文摘
In this study, a series of Ni/ZnO–Al2O3 mixed oxide (MO) adsorbents were prepared by the one-step homogeneous precipitation method and the cation–anion double hydrolysis (CADH) method for reactive adsorption desulfurization (RADS) using thiophene as a model fuel in a fixed bed reactor. The synthesized adsorbents were characterized by N2 sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS), and Raman spectroscopy. Results show that both Ni loading and the preparation method have a significant effect on the RADS activities of the adsorbent. Among the studied adsorbents, 10% Ni/ZnO–Al2O3 prepared by the one-step urea precipitation method showed the best RADS performance, with a thiophene conversion up to 96% and a sulfur adsorption capacity of 86 mg of S/g, which is 34% larger than that of CADH adsorbents. In addition, upon five RADS–regeneration cycles, sample 10% Ni/ZnO–Al2O3 exhibited a drop of only 3% in thiophene conversion, indicating the high stability of the Ni/ZnO–Al2O3 adsorbent prepared by homogeneous precipitation. Characterization results show that the one-step homogeneous precipitation method could facilitate the formation of small ZnO particles while suppressing the formation of inactive ZnAl2O4. On the other hand, by decreasing the formation of NiAl2O4, the homogeneous precipitation method could also generate high concentration of Ni0 sites, which are the active centers for the hydrogenolysis of C–S bonds. These findings indicate that a high-performance adsorbent for RADS can be obtained by employing a proper preparation method with good control on the adsorbent structure.
