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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Keywords
Investigate the feasibility of two processes , to produce glycerol-free FAME