Ruthenium selectivity over

Nishimura and Kasai studied the hydrogenation of acetophenone in f-butyl alcohol using carefully prepared ruthenium and rhodium blacks.176 The selectivities for the formation of cyclohexyl methyl ketone and 1-phenylethanol as simultaneous products have been determined by application of the equation in Scheme 11.7. The values of K and/as well as the composition of the final products obtained are summarized in Table 11.13. Three ruthenium blacks—Ru (A), Ru (N), and Ru (B)—were prepared from the ruthenium hydroxide precipitated at pH 5,7, and 7.8, respectively, by adding lithium hydroxide solution to an aqueous solution of ruthenium chloride. It is seen that the selectivity for the saturated ketone (see figures in parentheses) was considerably higher over Ru (B) (43%) than over Ru (A) (25%) and Ru (N) (20%). The selectivity over Ru (N) increased markedly to 65% at 100°C and 5.9-7.8 MPa H2. Over rhodium... 

Inoue and co-workers have used ruthenium(ll) porphyrin 80 (Figure 16) to mediate the photochemical epoxidation of several alkenes with excellent selectivity over the formation of other oxidation products, including cyclohexene (up to 97% selectivity), norbornene (up to 99.7% selectivity), and cyclooctene (up to 99.9% selectivity) <2003JA5734>. 

Ruthenium-dispersed sol-gel thick-film electrodes were developed by Wang and co-workers [219]. All of these systems showed shelf-life stability in excess of 4 months and excellent selectivity over common interferents such as ascorbic acid, acetaminophen and uric acid. Based on this work, electrodes for lactate and amino... 

Table IV. Hydrocarbon Selectivities over Ruthenium—Iron Catalysts (Mol %) ...

Metallic membranes made of palladium (Pd), platinum (Pt), niobium (Nb), tantalum (Ta), vanadium (V), Yttrium (Y), and Ruthenium (Ru) have very high H2 selectivity over other gases because only H2 can transport through these membrane via dissolution and diffusion mechanism, while the other gases can only transport through... 

In the CWAO of carboxylic acids, noble metals give the best performances and stability. Ruthenium supported over ceria-zirconia shows the best performance. These catalysts are also preferable for CWAO of N-containing compounds such as aniline. Over Ru/Ce02, ammonium ions formed in the reaction are selectively oxidized into molecular nitrogen in the temperature range of 180 to 200°C, but above 200°C nitrite and nitrate ions form. 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

Both amine oxides related to pyridines and aliphatic amine oxides (/25) are easily reduced, the former the more so. Pyridine N-oxide has been reduced over palladium, platinum, rhodium, and ruthenium. The most active was rhodium, but it was nonselective, reducing the ring as well. Palladium is usually the preferred catalyst for this type of reduction and is used by most workers 16,23,84 158) platinum is also effective 100,166,169). Katritzky and Monrol - ) examined carefully the selectivity of reduction over palladium of a... 

The development of highly efficient methanol fnel cells depends on a nnmber of scientific aspects (1) the development of more highly active catalysts for methanol oxidation at temperatnres not over 60 to 70°C (desirable in cells without ruthenium, which is in short supply) (2) the development of selective catalysts for the oxygen electrode (i.e., of catalysts insensitive to the presence of methanol) and (3) the development of new membrane materials having a lower methanol permeability. 

The hydrogenation of C02 in the presence of amines to give dialkylformamides has been carried out directly in an IL/scC02 system. In this case, the ionic liquid was shown to play a dual role [74]. It is an effective solvent for the ruthenium phosphine catalyst and at the same time allows a distinct phase distribution of the polar carbamate intermediates and the less polar products formed during the conversion of C02. As a result, the selectivity of the reaction can be increased over conditions where scC02 is used as the sole reaction medium. 

The final cyclization manifold has been realized with a different ruthenium catalyst (Scheme 22). The cationic [Cp Ru(MeCN)3]PF6 induces exclusive endo-dig cyclization of both homopropargylic and bis-homopropargylic alcohols.29 73 The clean reaction to form a seven-membered ring is noteworthy for several reasons intramolecular exo-dig cyclization with bis-homopropargylic alcohols is not well established, the platinum-catalyzed case has been reported to be problematic,80 and the selectivity for seven-membered ring formation over the exo-dig cyclization to form a six-membered ring is likely not thermodynamic. The endo-dig cyclization manifold was thus significant evidence that a re-examination of alkyne hydrosilylation mechanisms is necessary (see Section 10.17.2). 

Fig. 6 Effect of water addition on selectivity to C02 over a Co-Ru/Ti02 catalyst.39 Reprinted from Applied Catalysis A, Vol. 233, J. Li, G. Jacobs, T. Das and B. H. Davis, Fischer-Tropsch synthesis effect of water on the catalytic properties of a ruthenium promoted Co/Ti02 catalyst, pp. 255-262. Copyright (2002), with permission from Elsevier.

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