ИСТИНА

The interaction of CO with Co-ZSM-5 was investigated by a combination of IR spectroscopy and DFT calculations employing the ω/r correlation for calculations of CO stretching frequencies in order to gain more insight on Co2+cation coordination in the ZSM-5 zeolite and site-specificity of CO stretching frequency in IR spectra of CO/Co-ZSM-5 system. Experimental data were interpreted on the basis of a good agreement between experimental and theoretical results. Detailed analysis of both theoretical and experimental results reveals that no individual band can be assigned to specific type of CO–Co complex or to a one type of Co2+sites. On the contrary, several different type of carbonyl complexes contribute to each vibrational band discerned in the experimental IR spectra The new absorption band at 2215 cm-1 was assigned to the carbonyl complexes on Co(III) located in oxocations [Co2O2]2+. The data of quantum chemical DFT calculations showed that the most likely active centres in the oxidation of CO by oxygen on Co-ZSM-5 are the polynuclear oxocations [Co(III)-(µ-O)2-Co(III)]2+. The possible ways for the oxidation of carbon monoxide under these species were analysed