JPH0753416A - Purification of monoalienyl benzene compounds - Google Patents

Abstract

PURPOSE:To provide a method for purifying a monoalkenyl benzene by alkenylating the side chain of an aromatic hydrocarbon compound having one or more hydrogen atoms at the alpha-position of the side chain with a diolefin and subsequently purifying and obtaining the synthesized monoalkenyl benzene from the reaction solution containing the monoalkenyl benzene solution in a high purity and a high recovering degree. CONSTITUTION:This method for purifying a monoalkenyl benzene comprises inactivating and removing an alkali metal catalyst contained in the reactional product solution with a solid acid, a carbon material, a cation exchange resin, etc., and subsequently distilling the residual solution.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the use of a conjugated diene having 4 or 5 carbon atoms in the side chain of an aromatic hydrocarbon compound in which one or more hydrogen atoms are bonded to the α-position of the side chain. The present invention relates to a method for purifying monoalkenylbenzenes from a reaction product liquid after producing monoalkenylbenzenes by alkenylation with a metal catalyst. Monoalkenylbenzenes are useful as an intermediate raw material for various organic compounds such as polymer monomers and pharmaceuticals. For example, 5- (O-tolyl)-produced from O-xylene and 1,3-butadiene. 2-Pentene can be converted into 2,6 naphthalenedicarboxylic acid which is industrially useful by dehydrogenation, isomerization and oxidation after ring closure.

[0002]

2. Description of the Related Art As catalysts for producing monoalkenylbenzenes by alkenylating side chains of aromatic hydrocarbon compounds with conjugated dienes having 4 or 5 carbon atoms, alkali metals such as sodium and potassium and those A method of using a mixture obtained by heat treating a carrier obtained by firing a mixture of a basic potassium compound and alumina, under an inert gas and adding metallic sodium,
A method is known in which an alkali metal oxide or an alkaline earth metal oxide is loaded with metallic sodium or metallic potassium and used. Among these catalysts, alkali metals such as sodium and potassium and their alloys are used to separate and recover monoalkenylbenzenes from the obtained reaction product liquid.After the reaction is completed, the product liquid is cooled and allowed to stand. When the catalyst and the liquid phase containing the target substance are separated by decantation or filtration, and the monoalkenylbenzenes are separated and recovered by distillation, the monoalkylbenzenes are denatured, and the monoalkylbenzene can be obtained with high purity and a high recovery rate. Not known to be.

Therefore, in order to prevent the above-mentioned problems, in JP-A-51-4127, the total concentration of the alkali metal and the organic alkali metal compound in the hydrocarbon used as the distillation raw material is
Alkali metal component 0.09 to 15 per 1 kg of hydrocarbon phase
Proposals have been made to make it in the milligram atom range. However, this method does not completely remove the alkali metal catalyst component, but a part thereof is mixed in the liquid phase as a soluble alkyl or alkenyl complex. When this product liquid is directly introduced into the distillation column, coexistence of an active catalyst causes the monoalkenylbenzenes to further react with unreacted alkylbenzenes and monoalkenylbenzenes themselves to form a high molecular weight by-product. In the reverse reaction, the alkylbenzenes, which are the raw materials, are returned, or the isomers other than the desired monoalkenylbenzene are produced by the movement of the double bond. That is, the total concentration of the alkali metal and the organic alkali metal compound is lowered only by reducing the degree thereof, and the deterioration cannot be prevented at all. Further, when the distillation column is operated for a long period of time, the trace amount of alkali metal and organic alkali metal compound is concentrated in the distillation column, and finally it becomes impossible to obtain high-purity monoalkenylbenzenes, and the recovery rate is also lowered. I will end up. This alteration of monoalkenylbenzene can be suppressed to some extent by lowering the distillation temperature, but for that purpose it is necessary to carry out distillation under reduced pressure so that alteration of monoalkenylbenzene does not occur at all. In order to do so, a high vacuum is required and the equipment and operating costs are industrially high, which is not realistic.

Further, in Japanese Patent Application Laid-Open No. 49-70929, a method in which a catalyst is separated and removed from a reaction product solution and then treated with carbon dioxide and distilled, or a reaction product solution is treated with carbon dioxide and then the catalyst is separated and removed and distilled Is proposed. In this method, the alkali metal and the organic alkali metal compound are completely deactivated by the carbon dioxide treatment, and the alteration of the monoalkenylbenzene can be prevented in the distillation, but the generated alkali carbonate such as alkali carbonate or alkali carboxylate can be prevented. Is partially soluble in the organic solvent and is introduced into the distillation column. And
When unreacted aromatic hydrocarbons are distilled off in the distillation, alkali salts having a solubility or higher are precipitated as a solid and accumulated inside the distillation column. Therefore, not only the gas-liquid contact in the distillation column is reduced and the distillation efficiency is reduced, but finally the distillation column is closed and the distillation operation cannot be performed. That is, unless the alkali metal component is completely removed, it is impossible to stably operate the distillation column and obtain high-purity monoalkenylbenzenes.

Further, Japanese Patent Publication No. 57-26489 proposes a method in which alkenylbenzene and water are brought into contact with each other, and then the pH of water is adjusted to 6 or less to make the alkali metal catalyst water-soluble and then separated. However, this method has a risk of generation of a large amount of reaction heat and ignition when the reaction product liquid is brought into contact with water. The reaction can be controlled to some extent by the amount of water or reaction product solution to be contacted and the addition time, but when attempting to carry out the reaction on an industrial scale, it takes a long time for the treatment and the equipment will be large-scaled. It cannot be said that it is an effective method. Further, in USP 3,244,758, by adding isopropanol in advance before the distillation to inactivate the alkali metal or the alkali metal compound contained in the production liquid, it is possible to prevent an undesirable side reaction during the distillation. It is preventing. However, in this method, the risk of large amount of reaction heat generation and ignition that occur when contacting water can be avoided, but the deactivated alkali metal catalyst is introduced into the distillation column as an alkyl alcoholate soluble in an organic solvent, It is not preferable because it causes the above-mentioned problems.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
Although the reaction product solution was allowed to stand and separated into a liquid phase containing a catalyst and a target substance by filtration, an attempt was made to purify and separate and recover monoalkenylbenzenes by distilling the liquid phase.
In the distillation step, the target monoalkenylbenzenes were denatured, and the monoalkenylbenzenes could not be obtained with high purity and high recovery. In addition, accumulation of insoluble compounds also occurs in the distillation column, the distillation efficiency of the target substance decreases,
In addition, the distillation column was clogged and the distillation operation could not be performed. That is, the reaction product solution was allowed to stand still and filtration was attempted to separate the catalyst and the liquid phase containing the target substance, but it was not possible to completely remove the particulate catalyst by filtration alone, and part of the alkali metal was soluble. It was found that the above-mentioned alkyl or alkenyl complex was mixed in the liquid phase. When this product liquid is directly introduced into the distillation column, the monoalkenylbenzenes further react with unreacted alkylbenzenes and monoalkenylbenzenes due to the coexistence of an active catalyst to generate a high molecular weight by-product, By a reverse reaction, it returns to the starting material, alkylbenzenes, or moves double bonds to produce isomers other than the desired monoalkenylbenzene. Therefore, it has been found that it is not possible to obtain high-purity monoalkenylbenzenes and the recovery rate also decreases.

This alteration of monoalkenylbenzene can be suppressed to some extent by lowering the distillation temperature, but for that purpose, distillation must be carried out under reduced pressure, and alteration of monoalkenylbenzene does not occur at all. In order to do so, a high vacuum is required, and the cost of equipment and operation is industrially unpractical. In addition, some of the alkali metals are also introduced into the distillation column as alkali salts that are soluble in organic solvents, and when unreacted aromatic hydrocarbons are distilled off in the distillation, alkali salts with solubility or higher are precipitated as solids and distilled. It accumulates inside the tower. Therefore, not only the gas-liquid contact in the distillation column is reduced and the distillation efficiency is reduced, but finally the distillation column is closed and the distillation operation cannot be performed. That is, it was found that this problem cannot be avoided only by operating conditions of distillation. In view of such a fact, the object of the present invention is to use a conjugated diene having 4 or 5 carbon atoms as the side chain of an aromatic hydrocarbon compound in which one or more hydrogen atoms are bonded to the α-position of the side chain. In producing monoalkenylbenzenes by alkenylation with an alkali metal catalyst, it is intended to develop a method for purifying and obtaining monoalkenylbenzenes from the reaction product liquid with high purity and high recovery rate.

[0008]

The present inventors have prepared monoalkenylbenzenes by alkenylating an α-position of an aromatic hydrocarbon compound with an alkali metal catalyst using a conjugated diene having 4 or 5 carbon atoms. As a result of extensive studies on a method of separating and recovering monoalkenylbenzenes from the reaction product solution, after deactivating and / or removing the alkali metal catalyst from the reaction product solution, the monoalkenylbenzenes are separated and recovered by distillation. Found that by doing so, it is possible to purify and obtain monoalkenylbenzenes with high purity and high recovery rate.
The present invention has been completed. That is, the present invention, a reaction product liquid containing an alkali metal catalyst, a solid acid, a carbon material,
Completed purification method of monoalkenylbenzenes that can obtain monoalkenylbenzenes with high purity and high recovery by distilling after deactivating and / or removing the catalyst by contacting with cation exchange resin etc. Is.

The method of the present invention will be described in detail below. As the aromatic hydrocarbon compound in which one or more hydrogen atoms are bonded to the α-position of the side chain used in the present invention, the following compounds are used. As the monocyclic aromatic hydrocarbon,
Monoalkylbenzenes such as toluene, ethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, sec-butylbenzene and isobutylbenzene, o-, m-, p-xylene, o-, m-, p
-Dialkylbenzenes such as ethyltoluene, o-, m-, p-diethylbenzene, trialkylbenzenes such as mesitylene and pseudocumene, 1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene , Polymethylbenzenes such as pentamethylbenzene and hexamethylbenzene, and 1- and 2-methylnaphthalene, dimethylnaphthalene, tetrahydronaphthalene, indane and the like are used as polycyclic aromatic hydrocarbons. As the conjugated diene having 4 or 5 carbon atoms, which is one raw material, 1,3-butadiene, 1,3-pentadiene, or isoprene is used.

The alkali metal catalysts used in the present invention include sodium metal, potassium metal, and alloys of sodium and potassium metal. Further, other elements may be added and used in order to increase the specific gravity of these alkali metals. Although various reaction methods are adopted in using these catalysts in the reaction, generally, a method in which an aromatic hydrocarbon, which is one of the starting materials, is present in excess with respect to the conjugated diene is a monoalkylbenzene. It is possible to improve the selectivity to the class. For that purpose, a method of continuously supplying the conjugated dienes to the reaction system by a semi-batch method is preferable. When the reaction is carried out continuously in a complete mixing system, the reaction system can be divided into multiple stages and the concentration of conjugated dienes in the reactor can be reduced by supplying conjugated dienes to each stage. It is preferable to adopt (1) because it is possible to obtain a high selectivity.

The reaction temperature in the method of the present invention is 100 to 2
It is in the range of 00 ° C. If it is lower than this range, the reaction may occur, but a sufficient reaction rate cannot be obtained, and the selectivity tends to decrease. If the temperature is higher than this, by-products such as tar content increase, which is not preferable. In the present invention, the reaction is carried out under conditions in which the starting aromatic hydrocarbon and the product are in a substantially liquid state. The reaction pressure may be a pressure sufficient to allow the raw material aromatic hydrocarbon and the product to substantially exist as a liquid, and is not particularly limited, but is 0.05 to 100 in absolute pressure.
It is in the range of 5 atm, preferably 0.1 to 2 atm. The molar ratio of the conjugated diene having 4 or 5 carbon atoms to the starting aromatic hydrocarbon in the method of the present invention is 0.01 to 1, preferably 0.03 to 0.5. When the amount of the diene is larger than this, the produced monoalkenylbenzene further reacts with the diene and one molecule of the aromatic hydrocarbon contains 2 diene.
This is not preferable because the number of compounds added with molecules or more is increased and the diene is liable to be polymerized, and the selectivity is lowered.
The amount of the catalyst used in the method of the present invention is 0.01% by weight or more, preferably 0.1% by weight based on the aromatic hydrocarbon as a raw material.
It is 05% or more.

In the method of the present invention, a reaction system such as a batch system, a semi-batch system or a complete mixing / circulation system is adopted, and the reaction time in the batch system, the semi-batch system or the residence time in the complete mixing / distribution system is 0.1 -10 hours are adopted. When carrying out the reaction by suspending the catalyst, usually after the reaction,
The resulting solution is left to stand and most of the catalyst is first allowed to settle. Next, the product solution is extracted from the reaction tank and processed. At this time, as one method, first, most of the alkali metal catalyst is removed by filtering using a filter of 5 microns or less. When a filter having a coarser mesh than this is used, a part of the particulate catalyst is contained in the recovered product solution, which causes the alteration of monoalkylbenzene in the distillation step, which is not preferable. Even if the alkali metal catalyst is filtered and removed using a filter of 5 microns or less, a part of the alkali metal is mixed in the liquid phase as a soluble alkyl or alkenyl complex or an alkali salt.
When this product liquid is directly introduced into the distillation column, the active soluble catalyst causes alteration of the monoalkenylbenzene. Although the amount of the soluble catalyst is not large at all, when it is concentrated in the distillation column retention liquid and operated for a long period of time, the deterioration of the monoalkenylbenzene increases to a nonnegligible amount. Therefore, the active soluble catalyst needs to be deactivated before the product liquid is introduced into the distillation column. The other is to deactivate the alkali metal catalyst component from the product solution containing the insoluble alkali metal catalyst solid in the form of fine particles and the soluble alkyl or alkenyl complex or the alkali salt, and then use a filter of 5 microns or less to remove the alkali metal catalyst component. This is a method of removing the activated alkali metal catalyst by filtration. Although any of the above methods can be used, when the method described at the beginning is used, the active alkali metal catalyst collected on the filter induces alteration of monoalkenylbenzene on the filter and produces a high molecular weight monoalkenylbenzene. It may form a polymer of alkenylbenzene and cause filter clogging. Therefore, the latter method is more preferably used.

In order to deactivate and / or remove the catalyst, a method of contacting with a solid acid or carbon material or a cationic ion exchange resin is suitable. This method can control the generation of a large amount of reaction heat and there is no risk of ignition, and since all the alkali metal components can be removed, it is possible to operate the distillation column for a long period of time, and the operation method is simple and industrial scale. It can be said that the method is easy to implement. When a solid acid is used, the alkali metal component in the alkali metal catalyst active by the acid-base reaction is adsorbed on the solid acid and can be deactivated and / or removed. Solid acids that can be used include activated clay, alumina,
Examples include silica-alumina and various zeolites. When zeolite is used, hydrogen ion exchange type zeolite is particularly preferably used, and mordenite, Y type, X type, Z
The type of zeolite such as SM type and ferrierite is not particularly limited. When a carbon material is used, the alkali metal component in the active alkali metal catalyst is adsorbed on a functional group such as a surface hydroxyl group or a carboxylic acid group, or is occluded in the carbon material by an intercalation mechanism, It can be deactivated and / or removed. The carbon material that can be used is not particularly limited, such as graphite, activated carbon, amorofus carbon obtained by firing petroleum-based and coal-based pitch, PAN-based carbon fiber, etc., and firing, oxidation, and carbonization degree as necessary. The surface functional group and surface area can be adjusted before use. When using a cationic ion exchange resin,
The alkali metal component in the alkali metal catalyst active by the acid-base reaction can be adsorbed by the functional group on the cationic ion exchange resin to be deactivated and / or removed. Cationic ion exchange resins that can be used include sulfonic acid type resins and carboxylic acid type resins, but ion exchange resins having a higher degree of crosslinking than swelling resistance to organic solvents are preferable.

When these solids and the product solution are brought into contact with each other,
When there is a risk of generation of a large amount of reaction heat and ignition at the time of deactivation of the alkali metal catalyst, the deactivation reaction can be controlled at a suitable time by the introduction rate of the solid or product solution. Also,
A gas such as a mixed gas having an oxygen concentration of 20% or less diluted with an inert gas, steam, a mixed gas of carbon dioxide and carbon dioxide and an oxygen concentration of 20% or less, a mixed gas of carbon dioxide and steam, or the like, or
A liquid such as water, an aqueous acid solution, or alcohol is brought into contact with the production liquid to deactivate the active alkali metal catalyst in advance to some extent, and then these solids are brought into contact with the production liquid to completely deactivate the alkali metal catalyst and / or Alternatively, a method of removing can also be adopted.
The contact time may be a time sufficient to deactivate and / or remove the active alkali metal catalyst. The contact temperature can be selected within a wide range from room temperature to the boiling point of the starting aromatic hydrocarbon, but room temperature is sufficient. The contact method is batch method,
A reaction method such as a semi-batch method, a complete mixed flow method, or a fixed bed flow method is adopted, but any method is acceptable as long as solid-liquid contact is sufficient. The amount of solid used may be an amount sufficient to remove the alkali metal component.

[0015]

As described above, when alkenylbenzene is separated and recovered from the alkenylbenzene product solution in which the alkali metal catalyst is deactivated and / or removed by distillation, no deterioration occurs even by atmospheric distillation, and high purity is obtained. Alkenylbenzene can be obtained at a high recovery rate, and the distillation column can be operated stably, and its industrial significance is extremely large.

[0016]

EXAMPLES The method of the present invention will be described in detail below with reference to Examples and Comparative Examples. The present invention is not limited to the scope of the examples below. Example 1 60 g of metallic sodium and 100 g of metallic potassium were charged into a stirring reactor which was replaced with nitrogen and in which oxygen and water were not present, and then 100 kg of O-xylene dehydrated using a molecular sieve was added in a nitrogen stream to 140 °. Heated to C. 1,3-Butadiene 7.0 with stirring under normal pressure
kg was introduced for 1 hour to react. After the reaction, stirring was stopped, the mixture was allowed to stand, the temperature was lowered, and the product liquid was extracted. A part of this product solution was collected and analyzed by gas chromatography. The results are shown in Table 1. 5- (O- based on 1,3-butadiene
Trily) -2-pentene selectivity was 83.0%.
The reaction product solution is passed through a fixed bed column packed with activated clay to completely adsorb the alkali metal catalyst to deactivate and remove the reaction product solution, and then the reaction product solution is further provided with a stainless sintered metal filter having a pore size of 1 micron. Through This product solution was introduced into the orthoxylene recovery tower at a rate of 10 kg / hr. Table 2 shows the compositions and weights of the top liquid and the liquid discharged from the kettle when the orthoxylene recovery tower was operated at a kettle temperature of 230 ° C under normal pressure. The 5- (O-
No alteration of (tril) -2-pentene was observed.
Next, the 5- (O-tolyl) -2-pentene purification column was operated under atmospheric pressure at a kettle temperature of 250 ° C., and 5- (O-tolyl) -2-pentene was recovered from the top of the column. Purity is 99.8%
And the recovery rate was 98.5%.

Example 2 The same procedure as in Example 1 was carried out except that the adsorption and deactivation removal of the alkali metal catalyst was carried out using hydrogen ion type mordenite. The purity of 5- (O-tolyl) -2-pentene was 99.7%, and the recovery rate was 98.4%. Example 3 The same procedure as in Example 1 was carried out except that the operations of adsorbing or occluding the alkali metal-based catalyst and deactivating and removing were carried out using activated carbon. The purity of 5- (O-tolyl) -2-pentene is 99.
6% and the recovery rate was 98.4%.

Example 4 Example 1 was repeated except that graphite was used for the operations of adsorption, occlusion and deactivation removal of the alkali metal catalyst.
I went the same way. The purity of 5- (O-tolyl) -2-pentene was 99.6%, and the recovery rate was 98.8%. Example 5 The procedure of Example 1 was repeated, except that the sulfonic acid ion-exchange resin (Amberlyst 15) was used for the adsorption and deactivation removal of the alkali metal catalyst. The purity of 5- (O-tolyl) -2-pentene was 99.6%, and the recovery rate was 98.9%.

Comparative Example 1 The product liquid after the alkenylation reaction in Example 1 was allowed to stand,
It was taken out after cooling. This product liquid was directly introduced into the orthoxylene recovery column at a rate of 10 kg / hr without passing through the filter. Table 2 shows the compositions and weights of the top liquid and the liquid discharged from the kettle when the orthoxylene recovery tower was operated at a kettle temperature of 230 ° C under normal pressure. 5- (O in the pot liquid of the target product
-Tolyl) -2-Pentene changed its quality and 5
The amount of-(O-tolyl) -2-pentene was significantly decreased, and
High-boiling component due to reaction of-(O-tolyl) -2-pentene and ortho-xylene, increase of ortho-xylene due to reverse reaction of alkenylation reaction, transfer of double bond of 5- (O-tolyl) -2-pentene Formation of 5- (O-tolyl) -3-pentene and 5- (O-tolyl) -4-pentene, which are isomers, was observed.

Comparative Example 2 The product liquid after the alkenylation reaction in Example 1 was allowed to stand,
After cooling, the reaction product solution was extracted through a stainless sintered metal filter having a pore size of 1 micron. This product solution is used as it is for 20 times without deactivating the alkali metal catalyst component.
It was introduced at a rate of 10 kg / hr into an orthoxylene recovery column operating under a reduced pressure of mmHg and a kettle temperature of 120 ° C. Table 2 shows the compositions and weights of the top liquid and the kettle liquid one day after the operation of the ortho-xylene recovery column. 5- (O-tolyl)
The mass of -2-pentene decreased, but the by-products could not be suppressed. Comparative Example 3 Table 2 shows the compositions and weights of the top liquid and kettle liquid after the ortho-xylene recovery column was operated for 5 days in Comparative Example 2. 5
The mass variation of-(O-tolyl) -2-pentene increased.
Concentration of the alkali metal catalyst occurred in the distillation column, and it was not possible to reduce the variable mass of 5- (O-tolyl) -2-pentene and to purify it at a high recovery rate only by operating the distillation column. Comparative Example 4 In Comparative Example 2, the orthoxylene recovery column was further operated for 10 days, but the solid solution was precipitated in the vicinity of the feed stage of the distillation column, and it was difficult to supply the product liquid, and the operation was stopped.

[0021]

[Table 1] ─────────────────────────── Orthoxylene 81.87 wt% OTP-2 16.10 wt% OTP-3 0.003 wt % OTP-4 0.016wt% C20H 0.071wt% Other high boiling byproducts 2.03wt% ───────────────────────────── OTP-2; 5- (O-tolyl) -2-pentene. OTP-3; 5- (O-tolyl) -3-pentene. OTP-4; 5- (O-tolyl) -4-pentene. C20H; 5- (O-tolyl) -2-pentene, a compound having a molecular weight of 266 produced by the reaction of ortho-xylene.

[0022]

[Table 2] ──────────────────────────────────── Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 ──────────────────────────────────── Overhead liquid Weight kg / hr 8.19 8. 28 8.21 8.31 Composition wt% Ortho-xylene 99.99 99.99 99.99 99.99 99.99 OTP-2 0.001 0.001 0.001 0.001 0.001 ──────────── ───────────────────────── Kettle discharge weight kg / hr 1.81 1.72 1.79 1.69 Composition wt% Orthoxylene 0 0.001 0.001 0.001 0.001 OTP-2 88.36 71.46 85.43 60.45 OTP-3 0.015 0.71 0.14 0.83 TP-4 0.088 4.73 0.95 6.28 C20H 0.39 2.67 0.53 4.06 Other high boiling byproducts 11.15 20.42 12.95 28.38 ───── ─────────────────────────────── OTP-2; 5- (O-tolyl) -2-pentene. OTP-3; 5- (O-tolyl) -3-pentene. OTP-4; 5- (O-tolyl) -4-pentene. C20H; 5- (O-tolyl) -2-pentene, a compound having a molecular weight of 266 produced by the reaction of ortho-xylene.

Claims (6)

[Claims] 1. A side chain of an aromatic hydrocarbon compound in which one or more hydrogen atoms are bonded to the α-position of the side chain is alkenylated with an alkali metal catalyst using a conjugated diene having 4 or 5 carbon atoms. In producing monoalkenylbenzenes by deactivating the alkali metal catalyst from the reaction product solution and / or
Alternatively, the method for purifying monoalkenylbenzenes is characterized in that after removal, the monoalkenylbenzenes are separated and recovered by distillation. 2. The method according to claim 1, wherein the reaction product solution is filtered through a filter of 5 microns or less to remove the alkali metal catalyst. 3. The method according to claim 1, wherein the alkali metal catalyst is deactivated and / or removed by contacting with a solid acid. 4. The method according to claim 1, wherein the alkali metal catalyst is deactivated and / or removed by contacting with a carbon material. 5. The method according to claim 1, wherein the alkali metal catalyst is deactivated and / or removed by bringing it into contact with a cationic ion exchange resin. 6. The method according to claim 1, wherein metal potassium and metal sodium, or an alloy thereof is used as the alkali metal catalyst.