Synthesis of Hierarchical TS-1 Nanocrystals with Controllable Grain Size and Mesoporosity: Enhanced Performance for Chloropropylene Epoxidation

To control the preparation cost of titanium silicalite-1 zeolite while enhancing its performance in chloropropylene epoxidation, hierarchical porous titanium silicalite-1 (TS-1) nanocrystals were synthesized by a one-step preparation process without the involvement of additional mesoporous templates. The mesopore size and the particle size could be regulated by changing the amount of water during a vapor-assisted dry gel crystallization. The effects of dry gel/H2O ratios on the zeolite structure were investigated via X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-visible diffuse reflectance spectroscopy (UV-vis), scanning/transmission electron microscopy (SEM, TEM), etc. The hierarchical TS-1 zeolite with a dry gel/H2O ratio of 2.5 had high crystallinity and framework Ti content. The samples also performed remarkably in chloropropylene epoxidation. The conversion of hydrogen peroxide and selectivity of epichlorohydrin (ECH) attained 98.47 and 98.35%, respectively.