On the nature of post synthetic isolated zirconium site development in *BEA framework for ethanol-to-butadiene conversion : A mechanism study

Metallosilicates with isolated framework metal sites as well as Lewis acidity, e.g., Zr- β zeolite, is proven to be one of the most active for the conversion of ethanol to 1,3-butadiene (ETB), which is a potential process for sustainable butadiene production. However the development process of isolated Zr sites in *BEA framework and their structure–activity relationship in ETB process are still under debate. In this work, three post-synthetic procedures, Liquid Phase Incorporation (LPI), Solid State Ion Exchange (SSIE), and Direct Loading were applied for isolated framework Zr sites development, and the procedure as well as catalytic performance and mechanism were systematically investigated. The isolated framework sites could be developed by Liquid Phase Incorporation (LPI) process, where calcination was the key step for Zr-O-Si bond formation, thus representing Zr incorporation into *BEA framework, accompanying the absence of Zr ion exchange. Isolated Zr framework site was the active site in ETB process, for the strong Lewis acidity upon Zr incorporation. DRIFT and TPSR results revealed that the MPV reduction of crotonaldehyde on Zr site was rate-determining in ETB process.