Ruthenium oxide colloidal

The liquid phase hydrogenation of benzene on carrier-fixed ruthenium colloid catalysts suspended in an aqueous solution of sodium hydroxide proceeds with 59% cyclohexene selectivity at 50% benzene conversion. The catalysts are prepared by adsorbing a hydrophilic stabilized ruthenium metal colloid on lanthanum oxide. Protection of metal colloids with chiral molecules can lead to a new type of enan-tioselective catalyst combining good selectivity control with extraordinarily high activity in hydrogenation reactions. This concept has been applied for the first time in the form of platinum sols stabilized by the alkaloid dihydrocinchonidinel °°l (Fig. 7). 

Hara M, Waraksa CC, Lean JT, Lewis BA, Mallouk TE (2000) Photocatalytic water oxidation in a buffered tris(2,2 -bipyridyl)ruthenium complex-colloidal Ir02 system. 

Cui H, Park J-H, Park J-G. Effect of oxidizers on chemical mechanical planarization of ruthenium with colloidal silica based slurry. ECS J Solid State Sci 7ecfeioZ2013 2(l) P26—30. Cui H, Park J-H, Park J-G. Corrosion inhibitors in sodium periodate slurry for chemical mechanical planarization of ruthenium film. ECS J Solid State Sci Technol 2013 2(3) P71-5. 

Kim H, Popov BN (2002) Characterization of hydrous ruthenium oxide/carbon nanocomposite supercapacitors prepared by a colloidal method. J Power Sources 104 52-61... 

Jusys, Z., Kaiser, J., and Behm, R. J. (2003). Simulated air bleed oxidation of adsorbed CO on carbon supported Pt. J. Electroanal. Chem. 554-555 427- 37 Karuppaiah, C. and Lakshmanan, B. (2003). Carbon Monoxide Filter. US Patent No. 6517963 Kim, H. and Popov, B. N. (2002). Characterization of hydrous ruthenium oxide/carbon nanocomposite supercapacitors prepared by a colloidal method. J. Power Sources 104(1) 52-61 Knights, S. D., Colbow, K. M., St-Pierre, J., and Wilkinson, D. P. (2004). Aging mechanisms and lifetime of PEFC and DMFC. J. Power Sources 127(1-2) 127-134 Lakshmanan, B. and Weidner, J. W. (2002). Electrochemical CO filtering of fuel-cell reformate. Electrochem. Solid-State Letts. 5 A267-A270... 

It was found, that also Ru and Os colloids can act as catalysts for the photoreduction of carbon dioxide to methane [94, 95]. [Ru(bpy)3]2+ plays a role of a photosensitizer, triethanolamine (TEOA) works as an electron donor, while bipyridinium electron relays (R2+) mediate the electron transfer process. The production of hydrogen, methane, and small amounts of ethylene may be observed in such a system (Figure 21.1). Excited [Ru(bpy)3]2+ is oxidized by bipyridinium salts, whereas formed [Ru(bpy)3]3+ is reduced back to [Ru(bpy)3]2+ by TEOA. The reduced bipyridinium salt R + reduces hydrogen and C02 in the presence of metal colloids. Recombination of surface-bound H atoms competes with a multi-electron C02 reduction. More selective reduction of C02 to CH4, ethylene, and ethane was obtained using ruthenium(II)-trisbipyrazine, [Ru(bpz)3]2+/TEOA/Ru colloid system. The elimination of hydrogen evolution is thought to be caused by a kinetic barrier towards H2 evolution in the presence of [Ru(bpz)3]2+ and noble metal catalysts [96]. 

Over ruthenium dioxide quinoline was hydrogenated to tetrahydroquinoline in 97.5% yield at 80°C and 8.2 MPa H2 and to decahydroquinoline in 98% yield at 120°C and 9.3 MPa H2.3 Quinoline was also hydrogenated to tetrahydroquinoline over colloidal platinum in neutral solution or as the hydrochloride over platinum oxide in absolute ethanol.30 Hydrogenation to decahydroquinoline was performed with platinum black (Willstatter) or colloidal platinum (Skita) in acetic acid.73,74 Hiickel and Stepf hydrogenated quinoline under almost the same conditions as used by Skita and Meyer, and obtained the decahydroquinoline consisting of approximately 80% of trans and 20% of cis isomers (eq. 12.46). 

Visible light-induced cleavage of water has been reported for a mixed colloidal clay system consisting of a mixture of sepiolite clay-Ru02-Ru(bpy)3 + colloid (for O2 production) and Al,cEui (OH)3-Pt colloid (for H2 production) [165]. A turnover number of 20 with respect to the sensitizer, Ru(bpy)3 +, was observed. It was reported that the gas (H2 + O2) evolution displayed a damped oscillatory behavior. Photo-oxidation of water by tran5-diaqabis-(2,2 -bipyridine)ruthenium(2- -) adsorbed on the surface of hectorite clay has also been reported [166]. 

When referring to Ti02-based photocatalytic systems it is important to note that, in most cases, the semiconducting oxide is associated there with a noble metal or/and a noble metal oxide catalyst. While the role played by these catalysts in (partial) cathodic reactions seems relatively well understood it remains less clear with regard to the photoanodic reactions. In particular, the exact function of the extensively used ruthenium dioxide catalyst has been questioned The role of Ru02 as a hole-transfer catalyst has, for example, been established through laser-photolysis kinetic studies in the case of photo-oxidation of halide (Br and CP) ions in colloidal titanium dioxide dispersions. In fact, the yields of Brf and ClJ radical anions, photogenerated in the course of these reactions. 

Kleijn, J.M. and Lyklema, J., The electrical double layer on oxides Specific adsorption of chloride and methylviologen on ruthenium dioxide, J. Colloid Interf. Sci., 120, 511, 1987. 

The aim of this contribution is to present data on the preparation of catalysts containing as embedding species a large family of eolloids such as colloids of ruthenium, platinum, or palladium-gold alloys and triflate derivatives such as lanthanum and silver triflate or tert-butyldimethylsilyltrifluoromethanesulfonate (BMSTM). Silica, zirconia and tantalum oxides were used as carrier. All these preparations considered the polymeric sol-gel route using as starting materials silicon, zirconium or tantalum alcoxides. 

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