JPH0873410A - Production of dialkyl carbonate - Google Patents

Abstract

PURPOSE: To extremely advantageously produce a dialkyl carbonate in high yield and selectivity by reacting an alkylene carbonate with an alcohol using a specific catalyst. CONSTITUTION: This method for producing a dialkyl carbonate of formula III comprises reacting an alkylene carbonate of formula I (R is an alkyl) with an alcohol of formula II (R' is a 1-6C alkyl) using zinc carbonate as a catalyst. This compound can be separated and recovered from a reactional product containing the dialkyl carbonate of formula III by as necessary, filtering a catalyst from the reaction solution and distilling the solution under reduced pressure. The reaction temperature is preferably 100-200 deg.C. The reaction pressure is preferably atmospheric pressure to 20kg/cm<2> . The dialkyl carbonate is useful as a solvent for resins and coating, an alkylating agent or a synthetic raw material for carbamate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a dialkyl carbonate. More specifically, the present invention relates to a method for producing a dialkyl carbonate in a high yield by reacting an alkylene carbonate with an alcohol using a specific catalyst. Dialkyl carbonate is a compound useful as a solvent for resins and paints, an alkylating agent, or a raw material for synthesizing carbamates.

[0002]

2. Description of the Related Art As a catalyst used in a method for producing a dialkyl carbonate from an alkylene carbonate and an alcohol, various homogeneous catalysts such as aliphatic tertiary amines (JP-A-51-212025), alkali metals or Alkali metal compounds (JP-A-54-4871)
5) and thallium compounds (JP-A-54-48716).
No.), tin alkoxides (JP-A-54-63023).
), A quaternary phosphonium salt (JP-A-56-101)
No. 44) has been proposed. And in these methods, in order to isolate dimethyl carbonate which is a product, the distillation method is usually adopted as a separation operation. However, when a homogeneous catalyst is used,
(1) It is difficult to separate the reaction mixture and the catalyst;
(2) Since the catalyst is present during the distillation, reverse equilibrium is likely to occur and the selectivity of dimethyl carbonate is lowered.

On the other hand, as a method of using a heterogeneous catalyst which solves this problem, for example, a silica-titania solid acid catalyst (JP-A-54-125617) and a strong quaternary ammonium salt-containing exchange group are used. Basic exchange resins (JP-A-63-238043), cation exchange resins having a sulfonic acid group or a carboxylic acid group as exchange groups (JP-A-64-31737), and the like have been proposed. However, these solid catalyst systems have problems in heat resistance, stability in long-term use, and insufficient catalytic activity. Further, a basic compound of alkaline earth metal (Japanese Patent Laid-Open No. 6-48993) has been proposed,
The problem with this solid catalyst is that it is highly soluble in the reaction solution. Recently, oxides of Group 3B metals of the periodic table (Japanese Patent Laid-Open No. 6-211751) and the like have also been reported.

[0004]

The present invention provides a method for producing a dialkyl carbonate in a high yield by reacting an alkylene carbonate with an alcohol using a solid catalyst that does not elute in the reaction solution. The purpose is to

[0005]

The present invention is characterized by reacting an alkylene carbonate and an alcohol in the presence of zinc carbonate, whereby a dialkyl carbonate is obtained with a high yield and a high selectivity. It is a method for producing a dialkyl carbonate, which can be produced extremely advantageously.

The reaction between the alkylene carbonate and the alcohol proceeds as shown in the following formula to produce the corresponding dialkyl carbonate and the corresponding alkylene glycol.

[0007]

Embedded image

As the starting alkylene carbonate,
For example, an alkylene carbonate having 3 to 7 carbon atoms such as ethylene carbonate, propylene carbonate and butylene carbonate is used. As the alcohol, aliphatic alcohols having 1 to 6 carbon atoms such as methanol, ethanol, n-propyl, i-propanol, n-butanol, s-butanol and t-butanol are used.
In particular, methanol and ethanol are preferable from the viewpoint of reactivity.

The molar ratio of the alkylene carbonate to the alcohol is not particularly limited, but if the molar ratio of the alcohol to the alkylene carbonate is too large, the amount of alcohol recovered will be too large, and if it is too small, the conversion rate of the alkylene carbonate will be low. , The molar ratio of alcohol to alkylene carbonate is 0.1 to 5
It is set to 0, preferably 0.2 to 20. When the batch method is used, the molar ratio is usually 2 or more.

In the method of the present invention, zinc carbonate is used as a catalyst. Zinc carbonate is used as a solid catalyst in the form of powder, spheres, cylinders or the like. The amount of catalyst is not particularly limited, but is usually 0.001 to 10 mol, preferably 0.01 to 1 mol, based on 1 mol of alkylene carbonate.
It is in the molar range.

As a reaction method, in the case of a batch method, a method is generally used in which a predetermined amount of raw materials and a catalyst are charged in a reaction vessel all at once, and the inside of the reaction vessel is replaced with nitrogen, and then heated and pressurized to react for a predetermined time. is there. In the case of the continuous method, a reactor kept at a constant temperature is continuously fed with a mixed solution of alkylene carbonate and alcohol, and the produced dialkyl carbonate is continuously withdrawn as a mixed solution with unreacted raw materials. Done. As the reactor, when a powdered catalyst is used, a suspension bed type in which the catalyst is continuously supplied by suspending it in a mixed solution of feed materials is used. Fixed bed systems with reactors are commonly used.

The reaction temperature is usually in the range of 50 to 300 ° C. If the reaction temperature is too low, the reaction rate will decrease, and if it is too high, side reactions will increase, so it is preferably in the range of 100 to 200 ° C. The reaction time varies depending on the raw material alkylene carbonate, the type and molar ratio of alcohol, the reaction temperature, the amount of catalyst, the reaction method, etc.
It is usually in the range of 0.2 to 20 hours, preferably 0.5 to 5 hours. The reaction pressure is not particularly limited, but is usually 1 to 200 Kg / cm ² G, preferably atmospheric pressure to 20.
It is in the range of Kg / cm ² G.

The reaction product liquid contains the desired dialkyl carbonate, by-produced alkylene glycol, unreacted alkylene carbonate and alcohol, and some by-product. After completion of the reaction, the target product can be separated and recovered by filtering the catalyst from the reaction solution as necessary and distilling under reduced pressure.

[0014]

EXAMPLES The present invention will be described more specifically with reference to the following experimental examples. The reaction product was quantified by gas chromatography. (Example 1) 35.2 ethylene carbonate was added to a stainless steel autoclave equipped with a stirrer having a capacity of 300 ml.
g (0.4 mol), zinc carbonate 3.0 g (0.024 m
ol), and 128.0 g of methanol (4.0 mo)
After l) was charged and the inside of the reactor was replaced with nitrogen, nitrogen was injected under pressure to 2.0 Kg / cm ² G, and then the mixture was reacted at 140 ° C for 2 hours. The pressure during the reaction was 8.5 Kg / cm ² G. When the reaction solution was analyzed after the completion of the reaction, the conversion rate of ethylene carbonate was 67.4%. Further, since the yield of dimethyl carbonate was 65.7%, the selectivity of dimethyl carbonate based on ethylene carbonate was 97.5%. (Example 2) In Example 1, the amount of methanol was changed to 6
The reaction was carried out in the same manner as in Example 1 except that the pressure was 4.0 g (2.0 mol), and the pressure during the reaction was 9.0 Kg / cm ² G. As a result, the conversion rate of ethylene carbonate was 56.5% and the yield of dimethyl carbonate was 56.
It was 3%, and the selectivity of dimethyl carbonate based on ethylene carbonate was 99.6%.

Claims (1)

[Claims] 1. A method for producing a dialkyl carbonate, which comprises reacting an alkylene carbonate and an alcohol in the presence of zinc carbonate.