JP2000256309A - Production of epsilon-caprolactam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply produce the subject lactam useful for nylon, or the like, at a high addition ratio and a high selectivity and at a low cost according to a vapor-phase Beckmann rearrangement reaction by using a crystalline zeolite subjected to a specific treatment as a catalyst. SOLUTION: (B) A crystalline zeolite treated with (A) an acidic aqueous solution at pH 1-3 is used as a catalyst when producing ε-caprolactam from cyclohexanone oxime using the crystalline zeolite as the solid catalyst under vapor-phase reactional conditions. The component A is preferably an aqueous solution of an inorganic acid, especially at least one kind selected from the group consisting of hydrochloric acid, hydrofluoric acid, sulfuric acid and nitric acid and the hydrochloric acid is especially preferably used. Furthermore, the component B prepared by treating the component B having a decreased activity with the component A at pH 1-3 is preferably used as the catalyst. A <=6C aliphatic or a <=6C alicyclic alcohol is preferably made to coexist in the reactional system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing ε-caprolactam from cyclohexanone oxime under gas phase reaction conditions using a solid catalyst.

[0002]

2. Description of the Related Art ε-Caprolactam is an important basic chemical raw material used as a raw material for nylon and the like. A method for producing ε-caprolactam is to rearrange cyclohexanone oxime in a liquid phase using fuming sulfuric acid or concentrated sulfuric acid as a catalyst. A known method (hereinafter, referred to as a liquid phase Beckmann rearrangement reaction), a method of performing a Beckmann rearrangement of gaseous cyclohexanone oxime using a solid catalyst (hereinafter, referred to as a gas phase Beckmann rearrangement reaction), and the like are known.

The method using the liquid phase Beckmann rearrangement requires a large amount of ammonia to neutralize sulfuric acid, and as a result, about 1.7 tons of ammonium sulfate is generated as a by-product per ton of ε-caprolactam. For this reason, a method using a gas-phase Beckmann rearrangement reaction that does not require neutralization and can reduce the generation of by-products has been attracting attention for a long time.

[0004] The method using the gas phase Beckmann rearrangement reaction is as follows:
This is a method in which cyclohexanone oxime vapor is reacted in the presence of a solid catalyst (heterogeneous catalyst). Examples of the solid catalyst to be used include (1) a silica gel catalyst (US Pat.
No. 34566), (2) silica-alumina catalyst (GB 819772), (3) zeolite catalyst (Journal of Catalysis, Vol. 6, p. 247, 1).
966, U.S. Pat. No. 4,359,421 and U.S. Pat. No. 5,741,904) have been proposed.

[0005] Since zeolite catalysts are generally superior in selectivity to ε-caprolactam and catalyst life as compared with silica-based catalysts and the like, crystalline zeolite catalysts having various compositions have been developed. Although catalysts with considerably improved conversion and selectivity are introduced, they are not yet sufficient. In addition, the activity of these crystalline zeolite catalysts usually decreases according to the time of the reaction. When the activity of the catalyst is reduced, it is necessary to either regenerate the catalyst to recover the activity or replace the catalyst with a new catalyst. As a method of regenerating the catalyst,
Generally, a method of burning and removing a carbonaceous material deposited on a catalyst in the presence of a molecular oxygen-containing gas has been adopted (for example, US Pat. No. 5,071,802). Further, as a method for regenerating a solid catalyst such as a crystalline zeolite, a method of treating the solid catalyst with ammonia, or treating the solid catalyst with ammonia and then treating the solid catalyst with 5N hydrochloric acid (JP-A-5-9180) has been proposed. .

[0006] The inventors of the present invention have proposed that during the production of crystalline zeolite, the obtained crystalline zeolite is subjected to steam treatment,
Compared to an untreated crystalline zeolite by treating it with an aqueous solution of hydrochloric acid of H4-6, when this is used as a solid catalyst for the gas phase Beckmann rearrangement reaction, the conversion of cyclohexanone oxime and the selection of ε-caprolactam They found that the rate was improved, and filed an application as seen in JP-A-9-12540. Thus, the present inventors have found that crystalline zeolites having even better catalytic activity,
As a result of intensive studies to find an effective method for reactivating a degraded catalyst that is easy to operate and inexpensive to treat, as a result, a crystalline zeolite before being used as a catalyst with an acid having a specific acid concentration, Furthermore, when a crystalline zeolite catalyst with reduced activity is used as a catalyst, the conversion of cyclohexanone oxime and the selectivity of ε-caprolactam are improved, and a reactivated crystalline zeolite catalyst is obtained. And found that the present invention was completed.

[0007]

An object of the present invention is to provide a method for producing ε-caprolactam from cyclohexanone oxime under a gas phase reaction condition using a crystalline zeolite catalyst, which is simple and inexpensive as a solid catalyst. An object of the present invention is to improve the conversion of cyclohexanone oxime and the selectivity for ε-caprolactam of the crystalline zeolite used, and to provide a method for reactivating a crystalline zeolite catalyst having reduced activity.

[0008]

That is, the first aspect of the present invention is as follows.
Is a method for producing ε-caprolactam from cyclohexanone oxime using a crystalline zeolite as a solid catalyst under gas phase reaction conditions.
The present invention provides a method for producing ε-caprolactam, characterized by using a crystalline zeolite treated with an acidic aqueous solution.

A second aspect of the present invention is a method for producing ε-caprolactam from cyclohexanone oxime using a crystalline zeolite as a solid catalyst under gas phase reaction conditions. pH
Is a crystalline zeolite treated with an acidic aqueous solution having a value of 1 to 3, and a method for producing ε-caprolactam.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The catalyst targeted by the present invention is a crystalline zeolite catalyst, and examples thereof include crystalline aluminosilicate and crystalline metallosilicate. The crystalline metallosilicate used in the present invention has, for example, an Si / Me atomic ratio (where Me represents at least one metal element selected from the group consisting of B, Al, Ga, Fe, Ti, and Zr). Usually, it is 5 or more, preferably 500 or more. The so-called high-silica zeolite in which the metal component substantially constituting the zeolite framework is only Si or contains boron as the metal component
[B] -MFI zeolite is one of the particularly preferred crystalline zeolites. The Si / Me atomic ratio can be measured by atomic absorption analysis, X-ray fluorescence analysis and other methods.
The crystalline zeolite is produced by a known method. For example, a mixture of a silica source, water, an organic amine or a quaternary ammonium compound and, if necessary, a metal source is subjected to a hydrothermal synthesis reaction in an autoclave. It can be obtained by ion exchange with an ammonium salt or the like and drying. These crystalline metallosilicates have various structures,
Those belonging to the MFI, MEL, BEA type structure are preferred.

[0011] In the second aspect of the present invention, the degraded catalyst to be treated with an acidic aqueous solution refers to a crystalline zeolite catalyst whose activity has been reduced by reaction or thermal damage, and is usually used in a gas phase Beckmann rearrangement reaction. The crystalline zeolites used are of interest.

As the acidic aqueous solution used in the present invention, for example, an aqueous solution of an inorganic acid such as hydrochloric acid, hydrofluoric acid, sulfuric acid or nitric acid, preferably an aqueous solution of hydrochloric acid is used. These are contacted with a crystalline zeolite. Treatment of crystalline zeolites with acidic aqueous solutions
Any method can be used as long as the crystalline zeolite can be sufficiently contacted with an acid in an acidic aqueous solution.A method in which the crystalline zeolite is charged into a container, and then the acidic aqueous solution is poured into the container and immersed under stirring, or in a column or the like A method in which an acidic aqueous solution is allowed to pass in a filled state is exemplified. As a more specific method, for example, a crystalline zeolite is converted to an acidic aqueous solution,
Preferably mixed with an aqueous solution of an inorganic acid and refluxing the resulting mixture at a temperature of about 20 ° C. to about 100 ° C. for about 1 hour to about 50 hours, then filtering the crystalline zeolite, washing with deionized water, It may be carried out by a method of drying at about 100 ° C. for about 1 to 10 hours. In the present invention, the concentration of the acid for treating the crystalline zeolite is extremely important,
Requires treatment at about 1 to about 3, preferably about 2.
When the pH of the acidic aqueous solution is lower than about 1, the conversion of cyclohexanone oxime tends to decrease when applied to a gas phase Beckmann rearrangement reaction. On the other hand, when the pH of the acid is higher than about 3, when the obtained zeolite catalyst is applied to a gas-phase Beckmann rearrangement reaction, the selectivity for ε-caprolactam tends to decrease.

[0013] The crystalline zeolite subjected to the treatment with the acidic aqueous solution may be either a powder or a molded article formed into a desired shape as a catalyst. Further, these crystalline zeolites may be coated on a carrier and applied as a catalyst.

The thus obtained crystalline zeolite after the acid treatment is subjected to a Beckmann rearrangement reaction of cyclohexanone oxime in the same manner as a usual solid catalyst. The reaction is usually carried out by a known fixed bed or fluidized bed gas phase catalytic reaction. The raw material cyclohexanone oxime is introduced into the catalyst layer in a gaseous state. The reaction temperature is usually about 250 ° C to about 45 ° C.
It is in the range of 0 ° C. If the temperature is less than about 250 ° C,
The reaction rate is not sufficient, and the selectivity of ε-caprolactam tends to decrease. On the other hand, when the temperature exceeds about 450 ° C., thermal decomposition of cyclohexanone oxime cannot be ignored, and the selectivity for ε-caprolactam tends to decrease. A particularly preferred temperature range is from about 300C to about 400C.
° C. The reaction pressure is not particularly limited, but is usually about 5 kPa to about 10 MPa, preferably about 5 kPa.
kPa to 0.5 MPa.

The space velocity of the starting material cyclohexanone oxime is
Usually WHSV = about 0.1 h ^-1 to about 20 h ^-1 (that is, the feed rate of cyclohexanone oxime per kg of catalyst is about 0.1 kg / h to about 20 kg / h), preferably about 0.2 h ^-1 to about 10 h ^It is selected from the range of ^-1 .

In the rearrangement reaction of cyclohexanone oxime, a lower alcohol having 1 to 6 carbon atoms can coexist with cyclohexanone oxime in the reaction system. Examples of the lower alcohol having 1 to 6 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, n-amyl alcohol, n-hexanol,
And the like, and one or more of these are used. Among them, the use of methanol and ethanol is recommended. When a lower alcohol is used, its abundance is usually about 0.1 to 0.1% by weight relative to cyclohexanone oxime.
About 20 times is suitable, and preferably in the range of about 0.2 to about 10 times. Use of these lower alcohols is effective in improving the selectivity of ε-caprolactam and the catalyst life.

[0017] Separation of ε-caprolactam from the reaction mixture can be carried out by a conventional method. For example, the reaction product gas is cooled and condensed, and then ε-caprolactam purified by extraction, distillation or crystallization can be efficiently produced.

The crystalline zeolite used as a catalyst is
Although the activity decreases with use, the catalyst whose activity has decreased, ie, the deteriorated catalyst, can be reactivated by treating with the same acidic aqueous solution as described above, and can be used repeatedly as a catalyst. More specifically, a crystalline zeolite catalyst having reduced activity is prepared by using an aqueous acidic solution having a pH of about 1 to about 3, preferably about 2, particularly an aqueous hydrochloric acid solution,
The acid treatment may be performed at a temperature of 20 to 100 ° C., and may be performed in the same manner as the above-described acid treatment of the crystalline zeolite. In the present invention, before contacting the deteriorated catalyst with an acidic aqueous solution,
It is preferable to burn off a carbon substance previously deposited on the catalyst with a molecular oxygen-containing gas, for example, air.

[0019]

As described in detail above, the present invention is a very simple method of treating a crystalline zeolite using an aqueous acid solution having a specific concentration, and the crystalline zeolite before being used in a gas-phase Beckmann rearrangement reaction, It is intended to improve the conversion of cyclohexanone oxime and the selectivity of ε-caprolactam of a crystalline zeolite catalyst having reduced activity after use, and its industrial value is great.

[0020]

EXAMPLES The present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. Example 1 [B] -MFI zeolite was prepared by the following hydrothermal synthesis method.

[0021] 12.2 g of boric acid was added to 800 g of an aqueous solution of hexamethylenediamine (50% by weight) and dissolved by stirring.
64 g of SiO ₂ (trade name: Aerosil) was added to the obtained mixture, and the mixture was transferred to an autoclave and stirred at a temperature of 170 ° C., and a hydrothermal synthesis reaction was carried out under self-pressure for 14 days. After cooling the autoclave, the crystals were separated by filtration and then washed with ion-exchanged water. The white powder thus obtained is dried at 110 ° C. and then at 550 ° C. in air for 12 hours.
After calcining for an hour, [B] -MFI zeolite was obtained.

5 g of the obtained [B] -MFI zeolite was added to 0.01 M
The mixture was acid-treated by refluxing at 100 ° C. for 24 hours, filtered, washed with deionized water, and added to 100 g of concentrated hydrochloric acid aqueous solution (pH 2).
After drying at 0 ° C. for 4 hours, a zeolite catalyst was obtained.

[0023] 1.5 g of the zeolite catalyst thus obtained was charged into a tubular reactor having an inner diameter of 6 mm (the height of the catalyst layer was about 40 m).
m) A solution obtained by mixing 9 times by weight of ethanol as a solvent with respect to cyclohexanone oxime was vaporized by a pre-evaporator, mixed with a carrier gas, supplied to a reaction tube, and reacted. At this time, the space velocity WHSV of cyclohexanone oxime was 0.33 h ⁻¹ , the temperature of the catalyst layer (reaction temperature) was 300 ° C., and the reaction pressure was 10 kPa. The reaction product was collected in a low-temperature trap cooled with liquid nitrogen, thawed, and analyzed by gas chromatography. As a result, the conversion was 81.3% and the selectivity was
92.6%.

Here, the space velocity WHSV of cyclohexanone oxime was calculated by the following equation, and the conversion of cyclohexanone oxime and the selectivity of ε-caprolactam were also calculated by the following equations. WHSV (hr- ¹ ) = O / C Conversion of cyclohexanone oxime (%) = [(X-
Y) / X] × 100 ε-caprolactam selectivity (%) = [Z / (X−
Y)] × 100 Further, O, C, X, Y and Z are as follows, respectively. O = cyclohexanone oxime supply rate (kg / hr) C = catalyst weight (kg) X = mol number of supplied cyclohexanone oxime Y = mol number of unreacted cyclohexanone oxime Z = mol number of ε-caprolactam in the product

Comparative Example 1 [B] -MFI zeolite prepared under the same conditions as in Example 1
A gas phase Beckmann rearrangement reaction of cyclohexanone oxime was carried out under the same conditions as in Example 1 except that the treatment was not carried out with an aqueous solution of hydrochloric acid having a concentration of 01M (pH 2). As a result, the conversion was 72.2% and the selectivity was 91.2%. 3%.

Continued on the front page (72) Inventor Gerd Dahlhof, Germany Bergheim Hermann-Laotstraße 2 (72) Inventor Hiroshi Ichihashi 5-1 Sokai-cho, Niihama-shi, Ehime Prefecture Sumitomo Chemical Industries, Ltd.

Claims (9)

[Claims] Claims 1. Under the gas phase reaction conditions, cyclohexanone oxime is used to convert ε-
In the process for producing caprolactam, p
A process for producing ε-caprolactam, comprising using a crystalline zeolite treated with an acidic aqueous solution in which H is 1 to 3. 2. The method for producing ε-caprolactam according to claim 1, wherein the acidic aqueous solution is an aqueous solution of an inorganic acid. 3. The method for producing ε-caprolactam according to claim 2, wherein the inorganic acid is at least one selected from the group consisting of hydrochloric acid, hydrofluoric acid, sulfuric acid, and nitric acid. 4. The method for producing ε-caprolactam according to claim 2, wherein the inorganic acid is hydrochloric acid. 5. Use of crystalline zeolite as a solid catalyst under gas-phase reaction conditions to convert ε-
A method for producing caprolactam, comprising using a crystalline zeolite obtained by treating a crystalline zeolite having reduced activity as a catalyst with an acidic aqueous solution having a pH of 1 to 3, which is used as a catalyst. 6. The method for producing ε-caprolactam according to claim 5, wherein the acidic aqueous solution is an aqueous solution of an inorganic acid. 7. The method for producing ε-caprolactam according to claim 6, wherein the inorganic acid is at least one selected from the group consisting of hydrochloric acid, hydrofluoric acid, sulfuric acid, and nitric acid. 8. The method for producing ε-caprolactam according to claim 7, wherein the inorganic acid is hydrochloric acid. 9. Use of crystalline zeolite as a solid catalyst under the gas phase reaction conditions to convert ε-
The method for producing ε-caprolactam according to any one of claims 1 to 8, wherein an aliphatic or alicyclic alcohol having 6 or less carbon atoms coexists in a reaction system for producing caprolactam.