Evaluation of the catalytic oxidation of soot by CeO-LaMnO at different O pressures synthesized by ultrasonic-assisted hydrothermal method.

In this work, the synthesis of catalyst with perovskite structure and chemical formula LaCeMnO at x = 0 - 0.5 were successfully obtained by an ultrasonic-assisted hydrothermal method. Results show that the addition of Ce in LaCeMnO have not substantial effect in textural and morphological properties; however, the formation of a new crystalline phase with final composition CeO-LaCeMnO was detected at values x > 0.3. All synthesized catalysts were tested in the soot oxidation under both, loose and tight contact in 20% O/N or 5% O/N atmospheres. CeO-LaCeMnO at x = 0.3 resulted in the best catalytic activity with activation energy values of 57.9 kJmol. The interaction between Ce and Mn species in this catalyst can transfer electrons generating Mn and Ce. This reduction from Mn to Mn is accompanied by migration of vacancies to the surface promoting the adsorbed oxygen from the gas phase, need for balancing the chemical states. By increasing the temperature above 300 °C, the bulk oxygen migration to the surface is enhanced being the responsible for the oxygen availability. The formation of CeO-LaCeMnO promotes a stable redox cycle allowing the reusability of this catalyst even at low oxygen pressures after three different reaction cycles.