Selective Oxidation of Cyclohexane by Oxygen in a Solvent-Free System over Lanthanide-Containing AlPO-5

Ln-containing AlPO-5 (Ln = La, Ce, Sm, Dy, Y, Gd) were synthesized hydrothermally in the presence of HF, and characterized by XRD, UV-vis, SEM, N-2 adsorption/desorption, FT-IR, solid state Al-27 MAS NMR and ICP-AES techniques. The results showed that all the samples had good crystallinity and high specific area. Isomorphous substitution of Ln ions for Al+3 occurred. The lanthanide ions were incorporated into the frameworks or were highly dispersed on extra frameworks of the samples. The newly synthesized catalysts all were efficient for the oxidation of cyclohexane in a solvent-free system, especially Gd-AlPO-5. Near 13% conversion of cyclohexane were achieved on the catalyst Gd(60)-AlPO-5 with Al/Gd of 60 under the conditions of 0.5 MPa O-2, 413 K and 4 h reaction. The total selectivity to cyclohexanol and cyclohexanone was up to 92%. In addition, the catalyst Gd(60)-AlPO-5 was recyclable for the titled reaction system.