Method for evaluating oil-water interface adsorption film by using rotating droplet method

Abstract

The invention discloses a method for evaluating an oil-water interface adsorption film by using a rotating liquid drop method. The method comprises the following steps: (1) sequentially injecting a surfactant solution and measured oil drops into a quartz tube of a rotating drop interface tensiometer; and (2) controlling the rotating speed of the rotating drop interface tensiometer to periodically change to apply disturbance to the oil drops, recording the oil drop change process through a high-definition camera to obtain experimental data, and then evaluating the oil-water interface adsorption films of different oil-water systems. According to the invention, experimental data are directly obtained through the high-definition camera, and the obtained data can more accurately guide the evaluation of the oil-water interface adsorption film; oil-water interface parameters of a lower tension system can be measured, and the evaluation range of the oil-water interface adsorption film is wider.

Description

Technical Field

[0001] The invention belongs to the field of interface science, relates to an evaluation method of an oil-water interface, and specifically relates to a method for evaluating an oil-water interface adsorption film by using a rotating drop method. Background Art

[0002] Matter exists in three states: gas, liquid, and solid. The solid and liquid states are also called condensed states. There is a physical interface between different phases that intersect with each other. This interface between phases is simply called an interface, including five types of interfaces: solid-gas, liquid-gas, solid-liquid, liquid-liquid, and solid-solid. It is customary to call the interface between the condensed state and the gaseous state a surface, such as the solid-gas interface is the solid surface, and the liquid-gas interface is the liquid surface.

[0003] In terms of the physical properties of the interface, it is a two-dimensional geometric surface existing between two phases. Therefore, the interface phenomenon has two-dimensional characteristics; but in fact, the properties of the parts of each phase on both sides of the interface that are infinitely close to the physical interface are different from the bulk properties of the phase. Therefore, the interface is a very thin transition zone, usually with a thickness of one to several molecules. Various physical and chemical effects in three-dimensional space, such as phase changes and chemical reactions, can also occur on the interface.

[0004] There are a large number of interfaces in actual application systems: there is an oil-water interface in emulsions, a liquid-gas interface in foams, and mineral flotation involves solid-liquid and solid-gas interfaces... In recent years, with the development of materials science, interfacial catalysis and interfacial chemical reactions have developed vigorously, and the importance of interface science has increased day by day.

[0005] Interfacial tension measurement, even dynamic interfacial tension measurement, is static data. Although it is a measure of interfacial free energy, it cannot reflect the structure of the interfacial film and cannot obtain the microscopic information of the surfactant molecules on the interface. Therefore, in the past two decades, the study of interfacial rheology has been in the ascendant. Similar to bulk rheology, the research object of interfacial rheology is the relationship between the interfacial stress tensor and the interfacial deformation and the interfacial deformation rate tensor.

[0006] Dilational rheology is one of the important properties of fluid interfaces. In practice, it is closely related to the stability of emulsions and foams, and plays an important role in industrial, biological, pharmaceutical and household applications. Since the basis of dilational rheology is the microscopic relaxation process on or near the interface, the relevant parameters of dilational rheology can reflect the information of microscopic processes of the interface, and also have important guiding significance for industrial processes related to interfaces and surfaces, such as extraction, extraction, washing and drainage from solids. More importantly, dilational rheology can be used to study the behavior of adsorbed molecules on the interface and supramolecular aggregates at the fluid interface.

[0007] Surfactant refers to a substance that can significantly change the interfacial state of its solution system when added in a small amount. Because of its fixed hydrophilic and lipophilic groups, surfactants can be arranged in a directional manner on the surface of the solution. Surfactant molecules adsorb on the oil-water interface to form a dense adsorption film, so that the microscopic relaxation process of the interface change can be observed on or near the oil-water interface, which is the interfacial dilation rheological property of the fluid interface. Therefore, the relevant parameters of interfacial dilation rheology can reflect the information of the microscopic process of the interface. At present, most of the measurements of dilation rheological parameters of surfactant solutions use the hanging drop method, but most of the instruments on the market can only measure the dilation rheological parameters when the surface tension is above 5mN / m. When the interfacial tension reaches 5mN / m or even lower, the hanging droplets will be elongated, separated and finally fall due to the reduction of interfacial tension. It can be seen that measuring the interfacial dilation rheological parameters of oil-water adsorption film under low tension is an urgent problem to be solved in the evaluation of the adsorption film capacity of the oil-water interface and in the field of practical applications. New indoor test devices and screening technologies that can achieve cost reduction and efficiency improvement have broad market demand and good social benefits. Summary of the invention

[0008] The purpose of the present invention is to provide a method for evaluating oil-water interface adsorption film using a rotating drop method. The expansion parameters of different types of oil displacement systems can be directly obtained through a high-definition camera of an interfacial tension meter, and the oil displacement effects of different oil displacement systems can be qualitatively evaluated, thereby guiding practical applications.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is to provide a method for evaluating the adsorption film at the oil-water interface using the spinning drop method, comprising the following steps:

[0010] (1) Injecting the surfactant solution and the oil drop to be measured into the quartz tube of the spinning drop interfacial tension meter in sequence;

[0011] (2) The rotation speed of the rotating drop interfacial tension meter is controlled to change periodically to apply disturbance to the oil drop, and the change process of the oil drop is recorded by a high-definition camera to obtain experimental data. The oil-water interface adsorption film of different oil-water systems is then evaluated to obtain the characteristic parameters of the evaluation effect.

[0012] In the present invention, the experimental data is directly obtained by a high-definition camera, and the obtained data can more accurately evaluate the adsorption film at the oil-water interface; the expansion parameter measurement of a lower tension system can be performed, and the evaluation range of the adsorption film at the oil-water interface is wider.

[0013] As a preferred technical solution of the present invention, in step (1), the oil droplets in the surfactant solution should be independent and complete, easy to observe, and located in the center of the field of view.

[0014] As a preferred technical solution of the present invention, in step (2), the evaluation effect characteristic parameters include dilational rheology evaluation or oil-water interface adsorption film evaluation.

[0015] As a preferred technical solution of the present invention, when performing the pressure reduction and injection increase evaluation, the simulation experiment and evaluation include the following steps:

[0016] Step (1'), placing the quartz tube containing the oil droplets and the surfactant solution into a spinning drop interfacial tension meter, setting the required temperature and rotation speed, and causing the droplets in the quartz tube to deform and eventually reach a stable state under the influence of the rotation speed;

[0017] Step (2'), after the droplets in step (1') reach a stable state, the rotation speed of the rotating drop interfacial tension meter is controlled by a circuit to change sinusoidally, so as to apply periodic disturbance to the oil droplets, and the change of the oil droplets is recorded by a high-definition camera;

[0018] Step (3'), after the high-definition camera in step (2') has finished recording, the recorded video is framed at one second per frame, and the interfacial tension and surface area of ​​each frame are measured;

[0019] Step (4'), performing a sine fit on the interfacial tension and surface area measured in step (3') and calculating the dilation modulus, and then evaluating the adsorption film at the oil-water interface.

[0020] It is worth mentioning that the oil droplet injection size, tensiometer temperature and other parameters can be appropriately adjusted according to the experimental requirements to achieve a universal evaluation of the adsorption film at the oil-water interface in different practical applications.

[0021] The method for evaluating the oil-water interface adsorption film of the present invention can make an intuitive comparison of different types of oil-water interface adsorption films within the tension range of 0.1-10mN / m, and can evaluate all oil-water interface adsorption films with a tension lower than 5mN / m. It is simple and efficient while improving the extensiveness of the test.

[0022] As a preferred technical solution of the present invention, in step (1'), the rotation speed is 4000-12000 r / min, for example, it can be 4000 r / min, 5000 r / min, 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min or 12000 r / min, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable;

[0023] As a preferred technical solution of the present invention, in step (1') and step (2'), the rotation speed is the same;

[0024] As a preferred technical solution of the present invention, in step (2'), the speed cycle is 10-200s, for example, it can be 10s, 20s, 30s, 50s, 100s or 200s, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable;

[0025] As a preferred technical solution of the present invention, in step (2'), the amplitude of the rotation speed is 1000-3000r / min, for example, it can be 1000r / min, 1500r / min, 2000r / min, 2500r / min or 3000r / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] It is worth noting that the spinning drop interfacial tension meter is determined according to the actual temperature of the selected oil reservoir and is selected based on actual conditions.

[0027] As a preferred technical solution of the present invention, the spinning drop interfacial tension meter adopts a CNGTX intelligent spinning drop interfacial tension meter. In the evaluation screen of the tension meter display, the horizontal axis is the time phase variable x of the speed cycle, the left vertical axis is the interfacial tension y1, the right vertical axis is the surface area y2, and A is the amplitude variable of the speed. In step (4'), the fitting analysis is performed by using the following formula:

[0028] The area and tension function can be obtained by sine fitting:

[0029] Interfacial tension fitting:

[0030] y1=y 01 +A1*sin(π*(xx c1 ) / w1) (1)

[0031] Among them, y 01 is the interfacial tension value at the steady state speed, A1 is the speed amplitude of the interfacial tension, x c1 is the interfacial tension phase, w1 is the interfacial tension frequency, and is related to the interfacial tension phase x c1 correspond;

[0032] Surface area fitting:

[0033] y2=y 02 +A2*sin(π*(xx c2 ) / w2) (2)

[0034] Among them, y 02 is the surface area value at steady state speed, A2 is the speed amplitude of the surface area, x c2 is the surface area phase, w2 is the surface area frequency, and is related to the surface area phase x c2 correspond;

[0035] Dilation modulus calculation:

[0036] ε=dγ / (d ln A)=2A1 / (2A2 / (y 02 -A2)) = A1 / (A1 / (y 02 -A2)) (3)

[0037] Phase angle calculation:

[0038] θ=(x c2 / w2-x c1 / w1)*π*(180°) / π=(x c2 / w2-x c1 / w1)*180° (4)

[0039] Calculation of elastic modulus:

[0040] ε d =|ε|cosθ (5)

[0041] Calculation of viscosity modulus:

[0042] ωη d =|ε|sinθ (6).

[0043] As a preferred technical solution of the present invention, the simulation experiment and evaluation also include the following steps:

[0044] Step (5'), replace different external phase solutions in the quartz tube, re-introduce oil droplets, and then repeat steps (1')-(4'), and then evaluate different oil-water interface adsorption films.

[0045] In the present invention, ε, A, ε d and ωη d The value is the effect of evaluating the adsorption film at the oil-water interface of each system. The relevant parameters of interfacial dilation rheology can reflect the information of the microscopic process of the interface, and can be used to study the behavior of adsorbed molecules on the interface and the supramolecular aggregates of the fluid interface. It is closely related to the stability of emulsions and foams, and is used to evaluate the quality of the adsorption film at the oil-water interface.

[0046] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) Compared with the hanging drop method for evaluating the oil-water interface adsorption film system, the screening method of the present invention can obtain the dilational rheological evaluation under a lower tension flooding system, which is not limited to more than 5 mN / m. The obtained data can more accurately guide the evaluation of the interface film;

[0049] (2) Compared with the hanging drop method for evaluating oil-water interface adsorption film, the evaluation method of the present invention has the advantages of economy and operability. The external phase liquid is changed from a large amount of surfactant solution in the original water tank to a small amount of external phase liquid in the quartz tube, and the core device of the experiment is changed from a pressure sensor to a high-definition camera with more accurate measurement. In addition, the experimental operation does not require a complicated preparation process, and the screening work can be quickly completed by monitoring the dynamic pressure curve;

[0050] (3) Compared with the hanging drop method for evaluating the adsorption film at the oil-water interface, the screening method of the present invention changes the original pressure control into a speed change controlled by a circuit, and innovates in the disturbance of the oil droplets. The dilation rheological parameters of all adsorption films at the oil-water interface can be measured at a speed of 4000-12000 r / min and a speed amplitude of 1000-3000 r / min. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a graph showing the surface area and tension changes of different types of surfactant solutions and decane adsorption films when the first group of tension-area fitting is performed in the present invention;

[0052] Figure 2 The surface area and tension variation diagram of different types of surfactant solutions and decane adsorption films when the second group of tension-area fitting is performed in the present invention;

[0053] Figure 3 This is a graph showing the surface area and tension changes of different types of surfactant solutions and decane adsorption films when the third group of tension-area fitting is performed in the present invention;

[0054] Figure 4 This is a graph showing the changes in surface area and tension of different types of surfactant solutions and decane adsorption films when performing the fourth group of tension-area fitting in the present invention. DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with the accompanying drawings.

[0056] The present invention discloses a method for evaluating an adsorption film at an oil-water interface by using a rotating drop method. A person skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the method. It should be particularly noted that all similar substitutions and modifications are obvious to a person skilled in the art, and they are all deemed to be included in the present invention, and relevant persons can obviously modify or appropriately change and combine the contents described herein without departing from the content, spirit and scope of the present invention to achieve and apply the technology of the present invention.

[0057] In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0058] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0059] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] It should be noted that in the description of the present invention, the terms "first" and "second" are only used to facilitate the description of different components, and cannot be understood as indicating or implying a sequential relationship, relative importance, or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0061] like Figures 1 to 4 As shown, the present invention provides a method for evaluating an adsorption film at an oil-water interface by using a rotating drop method, comprising evaluating the adsorption film at an oil-water interface by driving through dilational rheological parameter measurement;

[0062] Furthermore, the method for evaluating the adsorption film at the oil-water interface by measuring the dilational rheological parameters includes the following steps:

[0063] In step (1'), the CNGTX intelligent spinning drop interfacial tension meter of Beijing Shengwei Jiye Technology Co., Ltd. is used for evaluation. A quartz tube containing n-decane oil droplets and anionic surfactant solution is placed in the spinning drop interfacial tension meter, and the temperature is set to 25°C and the rotation speed is 8000r / min. Under the influence of the rotation speed, the droplets in the quartz tube are deformed and finally reach a stable state.

[0064] Step (2'), after the n-decane oil droplet in step (1') reaches a stable state, the rotation speed of the rotating drop interfacial tension meter is controlled by a circuit to change sinusoidally, the amplitude of the rotation speed is set to 2000 r / min (i.e., the rotation speed is 8000±2000 r / min), and the period is 10s to apply periodic disturbance to the n-decane oil droplet. At the same time, a high-definition camera is used to record the change of the oil droplet.

[0065] Step (3'), after the high-definition camera in step (2') has finished recording, the recorded video is framed at 0.1 s per frame, and the interfacial tension and area at each frame are measured.

[0066] Step (4') performs sinusoidal fitting on the tension and area to obtain y1 and y2, and calculates the expansion modulus ε, phase angle θ, and elastic modulus ε d and the viscous modulus ωη d .

[0067] Interfacial tension fitting:

[0068] y1=y 01 +A1*sin(π*(xx c1 ) / w1)

[0069] Among them, y 01 is the interfacial tension value at the steady state speed, A1 is the speed amplitude of the interfacial tension, x c1 is the interfacial tension phase, w1 is the interfacial tension frequency, i.e. the rotation speed, and is related to the interfacial tension phase x c1 correspond;

[0070] Surface area fitting:

[0071] y2=y 02 +A2*sin(π*(xx c2 ) / w2)

[0072] Among them, y 02 is the surface area value at steady state speed, A2 is the speed amplitude of the surface area, x c2 is the surface area phase, w2 is the surface area frequency, and is related to the surface area phase x c2 correspond;

[0073] Dilation modulus calculation:

[0074] ε=dγ / (dlnA)=2A1 / (2A2 / (y 02 -A2)) = A1 / (A1 / (y 02 -A2))

[0075] Phase angle calculation:

[0076] θ=(x c2 / w2-x c1 / w1)*π*(180°) / π=(x c2 / w2-x c1 / w1)*180°

[0077] Calculation of elastic modulus:

[0078] ε d =|ε|cosθ

[0079] Calculation of viscosity modulus:

[0080] ωη d =|ε|sinθ

[0081] (5') Turn off the spinning drop interfacial tension meter, remove the quartz tube, clean it, and re-inject new surfactant solution and n-decane oil droplets, repeat steps (2')-(4'), and compare the obtained values ​​to evaluate the oil-water interface adsorption film of the surfactant aqueous solution.

[0082] In this example, four surfactant solutions and n-decane interfaces were used to evaluate the adsorption film at the oil-water interface, and the test data are shown in Table 1;

[0083] Table 1

[0084]

[0085] In Table 1, the magnitude of the interfacial dilation modulus can reflect the strength of the interfacial film from a dynamic perspective. The phase angle is the phase difference between the interfacial tension and interfacial area change curves during the dilatation rheology test, which is equal to the ratio of the dilational viscous modulus to the dilational elastic modulus. The elastic part of the dilational modulus represents the interaction between the surfactant molecules on the interface, and the viscous part represents the sum of a series of relaxation processes occurring at and near the interface, including the interfacial rearrangement of the surfactant molecules, diffusion exchange with the bulk phase, etc. As can be seen from the figure, in terms of interfacial film strength, zwitterionic surfactants are > anionic and anionic-nonionic surfactants > nonionic surfactants, which is due to the arrangement of the surfactant at the interface and its own special structure.

[0086] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating an adsorption film at an oil-water interface using a spinning drop method, characterized in that: The following steps are involved: (1) Injecting the surfactant solution and the oil drop to be measured into the quartz tube of the spinning drop interfacial tension meter in sequence; (2) The rotation speed of the rotating drop interfacial tension meter is controlled to change periodically to apply disturbance to the oil drop, and the change process of the oil drop is recorded by a high-definition camera to obtain experimental data. The oil-water interface adsorption film of different oil-water systems is then evaluated to obtain the characteristic parameters of the evaluation effect.

2. The method for evaluating the adsorption film at the oil-water interface by the spinning drop method according to claim 1, characterized in that: In step (1), the oil droplets in the surfactant solution should be independent and complete, easy to observe, and located in the center of the field of view.

3. The method for evaluating the adsorption film at the oil-water interface by the spinning drop method according to claim 1, characterized in that: In step (2), the evaluation effect characteristic parameters include dilational rheology evaluation or oil-water interface adsorption film evaluation.

4. The method for evaluating the adsorption film at the oil-water interface by the spinning drop method according to claim 3, characterized in that: When conducting a pressure reduction and injection assessment, the simulation experiment and assessment includes the following steps: Step (1'), placing the quartz tube containing the oil droplets and the surfactant solution into a spinning drop interfacial tension meter, setting the required temperature and rotation speed, and causing the droplets in the quartz tube to deform and eventually reach a stable state under the influence of the rotation speed; Step (2'), after the droplets in step (1') reach a stable state, the rotation speed of the rotating drop interfacial tension meter is controlled by a circuit to change sinusoidally, so as to apply periodic disturbance to the oil droplets, and the change of the oil droplets is recorded by a high-definition camera; Step (3'), after the high-definition camera in step (2') has finished recording, the recorded video is framed at one second per frame, and the interfacial tension and surface area of ​​each frame are measured; Step (4'), performing a sine fit on the interfacial tension and surface area measured in step (3') and calculating the dilation modulus, and then evaluating the adsorption film at the oil-water interface.

5. The method for evaluating the adsorption film at the oil-water interface by the spinning drop method according to claim 4, characterized in that: In step (1'), the rotation speed is 4000-12000 r / min; In step (1') and step (2'), the rotation speeds are the same; In step (2'), the speed cycle is 10-200s; In step (2'), the amplitude of the rotation speed is 1000-3000 r / min.

6. The method for evaluating an adsorption film at an oil-water interface using a spinning drop method according to claim 4 or 5, wherein: The spinning drop interfacial tension meter adopts the CNGTX intelligent spinning drop interfacial tension meter. In the evaluation screen of the tension meter display, the horizontal axis is the time phase variable x of the rotation speed cycle, the left vertical axis is the interfacial tension y1, the right vertical axis is the surface area y2, and A is the amplitude variable of the rotation speed. In step (4'), the fitting analysis is performed by using the following formula: The area and tension function can be obtained by sine fitting: Interfacial tension fitting: y1=y 01 +A1*sin(π*(xx c1 ) / w1) (1) Among them, y 01 is the interfacial tension value at the steady state speed, A1 is the speed amplitude of the interfacial tension, x c1 is the interfacial tension phase, w1 is the interfacial tension frequency, and is related to the interfacial tension phase x c1 correspond; Surface area fitting: y2=y 02 +A2*sin(π*(xx c2 ) / w2) (2) Among them, y 02 is the surface area value at steady state speed, A2 is the speed amplitude of the surface area, x c2 is the surface area phase, w2 is the surface area frequency, and is related to the surface area phase x c2 correspond; Dilation modulus calculation: <h2 style=";text-align:left;direction:ltr">ε=dγ / (d ln A)=2A1 / (2A2 / (y<h2 style=";text-align:left;direction:ltr"> 02 <h2 style=";text-align:left;direction:ltr"> -A2)) = A1 / (A1 / (y<h2 style=";text-align:left;direction:ltr"> 02 <h2 style=";text-align:left;direction:ltr"> -A2)) (3) Phase angle calculation: θ=x c2 / w2-x c1 / w1)*π*(180°) / π=(x c2 / w2-x c1 / w1)*180° (4) Elastic modulus calculation: e d =|ε|cosθ (5) Viscous modulus calculation: oh d =|ε|sinθ (6).

7. The method for evaluating an adsorption film at an oil-water interface using a spinning drop method according to claim 4 or 5, characterized in that: The simulation experiment and evaluation also include the following steps: Step (5'), turn off the spinning drop interfacial tension meter, take out the quartz tube, clean it, re-inject new surfactant solution and n-decane oil droplets, repeat steps (2')-(4'), and evaluate the oil-water interface adsorption film of the surfactant aqueous solution by comparing the obtained values.

8. The method for evaluating the adsorption film at the oil-water interface by the spinning drop method according to claim 6, characterized in that: The simulation experiment and evaluation also include the following steps: Step (5'), turn off the spinning drop interfacial tension meter, take out the quartz tube, clean it, re-inject new surfactant solution and n-decane oil droplets, repeat steps (2')-(4'), and evaluate the oil-water interface adsorption film of the surfactant aqueous solution by comparing the obtained values.

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