Study on the basic centers and active oxygen species of solid-base catalysts for oxidation of iso-mercaptans

• Solid-base catalyst for the sweetening of iso-mercaptans in hydrogenated gasoline.
• Part of O3C2−−Mg3C2+ provides medium basic centers.
• The other part of O3C2−−Mg3C2+ supplies as strong basic centers.
• Superoxide anions O2− served as the active oxygen species.

It is a challenge to remove mercaptans as well as to keep octane value in clean gasoline production. In this work, gas–liquid–solid heterogeneous base-catalyzed oxidation of tert-butyl thiol by molecular oxygen was investigated. The reactivity and stability of modified MgO catalysts were studied. The catalysts were further characterized by XRD, FT-IR, CO2-TPD, H2-TPD, O2-TPD and EPR. Compared with commercial cobalt phthalocyanine catalyst (CoPc catalyst), the modified MgO catalyst displayed an enhanced stability to the oxidation of tert-butyl thiol, and the catalytic lifetime is 10 h longer than that of CoPc catalyst at 3.0 h−1 of LHSV. It was found that the active sites of the catalysts are defects and basic centers. In addition, the basic sites responsible for the reactivity are mainly the medium and strong basic centers. It is interesting that the part of O3C2−−Mg3C2+ provides medium basic centers, however, the other part of it supplies as strong basic centers. It was demonstrated that superoxide anions O2− served as the active oxygen species.

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