Published January 1976
The Process Economics Program (PEP) Report No. 7A on caprolactam was issued in 1968. Since that time, most of the process developments have been directed toward reducing or even eliminating the formation of ammonium sulfate.
During caprolactam manufacture, ammonium sulfate is produced in the hydroxylamine formation and in the Beckmann rearrangement steps. The hydroxylamine phosphate oxime process (HPO) offered by Dutch State Mines (DSM) produces no ammonium sulfate in the hydroxylamine formation step; however, ammonium sulfate is still produced when the Becktnann rearrangement mixture is neutralized. Extracting the caprolactam from the rearrangement mixture eliminates the need for neutralization and thus avoids the formation of ammonium sulfate. Such an extraction pro- cess currently is piloted by SNIA Viscosa. DSM also offers a process in which the Beckmann rearrangement mixture is only partially neutralized to ammonium bisulfate. The bisulfate is then pyrolyzed to sulfur dioxide that in turn is converted to sulfuric acid. When this pyrolysis process is combined with the HP0 process, no by-product ammonium sulfate has to be sold.
This supplement presents new process designs for the manufacture of caprolactam by the HP0 route and by the hexahydrobenzoic acid (HBA) routes. In addition, the PNC process design has been updated to reflect improvements since Report 7A was issued. The economics of the NO reduction and Raschig processes also have been updated. Furthermore, the scope of the report has been extended to include the manufacture of cyclohexane from benzene by vapor phase hydrogenation.
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