2022 Annual Meeting
(532cl) Enhancing Epoxidation Activity with Hydrogen Peroxide over Highly Dispersed Tantalum Incorporated Mesoporous Silicates
Authors
The catalytic performance evaluated under similar reaction conditions revealed that compared to other metals, Ta (2 wt%) loadings display higher and stable (10 h) catalytic activity (96 % selectivity) with high H2O2 utilization efficiency (80%). Further, ex situ DR UV-Vis (Figure 1), XPS, Raman, and EXAFS studies reveal that the isolated TaV species are dominant at lower loadings and mixed oligomeric species (Ta-O-Ta) are evident with increasing metal loadings. Moreover, dominant Lewis acid sites were identified from Py IR experiments. Such an enhancement in the activity is due to the favorable coordination of the TaV sites which tunes the electronic environment to stabilize the epoxide intermediates and selectively catalyze the epoxidation pathway.
Our results clearly show that catalyst synthesis techniques that maximize the Ta utilization by forming the isolated sites are essential to maximizing the epoxidation TOFs. The influence of metal loadings, reaction conditions, H2O2 utilization, along with detailed catalyst characterization results (TEM, DR UV-Vis, XPS, in situ Py-IR, EXAFS, TPR-H2, Raman, and 15N Pyridine NMR) will be presented to provide structure-activity relationships.