JPH11279125A - Production of dialkyl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas-phase method, for producing a dialkyl carbonate by decarbonylating a dialkyl oxalate, which allows high-yield and highly selective production of a dialkyl carbonate, and easy separation/recovery of products and a catalyst. SOLUTION: This method comprises the steps of (1) catalytically reacting carbon monoxide with alkyl nitrite to form dialkyl oxalate and nitrogen monoxide, and (2) decarbonylating the obtained dialkyl oxalate into a dialkyl carbonate and carbon monoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a dialkyl carbonate, and more particularly to a method for producing a dialkyl carbonate by subjecting a dialkyl oxalate to a decarbonylation reaction. That is, in the present invention, in the first step, carbon monoxide and alkyl nitrite are contact-reacted to generate dialkyl oxalate and nitric oxide, and in the second step, the dialkyl oxalate is de-CO-reacted. Dimethyl carbonate by a completely new industrial process of producing dialkyl carbonate and carbon monoxide (and recovering carbon monoxide produced in the second step and reusing it as a raw material in the first step) And the like. Dialkyl carbonate such as dimethyl carbonate is a compound useful as a raw material for producing pharmaceuticals, agricultural chemicals, urethane, polycarbonate and the like.

[0002]

2. Description of the Related Art As a method for producing a dialkyl carbonate by subjecting a dialkyl oxalate to a decarbonylation reaction, a dialkyl oxalate is prepared in the presence of an alcoholate catalyst in the range of 50 to 15 to 50 to 15%.
A method of heating in the liquid phase at 0 ° C. is known (US Pat. No. 4,544,507). However, this method has a problem that the yield of the target substance is low and the selectivity of the target substance is low because various by-products are formed, which is not industrially satisfactory. Furthermore, as for the method based on the decarbonylation reaction of dialkyl oxalate, no industrially suitable process including production of raw materials is known at all.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a dialkyl carbonate by subjecting a dialkyl oxalate to a decarbonylation reaction, wherein the dialkyl carbonate can be produced in a high yield and a high selectivity. It is an object to provide an industrially suitable manufacturing process including manufacturing. It is another object of the present invention to provide an industrially suitable process for producing a dialkyl carbonate, including production of a raw material, by a gas phase method in which a product and a catalyst can be easily separated and recovered.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a first step in which carbon monoxide and an alkyl nitrite are contact-reacted to produce a dialkyl oxalate and a nitric oxide. The problem is solved by a method for producing dialkyl carbonate, which comprises reacting a dialkyl acid with CO to produce a dialkyl carbonate and carbon monoxide. The object of the present invention is to recover the dialkyl carbonate generated in the second step, recover the generated carbon monoxide and supply it to the first step for the production of dialkyl oxalate. It is solved by the same method for producing dialkyl carbonate as described above.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention generally comprises a first step of producing dialkyl oxalate and nitric oxide from carbon monoxide and alkyl nitrite as shown in FIG. 1, and producing dialkyl carbonate and carbon monoxide from the dialkyl oxalate. Go through the second step,
It is done according to the process.

In the present invention, for example, in the first step, carbon monoxide is contacted with an alkyl nitrite (particularly methyl nitrite) in the presence of a platinum group metal catalyst to form a dialkyl oxalate (particularly dimethyl oxalate). And nitric oxide to produce dialkyl oxalate, and to collect nitric oxide and supply it to the separately provided alkyl nitrite regeneration step, and to regenerate the alkyl nitrite and supply it to the first step. Then, in the second step, the dialkyl oxalate is subjected to a CO removal reaction in a gas phase or a liquid phase in the presence of a CO removal catalyst to form a dialkyl carbonate (particularly dimethyl carbonate; DMC) and carbon monoxide, thereby forming the dialkyl carbonate. By collecting and supplying carbon monoxide to the first step or the alkyl nitrite regeneration step, dialkyl carbonate (particularly dimethyl carbonate;
DMC) is industrially suitably carried out.

In the first step of the present invention, it is industrially necessary to produce a dialkyl oxalate and nitric oxide by contacting carbon monoxide with alkyl nitrite in the gas phase in the presence of a platinum group metal catalyst. Particularly preferred. Then, in the reaction of the first step, nitric oxide generated when carbon monoxide and alkyl nitrite are contacted and reacted with molecular oxygen and lower alcohol to regenerate to alkyl nitrite, and the regenerated It is particularly preferable industrially to supply the alkyl nitrite to the supply line of the raw material of the first step and reuse it for the reaction of the first step.

In the first step of the present invention, when, for example, carbon monoxide and alkyl nitrite are contacted in the gas phase, according to reaction formula (1), carbon monoxide (CO 2) is present in the presence of a platinum group metal catalyst. ) And alkyl nitrite (RONO) produce dialkyl oxalate.

[0009]

Embedded image

The above-mentioned alkyl nitrite can be represented by the chemical formula (RONO) shown in the formula (1), wherein R is, for example, a methyl group, an ethyl group, an n-propyl group, an i-propyl group,
and a lower alkyl group having 1 to 6 carbon atoms such as an n-butyl group, an i-butyl group, a pentyl group, and a hexyl group. Examples of the alkyl nitrite include those in which R is one of these alkyl groups. Among them, methyl nitrite, ethyl nitrite, n-propyl nitrite, i-propyl nitrite, n-butyl nitrite, i-nitrite Alkyl nitrite having 1 to 4 carbon atoms such as butyl is preferred.

In the second step of the present invention, for example, a dialkyl carbonate and carbon monoxide are produced from the dialkyl oxalate by a de-CO reaction in the presence of a de-CO catalyst, if necessary, according to the reaction formula (2). The generated carbon monoxide is preferably supplied to the first step or the nitrite regenerating step.

[0012]

Embedded image

The first step will be described in more detail. Examples of the platinum group metal catalyst used in the first step include a platinum group metal or a compound thereof. It is preferable that the platinum group metal compound is reduced and used in the form of a platinum group metal (Japanese Patent Publication No. No. 28903, JP-B-56-28
904, JP-B-61-6057, JP-B-6
1-269977). Examples of the platinum group metal include platinum metal, palladium metal, rhodium metal, iridium metal and the like, and examples of the compound include inorganic acid salts (nitrates, sulfates, phosphates, etc.) and halides of these metals ( Chloride, bromide, etc.), organic acid salts (acetate, oxalate, benzoate, etc.), complexes and the like are used. Among the platinum group metals or compounds thereof, palladium metals or compounds thereof are particularly preferred.

As the palladium compound, for example, inorganic salts of palladium (palladium nitrate, palladium sulfate,
Palladium phosphate, etc.), halides of palladium (palladium chloride, palladium bromide, etc.), organic acid salts of palladium (palladium acetate, palladium oxalate, palladium benzoate, etc.), or complexes of palladium (alkyl phosphines, such as trimethylphosphine) , An aryl phosphine such as triphenyl phosphine, an alkyl aryl phosphine such as diethyl phenyl phosphine, or a complex having an aryl phosphite such as triphenyl phosphite as a ligand).

The platinum group metal catalyst is preferably supported on an inert carrier of the platinum group metal or a compound thereof in an amount of preferably 0.01 to 10% by weight, more preferably 0.2 to 2% by weight in terms of platinum group metal. It is industrially preferred to use it in the form of a solid catalyst. For example, palladium metal or a compound thereof is activated carbon, alumina (such as α-alumina), silica, diatomaceous earth, pumice, zeolite, molecular sieve,
It is preferable that the carrier is supported on an inert carrier such as spinel (eg, lithium aluminate spinel) in the above-described amount.
When a solid catalyst in which a platinum group metal compound is supported on a carrier is used, the platinum group metal compound is reduced to a platinum group metal with a reducing substance such as hydrogen in advance, or is oxidized in a reactor before the reaction. It is preferable to reduce the platinum group metal with a reducing substance such as carbon before use. The platinum group metal catalyst is prepared by a known method (impregnation method, evaporation to dryness method, etc.).

The platinum group metal catalyst used in the first step can contain, for example, iron or a compound thereof (JP-A-59-80630). As iron or its compound, metallic iron, iron (II) compound or iron (III) compound is used. As the iron (II) compound, ferrous sulfate, ferrous nitrate, ferrous chloride, ammonium ferrous sulfate, ferrous lactate, ferrous hydroxide and the like are used, and as the iron (III) compound, Ferric sulfate, ferric nitrate, ferric chloride, ammonium ferric sulfate, ferric lactate, ferric hydroxide, ferric citrate and the like are used. Iron or its compound has a platinum group metal: Fe (atomic ratio) of preferably 10,000: 1 to 1.
It is used so as to be in the range of 1: 4, more preferably 5000: 1 to 1: 3. The catalyst containing iron or its compound is prepared by a known method.

The carbon monoxide used in the first step may be pure, but may be diluted with an inert gas such as nitrogen, or may contain small amounts of hydrogen gas or methane. Further, in the present invention, carbon monoxide generated in the second step can also be suitably used in the first step. For example, when the first step is performed in a gas phase continuous process, the carbon monoxide generated in the second step compensates for the carbon monoxide consumed in the reaction and the carbon monoxide lost by purging the circulating gas, For example, it is mixed with a regeneration gas described below and supplied to the first step, or is mixed with a non-condensable gas described later and supplied to the regeneration step.

The reaction in the first step is suitably carried out by contacting carbon monoxide and alkyl nitrite in the gas phase in the presence of a platinum group metal catalyst (Japanese Patent Publication No. 6057/1986).
And Japanese Patent Publication No. 61-26977). At this time, the contact time between the raw material gas containing carbon monoxide and alkyl nitrite and the platinum group metal catalyst is 10 seconds or less, and more preferably 0.1 second or less.
Preferably, the reaction temperature is 50 to 20 seconds.
The temperature is preferably 0 ° C, more preferably 80 to 150 ° C. The reaction pressure is from normal pressure to 10 kg / cm ² G, furthermore, from normal pressure to 5 kg / cm ² G, especially 2 to 5 kg / cm ^2.
It is preferably in the range of G. As the reactor, a single-tube or multi-tube heat exchange reactor is effective.

The concentration of carbon monoxide in the raw material gas is 2 to
It is preferable to be selected in the range of 90% by volume. Although the concentration of alkyl nitrite in the raw material gas can be changed in a wide range, in order to obtain a satisfactory reaction rate, the alkyl nitrite must be present so that the concentration in the raw material gas becomes 1% by volume or more. Is preferred. The concentration of the alkyl nitrite in the source gas is preferably selected, for example, in the range of 5 to 30% by volume.

The reaction product (reaction gas) containing the dialkyl oxalate is obtained by the above-mentioned gas phase contact reaction. When the gas phase catalytic reaction is carried out in a continuous process, the reaction product (reaction gas) is then led to a condenser, cooled to a temperature at which the dialkyl oxalate condenses, and combined with the condensate containing the dialkyl oxalate. It is separated into non-condensable gases containing nitric oxide. At this time, in order to prevent the dialkyl oxalate from being entrained in the non-condensable gas, it is preferable to condense the reaction product by cooling it to a temperature lower than the boiling point of the lower alcohol while contacting the reaction product with the lower alcohol. For example, when the target substance is dimethyl oxalate, 100 parts by weight of the above reaction product are mixed with 30% to 60 ° C of methanol at 0.001%.
It is preferable to make contact with 0.1 volume part. The operating pressure at this time is 10 kg / cm ² from the atmospheric pressure, even 5 kg / cm ² from the atmospheric pressure, is preferably in the range particularly 2~5kg / cm ^2.

As the lower alcohol, it is preferable to use a lower alcohol which is a component of alkyl nitrite and dialkyl oxalate. Examples of the lower alcohol (ROH) include those in which R is the same as the above-mentioned alkyl nitrite, and among them, among those having 1 to 1 carbon atoms such as methanol, ethanol, n-propanol, i-propanol, n-butanol and i-butanol. Four aliphatic alcohols are preferred.

The condensate contains a small amount of by-products such as dialkyl carbonate and alkyl formate in addition to the target dialkyl oxalate. Can be easily separated and recovered. The recovered dialkyl oxalate is supplied to the second step.

On the other hand, since the non-condensed gas contains nitrogen monoxide generated by the above-mentioned contact reaction in addition to unreacted carbon monoxide and alkyl nitrite, this nitric oxide is regenerated into alkyl nitrite. Then, it is industrially preferable to supply it to the first step (JP-B-61-6057, JP-B-61-26977, etc.). This playback, for example,
This is carried out by introducing the non-condensable gas to the regeneration tower, and bringing nitric oxide in the non-condensable gas into contact with molecular oxygen and a lower alcohol. At this time, as the lower alcohol,
A lower alcohol which is a component of the above-mentioned alkyl nitrite is used, and as molecular oxygen, oxygen gas or air is used. Further, in order to compensate for carbon monoxide consumed in the reaction and carbon monoxide lost by purging the circulating gas, carbon monoxide generated in the second step may be recovered and mixed with the non-condensable gas. In addition, as a regeneration tower, a normal gas-liquid contacting device such as a packed tower, a bubble tower, a spray tower, and a step tower is used.

In the regeneration of alkyl nitrite, the reaction is controlled so that the concentration of nitric oxide in the gas (regeneration gas) derived from the regeneration tower is 2 to 7% by volume. For this reason, 0.08 to 0.2 mol of molecular oxygen is supplied to 1 mol of nitrogen monoxide in the non-condensed gas introduced into the regeneration tower, and the boiling point of the lower alcohol at the pressure at the time of regeneration is not higher than ( For example, it is preferred to contact nitric oxide with molecular oxygen and a lower alcohol at a temperature of from 0 ° C. to the boiling point of the lower alcohol. The supply amount of the lower alcohol is preferably 1 to 5 parts by volume with respect to 1 part by volume of nitric oxide in the non-condensed gas, and the contact time is preferably 0.5 to 20 seconds. Operating pressure is 10kg / c from normal pressure
m ² , and further from normal pressure to 5 kg / cm ² , especially 2 to 5 kg
/ Cm ² . When the first step is performed in a continuous process, alkyl nitrite, nitrogen oxides (nitrogen monoxide, nitrogen dioxide, nitrous oxide, Dinitrogen tetroxide) or nitric acid.

Thus, the concentration of nitric oxide is 2 to
7% by volume, substantially free of nitrogen dioxide and oxygen,
Regenerated gas containing alkyl nitrite (regenerated gas)
Is supplied to the first step. Further, in order to compensate for the carbon monoxide consumed in the reaction and the carbon monoxide lost by purging the circulating gas, it is preferable that the carbon monoxide generated in the second step is recovered and mixed with the regenerated gas.

The reaction of the first step can be carried out in a liquid phase. In this case, the reaction is carried out by contacting a gas containing carbon monoxide and molecular oxygen, and a mixed solution of a lower alcohol containing a platinum group metal catalyst and alkyl nitrite in a liquid phase under pressure. (Japanese Patent Publication 56-28903
And Japanese Patent Publication No. 56-28904).

In the case of the liquid phase contact reaction, the contact time is 5
To 60 minutes, and the reaction temperature is 40 to 20 minutes.
The temperature is preferably 0 ° C, more preferably 60 to 150 ° C, and the reaction pressure is 5 to 250 kg / cm ² G, more preferably 10 to 20 kg / cm ² G.
It is preferably 0 kg / cm ² G. Further, carbon monoxide and molecular oxygen are supplied so that carbon monoxide is 5 to 80% by volume per 1% by volume of oxygen, and the nitrite is 8 to 50% by weight in the mixed solution. Supplied. The platinum group metal catalyst is preferably used by being supported on a carrier such as activated carbon, alumina (α-alumina or the like), silica or the like, similarly to the gas phase contact reaction. 0.1% by weight to 2% by weight,
Furthermore, it is preferable to use 10 to 200 ppm by weight. In addition, as a reactor, a hollow cylindrical column, a packed column, a tray column, or the like is effective.

The reaction solution obtained by the liquid phase contact reaction contains by-products such as water, dialkyl carbonate, and alkyl formate in addition to the target product, dialkyl oxalate. After water is removed by distillation, dialkyl oxalate is recovered by an operation such as distillation. Also,
When the liquid phase contact reaction is performed in a continuous process, the carbon monoxide generated in the second step is converted to the first step in order to compensate for the carbon monoxide consumed in the reaction and the carbon monoxide lost in purging the circulating gas. Preferably it is supplied.

Next, the second step will be described in more detail. In the second step of the present invention, the dialkyl oxalate obtained in the first step is subjected to a CO removal reaction to produce dialkyl carbonate and carbon monoxide, and the dialkyl carbonate is recovered from the reaction mixture, and the carbon monoxide is removed. This is a step of collecting and supplying to the first step. This CO removal reaction is preferably performed in a liquid phase or a gas phase in the presence of a CO removal catalyst, but is particularly preferably performed in a gas phase in the presence of a CO removal catalyst.

As the CO removal catalyst, the CO removal reaction of the dialkyl oxalate can be carried out at a relatively low temperature (about 100 to 350 ° C.), and the dialkyl carbonate has a high selectivity (at least 50% or more, more preferably 60 to 50%). 100%, especially 80-
(100%). CO removal
Preferred examples of the catalyst include alkali metal compounds, organic phosphonium salts, organic ammonium salts, and the like.

Examples of the alkali metal compound include alkali metal salts of organic acids, alkali metal salts of inorganic acids, and hydroxides of alkali metals. In the alkali metal compound, an alkali metal salt of an organic acid or an alkali metal salt of an inorganic acid is preferable. Among them, an alkali metal salt of an aliphatic dicarboxylic acid (particularly, an alkali metal salt of oxalic acid) and a monoester of an aliphatic dicarboxylic acid are preferable. Alkali metal salts (especially alkali metal salts of oxalic acid monoester) and alkali metal carbonates are more preferable. Also, as the alkali metal,
Potassium is most preferred.

Examples of the alkali metal salts of organic acids include alkali metal salts of aliphatic monocarboxylic acids having 1 to 10 carbon atoms such as sodium acetate, potassium acetate, rubidium acetate, cesium acetate, sodium propionate and potassium propionate. Or sodium oxalate, potassium oxalate,
Rubidium oxalate, cesium oxalate, etc.
Alkali metal salts of aliphatic dicarboxylic acid monoesters having 2 to 10 carbon atoms, such as an alkali metal salt of an aliphatic dicarboxylic acid of 10 or methyl sodium oxalate, methyl potassium oxalate, methyl rubidium oxalate, and methyl cesium oxalate; , Sodium benzoate, potassium benzoate,
7 to 7 carbon atoms such as rubidium benzoate and cesium benzoate
And 12 alkali metal salts of aromatic carboxylic acids.

Examples of the alkali metal salts of inorganic acids include alkali metal salts of carbonic acid such as sodium carbonate, sodium potassium carbonate, potassium carbonate, rubidium carbonate and cesium carbonate, potassium chloride, rubidium chloride, cesium chloride and potassium bromide. Alkali metal salts of hydrohalic acids such as potassium, potassium iodide, alkali metal salts of nitric acid such as potassium nitrate, rubidium nitrate and cesium nitrate; alkali metal salts of phosphoric acid such as potassium phosphate, rubidium phosphate and cesium phosphate And the like. Examples of the alkali metal hydroxide include potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

As the above-mentioned organic phosphonium salt, an organic phosphonium salt having at least one carbon-phosphorus bond is preferable, and an organic phosphonium salt represented by the following formula can be preferably mentioned.

[0035]

Embedded image (In the formula, R ¹ , R ² , R ³ , and R ⁴ represent an alkyl group, an aryl group, an aralkyl group having 7 to 22 carbon atoms, a heterocyclic group, or an aryloxy group. And X represents an atom or an atomic group capable of forming a counter ion.)

Examples of the groups represented by R ^{1 to} R ⁴ include, for example, an alkyl group having 1 to 16 carbon atoms (methyl, ethyl, n-propyl, i-propyl, n-butyl,
an i-butyl group, an n-pentyl group, etc., an aryl group having 6 to 16 carbon atoms (phenyl group, methylphenyl group, ethylphenyl group, methoxyphenyl group, ethoxyphenyl group,
Chlorophenyl group, fluorophenyl group, naphthyl group,
A methylnaphthyl group, a methoxynaphthyl group, a chloronaphthyl group, etc., an aralkyl group having 7 to 22 carbon atoms (benzyl group, phenethyl group, 4-methylbenzyl group, 4-methoxybenzyl group, p-methylphenethyl group, etc.), carbon Number 4
To 16 heterocyclic groups (thienyl group, furyl group, etc.) and aryloxy groups having 6 to 16 carbon atoms (phenoxy group, naphthoxy group, etc.).

The above aryl group, aralkyl group, heterocyclic group and aryloxy group each have a substituent of 1 to 16 carbon atoms as a substituent directly bonding to the carbon forming the aromatic or heterocyclic ring. And at least one substituent selected from an alkoxy group having 1 to 16 carbon atoms, a nitro group, and a halogen atom (such as a fluorine atom, a chlorine atom, and a bromine atom).

The organic phosphonium salts include R ^{1 to} R ⁴
Are all aryl groups (tetraarylphosphonium salts), but one to three of them may be aryl groups, and the rest may be other groups. For example, a phosphonium salt in which all of R ^{1 to} R ⁴ are aryl groups and the counter ion X ⁻ is a halogen ion, hydrogen dihalide ion, carboxylate, fluoroborate ion, aryloxy ion, or thiolate ion, etc. Preferably, R ^{1 to} R ⁴ are 1 to 3;
In particular, two to three are aryl groups, the rest being other groups, and the counter ion X ⁻ is a halogen ion, a hydrogendihalide ion, a carboxylate, a fluoroborate ion, an aryloxide ion, or a thiolate ion. It may be something.

Examples of the phosphonium salt in which all of R ^{1 to} R ⁴ are an aryl group (tetraaryl phosphonium salt) include, for example, tetraphenylphosphonium chloride,
Tetraphenylphosphonium bromide, 4-chlorophenyltriphenylphosphonium chloride, 4-chlorophenyltriphenylphosphonium bromide,
Examples thereof include tetraarylphosphonium halides such as ethoxyphenyltriphenylphosphonium chloride, 4-ethoxyphenyltriphenylphosphonium bromide, 4-methylphenyltriphenylphosphonium chloride, and 4-methylphenyltriphenylphosphonium bromide.

Further, tetraarylphosphonium hydrogendihalides such as tetraphenylphosphonium hydrogendichloride and tetraphenylphosphonium hydrogendibromide are also included. Others
For example, tetraphenylphosphonium acetate, tetraarylphosphonium carboxylate such as tetraphenylphosphonium benzoate, tetraarylphosphonium fluoroborate such as tetraphenylphosphonium fluoroborate, tetraarylphosphonium aryloxide such as tetraphenylphosphonium phenoxide, and tetraphenylphosphonium Examples include tetraarylphosphonium thiolates such as 2-thionaphthoxide.

Examples of the organic phosphonium salt in which three of R ^{1 to} R ⁴ are an aryl group and the rest are other groups include, for example, methyltriphenylphosphonium chloride, methyltriphenylphosphonium acetate, methyltriphenylphosphonium fluoroborate, Benzyltriphenylphosphonium chloride, 2-thiophenetriphenylphosphonium chloride, phenoxytriphenylphosphonium chloride and the like can be mentioned.

As the above-mentioned organic ammonium salt, an organic ammonium salt represented by the following formula can be preferably mentioned.

[0043]

Embedded image (Wherein, R ⁵ , R ⁶ , R ⁷ , and R ⁸ represent an alkyl group, an aryl group, an aralkyl group, or a heterocyclic group, and may be the same or different. In addition, Y is a counter ion. Represents an atom or an atomic group capable of forming

Examples of the groups represented by R ^{5 to} R ⁸ include the same groups as R ^{1 to} R ⁴ in the organic phosphonium salts. Further, the counter ion Y ⁻ is the same as the counter ion X ⁻ in the organic phosphonium salt. The organic ammonium salts, which all of R ⁵ to R ⁸ is an alkyl group (tetraalkylammonium salts) are preferred, a 1-3 that is an alkyl group, those remaining are other groups There may be. For example, an ammonium salt in which all of R ^{5 to} R ⁸ are alkyl groups and the counter ion X ⁻ is a halogen ion or a carboxylate ion is preferable.

Examples of the organic ammonium salt include tetraalkylammonium halides such as tetramethylammonium chloride, tetramethylammonium bromide and tetramethylammonium iodide, and tetraalkylammonium carboxylate such as tetramethylammonium acetate and tetramethylammonium benzoate. And the like.

When the CO removal reaction is performed in the gas phase, the CO removal
The reaction is carried out, for example, by adding a dialkyl oxalate (and, if necessary, an inert gas such as nitrogen gas or a lower alcohol) to a reactor filled with a CO removal catalyst (preferably an alkali metal compound). The solvent is preferably supplied in a continuous manner by supplying a source gas containing the solvent and heating the dialkyl oxalate in a gas phase. At this time,
According to the above reaction formula, dialkyl carbonate is generated from dialkyl oxalate and carbon monoxide is generated. The dialkyl oxalate is supplied to the reactor by vaporizing a solid state, a molten state, or a solution state (which may be dissolved in a solvent) with a vaporizer or a vaporization layer.

In the gas phase CO removal reaction, the reaction temperature is 17
0-450 ° C, more preferably 200-400 ° C, especially 200-
Preferably it is 300 ° C. The reaction pressure is not particularly limited as long as the reaction can be performed in a gas phase.
Hg to 10 kg / cm ² G may be used.
If the carbon monoxide produced in step considering that supplied to the first step, from atmospheric pressure 10 kg / cm ² G, more is from atmospheric pressure 5 kg / cm ² G, particularly 2~5kg / cm ² G Is preferred. The source gas is 100 to 5
It is preferably fed to the reactor at a space velocity of 000 hr ^-1 , more preferably 400 to 3000 hr ^-1 .

In the gas phase de-CO reaction, the alkali metal compound can be used as it is in the form of powder, granules, crushed particles, beads or molded products, but if necessary, activated carbon, silica, alumina, silica-alumina, etc. The carrier of
Preferably 0.01 to 80% by weight as an alkali metal,
More preferably, it is preferable to use 0.1 to 50% by weight of the carrier. The carrier is, for example, 20 to 100 μmφ
Powder, granules of 4 to 200 mesh, crushed shape, beads, or a molded product having a length of about 0.5 to 10 mm, and a BET specific surface area of 0.1 to 3000 m ² /
It is preferably about g. The method of supporting the alkali metal compound on the carrier is not particularly limited, and for example, a usual catalyst preparation method such as an impregnation method and an evaporation to dryness method can be adopted.

The condensate obtained by condensing the reaction gas derived from the reactor in the gas-phase de-CO reaction contains unreacted dialkyl oxalate and the like. Dialkyl carbonate can be easily recovered from the condensate by a general method of distillation using a multi-stage distillation column.

The CO removal reaction can be carried out in the liquid phase in the presence of a CO removal catalyst. When the de-CO reaction is performed in the liquid phase,
For the CO removal reaction, for example, a dialkyl oxalate and a CO removal catalyst (preferably a compound of an alkali metal other than lithium and sodium, an organic phosphonium salt, or an organic ammonium salt) are placed in a reactor, and the dialkyl oxalate is heated in a liquid phase. By doing so, it is performed in a batch type or a continuous type. At this time, according to the above reaction formula, dialkyl carbonate is generated from dialkyl oxalate and carbon monoxide is generated.

In the liquid phase de-CO reaction, the reaction temperature is 10
0-450 ° C, furthermore 140-350 ° C, especially 160-
Preferably it is 300 ° C. The reaction pressure is preferably increased when the reaction temperature exceeds the boiling point of dialkyl oxalate, but is not particularly limited. The reaction pressure may be, for example, in the range of 10 mmHg to 10 kg / cm ² G, and carbon monoxide generated in the second step is converted to the first pressure.
Considering supply to the process, from normal pressure to 10kg /
cm ² G, and further from normal pressure to 5 kg / cm ² G,
It is preferably 5 kg / cm ² G.

In the liquid phase deCO reaction, the CO removal catalyst may be used alone or as a mixture of two or more kinds, and may be uniformly dissolved and / or suspended in the reaction solution. .
The amount of the CO-removing catalyst used in the second step is 0.001 to 50 mol%, and more preferably 0.01 to 50 mol% based on the dialkyl oxalate.
It is preferably about 20 mol%. A special solvent is not required for the reaction in the liquid phase, but an aprotic solvent such as diphenyl ether, sulfolane, N-methylpyrrolidone, dimethylimidazolidone and the like may be used as appropriate.

In the liquid phase deCO reaction in the second step, unreacted dialkyl oxalate and CO
Since a catalyst is contained, to recover dialkyl carbonate from the reaction solution, the catalyst is separated and recovered by an evaporator such as an evaporator or a thin film evaporator, and then the evaporation fraction is subjected to a certain number of theoretical plates. A commonly used method of distilling using a distillation apparatus such as a packed column or a tray column is preferably used. Further, the reaction solution is distilled by a distillation apparatus such as the above-mentioned packed tower or tray column to extract dialkyl carbonate from the top of the column, and to remove unreacted dialkyl oxalate or de-C
A method of extracting a can solution containing an O catalyst is also used. The withdrawn can solution is circulated and supplied to the reactor for the CO removal reaction. Thus, high purity dialkyl carbonate can be obtained by recovering dialkyl carbonate from the reaction solution.

As a reaction apparatus (reactor) in the second step, a dialkyl oxalate is subjected to a de-CO reaction (if necessary in the presence of a de-CO catalyst) to produce a dialkyl carbonate together with carbon monoxide. Any type of reactor that can be used can be used. As the reactor, when the CO removal reaction is performed in the gas phase, a single-tube or multi-tube heat exchange tube reactor can be used, and when the CO removal reaction is performed in the liquid phase. A single- or multi-tank complete mixing reactor (stirred tank), a tower reactor, or the like can be used. The material of the reactor is not particularly limited as long as it has sufficient heat resistance in the CO removal reaction. For example, glass, stainless steel (SU
S), an aluminum alloy, a nickel alloy or the like is appropriately used.

In the present invention, when the first step is performed in a continuous process, the carbon monoxide produced in the second step is supplied to the first step for the production of dialkyl oxalate and is reused as a raw material. Is preferred. This carbon monoxide is
Since it is almost 100% pure, it can be supplied to the first step without any particular purification. However, if impurities are contained depending on the type of catalyst and reaction conditions in the third step, a simple method such as an absorption tower or a scrubber can be used. It is preferable to supply to the first step after passing through a suitable purification device. At this time, when the reaction pressure in the third step is lower than that in the first step, the pressure is increased by a compressor and supplied. In the case where the first step is performed in a gas phase continuous process, the carbon monoxide generated in the second step is passed through a simple purification device if necessary, and then the nitrite regenerating step (regeneration tower) is performed. ), And can be similarly reused as a raw material in the first step. That is, while recovering the nitric oxide generated in the first step, recovering the carbon monoxide generated in the second step, and supplying the carbon monoxide, the nitric oxide is converted into molecular oxygen and a lower alcohol. To produce alkyl nitrite, and the alkyl nitrite can be supplied to the first step together with the carbon monoxide.

[0056]

Next, the present invention will be described specifically with reference to examples. The analysis was performed by gas chromatography. The space-time yield and selectivity of dimethyl oxalate and the space-time yield and selectivity of dimethyl carbonate were determined by the following equations, respectively.

[0057]

(Equation 1) (L indicates liter. The same applies hereinafter.)

[0058]

(Equation 2) (A indicates dimethyl oxalate, b indicates dimethyl carbonate, and c indicates the number of moles of carbon dioxide produced.)

[0059]

(Equation 3)

[0060]

(Equation 4)

Example 1 [Production of dimethyl oxalate 1] In a stainless steel reactor consisting of a tube having an inner diameter of 27.1 mm and a height of 500 mm,
A solid catalyst in which 0.5% by weight of palladium (metal) was supported on pelletized α-alumina (diameter 5 mm, length 3 mm) was filled. Next, the temperature of the catalyst layer is maintained at 103 to 115 ° C. by passing hot water through the shell side of the reactor, and then the raw material gas previously heated to 90 ° C. by a heat exchanger by a diaphragm gas circulation pump from the top of the catalyst layer. (Composition: carbon monoxide 22.0% by volume, methyl nitrite 10.0% by volume, nitric oxide 4.0% by volume, methanol 5.2% by volume, carbon dioxide 1.7% by volume, nitrogen 57.1% by volume) %), 1.1
Dimethyl oxalate was produced by supplying 5 Nm ³ / hr at 2 kg / cm ² G.

The gas that has passed through the catalyst layer is supplied to a gas-liquid contact absorption tower filled with Raschig rings (inner diameter 43 mm, height 1000
mm), and was brought into countercurrent contact with 0.42 L / hr of methanol introduced from the top at about 35 ° C (top temperature 30 ° C, bottom temperature 40 ° C). And 0.3 kg / hr of condensate (composition: dimethyl oxalate 42.6% by weight, dimethyl carbonate 1.8% by weight, methyl formate 0.03% by weight, methanol 42.6% by weight) was obtained from the bottom of the column. From the top, a non-condensable gas (composition: carbon monoxide 16.2% by volume,
4.9% by volume of methyl nitrite, 8.1% by volume of nitric oxide,
15.9% by volume of methanol, 1.8% by volume of carbon dioxide,
(Nitrogen 53.1% by volume) 1.23 Nm ³ / hr was obtained. The space-time yield of dimethyl oxalate was 450 g / L-hr, and the selectivity was 96.3%.

This non-condensable gas contains 13.8 NL / hr of oxygen.
And a gas mixture of 0.5 NL / hr of carbon monoxide and a gas-liquid contact type regenerator (inner diameter 83 mm, height 1000 mm) was introduced to the bottom of the column, and methanol 0.3 was introduced from the top of the column.
3 L / hr was brought into contact with the column at a top temperature of 30 ° C. and a bottom temperature of 40 ° C. to regenerate nitric oxide in the gas into methyl nitrite. Regeneration gas (composition: carbon monoxide 18.2 vol%, methyl nitrite 10.4 vol%, nitric oxide 4.2 vol%, methanol 5.4 vol%, carbon dioxide 2.0% by volume, 53.0% by volume of nitrogen) 1.1Nm ³ /
hr is led to the circulation pump and pressurized to 2.1 kg / cm ^2, and 49 NL / hr of carbon monoxide (2.1 kg / cm 2)
After supplying ² ), the mixture was supplied to the reactor. as a result,
The reaction results were stable for a long time (200 hours or more).

It is to be noted that 5. derived from the bottom of the regeneration tower.
0.48 L / hr of methanol containing 7% by weight of water
Was used as a methanol source in the regeneration tower after removing water by distillation. On the other hand, the condensate was subjected to batch distillation for 50 hours in a distillation column having an inner diameter of 150 mm and a height of 7500 mm (capacity at the bottom portion of 100 L) (column temperature 140 ° C., pressure 350 mmHg). And a purity of 9
5.8 kg of 9.9% by weight of dimer oxalate was obtained.

[Production of dimethyl carbonate] Using the dimethyl oxalate obtained above, dimethyl carbonate was produced as follows. In a quartz reactor having an inner diameter of 18 mm and a length of 400 mm, a solid catalyst comprising 10% by weight of potassium oxalate supported on pelleted activated carbon (diameter: 2 mm, length: 5 mm) 5 m
l. Heating the temperature of the catalyst layer to 210 ° C.,
After heating and controlling the temperature of the vaporized layer above the catalyst layer to 180 ° C., 97.4 mmol / hr of dimethyl oxalate previously heated and melted from the upper part of the reactor (LHSV:
2.3 g / ml-hr) and reacted at 210 ° C. under normal pressure. When the liquid collected in the trap was analyzed between 2 hours and 24 hours after the start of the reaction, the space-time yield of dimethyl carbonate was 1702 g / L-hr and the selectivity was 97.
1%. From this collected liquid, the purity was 99.
5% of dimethyl carbonate was obtained. On the other hand, the gas extracted from the reactor (about 2.4 L / hr) contains 95.000 carbon monoxide.
0% was contained.

[Production of dimethyl oxalate 2] As carbon monoxide to be supplied to the regeneration gas of production 1 of dimethyl oxalate, carbon monoxide generated in the production of dimethyl carbonate was used.
5 NL / hr 2.1 kg / c with diaphragm compressor
The pressure was raised to m ² G, and carbon monoxide was 24 NL / hr (2.
1 kg / cm ² G)
Dimethyl oxalate was produced in the same manner as in Production 1 of dimethyl oxalate. The results were the same as in Production 1 of dimethyl oxalate.

Example 2 [Production of dimethyl oxalate 3] Dimethyl oxalate was produced in the same manner as in Production 1 of dimethyl oxalate of Example 1.

[Production of dimethyl carbonate] Dimethyl carbonate was produced in the same manner as in Example 1 except that the potassium oxalate was replaced with methyl potassium oxalate using the dimethyl oxalate obtained above. However, methyl potassium oxalate can be obtained by a known method [J. Am. Chem. SOoc. , 71,2
532 (1949)].
The carrier and the loading amount were the same as in Example 1. The results were the same as in Example 1.

[Production of dimethyl oxalate 4] As carbon monoxide to be supplied to the regeneration gas of production 3 of dimethyl oxalate, the carbon monoxide generated in the production of dimethyl carbonate and further carbon monoxide were used. Dimethyl oxalate was produced in the same manner as in the production of dimethyl oxalate 3 except that the regeneration gas was supplied in the same manner as in the production 2 of dimethyl oxalate. The result was similar to that of Production 3 of dimethyl oxalate.

[0070]

Industrial Applicability According to the present invention, carbon monoxide and alkyl nitrite are contact-reacted to produce dialkyl oxalate and nitric oxide, and the dialkyl oxalate is subjected to CO removal reaction.
By the method of producing dialkyl carbonate and carbon monoxide,
An entirely novel method for producing dialkyl carbonate, which can solve the problems in the method for producing dialkyl carbonate by a known method, can be provided. That is, according to the present invention, in a method for producing a dialkyl carbonate by subjecting a dialkyl oxalate to a decarbonyl reaction, it is possible to produce the dialkyl carbonate in a high yield and a high selectivity and to remove the C from the dialkyl oxalate.
Since the carbon monoxide removed to the outside of the reaction system by the O reaction can be recovered and reused for the reaction for producing a dialkyl oxalate, an industrially suitable production process including the production of raw materials can be performed. Can be provided. Further, according to the present invention, it is possible to provide an industrially suitable process for producing dialkyl carbonate including production of a raw material by a gas phase method in which a product and a catalyst can be easily separated and recovered. The present invention
This is an industrially superior method for producing dialkyl carbonate.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an example of a manufacturing process of the present invention.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07C 67/36 C07C 67/36 69/36 69/36 (72) Inventor Toshio Kurato 5 Ube Kogyo stock at 1978 Kogushi, Oaza, Ube City, Yamaguchi Prefecture (72) Inventor Toshihiro Shimakawa 5 Ube, Ube City, Yamaguchi Prefecture

Claims (10)

[Claims] 1. In a first step, carbon monoxide and an alkyl nitrite are contact-reacted in a gas phase to generate dialkyl oxalate and nitric oxide. In a second step, the dialkyl oxalate is subjected to a CO removal reaction. Producing a dialkyl carbonate and carbon monoxide. 2. The process for producing dialkyl carbonate according to claim 1, wherein the catalytic reaction between carbon monoxide and alkyl nitrite is carried out in the presence of a platinum group metal catalyst. 3. A process for recovering nitric oxide produced in the first step, reacting the nitric oxide with molecular oxygen and a lower alcohol to produce alkyl nitrite, and supplying the alkyl nitrite to the first step. The method for producing a dialkyl carbonate according to claim 1, wherein 4. The method for producing a dialkyl carbonate according to claim 1, wherein the carbon monoxide produced in the second step is recovered and supplied to the first step. 5. A method for recovering nitrogen monoxide generated in the first step and recovering carbon monoxide generated in the second step,
While supplying the carbon monoxide, the nitric oxide is reacted with molecular oxygen and a lower alcohol to generate an alkyl nitrite, and the alkyl nitrite is supplied to the first step together with the carbon monoxide. The method for producing a dialkyl carbonate according to claim 1, wherein 6. The method for producing a dialkyl carbonate according to claim 1, wherein the alkyl nitrite is methyl nitrite. 7. The method of removing CO from a dialkyl oxalate by removing C
The method for producing a dialkyl carbonate according to claim 1, wherein the method is carried out in the presence of an O catalyst. 8. The method for producing a dialkyl carbonate according to claim 7, wherein the CO removal catalyst is an alkali metal compound. 9. The method for producing a dialkyl carbonate according to claim 8, wherein the alkali metal compound is an alkali metal salt of an organic acid, an alkali metal salt of an inorganic acid, or a hydroxide of an alkali metal. 10. The method for producing a dialkyl carbonate according to claim 7, wherein the catalyst for removing CO is an organic phosphonium salt or an organic ammonium salt.