2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 69 -
Batch Process Esterification of Crude Palm Oil
with Ethanol Assisted under Ultrasonic
Irradiation
T. Waisuwan, S. Sukmanee and C. Tongurai
Department of Chemical Engineering, Faculty of Engineering, Prince of Songkla University, (
Thailand
)
Abstract
--One of the obstacles for transesterification of
crude palm oil (CPO) as a raw material in biodiesel
production is free fatty acid (FFA) content. This research
was aimed to study FFA reducing by using batch process
esterification of CPO with ethanol assisted under ultrasonic
irradiation. The research exploited Taguchi methods as a
methodology. The result was shown FFA content could be
reduced from 5 to 0.5% wt/wt by conducting these optimum
conditions, 60% catalyst by wt. of FFA, molar ratio of
ethanol: FFA of 30, reaction temperature at 60
°
C, within 2
hours and amplitude of acoustic power at 75%. Anyway the
reaction time and amplitude can be reduced because they
are insignificant factors. The obvious advantages of this
method is no need outsourcing heat for the reaction and it
required less reaction time to achieve a lower FFA content
compared with methanol esterification. Finally, this method
is a good alternative way for pretreating FFA of triglyceride
before transesterification process.
Index Terms
—
Esterification, Ultrasonic Irradiation,
Biodiesel Production, Free Fatty Acid Content
I. N
OMENCLATURE
CPO Crude palm oil
FFA Free fatty acid
Conf. Confirmation
T
The overall experiment average
y
Quality characteristic
P
Prediction equation
II.
I
NTRODUCTION
The energy crisis and global warming expanding over
the world are the crucial factors which activate many
countries to concentrate on development of substituted
energy, especially, biodiesel. The main advantages of
using biodiesel are its renewability, better-quality exhaust
gas emissions, its biodegradability and given that all the
organic carbon present is photosynthetic in origin, it does
not contribute to a rise in the level of carbon dioxide in
the atmosphere and consequently to the greenhouse effect
[5]. The biodiesel can be used as a substituted petroleum
diesel in every concentration and produced to various
sources of oil and fat of plants and animals which mainly
contain triglyceride.
In Thailand, crude palm oil (CPO) is the most potential
source for biodiesel production because there are huge oil
palm plantations in southern of Thailand and its highest
oil yield (5,000 kg/ha/year) compared to others oil plants
[2] and [6]. Reasonably, CPO is the most promising raw
material in Thailand for industrial scale of biodiesel
manufacturing which should be process in continuous
stream. In fact, alkali catalyzed transesterification is
actually used to convert most of glyceride to ester or
biodiesel and obtain a good yield if raw material is
refined oil or has low content of free fatty acid (FFA). If
an oil contains higher amounts of FFA (>1% w/w), FFAs
form soap with the base catalysts. Consequently, it is
considered that the ester conversion is decreased by the
formation of soap that can prevent separation of the
biodiesel fuel from the glycerin [1]. Subsequently, raw
material pretreatment becomes an important role,
especially, FFA reducing which is named as de-acid
steps. Unfortunately, CPO has higher phosphorus and
free fatty acid content, therefore if CPO is subjected as
the raw material for alkali catalyzed transesterification
mainly used for biodiesel production, it should be
previously pretreated by degumming and de-acid steps.
Both steps are purposed to reduce phosphorus and FFA
content, respectively. So as to obtain a good yield of
transesterification, FFA content of raw material feed
should be lowered than 1%. Typical CPO has FFA
content 3-5%. There are two methods to reduce FFA
content, one is saponification or neutralization of FFA
with alkali solution (sodium or potassium hydroxide) and
another one is esterification by using acid as catalyst. The
main product of the first method is soap that is
troublesome for further process management. The latter
will obtain fatty acid alkyl ester as a main product and
water as a by product. Entirely, this method will increase
the ester yield of overall process and no need to separate
this pretreatment product before feeding to the
subsequent transesterification step. Obviously, the
esterification will be considered as a proper method to
optimize FFA content of the feed before
transesterification.
Ultrasound can also be efficiently utilized to optimize
the conversion of triglycerides to biofuel. For instance,
the influence of low-frequency ultrasound (28 and 40
kHz) on biofuel production from triglycerides, free fatty
acids
and fatty acid odor cut (C8
–
C10) was tested using
either methanol or ethanol in the presence of different
catalysts, such as sodium hydroxide (NaOH), potassium
hydroxide (KOH) and sulfuric acid (H
2
SO
4
)
and
compared to a conventional transesterification process.
These studies demonstrated that the use of ultrasound
significantly reduced the amount of required catalyst,
eliminated saponification
and dramatically shortened the
reaction time from 2 h to 30 min. In addition, an up to
