Journal of Power and Energy Engineering, 2013, 1, 84-89 Published Online October 2013 (
Copyright © 2013 SciRes. JPEE
Develop m ents of Multifunctional Additives for High
Quality Lube Oil
Noura El Mehbad
Faculty of Science, Nagran University, Saudi Arabia of Kingdom.
Received October 2013
In most lubrication systems, the oil is mixed with air, in contact with air, in contac t with metals and at high temperature.
This is mean cause of premature lubricant, deterioration which can result in oxidation products, which are mainly acid.
Hydrocarbon oxidation in the liquid phase proceeds by a radical chain reaction. In the present paper polyalkylphenol
formaldehyde sulphonate and its ethoxylate were synthesized and evaluated as pour point depressant, viscosity improv-
er and antioxidant. The efficiency of these additives depends on their chemical structure and degree of mixing (mole
fraction). Values of surface tension of these additives were measured in oil phase and consequently CMC was deter-
mined for all additives and their mixtures. A novel method of inhibiting oxidation was proposed. The author suggests
the mechanism of inhibiting oxidation according to surface activity of additive in oil phase. More confirmations for
suggested mechanism were investigated by measuring the area occupied per molecule of additive at oil phase. The re-
sults indicate that the compatibility of sulphonate with ethoxylate group and forming stable micelle which acts as wax
dispersant and improver vi s cosit y .
Keywords: Lubrication Oil; Polymers; Additiv es of Base Oil; Micelles
1. Introduction
Paraffin wax deposition from middle distillate fuel low
temperature is one of the serious and long standing prob-
lems in petroleum industry. At low temperature, the crys-
tals of wax easily form impermeable cakes, which can
block filters and eventually lead to engine failure. Many
methods have been attempted for the prevention of the
crystals mating together. Some anionic surfactants had
been applied as pour point depressant by Omar et al. [1].
It is found that the surface parameters and free energies
of micellization and adsorption confirm the decreasing
and improving of pour point. Also it is found that there is
a good relation between surface properties especially
interfacial tension of the surfactants and their efficiency
in depres sing the po ur point.
Cacium octadecyl benzene sulphonate and octadecyl
phenol ethoxylate with 6 units of ethylene oxide were
synthesized and evaluated as pour, cloud points depres-
sants and viscosity index improvers. These additives were
compared with imported natural wax dispersing agent.
The surface tensions of these additives were measured in
oil phase. The values of critical micelle concentration,
CMC, minimum area per molecule and surface excess
were determined. It is found that increasing concentra-
tion of these additives is accompanied by an increase in
the minimum area occupied per molecule and surface
excess concentration. There is a good relationship be-
tween the structure of hydrophilic group of the additive
and its efficiency. Mixing the binary additives enhances
its efficiency. The results were discussed according to sur-
face excess concentration at oil/air interface [2]. On the
other hand the physical properties of the mixed system of
cationic/nonionic surfactant and its efficiency in pour
point depression were studied elsewhere [3]. It is found
that the pour point depressing depends on CMC. The
Widespread applications of surfactants originate from the
intrinsic duality in their molecular characteristics namely;
they are composed of a polar head group (hydrophilic)
part and nonpolar tail group (hydrophobic) part. The mod-
ification of the lyophobic and lyophilic groups, in the
structure of the surfactant, may become necessary to main-
tain surface activity at a suitable level.
The tribochemical reactions of n-hexadecane proceed-
ing in a tribosystem lubricated was studied elsewhere [4].
It is hypothesized that at ambient temperature reactions
are mostly initiated by the mechanical action of the sys-
tem and elevated temperature (200˚C) thermochemical
reactions should be dominant. One of the most important
modes of lubricant degradation is oxidation, which is the
primary cause of increase in viscosity, pour point, sludge,
Developments of Multifunctional Additives for High Quality Lube Oil
Copyright © 2013 SciRes. JPEE
acidic component formation. The author studied new an-
tioxidant for lube oil. This antioxidant dibenzyl-s-phenyl
thio glyconitrile and other derivatives were prepared phase
transfere catalysts. These compounds were added to oil
in different concentrations. The antioxidants activities of
different dosages were evaluated and suggested mechan-
ism according to micelle and their thermodynamic. The
oxidation stability of lubricating oil has a critical influ-
ence on the oil performance during service. In this paper
dibenzyl-s-phenyl thioglyconitrile and other derivative
were prepared by phase transfer catalysts and investi-
gated as antioxidants. These compounds were added to
oil in different concentr ations. The antioxidants activities
of different dosages were evaluated and suggested me-
chanism according to micelle and their thermodynamics.
The oxidation of the oil has been carried for different
time intervals. The degradation of the oil has been moni-
tored by total acid formation. Oxidation stability of lube
oil was largely affected by sulphur and aromatic hydro-
carbons concentration in oil, with increased sulphur con-
tent increase oxidation stability. The prepared compounds
gave higher oxidation stability than imported compound
(IRCANOX L 135-CIBA) [5].
The structural effect of polymeric sodium nonyl phe-
nol formaldehyde sulphonate and its mixture withpoly-
nonyl phenol formaldehyde ethoxylate with 12 ethox-
ylate units was prepared and evaluated for metal working
fluid at different interface by Omar 2004 [6].
Suitable detergents are alcohols and ammonium salts,
these applications encouraged us to initiate the symme-
tric studies on the physic-chemical behavior of ammo-
nium soaps and different captions salts. The purpose of
the present work was to characterize ammonium, poly
alkylphenol formaldehyde sulphonate and its ethoxylate
on pour point and oxidation stability of the paraffinic gas
2. Experimental
Raw Materials
The physicochemical properties of lubricating were car-
ried out using ASTM and IP standard test methods (Ta-
ble 1).
Synthesis of the additive (ammonium poly dodecyl
phenol sulphonate).
The polymeric surfactant utilized in this study was
prepared by sulphonation of dodecyl phenol which pre-
pared elsewhere by alkylation of phenol with chlorodo-
decane in the presence of mixture of catalysts (benzyl
triethyl ammonium chloride as phase transfere catalysts
and zinc chloride) The prepared dodecyl phenol was sul-
phonated with fuming sulphoric acid and neutralized with
ammonium solution. The result compound is ammonium
dodecyl phenol sulphonate which are dected by IR and
Table 1. Physicochemical properties of base oil.
Properties Base oil Test
Denisty (g/ml) at 15.5 ˚C 0.809 D. 1298
Cloud point 22 IP 219/82
ASTM colour 4.5 D. 1500
Kinematic viscoslty cSt
at 40 ˚C
at 100 ˚C
D. 445
D. 455
Pour point ˚C 12 ASTM D 97
Flash point ˚C 70 ASTM D 93
Molecular weight 450 GPC
Total paraffinic content, wr% 38.9 Urea adduction (7)
Carbon residue contenty, wt% 1.5 ASTM D524
Ash content, wt% 0.0297 ASTM D482
Resin wt% 10.8 ASTM 3238/85
Aromatic wt% 49.5 ASTM 3238/85
elementary analysis (carbon, hydrogen, oxygen, sulphur
and nitrogen). Then then product was condensed with pa-
raformaldhyde to obtain polymeric dodecyl phenol for-
maldehyde sulphonate (PAS). The purity of the polymer
was about 92.5% [6-8] and average molecular weight
The polymeric dodecyl phenol formaldehyde was ethox-
ylated which has on an average 12 moles of ethylene
oxide per mol of polymeric dodecyl phenol formalde-
hyde polymer (non ionic polymer PAN).
Surface and interfacial tension measurement.
Surface tension of different concentrations for 107 to
0.1 mol/L of the synthesized additives was measured by
using Kruss Model 8451 in petroleum ether at 30˚C ac-
cording to omar et al. [9].
3. Results and Discussions
Detailed physic-chemical characteristics of the paraffinic
oil are reported in Table 1 . The data reveal that the oil is
rich in n-paraffin and has low carbon residue content and
total acid number. The above lube oil analyzed by gas
chromatography as shown in Figure 1. From this figure
the band represents different carbon number of paraffin
compounds and the carbon distribution in the wax oil.
Moreover, data in Table 1, show the carbon distribution
and the average number of carbon distribution in the
sample and the average number of benzene ring per mo-
lecule is 0.7, which mean that each molecule contains
one aromatic ring according to Hasting et al. 1958 [10].
The infra red spectra of the anionic polymer (PAS) are
given in Figu re 2. The characteristic absorption frequen-
cies of this polymer is given in Table 2.
The sulphonate group display avery broad and intense
peak. We observe sulphon ate group in the region of 3550
- 3030 cm1 and a lower frequency of sulphonate just
below 1575 - 1544 cm1.
Developments of Multifunctional Additives for High Quality Lube Oil
Copyright © 2013 SciRes. JPEE
Figure 1. Gas chromatography of analysis paraffinic oil.
The variation of surface tension with concentration is
shown in Figure 3. It is clear that the surface tension
decreases more with increasing the polymer concentra-
tions. The difference between them is attributed to func-
tional group of each molecule (hydrophilic group). The
action of additive of oil phase can be calculated using
Gibbs adsorption Equation (6). Comparing the data in
Table 3 shows that the CMC value for the polymer PAS
was lower than that of the polymer PAN, which indicates
that the former PAS favors micellization processes at a
lower concentration than the latter compound. Studying
the results in Table 3 shows that, the synthesized poly-
mer PAS has large values of surface excess and mini-
mum surface area, indicating the PAS is the most effi-
cient and gives a greater lowering in surface tension of
oil. Thus the change in head group of polymer (hydro-
philic part) affect of degree of micellization which will
be reflect of efficiency of the additive of its activity in oil
phase. This concept is clearly observed in Figure 3. From
this figure, as concentration increase, the surface excess
concentration increase to reach a constant value at CMC,
while the additive PAS has large value than PAN as
shown in Table 3. This is due to area occupied of sul-
phonate group. These results confirm sulphonate more
solublize and more active in oil phase while ethoxylate
group less soluble in oil phase depend on its hydrophilic
and hydrophobic balance (HLB). The au thor prefers num-
ber of exylene oxide units about 12 to give the best solu-
bility in oil phase according the above mention HLB.
These results are compatible by Omar et al. [6].
In addition, the variation of mixing ratios of nonionic
at constant concentration of PAS (105 mol/L) shows
reduction in surface tension and decrease in CMC. At the
same time, the best surface tension reduction with mini-
mum total concentration obtained at mole 0.7 of PAS/
PAN is shown in Table 4. The addition of PAN to PAS
reduces the surface tension due to formation stable mi-
celle in oil phase, which act as trap for wax and disperse
Developments of Multifunctional Additives for High Quality Lube Oil
Copyright © 2013 SciRes. JPEE
Figure 2. IR spectrum of the anionic polymer.
Table 2. Charac teristic absorption frequencies ( cm1) of PAS
Assignment Frequencies
CH2, C-H antisymmetrical stretching 2918 cm1
CH2, C-H symmetrical stretching 2860 cm1
CH2, deformation 1467 cm
C-O, symmetrical stretching 1408 cm1
CH3, symmetric deformation 1330 cm1
Figure 3. Effec t of additive concentration on surface tension
reduction of oil.
Table 3. Surface properties of additives.
Conc mol/L Aionic additive Nonionic additive
CMC mol/L 3.5 × 106 2.4 × 106
Surface area nm2 2.9 2.5
Surface excess mol/m2 7.11 × 107 6.3 × 107
Table 4. Surface properties of additives at different mole
fractions Nonioic/Anionic.
Mole fraction CMCmol/L.106 Surface tension
at CMC mN/m2 Area occupied per
molecule nm2
0.2 3.5 22 2.9
0.4 3.1 20 3.3
0.6 2.9 18 6.5
0.7 1.6 12 8.6
0.8 2.2 15 5.5
in oil phase. It can be conclude that, the activity of addi-
tive PAS in oil phase enhances by degree of mixing with
nonionic additive PAN. This is due to the fact the moiety
of large ethelene oxide units act as shield between sul-
phonate groups of PAS, as results decrease repulsion
Su rface ten sio n mNlm
Conc entra tion of the addi tive mol l L
Aio n i c ad dit iv e
Developments of Multifunctional Additives for High Quality Lube Oil
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between them giving stable micelle. These results are
depicted on Table 4.
The investigation of the ability of additives and their
mixtures as pour point depressant and viscosity improver
are shown in Tables 5 and 6. It is clear that, the pour
point and kinematic viscosity are improved by increasing
the additive concentration. The optimum value for reduc-
tion pour and kinematic viscosity appear at the critical
micelle concentration of additive and at mole fraction of
PAN/PAS equal 0.7. These results can be discussed ac-
cording the surface activity of the additive and according
the stability of micelle. From the structure of additive, it
has lyophilic part like the paraffinic wax which com-
pletely miscible with wax molecule, while the lyophobic
group (sulphonate, or ethylene group) arrange in geome-
trical shape act as micelle. These micelles disperse wax
crystal lattice to s mall sizes. A s the results, the pour point
decrease and viscosity improve. The addition of PAN to
pas form mixture exhibiting pettier performance in re-
duction pour point and enhancing viscosity (Table 6).
The author confirms degree of mixing has predominant
factor in enhance property of oil. This is due to stability
of micelle inc ease with incr easing ratio of P AN and CMC
decrease until mole fraction eqal 0.7 of PAN/PAS. As the
results more dispersion of wax crystal by micelle core,
consequently improve viscosity of oil, i.e these additive
have multifunction purposes, which act by lyophilic por-
tion of each molecule and lyophobic part (sulphonate,
ehelen oxide group). Moreover,these results are more con-
firmed by increasing the activity of each additive in oil
phase which has surface property depend on CMC and
degree of mixing (Table 4).
The effect of these additive on the oxidation stability
of oil is given in Figure 4 and 5. The data show the addi-
tive retards the oxidation of oil by phenol group in each
additive, which act as trap for free radical of R-O. From
Figures 4 and 5, the total acid decrease by increasing the
additive concentrations and reach the optimum value at
CMC each additive and their mixtures. Further increase
concentration of the additive, the oxidation stability de-
crease due to the additive tend to adsorption rather than
forming micelle and reverse its orientation at oil phase as
confirmed by omar et al. [6]. Comparing between two
additives in increasing oil stability, the additive PAS is
the best, due to it has the best surface properties. The
mole fraction 0.7 of PAN/PAS is the best in its oxidation
stability. The author concludes tha t the ability and stabil-
ity of micelle is predominant factor for increase oxida-
tion stability of oil. The micelle and inhibit propagation
of free radicals and terminate reaction processes of free
radicals. More confirmation, the increasing surface area
occupied per molecule of mixture attend at mole fraction
0.7 PAN/PAS (Table 4), these prevent contact the free
radicals R-O With other hydrocarbon molecules and ter-
minate it as R-O-R.
4. Conclusions
1) The oxidation stability of oil as measured by total
acid number indicates that, the oxidation inhibitor effi-
ciency follows the order.
PAN/PAS > PAS > PAN and the mole fraction affect
on degree of oil stability. These results depend on value
of CMC and area occupied per molecule at oil phase.
Table 5. Effect of different additives on pour point at different concentration.
Kinematics viscosity, cSt at different temperatures Pour point, C Conc mollL Adittive
60˚C 40˚C
Anionic additive
26.14 17
12 6.6 0.0000025
4.5 10
5 0.000003
5.1 7 3
5.5 7 3 0.000004
27 18 12 0.000002
Nonionic additive
26.5 13.7 7
6.5 12.5 6 0.000003
7 13 6.5 0.0000035
7 12.5 6.5 0.000004
Table 6. Effect of different mole fraction Nonionic/Anionic on pour point at different concentration.
Kinematics viscosity, cSt at different temperatures Pour point, ˚C Mole fraction Adittive
60˚C 40˚C
Nonionic/ Anionic additive
5.14 6.1
5.5 2.5 0.4
3.5 4.8 2 0.6
2.1 3.8 1.8 0.7
4.5 5 2.5 0.8
Developments of Multifunctional Additives for High Quality Lube Oil
Copyright © 2013 SciRes. JPEE
Figure 4. Effect of different concentration of the anionc additive on total acid number at different times.
Figure 5. Effect of different mole fraction of Nonionicl Anionic addive on acid number.
2) The synthesized additives and their mixtures have a
multifunction for pour point depressant, improving vis-
cosity and enhance oxidation stability of oil. These re-
sults depend on activity of additives and their mixtures at
oil phase. Further work will study the composition of
mixed micelles and measure the hydrophilic and hydro-
phobic balance of additives HLB.
[1] T. T. Khidr, E. M. S. Azzam, S. Mutwaa and A. M. A.
Omar, “Study of Some Anionic Surfactants as Pour Point
Depressant Additives for Wax Gas Oil,” Industrial Lu-
brication and Tribology, Vol. 59, No. 2, 2007. pp. 64-68.
[2] T. T. Khidr and A. M. A. Omar, “Anionic/Nonionic Mix-
ture of Surfactants for Pour Point Depression of Gas Oil
Egyptian,Journal of Petroleum, Vol. 12, 2003, pp. 21-26.
[3] T. T. Khidr, D. Ismail and A. M. A. Omar, “Improving
the Flow Properties of n-Paraffin Gas Oil by Cationic and
Non-Ionic Surfactants,” Journal of Faculty of Education,
Vol. 25, 2000, pp. 121-135.
[4] C. Kaidas, M. Makowska and M. Gradkowski, “Influence
of Temperature on Tribochemical Reactions of n-Hexa-
decane,” 2nd World Tribology Congress, 3-7 September
2001, p. 225.
[5] N. Elmehbad, “Development Antioxidants Synthesized
by Phase Transfer Catalysts for Lubricating Oil,” Biotech
Conference, Expo, 12-16 May 2013.
[6] A. M. A. Omar, “Micellization and Adsorption of Anio-
nic/Nonionic Polymer Surfact ant s for Metal Working Fluid
at Different Interfaces,” Industrial Lubrication and Tri-
bology, Vol. 56, No. 3, 2004, pp. 171-176.
[7] T. R. Marquat, G. B. Dellow and E. R. Freitaus, Analyti-
cal Chemistry, Vol. 40, No. 11, 1968, p. 1633.
[8] A. M. A. Omar, Journal of Petroleum Science and Tech-
nology, Vol. 19, No. 7-8, 2001, pp. 11-21.
[9] M. Y. El Kady, A. K. El Morsi, N. Tantawi, A. Z. El
Tabei and A. M. A. Omar, “A New Trend for Preparing
Polymeric Calcium Sulphonates for Metal q Working
Fluids,” Journal of Annals of University, Dunarea De Jos
of Galati, Tribology, Fascice, Romania, Vol. 11, 2006.
[10] S. H. Hasting, B. H. Johnson, H. E. lumpkin and R. B.
Wiliam, “Symposium on Composition of Petroleum Oils
Determination,” American Society for Testing Materials,
Ac id number mg KOHlmg
Time , hour s
0. 000002
0. 000003
0. 0000035
Acid number , mgl KOHlgm
Tim e , hours
0.2mole fraction NlA
0.4mole fraction NlA
0.6mole fraction NlA
0.7mole fraction NlA
0.8mole fraction NlA
Anionic additive
Nonn ionic additive