Promotion effect of Al species on silica-supported cesium oxide catalyst in the vapor-phase dehydration of 1,2-propanediol to propylene oxide

The introduction of Al into SiO 2 -supported cesium oxide (Cs/SiO 2 ) promoted catalytic activity for the dehydration of 1,2-propanediol (1,2-PDO) to propylene oxide (PO). This improvement was attributed to the promotion of CsNO 3 decomposition and the ability of Al to keep the morphology of the SiO 2 -supported catalyst, even though the Al component slightly reduced the concentration of the base site. The optimum molar component of Al was proven to improve the activity of Cs/SiO 2 catalyst, while maintaining a low rate of side reactions, such as isomerization of PO to allyl alcohol and dehydration of 1,2-PDO to propanal. Several parameters, such as reaction temperature, contact time, Cs 8 Al 2 content, and Al molar component influenced catalytic activity and product distributions. The poisoning experiment by use of CO 2 revealed the importance of the base sites of Cs 8 Al 2 /SiO 2 catalyst, while the role of acid sites was negligible as confirmed by the poisoning experiment with NH 3 . • 1,2-Propanediol was converted to propylene oxide over CsAl/SiO 2 catalyst. • Al eased the decomposition of CsNO 3 and maintained the morphology of CsAl/SiO 2 . • Optimum Cs/Al ratio is essential for efficient formation of propylene oxide. • Al improved the activity and stability of the CsAl/SiO 2 catalyst. • The base sites acted as the active sites for the propylene oxide formation.