JPS6024775B2 - Manufacturing method of ethylene glycol - Google Patents

Description

[Detailed description of the invention] The present invention involves reacting carbon monoxide and hydrogen with
The present invention relates to a method for producing ethylene glycol.

According to the present invention, it is possible to efficiently produce ethylene glycol under relatively pressure.

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. Regarding the production of ethylene glycol, rhodium has superior catalytic activity compared to other metals, but since rhodium metal is expensive, it is necessary to increase the rate of ethylene glycol production per unit rhodium atom.
Furthermore, efficient recovery and recycling of rhodium is an important issue 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, in Mochiseki No. 51-32507, y-butyrolactone and 6-valerolactone solvents are
In the 1980 Ichiiso No. 902 publication, dimethyl sulfone or tetramethylene sulfone solvent was used,
In Publication No. 8, a mixed solvent of tetraglyme and sulfolane is
Furthermore, Japanese Patent Application Laid-Open No. 124204 proposes the use of a crown ether solvent. However, in a reaction system containing only rhodium metal compounds and these solvents, 1000k
Almost no production of ethylene glycol is observed at reaction pressures below 9/1/2, and N.N.
A method using organic nitrogen ligands such as N'/N'-tetramethylethylenediamine (e.g., Tokusekki No. 48-Fuku 50y), alkali metal cations (e.g., JP-A-51-36403), etc. as promoters. is proposed.
Furthermore, W. Keim et al.
N- in l侭is, 61, 359-365 (1we0)
Although the results using methylpyrrolidine solvent were reported, they were carried out under harsh conditions with a reaction pressure of 2000 bar. The present inventors realized the importance of the reaction solvent in this reaction system and conducted a wide range of solvent studies, and found that even in systems where the above-mentioned cocatalyst is not present, it is possible to use N-alkylureas as the reaction solvent. Surprisingly, the inventors found that ethylene glycol could be efficiently produced under relatively mild reaction pressure conditions, and completed the present invention.

That is, the present invention provides a method for producing an alkane polyol by reacting carbon monoxide and hydrogen in the presence of a rhodium-based catalyst, which is characterized by using N-alkylureas as a reaction solvent. It is on offer.

The N-alkylureas used in the present invention include tetraalkylureas represented by the following general formula '11, provided that:
R,, R2, R3, R4 are respectively C, ~6 aliphatic hydrocarbons and N-alkylalkylesoureas represented by the general formula (2), provided that R,, R2 are C, ~6 aliphatic hydrocarbons, respectively. Hydrogen, n=an integer of 2 to 4.

More specifically, N・N・N′・N′-tetramethylurea, N・N・N′・N′-tetraethylurea, N・N
・N′・N′-tetrabropylurea, N・N・N′・N
'-tetra(n-butyl)urea, N・N-dimethyl, N
', N'-dimethyl urea, N, N'-dimethyl ethylene urea, N, N'-dimethyl ethylene urea, N, N'-diisopropylethylene urea, N-methyl, N'-isopropylethylene urea, Examples include N.N'-dimethylpropylene urea and N.N'-dimethylpropylene urea. Among these, N.N.N'.N'tetramethylurea, N.N'-dimethylimidazolidinone, etc., which are generally considered to be easily available industrially, are particularly preferred. Furthermore, when using these solvents, they can also be used as a mixed solvent system with other solvents such as tetragraphime, sulfolane, y-butyrolactone, crown ethers, and the like. In this case, the concentration of the ureas in the mixed solvent ranges from 5 to 10 weight percent, more preferably from 10 to 10 weight percent. The present invention is characterized in that it provides a high rate of production of alkane polyols, especially ethylene glycol, and high selectivity for ethylene glycol under relatively mild reaction conditions.

A further point to be noted is that the rhodium compound supplied to the reaction system is recovered as rhodium metal after the reaction is completed without being deposited inside the reactor and inactivated. As the rhodium-based catalyst used in the method of the present invention, any catalyst can be used as long as it does not go beyond the spirit of the present invention, and specifically, rhodium acids, hydroxides, formic acid, Organic carboxylic acid salts such as acetic acid and propionic acid,
Metals such as rhodium can be listed.

Furthermore, it is also possible to use rhodium carbonyl fins with rust bonds with carbon monoxide or carbon monoxide and hydrogen. These rhodium carbonyl chains include so-called rhodium carbonyl clusters, rhodium hydride carbonyl clusters, and the like. For example, dirhodium octacarbonyl, tetrarhodium dodetricarbonyl, hexalhodium hexadelphonyl, rhodium trisacetylacetonate, rhodium carbonylacetylacetonate and [Rh(CO)4]-, [Rh(CO)4] ,5]2-,[Rh6(CO),4]4-[R
h7 (CO), 6] 3-, [Rh, 2 (CO) ■] 2-
, [Rh8(CO),51]-, [Rh6(CO),5
Examples include salts with organic or trout cations such as C]2-. 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 arbitrarily selected, but from the viewpoint of reaction rate and economy, the concentration of rhodium atoms in the reaction solvent is usually from 1 to 1 x 10-6 grams. atom/s, preferably 1×10
-1 is used in the range of 1 x 10-5 gram atom/s.

At this time, the N-alkylurea used in the method of the present invention, which is a reaction solvent for solubilizing or suspending the rhodium compound, may be used alone or in combination with other organic solvents as long as the effect of the solvent is not impaired. Can be used as a solvent. In the method of the invention, the reaction is carried out under heated and pressurized conditions.

The reaction pressure is usually 1 or less, and 2000k9/mass G,
Preferably, the G range is between 30 and 1000 k9'. The method of the present invention is characterized in that the yield of ethylene glycol is large even without the use of a promoter under relatively low pressure, and the selectivity of ethylene glycol is high. The ratio of carbon monoxide and hydrogen gas supplied to the reaction system as the raw material gas for producing ethylene glycol of the present invention is usually 0.05 to 20, preferably 0.05 to 20, as a molar ratio of carbon monoxide to hydrogen gas. .1 to 10.

Further, the reaction temperature is usually in the range of 50 to 35 qo, preferably 120 to 300 qo, and the reaction time is usually 0.1 to 20 hours, preferably 0 qo.
．． A range of 3 and 10 hours is used. The reaction products obtained in the method of the present invention include alkane polyols such as ethylene glycol, propylene glycol, and glycerin, monoalcohols such as methanol and ethanol, and esters of these alcohols with formic acid, acetic acid, etc. is included.

As a method for separating the target ethylene glycol from these reaction products, known methods such as distillation and extraction can be used. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative 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,
Twenty units of N.N.N'.N'-tetramethylurea and 0.8 milligram atoms of tetradium 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 was heated to room temperature. The mixed gas was charged so that the charging pressure was 280k9/c. The reaction temperature was set at 20,000 ℃, and the reaction was carried out for 4 hours from the time when the temperature in the reaction system reached 200 qo. After the reaction was completed, the autoclave was cooled to room temperature, gas components were released, and the liquid product was recovered.

As a result of quantifying this by gas chromatography,
4.51 mmol of ethylene glycol, 2.
11 mmol was produced. Traces of ethanol, methyl formate, and 1,2-propanediol were also detected in the liquid product, and traces 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 a fraction of the rhodium charged was recovered. Examples 2 to 5 As shown in Table 1, the reaction solution was converted from N・N・N′・N′-tetramethylurea of Example 1 to N・N′-dimethylimidazolidinone and N・N′-diethylimidazolidinone. , N.N'-dimethylbropyleneurea and N.N.N'.N'-tetraethylurea 1
An experiment was carried out in the same manner as in Example 1, except that the mixed solvents were changed to 0' and y-butyrolactone, respectively, and the results shown in Table 1 were obtained.

Table 1 Example 6 The same reaction as in Example 1 was carried out except that 0.8 milligram atom of rhodium dicarponylacetylacetylacetonate was used as the catalyst.

As a result, the resulting liquid contained 4.37 mmol of ethylene glycol and 2.3 mmol of methanol. Spots were forming. Comparative Examples 1 to 5 Except for using tetraglyme, y-butyrolactone, sulfolane, 18-crown-6, and pyridine as shown in Table 2 as reaction solvents,
Experiments were conducted using the method described in Example 1.

As shown in Table 2, ethylene glycol was produced in trace amounts or less in all solvent systems. still,
In Examples 1 to 6, 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'N・N' was used as the reaction solvent.
-dimethylimidazolidinone, using 0.1 milligram atoms of Ru3(CO),2 as catalyst, reaction pressure 561
The reaction was carried out in the same manner as in Example 1, except that the reaction temperature was 230° C. and the reaction time was 2 hours.

Claims (1)

[Claims] 1 In a method for producing ethylene glycol by reacting carbon monoxide and hydrogen in the presence of a rhodium catalyst, N
- A method for producing ethylene glycol, characterized in that an alkyl urea is used as a reaction solvent.