Zeolites ruthenium oxide support

Dutta P K and Vaidyalingam A S (2003), Zeolite-supported ruthenium oxide catalysts for photochemical reduction of water to hydrogen , Micropor Mesopor Mater, 62, 107. 

Iron and its compounds (carbide, nitride), as well as ruthenium, cobalt, rhodium, and molybdenum compounds (sulfide, carbide), are used most frequently to produce high-molecular-weight hydrocarbons. Iron can be prepared as a high-surface-area catalyst (==300 m /g) even without using a microporous oxide support. 7-AI2O3, Ti02, and silica are frequently used as supports of the dispersed transition-metal particles. Recently zeolites, as well as thorium oxide and lanthanum oxide, have... 

Irrespective of the nature of the reaction intermediate, enolic type (11) or surface carbide (12), the dechne of the turnover number for the zeolites with higher Si/Al ratio can be explained as follows. For platinum (13) and palladium (14,15) loaded zeolites, support effects are known to exist. The higher the acidity (and the oxidizing power) of the zeolite, the higher will be the electron-deficient character of the supported metal. It also is well established now (16) that the average acidity of hydrogen zeohtes increases with the Si/Al ratio. This explains why the electron deficient character of ruthenium should increase with the Si/Al ratio of the zeolite, and a stronger interaction with adsorbed CO should be expected. Vannice (19,20) reported that the N value for CH4 formation decreases when the heat of adsorption for CO increases. All this explains why the tmnover number of the methanation reaction over ruthenium decreases when the Si/Al ratio of the zeolite support increases. 

The early chemistry of hexanuclear carbonyl clusters, including those of ruthenium and osmium, has been reviewed.The hexaruthenium dianion [RuslCOlis] is prepared inside NaX-zeolite cages in 80-90% yields by treatment of [Ru(NH3)6] /NaX with CO and H2. Oxidation of the supported dianion results in cluster degradation to mononuclear ruthenium products, a process that is reversible on re-exposure to CO/H2. A redetermination of the crystal structure of Os6(CO)i8, as its chloroform solvate, confirms the bicapped tetrahedral metal core seen with the unsolvated cluster. 

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