Mn-modified Co3O4 catalysts with spinel structure with various Co/Mn ratios prepared by co-precipitation method were characterized by XRD, Raman, TEM, HRTEM, XPS and H-2-TPR, and used in catalytic combustion of 1,2-dichlorobenzene (o-DCB), as a model of dioxins. The results revealed that the catalyst with Co/Mn ratio of nine presented the highest activity with T-90 of 347 degrees C and high stability at least 35h at 3000 ppm o-DCB and 10% O-2 at GHSV = 15,000 h(-1). High activity could be ascribed to synergetic effect between activation of o-DCB on Co2+ sites and oxidation by surface active oxygen from Co3O4 nano-particles. Additionally, 1,2,4-trichloro-benzene was formed over Co3O4 to a significant extent through the reaction of adsorbed Cl species with o-DCB, while the incorporation of Mn in Co3O4 can effectively retard chlorination of o-DCB. A possible reaction pathway for the catalytic combustion of o-DCB on CoxMny catalysts was also investigated by in situ FTIR spectroscopy. (C) 2014 Published by Elsevier B.V.