Post-synthesis and structural evolution of hollow titanium silicalite-1 with solvent-free method

Generating hollow structure inside titanium silicalite-1 (TS-1) is a widely used method to improve its liquid-phase oxidation catalytic performance in industry. However, traditional dissolution-recrystallization method usually required a large amount of aqueous solution of organic template, leading to unfavorable polluted waste, low production efficiency, and high manufacture cost. Here, a facile and environmental friendly strategy was proposed for the post-synthesis of hollow TS-1 zeolite with a solvent-free method utilizing NH₄HCO₃ and tetrapropylammounium bromide as selective etching agents, which reduced the usage of organic template and avoided the liquid waste. The high crystallinity, the microporous structure, and the active Ti sites were preserved at a high product yield (> 93%). The formation mechanism of hollow structure was also investigated by exploring effects of different reactants and experimental parameters. Meanwhile, the obtained hollow TS-1 showed an outstanding performance in the epoxidation of 1-hexene in comparison to the parent zeolite.