Polymer-alumina dually supported palladium catalysts (PVP-Pd/Al2O3, PVP = poly(N-vinyl-2-pyrrolidone); PPPO-Pd/Al2O3, PPPO = phosphinated poly(phenylene oxide)) were used to catalyze the carbonylation of allyl halides to form butenoic acid under the mild conditions of 40 degrees C and 0.1 MPa. These catalysts exhibit high activity and stability towards the carbonylation of allyl halides. The maximum turnovers (mol CO/mol Pd) of PPPO-Pd/Al2O3 are up to 8.2 x 10(5) and 4.6 x 10(5) for the carbonylation of allyl bromide and allyl chloride respectively in an aqueous NaOH/benzene medium.