The hydrodealkylation of 1,2,4-trimethylbenzene (1,2,4-TMB) was investigated on partially reduced Ni-Al mixed oxide catalysts prepared by the co-precipitation method. The catalytic performances of these Ni-Al mixed oxides were considerably influenced by different factors, such as the molar ratio of Ni/Al, calcination temperature of the catalysts, etc. The sample with a Ni/Al molar ratio of 1:8 calcined at 500 degrees C (denoted as NiAl8-500) showed the highest activity and total selectivity to lighter aromatics with a 62.3% conversion and a 60.2% selectivity to xylene. Characterization results showed that the unreduced NiAl8-500 catalyst mainly consisted of pseudo-spinel like solid solution (NiAl2O4), and could produce monodispersed nickel atoms (Ni(0)), which are closely associated with alumina sites (Lewis acid) upon reduction. We propose that the relatively high hydrodealkylation activity of the NiAl8-500 catalyst could be mainly assigned to the presence of a number of neighboring metallic Ni(0) atoms and Lewis acidic sites. (C) 2010 Elsevier B.V. All rights reserved.