JP7141219B2 - Method for producing alicyclic carbonate - Google Patents

Description

The present invention relates to a method for producing an alicyclic carbonate.

Aliphatic polycarbonates have been known to be useful as medical materials and engineering plastics because of their excellent properties such as impact resistance and light weight. have a problem.
On the other hand, among aliphatic polycarbonates, an alicyclic polycarbonate having an alicyclic structure in its main chain structure is an attractive polymer material because it exhibits a higher glass transition point than other aliphatic polycarbonates. In particular, polycyclohexene carbonate (hereinafter sometimes referred to as PCHC) is a representative alicyclic polycarbonate, and its production method has been actively taken up as an object of development.

As a method for producing PCHC, a method of reacting cyclohexene oxide as a raw material with carbon dioxide in the presence of a catalyst such as a zinc dinuclear complex is generally known.
However, the existing production method has the problem that it is difficult to apply it industrially because the catalyst cost for general-purpose polymer production is high and high pressure conditions are required. Establishment of an efficient production method using a high carbonate monomer is required.

On the other hand, cyclohexene carbonate (hereinafter sometimes referred to as CHC) is a raw material monomer for polycarbonate having an alicyclic structure, and is known as a monomer from which PCHC can be synthesized by its polymerization reaction.
Since the physical properties of CHC are greatly dependent on the steric structure of its carbonate group, there is a demand for a method for geometrically obtaining CHC having a desired steric structure. In particular, the trans isomer, which has a highly strained structure, has high reactivity, and is thought to contribute to the improvement of production methods, such as energy saving in the polymer production process.
Conventionally, technical proposals have been made regarding methods for producing such CHC (see, for example, Non-Patent Documents 1, 2, and 3).

Z. Zhao, J. Qin, C. Zhang, Y. Wang, D. Yuan, Y. Yao, Inorg. Chem. 2017, 56, 4568-4575. K. Tezuka, K. Komatsu, O. Haba, Polymer Journal, 2013, 45, 1183-1187. B. Gabriele, R. Mancuso, G. Salemo, L. Veltri, M. Costa, A. Dibenedetto, ChemSusChem, 2011, 4, 1178-1786.

Carbon dioxide insertion reaction into epoxides is widely known as a method for producing carbonates. In the production of cyclohexene carbonate (CHC), the two CO bonds forming the epoxide group of the corresponding epoxide, cyclohexane oxide, are in the cis configuration with respect to the cyclo ring, so trans cyclohexene carbonate (hereinafter referred to as trans-CHC) is not obtained, and only cis-cyclohexene carbonate (hereinafter referred to as cis-CHC) is produced.

On the other hand, Non-Literature Patent 1 discloses a method for producing trans-CHC from cyclohexane oxide by precisely controlling the steric configuration of a metal complex catalyst with a ligand.
However, since trans-CHC is less stable than cis-CHC, it is difficult to produce it with high selectivity. However, there is a problem that trans-CHC cannot be obtained in high yield. In addition, since trans-CHC easily polymerizes due to its high reactivity, it is impossible to selectively produce trans-CHC monomer from epoxide and carbon dioxide while suppressing heterogeneous polymerization. have.

Non-Patent Documents 2 and 3 disclose a production method using cyclohexanediol as a starting material as a method for geometrically producing trans-CHC.
However, in the production method disclosed in Non-Patent Document 2, the yield of trans-CHC is poor, and a toxic phosgene-derived compound is used as the carbonyl source compound. has the problem of stoichiometric base consumption. Furthermore, there is also the problem that using a halogen-containing compound as a carbonyl source compound is not preferable from the viewpoint of environmental load.
In the production method disclosed in Non-Patent Document 3, it is essential to use an inorganic base and a dehydrating agent in addition to the transition metal catalyst in order to promote the reaction, and the reaction does not occur at all in the absence of the dehydrating agent. I have a problem that it won't progress.
As described above, these conventional methods can produce trans-CHC in a geometrically selective manner, but the yield is low. There is a problem that the manufacturing process becomes complicated.
In other words, no method has been found to obtain trans-CHC or cis-CHC from corresponding raw materials in a geometrically selective manner and in high yield, and its development is desired.

Accordingly, the present invention provides a method for selectively producing a trans- or cis-type alicyclic carbonate monomer from a corresponding alicyclic diol and a halogen element-free carbonyl source compound at a high yield. intended to

As a result of intensive studies in order to solve the above-described problems of the prior art, the present inventors have found that, in the transesterification reaction between an alicyclic diol and a carbonyl source compound, the corresponding alicyclic diol can be obtained by using a given catalyst. The inventors have completed the present invention based on the finding that an alicyclic carbonate having a desired stereostructure can be selectively obtained from a carbonyl source compound and a carbonyl source compound in a high yield.
That is, the present invention is as follows.

[1]
In the presence of a solid catalyst that is at least one metal oxide selected from the group consisting of calcium oxide, magnesium oxide, lanthanum oxide, and zinc oxide ,
a trans-type alicyclic diol having a structure of the following general formula (1);
a carbonyl source compound having a structure represented by the following general formula (2) that does not contain a halogen element in its chemical structure;
A method for producing a trans- alicyclic carbonate, comprising the step of reacting
[2]
The method for producing a trans- alicyclic carbonate according to [1] above, wherein the alicyclic diol is cyclohexanediol.

According to the present invention, a solid catalyst system that exhibits catalytic ability for transesterification reaction suppresses the polymerization reaction of alicyclic carbonate, and geometrically selects from an alicyclic diol and a carbonyl source compound in a high yield. A method for producing an alicyclic carbonate having a desired steric structure can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail.
It should be noted that the present embodiment below is an example for explaining the present invention, and is not intended to limit the present invention to the following contents. The present invention can be carried out with various modifications within the scope of its gist.

[Method for producing alicyclic carbonate]
The method for producing an alicyclic carbonate of the present embodiment includes
In the presence of a solid catalyst,
an alicyclic diol;
a carbonyl source compound that does not contain a halogen element in its chemical structure;
is reacted.

(solid catalyst)
A solid catalyst is used in the method for producing an alicyclic carbonate of the present embodiment.
As the solid catalyst, it is preferable to use a metal oxide that functions as a heterogeneous catalyst that does not dissolve in the reaction solution in the transesterification reaction.
The metal oxide is preferably a compound exhibiting basicity and/or acidity.
In addition, the case where the metal oxide exhibits basicity and acidity means, for example, when the metal oxide is solid, a state in which there are sites exhibiting acidity and sites exhibiting basicity.
Examples of metal oxides include, but are not limited to, calcium oxide, magnesium oxide, lanthanum oxide, zinc oxide, aluminum oxide, cerium oxide, iron oxide, cobalt oxide, silicon oxide, copper oxide, and silver oxide. , gold oxide and the like.
Among these, from the viewpoint of acid-basicity, that is, from the viewpoint of the strength and the number per unit area of active points showing acidity (acid points) and active points showing basicity (basic points) on the solid catalyst, calcium oxide , magnesium oxide, lanthanum oxide, zinc oxide, aluminum oxide, cerium oxide and iron oxide. Basic metal oxides are more preferable from the viewpoint of catalytic activity, and examples of basic metal oxides include calcium oxide, magnesium oxide, and lanthanum oxide.

(material)
In the method for producing an alicyclic carbonate of the present embodiment, an alicyclic diol and a carbonyl source compound containing no halogen element in its chemical structure are used as raw materials.

<Alicyclic diol>
Alicyclic diols include, for example, those represented by the following general formula (1).

(In general formula (1), n is an integer of 1 or more, preferably 1 to 10, more preferably 1 to 6. Further, the alicyclic ring may have a substituent. Two adjacent hydroxy groups may be in either the trans or cis conformation.)

Alicyclic diols used in the present embodiment include, but are not limited to, cyclopentanediol, cyclohexanediol, cycloheptanediol, and cyclooctanediol. Among these, cyclohexanediol is preferable from the viewpoint of product stability.
Alicyclic diols include trans-type and cis-type. of cycloaliphatic carbonate is obtained in the same ratio as the raw materials.
That is, when the alicyclic diol is a trans-alicyclic diol, the production method of the present embodiment selectively yields a trans-alicyclic carbonate in high yield.

<Carbonyl source compound containing no halogen element in chemical structure>
A carbonyl source compound that does not contain a halogen element in its chemical structure used in the present embodiment does not have a halogen element in its chemical formula and has a carbonyl group for forming a carbonate group in the target alicyclic carbonate. Say a compound.
The halogen-free carbonyl source compound includes, but is not limited to, urea, carbon monoxide, carbon dioxide, carbonate compounds, and the like.
Among these, carbonate compounds are preferred from the viewpoint of reactivity.

Examples of carbonate compounds include compounds represented by the following general formula (2).

(In general formula (2), R ₁ and R ₂ represent a hydrocarbon group which may have a substituent, and may be the same or different. R ₁ and R ₂ are bonded to each other. may form a ring together with the carbonyl group shown in general formula (2).)

The hydrocarbon groups represented by R ₁ and R ₂ are not limited to the following, but examples include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and these groups. A group in which two or more are bonded can be mentioned. Preferred are aliphatic hydrocarbon groups having 1 to 4 carbon atoms, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and groups in which two or more of these groups are bonded.
Although the carbonate compound is not limited to the following, from the viewpoint of reactivity, a carbonate compound having an aromatic hydrogen group, such as diphenyl carbonate, is preferable.

(solvent)
The reaction in the method for producing an alicyclic carbonate of the present embodiment is preferably carried out in the presence of a solvent.
Examples of solvents include, but are not limited to, water, hydrocarbon solvents (e.g., toluene, benzene, xylene, pentane, hexane), ether solvents (e.g., tetrahydrofuran, dioxane), and alcohol solvents. (ethylene glycol, ethanol, methanol, t-butanol), amide solvents (dimethylacetamide, acetamide, dimethylformamide, N-methylpyrrolidone) and the like.
Among these, highly polar and high-boiling solvents are preferred, such as dimethylformamide and N-methylpyrrolidone.

(Reaction conditions)
In the alicyclic carbonate production process of the present embodiment, the amount of the solid catalyst used is, for example, based on 1 gram of cyclohexanediol, which is the alicyclic diol starting material, from the viewpoint of the reaction rate and separation of the catalyst after the reaction. , preferably 0.05 grams to 1.0 grams, more preferably 0.05 grams to 0.8 grams, even more preferably 0.1 grams to 0.5 grams.
The amount of the carbonyl source compound that does not contain a halogen element in its chemical structure is, from the viewpoint of yield and isolation of the product after the reaction, relative to the starting alicyclic diol, such as cyclohexanediol, for example, 0.5. Equivalents to 10 equivalents are preferred, more preferably 1.0 equivalents to 4.0 equivalents, and still more preferably 1.1 equivalents to 2.0 equivalents.
The reaction temperature is, for example, preferably 30°C to 250°C, more preferably 30°C to 180°C, still more preferably 90°C to 180°C.
In the production method of the present embodiment, the reaction between the alicyclic diol and the carbonyl source compound can be carried out by a conventional method such as a batch system, a semi-batch system, or a continuous system.
After completion of the reaction, the reaction product, alicyclic carbonate such as CHC, can be separated and purified by separation means such as concentration, distillation, extraction, crystallization, recrystallization, or a combination of these separation means.

EXAMPLES The present invention will be described in detail below with reference to specific examples and comparative examples, but the present invention is not limited by the following examples.

[Example 1]
0.3 g of solid catalyst calcium oxide, 1.0 g of transcyclohexanediol, 3.7 g of diphenyl carbonate (2 equivalents of diphenyl carbonate per 1 equivalent of transcyclohexanediol), 6.5 g of N-methylpyrrolidone were placed in a glass eggplant flask. 0 g was added and stirred at 150° C. for 2 hours to obtain trans-CHC (trans-cyclohexene carbonate) (trans-cyclohexanediol conversion rate: 93.7%, trans-CHC yield: 93.7%, trans-CHC Selectivity: >99%).
The conversion rate of trans-cyclohexanediol and the yield of trans-CHC were measured by an internal standard method using gas chromatography.
The selectivity was calculated by (yield/conversion)×100.
The results are shown in Table 1 below.

(Analysis conditions)
Apparatus Shimadzu Gas Chromatography GC2010
Column DB-1
Conditions injection temperature: 250°C, detection temperature: 250°C
Carrier gas: nitrogen (column flow rate 0.51 mL/min, SP ratio 200)
Detector gas: dry air 400 mL/min, hydrogen 40 mL/min
Heating rate: 40°C (holding for 2 minutes) ~ (5°C/min) ~ 165°C ~ (10°C/
min) to 250°C (held for 35 minutes)
Internal standard Cycloheptanone

[Examples 2 to 4, Reference Examples 5 to 7]
In Examples 2-4 and Reference Examples 5-7, calcium oxide was changed to the metal oxides shown in Table 1 below. Other conditions were the same as in [Example 1] to obtain trans-CHC (trans-cyclohexene carbonate).
The measurement results are shown in Table 1 below.

[Examples 8 to 15]
In Examples 8 to 15, the molar ratio of diphenyl carbonate/transcyclohexanediol (described as DPC/CHDL in Table 2 below) and the reaction temperature were changed to the values shown in Table 2. Other conditions were the same as in [Example 1] to obtain trans-CHC (trans-cyclohexene carbonate).
The measurement results are shown in Table 2 below.

[ Reference Example 16]
In Reference Example 16, cis-cyclohexanediol was used instead of trans-cyclohexanediol. Other conditions were the same as in [Example 1] to obtain cyclohexene carbonate.
In this example, trans-CHC was not produced, and cis-CHC was produced in a yield of 96.0% (
conversion: 96.0%, selectivity: >99%).

[Comparative Example 1]
Sodium methoxide was used instead of calcium oxide.
Other conditions were the same as in [Example 1] to obtain trans-CHC (trans-cyclohexene carbonate).
As shown in the above examples, it is necessary to use a solid catalyst in order to suppress the polymerization reaction and obtain a high yield of carbonate. However, the trans-CHC yield and selectivity decreased as described below.
Yield: 47.5% (conversion: 93.1%, selectivity: 51.0%)

[Comparative Example 2]
500 g of transcyclohexanediol and 5.0 L of 1,4-dioxane were added to a glass eggplant flask and cooled with ice, and 700 g of ethyl chloroformate was added dropwise to the reaction solution.
Subsequently, a solution obtained by diluting 870 g of triethylamine with 2.5 L of toluene was added dropwise and stirred for 1 hour to obtain 303.2 g of trans-CHC (yield: 49.5%).
As shown in this comparative example, when a halogen-containing carbonyl source compound was used, a base was required as a trapping agent, which was an unfavorable example.

The present invention uses a solid catalyst system that exhibits catalytic ability for transesterification to suppress the polymerization reaction of an alicyclic carbonate, while geometrically selective and highly selective from an alicyclic diol and a halogen-free carbonyl source compound. Since an alicyclic carbonate can be obtained in a high yield, it has industrial applicability as a method for producing an alicyclic carbonate monomer.

Claims (2)

In the presence of a solid catalyst that is at least one metal oxide selected from the group consisting of calcium oxide, magnesium oxide, lanthanum oxide, and zinc oxide ,
a trans-type alicyclic diol having a structure of the following general formula (1);
a carbonyl source compound having a structure represented by the following general formula (2) that does not contain a halogen element in its chemical structure;
A method for producing a trans- alicyclic carbonate, comprising the step of reacting

(In general formula (1), n is an integer of 1 or more and 10 or less . Further, the alicyclic ring may have a substituent.)

(In general formula (2), R ₁ and R ₂ represent a hydrocarbon group which may have a substituent and may be the same or different. R ₁ and R ₂ are may be combined to form a ring together with the carbonyl group shown in general formula (2).) 2. The method for producing a trans- alicyclic carbonate according to claim 1 , wherein the alicyclic diol is cyclohexanediol.