David Edouard

Nitrogen-doped carbon nanotubes as a highly active metal-free catalyst for selective oxidation.

Catalytic reactions are generally carried out on supported metals or oxides, which act as an active phase and require impregnation and thermal treatment steps. During tests, the metal or oxide nanoparticles could be further sintered, which would induces deactivation. Direct incorporation of the active phase into the matrix of a support could be an elegant alternative to prevent catalyst deactivation. Here, we report that nitrogen-doped carbon nanotubes (N-CNTs) can be efficiently employed as a metal-free catalyst for oxidative reactions that allow the selective transformation of the harmful, gaseous H(2)S into solid sulfur. The catalyst exhibits a high stability during the test at high space velocity. The macroscopic shaping of the catalyst on the silicon carbide foam also increases its catalytic activity by improving the contact between the reactants and the catalyst. Such macroscopic shaping allows the avoidance of problems linked with transport and handling of nanoscopic materials and also reduces the pressure drop across the catalyst bed to a large extent.

UV-A photocatalytic treatment of Legionella pneumophila bacteria contaminated airflows through three-dimensional solid foam structured photocatalytic reactors

A 3D-structured photocatalytic media was designed for allowing a tubular reactor to work in a traversing-flow mode at low pressure drops with a strong increase in the surface area-to-volume ratio inside the reactor. A protective polysiloxane coating was performed for protecting a structured polyurethane foam and anchoring the active TiO(2) particles. Filled with the 3D-structured solid foam supporting TiO(2) photocatalyst, the reactor could thus take advantages from the static mixer effect and from the low pressure drop resulting from the reticulated foam support. Very efficient decontamination levels towards airborne Legionella pneumophila bacteria were reached in a single-pass test mode.

1D SiC decoration of SiC macroscopic shapes for filtration devices

The synthesis of a hierarchical support, constituted of a network of SiC nanofibers deposited on a SiC foam host resulting in a ceramic material with a controlled macroscopic shape and associated high specific surface area superior to 50 m2 g−1, has been reported for the first time. The new composite combines the nanoscopic properties of the SiC nanofibers’ network and controlled macroscopic shape and open porosity, typical of a SiC foam structure. The introduction of the nanostructures onto the host material allows a dramatic increase in the effective surface area which is extremely useful for the chosen field of application. This new type of material has been efficiently employed as a diesel particulate filter at high space velocity and without a detrimental pressure drop. In addition, the combination of such a hierarchical structure with high thermal conductivity could give rise to unexpected results in the field of heterogeneous catalysis where the mass and heat transport limitations still need to be improved.