Molecular and Experimental Insights into the Role of Ti-M in the Structure, Stability, and Acidity of M-Ts-1 Catalysts (M=B, Al, Ga, Zr, Sn)

Abstract

The titanium silicalite-1 (TS-1) exhibits excellent catalytic performance in selective oxidation, with the incorporation of specific elements and the local environment of catalytic sites playing crucial role in its behavior. In this study, a combined density functional theory calculations and experimental methods were employed to investigate the location, stability, and Lewis and Brønsted acidities of various trivalent (M3+) and tetravalent (M4+) metal-doped-TS-1 (M-TS-1). No competition between Ti and B was observed for catalytic site location due to their differential preferential sites. However, Al, Ga, Zr, and Sn may compete with Ti for incorporation. Notably, incorporating Sn, B, and Zr into TS-1 enhances the formation of Ti-OH defect, while the creation of Si vacancies in M-TS-1 becomes thermodynamically more favorable compared to TS-1. The introduction of heteroatoms increases the acidity of TS-1, which significantly impact acid-catalyzed reactions. This study provides a comprehensive understanding of the structure and acidity of heteroatom-doped TS-1, providing valuable insights for the targeted optimization of TS-1 for improved catalytic performance.

Keywords: Titanium silicalite-1, Chemical structure, Lewis acidity, Brønsted acidity, Density functional theory