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Keywords:

  • aldehydes;
  • hydrogenation;
  • nanotubes;
  • supported catalysts;
  • surface chemistry

Abstract

Platinum and iridium organometallic precursors are used to prepare nanosized, thermally stable multiwalled carbon nanotube-supported catalysts. The materials are characterized by N2 adsorption at 77 K, temperature-programmed desorption coupled with mass spectrometry, H2 chemisorption, transmission electron microscopy and thermogravimetric analysis; they are tested in the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol under mild conditions (363 K and 1 MPa). A thermal activation at 973 K is found to have a very positive effect over both activity and selectivity, leading to selectivities of approximately 70 %, at 50 % conversion, regardless of the active metal phase (Pt or Ir). Since no noticeable differences in the metal particle sizes are detected, the results are interpreted in light of an enhanced metal/support interaction. This effect, induced by the removal of oxygenated surface groups, is thought to change the adsorption mechanism of the cinnamaldehyde molecule.