Adsorption behavior and mechanism of ethyl mercaptan in natural gas on Cu-modified hexaniobate nanotubes

Abstract

The presence of sulfur compounds in natural gas seriously affects the yield of hydrogen production from natural gas reforming and the lifespan of catalysts. This study aims to clarify the characteristics and mechanism of the removal of ethyl mercaptan (EM) in equilibrium CH4 by Cu-modified hexaniobate nanotubes (Cu-HNT-450), which was synthesized through a method of copper ions exchange-flocculation-calculation. The EM breakthrough adsorption experiments and the valence state of copper and the types of sulfur on Cu-HNT-450 during dynamic tests were investigated. The removal of EM is mainly achieved through the chemical adsorption of CuO, Cu2O and oxygen on Cu-HNT-450. In the process of EM removal, catalytic oxidation, sulfonate formation and reactive adsorption lead to the formation of sulfide, copper sulfonate and copper thiolate, respectively. Cu-HNT-450 has the highest breakthrough adsorption capacity for EM, reaching 103.6 mg/g at 50 °C. The exhausted Cu-HNT-450 can also be regenerated by thermal treatment at different temperatures under nitrogen atmosphere. However, due to the strong chemical adsorption of sulfur containing compounds, the recovery of nitrogen thermal regeneration removal efficiency is limited. This research work provides guidance for the design of mercaptans removal catalysts and deepens the understanding of the reaction mechanism of mercaptans removal.