Reflectance Spectroscopic and Thermogravimetric Identification of Complexes in the Dehydration of Cu 2+ and Mn 2+ A -zeolites

A series of five samples of Cu. A and only one sample of Mn A-zeolites were prepared and investigated. Diffuse reflectance spectroscopic and thermogravimetric techniques were employed for identi­fication of the species arising from the dynamic vacuum  ehydration of the samples at different temperatures.1. Cu 2iH20)6 (distorted octahederal) Cu H20)4 (square planar) 400  Cu {OX)3 (H20) {tetrahedral  Cu (OX)3 (trigonal). 2+ 2+ 2. Mn 20)6 (Octahedral) 298 K ~ Mn {OX)3 {H20)2 (trigonal bipyramid) Mn (OX)3 (H20) (tetrahederal) 623 K ) Mn{OX)3 (trigonal) (where OX designates an oxygen of the lattice). Jahn-Teller effect is responsible fOh the formation of2+the elongated octahedera 1 (tetragona 1) complex of Cu in hydrated Cu A-zeo 1 ites. 2+ Reflectance spectra of Mn3.5 A were featurless, because the transitions are spin-forbidden, therefore the species are identified mainly by thermogravimetry. No structural collapase was detected, only CU4.9 A gave partial lattice destruction.

S AKBER ,