Synthesis of Sheet-like Zeolite TS-1 with Short b-Axis for Epoxidation of 1-Hexene

摘要

In zeolite TS-1, the straight channel parallelled to the b-axis direction has larger pore size and thus is main diffusion channel for molecules. Shorter b-axis brings about shorter diffusion channel, which can leads to higher adsorption and diffusion rate. Therefore, with regard to the morphology modification of MFI zeolites, many studies touch on short b-axis zeolites have been reported. Unfortunately, most of the preparation processes require harsh synthesis conditions and complex organic templates, and they are not conducive to large-scale applications. In this work, cheap organic additive urea and seed crystals were added to synthesize sheet-like TS-1, which boasts short b-axis. At the same time a pre-crystallization was performed at the aging solution stage. In the b-axis direction, the zeolite TS-1 prepared in this way had a minimum thickness of about 50 nm. This is because urea can inhibit the growth of crystals in the b-axis direction, and the guiding effect of the seed liquid also plays the function of adjusting the b-axis thickness. In the epoxidation of 1-hexene with H2O2 when catalyzed by sheet-like TS-1, the selectivity of the target product 1,2-epoxyhexane was significantly improved.