Synthesis of early-transition-metal carbide and nitride nanoparticles through the urea route and their use as alkylation catalysts.

The use of urea as either a carbon or a nitrogen source enabled the synthesis of various early-transition-metal nitride and carbide nanoparticles (TiN, NbN, Mo(2)N, W(2)N, NbC(x)N(1-x), Mo(2)C and WC). The ability of these particles to promote alkylation reactions with alcohols was tested on benzyl alcohol and acetophenone at 150 degrees C for 20 h in xylene. Group IV and V ceramics proved to be able to catalyse the formation of 1,3-diphenyl propenone, whereas group VI ceramics showed a tendency to promote the Friedel-Crafts-type reaction of benzyl alcohol on xylene (the solvent). TiN featured the highest activity for the alkylation of ketones and was further tested for more difficult alkylations. Group VI ceramics were further investigated as catalysts for the Friedel-Crafts-type alkylation of aromatics with activated alcohols. Interestingly, even hexanol could be effectively used for these reactions.

High-surface-area TiO2 and TiN as catalysts for the C-C coupling of alcohols and ketones.

To design more sustainable processes for the alkylation of ketones, the use of both atom-ineffective leaving groups such as halides and boron as well as noble-metal-based catalysts should be avoided. For that purpose, high-surface-area titanium nitride was prepared from high-surface-area titanium dioxide using cyanamide as a transcription agent. The resulting nitride as well as the initial oxide proved to be effective and versatile catalysts for the alkylation of ketones with alcohols. Interestingly, the TiN catalyst yields unsaturated compounds, while the oxide-based catalyst mainly yields saturated coupling products. As a result of its metallic properties, TiN shows a strong tendency to catalyse the dehydrogenation of alcohols, which then undergo aldol condensation with ketones. In contrast, TiO(2) promotes the direct nucleophilic attack of ketones on alcohols.

Selective partial hydrogenation of hydroxy aromatic derivatives with palladium nanoparticles supported on hydrophilic carbon.

Selective hydrogenation of phenol to cyclohexanol in the aqueous phase was achieved using a new catalytic system based on palladium particles supported on hydrophilic carbon prepared by one-pot hydrothermal carbonisation.