APPENDIX
%to compute the 4th degree polynomial equation using
cftool
t=[0,30,60,90,120,150,180];
TGc=[4.2,3.0,2.6,2.0,1.8,1.7,1.5];
DGc=[0,4,5.8,5,3.8,2.2,1.7];
MGc=[0,-1,2,6,8,10,6];
TGe=[4,2.8,2.6,2.2,1.8,1.6,1.4];
DGe=[0,3,5.4,4.8,3.6,1.8,1.4];
MGe=[0,0.2,2.2,5.8,7.7,10.2,6.1];
cftool(t,TGc);
cftool(t,DGc);
cftool(t,MGc);
cftool(t,TGe);
cftool(t,DGe);
cftool(t,MGe);
cftool(TGc,TGe);
cftool(DGc,DGe);
cftool(MGc,MGe);
error=stderror(p1,p2,p3,p4,p5);
%to calculate the standard error between the experimental
and calculated data
function stderror=jj(see)
see(1,1)=0;
for x=1:n:m
see(1,i)=((pc1*x^4+pc2*x^3+pc3*x^2+pc4*x+pc5)(pe1*x^4+pe2*x^3+pe3*x^2+pe4*x+pe5))^2;
i=i+1;
end
se=0;
i=1;
for x=1:n:m
se=se+see(1,i);
i=i+1;
end
stderror=sqrt(se/m);
fprintf('%f',stderror);
end
//C program to find the rate constants using runge-Kutta
method
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void main()
{
double x1, y1, z1, x, y, z, t, dt, t0=0.0;
FILE *file, *file2, *file3, *file4;
file=fopen("output.m", "w");
/* Holds x-z plane
view of
attractor */
file2=fopen("x.m", "w");
/* x versus time */
file3=fopen("y.m", "w");
/* y versus time */
file4=fopen("z.m", "w");
/* z versus time */
x1=(y1=(z1=(t=0.0001)));
/* Initial conditions
*/
dt=TIMESTEP;
fprintf(file2,"xq=[");
fprintf(file3,"yq=[");
while((t*TSCALE)<ll)
{
x=x1 + ( -k1*x1 + k2*y1
) * dt; /* Solve system
numerically */
y=y1 + ( k3*x1
- y1 - k4*x1*z1 ) * dt;
z=z1 + ( -k5*z1 + k6*x1*y1
) * dt;
t=t +
dt;
if (t>=(t0+INTERVAL*TIMESTEP))
output to files */
{
fprintf(file, "%f %f\n", x, z);
fprintf(file2, "%f\n", x);
fprintf(file3, "%f\n", y);
fprintf(file4, "%f %f\n", t, z);
t0=t;
}
x1=x;
y1=y;
z1=z;
}
fprintf(file2,"]");
fprintf(file3,"]");
fclose(file);
fclose(file2);
fclose(file3);
fclose(file4);
}
/* Write
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
KINETIC STUDIES OF HETEROGENEOUSLY CATALYZED
TRANSESTERIFICATION OF COTTONSEED
OIL TO BIODIESEL
N. Jaya*1 and K. Ethirajulu2
1. Department of Petrochemical Technology, Anna University of Technology, Tiruchirappalli (INDIA)
* E-mail : [email protected]
Received October 13, 2010
PY
2. Krishnasamy College of Engineering and Technology, Cuddalore (INDIA)
Accepted February 04, 2011
CO
ABSTRACT
IM
EN
The main thrust of this work is to study the kinetics of ion-exchanged catalyzed transesterification of
cottonseed oil. Transesterification of cottonseed oil with methanol was carried out at different
temperatures in the presence of cation exchange resin and characterization of oil and products. The
effects of the molar ratio of methanol to oil, reaction temperature, reaction time, mass ratio of catalyst
to oil and stirring rates were studied to optimize the reaction conditions. The experimental results
showed that the optimum conditions were 6:1 molar ratio of methanol to oil, 1.5 wt % cation exchange
resin catalyst, at reaction temperature of 338 K with a stirring rate of 10 Hz and reaction time of 3 h.
The fatty acid methyl ester (Biodiesel) contents were higher than 80 %. We have found that the
activation energy of resin catalyzed transesterification of cottonseed oil is 22090.30 J/mol. It was also
indicated that the catalysis performance of ion-exchange resins were better than that of homogeneous
catalysts. The spent catalysts can be easily regenerated and the same activity can be retained. A few
fuel properties were also measured for biodiesel to observe its competitiveness with conventional
diesel fuel.
Key Words : Heterogeneous catalysis, Ion-exchange resins, Reaction kinetics,
Transesterification, Biodiesal
INTRODUCTION
SP
EC
biodiesel compared with petroleum diesel 1,2 .
Transesterification of vegetable oils with shortchain alcohols in catalytic environment is the
commonly used method for producing biodiesel.
The transesterification reactions can be carried
out using either homogeneous (Acid or base) and
heterogeneous (Acid, Base or Enzymatic)
catalysts. Homogeneous base catalysts provide
much faster reaction rates than heterogeneous
catalyst, but it is considerably more expensive to
separate homogeneous catalyst from the reaction
mixture3-6. In homogeneous catalysis transesterification, the vegetable oils should have an acid
value less than one and all materials should be
substantially anhydrous. To overcome these
problems associated with homogeneous catalysts,
heterogeneous catalysts have been investigated
for biodiesel production7,8.
Biodiesel, defined as the esters of long chain fatty
acids can be used as biodiesel fuel or can be used
as an additive to diesel fuel in compression
engines with little or without modification.
Biodiesel, a renewable and biological source has
been receiving more attention all over the world
due to the energy needs and environmental
consciousness. Biodiesel is mono-alkyl esters of
long chain fatty acids, which falls in the carbon
range C12-C23. It contributes no net carbon
dioxide or sulfur to the atmosphere and emits less
gaseous pollutants than normal petroleum diesel.
Carbon monoxide, aromatics, polycyclic aromatic
hydrocarbons (PAHs) and partially burned or
unburned hydrocarbon emissions are all reduced
during combustion in vehicles operating on
*Author for correspondence
1
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
In most of the experiments using heterogeneous
catalysts, the transesterification reaction proceeds
at the relatively slow rate compared to those
conducted with homogeneous catalysts. The slow
reactions are due to diffusion problems because
these heterogeneous media behave as a three
phase system (oil/methanol/catalyst) and are not
possessing strong acidic or basic sites required
for transesterification9-11. Therefore, new catalytic
materials with a high reaction rate are extremely
desirable for transesterification. In general the ionexchanged resins can catalyze more organic
reactions. We have found cation exchanged resin
as an appr opriate catalyst for the
transesterification of edible and non-edible oils
under ambient reaction conditions.
Then the resins were dried at 378 K under vacuum
for 12 h and were swelled in methanol for 12 h
before use. Oil was kept under vacuum for 2 h to
remove moisture and preheated to reaction
temperature.
CO
PY
The transesterification of cottonseed oil with
methanol to produce biodiesel using ion-exchange
resin were performed. The oil is immiscible with
methanol, and reactants initially form a three-phase
system (Triglycerides / Methanol / Catalyst). The
upper layer is methanol, the lower layer is oil and
the catalysts were settled down at the bottom of
the flask. A stirrer must be used to reduce mass
transfer resistance and to increase the contact
area of the reactants with catalysts. Otherwise,
the reaction takes place only at the boundary
between the two phases. A 250 cm3 three necked
round bottom flask, an electrical stirrer, a reflux
condenser and a thermometer pocket with
thermometer were used in the transesterification.
Firstly, 100 cm3 of pre-heated cottonseed oil and
pre-calculated amount of methanol according to
the investigated molar ratio of methanol to
cottonseed oil were displaced into the flask. The
mixture was stirred and heated to pre-established
temperature (303-343 K). Then, the ion-exchange
resin catalyst with scheduled amount (0.5-2.5 wt
% relative to cottonseed oil) was introduced to
the reaction system. The reaction was carried out
for 1-6 h under the stirring rate of 2 to 10 Hz. A
sample 3 cm3 was collected by drip tube each
time at 1200 s intervals in the first hour, and then
collected at 1 h intervals. Then the samples were
washed with hot deionized water, dried over
anhydrous sodium sulfate and then dissolved in
n-hexane to form 10 mg/cm3 solution for gas
chromatographic analysis (GC). The spent
catalysts are separated from reaction mixture by
filtration.
IM
EN
The present work reports on the characterization
of cottonseed oil, production of biodiesel,
separation and characterization of products. This
study also reports on the various operating
parameters for cottonseed oil in a batch reactor.
The effects of temperature, amount of catalyst,
molar ratio of methanol to triglycerides and stirring
rates were investigated. The main thrust of the
present work is to study the kinetics of ionexchanged catalyzed transesterification of
cottonseed oil12-16. A few fuel properties were also
measured for biodiesel to observe its
competitiveness with conventional diesel fuel.
SP
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MATERIAL AND METHODS
All the analytical grade chemicals sodium
hydroxide, potassium hydroxide, hydrochloric acid,
methanol, n-Hexane and Karl-Fisher reagents are
obtained from Merck chemicals (INDIA). The
cation resins are obtained from Ion- Exchange
resin India Ltd. The refined cottonseed oil was
purchased from local oil stores.
Experimental section
Characterization of Oil
Characterization of Biodiesel
The kinematic viscosity, density, flash point, water
and sediment, copper strip corrosion, carbon
residue and distillation temper ature were
estimated as per ASTM standards.
The kinematic viscosity, density, flash point, acid
value, saponification value, and moisture content
were analyzed by American Society for Testing
and Materials (ASTM) standard methods.
Regeneration of Catalyst
The spent cation resin were regenerated by
following three steps, washed with methanol
containing 5 % (v/v) citric acid to remove the
organic substance covering the active sites of
Reaction and Separation
The cation exchange resins were mixed with
1M HCl solution to displace hydroxyl ions with
chloride ions and then washed with pure water.
2
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
resin. Regenerating with 1 M HCl solution to be
replaced with H+ ions, washed with pure water
and then washed with methanol to restore the
initial swelled condition12.
methanol/oil ratio increases, the driving force for
methanol adsorption increases as well, thus
favoring the transesterification reaction.
Table 1 : Properties of oil
Table 2 : Properties of resin
RESULTS AND DISCUSSION
Properties of oil and resin
Property
Values
Kinematic viscosity
at 313 K
32.5 mm2/s
Density at 293 K
915 kg/m3
Flash point (closed cup)
493 K
Acid value
0.1683 mg/g
Saponification value
Moisture content
(volume %)
Values
Moisture holding capacity
51-55 %
Particle size distribution
355-1200 µ
CO
Property
PY
The properties of cotton seed oil and cation ionexchange resin used in the transesterification
reactions are given in Table 1 and Table 2.
In this work, the effects of the molar ratio of
methanol to cottonseed oil in the range of 3-12
and the results shows that 6:1 molar ratio
gives >80 % of conversion within 3 h as shown in
Fig. 1. Higher molar ratio of alcohol to vegetable
oil interferes with separation of glycerol because
there is an increase in solubility. When glycerol
0.45-0.6 mm
pH range
0-14
Operating temperature
393-423 K
Regenerant recommended
HCl
263.3 mg/g
Maximum operating
423 K
0.005
temperature
Ionic form supplied
Hydrogen
EN
Effective size
remains in solution, it helps to drive the equilibrium
back to the left, lowering the yield of esters7,17.
The methoxide species, which are thought to be
the active species in transesterification reactions,
are formed upon adsorption of methanol on the
catalysts surface and the transesterification
reaction becomes mass transfer-controlled. As the
Effect of amount of catalyst on biodiesel yield
IM
Effect of oil to methanol molar ratio on
biodiesel yield
SP
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By increasing the amount of catalyst, the total
amount of acidic sites and their contacting
chances with reactants increases and this
obviously increases the yield of biodiesel17. We
Fig. 1 : Effect of molar ratio of methanol to cottonseed oil on the
biodiesel yield at 338 K with 1.5 wt % of cation resin catalyst
3
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
Effect of stirring rate on biodiesel yield
observed that, when the amount of cation catalyst
arrives 1.5 wt %, the yield of biodiesel reaches
higher value in 3 h as shown in Fig. 2.
As the heterogeneous reaction of transesterification takes place among three-phase system,
the reaction may become diffusion-controlled
when there is no agitation or the stirring rate is
not enough10. With increasing stirring rate, the
mass transfer resistance can be reduced and the
contact area may increase. Thus an apparent
increase in the yield of biodiesel in a short time of
reaction is obtained. When stirring rate reaches
10 Hz the yield of biodiesel for cation catalyst
reaches greater than 80 % within 3 h as shown in
Fig. 4.
Effect of reaction temperature on biodiesel
yield
PY
The impact of reaction temperature of the
transesterification reaction in the range of 303343 K on the yield of biodiesel was examined as
shown in Fig. 3. With increasing temperature,
due to higher energy state of the molecules
resulting more fruitful collision and higher solubility
of reactants at elevated temperature, the reaction
rate increases. At the reaction temperature of 338
K, an elevated yield of biodiesel was observed in
cationic environment within 3 h. At higher reaction
temperatures, there is a chance of loss of
methanol and increase in darkness of the product.
This also increases the production cost of
biodiesel9,18.
CO
Characterization of biodiesel
The significant fuel properties were determined
by ASTM standard methods and were listed in
Table 3. The viscosity of an engine fuel acts as
important role in the fuel spray, mixture formation
EN
Table 3 : Properties of cottonseed oil fatty acid methyl
ester
Values
Kinematic viscosity
at 313 K
2.2 mm2/s
IM
Properties Biodiesel
900 kg/m3
Flash point (closed cup)
393 K
Water and sediments
0.050 volume %
Copper strip corrosion
No. 2
Carbon residue
0.060 mass %
Distillation temperature
(90 % recovery)
613 K
SP
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Density at 293 K
of biodiesel is the oxidation stability. This property
shows the fuel’s resistance to oxidation during
extended storage. Oxidation stability is determined
by copper strip corrosion test since it has the
strongest catalyzing effect on oxidation. Due to
the formation of gums, the fuel does not combust
completely19 .
and combustion process. The high viscosity leads
to insufficient fuel atomization causes incomplete
combustion.
The density of fuel has some effect on the break
up of the fuel injected into the cylinder. All
biodiesels regardless of produced from vegetable
oils or from fats are denser and less compressible
than the diesel fuel. Flash point is an important
temperature from the safety point of view during
storage and transportation. A fuel of high viscosity
and high flash point causes bad engine start-up
ignition delay and carbon deposits in the
combustion chamber. Another important property
Determination of Kinetic Parameters
In excess of methanol, the transesterification is a
pseudo- first order reaction 20,21 . The rate of
pseudo-first order kinetic law can be considered
as follows,
r  kC G
4
(1)
Vol. 5 No. 3, January-March 2011
PY
Journal of Environmental Research And Development
IM
EN
CO
Fig. 2 : Effect of amount of cation catalyst on the biodiesel yield at with 6:1 molar ratio and 10 Hz stirring rate
SP
EC
Fig. 3 : Effect of reaction temperature on the yield of biodiesel with 1.5 wt % of cation catalyst, 6:1 molar ratio and 10 Hz
Fig. 4 : Effect of stirring rate on the yield of biodiesel at 338 K with 1.5 wt % of cation catalyst and 6:1 molar ratio
5
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
Where CG is the concentration of glyceride group,
Equation (1) can also be written by introducing
the glyceride group’s conversion (XG),
Where, t is the time. The average overall reaction
rate constant at different temperature can be
calculated according to the experimental data.
According to Arrhenius theory, the overall
reaction rate constant has relationship with
temperature as follows :
r  kC G0 X G
(2)
As for non-acid oil, the yield (ç) corresponds to
the glyceride group conversion (XG); relation (2)
can also be written as
r  kC G0 
Where Ea is the activation energy (J/mol), R is
the gas constant (J mol-1K-1), T is the absolute
temperature (K) and C is constant. The plot of ln
k versus 1/T gives the slope of (-Ea/R) Fig.5.
Thus, a value for Ea of 22090.30 J/mol was
calculated for this reaction.
(3)
k   ln(1  ) / t
PY
The kinetic constant (k) can then be calculated
at each temperature by integration of relation (3).
SP
EC
IM
EN
CO
(4)
Fig. 5 : Plot of ln k vs. 1/T for the transesterification reaction
CONCLUSION
catalyst amount of 1.5 wt %, a reaction
temperature of 338 K, a stirring rate of 10 Hz
and a reaction time of 3 h. We have also found
that the activation energy of cation catalyzed
transesterification of cottonseed oil is 22090.30
J/mol. The lower activation energy indicating that
methanol biodiesel has better combustion
properties. The reactions are completed under
mild temperature and pressure conditions. This
ion exchange catalyst can also be applied in other
chemical reactions as solid acid catalysts. This
can be easily recovered by simple filtration and
reused several times with consistent activity. From
the practical point of view further investigation
should be done to intensify the stability and
increase the lifetime of the catalyst.
Now days, biodiesel is produced in great amount
and its production continues to grow. The main
technology used in the industrial production is
based on the transesterification of refined oils with
methanol using basic homogeneous catalysts.
However, the problems related with this technology
have stimulated research in the field of
heterogeneous catalysis for biodiesel production.
In view of these results, we found that when the
heterogeneous catalyst was used in the
transesterification of cottonseed oil with methanol
to produce biodiesel, high production efficiency
was obtained with mild reaction conditions. The
biodiesel as high as 80 % was obtained with the
molar ratio of methanol to cottonseed oil of 6:1, a
6
Journal of Environmental Research And Development
Vol. 5 No. 3, January-March 2011
12.
13.
14.
EN
15.
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