Silica waste with different surface properties for solvent-free synthesis of TS-1 and its efficient epoxidation of chloropropene

Utilizing silica-rich wastes for synthesis of zeolite can realize a green production protocol and make best use of solid waste. However, industrial solid wastes usually require a complicated pretreatment process and their surface properties are underestimated for the final products. In this study, silica wastes with different acid or basic surface properties are directly used for the solvent-free synthesis of TS-1 zeolites. The states of Ti species, Si/Ti molar ratios, and morphology of final TS-1 zeolites can be controlled by the pristine surface properties and additional ammonium carbonate. TS-1 zeolite synthesized from acid silica waste exhibits lower crystallinity, abundant highly coordinating titanium species, and an elongated c-axis compared to that from basic silica waste. More importantly, TS-1 zeolite (nSi/nTi = 30) synthesized from silica with acid property possesses excellent performance in the epoxidation of chloropropene with 66.2% conversion and 98.5% selectivity to epichloro-hydrin, which is attributed to the presence of abundant high-coordination Ti species of mononuclear TiO6. Our strategy provides a novel idea for totally green synthesis of zeolite by utilizing solid wastes.

Automated summary

Using silica-rich wastes is a green approach to synthesize zeolite and utilize solid waste effectively. However, the complex pretreatment process and underestimation of surface properties are common challenges in utilizing industrial solid wastes. In this study, silica wastes with different acid or basic surface properties were directly used for solvent-free synthesis of TS-1 zeolites. The properties and morphology of the final products can be controlled by the pristine surface properties and additional ammonium carbonate. TS-1 zeolite synthesized from acid silica waste exhibits lower crystallinity, abundant highly coordinating titanium species, and an elongated c-axis compared to that from basic silica waste. Moreover, TS-1 zeolite synthesized from acid silica waste shows excellent performance in the epoxidation reaction, with a conversion of 66.2% and selectivity of 98.5% to epichloro-hydrin, due to the presence of abundant high-coordination Ti species. This study provides a new idea for the green synthesis of zeolite by utilizing solid waste.