JPH0429655B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing alkylene glycols by catalytic hydration of alkylene oxides. More specifically, the present invention relates to a process for the catalytic hydration of alkylene oxides, the main characteristics of which are the catalysts used. Ethylene glycols such as ethylene glycol (EG) and diethylene glycol (DEG) are important industrial raw materials. As a method for producing ethylene glycols, hydration of ethylene oxide (EO) is considered to be a preferable method. Prior Art The first method that can be considered as a hydration method for EO is the direct hydration method. However, in the conventionally proposed direct hydration method, it is necessary to use a large excess of water to prevent by-products such as dimers and trimers, and as a result, the produced EG is obtained in a diluted state. As a result, large amounts of power and equipment are required for concentration. Moreover, the reaction temperature is also high, at 180 to 200°C. Yet another problem with the direct hydration process is that it is not possible to selectively obtain certain alkylene glycols (eg mono- or dialkylene glycols). To solve these difficulties of the direct hydration method, a method has been proposed in which the hydration reaction is carried out catalytically under pressurized carbon dioxide (Japanese Patent Publication No. 1973-
24448, Japanese Patent Application Laid-open No. 51-127010, Japanese Patent Application Publication No. 54-19905, etc.). This method uses a nearly stoichiometric amount of water to the alkylene oxide in the presence of a catalyst such as a quaternary phosphonium salt, and can achieve high yields without producing large amounts of by-products such as diglycols and triglycols. In that monoalkylene glycol can be obtained, this method can be said to be a significant improvement over the drawbacks of the previous direct hydration method. In addition to these proposals, various catalytic hydration methods have been proposed, including a method using quaternary phosphonium salts/alkali metal halides/ammonium salts as catalysts in the coexistence of alkylene carbonate (Japanese Patent Laid-Open No. No. 55-145623, No. 56-8335 and No. 56
-8336 Publication) is of interest. According to this method, the amount of water required for the reaction can be reduced to almost the stoichiometric amount without supplying carbon dioxide, and furthermore, by-products such as dialkylene glycol and trialkylene glycol are also significantly reduced. This is because monoalkylene glycol can be obtained in high yield with a small amount of monoalkylene glycol. However, according to the knowledge of the present inventors, this method is still not completely satisfactory. That is, although monoalkylene glycol can be selectively obtained, dialkylene glycol cannot be selectively obtained. Since dialkylene glycol itself or in its etherified form is useful as a "carbitol" solvent, the problem with this prior art is that dialkylene glycol cannot also be selectively obtained. I have no choice but to point this out. SUMMARY OF THE INVENTION The present invention aims to provide a solution to the above points, and attempts to achieve this aim by employing a specific catalyst. Therefore, the method for producing alkylene glycols according to the present invention is characterized in that the catalyst used in the method for producing alkylene glycols by catalytically hydrating alkylene oxide is an organic antimony compound. Effects According to the present invention, first, alkylene glycols can be obtained in the presence of alkylene carbonate or without requiring a large amount of water under pressure injection of carbon dioxide gas, and by changing the amount of water relative to the raw material alkylene oxide. Monoalkylene glycols and dialkylene glycols can be obtained selectively and at high conversion rates. Of course, it is also possible to co-produce both glycols. Depending on the type of organic antimony compound catalyst used in the method of the present invention, the purpose is often achieved more rationally by adding alkylene carbonate or pressurizing carbon dioxide gas, but these additives and Since the catalyst used is not destroyed during this reaction, it can be recovered and reused as necessary after the reaction. Detailed Description of the Invention Raw Material Alkylene Oxide The alkylene oxide to be catalytically hydrated according to the present invention is an oxide of C _o H _2o (n = about 2 to 12),
In particular, oxides of ethylene and propylene are typical, but substituted alkylenes such as styrene, chloropropylene and other oxides may also be covered by the present invention. Catalyst The catalyst used in the present invention is an organic antimony compound. Being an organic antimony compound, the compound should have at least one carbon-antimony bond. This antimony compound is
The antimony valence may be either trivalent or pentavalent. The catalyst of the present invention may be a mixture of organic antimony compounds. One group of organic antimony compounds suitable for use in the present invention are those represented by the following formula (). R _n SbX _o ... () (Here, R is a hydrocarbon residue or halohydrocarbon group, X is a halogen atom, m is an integer from 1 to 5, n is 0 or such that m+n is 3 or 5) In the compound (), R is an aliphatic (including cycloalkyl) hydrocarbon having about 1 to 8 carbon atoms, an aromatic (including alkaryl and aralkyl) hydrocarbon having about 6 to 9 carbon atoms, and Preferred are halo-substituted products (halogen is fluorine, chlorine, bromine or iodine). Among these, methyl,
Lower alkyl groups such as ethyl and butyl, and phenyl
Simple aryl groups such as tolyl are particularly preferred. X in compound () is fluorine, chlorine, bromine or iodine, especially the latter three. Specific examples of such organic antimony compounds include Ph ₄ SbBr, Ph ₄ SbCl, (p-
CH ₃ C ₆ H ₄ ) ₃ SbBr ₂ , Ph ₃ SbBr ₂ , (p-
_{ClC6H4 ) 3SbBr2 ,} ( _CH3 ) _{3SbI2 ,} ( _CH3 ) _{3SbBr2 ,}
(CH ₃ ) ₃ SbCl ₂ , Ph ₅ Sb, Ph ₃ Sb, and others (Pn=phenyl). These are organometallic compounds,
In particular, it can be synthesized by any method available for the synthesis of organic antimony compounds. Alkylene Carbonate A cyclic carbonate having an alkylene group having about 2 to 12 carbon atoms is used as an additive in the present invention, if necessary. The alkylene moiety of the raw material alkylene oxide and the alkylene moiety of the alkylene carbonate used may or may not be the same. Catalytic hydration reaction: Depending on the catalyst used as described above and, if necessary, the type of target alkylene glycol, the reaction is carried out by adding alkylene carbonate to the reaction system or under pressure of carbon dioxide gas. Other than this point, the catalytic hydration reaction of the present invention can be carried out in a manner not essentially different from conventional catalytic hydration methods for alkylene oxides. First, water, which is an essential reactant, has a major feature in that according to the present invention, it is sufficient in a molar amount of about 0.5 to 2 times the amount of the raw material alkylene oxide. Furthermore, a major feature of the method of the present invention is that by adjusting the amount of water within this range, the selectivity of the target product can be changed arbitrarily. The amount of catalyst used is at least 0.05 mol % based on the raw alkylene oxide. The upper limit of the amount used is about 10 mol%. The preferred usage amount is 0.1
It is about 3 mol%. The reaction temperature and reaction pressure can be any suitable depending on the given above conditions. Specifically, the reaction temperature is about 40 to 180°C, preferably about 100 to 150°C, and the reaction pressure is preferably a pressure that maintains the reaction system in a liquid phase at a given temperature, especially a naturally occurring pressure. be. The amount of alkylene carbonate is at least 0.05 mol per 1 mol of raw material alkylene oxide,
Preferably it is about 0.2 mol. The upper limit of the amount used is not a particular problem, but is preferably about 1 mol. Pressure injection of carbon dioxide gas is applied particularly when the purpose is to selectively obtain dialkylene glycol, and it has a particularly favorable effect when the catalyst used is X=Cl in the general formula (). . In this case, a pressure of about 0.5 to 10 atm is sufficient, and a low pressure of about 2 to 5 atm is usually preferable. When the catalyst used is X=Br in the general formula (), monoalkylene glycol can be produced in extremely high yield simply by adding alkylene carbonate without pressurizing carbon dioxide gas, and the ratio of water to raw material alkylene oxide can be reduced. It is also possible to produce dialkylene glycol alone by changing the . Experimental Examples Examples 1 to 3 Cool an autoclave with an internal volume of 50 ml in a dry ice acetone bath, and add 50 mmol of ethylene oxide (EO), 10 mmol of ethylene carbonate,
Add 0.5 mmol of Ph ₄ SbBr and water in the proportions shown in Table 1, then heat in an electric furnace at 120°C for 2 hours.
The reaction was carried out under magnetically induced stirring for an hour. Thereafter, the autoclave was cooled with ice water, and the contents were analyzed and quantified using a gas chromatograph. The results were as shown in Table 1.

[Table] The above results show that EG and DFG can be obtained at any ratio by changing the H ₂ O/EO ratio. It is also possible to obtain EG and DEG quite selectively. It was confirmed that almost all of the added amounts of ethylene carbonate and Ph ₄ SbBr remained. Examples 4 to 6 The reaction was carried out in the same manner as in Example 1, except that ethylene carbonate (EG) was removed and CO ₂ was injected at room temperature to a concentration of 5 kg/cm ² G. However, the addition ratio of water is as shown in Table 2. The results were as shown in Table 2.

[Table] From the above results, if EC is not used, EG and DEG can be reduced by injecting carbon dioxide gas.
can be obtained in any ratio. Examples 7-10 Examples 4-6 except that Ph ₄ SbCl was used as the catalyst
The reaction was carried out in the same manner. However, in Example 10, the reaction time was 5 hours. The results were as shown in Table 3.

[Table] Example 11 The reaction was carried out in the same manner as in Example 1 except that Ph ₄ SbCl was used as a catalyst and H ₂ O/EO = 1 (molar ratio), and the EO conversion rate was 99% and the EG selectivity was 46%. , a DEG selectivity of 50 and an EG selectivity of 3% were obtained. Examples 12-13 The reaction was carried out in the same manner as in Example 11, except that neither EC was added nor carbon dioxide gas was pressurized, and Ph ₄ SbBr (Example 12) and Ph ₄ SbCl were used as catalysts. The results were as shown in Table 4.

[Table] From the results of Examples 7 to 11 and 13, X=Cl of the organic antimony compound (formula (1)) used as a catalyst.
In this case, when carbon dioxide gas is injected, the amount is less than the equivalent mole, especially about 0.5 mole, relative to the raw material EO.
It can be seen that diethylene glycol can be obtained in extremely high yield in the presence of water. Example 14 The reaction was carried out in the same manner as in Example 1 except that propylene carbonate was used instead of ethylene carbonate as an additive, and the EO conversion rate was 90% and the EG selectivity was
Got 100% and other tr results. Examples 15 to 17 The reaction was carried out in the same manner as in Example 4, except that the organic antimony compounds shown in Table 5 were used as catalysts. The results were as shown in Table 5.

[Table] Examples 18-22 The reaction (hydration of propylene oxide) was carried out in the same manner as in Example 1, except that propylene oxide was used as a raw material and the reaction conditions were as indicated. The results were as shown in Table 6.

[Table] It can be seen that the same results as above can be obtained for catalytic hydration of propylene oxide.

Claims (1)

[Scope of Claims] 1. A method for producing alkylene glycols by catalytically hydrating alkylene oxide, characterized in that the catalyst used is an organic antimony compound. 2. The method according to claim 1, wherein the organic antimony compound is represented by the following formula. R _n SbX _o (where R is a hydrocarbon residue or halohydrocarbon residue, X is a halogen atom, m is an integer from 1 to 5, n
is 0 or an integer such that m+n is 3 or 5) 3. The catalytic hydration reaction is carried out in the presence of alkylene carbonate and/or carbon dioxide, according to any one of claims 1 to 2. the method of.