Acidic sites enhanced ultra-deep desulfurization performance of novel NiZnO-based mixed oxides mesoporous adsorbents

A series of novel mixed metal oxides (MOs), such as ZnO-Al2O3, ZnO-Al2O3-SiO2, and ZnO-SiO2, were prepared through the double hydrolysis technique and applied as supports for Ni/MOs. The desulfurization activities of these Ni/MOs-based sorbents were investigated in a fixed bed reactor by model gasoline. Results reveal that the reactive adsorption desulfurization efficiency of sorbents was reduced in the order: 10%Ni/ZnO-Al2O3 > 10%Ni/ZnO-Al2O3-SiO2 > 10%Ni/ZnO-SiO2. Among them, the 10%NiZnO-Al2O3 adsorbent exhibited superior desulfurization performance. It achieved the highest breakthrough (10 ppm) up to 78 mL of model gasoline fuel flow, corresponding to 154 mg S/g accumulated sulfur capacity at a breakthrough point, which is four folds higher than the previously reported studies on NiZnO-based materials. The characterizations indicated that the 10% NiZnO-Al2O3 based mixed oxide adsorbent prepared using the double hydrolysis procedure comprises higher Lewis and Lewis/Bronsted ratio acid sites, higher surface area, greater pore size distribution, and a lesser amount of inactive ZnAl2O4 spinel, resulting in a better ZnO dispersion. Moreover, the well-developed pore volume reduced the diffusion resistance of reactant molecules to highly concentrated acid sites, thus leading to higher thiophene conversion and accumulated sulfur adsorption capacity. Based on our results, a mechanism is planned for the reactive adsorption desulfurization activity.