JPS606930B2 - Manufacturing method of ethylene glycol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a completely new method for efficiently producing ethylene glycol.

More specifically, the present invention relates to a method for efficiently producing ethylene glycol from methanol by photocatalytic reaction. Ethylene glycol is a basic chemical product that is industrially important and in high demand as a raw material for polyester, an organic solvent, a non-volatile antifreeze agent, a coolant, etc.

This ethylene glycol is currently produced by a petrochemical method using ethylene as a raw material. However, due to the recent sharp rise in oil prices and the depletion of oil resources, there is an urgent need to convert chemical products currently derived from oil to a method of producing them from raw materials other than oil. Methods for producing ethylene glycol from raw materials other than petroleum include natural gas whose main component is methane, synthetic gas that can be easily obtained from coal, etc., which is present in larger quantities than petroleum, and formaldehyde derived from it. Many methods for producing ethylene glycol using a compound having 1 carbon atom as a raw material have been proposed so far.

For example, a method for producing ethylene glycol directly from synthesis gas in the presence of a rhodium catalyst (Japanese Patent Application Laid-Open No. 50-13211
No. 7, No. 51-32507, etc.) have been developed.

However, this method needs to be carried out under high pressure of 50 p atm or more, and is difficult to implement industrially. Many methods using formalin or its derivatives as raw materials have also been proposed. For example, a method to obtain ethylene glycol by reacting formaldehyde with synthesis gas (Tokukan Sho 51-12890
No. 3, No. 53-53607) is known, but the selectivity for ethylene glycol is low and the yield relative to formalin is 40%.
% or less. Furthermore, a method of reacting the secondary acetal of formaldehyde with synthesis gas to produce ethylene glycol monoether and then obtaining ethylene glycol by hydrolysis (Mochiseki Sho 56-1118026), copolymerization of formaldehyde and carbon monoxide A method is known in which ethylene glycol is produced by solvolyzing the resulting polymer with alcohol to obtain a glycolic acid ester, and hydrogenating this (Japanese Patent Application Laid-Open No. 106408/1989, etc.). The reaction needs to be carried out under high pressure in the presence of carbon monoxide or synthesis gas, and there are many points to be improved, such as the large number of reaction steps and insufficient selectivity, making it difficult to carry out industrially. Met. On the other hand, there is also a method in which formaldehyde and carbon monoxide are reacted in concentrated sulfuric acid in the presence of copper carbonyl at room temperature and pressure, and then treated with methanol to form methyl glycolate, which is then hydrogenated to obtain ethylene glycol (Soma Yoshie, Hiroshi Sano, Catalyst 23 48 (1981)), but this method also involves many reaction steps and uses a large amount of sulfuric acid, which is difficult due to its corrosivity and troublesome disposal. on the other hand,
A few methods have been proposed for producing ethylene glycol using methanol as a raw material, and these are expected to be more economically advantageous than methods using formaldehyde derived from methanol as a raw material.

As such a method, for example, a method for producing ethylene glycol by coupling a methanol transferor is known. That is, there is a method in which the hydroxyl group of methanol is protected with a trialkylsilyl group, and then 1,2-bis(trialkylsiloxy)ethane is obtained by a coupling reaction with an organic peroxide, and then ethylene glycol is obtained by methanolysis. However, this method is also complicated, including a large number of reaction steps and the use of trialkylsilyl groups and organic peroxides, and there are still many problems to be solved as a method for industrial implementation. The present inventors have discovered the drawbacks of such conventionally known methods for producing ethylene glycol,
As a result of various studies to overcome these problems, it was discovered that ethylene glycol can be obtained directly and efficiently in a one-step reaction by irradiating methanol with light in the presence of a specific catalyst at room temperature and pressure. Based on this finding, the present invention has been completed. That is, the present invention provides a method for producing ethylene glycol, which is characterized in that methanol is irradiated with light in the presence of rhodium rust and acetone.

The reaction of the method of the present invention is represented by the following formula.

Light2CH30H--HOCH2CH20H+day2catalyst In the method of the present invention, a rhodium chain body is used as a catalyst.

This rhodium body is a mononuclear substance characterized by having rhodium coordinated with at least one selected from phosphorus compounds such as phosphines, halogens, and carbon monoxide as a ligand. Or it means a dinuclear rust body, and specific examples include chlorotristriphenylphosphine rhodium, bromotrystriphenylphosphine rhodium, chlorocarponylbistriphenylphosphine rhodium, 1,5
Examples include -cyclooctadiene bistriphenylphosphine rhodium (1) perchlorate, /rubornadiene bistriphenylphosphine rhodium (1) tetrafluoroborate, and tricarbonyl bis(acetato)triphenylphosphine rhodium. When carrying out the method of the present invention, the rhodium ring precursor and the ligand (for example, triphenylphosphine) are directly mixed under the reaction conditions without adding the rhodium ring body to the reaction system from the beginning. The catalytically active species may be generated by Examples of such rhodium ring body precursors include dichlorotetracarbonyl dirhodium, chlorobiscycloocten rhodium, and dichlorodinorbornadiene dirhodium. In addition, as a phosphine as a ligand of a rhodium complex, triphenylphosphine is exemplified as a representative example, but of course it is not limited to this, and the general formula (wherein R, , R2 and R3 are monovalent A phosphine represented by (indicating a lipophilic group or an aromatic group, respectively) can be used as a ligand.

In the above phosphine, the substituent R. , R2 and R3 may be different from each other, but are preferably the same for economical reasons. Suitable aliphatic substituents include methyl, ethyl, propyl, butyl, octyl, dedecyl, 8-phenylethyl, cyclohexyl, cyclooctyl groups, and the like. In addition, as aromatic substituents,
Tolyl, xylyl, p-ethyl phenyl, p-te-
Examples include butylphenyl, p-octylphenyl, p-methoxyphenyl, p-chlorophenyl, p-fluorophenyl, m-trifluoromethylphenyl, 2-naphthyl group, and the like. Further, as a phosphine ligand, diphosphine represented by the general formula (in which R4, R5, R6 and R7 are aliphatic or aromatic groups, and n is an integer of 1 to 10) is also effective in the present invention.

Examples of this diphosphine include bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino/)propane, and 1,4-bis(diphenylphosphino)propane. )butane,
1,5-pis(diphenylphosphino)pentane, 1,
6-pis(diphenylphosphino)hexane, 1,4-bis(dicyclohexylphosphino)butane, 1,4-
Examples include bis(dibutylphosphino)butane.
Under the reaction conditions, the catalysts exemplified above may simultaneously form different active species other than those mentioned above, but these do not impair the reaction of the present invention.

There is no particular limit to the amount of rhodium body used, but it is 5.0X
A range of IO-2 to 1 x 10-3 mmol/mol-methanol is preferred.

If this amount is too small, the reaction rate will be insufficient, and if it is too large, the effect will not be sufficient. Next, in the present invention, it is necessary to carry out the reaction in the presence of acetone, and the amount of acetone added is 1.4 × 10-4 mol ~
A range of 1 mol/mol methanol is preferred.

As the irradiation light in the present invention, a wide range of white light or monochromatic light ranging from ultraviolet light to visible light can be used, but white light generated from a mercury lamp is preferably used.

The light irradiation time varies depending on the irradiation conditions such as the intensity of the light source and the irradiation distance, the reaction capacity, etc., but is usually in the range of 1 to 2 hours. In the present invention, the reaction is usually carried out at room temperature, but may be heated or cooled if necessary, and the temperature range is from 1970 to 65 qo, preferably from 0 to 60 oo.

In this case, if the temperature is too low, the reaction rate will be insufficient, and if the temperature is too high, it will exceed the boiling point of methanol, which is not desirable. As described above, according to the method of the present invention, ethylene glycol can be easily produced from methanol at room temperature and under normal pressure with good yield and selectivity by irradiating methanol with light in the presence of a rhodium key body and acetone. Since the reaction proceeds in one step and is not complicated, it is of great significance as it provides a method for producing ethylene glycol based on a completely new reaction system.

Next, the present invention will be explained in more detail based on Examples and Comparative Examples.

Example 1 302 methanol (9.4 mol), acetone 15.8 mol (0.27 mol) and chlorotristriphenylphosphine rhodium (RhCl Pph3)3
) 40-9 (0.041 mmol) and stirred for 30 minutes.

Next, while stirring the reaction solution, light irradiation was started from a 100 W high-pressure mercury lamp, and the reaction was carried out for 6 hours.
The reaction temperature was maintained at 220°C using a temperature bath. After the reaction was completed, the reaction solution was analyzed and found that ethylene glycol was 3.
It was found that 7 yen (6th place hmol) was produced. Example 2 Using the same reaction vessel as in Example 1, 302 methanol (
9.4 mol), acetone 15.8 mol (0.27 mol)
) and chlorotritriphenylphosphine rhodium 1
00 female (0.1 mmol) was added and stirred for 1 hour.

Next, while stirring the reaction solution, irradiation was started using a 100 W high-pressure mercury lamp, and the reaction was carried out under light irradiation for 1 hour and 30 minutes. During this time, the reaction temperature was maintained at 220°C using a temperature bath. After the reaction was completed, the product was taken out and analyzed, and it was found that 6.6 units (108 hmol) of ethylene glycol had been produced. Example 3 Using the same reaction vessel as in Example 1, 238.2 m of methanol (7.4 m
ol), acetone 79.2 mol (1.4 mol) and chlorotristriphenylphosphine rhodium 40 9 (0
．． 041 mmol) and stirred for 1 hour.

Next, while stirring the reaction solution, light irradiation was started using a 100 W high-pressure mercury lamp, and the reaction was carried out for 6 hours.
The reaction temperature was maintained at 220°C using a constant temperature bath. After the reaction was completed, the product was analyzed and found to be ethylene glycol 4.7 hours (7 hours).
It was found that 8 hmol) was produced. Example
4 Using the same reaction vessel as in Example 1, add 3 methanol to it.
02 mol (9.4 mol), acetone 15.8 mol (0.2 mol)
7 mol) and chlorocarbonylbistriphenylphosinrhodium (RhC○CI(Pph3)2) 74.7
Female (0.1 mmol) was added and stirred for 1 hour.

Next, while stirring the reaction solution, irradiation was started using a 100 W high-pressure mercury lamp, and the reaction was carried out under light irradiation for one hour. During this time, the reaction temperature was maintained at 0 using a constant temperature bath.
After the reaction was completed, the product was analyzed and it was found that 4.15 mmol (67 mmol) of ethylene glycol was produced. Comparative Example 1 Using the same reaction vessel as in Example 1, methanol 3
18 min (9.9 hol) and chlorotriphenylphosphine rhodium 40 part (0.041 mmol) were added and stirred for 1 hour.

Next, while stirring the reaction solution, irradiation was started using a 100 W high-pressure mercury lamp, and the reaction was allowed to proceed for 6 hours under irradiation. The reaction temperature was maintained at 220'. After the reaction was completed, the reaction solution was analyzed, but no formation of ethylene chloride was observed. Comparative Example 2 Using the same reaction vessel as in Comparative Example 1, 320 ghol of methanol and 16 g of acetone were added to it.
．． 0 (2.8 × 10-l mol) and chlorotristriphenylphosphine rhodium 40 (0.041 mm)
ol) without light irradiation (i.e., by fat reaction)
The reaction solution was stirred for 6 hours.

The reaction temperature was maintained at 2°C. After the reaction was completed, the product was analyzed, but no production of ethylene glycol was observed. The reaction conditions and results of Examples 1 to 4 and Comparative Examples 1 to 2 are summarized in the following table.

(Reaction temperature: 22℃)

Claims (1)

[Claims] 1. A method for producing ethylene glycol, which comprises irradiating methanol with light in the presence of a rhodium complex and acetone.