Metal ligand complexes in CoH-BEA relevant to ethane ammoxidation to acetonitrile:: an FTIR study

Local lattice perturbation induced by bonding of a single cobalt ion at cationic sites in dehydrated Coil-beta zeolite (Si/Al 11.5-12.2, Co/Al 0.06-0.4) decreases after cobalt interaction with basic molecules, i.e. C2H4, C2H5NH2, NH3, and CD3CN. Lattice perturbation is manifested by a reverse change of an IR band at the transmission window region for a bare cation at 916 cm(-1), giving a relaxation shift for the 1 : 1 complex, Delta(r), equal to 10-26 cm(-1). The order of Delta(r) values was as follows: C2H5NH2 congruent to CD3CN > NH3 much greater than C2H4. The Value of the 'relaxation shift' correlates well with the strength of the cobalt-ligand bonding in Go-adsorbate complexes. It has been found that during the desorption experiment on CoH-BEA of Co/Al> 0.2 at temperatures above 300 degrees C, the Co-ethylamine is converted into the Go-acetonitrile complex without oxygen present in the gas phase. This transformation occurs on the single Co ions and is not connected with non-specified Co oxidic species present in some highly Go-loaded CoH-beta zeolites. (C) 1999 Elsevier Science B.V. All rights reserved.