Dispersion and Reactivity of Copper Catalysts Supported on Al₂O₃−ZrO₂

Abstract

A series of CuO/Al(2)O(3)-ZrO(2) catalysts with Cu loadings varying from 1.0 to 20 wt % were prepared and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of CO(2) and NH(3), electron spin resonance (ESR), and Brunauer-Emmett-Teller surface area measurements. The dispersion and metal area of copper were determined by the N(2)O decomposition method. XRD results suggest that the copper oxide is present in a highly dispersed amorphous state at copper loadings < 10 wt % and as a crystalline CuO phase at higher Cu loadings. ESR results suggest the presence of two types of copper species on the Al(2)O(3)-ZrO(2) support. TPR results suggest well-dispersed copper oxide species at low Cu loadings and crystalline copper oxide species at high Cu loadings. Well-dispersed copper oxide species were reduced more easily than large copper oxide species by H(2). The results of CO(2) TPD suggest that the basicity of the catalysts was found to increase with an increase of copper loading up to 5.0 wt % and decreases with a further increase of copper loading. The results of NH(3) TPD suggest that the acidity of the catalysts was found to decrease with an increase of copper loading up to 5.0 wt % and increases with a further increase of copper loading. The catalytic properties were evaluated for the vapor-phase dehydrogenation of cyclohexanol to cyclohexanone and correlated with the results of CO(2) TPD measurements and the dispersion of Cu on the Al(2)O(3)-ZrO(2) support.

Correlation between Structural and Catalytic Properties of Copper Supported on Porous Alumina for the Ethanol Dehydrogenation Reaction

“…The presence of two peaks is generally associated with lower dispersion. [32][33][34] Compared to values obtained by N 2 Ot itration for copperc atalysts with equivalentm etal loadings, [35,36] the dispersion values obtained herea re higher,b ut they are of the same order as those estimated for 10 Cu/ZrO 2 catalysts using the same methodology. [15] This finding highlights the key role of the textural features of macro/mesopore alumina with ah igh surface area and high total pore volume in the production of catalysts with well-dispersed Cu 0 and Cu + species, even at high copperl oadings.…”

Cross-Aldol Condensation of Acetone and n-Butanol into Aliphatic Ketones over Supported Cu Catalysts on Ceria-Zirconia

“…(Table 1). However, it should be noted here that the NNH3 value measured in this work is a combination result of surface Cu species and xCeZr support, because acid sites can be generated by deposition of metallic Cu particles onto support materials [28,29]. For Pd/ceria-zirconia catalysts, surface acidity was reported to be associated primarily with zirconia and not with ceria and Pd particles [16].…”

Direct transformation of ethanol to ethyl acetate on Cu/ZrO2 catalyst

“…Broad peaks at 2h = 30.5°pointing to an amorphous or semicrystalline nature of the zirconia in these samples [12]. The absence of crystalline CuO or Cu 2 O peaks cannot be ruled out as they might be less than 40 Å in size, which is beyond the detection capacity of the XRD technique [13].…”