Suppression of TS-1 Aggregation by Freeze-Drying to Enhance Au Dispersion for Propylene Epoxidation Using H<sub>2</sub> and O<sub>2</sub>
Yanqi Guo, Zhihua Zhang, Jialun Xu, Xuezhi Duan, Xinggui Zhou
Abstract
Au particles immobilized on uncalcined TS-1 (i.e., TS-1-B) have emerged as highly active catalysts for propylene epoxidation using H 2 and O 2 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 as-prepared Au/TS-1-B catalyst shows a significantly improved propylene oxide (PO) formation rate (ca 240 g po ·h –1 ·kg cat –1 ) together with high PO selectivity (ca 92%) and hydrogen efficiency (ca 41%).