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Demulsification and Interfacial Properties ofCrosslinking Phenol-Amine Resin Block PolyetherDemulsifiersYanjiao Xie a , Feng Yan b , Zhenjia Yan b , Jimei Zhang b & Jianxin Li aa State Key Laboratory of Hollow Fiber Membrane Materials and Processes , School ofMaterials Science and Engineering, Tianjin Polytechnic University , Tianjin , P. R. Chinab School of Environment and Chemical Engineering , Tianjin Polytechnic University , Tianjin ,P. R. ChinaAccepted author version posted online: 11 Jan 2012.

To cite this article: Yanjiao Xie , Feng Yan , Zhenjia Yan , Jimei Zhang & Jianxin Li (2012) Demulsification and InterfacialProperties of Crosslinking Phenol-Amine Resin Block Polyether Demulsifiers, Journal of Dispersion Science and Technology,33:12, 1674-1681, DOI: 10.1080/01932691.2011.635500

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Demulsification and Interfacial Properties ofCrosslinking Phenol-Amine Resin Block PolyetherDemulsifiers

Yanjiao Xie,1 Feng Yan,2 Zhenjia Yan,2 Jimei Zhang,2 and Jianxin Li11State Key Laboratory of Hollow Fiber Membrane Materials and Processes, School of MaterialsScience and Engineering, Tianjin Polytechnic University, Tianjin, P. R. China2School of Environment and Chemical Engineering, Tianjin Polytechnic University, Tianjin,P. R. China

Six novel crosslinking phenol-amine resin block polyether demulsifiers were synthesized fordemulsification of surfactant-polymer flooding emulsion. The demulsification performances ofthese demulsifiers were investigated by conventional graduated bottle test. Their interfacial beha-viors at water-oil interface were explored by dynamic interfacial tension and interfacial dilationalviscoelasticity measurements. The results show that the demulsification efficiency is dependant onthe hydrophilic-hydrophobic balance (HLB) value of these demulsifiers. It was also correlated tothe interfacial activity and the dilational elasticity at the water-oil interface. The higher the HLBvalue of demulsifiers, the better the demulsification efficiency is.

Keywords Crosslinking phenol-amine resin block polyether, demulsification, hydrophilic-hydrophobic balance, interfacial dilational rheology, interfacial tension

INTRODUCTION

It is well known that crude oil plays an important role inproviding the energy supply of the world among varioussources of energy. Recently, surfactant and polymers havebeen used as flooding agent to improve oil recovery in theoil industry, especially in China. Industrial experiencesshow that surfactant-polymer flooding as a key role in oilexploitation can enhance oil recovery by up to 12%.However, a fatal problem is that the emulsions ofsurfactant-polymer flooding crude oil with high stabilityoccurred, leading to the development of novel emulsionbreaking technology or demulsifier.

Chemical demulsification using demulsifier is incommon used in oil exploitation. A great number ofdemulsifiers have been developed during the past decades.Currently, the selection of demulsifier is still mainly basedon trial and error after some preliminary screening suchas bottle testing in the oil industry. However, the attemptshave been made to correlate the efficiency of demulsifierswith their chemical properties.[1] Herein, the demulsifi-cation ability of demulsifier is mainly controlled by thehydrophilic-hydrophobic ability (HLB value)[2–5] and theability to destroy the rigid oil-water interfacial film formedby the presence of surfactants, polymer, resins and asphal-tenes.[6–9] The demulsifier molecules are adsorbed onto thewater=oil interface, leading to the changes on the interfa-cial properties, such as interfacial rheology, interfacial ten-sion or film pressure. Finally, the film thinning (drainage)rate is enhanced and its stability is reduced.[10–14]

For water-in-oil (W=O) emulsion, it is generally recog-nized that the stability is controlled by the viscoelasticproperties of the interfacial film. Although the interfacialviscoelastic properties could be measured by dilational rhe-ology and shear rheology, dilational viscoelastic para-meters are several orders of magnitude larger than theshear ones.[15] So it seems that the interfacial dilationalviscoelasticity plays a much significant role in emulsionstability. Although the interfacial dilational rheologyproperties of the film-forming substance (emulsifier)including low weight surfactants such as sodium dodecyl

Received 22 September 2011; accepted 4 October 2011.The authors are thankful for the financial support from the

National Science & Technology Major Project (2011ZX05011).The authors are also grateful to Dr Hongbo Fang, the DesignResearch Institute of Shengli Oilfield Co. Ltd., China SINOPEC(Dongying, Shandong, 257026) for partial experimental supportof these studies.

Address correspondence to Feng Yan, School of Environmentand Chemical Engineering, Tianjin Polytechnic University,Tianjin 300160, P. R. China. E-mail: yanfeng.yxm@hotmail.com;and Jianxin Li, State Key Laboratory of Hollow Fiber MembraneMaterials and Processes, School of Materials Science andEngineering, Tianjin Polytechnic University, Tianjin, P. R. China.E-mail: jxli0288@yahoo.com.cn

Journal of Dispersion Science and Technology, 33:1674–1681, 2012

Copyright # Taylor & Francis Group, LLC

ISSN: 0193-2691 print=1532-2351 online

DOI: 10.1080/01932691.2011.635500

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sulfate (SDS),[16–18] polymers such as partly hydrolyzedpolyacrylamide (HPAM)[19,20] and natural emulsifiers suchas asphaltenes[21] have been extensively studied, only fewstudies reported the interfacial dilational rheology proper-ties of demulsifier.[2,22–24] Kim et al.[22] studied rheologicalproperties of several commercial-type demulsifiers, andfound a strong connection between good performance (fastcoalescence) and dynamic film rheological properties. Theresults demonstrate the rheology study of crude oil film isparticularly useful in modeling event leading to coalescencein oilfield emulsion.

The aim of the study is to investigate the demulsificationof crosslinking phenol-amine resin block polyether demul-sifiers for the surfactant-polymer flooding emulsion andexplore the demulsification mechanism by the interfacialdilational viscoelasticity measurement. In the work, twoseries of novel crosslinking phenol-amine resin block poly-ethers were synthesized and used. The relationship betweendemulsification performance with molecule structure, aswell as interfacial behavior of the demulsifiers was exploredin order better to understand the effect of molecular inter-actions on the demulsification process.

EXPERIMENTAL SECTION

Materials

Phenol-amine resin was provided by Shengli Engineer-ing & Consulting Co., Ltd., China. Ethylene oxide (EO)was from Liaoning Oxiranchem Group Co., Ltd., China.Propylene oxide (PO) was purchased from Befar GroupCo., Ltd., China. Partly hydrolyzed polyacrylamide(HPAM) and petroleum sulfonate were provided by theShengLi Oilfield Engineering Consulting Co., Ltd., China.Kerosene, C. P., was purchased from Sinopec ShanghaiPetrochemical Co. Ltd., China, and was used after columnchromatography.

Experimental Methods

Synthesis of crosslinking phenol-amine resin block poly-ether demulsifiers: The precursor (phenol-amine resin) wasreacted with PO and EO in the presence of potassiumhydroxide to present the intermediate, phenol-amine resinblock polyethers. The reactions were carried out at tem-perature of 120�C and 0.3MPa in a pressure kettle with

an agitator under the protection of nitrogen. The inter-mediates were then reacted with crosslinking agent furtherto present the crosslinking phenol-amine resin block poly-ether demulsifiers (CPAPEs). Two series of demulsifierwere obtained on the basis of the amount of crosslinkingagent, CPAPEIn and CPAPEIIn (n¼ 1, 2, or 3). The HLBvalue for each series (shown in Table 1) was altered bychanging the proportion of EO and PO in the molecules.It can be seen from Table 1 that the HLB value of demul-sifiers increased with the increase on the n value (i.e., thehydrophility) in each series.

Preparation of surfactant-polymer flooding emulsion: Asimulated surfactant-polymer flooding emulsion was pre-pared in the laboratory by mixing of 10mL oil phase and10mL water phase. The oil phase was solution of crudeoil in kerosene (20wt%), and the water phase was solutionof HPAM (100mg=L) and petroleum sulfonate (500mg=L). Then the mixture was sheared by an IKA T18 basicshear apparatus (IKA Corp., Germany) at 15,500 rpm for5 minutes to form a stable simulated emulsion.

Demulsification

The demulsification was examined by using the standardbottle-test at 30�C. The prepared emulsion and a certainamount of demulsifier were added into the test bottle. Themixture was well mixed by a hand shaking motion. The per-formance of the demulsifiers was measured in terms of thepercent volume of water separated, which is defined as:

Xð%Þ ¼ V=V 0 � 100 ½1�

where X is the demulsification ratio of the simulatedemusion, that is, the percent volume of water separated;V is the volume of the water separated; V0 is the originalvolume of water contained in the emulsion.

Measurement of Interfacial Tension

The dynamic and equilibrium interfacial tensions forcrude oil with the density of 0.9489 g=cm3 (at 30�C) fromChina Shengli Gudong Oilfield against demulsifier solutionin different concentrations at 30�C were determined. Thedemulsifiser was dissolved in stimulation water from ChinaShengli Gudong Oilfield. The components of thestimulation water are shown in Table 2. A high precision

TABLE 1The HLB values of the crosslinking phenol-amine resin block polyether demulsifiers

Series I (CPAPEIn) Series II (CPAPEIIn)

Samples CPAPEI1 CPAPEI2 CPAPEI3 CPAPEII1 CPAPEII2 CPAPEII3

HLB value 7.5 10.4 12.1 5.7 10.9 11.6

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spinning drop interfacial tensiometer (JJ2000, PowereachLtd., Shanghai China) was utilized to measure the IFT.A drop of the less dense phase (crude oil) was injected bymeans of a microliter syringe into a rotating capillary tubecontaining the demulsifier aqueous phase. The diameter ofthe elongated oil drop at a fixed temperature and speed ofrotation was monitored as functions of time until it reacheda constant value. From the drop diameter’s value, thedynamic and equilibrium IFT were calculated by thesoftware attached.

2.5. Measurement of Interfacial DilationalViscoelasticity Properties

The background of interfacial dilational viscoelasticityhas been described in literatures.[26–29] The surface dilationalmodulus E is defined as the ratio between a small change insurface tension (c) and a change in surface area (A):

e ¼ dcd lnA

½2�

The dilational modulus can also be decoupled into elas-tic part (Ed) and viscous part (Eg), which correspond to therecoverable energy stored in the interface and the loss ofenergy in the relaxation process, respectively:

ed ¼ jej cos h ½3�

eg ¼ jej sin h; ½4�

where h is phase angle, which describes the phase differ-ence between dynamic interfacial tension variation andinterfacial area variation.

For an instantaneous area change rising from DA(t)¼ 0for t� 0 to DA(t)¼DA for t> 0, the values of E areobtained as a function of the frequency by Fourier trans-formation (FT) of the interfacial tension decay obtainedfrom the experiment by the following relationship:[30,31]

eðxÞ ¼ FTDcðtÞFTðDA=AÞðtÞ ¼

R10 DcðtÞ expð�ixtÞdtR1

0 ½DAðtÞ=A� expð�ixtÞdt; ½5�

where x is the angular frequency. In an ideal systemwhich is not diffusion controlled and in which only onerelaxation mechanism occurs the decay curve of c versust can be represented by an exponential equation.

For a real system, a number of relaxation processes mayoccur and the decay curve would be expressed by the sum-mation of a number of exponential functions:

Dc ¼Xn

i¼1

Dci expð�sitÞ; ½6�

where si is the characteristic frequency of the ith process;Dci is the fractional contribution which the relaxation pro-cess makes to restore the equilibrium; n is the total numberof the relaxation processes.

In this study, the interfacial dilational viscoelasticitymeter JMP2000A (Powereach Ltd., Shanghai, China) wasemployed. It includes a Langmuir trough with two symme-trically oscillating barriers for changing the interfacial areaand a Wilhelmy plate for measuring the interfacial ten-sion.[32] The Langmuir trough was filled with 80mL waterphase (solution of 100mg=LHPAMand20mg=Lpetroleumsulfonate) and 60mL oil phase (solution of crude oil in kero-sene, 5wt%). The dilational viscoelasticity experiment beganafter 6 h of pre-equilibrium. Then, the barriers wereexpanded and compressed sinusoidally with small amplitudein the frequency range 0.0033 to 0.1Hz. Then, the interfacialtension relaxation measurement was carried out (the filmwas expanded about 10% in area by a sudden expansion in3 s). All experiments were performed at 30�C.

RESULTS AND DISCUSSION

Demulsification Efficiency through the ConventionalBottle Test

The demulsification performances of the novel crosslink-ing demulsifiers measured by conventional graduated bottletest were shown in Figure 1. It can be found from Figure 1that the demulsification ratio (X) was less than 10% (Blank)from the initial time to 100 minutes after it was prepared. Itimplies that the emulsion is quite stable. The demulsificationrate increased rapidly after the demulsifiers (5mg=L) wereadded to the emulsion in both the series (Figure 1). The Xvalues are 57.0%, 87.1% and 96.0% for CPAEI1, CPAEI2,andCPAEI3 in series I after 60minutes the demulsifier added(Figure 1a). It suggests that the increasing tendency ofdemulsification ratio is related to the proportion of EOand PO in the polymeric chains of the demulsifier. The

TABLE 2Component of oilfield stimulation water

Component Cl� HCO�3 Kþ Naþ Mg2þ Ca2þ Mineralization

Content (mg=L) 6529.2 248.1 38.6 3276.1 109.9 692.6 10894.5

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similar results can also be found from series II (Figure 1b).The results indicate that the demulsification ratio increasedwith the increase of HLB value of demulsifier.

Furthermore, it can be seen from Figure 1 that bothCPAPEI3 and CPAPEII3 showed excellent performance inthe demulsification (Figure 1). Moreover, the waterobtained after demulsification showed clear. The oil con-centration in the separated water phase was less than100mg=L except for CPAPEI1 and CPAPEII1 measuredby absorption methods.[33]

In general, the emulsion is water-in-oil emulsions, inwhich the oil is the continuous or external phase and thewater droplets are enwrapped or dispersed in oil phase toform the dispersed or internal phase. The role of the demul-sifier is to change the interfacial properties and to destabi-lize the surfactant-stabilized emulsion film in thedemulsification process.

In order to visualize the demulsification processes, amicroscope (BX51, Olympus Ltd., Japan) was employedto observe the size distribution of the emulsion obtainedand the coalescence processes of drops after adding the

demulsifier CPAPEI 3 (5mg=L) as shown in Figure 2. Anemulsion with small and uniform drops flocculate formedas displayed in Figure 2a. It also can be seen fromFigure 2 that the size of the water droplets grew and thenumber of the droplets reduces after 77 seconds CPAPEI

3 was added (Figure 2b) and became larger after 139 sec-onds (Figure 2c). By comparison with the drops inFigure 2b, two or more large drops continue to form asingle larger drop in Figure 2c. Thus the coalescencehappened and the emulsion was broken.

Interfacial Activity of Crosslinking Phenol-Amine ResinBlock Polyether Demulsifiers

Dynamic Interfacial Tensions of CPAPE Demulsifiers

Usually, the film drainage during the coalescence pro-cess results in the changes on dynamic interfacial propertiesof the emulsion. Consequently, it is essential to know therelationship between the dynamic interfacial tension ofthe emulsion and the activity of demulsifiers. The changeson dynamic interfacial tension of the crude oil-water sys-tem after adding CPAPEI3 with different concentrationsfrom 50 to 1500mg=L was summarized in Figure 3. Theinterfacial tension decreased sharply from 8.54 mN=m to1.5 mN=m within 15 minutes after adding CPAPEI3

(50mg=L), and then reached a plateau value (equilibriuminterfacial tension). Obviously, the equilibrium interfacialtension decreased with an increase in the CPAPEI3 concen-tration. It reached 10�2 mN=m order of magnitude at con-centrations above 500mg=L. A low interfacial tension isbenefit for demulsification.[34] The results obtained indicatethat the molecules of CPAPEI3 diffused rapidly in the sol-ution and were adsorbed at the interface promptly.

Influence of Molecule Structure on Equilibrium InterfacialTensions

As the dynamic interfacial tension reached a plateauvalue and maintained stability, the equilibrium interfacialtension was then obtained. Herein, the equilibrium

FIG. 2. The micrographs of the emulsion and demulsification pro-

cesses of surfactant-polymer flooding emulsion: a) original simulated

emulsion; b) 77 seconds after CPAPEI 3 was added; (c) 139 seconds after

CPAPEI 3 was added.

FIG. 1. Demulsification ratio of different demulsifiers (5mg=L): a)

series I; b) series II. (Figure available in color online.)

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interfacial tensions of the six demulsifiers against theconcentration were illustrated in Figure 4. Commonly, theHLB value of demulsifier as an important parameter effectson interfacial activity. As can be seen in Figure 4, the equi-librium interfacial tension markedly declined from 2.19mN=m for CPAPEI1 to 0.01 mN=m for CPAPEI3 with theincreasing of their HLB values from 7.5 for CPAPEI1to12.1 for CPAPEI3 at concentration of 1000mg=L. The simi-lar results can also be obtained in series II. The equilibriuminterfacial tension declined from 4.67 mN=m for CPA-PEII1to 0.01 mN=m for CPAPEII3 with the increasing oftheir HLB values from 5.7 for CPAPEII1to 11.6 for CPA-PEII3at concentration of 1000mg=L.

Obviously, CPAPEI3 and CPAPEII3 with the largestHLB value for each series showed the lowest equilibriuminterfacial tensions and the highest interfacial activity,whereas CPAPEI1 and CPAPEII1 with the smallest HLBvalue displayed the lowest interfacial activity.

On the one hand, if the HLB value of demulsifier is toolarge and presents a strong hydrophilic property, the mol-ecule of demulsifier would be dissolved in the water phase.Thus, the interfacial activity would decline with thedecrease in the amount of molecules distributing on theinterface. On the other hand, if the hydrophobic propertyof demulsifier is too strong, the molecules of demulsifiermay be dissolved more easily in the oil phase, leading toa lower interfacial activity. This is why CPAPEI1 and CPA-PEII1 with the smallest HLB value of each series show ahigher interfacial tension. In a word, the interfacial tensiondecreased with the increasing of HLB value in the range ofthis work. That means, the increasing of hydrophillicity ofthe demulsifier promotes the molecules of demulsifier to gotoward the interface of emulsion droplet, which may bringabout the demulsifier to displace the adsorbed film-formingcomponents in the interface effectively. At the same time,this adsorption may result in the reduction of the interfacepotential and enhances the rupture process of the film.Finally, the coalescence occurs further in the separation.

Interfacial Dilational Properties of Demulsifiers byLongitudinal Wave Measurements

Dilational rheological properties are the main character-istics of the dynamic properties of a film. In surfactant sys-tems, when the interface is perturbed, different processeswhich contribute to the re-equilibration (the adsorptiondynamics) of the system occur. Among the mechanismsinvolved in the adsorption dynamics, there is the diffusionin the bulk phases and kinetic processes inside the adsorbedlayer such as re-orientation, aggregation and otherre-arrangements of the layer or the molecular structure.Therefore, the measurement of the dilational rheology isa very effective approach to assess the existence of theseprocesses and characterize film properties.[35]

In order to explore the influence of adding CPAPEdemulsifiers on the interfacial film of surfactant-polymerflooding emulsion, dilational rheological method wasemployed. The dilational rheological parameters wereobtained by interfacial dilational viscoelasticity meter afteradding different concentrations of demulsifier into the waterphase. The dilational elasticitis Ed for CPAPEs at differentconcentrations were shown in Figure 5. The Ed value of theblank interface film (formed by molecules of surfactant,polymer, and component of crude oil) was about 15.41mN=m as the dotted line shown in Figure 5. However, theEd values declined abruptly when demulsifiers were addedto the system. The Ed value declined approximately to halfof that of the initial value after adding 10mg=L of CPAPEs.

FIG. 3. Changes in dynamic interfacial tensions of the crude oil-water

system after adding CPAPEI3 with different concentrations. (Figure avail-

able in color online.)

FIG. 4. Equilibrium interfacial tensions vs the concentrations of the

CPAPE demulsifiers. (Figure available in color online.)

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It is worthwhile to note in Figure 5 that the dilationalelasticity of CPAPEI1 and CPAPEII1 with the HLB valueof 7.5 and 5.7, respectively, almost remains unchanged withthe increasing of their concentrations added. On the con-trary, the dilational elasticity of CPAPEI3 and CPAPEII3

with the HLB value of 12.1 and 11.6, respectively,decreased gradually with the increase in the concentrationfrom 50ml=L to 200ml=L. It was close to zero at200mg=L. It suggests that the demulsification of CPAPEdemulsifiers could improve by increasing HLB value.

Interfacial Dilational Properties of Demulsifiers byRelaxation Measurements

The interfacial dilational viscoelasticity is generallybelieved to be caused by the microscopic relaxation pro-cesses at the interface and near the interface. Therefore,the data of dilational viscoelasticity can provide the infor-mation about molecular interaction and structure at theinterface. The two types of relaxation processes usuallyconsidered are the exchange of molecules between the bulkand the interface and the interfacial conformationalchanges in the interface.[36] To confirm the experimentaldata and deductions above, the method of interfacial ten-sion relaxation measurement has been employed to detectthe microscopic relaxation processes in the interface atequilibrium. A typical result for the experimental interfa-cial tension decay and the fitted curve for CPAPE II 2

(50mg=L) are shown in Figure 6. It can be seen fromFigure 6 that the fitting is in good agreement with theexperimental data. From the fitting results, the character-istic relaxation time Ti and contribution of different relax-ation process (Dci) were obtained, which are connectedwith the dynamic characteristics of demulsifier molecules

and can provide the most important information aboutrelaxation processes.

The characteristic relaxation times and contributions ofthe relaxation processes at different concentrations of seriesII demulsifiers are listed in Table 3. As can be seen fromTable 3, there are two main relaxation processes for CPA-PEII n demulsifiers. On the one hand, the fast relaxationprocess with a characteristic relaxation time (T1) of severalto more than ten seconds may correspond to the exchangeof molecules between the bulk and the interface. On theother hand, the slower relaxation process with a character-istic relaxation time (T2) of several dozen of seconds maycorrespond to the conformational changes of demulsifiermolecules at the interface. Accordingly, it can be foundfrom Table 3 that the characteristic relaxation times forthe exchange of molecules between the bulk and the inter-face (T1) are more than ten seconds at concentration below50mg=L (except for CPAPEII3 at 50mg=L, the T1 forwhich is 3.57 s), while they drop to several seconds at con-centration of 100mg=L(except for CPAPEII3, the T1 forwhich is 0.56 s). This indicates that the diffusion exchangeprocess becomes fast at high concentration. The character-istic relaxation times for the conformational changes ofdemulsifier molecules at the interface (T2) show amaximum value at 50mg=L, and then decrease withincreasing of concentration for CPAPEII1 and CPAPEII2.While it decreases with increase of concentration withinthe experimental range for CPAPEII3.

As can be seen from Table 3, the HLB has an effect onthe characteristic relaxation time of diffusion exchangeprocess (T1) especially at high concentration, 50 or100mg=L for example. The characteristic relaxation time(T1) gets shorter obviously as the increase of HLB value.

FIG. 5. Influence of the CPAPE demulsifier concentration on dila-

tional elasticity of interfacial film formed by molecules of surfactant, poly-

mer, and component of crude oil. (Figure available in color online.)

FIG. 6. Interfacial relaxation curve for CPAPEII 2 (50mg=L). The

black line corresponds to experiment curve and the red line corresponds

to the fitted curve. (Figure available in color online.)

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That means the diffusion exchange process is enhanced.In the case, the molecules of demulsifier are easy to distrib-ute and be adsorbed at the interface, which can stronglyaffect the water-oil dynamic interfacial properties, such asthe interfacial tension gradient or the Marangoni-Gibbsstabilizing effect.[2]

It can also been seen from Table 3 that the characteristicrelaxation times of the conformational changes process(T2) are also effected by HLB value. The characteristicrelaxation time (T1) got longer at low concentration(10mg=L), whereas T2 got shorter obviously at high con-centration (50 or 100mg=L) as the increase of HLB value.It implies that CPAPEII3 and CPAPEII2 show betterdemulsification efficiency than CPAPEII1. These resultsobtained from interfacial tension relaxation measurementsare accordant with those by dilational viscoelasticity andinterfacial tension measurements.

CONCLUSIONS

Two series of novel crosslinking phenol-amine resinblock polyether demulsifiers (six types of demulsifiers) havebeen successfully synthesized for demulsification ofsurfactant-polymer flooding emulsion. Those CPAPEdemulsifiers show different defulsificaiton properties aswell as affect the stability of the model emulsion obviously.The demulsification properties were enhanced with increaseof HLB value for each series. The results showed that theinterfacial tension of crude oil-water interface and thestrength of interfacial film of emulsion decreased immedi-ately after CPAPE demulsifiers were added. The low inter-facial tension and strength of interfacial film wereassociated with demulsification efficiency of the demulsi-fiers with variation of HLB value. Further, the demulsifi-cation mechanism for demulsification of surfactant-polymer flooding emulsion demonstrates that the mole-cules of CPAPE demulsifiers with high interfacial activityand with a fast diffusion-exchange relaxation process wereeasy to adsorb at the interface. Then they could easily

displace the original film-forming components to form anew mixed adsorption film. The weak interaction of mole-cules at the new mixed adsorption film may be the drivingforce leading to the destabilization of the emulsion, and thenpromotes the coalescence and phase separation.

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TABLE 3Interfacial relaxation processes and their characteristic times for series II demulsifiers

Demulsifier Concentration (mg=L) Dc1 (mN=m) T1 (s) Dc2 (mN=m) T2 (s)

CPAPE II 1 10 0.28 14.19 0.38 42.5150 0.47 16.33 0.30 81.04

100 0.44 8.92 0.29 56.79CPAPE II 2 10 0.84 19.87 0.50 52.63

50 0.29 10.46 0.53 66.80100 0.22 5.09 0.21 42.41

CPAPE II 3 10 1.52 15.62 0.20 90.9150 0.16 3.57 0.21 50.00

100 0.30 0.56 0.08 5.26

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