Seed-assisted synthesis of ZSM-23 zeolites in the absence of alkali metal ions

The seed-assisted synthesis of ZSM-23 zeolite in the absence of alkali metal ions (denoted as SNNa) was investigated. Highly crystallized SNNa with needle-shape morphology and size of 500–1100 nm in length and 50–200 nm in diameter can be synthesized. Much attention was paid to the roles of alkali metal ions during the crystallization process . The absence of Na + can effectively avoid the impurity-quartz formation and promote SNNa crystallization in a broad range of SiO 2 /Al 2 O 3 ratio between 80 and 200, whereas the crystallization rate was slowed down at the same time. On the contrary, the presence of Na + had a significant effect both on the nucleation and crystal growth processes. The bifunctional catalyst Pt/H-SNNa prepared, showed good catalytic performance in the hydroisomerization of n-hexadecane due to its small crystal size, appropriate acidity and acid site distribution.