CN114853651A - Method for synthesizing liquid sodium N-methyldithiocarbamate by microchannel reactor - Google Patents
Method for synthesizing liquid sodium N-methyldithiocarbamate by microchannel reactor Download PDFInfo
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- 239000007788 liquid Substances 0.000 title claims abstract description 46
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000002194 synthesizing effect Effects 0.000 title claims abstract description 16
- AFCCDDWKHLHPDF-UHFFFAOYSA-M metam-sodium Chemical compound [Na+].CNC([S-])=S AFCCDDWKHLHPDF-UHFFFAOYSA-M 0.000 title claims description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 123
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 claims abstract description 108
- BAVYZALUXZFZLV-UHFFFAOYSA-N Methylamine Chemical compound NC BAVYZALUXZFZLV-UHFFFAOYSA-N 0.000 claims abstract description 82
- 238000006243 chemical reaction Methods 0.000 claims abstract description 67
- QGJOPFRUJISHPQ-NJFSPNSNSA-N carbon disulfide-14c Chemical compound S=[14C]=S QGJOPFRUJISHPQ-NJFSPNSNSA-N 0.000 claims abstract description 17
- 239000002994 raw material Substances 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims description 20
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 12
- 230000035484 reaction time Effects 0.000 abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 238000007086 side reaction Methods 0.000 abstract description 6
- 238000003756 stirring Methods 0.000 abstract description 6
- 239000012071 phase Substances 0.000 abstract description 5
- BIHPYCDDPGNWQO-UHFFFAOYSA-N 5-iai Chemical compound C1=C(I)C=C2CC(N)CC2=C1 BIHPYCDDPGNWQO-UHFFFAOYSA-N 0.000 abstract description 4
- 239000012990 dithiocarbamate Substances 0.000 abstract description 3
- 238000005265 energy consumption Methods 0.000 abstract description 2
- 239000012074 organic phase Substances 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 89
- 239000000243 solution Substances 0.000 description 56
- 230000000052 comparative effect Effects 0.000 description 24
- 239000012263 liquid product Substances 0.000 description 24
- 239000013078 crystal Substances 0.000 description 21
- HYVVJDQGXFXBRZ-UHFFFAOYSA-N metam Chemical compound CNC(S)=S HYVVJDQGXFXBRZ-UHFFFAOYSA-N 0.000 description 20
- 238000003786 synthesis reaction Methods 0.000 description 17
- 230000015572 biosynthetic process Effects 0.000 description 12
- 238000001035 drying Methods 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 239000003513 alkali Substances 0.000 description 7
- DQRQIQZHRCRSDB-UHFFFAOYSA-M potassium;n-methylcarbamodithioate Chemical compound [K+].CNC([S-])=S DQRQIQZHRCRSDB-UHFFFAOYSA-M 0.000 description 7
- 239000002689 soil Substances 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 5
- 241000196324 Embryophyta Species 0.000 description 4
- 239000002169 Metam Substances 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 4
- 241000607479 Yersinia pestis Species 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
- 238000005070 sampling Methods 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000006283 soil fumigant Substances 0.000 description 3
- 239000001293 FEMA 3089 Substances 0.000 description 2
- 241000233866 Fungi Species 0.000 description 2
- 241000244206 Nematoda Species 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- GZUXJHMPEANEGY-UHFFFAOYSA-N bromomethane Chemical compound BrC GZUXJHMPEANEGY-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000003784 tall oil Substances 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- 235000001674 Agaricus brunnescens Nutrition 0.000 description 1
- 241000894006 Bacteria Species 0.000 description 1
- 241000722731 Carex Species 0.000 description 1
- 235000002722 Dioscorea batatas Nutrition 0.000 description 1
- 235000006536 Dioscorea esculenta Nutrition 0.000 description 1
- 240000001811 Dioscorea oppositifolia Species 0.000 description 1
- 235000003416 Dioscorea oppositifolia Nutrition 0.000 description 1
- 241000238631 Hexapoda Species 0.000 description 1
- LGDSHSYDSCRFAB-UHFFFAOYSA-N Methyl isothiocyanate Chemical compound CN=C=S LGDSHSYDSCRFAB-UHFFFAOYSA-N 0.000 description 1
- -1 N-methyl dithiocarbamic acid sodium formate Chemical compound 0.000 description 1
- 244000061176 Nicotiana tabacum Species 0.000 description 1
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 1
- 235000004876 Physalis pruinosa Nutrition 0.000 description 1
- 240000006285 Physalis pubescens Species 0.000 description 1
- 235000009230 Physalis pubescens Nutrition 0.000 description 1
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 1
- 235000011613 Pinus brutia Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 244000273928 Zingiber officinale Species 0.000 description 1
- 235000006886 Zingiber officinale Nutrition 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000003889 chemical engineering Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000003958 fumigation Methods 0.000 description 1
- 235000008397 ginger Nutrition 0.000 description 1
- 241000411851 herbal medicine Species 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 229940102396 methyl bromide Drugs 0.000 description 1
- 150000004702 methyl esters Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000009335 monocropping Methods 0.000 description 1
- 239000005645 nematicide Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
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- 230000002265 prevention Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000029058 respiratory gaseous exchange Effects 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C333/00—Derivatives of thiocarbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
- C07C333/14—Dithiocarbamic acids; Derivatives thereof
- C07C333/16—Salts of dithiocarbamic acids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0093—Microreactors, e.g. miniaturised or microfabricated reactors
Abstract
The invention provides a method for synthesizing liquid N-methyl sodium dithiocarbamate by a microchannel reactor, which adopts the raw materials of carbon disulfide, monomethylamine and sodium hydroxide, wherein the molar ratio of the carbon disulfide to the monomethylamine to the sodium hydroxide is 1: (1.006-1.012): (0.999-1.016). The invention uses a pipeline reactor to replace a kettle reactor of the traditional process to produce metham sodium, an organic phase (CS) 2 ) And the mass transfer and reaction processes of the two phases of the water phase (the monomethylamine solution and the sodium hydroxide solution) are finished in a micro-reactor channel, so that metham sodium is directly synthesized in one step, the production process is continuous, and the conventional stirring process is not needed, so that the reactor structure is simplified, and the power energy consumption is reduced. The reaction time is shortened from that of the traditional batch reaction kettle type reactor which needs several hours to that of the traditional batch reaction kettle type reactor which adopts a microchannel reactor for 20-30s, and the reaction efficiency is improved. The invention has less side reaction, high product purity and yield.
Description
Technical Field
The invention relates to a method for synthesizing sodium N-methyldithiocarbamate, in particular to a method for synthesizing liquid sodium N-methyldithiocarbamate by a microchannel reactor, belonging to the field of chemical synthesis.
Background
The N-methyl dithiocarbamic acid sodium formate is named as 'metam' in the pesticide and agricultural fields, is a thioisothiocyanic acid methyl ester nematicide with low toxicity, no pollution and wide application range and sterilization and weeding effects, is applied to soil before crop planting, gradually releases isothiocyanic acid methyl ester, has fumigation effect, can effectively kill pests such as nematodes, underground pests, fungi, weed seeds, weeds and the like in the soil by inhibiting biological cell division and synthesis of DNA, RNA and protein and causing biological respiration obstruction, thereby obtaining clean and healthy soil. The fumigating and fumigating prevention agent is suitable for the seedbed soil of economic crops such as greenhouses, plastic arched sheds, flowers, tobacco, Chinese herbal medicines, ginger, Chinese yam and the like, the soil for continuous cropping planting, culture substrates of tissue culture seedlings, bonsai soil, edible mushroom bed soil and the like, can prevent various plant diseases and insect pests caused by nematodes, fungi, bacteria, underground pests and the like, and can prevent weeds such as marshlands, physalis pubescens, sedges and the like. As a soil fumigant which replaces methyl bromide and is registered and used internationally, metham will occupy the main market of domestic soil fumigants in a future period of time; in addition, the fresh needle leaves are accumulated and stored, the tall oil and the turpentine oil of the needle leaves are rapidly lost, after the pine wood pieces are treated by the sodium N-methyl dithiocarbamate, the wood does not generate heat, and the tall oil and the turpentine oil are not lost, so that the needle leaves are highly regarded in the industry. Therefore, studies to improve the yield, reduce the cost, and improve the purity so as to be suitable for special use have become important issues of domestic and foreign research and attention.
The existing metham has the main research results: the synthesis method is introduced in the third phase 2001 of Hebeile published article "high-efficiency soil fumigant Weibaimu" in Sichuan chemical industry and corrosion control, but specific technological parameters, raw material conversion rate, finished product yield and other indexes are not provided; in the synthesis process proposed in Chinese patent publication No. CN102267931A (patent name: metham production process), a 40% monomethylamine solution and carbon disulfide are mixed and reacted at 10-30 ℃ for 2-3 hours to obtain N-methyldithiocarbamic acid, and then a 30% sodium hydroxide solution is added dropwise and reacted at 35-60 ℃ for 2 hours to obtain the product with the solid content of 97.5% and the yield of 98.6%. Chinese patent publication No. CN111848478A (patent name: method for synthesizing metham in one step) proposes a method for synthesizing metham in one step, which comprises mixing water, monomethylamine aqueous solution and sodium hydroxide aqueous solution under stirring, dripping carbon disulfide for 2 hours, and continuously stirring for 0.5 hour after dripping to obtain a liquid product with content of 36.3%, yield of 98.0% and yellow to reddish brown appearance. The main defects of the patent are as follows: 1. the yield is low (98.0%); 2. the appearance is poor (the appearance is yellow to red brown liquid), which indicates that side reaction occurs in the synthesis process to generate colored substances; 3. the reaction time is long (carbon disulfide is dripped for 2 hours, and the stirring is continued after the carbon disulfide is dripped for 0.5 hour after the reaction is finished).
In the synthesis process of potassium N-methyldithiocarbamate which has the same structure and similar function as sodium N-methyldithiocarbamate, Yi cham et al published in Shandong chemical engineering, 2017, New Process for producing potassium N-methyldithiocarbamate, the monomethylamine solution is reacted with carbon disulfide to obtain N-methyldithiocarbamate, then potassium hydroxide solution is dripped to obtain the aqueous solution of potassium N-methyldithiocarbamate; chinese patent publication No. CN102391165B (patent No.: production process of potassium N-methyldithiocarbamate) mixes carbon disulfide and monomethylamine to react to generate N-methyldithiocarbamate, and then reacts with potassium hydroxide to obtain potassium N-methyldithiocarbamate, thus obtaining potassium N-methyldithiocarbamate solution, wherein the mass percentage concentration of the potassium N-methyldithiocarbamate solution is 60%, and the yield is 98.9%.
Although the existing process is mature and widely applied to large-scale industrial production, the following problems still exist: (1) the reactors of the existing patents and the traditional synthesis process are all reaction kettles with stirring, batch production is mostly adopted, the reaction is carried out at normal pressure or near normal pressure, liquid-liquid heterogeneous mass transfer obstacles exist in a reaction system, and the reaction time is long; in the reaction process, because the traditional reaction kettle has small heat exchange area, low heat exchange capacity, difficult control of temperature, pressure, heat transfer and mass transfer and the like, poor stable temperature control effect and high temperature runaway risk, the quality stability of products in different batches cannot be ensured, and the quality index difference between different batches is large; (2) the production time is long, and the production efficiency is low; (3) the side reaction is more, the purity is low, and the yield is lower than 99 percent; (4) the appearance and quality of the product still need to be improved; (5) the product has short shelf life.
So far, no technical research on metam synthesis in a micro-channel continuous reaction mode is found.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for synthesizing liquid sodium N-methyldithiocarbamate by a microchannel reactor, which realizes the following purposes:
1. realizing continuous production of metham;
2. the reaction time is shortened;
3. the occurrence of side reactions is reduced, the purity and the yield of the product are improved, and the production cost is reduced;
4. the appearance and the internal quality of the product are improved, and the product benefit is improved;
5. the shelf life of the product is prolonged.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for synthesizing liquid N-methyl sodium dithiocarbamate by a microchannel reactor adopts the raw materials of carbon disulfide, monomethylamine and sodium hydroxide, and the molar ratio of the carbon disulfide to the monomethylamine to the sodium hydroxide is 1: (1.006-1.012): (0.999-1.016). Controlling the reaction temperature in the microchannel reactor to be 75-88 ℃; the residence time is 20-30 seconds, and the reaction pressure is not more than 2.0 MPa.
The reaction pressure is 1.8-1.95 MPa.
And simultaneously introducing carbon disulfide, monomethylamine solution and sodium hydroxide solution into an inlet of the microchannel reactor, wherein the temperature of the materials when the materials are introduced into the microchannel reactor is room temperature.
Introducing the carbon disulfide into the microchannel reactor at a speed of 40.8-41.2 ml/min; introducing the monomethylamine solution into a microchannel reactor at the speed of 56.5-56.8 ml/min; the sodium hydroxide solution is introduced into the microchannel reactor at a rate of 61-61.9 ml/min.
The mass concentration of the monomethylamine solution is 30-40%, and the mass concentration of the sodium hydroxide solution is 30-40%.
The mass concentration of the monomethylamine solution is 38-42%, and the mass concentration of the sodium hydroxide solution is 31-33%.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention uses a pipeline reactor to replace a kettle reactor of the traditional process to produce metham sodium, an organic phase (CS) 2 ) And the mass transfer and reaction processes of the two phases of the water phase (the monomethylamine solution and the sodium hydroxide solution) are finished in a micro-reactor channel, so that metham sodium is directly synthesized in one step, the production process is continuous, and the conventional stirring process is not needed, so that the reactor structure is simplified, and the power energy consumption is reduced.
2. The reaction time is shortened from that of the traditional batch reaction kettle type reactor which needs several hours to that of the traditional batch reaction kettle type reactor which adopts a microchannel reactor for 20-30s, and the reaction efficiency is improved.
3. The invention has less side reaction, high product purity and yield, the product purity is 99.11-99.26%, and the product yield is 99.71-99.89%.
4. The preparation method has the advantages of simple synthesis process, convenient operation, mild reaction conditions, easy control in the production process, low production cost, no discharge of three wastes and obvious improvement of production environment.
5. The product prepared by the preparation method is light yellow transparent liquid with the appearance of 42.2-42.5 percent, the density of 1.201-1.211g/ml (20 ℃), the pH value (25 ℃) of 10.5-11.1 and the free alkali (calculated by NaOH) of 0.21-0.25 percent.
6. The liquid product prepared by the invention is analyzed after being stored for one year in a dark and ventilated environment at the temperature of not higher than 25 ℃, the appearance is light yellow transparent liquid, and the content is 42-42.2%.
Detailed Description
In order that the present disclosure may be more readily understood, the process of the present disclosure will now be described in further detail with reference to specific embodiments thereof. It should not be understood that the scope of the above-described subject matter of the present invention is limited to the following examples. The present invention uses a microchannel reactor manufactured by corning corporation.
In the present document,% represents% by weight (percent by mass) unless otherwise specified.
Example 1
1. Stock preparation
Pressing carbon disulfide into a carbon disulfide metering tank from a storage tank by using nitrogen (the height of water used as a liquid seal in the metering tank is required to be ensured to be not less than 15 mm), and setting a low liquid level alarm for the metering tank;
injecting a methylamine solution with the concentration of 40% into a high-level tank, and setting a low liquid level alarm for the metering tank;
sodium hydroxide solution with the concentration of 32% is injected into a high-level tank, and a low liquid level alarm is arranged on the metering tank.
2. Synthesis of
Setting the reaction temperature at 76 ℃, setting the material to stay in the reaction channel for 30 seconds, setting the reaction pressure at 1.8MPa, and setting a high-pressure alarm and DCS interlocking control system.
The flow data of the carbon disulfide, the 40% monomethylamine solution and the 32% sodium hydroxide solution are checked and set from a microcomputer, and the process data such as reaction temperature, reaction pressure and the like are checked and confirmed for the second time;
after checking and confirming that the volume flow of reaction raw materials is set by DCS, carbon disulfide, 40% monomethylamine solution and 32% sodium hydroxide solution are simultaneously pumped into the inlet of the microchannel reactor from respective metering tanks by using a metering pump according to the flow of 41ml/min, 56.5ml/min and 61.5ml/min, the temperature when the carbon disulfide is injected into the microchannel reactor is room temperature, and the reaction temperature is accurately controlled by DCS to carry out synthesis reaction. And observing the appearance of the generated metham, sampling and analyzing the obtained finished product in time, and obtaining the analysis result shown in table 1.
TABLE 1 analysis results of the products
And when the operation is carried out to obtain 2 tons of products, the yield of the products is 99.71 percent by taking carbon disulfide as a reference.
Storing the liquid product prepared in the example 1 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 99.26%;
the liquid product prepared in example 1 was analyzed after being stored for one year at a temperature of not higher than 25 ℃ in a dark and ventilated environment, and was a light yellow transparent liquid in appearance, and the content was 42.1%.
Example 2
1. Stock preparation
Pressing carbon disulfide into a carbon disulfide metering tank from a storage tank by using nitrogen (the height of water used as a liquid seal in the metering tank is required to be ensured to be not less than 15 mm), and setting a low liquid level alarm for the metering tank;
injecting a methylamine solution with the concentration of 40% into a high-level tank, and setting a low liquid level alarm for the metering tank;
sodium hydroxide solution with the concentration of 32% is injected into a high-level tank, and a low liquid level alarm is arranged on the metering tank.
2. Synthesis of
Setting the reaction temperature to 82 ℃, setting the material to stay in the reaction channel for 25 seconds, setting the reaction pressure to 1.8MPa and setting a high-pressure alarm and DCS interlocking control system.
Checking the flow data of the carbon disulfide, the 40% monomethylamine solution and the 32% sodium hydroxide solution from a microcomputer, checking for the second time, and confirming the process data such as reaction temperature, reaction pressure and the like;
after checking and confirming that the volume flow of reaction raw materials is set by DCS, carbon disulfide, 40% monomethylamine solution and 32% sodium hydroxide solution are simultaneously pumped into the inlet of the microchannel reactor from respective metering tanks by using a metering pump according to the flow of 41ml/min, 56.6ml/min and 61ml/min, the temperature when the carbon disulfide is injected into the microchannel reactor is room temperature, and the reaction temperature is accurately controlled by DCS to carry out synthesis reaction. And observing the appearance of the generated metham, sampling and analyzing the obtained finished product in time, and showing the analysis result in table 2.
TABLE 2 analysis results of the products
And when the operation is carried out to obtain 2 tons of products, the yield of the products is 99.83 percent by taking carbon disulfide as a reference.
Storing the liquid product prepared in the example 2 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 99.11%;
the liquid product prepared in example 2 is analyzed after being stored for one year in a dark and ventilated environment at a temperature of not higher than 25 ℃, and the appearance of the liquid product is light yellow transparent liquid, and the content of the liquid product is 42.2 percent.
Example 3
1. Stock preparation
Pressing carbon disulfide into a carbon disulfide metering tank from a storage tank by using nitrogen (the height of water used as a liquid seal in the metering tank is required to be ensured to be not less than 15 mm), and setting a low liquid level alarm for the metering tank;
injecting a methylamine solution with the concentration of 40% into a high-level tank, and setting a low liquid level alarm for the metering tank;
sodium hydroxide solution with the concentration of 32% is injected into a high-level tank, and a low liquid level alarm is arranged on the metering tank.
2. Synthesis of
Setting the reaction temperature to 85 ℃, setting the material to stay in the reaction channel for 25 seconds, setting the reaction pressure to 1.95MPa and setting a high-pressure alarm and DCS interlocking control system.
Checking the flow data of the carbon disulfide, the 40% monomethylamine solution and the 32% sodium hydroxide solution from a microcomputer, checking for the second time, and confirming the process data such as reaction temperature, reaction pressure and the like;
after checking and confirming that the volume flow of the reaction raw materials is set by DCS, using a metering pump to simultaneously drive carbon disulfide, 40% monomethylamine solution and 32% sodium hydroxide solution into the inlet of the microchannel reactor from respective metering tanks according to the flow of 41ml/min, 56.8ml/min and 61.9ml/min, wherein the temperature when the carbon disulfide, the monomethylamine solution and the 32% sodium hydroxide solution are injected into the microchannel reactor is room temperature, and the reaction temperature is accurately controlled by DCS to carry out synthesis reaction. And observing the appearance of the generated metham, sampling and analyzing the obtained finished product in time, and showing the analysis result in table 3.
TABLE 3 analysis results of the products
And when the operation is carried out to obtain 2 tons of products, the yield of the products is 99.86 percent by taking carbon disulfide as a reference.
Storing the liquid product prepared in the example 3 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 99.17%;
the liquid product prepared in example 3 was analyzed after being stored for one year at a temperature of not higher than 25 ℃ in a dark and ventilated environment, and the appearance was a pale yellow transparent liquid with a content of 42.0%.
Example 4
1. Stock preparation
Pressing carbon disulfide into a carbon disulfide metering tank from a storage tank by using nitrogen (the height of water used as a liquid seal in the metering tank is required to be ensured to be not less than 15 mm), and setting a low liquid level alarm for the metering tank;
injecting a methylamine solution with the concentration of 40% into a high-level tank, and setting a low liquid level alarm for the metering tank;
sodium hydroxide solution with the concentration of 32% is injected into a high-level tank, and a low liquid level alarm is arranged on the metering tank.
2. Synthesis of
Setting the reaction temperature to 88 ℃, setting the material to stay in the reaction channel for 20 seconds, setting the reaction pressure to 1.9MPa and setting a high-pressure alarm and DCS interlocking control system.
Checking the flow data of the carbon disulfide, the 40% monomethylamine solution and the 32% sodium hydroxide solution from a microcomputer, checking for the second time, and confirming the process data such as reaction temperature, reaction pressure and the like;
after checking and confirming that the volume flow of the reaction raw materials is set by DCS, using a metering pump to simultaneously drive carbon disulfide, 40% monomethylamine solution and 32% sodium hydroxide solution into the inlet of the microchannel reactor from respective metering tanks according to the flow of 41ml/min, 56.8ml/min and 61.5ml/min, wherein the temperature when the carbon disulfide, the monomethylamine solution and the 32% sodium hydroxide solution are injected into the microchannel reactor is room temperature, and the reaction temperature is accurately controlled by DCS to carry out synthesis reaction. And observing the appearance of the generated metham, sampling and analyzing the obtained finished product in time, and showing the analysis result in table 4.
TABLE 4 analysis results of the products
And when the operation is carried out to obtain 2 tons of products, the product yield is 99.89 percent by taking carbon disulfide as a reference.
Storing the liquid product prepared in the example 4 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 99.13%;
example 4 the liquid product, analyzed after one year storage at not more than 25 ℃ in the dark, ventilated environment, was a pale yellow transparent liquid with a content of 42.2%.
Comparative example 1
The same procedure and material ratios as in example 2 were used, except that the reaction temperature was varied. The reaction temperature of this comparative example was 74 ℃. The quality of the product prepared is shown in table 5.
TABLE 5 analysis results of the products
The product yield is 95.36% calculated by taking carbon disulfide as a reference when 200Kg of product is obtained by operation.
Storing the liquid product prepared in the comparative example 1 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 97.22%;
the liquid product prepared in the comparative example 1 is analyzed after being stored for one year in a dark and ventilated environment at the temperature of not higher than 25 ℃, and the appearance is faint yellow opaque liquid, and the content is 38.2 percent;
the product analysis result shows that the product is unqualified, and the product appearance, density, pH value and free alkali are unqualified due to low reaction temperature.
Comparative example 2
The same procedure and material ratios as in example 2 were used, except that the reaction temperature was varied. The reaction temperature of this comparative example was 90 ℃. The quality of the product prepared is shown in table 6.
TABLE 6 analysis results of the products
The product yield is 94.92% calculated by taking carbon disulfide as a reference when 200Kg of product is obtained by operation.
Storing the liquid product prepared in the comparative example 2 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 96.51%;
the liquid product prepared in the comparative example 2 is analyzed after being stored for one year in a dark and ventilated environment at the temperature of not higher than 25 ℃, and the appearance is faint yellow opaque liquid, and the content is 38.2 percent;
the product analysis result shows that the product appearance is brown yellow liquid instead of light yellow liquid, which indicates that the reaction temperature is higher, and the four indexes of the product appearance, the density, the pH value and the free alkali are unqualified.
Comparative example 3
The same procedure and material ratios as in example 2 were used, except for the reaction times. The reaction time of this comparative example was 18 seconds. The quality of the products prepared is shown in Table 7.
TABLE 7 analysis results of products
The product yield is 96.38 percent by taking the carbon disulfide as the reference when 200Kg of the product is obtained by operation.
Storing the liquid product prepared in the comparative example 3 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 96.91%;
the liquid product prepared in the comparative example 3 is analyzed after being stored for one year in a dark and ventilated environment at the temperature of not higher than 25 ℃, and the appearance is faint yellow opaque liquid with the content of 39.1 percent;
according to the product analysis result, when the reaction time is 18 seconds, the product appearance, the density, the pH value and the free alkali are unqualified, and the product is an unqualified product.
Comparative example 4
The same procedure and material ratios as in example 2 were used, except for the reaction times. The reaction time of this comparative example was 35 seconds. The quality of the products prepared is shown in Table 8.
TABLE 8 analysis results of products
The product yield is 96.01% calculated by taking carbon disulfide as a reference when 200Kg of product is obtained by operation.
Storing the liquid product prepared in the comparative example 4 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 95.83%;
the liquid product prepared in comparative example 4 was analyzed after being stored for one year at a temperature of not higher than 25 ℃ in the dark and ventilated environment, and was a deep yellow turbid liquid with a content of 40.1%.
As can be seen from the product analysis results, the product appearance is poor, and although the content, the pH value and the free alkali are qualified, the product is judged to be unqualified according to the quality standard. The product prepared with the reaction time of 35 seconds has qualified content, pH value and free alkali, but has poor appearance, and is an unqualified product.
Comparative example 5
The same procedure as in example 2 was used, with the same operating parameters, except that the material ratios, i.e. the flow rates of the three raw materials, were changed. In this comparative example, carbon disulfide, 40% monomethylamine solution and 32% sodium hydroxide solution were simultaneously fed from respective metering tanks into the inlet of the microchannel reactor at flow rates of 41ml/min, 61.1ml/min and 61 ml/min. The quality of the product prepared is shown in table 9.
TABLE 9 analysis results of products
The product yield is 96.59 percent by taking the carbon disulfide as the reference when 200Kg of the product is obtained by operation.
Storing the liquid product prepared in the comparative example 5 at 5 ℃ for 2 hours to obtain crystals (with crystal materials attached to the surfaces), drying for 20 minutes under negative pressure (with the vacuum degree of 0.08 MPa), and detecting the purity of the product to be 96.06%;
the liquid product prepared in comparative example 5 was analyzed after being stored for one year at a temperature of not higher than 25 ℃ in a dark and ventilated environment, and the appearance was a dark yellow turbid liquid, in which the solution had floating crystal particles in an amount of 41.15%;
the product analysis results show that the product appearance is poor, only the content is qualified, and the product is unqualified if the pH value and the free alkali of other indexes are not qualified. Therefore, the content of the product prepared after the flow of the monomethylamine solution is increased by 40% is qualified, the other indexes are not qualified, the product yield is low, and the product is an unqualified product.
Comparative example 6
The same procedure as in example 2 was used, with the same operating parameters, except that the material ratios, i.e. the flow rates of the three raw materials, were changed. The comparative examples carbon disulfide, 40% monomethylamine solution, and 32% sodium hydroxide solution were simultaneously fed from respective metering tanks into the inlet of the microchannel reactor at flow rates of 41ml/min, 56.6ml/min, and 64.1 ml/min. The quality of the product prepared is shown in Table 10.
TABLE 10 analysis results of products
The product yield is 98.47% calculated by taking carbon disulfide as a reference when 200Kg of product is obtained by operation.
Storing the liquid product prepared in the comparative example 6 at 5 ℃ for 2 hours to obtain crystals, drying the crystals for 20 minutes under negative pressure (the vacuum degree is 0.08 MPa), and detecting the purity of the product to be 97.52%;
the liquid product prepared in the comparative example 6 is analyzed after being stored for one year in a dark and ventilated environment at the temperature of not higher than 25 ℃, the appearance is brown yellow transparent liquid, and flaky suspended matters exist in the liquid, and the content is 41.2 percent;
the product analysis results show that the product has poor appearance, only the content is qualified, and other indexes are not qualified. Therefore, the product prepared by increasing the flow of the sodium hydroxide solution by 32 percent is not qualified except for other indexes, and is judged to be unqualified.
Principle of reaction
The general equation for the metam synthesis reaction is:
CH 3 NH + CS 2 + NaOH → CH 3 NCS 2 Na + H 2 O
the detailed reaction process, which is relatively approved by academia at present, is as follows: the reaction is divided into two steps, wherein the first step is that methylamine and carbon disulfide firstly generate N-methyl dithiocarbamic acid, and the second step is that the N-methyl dithiocarbamic acid reacts with sodium hydroxide to generate metam.
(II) production operation step
And (3) respectively pumping three raw materials of monomethylamine solution, carbon disulfide and sodium hydroxide solution into an inlet of the microchannel reactor by using a metering pump, controlling the material ratio (flow), reaction temperature and reaction pressure, and obtaining the metham product at an outlet.
In the process of the invention, respective starting control valves for introducing three raw materials, namely, the monomethylamine solution, the carbon disulfide and the sodium hydroxide solution, are connected with a DCS system, and after the starting control valves are started, the materials can be automatically fed, and the flow of the three raw materials, namely, the monomethylamine solution, the carbon disulfide and the sodium hydroxide solution, the flow rate of the materials in a channel and the length of the channel can be accurately and effectively controlled by a metering pump, so that not only can the materials be accurately proportioned, but also the retention time and the reaction time of the materials under the reaction condition can be accurately controlled, thereby improving the production rate and ensuring the stability of the reaction; the control points are reasonably arranged in the microchannel reactor, the control instrument is connected with the DCS system, a chain loop is formed, the reaction pressure and the reaction temperature can be effectively controlled, manual control is reduced, automatic control is realized, the generation of other side reactions is reduced, the reaction can be stably carried out, the artificial factors and errors are reduced, the formation of explosive mixtures of carbon disulfide and air is avoided, the artificial potential safety hazard is eliminated, and the safety is improved.
Claims (7)
1. A method for synthesizing liquid sodium N-methyldithiocarbamate by a microchannel reactor is characterized by comprising the following steps: the raw materials adopted are carbon disulfide, monomethylamine and sodium hydroxide, and the molar ratio of the carbon disulfide to the monomethylamine to the sodium hydroxide is 1: (1.006-1.012): (0.999-1.016).
2. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 1, wherein: controlling the reaction temperature in the microchannel reactor to be 75-88 ℃; the retention time is 20-30 seconds, and the reaction pressure is not more than 2.0 MPa.
3. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 2, wherein: the reaction pressure is 1.8-1.95 MPa.
4. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 1, wherein: and simultaneously introducing carbon disulfide, monomethylamine solution and sodium hydroxide solution into an inlet of the microchannel reactor, wherein the temperature of the materials when the materials are introduced into the microchannel reactor is room temperature.
5. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 1, wherein: introducing the carbon disulfide into the microchannel reactor at a speed of 40.8-41.2 ml/min; introducing the monomethylamine solution into a microchannel reactor at the speed of 56.5-56.8 ml/min; the sodium hydroxide solution is introduced into the microchannel reactor at a rate of 61-61.9 ml/min.
6. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 4, wherein: the mass concentration of the monomethylamine solution is 30-40%, and the mass concentration of the sodium hydroxide solution is 30-40%.
7. The method for synthesizing liquid sodium N-methyldithiocarbamate by using the microchannel reactor as claimed in claim 6, wherein: the mass concentration of the monomethylamine solution is 38-42%, and the mass concentration of the sodium hydroxide solution is 31-33%.
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