Enhancement of the activity of calcium aluminosilicate (Ca12Al10Si4O35) for the combustion of diesel soot via the substitution of Ca2+ ions with transition metal ions

The activity of calcium aluminosilicate or mayenite (Ca12Al10Si4O35) was examined for the combustion of diesel soot. Mayenite was synthesized via hydrothermal reaction of a mixture of CaO, alumina-sol, and amorphous silica. Metal-substituted mayenite was similarly prepared by adding a corresponding metal salt to the starting mixture. Carbon black (CB) powders were used as model diesel soot. Although mayenite itself was active for CB combustion, substitution of a part of Ca2+ in mayenite with transition metal ions resulted in a marked increase in the activity for CB combustion. Among substituting transition metal ions examined, the highest activity for CB combustion was obtained for substitution with Cu2+, i.e., the combustion temperature was 741 K for Cu-substituted mayenite, while 803 K for unsubstituted mayenite and 903 K without mayenite.