The gas-phase dehydration of aqueous glycerol to acrolein was investigated using phosphorus-containing MCM-41 (HP-MCM-41) mesoporous molecular sieves, which were prepared via impregnation of phosphoric acid on the MCM-41. The catalysts were characterized by XRD, nitrogen adsorption-desorption, FTIR, NH3-TPD, and pyridine-FTIR measurements. Nitrogen adsorption studies suggested that the uniform framework of MCM-41 remained unchanged even after grafting phosphorus species on its surface. NH3-TPD analysis confirmed that moderate acidic sites had a positive effect on the formation of acrolein. Pyridine-FTIR results indicated that MCM-41 with grafted phosphorus species can noticeably enhance the percentage of BrOnsted acid sites. Moreover, BrOnsted acid sites facilitated the production acrolein selectively confirmed by catalytic results. The effects of H3PO4 loading, calcination temperature, reaction temperature, and glycerol concentrations were also examined. The optimized 25HP-MCM-41 catalyst showed an 84% selectivity of acrolein with glycerol conversion of 97% at 320 degrees C.