JPH06306018A - Production of carbonic acid ester - Google Patents

Abstract

PURPOSE:To provide a process for producing a carbonic acid ester from carbon monoxide and a nitrous acid ester, capable of keeping the catalyst in a highly active state over a long period and stably producing a carbonic acid ester over a long period in a high reaction rate and selectivity while suppressing the corrosion of apparatuses such as reactor. CONSTITUTION:A carbonic acid ester is produced by the catalytic reaction of carbon monoxide with a nitrous acid ester in the presence of a solid catalyst. In the above process, a small amount of chlorine is added to a raw material gas containing carbon monoxide and the nitrous acid ester before the catalytic reaction of carbon monoxide with the nitrous acid ester.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a carbonic acid ester from carbon monoxide and a nitrite in the presence of a solid catalyst, in which a raw material gas containing carbon monoxide and a nitrite contains chlorine. The present invention relates to a method for stably producing a carbonate ester for a long period of time at a high reaction rate and a high selectivity by carrying out a catalytic reaction of the raw material gas. Carbonic acid ester is a synthetic raw material for polymers such as polycarbonate and urethane, intermediates for medical and agricultural chemicals, and various chemicals.
Further, it is a compound industrially useful as a solvent.

[0002]

2. Description of the Related Art Although a method of reacting phosgene with alcohol has been practiced for a long time as a method for producing carbonic acid ester, phosgene is extremely toxic and is not always a preferable material as a raw material for production in view of environmental hygiene. There wasn't. Further, in this method, hydrochloric acid is duplicated and corrodes the apparatus. Therefore, it is necessary to select an expensive material. Therefore, industrially, development of a method for producing a carbonate ester without using phosgene has been desired.

For this reason, as a production method without using phosgene, a method of synthesizing a carbonic acid ester from carbon monoxide and an alcohol has been studied and proposed in various fields (for example, Japanese Patent Laid-Open No. 60-75447). Kaisho 63-72
650, Japanese Patent Publication No. 63-38018, etc.). These are methods of synthesizing carbonic acid ester in a liquid phase by oxygen oxidation reaction of carbon monoxide and alcohol using copper halide, palladium halide, etc. as a catalyst, but carbon dioxide is a by-product. The selectivity of carbonic acid ester based on carbon monoxide was low, and the production of water made it difficult to purify the carbonic acid ester. Furthermore,
Since these methods are liquid phase reactions, a step of separating the product from the catalyst is required, and it cannot be said that the methods are industrially advantageous.

Therefore, as an improved method thereof, for example, carbon monoxide and a nitrite ester are solid catalysts in which a platinum group metal or a compound thereof is supported on a carrier and O per carbon monoxide.
_A method for producing a carbonic acid ester comprising reacting in the gas phase in the presence of 10 mol% or more of an oxidizer as ₂ is JP-A-60 / 1985.
No. 181051. However, in this method, in order to suppress the by-product of oxalic acid diester, an oxidizing agent such as oxygen is coexisted with carbon monoxide in the above proportion, but a considerable amount of oxalic acid diester is present. As a by-product, the selectivity of carbonate ester was lowered, and the reaction rate and the catalyst life were not satisfactory either. Further, since the concentration range of nitrite used in the mixed gas consisting of carbon monoxide, nitrite, alcohol, oxygen, etc. used for the reaction exceeds the explosion limit, it is industrially important for safety reasons. Not the preferred method.

Further, JP-A-3-141243 and JP-A-4-139152 describe a method for producing dimethyl carbonate by catalytically reacting carbon monoxide and methyl nitrite in a gas phase, such as palladium chloride and sulfuric acid. Disclosed is a production method using a catalyst in which a compound of a platinum group metal such as palladium and at least one compound of a metal selected from the group consisting of iron, copper, bismuth, cobalt, nickel and tin are supported on a carrier such as activated carbon. However, even with these methods, the life of the catalyst is not sufficient for industrial use. Therefore, JP-A-4-89458 discloses a method of reacting carbon monoxide and methyl nitrite in the gas phase in the presence of a platinum group metal compound in the presence of a small amount of hydrogen chloride. The life of the catalyst is not always sufficient, and the corrosion of the reactor and the like due to the use of hydrogen chloride is unavoidable, leaving room for improvement for industrial implementation.

[0006]

A known method for producing a carbonic acid ester using a nitrite is as described above.
The reaction rate, the selectivity and the life of the catalyst were not always satisfactory, and the apparatus corrosion due to hydrogen chloride was not satisfactory. An object of the present invention is to industrially maintain a high reaction rate and selectivity with almost no deterioration of a catalyst, suppress corrosion of a device such as a reactor, and stably produce a carbonate ester for a long period of time. Another object of the present invention is to provide a suitable method for producing a carbonate ester.

[0007]

In order to solve the above-mentioned problems in the conventionally known carbonic acid ester production methods, the present inventors have developed a carbonic acid ester by a catalytic reaction with carbon monoxide and a nitrite ester. As a result of diligently studying the reaction to be synthesized, in the presence of a solid catalyst, a raw material gas containing carbon monoxide and a nitrite ester was allowed to contain chlorine to carry out a catalytic reaction, thereby suppressing corrosion of a device such as a reactor. , The catalytic activity is kept high for a long time,
The present invention has been accomplished by finding that the target ester carbonate can be obtained with high reaction rate and selectivity. That is, the present invention is a method for producing a carbonic acid ester by catalytically reacting carbon monoxide and a nitrite ester in the presence of a solid catalyst, chlorine is contained in the raw material gas containing carbon monoxide and a nitrite ester. The present invention relates to a method for producing a carbonic acid ester, which comprises reacting carbon monoxide with a nitrite ester.

The method of the present invention will be described in detail below.
The solid catalyst used in the present invention may be a platinum group metal or a platinum group metal compound and, if necessary, one or more kinds of other metal compounds supported on a carrier. Examples of the platinum group metal include palladium, ruthenium and rhodium, and examples of the platinum group metal compound include palladium chloride, palladium bromide, palladium iodide, palladium fluoride, ruthenium chloride and rhodium chloride. Palladium, ruthenium or rhodium halides, nitrates, sulfates, phosphates, acetates of these platinum group metals may be mentioned, but may be complexes of these metals, for example, tetrachloropalladic acid, tetra It is also possible to use an alkali metal salt of bromopalladic acid. Among these, the platinum group metal is preferably palladium, and the platinum group metal compound is preferably palladium chloride, palladium bromide,
Palladium nitrate, palladium sulfate, and alkali metal salts of tetrachloropalladic acid and tetrabromopalladic acid, more preferably palladium chloride and alkali metal salts of tetrachloropalladic acid are used.

As the other metal compound, for example, at least one kind selected from compounds of metals such as iron, copper, bismuth, cobalt, nickel, tin, antimony, aluminum, vanadium, niobium, tantalum and manganese. Compounds of metals, particularly chlorides, bromides, iodides and other halides, nitrates, sulfates, inorganic acid salts such as phosphates, and organic acid salts such as acetates and benzoates are preferably used. However, preferably the above chloride,
Bromides, nitrates and sulfates are used, more preferably chlorides.

The amount of the platinum group metal or platinum group metal compound supported on the carrier is usually 0.1 to 10% by weight based on the metal of the platinum group metal, and particularly preferably 0.1.
It is preferably 5 to 2% by weight. In addition, the amount of the compound of other metal supported is preferably 0.1 to 50 gram atom equivalents, and more preferably 1 to 10 gram atom equivalents, based on the amount of these metals, with respect to the platinum group metal.

In the present invention, the above-mentioned catalyst is used in the form of powder, granules, or molded bodies, but the size thereof is not particularly limited, and in the case of powder, those usually used in the range of 20 to 100 μm are used. , 4 to 2 if granular
A generally used mesh having a size of about 00 mesh and a molded body having a size of 0.5 to 10 mm are preferably used.

The carrier used in the present invention is
Examples thereof include carriers such as alumina, silica gel, activated carbon, silica-alumina, zeolite, molecular sieve, pumice, diatomaceous earth, silicon carbide, titania and zirconia. Among them, activated carbon and alumina are preferably used. The method of loading each catalyst component on these carriers does not need to be special, and is a commonly used method, that is, an impregnation method (immersion adsorption method), a kneading method, a deposition method, an evaporation-drying method, a coprecipitation method. Although it may be carried out by a method or the like, it is preferably prepared by an impregnation method or an evaporation-drying method because it is simple in the present invention. The catalyst components may be loaded on the carrier at the same time or sequentially.

Examples of the nitrite used in the present invention include methyl nitrite, ethyl nitrite, n- (or i) nitrite.
-) Propyl ester, n- (or i-, sec-) butyl nitrite ester of a lower aliphatic monohydric alcohol having 1 to 4 carbon atoms, cyclohexyl nitrite cycloaliphatic alcohol nitrite ester, Preferable examples include nitrites of aralkyl alcohols such as benzyl nitrite and phenylethyl nitrite. Particularly, nitrites of lower aliphatic monohydric alcohols having 1 to 4 carbon atoms are preferable, and methyl nitrite is particularly preferable. And ethyl nitrite are most preferred.

In the present invention, it is desirable that carbon monoxide and nitrite be diluted with an inert gas such as nitrogen gas and fed to the reaction system as a raw material gas. From the viewpoint of safety, the concentration of the nitrite ester in the raw material gas is 20% by volume or less, preferably 5 to 20% by volume.

The concentration of carbon monoxide can be up to 80% by volume if nitrite is fed in a form diluted with carbon monoxide instead of the above-mentioned inert gas. However, in the case of an industrial manufacturing process, gases such as carbon monoxide and nitrite to be used for the reaction are circulated and used,
It is preferable to purge a part of the circulating gas out of the system,
Furthermore, the conversion rate of one cycle of carbon monoxide is 20 to 30.
%, The concentration of carbon monoxide is 20% by volume.
If it is made higher, the loss only increases, and if it is lower than 5% by volume, problems such as a drop in productivity will occur.
Therefore, in practice, the concentration of carbon monoxide in the source gas is 5
It is economically desirable to set the content in the range of 20% by volume.

The ratio of carbon monoxide to nitrite ester used in the raw material gas is in the range of 0.1 to 10 moles, preferably 0.25 to 2 moles, of carbon monoxide to 1 mole of nitrite ester. Is desirable. Further, the reaction system to Fi - de is the carbon monoxide and the space velocity in the range of 500～50000Hr ^-1 raw material gas containing nitrous acid ester, preferably, is preferably in the range of 2000~40000hr ^-1.

The chlorine used in the present invention is used by diluting chlorine gas with nitrogen to an appropriate concentration and mixing it with a raw material gas containing carbon monoxide and nitrite. At this time, the amount of chlorine contained in the raw material gas is 1 to 1000 ppm, preferably 10 to 500 p in terms of volume%.
The ratio of chlorine, carbon monoxide and nitrite ester in the raw material gas is preferably in the range of pm, and carbon monoxide and nitrite ester each exceed 100 mol per mol of chlorine.

In the present invention, the catalytic reaction between carbon monoxide and nitrite is carried out under extremely mild conditions, for example, the reaction temperature is 0 to 200 ° C., preferably 50 to 140 ° C., and the reaction pressure is It can be performed at atmospheric pressure. Of course, the reaction can be carried out without problems even with a pressurized system, for example, 1 to 20 kg / cm.
It can be carried out at a pressure of ² G and a temperature range of 50 to 140 ° C. The form of this catalytic reaction is in the gas phase,
Either a batch type or a continuous type may be used, but industrially the gas phase or continuous type is more advantageous. The catalyst may be present in the reaction system in either a fixed bed or a fluidized bed, but a fixed bed is preferred.

As described above, from the reaction vessel, by-products such as oxalic acid diester, unreacted carbon monoxide and nitrite, chlorine, nitric oxide, carbon dioxide, in addition to the carbonic acid ester of the desired product, are obtained. Carbon dioxide ester is circulated to the reactor again after cooling the reaction mixture and purging uncondensed gas containing carbon monoxide, nitrite ester, chlorine, nitric oxide, carbon dioxide, etc. On the other hand, it can be easily separated and purified by a conventional method such as distillation. Examples of the carbonic acid ester produced by the method of the present invention include dialkyl carbonates such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate, and dicyclohexyl carbonate and dibenzyl carbonate depending on the kind of nitrite. But,
In the present invention, a carbonic acid di-lower alkyl ester such as dimethyl carbonate can be preferably produced.

[0020]

EXAMPLES Next, the method of the present invention will be specifically described with reference to examples and comparative examples, but these do not limit the present invention in any way. The space-time yield (STY) Y (g / l · h) of carbonic acid ester in each Example and Comparative Example is θ (h) when the contact reaction time between carbon monoxide and nitrite is The amount was a (g), and the amount of the catalyst packed in the reaction tube was b (l).

[0021]

[Equation 1]

The selectivity X (%) of the carbonic acid ester in each of the examples and comparative examples is based on the supplied carbon monoxide, and the carbonic acid ester and oxalic acid produced during the above-mentioned catalytic reaction time θ (h). The amounts of diester and carbon dioxide were calculated from the following equation as c (mol), d (mol), and e (mol), respectively.

[0023]

[Equation 2]

In addition, the catalyst activity reduction rate D (% / h) in each of the Examples and Comparative Examples is the space-time yield Y at the initial stage of the reaction (after 2 hours from the start of the reaction) under predetermined reaction conditions. ₀
(G / l · h) and the space-time yield Y _t after the lapse of t hours from the start of the reaction were determined by the following formula.

[0025]

[Equation 3]

Example 1 Cupric chloride was supported on activated carbon (BET surface area: 1000 m ² / g) so that 1% by weight of palladium chloride in terms of palladium metal and the atomic ratio of palladium / copper would be 1/2. After filling 1 ml of the prepared catalyst into a gas phase reaction tube (with an outer jacket) having an inner diameter of 13 mmφ, the reaction tube was fixed vertically and a heating medium was circulated in the reaction tube jacket to bring the temperature in the catalyst layer to 120 ° C. The heating was controlled as follows. Then, a mixed gas of a gas containing methyl nitrite synthesized from nitric oxide, oxygen and methanol and passed through a 5 ° C. cold trap, chlorine diluted with nitrogen, and carbon monoxide, that is,
Methyl nitrite: 10% by volume, carbon monoxide: 10% by volume,
Nitric oxide: 1% by volume, methanol: 5% by volume, chlorine:
A raw material gas having a composition of 500 volume ppm and nitrogen: 73 volume% was supplied from the upper part of the reaction tube at a space velocity (GHSV) of 30,000 h ⁻¹ , and the reaction was carried out at 120 ° C. under normal pressure. The reaction product passed through the reaction tube was collected in ice-cooled methanol, and the collected liquid was analyzed by gas chromatography. As a result, the STY of dimethyl carbonate 2 hours after the start of the reaction was 430 g / l. h, selectivity is 92%
The STY of dimethyl carbonate 8 hours after the start of the reaction was 39.
It was 0 g / l · h and the selectivity was 89%. From this result, the activity reduction rate D was 1.6% / h.

Comparative Example 1 The product was analyzed by carrying out the reaction exactly as in Example 1 except that chlorine was changed to hydrogen chloride in Example 1. As a result, the STY of dimethyl carbonate 2 hours after the start of the reaction was 3
The selectivity was 10 g / l · h and the selectivity was 92%, and the STY of dimethyl carbonate 8 hours after the start of the reaction was 270 g / l · h and the selectivity was 85%. From this result, the activity reduction rate D was 2.
It was 2% / h.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that chlorine was not added, and the product was analyzed. As a result, the STY of dimethyl carbonate 2 hours after the start of the reaction was 44.
0 g / l · h, the selectivity was 92%, and STY of dimethyl carbonate 8 hours after the start of the reaction was 220 g / l · h, the selectivity was 83%. From this result, the activity decrease rate D is 8.2.
% / H.

Example 2 1% by weight of lithium tetrac converted to palladium metal
Loro Paradate (Li ₂PdCl_Four) To γ-alumina
(BET surface area: 180m²/ M) of the catalyst supported on 1 m
Reaction was performed in the same manner as in Example 1 except that 1 was used.
The product was analyzed. As a result, carbonic acid 2 hours after the start of reaction
Dimethyl STY is 1020g / l · h, selectivity is 98
%, The STY of dimethyl carbonate 8 hours after the start of the reaction was 6
The rate was 80 g / l · h and the selectivity was 98%. Is this the result
As a result, the activity reduction rate D was 5.6% / h.

Comparative Example 3 The reaction was carried out in the same manner as in Example 2 except that chlorine was changed to hydrogen chloride in Example 2, and the product was analyzed. As a result, the STY of dimethyl carbonate 2 hours after the start of the reaction was 7
The selectivity was 20 g / l · h and the selectivity was 98%, and the STY of dimethyl carbonate 8 hours after the start of the reaction was 460 g / l · h and the selectivity was 98%. From this result, the activity decrease rate D was 6.
It was 0% / h. The results of each Example and Comparative Example are shown in Table 1.

[0031]

[Table 1]

[0032]

The method of carrying out the catalytic reaction of carbon monoxide and nitrite in the presence of a solid catalyst of the present invention by adding a trace amount of chlorine to the raw material gas containing carbon monoxide and nitrite. As a result, the activity of the catalyst used is stable over a long period of time, and it is possible to stably produce a carbonate ester for a long period of time with a high reaction rate and a high selectivity while suppressing the corrosion of a device such as a reactor.

Claims (1)

[Claims] 1. A method for producing a carbonic acid ester by reacting carbon monoxide and a nitrite ester in the presence of a solid catalyst, wherein chlorine is contained in a raw material gas containing carbon monoxide and a nitrite ester. A method for producing a carbonic acid ester, which comprises carrying out a catalytic reaction between carbon monoxide and a nitrite.