The Clean Synthesis of Small-Particle TS-1 with High-Content Framework Ti by Using NH₄HCO₃ and Suspended Seeds as an Assistant

Abstract

The synthesis of a TS-1 zeolite with high-content framework Ti and small particles has been developed by adding NH₄HCO₃ and suspended seeds as an assistant. With the addition of NH₄HCO₃, the Hofmann decomposition of the tetrapropylammonium cation (TPA⁺) decreased, and the framework Ti content of the zeolite increased first and then decreased while the particle became larger. With the assistance of suspended seeds, the TS-1 synthesized under a low-alkalinity system possesses small particle size and high-content framework Ti, and it shows the best catalytic activity among the prepared catalysts. Because the decomposition of TPA⁺ decreased, the mother liquid could be reused in the next run of preparation. Even though the recycled mother liquid was reused five times, all obtained TS-1 samples exhibited similar catalytic performances in propylene epoxidation. This work provides an efficient process for preparing TS-1 with good catalytic performance and reduces the discharge of the waste liquid.