Collaborative Interactions between EO-PO Copolymers upon Mixing

Article pubs.acs.org/IECR

Collaborative Interactions between EO-PO Copolymers upon Mixing Ishpinder Kailey,*,† Catherine Blackwell,‡ and Jacqueline Behles† †

Baker Hughes Canada Company, 7020 45th Street, Leduc, Alberta T9E 7E7, Canada Baker Hughes Incorporated, 12645 West Airport Boulevard, Sugar Land, Texas 77478, United States

‡

ABSTRACT: Chemical demulsification is the most extensively used method for breaking water-in-diluted bitumen emulsions in oil sands processing. In this paper, the properties and performance of three demulsifier formulations and their individual EO-PO polymer components were studied. The EO-PO polymers and demulsifier formulations were characterized by their relative solubility number (RSN). The results showed that the RSN is an additive property. The dehydration efficiency of the demulsifier formulation was higher than the individual components at the same dosage, signifying that there were collaborative interactions among the polymers on mixing. Correlations between performance of the demulsifiers and interfacial tension (IFT), yield stress of underflow, and bitumen loss to tailings were investigated. The results showed no correlation between the performance of the demulsifiers and equilibrium IFT. Correlations were observed between dehydration efficiency and both yield stress of the underflow and bitumen loss to tailings. The yield stress of the underflow, which included settled solids, water, and a rag layer, increased with increasing dosage of either component or demulsifier formulation. In addition, the bitumen loss to underflow increased with increasing dosage of either component or demulsifier formulation. The yield stress and bitumen loss to underflow decreased on mixing the components. The bitumen loss to underflow increased the size of the aggregates present in the underflow, increasing their immobility and constriction to flow and eventually leading to higher yield stress.

1. INTRODUCTION The formation of extremely stable water-in-oil emulsions is a key challenge for the petroleum industry. Natural surfactants such as asphaltenes, resins, naphthenic acids, and clays stabilize these emulsions by forming a rigid interfacial film at the oil/ water interface, preventing coalescence between the water droplets.1−3 The heavy crude oil, or bitumen, obtained from oil sands, is produced using a water-based extraction method. During this process, an aerated slurry containing bitumen, sand grains, fine mineral solids, and water is formed. The slurry is fed into a primary separation vessel where the solids begin to settle and separate from the aerated bitumen froth. The bitumen froth is recovered and diluted with a solvent to reduce the viscosity and promote the removal of the remaining solids and water using centrifugation or gravity settling processes. Chemical demulsifiers can be added to this process to promote emulsion destabilization and water removal. The removal of emulsified water from crude oil during processing is necessary because the dissolved salts in the water pose serious corrosion problems to pipelines and downstream refining infrastructure. These salts can poison downstream refinery catalysts and initiate problems associated with increased oil viscosity as a consequence of finely dispersed water within crude oil. Consequently, there are a number of economical and operational reasons to better understand how chemical demulsifiers can help remove the emulsified water from the crude oil. Complications in oil sands froth treatment occur due to the buildup of material at the oil/water interface.4,5 The interfacial layer, also known as the rag layer, is a mixture of flocculated water droplets and complex emulsions stabilized by a small fraction of asphaltenes, resins, sodium naphthenates, and fine solids. The rag layer can build up over time and can grow thick © XXXX American Chemical Society

enough to overflow into the diluted bitumen or the tailings stream, eventually shutting down the entire treatment process. To meet industry specifications, emulsions are treated using a combination of mechanical means and chemical treatment with demulsifiers. Chemical demulsification is an inexpensive, convenient, and effective method for breaking water-in-oil emulsions in the petroleum industry. The demulsifier alters the interfacial properties and disrupts the asphaltenic-stabilized interfacial film from the oil/water interface. Amphiphilic block copolymers based on hydrophilic ethylene oxide (EO) and hydrophobic propylene oxide (PO) are commercially available and widely used as demulsifiers. In froth treatment, the industry always looks for demulsifiers that effectively dehydrate the oil, minimize rag layer formation, and reduce solvent/bitumen loss to tailings. Generally, chemical demulsifiers are blended mixtures of several polymers with various chemical structures, and a wide molecular weight distribution. They are formulated in solvents including shortchain alcohols, aromatics, or heavy aromatic naphtha. Each component in a blend possesses a different partitioning ability and a different interfacial activity due to varying chemical structures. The individual components of the final demulsifier package are carefully chosen, as the total of the combined package has better performance than the performance of each individual component. Numerous attempts have been made to correlate performance with demulsifier characteristics such as molecular structure, hydrophile−lipophile balance (HLB),6 interfacial viscosity, relative solubility number (RSN),7,8 chemical Received: August 29, 2013 Revised: November 10, 2013 Accepted: November 11, 2013

A

dx.doi.org/10.1021/ie402851a | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

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composition (EO and PO number),8,9 partition coefficient, oil/ water interfacial tension (IFT), 8 and yield stress and composition of the underflow.8 This study represents an initial effort to investigate the influence of individual demulsifier components and blended mixtures on the performance in the naphtha-based froth treatment process. To achieve results, six EO-PO polymers and three demulsifier formulations of these EO-PO polymers were prepared. The objective of the study was to investigate the effect of blending EO-PO polymers on the RSN value, dehydration efficiency, IFT, and underflow yield stress and composition.

where Wo is the water content in the blank test, and Wd is the water content in the presence of demulsifier. The results reported for each demulsifier are the average of three measurements. 2.4. RSN Measurement. The RSNs of the demulsifiers were determined using toluene−EGDE as the RSN solvent. In this method, 1 g of demulsifier was dissolved in 30 mL of RSN solvent and the resulting solution was then titrated with deionized (DI) water until a visible, persistent turbidity appeared. The end point was detected by an 888 Titrando colorimeter. The volume of the DI water in milliliters used as titrant was recorded as the RSN value. The details of the method can be found in ref 6. 2.5. IFT Measurement. IFT measurements were conducted using a Teclis TRACKER H automated drop tensiometer. Measurements were carried out at 25 ± 1 °C using DI water as the aqueous phase and toluene-diluted bitumen (toluene-to-bitumen ratio of 0.70). The demulsifiers were evaluated at 100 ppm, based on weight. At the start of each measurement, a fresh oil droplet was formed at the tip of an inverted needle submerged in the aqueous phase, and monitoring of IFT was immediately initiated. The instrument software determines the dynamic IFT using a method of successive approximation to fit a form of the Young−Laplace equation to the drop shape. 2.6. Underflow Preparation. The detailed procedure for froth homogenization and settling is mentioned in section 2.3. After shaking diluted froth for 6 min, the mixture was transferred into a settling column and allowed to settle at 80 °C for 1 h. The disturbances to the underflow structure were reduced by collecting underflow directly in a measuring cup connected to the bottom of the settling column. The column was allowed to cool to 30 °C after settling for 1 h at 80 °C. The supernatant, which is diluted bitumen, was discharged from the side tap of the settling column. The measuring cup was then disconnected from the settling column for yield stress measurements. Blank tests were performed as controls in each set of experiments. 2.7. Yield Stress Measurement. An Anton Paar Physica MCR101 rheometer with vane geometry was used for yield stress measurements. Yield stress is defined as the level of stress at which substantial deformation suddenly occurs. For underflow, the yield stress may be defined as the stress at which the underflow structure breaks down and flows freely. There are numerous methods for yield stress determination.10 In this work, the shear stress vs shear strain method was used. The vane geometry causes fewer sample disturbances, minimizes thixotropic breakdown, experiences fewer effects from artifacts arising from large particle sizes, and minimizes wall-slip effects as yielding occurs between layers of fluid.10,11 The shear stress as a function of shear strain was determined for underflow at 0, 25, 50, 75, and 100 ppm dosages. All yield stress measurements were conducted at 30 °C. The results reported are the average of three measurements. 2.8. Composition Analysis. The underflow composition was determined by a Dean−Stark extraction method. Settled material was transferred to a Soxhlet extraction thimble and then repeatedly extracted with toluene under reflux. The solids remained in the thimble, and the water was collected in the side trap. The absolute amount of bitumen was determined by a filter paper method while the absolute weights of water and solids were determined by weighing. The solvent content was determined by mass balance.

2. MATERIALS AND METHODS 2.1. Materials. Bitumen froth and naphtha were obtained from oil sands mining producers in Alberta, Canada. The composition of the froth samples was analyzed using a Dean−Stark extraction method and averaged approximately 60 wt % bitumen, 30 wt % water, and 10 wt % solids. The bitumen sample used in the IFT measurement was Syncrude vacuum distillation feed bitumen. American Chemical Society (ACS)-grade toluene was purchased from Fisher Scientific. Ethylene glycol dimethyl ether (EGDE), to determine RSN values, was high performance liquid chromatography (HPLC)-grade, purchased from Sigma-Aldrich and used as received. 2.2. Demulsifiers. The demulsifiers were synthesized in the Baker Hughes Evan Ginn Research & Development Center in Sugar Land, TX. In this work, six EO-PO polymers and three demulsifier formulations were prepared and studied. Table 1 shows the composition of the blends.

Table 1. Composition of the Blends blend

component 1 30 wt %

component 2 30 wt %

component 3 40 wt %

1 2 3

A D A

B B E

C C F

2.3. Demulsification Tests. The jar tests were designed to evaluate demulsifier performance in inclined plate settlers and settling tanks. These tests simulate the current settling operation in the industry. The jar tests were conducted on fresh froth samples from the industry and used to determine the demulsifier dehydration efficiency. To mimic an actual system, fresh industry-generated bitumen froth was used. Note that the same batch of bitumen froth was used for all completed jar tests. The bitumen froth was homogenized by mechanically stirring at 1050 rpm at 80 °C for 3 h in a baffled stainless steel beaker with a water jacket. The homogenized froth was collected from the bottom of the beaker and placed in a set of numbered jars. Based on the mass of froth in each jar, the amount of naphtha required to give a naphtha-to-bitumen ratio of 0.70 was weighed into another set of numbered jars and dosed at 10, 20, 30, 50, and 100 ppm with demulsifier. Two undosed “blank” jar tests were performed as controls in each set of experiments. The froth and naphtha jars were transferred to a water bath at 80 °C. After 30 min, the naphtha jars were shaken for 1 min on a horizontal shaker at high speed and then added to the respective froth jars. The mixed samples were allowed to settle at 80 °C for 15 min and then shaken for 6 min on a horizontal shaker at high speed. After shaking, the jars were transferred to a water bath at 80 °C and allowed to settle. Oil samples were extracted at 1/3 height from the surface at 10 and 30 min, respectively, from each jar, and the water content was determined by Karl Fisher titration. The average water content in the two blank tests was used as a baseline. The dehydration efficiency of each demulsifier was evaluated by the water removal percentage calculated from:

(Wo − Wd) dehydration efficiency (%) = × 100 Wo

3. RESULTS AND DISCUSSION 3.1. Effect of Mixing EO-PO Copolymers on RSN Values. Table 2 illustrates the effect of the mixing EO-PO polymers on the RSN value. The estimated RSN values of demulsifier formulations were calculated from: estimated RSN value = (comp1%) × RSN1 + (comp2%) × RSN2 + (comp3%) × RSN3

(2)

where comp1 %, comp2 %, and comp3 % are the percentages of components 1, 2, and 3, respectively, in the demulsifier

(1) B



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Table 2. RSN Values of Components and Demulsifier Formulations component/ demulsifier formulation A B C D E F blend 1 blend 2 blend 3

components in demulsifier formulation

estimated RSN value

measured RSN value

A, B, C B, C, D A, E, F

− − − − − − 9.26 9.28 7.85

6.01 11.03 10.30 6.16 18.89 8.61 9.32 9.11 7.72

Figure 2. Dehydration efficiency in naphtha-based bitumen emulsions as a function of dosage in ppm at a 30-min residence time for blend 2 and its components B, C, and D.

formulation. RSN1, RSN2, and RSN3 are the RSN values of components 1, 2, and 3, respectively, in the demulsifier formulation. The results reported for each component and demulsifier formulation is the average of three measurements. The results indicate that the RSN value is an additive property. For all demulsifier formulations, the measured RSN value correlated well with the estimated RSN value. These results reveal that the RSN value of a demulsifier formulation can be estimated if the percentages and RSN value of components in a demulsifier formulation are known. 3.2. Effect of Mixing EO-PO Copolymers on Demulsification Efficiency. The effect of mixing EO-PO polymers on the dehydration efficiency is shown in Figures 1−3. Figure 1

observation is that blend 1 provided dehydration efficiency better than that of blend 2 at the dosage range studied. For instance, at a 50-ppm dosage and 30-min residence time, the dehydration efficiencies of blend 1 and blend 2 are 60.4% and 57.5%, respectively. This difference is attributed to the superior performance of component A over component D, which is reflected in the performance of blend 1 as well. The difference between A and D is the number of EO-PO branches. The number of EO-PO branches in A and D are 5 and 3, respectively. Higher dehydration efficiency of A is associated with higher branching. Kailey and Feng reported previously that higher dehydration efficiency is associated with higher EOPO branching in EO-PO copolymers.8 Overall, the EO-PO copolymers also showed synergism upon mixing in blend 2. Figure 3 shows the dehydration efficiency as a function of dosage at a 30-min residence time for blend 3 and its

Figure 1. Dehydration efficiency in naphtha-based bitumen emulsions as a function of dosage in ppm at a 30-min residence time for blend 1 and its components A, B, and C. Figure 3. Dehydration efficiency in naphtha-based bitumen emulsions as a function of dosage in ppm at a 30-min residence time for blend 3 and its components A, E, and F.

shows the dehydration efficiency as a function of dosage at a 30-min residence time for demulsifier formulation “blend 1” and its components A, B, and C. The dehydration efficiency for all the components and blend 1 increased with dosage at a 30min residence time. Results show that the dehydration efficiency of blend 1 is higher than that of all its components at the dosage range studied. For instance, at 50 ppm dosage and 30-min residence time, the dehydration efficiencies of components A, B, and C and blend 1 are 49.1%, 52.8%, 42.4%, and 60.4%, respectively. Mixing enhances the demulsifiers’ performance by synergistic interactions among the individual components. Figure 2 shows the dehydration efficiency as a function of dosage at a 30-min residence time for blend 2 and its components B, C, and D. Compared to blend 1, in blend 2 the EO-PO copolymer A is replaced with EO-PO copolymer D and the EO-PO copolymers B and C are kept constant. The key

components A, E, and F. Comparative to blend 1 and blend 2, in blend 3, components B and C are replaced with components E and F and the component A is kept constant. Clearly, the performance of component F and blend 3 is very close over the dosage range studied at a 30-min residence time. For example, at a 50-ppm dosage and a 30-min residence time, the dehydration efficiencies of component F and blend 3 are 59.9% and 60.2%, respectively. Blend 3 did not show any synergistic interactions. This may be due to lack of intermolecular interactions among its components. Demulsifiers A and E may not be able to orient themselves at the interface due to bigger dimensions. The demulsifier A has five C



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and dehydration efficiency. For example, EO-PO copolymers B and C have similar interfacial tensions yet result in varying dehydration efficiencies. This is not a surprising result, as measurements of the equilibrium interfacial tension often do not correlate well to demulsifier performance12 because coalescence is a dynamic process that depends on the hydrodynamic film stability of the droplet surface.13,14 Representative curves depicting the dynamic IFT measured during the first 60 s following drop formation for 100 ppm blend 1, and its components in toluene-diluted bitumen, are presented in Figure 7. The dynamic IFT during this period was

EO-PO branches, while demulsifier E is a cross-linked EO-PO copolymer. Among the three demulsifier formulations, dehydration efficiencies were on the order of blend 1 > blend 3 > blend 2 at a dosage of 0 to 100 ppm. These results indicate that the components significantly influence the demulsification performance of the final product. The performance upon mixing EOPO copolymers will be enhanced, if there are synergistic interactions among the components incorporated in a demulsifier formulation. 3.3. Effect of Mixing EO-PO Copolymers on the IFT. The impact of the individual components and demulsifier formulations on the interfacial tension of the oil/water interface was investigated at a dosage of 100 ppm. Figures 4−6 show the

Figure 7. Dynamic interfacial tension with respect to time for components A, B, and C and blend 1. The solid lines represent the best fit with an exponential-decay function, eq 3

Figure 4. Equilibrium IFT of toluene-diluted bitumen samples dosed with 100 ppm of blend 1 and its components A, B, and C.

highest for blend 1, followed by components B, C, and A. The curves exhibit a relatively fast relaxation period during the initial 20 s following surface expansion, followed by a slower period of relaxation. During the initial period of relaxation after droplet expansion/formation, the IFT data demonstrate a good fit to a single exponential-decay equation, as shown in eq 3, that describes nondiffusion-controlled relaxation processes. σ − σeq σ0 − σeq

⎛ t − t0 ⎞ = exp⎜ − ⎟ τd ⎠ ⎝

(3)

where σ0 is the initial IFT, σeq is the equilibrium IFT, σ the experimental IFT at time t, t0 is the time corresponding to the start of the relaxation, and τd is the apparent interfacial tension relaxation time. In Figure 7, the initial portion of the experimental data correlates well with the predicted values for IFT, which indicates that the relaxation of the interface at this time period is not diffusion controlled but rather dominated by the relaxation kinetics of molecules within the interface.15 The rate of relaxation of the interface does demonstrate a correlation with dehydration efficiency when comparing the individual EO-PO polymer components. The apparent relaxation time for A was the lowest at 5.0 s, followed by B (5.8 s) and C (21 s). The calculated relaxation time for blend 1 was 9.0 s, indicating that the individual components may be impacting the interfacial relaxation process by different mechanisms. Demulsifiers capable of increasing the rate of interfacial relaxation processes at the interface would be expected to be more effective at promoting coalescence by lowering the interfacial elasticity and result in faster drainage of the film between two approaching droplets. The results for the relaxation time and high dehydration efficiency of blend 1,

Figure 5. Equilibrium IFT of toluene-diluted bitumen samples dosed with 100 ppm of blend 2 and its components B, C, and D.

Figure 6. Equilibrium IFT of toluene-diluted bitumen samples dosed with 100 ppm of blend 3 and its components A, E, and F.

relationship between dehydration efficiency and the equilibrium IFT measured at 30 min post drop formation for each of the components and demulsifier formulations studied. In general, there was not a strong correlation between interfacial tension D



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along with the observation that at extended times the fit of the measured values of IFT to the predicted values begins to deteriorate for the measured dynamic IFT profiles, are indicative of the complex nature of demulsification. Breen demonstrated that along with the relaxation kinetics of an individual demulsifier component, the adsorption thermodynamics play an equally important role.16 While the relaxation kinetics may be rapid enough to maintain low interfacial elasticity, if the adsorption thermodynamics are too low, the forces that resist drainage of the interfacial area between two coalescing drops will not be overcome. Further investigation into the time-dependent dynamic processes that govern the droplet film stability is needed to clearly understand the relationship between the IFT profiles observed in the presence of the demulsifiers studied in this work. 3.4. Effect of Mixing EO-PO Polymers on the Underflow Yield Stress. Figure 8 shows shear stress as a

Table 3. Composition of the Underflow in the Absence and Presence of EO-PO Copolymer Aa DMO, ppm 0 25 50 75 100 a

bitumen, % 28.6 28.6 28.8 29.1 29.7

± ± ± ± ±

0.2 0.1 0.2 0.0 0.1

solids, % 12.3 12.2 12.2 11.9 11.7

± ± ± ± ±

0.1 0.1 0.2 0.0 0.1

water, % 38.6 38.8 38.1 38.5 38.9

± ± ± ± ±

0.1 0.3 0.4 0.1 0.2

solvent, % 20.5 20.4 20.9 20.5 19.7

± ± ± ± ±

0.2 0.5 0.6 0.4 0.3

The demulsifier dosage is based on the mass of bitumen.

8 and Table 3 show that the bitumen loss to underflow increases with the increase in the EO-PO copolymer A dosage. Figure 9 shows the correlation between the percentage yield stress increase and the bitumen loss to the underflow as a

Figure 9. Correlation among yield stress increase, bitumen loss to underflow, and dosage for EO-PO copolymer A. Figure 8. Shear stress as a function of shear strain for underflow in the absence and presence of component A. The dosage of demulsifier is based on the mass of bitumen.

function of EO-PO copolymer A dosage. The results reveal that the yield stress and the bitumen loss to underflow increases with an increase in the EO-PO copolymer A dosage. A possible reason for the increase in yield stress with increasing dosage of A is bitumen loss to the underflow. For instance, when the EOPO copolymer A dosage is increased from 25 to 100 ppm, the yield stress shifted from 60% to 450%, and the bitumen loss to the underflow went from 28.6% to 29.7%. The bitumen lost to the underflow increases the number of aggregates present in the underflow and increases the aggregate immobility and constriction to flow. Kailey and Feng reported previously that the high yield stress and bitumen loss to the underflow with an increase in the demulsifier dosage is due to the rise in the number of aggregates present in the underflow.8 Figure 10 shows the shear stress as a function of shear strain for underflow in the presence of blend 1 and its components A, B, and C. The results in Figure 10 reveal that while keeping the dosage constant, the components A, B, and C provided a higher yield stress as compared to the blend 1. For instance, at 100 ppm the yield stress values for blend 1 and components A, B, and C are 9.9, 11.4, 10.4, and 12.5, respectively. Figure 11 and Table 4 show the relationship between a yield stress increase, bitumen loss to underflow, and dosage for blend 1 and its components A, B, and C at 100 ppm. Clearly, the increase in yield stress is directly related to the bitumen loss to the underflow. Increases in the yield stress and the bitumen loss to underflow were reduced upon blending components A, B, and C to form blend 1. The higher bitumen loss to the underflow for the components could be the possible reason for the higher yield stress increase. Similar results were obtained for blend 2 and blend 3. These results show that the final demulsifier

function of shear strain for the underflow in the absence and presence of EO-PO copolymer A at a dosage from 0 to 100 ppm, based on the mass of bitumen. The mass of froth was kept constant in all tests. The results in Figure 8 illustrate that keeping the mass of underflow constant, the yield stress increases as the dosage of EO-PO copolymer A increases. Similar trends were obtained for all other components and demulsifier formulations. To evaluate the performance of components and demulsifier formulations, the percentage of yield stress increases for each component and demulsifier formulation was calculated from: yield stress increase (%) =

(y0 − y) yo

× 100 (4)

where yo is the yield stress of underflow in the absence of the component/demulsifier formulation, and y is the yield stress of underflow in the presence of the component/demulsifier formulation. The effect of demulsifiers on the naphtha-based froth treatment was further evaluated by analyzing the underflow composition for all samples with and without an application of demulsifier using Dean−Stark analysis. The results are presented in Table 3 for EO-PO copolymer A. Note that the results in Table 3 and Figure 8 were obtained from the same batch of testing samples. The reported solvent content in Table 3 was calculated based on the underflow mass. The precise determination of solvent content in the underflow was not carried out in the present work. The results reported in Figure E



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was intermediate to the individual components, although the dehydration efficiency was improved for the blend as compared to the individual components. The underflow yield stress, which includes settled solids, water, and rag layer, increases with an increase in the component/demulsifier formulation dosage. The increase in yield stress with dosage is due to bitumen loss to the underflow. The yield stress and bitumen loss to underflow was reduced upon mixing the components. The bitumen lost to the underflow increases the number of aggregates present in underflow and increases the aggregate immobility and constriction to flow. These results emphasize the need for careful evaluation and selection of demulsifier components to achieve optimum performance.

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Figure 10. Shear stress as a function of shear strain for the underflow in the presence of blend 1 and its components A, B, and C. The dosage of demulsifiers is 100 ppm based on the mass of bitumen.

AUTHOR INFORMATION

Corresponding Author

*Tel: (780) 980-5978. Fax: (780) 980-5989. E-mail: ishpinder. [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We acknowledge the support from our colleagues in Sugar Land, Texas. We also thank Baker Hughes for the permission to publish this research work.

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(1) Wu, X. Investigating the stability mechanism of water-in-diluted bitumen emulsions through isolation and characterization of the stabilizing materials at the interface. Energy Fuels 2003, 17, 179−190. (2) Wu, X. A. Selective Creaming: A novel technique to isolate interfacial organics and mineral solids from water-in-oil emulsions. Energy Fuels 2008, 22, 2346−2352. (3) Gao, S.; Moran, K.; Xu, Z.; Masliyah, J. Role of bitumen components in stabilizing water-in-diluted oil emulsions. Energy Fuels 2009, 23, 2606−2612. (4) Czarnecki, J.; Moran, K.; Yang, X. On the “Rag layer” and diluted bitumen froth dewatering. Can. J. Chem. Eng. 2007, 85, 748−755. (5) Saadatmand, M.; Yarranton, H. W.; Moran, K. Rag layers in oil sand froths. Ind. Eng. Chem. Res. 2008, 47, 8828−8839. (6) Wu, J.; Xu, Y.; Dabros, T.; Hamza, H. Development of a method for measurement of relative solubility of nonionic surfactants. Colloids Surf., A 2004, 232, 229−237. (7) Xu, Y.; Wu, J.; Dabros, T.; Hamza, H. Optimizing the polyethylene oxide and polypropylene oxide contents in diethylenetriamine-based surfactants for destabilization of water-in-oil emulsions. Energy Fuels 2005, 19, 916−921. (8) Kailey, I.; Feng, X. Influence of structural variations of demulsifiers on their performance. Ind. Eng. Chem. Res. 2013, 52, 785−793. (9) Wu, J.; Xu, Y.; Dabros, T.; Hamza, H. Effect of EO and PO positions in nonionic surfactants on surfactant properties and demulsification performance. Colloids Surf., A 2005, 252, 79−85. (10) Barnes, H. A.; Nguyen, Q. D. Rotating vane rheometry − a review. J. Non-Newtonian Fluid Mech. 2001, 98, 1−14. (11) Barnes, H. A. The yield stress − a review or ‘παντα ρει’ − everything flows? J. Non-Newtonian Fluid Mech. 1999, 81, 133−178. (12) Kim, Y. H.; Wasan, D. T.; Breen, P. J. A study of dynamic interfacial mechanisms for demulsification of water-in-oil emulsions. Colloids Surf. 1995, 95, 235−247. (13) Wang, Y.-Y.; Dai, Y.-H.; Zhang, L.; Tang, K.; Luo, L.; Gong, Q.; Zhao, S.; Li, M.-Z.; Wang, E.-J.; Yu, J.-Y. The interfacial dilational properties of hydrophobically modified associating polyacrylamide studied by the interfacial tension relaxation method at an oil-water interface. J. Colloid Interface Sci. 2004, 280, 76−82.

Figure 11. Correlation among the yield stress increase, bitumen loss to underflow, and dosage for blend 1 and its components A, B, and C at 100 ppm.

Table 4. Composition of the Underflow in the Absence and Presence of Blend 1 and Its Components A, B, and Ca

a

DMO name

ppm

bitumen, %

A B C blend 1

100 100 100 100

29.7 29.5 30.3 29.2

± ± ± ±

0.1 0.1 0.1 0.2

solids, % 11.7 12.2 11.9 12.6

± ± ± ±

0.1 0.3 0.2 0.4

water, % 38.9 39.0 38.6 39.5

± ± ± ±

0.2 0.2 0.3 0.1

solvent, % 19.7 19.3 19.2 18.7

± ± ± ±

REFERENCES

0.3 0.5 0.6 0.4

The demulsifier dosage is based on the mass of bitumen.

formulation has better performance than the performance of each individual EO-PO copolymer.

4. CONCLUSIONS The formulation and chemical nature of the individual components in a demulsifier blend can greatly impact the performance of the demulsifier. The results indicate that RSN of a demulsifier blend is an additive property and can be estimated from the composition and RSN value of its components. The dehydration efficiency of demulsifiers improved upon blending due to synergistic interactions among the individual EO-PO copolymers. Among the three blends, dehydration efficiencies were on the order of blend 1 > blend 3 > blend 2 from 0 to 100 ppm dosage. The equilibrium interfacial tension did not correlate to the dehydration efficiency of the components or the final demulsifier formulations. When the dynamic interfacial tension relaxation profiles of the individual components in blend 1 were compared, higher dehydration efficiencies were correlated with faster relaxation times. The relaxation time for blend 1 F



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(14) Kim, Y. H.; Wasan, D. T. Effect of Demulsifier Partitioning on the Destabilization of Water-in-Oil Emulsions. Ind. Eng. Chem. Res. 1996, 35, 1141−1149. (15) Tambe, D.; Paulis, J. Factors Controlling the Stability of Colloid-Stabilized Emulsion IV. Evaluating the Effectiveness of Demulsifiers. J. Colloid Interface Sci. 1995, 171, 463−469. (16) Breen, P. J. Adsorption Kinetics of Demulsifiers to an Expanded Oil-Water Interface; Sharma, R., Ed.; ACS Symposium Series 615; American Chemical Society: Washington, DC, 1995; pp 268−279.

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Collaborative Interactions between EO-PO Copolymers upon Mixing

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