2. Experimental
2.1. Catalyst preparation
Na-ZSM-5 zeolites with Si/Al atomic ratio of x (x = 23, 51, 62,
and 107) were hydrothermally synthesized.
Tetrapropylammonium bromide was used as a templating agent.
Water glass and aluminum sulfate were used as silicon and aluminum sources, respectively.
The Si/Al ratio was adjusted by changing the amount of aluminum sulfate.
The starting gel was put in the autoclave at 433K for 2 days.
The obtained products were washed with ion-exchanged water and calcined at 823K for 8 h in air. The asprepared Na-ZSM-5 zeolites were ion-exchanged with an aqueous solution of 0.1 mol L−1 ammonium nitrate in static condition at 343K for 3 days and washed with ion-exchanged water to obtain their NH4 + forms.
They were transformed into H-ZSM-5 by calcining at 823K for 8 h in the air.