which suggests the formation of additional micropores
with increasing dealumination through acid leaching.
Detailed analysis of the data is required to understand
the type of micropores responsible for the increased
micropore volume.
Though the acid leached sample ATHM-3 exhibited
increased micropore volume (0–20 A ˚ ), the shape of the
curve indicates that the increase is not uniform. For
example, the ATHM-3 curve exhibits a maximum slope
between the points A and B, corresponding to the pore
diameter of (4.5–6A ˚ ) and the slope of the curve
decreases with increasing pore diameter (lines B–C,
and G–H). Thus, from the slope of the pore volume
curve, it is clear that the major amount of the increased
micropore volume in acid leached samples is due to the
increase in the volume of pores with diameter of 4.5–
6 A˚ . The starting point of the cumulative pore volume
curves (Fig. 1) of the samples also indicates the diameter
of the smallest micropores, and this is 5.2A ˚ , 4.8A ˚ and
4.5A ˚ for HM, ATHM-1 and ATHM-3 samples, respectively.
As the pores in the main channel of the mordenite
start from 6.5A ˚ , the increase in volume of pores 4.5–6A ˚
can be ascribed to the increase in the volume of side
pockets, and this observation suggests the possible
opening of side pockets of mordenite by acid leaching
which are accessible for the adsorption of nitrogen in
acid leached samples.