Natural gas desulfurization compound solvent as well as preparation method and application thereof

Abstract

The invention provides a natural gas desulfurization compound solvent as well as a preparation method and application thereof. The natural gas desulfurization compound solvent is prepared from the following components in parts by weight: 10 to 30 parts of diisohexyltertiary amine, 2 to 10 parts of sulfolane, 15 to 25 parts of N-methyldiethanolamine, 8 to 15 parts of nitrogen-containing heterocyclic compound and the balance of deionized water, and the nitrogen-containing heterocyclic compound comprises N-hydroxyethyl piperazine and / or N-hydroxypropyl piperazine. The bis-iso-hexyl tertiary amine, the N-methyldiethanolamine and the nitrogen-containing heterocyclic compound cooperate to reduce the absorption of carbon dioxide by improving the selectivity of organic sulfur, so that the removal efficiency of the organic sulfur in the natural gas is improved, and finally the purpose of improving the quality of the acid gas is achieved.

Description

Technical Field

[0001] This invention belongs to the field of gas purification, and relates to a natural gas desulfurization compound solvent, its preparation method, and its application. Background Technology

[0002] In the oil and gas industry, light hydrocarbon streams such as natural gas and refinery gas typically contain large amounts of H2S, CO2, and a certain amount of acidic impurities such as organic sulfur. Organic sulfur includes various forms such as carbonyl sulfide, thiols, and thioethers, with carbonyl sulfide and thiols being the most common forms in gaseous gases. In recent years, the state has imposed stringent requirements on hydrogen sulfide and total sulfur in purified gases.

[0003] Organic sulfur compounds have high activation energies, making it difficult for conventional solvents to react deeply with them, resulting in low removal rates of organic sulfur by current desulfurization solvents. When the organic sulfur content in the feed gas is high, it is difficult to ensure compliance with standards, and the product gas still carries the risk of exceeding total sulfur limits. When the organic sulfur content in the feed gas is high, only a complete removal type desulfurization solvent can meet the requirements for achieving product gas compliance. However, the complete removal type solution preferentially removes carbon dioxide from the feed gas while removing organic sulfur, making it difficult to balance the removal rate of carbonyl sulfur and the retention rate of carbon dioxide in terms of reaction selectivity. This leads to problems such as high regeneration energy consumption, poor acid gas quality, and reduced purification economics. Patent CN106823744A discloses a highly selective low eutectic compound desulfurizing agent, but this solvent has not demonstrated good removal performance for organic sulfur and is not suitable for gases with high organic sulfur content. Zhang F, Shen B, Sun H, et al. Rational Formulation Design and Commercial Application of a NewHybrid Solvent for Selectively Removing H2S and Organosulfurs from SourNatural Gas[J]. Energy & Fuels, 2015, 30(1): 12-19. The reported UDS-2 desulfurization solvent can effectively remove hydrogen sulfide from acid gas, but its effect on the removal of organic sulfur is not good, and it is not suitable for complex gases with high carbon and sulfur content.

[0004] Therefore, it is of great significance to develop a desulfurization compound solvent that can improve the quality of acid gas, promote efficient sulfur conversion, and reduce operating energy consumption. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a natural gas desulfurization compound solvent, its preparation method, and its application. This invention involves compounding diisohexyl tertiary amine, sulfolane, N-methyldiethanolamine, and nitrogen-containing heterocyclic compounds to obtain the natural gas desulfurization compound solvent. The nitrogen-containing heterocyclic compounds include N-hydroxyethylpiperazine and / or N-hydroxypropylpiperazine. The synergistic effect of diisohexyl tertiary amine, N-methyldiethanolamine, and the nitrogen-containing heterocyclic compounds can improve the selectivity for organic sulfur and reduce the absorption of carbon dioxide, thereby enhancing the removal efficiency of organic sulfur from natural gas and ultimately improving the quality of acid gas.

[0006] This invention provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight:

[0007] 10–30 parts diisohexyl tertiary amine, 2–10 parts sulfolane, 15–25 parts N-methyldiethanolamine, 8–15 parts nitrogen-containing heterocyclic compounds, balance deionized water;

[0008] The nitrogen-containing heterocyclic compounds include N-hydroxyethylpiperazine and / or N-hydroxypropylpiperazine.

[0009] In one optional embodiment, the desulfurization compound solvent comprises the following components in parts by weight:

[0010] 20-30 parts of diisohexyl tertiary amine, 8-10 parts of sulfolane, 15-20 parts of N-methyldiethanolamine, and 10-12 parts of the nitrogen-containing heterocyclic compound, with the balance being deionized water.

[0011] In one optional embodiment, the desulfurization compound solvent comprises the following components in parts by weight:

[0012] 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 20 parts of N-methyldiethanolamine, and 12 parts of the nitrogen-containing heterocyclic compound, with the remainder being deionized water.

[0013] In one optional embodiment, the total amine concentration of the desulfurization compound solvent is 25 wt% to 55 wt%.

[0014] In one optional embodiment, the total amine concentration of the desulfurization compound solvent is 40 wt% to 45 wt%.

[0015] The present invention also provides a method for preparing the natural gas desulfurization compound solvent as described above, comprising the following steps:

[0016] 10-30 parts of diisohexyl tertiary amine, 2-10 parts of sulfolane, 15-25 parts of N-methyldiethanolamine, and 8-15 parts of nitrogen-containing heterocyclic compounds are mixed to obtain a mixture; deionized water is added to the mixture to obtain the natural gas desulfurization compound solvent.

[0017] In one optional embodiment, the desulfurization compound solvent is used to desulfurize the natural gas.

[0018] In one optional embodiment, the temperature of the desulfurization treatment is 30–40°C.

[0019] In one optional embodiment, the total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–900 mg / Nm³. 3 .

[0020] In one optional embodiment, the total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–500 mg / Nm³. 3 .

[0021] The implementation of this invention has at least the following advantages:

[0022] 1) The natural gas desulfurization compound solvent of this invention uses diisohexyl tertiary amine and N-methyldiethanolamine as dual-base catalysts to hydrolyze carbonyl sulfide, generating hydrogen sulfide and carbon dioxide. Nitrogen-containing heterocyclic compounds react with hydrogen sulfide to form the corresponding salts. Diisohexyl tertiary amine, as a sterically hindered amine, reduces the solvent's absorption of carbon dioxide and promotes the hydrolysis of carbonyl sulfide. This invention improves the selective absorption efficiency of organic sulfur in natural gas by increasing the solvent's selectivity for organic sulfur, thereby reducing the amount of carbon dioxide absorbed by the solvent and ultimately improving the quality of acid gas. The lower carbon dioxide absorption in the desulfurizing agent also reduces the regeneration load of the desulfurizing agent, which is beneficial for its recycling and shortens the desulfurization time.

[0023] 2) The natural gas desulfurization compound solvent of the present invention also contains sulfolane as a co-solvent, which can promote the dissolution of organic sulfur and thus improve the removal efficiency of organic sulfur in natural gas. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] The first aspect of this invention provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight:

[0026] 10–30 parts diisohexyl tertiary amine, 2–10 parts sulfolane, 15–25 parts N-methyldiethanolamine, 8–15 parts nitrogen-containing heterocyclic compounds, balance deionized water;

[0027] The nitrogen-containing heterocyclic compounds include N-hydroxyethylpiperazine and / or N-hydroxypropylpiperazine.

[0028] This invention utilizes diisohexyl tertiary amine and N-methyldiethanolamine as dual-base catalysts. The natural gas desulfurization compound solvent includes diisohexyl tertiary amine, a sterically hindered amine. Steroidally hindered amines are organic amine compounds with steric hindrance effects; one or two hydrogen atoms on their amine group are replaced by a larger alkyl or other group. Steroidally hindered amines possess special chemical properties; when certain components in the acid gas approach these steric groups in their molecules, the groups exert a steric hindrance effect, thereby reducing their reactivity. Adding an appropriate amount of diisohexyl tertiary amine to the natural gas desulfurization compound solvent, under the influence of its steric group, reduces the reaction ratio with carbon dioxide and increases the reaction ratio with organic sulfur, thus improving the selectivity and removal efficiency of organic sulfur. Furthermore, both diisohexyl tertiary amine and N-methyldiethanolamine are basic compounds, which can, to some extent, increase the absorption efficiency of hydrogen sulfide by the desulfurizing agent.

[0029] The natural gas desulfurization compound solvent includes N-methyldiethanolamine. N-methyldiethanolamine primarily acts as a catalyst, catalyzing the formation of hydrogen sulfide and carbon dioxide from carbonyl sulfide. The reaction between N-methyldiethanolamine and carbonyl sulfide is actually a three-step process, including catalytic hydrolysis, proton transfer, and CO2 dissociation. Amine-catalyzed hydrolysis is the rate-determining step. An appropriate amount of N-methyldiethanolamine is beneficial for increasing the rate of carbonyl sulfide hydrolysis, but excessive N-methyldiethanolamine can adversely affect the reaction, including excessive reaction with carbon dioxide affecting selectivity and causing severe corrosion to equipment due to excessive carbon dioxide absorption.

[0030] The co-solvent used in natural gas desulfurization includes sulfolane. On one hand, sulfolane acts as a co-solvent, promoting the dissolution of carbonyl sulfide in the solution system. Sulfolane is an organic compound with a unique structure containing a cyclic structure and two sulfone groups. Due to the polarity of its sulfone groups, sulfolane is miscible with polar organic solvents such as water, alcohols, esters, and ethers. This allows it to form stable complexes with carbonyl sulfide compounds, thus promoting their dissolution. On the other hand, both diisohexyl tertiary amine and N-methyldiethanolamine are hydrophilic, and using sulfolane as a co-solvent also facilitates their miscibility. While an appropriate amount of sulfolane promotes dissolution, excessive amounts will decrease the total amine concentration of the desulfurizing agent, which is detrimental to the reaction.

[0031] Among them, the natural gas desulfurization compound solvent includes nitrogen-containing heterocyclic compounds. After carbonyl sulfide is converted into hydrogen sulfide and carbon dioxide, the nitrogen-containing heterocyclic compounds can rapidly absorb hydrogen sulfide and react with it to form corresponding salt compounds.

[0032] Among them, nitrogen-containing heterocyclic compounds include N-hydroxyethylpiperazine and / or N-hydroxypropylpiperazine. Both N-hydroxyethylpiperazine and N-hydroxypropylpiperazine are piperazine compounds. Piperazine itself is a weakly basic compound. On the one hand, creating an alkaline environment is conducive to the absorption of hydrogen sulfide. On the other hand, the weakly basic nature can reduce the large-scale absorption of carbon dioxide, which is beneficial to the regeneration of the desulfurizing agent.

[0033] The natural gas desulfurization compound solvent also includes deionized water. Deionized water participates in the hydrolysis reaction of carbonyl sulfide as a reactant; an appropriate amount of deionized water can promote the hydrolysis reaction of carbonyl sulfide and improve the removal efficiency of organic sulfur from natural gas by the natural gas desulfurization compound solvent.

[0034] In summary, this invention obtains a natural gas desulfurization compound solvent by synergistically compounding specific mass fractions of diisohexyl tertiary amine, sulfolane, N-methyldiethanolamine, and nitrogen-containing heterocyclic compounds. By improving the selectivity of the solvent for organic sulfur and reducing the amount of carbon dioxide absorbed by the solvent, the absorption efficiency of organic sulfur is improved, ultimately achieving the goal of improving the quality of acid gas.

[0035] In one specific embodiment, the natural gas desulfurization compound solvent comprises the following components in parts by weight:

[0036] 20-30 parts of diisohexyl tertiary amine, 8-10 parts of sulfolane, 15-20 parts of N-methyldiethanolamine, and 10-12 parts of the nitrogen-containing heterocyclic compound, with the balance being deionized water.

[0037] Optimizing the ratio of sulfolane significantly improves the solubility of carbonyl sulfide; optimizing the ratio of diisohexyl tertiary amine and N-methyldiethanolamine significantly promotes the formation of carbonyl sulfide and hydrogen sulfide; and optimizing the ratio of nitrogen-containing heterocyclic compounds increases the absorption rate of hydrogen sulfide while reducing the carbon dioxide absorption rate. Within this preferred range, the natural gas desulfurization compound solvent of the present invention significantly improves the removal efficiency of organic sulfur.

[0038] In one specific embodiment, the natural gas desulfurization compound solvent comprises the following components in parts by weight:

[0039] 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 20 parts of N-methyldiethanolamine, and 12 parts of the nitrogen-containing heterocyclic compound, with the remainder being deionized water.

[0040] The natural gas desulfurization compound solvent prepared according to the above ratio of sulfolane, diisohexyl tertiary amine, N-methyldiethanolamine and nitrogen-containing heterocyclic compounds has a better effect on removing carbonyl sulfur.

[0041] In one specific embodiment, the total amine concentration of the desulfurization compound solvent is 25 wt% to 55 wt%. Here, the total amine concentration refers to the mass concentration of the sum of three types of substances—diisohexyl tertiary amine, N-methyldiethanolamine, and nitrogen-containing heterocyclic compounds—in the natural gas desulfurization compound solvent. Controlling the total amount of these three types of substances within the above range achieves a better effect in removing carbonyl sulfides.

[0042] In one specific embodiment, the total amine concentration of the desulfurization compound solvent is 40wt% to 45wt%. Controlling the total amount of the three types of substances—diisohexyl tertiary amine, N-methyldiethanolamine, and nitrogen-containing heterocyclic compounds—within this range effectively removes carbonyl sulfides.

[0043] Furthermore, the optimal total amine concentration in the desulfurization compound solvent is 40 wt%. Controlling the total amount of the three types of substances—bisisohexyl tertiary amine, N-methyldiethanolamine, and nitrogen-containing heterocyclic compounds—to 40 wt% results in better removal of carbonyl sulfides.

[0044] The second aspect of this invention provides a method for preparing the desulfurization compound solvent of the first aspect. The preparation method is not specifically limited, as long as the diisohexyl tertiary amine, sulfolane, N-methyldiethanolamine, nitrogen-containing heterocyclic compound and water are mixed evenly in proportion.

[0045] In one specific embodiment, the mixture can be prepared according to the following steps:

[0046] 10–30 parts of diisohexyl tertiary amine, 2–10 parts of sulfolane, 15–25 parts of N-methyldiethanolamine, and 8–15 parts of nitrogen-containing heterocyclic compounds were mixed to obtain a mixture; deionized water was added to the mixture to obtain a natural gas desulfurization compound solvent.

[0047] The second aspect of the present invention provides a natural gas desulfurization method, which uses the desulfurization compound solvent provided in the first aspect to desulfurize the natural gas.

[0048] Sulfides in natural gas include inorganic sulfur and organic sulfur. Organic sulfur mainly includes carbonyl sulfur and methanethiol, while inorganic sulfur mainly includes hydrogen sulfide.

[0049] Furthermore, organic sulfur mainly refers to carbonyl sulfur and methanethiol.

[0050] In one specific implementation, the desulfurization treatment temperature is 30–40°C.

[0051] Furthermore, the desulfurization temperature is preferably 35–40°C, more preferably 40°C. When using the natural gas desulfurization compound solvent of the present invention to remove carbonyl sulfide and methanethiol, the removal system temperature is within the above range, exhibiting a significant effect in promoting carbonyl sulfide removal, especially when the removal system temperature is 40°C, where the promoting effect is most pronounced.

[0052] In one specific implementation, the total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–900 mg / Nm³. 3 Total sulfur content includes total organic sulfur content and total inorganic sulfur content. Total organic sulfur content refers to the total amount of sulfur in natural gas bound to organic matter. The national standard GB17820-2018 sets requirements for natural gas entering long-distance pipelines, stipulating that hydrogen sulfide in purified gas should be ≤6 mg / m³. 3 Carbon dioxide ≤3%, total sulfur ≤20mg / m³ 3 It imposes stringent requirements on hydrogen sulfide and total sulfur content.

[0053] In one specific implementation, the total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–500 mg / Nm³. 3 .

[0054] The natural gas desulfurization compound solvent provided by the present invention will be further described below with reference to specific embodiments.

[0055] Unless otherwise specified, the experimental methods used in the following embodiments can be conventional methods in the art.

[0056] In the following embodiments, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.

[0057] Example 1

[0058] 1. This embodiment discloses a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 10 parts of diisohexyl tertiary amine, 2 parts of sulfolane, 15 parts of N-methyldiethanolamine and 8 parts of nitrogen-containing heterocyclic compound; wherein the nitrogen-containing heterocyclic compound is composed of 4 parts of N-hydroxyethylpiperazine and 4 parts of N-hydroxypropylpiperazine.

[0059] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, including the following steps: heating 2 parts of sulfolane at 45°C until it is completely dissolved, then adding 15 parts of N-methyldiethanolamine and stirring for 20 minutes to mix evenly; then adding 10 parts of diisohexyl tertiary amine, 4 parts of N-hydroxyethylpiperazine and 4 parts of N-hydroxypropylpiperazine and stirring, mixing evenly, then adding water to make up to 100 parts, then controlling the temperature program to rise to 50°C in 10 minutes, and continuing to stir for 20 minutes to obtain the natural gas desulfurization compound solvent.

[0060] Example 2

[0061] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components by weight: 20 parts of diisohexyl tertiary amine, 8 parts of sulfolane, 15 parts of N-methyldiethanolamine, and 10 parts of a nitrogen-containing heterocyclic compound, wherein the nitrogen-containing heterocyclic compound consists of 4 parts of N-hydroxyethylpiperazine and 6 parts of N-hydroxypropylpiperazine. 2. This embodiment provides a method for preparing the natural gas desulfurization compound solvent, which is basically the same as in Example 1, except that:

[0062] The natural gas desulfurization compound solvent contains 20 parts of diisohexyl tertiary amine, 8 parts of sulfolane, 15 parts of N-methyldiethanolamine and 10 parts of nitrogen-containing heterocyclic compounds, wherein the nitrogen-containing heterocyclic compounds consist of 4 parts of N-hydroxyethylpiperazine and 6 parts of N-hydroxypropylpiperazine.

[0063] Example 3

[0064] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 20 parts of N-methyldiethanolamine and 12 parts of N-hydroxyethylpiperazine.

[0065] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0066] The natural gas desulfurization compound solvent contains 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 20 parts of N-methyldiethanolamine, and 12 parts of N-hydroxyethylpiperazine.

[0067] Example 4

[0068] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 30 parts of diisohexyl tertiary amine, 8 parts of sulfolane, 20 parts of N-methyldiethanolamine and 10 parts of nitrogen-containing heterocyclic compound; wherein the nitrogen-containing heterocyclic compound includes 5 parts of N-hydroxyethylpiperazine and 5 parts of N-hydroxypropylpiperazine.

[0069] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0070] The natural gas desulfurization compound solvent contains 30 parts of diisohexyl tertiary amine, 8 parts of sulfolane, 20 parts of N-methyldiethanolamine, 5 parts of N-hydroxyethylpiperazine, and 5 parts of N-hydroxypropylpiperazine.

[0071] Example 5

[0072] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 15 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 30 parts of N-methyldiethanolamine, and 10 parts of nitrogen-containing heterocyclic compound; wherein the nitrogen-containing heterocyclic compound includes 5 parts of N-hydroxyethylpiperazine and 5 parts of N-hydroxypropylpiperazine.

[0073] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0074] The natural gas desulfurization compound solvent contains 15 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 30 parts of N-methyldiethanolamine, 5 parts of N-hydroxyethylpiperazine, and 5 parts of N-hydroxypropylpiperazine.

[0075] Example 6

[0076] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 20 parts of diisohexyl tertiary amine, 20 parts of sulfolane, 20 parts of N-methyldiethanolamine, and 10 parts of nitrogen-containing heterocyclic compound; wherein the nitrogen-containing heterocyclic compound comprises 6 parts of N-hydroxyethylpiperazine and 4 parts of N-hydroxypropylpiperazine.

[0077] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0078] The natural gas desulfurization compound solvent contains 20 parts of diisohexyl tertiary amine, 20 parts of sulfolane, 20 parts of N-methyldiethanolamine, 6 parts of N-hydroxyethylpiperazine, and 4 parts of N-hydroxypropylpiperazine.

[0079] Example 7

[0080] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 10 parts of diisohexyl tertiary amine, 20 parts of sulfolane, 10 parts of N-methyldiethanolamine, 3 parts of N-hydroxyethylpiperazine, and 2 parts of N-hydroxypropylpiperazine.

[0081] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0082] The natural gas desulfurization compound solvent contains 10 parts of diisohexyl tertiary amine, 20 parts of sulfolane, 10 parts of N-methyldiethanolamine, 3 parts of N-hydroxyethylpiperazine, and 2 parts of N-hydroxypropylpiperazine.

[0083] Comparative Example 1

[0084] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 25 parts of diisohexyl tertiary amine, 20 parts of N-methyldiethanolamine and 12 parts of N-hydroxyethylpiperazine.

[0085] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0086] The natural gas desulfurization compound solvent contains 25 parts of diisohexyl tertiary amine, 20 parts of N-methyldiethanolamine and 12 parts of N-hydroxyethylpiperazine, but does not contain sulfolane.

[0087] Comparative Example 2

[0088] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 25 parts diisohexyl tertiary amine, 10 parts sulfolane, and 12 parts N-hydroxyethylpiperazine.

[0089] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0090] The natural gas desulfurization compound solvent contains 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane and 12 parts of N-hydroxyethylpiperazine, but does not contain N-methyldiethanolamine.

[0091] Comparative Example 3

[0092] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 10 parts sulfolane, 20 parts N-methyldiethanolamine and 12 parts N-hydroxyethylpiperazine.

[0093] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0094] The natural gas desulfurization compound solvent contains 10 parts sulfolane, 20 parts N-methyldiethanolamine and 12 parts N-hydroxyethylpiperazine, but does not contain diisohexyl tertiary amine.

[0095] Comparative Example 4

[0096] 1. This embodiment provides a natural gas desulfurization compound solvent, comprising the following components in parts by weight: 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane and 20 parts of N-methyldiethanolamine.

[0097] 2. This embodiment provides a method for preparing a natural gas desulfurization compound solvent, which is basically the same as that in Example 1, except that:

[0098] The natural gas desulfurization compound solvent contains 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane and 20 parts of N-methyldiethanolamine, but does not contain nitrogen-containing heterocyclic compounds.

[0099] To facilitate comparison of the components and total amine concentrations of the above examples and comparative examples, the components and total amine concentrations of the natural gas desulfurization compound solvents of Examples 1-10 and Comparative Examples 1-4 are shown in Table 1 below:

[0100] Table 1

[0101]

[0102]

[0103] Test case

[0104] The natural gas desulfurization compound solvent prepared in the above examples and comparative examples was used to desulfurize the feed gas. The feed gas used was a mixture of carbon dioxide, carbonyl sulfide, thiomethyl alcohol, and methane. The specific contents of carbon dioxide, carbonyl sulfide, and methanethiol are shown in Table 2 below.

[0105] Table 2

[0106]

[0107] The natural gas desulfurization compound solvent prepared in the above examples and comparative examples was used to desulfurize the feed gas. The test temperature was 40℃. After desulfurization, the remaining amounts of carbon dioxide, carbonyl sulfide, and methanethiol in the feed gas were measured, and the carbon dioxide removal rate, carbonyl sulfide removal rate, and methanethiol removal rate were calculated. The specific results are shown in Table 3 below:

[0108] Table 3

[0109]

[0110]

[0111] It can be seen from Table 3 above:

[0112] As can be seen from Example 3 and Comparative Example 1, when sulfolane is lacking in the desulfurization system, the removal rates of carbon dioxide, methanethiol and carbonyl sulfur are all reduced, and the contents of the three in the raw gas after desulfurization are all increased.

[0113] As can be seen from Example 3 and Comparative Example 2, when N-methyldiethanolamine is missing in the desulfurization system, the removal rates of carbon dioxide, methanethiol and carbonyl sulfide are all reduced, and the contents of the three in the raw gas after desulfurization are all increased.

[0114] As can be seen from Example 3 and Comparative Example 3, when the desulfurization system lacks diisohexyl tertiary amine, the carbon dioxide removal rate is significantly increased, and the carbon dioxide content in the desulfurized raw gas is significantly reduced, indicating that the addition of diisohexyl tertiary amine can inhibit the removal of carbon dioxide.

[0115] As can be seen from Example 3 and Comparative Example 4, when N-hydroxyethylpiperazine is missing from the desulfurization system, the removal rates of carbon dioxide, methanethiol and carbonyl sulfur are not significantly different.

[0116] During the test, the natural gas desulfurization compound solvent prepared in Example 1 was used to desulfurize the feed gas. The test temperatures were 20℃ and 60℃. After desulfurization, the remaining amounts of carbon dioxide, carbonyl sulfide, and methanethiol in the feed gas were measured, and the carbon dioxide removal rate, carbonyl sulfide removal rate, and methanethiol removal rate were calculated, as shown in Table 4 below:

[0117] Table 4

[0118]

[0119] It can be seen from Table 4 above:

[0120] When the system temperature is 40℃, the removal efficiency of carbon dioxide, carbonyl sulfide and methanethiol is better than that when the system temperature is 20℃, because appropriately increasing the temperature is beneficial to the removal of carbon dioxide, carbonyl sulfide and methanethiol.

[0121] When the system temperature is 40℃, the removal efficiency of carbon dioxide, carbonyl sulfide and methanethiol is better than that when the system temperature is 60℃, because excessively increasing the temperature is not conducive to the removal of carbon dioxide, carbonyl sulfide and methanethiol.

[0122] Experiments showed that when the desulfurization temperature was 35-40℃, the solubilizing effect of sulfolane was particularly significant, which could further shorten the removal time of methanethiol and reduce the methanethiol content to a smaller range, thereby reducing the amount of compound solvent used in natural gas desulfurization.

[0123] The natural gas desulfurization compound solvent disclosed in this invention is particularly suitable for the purification of natural gas with high organic sulfur content, and can reduce the total sulfur content to 20 mg / m³. 3 Furthermore, carbon dioxide levels can be reduced to approximately 3%. Moreover, when the natural gas desulfurization compound solvent of this invention is used in the desulfurization process, the desulfurization effect is better when the desulfurization system temperature is within the range of 35–40°C, and this temperature is easily achievable. In summary, the natural gas desulfurization solvent disclosed in this invention is worthy of widespread use.

[0124] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A natural gas desulfurization compound solvent, characterized in that, The following components are included in parts by weight: 10–30 parts diisohexyl tertiary amine, 2–10 parts sulfolane, 15–25 parts N-methyldiethanolamine, 8–15 parts nitrogen-containing heterocyclic compounds, balance deionized water; The nitrogen-containing heterocyclic compounds include N-hydroxyethylpiperazine and / or N-hydroxypropylpiperazine.

2. The natural gas desulfurization compound solvent according to claim 1, characterized in that, The desulfurization compound solvent comprises the following components in parts by weight: 20-30 parts of diisohexyl tertiary amine, 8-10 parts of sulfolane, 15-20 parts of N-methyldiethanolamine, and 10-12 parts of the nitrogen-containing heterocyclic compound, with the balance being deionized water.

3. The natural gas desulfurization compound solvent according to claim 2, characterized in that, The desulfurization compound solvent comprises the following components in parts by weight: 25 parts of diisohexyl tertiary amine, 10 parts of sulfolane, 20 parts of N-methyldiethanolamine, and 12 parts of the nitrogen-containing heterocyclic compound, with the remainder being deionized water.

4. The natural gas desulfurization compound solvent according to any one of claims 1-3, characterized in that, The total amine concentration of the desulfurization compound solvent is 25 wt% to 55 wt%.

5. The natural gas desulfurization compound solvent according to claim 4, characterized in that, The total amine concentration of the desulfurization compound solvent is 40 wt% to 45 wt%.

6. A method for preparing a natural gas desulfurization compound solvent according to any one of claims 1-5, characterized in that, Includes the following steps: 10-30 parts of diisohexyl tertiary amine, 2-10 parts of sulfolane, 15-25 parts of N-methyldiethanolamine, and 8-15 parts of nitrogen-containing heterocyclic compounds are mixed to obtain a mixture; deionized water is added to the mixture to obtain the natural gas desulfurization compound solvent.

7. A method for desulfurizing natural gas, characterized in that, Natural gas is desulfurized using the desulfurization compound solvent described in any one of claims 1-6.

8. The desulfurization method according to claim 7, characterized in that, The desulfurization treatment temperature is 30–40°C.

9. The preparation method according to claim 7 or 8, characterized in that, The total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–900 mg / Nm³. 3 .

10. The preparation method according to claim 9, characterized in that, The total organic sulfur content in the natural gas, calculated as elemental sulfur, is 300–500 mg / Nm³. 3 .

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