Application of N-acylamino acid type surfactant in preparation of gas hydrate

Abstract

The invention discloses a method for using an N-acylamino acid type surfactant as a hydrate generation accelerant and applying the N-acylamino acid type surfactant to preparation of a gas hydrate, the structural general formula of the N-acylamino acid type surfactant is as follows: # imgabs0 #, and R is selected from one of lauroyl, cocoyl and oleic acid group; r1 and R2 are independently selected from one of glutamic acid, glycine, alanine and sarcosine. The N-acylamino acid type surfactant is used as the hydrate generation accelerant, the generation efficiency of the gas hydrate can be effectively improved, the environmental problem that a traditional surfactant is difficult to decompose when used as the hydrate generation accelerant is solved, and the N-acylamino acid type surfactant has the advantages of being environmentally friendly, efficient, economical, safe and the like; good application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the field of hydrate formation promoters, and in particular relates to a method for using an N-acylamino acid type surfactant as a gas hydrate promoter and applying it in gas hydrate preparation. Background Art

[0002] In recent years, due to the increasingly serious environmental problems caused by traditional fossil fuels, clean energy such as methane and hydrogen has attracted more and more attention. Although gas fuel is greener and cleaner, it has low energy density and poor safety using traditional storage and transportation methods, resulting in gas fuels not being widely used. In this context, the safer and more environmentally friendly hydrate solidification gas technology has attracted widespread attention from scholars.

[0003] Gas hydrates are non-stoichiometric cage-like crystalline substances formed by water and small molecular gases such as methane, ethane and hydrogen under suitable temperature and pressure conditions. The main water molecules are connected by hydrogen bonds to form some polyhedral cage holes, and the guest gas molecules are filled in these cage holes, making them thermodynamically stable. Depending on the size of the guest molecules, 160 to 180 cubic meters of gas can be stored per cubic meter of hydrate. However, due to the extremely slow formation rate of gas hydrates in pure water systems and low gas storage efficiency, scholars have proposed a series of physical and chemical methods to strengthen the reaction. The use of physical methods requires a lot of energy, which is not conducive to the industrialization of hydrate solidification gas technology. The chemical method is mainly strengthened by adding a small amount of promoter, which can effectively reduce energy consumption, simplify the operation process, thereby reducing costs and improving economic effects.

[0004] At present, it has been reported that surfactants are used as gas hydrate formation promoters. The mechanism is due to the adsorption effect on the surface of the solution. In order to make the system more stable, surfactant molecules will automatically enrich on the surface layer of the liquid phase after dissolving in water. Because this type of molecule belongs to organic compounds, the interaction between molecules is weak. Therefore, when the molecule is enriched on the surface of the liquid phase, the surface tension of the liquid phase will decrease rapidly with the increase of its concentration, thereby reducing the surface Gibbs function. As a result, the solubility and diffusion coefficient of the sparingly soluble gas in the liquid phase are increased, and the gas-liquid contact is strengthened at the molecular level, thereby promoting the rapid start of gas hydrate formation. Secondly, due to the good dispersion performance, the addition of this molecule also prevents gas hydrates from agglomerating on the surface of the liquid phase to isolate the gas-liquid contact and prevent further reaction. Therefore, adding surfactants as kinetic promoters in the process of gas hydrate formation can greatly increase the reaction rate of the gas hydrate formation process and make the reaction more complete, thereby having a larger gas storage capacity and greatly improving the efficiency of gas hydrate formation. However, the use of traditional surfactants has two fatal problems: one is the challenge of non-degradability to the environment; the other is that a large amount of foam will be generated during the decomposition and recovery of gas hydrates, which will increase the difficulty of the recovery process. Summary of the invention

[0005] In view of the problems existing in traditional surfactants when used as gas hydrate formation promoters, the present invention provides a new type of hydrate formation promoter and an application method thereof, which is green, efficient, economical, safe, etc. and has good application prospects.

[0006] To achieve the above object, the present invention adopts the following technical solutions: One of the purposes of the present invention is to protect a class of hydrate formation promoters, which are specifically N-acylamino acid type surfactants, and their general structural formula is as follows: , Among them, R is selected from one of lauroyl, coconut oil acyl, oleic acid, etc.; R1 and R2 are independently selected from one of glutamic acid, glycine, alanine, and sarcosine.

[0007] The second purpose of the present invention is to protect the use of the hydrate in the preparation of gas hydrates, especially high gas storage density gas hydrates.

[0008] Furthermore, the application method is specifically to add the hydrate formation promoter into water to form a mixed solution, and then introduce gas to react, thereby obtaining solid gas hydrate.

[0009] Furthermore, the amount of the hydrate formation promoter added to water is 50 ppm to 5000 ppm.

[0010] Furthermore, the mixed solution can be frozen and crushed into particles for use.

[0011] Furthermore, the particle size of the particles is 0.1 mm to 1 mm.

[0012] Furthermore, the gas is a gas that is poorly soluble in water, such as methane, ethane, propane, ethylene, hydrogen, hydrogen sulfide, oxygen, nitrogen, argon, krypton, xenon, etc.

[0013] Furthermore, the reaction is carried out at a temperature of 268.15-288.15 K and a pressure of 0.5-15.0 MPa for a time of 0.5-12 h.

[0014] N-acyl amino acid surfactants are biodegradable and extremely mild surfactants. They do not produce a lot of foam like traditional surfactants, which makes them more suitable for hydrate solidification gas. At the same time, N-acyl amino acid surfactants, such as sodium cocoyl glycinate and sodium lauroyl glycinate, are already mature commercial products with guaranteed product quality and low prices. In addition, when using N-acyl amino acid surfactants as hydrate formation promoters, the dosage required for each reaction is extremely small, and the optimal dosage for the promotion effect is only 500 parts per million (500 ppm), which can effectively control its cost in industrial applications.

[0015] The present invention has the following advantages and characteristics: (1) N-acyl amino acid surfactants are mild, biodegradable, and economical anionic surfactants. While retaining the excellent properties of traditional surfactants, they can solve the environmental damage problems caused by the use of traditional surfactants and the foam problem during recycling.

[0016] (2) The present invention uses N-acylamino acid type surfactant as a gas hydrate formation promoter, which can greatly increase the gas hydrate formation rate and gas storage capacity, improve the gas storage efficiency, and provide a feasible solution for the industrialization of the storage and transportation method of hydrate-solidified gas.

[0017] (3) The method of using N-acyl amino acid type surfactant as a promoter to prepare high gas storage density hydrate is simple to operate, green and environmentally friendly, low cost and good economic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the transparent sapphire high-pressure reaction system used.

[0019] Figure 2 Graph showing pressure changes during methane hydrate generation in Example and Comparative Example.

[0020] Figure 3 Graph showing changes in methane gas absorption per unit volume of hydrate in the examples and comparative examples.

[0021] Figure 4 The induction time and T 90 Comparison chart of the graph. DETAILED DESCRIPTION

[0022] The technical scheme and implementation effects of the present invention are further described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of implementation of the present invention.

[0023] In order to study the effect of N-acyl amino acid surfactant as hydrate kinetic promoter on gas hydrate formation, sodium cocoyl glycinate was used as an example. Figure 1 The experiment was carried out using a visualized transparent sapphire high-pressure reaction system, which mainly consists of a high-pressure reactor, a balance reactor, a water bath, a temperature sensor, a pressure sensor data collection system, etc. The maximum working volume of the high-pressure reactor is 425 cm 3 , the maximum working pressure is 20 MPa and the working temperature range is -80-150 ℃.

[0024] Before the reaction begins, the entire experimental system is cleaned with deionized water. After vacuum drying, the prepared drugs are placed in a high-pressure reactor, and the water bath temperature is set to the experimental temperature. After the system temperature stabilizes for 2 hours, pure methane gas is introduced from the equilibrium reactor into the reactor, replacing the air in the reactor 3-4 times, and an experimental gas of a certain pressure (less than the equilibrium pressure of hydrate formation at this temperature, the hydrate equilibrium pressure is calculated using the Chen-Guo hydrate model) is introduced to achieve dissolution equilibrium. Then, the experimental gas is introduced from the equilibrium reactor to raise the system pressure to the test pressure, and the air inlet valve is closed to start the reaction. When the reaction pressure remains unchanged for 2 hours, the reaction is considered to be over.

[0025] Example 1 The reaction system is a mixed solution of 0.004 g of sodium cocoyl glycinate and 39.996 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 100 ppm. The mixed solution is fed into a reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 275.15 K.

[0026] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0027] Example 2 The reaction system is a mixed solution of 0.02 g of sodium cocoyl glycinate and 39.98 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 500 ppm. The mixed solution is fed into a reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 275.15 K.

[0028] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0029] Example 3 The reaction system is a mixed solution of 0.04 g of sodium cocoyl glycinate and 39.96 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 1000 ppm. The mixed solution is fed into a reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 275.15 K.

[0030] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0031] Example 4 The reaction system is a mixed solution of 0.004 g of sodium cocoyl glycinate and 39.996 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 100 ppm. The obtained mixed solution is frozen and crushed into frozen particles with a particle size of 0.1 mm to 1 mm in an environment of -20°C. The frozen particles are sent to the reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 272.15 K.

[0032] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0033] Example 5 The reaction system is a mixed solution of 0.02 g of sodium cocoyl glycinate and 39.98 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 500 ppm. The obtained mixed solution is frozen and crushed into frozen particles with a particle size of 0.1 mm to 1 mm in an environment of -20°C. The frozen particles are sent to the reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 272.15 K.

[0034] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0035] Example 6 The reaction system is a mixed solution of 0.04 g of sodium cocoyl glycinate and 39.96 g of deionized water, wherein the mass fraction of sodium cocoyl glycinate is 1000 ppm. The obtained mixed solution is frozen and crushed into frozen particles with a particle size of 0.1 mm to 1 mm in an environment of -20°C. The frozen particles are sent to the reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 272.15 K.

[0036] The results showed that hydrates were formed rapidly during the entire experiment, indicating that the hydrate promoter had a good effect in promoting hydrate formation.

[0037] Comparative Example 1 The reaction system was 40 g of deionized water. The solution was fed into the reactor. The experimental gas introduced was pure methane. The experimental pressure was 6.0 MPa and the experimental temperature was 275.15 K.

[0038] The results showed that hydrate formation was slow throughout the experiment.

[0039] Comparative Example 2 The reaction system is a mixed solution of 0.02 g of glycine and 39.96 g of deionized water, wherein the mass fraction of glycine is 500 ppm. The mixed solution is fed into the reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 275.15 K.

[0040] The results show that during the entire experiment, the hydrate formation rate was slow and the gas storage capacity was low.

[0041] Comparative Example 3 The reaction system is a mixed solution of 0.02 g of sodium dodecyl sulfate and 39.96 g of deionized water, wherein the mass fraction of sodium dodecyl sulfate is 500 ppm. The mixed solution is fed into the reactor, the experimental gas introduced is pure methane, the experimental pressure is 6.0 MPa, and the experimental temperature is 275.15 K.

[0042] The results showed that hydrates formed rapidly throughout the experiment, but the gas storage capacity was low.

[0043] Table 1 shows the induction time of the embodiments and comparative examples. T 90 (the time required for the gas storage volume to reach 90% of the final gas storage volume) and the final gas storage volume.

[0044] Table 1 Summary of results

[0045] As can be seen from Table 1, the use of N-acylamino acid type surfactant as a gas hydrate formation promoter can greatly increase the formation rate and gas storage capacity of gas hydrates and improve the gas storage efficiency.

[0046] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. Application of N-acylamino acid type surfactant as hydrate formation promoter, characterized in that: The general structural formula of the N-acylamino acid type surfactant is as follows: ， Wherein, R is selected from one of lauroyl, coconut oil acyl and oleic acid; R1 and R2 are independently selected from one of glutamic acid, glycine, alanine and sarcosine.

2. A method for preparing gas hydrates using an N-acylamino acid type surfactant as a hydrate formation promoter, characterized in that: N-acylamino acid type surfactant is added to water as a hydrate formation promoter to form a mixed solution, and then gas is introduced to react, thereby obtaining a solid gas hydrate.

3. The method according to claim 2, characterized in that The amount of the N-acylamino acid type surfactant added to water is 50 ppm to 5000 ppm.

4. The method according to claim 2, characterized in that: The mixed solution was frozen and pulverized into particles for use.

5. The method according to claim 4, characterized in that The particle size of the particles is 0.1 mm to 1 mm.

6. The method according to claim 2, characterized in that The gas is methane, ethane, propane, ethylene, hydrogen, hydrogen sulfide, oxygen, nitrogen, argon, krypton or xenon which is hardly soluble in water.

7. The method according to claim 2, characterized in that: The reaction is carried out at a temperature of 268.15-288.15 K and a pressure of 0.5-15.0 MPa for a time of 0.5-12 h.

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