Synthesis and catalytic uses of carbon and silicon carbide nanostructures

Carbon nanofibers and nanotubes with controlled diameters were synthesized by catalytic decomposition of an ethane/ hydrogen mixture over nickel and iron supported catalysts. The synthesis of the first silicon carbide (SiC) nanotubes was performed according to the shape memory synthesis (SMS) method. The benefit of using carbon and SiC nanotubes as catalyst supports was evidenced, respectively in the case of the selective C=C bond hydrogenation in the alpha,beta-unsaturated cinnamaldehyde and the low temperature selective oxidation of H2S into elemental sulfur (60degreesC). Carbon nanotubes as support allowed to increase both cinnamaldehyde conversion and selectivity toward C=C bond hydrogenation. Supporting a nickel-based catalyst on SiC nanotubes allowed to increase both desulfurization activity of the catalyst and its solid sulfur storage capacity. The inner partial pressure concept, or confinement effect, was developed to explain the high performances of this new SiC-based catalyst. The last section is devoted to further objectives for developing such highly performing new support materials. (C) 2002 Elsevier Science B.V. All rights reserved.