Studies in Surface Science and Catalysis vol:105 pages:1069-1076
Adsorption of cyclic triamines such as 1,4,7-triazacyclononane (TACN) or its methylated analog TMTACN on Mn zeolites results in a new class of redox-active zeolites. These materials were investigated as catalysts for the oxidation of alkenes and alkanes with different peroxides. Under appropriate reaction conditions, a Mn-TMTACN faujasite is an excellent catalyst for olefin epoxidation with H2O2. From styrene and cyclohexene, the epoxides are obtained with over 95 % selectivity. This Mn-TMTACN-NaY material also catalyses the selective epoxidation of styrene with tert-butylhydroperoxide (tBuOOH). In some of the tBuOOH oxidations, allylic oxidation becomes a competitive reaction, e.g., with cyclohexene. The more radical-like character of the active site in the tBuOOH reactions was confirmed in reactions with alkanes. With both tBuOOH and H2O2, far better epoxide selectivities are obtained with the methylated ligand than with the unmethylated ligand. Differences in the catalytic reactions with the two peroxides can be related to ESR spectroscopic observations.