JPS6015605B2 - Manufacturing method of ethylene glycol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing ethylene glycol from a mixture of carbon monoxide and hydrogen.

According to the present invention, ethylene glycol can be efficiently produced under relatively mild conditions.

Conventionally, many methods using rhodium-based catalysts have been proposed as one method for directly producing alkane polyols, particularly ethylene glycol, by reacting carbon monoxide and hydrogen.

Rhodium has superior catalytic activity compared to other metals in the production of ethylene glycol, but since rhodium metal is expensive, it is necessary to limit the ethylene glycol production rate per unit rhodium atom, and to make rhodium more efficient. Recovery and recycling are important issues for the practical application of this process. One important factor for solving the above-mentioned problems is considered to be the selection of a reaction solvent, and several methods have been proposed from this point of view. For example, JP-A No. 51-32507 uses butyrolactone and 6-valerolactone solvents, JP-A No. 51-88902 uses dimethylsulfone or tetramethylene sulfone solvent, and Mokoseki No. 52-42808 uses tetraclyme and sulfolane. The mixed solvent of
No. 242 proposes the use of a crown ether solvent. However, in a reaction system containing only rhodium metal compounds and these solvents, the production of ethylene glycol is hardly observed at reaction pressures below 1000 k9', and there is usually no means to increase the yield of ethylene glycol within the reaction pressure range mentioned above. Organic nitrogen ligands such as N, N, N', N'-tetramethylethylenediamine (e.g., Tokusekki Publication No. 48-6850) or alkali metal cations (e.g., Tokusekki No. 51-36406) ) etc. have been proposed as a promoter. Furthermore, W
．． Kejm et al. is Jo Yamahada of Catal$is, 61
, 359-365 (1980) reported the results using N-methylpyrrolidinone solvent, but the results were carried out under harsh conditions with a reaction pressure of 2000 bar. In view of the importance of the reaction solvent in this reaction system, the present inventors conducted a wide range of solvent studies, and found that a specific N-alkyl cyclic carboxylic acid amide was used as the reaction solvent even in a system in which the above cocatalyst was not present. Surprisingly, the present invention was completed based on the discovery that alkane polyols, especially ethylene glycol, can be efficiently produced under relatively mild reaction pressure conditions.

That is, the present invention provides a method for producing ethylene glycol by reacting carbon monoxide and hydrogen in the presence of a rhodium-based catalyst.
The present invention provides a method for producing ethylene glycol, which is characterized by using a mountain alkyl cyclic carboxylic acid amide.

Examples of N-alkyl cyclic carboxylic acid amides having 6 or more carbon atoms in the molecule used in the method of the present invention include N-alkylpyridinones, N-alkyl-6-valerolactams, N-alkyl-go-caprolactams, etc. I can give an example.

More specifically, N-ethylpyrrolidinone, N-normalpropylpyrrolidinone, N-isopropylpyrrolidinone, N-normalbutylpyrrolidinone, N-isobutylpyrrolidinone, N-tert-butylpyrrolidinone,
N-normalbentylpyrrolidinone, N-neobentylpyrrolidinone, N-(1,1,3,3-tetramethyl)
Butylpyrrolidinone, 1,5-dimethylpyrrolidinone,
1-methyl-5-ethylpyrrolidinone, N-methyl-6-
Valerolactam, N-isopropyl-6-valerolactam, N-methyl-6-valerolactam. Examples include rolactam and N-isopropyl-cabrolactam. Among these, N-ethylpyrrolidinone, N-n-butylpyrrolidinone, N-inbutylpyrrolidinone, N-tert-butylpyrrolidinone, 1., N-/
Preferred are rumalbentylpyrrolidinone, N-neobentylpyrrolidinone, N-(1,1,3,3-tetramethyl)butylpyrrolidinone, 1,5-dimethylpyrrolidinone, and 1-methyl-5-ethylpyrrolidinone. The N-alkyl cyclic carboxamide used in the present invention can be used as long as the number of carbon atoms in the molecule is 6 or more, but if the number of carbon atoms is too large, the amide will have a high melting point or become hydrophobic, and is generally not used. Since the properties as a solvent change, a carbon number of 6 to 20 is particularly preferable. In addition to using only N-alkyl cyclic carboxylic acid amides having 6 or more carbon atoms in the molecule used in the method of the present invention, other solvents such as chain ethers such as tetraglyme, 18-
Crown ethers such as Crown-6, sulfolane,
It can be used in combination with sulfones such as dimethylsulfolane and lactones such as y-butyrolactone and 6-valerolactone.

In this case, the concentration of the pyrrolidinones in the mixed solvent is 10 to 10 percent by weight. The present invention is characterized in that it provides a high rate of production of alkane polyols, particularly ethylene glycol, and a high selectivity for ethylene glycol under relatively mild reaction conditions. A further noteworthy point is that the rhodium compound supplied to the reaction system can be recovered as rhodium metal after the reaction is completed without being deposited inside the reactor and inactivated.

Further, the form of the rhodium compound used as a catalyst in the method of the present invention can be any form, such as rhodium oxide, hydroxide, formic acid,
Examples include organic acid salts such as acetic acid and propionic acid, and metal rhodium.

Furthermore, it is also possible to use a rhodium carbonyl body having a complex bond with carbon monoxide or carbon monoxide and hydrogen. These rhodium carbonyl coin bodies include so-called rhodium carbonyl clusters, rhodium hydride carbonyl clusters, and the like. For example, dirhodium octacarbonyl, tetrarhodium dodetricarbonyl, hexalodium hexadetetracarbonyl, rhodium trisacetylacetonate, rhodium carbonylacetylacetonate and [Rh(CO)4]-, [R
~(CO),5]2-,[R~(CO),4]4-,[
Rh7 (C.) 16] 3-, [Rhne (C.) 30] 2
-, [Rh6(CO),51]-, [R~(CO),5
C] Salts with organic or inorganic cations such as 2- can be mentioned. Moreover, an organic or inorganic Lewis base promoter can be used as a cocatalyst in the above-mentioned rhodium compound, if necessary. The concentration of the rhodium-based catalyst used in the method of the present invention can be selected arbitrarily, but from the viewpoint of reaction rate and economical efficiency, the concentration of rhodium atoms in the reaction solvent is usually 1 to 1 x 10-6 gram atom/s. , preferably in the range of 1 x 10-1 to 1 x 10-5 gram atoms per gram atom.

In the method of the invention, the reaction is carried out under heated and pressurized conditions.

The reaction pressure is usually 1, 2000k9/G,
Preferably it is in the range of 30 none to 1000k9/earth. The method of the present invention is characterized by a large yield of ethylene glycol without the use of a cocatalyst under relatively low pressure, which is neither expected nor suggested by known techniques, and in addition, the selectivity of ethylene glycol is high. At this time, the ratio of carbon monoxide and hydrogen supplied to the reaction system as raw material gas for ethylene glycol production is usually 0.05 to 2, preferably 0.1 or less, as a molar ratio of carbon monoxide to hydrogen gas. , and 10. In addition, the reaction temperature is usually 50 to 350 qo, preferably 10
The reaction time used is usually 0.1 to 2 lull hours, preferably 0.3 to 1 lull hour. The reaction products obtained in the method of the present invention include, in addition to alkane polyols such as ethylene glycol, propylene glycol, and glycerin, monoalcohols such as methanol and ethanol, and their formic acid or acetate esters.

As a method for separating the target alkane polyol from these reaction products, known techniques such as distillation and extraction can be used. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 In a Hastelloy C autoclave with an internal volume of 100,
20 of N-isopropylpyrrolidinone, and 0.
Eight milligram atoms of tetrarhodium dodecacarbonyl were encapsulated.

After installing this autoclave in a heating furnace, a mixed gas with a molar ratio of carbon monoxide to hydrogen of 1:1 was introduced and exhausted several times from the gas introduction pipe to replace the gas in the system, and the gas in the system was replaced. The mixed gas was charged so that the charging pressure was 450 kg'G. The reaction temperature was set at 240 oo, and the reaction was carried out for 1 hour from the time when the inside of the reaction system reached that temperature. During that time, the reaction pressure reached a maximum of 660k9/G, and decreased to 605k9/G just before the reaction stopped. After the reaction was completed, the autoclave was cooled to room temperature, gas components were released, and the liquid product was recovered.

When this liquid product was quantitatively determined by gas chromatography, it was found that ethylene glycol was 15.82 mmol.
11.03 mmol of methanol was produced. In addition, small amounts of 1,2-propanediol, ethanol, and methyl formate were detected in the liquid product, and small amounts of methane and carbon dioxide were detected in the gas components. Furthermore, when the rhodium in the liquid product was quantified, it was found that more than 98% of the charged rhodium was recovered. Example 2 - The reaction was carried out in the same manner as in Example 1, except that the reaction solvents shown in Table 1 were used.

However, the charging pressure of the reaction gas is 280k9/block○, the reaction time is 4 hours, and the maximum pressure reached during the reaction is 400-410k9/
It was my enemy. The results are shown in Table 1. Table 1 Example 8 The same reaction as in Example 4 was carried out except that 0.8 milligram atom of rhodium dicarbonylacetylacetonate was used as the catalyst.

As a result, 5.83 mmol of ethylene glycol and 6.27 mmol of methanol were produced in the product liquid.
Comparative Examples 1 to 5 Reactions were carried out in the same manner as in Example 1, except that the reaction solvents shown in Table 2 were used.

The results are shown in Table-2. In all solvent systems, the production of ethylene glycol was less than a trace amount. still,
In Examples 1 to 8, the reaction solutions were all recovered as homogeneous solutions, but in Comparative Examples 1 to 5, black precipitates that appeared to be metallic rhodium were formed, and the rhodium dissolved in the solvent was 15% of the charged rhodium. It was below. Table 2 Comparative Example 6 In Example 1, 7.5 M of N-isopropylpyrrolidinone and 0.1 milligram atom of Rh3(CO
), 2, the reaction pressure was 568 k9/c fin G, and the reaction time was 2 hours, but the reaction was carried out in the same manner as in Example 1.

Claims (1)

[Claims] 1. A method for producing ethylene glycol by reacting carbon monoxide and hydrogen in the presence of a rhodium-based catalyst, characterized in that an N-alkyl cyclic carboxylic acid amide having 6 or more carbon atoms in the molecule is used as a reaction solvent. A method for producing ethylene glycol.