Sulfur Removal from Heavy Crude Oils Based on the Adsorption Process Using CuO- and AgO-Modified SiO₂-Based Nanomaterials: Experimental and Theoretical Study

This work presents the development and validation of a highly sulfur-selective nanomaterial based on silica doped with active metal phases for the desulfurization of heavy crude oils. Initially, various transition element oxide nanoparticles (Fe3O4, NiO, ZnO, MoO3, CuO, and AgO) were synthesized and screened for sulfur adsorption in batch mode. AgO and CuO exhibited the highest removal efficiencies─24% and 21%, respectively─at an adsorbent-to-crude oil ratio of 2:40 (g/g). These were then used to modify silica supports through incipient wetness impregnation to obtain seven materials: SiCu2, SiAg2, SiCu4, SiAg4, SiAg2Cu2, SiAg1.32Cu1.32, and SiAg1.5Cu1.4. Among them, SiAg1.5Cu1.4 showed the best performance, achieving an adsorption capacity of ∼390 mg of S·g–1, significantly outperforming the undoped SiO2 (∼80 mg of S·g–1). Adsorption isotherms were constructed at 25, 35, and 55 °C and fitted using both the Freundlich and Solid–Liquid Equilibrium (SLE) models. The isotherms indicated multilayer adsorption with a type III behavior (IUPAC classification), and thermodynamic analysis confirmed the process was spontaneous and exothermic at all tested temperatures. Dynamic adsorption tests using a fixed-bed column demonstrated high performance for SiAg1.5Cu1.4, with a breakthrough time of ∼350 min and complete saturation reached at 425 min. Numerical simulation of the breakthrough curve using Aspen Adsorption showed strong agreement with experimental data (maximum relative error = 5.0%). The model was further applied to evaluate scale-up scenarios by varying flow rates and bed dimensions, achieving projected treatment capacities of up to 3280 barrels in 57 h for a bed 5 m tall and 1.25 m in diameter. These results establish a scalable framework for sulfur removal from heavy crude oils using engineered bimetallic nanoadsorbents.