Self-sulfidation adsorbent for reactive adsorption desulfurization

The Ni/ZnO-Al 2 O 3 -SiO 2 adsorbent is a widely used industrial adsorbent for reactive adsorption desulfurization (RADS) process. Metallic Ni and NiO are assumed as the main RADS active sites, and NiS x is the intermediate phase to transfer sulfur to ZnO. However, NiS x could also be the active center for RADS process. In this work, to conduct the desulfurization activity of NiS x , a novel NiSO 4 /ZnO-Al 2 O 3 -SiO 2 adsorbent was prepared and examined through a serious experimental and theoretical study over the conventional adsorbents. Results showed that NiSO 4 based adsorbents could first self-sulfide to NiS x phases, and then NiS x plays as main active sites for RADS. The NiSO 4 phases improved the direct desulfurization selectivity of dibenzothiophene (DBT). By adjusting the content of nickel, the sulfur removal rate of adsorbent with 3 wt% Ni from NiSO 4 could achieve the same level of adsorbent prepared with 18 wt% Ni from NiO. Moreover, NiSO 4 based adsorbent performs excellent desulfurization activity, and its breakthrough sulfur capacity achieves 122.0 mgS/g. The evolution of Ni species on NiSO 4 adsorbent has been studied, and a desulfurization mechanism that takes both NiO and NiS x as active phases has been carried out. NiO phase mainly promotes the hydrodesulfurization pathway, while NiS x phase prefers the direct desulfurization pathway. Finally, the mechanism of RADS on NiS x and the reaction pathways of DBT are also presented.