What is the current production process of caprolactam?

At present, the main starting materials for producing CPL are benzene/cyclohexane (cyclohexane is made from benzene hydrogenation), followed by phenol and toluene. The proportions of the three raw materials in the production capacity are 78.60%, 65,438+09.90% and 65,438+0.50% respectively.

Since 1980s, only the newly-built CPL plant in Shijiazhuang, China has used toluene as raw material, and all other plants have used benzene/cyclohexane as raw material instead of phenol.

At present, the main production process of caprolactam in the world is cyclohexanone-hydroxylamine route based on Beckmann rearrangement of cyclohexanone oxime. DSM/HPO process and communication process are its representative processes. The global ability to adopt this process accounts for 78%, while the ability to adopt other processes and raw materials only accounts for 22%.

Oxime is rearranged under the action of sulfuric acid, polyphosphoric acid, phosphorus pentachloride, phosphorus trichloride, benzenesulfonyl chloride, thionyl chloride and other acids that can generate strong acids to generate corresponding substituted amides. For example, cyclohexanone oxime is rearranged under the action of sulfuric acid to produce caprolactam. The reaction mechanism is as follows: under the action of acid, oxime is protonated first, then one molecule of water is removed, and the group opposite to hydroxyl group migrates to the electron-deficient nitrogen atom, and the formed carbocation reacts with water to obtain amide.

If the migration group is a chiral carbon atom, its configuration remains unchanged before and after migration, for example:

Process indexes of various caprolactam production routes

company

Oxime process

Beckmann rearrangement process

1t caprolactam and thiamine /t

Capropol

Lassig

oleum

4.2

Invista

no

oleum

2.8

a surname

photochemistry

oleum

1.5

Medal of Meritorious Service

high pressure oxygen

oleum

4.3

Medal of Meritorious Service

Improved HPO

oleum

1.4

Sumitomo chemistry

Aminoximation

fluidized bed