Biodiesel production from Jatropha caucus oil in a batch reactor using zinc oxide as catalyst


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INTRODUCTION

Majority of the world energy needs are supplied through
petrochemical sources, coal, and natural gases, with the
exception of hydroelectricity and nuclear energy. Of all
these sources that are finite, the current usage rates will
be consumed shortly. Non-renewable energy sources
such as petroleum are related to several drawbacks
including; increase green house emission, high cost of
processing the crude petrol and energy demand during
the process, non-renewable etc. This has provided
incentives to seek for alternative sources for petroleumbased
fuels.


RESULTS AND DISCUSSION

Transesterification reactions were carried out with
Jatropha oil with different reaction conditions, shown in
Figures 1, 2, and 3. The effect of the different process
variables; catalyst concentration, alcohol to oil ratio,
temperature of the reaction and reaction time were
analyzed experimentally.
The main role of catalyst in reaction kinetics is to reduce
the activation energy. Four different concentrations,
(0.25, 0.50, 1.0 and 1.5% w/w of oil) of sodium hydroxide
were used to study the effect of catalyst on
transesterification. It was observed in all experiments that
the equilibrium conversions were achieved between 80 to
100 min. Moreover, the average JCO biodiesel yield of
51.93, 87.22, 93.89 and 93.89% were obtained for each
of the experiment. This is shown in Figure 1. It is to be
noted that at any given condition, changing catalyst
concentration has no significant effect on the equilibrium
conversion.


Procedure

The transesterification reaction of Jatropha oil was carried out by
using zinc oxide as a catalyst. 2.0 g (2.5 ml) of methanol was
measured and poured into a test tube after which 0.09114 g of ZnO
pellet was carefully added to the test tube. A cork was replaced
tightly. The test tube was swirled round thoroughly for about two
minutes repeatedly about six times for complete dissolution of ZnO
pellet in the methanol. 9.115 g (10 ml) of JCO was measured out,
pre-heated to 65°C in a three-necked flat bottom flask with reflux
condenser using a water bath and thermometer to observe the
temperature. The pre-heated JCO is poured in a 250 ml beaker
placed on a magnetic stirrer. The prepared zinc methoxide from the
test tube was carefully poured into the JCO. Then the beaker was
secured tightly using a stopper and the magnetic stirrer switched on
and moderate agitation in the beaker was maintained for 25 min.
The mixture was poured from the beaker into a second test tube for
settling and the top secured using cork.


Conclusions
The effects of different reaction factors on the production
of biodiesel using zinc oxide as a hetereogeneous
catalyst were studied. Four replicate transesterification
experimental runs were carried out for each of the mixing
duration 25, 50, 75, and 100 min under different typical
transesterification reaction conditions of 9.115 g JCO,
temperature (37, 57, and 67°C), ZnO concentration (0.25,
0.5, 1.0 and 1.5%) (wt% JCO), methanol to oil ratio (6:1,
8:1, 12:1 and 24:1) at a constant mixing rate. The
optimum conditions were found to be 1% ZnO, 18:1
methanol to oil ratio, 67°C temperature. From this study
the highest conversion is 98%.