Carbon gels derived from naturals resources

pp. 2-7

A. Celzard, V. Fierro, G. Amaral-Labat, A. Szczurek, F. Braghiroli, J. Parmentier, A. Pizzi, L.I. Grishechko, B.N. Kuznetsov

ABSTRACT: Most carbon gels investigated so far and reported in the literature were prepared from resorcinol crosslinked with formaldehyde in water, and were generally dried with supercritical CO₂ before being pyrolysed. In the present paper, through some selected examples, we show how valuable carbon gels can be derived from other phenolic resources having a natural origin. Special emphasis is given to tannin and lignin, both derived from wood, as potential precursors of carbon aero- and cryogels. However, natural compounds not obeying the usual concepts of sol-gel chemistry may also be used for preparing carbon gels, such as cellulose, and even glucose. In the latter case, hydrothermal treatment forces the phase separation to occur, and leads to monoliths which can be advantageously converted into carbon aerogels by supercritical drying and subsequent pyrolysis.

Controlling the Morphology of Carbon Gels

pp. 8-11

S. R. Mukai

ABSTRACT: Carbon gels are unique porous carbons, which are typically obtained through the carbonization of resorcinol-formaldehyde gels. This material is practically an aggregate of nanometer-sized carbon particles. Nanopores, mostly in the size range of mesopores, exist between the particles. Smaller pores, micropores being the majority, also exist within the particles. Therefore, this material has a hierarchical pore system in which short micropores are directly connected to mesopores.
The precursor of carbon gels can be obtained through sol-gel transition. Therefore there is a high possibility that the morphology of the resulting carbon can be easily controlled using various molding methods. We have actually challenged the controlling of the morphology of carbon gels, and have succeeded in obtaining them in the form of disks, microspheres and microhoneycombs. Details of such carbon gels will be reported.

Carbon xerogels for catalytic applications

pp. 12-17

J. L. Figueiredo

ABSTRACT: The synthesis and properties of carbon xerogels are briefly described, emphasizing the methods used for tuning of their surface chemistry and textural properties, in order to design catalysts suitable for specific applications.

Mass transport in carbon gels with tuned porosity

pp. 18-23

N. Job

ABSTRACT: Diffusional limitations in carbon gel-supported catalysts are often encountered despite their open structure. However, the analysis of mass transport is rarely taken into account in studies dealing with catalyst preparation and test using these nanostructured carbons as supports. Any catalytic system should be first subject to mass transport analysis before any conclusion can be drawn about relationships between the physico-chemical properties and the measured activity of the catalyst.