PECULIARITIES OF MN2-5 TYPE ZEOLITE AS STUDIED BY ESR( CATION DISTRIBUTION IN ZSM)

ESR spectroscopy in the X band (lambda = 3.2 cm) is used for monitorin g both the valence state and distribution of manganese cations in H-Ts VM zeolite calcined in different conditions for the samples with a Mn2 + content of 0.5, 0.9, 1.8, 2.6, and 3.5 ions per one unit cell. In th e samples prepared by incipient wetness impregnation of zeolite by Mn( NO3)(2) solutions and dried at 20 degrees C, Mn2+ cations are stabiliz ed as isolated hexaaqua-complexes, and interaction between cations inc reases with a rise in the metal content. Calcination of the samples in air at 500 degrees C is accompanied by oxidation of some part of Mn2 cations to the Mn4+ state. Subsequent sample treatment with Hz at 500 degrees C does not provide the complete reduction of Mn4+ to Mn2+. Re hydration of calcined samples leads to the formation of isolated Mn2hexaaqua-complexes characterized by a specific ESR signal. This is ind icative of the presence of the isolated Mn2+ cations distributed in th e structure of calcined samples in the same manner as in the starting dried samples.