Determination of iron ion content in gas purification amine solution

Abstract

The present invention discloses a method for determining the iron ion content in a gas purification amine solution, belonging to the field of organic analysis. The method comprises adjusting the pH value of the gas purification amine solution to a set value, then adding a first complexing solution to the gas purification amine solution to obtain a pretreatment solution; treating the pretreatment solution with an ion exchange column to separate the iron ions of different valences in the pretreatment solution to obtain a post-treatment solution; reacting the post-treatment solution with a color-developing solution in a tubular reactor to form derivatives with light-absorbing groups from the iron ions of different valences in the post-treatment solution to obtain a test solution; and measuring the test solution using an absorption spectrophotometer to obtain the content of iron ions of different valences in the gas purification amine solution. The method is simple and reliable, and can complete the measurement of iron ions of different valences through a single injection.

Description

Technical Field

[0001] The invention relates to the field of organic analysis, in particular to a method for determining the iron ion content in a gas purification amine solution. Background Art

[0002] The gas purification amine liquid in natural gas purification plants and refineries contains iron ions of different valences. The determination of the content of iron ions of different valences is of great guiding significance for evaluating the solution load and regeneration effect, as well as for timely adjusting the process parameters of the purification device.

[0003] At present, the analytical methods for the iron ion content in the solution mainly include: atomic absorption spectrometry, inductively coupled plasma spectrometry and chemical method. Among them, atomic absorption spectrometry and inductively coupled plasma spectrometry can only measure the total iron content, and cannot achieve quantitative analysis of the content of iron ions in different valence states. Although the spectrophotometry and volumetric method in the chemical method can measure the content of iron ions in different valence states, their testing steps at least include the following: the iron ion content of a certain valence state must be measured first, then the iron ion in another valence state is converted into the iron ion in this valence state, the total iron ion content after conversion is measured, and then the iron ion content in another valence state is obtained by subtraction. It can be seen that although the chemical method can indirectly measure the content of two valence states of iron ions, it has at least the following disadvantages: complicated steps, long time consumption, low sensitivity, etc.

[0004] It can be seen that it is necessary to provide a method for determining the iron ion content in gas purification amine liquid, which can not only directly measure the content of iron ions in different valence states, but also has the advantages of simple operation and high sensitivity. Summary of the Invention

[0005] In view of this, the present invention provides a method for determining the iron ion content in a gas purification amine solution, which can solve the above technical problems.

[0006] Specifically, the following technical solutions are included:

[0007] A method for determining the iron ion content in a gas purification amine liquid, the method comprising: adjusting the pH value of the gas purification amine liquid to a set value, and then adding a first complexing solution to the gas purification amine liquid to obtain a pretreatment liquid;

[0008] treating the pretreatment liquid through an ion exchange column to separate iron ions of different valence states in the pretreatment liquid to obtain a post-treatment liquid;

[0009] In a tubular reactor, the post-treatment liquid is reacted with a color developing liquid so that the iron ions of different valence states in the post-treatment liquid form derivatives with light-absorbing groups to obtain a test liquid;

[0010] The liquid to be tested is measured by using an absorption spectrophotometer to obtain the content of iron ions of different valence states in the gas purification amine liquid.

[0011] In some possible implementations, adjusting the pH value of the gas-purifying amine liquid to a set value includes: adjusting the pH value of the gas-purifying amine liquid to the set value by dripping an acid solution into the gas-purifying amine liquid.

[0012] In some possible implementations, the acid solution is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0013] In some possible implementations, the first complexing solution includes: a complexing agent and a solvent;

[0014] The complexing agent is selected from at least one of 2,6-pyridinedicarboxylic acid, disodium ethylenediaminetetraacetic acid, sodium ethylenediaminetetramethylenephosphate and 1,10-o-phenanthroline;

[0015] The solvent is selected from at least one of potassium hydroxide, potassium sulfate and formic acid.

[0016] In some possible implementations, when the pretreatment liquid is treated by an ion exchange column, a second complexing solution is used as a washing liquid, so that the pretreatment liquid is brought into the ion exchange column by the second complexing solution;

[0017] The second complexing solution has the same composition as the first complexing solution.

[0018] In some possible implementations, the second complexing solution passes through the ion exchange column at a speed of 0.6 mL / min-1 mL / min.

[0019] In some possible implementations, the ion exchange column is filled with both sulfonic acid type cation exchange filler and quaternary amine type anion exchange filler.

[0020] In some possible implementations, allowing the post-treatment liquid to react with the color-developing liquid in the tubular reactor includes: continuously pumping the color-developing liquid into the tubular reactor at a speed of 0.3 mL / min-0.6 mL / min through a pump, so that the post-treatment liquid reacts with the color-developing liquid.

[0021] In some possible implementations, the color developing solution includes: a color developing agent and a color developing auxiliary agent;

[0022] The color-developing auxiliary agent is selected from at least one of N,N-dimethylethanolamine, ammonium hydroxide, and sodium bicarbonate.

[0023] In some possible implementations, the color developer is at least one of o-phenanthroline, 4-(2-pyridylazo)resorcinol, phenolphthalein, and bromocresol green.

[0024] The beneficial effects of the technical solution provided by the embodiment of the present invention include at least:

[0025] The method for determining the content of iron ions in the gas purification amine liquid provided by the embodiment of the present invention is as follows: before determining the content of iron ions in the gas purification amine liquid, the gas purification amine liquid is pretreated, specifically by adjusting the pH value of the gas purification amine liquid to a set value, eliminating the interference of the sample itself on the eluent, which is conducive to accelerating the coordination process. Then, a first complexing solution is added to the gas purification amine liquid so that the iron ions of different valences are complexed with the complexing agent in the first complexing solution in advance, which can avoid the oxidation of divalent iron ions and ensure that the measurement result is accurate. The treatment liquid is treated by an ion exchange column, so that the iron ions of different valences in the treatment liquid can be separated. In a tubular reactor, the post-treatment liquid can be fully mixed and reacted with the developer so that the iron ions of different valences in the post-treatment liquid form derivatives with light-absorbing groups. In this way, the content of iron ions of different valences in the gas purification amine liquid can be obtained by absorption spectrophotometry. The method for determining the content of iron ions in the gas purification amine liquid can not only directly measure the content of iron ions of different valences, but also has the advantages of simple operation and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A flow chart of a method for determining the iron ion content in an exemplary gas purification amine solution provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To make the technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0029] The embodiment of the present invention provides a method for determining the iron ion content in a gas purification amine solution, as shown in the attached Figure 1 As shown, the method for determining the iron ion content in the gas purification amine solution comprises the following steps:

[0030] Step 1: adjusting the pH value of the gas purification amine solution to a set value, and then adding the first complexing solution to the gas purification amine solution to obtain a pretreatment solution.

[0031] Step 2: The pretreatment liquid is treated by an ion exchange column to separate iron ions of different valence states in the pretreatment liquid to obtain a post-treatment liquid.

[0032] Step 3: In a tubular reactor, the post-treatment liquid is reacted with the color developing liquid so that the iron ions of different valence states in the post-treatment liquid form derivatives with light-absorbing groups to obtain a test liquid.

[0033] Step 4: Measure the test liquid using the spectrophotometric method to obtain the content of iron ions of different valence states in the gas purification amine liquid.

[0034] The method for determining the content of iron ions in the gas purification amine liquid provided by the embodiment of the present invention is as follows: before determining the content of iron ions in the gas purification amine liquid, the gas purification amine liquid is pretreated, specifically by adjusting the pH value of the gas purification amine liquid to a set value, eliminating the interference of the sample itself on the eluent, which is conducive to accelerating the coordination process. Then, a first complexing solution is added to the gas purification amine liquid so that the iron ions of different valences are complexed with the complexing agent in the first complexing solution in advance, which can avoid the oxidation of divalent iron ions and ensure that the measurement result is accurate. The treatment liquid is treated by an ion exchange column, so that the iron ions of different valences in the treatment liquid can be separated. In a tubular reactor, the post-treatment liquid can be fully mixed and reacted with the developer so that the iron ions of different valences in the post-treatment liquid form derivatives with light-absorbing groups. In this way, the content of iron ions of different valences in the gas purification amine liquid can be obtained by absorption spectrophotometry. The method for determining the content of iron ions in the gas purification amine liquid can not only directly measure the content of iron ions of different valences, but also has the advantages of simple operation and high sensitivity.

[0035] The following is an exemplary description of the multiple steps involved in the method for determining the iron ion content in the gas purification amine solution:

[0036] For step 1, the pH value of the gas purification amine solution is adjusted to a set value, and then the first complexing solution is added to the gas purification amine solution to obtain a pretreatment solution.

[0037] The pH value of the gas-purifying amine liquid can be adjusted to a set value by adding an acid solution dropwise to the gas-purifying amine liquid.

[0038] It's important to note that when the treatment fluid is subsequently processed through an ion exchange column, an acidic eluent is typically used to introduce the gas-purifying amine solution sample to the treatment system. Since the eluent itself is generally acidic, and the gas-purifying amine solution sample is typically strongly alkaline, this allows the iron ions in the gas-purifying amine solution sample to complex with the complexing agent in the eluent under acidic conditions. Therefore, if the gas-purifying amine solution sample is directly introduced into the eluent without adjusting its acidity, the pH of the eluent will change, preventing the iron ions in the gas-purifying amine solution from being complexed.

[0039] In response to the above problems, in an embodiment of the present invention, the gas purification amine liquid is pretreated, specifically by adjusting the pH value of the gas purification amine liquid to a set value, for example, to a pH value of 3-6, to solve the above technical problems, eliminate the interference of the sample itself on the eluent, and help accelerate the coordination process.

[0040] Therefore, in the embodiment of the present invention, the pH value of the gas purification amine solution is expected to be in the range of 3 to 6. Within this pH value range, the gas purification amine solution can eliminate the interference of the sample itself on the eluent, which is conducive to accelerating the coordination process.

[0041] In some possible implementations, the applicable acid solution is selected from at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0042] After the pH value of the gas-purifying amine liquid is adjusted to the desired range, a first complexing solution is continuously added to the gas-purifying amine liquid to obtain a pretreatment liquid. The first complexing solution includes a complexing agent. In this way, iron ions of different valence states in the gas-purifying amine liquid are complexed with the complexing agent in advance, thereby avoiding the oxidation of divalent iron ions and ensuring accurate measurement results.

[0043] In an embodiment of the present invention, the first complexing solution includes: a complexing agent and a solvent; the complexing agent is selected from at least one of 2,6-pyridinedicarboxylic acid, disodium ethylenediaminetetraacetic acid, sodium ethylenediaminetetramethylenephosphate and 1,10-o-phenanthroline; and the solvent is selected from at least one of potassium hydroxide, potassium sulfate and formic acid.

[0044] Regarding the amount of the first complexing solution added, the concentration of the complexing agent in the gas purification amine solution can be 30-40 mmol / L, for example, 30 mmol / L, 32 mmol / L, 35 mmol / L, 37 mmol / L, 40 mmol / L, etc.

[0045] In the process of adding the first complexing liquid to the gas purification amine liquid to obtain the pretreatment liquid, the following method can be used:

[0046] The complexing agent is mixed with at least one of potassium hydroxide, potassium sulfate and formic acid to form a first complexing solution; the first complexing solution is added to the gas purification amine solution after pH adjustment to obtain a pretreatment solution.

[0047] Wherein, mixing the complexing agent with at least one of potassium hydroxide, potassium sulfate and formic acid is not only beneficial for assisting complexation, but also beneficial for adjusting the pH value of the system.

[0048] Furthermore, when the pretreatment liquid is treated by the ion exchange column, the second complexing solution is used as a rinse solution to carry the pretreatment liquid into the ion exchange column through the second complexing solution. The second complexing solution has the same composition as the first complexing solution, that is, the two have substantially the same composition.

[0049] After the complexing agent and the solvent are mixed, the second complexing solution is used as an eluent in the ion chromatograph where the ion exchange column is located to bring the pretreatment liquid into the ion exchange column and simultaneously carry out a complexing reaction with the iron ions of the gas purification amine solution sample.

[0050] In the embodiment of the present invention, when pretreating the gas purification amine liquid, a first complexing solution having the same composition as the eluent is used for pretreating the gas purification amine liquid. While achieving the above-mentioned pretreatment purpose, interference caused by the additional addition of other substances can also be avoided, making the operation more convenient.

[0051] For example, in the first complexing solution and the second complexing solution, when at least one of potassium hydroxide, potassium sulfate and formic acid is present, the mass ratio of complexing agent: potassium hydroxide is 1:2-4; the mass ratio of complexing agent: potassium sulfate is 1:0.5-1; the mass ratio of complexing agent: formic acid is 1:25-35; and the mass ratio of complexing agent: potassium hydroxide: potassium sulfate: formic acid is 1:2-4:0.5-1:25-35.

[0052] For example, the mass parts of potassium hydroxide include but are not limited to: 2, 2.2, 2.5, 2.8, 3, 3.1, 3.2, 3.3, 3.5, 3.8, etc.;

[0053] The mass fractions of potassium sulfate include but are not limited to: 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc.;

[0054] The mass parts of formic acid include but are not limited to: 25, 26, 27, 28, 29, 30, 31, 32, 33, etc.

[0055] The second complexing solution is mixed with the gas-purifying amine solution as an eluent. The second complexing solution flows through the ion exchange column at a constant flow rate. To maintain a controllable complexing rate and ensure that the iron ions in the gas-purifying amine solution are fully complexed, the second complexing solution flows through the ion exchange column at a rate of 0.6 mL / min to 1 mL / min.

[0056] For example, the flow rate of the second complexing solution in the ion exchange column is 0.6 mL / min, 0.7 mL / min, 0.8 mL / min, 0.9 mL / min, 1 mL / min, etc.

[0057] In step 2, the treatment liquid is treated by an ion exchange column to separate iron ions of different valence states in the treatment liquid to obtain a post-treatment liquid.

[0058] An ion exchange column is a cylindrical pressure vessel used for ion exchange reactions and serves as the exchange equipment for column-based ion exchange. Ion exchange columns are typically cylindrical, with the solution introduced through one end of the column, where it fully contacts the ion exchange medium within the column, allowing ion exchange to occur. Using an ion exchange column involves exchanging the ion exchange medium with the solution in multiple batches.

[0059] For the ion exchange column used in the embodiment of the present invention, the ion exchange column is filled with sulfonic acid type cation exchange filler and quaternary ammonium type anion exchange filler at the same time. The sulfonic acid type cation exchange filler and the quaternary ammonium type anion exchange filler are fully and evenly mixed in the ion exchange column, which can achieve effective separation of iron ions with different valences.

[0060] For example, the mass ratio of the sulfonic acid type cation exchange filler to the quaternary amine type anion exchange filler is 1:1-2, such as 1:1, 1:1.5, etc.

[0061] Sulfonic acid cation exchange resins, also known as sulfonic acid cation exchange resins, are common in the art. Sulfonic acid cation exchange resins are produced by introducing sulfonic acid groups onto the benzene rings of cross-linked polystyrene through the action of sulfonating reagents such as concentrated sulfuric acid, chlorosulfonic acid, sulfur trioxide, and fuming sulfuric acid. For example, fatty sulfonic acid strong acid cation exchange resins and polystyrene sulfonic acid ion exchange resins are suitable for use in the embodiments of the present invention. Of course, it is not excluded that sulfonic acid cation exchange resins can also be obtained commercially.

[0062] Quaternary ammonium anion exchange fillers, also known as quaternary ammonium anion exchange resins, refer to anion exchange resins with quaternary ammonium exchange groups. Common commercially available materials such as 201×7, 201×4, D201, D202, or A-32 Fine Mesh are suitable for use in the present invention. In particular, embodiments of the present invention utilize alkanol quaternary ammonium anion exchange fillers, which are commercially available.

[0063] When the treatment liquid is subjected to ion exchange treatment using an ion exchange column, the column temperature controller controls the column temperature to be 20°C-40°C, for example, 20°C, 22°C, 25°C, 27°C, 29°C, 30°C, 32°C, 35°C, 37°C, 38°C, etc. In the embodiment of the present invention, controlling the column temperature between 20°C-40°C, for example, at 30°C, not only helps shorten the retention time of each ion chromatographic peak, but also helps improve separation selectivity and ensure quantitative accuracy.

[0064] In step 3, the post-treatment liquid is reacted with the color developing liquid in a tubular reactor so that the iron ions of different valence states in the post-treatment liquid form derivatives with light-absorbing groups to obtain a test liquid.

[0065] In the embodiment of the present invention, the tubular reactor used is a slender tube. For example, the volume of the tubular reactor is 300μL-500μL, such as 374μL. In addition, the flow rate of the fluid in the tubular reactor can be controlled at 0.8mL / min-1.2mL / min, such as 1mL / min.

[0066] In some possible implementations, the post-treatment liquid is reacted with the color-developing liquid in a tubular reactor, including: continuously pumping the color-developing liquid into the tubular reactor at a rate of 0.3 mL / min-0.6 mL / min through a pump, so that the post-treatment liquid reacts with the color-developing liquid.

[0067] Studies have found that increasing the flow rate improves the complexation efficiency of the developer and iron ions, but when the flow rate is further increased, the improvement in complexation is less than the concentration dilution effect at high flow rates. To ensure complexation efficiency and obtain good complexation effect, the flow rate of the developer solution in the embodiment of the present invention is controlled at 0.3mL / min-0.6mL / min.

[0068] For example, the flow rate of the developing solution includes but is not limited to the following: 0.3 mL / min, 0.35 mL / min, 0.4 mL / min, 0.45 mL / min, 0.5 mL / min, 0.55 mL / min, 0.58 mL / min, 0.6 mL / min, etc.

[0069] In some possible implementations, the color developing solution includes: a color developer and a color developing auxiliary agent, wherein the color developing auxiliary agent is selected from at least one of N,N-dimethylethanolamine, ammonium hydroxide, and sodium bicarbonate.

[0070] For example, the color developer is used in combination with N,N-dimethylethanolamine, and the color developer:N,N-dimethylethanolamine=1:743 (mass ratio).

[0071] For example, the color developer is used in combination with ammonium hydroxide, and the color developer:ammonium hydroxide=1:146 (mass ratio).

[0072] For example, the color developer is used in combination with sodium bicarbonate, and the color developer: sodium bicarbonate = 1:210 (mass ratio).

[0073] Using at least one of N,N-dimethylethanolamine, ammonium hydroxide, and sodium bicarbonate as a color development aid can adjust the pH of the system, assist color development, and maintain the stability of the color development system.

[0074] Considering the need to color the fully complexed iron ions of different valences, in order to obtain excellent color development effect, the color developer used is at least one of o-phenanthroline, 4-(2-pyridylazo)resorcinol, phenolphthalein, and bromocresol green.

[0075] The above-mentioned color developer can react with iron ions of different valence states to produce a stable colored complex with a certain color. The concentration of iron ions of different valence states can be obtained by subsequently measuring the absorbance of the colored complex.

[0076] For step 4, the liquid to be tested is measured by absorptiometry to obtain the content of iron ions of different valence states in the gas purification amine liquid.

[0077] Absorbance photometry refers to a method of measuring the absorbance of a solution with the help of a spectrophotometer and determining the concentration of a substance solution according to the Lambert-Beer law.

[0078] In an embodiment of the present invention, an ultraviolet detector is used to perform the specific operation of the above-mentioned absorbance spectrophotometry. Specifically, the ultraviolet detector is a detector designed based on the principle that solute molecules absorb ultraviolet light. Its working principle is based on the Lambert-Beer law, that is, when a beam of monochromatic light passes through a flow cell, if the mobile phase does not absorb light, the absorbance A is proportional to the concentration C of the absorbing component and the optical path length L of the flow cell.

[0079] Determining the content of the colored complex in the test solution (ie, the iron ion content in the present application) by using the spectrophotometric method is a common testing method in the art, and will not be described in detail in the present embodiment.

[0080] In the embodiment of the present invention, when the test liquid is measured by the absorbance spectrophotometry method, the wavelength of the ultraviolet detector is set to 530 nm. This is because the baseline of the color development reaction is relatively stable, the absorption is the best, and the peak height is higher when the detection wavelength is 530 nm.

[0081] In addition, during the ion exchange process, the nitrogen pressure is controlled at 3-6 psi. This can protect the eluent (i.e., complexing liquid) and the color developer from the air and avoid the influence of carbon dioxide and oxygen in the atmosphere. The color developer is easily oxidized in the air. In addition, it can also pressurize the eluent to prevent bubbles from forming in the pipeline.

[0082] It will be understood by those skilled in the art that when measuring the test liquid using the spectrophotometric method, it is necessary to prepare standard gas-purified amine liquid samples with different iron ion concentrations, and use the same chromatographic conditions as those used in the formal test to obtain an iron ion standard curve. Using this iron ion standard curve as a reference, the content of iron ions of different valences in the gas-purified amine liquid can be calculated.

[0083] For example, standard gas purification amine solution samples containing ferrous iron and ferric iron may be prepared with concentrations of 0.5 ppm, 2 ppm, 4 ppm, 6 ppm, and 8 ppm, respectively.

[0084] In summary, the method for determining the iron ion content in the gas purification amine liquid provided by the embodiment of the present invention uses an ion exchange column in combination with an ultraviolet detector. Specifically, iron ions of different valences are separated in the ion exchange column, and then a color developer is continuously added to the tubular reactor, so that the iron ions of different valences react with the color developer to generate derivatives with light-absorbing groups, thereby making it possible to measure the iron ion content by spectrophotometry, thereby realizing the determination of the iron ion content of different valences in the gas purification amine liquid.

[0085] In the process of implementing the above method, research on the interference elimination process, chemical reaction reagents and analysis conditions is involved, so that the method provided in the embodiment of the present invention can not only directly measure the content of iron ions of different valences in the gas purification amine solution, but also make the testing process have at least the following advantages: simple and reliable, high sensitivity, low detection limit, reliable analysis results, etc.

[0086] Specifically, the interference elimination process involves pre-treating the gas purification amine solution by adding a suitable acid solution to adjust its pH. This eliminates any interference the gas purification amine solution may have on the eluent, accelerating the coordination process. A complexing agent is then added to the gas purification amine solution to pre-complex the iron ions, preventing oxidation of the ferrous ions and ensuring accurate measurement results.

[0087] The method for determining the content of iron ions in the gas purification amine liquid provided by the embodiment of the present invention realizes that the qualitative and quantitative analysis of iron ions of different valence states in the gas purification amine liquid can be completed by a single injection. Compared with the traditional method, the method provided by the embodiment of the present invention not only completes the analysis of iron ions of different valence states, but also the analysis method is fast and effective. The method provided by the embodiment of the present invention analyzes iron ions of different valence states in the gas purification amine liquid, and its relative standard deviation RSD / (%) is less than 1, the minimum detection limit is less than 1ppm, and the linear correlation coefficient R2 is greater than or equal to 0.999. The method provided by the embodiment of the present invention has a low detection limit, good repeatability and accuracy, is simple, fast, and has a wide linear range of determination, and can be widely used in the field of analysis and testing of sweetening amine solutions in the petrochemical, coal chemical, and oil refining chemical industries.

[0088] In order to more clearly understand the technical solution of the present invention, the present invention will be further described below through specific examples:

[0089] Example 1

[0090] This embodiment provides a method for determining the iron ion content in a gas purification amine solution, the method comprising the following steps:

[0091] Step 1: Adjust the pH of the gas-purifying amine solution to 3-6 by dropwise adding hydrochloric acid solution to the gas-purifying amine solution. Then, mix a complexing agent with a mixture of potassium hydroxide, potassium sulfate, and formic acid (complexing agent: potassium hydroxide: potassium sulfate: formic acid = 1:3.16:0.83:29.11) to form a first complexing solution. The first complexing solution is added to the gas-purifying amine solution to obtain a pretreatment solution. The concentration of the complexing agent in the gas-purifying amine solution is 35 mmol / L.

[0092] Step 2: The treated liquid is processed through an ion exchange column to separate the iron ions of different valence states in the treated liquid, obtaining a post-treated liquid. The ion exchange column is packed with a sulfonic acid cation exchange filler and a quaternary ammonium anion exchange filler, D201, in a 1:1 mass ratio. During the ion exchange process, a column temperature controller maintains a temperature of 30°C and a nitrogen pressure of 4 psi. A second complexing solution, identical in composition to the first complexing solution, is passed through the ion exchange column as an eluent at a rate of 1 mL / min.

[0093] Step 3: Continuously pump the color-developing solution into the tubular reactor at a rate of 0.6 mL / min via a pump, allowing the post-treatment solution to react with the color-developing solution, so that the iron ions of different valence states in the post-treatment solution form derivatives with light-absorbing groups, thereby obtaining a test solution. The color-developing solution comprises a color developer and a color-developing auxiliary at a mass ratio of 1:743; the color-developing auxiliary is N,N-dimethylethanolamine, and the color developer is o-phenanthroline.

[0094] Step 4: Using an ultraviolet detector, measure the test solution by absorptiometry to obtain the content of iron ions of different valences in the gas-purifying amine solution. The wavelength of the ultraviolet detector is 530 nm.

[0095] Based on the same chromatographic conditions as above, mixed standards of 0.5 ppm, 2 ppm, 4 ppm, 6 ppm, and 8 ppm of divalent and trivalent iron ions were prepared and injected under the above chromatographic conditions to draw a standard curve for iron ions for comparison.

[0096] After using the above method to test the iron ions in the gas purification amine liquid, the test results showed that the iron ions of different valences in the gas purification amine liquid were effectively separated with good peak shapes. Finally, the content of iron ions of different valences was calculated through the iron ion standard curve: the content of divalent iron ions was 1.3999ppm, and the content of trivalent iron ions was 1.4719ppm.

[0097] Example 2

[0098] This embodiment provides a method for determining the iron ion content in a gas purification amine solution, the method comprising the following steps:

[0099] Step 1: The pH of the gas-purifying amine solution is adjusted to a set value by dropwise adding sulfuric acid solution to the gas-purifying amine solution. A complexing agent is then mixed with a mixture of potassium hydroxide, potassium sulfate, and formic acid (complexing agent: potassium hydroxide: potassium sulfate: formic acid = 1:3.16:0.83:29.11) to form a first complexing solution. The first complexing solution is then added to the gas-purifying amine solution to obtain a pretreatment solution. The concentration of the complexing agent in the gas-purifying amine solution is 35 mmol / L.

[0100] Step 2: The treated liquid was processed through an ion exchange column to separate the iron ions of different valence states in the treated liquid, obtaining a post-treated liquid. The ion exchange column was packed with a sulfonic acid cation exchange filler and a quaternary ammonium anion exchange filler, A-32 Fine Mesh, in a 1:1 mass ratio. During the ion exchange process, the column temperature was maintained at 30°C and the nitrogen pressure at 5 psi. A second complexing solution, identical in composition to the first complexing solution, was passed through the ion exchange column as an eluent at a rate of 0.8 mL / min.

[0101] Step 3: Continuously pump the color-developing solution into the tubular reactor at a rate of 0.4 mL / min. The post-treatment solution reacts with the color-developing solution, causing the iron ions of varying valence in the post-treatment solution to form derivatives with light-absorbing groups, yielding the test solution. The color-developing solution comprises a color developer and a color-developing auxiliary agent in a mass ratio of 1:146; the color-developing auxiliary agent is ammonium hydroxide. The color developer is 4-(2-pyridyl azo) resorcinol.

[0102] Step 4: Using an ultraviolet detector, measure the test solution by absorptiometry to obtain the content of iron ions of different valences in the gas-purifying amine solution. The wavelength of the ultraviolet detector is 530 nm.

[0103] Based on the same chromatographic conditions as above, mixed standards of ferrous and ferric ions at concentrations of 2 ppm, 5 ppm, 10 ppm, 15 ppm, and 20 ppm were prepared and injected under the above chromatographic conditions to draw a standard curve for iron ions for comparison.

[0104] After using the above method to test the iron ions in the gas purification amine liquid, the test results showed that the iron ions of different valences in the gas purification amine liquid were effectively separated with good peak shapes. Finally, the content of iron ions of different valences was calculated through the iron ion standard curve: the content of divalent iron ions was 2.0324ppm, and the content of trivalent iron ions was 7.8792ppm.

[0105] Example 3

[0106] This embodiment provides a method for determining the iron ion content in a gas purification amine solution, the method comprising the following steps:

[0107] Step 1: The pH value of the gas-purifying amine solution is adjusted to a set value by dropwise adding a hydrochloric acid solution to the gas-purifying amine solution. Then, a complexing agent and formic acid are mixed in a mass ratio of 1:29.11 to form a first complexing solution. The first complexing solution is added to the gas-purifying amine solution to obtain a pretreatment solution, wherein the concentration of the complexing agent in the gas-purifying amine solution is 38 mmol / L.

[0108] Step 2: The treated liquid is treated with an ion exchange column to separate the iron ions of different valence states in the treated liquid to obtain a post-treated liquid. The ion exchange column is simultaneously filled with a sulfonic acid cation exchange filler and an alkanol quaternary amine anion exchange filler in a mass ratio of 1:1. During the ion exchange process, the column temperature controller controls the column temperature to 30°C, the nitrogen pressure to 6 psi, and a second complexing solution with the same composition as the first complexing solution is flowed through the ion exchange column at a rate of 0.9 mL / min as an eluent.

[0109] Step 3: Continuously pump the color-developing solution into the tubular reactor at a rate of 0.6 mL / min via a pump. The post-treatment solution reacts with the color-developing solution, causing the iron ions of varying valence in the post-treatment solution to form derivatives with light-absorbing groups, yielding a test solution. The color-developing solution comprises a color-developing agent and a color-developing auxiliary agent in a mass ratio of 1:210; the color-developing auxiliary agent is sodium bicarbonate, and the color-developing agent is phenolphthalein.

[0110] Step 4: Using an ultraviolet detector, measure the test solution by absorptiometry to obtain the content of iron ions of different valence states in the gas-purifying amine solution. The wavelength of the ultraviolet detector is 530 nm.

[0111] Based on the same chromatographic conditions as above, mixed standards of 0.5 ppm, 2 ppm, 4 ppm, 6 ppm, and 8 ppm of divalent and trivalent iron ions were prepared and injected under the above chromatographic conditions to draw a standard curve of iron ions for comparison.

[0112] After using the above method to test the iron ions in the gas purification amine liquid, the test results showed that the iron ions of different valences in the gas purification amine liquid were effectively separated with good peak shapes. Finally, the content of iron ions of different valences was calculated through the iron ion standard curve: the content of divalent iron ions was 1.5471ppm, and the content of trivalent iron ions was 4.8792ppm.

[0113] Example 4

[0114] This embodiment provides a method for determining the iron ion content in a gas purification amine solution, the method comprising the following steps:

[0115] Step 1: By adding an acid solution (the acid solution is hydrochloric acid, sulfuric acid, and nitric acid in a volume ratio of 1:1) to the gas purification amine solution, the pH value of the gas purification amine solution is adjusted to 3-6, and then the complexing agent is mixed with a mixed solution of potassium hydroxide, potassium sulfate, and formic acid (mass ratio, complexing agent: potassium hydroxide: potassium sulfate: formic acid = 1:3.16:0.83:29.11) to form a first complexing solution, and the first complexing solution is added to the gas purification amine solution to obtain a pretreatment solution, wherein the concentration of the complexing agent in the gas purification amine solution is 40 mmol / L.

[0116] Step 2: The treated liquid is processed through an ion exchange column to separate the iron ions of different valence states in the treated liquid, obtaining a post-treated liquid. The ion exchange column is packed with a sulfonic acid cation exchange filler and a quaternary ammonium anion exchange filler in a 1:1 mass ratio. During the ion exchange process, the column temperature is maintained at 30°C by a column temperature controller. The nitrogen pressure is 6 psi, and a second complexing solution with the same composition as the first complexing solution is passed through the ion exchange column as an eluent at a rate of 0.6 mL / min.

[0117] Step 3: Continuously pump the color-developing solution into the tubular reactor at a rate of 0.6 mL / min via a pump. The post-treatment solution reacts with the color-developing solution, causing the iron ions of varying valence in the post-treatment solution to form derivatives with light-absorbing groups, yielding the test solution. The color-developing solution comprises a color developer and a color-developing auxiliary in a mass ratio of 1:0.2:0.3. The color-developing auxiliary is a mixture of N,N-dimethylethanolamine, ammonium hydroxide, and sodium bicarbonate in a mass ratio of 1:0.2:0.3. The color developer is a mixture of 4-(2-pyridyl azo) resorcinol and phenolphthalein in a mass ratio of 1:0.3.

[0118] Step 4: Using an ultraviolet detector, measure the test solution by absorptiometry to obtain the content of iron ions of different valences in the gas-purifying amine solution. The wavelength of the ultraviolet detector is 530 nm.

[0119] Based on the same chromatographic conditions as above, mixed standards of ferrous and ferric ions at concentrations of 2 ppm, 5 ppm, 10 ppm, 15 ppm, and 20 ppm were prepared and injected under the above chromatographic conditions to draw a standard curve for iron ions for comparison.

[0120] After using the above method to test the iron ions in the gas purification amine liquid, the test results showed that the iron ions of different valences in the gas purification amine liquid were effectively separated with good peak shapes. Finally, the content of iron ions of different valences was calculated through the iron ion standard curve. The content of divalent iron ions was 4.0638ppm and the content of trivalent iron ions was 14.2716ppm.

[0121] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for determining the iron ion content in a gas purification amine solution, characterized in that: The method for determining the iron ion content in the gas purification amine solution comprises: adjusting the pH value of the gas purification amine solution to 3-6, and then adding a first complexing solution to the gas purification amine solution to obtain a pretreatment solution, wherein the first complexing solution comprises a complexing agent and a solvent, the complexing agent is selected from at least one of 2,6-pyridinedicarboxylic acid, disodium ethylenediaminetetraacetic acid, sodium ethylenediaminetetramethylenephosphate and 1,10-o-phenanthroline, and the solvent is selected from at least one of potassium hydroxide, potassium sulfate and formic acid; Using a second complexing solution as an eluent, carrying the pretreatment liquid into an ion exchange column via the second complexing solution, treating the pretreatment liquid via the ion exchange column to separate iron ions of different valence states in the pretreatment liquid to obtain a post-treatment liquid; wherein the second complexing solution has the same composition as the first complexing solution; The color-developing solution is continuously pumped into a tubular reactor at a rate of 0.3 mL / min to 0.6 mL / min by a pump. In the tubular reactor, the post-treatment solution and the color-developing solution react so that the iron ions of different valence states in the post-treatment solution form derivatives with light-absorbing groups to obtain a test solution. The color-developing solution comprises: a color developer and a color-developing auxiliary agent, wherein the color developer is at least one of o-phenanthroline, 4-(2-pyridylazo)resorcinol, phenolphthalein, and bromocresol green, and the color-developing auxiliary agent is at least one of N,N-dimethylethanolamine, ammonium hydroxide, and sodium bicarbonate. The liquid to be tested is measured by using an absorption spectrophotometer to obtain the content of iron ions of different valence states in the gas purification amine liquid.

2. The method for determining the iron ion content in the gas purification amine solution according to claim 1, wherein: The step of adjusting the pH value of the gas-purifying amine liquid to a set value comprises: adding an acid solution dropwise to the gas-purifying amine liquid to adjust the pH value of the gas-purifying amine liquid to the set value.

3. The method for determining the iron ion content in the gas purification amine solution according to claim 2, wherein: The acid solution is selected from at least one of sulfuric acid, hydrochloric acid and phosphoric acid.

4. The method for determining the iron ion content in the gas purification amine solution according to claim 1, wherein: The second complexing solution passes through the ion exchange column at a speed of 0.6 mL / min to 1 mL / min.

5. The method for determining the iron ion content in the gas purification amine solution according to claim 1, characterized in that: The ion exchange column is filled with sulfonic acid type cation exchange filler and quaternary amine type anion exchange filler at the same time.

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