Dehydration of methyl lactate (ML) to methyl acrylate (MA) and acrylic acid (AA) over silica supported sodium phosphates was investigated in a fixed-bed continuous flow reactor. On NaH2PO4/SiO2 a significantly higher selectivity to MA + AA than on Na2HPO4/SiO2 and Na3PO4/SiO2 was observed. For NaH2PO4/SiO2, there is an optimum loading of NaH2PO4, With which a higher selectivity to MA + AA could be obtained. It was found that the ratio of Na2O to P2O5 Of the phosphates influenced the catalyst performance in the conversion of ML. The catalysts were characterized using XRD, Raman, NMR, and NH3-TPD techniques, The higher selectivity for the dehydration of ML to MA + AA on NaH2PO4/SiO2 is assumed to be related to the acidity and the amount of the terminal POH groups oil the polyphosphate chains.