JPH0825961B2 - Method for producing carbonic acid diester - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbonic acid diester, and more particularly to a method for selectively producing a carbonic acid diester from carbon monoxide and a nitrite ester.

Carbonic acid diester is a very useful compound as an organic synthetic raw material for medicines, agricultural chemicals and the like, and as an intermediate for the production of polycarbonate, urethane and the like.

[Description of the Prior Art] As a method for producing a carbonic acid diester, a method of reacting phosgene with an alcohol has been practiced for a long time, but phosgene is extremely toxic, and the reaction of phosgene with an alcohol causes hydrochloric acid. Since there is a by-product, there is a problem in the material of the device, and a manufacturing method that does not use phosgene has been desired.

From this, as a production method without using phosgene, a method of synthesizing a carbonic acid diester from alcohol and carbon monoxide has been studied and proposed in various fields (for example, JP-A-60-75447 and JP-A Sho-75447). 63-72650, Japanese Patent Publication Sho 63
-38018, WO-87 / 7601 specification, etc.). These are methods of synthesizing a carbonic acid diester by an oxygen oxidation reaction of an alcohol and carbon monoxide using copper halide, palladium halide, etc. as a catalyst. It has the disadvantages that the selectivity of carbonic acid diester is low and that it takes time to purify the carbonic acid diester due to the generation of water.

Therefore, as an improved method thereof, for example, a nitrite and carbon monoxide are used as a solid catalyst in which a platinum group metal or a compound thereof is supported on a carrier and O ₂ per carbon monoxide of 10
JP-A-60-181051 proposes a method for producing a carbonic acid diester, which comprises reacting in a gas phase in the presence of an oxidant in an amount of at least mol%.

However, in this method, in order to suppress the by-production of oxalic acid diester, an oxidizing agent such as oxygen coexists with carbon monoxide in the above proportion,
A considerable amount of oxalic acid diester is by-produced, the selectivity of carbonic acid diester is low, and the reaction rate is not sufficient. Also, the range of use of nitrite in the "mixed gas consisting of nitrite, carbon monoxide, alcohol, oxygen, etc." used in the reaction exceeds the explosion limit,
It is not always an industrially satisfactory method because of safety issues.

[Problems to be Solved by the Invention]

A conventionally known method for producing a carbonic acid diester using a nitrite is, as described above, produced because the reaction rate between carbon monoxide and a nitrite is not sufficient and the carbonic acid diester selectivity is low. The drawback is that the purification process of the carbonic acid diester becomes complicated. Further, there is a problem that the range of concentration of nitrite ester used in the reaction system exceeds the explosion limit, which is dangerous in operation.

Therefore, an object of the present invention is an industrially suitable method capable of producing a carbonic acid diester with a high selectivity and a high yield under mild reaction conditions by a gas phase method in which a reaction product is easily separated and recovered. It is to provide a method for producing a carbonic acid diester.

[Means for solving the problem]

In order to overcome the above-mentioned problems in the conventionally known production method of carbonic acid diester, the present inventors have proposed a catalyst for producing carbonic acid diester by a gas phase catalytic reaction of carbon monoxide and nitrite ester. As a result of intensive studies on the synthesis reaction of carbonic acid diester by using nitrite, it was found that the carbonic acid diester of the target product can be obtained in extremely high yield by using the above-mentioned fixed catalyst under mild reaction conditions. Heading to this invention.

That is, the present invention provides a solid catalyst in which a platinum group metal or a compound thereof and a compound of at least one metal selected from the group consisting of iron, copper, bismuth, cobalt, nickel and tin are supported on a carrier. , A method for producing a carbonic acid diester, which comprises reacting carbon monoxide and a nitrite ester in a gas phase.

[Detailed description of each requirement of the present invention]

 The method of the present invention will be described in detail below.

Examples of the nitrite used in the present invention include methyl nitrite, ethyl nitrite, n- (or i-) propyl nitrite, n- (or i-) butyl nitrite, sec-nitrite.
-Nitrite esters of lower aliphatic monohydric alcohols having 1 to 4 carbon atoms such as butyl, nitrite esters of cycloaliphatic alcohols such as cyclohexyl nitrite, and alalkyl alcohols such as benzyl nitrite and phenylethyl nitrite. Suitable examples include nitrous acid ester and the like, but especially the above-mentioned carbon number 1
Nitrite esters of 4 to 4 lower aliphatic monohydric alcohols are preferred, of which methyl nitrite and ethyl nitrite are most preferred.

The solid catalyst used in the present invention is selected from the group consisting of a platinum group metal such as palladium, platinum, iridium, ruthenium and rhodium or a compound of the metal, and iron, copper, bismuth, cobalt, nickel and tin. At least one metal compound is supported on a carrier, more preferably, the platinum group metal compound,
The carrier is loaded with a compound of at least one metal selected from the group consisting of iron, copper, bismuth, cobalt, nickel and tin.

The compound of the platinum group metal, hydrochloride of the metal,
Preferable examples include halogen compounds such as bromate, iodate, and fluorate, nitrates, sulfates, phosphates, acetates, oxalates, and benzoates.

More specifically, palladium chloride, palladium bromide,
Palladium iodide, palladium fluoride, palladium nitrate, palladium sulfate, palladium phosphate, palladium acetate, palladium oxalate, palladium benzoate, platinum chloride, iridium chloride, ruthenium chloride, ruthenium iodide, rhodium chloride, rhodium bromide, iodide Rhodium, rhodium nitrate,
Examples thereof include rhodium sulfate and rhodium acetate.

Among the above, halogen compounds of palladium, ruthenium or rhodium are particularly preferable, and palladium chloride is most preferable.

Examples of compounds of metals such as iron, copper, bismuth, cobalt, nickel and tin include chlorides and bromides of these metals,
Halide compounds such as iodides and fluorides, nitrates, sulfates,
Phosphates, acetates and the like can be mentioned, and among them, the above halogen compounds are particularly preferable.

Platinum group metals or compounds thereof, and, as a carrier carrying a compound of at least one metal selected from the group consisting of iron, copper, bismuth, cobalt, nickel and tin, diatomaceous earth, activated carbon, silicon carbide, titania, Alumina and the like are preferred, but activated carbon is most preferred.

The platinum group metal or a compound thereof, and iron,
The method for supporting the compound of a metal such as copper, bismuth, cobalt, nickel or tin does not need to be special and is usually carried out, that is, an impregnation method (immersion adsorption method), a kneading method, a deposition method, Although a precipitation method or the like may be used, in the present invention, it is preferably prepared by an impregnation method or a kneading method.

Then, the amount of the platinum group metal or the compound supported on the carrier is determined by converting the platinum group metal to the carrier,
Usually, 0.1 to 10% by weight, particularly 0.5 to 2% by weight is preferable.

Further, the supported amount of a compound of a metal such as iron, copper, bismuth, cobalt, nickel, or tin is 1 to 50 g atomic equivalent, preferably 1 to 10 g, based on the platinum group metal in terms of the amount of these metals. Atomic equivalents are preferred.

In the present invention, as described above, in addition to the platinum group metal or the compound thereof, at least one metal compound selected from the group consisting of iron, copper, bismuth, cobalt, nickel and tin is supported on the carrier. It is particularly characteristic to use solid catalysts. That is, in the present invention, the compounds of these metals play a co-catalyst function, and by supporting these metal compounds in the above amounts on the carrier, the platinum group metal or its compound alone is supported. In comparison, the reaction rate of carbon monoxide and nitrite is significantly improved, and the deactivation rate of the catalyst is also slowed.

Further, in the present invention, the above catalyst is used in the form of powder or particles, but the particle size is not particularly limited, and in the case of powder, it is usually used.
Those having a particle size of from 20 to 100 μm and, in the case of a granular material, those having a mesh size of from 4 to 200 mesh and generally used are suitable.

Furthermore, the catalytic reaction between carbon monoxide and nitrite is
One of the features of the present invention is that it can be performed under extremely mild conditions. For example, it can be carried out at a temperature of 0 to 200 ° C., preferably 50 to 120 ° C. and normal pressure. Of course, a pressurized system can also be used without problems, pressures of 1 to ²⁰ kg / cm ² G and 50 to 150
It can be carried out in the temperature range of ° C.

By the way, the raw material nitrite ester as described above,
For example, decomposition of nitric acid or sulfuric acid in an aqueous solution of sodium nitrite produces a mixed gas of nitric oxide (NO) and nitrogen dioxide (NO ₂ ), and then some of the NO in this mixed gas is oxidized with molecular oxygen. To form nitrogen dioxide (NO ₂ ), N
O / NO ₂ = 1/1 (volume ratio) NO _X gas is obtained, and it is easily synthesized by bringing it into contact with alcohol. However, including the synthesis of this nitrite ester, The catalytic reaction between the carbon monoxide and the nitrite is
A slight pressure system of about ^{2 to 3} kg / cm ² G is particularly desirable.

The reaction between the carbon monoxide and the nitrite can be carried out in a gas phase in either a batch system or a continuous system, but the continuous system is industrially advantageous. Also,
The catalyst may be present in the reaction system in either a fixed bed or fluidized bed reactor.

In the present invention, the carbon monoxide and the nitrite ester of the raw material gas are preferably diluted with an inert gas such as nitrogen gas and fed to the above reactor. It is not limited. However, from the viewpoint of safety, it is desirable that the concentration of the nitrite is 20% by volume or less, preferably 5 to 20% by volume. Accordingly, the concentration of carbon monoxide is 5 to
It is economically preferable to set it in the range of 20% by volume. That is, considering an industrial production process, it is preferable to circulate and use a gas such as carbon monoxide or a nitrite ester to be subjected to the reaction, and to purge a part of the circulated gas out of the system. Since the one-pass conversion rate is about 20 to 30%, even if the concentration of carbon monoxide is higher than 20% by volume, the loss will only increase, and if it is lower than 5% by volume, the productivity will decrease. There are problems such as falling. However, ignoring this economy, the concentration of carbon monoxide is
Actually, up to 80% by volume is possible. That is, it is possible to feed the nitrite in a form diluted with carbon monoxide instead of the inert gas.

Therefore, the usage ratio of carbon monoxide and nitrite is
Carbon monoxide is 0.1 to 1 with respect to 1 mol of nitrite.
It is desirable that the amount is 0 mol, preferably 0.25 to 1 mol.

Further, in the present invention, it is fed to the reactor,
The space velocity of the gas containing carbon monoxide and nitrite is in the range of 500 to 20000 hr ^-1 , preferably 2000 to 50.
It is desirable to carry out in the range of 00 hr ^-1 .

Further, in the production method of the present invention, the nitrite ester is decomposed to generate nitric oxide (NO) after being involved in the reaction, but the NO is recovered from the reaction gas discharged from the reactor. However, it is preferable to react with oxygen and an alcohol corresponding to the nitrite to convert the nitrite to the nitrite again, and to reuse the nitrite.

As described above, from the reactor, in addition to the carbonic acid diester of the desired product, by-products such as oxalic acid diester, unreacted carbon monoxide and nitrite, nitric oxide, carbon dioxide, inert gas, etc. The reaction gas containing is discharged. For example, after the reaction gas is cooled, uncondensed gases such as carbon monoxide, nitrite, nitric oxide, carbon dioxide, and an inert gas are mixed as described above. While purging the part, it is circulated again in the reactor, while the diester carbonate is separated and purified from the condensate by a conventional method such as distillation.

The nitrite ester as a raw material is usually prepared by reacting an alcohol and a nitrogen oxide in the presence of molecular oxygen as necessary, as described above, and the gas contains other than the nitrite ester. , Unreacted alcohol, nitrogen oxides (especially nitric oxide), and in some cases trace amounts of water and oxygen. According to the present invention, good results are obtained even when such a nitrite-containing gas is used as a nitrite source.

〔Example〕

Next, the method of the present invention will be specifically described with reference to Examples and Comparative Examples, but these do not limit the method of the present invention in any way.

The space-time yield (ST
Y) Y (g / l · hr) is the contact reaction time of carbon monoxide and nitrite is θ (hr), the amount of carbonic acid diester formed during that is a (g), and the amount of the catalyst to the reaction tube is Filling amount b
As (l), it was determined by the following equation.

Y = a / (b × θ) Further, the selectivity X (%) in each Example and Comparative Example
Is the supplied carbon monoxide standard, and the above θ
The amounts of carbonic acid diester, oxalic acid diester and carbon dioxide produced in (hr) are c (mol) and d (m
ol) and e (mol) were obtained by the following formula.

X = {c / (c + 2 × d + e)} × 100 Example 1 [Production of catalyst] 0.35 g of palladium chloride and cupric chloride (dihydrate)
0.34 g was dissolved in 100 ml of 5N hydrochloric acid, 10 g of granular activated carbon was immersed in the solution, filtered, washed with water and dried at 100 ° C.,
A catalyst (PdCl ₂ -CuCl ₂ / C) having palladium chloride and cupric chloride supported on activated carbon was prepared.

[Production of carbonic acid diester]

After filling 7 ml of the above catalyst into a gas-phase reaction tube with an inner diameter of 20 mm (with an outer jacket), this reaction tube was fixed vertically, and the heating medium was circulated in the reaction tube jacket to keep the temperature in the catalyst layer at 100
The heating was controlled so that the temperature became ° C.

From the upper part of this reaction tube, a mixed gas of carbon monoxide and a gas containing methyl nitrite synthesized from nitric oxide, oxygen and methanol, that is, methyl nitrite; 15% by volume,
A mixed gas composed of carbon monoxide; 10% by volume, nitric oxide; 3% by volume, methanol; 6% by volume and nitrogen; 66% by volume was supplied at a space velocity (GHSV) of 3000 hr ^-1 under normal pressure. To react.

Then, the reaction product passing through this reaction tube was passed through ice-cooled methanol and collected.

The obtained collected liquid was analyzed by gas chromatography to find that dimethyl carbonate had a STY of 220 g / lhr and a selectivity of 96.
It was found that it was generated in%. In addition, dimethyl oxalate and methyl formate were confirmed as by-products.

Comparative Example 1 [Production of catalyst] 0.35 g of palladium chloride was dissolved in 100 ml of 5N hydrochloric acid, 10 g of granular activated carbon was immersed in the solution, filtered and washed with water to give 100
After drying at ℃, a catalyst (PdCl ₂ / C) in which only palladium chloride was supported on activated carbon was produced.

[Production of carbonic acid diester]

Example 1 was repeated except that the above catalyst was used.
Dimethyl carbonate was produced.

As a result of analyzing the collected liquid by gas chromatography, it was found that dimethyl carbonate was produced with STY of 120 g / l · hr and a selectivity of 90%.

Comparative Example 2 (Production of carbonic acid diester) The catalyst prepared in Comparative Example 1 was used, and the composition of the mixed gas supplied from the upper part of the reaction tube was methyl nitrite; 15% by volume, carbon monoxide; 10 The reaction between carbon monoxide and methyl nitrite was carried out in the same manner as in Example 1 except that the content was% by volume, 2% by volume of oxygen, 6% by volume of methanol and 67% by volume of nitrogen, and dimethyl carbonate was reacted. Was manufactured.

As a result of gas chromatography analysis of the obtained collected liquid, it was found that dimethyl carbonate was produced with STY of 90 g / l · hr and a selectivity of 72%.

Examples 2 to 8 [Manufacture of catalyst] In each example, "a platinum group metal compound and at least one kind selected from iron, copper and bismuth" shown in Table 1 were prepared according to the method of Example 1. Catalyst carrying metal compound ”was produced.

The loading amount of the platinum group metal compound in these catalysts was 1% by weight based on the carrier as platinum group metal.

[Production of carbonic acid diester]

In each of the Examples, the above-mentioned catalyst was used, and in Example 8, a gas containing carbon monoxide synthesized from nitric oxide, oxygen and ethanol and carbon monoxide was further added from the upper part of the reaction tube. Mixed gas with,
That is, except that a mixed gas having a composition of ethyl nitrite; 15% by volume, carbon monoxide; 10% by volume, nitric oxide; 3% by volume, methanol; 6% by volume and nitrogen; 66% by volume was supplied. In the same manner as in Example 1, dimethyl carbonate was produced in Examples 2 to 7, and diethyl carbonate was produced in Example 8.

 The results are shown in Table 1.

Example 9 [Production of carbonic acid diester] Dimethyl carbonate was produced in the same manner as in Example 1 except that the reaction pressure was 3 kg / cm ² G.

As a result of gas chromatography analysis of the obtained collection liquid, it was found that dimethyl carbonate was produced with STY of 350 g / l · hr and a selectivity of 95%.

[Explanation of Action and Effect] As described above, the method of the present invention is a conventionally known method for producing a carbonic acid diester by a gas phase catalytic reaction of carbon monoxide and a nitrite, and the reaction rate thereof is sufficiently satisfactory. Moreover, the selectivity of carbonic acid diester is low, and there is a drawback that the operation for separating and purifying carbonic acid diester from the reaction product is complicated, and further, the concentration range of nitrite ester used in the reaction system has an explosion limit. There is also a problem in that it is dangerous in operation due to exceeding, on the other hand, carbon monoxide and nitrite ester, platinum group metal or its compound, and iron, copper, bismuth, cobalt as the second component. A gas phase reaction in the presence of a catalyst having at least one metal compound selected from the group consisting of nickel, tin and tin supported on a carrier at low temperature and low pressure. With the above, it is possible to provide a method for producing a carbonic acid diester with a high selectivity and a high yield under mild conditions without any danger in the operation.

Further, as compared with the conventionally known liquid phase method, since the method of the present invention can be carried out in the gas phase, there is no need to separate the catalyst from the reaction solution, and there is no elution of metal components from the catalyst. It is easy to separate and purify the carbonic acid diester, and also has an effect of having a high advantage in industrial scale production.

Claims (1)

[Claims] 1. Carbon monoxide and nitrous acid in the presence of a solid catalyst in which a platinum group metal or a compound thereof and a compound of at least one metal selected from the group consisting of iron, copper and bismuth are supported on a carrier. A process for producing a carbonic acid diester, which comprises subjecting an ester to a gas phase catalytic reaction.