Process for preparing epsilon-hexanolactam by catalyzing cyclohexanone-oxime rearranging

Abstract

The present invention relates to catalytic Beckmann rearrangement process of cyclohexanone-oxime by using the Bronsted acid ion liquid with N-protonated hexanolactam as cationic group serving as the catalyst and reaction medium to prepare epsilon-hexanolactam. The present invention produces epsilon-hexanolactam in mild reaction temperature, short reaction period, high conversion rate and high selectivity, and the acid ion liquid may be reused. The product is no longer combined with the acid ion liquid and needs no alkali neutralization, and the reaction system is simple, without environmental pollution, no corrosion on the apparatus, low cost of the acid ion liquid, and excellent industrial application foreground.

Description

technical field [0001] The invention relates to a method for preparing ε-caprolactam by catalyzing the rearrangement of cyclohexanone oxime. Specifically, the invention relates to a Brnsted acidic room-temperature ionic liquid with N-protonated caprolactam as a cationic group as a catalyst and reaction Catalytic method of cyclohexanone oxime via Beckmann rearrangement to prepare ε-caprolactam. Background technique [0002] ε-caprolactam is an important chemical raw material, mainly used as a polymerized monomer in the production of nylon 6 fiber and resin, and widely used in textile, plastic and artificial leather industries. The traditional production process of ε-caprolactam is to prepare ε-caprolactam through Beckmann rearrangement of cyclohexanone oxime. rearrangement using 30% SO 3 The fuming sulfuric acid is carried out at 100-130°C. After the reaction, a large amount of ammonia water is added to free the caprolactam combined with the concentrated sulfuric acid. Bu...

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Problems solved by technology

However, this process has many disadvantages: (1) a large amount of ammonium sulfate (2-4 tons / ton caprolactam) with low added value is produced by-product; (2) equipment corrosion is serious; (3) complicated follow-up caprolactam purification process; (4) produces A large amount of acidic wastewater pollutes the environment

In 2001, Deng Youquan et al. (Tetrahedron Letters, 2001, 42, 403-405) successfully realized the high-conversion and high-selectivity Beckmann rearrangement of cyclohexanone oxime to prepare ε-caprolactam in an imidazole-based room temperature ionic liquid using a phosphorus compound as a catalyst. It cannot be reused, and it is difficult to separate the product from the catalytic system

In 2004, it was reported in the literature (Tetrahedron Letters, 2004, 45, 2681-2683) that the use of imidazole cation functionalized ionic liquids as reaction medium and catalyst can carry out effective Beckmann rearrangement, but the weakly basic product caprolactam and acidic ionic liquid are still There is a considerable degree of combination, which makes it difficult to separate the product from the catalyst, thus limiting its industrial application prospects

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