Removal of ethyl mercaptan from gas streams using chromium modified hexaniobate nanotubes

Abstract

In this study, chromium modified hexaniobate nanotubes with high dispersion of the chromium species were first prepared by the ion exchange–flocculation–calcination process for removal of C₂H₅SH. According to XRD, UV-vis DRS, SEM, TEM, BET and XPS characterization, we conclude that chromium species exist in the form of Cr³⁺ and Cr⁶⁺ in hexaniobate nanotubes, and chromium loading can improve the specific surface area, micro-structure and thermal stability of the as-prepared nanotubes. The removal performance for C₂H₅SH was evaluated in a fixed-bed adsorption column. The desulfurization results show that 15 wt% Cr-modified hexaniobate nanotubes have the highest C₂H₅SH breakthrough adsorption capacity of up to 34.95 mg g⁻¹, which is more than 2.5 times that of pure hexaniobate nanotubes calcined at 300 °C. The used 15 wt% Cr-modified hexaniobate nanotubes can also be regenerated by heat treatment at 300 °C in nitrogen atmosphere, and have relatively stable regeneration performance. The removal of C₂H₅SH on the Cr-modified hexaniobate nanotubes proceeds via an adsorption/oxidation process, and the adsorbed C₂H₅SH is further oxidized under the action of adsorbed oxygen and chromium species. Finally, a potential mechanism for C₂H₅SH removal over the Cr-modified hexaniobate nanotubes was proposed.