Industrial preparation method of methyl iodide
By using iodine, sulfur dioxide, and methanol as raw materials, combined with aluminum trichloride catalyst, the safety and environmental protection issues in the existing iodomethane production have been solved, and a highly efficient and environmentally friendly iodomethane preparation method has been achieved, with a product purity of up to 99.9%.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG HAIZHOU PHARMA CO LTD
- Filing Date
- 2026-02-24
- Publication Date
- 2026-04-14
AI Technical Summary
Existing iodomethane production processes pose safety hazards and environmental problems, especially the dimethyl sulfate process and the red phosphorus process, which have environmental pollution and safety risks in industrial production.
Using iodine, sulfur dioxide, and methanol as raw materials and aluminum trichloride as a catalyst, the reaction is carried out at 50–60 °C. The distillate is collected and post-processed to obtain high-purity iodomethane.
A safe and environmentally friendly method for preparing iodomethane has been achieved, which is suitable for large-scale production, with high yield and product purity up to 99.9%.
Smart Images
Figure CN121850830A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an industrial preparation method for iodomethane, belonging to the field of chemical product preparation technology. Background Technology
[0002] Iodomethane, also known as methyl iodine, has the molecular formula CH3I, a molecular weight of 141.94, and CAS number 74-88-4. It is a colorless, flammable gas with a melting point of -66.45℃, a boiling point of 42.4℃, a relative density of 2.279 (20 / 4℃), and a refractive index of 1.5317. It is miscible with ethanol and ether, soluble in acetone and benzene, and slightly soluble in water. It turns red upon exposure to light.
[0003] Currently, the main industrial processes for producing iodomethane include the following routes:
[0004] The literature (Organic Syntheses, 1938, vol. 18, p. 88) describes the preparation of iodomethane by reacting sodium iodide with dimethyl sulfate. However, patent JP 2016-222548 A (published on December 28, 2016) uses iron powder as a catalyst. A mixture of sodium iodide and methanol is heated to reflux, and sulfuric acid is added dropwise while the product iodomethane is distilled. By changing the method of adding sulfuric acid dropwise into methanol to react and generate dimethyl sulfate, the amount of dimethyl sulfate is controlled (dimethyl sulfate acts as an intermediate transition state, a byproduct), thus avoiding the safety hazards caused by excessive amounts of the toxic gaseous byproduct dimethyl sulfate.
[0005] Other literature records that iodine, methanol, and red phosphorus are added to a reaction flask and heated to produce iodomethane. The basic idea is that iodine reacts with red phosphorus to produce phosphorus triiodide, which then reacts with methanol to produce iodomethane.
[0006] Market research revealed that, among the aforementioned process routes, only the dimethyl sulfate method and the red phosphorus method are suitable for industrial-scale iodomethane production due to limitations in equipment and process operability.
[0007] However, both the dimethyl sulfate process and the red phosphorus process for producing iodomethane have significant drawbacks. The dimethyl sulfate process requires the use of highly toxic dimethyl sulfate, which causes irreversible damage to the environment and personnel during actual production, posing significant safety and environmental risks. The red phosphorus process, due to the flammable nature of red phosphorus, significantly increases safety risks during storage, transportation, and production, and the treatment of phosphorus-containing wastewater also presents considerable problems. Summary of the Invention
[0008] The technical problem to be solved by the present invention is to provide a new method for preparing iodomethane, which uses iodine, sulfur dioxide and methanol as raw materials, and is safe, environmentally friendly and suitable for large-scale production.
[0009] To address the above technical problems, this invention discloses an industrial-scale preparation method for iodomethane. This method uses iodine, sulfur dioxide, and methanol as raw materials, and aluminum trichloride as a catalyst, reacting at a temperature of 50–60°C. Iodomethane gas is distilled off, and the gas undergoes post-treatment to produce a high-purity iodomethane product. The reaction formula is as follows:
[0010]
[0011] Further, in the reaction vessel, iodine and methanol are added in proportion, the temperature is raised to 50-60℃, aluminum trichloride is added, and sulfur dioxide is slowly introduced (the introduction rate of sulfur dioxide is adjusted according to the reaction phenomena and distillation rate of the distillate during the reaction process). The distillate is collected, and the introduction of sulfur dioxide is stopped after the solution in the reaction vessel becomes clear or no distillate flows out. The distillate iodomethane gas is condensed, and a 0.5wt% sodium bicarbonate aqueous solution is added, accounting for 1 / 5 to 1 / 2 of its volume. The layers are washed with water, the organic layer is collected, and anhydrous calcium chloride or magnesium sulfate is used for dehydration. Then, the product is distilled in a column, and the fraction at 35-45℃ is collected to obtain high-purity iodomethane.
[0012] Furthermore, the reaction temperature is 55–60°C.
[0013] Furthermore, the sulfur dioxide is sulfur dioxide gas or a methanol solution of sulfur dioxide.
[0014] Furthermore, the weight ratio of iodine to methanol is 1:1 to 20. When sulfur dioxide is a methanol solution of sulfur dioxide, the methanol includes the methanol in the methanol solution of sulfur dioxide.
[0015] Furthermore, the weight ratio of iodine to methanol is 1:5 to 10.
[0016] Furthermore, the amount of catalyst fed is 0.1 wt% to 0.5 wt% of the amount of iodine fed.
[0017] Furthermore, the amount of catalyst fed is 0.1 wt% to 0.3 wt% of the amount of iodine fed.
[0018] This invention presents a novel route for preparing iodomethane, avoiding the use of the highly toxic raw material dimethyl sulfate, as well as the transportation of red phosphorus and the problems associated with phosphorus wastewater treatment. The entire reaction route is green, environmentally friendly, safe, and suitable for large-scale production. The reaction yield is high, and the iodomethane obtained after post-treatment of the distillate has high purity (GC content approximately 99.9%). Attached Figure Description
[0019] Figure 1 The GC spectrum of the crude iodomethane obtained in Example 1 of this invention;
[0020] Figure 2 This is the GC spectrum of the refined iodomethane obtained in Example 1 of the present invention. Detailed Implementation
[0021] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0022] Example 1: Preparation of iodomethane
[0023] Add 254 kg (1 kmol) of elemental iodine to a 3000 L enamel-lined reactor, along with 1300 kg of methanol, and then 0.3 kg (0.12 wt% of the iodine input) of aluminum trichloride. Stir and heat to 55°C. At this point, the liquid inside the reactor should be brown. Slowly introduce sulfur dioxide gas and turn on the condensers (first-stage condenser temperature 10–20°C, second-stage condenser -10–0°C). Begin collecting the distillate. Once the reaction liquid in the reactor becomes clear and transparent, turn off the sulfur dioxide gas. The sulfur dioxide gas cylinder should have consumed approximately 90 kg. Continue distilling at 55°C until no more distillate flows out. Take a sample of the distillate for GC analysis; the purity is approximately 99.5% (see [link to GC analysis]). Figure 1 The sample weighed approximately 282 kg (approximately 128 L, 1.9859 kmol), with a molar yield of 99.3% (calculated as elemental iodine).
[0024] The crude iodomethane was transferred to a 500L reactor, and 60L of a 0.5% sodium bicarbonate aqueous solution was added. The mixture was washed with water to separate the layers. The aqueous layer was discharged, and the organic layer was dehydrated with anhydrous magnesium sulfate. After dehydration, the mixture was filtered into a distillation vessel. The fraction distilled at 35–45℃ was collected in the distillation column until no more distillate was obtained. A sample was taken, and GC analysis showed a purity of approximately 99.9% (see...). Figure 2 The sample weighed approximately 279 kg (1.9648 kmol), with a total molar yield of approximately 98.24% (based on elemental iodine). The refined iodomethane was transferred into a 25 kg opaque PTFE-lined metal drum, and approximately 1 g of copper powder was added as a stabilizer.
[0025] Example 2: Preparation of iodomethane
[0026] Add 254 kg of elemental iodine to a 3000 L enamel-lined reactor, then add 2500 kg of methanol, followed by 0.5 kg of aluminum trichloride (0.2 wt% of elemental iodine). Stir and heat to 55 °C. At this point, the liquid in the reactor should be brown. Slowly introduce sulfur dioxide gas and turn on the condenser (first-stage condenser temperature 10–20 °C, second-stage condenser -10–0 °C). Begin collecting the distillate. Once the reaction liquid in the reactor becomes clear and transparent, turn off the sulfur dioxide. The sulfur dioxide gas cylinder should weigh approximately 75 kg. Continue distilling at 55 °C until no more distillate flows out. Take a sample of the distillate for GC analysis. The content is approximately 99.5%, and the weight is approximately 283 kg (1.9929 kmol), with a molar yield of 99.6% (based on elemental iodine).
[0027] The crude product was refined using the same process as in Example 1, yielding approximately 280 kg (1.9718 kmol) of refined iodomethane, with a total molar yield of approximately 98.6% (calculated based on elemental iodine) and a purity of 99.9%.
[0028] Example 3: Preparation of iodomethane
[0029] Add 254 kg of elemental iodine to a 3000 L enamel-lined reactor, then add 2500 kg of methanol, followed by 1 kg of aluminum trichloride (0.39 wt% of elemental iodine). Stir and heat to 55 °C. At this point, the liquid in the reactor should be brown. Slowly introduce sulfur dioxide gas and turn on the condenser (first-stage condenser temperature 10–20 °C, second-stage condenser -10–0 °C). Begin collecting the distillate. Once the reaction liquid in the reactor becomes clear and transparent, turn off the sulfur dioxide. The sulfur dioxide gas cylinder should weigh approximately 75 kg. Continue distilling at 55 °C until no more distillate flows out. Take a sample of the distillate for GC analysis. The content is approximately 99.1%, and the weight is approximately 280 kg. The molar yield is 98.6% (based on elemental iodine).
[0030] The crude product was refined using the same process as in Example 1, yielding approximately 276 kg (1.9437 kmol) of refined iodomethane with a purity of 99.9% and a total molar yield of 97.2% (calculated based on elemental iodine).
Claims
1. An industrial method for preparing iodomethane, characterized in that: This method uses iodine, sulfur dioxide and methanol as raw materials, and aluminum trichloride as a catalyst to react and obtain iodomethane at a reaction temperature of 50-60℃.
2. The industrial preparation method of iodomethane according to claim 1, characterized in that: In a reaction vessel, iodine and methanol are added in proportion, the temperature is raised to 50-60°C, aluminum trichloride is added, sulfur dioxide is slowly introduced, the distillate is collected, and the introduction of sulfur dioxide is stopped after the solution in the reaction vessel becomes clear or no more distillate flows out. The distillate is then post-processed to obtain high-purity iodomethane.
3. The industrial preparation method of iodomethane according to claim 1 or 2, characterized in that: The reaction temperature is 55–60°C.
4. The industrial preparation method of iodomethane according to claim 1 or 2, characterized in that: The sulfur dioxide is sulfur dioxide gas or a methanol solution of sulfur dioxide.
5. The industrial preparation method of iodomethane according to claim 2, characterized in that: The weight ratio of iodine to methanol is 1:1 to 20.
6. The industrial preparation method of iodomethane according to claim 5, characterized in that: The weight ratio of iodine to methanol is 1:5 to 10.
7. The industrial preparation method of iodomethane according to claim 1, characterized in that: The catalyst is fed in an amount of 0.1 wt% to 0.5 wt% of the iodine.
8. The industrial preparation method of iodomethane according to claim 7, characterized in that: The amount of catalyst fed is 0.1 wt% to 0.3 wt% of the amount of iodine fed.