519
Zhang et al. [94] studied the size and acidity of pore in SAPO-11 by introducing
surfactant cetyltrimethylammonium bromide (CTAB), nonionic copolymer
poly(ethyleneoxide) block poly(propylene oxide)-block-poly(ethylene oxide)
(F127), and both in synthesis. 0.5 wt% Pt/SAPO-11 (synthesized with CTAB+F127)
was studied for 86.9% with 97.2% selectivity toward C 8 isomers. The increase in
isomerization yield was due to large pores formed in SAPO-11 (synthesized in presence of both CTAB and F127) which resists cracking of di-branched products and
reduces probability of coke formation.
3.2.3 Studies over SAPO-5
Katikaneni et al. [95] studied the performance of aluminophosphate molecular sieve
catalysts for the production of hydrocarbons from wood-derived and vegetable oils.
The reaction was carried out over temperature range of 330–410 °C, with WHSV of
3.6 h
-1
. SAPO-5 and SAPO-11 showed highest selectivity toward the aromatic
hydrocarbons compared to MgAPO-36. Both the SAPO catalysts were highly selective for benzene formation. SAPO-5 in particular was selective for ethylene and
propylene, SAPO-11 for propylene and MgAPO-36 for iso-butane.
3.3 Fuels from CO 2
Increasing CO 2 concentration causes global rise in atmospheric temperature, ocean
acidification, and climate change. Hence the scientific community is making efforts
for CO 2 utilization [96]. There are two main reaction paths for the CO 2 hydrogenation to lower olefins: (1) a two-step process, with initial reduction of CO 2 to CO via
the reverse water gas shift (RWGS) reaction followed by the conversion of CO to
lower olefins via a Fischer-Tropsch; (2) lower olefins production from CO 2 and H 2
by two consecutive processes, viz., methanol synthesis and methanol-to-olefin
(MTO) reaction [97, 98]. The use of a bifunctional catalyst (i.e., metal oxides/zeolites) for CO 2 conversion to light olefins is a promising approach to tackle CO 2
emissions [99, 100]. Ramirez et al. [99] have reported the synthesis of coated sulfated zirconia/SAPO-34 (ZrS/SAPO-34) for the direct conversion of CO 2 to light
olefins. SAPO-34 causes light olefin selectivity, while ZrS layer allows the cracking
of C 5
+
heavy hydrocarbons. Similarly, Li et al. [100] developed bifunctional ZnOY 2 O 3 oxide and SAPO-34 zeolite, which catalyzes the selective hydrogenation of
CO 2 to light olefins with a selectivity of 83.9% and conversion of 27.6% at
390 °C. Several other composite catalysts such as In 2 O 3 -ZnZrO x /SAPO-34 [101],
CuO-ZnO)-kaolin/SAPO-34 [102], ZnGa 2 O 4, and SAPO-34 [103], ZnO-ZrO 2 and
SAPO-34 [104] have been reported in CO 2 to hydrocarbons conversion with high
light olefin selectivity.
Recent Developments on Clean Fuels over SAPO-Type Catalysts
Zhang et al. [94] studied the size and acidity of pore in SAPO-11 by introducing
surfactant cetyltrimethylammonium bromide (CTAB), nonionic copolymer
poly(ethyleneoxide) block poly(propylene oxide)-block-poly(ethylene oxide)
(F127), and both in synthesis. 0.5 wt% Pt/SAPO-11 (synthesized with CTAB+F127)
was studied for 86.9% with 97.2% selectivity toward C 8 isomers. The increase in
isomerization yield was due to large pores formed in SAPO-11 (synthesized in presence of both CTAB and F127) which resists cracking of di-branched products and
reduces probability of coke formation.
3.2.3 Studies over SAPO-5
Katikaneni et al. [95] studied the performance of aluminophosphate molecular sieve
catalysts for the production of hydrocarbons from wood-derived and vegetable oils.
The reaction was carried out over temperature range of 330–410 °C, with WHSV of
3.6 h
-1
. SAPO-5 and SAPO-11 showed highest selectivity toward the aromatic
hydrocarbons compared to MgAPO-36. Both the SAPO catalysts were highly selective for benzene formation. SAPO-5 in particular was selective for ethylene and
propylene, SAPO-11 for propylene and MgAPO-36 for iso-butane.
3.3 Fuels from CO 2
Increasing CO 2 concentration causes global rise in atmospheric temperature, ocean
acidification, and climate change. Hence the scientific community is making efforts
for CO 2 utilization [96]. There are two main reaction paths for the CO 2 hydrogenation to lower olefins: (1) a two-step process, with initial reduction of CO 2 to CO via
the reverse water gas shift (RWGS) reaction followed by the conversion of CO to
lower olefins via a Fischer-Tropsch; (2) lower olefins production from CO 2 and H 2
by two consecutive processes, viz., methanol synthesis and methanol-to-olefin
(MTO) reaction [97, 98]. The use of a bifunctional catalyst (i.e., metal oxides/zeolites) for CO 2 conversion to light olefins is a promising approach to tackle CO 2
emissions [99, 100]. Ramirez et al. [99] have reported the synthesis of coated sulfated zirconia/SAPO-34 (ZrS/SAPO-34) for the direct conversion of CO 2 to light
olefins. SAPO-34 causes light olefin selectivity, while ZrS layer allows the cracking
of C 5
+
heavy hydrocarbons. Similarly, Li et al. [100] developed bifunctional ZnOY 2 O 3 oxide and SAPO-34 zeolite, which catalyzes the selective hydrogenation of
CO 2 to light olefins with a selectivity of 83.9% and conversion of 27.6% at
390 °C. Several other composite catalysts such as In 2 O 3 -ZnZrO x /SAPO-34 [101],
CuO-ZnO)-kaolin/SAPO-34 [102], ZnGa 2 O 4, and SAPO-34 [103], ZnO-ZrO 2 and
SAPO-34 [104] have been reported in CO 2 to hydrocarbons conversion with high
light olefin selectivity.
Recent Developments on Clean Fuels over SAPO-Type Catalysts