Oxidation of cyclooctane over metalloporphyrin-exchanged Al,Si-mesoporous molecular sieves of HMS (MMS) type

Me(TMPyP) metalloporphyrin catalysts (Me = Mn, Fe, Co) supported on aluminated MMS (HMS) mesoporous silicas were investigated in the liquid phase oxidation of cyclooctane with molecular oxygen (as air) without the use of sacrificial co-reductant. Catalytic activity was shown to depend on the the metalloporphyrin surface density, the pore size of the support and the nature of the metal centre in Me(TMPyP). Increase in metalloporphyrin loading above a certain optimum value resulted in reduction of the catalyst activity attributed to the lessening of site isolation effect. Cyclooctanone and small amounts of cyclooctanol were the only products of the reaction. The enhanced selectivity to cyclooctanone (over 90%) was assigned to steric effect imposed by the mesoporous silica supports. The supported metalloporphyrin catalyst could be reused without any significant loss of its activity.