Pore Condensation in Glycerol Dehydration: Modification of a Mixed Oxide Catalyst

Pore condensation has been suggested as an initiator of deactivation in the dehydration of glycerol to acrolein. To avoid potential pore condensation of the glycerol, a series of WO₃ supported on ZrO₂ catalysts have been prepared through thermal sintering, with modified pore systems. It was shown that catalysts heat treated at temperatures above 800 °C yielded suitable pore system and the catalyst also showed a substantial increase in acrolein yield. The longevity of the heat-treated catalysts was also improved, indeed a catalyst heat treated at 850 °C displayed significantly higher yields and lower pressure-drop build up over the 600 h of testing. Further, the catalyst characterisation work gave evidence for a transition from monoclinic to triclinic tungsten oxide between 850 and 900 °C. There is also an increase in acid-site concentration of the heat-treated catalysts. Given the improved catalyst performance after heat-treatment, it is not unlikely that pore condensation is a significant contributing factor in catalyst deactivation for WO₃ supported on ZrO₂ catalysts in the glycerol dehydration reaction.