CO2 role on the glycerol conversion over catalyst containing CaO-SiO2 doped with Ag and Pt

Solids with strong base sites of calcium-silica mixed oxides (CaO-SiO2), and zirconia (ZrO2), both doped with platinum (Pt) or argentum (Ag), were synthesized and catalytically evaluated in the dehydration of glycerol for valuable chemical intermediates production. The samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDS), Basicity measurements by CO2 temperature programmed desorption (CO2-TPD), thermal analyses (TG/DTA) and N-2 adsorption-desorption isotherms. The effect of two different carrier gas, inert (N-2) or a soft oxidant (CO2) over the activity and selectivity were evaluated in glycerol dehydration for all the samples. The high affinity between Ca and glycerol has effect over the product selectivity, which shows CO2 effect. The promotion with Ag or Pt (0.2 wt%) increase the glycerol conversion and change the product selectivity. The data points out to the hydrogen transfer improving due to the Pt presence. Both, Pt or Ag doping or CO2 addition as the carrier gas may inhibit the acetic acid production, over calcium containing catalyst. The promotion of ZrO2 with Ag or Pt play a less marked effect over the glycerol conversion, under CO2 or N-2.