Catalytic Performance and Characterization of Silica Supported Sodium Phosphates for the Dehydration of Methyl Lactate to Methyl Acrylate andAcrylic Acid

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 NaH 2 PO 4 /SiO 2 a significantly higher selectivity to MA + AA than on Na 2 HPO 4 /SiO 2 and Na 3 PO 4 /SiO 2 was observed. For NaH 2 PO 4 /SiO 2, there is an optimum loading of NaH 2 PO 4, with which a higher selectivity to MA + AA could be obtained. It was found that the ratio of Na 2 O to P 2 O 5 of the phosphates influenced the catalyst performance in the conversion of ML. The catalysts were characterized using XRD, Raman, NMR, and NH 3 -TPD techniques. The higher selectivity for the dehydration of ML to MA + AA on NaH 2 PO 4 /SiO 2 is assumed to be related to the acidity and the amount of the terminal POH groups on the polyphosphate chains.