JP3912963B2 - Process for producing dialkyl carbonate - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for producing dialkyl carbonate. More specifically, the present invention relates to a method for efficiently producing dialkyl carbonate from CO, O ₂ and alcohol.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
In recent years, aromatic polycarbonates have been widely used in many fields as engineering plastics having excellent mechanical properties such as impact resistance, heat resistance, and transparency.
As a method for producing this aromatic polycarbonate, a so-called phosgene method in which an aromatic dihydroxy compound such as bisphenol and phosgene are reacted by an interfacial polycondensation method has been industrialized. However, the industrially practiced phosgene method requires the use of extremely toxic phosgene, the problem of treating sodium chloride by-produced in large quantities, and the hygienic problem of methylene chloride, which is usually used as a reaction solvent. Many problems have been pointed out, such as environmental problems.
[0003]
As a method for producing an aromatic polycarbonate other than the phosgene method, a method (melting method) in which an aromatic dihydroxy compound and a carbonic acid diester are transesterified using an alkali metal compound such as sodium hydroxide as a catalyst is known. This method has an advantage that an aromatic polycarbonate can be produced at a low cost, and since it does not use toxic substances such as phosgene and methylene chloride, it is preferable in terms of environmental hygiene and has attracted particular attention in recent years.
[0004]
When the polycarbonate is produced by such a melting method, diaryl carbonate such as diphenyl carbonate is used as the carbonic acid diester. This diaryl carbonate is produced by a transesterification reaction between a dialkyl carbonate and a hydroxyl group-containing aromatic hydrocarbon such as phenol. The dialkyl carbonate used as a raw material for the diaryl carbonate is obtained from a carbon monoxide, oxygen and an alcohol. Manufactured using a catalyst comprising cuprous halide such as monocopper.
[0005]
For example, when methanol is used as the alcohol, the following reaction:
2CH ₃ OH + CO + 1 / 2O ₂ → (CH ₃ O) ₂ CO + H ₂ O
As a result, dimethyl carbonate is produced.
At this time, cuprous chloride used as a catalyst is a primary reaction,
2CuCl + 2CH ₃ OH + 1 / 2O ₂ → 2Cu (OCH ₃ ) Cl + H ₂ O
To form cupric methoxychloride,
As a secondary reaction,
2Cu (OCH ₃ ) Cl + CO → (CH ₃ O) ₂ CO + 2CuCl
It is estimated that it is regenerated by the reaction of
[0006]
By the way, in order to improve the catalytic activity of cuprous halide used as such a catalyst, it has been disclosed that hydrohalic acid is added to the reaction system (see JP-A-5-194327). ).
However, in the method using cuprous halide as a catalyst as described above, the yield of dialkyl carbonate obtained is not always sufficient because the conversion rate of the cupric alkoxy chloride is low, and the use of the cupric halide is not sufficient. The reaction tank and piping may be clogged with the catalyst which is carried out, and there existed a problem that manufacturing efficiency was inadequate.
[0007]
In addition, there is a major problem that requires countermeasures for equipment against corrosion of the equipment by halogen.
Under such circumstances, the present inventors have intensively studied a method capable of efficiently producing dialkyl carbonate, and as a catalyst, (i) a copper compound containing no halogen atom, and (ii) the copper compound ( by using a catalyst comprising an alkoxide compound that can react with i) to form a copper alkoxide,
While maintaining high catalytic activity, the reaction proceeds and the catalyst prevents clogging of the reaction tank and piping, etc., so that carbonic acid diesters can be obtained in high yield. The present inventors have found that there is no need for handling and have completed the present invention.
[0008]
OBJECT OF THE INVENTION
The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a method for efficiently producing dialkyl carbonate from CO, O ₂ and alcohol.
[0009]
SUMMARY OF THE INVENTION
The method for producing a dialkyl carbonate according to the present invention comprises:
When producing dialkyl carbonate using carbon monoxide, oxygen and alcohol as starting materials,
(i) a copper compound containing no halogen atom;
(ii) A catalyst comprising an alkoxide compound capable of reacting with the copper compound (i) to form a copper alkoxide is used.
[0010]
The copper compound containing no (i) halogen atom includes cupric hydroxide (Cu (OH) ₂ ), cupric nitrate (Cu (NO ₃ ) ₂ ), cupric acetate (Cu (OCOCH ₃ )). ₂ ), at least one compound selected from the group consisting of cupric sulfate (CuSO ₄ ), basic copper carbonate (CuCO ₃ · Cu (OH) · H ₂ O), and cupric sulfide (CuS) is preferred. .
As the alkoxide compound (ii) capable of producing the copper alkoxide,
At least one compound selected from the group consisting of an alkali metal alkoxide, an alkaline earth metal alkoxide, a quaternary ammonium alkoxide represented by the following formula (1), and a quaternary phosphonium alkoxide represented by the following formula (2): preferable.
[0011]
R ¹ R ² R ³ R ⁴ NOR ⁵ ...... (1)
R ¹ R ² R ³ R ⁴ POR ⁵ ...... (2)
(R ^{1 to} R ⁴ may be the same as or different from each other, and each represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ represents a hydrocarbon group having 1 to 20 carbon atoms.)
The alkoxide compound (ii) capable of producing the copper alkoxide is preferably used in an amount of 0.05 to 2.0 mol with respect to the copper compound (i) not containing a halogen atom.
[0012]
Methanol is suitable as the alcohol used in the method for producing dialkyl carbonate according to the present invention.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the manufacturing method of the dialkyl carbonate based on this invention is demonstrated concretely.
First, the starting materials and catalyst used in the method for producing dialkyl carbonate according to the present invention will be described.
[Starting materials and catalysts]
In the present invention, carbon monoxide (CO), oxygen (O ₂ ) and alcohol are used as starting materials.
[0014]
The alcohol used as the starting material is not particularly limited, and for example, methanol, ethanol, propanol, butanol, isopropanol, isobutanol, hexanol and the like are used. Of these, methanol is preferably used.
In the present invention, (i) a copper compound containing no halogen atom and (ii) an alkoxide compound capable of reacting with the copper compound (i) to form a copper alkoxide are used as the catalyst.
[0015]
The copper compound containing no (i) halogen atom includes cupric hydroxide (Cu (OH) ₂ ), cupric nitrate (Cu (NO ₃ ) ₂ ), cupric acetate (Cu (OCOCH ₃ )). ₂ ), cupric oxalate, cupric sulfide, cupric phosphate, cupric phthalate, cupric formate, cupric sulfate (CuSO ₄ ), basic copper carbonate (CuCO ₃ Cu ( OH) ・ H ₂ O), cuprous hydroxide (CuOH), cuprous nitrate (CuNO ₃ ), cuprous acetate (CuOCOCH ₃ ), cuprous oxalate, cuprous sulfide, cuprous phosphate Inorganic copper compounds such as copper, cuprous phthalate, cuprous formate, and cuprous sulfate (Cu ₂ SO ₄ ) are used.
[0016]
Of these, compounds containing divalent copper are preferred, and cupric hydroxide (Cu (OH) ₂ ), cupric nitrate (Cu (NO ₃ ) ₂ ), cupric acetate (Cu (OCOCH) ₃ ) ₂ ), at least one compound selected from the group consisting of cupric sulfate (CuSO ₄ ), basic copper carbonate (CuCO ₃ · Cu (OH) · H ₂ O), cupric sulfide (CuS) Is preferred.
Two or more kinds of these copper compounds not containing a halogen atom may be used in combination.
[0017]
(Ii) Examples of the alkoxide compound that can react with the copper compound (i) to form a copper alkoxide include alkali metal alkoxides, alkaline earth metal alkoxides, quaternary ammonium alkoxides represented by the following formula (1), And at least one compound selected from the group consisting of quaternary phosphonium alkoxides represented by the following formula (2) is preferably used.
[0018]
R ¹ R ² R ³ R ⁴ NOR ⁵ ...... (1)
R ¹ R ² R ³ R ⁴ POR ⁵ ...... (2)
(R ^{1 to} R ⁴ may be the same as or different from each other, and each represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ represents a hydrocarbon group having 1 to 20 carbon atoms.)
Specific examples of the alkali metal alkoxide include sodium methoxide, lithium methoxide, potassium methoxide, rubidium methoxide, cesium methoxide, sodium ethoxide, lithium ethoxide, potassium ethoxide, rubidium ethoxide, cesium ethoxide, Sodium propoxide, lithium propoxide, potassium propoxide, rubidium propoxide, cesium propoxide, sodium butoxide, lithium butoxide, potassium butoxide, rubidium butmethoxide, cesium butoxide, sodium pentoxide, lithium pentoxide, potassium pentoxide, rubidium Pentoxide, cesium pentoxide, sodium hexoxide, lithium hexoxide, potassium hexoxide, rubidium Toxide, cesium hexoxide, sodium heptoxide, lithium heptoxide, potassium heptoxide, rubidium heptoxide, cesium heptoxide, sodium octoxide, lithium octoxide, potassium octoxide, rubidium octoxide, cesium octet Examples include oxide, sodium phenoxide, lithium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide and the like.
[0019]
Specific examples of the alkaline earth metal alkoxide include beryllium, magnesium, calcium, strontium, barium methoxide, ethoxide, propoxide, butoxide, pentoxide, hexoxide, heptoxide, octoxide, phenoxide, and other mono and dialkoxide compounds. Can be mentioned.
Specific examples of quaternary ammonium alkoxides include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetraheptylammonium methoxide, tetraoctylammonium, tetraphenylammonium methoxide, ethoxide, and propoxy. And alkoxide compounds such as butoxide, pentoxide, hexoxide, heptoxide, octoxide and phenoxide.
[0020]
Specific examples of the quaternary phosphonium alkoxide include tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, tetrapentylphosphonium, tetraheptylphosphonium methoxide, tetraoctylphosphonium, tetraphenylphosphonium methoxide, ethoxide, propoxy. And alkoxide compounds such as butoxide, pentoxide, hexoxide, heptoxide, octoxide and phenoxide.
[0021]
Two or more of these alkoxide compounds may be used in combination.
The (i) copper compound containing no halogen atom and (ii) an alkoxide compound capable of reacting with the copper compound (i) to produce a copper alkoxide react to produce a copper alkoxide containing no halogen atom. To do.
As described above, when (i) a copper compound not containing a halogen atom and (ii) an alkoxide compound capable of reacting with the copper compound to form a copper alkoxide are used in combination as a catalyst, carbon monoxide, oxygen and alcohol are used as starting materials. Since the catalytic activity in producing dialkyl carbonate as a raw material is high and stable during the reaction, the activity as a catalyst can be maintained for a long time.
[0022]
[Production of dialkyl carbonate]
In the present invention, the above catalyst is used when producing dialkyl carbonate using carbon monoxide, oxygen and alcohol as starting materials.
Specifically, first, a catalyst comprising: (i) a copper compound not containing a halogen atom; and (ii) an alkoxide compound that can react with the copper compound (i) to form a copper alkoxide, is used as a starting alcohol. The raw material alcohol containing the catalyst component is prepared by adding to and reacting.
[0023]
Note that (i) the copper compound containing no halogen atom is added in an amount of 0.001 to 1.0 mol, preferably 0.005 to 0.2 mol, per mol of alcohol.
(i) the copper compound and (ii) an alkoxide compound capable of reacting with the copper compound to form a copper alkoxide is: (i) a copper atom in a copper compound not containing a halogen atom; The mole of the alkoxy group in the alkoxide compound capable of reacting with the compound (i) to form a copper alkoxide is such that the (alkoxy group / Cu) is 0.05 to 2.0 moles, preferably 0.1 to 1.2 moles. It is preferable to add in the amount of the range.
[0024]
Next, carbon monoxide and oxygen gases are introduced under pressure into the alcohol containing the catalyst component. Carbon monoxide and oxygen may be supplied individually to the alcohol containing the catalyst component, or may be supplied after mixing in advance. At this time, a gas that does not generate a reaction product in the reaction system, specifically, an inert gas such as hydrogen, nitrogen, carbon dioxide, methane, or argon may be present.
[0025]
It is desirable that the amount of carbon monoxide introduced is greater than the stoichiometric number. For this reason, it is desirable that the molar ratio of carbon monoxide and oxygen (carbon monoxide / oxygen) to be introduced is in the range of 3/1 to 100/1, preferably 20/1 to 100/1.
The reaction is usually carried out at a temperature of 50 to 200 ° C., preferably 100 to 150 ° C., and at a pressure of atmospheric pressure to 150 atmospheres, preferably 10 to 100 atmospheres.
[0026]
By the reaction as described above, dialkyl carbonate is produced.
According to such this invention, the yield of the dialkyl carbonate obtained can be improved.
The produced dialkyl carbonate is recovered using a known separation method such as distillation, filtration, decanting, centrifugation, demixing, and osmotic membrane separation. These separation methods may be used in combination of two or more.
[0027]
The catalyst, unreacted alcohol and the like contained in the reaction liquid from which the produced dialkyl carbonate is recovered can be recovered and reused.
Such a reaction can be carried out using either a batch type reaction vessel or a continuous type reaction vessel. It is desirable to use a pressure vessel such as an autoclave.
[0028]
When using a continuous reaction vessel, alcohol, carbon monoxide and oxygen are reacted with (i) a copper compound containing no halogen atom and (ii) the copper compound (i) under the conditions described above. Then, an alcohol containing an alkoxide compound capable of producing a copper alkoxide and a solution are supplied and reacted. Subsequently, the produced reaction solution containing dialkyl carbonate, water and alcohol and unreacted carbon monoxide and water vapor are taken out, and further, dialkyl carbonate and water are removed from the reaction solution, and other components are recycled to the reaction system.
[0029]
The unrecovered dialkyl carbonate may be contained in the reaction solution to which the alcohol, carbon monoxide and oxygen are supplied. The reaction solution supplied with alcohol, carbon monoxide and oxygen has an alcohol concentration of 30 to 80% by weight, preferably 35 to 80% by weight, and a water concentration of 1 to 10% by weight and 2 to 7% by weight. It is desirable. In the method for producing a dialkyl carbonate according to the present invention as described above, (i) a copper compound not containing a halogen atom and (ii) an alkoxide compound capable of reacting with the copper compound (i) to form a copper alkoxide, Used as a catalyst. Therefore, in the present invention, dialkyl carbonate can be efficiently produced while maintaining high catalytic activity.
[0030]
【The invention's effect】
According to the method for producing a dialkyl carbonate according to the present invention, since a specific catalyst is used in combination, the dialkyl carbonate is maintained in a state in which high catalyst activity is maintained without clogging the piping and the reaction tank with the catalyst. Can be manufactured efficiently. Moreover, when polycondensation of a polycarbonate is performed using a diaryl carbonate produced using a dialkyl carbonate thus obtained as a raw material, a polycarbonate having an improved hue can be obtained. It is suitably used not only for molding materials but also for building materials such as sheets, automotive headlamp lenses, optical lenses such as eyeglasses, optical recording materials, and the like, and particularly suitable as a molding material for optical disks.
[0031]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
The physical properties shown in the examples of the present invention are measured as follows.
[0032]
[Example 1]
A 300 ml Hastelloy autoclave was charged with 47.4 g of methanol, 9.27 g of cupric acetate and 1.92 g of sodium methoxide (NaOCH ₃ / Cu (OCOCH ₃ ) ₂ molar ratio = 0.7) and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 4.16%, N ₂ = 1.52%, CO = 94.32%, CO ₂ = 0.00%) was changed to 27 At a feed rate of 0.0 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa, and reacted for 60 minutes.
[0033]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 2.9 mol%, and the amount of dimethyl carbonate produced was 1.84 g.
[0034]
Methylal was confirmed as a by-product.
[0035]
[Example 2]
In a 300 ml Hastelloy autoclave with an internal volume of 300 ml, methanol 47.0 g, cupric hydroxide (Cu (OH) ₂ ); 5.06 g, and sodium methoxide 1.36 g (NaOCH ₃ / Cu (OH) ₂ molar ratio = 0.48) was charged and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 4.54%, N ₂ = 4.38%, CO = 91.08%, CO ₂ = 0.00%) was added to 17 At a feed rate of 0.5 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0036]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 3.4 mol%, and the amount of dimethyl carbonate produced was 2.16 g.
[0037]
Methylal was confirmed as a by-product.
[0038]
[Example 3]
A 300 ml Hastelloy autoclave was charged with 48.7 g of methanol, cupric sulfide (CuS); 4.97 g, and 2.07 g of sodium methoxide (NaOCH ₃ / CuS molar ratio = 0.74) and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 5.08%, N ₂ = 2.53%, CO = 92.39%, CO ₂ = 0.00%) was added to 17 At a feed rate of 0.5 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0039]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 3.7 mol%, and the amount of dimethyl carbonate produced was 2.38 g.
[0040]
Methylal was confirmed as a by-product.
[0041]
[Example 4]
A 300 ml Hastelloy autoclave was charged with 47.7 g of methanol, 9.20 g of cupric acetate and 2.56 g of potassium methoxide (KOCH ₃ / Cu (OCOCH ₃ ) ₂ molar ratio = 0.72) and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 4.16%, N ₂ = 1.52%, CO = 94.32%, CO ₂ = 0.00%) was added to 24 At a feed rate of 1 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0042]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 2.5 mol%, and the amount of dimethyl carbonate produced was 1.61 g.
[0043]
Methylal was confirmed as a by-product.
[0044]
[Comparative Example 1]
A 300 ml Hastelloy autoclave was charged with 47.2 g of methanol and 9.23 g of cupric acetate Cu (OCOCH ₃ ) ₂ : and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 5.08%, N ₂ = 2.53%, CO = 92.39%, CO ₂ = 0.00%) was added to 25 At a feed rate of 0.0 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0045]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 0.7 mol%, and the amount of dimethyl carbonate produced was 0.47 g.
[0046]
Methylal was confirmed as a by-product.
[0047]
[Comparative Example 2]
A 300 ml Hastelloy autoclave was charged with 47.2 g of methanol and 5.11 g of cupric hydroxide Cu (OH) ₂ and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 5.08%, N ₂ = 8.44%, CO = 85.88%, CO ₂ = 0.00%) was changed to 27 At a feed rate of 0.0 ml / min, the autoclave was fed so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0048]
After the autoclave was cooled, unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 0.3 mol%, and the amount of dimethyl carbonate produced was 0.23 g.
[0049]
Methylal was confirmed as a by-product.
[0050]
[Comparative Example 3]
A 300 ml Hastelloy autoclave was charged with 47.9 g of methanol and cupric sulfide: CuS: 4.91 g and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 5.08%, N ₂ = 8.44%, CO = 85.88%, CO ₂ = 0.00%) was added to 21 The autoclave was fed at a feed rate of 0.5 ml / min so that the total pressure was 2.5 to 2.6 MPa and reacted for 60 minutes.
[0051]
After the autoclave was cooled, the unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 0.2 mol%, and the amount of dimethyl carbonate produced was 0.11 g.
[0052]
Methylal was confirmed as a by-product.
[0053]
[Comparative Example 4]
A 300 ml Hastelloy autoclave was charged with 46.7 g of methanol and 6.20 g of copper dimethoxide Cu (OCH ₃ ) ₂ and sealed.
Next, the autoclave was heated to 125 ° C., and the reaction gas (composition: O ₂ = 5.93%, N ₂ = 1.05%, CO = 93.02%, CO ₂ = 0.00%) The pressure was supplied to the autoclave so that the pressure became 2.5 to 2.6 MPa, and the reaction was performed for 30 minutes.
[0054]
After the autoclave was cooled, the unreacted gas was slowly purged, the reaction solution was taken out, and the gas composition and reaction solution composition after the reaction were quantitatively analyzed by gas chromatography.
As a result, the dimethyl carbonate conversion rate of methanol was 0.8 mol%, and the amount of dimethyl carbonate produced was 0.53 g.
[0055]
Methylal was confirmed as a by-product.

Claims (3)

When producing dialkyl carbonate using carbon monoxide, oxygen and alcohol as starting materials,
(i) at least one copper compound selected from the group consisting of cupric hydroxide (Cu (OH) ₂ ) , cupric acetate (Cu (OCOCH ₃ ) ₂ ) , cupric sulfide (CuS) ;
(ii) A process for producing a dialkyl carbonate characterized by using a catalyst satisfying the following requirement (a) and comprising an alkoxide compound capable of reacting with the copper compound (i) to form a copper alkoxide;
(A) At least one selected from the group consisting of alkali metal alkoxides, alkaline earth metal alkoxides, quaternary ammonium alkoxides represented by the following formula (1) , and quaternary phosphonium alkoxides represented by the following formula (2) A compound of
R ¹ R ² R ³ R ⁴ NOR ⁵ ...... (1)
R ¹ R ² R ³ R ⁴ POR ⁵ ...... (2)
(R ^{1 to} R ⁴ may be the same as or different from each other, and represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and R ⁵ represents a hydrocarbon group having 1 to 20 carbon atoms.) . The alkoxide compound capable of generating a copper alkoxide (ii), the copper compound with respect to (i), a dialkyl carbonate according to claim 1, characterized in that used in the range of 0.05 to 2.0 mole Manufacturing method. Method for producing a dialkyl carbonate according to any one of claims 1-2, wherein the alcohol is methanol.