Non-catalytic supercritical methanol (SCM) and superheated methanol vapour (smv) for fatty acid methyl esters (FAME) synthesis from jatropha and sea mango oils
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Date
2016-06-01
Authors
Ang Gaik Tin
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Abstract
This research project was carried out to investigate the potential of one-step
non-catalytic transesterification reaction of jatropha curcas and sea mango oils for
biodiesel or fatty acid methyl esters (FAME) production. Initially, non-catalytic
supercritical methanol (SCM) was carried out by utilizing sea mango oil as
triglycerides (TG) feedstock. Statistical analysis method of design of experiment
(DOE) was employed to investigate the effect of reaction time, reaction temperature
and molar ratio of methanol to oil in the range of 10 – 50 min, 320 – 400 °C and 20
– 60 mol/mol, respectively. The optimum conditions were found to be 380 °C, 40
min and 45:1 mol/mol of methanol to oil, resulting in 78 % w/w biodiesel content.
Subsequently, development of mathematical model based on SCM reaction
mechanism was conducted. This maiden model of FAME production incorporating
both reversible transesterification and esterification was verified using an ordinary
differential equation (ODE45) solver. The highest activation energy of 40 kJ/mol
and the lowest reaction rate constant of 2.50 ×10-5 dm3/mol s confirmed that the first
stepwise reaction of TG to produce diglycerides (DG) was the rate-limiting step in
SCM system. Apart from that, new technology which is non-catalytic superheated
methanol vapour (SMV) was developed for transesterification and esterification of
oil feedstock. In the initial development, jatropha curcas oil was utilized as TG
feedstock in the SMV system. The effects of reaction time, reaction temperature,
methanol flow rate and initial oil mass on the FAME production rate and FAME
content were studied at the range of 0 – 240 min, 260 – 300 °C, 1 – 3 mL/min and
40.0 – 70.0 g, respectively. Results obtained showed that the highest biodiesel yield
at 71.54 % w/w was achieved at reaction temperature of 290 °C, methanol flow rate
at 2 mL/min for the initial oil mass at 40.0 g with 88.81 % w/w FAME content,
implying the huge potential of SMV technology in producing FAME. In addition, it
was observed that higher FAME production rate can be obtained when the initial oil
mass is increased. Therefore, initial oil mass was fixed at higher volume which was
100 mL and experimental system was modified by replacing the preheater to a high
temperature crucible furnace and introducing obstacle into the reaction chamber. Sea
mango oil was utilized after modification had been carried out. From the results,
obstacle which refers to cylinder cap with two perforated plates had successfully
increased the FAME production (g). The effects of methanol flow rate and reaction
temperature between the range of 1 – 4 mL/min and 260 – 290 °C, respectively on
FAME yield (%), FAME production (g) and FAME production rate (g/min) was
studied accordingly at a constant oil volume of 100 mL. Results showed that higher
methanol flow rate and reaction temperature can increase the FAME yield and
production. Subsequently, mathematical modelling of semi-batch SMV system,
incorporating both reversible transesterification and esterification was developed and
verified by using ODE45 solver. The highest activation energy of 50 kJ/mol and the
low reaction rate constant of 1.62×10-4 dm3/mol min corroborated that the reaction
of TG to become DG as the rate limiting step in SMV system. As a conclusion,
SMV reaction is showing its great potential in biodiesel production by using
feedstock with high content of FFA.