Struktur-Aktivit�tsbeziehungen von Hydrierkatalysatoren

Abstract

Structure / Activity Correlations of Hydrogenation Catalysts The reason for different activities of group VIII metal catalysts in several hydrogenation reactions is unknown. The activity of group VIII metal catalysts decreases in the hydrogenation of crotonaldehyde to butyraldehyde in the following sequence Pd > Pt > Ni > Rh > Co; Ir. However in the hydrogenation of butyraldehyde to butanol the sequence of metals is inversely. The hydrogenations of crotonaldehyde and butyraldehyde proceed as ligand addition reactions. The reaction rate depends on the nucleophilicity of atomically chemisorbed hydrogen. Whereas the reaction rate in the hydrogenation of crotonaldehyde increases, the hydrogenation rate of butyraldehyde decreases with the nucleophilicity of atomically chemisorbed hydrogen.

Hydrodechlorination of Et3NBCl3 Catalyzed by Amorphous Nickel Boride – A Mechanistic Approach

“…In respect to the solvent triethylamine, one needs to state that the catalyst is able to activate the N-CH 2 hydrogen atoms, as has been demonstrated by deuterium labeling experiments. Although it cannot directly be isolated from the dehydrogenation reaction because of its minute concentration, the formation of an intermediate iminium ion was indirectly demonstrated by the suppression of the subsequent catalytic reaction to Et 3 NHCl [Equation (1)] by conducting the experiment without molecular hydrogen.…”

“…The solvent was removed by vacuum distillation, and a white precipitate was obtained. 1 H NMR (CDCl 3 ): δ = 1.41 (t, 3 H, CH 3 ), 3.42 (q, 2 H, CH 2 ) ppm. 11 B{ 1 H} NMR (CDCl 3 ): δ = 10 (s) ppm.…”

“…All volatiles were removed in vacuo, and the white residue was finally extracted with a hexane/toluene (20 mL/2 mL) mixture. 1 H NMR (CDCl 3 ): δ = 1.2 (t, 3 H, CH 3 ), 2.9 (q, 2 H, CH 2 ), 2.7 (s, 2 H, BH) ppm. 11 B{ 1 H} NMR (CDCl 3 ): δ = -4.2 (s) ppm.…”

“…An important objective in sustainable chemistry is the replacement of precious and expensive reducing agents such as NaBH 4 , LiAlH 4 , R 3 SnH, R 3 SiH, and N 2 H 4 by earth‐abundant hydrogen through the use of appropriate catalysts. The number of heterogeneous hydrogenation catalysts developed and their use in a large range of hydrogenation procedures is legion 1. Hydrodehalogenation reactions are a related problem but provide a much more complicated task in respect to catalyst requirements 2.…”

A Short Review on Ni‐Catalyzed Methanation of CO2: Reaction Mechanism, Catalyst Deactivation, Dynamic Operation

“…As already described, Ni-catalyzed methanation is a structure-sensitive reaction with an activity and selectivity highly depending on the metal dispersity [50,70,71]. Thus, a change in surface geometry is particularly crucial in this case [44,52].…”