CN107824119B - An emulsion stabilization system with pH-responsive Gemini surfactant - Google Patents

Abstract

The invention discloses an emulsion stabilization system with a pH-responsive Gemini surfactant, belonging to the technical field of surfactants. The linking group of the present invention is a carboxylate gemini surfactant with three methylene groups, and the emulsion is kept at a constant temperature of 25° C. for 150 days without demulsification. However, at the same concentration, the carboxylate gemini surfactant with six methylene groups as the linking group has oil-water stratification after 60 days, and the carboxylate gemini surfactant with ten methylene groups as the linking group After 50 days, there is a very obvious oil-water stratification phenomenon. In addition, the pH of the emulsion after beating is adjusted to about 5 immediately, and the emulsion can be broken after two minutes. The cost reduction effect can be achieved by applying the pH-responsive surfactants with different chain lengths to oil transportation of different routes.

Description

An emulsion stabilization system with pH-responsive Gemini surfactant

technical field

The invention relates to an emulsion stabilization system with a pH-responsive Gemini surfactant, belonging to the technical field of surfactants.

Background technique

Gemini surfactants, also known as gemini surfactants, twinned surfactants, gemini surfactants or conjugated surfactants, are two traditional surfactant molecules connected to their hydrophilic head groups or close to each other through a linking group. A new class of surfactants formed by joining together at the hydrophilic head groups. Due to the particularity of its structure, gemini surfactants exhibit unique properties that many conventional surfactants do not possess, so they have strong application potential. Gemini surfactants have good solubilization, wetting, foaming and saponification dispersing ability, and can be widely used in synthetic rubber industry, coatings or functional emulsion fields. It also includes applications in the preparation of environmentally friendly building latex and anti-adhesives, sewage and soil treatment, discolored latex, oil and gas fields, natural latex reinforcement technology, oil recovery or fine chemicals.

An emulsion is a dispersion system formed by emulsification of two incompatible liquids in the presence of an emulsifier. Emulsifier is an important part of emulsion. Compared with common surfactant, gemini surfactant has low critical micelle concentration and low interfacial mobility, so it has the advantages of small amount of emulsifier and less foam when preparing emulsion. Compared with traditional gemini surfactants, carboxylate anionic gemini surfactants with flexible link chains have better emulsifying properties. Generally, we think that polymethylene, polyethoxy, etc. are flexible linking groups. Such linking groups have a large degree of freedom and can spontaneously adjust the configuration in the aggregate according to the specific system. In contrast, a rigid linking group refers to a linking group containing an aromatic group or an alkynyl group. Studies have shown that when the length of the rigid linking group is less than the electrostatic equilibrium distance of two headgroups, its self-assembly behavior is similar to that of Gemini surfactants with similar lengths of flexible linking groups; When its length exceeds or even far exceeds the electrostatic equilibrium distance of the two head groups, Gemini surfactants may exhibit some special properties.

Compared with the Gemini surfactant with a benzene ring, the Gemini surfactant with flexible linking group has a lower cmc value and is more prone to the micellization process. The research group of Fan Yaxun of the Chinese Academy of Sciences has systematically studied the solution properties of Gemini surfactants with different linking groups, including six methylene groups and p-xylene. Studies have shown that hydrophilic and flexible linking groups can promote the formation of micelles, resulting in a decrease in cmc and ionization degree, an increase in the aggregation number, and a more negative Gibbs free energy of micelles. Microviscosity measurements also indicated that such Gemini surfactants tend to form more tightly packed micellar structures than linking groups that are hydrophobic and rigid.

Existing import and export of gasoline, diesel, kerosene and a series of oil products require special oil transportation vessels and oil transportation personnel with special qualifications, and the long distance transportation of oil products leads to high transportation costs. , flammable and explosive and other high risks. The existing emulsion stabilization system is used for oil transportation, but the existing emulsion stabilization system has defects such as short stabilization time or difficult demulsification, and still has high risks and processing difficulties when applied to oil transportation.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides an emulsion stabilization system with a pH-responsive Gemini surfactant. On the one hand, the emulsion stabilization system of the present invention has a long stabilization time; on the other hand, the emulsion stabilization system of the present invention has carboxylate For the ionic head group, we can adjust the pH as required, and the surfactant can be switched between with or without surface activity to achieve rapid changes in emulsification and demulsification.

The first object of the present invention is to provide an emulsion stabilization system with a pH-responsive Gemini surfactant, which is prepared from a carboxyl group-containing gemini surfactant; wherein the carboxyl group-containing The molecular structure of the group of gemini surfactants is as (1):

where n=3, 6 or 10.

In one embodiment of the present invention, the concentration of gemini surfactant is 0.4-4 mM.

In one embodiment of the invention, the concentration of gemini surfactant is 0.5 mM.

In one embodiment of the present invention, the emulsion stabilization system is demulsification broken when pH is adjusted to 4-6.

In one embodiment of the present invention, the emulsion system is prepared by using n-decane as the oil phase and ultrapure water (conductivity 18.2Ω) as the water phase.

In an embodiment of the present invention, the emulsion system is prepared by homogenizing under the conditions of a homogenizer of 10000-15000 r/min.

In one embodiment of the present invention, the preparation of the emulsion system is made by homogenizing under the condition of a homogenizer at 11000 r/min.

The second object of the present invention is to provide the application of said emulsion system.

In one embodiment of the present invention, the application includes applications in the synthetic rubber industry, coatings or functional emulsion fields.

In one embodiment of the present invention, the application further includes application in oil transportation, preparation of environmentally friendly building latex and anti-adhesive, treatment of sewage and soil, discolored latex, oil and gas field, natural latex reinforcement technology, oil recovery or fine chemicals.

Beneficial effects of the present invention:

The linking group of the present invention is a carboxylate gemini surfactant with three methylene groups, and the emulsion is kept at a constant temperature of 25° C. for 150 days without demulsification. However, at the same concentration, the carboxylate gemini surfactant with six methylene groups as the linking group has oil-water stratification after 60 days, and the carboxylate gemini surfactant with ten methylene groups as the linking group After 50 days, there is a very obvious oil-water stratification phenomenon. However, we adjusted the pH of the emulsion to about 5 immediately after beating, and the emulsion could be broken after two minutes. The series of pH-responsive dairy stabilization systems of the present invention are applied to the transportation of oil products, emulsifying the petroleum of special dangerous goods into emulsions for normal transportation, and the gemini surfactants with different linking chain lengths can be selected according to the distance of the journey, so as to achieve the purpose. After the ground, the pH of the emulsion can be lowered to achieve the effect of rapid demulsification. The invention can effectively reduce the cost of transnational transportation of oil products, and has application value.

Description of drawings

Fig. 1 is the ¹ HNMR chart of the product of embodiment 1 measured in CD ₃ OD;

Fig. 2 is the ¹ HNMR chart of the product of embodiment 2 measured in CD ₃ OD;

Figure 3 is the ¹ HNMR chart of the product of Example 3 measured in CD ₃ OD.

Detailed ways

Emulsion particle size test

The particle size of the emulsion was measured using a three-dimensional microscope with super depth of field from Keyence (Hong Kong) Co., Ltd., which used a lower light source with a magnification of 250-2500 times, and the test temperature was also controlled at 25°C.

Example 1: Synthesis of SL-3-SL

Synthesis of 2-decyldiethylmalonate with diethylmalonate and bromo-n-decane as starting materials. Bilateral substitution between 2-decyldiethylmalonate and 1,3-dibromopropane Reaction to generate tetraethyltetracosane-11,11,15,15-tetracarboxylic acid tetraethyl ester, tetraethyltetracosane-11,11,15,15-tetracarboxylic acid tetraethyl ester and then The final SL-3-SL carboxylate-type anionic Gemini surfactant was obtained through saponification, acidification, deacidification and acid-base neutralization in sequence, and the yield was 65%.

Example 2: Synthesis of SL-6-SL

Synthesis of 2-decyl diethyl malonate with diethyl malonate and bromo-n-decane as starting materials Substitution reaction to generate tetraethylheptadecane-11,11,18,18-tetracarboxylic acid tetraethyl ester, tetraethylheptadecane-11,11,18,18-tetracarboxylic acid tetraethyl ester The final SL-6-SL carboxylate-type anionic Gemini surfactant was obtained through saponification, acidification, deacidification and acid-base neutralization in sequence, and the yield was 63%.

Example 3: Synthesis of SL-10-SL

Synthesis of 2-decyl diethyl malonate with diethyl malonate and bromo-n-decane as starting materials Substitution reaction to generate tetraethyl tridecane-11,11,22,22-tetracarboxylic acid tetraethyl ester, tetraethyl tridecane-11,11,22,22-tetracarboxylic acid tetraethyl ester The final SL-10-SL carboxylate-type anionic Gemini surfactant was obtained through saponification, acidification, deacidification and acid-base neutralization in sequence, and the yield was 60%.

Example 4: Preparation of Emulsion System

Prepare 0.5mmol/L aqueous solutions of SL-3-SL, SL-6-SL and SL-10-SL, take 2ml of each and put them into three bottles, and then add 2ml of n-decane dropwise to the bottles as oil phase. Placed under a homogenizer with a rotational speed of 11000 r/min, each homogenized for 1 min, and an emulsion of the mixed system was formed.

Example 5: Characterization of Emulsion Particle Size Distribution

The particle size of the emulsion was measured using a three-dimensional microscope with super depth of field from Keyence (Hong Kong) Co., Ltd., which used a lower light source with a magnification of 250-2500 times, and the test temperature was also controlled at 25°C. The detection results are shown in Table 1. When the linking group is short, two head groups with the same charge and repelling each other are drawn closer together. The intermolecular and intramolecular hydrophobic interactions are enhanced, and the measured particle size is finer and the emulsion is more stable. However, with the increase of carbon atoms on the linking group, the molecular occupied area on the interface increases. The distance of the charged head group is similar to that of the traditional single-chain surfactant, and the particle size of the emulsion is shorter and the linking chain is larger. So there is a 50-day demulsification phenomenon.

Table 1 Particle size distribution analysis results

Example 6: Characterization of Emulsion Stability

The homogeneous emulsion was placed in a constant temperature oven at 25 °C for a period of time, and the results showed that the carboxylate gemini surfactant with three methylene groups as the linking group, the emulsion was maintained at a constant temperature of 25 °C for 150 days without breaking. milk. However, at the same concentration, the carboxylate gemini surfactant with six methylene groups as the linking group has oil-water stratification after 60 days, and the carboxylate gemini surfactant with ten methylene groups as the linking group After 50 days, there is a very obvious oil-water stratification phenomenon. The inventors believe that when the linking group is short, two head groups with the same charge and repelling each other are drawn closer, and the hydrophobic interaction between molecules and molecules is enhanced, and then a stable emulsion system is formed. However, with the increase of carbon atoms on the linking group, the occupied area of the molecules on the interface increases, and the distance of the charged head group is similar to that of traditional single-chain surfactants, so the phenomenon of 50-day demulsification occurs.

In addition, after the homogeneous emulsion was prepared in Example 4, the pH was adjusted to about 5 immediately, and it was found that the emulsion could be broken after two minutes.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone who is familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention should be defined by the claims.

Claims (6)

1. An emulsion system with a flexible connecting chain type anion Gemini surfactant is characterized in that the emulsion system is prepared from a Gemini surfactant containing carboxyl groups; wherein the molecular structural formula of the gemini surfactant containing carboxyl groups is shown as (1):

wherein n is 3;

the concentration of the carboxylate anionic Gemini surfactant emulsion was 0.5 mM.

2. The carboxylate anionic Gemini surfactant as claimed in claim 1, wherein the cationic portion of the carboxylate anionic Gemini surfactant is Na⁺、K⁺、Li⁺Or NH₄ ⁺。

3. The emulsion system according to claim 1, wherein the emulsion system is prepared with n-decane as oil phase and ultrapure water as water phase.

4. The emulsion system according to claim 1, wherein the emulsion system is prepared by homogenizing under conditions of a homogenizer of 10000-.

5. The emulsion system according to claim 1, wherein the emulsion system is prepared by homogenizing in a homogenizer at 11000 r/min.

6. The use of the emulsion system according to any one of claims 1 to 5, wherein the use comprises use in the synthetic rubber industry, in paints, functional emulsions, in oil transportation, in the preparation of environmentally friendly building latex and anti-adhesives, in the treatment of sewage and soil, in color-changing latex, in the field of oil and gas fields, in natural latex reinforcement, in the field of oil extraction or in the field of fine chemistry.

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