Synthesis of titanium silicalite-1 with small crystal size by using mother liquor of titanium silicalite-1 as seeds (II): Influence of synthesis conditions on properties of titanium silicalite-1

Titanium silicalite-1 with small crystal size (small-crystal TS-1) was synthesized in a TPABr–ethylamine hydrothermal system by using the mother liquor of nano-sized TS-1 as seeds. The synthesis conditions were systematically studied, including the purification methods of the small-crystal TS-1, Si/Ti molar ratio in TS-1, amount of the added seed and the crystallization period. The as-synthesized TS-1 was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR), Ultraviolet–visible diffuse reflectance (UV–vis), Ultraviolet Raman spectroscopy (UV-Raman), nitrogen sorption, elemental analysis, atomic force microscope (AFM) and scanning electron microscopy (SEM). The size of the TS-1 crystals formed (about 600 nm × 400 nm × 250 nm) was not significantly affected by the synthesis conditions except for the amount of added seed. The catalytic performance of the synthesized small-crystal TS-1 for the epoxidation of propylene was evaluated. The conversion of hydrogen peroxide, the selectivity of propylene oxide and the utilization of hydrogen peroxide reached 92.2%, 98.0% and 97.0%, respectively, when the mother liquor of small-crystal TS-1 was purified three times by precipitation, the Si/Ti molar ratio was 50, the seed/SiO2 weight ratio was 0.06 and the crystallization time was 48 h.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Small-crystal TS-1 was synthesized in a TPABr–ethylamine hydrothermal system. ► The three times precipitating separation was effective in purification of crystals. ► The crystal size was only affected by the amount of seeds after the crystal formed. ► Small-crystal TS-1 showed an excellent catalytic performance in propylene epoxidation. ► The amount of Na+ in small-crystal TS-1 affected the catalytic performance obviously.