Method for production of hydroxylamine sulfate in the conventional process for the synthesis of caprolactam

In a process for the production of caprolactam, which comprises:

• (a) reacting air with ammonia gas in an ammonia conversion zone to produce nitric oxide;
• (b) oxidizing a portion of the nitric oxide to nitrogen dioxide to thereby produce an NOx-rich process gas stream;
• (c) reacting the NOx-rich stream with ammonium carbonate in a nitriting zone to produce ammonium nitrite;
• (d) reducing the ammonium nitrite to hydroxylamine diammonium sulfate;
• (e) hydrolyzing the hydroxylamine diammonium sulfate to hydroxylamine sulfate;
• (f) oximating the hydroxylamine sulfate with cyclohexanone to produce cyclohexanone oxime;
• and
• (g) converting the cyclohexanone oxime to caprolactam;
• the improvement comprising adding supplemental oxygen downstream of the ammonia conversion zone while simultaneously rerouting secondary air to the ammonia conversion zone to increase the production of nitric oxide formed in the ammonia conversion zone and the quantity and rate of formation of nitrogen dioxide in the nitriting zone, while maintaining a substantially equimolar NO:NO2 ratio in the NOx-rich stream in the nitriting zone.