Reactive Adsorption Desulfurization of Fluid Catalytic Cracking Gasoline: The Effect of Promoters (Fe, Mo, and W) on the Structural and Catalytic Properties of Ni/ZnO Adsorbents

A series of Ni/ZnO adsorbents containing pro-moters (Fe, Mo, and W) were prepared for reducing the loss of the octane number because of olefin saturation during the reactive adsorption desulfurization (RADS) process. The bimetallic adsorbents synthesized by a two-step impregnation method were analyzed by a series of characterization methods to evaluate the effect of additional metal on the structural and catalytic properties of the traditional Ni/ZnO adsorbent. Hydrogen temperature-programmed reduction (H2-TPR) results showed that the addition of promoter Fe enhanced the reduction performance of NiO, while W hindered the reduction of NiO. The electron density of Ni was modified following the introduction of Fe and W, as analyzed by X-ray photoelectron spectroscopy (XPS), which weakened the adsorption of pi complexation between olefins and Ni. Experimental results showed that the desulfurization performance of Ni- Mo was improved but aggravated the loss of the octane number. Ni-W effectively attenuated the olefin saturation reaction but seriously shortened the breakthrough time. The adsorbent modified by Fe can reduce the saturation reaction of olefins and improve the desulfurization performance. In addition, multicycle regeneration experiments proved the excellent regeneration performance of the adsorbent modified by an appropriate amount of Fe. Therefore, the Ni-Fe bimetallic adsorbent may become a novel adsorbent for reactive adsorption desulfurization, which achieves high desulfurization activity and olefin retention ability to satisfy the requirements of fluid catalytic cracking (FCC) gasoline refining.