SELECTIVE CHEMISORPTION AND OXIDATION REDUCTION KINETICS OF SUPPORTED COPPER-OXIDE CATALYSTS PREPARED FROM COPPER(II) ACETYLACETONATE

Copper(II) oxide catalysts, prepared by non-aqueous adsorption of Cu(acac)2 on Cab-O-Sil followed by thermal decomposition, were titrated by NO and N20 to characterize the dispersion of the copper ions. These catalysts showed molar ratios of NO/Cu close to unity when the Cu loadings were less than 2.5 wt%. For samples having loadings greater than 3.8 wt% Cu, the NO/Cu molar ratios were near 0.7. The NO/Cu molar ratio also depended upon the catalyst preparation technique subsequent to the initial impregnation with Cu(acac)2 when the Cu loadings were ≥ 3.5 wt%. Samples washed with fresh acetonitrile showed NO/Cu ratios close to unity, whereas, those not so washed showed NO/Cu ratios near 0.7. IR spectra of NO sorbed on partially decomposed samples showed only "bent" CuNO, whereas, NO sorbed to the sample which was totally decomposed showed both linear and bent CuNO. Selected samples (3.8 and 8.6 wt% Cu) were reacted with N2O to determine the dispersion of the Cu. The sample having 8.6 wt% Cu reacted with the N2O to give a dispersion of 0.43; whereas the other sample (3.8 wt%) did not react with the N2O. This dispersion determined by N2O agreed with that calculated from NO titration (0.47) if the NO/Cu stoichiometry was assumed equal to unity. Subsequently, these catalysts were reduced in H2 and reoxidized in O2 to determine the oxidation and reduction kinetics as a function of copper loading. The 3.8 wt% Cu sample lost 1 O/Cu upon reduction in H2 and gained l O/Cu for reoxidation in O2 for up to five redox cycles; whereas, the 8.6 wt% Cu sample showed a stoichiometry of O/Cu which decreased from 1.00 to 0.57 after five redox cycles. © 1991.