A possible reaction mechanism of desulfurization on NiO/ZnO–Al₂O₃–SiO₂ is discussed.

The reactive adsorption desulfurization (RADS) of a model gasoline n-hexane containing thiophene was carried out with a NiO/ZnO-Al₂O₃-SiO₂ adsorbent in N₂ and H₂, respectively. A declining RADS trend has been observed in N₂, without the presence of H₂, indicating that NiO is sulfurized and exhibits activity for RADS. TPR and XPS results presented NiO in the adsorbent is hard to be reduced because of the powerful interaction between NiO and the support. The sulfurization of NiO into NiSx is a primary condition for the RADS process, the same as the presulfurization of hydrotreating catalyst, while metallic Ni is an intermediate reduction product of NiSx. Results of a low RADS temperature at 300 °C, much lower than the reduction temperature of NiO, suggest that NiO plays an important role. Based on assumption of NiO as the main active component, the RADS could reduce the reaction temperature and energy consumption significantly. The participation of hydrogen and n-hexane in pretreatment conducted at 420 °C contributes to the activation of adsorbent. Also, these methods of pretreatment improved the desulfurization performance under the reaction temperature of 300 °C.