Studies on the Influence of Long Chain Acrylic Esters Co-Polymers Grafted With Vinyl Acetate as ...

14 Pages·2011·0.58 MB·English

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Pelagia Research Library

Advances in Applied Science Research, 2011, 2 (5): 476-489

ISSN: 0976-8610
CODEN (USA): AASRFC

Studies on the Influence of Long Chain Acrylic Esters Co-Polymers
Grafted With Vinyl Acetate as Flow Improver Additives of Crude Oils

Al-Shafey H. I.1, A.I. Hashem .2, R. S. Abdel Hameed.*3, E. A. Dawood 4.

1Egyptian Petroleum Research Institute, Petroleum application department, Nasr city, Cairo, Egypt
2Faculty of Science, Ain Shams Univrsty, Cairo, Egypt.
3Faculty of Science, Alazhar Univrsty, Cairo, Egypt.
4Environmental Sector, Town Gas, Cairo, Egypt
______________________________________________________________________________

ABSTRACT

A variety of techniques have been employed in order to reduce problems caused by the
crystallization of paraffin during the production and/or transportation of waxy crude oil. Flow
improvers are used extensively to increase the mobility of crude oil. In this study, the influence of
the PEAA graft co-polymer (PEAA- g-VA), as flow improver, on the viscosity and pour point of
some Egyptian waxy crude oils. The produced purified and characterized by FT-IR and 1HNMR
and rheological measurements. The shear rate-shear stress and shear rate-apparent viscosity
were measured at different concentration (from 500 to 3000 ppm) and temperatures below and
equal the pour point temperature. The copolymer leads to a large reduction in the pour point of
samples of Khalda Petroleum Co. (KhPC) crude oils. The polymeric additives were diluted with
xylene and added by different doses ranged from 500 to 3000 ppm to crude oil to reduce its pour
point. The pour point measurements show good reduction of pour point temperature depending
on the composition and location of Khalda crude oil. Thus establishing the large efficiency of the
products synthesized in this work.

Keywords: Waxy crudes, Pour point depressants, Flow improvers.
______________________________________________________________________________

INTRODUCTION

Polymers such as vinyl acetate copolymer, acrylate copolymer and their derivatives [1, 2] are the
main additives used to improve the flowability of very waxy crude oil, diesel fuel and other base
oils at low temperature. It should be noted that polymer additives are not equally effective with
the various crude oils, nor are they necessarily effective at all [3]. It is presumed that effective
additives have a good match between the polymer and crude 7, such as structure, composition
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R. S. Abdel Hameed et al Adv. Appl. Sci. Res., 2011, 2 (5):476-489
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and content. However, how the polymer flow improver works is not clear. Usually, more
attention has been paid to the interaction of the polymer flow improver with wax [5-8].

Inhibition of wax crystallization is considered to occur in the presence of polymer by nucleation,
co-crystallization or adsorption [7, 8]. It is reported that resin and asphaltene are natural pour
point depressants [9]. Recently, Ei-Gamal et al. pointed out that the combination of polymer
flow improver with asphaltene is highly efficient in improving the flowability of waxy crude [5].
The rheological behaviour of a crude oil is highly influenced by its chemical composition,
temperature and the current, as well as previous thermal history. High waxy crudes exhibit a
non-Newtonian character, often with a yield stress at and below their pour point temperature. At
a sufficiently high temperature the crude oil, although chemically very complex, is a simple
Newtonian liquid [10]. If the waxy crude oil is allowed to cool, wax will crystallize,
agglomerate and entrap the oil into its structure. This phenomenon often happens if the ambient
temperature of the place is below the pour point of the crude oil. Pretreatment of the crude oil is
necessary for transportation of these waxy crudes through the pipeline. Pretreatment of the crude
oil with flow improver is one method by which the rheological character of the gelled waxy
crude is changed for easier transportation [10].

The present work, aims to synthesis of co-polymers from PEAA and grafted with vinyl acetate
by reaction of PEAA with fatty alcohol or amine then graft by vinyl acetate in presence of
benzoyl peroxide as initiator, and investigates the obtained graft co-polymers as pour point
depressants and flow improvers for waxy crude oil.

MATERIALS AND METHODS

2.1. Materials
Poly Ethylene acrylic acid (PEAA) collected from waste material. Hexadecyl alcohol (HDA),
Hexadecyl amine (HDM), Vinyl acetate (VA), Benzoyl peroxide (BzPO) and P-Toluene sulfunic
acid monohydrate (PTSA) are from Aldrich Chemicals. Egyptian waxy crude oil, Khalda
Petroleum Co. (KhPC), was used for evaluating the performance of the synthesized polymeric
additives.

2.2. Synthesis of Graft copolymers
PEAA-HDA and HDM copolymers were prepared by reacting PEAA waste with HDA or HDM
under N gas at 140 oC in o-xylene in the presence of 1% PTSA (wt % based on total weight of
2
reactants). The reaction was carried out in a four-neck glass flask equipped with a stirrer,
thermometer, nitrogen gas inlet and a reflux condenser. The water of the reaction was removed
throughout the course of the reaction using Dean and Stark separator. The PEAA copolymer was
first dissolved in refluxing o-xylene, and then PTSA catalyst and HDA or HDM were added to
reaction medium. The product was grafted with vinyl acetate (ratio of reactants are 65% co-
polymer to 35% vinyl acetate) in the presence of benzoyl peroxide as initiator for 6h to produced
four samples as the fowling types (PEAA-C OH, PEAA-C NH , PEAA-C OHVA and PEAA-
16 16 2 16
C NH VA).
16 2

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R. S. Abdel Hameed et al Adv. Appl. Sci. Res., 2011, 2 (5):476-489
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2.3. Pour point measurement
The tested crude oils (50 ml) were heated up to 60 oC and the PPD additives were added at
different concentration. The solution was transferred to bottle test tube in water bath cooled at 48
oC. The tube was transferred to another cooling bath cooled down to 24 oC. The tube was
transferred to cooling bath cooled down to 0 oC, then the pour point temperature was measured at
temperature 48 oC, ASTM D 97-93.

2.4. Rheological measurements
A Haake viscometer model Rotovisco RV12 was utilized to measure the dynamic viscosity for
untreated and treated crude oil with some selected pour point depressants at different
concentrations (from 500 to 3000 ppm) and at different temperatures above and below pour point
of crude oils ranging from 36 to 15 °C. Yield point, and apparent viscosity values were
determined [11].

RESULTS AND DISCUSSION

3.1. Characterization of Graft Co-polymers
The present work aims to prepare graft co-polymers soluble in petroleum crude oil to be
evaluated for improving flow properties of waxy crude oil. All graft co-polymers have to be
purified before characterization. The purified copolymers were analyzed by FTIR spectroscopy.
In this respect, increasing of peak intensity at 1735 cm-1 and decreasing of peak intensity at 1700
cm-1, which represent C=O stretching of ester group and carboxylic groups, indicates the
conversion of carboxylic acid groups into ester groups. Furthermore, the appearance of strong
peak at 1100 cm-1 in all spectra, C-O vibration, indicates the formation of ester grafts for PEAA
copolymers. On the other hand, the disappearance of the broad peak at 3450-2800 cm-1 (–OH
stretching of COOH group) can be attributed to the formation of ester groups for all grafts. A
strong absorption of bending vibration at 721cm-1 can be attributed to the presence of C-(CH2) -
n
C as long alkyl chain moiety of the ester graft. On the other hand appearance of peak at 3010 cm-
1 (CH stretching of aromatic) indicates the ester groups produced onto PEAA backbone as side
chain.

To analyses co-polymer containing > 20-40 mol% VA, the absorption bands at 1372 cm-1
(rocking CH in acetate groups) and at 2925 cm-1 (stretching CH in ethylene units) [12, 13] were
3 3
used.

The new signals at 1.97, 4.9-5.3 and 3.8 ppm in all spectra of PEAA grafts which attributed to
COOCH , COOCH and CHCO of VA, indicate that VA was grafted onto PEAA chains. On the
3 2
other hand, the signals at 1.188 and 1.42 ppm are observed in all spectra and can be attributed to
CH of ethylene and VA, respectively. The presence of singlet and triplet signals at 0.812, 1.2
2
ppm (CH ) in spectra of all samples were studied indicate that COOH group of PEAA were
3
esterified with alcohols and amides.

On the other hand, the signals at δ= 1.25 ppm of the methylene protons in the PE backbone and
δ= 3.65 ppm of the grafts copolymers are observed in all spectra and indicate that the ester and
amide groups were formed from PEAA with alcohols and amides.

478
R. S. Abdel Hameed et al AAddvv.. AAppppll.. SSccii.. RReess..,, 22001111,, 22 ((55))::476-489
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33..22.. PPoouurr ppooiinntt mmeeaassuurreemmeenntt
3.2.1. EEffffeecctt ooff AAddddiittiivveess oonn PPoouurr PPooiinntt ooff the Tested Crude Oils
TTThhheee hhhiiiggghhh wwwaaaxxx cccrrruuudddeee oooiiilllsss aaarrreee ccchhhaaarrraaacccttteeerrriiizzzeeeddd bbbyyy hhhiiiggghhh pppooouuurrr pppoooiiinnnttt,,, hhhiiiggghhh vvviiissscccooosssiiitttyyy,,, hhhiiiggghhh gggeeelll ssstttrrreeennngggttthhh,,,
and abundant wax dddeeepppooosssiiitttsss... IIIttt iiisss wwweeellllll kkknnnooowwwnnn ttthhhaaattt,,, aaasss ttthhheee pppaaarrraaaffffffiiinnn wwwaaaxxx cccooonnnttteeennnttt iiinnncccrrreeeaaassseeesss iiinnn cccrrruuudddeee
oooiiilll,,, ttthhhiiisss llleeeaaadddsss tttooo dddiiiffffffiiicccuuulllttt sssooollluuubbbiiillliiitttyyy ooofff wwwaaaxxx iiinnn oooiiilll,,, iiinnn sssooommmeee cccaaassseeesss fffooorrrmmmiiinnnggg aaa ssseeepppaaarrraaattteee sssooollliiiddd ppphhhaaassseee...

CCChhheeemmmiiicccaaalll aaaddddddiiitttiiivvveeesss,,, rrreeefffeeerrrrrreeeddd aaasss pppooouuurrr pppoooiiinnnttt dddeeeppprrreeessssssaaannntttsss,,, ffflllooowww iiimmmppprrrooovvveeerrrsss,,, pppaaaraffin inhibitors or
wwwaaaxxx cccrrryyyssstttaaalll mmmooodddiiifffiiieeerrrsss,,, aaarrreee wwwiiidddeeelllyyy uuussseeeddd fffooorrr ooovvveeerrrcccooommmiiinnnggg ttthhheee ppprrrooobbbllleeemmm wwwooorrrllldddwwwiiidddeee... TTThhheeessseee aaaddddddiiitttiiivvveeesss
hhhaaavvveee rrreeeccceeeiiivvveeeddd ttthhheee gggrrreeeaaattteeesssttt aaacccccceeeppptttaaannnccceee ddduuueee tttooo iiitttsss sssiiimmmpppllliiiccciiitttyyy aaannnddd eeecccooonnnooommmyyy... TTThhheeessseee aaaddddddiiitttiiivvveeesss
ffuunnccttiioonn bbyy oonnee oorr mmoorree sseevveerraall ppoossttuullaatteedd mmeecchhaanniissmmss,, vviizz.. nnuucclleeaattiioonn,, aaddssoorrppttiioonn,, ccoo-
ccrryyssttaalllliizzaattiioonn aanndd iimmpprroovveedd wwaaxxy solubility, which rreessuulltt iinn tthhee ffoorrmmaattiioonn ooff ssmmaalllleerr wwaaxx
ccrryyssttaallss wwiitthh mmoorree rreegguullaarr sshhaappee [14].
PPPooolllyyymmmeeerrrsss sssuuuccchhh aaasss vvviiinnnyyylll aaaccceeetttaaattteee cccooopppooolllyyymmmeeerrr,,, aaacccrrryyylllaaattteee cccooopppooolllyyymmmeeerrr aaannnddd ttthhheeeiiirrr dddeeerrriiivvvaaatttiiivvveeesss [14] are the
mmmaaaiiinnn aaaddddddiiitttiiivvveeesss uuussseeeddd tttooo iiimmmppprrrooovvveee ttthhheee ffflllooowwwaaabbbiiillliiitttyyy ooofff vvveeerrryyy wwwaaaxxxyyy cccrrruuudddeee oooiiilll,,, dddiiieeessseeelll fffuuueeelll aaannnddd ooottthhheeerrr base
oils at low temperature.

The relations between ∆PPP aaannnddd aaaddddddiiitttiiivvveee cccooonnnccceeennntttrrraaatttiiiooonnnsss fffooorrr cccrrruuudddeee oooiiilllsss wwwiiittthhhooouuuttt aaannnddd wwwiiittthhh aaaddddddiiitttiiivvveeesss
(PEAA-C OH, PEAA-C NNHH , PEAA-C OHVA and PEAA-C NH VA)) aarree sshhoowwnn iinn Figures
16 16 2 16 16 2
(1-5). TThhee ppoouurr ppooiinntt rreedduuccttiioonn wwaass ccaallccuullaatteedd bbyy tthhee ffoolllloowwiinngg eeqquuaattiioonn::

PPoouurr ppooiinntt rreedduuccttiioonn ((∆P) = PP – PP
pure add

Where, PP iiss tthhee ppoouurr ppooiinntt ooff tthhee ppuurree crude oil and PP iiss tthhee ppoouurr ppooiinntt ooff tthhee ccrruuddee ooiill
pure add
containing additives.
These figures show tthhaatt tthhee ∆∆PP vvaalluuee iinnccrreeaasseedd wwiitthh iinnccrreeaassiinngg ooff aaddddiittiivvee ccoonncceennttrraattiioonnss ffrroomm
550000 ppppmm ttoo 55000000 ppppmm ffoorr KKhhPPCC ccrruuddee ooiill.. OOnn tthhee ootthheerr hhaanndd,, tthhee ffiigguurreess ((11-5) indicate that the
prepared graft co-pppooolllyyymmmeeerrrsss cccaaannn bbbeee uuussseeeddd aaasss pppuuurrreee pppoooiiinnnttt dddeeeppprrreeessssssaaannnttt dddeeepppeeennndddiiinnnggg ooonnn ttthhheee cccooommmpppooosssiiitttiiiooonnn
of crude oils.

20
18
16
14
12
P 10
∆
8
6 PPEEAAAA-C16OH
PPEEAAAA-C16NH2
4
PPEEAAAA-C16OHVA
2 PPEEAAAA-C16NH2VA
0
0 550000 1000 1500 22000000 2500
Concentration, PPm

Figure 1: Relation between ∆∆P and concentration of the graft co-ppoollyymmeerrss oonn OOuumm BBaarraakkaa ccrruuddee ooiill.

479
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30
25
20
P 15
∆
10
PEAA--C16OH
PEAA--C16NH2
5 PEAA--C16OHVA
PEAA--C16NH2VA
0
0 1000 2000 3000 4000 55000000 6000
Concentration, PPm

FFiigguurree 22:: RReellaattiioonn bbeettwweeeenn ∆P and concentration of the graft co-ppoollyymmeerrss oonn KKhheepprr ccrruuddee ooiill..

25
20
15
P
∆
10
PEAA--C16OH
5 PEAA--C16NH2
PEAA--C16OHVA
PEAA--C16NH2VA
0
0 500 1000 1500 2000 2500 3000 3500
Concentration, PPm

FFiigguurree 33:: RReellaattiioonn bbeettwweeeenn ∆P and concentration of the graft co-ppoollyymmeerrss oonn SSuummppeettccoo ccrruuddee ooiill..

480
R. S. Abdel Hameed et al AAddvv.. AAppppll.. SSccii.. RReess..,, 22001111,, 22 ((55))::476-489
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30
25
20
P15
∆
10
PEAA--C16OH
PEAA--C16NH2
5
PEAA--C16OHVA
PEAA--C16NH2VA
0
0 1000 2000 3000 4000 55000000 6000
Concentration, PPm

Figure 4: Relation between ∆∆P and concentration of the graft co-ppoollyymmeerrss oonn SSaallaamm BBaassee ccrruuddee ooiill..

25
20
15
P
∆
10
PPEEAAAA-C16OH
5
PPEEAAAA-C16NH2
PPEEAAAA-C16OHVA
PPEEAAAA-C16NH2VA
0
0 1000 2000 3000 4000 55000000 6000
Concentration, PPm

FFiigguurree 55:: RReellaattiioonn bbeettwweeeenn ∆P and concentration of the graft co-ppoollyymmeerrss oonn Khalda crude oil.

Figures (1-5) illustrate ttthhheee rrreeesssuuullltttsss ooobbbtttaaaiiinnneeeddd fffrrrooommm ttthhheee pppooouuurrr pppoooiiinnnttt mmmeeeaaasssuuurrreeemmmeeennntttsss fffooorrr KKKhhhPPPCCC crude
oil. Pour point values rreedduuccttiioonn hhigher than 21 oC (∆P values) were aacchhiieevveedd bbyy aaddddiinngg 550000 aanndd
481
R. S. Abdel Hameed et al AAddvv.. AAppppll.. SSccii.. RReess..,, 22001111,, 22 ((55))::476-489
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555000000000 ppppppmmm ooofff gggrrraaafffttt PPPEEEAAAAAA cccooopppooolllyyymmmeeerrrsss tttooo ttthhheee cccrrruuudddeee oooiiilll... TTThhhiiisss mmmeeeaaannnsss ttthhhaaattt,,, iiinnn ttthhhiiisss cccooonnnccceeennntttrrraaatttiiiooonnn
range, the additive co-ccrryyssttaalllliizzeess wwiitthh tthhee ppaarraaffffiinn,, mmooddiiffyyiinngg tthheeiirr ccrryyssttaallss..

3.3. RRhheeoollooggiiccaall MMeeaassuurreemmeennttss::
3.3.1. EEvvaalluuaattiioonn ooff PPEEAAAA GGrraaffttss as Flow Improver
PEAA graft co-polymers wwweeerrreee eeevvvaaallluuuaaattteeeddd fffooorrr ttthhheeeiiirrr pppeeerrrfffooorrrmmmaaannnccceee aaasss ffflllooowww iiimmmppprrrooovvveeerrrsss fffooorrr ttthhheee ttteeesssttteeeddd
crude oils ttthhhrrrooouuuggghhh rrrhhheeeooolllooogggiiicccaaalll mmmeeeaaasssuuurrreeemmmeeennntttsss aaattt cccooonnnccceeennntttrrraaatttiiiooonnn fffrrrooommm 555000000 tttooo 555000000000 ppppppmmm...
MMeeaassuurreemmeennttss ooff tthhee sshheeaarr ssttrreessss – sshheeaarr rraattee rreellaattiioonnsshhiipp wweerree ccaarrrriieedd oouutt aatt ddiiffffeerreenntt
tteemmppeerraattuurreess rraannggiinngg ffrroomm 3366 oC to 15 oC. The apparent viscosity – sshheeaarr rraattee rreellaattiioonnsshhiippss ffoor
tthhee uunnttrreeaatteedd aanndd ttrreeaatteedd ccrruuddee ooiillss aatt the selected concennttrraattiioonn ((33000000 ppppmm)) of PEAA graft
copolymers are plotted in FFiigguurreess ((66-8) aass ffllooww iimmpprroovveerrss aatt ddiiffffeerreenntt tteemmppeerraattuurreess..

IItt wwaass oobbsseerrvveedd tthhaatt tthhee PPEEAAAA ggrraafftt ccoo-ppoollyymmeerrss hhaavviinngg aallkkyyll ssiiddee cchhaaiinnss aarre efficient additives
aass ffllooww iimmpprroovveerr.. OOnn tthhee ootthheerr hhaanndd,, the apparent viscosity – sshheeaarr rraattee rreellaattiioonnsshhiippss show non-
NNNeeewwwtttooonnniiiaaannn pppssseeeuuudddoooppplllaaassstttiiiccc bbbeeehhhaaavvviiiooorrrsss aaattt dddiiiffffffeeerrreeennnttt lllooowww cccooonnnccceeennntttrrraaatttiiiooonnnsss aaannnddd ttteeemmmpppeeerrraaatttuuurrreeesss (((eeeqqquuuaaalll ooorrr
bbeellooww tthheeiirr ppoouurr ppooiinntt)) bbuutt tthheeiirr yyiieelldd ssttrreessss aanndd vviissccoossiittyy vvaalluueess wweerree ddeeccrreeaasseedd aass ccoommppaarreedd
wwwiiittthhh uuunnntttrrreeeaaattteeeddd cccrrruuudddeee oooiiilllsss eeevvveeennn aaattt lllooowww ttteeemmmpppeeerrraaatttuuurrreeesss... HHHooowwweeevvveeerrr,,, ttthhheee dddyyynnnaaammmiiiccc vvviiissscccooosssiiitttyyy dddeeecccrrreeeaaassseeesss
wwwiiittthhh iiinnncccrrreeeaaasssiiinnnggg ttthhheee ssshhheeeaaarrr rrraaattteee rrreeeaaaccchhhiiinnnggg aaa llliiimmmiiitttiiinnnggg vvvaaallluuueee aaattt hhhiiiggghhh ssshhheeeaaarrr rrraaattteee... TTThhhiiisss iiinnnfffiiinnniiittteee ssshhheeeaaarrr rrraaattteee
viscosity iss kknnoowwnn aass tthhee aappppaarreenntt vviissccoossiittyy [15].

TThheessee ddaattaa iinnddiiccaattee tthhaatt PPEEAAAA ccoo-ppoollyymmeerriicc aaddddiittiivveess hhaavvee tthhee aabbiilliittyy ttoo ddiissppeerrssee aasspphhaalltteennee
pppaaarrrtttiiicccllleeesss aaarrrooouuunnnddd ttthhheee wwwaaaxxx cccrrryyyssstttaaalllsss aaannnddd iiimmmppprrrooovvveee ttthhheee ffflllooowww bbbeeehhhaaavvviiiooorrr ooofff ttthhheee ttteeesssttteeeddd cccrrruuudddeee oooiiilllsss... The
behavior of decreasing rrrhhheeeooolllooogggiiicccaaalll pppaaarrraaammmeeettteeerrrsss aaafffttteeerrr aaaddddddiiitttiiiooonnn ooofff ttthhheee ppprrreeepppaaarrreeeddd cccooo-polymers can
ttthhhuuusss bbbeee aaattttttrrriiibbbuuuttteeeddd tttooo ttthhheeeiiirrr ccchhheeemmmiiicccaaalll ssstttrrruuuccctttuuurrreee... TTThhheee hhhiiiggghhh pppooolllaaarrriiitttyyy ooofff oooxxxyyygggeeennn iiinnn ttthhheee eeesssttteeerrr gggrrrooouuuppp
along the co-pppooolllyyymmmeeerrr ccchhhaaaiiinnn ppplllaaayyyeeeddd aaa rrrooollleee iiinnn ppprrreeevvveeennntttiiinnnggg ttthhheee aaagggggglllooommmeeerrraaatttiiiooonnn ooofff wwwaaaxxx cccrrryyyssstttaaalllsss iiinnn
crude oil [16].

2400
bbllaannkk
PPEEAAAA-C16OH
s 2200
a PPEEAAAA-C16NH2
P
m PPEEAAAA-C16OH-VA
2000
y, PPEEAAAA-C16NH2-VA
t
i
os 1800
c
s
i
v 1600
t
n
e
ar 1400
p
p
A
1200
1000
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 6: RRReeelllaaatttiiiooonnn bbbeeetttwwweeeeeennn ssshhheeeaaarrr rrraaattteee aaannnddd aaappppppaaarrreeennnttt vvviiissscccooosssiiitttyyy ooofff KKKhhhaaallldddaaa CCCrrruuudddeee oooiiilll wwwiiittthhh PPPEEEAAAAAA gggrrraaafffttt cccooo-
polymers at 3000 ppm and at 15 oC.
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1500
bbllaannkk
PPEEAAAA-C16OH
1300 PPEEAAAA-C16NH2
s PPEEAAAA-C16OH-VA
a
P PPEEAAAA-C16NH2-VA
1100
m
y,
osit 900
c
s
vi
nt 700
e
r
a
p
p
A 500
300
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 7: RRReeelllaaatttiiiooonnn bbbeeetttwwweeeeeennn ssshhheeeaaarrr rrraaattteee aaannnddd aaappppppaaarrreeennnttt vvviiissscccooosssiiitttyyy ooofff KKKhhhaaallldddaaa CCCrrruuudddeee oooiiilll wwwiiittthhh PPPEEEAAAAAA gggrrraaafffttt cccooo-
polymers at 3000 ppm and at 27 oC.

600
bbllaannkk
500 PPEEAAAA-C16OH
PPEEAAAA-C16NH2
s PPEEAAAA-C16OH-VA
Pa 400 PPEEAAAA-C16NH2-VA
m
y,
t 300
i
s
o
c
s
i 200
v
t
n
e
ar 100
p
p
A
0
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 8: RRReeelllaaatttiiiooonnn bbbeeetttwwweeeeeennn ssshhheeeaaarrr rrraaattteee aaannnddd aaappppppaaarrreeennnttt vvviiissscccooosssiiitttyyy ooofff KKKhhhaaallldddaaa CCCrrruuudddeee oooiiilll wwwiiittthhh PPPEEEAAAAAA gggrrraaafffttt cccooo-
polymers at 3000 ppm and at 36 oC.

483
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3.3.2. Effect of tteemmppeerraattuurreess aanndd shear on the Rheologiiccaall bbeehhaavviioorr of Untreated and
Treated Crude Oils
The ssshhheeeaaarrr aaannnddd ttthhheeerrrmmmaaalll hhhiiissstttooorrryyy ppplllaaayyy aaannn eeesssssseeennntttiiiaaalll rrrooollleee iiinnn iiidddeeennntttiiifffyyyiiinnnggg ttthhhiiisss ffflllooowww bbbeeehhhaaavvviiiooorrr... TTThhheee
lllooowwweeerrriiinnnggg ooofff ttteeemmmpppeeerrraaatttuuurrreee ooofff cccrrruuudddeee oooiiilllsss iiinnncccrrreeeaaasssiiinnnggg pppooouuurrr pppoooiiinnnttt,,, yyyiiieeelllddd ssstttrrreeessssss,,, vvviiissscccooosssiiitttyyy aaannnddd
progressive wax deposition [117].
TToo ssuupppplleemmeenntt aa rreeaalliissttiicc llooww tteemmppeerraattuurree ffllooww bbeehhaavviioorr ooff tthhee tteesstteedd ccrruuddeess,, rrhheeoollooggiiccaall
mmmeeeaaasssuuurrreeemmmeeennntttsss hhhaaavvveee tttooo bbbeee eeevvvaaallluuuaaattteeeddd... HHHeeennnccceee,,, ttthhheeessseee aaaddddddiiitttiiivvveeesss wwweeerrreee eeevvvaaallluuuaaattteeeddd fffooorrr ttthhheeeiiirrr pppeeerrrfffooorrrmmmaaannnccceee
aass ffllooww iimmpprroovveerrss ffoorr tthhee tteesstteedd ccrruuddee tthhrroouugghh rrhheeoollooggiiccaall mmeeaassuurreemmeennttss aatt ccoonncceennttrraattiioonn ooff
500-55000000 ppppmm.. MMeeaassuurreemmeennttss ooff tthhee sshheeaarr ssttrreessss – sshheeaarr rraattee rreellaattiioonnsshhiipp wweerree ccaarrrriieedd oouutt aatt
ddiiffffeerreenntt tteemmppeerraattuurreess rraannggiinngg ffrroomm 1155 oC to 36 oC.

The shear stress – ssshhheeeaaarrr rrraaattteee rrreeelllaaatttiiiooonnnssshhhiiipppsss fffooorrr ttthhheee uuunnntttrrreeeaaattteeeddd aaannnddd tttrrreeeaaattteeeddd cccrrruuudddeee oooiiilllsss aaattt dddiiiffffffeeerrreeennnttt
concentrations of PEAA-DDccAA aarree ppllootttteedd iinn Figures (7-10) aatt ddiiffffeerreenntt tteemmppeerraattuurreess.. TThheessee
figures iiilllllluuussstttrrraaattteee ttthhheee fffiiitttttteeeddd eeexxxpppeeerrriiimmmeeennntttaaalll dddaaatttaaa ooofff bbbooottthhh ssshhheeeaaarrr ssstttrrreeessssss aaannnddd ssshhheeeaaarrr rrraaattteee mmmeeeaaasssuuurrreeemmmeeennntttsss
aaccccoorrddiinngg ttoo tthhee BBiinngghhaamm ppllaassttiicc mmooddeell.. TThhee oobbttaaiinneedd ddaattaa ooff η τ aanndd ccoorrrreellaattiion coefficient
p, y
wwweeerrreee dddeeettteeerrrmmmiiinnneeeddd fffooorrr aaallllll ttteeesssttteeeddd cccrrruuudddeee oooiiilllsss aaattt dddiiiffffffeeerrreeennnttt ttteeemmmpppeeerrraaatttuuurrreeesss aaannnddd aaarrreee llliiisssttteeeddd iiinnn Tables (1-4).
However, tthhee lliinneeaarr pplloottss ooff tthhee sshheeaarr rraattee-sshheeaarr ssttrreessss ccuurrvveess ccaann bbee eexxttrraappoollaatteedd ttoo zzeerroo sshheeaarr
rraatteess aanndd tthhee iinntteerrcceepptt wwiitthh tthhee yy aaxxiiss iiss the Bingham yield value (τβ)).. TThhee BBiinngghhaamm yyiieelldd vvaalluuee
iiisss dddeeefffiiinnneeeddd aaasss ttthhheee ssshhheeeaaarrr ssstttrrreeessssss rrreeeqqquuuiiirrreeeddd fffooorrr iiinnniiitttiiiaaatttiiinnnggg ffflllooowww aaannnddd iiittt iiisss iiimmmpppooorrrtttaaannnttt bbbeeecccaaauuussseee iiittt mmmeeeaaasssuuurrreeesss
tthhee aabbiilliittyy ooff fflluuiidd ttoo rreessttaarrtt iittss ffllooww aafftteerr sshhuuttddoowwnn [18].

3500
Blank
3000
PEAA-CC1166OOHH
PEAA-CC1166NNHH22
2500 PEAA-CC1166OOHHVVAA
PEAA-CC1166NNHH22VVAA
a 2000
P
s,
es 1500
r
t
s
ar 1000
e
h
S
500
0
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 9: RReellaattiioonn bbeettwweeeenn sshheeaarr rraattee - shear stress of KKhhaallddaa CCrruuddee ooiill wwiitthh PPEEAAAA ggrraafftt ccoo-polymers at
3000 ppm and at 15 oC.

484
R. S. Abdel Hameed et al AAddvv.. AAppppll.. SSccii.. RReess..,, 22001111,, 22 ((55))::476-489
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________
3000
Blank
2500
PEAA-CC1166OOHH
PEAA-CC1166NNHH22
a 2000 PEAA-CC1166OOHHVVAA
P PEAA-CC1166NNHH22VVAA
s,
es 1500
r
t
s
r
a 1000
e
h
S
500
0
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 10: RReellaattiioonn bbeettwweeeenn sshheeaarr rraattee - sshheeaarr ssttrreessss ooff KKhhaallddaa CCrruuddee ooiill wwiitthh PPEEAAAA ggrraafftt ccoo-polymers at
3000 ppm and at 27 oC.

1400
Blank
1200
PEAA-CC1166OOHH
PEAA-CC1166NNHH22
1000 PEAA-CC1166OOHHVVAA
a PEAA-CC1166NNHH22VVAA
P
s, 800
s
e
r 600
t
s
r
a
e 400
h
S
200
0
0 200 400 600 800 1000 1200 1400
Shear rate, S-1

Figure 11: RReellaattiioonn bbeettwweeeenn sshheeaarr rraattee - sshheeaarr ssttrreessss ooff KKhhaallddaa CCrruuddee ooiill wwiitthh PPEEAAAA ggrraafftt ccoo-polymers at
3000 ppm and at 36 oC.

OOOnnn ttthhheee ooottthhheeerrr hhhaaannnddd,,, ttthhheee aaappppppaaarrreeennnttt vvviiissscccooosssiiitttiiieeesss (((mmmPPPaaaSSS))) ooofff ttthhheee uuunnntttrrreeeaaattteeeddd aaannnddd aaalllsssooo tttrrreeeaaattteeeddd cccrrruuudddeee oooiiilll
with PEAA graft co-ppoollyymmeerrss wweerree ddeetteerrmmiinneedd aatt ddiiffffeerreenntt tteemmppeerraattuurreess ttoo eevvaalluuaattee tthhee eeffffeecctt ooff
the polymers ooonnn ttthhheee vvviiissscccooosssiiitttiiieeesss ooofff ttthhheee cccrrruuudddeee oooiiilll... TTThhheee dddaaatttaaa iiinnndddiiicccaaattteee ttthhhaaattt ttthhheee vvviiissscccooommmeeetttrrriiiccc bbbeeehhhaaavvviiiooorrrsss
ooff tthhee ttrreeaatteedd ccrruuddee ooiill ddeeppeenndd oonn tthhee ccrruuddee ooiill ccoommppoossiittiioonnss aanndd tthhee ssttrruuccttuurree ooff tthhee pprreeppaarreedd
PEAA co-pppooolllyyymmmeeerrriiiccc aaaddddddiiitttiiivvveee... IIInnn ttthhhiiisss rrreeessspppeeecccttt,,, ttthhheee vvvaaallluuueeesss ooofff ttthhheee ppplllaaassstttiiiccc vvviiissscccooosssiiitttyyy (((mmmPPPaaaSSS))) aaannnddd yyyiiieeelllddd
vvaalluueess ((PPaa)) aarree ffoouunndd ttoo ddeeccrreeaassee bbyy tthhee aaddddiittiioonn ooff PEAA graft co-ppoollyymmeerriicc additives even at
low concentrations (50000 ppppmm)).. IItt iiss oobbvviioouuss tthhaatt tthhee ppllaassttiicc vviissccoossiittyy aanndd yyiieelldd ssttrreessss vvaalluueess
ddeeccrreeaasseedd ssiiggnniiffiiccaannttllyy wwiitthh iinnccrreeaassiinngg tthhee ccoonncceennttrraattiioonn ooff tthhee aaddddiittiivveess with crude oil up to
485