Preparation method of aminocaprolactam

Abstract

The invention discloses a preparation process for caprolactam which is characterized in that the acetic anhydride acts as the catalyzer to make a Beckmann rearrangement reaction of cyclohexanone oxime in ionic liquid homogeneous system , then the orgainic solvent is used to extract the ionic liquid and fully transfer the cyclohexanone oxime and the catalyzer into the organic solvent, finally the separation of the cyclohexanone oxime and the catalyzer is realized by the extraction to the solvent.

Description

technical field [0001] The invention relates to a method for preparing organic chemical raw materials, more specifically to a method for preparing caprolactam through Beckmann rearrangement reaction of cyclohexanone oxime. Background technique [0002] Caprolactam is a widely used important organic chemical raw material. About 90% of caprolactam in the world is prepared from cyclohexanone oxime through Beckmann rearrangement reaction. The traditional Beckmann rearrangement reaction process is: use oleum to make cyclohexanone oxime form caprolactam salt of sulfuric acid, in order to obtain a high yield of caprolactam, it is necessary to add excess nicotinic acid, and then neutralize the mixture with ammonia water to obtain ammonium sulfate and caprolactam. In a typical industrial rearrangement process, the conversion of cyclohexanone oxime is almost 100%, the selectivity to caprolactam is 99%, yielding 1.3-1.8 kg ammonium sulfate / kg oxime (or 1.0-1.3 mol oxime). This traditi...

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Problems solved by technology

[0007] Although the conversion rate of cyclohexanone oxime and the selectivity of caprolactam in some patents are relatively high, due to economic and technical reasons, the liquid phase rearrangement process catalyzed by non-oleum has not been industrialized so far.

[0008] At present, the main problems faced in the development of the liquid-phase Beckmann rearrangement process are: (1) Inventa's acetic anhydride and acetic acid catalytic rearrangement process uses ion exchange resins to adsorb and separate caprolactam, and the processing capacity is small; (2) in the ionic liquid homogeneous system or in an ionic liquid / organic solvent two-phase system, with phosphorus-containing compounds (P 2 o 5 , PCl 3 , PCl 5 or POCl 3 ) carry out the rearrangement reaction for the catalyst, all generate the complex with strong binding force with the phosphorus-containing compound, and be difficult to separate the caprolactam of free state from the ionic liquid, the recycle use difficulty of ionic liquid and catalyst; (3) rearrangement The neutralization step in ammonia after the reaction will by-produce ammonium sulfate or other ammonium salts, and cause the catalyst to be unable or difficult to recycle; (4) some catalysts (such as phosphorus-containing compounds or SO 3 etc.) will endanger the environment and human health