JP2002090355A - Analysis method for dissolved ozone in acetic anhydride solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analysis method for dissolved ozone in an acetic anhydride solution allowing accurate determination of a dissolved ozone amount in the acetic anhydride solution prepared by ozone treatment of crude acetic anhydride obtained by a ketene method and the like without any influence of an ozonide amount. SOLUTION: In the solution prepared by ozone treatment of crude acetic anhydride, an excess unsaturated organic compound is added so as to bring the dissolved ozone in the solution into reaction with it, and then, a quantity of the unreacted unsaturated organic compound in the reactant is determined by gas chromatography. In this way, the dissolved ozone amount in the solution is found in this analysis method for the dissolved ozone in the acetic anhydride solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for analyzing dissolved ozone in an acetic anhydride solution obtained by treating crude acetic anhydride with ozone. The present invention also relates to a Wakka method (ketene method) obtained by thermally decomposing acetic acid to obtain ketene and absorbing and reacting the ketene with acetic acid, a Halcon method obtained by reacting methyl acetate with carbon monoxide, and the like. The present invention relates to a method for analyzing dissolved ozone in an acetic anhydride solution obtained by subjecting crude acetic anhydride to ozone treatment (preferably obtained by the ketene method).

[0002]

2. Description of the Related Art An industrial method for producing acetic anhydride includes:
A ketene method (wacker method) in which acetic acid is thermally decomposed to obtain ketene, and the ketene is absorbed and reacted with acetic acid to obtain acetic anhydride.
The Halcon method and the like for obtaining acetic anhydride by reacting carbon monoxide with methyl acetate are known. However, impurities such as unsaturated compounds are mixed in crude acetic anhydride obtained by these methods.

Further, acetic acid concentrated and recovered from an aqueous acetic acid solution discharged from a cellulose acetate production process is used as a raw material acetic acid for acetic anhydride produced by absorbing and reacting ketene obtained by thermally decomposing acetic acid with acetic acid. In this case, since the concentrated acetic acid contains impurities from the cellulose acetate production process without being completely removed, the produced acetic anhydride is also affected by the impurities.

[0004] As described above, crude acetic anhydride contains impurities such as unsaturated compounds having a low boiling point and a high boiling point. However, purification by distillation requires a large amount of thermal energy, and acetic anhydride having a boiling point close to or azeotropic cannot be sufficiently separated. In order to solve such a problem of purification by distillation, a method of purifying acetic anhydride by ozone treatment has been proposed. By ozone treatment of the crude acetic anhydride, impurities such as unsaturated compounds are ozonized,
It is presumed to be degraded through the formation of ozonide. Japanese Patent Application Laid-Open No. 4-34537 discloses a method for purifying acetic anhydride by ozone treatment.
No. 0-39180 discloses a method for purifying acetic anhydride by combining ozone treatment and distillation.

[0005] In a solution obtained by treating crude acetic anhydride with ozone, ozonide generated by the reaction of ozone with impurities such as unsaturated compounds, decomposition products of ozonide, and unreacted ozone are present as dissolved ozone. Dissolved ozone is expected to react with newly generated impurities such as unsaturated compounds to be decomposed when a solution obtained by ozone-treating crude acetic anhydride is stored or further processed (heating, distillation, etc.). Therefore, the amount of dissolved ozone in the solution greatly affects the quality of the solution. It is important to grasp the amount of dissolved ozone in the solution, and it is necessary to accurately determine the amount of dissolved ozone in the solution.

[0006] The determination of dissolved ozone in the above solution has been conventionally performed by
The so-called KI method, that is, a method in which an aqueous solution of potassium iodide is added to the above solution and the released iodine is titrated with a sodium thiosulfate standard solution or the like. However, in the KI method, not only the dissolved ozone but also the total amount of ozonide is determined, and it is not possible to determine only the dissolved ozone. For this reason, an analytical method for accurately quantifying only dissolved ozone is required.

[0007]

An object of the present invention is to provide a method for analyzing dissolved ozone in an acetic anhydride solution obtained by subjecting crude acetic anhydride obtained by the ketene method or the like to ozone treatment. It is an object of the present invention to provide a method for analyzing dissolved ozone which can accurately determine the amount of dissolved ozone in the acetic anhydride solution even when ozone is contained therein.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, reacted dissolved ozone with an unsaturated organic compound (preferably diketene), and determined the amount of the reacted unsaturated organic compound. The present inventors have found that the amount of dissolved ozone not including the amount of ozonide can be accurately determined by determining the amount of dissolved ozone from the above, and completed the present invention.

That is, in the present invention, ketene is obtained by thermally decomposing acetic acid, crude acetic anhydride is obtained by a ketene method or a Halcon method in which the ketene is absorbed and reacted with acetic acid, and the crude acetic anhydride is treated with ozone. After adding an excessive amount of unsaturated organic compound to the obtained solution and reacting dissolved ozone in the solution, the amount of unreacted unsaturated organic compound in the reaction product is determined by gas chromatography. A method for analyzing dissolved ozone in an acetic anhydride solution, which comprises determining the amount of dissolved ozone in the solution.

[0010] Another invention of the present invention is to provide a crude acetic anhydride which is subjected to ozone treatment, followed by heating or distillation, followed by addition of excess unsaturated organic compound to react dissolved ozone in the solution, followed by reaction. A method for analyzing dissolved ozone in an acetic anhydride solution, characterized by determining the amount of dissolved ozone in the solution by quantifying the amount of unreacted unsaturated organic compound in the product by gas chromatography. .

Another aspect of the present invention is to provide a crude acetic anhydride by a ketene method or a Halcon method in which acetic acid is thermally decomposed to obtain ketene, and the ketene is absorbed and reacted with acetic acid. , To the solution obtained by ozone treatment,
After reacting the dissolved ozone in the solution by adding an excess of the unsaturated organic compound, the amount of the unreacted unsaturated organic compound in the reaction product is quantified by gas chromatography. This is a method for analyzing dissolved ozone in an acetic anhydride solution, which comprises determining the amount of dissolved ozone.

Still another aspect of the present invention is to provide an acetic anhydride solution characterized by using acetic acid concentrated and recovered from an aqueous acetic acid solution discharged from a cellulose acetate production step as a raw acetic acid for obtaining ketene by pyrolysis. This is a method for analyzing dissolved ozone.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a solution to be analyzed is a solution obtained by treating crude acetic anhydride with ozone.

The crude acetic anhydride used in the present invention can be produced by the ketene method which is an industrial production method (namely, a method of producing ketene by pyrolyzing acetic acid and subjecting the ketene to absorption reaction with acetic acid) or It can be manufactured by the Halcon method or the like. Further, acetic acid concentrated and recovered from an aqueous acetic acid solution discharged from a cellulose acetate production step can be used as a raw material acetic acid in the ketene method.

Examples of the unsaturated organic compound used in the present invention include compounds having a double bond or a triple bond, and these may be cyclic or chain compounds, such as 1,3-butadiene and 1-butadiene. Buten-3-yne, 2-butyne, 1,4-pentadiene, 1,3-pentadiene,
Examples thereof include cyclopentadiene, 1,2-butadiene, and 2-methylfuran, and preferably include diketene.

The ozone used in the present invention includes, for example, ozone generated by silent discharge using air as a raw material. The method of ozone-treating the above-mentioned crude acetic anhydride using such ozone,
There is no particular limitation. For example, using a processing apparatus such as a stirring tank system or a bubble column system, at a processing temperature of room temperature, preferably 20 to 30 ° C., the ozone concentration in the ozone-containing air,
³ to 25 g / Nm ³ (preferably 10 to 20 g / Nm ³⁾
), And the supply amount of the ozone-containing air is preferably set to 5 g with respect to 100 g of the treated sample (the above-mentioned crude acetic anhydride).
0 to 300 Nl / hr (preferably 90 to 270 Nl)
/ Hr), the processing time is from 20 minutes to 120 minutes.

The method of distillation used in the present invention comprises:
It is not particularly limited, for example, as a distillation column,
A tray tower such as a sieve tray, a bubble cap tray, and a valve tray, and a packed tower such as an interlock saddle, a pole ring, and a Sulzer pack can be used. When a tray tower is used, the number of trays is preferably 10 to 80 (preferably 10 to 60). When a packed tower is used, the filling height corresponding to the number of trays in the tray tower is preferably This is the best thing to do. The ratio of the reflux liquid flow rate to the recovery liquid flow rate (reflux ratio) is 1 to 1000 (preferably 1 to 20).
0) is preferable.

The analysis method of the present invention will be described in detail below.

In the analysis method of the present invention, an excess of an unsaturated organic compound is added to a solution obtained by treating the crude acetic anhydride obtained as described above with ozone, and the mixture is gently stirred at room temperature. After reacting the dissolved ozone in the solution with the added unsaturated organic compound, the amount of unreacted residual unsaturated organic compound in the reaction product is analyzed by gas chromatography.

From the chromatogram thus obtained, the amount of the unreacted unsaturated organic compound was determined, and from this amount and the amount of the added unsaturated organic compound, the following formula 1 (as an unsaturated organic compound) when using diketene) X = (molecular weight of molecular weight / diketene ozone) × (a-B) (equation 1) [X: amount of dissolved ozone in the solution (g / solution 10 ⁶ g),
A: The amount of diketene added (g / solution 10 ⁶ g), B:
Determine the amount of dissolved ozone in the solution than the amount of diketene unreacted (g / solution 10 ⁶ g)].

In the present invention, the amount of the unsaturated organic compound such as diketene may be added in excess of the amount of dissolved ozone in the solution (the amount required for the reaction), and can be appropriately selected from these amounts. , when using diketene as the unsaturated organic compound, such as solutions 10 ⁶ g per diketene 10-20
0 g can be used.

In the present invention, the unsaturated organic compound such as diketene can be added after being dissolved in a solvent. In this case, for example, hexane, cyclohexane, benzene, acetic anhydride, and acetic acid can be used as the solvent, and the concentration of the unsaturated organic compound such as diketene is preferably 1 to 10% by weight.

In the present invention, the method for measuring gas chromatography is not particularly limited as long as an unsaturated organic compound such as diketene can be measured. For example, a capillary column can be used as the stationary phase column, helium or nitrogen can be used as the carrier gas, and gas chromatography using a flame ion detector can be used as the detector. The column temperature is 40 to 300 ° C., and the inlet temperature is 200.
° C, detector temperature 200 ° C, injection volume 0.5-5.0μ
1 is performed.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0025]

EXAMPLES Preparation Example 1 Acetic acid was thermally decomposed to obtain ketene, and 200 g of crude acetic anhydride obtained by a ketene method in which the ketene was absorbed and reacted with acetic acid.
Then, ozone-containing air (ozone concentration: 22.5 g / Nm ³ ) was bubbled at 75 Nl / hr for 1 hour at room temperature to prepare an acetic anhydride solution in which ozone was dissolved (Sample 1).

Preparation Example 2 200 g of crude acetic anhydride obtained in the same manner as in Preparation Example 1 was mixed with 75 ozone-containing air (ozone concentration: 9.6 g / Nm ³ ).
Bubbling was performed at room temperature for 1 hour at Nl / hr to prepare an acetic anhydride solution in which ozone was dissolved (sample 2).

Control Preparation Example 1 200 g of crude acetic anhydride obtained in the same manner as in Preparation Example 1 was treated with 7 air containing ozone (ozone concentration 22.5 g / Nm ³ ).
Bubbling was performed at 5 Nl / hr for 1 hour at room temperature, and then heating was performed at 110 ° C. for 6 hours to obtain a solution from which dissolved ozone and ozonide in the solution had been removed. The ozone-containing air (ozone concentration 22.5 g / N
m ³ ) was bubbled at 75 Nl / hr for 1 hour at room temperature to prepare an acetic anhydride solution containing no dissolved ozone without ozonide (control sample 1). Control Preparation Example 2 To 200 g of crude acetic anhydride obtained in the same manner as in Preparation Example 2, 75 air containing ozone (ozone concentration of 9.6 g / Nm ³ ) was added.
Bubble at room temperature for 1 hour at Nl / hr then 1
The solution was heated at 10 ° C. for 6 hours to obtain a solution from which dissolved ozone and ozonide in the solution had been removed. The ozone-containing air (ozone concentration 9.6 g / N) was again added to the solution thus obtained.
m ³ ) was bubbled at 75 Nl / hr for 1 hour at room temperature to prepare an acetic anhydride solution containing no dissolved ozone without ozonide (control sample 2).

Example 1 The dissolved ozone in Samples 1 and 2 was analyzed by the following method (Diketene method). That is, 10 mg of diketene was added to 100 g of each of Sample 1 and Sample 2, and lightly stirred at room temperature to react dissolved ozone with diketene. Then, gas chromatography was measured under the following conditions. From the obtained chromatogram, the amount of unreacted diketene was quantified, and the amount of ozone was further determined as follows: X = (molecular weight of ozone / molecular weight of diketene) × (100−B) (Formula 1 ′) [X: Amount (g / sample 10 ⁶ g), B: Amount of unreacted diketene (g / sample 10 ⁶ g)]. The results are shown in Table 1.

Column: Capillary DB-1, 0.32 m
mx 30m (manufactured by Shimadzu Corporation), Column temperature:
40-280 ° C, inlet temperature: 200 ° C, detector temperature:
200 ° C, carrier gas: helium, flow rate: 30ml
/ Min, detector: flame ion detector, injection amount: 2
μl

Control Examples 1 and 2 Control samples 1 and 2 containing only dissolved ozone without ozonide
The dissolved ozone was analyzed by the same method as in Example 1 except for the above. The results are shown in Table 1.

Comparative Example 1 Using the samples 1 and 2, the dissolved ozone in the samples 1 and 2 was analyzed by the following method (KI method). That is, 10 ml each of sample 1 and sample 2
Was added with 30 cc of a 0.2 N aqueous KI solution, left for 20 minutes, and the generated iodine was titrated with a 0.01 N aqueous sodium thiosulfate solution to determine the amount of iodine. From this amount, the amount of dissolved ozone was determined. The results are shown in Table 1.

[0032]

[Table 1]

As shown in Table 1, when comparing Samples 1 and 2 containing ozonide and dissolved ozone and Control Samples 1 and 2 containing only dissolved ozone without ozonide, the values of the amount of ozone were almost the same (40). And 42, 18 and 20), indicating that only the dissolved ozone which does not contain ozonide can be accurately quantified by the analysis method of the present invention. In contrast, the conventional KI
The amount of ozone obtained by the method (Comparative Example 1) is larger than the value obtained by the analysis method of the present invention due to the effect of ozonide,
Therefore, it is understood that only the dissolved ozone cannot be accurately quantified by the KI method.

[0034]

According to the analysis method of the present invention, the crude acetic anhydride obtained by the ketene method or the like is treated with ozone, and the amount of ozonide is not contained in the dissolved ozone in the obtained acetic anhydride solution (the amount of ozonide is not included). The exact amount of dissolved ozone alone (unaffected) can be determined.

Claims (9)

[Claims] 1. A solution obtained by treating a crude acetic anhydride with ozone by adding an excess of an unsaturated organic compound to react dissolved ozone in the solution, and then reacting unreacted unsaturated organic compounds in the reaction product. A method for analyzing dissolved ozone in an acetic anhydride solution, wherein the amount of dissolved ozone in the solution is determined by quantifying the amount of the compound by gas chromatography. 2. The acetic anhydride solution according to claim 1, wherein the crude acetic anhydride is a crude acetic anhydride obtained by thermally decomposing acetic acid to obtain ketene and allowing the ketene to undergo an absorption reaction with acetic acid. For analyzing dissolved ozone in air. 3. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 1, wherein the unsaturated organic compound is diketene. 4. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 1, wherein after the crude acetic anhydride is treated with ozone, a step of heating or distillation is performed before adding an excess amount of unsaturated organic compound. 5. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 4, wherein the unsaturated organic compound is diketene. 6. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 1, wherein an excess of an unsaturated organic compound is added to a solution obtained by distilling the crude acetic anhydride and then subjecting the mixture to ozone treatment. 7. The crude acetic anhydride according to claim 4, wherein the crude acetic anhydride is a crude acetic anhydride obtained by thermally decomposing acetic acid to obtain ketene and causing the ketene to undergo an absorption reaction with acetic acid. 2. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 1. 8. The method for analyzing dissolved ozone in an acetic anhydride solution according to claim 7, wherein the unsaturated organic compound is diketene. 9. The analysis of dissolved ozone in an acetic anhydride solution according to claim 2, wherein the acetic acid obtained by thermal decomposition to obtain ketene is acetic acid concentrated and recovered from an aqueous acetic acid solution discharged from a cellulose acetate production process. Method.