Abstract
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.
Highlights
The selective catalytic oxidation of H S by oxygen 2 into elemental sulfur is the most interesting and efficient way for removing last traces of H2S from waste acid gases generated by petrochemical refineries or natural gas plants.[1, 2] This reaction is of high environmental interest, due to the high toxicity of H S
New Catalysts Based on Silicon Carbide Support that silicon carbide grains or extrudates (SiC) nanotubes could be efficiently used as catalyst support compared to a macroscopic SiC support, by comparison with carbon nanotubes or nanofibers, which increase the catalytic efficiency when compared to carbon grains in liquid-phase applications.[8]
The XRD pattern of the SiC nanotubes only displayed diffraction lines corresponding to SiC crystallized in the low temperature β-face centered cubic structure, together with the low angle peak assigned to the non reacted remaining carbon (Figure 1)
Summary
The selective catalytic oxidation of H S by oxygen 2 into elemental sulfur is the most interesting and efficient way for removing last traces of H2S from waste acid gases generated by petrochemical refineries or natural gas plants.[1, 2] This reaction is of high environmental interest, due to the high toxicity of H S. This reaction is interesting from an economical point of view, leading to the transformation of a hazardous compound into a more valuable one for further chemical processes.
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