Mechanism and kinetics of magnesium sulfite oxidation catalyzed by multiwalled carbon nanotube

- A CNTs catalyst was prepared to promote the oxidation rate of magnesium sulfite.
- The CNTs catalysts loaded with dissimilar contents of cobalt were characterized.
- The dependency of catalytic performance on the cobalt content was revealed.
- The catalytic kinetics of magnesium sulfite oxidation was investigated.
- The overall reaction rate of was controlled by the internal diffusion of oxygen.

Oxidation of magnesium sulfite is crucial for recycling the byproduct in magnesia desulfurization. Using impregnation method, a multiwalled carbon nanotube catalyst loaded with cobalt was prepared to promote the oxidation rate of magnesium sulfite (MgSO3). The performance of catalysts impregnated by different concentration of Co(NO3)2 were compared, which showed that the optimal impregnating concentration was 30%. The catalysts prepared with various concentration of Co(NO3)2 were characterized by Brunauer-Emmett-Teller analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyzed oxidation kinetics of magnesium sulfite was investigated in a bubbling tank, indicating that the general reaction orders with respect to carbon nanotube, oxygen, and magnesium sulfite were 0.22, 0.45, and 0.01, respectively. The apparent activation energy was 23.43 kJ mol−1. The three-phases reaction model revealed that the internal diffusion of oxygen might be the rate-controlling step of magnesium sulphite oxidation. The results can serve as a useful reference for designing sulfite oxidation by using multiwalled carbon nanotube catalyst.

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