Suppression of TS-1 Aggregation by Freeze-Drying to Enhance Au Dispersion for Propylene Epoxidation Using H2 and O2

Au particles immobilized on uncalcined TS-1 (i.e., TS-1-B) have emerged as highly active catalysts for propylene epoxidation using H2 and O2 owing to their good stability. However, it is challenging to enhance the dispersion of Au due to the limited exposed Ti sites for Au adsorption. In this work, we develop a simple method to improve the dispersion of Au particles by employing freeze-dried TS-1-B as a support. Compared with the generally used oven-drying method, the freeze-drying technology can significantly enhance the dispersion of TS-1-B particles, thus giving a small contact angle (indicating good wettability), which is beneficial to achieving the uniform adsorption of Au precursors on TS-1-B, hence forming highly dispersed Au particles. Thus, the asprepared Au/TS-1-B catalyst shows a significantly improved propylene oxide (PO) formation rate (ca 240 gpo center dot h-1 center dot kgcat-1) together with high PO selectivity (ca 92%) and hydrogen efficiency (ca 41%).