PdO/Al2O3–(Ce1-X Zr X )O2 catalysts: effect of the sol-gel support composition

Abstract

The contribution of (Ce 1-X Zr X )O 2 additives to alumina supports prepared by sol-gel and the catalytic properties of PdO/Al 2 O 3 -(Ce 1-X Zr X )O 2 catalysts ($0.3 wt% Pd, $5 wt% (Ce 1-X Zr X )O 2 ) in CO oxidation was herein investigated. The addition of (Ce 1-X Zr X )O 2 to the support enhanced the surface area and decreased the size of Al 2 O 3 particles. The UV-Vis bands of PdO particles and Pd 2+ ions indicate that zirconia in (Ce 1-X Zr X )O 2 promotes palladium-support interactions by forming highly dispersed PdO particles. Temperature-programmed reduction (TPR) in hydrogen revealed that ceria enhanced the redox capacity of the supports while zirconia lowered the reduction temperature of palladium oxide species. The comprehensive study revealed that the Ce/Zr ratio was a key factor influencing the catalytic activity of samples in CO oxidation, because palladium oxide-support interactions had a significant effect in changing of the reducibility of samples. So, the PdO/Al 2 O 3 -(Ce 0.5 Zr 0.5 )O 2 exhibited the highest catalytic activity.

Aerobic Oxidative Esterification of Benzyl Alcohol and Acetaldehyde over Gold Supported on Nanostructured Ceria–Alumina Mixed Oxides

“…Catalyst preparation Nanostructured Ce-Al mixed oxides with different contents of ceria (10 and 30 wt %) were prepared by a sol-gel method using organometallic precursors as described previously. [41] A solution of cerium(III) 2,4-pentanedionate hydrate (Alfa-Aesar) in ethanol with moderate agitation was added to a mixture of aluminum sec-butoxide (Alfa-Aesar) in 2-methyl-2,4-pentanediol (Alfa-Aesar), and the mixture was heated to reflux with moderate agitation for 3 h. Hydrolysis was performed by the addition of the deionized water. The gel obtained was aged for 10 h. The samples were dried under vacuum ( % 10 À3 torr) at 100 8C for 12 h then heated to 450 8C under N 2 and kept at this temperature for 12 h. Finally, the samples were treated in O 2 at 650 8C for 4 h for the decomposition of organic residuals.…”

Photocatalytic Degradation of Diclofenac Using Al2O3-Nd2O3 Binary Oxides Prepared by the Sol-Gel Method

“…The UV-Vis spectra of the γ-Al2O3 and Nd2O3 references as well as the Al-Nd-x binary oxides are shown in Figure 7. The spectrum of γ-Al2O3 presented a broad absorption in the 240-330 nm range, which is associated with electronic charge transfer and also with the accumulation of defects in the structure of this compound [25]. Regarding the Nd2O3 sample, the spectrum contains an intense band in the 200-290 nm range associated with an exchange of electrons between the valence and conduction bands [9,26]; also, a set of sharp absorption bands between 330 and 760 nm correspond to electron transitions within the 4f shell of neodymium [3,27].…”

Influence of thermal treatment on catalytic performance of Pd/(Ce,Zr)Ox–Al2O3 three-way catalysts

“…So investigation of CZA mixed oxide is significant to enhance performance of TWC. Moreover, these materials would eventually help to decrease the cold-start emissions mainly by permitting the catalyst to be located closer to the engine [20][21][22][23]. The chemical and structural characteristics of CZA mainly depend on the preparation method.…”