JP5038680B2 - Hydrogen iodide production method, hydrogen production method, and apparatus for the production method - Google Patents

Description

  The present invention relates to a hydrogen iodide production method and a hydrogen production method using a thermochemical decomposition method (IS method), and an apparatus that can be used in these production methods.

  There is a thermochemical decomposition process as a method for extracting hydrogen from water. Water is chemically converted to a chemical form containing hydrogen, and hydrogen is extracted using thermal energy. Depending on the type of chemical used, there are many different approaches.

  One of the thermochemical decomposition processes is the IS method (see Patent Documents 1 to 7, Non-Patent Documents 1 and 2). The IS method is based on the following three basic reactions.

I ₂ + SO ₂ + 2H ₂ O → 2HI + H ₂ SO ₄ (1)
2HI → H ₂ + I ₂ (2)
2H ₂ SO ₄ → 2SO ₂ + 2H ₂ O + O ₂ (3)
First, water is reacted with iodine (I ₂ ) and sulfur dioxide (SO ₂ ) to produce hydrogen iodide (HI) and sulfuric acid (H ₂ SO ₄ ). This reaction is also called the Bunsen reaction. The produced hydrogen iodide is thermally decomposed at 400 ^° C. or more and decomposed into hydrogen (H ₂ ) and iodine. Hydrogen, which is the thermal decomposition product of hydrogen iodide, is the final goal produced by the thermochemical decomposition process. The iodine produced at this time is returned to the Bunsen reaction and reused. The sulfuric acid produced by the Bunsen reaction is also thermally decomposed at a high temperature of 600 ^° C. or higher, and the generated sulfur dioxide is also returned to the Bunsen reaction and reused.

In general, hydrogen iodide production by the IS method is carried out at about atmospheric pressure, but the concentration of hydrogen iodide in the lower phase liquid obtained by two-phase separation does not exceed the azeotropic composition. As a reason why the concentration of hydrogen iodide in the lower phase liquid does not exceed the azeotropic composition, it is considered that the solubility of sulfur dioxide in water under atmospheric pressure conditions is not so large as about 5% by weight. When dissolved in water, sulfur dioxide hydrates and changes to sulfurous acid (H ₂ SO ₃ ) as shown in the following reaction formula. A chemical species in which one molecule of water is hydrated per one molecule of sulfur dioxide is generally known sulfurous acid.

SO ₂ + H ₂ O → H ₂ SO ₃ (4)
SO ₂ + nH ₂ O → SO ₂ .nH ₂ O (5)
Sulfurous acid is reducible and causes an oxidation-reduction reaction with iodine to produce hydrogen iodide and sulfuric acid.

H ₂ SO ₃ + I ₂ + H ₂ O → 2HI + H ₂ SO ₄ (6)
The inventors of the present invention performed hydrogen iodide generation reaction (reaction formula (1)) under pressurized conditions, so that hydrogen iodide in the lower phase exceeded 57%, which is an azeotropic composition, and increased to 70% or more. Make sure you can reach it. The hydrogen iodide concentration at this time is obtained by dividing the total mass of hydrogen iodide in the lower phase liquid by the sum of the masses of hydrogen iodide and water and multiplying by 100 (formula (7)).

[HI]
= Total hydrogen iodide mass [g] / (hydrogen iodide mass [g] + water mass [g]) in lower phase liquid
× 100 (7)
Further, the produced hydrogen iodide needs to be separated from the sulfuric acid produced simultaneously in the reaction formula (1) as two phases by using an excess iodine with a difference in specific gravity. Since hydrogen iodide has a high affinity with iodine, it forms a complex with iodine and moves to the lower phase liquid. The complex formation reaction between main iodide ions and iodine is shown below.

I ₂ + I ⁻ → I ₃ ⁻ (8)
2I ₂ + I ⁻ → I ₅ ⁻ (9)
3I ₂ + I ⁻ → I ₇ ⁻ (10)
4I ₂ + I ⁻ → I ₉ ⁻ (11)
Iodide ions are thought to stably concentrate in the lower phase by complexing with iodine. In addition, sulfuric acid and hydrogen iodide, which are slightly dissolved in the lower phase liquid, react with each other, and sulfur compounds such as sulfur and hydrogen sulfide are generated as by-products, and hydrogen iodide in the lower phase is reduced.
Japanese Patent Publication No. 60-52081 Japanese Examined Patent Publication No. 60-48442 Japanese Examined Patent Publication No. 4-37001 Japanese Examined Patent Publication No. 4-37002 Japanese Patent No. 40899939 Japanese Patent No. 4089940 Japanese Patent No. 4127644 M. Sakurai, H. Nakajima, R. Amir, K. Onuki, and S. Shimizu, Experimental study on side-reaction occurrence condition in the iodine-sulfur thermochemical hydrogen production process, International Journal of Hydrogen Energy, 25 (2000) 613-619. M. Sakurai, H. Nakajima, K. Onuki, and S. Shimizu, Investigation of 2 liquid phase separation characteristic on the iodine-sulfur thermochemical hydrogen production process, International Journal of Hydrogen Energy, 25 (2000) 605-611.

  In the prior art, the Bunsen reaction, which is a hydrogen iodide production reaction, is performed, followed by two-phase separation, and the produced hydrogen iodide and sulfuric acid are separated by a specific gravity difference. At this stage, the upper phase sulfuric acid is separated. Dissolves in a mixed aqueous solution of hydrogen iodide and iodine in the lower phase, and hydrogen iodide and sulfuric acid react to reduce hydrogen iodide. Further, if the lower phase liquid is distilled with sulfuric acid mixed, it reacts with hydrogen iodide to produce sulfur and hydrogen sulfide.

14HI + 2H ₂ SO ₄
→ H ₂ S + 7I ₂ + S + 8H ₂ O (12)
As can be seen from the reaction formula (12), 7 mol of hydrogen iodide is consumed per 1 mol of sulfuric acid. Therefore, if there is even a slight amount of sulfuric acid, hydrogen iodide that can be concentrated in the lower phase under pressurized conditions will disappear.

  A similar reaction occurs with sulfur dioxide. That is, as can be seen from the following reaction formula (13), 5 mol of hydrogen iodide is consumed per 1 mol of sulfur dioxide.

10HI + 2SO ₂ → H ₂ S + 5I ₂ + S + 4H ₂ O (13)
Therefore, it is desirable to remove the sulfur compound from the lower phase liquid before isolating hydrogen iodide by distillation.

  This invention is made | formed in view of the said situation, Comprising: While making a hydrogen iodide production | generation reaction (reaction formula (1)), hydrogen sulfide is separated by isolate | separating the produced | generated sulfuric acid and hydrogen iodide. The purpose is to improve the production efficiency and consequently the hydrogen production efficiency.

  In order to achieve the above object, a method for producing hydrogen iodide according to the present invention generates iodine solution by dissolving iodine in a predetermined solvent that can dissolve iodine and hydrogen iodide and is not mixed with an aqueous solution. Injecting sulfur dioxide and sulfur dioxide dissolved in water into the iodine solution to cause bunsen reaction to produce hydrogen iodide and sulfuric acid, and dissolving hydrogen iodide produced by the bunsen reaction in the predetermined solvent And separating from the sulfuric acid aqueous solution produced by the Bunsen reaction.

  In addition, the method for producing hydrogen iodide according to the present invention can dissolve iodine and hydrogen iodide in a container containing iodine, an aqueous solution of hydrogen iodide produced by the Bunsen reaction and an aqueous sulfuric acid solution, and mixed with the aqueous solution. A method for producing hydrogen iodide, comprising mixing a predetermined solvent not to be dissolved, dissolving iodine and hydrogen iodide in the predetermined solvent and separating from the aqueous sulfuric acid solution.

  In addition, the hydrogen iodide production apparatus according to the present invention includes a sulfur dioxide dissolving tank that dissolves sulfur dioxide in water under pressure to produce a sulfurous acid aqueous solution, and can dissolve iodine and hydrogen iodide, and is mixed with the aqueous solution. An iodine solution in which iodine is dissolved in a predetermined solvent; a Bunsen reaction tank that receives a sulfurous acid aqueous solution from the sulfur dioxide dissolution tank and causes a Bunsen reaction in a pressurized state to generate hydrogen iodide and sulfuric acid; and the Bunsen Distillation tower reboiler and condenser for obtaining hydrogen iodide by distilling the predetermined solvent taken out from the lower part of the reaction tank and hydrogen iodide and iodine dissolved in the solvent, and iodine separated by the condenser And a pipe for returning the predetermined solvent to the Bunsen reaction layer, and a sulfuric acid aqueous solution taken out from the upper part of the Bunsen reaction tank into sulfur dioxide, water and oxygen. Sulfuric acid decomposing column that is characterized by having a a piping sulfur dioxide obtained by the sulfuric acid decomposing column back into the sulfur dioxide dissolving tank.

  Further, the hydrogen production apparatus according to the present invention includes a sulfur dioxide dissolution tank that dissolves sulfur dioxide in water under pressure to produce a sulfurous acid aqueous solution, a predetermined that can dissolve iodine and hydrogen iodide and does not mix with the aqueous solution. An iodine solution in which iodine is dissolved in the solvent, a Bunsen reaction tank that receives a sulfurous acid aqueous solution from the sulfur dioxide dissolution tank and causes a Bunsen reaction to occur under pressure to generate hydrogen iodide and sulfuric acid, and the Bunsen reaction tank A distillation tower reboiler and condenser for obtaining hydrogen iodide by distilling hydrogen iodide and iodine dissolved in the solvent, and iodine separated by the condenser and the A pipe for returning a predetermined solvent to the Bunsen reaction layer, and a sulfuric acid solution for decomposing the sulfuric acid aqueous solution taken out from the upper part of the Bunsen reaction tank into sulfur dioxide, water and oxygen. A decomposition tower, a pipe for returning the sulfur dioxide obtained in the sulfuric acid decomposition tower to the sulfur dioxide dissolution tank, a hydrogen iodide decomposition tower for decomposing hydrogen iodide obtained in the condenser into hydrogen and iodine, And a pipe for returning iodine obtained in the hydrogen iodide decomposition tower to the Bunsen reaction layer.

  According to the present invention, while the hydrogen iodide production reaction proceeds, the sulfuric acid and hydrogen iodide produced thereby are separated, thereby improving the hydrogen iodide production efficiency and thus the hydrogen production efficiency.

  Hereinafter, embodiments of the method for separating and producing hydrogen iodide and sulfuric acid according to the present invention will be described.

[First Embodiment]
FIG. 1 is a flowchart showing a hydrogen iodide production method (hydrogen production method) according to the first embodiment of the present invention.

  Sulfur dioxide or an aqueous solution of sulfurous acid in which sulfur dioxide is dissolved in water is added to an aqueous solution containing iodine, and the produced sulfuric acid and hydrogen iodide are separated into two phases while causing the Bunsen reaction. Due to the difference in specific gravity, the produced hydrogen iodide moves to the lower phase containing iodine, and the sulfuric acid is separated into the upper phase. An ionic liquid is added to the two-phase liquid produced by the Bunsen reaction. The ionic liquid is generally a “salt” composed of only ions (anions and cations), and particularly refers to a liquid compound. The ionic liquid used here is selected so that iodine and hydrogen iodide can be dissolved and not mixed with an aqueous solution.

  Iodine dissolves into the ionic liquid in contact with the two-phase liquid, and hydrogen iodide is also taken into the ionic liquid. The sulfuric acid aqueous solution remains in the upper phase without being mixed with the ionic liquid. The phase of the ionic liquid containing hydrogen iodide and iodine is transferred to a distillation column, and hydrogen iodide is isolated and decomposed into hydrogen. Sulfur dioxide that decomposes and produces iodine, ionic liquid, and sulfuric acid is returned to the Bunsen reactor.

  Next, the operation of this embodiment will be described. Sulfur dioxide is dissolved in water to form sulfurous acid and then reacted with iodine. Sulfur dioxide is hydrated by dissolving in water, and is converted into sulfurous acid to have reducing properties. Therefore, it reacts with iodine to produce hydrogen iodide and sulfuric acid. In the stage where the amount of iodine is excessive with respect to the amount of hydrogen iodide produced by the Bunsen reaction, phase separation occurs simultaneously with the Bunsen reaction. Since iodine and hydrogen iodide have a high affinity, a complex-forming reaction between iodide ions and iodine (formulas (4) to (7)) proceeds to produce polyiodide, which is concentrated to the lower phase.

  The sulfuric acid aqueous solution having a small specific gravity is phase-separated into the upper phase. Iodine is dissolved in a two-phase solution of an aqueous sulfuric acid solution and an aqueous polyhydroiodic acid solution, and a solvent that does not mix with the aqueous solution is added. As such a solvent, for example, trioctylmethylammonium bis (trifluoromethylsulfonyl) imide, which is an ionic liquid, is suitable. Immediately after the addition, the ionic liquid phase is located between the uppermost sulfuric acid aqueous solution phase and the lowermost polyhydroiodic acid aqueous solution phase, but iodine in the polyhydroiodic acid aqueous solution phase moves to the ionic liquid phase. As the iodine moves, hydrogen iodide also moves, and two phases of an aqueous sulfuric acid phase and an ionic liquid phase in which polyhydroiodic acid is dissolved are formed. Since sulfuric acid does not dissolve in the ionic liquid, sulfuric acid and hydrogen iodide can be completely separated at this stage. Hydrogen iodide can be isolated by separating and distilling the phase of the ionic liquid in which polyhydroiodic acid is dissolved. This distillation is preferably performed at 150 ° C. or higher, for example.

  According to this embodiment, sulfuric acid and hydrogen iodide produced by the Bunsen reaction can be completely separated by using an ionic liquid as an extractant for polyhydroiodic acid. By using an ionic liquid that does not dissolve in the aqueous solution, the sulfuric acid aqueous solution is not mixed into the ionic liquid, and the water in the lower phase of the two-phase liquid that is generated as the Bunsen reaction proceeds is also included in the ionic liquid. Does not dissolve.

  By completely separating the sulfuric acid and hydrogen iodide, it is possible to completely suppress the formation of sulfur compounds due to the side reaction of sulfuric acid and hydrogen iodide in the distillation carried out after the Bunsen reaction (formula (12)).

  On the other hand, all the sulfur dioxide can be converted into sulfurous acid by dissolving it in water. Since sulfurous acid reacts quantitatively with iodine, hydrogen iodide produced by the Bunsen reaction and excess sulfur dioxide cause a side reaction and hydrogen iodide is not consumed (formula (13)).

[Second Embodiment]
FIG. 2 is a flowchart showing a hydrogen iodide production method (hydrogen production method) according to the second embodiment of the present invention.

  An aqueous sulfite solution in which iodine is dissolved in an ionic liquid that dissolves iodine but does not dissolve in aqueous solution and sulfur dioxide is dissolved in water is contact-mixed. The Bunsen reaction occurs at the contact surface between the ionic liquid phase and the aqueous sulfite solution, and iodine and sulfite in the ionic liquid react to produce hydrogen iodide and sulfuric acid. The produced hydrogen iodide combines with iodine and moves into the ionic liquid. The sulfuric acid aqueous solution forms an upper phase without mixing into the ionic liquid phase.

  The phase of the ionic liquid containing hydrogen iodide and iodine is transferred to a distillation column, and hydrogen iodide is isolated and decomposed into hydrogen. Sulfur dioxide that decomposes and produces iodine, ionic liquid, and sulfuric acid is returned to the Bunsen reactor. The distillation of the ionic liquid containing hydrogen iodide is preferably performed at 150 ° C. or higher, for example.

  Similar to the first embodiment, sulfur dioxide is dissolved in water to form sulfurous acid, and then reacted with iodine. Sulfur dioxide is hydrated by dissolving in water, and is converted into sulfurous acid to have reducing properties. Therefore, it reacts with iodine to produce hydrogen iodide and sulfuric acid. In the stage where the amount of iodine is excessive with respect to the amount of hydrogen iodide produced by the Bunsen reaction, phase separation occurs simultaneously with the Bunsen reaction. Since iodine and hydrogen iodide have a high affinity, a complex-forming reaction between iodide ions and iodine (formulas (4) to (6)) proceeds to produce polyhydrogen iodide, which is concentrated to the lower phase.

  The sulfuric acid aqueous solution having a small specific gravity is phase-separated into the upper phase. Iodine is dissolved in a two-phase solution of an aqueous sulfuric acid solution and an aqueous polyhydroiodic acid solution, and a solvent that does not mix with the aqueous solution is added. As such a solvent, for example, trioctylmethylammonium bis (trifluoromethylsulfonyl) imide, which is the ionic liquid described in the first embodiment, is suitable. Immediately after the addition, the ionic liquid phase is located between the uppermost sulfuric acid aqueous solution phase and the lowermost polyhydroiodic acid aqueous solution phase, but iodine in the polyhydroiodic acid aqueous solution phase moves to the ionic liquid phase. As the iodine moves, hydrogen iodide also moves, and two phases of an aqueous sulfuric acid phase and an ionic liquid phase in which polyhydroiodic acid is dissolved are formed. Since sulfuric acid does not dissolve in the ionic liquid, sulfuric acid and hydrogen iodide can be completely separated at this stage. Hydrogen iodide can be isolated by separating and distilling the phase of the ionic liquid in which polyhydroiodic acid is dissolved.

  In this embodiment, the Bunsen reaction is caused at the interface of the ionic liquid or in the ionic liquid, and the produced hydrogen iodide is extracted into the ionic liquid as polyhydriodic acid, thereby allowing sulfuric acid and hydrogen iodide produced by the Bunsen reaction to be extracted. It can be completely separated. By using an ionic liquid that does not dissolve in the aqueous solution, the sulfuric acid aqueous solution is not mixed into the ionic liquid, and the water in the lower phase of the two-phase liquid that is generated as the Bunsen reaction proceeds is also included in the ionic liquid. Does not dissolve.

  By completely separating the sulfuric acid and hydrogen iodide, it is possible to completely suppress the formation of sulfur compounds due to the side reaction of sulfuric acid and hydrogen iodide in the distillation carried out after the Bunsen reaction (formula (12)).

  On the other hand, all the sulfur dioxide can be converted into sulfurous acid by dissolving it in water. Since sulfurous acid reacts quantitatively with iodine, hydrogen iodide produced by the Bunsen reaction and excess sulfur dioxide cause a side reaction and hydrogen iodide is not consumed (formula (13)).

[Third Embodiment]
FIG. 3 is a schematic configuration diagram of a hydrogen iodide production apparatus (hydrogen production apparatus) according to a third embodiment of the present invention.

  The hydrogen production apparatus includes a sulfur dioxide dissolving section (1, 2), a pressurized Bunze reaction tank 3, a distillation section (4, 5, 6), a hydrogen iodide decomposition tower 8, a sulfuric acid decomposition tower 10, pipes 11 to 18, a pressure It is comprised from an adjustment part (19,20,21) etc.

  The sulfur dioxide dissolving section includes a sulfur dioxide dissolving tank 1 and a water supply tank 2, and sulfur dioxide generated from the sulfuric acid decomposition tower 10 is combined with water from the water supply tank 2 via the pipe 11 and the sulfur dioxide dissolving tank 1. To introduce. At this time, sulfur dioxide is adjusted and controlled using a pressure pump (not shown) and a back pressure valve 19 so that the pressure in the sulfur dioxide dissolution tank 1 is 0.1 MPa or more by a gauge pressure gauge. After sulfur dioxide is completely dissolved and hydrated in the sulfur dioxide dissolution tank 1 to produce a sulfurous acid aqueous solution, the hydrated sulfur dioxide is supplied to the pressurized Bunsen reaction tank 3.

  In the pressurized Bunsen reaction tank 3, iodine, water and a predetermined solvent are put in advance. As in the first and second embodiments, the predetermined solvent is a solvent that can dissolve iodine and hydrogen iodide and does not mix with an aqueous solution, and is, for example, an ionic liquid having such characteristics. In the pressurized Bunsen reactor 3, iodine and sulfur dioxide hydrated water (sulfurous acid aqueous solution) is subjected to a Bunsen reaction to generate hydrogen iodide and sulfuric acid. A back pressure valve 20 is connected to the pressurized Bunsen reaction tank 3, and the pressure in the pressurized Bunsen reaction tank 3 is adjusted to be, for example, 0.1 MPa or more with a gauge pressure gauge.

  After the Bunsen reaction, only the lower phase liquid in the pressurized Bunsen reaction tank 3 containing iodine and hydrogen iodide is pumped to the distillation tower reboiler 4 via the pipe 12 to perform distillation. The hydrogen iodide distilled by the distillation column reboiler 4 is led to the condenser 5, cooled with a refrigerant, and collected as a liquefied gas in the hydrogen iodide recovery pipe 6. After distillation, the ionic liquid containing iodine remaining in the distillation column reboiler 4 is returned to the pressurized Bunsen reactor 3 via the pipe 15.

  On the other hand, the sulfuric acid aqueous solution separated into the upper phase of the pressurized Bunsen reactor 3 is sent to the sulfuric acid decomposition tower 10 via the pipe 13. Water generated during the decomposition of sulfuric acid returns to the water supply tank 2 via the pipe 17. Sulfur dioxide generated from the sulfuric acid decomposition tower 10 is returned to the sulfur dioxide dissolution tank 1 via the pipe 18.

  The hydrogen iodide collected in the hydrogen iodide recovery pipe 6 is sent to the hydrogen iodide storage tank 7 through the back pressure valve 21. Hydrogen iodide is vaporized in the hydrogen iodide storage tank 7 and sent to the hydrogen iodide decomposition tower 8 via the pipe 14 where it is decomposed into hydrogen and iodine. Hydrogen generated in the hydrogen iodide decomposition tower 8 is recovered as a product, and iodine is returned to the pressurized Bunsen reactor 3 through the pipe 16 and reused in the Bunsen reaction. In FIG. 3, two hydrogen iodide decomposition towers 8 are juxtaposed, but any number may be used.

  Before the hydrogen production apparatus described above reacts iodine, sulfur dioxide, and water to produce hydrogen iodide and sulfuric acid, first, sulfur dioxide is dissolved in water under pressure and hydrated. By injecting sulfur dioxide into water in the sulfur dioxide dissolving tank 1 under a pressurized condition, sulfur dioxide can be completely dissolved in water, and an aqueous sulfite solution is generated. Since hydrated sulfur dioxide has reducibility, when it is added to iodine, it causes an oxidation-reduction reaction with iodine to produce hydrogen iodide and sulfuric acid. By carrying out pressure feeding to the pressurized Bunsen reaction tank 3 while maintaining the pressurized state, an aqueous sulfurous acid solution maintaining a high concentration can be subjected to an oxidation-reduction reaction with iodine. Therefore, the hydrogen iodide produced per unit amount of sulfur dioxide to be used in comparison with atmospheric pressure conditions is larger under pressurized conditions.

  In the stage where the amount of iodine is excessive with respect to the amount of hydrogen iodide produced by the Bunsen reaction, phase separation occurs simultaneously with the Bunsen reaction. Since iodine and hydrogen iodide have a high affinity, a complex-forming reaction between iodide ions and iodine (formulas (4) to (6)) proceeds to produce polyhydrogen iodide, which is concentrated to the lower phase.

  The sulfuric acid aqueous solution having a small specific gravity is phase-separated into the upper phase. At this time, if a solvent (ionic liquid) that dissolves iodine but does not dissolve in aqueous solution exists in the two-phase liquid, iodine in the lower phase dissolves and moves into the ionic liquid. Transition to ionic liquid phase. Since sulfuric acid does not dissolve in the ionic liquid, hydrogen iodide and sulfuric acid can be completely separated at this stage.

  Phase separation of hydrogen iodide and sulfuric acid can be improved by using an ionic liquid that is chemically inert and does not react with the upper and lower phases as a solvent that dissolves iodine and does not dissolve in aqueous solution. . In normal two-phase separation, polyiodide produced by the complexing reaction of iodine and hydrogen iodide is concentrated to the lower phase solution, but the upper phase sulfuric acid aqueous solution is always in contact with the lower phase. The sulfuric acid aqueous solution of the upper phase moves to the lower phase until the mutual equilibrium is reached from the interface between the lower phase and the lower phase. In addition, generation of sulfur due to side reactions is also observed at the interface. The ionic liquid does not dissolve in most solvents such as water, and is chemically stable so that it does not react and decompose.

  Thus, hydrogen iodide and sulfuric acid can be completely separated in the phase separation of hydrogen iodide and sulfuric acid produced by the Bunsen reaction. When a Bunsen reaction occurs in an ionic liquid phase containing iodine, hydrogen iodide remains in the ionic liquid phase as it is because of its affinity with iodine, but sulfuric acid has a low specific gravity and does not dissolve in the ionic liquid, so it moves to the upper phase. To do. The sulfuric acid transferred to the upper phase is not mixed into the aqueous solution of polyiodide in the lower ionic liquid phase.

  According to this embodiment, sulfur dioxide is preliminarily dissolved in water to form a sulfurous acid aqueous solution, so that generation of sulfur due to the reaction of sulfur dioxide and water can be avoided. All of the injected sulfur dioxide can be reacted with iodine. As a result, sulfur dioxide that is not hydrated is not brought into the pressurized Bunsen reactor, and sulfur dioxide and hydrogen iodide produced by the Bunsen reaction cause a side reaction to produce sulfur compounds such as sulfur and hydrogen sulfide. Risk can be avoided (formula (13)).

  In the phase separation of hydrogen iodide and sulfuric acid produced by the Bunsen reaction, by incorporating iodine and hydrogen iodide in the lower phase into the ionic liquid phase, sulfuric acid is transferred to the upper phase, and hydrogen iodide is transferred to the ionic liquid phase. Polyiodic acid and sulfuric acid can be completely separated. Since sulfuric acid does not dissolve in the ionic liquid phase containing polyhydroiodic acid, side reaction between hydrogen iodide and sulfuric acid can be avoided in the lower phase (formula (12)). In addition, since the ionic liquid phase does not contain water, the ionic liquid phase is composed only of iodine, hydrogen iodide, and ionic liquid, and under a pressurized condition, the ratio of hydrogen iodide to water is 57%, which is an azeotropic composition. Therefore, hydrogen iodide can be isolated from the lower phase liquid by distillation. Since the lower phase liquid distilled at this time does not contain sulfur compounds such as sulfuric acid, hydrogen iodide can be isolated without causing a side reaction between hydrogen iodide and sulfuric acid during the lower phase liquid distillation. .

It is a flowchart which shows the hydrogen iodide manufacturing method (hydrogen manufacturing method) which concerns on the 1st Embodiment of this invention. It is a flowchart which shows the hydrogen iodide manufacturing method (hydrogen manufacturing method) which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram of the hydrogen iodide manufacturing apparatus (hydrogen manufacturing apparatus) which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sulfur dioxide dissolution tank 2 ... Water supply tank 3 ... Pressurized Bunsen reaction tank 4 ... Distillation tower reboiler 5 ... Condenser 6 ... Hydrogen iodide recovery pipe 7 ... Hydrogen iodide storage tank 8 ... Hydrogen iodide decomposition tower 10 ... Sulfuric acid decomposition tower 11, 12, 13, 14, 15, 16, 17, 18 ... piping 19, 20, 21 ... back pressure valve

Claims (8)

Iodine is dissolved in a predetermined solvent that can dissolve iodine and hydrogen iodide and not mixed with an aqueous solution to produce an iodine solution,
In this iodine solution, sulfur dioxide and sulfur dioxide dissolved in water are injected to cause Bunsen reaction to produce hydrogen iodide and sulfuric acid,
Dissolving hydrogen iodide produced by the Bunsen reaction in the predetermined solvent and separating from the sulfuric acid aqueous solution produced by the Bunsen reaction;
A process for producing hydrogen iodide, characterized in that   A predetermined solvent that can dissolve iodine and hydrogen iodide and is not mixed with the aqueous solution is mixed in a container containing iodine and an aqueous solution of hydrogen iodide and sulfuric acid generated by the Bunsen reaction. A method for producing hydrogen iodide, comprising dissolving iodine and hydrogen iodide in a solution to separate from an aqueous sulfuric acid solution. 3. The hydrogen iodide production according to claim 2, wherein the predetermined solvent dissolved with the sulfuric acid aqueous solution and dissolving iodine and hydrogen iodide is distilled to isolate hydrogen iodide. Method. The method for producing hydrogen iodide according to any one of claims 1 to 3, wherein the predetermined solvent is an ionic liquid . 5. The method for producing hydrogen iodide according to claim 4, wherein the ionic liquid is trioctylmethylammonium bis (trifluoromethylsulfonyl) imide . A method for producing hydrogen, comprising decomposing hydrogen iodide produced by the method for producing hydrogen iodide according to any one of claims 1 to 5 into hydrogen and iodine . A sulfur dioxide dissolution tank that dissolves sulfur dioxide in water under pressure to produce a sulfurous acid aqueous solution;
  An iodine solution in which iodine is dissolved in a predetermined solvent that can dissolve iodine and hydrogen iodide but not mixed with the aqueous solution, and a sulfurous acid aqueous solution is received from the sulfur dioxide dissolution tank to cause a Bunsen reaction under pressure to cause iodine. A Bunsen reactor that produces hydrogen fluoride and sulfuric acid;
  A distillation column reboiler and a condenser for distilling the predetermined solvent taken out from the lower part of the Bunsen reactor and hydrogen iodide and iodine dissolved in the solvent to obtain hydrogen iodide;
  Piping for returning iodine separated by the condenser and the predetermined solvent to the Bunsen reaction layer;
  A sulfuric acid decomposition tower for decomposing sulfuric acid aqueous solution taken out from the upper part of the Bunsen reactor into sulfur dioxide, water and oxygen;
  Piping for returning the sulfur dioxide obtained in the sulfuric acid decomposition tower to the sulfur dioxide dissolving tank;
  An apparatus for producing hydrogen iodide, comprising: A sulfur dioxide dissolution tank that dissolves sulfur dioxide in water under pressure to produce a sulfurous acid aqueous solution;
  An iodine solution in which iodine is dissolved in a predetermined solvent that can dissolve iodine and hydrogen iodide but not mixed with the aqueous solution, and a sulfurous acid aqueous solution is received from the sulfur dioxide dissolution tank to cause a Bunsen reaction under pressure to cause iodine. A Bunsen reactor that produces hydrogen fluoride and sulfuric acid;
  A distillation column reboiler and a condenser for distilling the predetermined solvent taken out from the lower part of the Bunsen reactor and hydrogen iodide and iodine dissolved in the solvent to obtain hydrogen iodide;
  Piping for returning iodine separated by the condenser and the predetermined solvent to the Bunsen reaction layer;
  A sulfuric acid decomposition tower for decomposing sulfuric acid aqueous solution taken out from the upper part of the Bunsen reactor into sulfur dioxide, water and oxygen;
  Piping for returning the sulfur dioxide obtained in the sulfuric acid decomposition tower to the sulfur dioxide dissolving tank;
  A hydrogen iodide decomposition tower that decomposes hydrogen iodide obtained in the condenser into hydrogen and iodine;
  Piping for returning iodine obtained in the hydrogen iodide decomposition tower to the Bunsen reaction layer;
  The hydrogen production apparatus characterized by having.

Images