In situ fabrication of robust three dimensional ordered macroporous γ-MnO2/LaMnO3.15 catalyst for chlorobenzene efficient destruction

Catalytic activity of perovskite oxides as LaMnO3+delta is greatly limited by their low surface area and deficient active site density though they are thought to be one category of desired candidates for noble metal-based catalysts. Here, a robust three dimensional ordered macroporous (3DOM) gamma-MnO2/LaMnO3.15 (Mn/3DLM) was in situ fabricated by the strategy of selectively dealloyed surface La cations. Mn/3DLM displayed excellent activity with 90% of chlorobenzene destructed at 207 degrees C (apparent activation energy of 45.4 kJ/mol), obviously lower than those of gamma-MnO2 (244 degrees C; 51.9 kJ/mol) and bulk LaMnO3.15 (311 degrees C; 70.2 kJ/mol) owing to large surface area, excellent reducibility, and improved surface active oxygen concentration. Nucleophilic substitution was the main process for active oxygen attacking, while electrophilic substitution mainly contributed to chlorinated byproducts formation. Remarkably, reaction byproducts as phenol, o-dichlorobenzene, trichloroethylene, and bichloroethylene over Mn/3DLM can be efficiently inhibited during the long-term operations via weakened the electrophilic substitution effect.

Automated summary

A three-dimensional ordered macroporous (3DOM) γ-MnO2 / LaMnO3.15 (Mn / 3DLM) with excellent catalytic activity was fabricated by selectively dealloying surface La cations. The material exhibited high activity in chlorobenzene decomposition due to its large surface area, excellent reducibility, and improved surface active oxygen concentration. Active oxygen attacking mainly through nucleophilic substitution, while chlorinated byproducts formation was mainly contributed by electrophilic substitution. Efforts to weaken the electrophilic substitution effect on Mn/3DLM can effectively inhibit the formation of reaction byproducts such as phenol, o-dichlorobenzene, trichloroethylene, and bichloroethylene during long-term operations.