Destruction of chlorinated aromatic compounds was carried out over mesoporous CuxMg1-xAl2O4 spinel oxides with x=0, 0.2, 0.5 and 0.8, which were prepared by the coprecipitation method. All the catalyst samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherms. The performances of these catalysts on the decomposition of hexachlorobenzene (HCB) and the catalytic formation of polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) were evaluated in a closed system. The activities of these catalysts for dechlorination of HCB increased with increasing the magnesium content in them. The Cu0.2Mg0.8Al2O4 presented a higher catalytic activity for the hydrodechlorination of HCB than CuO. Al2O3, as well as the other CuxMg1-xAl2O4 spinels. More than 99% dechlorination efficiency of HCB was achieved at low temperatures (<= 300 degrees C) for a short time (30 min) under air atmosphere over Cu0.2Mg0.8Al2O4 spinet. In comparison to air atmosphere, nitrogen atmosphere seemed to be more beneficial for the dechlorination of HCB with a dechlorination efficiency of 90% at 250 degrees C for 10 min. For the Cu0.2Mg0.8Al2O4 catalyst, the I-TEQ of PCDD/F formed was 4.5 pg/g, far below the value of 15122.5 pg/g on CuO. The Cu0.2Mg0.8Al2O4 catalyst inhibited the chlorination reaction and enhanced the dechlorination reaction. The catalytic behavior including catalytic dechlorination of HCB and catalytic formation of PCDD/F related to the physical characteristics of CuxMg1-xAl2O4 spinel was discussed. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.