Novel multi-metal ion-exchanged zeolite for oxidative-adsorptive desulfurization of model and real diesel fuel: a response surface methodology (RSM) study

The efficient removal of refractory organosulfur compounds, such as dibenzothiophene, remains a critical bottleneck in achieving ultra-low sulfur diesel standards. While oxidative-adsorptive desulfurization is promising, there is a significant research gap in rationally designing adsorbents that utilize synergistic multi-metal active sites to enhance the capture of sterically hindered species. To address this, we synthesized a novel multi-metal ion-exchanged zeolite (AgNiCeY) via a sequential ion-exchange process, aiming to strategically incorporate Lewis acid sites (Ag⁺, Ni²⁺, Ce³⁺) within the NaY framework. BET surface area for NaY and AgNiCeY was 623 and 540 [Formula: see text] respectively .The desulfurization performance and underlying adsorption mechanisms were rigorously evaluated. Using response surface methodology (RSM) on a model fuel system (DBT in n-octane)), the optimal capacity was determined at a contact time of 55 min and an oil/adsorbent ratio of 18.2 ml/g. The resulting AgNiCeY adsorbent demonstrated a remarkable increase in equilibrium adsorption capacity from 12.61 mg/g (NaY) to 33.26 mg/g, marking a 164% enhancement. Mechanistic analysis, supported by FT-IR and electronic structure visualization, confirms that the synergy between the exchanged cations acts as Lewis acids, facilitating superior σσσ-bond formation with the sulfur atom. Crucially, when tested under realistic conditions using real diesel fuel containing 2544 ppm sulfur, the modified AgNiCeY maintained high efficiency, achieving a 61.3% sulfur removal, significantly outperforming the parent NaY (57.8%). This study validates a novel design principle for heterogeneous catalysts, demonstrating that precise, sequential multi-metal exchange in zeolites offers a robust and scalable strategy for improving the selective adsorption of refractory sulfur compounds. Regeneration experiments were also conducted to assess the recyclability of the catalysts over multiple cycles.