2 h, and then raised to 773 K and held for 4 h. Air circulation was
maintained throughout the heating process. After calcination,
XRD (X’Pert PRO, PANalytical, Netherlands) was used to confirm
that no drastic structural change occurred. The zeolite beta pellets
with SiO2/Al2O3 molar ratios of 32 and 78 were synthesized in the
laboratory using a hydrothermal method reported by Camblor and
Perez-Pariente [13]. The pellets were in their protonated form and
calcined at 773 K in air for 4 h prior to use. Their crystal structures
were studied by the XRD