A set of new materials with general formula [M(H20)]x(VO)l_xPO4-2H20 (M 3+-A1, Cr, Ga, Mn), isomorphous with layered tetragonal VOPO4.2H20 and having potential catalytic properties, have been characterized by TG and DTA, X-ray diffraction and surface acid strength. During heating the compounds transform in the monohydrated and anhydrous phases, all maintaining a layered structure, with a proper interlayer spacing. Catalytic tests performed with 1-butene show that the M3+-vanadyl phosphates greatly improve the conversion of the olefine with respect to pure vanadyl phosphate.