4 wt%, g cat./g oil), 9/1 mixed methanol/ethanol molar ratio, 65 °C and 2 h, were the optimum reaction conditions, which synthesized the highest yield of methyl/ethyl esters (93.12%). After being reused for six cycles, the 50K400/WTAC remained owns a rather high catalytic activity. The FTIR and 1HNMR spectroscopy affirmed the conversion of the oils mixture to biodiesel. Furthermore, the specified properties of biodiesel agreed with the quality necessities established by ASTM 6751 and EN 14214. Finally, The transesterifcation of the oil with both methanol and mixed methanol/ethanol adopted the pseudo-first-order model with an activation energy of 20.10 kJ/mol and 18.64 KJ/mol.