Device and method for preparing bromomethane by using bromine salt wastewater
By reacting bromide wastewater with concentrated sulfuric acid to generate hydrogen bromide, and reacting with methanol to prepare methyl bromide, the problem of long process route, high energy consumption and safety hazards in the existing technology has been solved, and efficient and safe bromine resources have been achieved. utilization.
Patent Information
- Application Number
- CN202411180402.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-27
- Publication Date
- 2025-01-21
AI Technical Summary
In the prior art, the process route for the preparation of bromine methane using bromine salt wastewater is long, has high energy consumption, poor economy, and has safety hazards and environmental pollution risks.
A device and method were designed to generate hydrogen bromide by reacting bromide wastewater with concentrated sulfuric acid, and then reacting with methanol to prepare methyl bromide. The method includes performing an insulated reaction in a reaction vessel, and utilizing a condenser and a drying tower to improve the purity and yield of methyl bromide.
It achieves a high conversion rate of bromide ions (above 98%) and a high purity of methyl bromide (above 99%), while reducing the energy consumption and safety risks of the process and improving resource utilization efficiency.
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Figure CN119327388A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a device and a method for preparing methyl bromide by utilizing bromide salt wastewater, belonging to the technical field of resource utilization of high-bromine salt wastewater. Background Art
[0002] Bromine, as an active non-metallic element, can react with a variety of substances. The bromides generated are widely used in medicine, pesticides, flame retardants, photosensitive materials, petroleum products and other fields. Bromine in nature mainly exists in the form of inorganic bromides in seawater, salt lake water, underground brine, oil and gas field water and other resources. my country's bromine resources are mainly concentrated in the Bohai Bay area, and bromine production accounts for more than 70% of the total domestic production. With the continuous exploitation of underground brine, domestic bromine production is seriously insufficient, and about 40,000 to 60,000 tons of bromine are imported each year.
[0003] Many chemical companies use bromine-containing raw materials or reagents, such as methyl bromide, ethyl bromide, benzyl bromide, N-bromosuccinimide (NBS), dibromohydantoin, hydrobromic acid, etc., which will produce bromine-containing byproducts, such as solid or liquid waste of bromide salts. Bromine only plays a role of bridging and positioning in some reaction processes, and does not enter the target product. It is finally presented in the form of solid or liquid waste of bromide salts. In the early years, many companies did not pay attention to the recovery and utilization of bromine resources from bromide salts. The main reasons are: (1) the amount of bromine salts produced is small, the price of bromine is low, and the recycling value is not high; (2) the process of extracting bromine from bromine salts is complicated, bromine is volatile and highly corrosive, there are many safety hazards, high environmental pollution risks, and it is not easy to pass the safety and environmental impact assessment. In recent years, with the intensification of global industrial chain competition and the sharp fluctuations in bromine prices, the importance of bromine resources has become increasingly obvious and has become one of the main factors affecting corporate production and benefits. Therefore, the recovery and reuse of bromine resources have received more and more attention from the industry.
[0004] Methyl bromide, also known as methyl bromide or methyl bromide, is a typical organic bromide. It is an odorless gas at room temperature and pressure, with a boiling point of 3.6°C. Methyl bromide has a strong fumigation effect and can kill various harmful organisms efficiently and broadly. In addition, methyl bromide is also a key raw material in the preparation process of many fine chemical products such as medicines and pesticides, and has a wide range of applications in the chemical industry. There are three main methods for the preparation of methyl bromide: (1) methane reacts with O2 and HBr / H20 in the presence of a catalyst to prepare methyl bromide; (2) methanol reacts directly with hydrogen bromide to prepare methyl bromide; (3) sulfur reacts with bromine first, and then reacts with methanol to prepare methyl bromide. In industrial production, method (3) is generally used, that is, the route of preparing methyl bromide using sulfur, bromine and methanol as raw materials, because this route has a lower raw material cost and a higher yield.
[0005] In industrial production, bromine salt wastewater is usually treated by triple-effect evaporation, recrystallization, etc. to obtain solid bromine salt, and then bromine is extracted from bromine salt to prepare bromine downstream compounds to achieve bromine reuse. However, extracting bromine from bromine salt wastewater and then preparing methyl bromide using the above method (3) has a long process route, high energy consumption, and poor economic efficiency. Summary of the invention
[0006] In view of the above shortcomings of the prior art, the purpose of the present invention is to provide a device and method for preparing methyl bromide using bromide salt wastewater. The process method can achieve a bromide ion conversion rate of more than 98% and a methyl bromide purity of more than 99%. Effectively realize the efficient resource utilization of bromide ions in bromine-containing wastewater.
[0007] To achieve the above objectives, the technical solutions adopted are:
[0008] One of the purposes of the present invention is to provide a device for preparing methyl bromide by using bromine salt wastewater, comprising a reaction container, the reaction container is provided with a gas phase outlet, the gas phase outlet is connected to the gas phase inlet of a neutralization container through a primary condenser, the gas phase outlet of the neutralization container is connected to the material inlet of a secondary condenser through a primary drying tower, the material outlet of the secondary condenser is connected to a low-temperature liquid storage tank, the gas phase outlet of the low-temperature liquid storage tank is connected to an emptying port through a third-stage condenser and a secondary drying tower in sequence, the low-temperature liquid storage tank is provided with a methyl bromide liquid outlet, the reaction container is also provided with at least one material inlet, and the neutralization container is also provided with an alkali solution inlet.
[0009] The beneficial effects of adopting the above technical solution include: the main function of the three-stage condenser is to reflux the trace methyl bromide gas from the low-temperature liquid storage tank into the low-temperature liquid storage tank under the action of the three-stage condenser, and the function of the secondary drying tower is to dry the trace air entering through the exhaust port to prevent moisture in the air from affecting the purity of the methyl bromide product.
[0010] On the basis of the above technical solution, the present invention can also make the following improvements:
[0011] Furthermore, a reaction liquid outlet is provided at the bottom of the reaction container.
[0012] Furthermore, a stirrer is provided in the reaction container.
[0013] Furthermore, the cryogenic liquid storage tank is provided with a refrigeration assembly.
[0014] Furthermore, the refrigeration component is a refrigerator.
[0015] Furthermore, the reaction container is provided with a vent.
[0016] The beneficial effect of adopting the above further technical solution is that the vent needs to be opened during the feeding process to release the internal pressure, so as to facilitate the feeding.
[0017] Furthermore, the material inlet is connected to a feed pump.
[0018] Furthermore, the primary condenser is connected to the neutralization container through a buffer.
[0019] Further, the end of the gas phase inlet of the neutralization container is inserted below the liquid level of the neutralization container.
[0020] The beneficial effects of the above two-step further technical solution are: the buffer can stabilize pressure fluctuations, regulate flow, isolate and reduce impact, and improve system efficiency, prevent backflow, and the end of the gas phase inlet of the neutralization container is inserted below the liquid level of the neutralization container, so that the acidic components in the methyl bromide can fully react with the dilute alkaline solution in the neutralization container.
[0021] Furthermore, the neutralization container is provided with a neutralization liquid outlet.
[0022] Furthermore, pressure gauges are provided between the primary condenser and the neutralization container, between the neutralization container and the primary drying tower, and between the primary drying tower and the secondary condenser.
[0023] Furthermore, a tail gas absorption device is provided between the secondary drying tower and the exhaust port.
[0024] Furthermore, the low-temperature liquid storage tank is connected to a pressure gauge.
[0025] The second object of the present invention is to provide a method for preparing methyl bromide using bromide salt wastewater, comprising the following steps:
[0026] (1) adding bromine salt waste water into a reaction vessel through a material inlet, and starting a primary condenser, adding a dilute alkali solution into a neutralization container through an alkali solution inlet, and adding concentrated sulfuric acid into the reaction vessel through a material inlet under stirring of a stirrer, and controlling the speed of adding concentrated sulfuric acid according to the temperature of the reaction solution in the reaction vessel, adjusting the reaction temperature, and performing a heat preservation reaction;
[0027] (2) Start the refrigeration components of the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank to make the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank reach the cooling temperature, slowly add methanol to the reaction container, gradually increase the temperature, and control the temperature to ensure that the raw materials in the system are completely reacted. The gas generated in the reaction container passes through the primary condenser, the neutralization container, the primary drying tower in sequence, and then passes through the secondary condenser to form methyl bromide liquid and enter the cryogenic liquid storage tank.
[0028] The beneficial effect of adopting the above technical solution is that the methyl bromide gas generated by the reaction container first passes through a primary condenser, and the primary condenser can reflux the methanol entrained in the methyl bromide gas into the reaction container, and then passes through a buffer to enter a neutralization container, and there is a dilute alkali solution in the neutralization container, and its function is to remove acidic gases such as hydrogen bromide in the methyl bromide gas, and then passes through a drying tower to remove water and dry, and enters a secondary condenser, where the methyl bromide gas is condensed into methyl bromide liquid and enters a low-temperature liquid storage tank.
[0029] Furthermore, the method for preparing methyl bromide using bromine salt wastewater also includes the following steps: after the reaction is completed, the methyl bromide liquid is transferred to a gas storage cylinder using a compression device.
[0030] Furthermore, the method for preparing methyl bromide using bromide salt wastewater also includes the following steps: discharging the reaction liquid in the reaction container through the reaction liquid outlet, and performing treatments such as neutralization and salt precipitation.
[0031] Furthermore, the bromide wastewater contains at least one of sodium bromide, potassium bromide, magnesium bromide and zinc bromide; the mass concentration of bromide ions in the bromide wastewater is 28% to 39%, the total mass concentration of other halogen ions is less than 0.01%, the pH of the bromide wastewater is 1 to 12; and the chemical oxygen demand COD is less than 2000 mg / L.
[0032] Furthermore, the mass concentration of the concentrated sulfuric acid is 95% to 98%, the molar ratio of H2SO4 to bromide ions is 1.3 to 2.0:1, and the molar ratio of methanol to bromide ions is 1.5 to 2.0:1.
[0033] Furthermore, the cooling temperature of the first-stage condenser is 5 to 15°C, the cooling temperature of the second-stage condenser is -25 to -35°C, the cooling temperature of the third-stage condenser is -20 to -30°C, and the cooling temperature of the low-temperature liquid storage tank is -20 to -25°C.
[0034] Furthermore, when the concentrated sulfuric acid is added in step (1), the internal temperature of the reaction container is ≤40°C. After the concentrated sulfuric acid is added, the temperature is raised to 45-55°C and kept warm for reaction for 0.5-1 hour.
[0035] Furthermore, when the methanol is added in step (2), the internal temperature of the reaction container is 45-55° C. After the methanol is added, the temperature is slowly raised to 70-80° C. and kept warm for 3-4 hours.
[0036] Furthermore, the dilute alkaline solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass concentration of 1% to 3%.
[0037] Compared with the prior art, the beneficial effects of the present invention are:
[0038] The present invention provides a device and method for preparing methyl bromide using bromide salt wastewater as a raw material, and realizes efficient resource utilization of bromide ions in wastewater. The present invention first generates hydrogen bromide and sodium bisulfate by reacting bromide salt and concentrated sulfuric acid, and then reacts the generated hydrogen bromide with methanol to obtain methyl bromide. Compared with the traditional method for preparing methyl bromide, the present invention directly uses bromide ions in wastewater to prepare methyl bromide, avoiding the use of volatile and highly corrosive bromine as a raw material to prepare methyl bromide. The process does not involve the oxidation-reduction reaction process of preparing sulfur bromide by bromine and sulfur, and there is no violent exothermic process. The process is safer, simpler and more efficient. The method can make the bromide ion conversion rate reach more than 98%, and the methyl bromide purity reach more than 99%, and can maximize the resource utilization of bromide ions in wastewater. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 The present invention is a process flow chart for preparing methyl bromide using bromide salt wastewater. DETAILED DESCRIPTION
[0040] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.
[0041] A device for preparing methyl bromide by using bromine salt waste water comprises a reaction container, the reaction container is provided with a gas phase outlet, the gas phase outlet is connected to the gas phase inlet of a neutralization container through a primary condenser, the gas phase outlet of the neutralization container is connected to the material inlet of a secondary condenser through a primary drying tower, the material outlet of the secondary condenser is connected to a low-temperature liquid storage tank, the gas phase outlet of the low-temperature liquid storage tank is connected to an emptying port through a third-stage condenser and a secondary drying tower in sequence, the low-temperature liquid storage tank is provided with a methyl bromide liquid outlet, the reaction container is also provided with at least one material inlet, and the neutralization container is also provided with an alkali liquid inlet.
[0042] As a preferred embodiment, a reaction liquid outlet is provided at the bottom of the reaction container.
[0043] As a preferred embodiment, a stirrer is provided in the reaction container.
[0044] As a preferred embodiment, the low-temperature liquid storage tank is provided with a refrigeration assembly.
[0045] In this embodiment, a vent is provided on the reaction container.
[0046] In this embodiment, the material inlet is connected to a feed pump.
[0047] In an optional embodiment, the primary condenser is connected to the neutralization container via a buffer.
[0048] As a preferred embodiment, the end of the gas phase inlet of the neutralization container is inserted below the liquid level of the neutralization container.
[0049] As a preferred embodiment, the neutralization container is provided with a neutralization liquid outlet.
[0050] In an optional embodiment, a pressure gauge is provided between the primary condenser and the neutralization container, between the neutralization container and the primary drying tower, and between the primary drying tower and the secondary condenser.
[0051] In an optional embodiment, a tail gas absorption device is provided between the secondary drying tower and the exhaust port.
[0052] In this embodiment, a pressure gauge is connected to the low-temperature liquid storage tank.
[0053] The present invention also provides a method for preparing methyl bromide using bromine salt wastewater, comprising the following steps:
[0054] (1) adding bromine salt waste water into a reaction vessel through a material inlet, and starting a primary condenser, adding a dilute alkali solution into a neutralization container through an alkali solution inlet, and adding concentrated sulfuric acid into the reaction vessel through a material inlet under stirring of a stirrer, and controlling the speed of adding concentrated sulfuric acid according to the temperature of the reaction solution in the reaction vessel, adjusting the reaction temperature, and performing a heat preservation reaction;
[0055] (2) Start the refrigeration components of the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank to make the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank reach the cooling temperature, slowly add methanol to the reaction container, gradually increase the temperature, and control the temperature to ensure that the raw materials in the system are completely reacted. The gas generated in the reaction container passes through the primary condenser, the neutralization container, the primary drying tower in sequence, and then passes through the secondary condenser to form methyl bromide liquid and enter the cryogenic liquid storage tank.
[0056] In this embodiment, the method for preparing methyl bromide using bromine salt wastewater further includes the following steps: after the reaction is completed, the methyl bromide liquid is transferred to a gas storage cylinder using a compression device.
[0057] In this embodiment, the method for preparing methyl bromide using bromide salt wastewater further includes the following steps: discharging the reaction liquid in the reaction container through the reaction liquid outlet, and performing treatments such as neutralization and salt precipitation.
[0058] In an optional embodiment, the bromide salt wastewater contains at least one of sodium bromide, potassium bromide, magnesium bromide, and zinc bromide; the mass concentration of bromide ions in the bromide salt wastewater is 28% to 39%, the total mass concentration of other halogen ions is less than 0.01%, the pH of the bromide salt wastewater is 1 to 12; and the chemical oxygen demand COD is less than 2000 mg / L.
[0059] In this embodiment, the mass concentration of the concentrated sulfuric acid is 95% to 98%, the molar ratio of concentrated sulfuric acid to bromide ions is 1.3 to 2.0:1, and the molar ratio of methanol to bromide ions is 1.5 to 2.0:1.
[0060] In an optional embodiment, the cooling temperature of the first-stage condenser is 5 to 15°C, the cooling temperature of the second-stage condenser is -25 to -35°C, the cooling temperature of the third-stage condenser is -20 to -30°C, and the cooling temperature of the low-temperature liquid storage tank is -20 to -25°C.
[0061] In this embodiment, specifically, the internal temperature of the reaction container is ≤40°C when the concentrated sulfuric acid is added in step (1). After the concentrated sulfuric acid is added, the temperature is raised to 45-55°C and kept warm for reaction for 0.5-1 hour.
[0062] In an optional embodiment, the internal temperature of the reaction container is 45-55°C when the methanol is added in step (2). After the methanol is added, the temperature is slowly raised to 70-80°C and kept warm for reaction for 3-4 hours.
[0063] As a preferred embodiment, the dilute alkaline solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass concentration of 1% to 3%.
[0064] Example 1
[0065] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 28%, the pH is 5, and the COD (chemical oxygen demand) is 1200 mg / L. Open valve 1 for controlling the material inlet and valve 3 for controlling the vent, and add 20 kg of bromide salt wastewater into the reaction vessel through the feed pump 1 connected to valve 1. After the addition is completed, close valve 1 and valve 3. Open valve 4 for controlling the gas phase outlet of the reaction vessel, valve 5 for controlling the gas phase inlet of the neutralization vessel, valve 7 for controlling the gas phase outlet of the neutralization vessel, valve 6 for controlling the alkali liquid inlet, valve 8 for controlling the methyl bromide inlet of the low-temperature liquid storage tank, valve 9 for controlling the methyl bromide gas outlet of the low-temperature liquid storage tank, and start the primary condenser, add 10L of dilute alkali solution with a mass concentration of 1% into the neutralization vessel through valve 6, and close valve 6 after the addition is completed. Turn on the agitator of the reaction vessel for stirring, wait until the first-stage condenser reaches 5°C, open valve 2, add 13.7kg of concentrated sulfuric acid with a mass concentration of 98% into the reaction vessel through the feed pump 2 through the material inlet, control the temperature in the reaction vessel to be ≤40°C for feeding, close valve 2, heat to 45°C, and keep warm for 0.5 hours. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature, wherein the cooling temperature of the secondary condenser is -25 to -35°C, the cooling temperature of the tertiary condenser is -20 to -30°C, and the cooling temperature of the low-temperature liquid storage tank is -20 to -25°C. After the insulation is completed, open valve 1, slowly add 4.4kg of methanol to the reaction vessel through the feed pump 1, control the reaction temperature between 45 and 55°C for feeding, and after the addition of methanol is completed, slowly heat to 70°C and keep warm for 3 hours. After the reaction is finished, valve 8 is closed, and the methyl bromide liquid is transferred to the gas storage bottle through valve 10 at the bottom of the cryogenic liquid storage tank to control the outlet of the methyl bromide liquid. Valve 4 is closed, valve 3 is opened, and the reaction liquid in the reaction container is discharged through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.2%, the methyl bromide yield is 97.1%, and the purity is 99.2%.
[0066] Example 2
[0067] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 34%, the pH is 8, and the COD (chemical oxygen demand) is 1500 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 1.5% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 7°C, open valve 2, and add 14.2kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel ≤40°C to add materials. After the addition is completed, close valve 2, heat to 47°C, and keep warm for 40 minutes. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 4.6 kg of methanol to the reaction vessel through the feed pump 1, control the internal temperature of the reaction between 45 and 55 ° C, add the material, and after the addition of methanol is completed, slowly heat up to 72 ° C, and keep the reaction for 3.5 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.6%, the methyl bromide yield is 97.8%, and the purity is 99.3%.
[0068] Example 3
[0069] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 39%, the pH is 1, and the COD (chemical oxygen demand) is 1100 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 3% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 10°C, open valve 2, and add 13.1 kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel to ≤40°C and add materials. After the addition is completed, close valve 2, heat to 55°C, and keep warm for reaction for 1 hour. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 4.7kg of methanol to the reaction vessel through the feed pump 1, control the internal temperature of the reaction between 45 and 55°C, add the material, and after the addition of methanol is completed, slowly heat up to 80°C and keep the reaction for 4 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.8%, the methyl bromide yield is 98.1%, and the purity is 99.3%.
[0070] Example 4
[0071] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 30%, the pH is 11, and the COD (chemical oxygen demand) is 1800 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 1.2% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 8°C, open valve 2, and add 11.1 kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel to ≤40°C and add materials. After the addition is completed, close valve 2, heat to 50°C, and keep warm for reaction for 35 minutes. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 3.8 kg of methanol to the reaction vessel through the feed pump 1, control the internal temperature of the reaction between 45 and 55 ° C, add the material, and after the addition of methanol is completed, slowly heat up to 75 ° C, and keep the reaction for 3 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.3%, the methyl bromide yield is 97.5%, and the purity is 99.1%.
[0072] Example 5
[0073] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 36%, the pH is 3, and the COD (chemical oxygen demand) is 1000 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 2.5% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 15°C, open valve 2, and add 12.4 kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel ≤40°C to add materials. After the addition is completed, close valve 2, heat to 53°C, and keep warm for reaction for 50 minutes. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 5.2 kg of methanol to the reaction vessel through the feed pump 1, control the internal temperature of the reaction between 45 and 55 ° C, add the material, and after the addition of methanol is completed, slowly heat up to 77 ° C, and keep the reaction for 4 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.9%, the methyl bromide yield is 98.1%, and the purity is 99.5%.
[0074] Example 6
[0075] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 32%, the pH is 9, and the COD (chemical oxygen demand) is 1600 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 2% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 12°C, open valve 2, and add 14.1kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel ≤40°C to add materials. After the addition is completed, close valve 2, heat to 50°C, and keep warm for 45 minutes. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 4.1kg of methanol to the reaction vessel through the feed pump 1, control the reaction temperature between 45 and 55°C, add the material, and after the methanol is added, slowly heat it to 78°C and keep the reaction for 3.5 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.3%, the methyl bromide yield is 97.6%, and the purity is 99.4%.
[0076] Example 7
[0077] Check all components and connecting valves of the reaction equipment to ensure that all components are working properly. The mass concentration of bromide ions in bromide salt wastewater is 37%, the pH is 7, and the COD (chemical oxygen demand) is 900 mg / L. Open valve 1 and valve 3, and add 20 kg of wastewater to the reaction vessel through feed pump 1. After the addition is completed, close valve 1 and valve 3. Open valves 4, 5, 7, 6, 8, 9, and start the primary condenser. Add 10L of 2.8% dilute alkaline solution to the neutralization container through valve 6, and close valve 6 after the addition is completed. Start stirring, wait until the temperature of the primary condenser reaches 6°C, open valve 2, and add 14.5kg of 98% concentrated sulfuric acid to the reaction vessel through feed pump 2. Control the temperature in the reaction vessel ≤40°C to add materials. After the addition is completed, close valve 2, heat to 54°C, and keep warm for 55 minutes. 30 minutes before the end of the insulation, start the refrigeration components of the secondary condenser, the tertiary condenser and the low-temperature liquid storage tank to make the condenser and the low-temperature liquid storage tank reach the cooling temperature. After the insulation is completed, open valve 1, slowly add 5.6 kg of methanol to the reaction vessel through the feed pump 1, control the internal temperature of the reaction between 45 and 55 ° C, add the material, and after the addition of methanol is completed, slowly heat up to 70 ° C, and keep the reaction for 4 hours. After the reaction is completed, close valve 8, and use the compression equipment to transfer the methyl bromide liquid to the gas storage bottle through valve 10. Close valve 4, open valve 3, and release the reaction liquid in the reaction vessel through valve 11 for neutralization, salt precipitation and other treatments. The bromide ion conversion rate is 98.9%, the methyl bromide yield is 98.0%, and the purity is 99.6%.
[0078] Comparative Examples 1-3
[0079] The only difference between Comparative Examples 1-3 and Example 1 is that the amount of methanol added is different, resulting in different molar ratios of methanol to bromide ions, as shown in Table 1.
[0080] Table 1. Raw material ratios and yields of Examples 1-7 and Comparative Examples 1-3
[0081] name Molar ratio of methanol to bromide ion Methyl bromide purity Methyl bromide yield Examples 1-7 1.5～2.0:1 ≥99％ ＞97％ Comparative Example 1 1.0:1 98.6％ 78.2％ Comparative Example 2 1.2:1 99.1％ 88.7％ Comparative Example 3 2.2:1 98.8％ 97.3％
[0082] As can be seen from the data in Table 1, when the molar ratio of methanol to bromide ion is less than 1.5:1, the yield of methyl bromide is low, which is mainly due to incomplete reaction. When the molar ratio of methanol to bromide ion is greater than 2.0:1, the purity of methyl bromide is reduced, mainly due to the increase of impurities caused by side reactions. Therefore, the molar ratio of methanol to bromide ion in the present invention is 1.5 to 2.0:1.
[0083] Comparative Examples 4-5
[0084] The difference between Comparative Examples 4-5 and Example 1 is that the order of adding methanol and concentrated sulfuric acid is different. In the comparative examples, methanol or part of methanol is added first, and then concentrated sulfuric acid is added. See Table 2 for details.
[0085] Table 2. Addition sequence and yield of Example 1 and Comparative Examples 4-5
[0086]
[0087] It can be seen from the data in Table 2 that adding methanol first and then concentrated sulfuric acid will result in lower purity and yield of methyl bromide, mainly because concentrated sulfuric acid has oxidizing and dehydrating properties, and methanol undergoes side reactions such as oxidation and etherification. The present invention adopts the method of first adding concentrated sulfuric acid, allowing the concentrated sulfuric acid to undergo double decomposition reaction with bromine salt to lose oxidizing and dehydrating properties, and then adding methanol for substitution reaction to prepare methyl bromide.
[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A device for preparing methyl bromide using bromide wastewater, comprising a reaction vessel, characterized in that: The reaction container is provided with a gas phase outlet, which is connected to the gas phase inlet of the neutralization container through a primary condenser, and the gas phase outlet of the neutralization container is connected to the material inlet of the secondary condenser through a primary drying tower, and the material outlet of the secondary condenser is connected to a low-temperature liquid storage tank, and the gas phase outlet of the low-temperature liquid storage tank is connected to an emptying port through a third-stage condenser and a secondary drying tower in sequence, and the low-temperature liquid storage tank is provided with a methyl bromide liquid outlet, the reaction container is also provided with at least one material inlet, and the neutralization container is also provided with an alkali solution inlet.
2. The device for preparing methyl bromide using bromide wastewater according to claim 1, characterized in that: A reaction liquid outlet is arranged at the bottom of the reaction container, and a stirrer is arranged in the reaction container.
3. The device for preparing methyl bromide using bromide wastewater according to claim 1, characterized in that: The cryogenic liquid storage tank is provided with a refrigeration assembly.
4. A method for preparing methyl bromide using bromide wastewater, characterized in that: The following steps are involved: (1) adding bromine salt wastewater into a reaction vessel through a material inlet, and starting a primary condenser, adding a dilute alkali solution into a neutralization container through an alkali solution inlet, and under stirring of a stirrer, adding concentrated sulfuric acid into the reaction vessel through a material inlet, adjusting the reaction temperature, and performing a heat preservation reaction; (2) Start the refrigeration components of the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank to make the secondary condenser, the tertiary condenser and the cryogenic liquid storage tank reach the cooling temperature, slowly add methanol to the reaction container, and gradually increase the temperature to ensure that the raw materials are reacted completely. The gas generated in the reaction container passes through the primary condenser, the neutralization container, the primary drying tower in sequence, and then passes through the secondary condenser to form methyl bromide liquid and enters the cryogenic liquid storage tank.
5. The method for preparing methyl bromide using bromide salt wastewater according to claim 4, characterized in that: The bromide wastewater contains at least one of sodium bromide, potassium bromide, magnesium bromide and zinc bromide; the mass concentration of bromide ions in the bromide wastewater is 28% to 39%, the total mass concentration of other halogen ions is less than 0.01%, the pH of the bromide wastewater is 1 to 12, and the chemical oxygen demand COD is less than 2000 mg / L.
6. The method for preparing methyl bromide using bromide salt wastewater according to claim 4, characterized in that: The mass concentration of the concentrated sulfuric acid is 95% to 98%, the molar ratio of H2SO4 to bromide ions is 1.3 to 2.0:1, and the molar ratio of methanol to bromide ions is 1.5 to 2.0:
1.
7. The method for preparing methyl bromide using bromide salt wastewater according to claim 4, characterized in that: The cooling temperature of the first-stage condenser is 5 to 15°C, the cooling temperature of the second-stage condenser is -25 to -35°C, the cooling temperature of the third-stage condenser is -20 to -30°C, and the cooling temperature of the low-temperature liquid storage tank is -20 to -25°C.
8. The method for preparing methyl bromide using bromide salt wastewater according to claim 4, characterized in that: When the concentrated sulfuric acid is added in step (1), the internal temperature of the reaction container is ≤40°C. After the concentrated sulfuric acid is added, the temperature is raised to 45-55°C and kept warm for reaction for 0.5-1 hour.
9. The method for preparing methyl bromide using bromide wastewater according to claim 4, characterized in that: When the methanol is added in step (2), the internal temperature of the reaction container is 45-55°C. After the methanol is added, the temperature is slowly raised to 70-80°C and kept warm for reaction for 3-4 hours.
10. The method for preparing methyl bromide by utilizing bromide salt wastewater according to any one of claims 4 to 9, characterized in that: The dilute alkali solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass concentration of 1% to 3%.