A number of orthorhombic Mo3VO chi oxide catalysts with different external surface areas measured by N-2 adsorption and with the same micropore volumes measured by ethane adsorption were synthesized hydrothermally by adding sodium dodecyl sulphonate (SDS, C12H25SO3Na) and by changing synthesis temperature. The synthesized catalysts were then tested for the selective oxidations of ethane accessible to the micropore and of 2-propanol inaccessible to the micropore in order to investigate the role of the micropore in the gas-phase oxidation of ethane. It was found that the conversion of ethane was almost similar for all the catalysts irrespective of their largely different external surface areas. On the other hand, the oxidation of 2-propanol to acetone clearly depended on the external surface area of the catalysts. Since other catalytically affective properties such as crystal structure, elemental compositions, and. oxidation states of Mo and V were comparable for all the catalysts, it was concluded that the heptagonal channel micropore of the orthorhombic Mo3VO chi oxide catalyst was responsible for the catalytic activity for the ethane selective oxidation and that the catalytic oxidation of ethane could take place inside the micropore. (C) 2013 Elsevier B.V. All rights reserved.