Reproducible preparation of Au/TS-1 with high reaction rate for gas phase epoxidation of propylene

A refined and reliable synthesis procedure for Au/TS-1(Si/Ti molar ratio ∼100) with high reaction rate for the direct gas phase epoxidation of propylene has been developed by studying the effects of pH of the gold slurry solution, mixing time, and preparation temperature for deposition precipitation (DP) of Au on TS-1 supports. Au/TS-1 catalysts prepared at optimal DP conditions (pH ∼ 7.3, mixing for 9.5 h, room temperature) showed an average PO rate ∼image at 200 °C at 1 atm. A reproducibility better than ±10% was demonstrated by nine independent samples prepared at the same conditions. These are the highest rates yet reported at 200 °C. No visible gold particles were observed by the HRTEM analysis in the fresh Au/TS-1 with gold loading up to ∼0.1 wt%, indicating that the gold species were smaller than 1 nm. Additionally, the rate per gram of Au and the catalyst stability increased as the Au loading decreased, giving a maximum value of image, and Si/Ti molar ratios of ∼100 gave the highest rates.