PURIFICATION AND PHYSIO-CHEMICAL
CHARACTERIZATION OF GLYCEROL BY-PRODUCT OF
PALM OIL BIODIESEL INDUSTRY AS POTENTIAL BASE
FLUID FOR SYNTHETIC
OIL-BASED DRILLING FLUID SYSTEM
Marbun, B. T. H*, Hutapea, P. A, Aristya, R, Husin
Department of Petroleum Engineering, Institut Teknologi Bandung, Bandung, West Java, Indonesia
bonar.marbun@tm.itb.ac.id, philiphutapea@ymail.com, ramadhana.aristya@yahoo.com,
husin_aidid@yahoo.com
Abstract:
The development of an OBM from glycerol was carried out in this work. Glycerol used in
this study, which is by-product of palm oil biodiesel industry, is a new alternative for OBM.
In this study, crude glycerol will be purified using H3PO4 solution to increase the purity of
glycerol from about 50% to more than 80% (Farobie, 2009). The characterization of glycerol
properties include chemical compound, density, flash point, pour point, and cloud point.
The preliminary tests result indicates that purified glycerol can be used as synthetic OBM in
accordance with the API standard and also can become the reference for this synthetic OBM
development which is very potential due to its environmentally friendly characteristics and
since it may be derived from the abundant and low cost raw materials from by-product of
biodiesel production.
Keywords: Glycerol, purification, synthetic oil-based mud
1. Introduction
1.1. Palm oil
Palm oil has fatty acid content varies with carbon chain lengths ranging from C12 to C20
carbon atoms. Fatty acid composition determined the physical and chemical properties of
palm oil [1]. Palm oil has a major component in the form of triglycerides by 94%. In addition,
palm oil also contain fatty acids by 3-5% and the non-trigliserida by 1% called minor
components such as carotenoids, tocopherols, tocotrienols, sterols, phospatida, and aliphatic
alcohols. Palm oil fatty acid composition is presented in Table 1.
1
Table 1 Composition of Fatty Acid in Crude Palm Oil [2]
Fatty Acid
Saturated Fatty Acid
Capric Acid (C10:0)
Lauric Acid (C12:0)
Myristic Acid (C14:0)
Palmitic Acid (C16:0)
Stearic Acid (C18:0)
Unsaturated Fatty Acid
Oleic Acid (C18:1)
Linoleic Acid (C18:2)
Linolenic Acid (C18:3)
Carbon Chain
Content (%)
Melting Point (°C)
10:0
12:0
14:0
16:0
18:0
1-3
0-1
0.9-1.5
39.2-45.8
3.7-5.1
31.5
44
58
64
70
18:1
18:2
18:3
37.4-44.1
8.7-12.5
0-0.6
14
-11
-9
1.2. Glycerol
Glycerol is a liquid that is colourless, odorless and is a viscous liquid that has a sweet taste
[3]. The molecular formula of glycerol is C3H5(OH)3 (Figure 1) with the chemical name
1,2,3-propanetriol [4]. The properties of glycerol are soluble in water easily, increasing the
solution viscosity, water binding and lowered water activity.
Figure 1 Visualization of molecular and molecular formula of glycerol [5]
This compound is soluble in water and dissolved in alcohol. It can be dissolved in a solvent
such as ether and ethyl acetate, but insoluble in hydrocarbons. The characteristic of glycerol
is showed in Table 2.
Table 2 Characteristic of glycerol [6]
Parameter
CAS number
Molecular formula
Molar mass
Phase
Colour
Value/Characteristic
56-81-5
C3H8O3
92.1 g mol-1
Fluid
Colourless
Tovbin et al (1976) [7] explain that the production of glycerol from fat can be done through
three methods, such as transesterification, saponification and hydrolysis. The result of this
methods produced crude glycerol compounds which are still a lot of containing impurities
particle such as residual catalyst and free fatty acids.
2
This study described the preliminary test of glycerol by-product of palm oil biodiesel industry
as the potential base fluid for synthetic-based drilling fluid system. The developments of
glycerol utilization were to make it as base oil drilling mud for oil-based mud and lubricity
for water-based mud.
1.3. Biodiesel
Biodiesel made from vegetable oil also has a lower cetane number than petrodiesel so that
power can be generated lower. The characteristic differences can be solved by esterification
process. One of vegetable oil that developed to biodiesel was derivative products by palm oil.
According to Hambali (2013) biodiesel is defined as the methyl ester as produced from
vegetable oils or animal fats and qualified to be used as fuel in diesel engines. Chemically,
biodiesel is derived from a group of lipid monoalkyl esters of fatty acids with 12-20 of carbon
chain length.
Physio-chemical properties of biodiesel are similar to diesel fuel (petrodiesel), but in some
case biodiesel is more desired. Biodiesel has the environmentally friendly nature as compared
to petrodiesel because biodiesel contained no sulfur and benzene.
1.4. Crude glycerol
In this study, crude glycerol is derived from transesterification process. In the
transesterification of palm oil, triglyceride is reacted by alcohol with the help of strong acid
or strong base. The resulting product is a methyl ester or biodiesel and glycerol as a byproduct (Figure 2).
Figure 2 Transesterification process of palm oil to biodiesel and glycerol [8]
Glycerol used was crude glycerol which is a by-product of palm oil biodiesel industry that
has purity 50% that derived from transesterification process. Glycerol was a by-product of
biodiesel production that has the highest number compared with the other side. Amount of
glycerol produced from each biodiesel production approximately 10% of the total production
of biodiesel [9]. This crude glycerol still contains residual methanol, residual catalyst, and
impurity materials derived from oil as biodiesel raw materials.
2. Methods
2.1. Transesterification of Palm Oil
Glycerol to be used in this study is a by-product of the production of methyl esters
(biodiesel). Glycerol is obtained by a process of transesterification, the process of
triglycerides to alcohol reaction using base catalyst to produce alkyl esters of fatty acid and
glycerol. In the trans-esterification process, methanol is added as much as 15% (v/v) of the
total raw materials of olein/stearin oil to be processed and mixed with KOH as much as 1%
(v/v) of the total raw materials olein/stearin oil to be processed to form methoxide solution.
Then, olein/stearin oil and mixed with a solution of methoxide transesterification reactor.
Transesterification process is be held for 1 hour and stirred at a temperature of 55 oC by 100
3
rpm. Settling process is then performed to separate the crude methyl ester and crude glycerol
produced.
Figure 3 Diagram of Transesterification Process
Figure 4 The result of Transesterification Process [10]
2.2. Purification of Crude Glycerol
Crude glycerol by-product of palm oil biodiesel industry was still many impurities found
(Figure 5). Common impurities in crude glycerol are non-reacting methanol, soap, and
potassium hydroxide catalyst [11], [12]. Therefore, purification process is required to reduce
any unwanted chemical compound.
4
Figure 5 Crude Glycerol as a Side Result from Palm Oil Biodiesel Production
Farobie (2009) used crude glycerol derived from Jatropha’s biodiesel production in his thesis
which has glycerol content was 40.19%. The purification method based on Kocsisová and
Cvengroš Cvengros (2006) method to obtain the result of glycerol content was 82.15%.
Based on this method, crude glycerol is added by phosphoric acid 5% (v/v). Then, the
solution was stirred using a magnetic stirrer for 30 minutes. Solution formed is waited to
separate for 60 minutes.
In this study, the separation of this impurities compound from glycerol is able to be done by
adding phosphoric acid and stirring by low RPM mixer. Initially, the phosphoric acid that
was used is a solid phase (Figure 6 A).
Then, phosphoric acid solid is added water to be changed in solution (Figure 6 B).
Phosphoric acid solution has 85% concentration. Then, crude glycerol was added by this
phosphoric acid 5% (v/v).
Figure 6 Phosphoric acid solid phase (A) and Phosphoric acid solution (B)
This acid will react with residue of potassium hydroxide catalyst and form potassium
phosphate salt (Figure 7 A). Furthermore, phosphoric acid will modify the soap into free fatty
acid (Figure 7 B).
5
(A)
(B)
Figure 7 Reaction of (A) Potassium Phosphate Salt and (B) Free Fatty Acid Formation [10]
Based on this research, the increase of phosphate acid in crude glycerol forms 3 layers with
mass distribution percentage as follows:
a. Upper layer (FFA), solid phase
b. Middle layer (glycerol), liquid phase
c. Lower layer (K3PO4 salt), solid phase
The layers formed by adding phosphate acid are shown in Figure 8, after the mixture is
settled within one hour at room temperature.
Figure 8 Three Layers Formed after Adding Phosphate Acid
The separation of glycerol layer from K3PO4 salt and FFA is done by screening using
decantation method combined with 200 mesh funnel while giving flow space from the FFA
solid. At the screening process, the upper layer (FFA) and lower (salt) are kept remain in the
chemical glass, then the middle layer (glycerol) is filtered. In order to ensure that the salt is
not screened along the process, then the screening use Filter Press Apparatus with 30 – 50 psi
pressure. This method is different with the previous method [9] in which his method use
Butchner funnel and separation funnel that separate glycerol and FFA from K3PO4 first, and
then continued with the screening of glycerol from FFA.
The screening result of potassium phosphate salt is shown in Figure 9. This salt is able to be
used as fertilizer. However, it still consists of glycerol which is easily melted so that
crystallization process is required.
6
Figure 9 Potassium Phosphate Salt as a Result of Glycerol Screening
The upper layer is a Free Fatty Acid (FFA) residue with pH of 5.0 (Figure 10) whereas the
middle layer is glycerol with pH of 6. Glycerol solution as a result of screening process is
shown in Figure 11 B. It can be seen from the figure that glycerol from screening process is
clearer than crude glycerol.
Figure 10 FFA as a Result of Glycerol Screening
Figure 11 Crude Glycerol (A) and Purification Result (B)
7
Figure 12 Diagram of Purification Process
2.3. Fluid Testing
In this study, the American Society of Testing and Material (ASTM) was used as standard
practice in fluid testing. It is important to note whether the physio-chemical properties of
glycerol by-product of palm oil biodiesel industry as potential base fluid is the primary focus
in this study. According to previous studies by Amanullah (2005) [13], Rubiandini et al
(2006) [14], and Setyawan et al (2011) [15], most vegetable oils were proven to be
compatible with components and additives commonly used in diesel or mineral oil mud
system. By comparison the result of several tests, it was performed to find the appropriate
additive materials and the weaknesses of vegetable oil due to its undesired properties. The
most undesired properties of vegetable oil are the relatively very high viscosity compared to
minerals or diesel oil, as primary study [15].
Since there are so many additives used in the making of OBM, where new more
environmentally characteristics and low cost additives were continually developed to
replace those which have detrimental impacts on the environment, further research should
always be done to find suitable additives for vegetable oil use.
The testing is conducted to determine the physical and chemical properties of the fluids that
were used before OBM formulation. The fluid parameters to be tested are:
a. Specific gravity; shows the weight of the fluid.
b. Kinematic viscosity; shows the reluctance of fluid that under the effect of gravity force to
flow.
c. Flash point; shows the temperature of fluid begins to burn. Meanwhile, the fluid used
should have a high flash point value.
d. Pour point; shows the lowest temperature of fluid that still able to flow. Meanwhile, the
fluid used should have a low pour point value.
8
Physical properties of the fluids in this study will be compared with other synthetic oil and
vegetable oils had been previously published. Biodiesel Palm Oil and Glycerol were used for
the sample of synthetic oils. The comparison of these base oils are shown on the Table 3.
Table 3 Physical Properties of Base Fluids
Parame
ter
SG
Pour
Point
Boiling
Point
Flash
Point
Kinema
tic visco
sity
Biodie
sel
palm
oil
(Rubi
andini
et al,
2007)
Biodie
sel
Jatrop
ha oil
(Pri
wan
za,
2007)
Sara
line
(Setya
wan et
al,
2011)
0.87
0.85
0.78
0.76
°C
6.11
11
-16
°C
80
120
°C
112.2
cSt
3.7
Unit
Crude
Sara
castor
par
oil
(Setya
(Setya
wan et
wan et
al,
al,
2011)
2011)
Biodie
sel
Palm
Oil
Crud
e
Glyce
rol
Glyce
rol
Puri
fied
0.95
0.9
1.09
1.24
-11
-21
5.9
4.4
-12
N/A
N/A
N/A
N/A
N/A
N/A
81
81
112.2
271.1
250
82
99
4.5
3.3
2.5
251.1
5
N/A
N/A
2.4. Nuclear Magnetic Resonance Spectroscopy
NMR that was used in this study is operated at frequency 500MHz (1H-NMR) and 125 MHz
(13C-NMR). The results of NMR Spectrometry of several fluids are shown in Figure 13 and
Figure 14.
Figure 13 NMR Spectrum of Crude Glycerol
9
Figure 14 NMR Spectrum of Purified Glycerol
3. Results and Discussions
3.1. Specific Grafity
The chart on Figure 15 shows the comparison of specific gravity with other base fluids.
Specific gravity characteristics of the fluids were measured using the Picnometer according to
API RP 13B procedure.
Figure 15 Specific Gravity of Glycerol Compared with Other Base Fluid
10
3.2. Cloud Point and Pour Point
The chart on Figure 16 and Figure 17 show the comparison of cloud point and pour point
with other base fluids. Cloud point and pour point characteristics of the fluids were measured
using the Cloud Point and Pour Point Apparatus according to ASTM D 97 procedure.
Figure 16 Cloud Point of Glycerol Compared with Other Base Fluid
Figure 17 Pour Point of Glycerol Compared with Other Base Fluid
3.3. Flash Point
The chart on Figure 18 shows the comparison of flash point with other base fluids. Flash
point characteristics of the fluids were measured using the Pensky-Martens Closed Cup
Tester according to ASTM D 93 procedure.
11
Figure 18 Flash Point of Glycerol Compared with Other Base Fluid
4. Conclusions
1. The specific gravity minerals and biodiesel are lower than pure water due to kind of
oils. Specific gravity of glycerol is lower than glycerol purified due to impurities
compound especially non-reacting methanol.
2. Biodiesel palm oil has higher flash point compared to glycerol, mineral, and other
biodiesel, except crude castor oil (Setyawan, 2011). Hence, transportation and handling
of biodiesel will have significantly lower fire hazard risk compared to glycerol,
mineral, and other biodiesel.
3. Glycerol purified has excellent pour point characteristics compared to minerals and
biodiesel, except saraline and crude castor oil (Setyawan, 2011), which are suitable for
synthetic oil-based mud application in both tropical areas and cold weather. Glycerol
purified also has advantages in terms of transportation, processing, storage, and
material handling.
4. By adding phosphate acid to crude glycerol, the impurities are reduced and the crude
glycerol became the glycerol purified. Hence, glycerol purified have characteristic such
as higher flash point and lower cloud point and pour point compared to crude glycerol.
5. The characteristics and the properties of glycerol purified were found better than crude
glycerol. Meanwhile, after purification, glycerol content is suitable for synthetic oilbased mud application.
5. References
[1] Hambali, E., et al. 2007. Teknologi Bioenergi. Cet.1. Agromedia Pustaka, Jakarta.
[2] Sahirman. 2009. “Analisis Finansial Dan Produksi Biodiesel.” Materi Diklat Level
Menengah. Departemen Pendidikan Nasional Dirjen Peningkatan Mutu Pendidik Dan
Tenaga Pendidikan, Pusat Pengembangan Dan Peberdayaan Pendidik Dan Tenaga
Pendidikan Pertanian. Cianjur.
[3] Pagliaro, M., Rossi, M. 2008. The Future of Glycerol: New Uses of a Versatile Raw
12
Material. RSC Green Chemistry Book Series.
[4] Hambali, E. 2013. Materi Kuliah Teknologi Bioenergi. Sekolah Pascasarjana Institut
Pertanian Bogor.
[5] Winarno, F. G. 1992. Kimia Pangan dan Gizi. PT. Gramedia Pustaka Utama, Jakarta.
[6] SIDS Initial Assesment Report: Glycerol (CAS Number : 56-81-5). 2002. SIDS Initial
Assessment Meeting (SIAM), France.
[7] Tovbin, LM, et al. 1976. Soap Manufacturing Second Edition.
[8] Lotero, et al. 2005. “Synthesis of Biodiesel via Acid Catalysis”. Industrial & Engineering
Chemistry Research 44, 5353–5363.
[9] Dasari. 2006. “Catalytic Conversion of Glycerol and Sugar Alcohols to Value Added
Product [Dissertation].” Missouri: University of Missouri.
[10] Farobie, O. 2009. “Pemanfaatan Gliserol Hasil Samping Produksi Biodiesel Sebagai
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Pertanian Bogor.
[11] Kocsisová, T., et al. 2006. G-phase from Methyl Ester Production-Splitting and
Refining. Petroleum & Coal 48(2): 1-5.
[12] El-Diwani, G., et al. 2009. “Development and Evaluation of Biodiesel Fuel and ByProducts from Jatropha Oil.” Int J Environ Scien Technol 6(2): 219-224.
[13] Amanullah, Md. 2005. “Physio-chemical Characterization of Vegetable Oils and
Preliminary Tests of Vegetable Oil-Based Muds.” SPE/IADC Middle East Drilling
Technology Conference & Exhibition.
[14] Rubiandini, R., Cahyono, G., Sumirat, I., Susetyo, N., 2006, Penelitian Penggunaan
Biodiesel Kelapa
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Environmentally Friendly Potential Domestic Oil-Base Mud.” Proceedings, Indonesian
Petroleum Association Thirty-Fifth Annual Convention & Exhibition.
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