Abstract
CoAPO-5 has been found to be a potential catalyst for the one-step liquid-phase oxidation of cyclohexane to produce cyclohexanone and adipic acid (without any promoter being added and with no induction period). Effects of various reaction conditions, including catalyst loading (10–5–2.5 × 10–3 kg), concentration of cyclobexane (1.44–4.33 × 103 mol/m3), oxygen pressure (5–15 × 105 Pa), temperature of reaction (115–135°C) and amount of acetic anhydride (0–60 × 10–6 m3) on the conversion and selectivity of liquid-phase oxidation of cyclohexane using CoAPO-5 as catalyst have been investigated. The results reveal that the selectivity of adipic acid is higher at reaction conditions of higher cyclohexane concentration, higher reaction temperature (135°C) and higher oxygen pressure (15 × 105 Pa) before 4 hrs. Accumulated water in the reaction mixture will affect conversion and selectivity of reaction if its amount is large enough. Addition of acetic anhydride increases the rate of cyclohexane oxidation and the selectivity of cyclohexylacetate (from the esterification of cyclohexanol and acetic acid) and succinic acid but lowers the selectivity of adipic acid.
