Temperature programmed desorption of ammonia (NH3-TPD)
to measure the number of acid sites was performed by Lopenz-
Fonseca et al. [20]. The number of acid sites was obtained by integration
of the NH3-TPD curves and the results are shown in Table 1.
N2 adsorption/desorption isotherms were measured at 196 C
with a ASAP 2010 analyzer (Micromeritics, USA). The zeolites were
outgassed in vacuum at 300 C for 1 h prior to analysis. Table 1
shows BET specific surface area and pore volume by t-plot. The
maximum BET specific surface area was observed on faujasites to
be in the range from 540 m2/g to 604 m2/g. Total pore volume
and mesopore volume on HY901 showed a maximum value of
0.448 cm3/g and 0.260 cm3/g, respectively.