Selective propylene epoxidation to propylene oxide (PO) with hydrogen peroxide (H2O2) 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 H2O2 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. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.