Chlorinated volatile organic compounds (Cl-VOCs), released to the atmosphere from a wide range of industrial processes, have been considered potent environmental pollutants. Catalytic combustion is one of the most promising technologies for the removing of volatile organic compounds. About the catalysts for Cl-VOCs catalytic combustion, most report have focused on three types of catalysts based on noble metals, transition metals and zeolites.

Researchers with Institute of Process Engineering (IPE) prepared Lanthanide (Ln, including La, Ce and Nd) modified Co/HMS via two methods: extra-framework modified post-loading and framework modified direct synthesis. The influence of modified methods, rare earths kind and rare earths loading on the catalytic performance of Co/HMS were studied by the catalytic combustion of chlorobenzene (CB).

The experimental results showed that the extra-framework Ce modified catalysts have better catalytic performance than the framework Ln modified ones due to the formation of CeO2 and the reduction of Ce4+ ions to Ce3+ species. CeO2 was advantaged to obtain the fine Co3O4 crystal clusters and reduction of Ce4+ ions to Ce3+ species probably would promote neighboring reduction of Co species.

The suitable extra-framework Ce loading (6%, mass fraction) can effectively ameliorate the redox ability of Co species in the channel of HMS. Since the channel of HMS itself and Co(NO3)3·6H2O aqueous solution both were hydrophilic, the diffusion and distribution of Co(NO3)3·6H2O in HMS channel did not improve greatly by the framework Ln. However, the slightly improved redox ability and weak acidity originated from framework Ln still can do some contribution to the catalytic performance.

Besides, the electronic structure of Co and Ce was advantageous to the delocalization of π-electrons and the forming of radical species. Based on the analysis, a tentative radical mechanism was proposed.

More informationplease see Applied Catalysis B : Environmental.