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Scientifica Acta 2, No. 2, 8 11 (2008)
Chemistry
Experimental evaluation of the hydroesterification process:
production of biodiesel from Canola oil
Immacolata Manco
Dipartimento Chimica Generale, Universit di Pavia , Viale
Taramelli 12, 27100 Pavia, Italy,
[email protected]
The objective of this work is to optimise biodiesel production,
obtained by esterification of the fatty acid
derived from hydrolysis of rapeseed oil.Powdered niobic acid
(Nb2O5.xH2O) was used as catalyst. The temperature and the mixing
velocity re-mained constant during all reaction. The best
conversion yields for the hydrolysis were observed at 300Cwith 20%
of catalyst: at the highest molar ratio the yield was 88.49% and at
the lowest molar ratio the yieldwas 84.53%. The best conversion
yield obtained in the esterification was observed working in the
excess ofmethanol and at a temperature of 200C; the concentration
of catalyst is only relevant in the first 40 minutesof reaction.
After one hour, even non-catalytic reaction produced high
conversions at 200 C.
1 Introduction
Nowadays one of the main problems in the production of biodiesel
using first generation processes is the
availability of raw materials and the cost of refined vegetable
oils.
The process for producing biodiesel from oil is called
transesterification. The process is simple and can
work at low temperatures and with low cost catalysts, having
conversions near to 100%.However, this process has some
drawbacks:
the separation glycerol / biodiesel is long and costly
the cost of feedstocks is about 80% of the biodiesel production
cost [1]
industrial transesterification process occurs by means of basic
homogeneous catalysis always produc-
ing soap and demanding refined oils (more expensive than crude
ones) to minimise saponification.
[2]
The research is now geared towards the improvement of chemical
and biological processes necessary to
achieve second generations biofuels, using waste materials such
as exhausted vegetable oils.
The objective of this work is to optimise biodiesel production,
obtained by esterification of the fatty
acid derived from hydrolysis of rapeseed oil. This process can
be applied to any fatty feedstock with anyacidity or even
humidity.
In the hydroesterification process, hydrolysis is a chemical
reaction between triglycerides and water,
producing fatty acids and glycerol (Fig.1). Thus, hydrolysis
increases the acidity of the fatty material
instead of free fatty acid removal through refining. Moreover,
glycerol obtained from hydrolysis is cleaner
than one using transesterification process [2]. In
hydroesterification, food grade feedstocks produce food
grade glycerol. This never occurs in transesterification where
glycerol is generated in the presence of
significant amount of salts and methanol.
After hydrolysis, fatty acids are esterificated with methanol or
ethanol producing pure esters. There
is no contact between glycerol (removed during hydrolysis) and
biodiesel. Water, a by-product in the
esterification (Fig. 2) is re-used in the hydrolysis step in a
continuous way.
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Scientifica Acta 2, No. 2 (2008) 9
Fig. 1: Diagram of the reaction of hydrolysis.
Fig. 2: Diagram of the esterification reaction.
The highest is the feedstock acidity, the better will be the
yield of the process. Thus, beef tallow,
chicken fat, pork fat, yellow grease, crude palm oil, crude
jatropha oil, can be used and be transformed
in international biodiesel standards at yields higher than 98%.
Transesterification cannot be efficiently
applied in these raw materials. About 80% of the biodiesel
production cost is ascribed to fatty material
costs. Thus, hydroesterification is a choice that can really
improve biodiesel feasibility [2].
2 Experimental
2.1 Material and methods
All reactions, hydrolysis and esterification, were conducted in
a reactor (Parr Instruments Inc. - Model
4842)-type autoclave, consisting of stainless steel volume of
600 ml and maximum pressure up to 10,000
psi job, with a pipe to extract the sample, automatic rotation
and heating mantle.
Reagents:
canola oil: from a grocery store (initial acidity: 0.17%);
niobic acid (HY-340): to CBMM (Companhia Brasileira de Minerao e
Metalurgia), powder and
pellets, it was put in an oven at 150 C.
solution of 0.25 N NaOH for titrations is made in the laboratory
from NaOH produced by VETEC(cod1137);
anhydrous methanol for esterification.
The temperature (250, 275, 300C for hydrolysis and 150, 175,
200C for esterification) and the mixing
velocity (700 rpm) remained constant during all reaction.
The conversion of the reactions were evaluated evaluating the
percentage of free fatty acid and calculated
by titration with NaOH 0.25 N (Method proposed from AOCS
[American Oil Chemists Society) Ca-40].
Additional biodiesel evaluation was carried out according to EN
14214, European biodiesel standard.
In the Erlenmeyer flask there are about 1 g of sample, 25 ml of
ethanol, 1 ml of phenolphthalein, 3 drops
of 0.1 N NaOH, and the title with NaOH 0.25 N[2].
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10 Scientifica Acta 2, No. 2 (2008)
2.2 Hydrolysis
The percentage of fatty acid formed during the hydrolysis was
calculated by the following equation:
Index of acidity (%) = At = (R*V)/Ma
Ma = mass of the sample taken
V = volume of 0.25 N NaOH used for titration
R = value ranging between 6.99 and 7.05
Because the acidity calculated at time t is "contaminated" by
water and glycerol, the final values are
calculated by reference to the dry sample.
Efficiency of Hydrolysis (%) =R= At x {[(As - Au)x 100]/ As} +
At
At = acidity at the time tAs= the dry acidity
Au = acidity of the sample 60 min.
At the end of the hydrolysis, the fatty acid was separated from
glycerol, the catalyst, when used, can be
recovered through filtration.
2.3 Esterification
The esterifications efficiency was calculated by the
equation:
Efficiency (%)= [(Abco-Aa)/Abco]*100
Abco = acidity of white sample (taken before the T reactor
reaches the value set)
Aa = acidity of the sample time t
At the end of the reaction the product was centrifuged to
separate the catalyst and then it was heated to
remove water, which is by-product of the reaction of
esterification.
3 Results and discussion
The best yield obtained in the hydrolysis were observed at 300C
with 20% of catalyst: at the highest
molar ratio (oil:water 1:20) the conversion yield was 88.49% and
at the lowest molar ratio (oil:water 1:5)
the conversion yield was 84.53%.
The best yield obtained in the esterification was observed
working with excess methanol (fatty acid:
methanol 1:3) and at a temperature of 200C, the concentration of
catalyst is only relevant in the first 40
minutes of reaction. After one hour, even non-catalytic reaction
produced high conversion yields at 200 C.
Glycerol obtained by hydrolysis is very pure (food grade) and
methyl esters obtained in the esterification
step comply with European standards.
4 Conclusion
The minimisation of variables (T, C, RM) is a very relevant
research, which can be further developed; it
would be interesting to study the reactions occurring under
conditions of temperature between 260 and 280
C; amount of catalyst between 5-10%, with RM = 1:5, using crude
oil.
These preliminary results show that the chemical and physical
conditions of the two processes (hydrol-
ysis and esterification) allow continuing the implementation of
a continuous process.
In conclusion, it can be asserted that the process of
hydroesterification is a potential alternative to
transesterification, but further studies are needed and
especially the development of a more advanced tech-
nology.
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Scientifica Acta 2, No. 2 (2008) 11
0,0
10,0
20,0
30,0
40,0
50,0
60,0
70,0
80,0
90,0
100,0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
t i m e ( m i n . )
conversion
(%
)
5 R.M. 300C T 20% cat.
20 R.M. 30 0C T 20% cat.
0,0
10,0
20,0
30,0
40,0
50,0
60,0
70,0
80,0
90,0
100,0
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
t e m p o (m i n .)
conversione(%
)
3 R.M. 200C T 0 % c at.
3 R.M. 200C T 20%c at.
Fig. 3: Left:best yield of hydrolysis; Right: best yield of
esterification.
Acknowledgements I am gratefully acknowledged to prof. Helder
Queiroz Pinto Jr., Energy Economics Group, In-
stitute of Economics, Federal University of Rio de Janeiro, and
prof. Donato A. G. Aranda, Chemical Eng. Department
Federal University of Rio de Janeiro.
References
[1] L. G. Carvalho, P. P. Britto, L. Camacho, J. A.
Morsn-Villarreyes, M. G. Montes DOca, D. G. A. Aranda,
Produo de Biodiesel utilizando cido graxo de arroz e cido graxo
de palma. Anais do XX SICAT Simposio
Ibero-Americano de Catlise (2006).
[2] D. G. A. Aranda, Novas Tecnologias para a Produo de
Biodiesel 3o Seminrio OCB Rio de Janeiro, 25 de
outubro de 2007.
[3] L. L. L. Rocha, J. A. Gonalves, G. J. Reinaldo, A. K.
Domingos, M. Mello, N. R. Antoniossi Filho, D. G. A.Aranda, Produo
de cido graxo a partir da reao de hidrlise dos leos de mamona
(Ricinus communis L.) e
soja (Glycine max).14o Congresso Brasileiro de Catlise Anais do
Congresso Brasileiro de Catlise (2007).
2008 Universit degli Studi di Pavia
