JP2012153909A - Method for producing carbonic acid diester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce carbonic acid diester with a sufficient yield and selectivity by an electrolytic reaction which has not been produced with a sufficient yield and selectivity in a conventional electrolytic reaction.SOLUTION: In the method for producing the carbonic acid diester, an alkoxy compound and a carbon monoxide are subjected to an electrolytic reaction by using a carbon electrode containing a platinum group element supporting a catalyst obtained by supporting the platinum group element on a carrier comprising conductive carbon having a primary particle diameter of 100 nm or smaller. Since the conductive carbon is an ultrafine particle having such a primary particle diameter of 100 nm or smaller, a volume resistivity value of the carrier is reduced, and catalyst-electrode performance is improved by the improvement of electrical conducting property.

Description

  The present invention relates to a method for producing a carbonic acid diester by electrolytically reacting an alkoxy compound 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 manufactured by the phosgene method in the past, but in recent years, it has been increasingly manufactured 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 of them are phosgene methods or esters of dialkyl carbonate and phenol. Manufactured by the exchange 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; 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), etc. are known. ing.

  On the other hand, various methods are known for advancing the oxidation of a substance in a synthesis reaction. One of them is to bring an electrode into contact with a solution of a substance to be oxidized and apply a voltage between both electrodes. There is a method of oxidizing a substance using an electrolysis reaction (hereinafter referred to as an “electrolytic reaction”) caused by the above. 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. In the case where the reaction-participating substance 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 through 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).

  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 above conventional electrolytic reaction, the reaction proceeds only with an organic hydroxy compound having a specific structure, 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 compound. The reaction between the group organic hydroxy compound and carbon monoxide did not proceed efficiently, and the carbonic acid diester was not produced at all, or even when produced, the yield and selectivity were very low, which was not satisfactory.

  In view of this problem, the present inventors have intensively studied to provide a method for efficiently producing a wider range of carbonic acid esters by electrolytic reaction. As a result, the organic hydroxy compounds are converted into alkoxy compounds, and further in the reaction solution. By making the water content of 5% by weight or less, the reaction with carbon monoxide proceeds efficiently, and a carbonic diester that could not be produced with sufficient yield and selectivity by the conventional electrolytic reaction was efficiently produced by the electrolytic reaction. The patent application was filed prior to the present applicant (Patent Document 9, hereinafter referred to as “prior application”).

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 Japanese Patent Application No. 2009-028581

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

  The present invention further improves the method of the prior application, and makes it possible to more efficiently produce a carbonic acid diester that could not be produced with sufficient yield and selectivity by the conventional electrolytic reaction with sufficient yield and selectivity by the electrolytic reaction. It is an object of the present invention to provide a manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have found that a carbonic acid diester can be produced more efficiently by using an anode having a specific structure in an electrolytic reaction apparatus for performing an electrolytic reaction. The present invention has been completed.

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

(1) A platinum group element in which a platinum group element is supported on a carrier made of conductive carbon having a primary particle size of 100 nm or less in a method for producing a carbonic acid diester by electrolytic reaction of an alkoxy compound and carbon monoxide. A method for producing a carbonic acid diester, comprising using a carbon electrode containing a supported catalyst.

(2) The method for producing a carbonic acid diester according to (1), wherein the alkoxy compound is a phenoxy compound and the carbonic acid diester is diphenyl carbonate.

(3) The method for producing a carbonic acid diester according to (1) or (2), wherein the conductive carbon has a BET specific surface area of 100 m ² / g or more.

(4) The method for producing a carbonic acid diester according to any one of (1) to (3), wherein the conductive carbon is carbon black.

(5) The method for producing a carbonic acid diester according to any one of (1) to (4), wherein the carbon electrode is formed by mixing a platinum group element-supported catalyst with a conductive auxiliary agent.

(6) The method for producing a carbonic acid diester according to (5), wherein the conductive auxiliary agent is conductive carbon having a powder resistivity of 0.5 Ω · cm or less.

(7) The method for producing a carbonic acid diester according to any one of (1) to (6), wherein the platinum group element is palladium.

(8) The catalyst according to any one of (1) to (7), wherein the platinum group element-supported catalyst is obtained by supporting a single metal of a platinum group element on a carrier made of conductive carbon. A method for producing a carbonic acid diester.

  According to the present invention, carbonic acid diesters useful in a wide range of fields such as solvents such as electrolytes, synthetic raw materials such as alkylating agents and carbonylating agents, gasoline and diesel fuel additives, polycarbonate and polyurethane raw materials, etc. In other words, a wide range of carbonic acid diesters, including carbonic acid diesters that could not be produced by conventional electrolytic reactions, can be industrially put into practical use by electrolytic reactions without using harmful substances such as phosgene. It can be produced efficiently with yield and selectivity.

It is a block diagram which shows an example of the electrolytic reaction apparatus suitable for implementation of this invention. It is a block diagram which shows the other 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 is a method for producing a carbonic acid diester by subjecting an alkoxy compound and carbon monoxide to an electrolytic reaction using a specific carbon electrode, and an alkoxy represented by the following formula (1): A carbonic acid diester is produced by the reaction of the compound and carbon monoxide (CO) according to the following reaction formula (2).

RO ^- X ⁺ (1)
(R represents an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, and these hydrocarbon groups may have a substituent. X ⁺ represents RO ^- showing the cationic species constituting the salt, however, ^{X +} is not a hydrogen ion ^{(H +))..
2RO - X + + CO → RO} -C (= O) -OR + 2e - + 2X + (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.

In addition, the method of the present invention is not limited to a method of producing a carbonic acid diester (RO—C (═O) —OR) using one kind of alkoxy compound, and using two or more kinds of alkoxy compounds, method of producing a different carbonic diester, for example, alkoxy compound ^{(R 1 O} - ^{X +)} and alkoxy compound - using ^{(2 O} R ^{X +)} and carbonate diester ^{(R 1 O-C (=} O) -OR ² ) is also included (wherein R ¹ and R ² have the same meanings as R and R ¹ ≠ R ² ).

[Alkoxy compound]
In the present invention, the alkoxy compound 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 or substituted aryl groups such as tilphenyl, naphthyl, and anthracenyl groups, and derivatives thereof (hydrogen atoms are substituted with alkyl groups, aryl groups, halogen atoms, nitro groups, sulfonic acid groups, sulfone groups, amino groups, etc. And 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, such as an aromatic hydrocarbon group, and particularly a phenyl group is preferable. The carbonic acid diester having 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. RO ⁻ represents an anion species formed by combining R and an oxygen atom, and may be an anion having a valence of 2 or more depending on the corresponding cation species. These may be used individually by 1 type and may use 2 or more types together. X ⁺ represents a cationic species that forms a salt with RO ^−, and X ⁺ represents an alkali metal ion such as lithium, sodium, or potassium, or an alkaline earth metal ion such as magnesium or calcium, trimethylammonium, triethylammonium, or tributyl. Tertiary ammonium cations such as ammonium, triphenylammonium, dimethylanilinium, pyridinium, secondary ammonium cations such as diisopropylammonium, primary ammonium cations such as methylammonium, ethylammonium, propylammonium, butylammonium, benzylammonium, NH ₄ Examples include ammonium cation represented by ⁺ , quaternary ammonium cation such as tetramethylammonium and tetraethylammonium. X ⁺ may be not only a monovalent cation but also a divalent or higher cation. These may be used individually by 1 type and may use 2 or more types together.
Examples of the phenoxide compound represented by RO ^- X ⁺ include sodium phenoxide, lithium phenoxide, potassium phenoxide and the like.

  The alkoxy compound used in the reaction is produced by reacting an organic hydroxy compound (that is, an organic hydroxy compound represented by the following formula (3)) with a basic substance to desorb hydrogen ions of the organic hydroxy compound. May be. This alkoxy compound may be synthesized simultaneously with the electrolytic reaction in the electrolytic reaction apparatus, or may be synthesized separately.

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

  Specific examples of the organic hydroxy compound used for the preparation of the alkoxy compound include ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, n-hexanol, and n-heptanol. , Saturated or unsaturated, linear or branched aliphatic alcohols such as allyl alcohol, crotyl alcohol, etc., preferably linear or branched saturated or unsaturated fats having 2 or more carbon atoms, more preferably 2 to 10 carbon atoms Saturated or unsaturated alicyclic alcohols such as aromatic alcohol, cyclopentanol, cyclohexanol, cycloheptanol, methylcyclohexanol, 3-hydroxy-1-cyclohexene, 4-hydroxy-1-cyclohexene, preferably 5 or more carbon atoms , More preferably 5 carbon atoms 10 saturated or unsaturated alicyclic alcohols, aryl-substituted alcohols such as benzyl alcohol, hydroxybenzyl alcohol, diphenylcarbinol, aromatic organic hydroxy compounds such as phenol, cresol, xylenol, naphthol, hydroxyanthracene or derivatives thereof (aromatic Ring hydrogen atoms are substituted with alkyl groups, aryl groups, halogen atoms, nitro groups, sulfonic acid groups, amino groups, etc.).

  The basic substance used for the preparation of the alkoxy compound must be selected according to the reactivity with the organic hydroxy compound, but alkali metals such as metallic lithium, metallic sodium and metallic potassium or alkaline such as metallic calcium and metallic magnesium. Alkali metals such as earth metals, lithium hydroxide, sodium hydroxide and potassium hydroxide, or hydroxides of alkaline earth metals such as calcium hydroxide and magnesium hydroxide, alkali metals such as lithium hydride and sodium hydride, or calcium hydride Alkaline earth metal hydrides such as magnesium hydride, alkali metal or alkaline earth metal acetates such as sodium acetate and potassium carbonate, weak acid salts such as carbonates, trimethylamine, triethylamine, tributylamine, triphenyl Amine, diisopropylamine, dimethylaniline, amines such as pyridine, manufactured by Mitsubishi Chemical Corporation, Diaion (registered trademark) basic ion exchange resin such as SA10A 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 compound 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.

[Platinum group element supported catalyst]
Examples of the platinum group element of the platinum group element-supported catalyst used in the electrolytic reaction of the present invention include ruthenium, rhodium, palladium, osmium, iridium, platinum and the like, and these may be used alone or in combination. You may use the above together. Of these, palladium is preferred because the desired reaction proceeds efficiently.

  In the present invention, these platinum group elements are used by being supported on a carrier made of conductive carbon. As the conductive carbon, conductive carbon fine particles having a primary particle diameter of 100 nm or less, preferably 50 nm or less, or an aggregate thereof is used.

  The term “primary particle diameter” as used herein refers to an average value of individual particle diameters observed from a photograph of a plurality of particles dispersed using an electron microscope such as a transmission electron microscope. When calculating the particle size, if the shape of the particle observed from the photograph is a columnar shape such as a columnar shape, the short side length should be used as the particle size, and the number of particles used to determine the average value is particularly limited However, it is preferable to observe as many particles as possible. Specifically, it is preferable to observe 100 or more particles, more preferably 1000 or more particles, for example, 5000 to 10,000 particles. In calculating the average value, commercially available software for particle size measurement may be used.

  Although the details of the working mechanism of the effect of the present invention produced by using conductive carbon in the form of ultrafine particles having a primary particle diameter of 100 nm or less as a carrier are not clear, such ultrafine particles may be used. For example, it is considered that the volume resistivity value of the support is lowered and the electrical conductivity is improved, whereby the catalyst and electrode performance is improved, thereby increasing the reaction efficiency.

In the present invention, among conductive carbons having a primary particle size of 100 nm or less, conductive carbon having a large specific surface area having a BET specific surface area of 100 m ² / g or more, particularly 200 m ² / g or more is used as a carrier. In view of increasing the reaction point per unit weight of the catalyst.

Here, the BET specific surface area of the conductive carbon is measured as follows.
First, the sample is put into a sample tube (adsorption cell), evacuated while being heated, and the sample weight after degassing is measured. Next, a change in the amount of adsorption with respect to a change in pressure is plotted while feeding nitrogen gas into the cell and adsorbing nitrogen gas on the sample surface. From this graph, the adsorption amount of gas molecules adsorbed only on the sample surface is obtained from the BET adsorption isotherm. Since the nitrogen occupancy area is known in advance, the surface area of the sample can be measured from the gas adsorption amount.

The lower limit of the primary particle diameter and the upper limit of the BET specific surface area of the conductive carbon used in the present invention are not particularly limited, but the primary particle diameter is usually 10 nm or more due to limitations on the manufacturing method and mechanical strength. The BET specific surface area is 10000 m ² / g or less.

  The carbon material of the conductive carbon is not particularly limited, but preferably usable carbon materials include carbon black, graphite, fullerene, carbon nanotubes, graphene, activated carbon fibers, and the like. These may be used alone or in combination of two or more. Among these, carbon black is preferable from the viewpoints of availability as a carrier and price.

  A platinum group element-supported catalyst is formed by supporting a platinum group metal (platinum group metal simple substance, including an alloy) or a compound containing a platinum group metal on a carrier made of conductive carbon as described above. However, in terms of electrolytic reaction efficiency, a material in which a platinum group element is supported as a simple metal is preferable.

  The method for producing such a platinum group element-supported catalyst is not particularly limited, but a method in which a predetermined amount of an aqueous solution in which a salt of a platinum group element is dissolved is dropped into water in which conductive carbon is dispersed and evaporated to dryness. Is mentioned. This is further heated to about 100 to 500 ° C. under a hydrogen stream to reduce platinum group element salts on the carrier, and a platinum group element-supported catalyst in which the platinum group metal is supported on conductive carbon as a simple substance. Can be obtained.

[Carbon electrode]
The carbon electrode used in the present invention includes the above platinum group element-supported catalyst.
This carbon electrode can be manufactured, for example, by adding a binder such as polytetrafluoroethylene (PTFE) to the above platinum group element-supported catalyst. Or it can manufacture by knead | mixing and shape | molding the above-mentioned platinum group element carrying | support catalyst with the said conductive additive which does not carry | support the binder and platinum group element. The conductive auxiliary agent used here may be the same as or different from the conductive carbon used as the platinum group element support of the platinum group element-supported catalyst. It is preferable to use conductive carbon having a body resistivity of 0.5 Ω · cm or less, preferably 0.25 Ω · m or less. By using a conductive auxiliary agent such as conductive carbon in combination, the effect that the internal resistance of the electrode is suppressed is exhibited, but when the powder resistivity of the conductive auxiliary agent used exceeds 0.5 Ω · cm, The resistance in the electrode increases and the current efficiency decreases. Although there is no restriction | limiting in particular in the minimum of the powder resistivity of electroconductive carbon, Usually, it is about 0.01 ohm * cm.
Here, the powder resistivity is generated between the two inner probes by placing four needle-shaped electrodes (four probe probes) on a straight line on the sample and passing a constant current between the two outer probes. It can be obtained by measuring the potential difference (four probe method).

If the amount of the platinum group element-supported catalyst in such a carbon electrode 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 platinum group element-supported catalyst in the carbon electrode can be appropriately selected according to the reaction system using the carbon electrode. For example, the amount of the active ingredient contained in the electrode (in terms of platinum group element) is 0. 1-20 micromol / cm < ² > is preferable and 1-15 micromol / cm < ² > is still more preferable.

  Accordingly, in forming the carbon electrode, the binder and the conductive auxiliary agent are appropriately adjusted so that the supported amount of the platinum group element per electrode area of the carbon electrode is within the above range, and the platinum group element supported catalyst. Mix with.

[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 above-described alkoxy compound or a basic substance added to produce the alkoxy compound may function as an electrolyte, and there is no need to add a supporting electrolyte separately. 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 compound 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 inhibited by the moisture in the reaction solution, the amount of moisture in the reaction solution is preferably 5% by weight or less by using a raw material or a solvent having a low water content. Preferably it is 1 weight% or less, More preferably, it is 1000 weight ppm or less, Most preferably, it is 800 weight ppm 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 it 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 compound may be passed through the reaction solution containing the alkoxy compound 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, but generally it implements at about room temperature (for example, about 20-30 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, and if it is high, the oxidation of the basic substance added to produce the alkoxy compound 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 electrolysis potential increases depending on the resistance of the electrolysis reactor, and the direct oxidation of the organic hydroxy compound or basic substance proceeds. The rate drops. Since the preferred current density depends on the resistance value, it is preferable to make the resistance value as low as possible so that the current density and the electrolytic potential are in the preferred ranges.

<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 multiple reactors, raw materials such as unreacted organic hydroxy compounds, alkoxy compounds, basic substances, carbon monoxide, etc. contained in the reaction products from the recovery line are supplied to the same or different reactor supply lines. It may circulate.

[Reactor]
In the electrolytic reaction of the present invention, an oxidation reaction of an alkoxy compound 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. However, this is not an essential requirement, and it is possible to place the anode and cathode in a single reaction compartment as shown in FIG. 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, cadmium, lead, gold, an alloy containing them, or the like can be used.
As the anode material, the aforementioned carbon electrode is used.

  1 and 2 are schematic configuration diagrams showing an example of an electrolytic reaction apparatus suitable for carrying out the method for producing a carbonic acid diester of the present invention.

  In FIG. 1, reference numeral 10 denotes a reactor (electrolysis cell), in which a bottomed cylindrical container part constituting the anode chamber 11 and a bottomed cylindrical container part constituting the cathode chamber 12 are cylindrical communication parts. 13 connected to each other. The above-described carbon electrode is provided as the anode 11A at the bottom of the anode chamber 11, the cathode 12A is provided in the cathode chamber 12, and these anode 11A and cathode 12A are connected to a power source 19. 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 gas sampling pipe. Reference numeral 18 denotes a gas vent pipe that also serves as a gas sampling pipe.

In this electrolytic reaction apparatus, a reaction solution containing an organic hydroxy compound and a basic substance or an alkoxy compound is introduced into the anode chamber 11, and a reaction solution containing the organic hydroxy compound is introduced into the cathode chamber 12, and monoxide is obtained from the gas supply pipe 15. When carbon is supplied and the anode 19A is energized between the anode 11A and the cathode 12A by the power source 19, in the presence of the platinum group element supported catalyst contained in the carbon electrode of the anode 11A in the anode chamber 11, the organic hydroxy compound and the basic substance The alkoxy compound produced by the above reaction and carbon monoxide 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.

  In FIG. 2, 20 is a reactor (electrolysis cell) having a bottomed cylindrical container 20A and a stopper 20B for covering the upper opening of the container 20A. The aforementioned carbon electrode is provided as the anode 21 at the bottom of the container 20A. Further, the cathode 22 is inserted from the stopper 20B to an intermediate position in the height direction in the container portion 20A. These anode 21 and cathode 22 are connected to a power source 23. Reference numeral 24 denotes a current collector that conducts the power source 23 and the anode 21. Reference numeral 25 denotes a gas supply pipe for supplying carbon monoxide to the reaction solution in the container 20A. The gas supply pipe 25 also serves as a gas supply pipe for circulating an inert gas such as He. A gas vent pipe 26 also serves as a gas sampling pipe.

In this electrolytic reaction apparatus, a reaction liquid containing an organic hydroxy compound and a basic substance or an alkoxy compound is introduced into a container portion 20A, carbon monoxide is supplied from a gas supply pipe 25, and an anode 21 and a cathode 22 are supplied from a power source 23. In the presence of the platinum group element-supported catalyst contained in the carbon electrode of the anode 21 in the container portion 20A, the alkoxy compound and carbon monoxide produced by the reaction between the organic hydroxy compound and the basic substance are produced. Electrolytic reaction produces carbonic acid diester. At the same time, carbon dioxide may be generated by the oxidation of carbon monoxide. On the other hand, in the vicinity of the cathode chamber 22, hydrogen ions are reduced to generate hydrogen gas.
Prior to the reaction, the amount of water in the reaction solution can be reduced by flowing an inert gas such as He from the gas supply pipe 25.

  1 and 2 show an example of an electrolytic reaction apparatus that can be applied to the present invention, and do 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 diester produced by the electrolytic reaction of the present invention is widely used as a solvent such as an electrolytic solution, a synthetic raw material such as an alkylating agent and a carbonylating agent, an additive for gasoline and 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 platinum group element-supported catalyst In a 200 mL beaker, 80 mL of ion exchange water and a conductive carbon carrier, carbon black having a primary particle diameter and a BET specific surface area shown in Table 1 (manufactured by Ketjen Black International Co., Ltd., “ 650 mg of carbon ECP ”(hereinafter abbreviated as“ ECP ”) was added, and 4.19 mL of 0.03 mo1 / L aqueous solution of chloropalladium acid (H ₂ PdCl ₄ ) was added dropwise while stirring with a magnetic stirrer. 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 moisture, thereby obtaining a black powder. This black powder contained 2.06 wt% palladium chloride (PdCl ₂ ) based on the Pd metal standard. By treating this at 150 ° C. for 1 hour and then at 300 ° C. for 2 hours in a hydrogen stream (20 mL / min), the supported Pd ²⁺ becomes Pd (0) by hydrogen reduction, and Pd becomes a conductive carbon support. A platinum group element-supported catalyst in the form of a black powder supported on the catalyst was obtained. The amount of Pd supported by this platinum group element supported catalyst is 2.06% by weight with respect to the conductive carbon.

(2) Production of Carbon Electrode (Anode) Polytetrafluoroethylene powder (F-104, manufactured by Daikin Co., Ltd.) as a binder to 155 mg (Pd content 30 μmol) of the platinum group element-supported catalyst obtained in (1) above. 40 mg) was added and kneaded in an agate mortar. It was rolled on a hot plate at 120 ° C. and formed into a round sheet shape to produce a carbon electrode (anode) having an electrode area of 5 cm ² (geometric area) and a thickness of about 1.6 mm. The amount of Pd supported per electrode area of this carbon electrode is 6 μmol / cm ² .

(3) Electrolytic Reaction The carbon electrode produced by the above method was used as the anode 21 and constant current electrolysis was performed using the electrolytic reaction apparatus shown in FIG.
A platinum wire was used as the cathode 22.
In the reaction solution, 40 mL of acetonitrile (made by Wako Pure Chemicals, for organic synthesis) as a reaction solvent, 30 mmol of phenol (made by Wako Pure Chemicals, special grade) as an organic hydroxy compound, and anhydrous sodium phenoxide (Alfa Aeser as a phenoxide compound) 0.5 mmol) and lithium chloride (Wako Pure Chemical Industries, special grade) 0.78 mmol were added as a supporting electrolyte. About 5 g of molecular sieves 3A (manufactured by Wako Pure Chemical Industries, Ltd., for chemical use) calcined at 300 ° C. for 10 hours in advance was added to the solvent acetonitrile, and dehydrated by placing it for 12 hours or more with occasional shaking.
By dissolving helium (Japan Helium Center Co., Ltd., purity: 99.9995%) at 900 mL / Hr for 10 minutes in the gas phase portion of the electrolysis cell 20, dissolved oxygen and moisture are removed, and carbon monoxide (Japan Oxygen) Made by the company, purity 99.95%) was circulated at 900 mL / Hr for 60 minutes, and then the constant current electrolysis was carried out at a current density of 0.2 mA / cm ² for 10 hours.

  The electrolytic reaction solution was sampled in a timely manner, followed by gas chromatography (detector: FID, column GC-2010 manufactured by Shimadzu Corporation, ZB-1 capillary column, φ0.25 mm × 30 m, analysis conditions: injection temperature 220 ° C., column temperature 190 ° C. (The detector temperature was 250 ° C.) (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. Carbon dioxide in the sampling gas was analyzed by gas chromatography (detector: TCD, GC-8A, Shimadzu Corp., PorapakQ packed column, 70 ° C. In the constant temperature analysis, hydrogen was analyzed by gas chromatography (detector: TCD, GC-8A manufactured by Shimadzu Corporation, activated carbon column (4 mm × 2 m), constant temperature analysis at 120 ° C.).

As a result, it was found that the amount of diphenyl carbonate (DPC) increased almost linearly at a rate of about 23 μmol per hour, and the amount generated at 5 hours after the start of the reaction reached 114.7 μmol. It was. The current efficiency of DPC generation was almost 100%, and an amount of hydrogen corresponding to a current efficiency of 100% was detected from the sampling gas. The TON (turnover number) of the catalyst when reacted for 5 hours was 3.8 mol-DPC / mol-Pd, and TON after 10 hours was 7.2 mol-DPC / mol-Pd.
A summary of the results is shown in Table 1.

[Example 2]
(1) Preparation of platinum group element-supported catalyst In a 200 mL beaker, carbon black having a primary particle size and a BET specific surface area shown in Table 1 as a conductive carbon carrier (100 mL, manufactured by Ketjen Black International Co., Ltd., “ Carbon ECP600JD ”(hereinafter abbreviated as“ ECP600JD ”) (0.5 mg) was added, and 20 mL of a 0.03 mo1 / L aqueous solution of palladium chloride (H ₂ PdCl ₄ ) was added dropwise while stirring with a magnetic stirrer. 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 moisture, thereby obtaining a black powder. This black powder contained 10.6 wt% palladium chloride (PdCl ₂ ) based on the Pd metal standard. By treating this at 150 ° C. for 1 hour and then at 300 ° C. for 2 hours in a hydrogen stream (20 mL / min), the supported Pd ²⁺ becomes Pd (0) by hydrogen reduction, and Pd becomes a conductive carbon support. A supported platinum group element-supported catalyst of a black powder was obtained. The amount of Pd supported by this platinum group element supported catalyst is 10.6% by weight with respect to the conductive carbon.

(2) Production of carbon electrode (anode) ECP600JD in which Pd is not supported as a conductive auxiliary agent on 30 mg (Pd content 30 μmol) of the platinum group element-supported catalyst obtained in (1) above. The powder resistivity was as shown in Table 1) and 125 mg of polytetrafluoroethylene powder (F-104, manufactured by Daikin) was added as a binder and kneaded in an agate mortar. It was molded on a hot plate at 120 ° C. to prepare a carbon electrode (anode) having an electrode area of 5 cm ² (geometric area). The amount of Pd supported per electrode area of this carbon electrode is 6 μmol / cm ² .

(3) Electrolytic reaction Constant current electrolysis was performed for 10 hours in the same manner as in Example 1 except that the carbon electrode produced by the above method was used as the anode.
As a result, it was found that the amount of DPC produced increased almost linearly at a rate of about 19 μmol per hour, and the amount produced at 6 hours after the start of the reaction reached 110.8 μmol. The current efficiency of DPC generation was 99.0%, and an amount of hydrogen corresponding to a current efficiency of 100% was detected in the sampling gas. The TON of the catalyst at a reaction time of 6 hours is 3.7 mol-DPC / mol-Pd, and the TON of the catalyst is 7.5 mol-DPC / mol-Pd by further reacting for 4 hours (total reaction time 10 hours). Rose to.

[Example 3]
Constant current electrolysis was carried out for 10 hours in the same manner as in Example 2 except that both the support of the platinum group element-supported catalyst and the conductive auxiliary of the carbon electrode were ECP.
As a result, the production amount of DPC increased almost linearly, the production amount of DPC at 6 hours after the start of the reaction was 93.4 μmol, the current efficiency was 83.5%, and the TON of the catalyst was 3.1 mol-DPC. / Mol-Pd.
By further reacting for 4 hours (total reaction time 10 hours), the TON of the catalyst increased to 5.9 mol-DPC / mol-Pd.

[Example 4]
The carrier for the platinum group element-supported catalyst is ECP600JD, and the carbon electrode conductive assistant is a vapor-grown carbon fiber having an average fiber diameter of 150 nm and a fiber length of 10 to 20 μm (manufactured by Showa Denko KK, normal product, hereinafter “VGCF”) Constant current electrolysis was carried out for 7 hours in the same manner as in Example 2, except that the powder resistivity was as shown in Table 1.
The amount of DPC produced slightly decreased with time, and 62.9 μmol was produced at 6 hours from the start of the reaction. The current efficiency was 56.2%, and the TON of the catalyst was 2.1 mol-DPC / mol-Pd.

[Example 5]
Constant current electrolysis was carried out for 7 hours in the same manner as in Example 2 except that the support of the platinum group element-supported catalyst was ECP and the conductive auxiliary of the carbon electrode was VGCF.
The amount of DPC produced decreased with time. At 6 hours, the amount was 52.0 μmol, the current efficiency was 46.4%, and the TON of the catalyst was 1.7 mol-DPC / mol-Pd.

[Example 6]
The support of the platinum group element-supported catalyst is carbon black XC-72 (“VULCAN XC-72” manufactured by Cabot, hereinafter abbreviated as “XC72”) having a primary particle diameter and a BET specific surface area shown in Table 1, and is electrically conductive. Constant current electrolysis was carried out for 6 hours in the same manner as in Example 2 except that the auxiliary agent was VGCF.
The amount of DPC produced decreased with time. At 6 hours, 34.3 μmol, the current efficiency was 30.6%, and the TON of the catalyst was 1.1 mol-DPC / mol-Pd.

[Comparative Example 1]
The support of the platinum group element-supported catalyst was activated carbon (made by Wako Pure Chemical Industries, special grade, hereinafter abbreviated as “AC”) having the primary particle size and BET specific surface area shown in Table 1, and the conductive auxiliary agent was VGCF. Except for the above, constant current electrolysis was performed in the same manner as in Example 2 for 6 hours.
The amount of DPC produced increased almost linearly, but the amount produced was small. At 6 hours, 17.7 μmol, the current efficiency was 15.8%, and the TON of the catalyst was 0.6 mol-DPC / mol-Pd.

[Comparative Example 2]
Constant current electrolysis was carried out for 6 hours in the same manner as in Example 2 except that the carrier of the platinum group element supported catalyst was VGCF and the conductive auxiliary was VGCF, but DPC was not generated.

[Comparative Example 3]
Pd was not supported on 155 mg of carbon black powder (ECP), and 30 μmol of Pd as a simple metal (Pd black) was mixed with 40 mg of polytetrafluoroethylene powder as a binder and kneaded in an agate mortar. It was molded on a hot plate at 120 ° C. to produce a carbon electrode having an electrode area of 5 cm ² (geometric area). The amount of Pd supported per electrode area is 6 μmol / cm ² .
Constant current electrolysis was performed for 6 hours in the same manner as in Example 1 except that this carbon electrode was used as the anode, but no DPC was produced.

From Table 1, according to the present invention, a platinum group element is added to a conductive carbon support having a primary particle diameter of 100 nm or less, particularly a conductive carbon support having a primary particle diameter of 100 nm or less and a BET specific surface area of 100 m ² / g or more. It can be seen that by using a carbon electrode containing a catalyst on which carbon is supported, a diester carbonate such as diphenyl carbonate can be efficiently produced by an electrolytic reaction.

  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.

10,20 reactor (electrolysis cell)
DESCRIPTION OF SYMBOLS 11 Anode chamber 11A, 21 Anode 12 Cathode chamber 12A, 22 Cathode 14 Diaphragm 15, 16, 25 Gas supply pipe 18, 23 Power supply

Claims (8)

In the method of producing a carbonic acid diester by electrolytic reaction of an alkoxy compound and carbon monoxide,
A method for producing a carbonic acid diester, comprising using a carbon electrode containing a platinum group element-supported catalyst in which a platinum group element is supported on a carrier made of conductive carbon having a primary particle size of 100 nm or less.   The method for producing a carbonic acid diester according to claim 1, wherein the alkoxy compound is a phenoxy compound, and the carbonic acid diester is diphenyl carbonate. The method for producing a carbonic acid diester according to claim 1 or 2, wherein the conductive carbon has a BET specific surface area of 100 m ² / g or more.   The method for producing a carbonic acid diester according to any one of claims 1 to 3, wherein the conductive carbon is carbon black.   5. The carbonic acid diester production method according to claim 1, wherein the carbon electrode is formed by mixing a platinum group element-supported catalyst with a conductive auxiliary agent.   The method for producing a carbonic acid diester according to claim 5, wherein the conductive auxiliary agent is conductive carbon having a powder resistivity of 0.5 Ω · cm or less.   The method for producing a carbonic acid diester according to any one of claims 1 to 6, wherein the platinum group element is palladium.   The method for producing a carbonic acid diester according to any one of claims 1 to 7, wherein the platinum group element-supported catalyst is obtained by supporting a metal element of a platinum group element on a support made of conductive carbon. .

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