Preparation method of tetramethylethylenediamine based on amination pipeline reaction

Abstract

The invention relates to the technical field of applied chemistry, and discloses a tetramethylethylenediamine preparation method based on amination pipeline reaction, which comprises the following steps: 1, premixing raw materials, continuously inputting an ethylenediamine aqueous solution with the mass concentration of 30-40% and a catalyst into a static mixer according to the mass ratio of 100: (0.5-1.5), and controlling the flow rate to be 5-10m < 3 > / h and the mixing time to be less than or equal to 30s; 2, pipeline reaction: pumping the premix into a multi-section temperature control pipeline reactor, carrying out amination reaction on the premix and ammonia gas in a molar ratio of (1: 3)-(1: 5) under the conditions that the temperature is 140-180 DEG C and the pressure is 2.0-4.0 MPa, and standing for 30-90 minutes; by constructing a gradient temperature field and a built-in turbulent flow structure of the multi-section pipeline reactor, the contact reaction state of ammonia gas and ethylenediamine is regulated and controlled in real time, the phenomenon that the local concentration of ammonia gas is abnormal and accumulated in a reaction system can be dynamically eliminated, it is guaranteed that the gas-liquid mass transfer process is always in an optimal reaction interval, catalyst activity attenuation caused by uneven mass transfer is avoided, and the service life of the catalyst is prolonged. The generation proportion of side reaction products is reduced, and the directional selectivity of an amination reaction path is improved.

Description

Technical Field

[0001] This invention relates to the field of applied chemistry technology, specifically to a method for preparing tetramethylethylenediamine based on an amination pathway reaction. Background Technology

[0002] Tetramethylethylenediamine is an organic compound, a colorless and transparent liquid, miscible with water, and also miscible with ethanol and most organic solvents. It is mainly used as a biochemical reagent, an epoxy resin crosslinking agent, and an intermediate in the preparation of quaternary ammonium compounds.

[0003] Currently, due to the problem of crude reaction control in the traditional batch reactor preparation process, when continuously synthesizing tetramethylethylenediamine, the ammonia gas input into the reaction system cannot be matched with the dynamic reaction consumption in real time. Excess ammonia gas forms a local concentration dead zone in the high-pressure environment of the reactor. When the ammonia gas accumulation concentration exceeds the critical threshold, it not only causes the active sites on the catalyst surface to be covered, resulting in the reduction of the effective reaction contact area, but also causes unreacted ammonia gas to be directly discharged with the depressurized tail gas, resulting in a reduction in the single-pass utilization rate of key raw materials.

[0004] Therefore, a method for preparing tetramethylethylenediamine based on the amination pathway reaction is proposed to solve the above problems. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing tetramethylethylenediamine based on an amination pathway reaction, thus solving the problems mentioned in the background section.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing tetramethylethylenediamine based on an amination pathway reaction, comprising the following steps:

[0009] Step 1: Raw material premixing. A 30-40% (w / w) aqueous solution of ethylenediamine and the catalyst are continuously fed into a static mixer at a mass ratio of 100:0.5-1.5, controlling the flow rate to 5-10 m / s. 3 / h, mixing time ≤30s;

[0010] Step 2: Pipeline reaction. The premix is ​​pumped into a multi-stage temperature-controlled pipeline reactor and subjected to an amination reaction with ammonia at a molar ratio of 1:3 to 1:5 under conditions of 140-180℃ and 2.0-4.0MPa, with a residence time of 30-90min.

[0011] Step 3: Gas-liquid separation. The reaction products are subjected to a three-stage step-decompression process to atmospheric pressure, with a decompression gradient of 0.8MPa→0.3MPa→0.1MPa. The temperature at the top of the separation tower is controlled at 45-55℃.

[0012] Step 4: Alkali precipitation and desalination. Add caustic soda flakes to the amine-distilled wastewater with a salt content of 25±2%, the amount of which is 10-15% of the wastewater mass. Stir in an enamel-lined reactor with variable frequency stirring at 25-40℃ and 150-300rpm for 30-60min. Let it stand for stratification time ≥1h.

[0013] Step 5: Salt-alkali separation. The lower salt slurry is separated by a horizontal centrifuge at 3000-4000 rpm for 5-10 minutes. Sodium chloride with a water content of ≤8% is collected. The upper alkaline solution is reused at a ratio adjusted by an online pH monitoring system.

[0014] Step Six: Product Distillation. The organic phase enters the dual-tower distillation system. The operating pressure of the first tower is -0.08 to -0.085 MPa and the top temperature is 70±2℃. The operating pressure of the second tower is -0.095 to -0.098 MPa and the top temperature is 65±2℃. Tetramethylethylenediamine with a purity of ≥99.5% is collected.

[0015] Preferably, the catalyst is a nickel-lanthanum-aluminum composite catalyst, the preparation of which includes preparing a 30% aqueous solution of nickel nitrate and lanthanum nitrate at a mass ratio of 8:1, and impregnating an equal volume of the solution onto a substrate with a specific surface area ≥200 m². 2 / g of y-Al2O3 support was dried at 120℃ for 4h and then calcined in a muffle furnace at 450℃ for 3h. Hydrogen was then introduced and reduced at 400℃ for 2h. The final catalyst had a nickel loading of 18±0.5wt% and a lanthanum loading of 2.25wt%.

[0016] Preferably, the pipeline reactor includes a three-section temperature control structure:

[0017] Preheating section: accounting for 15% of the length, made of 316L stainless steel, covered with an electric heating tape to maintain 40-60℃;

[0018] Main reaction section: accounting for 70% of the length, with spiral titanium alloy baffles with a pitch of 30-50mm installed on the inner wall, and oil bath temperature control accuracy of ±1℃;

[0019] Cooling section: accounting for 15% of the length, jacketed cooling water circulation system, water temperature control accuracy ±2℃.

[0020] Preferably, after settling and stratification in step four, the density of the lower salt slurry is ≥1.25 g / cm³. 3 The density of the upper alkaline solution is ≤1.15 g / cm³. 3 With an alkali concentration of 35-38%, automatic interface recognition and separation are achieved through density difference.

[0021] Preferably, the alkali solution reuse is controlled in real time by an online pH monitoring system, which controls the mixing ratio of reused alkali solution and fresh caustic soda flakes to be between 1:0.2 and 1:0.5, maintains the pH value of the reaction system at 9.0-10.5, and the COD load of the reused alkali solution is ≤500mg / L.

[0022] Preferably, the pretreatment of amine-containing wastewater adopts a triple-effect falling film evaporator, with the first effect evaporation temperature at 70-75℃ and steam pressure at 0.3MPa, the second effect evaporation temperature at 60-65℃ and vacuum degree at -0.06MPa, and the third effect evaporation temperature at 45-50℃ and vacuum degree at -0.08MPa. The concentration endpoint is monitored by an online refractometer to ensure that the solid content reaches 40-45%.

[0023] Preferably, the by-product sodium chloride is processed by a fluidized bed drying system with an inlet air temperature of 80±5℃, a material residence time of 30-40min, and an outlet moisture content of ≤0.5%, chloride ion content of ≤100ppm, and sulfate ion content of ≤50ppm, meeting the standards for industrial-grade refined salt.

[0024] Preferably, in step two, methyltrioctylammonium chloride is added as a phase transfer catalyst, the amount added is 0.05-0.1% of the mass of ethylenediamine, and dissolved in isopropanol co-solvent, the volume ratio of co-solvent to ethylenediamine is 1:10 to 1:15.

[0025] Preferably, in a dual-tower distillation system, the front tower has ≥30 theoretical plates and a reflux ratio of 8:1 to 10:1, the rear tower has ≥40 theoretical plates and a reflux ratio of 15:1 to 20:1, and the organic matter content in the bottom residue is ≤0.5%.

[0026] Preferably, the exhaust gas treatment system includes two stages of falling film absorption towers connected in series. The first stage uses 15% dilute sulfuric acid spraying, with a liquid-to-gas ratio of 3 L / m³. 3 In the second stage, a 5% sodium hydroxide solution is used for spraying, with a liquid-to-gas ratio of 2 L / m³. 3 Ammonia concentration in exhaust gas ≤10mg / m³ 3 .

[0027] (III) Beneficial Effects

[0028] Compared with the prior art, the present invention provides a method for preparing tetramethylethylenediamine based on an amination pathway reaction, which has the following beneficial effects:

[0029] 1. In this invention, during the continuous synthesis of tetramethylethylenediamine, by constructing a gradient temperature field and an internal turbulence structure in a multi-segment pipeline reactor, the contact reaction state between ammonia and ethylenediamine can be controlled in real time. This can dynamically eliminate the abnormal accumulation of ammonia concentration in the local reaction system, ensure that the gas-liquid mass transfer process is always in the optimal reaction range, avoid catalyst activity decay caused by uneven mass transfer, reduce the proportion of by-products, and improve the directional selectivity of the amination reaction pathway.

[0030] 2. In this invention, during the separation of by-products, the interface changes between the salt slurry and the alkali solution are continuously monitored through a real-time feedback system of density difference in the alkali precipitation unit. This allows the system to promptly correct the stratification deviations caused by the phase separation process and automatically adjust the stirring rate and settling parameters when the material viscosity fluctuates. This ensures that the salt and alkali phases are precisely separated at the critical separation point, preventing unseparated alkali solution from mixing into the salt slurry or salt back-dissolving and contaminating the recycling system, thus ensuring the purity and stability of resource recovery.

[0031] 3. In this invention, during product purification and wastewater treatment, a step-separation mechanism of triple-effect evaporator and double-tower distillation is used to simultaneously track the phase transition trajectory of different components in the temperature gradient field, and to determine the evaporation concentration endpoint and distillation cut-off point status in real time. This allows the system to dynamically optimize the separation path based on the thermal sensitivity of the material, avoid damage to the molecular structure of the target product caused by the high-temperature environment, block the accumulation of impurity components in the recycling system, and ultimately achieve synergistic enhancement of product purity and wastewater resource utilization. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method for preparing tetramethylethylenediamine based on the amination pathway reaction of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: A method for preparing tetramethylethylenediamine based on an amination pathway reaction, comprising the following steps:

[0035] Step 1: Raw material premixing. A 30% (w / w) aqueous solution of ethylenediamine and the catalyst are continuously fed into a static mixer at a mass ratio of 100:0.5, with the flow rate controlled at 5 m / s. 3 / h, mixing time ≤30s;

[0036] Step 2: Pipeline reaction. The premix is ​​pumped into a multi-stage temperature-controlled pipeline reactor and subjected to an amination reaction with ammonia at a molar ratio of 1:3 under conditions of 140℃ and 2.0MPa, with a residence time of 30min.

[0037] Step 3: Gas-liquid separation. The reaction products are subjected to a three-stage stepped decompression to atmospheric pressure, with a decompression gradient of 0.8MPa→0.3MPa→0.1MPa. The temperature at the top of the separation tower is controlled at 45℃.

[0038] Step 4: Alkali precipitation and desalination. Add caustic soda flakes to the amine-distilled wastewater with a salt content of 25±2%, the amount of which is 10% of the wastewater mass. Stir at 150 rpm for 30 min at 25℃ in an enamel-lined reactor with variable frequency stirring. Let it stand for stratification time ≥1 h.

[0039] Step 5: Salt-alkali separation. The lower salt slurry is separated by a horizontal centrifuge at 3000 rpm for 5 minutes. Sodium chloride with a water content of ≤8% is collected. The upper alkaline solution is reused at a rate adjusted by an online pH monitoring system.

[0040] Step Six: Product Distillation. The organic phase enters a dual-tower distillation system. The operating pressure of the first tower is -0.08 MPa and the top temperature is 68°C. The operating pressure of the second tower is -0.095 MPa and the top temperature is 63°C. Tetramethylethylenediamine with a purity of ≥99.5% is collected.

[0041] The catalyst is a nickel-lanthanum-aluminum composite catalyst, which is prepared by mixing nickel nitrate and lanthanum nitrate in a mass ratio of 8:1 to form a 30% aqueous solution, and then impregnating an equal volume of the solution onto a substrate with a specific surface area ≥200 m². 2 / g of y-Al2O3 support was dried at 120℃ for 4h and then calcined in a muffle furnace at 450℃ for 3h. Hydrogen was then introduced and reduced at 400℃ for 2h. The final catalyst had a nickel loading of 17.5wt% and a lanthanum loading of 2.25wt%.

[0042] The pipeline reactor includes a three-section temperature control structure:

[0043] Preheating section: accounting for 15% of the length, made of 316L stainless steel, covered with an electric heating tape to maintain 40°C;

[0044] Main reaction section: accounting for 70% of the length, with spiral titanium alloy baffles with a pitch of 30mm installed on the inner wall, and oil bath temperature control accuracy of ±1℃;

[0045] Cooling section: accounting for 15% of the length, jacketed cooling water circulation system, water temperature control accuracy ±2℃.

[0046] After settling and separating in step four, the density of the lower layer of salt slurry is ≥1.25 g / cm³. 3 The density of the upper alkaline solution is ≤1.15 g / cm³. 3With an alkali concentration of 35%, automatic interface recognition and separation are achieved through density difference.

[0047] The reuse of alkali solution is regulated in real time by an online pH monitoring system. The mixing ratio of reused alkali solution and fresh caustic soda flakes is controlled at 1:0.2, the pH value of the reaction system is maintained at 9.0, and the COD load of the reused alkali solution is ≤500mg / L.

[0048] The pretreatment of amine-containing wastewater uses a triple-effect falling film evaporator. The first effect evaporation temperature is 70℃ and the steam pressure is 0.3MPa. The second effect evaporation temperature is 60℃ and the vacuum degree is -0.06MPa. The third effect evaporation temperature is 45℃ and the vacuum degree is -0.08MPa. The concentration endpoint is monitored by an online refractometer to ensure that the solid content reaches 40%.

[0049] The by-product sodium chloride is processed by a fluidized bed drying system with an inlet air temperature of 75℃, a material residence time of 30 minutes, and an output moisture content of ≤0.5%, chloride ion content of ≤100ppm, and sulfate ion content of ≤50ppm, meeting the standards for industrial-grade refined salt.

[0050] In step two, methyltrioctylammonium chloride is added as a phase transfer catalyst at a concentration of 0.05% of the mass of ethylenediamine. It is dissolved in isopropanol as a co-solvent, with a volume ratio of co-solvent to ethylenediamine of 1:10.

[0051] The dual-tower distillation system has a theoretical plate count of ≥30 in the front column and a reflux ratio of 8:1, a theoretical plate count of ≥40 in the rear column and a reflux ratio of 15:1, and an organic content of ≤0.5% in the bottom residue.

[0052] The exhaust gas treatment system includes two stages of falling film absorption towers connected in series. The first stage uses 15% dilute sulfuric acid spraying with a liquid-to-gas ratio of 3 L / m³. 3 In the second stage, a 5% sodium hydroxide solution is used for spraying, with a liquid-to-gas ratio of 2 L / m³. 3 Ammonia concentration in exhaust gas ≤10mg / m³ 3 .

[0053] Example 2: A method for preparing tetramethylethylenediamine based on an amination pathway reaction, comprising the following steps:

[0054] Step 1: Raw material premixing. A 35% (w / w) ethylenediamine aqueous solution and catalyst are continuously fed into a static mixer at a mass ratio of 100:1.0, with a controlled flow rate of 8 m / s. 3 / h, mixing time ≤30s;

[0055] Step 2: Pipeline reaction. The premix is ​​pumped into a multi-stage temperature-controlled pipeline reactor and subjected to an amination reaction with ammonia at a molar ratio of 1:4 under conditions of 160℃ and 3.0MPa, with a residence time of 60min.

[0056] Step 3: Gas-liquid separation. The reaction products are subjected to a three-stage stepped decompression to atmospheric pressure, with a decompression gradient of 0.8MPa→0.3MPa→0.1MPa. The temperature at the top of the separation tower is controlled at 50℃.

[0057] Step 4: Alkali precipitation and desalination. Add caustic soda flakes to the amine-containing wastewater with a salt content of 25%, the amount of which is 13% of the wastewater mass. Stir at 230 rpm for 45 min at 33℃ in an enamel-lined reactor with variable frequency stirring. Let it stand for stratification time ≥1 h.

[0058] Step 5: Salt-alkali separation. The lower salt slurry is separated by a horizontal centrifuge at 3500 rpm for 8 minutes. Sodium chloride with a water content of ≤8% is collected. The upper alkaline solution is reused at a rate adjusted by an online pH monitoring system.

[0059] Step Six: Product Distillation. The organic phase enters the dual-tower distillation system. The operating pressure of the first tower is -0.083 MPa and the top temperature is 70°C. The operating pressure of the second tower is -0.096 MPa and the top temperature is 65°C. Tetramethylethylenediamine with a purity of ≥99.5% is collected.

[0060] The catalyst is a nickel-lanthanum-aluminum composite catalyst, which is prepared by mixing nickel nitrate and lanthanum nitrate in a mass ratio of 8:1 to form a 30% aqueous solution, and then impregnating an equal volume of the solution onto a substrate with a specific surface area ≥200 m². 2 / g of y-Al2O3 support was dried at 120℃ for 4h and then calcined in a muffle furnace at 450℃ for 3h. Hydrogen was then introduced and reduced at 400℃ for 2h. The final catalyst had a nickel loading of 18wt% and a lanthanum loading of 2.25wt%.

[0061] The pipeline reactor includes a three-section temperature control structure:

[0062] Preheating section: accounting for 15% of the length, made of 316L stainless steel, covered with an electric heating tape to maintain 50°C;

[0063] Main reaction section: accounting for 70% of the length, with spiral titanium alloy baffles with a pitch of 40mm installed on the inner wall, and oil bath temperature control accuracy of ±1℃;

[0064] Cooling section: accounting for 15% of the length, jacketed cooling water circulation system, water temperature control accuracy ±2℃.

[0065] After settling and separating in step four, the density of the lower layer of salt slurry is ≥1.25 g / cm³. 3 The density of the upper alkaline solution is ≤1.15 g / cm³. 3 With an alkali concentration of 37%, automatic interface recognition and separation are achieved through density difference.

[0066] The reuse of alkali solution is regulated in real time by an online pH monitoring system, which controls the mixing ratio of reused alkali solution and fresh caustic soda flakes to be between 1:0.4, maintains the pH value of the reaction system at 9.8, and ensures that the COD load of the reused alkali solution is ≤500mg / L.

[0067] The pretreatment of amine-containing wastewater uses a triple-effect falling film evaporator. The first effect evaporation temperature is 73℃ and the steam pressure is 0.3MPa. The second effect evaporation temperature is 63℃ and the vacuum degree is -0.06MPa. The third effect evaporation temperature is 48℃ and the vacuum degree is -0.08MPa. The concentration endpoint is monitored by an online refractometer to ensure that the solid content reaches 43%.

[0068] The by-product sodium chloride is processed by a fluidized bed drying system with an inlet air temperature of 80℃, a material residence time of 35 minutes, and an output moisture content of ≤0.5%, chloride ion content of ≤100ppm, and sulfate ion content of ≤50ppm, meeting the standards for industrial-grade refined salt.

[0069] In step two, methyltrioctylammonium chloride is added as a phase transfer catalyst at an amount of 0.08% of the mass of ethylenediamine. It is dissolved in isopropanol as a co-solvent, with a volume ratio of co-solvent to ethylenediamine of 1:13.

[0070] The dual-tower distillation system has a theoretical plate count of ≥30 in the front column and a reflux ratio of 9:1, a theoretical plate count of ≥40 in the rear column and a reflux ratio of 18:1, and an organic content of ≤0.5% in the bottom residue.

[0071] The exhaust gas treatment system includes two stages of falling film absorption towers connected in series. The first stage uses 15% dilute sulfuric acid spraying with a liquid-to-gas ratio of 3 L / m³. 3 In the second stage, a 5% sodium hydroxide solution is used for spraying, with a liquid-to-gas ratio of 2 L / m³. 3 Ammonia concentration in exhaust gas ≤10mg / m³ 3 .

[0072] Example 3: A method for preparing tetramethylethylenediamine based on an amination pathway reaction, comprising the following steps:

[0073] Step 1: Raw material premixing. A 40% (w / w) ethylenediamine aqueous solution and catalyst are continuously fed into a static mixer at a mass ratio of 100:1.5, with the flow rate controlled at 10 m / s. 3 / h, mixing time ≤30s;

[0074] Step 2: Pipeline reaction. The premix is ​​pumped into a multi-stage temperature-controlled pipeline reactor and subjected to an amination reaction with ammonia at a molar ratio of 1:5 under conditions of 180℃ and 4.0MPa, with a residence time of 90min.

[0075] Step 3: Gas-liquid separation. The reaction products are subjected to a three-stage stepped decompression to atmospheric pressure, with a decompression gradient of 0.8MPa→0.3MPa→0.1MPa. The temperature at the top of the separation tower is controlled at 55℃.

[0076] Step 4: Alkali precipitation and desalination. Add caustic soda flakes to the amine-containing wastewater with a salt content of 27%, the amount of which is 15% of the wastewater mass. Stir at 300 rpm for 60 min at 40℃ in an enamel-lined reactor with variable frequency stirring. Let it stand for stratification time ≥1 h.

[0077] Step 5: Salt-alkali separation. The lower salt slurry is separated by a horizontal centrifuge at 4000 rpm for 10 minutes. Sodium chloride with a water content of ≤8% is collected. The upper alkaline solution is reused at a rate adjusted by an online pH monitoring system.

[0078] Step Six: Product Distillation. The organic phase enters the dual-tower distillation system. The operating pressure of the first tower is -0.085 MPa and the top temperature is 72°C. The operating pressure of the second tower is -0.098 MPa and the top temperature is 67°C. Tetramethylethylenediamine with a purity of ≥99.5% is collected.

[0079] The catalyst is a nickel-lanthanum-aluminum composite catalyst, which is prepared by mixing nickel nitrate and lanthanum nitrate in a mass ratio of 8:1 to form a 30% aqueous solution, and then impregnating an equal volume of the solution onto a substrate with a specific surface area ≥200 m². 2 / g of y-Al2O3 support was dried at 120℃ for 4h and then calcined in a muffle furnace at 450℃ for 3h. Hydrogen was then introduced and reduced at 400℃ for 2h. The final catalyst had a nickel loading of 18.5wt% and a lanthanum loading of 2.25wt%.

[0080] The pipeline reactor includes a three-section temperature control structure:

[0081] Preheating section: accounting for 15% of the length, made of 316L stainless steel, covered with an electric heating tape to maintain 60°C;

[0082] Main reaction section: accounting for 70% of the length, with spiral titanium alloy baffles with a pitch of 50mm installed on the inner wall, and oil bath temperature control accuracy of ±1℃;

[0083] Cooling section: accounting for 15% of the length, jacketed cooling water circulation system, water temperature control accuracy ±2℃.

[0084] After settling and separating in step four, the density of the lower layer of salt slurry is ≥1.25 g / cm³. 3 The density of the upper alkaline solution is ≤1.15 g / cm³. 3 With an alkali concentration of 38%, automatic interface recognition and separation are achieved through density difference.

[0085] The reuse of alkali solution is regulated in real time by an online pH monitoring system, which controls the mixing ratio of reused alkali solution and fresh caustic soda flakes to be between 1:0.5, maintains the pH value of the reaction system at 10.5, and ensures that the COD load of the reused alkali solution is ≤500mg / L.

[0086] The pretreatment of amine-containing wastewater uses a triple-effect falling film evaporator. The first effect evaporation temperature is 75℃ and the steam pressure is 0.3MPa. The second effect evaporation temperature is 65℃ and the vacuum degree is -0.06MPa. The third effect evaporation temperature is 50℃ and the vacuum degree is -0.08MPa. The concentration endpoint is monitored by an online refractometer to ensure that the solid content reaches 45%.

[0087] The by-product sodium chloride is processed by a fluidized bed drying system with an inlet air temperature of 85℃, a material residence time of 40 min, and an output moisture content of ≤0.5%, chloride ion content of ≤100ppm, and sulfate ion content of ≤50ppm, meeting the standards for industrial-grade refined salt.

[0088] In step two, methyltrioctylammonium chloride is added as a phase transfer catalyst at a concentration of 0.1% of the mass of ethylenediamine. It is dissolved in isopropanol as a co-solvent, with a volume ratio of co-solvent to ethylenediamine of 1:15.

[0089] The dual-tower distillation system has a theoretical plate count of ≥30 in the front column and a reflux ratio of 10:1, a theoretical plate count of ≥40 in the rear column and a reflux ratio of 20:1, and an organic content of ≤0.5% in the bottom residue.

[0090] The exhaust gas treatment system includes two stages of falling film absorption towers connected in series. The first stage uses 15% dilute sulfuric acid spraying with a liquid-to-gas ratio of 3 L / m³. 3 In the second stage, a 5% sodium hydroxide solution is used for spraying, with a liquid-to-gas ratio of 2 L / m³. 3 Ammonia concentration in exhaust gas ≤10mg / m³ 3 .

[0091] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not have an alkaline precipitation desalination unit.

[0092] Comparative Example 2 differs from Example 1 in that it uses a single-tower distillation system instead of a double-tower distillation system.

[0093] Comparative Example 3 differs from Example 1 in that an atmospheric pressure reactor is used instead of a pipeline reactor in this comparative example.

[0094] Performance testing: The tetramethylethylenediamine prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was subjected to performance testing.

[0095] Raw material conversion rate: Calculate the percentage of ethylenediamine consumption to the initial feed amount;

[0096] Product purity: Detect the percentage of the main peak area of ​​tetramethylethylenediamine;

[0097] Wastewater COD value: Measured index of amine-containing wastewater before treatment;

[0098] Unit energy consumption: Record the total power consumption of the entire process of reaction, separation and distillation, and convert it into energy consumption per ton of product.

[0099] The obtained test data is recorded in the table below:

[0100] Testing items Ethylenediamine conversion rate (%) Product purity (%) Wastewater COD (mg / L) Energy consumption per unit (kW·h / t) Example 1 94.7 99.52 480 580 Example 2 95.3 99.61 420 570 Example 3 96.1 99.78 390 560 Comparative Example 1 82.1 95.43 20800 720 Comparative Example 2 87.5 97.26 1250 650 Comparative Example 3 76.8 92.15 18500 940

[0101] Comparison and analysis of the data in the table show that the tetramethylethylenediamine prepared using the process described in the example exhibits significantly superior performance. This indicates that the multi-stage temperature control structure of the pipeline reactor, combined with the spiral baffles, continuously renews the micro-regions at the gas-liquid interface, eliminates localized dead zones in ammonia concentration, and improves mass transfer efficiency. The alkali precipitation and desalination unit identifies the salt-alkali interface in real time through density gradients, accurately separating by-product sodium chloride from reusable alkali solution, forming a closed-loop circulation mechanism to prevent the discharge of high-salt wastewater. The step-separation mechanism of the triple-effect evaporator and dual-tower distillation simultaneously tracks the phase transition trajectories of different components in the temperature gradient field, determines the endpoint of evaporation and concentration and the state of the distillation cut-off point in real time, avoids the destruction of the target product's molecular structure by the high-temperature environment, and prevents the accumulation of impurity components in the circulation system, ultimately achieving a synergistic enhancement of product purity and wastewater resource utilization.

[0102] By comparing and analyzing the relevant data in the table, it can be seen that the tetramethylethylenediamine prepared by the method of the present invention not only has high conversion rate and electronic-grade purity, but also achieves near-zero wastewater discharge and optimized energy consumption. This indicates that the continuous preparation process provided by the present invention has a broader market prospect and is more suitable for widespread application.

[0103] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing tetramethylethylenediamine based on an amination pathway reaction, characterized in that: Includes the following steps: Step 1: Raw material premixing. A 30-40% (w / w) aqueous solution of ethylenediamine and the catalyst are continuously fed into a static mixer at a mass ratio of 100:0.5-1.5, controlling the flow rate to 5-10 m / s. 3 / h, mixing time ≤30s; Step 2: Pipeline reaction. The premix is ​​pumped into a multi-stage temperature-controlled pipeline reactor and subjected to an amination reaction with ammonia at a molar ratio of 1:3 to 1:5 under conditions of 140-180℃ and 2.0-4.0MPa, with a residence time of 30-90min. Step 3: Gas-liquid separation. The reaction products are subjected to a three-stage step-by-step decompression to atmospheric pressure, with a decompression gradient of 0.8MPa→0.3MPa→0.1MPa. The temperature at the top of the separation tower is controlled at 45-55℃. Step 4: Alkali precipitation and desalination. Add caustic soda flakes to the amine-distilled wastewater with a salt content of 25±2%, the amount of which is 10-15% of the wastewater mass. Stir in an enamel-lined reactor with variable frequency stirring at 25-40℃ and 150-300rpm for 30-60min. Let it stand for stratification time ≥1h. Step 5: Salt-alkali separation. The lower salt slurry is separated by a horizontal centrifuge at 3000-4000 rpm for 5-10 minutes. Sodium chloride with a water content of ≤8% is collected. The upper alkaline solution is reused at a ratio adjusted by an online pH monitoring system. Step Six: Product Distillation. The organic phase enters the dual-tower distillation system. The operating pressure of the first tower is -0.08 to -0.085 MPa and the top temperature is 70±2℃. The operating pressure of the second tower is -0.095 to -0.098 MPa and the top temperature is 65±2℃. Tetramethylethylenediamine with a purity of ≥99.5% is collected.

2. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The catalyst is a nickel-lanthanum-aluminum composite catalyst, the preparation of which includes preparing a 30% aqueous solution of nickel nitrate and lanthanum nitrate at a mass ratio of 8:1, and impregnating an equal volume of the solution onto a substrate with a specific surface area ≥200m². 2 / g of y-Al2O3 support was dried at 120℃ for 4h and then calcined in a muffle furnace at 450℃ for 3h. Hydrogen was then introduced and reduced at 400℃ for 2h. The final catalyst had a nickel loading of 18±0.5wt% and a lanthanum loading of 2.25wt%.

3. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The pipeline reactor includes a three-section temperature control structure: Preheating section: accounting for 15% of the length, made of 316L stainless steel, covered with an electric heating tape to maintain 40-60℃; Main reaction section: accounting for 70% of the length, with spiral titanium alloy baffles with a pitch of 30-50mm installed on the inner wall, and oil bath temperature control accuracy of ±1℃; Cooling section: accounting for 15% of the length, jacketed cooling water circulation system, water temperature control accuracy ±2℃.

4. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: After settling and separating in step four, the density of the lower layer of salt slurry is ≥1.25 g / cm³. 3 The density of the upper alkaline solution is ≤1.15 g / cm³. 3 With an alkali concentration of 35-38%, automatic interface recognition and separation are achieved through density difference.

5. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The reuse of alkali solution is controlled in real time by an online pH monitoring system, which controls the mixing ratio of reused alkali solution and fresh caustic soda flakes to be between 1:0.2 and 1:0.5, maintains the pH value of the reaction system at 9.0-10.5, and the COD load of the reused alkali solution is ≤500mg / L.

6. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The pretreatment of amine-containing wastewater uses a triple-effect falling film evaporator. The first effect evaporation temperature is 70-75℃ and the steam pressure is 0.3MPa. The second effect evaporation temperature is 60-65℃ and the vacuum degree is -0.06MPa. The third effect evaporation temperature is 45-50℃ and the vacuum degree is -0.08MPa. The concentration endpoint is monitored by an online refractometer to ensure that the solid content reaches 40-45%.

7. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The by-product sodium chloride is processed by a fluidized bed drying system with an inlet air temperature of 80±5℃, a material residence time of 30-40 min, and an output moisture content of ≤0.5%, chloride ion content of ≤100ppm, and sulfate ion content of ≤50ppm, meeting the standards for industrial-grade refined salt.

8. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: In step two, methyltrioctylammonium chloride is added as a phase transfer catalyst at a concentration of 0.05-0.1% of the mass of ethylenediamine. It is dissolved in isopropanol as a co-solvent, with a volume ratio of co-solvent to ethylenediamine of 1:10 to 1:

15.

9. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The dual-tower distillation system has a theoretical plate count of ≥30 in the front column and a reflux ratio of 8:1 to 10:1, and a theoretical plate count of ≥40 in the rear column and a reflux ratio of 15:1 to 20:

1. The organic matter content in the bottom residue is ≤0.5%.

10. The method for preparing tetramethylethylenediamine based on an amination pathway reaction according to claim 1, characterized in that: The exhaust gas treatment system includes two stages of falling film absorption towers connected in series. The first stage uses 15% dilute sulfuric acid spraying with a liquid-to-gas ratio of 3 L / m³. 3 In the second stage, a 5% sodium hydroxide solution is used for spraying, with a liquid-to-gas ratio of 2 L / m³. 3 Ammonia concentration in exhaust gas ≤10mg / m³ 3 .

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