Vapor-phase oxidations of ethane, propane, and acrolein were carried out over crystalline (orthorhombic) and amorphous Mo-V-O catalysts. The Mo-V-O crystalline catalyst was prepared by hydrothermal synthesis for the first time in a new orthorhombic structure. The orthorhombic Mo-V-O catalyst showed extremely high activity for the reactions compared to the amorphous one. Te in the orthorhombic Mo-V-O catalyst increased the selectivity to acrylic acid from propane dramatically. (C) 2004 Elsevier B.V. All rights reserved.