Method and device for preparing HTDA by one-step hydrogenation of DNT based on TDA solvent

Abstract

The application discloses a method and device for preparing HTDA by one-step hydrogenation of DNT based on TDA solvent, and belongs to the field of catalytic reaction process. The method process comprises reaction raw material pretreatment, catalytic hydrogenation, material circulation and continuous production. The method of the application not only improves the conversion rate of DNT and the selectivity of the target product HTDA, and can still reach 100% and 90% respectively after 24 hours of continuous production, but also does not involve the separation problem of the product and the solvent, shortens the HTDA production reaction process, and improves the production efficiency and resource utilization rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a method and device for preparing HTDA by one-step hydrogenation of DNT based on TDA solvent. BACKGROUND

[0002] At present, the global total production capacity of toluene diisocyanate (TDI) is 3.345 million tons, and the production capacity of TDI in China is about 1.46 million tons. TDI is mainly used for the production of polyurethane materials. TDI has an aromatic group and can produce a benzene ring conjugated quinone chromophore, so the mechanical properties, chemical stability and light resistance of its products are poor. If hexamethylene diisocyanate (HTDI) is used to replace the currently used TDI, the performance and quality of polyurethane can be greatly improved, and the economic and social benefits are huge. According to estimates, the economic benefit of HTDI is 198 times that of TDI. In addition, HTDI has important application prospects in the fields of aerospace and military industry (ship paint, new rocket propellant curing agent, transparent armor, etc.), high-end equipment manufacturing (aircraft, high-speed train, high-end car, marine equipment, etc. Functional coating materials), new energy (new energy vehicle coating, wind turbine blade coating, photovoltaic support coating) and energy-saving and environmental protection industry. At present, the world's large factories producing aliphatic diisocyanate (including HTDI) are mainly distributed in Western Europe, North America, Japan and other countries and regions. German companies such as Wanhua, BASF and Bayer, French company Rhodia, Japanese company Asahi Kasei and other companies have mastered and controlled the most advanced aliphatic diisocyanate (including HTDI) manufacturing technology. So far, China has not realized the industrialization of HTDI, and the national isocyanate industry is facing great challenges.

[0003] The production method of HTDI mainly uses toluene diamine (TDA) as a starting material, and 1-methyl-2,4-cyclohexanediamine (HTDA) is prepared by catalytic hydrogenation under a certain pressure, and then HTDI is prepared by two-stage phosgene reaction. In the future, who first masters the advanced HTDI production technology in the world will be in a leading position in the polyurethane industry, and the efficient preparation technology of HTDA as a prerequisite for the industrialization of HTDI has become the key to the localization of HTDI production technology. In addition, HTDA can be used in the synthesis of various drug molecules (such as antibiotics, antitumor drugs, antiviral drugs, etc.), agricultural chemicals (insecticides, herbicides, etc.), high-performance polymers, functional polymer materials, coatings, dyes, fragrances, etc. The market price of the end product sold directly is about 70,000 yuan / ton, and the market prospect is very promising. Unfortunately, domestic HTDA still relies heavily on imports, and the main supplier is BASF in Germany; Henan Leibailai New Material Technology Co., Ltd. realized the localization of HTDA in May 2024, but the production scale is small. The fundamental reason for the limitation of HTDA production technology is that the HTDA production process is complex and the performance of the hydrogenation catalyst involved is poor.

[0004] Currently, the HTDA preparation process mainly uses two-step hydrogenation of dinitrotoluene (DNT), that is, using DNT as a starting material, usually using a Ni-based catalyst to reduce TDA, and then using a noble metal catalyst to hydrogenate TDA to HTDA, which has the serious shortcomings of complex process, high cost investment, and low raw material utilization. Therefore, it is urgent to develop a new process for one-step hydrogenation of DNT to HTDA and realize high selectivity regulation of HTDA. SUMMARY

[0005] The present application aims to overcome the shortcomings of existing noble metal catalysts and DNT two-step hydrogenation process, and provides a DNT one-step hydrogenation method and device for preparing HTDA based on TDA solvent, which realizes the continuous production of DNT one-step hydrogenation to prepare HTDA, and does not need to separate the solvent during production, so that the performance of the product is more stable and reliable, and the production efficiency and resource utilization are improved through material circulation and product heat reuse.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] In the first aspect, the present application provides a DNT one-step hydrogenation method for preparing HTDA based on TDA solvent, which comprises the following steps:

[0008] (1) Pretreatment of reaction raw materials

[0009] The DNT is added into a proper amount of liquid TDA to prepare a first raw material liquid, the NaOH is added into a proper amount of liquid TDA to prepare a second raw material liquid after preheating, and the high-dispersed RuRhSn alloy catalyst precursor is pretreated to obtain a high-dispersed RuRhSn alloy catalyst;

[0010] (2) Catalytic hydrogenation

[0011] The high-dispersed RuRhSn alloy catalyst, the first raw material liquid and the second raw material liquid are added into a high-pressure reaction kettle, high-purity nitrogen gas is introduced into the high-pressure reaction kettle to replace the air therein, high-purity hydrogen gas is filled into the high-pressure reaction kettle, and the high-pressure reaction kettle is stirred at 100 r / min and heated, until the temperature is raised to 120-200℃, the stirring rate is raised to 1500 r / min, the reaction is started to be timed, and the reaction lasts for 1-4 h.

[0012] (3) Material circulation

[0013] After the reaction, the product is subjected to solid-liquid separation, the liquid phase component is sent into a rectifying column, and the liquid material discharged from the bottom of the rectifying column is used to flush the solid phase component separated in the solid-liquid separation process into the high-pressure reaction kettle for recycling.

[0014] (4) Continuous production

[0015] The product at the top of the rectifying column is preheated by using a jacket heat exchange method in sequence for the second raw material liquid and the first raw material liquid, and then the product is collected and stored, the first raw material liquid and the second raw material liquid are added into the high-pressure reaction kettle in a continuous feeding mode, and the continuous production is carried out.

[0016] As a preferred solution, in step (1), the liquid TDA is obtained by heating solid TDA to liquid state at 120℃, the purity of the DNT is not less than 99.9%, the use amount ratio of DNT to TDA in the first raw material liquid is 0.5 g:50.0 g, and the use amount ratio of NaOH to TDA in the second raw material liquid is 0.1:20 g.

[0017] As a preferred solution, the heating temperature of the toluene diamine (TDA) is 120℃.

[0018] As a preferred solution, in step (1), the method for pretreating the high-dispersion RuRh alloy catalyst precursor is: the high-dispersion RuRh alloy catalyst precursor is passed through a 200-mesh sieve, filled into a fixed-bed reactor, and then heated to 300-400℃ at a heating rate of 3-5℃ / min under the protection of high-purity nitrogen, and then reduced by hydrogen for 2-4h, and then cooled to room temperature to obtain the high-dispersion RuRhSn alloy catalyst, wherein the carrier of the high-dispersion RuRhSn alloy catalyst is a TiO2-Al2O3 composite carrier, and the mass ratio of TiO2 to Al2O3 is 1:2, and the mass ratio of Ru to Rh to Sn is (2-5):1:1; the use amount ratio of the RuRhSn alloy catalyst to the first raw material liquid and the second raw material liquid is 0.01g:25g:25g.

[0019] As a preferred solution, in step (2), the high-purity nitrogen has a pressure of 2-6MPa and is replaced for 3-5 times; the hydrogen has a pressure of 3-8MPa.

[0020] As a preferred solution, in step (3), the temperature of the distillation column is controlled at 220℃.

[0021] As a preferred solution, in step (3), the liquid-phase component is sent into the distillation column after the composition of the product is analyzed by gas chromatography, gas chromatography-mass spectrometry and liquid chromatography.

[0022] In a second aspect, the application provides a device for preparing HTDA by one-step hydrogenation of DNT based on a TDA solvent, which comprises a first raw material liquid tank, a second raw material liquid tank, a high-pressure reaction kettle, a solid-liquid separation device, a nitrogen tank, a hydrogen tank, a distillation column and an HTDA product tank, the first raw material liquid tank is used for storing the first raw material liquid, the second raw material liquid tank is used for storing the second raw material liquid, the high-pressure reaction kettle is connected with the first raw material liquid tank, the second raw material liquid tank and the solid-liquid separation device, a first feeding pump is arranged on the pipeline between the first raw material liquid tank and the high-pressure reaction kettle, a second feeding pump is arranged on the pipeline between the second raw material liquid tank and the high-pressure reaction kettle, the nitrogen tank and the hydrogen tank are respectively connected with the inlet of a compressor, the outlet of the compressor is connected with the high-pressure reaction kettle, the upper part of the solid-liquid separation device is connected with the distillation column through a pipeline, the product outlet at the top of the distillation column is connected with the second raw material liquid tank jacket, the first raw material liquid tank jacket and the HTDA product tank in sequence through a pipeline, a product conveying pump is arranged on the pipeline between the product outlet at the top of the distillation column and the second raw material liquid tank jacket, the outlet of the distillation column column is connected with the bottom of the solid-liquid separation device, and then connected with the high-pressure reaction kettle, and a catalyst feeding port is further arranged on the high-pressure reaction kettle.

[0023] Compared with the prior art, the application has the following beneficial technical effects:

[0024] 1.The present application adopts TDA as a solvent, which can completely avoid the nucleophilic substitution side reaction between traditional organic alcohol solvents and HTDA, and TDA can be converted into HTDA by hydrogenation, thereby improving the specificity and yield of HTDA, and subsequent sections do not need to be separated, which not only reduces the impurities and isomers introduced in the multi-part reaction, promotes the stable and reliable performance of the product HTDA, but also saves the cost caused by solvent separation.

[0025] 2.The present application directly converts DNT into HTDA by one-step catalytic hydrogenation, which has high atomic utilization rate, can effectively avoid the generation of intermediate products and by-products generated by multi-step reaction, does not need complex intermediate product separation and purification steps, reduces the waste of raw materials, shortens the process flow, improves the stability and controllability of production, and improves the production efficiency and raw material utilization rate of HTDA through continuous production, material circulation, and product heat recycling, which is more in line with the development concept of green chemical industry. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a scanning electron microscope image of the catalyst in Example 1.

[0027] Figure 2 It is a product gas chromatogram of Example 1.

[0028] Figure 3 It is a chromatogram mass spectrum image of Example 1, wherein (a) is a product liquid chromatogram; (b) is a mass spectrum of the reactant; (c) is a mass spectrum of the product; (d) is a mass spectrum of the by-product.

[0029] Figure 4 It is a standard curve drawn in the test example of the present application.

[0030] Figure 5 It is a structural diagram of a DNT one-step hydrogenation preparation HTDA device based on TDA solvent of the present application.

[0031] The figure legend: 1-First raw material liquid tank, 2-Second raw material liquid tank, 3-First feed pump, 4-Second feed pump, 5-Nitrogen tank, 6-Hydrogen tank, 7-Compressor, 8-High-pressure reaction kettle, 9-Solid-liquid separation device, 10-Fractionating column, 11-HTDA product tank, 12-Product delivery pump. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0033] Example 1

[0034] The dried high-dispersion RuRhSn alloy catalyst precursor was sieved with a 200-mesh sieve and then loaded into a fixed-bed reactor. Under the protection of high-purity nitrogen, the temperature was raised to 400°C at a rate of 4°C / min, and then the precursor was reduced by hydrogen for 3h. After cooling to room temperature, the RuRhSn alloy catalyst was obtained. The carrier of the high-dispersion RuRh alloy catalyst was TiO2-Al2O3, and the mass ratio of TiO2 to Al2O3 was 1:2, and the mass ratio of Ru to Rh to Sn was 4:1:1. The solid TDA was heated to a liquid state at 120°C to obtain a liquid TDA. The purity and crystallinity of the purchased 2,4-dinitrotoluene (DNT) were detected, and 0.50g of DNT with a purity of 99.9% was added to 50.0g of liquid TDA to prepare a first raw material liquid. 0.1g of NaOH and 40.0g of liquid TDA were prepared into a second raw material liquid. 6MPa of high-purity nitrogen was introduced to replace the air therein. 0.01g of high-dispersion RuRhSn alloy catalyst, 25g of first raw material liquid, and 25g of second raw material liquid were added to a 100mL high-pressure reaction kettle, respectively. Then, 6MPa of high-purity hydrogen was filled into the high-pressure reaction kettle, and the mixture was stirred at 100r / min and heated. When the temperature rose to 180°C, the stirring rate was increased to 1500r / min, and the reaction was started to be timed. After the reaction was completed, the pressure was slowly released, and the reaction mixture was transferred to a solid-liquid separation device for solid-liquid separation. The liquid phase components were analyzed by gas chromatography, gas chromatography-mass spectrometry, and liquid chromatography.

[0035] It should be noted that in this example, the product was only analyzed by gas chromatography, gas chromatography-mass spectrometry, and liquid chromatography, and was not treated by a rectifying column. This is mainly for product analysis in the following test examples to verify the feasibility of the method of the present application. In actual production, the product needs to be treated by a rectifying column, and the rectifying column temperature is controlled at 220°C.

[0036] Example 2

[0037] The solid phase components separated by solid-liquid separation in Example 1 were returned to the high-pressure reaction kettle, and the high-dispersion RuRhSn alloy catalyst was repeatedly reacted for 10 times according to the method of Example 1.

[0038] Example 3

[0039] The same as Example 1, only the catalyst dosage was changed to 1.0g, and a continuous reaction test was adopted. After 2h of reaction, the first raw material liquid and the second raw material liquid were introduced at a rate of 20mL / min, and the products in the reaction kettle were detected in real time. The rectifying column temperature was controlled at 220°C, and the unreacted heavy components were re-added to the raw material tank.

[0040] Comparative Example 1

[0041] The method of Example 2 was followed, except that the liquid TDA solvent was changed to isopropanol.

[0042] Comparative Example 2

[0043] The method of Example 2 was followed, except that the liquid TDA solvent was changed to tetrahydrofuran.

[0044] Comparative Example 3

[0045] The method of Example 2 was followed, except that the metal Sn was removed.

[0046] Comparative Example 4

[0047] Into a 100 mL autoclave, 0.01 g Raney Ni catalyst, 0.05 g DNT and 50 mL methanol solvent were added by ultrasonic mixing, after which, 6 MPa high-purity nitrogen was injected to test the sealing of the reactor, and the air in the reactor was replaced with high-purity nitrogen, and finally the nitrogen in the reactor was replaced with high-pressure hydrogen; then, the high-purity hydrogen pressure was charged to 2.0 MPa, the temperature was raised to 90°C, and the stirring speed was increased to 1500 r / min, and the reaction continued for 30 min. After the reaction was completed, the product was centrifuged to remove the solid catalyst at the bottom; then, a Ru-based catalyst was added to the reactor, and the air in the reactor was replaced with high-purity nitrogen, and finally the nitrogen in the reactor was replaced with high-pressure hydrogen, and the hydrogen pressure was charged to 6 MPa, and the high-pressure reactor was heated to the reaction temperature, and the stirring speed was increased to 1500 r / min, and the reaction was started when the reaction temperature reached 180°C. The reaction process was sampled, and the product composition was analyzed by gas chromatography, GC / MS, and liquid chromatography.

[0048] Test Example

[0049] The products of Examples 1-2 and Comparative Examples 1-3 were subjected to chromatographic quantitative analysis.

[0050] Gas chromatography test method: Agilent 8860 gas chromatograph equipped with HP-5 column was used to analyze the sample of the solution after reaction, and the analysis conditions were as follows: the gasification chamber temperature was 280°C; the detector temperature was 280°C; the programmed temperature was used, the column temperature was 60°C, the initial state was kept for 3 min, the temperature rising rate was 10°C / min, the end temperature was 200°C, and the end time was kept for 10 min; high-purity N2 was used as the carrier gas, the carrier gas flow rate was 30 mL / min, the split ratio was 1:45; the sample amount was 1 μL.

[0051] GC / MS test method: Agilent 8860 GC / 5077 MSD gas chromatography-mass spectrometer equipped with HP-5 MS column was used for qualitative analysis of the reaction product, and the analysis conditions were the same as Agilent 8860 gas chromatograph.

[0052] Liquid chromatograph test method: LC2030 Shimadzu high performance liquid chromatograph equipped with a reversed-phase C18 column is used to determine the content of coupling by-products (tar). The analysis conditions are as follows: the mobile phase is a methanol / water mixture with a volume ratio of 40 / 60, the flushing speed is 1.0 mL / min, and the ultraviolet detection wavelength is 200-220 nm.

[0053] External standard method for determining standard curve

[0054] (1) Preparation of standard substance: TDA is selected as the standard substance, and product HTDA is used as the solvent to prepare standard solutions with concentrations of 0.079 mol / L, 0.157 mol / L, 0.236 mol / L and 0.314 mol / L.

[0055] (2) Drawing of standard curve: the standard solutions are injected into the gas chromatograph respectively, and the peak areas of the standard solutions are recorded; the concentration of the standard solution is taken as the abscissa, and the peak area of TDA in the standard solution is taken as the ordinate, to draw a standard curve, as shown in Figure 3 .

[0056] (3) Sample determination: the sample to be tested is injected into the gas chromatograph, and the peak area of TDA is recorded.

[0057] (4) Result calculation: the sample peak area of the sample to be tested is brought into the standard curve to determine the concentration of TDA in the sample; the total amount of TDA in the sample is calculated, and the actual amount of TDA is compared with the amount of TDA obtained by complete conversion of DNT, so that the selectivity of the intermediate product TDA can be obtained.

[0058] Calculation formula:

[0059]

[0060]

[0061] Since there is no other by-product in the reaction except the deamination by-product (containing tar), then

[0062] .

[0063] The test data results are shown in Table 1 and Figures 1-4 .

[0064] Table 1 Test data results of catalyst performance evaluation

[0065]

[0066] From the data results in Table 1 and Figures 1-4 , it can be seen that the DNT one-step hydrogenation method based on TDA solvent for preparing HTDA is efficient and feasible for continuous production of HTDA.

[0067] Embodiment 3

[0068] Please refer to the accompanying Figure 4 As shown in the figure, the embodiment provides a device for preparing HTDA by one-step hydrogenation of DNT based on high-efficiency Ru-based catalyst, which comprises a first raw material liquid tank 1, a second raw material liquid tank 2, a high-pressure reaction kettle 8, a solid-liquid separation device 9, a nitrogen tank 5, a hydrogen tank 6, a rectifying tower 10, and an HTDA product tank. The first raw material liquid tank 1 is used for storing a first raw material liquid, and the second raw material liquid tank 2 is used for storing a second raw material liquid. The high-pressure reaction kettle 8 is connected with the first raw material liquid tank 1, the second raw material liquid tank 2, and the solid-liquid separation device 9, respectively. A first feeding pump 3 is arranged on a pipeline between the first raw material liquid tank 1 and the high-pressure reaction kettle 8, and a second feeding pump 4 is arranged on a pipeline between the second raw material liquid tank 2 and the high-pressure reaction kettle 8. The nitrogen tank 5 and the hydrogen tank 6 are connected with an inlet of a compressor 7, respectively. An outlet of the compressor 7 is connected with the high-pressure reaction kettle 8. The rectifying tower 10 is connected with the solid-liquid separation device 9 through a pipeline at an upper portion. A product outlet at a top portion of the rectifying tower 10 is connected with a jacket of the second raw material liquid tank 2, a jacket of the first raw material liquid tank 1, and the HTDA product tank 11 in sequence through pipelines. A product conveying pump 12 is arranged on a pipeline between the product outlet at the top portion of the rectifying tower 10 and the jacket of the second raw material liquid tank 2. A tower kettle outlet of the rectifying tower 10 is connected with the high-pressure reaction kettle 8 after being connected with a bottom portion of the solid-liquid separation device 9 in parallel. A catalyst feeding port is further arranged on the high-pressure reaction kettle 8.

[0069] In the embodiment, the first raw material liquid tank 1 is used for storing a first raw material liquid prepared by mixing DNT and TDA, and the second raw material liquid tank 2 is used for storing a second raw material liquid prepared by mixing NaOH and TDA.

[0070] 1-first raw material liquid tank, 2-second raw material liquid tank, 3-first feeding pump, 4-second feeding pump, 5-nitrogen tank, 6-hydrogen tank, 7-compressor, 8-high-pressure reaction kettle, 9-solid-liquid separation device, 10-rectifying tower, 11-HTDA product tank, 12-product conveying pump

[0071] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the technical solutions and concepts of the present application shall be included in the protection scope of the present application.

Claims

1. A one-step hydrogenation method for preparing HTDA from DNT using TDA solvent, characterized in that, Includes the following steps: (1) Pretreatment of reaction raw materials DNT was added to an appropriate amount of liquid TDA to prepare the first raw material solution. NaOH was added to an appropriate amount of liquid TDA and preheated to prepare the second raw material solution. The highly dispersed RuRhSn alloy catalyst precursor was pretreated to obtain the highly dispersed RuRhSn alloy catalyst. The method for pretreatment of highly dispersed RuRhSn alloy catalyst precursor is as follows: the highly dispersed RuRhSn alloy catalyst precursor is passed through a 200-mesh sieve and packed into a fixed-bed reactor. Under the protection of high-purity nitrogen, the temperature is raised to 300-400℃ at a heating rate of 3-5℃ / min, and then hydrogen is introduced for reduction for 2-4 hours. The temperature is then lowered to room temperature to obtain highly dispersed RuRhSn alloy catalyst. The support of the highly dispersed RuRhSn alloy catalyst is a TiO2-Al2O3 composite support. By mass ratio, TiO2:Al2O3=1:2, Ru:Rh:Sn=(2-5):1:1; the ratio of RuRhSn alloy catalyst to the first feed liquid and the second feed liquid is 0.01g:25g:25g. (2) Catalytic hydrogenation The highly dispersed RuRhSn alloy catalyst, the first feed liquid, and the second feed liquid were added to a high-pressure reactor. High-purity nitrogen was introduced into the high-pressure reactor to replace the air, and high-purity hydrogen was introduced into the high-pressure reactor. The reactor was stirred and heated at 100 r / min. When the temperature reached 120-200℃, the stirring rate was increased to 1500 r / min, and the reaction was started. The reaction lasted for 1-4 hours. (3) Material circulation After the reaction, the product undergoes solid-liquid separation. The liquid phase is sent to a distillation column, and the liquid material discharged from the bottom of the distillation column flushes the solid phase separated during the solid-liquid separation back into the high-pressure reactor for recycling. (4) Continuous production The product at the top of the distillation column is preheated sequentially by the second and first feed liquids using a jacketed heat exchanger before being collected and stored. The first and second feed liquids are then fed into a high-pressure reactor for continuous production.

2. The method for one-step hydrogenation of DNT to HTDA based on TDA solvent according to claim 1, characterized in that: In step (1), the liquid TDA is obtained by heating solid TDA to liquid state at 120°C, the purity of DNT is not less than 99.9%, the ratio of DNT to TDA in the first raw material solution is 0.5g:50.0g, and the ratio of NaOH to TDA in the second raw material solution is 0.1:20g.

3. The method for one-step hydrogenation of DNT to HTDA based on TDA solvent according to claim 2, characterized in that: In step (2), the pressure of high-purity nitrogen is 2-6 MPa, and it is replaced 3-5 times; the pressure of hydrogen is 3-8 MPa.

4. The method for one-step hydrogenation of DNT to HTDA based on TDA solvent according to claim 3, characterized in that: In step (3), the temperature of the distillation column bottom is controlled at 220℃.

5. The method for one-step hydrogenation of DNT to HTDA based on TDA solvent according to claim 4, characterized in that: In step (3), the liquid phase components are sent to the distillation column after being analyzed by gas chromatography, gas chromatography-mass spectrometry and liquid chromatography.

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