Effects of Demulsiﬁer Structure

Petroleum Science and Technology, 24:673–688, 2006Copyright © Taylor & Francis Group, LLCISSN: 1091-6466 print/1532-2459 onlineDOI: 10.1081/LFT-200041172

Effects of Demulsifier Structure onDesalting Efficiency of Crude Oils

Xinru Xu, Jingyi Yang, and Jinshen GaoResearch Institute of Petroleum Procession,

East China University of Science & Technology,Shanghai, P.R. China

Abstract: The desalting and dewatering of six crude oils with deferent propertieshave been studied. The contents of asphaltene and resin of #1, #2, and #4 crudeoil are high; the demulsifiers with higher lipophilic values than others in the sameseries such as DA2, DB2, and DC2 can be easily absorbed on the interface of awater–oil emulsion and reveal better dewatering and desalting efficiency. The car-bon atom number of alkyl on phenol core in nonyl-alkylphenol formaldehyde resin,which is the initiator of the DC series, is more than that of the DB series. DC waseasier to diffuse into the interface of water in oil, and the dewatering efficiency in-creased. Because more multipoint adsorbed, their dewatering rate was slower, andthe salts can dissolve in washing water and be removed with water. The densityand viscosity of #3 crude oil are lower, and wax content is high. The hydrophilicgroup and lipophilic group in the molecular of DA4, DB4, and DC4 demulsifier canwell be absorbed on the interface of water–oil emulsion of #3 crude oil, which havebetter efficiencies of desalting and dewatering than other demulsifiers of their sameseries. The density, viscosity, and wax content of #5 and #6 crude oils are lower;however, sulfur content is high. The self-made demulsifiers have excellent dewater-ing efficiency for #5 and #6 crude oil, but the desalting efficiency is unsatisfied,because the content of salts sulfate and sulfide in #5 and #6 crude oil is high asshown in the analysis of anion content before and after desalting. It can be improvedby adding acid assistant TJ1, TJ2, and TJ3, thus indiffluent salts sulfate and sulfidetransform into diffluent salts that can be removed, so the desalting efficiency obviouslyincreases.

Keywords: desalting, dewatering, demulsifier, crude oil

Address correspondence to Jinshen Gao, Research Institute of Petroleum Proces-sion, East China University of Science & Technology, Meilong Rd. 130, Shanghai,200237, P.R. China. E-mail: [email protected]

673

674 X. Xu et al.

INTRODUCTION

Crude oil from underground reservoirs contains water to form water-in-oilemulsion. The majority of the salts, such as sodium, magnesium, and calciumchloride, are dissoluble in water. In oil fields, the newly exploited crude oilhas to be treated to remove water and salts. Its water content is limited toless than 0.5% and salt content less than 50 mg/L. But this salt content ofcrude oil is still high for the refinery. Therefore, pretreatment of crude oilin which the salts are removed is the first operation in petroleum refining(Barnett, 1988).

Formerly the desalting of crude oil was conducted only as a measure todecrease corrosion and stabilize operation. In recent years, desalting technol-ogy has played an important part in protecting catalysts in the latter refiningoperations, because after distillation, the majority of salts are left in residualand heavy stocks which leads to the poisoning and deactivation of catalystsin the heavy oil catalytic cracking, hydrocracking, and hydrorefining (Samsand Zaouk, 2000).

Another noticeable problem is that a series of enhanced recovery tech-nologies have been widely applied in oil fields (Zheng and Wu, 2000), forexample, using surfactant, polymer, and alkali flooding to drive heaver oil.At the same time, they can enter into the oil layer and make the emulsionmore stable.

During the past decades, nonionic surfactants have been widely used asdemulsifiers. Nowadays, alkoxylated polyhydric alcohol, alkoxylated alkylphe-nol formaldehyde resin, alkoxylated polyethylenemine, and their derivativesare main demulsifiers for the desalting and dewatering of crude oil (Samsand Zaouk, 2000; Talor, 1992). As the properties of crude oils from differ-ent oil fields are different, a demulsifier fitted to one type of crude oil isusually not as effective with other types. Attempts have been made to corre-late the efficiency of demulsifiers with their surface, interfacial, and chemicalproperties (Chen, 1993; Mohammed, 1993, 1994; McLean and Kilpatrick,1997; Ovalles, 1998; Acevedo, 1999; Goldszal and Bourrel, 2000; Runacand Tabakovic, 1978; Aveyard et al., 1990; Zaki et al., 2000; Wu, 2003).Runnac and Tabakovic (1978) reported a correlation between demulsificationand the size of the hydrophilic group for block copolymers. Aveyard et al.(1990) and Zaki et al. (2000) described the correlations between demulsifi-cation efficiency and HLB of demulsifier. Wu (1993) investigated whether arelationship exists between demulsification performance and the properties ofthe demulsifier, including relative solubility number (RSN) value and molec-ular weight. However, there are many works researching the relation betweenthe property of crude oil and the molecular structure of demulsifiers.

In this paper, three series demulsifiers are synthesized, and the effect ofthe molecular structure of these demulsifiers on their desalting and dewateringabilities for Shengli, Luning, Daqing, Cabinda, Saudi, and Iran crude oil are

Desalting Efficiency of Crude Oils 675

examined. The impact of an acid assistant on desalting ability for Saudi crudeoil and Iran crude oil is also discussed.

EXPERIMENTAL

Synthesis of Demulsifier

In a 500 ml high-pressure reactor fitted with a condenser, mechanical stirrer,thermocouple, and manometer, polyhydric alcohol, octyl-alkylphenol formal-dehyde resin, and nonyl-alkylphenol formaldehyde resin as initiators werepolymerized with a certain amount of propylene oxide (PO) and ethyleneoxide (EO) at a proper reactive condition. In order to fit the demulsifyingbehavior to different types of crude oil, the weight ratio of EO/PO was varied.Using this method, a series of block copolymers (DA, DB, DC series) demul-sifiers were obtained and used for the experiment.

Process of Static Electric Desalting of Crude Oil

PDY-1 instrument of electric desalting for crude was used in the experiments.Having been preheated and uniformly stirred, the oil sample was deliveredinto the mixer where a certain amount of washing water was put in, andthis was then stirred at 9,000 r/min for 1 min. After that, the emulsion andappropriate demulsifier were put into test bottles. These bottles equipped withelectrodes were fixed in the oscillator and shaken for 1 min then stored ina constant-temperature bath at 85 ± 2◦C for 10 min, and shaken again for1 min, which ensured uniform distribution of the demulsifier in the emulsion.These bottles were placed on the DPY-1 for 20 min at 2,100 V/cm electricfield and 85◦C, then the electric was remoed and then stored 15 min at 85◦C.The volume of the separated water was recorded; the salt content in oil afterdesalting was analyzed.

Analysis of Salt Content in Crude Oil

In the experiment, WC-2 microcoulometric detector of salt content was usedto detect the salt content in crude oil. The principle of the WC-2 microcoulo-metric detector is that crude oil mixed with polar solvent was first heated toextract the salt and then centrifuged. A small amount of extracted liquid wastaken out with an injector and delivered into the ethanoic acid electrolytecontaining a certain amount of silver ion, so chlorine ion in the sample canreact with silver ion as follows:

Cl− + Ag+ → AgCl ↓

676 X. Xu et al.

The lost silver ion for the reaction will be supplied by electrode, soaccording to Faraday’s law (of electrolysis), the salt content in the samplewill be obtained by measuring the change of electric quantity for supplyingsilver ion.

Analysis Method of the Anion Concentration of Crude Oil

The instrument of ion chromatogram (DIONEX Model 500) was used todetect the anion concentration of crude oil. The analyses conditions for ionchromatogram were provided as follows: separate column is AS4A-SC4 mm,flow of Na2CO3/NaHCO3 is 2 ml/min, washing liquid is NaCO3, the detectoris restrain conductivity.

A 12.00 g oil sample, 18 ml xylene, and 18 ml deionized water weredelivered into a cylinder and stored in a constant-temperature bath at 80◦Cfor 15 min. Then 6 ml ethanol was added, and it was shaken for 4 min in anoscillator and again placed in water bath for 30 min at 80◦C. The extractedwater was taken out by using an injector—the left oil was extracted twice bythe same method. The three extracted water samples were put together andtaken for detection on the ion chromatogram.

Properties of Several Crude Oils

The desalting and dewatering of Shengli (#1), Luning (#2), Daqing (#3),Cabinda (#4), Saudi (#4), and Iran (#5) crude oils, which are typically foundin Chinese refineries, were studied, and their properties are shown in Table 1.

RESULTS AND DISCUSSION

Effect of DA Series Demulsifiers on the Desalting and Dewatering ofCrude Oil

Generally, a small proportion of washing water is mixed with crude oil sothat the salts and impurities in oil can be dissolved, the washing water shouldbe dispersed in crude oil to form emulsion, which extracts the salts fromoil. However, these brine droplets are prevented from coalescing due to theelastic film on the interface between water and oil. Normally, this film isstabilized by natural emulsifiers in crude oil, such as wax, resin, asphaltene,naphthenic acid, and so forth. The demulsifier usually has a higher surfaceactivity than these natural emulsifiers, so it can displace them and weaken thefilm, thereby promoting the droplets of brine to coalesce when they contacteach other (Figure 1).

Tabl

e1.

Prop

ertie

sof

seve

ral

crud

eoi

ls

Cru

deoi

l#1

#2#3

#4#5

#6

Den

sity

(g/c

m3)

20◦ C

0.91

560.

9108

0.86

090.

8930

0.86

030.

8573

Vis

cosi

ty(m

m2/s

)50

◦ C98

.13

90.9

625

.44

7.60

23.4

85.

0010

0◦C

17.0

314

.49

7.48

2.86

6.34

—So

lidifi

catio

npo

int

(◦C

)15

2134

−1−6

−9A

cid

umbe

r(m

gKO

H/g

)1.

461.

020.

050.

120.

320.

24W

ax(w

%)

9.66

12.3

427

.39

5.58

4.12

6.84

Res

in(w

%)

27.3

032

.06

16.7

222

.97

20.9

78.

51A

spha

ltene

(w%

)1.

822.

520.

552.

282.

740.

92S

(w%

)0.

910.

210.

190.

502.

711.

61Sa

lt(m

g/L

)14

.96

6.97

7.63

8.24

12.2

319

.99

Prin

cipl

ech

arac

ter

h-de

nsity

h-de

nsity

h-w

axh-

cont

ents

h-su

lfur

h-su

lfur

h-vi

scos

ityh-

visc

osity

cont

ent

ofre

sin

cont

ent

cont

ent

h-co

nten

tsh-

cont

ents

asph

alte

neh-

cont

ents

h-sa

ltof

resi

nof

resi

nof

resi

nco

nten

tas

phal

tene

asph

alte

neas

phal

tene

677

678 X. Xu et al.

Figure 1. Water in oil emulsion.

DA series demulsifiers were synthesized using alkoxylated polyhydricalcohol. Polyhydric alcohol, as an initiator, was polymerized with an ap-propriate amount of propylene oxide (PO) to form the intermediate polymer,with the weight ratio of polyhydric alcohol and propylene oxide at 1:90. Thenthe intermediate prepolymer was polymerized with an appropriate amount ofethylene oxide (EO), and the DA series demulsifiers, DA1–DA5, were ob-tained. The weight percents of EO/PO in them successively were 15%, 30%,40%, 48%, and 60%. Relatively speaking, its structure is illustrated as fol-lows:

The EO chain is a hydrophilic group, and the PO chain is a lipophilic groupin the molecular structure of demulsifiers. With the weight ratio of EO incopolymer increasing, the hydrophilic property of demulsifier increases. Fig-ures 2 and 3 and Table 2 show the effect of DA series demulsifiers on thedesalting and dewatering of demulsifiers for several crude oils.

The #1, #2, and #4 crude oils contain high contents of asphaltene andresin. The basic structure of asphaltene is considered as having condensedaromatic rings as a core, linked with many naphthenic, aromatic rings in

Table 2. Dewatering efficiency of DA series demulsifiers for several crude oils

Demulsifiers #1 #2 #3 #4 #5 #6

DA1 70.0 75.0 85.0 90.0 80.0 84.0DA2 80.0 84.0 90.0 95.0 84.0 90.0DA3 80.0 80.0 90.0 95.0 90.0 96.0DA4 78.0 80.0 94.0 90.0 94.0 94.0DA5 76.0 70.0 92.0 90.0 90.0 80.0


Figure 2. Desalting efficiency of DA series demulsifiers for #1, #2, #3 crude oils.

addition to naphthenic rings, which carry many chains of different length.Asphaltenes also contain many groups of sulfur, nitrogen, oxygen, and evenmany metal complexes of iron, nickel, and vanadium, so they have highsurface activity and can be strongly absorbed on the interface of the oil–water emulsion. DA2 with a low EO/PO weight ratio of 30% is provided witha superior lipophilic property. Its molecular can be easily absorbed on theinterface of oil–water through the oil phase, which peptizes the hydrophobicgelatinous film surrounding the water droplets in the emulsion and weakensthe rigidity of the interfacial film by a diffusion partitioning process. Thedesalting efficiency, salt content, and dewatering efficiency of demulsifierDA2 for #1 crude oil, respectively, were 75.00%, 3.74 mg/L, and 80.0%; for#2 crude oil, respectively, were 67.00%, 2.30 mg/L, and 84.0%; for #4 crudeoil, respectively, were 64.47%, 2.91 mg/L, and 95.0%.

Figure 3. Desalting efficiency of DA series demulsifiers for #4, #5, #6 crude oils.

680 X. Xu et al.

The wax content with 27.3% in #3 crude oil is high. Wax, a high-meltingparaffin, easily forms many fine and net-like wax crystals in crude oil, whichmakes a barrier on the interface beween the brine droplets and crude oil. Sucha barrier increases the strength of interfacial film and hinders the aggrega-tion of the drops, so the emulsion becomes right stable. The weight percentof EO/PO in DA4 is 48%, and its hydrophilic property is higher. It can beabsorbed on the interface and displace the wax crystals and other originalemulsifying impurities, which is appropriate for #3 crude oil with high waxcontent. For #3 crude oil, the desalting efficiency, salt content, and dewa-tering efficiency of demulsifier DA4, respectively, were 67.63%, 2.47 mg/L,and 94.0%.

Effect of DB Series Demulsifiers on the Desalting and Dewatering ofCrude Oils

DB series demulsifiers are synthesized as follows: octyl-alkylphenol formal-dehyde resin, as an initiator, was polymerized with an appropriate amountof propylene oxide to form the intermediate polymer, with the weight ratioof octyl-phenolic resin and propylene oxide is 1:10. Then the intermediatepolymer, polymerized with an appropriate amount of ethylene oxide, allowedfor the DB series demulsifiers, DB1–DB5, to be obtained. Their EO/PO wt%in them successively is 15%, 30%, 40%, 48%, and 60%. Its structure isdescribed as follows:

The octyl-alkylphenol formaldehyde resin is synthesized by octyl-alkylphenol,paraformaldehyde, and acid catalyst. The net structure was formed by the ini-tiator, which is lipophilic property polymerized with PO and EO. Figures 4and 5 and Table 3 show the effect of desalting and dewatering of DB seriesdemulsifiers for several crude oils.

DB2, similar to DA2 and with the same EO/PO weight ratio of 30%,has better lipophilic property and is also appropriate for #1, #2, and #4 crudeoils with high contents of asphaltene and resin. These demulsifiers contain aphenol structure with aromatic ring and polarity which have stronger affinitywith asphaltene and resin. The demulsifier DB2 formed multipoint absorptionon the interface of water–oil emulsion, which affected the coalescence of thebrine droplets, so the dehydration rate was slower. The dewatering efficiency


Figure 4. Desalting efficiency of CB series demulsifiers for #1, #2, #3 crude oils.

Figure 5. Desalting efficiency of DB series demulsifiers for #4, #5, #6 crude oils.

Table 3. Dewatering efficiency of DB series demulsifiers for several crude oils


DB1 65.0 72.0 70.0 80.0 75.0 80.0DB2 70.0 75.0 75.0 82.0 78.0 82.0DB3 68.0 75.0 80.0 82.0 76.0 82.0DB4 65.0 70.0 85.0 80.0 76.0 80.0DB5 65.0 70.0 80.0 76.0 75.0 80.0

682 X. Xu et al.

of DB series demulsifiers is lower than DA series demulsifiers for these crudeoils. For #1 crude oil, the desalting efficiency, salt content, and dewateringefficiency of demulsifier DB2, respectively, reached 70.00%, 2.50 mg/L, and70.0%; for #2 crude oil, respectively, 64.13%, 2.50 mg/L, and 75.0%; for #4crude oil, respectively, 61.17%, 3.20 mg/L, and 82.0%.

The weight percent of EO/PO in DB4 is 48%, its hydrophilic prop-erty is higher, and it is appropriate for #3 crude oil with high wax content.The dehydration rate of DB4 was lower, which favored dissolving salts intofreshwater. The desalting efficiency, salt content, and dewatering efficiency ofdemulsifier DB4 for #3 crude oil, respectively, reaches 76.67%, 1.78 mg/L,and 85.0%.

Effect of DC Series Demulsifiers on the Desalting and Dewatering ofCrude Oils

DC series demulsifiers are alkoxylated nonyl-alkylphenol formaldehyde poly-mer, which are synthesized using nonyl-alkylphenol formaldehyde resin asan initiator, and polymerized with appropriate amount of propylene oxide toform the intermediate polymer, with the weight ratio of nonyl-alklyphenolformaldehyde resin and propylene oxide being 1:10. Then the intermediatepolymer is polymerized with an appropriate amount of ethylene oxide, anda DC series of demulsifiers, DC1, DC2, DC3, DC4, and DC5, was obtained.EO/PO wt% in them successively is 15%, 30%, 40%, 48%, and 60%. Itsstructure is presented as follows:

Figures 6 and 7 and Table 4 show the effects of desalting and dewatering ofDC series demulsifiers for several crude oils.

Nonyl-alkylphenol formaldehyde resin is synthesized by nonyl-alkyl-phenol, paraformaldehyde, and acid catalyst. The structure with net formwas formed by the initiator which has better lipophilic property polymer-ized with PO and EO. The carbon atom number of alkyl on phenol core innonyl-alkylphenol formaldehyde resin is more than that of the DB series, sothe lipophilic property of DC was higher than that of DB. DC was easierto diffuse into the interface between water and oil, and the dewatering effi-ciency increased. Because the demulsifier DC formed multipoint adsorptionon the interface between the water and crude oil, the dehydration rate was


Figure 6. Desalting efficiency of DC series demulsifiers for #1, #2, #3 crude oils.

Figure 7. Desalting efficiency of DC series demulsifiers for #4, #5, #6 crude oils.

Table 4. Dewatering efficiency of DC series demulsifiers for several crude oils


DC1 75.0 75.0 76.0 80.0 80.0 85.0DC2 78.0 80.0 76.0 85.0 80.0 84.0DC3 78.0 80.0 80.0 85.0 85.0 85.0DC4 75.0 78.0 80.0 80.0 80.0 86.0DC5 75.0 75.0 78.0 78.0 80.0 85.0

684 X. Xu et al.

slower, and salts were dissolved into freshwater. The demulsifier DC2 is theappropriate demulsifier in DC series demulsifiers for #1, #2, and #4 crude oil.The desalting efficiency, salt content, and dewatering efficiency of demulsifierDC2 for #1 crude oil, respectively, reaches 77.07%, 3.43 mg/L, and 78.0%;for #2 crude oil, respectively, reaches 77.91%, 2.47 mg/L, and 85.0%; for #4crude oil, respectively, reaches 70.02%, 2.47 mg/L, and 85.0%.

The demulsifier DC4 with a higher EO/PO ratio is the appropriate demul-sifier for #3 crude oil in DC series demulsifiers. The desalting efficiency, saltcontent, and dewatering efficiency of demulsifier DC4 for #3 crude oil, re-spectively, reaches 72.08%, 2.13 mg/L, and 80.0%.

Effect of Assistant on the Desalting of Crude Oils

In the above experiments, all demulsifiers have excellent dewatering efficiencyfor #5 crude oil and #6 crude oil, but the desalting efficiency of the DA4demulsifier for #5 crude oil is 40.15%, and that of the DC2 demulsifier for#6 crude oil is 31.22%.

Inorganic salts in crude oil include chloride, carbonate, phosphate, nitrate,sulfate, and sulfide, most of which can dissolve in water. With the temperatureincreasing, the solubility of most salts increases. However, some sulfates andsulfides are difficult to dissolve and to be removed with water. From Table 5,it is concluded that the content of sulfate and sulfide in #5 crude oil and #6crude oil are higher than in other salts, which is the predominant cause ofpoor desalting efficiency.

Three assistants—ammonium nitrate (TJ1), N-2 carboxyl diaminoethanetriacetic acid (TJ2), and nitric acid (TJ3)—are used to improve the desaltingefficiency for those two crude oils.

Figure 8 showed that TJ1 and TJ3 have better desalting efficiency for#5 crude oil. When the concentration of demulsifier DA4 is 50 ppm in #5

Table 5. Anion concentration in various crude oils

Cl− Br− NO−3 PO3−

4 SO2−4 + S2−

(µg/ml) (µg/ml) (µg/ml) (µg/ml) (µg/ml)

#5 crude oil 1 5.40 0.04 0.80 1.22 9.872 3.84 0 0.65 0.55 7.983 1.86 0 0.20 0 4.53

#6 crude oil 1 8.22 0.06 0.79 0.98 17.602 6.32 0 0.31 0.12 14.523 2.12 0 0.20 0 2.73

1: Before desalting process; 2: after desalting process, only used demulsifier; 3: afterdesalting process, used demulsifier and assistant.


Figure 8. Desalting efficiency of assistants for #5 crude oils.

crude oil, with the concentration of TJ1 increasing, the desalting efficiencyincreases. When the concentration of TJ1 in crude oil is up to 80 ppm, thedesalting efficiency reaches 58.46%.

From Figure 9 it is concluded that TJ3 has better desalting efficiencyfor #6 crude. With the increase of TJ3 concentration from 0 to 80 ppm, thedesalting efficiency increases from 31.22% to 73.54%, when the concentrationof demulsifier DA2 in #6 crude oil is 50 ppm.

The anions in #5 crude oil and #6 crude oil are mainly chloride, sulfate,and sulfide. If only demulsifier is used, the content of sulfate and sulfidein #5 crude oil or #6 crude oil have only a small decrease in the desaltingprocess. However, after adding assistants, indiffluent salt sulfate and sulfide

Figure 9. Desalting efficiency of assistants for #6 crude oils.

686 X. Xu et al.

transform into diffluent salts. It makes the contents of sulfate and sulfide in #5and #6 crude oils obviously decreased, so the desalting efficiency apparentlyincreases.

CONCLUSION

The desalting and dewatering of six crude oils with different properties havebeen studied. The contents of asphaltene and resin of #1, #2, and #4 crudeoil are high; the density and viscosity of #1 and #2 crude oil are large. Thedemulsifiers with higher lipophilic properties than others in the same series,such as DA2, DB2, DC2, which can be easily absorbed on the interfacebetween the water in oil emulsion of #1, #2, #4 crude oil and reveal optimumefficiencies of dewatering and desalting.

The carbon atom number of alkyl on the phenol core in nonyl-alkylphenolformaldehyde resin, which was the initiator of the DC series, is more thanthat of the DB series, so the lipophilic property of DC was higher than DB.DC was easier to diffuse into the interface beween water and oil, and thedewatering efficiency increased. Because the net form structure was formed,more multipoint adsorbed, their dewatering rate was slower, the salts couldwell dissolve in washing water and be removed. The lipophilic property ofdemulsifier DC2 with EO/PO weight percent of 30% is superior. Its desaltingefficiency, salt content after desalting and dewatering efficiency for #1 crudeoil, respectively, reached 77.07%, 3.43 mg/L, and 78.0%; for #2 crude oil,respectively, 77.91%, 2.47 mg/L, and 85.0%; for #3 crude oil, respectively,72.08%, 2.13 mg/L, and 80.0%.

The density and viscosity of #3 crude oil are lower, and wax content ishigh. The hydrophilic group and lipophilic group in the molecular structureof DA4, DB4, and DC4 demulsifier form a certain hydrophilic–lipophilic bal-ance on the interface between water in oil emulsion of #3 crude oil, whichleads to better efficiencies of desalting and dewatering than other demulsifiersof their same series. DA4, with polyhydric alcohol as initiator has better dewa-tering efficiency for #3 crude oil, DB4, with an initiator of octyl-alkylphenolformaldehyde resin, has a slower dewatering rate and better efficiency for thedesalting of #3 crude oil. The desalting efficiency, salt content after desalting,and dewatering efficiency of demulsifier DB4 for #3 crude oil, respectively,reached 76.67%, 1.78 mg/L, and 85.0%.

The density, viscosity, and wax contents of #5 and #6 crude oils arelower; however, the sulfur content is high. The self-made demulsifiers showedexcellent dewatering efficiency for #5 and #6 crude oil, but the desaltingefficiency was unsatisfied. By using demulsifier and acid assistant TJ1, TJ2,and TJ3, better desalting efficiency for #5 and #6 crude oil was obtained. Withthe concentration of assistant TJ1 increasing, the desalting efficiency of #5crude oil increases. When the concentration of assistant TJ1 in crude oil was


up to 80 ppm, the desalting efficiency increased from 31.22% to 58.46%.With the concentration of assistant TJ3 increasing, the desalting efficiencyof #6 crude oil also increased. When the concentration of assistant TJ1 incrude oil is up to 80 ppm, the desalting efficiency increased from 31.22% to73.54%. It is concluded that the content of salts sulfate and sulfide in #5 and#6 crude oil is high as shown in analysis of anion content before and afterdesalting. After adding acidic assistants, indiffluent salts sulfate and sulfidetransform into diffluent salts that can be removed, so the desalting efficiencyobviously increases.

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Mohammed, R. A., Bailey, A. I., Luckham, P. F., and Taylor, S. E. (1994). Theeffect of demulsifiers on the interfacial rheology and emulsion stabilityof water-in-crude oil emulsions. Colloids and Surfaces 91:129–139.

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Effects of Demulsiﬁer Structure