JP4434833B2 - Method for regenerating catalyst solution - Google Patents

Description

  The present invention relates to a method for regenerating a catalyst solution containing a Group 8 metal catalyst and a corrosive metal product. In particular, it relates to improvements in the process for producing carboxylic acids by carbonylation of alcohols and / or reactive derivatives thereof using Group 8 metal catalysts. Specifically, the present invention relates to an improved method for regenerating a Group 8 metal-containing catalyst solution used for carbonylation.

Methods for carbonylating alcohol and / or reactive derivatives thereof with a catalyst solution formed by mixing a Group 8 metal catalyst such as rhodium and an alkali metal salt and / or a halogen component are already known (for example, patents). The method for producing carboxylic acid is the most commercially effective method. This rhodium-containing catalyst solution is separated from the reactor effluent and recycled to the reactor. However, in continuous operation for a long time, corrosive metals such as iron, nickel, chromium, molybdenum, tungsten, and manganese dissolve and accumulate in the reaction solution due to corrosion of the material of the device, and these promote the side reaction, It is known that by-product gases such as methane, hydrogen, and carbon dioxide are generated (see, for example, Patent Document 2). The promotion of by-product gas generation due to the presence of such corrosive metal products not only deteriorates the use rate of carbon monoxide and alcohol and / or reactive derivatives thereof as raw materials, but also reduces the total pressure during the reaction. There is a need to increase the pressure of the reactor more than necessary, or measures such as lowering the gas partial pressure at the expense of productivity. Furthermore, the corrosive metal product is said to react with ionic iodine, thereby reducing the reactivity of rhodium with ionic iodine and destabilizing the catalyst system. Therefore, a process for regenerating and reusing the rhodium-containing catalyst solution is required. As a method for regenerating a rhodium-containing catalyst solution, a method in which a rhodium-containing catalyst solution is brought into contact with an ion exchanger is already known (see, for example, Patent Document 3 and Patent Document 4). For example, the removal rate of chromium and molybdenum is not high, and the temperature in the ion exchange treatment is increased in order to increase the removal rate, so that the lifetime of the ion exchanger is shortened and the cost of heat treatment is high. There is still room for improvement. Further, in Patent Document 5, in order to optimize the removal of the corrosive metal product, water is added when the catalyst solution is brought into contact with the ion exchange resin to increase the water concentration in the catalyst solution (about 50 wt%). ), But the removal efficiency is still not sufficient.
Japanese Patent Publication No.47-3334 Japanese Patent Publication No. 8-011199 Japanese Patent Publication No.59-18099 Japanese Patent Application No. 9-516650 Japanese National Patent Publication No. 2000-511100

  An object of the present invention is to recover a catalyst solution having a reduced corrosive metal product content from a catalyst solution containing a Group 8 metal catalyst and a corrosive metal product. In particular, by removing the corrosive metal product contained in the Group 8 metal-containing catalyst solution used in the production of carboxylic acids by carbonylation of alcohol and / or reactive derivatives thereof, the Group 8 metal content is removed. It is an object to regenerate the high productivity of the catalyst solution. Specifically, it is an object to improve a method for regenerating a Group 8 metal-containing catalyst solution using an ion exchanger.

  As a result of intensive studies on a method for recovering a catalyst solution having a reduced corrosive metal product content from a catalyst solution containing a Group 8 metal catalyst and a corrosive metal product, the present inventors have completed the present invention. Is. That is, a catalyst solution containing a Group 8 metal catalyst and a corrosive metal product is treated with a strong acid, and then contacted with a cation exchanger to recover a catalyst solution having a reduced corrosive metal product content. A method for regenerating the catalyst solution is provided. In particular, a group 8 metal-containing catalyst solution used in the production of carboxylic acids by carbonylation of alcohols and / or reactive derivatives thereof, and the group consisting of iron, nickel, chromium, molybdenum, tungsten, manganese and mixtures thereof A catalyst characterized by increasing the removal rate of corrosive metal products by treating a carbonylation reaction catalyst solution containing at least one metal selected from the group consisting of strong acid and then contacting with a cation exchanger. A method for regenerating a liquid is provided.

  According to the present invention, a Group 8 metal-containing catalyst solution containing a corrosive metal product is treated with a strong acid such as hydroiodic acid, hydrochloric acid, sulfuric acid, or nitric acid, and then contacted with a cation exchanger. A catalyst solution having a reduced content of corrosive metal products can be recovered. In particular, the removal rate of some corrosive metal products such as chromium and molybdenum remains at room temperature, compared with the case of contacting with a lithium ion exchange resin without performing a strong acid treatment. Can be increased. Further, the Group 8 metal, which is the main component of the catalyst solution, is not removed even by the strong acid treatment, and the corrosive metal product can be selectively and efficiently removed.

  The process of the present invention includes Group 8 metal catalysts and corrosive metal products, ie, metals and metal products that are eluted and accumulated by corrosion of equipment materials such as iron, nickel, chromium and molybdenum, tungsten, manganese, etc. It can be used to regenerate the catalyst solution. The catalyst solution in which the regeneration method of the present invention can be particularly preferably used is a catalyst solution in the production of carboxylic acid by carbonylation in which alcohol and / or a reactive derivative thereof is reacted with carbon monoxide.

Next, a method for producing a carboxylic acid by carbonylation of the alcohol and / or reactive derivative thereof and a catalyst solution will be described. As the catalyst used for the carbonylation reaction of an alcohol and / or a reactive derivative thereof to a carboxylic acid, a Group 8 metal component and a halogenation promoter are preferably used. Examples of the Group 8 metal component include rhodium, iridium, palladium, ruthenium and the like, but rhodium is preferably used among rhodium and iridium. In general, the rhodium component exists in the form of a coordination compound of rhodium, for example, [Rh (CO) ₂ Cl] ₂ , Li [Rh (CO) ₂ I ₂ ], [Rh (CO) ₂ I] ₂ , [Rh (COD) Cl] ₂ (COD means cyclooctadiene), etc., and RhCl ₃ , RhCl ₃ .3H ₂ O, RhBr ₃ , RhI ₃ , rhodium acetate (II), dicarbonylacetylacetate Natrodium, RhCl (CO) (PPh ₃ ) ₂ and the like are used. When a rhodium component is used, the concentration of the rhodium compound in the reaction solution is a rhodium concentration, and is 50 to 5000 ppm, preferably 100 to 1500 ppm, more preferably 400 to 800 ppm.

  As halogen promoters, organic halides, ie alkyl, aryl, substituted alkyl or aryl halides can be used. The halogenated cocatalyst is preferably an alkyl halide corresponding to the alkyl group of the supplied alcohol. For example, the halogenated cocatalyst for the carbonylation reaction of methanol to acetic acid is a methyl halide, particularly methyl iodide, methyl bromide or methyl chloride. Although methyl iodide is particularly preferable, methyl iodide is preferably used. The concentration of the alkyl halide in the reaction solution is 1 to 20 wt%, preferably 2 to 16 wt%, more preferably 5 to 16 wt%.

For the purpose of stabilizing the catalyst and suppressing side reactions, iodide salts are preferably used particularly under low moisture conditions (for example, about 0.1 to about 5 wt% in the reaction solution). The iodide salt may be any as long as it generates iodine ions in the reaction solution. For example, alkali metal iodide salts such as LiI, NaI, KI, RbI, and CsI, BeI _2, MgI _2, alkaline earth metal iodide salts such as CaI _2, there is a BI _3, AlI aluminum metal iodide salts such as _3. In addition to metal iodide salts, organic iodide salts may be used, for example, quaternary phosphonium iodide salts (methyl iodide adducts such as tributylphosphine and triphenylphosphine or hydrogen iodide adducts), quaternary ammonium iodide salts. (Methyl iodide adducts or hydrogen iodide adducts such as tertiary amines, pyridines, imidazoles, imides, etc.). In particular, alkali metal iodide salts such as LiI are preferred. The amount of the iodide salt used is 0.01 to 35 wt%, preferably 0.05 to 20 wt% as iodide ions in the reaction solution.

Suitable alcohols used in the carbonylation reaction include, for example, C _1-10 alkyl alcohols such as methanol, ethanol, propanol, isopropanol, butanol and hexanol, C _3-10 cycloalkyl alcohols such as cyclohexanol and cyclooctanol, and phenol. Phenols such as benzyl alcohol, aralkyl alcohols such as phenethyl alcohol, and the like, and C _1-10 alkyl alcohols such as methanol, ethanol, propanol, butanol, pentanol, and hexanol are preferable, and methanol is particularly preferable.
As the reactive derivative of an alcohol, esters such as methyl acetate, C _2-6 alkyl carboxylic acids -C _1-6 alkyl esters such as ethyl acetate, dimethyl ether, diethyl ether, diisopropyl ether, and di-butyl ether C _1-6 And ethers such as alkyl ethers.

  The water concentration in the reaction solution is 15 wt% or less, preferably 10 wt% or less, more preferably 0.1 to 5 wt%, and the remaining main component is a carboxylic acid that is a product and a reaction solvent. Depending on the raw material used and the water concentration, carboxylic acid (for example, acetic acid) and carboxylic anhydride (for example, acetic anhydride) can be produced together. Typical temperatures for the carbonylation reaction are in the range of about 150-250 ° C, preferably about 180-220 ° C. The carbon monoxide partial pressure in the reactor can vary widely, but is typically about 2 to 30 atmospheres, preferably 4 to 15 atmospheres. The hydrogen partial pressure can also vary over a wide range, but it is preferable to control it to 2 atmospheres or less, preferably 1 atmosphere or less. The total reactor pressure is preferably in the range of about 15-40 atmospheres due to the vapor pressure of the liquid, including by-products and partial pressure. The reaction may be a continuous reaction or a batch reaction, but is preferably carried out by a continuous reaction. The liquid product obtained under the above reaction conditions is removed from the reactor and introduced into a flasher, for example in the case of the production of acetic acid by methanol carbonylation, mainly from acetic acid, methyl iodide, methyl acetate and water. Is separated into a volatile component consisting mainly of catalyst, iodide salt and a small amount of non-volatile component consisting of methyl acetate, methyl iodide, water, and the volatile component is removed from the top of the flasher and methyl iodide-acetic acid Sent to further purification steps including splitter-column. Non-volatile components are removed from the flasher bottom and returned to the reactor.

  As the catalyst solution subjected to the treatment of the present invention, any liquid containing a Group 8 metal catalyst and a corrosive metal product can be applied during the above-mentioned step. Preferably, the catalyst solution is taken out from the bottom of the flasher, Applies to non-volatile components returned to the reactor.

  In the present invention, the strong acid for treating the corrosive metal product contained in the Group 8 metal-containing catalyst solution is an acid having a logarithmic value (pKa) of the reciprocal of the acid dissociation constant smaller than 4, such as hydrochloric acid or sulfuric acid. , Nitric acid, hydrogen peroxide, and the like, and acidic gases having the same oxidizing power as the above acids, such as ozone, chlorine, iodine, etc., preferably hydroiodic acid. When hydroiodic acid is used as the acidic solution, the concentration of hydrogen iodide in hydroiodic acid is 40% to 60% by weight, preferably 50% by weight or more. The temperature for carrying out the strong acid treatment is 0 ° C. to 120 ° C., preferably 100 ° C. or higher. If the strong acid treatment is performed at a temperature equal to or higher than the boiling point of the catalyst solution, the operation can be performed at 120 ° C. or higher as long as the catalyst solution can be operated under a pressure condition for maintaining the catalyst solution as a liquid phase. Therefore, the strong acid treatment for regenerating the catalyst solution is performed in the reactor that performs carbonylation, in the vessel that separates the catalyst solution from the reactor effluent, or in the piping that transports the catalyst solution to each vessel. The catalyst solution can be taken out to the outside, and if desired, the catalyst solution can be taken out and contacted with a strong acid treatment and ion exchanger. It is also possible to charge. The amount of the acidic solution used for the strong acid treatment is at least 3 mol times, preferably 10 mol times or more, based on the total number of moles of all corrosive metal products contained in the catalyst solution. It is. The time required for the strong acid treatment is preferably 1 hour or more, but may be within 1 hour depending on the kind and amount of the acidic solution to be added and the reaction temperature.

  The cation exchanger used for the regeneration of the Group 8 metal catalyst solution is not particularly limited, and examples thereof include organic exchangers and inorganic exchangers. Organic exchangers are particularly preferable, and ion exchange resins are particularly preferable. Suitable resins are strong acid or weak acid cation exchange resins. The strong acid cation exchange resin is, for example, a sulfonated styrene-divinylbenzene copolymer, and many phenol-formaldehyde condensation polymers are commercially available. Weakly acidic cation exchange resins include acrylic acid or methacrylic acid or esters or corresponding nitrile copolymers, and many phenolic resins are commercially available. In the present invention, a strongly acidic cation exchange resin is preferably used. A gel type or macroreticular type resin is suitable, but a macroreticular type is preferable.

  Since the iodide salt is contained in the catalyst solution, the ion exchanger used is a type corresponding to the cation part of the iodide salt, for example, an alkali metal type when an alkali metal iodide salt is contained. If an alkaline earth metal iodide salt is contained, an alkaline earth metal ion exchanger is used. If an organic iodide salt is contained, the corresponding organic ion is used. By using the exchanger, only the corrosive metal product can be efficiently removed. In this specification, a lithium ion exchange resin is illustrated as an ion exchanger. The temperature at which the ion exchange treatment is performed may be room temperature (0 ° C. to 30 ° C.), and chromium that could not be removed without treatment at a high temperature in the conventional technique is easily contacted with the ion exchanger after the strong acid treatment, preferably by permeation. Can be removed. In removing the corrosive metal product, the flow rate of the catalyst solution through the ion exchanger is a flow rate that can sufficiently bring out the performance of the ion exchanger itself, that is, the flow rate recommended by the ion exchanger manufacturer, Usually about 1 to 20 bed volumes per hour. Preferably, the flow rate is about 1-12 bed volumes per hour. After contacting the rhodium-containing catalyst solution and the ion exchanger and exhausting the ion exchanger, the organic salt, preferably lithium acetate, is contacted at a concentration in the range of about 1 wt% to about 20 wt%, preferably permeated. By doing so, the ion exchanger can be regenerated.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Hereinafter, Examples 1 to 5 and Comparative Examples 1 to 5 show regeneration methods by removing corrosive metals from the carbonylation reaction catalyst solution. The analysis conditions of the ICP emission analyzer are as follows.
<ICP analysis conditions (chromium, molybdenum, rhodium)>
ICP condition; high frequency power 1.4kW
Coolant gas flow rate 20L / min
Plasma gas flow rate 1.4L / min
Carrier gas flow rate 1.0L / min
Carrier gas Ar
Sample preparation method; Sample dilution solvent DMF
Sample preparation Dilute with DMF so that each metal concentration in the sample is 10ppm or less.
Calibration curve method The standard solution of each metal was diluted with DMF, and a calibration curve was created at three points of 10 ppm, 5 ppm, and 1 ppm.

<Example 1>
Hydroiodic acid (44% by weight of water, 56% by weight of hydrogen iodide) in 300 g of a rhodium-containing catalyst solution (water concentration 8%) containing chromium, molybdenum, and rhodium as corrosive metal products taken out from the bottom of the flasher. 58.43 g (85 mol times the total molar amount of the corrosive metal product in the rhodium-containing catalyst solution), and poured into a glass 500 ml round bottom flask, The reaction temperature was adjusted to 100 ° C., and a strong acid treatment was performed for 3 hours. Thereafter, 50 ml of the reaction solution cooled to 25 ° C. was permeated through the ion exchange resin. As the ion exchange resin, commercially available Amberlyst 15 (sulfonated styrene-divinylbenzene copolymer) was used, and a glass column packed with 33 ml (packing height: 17 cm) at a bulk density of 0.62 g / ml was used. . The ion exchange resin was previously washed with pure water and then permeated with an aqueous lithium acetate solution to replace the lithium form. The permeation of the strong acid treated liquid to the ion exchange resin was performed at room temperature (25 ° C.) and normal pressure, and permeated at a flow rate of 100 ml / hr. The concentration of chromium, molybdenum and rhodium in the reaction solution immediately after the strong acid treatment (before permeation of the ion exchange resin) and the concentration of chromium, molybdenum and rhodium in the recovered solution after contact with the ion exchange resin are measured with an ICP emission spectrometer. It was measured. The results are shown below for the amount of metal in 50 ml of the reaction solution before permeation of the ion exchange resin and the amount of metal in the recovered solution after permeation of the ion exchange resin.

<Comparative Example 1>
The rhodium-containing catalyst solution (water concentration 8%) used in Example 1 was permeated through the ion exchange resin under the same conditions as in Example 1 without performing strong acid treatment, and the metal concentration before and after permeation was determined by ICP analysis. did. As a result, the removal rates of chromium, molybdenum and rhodium were all less than 1%.
<Comparative example 2>
The catalyst solution prepared by adding pure water to the rhodium-containing catalyst solution used in Example 1 and adjusting the water concentration to 50% was permeated through the ion exchange resin under the same conditions as in Example 1 without performing a strong acid treatment. The metal concentration before and after permeation was quantified by ICP analysis. As a result, the maximum removal rate of chromium was 15%, the maximum removal rate of molybdenum was 20%, and the maximum removal rate of rhodium was 17%.

Claims (8)

A catalyst solution containing a Group 8 metal catalyst and a corrosive metal product is treated with a strong acid, and then contacted with a cation exchanger to recover a catalyst solution having a reduced content of the corrosive metal product. A method for regenerating a catalyst solution , wherein the corrosive metal product contains at least one metal selected from the group consisting of iron, nickel, chromium, molybdenum, tungsten, manganese, and mixtures thereof. Playback method.   The method according to claim 1, wherein the strong acid is an acid having a logarithmic value (pKa) of the reciprocal of the acid dissociation constant of less than 4.   The method of claim 1, wherein the strong acid treatment is performed at a temperature of about 0 ° C to 120 ° C.   The method according to claim 1, wherein the cation exchanger is a strongly acidic cation exchange resin.   The process according to claim 1, wherein the reaction catalyst solution contains an alkali metal salt and / or a halogen component. The method according to any one of claims 1 to 5 , wherein the strong acid is hydroiodic acid. The method according to claim 6 , wherein the concentration of hydrogen iodide in hydroiodic acid is 40 to 60% by weight. Strong acid treatment, to the molar content of any corrosive metal products of the reaction the catalyst solution, according to claim 1 to 7 or of terms is performed by adding hydroiodic acid at least 3 times the molar amount or more Method.