Catalyst pretreatment and CO disproportionation reaction conditions were observed to strongly affect the diameter uniformity of single-wall carbon nanotubes (SWNT) grown on Co-MCM-41 catalysts. The prereduction and CO disproportionation reaction temperatures were varied systematically while the carbon loading and the SWNT diameter uniformity were monitored by TGA, Raman spectroscopy, and TEM. The state of the catalyst during prereduction and the

he fate of hydroxyls at the surface of gamma-Al2O3 supported palladium oxide catalysts under lean methane combustion reaction conditions was investigated by in situ diffuse reflectance-fourier transform infrared (DR-FTIR) spectroscopy. Direct evidence was obtained for the formation and accumulation of hydroxyls at the catalyst surface during methane oxidation to CO2 and water. Several well-resolved absorption bands were observed in the wave number

Prima sinteza a nanotuburilor pure de bor cu un singur perete a fost confirmata prin microscopie electronica, spectroscopie Raman si EELS. Detalii la http://dx.doi.org/10.1021/jp049301b

We report here the first synthesis of pure boron single-wall nanotubes by reaction of BCl3 with H2 over an Mg-MCM-41 catalyst with parallel, uniform diameter (36 ? 1 ?) cylindrical pores. The composition of the tubular structures observed in TEM was confirmed by electron energy loss spectroscopy, and the tubular geometry was confirmed by the presence of the characteristic spectral features in the Raman breathing mode region.

ingle-walled carbon nanotubes of uniform diameter were grown in cobalt-substituted MCM-41 molecular sieves templated with C12 and C16 alkyl chains to result in pore diameters of 2.6 and 3.3 nm, respectively. The narrow diameter distribution of the tubes grown was probed by Raman, UV-visible, and NIR spectroscopy, as well as by high-resolution transmission electron microscopy. Tube diameters have been observed to vary with the size of the Co clusters

Palladium-based catalysts are widely applied in exhaust catalytic converter and catalytic combustion systems. The mechanism for methane oxidation reaction on Pd-based catalyst is complex. Catalyst activity is influenced by variations in the process pressure and temperature, by the gas mixture composition, by the type of support and various additives, and by pretreatment under reducing or oxidizing atmospheres. In this paper, we review the literature

The methane combustion mechanism was investigated by means of pulsed reaction experiments using a reaction mixture labeled with 18O2. The catalysts employed were pure PdO, zirconia and ceria-zirconia-supported PdO particles fully oxidized with 16O. Complementary continuous flow temperature programmed reaction experiments were also used. Our results confirmed the redox combustion mechanism. Exchange of oxygen from the bulk and from the support with

Temperature programmed isotopic exchange (TPIE) of oxygen and pulsed methane combustion experiments were used to investigate the contribution of oxygen from the support in the methane combustion reaction over alumina- and zirconia-supported palladium. TPIE experiments show that PdO is more active than reduced palladium for oxygen exchange between the catalyst and gas phase. Experiments performed on initially reduced catalysts produced a partially

Niobia, zirconia, ceria-niobia and ceria-zirconia oxide nanoparticles are prepared by soft chemical routes and show valuable textural properties, The pore volume and specific surface area keep significant values even after calcination at 873 K. According to DRX and STEM-EDX measurements, solid solutions are obtained in the case of ceria-zirconia, whereas separate phases are identified in ceria-niobia; in the latter case, however, W-Vis diffuse reflectance

Zirconia-supported (PdO)-O-16 and bulk (PdO)-O-16 were used as methane combustion catalysts for a reaction mixture containing 1% methane and 4% O-18(2) in helium. The methane oxidation reaction was performed in pulsed experiments and the distribution of oxygen isotopes among the reaction products was monitored. The O-18 content of the catalyst following labeled reaction mixture pulses was determined by catalyst reduction with either diluted hydrogen