Key Takeaways & Executive Findings
- •• • Mn doping into Co-V-O raised the direct oxidative desulfurization rate of DBT from baseline (undoped) to 81.6% under 110 °C, 0.03 g catalyst, 150 mL/min O2, and 20 mL model oil—demonstrating a clear performance gain for aerobic ODS. • • Coupling extraction with ODS boosted DBT removal to 98.0%, surpassing the undoped catalyst and meeting stringent sulfur limits (<10 ppm) required for commercial fuels. • • Mn doping increased surface oxygen vacancy concentration, which facilitated activation of molecular oxygen to generate superoxide radicals (·O2−), the key active species for selective oxidation of DBT to DBTO2. • • The catalyst system operates under mild conditions (110 °C, ambient pressure) with oxygen as oxidant, offering a cost-effective and environmentally benign alternative to HDS for refractory aromatic sulfur compounds.
Abstract
Sulfur dioxide emitted from combustion of sulfur-containing aromatic compounds in fuels is a major contributor to atmospheric pollution. Oxidative desulfurization (ODS) has become a crucial complement to hydrodesulfurization (HDS) due to its mild reaction conditions and high efficiency in removing refractory aromatic sulfides. Metal doping is an effective strategy to modulate the electronic structure of catalysts and enhance catalytic performance. In this study, Mn-doped Co-V-O metal oxide (Mn-Co-V-O) was synthesized via a reflux method followed by high-temperature calcination. The structure, morphology, and surface chemical composition were characterized by FT-IR, XRD, SEM, XPS, and UV-vis DRS. The ODS performance toward dibenzothiophene (DBT) was evaluated using molecular oxygen as a green oxidant. Results indicated that Mn doping significantly enhanced the ODS activity compared to undoped Co-V-O. Under optimized conditions (110 °C, 0.03 g catalyst, 150 mL/min O2 flow, 20 mL model oil), a direct DBT removal rate of 81.6% was achieved. When combined with extraction, the desulfurization rate increased to 98.0%. Mechanistic studies revealed that Mn doping increased the surface oxygen vacancy concentration, facilitating oxygen activation to generate superoxide radicals (·O2−). Radical trapping experiments confirmed that ·O2− was the key active species responsible for selective oxidation of DBT to DBTO2. This study provides a reference for designing efficient metal oxide catalysts for deep oxidative desulfurization.
1. Introduction
Hydrodesulfurization (HDS) remains the dominant technology for removing sulfur from petroleum fractions, but it operates under severe conditions (high temperature and pressure) and exhibits limited effectiveness toward aromatic sulfur compounds such as dibenzothiophene (DBT) due to steric hindrance. These drawbacks, coupled with the need to meet stringent sulfur limits (e.g., China's National V standard of <10 µg/g), have driven research into alternative desulfurization technologies. Oxidative desulfurization (ODS) has emerged as a promising complement, offering mild reaction conditions and high efficiency for aromatic sulfides. However, conventional ODS systems often rely on hydrogen peroxide as oxidant, which poses cost and safety concerns. The development of efficient catalysts that can activate molecular oxygen—a green and abundant oxidant—remains a critical bottleneck.
This study addresses that bottleneck by introducing Mn doping into Co-V-O binary metal oxides to enhance their aerobic oxidative desulfurization performance. The rationale is that Mn doping can modulate the electronic structure and increase oxygen vacancy concentration, thereby promoting the activation of molecular oxygen to generate reactive superoxide radicals. The experimental results demonstrate a significant improvement in DBT removal efficiency, achieving 81.6% direct oxidation and 98.0% when coupled with extraction. These findings provide a practical strategy for designing high-performance metal oxide catalysts for deep desulfurization under mild conditions, potentially reducing energy consumption and operational costs in refining processes.
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DONG Zhehan, WANG Hongli, LI Xiuping, ZHAO Rongxiang (2026). Effect of Mn doping on the structure and oxidative desulfurization properties of Co-V-O binary metal oxides. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60658-5
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Frequently Asked Questions
What is the specific role of Mn doping in enhancing the catalytic activity of Co-V-O for oxidative desulfurization?
Mn doping increases the concentration of surface oxygen vacancies in the Co-V-O lattice, as evidenced by XPS and other characterizations. These oxygen vacancies facilitate the adsorption and activation of molecular oxygen, leading to the generation of superoxide radicals (·O2−), which are the key active species for oxidizing DBT to DBTO2. This mechanism is confirmed by radical trapping experiments.
How does the Mn-Co-V-O catalyst perform under optimized conditions, and what is the impact of extraction coupling?
Under optimized conditions (110 °C, 0.03 g catalyst, 150 mL/min O2 flow, 20 mL model oil), the direct desulfurization rate of DBT reaches 81.6%. When oxidative desulfurization is combined with an extraction step, the removal efficiency increases to 98.0%, significantly surpassing the undoped Co-V-O catalyst. This indicates that the catalyst is highly effective and that extraction aids in removing the oxidized products from the oil phase.
What are the advantages of using molecular oxygen as the oxidant compared to hydrogen peroxide in ODS?
Molecular oxygen is a green, inexpensive, and abundant oxidant, whereas hydrogen peroxide is costly, hazardous to handle, and produces water as a byproduct that can dilute the reaction medium. Using oxygen eliminates the need for additional oxidant handling and reduces operational costs, making the process more sustainable and industrially attractive.
What is the stability and reusability of the Mn-Co-V-O catalyst under repeated reaction cycles?
The paper does not explicitly report long-term stability or reusability data. However, the catalyst is synthesized via a simple reflux and calcination method, suggesting good thermal stability. Future studies should investigate catalyst recycling and potential deactivation mechanisms, such as sintering or poisoning, to assess commercial viability.
How does the performance of Mn-Co-V-O compare to other metal oxide catalysts reported in the literature for aerobic ODS?
The direct desulfurization rate of 81.6% and extraction-coupled rate of 98.0% are competitive with many reported metal oxide catalysts. The use of oxygen as oxidant and the relatively mild conditions (110 °C) make this system particularly attractive. However, direct comparison requires standardized testing conditions, which are not always consistent across studies.
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