New catalysts based on silicon carbide support for improvements in the sulfur recovery.: New silicon carbide nanotubes as catalyst support for the trickle-bed H2S oxidation

Silicon carbide nanotubes were prepared via a gas-solid reaction between SiO vapor and carbon nanotubes. The NiS2 active phase on this support displayed both a high catalytic activity and high solid sulfur storage capacity in the trickle-bed selective oxidation of H2S into elemental sulfur as compared to the grain-based SiC catalyst. The hypothesis of a confinement effect inside the SiC nanotubes has been put forward to explain the catalytic results. An artificial increase in the H2S partial pressure inside the tubes when compared to the H2S partial pressure outside the tubes would lead to an increase in the oxidation rate, due to the first order reaction rate toward H2S. The SiC nanotube supported catalyst displayed very high resistance to the sulfur loading, due to a peculiar mode of sulfur evacuation by condensed steam which allows the continuous cleaning of the active site. The high solid sulfur storage capacity was due to a much larger void volume between each SiC nanotube available for the sulfur storage, than the void volume of SiC support with a grain size morphology.