Removal of Cl adsorbed on Mn–Ce–La solid solution catalysts during CVOC combustion

摘要

Mn–Ce–La oxide-mixed catalysts prepared by the method of complexation followed by calcination at 750 ℃ were tested in the catalytic combustion of chlorobenzene (CB) taken as a model of chlorinated aromatics. XRD analyses show that Mn and La enter CeO_2 matrix with a fluorite-like structure to form solid solution. The catalysts with high ratio of Mn/Mn + Ce + La exhibit high activity for CB combustion, due to high oxygen mobility. For all Mn–Ce–La catalysts, deactivation due to Cl adsorption is observed at different temperatures, depending on composition. At 330 ℃ or higher temperature, the removal of Cl species from the surface in the forms of Cl_2 (produced through Deacon reaction) and HCl (produced through hydrolysis of Cl) occurs and the activity of catalysts for CB combustion becomes thus stable. Either the addition of water or the increase in gaseous oxygen concentration can promote the removal of Cl species, and thus to increase the activity for CB combustion. High stable activity of Mn–Ce–La catalysts can be related to the combination of good oxidation and Deacon reaction performances.