Allyl thiourea preparation process capable of reducing metal corrosion rate

Abstract

The invention relates to the technical field of metal protection, in particular to a preparation process of allylthiourea capable of reducing the metal corrosion rate, and aims to overcome the defects that although a traditional metal corrosion inhibitor containing a thiourea group can slow down the corrosion rate to a certain extent, the corrosion inhibition effect is limited, and the environmental adaptability is poor. The industrial application of the material in the field of metal protection is limited. The molecular structure of the allylthiourea contains a plurality of thiourea groups, pyridine rings and trifluoromethyl, the thiourea groups, the pyridine rings and the trifluoromethyl jointly act on the metal surface under the synergistic effect, the overall performance is improved through the enhancement effect, the prepared allylthiourea has excellent corrosion inhibition performance, and the corrosion inhibition effect is good. The metal corrosion rate can be effectively reduced, and more excellent performance is shown in the field of metal protection.

Description

Technical Field

[0001] The invention relates to the technical field of metal protection, and in particular to a preparation process of allylthiourea which can reduce the metal corrosion rate. Background Art

[0002] Metal corrosion is one of the key problems that need to be solved in industrial production. It not only affects the normal operation and service life of equipment, but also may cause safety accidents and cause huge economic losses. Therefore, it is of great significance to develop efficient and environmentally friendly metal corrosion inhibitors. Compounds containing thiourea groups can form a stable protective film with the metal surface because of the sulfur and nitrogen atoms in their molecular structure, thereby effectively inhibiting metal corrosion and becoming a research hotspot in the field of metal protection. However, although traditional metal corrosion inhibitors containing thiourea groups can slow down the corrosion rate to a certain extent, they often have the disadvantages of limited corrosion inhibition effect and poor environmental adaptability, which limits their industrial application in the field of metal protection. Therefore, it is of great practical significance and application value to develop a preparation process of allyl thiourea that can reduce the metal corrosion rate. Summary of the invention

[0003] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide an allylthiourea preparation process that can reduce the metal corrosion rate, thereby solving the problem that traditional metal corrosion inhibitors containing thiourea groups can slow down the corrosion rate to a certain extent, but often have the disadvantages of limited corrosion inhibition effect and poor environmental adaptability, which limits their industrial application in the field of metal protection.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A process for preparing allylthiourea capable of reducing metal corrosion rate comprises the following steps:

[0006] Step 1: Add 3-chloro-5-trifluoromethylpyridine and concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer, a constant pressure dropping funnel and a reflux condenser, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add the mixed acid dropwise while stirring, and control the dropping rate to 1-3mL / min. After the dropwise addition is completed, the temperature is raised to reflux and the stirring reaction is continued for 6-8h. After the reaction is completed, the reaction product is added to ice water, and then the pH is adjusted to 5.5-6.5 with an ammonia solution to precipitate, and then vacuum filtration is performed, and the filter cake is placed in a vacuum drying oven and dried at a temperature of 60-65°C for 2-3h to obtain intermediate 1;

[0007] Step 2: Add intermediate 1, pentaerythritol, anhydrous potassium carbonate and N,N-dimethylformamide to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then heat to 75-80°C and stir for 6-8 hours, add the reaction product to distilled water after the reaction is completed, precipitate, and then vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 60-65°C for 2-3 hours to obtain intermediate 2;

[0008] Step 3: Add intermediate 2, 10% palladium carbon and anhydrous ethanol to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a constant pressure dropping funnel and a reflux condenser, introduce nitrogen protection, stir and react for 5-10 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add hydrazine hydrate solution dropwise while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 15-20h under reflux conditions after the dropwise addition is completed. After the reaction is completed, filter the reaction product while hot, add the filtrate to ice water, precipitate, and then vacuum filter, wash the filter cake with distilled water 3-5 times, and then place it in a vacuum drying oven and dry it at a temperature of 60-65°C for 4-5h to obtain intermediate 3;

[0009] Step 4: Add potassium thiocyanate and anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 10-15 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, heat the temperature to 65-70°C and continue stirring and reacting for 2-3h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, and distill the filtrate under reduced pressure to collect the fraction with a temperature of 72°C and a pressure of 0.087MPa to obtain intermediate 4;

[0010] Step 5: Add intermediate 3 and dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 10-15 minutes at a temperature of 0-5°C and a stirring rate of 300-400r / min, then add the intermediate 4 solution dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 25-30°C and the stirring reaction is continued for 8-10 hours. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent to obtain allyl thiourea that can reduce the metal corrosion rate.

[0011] As a further solution of the present invention: the usage ratio of the 3-chloro-5-trifluoromethylpyridine, concentrated sulfuric acid and mixed acid in step 1 is 10 mmol: 15-20 mL: 15-20 mL.

[0012] As a further solution of the present invention: the mixed acid in step 1 is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the concentrated nitric acid is 67%.

[0013] As a further solution of the present invention: the mass fraction of the ammonia solution in step 1 is 22-25%.

[0014] As a further scheme of the present invention: the usage ratio of the intermediate 1, pentaerythritol, anhydrous potassium carbonate and N,N-dimethylformamide in step 2 is 42-46 mmol: 10 mmol: 50-55 mmol: 70-80 mL.

[0015] As a further solution of the present invention: the usage ratio of the intermediate 2, 10% palladium carbon, anhydrous ethanol and hydrazine hydrate solution in step 3 is 10 mmol: 5.5-6.5 g: 100-120 mL: 45-50 g.

[0016] As a further solution of the present invention: the mass fraction of the hydrazine hydrate solution in step three is 80%.

[0017] As a further solution of the present invention: the usage ratio of the potassium thiocyanate, anhydrous ethanol and 3-bromo-1-propylene in step 4 is 10 mmol: 25-30 mL: 10 mmol.

[0018] As a further solution of the present invention: the usage ratio of the intermediate 3, dichloromethane and the intermediate 4 solution in step 5 is 10 mmol: 30-40 mL: 42-45 mL.

[0019] As a further solution of the present invention: the intermediate 4 solution in step 5 is a solution formed by dissolving the intermediate 4 in dichloromethane at a ratio of 10 mmol:10 mL.

[0020] As a further solution of the present invention: the mixed solvent in step 5 is a mixture of petroleum ether and ethyl acetate in equal volumes.

[0021] Beneficial effects of the present invention:

[0022] The invention discloses a preparation process of allyl thiourea capable of reducing metal corrosion rate. The process comprises the following steps: using 3-chloro-5-trifluoromethyl pyridine as a raw material to carry out nitration in a mixed acid, introducing a nitro group on the pyridine ring, obtaining an intermediate 1, then reacting the intermediate 1 with pentaerythritol, reacting the chlorine atom on the intermediate 1 with a hydroxyl group on the pentaerythritol, forming an intermediate 2 containing four pyridine rings connected with a nitro group and a trifluoromethyl group, then reacting the intermediate 2 with hydrazine hydrate, reducing the nitro group on the intermediate 2 to an amino group by the hydrazine hydrate, obtaining an intermediate 3, then using potassium thiocyanate and 3-bromo-1-propylene as raw materials, obtaining a compound allyl isothiocyanate through a nucleophilic substitution reaction, obtaining an intermediate 4, finally reacting the intermediate 3 with the intermediate 4, causing the amino group on the intermediate to undergo a nucleophilic addition reaction with the isothiocyanate in the intermediate 4, forming a thiourea group, and obtaining a compound containing four thiourea groups, namely the allyl thiourea capable of reducing metal corrosion rate.

[0023] The molecular structure of the allylthiourea contains multiple thiourea groups, pyridine rings and trifluoromethyl groups. The sulfur atom and nitrogen atom in the thiourea group have strong coordination ability and can form stable coordination bonds with the empty orbits on the metal surface. This coordination effect not only enhances the adhesion of the compound on the metal surface, but also blocks the direct contact between the corrosive medium (such as water, oxygen, chloride ions, etc.) and the metal by occupying the active sites on the metal surface, thereby slowing down the corrosion reaction. The pyridine ring has a good planar structure and π electron system, which enables it to be tightly adsorbed on the metal surface. This adsorption not only increases the stability of the compound, but also through its large steric hindrance effect , further blocking the corrosion of the corrosive medium on the metal surface. At the same time, the nitrogen atom on the pyridine ring may also participate in the coordination to form a more complex protective film structure. The introduction of trifluoromethyl brings multiple fluorine atoms to the compound. These fluorine atoms have strong electronegativity and small atomic radius, which can enhance the overall polarity and stability of the compound and promote the formation and stability of the protective film. Therefore, under the synergistic effect of multiple thiourea groups, pyridine rings and trifluoromethyl groups, they act on the metal surface together, and the overall performance is improved through the enhancement effect, so that the prepared allyl thiourea has excellent corrosion inhibition performance, which can effectively reduce the metal corrosion rate and show more excellent performance in the field of metal protection. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1:

[0026] This embodiment is a process for preparing allylthiourea that can reduce the metal corrosion rate, comprising the following steps:

[0027] Step 1: add 10mmol 3-chloro-5-trifluoromethylpyridine and 15mL of 98% concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer, a constant pressure dropping funnel and a reflux condenser, stir and react for 20min at a temperature of 25°C and a stirring rate of 300r / min, then add dropwise 15mL of a mixed acid of 98% concentrated sulfuric acid and 67% concentrated nitric acid in a volume ratio of 1:1 while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 6h under reflux conditions after the dropwise addition is completed. After the reaction is completed, add the reaction product to ice water, and then adjust the pH to 5.5 with a 22% ammonia solution to precipitate, and then vacuum filter, place the filter cake in a vacuum drying oven, and dry it at 60°C for 2h to obtain intermediate 1;

[0028] Step 2: 42 mmol of intermediate 1, 10 mmol of pentaerythritol, 50 mmol of anhydrous potassium carbonate and 70 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas duct, and nitrogen was introduced for protection. The mixture was stirred at 25° C. and a stirring rate of 300 r / min for 20 min, and then the mixture was heated to 75° C. and stirred for 6 h. After the reaction, the reaction product was added to distilled water to precipitate, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 60° C. for 2 h to obtain intermediate 2;

[0029] Step 3: Add 10mmol of intermediate 2, 5.5g of 10% palladium carbon and 100mL of anhydrous ethanol to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a constant pressure dropping funnel and a reflux condenser, introduce nitrogen protection, stir and react for 5min at a temperature of 25°C and a stirring rate of 300r / min, then add 45g of 80% hydrazine hydrate solution dropwise while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 15h under reflux conditions after the dropwise addition is completed. After the reaction is completed, filter the reaction product while hot, add the filtrate to ice water, precipitate, and then vacuum filter. Wash the filter cake with distilled water 3 times, then place it in a vacuum drying oven, and dry it at a temperature of 60°C for 4h to obtain intermediate 3;

[0030] Step 4: Add 10mmol potassium thiocyanate and 25mL anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 10min at a temperature of 25°C and a stirring rate of 300r / min, then add 10mmol 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 65°C and the stirring reaction is continued for 2h. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, and the filtrate is distilled under reduced pressure, and the fraction with a temperature of 72°C and a pressure of 0.087MPa is collected to obtain intermediate 4;

[0031] Step 5: Add 10 mmol of intermediate 3 and 30 mL of dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stir the reaction for 10 min at a temperature of 0°C and a stirring rate of 300 r / min. Then, add 42 mL of intermediate 4 dropwise while stirring, wherein the intermediate 4 solution is formed by dissolving 42 mL of intermediate 4 in dichloromethane at a ratio of 10 mmol:10 mL. The dropping rate is controlled to be 1-3 mL / min. After the addition is completed, the temperature is raised to 25°C and the stirring reaction is continued for 8 h. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent prepared by mixing equal volumes of petroleum ether and ethyl acetate to obtain allyl thiourea that can reduce the metal corrosion rate.

[0032] Embodiment 2:

[0033] This embodiment is a process for preparing allylthiourea that can reduce the metal corrosion rate, comprising the following steps:

[0034] Step 1: add 10mmol 3-chloro-5-trifluoromethylpyridine and 18mL of 98% concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer, a constant pressure dropping funnel and a reflux condenser, stir and react for 25min at a temperature of 28°C and a stirring rate of 350r / min, then add dropwise 18mL of a mixed acid of 98% concentrated sulfuric acid and 67% concentrated nitric acid in a volume ratio of 1:1 while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 7h under reflux conditions after the dropwise addition is completed. After the reaction is completed, add the reaction product to ice water, and then adjust the pH to 6 with a 24% ammonia solution to precipitate, and then vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 62°C for 2.5h to obtain intermediate 1;

[0035] Step 2: 44 mmol of intermediate 1, 10 mmol of pentaerythritol, 52 mmol of anhydrous potassium carbonate and 75 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas duct, and nitrogen was introduced for protection. The mixture was stirred for 25 min at a temperature of 28° C. and a stirring rate of 350 r / min, and then the mixture was stirred for 7 h at a temperature of 78° C. After the reaction was completed, the reaction product was added to distilled water to precipitate, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at a temperature of 62° C. for 2.5 h to obtain intermediate 2;

[0036] Step 3: Add 10mmol of intermediate 2, 6g of 10% palladium carbon and 110mL of anhydrous ethanol to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a constant pressure dropping funnel and a reflux condenser, introduce nitrogen protection, stir and react for 8min at a temperature of 28°C and a stirring rate of 350r / min, then add 48g of 80% hydrazine hydrate solution dropwise while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 18h under reflux conditions after the dropwise addition is completed. After the reaction is completed, filter the reaction product while hot, add the filtrate to ice water, precipitate, and then vacuum filter. Wash the filter cake with distilled water 4 times, then place it in a vacuum drying oven, and dry it at a temperature of 62°C for 4.5h to obtain intermediate 3;

[0037] Step 4: Add 10mmol potassium thiocyanate and 28mL anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 12min at a temperature of 28°C and a stirring rate of 350r / min, then add 10mmol 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, heat the temperature to 68°C and continue stirring and reacting for 2.5h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, distill the filtrate under reduced pressure, collect the fraction with a temperature of 72°C and a pressure of 0.087MPa, and obtain intermediate 4;

[0038] Step 5: Add 10 mmol of intermediate 3 and 35 mL of dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stir the reaction for 12 minutes at a temperature of 3°C and a stirring rate of 350 r / min. Then, add 44 mL of intermediate 4 dropwise while stirring, wherein the intermediate 4 solution is formed by dissolving 44 mL of intermediate 4 in dichloromethane at a ratio of 10 mmol:10 mL. The dropping rate is controlled to be 1-3 mL / min. After the addition is completed, the temperature is raised to 28°C and the stirring reaction is continued for 9 hours. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent prepared by mixing equal volumes of petroleum ether and ethyl acetate to obtain allyl thiourea that can reduce the metal corrosion rate.

[0039] Embodiment 3:

[0040] This embodiment is a process for preparing allylthiourea that can reduce the metal corrosion rate, comprising the following steps:

[0041] Step 1: add 10mmol 3-chloro-5-trifluoromethylpyridine and 20mL of 98% concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer, a constant pressure dropping funnel and a reflux condenser, stir and react for 30min at a temperature of 30°C and a stirring rate of 400r / min, then add dropwise 20mL of a mixed acid of 98% concentrated sulfuric acid and 67% concentrated nitric acid in a volume ratio of 1:1 while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 8h under the condition of heating to reflux after the dropwise addition is completed. After the reaction is completed, add the reaction product to ice water, and then adjust the pH to 6.5 with a 25% ammonia solution to precipitate, and then vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 65°C for 3h to obtain intermediate 1;

[0042] Step 2: 46 mmol of intermediate 1, 10 mmol of pentaerythritol, 55 mmol of anhydrous potassium carbonate and 80 mL of N,N-dimethylformamide were added to a three-necked flask equipped with a stirrer, a thermometer and a gas duct, and nitrogen was introduced for protection. The mixture was stirred at 30° C. and a stirring rate of 400 r / min for 30 min, and then the mixture was heated to 80° C. and stirred for 8 h. After the reaction was completed, the reaction product was added to distilled water to precipitate, and then vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 65° C. for 3 h to obtain intermediate 2;

[0043] Step 3: Add 10mmol of intermediate 2, 6.5g of 10% palladium carbon and 120mL of anhydrous ethanol to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a constant pressure dropping funnel and a reflux condenser, introduce nitrogen protection, stir and react for 10min at a temperature of 30°C and a stirring rate of 400r / min, then add 50g of 80% hydrazine hydrate solution dropwise while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 20h under reflux conditions after the dropwise addition is completed. After the reaction is completed, filter the reaction product while hot, add the filtrate to ice water, precipitate, and then vacuum filter. Wash the filter cake with distilled water 5 times, then place it in a vacuum drying oven, and dry it at a temperature of 65°C for 5h to obtain intermediate 3;

[0044] Step 4: Add 10mmol potassium thiocyanate and 30mL anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then add 10mmol 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 70°C and the stirring reaction is continued for 3h. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, and the filtrate is distilled under reduced pressure, and the fraction with a temperature of 72°C and a pressure of 0.087MPa is collected to obtain intermediate 4;

[0045] Step 5: Add 10 mmol of intermediate 3 and 40 mL of dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stir the reaction for 15 minutes at a temperature of 5°C and a stirring rate of 400 r / min. Then, add 45 mL of intermediate 4 dropwise while stirring, wherein the intermediate 4 solution is formed by dissolving 10 mmol:10 mL of intermediate 4 in dichloromethane. The dropping rate is controlled to be 1-3 mL / min. After the addition is completed, the temperature is raised to 30°C and the stirring reaction is continued for 10 hours. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent prepared by mixing equal volumes of petroleum ether and ethyl acetate to obtain allyl thiourea that can reduce the metal corrosion rate.

[0046] Comparative Example 1:

[0047] This comparative example is the stainless steel surface corrosion inhibitor in patent example 1 with application number CN201911048284.0.

[0048] Comparative Example 2:

[0049] This comparative example is a process for preparing allylthiourea that can reduce the metal corrosion rate, comprising the following steps:

[0050] Step 1: Add 10mmol potassium thiocyanate and 30mL anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then add 10mmol 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 70°C and the stirring reaction is continued for 3h. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, and the filtrate is distilled under reduced pressure, and the fraction with a temperature of 72°C and a pressure of 0.087MPa is collected to obtain intermediate 4;

[0051] Step 2: Add 10mmol of p-phenylenediamine and 40mL of dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stir the reaction for 15 minutes at a temperature of 5°C and a stirring rate of 400r / min. Then, add 45mL of the intermediate 4 solution formed by dissolving the intermediate 4 in dichloromethane at a ratio of 10mmol:10mL dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 30°C and the stirring reaction is continued for 10 hours. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent prepared by mixing equal volumes of petroleum ether and ethyl acetate to obtain allyl thiourea that can reduce the metal corrosion rate.

[0052] Comparative Example 3:

[0053] This comparative example is a process for preparing allylthiourea that can reduce the metal corrosion rate, comprising the following steps:

[0054] Step 1: Add 10mmol potassium thiocyanate and 30mL anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 15min at a temperature of 30°C and a stirring rate of 400r / min, then add 10mmol 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 70°C and the stirring reaction is continued for 3h. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, and the filtrate is distilled under reduced pressure, and the fraction with a temperature of 72°C and a pressure of 0.087MPa is collected to obtain intermediate 4;

[0055] Step 2: Add 10mmol 2,3-diaminotrifluorotoluene and 40mL dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, and stir the reaction for 15min at a temperature of 5°C and a stirring rate of 400r / min. Then, add 45mL of the intermediate 4 solution formed by dissolving 10mmol:10mL of the intermediate 4 in dichloromethane dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 30°C and the stirring reaction is continued for 10h. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent prepared by mixing equal volumes of petroleum ether and ethyl acetate to obtain allyl thiourea that can reduce the metal corrosion rate.

[0056] 2g of allylthiourea of ​​Examples 1-3 and Comparative Examples 1-3 were added to 1L of 1mol / L hydrochloric acid solution, and then heated to 50°C. The N80 steel sheet was then immersed for 48h and then taken out to measure its corrosion inhibition rate. The test results are shown in the following table:

[0057] sample Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Corrosion inhibition rate, % 98.2 98.5 98.9 85.04 91.29 95.12

[0058] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-3, it can be known that the allyl thiourea of ​​the present invention has excellent corrosion inhibition effect and can significantly reduce the metal corrosion rate.

[0059] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0060] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A process for preparing allylthiourea that can reduce metal corrosion rate, characterized in that: The following steps are involved: Step 1: Add 3-chloro-5-trifluoromethylpyridine and concentrated sulfuric acid to a three-necked flask equipped with a stirrer, a thermometer, a constant pressure dropping funnel and a reflux condenser, stir and react for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add the mixed acid dropwise while stirring, and control the dropping rate to 1-3mL / min. After the dropwise addition is completed, the temperature is raised to reflux and the stirring reaction is continued for 6-8h. After the reaction is completed, the reaction product is added to ice water, and then the pH is adjusted to 5.5-6.5 with an ammonia solution to precipitate, and then vacuum filtration is performed, and the filter cake is placed in a vacuum drying oven and dried at a temperature of 60-65°C for 2-3h to obtain intermediate 1; Step 2: Add intermediate 1, pentaerythritol, anhydrous potassium carbonate and N,N-dimethylformamide to a three-necked flask equipped with a stirrer, a thermometer and an air guide tube, introduce nitrogen protection, stir for 20-30 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then heat to 75-80°C and stir for 6-8 hours, add the reaction product to distilled water after the reaction is completed, precipitate, and then vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 60-65°C for 2-3 hours to obtain intermediate 2; Step 3: Add intermediate 2, 10% palladium carbon and anhydrous ethanol to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a constant pressure dropping funnel and a reflux condenser, introduce nitrogen protection, stir and react for 5-10 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add hydrazine hydrate solution dropwise while stirring, control the dropping rate to 1-3mL / min, and continue stirring and reacting for 15-20h under reflux conditions after the dropwise addition is completed. After the reaction is completed, filter the reaction product while hot, add the filtrate to ice water, precipitate, and then vacuum filter, wash the filter cake with distilled water 3-5 times, and then place it in a vacuum drying oven and dry it at a temperature of 60-65°C for 4-5h to obtain intermediate 3; Step 4: Add potassium thiocyanate and anhydrous ethanol to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 10-15 minutes at a temperature of 25-30°C and a stirring rate of 300-400r / min, then add 3-bromo-1-propylene dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, heat the temperature to 65-70°C and continue stirring and reacting for 2-3h. After the reaction is completed, cool the reaction product to room temperature, then vacuum filter, and distill the filtrate under reduced pressure to collect the fraction with a temperature of 72°C and a pressure of 0.087MPa to obtain intermediate 4; Step 5: Add intermediate 3 and dichloromethane to a three-necked flask equipped with a stirrer, a thermometer and a constant pressure dropping funnel, stir and react for 10-15 minutes at a temperature of 0-5°C and a stirring rate of 300-400r / min, then add the intermediate 4 solution dropwise while stirring, and control the dropping rate to 1-3mL / min. After the addition is completed, the temperature is raised to 25-30°C and the stirring reaction is continued for 8-10 hours. After the reaction is completed, the reaction product is rotary evaporated to remove the solvent, and then silica gel column chromatography is performed with a mixed solvent to obtain allyl thiourea that can reduce the metal corrosion rate.

2. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The usage ratio of the 3-chloro-5-trifluoromethylpyridine, concentrated sulfuric acid and mixed acid in step 1 is 10 mmol: 15-20 mL: 15-20 mL.

3. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The mixed acid in step 1 is a mixture of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the concentrated nitric acid is 67%.

4. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The usage ratio of the intermediate 1, pentaerythritol, anhydrous potassium carbonate and N,N-dimethylformamide in step 2 is 42-46 mmol: 10 mmol: 50-55 mmol: 70-80 mL.

5. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The usage ratio of the intermediate 2, 10% palladium carbon, anhydrous ethanol and hydrazine hydrate solution in step 3 is 10 mmol: 5.5-6.5 g: 100-120 mL: 45-50 g.

6. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The mass fraction of the hydrazine hydrate solution in step 3 is 80%.

7. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The usage ratio of the potassium thiocyanate, anhydrous ethanol and 3-bromo-1-propylene in step 4 is 10 mmol: 25-30 mL: 10 mmol.

8. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The usage ratio of the intermediate 3, dichloromethane and the intermediate 4 solution in step 5 is 10 mmol: 30-40 mL: 42-45 mL.

9. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The intermediate 4 solution in step 5 is a solution formed by dissolving the intermediate 4 in dichloromethane at a ratio of 10 mmol:10 mL.

10. The process for preparing allylthiourea capable of reducing metal corrosion rate according to claim 1, characterized in that: The mixed solvent in step 5 is a mixture of petroleum ether and ethyl acetate in equal volumes.