上海科技大学知识管理系统

Based on monolayer dispersion theory, Co3O4/ZSM-5 catalysts with different loadings have been prepared for selective catalytic reduction of nitrogen oxides by ammonia. Co(3)O(4)can spontaneously disperse on HZSM-5 support with a monolayer dispersion threshold of 0.061 mmol 100 m(-2), equaling to a weight percentage around 4.5%. It has been revealed that the quantities of surface active oxygen (O-2(-)) and acid sites are crucial for the reaction, which can adsorb and activate NOx and NH3 reactants effectively. Below the monolayer dispersion threshold, Co3O4 is finely dispersed as sub-monolayers or monolayers and in an amorphous state, which is favorable to generate the two kinds of active sites, hence promoting the performance of ammonia selective catalytic reduction of nitrogen oxide. However, the formation of crystalline Co3O4 above the capacity is harmful to the reaction performance. 4% Co3O4/ZSM-5, the catalyst close to the monolayer dispersion capacity, possesses the most abundant active O-2(-) species and acidic sites, thereby demonstrating the best reaction performance in all the samples. It is proposed the optimal Co3O4/ZSM-5 catalyst can be prepared by loading the capacity amount of Co(3)O(4)onto HZSM-5 support.