Toward longer life catalysts for dehydration of glycerol to acrolein

• Correlation between stability and the pore diameter was evidenced for the first time.
• Preparation parameters increasing the pore diameter were determined.
• High proportion of big mesopores (>10 nm) insures high stability.
• The presence of small pores (<5 nm) appears to be critical.

In this work, tungstated zirconias were prepared by different methods and evaluated for glycerol dehydration to acrolein. For all the tested catalysts, the absence of crystalline WO3 was checked by XRD and Raman microscopy. Textural properties were determined by liquid N2 adsorption and mercury penetration measurements. For catalysts prepared from hydrous zirconia (ZrO2·xH2O) incorporating W by anionic exchange, clear correlation between stability and pore diameter was shown for the first time and it was confirmed that SiO2 addition favors the formation of bigger mesopores. This effect was not observed for catalysts obtained by simple W impregnation of hydrous zirconia. In this case, among different preparation parameters investigated, only the addition of a reflux step increased the pore diameter. Finally, tungstated zirconias were prepared by W impregnation of crystalline ZrO2 thermally stable and owning chosen textural properties. As coking leads to pore shrinkage, much higher stability was obtained for catalysts owning high proportion of big mesopores (>10 nm) and small proportion of pores below 5 nm. These characteristics appeared to be key parameters to tailor longer life catalysts for dehydration of glycerol.

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