Cu-Ru-TA catalysts

Comparison of the chiral bimetallic catalysts, Cu-Pd-TA and Cu-Ru-TA, showed significant differences. In the case of Cu-Ru-TA catalyst, introducing 0.1-0.5% Ru into Cu-TA leads to almost complete loss of enantioselectivify, while in the cases of Cu-Ru and Cu-Pd catalysts such chiral deactivation proceeds only after introduction of more than 5% Pd. The general catalytic activity of the Cu-Ru-TA catalysts increased with increasing Ru content, while the Cu-Pd catalysts exhibited a synergism of catalytic activity, which was explained by a peculiar structure of the active center and by invoking a ligand effect A similar effect for skeletal Cu-Ru-TA catalysts was... 

Promotion of Ru -TA catalyst with Cu, preserved the high overall reaction rate characteristic for pure Ru catalyst and somewhat inereased the ee from 1.4% to 3.3% for Cu-Ru eatalysts. This revealed a synergism in the aetion of mixed bimetal catalysts. 

In other conditions the ee s of 17-20% for pure Cu-TA eatalyst dropped to an ee of 0.6% after introduction 0.5% Ru into the eatalyst and then increased after further increasing Ru content up to an ee of 2.5%, which is characteristic for the pure Ru-TA catalyst. 

Comparison of the properties of Cu-Ru-TA and Cu-Pd-TA catalysts using electrochemical methods showed that the strength of adsorption of... 

The Ru-Cu catalysts modified with TA also proved to be not very effective. Skeletal Cu-Ru catalysts (1 1) were prepared by leaching a Cu-Ru-A1 alloy (15 15 70) at 60°C with a 20% aqueous NaOH solution. Modification of the Cu-Ru (1 1) catalyst was carried out in a 4% aqueous solution of (2R,3R)-tartaric acid at pH 4.4. Hydrogenation of EAA was carried out without solvent at 30°C and 140 bar for 5h. For comparison the hydrogenation of EAA using skeletal Ru and Cu catalysts were also examined under the same conditions. Results are summarized in Table 4.14. 

Studies of the hydrogenation of EAA at 90°C and 100 bar using supported 10% (Cu-Ru)-aerosil-TA catalysts with different Cu-Ru compositions showed that there is an antiparallel dependence between the optical 5deld and the reaction rate. This was especially tme at the 4 to 6 Ru Cu ratio, in which the ee dropped from Ihe 4% of the Ru-Cu catalyst to almost zero, while the rate ineresed linearly. ... 

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