JPS61280450A - Device for purifying and recovering acetic ester - Google Patents

Abstract

PURPOSE:To obtain a purified acetic ester, by treating the acetic ester containing acetic acid collected by active carbon adsorption process with potassium carbonate or sodium carbonate, and removing effectively and efficiently acetic acid. CONSTITUTION:A raw material gas is pretreated by the pretreating device 101, introduced to the adsorption tank 103, a solvent component is adsorbed on active carbon and collected, and the collected solvent component is desorbed with steam. The distillate solution is condensed and liquefied by the condenser 104, and separated into a solvent phase and an aqueous phase by the separator 105. The solvent phase is sent to the catalytic deacidifying column 111, brought into contact with potassium carbonate or sodium carbonate from the circulating line J in counter current, so acetic acid contained in the solvent phase is converted into K salt or Na salt. The deacidifying solvent stored in the middle tank 113 is dehydrated by the dehydrating distillation column 108, purified by the purifying column 114 so K salt and Na salt are removed to give a purified acetic ester. The aqueous phase separated by the separator 105 is sent to the dehydrating column 106, the solvent component contained in the aqueous phase is recovered and returned to the separator.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to the production of potassium carbonate or carbonic acid from acetic acid ester containing acetic acid collected by activated carbon adsorption method. The present invention relates to a recovery device that effectively removes sodium acetate and recovers purified acetate.

[Conventional technology]

Recovery technology for hydrocarbon solvents in exhaust gas using activated carbon adsorption has already become commonplace, and most of the problems have been solved, but many problems still remain regarding esters, keto/hydrocarbons, etc.

As one example, when acetate is adsorbed and collected using activated carbon and subjected to steam desorption, the acetate is partially hydrolyzed into acetic acid and alcohol due to the catalytic action of the activated carbon. For example, a very small portion of ethyl acetate decomposes as shown in formula (1), and the acetic acid produced lowers the pH of the recovered ethyl acetate, making it difficult to reuse the recovered solvent.

+H2O 0H3COOO2H5CH3000H+ C! 2H6
0H...' (catalytic action) Therefore, it is necessary to deacidify the recovered subacetic ester by some method and then reuse it as a neutral solvent.

FIG. 2 is a flow diagram showing the process of a conventional apparatus for recovering acetic ester from acetic acid-containing solvent gas.

In FIG. 2, first, the raw gas containing acetate is passed through a pretreatment device 1 such as a filter, a blower 2, and an activated carbon 3-
1 and sent to the vacuum adsorption tank 3 to adsorb and collect the solvent,
It is desorbed by the water vapor introduced from the steam line E, and is condensed and liquefied in the condenser 4. The liquefied acetic acid ester and water are separated by a separator 5, and the aqueous phase is recovered from the solvent by a wastewater distillation column 6 connected to a condenser 7, and returned to the separator 5. The solvent phase is dehydrated by a dehydration distillation column 8 connected to a condenser 9, and then sent to a product recovery tank 10.

[Problem that the invention seeks to solve]

However, as shown in Figure 2, ethyl acetate recovered by the conventional method contains 100 to 11,000 pp of acetic acid and is acidic, resulting in product quality problems during reuse, corrosion of equipment, and a work environment due to acetic acid odor. This may cause deterioration.

Particularly in the fields of application such as magnetic tape and synthetic film paper, it is necessary to use the acetic acid containing less than 10 ppm, and it is impossible to reuse it without deacidification treatment.

Normally, it is difficult to suppress the decomposition of acetate ester during adsorption as a countermeasure against this type of organic acid, and deacidification treatment after recovery is required.

In general, the following methods are known: (1) a method of neutralizing by adding an alkaline solvent such as ethanolamine, (2) a method of deoxidizing with an inorganic alkaline substance such as aqueous soda, and (3) a method of purifying by distillation. However, in (1) the purity decreases, and in (2) the decomposition of acetate ester is accelerated and the recovery rate of acetate ester decreases.
3) is difficult to purify to an acetic acid concentration of 10 ppm or less, and if it contains other solvents, a very complicated distillation operation is required, making it impractical.

As described above, no method has been found to effectively and efficiently deoxidize or separate the 9 organic acids contained in acetate esters, and in these 11, the recovered solvent has little utility value, and the recovery device only has the function of preventing air pollution. Tonashi, the original intention of reuse is halved.

The present invention aims to solve these problems, and aims to provide an acetate ester purification and collection device that can efficiently remove acetic acid from the solvent phase in a solvent gas treatment device containing acetate ester. This method can be applied to the purification of recovered solvent in a solvent recovery device containing acetate ester.

[Means for solving problems]

Ninthly, the acetate ester purification and recovery apparatus of the present invention includes a pretreatment device and introduction means for introducing raw gas into an adsorption tank, and means for adsorbing and collecting solvent components of the introduced raw gas; means for wetting out the adsorbed and collected solvent components by desorption and condensing and liquefying them; means for separating the liquefied components into a solvent phase and an aqueous phase; and a separating means for recovering the solvent contained in the separated aqueous phase. a deoxidizing means for deoxidizing the solvent phase separated by the separating means by bringing it into countercurrent contact with an aqueous potassium rum carbonate solution or an aqueous sodium carbonate solution via a circulation line; The present invention is characterized by comprising a means for removing and purifying the potassium salt contained in the solvent after dehydration, and a means for recovering a good solvent purified by the purifying means.

[For production]

In the acetate ester purification and recovery equipment described above, after the raw gas is collected in an adsorption tank, the condensate is separated into an aqueous phase and a solvent phase, and the solvent phase is converted into an aqueous potassium carbonate solution (or sodium carbonate) in a deoxidizing tower equipped with a circulation line. The solvent is deoxidized by countercurrent contact with an aqueous solution), dehydrated and potassium salts are removed using a dehydration tower and a purification tower, and then the purified solvent is recovered.

That is, in the present invention, raw gas containing acetate ester is sent to an activated carbon adsorption tank, the solvent is adsorbed and collected, and then desorbed in a desorption step, separated into a solvent phase and an aqueous phase by a condensation and liquefaction means and a separation means. After deoxidizing the phase with a deoxidizing means that brings the phase into countercurrent contact with an aqueous potassium carbonate solution or an aqueous sodium carbonate solution, dehydration and purification are performed using a dehydrating means and a purifying means to recover the purified acetate ester. Formula (2), (
3).

K2C! 03+ 0H3000H→(OH3000)2
ni+C! 02+H20...(2) Na2003+0H3C00H→(OH3000)2N
a+CO2+H2O...(3) [Example] Hereinafter, 70- of the acetate ester purification and recovery apparatus shown in FIG.
An embodiment of the present invention will be described based on the drawings.

In the figure, 101 is a pretreatment device, 102 is a blower, and 10
3 is an adsorption tank, 103-1 is an activated carbon layer, 104 is a condenser, 105 is a separator, 106 is a wastewater distillation column (hereinafter referred to as
107 is a condenser, 108 is a dehydration distillation column (
109 is a condenser, and 11o is a product recovery tank.

111 is a catalytic deoxidizing group that deoxidizes the solvent phase separated by the separator 105 by bringing it into countercurrent contact with an aqueous potassium carbonate solution (or an aqueous sodium carbonate solution); 112 is disposed in the circulation line J; A pump that circulates an aqueous potassium carbonate solution (or an aqueous sodium carbonate solution) that is brought into countercurrent contact with the solvent phase, and a portion of the circulating fluid containing a large amount of potassium acetate (or sodium acetate) is drained as waste through line G. The discharged potassium carbonate aqueous solution (or sodium carbonate aqueous solution) which is in short supply is supplied from the tank 117 to the circulation line J with high concentration potassium carbonate aqueous solution (or high concentration sodium carbonate aqueous solution).

Reference numeral 113 denotes an intermediate tank for storing a deacidified solvent that has been deoxidized by countercurrent contact with an aqueous potassium carbonate solution (or an aqueous sodium carbonate solution). to remove potassium salts.

115 is a condenser connected to the purification column 114, 116
is a drain tank connected to the bottom of the dehydration tower 108, in which the potassium salt (potassium carbonate, potassium acetate, or sodium carbonate, sodium acetate) removed in the purification tower 114 is condensed at the bottom of the dehydration tower 108, and the drain tank is connected to the bottom of the dehydration tower 108. tank 116
Process with.

The raw gas containing acetate ester is sent to an adsorption tank 103 equipped with an activated carbon layer 103-1 through a pretreatment device 101 such as a filter and a blower 102. In the adsorption tank 103, the solvent is collected by the activated carbon layer 105-1, and the purified exhaust gas is discharged into the air through the exhaust port F.

On the other hand, the collected solvent is desorbed by the steam introduced from the steam line E, and the wetting liquid is condensed and liquefied in the condenser 104 and sent to the separator 105. Separator 10
In step 5, the condensate is separated into acetate ester and water, and the aqueous phase is sent to a drainage base 106 connected to a condenser 107, where the solvent contained in the aqueous phase is recovered and returned to the separator 105 again.

The solvent phase separated by the separator 105 is a catalytic deoxidizing group 11
1. Potassium carbonate aqueous solution (or sodium carbonate aqueous solution)
The deoxidizing agent is brought into countercurrent contact with the deoxidizer and is stored in the intermediate tank 113. The potassium carbonate aqueous solution (or sodium carbonate aqueous solution) supplied to the catalytic deoxidizing group 111 is supplied via a circulation 2-in J equipped with an expansion pump 112, and the highly concentrated potassium carbonate aqueous solution in the tank 117 is fed to the circulation line J by pH control. (or sodium carbonate aqueous solution) is replenished. Further, a part of the circulating fluid containing a large amount of potassium acetate (or sodium acetate) due to the countercurrent contact is discharged through line G as waste fluid.

The deoxidized solvent stored in the intermediate tank 113 is dehydrated in the dehydration tower 108 connected to the condenser 109, and then transferred to the condenser 1.
The potassium salt (
or sodium salt) t-removed and product recovery tank 110
sent to. Potassium salts such as potassium carbonate and potassium acetate (or sodium salts such as sodium carbonate and sodium acetate) contained in trace amounts in the deacidifying solvent and removed in the purification column 114
is again sent to the bottom of the dehydration tower 108, where it is concentrated and extracted to the drain tank 116 for treatment.

The reason why potassium carbonate or sodium carbonate is suitable for deacidifying acetic ester containing acetic acid is that it has a relatively small dissociation constant and a moderately weak alkaline strength compared to sodium hydroxide. If the alkaline strength is too strong, not only the neutralization of acetic acid but also the decomposition of the acetate ester is promoted, leading to a decrease in the recovery rate. Incidentally, the decomposition rate of ethyl acetate under the following contact conditions is about 102 degrees, and the decomposition product ethanol is a component contained in the ethyl acetate manufacturing process. Also, the decomposition rate in the device for 48 hours after ethyl acetate phase separation is Q
, 01%.

Contact conditions Ethyl acetate 100 d potassium carbonate aqueous solution (5 cm, 003) 100 d Contact time (stirring) 5 minutes Next, the potassium carbonate aqueous solution and ethyl acetate containing acetic acid were brought into contact with stirring in a batch method under the following contact conditions. The test results are shown below.

Contact conditions Acetic acid in ethyl acetate 2000 ppm potassium carbonate aqueous solution 5 wt% ethyl acetate 1 Mixing ratio (potassium carbonate aqueous solution 1 Contact temperature
25℃ contact time
Removal rate of acetic acid in 5 minutes is 99.9
4 or more (2 ppm). Further, the pH of the p-recovery solvent was not affected by the distillation, and no increase in decomposition products or ethanol was observed due to the distillation operation.

〔Effect of the invention〕

As described in detail above, the acetate ester purification and recovery apparatus of the present invention includes a pretreatment device and an introduction means for introducing the raw gas into the adsorption tank, and adsorbs and collects the solvent components of the introduced Kuhara gas. means for leaching out the collected solvent components by desorption and condensing them into liquid; means for separating the condensed liquid into a solvent phase and an aqueous phase; a drainage means for recovering and returning it to the separation means; a deoxidizing means for deoxidizing the separated solvent phase by bringing it into countercurrent contact with an aqueous potassium carbonate solution or an aqueous sodium carbonate solution via a circulation line; Acetic acid ester can be effectively produced by a configuration including a dehydration means for dehydrating an acid solvent, a means for removing and purifying the potassium salt contained in the solvent after dehydration, and a means for recovering the solvent purified by the purification means. It can be recovered efficiently, which eliminates the conventionally required deoxidizing treatment after solvent recovery, increasing the reuse value of the recovered solvent, and preventing deterioration of the working environment and corrosion of equipment, etc. .

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an example of an embodiment of the present invention, and FIG. 2 is a flowchart for explaining the prior art.

Claims (1)

[Claims] A means for adsorbing and collecting the solvent components of the introduced raw gas, and a means for distilling the collected solvent components by desorption, comprising a pretreatment device and an introduction means for introducing the raw gas into the adsorption and collection means. a means for condensing and liquefying a distillate component; a means for separating the condensate into a solvent phase and an aqueous phase; and a means for directing the separated solvent phase to an aqueous potassium carbonate solution or an aqueous sodium carbonate solution supplied via a circulation line. A means for deacidifying the deacidified solvent by bringing it into contact with the solvent, a means for dehydrating the deacidized solvent, a means for removing and purifying the potassium salt or sodium salt contained in the dehydrated solvent, and recovering the purified solvent. An acetate ester purification and recovery device characterized by comprising means.