Role of mixed metal oxides in catalysis science—versatile applications in organic synthesis

Steam reforming of ethanol over CuO/CeO2 was studied. Acetaldehyde and hydrogen were mainly produced at 260degreesC. At 380degreesC, acetone was the main product, and 2 mol of hydrogen was produced from 1 mol of ethanol. The formation of hydrogen accompanied by the production of acetone was considered to proceed through the following, consecutive reactions: dehydrogenation of ethanol to acetaldehyde. aldol condensation of the acetaldehyde, and the reaction of the aldol with the lattice oxygen [O(s)] on the catalyst to form a surface intermediate, followed by its dehydrogenation and decarboxylation. The overall reaction was expressed by2C(2)H(5)OH + H2O --> CH3COCH3 + CO2 + 4H(2). Ceria played an important role as an oxygen supplier. The addition of MgO to CuO/CeO2 resulted in the production of hydrogen at lower temperatures by accelerating aldol condensation. (C) 2004 Elsevier B.V. All rights reserved.

Catalytic steam reforming of ethanol to produce hydrogen and acetone

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.

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

Studies on nano-sized particles have been the range for the past 10–15 years. With rapid growth of metal oxide nanotechnologies during the last decades, the application of this material in the field of catalysis has become a substantial research area. In the past decades, the utilization of transition metal oxide nanoparticle catalysts for industrial application in the synthesis of important chemical intermediates has been investigated by industrial and academic communities. Compared to other catalysts, one of the outstanding properties of metal oxide nanoparticles in catalysis is represented by the high selectivity which allows discrimination within chemical groups and geometrical positions, favoring high yields of the desired product. This review is devoted to dealing with the application of transition metal oxide nanoparticles as catalyst for oxidations of sulfides, alcohols, olefins, and alkanes toward the synthesis of a variety of organic compounds, such as sulfoxides, aldehydes and ketones, carboxylic acids, epoxides and alcohols.

Transition metal oxide nanoparticles as efficient catalysts in oxidation reactions

Partial oxidation of methane (POM) to synthesis gas was studied over Ru catalysts (1% (w/w)) supported on silica, alumina and ceria-zirconia. Catalyst samples were prepared by incipient wetness and ...

Partial oxidation of methane over supported ruthenium catalysts

Three kinds of Ru/CeO2 catalysts were prepared. The mobility of the oxygen on Ru and their catalytic activity in the wet oxidation of acetic acid was investigated. Ru was present in the form of RuO2, and TPR experiment showed that the reaction, RuO2 + 2H2 → Ru + 2H2O, took place in different temperature ranges depending upon the kind of the catalysts. The catalyst with easily reducible oxygen on Ru had high activity in wet oxidation, and the importance of the release of oxygen from Ru to the reactant was suggested.

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Selective epoxidation of allyl acetate with tert -butyl hydroperoxide (TBHP) over the groups IV–VI metal oxides supported on SiO 2 , Al 2 O 3 and TiO 2 has been studied. The epoxidation required higher temperatures than those of α-olefins and cycloolefins did. The poor epoxidation selectivity was attributed to concurrently occurring reactions of epoxides produced during epoxidation. The highest yield of epoxide was achieved over MoO 3 /TiO 2 with an adequate MoO 3 loading which was determined so that the surfaces of TiO 2 were two-dimensionally and fully covered with MoO 3 .

Yoshio Ikeda

Papers

Reduction behavior of Ru/CeO2 catalysts and their activity for wet oxidation

Epoxidation of allyl acetate with tert-butyl hydroperoxide catalyzed by MoO3/TiO2