VOLUME 18, NUMBER 3 MAY/JUNE 2004

© Copyright 2004 American Chemical Society

Articles
New Additives for the Pour Point Reduction of
Petroleum Middle Distillates
Ä lvares,‡,§ and Elizabete F. Lucas*,†
Cristiane X. da Silva,† Dellyo R. S. A
Insituto de Macromoléculas da Universidade Federal do Rio de Janeiro, CT bl. J,
Ilha do Fundão, P.O. Box 68525, 21945-970, Rio de Janeiro, Brazil, and PETROBRAS
Research Center, Ilha do Fundão, Q.7, 21949-900, Rio de Janeiro, Brazil

Received June 23, 2003

Petroleum, as well as its middle distillate fractions (boiling between 150-400 °C), shows a
tendency to crystallize paraffin molecules whenever the temperature is lowered below the cloud
point. Paraffin deposition may occur in storage tanks, pipelines, or conduits, this leading to the
impairing of fluid pumping, with even filter plugging of diesel engines. Such a drawback may be
overcome by the addition of chemical compound.

This work relates the preparation and characteriza- nucleation and crystallization temperature. Such tem-
tion of poly(ethylene-co-vinyl acetate)-based structures perature is called the cloud point. From this point on,
and their assessment as pour point reducing agents for there is observed a process leading to the growing and
one kind of diesel oil and three kinds of lube oils: light agglomeration of the formed crystals, with the conse-
neutral,medium neutral, and heavy neutral or bright quent increase in the system viscosity, impaired fluidity,
stock. Results indicate that the hydrophilic-lipophilic and generation of solid deposits that tend to reduce or
balance of the additive seems to be more relevant for even render impossible oil production and use of related
its performance than molecular weight itself. A few products.2
structures appear to have a better performance than Highly paraffinic lubes should be previously treated
currently marketed commercial products. by separating the heavier fractions with the aid of
solvents and filtration, or otherwise by catalytic treat-
Introduction ment under nitrogen. The filtration process may be
Aliphatic hydrocarbons, the main constituents of jeopardized by the presence of paraffin crystals that
paraffin waxes (normal or n-paraffins), predominate in increase oil viscosity, reducing the filtration rate. Then,
petroleum as well as in its high- and medium-boiling the use of additives that modify the paraffin crystal size
point related products, such as lube oil and diesel.1 and morphology reduces their pour point and improves
Whenever the oil temperature is reduced, there is a oil filtration rate.3
threshold temperature where is started the paraffin As for diesel oil, paraffin deposits formed in diesel
causes drawbacks such as difficult pumping, and vehicle
* Author to whom correspondence should be addressed. E-mail: filters plugging, among others.
elucas@ima.ufrj.br.
† Insituto de Macromoléculas da Universidade Federal do Rio de

Janeiro. (2) Misra, S.; Baruah, S.; Singh, K. Soc. Pet. Eng. 1994, 28181, 50-
‡ PETROBRAS Research Center. 54.
§ E-mail: dellyo@cenpes.petrobras.com.br. (3) Denis, J.; Durand, J. P. Rev. Inst. Fr. Pét. 1991, 46 (5), 637-
(1) Holder, G. A.; Winkler, J. J. Inst. Pet. 1965, 51 (499), 228-252. 645.

10.1021/ef030132o CCC: $27.50 © 2004 American Chemical Society

Published on Web 03/04/2004
600 Energy & Fuels, Vol. 18, No. 3, 2004 da Silva et al.

Aiming at solving the problems generated by the Table 1. Data for Lube Oils
deposition of paraffin crystals, a few techniques may be lube oilsa
useful. Such techniques are of two kinds: those directed properties NL NM NH
to the removal of deposits (mechanical, thermal, and viscosity, cSt 40 °C 32.34 69.05 391.6
chemical methods) and those directed to the prevention 100 °C 5.424 8.759 27.7
or inhibition of deposit formation (dispersants and viscosity index 101 99 97
organic deposition inhibitorssODI).4,5 density (20/4°C) 0.8664 0.8736 0.8934
molar mass (mol/g) 406 480 678
Organic deposition inhibitorss(ODI) are generally boiling point (°C) 334 360 382
made up of high molecular weight polymeric compounds carbon distribution (w/w%)
having a structure similar to the paraffin present in the aromatic 5.4 4.6 9.0
naphthenic 28.1 28.1 22.0
organic deposit, this making possible that it may
paraffinic 66.5 67.3 69.0
intervene in the crystallization process. Such materials
a NL ) neutral light; NM ) neutral medium; NH ) neutral
are used to prevent the formation of huge paraffin
heavy.
crystals through modification of the crystalline network
formation. Therefore such inhibitors are not universal Three basic lube oils were selected (neutral light, neutral
ones, their action being restricted to a certain molecular medium, and neutral heavy or bright stock - supplied by the
weight interval, this requiring experimental tests to Landulpho Alves (RLAM) refinery (PETROBRAS-Bahia-
assess the best inhibitor product to be used in each Brazil). Data about lube oils are summarized in Table 1.
particular system.6-8 The petroleum sample used in the experiments was supplied
Among commercial products used as paraffins deposi- by the Campos Basin, Rio de Janeiro, Brazil. This sample
tion inhibitors, ethylene-co-vinyl acetate copolymers presents the following properties: relative density (20/4 °C)
) 0.8833; density (60/60 F) ) 28° API; Shell paraffin content
(EVA) may be pointed out. Polar groups present in the
) 3.6 w/w %; asphaltenes content ) 4.5 w/w %.
structure of these materials are able to generate a Methods. Chemical Modification Reaction of the Ethylene-
repulsion effect, thus contributing in a more intense way Vinyl Acetate Copolymers. The chemical modification reactions
to the formation of low and ill-structured crystals, those aim at introducing hydrocarbon pendant chains throughout
remaining suspended in the oil.8-12 The presence of such the EVA structure. The first step of the chemical modification
polar groups also favors chemical modifications through reactions is the EVA hydrolysis, a procedure described in the
the insertion of hydrocarbon chains, which makes literature.13 Then the hydrolyzed EVA was esterified (EVAOH)
possible the synthesis of various additives, these being in the presence of the corresponding acid chloride. The
suitable to the kind of paraffins present in oils.8 apparatus used in the reaction was provided with reflux and
an addition funnel equipped with pressure equalizer and
EVA copolymers are also used as paraffin crystal
nitrogen inlet. The 5% EVAOH reaction solution in toluene
modifiers in lube oils and diesel; however, these materi- (previously Na-dried) was magnetically agitated for 24 h at
als should show a lower molecular weight than those 65 °C. After the contact time two pyridine drops were added
used in petroleum oils. This is due to the lower size of (which are intended to react with the hydrochloric acid
the n-paraffin chains present in lube oils and diesel oil normally formed in the reaction). An acid chloride solution in
(in the approximate range of C10 to C20 for the lube oil, toluene was slowly dropped into the reaction system under
and of from C8 to C30 for diesel1). vigorous magnetic agitation. The reaction occurred during 2
This work aimed at the development of polymeric h at 85 °C. The formed copolymer was precipitated in ethyl
materials based on the chemical modification of poly- alcohol, filtered and vacuum-dried. This reaction was carried
out by varying the amount and type of acid chloride, yielding
(ethylene-co-vinyl acetate) copolymers, to be used as
copolymers of pendant side chains of different length and
pour point reducing additives for crude oils as well as percentage.
petroleum medium distillates, such as lube oils and
diesel oil.

Experimental Section
Materials. Commercial copolymers based on poly(ethylene-
co-vinyl acetate) (EVA) were supplied by Politeno S.A-Brazil.
Vinyl acetate nominal contents of EVA samples were 20% and where R represents hydrocarbon chains of 12 or 18 carbon
33%. atoms, according to the acid used. Stearoyl chloride (C17H35-
Diesel oil was supplied by the Duque de Caxias Refinery COCl) and lauroyl chloride (C11H23COCl) were supplied by
(PETROBRAS - Rio de Janeiro - RJ - Brazil). Aldrich, at 99% purity.
Characterization of the EVA and EVA Modified Copolymers.
(4) Irani, C.; Zajac, J. J. Pet. Technol. 1982, 34, 289-193. The characterization of all the EVA copolymers was carried
(5) Slater, G.; Davis, A. Pipeline Transportation of High Pour Point out by hydrogen nuclear magnetic resonance, in a VARIAN
New Zealand Crude SPE 15656, 1986. GEMINI 300 apparatus, the solvent being deuterated toluene
(6) Vos, B.; Haak, K. Proceedings of the Indonesian Petroleum at 85 °C. The molar composition of the EVA copolymers was
Association, Ninth Annual Convention, May, 1980, pp 98-101.
(7) Petinelli, J. C. Rev. Inst. Fr. Pét. 1979, 34 (5), 771-790. calculated by integrating the peak areas related to the
(8) Alvares, D. R. S.; Lucas, E. F. Pet. Sci. Technol. 2000, 18 (1 & hydrogen atoms present in ethylene and vinyl acetate, accord-
2), 195-202. ing to eq 1 below.
(9) Machado, A. L. C.; Lucas, E. F. Pet. Sci. Technol. 1999, 17 (9 &

{ [ ]}
10), 1029-1041.
(10) Machado, A. L. C.; Lucas, E. F. Pet. Sci. Technol. 2001, 19 (1 & (Σ areasethylene) - 2
2), 197-204. mole % VA ) 1 - (1)
4
(11) Machado, A. L. C.; Lucas, E. F.; González, G. J. Pet. Sci. Eng.
2001, 32 (2-4), 159-165.
(12) Machado, A. L. C.; Lucas, E. F. J. Appl. Polym. Sci. 2002, 85 where the term mole % VA represents the mole percentage of
(6), 1337-1348. vinyl acetate in the EVA copolymers and the term
Additives for Pour Point Reduction of Petroleum Distillates Energy & Fuels, Vol. 18, No. 3, 2004 601

Figure 2. 1H nuclear magnetic resonance spectrum of the

Figure 1. 1H nuclear magnetic resonance spectrum of the
hydrolyzed ethylene-vinyl acetate copolymer (EVA).
ethylene-vinyl acetate copolymer (EVA-20).
Table 2. Characterization Data for Commercial EVA
Σ areas ethylene is the sum of the ethylene-related peak areas. Copolymers as for the Vinyl Acetate Content (1H-NMR
The degree of hydrolysis and esterification was assessed from obtained) and Molecular Weight (SEC obtained)
calculations based on the measurement of the peak areas vinyl acetate content molecular weight
typical of hydrolyzed EVA and esterified EVA as compared to
the peak areas related to the assignments of the vinyl acetate nominal calculated calculated
(weight %) (% mole) (weight %) hn
M h w/M
M hn
and hydrolyzed compound groups, respectively.
The molecular weight of commercial samples was assessed 20 7.5 19.9 25600 4.6
by size exclusion chromatography (SEC) in a WATERS 150- 33 12.3 35.1 34300 3.4
CV plus apparatus, and STYRAGEL HT 3 column, at a 1.0
mL/min flow rate. the ratio between the areas related to the vinyl acetate
Pour Point Assessment. The method used to assess the pour and ethylene groups, with the assignment area at δ )
point of the oil samples was adapted from ASTM Method D97/ 2.09, corresponding to deuterated toluene considered as
93.14 Thus, the oil sample, either containing or not the additive, irrelevant. As shown in Table 2, obtained results
was heated in a water bath up to 71°C. Then the sample was matched nominal values.
transferred to an appropriate vessel provided with an external
label. The vessel was then stoppered with a cork stopper
Molecular weights for commercial EVA samples were
pierced by a thermometer, the bulb of which did not touch the assessed by SEC (size exclusion chromatography) with
liquid beneath. After 5 min the thermometer bulb was inserted the obtained results also being presented in Table 2.
in the oil and the vessel was coupled to a cooling bath at a As may be observed, the molecular weight of the
temperature lower than -40 °C. The system remained in the selected polymers are in the range 25000-35000.
cooling bath until the temperature of -20 °C was reached; the Chemical Modification of the EVA Copolymers.
vessel was withdrawn from the bath, heated to 48 °C and left Copolymers were esterified with commercial acid chlo-
to cool spontaneously until 32 °C. Then, the vessel was again rides (lauric and stearic), in a two-step reaction: (1)
inserted in the cooling bath and, for every 2 °C cooling, the oil hydrolysis of acetate groups, and (2) esterification
flowing condition was assessed by observing the label on the
reaction of the hydrolyzed EVAs (hydrocarbon chain
vessel. Whenever the flow of oil was no longer observed under
the action of gravity alone, at a time interval of 5 s, the insertion).
temperature was read, to which were added 2 °C to assess the In the first step, based on calculations directed to
pour point value. obtaining total conversion of the acetate groups into
hydroxyl groups, EVA copolymers of vinyl acetate
Results and Discussion content of 20% and 33% were submitted to hydrolysis.
Characterization as for the actual hydrolysis degree was
Characterization of EVA Commercial Samples. effected by hydrogen nuclear magnetic resonance. Fig-
EVA copolymers of vinyl acetate nominal contents of ure 2 illustrates the 1H NMR spectrum of the hydro-
20% and 33% w/w were characterized by hydrogen lyzed EVA 20% copolymer. Assignment analysis sug-
nuclear magnetic resonance. gests that the EVA 20% copolymer, with 19.9 w/w
Figure 1 shows the 1H NMR spectrum of EVA sample acetate groups, has been nearly completely hydrolyzed.
containing 20% w/w vinyl acetate. According to litera- Peaks detected in the δ ≈ 4.8 ppm area (related to the
ture data,15 assignments indicated in the spectrum as hydrogen present in the acetate-bearing carbon atom),
well as the chemical shifts confirm the identification of indicated in Figure 1, are nearly imperceptible in the
the sample as an EVA copolymer. Vinyl acetate content hydrolyzed copolymer spectrum. Besides, the presence
calculations were obtained from 1H NMR spectra, using of further peaks in the area between δ ) 3.5 ppm and
δ ) 4 ppm may be observed, this suggesting the
(13) Dutra, R. C. L.; Lourenço, V. L.; Diniz, M. F.; Azevedo, M. F. presence of hydrogen directly linked to the hydroxyl-
P.; Barbosa, R. V.; Soares, B. G. Polym. Bull. 1996, 36, 593-597.
(14) American Society for Testing and Materials - ASTM D-97 (66), bearing carbon atom.
Standard test method for pour point of petroleum oils, Reprint, 1971. Calculations based on the reduction in area for these
(15) Pha, Q. T.; Petiaud, H. W.; Llauro-Darricades, M. F. Proton
and carbon NMR spectra of polymers, CRC Press, Inc., Boca Raton, peaks revealed a hydrolysis degree of 94%. The same
1991; pp 272-273. procedure was used to calculate the hydrolysis degree
602 Energy & Fuels, Vol. 18, No. 3, 2004 da Silva et al.

Table 4. Pour Point of Petroleum with EVA 20 and

Modified EVA 20 Copolymers as Additives at a 0.1%
Additive Concentration
additive pour point (°C)
net oil 15
EVA-20 -28
hydrolyzed EVA-20 -9
copolymer 1 (EVA-20 + 21% C18) -8
copolymer 2 (EVA-20 + 17% C18) 7

From Table 4 it is noticed that the deeper pour point

reduction was obtained by using the commercial EVA
20 copolymer (-28 °C). This was due to the similarity
between the long paraffin chains of petroleum and the
macromolecules of the EVA 20 copolymer (of Mn ≈ 26
× 103). The hydrolyzed copolymer showed a lower
reduction in pour point (-9 °C) probably due to the
Figure 3. 1H nuclear magnetic resonance spectrum of the
ethylene-vinyl acetate copolymer (EVA) esterified with lauroyl higher molecular polarity imparted by hydroxyl groups
chloride. and, as a consequence, a poorer interaction between the
additive and petroleum, as well as to the changing
Table 3. Esterification Degree of EVA Esterified solubility of this molecule in the medium.
Copolymers (EVAE) (obtained by 1H-NMR)
The efficacy in pour point reduction of partially
copolymer esterification degree esterified EVA 20 copolymers containing a long ester
(theoretical mole %) (actual mole %)
group (C18) was impaired because of the presence of
EVA-20 + 10% C12 9.2% hydroxyl groups throughout the chain. Besides this
EVA-20 + 25% C12 23.7% parameter, the percentage of long chains incorporated
EVA-20 + 50% C12 49.1%
EVA-20 + 10% C18 8.4% to the copolymer is a further, significant influence to
EVA-20 + 50% C18 42.0% the pour point reduction.
EVA-20 + 12% C12 + 12% C18 25.4% For copolymer 1, which contains 21% of C18 chains,
EVA-33 + 10% C12 8.1% there was a reduction in the pour point from 15 °C (net
EVA-33 + 25% C12 24.1%
EVA-33 + 50% C12 40.6% oil) to -8 °C (petroleum and copolymer as additive).
EVA-33 + 10% C18 8.5% Copolymer 2 (with the incorporation of nearly 17% of
EVA-33 + 50% C18 42.8% C18 chains) reduced the pour point to 7 °C. The observa-
tion of these results shows that a higher incorporation
of C18 chains imparts higher efficiency to the pour point
of the hydrolyzed EVA 33, which indicated 94% hy- reduction. Aiming at evaluating compositions of still
drolysis degree. higher content in C18 chains different copolymers were
Esterification reactions of the second step comprised synthesized, having several incorporation contents of
the incorporation of 12 carbon atoms (lauroyl chloride C18 chains (higher than 50%). However, all of them
reactions) and 18 carbon atoms hydrocarbon chains produced gel, this condition impairing their use as a
(stearoyl chloride reactions) at the theoretical amount pour point reducing agent.
of 10% molar. The obtained products were characterized Use of the Modified Copolymers as Additives for Lube
by nuclear magnetic resonance for the calculus of the Oils. EVA 20 and EVA 33 copolymers were chemically
acetate group esterification degree. Figure 3 illustrates modified through hydrolysis reactions followed by es-
the 1H NMR spectrum for the EVA 20 copolymer terification with C12 and C18 chains. Products obtained
esterified with lauroyl chloride. The spectrum indicates by chemical modification were used as additives for base
an area reduction for the hydroxyl typical peaks of the lube oils (neutral light, neutral medium, and bright
hydrolyzed material, assigned in the area between δ ) stock), the pour point measurement being taken as a
3.5 ppm and δ ) 4 ppm (Figure 2). Besides, there is a means for evaluating the action of these materials, as
new peak of chemical shift at δ ) 5.1 ppm, attributed illustrated in Table 5. Lube oils were characterized by
to hydrogen in the -HCO(CdO)C11 moiety. Esterifica- distillation temperatures. PNL is a light neutral oil,
tion degree was calculated on the basis of the area PNM a medium neutral oil, and PBS a heavy neutral.
reduction of the typical hydroxyl groups, and the results This way, the average paraffin size increases according
are listed in Table 3. It may be observed that the as- to the following order: neutral light < neutral medium
obtained esterification degree was close to the amount < bright stock.
added to the feed. Contrary to the behavior observed for petroleum, the
Assessment of the Performance of the Copoly- additive performance for lube oils was significantly
mers as Pour Point Reducing Agents for Petro- improved after the hydrolysis of the commercial EVA
leum and Lube Oil. Use of the Modified Copolymers and still better results were obtained after an esterifi-
as Additives for Petroleum. At first, only EVA 20 (of 20% cation reaction with certain contents of long hydrocar-
vinyl acetate) was tested as a reducing agent for the bon chains. For the PNL lube oil (Table 5), EVA
petroleum pour point. Besides commercial EVA 20, copolymers esterified with C12 chains led to the best
hydrolyzed EVA 20 and esterified EVA 20 were tested. results; a pour point reduction from -7 °C (net petro-
Table 4 lists the figures for the pour point of petroleum leum) to -23 °C (EVA-20 + 9.2% C12) and to -20 °C
to which the copolymers have been added. (EVA-33 + 8.1% C12). This behavior may be attributed
Additives for Pour Point Reduction of Petroleum Distillates Energy & Fuels, Vol. 18, No. 3, 2004 603

Table 5. Pour Point of Neutral Light, Neutral Medium,

and Bright Stock Lube Oils, to Which Commercial and
Chemically Modified EVA Copolymers Have Been Added,
at an Additive Concentration of 0.1%
pour point (°C) ((1°C)
additive PNL PNM PBS
net oil -7 -5 -4
EVA-20 -9 -12 -17
hydrolyzed EVA-20 -18 -14 -20
EVA-20 esterified with 9.2% C12 -23 -17 -20
EVA-20 esterified with 23.7% C12 -19 -18 -20
EVA-20 esterified with 49.1% C12 -18 -15 -22
EVA-20 esterified with 8.4% C18 -18 -16 -22
EVA-20 esterified with 42% C18 -17 -17 -22
EVA-20 esterified with ≈12% C12 + ≈12% C18 -22 -20 <-23
EVA-33 -9 -11 -16
hydrolyzed EVA-33 -18 -15 -19
EVA-33 esterified with 8.1% C12 -20 -16 -22 Figure 4. Effect of the EVA-20 + 9.2% C12 additive concen-
EVA-33 esterified with 24.1% C12 -17 -18 <-23 tration on the pour point of the PNL oil.
EVA-33 esterified with 40.6% C12 -17 -17 -22
EVA-33 esterified with 8.5% C18 -19 -16 -22
EVA-33 esterified with 42.8% C18 -17 -14 -22 The basic feature of this oil is a higher viscosity as
compared to the equally analyzed PNL and PNM oils,
it having for the most part larger size hydrocarbon
to the nature of the hydrocarbon chains present in this chains, that is, higher molecular weight n-paraffins.
oil that, due to the fact of the light neutral nature of This fact seems to have contributed for the better
this oil, its n-paraffin chains are not very long, if performance of the additives toward this oil (pour point
compared to the paraffins present in other tested oils reduction higher than 19 °C), since the molecular weight
(PNM and PBS). EVA 20 copolymer esterified with
range of the copolymers used in this work is Mn ) 26
≈12% C12 + ≈12% C18 presented as well a satisfactory
× 103 - 47 × 103 (Table 2).
performance since it reduced to -22 °C the pour point
of PNL oil. This copolymer was synthesized aiming at Effect of the Concentration of EVA 20 + 9.2% C12
associating, in the same EVA molecule, side chains of Additive on PNL Oil. The study of the effect of the
different sizes, which would allow a higher number of additive concentration on the pour point reduction of
oil paraffins, since lube oils are made up of a hydrocar- the lube oil arose from the need to establish the
bon chain distribution of several sizes. minimum amount of the additive which would impart
Upon comparison of the results for modified products a reasonable performance on the pour point depression.
obtained from EVA 20 and EVA 33, no significant According to the literature,3 the additive concentration
modifications on the pour point were observed, that is, to be employed in the lube oil should be in the range of
for these materials apparently no influence of the EVA 0.1 to 20%, the choice of the specific amount depending
composition could be felt on the pour point of the PNL on the kind of oil as well as on the end application.
lube oil. A perusal of the EVA 20 copolymers of 23.7% The system chosen for this experiment was PNL oil
C12 and 49.1% C12 having pour points -19 °C and -18 and EVA 20 + 9.2% C12 copolymer, in view of the best
°C, respectively, and the EVA 33 copolymers having result attained for the pour point reduction. Toluene
24.1% C12 and 40.6% C12 having pour points -17 °C, solutions of concentrations ranging from 100 to 1000
leads to the conclusion that for this composition range, ppm in additive were prepared and added to the lube
the fact that the copolymer bears a larger number of oil and immediately after, pour point was measured.
pendant side chains seems irrelevant to the pour point Results are plotted in Figure 4. The shape of the curve
reduction of this oil. indicates there is an ideal region of additive concentra-
Table 5 lists further the figures for pour point of tion from 650 to 1000 ppm, which shows the same
neutral medium lube oil. This oil differs from the values of pour point, that is, 650 ppm of this additive
neutral light oil as for the features of its hydrocarbon are enough to obtain the desired result. Results obtained
chains, which show a tendency toward higher paraffins. for this system lead to savings in additive as well as in
The observation of the pour point figures leads to the solvent, chiefly for large volumes. It is important to
conclusion that there is no significant influence of the stress that this experiment is valid for this system only,
EVA copolymers composition, nor either of the esteri- while for other oils (PNM, PBS, and diesel oil) further
fication degree. The best performance was attributed experiments are required.
to the EVA 20 copolymer esterified with approximately Use of the Modified Copolymers as Additives for Diesel
12% C12 + 12% C18, which reduced the pour point to Oil. Commercial EVA 20 and EVA 33 copolymers
-20 °C. chemically modified through hydrolysis reactions fol-
For the PBS oil to which have been added the EVA lowed by esterification with C12 and C18 chains were also
copolymers, at first a significant reduction in pour point used as pour point reducing agents for diesel oil, the
may be observed. The pour point of the net oil was -4 results being listed in Table 6.
°C, and attained values lower than -23 °C (EVA-33 + Result analysis indicates acceptable performance of
24.1% C12). For this oil no relationship could be observed the chemically modified copolymers as pour point reduc-
between the esterification degree and the EVA copoly- ing agents, with special mention to the EVA-33 + 43%
mers composition with the pour point, for which figures C18 copolymer, which was able to reduce the pour point
were rather close. to -18 °C (∆T ) 19 °C). It could also be observed that
604 Energy & Fuels, Vol. 18, No. 3, 2004 da Silva et al.

Table 6. Pour Point of Diesel Oil to Which Commercial which could encompass the highest possible number of
and Chemically Modified EVA Have Been Added, at an n-paraffins.17
Additive Concentration of 0.1%
pour point (°C)
additive ((1°C) Conclusions
net oil 1
EVA-20 -3 Commercial EVA copolymers are more effective pour
hydrolyzed EVA-20 -8 point reducing agents for petroleum than the chemically
EVA-20 esterified with 9.2% C12 -9 modified samples. On the other hand, the EVA copoly-
EVA-20 esterified with 23.7% C12 -13 mers chemically modified by the incorporation of side
EVA-20 esterified with 49.1% C12 -14
EVA-20 esterified with 8.4% C18 -10 chains are more effective in the n-paraffin crystalliza-
EVA-20 esterified with 42% C18 -11 tion process, causing a more accentuated pour point
EVA-20 esterified with ≈12% C12 + ≈12% C18 -13 reduction in the lube and diesel oils than the nonmodi-
EVA-33 -3 fied EVA commercial samples.
hydrolyzed EVA-33 -7
EVA-33 esterified with 8.1% C12 -7 Broadly speaking, the C12- and C18-chain containing
EVA-33 esterified with 24.1% C12 -13 copolymer showed satisfactory results for the three
EVA-33 esterified with 40.6% C12 -14 tested lube oils, indicating the influence of the pendant
EVA-33 esterified with 8.5% C18 -6
EVA-33 esterified with 42.8% C18 -18 chain size distribution on the additive performance. The
additive hydrophilic-lipophilic balance seems to exert
for a group of EVA copolymers of the same vinyl acetate a more significant influence on the copolymer perfor-
composition, there was a reduction in the pour point mance than molecular weight. For the specific PNL lube
temperatures upon the increased content of incorpo- oil system, 650 ppm additive are well enough to reach
rated side chains. This fact is related to the diesel oil the desired pour point level. Upon applying the same
composition, formed by a hydrocarbon mixture, the additive, PBS lube oil has shown a more marked pour
constituting paraffins being situated in an approximate point reduction (∆T ) 19 °C) than PNL and PNM oils,
size range from C8 to C30. The chain distribution of this probably being due to the outweigh of larger size
varied molecular weights that make up diesel oil seems hydrocarbon chains, that is, higher molecular weight
to add to the reasonable performance of the copolymers n-paraffins.
tested in this system, since these materials work on the Pour point results obtained for lube oils and diesel
basis of the similarity between the additive structure according to the present work using modified EVA
and that of the oil n-paraffins, besides the influence of copolymers are the same or better than those obtained
the solubility. In other words, for oil that shows a larger from the use of commercial additives.
distribution of hydrocarbon chains,16 the additive action
is favored toward certain molecular weight ranges,
Acknowledgment. The authors thank ANP/FINEP/
which enhances its range of action. The ideal situation
CTPETRO, CNPq, and CENPES/PETROBRAS.
would be, based on the knowledge of the oil composition
as regards the nature of the hydrocarbon chains, to be EF030132O
able to design an additive or an additive association,
(17) Brown, G. I.; Tack, R, D.; Chndler, J. E. SAE Meeting, paper
(16) Knepper, J. I. Hydrocarbon Process. 1975, 54 (9), 129. 881652, Portland, October, 1988.