Tailoring the surface islands to modulate the diffusion of guest molecules over the TS-1 zeolites for enhanced selectivity in the 1-hexene epoxidation

Tailoring the surface mass transfer of guest molecules to achieve enhanced product selectivity is fundamentally and scientifically attractive in the field of catalysis. However, compared with the well-known intra-crystalline transport resistance, tailoring the surface diffusion of guest molecules still remains a great challenge. Herein, we demonstrate that the surface diffusion rate of 1,2-epoxyhexane guest molecules can be governed by SiO2 islands- deposited TS-1 in 1-hexene epoxidation. By quantitative analysis including kinetic experiments and DFT calculation, it is found that the adsorption capacity of 1,2-epoxyhexane around the external surface Ti-sites are significantly reduced by 80%. This successfully inhibits ring-opening reaction of 1,2-epoxyhexane on catalyst surface. Notably, the selectivity of 1,2-epoxyhexane can be significantly improved from 83.5% to 98.5% without sacrificing the activity. This work will open a potential avenue to improve the target product selectivity by precisely constructing the surface islands on the zeolite.