High purity bisthiazolyl derivatives and methods for their preparation

Abstract

The application discloses a high-purity dithiadiazole derivative and a preparation method thereof. 2,5-dimercapto-1,3,4-thiadiazole, a binary mercaptan and hydrogen peroxide are added into ethanol to produce an intermediate through reaction, then alkyl mercaptan and hydrogen peroxide are added into a mixed solution of the intermediate to obtain a crude product after reaction, and finally, the crude product is purified through a molecular distillation technology. The dithiadiazole derivative obtained by the application has high sulfur content, excellent extrusion performance and corrosion inhibition performance, and the product post-processing process is green and efficient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lubricating oil additives, and particularly relates to a high-purity bis-thiadiazole derivative. BACKGROUND

[0002] Sulfurized olefins are widely used in gear oils due to high active sulfur content, excellent thermal stability and extreme pressure performance. However, sulfurized olefins have strong irritating odor and have corrosion effect on metals, so the research on the replacement of sulfurized olefins has become a hot spot in recent years. 2,5-dimercapto-1,3,4-thiadiazole is a heterocyclic compound containing S and N, and has good tribological properties. Its dimer derivative is used as a corrosion inhibitor in the early stage, which overcomes the drawbacks of traditional extreme pressure additives, such as reduction of antioxidant performance of oil and serious copper corrosion.

[0003] Patent CN103509632B discloses a bis-thiadiazole dimer and a preparation method thereof. The compound has high sulfur content, and has both extreme pressure performance and corrosion inhibition performance, but is often used in greases due to poor oil solubility. Patent CN103319435B discloses a bis-thiadiazole derivative and a preparation method thereof. The method first reacts dimercaptothiadiazole and chloroalkane to generate monoalkylthiadiazole, and then generates the bis-thiadiazole derivative through coupling reaction of the oxidizing agent. The compound has excellent extreme pressure performance and friction reduction performance. Patent CN110194751A discloses a preparation method of a bis-thiadiazole derivative. The method first prepares dimercaptothiadiazole dimer through dimercaptothiadiazole and hydrogen peroxide, and then adds hydrogen peroxide into the mixed solution of dimercaptothiadiazole again. The reaction product is obtained through liquid separation, water washing and reduced pressure distillation. The compound has high sulfur content, has extreme pressure performance, and can also be used as a metal deactivator. However, the preparation method does not disclose the residual amount of alkyl mercaptan in the prepared thiazole derivative. Silver strip corrosion is an important index of aviation oil. Elemental sulfur, hydrogen sulfide and mercaptan are the main reasons for unqualified silver strip corrosion. Although only sulfur-containing active sulfur, the content of mercaptan reaches 100 ppm, which will not cause unqualified silver strip corrosion, but when elemental sulfur, hydrogen sulfide and mercaptan coexist, the two have a synergistic effect to aggravate corrosion, and the content of 0.3 ppm can cause unqualified silver strip corrosion. However, the conventional reduced pressure distillation cannot completely remove the residual mercaptan.

[0004] As can be seen from the above patents, the bis-thiadiazole derivative has high sulfur content, and has both extreme pressure and corrosion inhibition performance, but the conventional post-treatment process is often used, which has a certain influence on the corrosion inhibition performance. SUMMARY

[0005] The present application aims to provide a high-purity bis-thiadiazole derivative with high sulfur content, excellent extreme pressure performance and metal corrosion inhibition performance.

[0006] Another object of the present application is to provide a preparation method of the high-purity bis-thiadiazole derivative, which can effectively remove residual alkyl mercaptan impurities and reduce the corrosion of the product to metal.

[0007] The first technical solution adopted by the present application is a high-purity bis-thiadiazole derivative, which has the following structural formula:

[0008]

[0009] In the structural formula, R1 is a linear or branched alkyl group with 7 to 12 carbon atoms, and n is an integer from 4 to 10.

[0010] The first technical solution of the present application is further characterized in that,

[0011] R1 is selected from one of n-heptyl, octyl, tert-octyl, 2-ethylhexyl, nonyl, tert-nonyl, decyl, dodecyl or tert-dodecyl.

[0012] The second technical solution adopted by the present application is a preparation method of a high-purity bis-thiadiazole derivative, which comprises the following steps:

[0013] Step 1: adding 2,5-dimercapto-1,3,4-thiadiazole and a binary mercaptan into ethanol, then adding hydrogen peroxide dropwise, and reacting to generate an intermediate thiadiazole dimer;

[0014] Step 2: adding an alkyl mercaptan into the intermediate thiadiazole dimer obtained in Step 1, then adding hydrogen peroxide dropwise again, and after the reaction is completed, the reaction solution is sequentially subjected to liquid-liquid separation and filtration to obtain a crude bis-thiadiazole derivative product;

[0015] Step 3: subjecting the crude bis-thiadiazole derivative product obtained in Step 2 to molecular distillation treatment to remove light phase distillates, and collecting heavy phase distillates to obtain the product.

[0016] The second technical solution of the present application is further characterized in that,

[0017] In Step 1, the temperature of the reaction system is maintained at 30 to 50°C when hydrogen peroxide is added dropwise, and after the addition of hydrogen peroxide is completed, the temperature is increased to 70 to 80°C, and then reacted for 0.5 to 2 hours to obtain the intermediate.

[0018] The binary mercaptan in Step 1 is selected from one of 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol or 1,10-decanedithiol.

[0019] The temperature of the reaction system is kept at 30-50 DEG C when the hydrogen peroxide is added dropwise in step 2, and the temperature is raised to 70-80 DEG C after the addition of the hydrogen peroxide is completed, and then the reaction liquid is filtered after being separated and reacted for 2-5 hours to obtain the crude product of the bisthiazole derivative.

[0020] The evaporation temperature is 80-150 DEG C and the vacuum degree is 0.01-50 Pa in step 3, and the light phase distillate accounts for 5-20% of the total distillate.

[0021] The bisthiazole derivative of the present application has high sulfur content, excellent extreme pressure performance and metal corrosion inhibition performance, and can effectively reduce the irritating odor of industrial gear oil. The bisthiazole derivative of the present application is treated by molecular distillation technology in the post-treatment process, which can effectively remove residual impurities such as alkyl mercaptan and reduce the corrosion of the product to copper, silver and other metals; using binary mercaptan as raw material can avoid the consumption of a large amount of ethanol in the direct coupling reaction of 2,5-dimercapto-1,3,4-thiadiazole, and reduce the generation of three wastes. DETAILED DESCRIPTION

[0022] The present application will be described in detail below in combination with specific embodiments.

[0023] The present application provides a high-purity bisthiazole derivative, the structural formula of which is as follows:

[0024]

[0025] In the structural formula, R1 is a linear or branched hydrocarbon group with 7-12 carbon atoms, and R1 is selected from one of n-heptyl, octyl, tert-octyl, 2-ethylhexyl, nonyl, tert-nonyl, decyl, dodecyl or tert-dodecyl; n is an integer of 4-10.

[0026] The present application also provides a preparation method of the high-purity bisthiazole derivative, which comprises the following steps:

[0027] In step 1, 2,5-dimercapto-1,3,4-thiadiazole and binary mercaptan are added in ethanol, and then hydrogen peroxide is added dropwise, the temperature of the reaction system is kept at 30-50 DEG C when the hydrogen peroxide is added dropwise, the temperature is raised to 70-80 DEG C after the addition of the hydrogen peroxide is completed, and then the intermediate bisthiazole dimer is generated after reacting for 0.5-2 hours; wherein the binary mercaptan is selected from one of 1,4-butanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol or 1,10-decanedithiol.

[0028] Step 2: Add alkyl mercaptan to the intermediate thiadiazole dimer obtained in step 1, and then add hydrogen peroxide dropwise twice. When adding hydrogen peroxide dropwise, the reaction system temperature is maintained at 30-50° C. After the addition of hydrogen peroxide is completed, the temperature is raised to 70-80° C., and the reaction is continued for 2-5 hours. The reaction solution is then separated and filtered to obtain a crude product of the bis-thiadiazole derivative.

[0029] Step 3: The crude product of the bis-thiadiazole derivative obtained in Step 2 is subjected to molecular distillation to remove the light phase distillate. The evaporation temperature is 80-150° C. and the vacuum is 0.01-50 Pa. The light phase distillate is maintained at 5%-20% by weight of the total distillate. Other molecular distillation parameters, such as the injection rate, film forming speed, and condensing surface temperature, can be set and appropriately adjusted by those skilled in the art based on actual conditions and operational experience. Impurities such as alkyl mercaptans, water, and ethanol are removed from the light phase distillate, and the bis-thiadiazole derivative is collected as the heavy phase distillate.

[0030] Through the above-mentioned method, the high-purity bithiadiazole derivative of the present invention has a high sulfur content, excellent extreme pressure performance and metal corrosion inhibition properties, and can effectively reduce the pungent odor in industrial gear oil. The bithiadiazole derivative of the present invention utilizes molecular distillation technology in the post-processing process to effectively remove residual impurities such as alkyl mercaptan, water, and ethanol, thereby reducing the product's corrosion effect on metals such as copper and silver. The preparation process of the present invention uses dihydric mercaptan as a raw material, avoiding the large amount of ethanol required for the direct coupling reaction of 2,5-dimercapto-1,3,4-thiadiazole, thereby reducing the generation of three wastes.

[0031] Example 1 (Comparative Example)

[0032] In order to better illustrate the key technical features of the present invention, this example is a bithiadiazole derivative prepared by conventional water washing and reduced pressure distillation as a post-treatment process after the preparation reaction, which is used as a comparative example to illustrate the present invention.

[0033] In a four-necked jacketed reaction flask equipped with a mechanical stirrer and a thermometer, 150 g of 2,5-dimercapto-1,3,4-thiadiazole, 75 g of hexanedithiol, and 135 g of ethanol were added. Mechanical stirring was initiated, and after the raw materials were evenly dispersed, 125 g of a 30% aqueous hydrogen peroxide solution was added dropwise. A cooling medium was introduced into the jacket of the four-necked flask to maintain the reaction temperature at 30°C. After the addition was complete, a heating medium was introduced into the jacket of the four-necked flask to raise the temperature to 70°C. The reaction was allowed to proceed for 0.5 h to obtain the intermediate. The cooling medium was continued to be introduced into the jacket of the four-necked flask to lower the temperature to 30°C. 160 g of tert-nonylmercaptan was added, and 130 g of a 30% aqueous hydrogen peroxide solution was added dropwise again. After the addition was complete, a heating medium was introduced into the jacket of the four-necked flask to raise the temperature to 70°C. The reaction was allowed to proceed for 2 h, followed by separation, filtration, and vacuum distillation to obtain the bis-thiadiazole derivative product.

[0034] Example 2

[0035] In a four-necked jacketed reaction flask equipped with mechanical stirrer and thermometer, 2,5-dimercapto-l,3,4-thiadiazole 150 g, hexanedithiol 75 g, ethanol 135 g were added, and the mechanical stirrer was started. After the raw materials were uniformly dispersed, 30% hydrogen peroxide aqueous solution 125 g was added dropwise, and cold medium was passed through the jacket of the four-necked flask to keep the reaction temperature at 30°C. After the dropwise addition was completed, hot medium was passed through the jacket of the four-necked flask to warm the reactants to 70°C, and the reaction was carried out for 0.5 h to obtain an intermediate. Cold medium was continuously passed through the jacket of the four-necked flask to cool to 30°C, and tert-nonyl mercaptan 160 g was added, and 30% hydrogen peroxide aqueous solution 130 g was added dropwise again. After the dropwise addition was completed, hot medium was passed through the jacket of the four-necked flask to warm the reactants to 70°C, and the reaction was carried out for 2 h. After separation and filtration, a crude product of bis-thiadiazole derivative was obtained.

[0036] The above crude product was introduced into a molecular distillation device for removal of light phase impurities. The evaporation temperature was set to 130°C, the vacuum degree was set to 10 Pa, and the mechanical stirring rate was set to 370 rpm. The remaining molecular distillation parameters were adjusted to keep the mass percentage of light phase distillate in total distillate at 10%, and the heavy phase distillate was collected as a high-purity bis-thiadiazole derivative.

[0037] Example 3

[0038] In a four-necked jacketed reaction flask equipped with mechanical stirrer and thermometer, 2,5-dimercapto-l,3,4-thiadiazole 150 g, decanedithiol 103.2 g, ethanol 150 g were added, and the mechanical stirrer was started. After the raw materials were uniformly dispersed, 30% hydrogen peroxide aqueous solution 125 g was added dropwise, and cold medium was passed through the jacket of the four-necked flask to keep the reaction temperature at 50°C. After the dropwise addition was completed, hot medium was passed through the jacket of the four-necked flask to warm the reactants to 80°C, and the reaction was carried out for 2 h to obtain an intermediate. Cold medium was continuously passed through the jacket of the four-necked flask to cool to 50°C, and tert-dodecyl mercaptan 202 g was added, and 30% hydrogen peroxide aqueous solution 130 g was added dropwise again. After the dropwise addition was completed, hot medium was passed through the jacket of the four-necked flask to warm the reactants to 80°C, and the reaction was carried out for 5 h. After separation and filtration, a crude product of bis-thiadiazole derivative was obtained.

[0039] The above crude product was introduced into a molecular distillation device for removal of light phase impurities. The evaporation temperature was set to 80°C, the vacuum degree was set to 0.01 Pa, and the mechanical stirring rate was set to 370 rpm. The remaining molecular distillation parameters were adjusted to keep the mass percentage of light phase distillate in total distillate at 20%, and the heavy phase distillate was collected as a high-purity bis-thiadiazole derivative.

[0040] Example 4

[0041] In a four-necked reaction flask equipped with mechanical stirring, thermometer, 2,5-dimercapto-1,3,4-thiadiazole 150 g, butanediol 122 g, ethanol 163 g, start mechanical stirring, after the raw material is evenly dispersed, add 30% hydrogen peroxide solution 125 g dropwise, pass cold medium in the four-necked flask jacket to keep the reaction temperature at 40°C. After the dropwise addition is completed, pass hot medium in the four-necked flask jacket to warm the reactants to 75°C, and after reaction for 1 h, the intermediate is obtained. Continue to pass cold medium in the four-necked flask jacket to cool to 40°C, add t-octyl mercaptan 146 g, and again add 30% hydrogen peroxide solution 130 g dropwise. After the dropwise addition is completed, pass hot medium in the four-necked flask jacket to warm the reactants to 75°C, and after reaction for 3 h, the crude product of the bis-thiadiazole derivative is obtained after separation and filtration.

[0042] The above crude product is introduced into a molecular distillation device for light phase impurity removal treatment. The evaporation temperature is set to 150°C, the vacuum degree is 50 Pa, and the mechanical stirring rate is 370 rpm. The remaining molecular distillation parameters are adjusted to keep the light phase distillate at 5% of the total distillate mass percentage, and the heavy phase distillate is collected as the high-purity bis-thiadiazole derivative.

[0043] The sulfur content of the product is tested by the standard method SH / T0303, the additive is added to the MVI500 base oil at 1.0% (mass fraction), and the performance is evaluated by copper strip corrosion and four-ball machine test method. The results are shown in Table 1.

[0044] Table 1

[0045]

[0046] As can be seen from Table 1, the sulfur content of the bis-thiadiazole derivative of Examples 1-4 is significantly higher than that of the commercial product T561, and after being added to the MVI500 base oil, the extreme pressure and wear resistance is also significantly better than that of the commercial product T561. At the same time, after being introduced into the MVI500 base oil, it can significantly inhibit copper strip corrosion.

[0047] T561 and the products of Examples 1-4 are introduced into aviation lubricating oil, the mercaptan sulfur content of the oil is tested by the standard method GB / T1792-2015, and the silver strip corrosion test of the oil is carried out by the standard method SH / T 0023-1990. The results are shown in Table 2.

[0048] Table 2

[0049]

[0050] From Table 2, it can be seen that after the T561 and the product of the comparative example were introduced into the aviation lubricating oil, the mercaptan sulfur content was 30 mg / g and 25 mg / g respectively, and the silver strip corrosion test was level 2. After the products of Examples 2-4 were introduced into the aviation lubricating oil, the mercaptan sulfur content was 3 mg / g, 4 mg / g and 3 mg / g respectively, and the silver strip corrosion test was level 0. It is indicated that the molecular distillation treatment can effectively reduce the content of mercaptan sulfur, thereby improving the silver strip corrosion of the oil.

Claims

1. A method for preparing a high-purity bithiadiazole derivative, characterized in that: The following steps are involved: Step 1, adding 2,5-dimercapto-1,3,4-thiadiazole and dihydric mercaptan to ethanol, and then adding hydrogen peroxide dropwise, maintaining the temperature of the reaction system at 30-50° C. when adding hydrogen peroxide, and heating to 70-80° C. after the addition of hydrogen peroxide is completed, and reacting for 0.5-2 hours to generate an intermediate thiadiazole dimer; Step 2: adding alkyl mercaptan to the intermediate thiadiazole dimer obtained in step 1, and then dropping hydrogen peroxide twice, maintaining the temperature of the reaction system at 30-50° C. during the dropwise addition of hydrogen peroxide, heating the reaction system to 70-80° C. after the completion of the dropwise addition of hydrogen peroxide, and reacting for 2-5 hours, and then separating and filtering the reaction solution to obtain a crude product of the bis-thiadiazole derivative; Step 3: The crude product of the bis-thiadiazole derivative obtained in step 2 is subjected to molecular distillation to remove the light phase distillate. The evaporation temperature is 80-150° C. and the vacuum degree is 0.01-50 Pa. The light phase distillate is maintained at 5%-20% by mass of the total distillate. The heavy phase distillate is collected to obtain the bis-thiadiazole derivative, which has the following structural formula: In the structural formula, R1 is selected from one of n-heptyl, octyl, tert-octyl, 2-ethylhexyl, nonyl, tert-nonyl, decyl, dodecyl and tert-dodecyl, and n is an integer of 4 to 10.

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