JPS62142129A - Recovery of alcohol - Google Patents

Abstract

PURPOSE:When alcohol is recovered from a lower aliphatic alcohol solution containing surlfuric acid, the distillation is carried out in the presence of a certain or more amount of water based on the sulfuric acid to facilitate the recovery of alcohol almost free from ether. CONSTITUTION:In the recovery of a lower aliphatic alcohol such as methanol, ethanol, propanol, or butanol from a sulfuric acid-containing aliphatic alcohol with is used as a reaction solvent or reaction substrate, the distillation is conducted, after water is added to the distillation system in an amount of 0.3 or more, preferably 0.3-9pt.wt. per 1pt.wt. of the sulfuric acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering alcohol used in a reaction as a reaction solvent or a reaction substrate.

Specifically, in the presence of a reducing catalyst in a sulfuric acid-alcohol reaction medium, catalytic hydrogenation of an aromatic nitro compound by Pamberger rearrangement reaction or electrolytic reduction is carried out, in which alcohol is converted into a reaction solvent and a reactive group. When producing methoxyanilines etc. by reaction, or in the production method of N-acylphenylalanine using N-acyl-β-phenylserine as a raw material, lower aliphatic alcohol is used as a solvent to make the reaction proceed smoothly. The present invention relates to an efficient method for recovering alcohol containing sulfuric acid, which is obtained by adding DQ with an acid such as sulfuric acid or hydrochloric acid and performing a catalytic reduction reaction in the presence of a reduction catalyst.

The invention attempts to understand the conventional technology. Point 1: Recovery of the alcohol solution used as the source medium is usually carried out by simple distillation or distillation equipment equipped with a rectification column to recover and distill the aliphatic alcohol. When an alcohol solution containing sulfuric acid is subjected to recovery distillation, an ether compound in which two molecules of alcohol are combined is detected in the distilled alcohol.

In particular, in order to increase the recovery rate of alcohol, it is necessary to raise the temperature inside the distillation can, and if distillation is carried out at a high temperature, the amount of ether compounds in the distilled alcohol will reach several to ten-odd parts.

The reason for the formation of ether is firstly due to the reaction shown in equation (1), which generates the corresponding acidic sulfuric ester in the alcohol solution.Furthermore, when a large amount of alcohol is present, ether is formed by the reaction shown in equation (2). Since this reaction tends to proceed when heat is applied, a non-negligible amount of ether is produced over time due to heating during the distillation operation.

R-O8O20H+ R-OH→Todo R+ H2SO4
(2) If ether is contained in the alcohol recovered in this way, it becomes difficult to reuse the alcohol, and since highly volatile ether is mixed in the alcohol, its flammability increases, making it difficult to recover. It becomes difficult to ensure the safety of the entire facility that uses alcohol.

In order to prevent the formation of this ether, that is, the contamination of ether in the recovered alcohol, distillation is carried out under reduced pressure and the temperature in the distillation vessel is lowered to suppress the reaction shown in the equation (2) and to reduce the alcohol recovery rate. Lower the temperature of the still,
There are methods of suppressing the reaction of formula (2), but for example, in the former case, distillation equipment becomes expensive, and in the latter case, the amount of alcohol lost increases, which is disadvantageous in economic efficiency.

Means for Solving the Problems As a result of intensive study on a method for recovering alcohol by distillation from an alcoholic solution containing sulfuric acid, the inventors found that They discovered that the production of ether was suppressed by distilling a predetermined amount of water for 8 times, thereby completing the present invention.

That is, the present invention is a coal recovery method for recovering alcohol from a lower aliphatic alcohol solution containing sulfuric acid by distillation.

In the method of the present invention, the sulfuric acid-containing alcohol solution to be subjected to distillation may be the reaction mass in which the product is dissolved in the alcohol solution after completion of the reaction, or the product may be separated from the reaction mass by liquid separation or the like. Any alcohol solution may be used. Distillation can be carried out either continuously or batchwise at the boiling point of the solution under normal pressure, or it can be carried out after diluting the solution by adding water in advance, or water or steam can be directly poured into the distillation vessel. Distillation may be carried out with continuous charging.

For methanol solutions that do not form an azeotrope with water, the present invention is a particularly efficient method for methanol recovery.

In this case, the amount of water added to the solution is at least 0.3 times by weight, preferably 0.5 to 9 times by weight, more preferably 0.3 to 9 times by weight, and more preferably It is added within the range of 0.6 to 8 times the weight and subjected to distillation.

If the water content during distillation is less than 0.3 times the weight of the sulfuric acid in sulfuric acid and/or monomethyl sulfate, the effect of suppressing ether will be poor, and even if a large amount of water, 9 times the weight or more, is added, ether will not be suppressed. Although the effect is the same, the distillation efficiency decreases, so it is not a good idea.

In the case of other alcohols that form an azeotrope with water, in the batch distillation method, all of the alcohol in the solution to be distilled is distilled out, and 0.3% by weight based on sulfuric acid and/or acidic sulfuric ester in the solution is used. It is preferable to carry out distillation by adding at least twice as much water from the beginning.

In the continuous distillation method, water is continuously charged into the distillation column during distillation so that water is present at least 0.3 times the weight of sulfuric acid and/or acidic sulfuric ester in the solution to be distilled. good.

If the aqueous alcohol solution after distillation has a low concentration due to its azeotropic composition, it is optional to further distill the alcohol to a higher concentration.

Actions and Effects When recovering alcohol containing sulfuric acid used as a reaction medium during a chemical reaction by distillation, if batch distillation is performed, the ether concentration in the recovered alcohol is below the detection limit at the start of distillation, but gradually increases. It increases to several coefficients to several tens of coefficients at the end of the period.

In addition, in the case of continuous distillation, after adding at least 0.3 times the weight of water to the sulfuric acid content in the alcohol solution and/or the sulfuric acid content in the acidic sulfuric ester, it is added to the sulfuric acid content in the alcohol solution and/or the sulfuric acid content in the acidic sulfuric ester, and then The above alcohol solution is continuously charged and distillation operation is performed at normal pressure. When the recovered alcohol obtained by distillation is analyzed by gas chromatography, the ether concentration in the recovered alcohol is always below the detection limit, regardless of the alcohol recovery rate. On the other hand, if water is not added to the alcohol solution and a similar continuous distillation operation is performed, the ether concentration in the recovered alcohol will reach the detection limit when the alcohol recovery rate is low (i.e., when the temperature inside the still is low). As shown below, when the alcohol recovery rate is increased and alcohol is present in the distillation can in a state where only a small amount exists (that is, when the temperature inside the distillation can is high), the ether concentration in the recovered alcohol increases.

Furthermore, in continuous operation, no water is added to the alcohol solution.
Continuously charge the continuous distillation apparatus without adding water to the distillation vessel, and add 0.3 times the weight of water or more to the sulfuric acid in the alcohol solution and/or the sulfuric acid content in the acidic sulfuric ester directly to the distillation can. Even if the alcohol is charged continuously, the ether concentration in the recovered alcohol remains below the detection limit, similar to the continuous method described above.

The target alcohols for this distillation recovery method may be any aliphatic alcohols that produce sulfuric acid and acidic sulfuric esters, but especially lower alcohols commonly used in various reactions, such as methanol, ethanol, propyl alcohol, and butyl alcohols. Useful for alcohol, etc.

As described above, according to the present invention, alcohol containing almost no ether can be easily recovered from an alcohol solution, which is very advantageous industrially.

Hereinafter, the method of the present invention will be explained with reference to Examples.

Example-1 Into a flask 21 equipped with a stirring device, 1079 (0.78 mole) of 0-nitrotoluene and 799 (0.78 mole) of methanol (
After charging 138 g of 1,98 thiosulfuric acid, 36 g of pure water, and 0.52 g of trivalent platinum carbon catalyst, and replacing the gas phase in the system with hydrogen, 9/cr was added to 0.3' while stirring at 60"C.
Hydrogen was added under pressure to carry out a hydrogenation reaction. The reaction was terminated when the absorption of hydrogen almost stopped, the reaction liquid was passed through to remove the catalyst, and a portion of 860 g of this p liquid was used as a reaction product liquid for distillation.

The composition of the reaction product liquid was as follows: 73.3% by weight of methanol, 2.2% by weight of dimethyl ether, 2.2% by weight of sulfuric acid, 11.9% by weight of monomethyl sulfate, 3.27% by weight of water and 6.6% by weight of methyl-4-methoxyaniline. It contained 299% by weight and 3.011% by weight (orthotoluidine, 2-methyl-6-methoxyaniline, methylvalaminophenol).

172 g of water was added to 860.9 g of this reaction product liquid to adjust the feed liquid for distillation so that the water content was approximately 19 times higher than the sulfuric acid content in the sulfuric acid and monomethyl sulfate in the reaction product liquid. .

The following feed liquid was supplied at a flow rate of 203.4 g/hour to a glass distillation apparatus having a diameter of 25 M11 and a height of 500 mm, consisting of a packed column filled with glass rings, and a condenser.

Bottom temperature 109.5-111°C1 Tower top temperature 68-73
．． Distillation was carried out at 5°C to obtain 132.1 g/hour of distillate.

Its composition was 92.1% by weight of methanol and trace of dimethyl ether.

Example-2 Using the same equipment and distillation feed liquid as in Example-1, 227.
At a flow rate of 897 hours, the bottom temperature of the distillation column was 114-11
Distillation was carried out at a tower top temperature of 71 to 73.5°C to obtain a distillate of 152.1j9/hour.

Its composition was 89.4% by weight of methanol and trace of dimethyl ether. Example-3 Water = 860 J of the reaction product liquid for distillation used in Example-1.
By adding 1111 g of 13 g, the water content is approximately 0.0% relative to the sulfuric acid content in the sulfuric acid and monomethyl sulfate in the reaction product solution.
The feed liquid for distillation was adjusted to be 6 times the weight.

The above feed liquid was added to the same distillation apparatus as in Example-1.
(The liquid was supplied at a flow rate of 1/hour.

Tower bottom temperature 110-113°C, tower top temperature 66. ．． Distillation was carried out at 5° C. to obtain a distillate of 139.7°.

Its composition was 94.4 parts by weight of methanol and 0.05 parts by weight of dimethyl ether.

Example-4 n-butanol 82#, 98% sulfuric acid 0 in a hydrogenation flask
．． 7 J (0,007 mol), N-acetyl-β-phenylserine 34.9 (0.15 mol), 5 pd/c
Ito& was charged and stirred at 80° C. for 6 hours. During this period, approximately 3.1 kg of hydrogen was absorbed. Subsequently, the catalyst was separated from the furnace and washed with 3 (l) of n-butanol.

Pour the washing liquid into a distillation flask and add 63.3 I! of water! added.

A glass distillation apparatus with a diameter of 25 mm and a height of 500 m, consisting of a packed column filled with glass rings, and a condenser, was charged with the reaction solution and washing solution described above, and distillation was carried out at 100 ° C. under normal pressure. The azeotrope of water and n-butanol is 147.711
A distillate containing approximately 40% water was obtained.

The distillate was separated into two phases and the butanol phase was taken out. The ether in it was trace.

Comparative Example-1 Distillation reaction product liquid s6o# obtained in the same manner as Example-1
(The composition is the same as in Example-1, the water content is 0.26 times the weight of the sulfuric acid in sulfuric acid and monomethyl sulfate), and the flow rate was set to 206.
The liquid was supplied at a rate of 1.9/hour.

The bottom temperature is 109.5~11@'C, the top temperature is 68~7
Distilled at 3.5℃ and the result was 125.71! / hour of distillate was obtained.

Its composition was 96.2 parts by weight of methanol and 1.0 parts by weight of dimethyl ether.

Comparative Example-2 Using the reaction product liquid for distillation and distillation apparatus used in Comparative Example-1, the supply amount was 204.5 g/hour, and the bottom temperature was 11.
Distillation was carried out at a temperature of 4 to 116°C and a top temperature of 71 to 73.5°C.

The distillate was 146.5 g/hour, and its composition was 96.2 parts by weight of methanol and 1.8 parts by weight of dimethyl ether.

Comparative Example-3 Same as Example-3, 88% of n-butanol was added to the hydrogenation flask.
2.9,98% sulfuric acid 047g, N-acetyl-β-phenylserine 34.9.5% pd/c 1. O# was charged and reacted at 80° C. for 6 hours, during which time about 3.11 hydrogen atoms were absorbed. Next, separate the catalyst into a furnace and add 30g of butanol.
Washed with. The washing solution was also added to the distillation flask.

When the above liquid was charged into a distillation apparatus similar to that in Example 3 and distilled at 100°C under normal pressure, water and n-butanol were azeotropically distilled and 10I (containing about 40% of water) was distilled. did. Distillation was continued when no more water was distilled out, and 78.4 g of n-butanol was recovered.

The distillate was collected in one column, separated into two phases, and 1-butanol was taken out. Butyl ether in butanol 0
．． There were 9 chis.

Claims (1)

[Claims] 1) A method for recovering alcohol by distillation from a solution of a lower aliphatic alcohol containing sulfuric acid, in which distillation is carried out in the presence of water in an amount of 0.3 times or more the weight of sulfuric acid in the distillation system. A method for recovering alcohol, which is characterized by: 2) The method according to claim 1, wherein the lower aliphatic alcohol is methanol. 3) Recovery of methanol is 0.0% with respect to sulfuric acid in the distillation system.
Claim 2: Distillation by adding 3 to 9 times the weight of water
The method described in section.