Method for producing C4-C15 lactams

A process for preparing C4-C15 lactams, comprising the steps of:

• a) converting a first mixture (M1) comprising a C1-C10 alcohol, nitrogen oxides and oxygen to obtain a C1-C10-alkyl nitrite,
• b) converting a second mixture (M2) comprising the C1-C10-alkyl nitrite obtained in step a) and a C4-C15-cycloalkane to obtain a first product mixture (P1) comprising a C4-C15-nitrosocycloalkane, a dimeric C4-C15-nitrosocycloalkane, a C4-C15-cycloalkanone oxime and a C1-C10 alcohol,
• wherein the second mixture (M2) is illuminated during the conversion with a light-emitting diode that emits light having a wavelength in the range from 300 to 500 nm,
• c) preparing the C4-C15 lactam by conversion of the C4-C15-cycloalkanone oxime obtained in step b) in the presence of a catalyst by one of the following steps:
• c1) separating the C1-C10 alcohol from the first product mixture (P1) obtained in step b) to obtain a second product mixture (P2) comprising the C4-C15-cycloalkanone oxime,
• recycling the C1-C10 alcohol removed into the first mixture (M1) in step a) and
• converting the C4-C15-cycloalkanone oxime present in the second product mixture (P2) in the presence of the catalyst to obtain the C4-C15 lactam,
• or
• c2) converting the C1-C15-cycloalkanone oxime present in the first product mixture (P1) in the presence of the catalyst to obtain a third product mixture (P3) comprising the C4-C15 lactam and the C1-C10 alcohol,
• removing the C1-C10 alcohol present in the third product mixture (P3) to obtain the C4-C15 lactam and
• recycling the C1-C10 alcohol removed into the first mixture (M1) in step a).