Direct coating of carbon-supported catalysts on monoliths and foams – Singular behaviour of Pd/MWCNT

• Carbon-supported Pd catalysts were coated on ceramic monoliths and metallic foams.
• The catalysts were directly coated on the substrates by the suspension method.
• Nitrobenzene hydrogenation was used as a model reaction.
• Despite a lower activity than the commercial catalyst, Pd/MWCNT outperformed other coated Pd/C catalysts once coated.
• The sintering during the thermal treatment of the coating was less severe for Pd/MWCNT than for the other catalysts.

Monolith or foam substrates were coated with various Pd/C suspensions by the washcoating method. The resulting structured catalysts were characterized by thermal analysis (TGA), physisorption of nitrogen (BET method) and electron microscopies (SEM and TEM). Their catalytic activity was evaluated in the model reaction of nitrobenzene hydrogenation. It was found that depending on the carbon source (carbon black, activated carbon or carbon nanotubes), the Pd/C deposits were more or less resistant to the coating procedure. All the samples were adherent to the substrates, but only Pd/MWCNT was still highly active after coating. The one-step deposition of nanotubes-based catalysts does not alter significantly the catalytic properties of the catalyst and is a promising alternative to nanotube layers grown in situ.

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