US Patent 7339056 Continuous process for preparing caprolactam

The invention relates to a continuous process for preparing caprolactam by Beckmann rearrangement of cyclohexanone oxime, said process comprisinga) feeding (i) oleum and (ii) cyclohexanone oxime into a first reaction mixture comprising caprolactam, sulfuric acid and SO3,b) feeding (iii) a portion of the first reaction mixture and (iv) cyclohexanone oxime into a second reaction mixture comprising caprolactam, sulfuric acid and SO3,c) withdrawing a portion of the second reaction mixture, wherein the process further comprises obtaining the cyclohexanone oxime that is fed to the reaction mixtures by:1) preparing an organic medium comprising cyclohexanone oxime dissolved in an organic solvent2) separating, by distillation, cyclohexanone oxime from said organic medium.