Interactions of Ni/ZnO with alumina support and their influence on deep reactive adsorption desulfurization

Double hydrolysis mesoporous alumina (DHA) synthesized via hydrothermal technique and used as support for the loading of ZnO and Ni. The desulfurization activities and their interactions of Ni/ZnO/DHA adsorbents were compared with Ni/ZnO supported on commercially prepared alumina (Com). The higher breakthrough desulfurization activity and sulfur adsorption capability of these catalysts are influenced by the binding extant of Zn/Ni atoms with Al₂O₃ support, more free ZnO/Ni species and the formation of inactive ZnAl₂O₄ phases. The catalysts were characterized using nuclear magnetic resonance (NMR) spectroscopy, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, H₂-temperature programmed reduction (H₂-TPR) and N₂ adsorption-desorption. Desulfurization activity shows that Ni/ZnO/DHA-80 °C catalyst achieved an excellent breakthrough sulfur removal (10 mg/L) up to 30.26 mL responsible for 110.4 mg S/g sulphur adsorption capability. This desulfurization performance is one fourth fold higher as compared to commercial Ni/ZnO/Com catalyst, achieving a compromised desulfurization activity of 1300 mg/L at set 30.26 mL model fuel flow with 38 mg S/g accumulative sulfur capacity. Detailed characterization results show that, the superior desulfurization activity shown by Ni/ZnO/DHA catalyst is due to the presence of meagre amount of unsaturated pentacoordinate Al³⁺ centers on Ni/ZnO/DHA surface which are responsible for lesser interaction of Ni/ZnO with Al₂O₄ and reduce the formation of inactive spinal ZnAl₂O₄ and NiAl₂O₄ phase even after many regeneration cycles which increases the active ZnO molar concentration as compared to Ni/ZnO/Com catalyst.