2.2. General characterization
X-ray diffraction (XRD) patterns and average crystal size were
collected with Bruker axs, D8 Advance. N2 adsorption and desorption
isotherms were obtained at 77 K using a volumetric
adsorption apparatus (Nova2000 series, Chromatech). The pore
structures were estimated according to the Brunauer–Emmett Teller
(BET) method. The samples were degassed at 573 K for 24 h
under vacuum prior to the analysis. The micropore area and volume
were calculated by the t-plot method. The mesopore area
was obtained by subtracting the micropore area from the BET surface
area, and the mesopore volume was calculated by subtracting
the micropore volume from the total pore volume at 0.985P/Po
according to the method reported in the literature [11]. The micropore
size distribution was obtained by applying the Horvath–
Kawazoe method (H–K) [12]. FT-IR spectra were recorded using
Jasco FT-IR-460 plus, Japan; the zeolite samples were also characterized
by scanning electron microscopy using a Jeol scanning
microscope model JSM5410. Elemental analysis was carried out
using link, ISIS-300, Oxford EDS (energy dispersion spectroscopy)
detector. Thermal analysis data (Shimadzu TGA-50/DT-50) were
investigated to define the weight loss and thermal change at room
temperature to 800 C, where in atmosphere was nitrogen and the
rate flow was 20.00 ml/min.