Natural gas complex iron desulfurization solution and preparation method thereof

Abstract

The invention discloses a natural gas complex iron desulfurization solution and a preparation method thereof. The natural gas complex iron desulfurization solution comprises the following raw materials: soluble iron salt, an iron salt complexing agent, a chelating agent, an amino acid compound, inorganic weak acid amine salt, an alkali source and water. The molecular structure of the amino acid compound comprises at least one amino group and at least one carboxylic acid group, or comprises at least one amino group and at least one sulfonic acid group; the inorganic weak acid amine salt is any one or more of phosphoethanolamine and boric acid monoethanolamine. According to the desulfurization solution, the potential stability of iron ions in the alkaline solution is enhanced, the oxidation reduction potential of Fe < 3 + > / Fe < 2 + > is reduced, the desulfurization efficiency is improved, and byproducts are reduced. The treatment effect of the hydrogen sulfide is further improved, so that all the hydrogen sulfide in the tail gas is removed, and the sulfur capacity is improved to 1.0 g / L or above. And the removal rate of carbon dioxide reaches 90% or above.

Description

Technical Field

[0001] This invention belongs to the field of natural gas purification technology, specifically relating to a natural gas complexed iron desulfurization solution and its preparation method. Background Technology

[0002] During natural gas exploration and development, since the majority of the produced natural gas contains sulfur, it needs to undergo desulfurization treatment before entering the gas transmission network and being supplied to downstream users. Generally speaking, for the purification of low-to-medium sulfur content (potential sulfur content S < 50 t / d, especially S < 10 t / d) natural gas with a small processing capacity (below 50 × 10⁴ m³ / d), the following methods are mainly used: for very low potential sulfur content (S ≤ 0.1 t / d), dry desulfurization process is the main method; for high potential sulfur content (S ≥ 5 t / d), amine desulfurization combined with secondary conventional Claus sulfur recovery and tail gas incineration is used; and for medium potential sulfur content (0.1–5 t / d) between the above two, liquid phase oxidation-reduction method is used.

[0003] Under certain circumstances, the above methods all have certain limitations. The main limitations are: dry desulfurization has limited operational flexibility and cannot adapt well to large variations in H2S content; moreover, it generates waste desulfurizing agent that requires further treatment. The amine method combined with conventional Claus and tail gas incineration has a small processing scale and low sulfur recovery rate, resulting in insufficient sulfur dioxide content in the tail gas and causing air pollution; if a tail gas treatment device is installed, it will increase investment costs significantly. In recent years, Southwest Oil and Gas Field Company has developed many new wells. To understand formation conditions, single-well trial production is often conducted. The natural gas production in these trial wells is unstable, with large and fluctuating potential sulfur content, making solid desulfurization unsuitable. The amine method + Claus + tail gas technology is not only complex and resource-intensive, but may also lead to unstable operation and excessive tail gas emissions. Therefore, the complexed iron method liquid-phase oxidation-reduction desulfurization is a better technical choice.

[0004] However, the main limitation of the industrial application of complex iron desulfurization technology is the improvement of sulfur capacity, especially in the exploration and development of natural gas with high sulfur and high carbon dioxide content. The problem of improving sulfur capacity has a more significant impact on the removal efficiency of hydrogen sulfide and carbon dioxide. Summary of the Invention

[0005] The purpose of this patent application is to address the significant impact of the sulfur capacity of the complexing agent on the removal efficiency of hydrogen sulfide and carbon dioxide in the liquid phase redox desulfurization method using complexed iron. This invention provides a natural gas complexed iron desulfurization solution and a method for preparing the desulfurization solution, which improves the sulfur capacity of the desulfurization process and greatly enhances the removal efficiency of hydrogen sulfide, achieving complete removal of hydrogen sulfide and a carbon dioxide removal rate of over 90%.

[0006] This invention is achieved through the following technical solution:

[0007] The first objective of this invention is to provide a natural gas complexed iron desulfurization solution, the raw materials of which include soluble iron salts, iron salt complexing agents, chelating agents, amino acid compounds, inorganic weak acid amine salts, and an alkaline source;

[0008] The molecular structure of the amino acid compound contains at least one amino group and at least one carboxylic acid group, or contains at least one amino group and at least one sulfonic acid group;

[0009] The inorganic weak acid amine salt is any one or more of ethanolamine phosphate and monoethanolamine borate.

[0010] In this embodiment of the invention, a chelating agent with chelating effect is formed using an iron salt complexing agent and a chelating agent. The chelating agent with encapsulation effect can maintain the activity of iron ions, while the complexing agent can enhance the potential stability of iron ions in alkaline solution, effectively preventing the precipitation and loss of iron ions in alkaline solution; it also reduces Fe 3+ / Fe 2+ The redox potential is adjusted to achieve both high desulfurization efficiency and reduced formation of byproducts such as thiosulfate. The chelating agent and Fe... 3+ A complexed Fe state is formed with a redox electrode potential of approximately 0.1V. 3+ L (L represents the complexing agent) has a redox electrode potential of 0.1V, which is much higher than the electrode potential of the H2S(g) / S couple, which is -0.24V (pH=7.0). － Fe 3+ The reaction of L-catalytic oxidation to produce elemental sulfur (S) provides a sufficiently high driving force for the oxidation of H₂S. － The reaction is extremely rapid, shifting the equilibrium towards sulfur formation, resulting in very low hydrogen sulfide content in the exhaust gas and significantly improving desulfurization efficiency. Furthermore, the action of amino groups, carboxylic acid groups, or sulfonic acid groups in amino acid compounds, and the -NH2 group of inorganic weak acid amine salts, further enhances the treatment effect of hydrogen sulfide, completely removing it from the exhaust gas and increasing the sulfur capacity from the existing 0.5 g / L to over 1.0 g / L.

[0011] Therefore, in the embodiments of the present invention, under the combined action of iron salt complexing agent, chelating agent, amino acid compound and inorganic weak acid amine salt, a desulfurization solution with low consumption, strong complexing ability, strong applicability to the use environment, high sulfur capacity and high carbon dioxide removal rate is obtained.

[0012] The amino acid compounds and inorganic weak acid amine salts in the embodiments of this invention can not only improve the desulfurization effect, but also absorb carbon dioxide in natural gas, with a carbon dioxide removal rate of over 90%, which is of great significance in the exploration and development of natural gas with high sulfur and high carbon dioxide content.

[0013] In an optional embodiment, the raw materials, by weight, are: 5 to 20 parts of soluble iron salt, 10 to 25 parts of iron salt complexing agent, 0.2 to 3 parts of chelating agent, 5 to 8 parts of amino acid compound, and 3 to 6 parts of inorganic weak acid amine salt.

[0014] In this embodiment of the invention, the raw materials are rationally compounded to determine the most suitable ratio, and the proportions of iron salt complexing agents and chelating agents are rationally designed to maintain the potential stability of iron ions in alkaline solutions, which is beneficial for reducing Fe. 3+ / Fe 2+ The redox potential of the complexed Fe 3+ Maintaining the difference between the redox potential of L and the electrode potential of the H2S(g) / S couple within a reasonable range improves desulfurization efficiency and effect, and increases sulfur capacity; and rationally designing the ratio of amino acid compounds and inorganic weak acid amine salts to achieve complexation of Fe 3+ The increased solubility of L in alkaline solution further enhances the sulfur capacity. Simultaneously, the appropriate combination of amino acid compounds and inorganic weak acid amine salts also improves the carbon dioxide removal rate.

[0015] In an optional embodiment, the amino acid compound contains 2 to 4 carbon atoms in its molecular structure. Selecting 2 to 4 carbon atoms to form a short-chain molecular structure can reduce the solubility barrier of the amino acid compound in alkaline solutions, and also reduces the likelihood of complexation with Fe. 3+ The steric hindrance during L-interaction is beneficial for improving the complexed state of Fe. 3+ Solubility of L in alkaline solution.

[0016] In an optional embodiment, the amino acid compound is any one or more of alanine, 3-aminopropionic acid, 3-methylaminopropionic acid, N-methylpiperidine-3-carboxylic acid, taurine, carbamate, and methionine.

[0017] In an optional embodiment, the soluble iron salt is ferric nitrate or ferrous sulfate heptahydrate;

[0018] The iron salt complexing agent is any one or more of glutamic acid, diethylenetriaminepentaacetic acid, and hydroxyethylethylenediaminetriacetic acid.

[0019] In an optional embodiment, the chelating agent is any one or more of glucoheponic acid and ethanol digluconic acid.

[0020] In an optional embodiment, the alkali source is ammonium bicarbonate or ammonia.

[0021] In an optional embodiment, the pH of the desulfurization solution is 5 to 13.

[0022] The second objective of this invention is to provide a method for preparing a natural gas complexed iron desulfurization solution, wherein iron salt, complexing agent, and chelating agent are mixed in proportion, an alkali source is added, and the mixture is stirred to obtain a first solution;

[0023] Add amino acid compounds and inorganic weak acid amine salts to the first solution and stir.

[0024] In an optional embodiment, the reaction temperature of the iron salt, complexing agent, and chelating agent is 40–60°C, and the mixture is stirred for 3–5 hours.

[0025] The reaction temperature of the first solution with amino acid compounds and inorganic weak acid amine salts is 50-60℃, and the stirring time is 5 hours.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] (1) The natural gas complexed iron desulfurization solution provided in this embodiment of the invention uses iron salt complexing agents and chelating agents to form a complexing agent with chelating effect, thereby enhancing the potential stability of iron ions in alkaline solution and reducing Fe 3+ / Fe 2+ The oxidation-reduction potential is adjusted to achieve both high desulfurization efficiency and reduced formation of byproducts such as thiosulfate. Furthermore, the treatment effect of hydrogen sulfide is further enhanced by the action of amino groups, carboxylic acid groups, or sulfonic acid groups in amino acid compounds, and the -NH2 group of inorganic weak acid amine salts, resulting in complete removal of hydrogen sulfide from the exhaust gas and increasing the sulfur capacity from the existing 0.5 g / L to over 1.0 g / L. Simultaneously, the removal rate of carbon dioxide reaches over 90%.

[0028] (2) The natural gas complexed iron desulfurization solution provided in this embodiment of the invention, by rationally compounding each raw material and determining the most suitable ratio, can maintain the potential stability of iron ions in the alkaline solution, which is beneficial to reducing Fe 3+ / Fe 2+ The redox potential; and the rational design of the ratio of amino acid compounds and inorganic weak acid amine salts to achieve complexation of Fe 3+ The increased solubility of L in alkaline solution further enhances the sulfur capacity. Simultaneously, the appropriate combination of amino acid compounds and inorganic weak acid amine salts also improves the carbon dioxide removal rate. Attached Figure Description

[0029] Figure 1 The graph shows the maximum iron ion concentration that can be generated in the desulfurization solution obtained from each embodiment and comparative example.

[0030] Figure 2 The graph shows the redox electrode potential results of the desulfurization solutions obtained in each embodiment and comparative example.

[0031] Figure 3 The figure shows the results of forced oxidation experiments on the desulfurization solutions obtained in each embodiment and comparative example. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0033] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known methods have not been specifically described in order to avoid obscuring the invention.

[0034] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0035] In the description of this invention, the terms "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "high," "low," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention.

[0036] Example 1: A natural gas complexed iron desulfurization solution

[0037] The raw material ratio is shown in Table 1 below:

[0038] Table 1

[0039]

[0040] Production process:

[0041] 140 kg of industrial-grade ferrous sulfate heptahydrate (FeSO4·7H2O), 100 kg of glutamic acid, 84 kg of diethylenetriaminepentaacetic acid, 40 kg of hydroxyethylethylenediaminetriacetic acid, 5 kg of glucoheponic acid, and 5 kg of ethanolic digluconic acid were stirred and mixed at room temperature. 247 kg of ammonium bicarbonate was added, followed by 259 kg of water. The mixture was heated to 50°C and stirred in a reaction vessel for 4 hours.

[0042] Add 20 kg of alanine, 40 kg of 3-aminopropionic acid, 40 kg of ethanolamine phosphate, and 20 kg of monoethanolamine borate. Heat to 60°C and continue stirring for 2 hours to form a dark brown-red complexed iron desulfurization solution, formulation 1.

[0043] Example 2: A natural gas complexed iron desulfurization solution

[0044] The raw material ratio is shown in Table 2 below:

[0045] Table 2

[0046]

[0047] Production process:

[0048] 180 kg of industrial grade ferric nitrate nonahydrate (Fe(NO3)3·9H2O), 120 kg of glutamic acid, 60 kg of diethylenetriaminepentaacetic acid, 5 kg of glucoheponic acid, and 10 kg of ethanolic digluconic acid were stirred and mixed at room temperature. 180 kg of ammonium bicarbonate was added, followed by 339 kg of water. The mixture was heated to 50°C and stirred in a reaction vessel for 4 hours.

[0049] Add 40 kg of alanine, 15 kg of 3-methylaminopropionic acid, 35 kg of ethanolamine phosphate, and 16 kg of monoethanolamine borate. Heat to 60°C and continue stirring for 2 hours to form a dark brown-red complexed iron desulfurization solution, formulation 2.

[0050] Example 3: A natural gas complexed iron desulfurization solution

[0051] The raw material ratio is shown in Table 3 below:

[0052] Table 3

[0053]

[0054]

[0055] Production process:

[0056] 60 kg of industrial grade ferric nitrate nonahydrate (Fe(NO3)3.9H2O), 80 kg of ferrous sulfate heptahydrate, 92 kg of glutamic acid, 43 kg of diethylenetriaminepentaacetic acid, 26 kg of hydroxyethyl ethylenediaminetriacetic acid, 8 kg of glucoheponic acid, and 6 kg of ethanolic digluconic acid were stirred and mixed at room temperature. 208 kg of ammonium bicarbonate was added, followed by 355 kg of water. The mixture was heated to 50°C and stirred in a reaction vessel for 4 hours.

[0057] Add 35 kg of alanine, 10 kg of 3-aminopropionic acid, 10 kg of N-methylpiperidine-3-carboxylic acid, 16 kg of methanesulfonic acid, 35 kg of ethanolamine phosphate, and 16 kg of monoethanolamine borate. Heat to 60°C and continue stirring for 4 hours to form a dark brown-red complexed iron desulfurization solution, formulation 3.

[0058] Example 4: A natural gas complexed iron desulfurization solution

[0059] The raw material ratio is shown in Table 4 below:

[0060] Table 4

[0061]

[0062] Production process:

[0063] 140 kg of industrial grade ferrous sulfate heptahydrate, 224 kg of glutamic acid, and 10 kg of ethanol digluconic acid were mixed at room temperature with stirring. 247 kg of ammonium bicarbonate was added, followed by 259 kg of water. The mixture was heated to 50°C and stirred in a reaction vessel for 4 hours.

[0064] Add 20 kg of alanine, 40 kg of 3-methylaminopropionic acid, 40 kg of ethanolamine phosphate, and 20 kg of monoethanolamine borate. Heat to 60°C and continue stirring for 2 hours to form a dark brown-red complexed iron desulfurization solution, formulation 4.

[0065] Example 5: A natural gas complexed iron desulfurization solution

[0066] The raw material ratio is shown in Table 5 below:

[0067] Table 5

[0068]

[0069] Production process:

[0070] 180 kg of industrial grade ferric nitrate nonahydrate, 180 kg of diethylenetriaminepentaacetic acid, 5 kg of glucoheponic acid, and 10 kg of ethanol digluconic acid were mixed at room temperature with stirring. 180 kg of ammonium bicarbonate was added, followed by 339 kg of water. The mixture was heated to 50°C and stirred in a reaction vessel for 4 hours.

[0071] Add 40 kg of alanine, 15 kg of 3-methylaminopropionic acid, and 51 kg of ethanolamine phosphate. Heat to 60°C and continue stirring for 2 hours to form a dark brown-red complexed iron desulfurization solution, formulation 5.

[0072] Example 6: A natural gas complexed iron desulfurization solution

[0073] The raw material ratio is shown in Table 6 below:

[0074] Table 6

[0075]

[0076]

[0077] The production process is the same as in Example 1, and the final product is a dark brown-red complexed iron desulfurization solution formulation 6.

[0078] Example 7: A natural gas complexed iron desulfurization solution

[0079] The raw material ratio is shown in Table 7 below:

[0080] Table 7

[0081]

[0082] The production process is the same as in Example 1, ultimately forming a dark brown-red complexed iron desulfurization solution, formulation 7. Comparative Example 1:

[0083] The raw material ratio table is shown in Table 8 below:

[0084] Table 8

[0085]

[0086]

[0087] Experimental research:

[0088] 1. Study the chelating performance of the desulfurization solutions obtained in each embodiment and comparative example for iron ions.

[0089] Under strongly alkaline conditions (pH 12.0), a higher saturation concentration of iron ions indicates a stronger complexing ability. Equal volumes of desulfurization solutions obtained from each example and comparative example were taken, and the pH was adjusted to 12.0. The maximum iron ion concentration that could be generated in the solution was measured, and the results are shown below. Figure 1 As shown in the image.

[0090] Depend on Figure 1It can be seen that the desulfurization solution maintains the iron ion concentration at a maximum of 0.96–1.105 mol / L. The iron ion concentrations in formulations 1–7 are all increased to a certain extent compared to Comparative Example 1, indicating that the desulfurization solution obtained in the examples has a stronger complexing ability for iron ions than Comparative Example 1, resulting in a higher iron ion concentration.

[0091] 2. Study the redox electrode potentials of the desulfurization solutions obtained in each embodiment and comparative example.

[0092] [Fe] in desulfurization liquid 3+ L] / [Fe 2+ The iron-to-liquid (IL) concentration ratio is one of the most important parameters characterizing the desulfurization process using complexed iron. In practical operation, potentiometric measurement can quickly reflect changes in the IL ratio of the desulfurization liquid.

[0093] The redox electrode potentials of the desulfurization solutions in each example and comparative example were measured, and the results are shown in [the table below]. Figure 2 As shown. By Figure 2 It can be seen that the redox potential of the desulfurization solution obtained by the formulation in the examples is lower than that of the comparative example, indicating that the formulation in the examples can reduce [Fe] 3+ L] / [Fe 2+ The L] concentration ratio is beneficial to the desulfurization reaction and reduces the formation of by-products.

[0094] 3. Study the complexing agent consumption of the desulfurization solutions obtained in each embodiment and comparative example.

[0095] In the laboratory, forced oxidation experiments were conducted on the formulations of Examples and Comparative Example 1 using 1% H2O2. The results of the complexing agent concentration change over time are as follows: Figure 3 As shown. Figure 3 As shown, during the forced oxidation process, initially, due to the high concentration of hydrogen peroxide, there was significant initial oxidation and decomposition. However, after more than 10 hours, oxidation essentially ceased. Formula 5 exhibited the least reduction in oxidation; considering only the forced oxidation aspect, Formula 5 showed lower oxidation consumption compared to the original formula.

[0096] On the other hand, under long-term high sulfur capacity (1.0 g / L) conditions, the complexing agent formulation 5 was tracked and analyzed. The results showed that the new formulation 5 reduced sulfur consumption per ton by more than 5% compared with the formulation of comparative example 1, and had obvious stability.

[0097] 4. Natural gas desulfurization and decarbonization

[0098] Example 1: Using natural gas with an H2S volume content of 1%–2% (15.0–20 g / m³) 3 The CO2 volume content is 2.0%–5.0% (36.8–92.0 g / m³). 3Under a pressure of 3.0 MPa, the desulfurization solution of Formula 1 in Example 1 was passed through the desulfurization solution for 25 seconds, and the contents of hydrogen sulfide and carbon dioxide after removal were measured. The results are shown in Table 9.

[0099] Example 2: The volumetric H2S content in the feedstock natural gas is 1%–5% (15.0–72 g / m³). 3 The CO2 volume content is 2.0%–5.0% (36.8–92.0 g / m³). 3 Under a pressure of 3.0 MPa, it is contacted with the desulfurization solution of Formula 2 for 25 seconds.

[0100] Example 3: The volumetric H2S content in the feedstock natural gas is 0.1%–10% (1.50–143 g / m³). 3 CO2 volume content 1.0%–8.0% (18.5–148 g / m³) 3 Under a pressure of 3.0 MPa, it is contacted with the desulfurization solution of Formula 3 for 25 seconds.

[0101] Examples 4-7: Using the same raw material natural gas as in Example 1.

[0102] Comparative Example 1: The same raw material, natural gas, and conditions as in Example 1 were used.

[0103] Table 9

[0104] Case <![CDATA[H2S content after removal (g / m 3 )]]> <![CDATA[CO2 content after removal (g / m 3 )]]> Example 1 Not detected 3.6～5.2 Example 2 Not detected 2.4～4.6 Example 3 Not detected 2.0～12.0 Example 4 Not detected 3.1～5.0 Example 5 Not detected 2.8～4.7 Example 6 Not detected 2.7～4.8 Example 7 Not detected 3.2～5.0 Comparative Example 1 3.0 7.2～8.3

[0105] It is evident that the desulfurization solution of this invention has a strong complexing ability for iron ions, and can reduce [Fe] 3+ L] / [Fe 2+ The concentration ratio of [L] is favorable for the desulfurization reaction and reduces the formation of by-products. It has low consumption, high stability, can completely remove hydrogen sulfide, has a carbon dioxide removal rate of more than 90%, and a sulfur capacity of up to 1.0 g / L.

[0106] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are 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 within the scope of protection of the present invention.

Claims

1. A natural gas complexed iron desulfurization solution, characterized in that, The raw materials include soluble iron salts, iron salt complexing agents, chelating agents, amino acid compounds, inorganic weak acid amine salts, alkali sources, and water; The molecular structure of the amino acid compound contains at least one amino group and at least one carboxylic acid group, or contains at least one amino group and at least one sulfonic acid group; The inorganic weak acid amine salt is any one or more of ethanolamine phosphate and monoethanolamine borate.

2. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The raw materials, by weight, are as follows: 5 to 20 parts soluble iron salt, 10 to 25 parts iron salt complexing agent, 0.2 to 3 parts chelating agent, 5 to 8 parts amino acid compound, and 3 to 6 parts inorganic weak acid amine salt.

3. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The molecular structure of the amino acid compounds contains 2 to 4 carbon atoms.

4. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The amino acid compound is any one or more of alanine, 3-aminopropionic acid, 3-methylaminopropionic acid, N-methylpiperidine-3-carboxylic acid, taurine, carbamate, and methionine.

5. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The soluble iron salt is ferric nitrate or ferrous sulfate heptahydrate; The iron salt complexing agent is any one or more of glutamic acid, diethylenetriaminepentaacetic acid, and hydroxyethylethylenediaminetriacetic acid.

6. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The chelating agent is any one or more of glucoheponic acid and ethanol digluconic acid.

7. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The alkali source is ammonium bicarbonate or ammonia.

8. The natural gas complexed iron desulfurization solution according to claim 1, characterized in that, The pH of the desulfurization solution is 6.0 to 12.

5.

9. A method for preparing a natural gas complexed iron desulfurization solution according to any one of claims 1 to 8, characterized in that, Iron salt, complexing agent, and chelating agent are mixed in proportion, an alkali source is added, and the mixture is stirred to obtain the first solution. Add amino acid compounds and inorganic weak acid amine salts to the first solution and stir.

10. The method for preparing a natural gas complexed iron desulfurization solution according to claim 9, characterized in that, The reaction temperature for iron salts, complexing agents, and chelating agents is 40–60°C, and the mixture is stirred for 3–5 hours. The reaction temperature of the first solution with amino acid compounds and inorganic weak acid amine salts is 50-60℃, and the stirring time is 5 hours.

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