512
(0.5–2 wt%) resulted in decreased conversion from 91.0 to 83.0% with higher isomers selectivity from 91.4 to 94.3%. The decrease in the conversion was reported
due to masking of active acidic sites whereas an increase in selectivity is due to high
metal dispersion.
López et al. [50] studied the hydroisomerization of n-pentane over 0.5 wt% Pt/
SAPO-11 and compared its catalytic activity with zeolites (0.5 wt% Pt loaded
HZSM-5 and acid treated HBEA). Rise in temperature from 523 to 673 K resulted
an increase in the conversion for all the catalysts. However, 0.5 wt% Pt/SAPO-11
showed least conversion among all the catalysts. The Pt/HBEA catalyst showed
about 95% selectivity toward iso-pentane, whereas it is 60–80% in the case of
0.5 wt% Pt/HZSM-5 and nearly 60% for 0.5 wt% Pt/SAPO-11 which is due to
higher acidity in the case of zeolite catalysts. Liu et al. [51] studied the effect of
addition of rare earth metals (La and Ce) as promoters over 0.2 wt% Pt/SAPO-11
and studied it for hydroisomerization of n-heptane. The bimetallic catalysts 0.2 wt%
La 0.2 wt% Pt/SAPO-11 and 0.2 wt% Ce 0.2 wt% Pt/SAPO-11 were prepared by
the impregnation method. These additive additions could lead to an increase in the
amount of Lewis acid. LaPt/SAPO-11 and CePt/SAPO-11 showed good conversion
of about 77–78% with i-C 7 yield of 67–68% whereas Pt/SAPO-37 showed a conversion of 65% with i-C 7 yield of 62%. The higher conversion in the case of rare earth
metal-–promoted catalyst was reported due to higher Pt dispersion.
Pölczmann et al. [57] compared microporous and mesoporous molecular sieves
for the isomerization and hydrocracking of Fischer–Tropsch wax (C 20 –C 60 ). The
isomerization of wax produces base oil and hydrocracking gives fuel. The authors
found that 0.5 wt% Pt/AlSBA-15 catalyst over the temperature range of 548–623 K
showed higher isomer content (about 70% at 623 K) compared to 0.5 wt% Pt/
SAPO-11 (about 40% at 623 K) which might be due to higher concentration of
Brönsted acidic sites on 0.5 wt% Pt/AlSBA-15. Fan et al. [58] reported aluminosilicate/silicoaluminophosphate composite zeolite ZSM-5/SAPO-11 for fluid catalytic
cracking (FCC). The composite was prepared by adding pre-formed ZSM-5 to
SAPO-11 synthesis gel followed by hydrothermal treatment. The obtained catalyst
was calcined and Ni-Mo was added to it using ion exchange. The obtained catalyst
showed better catalytic activity compared to physical mixture of ZSM-5 and
SAPO-11 due to the synergic effect between the acidic sites.
3.1.3 Studies over SAPO-5
Different reaction conditions for hydrocarbon conversion over SAPO-5 are summarized in Table 2. Hajfarajollah et al. [59] compared SAPO-34 and SAPO-5 and
varied the silica source in the catalysts preparation. The SAPO-34 catalyst possessed a high number of strong acidic sites essential for methanol conversion. The
crystallite size played the main role in role in the selectivity and conversion.
SAPO-34 synthesized using tetraethyl orthosilicate (TEOS) obtained small crystallite size compared to catalyst synthesized with fumed silica. The catalyst with small
R. Yadav and A. K. Singh
(0.5–2 wt%) resulted in decreased conversion from 91.0 to 83.0% with higher isomers selectivity from 91.4 to 94.3%. The decrease in the conversion was reported
due to masking of active acidic sites whereas an increase in selectivity is due to high
metal dispersion.
López et al. [50] studied the hydroisomerization of n-pentane over 0.5 wt% Pt/
SAPO-11 and compared its catalytic activity with zeolites (0.5 wt% Pt loaded
HZSM-5 and acid treated HBEA). Rise in temperature from 523 to 673 K resulted
an increase in the conversion for all the catalysts. However, 0.5 wt% Pt/SAPO-11
showed least conversion among all the catalysts. The Pt/HBEA catalyst showed
about 95% selectivity toward iso-pentane, whereas it is 60–80% in the case of
0.5 wt% Pt/HZSM-5 and nearly 60% for 0.5 wt% Pt/SAPO-11 which is due to
higher acidity in the case of zeolite catalysts. Liu et al. [51] studied the effect of
addition of rare earth metals (La and Ce) as promoters over 0.2 wt% Pt/SAPO-11
and studied it for hydroisomerization of n-heptane. The bimetallic catalysts 0.2 wt%
La 0.2 wt% Pt/SAPO-11 and 0.2 wt% Ce 0.2 wt% Pt/SAPO-11 were prepared by
the impregnation method. These additive additions could lead to an increase in the
amount of Lewis acid. LaPt/SAPO-11 and CePt/SAPO-11 showed good conversion
of about 77–78% with i-C 7 yield of 67–68% whereas Pt/SAPO-37 showed a conversion of 65% with i-C 7 yield of 62%. The higher conversion in the case of rare earth
metal-–promoted catalyst was reported due to higher Pt dispersion.
Pölczmann et al. [57] compared microporous and mesoporous molecular sieves
for the isomerization and hydrocracking of Fischer–Tropsch wax (C 20 –C 60 ). The
isomerization of wax produces base oil and hydrocracking gives fuel. The authors
found that 0.5 wt% Pt/AlSBA-15 catalyst over the temperature range of 548–623 K
showed higher isomer content (about 70% at 623 K) compared to 0.5 wt% Pt/
SAPO-11 (about 40% at 623 K) which might be due to higher concentration of
Brönsted acidic sites on 0.5 wt% Pt/AlSBA-15. Fan et al. [58] reported aluminosilicate/silicoaluminophosphate composite zeolite ZSM-5/SAPO-11 for fluid catalytic
cracking (FCC). The composite was prepared by adding pre-formed ZSM-5 to
SAPO-11 synthesis gel followed by hydrothermal treatment. The obtained catalyst
was calcined and Ni-Mo was added to it using ion exchange. The obtained catalyst
showed better catalytic activity compared to physical mixture of ZSM-5 and
SAPO-11 due to the synergic effect between the acidic sites.
3.1.3 Studies over SAPO-5
Different reaction conditions for hydrocarbon conversion over SAPO-5 are summarized in Table 2. Hajfarajollah et al. [59] compared SAPO-34 and SAPO-5 and
varied the silica source in the catalysts preparation. The SAPO-34 catalyst possessed a high number of strong acidic sites essential for methanol conversion. The
crystallite size played the main role in role in the selectivity and conversion.
SAPO-34 synthesized using tetraethyl orthosilicate (TEOS) obtained small crystallite size compared to catalyst synthesized with fumed silica. The catalyst with small
R. Yadav and A. K. Singh