3. Results and discussion

3.1 Nucleation/crystal growth mechanism of ZSM-5 zeolites

The nucleation/crystal growth mechanism is significant for the controllable synthesis of ZSM-5 zeolites. The characterization methods with high sensitivity to the amorphous matrix and crystalline species are necessary for the mechanism study [28]. FTIR spectroscopy is often employed to observe the short-range order structures of crystals, and IR vibrations of the structural units of zeolites are intense in the nucleation process [29]. XRD analysis is usually used to study the long-range order structures of crystals, which is beneficial to studying the growth process of zeolites [30]. Fig. 2 displays the FTIR spectra of solid aliquots drawn off the reaction mixture at t = 0.5 h (after RPB premix) and t = 1.5-8.5 h (under dynamic crystallization at 130 ℃).