An anion-promoted increase of the SiO2/Al2O3 ratio of zeolites

In this work, we reported a facile strategy to improve the SiO2/Al2O3 ratio of zeolites by introducing NaI as an efficient additive. The SiO2/Al2O3 ratio of MOR was increased by 0.87 with the aid of NaI. The experimental results indicated that the I- anion played a key role in increasing the SiO2/Al2O3 ratio of MOR. Density functional theory calculations (DFT) indicated that I- facilitated the formation of Si-O-Si bonds (significantly decreasing free energy barriers for the formation of Si-O-Si bonds by 35.5 kJ mol(-1)) and hindered the formation of Si-O-Al bonds (increasing free energy barriers for the formation of Si-O-Al bonds by 18.6 kJ mol(-1)), thus leading to an increase of the SiO2/Al2O3 ratio of zeolites and accelerating the crystallization of zeolites. With this method, we could not only increase the SiO2/Al2O3 ratio of MOR, but also increase the SiO2/Al2O3 ratio of NaY (FAU) and ZSM-5 (MFI).

Automated summary

In this study, a facile strategy to improve the SiO2/Al2O3 ratio of zeolites by introducing NaI as an efficient additive was reported. The experimental results and density functional theory calculations showed that NaI facilitated the formation of Si-O-Si bonds and hindered the formation of Si-O-Al bonds, leading to an increase in the SiO2/Al2O3 ratio of zeolites and accelerating their crystallization.