Transesterification/Esterification Of Non-Edible And Waste Cooking Oils To Fame And Glycerol Free Fame Using Carbon And Silica-Based Catalysts

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Date
2014-09
Authors
Chin, Lip Han
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Abstract
Biodiesel, also known as fatty acid methyl esters (FAME), is an alternative fuel for diesel engines that is gathering attention worldwide. However, the burden of excess low-value glycerol by-product that is produced in traditional transesterification may thwart the growth of the biodiesel industry. Therefore, this study aims to investigate the feasibility of two processes (two-step and single-step) to produce glycerol-free FAME. First process involved two-step of reaction, which converted palm fatty acid distillate (PFAD) and waste cooking oil (WCO) to FAME and glycerol by-product with sugar cane bagasse (SCB) and ZrSi-2 catalysts and followed by converting glycerol to glycerol carbonate with dimethyl carbonate (DMC) in the second step with Na/AC catalyst. Second process involved only single-step reaction, which converted WCO and non-edible oils (jatropha oil (JO), karanj oil (KO) and crude palm kernel oil (CPKO)) with DMC to produce glycerolfree FAME and fatty acid glycerol carbonates (FAGC) with Na/AC catalysts. All the reactions were studied in a batch process and the reaction was carried out at autogenous pressure. Developed carbon and silica-based catalysts were characterized by scanning electron microscopy, energy dispersive X-ray, surface area and Fourier transform infrared spectrometry. The BET surface area of the SCB, ZrSi-2 and Na/AC catalysts were found to be 55 m2g-1, 303 m2g-1 and (495 – 897) m2g-1, respectively. Various parameters such as methanol/DMC to oil/glycerol molar ratio (1 – 18), catalyst loading (1 – 30) wt%, temperature (100 – 200) °C and reaction time (0.5 – 6) h were investigated. The optimum conditions obtained for first two-step were 0.5 – 5 h, 2 – 9, 150 – 175 oC, 9 – 11.5 wt%, respectively, for reaction time, methanol to oil molar ratio, temperature and amount of catalyst for transesterification/esterification of PFAD and WCO. Moreover, the optimum conditions obtained were 1 h reaction time, DMC/glycerol molar ratio of 2, 5 wt% catalyst loading and 100 °C reaction temperature for the second two-step process. The optimum FAME content of 80% and glycerol conversion of 90% were found for the first and second two-step, respectively. However, the single-step optimum conditions obtained were 150 °C reaction temperature, 2 hours reaction time, 3 – 9 DMC to oil molar ratio and 3 – 15 wt% catalyst loading. The oil conversion of 95%, the FAME yield of 85% and FAGC yield of 40% were obtained. The results indicate that the developed carbon and silica-based catalysts can be used in glycerol-free FAME production as solid catalysts. However, Na/AC catalyst was found to be greater in terms of activity and reusability when using DMC as a source of methoxide anion compare to methanol. In summation, it was clearly shown from these studies that high yield of FAME over 90% could be obtained in single-step process reaction compared to two-step process. The kinetic study showed that transesterification process using jatropha as reference oil with DMC could be described by pseudo first order within the limits of the experimental date range considered with an activation energy of 30.2 kJ mol-1 and reaction constant of 0.0354 min-1.
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Investigate the feasibility of two processes , to produce glycerol-free FAME
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