Nickel Sulfides Decorated SiC Foam for the Low Temperature Conversion of H2S into Elemental Sulfur

Abstract

The selective oxidation of H2S to elemental sulfur was carried out on a NiS2/SiCfoam catalyst under reaction temperatures between 40 and 80 °C using highly H2S enriched effluents (from 0.5 to 1 vol.%). The amphiphilic properties of SiC foam provide an ideal support for the anchoring and growth of a NiS2 active phase. The NiS2/SiC composite was employed for the desulfurization of highly H2S-rich effluents under discontinuous mode with almost complete H2S conversion (nearly 100% for 0.5 and 1 vol.% of H2S) and sulfur selectivity (from 99.6 to 96.0% at 40 and 80 °C, respectively), together with an unprecedented sulfur-storage capacity. Solid sulfur was produced in large aggregates at the outer catalyst surface and relatively high H2S conversion was maintained until sulfur deposits reached 140 wt.% of the starting catalyst weight. Notably, the spent NiS2/SiCfoam catalyst fully recovered its pristine performance (H2S conversion, selectivity and sulfur-storage capacity) upon regeneration at 320 °C under He, and thus, it is destined to become a benchmark desulfurization system for operating in discontinuous mode.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…In addition, the amphiphilic surface properties of SiC created preferential areas for the growth of sulfur deposits thus ensuring longer-term desulfurization stability to the composite (Figure 49B). 462 Other reports from the same authors have additionally contributed to highlight the important properties of SiC supports in such a highly exothermic process. 463,464 Indeed, the ability of a mesoporous SiC support to host a homogeneously dispersed Fe 2 O 3 active phase for the efficient and highly selective H 2 S direct oxidation has also pointed out the ability of this thermal conductive ceramic to mitigate the generation of local hotspots during the process.…”

“…459,461 Following the same concept, these authors have recently compared and discussed a series of NiS 2 -decorated SiC catalysts prepared from non-oxide carriers of variable size and shape. 462 They have demonstrated the superior performance of a 3D open-cell SiC foam as support in the lowtemperature desulfurization process compared to SiC rings and SiC extrudates, with the foam showing a sulfur-storage capacity up to 140 wt % in a discontinuous setup for the treatment of highly H 2 S-enriched (from 0.5 to 1 vol %) gas effluents (Figure 49A).…”

“…Reaction conditions: [H 2 S] = 0.5 vol %, [O 2 ] = 1.25 vol %, O 2 -to-H 2 S ratio = 2.5, [H 2 O] = 30 vol %, balance helium, reaction temperature = 60 °C, GHSV (STP) = 1200 h –1 . Adapted from ref . MDPI, Basel, Switzerland 2018 under [CC BY license 4.0] [].…”

“…The unique chemicophysical and morphological properties of the SiC foam allowed good reagent accessibility to the catalyst active sites even when large deposits of sulfur were formed. In addition, the amphiphilic surface properties of SiC created preferential areas for the growth of sulfur deposits thus ensuring longer-term desulfurization stability to the composite (Figure B) …”

Microwave-assisted Isopropanol-to-Propylene Process with A Structured Co3O4@silicalite-1/SiC Foam Catalyst

“…Cobalt oxide is an brillian catalyst for numerous catalytic applications, such as hydrolysis, oxidation and dihydrogen, due to its unique properties, such as high reducibility, abundant surface oxygen species, and multiple oxidation states [17,18]. Silicon carbide (SiC), as a new catalyst carrier with microwave-absorption capacity, has been attempted to be used in various reactions, such as fast pyrolysis [19], bio-oil upgrading [20], methane conversion [21], desulphurization [22], etc.…”