Kinetic analysis of morphologies and crystal planes of nanostructured CeO2 catalysts on soot oxidation

Abstract

Soot oxidation is a triple-phase reaction system involved in solid soot, solid catalyst and gaseous oxidant, which makes its kinetic behavior difficult to be determined. Herein, we report the kinetic behavior of crystal planes on the CeO2 catalysts with various morphologies for soot oxidation. We establish a kinetic model of crystal planes of CeO2 in soot oxidation by means of the distributed activation energy model (DAEM). Through analyzing the distribution function of apparent activation energies (f (Ea)) under loose contact condition, we discover that the Ea of the exposed (1 0 0), (1 1 1) planes and non-catalytic gaseous O2 on soot oxidation distributes in the range of 60–100, 100–150, and 150–250 kJ mol−1, respectively. Our findings show that compared with other catalysts, CeO2 nanocubes exhibit the higher intrinsic activity (turnover frequency, TOF) under loose contact condition, because of the higher f (Ea) value of abundant active exposed (1 0 0) planes located at the lower Ea range. Our work develops a methodology of kinetic analysis to investigate the soot oxidation reaction, which could be potentially extended to other complex oxidation systems.