Influence of co-feeds additive on the photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst

In this work, the effects of co-feed species, namely, H₂O or H₂, on the photocatalytic epoxidation of propylene over V-Ti/MCM-41 are examined. A promoting effect on the C₃H₆ consumption rate is found under 0.6 kPa H₂O co-feed when the PO (propylene oxide) formation rate is not proportionally promoted, resulting a slightly decreased PO selectivity. With increasing H₂O concentration, the reaction activity decreases and this can be attributed to surface site blocking by excess H₂O. The presence of H₂O also increases the stability of photocatalyst during reaction. Similar observation of the enhanced C₃H₆ consumption rate and the improved stability is found when 5.6 kPa H₂ is used as co-feed. We found that the catalyst stability is improved when the AA (acetaldehyde) is increased. This suggests that AA accumulation on the catalyst surface may lead to surface fouling and the observed deactivation. The presence of H₂O or H₂ co-feed, which can lead to hydroxyl radical (OH•), may impose a shift in the production formation of photocatalytic reaction.