Enhancing aerobic oxidative desulfurization: Curvature-tailored local environments for efficient two-phase reactant delivery

Aerobic oxidative desulfurization (AODS) is a carbon-neutral approach for producing ultra-clean petroleum, yet it faces challenges of low efficiency and high temperature. Modifying the electronic structure of active sites can facilitate O2 activation, while potential improvement may be compromised by inadequate delivery of reactants to these sites. Herein, we showcase a broadly applicable method to ensure the simultaneous supply of two-phase reactants by engineering hollow spherical encapsulated catalysts with a suitable curvature. Combined experimental and theoretical analyses reveal that a local concentration gradient drives targeted diffusion of reactant from the exterior to the interior of the hollow sphere, facilitating catalytic reactions at the three-phase interface while maintaining low internal concentration within the confined space. An optimal balance between gains in reactants enrichment and losses in O2 activation has been struck by adjusting the curvature of hollow sphere, affording the active sites a kinetically favorable local environment. Accordingly, the complete desulfurization was accomplished within 3 h at 100 °C with O2 flow rate of 50 mL min−1, surpassing the reported optimum performance of noble metal-based catalysts in the literature. This work provides a different strategy from conventional catalyst engineering to improve AODS activity by adjusting local environment, offering significant potential and applicability across diverse application scenarios.