The most representative impurities in e-caprolactam produced from cyclohexanol obtained by partial hydrogenation of benzene are the δ-valerolactams. These impurities come from the dehydrogenation−oximation−Beckmann rearrangement of the methylcyclopentanols that are typical impurities in the cyclohexanol obtained from benzene. The dehydrogenation of cyclohexanol is carried out in a fixed-bed reactor with a commercial catalyst based on copper oxide. The evolution of these 1-, 2-, and 3-methylcyclopentanol impurities during dehydrogenation is analyzed separately and in a combined way, and the products are identified and quantified. The cyclohexanone obtained after cyclohexanol dehydrogenation and reaction mixture rectification is taken as a reactant for the oximation and Beckmann rearrangement stages. The evolution of the 1-methylcyclopentanol and 2- and 3-methylcyclopentanones impurities contained on this purified cyclohexanone to the final impurities found in e-caprolactam are analyzed.
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