JPH09291058A - Removal of iodine compound in organic medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove iodine compounds in an organic medium by bringing them into contact with an ion exchange resin. SOLUTION: Iodine compound(s) in an organic Inedium, esp. acetic acid or its mixture with acetic anhydride is brought into contact with a cation exchange resin bearing active sites on its surface alone with at least 1% of the sites exchanged with silver or mercury form and having an average pore size of >=100Å at a temperature higher than the solidifying point of the liquid to be treated but lower than the heat-resistant temperature of the resin. Owing to using the above ion exchange resin, the diffusion resistance inside the ion exchange resin granules is reduced to effect improved reaction rate and utilization of the silver or mercury supported, resulting in efficient removal of the iodine compound(s) in the organic medium.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing iodine compounds contained in an organic medium.

In particular, the present invention relates to a method for removing iodine compounds contained in acetic acid or a mixture of acetic acid and acetic anhydride.

[0003]

2. Description of the Related Art Various methods for removing iodine compounds from an organic medium have been disclosed. Among them, the presence of iodine compounds contained in acetic acid cannot be often removed even by separation by distillation, leaving behind acetic acid. When it is chemically changed in 1., since it has a serious problem of causing iodine compound contamination such as shortening the life of a metal catalyst in the production of vinyl acetate, many removal methods have been studied.

For example, Japanese Patent Application Laid-Open No. 58-18529 discloses the use of anion exchange resin. In this case, it is necessary to remove the iodine portion which is difficult to separate after the ion exchange treatment by distillation. Japanese Patent Publication No. 5-21031
In Japanese Patent Laid-Open No. 1982339/1992, a strongly acidic cation exchange resin having a macroreticular porous structure and containing silver and mercury is used. Although the use of a resin is disclosed, the reaction mechanism between the iodine compound and the supported silver has not been analyzed, and the reaction rate and removal performance inside the resin are not satisfactory. That is, it has a drawback that the supported silver and mercury are not effectively used for removing iodine compounds.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently remove iodine compounds contained in an organic medium. In particular, it is to provide a method for efficiently removing an iodine compound contained in acetic acid or a mixture of acetic acid and acetic anhydride. More specifically, it is intended to improve the reaction rate by reducing the diffusion resistance in the ion-exchange resin particles and to provide the use of the ion-exchange resin having a structure capable of effectively using the supported silver or mercury.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies to achieve the above-mentioned object, and as a result, brought an organic medium containing an iodine compound into contact with an ion exchange resin to obtain an iodine compound contained in the medium. In addition to the kinetic analysis of the mechanism of iodine compound removal in the method of removing methane, the analysis of the waste resin after use showed that the diffusion resistance in the resin pores was dominant and that the reaction was caused by the reaction. The inventors have found that silver and mercury in the active sites inside the resin are not effectively used because crystals of silver iodide are deposited on the surface of the resin and hinder the reaction inside the resin, thus completing the present invention. That is, by using a cation exchange resin having an active site only on the resin surface and at least 1% of the active site being exchanged into a silver form or a mercury form, the reaction occurs only on the surface and / or the reaction progresses. By avoiding the clogging of the pore entrance due to the generated silver iodide or mercury iodide crystals, the reaction rate can be improved and the supported silver or supported mercury can be effectively used, and the iodine compound can be most effectively removed. After finding out the above, the present invention was achieved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically.

The ion exchange resin used in the present invention is preferably a cation exchange resin composed of a sulfonated copolymer of styrene and divinylbenzene.

The method of converting the ion exchange resin to the silver or mercury form is not particularly important, and any silver salt having a suitable solubility in water or a non-aqueous organic medium can be used. Silver oxide, silver acetate, and silver nitrate are typical silver salts. The required amount of silver is 1 or more times the molar ratio of the iodine compound to be removed.

The average pore diameter of the ion exchange resin is 10
It is preferably 0 angstrom or more, and more preferably 600 angstrom or more.

The surface layer having active sites is preferably up to ½ of the distance from the surface to the center as viewed from the outer surface. More preferably, it is up to 1/4. From this point of view, it is effective to use ion exchange fibers. As the ion exchange resin having an active site only on the surface layer, a surface-supported ion exchange resin is preferably used, but by adjusting so that only the surface has an active site without using the above-mentioned special resin. The obtained ion exchange resin can also be used. As a method for supporting the ion exchange resin on the surface layer, a carrier used industrially, such as a filler used in liquid chromatography, for example, alumina, silica, silica-alumina, zeolite, styrene on the outside of activated carbon, etc. There is a method of supporting a layer of an ion exchange resin having a divinylbenzene copolymer as a main skeleton. The active site of this surface layer may be replaced with silver or mercury type. As another method without using such a special resin, a cation system other than silver or mercury and having a smaller selection coefficient ratio than silver ion-proton exchange or mercury ion-proton exchange is used. The active site of the exchange resin is exchanged in advance, and then temperature, concentration, p
There is a method of selectively exchanging the active site of the surface layer of the ion exchange resin with silver or mercury by appropriately selecting the ion exchange conditions such as H, solvent and time.

The organic medium containing an iodine compound is an organic acid, alcohol, ester or the like, and is particularly suitable for removing the iodine compound contained in acetic acid or a mixture of acetic acid and acetic anhydride. More specifically, in the presence of a catalyst system containing a rhodium compound, methyl iodide and an alkali metal iodide as a co-catalyst, at least one selected from methanol, methyl acetate and dimethyl ether and carbon monoxide or carbon monoxide and hydrogen. It is most suitable for removing the iodine compound contained in the mixture of acetic acid or acetic anhydride obtained by reacting with the mixture of. The present invention is not limited to the removal of the halogen compound in the organic medium, but can be applied to the removal of the halogen compound in water or an aqueous solution.

The iodine compounds to be removed include hydrogen iodide, methyl iodide, ethyl iodide, protyl iodide,
Carbon number of alkyl group such as butyl iodide, pentyl iodide, hexyl iodide, heptyl iodide, octyl iodide
Inorganic iodide salts, such as lithium iodide, for alkyl iodides up to about 0 and mixtures thereof,
It is also effective against iodine ions. Also, halogens other than iodine, such as chlorine, are effective against the corresponding alkyl chlorides, inorganic chloride salts, and chloride ions. The method of the present invention can be widely applied to the removal of any concentration of iodine compounds present in an organic medium, and can also be applied to the removal of minute amounts of iodine compounds such as 1 ppm or less and 1 ppb or less.

When the ion exchange resin is used industrially,
The fluid to be continuously processed is generally flowed in the form of a packed bed, but it may be used in a batch system or a fluidized bed system. When used in a continuous flow system, it is common to adopt a flow rate and a bed volume per hour that reduce the influence of the diffusion resistance of the membrane, for example, 0.5 to 40 per hour.
Although they can be contacted in a bed volume, economically advantageous conditions may be used depending on the characteristics of the resin used, the type, characteristics, and concentration of the iodine compound to be removed.

The treatment temperature is preferably above the freezing point of the liquid to be treated and below the heat-resistant temperature of the resin, for example 17 to 120 ° C. when used in acetic acid. When handling acetic acid, stainless steel is generally used.
There is no risk of corrosion even when used at 20 ° C.

These methods are not limited to ion exchange resins, but are industrially used carriers such as, for example,
It can also be applied when alumina, silica, silica-alumina, zeolite, activated carbon or the like is used.

[0017]

According to the present invention, by using an ion exchange resin containing silver or mercury having an active site only on the surface, the reaction rate is improved by reducing the diffusion resistance in the ion exchange resin particles, The supported silver or mercury can be effectively used, and the iodine compound in the organic medium can be efficiently removed.

[0018]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

The method for removing the iodine compound in the organic medium when the ion exchange resins shown in Comparative Examples 1 and 2 and Example 1 are used is as follows.

A strongly acidic ion exchange resin having silver supported on the active site of the resin was placed in a 500 ml separable flask and kept at 31 ° C. in a constant temperature water bath. 40 as an iodine compound
Acetic acid to which ppm hexyl iodide has been added is charged into a separable flask containing an ion exchange resin, and the resin and acetic acid are batch-contacted by stirring with an anchor type stirring blade at a rotation speed of 350 rpm. In this case, hexyl iodide in the feed solution:
The amount of silver supported on the ion exchange resin is 1: 4 in molar ratio. Acetic acid in a separable flask was collected every certain time, and a gas chromatograph with an electron capture detector (ECD-
The hexyl iodide concentration is analyzed by GC) to obtain the removal rate of hexyl iodide.

[0021]

[Comparative Example 1] [Amber list 15 (giant reticulated resin)] Amber list 15 (product of Rohm and Haas Co., exchange capacity 1.8 meq / ml, average pore diameter) in which 41% of the resin active sites were exchanged for silver. 240 angstrom) particle size 0.59 ~
0.5 ml of 0.84 mm was stirred and contacted with 500 g of iodine compound-containing acetic acid. Table 1 shows the removal rates of iodine compounds.

[0022]

Comparative Example 2 [Bayer Catalyst K2631 (giant net resin)]
Bayer Catalyst K2631 with 57% of the resin active sites replaced by silver (Bayer product, exchange capacity 1.3 m
eq / ml, average pore size 650 angstroms) 0.59 to 0.84 mm in particle size 0.5 ml
Is contacted with 500 g of acetic acid as in Comparative Example 1. Table 1 shows the removal rates of iodine compounds.

[0023]

Example 1 [MCIGEL SCK01 (Surface-Supporting Resin)] Strongly acidic ion exchange resin MCIGEL SCK01 (Mitsubishi Chemical Co., particle size 11 μm, exchange capacity) in which almost 100% of active sites existing only on the surface were exchanged for silver form. 25 μeq / g,
4.5 g of average pore diameter of 1250 angstroms or less and surface layer thickness of 1/4 to 1/5 of radius) is brought into contact with 150 g of acetic acid containing an iodine compound. Table 1 shows the removal rates of iodine compounds. Table 1 shows the removal rates of iodine compounds.

[0024]

[Table 1] From Table 1, it can be seen that the surface-supported ion exchange resin SCK01 has a very high reaction rate, and the supported silver is effectively used for removing the iodine compound. In addition, when the cross section of the resin was analyzed after the experiment, Amberlyst 1
5. Unused silver was confirmed in the central part of both resins of Catalyst K2631. The amount is almost equivalent to the removal rate,
There were more amberlists. Therefore, if an ion exchange resin containing silver or mercury having an active site only on the surface is used, the usage rate of silver or mercury is significantly improved,
A great effect is obtained such that the life for the removal of the iodine compound is remarkably increased.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C07C 53/12 2115-4H C07C 53/12 // C07B 61/00 300 C07B 61/00 300

Claims (7)

[Claims] 1. A method for removing an iodine compound contained in a medium by bringing an organic medium containing an iodine compound into contact with the ion exchange resin, wherein the ion exchange resin has an active site only on the surface thereof. A method for removing an iodine compound contained in an organic medium, characterized in that at least 1% is a cation exchange resin exchanged into a silver form or a mercury form. 2. A surface having an active site of an ion exchange resin,
2. A method according to claim 1, characterized in that it is up to 1/2 of the distance from the surface to the center as seen from the outer surface. 3. The method according to claim 1 or 2, wherein the cation exchange resin has an average pore diameter of 100 angstroms or more. 4. The method according to claim 1, 2 or 3, characterized in that 1% to 100% of the active sites are exchanged for silver or mercury form. 5. The organic medium according to claim 1, wherein the organic medium is acetic acid or a mixture of acetic acid and acetic anhydride.
The method described in the section. 6. An organic medium containing an iodine compound, selected from the group consisting of methanol, methyl acetate and dimethyl ether in the presence of a catalyst system containing a rhodium compound, methyl iodide and an alkali metal iodide as a cocatalyst. 6. The method according to claim 5, which is acetic acid or a mixture of acetic acid and acetic anhydride obtained by reacting the above with carbon monoxide or a mixture of carbon monoxide and hydrogen. 7. The method according to claim 6, wherein the iodine compound is selected from alkyl iodides such as methyl iodide and hexyl iodide, and mixtures thereof.