Low temperature dew point neutralizing corrosion inhibitor and preparation method thereof

Abstract

The invention discloses a low-temperature dew point neutralizing corrosion inhibitor and a preparation method thereof, belonging to the technical field of corrosion protection in a petroleum processing process, comprising a Mannich base derivative, an organic amine compound and a solvent, wherein the Mannich base derivative uses 2,4-dihydroxy-6-methoxy-3-methylacetophenone as a raw material, undergoes Claisen-Schmidt condensation with p-hydroxybenzaldehyde under alkaline conditions to obtain an intermediate, and then undergoes a Mannich reaction with N-ethylpiperazine to obtain the intermediate; the invention performs modification and adjustment on the basis of the existing Mannich base to obtain a neutralizing corrosion inhibitor having both good corrosion protection performance and anti-emulsification performance.

Description

Technical Field

[0001] The invention relates to the technical field of corrosion prevention in the process of petroleum processing, and in particular to a low-temperature dew point neutralizing corrosion inhibitor and a preparation method thereof. Background Art

[0002] In recent years, the trend of heavy and inferior crude oil has become increasingly obvious, and the acid content, sulfur content and salt content have gradually increased. At the same time, since most of the imported crude oil is high-acid crude oil, the proportion of high-sulfur, high-acid value and high-salt crude oil processed by domestic refineries is increasing. The corrosion problem of refinery equipment is particularly prominent, especially the corrosion of atmospheric tower top circulation and tower top condensation system, which seriously affects the normal operation of atmospheric tower distillation unit and becomes the main problem restricting the long-term safe operation of the unit, and also affects the benefits of enterprises. Crude oil has a complex composition, mainly carbon and hydrogen, with a hydrocarbon content of more than 95%, and the remaining 5% is organic and inorganic compounds composed of sulfur, oxygen, nitrogen, chlorine and metal elements. Although the content of such compounds is small, the inorganic salts, sulfides, cyclohexane acids and various additives in the process of oil extraction and refining composed of such compounds affect the production process and product quality of the entire refinery, and are the main factors affecting the corrosion of refinery distillation units.

[0003] The main cause of corrosion in atmospheric tower distillation units is chemical corrosion. Chlorides and active sulfides contained in crude oil can decompose to form HCl and H2S. HCl and H2S volatilize with light components in crude oil into the top of the atmospheric tower and the top condensation system. According to the solubility relationship and equilibrium partial pressure of HCl and H2S in water, when the temperature is less than 120°C, HCl first dissolves in the condensate to form a dilute hydrochloric acid environment (the pH value drops rapidly to below 3.0), thus forming a highly corrosive dilute hydrochloric acid corrosion environment; when the condensate increases, the amount of HCl dissolved also increases. When the condensate reaches a certain amount, H2S begins to dissolve in the condensate, thereby accelerating the corrosion of this part, forming an HCl-H2S-H2O corrosion environment in the atmospheric tower top system, and forming an HCl-H2S-H2O type chemical corrosion, especially in the dew point phase change zone, where there is little water vapor condensation, a large amount of HCl enters a small amount of initial condensate, and the hydrochloric acid concentration is very high, which in turn causes a series of corrosion.

[0004] The current corrosion protection policy is mostly to prevent corrosion through technological means, among which adding neutralizing corrosion inhibitors is the simplest, most effective and economical method. Corrosion inhibitors are mainly long-chain amides, pyridine derivatives, imidazoline derivatives, quaternary ammonium salts, Mannich bases and other types of compounds, which can form a hydrophobic protective layer on the metal surface through metal coordination atoms to achieve corrosion inhibition. However, the protective effect on high-concentration corrosion of pipelines in the dew point area of ​​the initial condensation zone of the top condensation cooling system is relatively limited. In addition, the above-mentioned corrosion inhibitors have obvious distinction between hydrophilic and hydrophobic parts, have low anti-emulsification properties, and have a strong emulsification tendency. They are very easy to emulsify and foam in the system and stabilize. Generally, acetylene alcohols are added to defoam, break emulsions and enhance efficiency, but acetylene alcohols have the disadvantage of high toxicity, and their environmental protection still needs to be improved. Summary of the invention

[0005] In view of the above problems, the present invention provides a low-temperature dew point neutralizing corrosion inhibitor and a preparation method thereof.

[0006] The purpose of the present invention is achieved by adopting the following technical solutions:

[0007] A low-temperature dew point neutralization corrosion inhibitor comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0008] (1) Preparation of intermediate products

[0009] Weigh 2,4-dihydroxy-6-methoxy-3-methylacetophenone and disperse it in an anhydrous ethanol solvent, add a base, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir and react for 4-6 hours at a temperature of 400-600 °C. After the reaction is completed, cool it to room temperature, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product.

[0010] (2) Preparation of derivatives

[0011] The intermediate product is dispersed in anhydrous ethanol solvent, paraformaldehyde is added, the temperature is raised and stirred until it is completely dissolved, N-ethylpiperazine is added and the mixture is stirred and reacted for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature, dichloromethane is added for extraction, the upper organic phase is taken, concentrated and purified to remove unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative.

[0012] In some preferred embodiments, the mass fraction of the Mannich base derivative in the low-temperature dew point neutralizer and the corrosion inhibitor is 30-50%.

[0013] In some preferred embodiments, the mass fraction of the organic amine compound in the low-temperature dew point and the corrosion inhibitor is 10-18%.

[0014] In some preferred embodiments, the organic amine compound is one or more of propylamine, butylamine, pentylamine, cyclohexylamine, ethylenediamine, ethanolamine, methoxypropylamine, dimethylethylamine, dimethylethanolamine, dimethylisopropanolamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0015] In some preferred embodiments, the solvent is deionized water and / or lower alcohol.

[0016] In some preferred embodiments, the lower alcohol is one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.

[0017] In some preferred embodiments, the mass ratio of the 2,4-dihydroxy-6-methoxy-3-methylacetophenone to the base and the p-hydroxybenzaldehyde in step (1) is 1:(0.74-0.76):(0.7-0.72).

[0018] In some preferred embodiments, the mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine in step (2) is 1:(0.56-0.62):(2.2-2.3).

[0019] Another aspect of the present invention is to provide a method for preparing the low-temperature dew point neutralizing corrosion inhibitor, which specifically comprises the following steps:

[0020] S1, preparing the Mannich base derivative;

[0021] S2, dissolving the Mannich base derivative in the solvent to obtain solution 1; dissolving the organic amine compound in the solvent to obtain solution 2; and uniformly mixing solution 1 and solution 2 to obtain the low-temperature dew point neutralizing corrosion inhibitor.

[0022] The beneficial effects of the present invention are:

[0023] In view of the problems that the neutralizing corrosion inhibitor described in the prior art has insufficient protection performance against high-concentration corrosion in the dew point phase change zone and low anti-emulsification performance, the present invention modifies and adjusts the existing Mannich base to obtain a low-temperature dew point neutralizing corrosion inhibitor with good corrosion protection performance and anti-emulsification performance. Specifically, the present invention uses 2,4-dihydroxy-6-methoxy-3-methylacetophenone as a raw material, and performs Claisen-Schmidt condensation with p-hydroxybenzaldehyde under alkaline conditions to obtain an intermediate, and then obtains a flavonoid-derived Mannich base through a Mannich reaction. On the one hand, the Mannich base derivative has a flavonoid group, and its coordinated active atoms can realize rapid adsorption and film formation on the metal surface and form a hydrophobic protective layer. At the same time, the large conjugated structure of the flavonoid structure can reduce the probability of electron transfer, inhibit the corrosion and oxidation of the surface metal, and thus achieve efficient corrosion inhibition. On the other hand, the present invention uses 2,4-dihydroxy-6-methoxy-3-methylacetophenone as a raw material, and the special distribution of hydrophilic and hydrophobic groups is different from the structure with obvious distinction between hydrophilic and hydrophobic parts in the prior art, which greatly reduces its surface active emulsification effect and avoids the use of toxic acetylenic alcohols. DETAILED DESCRIPTION

[0024] The present invention is further described in conjunction with the following examples. Example 1

[0025] A low-temperature dew point neutralization corrosion inhibitor comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0026] (1) Preparation of intermediate products

[0027] Weigh 2,4-dihydroxy-6-methoxy-3-methylacetophenone and disperse it in an anhydrous ethanol solvent, add sodium hydroxide, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir and react for 5 hours at a temperature of 100 °C. After the reaction is completed, cool it to room temperature, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product.

[0028] Wherein, the mass ratio of the 2,4-dihydroxy-6-methoxy-3-methylacetophenone to the sodium hydroxide and the p-hydroxybenzaldehyde is 1:0.75:0.71;

[0029] (2) Preparation of derivatives

[0030] The intermediate product is dispersed in anhydrous ethanol solvent, paraformaldehyde is added, the temperature is raised and stirred until it is completely dissolved, N-ethylpiperazine is added and the mixture is stirred and reacted for 4 hours at a temperature maintained. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. The upper organic phase is taken, concentrated, and purified by a silica gel column (500 mesh silica gel, eluent is dichloromethane / methanol, v / v=20 / 1) to remove unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative;

[0031] Wherein, the mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine is 1:0.58:2.2;

[0032] The organic amine compound is a mixture of cyclohexylamine and diethylenetriamine, with a mass ratio of 1:2;

[0033] The solvent is an ethanol aqueous solution with a volume fraction of 50%;

[0034] The mass fraction of the Mannich base derivative in the low temperature dew point and the corrosion inhibitor is 38wt%;

[0035] The mass fraction of the organic amine compound in the low-temperature dew point and corrosion inhibitor is 14%;

[0036] The preparation method of the low-temperature dew point neutralizing corrosion inhibitor specifically comprises the following steps:

[0037] S1, preparing the Mannich base derivative;

[0038] S2, dissolving the Mannich base derivative in the solvent to obtain solution 1; dissolving the organic amine compound in the solvent to obtain solution 2; uniformly mixing solution 1 and solution 2 and adding the remaining amount of solvent to obtain the low-temperature dew point neutralizing corrosion inhibitor. Example 2

[0039] A low-temperature dew point neutralization corrosion inhibitor comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0040] (1) Preparation of intermediate products

[0041] Weigh 2,4-dihydroxy-6-methoxyacetophenone and disperse it in anhydrous ethanol solvent, add sodium hydroxide, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir and react for 5 hours at a temperature of 100 °C. After the reaction is completed, cool it to room temperature, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product.

[0042] Wherein, the mass ratio of the 2,4-dihydroxy-6-methoxyacetophenone to the sodium hydroxide and the p-hydroxybenzaldehyde is 1:0.75:0.71;

[0043] (2) Preparation of derivatives

[0044] The intermediate product is dispersed in anhydrous ethanol solvent, paraformaldehyde is added, the temperature is raised and stirred until it is completely dissolved, N-ethylpiperazine is added and the mixture is stirred and reacted for 4 hours at a temperature maintained. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. The upper organic phase is taken, concentrated, and purified by a silica gel column (500 mesh silica gel, eluent is dichloromethane / methanol, v / v=20 / 1) to remove unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative;

[0045] Wherein, the mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine is 1:0.58:2.2;

[0046] The organic amine compound is a mixture of cyclohexylamine and diethylenetriamine, with a mass ratio of 1:2;

[0047] The solvent is an ethanol aqueous solution with a volume fraction of 50%;

[0048] The mass fraction of the Mannich base derivative in the low temperature dew point and the corrosion inhibitor is 38wt%;

[0049] The mass fraction of the organic amine compound in the low-temperature dew point and corrosion inhibitor is 14%;

[0050] The preparation method of the low-temperature dew point neutralizing corrosion inhibitor is the same as that of Example 1. Example 3

[0051] A low-temperature dew point neutralization corrosion inhibitor comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0052] (1) Preparation of intermediate products

[0053] Weigh 3-methoxy-5-methylacetophenone and disperse it in anhydrous ethanol solvent, add sodium hydroxide, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir and react for 5 hours at a temperature of 100 °C. After the reaction is completed, cool it to room temperature, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product.

[0054] Wherein, the mass ratio of the 3-methoxy-5-methylacetophenone to the sodium hydroxide and the p-hydroxybenzaldehyde is 1:0.75:0.71;

[0055] (2) Preparation of derivatives

[0056] The intermediate product is dispersed in anhydrous ethanol solvent, paraformaldehyde is added, the temperature is raised and stirred until it is completely dissolved, N-ethylpiperazine is added and the mixture is stirred and reacted for 4 hours at a temperature maintained. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. The upper organic phase is taken, concentrated, and purified by a silica gel column (500 mesh silica gel, eluent is dichloromethane / methanol, v / v=20 / 1) to remove unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative;

[0057] Wherein, the mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine is 1:0.58:2.2;

[0058] The organic amine compound is a mixture of cyclohexylamine and diethylenetriamine, with a mass ratio of 1:2;

[0059] The solvent is an ethanol aqueous solution with a volume fraction of 50%;

[0060] The mass fraction of the Mannich base derivative in the low temperature dew point and the corrosion inhibitor is 38wt%;

[0061] The mass fraction of the organic amine compound in the low-temperature dew point and corrosion inhibitor is 14%;

[0062] The preparation method of the low-temperature dew point neutralizing corrosion inhibitor is the same as that of Example 1. Example 4

[0063] A low-temperature dew point neutralization corrosion inhibitor comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0064] (1) Preparation of intermediate products

[0065] Weigh 2,4-dihydroxy-6-methoxy-3-isobutylacetophenone and disperse it in an anhydrous ethanol solvent, add sodium hydroxide, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir and react for 5 hours at a temperature of 100 °C. After the reaction is completed, cool it to room temperature, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product.

[0066] Wherein, the mass ratio of the 2,4-dihydroxy-6-methoxy-3-isobutylacetophenone to the sodium hydroxide and the p-hydroxybenzaldehyde is 1:0.75:0.71;

[0067] (2) Preparation of derivatives

[0068] The intermediate product is dispersed in anhydrous ethanol solvent, paraformaldehyde is added, the temperature is raised and stirred until it is completely dissolved, N-ethylpiperazine is added and the mixture is stirred and reacted for 4 hours at a temperature maintained. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. The upper organic phase is taken, concentrated, and purified by a silica gel column (500 mesh silica gel, eluent is dichloromethane / methanol, v / v=20 / 1) to remove unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative;

[0069] Wherein, the mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine is 1:0.58:2.2;

[0070] The organic amine compound is a mixture of cyclohexylamine and diethylenetriamine, with a mass ratio of 1:2;

[0071] The solvent is an ethanol aqueous solution with a volume fraction of 50%;

[0072] The mass fraction of the Mannich base derivative in the low temperature dew point and the corrosion inhibitor is 38wt%;

[0073] The mass fraction of the organic amine compound in the low-temperature dew point and corrosion inhibitor is 14%;

[0074] The preparation method of the low-temperature dew point neutralizing corrosion inhibitor is the same as that of Example 1. Example 5

[0075] A low-temperature dew point neutralizing corrosion inhibitor comprises a quaternary ammonium salt of imidazoline benzoate, an acetylenic alcohol, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps:

[0076] The organic amine compound is a mixture of cyclohexylamine and diethylenetriamine, with a mass ratio of 1:2;

[0077] The solvent is an ethanol aqueous solution with a volume fraction of 50%;

[0078] The mass fraction of the benzoic acid imidazoline quaternary ammonium salt in the low-temperature dew point neutralization and corrosion inhibitor is 28wt%, and the mass fraction of the acetylenic alcohol in the low-temperature dew point neutralization and corrosion inhibitor is 10%;

[0079] The mass fraction of the organic amine compound in the low-temperature dew point and corrosion inhibitor is 14%;

[0080] The preparation method of the low-temperature dew point neutralizing corrosion inhibitor is the same as that of Example 1, specifically, the benzoic acid imidazoline quaternary ammonium salt, acetylene alcohol and organic amine compound are respectively dissolved in the solvent and then mixed to prepare the neutralizing corrosion inhibitor.

[0081] The static hanging piece weight loss method was used to test the corrosion inhibition efficiency. Acidic water was used as the corrosive liquid. The cleaned and weighed carbon steel hanging piece was tied with a corrosion-resistant plastic rope and completely immersed in a conical flask containing 1000 mg / L HCl-500 mg / L H2S solution (pH 2-3) and the corrosion inhibitor described in Examples 1-5 (40 mg / L, calculated based on the sum of the masses of the Mannich base derivative or benzoic acid imidazoline quaternary ammonium salt and alkynol). The hanging rope was clamped and fixed with a bottle cap, and the conical flask was placed in a constant temperature water bath at 95°C. After keeping warm for 3 hours, the hanging piece was taken out for treatment and weighing, and a blank test was performed at the same time. The corrosion inhibition efficiency was calculated by the weight loss of the hanging piece. The test results are shown in Table 1.

[0082] Table 1 Evaluation results of the corrosion inhibition efficiency of the corrosion inhibitors described in Examples 1-5

[0083]

[0084] The anti-emulsification performance experiment was tested using the GB / T7305-2003 petroleum method. 40 mL of corrosion inhibitor was added to 40 mL of distilled water and placed in a constant temperature bath at 82°C for 10 minutes. After stirring with a stirrer at a speed of 1500 r / min for 5 minutes, the time for separating 5 mL of water and the water output after 5 minutes were recorded. The test results are shown in Table 2.

[0085] Table 2 Evaluation results of the demulsification performance of the corrosion inhibitors described in Examples 1-5

[0086]

[0087] The corrosion inhibitors described in Examples 1 and 5 were put into actual industrial application in a normal and vacuum distillation unit of a refinery. The use concentration of the neutralizing corrosion inhibitor was 15-30ppm (relative to crude oil). The injection amount was related to the properties of the crude oil. As the acid value, sulfur content and salt content of the crude oil after desalination increased, the injection amount should be increased accordingly. The larger the injection amount, the higher the pH value of the condensed water. When used, the pH value of the condensed water was maintained between 5.5 and 6.5. The average oil content of the condensed water in the normal and vacuum distillation unit before the use of the corrosion inhibitor was 684mg / L, the average oil content of the condensed water after the use of the neutralizing corrosion inhibitor described in Example 1 was 125mg / L, and the average oil content of the condensed water after the use of the neutralizing corrosion inhibitor described in Example 5 was 317mg / L.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A low-temperature dew point neutralizing corrosion inhibitor, characterized in that: The invention comprises a Mannich base derivative, an organic amine compound and a solvent, wherein the preparation method of the Mannich base derivative comprises the following steps: (1) Preparation of intermediate products Weigh 2,4-dihydroxy-6-methoxy-3-methylacetophenone and disperse it in an anhydrous ethanol solvent, add a base, heat and stir until it is completely dissolved, add p-hydroxybenzaldehyde and stir to react for 4-6 hours, cool to room temperature after the reaction is completed, adjust the pH to neutral, separate the precipitate and wash it to obtain an intermediate product; the base is sodium hydroxide and / or potassium hydroxide; the mass ratio of the 2,4-dihydroxy-6-methoxy-3-methylacetophenone to the base and the p-hydroxybenzaldehyde is 1: (0.74-0.76): (0.7-0.72); (2) Preparation of derivatives The intermediate product is dispersed in anhydrous ethanol solvent, and paraformaldehyde is added. The temperature is raised and stirred until it is completely dissolved. N-ethylpiperazine is added and the mixture is stirred and reacted for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature, and dichloromethane is added for extraction. The upper organic phase is taken, concentrated, purified and removed of unreacted reactants, and the solvent is evaporated to obtain the Mannich base derivative. The mass ratio of the intermediate product to the paraformaldehyde and the N-ethylpiperazine is 1: (0.56-0.62): (2.2-2.3).

2. A low-temperature dew point neutralization corrosion inhibitor according to claim 1, characterized in that: The mass fraction of the Mannich base derivative in the low-temperature dew point neutralizer and the corrosion inhibitor is 30-50%.

3. A low-temperature dew point neutralization corrosion inhibitor according to claim 1, characterized in that: The mass fraction of the organic amine compound in the low-temperature dew point and the corrosion inhibitor is 10-18%.

4. The low-temperature dew point neutralization corrosion inhibitor according to claim 1, characterized in that: The organic amine compound is one or more of propylamine, butylamine, pentylamine, cyclohexylamine, ethylenediamine, ethanolamine, methoxypropylamine, dimethylethylamine, dimethylethanolamine, dimethylisopropanolamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

5. The low-temperature dew point neutralization corrosion inhibitor according to claim 1, characterized in that: The solvent is deionized water and / or lower alcohol.

6. A low-temperature dew point neutralization corrosion inhibitor according to claim 5, characterized in that: The lower alcohol is one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

7. A method for preparing a low-temperature dew point neutralizing corrosion inhibitor according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, preparing the Mannich base derivative; S2, dissolving the Mannich base derivative in the solvent to obtain solution 1; dissolving the organic amine compound in the solvent to obtain solution 2; and uniformly mixing solution 1 and solution 2 to obtain the low-temperature dew point neutralizing corrosion inhibitor.

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