JP3204576B2 - Method for producing carbonic acid diester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbonic acid diester by reacting an alcohol, carbon monoxide and oxygen in the presence of a solid catalyst.

[0002]

2. Description of the Related Art Carbonic diesters are used as additives and organic solvents for gasoline and in the production of fine chemicals such as various carbonates, carbamates, urethanes, pharmaceuticals and agricultural chemicals. It is a compound useful as a reactant in place of

As a method for producing a carbonic diester, a method of reacting phosgene with alcohols has been industrially employed. However, this method requires the use of highly toxic phosgene, and a large amount of highly corrosive hydrochloric acid is produced as a by-product due to the reaction between alcohol and phosgene.

Therefore, there has been proposed a method of producing a carbonic acid diester by reacting alcohol, carbon monoxide and oxygen in a liquid phase in the presence of a catalyst without using phosgene. The catalyst is roughly classified into a palladium catalyst containing a palladium compound as a main catalyst and a copper catalyst containing a copper compound as a main catalyst.

The reaction using a palladium catalyst is described in JP-B-61-8816 and JP-B-61-433.
No. 38 discloses this. In this method, a palladium compound is used as a main catalyst, and a copper compound and an alkali metal compound are used in combination. The palladium compound has a high activity and has an advantage that the reaction proceeds rapidly even under a condition of a low carbon monoxide partial pressure, but has a disadvantage that oxalic acid is by-produced.

On the other hand, regarding the reaction using a copper-based catalyst,
It is disclosed in Japanese Patent Publication No. 56-8020. The copper-based catalyst has a simple catalyst composition and has no oxalic acid by-product, but has lower activity than the palladium-based catalyst, requires a large amount of the catalyst, and requires a high carbon monoxide partial pressure.

However, regardless of the palladium-based or copper-based catalyst system, since the reaction solution in which the catalyst is dissolved exhibits strong corrosiveness, a pressure-resistant protective film such as a glass lining or a hollow lining is provided. Containers need to be used. Since there is a limit in the size of the pressure-resistant container provided with the corrosion-resistant lining, it is difficult to industrially produce a large amount of diester carbonate in the liquid phase using the above-mentioned catalyst.

In order to avoid such a corrosion problem accompanying the liquid phase reaction, there has been proposed a method for producing a carbonic acid diester by reacting alcohol, carbon monoxide and oxygen in a gas phase using a solid catalyst. . For example, JP-T-63-503
No. 460 (WO 87/07601) discloses a catalyst in which a metal halide is supported on a carrier by an impregnation method.
A method is disclosed in which all the raw material components are reacted in the gas phase. This method is less corrosive and is considered a method suitable for mass production.

However, when dimethyl carbonate is produced from methanol, the selectivity of dimethyl carbonate based on methanol is 95% or more in the liquid phase method, whereas the selectivity in the gas phase method is reduced in the gas phase method. That is, in Example 1 of the above publication, 64.9% of carbon monoxide and 10.8% of oxygen were used under the conditions of a reaction temperature of 115 ° C. and a reaction pressure of 20 atm by using a catalyst in which cupric chloride was supported on activated carbon. % And methanol 2
It is described that when a raw material gas having a composition of 4.3% is introduced into the catalyst layer and reacted, the selectivity is 80%.

Further, WO 90/15791 discloses a method in which an alcohol, carbon monoxide and oxygen are reacted in the gas phase in the presence of a catalyst in which a copper-tertiary organic phosphorus compound complex is supported on activated carbon. It has been disclosed. In the examples of the specification of this publication, each of the compositions has a composition of 48.6% of carbon monoxide, 2.8% of oxygen and 48.6% of methanol under the conditions of a reaction temperature of 150 ° C. and normal pressure or 6.8 atm. The reaction is performed using the raw material gas. However, according to additional tests by the present inventors, the selectivity under this condition is about 80 to 85%.

As described above, the selectivity is low in the method for producing a carbonic acid diester by a gas phase reaction, which not only increases the cost of the raw material alcohol but also requires the treatment of by-products. Can be a very big problem.

Accordingly, an object of the present invention is to provide a method for producing a carbonic acid diester with a high selectivity, despite the fact that the reaction is carried out by a gas phase method which is less corrosive and enables mass production.

[0013]

The present inventors have conducted intensive studies to achieve the above object, and as a result, set the alcohol content and carbon monoxide content in the gas supplied to the reaction system to specific ranges,
It has been found that by reacting in the gaseous phase, side reactions are remarkably suppressed, and a diester carbonate can be produced with an extremely high selectivity without lowering the reaction rate, and the present invention has been completed.

That is, the present invention provides a method for producing a carbonic acid diester by reacting an alcohol, carbon monoxide, and oxygen in the gas phase in the presence of a solid catalyst, wherein the alcohol content in the gas supplied to the reaction system is reduced. Provided is a method for producing a carbonic acid diester having 1 to 20% by volume and a carbon monoxide content of 70 to 95% by volume.

The alcohol includes a compound having one or more hydroxyl groups in a molecule, for example, methanol,
Ethanol, 1-propanol, 2-propanol, 1
-Saturated aliphatic alcohols such as butanol; unsaturated aliphatic alcohols such as allyl alcohol; alicyclic alcohols such as cyclohexanol; aromatic alcohols such as benzyl alcohol and phenol; polyhydric alcohols such as ethylene glycol and polyethylene glycol. included. In addition, the aromatic alcohol is used to include phenols having a phenolic hydroxyl group.

Preferred alcohols are monovalent saturated or unsaturated alcohols, for example, alcohols having about 1 to 6 carbon atoms. Particularly preferred alcohols include methanol,
It contains ethanol and the like, and methanol is especially popular.

The solid catalyst is not particularly limited as long as it is a solid catalyst used as a catalyst for the oxidative carbonylation reaction. For example, a halide or a salt of a transition metal such as copper can be used. From the viewpoints of reaction selectivity, catalyst life and the like, a solid catalyst containing a copper atom is preferred.

The solid catalyst containing copper atoms includes inorganic compounds, organic compounds and complexes containing copper atoms. Examples of the inorganic compound containing a copper atom include cuprous fluoride, cuprous chloride, cuprous bromide, cuprous halide of cuprous iodide; cupric fluoride, cupric chloride, and odor. Cupric halides such as cupric halide; copper carbonyl halides such as copper carbonyl chloride; copper nitrate; copper sulfate; copper carbonate; copper phosphate; Examples of the organic compound containing a copper atom include copper alkoxy halides such as copper methoxy chloride, copper methoxy bromide, and copper ethoxy chloride; copper alkoxy carbonyl halides such as copper methoxy carbonyl chloride;
Carboxylates such as copper formate, copper acetate, copper pivalate, and copper benzoate; and salts of phenols such as copper phenoxide. Examples of the complex containing a copper atom include, for example, copper inorganic or organic compounds such as cuprous chloride and copper acetate, amines such as ethylenediamine, nitrogen-containing heterocyclic compounds such as pyridine, and organic phosphorus compounds such as triphenylphosphine; Complexes with a coordinating compound such as nitriles such as benzonitrile are exemplified. The valence of copper may be either monovalent or divalent.

Among the solid catalysts containing a copper atom, a solid catalyst containing a halogen atom and a copper atom is preferred. The halogen atom includes fluorine, chlorine, bromine and iodine.

Examples of the solid catalyst containing a halogen atom and a copper atom include the above-mentioned cuprous halides, cupric halides, copper alkoxy halides, copper carbonyl halides, copper alkoxy carbonyl halides, and the like. Of these, cuprous halides such as cuprous halides such as cuprous chloride and cupric halides such as cupric chloride are particularly preferably used.

As the solid catalyst containing a halogen atom and a copper atom, a solid catalyst obtained by combining a compound containing a halogen atom and a compound containing a copper atom can be used.

As the compound containing a halogen atom,
Halides of transition metals such as iron, nickel and cobalt; alkoxy halides such as methoxy chloride of the transition metals; halides of alkali metals such as lithium, sodium and potassium; halides of alkaline earth metals such as magnesium, calcium, strontium and barium. And the like.

The compound containing a copper atom includes the above-mentioned inorganic compounds, organic compounds and complexes containing a copper atom.

The above-mentioned solid catalyst containing a copper atom can be used alone or in combination of two or more. Other catalysts not containing a copper atom, for example, compounds of transition metals other than copper, alkali metal compounds, alkali It can be used in combination with an earth metal compound or the like.

The solid catalyst used in the present invention is obtained by impregnating a catalytically active component with a carrier such as activated carbon, alumina, silica, silica-alumina, titania, zirconia, magnesia, silicon carbide, diatomaceous earth, pumice and alundum. Coating method, a catalyst supported by a method such as an adsorption method may be used.
The catalyst may be formed by tableting, extrusion, or the like.

When a solid catalyst in which the catalytically active component is supported on a carrier is used, the amount of the catalytically active component varies depending on the type of the catalytically active component and the carrier.
To 50% by weight, preferably about 0.5 to 20% by weight. In addition, when using a catalyst formed of a catalytically active component,
The content of the catalytically active component is usually about 5 to 99% by weight.

The main feature of the present invention is that the content of alcohol in the gas supplied to the reaction system is 1 to 20% by volume, and
The point is to set the carbon monoxide content to 70 to 95% by volume.

In the present specification, the alcohol content and the carbon monoxide content mean the volume% based on the total amount of the three components of alcohol, carbon monoxide and oxygen in the gas supplied to the reaction system.

When the alcohol content is less than 1% by volume, the reaction rate decreases. On the other hand, if the alcohol content exceeds 20% by volume, the amount of by-products such as formate esters such as methyl formate and ketals such as methylal increases, so that diester carbonate cannot be obtained with high selectivity. .

The carbon monoxide content is 70% by volume.
If it is less than 95%, the amount of the by-products increases, and if it exceeds 95% by volume, the oxygen content relatively decreases, so that a sufficient reaction rate cannot be obtained.

The preferred alcohol content is 4-18% by volume
And the preferred carbon monoxide content is about 75-95% by volume.

The oxygen content of the gas supplied to the reaction system constitutes the balance of alcohol and carbon monoxide, and is usually 0.5 to
It is about 28% by volume, preferably about 1 to 15% by volume.

The supply molar ratio of carbon monoxide to oxygen (C
O / O ₂ ) is, for example, 10 to 200, preferably 15 to 200.
150, more preferably about 20 to 100.

The supply molar ratio of alcohol to oxygen (alcohol / O ₂ ) is, for example, about 0.05 to 20, preferably about 0.1 to 10. The supply molar ratio of carbon monoxide to alcohol (CO / alcohol) is usually 3.5.
~ 95, preferably 4 ~ 40, more preferably 10 ~ 10
It is about 40, and good results are obtained particularly in the range of 12 to 30.

The supply molar ratio of carbon monoxide to oxygen (CO / O ₂ ) is 10 to 200, preferably 15 to 1
When the molar ratio of carbon monoxide to alcohol (CO / alcohol) is 3.5 to 95, preferably 4 to 40, and more preferably about 12 to 30, the carbonic acid Alcohol-based selectivity of the diester is significantly improved.

The gas supplied to the reaction system may be a mixed gas comprising alcohol, carbon monoxide and oxygen,
If necessary, it may be diluted with a gas inert to the reaction, for example, nitrogen, helium, argon, carbon dioxide or the like. In this case, air may be used instead of oxygen, and nitrogen in the air may be used as an inert gas. Alternatively, carbon dioxide produced as a by-product of the reaction may be recycled to the reaction system and used as an inert gas for dilution.

When the alcohol content and the carbon monoxide content in the gas supplied to the reaction system are respectively set within the above-mentioned specific ranges, the formation of by-products is significantly suppressed without reducing the reaction rate, and The rate is greatly improved.

It is considered that such a remarkable effect is exhibited by the above configuration for the following reasons.

The so-called carbonyl oxidation reaction in which alcohol, carbon monoxide and oxygen react in a liquid phase in the presence of a copper catalyst to form a carbonic acid diester has been reported in detail using dimethyl carbonate as an example [ U. Romano et
al., Ind. Eng. Chem., 19 , 396 (1980)]. In this report, as a reaction mechanism when cuprous chloride is used as a catalyst,
(1) First, cuprous chloride reacts with methanol and oxygen to form copper methoxy chloride. (2) On the other hand, cuprous chloride reacts with carbon monoxide to form copper carbonyl chloride. (3) the copper methoxy chloride reacts with the copper carbonyl chloride to produce copper methoxy carbonyl chloride, and (4) the produced copper methoxy carbonyl chloride further reacts with the copper methoxy chloride to produce dimethyl carbonate. At the same time, a mechanism has been proposed in which cuprous chloride is regenerated. In addition, the report states that, for example, at a temperature of 100 ° C., a carbon monoxide partial pressure of 20 atm or more is required from the viewpoint of the stability of copper carbonyl chloride. In fact, according to our studies,
In the liquid phase reaction, when the reaction temperature is 100 ° C. or more, the reaction rate becomes very slow when the carbon monoxide partial pressure becomes 10 atm or less.

On the other hand, the gas-phase reaction in which methanol, carbon monoxide and oxygen are reacted in the presence of a solid catalyst is characterized in that a sufficiently high reaction rate can be obtained even at a pressure of 10 atm or less, and that by-products such as methyl formate and methylal are obtained. Differs from the liquid phase reaction in that the formation of However, according to the detailed reaction analysis of the present inventors, the gas-phase reaction and the liquid-phase reaction show slight differences in the contact efficiency between the raw material gas and the catalyst and the equilibrium constant of the carbonyl complex formation reaction. It turned out that the mechanism and the behavior of the reactive components were almost the same.

That is, in the gas phase reaction, dimethyl carbonate is considered to be formed according to the reaction mechanism described in the report. Methyl formate and methylal, which are by-products, are formed when the hydrogen atom of the methyl group of copper methoxychloride generated by the reaction of cuprous chloride with methanol and oxygen is β-eliminated to formyl group. It is presumed. Β of copper methoxy chloride
Since the elimination reaction and the reaction in which copper methoxycarbonyl chloride, which is a precursor of dimethyl carbonate, is formed from copper methoxychloride and copper carbonyl chloride are competitive reactions,
In order to reduce the generation of the by-products, it is considered effective to generate a large amount of copper carbonyl chloride near the copper methoxy chloride on the catalyst surface.
For this purpose, a method of reducing the oxygen content in the gas supplied to the reaction system and a method of reducing the alcohol content are considered.

According to the method of the present invention, since the content of alcohol such as methanol among the raw material gas components is kept low and the content of carbon monoxide is large, for example, a solid catalyst supporting cuprous chloride is used. When used, the concentration of copper carbonyl chloride on the surface of the catalyst increases, and conversely, the concentration of copper alkoxy chloride such as copper methoxy chloride decreases. Therefore, a large amount of copper carbonyl chloride is present in the vicinity of the copper alkoxy chloride, and the reaction between the copper alkoxy chloride and the copper carbonyl chloride occurs in preference to the β-elimination reaction of the copper methoxy chloride.
It is considered that the formation of by-products is remarkably suppressed, and the target compound, dimethyl carbonate, can be obtained with extremely high selectivity. And this means that in order to suppress side reactions,
It has been shown that of the above two methods, the method of reducing the alcohol content is particularly effective.

The process according to the invention can be carried out in fixed-bed or fluidized-bed reactors. The reaction takes place in the gas phase. The reaction pressure is not particularly limited, but is usually from atmospheric pressure to 6 to 6 in consideration of economical aspects such as equipment costs while obtaining a sufficient reaction rate.
0 atm, preferably about atmospheric pressure to about 30 atm.

The reaction temperature can be selected within a range that does not decrease the reaction rate and suppresses side reactions.
° C, preferably about 80 to 150 ° C. The space velocity of the gas supplied to the reaction system is, for example, 10 to 5000.
0h ^-1, preferably 100~5000h about ^-1.

[0045]

According to the method of the present invention, the alcohol content and the carbon monoxide content in the gas supplied to the reaction system are limited to specific ranges, and the reaction is carried out in the gas phase. Production is possible, and side reactions are significantly suppressed, so that dimethyl carbonate can be produced with extremely high selectivity without reducing the reaction rate.

[0046]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 3.9 g of cuprous chloride was activated carbon [produced by Takeda Pharmaceutical Co., Ltd., Granulated Shirasagi C] by an ordinary method using an acetonitrile solvent.
₂ X 4 / 6-2, specific surface area of about 1200 m ² / g] to prepare a solid catalyst.

This solid catalyst was used for an inner diameter of 10 mm and a length of 45 mm.
A 0 mm stainless steel reaction tube was filled to a layer length of 70 mm, the reaction temperature was set to 120 ° C., and CO / O
_A mixed gas consisting of ₂ / methanol = 80/4/16 (volume ratio) was allowed to flow at a space velocity of 500 h ^-1 for 2 hours. During this time, the pressure in the reaction tube was maintained at a gauge pressure of 7 kg / cm ² . The reaction product gas flowing out of the reaction tube outlet is cooled to -70 ° C.
To agglomerate. The obtained aggregated liquid and non-aggregated gas were analyzed using a gas chromatograph by an internal standard method and an absolute calibration curve method, respectively.

As a result, dimethyl carbonate was obtained at a production rate of 1.0 mol / H per liter of the catalyst. The selectivity based on methanol of dimethyl carbonate was 95%, and the remaining 5% was by-product methyl formate.

Comparative Example 1 CO / O ₂ / methanol = 65/11/24 (volume ratio)
Example 1 except that a mixed gas consisting of
The reaction was carried out in the same manner as described above.

As a result, dimethyl carbonate was obtained at a production rate of 1.0 mol / H per liter of the catalyst, and the selectivity of dimethyl carbonate based on methanol was 83%.

Example 2 The reaction temperature was 140 ° C., and the pressure in the reaction tube was set to a gauge pressure of 20K.
g / cm ² , CO / O ₂ / methanol = 92/1.
The reaction was carried out in the same manner as in Example 1 except that a mixed gas of 5 / 6.5 (volume ratio) was supplied to the reaction tube.

As a result, dimethyl carbonate was obtained at a production rate of 1.8 mol / H per liter of the catalyst, and the selectivity of dimethyl carbonate based on methanol was 98%.

Example 3 The reaction temperature was set to 125 ° C. and the pressure in the reaction tube was set to a gauge pressure of 20K.
g / cm ² , CO / O ₂ / methanol = 93/0.
The reaction was carried out in the same manner as in Example 1 except that a mixed gas of 5 / 6.5 (volume ratio) was supplied to the reaction tube.

As a result, dimethyl carbonate was obtained at a production rate of 1.5 mol / H per liter of the catalyst, and the selectivity of dimethyl carbonate based on methanol was 100%.

Example 4 A solid catalyst was packed so as to have a layer length of 175 mm, the reaction temperature was 140 ° C., and the pressure inside the reaction tube was 20 kg / g.
cm ² , CO / O ₂ /methanol=92/1.5/
A mixed gas consisting of 6.5 (volume ratio) is supplied at a space velocity of 200 h.
^The reaction was carried out in the same manner as in Example 1, except that the mixture was fed to the reaction tube at ^-1 .

As a result, dimethyl carbonate was obtained at a production rate of 1.2 mol / H per liter of the catalyst, and the selectivity of dimethyl carbonate based on methanol was 98%.

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Claims (12)

(57) [Claims] 1. A method for producing a carbonic acid diester by reacting an alcohol, carbon monoxide and oxygen in the gas phase in the presence of a solid catalyst, wherein the alcohol content in the gas supplied to the reaction system is 1 to 20 vol. %, Carbon monoxide content of 70-9
A method for producing a carbonic acid diester at 5% by volume. 2. The process for producing a carbonic diester according to claim 1, wherein the alcohol content in the gas supplied to the reaction system is 4 to 18% by volume and the carbon monoxide content is 75 to 95% by volume. 3. The process for producing a carbonic diester according to claim 1, wherein the supply molar ratio of carbon monoxide to alcohol (CO / alcohol) is from 3.5 to 95. 4. The process for producing a carbonic diester according to claim 1, wherein the supply molar ratio of carbon monoxide to oxygen (CO / O ₂ ) is 10 to 200. 5. A supply molar ratio of carbon monoxide to alcohol (CO / alcohol) is from 3.5 to 95, and a supply molar ratio of carbon monoxide to oxygen (CO / O ₂ ) is 1 to 5.
The method for producing a carbonic acid diester according to claim 1, wherein the number is from 5 to 150. 6. The method according to claim 1, wherein a solid catalyst containing copper atoms is used.
A process for producing the carbonic diester according to the above. 7. The method for producing a carbonic acid diester according to claim 6, wherein the solid catalyst containing a copper atom is supported on a carrier. 8. The method for producing a carbonic acid diester according to claim 1, wherein an alcohol having 1 to 6 carbon atoms is used. 9. The method for producing a carbonic acid diester according to claim 8, wherein methanol is used as the alcohol. 10. An alcohol having 1 to 6 carbon atoms as an alcohol, a solid catalyst containing a copper atom as a solid catalyst, and a supply molar ratio of carbon monoxide to alcohol (CO / alcohol) of 3.5 to 1.5. 95, the supply molar ratio of carbon monoxide to oxygen (CO / O ₂ ) is 15 to 150
The method for producing a carbonic acid diester according to claim 1, wherein 11. The supply molar ratio of carbon monoxide to alcohol (CO / alcohol) is 4 to 40, and the supply molar ratio of carbon monoxide to oxygen (CO / O ₂ ) is 20 to 100.
The method for producing a carbonic acid diester according to claim 10. 12. Use of methanol as an alcohol,
The method for producing a carbonic acid diester according to claim 10, wherein a copper halide is used as the solid catalyst containing a copper atom.