Effect of Mno2 Phase Structure and The Guest K+ Ions on the Complete Catalytic Oxidation of Benzene

Abstract

Four different MnO₂ phase structures prepared by hydrothermal method and tested for complete oxidation of benzene and observed their very different activities as in the following order α-MnO₂>δ-MnO₂>γ-MnO₂>β-MnO₂. Further, ion exchange of guest K⁺ cations with H⁺ ions by acid treatment of α and δ-MnO₂ catalysts significantly enhanced benzene activity. However, for H-α-MnO₂ it is minimum; T_90% decreased from 264 to 261 ^oC, whereas for H-δ-MnO₂ maximum; T_90% decreased from 268 to 238 ^oC and maintained good stability. The significant activity of H-δ-MnO₂ due to better diffusion of benzene from 2D interlayer channels due to lack of bigger K⁺ cations.