A safe absorption method for improving the absorption efficiency of monomethylamine

Abstract

The present invention provides a safe absorption method for improving the absorption efficiency of monomethylamine, comprising the following steps: step 1: transporting the mixed gas containing monomethylamine into an absorption device through a pipeline; step 2: transporting the mixture condensed and absorbed into a liquid in the absorption device into a receiving device. The method of the present invention can absorb monomethylamine very effectively.

Description

Technical Field

[0001] The invention relates to a chemical process, in particular to a safe absorption method for improving the absorption efficiency of monomethylamine. Background Art

[0002] In the production process of acetamiprid, the use of monomethylamine is a key step in the synthesis of the intermediate N-(6-chloro-3-pyridylmethyl)methylamine. Monomethylamine reacts with 2-chloro-5-chloromethylpyridine under the action of a catalyst to generate the desired intermediate. First, prepare 2-chloro-5-chloromethylpyridine and monomethylamine as the main raw materials for the reaction. Add an appropriate catalyst to the reaction system to promote the reaction. The type and amount of the catalyst will affect the reaction rate and the purity of the product. Under the action of the catalyst, 2-chloro-5-chloromethylpyridine and monomethylamine undergo a substitution reaction to generate N-(6-chloro-3-pyridylmethyl)methylamine. After the reaction is completed, the product is purified and separated by steps such as alkali washing and desolventizing. Alkali washing can remove the acidic by-products produced in the reaction, while desolventizing can separate the product from the solvent.

[0003] In the entire production process of acetamiprid, the use of monomethylamine is indispensable.

[0004] Monomethylamine is a colorless gas with a pungent odor, which is widely used in the chemical, pharmaceutical and other industries. The safe absorption method to improve the absorption efficiency of monomethylamine is mainly aimed at the effective recovery and reuse of the tail gas of monomethylamine generated in the industrial process to reduce environmental pollution and waste of resources. In industrial production, if the tail gas emission of monomethylamine is not treated, it will pollute the environment. Traditional absorption methods often have problems such as low efficiency, high energy consumption, and complex equipment. Therefore, a new technical solution is needed that can both improve the absorption efficiency and ensure operational safety.

[0005] The prior art includes: using a device including a separation tower mechanism to improve the recovery efficiency of monomethylamine; connecting a new methylamine spray device in series in the tail gas absorption system, and a wastewater quality detection device to detect the concentration of amine water and the pH value, so as to achieve effective recovery and reuse of monomethylamine tail gas; using a two-stage single-tower absorption process, first absorbing the tail gas with methanol in the lower section of the absorption tower, and then absorbing the tail gas with water in the upper section of the absorption tower, so as to ensure that the ammonia and amines in the tail gas are fully absorbed while reducing the methanol consumption and the energy consumption of repeated distillation.

[0006] Chinese patent document CN212701226U discloses a separation device for effectively improving the recovery efficiency of monomethylamine gas, comprising a separation tower mechanism, a primary water absorption tower and a secondary water absorption tower connected in sequence; the separation tower mechanism comprises a separation tower and an injection system, a capillary pipe is provided above the separation tower, the capillary pipe is connected to at least one circulating water condensation pipe, and the bottom of the separation tower is connected to at least one circulating water condensation pipe, and the injection system comprises a jet vacuum pump, which is connected to the upper part of the separation tower. The separation tower mechanism of the utility model realizes the negative pressure operation of the methylamine separation tower through the injection system, and effectively ensures the positive pressure operation of the two-stage water absorption tower, thereby realizing 100% absorption and utilization of monomethylamine and effectively reducing the steam energy consumption of the separation tower.

[0007] Chinese patent document CN115722034A discloses a method for recovering and reusing monomethylamine tail gas. Step one: adding a methylamine spray device in series with an existing tail gas absorption system. Step two: adding a wastewater quality detection device to detect the concentration and pH value of amine water and then discharging the wastewater through the bottom of the methylamine spray device into an amine water recovery and reuse device.

[0008] In the prior art, the original monomethylamine tail gas spray discharge process adopts a spray tower to circulate the production water in the tower through a spray circulation pump to spray and absorb the amine gas in the monomethylamine tail gas from the top and the middle of the tower. When the pH value of the aqueous solution in the tower is ≥9, it is discharged to the production system wastewater storage tank through the drain valve at the bottom of the tower, and then discharged to the sewage treatment system for treatment. However, this type of wastewater contains a large amount of monomethylamine gas. When the sewage station disposes of this type of wastewater, the ammonia nitrogen and total nitrogen indicators of the discharged wastewater often exceed the standard, which also leads to an increase in the amount of sewage treatment chemicals, that is, an increase in material consumption.

[0009] The existing technology has the problems of low absorption efficiency, potential safety hazards in long-term operation, and the generation of a certain amount of waste, which has an impact on the environment. Summary of the invention

[0010] In view of the deficiencies of the prior art, the present invention provides a safe absorption method for improving the absorption efficiency of monomethylamine, comprising the following steps:

[0011] Step 1: transporting the mixed gas containing monomethylamine into the absorption device through a pipeline;

[0012] Step 2: The mixture condensed and absorbed into liquid in the absorption device is sent to the receiving device.

[0013] Furthermore, the operating temperature of the absorption device in step 1 is -8°C to -15°C.

[0014] Furthermore, in step 1, an alkaline adsorption material is used.

[0015] Furthermore, the alkaline adsorption material in step 1 is an adsorption net coated with chitosan / polyaniline nanocomposite material alkalized by ammonia.

[0016] Furthermore, the preparation method of ammonia-alkalized chitosan / polyaniline nanocomposite material is as follows: dispersing aniline monomer in nitrogen-methylpyrrolidone, and adding an oxidant to start the polymerization reaction to obtain the desired polyaniline nanostructure; dispersing the prepared polyaniline nanostructure in a chitosan solution; and exposing the uniformly mixed composite material to an ammonia environment for alkalization treatment.

[0017] Furthermore, the method for preparing the adsorption net coated with the chitosan / polyaniline nanocomposite material alkalized by ammonia in step 1 is: immersing the filter net in the nanocomposite material solution, and adsorbing the composite material on the surface of the filter net by immersing and oscillating.

[0018] Furthermore, the operating temperature of the receiving device in step 2 is -25°C to -35°C.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1. By using chitosan / polyaniline nanocomposite materials alkalized by ammonia, the adsorption net can quickly and effectively adsorb monomethylamine molecules in the mixed gas. This composite material not only has excellent adsorption performance, but also can work stably under low temperature conditions of -8°C to -15°C, providing ideal conditions for the adsorption of monomethylamine. 2. By coating the composite material on the filter net, the contact area with the mixed gas is increased, thereby improving the adsorption efficiency. This design ensures that efficient adsorption can be achieved even in a high concentration of monomethylamine environment. 3. The receiving device can effectively facilitate subsequent separation and recovery operations by maintaining a low temperature condition of -25°C to -35°C. This treatment method not only improves the recycling rate of resources, but also helps to reduce treatment costs. DETAILED DESCRIPTION

[0021] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention are further described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0022] The core of the safe absorption method for improving the absorption efficiency of monomethylamine of the present invention is to use a new adsorbent. The adsorbent is a chitosan / polyaniline nanocomposite material alkalized with ammonia. Due to the chemical structure of the monomethylamine molecule, the adsorbent used in the present invention improves the combination efficiency of monomethylamine and the nanocomposite material through experiments.

[0023] The preparation of ammonia alkalized chitosan / polyaniline (CS / PANI) nanocomposites first requires material preparation. Chitosan (CS), aniline monomer, oxidant: used for the polymerization reaction of aniline, such as ammonium persulfate, etc. Ammonia: used in the subsequent alkalization process.

[0024] First, polyaniline (PANI) is prepared. Aniline monomer is dispersed in nitrogen methyl pyrrolidone (NMP), and an oxidant is added to start the polymerization reaction. The reaction conditions are controlled to obtain the desired polyaniline nanostructure. The molar ratio of aniline to ammonium persulfate is 0.8, and the reaction time is 24 hours, and polyaniline nanofibers with good morphology can be obtained.

[0025] Preparation of chitosan / polyaniline (CS / PANI) nanocomposites: The prepared polyaniline nanostructures were dispersed in the chitosan solution and uniformly mixed by stirring and ultrasonication.

[0026] Ammonia alkalization process. The mixed CS / PANI nanocomposite is exposed to an ammonia environment for alkalization. For the ammonia alkalization process, special attention should be paid to safety issues, ensuring that the operation is carried out in a well-ventilated environment and wearing appropriate protective equipment.

[0027] Post-treatment: The alkalized CS / PANI nanocomposite material is subjected to necessary post-treatment, such as washing, drying, etc.

[0028] The chitosan / polyaniline nanocomposite material treated with ammonia gas is modified by a process of treating with ammonia gas, and a novel nanomaterial with excellent physical and chemical properties is prepared by this method.

[0029] Subsequently, the chitosan / polyaniline (CS / PANI) nanocomposite material alkalized by ammonia was loaded onto the filter.

[0030] The filter screen is made of polyethylene or polypropylene and has good strength.

[0031] Pretreatment of the filter. Use deionized water or an appropriate cleaning agent to thoroughly clean the filter to remove dust and impurities on the surface. Place the cleaned filter in a drying oven and dry it at an appropriate temperature (such as 50°C) to constant weight.

[0032] Pretreatment: Plasma treatment was used to increase its affinity with CS / PANI nanocomposites.

[0033] Loading process: Immerse the filter in the CS / PANI nanocomposite solution, and adsorb the composite material on the surface of the filter by soaking and shaking. Take out the adsorbed filter, wash it with deionized water to remove excess solution and impurities, and then dry it.

[0034] In the present invention,

[0035] A safe absorption method for improving the absorption efficiency of monomethylamine comprises the following steps:

[0036] Step 1: transporting the mixed gas containing monomethylamine into the absorption device through a pipeline; the working temperature of the absorption device is -8°C to -15°C; using an alkaline adsorption material, the alkaline adsorption material is an adsorption net coated with a chitosan / polyaniline nanocomposite material alkalized by ammonia; the preparation method of the chitosan / polyaniline nanocomposite material alkalized by ammonia is: dispersing aniline monomer in nitrogen methyl pyrrolidone, and adding an oxidant to start the polymerization reaction to obtain the desired polyaniline nanostructure; dispersing the prepared polyaniline nanostructure in the chitosan solution; exposing the mixed composite material to an ammonia environment for alkalization treatment; the preparation method of the adsorption net coated with the chitosan / polyaniline nanocomposite material alkalized by ammonia is: immersing the filter net in the nanocomposite material solution, and adsorbing the composite material on the surface of the filter net by soaking and shaking.

[0037] Step 2: The mixture condensed and absorbed into liquid in the absorption device is sent to the receiving device, and the operating temperature of the receiving device is -25℃~-35℃.

[0038] The specific details of the present invention are described in detail below.

[0039] 1. Preparation and operation of absorption device

[0040] Step 1: Introduction of mixed gas.

[0041] First, the mixed gas containing monomethylamine needs to be transported to the absorption device through a pipeline system. The pipeline system must not only ensure the smoothness of the gas, but also have safety measures to prevent leakage and explosion. During the transportation process, the gas flow, temperature and pressure need to be monitored in real time to ensure the safety and stability of the entire treatment process.

[0042] Next, the mixed gas enters the absorption device. The operating temperature of the device is set between -8℃ and -15℃. Within this temperature range, the vapor pressure of monomethylamine is low, which is conducive to its adsorption on the adsorption material, while avoiding freezing or clogging of the adsorption material due to too low a temperature. In the traditional process, the absorption of monomethylamine requires about minus 30 degrees, and monomethylamine cannot be absorbed very well.

[0043] Step 2: Selection and preparation of alkaline adsorption materials

[0044] In the absorption device, an adsorption net coated with ammonia-alkalized chitosan / polyaniline nanocomposite material is used as the main adsorption material. This material combines the advantages of chitosan and polyaniline, and not only has good adsorption performance, but also has good stability and regeneration ability.

[0045] The process of preparing ammonia-alkalized chitosan / polyaniline nanocomposites is as follows: first, aniline monomers are dispersed in nitrogen-methylpyrrolidone, and a suitable amount of oxidant is added to initiate the polymerization reaction to obtain the desired polyaniline nanostructure. Then, the prepared polyaniline nanostructure is dispersed in the chitosan solution and mixed uniformly by stirring and ultrasound. Next, the uniformly mixed composite material is exposed to an ammonia environment for alkalization treatment to improve its adsorption performance.

[0046] After obtaining the chitosan / polyaniline nanocomposite material alkalized by ammonia, it needs to be coated on an adsorption net. The specific method is: immersing the filter net in the nanocomposite material solution, and adsorbing the composite material uniformly on the surface of the filter net by immersing and oscillating.

[0047] Finally, the coated adsorption net is fixed in the absorption device, ready for absorbing the mixed gas.

[0048] Step 3: Absorption of mixed gas

[0049] When the mixed gas enters the absorption device, the monomethylamine in it will be adsorbed on the chitosan / polyaniline nanocomposite material alkalized by ammonia. This material has a high affinity for monomethylamine and can quickly separate it from the mixed gas. At the same time, due to the presence of the adsorption net, the contact area between the adsorption material and the mixed gas is increased, thereby improving the adsorption efficiency.

[0050] 2. Processing of the receiving device.

[0051] Step 1: Condensate the absorbed mixture into a liquid.

[0052] After being treated by the absorption device, the monomethylamine in the mixed gas is adsorbed on the chitosan / polyaniline nanocomposite material alkalized by ammonia, forming a liquid mixture containing monomethylamine. This mixture needs to be sent to the receiving device for further treatment.

[0053] The operating temperature of the receiving device is set between -25℃ and -35℃. Within this temperature range, the monomethylamine in the mixture will remain in a liquid state, which is convenient for subsequent separation and recovery. At the same time, the lower temperature can also reduce the volatilization and loss of the mixture.

[0054] Step 2: Separation and recovery of the mixture

[0055] In the receiving device, the mixture condensed into liquid needs to be separated and recovered, and the monomethylamine is separated from the mixture by physical and chemical methods. The separated monomethylamine can be regenerated or reused as a raw material, thereby realizing the recycling of resources.

[0056] Example 1

[0057] Equipment preparation:

[0058] Adsorbent material. Adsorbent net coated with chitosan / polyaniline nanocomposite material alkalized with ammonia. Pipeline system. Pipeline system for transporting gas mixture containing monomethylamine, with anti-leakage and explosion-proof functions. Absorbent device. Closed container with working temperature set at -8°C to -15°C, with built-in bracket coated with adsorbent net. Receiving device. Closed container with working temperature set at -25°C to -35°C, used to receive the condensed liquid mixture.

[0059] Method steps

[0060] Step 1: After the mixed gas enters the absorption device, it contacts the adsorption net coated with chitosan / polyaniline nanocomposite material alkalized with ammonia. Under low temperature conditions of -8°C to -15°C, monomethylamine is rapidly adsorbed on the composite material.

[0061] Step 2: The liquid mixture containing monomethylamine is discharged from the absorption device and sent to a receiving device for further treatment. In the receiving device, the low temperature condition is -25°C to -35°C. Subsequently, the monomethylamine is separated from the mixture through separation and recovery operations and reused as a raw material or regenerated.

[0062] The monomethylamine content of the mixed gas before and after treatment was tested. The results showed that after being treated by the absorption device, the monomethylamine content in the mixed gas was reduced from the initial high level to no more than 0.03%.

[0063] Comparative Example 1:

[0064] Equipment preparation:

[0065] Adsorption material: Uncoated adsorption net (chitosan / polyaniline nanocomposite material without ammonia alkalization). The pipeline system, absorption device, and receiving device are the same as those in the embodiment.

[0066] Method steps:

[0067] Step 1: After the mixed gas enters the absorption device, it contacts with the uncoated adsorption net. At low temperature conditions of -8℃ to -15℃, try to adsorb monomethylamine.

[0068] Step 2: The potentially adsorbed liquid mixture is discharged from the absorber and sent to a receiving device for further processing.

[0069] Results: After testing, the reduction of the content of monomethylamine in the mixed gas was not obvious, far lower than the effect in the embodiment, which indicates that the adsorption capacity of the uncoated adsorption net for monomethylamine is limited.

[0070] Comparative Example 2:

[0071] Equipment preparation: Adsorption material, same as in the embodiment, ammonia alkalized chitosan / polyaniline nanocomposite coated adsorption net. Pipeline system and receiving device are the same as in the embodiment. Absorption device, closed container with working temperature set to 0°C to 5°C (higher than the temperature range in the embodiment).

[0072] Method steps:

[0073] Step 1: After the mixed gas enters the absorption device, it contacts the adsorption net coated with the composite material. At a low temperature of 0°C to 5°C, try to adsorb monomethylamine.

[0074] Step 2: Same as in the example, the liquid mixture containing monomethylamine is sent to a receiving device for further treatment.

[0075] Results: After testing, the content of monomethylamine in the mixed gas was about 3%, indicating that the appropriate temperature was more conducive to the adsorption of monomethylamine.

[0076] Comparative Example 3:

[0077] Equipment preparation: Adsorption material, using activated carbon coated adsorption net. Pipeline system, absorption device, receiving device are the same as the embodiment.

[0078] Method steps:

[0079] Step 1: After the mixed gas enters the absorption device, it contacts the adsorption net coated with other materials. At low temperature conditions of -8℃ to -15℃, try to adsorb monomethylamine.

[0080] Step 2: Same as in the example, the liquid mixture containing monomethylamine is sent to a receiving device for further treatment.

[0081] Results: The content of monomethylamine in the mixed gas was about 7% after testing, indicating that the chitosan / polyaniline nanocomposite material alkalized by ammonia had a better adsorption effect on monomethylamine.

[0082] The gas containing monomethylamine was treated by water spraying. After the treatment, the proportion of monomethylamine in the gas was 2%. After the water spraying treatment, the content of monomethylamine in the gas was reduced to less than 2%, but it was still lower than the effect of Example 1. In addition, the present invention recovers monomethylamine through a receiving device to achieve resource recycling. The method of the present invention has obvious advantages over the water spraying method: significantly higher treatment efficiency, which can reduce the content of monomethylamine to an extremely low level. Monomethylamine is recovered, resource utilization is high, and environmental benefits are significant. The operation is stable, the safety is high, and the operation risk is reduced.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A safe absorption method for improving the absorption efficiency of monomethylamine, characterized in that The following steps are involved: Step 1: transporting the mixed gas containing monomethylamine through a pipeline into an absorption device, in which an adsorption net coated with ammonia-alkalized chitosan / polyaniline nanocomposite material is used as the main adsorption material. The process of ammonia-alkalized chitosan / polyaniline nanocomposite material is as follows: dispersing aniline monomer in nitrogen methyl pyrrolidone, and adding a proper amount of oxidant to start the polymerization reaction to obtain the desired polyaniline nanostructure; dispersing the prepared polyaniline nanostructure in the chitosan solution, and mixing it evenly by stirring and ultrasonication; exposing the evenly mixed composite material to an ammonia environment for alkalization treatment; after obtaining the ammonia-alkalized chitosan / polyaniline nanocomposite material, immersing the filter net in the nanocomposite material solution, and adsorbing the composite material evenly on the surface of the filter net by immersion and oscillation; The operating temperature of the absorption device in step 1 is -8°C to -15°C; Step 2: The mixture condensed and absorbed into a liquid in the absorption device is sent to a receiving device, and the operating temperature of the receiving device is set between -25°C and -35°C; in the receiving device, monomethylamine in the mixture condensed into a liquid is separated from the mixture.

2. The safe absorption method for improving the absorption efficiency of monomethylamine according to claim 1, characterized in that: In step 1, a basic adsorption material is used.

3. The safe absorption method for improving the absorption efficiency of monomethylamine according to claim 1, characterized in that: The operating temperature of the receiving device in step 2 is -25°C to -35°C.