JP2009215647A - Method for producing carbonic acid diester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce carbonic acid diester which could not be produced with sufficient yield and selectivity in the conventional electrolytic reaction at sufficient yield and selectivity by electrolytic reaction. <P>SOLUTION: Regarding the method for producing carbonic acid diester by bringing an alkoxy anion and carbon monoxide into electrolytic reaction in a reaction liquid with a water content of ≤5 wt.% in the presence of a catalyst comprising a platinum group element. By converting organic hydroxy compounds into an alkoxy anion, and further controlling the water content in the reaction liquid to ≤5 wt.%, its reaction with carbon monoxide efficiently progresses, and carbonic acid diester which could not be produced with sufficient yield and selectivity can be efficiently produced by electrolytic reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a carbonic acid diester by electrolytically reacting an alkoxy anion and carbon monoxide in the presence of a catalyst containing a platinum group element.

  Carbonic diesters are widely used as solvents such as electrolytes, synthetic raw materials such as alkylating agents and carbonylating agents, additives for gasoline and diesel fuel, and raw materials for polycarbonate and polyurethane.

  Conventionally, phosgene methods, oxidative carbonylation methods, transesterification methods, and the like are known as methods for producing carbonic acid diesters, and among these, methods that do not use phosgene, which is a harmful substance, are required.

  For this reason, dialkyl carbonate, which is increasing in demand as an electrolyte solvent, has been produced by the phosgene method in the past, but in recent years, it has been increasingly produced by an oxidative carbonylation method or a transesterification method. On the other hand, diphenyl carbonate, which is attracting attention as a polycarbonate raw material, cannot be produced by the same reaction as dialkyl carbonate because of the low nucleophilicity of the phenoxy anion produced from phenol, and many are still produced by the phosgene method.

  Among the synthesis methods of carbonic acid diesters, the oxidative carbonylation method is based on the reaction of an organic hydroxy compound and carbon monoxide, and examples thereof include those in Group IB, IIB or VIII of the periodic table. A method of reacting a mixed gas of carbon monoxide and oxygen with liquid methanol in the presence of a metal-containing catalyst (see Patent Document 1), oxygen, carbon monoxide and alkanol in the presence of a metal halide catalyst; There are a method of reacting in a phase (see Patent Document 2), a method of reacting nitrite and carbon monoxide in the gas phase in the presence of a solid catalyst containing a platinum group metal (see Patent Document 3), and the like. As described above, the synthesis of dimethyl carbonate by the oxidative carbonylation method has already been put into practical use, but diphenyl carbonate has not yet been put into practical use because neither the conversion rate nor the selectivity is sufficient.

  On the other hand, various methods are known as a method for oxidizing a substance. One of them is an electrolysis reaction that occurs when an electrode is brought into contact with a solution of a substance to be oxidized and a voltage is applied between both electrodes ( There is a method of oxidizing a substance by utilizing this (hereinafter referred to as “electrolytic reaction”). In the electrolytic reaction, the oxidation of the substance takes place at the anode of the electrode and the reduction reaction takes place at the cathode. In such an electrolytic reaction, in order to easily cause electrolysis, a supporting electrolyte that does not participate in the target reaction is added to the solution. When the substance to be oxidized itself serves as an electrolyte, a supporting electrolyte may not be added.

  Conventionally, as an application example of an electrolytic reaction, a reaction for generating ether and acetal from methanol and ethanol (see Non-Patent Document 1), a reaction for generating formaldehyde from anhydrous methanol (see Non-Patent Document 2), methanol and ethanol Reactions such as a reaction (see Non-Patent Document 3) for producing a formic acid ester from the reaction are known.

  There are also some known attempts to produce carbonic acid diesters by electrolytic reaction. For example, a method is disclosed in which dimethyl carbonate and ethylene carbonate are obtained by electrolytic reaction of mono- or dihydric alcohol and carbon monoxide in the presence of an electrolyte containing halogen (excluding fluorine) (Patent Document 4). reference). Also disclosed is a method of obtaining dimethyl carbonate by electrolytic reaction of alcohol and carbon monoxide in the presence of a periodic table VIIIB group catalyst and an electrolyte containing chlorine, bromine or iodine (see Patent Document 5). Furthermore, a method is disclosed in which an alcohol and carbon monoxide are electrolyzed using an anode containing a platinum group element in the presence of a supporting electrolyte to simultaneously produce a carbonate ester and a formate ester (see Patent Document 6). ).

  In addition, by using a reactor in which the reactor is partitioned into two reaction spaces on the anode side and the cathode side by a diaphragm in which an anode and a cathode are formed via a proton conducting membrane, alcohol and alcohol are introduced into the reaction space on the anode side. Carbon monoxide is supplied, oxygen is supplied to the reaction space on the cathode side, and a voltage is applied to the anode and the cathode to perform an electrolytic oxidation-reduction reaction, thereby generating carbonic acid diester on the anode side and water on the cathode side. (Refer to Patent Document 7). In this method, it is possible to prevent contact between the catalyst supported on the cathode and water and formation of an explosive gas mixture.

  Furthermore, an organic electrolysis reaction apparatus for electrolytic oxidation of a system containing a substrate and a reducing substance, comprising a casing, an anode active material, an ion conductive or active species conductive anode, a cathode active material, and an ion Including a cathode that is conductive or active species conductive, and means for applying a voltage between the anode and the anode provided outside the casing and connected to the cathode, the anode And the cathode are spaced apart in the casing, and the inside of the casing is divided into an intermediate chamber formed between the inside of the anode and the inside of the cathode, and an anode chamber outside the anode. It is disclosed to synthesize dimethyl carbonate from methanol and carbon monoxide using an organic electrolysis reactor characterized by being partitioned. (See Patent Document 8).

  However, in the conventional electrolytic reaction, the reaction between an aliphatic organic hydroxy compound having 2 or more carbon atoms, an alicyclic organic hydroxy compound having 5 or more carbon atoms or an aromatic organic hydroxy compound and carbon monoxide is efficient. The carbonic acid diester was not produced at all, or even when produced, the yield and selectivity were very low, which was not satisfactory.

Patent No. 1,492,757 Special Table Sho 63-503460 Patent No. 2,850,859 U.S. Pat. No. 4,131,521 U.S. Pat. No. 4,310,393 JP-A-6-173057 JP-A-6-73582 WO2003 / 004728

J.Electroanal.Chem, 31 (1971) 265-267 J. Electrochem Soc., 123 (1976) 818-823 J. Electrochem Soc., 124 (1977) 1177-1184

  In view of the above problems, the present invention provides a method for producing a carbonic acid diester that could not be produced with a sufficient yield and selectivity by a conventional electrolytic reaction with a sufficient yield and selectivity by an electrolytic reaction. Is an issue.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have converted organic hydroxy compounds into alkoxy anions and further reduced the water content in the reaction solution to 5% by weight or less, so that carbon monoxide and It was found that the carbonic acid diester that could not be produced with sufficient yield and selectivity by the conventional electrolytic reaction can be efficiently produced by the electrolytic reaction, and the present invention has been completed. It was.

  That is, the gist of the present invention is as follows.

(1) A method for producing a carbonic acid diester, comprising subjecting an alkoxy anion and carbon monoxide to an electrolytic reaction in a reaction solution having a water content of 5% by weight or less in the presence of a catalyst containing a platinum group element.

(2) The method for producing a carbonic acid diester according to (1), wherein the catalyst containing a platinum group element is an electrode catalyst in which the platinum group element is supported on an electrode.

(3) The method for producing a carbonic acid diester according to (1) or (2), wherein the alkoxy anion is an aliphatic alkoxy anion having 2 or more carbon atoms or an alicyclic alkoxy anion having 5 or more carbon atoms.

(4) The method for producing a carbonic acid diester according to (1) or (2), wherein the alkoxy anion is an aromatic alkoxy anion having 6 or more carbon atoms.

(5) The method for producing a carbonic acid diester according to (4), wherein the alkoxy anion is a phenoxy anion and the carbonic acid diester is diphenyl carbonate.

(6) The method for producing a carbonic acid diester according to any one of (1) to (5), wherein the electrolytic reaction is an electrolytic reaction not using a supporting electrolyte.

  According to the present invention, a solvent such as an electrolytic solution, a synthetic raw material such as an alkylating agent or a carbonylating agent, an additive for gasoline or diesel fuel, a carbonic acid diester useful in a wide range of fields as a raw material for polycarbonate or polyurethane, etc. Thus, it can be efficiently produced at a yield and selectivity that are industrially practical without using harmful substances such as phosgene.

It is a block diagram which shows an example of the electrolytic reaction apparatus suitable for implementation of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The method for producing a carbonic acid diester of the present invention produces a carbonic acid diester by electrolytically reacting an alkoxy anion and carbon monoxide in the presence of a catalyst containing a platinum group element in a reaction solution having a water content of 5% by weight or less. A carbonic acid diester is produced by the reaction of an alkoxy anion represented by the following formula (1) with carbon monoxide (CO) according to the following reaction formula (2).

RO ^- (1)
(R represents an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, and these hydrocarbon groups may have a substituent.)
^{2RO - + CO → RO-C} (= O) -OR + 2e - (2)

  In the present specification, “alkoxy” means “in the general organic chemical nomenclature in which R in the above formula (1) is an aliphatic (that is, chain) hydrocarbon group or alicyclic hydrocarbon group. It includes not only “alkoxy” but also “aryloxy” in which R is an aromatic hydrocarbon group.

The method of the present invention is not limited to a method of producing a carbonic acid diester (RO—C (═O) —OR) using one type of alkoxy anion, and using two or more types of alkoxy anions, Methods for producing different carbonic acid diesters, for example, carbonic acid diesters (R ¹ O—C (═O) —OR ² ) are produced using alkoxy anions (R ¹ O ⁻ ) and alkoxy anions (R ² O ⁻ ). (Wherein R ¹ and R ² have the same meaning as R, and R ¹ ≠ R ² ).

[Alkoxy anion]
In the present invention, the alkoxy anion used as a raw material is represented by the formula (1). In the formula (1), R is a saturated or unsaturated aliphatic hydrocarbon group, saturated or An unsaturated alicyclic hydrocarbon group or an aromatic hydrocarbon group may be mentioned. In addition, examples of the substituent that these hydrocarbon groups may have include an alkyl group, a hydroxy group, an aryl group, a halogen atom, a nitro group, a sulfonic acid group, a sulfone group, and an amino group.

  More specifically, R is an ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, n-heptyl group. A saturated or unsaturated, linear or branched aliphatic hydrocarbon group such as an allyl group or a crotyl group, preferably a linear or branched alkyl group or alkenyl having 2 or more carbon atoms, more preferably 2 to 10 carbon atoms. Group: a saturated or unsaturated alicyclic hydrocarbon group such as cyclopentyl group, cyclohexyl group, cycloheptyl group, methylcyclohexyl group, cyclohexenyl group, preferably a cyclohexane having 5 or more carbon atoms, more preferably 5 to 10 carbon atoms. Alkyl group or cycloalkenyl group; aralkyl group such as benzyl group and α-phenylethyl group; phenyl group, methylphenyl group, di- Aryl groups or substituted aryl groups such as tilphenyl group, naphthyl group, anthracenyl group, and derivatives thereof (hydrogen atoms substituted with halogen atoms, nitro groups, sulfonic acid groups, sulfone groups, amino groups, etc.), Examples thereof include an aromatic hydrocarbon group having 6 or more carbon atoms, which may have a substituent.

  Among these, as R, in particular, a chain aliphatic hydrocarbon group having 2 or more carbon atoms, preferably 2 to 10 carbon atoms, an alicyclic hydrocarbon group having 5 or more carbon atoms, preferably 5 to 10 carbon atoms, An aromatic hydrocarbon group having 6 or more carbon atoms, preferably 6 to 14 carbon atoms is preferable. Thus, a carbonic acid diester having such an alkoxy group in the ester portion, which has been difficult to synthesize by an electrolytic reaction, is conventionally used. It can be synthesized industrially advantageously. Here, the “carbon number” is the carbon number including the carbon number of the substituent when the group has a substituent.

  As the alkoxy anion used for the reaction, a commercially available alkoxy anion compound may be used, or an alkoxy anion prepared by the method described below may be used. As a method for preparing an alkoxy anion, a corresponding organic hydroxy compound (that is, an organic hydroxy compound represented by the following formula (3)) and a basic substance are reacted to desorb hydrogen ions of the organic hydroxy compound. And the like. The alkoxy anion may be synthesized in the electrolytic reaction apparatus simultaneously with the electrolytic reaction or may be synthesized separately.

R-OH (3)
(R has the same meaning as in formula (1).)

  The basic substance used for the preparation of the alkoxy anion needs to be selected according to the reactivity with the organic hydroxy compound, but alkali metal or alkaline earth metal such as metal lithium, metal sodium and metal potassium, lithium hydroxide Alkali metal or alkaline earth metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal or alkaline earth metal hydrides such as lithium hydride and sodium hydride, alkali metals such as sodium acetate and potassium carbonate, or Weak acid salts of alkaline earth metals, trimethylamine, triethylamine, tributylamine, triphenylamine, diisopropylamine, dimethylaniline, amines such as pyridine, basic ion exchange resins such as Diaion (registered trademark) SA10A manufactured by Mitsubishi Chemical Corporation Etc. can be mentioned. These may be used alone or in combination of two or more.

The usage-amount of a basic substance should just be more than the reaction equivalent which can produce | generate an alkoxy anion from an organic hydroxy compound.
In addition to supplying the necessary amount of the basic substance prior to the electrolytic reaction, the basic substance can be dividedly supplied in a plurality of times or continuously supplied during the electrolytic reaction.

[Catalysts containing platinum group elements]
Examples of the platinum group metal element of the catalyst containing the platinum group element used in the electrolytic reaction of the present invention include ruthenium, rhodium, palladium, osmium, iridium, platinum, etc., and these may be used alone. Two or more kinds may be used in combination. Of these, palladium is preferred because the desired reaction proceeds efficiently.

The platinum group metal component can be used as the metal itself or in a state of being supported on a carrier. Examples of the carrier include C (carbon or activated carbon) and metal oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , and SnO ₂ . One type of carrier may be used alone, or two or more types may be used in combination. The amount of platinum group metal supported on the carrier is usually about 0.1 to 10% by weight. Further, for _{example, M (OCOCH 3) n,} M (OC 6 H 5) n, MCl n, MBr n, M (acac) n (M represents a platinum group metal element such as Pd, acac is acetylacetonate group N is a valence of M, and is an integer of 1 to 3).

  The catalyst can be used in such a manner that one or more of these platinum group metals, platinum group metals supported on a carrier, or compounds containing platinum group metals are supported and molded on a conductive solid. It can be used as an electrode (anode) catalyst. The conductive solid electrode used in this case can be produced, for example, by kneading a conductive powder mainly composed of carbon or metal and a binder powder such as polytetrafluoroethylene and rolling and forming the electrode (anode ) The catalyst can be prepared, for example, by appropriately mixing one or more of the above-described catalyst components in the kneaded material when the conductive solid electrode is thus prepared.

If the amount of the catalyst component supported on such an electrode catalyst is small, the reaction rate decreases, and if it is too large, it is detached from the electrode and inactivated, which is not economical. Therefore, the amount of the catalyst component supported on the electrode catalyst can be appropriately selected according to the reaction system using the same. For example, the amount of the active component (in terms of platinum group metal) supported per electrode area is 0.1. -20 μmol / cm ² is preferable, and 1-15 μmol / cm ² is more preferable.

[Supporting electrolyte]
In the electrolytic reaction of the present invention, a supporting electrolyte can be used to accelerate the reaction.

  Examples of supporting electrolytes include alkali metal halides such as sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, lithium chloride, lithium bromide and lithium iodide; potassium hypochlorite Alkaline metal hypohalites such as lithium hypochlorite, potassium hypoiodite, lithium hypoiodite; alkali metal halides such as potassium chlorate, lithium chlorate; sodium perchlorate, Perhalogenates of alkali metals such as sodium periodate; tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, Tetrabu bromide Examples thereof include halides of alkyl quaternary ammonium such as til ammonium ammonium and tetrabutyl ammonium iodide; perhalogenates of alkyl quaternary ammonium such as tetrabutyl ammonium perchlorate and tetramethyl ammonium perchlorate. These may be used alone or in combination of two or more.

  However, in the electrolytic reaction system of the present invention, the basic substance or alkoxy anion compound added to generate the alkoxy anion described above may function as an electrolyte, and there is no need to separately add a supporting electrolyte. If the supporting electrolyte is not added, a separation operation between the target product after the reaction and the supporting electrolyte becomes unnecessary, which is industrially advantageous.

[solvent]
In the electrolytic reaction of the present invention, a solvent may or may not be used.

  When a solvent is used, it is necessary to select a solvent that is inert to the electrolytic reaction (high oxidation potential). Examples of such a solvent include acetonitrile, carbon tetrachloride, dichloromethane (methylene chloride), N, N-dimethylformamide, N-methylpyrrolidone and the like. These may be used alone or in combination of two or more.

  When preparing an alkoxy anion as a reaction substrate of the present invention by adding a basic substance to a reaction solution containing an organic hydroxy compound as a raw material, dissolve the organic hydroxy compound in the solvent. Can be used. Although the density | concentration of the organic hydroxy compound in a solvent can be selected in arbitrary ranges, 0.01 mol / L or more is preferable and 0.1 mol / L or more is further more preferable. The upper limit of the concentration depends on the solubility of the supporting electrolyte in the organic hydroxy compound, and can be selected as appropriate. However, if the solubility of the supporting electrolyte in the organic hydroxy compound is low, the concentration of the organic hydroxy compound needs to be kept low. There is. When the organic hydroxy compound dissolves the supporting electrolyte well or when the supporting electrolyte is not used, it is not always necessary to use a solvent. When no solvent is used, the separation of the target product and the solvent after the reaction is unnecessary, which is industrially advantageous.

[amount of water]
Since the reaction of the electrolytic reaction of the present invention is hindered by the water in the reaction solution, the water content in the reaction solution is reduced to 5% by weight or less, preferably 1 by using a raw material or solvent having a low water content. % By weight or less, more preferably 1000 ppm by weight or less, and most preferably 800 ppm by weight or less. The smaller the amount of water in the reaction solution, the more advantageous in terms of reaction efficiency. However, it is difficult to operate to make the amount of water in the reaction solution less than 0.1 ppm by weight, which is economically disadvantageous. Usually, the water content in the reaction solution is 0.1 ppm by weight or more.

  In the present invention, the amount of water in the reaction solution indicates the amount of water contained in the reaction solution in the same reaction zone as the anode. Specifically, when the electrolytic reaction is carried out batchwise, the amount of water before the start of the reaction is indicated, and when the electrolytic reaction is carried out continuously, the amount of water in the supply liquid is indicated. Examples of the method for measuring the amount of water in the reaction solution include a method of sampling the reaction solution in the same reaction zone as the anode and measuring this with a Karl Fischer moisture meter or the like.

  In order to bring the amount of water in the reaction solution into the above range, a method of removing water from the raw material and the solvent is used, and as this specific method, any of the commonly used water removal methods can be used. For example, dehydration by distillation, adsorption dehydration by a moisture adsorbent such as molecular sieve, dehydration by membrane separation, etc. may be mentioned.

  It is also effective to remove residual moisture and oxygen by circulating an inert gas such as nitrogen or helium in the reaction solution prior to the reaction. Furthermore, the reaction rate at the initial stage of the reaction can be improved by increasing the carbon monoxide concentration in the reaction solution by circulating carbon monoxide in the reaction solution prior to the reaction.

[Carbon monoxide]
Carbon monoxide to be reacted with the alkoxy anion may be passed through the reaction liquid containing the alkoxy anion with a supply amount corresponding to the scale of the reaction system. Carbon monoxide can be supplied to the reaction solution during the electrolytic reaction, but generally, it takes time to reach a certain concentration (= saturated concentration) after starting aeration. That is, prior to energization for the electrolytic reaction, a sufficient amount of carbon monoxide is circulated and dissolved in the reaction solution, and then the electrolytic reaction is started.

[Reaction conditions]
<Reaction temperature>
The reaction temperature of the electrolytic reaction of the present invention can be freely set within a range where the reaction substrate does not solidify. Preferably it is 0 degreeC-200 degreeC, More preferably, it is 20 degreeC-100 degreeC. In order to lower the reaction temperature, equipment for cooling is required, which is economically disadvantageous. Further, when the reaction temperature is increased, it is necessary to apply pressure in order to suppress evaporation of the reaction substrate, and reactions such as thermal decomposition of raw materials are likely to occur.

<Reaction pressure>
Although the reaction pressure can be reduced, it can usually be carried out at normal pressure or under pressure. Preferably it is 1-15 atmospheres. If the pressure is lower than 1 atm, the CO partial pressure decreases and the reaction rate decreases, which is not preferable, and if it exceeds 15 atm, the equipment cost becomes expensive.

<Potential / current>
The electrolytic reaction of the present invention can be either constant potential electrolysis or constant current electrolysis.
In the case of constant potential electrolysis, if the potential is low, the reaction does not proceed. If it is high, the oxidation of the basic substance added to generate the alkoxy anion proceeds and the reaction does not proceed. A preferred potential is 0.01 to 5 V (vs. Ag / AgCl), more preferably 0.1 to 2 V (vs. Ag / AgCl).

In the case of constant current electrolysis, if the current density is low, the reaction does not proceed. If the current density is high, the direct oxidation of the alkoxy anion or basic substance proceeds and the selectivity decreases. A preferred current density is 0.01 to 10 mA / cm ² , more preferably 0.05 to 5 mA / cm ² .

<Reaction time>
The electrolytic reaction time is appropriately selected. In the case of a batch system, for example, it is about 0.5 to 24 hours.

<Reaction method>
The electrolytic reaction of the present invention may be carried out batchwise, but is preferably carried out continuously. The reactor does not need to be configured by a single reactor, and may be configured by connecting a plurality of reactors in series or in parallel. When configured with a plurality of reactors, raw materials such as unreacted alkoxy anions, basic substances, and carbon monoxide contained in the reaction product from the recovery line may be circulated to the same or different reactor supply lines. good.

[Reactor]
In the electrolytic reaction of the present invention, an oxidation reaction of an alkoxy anion and carbon monoxide proceeds on the anode side to produce a carbonic acid diester, and hydrogen ions are reduced on the cathode side. Therefore, as shown in FIG. 1, the apparatus used may be one in which the anode and the cathode are separated by an ion permeable membrane, for example, a glass filter, an anion exchange membrane, etc., and divided into an anode chamber and a cathode chamber. Although it is not a requirement, it is possible to place the anode and cathode in a single reaction compartment. In general, a reactor having a single reaction section has a simpler structure and is advantageous in terms of equipment cost.

  The cathode material is not limited in shape and material as long as it can be used for a normal electrolytic reaction, but a cathode material having a low hydrogen overvoltage is preferable. Specifically, carbon, platinum, or the like can be used. As the anode material, the same material as the cathode material may be used, and a catalyst containing a platinum group element may be separately present in the anode chamber, but the above-described electrode catalyst is preferably used.

  FIG. 1 is a schematic configuration diagram showing an example of an electrolytic reaction apparatus suitable for carrying out the method for producing a carbonic acid diester of the present invention.

  Reference numeral 10 denotes a reactor (electrolysis cell), and a bottomed cylindrical container part constituting the anode chamber 11 and a bottomed cylindrical container part constituting the cathode chamber 12 are connected by a cylindrical communication part 13. Has a structure. An electrode catalyst is provided as an anode 11A at the bottom of the anode chamber 11, and a cathode 12A is provided in the cathode chamber 12. These anode 11A and cathode 12A are connected to a power source 20. In addition, the communication part 13 is provided with an ion-permeable diaphragm 14. 11B and 12B are stoppers for covering the upper part of each electrode chamber. Reference numeral 15 denotes a gas supply pipe for supplying carbon monoxide to the reaction solution in the anode chamber 11. The gas supply pipe also serves as a gas supply pipe for circulating an inert gas such as He. Reference numeral 16 denotes a gas supply pipe for circulating an inert gas such as He. Reference numeral 17 denotes a basic substance supply pipe which also serves as a gas sampling pipe, and is configured so that gas sampling can be performed by switching a valve 17A provided in the supply pipe 17. Reference numeral 18 denotes a gas vent pipe.

In this electrolytic reaction apparatus, a reaction liquid containing an organic hydroxy compound is introduced into the anode chamber 11 and the cathode chamber 12, carbon monoxide is supplied from the gas supply pipe 15, and a basic substance is supplied from the supply pipe 17. When the power source 20 energizes between the anode 11A and the cathode 12A, the alkoxy anion and carbon monoxide generated by the reaction of the organic hydroxy compound and the basic substance in the presence of the electrode catalyst of the anode 11A in the anode chamber 11 And undergo an electrolytic reaction to produce a carbonic acid diester. At the same time, carbon dioxide may be generated by the oxidation of carbon monoxide. On the other hand, in the cathode chamber 12, hydrogen ions are reduced and hydrogen gas is generated.
Prior to the reaction, the water content of the reaction solution can be reduced by circulating an inert gas such as He from the gas supply pipes 15 and 16.

  The electrolytic reaction apparatus of FIG. 1 shows an example of an electrolytic reaction apparatus that can be applied to the present invention, and does not limit the embodiment of the present invention.

[Recovery of carbonic acid diester]
The carbonic acid diester produced by the electrolytic reaction of the present invention is recovered by a conventional method known per se. Examples of the recovery method include a method by distillation, extraction, or crystallization.

[Usage]
The diphenyl carbonate produced by the electrolytic reaction of the present invention can be used in the same applications as diphenyl carbonate produced by a known method. For example, when an aromatic polycarbonate is produced by transesterification with a dihydroxy compound. Can be used as raw material. In addition, the carbonic acid ester produced by the electrolytic reaction of the present invention is widely used as a solvent such as an electrolytic solution, an alkylating agent, a synthetic raw material such as a carbonylating agent, an additive for gasoline or diesel fuel, a raw material for polyurethane, etc. Useful for.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Example 1]
(1) Preparation of supported catalyst In a 200 mL beaker, 100 mL of ion exchange water and 0.5 g of activated carbon (made by Wako Pure Chemical Industries, Ltd., special grade) are added and stirred with a magnetic stirrer, and a concentration of 0.03 mol / L palladium chloride. An aqueous solution of (H ₂ PdCl ₄ ) was added dropwise. After all the solutions had been dropped, a beaker containing the solution was placed on a hot plate heated to 100 ° C. and evaporated to dryness until there was no water, thereby obtaining a black powder. This black powder contained 10.6 wt% palladium chloride (PdCl ₂ ) based on the Pd metal standard.

(2) Production of Electrocatalyst 125 mg of vapor grown carbon fiber (VGCF) (manufactured by Showa Denko KK, normal product) was added to 30 mg of the black powder obtained in (1) above (Pd content 30 μmol), polytetra 40 mg of fluoroethylene powder (F-104, manufactured by Daikin) was added and kneaded in an agate mortar. It was molded on a hot plate at 120 ° C. to prepare an anode having an electrode area of 5 cm ² (geometric area). The amount of Pd supported per electrode area of this electrode catalyst is 6 μmol / cm ² .

(3) Electrolytic Reaction Constant current electrolysis was performed using the electrolytic reaction apparatus shown in FIG.
The electrode catalyst produced by the above method was used as the anode, platinum wire was used as the cathode, and a glass filter was used as the diaphragm. In each of the anode chamber and the cathode chamber, the concentrations of phenol (made by Wako Pure Chemical Industries, special grade) and tetra n-butylammonium perchlorate (TBAP) (made by Tokyo Chemical Industry Co., Ltd., special grade) are 1M and 0.1M, respectively. 33 mL of a solution of methylene chloride (CH ₂ Cl ₂ ) (manufactured by Wako Pure Chemical Industries, Ltd., special grade) adjusted so as to become Dissolved oxygen and water were removed by flowing helium (Japan Helium Center Co., Ltd., purity 99.9995%) at 900 mL / Hr for 10 minutes in the gas phase part of the anode chamber and the cathode chamber, and carbon monoxide ( Nippon Oxygen Co., Ltd., purity 99.95%) was circulated at 900 mL / Hr for 60 minutes, followed by constant current electrolysis at a current density of 0.2 mA / cm ² for 250 minutes. However, methylene chloride as a solvent was dehydrated in advance with molecular sieve MS4A (manufactured by Wako Pure Chemical Industries, Ltd., for chemical use), and the water content was 2 ppm. At the start of the electrolytic reaction, 0.00607 g (60 μmol) of triethylamine (Et ₃ N) (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was added, and then 60 μmol was added every 60 minutes (total 240 μmol).

  Before and after the reaction, the reaction solution in the anode chamber and the cathode chamber was sampled, and the amount of water contained was measured with a Karl Fischer moisture meter (KF Coulometer 831 manufactured by Metrohm). The moisture content is 96 ppm by weight, the moisture content of the reaction solution in the cathode chamber is 133 ppm by weight, the moisture content in the reaction solution in the anode chamber after the reaction is 97 ppm by weight, and the moisture content in the reaction solution in the cathode chamber is 109 ppm by weight. Met.

  The electrolytic reaction solution was sampled in a timely manner, and gas chromatography (detector: FID, column GC-2010, ZB-1 capillary column, φ0.25 mm × 30 m, Shimadzu Corporation, analysis conditions: injection temperature 220 ° C., column temperature (The phenanthrene (manufactured by Wako Pure Chemicals, special grade) was added as 0.004% as an internal standard substance at the time of analysis).

  The reaction product after completion of the reaction was analyzed in the same manner. In addition, the sampling gas on the anode chamber side was injected online into gas chromatography (detector: TCD, GC-8A, Column Shimadzu Corp. GC, Porapak Q packed column), and carbon dioxide was analyzed (70 ° C. constant temperature analysis).

As a result, 15 μmol of diphenyl carbonate was produced in the first 60 minutes, and thereafter, the amount of production increased almost linearly, and the amount of production at 250 minutes after the start of the reaction reached 48.7 μmol. I understood. At this time, the amount of carbon dioxide produced by the reaction by-product was 4.2 μmol, the amount of energization was 14.4 C, and the current efficiency for producing diphenyl carbonate (DPC) was 65.3%. The catalyst had a TON (turnover number) of 1.62 mol-DPC / mol-Pd.
A summary of the results is shown in Table 1.

[Comparative Example 1: Electrolytic reaction not producing phenoxy anion]
A constant potential electrolysis reaction was carried out in the same reaction solution and reaction apparatus as in Example 1 except that triethylamine for generating a phenoxy anion was not added at the start of the electrolysis reaction and during the electrolysis reaction. As a result of performing constant potential electrolysis at 1.0 V (Ag / AgCl) for 1 hour, the average current density was 0.4 mA / cm ² and the energization amount was 2.90 C. However, the production of diphenyl carbonate and carbon dioxide was It was not confirmed.

[Example 2: Modification of triethylamine addition method]
Constant current electrolysis was carried out in the same procedure as in Example 1. However, 60 μmol of triethylamine was added at the start of the reaction, and no additional addition was performed. When the reaction was carried out at a current density of 0.2 mA / cm ² for 120 minutes, 20.5 μmol of diphenyl carbonate and 15.5 μmol of carbon dioxide were produced with an energization amount of 7.2 C. A summary of the results is shown in Table 1.

[Example 3: Change of current density 1]
Constant current electrolysis was carried out in the same procedure as in Example 2. However, the current density was 0.4 mA / cm ² . When the reaction was performed for 120 minutes, 18.6 μmol of diphenyl carbonate and 8.3 μmol of carbon dioxide were generated at an energization amount of 14.4 C. The summary of the results is shown in Table 1, but it was found that good results could be obtained even when the current density was 0.4 mA / cm ² .

[Example 4: Change of current density 2]
Constant current electrolysis was carried out in the same procedure as in Example 2. However, the current density was 0.82 mA / cm ² . When the reaction was performed for 60 minutes, 16.8 μmol of diphenyl carbonate and 2.1 μmol of carbon dioxide were generated at an energization amount of 14.4 C. The summary of the results is shown in Table 1, but it was found that good results were obtained even when the current density was 0.82 mA / cm ² .

[Example 5: Change of palladium loading]
When constant current electrolysis was carried out for 120 minutes in the same procedure as in Example 3 except that the content of palladium in the electrode catalyst was 10 μmol and the amount of triethylamine added at the start of the reaction was 20 μmol, the energization amount was 14.4 C. Then, 5.3 μmol of diphenyl carbonate and 6.7 μmol of carbon dioxide were produced. The summary of the results is shown in Table 1. It was found that good results were obtained even when the palladium amount was 10 μmol.

[Example 6: Effect of solvent pre-dehydration]
Constant current electrolysis was performed at a current density of 1 mA / cm ² in the same procedure as in Example 2. The water content of the reaction solution was 98 ppm by weight in the anode chamber. When reacted for 60 minutes, 20.8 μmol of diphenyl carbonate and 0.9 μmol of carbon dioxide were generated with an energization amount of 7.2 C. A summary of the results is shown in Table 1. It was found that better results were obtained when the solvent was dehydrated, compared to the results of Example 8 described below, where the solvent was not dehydrated under the same conditions.

[Example 7: Examination of sodium phenoxide as a basic substance]
Constant current electrolysis was carried out in the same procedure as in Example 2. However, 240 μmol of anhydrous sodium phenoxide (PhONa) (Alfa Aeser) was added as a basic substance to be added instead of triethylamine. The amount of water in the reaction solution was 118 ppm by weight for the anode chamber after circulation of helium, 112 ppm by weight for the cathode chamber, 167 ppm by weight for the anode chamber after completion of the reaction, and 143 ppm by weight for the cathode chamber. When reacted at a current density of 0.2 mA / cm ² for 240 minutes, 16.8 μmol of diphenyl carbonate and 1.4 μmol of carbon dioxide were produced. The summary of the results is shown in Table 1. It was found that good results were obtained even when sodium phenoxide was added as a basic substance.

[Example 8: Effect of solvent pre-dehydration]
Constant current electrolysis was performed in the same procedure as in Example 6. However, the solvent was used without dehydration. As a result, the water content of the reaction solution was 140 ppm by weight in the anode chamber, and 16.8 μmol of diphenyl carbonate and 10.0 μmol of carbon dioxide were generated with an energization amount of 7.2 C. A summary of the results is shown in Table 1.

[Example 9: Change of diaphragm, solvent, and non-addition of supporting electrolyte]
Constant current electrolysis was performed using an anion exchange membrane (A-501 manufactured by Asahi Kasei Co., Ltd.) as the diaphragm of the electrolytic cell shown in FIG. 30 mL of dehydrated acetonitrile (MeCN) was added to the anode chamber, and 30 mL of similarly dehydrated acetonitrile and 30 mmol of phenol and 0.15 mmol of anhydrous sodium phenoxide (Alfa Aeser) were added to the cathode chamber. The dehydration of acetonitrile is about 5 g of molecular sieves 3A (manufactured by Wako Pure Chemical Industries, Ltd., for chemical use) baked at 300 ° C. for 10 hours per 100 mL of commercially available dehydrated acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd. for organic synthesis (dehydrated products)). It was done by leaving it to stand for 12 hours or more with occasional shaking. The supporting electrolyte, tetra-n-butylammonium perchlorate, was not added to either the anode chamber or the cathode chamber. Dissolved oxygen and water were removed by flowing helium (Japan Helium Center Co., Ltd., purity 99.9995%) at 900 mL / Hr for 10 minutes in the gas phase part of the anode chamber and the cathode chamber, and carbon monoxide ( Nippon Oxygen Co., Ltd., purity 99.95%) was circulated at 900 mL / Hr for 60 minutes, the current density was 0.2 mA / cm ^2, and 360 μmol of sodium phenoxide was added to the anode chamber every 60 minutes. Constant current electrolysis was performed for a minute. The water content of the reaction solution was 40 ppm by weight in the anode chamber after circulation of helium and 115 ppm in the cathode chamber.

  As a result of the reaction, the amount of diphenyl carbonate produced in the anode chamber reached 52.7 μmol at 360 minutes after the start of the reaction. At this time, diphenyl carbonate in the cathode chamber was 0.24 μmol (total 52.9 μmol), and the amount of carbon dioxide produced was 31.8 μmol. A summary of the results is shown in Table 1.

[Example 10: Electrolytic reaction apparatus without diaphragm]
The diaphragm of the electrolytic cell shown in FIG. 1 was removed and constant current electrolysis was performed. The cell was charged with 60 mL of acetonitrile dehydrated by the same procedure as in Example 9, 60 mmol of phenol and 1.0 mmol of anhydrous sodium phenoxide dissolved in 20 mL of acetonitrile. The supporting electrolyte, tetra n-butylammonium perchlorate, was not added. The current density was 0.2 mA / cm ² and constant current electrolysis was performed for 17 hours. Sodium phenoxide was not added. The water content of the reaction solution was 100 ppm by weight.
As a result of the reaction, 37.4 μmol of diphenyl carbonate and 23.6 μmol of carbon dioxide were produced. A summary of the results is shown in Table 1.

[Example 11: Influence of moisture in reaction solution (use of non-dehydrated solvent)]
Constant current electrolysis was performed in the same manner as in Example 10. However, acetonitrile was used without dehydration. The water content of the reaction solution was 637 ppm by weight. As a result of reaction for 10 hours, 19.7 μmol of diphenyl carbonate and 39.6 μmol of carbon dioxide were generated. A summary of the results is shown in Table 1.

[Comparative Example 2: Effect of reaction solution moisture]
Constant current electrolysis was performed in the same manner as in Example 10. However, acetonitrile was used without dehydration, and 16 mmol of sodium phenoxide trihydrate (manufactured by Aldrich, special grade) was added as a basic substance. As a result, the water content of the reaction solution was 64,000 ppm by weight. Although the reaction was conducted for 3 hours, formation of diphenyl carbonate was not confirmed.

[Example 12: Investigation of lithium phenoxide as a basic substance]
After neutralizing by dissolving 3 mmol of phenol and 3 mmol of lithium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) in 100 mL of ion-exchanged water, vacuum drying was performed with an evaporator to obtain lithium phenoxide (PhOLi). Thereafter, acetonitrile dehydrated by the same procedure as in Example 9 was added to prepare a 50 mM solution. Constant current electrolysis was performed for 15 hours in the same procedure as in Example 10 except that lithium phenoxide produced by the above method was replaced with sodium phenoxide. The water content of the reaction solution was 115 ppm by weight.
As a result of the reaction, 31.0 μmol of diphenyl carbonate and 23.0 μmol of carbon dioxide were generated. A summary of the results is shown in Table 1.

[Example 13: Examination of potassium phenoxide as a basic substance]
The procedure was the same as that of lithium phenoxide in Example 12, except that potassium phenoxide (PhOK) was produced from 3 mmol of phenol and 3 mmol of potassium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) and replaced with sodium phenoxide. The constant current electrolysis was performed for 16 hours in the same procedure as in Example 10. The water content of the reaction solution was 122 ppm by weight.
As a result of the reaction, 42.9 μmol of diphenyl carbonate and 15.7 μmol of carbon dioxide were produced. A summary of the results is shown in Table 1.

[Reference Example 1: Stoichiometric reaction]
30 μmol of palladium chloride (PdCl ₂ ) prepared in the same manner as described in Example 1 (1) was added to a flask equipped with a condenser with cooling water passed through the top, and methylene chloride (Wako Pure Chemical Industries, Ltd.). 20 ml, tetra n-butylammonium perchlorate (Tokyo Kasei Kogyo Co., Ltd., special grade) as an electrolyte, and helium (Japan Helium Center Co., Ltd., purity 99.9995%) are circulated for 10 minutes. Water was removed.
Then, 10 mL of 3M phenol (made by Wako Pure Chemical Industries, special grade) / methylene chloride (made by Wako Pure Chemical Industries, special grade) was added, and carbon monoxide was circulated for 1 hour. Furthermore, when 60 μmol of triethylamine (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was added and reacted at 30 ° C. for 1 hour, 7.3 μmol of diphenyl carbonate and 6.4 μmol of carbon dioxide were generated. From this, under these reaction conditions, 7.3 μmol of diphenyl carbonate and 6.4 μmol of carbon dioxide are generated regardless of the electrolytic reaction per 30 μmol of palladium.

  The present invention provides a method for producing a carbonic acid diester useful as a raw material for an electrolytic solution and polycarbonate, etc. as efficiently as it can be put into practical use without using a toxic substance such as phosgene.

10 Reactor (electrolysis cell)
DESCRIPTION OF SYMBOLS 11 Anode chamber 11A Anode 12 Cathode chamber 12A Cathode 14 Diaphragm 15,16 Gas supply pipe 20 Power supply

Claims (6)

  A method for producing a carbonic acid diester, comprising subjecting an alkoxy anion and carbon monoxide to an electrolytic reaction in a reaction solution having a water content of 5% by weight or less in the presence of a catalyst containing a platinum group element.   The method for producing a carbonic acid diester according to claim 1, wherein the catalyst containing a platinum group element is an electrode catalyst in which a platinum group element is supported on an electrode.   The method for producing a carbonic acid diester according to claim 1 or 2, wherein the alkoxy anion is an aliphatic alkoxy anion having 2 or more carbon atoms or an alicyclic alkoxy anion having 5 or more carbon atoms.   The method for producing a carbonic acid diester according to claim 1 or 2, wherein the alkoxy anion is an aromatic alkoxy anion having 6 or more carbon atoms.   The method for producing a carbonic acid diester according to claim 4, wherein the alkoxy anion is a phenoxy anion and the carbonic acid diester is diphenyl carbonate.   6. The method for producing a carbonic acid diester according to claim 1, wherein the electrolytic reaction is an electrolytic reaction that does not use a supporting electrolyte.

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