CN114195616B - Preparation method of methyl iodide - Google Patents
Preparation method of methyl iodide Download PDFInfo
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- CN114195616B CN114195616B CN202111585913.0A CN202111585913A CN114195616B CN 114195616 B CN114195616 B CN 114195616B CN 202111585913 A CN202111585913 A CN 202111585913A CN 114195616 B CN114195616 B CN 114195616B
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- INQOMBQAUSQDDS-UHFFFAOYSA-N iodomethane Chemical compound IC INQOMBQAUSQDDS-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 238000002360 preparation method Methods 0.000 title abstract description 11
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 123
- 238000006243 chemical reaction Methods 0.000 claims abstract description 53
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 50
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 claims abstract description 48
- 229910052740 iodine Inorganic materials 0.000 claims abstract description 48
- 239000011630 iodine Substances 0.000 claims abstract description 48
- 238000010992 reflux Methods 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims abstract description 20
- 238000005406 washing Methods 0.000 claims abstract description 17
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000006555 catalytic reaction Methods 0.000 claims abstract description 6
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 5
- 238000011049 filling Methods 0.000 claims abstract description 5
- 238000004519 manufacturing process Methods 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 13
- 238000009833 condensation Methods 0.000 claims description 12
- 230000005494 condensation Effects 0.000 claims description 12
- 239000011574 phosphorus Substances 0.000 claims description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims description 11
- 239000011261 inert gas Substances 0.000 claims description 8
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 7
- 239000001110 calcium chloride Substances 0.000 claims description 7
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 239000002808 molecular sieve Substances 0.000 claims description 6
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 6
- 238000004821 distillation Methods 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 abstract description 9
- 239000002994 raw material Substances 0.000 abstract description 8
- 239000007788 liquid Substances 0.000 description 19
- 238000003786 synthesis reaction Methods 0.000 description 12
- 239000007789 gas Substances 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 239000011521 glass Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 239000002351 wastewater Substances 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 3
- 235000019345 sodium thiosulphate Nutrition 0.000 description 3
- 238000010025 steaming Methods 0.000 description 3
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 210000003298 dental enamel Anatomy 0.000 description 2
- VAYGXNSJCAHWJZ-UHFFFAOYSA-N dimethyl sulfate Chemical compound COS(=O)(=O)OC VAYGXNSJCAHWJZ-UHFFFAOYSA-N 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- PZHNNJXWQYFUTD-UHFFFAOYSA-N phosphorus triiodide Chemical compound IP(I)I PZHNNJXWQYFUTD-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 241000872198 Serjania polyphylla Species 0.000 description 1
- SWJBITNFDYHWBU-UHFFFAOYSA-N [I].[I] Chemical compound [I].[I] SWJBITNFDYHWBU-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- MCYYJHPHBOPLMH-UHFFFAOYSA-L disodium;dioxido-oxo-sulfanylidene-$l^{6}-sulfane;hydrate Chemical compound O.[Na+].[Na+].[O-]S([O-])(=O)=S MCYYJHPHBOPLMH-UHFFFAOYSA-L 0.000 description 1
- 239000012847 fine chemical Substances 0.000 description 1
- 150000005826 halohydrocarbons Chemical class 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- 238000006192 iodination reaction Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000012074 organic phase Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
- C07C17/16—Preparation of halogenated hydrocarbons by replacement by halogens of hydroxyl groups
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a preparation method of methyl iodide, which comprises the following steps: filling methanol and red phosphorus into a reactor, filling iodine into an iodine high-level tank, and replacing air in a reaction system with protective gas; firstly, gasifying methanol by controlling the temperature in a reactor, condensing, then entering an iodine high-level tank to dissolve iodine, carrying iodine to reflux the reactor, reacting the iodine in the reactor with the methanol under the catalysis of red phosphorus to generate methyl iodide, then gasifying the methyl iodide by controlling the temperature in the reactor, condensing, carrying iodine to reflux the reactor, and carrying out continuous reflux reaction; after the reaction is finished, the reaction product is distilled and condensed to obtain methyl iodide, and the methyl iodide is obtained after washing and drying. The preparation method has the advantages of cost saving, simple and convenient operation, stable and safe operation, realization of mass production, large capacity and high efficiency, and can prepare the methyl iodide which has high purity and stable quality and can be used as the raw material of the electronic grade MO source by using industrial grade raw materials.
Description
Technical Field
The invention belongs to the field of fine chemical industry, and particularly relates to a preparation method of methyl iodide.
Background
Methyl iodide is a halohydrocarbon, and the molecular formula is written as CH 3 I. MeI, a monoiodo substituent of methane, has a density of 2.28g/cm 3 (25 ℃ C.) with a melting point of-66.4 ℃ C. And a boiling point of 42.5 ℃ C.). Methyl iodide is colorless transparent liquid, has odor, is slightly soluble in water, and is soluble in ethanol and diethyl ether.
The method for preparing methyl iodide, which can be suitable for mass production of electronic grade MO source raw materials, has few reports, and the currently reported method for preparing methyl iodide mainly comprises the following steps:
(1) Methyl iodide is prepared by reacting dimethyl sulfate with potassium iodide in the presence of calcium carbonate, distilling the reaction product, and then using Na 2 S 2 O 3 Water and Na 2 CO 3 Washing the solution to obtain pure methyl iodide. The method has the advantages of convenient post-treatment and good product purity, but the reactant dimethyl sulfate is extremely toxic and easy to pairThe operator is injured.
(2) Methanol and potassium iodide are used as raw materials, exchange reaction is carried out under the pressure of 0.1-0.5 MPa and the existence of a solid phosphoric acid catalyst, and methyl iodide is collected from an organic phase. The method has the advantages that the damage to personnel caused by materials is low, more raw materials and auxiliary materials are added, the operation steps are more complicated, and the safety risk of the reaction under pressure is higher.
(3) Methyl iodide is prepared by adopting methanol, red phosphorus, white phosphorus, iodine and alcohol, washing with ice water, drying with calcium chloride and distilling to obtain 96% methyl iodide.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide the preparation method of the methyl iodide which is low in cost, simple and convenient to operate, capable of realizing mass production, high in productivity, safe and stable in operation, high in efficiency, high in purity and stable in quality and can be used as the raw material of the electronic-grade MO source.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a process for the preparation of methyl iodide comprising:
(1) Filling methanol and red phosphorus into a reactor, filling iodine into an iodine high-level tank, and replacing air in the whole reaction system with nitrogen or inert gas;
(2) In the first stage, methanol is vaporized by controlling the temperature in a reactor, condensed and enters an iodine high-level tank to dissolve iodine, iodine is carried back to the reactor, and the iodine in the reactor reacts with the methanol under the catalysis of red phosphorus to generate methyl iodide;
(3) In the second stage, methyl iodide is vaporized by controlling the temperature in the reactor, condensed and then enters an iodine high-level tank, and then flows back to the reactor for reflux reaction, and after all iodine in the iodine high-level tank enters the reactor, the methyl iodide is continuously vaporized, and then enters the reactor for reflux reaction through condensation and reflux;
(4) After the synthesis reaction is finished, the reaction product is distilled and condensed to obtain methyl iodide, and then the methyl iodide is washed and dried to obtain pure methyl iodide.
In the technical scheme, the whole reaction process is carried out under a protective atmosphere (nitrogen or inert gas environment), when iodine is added into a mixture of methanol and red phosphorus, exothermic reaction can occur to generate methyl iodide, and the reaction equation is as follows: 10CH 3 OH+5I 2 +2P=10CH 3 I+2H 3 PO 4 +2H 2 O；
The phosphorus triiodide intermediate is generated in the reaction, and then the phosphorus triiodide intermediate is subjected to an iodination reaction with methanol to generate methyl iodide.
In the technical scheme, in the step (3), the second stage comprises two parts, wherein the first part is that the generated methyl iodide is vaporized and then condensed into an iodine high-level tank to dissolve iodine, and then iodine is carried back to the reactor, and the second part is that when all iodine is already introduced into the reactor, the generated methyl iodide is vaporized and then condensed back to the reactor to carry out continuous reflux reaction until the reaction is fully completed.
In the step (1), methanol and red phosphorus can be filled into a reactor at normal temperature and normal pressure; the reactor is preferably a reaction kettle; preferably methanol and red phosphorus are charged to the reactor under nitrogen or an inert gas atmosphere.
Preferably, the mass ratio of the methanol to the red phosphorus to the iodine is 5-8:1-3:16-18.
Preferably, in the step (2), the temperature of the first stage reactor is controlled to be 60-80 ℃; the condensation is carried out by adopting a condenser, and the temperature of the condensation is controlled below 10 ℃.
Preferably, in the step (3), the temperature of the second stage reactor is controlled to be 40-50 ℃; the condensation is carried out by adopting a condenser, and the temperature of the condensation is controlled below 10 ℃; the total reflux reaction time of the second stage is 20-24 h.
Preferably, in step (1), the loading of methanol and red phosphorus into the reactor comprises: firstly adding the methanol and the red phosphorus into a phosphorus overhead tank, then replacing air in the phosphorus overhead tank with nitrogen or inert gas, and then adding the methanol and the red phosphorus in the phosphorus overhead tank into a reactor; the feeding can be carried out step by step, when the last feeding is finished, the valve of the phosphorus overhead tank is closed, then methanol and red phosphorus are added into the phosphorus overhead tank, then the phosphorus overhead tank is ventilated again, and after ventilation, the materials are put into the reactor again, and the process is repeated until the needed amount of methanol and red phosphorus are added. In the actual large-scale production process, an enamel reaction kettle is usually preferred to be used as a reactor, and if methanol and red phosphorus are directly added into the enamel reaction kettle, static ignition materials can be generated, so that the methanol and red phosphorus can be prevented from being burnt by adding a phosphorus overhead tank (the overhead tank is filled with nitrogen or inert gas) and then entering the reaction kettle from the phosphorus overhead tank.
Preferably, in step (2) and step (3), the temperature in the reactor is controlled to be not more than 90 ℃ and the pressure is controlled to be not more than 120kPa. By controlling the upper limit of the temperature and the pressure in the reactor, the whole reaction process can be effectively controlled to be carried out smoothly and safely.
Preferably, the reaction proceeds from the first stage to the second stage when the temperature in the reactor is reduced by 10 to 20 ℃.
Preferably, in step (4), the washing comprises: firstly, na is adopted 2 S 2 O 3 And washing the methyl iodide, and then washing the methyl iodide by adopting pure water.
Preferably, in step (4), the drying is secondary drying; the secondary drying comprises: drying by a calcium chloride dryer, and then drying by a molecular sieve rectifying column.
Preferably, in the step (4), the distillation temperature is 40 to 90 ℃; the condensation is performed by a condenser, and the temperature of the condenser is controlled to be below 10 ℃.
Preferably, the purity of the obtained methyl iodide is 99.5-99.9%, and the moisture content is less than 200ppm.
Compared with the prior art, the invention has the following beneficial effects:
1. the preparation method of the methyl iodide can adopt industrial-grade raw materials to produce high-quality methyl iodide, and the prepared methyl iodide can be used as an electronic-grade MO source raw material.
2. The purity of the methyl iodide prepared by the preparation method can reach more than 99.8%, and the moisture content is below 200 ppm; the preparation method adopts excessive red phosphorus and methanol, ensures complete reaction, and ensures the utilization rate of iodine to be up to 95%.
3. The preparation method of the invention distills the reaction product after the synthesis reaction is finished to obtain methyl iodide, and then uses Na 2 S 2 O 3 Pure water is used for washing, and pure methyl iodide is obtained after secondary drying consisting of a calcium chloride dryer and a molecular sieve rectifying column, and the material transfer in the whole process is realized through distillation and inert gas transfer, so that the purity of the product is ensured.
4. The spontaneous combustion of the methanol and the red phosphorus can be avoided by optimizing the feeding modes of the methanol and the red phosphorus; the upper limit of the temperature and the pressure in the reaction system is reasonably controlled, so that the reaction is more stable and safer.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The invention will be described more fully hereinafter with reference to the accompanying drawings and preferred embodiments in order to facilitate an understanding of the invention, but the scope of the invention is not limited to the following specific embodiments.
Example 1
The air in the whole reaction system is replaced by protective gas, the air is realized by a red phosphorus elevated tank, the elevated tank is vacuumized until the pressure of the elevated tank is minus 0.02MPa, then the protective gas is filled to normal pressure, the operation is repeated for more than three times, the control in the reaction system is realized by replacing the protective gas, 36kg of red phosphorus (98.5%) and 144kg of methanol (99.5%) are added into the reaction kettle in batches from the red phosphorus elevated tank (the air is replaced by the red phosphorus elevated tank), namely, after the red phosphorus and the methanol are added into the red phosphorus elevated tank, the air in the red phosphorus elevated tank is replaced by the protective gas, then the red phosphorus and the methanol are put into the reaction system, simultaneously 360kg of crude iodine (95%) is put into the iodine elevated tank, and the air in the iodine elevated tank is replaced by the protective gas, the internal temperature of the first stage of the synthetic reaction kettle is controlled to be 70-73 ℃ (the temperature of the reaction kettle, the kettle pressure is interlocked with a pneumatic valve PLC, the upper limit of the kettle temperature is set to be 90 ℃, the pneumatic valve on the reaction kettle is interlocked after the upper limit of the kettle is 120KPa and the overtemperature and the overpressure are carried out, a switch is switched, the communication of a bypass (without passing through an iodine high-level tank) is realized, the main path (passing through the iodine high-level tank) is closed, the manual reset is required after the manual confirmation, the safe reaction is ensured, namely, the upper limit of the temperature of the reaction kettle is controlled to be 90 ℃ in the whole reaction process, the upper limit of the kettle is controlled to be 120 KPa), the methanol is gasified, the methanol condensate enters the iodine high-level tank to dissolve iodine by controlling the liquid outlet temperature of a graphite condenser to be 0-10 ℃, finally the methanol condensate flows back into the synthetic reaction kettle to react with the methanol in the kettle under the catalysis of red phosphorus, and reducing the internal temperature after the methyl iodide is generated to a certain extent (the starting point of the second stage is that the temperature in the reaction kettle is reduced by 10-20 ℃), and maintaining the internal temperature at 39-40 ℃ in the second stage to reach the boiling point of the methyl iodide, so that the methyl iodide is gasified, and passes through a graphite condenser, and condensate enters an iodine high-level tank to dissolve iodine and flows back into the synthesis kettle to react to continuously generate the methyl iodide. After the reflux sight glass is changed into colorless transparent liquid (the liquid is purple black with iodine, the colorless transparent represents that iodine in the liquid has no iodine-iodine high-level tank has all entered into the reaction kettle), the total reflux is maintained for 6-8h, so that the materials in the reaction kettle fully react; after the reaction is finished, gradually heating the synthesis reaction kettle to 90 ℃, steaming methyl iodide into a decoloring kettle (filled with sodium thiosulfate solution) for 10-12 hours (stopping heating at 90 ℃ until the sight glass does not reflux); decolorizing (stirring in a decolorizing kettle for 15min, standing for 1-2 hr, separating to obtain upper liquid (waste water, repeating) for 2 times, transferring to a water washing kettle, washing with water (stirring in pure water for 15min, standing for 1-2 hr, separating to obtain upper liquid (waste water, repeating) for 2 times, and drying in a drying kettle (adding 40kg calcium chloride dryer+8 kg4A molecular sieve rectifying column) to obtain pure methyl iodide with water content of 99.5% and water content of less than 200ppm, with yield of 95%.
Example 2
Adding 32kg of red phosphorus (99%) and 120kg of methanol (99.5%) into a reaction kettle from a red phosphorus high-level tank in batches, simultaneously adding 360kg of crude iodine (95%) into an iodine high-level tank, replacing air in a reaction system with protective gas, controlling (through a heat conducting oil unit) the internal temperature of the first stage of the synthesis reaction kettle to be 70-73 ℃ (the upper limit of the temperature of the reaction kettle is controlled to be 90 ℃ in the whole reaction process) and the upper limit of the kettle to be 120 KPa), gasifying the methanol, passing through a graphite condenser (the liquid outlet temperature of the condenser is controlled to be 0-10 ℃), enabling the condensate to enter the iodine high-level tank to dissolve iodine, finally refluxing the condensate to enter the synthesis reaction kettle, reacting with the methanol in the kettle under the catalysis of red phosphorus to generate methyl iodide, reducing the internal temperature after the methyl iodide is generated to a certain extent (the starting point of the second stage is 10-20 ℃ after the starting of the temperature reduction in the reaction kettle), maintaining the internal temperature of the second stage to be 42-45 ℃ until the methyl iodide is gasified, enabling the condensate to enter the iodine high-level tank to dissolve iodine, refluxing to enter the iodine, and continuously enter the synthesis reaction kettle to generate methyl iodide until refluxing is changed into colorless transparent liquid until the sight glass is refluxed for 8h; gradually heating the synthesis kettle to 90 ℃, steaming methyl iodide into a decoloring kettle (filled with sodium thiosulfate solution) for about 10 hours (stopping heating at 90 ℃ until the sight glass does not reflux); decolorizing (stirring in a decolorizing kettle for 15min, standing for 2 hr, separating liquid, collecting the upper liquid as waste water, repeating for 2 times), transferring to a water washing kettle, washing with water (stirring in pure water for 15min, standing for 2 hr, separating liquid, collecting the upper liquid as waste water, repeating for 2 times), and drying in a drying kettle (adding 40kg calcium chloride dryer +8kg4A molecular sieve rectifying column) to obtain pure methyl iodide with content of 99.7% and water content less than 80ppm, with yield of 96%.
Example 3
Adding 28kg of red phosphorus (98.5%) and 110kg of methanol (99.5%) into a reaction kettle from a red phosphorus high-level tank in batches, simultaneously adding 360kg of crude iodine (96%) into an iodine high-level tank, replacing air in a reaction system with protective gas, controlling the internal temperature of the first stage of the synthesis reaction kettle to be 73-75 ℃ (the upper limit of the temperature of the reaction kettle is controlled to be 90 ℃ in the whole reaction process through a heat conducting oil unit), enabling the methanol to be gasified, controlling the liquid outlet temperature of a graphite condenser to be 0-10 ℃ through the upper limit of the kettle, enabling the condensate to enter the iodine high-level tank to dissolve iodine, finally refluxing the condensate to enter the synthesis reaction kettle, reacting with methanol in the kettle under the catalysis of red phosphorus to generate methyl iodide, reducing the internal temperature after the methyl iodide is generated to a certain extent (the starting point of the second stage is that the temperature in the reaction kettle is reduced by 10-20 ℃), maintaining the internal temperature in the second stage to be 43-45 ℃ to reach the boiling point of methyl iodide, enabling the condensate to enter the iodine high-level tank to dissolve iodine, refluxing the synthesis reaction to continuously generate methyl iodide until the reflux is colorless liquid, and maintaining the total reflux view mirror for 8h; gradually heating the synthesis kettle to 90 ℃, steaming methyl iodide into a decoloring kettle (filled with sodium thiosulfate solution) for 8 hours (stopping heating at 90 ℃ until no reflux exists on the sight glass); decolorizing (stirring in a decolorizing kettle for 15min, standing for 2 hr, separating liquid, adding water as the upper liquid, repeating for 2 times), transferring to a water washing kettle, washing with water (stirring in pure water for 15min, standing for 2 hr, separating liquid, adding water as the upper liquid, repeating again), adding 40kg calcium chloride dryer and 8kg4A molecular sieve rectifying column into a drying kettle, and drying to obtain pure methyl iodide with content of 99.6% and water content of less than 80ppm, with yield of 95.6%.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (6)
1. A process for producing methyl iodide, comprising:
(1) Adding methanol and red phosphorus into a phosphorus overhead tank, filling iodine into the iodine overhead tank, replacing air in the phosphorus overhead tank with nitrogen or inert gas, replacing air in a reaction system with nitrogen or inert gas, and adding the methanol and the red phosphorus in the phosphorus overhead tank into a reactor;
(2) In the first stage, methanol is vaporized by controlling the temperature in a reactor, condensed and enters an iodine high-level tank to dissolve iodine, iodine is carried back to the reactor, and the iodine in the reactor reacts with the methanol under the catalysis of red phosphorus to generate methyl iodide;
(3) In the second stage, methyl iodide is vaporized by controlling the temperature in the reactor, condensed and then enters an iodine high-level tank, and then flows back to the reactor for reflux reaction, and after all iodine in the iodine high-level tank enters the reactor, the methyl iodide is continuously vaporized, and then enters the reactor for reflux reaction through condensation and reflux;
(4) After the reaction is finished, distilling and condensing a reaction product to obtain methyl iodide, washing, and drying to obtain methyl iodide;
in the step (2) and the step (3), controlling the temperature in the reactor to be not more than 90 ℃ and the pressure to be not more than 120kPa;
when the temperature in the reactor is reduced by 10-20 ℃, the reaction enters a second stage from the first stage;
the purity of the obtained methyl iodide is 99.5-99.9%, and the water content is less than 200ppm.
2. The method for preparing methyl iodide according to claim 1, wherein the mass ratio of methanol, red phosphorus and iodine is 5-8:1-3:16-18.
3. The process for producing methyl iodide according to claim 1, wherein in the step (2), the temperature of the first stage reactor is controlled to 60 to 80 ℃; the condensation is carried out by adopting a condenser, and the temperature of the condensation is controlled below 10 ℃.
4. The process for producing methyl iodide according to claim 1, wherein in the step (3), the temperature of the second stage reactor is controlled to 40 to 50 ℃; the condensation is carried out by adopting a condenser, and the temperature of the condensation is controlled below 10 ℃; the total reflux reaction time of the second stage is 20-24 h.
5. The method for producing methyl iodide according to claim 1, wherein in the step (4), the distillation temperature is 40 to 90 ℃; the condensation is performed by a condenser, and the temperature of the condenser is controlled to be below 10 ℃.
6. The method for producing methyl iodide according to any one of claims 1 to 5, wherein in the step (4), the washing comprises: firstly, na is adopted 2 S 2 O 3 Washing methyl iodide, and then washing with pure water;
the drying is secondary drying; the secondary drying comprises: drying by a calcium chloride dryer, and then drying by a molecular sieve rectifying column.
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