JP2015229646A - Method of producing carboxylic acid and ketone and/or alcohol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing ketone and/or alcohol at a high yield.SOLUTION: A method of producing carboxylic acid and ketone and/or alcohol includes: a process of mixing an oxidation reaction liquid which is obtained by oxidizing a hydrocarbon compound with molecular oxygen, with water, and separating the liquid mixture into an oil phase containing a hydroperoxide and an aqueous phase containing carboxylic acid; a process of concentrating the aqueous phase to obtain a concentrated liquid containing the carboxylic acid, and recovering the water; a process of removing the carboxylic acid in the water recovered in the process of concentration; a process of reusing the water from which the carboxylic acid is removed, in the process of liquid separation; and a process of decomposing the hydroperoxide in the oil phase into the ketone and/or the alcohol.

Description

  The present invention relates to a process for producing carboxylic acids and ketones and / or alcohols.

  Methods for oxidizing hydrocarbon compounds with molecular oxygen to produce the corresponding ketones and / or alcohols have been well known for a long time. In particular, cyclohexanone and / or cyclohexanol obtained by oxidation of cyclohexane is a very important compound as a raw material for nylon 6 and nylon 6,6.

  Oxidation of the hydrocarbon compound with molecular oxygen proceeds via the corresponding hydroperoxide. In general, the selectivity of the oxidation reaction from a hydrocarbon compound to hydroperoxide is high. However, when hydroperoxide is decomposed, various by-products are generated, and the selectivity is lowered. In order to prevent this reduction in selectivity, the oxidation reaction is terminated at a stage where the conversion rate is low, and the oxidation reaction solution is sent to the next process in a state where the hydroperoxide remains without being decomposed, so that the hydroperoxide is increased. A method of decomposing at a selectivity is generally employed.

  However, even if the oxidation reaction is terminated at a stage where the conversion rate is low, the production of by-products cannot be avoided. By-products include, for example, various hydrocarbons, alcohols, ketones, peroxides, aldehydes, esters, carboxylic acids, various condensates, carbon monoxide, and carbon dioxide that are different from the raw materials and the target product. Among these by-products, carboxylic acids and esters are particularly produced.

  Among these by-products, carboxylic acids contain useful compounds having industrial utility value. For example, adipic acid by-produced during the oxidation of cyclohexane is useful as a raw material for nylon 6,6. Further, 1,6-hexanediol obtained by hydrogenating adipic acid is a useful compound as a raw material for polyester and polyurethane. It is valuable as an effective use of by-products to separate these valuable carboxylic acids and the like from the oxidation reaction solution and separately produce valuable materials.

  Methods for separating and obtaining carboxylic acid in the oxidation reaction solution are roughly divided into two. One is a method in which an oxidation reaction solution is neutralized with an aqueous alkaline solution and extracted into a water phase as a carboxylate. The other is a method in which the carboxylic acid is obtained by extraction with water (hereinafter referred to as “water extraction step”). Although the former has a high extraction rate, it is necessary to add an acid stronger than a carboxylic acid such as a mineral acid to liberate the carboxylic acid and extract and separate it again. Therefore, the former method has a complicated process and a low yield. In addition, this method requires auxiliary materials such as mineral acids. Therefore, the latter method is generally employed industrially.

  In the latter process, the aqueous solution containing the carboxylic acid is concentrated and dehydrated and then esterified by adding alcohol. Thereafter, valuable diols such as 1,6-hexanediol are obtained through hydrogenation and distillation purification. The alcohol produced during the hydrogenation can be recycled to the esterification step.

  Further, the water collected during the concentration and dehydration may be recycled to the water extraction step (hereinafter, the collected and recycled water is referred to as “circulated water”). The purpose of recycling is the effective use of water and the recovery of target products such as cyclohexanone and / or cyclohexanol dissolved in the aqueous phase during water extraction.

Special table 2011-512339 gazette Special table 2012-512876 gazette

  The object of the present invention is to provide a process for producing ketones and / or alcohols in high yield.

  According to one aspect of the present invention, an oxidation reaction liquid obtained by oxidizing a hydrocarbon compound with molecular oxygen and water are mixed, and separated into an oil phase containing hydroperoxide and an aqueous phase containing carboxylic acid. A step of concentrating the aqueous phase to obtain a concentrated solution containing carboxylic acid and recovering water, a step of removing carboxylic acid in the water recovered in the concentration step, and removal of the carboxylic acid A method for producing a carboxylic acid and a ketone and / or an alcohol, comprising a step of reusing the separated water for the liquid separation step and a step of decomposing the hydroperoxide in the oil phase into a ketone and / or an alcohol. Provided.

  According to the present invention, it is possible to produce ketones and / or alcohols in high yield.

  Generally, hydroperoxide is decomposed by acid or alkali. Among hydroperoxides, with regard to hydroperoxides obtained from aliphatic hydrocarbons or alicyclic hydrocarbons, the corresponding ketones and / or alcohols can be obtained with a relatively high selectivity in the decomposition with alkali. However, the selectivity in acid degradation is low. As described above, in the water extraction step, hydroperoxide is decomposed under acidic conditions, so its decomposition selectivity is low. Therefore, the decomposition of hydroperoxide in the water extraction process should be avoided as much as possible.

  The decomposition rate of hydroperoxide under acidic conditions depends on the hydrogen ion concentration in the aqueous phase. In the circulating water recycled to the water extraction process, the carboxylic acid having a boiling point close to that of water is azeotropically concentrated with the water, so that the circulating water shows strong acidity. Therefore, it is estimated that the decomposition of hydroperoxide is suppressed by neutralizing these acids and lowering the hydrogen ion concentration (that is, raising the pH).

  However, as a result of intensive studies by the present inventors, it has been found that even if the carboxylic acid in the circulating water is neutralized, the decomposition of the hydroperoxide is not suppressed but rather accelerated.

  That is, the present inventors have discovered that it is necessary to remove not only hydrogen ions but also carboxylic acid anions in order to prevent decomposition of hydroperoxide in the water extraction step, and the present invention has been completed. It was.

  Hereinafter, embodiments of the present invention will be described in detail.

  There is no restriction | limiting in particular in the structure of the hydrocarbon compound used by this invention. Examples of the hydrocarbon compound used in the present invention include chain saturated hydrocarbons, chain unsaturated hydrocarbons, cyclic saturated hydrocarbons, and cyclic unsaturated hydrocarbons.

  The chain saturated hydrocarbon is preferably a chain saturated hydrocarbon having 3 to 10 carbon atoms. Specific examples of the chain saturated hydrocarbon having 3 to 10 carbon atoms include propane, butane, pentane, hexane, heptane, octane, nonane and decane.

  As the chain-like unsaturated hydrocarbon, a chain-like unsaturated hydrocarbon having 3 to 6 carbon atoms is preferable. Specific examples of the chain unsaturated hydrocarbon having 3 to 6 carbon atoms include propylene, butylene, pentene, hexene and the like.

  As the cyclic saturated hydrocarbon, a cyclic saturated hydrocarbon having 5 to 12 carbon atoms is preferable. Specific examples of the cyclic saturated hydrocarbon having 5 to 12 carbon atoms include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, cycloundecane, and cyclododecane.

  As the cyclic unsaturated hydrocarbon, a cyclic unsaturated hydrocarbon having 5 to 12 carbon atoms is preferable. Specific examples of the cyclic unsaturated hydrocarbon having 5 to 12 carbon atoms include side chains such as cyclopentene, cyclohexene, cyclooctene, cycloundecene, cyclododecene, cyclohexadiene, cyclooctadiene, cyclododecadiene, and cyclododecatriene. Aliphatic cyclic unsaturated hydrocarbons having or not having aromatic hydrocarbons; aromatic hydrocarbons having side chains such as toluene and xylene.

  Examples of these hydrocarbon compounds include structural isomers thereof. Moreover, these hydrocarbon compounds may have a substituent. Examples of the substituent include an alkyl group, an aryl group, a carbonyl group, a carboxyl group, an amino group, a nitro group, a cyano group, an alkoxy group, and a halogen atom. In addition, it is more preferable that the carbon atom number of the whole substituted hydrocarbon compound exists in said range.

  Among these hydrocarbon compounds, particularly industrially important hydrocarbon compounds include cyclohexane, cyclododecane, toluene, xylene and the like.

  The hydrocarbon compound used in the present invention is oxidized by molecular oxygen and becomes at least one of alcohol, ketone, and hydroperoxide having the same number of carbon atoms as the hydrocarbon compound. The alcohol and / or ketone is further oxidized to produce a carboxylic acid. Although the carbon number of the by-product carboxylic acid is often the same as that of the hydrocarbon compound, a carboxylic acid having a carbon number smaller than that of the hydrocarbon compound is also generated by decarboxylation and de-CO reaction.

  For example, when the hydrocarbon compound is cyclohexane, the alcohol is cyclohexanol, the ketone is cyclohexanone, the hydroperoxide is cyclohexyl hydroperoxide, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, oxalic acid, glutaric acid Adipic acid, 1-oxycaproic acid and the like are by-produced.

  The oxidation of the hydrocarbon compound with molecular oxygen may be performed using a transition metal such as cobalt as a catalyst, or may be performed without using a catalyst. The temperature of the oxidation reaction varies depending on the bond energy of the C—H bond of the hydrocarbon compound, the presence or absence of a catalyst, etc., but is generally 100 to 180 ° C., more generally 120 to 170 ° C. When the temperature is too low, the oxidation reaction does not proceed at a sufficient rate, and the productivity may be deteriorated, for example, a long oxidation reaction tank is required. If the reaction temperature is too high, the selectivity of the desired product may be reduced. The oxidation step is generally performed under a pressure higher by 0.01 to 1 MPa than the vapor pressure of the hydrocarbon compound.

The water extraction step is a step in which the oxidation reaction solution and circulating water are mixed, water-soluble byproducts such as carboxylic acid are extracted into an aqueous phase, and then both phases are separated. The ratio of the circulating water to the oxidation reaction solution is not particularly limited as long as it is an amount sufficient to extract a water-soluble by-product such as carboxylic acid into the aqueous phase, but is preferably 0.1% by volume to 50% by volume, A volume% or more and 30 volume% or less is more preferable. When the ratio of circulating water is too small, water-soluble by-products such as carboxylic acid may not be sufficiently extracted in the aqueous phase.
When the ratio of circulating water is excessive, a large amount of energy may be required to collect the circulating water.

  The temperature of the water extraction step may be the same as the temperature of the oxidation step or may be different from the temperature of the oxidation step. In the latter case, for example, for the purpose of improving the extraction rate and preventing hydroperoxide decomposition, the oxidation reaction solution may be cooled to lower the temperature. Generally the temperature of a water extraction process is 100 to 170 degreeC, Preferably 120 to 165 degreeC is employ | adopted. If the temperature is too high, hydroperoxide may decompose in the water extraction process. When the temperature is too low, hydroperoxide may remain in the hydroperoxide decomposition step discharge liquid, or ester hydrolysis may not sufficiently proceed in the ester decomposition step. In order to avoid the above problem, the water extracted from the water extraction process can be heated, but in this case, the thermal decomposition of hydroperoxide is induced, and the final alcohol and / or ketone selectivity may be reduced. There is sex.

  There are no particular restrictions on the water extraction apparatus. In the water extraction, for example, water extraction and liquid separation operation may be performed in one apparatus using an extraction tower such as a perforated plate extraction tower, a rotating disk extraction tower, a pulsating perforated plate tower, and a vibrating plate tower. Alternatively, an apparatus in which the water extraction part and the liquid separation part are separated may be used. In the latter case, for example, a stirring / mixing tank, a static mixer, or the like is used for the water extraction portion, and for example, a settler, a centrifugal separator, or a liquid cyclone is used for the liquid separation portion. Among these, the combination of a static mixer and a settler is the simplest and most convenient device. In addition, parts that promote liquid separation, such as coalescers, may be installed inside the setler. The temperature of the liquid separation step may be different from the temperature of the water extraction step, but is generally the same temperature.

  Although the residence time of the water extraction step and the liquid separation step varies depending on each device, the residence time of both steps is preferably 1 minute or more and 60 minutes or less, and more preferably 1 minute or more and 30 minutes or less. . If the residence time is too short, separation between the oil phase and the water phase may be insufficient. If the residence time is too long, a long apparatus is required.

  In the water extraction step, divalent carboxylic acid, oxycarboxylic acid, and monovalent carboxylic acid having a short carbon chain are mainly extracted. For example, when the hydrocarbon compound is cyclohexane, formic acid, acetic acid, propionic acid, succinic acid, glutaric acid, adipic acid, 1-oxycaproic acid and the like are extracted. The oil phase discharged from the water extraction and liquid separation process is sent to the hydroperoxide decomposition process which is the next process.

  Hydroperoxide decomposition can be performed using transition metal catalysts such as vanadium, molybdenum, chromium, ruthenium, cobalt, etc., but the method of decomposition by contacting with an alkaline aqueous solution is an optional ester decomposition. In combination with the process, it is also possible to simplify to a single process (hereinafter, the hydroperoxide decomposition process and the ester decomposition process are collectively referred to as “saponification process”).

  Examples of the alkali used in the saponification step include alkali metal hydroxide aqueous solutions such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxide aqueous solutions such as magnesium hydroxide and calcium hydroxide, and sodium carbonate and potassium carbonate. An alkali metal carbonate aqueous solution is preferably used. These alkalis may be used alone or in combination.

  The amount of alkali used is not particularly limited as long as it is equal to or greater than the total amount of carboxylic acid and ester discharged from the liquid separation step, but is preferably 1.05 to 10 times, more preferably 1. It is 15 times or more and 3 times equivalent or less. If the amount of alkali used is too small, the ester may remain and the yield of ketone and / or alcohol may decrease. If the amount of alkali used is excessive, alkali is wasted.

  In general, no special overheating or cooling device is provided between the liquid separation step, the hydroperoxide decomposition step, and the ester decomposition step. Accordingly, the water extraction, liquid separation, hydroperoxide decomposition, and ester decomposition processes are performed at the same temperature, or because of the heat of decomposition of hydroperoxide, the hydroperoxide decomposition and ester decomposition processes are performed in water. It may be carried out at a temperature slightly higher than the extraction and liquid separation steps. In the latter case, the hydroperoxide decomposition and ester decomposition steps are generally performed at a temperature 5 to 30 ° C. higher than the water extraction and liquid separation steps.

  Note that, as described above, the hydroperoxide decomposition step and the ester decomposition step may be performed as a single step or may be performed as separate steps. In the latter case, hydroperoxide decomposition may be performed using a catalyst.

  On the other hand, the aqueous phase discharged from the water extraction and liquid separation step is concentrated in the concentration step and separated into a concentrated solution containing carboxylic acid and water. That is, valuable carboxylic acid is acquired by this process. The concentration temperature and pressure in this step are not particularly limited as long as water evaporates, but it is usually performed at 100 ° C. or higher and 130 ° C. or lower under normal pressure.

  The carboxylic acid concentrate concentrated in the concentration step contains valuable carboxylic acid. This carboxylic acid is appropriately subjected to a reaction and purification step to produce another useful compound. For example, 1,6-hexanediol is produced from a carboxylic acid concentrate containing adipic acid and oxycaproic acid produced during air oxidation of cyclohexane through an esterification reaction and a hydrogenation reaction.

  The circulating water recovered in the concentration step is recycled to the water extraction step. Circulating water contains carboxylic acid which has a boiling point close to that of water and can azeotrope with water. For example, the circulating water may contain formic acid, acetic acid, propionic acid and the like. Hydroperoxide decomposition is accelerated by acid. As described above, the decomposition of hydroperoxide with an acid has a lower selectivity for the desired ketone and / or alcohol than the decomposition with an alkali or catalyst. Therefore, the acid in the circulating water must be neutralized. Moreover, as described above, when the acid is an organic acid, the present inventors promote not only hydrogen ions but also organic acid radicals themselves to decompose hydroperoxide, and therefore, from circulating water, not only hydrogen ions, It has been found that the organic acid radical itself needs to be removed. That is, the present inventors have found that the removal of the carboxylic acid in the circulating water greatly contributes to the high yield of the desired ketone and / or alcohol.

  In the present specification and claims, “removal” of carboxylic acid means reducing the concentration of carboxylic acid in the water to 50 mmol / L or less.

  There is no particular limitation on the method for removing the carboxylic acid in the circulating water. Although distillation purification, which is the simplest method, can be used, formic acid, acetic acid and the like may azeotrope with water. In the removing step, a method of distilling and purifying water after neutralizing the carboxylic acid with an alkali may be used. Alternatively, a method of purifying water using a separation membrane may be used. The industrially simplest method is a method of purification using an ion exchange resin.

  As an ion exchange resin, an anion exchange resin is generally used. Considering the ease of regeneration, weakly basic anion exchange resins are preferably used. As this weakly basic anion exchange resin, for example, those having polyamine or dimethylamine as an exchange group can be used. The treatment temperature with the ion exchange resin is limited by the heat resistance of the ion exchange resin. In the case of a weakly basic anion exchange resin, it is usually used at 100 ° C. or lower, and in the case of a strongly basic anion exchange resin, it is usually used at 60 ° C. or lower.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

<Effect of removing carboxylic acid in hydroperoxide decomposition in water extraction process>
[Example 1]
A 1% by weight aqueous solution of formic acid (pH 2.2) was prepared. This was passed through a column packed with a weakly basic ion exchange resin (Diaion WA20 manufactured by Mitsubishi Chemical Corporation) at 60 ° C. and a superficial velocity of 1.5 (1 / h) to remove formic acid. As a result of analyzing the effluent from the column by liquid chromatography, no formic acid was detected and the pH was 6.6.

  To a 1 L autoclave, 211 g of the ion exchange treated water and 383 g of cyclohexane were added. After heating this to 160 ° C., 36.2 g of a cyclohexane solution of 10% by weight of cyclohexyl hydroperoxide was injected and reacted for 1 hour. As a result of analyzing the reaction solution by gas chromatography, the decomposition rate of cyclohexyl hydroperoxide was 54.4%, the selectivity of cyclohexanone was 24.1%, and the selectivity of cyclohexanol was 41.5%.

[Comparative Example 1]
The cyclohexyl hydroperoxide was decomposed in the same manner as in Example 1 except that the ion exchange resin treatment was not performed. The decomposition rate of cyclohexyl hydroperoxide was 99.8%, the cyclohexanone selectivity was 22.0%, and the cyclohexanol selectivity was 38.0%.

[Comparative Example 2]
Cyclohexyl hydroperoxide was decomposed in the same manner as in Comparative Example 1 except that the aqueous formic acid solution was neutralized with sodium hydroxide and the pH was adjusted to 7.2. The decomposition rate of cyclohexyl hydroperoxide was 100%, the cyclohexanone selectivity was 20.8%, and the cyclohexanol selectivity was 35.8%.

<Effect of removing carboxylic acid in circulating water>
[Example 2]
To 500 ml of SUS316L autoclave, 250 g of cyclohexane and 293 mg of cyclohexane solution of 0.1 wt% cobalt octylate (0.2 wt ppm as Co metal) were added, and the internal temperature was adjusted while introducing nitrogen from the gas blowing nozzle. Heated to 157 ° C. After the internal temperature reached 157 ° C., the blowing gas was switched to air, and the cyclohexane oxidation reaction was performed for 21 minutes while blowing air at a rate of 1 L / min. The batch reaction was performed 10 batches to obtain an oxidation reaction solution. Cyclohexane conversion in the oxidation reaction is 4.2%, cyclohexanone selectivity is 19.4%, cyclohexanol selectivity is 41.6%, selectivity of cyclohexyl peroxide is 16.3%, adipic acid selectivity 1.7%, and oxycaproic acid selectivity was 3.1%.

  350 g of water was added to the oxidation reaction solution and stirred, and then this was separated to extract extracted water. The extracted water was simply distilled at a bottom temperature of 100 ° C. to 120 ° C. and concentrated until the water content in the residue in the kettle became 3% by weight to obtain circulating water. As a result of analyzing the circulating water by liquid chromatography, it contained 1.02% by weight of formic acid, 0.33% by weight of acetic acid, 0.04% by weight of propionic acid and 0.03% by weight of butyric acid, and the pH was 2.17. Met. The circulating water was treated with an ion exchange resin in the same manner as in Example 1. As a result, no formic acid, acetic acid, propionic acid, or butyric acid was detected in the ion-exchanged water, and the pH was 6.59.

  On the other hand, the oxidation reaction liquid was concentrated about 10 times to obtain an oxidation concentrated liquid containing 12.52% by weight of cyclohexanone, 27.40% by weight of cyclohexanol and 12.45% by weight of cyclohexyl hydroperoxide. After adding 440 g of cyclohexane and 70 g of the ion exchange treated water to a 1 L autoclave and heating to 160 ° C., 45 g of the oxidized concentrated solution was injected and stirred for 5 minutes to carry out the reaction, followed by liquid separation. The separated oil phase was concentrated about 10 times, and the same reaction operation was repeated using fresh ion-exchanged water. After repeating the reaction separation operation three times in total, gas chromatographic analysis of the oil phase and the water phase revealed that the cyclohexyl hydroperoxide decomposition rate was 37.6%, cyclohexanone selectivity 24.7%, cyclohexanol selection The rate was 42.5%. On the other hand, as a result of quantitative analysis using liquid chromatography for adipic acid and oxycaproic acid in the aqueous phase, the adipic acid extraction rate was 82.5% and the oxycaproic acid extraction rate was 81.9%.

  The separated oil phase was again concentrated 10 times, mixed with 400 g of cyclohexane and 80 g of a 17 wt% aqueous sodium carbonate solution, and press-fitted into a liquid mixture previously heated to 160 ° C., and stirred at the same temperature for 60 minutes. Thereby, decomposition | disassembly of the remaining cyclohexyl hydroperoxide and hydrolysis of ester were performed simultaneously (saponification process). As a result of gas chromatographic analysis of the oil phase and the water phase after the liquid separation, the decomposition rate of cyclohexyl hydroperoxide was 100%, and the cyclohexanone selectivity based on cyclohexyl hydroperoxide in the oxidation reaction solution was 44. The selectivity for 4% and cyclohexanol was 34.3%.

[Comparative Example 4]
The same experimental operation as in Example 3 was performed except that the ion exchange resin treatment was not performed. The decomposition rate of cyclohexyl hydroperoxide after the water extraction operation was 60.3%, the cyclohexanone selectivity was 22.5%, the cyclohexanol selectivity was 39.3%, the adipic acid extraction rate was 81.9%, oxy The caproic acid extraction rate was 80.5%. Further, the decomposition rate of cyclohexyl hydroperoxide after saponification treatment was 100%, the cyclohexanone selectivity based on cyclohexyl hydroperoxide in the oxidation reaction solution was 37.9%, and the cyclohexanol selectivity was 35.3%. there were.

The above results are summarized in Table 1 below. As is apparent from Table 1, it was possible to achieve a high yield of the desired ketone and / or alcohol by removing the carboxylic acid from the circulating water.

Claims (6)

A step of mixing an oxidation reaction solution obtained by oxidizing a hydrocarbon compound with molecular oxygen and water, and separating the mixture into an oil phase containing hydroperoxide and an aqueous phase containing carboxylic acid;
Concentrating the aqueous phase to obtain a concentrated liquid containing carboxylic acid and recovering water;
Removing the carboxylic acid in the water recovered in the concentration step;
Recycling the water from which the carboxylic acid has been removed to the liquid separation step;
A method for producing a carboxylic acid and a ketone and / or an alcohol, comprising a step of decomposing the hydroperoxide in the oil phase into a ketone and / or an alcohol.   The method of claim 1, wherein the oil phase further comprises a carboxylic acid ester, and the method further comprises hydrolyzing the carboxylic acid ester to a carboxylic acid and an alcohol.   The method according to claim 2, wherein the hydroperoxide decomposition step and the carboxylic acid ester decomposition step are performed as a single step by bringing the oil phase into contact with an aqueous alkali solution.   The method according to any one of claims 1 to 3, wherein the removal of the carboxylic acid is performed using an ion exchange resin.   The method according to claim 4, wherein the ion exchange resin is an anion exchange resin. The method according to any one of claims 1 to 5, wherein the hydroperoxide is cyclohexyl hydroperoxide, the ketone is cyclohexanone, and the alcohol is cyclohexanol.