JPH0977706A - Simultaneous production of dialkyl carbonate and glycol - Google Patents

Abstract

(57) Abstract: A method for producing a dialkyl carbonate and a glycol from an alkylene carbonate and an alcohol in a high yield is provided. SOLUTION: In the simultaneous production of dialkyl carbonate and glycol by reacting alkylene carbonate and alcohol, it is efficient to use at least one of scandium, yttrium, lanthanide metal and actinide metal carbonate as a catalyst. Get the target.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for simultaneously producing dialkyl carbonate and glycol.
More specifically, it relates to a method for efficiently producing a dialkyl carbonate and a glycol in a high yield by reacting an alkylene carbonate and an alcohol in the presence of a catalyst.

[0002]

2. Description of the Related Art Dialkyl carbonate is a compound useful as a solvent, a gasoline additive, an alkylating agent, an intermediate raw material for polycarbonate, and the like. On the other hand, glycols such as ethylene glycol and propylene glycol are industrially extremely important compounds as raw materials for polyesters, which are widely used as resins, films and fibers, as well as urethane raw materials and additives.

As a method for producing a dialkyl carbonate, there have been proposed many methods for producing a dialkyl carbonate by reacting an alkylene carbonate with an alcohol in the presence of a catalyst. The catalysts, each having transesterification ability, are classified into a homogeneous catalyst soluble in the reaction system and a heterogeneous catalyst hardly soluble or insoluble in the reaction system.

As a homogeneous catalyst, for example, a method using a tertiary aliphatic amine as a catalyst (Japanese Patent Publication No. 59-28542), a method using an alkali metal or an alkali metal derivative (US Pat. No. 3642858, Japanese Patent Publication No. Sho) is used. 61-16267), a method using alkyl tin alkoxide (Japanese Patent Publication No.
56-40708), a method using alkoxides of zinc, aluminum and titanium (Japanese Patent Publication No. 60-22697), a method using a thallium compound (Japanese Patent Publication No. 60-27658),
A method using a mixture of a Lewis acid and a nitrogen-containing organic base (Japanese Patent Publication No. 60-22698), a method using a phosphine compound (Japanese Patent Publication No. 61-4381), and a method using a quaternary phosphonium salt (Japanese Patent Laid-Open Publication No. Sho 60 (1999)). 56-10144) and the like have been proposed.

The methods using these homogeneous catalysts have the advantage that high activity can be obtained with a small amount of catalyst.
The disadvantage is that the reaction mixture and the catalyst are difficult to separate. This transesterification reaction is an equilibrium reaction, and when trying to separate the target dialkyl carbonate and glycol by distillation, the equilibrium shifts during distillation in the presence of a catalyst, and a reverse reaction easily occurs, and dialkyl carbonate and glycol form alkylene carbonate. The reaction to return to alcohol occurs. Further, reactions such as dehydration condensation and decomposition occur, which is not preferable in the process.

To prevent this, heterogeneous catalysts have been proposed. In the case of a heterogeneous catalyst, the reaction mixture and the catalyst can be easily separated, and the above-mentioned problems are solved. As the method using such a heterogeneous catalyst, for example, a method using a silica-titania solid acid catalyst (Japanese Patent Publication No. 61-5467) and a method using an alkali metal or alkaline earth metal silicate-supported catalyst (Japanese Patent Laid-Open No. Sho 61-46) 64-31737), and a method using oxides of zirconium, titanium, and tin (JP-A-63-63).
-41432), a method using a lead compound (JP-A-4-9356)
JP-A-6-43354), a method using a hydrotalcite compound containing magnesia and alumina (JP-A-3-43354), and a method using a metal oxide such as zinc oxide (JP-A-6-63).
211751 and JP-A-6-239806), methods using an inorganic solid catalyst have been proposed.

Further, as a heterogeneous catalyst, a method using an ion exchange resin, for example, a solid basic anion exchange resin having a quaternary ammonium group or a tertiary amine group as a catalyst (Japanese Patent Laid-Open No. 3-109358, Japanese Patent Laid-Open No. 109358/1988) 64-31737, JP 63
-238043, Japanese Patent Publication No. 59-28542), a method using an acidic ion exchange resin as a catalyst (Japanese Patent Laid-Open No. 64-31737)
Method using carboxylic acid type cation exchange resin
6-345696 publication) and the like are also known.

However, these conventionally known heterogeneous catalysts are generally low in activity, and none of them has reached a practical level in the case of inorganic solid catalysts. Further, the method using an ion exchange resin shows a relatively high catalytic activity, but there is a problem in heat resistance and durability for industrial use, and the catalytic activity is insufficient at a low temperature where durability can be maintained. I have a problem.

[0009]

The object of the present invention is to find a catalyst having an unprecedentedly high activity among compounds that have not been known as a catalyst, and to use it to obtain the above-mentioned drawbacks. Another object of the present invention is to provide a method for producing a dialkyl carbonate and a glycol simultaneously in a high yield with high efficiency and without any problems.

[0010]

Means for Solving the Problems As a result of intensive research to solve the above problems, the present inventors have found an excellent new catalyst and arrived at the present invention. Thus, according to the invention,
By using a carbonate of a rare earth metal as a catalyst in the transesterification reaction of an alkylene carbonate and an alcohol, a method for simultaneously producing a dialkyl carbonate and a glycol in a high yield and efficiently is provided.

That is, according to the present invention, the alkylene carbonate represented by the general formula [1] is transesterified with the alcohol represented by the general formula [2] to give a dialkyl carbonate represented by the general formula [3]. And a glycol represented by the above general formula [4], wherein at least one compound selected from scandium, yttrium, lanthanide metal and actinide metal carbonates is used as a catalyst. Is the way to do it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The following general formula [1] used as a raw material in the present invention

[0013]

Embedded image

(In the above formula [1], R ¹ , R ² , R ³ and R ⁴ are the same or different from each other and represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms with or without a side chain. The alkyl group may be cyclic or may contain a double bond.) Specific examples of the alkylene carbonate represented by the formula: ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3
-Butylene carbonate, styrene carbonate and the like. Among these, ethylene carbonate or propylene carbonate is most preferably used because of the usefulness of the desired glycol and industrial availability.

Another raw material in the present invention is the following general formula [2] R ⁵ OH [2] (in the above formula [2], R ⁵ has 1 to 12 carbon atoms with or without a side chain. Specific examples of the alcohol represented by an alkyl group, which may be a cyclic group or a group containing a double bond, include methyl alcohol, ethyl alcohol, n-propyl alcohol, is
o-propyl alcohol, n-butyl alcohol, iso
-Butyl alcohol, sec-butyl alcohol, pentyl alcohol, hexyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, dodecyl alcohol, allyl alcohol, cyclohexyl alcohol, benzyl alcohol, etc. Lower aliphatic alcohol,
Particularly, methyl alcohol or ethyl alcohol is most useful and is preferably used.

In the present invention, the following stoichiometric formula [5] is obtained by reacting the above alkylene carbonate and monohydric alcohol in the presence of a specific catalyst.

[0017]

Embedded image

(In the above formula [5], R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same as above.) According to the following general formula [3]

[0019]

[Chemical 6]

(In the above formula [3], R ⁵ is the same as above), and a dialkyl carbonate represented by the following general formula [4]

[0021]

[Chemical 7]

(In the above formula [4], R ¹ , R ² , R ³ and R ⁴ are the same as above) and glycol is simultaneously produced.

Therefore, the catalyst used in the present invention is at least one selected from the carbonates of metals (elements) selected from the group 3 (former 3B group) rare earth elements of scandium, yttrium, lanthanide and actinide. And a compound containing. Specific examples of these rare earth elements are Sc, Y and lanthanide group La, Ce, Pr, N.
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, Lu, Actinide Ac, Th, Pa,
U, etc. can be mentioned. In the present invention, these rare earth element carbonates are used as catalysts. Usually, these carbonates have a valence of 3, but some of them have a valence of 4, and some have a valence of 2, but any of them can be used in the present invention. Generally, trivalent carbonate is a compound represented by the following general formula [6].

Ln ₂ (CO ₃ ) ₃ [6] (In the above formula [6], Ln represents scandium, yttrium, or a rare earth metal element such as lanthanide and actinide.)

In the above formula [6], scandium,
Carbonates of yttrium, lanthanide metal, and actinide metal are expressed in the form of trivalent monomers, but depending on the type of these metals and the type and combination of aliphatic hydrocarbon groups, dimers or higher polymers Alternatively, it may form a mixture of a monomer and a multimer, and both can be used as the carbonate in the present invention.

Further, even if a part of the carbonate is replaced with a hydroxyl group or an oxide, it is used in the same manner. An example of this is a carbonate, part of which is known as a basic carbonate, replaced by a hydroxyl group.

As mentioned above, scandium (Sc), yttrium (Y), and lanthanide metals (La, Ce, Pr, N).
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m, Yb, Lu) and actinide metal (Ac, Th,
All of the carbonates of metals (elements) selected from Pa, U) have a high catalytic activity for this reaction and can be suitably used in the present invention. Among them, Y, La, Ce, Pr,
Rare earth elements belonging to the so-called cerium group of Nr and Sm have a large amount of endowment and are particularly preferably used on an industrial scale.

As the catalyst composed of a carbonate of these rare earth elements, a commercially available catalyst may be used as it is, but it can be easily prepared by the following well-known method. For example, a method of reacting carbon dioxide with a basic compound such as a lanthanide metal hydroxide or alkoxide, or a water-soluble alkali metal or alkaline earth metal salt of a lanthanide metal hydrochloride, nitrate, sulfate or the like. A method of reacting a metal carbonate, hydrogen carbonate or ammonium carbonate can be adopted. In particular, the latter method has a wide range of applicability because the carbonate of the rare earth element is almost insoluble in water, so that the carbonate can be easily obtained. For example, it is known that a carbonate partially hydrolyzed and containing a hydroxyl group, a complex carbonate containing an alkali metal element or another metal element, and the like can be prepared by manipulating the preparation conditions. The fact that it is effective as a catalyst is as described above. As a method for producing a special carbonate, a method in which trichloroacetic acid salt is decomposed in an aqueous solution is known, and such a method can be adopted in the catalyst preparation of the present invention.

The advantages of these rare earth element carbonates used in the present invention are not only that they are highly active as catalysts for this reaction, but they are hardly dissolved in the reaction system and can be used as heterogeneous catalysts. That is the point. Under the conditions used for the reaction, it is extremely stable both thermally and chemically, and can be easily separated from the reactant and recycled.

In general, the above catalyst can be used in a catalytic amount to produce a dialkyl carbonate and an alkylene glycol by reacting an alkylene carbonate with an alcohol according to the above general formula [5].

The reaction temperature is 40 to 300 ° C., preferably 50 to 2
50 ° C. If it is lower than this temperature range, the reaction rate is not sufficient, and if it is higher than this temperature range, side reactions such as decomposition may occur, which is not preferable.

In the present invention, the composition ratio of the alkylene carbonate as a raw material and the alcohol is a stoichiometrically molar ratio of 1 alcohol to 2 alkylene carbonate, but this reaction is controlled by chemical equilibrium. In order to increase the conversion of alkylene carbonate, alcohol is generally used in excess. Usually, the alcohol is used in a molar ratio of 2 to 20, more preferably 2 to 10 with respect to the alkylene carbonate.

When this reaction is carried out in a closed form, or when it is carried out even in an open system at total reflux, the reaction apparently stops when it reaches an equilibrium composition based on the equilibrium constant at the reaction temperature used. Therefore, in order to further proceed the reaction ultimately, it is necessary to separate the catalyst and the reactant from the equilibrium composition and the raw material and the product. Since the catalyst used in the present invention exhibits a substantially heterogeneous system, the separation of the catalyst and the reaction product is relatively easy, the separated catalyst is reused as it is, and the reaction product does not react with the target product. The raw materials are separated by a method such as distillation.

[0034]

The present invention will be described below with reference to examples.
It goes without saying that the invention is not limited to these examples.

[Example 1] Autoclave having a capacity of 100 ml
17.6 g of ethylene carbonate (EC) and
And 32.0 g of methanol were charged, and lanthanum carbonate was used as a catalyst.
Tan La₂(CO _Three)_Three Add 1.5g and stir
The temperature of the oil bath was set to 150 ° C. and the reaction was carried out for 1 hour. After reaction
The reaction product is proton H except for the catalyst.¹NMR (Nuclear
Use the magnetic resonance spectrum) to determine the peak area ratio of each component.
Quantitative analysis was performed.

As a result, the composition of the reaction mixture was ethylene carbonate (EC); 8.1 g, methanol; 21.8.
g, dimethyl carbonate (DMC); 9.5 g, ethylene glycol (EG); 5.9 g, 2-hydroxyethyl methyl carbonate, etc .; 4.4 g. The conversion rate based on ethylene carbonate is 54.0.
%, And the DMC yield is 52.8%. In addition, 2-
Hydroxyethylmethyl carbonate and the like include bis2-hydroxyethyl carbonate, 1,2-ethanediyldimethyl carbonate, and the like, which are equilibrium intermediates.

[Embodiment 2] As in Embodiment 1, the capacity is 100.
17.6g ethylene carbonate in a ml autoclave
And 32.0 g of methanol and catalyst neodymium carbonate
_{Nd 2 (CO 3) 3 ·} 8H 2 was O 1.5 g reacted at 0.99 ° C. placed. As a result of analyzing the reaction results in the same manner as in Example 1, 3.7 g of ethylene carbonate and 21.8 g of methanol were recovered, and dimethyl carbonate; 1
It was found that 2.8 g, ethylene glycol; 7.9 g and 2-hydroxyethyl methyl carbonate; 3.4 g were obtained. The conversion rate of ethylene carbonate is 78.
7%, and the yield of dimethyl carbonate was 71.7%.

[Examples 3-5, Comparative Examples 1-2] 100 ml
In an autoclave, 17.6 g of ethylene carbonate, 16 g of methanol and 1.5 g of the compound shown in Table 1 as a catalyst were added and stirred at 150 ° C. for 1 hour. After the reaction, the reaction product was taken out immediately after quenching and gas chromatography (filler; Porapak Type P (Waters), analysis temperature;
Quantitative analysis was performed using 200 ° C.). The conversion rate was calculated from the recovered amount of ethylene carbonate, and the production amounts of dimethyl carbonate and free ethylene glycol were compared.
Table 1 shows the results.

[0039]

[Table 1]

Example 6 After the neodymium carbonate used in Example 3 was filtered to separate it from the reaction product, Example 3 was mixed with 17.6 g of ethylene carbonate and 32.0 g of methanol in a 100 ml autoclave. The reaction was carried out under the same conditions as above at 150 ° C. for 1 hour. After the reaction, the reaction product was similarly quantitatively analyzed using gas chromatography. As a result, the conversion rate of ethylene carbonate was 65%, the amount of DMC produced was 10.2 g, and the amount of EG produced was 8.1 g.

[0041]

According to the method of the present invention as described above, it is possible to simultaneously produce a dialkyl carbonate useful as a polymer raw material and a glycol from an alkylene carbonate and an alcohol in a high yield.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C07C 69/96 C07C 69/96 Z // C07B 61/00 300 C07B 61/00 300

Claims (6)

[Claims] 1. A compound of the general formula [1] (In the above formula [1], R ¹ , R ² , R ³ and R ⁴ are the same or different from each other and are a hydrogen atom or an alkyl group having 1 to 2 carbon atoms with or without a side chain.)
And an alcohol represented by the general formula [2] R ⁵ OH [2] (in the above formula [2], R ⁵ is an alkyl group having 1 to 12 carbon atoms), General formula [3] (In the above formula [3], R ⁵ is the same as the above formula [2].) And the dialkyl carbonate represented by the general formula [4] (In the above formula [4], R ¹ , R ² , R ³ and R ⁴ are the same as those in the above formula [1].) In the method for simultaneously producing glycol, scandium, yttrium, lanthanide metal and actinide are used as catalysts. A method for producing, characterized in that at least one compound selected from metal carbonates is used. 2. The production method according to claim 1, wherein at least one compound selected from scandium, yttrium and lanthanide metal carbonates is used as the catalyst. 3. The method according to claim 1, wherein at least one compound selected from yttrium, lanthanum, cerium, neodinium and samarium carbonates is used as a catalyst. 4. The production method according to claim 1, wherein the reaction is performed under a temperature condition of 40 to 300 ° C. 5. The production method according to claim 1, wherein the alkylene carbonate is either ethylene carbonate or propylene carbonate. 6. The method according to any one of claims 1 to 5, wherein the alcohol is either methanol or ethanol.