Effect of additive Ag on the physicochemical and catalytic properties of LaMn0.9Co0.1O3.5 perovskite

Perovskite-type compounds La1−xAgxMn0.9Co0.1O3 (xAg = 0.0, 0.1, 0.2, 0.3) were prepared by the amorphous citrate method, characterized by nitrogen adsorption, XRD, FTIR, SEM-EDAX, TPR, O2-TPD and XPS techniques, and tested in the catalytic removal of n-hexane in a flow reactor under an excess of oxygen. Partial substitution of La3+ by Ag+ was found to produce a large increase in the catalytic activity. Since all the samples exhibit almost the same specific area, the catalyst activity was found to depend mainly on the crystalline structure and on a new source of surface oxygen that comes from the interaction between O– and the low coordinated metal site. For the studied composition, characterization data revealed that the degree of substitution of xAg = 0.1 shows the cleanest surface composition, i.e. almost total insertion of silver in the LaMn0.9Co0.1O3.5. The highest reaction rate found for xAg = 0.3 is explained considering that almost the same Ag insertion is obtained, but the larger surface of segregated Ag particles contributes to enhancement in activity.

The substitution degree of xAg = 0.1 shows the cleanest surface composition, i.e. almost total insertion of silver in the LaMn0.9Co0.1O3.5. The highest reaction rate found for xAg = 0.3 is explained considering that almost the same Ag insertion is obtained, but the larger surface of segregated Ag is responsible for the increased activity.Figure optionsDownload as PowerPoint slide