JPH04103561A - Production of dialkylcarbonate - Google Patents

Abstract

PURPOSE:To obtain a dialkyl carbonate in high yield by reacting a cyclic carbonate with an alcohol using a heterogeneous catalyst having high activity and extremely reduced in the eluting quantity of catalyst into the reaction liquid and having a nitrogen-containing heterocyclic group. CONSTITUTION:A cyclic carbonate (e.g. ethylene carbonate) is reacted with an alcohol (e.g. methanol) by using a catalyst being a macromolecular net-like and gel type organic polymer or a heterogeneous catalyst having heterocyclic group containing at least one nitrogen atom as an inorganic carrier to afford a dialkyl carbonate (e.g. dimethyl carbonate). This reaction extremely reduces the elution of catalytic ingredient into the reaction liquid and is free from the reverse equilibrium reaction and enables the distillation of dialkyl carbonate. Thereby, the objective compound can be obtained in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing dialkyl carbonates.

(Prior Art) Various proposals have been made as methods for producing dialkyl carbonates by reacting cyclic carbonates and alcohols in the presence of catalysts. For example, a method using a tertiary aliphatic amine as a catalyst (Japanese Patent Publication No. 59-28
542), a method using an alkali metal or an alkali metal compound (U.S. Pat. No. 3,642,858), a method using a thallium compound (Japanese Patent Publication No. 60-27
658), a method using tin alkoxides (Japanese Patent Publication No. 56-40708), a method using a mixture of a Lewis acid and a nitrogen-containing organic base (Japanese Patent Publication No. 60-22698)
JP-A-56-10144), and a method using a quaternary phosphonium salt (JP-A-56-10144).

Distillation is usually required as a separation operation to obtain the dialkyl carbonate product. However, when such a homogeneous catalyst is used, it is difficult to separate the reaction mixture from one catalyst, and the presence of the catalyst during distillation tends to cause a reverse equilibrium reaction, resulting in a reaction between dialkyl carbonate and alcohol. There are problems in that it can only be obtained as an azeotropic composition and that it produces high-boiling products.

In order to prevent this, a method using a heterogeneous catalyst has been announced. For example, silica-titania solid acid catalyst (Japanese Patent Publication No. 61-5467), cation exchange resin having a sulfonic acid group or a carboxylic acid group as an exchange group (Japanese Patent Publication No. 64/1989)
There is a method using, for example, JP-A-31737. However, these catalysts have the drawbacks of insufficient catalytic activity and low reaction rate.

Therefore, as a heterogeneous catalyst that satisfies the catalytic activity,
A weakly basic exchange resin containing a tertiary aliphatic amine group (Japanese Patent Publication No. 51-28542), a strongly basic exchange resin containing a quaternary ammonium group as an exchange group (Japanese Patent Publication No. 63/1986)
-238043), etc. However, with such catalysts, it is not possible to completely avoid mixing of catalyst components (referring to catalyst eluates, decomposition products, etc.) into the reaction solution.
The presence of a catalyst component during distillation tends to cause a reverse equilibrium reaction, which means that it can only be obtained with an azeotropic composition of dialkyl carbonate and alcohol, and that the homogeneous catalyst mentioned above produces a high-boiling composition. I have a similar problem.

(Problems to be Solved by the Invention) As described above, in the reaction between a cyclic carbonate and an alcohol, a heterogeneous catalyst that provides dialkyl carbonate with high selectivity and has very few catalyst components eluted into the reaction solution. As for that, I haven't gotten it yet.

(Means for Solving the Problems) The present inventors have made intensive studies aimed at solving the conventional problems related to the production of dialkyl carbonates and obtaining dialkyl carbonates in high yield, and as a result, they have developed the present invention. It's arrived.

That is, the present invention is a method for producing a dialkyl carbonate, which is characterized by reacting a cyclic carbonate and an alcohol in the presence of a heterogeneous catalyst having a nitrogen-containing heterocyclic group.

In the present invention, a heterogeneous catalyst having a nitrogen-containing heterocyclic group refers to a macroreticular or gel-type organic polymer to which a heterocyclic group containing at least one nitrogen atom is bonded, or a small number (at least one nitrogen atom). A catalyst that is an inorganic carrier to which a heterocyclic group containing a nitrogen atom is bonded, that can generate a dialkyl carbonate by reacting a cyclic carbonate with an alcohol, and that does not easily elute the catalyst component into the reaction solution. be.

In the present invention, an organic polymer serving as a heterogeneous catalyst and an inorganic carrier may be mixed and used.

In the present invention, a heterocyclic group is a heteromonocyclic group or a fused heterocyclic group. The heterocyclic group may contain heteroatoms other than carbon and nitrogen atoms.

In the present invention, the heteromonocyclic group includes the above (A),
It is a group having the basic skeleton of (B), in which at least one of the atoms constituting the ring is a nitrogen atom, and the remaining atoms are selected from carbon, nitrogen, and oxygen atoms.

(A)-1 and (B)-1 are carbon or nitrogen atoms, and either directly from this atom or one or more carbon-carbon bonds (this carbon-carbon bond is replaced by one or more carbon heteroatom bonds) bonded to an organic polymer or an inorganic carrier via an organic polymer or an inorganic carrier.

(A), (B) The bonds on the rings are single bonds or double bonds (carbon-carbon double bond, carbon-nitrogen double bond, nitrogen-
consisting of nitrogen double bonds).

Further, when there is a nitrogen atom having no double bond at positions other than positions (A)-1 and (B)-1, the hydrogen atom on the nitrogen atom is substituted with an alkyl group.

A hydrogen atom on a carbon atom can be an alkyl group, an alkyl group, an alkoxy group, a dialkylamino group, a halo group, an acyl group,
Aroyl group, amide group, nitro group, cyano group, alkylthio group, alkylsulfonyl group, etc., and (A)
Alternatively, it may be substituted with a heteromonocyclic group (B).

In the present invention, examples of preferable heteromonocyclic groups include: etc. (However, R represents an alkyl group).

In the present invention, as the fused heterocyclic group, the above (C)
It has a basic skeleton of ~(G), and the atoms of the condensation part ((C)-1,5, (D)-1,6, (E)-1°6.
7.12, (F)-1,6,8,13, (G)-1,6
, 9, 14) is a carbon atom, and other atoms are selected from carbon, nitrogen, and oxygen atoms, and include at least one nitrogen atom.

The bonds on the rings (C) to (G) are single bonds or double bonds (
carbon-carbon double bond, carbon-nitrogen double bond, nitrogen-nitrogen double bond).

Groups (C) to (G) may be directly connected to a moiety other than an atom of the condensation moiety, or one or more carbon-carbon bonds (this carbon-carbon bond is substituted with one or more carbon-heteroatomic bonds). bonded to an organic polymer or an inorganic carrier via an organic polymer or an inorganic carrier.

When there is a nitrogen atom having no double bond other than the atom bonded to the organic polymer or inorganic carrier, the hydrogen atom on the nitrogen atom is substituted with an alkyl group.

The hydrogen atom on the carbon atom is an alkyl group, an IJ-al group,
Alkoxy groups, dialkylamino groups, octoday groups, acyl groups, aroyl groups, amido groups, nitro groups, cyano groups, alkylthio groups, alkylsulfonyl groups, and the above-mentioned heteromonocyclic groups (A) or (B). It may be substituted with a group.

In the present invention, examples of preferable fused heterocyclic groups include: (However, R represents an alkyl group).

The heterocyclic group in the heterogeneous catalyst may be a monocyclic group or a condensed ring group, or may be a mixture of several types selected from these groups.

In the present invention, the heterocyclic group is attached directly or via one or more carbon-carbon bonds to the organic polymer and the inorganic carrier.

Moreover, this carbon-carbon bond may be substituted with one or more carbon heteroatom bonds.

In the present invention, examples of macroreticular and gel-type organic polymers include polystyrene polymers, polyacrylic acid polymers, polymethacrylic acid polymers, phenolic polymers, and cellulose. Also,
These polymers may be cross-linked by divinylbenzene.

Examples of inorganic carriers include silica, alumina, silica alumina, titania, zeolite, and the like. By modifying some or all of the surface hydroxyl groups of these carriers, they can be bonded to heterocyclic groups.

In the present invention, cyclic carbonate refers to the following general formula (
1).

In formula C, Ro represents a divalent group -(CHz)--.

m is an integer from 2 to 6. Furthermore, the hydrogen atom in R3 may be substituted with an alkyl group or aryl group having 1 to 8 carbon atoms. ] Specific examples include alkylene carbonates such as ethylene carbonate and propylene carbonate; 1,
Examples include 3-dioxacyclohex-2-one, 1,3-dioxacyclohex-2-one, and the like. Alternatively, a mixture thereof may be used.

In the present invention, alcohol is one that reacts with a cyclic carbonate to give a carbonate ester. Preferably, the general formula Rt OHCRt is a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms. Furthermore, the hydrogen atom of R2 may be substituted with an alkoxy group or the like. ]. Specific examples include methanol, ethanol, propatool, 1-methylethanol, allyl alcohol, butanol, 2-butanol, 2-methyl-2-propatool, 3-buten-1-ol, cyclohexanol,
Examples include benzyl alcohol and 2-methoxyethanol. Alternatively, a mixture of these may be used.

In the present invention, as shown in the following formula (2), by reacting cyclic carbonate (1) with two molecules of alcohol (2), dialkyl carbonate (3) and glycol (4), which is a symbiotic acid, are combined. A well-known reaction can be applied to obtain .

In the reaction of the present invention, a batch reactor or a flow reactor may be used.

The quantitative ratio of the cyclic carbonate to the alcohol in the raw material liquid used for the reaction can be used within a wide range.

However, preferably the molar ratio of alcohol to raw cyclic carbonate is from 0.2 to 20.

More preferably, it is 1-5.

The reaction temperature of the present invention is usually 30 to 300°C, preferably 50 to 260°C. However, if the catalyst used has a specific withstand temperature, it is preferable to carry out the reaction in a temperature range below the specific withstand temperature.

The reaction time of the present invention may vary depending on the type and composition ratio of the cyclic carbonate and alcohol used as raw materials, and the reaction temperature. For example, when performing a flow reaction, it is usually expressed as liquid hourly space velocity (LHSV) (volume rate of supply of reaction liquid per unit volume of reactor) with respect to the total feed liquid, and is usually 0.0.
5 to 40 hr" preferably 0.2 to 10 hr" is used. In addition, in the case of batch reaction, it is usually 0.05 to 6
0 hours, preferably 0.2 to 20 hours are used.

In the present invention, the pressure during the reaction is not important and may be the self-generated pressure of the reactant depending on the size of the reactor and reaction temperature, but here preferably normal pressure to 20 kg/c
d (gauge pressure) is used, more preferably normal pressure to 1
0 kg/elN is used.

In the case of a batch method, the amount of catalyst used in the reaction of the present invention is 0.01 to 20% by weight based on the raw materials, preferably 0.5% by weight.
It is ~10%. In addition, in the case of a flow type, the above-mentioned L
Keep it within the HSV range.

In the present invention, the reaction solution obtained was subjected to a distillation operation, and the occurrence of the reverse equilibrium reaction and the accumulation of high-boiling components were suppressed, so it was evaluated that it is a heterogeneous catalyst with extremely low elution of catalyst components. ing. The heterogeneous catalyst of the present invention has extremely low elution of catalyst components into the reaction solution, making it possible to distill dialkyl carbonate without causing a reverse equilibrium reaction, and as a result, dialkyl carbonate can be distilled in high yield. can be obtained.

(Example) EXAMPLES The present invention will be specifically described with reference to Examples below.

Example 1 (Catalyst pretreatment) Sumikire CR-2 (weakly basic anion exchange resin manufactured by Sumima Kagaku Co., Ltd., the exchange group is a pyridine group, and it is a sulfate salt)
was pretreated by the method described below to convert the pyridium base to a pyridine group.

100 d of Sumikire CR-2 was stirred in 300 d of 5% NaOH aqueous solution at room temperature for 1 hour, and then washed five times with 200 d of distilled water. Subsequently, it was washed five times with 200 d of methanol, and then vacuum-dried at 80° C. for 5 hours.

(Reaction) The tubular reactor containing the above dry catalyst was used for the reaction. Ethylene carbonate (EC) and methanol (MeOH)
A mixed solution (MeOH/PC molar ratio = 2) at a flow rate of 11
0jli! /hr (LH3V=3hr-'), and the reactor was heated to 100°C while maintaining the pressure of the reaction system at 7kg/cd (gauge pressure). The delivered liquid was analyzed by gas chromatography, and from the time when the composition of the delivered liquid reached a steady state, the reaction liquid was collected for the next step of distillation. The conversion rate of EC was 30%.

(Distillation) 300.0 g of the reaction solution was charged into a 500 d glass distillation apparatus and distilled. Distillation was carried out by increasing the temperature under normal pressure, and when the temperature reached 180°C over 2 hours, the distillation pressure was lowered from normal pressure, and over 2 hours MeOH/
The 0MC azeotrope, DMC, EG and EC were extracted sequentially. The amount of high-boiling residue was 0.1 g or less. As a result of analysis by gas chromatography, 300.0 g of the reaction solution contained 53.3 g of DMC, and D in the distillation recovery fraction, that is, the DMC/MeOH azeotropic fraction, and the DMC fraction.
The total amount of MC was 53.1 g.

As a result, it was found that no reverse equilibrium reaction or accumulation of high-boiling by-products occurred during distillation, and it is thought that the elution of catalyst components into the reaction solution was extremely small.

Comparative Example 1 (Catalyst Pretreatment) 500d DOWEX MSA-1 (manufactured by Dow Chemical Company, is a strong basic anion exchange resin made by copolymerizing styrene and divinylbenzene, and has a trimethylammonium group as an exchange group. , the anion species being chlorine ion) was dried by heating to 60° C. under reduced pressure, and then filled into a tubular reactor.

(Reaction) The flow rate of raw materials fed into the tubular reactor was set at 37 d/hr (LH
The reaction was carried out in the same manner as in Example 1, except that the reaction time was changed to 3V=1hr-'). The conversion rate of EC was 29%.

(Distillation) Distillation was performed in the same manner as in Example 1. Reaction liquid 30
Recovered DM for 51.4g of DMC in 0.0g
C was 40.3g. Moreover, the distillation residue was 7.2 g.

Comparative Example 2 Amberlyst A-21 (manufactured by Rohm & Haas, tertiary aliphatic amine type) was dried by heating to 6°C under reduced pressure, and then reacted and treated in the same manner as in Example 1. Distilled. The conversion rate of EC in the reaction was 32%.

Further, when 300.0 g of the reaction solution containing 56.88 DMC was distilled, only 43.0 gL of DMC was distilled and recovered, and the high-boiling residue was 3.8 g.

Example 2 (Synthesis of catalyst) Porous glass particles (surface area approximately 5-20rd/g, particle size 50
~200 μm) in a 10% methanol solution of aminopropyltriethoxysilane at reflux for 24 hours. After washing the glass particles with ethanol and water, 10 g of 3-quinolinecarboxylic acid chloride and 5 g of triethylamine were added.
Chloroform solution containing 1! and reflux for 2 hours.

The particles are separated by filtration and washed five times with chloroform to obtain an inorganic carrier having a quinoline group.

(Reaction and Distillation) The above-mentioned inorganic carrier was placed in a tubular reactor, and reaction and distillation were performed in the same manner as in Example 1, except that the catalyst was changed.

The conversion rate of EC in the reaction was 27%.

In addition, 300.0 g of the reaction solution containing 48.0 g of DMC was added.
When 0g was distilled, 47.7g of DMC could be distilled and recovered, and the high-boiling residue was less than 0.1g.

Example 3 In place of 3-quinolinecarboxylic acid chloride in Example 2, 2-quinoxaloyl chloride was used to obtain an inorganic carrier having a quinoxaline group.

Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion rate of EC in the reaction was 23%.

When 300.0g of the reaction solution was distilled, 40.0g of DMC was found out of 40.9g of DMC contained in the reaction solution.
could be recovered by distillation, and the amount of high-boiling residue was 0.1 g or less.

Example 4 Using 4-morpholinopropionic acid chloride instead of 3-quinolinecarboxylic acid chloride in Example 2,
An inorganic carrier having a morpholine group was obtained. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion of EC in the reaction was 16%.

When 300.0 g of the obtained reaction solution was subjected to distillation, 28.3 g of DMC was extracted from 28.4 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 5 In place of 3-quinolinecarboxylic acid chloride in Example 2, 1-N-methyl-4-imidazolecarboxylic acid chloride was used to obtain an inorganic carrier having 1 to N-methylimidazole groups. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion rate of EC in the reaction was 24%.

When 300.0 g of the obtained reaction solution was subjected to distillation, 42.5 g of DMC was extracted from 42.6 g of DMC produced.
was recovered, and the amount of high-boiling residue was 0.21 g or less.

Example 6 In place of 3-quinolinecarboxylic acid chloride in Example 2, 2-pyrazinecarboxylic acid chloride was used to obtain an inorganic carrier having a pyrazine group.

Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion of EC in the reaction was 21%.

When 300.0 g of the obtained reaction solution was subjected to distillation, 37.1 g of DMC was extracted from 37.3 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 7 In place of 3-quinolinecarboxylic acid chloride in Example 2, 2,2'-bipyridine-4-carboxylic acid chloride was used to obtain an inorganic carrier having a 2,2'-bipyridine group. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion rate of EC in the reaction was 22%.

When 300.0 g of the obtained reaction solution was subjected to distillation, 39.1 g of DMC was extracted from 39.2 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 8 In place of 3-quinolinecarboxylic acid chloride in Example 2, 1-N-methylindole-2-carboxylic acid chloride was used to obtain an inorganic carrier having a 1-N-methylindole group. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion of EC in the reaction was 15%.

When 300.0 g of the resulting reaction solution was subjected to distillation, 26.4 g of DMC was extracted from 26.6 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 9 In place of 3-quinolinecarboxylic acid chloride in Example 2, 7-N-methyl-6-purinecarboxylic acid chloride was used to obtain an inorganic carrier having a 7-N-methylpurine group. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion rate of EC in the reaction was 24%.

When 300.0 g of the obtained reaction solution was subjected to distillation, 42.4 g of DMC was extracted from 42.6 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 10 Instead of 3-quinolinecarboxylic acid chloride in Example 2, 1,10-phenanthroline-5-propionic acid chloride was used to obtain an inorganic carrier having a 1,10-phenanthroline group. Using this catalyst, reaction and distillation were carried out in the same manner as in Example 1.

The conversion rate of EC in the reaction was 19%.

When 300.0 g of the resulting reaction solution was subjected to distillation, 33.6 g of DMC was extracted from 33.7 g of DMC produced.
was recovered, and the amount of high-boiling residue was less than 0.1 g.

Example 11 The reaction and distillation were carried out in the same manner as in Example 1, except that propylene carbonate was used instead of ethylene carbonate. The conversion rate of propylene carbonate was 35%, the recovery rate of DMC after distillation was 99% or more, and the high boiling residue was 0.1 g or less.

Example 12 The reaction and distillation were carried out in the same manner as in Example 1, except that ethanol was used instead of methanol.

The conversion rate of ethylene carbonate was 33%, and
The recovery rate of DMC after distillation is over 99%, and the high boiling residue is 0.
It was less than 1g.

(Effects of the Invention) The present invention makes it possible to distill dialkyl carbonate without elution of catalyst components into the reaction solution and without causing a reverse equilibrium reaction, and as a result, dialkyl carbonate can be distilled in high yield. Obtainable.

(1 idiot)

Claims (1)

[Claims] A method for producing a dialkyl carbonate, which comprises reacting a cyclic carbonate and an alcohol in the presence of a heterogeneous catalyst having a nitrogen-containing heterocyclic group.