Seed-induced synthesis of ZSM-5 aggregates using the Silicate-1 as a seed: Characterization and effect of the Silicate-1 composition

The effect of the seed composition was investigated on physiochemical properties of the synthesized ZSM-5 aggregates. While various tetra propyl ammonium hydroxide/Silicate-1 (TPAOH/Si) ratios were used for seed preparation, ratios of TPAOH/Si in the final gels were around 0.04, 0.08 and 0.16. Samples were characterized by XRD, BET, FT-IR, FE-SEM, NH3-TPD and TG-DTA. High pure ZSM-5 aggregates were obtained with higher crystallinity than the conventional ZSM-5 zeolite. The seed played a key role in the single-direction crystal growth, so that the aggregates were composed of compacted layers with nano-metric long rectangular crystals. Also, the higher the TPAOH/Silicate-1 ratio, the smaller the seed size. The final size of the ZSM-5 aggregates, however, was raised due to higher rate of crystal growth. Moreover, the hierarchy pore size was shaped in the bimodal distribution pattern. The surface acidity was not significantly changed whilst the weak/medium acid site ratio was enhanced with the TPAOH/Silicate-1 ratio.