Synthetic base stock based on Guerbet alcohols

Article abstract of DOI:10.1007/s11746-014-2484-4

Guerbet (β branched) alcohols of varying chain length of even carbon numbers were synthesized by using single linear fatty alcohols ranging from 1-octanol to 1-dodecanol. All Guerbet alcohols having fewer than 28 carbon atoms and are liquid at 0 °C due to β branching. Synthetic base oils were prepared by reacting commonly available unsaturated fatty acids and dicarboxylic acids with Guerbet alcohols using p-toluenesulfonic acid as a catalyst. These base oils were characterized by physical and tribological properties like viscosity, viscosity index, pour point, flash point, wear scar, weld load, coefficient of friction etc. and compared with commercially available 150 and 500 N base oils.

Full text of DOI:10.1007/s11746-014-2484-4

J Am Oil Chem Soc
DOI 10.1007/s11746-014-2484-4
ORIGINAL PAPER
Synthetic Base Stock Based on Guerbet Alcohols
•
Chetan Waykole DiptiNarayan Bhowmick
•
Amit Pratap
Received: 6 December 2013 / Revised: 4 May 2014 / Accepted: 13 May 2014
Ó AOCS 2014
Abstract Guerbet (b branched) alcohols of varying chain
length of even carbon numbers were synthesized by using
single linear fatty alcohols ranging from 1-octanol to
1-dodecanol. All Guerbet alcohols having fewer than 28
carbon atoms and are liquid at 0 °C due to b branching.
Synthetic base oils were prepared by reacting commonly
available unsaturated fatty acids and dicarboxylic acids
with Guerbet alcohols using p-toluenesulfonic acid as a
catalyst. These base oils were characterized by physical
and tribological properties like viscosity, viscosity index,
pour point, flash point, wear scar, weld load, coefficient of
friction etc. and compared with commercially available
150 and 500 N base oils.
However; their utilization has been limited so far due to
their intrinsic problems of oxidative and low temperature
stability [4, 5].
Ester-based lubricants have better lubricity, higher flash
point and biodegradability that make them superior to other
base oils. Ester-based oils with a high percentage of linear
and saturated fatty acids are generally solid at ambient
temperature and have a limited spectrum of applications.
The introduction of branching into the structure of esters can
enhance cold flow properties [6–8]. This approach was used
to synthesize Guerbet alcohols to introduce branching [9–
12]. The Guerbet reaction involves condensation of alcohols
forming a dimer alcohol with b-branching and carried out by
heating the alcohol, an alkaline condensing agent and a
hydrogenation-dehydrogenation catalyst. Guerbet reaction
can be carried out in some instances using a base (KOH)
alone, typically a co-catalyst (ZnO, Rh, and many others) is
added in order to accelerate the overall reaction rate. Cata-
lysts described in the patent literature include Ni, Pb salts
[13], and oxides of Cu, Pb, Zn, Cr, Mo, W, Mn [14], Pd
compounds [15] and Ag compounds [16]. The Guerbet
reaction was studied by using various catalysts including
Raney Ni [11], U.O.P. nickel [12], copper-bronze [17],
copper chromite, manganese chromite, copper-magnesium
chromite, zinc chromite. Various basic reagents like mag-
nesium oxide [18], potassium carbonate, calcium carbonate,
sodium carbonates have been tried [11]. In addition, various
combinations of catalysts like mixtures of potassium
hydroxide and boric anhydride [19], Tripotassium phosphate
with Ni or copper chromite [20] have been used. The iridium
catalysts [IrCl (cod)]2 or [Cp 9 IrCl2]2, have been shown to
efficiently catalyze the Guerbet reaction [21]. The Guerbet
reaction was also carried out at 200–250 °C under atmo-
spheric pressure using a wide variety of aldehydes and
ketones as the carbonyl promoter [22].
Keywords Guerbet alcohols Á Synthetic base oil Á Weld
load Á Wear scar Á Coefficient of friction
Introduction
Lubricants obtained from petroleum sources are widely
used for industrial and domestic applications. The base
stocks (oils) are complex mixtures of hydrocarbons, which
pose a serious environmental hazard due to their poor
biodegradability. Synthetic lubricants are renewable
resources and are environmentally acceptable lubricating
oils, which are nontoxic and biodegradable [1–3].
C. Waykole Á D. Bhowmick Á A. Pratap (&)
Department of Oils, Oleochemicals and Surfactants Technology,
Institute of Chemical Technology, (University under Section 3
of UGC Act 1956; Formerly UDCT/UICT), Nathalal Parekh
Road, Matunga (East), Mumbai 400 019, India
e-mail: amitpratap0101@rediffmail.com;
ap.pratap@ictmumbai.edu.in
URL: http://www.ictmumbai.edu.in
123

J Am Oil Chem Soc
In the present research work, heptanal was used as a
carbonyl compound in place of a metallic catalyst. Guer-
bet alcohols of various chain lengths (C16, 20 and 24) were
synthesized by using 1-octanol (C8), 1-decanol (C10) and
1-dodecanol (C12). Being primary alcohols, they were more
reactive than secondary alcohols. These Guerbet alcohols
were subsequently reacted with unsaturated fatty acids
(oleic and erucic) and also dicarboxylic acids (adipic and
sebacic) to get corresponding branch esters. The prepared
esters were named as the Guerbet oleate (GO), Guerbet
erucate (GE), di-Guerbet adipate (DGA), di-Guerbet se-
bacate (DGS). All Guerbet esters were characterized by
physical and tribological properties like viscosity, viscosity
index, pour point, flash point, wear scar, weld load, coef-
ficient of friction etc. and compared with commercially
available 150 and 500 N base oils.
Dean–Stark apparatus with a reflux condenser. The Vi-
gruex column was used to enhance removal of the water
formed during the reaction. The flask was charged with
1-octanol (600 g, 4.62 mol) and KOH (7.8 g, 3 mol%).
The reaction mixture was heated to reflux temperature with
vigorous stirring. The water of dehydration of KOH was
formed which was removed by refluxing in the Dean–Stark
apparatus. At reflux temperature, heptanal (15.8 g,
3 mol%) was added dropwise over a period of half hour.
The reaction was continued by vigorous stirring and re-
fluxing in the Dean–Stark apparatus. The progress of the
reaction was monitored by measuring the water collected
during the reaction. The reaction was carried until the
temperature had increased to 245 °C. The reaction mixture
was cooled and acidified with dilute sulfuric acid (10 %).
The reaction product was washed with water to neutral pH
and dried over anhydrous sodium sulfate. This dried
product was taken for further analysis by gas chromatog-
raphy. C16 Guerbet alcohol from the reaction product was
separated by fractional distillation under a vacuum.
Materials and Methods
Materials
C20, C24 Guerbet alcohols were prepared from C10, C12
linear alcohols in same way as described above (Fig. 1a).
Table 1 shows the reaction parameters for C20 and C24
Guerbet alcohols. Due to the high boiling point of C12
linear alcohol, the preparation of C24 Guerbet alcohol was
carried out at 250 °C under a pressure of 300 mmHg.
1-Octanol (99.98 % purity), 1-decanol (99.86 % purity),
1-dodecanol (99.95 % purity) were obtained as gift sam-
ples from M/s Godrej Industries Ltd., Mumbai. 1-Heptanal
(Heptaldehyde) was obtained from M/s Biotor Industries
Ltd., Mumbai (Formerly Jayant Oils and Derivatives Ltd.),
as gift sample and showed purity of 99.4 % by Gas chro-
matography. Commercial grade Oleic acid (70 %) and
Erucic acid (92 %) were received as gift sample from M/s
VVF. Ltd., Mumbai. Adipic acid and sebacic acid (AR)
were procured from local market. 150 and 500 N base oils
were obtained from M/s Savita Chemicals Ltd., Navi
Mumbai. Sodium hydroxide (AR), potassium hydroxide
(AR) were procured from M/s Thomas Baker Pvt. Ltd.,
Mumbai. Potassium dichromate (AR), sodium thiosulfate
(AR), potassium iodide (AR), potato starch, phenolphtha-
lein (AR), p-toluenesulfonic acid (LR), sulfuric acid (AR),
Wij’s solution, hydrochloric acid 35 % (AR) were pro-
cured from M/s S. D. Fine-Chem Ltd., Mumbai. All sol-
vents were purchased from M/s S. D. Fine-Chem Ltd.,
Mumbai and used as received.
Analytical Methods
Relative fatty alcohol and Guerbet alcohol compositions
were determined using a gas chromatograph (Chemito
1000, Thermo Scientific, Nasik, India.) equipped with a
flame ionization detector. Analysis was conducted on a
BPX-5 column (30 m length 9 0.25 mm i.d.) under the
following temperature program and conditions: Solvent—
hexane; sample concentration—1 %; amount of sample
injected—1 lL; 100 °C for 2 min; from 100 to 200 °C at
10 °C/min; at 200 °C for 1 min; from 200 to 300 °C at
10 °C/min; at 300 °C for 20 min; injector temperature at
260 °C; flame ionization detector temperature at 290 °C
with nitrogen as the carrier gas at a flow rate of 0.8 mL/
min; split ratio of 1:50. From the chromatograms, the
contents of alcohols were calculated in such a manner that
their total amounted to 100 %.
Methods
Synthesis of Esters of Dicarboxylic Acids
Synthesis of Guerbet Alcohols
Synthesis of C16 Guerbet Alcohol from 1-Octanol (C8)
and Unsaturated Fatty Acids with Guerbet Alcohols
Several esters were synthesized from dicarboxylic acids
(adipic, sebacic) as well as some unsaturated fatty acids
(oleic, erucic) and Guerbet alcohols (‘‘C16 G.A.’’ = 2-
hexyl-1-decanol, ‘‘C20 G.A.’’ = 2-octyl-1-dodecanol, ‘‘C24
G.A.’’ = 2-decyl-1-tetradecanol) (Fig. 1b).
A 1-L, four-necked, round-bottom flask, equipped with an
dropping funnel, mechanical stirrer and an internal ther-
mometer, and Vigruex column, which was fitted with a
123

J Am Oil Chem Soc
Fig. 1 Guerbet alcohol
formation and its esterification
with unsaturated fatty acids and
dicarboxylic acids
Table 1 Reaction parameters
for Guerbet alcohols
synthesized in the present work
Batch
C 16 Guerbet alcohol
C 20 Guerbet alcohol
C 24 Guerbet alcohol
Alcohol used
KOH
1-Octanol
3 mol%
3 mol%
245 °C
760 mmHg
9 h
1-Decanol
3 mol%
3 mol%
245 °C
760 mmHg
6 h
1-Dodecanol
3 mol%
3 mol%
250 °C
Heptanal
Reaction Temp.
Pressure
300 mmHg
Time
4 h
Conversion (%)
71.77
71.23
68.73
Composition of products (% w/w By GC)a
a
All determinations were
Monomer (unreacted alcohols)
Dimer (Guerbet alcohols)
Others
14.70 0.29
73.00 0.15
12.30 0.19
15.30 0.10
71.00 0.22
13.70 0.13
25.50 0.17
64.30 0.13
carried out in triplicate and
mean values standard
deviations (SD) reported
10.20
0.09
A 1-L, three-necked, round-bottom flask, fitted with a
mechanical stirrer, a Dean–Stark apparatus (for removal of
the water of reaction) with a reflux condenser and ther-
mocouple, was charged with C16 Guerbet alcohol (100 g,
2 mol), adipic acid (30.5 g, 1 mol) and p-toluenesulfonic
acid (1.3 g, 1 %). Toluene was added to the reaction
mixture as a solvent. The reaction mixture was heated with
vigorous stirring. The mixture became homogeneous at
approximately 70 °C. The reaction was carried out at
temperature of 120 °C. The reaction was continued by
123

J Am Oil Chem Soc
Extreme Pressure Properties of Lubricating Fluids
refluxing in the Dean–Stark apparatus. The water of reac-
tion was removed by phase separation in the Dean–Stark
apparatus. The progress of the reaction was monitored by
measuring the water of the reaction. The reaction com-
pletion was about 99 % in 6 h. After completion of the
reaction, NaOH was added to neutralize the p-TSA catalyst
and the product washed with distilled water until a neutral
pH 7 was obtained. The organic layer was dried over
anhydrous sodium sulfate and desolventized using a rotary
vacuum evaporator. The product was further analyzed by
acid value, FT-IR and Thin Layer Chromatography.
The extreme pressure test determination was carried out
according to the American Society for Testing and Mate-
rials (ASTM D 2783) using a four ball tester (Make: Du-
com; Model TR 30L). The balls (52 100 steel, 12.7 mm in
diameter, 64–66 Rc hardness, and extreme polish) were
thoroughly cleaned with methylene chloride and hexane
before each experiment. The tester was operated with one
steel ball under load rotating against three steel balls held
stationary in the form of a cradle. Guerbet ester covered the
lower three balls. The rotating speed was kept at
1,760 40 rpm/min. The machine and the lubricant were
brought between 65 and 95 °F and then a series of tests of
10 s duration are made at increasing loads until welding
occurred. Ten tests were made below the welding point.
Lubricant Performance Properties Tests
Viscosity and Viscosity Index Measurements
The kinematic viscosities of various esters of Guer-
bet alcohol were measured using a Cannon–Fenske cali-
brated viscometer (Cannon Instrument Co., State College,
PA) in a Cannon temperature bath (CT-1000) from 35 to
100 °C at 5 °C intervals, as per the ASTM D 445-95
method. The viscosities obtained were average values of
2–3 determinations and the precision was within the limits
of ASTM specification. The viscosity index (VI) is an
arbitrary measure for the change of kinematic viscosity
with temperature. The viscosity index was calculated using
ASTM D 2270.
Wear Characteristics of Lubricating Fluids
The experiment is designed to study the anti-wear prop-
erties of samples under sliding contact by four-ball test
geometry using a Four ball tester apparatus (Make: Ducom;
Model TR 30L), at ambient temperature. This test method
covers a procedure for making a preliminary evaluation of
the anti-wear properties of fluid lubricants in sliding con-
tact by means of the four-ball wear test machine (ASTM D
4172). The balls (52100 steel, 12.7 mm diameter, 64–66
Rc hardness and extreme polish) were thoroughly cleaned
with dichloromethane and hexane before each experiment.
15 mL Guerbet ester was poured in the test cup to cover the
three stationary balls. For experiments, a set rpm of 1,200,
a temperature of 75 °C, and a normal load of 40 kg
(392 N) was applied for 60 min. Temperature of the ester
was 75 °C which had increased to 78–79 °C at the end of
the 60 min run. The wear scar diameters on balls were
measured using a digital optical microscope. Two mea-
surements, perpendicular to each other, were recorded for
each scar on a ball and the average of six measurements,
for three balls, was taken in each case. The scar diameter
was reported in millimeters. Duplicate tests were always
done with a new set of balls and the standard deviation of
six measurements was less than 0.04 in all the experiments
[23].
Pour Point
Pour points were measured by following the ASTM D 97
method. A pour point instrument (Make: Krisspair, Model
PPA) was used to determine the pour points of the pro-
ducts. After preliminary heating, 5 mL Guerbet ester was
placed in a stoppered test tube. The stopper contained a
thermometer measuring from ?20 to -80 °C that was
immersed into the sample. These test tubes were placed in
a digital pour point apparatus. The temperature was mea-
sured in 3 °C increments until the sample stopped pouring.
Each sample was run in triplicate and average values
rounded to the nearest whole degree are reported.
Flash Point Measurement
Coefficient of Friction
Flash point determination was run according to the
American National Testing Method using the Cleveland
open cup method (ASTM D 92). The test cup was filled to
a specified level with Guerbet ester. The temperature was
rapidly increased at first, and then at a slow constant rate as
the flash point was approached. At specified intervals a
small test flame was passed across the cup. The lowest
temperature at which the vapour above the surface of the
liquid caught fire was noted as the flash point.
High Frequency Reciprocating (Make: Ducom; Model TR-
282) instrument was used for this test. Boundary lubrica-
tion properties of Guerbet esters were studied using a ball-
on-disk configuration on the instrument under the pre-
scribed test conditions. The balls and the disks were thor-
oughly cleaned with fresh reagent-grade methylene
chloride and hexane prior to each experiment. These balls
123

J Am Oil Chem Soc
were AISIE-52100 steel, hardened for 62 h, Ra\0.05 mm,
size: 6 mm diameter. Disc material was AISI E-52100
steel, hardness 200 HV, annealed, Ra 0.02 mm, size:
10 9 4 mm wide. All output characteristics prescribed by
ASTM method D 6079-99. A 2-mL sample of the test fluid
was poured into the test reservoir to totally immerse the
ball and disk of the HFRR and adjusted to the standard
temperature of 60 °C. When the fuel temperature had sta-
bilized, a vibrator arm holding a non-rotating steel ball and
loaded with a 200 g mass was lowered until it contacted a
test disk completely submerged in the lubricant. The ball
was caused to rub against the disk with a 1 mm stroke at a
frequency of 50 Hz for 75 min. Values of the coefficient of
friction in time were plotted as a graph and these values
were used to calculate mean value of it. The coefficient of
friction (CoF) values reported are averages of three inde-
pendent experiments with the standard deviation [24].
stable temperature and reduced pressure. The purity of
distilled C16, 20 and 24 Guerbet alcohols was 98.8, 98.4
and 87 % respectively. All the pure Guerbet alcohols were
colorless liquids. Acid and iodine values were below
detection level (BDL). The hydroxyl values of C16, 20 and
24 pure Guerbet alcohols were 229 0.7, 186 0.9 and
156 0.6 mg of KOH/g respectively.
Guerbet alcohols were synthesized at a relatively lower
temperature by use of aldehydes as intermediates and does
not includes any expensive hydrogen transfer metal cata-
lyst. The wet analyses of prepared Guerbet esters are
shown in Table 2.
Fourier Transform Infrared Spectroscopy (FT-IR)
A FT-IR Shimadzu (Model IRAffinity-1, Japan) was used to
identify the functionality of the Guerbet esters. The main
peaks and their assignment to functional groups are given in
Fig. 2. In the FT-IR spectra of prepared C16 di-Guerbet esters
compounds (Fig. 2a), FT-IR peaks indicated the disappear-
ance of an absorption band at 3,335 cm-1 which belongs to
theOHstretchingalcohol group. This fact suggestedcomplete
esterification. Bands representing C–H stretching groups
Results and Discussion
In a Guerbet alcohol process, the starting alcohol was
condensed in the presence of KOH (base) to produce a b-
branched alcohol with double the number of carbon atoms.
In this work, Heptanal was used to promote the conversion
of starting alcohol to Guerbet alcohol. Synthesis of C16
Guerbet alcohol takes much more time than C20 and C24
Guerbet alcohols, because of the low the initial reflux
temperature of 1-octanol (195 °C). At this temperature the
reaction rate was slow. Reaction rate increased with
increasing temperature and removal of the reaction water.
Guerbet alcohol formation was faster within the tempera-
ture range of 230–245 °C. The temperature was allowed to
rise to 245 °C and maintained there. In the synthesis of C20
Guerbet alcohol, the initial reflux temperature was 230 °C.
The initial rate of conversion was slow and further
increased with increases in the formation of dimer alcohol
and the subsequent rise in temperature. A reaction tem-
perature above 245 °C was avoided to minimize trimer
formation. In preparation of C24 Guerbet alcohol from
1-dodecanol, due to the high boiling point of the starting
alcohol, the reaction was carried out under a pressure of
300 mm Hg. The temperature was allowed to rise to
250 °C and maintained there. All these reaction products
were analyzed by gas chromatography. The relative fatty
alcohol and Guerbet alcohol compositions of all reaction
products are shown in Table 1. All these reaction products
were further purified by a fractional distillation technique
under reduced pressure (0.5 mmHg) to obtain purified
Guerbet alcohols. The fractional distillation column was
provided with the Hyflux structured packing to maximize
the purity of product within the limited height of the col-
umn. The fractions of pure products were collected at the
(2,968.60–2,858.31 cm-1),
(1,760–1,670 cm-1), C–H bending groups (1,458.08 cm-1
C=O
stretching
groups
)
and also C–O stretching groups (1,170.71 cm-1) were clearly
visible in the spectra. The presence of new peak in the FT-IR
spectra of C16 Guerbet esters of unsaturated fatty acid
(Fig. 2b) at 1,680–1,640 cm-1 are attributed to the C=C
stretching group.
1H-Nuclear Magnetic Resonance Spectroscopy (1H
NMR)
1
Structures of Guerbet esters were confirmed by H NMR
obtained with a Mercury Plus 300 NMR Spectrometer
(model 300 MHz, Varian, USA) recorded in chemical
shifts expressed as ppm downfield from tetramethylsilane
as an internal standard reference in CDCl3 as solvent.
1H-NMR spectra of C16 DGA and C16 GO were shown
in Fig. 3 respectively. 1H NMR (CDCl3) of C16 DGA
(Fig. 3a) shows a characteristic peak at d 0.9 t corre-
sponding to a terminal CH3 group (a), d 1.2–1.4 corre-
sponds to CH2 protons in alkyl chain (b), d 1.5 m assigned
to –CH2 (c), d 2.3 m assigned to tertiary CH (d), d 4 d
assign to –CH2O (e).
1H NMR (CDCl3) of C16 GO (Fig. 3b) shows a char-
acteristic peak at d 0.96 t corresponds to a terminal CH3
group (a), d 1.2–1.4 corresponds to CH2 protons in the
alkyl chain (b), d 1.55 m assign to –CH2 (c), d 2 m cor-
responds to –CH2 attached to a double bond (d), d 2.3 m
assigned to tertiary CH (e), d 2.75 t corresponds to O=C–
CH2 (f), d 4 d –CH2O (g), d 5.37 d CH=CH (h).
123

J Am Oil Chem Soc
Table 2 Wet analysis of prepared Guerbet esters
Samples
Wet analysis of estersa
AOCS method of analysis
Saponification value
(mg KOH/g)
AOCS T1-1a-64
Acid value
(mg KOH/g)
AOCS Te-1a-64
Iodine value
(% Iodine)
AOCS Tg-1a-64
Hydroxyl value
(mg KOH/g)
AOCS Cd-13-60
C16 DGA
C16 DGS
C16 GO
C16 GE
188.53 0.56
172.67 0.34
110.95 0.52
99.65 0.47
158.86 0.61
147.52 0.38
99.89 0.44
90.63 0.55
137.17 0.41
128.24 0.67
90.83 0.59
83.11 0.53
0.40 0.09
0.96 0.14
0.70 0.21
0.44 0.08
0.47 0.18
0.51 0.15
0.84 0.26
0.78 0.27
0.69 0.17
0.73 0.08
0.59 0.23
0.84 0.16
BDLb
0.38 0.12
0.81 0.19
0.92 0.26
1.07 0.09
0.99 0.14
0.64 0.25
0.49 0.22
0.55 0.17
0.71 0.23
0.38 0.31
0.55 0.28
0.62 0.14
BDL
46.86 0.19
43.77 0.27
BDL
C20 DGA
C20 DGS
C20 GO
C20 GE
BDL
43.16 0.14
40.19 0.24
BDL
C24 DGA
C24 DGS
C24 GO
C24 GE
BDL
41.40 0.21
38.73 0.15
C16 DGA, 2-hexyldecyl-bis-hexanedioate; C16 DGS, 2-hexyldecyl-bis-decanedioate; C16 GO, 2-hexyldecyl-9(Z)-octadecenoate; C16 GE,
2-hexyldecyl-13(Z)-docosenoate; C20 DGA, 2-octyldodecyl-bis-hexanedioate; C20 DGS, 2-octyldodecyl-bis-decanedioate; C20 GO, 2-octyld-
odecyl-9(Z)-octadecenoate; C20 GE, 2-octyldodecyl-13(Z)-docosenoate; C24 DGA, 2-decyltetradecyl-bis-hexanedioate; C24 DGS, 2-decylte-
tradecyl-bis-decanedioate; C24 GO, 2-decyltetradecyl-9(Z)-octadecenoate; C24 GE, 2-decyltetradecyl-13(Z)-docosenoate
a
All determinations were carried out in triplicate and mean values standard deviations (SD) reported
b
BDL below detection level
Fig. 2 FT-IR spectra of Guerbet esters a Di-Guerbet esters, b Guerbet esters
123

J Am Oil Chem Soc
Fig. 3 1H nuclear magnetic resonance of Guerbet esters a C16 DGA, b C16 Guerbet oleate
Fig. 5 Kinematic viscosity of C20 Guerbet esters obtained using a
Cannon–Fenske viscometer from 40 to 100 °C with 5 °C intervals
Fig. 4 Kinematic viscosity of C16 Guerbet esters obtained using a
Cannon–Fenske viscometer from 40 to 100 °C with 5 °C intervals
Tribological Performance Properties
Viscosity
The kinematic viscosity values of all Guerbet esters were
compared with 150 and 500 N base oils. For all Guerbet
esters, the kinematic viscosity increased by an overall
increase in the molecular weights of the esters with
increased chain length (number of carbons) and decreased
with increase in temperature. While comparing viscosity of
C16 Guerbet esters with base oils, 150 N base oil displayed
higher viscosity values. For C20–24 DGA, C24 DGS esters,
the kinematic viscosity was higher in comparison with
150 N Base oil at different temperatures (Figs. 4, 5, 6).
500 N base oil showed higher viscosity than all esters
involved in this work.
Fig. 6 Kinematic viscosity of C24 Guerbet esters obtained using a
Cannon–Fenske viscometer from 40 to 100 °C with 5 °C intervals
123

J Am Oil Chem Soc
Table 3 Viscosity index, pour
point, flash point, weld load
capacity, wear scar diameter,
CoF of Guerbet esters
Samples Viscosity
Index
Pour point
(°C)
Flash point
(°C)
Weld load
(kg)
War scar diameter
(mm)a
CoFa
C16
DGA
C16
DGS
121
139
-36
-33
224
240
195
210
0.82 0.011
0.044 0.02
0.042 0.02
0.78 0.011
C16 GO 202
C16 GE 214
-35
-26
-18
212
230
245
180
195
210
0.83 0.012
0.68 0.010
0.59 0.020
0.052 0.02
0.049 0.02
0.028 0.02
C20
DGA
C20
DGS
153
163
-16
267
225
0.55 0.015
0.026 0.02
C20 GO 184
C20 GE 198
-24
-8
241
263
268
180
210
210
0.61 0.017
0.52 0.020
0.56 0.012
0.046 0.02
0.045 0.02
0.020 0.02
C24
DGA
C24
DGS
146
-11
173
-6
273
225
0.47 0.015
0.018 0.02
a
All determinations were
carried out in triplicate and
mean values standard
deviations (SD) reported
C24 GO 196
C24 GE 212
-13
259
269
195
225
0.59 0.010
0.44 0.020
0.041 0.02
0.039 0.02
2
Viscosity Index
below a temperature of 0 °C, except C24 GE ester. C16
DGA, DGS, GO, GE, C20 GO esters had a much better PP,
in the range of -22 to -36 °C, while 150 N and 500 N
base oils had PP of about -21 and -9 °C respectively. C20
GE, C24 DGS, GE ester showed higher pour point values
than 500 N Base oil. Esters of adipic, sebacic and oleic
acid with C16 Guerbet alcohol were the most effective
decreasing the pour points to -36, -33 and -35 °C
respectively. It can be assumed that the presence of
branching on the fatty acid ester created a steric barrier
around the individual molecules and inhibited crystalliza-
tion, resulting in a lower pour point. The esters containing a
branched moiety exhibited lower pour point values than
those of standard 150 and 500 N Base oils. This statement
only applies to the esters prepared from the lower carbon
chain length Guerbet alcohol. Increasing the carbon num-
ber in the Guerbet ester fails to lower the temperature
characteristics of esters. From pour point values it was
observed that branching in the ester molecule enhances the
cold flow properties.
Generally, the least viscous oil which still forces the two
moving surfaces apart is desired. If the oil is too viscous, it
will require a large amount of energy to move; if is too
thin, the surfaces will rub and friction will increase.
Table 3 shows the viscosity index (VI) values of the
Guerbet esters. The effect of temperature on lubricant
viscosity is a measure of its viscosity index. VI found to be
of 150 N base oil was 102 and of 500 N base oil was 95.
All the Guerbet esters showed a higher viscosity index than
150 and 500 N base oils. All Guerbet esters showed higher
viscosity index i.e. a minimum change in viscosity over
such a temperature range. In this work, the increased vis-
cosity index (VI) of Guerbet esters was the result of their
higher molecular weight. The efficiency of the base oil in
reducing friction and wear was greatly influenced by its
viscosity, which decreased at increased temperatures.
Pour Point
Branching in the structure of esters may disrupt to form
macro crystalline structure through a uniform stacking
process and results in improved low temperature proper-
ties. This approach was used here to introduce branching
into the structure of esters by using branched alcohol as a
starting material. The pour point (PP) of 150 N base oil
was found to be -21 °C and of 500 N base oil was -9 °C.
Table 3 shows that as the number of carbons of the ester
molecule increases, there was decrease in pour point of the
esters. All the Guerbet esters showed pour point values
Flash Point
Table 3 shows the flash point values of Guerbet esters. The
flash point found for 150 N base oil was 216 °C and for
500 N base oil it was 254 °C. All Guerbet esters showed
higher flash points than that of the 150 N Base oil, except
the C16 GO ester. The esters prepared from C24 Guer-
bet alcohol and C20 DGS, GE exhibited higher flash points
than 500 N base oil. Comparing all the prepared esters, C24
DGS showed the highest flash point. The flash point was
123

J Am Oil Chem Soc
found to increase with the carbon number in the ester
molecule. Ester linkages present in the structure is
responsible for its higher flash point and lower volatility.
Prepared esters showed higher flash points than mineral
base oils due to polarity differences. The polarity of the
ester molecules attracted another molecule and this inter-
molecular attraction required more energy (heat) for the
esters to transform from a liquid to a gaseous state.
Therefore, at a given molecular weight or viscosity, the
esters exhibited a lower vapour pressure which translated
into a higher flash point and a lower rate of evaporation for
the lubricant.
objective is the creation of such boundary friction layers in
a variety of dynamic, geometric and thermal conditions.
Such layers are of great importance in practical applica-
tions when thick, long-lasting lubricant films to separate
two surfaces are technically impossible. Boundary lubri-
cating films are created from surface-active substances and
their chemical reaction products. Adsorption, chemisorp-
tion, and tribochemical reactions also play significant roles.
The coefficient of friction of base oil 150 N was found to
be 0.13 0.01 and for 500 N it was 0.11 0.01. The C24
DGS ester showed a lower CoF of 0.018. The maximum
CoF was observed in the case of C16 GO ester, namely
0.052. This is consistent with earlier friction findings that
the CoF was reduced by increasing the carbon chain length.
Guerbet esters prepared from the unsaturated fatty acids
exhibited maximum CoF than the respective di-Guerbet
ester.
Extreme Pressure Properties of Lubricating Fluids
The load carrying capacity of all Guerbet esters are listed
in Table 3. The ability of a lubricant to maintain an
effective lubricating film under high loads or pressures is a
measure of its load carrying or extreme pressure (EP)
characteristics. The effectiveness of all Guerbet esters was
compared with mineral base oils such as 150 and 500 N.
The weld load of 150 N base oil was found to be 150 kg
and for 500 N base oil it was 165 kg. From overall Guerbet
esters, C20, C24 DGS and C24 GE showed the highest load
capacity of 225 kg. All the products showed a higher load
carrying capacity than the 150 and 500 N base oils. The
load carrying capacity became more effective with
increasing chain length of the ester molecule.
Conclusion
The kinematic viscosity, viscosity index and load carry-
ing capacity of Guerbet esters increased with carbon
number (molecular weight). Guerbet esters prepared from
unsaturated fatty acids showed lower viscosities. A neg-
ative influence on the low temperature properties was
observed with increases in the chain length of the ester
because of increases in the molecular weight of the
Guerbet esters. Guerbet esters had higher flash points
than mineral base oils due to induced polarity caused by
ester linkages. One possible reason behind the lower flash
point of 150 and 500 N base oils was that base oils were
a complex mixture of hydrocarbons. One of the signifi-
cant findings of this work relates to the load carrying
capacity of prepared esters being higher than the 150 and
500 N base oils. The wear scar of the prepared esters
decreased with the carbon number of the ester molecule.
The coefficient of friction was lowered with carbon
number in the Guerbet ester. Overall Guerbet esters
proved to be better synthetic base oils than commercial
petroleum base oils 150 and 500 N.
Wear Characteristics of Lubricating Fluids
Table 3 shows the wear diameter of Guerbet esters ana-
lyzed by the four ball wear test method. The wear scar of
base oil 150 N was found to be 0.68 0.012 mm and for
500 N it was 0.62 0.013 mm. The C24 GE ester showed
a minimum wear scar diameter of 0.442 mm. The maxi-
mum wear scar diameter was observed in the case of the
C16 GO ester. Among all Guerbet esters, increasing the
carbon number of ester molecule causes a considerable
reduction in wear. One possible reason was increased vis-
cosity due to an increase in molecular weight. The products
having smaller wear scar diameter characteristics showed
better lubricity. These Guerbet esters had excellent lubri-
cation properties due to the functional groups present in the
molecules. The polar ester groups of such molecules adhere
to positively-charged metal surfaces creating protective
films which slow down the wear of the metal surfaces and
the dissipation of heat generated at these wear surfaces.
Acknowledgments This study was financially supported by the
Department of Science and Technology (DST), New Delhi, Govern-
ment of India.
References
1. Zaher FA, Nomany HM (1988) Vegetable oils and lubricants.
Grasas Aceites (Seville) 39:235–238
2. Mang T (997) In: Gunstone FD, Padley FB (eds) Lipid technol-
ogies and applications. Marcel Decker, New York, pp 737–758
3. Legrand J, Durr K (1998) High-performing lubricants based on
renewable resources. Agro Food Ind Hi-Tech 9:16–18
Coefficient of Friction
Boundary frictions of all prepared esters are listed in
Table 3. In lubricant development, the most important
123

J Am Oil Chem Soc
4. Becker R, Knorr A (1996) An evaluation of antioxidants for
vegetable oils at elevated temperatures. Lubr Sci 8:95–117
5. Kasturi L, Carrick V (1994) Performance testing of lubricants
based on high oleic vegetable oils. J Synth Lubr 11:189–206
6. Gruening B, Weitemeyer C (Goldschmidt, Th., AG) (1994)
Cosmetic or pharmaceutical preparations. European Patent
596304; Chem. Abstr. 121:163700
7. Sakurai K, Nobe T (Shin Nippon Rika Kk) (1994) Cyclopoly-
olefin resin composition. Japanese Patent 06306252; Chem.
Abstr. 124:119007
15. Yates JE (1976) Process for condensation of Alcohols. US Patent
3,979,466
16. Yates JE (1975) Catalytic process for producing higher molecular
weight. US Patent 3,864,407
17. Weizmann C, Bergmann E, Sulzbacher M (1950) Further
observation on the Guerbet reaction. J Org Chem 5:54–57
18. Ueda W, Kuwabara T, Ohshida T, Morikawa Y (1990) A low
pressure Guerbet reaction over magnesium oxide catalyst.
J Chem Soc (Chem Commun) 22:1558–1559
19. Sulzbacher M (1955) The Guerbet reaction of cetyl alcohol.
J Appl Chem 5:637–641
20. Miller RE, Bennett GE (1961) Producing 2-Ethylhexanol by the
Guerbet reaction. Ind Eng Chem 53(1):33–36
8. Mondet J (L’Oreal) (1999) Composition for topical application
containing an olefin copolymer crystallization controlled. Euro-
pean Patent 951897; Chem. Abstr. 131:314093
9. Guerbet M (1899) C R Acad Sci Paris 128 511:1002
10. Veibel S, Nielsen JI (1967) On the mechanism of the Guerbet
reaction. J Tetrahedron 23:1723–1733
11. Dvornikoff ME, Farrar MW (1957) Condensation of alcohols.
J Org Chem 22:540–542
21. Matsu-ura T, Sakaguchi S, Obara Y, Ishii Y (2006) Guerbet
reaction of primary alcohols leading to b-alkylated dimer alco-
hols catalyzed by Iridium complexes. J Org Chem 71:8306–8308
22. Miller Joseph A, Virnig Michael J (1991) Improved Guerbet
process. WO/1991/004242
12. Pratt EF, Kubler DG (1954) Disproportionate condensations.
I. Modified Guerbet reactions. J Am Chem Soc 76:52–56
13. Kollar J, Schulz JGD (1964) Condensation of alcohols. US Patent
3,119,880
14. Engelhardt F, Schritt W (1971) Method of producing b branched
aldehydes. US Patent 3,558,716
23. ASTM D 4172: Standard test method for wear preventive char-
acteristics of lubricating fluid (Four-Ball Method). ASTM, West
Conshohocken, PA, USA
24. ASTM D 6079-99: Standard test method for evaluating lubricity
of diesel fuels by the High-Frequency Reciprocating Rig (HFRR).
ASTM, West Conshohocken, PA, USA
123