517
selectivity (11%), owing to its constraint pore opening suitable for smaller molecular diffusion [76]. The application of SAPOs is not only limited to biofuel production but also in the synthesis of platform chemicals like xylene and furan [77, 78].
Hierarchical SAPO-34 has been used for p-xylene production from biomass-derived
2, 5-dimethylfuran (DMF) and ethylene, with a good selectivity (~75%). Similar
trends have been reported for SAPO-11, the large-pore system [77].
3.2.2 Studies over SAPO-11
Xing et al. [79] studied the effect of Si/Al ratio of SAPO-11 for isomerization and
cracking of n-alkanes (castor oil, C 15 –C 18 ). SAPO-11 with different Si/Al molar
ratio of 0.2, 0.4, 0.6 were synthesized and wet impregnated using 15 wt% Ni and
5 wt% Mo. The catalyst Ni-Mo/SAPO-11 with 0.4 Si/Al showed optimum conversion of 97.2% and jet fuel selectivity of 81.6%. The catalyst Ni-Mo/SAPO-11(0.4)
was further explored to study the effect of temperature on conversion and selectivity
of long-chain n-alkanes. It is reported that with an increase in temperature from 583
to 623 K, the conversion and selectivity of C 15 increases compared to higher hydrocarbon chain.
Yang et al. [80] studied the effect of Ni loading on SAPO-11 for the hydroisomerization of oleic acid to iso-alkanes. The acidity of the catalyst was decreased
with an increase in Ni loading. Among all the catalysts, catalysts with 7 wt% Ni
showed the highest conversion and 67.3 mol% of iso-alkanes. The high amount of
hydroisomerized products were obtained due to synergic effect between the metal
center and Lewis/Brönsted acid sites.
Herskowitz et al. [81] studied conversion of soybean oil to green diesel over 1
wt% Pt/SAPO-11(to increase the surface area the catalyst, catalyst pellets were prepared by combining it with alumina binder). During the catalytic activity, no gas
products were recorded only liquid phase products were obtained. The product contained branched paraffins, naphthenes, and mono-aromatics which qualified for diesel fuel blends. Rabaev et al. [82] reported >99% deoxygenation of soybean oil over
Pt/ SAPO-11–Al 2 O 3 .
Rabaev et al. [83] studied 0.5 wt% Pt/SAPO-11 for vegetable oils conversion to
diesel and jet fuels. The steady-state performance of the catalyst was studied after
200 h on stream rather than its initial activity. The authors reported three-stage processes to produce drop-in diesel and jet fuel. This stage followed are fractionation,
mild hydrocracking on Ni 2 P/HY catalyst followed by isomerization on 0.5%Pt/
Al 2 O 3 /SAPO-11. The fractionation 42–48 wt% of jet fuel with >12% aromatics was
obtained with C 14 – 16 % monoaromatic and >60% iso-paraffinic compounds.
Hancsók et al. [84] studied the oleic acid hydroisomerization over 0.5 wt% Pt/
SAPO-11 in detail and found that the addition of a small amount of oxygenic compounds (0.06–0.5%) yielded high isomer concentration in products. Further the
decrease in the catalytic activity was due to structure collapse as a result of water
formation during conversion. In a similar study the catalyst was found active for the
Recent Developments on Clean Fuels over SAPO-Type Catalysts
selectivity (11%), owing to its constraint pore opening suitable for smaller molecular diffusion [76]. The application of SAPOs is not only limited to biofuel production but also in the synthesis of platform chemicals like xylene and furan [77, 78].
Hierarchical SAPO-34 has been used for p-xylene production from biomass-derived
2, 5-dimethylfuran (DMF) and ethylene, with a good selectivity (~75%). Similar
trends have been reported for SAPO-11, the large-pore system [77].
3.2.2 Studies over SAPO-11
Xing et al. [79] studied the effect of Si/Al ratio of SAPO-11 for isomerization and
cracking of n-alkanes (castor oil, C 15 –C 18 ). SAPO-11 with different Si/Al molar
ratio of 0.2, 0.4, 0.6 were synthesized and wet impregnated using 15 wt% Ni and
5 wt% Mo. The catalyst Ni-Mo/SAPO-11 with 0.4 Si/Al showed optimum conversion of 97.2% and jet fuel selectivity of 81.6%. The catalyst Ni-Mo/SAPO-11(0.4)
was further explored to study the effect of temperature on conversion and selectivity
of long-chain n-alkanes. It is reported that with an increase in temperature from 583
to 623 K, the conversion and selectivity of C 15 increases compared to higher hydrocarbon chain.
Yang et al. [80] studied the effect of Ni loading on SAPO-11 for the hydroisomerization of oleic acid to iso-alkanes. The acidity of the catalyst was decreased
with an increase in Ni loading. Among all the catalysts, catalysts with 7 wt% Ni
showed the highest conversion and 67.3 mol% of iso-alkanes. The high amount of
hydroisomerized products were obtained due to synergic effect between the metal
center and Lewis/Brönsted acid sites.
Herskowitz et al. [81] studied conversion of soybean oil to green diesel over 1
wt% Pt/SAPO-11(to increase the surface area the catalyst, catalyst pellets were prepared by combining it with alumina binder). During the catalytic activity, no gas
products were recorded only liquid phase products were obtained. The product contained branched paraffins, naphthenes, and mono-aromatics which qualified for diesel fuel blends. Rabaev et al. [82] reported >99% deoxygenation of soybean oil over
Pt/ SAPO-11–Al 2 O 3 .
Rabaev et al. [83] studied 0.5 wt% Pt/SAPO-11 for vegetable oils conversion to
diesel and jet fuels. The steady-state performance of the catalyst was studied after
200 h on stream rather than its initial activity. The authors reported three-stage processes to produce drop-in diesel and jet fuel. This stage followed are fractionation,
mild hydrocracking on Ni 2 P/HY catalyst followed by isomerization on 0.5%Pt/
Al 2 O 3 /SAPO-11. The fractionation 42–48 wt% of jet fuel with >12% aromatics was
obtained with C 14 – 16 % monoaromatic and >60% iso-paraffinic compounds.
Hancsók et al. [84] studied the oleic acid hydroisomerization over 0.5 wt% Pt/
SAPO-11 in detail and found that the addition of a small amount of oxygenic compounds (0.06–0.5%) yielded high isomer concentration in products. Further the
decrease in the catalytic activity was due to structure collapse as a result of water
formation during conversion. In a similar study the catalyst was found active for the
Recent Developments on Clean Fuels over SAPO-Type Catalysts