A method for the continuous production of hydriodic acid

Abstract

The application discloses a method for continuously preparing hydriodic acid. The method comprises the following steps: dissolving phosphorous acid in oxygen-free water to obtain an aqueous phase feed liquid; dissolving elemental iodine in a water-insoluble inert organic solvent to obtain an organic phase feed liquid; continuously contacting the organic phase feed liquid with the aqueous phase feed liquid through micro-interface mass transfer to generate a reduction reaction; continuously discharging a mixed liquid obtained after the reaction; and collecting a lower aqueous phase after the mixed liquid is allowed to stand and separate into layers, and then filtering and performing vacuum rectification to obtain the hydriodic acid. The method for continuously preparing the hydriodic acid by using the water-inert organic solvent two-phase micro-interface mass transfer technology not only completely avoids the problem of excessively high local iodine concentration in the aqueous phase, reduces the generation of free iodine from the source, but also improves the inter-phase mass transfer efficiency, so that the reaction can be completely performed under low-temperature conditions, the thermal decomposition rate of the hydriodic acid is significantly reduced, and the decomposition and oxidation of the hydriodic acid are effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of inorganic chemical technology, specifically relating to a method for the continuous preparation of hydroiodic acid. Background Technology

[0002] Hydroiodic acid is the most potent reducing inorganic hydrogen halide, possessing the triple properties of strong acidity, strong reducing power, and nucleophilic substitution of iodide ions. Based on purity levels, it can be classified into industrial grade, pharmaceutical grade, and electronic ultra-high purity grade, and is widely used in pharmaceuticals, optoelectronics, acetic acid catalysis, and new organic synthesis materials.

[0003] Currently, the main industrial methods for preparing hydroiodic acid include the red phosphorus reduction method, the hydrogen sulfide reduction method, and the phosphorous acid-iodine aqueous phase reduction method. However, all of these methods have significant technical drawbacks:

[0004] 1. Red phosphorus reduction method: There is a problem of solid particle residue, and the reaction is highly exothermic, and the distillation process is prone to boiling and material overflow, which poses a safety hazard; at the same time, solid impurities are easily introduced into the product, affecting the purity.

[0005] 2. Hydrogen sulfide reduction method: This method uses highly toxic hydrogen sulfide gas, and the costs of safety management and environmental treatment are extremely high.

[0006] 3. Chinese patent CN104085857A reported a phosphorous acid-iodine aqueous phase reduction method. This method is a single aqueous phase intermittent reaction and has the following defects: (1) Iodine is directly added to the aqueous phase, and the local iodine concentration is too high, which can easily cause local overheating, accelerate the decomposition of hydroiodic acid to generate free iodine, and result in poor product color and insufficient stability; (2) The reaction temperature is generally too high (above 70 ℃), which further aggravates the side reaction; (3) Most of the production is intermittent, and the product quality varies greatly between batches, resulting in low production efficiency and difficulty in meeting the needs of large-scale continuous production.

[0007] Therefore, it is of great significance to develop a method for preparing hydroiodic acid that has mild reaction conditions, is environmentally friendly and efficient, and has controllable costs. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for the continuous preparation of hydroiodic acid. The method uses water-inert organic solvent two-phase micro-interface mass transfer technology to continuously prepare hydroiodic acid, which improves production efficiency, ensures stable product quality, and is suitable for industrial production.

[0009] To address the above technical problems, this invention discloses a continuous method for preparing hydroiodic acid, comprising the following steps:

[0010] Phosphorous acid is dissolved in oxygen-free water to obtain an aqueous phase solution; elemental iodine is dissolved in a water-insoluble inert organic solvent to obtain an organic phase solution; the organic phase solution is continuously contacted with the aqueous phase solution through micro-interface mass transfer to undergo a reduction reaction, and the resulting mixture is continuously discharged; the resulting mixture is allowed to stand and separate into layers, the lower aqueous phase is collected, filtered, and distilled under reduced pressure to obtain the hydroiodic acid.

[0011] The reaction formula for the preparation of hydroiodic acid in this invention is as follows:

[0012]

[0013] Furthermore, the specific steps include:

[0014] (1) At room temperature, nitrogen gas is introduced into deionized water and bubbled below the liquid surface to remove oxygen. The dissolved oxygen content in the water is controlled to be ≤0.15 mg / L. The water is then stored under nitrogen to obtain oxygen-free water.

[0015] (2) At room temperature, completely dissolve phosphorous acid in the oxygen-free water obtained in step (1) to prepare an aqueous phase solution with a mass concentration of 5-95%; completely dissolve elemental iodine in a water-insoluble inert organic solvent to prepare an organic phase solution with a mass concentration of 5-80%.

[0016] (3) Under conditions of a temperature of 40–60 °C, nitrogen gas is introduced to maintain a pressure of 1–5 kPa (to prevent air from entering the reaction system) and light protection, the aqueous phase solution and organic phase solution obtained in step (2) are continuously introduced into a reaction device with strong stirring at a certain flow ratio. The two phases are fully contacted and a reduction reaction occurs. The resulting mixture is continuously discharged after the reaction. The strong stirring is used to form a stable water-organic micro-interface. The reaction device is one of the following: micro-interface reaction vessel, tubular static mixing reactor, microchannel reactor, liquid-liquid impingement reactor, and external circulation tubular circulating reactor, or it is composed of one or more of the following connected in series: micro-interface reaction vessel and tubular static mixing reactor, microchannel reactor, liquid-liquid impingement reactor, and external circulation tubular circulating reactor. The inner wall and flow parts of the above reaction device are all made of polytetrafluoroethylene (PTFE), fusible polytetrafluoroethylene (PFA), or silicon carbide to prevent hydroiodic acid corrosion.

[0017] (4) The mixture obtained after the reaction in step (3) is transferred into a phase separation tank and allowed to stand at room temperature to separate the layers. The lower aqueous phase crude hydroiodic acid solution is separated, and the upper organic phase is collected and recycled. Under the protection of nitrogen positive pressure, the obtained crude hydroiodic acid solution is filtered through a PTFE microporous membrane to remove trace suspended matter and unreacted trace iodine. The solution is then subjected to vacuum distillation to collect the azeotropic fraction and obtain the hydroiodic acid.

[0018] (5) Add hypophosphite aqueous solution to the hydroiodic acid obtained in step (4), stir evenly at room temperature in the dark, and seal and fill under nitrogen protection to obtain the finished hydroiodic acid product. The hypophosphite acts as a stabilizer, allowing the hydroiodic acid to be stored at room temperature in the dark for more than 18 months.

[0019] Furthermore, in step (1), the bubbling deoxygenation time is 4 to 6 hours; the purity of the nitrogen gas is ≥99.999%.

[0020] Furthermore, in step (2), the water-insoluble inert organic solvent is one or more of propylcyclohexane, mesitylene, and isopropylbenzene; the molar ratio of iodine to phosphorous acid is 1.0:0.5-2.0, preferably 1:1.1. The water-insoluble inert organic solvent has a miscibility with water of <0.01% and a boiling point higher than 150 °C, ensuring that it will not distill off with hydroiodic acid during the subsequent vacuum distillation process.

[0021] Furthermore, in step (2), the mass concentration of the aqueous phase feed solution is 25%; and the mass concentration of the organic phase feed solution is 50%.

[0022] Furthermore, in step (3), the flow rate ratio is the flow rate ratio of the aqueous phase liquid to the organic phase liquid when they are fed in the same amount of time; the speed of the strong stirring is 300-600 r / min; and the time of the reduction reaction is 1.0-2.0 h.

[0023] Furthermore, in step (4), the pore size of the PTFE microporous filter membrane is 0.45 to 1.0 μm, preferably 0.8 μm.

[0024] Furthermore, in step (4), vacuum distillation is carried out under the conditions of vacuum degree -0.07 to -1.0 MPa (preferably -0.095 MPa), temperature 88 to 89 °C, and protection from light.

[0025] Furthermore, in step (5), the mass concentration of the hypophosphite aqueous solution is 20-70%, preferably 50%.

[0026] Furthermore, in step (5), the mass of the hypophosphite aqueous solution is 0.01% to 1.0% of the mass of hydroiodic acid, preferably 0.1%.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention uses water and a high-boiling-point inert organic solvent to construct a two-phase system, and relies on high-speed stirring to form a micron-level two-phase micro-interface. Iodine is first dissolved in the organic solvent, and then slowly released into the aqueous phase through mass transfer at the micro-interface. This not only completely avoids the problem of excessively high local iodine concentration in the aqueous phase and reduces the generation of free iodine from the source, but also improves the interphase mass transfer efficiency, allowing the reaction to proceed completely at low temperature (40-60 °C), significantly reducing the thermal decomposition rate of hydroiodic acid and effectively inhibiting its decomposition. At the same time, the byproduct phosphoric acid generated by the reaction is a high-boiling-point compound, which can be separated from hydroiodic acid by vacuum distillation, ensuring product purity.

[0029] (2) Compared with traditional batch reactor production, this invention achieves continuous operation of feeding, reaction and phase separation, which significantly improves production efficiency. At the same time, by combining deep deoxygenation, full-process nitrogen micro-positive pressure, light-proof operation and post-addition of stabilizers, it ensures that hydroiodic acid products can be stored for a long time without yellowing or decomposition, and that batch stability is consistent, meeting the requirements of high-end fields such as pharmaceuticals and electronic chemicals, and is suitable for industrial scale-up production.

[0030] (3) The organic solvent used in this invention does not react with the raw materials or products and has extremely low miscibility with water. This not only avoids introducing new impurities into the hydroiodic acid product and further ensures the purity of the product, but also allows the organic solvent after phase separation to be directly collected and recycled, which improves the utilization rate of raw materials, reduces production costs and the amount of waste generated, and is in line with the concept of green chemistry. Detailed Implementation

[0031] 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.

[0032] Example 1

[0033] (1) At room temperature, high-purity nitrogen gas was introduced into 1000 g of deionized water using a microporous aeration head, and the oxygen was removed by bubbling below the liquid surface for 5 h. The dissolved oxygen content in the water was measured to be 0.11 mg / L. The water was then stored under nitrogen to obtain oxygen-free water.

[0034] (2) At room temperature, add 192 g of industrial phosphorous acid with a purity of 98.0% to 600 g of the oxygen-free water obtained in step (1) and stir until completely dissolved to obtain an aqueous phase solution. Add 520 g of iodine with a purity of 99.0% to 520 g of propylcyclohexane and stir until completely dissolved to obtain an organic phase solution.

[0035] (3) The aqueous phase solution and organic phase solution obtained in step (2) are continuously fed into the micro-interface reactor at a flow ratio of 1:1.313. Under the conditions of reaction temperature of 50 °C, stirring speed of 450 r / min, nitrogen gas is introduced throughout the process to maintain micro-positive pressure and light protection, the two phases are fully contacted and a reduction reaction occurs. The reaction time is 1.5 h, and the reaction mixture is continuously discharged.

[0036] (4) The reaction mixture obtained in step (3) was transferred to a phase separation tank and allowed to stand at room temperature for 15 min. After separation, the lower aqueous phase crude hydroiodic acid solution was collected, and the upper propylcyclohexane layer was collected separately for recycling. Under nitrogen positive pressure protection, the obtained aqueous phase crude hydroiodic acid solution was filtered under pressure using a PTFE microporous membrane with a pore size of 0.8 μm to obtain a clear filtrate. The filtrate was sent to a light-protected vacuum distillation apparatus and subjected to vacuum distillation under a vacuum degree of -0.095 MPa and a column top temperature of 88-89℃. The azeotropic fraction was collected to obtain hydroiodic acid. The organic phase was recycled a total of 22 times, and the reaction efficiency did not decrease significantly.

[0037] (5) Add 0.10% of the hydroiodic acid obtained in step (4) to a 50% aqueous solution of hypophosphite, stir for 40 min in the dark, and seal and fill under nitrogen protection to obtain 888.95g of hydroiodic acid product with a yield of 98.0%.

[0038] The hydroiodic acid product obtained above was tested and found to have a hydroiodic acid content of 57.2%, a free iodine content of 21 ppm, no heavy metals (Pb) detected, and an evaporation residue of 0.004%.

[0039] Example 2

[0040] The difference between this embodiment and Example 1 is that propylcyclohexane in step (2) is replaced with mesitylene, while other conditions are the same as in Example 1. Finally, 893g of hydroiodic acid product is obtained, with a yield of 98.1%.

[0041] The above-obtained hydroiodic acid product was tested and found to have a hydroiodic acid content of 57.0%, a free iodine content of 18 ppm, no heavy metals (Pb) detected, and an evaporation residue of 0.003%.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that the reaction temperature in step (3) is adjusted to 60°C and the stirring speed is adjusted to 350 r / min. Other conditions are the same as in Example 1. Finally, 894g of hydroiodic acid product is obtained, with a yield of 98.4%.

[0044] The above-obtained hydroiodic acid product was tested and found to have a hydroiodic acid content of 57.1%, a free iodine content of 24 ppm, no heavy metals (Pb) detected, and an evaporation residue of 0.004%.

[0045] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for continuous preparation of hydroiodic acid, characterized in that, Includes the following steps: Phosphorous acid is dissolved in oxygen-free water to obtain an aqueous phase solution; elemental iodine is dissolved in a water-insoluble inert organic solvent to obtain an organic phase solution; the organic phase solution is continuously contacted with the aqueous phase solution through micro-interface mass transfer to undergo a reduction reaction, and the resulting mixture is continuously discharged; the resulting mixture is allowed to stand and separate into layers, the lower aqueous phase is collected, filtered, and distilled under reduced pressure to obtain the hydroiodic acid.

2. The method according to claim 1, characterized in that, Specifically, the following steps are included: (1) At room temperature, nitrogen gas is introduced into deionized water and bubbled below the liquid surface to remove oxygen. The dissolved oxygen content in the water is controlled to be ≤0.15mg / L. The water is then stored under nitrogen to obtain oxygen-free water. (2) At room temperature, completely dissolve phosphorous acid in the oxygen-free water obtained in step (1) to prepare an aqueous phase solution with a mass concentration of 5-95%; completely dissolve elemental iodine in a water-insoluble inert organic solvent to prepare an organic phase solution with a mass concentration of 5-80%. (3) Under the conditions of temperature of 40-60℃, nitrogen gas is introduced to maintain pressure of 1-5Kpa and light protection, the aqueous phase liquid obtained in step (2) and the organic phase liquid are continuously introduced into the reaction device with strong stirring at a certain flow ratio. The two phases are fully contacted and a reduction reaction occurs. The resulting mixture is continuously discharged after the reaction. (4) The mixture obtained after the reaction in step (3) is transferred into a phase separation tank, allowed to stand at room temperature to separate the layers, and the lower aqueous phase crude hydroiodic acid solution is separated. The upper organic phase is collected and recycled. Under the protection of nitrogen positive pressure, the obtained crude hydroiodic acid solution is filtered through a PTFE microporous membrane, and then distilled under reduced pressure to collect the azeotropic fraction to obtain the hydroiodic acid. (5) Add hypophosphite aqueous solution to the hydroiodic acid obtained in step (4), stir evenly at room temperature in the dark, and seal and fill under nitrogen protection to obtain the hydroiodic acid product.

3. The method according to claim 2, characterized in that, In step (1), the bubbling deoxygenation time is 4 to 6 hours; the purity of the nitrogen gas is ≥ 99.999%.

4. The method according to claim 2, characterized in that, In step (2), the water-insoluble inert organic solvent is one or more of propylcyclohexane, mesitylene, and isopropylbenzene; the molar ratio of iodine to phosphorous acid is 1.0:0.5-2.

0.

5. The method according to claim 2, characterized in that, In step (2), the mass concentration of the aqueous phase feed solution is 25%; the mass concentration of the organic phase feed solution is 50%.

6. The method according to claim 2, characterized in that, In step (3), the flow rate ratio is the flow rate ratio of the aqueous phase liquid to the organic phase liquid when they are fed in the same amount of time; the speed of the strong stirring is 300-600 r / min; and the time of the reduction reaction is 1.0-2.0 h.

7. The method according to claim 2, characterized in that, In step (4), the pore size of the PTFE microporous filter membrane is 0.45 to 1.0 μm.

8. The method according to claim 2, characterized in that, In step (4), vacuum distillation is carried out under conditions of vacuum degree -0.07 to -1.0 MPa, temperature 88 to 89 °C, and protection from light.

9. The method according to claim 2, characterized in that, In step (5), the mass concentration of the hypophosphoric acid aqueous solution is 20-70%.

10. The method according to claim 2 or 9, characterized in that, In step (5), the mass of the hypophosphite aqueous solution is 0.01% to 1.0% of the mass of hydroiodic acid.