An inhibitor, its preparation method and application

Abstract

The application provides an inhibitor, a preparation method and application thereof. The inhibitor comprises sodium sulfite (Na2SO3), N-methyl pyrrolidone, isopropyl alcohol and an amine aqueous solution. The sodium sulfite accounts for 0.05-0.2 wt% of the total amount of the inhibitor, the N-methyl pyrrolidone accounts for 0.05-0.2 wt% of the total amount of the inhibitor, and the isopropyl alcohol accounts for 0.05-0.2 wt% of the total amount of the inhibitor. The amine liquid in the inhibitor can effectively remove H2S and CO2 in high-acidity natural gas, and the inhibitor composition provided by the application can effectively remove H2S and CO2 in high-acidity natural gas and slow down the corrosion of the device.

Description

Technical Field

[0001] This invention belongs to the field of gas purification technology, specifically relating to a corrosion inhibitor, its preparation method, and its application. Background Technology

[0002] With economic development, the demand for natural gas has surged, and after years of development, its application scope has continuously expanded, gradually becoming a primary energy source. Natural gas, as a clean fuel, contains a certain amount of H2S and CO2. H2S is a highly toxic, colorless, and flammable gas, posing a serious threat to personal safety and causing corrosion of equipment and pipelines. Industrially, processes such as the amine method, liquid desulfurizing agents, and hot potassium alkali are widely used to remove H2S and CO2 from natural gas. During desulfurization and decarbonization, corrosion of pipelines and equipment is inevitable, leading to destructive behaviors such as pipeline thinning, perforation and leakage, and equipment failure. Corrosion inhibitors, existing in appropriate forms and concentrations in corrosive environments, can effectively prevent or slow down material corrosion. They are characterized by low cost, simple operation, rapid effect, and suitability for long-term use, and are currently widely used in corrosion protection of natural gas desulfurization and decarbonization systems. For highly acidic gas field corrosive environments and morphologies, corrosion inhibitors require high selectivity and specificity.

[0003] Therefore, there is an urgent need for a highly efficient corrosion inhibitor formulation for amine-based desulfurization and decarbonization equipment, which is of great significance for improving the corrosion inhibition performance of desulfurization and decarbonization solutions. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention proposes a corrosion inhibitor, its preparation method, and its application.

[0005] In a first aspect, the present invention provides a corrosion inhibitor comprising: sodium sulfite (Na2SO3), N-methylpyrrolidone, isopropanol and an aqueous amine solution.

[0006] As a specific embodiment of the present invention, the sodium sulfite accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor, N-methylpyrrolidone accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor, and isopropanol accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor.

[0007] In a specific embodiment of the present invention, the amine aqueous solution is composed of a main agent and an activator, wherein the main agent includes N-methyldiethanolamine (MDEA); the traditional technology uses a single amine, which has a slow reaction rate and causes severe system corrosion. The present invention, by adding an activator and a corrosion inhibitor, not only improves the reaction rate and desulfurization and decarbonization performance, but also proposes a special corrosion inhibitor for natural gas, significantly alleviating the corrosion of the equipment.

[0008] The activator includes one or more of diethanolamine (DEA), monoethanolamine (MEA), methylmonoethanolamine (MMEA), hydroxyethylpiperazine (HPZ), and 2-amino-2-methyl-1-propanol (AMP).

[0009] In a specific embodiment of the present invention, the main agent accounts for 25-45 wt% of the total amount of corrosion inhibitor; the activator accounts for 3-10 wt% of the total amount of corrosion inhibitor.

[0010] As a specific embodiment of the present invention, the corrosion inhibitor is used in a temperature range of 25 to 150°C and a pressure range of 0.5 to 8.5 MPa.

[0011] Secondly, the present invention provides a method for preparing the corrosion inhibitor, comprising: adding sodium sulfite (Na2SO3), N-methylpyrrolidone, and isopropanol to an aqueous amine solution to obtain the corrosion inhibitor.

[0012] In a specific embodiment of the present invention, in step S1, the main agent includes N-methyldiethanolamine (MDEA);

[0013] The activator includes one or more of diethanolamine (DEA), monoethanolamine (MEA), methylmonoethanolamine (MMEA), hydroxyethylpiperazine (HPZ), and 2-amino-2-methyl-1-propanol (AMP);

[0014] The main agent accounts for 25-45 wt% of the total amount of corrosion inhibitor; the activator accounts for 3-10 wt% of the total amount of corrosion inhibitor.

[0015] As a specific embodiment of the present invention, in step S2, the sodium sulfite accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor, N-methylpyrrolidone accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor, and isopropanol accounts for 0.05 to 0.2 wt% of the total amount of the corrosion inhibitor.

[0016] As a specific embodiment of the present invention, the mixing method in steps S1 and S2 is conventional mixing at room temperature, and is not particularly limited here.

[0017] All of the above-mentioned raw materials used in this invention can be prepared in-house or purchased commercially; this invention does not impose any particular limitations on them.

[0018] Thirdly, the present invention provides the application of the corrosion inhibitor in the field of desulfurization and decarbonization equipment.

[0019] As a specific embodiment of the present invention, the corrosion inhibitor is applied to the acidic gas in natural gas, wherein the acidic gas comprises 1-10% H2S(v) by volume, 1-20% CO2(v) and the remainder is N2.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The corrosion inhibitor of the present invention, the amine liquid can effectively remove H2S and CO2 from highly acidic natural gas, and when combined with the corrosion inhibitor composition provided by the present invention, it can efficiently remove H2S and CO2 from highly acidic natural gas while slowing down the corrosion of the equipment.

[0022] 2. Compared with conventional corrosion inhibitors, the corrosion inhibitor of the present invention has a 20% higher slow-release efficiency.

[0023] 3. Compared with traditional corrosion inhibitors, the corrosion inhibitor of the present invention has a lower dosage, is non-toxic, and is environmentally friendly. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0025] The specific details of the testing methods used in the various embodiments of the present invention are as follows:

[0026] The test method for corrosion inhibitor performance is to measure the corrosion rate of metals before and after adding corrosion inhibitor to the corrosive medium under different conditions, and then compare the results to determine the corrosion inhibition efficiency and optimal use conditions. In this invention, the corrosion inhibition performance of amine solution was determined by a plate test.

[0027] Corrosion rate as r c The mark, its calculation formula is:

[0028]

[0029] In the formula, r c For uniform corrosion rate, the unit is millimeters per year (mm / year);

[0030] M represents the mass of the sample before the experiment, in grams (g).

[0031] m1 is the mass of the test piece after the test, in grams (g);

[0032] S represents the total area of ​​the test piece, in square centimeters (cm²). 2 );

[0033] ρ is the density of the sample material, expressed in grams per cubic centimeter (g / cm³). 3 );

[0034] t represents the test time, in hours (h).

[0035] Corrosion inhibition efficiency is η w The mark, its calculation formula is:

[0036]

[0037] In the formula, η w For corrosion inhibition efficiency, %;

[0038] r0 represents the corrosion rate of the blank sample, expressed in mm / a (millimeters per year).

[0039] r1 represents the corrosion rate of the test piece after the addition of the corrosion inhibitor, expressed in mm / a (millimeters per year).

[0040] The experimental material was a carbon steel 20# hanging piece (40mm×13mm×2mm). The hanging piece was polished with wet sandpaper of not less than 120-2000 grit, with the grit increasing from low to high, to remove rust, blemishes, and burrs until the surface of the hanging piece was bright and free of marks. It was then held with tweezers and cleaned in petroleum ether or acetone to remove the oily protective film on the surface. The dimensions were measured with vernier calipers. After soaking in anhydrous ethanol for about 1 minute, it was taken out and air-dried. It was wrapped in filter paper and placed in a desiccator to dry for 1 hour. It was then weighed with a balance to an accuracy of 0.0001g and stored in a desiccator for later use.

[0041] 150 ml of the prepared mixed amine aqueous solution was placed in a 250 ml three-necked round-bottom flask. A serpentine condenser was installed at one neck, a line for introducing a mixed gas with a high H2S content was installed at the other neck, and the treated test piece was immersed and suspended in the solution at the other neck. The condenser was connected to cooling water. The flask was placed in a constant-temperature oil bath and heated to 120 °C. A mixed gas with a high H2S content was introduced and the temperature was maintained for 72 hours. The test piece was then removed and the corrosion was observed, paying particular attention to any cracks or pits. After observation, the sample was immediately rinsed with deionized water, then scrubbed with a soft brush or a hard rubber brush to remove the loose corrosion products on the surface. Finally, it was gradually cleaned with acetone and anhydrous ethanol, dried with cold air, wrapped in filter paper, and placed in a desiccator to dry for 1 hour before weighing, accurate to 0.0001 g.

[0042] The highly acidic corrosive environment in the comparative examples and embodiments was: H2S 5% (v), CO2 10% (v), and the remainder N2 (v).

[0043] The low-acid corrosion environment in the comparative examples and embodiments was: H2S 500ppm, CO2 3.5% (v), and the remainder N2 (v).

[0044] Example 1

[0045] This embodiment provides a corrosion inhibitor and its preparation method, the details of which are as follows:

[0046] S1: Mix the main agent MDEA and activators MMEA and DEA at room temperature to obtain an aqueous amine solution;

[0047] S2: Add sodium sulfite, N-methylpyrrolidone and isopropanol to the amine aqueous solution obtained in step S1, and mix evenly to obtain the corrosion inhibitor.

[0048] The corrosion inhibitor obtained in Example 1 contained 40 wt% MDEA, 2 wt% MMEA, 3 wt% DEA, 0.05 wt% sodium sulfite, 0.05 wt% N-methylpyrrolidone, 0.05 wt% isopropanol, and the balance was water.

[0049] Examples 2-16

[0050] The corrosion inhibitors prepared in Examples 2-16 were prepared using the same method as those in Example 1, except that their components were different. The specific components are shown in Tables 1 and 2.

[0051] Comparative Examples 1-22

[0052] The corrosion inhibitors prepared in Comparative Examples 1-17 and 19-22 were prepared using the same methods as those in Example 1, except that their components were different. Comparative Example 18 only had step S1 and was the same as that in Example 1. The specific components are shown in Tables 1 and 2.

[0053] The corrosion inhibitors prepared in Examples 1-16 and Comparative Examples 1-22 were tested. Examples 1-11 and Comparative Examples 1-17 were tested for high acid corrosion, and Examples 12-16 and Comparative Examples 18-22 were tested for low acid corrosion. The test results are shown in Tables 1 and 2.

[0054] Table 1. Corrosion results of corrosion inhibitors in highly acidic environments for Comparative Examples 1-17 and Examples 1-11.

[0055]

[0056]

[0057]

[0058] Table 2 shows the corrosion results of the corrosion inhibitors in low-acid environments for Comparative Examples 18-22 and Examples 12-16.

[0059]

[0060]

[0061] Explanation of test results for comparative examples and embodiments:

[0062] Comparative Example 1 shows that with the addition of two activators, the corrosion rate of the desulfurization and decarbonization unit is high without the addition of corrosion inhibitors. Without corrosion inhibitors, corrosion will worsen over time. Comparative Example 2 shows that when the dosage of corrosion inhibitor added is below the protected range, the release rate is less than 10%, providing little protection. Comparative Example 3 shows that when the corrosion inhibitor is added in excess, the release rate is not significantly improved compared to the range of this invention, only reaching 91.4%, indicating a waste of corrosion inhibitors. Comparative Examples 4-15 show that the corrosion inhibition effect of any two of the three corrosion inhibitor components of this invention—sodium sulfite (Na2SO3), N-methylpyrrolidone, and isopropanol—is not as good as the corrosion inhibition effect of the combination of the three inhibitors. The corrosion inhibitor formulation of this invention does not have a good corrosion inhibition effect on the desulfurization and decarbonization unit of low-acid natural gas. Comparative Examples 16 and 17 show that when the main agent or activator exceeds the range of this invention, the corrosion inhibition effect will decrease significantly. As can be seen from Examples 12-16, the corrosion inhibitor of the present invention still exhibits excellent corrosion inhibition effect under low acid environment. As can be seen from Comparative Examples 19 and 20, too little corrosion inhibitor has no effect, and too much does not significantly enhance the corrosion inhibition effect, which is the same as the corrosion inhibition effect in high acid environment. As can be seen from Comparative Examples 20 and 21, the three corrosion inhibitor components of the present invention, sodium sulfite (Na2SO3), N-methylpyrrolidone, and isopropanol, have poor effects when any two are selected in the ratio or only one is selected.

[0063] Examples 1-16 are compared, with the preferred range of the main agent being 35-45 wt%, the preferred range of the activator being 5-6 wt%, the preferred range of sodium sulfite being 0.10-0.15 wt%, the preferred range of N-methylpyrrolidone being 0.10-0.15 wt%, and the preferred range of isopropanol being 0.10-0.15 wt%.

[0064] Using the desulfurization and decarbonization solvent and process parameters proposed in this invention, as well as the corrosion inhibitor proposed in this invention, has the following significant characteristics: the corrosion inhibition performance is significantly improved, and a significant corrosion inhibition effect is achieved. This helps to improve the corrosion resistance of the desulfurization and decarbonization unit when 20# carbon steel is selected, improves the service life of pipelines and equipment, and reduces failures caused by corrosion.

[0065] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0066] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A corrosion inhibitor, characterized in that, Its components include: sodium sulfite, N-methylpyrrolidone, isopropanol and an aqueous amine solution; The sodium sulfite accounts for 0.05–0.2 wt% of the total corrosion inhibitor, N-methylpyrrolidone accounts for 0.05–0.2 wt% of the total corrosion inhibitor, and isopropanol accounts for 0.05–0.2 wt% of the total corrosion inhibitor. The aqueous amine solution is composed of a main agent and an activator, wherein the main agent includes N-methyldiethanolamine (MDEA); The activator includes one or more of diethanolamine (DEA), monoethanolamine (MEA), methylmonoethanolamine (MMEA), hydroxyethylpiperazine (HPZ), and 2-amino-2-methyl-1-propanol (AMP); The main agent accounts for 25-45 wt% of the total amount of corrosion inhibitor; the activator accounts for 3-10 wt% of the total amount of corrosion inhibitor.

2. The corrosion inhibitor according to claim 1, characterized in that, The corrosion inhibitor has an operating temperature range of 25–150°C and a pressure range of 0.5–8.5 MPa.

3. A method for preparing the corrosion inhibitor according to claim 1 or 2, characterized in that, The preparation method includes adding sodium sulfite, N-methylpyrrolidone, and isopropanol to an aqueous amine solution to obtain the corrosion inhibitor.

4. The preparation method according to claim 3, characterized in that, It also includes the following steps: S1: Mix the main agent and the activator to obtain an aqueous amine solution; In step S1, the main agent includes N-methyldiethanolamine (MDEA); The activator includes one or more of diethanolamine (DEA), monoethanolamine (MEA), methylmonoethanolamine (MMEA), hydroxyethylpiperazine (HPZ), and 2-amino-2-methyl-1-propanol (AMP).

5. The application of the corrosion inhibitor according to claim 1 or 2 or the corrosion inhibitor prepared by the preparation method according to claim 3 or 4 in the field of desulfurization and decarbonization equipment.

6. The application according to claim 5, characterized in that, The corrosion inhibitor is applied to the acidic gas in natural gas, which includes 1-10% H2S, 1-20% CO2, and the remainder N2 by volume.

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