High-efficiency synthesis of enhanced-titanium and anatase-free TS-1 zeolite by using a crystallization modifier

Abstract

Titanium silicalite-1 (TS-1) zeolite, as a promising shape-selective catalyst, has excellent catalytic activity in many oxidation reactions. However, there are still challenges to rapidly synthesize TS-1 and achieve a high content of Ti in TS-1 without anatase TiO₂. In this work, a high-efficiency strategy has been proposed by using 1,3,5-benzenetricarboxylic acid (H₃BTC) as a crystallization modifier to rapidly synthesize enhanced-Ti TS-1 zeolite without extra-framework anatase TiO₂. In such a synthetic system, a mixed liquid–solid precursor phase is formed within 4.5 hours, and then TS-1 crystals can be produced within one day based on the special combination mechanism of liquid-phase and solid-phase conversion. Ti species enter into the TS-1 framework by the transformation from the liquid phase to crystals as well as by the in situ transformation of the solid phase, which makes the content of framework Ti increase significantly, and the Si/Ti ratio can reach 48.5 without any anatase TiO₂. In the epoxidation of 1-hexene with H₂O₂ as an oxidant, the conversion of alkene over the synthesized TS-1 was improved by 8.01% compared to the traditional TS-1 (18.11% vs. 10.10%). The high-efficiency strategy reported in this paper will provide new opportunities for further promoting the industrial application of TS-1 zeolite.