New oxidation catalysts based on iron(III) porphyrins immobilized on Mg–Al layered double hydroxides modified with triethanolamine Original Research Article

An Mg–Al layered double hydroxide containing intercalated NO3− anions (LDH-N) was synthesized and subsequently submitted to a reaction with triethanolamine as modifying agent (LDH-TEA). A neutral iron(III) porphyrin was immobilized onto both solids LDH-N and LDH-TEA, and the catalytic activity of the resulting FePor-LDH-N and FePor-LDH-TEA was evaluated in the oxidation of (Z)-cyclooctene, cyclohexane, and heptane using iodosylbenzene as oxidant. Characterization of FePor-LDH-N and FePor-LDH-TEA by UV–vis, FTIR, XRD, XPS, EPR, TGA/DTA, and SEM was also accomplished. The products from the catalytic reactions were analyzed by GC, using an FID detector. The catalytic activity of FePor-LDH-TEA in the oxidation of cyclohexane was around 5 times higher than that obtained with FePor-LDH-N, which does not contain the modifying agent. Moreover, the FePor-LDH-TEA solid displayed significant selectivity in the oxidation of heptane, a substrate that is difficult to oxidize; in fact, a total product yield over 30.0% was achieved. Finally, the performance of the FePor-LDH-TEA catalyst can be attributed to the higher FePor load in this solid, which is 3 times larger compared with FePor-LDH-N. A proposal concerning the mode of FePor immobilization onto the modified LDH is suggested.