Synthesis and Performance Evaluation of a Betaine Surfactant

—Using sodium bisulfite and epichlorohydrin as raw materials, the ring-opening reaction is carried out under the action of acatalyst to produce sodium 3-chloro-2-hydroxypropane sulfonate, followed by dodecyl tertiary amine, isopropanol, sodium hydroxide and 3-chloro-2-hydroxypropane sulfonate sodium as raw materials, under certain conditions to synthesize dodecyl hydroxy sulfobetaine surfactant. The surface tension, interfacial tension, salt resistance and emulsification properties of the synthesized surfactants were tested and evaluated. The experimental results show that the surfactant has a low critical micelle concentration and surface tension; the interfacial tension decreases with the increase of surfactant concentration. When the concentration is greater than or equal to 0.3%, the interfacial tension reaches 10 -2 level; the dodecyl hydroxy sulfobetaine surfactant solution shows good salt resistance; when the concentration of dodecyl hydroxy sulfobetaine surfactant solution is 0.5%, the water separation rate in 120 minutes is the lowest and the emulsification ability is the strongest.


INTRODUCTION
The betaine has a wide range of uses in daily chemical production. Betaine-type surfactants are stable to hard water, have excellent foaming power and wetting power, and have good compatibility with other types of surfactants [1]. The dodecyl hydroxy sultanate is a kind of amphoteric surfactant. Its structure has not only anionic groups, but also cationic groups. Therefore, it has more good properties than other surfactants, such as excellent hard water resistance, electrolyte resistance, low toxicity, good compatibility, mild performance, and easy degradation by organisms. The hydroxy sulfobetaine not only contains all the characteristics and advantages of amphoteric surfactants, but also has numerous advantages such as better emulsification, antistatic and dispersibility. It has been widely used in daily chemical industry, oil displacement, fracturing, acidification and other fields [2][3]. In this paper, the sodium bisulfite and epichlorohydrin were used as raw materials to produce sodium 3-chloro-2hydroxypropane sulfonate [4]. Then, dodecyl tertiary amine, isopropanol, sodium hydroxide and sodium 3chloro-2-hydroxypropane sulfonate were used as raw materials to synthesize dodecyl hydroxy sulfobetaine surfactant, and the properties of the surfactant solution were studied [5]

2.3.Resolve resolution
The sodium bisulfite and water are put into three bottles, increasing the temperature and stirring it until the temperature rises to 70°C to ensure that the sodium bisulfite is completely dissolved. Then prepare to add epichlorohydrin, ensuring that the temperature has always been kept at 70 ℃ for 2 hours. After the dropwise addition, the temperature is increased to 85℃, after 1.5～ 2 hours of reaction, cooling it will precipitate white crystal. These white crystals were treated by vacuum filtration, placed in a culture dish and dried in a vacuum drying oven for 48 hours to obtain sodium 3-chloro-2hydroxypropanesulfonate [6]. The reaction equation is shown in Fig. 1. The volume ratio of water to isopropanol is 1:3, and then sodium hydroxide and sodium 3-chloro-2hydroxypropane sulfonate are added. The temperature is raised to 90 ℃ and the sodium 3-chloro-2hydroxypropanesulfonate is completely dissolved. At this time, the dodecyl tertiary amine is added, reaction time is 4 hours, and then vacuum distillation and extraction are carried out. The reaction equation is shown in Fig. 2.

3.1.Surface tension evaluation
0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% dodecyl hydroxy sulfobetaine surfactant solution were prepared with distilled water at room temperature, and then the surface tension was measured by platinum plate method. In order to reduce the error, three experiments were carried out for each concentration sample, and the mode number of the three experimental results was taken as the final experimental data.

3.3.Salt resistance evaluation
0.1% dodecyl hydroxy sulfobetaine surfactant solution was prepared with distilled water, and then potassium chloride, sodium chloride, anhydrous calcium chloride and magnesium chloride with different mineralization degrees were added respectively. The surface tension was measured by a platinum plate method, and the turbidity degree of the solution was observed.

3.4.Emulsification ability evaluation
0.1%, 0.2%, 0.3%, 0.4% and 0.5% dodecyl hydroxy sulfobetaine surfactant solutions were prepared with distilled water and mixed with crude oil at a volume ratio of 1:1. The water evolution rate was measured with a stopwatch at 40 ℃ and 50 ℃ for 2 hours.

4.1.Surface tension
It can be concluded from

4.2.Interfacial tension
At 30 ℃, it can be concluded from Table Ⅱ when the concentration of dodecyl hydroxy sulfobetaine surfactant solution is greater than or equal to 0.1%, the interfacial tension with kerosene is lower than 2×10-1mN/m. When the concentration of dodecyl hydroxy sulfobetaine surfactant solution is greater than or equal to 0.3%, the interfacial tension with kerosene reaches the order of 10-2 level. With the increase of surfactant concentration, the interfacial tension with kerosene shows a downward trend, and the downward trend becomes stable after the concentration is higher than 0.1%. The change trend of surface tension and interfacial tension of dodecyl hydroxy sulfobetaine surfactant is basically the same.

4.3.Salt resistance
It can be seen from Table Ⅲ that with the increase of salinity of the four salts, the solution is always transparent, indicating that the solution of dodecyl hydroxy sulfobetaine surfactant has good solubility with the four salts. With the increase of the salinity of the four salts, the surface tension of the four salts showed an upward trend. The rising trend of sodium salt, potassium salt and magnesium salt was first rapid and then slow, while the rising trend of calcium salt was relatively stable. When the salinity of four salts reached 100000 ppm, the surface tension change rate was about 10%. Therefore, with the increase of salinity of four salts, the dodecyl hydroxy sulfobetaine surfactant solution showed good salt resistance performance.

4.4.Emulsification
At 50 ℃, it can be seen from Fig. 3 that with the extension of time, more and more water will be precipitated from different concentrations of dodecyl hydroxy sulfobetaine surfactant solution. With the increase of the concentration, the water separation rate becomes lower and lower, but the water separation rate of different concentrations for 120 minutes is lower than 40%. The water separation rate of 0.1% dodecyl hydroxy sulfobetaine surfactant solution reached about 37% in 120 minutes, which was significantly higher than other concentrations, so the emulsifying ability was the worst when the concentration was 0.1%. The concentration of 0.5% dodecyl hydroxy sulfobetaine surfactant solution has the lowest water evolution rate, and the emulsification effect is the strongest. At 60 ℃, it can be seen from Fig. 4 that with the extension of time, more and more water will be precipitated from different concentrations of dodecyl hydroxy sulfobetaine surfactant solution. With the increase of the concentration, the water precipitation rate becomes lower and lower, but the water precipitation rate of different concentrations for 120 minutes is less than 40%. The water separation rate of 0.1% dodecyl hydroxy sulfobetaine surfactant solution in 120 minutes was significantly higher than that of other concentrations, so the emulsifying ability was the worst when the concentration was 0.1%. The concentration of 0.5% dodecyl hydroxy sulfobetaine surfactant is the lowest, and the emulsifying ability is the strongest. Compared with 50 ℃, the water separation rate of the same concentration of dodecyl hydroxy sulfobetaine surfactant solution increased at 60 ℃, and the increase rate of 0.5% dodecyl hydroxy sulfobetaine surfactant solution was the largest, which indicated that temperature had great influence on the emulsifying ability of 0.5% dodecyl hydroxy sulfobetaine surfactant solution.

CONCLUSIONS
The optimum synthesis conditions of dodecyl hydroxy sulfobetaine surfactant were as follows: the ratio of isopropanol to water was 3:1. The reaction temperature was 90 ℃, and the reaction time was 4 hours.
At room temperature, the critical micelle concentration of dodecyl hydroxy sulfobetaine surfactant aqueous solution is about 0.1%, and the surface tension corresponding to critical micelle concentration point is 29.8mN/m. The results showed that the critical micelle concentration and surface tension of the surfactant were low.
When the concentration of dodecyl hydroxy sulfobetaine surfactant solution is more than 0.1%, the interfacial tension with kerosene is less than 2×10 -1 mN/m. The interfacial tension decreases with the increase of surfactant concentration. When the concentration is greater than or equal to 0.3%, the interfacial tension reaches 10 -2 level.
With the increase of salinity of Na + , K + , Mg 2 + and Ca 2 + , the surface tension of dodecyl hydroxy sulfobetaine surfactant solution is always transparent, and the surface tension is increasing. When the salinity of four salts reaches 100 000 ppm, the surface tension change rate is about 10%, which indicates that the solution of dodecyl hydroxy sulfobetaine surfactant has good solubility with the four salts, and all show good salt resistance.
At the same temperature, with the extension of time, more and more water will be precipitated from different concentrations of dodecyl hydroxy sulfobetaine surfactant solution. With the increase of concentration, the water evolution rate becomes lower and lower, but the water evolution rate is less than 40% in 120 minutes. At different temperatures, the water evolution rate of the same concentration of dodecyl hydroxy sulfobetaine surfactant solution increases with the increase of temperature. When the concentration of dodecyl hydroxy sulfobetaine surfactant solution is 0.1%, the water separation rate is significantly higher than other concentrations, so the emulsifying ability is the worst when the concentration is 0.1%. The 0.5% dodecyl hydroxy sulfobetaine surfactant solution has the lowest water separation rate for 120 minutes and the strongest emulsification ability.

ACKNOWLEDGMENT
This work was financially supported by the grants from Open Fund of Shaanxi Key Laboratory of Carbon Dioxide Storage and Enhanced Oil Recovery(YJSYZX20SKF0008).