Sulfuric Acid → Sulfuric Acid

Participants

Reaction Steps

Such a process is for example described in U.S. Pat. No. 3,914,217. In the process as described in U.S. Pat. No. 3,914,217 the Beckmann rearrangement is carried out in three stages in series. Cyclohexanone oxime is fed to each stage containing a circulating rearrangement mixture having a sulfuric acid+SO3 to caprolactam weight ratio and a SO3 content within certain ranges. The circulating rearrangement mixture of the first stage has a sulfuric acid+SO3 to caprolactam weight ratio of 1.33 to 1.80 (molar ratio of 1.55 to 2.17) and a SO3 content of 2 to 14 wt. %; the circulating rearrangement mixture of the second stage has a sulfuric acid+SO3 to caprolactam weight ratio of 1.14 to 1.31 (molar ratio of 1.32 to 1.55) and a S03 content of at least 0.82 wt. %, preferably 0.82 to 6.5 wt. % and the circulating rearrangement mixture of the third stage has a sulfuric acid+SO3 to caprolactam weight ratio of 1.00 to 1.13 (molar ratio of 1.15 to 1.33) and a SO3 content of at least 0.4 wt. %, preferably 0.4 to 4 wt. %. The reaction mixture obtained in the third rearrangement stage essentially containing caprolactam, sulfuric acid and optionally residual sulfur trioxide is sent to a reactor system together with ammonia, water and a solvent such as toluene. The sulfuric acid and SO3 are neutralized by converting the sulfuric acid and SO3 into ammonium sulfate and the caprolactam is simultaneously extracted from the ammonium sulfate solution formed in this system.

Provenance & Evidence