Bimetallic platinum–ruthenium nanoparticles stabilised by pyridine‐ and monophosphine‐based ligands were prepared either in supercritical CO2 or in THF. TEM analyses evidenced a tendency of the nanoparticles prepared in supercritical CO2 to agglomerate. Both types of bimetallic nanoparticles were further confined into functionalised multiwalled carbon nanotubes. Upon confinement, PtRu nanoparticles stabilised by phosphine ligands appeared more agglomerated than those stabilised by the pyridine ligand. These materials were applied to cinnamaldehyde hydrogenation. Confined PtRu nanoparticles showed higher catalytic activity and selectivity than unsupported nanoparticles.

No abstract

Catalysts based on molybdenum carbide or nitride nanoparticles (2-5 nm) supported on titania were prepared by wet impregnation followed by a thermal treatment under alkane (methane or ethane)/hydrogen or nitrogen/hydrogen mixture, respectively. The samples were characterized by elemental analysis, volumetric adsorption of nitrogen, X-ray diffraction, and aberration-corrected transmission electron microscopy. They were evaluated for the hydrogenation of CO 2 in the 2-3 MPa and 200-300 • C ranges using a gas-phase flow fixed bed reactor. CO, methane, methanol, and ethane (in fraction-decreasing order) were formed on carbides, whereas CO, methanol, and methane were formed on nitrides. The carbide and nitride phase stoichiometries were tuned by varying the preparation conditions, leading to C/Mo and N/Mo atomic ratios of 0.2-1.8 and 0.5-0.7, respectively. The carbide activity increased for lower carburizing alkane concentration and temperature, i.e., lower C/Mo ratio. Enhanced carbide performances were obtained with pure anatase titania support as compared to P25 (anatase/rutile) titania or zirconia, with a methanol selectivity up to 11% at 250 • C. The nitride catalysts appeared less active but reached a methanol selectivity of 16% at 250 • C.