Biodiesel purification with activated bentonite
Ekkasit Tepveeragul
1*
and Nisakorn Saengprachum
2
1
Petrochemical and polymer science, Faculty of science, Chulalongkorn University, Bangkok 10330, Thailand
2
The international postgraduate program in environmental management, Graduate school, Chulalongkorn University, Bangkok 10330, Thailand
*
Author for correspondence; E-Mail: t_akasit@hotmail.com, Tel. +66 02 218 7671 2, Fax. +66 02 218 7671
Abstract
The objective of this research is to study the factor of activated
bentonite as adsorbent for removing soap from biodiesel product.
The factors were studied in the effect of solvent, concentration of
sulfuric acid, time and temperature. The result showed that 3% wt
of activated bentonite could adsorb 64.37 % (w/w) of soap and
exhibited acid value of purified biodiesel as 0.29 (mg KOH/g oil).
In addition, the specific surface area of activated bentonite was
increased from 48 to 55 m
2
g
-1
. The quality of purified biodiesel
met the requirement of biodiesel standards (ASTM D974).
Therefore, activated bentonite revealed more environmental
friendly in biodiesel purification than water washing because there
is no wastewater generated.
1. Introduction
Rapid growth in population coupled with industrial and
technological developments have been leading towards the
depletion of limited fossil fuel resources of the world. Currently,
research is progressively more directed towards exploration of
alternative renewable fuels. Biodiesel, an alternative diesel fuel, is
a promising, non-toxic and eco-friendly clean fuel [1]. It could be
regarded as petroleum-derived diesel substitute with many
advantages including reduction of exhaust emissions,
biodegradability, high flash point, inherent lubricity, and domestic
origin [2].
Biodiesel (fatty acid alkyl ester) is produced by transesterifying triglycerides, from vegetable oils or animal fats with an excess
alcohol, usually methanol, in the presence of a catalyst, usually a
strong base such as sodium or potassium hydroxide [3]. The
resulting product therefore can contain not only the desired alkyl
ester product but also unreacted material (mono-, di- and
triglycerides), residual alcohol, residual catal yst and soap. Soap
is formed as a by-product and separated from the biodiesel in the
production process, however, traces thereof can be found in the
final biodiesel product [4].
To meet the requirements of biodiesel standards, removal of
soap are especially important. Moreover, soap is especially
undesired in the fuel because it blocked fuel filter in engine. In
the usually industrial practice, water washing is wildly used to
purified biodiesel but it has been lately critically objected on an
environmental basis because it produced relatively large amounts
of wastewater.
To eliminate this problem, the use of waterless process
becomes an important role in removing biodiesel contaminants
then conventional water washing could be replaced by using
adsorbents. The study of various type of adsorbents is needed.
Bentonite clay was chosen to be adsorbent in this work because
of its ability to improve surface area and active site. Especially,
bentonite is a natural clay and it is available in Thailand with its
competitive cost.
2. Experimental
2.1 Transesterification of refined palm oil
Refined palm oil (500 g) was added into 1000 ml of round
bottom flask equipped with condenser. After the oil was heated to
65 °C, the solution of sodium hydroxide (5.0 g) in methanol
(144.82 ml), 6:1 molar ratio of methanol to oil, was slowly added
into the reaction and then the mixture was heated to 65
o
C for
1.50 h. The reaction was monitored by TLC developed by
hexane: ethyl acetate: acetic acid (90:10:1 v/v) and visualized by
vanillin solution. The mixture was then transferred to a separatory
funnel and allowed glycerin to separate. The methyl ester layer
was later brought to adsorption process.
2.2 The effect of sulfuric acid concentration, temperature, solvent
and time on bentonite
In order to study the effect of sulfuric acid concentration,
solvent, temperature and time for activating bentonite. Natural
bentonite (100 g) was treated with sulfuric acid (0.1, 0.3, 0.5 and
1 M respectively) in distilled water, isopropyl alcohol and ethanol
at the temperature of 60 ºC and 100 ºC under mechanical stirring
at 150 rpm for 1, 3, 6, 9 and 12 h. Then the samples were
washed with distilled water for several times until pH 5 of washed
water was achieved and dried at 110 °C for 48 h. The activated
Biodiesel purification with activated bentoniteEkkasit Tepveeragul1*and Nisakorn Saengprachum21Petrochemical and polymer science, Faculty of science, Chulalongkorn University, Bangkok 10330, Thailand2The international postgraduate program in environmental management, Graduate school, Chulalongkorn University, Bangkok 10330, Thailand*Author for correspondence; E-Mail: t_akasit@hotmail.com, Tel. +66 02 218 7671 2, Fax. +66 02 218 7671AbstractThe objective of this research is to study the factor of activated bentonite as adsorbent for removing soap from biodiesel product. The factors were studied in the effect of solvent, concentration ofsulfuric acid, time and temperature. The result showed that 3% wt of activated bentonite could adsorb 64.37 % (w/w) of soap and exhibited acid value of purified biodiesel as 0.29 (mg KOH/g oil).In addition, the specific surface area of activated bentonite was increased from 48 to 55 m2g-1. The quality of purified biodieselmet the requirement of biodiesel standards (ASTM D974). Therefore, activated bentonite revealed more environmental friendly in biodiesel purification than water washing because there is no wastewater generated.1. IntroductionRapid growth in population coupled with industrial andtechnological developments have been leading towards the depletion of limited fossil fuel resources of the world. Currently,research is progressively more directed towards exploration of alternative renewable fuels. Biodiesel, an alternative diesel fuel, is a promising, non-toxic and eco-friendly clean fuel [1]. It could be regarded as petroleum-derived diesel substitute with many advantages including reduction of exhaust emissions, biodegradability, high flash point, inherent lubricity, and domestic origin [2]. Biodiesel (fatty acid alkyl ester) is produced by transesterifying triglycerides, from vegetable oils or animal fats with an excess alcohol, usually methanol, in the presence of a catalyst, usually a strong base such as sodium or potassium hydroxide [3]. The resulting product therefore can contain not only the desired alkyl ester product but also unreacted material (mono-, di- and triglycerides), residual alcohol, residual catal yst and soap. Soapis formed as a by-product and separated from the biodiesel in the production process, however, traces thereof can be found in the final biodiesel product [4].To meet the requirements of biodiesel standards, removal of soap are especially important. Moreover, soap is especially undesired in the fuel because it blocked fuel filter in engine. In the usually industrial practice, water washing is wildly used to purified biodiesel but it has been lately critically objected on an environmental basis because it produced relatively large amounts of wastewater. To eliminate this problem, the use of waterless process becomes an important role in removing biodiesel contaminants then conventional water washing could be replaced by using adsorbents. The study of various type of adsorbents is needed.Bentonite clay was chosen to be adsorbent in this work because of its ability to improve surface area and active site. Especially, bentonite is a natural clay and it is available in Thailand with itscompetitive cost.2. Experimental2.1 Transesterification of refined palm oilRefined palm oil (500 g) was added into 1000 ml of round bottom flask equipped with condenser. After the oil was heated to 65 °C, the solution of sodium hydroxide (5.0 g) in methanol (144.82 ml), 6:1 molar ratio of methanol to oil, was slowly added into the reaction and then the mixture was heated to 65oC for 1.50 h. The reaction was monitored by TLC developed by hexane: ethyl acetate: acetic acid (90:10:1 v/v) and visualized by vanillin solution. The mixture was then transferred to a separatory funnel and allowed glycerin to separate. The methyl ester layer was later brought to adsorption process.2.2 The effect of sulfuric acid concentration, temperature, solventand time on bentoniteIn order to study the effect of sulfuric acid concentration, solvent, temperature and time for activating bentonite. Natural bentonite (100 g) was treated with sulfuric acid (0.1, 0.3, 0.5 and 1 M respectively) in distilled water, isopropyl alcohol and ethanol at the temperature of 60 ºC and 100 ºC under mechanical stirring at 150 rpm for 1, 3, 6, 9 and 12 h. Then the samples werewashed with distilled water for several times until pH 5 of washed water was achieved and dried at 110 °C for 48 h. The activated
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