Tetrapropylammonium Hydroxide Treatment of Aged Dry Gel to Make Hierarchical TS-1 Zeolites for Catalysis
Zhenyuan Yang, Yanan Guan, Lei Xu, Yangtao Zhou, Xiaolei Fan, Yilai Jiao
Abstract
High Resolution Image Download MS PowerPoint Slide This work presents the development and systematic study of a method to prepare hierarchical titanium silicalite-1 (TS-1) zeolites with high tetra-coordinated framework Ti species content. The new method involves (i) the synthesis of the aged dry gel by treating the zeolite precursor at 90 °C for 24 h; and (ii) the synthesis of hierarchical TS-1 by treating the aged dry gel using tetrapropylammonium hydroxide (TPAOH) solution under hydrothermal conditions. Systematic studies were conducted to understand the effect of the synthesis conditions (including the TPAOH concentration, liquid-to-solid ratio, and treatment time) on the physiochemical properties of the resulting TS-1 zeolites, and the results showed that the condition of a TPAOH concentration of 0.1 M, liquid-to-solid ratio of 1.0, and treatment time of 9 h was ideal to enable the synthesis of hierarchical TS-1 with a Si/Ti ratio of 44. Importantly, the aged dry gel was beneficial to the quick crystallization of zeolite and assembly of nanosized TS-1 crystals with a hierarchical structure ( S ext = 315 m 2 g –1 and V meso = 0.70 cm 3 g –1, respectively) and high framework Ti Species content, making the accessible active sites ready for promoting oxidation catalysis.