Green and efficient dry gel conversion synthesis of SAPO-34 catalyst with plate-like morphology
Green and efficient dry gel conversion synthesis of SAPO-34 catalyst with plate-like morphology
Chun-Yu Di 0 1
Xiao-Feng Li 0 1
Ping Wang 0 1
Zhi-Hong Li 0 1
Bin-Bin Fan 0 1
Tao Dou 0 1
Green MTO 0 1
0 CNPC Key Laboratory of Catalysis, College of Chemical Engineering, China University of Petroleum , Beijing 102249 , China
1 College of Chemistry and Chemical Engineering, Taiyuan University of Technology , Taiyuan 030024, Shanxi , China
SAPO-34 catalyst with plate-like morphology was designed and synthesized for the first time, by the dry gel conversion method using cheap triethylamine as a structure-directing agent assisted with seed suspension containing nanosheet-like SAPO-34 seed. The latter played an important role in formation of SAPO-34 (CHA-type) with plate-like morphology. In addition, the yield of the product in the synthesis system containing seed suspension reached 97%, 15% higher than that obtained in the corresponding synthesis system without the seed suspension. Meanwhile, the plate-like SAPO-34 catalysts synthesized by this method exhibited higher selectivity to light olefins and longer lifetime in methanol-to-olefins (MTO) reaction than the traditional cubic SAPO-34 catalyst. This work provides a new technical route for green and efficient synthesis of SAPO-34 catalysts with improved MTO performance.
SAPO-34; Dry gel conversion chemistry; Seed suspension; Plate-like
Ethylene and propylene are the most widely used basic
organic chemical materials, and they play an important role
in the petrochemical industry. At present, light olefins are
mainly produced by cracking light hydrocarbon (naphtha
and light diesel oil). However, with the shortage of oil
resources, developing alternative routes for ethylene and
propylene production has attracted intense attraction, in
which the conversion of natural gas or coal to light olefins
via methanol is the most promising route (Chen et al.
2005). The conversion process of coal or natural gas to
light olefins via methanol is an effective way to solve such
problems such as the limited oil resource and increasing
olefins demands (Qi et al. 2005), such as UOP/Hydro’s
methanol-to-olefins (USA) (Chen et al. 2005), syngas via
dimethylether to olefins of Dalian Institute of Chemical
Physics (China) (Tian et al. 2015) and Lurgi’s methanol to
propylene (Rothaemel and Holtmann 2002).
Silicoaluminophosphate (SAPO) molecular sieves have
been widely studied because of their many technological
applications. Among the SAPOs, SAPO-34 with a
chabazite-related structure has exhibited excellent catalytic
performance in the methanol-to-olefin (MTO) conversion due
to its relatively small pore diameter (Pastore et al. 2005),
medium acid strength and high hydrothermal stability
(Marchi and Froment 1991; Wei et al. 2012; Wilson and
Barger 1999). However, SAPO-34 is easily deactivated by
coke, which can heavily block the internal channels of the
SAPO-34 crystals and decrease both activity and
selectivity, resulting in a short catalyst lifetime (Qi et al. 2007; Lee
et al. 2007). During the MTO process, coke formation is
related to many factors, such as Si/Al ratio (Xu et al. 2008),
acidity (Ye et al. 2011), crystal morphology, as well as
crystal size (Chen et al. 1999; A´ lvaro-Mun˜oz et al. 2012),
in which the catalyst acidity and size are two important
factors. Studies on the crystal size and morphology have
shown that SAPO-34 catalysts with small crystal size or
with nanosheet-like morphology generally exhibit better
catalytic activity, selectivity and longer lifetime due to
enhancing the accessibility of methanol into its cages and
promoting the diffusion of the products. However, work on
synthesis of SAPO-34 with nanosheet-like or plate-like
morphology is very limited. Recently, Sun et al. (2014)
prepared nanosheet-like SAPO-34 and SAPO-18 molecular
sieves with different silicon contents under hydrothermal
conditions by using tetraethylammonium hydroxide
(TEAOH) as the template, and the catalysts showed high
catalytic activity in the MTO reaction. However, the
employed hydrothermal synthesis method has the
following problems: (1) producing large amounts of waste and
harmful gas; (2) using expensive TEAOH; and (3)
difficulties in solid–liquid separation (Roth et al. 2014; Choi
et al. 2009). In order to overcome these problems, a new
alternative synthesis method, i.e., zeolites-dry gel
conversion (DGC), used in the synthesis of SAPO molecular
sieves has recently shown good potential. This method
involves treating pre-dried gel powder at elevated
temperatures and pressures to form crystalline molecular
sieves (Xu et al. 1990; Rao et al. 1998). Compared with the
traditional hydrothermal method, DGC does not produce
mother liquor (Yang et al. 2012), can avoid complicated
separation processes (Yang et al. 2010) and can give high
product yield (Matsukata et al. 1999; Cundy and Cox
2003). In addition, DGC uses a lower amount of organic
template and the organic template is easy to recycle and
reuse. Therefore, DGC is more environmentally friendly
and economical. Many kinds of aluminophosphates (AlPO)
and silicoaluminophosphates (SAPOs) have been
synthesized by dry gel conversion (Askari et al. 2014). For
example, Hirota et al. (2010) synthesized SAPO-34 with an
average crystal size of 75 nm by DGC, using TEAOH as
the structure-directing agent. However, to our best
knowledge, nanosized crystalline catalysts often suffer
from some problems, such as low product yield, low
hydrothermal stability and crystalline defects due to the
intergrowth of crystals. Hence, a novel synthesis strategy is
desirable for design and synthesis of highly
hydrothermalstable and plate-like SAPO-34 molecular sieve with a high
yield by DGC. In addition, SAPO-34 molecular sieves with
low silicon content generally have longer lifetime in the
MTO reaction due to their low acid strength (Dahl et al.
1999; Izadbakhsh et al. 2009a, b). But reports on synthesis
of SAPO-34 molecular sieves with low silicon content by
DGC are scarce.
In this work, we developed a seed suspension-assisted
method (containing nanosheet-like SAPO-34 seed) for
preparation of SAPO-34 molecular sieves with plate-like
morphology by DGC (Fig. 1) using cheap triethylamine
(TEA) as the structure-directing agent (SDA). The results
showed that this novel strategy could synthesize highly
hydrothermal-stable and plate-like SAPO-34 molecular
sieve product with a low silicon content, and the product
yield was up to 97%. Compared with the traditional cubic
SAPO-34 molecular sieve, the plate-like SAPO-34
catalysts synthesized by this method exhibited high selectivity
to light olefins (ethylene ? propylene) and long lifetime in
methanol-to-olefins (MTO) reaction. The selectivity to
light olefins increased from 81% to 87%, and the catalyst
lifetime was more than doubled.
2.1 Synthesis of SAPO-34
The SAPO-34 seed suspension was prepared by
hydrothermal crystallization from a gel with a molar
composition of 1 Al2O3: 0.9 P2O5: 0.3 SiO2: 1.6 TEAOH:
60 H2O. The gel was put into a stainless steel autoclave
lined with Teflon, and then it was heated at 150 C for 6 h.
The obtained slurry mixture was the seed suspension
(denoted as SS), and the seed (denoted as SD) of SAPO-34
molecular sieve can be obtained by separating and drying
the solid product in the crystal seed suspension.
The SAPO-34 catalysts were synthesized by DGC
(Fig. 1) with triethylamine (TEA) as the SDA. The molar
composition of the initial gel was 1.0 Al2O3: 2.5 TEA: 0.9
P2O5: 0.3 SiO2: 60 H2O. Different mass percentages of SS
were added into the initial gel. The detailed synthesis
procedures were as follows. At first, pseudoboehmite
(73 wt% Al2O3), TEA (Alfa Aesar), silica sol (40 wt%
SiO2) and distilled water were mixed and stirred at room
Teflon lined autoclave
Fig. 1 Diagram of the reaction vessel used in the DGC method
temperature. Then, SS was added to the mixture and
stirred. Finally, phosphoric acid (85 wt% H3PO4) was added
dropwise to the mixture under stirring. The synthesis
mixture was stirred and then dried at 110 C to obtain a dry
gel. The dry gel with different amounts of SS was placed in
an autoclave, and crystallization was performed at 170 C
for 48 h.
The solid product was washed only once by centrifuging
with distilled water and then dried at 100 C over night.
The as-synthesized products were calcined at 550 C for
5 h to remove the template. The synthesis conditions of
different samples are given in Table 1.
The powder X-ray diffraction (XRD) patterns of
as-synthesized samples were obtained on a Rigaku D/max-3C
X-ray diffractometer (Rigaku Co., Japan) with Cu Ka
radiation at 36 kV and 40 mA. The patterns were recorded
from 5 to 35 with a step size of 0.02 . N2 adsorption–
desorption was performed at -196 C using a
Quantachrome AUTOSORB-1C instrument (Quantachrome Co.,
USA). Before the measurement, the samples were vacuum
degassed at 300 C for at least 10 h. The specific surface
area (SBET) and the micropore volume were calculated
according to Brunauer–Emmett–Teller (BET) equation and
t-plot method, respectively. Scanning electron microscope
(SEM) images were recorded on a HITACHI S-570
scanning electron microscope. Each sample had been placed
onto a carbon membrane, and an Au sputter coating was
applied to reduce charging effects. The
temperature-programmed desorption of ammonia (NH3-TPD) was
performed on a Micromeritics ASAP 2020C instrument. The
sample (0.1 g) was pretreated at 450 C for 2 h in an Ar
flow of 20 mL min-1. After cooling to 100 C, the sample
was saturated with 10 vol% NH3/Ar, and then the sample
was purged with Ar for 1 h to eliminate physically
absorbed NH3. Desorption of NH3 was carried out from 100 to
Table 1 Synthesis conditions, yield and phase of the synthesized
a SS content in the synthesis suspension
b SiO2/Al2O3 in dry gel
c Product yield calculated by the mass ratio of calcined solid product
to SiO2, Al2O3 and P2O5 in the synthesis gel
600 C at a heating rate of 5 C min-1. 29Si MAS NMR
spectra were recorded in 7 mm ZrO2 rotors at 79.5 MHz on
a Varian Infinity-plus 400 WB spectrometer, fitted with a
BBO (broadband observe) probe. The spinning rate of the
samples at the magic angle was 4 kHz. The internal
standard for chemical shifts was
2,2-dimethyl-2-silapentane-5sulfonate sodium salt (DSS).
2.3 Catalytic performance
Catalytic activity measurements were carried out in a
quartz tubular fixed-bed reactor. First, the catalysts were
pressed, crushed and sieved to obtain particle sizes between
250 and 500 lm. Second, 1.0 g of the shaped catalyst was
placed into a quartz tube (inner diameter 10 mm) between
two quartz-wool plugs. Prior to reaction, the catalyst was
activated at 550 C in air (30 mL min-1) for 2 h. Aqueous
methanol solution (95 wt%) was fed into the reactor under
atmospheric pressure. The volume hourly space velocity
(volume of methanol aqueous solution flowing through a
unit volume of catalyst in a unit time) was 3 h-1, and the
reaction temperature was 450 C. The analysis of the
reaction products was performed using an on-line gas
chromatograph Agilent GC (6890 N), equipped with a
flame ionization detector (FID) and Plot-Q column. The
conversion and selectivity were calculated on CH2 basis,
and dimethyl ether (DME) was considered to be a reactant
for the calculation.
3 Results and discussion
3.1 Crystalline structure and morphological
features of SAPO-34 seed
Figure 2a shows the XRD patterns of the as-synthesized
SAPO-34 seed (SD) contained in the seed suspension (SS).
From Fig. 2a, it can be seen that the representative
diffraction peaks at 9.5 , 13.0 , 16.2 , 20.7 , 26.0 and
31.0 were observed in the XRD pattern of the SD,
corresponding to pure SAPO-34 with a CHA-structure (Rao
and Matsukata 1996). Furthermore, the peaks of the SD are
wider than the other as-synthesized samples, indicating that
the crystallite size of SD is smaller (Li et al. 2014). This
can be further confirmed by the SEM images. As shown in
Fig. 2b, the SD has nanosheet-like morphology with an
average particle below 200 nm, indicating that the
precursor gel at low temperature and short crystallization time
can transform to nanosheet-like crystals. This is in
agreement with the results reported in the literature (Lei et al.
Fig. 2 XRD pattern (a) and SEM image (b) of the SAPO-34 seed (SD)
3.2 Physicochemical properties of SAPO-34
Figure 3 shows the XRD patterns of the SAPO-34 samples
prepared by dry gel conversion with different amounts of
SAPO-34 SS. It can be seen that all the synthesized
samples showed the typical diffraction patterns of
CHAstructure SAPO-34 without the presence of other impurity
phases (Lee et al. 2007). However, the SS added into the
initial gel influenced the relative intensity of the different
diffraction peaks. For S-2, S-3 and S-4 samples, their peak
intensities at 2h = 20.7 were much higher than that of
S-1, while their peak intensities at 2h = 13.0 were much
lower than that of S-1. These phenomena indicated that the
SS had great influence on the growth of different crystal
faces. In addition, as can be seen from Table 1, the SS can
significantly improve product yield and promote
Fig. 3 XRD patterns of the synthesized SAPO-34 samples
conversion of more amorphous materials into SAPO-34
molecular sieve. The yield of the sample S-3 was 97%,
15% higher than that of the sample S-1.
Figure 4 shows the SEM images of the different
samples. The S-1 sample had a larger cubic crystal structure of
about 4 lm, whereas the other synthesized samples
exhibited a more plate (or sheet)-like morphology. The
reason maybe that seed solution not only provided more
crystal nucleus (crystal growth site) but also hindered the
growth rate of crystals in one dimension in the dry gel
conversion system. Furthermore, with the increase in the
amount of SS in the dry gel, the framework of SAPO-34
particles transformed to a plate-like structure with a
decrease in thickness, suggesting that the particles mainly
grew on the periphery of the nanosheet-like structure of the
SD. The thickness of particle S-2 was about 1 lm, while
the thickness of particle S-3 was about 500 nm. But when
the amount of SS was further increased to 30%, the
particles of the obtained S-4 sample became smaller and
thinner. Moreover, their plate-like morphologies became very
regular. This can be attributed to the addition of the SS to
the dry gel. The added SS provided a large number of
nucleation sites and the formed silicoaluminophosphate
species aggregated into a plate structure.
Based on the XRD and SEM results, we can propose a
scheme that qualitatively describes the formation of
platelike SAPO-34 with the assist of seed suspension under the
DGC conditions (Fig. 5). The seed suspension contained a
large number of very thin SAPO-34 molecular sieve
particles. At the same time, there were a large number of
SAPO-34 molecular sieve secondary structure units in the
seed suspension (Sun et al. 2016). In the dry gel conversion
system, the microcrystalline structure guided the
surrounding silicon aluminum phosphate species to continue
Fig. 4 SEM images of the synthesized SAPO-34 samples
to grow in situ along its edges and eventually form a plate
(or sheet-like) SAPO-34 molecular sieve. In addition,
Zhang et al. (2011) studied of the crystallization process of
the synthesis of SAPO-34 in the dry gel conversion system
and found that in the early stage of the crystallization, the
gel samples generated a semi-crystalline layered phase. So,
they speculate that the layered phase is rich in the double
six ring structure, which is very important for the synthesis
of SAPO-34 molecular sieve by the dry gel conversion
The NH3-TPD plots of the four catalyst samples are
shown in Fig. 6. Four samples gave peaks at approximately
210 and 380 C, which correspond to the weak and strong
acid sites, respectively. The desorption peak at low
temperature was attributed to the hydroxyl groups (–OH)
bounded to the defect sites, i.e., POH, SiOH and AlOH
(Campelo et al. 2000; Dumitriu et al. 1997). As shown in
Fig. 6, the four samples had similar acid strength and weak
acid amounts, whereas their strong acid amounts slightly
decreased with the increase in the added SS.
The nitrogen adsorption–desorption isotherms of four
catalyst samples are presented in Fig. 7 with corresponding
textural data listed in Table 2. All of the samples had
similar micropore volumes in the range of 0.23–0.27 cm3
g-1, and the samples synthesized using seed suspension
exhibited higher BET surface areas.
In the MTO reaction, the catalyst is always used in a
harsh high temperature hydrothermal environment.
Therefore, it is very necessary to study the hydrothermal stability
of different types of catalysts. In this study, four catalyst
samples with different morphologies were treated by high
temperature hydrothermal aging, and the specific surface
area (SBET) was used to reflect their hydrothermal stability.
As shown in Fig. 8, the specific surface area (SBET) of the
sample S-4 with nanosheet-like structure decreased from
608 to 360 m2/g after 80 h of hydrothermal aging. In
Crystalline layered phase
Fig. 5 Illustration of the formation of plate-like SAPO-34 under DGC conditions
Fig. 6 NH3-TPD profiles of the synthesized SAPO-34 samples
contrast, the specific surface areas of cubic or plate-like
SAPO-34 molecular sieve samples decreased slightly after
the same treatment. These results demonstrated that cubic
(S-1) or plate-like SAPO-34 samples (S-2 and S-3) had
better hydrothermal stability than the nanosheet-like S-4.
3.3 Catalytic performance
As shown in Fig. 9, SAPO-34 samples synthesized at
different conditions showed different methanol conversions
and lifetimes. It can be seen that methanol was completely
Fig. 7 Nitrogen adsorption–desorption isotherms of the synthesized
converted over all the catalysts with ethylene and
propylene as the main products. Herein, catalyst lifetime is
defined as the time when the methanol conversion reaches
98%, and the highest selectivity to light olefins (ethylene
and propylene) in the catalyst lifetime is used to represent
Table 3 MTO reaction results
over SAPO-34 samples
Selectivity to product, %
Surface area, m2/g
Micro pore volume, cm3/g
Particle size, lm
the catalytic activity according to the literature (Zhu et al.
2010). Figure 9 and Table 3 show that under the same
reaction conditions, the lifetime of sample S-1 was about
80 min with 81% selectivity to ethylene and propylene,
whereas the lifetime of S-3 sample with the thinner layers
and the largest surface area could reach 180 min with 87%
selectivity to ethylene and propylene. The significant
improvement of catalyst lifetime and activity attributed to
the morphology of the SAPO-34 samples. In MTO
reaction, the successive polymerization, which would result in
coke formation, may be partly avoided over plate-like
SAPO-34 catalysts due to their short diffusion length. The
fast deactivation of the S-1 catalyst (conventional large
cubic morphology) can be attributed to the coke formation
that occurs near the external surface of the catalyst
Fig. 8 Duration of hydrothermal aging at 800 C and 100% steam
80 100 120 140 160 180 200 220
Time on stream, min
80 100 120 140 160 180 200 220
Time on stream, min
Fig. 9 Catalytic performance of SAPO-34 samples in MTO reaction at 450 C and 3.0 h-1
Fig. 10 XRD patterns of the synthesized SAPO-34 samples
Table 4 Synthesis conditions, yield and phase of the synthesized
particles, gradually blocking the diffusion path of
oxygenates to the inner core of catalysts. However, for S-4
catalyst with the thinnest sheet, its deactivation can
partially attribute to its poor hydrothermal stability, which
could cause its crystal structure destruction under the MTO
Fig. 11 SEM images of the synthesized SAPO-34 samples
Fig. 12 29Si MAS NMR spectra of prepared SAPO-34 samples
Relative pressure p/p0
Fig. 13 Nitrogen adsorption–desorption isotherms of the synthesized
Surface area, m2/g
Micro pore volume, cm3/g
Particle size, lm
3.4 Physicochemical properties of SAPO-34 with low silicon content
Apart from the morphology of SAPO-34 catalyst, the SiO2/
Al2O3 ratio of it is also an important factor for the catalytic
lifetime (Sastre et al. 1997; Izadbakhsh et al. 2009a, b; Tan
et al. 2002). In order to further improve the catalytic
performance of SAPO-34 catalyst in MTO reaction, a series of
plate-like SAPO-34 molecular sieve with low SiO2/Al2O3
ratio were synthesized by DGC (Table 4).
Samples S-5, S-6 and S-7 were synthesized by DGC
with the same compositions as S-3 except for silicon
content. The XRD patterns (Fig. 10) of S-5 and S-6 were in
agreement with that simulated from the CHA framework
type (pure SAPO-34), whereas a small amount of the
framework type of AEI was observed in the XRD patterns
of S-7 and S-8 (Simmen et al. 1991), indicating that
addition of seed suspension (SS) is beneficial to the
synthesis of SAPO-34 with low Si contents by DGC.
The SEM images (Fig. 11) showed that S-5, S-6 and S-7
samples exhibited uniform plate-like morphology with the
thickness of each plate in the range of 400-500 nm, whereas
S-8 synthesized in the absence of the SS showed conventional
cube-like morphology with a particle size of about 4 lm.
As shown in Fig. 12, all of the samples showed two
major resonances at around -91 and -95 ppm, which
were assigned to Si (4Al) and Si (3Al), respectively. The
peaks at around -100, -105 and -109 ppm correspond to
the signal of Si (2Al), Si (1Al) and Si (0Al), respectively
(Shen et al. 2012). Based on the integrated areas of the
resonance at -95 ppm, the concentration of Si (4Al)
species in the three samples had the following order: S-6 [
S5 [ S-3. It seems that under the DGC conditions, the Si
species existing in the samples were incorporated into the
frameworks via both SM2 (one Si substitution for one P,
which forms Si (4Al) species) and SM3 [double Si
substitution for pairs of Al and P, which forms Si (nAl)
(n = 0–3) species] substitution mechanisms (Tian et al.
2013). Decreasing the Si content in the dry gel can
efficiently promote the formation of the Si (4Al) unit. The
Time on stream, min
Fig. 14 Performance of SAPO-34 samples in MTO reaction at
450 C and 3.0 h-1 (1) Methanol conversion (black filled squares),
(2) selectivity to C2H4 and C3H6 (blue filled triangles), (3) selectivity
to C2H4 (green filled triangles), (4) selectivity to C3H6 (red filled
textual properties of the SAPO-34 samples determined with
N2 adsorption–desorption measurement are shown in
Fig. 13 and summarized in Table 5. All the isotherms
displayed the characteristic type I isotherms, confirming
the microporosity of the samples. The BET surface area of
S-5 and S-6 was 610 and 636 m2/g, respectively.
3.5 Catalytic performance of plate-like SAPO-34
with low silicon contents
As shown in Fig. 14, all the catalysts exhibited a long
catalyst lifetime and high selectivity to ethylene and
propylene because the plate-like crystals can greatly
enhance the mass transfer of reactant and generated
products during MTO process. Significantly, the S-6 sample
synthesized with SiO2/Al2O3 of 0.1 and the highest Si
(4Al) content (reducing the acidity of SAPO-34 catalysts)
can retain more coke species than the others without fast
deactivation (Izadbakhsh et al. 2009a, b). At the same time,
for the S-6 sample, the selectivity to ethylene and
propylene increased slightly faster than others, indicating that its
acidity is more suitable for MTO reaction than others.
This work provides a new technical route of green and
efficient synthetic strategies to create SAPO-34 molecular sieve
with plate-like morphology. SAPO-34 was synthesized by
the dry gel conversion method using cheap triethylamine
(TEA) as structure-directing agent with the assistance of
seed suspension containing nanosheet-like SAPO-34 seed.
In addition, the yield of the product in the synthesis system
containing seed suspension reached 97%, 15% higher than
that obtained in the corresponding synthesis system without
the seed suspension. Compared with the traditional cubic
SAPO-34 molecular sieve, the selectivity for olefins
(ethylene ? propylene) for the plate-like SAPO-34 reached
87%, and the catalyst lifetime was more than doubled.
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A´ lvaro-Mun ˜oz T, Ma´rquez-A´ lvarez C, Sastre E. Use of different templates on SAPO-34 synthesis: effect on the acidity and catalytic activity in the MTO reaction . Catal Today . 2012 ; 179 ( 1 ): 27 - 34 . doi:10.1016/j.cattod. 2011 .07.038.
Askari S , Sedighi Z , Halladj R. Rapid synthesis of SAPO-34 nanocatalyst by dry gel conversion method templated with morphline: investigating the effects of experimental parameters . Microporous Mesoporous Mater . 2014 ; 197 ( 10 ): 229 - 36 . doi:10. 1016/j.micromeso. 2014 .06.028.
Campelo JM , Lafont F , Marinas JM , et al. Studies of catalyst deactivation in methanol conversion with high, medium and small pore silicoaluminophosphates . Appl Catal A Gen . 2000 ; 192 ( 1 ): 85 - 96 . doi:10.1016/ S0926-860X(99)00329-4.
Chen JQ , Bozzano A , Glover B , et al. Recent advancements in ethylene and propylene production using the UOP/Hydro MTO process . Catal Today . 2005 ; 106 ( 1-4 ): 103 - 7 . doi:10.1016/j.cattod. 2005 .07.178.
Chen D , Moljord K , Fuglerud T , et al. The effect of crystal size of SAPO-34 on the selectivity and deactivation of the MTO reaction . Microporous Mesoporous Mater . 1999 ; 29 ( 1-2 ): 191 - 203 . doi:10.1016/ S1387 -1811( 98 ) 00331 - X .
Choi M , Na K , Kim J , et al. ChemInform abstract: stable single-unitcell nanosheets of zeolite MFI as active and long-lived catalysts . Nature . 2009 ; 461 ( 7261 ): 246 - 9 . doi:10.1038/nature08288.
Cundy CS , Cox PA . The hydrothermal synthesis of zeolites: history and development from the earliest days to the present time . Chem Rev . 2003 ; 103 ( 3 ): 663 - 702 . doi:10.1002/chin.200319217.
Dahl IM , Mostad H , Akporiaye D , et al. Structural and chemical influences on the MTO reaction: a comparison of chabazite and SAPO-34 as MTO catalysts . Microporous Mesoporous Mater . 1999 ; 29 ( 1 ): 185 - 90 . doi:10.1016/ S1387-1811(98)00330-8.
Dumitriu E , Azzouz A , Hulea V , et al. Synthesis , characterization and catalytic activity of SAPO-34 obtained with piperidine as templating agent . Microporous Mater . 1997 ; 10 ( 1-3 ): 1 - 12 . doi:10.1016/S0927-6513(96)00107- 1 .
Hirota Y , Murata K , Tanaka S , et al. Dry gel conversion synthesis of SAPO-34 nanocrystals. Mater Chem Phys . 2010 ; 123 ( 2-3 ): 507 - 9 . doi:10.1016/j.matchemphys. 2010 .05.005.
Izadbakhsh A , Farhadi F , Khorasheh F , et al. Effect of SAPO-34 's composition on its physico-chemical properties and deactivation in MTO process . Appl Catal A Gen . 2009a; 364 ( 1 ): 48 - 56 . doi:10.1016/j.apcata. 2009 .05.022.
Izadbakhsh A , Farhadi F , Khorasheh F , et al. Key parameters in hydrothermal synthesis and characterization of low silicon content SAPO-34 molecular sieve . Microporous Mesoporous Mater . 2009b; 126 ( 1-2 ): 1 - 7 . doi:10.1016/j.micromeso. 2008 .12.009.
Lee YJ , Baek SC , Jun KW . Methanol conversion on SAPO-34 catalysts prepared by mixed template method . Appl Catal A Gen . 2007 ; 329 ( 10 ): 130 - 6 . doi:10.1016/j.apcata. 2007 .06.034.
Lei W , Liu Z , Lin X , et al. Effect of SAPO-34 molecular sieve morphology on methanol to olefins performance . Chin J Catal . 2013 ; 34 ( 7 ): 1348 - 56 . doi:10.1016/ S1872-2067(12)60575-0.
Li J , Li Z , Han D , et al. Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins . Powder Technol . 2014 ; 262 : 177 - 82 . doi:10.1016/j.powtec. 2014 .04. 0820032 - 5910 .
Marchi AJ , Froment GF . Catalytic conversion of methanol to light alkenes on SAPO molecular sieves . Appl Catal . 1991 ; 71 ( 1 ): 139 - 52 . doi:10.1016/j.apcata. 2007 .06.034.
Matsukata M , Ogura M , Osaki T , et al. Conversion of dry gel to microporous crystals in gas phase . Top Catal . 1999 ; 9 ( 1 ): 77 - 92 . doi:10.1023/A:1019106421183.
Pastore HO , Coluccia S , Marchese L. Porous aluminophosphates: from molecular sieves to designed acids catalysts . Cheminformatics . 2005 ; 35 ( 44 ): 351 - 95 . doi:10.1002/chin.200544244.
Qi G , Xie Z , Yang W , et al. Behaviors of coke deposition on SAPO-34 catalyst during methanol conversion to light olefins . Fuel Process Technol . 2007 ; 88 ( 5 ): 437 - 41 . doi:10.1016/j.fuproc. 2006 .11.008.
Qi G , Xie Z , Zhong S , et al. Advances in process research on coal or natural gas to light olefins via methanol . Mod Chem Ind . 2005 ;. doi:10.16606/j.cnki.issn0253- 4320 . 2005 .02. 003 (in Chinese).
Rao PRHP , Leon CALY , Ueyama K , et al. Synthesis of BEA by dry gel conversion and its characterization . Microporous Mesoporous Mater . 1998 ; 21 ( 4-6 ): 305 - 13 . doi:10.1016/ S1387 -1811( 98 ) 00033 - X .
Rao PRHP , Matsukata M. Dry-gel conversion technique for synthesis of zeolite BEA . Chem Commun . 1996 ; 12 ( 12 ): 1441 - 2 . doi:10. 1039/CC9960001441.
Roth WJ , Nachtigall P , Morris RE , et al. Two-dimensional zeolites: current status and perspectives . Chem Rev . 2014 ; 114 ( 9 ): 4807 - 37 . doi:10.1021/cr400600f.
Rothaemel M , Holtmann HD . Methanol to propylene MTP-Lurgi's way . Oil Gas . 2002 ; 28 ( 1 ): 27 - 30 . doi:10.1016/S0167-2991(07)80 142 -X.
Sastre G , Lewis DW , Catlow CRA . Mechanisms of silicon incorporation in aluminophosphate molecular sieves . J Mol Catal A Chem . 1997 ; 119 ( 1-3 ): 349 - 56 . doi:10.1016/S1381-1169(96)00498- 0 .
Shen W , Li X , Wei Y , et al. A study of the acidity of SAPO-34 by solid-state NMR spectroscopy . Microporous Mesoporous Mater . 2012 ; 158 ( 8 ): 19 - 25 . doi:10.1016/j.micromeso. 2012 .03.013.
Simmen A , McCusker LB , Baerlocher C , et al. The structure determination and rietveld refinement of the aluminophosphate AIPO4-18 . Zeolites. 1991 ; 11 ( 7 ): 654 - 61 . doi:10.1016/S0144- 2449(05)80167- 8 .
Sun Q , Ma Y , Wang N , et al. High performance nanosheet-like silicoaluminophosphate molecular sieves: synthesis, 3D EDT structural analysis and MTO catalytic studies . J Mater Chem A . 2014 ; 2 ( 42 ): 17828 - 39 . doi:10.1039/C4TA03419H.
Sun Q , Wang N , Bai R , et al. Seeding induced nano-sized hierarchical SAPO-34 zeolites: cost-effective synthesis and superior MTO performance . J Mater Chem A . 2016 ; 4 : 14978 - 82 . doi:10.1039/ c6ta06613e.
Tan J , Liu Z , Bao X , et al. Crystallization and Si incorporation mechanisms of SAPO-34. Microporous Mesoporous Mater . 2002 ; 53 ( 1-3 ): 97 - 108 . doi:10.1016/ S1387-1811(02)00329-3.
Tian P , Li B , Xu S , et al. Investigation of the crystallization process of SAPO-35 and Si distribution in the crystals . J Phys Chem C . 2013 ; 117 ( 8 ): 24 - 9 . doi:10.1021/jp311334q.
Tian P , Wei Y , Ye M , et al. Methanol to olefins (MTO): from fundamentals to commercialization . ACS Catal . 2015 ; 5 ( 3 ): 1922 - 38 . doi:10.1021/acscatal.5b00007.
Wei Y , Li J , Yuan C , et al. Generation of diamondoid hydrocarbons as confined compounds in SAPO-34 catalyst in the conversion of methanol . Chem Commun . 2012 ; 48 ( 25 ): 3082 - 4 . doi:10.1039/ c2cc17676a.
Wilson S , Barger P. The characteristics of SAPO-34 which influence the conversion of methanol to light olefins . Microporous Mesoporous Mater . 1999 ; 29 ( 1-2 ): 117 - 26 . doi:10.1016/ S1387- 1811(98)00325-4.
Xu W , Dong J , Li J , et al. A novel method for the preparation of zeolite ZSM-5. J Chem Soc Chem Commun . 1990 ; 10 ( 10 ): 755 - 6 . doi:10.1039/C39900000755.
Xu L , Du A , Wei Y , et al. Synthesis of SAPO-34 with only Si (4Al) species: effect of Si contents on Si incorporation mechanism and Si coordination environment of SAPO-34. Microporous Mesoporous Mater . 2008 ; 115 ( 3 ): 332 - 7 . doi:10.1016/j.micromeso. 2008 .02.001.
Yang H , Liu Z , Gao H , et al. Synthesis and catalytic performances of hierarchical SAPO-34 monolith. J Mater Chem . 2010 ; 20 ( 16 ): 3227 - 31 . doi:10.1039/B924736J.
Yang N , Yue M , Wang Y. Synthesis of zeolites by dry gel conversion . Progress Chem . 2012 ; 24 ( 2 ): 253 - 61 . doi:10.16085/j.issn. 1000 - 6613 . 2012 .3. 0253 - 09 (in Chinese).
Ye L , Cao F , Ying W , et al. Effect of different TEAOH/DEA combinations on SAPO-34's synthesis and catalytic performance. J Porous Mater . 2011 ; 18 ( 2 ): 225 - 32 . doi:10.1007/s10934- 010 - 9374 -4.
Zhang L , Bates J , Chen D , et al. Investigations of formation of molecular sieve SAPO-34. J Phys Chem C . 2011 ; 115 ( 45 ): 22309 - 19 . doi:10.1021/jp208560t.
Zhu J , Cui Y , Zeeshan N. In situ synthesis of SAPO-34 zeolites in kaolin microspheres for a fluidized methanol or dimethyl ether to olefins process . Chin J Chem Eng . 2010 ; 18 ( 6 ): 979 - 87 . doi:10. 1016/j.cjche. 2010 . 18 .6. 979 - 987 .