JPH0463869B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a catalyst recovery method,
Specifically, 2,3,6-trimethylphenol (hereinafter abbreviated as TMP) is brought into contact with molecular oxygen in water and an aliphatic alcohol having 5 to 10 carbon atoms in the presence of a copper halogeno complex catalyst. The present invention relates to a method for recovering a catalyst in a method for producing 3,5-trimethylbenzoquinone (hereinafter abbreviated as TMBQ). TMBQ is a substance useful as a synthetic intermediate for vitamin E. [Prior art] In the presence of a catalyst, TMP is oxidized with oxygen to form TMBQ
Various methods are known for obtaining .
For example, Japanese Patent Publication No. 53-17585 discloses a method of oxidizing TMP with oxygen in the presence of copper and halogen ions, and Japanese Patent Publication No. 49-24465 discloses a method using a cobalt complex as a catalyst. These methods are limited under limited conditions to TMBQ
However, in order for these methods to be viable as industrial production methods, the catalyst must be easily recovered from the reaction system and the activity of the recovered catalyst must be maintained at all times. It is necessary to be present. However, although the above-mentioned publication states that the catalyst can be recovered, there is no description of a specific recovery method or the activity of the recovered catalyst. For example, in Japanese Patent Publication No. 53-17585, the reaction is carried out in an organic solvent that is easily soluble in water, such as dimethylformamide. is extracted and separated into an organic phase and an aqueous phase, and the separated aqueous phase can be used as an aqueous catalyst solution in the next reaction. However, there is no mention of the activity of the recovered catalyst, and according to other examples, when the reaction is carried out in a system where water is present, the activity of the catalyst is low and the reaction is extremely inefficient. Therefore, it is practically impossible to use the catalyst transferred to the aqueous phase as it is as an aqueous catalyst solution. Therefore, in Japanese Patent Publication No. 53-17585, in order for the recovered catalyst to exhibit sufficient catalytic activity, water must be completely evaporated from the aqueous catalyst solution to which the catalyst has migrated, and the catalyst must be recovered in a solid state and subjected to the reaction. It won't happen. However, this method requires evaporation of a large amount of water, resulting in high energy consumption, and the process from the end of the reaction to the recovery of the catalyst is complicated, such as the need to separate the reaction solvent and extraction solvent. There are many difficulties in industrial implementation. The method disclosed in Japanese Patent Publication No. 49-24465 may also be able to recover the catalyst, but for the same reasons as mentioned above, there are many difficulties in industrial implementation, and it also has the major drawback of short catalyst life. The present inventors previously proposed a method of oxidizing TMP in the coexistence of water and an organic solvent using a catalyst consisting of a copper halide complex or a copper halide complex and an alkali metal halide. The catalyst used here is one used in an aqueous medium. Further, in this method, a _C5 to _C10 aliphatic alcohol, which is almost insoluble in water, is used as an organic solvent. Therefore, although the reaction takes place in a completely liquid-liquid heterogeneous system, the reaction proceeds without any problems.
Further, after the reaction is completed, the aqueous phase containing the catalyst and the organic phase can be easily separated, and therefore the catalyst can be easily recovered, and the phase-separated catalyst liquid can be directly used for the reaction. However, the catalyst is present in the separated organic phase along with a small amount of water, and complete catalyst recovery cannot be achieved by phase separation alone. The amount of catalyst present in the organic phase depends on the type of copper halide complex and alkali metal halide used,
Although it varies depending on the amount, concentration in the aqueous phase, etc., omitting the catalyst recovery operation is not preferable because it results in a large loss of the catalyst. It is believed that after the reaction, the catalyst present in the separated organic phase can be easily extracted with water. However, when a copper halide complex is used in the reaction,
A small amount of a copper compound of unknown structure that is soluble in the organic phase but almost insoluble in water is produced, and during extraction with water, it precipitates as fine crystals in either the aqueous phase or the organic phase. . As a result, copper is present in the organic phase even after the extraction operation, resulting in incomplete extraction. In this case, it may be possible to continue the extraction operation by precipitating the copper compound using a decanter or the like to separate the solid and liquid, but this is not only complicated, but also requires the use of the separated copper compound of unknown structure as a catalyst again. There is a problem with the validity of the catalyst, and on the other hand, it is not preferable to discard it because it will result in a loss of catalyst. [Problems to be Solved by the Invention] Therefore, there is a need for an effective catalyst recovery method that can extract the catalyst through simple operations without affecting the activity of the catalyst at all. [Means for Solving the Problems] The present invention has been made in view of the above-mentioned points of view.
In the reaction of oxidizing TMP to obtain TMBQ, a method for recovering the catalyst from the separated organic phase after the reaction is to extract the catalyst with water while keeping the pH between 1.5 and 2.5, and then evaporate the water in the extract. This method is based on the knowledge that the catalyst can be recovered very easily and with low energy consumption without precipitation of copper compounds of unknown structure and without impairing the catalytic activity. The present invention is based on the general formula Ml[Cu()mXn]p (which may or may not contain water of crystallization) [in the formula,
M is an alkali metal or ammonium represented by IA in the periodic table, Cu () is divalent copper, X
is a halogen, l is an integer of 1 to 3, m is 1 or 2, n is an integer of 3 to 8, p is 1 or 2], or the copper halogeno complex and an alkali metal halide. In a method for producing 2,3,5-trimethylbenzoquinone by contacting 2,3,6-trimethylphenol with oxygen or an oxygen-containing gas in water and an aliphatic alcohol having 5 to 10 carbon atoms using a catalyst, after the reaction. , the catalyst is extracted from the separated organic phase using water while maintaining the pH in the extractor at 1.5 to 2.5, and then the water in the extract is evaporated to recover the catalyst. This concerns the collection method. The copper halide complex used in the present invention is a compound in which copper and halogen have a coordinate bond, that is, the general formula Ml[Cu()mXn]p (where M is an alkali metal or ammonium represented by IA in the periodic table). , Cu() is divalent copper, X is halogen, l is an integer from 1 to 3, m is 1
or 2, n is an integer from 3 to 8, p is 1 or 2,
l+2mp=np) (which may or may not contain water of crystallization). In the above formula, M is preferably an alkali metal or ammonium, and the alkali metals are Li,
K, Rb, Cs, preferably Li, K, Cs, particularly preferably Li. Also, as a halogen
Cl, Br, and I are preferred, and Cl and Br are particularly preferred.
Examples of copper halide complexes include Li[CuCl ₃ ].
2H ₂ O, NH ₄ [CuCl ₃ ]・2H ₂ O, (NH ₄ ) ₂ [CuCl ₄ ]・
2H ₂ O, K [CuCl ₃ ], K ₂ [CuCl ₄ ]・2H ₂ O, Cs
[CuCl ₃ ]・2H ₂ O, Cs ₂ [CuCl ₄ ]・2H ₂ O, Cs ₃
[Cu ₂ Cl ₇ ]・2H ₂ O.Li ₂ [CuBr ₄ ]・6H ₂ O, K
[CuBr ₃ ], (NH ₄ ) ₂ [CuBr ₄ ]・2H ₂ O, Cs ₂
Examples include [CuBr ₄ ] and Cs[CuBr ₃ ]. These copper halide complexes can be prepared by known methods, e.g.
Mellor's Comprehensive Treatment on
Inorganic and Theoretical Chemistry, Vol.
, p182-201 (Longman). The copper halide complex synthesized in this manner can be identified by measuring its melting point. For example, the synthesized copper chloride lithium complex Li[CuCl ₃ ].2H ₂ O has a reddish-brown color, which is completely different in appearance from the green crystals of cupric chloride CuCl _{2.2H 2} O, and its melting point is 130 ~ Indicates 135℃. Copper chloride lithium Li
[CuCl ₃ ]・2H ₂ O, the melting point of cupric chloride CuCl ₂・2H ₂ O is given in the literature (Mellor's Comprehensive Treatment
on Inorganic and Theoretical Chemistry,
According to Vol, p184, p169 (Longman), it is 130℃ and 110℃, respectively. Alkali metal halides include NaCl, LiCl,
KCl, CsCl, NaBr, _NH4Br , KBr, CsBr,
Nai, LiI, KI, CsI, etc., with LiCl being particularly preferred. Catalyst recovery in the present invention is achieved, for example, by the flow shown in FIG. As shown in FIG. 1, after the reaction, the liquid is separated into an organic phase and an aqueous phase. The organic phase is extracted with water (and acid, e.g. hydrochloric acid) and separated into organic and aqueous phases, and the aqueous phase containing the catalyst is concentrated together with the aqueous phase obtained by extraction of the reaction solution to recover the catalyst. . The catalyst thus recovered is used for the next reaction. In the present invention, the reaction is carried out using a catalyst comprising a copper halide complex or a copper halide complex and an alkali metal halide. The reaction is carried out as a reaction solvent.
The reaction is carried out using a C ₅ to _{C 10} aliphatic alcohol in a batch process or in a semi-batch process in which a TMP solution is added dropwise to an aqueous catalyst solution. Under standard conditions, the amount of catalyst used is TMP/Me[Cu()mXn] for batch reactions.
p/MX (molar ratio) = 1/1/2 to 1/1/4, in semi-batch reaction TMP/Ml[Cu()mXn]p/
MX (molar ratio) = 1/0.25/0.5 to 1/0.25/1. After the reaction, the aqueous phase as the catalyst phase and the organic phase containing the reaction products are easily separated. In the case of the standard semi-batch reaction described above, the copper halide complex is present in the phase-separated organic phase in an amount of 1 to 5 wt%, and the alkali metal halide is present in an amount of 0.5 to 2 wt%. Extraction of the catalyst from the separated organic phase is possible using various methods, but it is necessary to completely recover the catalyst from the organic phase, and since the catalyst liquid is corrosive, it is possible to extract the catalyst in a simple format and structure. Preferably a device. From these points of view, the most preferable device is a countercurrent multi-stage extraction device having a settling tank between each stirring tank. FIG. 2 illustrates a flowchart of extraction using a countercurrent multi-stage extraction device. In Figure 2, 1,
2 and 3 are the first, second and third stirring tanks, respectively.
4, 5, and 6 indicate the first, second, and third sedimentation tanks, respectively. The organic phase is subjected to multistage countercurrent extraction with an aqueous solution containing hydrochloric acid in a first stirring tank and a second stirring tank, and finally extracted with water in a third stirring tank, and separated and extracted in a third settling tank. The water supplied to the third stirring tank is separated after extracting the organic tank and is then sent to the second stirring tank.
It is supplied to a stirring tank, the pH is adjusted with hydrochloric acid in a second stirring tank, the organic phase is extracted, and it is separated in a second settling tank. The aqueous phase separated here is supplied to the first stirring tank, where the pH is adjusted, the organic phase is extracted, separated in the first settling tank, and extracted as an extract (aqueous phase containing the catalyst). It will be done. In the extraction of the catalyst from the organic phase of the present invention, it is most preferable to use a countercurrent multistage stirring tank as the extraction device as described above. Furthermore, the smaller the number of tanks used, the more economical and preferable it is in industrial implementation. The number of tanks is influenced by the amount of catalyst present at the entrance of the extraction tank (stirred tank) (the amount of catalyst varies depending on the method of reaction), the amount of extraction water used, the residence time of the organic phase in each tank, etc. Therefore, it cannot be determined unconditionally, but usually 2 to 5 tanks are required. It is preferable that the amount of extraction water used in the extraction of the catalyst from the organic tank of the present invention is as small as possible, since this reduces energy consumption in the subsequent concentration operation. However, when the amount of extraction water used is too small, for example, the concentration of catalyst in the extract entering the extraction tank may be high, which reduces the distribution ratio and makes extraction practically impossible, or the number of extraction tanks may be increased. The need may arise. Therefore, there is an optimal amount of extraction water to be used from the operational and economic aspects, and 20 to 30 wt% of extraction water to the organic phase,
When carrying out a semi-batch reaction, it is preferable to use 10 to 20 wt% of extraction water. In the extraction of the catalyst from the organic phase in the present invention, whether the reaction is carried out in a batch or semi-batch manner, fine crystals precipitate when the catalyst is extracted with water, making the extraction operation virtually impossible. becomes. Although the structure and physical properties of this crystal are not clear at all, it is a substance that is extremely easily soluble in mineral acids. Therefore, in order to perform the extraction operation smoothly, it is considered appropriate to dissolve the precipitated crystals. However, it is necessary that the mineral acid used does not inactivate the catalyst, and from this point of view it is preferable to use hydrohalic acid, specifically hydrochloric acid, hydrobromic acid, and hydroiodic acid. Hydrochloric acid is particularly effective. It is. In the extraction of the catalyst from the organic phase in the present invention, it is most preferable to use hydrochloric acid to dissolve fine crystals precipitated during extraction. However, if an excessive amount of hydrochloric acid is added in excess of an amount sufficient to dissolve the crystals, free hydrochloric acid remains in the catalyst solution, causing problems in the reaction. That is, when a catalyst solution containing free hydrochloric acid is used in the reaction, a large amount of 4-chloro-trimethylphenol (hereinafter abbreviated as Cl-TMP) will be present in the reaction product, leading to a decrease in the yield of TMBQ and to the oxidation reaction. This is not preferable because the speed may decrease.
Furthermore, in order to avoid this problem, if free hydrochloric acid is to be removed from the catalyst liquid, the catalyst liquid must be evaporated to dryness and the catalyst must be taken out as a solid.
This operation is not a preferred embodiment because it requires a large amount of energy to evaporate water, and it is complicated to take out the solid catalyst from the evaporator. Therefore, it is necessary to strictly control the amount of hydrohalic acid, such as hydrochloric acid, which can be easily controlled by controlling the pH. PH control range is 1.5~
2.5, and by controlling within this range, extremely smooth extraction operation is possible, and the catalyst can be extracted without impairing the activity of the catalyst. In a preferred embodiment, a PH controller is used to control the PH in the extraction tank, and the metering pump is operated by the PH controller to supply an aqueous hydrochloric acid solution into the tank. In the present invention, if the concentration of hydrochloric acid used to extract the catalyst from the organic phase is too low, the amount of water to be evaporated in the subsequent concentration step will increase, which is undesirable. This is undesirable because it decomposes TMBQ in the extraction tank and causes only a partial reaction with water-soluble copper compounds. The concentration of hydrochloric acid is preferably 1 to 10 wt%, particularly preferably 3 to 6 wt%. In the extraction of the catalyst from the organic phase in the present invention, the residence time of the organic phase in each extraction tank is one of the important factors for extraction efficiency, reaction of water-insoluble copper compound and hydrochloric acid, etc. The residence time of the organic phase is usually 10 to 60 minutes, preferably 20 to 40 minutes in the first phase, and usually 5 to 30 minutes, preferably 10 to 20 minutes in the second and subsequent tanks. The residence time in the settling tank is usually 10 to 60 minutes, preferably 20 to 50 minutes for the combined organic phase and aqueous phase. In the present invention, when the reaction is carried out using a copper halide complex or a copper halide complex and an alkali metal halide as a catalyst, and the extraction operation of the catalyst from the organic phase after the reaction is carried out in a preferred embodiment, after the extraction operation, The catalyst remaining in the resulting organic phase is usually
It is less than 10ppm in terms of Cu () ions and less than 1ppm in terms of Li ions, and the recovery rate of the catalyst is almost 100.
%, and the catalyst is extracted extremely efficiently. In the present invention, the aqueous solution containing the catalyst extracted from the organic phase is then combined with the aqueous catalyst solution separated immediately after the reaction and concentrated to a predetermined concentration, or the solid catalyst is removed by completely evaporating water from the extract containing the catalyst. to recover. The former method is advantageous because it can be operated continuously and is therefore easy to operate, and water generated during the reaction can be removed at the same time. The latter method is the so-called evaporation to dryness method, but it has to be a batch method, has difficulties in handling, such as difficulty in taking out the solid catalyst from the evaporator, and is difficult to handle. Disadvantages include the need for a separate evaporator to remove the water generated. When water is evaporated from the catalyst liquid in the present invention, the boiling point rises rapidly because the concentration of the catalyst in the aqueous solution is high. Therefore, evaporation under reduced pressure is considered to be advantageous, but if the evaporation temperature is set too low, the degree of vacuum will increase, and as a result, although the heating energy will decrease, it is not possible to use a steam effluent as a vacuum generator. etc., resulting in an increase in energy consumption. Furthermore, since the catalyst liquid is highly corrosive, it is preferable to keep the temperature inside the evaporator as low as possible when selecting materials for the evaporator. Therefore, the operating conditions for evaporating water from the catalyst are determined from both energy consumption and corrosive considerations, and the degree of vacuum in the evaporator is usually 50 to 400 mm.
Hg, preferably 50-200 mmHg. At this time, the temperature of the catalyst liquid in the evaporator is approximately 50 to 90°C. The evaporation of water from the catalyst in the present invention is carried out by a batch method,
Although any continuous method can be used, the continuous method is a preferred embodiment because of ease of operation and the ability to obtain a catalyst concentrate with a stable catalyst concentration. [Operations and Effects] According to the present invention, after the reaction, the catalyst consisting of the copper halide complex or the copper halide complex and the alkali metal halide present in the organic phase can be easily removed without impairing its activity or without loss of the catalyst. Can be implemented. In addition, after the reaction, the obtained extract can be separated from the organic phase and combined with the resulting aqueous phase to evaporate the water to obtain a catalyst concentrate, which can be used as is for the next reaction. can. In addition, the organic phase obtained by the catalyst extraction operation is
It contains only 10 ppm or less of catalyst in terms of Cu () ions and 1 ppm or less in terms of Li ions, and by directly reducing it, highly pure 2,3,5-trimethylhydroquinone, which is a precursor of vitamin E, can be obtained. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that the reaction rate and yield in Examples and Comparative Examples are expressed on a molar basis. Reference example 1 Copper halide complex Li is placed in the four-necked flask of 1.
[CuCl ₃ ]・2H ₂ O44.6g, lithium chloride 31.8g, water
99.2 g and 80 g of n-hexanol were added and stirred at 950 rpm. Catalyst concentration at this time (Li[CuCl ₃ ]+
LiCl) was 39.2wt%. The inside of the reaction system was replaced with a gas having an oxygen concentration of 40% and heated to 50°C. Then
460 g of a 30% hexanol solution of TMP was quantitatively added dropwise over 4 hours. Consumed oxygen was successively supplied by an oxygen holder. After the reaction was completed, it was separated into an organic phase and an aqueous phase (catalyst phase). The obtained organic phase was washed with water and then analyzed by gas chromatography. The result is reference example 1
and shown in Table 1.

[Table] Comparative Example 1 After carrying out the reaction in the same manner as in Reference Example 1,
The separated aqueous phase was analyzed for copper () ions by atomic absorption spectrometry and for chlorine ions by precipitation titration with silver nitrate, and it was found that 30.3 g of copper halide complex Li [CuCl ₃ ] and 28.4 g of lithium chloride were present. . The amounts of copper halide complex and lithium chloride in the aqueous phase were 68.6% and 89.3%, respectively, of the charged amount. Further, the catalyst concentration at this time was 40.5%. Example 1 After carrying out a reaction in the same manner as in Reference Example 1,
The organic phase was separated, and the separated organic phase was passed through a countercurrent extraction device having three stirring tanks and three settling phases at a rate of 600 g/hr. The residence time of the organic phase in the first, second, and third stirring tanks was 30 minutes, 15 minutes, and 10 minutes, respectively, and the residence time of the organic phase and sedimentation phase in each settling tank was 40 minutes. On the other hand, water was flowed from the third tank to the first tank at a rate of 90 g/Hr. PH in the first tank is 1.5-1.7, PH in the second tank is 2.0-
In order to maintain the pH at 2.5, a 4% hydrochloric acid aqueous solution was intermittently sent to the first and second tanks while being controlled by a PH meter. Although the extraction operation was carried out continuously for about 8 hours, no precipitation of water-insoluble copper compounds was observed. After the extraction operation reaches a steady state, sample the extract liquid and the organic phase at the exit of the extraction device at arbitrary time intervals, and perform chelate titration to detect Cu () ions in the extract liquid and organic phase, and perform atomic absorption spectrometry for Li ions. The amount of catalyst recovered per unit time was determined by analyzing Cl ions by precipitation titration using a silver nitrate solution.
The results are shown in Table 2. In the table, the catalyst content in the organic phase before and after supply to the extraction tank was determined by extracting the organic phase with dilute nitric acid and then analyzing Cu(), Li, and Cl ions in the extract. Water was evaporated from the resulting catalyst aqueous solution until it became dry, and the catalyst was recovered as a solid.

[Table] Comparative Example 2 In Example 1, the extraction operation was performed without supplying hydrochloric acid to the first tank and the second tank. One hour after the start of the extraction operation, it became impossible to extract the liquid from each tank and sedimentation tank due to the precipitation of water-insoluble copper compounds. Examples 2 to 3 In Example 1, the extraction operation was performed with the residence time in each extraction tank set as follows. The results were as shown in Table 3. Water was evaporated from the resulting catalyst aqueous solution until it became dry, and the catalyst was recovered as a solid.

[Table] Example 4 After carrying out the reaction in the same manner as in Reference Example 1,
The phase-separated aqueous phase (catalyst phase) and the organic phase extract obtained in the same manner as in Example 1 were combined and transferred to an evaporator maintained at a reduced pressure of 100 mmHg at 270 g/Hr.
water was continuously evaporated, and the concentrated catalyst (recovered catalyst) was taken out. The temperature inside the evaporator at this time was 73 to 75°C. A reaction was carried out in the semi-batch method of Reference Example 1 using this recovered catalyst. The results obtained are shown in Tables 4 and 5.

【table】

[Table] Comparative Example 3 In Example 1, the inside of the catalyst tanks of the first tank and the second tank
Extraction operations were carried out while keeping the pH at 0.5-1.0 and 1.0-1.4, respectively, and then the aqueous catalyst solution was concentrated and the reaction was carried out in the same manner as in Example 4. As a result, the reaction rate was lower than in Example 4, and Cl-TMP remained and the TMBQ yield decreased. The results obtained are shown in Tables 6 and 7.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a flowchart of catalyst recovery, and FIG. 2 is a flowchart of extraction using a countercurrent multi-stage extraction device. In Figure 2, 1, 2, and 3 are the first, second, and third stirring tanks, respectively, and 4, 5, and 6 are the first and third stirring tanks, respectively.
The second and third settling tanks are shown.

Claims (1)

[Claims] 1 General formula Ml[Cu()mXn]p (which may or may not contain water of crystallization) [in the formula,
M is an alkali metal or ammonium represented by IA in the periodic table, Cu () is divalent copper, X
is a halogen, l is an integer of 1 to 3, m is 1 or 2, n is an integer of 3 to 8, p is 1 or 2], or the copper halogeno complex and an alkali metal halide. In a method for producing 2,3,5-trimethylbenzoquinone by contacting 2,3,6-trimethylphenol with oxygen or an oxygen-containing gas in water and an aliphatic alcohol having 5 to 10 carbon atoms using a catalyst, after the reaction. , the catalyst is extracted from the separated organic phase using water while maintaining the pH in the extractor at 1.5 to 2.5, and then the water in the extract is evaporated to recover the catalyst. Collection method. 2. The method according to claim 1, wherein the catalyst is extracted using a countercurrent multistage stirring tank. 3. The method according to claim 1, wherein the amount of water used to extract the catalyst is 10 to 30 wt% based on the organic phase separated after the reaction. 4. The method according to claim 2, wherein the countercurrent multistage stirring tank has 2 to 5 stages. 5. The method according to claim 2, wherein a settling tank is provided between each tank of the countercurrent multistage stirring tank. 6 Residence time of organic phase in countercurrent multistage stirring tank
The method according to claim 2, wherein the heating time is 10 to 60 minutes. 7. The method according to claim 2, wherein a hydrohalic acid aqueous solution is added to maintain the pH in the stirring tank at 1.5 to 2.5. 8 1 to 10% by weight as an aqueous solution of hydrohalic acid
8. The method according to claim 7, wherein the method is performed using hydrochloric acid. 9. The method according to claim 1, wherein water in the extract is continuously evaporated under a vacuum of 50 to 200 Torr.