A new environment-friendly process for synthesizing accelerator mbts by oxidation of nitrogen oxide and oxygen mixture

Abstract

The present application belongs to the technical field of rubber vulcanization accelerator production, and relates to a novel environment-friendly process for synthesizing accelerator MBTS by oxidizing mixed gas of nitrogen oxide and oxygen. Dry MBT is put into water, wet grinding is performed by a wet grinding pump, and then the MBT is punched into a high-pressure kettle with a wind ring. Mixed gas generated by decomposition of concentrated nitric acid is punched into the high-pressure kettle, and the circulation is performed until the pressure in the high-pressure kettle is no longer reduced and the material reaches the end point. The material in the high-pressure kettle is filtered, left standing, drained, dehydrated and dried to obtain MBTS finished product and reaction liquid. The mixed gas and the reaction liquid are recycled. The present application is a novel environment-friendly process, which does not need to use metal catalyst and does not generate three wastes, has low production cost, and has a relatively broad industrial prospect. The reaction is sufficient, the product has high melting point, high purity and good quality.

Description

Technical Field

[0001] This invention belongs to the field of rubber vulcanization accelerator production technology, and relates to a novel environmentally friendly process for the oxidation synthesis of MBTS accelerator using a mixture of nitrogen oxides and oxygen. Background Technology

[0002] Accelerator MBTS is a grayish-white to pale yellow powder with a slightly bitter taste. It is non-toxic and odorless, with a specific gravity of 1.45-1.54 and a melting point above 164℃. It is soluble in benzene, toluene, chloroform, carbon tetrachloride, and carbon disulfide, but insoluble in ethanol, gasoline, water, dilute alkali, and ethyl acetate. MBTS is a general-purpose accelerator for natural rubber, synthetic rubber, and reclaimed rubber. Its properties and uses are basically similar to those of accelerator MBT. It has a higher vulcanization temperature, significant after-effects, and is safe to handle. It is usually used in combination with other types of accelerators to improve activity. It is mainly used in the manufacture of tires, hoses, rubber shoes, and tapes. High-purity products are used as raw materials for the synthesis of the pharmaceutical intermediate AE-active ester.

[0003] Methods for synthesizing the accelerator MBTS include the solvent-hydrogen peroxide method and the hydrogen peroxide mixed oxidation method for M-Na. Patent CN110698428A discloses a method for preparing the rubber accelerator MBTS, which uses ethanol as a solvent to dissolve the accelerator MBT and hydrogen peroxide as an oxidant to synthesize MBTS. Although this method achieves zero waste salt generation and is environmentally friendly, it results in solvent loss during production, requires distillation of the mother liquor, increases production costs, and has a low product yield. Patent CN103193732A discloses a method for preparing the rubber vulcanization accelerator DM. This method dissolves MBT into M-Na salt, adds a catalyst, and oxidizes it with a mixture of sulfuric acid and hydrogen peroxide to synthesize the product DM. Although this method yields a product with a high melting point, high yield, and large particle size, the process generates a large amount of wastewater and waste salt, with high COD, making it difficult to treat. Summary of the Invention

[0004] This invention addresses the problems existing in traditional MBTS production by proposing a novel method for synthesizing high-melting-point, high-yield, and high-purity MBTS products through mixed oxidation of nitrogen oxides and oxygen.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: A novel environmentally friendly process for the oxidation synthesis of a nitrogen oxide and oxygen mixture using MBTS as an accelerator includes the following steps: (1) Put the dry MBT into a prepared tank with water, crush it by a wet crushing pump, and then pump it into a high pressure vessel with a fan ring and stir it.

[0006] (2) Add concentrated nitric acid to the gas generator and heat it to the specified temperature. Then irradiate it with light. The mixed gas produced by decomposition is pumped into the above-mentioned high pressure vessel through a gas compression pump.

[0007] (3) At a certain temperature, the mixed gas in the high pressure vessel enters from the bottom of the high pressure vessel through the air ring under the action of the gas compression pump and stops after the gas flow reaches the reaction pressure. The mixed gas is circulated until the pressure in the high pressure vessel no longer decreases and the material reaches the end point.

[0008] (4) The material in the high-pressure reactor is filtered, allowed to stand, drained, dehydrated and dried to obtain MBTS product and reaction solution.

[0009] (5) The mixed gas and reaction liquid are recycled. After adding MBT dry product to the reaction liquid, it needs to be pulverized again by a wet pulverizer pump before entering the high pressure vessel. Nitrogen dioxide is not consumed in the mixed gas, but oxygen is consumed. Therefore, after the mixed gas is recycled, oxygen is injected to the reaction pressure.

[0010] As a preferred option, in step (1), the accelerator MBT dry product can be obtained by acid-base method or solvent method purification. The purity of MBT dry product is required to be above 97.5%. The mass ratio of MBT dry product to water is 1:10-15. The pulverizing pump is a wet pulverizing pump. The process requires that after pulverization by the wet pulverizing pump, the particle size D90 of MBT is less than 35μm.

[0011] Preferably, the stirring speed of the autoclave is 100-1000 rpm, the autoclave has a built-in aeration ring, and Φ8mm aeration holes are evenly distributed below the ring and to its left and right at 45° angles. Check valves are installed at both the inlet and outlet of the autoclave.

[0012] Preferably, in step (2), the temperature of the gas generator is 86-90°C, the light source is an incandescent lamp or a flashlight, and the mixed gas is nitrogen dioxide and oxygen.

[0013] Preferably, in step (3), the constant temperature of the autoclave is 20-50℃, and the initial pressure of the mixed gas in the autoclave is 0.05-0.3MPa.

[0014] The redox reaction mechanism of nitrogen oxides and oxygen in this invention is as follows.

[0015] .

[0016] Specifically, the nitrogen atoms in the nitrogen dioxide in the mixed gas have a +4 oxidation state, which oxidizes MBT to... and H + It is reduced to nitric oxide with a +2 oxidation state, and then oxidized to nitrogen dioxide by oxygen. The oxygen is reduced to O. 2- , with 2 H + Combined to form water, two Coupled together The reaction continues in this cycle until the reaction reaches its endpoint. During this reaction, oxygen and MBT dry product are consumed, while nitrogen oxides and the mother liquor can be recycled.

[0017] The process provided by this invention has been listed as a key research and development project funded by Shandong Province, project number: 2023CXGC010605.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. This invention is a novel green and environmentally friendly process. Nitrogen oxides and oxygen are produced by the decomposition of concentrated nitric acid. Concentrated nitric acid is inexpensive and readily available, and both the mixed gas and the reaction liquid can be recycled. No metal catalyst is required, and no waste is generated. The production cost is low, and it has broad industrial prospects.

[0019] 2. This invention does not use other organic solvents, but uses water as the solvent, resulting in a high product yield.

[0020] 3. This invention uses a wet grinding pump to break down the particle size of the accelerator MBT, which is not limited to the acid-base method or the solvent method for purifying MBT. The particle size D90 of the pulverized MBT is below 35μm, which solves the problem of insufficient reaction due to the large particle size of MBT obtained by solvent method. At the same time, the high pressure vessel is equipped with an aeration fan ring, and the mixed gas is continuously circulated, making the reaction more complete, resulting in a product with high melting point, high purity, and good quality.

[0021] 4. This invention is simple to operate and can also be used for continuous batch production, thereby improving production efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device structure used in the process of this invention.

[0023] Figure 2 This is the liquid chromatogram of the product in Example 1.

[0024] The attached diagrams are labeled as follows: 1. Material preparation tank; 2. Wet pulverizing pump; 3. High pressure vessel; 4. Gas generator; 5 and 6. Gas compression pumps; 7. Fan ring; 8 and 9. Check valves. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0026] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0027] The following embodiments employ Figure 1 The equipment shown is used for production. Unless otherwise specified in the following embodiments, the traditional MBTS production process is used, or the parameters are adjusted according to actual production needs. Figure 1 The intermediate material tank 1 is connected to the wet grinding pump 2 via an outlet pipe. The outlet end of the wet grinding pump 2 is connected to the upper part of the pressure vessel 3. The upper part of the pressure vessel 3 is also equipped with a gas inlet pipe, which is connected to the gas generator 4. A gas compression pump 5 is installed on the gas inlet pipe. The air ring 7 is located at the lower part of the pressure vessel 3. Different outlets with different gas directions are provided at different positions of the air ring 7. The upper and lower ends of the pressure vessel are also connected to the gas compression pump 6 via pipes. The outlet pipe of the gas compression pump 6 is connected to the lower part of the pressure vessel 3 and further connected to the inside of the pressure vessel 3 through the air hole on the air ring 7. The upper part of the pressure vessel 3 is also equipped with an vent pipe, which is equipped with valves. A check valve 8 is installed on the inlet pipe of the gas compression pump, and a check valve 9 is installed on the outlet pipe.

[0028] Example 1 Acid-base method MBT dry product and water are added to preparation tank 1 at a mass ratio of 1:15. Stirring is started, and the product is crushed by wet crushing pump 2 until the MBT particle size D90 is below 24.17 μm. Then, it is pumped into high-pressure reactor 3 equipped with a fan ring 7 and a stirring speed of 1000 rpm. Concentrated nitric acid is added to gas generator 4 and heated to 86°C. An incandescent lamp is turned on for irradiation. The resulting mixed gases, nitrogen dioxide and oxygen, are pumped into high-pressure reactor 3 through gas compression pump 5 to a pressure of 0.02 MPa. The material temperature in high-pressure reactor 3 is maintained at 20°C. Then, the mixed gas, under the action of gas compression pump 6, passes through fan ring 7 and exits from high-pressure reactor 3. The mixture is circulated until the pressure inside the autoclave 3 no longer decreases and the material reaches the endpoint. The remaining gas in the autoclave 3 is recovered for future use. The endpoint material is filtered through a 100-mesh stainless steel wire mesh and then enters the transfer tank. After standing for 5-10 minutes, the endpoint material is on the upper layer and the mother liquor is on the lower layer. The conical bottom valve of the autoclave is opened to drain the liquid to the specified position. At the same time, the valve is switched and the transfer tank is turned on to feed the dehydrator. After obtaining the MBTS semi-finished product, it is conveyed by a scraper into the airflow drying system and dried at 60°C to a constant temperature to finally obtain the MBTS finished product. The yield of the MBTS product is 99.3%. The reaction liquid is collected for recycling.

[0029] The melting point of the MBTS product in this embodiment was determined to be 178.9℃ using a melting point analyzer. The result was obtained through high-performance liquid chromatography (HPLC). Figure 2As shown, the purity of the product MBTS is 99.950%.

[0030] Example 2 Unless otherwise specified, this embodiment and the following embodiments are consistent with Embodiment 1.

[0031] Solvent-processed MBT dry product and water were added to preparation tank 1 at a mass ratio of 1:10. Stirring was started. After the MBT particle size (D90) was measured by a laser particle size analyzer and determined to be below 34.41 μm by wet pulverizing pump 2, it was pumped into a high-pressure reactor 3 equipped with a fan ring 7 and a stirring speed of 500 rpm. Concentrated nitric acid was added to a gas generator 4 and heated to 88°C. A flashlight was used to irradiate the gas, and the resulting mixed gases of nitrogen dioxide and oxygen were pumped into the high-pressure reactor 3 via a gas compression pump 5. In the high-pressure reactor 3, under conditions of 35°C and 0.15 MPa, the mixed gases were circulated from the bottom of the high-pressure reactor 3 by a gas compression pump 6 through the fan ring 7 until the pressure inside the reactor 3 no longer decreased and the material reached the endpoint. The remaining gas in the high-pressure reactor 3 was recovered for future use. The endpoint material was filtered, allowed to stand, drained, dehydrated, and dried to obtain the MBTS product. The MBTS yield was 99.2%. The reaction liquid was collected for recycling.

[0032] The melting point of the MBTS product in this embodiment is 178.6℃, as determined by a melting point analyzer. The purity of the MBTS product in this embodiment is 99.902%, as determined by high performance liquid chromatography.

[0033] Example 3 Solvent-processed MBT dry product and water were added to preparation tank 1 at a mass ratio of 1:11. Stirring was started, and the product was crushed by wet pulverizing pump 2 and then pumped into autoclave 3 equipped with a fan ring 7 and a stirring speed of 700 rpm. Laser particle size analyzer measurements showed that the MBT particle size D90 was below 28.41 μm. Concentrated nitric acid was added to gas generator 4 and heated to 89°C. An incandescent lamp was turned on for irradiation. The resulting mixed gases, nitrogen dioxide and oxygen, were pumped into autoclave 3 via gas compressor pump 5. In autoclave 3, under conditions of 50°C and 0.3 MPa, the mixed gases were circulated from the bottom of autoclave 3 by gas compressor pump 6 through fan ring 7 until the pressure inside autoclave 3 no longer decreased and the material reached the endpoint. The remaining gas in autoclave 3 was recovered for future use. The endpoint material was filtered, allowed to stand, drained, dehydrated, and dried to obtain the MBTS product. The MBTS yield was 99.1%, and the reaction liquid was collected for recycling.

[0034] The melting point of the MBTS product in this embodiment was determined to be 178.7°C by a melting point analyzer, and the purity of the MBTS product in this embodiment was determined to be 99.917% by high performance liquid chromatography.

[0035] Example 4 The dry MBT product and reaction solution (half the volume of the reaction mother liquor obtained in Examples 1 and 2 in this embodiment) were added to the preparation tank 1 at a mass ratio of 1:13. Stirring was started, and the product was crushed by the wet pulverizing pump 2 and then pumped into the autoclave 3 equipped with a fan ring 7 and a stirring speed of 900 rpm. The MBT particle size D90 measured by a laser particle size analyzer was below 24.82 μm. The mixed gases of nitrogen dioxide and oxygen collected in Examples 1 and 2 were pumped into the autoclave 3 through the gas compressor pump 5, and the oxygen was added until the pressure reached 0.2 MPa before the gas flow was stopped. Under the condition of 40°C, the mixed gas in the autoclave 3 was circulated from the bottom of the autoclave 3 through the fan ring 7 by the gas compressor pump 6 until the pressure inside the autoclave 3 no longer decreased and the material reached the endpoint. The remaining gas in the autoclave 3 was recovered for future use. The endpoint material was filtered, allowed to stand, drained, dehydrated, and dried to obtain the MBTS product. The MBTS yield was 99.0%, and the reaction solution was collected for recycling.

[0036] The melting point of the MBTS product in this embodiment was 178.8°C, as determined by a melting point analyzer. The purity of the MBTS product in this embodiment was 99.926%, as determined by high performance liquid chromatography.

[0037] To achieve the production volume, half the volume of the reaction mother liquor obtained in Examples 1 and 2 is used in this embodiment. In the actual production process, the generated reaction liquid mother liquor can be collected, stored, and recycled for later use. After testing, the purity of the product MBTS can still reach over 99.9% after the reaction liquid mother liquor is recycled 35 times, and the melting point is between 178.7 and 178.9. The nitrogen dioxide in the mixed gas is not consumed in the production process and can be recycled. Fresh oxygen only needs to be added as needed for production.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A novel environmentally friendly process for the oxidation synthesis of a mixture of nitrogen oxides and oxygen using MBTS as a promoter, characterized in that... The steps include the following: (1) Put the dry MBT into water, crush it with a wet crushing pump, and then put it into a high pressure vessel and stir. (2) Add concentrated nitric acid to the gas generator, heat it and expose it to light to decompose it and produce a mixed gas; (3) The pressure vessel is kept at a constant temperature. The mixed gas enters from the bottom of the pressure vessel through the gas compression pump and stops after reaching the reaction pressure. The mixed gas is kept circulating from bottom to top in the pressure vessel until the pressure inside the pressure vessel no longer decreases. (4) The material in the high-pressure reactor is filtered, allowed to stand, drained, dehydrated and dried to obtain MBTS product and reaction solution; (5) Recover the mixed gas and reaction liquid for recycling; In step (1), the mass ratio of dry MBT to water is 1:10-15. After being pulverized by a wet pulverizing pump, the particle size D90 of MBT is less than 35μm. The stirring speed of the autoclave is 100-1000 rpm. The lower part of the autoclave is equipped with an annular aeration ring with several aeration holes arranged in different directions.

2. The novel environmentally friendly process for the oxidation synthesis promoter MBTS of nitrogen oxides and oxygen mixture according to claim 1, characterized in that, Step (2) The gas generator is heated to 86-90℃, the light source is an incandescent lamp or a flashlight, and the mixed gas is nitrogen dioxide and oxygen.

3. The novel environmentally friendly process for the oxidation synthesis promoter MBTS of nitrogen oxides and oxygen mixture according to claim 1, characterized in that, Step (3) The constant temperature of the autoclave is 20-50℃, and the initial pressure of the mixed gas in the autoclave is 0.05-0.3MPa.

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