Kazunori Utani

State of Ru on CeO2 and its catalytic activity in the wet oxidation of acetic acid

Abstract The relationship between the state of Ru on CeO 2 and catalytic activity in the wet oxidation of acetic acid was investigated for Ru/CeO 2 catalysts prepared by different methods. The temperature programmed reduction (TPR) experiments of Ru/CeO 2 showed that the oxygen species of RuO 2 was reduced at different temperatures depending upon the methods of preparation. Ru species reduced at low temperatures could not be observed by TEM and XRD. It was concluded that RuOCe bonds in the well-dispersed Ru species are highly fragile and its mobile oxygen is the active species in the wet oxidation.

Combustion activity of Ag/CeO2 composite catalyst

Oxidation of methane and carbon monoxide was carried out on silver/ceria composite oxide prepared by co-precipitation, and the behavior of the lattice oxygen of silver was investigated. In the high temperature oxidation of methane, silver(I) oxide decomposed and aggregated to large particles of metallic silver and rapidly deactivated. On the other hand, silver retained high activity during the low temperature oxidation of carbon monoxide. It was found, however, that ceria accelerated the desorption of the lattice oxygen of silver, which was assumed to be related to the well known oxygen storage function of ceria. Although silver tends to be converted more easily to metallic state in the presence of ceria, the function of ceria of sustaining the dispersed state of silver will help to maintain the high activity of the latter in the oxidation of carbon monoxide.

Oxidative decomposition of formaldehyde on silver-cerium composite oxide catalyst

Silver-cerium composite oxide was active for low temperature oxidative decomposition of formaldehyde. Its high activity was due partly to the high dispersion of active silver on the CeO2. The surface oxygen of this composite catalyst was removed more easily than those on single component Ag2O or CeC2, which also seemed to contribute to the high activity of this catalyst. IR analysis revealed that formaldehyde was decomposed both on silver-cerium composite catalyst and CeO2 in the presence of oxygen to produce methoxide, dioxymethylene, and/or polyoxymethylene even at room temperature. In addition bi-carbonate was formed on silver-cerium composite catalyst and formate was produced on CeO2. These intermediates suffered further oxidation at higher temperatures (373 and 423 K) easily on silver-cerium composite catalyst, whereas degradation of them was rather difficult on CeO2.

DECOMPOSITION OF N2O ON RH-LOADED ZEOLITES

N2O was decomposed over Rh supported on NaY zeolite and ZSM5. With low Rh-loading (≤0.1 wt.%) the activity of Rh was much higher than that supported on SiO2 and CeO2. On the contrary, the activity of Rh-loaded zeolites (0.1 wt.%) was not so high or even lower than that on SiO2 for the oxidation of toluene, which has a larger molecular size than N2O. Thus the Rh present inside the zeolite cavity was especially effective in the decomposition of N2O.

Effect of the preparation condition on the properties of titania-silica derived from tetraisopropyl titanate(IV) and tetraethyl orthosilicate

Titania-silica mixed oxide was prepared by hydrolyzing tetraethyl orthosilicate and tetraisopropyl titanate(IV) with a mixture of ethanol and 0.01 N aqueous acetic acid. Surface Ti content, BET surface area, and the number of acid sites increased with an increase in 0.01 N aqueous acetic acid. Thus hydrolysis of both alkoxides occurred simultaneously with a large amount of the acetic acid solution, and there was extensive interaction between TiO2 and SiO2 phases. With small amount of 0.01 N aqueous acetic acid, however, titanium hydroxide was first formed and, then, it was covered with the silica phase produced in a later stage of the hydrolysis. Increase in the acetic acid solution also led to the formation of a large amount of tetrahedral Ti species, which were active for the epoxidation of oct-1-ene usingt-butyl hydroperoxide as an oxidant.

Epoxidation of 1-Octene with tert-Butyl Hydroperoxide Catalyzed by ZrO2/Aerosil-SiO2

Oxidation of 1-octene was carried out with tert-butyl hydroperoxide at 343 K over ZrO2/Aerosil-SiO2. Loading of less than 10 mol% of ZrO2 on ultrafine Aerosil-SiO2 gave exclusively 1,2-epoxyoctane. The pre-edge peak area of Zr K-edge XANES and g values of the ESR signals of O2− species on ZrO2/SiO2 discriminate structures of ZrO2. On the basis of these analyses it is concluded that the coordinatively unsaturated zirconium oxide is responsible for the selective epoxidation of 1-octene with tert-butyl hydroperoxide.

The Structure of Zirconium Oxide in Silica Matrix and its Epoxidation Activity

Zirconia-silica composite oxides were prepared by a sol-gel method, and the state of Zr in the silica matrix was analyzed in relation to its activity in the epoxidation of oct-1-ene with t-butyl hydroperoxide. XAFS analysis suggested that Zr in the composite oxides with low Zr content was in the coordinatively less saturated state compared with those in the oxides with higher Zr contents. Epoxidation of oct-1-ene proceeded effectively on the oxides with low Zr contents. The first step of the epoxidation was assumed to be the interaction of t-butyl hydroperoxide with the coordinatively unsaturated site of Zr.

Properties of χ-alumina as related to catalysis

Abstractχ-Alumina was synthesized by thermal decomposition of aluminium(III) isopropoxide, and its properties were investigated. The change in its surface area with increasing calcination temperature resembled that of γ-alumina. Both aluminas had the same acid strength, and their activities in isomerization of 1-butene were the same. χ-Alumina as a support for molybdenum catalyst in the epoxidation of allyl alcohol also behavedin the same manner as γ-alumina. Thus χ-alumina has almost the same catalytic properties as γ-alumina.