Dehydration of glycerol to acrolein over tungstated zirconias: key parameters for higher efficiency
Résumé
As by-product of biodiesel, glycerol is potential building block for the production of many chemicals by routes alternative to those of petrochemistry. Among them, gas phase dehydration of glycerol to acrolein is one of the most attractive. However, such process is limited by deactivation of catalysts with time on stream by coking and the acrolein selectivity has to be improved. In the present work, Si-doped and undoped W/ZrO2 catalysts were prepared by several methods, characterized and evaluated for dehydration of glycerol. Different preparation parameters such the pH of precipitation of hydrous zirconias, the maturation time, addition of basic reflux, the amounts of tungsten and silica precursors, the calcination temperature were varied in order to determine their influences on the pore size. In addition to identification of key parameters, it allowed to get catalysts with various pore sizes and then to evidence its influence on stability. Catalysts prepared from commercial ZrO2 exhibited higher stability than the best catalysts prepared from hydrous zirconias and owning similar mean pore sizes. This improvement was explained by different pore size distributions that appeared as the real key parameter.