Mesoporous SiO2–Al2O3 supported chromium sesquioxide catalyst for cyclohexane nitrosation to ε-caprolactam with high selectivity

Mesoporous SiO 2 –Al 2 O 3 supported Cr 2 O 3 catalysts were prepared by the sol–gel and impregnation methods. These catalysts were characterized and applied in cyclohexane nitrosation reaction. The effects of the preparation conditions and the catalyst deactivation were studied. The results show that 20% Cr 2 O 3 /SiO 2 –Al 2 O 3 catalyst calcined at 400 °C exhibits not only the larger surface area, smaller particle size, but also the larger amount of Cr 2+ and Brønsted acid sites. These catalysts show good catalytic performances in the cyclohexane nitrosation to ε-caprolactam and could be recycled for several times in this reaction system for the first time. The catalyst of Cr 2 O 3 /SiO 2 –Al 2 O 3 calcined at 400 °C gives 10.8% conversion with 79.9% selectivity to ε-caprolactam.