Synergetic photo-epoxidation of propylene over V-Ti/MCM-41 mesoporous photocatalysts

The photo-epoxidation of propylene has gained preference among many alternative processes because the current processes for propylene oxide (PO) production are neither economical nor environmentally sustainable. We synthesized various single and binary metal oxides (Ti and V) constructed within the MCM-41 framework and demonstrated their favorable efficiency for the photo-epoxidation of propylene. The results indicated that highly dispersed tetrahedral coordination states played a role in photoepoxidation. The maximum PO formation rate was 634 +/- 17 (mu mol g(-1) h(-1)) on V0.2Ti0.3/MCM-41 under UV-light irradiation of 0.3 mW cm(-2) at 323 K. The Delplot method revealed two pathways to produce PO. One is indirectly from propionaldehyde via either V or Ti oxides, and the other is directly from a C3H6 reactant via Ti oxides. This paper clearly illustrates how V and Ti oxides affect the photoepoxidation pathways. Furthermore, a possible photo-epoxidation mechanism via the metal oxide active site is proposed to elucidate the synergetic photoactivity. (C) 2015 Elsevier Inc. All rights reserved.