Core/Shell Ruthenium–Halloysite Nanocatalysts for Hydrogenation of Phenol

Halloysite tubular nanoclay was applied as a template for synthesis of ruthenium core–shell composite catalysts for the first time; 50 nm diameter ceramic tubular systems with metal seeded interiors were produced. The procedure for the metal deposition and prior halloysite modification had a significant influence on properties of the catalyst and, as a consequence, on its activity in hydrogenation of phenol. Cyclohexanol was the main reaction product, but its yield depended on the substrate conversion and nanoarchitectural composition of the catalysts used. The maximum catalytic activity (turnover frequency, TOF) achieved was 17 282 h –1 in terms of hydrogen uptake per surface Ru atoms. The substrate selectivity of halloysite-based catalysts was also demonstrated at the comparative hydrogenation of phenol and various cresols.