JPH0648993A - Method for producing dialkyl carbonate - Google Patents

Abstract

(57) [Summary] [Structure] An alkylene carbonate is reacted with an alcohol in the presence of a basic compound of an alkaline earth metal to produce a dialkyl carbonate. [Effect] Dialkyl carbonate is produced with high selectivity from alkylene carbonate and alcohol. Further, since the heterogeneous catalyst is used, the dialkyl carbonate can be efficiently separated, which is industrially advantageous.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a dialkyl carbonate from an alkylene carbonate and an alcohol. Dialkyl carbonate is an important substance as a solvent for resins and paints, an alkylating agent, and a raw material for carbamate synthesis.

[0002]

2. Description of the Related Art As a method for producing a dialkyl carbonate from an alkylene carbonate and an alcohol, methods using various catalysts are known. For example, JP-A-5
No. 1-122025, aliphatic tertiary amines, JP-A-54
No. -48715, an alkali metal or an alkali metal compound, JP-A-54-48716, a thallium catalyst, JP-A-54-63023, a tin alkoxide, and JP-A-56-10144, a phosphonium salt. Kaisho 63-
238043, solid basic anion exchangers; JP-A-64-31737, various ion exchange resins;
-44354 proposes a method using a hydrotalcite compound containing MgO and Al ₂ O ₃ at the same time, and JP-A-4-93356 proposes a method using a lead compound as a catalyst.

[0003]

The product liquid obtained by reacting an alkylene carbonate with an alcohol in the presence of a catalyst is a mixture of an alkylene carbonate, an alcohol, a dialkyl carbonate, an alkylene glycol and the like with a catalyst. As a method for separating each component from these reaction mixtures, a method by distillation is usually adopted. In the conventional method for producing a dialkyl carbonate from an alkylene carbonate and an alcohol, a homogeneous catalyst is mainly used, but in this case, when a catalyst is present in the reaction product solution when the components are separated by distillation, a reverse equilibrium reaction occurs. It has a drawback that the selectivity of dialkyl carbonate is lowered due to the decomposition or decomposition. As a method of using a heterogeneous solid catalyst to prevent this, there is a method using a thallium compound or a lead compound, but these are toxic and considerably expensive. In addition, solid basic anion exchangers, various ion exchange resins and hydrotalcite compounds are used in flow reactors, but the former cannot be used for a long time due to limited temperature, and the latter has low activity, so the operating temperature is low. There is a problem such as the need to raise.

[0004]

Means for Solving the Problems The inventors of the present invention have diligently studied a method for producing a dialkyl carbonate having the above-mentioned problems, and as a result, by using a basic compound of an alkaline earth metal as a catalyst, the dialkyl carbonate has a high selectivity. The present invention has been completed by finding that the dialkyl carbonate obtained in the above can be produced extremely advantageously.

That is, the present invention is a process for producing a dialkyl carbonate, which comprises reacting an alkylene carbonate with an alcohol in the presence of a basic compound of an alkaline earth metal.

The reaction of the present invention is represented by the following general formula, and is usually carried out by adding a catalyst into alkylene carbonate and alcohol and then heating.

[0007]

[Chemical 1]

In the above formula, R ₁ is a hydrogen group or a carbon number 1
Is an alkyl group having 4 to 4 and R ₂ is an alkyl group having 1 to 12 carbons or an alicyclic group. Therefore, examples of the alkylene carbonate used as the raw material include ethylene carbonate and propylene carbonate. Examples of alcohols include methyl alcohol, ethyl alcohol,
Examples thereof include aliphatic alcohols such as propyl alcohol and isopropyl alcohol, and alicyclic alcohols such as cyclohexanol. The amount ratio of alkylene carbonate and alcohol used in the reaction is not particularly limited, but is usually in the range of 1 to 20 in terms of molar ratio of alcohol to alkylene carbonate.

The alkaline earth metal basic compound used in the catalyst of the present invention is not particularly limited, but particularly calcium and barium oxides and hydroxides are preferably used. Also used are those obtained by reacting these alkaline earth metal basic compounds with organic compounds present in the reaction system, such as alkylene carbonate, alcohol, alkylene glycol, dialkyl carbonate and the like. These compounds may be used alone or in combination with two or more. Further, it can be used by mixing with a compound inert to the reaction or a carrier, or by supporting it.
The amount of the alkaline earth metal basic compound used as the catalyst is not particularly limited, but is usually 0.0001 to 10 mol, preferably 0.001 to 1 mol per 1 mol of alkylene carbonate.

The reaction temperature in the present invention is 50 to 200.
C is preferred. When the reaction temperature is too low, the reaction rate is low, and when it is too high, the amount of side reaction increases. The reaction time varies depending on the types and ratios of the alkylene carbonate and alcohol as raw materials, the type and amount of catalyst, the reaction temperature, etc., but is usually 0.2 to 10 hours. The reaction pressure in the present invention is not particularly important and may be the pressure indicated by the reactants at the reaction temperature, but usually from atmospheric pressure to 20 kg /
It is in the range of cm ² .

The alkylene carbonate produced by the reaction can be easily separated and recovered from the reaction solution by separating the catalyst by a conventional method after the reaction and distilling. The reaction of the present invention can be performed by either a batch method or a continuous method.

[0012]

EXAMPLES Next, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

Example 1 To an autoclave having a capacity of 100 ml, 0.4 mol of ethylene carbonate, 0.8 mol of methanol and 0.13 g of calcium oxide were added, and the inside of the system was replaced with nitrogen.
It was immersed in an oil bath at 00 ° C. and shaken and stirred. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and then the composition of the reaction solution was analyzed by gas chromatography to find that methanol was 26.0 wt% and dimethyl carbonate was 22.4 wt.
%, Ethylene glycol 15.5 wt%, and ethylene carbonate 35.9 wt%. This result shows that the selectivity of dimethyl carbonate based on the reacted ethylene carbonate is 99% or more.

Example 2 Example 1 except that the amount of charged methanol was 1.6 mol.
The reaction was carried out in the same manner as in. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and then the composition of the reaction solution was analyzed by gas chromatography.
The content was 3 wt%, dimethyl carbonate 20.8 wt%, ethylene glycol 14.4 wt%, and ethylene carbonate 20.3 wt%. This result shows that the selectivity of dimethyl carbonate based on the reacted ethylene carbonate is 99% or more.

Example 3 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 80 ° C. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and the reaction solution composition was analyzed by gas chromatography. As a result, methanol 27.5 wt%, dimethyl carbonate 20.4 wt%, ethylene glycol 14.0 wt% and ethylene carbonate 37 .8 wt%
Met. This result shows that the selectivity of dimethyl carbonate based on the reacted ethylene carbonate is 99% or more.

Example 4 The reaction was carried out in the same manner as in Example 1 except that the reaction temperature was 120 ° C. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and then the reaction liquid composition was analyzed by gas chromatography. As a result, methanol 23.9 wt%, dimethyl carbonate 25.5 wt%, ethylene glycol 17.6 wt%, ethylene carbonate 32 .9 wt
%Met. This result shows that the selectivity of dimethyl carbonate based on the reacted ethylene carbonate is 99% or more.

Example 5 The reaction was carried out in the same manner as in Example 1 except that the amount of calcium oxide charged was 1.3 g. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and then the composition of the reaction solution was analyzed by gas chromatography to find that methanol was 22.7 wt% and dimethyl carbonate was 27.0 wt.
%, Ethylene glycol 18.6 wt%, and ethylene carbonate 31.3 wt%. This result shows that the selectivity of dimethyl carbonate based on the reacted ethylene carbonate is 99% or more.

Examples 6 to 8 Reactions were carried out in the same manner as in Example 1 except that various alkaline earth metal basic compounds were used as catalysts.
The results are shown in Table 1.

[0019]

[Table 1] * 1: DMC indicates dimethyl carbonate. * 2: EC indicates ethylene carbonate.

Example 9 The reaction was carried out in the same manner as in Example 1 except that ethanol was used in place of the charged methanol. After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and the composition of the reaction solution was analyzed by gas chromatography.
4.0 wt%, diethyl carbonate 21.8 wt%,
It was 11.5 wt% of ethylene glycol and 32.5 wt% of ethylene carbonate. This result shows that the selectivity of reacted diethyl carbonate based on diethyl carbonate is 99% or more.

Example 10 The reaction was carried out in the same manner as in Example 1 except that the charged ethylene carbonate was replaced with propylene carbonate.
After reacting for 1 hour, the autoclave was taken out of the oil bath and cooled, and then the reaction solution composition was analyzed by gas chromatography. As a result, methanol 27.7 wt%, dimethyl carbonate 15.1 wt% and propylene glycol 12.8 w
t% and propylene carbonate 44.3 wt%. This result shows that the selectivity of dimethyl carbonate based on the reacted propylene carbonate is 99% or more.

[0022]

INDUSTRIAL APPLICABILITY As shown in the examples, in the present invention, dialkyl carbonate is produced from alkylene carbonate and alcohol with high selectivity. Since the catalyst of the present invention is a heterogeneous system, if the catalyst is separated and then distilled, a decrease in selectivity can be avoided and dialkyl carbonate can be separated efficiently. Further, since this catalyst is inexpensive, has no toxicity, and its use temperature is not limited, dialkyl carbonate can be produced extremely advantageously by the method of the present invention.

Claims (1)

[Claims] 1. A method for producing a dialkyl carbonate, which comprises reacting an alkylene carbonate with an alcohol in the presence of a basic compound of an alkaline earth metal.