Co3O4, Al2O3 and Co3O4/Al2O3 mesoporous powders were prepared by a sol-gel method with starting matierals of aluminum isopropoxide and cobalt (II) nitrate. A P123 template is employed as an active organic additive for improving the specific surface area of the mixed oxide by forming surfactant micelles. A transition metal cobalt oxide supported on alumina with and without P123 was tested to find the most active and selective conditions as a heterogeneous catalyst in the reaction of styrene epoxidation. A bBlock copolymer-P123 template was added to the staring materials to control physical and chemical properties. The properties of Co3O4/Al2O3 powder with and without P123 were characterized using an X-ray diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), a Bruner-Emmertt-Teller (BET) surface analyzer, and 27Al MAS NMR spectroscopy. Powders with and without P123 were compared in catalytic tests. The catalytic activity and selectivity were monitored by GC/MS, 1H, and 13C-NMR spectroscopy. The performance for the reaction of epoxidation of styrene was observed to be in the following order: [Co3O4/Al2O3 with P123-1173 K > Co3O4/Al2O3 with P123-973 K > Co3O4-973 K>Co3O4/Al2O3-973 K > Co3O4/Al2O3 with P123-1473 K > Al2O3-973 K]. The existence of γ-alumina and the nature of the surface morphology are related to catalytic activity.