506
Different amines, viz., triethylammonium hydroxide (TEAOH), dipropylamine
(DPA) isopropylamine, morpholie, triethylamine (TEA), diethyl amine(DEA), and
piperidine [9–14], have been reported for its synthesis. SAPO-11 (medium-pore
molecular sieve) is usually synthesized in the presence of DPA and DIPA from the
temperature range of 160–220 °C for 20–28 h [15, 16]. It shows structural analogy
with AEL-type zeolite having one-dimensional 10-ring pore structure
(0.4 × 0.65 nm). It exhibits good thermal stability and surface acidity which makes
it a prominent catalyst in alkane isomerization/hydroisomerization and dewaxing
processes [15, 16].
SAPO-5 has AFI topology with large-pore (0.73 nm × 0.73 nm) one-dimensional
framework. It consists of repetitive connection of double four-membered ring (D4R)
and double six-membered ring (D6R) as secondary building units (SBUs) framework with 12-membered pore opening [17, 18]. It is synthesized at various temperatures from 150 to 200 °C for 24–144 h. DPA, TEA, cyclohexylamine, and N, N,
dimethylbenzylamine have been successfully employed in its synthesis [19–22].
SAPO-5 finds extensive application in xylene isomerization, benzene alkylation,
cumene synthesis, transalkylation of toluene with trimethylbenzene, etc. [23–27].
One template can direct the synthesis of multiple structures and also multiple templates may lead to formation of same framework. For example, dipropyl amine
(DPA) has versatile application in the synthesis of almost all types of framework as
shown in Fig. 1. The extra-large pore system, VPI-5 (18 rings) can be synthesized in
the presence of triple helical periphery created by hydrogen bonded amine with
water [28]. Other amines used for its synthesis are tetrabutylammonium hydroxide
(TBAOH) [29, 30], di-n-pentylamine (DPeA), triethanolamine (TEOA), triisopropanolamine (TIPOA), cyclopentylamineand cyclohexylamine [31]. The vast variety
of organics employed in VPI-5 synthesis not only act as SDAs but also serve the
purpose of pH moderators. [31].
The catalytic performance of these solid acid catalysts has been employed in the
generation of clean fuels from various sources like hydrocarbons, CO 2, biological
feedstocks as well as by increasing the octane count of the petroleum products. The
following sections highlight the insights of the various SAPOs in clean fuel
production.
3 Catalytic Applications of Molecular Sieves in Clean
Fuel Production
3.1 Fuels from Hydrocarbons
Hydrocarbons are ubiquitous in nature. Broadly they have been grouped as aliphatic
and aromatic compounds. They range from simplest methane to complex catenated
and polymeric sugars with other functionalities. When we talk about the natural
sources of hydrocarbons, they are chiefly in the form of coal, petroleum, and natural
R. Yadav and A. K. Singh
Different amines, viz., triethylammonium hydroxide (TEAOH), dipropylamine
(DPA) isopropylamine, morpholie, triethylamine (TEA), diethyl amine(DEA), and
piperidine [9–14], have been reported for its synthesis. SAPO-11 (medium-pore
molecular sieve) is usually synthesized in the presence of DPA and DIPA from the
temperature range of 160–220 °C for 20–28 h [15, 16]. It shows structural analogy
with AEL-type zeolite having one-dimensional 10-ring pore structure
(0.4 × 0.65 nm). It exhibits good thermal stability and surface acidity which makes
it a prominent catalyst in alkane isomerization/hydroisomerization and dewaxing
processes [15, 16].
SAPO-5 has AFI topology with large-pore (0.73 nm × 0.73 nm) one-dimensional
framework. It consists of repetitive connection of double four-membered ring (D4R)
and double six-membered ring (D6R) as secondary building units (SBUs) framework with 12-membered pore opening [17, 18]. It is synthesized at various temperatures from 150 to 200 °C for 24–144 h. DPA, TEA, cyclohexylamine, and N, N,
dimethylbenzylamine have been successfully employed in its synthesis [19–22].
SAPO-5 finds extensive application in xylene isomerization, benzene alkylation,
cumene synthesis, transalkylation of toluene with trimethylbenzene, etc. [23–27].
One template can direct the synthesis of multiple structures and also multiple templates may lead to formation of same framework. For example, dipropyl amine
(DPA) has versatile application in the synthesis of almost all types of framework as
shown in Fig. 1. The extra-large pore system, VPI-5 (18 rings) can be synthesized in
the presence of triple helical periphery created by hydrogen bonded amine with
water [28]. Other amines used for its synthesis are tetrabutylammonium hydroxide
(TBAOH) [29, 30], di-n-pentylamine (DPeA), triethanolamine (TEOA), triisopropanolamine (TIPOA), cyclopentylamineand cyclohexylamine [31]. The vast variety
of organics employed in VPI-5 synthesis not only act as SDAs but also serve the
purpose of pH moderators. [31].
The catalytic performance of these solid acid catalysts has been employed in the
generation of clean fuels from various sources like hydrocarbons, CO 2, biological
feedstocks as well as by increasing the octane count of the petroleum products. The
following sections highlight the insights of the various SAPOs in clean fuel
production.
3 Catalytic Applications of Molecular Sieves in Clean
Fuel Production
3.1 Fuels from Hydrocarbons
Hydrocarbons are ubiquitous in nature. Broadly they have been grouped as aliphatic
and aromatic compounds. They range from simplest methane to complex catenated
and polymeric sugars with other functionalities. When we talk about the natural
sources of hydrocarbons, they are chiefly in the form of coal, petroleum, and natural
R. Yadav and A. K. Singh