Competitive Adsorption in a Multicomponent Diesel System Using Nickel Oxide/Activated Carbon

Nickel oxide, which acts as an intermediate Lewis acid, was loaded onto activated carbon (AC) to enhance the adsorption selectivity of AC in the desulfurization of model diesel. The total sulfur adsorption capacity increased from 2.46 to 4.42 mg-S·g adsorbent–1 and the total sulfur removal increased from 46.8 to 84.5% using the AC and Ni(10%)O/AC adsorbents, respectively. Multicomponent isothermal modeling showed that the incorporation of NiO onto AC significantly improved the synergistic interactions between the thiophenic compounds while mitigating competitive interactions between the more steric 4,6-dimethyl dibenzothiophene (4,6-DMDBT) and 4-methyl-dibenzothiophene (4-MDBT) compounds. The mitigation was attributed to new adsorbate-specific sites created by loading NiO on AC. Spent adsorbent characterization and pyridine adsorption-IR analysis suggested that higher desulfurization performance of the Ni(10%)O/AC adsorbent was attributed to an increase in the adsorbent's Lewis acidity upon loading with NiO, leading to increased Ni–S acid–base interactions, in addition to π-complexation.