Table Al # (wt%) Total acidity * (mmol/g) H-USY

Table 1
represents the physicochemical properties of H-USY, 10-30P-Y and 10-30S-Y
samples. In all H3PO4
treated samples i.e. 10-30P-Y, the P (wt%) was observed to be increased from 0.075%
to 1.8%, whereas Al (wt%) decreases from 2.84 (parent H-USY) to 0.93% (30P-Y).
Amongst P-Y samples, the reduction of Al is 58 (10P-Y) to 67% (30P-Y) compared
to parent H-USY. H2SO4 treated samples viz; 10, 20 &
30S-Y also showed a decrease of Al from 0.94 to 0.86 (wt%) which corresponds to
67 to 70% as compared to parent H-USY (2.84%) at identical sulphur content of 0.12 (wt%). This decrease of Al may be due
to Al separation from extra framework and from framework. In
overall, H3PO4 treatment showed less dealumination (
58-65%) than H2SO4 ( 67- 70%) due to formation of new
Al-O-P bond in framework as well as AlPO species generation with extra
framework Al.

 

 

 

 

 

Table 1:  Physico-Chemical Properties of  H-USY & different concentration of H3PO4
and H2SO4 treated H-USY Catalysts

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Catalyst

      P(wt %) #

     S(wt %) #

Al
#
(wt%)

 Total acidity * (mmol/g)

H-USY

2.84

0.86

10  P-Y

0.075

1.18

0.27

20
P-Y

0.085

1.14

0.58

30
P-Y

1.8 

0.93

0.98

10
S-Y

0.12

0.94

0.31

20
S-Y

0.12

1.16

0.18

30
S-Y

0.11

0.86

0.22

# Wt %  of
Phosphorous (P), Sulphur (S) & Aluminium (Al) Estimated by EDAX,  * Total acidity Estimated by NH3-TPD

 

Fig. 2A shows NH3-TPD profiles of H-USY, 10P-Y,
20P-Y & 30P-Y and
Fig. 2B depict NH3-TPD profiles of H-USY, 10S-Y, 20S-Y
& 30S-Y. NH3-TPD
profiles of parent H-USY shows two desorption peaks in temperature range of 100-250oC
and 250-450oC respectively, which corresponds to desorption of
ammonia adsorbed on sites of weak acidity (100-250oC) and relatively
strong acidity (250-450oC).27

 In NH3-TPD profiles of all 10-30P-Y (Fig. 2A), a
desorption peaks of strong acid sites decreases from 10 to 30P-Y samples as compared to parent H-USY.
 In case of 10P-Y peak of weak acid site significantly
decreased however it was further increased in 20P-Y and 30P-Y sample
respectively (Fig. 2A). The decrease of weak and strong acidity with 10P-Y may be due to
dealumination of framework & extraframework alumina and an increase of weak
acidity in 20P-Y & 30P-Y may be attributed to an increase of Al-O-P linkages &
comparatively lower dealumination (Table-1) than 10P-Y as compared to parent H-USY.28

The NH3-TPD profiles of all 10-30S-USY
exhibited significantly decreased of both (weak as well as strong) desorption
peaks which is attributed to the more dealumination than P-Y samples and there
is no additional species formation like 10-30P-Y.