Heterogeneous Gif oxidation of cyclohexane using Fe3+-picolinate complex encapsulated within zeolites

A series of catalysts containing the Fe3+-picolinate (FePA) complex inside the micropores of zeolite Y and mordenite has been synthesized by treating pre-exchanged Fe3+ zeolites with a solution with picolinic acid in dichloro methane. The Fe3+-content of the solids was purposely low to avoid the pres ence of uncomplexed, free Fe3+ ions that could decrease the selectivity of the catalysts. Formation of the FePA complex was ascertained by diffuse ref lectance UV-vis (characteristic absorption at 340 nm), FT-IR (vibrations at 1705 and 1480 cm(-1)) and luminescence (emission at 540 nm) spectroscopies . These solids have been found to act as heterogeneous catalysts for the ox idation of cyclohexane by H2O2 with a similar selectivity to that reported in the literature as much higher conversion for the same complex in solutio n. The beneficial influence of a high PA/Fe3+ ratio in the solid reflects t he need to use a large Fe3+ ions. In addition, mordenite (channels, 0.74 nm ) was found excess of PA to ensure the absence of uncomplexed Fe more effic ient(93% selectivity at 49.1% of the maximum conversion) as a support than the more open Y zeolite (spherical cavities, 1.3 nm diameter). (C) 1999 Els evier Science Ltd. All rights reserved.