Selective propylene epoxidation in liquid phase using highly dispersed Nb catalysts incorporated in mesoporous silicates

Selective propylene epoxidation to propylene oxide (PO) with hydrogen peroxide (H 2 O 2 ) was carried out in a catalytic semi-batch reactor. High propylene epoxidation activity (44   h −   1 ) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating conditions. The physical and chemical properties of the Nb based silicates characterized using BET, FTIR, TPD , TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO production. Catalyst synthesis methods were investigated for their effects on PO productivity, PO selectivity and H 2 O 2 utilization efficiency. It is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene epoxidation. Surface characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.