In situ generation of Mn1−xCex system on cordierite monolithic supports for combustion of n-hexane. Effects on activity and stability

Abstract

Mn1−xCex (x = 0, 0.05, 0.1, 0.2 and 1) mixed oxide catalysts supported on cordierite monolith were prepared by ultrasonic impregnation and examined for the catalytic combustion of n-hexane. All catalysts were characterized in detail using N2 adsorption, XRD, XRF, SEM, XPS, H2-TPR, O2-TPD and OSC measurements. The Ce-Mn mixed catalysts and Mn catalyst, showed excellent catalytic activity. However, the addition of cerium to manganese catalyst did not increase its activity. The Mn-Ce mixed catalyst, with an intermediate content of Ce, presented the same activity as the Mn catalyst, but it proved to be more stable under extreme conditions of reaction, i.e. conditions of 100% conversion at 350 °C for a maximum of 34 h. Deactivation of Mn catalyst was associated with a transformation to unstable phases of manganese oxides, while the stability of the Mn-Ce mixed catalyst was attributed to the strong Mn-Ce interaction, which likely occurs through the formation of a small amount of solid solution. The synthesis method used allows generating in situ a monometallic catalyst as active as a bimetallic Mn-Ce catalyst under extreme reaction conditions; cheapening the cost of the catalytic system.