Selective oxidation of propylene to propylene oxide by molecular oxygen over Ti-Al-HMS catalysts

Abstract

Ti- and Al-containing hexagonal mesoporous silicas (HMS) were synthesized at ambient temperature using dodecylamine as surfactant, and the resultant compounds were used as catalysts for the oxidation of propylene by molecular oxygen. Ti-Al-HMS, which was prepared by reaction of Ti(iso-OC3H7)4, Al(iso-OC3H7)3 and SiOC2H5)4 in an alcohol-aqueous solution in the presence of dodecylamine, showed 47.8 of conversion and 30.6 of selectivity for propylene oxide (PO) at 523K. The yield of PO over Ti-Al-HMS (14.6) was much higher than those over Ti-HMS (1.3) and Al-HMS (0.9) at the same reaction conditions. Ti-Al-HMS was also found to be more effective for PO formation than the supported catalysts (Ti/Al-HMS and Al/Ti-HMS) prepared by impregnation method. These results indicated that the simultaneous existence of Ti and Al in HMS was very important for improving the yield of PO from the oxidation of propylene, and the synthesis method influenced the catalytic activity of the Ti- and Al-containing HMS catalysts.