Reactive adsorption desulfurization of NiO and Ni(0) over NiO/ZnO–Al(2)O(3)–SiO(2) adsorbents: role of hydrogen pretreatment

Reactive adsorption desulfurization (RADS) of Fluidized Catalytically Cracked (FCC) gasoline on reduced and unreduced NiO/ZnO–Al(2)O(3)–SiO(2) adsorbents was studied. Various characterizations such as powder X-ray diffraction (XRD), H(2)-temperature-programmed reduction (H(2)-TPR), the H(2)/O(2) pulse titration (HOPT), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to evaluate the effects of hydrogen pretreatment of the adsorbents. XRD and HOPT results indicate that NiO is hard to be reduced to Ni(0) under the conditions of RADS. H(2)-TPR shows that NiO might be reduced to Ni(0) at the temperature of 598 °C, much higher than the temperature of RADS. The Ni 2p(3/2) spectrum of Ni(0) is not observed for the reduced adsorbent, but the main peak of Ni 2p(3/2) of NiS is found for the spent adsorbent. The unreduced NiO/ZnO–Al(2)O(3)–SiO(2) adsorbent performs a better desulfurization than the reduced adsorbent at the beginning of desulfurization process. NiO and Ni(0) are assumed as the main active components and present a good desulfurization ability in RADS. Finally, a change in the RADS mechanism is presented and discussed.