A fluid-bed tin-based catalyst for propane ammoxidation to acrylonitrile (ACN) was prepared by an original technique which combines incipient wetness impregnation (for the insertion of the metallic ions of the active phase inside the carrier) and neutralization (for the simultaneous co-precipitation of the different active sites inside the carrier). Tests were carried out using silica and alumina as the carrier. The silica-based catalyst was found to give the best performance. Different active phase loadings, vanadium concentrations and surface areas were tested in order to define the optimal composition of the Sn/V/Sb on SiO2 catalyst.