Organic compounds -- part of the class 532-570 series – Organic compounds – Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
2000-10-27
2002-02-05
Kifle, Bruck (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Unsubstituted hydrocarbyl chain between the ring and the -c-...
Reexamination Certificate
active
06344557
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for producing &egr;-caprolactam having low free basicity. Specifically, the present invention relates to a method for producing &egr;-caprolactam having low free basicity which comprises a step of producing &egr;-caprolactam by a gas phase Beckmann rearrangement reaction of cyclohexanone oxime using a solid catalyst in the presence of alcohol.
BACKGROUND OF THE INVENTION
&egr;-caprolactam is an important compound as an intermediate in producing nylon-6. A method for producing &egr;-caprolactam from cyclohexanone oxime by gas phase Beckmann rearrangement reaction using a solid catalyst is known, and as the solid catalyst, it is known to use a boron-based catalyst, silica-alumina catalyst, solid phosphoric acid catalyst, complex metal oxide catalyst, zeolite-based catalyst and the like. Further, Japanese Patent Application Laid-Open (JP-A) Nos. 62-123167 and 63-54358 show examples using a high-silica type metallosilicate catalyst, and the selectivity in gas phase Beckmann rearrangement reaction of cyclohexanone oxime using such a catalyst system has been fairly improved as compared with conventional catalyst systems. JP-A No. 2-275850 discloses that the selectivity is further improved in a method for producing &egr;-caprolactam in which a lower alcohol is allowed to exist together with a solid catalyst. Moreover, JP-A 5-201965 discloses that the selectivity and catalyst life are improved when &egr;-caprolactam is produced by gas phase catalytic reaction of cyclohexanone oxime in allowing water to exist in the reaction system using a zeolite catalyst in the presence of alcohol and/or ether compound.
On the other hand, it is known that by allowing an alkylating agent such as dimethyl sulfate and diazomethane to act on &egr;-caprolactam, a corresponding 1-aza-2-alkoxy-1-cycloheptene (hereinafter, sometimes abbreviated as AAH) is synthesized. However, it is not known at all that AAH is generated as a by-product in gas phase Beckmann rearrangement reaction of an oxime in the presence of alcohol, and that one of standards for the product, free basicity, may sometimes not be satisfied when AAH remains in the product, &egr;-caprolactam. The standard in free basicity varies depending on every user and is not restricted. It is required that the product usually have free basicity of about 1 meq/kg or less, preferably about 0.3 meq/kg or less, more preferably about 0.1 meq/kg or less. It is known that when free basicity in the product, &egr;-caprolactam, is high, reverse influence is exerted in polymerization to a nylon.
SUMMARY OF THE INVENTION
Under such circumstances, the present inventors have intensively studied to find an industrially advantageous method for producing &egr;-caprolactam having low free basicity and providing high yield. As a result, the present inventors have found that when &egr;-caprolactam is obtained by gas phase Beckman rearrangement reaction using a solid catalyst in the presence of alcohol with using cyclohexanone oxime as a raw material, AAH is usually produced and present in the reaction product in a selectivity of from about 0.1% to about 10% depending on the reaction conditions, and that when the AAH is contained in &egr;-caprolactam, the presence of the AAH causes to enhance free basicity and reduce qualities of the product, and that when the reaction product is treated with water, the free basicity is reduced and yield of &egr;-caprolactam is increased due to conversion of the AAH with water into &egr;-caprolactam, completing the present invention.
First, the present invention provides a method for producing &egr;-caprolactam which comprises the step of treating, with water, a reaction product containing 1-aza-2-alkoxy-1-cycloheptene, which is obtained by gas phase Beckmann rearrangement reaction of cyclohexanone oxime using a solid catalyst in the presence of alcohol, to eliminate the 1-aza-2-alkoxy-1-cycloheptene.
Secondly, the present invention provides a method for producing &egr;-caprolactam which comprises the steps of separating a component comprising 1-aza-2-alkoxy-1-cycloheptene from a reaction product containing 1-aza-2-alkoxy-1-cycloheptene obtained by gas phase Beckmann rearrangement reaction of cyclohexanone oxime using a solid catalyst in the presence of alcohol, and treating the separated component comprising 1-aza-2-alkoxy-1-cycloheptene with water to eliminate the 1-aza-2-alkoxy-1-cycloheptene.
Thirdly, the present invention provides a method for producing &egr;-caprolactam according to the above first-described method, wherein the reaction product to be treated with water is a reaction product obtained by substantially separating an alcohol.
Fourthly, the present invention provides a method for producing &egr;-caprolactam according to the above secondly-described method, wherein the reaction product to be used for separating the component containing 1-aza-2-alkoxy-1-cycloheptene is a reaction product obtained by substantially separating an alcohol.
Fifthly, the present invention provides a method for producing &egr;-caprolactam, which comprises the steps of separating a component containing 1-aza-2-alkoxy-1-cycloheptene from a reaction product containing 1-aza-2-alkoxy-1-cycloheptene obtained by gas phase Beckmann rearrangement reaction of cyclohexanone oxime using a solid catalyst in the presence of alcohol, treating the separated component containing 1-aza-2-alkoxy-1-cycloheptene with water to convert the 1-aza-2-alkoxy-1-cycloheptene into &egr;-caprolactam, and put the resulting product into a step prior to the step of separating the component containing 1-aza-2-alkoxy-1-cycloheptene from the gas phase Beckmann rearrangement reaction product.
Sixthly, the present invention provides a method for producing &egr;-caprolactam according to the above fifthly-described method, wherein the reaction product to be used for separating the component containing 1-aza-2-alkoxy-1-cycloheptene is a reaction product obtained by substantially separating an alcohol.
Seventhly, the present invention provides a method for producing &egr;-caprolactam by gas phase Beckmann rearrangement reaction of cyclohexanone oxime using a solid catalyst in the presence of alcohol, which comprises the step of treating 1-aza-2-alkoxy-1-cycloheptene generated as a by-product with water so that a 1-aza-2-alkoxy-1-cycloheptene content in the &egr;-caprolactam is 100 ppm or less.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
&egr;-Caprolactam in the present invention usually has an AAH content of about 100 ppm or less, preferably about 25 ppm or less, more preferably about 10 ppm or less, and has low free basicity and has excellent qualities.
The &egr;-caprolactam in the present invention having such physical properties can be produced by, for example, a method in which a reaction product containing AAH obtained by allowing cyclohexanone oxime to react under gas phase reaction conditions using a solid catalyst in the presence of alcohol is treated with water, or preferably a reaction product containing AAH obtained by substantially separating an alcohol from the above-described reaction product is treated with water, or a method in which a component mainly containing AAH is further separated from the reaction product by distillation or the like and then the component is treated with water. By such a water treatment, AAH is converted into &egr;-caprolactam so that &egr;-caprolactam having a small AAH content can be obtained.
In the above-described methods, silicon-oxide-containing catalysts, preferably crystalline metallosilicates may be used as the solid catalyst. In particular, it is more preferred to use crystalline metallosilicates having a Si/Me atomic ratio of 500 or more (wherein Me represents one or more metal elements selected from Al, Ga, Fe, B, Zn, Cr, Be, Co, La, Ge, Ti, Zr, Hf, V, Ni, Sb, Bi, Cu, Nb and the like). Also, it is more preferred to use a crystalline silicate composed of silicon dioxide containing substantially no Me component. The Si/Me atomic ratio can be measured by commonly-used analys
Fukao Masami
Nakamura Tomokazu
Takamine Kan
Birch & Stewart Kolasch & Birch, LLP
Kifle Bruck
Sumitomo Chemical Company Limited
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