Silica islands regulated external Ti‐site environment of TS‐1 for enhanced performance of 1‐hexene epoxidation

This is the authors' abstract. We don't add key points for this paper.

Rational regulation of the local environment of Ti‐sites in TS‐1 harbors tremendous industrial and scientific significance to epoxidation reactions. Herein, we report a facile and environment‐friendly strategy to boost catalytic selectivity by covering the Ti‐sites on an external surface of TS‐1 (ITS‐1) without sacrificing activity of internal Ti sites. By a quantitative analysis of d 3 ‐acetonitrile and quinoline‐DRIFTS, 1 H MAS NMR and XPS, it is found that the percentage of external Ti‐sites decreased from 11% to 6% after depositing surface silica islands. This successfully inhibits ring‐opening reaction of 1,2‐epoxyhexane on catalyst surface, as demonstrated by slower kinetic decomposition rate of 1,2‐epoxyhexane. Compared with conventional TS‐1 catalyst, selectivity of 1,2‐epoxyhexane over ITS‐1 catalyst significantly increased from 83.5% to 98.5% while maintaining high 1‐hexene conversion. Furthermore, overmuch surface silica coverage only leads to extremely low conversion (2%) due to inhibition of mass transfer. This work paves the way for rational construction of Ti‐containing catalysts for 1‐hexene epoxidation.