Desulfurization solvent for deeply removing hydrogen sulfide and organic sulfur as well as preparation method and application thereof

Abstract

The invention discloses a desulfurization solvent for deeply removing hydrogen sulfide and organic sulfur and application of the desulfurization solvent. The desulfurization solvent is a mixture. The desulfurization solvent comprises the following components in percentage by mass: 10-40% of di-iso-hexyl secondary amine, 10-20% of bicyclo-tertiary amine, 10-30% of ether and the balance of water, and the water content is greater than or equal to 10%. And the bicyclic amine and the isohexyl secondary amine form a dual steric hindrance effect in the solvent. By introducing ether, on one hand, the dissolvability of the solvent to organic sulfur is improved, and on the other hand, the concentration of amine ions in di-iso-hexylsecondary amine is reduced, so that the absorption of carbon dioxide is reduced, the method is suitable for feed gas mainly containing mercaptan, especially feed gas with mercaptan as high as 500mg / m < 3 > or above, and under the condition that the purified gas reaches the standard, the load of desulfurization agent regeneration is reduced, and the desulfurization efficiency is improved. Therefore, the energy consumption of desulfurizing agent regeneration is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas desulfurization, and in particular to a desulfurization solvent for deeply removing hydrogen sulfide and organic sulfur, and a preparation method and application thereof. Background Art

[0002] Most of the extracted natural gas contains acidic components such as hydrogen sulfide, carbon dioxide, and organic sulfur (carbonyl sulfide, mercaptan, and sulfide). GB17820-2018 Natural Gas sets index requirements for natural gas entering the long-distance pipeline network, which stipulates that the hydrogen sulfide content of purified gas should be ≤6mg / m 3 , carbon dioxide ≤ 3%, total sulfur ≤ 20mg / m 3 , mainly for hydrogen sulfide and total sulfur. For the mercaptan content in the raw gas exceeding 500mg / m 3 In this case, it is difficult for the existing desulfurization solvent to achieve a total sulfur content of ≤20mg / m 3 , and the existing solvents need to remove almost all carbon dioxide when removing hydrogen sulfide and mercaptans, resulting in low acid gas concentration in the sulfur recovery unit, high solution acid gas load, increased circulation volume, increased steam consumption, and increased operating energy consumption. Summary of the invention

[0003] The present invention is aimed at the mercaptan content in the raw gas exceeding 500mg / m 3 In this case, it is difficult for the existing desulfurization solvent to achieve a total sulfur content of ≤20mg / m 3 , and the existing solvents need to remove almost all carbon dioxide when removing hydrogen sulfide and mercaptans, resulting in low acid gas concentration in the sulfur recovery unit, high solution acid gas load, increased circulation volume, increased steam consumption, and increased operating energy consumption.

[0004] The invention provides a desulfurization solvent for deeply removing hydrogen sulfide and organic sulfur. The desulfurization solvent is a mixture; the desulfurization solvent comprises the following components by mass percentage: 10-40% of diisohexyl secondary amine, 10-20% of bicyclic tertiary amine, 10-30% of ether, and the balance is water with a water content of ≥10%.

[0005] The molecular structure of the diisohexyl secondary amine of the present invention has amino groups with active hydrogen atoms at both ends, and the solvent has strong alkalinity, and can react chemically with hydrogen sulfide and mercaptan to achieve a good removal effect and improve the removal depth. Under this alkaline condition, conventional solvents will also remove a large amount of carbon dioxide, but the diisohexyl secondary amine in the present invention has an isohexyl group in its molecular structure, and the isohexyl group is a steric hindrance group with a very strong steric hindrance effect. Two isohexyl groups are introduced into the molecular structure of the diisohexyl secondary amine of the present invention, which has an obstructive effect on carbon dioxide and can reduce the removal of carbon dioxide under high alkalinity conditions. Secondly, the isohexyl secondary amine has at least one hydroxyl group and is highly water-soluble.

[0006] Strong basic substances in the solvent help provide the H⁺ ions required for the nucleophilic substitution reaction. Under the strong basic conditions provided by diisopropylamine, the nitrogen atom in the -NH 2 group in the bicyclic amine attacks the sulfur atom in the thiol, and a nucleophilic reaction occurs, forming a thiourea group between the sulfur atom and the nitrogen atom. In this way, deep removal of thiol is achieved.

[0007] Ether compounds play a dual role in the solvent. On the one hand, the solubility of organic sulfur in ether solvents is greater than that in water, which plays a role in dissolving organic sulfur. On the other hand, both water and ether are neutral solvents, and the autoprotolysis constant and dielectric constant of the solvent itself determine the ease of dissociation of compounds in it. A large dielectric constant can weaken the attraction between opposite charges and help the dissociation of compounds in the solvent. Autoprotolysis constant of water: K 自 = [OH - [H + = 10 -14 mol·L -2 , and the dielectric constant is 78.39. The dielectric constant of ether solvents < 10, which is much smaller than that of water. Therefore, amine compounds are easily dissociated in water and not easily dissociated in ether compounds. Using this principle, in the present invention, an ether solvent is added to the system of diisopropylamine and bicyclic amine, which reduces the dissociation of amine to a certain extent, thereby reducing the concentration of ammonium ions in the solution. Compared with carbon dioxide, hydrogen sulfide is more acidic and more likely to react with amines. When the concentration of ammonium ions in the solution decreases, the reaction with hydrogen sulfide will be guaranteed first, and then the reaction with carbon dioxide will occur. Therefore, when the concentration of ammonium ions decreases, the removal rate of carbon dioxide by the solvent decreases. After the ether compound is added to the solvent system, it not only plays a role in increasing the removal rate of organic sulfur, but also plays a role in increasing selectivity and reducing the removal rate of carbon dioxide in synergy with diisopropylamine, achieving unexpected effects.

[0008] As a possible design, the desulfurization solvent comprises the following components in mass percentages: 30 - 40% of diisopropylamine, 10 - 20% of bicyclic tertiary amine, 20 - 30% of ether, and the balance is water with a water content ≥ 10%.

[0009] As a possible design, the desulfurization solvent comprises the following components in mass percentages: 40% of diisopropylamine, 20% of bicyclic tertiary amine, 30% of ether, and 10% of water.

[0010] As a possible design, the structural formula of the bicyclic amine is as follows:

[0011]

[0012] In the bicyclic amine described in the present invention, a methyl group or a propyl group is linked to the cyclic nitrogen atom. These two groups make the molecular structure have a steric hindrance effect, and the reaction rate of reacting with carbon dioxide to form carbamate becomes lower. In the solvent, the bicyclic amine and the isohexyl secondary amine form a double steric hindrance.

[0013] As a possible design, the ether solvent is one of tripropylene glycol monomethyl ether and triethylene glycol monomethyl ether. As a possible design, the structural formula of the diisohexyl secondary amine is as follows:

[0014]

[0015] Among them, R 1 It is hydrogen, methyl, ethyl or an alkyl group having more than 2 carbon atoms.

[0016] The invention also discloses a method for preparing the desulfurization solvent, which comprises adding diisohexyl secondary amine, dicyclic amine and ether into water, and stirring at room temperature for 10 to 40 minutes to obtain the desulfurization agent.

[0017] The beneficial effects of the present invention are:

[0018] 1. The desulfurization solvent disclosed in the present invention can effectively remove hydrogen sulfide and mercaptans in the raw gas, and can reduce the absorption of carbon dioxide to the greatest extent, thereby reducing the load of the desulfurization agent regeneration system.

[0019] 2. The desulfurization solvent disclosed in the present invention is suitable for raw gas with high mercaptan content, especially for raw gas with mercaptan content greater than 500 mg / m 3 of raw gas.

[0020] 3. The diisohexyl secondary amine provided by the present invention has a strong steric hindrance effect on carbon dioxide and can improve the removal effect of hydrogen sulfide; it contains two secondary amine groups, provides active H atoms, has strong solvent alkalinity, and can react chemically with hydrogen sulfide and mercaptan to achieve the purpose of deep removal of hydrogen sulfide and organic sulfur;

[0021] 4. The bicyclic amine in the present invention can react with thiols to generate thiourea groups, thereby increasing the removal depth of thiols. At the same time, in the bicyclic amine described in the present invention, a methyl group or a propyl group is linked to the cyclic nitrogen atom, and these two groups make the molecular structure have a steric effect, and the bicyclic amine and the isohexyl secondary amine form a double steric effect in the solvent.

[0022] 5. The ether compound introduced in the present invention, on the one hand, improves the solubility of the solvent for organic sulfur, and on the other hand, reduces the concentration of amine ions in diisohexyl secondary amine, thereby reducing the absorption of carbon dioxide, which helps to retain carbon dioxide in the purified gas. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0025] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientation or positional relationships, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0027] The desulfurization evaluation device used in the following embodiments and comparative examples is a common evaluation device in the art and will not be described in detail in the present invention.

[0028] Comparative Example

[0029] The desulfurizing agent in this comparative example is obtained by dissolving diisohexyl secondary amine in water, wherein the molecular structure of diisohexyl secondary amine is as follows:

[0030] Where R 1 It is hydrogen, and its molecular formula is: C 13 H 30 ON 2 The mass percentages of diisohexyl secondary amine and water are 40% and 60% respectively.

[0031] In this comparative example, diisohexyl secondary amine and water are mixed, the mixing temperature is controlled within the range of 20 to 30° C., the mixing time is 40 minutes, and the stirring speed can be 50 r / min to obtain a desulfurizing agent.

[0032] The desulfurization agent in this comparative example was evaluated using a desulfurization evaluation device, and the evaluation results are shown in Table 1.

[0033] Table 1

[0034]

[0035] It can be seen from Table 1 that when only diisohexyl secondary amine is used, the mercaptan content is greater than 500 mg / m 3 When the raw gas is desulfurized, although the carbon dioxide content in the purified gas meets the standard, the contents of hydrogen sulfide and mercaptan do not meet the standard, and the carbon dioxide removal rate is above 72%.

[0036] Example 1

[0037] In this embodiment 1, the desulfurizing agent is obtained by dissolving diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine in water, wherein the molecular structure of diisohexyl secondary amine is as follows:

[0038] Where R 1 It is hydrogen, and its molecular formula is: C 13 H 30 ON 2 The mass percentages of diisohexyl secondary amine, 2-methyl-2-azabicyclo[2.2.2]-5-octylamine and water are 40%, 20% and 40% respectively.

[0039] In this embodiment 1, diisohexyl secondary amine, 2-methyl-2-azabicyclo[2.2.2]-5-octylamine and water are mixed, the mixing temperature is controlled within the range of 20 to 30° C., the mixing time is 20 minutes, and the stirring speed can be 40 r / min to obtain a desulfurizing agent.

[0040] The desulfurization agent in Example 1 was evaluated using a desulfurization evaluation device. The evaluation results are shown in Table 2.

[0041] Table 2

[0042]

[0043] As shown in Table 2, by adding 2-methyl-2-azabicyclo[2.2.2]-5-octylamine to the system of Comparative Example 1, the contents of carbon dioxide, hydrogen sulfide and methyl mercaptan in the purified gas obtained all meet the requirements of GB17820-2018 "Natural Gas" that the content of hydrogen sulfide in the purified gas is ≤6 mg / m 3 , carbon dioxide ≤ 3%, total sulfur ≤ 20mg / m 3 At the same time, the removal rate of carbon dioxide decreased and the removal rate of mercaptan increased, indicating that diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine have a synergistic effect.

[0044] Example 2

[0045] In this embodiment 2, the desulfurizing agent is obtained by dissolving diisohexyl secondary amine, 2-methyl-2-azabicyclo[2.2.2]-5-octylamine, and tripropylene glycol monomethyl ether in water, wherein the molecular structure of diisohexyl secondary amine is as follows:

[0046] Where R 1 It is hydrogen, and its molecular formula is: C 13 H 30 ON 2 The mass percentages of diisohexyl secondary amine, 2-methyl-2-azabicyclo[2.2.2]-5-octylamine, tripropylene glycol monomethyl ether and water are 40%, 20%, 30% and 10% respectively.

[0047] In this embodiment 2, diisohexyl secondary amine, 2-methyl-2-azabicyclo[2.2.2]-5-octylamine, tripropylene glycol monomethyl ether and water are mixed, the mixing temperature is controlled within the range of 20 to 30° C., the mixing time is 40 minutes, and the stirring speed can be 50 r / min to obtain a desulfurizing agent.

[0048] The desulfurization agent in Example 2 was evaluated using a desulfurization evaluation device. The evaluation results are shown in Table 3.

[0049] Table 3

[0050]

[0051]

[0052] As shown in Table 3, by adding tripropylene glycol monomethyl ether to the system of Example 1, the contents of carbon dioxide, hydrogen sulfide and methyl mercaptan in the purified gas obtained all meet the requirements of GB17820-2018 "Natural Gas" that the content of hydrogen sulfide in the purified gas is ≤6 mg / m 3 , carbon dioxide ≤ 3%, total sulfur ≤ 20mg / m 3 At the same time, compared with Example 1, the carbon dioxide removal rate is reduced and the mercaptan removal rate is increased, indicating that tripropylene glycol monomethyl ether can promote the removal of diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine to remove mercaptans, while reducing the removal of carbon dioxide.

[0053] From Examples 1-2 and Comparative Example 1, it can be seen that the use of diisohexyl secondary amine alone has a significant effect on the degradation of high sulfur raw gas (thiol content greater than 500 mg / m 3) is used for desulfurization, the sulfur content and hydrogen sulfide content in the purified gas are not up to standard, but the carbon dioxide content is up to standard, and the removal rate of carbon dioxide is high, and the load of subsequent regeneration of the desulfurizer is large. When diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine are used in combination, the sulfur content, hydrogen sulfide content and carbon dioxide content in the purified gas are up to standard, and the removal rate of carbon dioxide is low, which reduces the load of subsequent regeneration of the desulfurizer, indicating that diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine have a synergistic effect. When ether compounds (such as tripropylene glycol monomethyl ether) were added to the system obtained by compounding diisohexyl secondary amine and 2-methyl-2-azabicyclo[2.2.2]-5-octylamine, the removal rates of hydrogen sulfide and methyl mercaptan continued to increase, while the removal rate of carbon dioxide decreased, further reducing the load of carbon dioxide removal in the desulfurizer, indicating that the addition of tripropylene glycol monomethyl ether can promote the removal rates of hydrogen sulfide and methyl mercaptan, and is worthy of promotion and use.

[0054] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0055] 1. The desulfurization solvent disclosed in the present invention can effectively remove hydrogen sulfide and mercaptans in the raw gas, and can reduce the absorption of carbon dioxide to the greatest extent, thereby reducing the load of the desulfurization agent regeneration system.

[0056] 2. The desulfurization solvent disclosed in the present invention is suitable for raw gas with high mercaptan content, especially for raw gas with mercaptan content greater than 500 mg / m 3 of raw gas.

[0057] 3. The diisohexyl secondary amine provided by the present invention has a strong steric hindrance effect on carbon dioxide and can improve the removal effect of hydrogen sulfide; it contains two secondary amine groups, provides active H atoms, has strong solvent alkalinity, and can react chemically with hydrogen sulfide and mercaptan to achieve the purpose of deep removal of hydrogen sulfide and organic sulfur;

[0058] 4. In the present invention, the diisohexyl secondary amine is dissolved in water, making the solution alkaline, which helps to provide the H ions required for the nucleophilic substitution reaction. Under alkaline conditions, the -NH 2 The nitrogen atom in the group attacks the sulfur atom in the thiol, a nucleophilic reaction occurs, and the sulfur atom and the nitrogen atom generate a thiourea group, thereby increasing the removal depth of the thiol. At the same time, in the bicyclic amine described in the present invention, a methyl group or a propyl group is linked to the cyclic nitrogen atom, and these two groups make the molecular structure have a steric effect, and the bicyclic amine and the isohexyl secondary amine form a double steric hindrance in the solvent.

[0059] 5. The ether compound introduced in the present invention improves the solubility of the solvent for organic sulfur on the one hand, and reduces the concentration of amine ions in diisohexyl secondary amine on the other hand. Compared with carbon dioxide, hydrogen sulfide is more acidic and more likely to react with amines. When the concentration of amine ions in the solution is reduced, the reaction with H 2 S reacts first, and then reacts with carbon dioxide, so the removal rate of carbon dioxide by the solvent decreases as the concentration of amine ions decreases. After the ether compound is added to the solvent system, it not only improves the removal rate of organic sulfur, but also improves the selectivity under the synergistic effect with diisohexyl secondary amine, thereby reducing the absorption of carbon dioxide and helping to retain carbon dioxide in the purified gas.

[0060] In practical applications, the 2-methyl-2-azabicyclo[2.2.2]-5-octylamine in Examples 1 and 2 can also be replaced by a substance with the following molecular structure:

[0061]

[0062] In practical application, the tripropylene glycol monomethyl ether in Example 2 can be replaced by diethylene glycol ethyl ether or triethylene glycol ethyl ether.

[0063] In practical application, R in the diisohexyl secondary amine in Examples 1-2 and Comparative Example 1 1 It can be replaced by methyl, ethyl or alkyl with carbon number greater than 2, which does not affect the desulfurization effect of diisohexyl secondary amine. Further, the alkyl with carbon number greater than 2 is a straight-chain normal alkyl or an isomeric alkyl.

[0064] In practical application, the mass percentage of each component in the desulfurizer can be: 35% to 45% of diisohexyl secondary amine, 15% to 25% of dicyclic amine, 25% to 35% of ether compound, and the balance is water.

[0065] The mass percentage of diisohexyl secondary amine can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45% and any value between any two values.

[0066] The mass percentage of dicyclomine can specifically be: 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% and any value between any two values.

[0067] The mass percentage of the ether compound can specifically be: 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% and any value between any two values.

[0068] When the desulfurizing agent is actually prepared, the main steps are: adding diisohexyl secondary amine, dicyclic amine and / or ether compounds to water according to the mass percentage of each component, heating to a reference temperature, and stirring at a reference speed for a reference time.

[0069] The reference temperature is 20-30°C, the reference speed is 30r-50r / min, and the reference time is 10-40min.

[0070] Generally, the reference time is determined by the reference speed and reference temperature. When the reference temperature is constant, the higher the reference speed, the shorter the reference time, and vice versa.

[0071] When the reference speed is constant, the higher the reference temperature, the shorter the reference time, and vice versa.

[0072] Diisohexyl secondary amine, dicyclic amine and ether compounds are all common substances in the art, and their preparation is not described in detail in the present invention.

[0073] The equipment involved in the process of preparing the desulfurizing agent are all commonly used equipment in the art, such as a magnetic stirrer, and the equipment is not described in detail in the present invention.

[0074] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur, Features: The desulfurization solvent is a mixture; the desulfurization solvent comprises the following components by mass percentage: 10-40% of diisohexyl secondary amine, 10-20% of bicyclic tertiary amine, 10-30% of ether, and the balance is water with a water content of ≥10%.

2. The desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to claim 1, Features: The desulfurization solvent comprises the following components in percentage by mass: 30-40% of diisohexyl secondary amine, 10-20% of bicyclic tertiary amine, 20-30% of ether, and the balance is water with a water content of ≥10%.

3. The desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to claim 1, Features: The desulfurization solvent comprises the following components in percentage by mass: 40% of diisohexyl secondary amine, 20% of bicyclic tertiary amine, 30% of ether, and 10% of water.

4. A desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to any one of claims 1 to 3, Features: The structural formula of the dicyclomine is shown below:

5. A desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to any one of claims 1 to 3, Features: The ether solvent is tripropylene glycol monomethyl ether or triethylene glycol monomethyl ether.

6. A desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to any one of claims 1 to 3, Features: The structural formula of the diisohexyl secondary amine is shown below: Among them, R 1 It is hydrogen, methyl, ethyl or an alkyl group having more than 2 carbon atoms.

7. The desulfurization solvent for deep removal of hydrogen sulfide and organic sulfur according to claim 6, Features: The structural formula of the diisohexyl secondary amine is shown below:

8. A method for preparing the desulfurization solvent according to any one of claims 1 to 7, Features: Add diisohexyl secondary amine, then add dicycloamine, then add ether into water, and stir at room temperature for 10 to 40 minutes to obtain the desulfurizing agent.

9. Use of the desulfurization solvent according to any one of claims 1 to 7 in natural gas purification.

10. Use of the desulfurization solvent according to claim 9 in natural gas purification, Features: The mercaptan content in the natural gas is greater than 500 mg / m 3 .

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