II International Symposium on Carbon for Catalysis ABSTRACTS

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can condition the adsorption phenols and other molecules with aromatic rings, since in this
case the interaction of the ring with the carbon surface is mainly through the π electron on the
graphene layers of the structure; their amount decreases with the increase in oxygen surface
groups, because of the high electronegativity of oxygen.
Carbon materials constitute a very flexible set of supports for heterogeneous catalysts
and, additionally, some of them can act also as catalysts by themselves. Their physical
(surface area and porous texture) and chemical surface properties (presence of surface
heteroatom functionalities, mainly oxygen groups) can be tailored to develop a large surface
area to disperse the active phase, the adequate pore size distribution to facilitate the diffusion
of reactants and products to and from the surface, and the hydrophobic/hydrophilic and
acid/base character needed to obtain the best performance.
Many types of carbon materials have been used as catalysts and catalyst supports:
graphite, carbon blacks, activated carbons, activated carbon fibres and cloths, nanotubes, etc.;
among them, the most important are, by far, activated carbons and carbon blacks. Nowadays,
the most important reactions carried out using carbon supported catalysts include
hydrogenations (mainly in fine chemistry processes), oxidation (CO), combustion (VOCs)
and electro-oxidation reactions in fuel cells. For these applications, the intrinsic properties of
carbonaceous materials play a major role in the catalytic properties. Thus, the absence of
surface oxygen functionalities gives the carbon an hydrophobic character that is very
important when it is going to be used as support for VOCs combustion catalyst, as these
compounds are generally going to be treated in the presence of humidity. On the other hand,
the presence of these oxygen functionalities is very important in the catalyst preparation stage,
where they can be used to control the dispersion of the active metal. Furthermore, oxygen
groups and surface sites generated on the carbon surface when they are removed under
activation or reaction conditions, can be used to direct catalytic selectivity towards desired
products in fine chemical selective hydrogenations. It is also worth to mention that in these
processes (and in many others) bimetallic catalysts are used, and the intrinsic inertia of carbon
supports can be used to facilitate the interaction between both metals. Finally, the easy control
of the porous texture of carbonaceous materials makes it easy to design the appropriate pore
size distribution to the size of the reactant molecules, allowing for the treatment of both large
molecules in the liquid phase and small compounds in the gas phase. On the other hand,
carbon-supported Pt or Pt-based alloys are the best electro-catalysts for the anodic and
cathodic reactions in fuel cells. Here, together with the carbon properties described above,
conductivity of carbon materials plays a major role.
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