Co(II)O was highly dispersed in the mesopores of SBA-15 by alcoholic impregnation method and characterized by XRD, TEM, UV-VIS DRS, TPR, and XRF techniques. It was found that tetrahedral coordinated Co(II)O was stabilized by SBA-15 at low Co-loading. Co/SBA-15 showed much higher activity than Co(OAc)(2) or Co3O4 in the liquid-phase aerobic oxidation of ethylbenzene under solvent-free condition.