3.3. Pore structure studies
The N2 adsorption–desorption isotherm of the prepared sample
are presented in Fig. 5. The large hysteresis loops in the isotherm
appear with relative pressure P/Po ranging from 0.4 to 1.0 was
due the mesopores structure. The pore structure parameters
[micropore, mesopore area (volume) and average pore diameter]
of the prepared sample are summarized in Table 2. The cumulative
pore volume curve of the prepared sample are given in Fig. 6, the
starting point of the cumulative pore volume of the prepared sample
indicates the diameter of the smallest micropores (0–20Å), and
this is 17 Å. The micropore volume is increased from 0.001 cm3/g
to 0.080 cm3/g as pore diameter increased from 17 Å to 20 Å. As
the mesopore diameter (20–1000 Å) increased from 20 Å to
1000 Å the mesopore volume increased from 0.080 cm3/g to
0.130 cm3/g. There are many reasons for the formation of mesopores
in zeolite crystals such as synthesis of zeolite nano particles,
steaming, acid leaching, base leaching and by using soft and hard
templates during synthesis [21,22]. In the prepared sample the
mesopore formed may be due to both of relatively high Si/Al molarratio and the presence of high percent of alkaline source (Na+)
which generates shorter intracrystalline diffusion path lengths
and relatively higher external (mesopore) surface area [14,23].