3 years ago

The evolution of titanium species in boron-containing Ti-MWW zeolite during post-treatment revealed by UV resonance Raman spectroscopy

The evolution of titanium species in boron-containing Ti-MWW zeolite during post-treatment revealed by UV resonance Raman spectroscopy
Although the catalytic performance of boron-containing Ti-MWW (B-Ti-MWW) zeolite can be greatly improved by acid treatment before calcination, there are still issues about the definite role of acid treatment and the evolution of titanium species during post-treatment of B-Ti-MWW not very clear due to the lack of advanced technique to thoroughly characterize titanium species. Herein, powerful UV resonance Raman spectroscopy excited at 244 nm was used to address these issues for the first time. It was surprisingly found out that acid treatment of as-synthesized B-Ti-MWW not only removed about half of the absolutely dominant non-framework TiO6 species but also made the other part converted into framework TiO4 species, which has never been reported before. While acid treatment of directly calcined B-Ti-MWW made most of the dominant non-framework TiO6 species transformed into anatase TiO2. Importantly, among all treated samples, only those obtained from acid treatment of as-synthesized B-Ti-MWW and subsequent calcination showed catalytic activity in 1-hexene epoxidation, fully demonstrating that the remarkable enhancement of catalytic performance by acid treatment before calcination was actually ascribed to the transformation of inactive non-framework TiO6 species into active framework TiO4 species. These understandings would be very helpful for the study of boron-containing titanosilicate zeolites.

Publisher URL: www.sciencedirect.com/science

DOI: S138718111730478X

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