SAPO-34 synthesized with n-butylamine as a template and its catalytic application in the methanol amination reaction

Article abstract of DOI:10.1016/S1872-2067(17)62775-X

SAPO-34 was synthesized with n-butylamine (BA) as a template for the first time. Crystallization temperature and initial Si amount were important factors leading to successful syntheses. Lamellar AlPO-kanemite tends to form as the major phase or as an impurity of SAPO-34 at lower crystallization temperatures, though a higher initial Si amount may offer a positive effect on the crystallization of SAPO-34 that mitigates the low temperature. Higher temperature (240 °C) can effectively suppress the generation of lamellar materials and allow the synthesis of pure SAPO-34 with a wider range of Si incorporation. The crystallization processes at 200 and 240 °C were investigated and compared. We used the aminothermal method to synthesize SAPO-34-BA at 240 °C and also found n-propylamine is a suitable template for the synthesis of SAPO-34. The SAPO-34-BA products were characterized by many techniques. SAPO-34-BA has good thermal stability, crystallinity and porosity. BA remained intact in the crystals with ～1.8 BA molecule per chabazite cage. The catalytic performance of SAPO-34 was tested in the methanol amination reaction, which showed high methanol conversion and selectivity for methylamine plus dimethylamine under the conditions investigated, suggesting that this material is a good candidate for the synthesis of methylamines.

Full text of DOI:10.1016/S1872-2067(17)62775-X

Chinese Journal of Catalysis 38 (2017) 574–582
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
SAPO‐34 synthesized with n‐butylamine as a template and its
catalytic application in the methanol amination reaction
Yuyan Qiaoa,b, Pengfei Wua,b, Xiao Xianga,b, Miao Yanga, Quanyi Wanga, Peng Tiana,*,
Zhongmin Liua,#
a National Engineering Laboratory for Methanol to Olefins, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning,
China
b University of Chinese Academy of Sciences, Beijing 100039, China
A R T I C L E I N F O
A B S T R A C T
Article history:
SAPO‐34 was synthesized with n‐butylamine (BA) as a template for the first time. Crystallization
temperature and initial Si amount were important factors leading to successful syntheses. Lamellar
AlPO‐kanemite tends to form as the major phase or as an impurity of SAPO‐34 at lower crystalliza‐
tion temperatures, though a higher initial Si amount may offer a positive effect on the crystallization
of SAPO‐34 that mitigates the low temperature. Higher temperature (240 °C) can effectively sup‐
press the generation of lamellar materials and allow the synthesis of pure SAPO‐34 with a wider
range of Si incorporation. The crystallization processes at 200 and 240 °C were investigated and
compared. We used the aminothermal method to synthesize SAPO‐34‐BA at 240 °C and also found
n‐propylamine is a suitable template for the synthesis of SAPO‐34. The SAPO‐34‐BA products were
characterized by many techniques. SAPO‐34‐BA has good thermal stability, crystallinity and porosi‐
ty. BA remained intact in the crystals with ~1.8 BA molecule per chabazite cage. The catalytic per‐
formance of SAPO‐34 was tested in the methanol amination reaction, which showed high methanol
conversion and selectivity for methylamine plus dimethylamine under the conditions investigated,
suggesting that this material is a good candidate for the synthesis of methylamines.
Received 28 November 2016
Accepted 25 December 2016
Published 5 March 2017
Keywords:
SAPO‐34 molecular sieve
n‐Butylamine
Primary amine
Synthesis
High temperature
Methanol amination
© 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1. Introduction
lar sieves remains of continuous interest. Many methods have
been developed to synthesize SAPO‐34, such as hydrothermal,
Silicoaluminophosphate (SAPO) molecular sieves, first re‐
ported by the scientists at Union Carbide Corporation in 1984,
are a class of important inorganic microporous materials [1,2].
Among them, SAPO‐34 is the most important member because
of its successful application in the commercial metha‐
nol‐to‐olefins (MTO) process in 2010 [3–6]. Investigation of the
synthesis and physicochemical properties of SAPO‐34 molecu‐
solvothermal, dry‐gel conversion, and solvent‐free syntheses
[7–11]. The presence of an organic template is necessary for all
the methods to prepare SAPO molecular sieves, and the tem‐
plate has a crucial impact on the physicochemical properties of
the
products
because
of
its
structure‐directing,
charge‐compensating and space‐filling roles in the crystalliza‐
tion process [12–15]. Many organic amines have been used as
* Corresponding author. Tel: +86‐411‐84379218; Fax: +86‐411‐84691570; E‐mail: tianpeng@dicp.ac.cn
# Corresponding author. Tel: +86‐411‐84379998; Fax: +86‐411‐84691570; E‐mail: liuzm@dicp.ac.cn
This work was supported by the National Natural Science Foundation of China(21676262, 21476228, 21506207) and the Key Research Program of
Frontier Sciences of CAS (QYZDB‐SSW‐JSC040).
DOI: 10.1016/S1872‐2067(17)62775‐X | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 38, No. 3, March 2017

Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
575
templating agents to synthesize SAPO‐34 [16–20]. The ele‐
mental composition, local microscopic structure and morphol‐
ogy of SAPO‐34 may change with the use of different templates.
Accordingly, the catalytic performance and adsorption proper‐
ties of the materials obtained may be different [15–20].
erating at 30 mA and 40 kV. Sample morphology was deter‐
mined by SEM on a Hitachi TM3000 microscope. The composi‐
tions of samples were determined with a Philips Magix‐601
XRF spectrometer. Textural properties of the calcined samples
were determined by N2 adsorption‐desorption at −196 °C on a
Micromeritics ASAP 2020 system. The total surface area was
calculated based on the Brunauer‐Emmett‐Teller (BET) equa‐
tion. The micropore volume and surface area were evaluated
using the t‐plot method. Mesopore volume and surface area
were evaluated from the adsorption isotherm by the Bar‐
rett‐Joyner‐Halenda (BJH) method. All the solid state NMR ex‐
periments were performed on a Bruker Avance III 600 spec‐
trometer equipped with a 14.1 T wide‐bore magnet. The reso‐
nance frequencies were set at 150.9, 156.4, 242.9, and 119.2
MHz for 13C, 27Al, 31P, and 29Si, respectively. Chemical shifts
were referenced to 1.0 mol/L Al(NO3)3 for 27Al, 85% H3PO4 for
31P, 2,2‐dimethyl‐2‐silapentane‐5‐sulfonate sodium salt for 29Si,
and adamantane for 13C. The NH3‐TPD was carried out with
Micromeritics Autochem 2920 equipment. The calcined sam‐
ples (200 mg, 40–60 mesh) were activated at 650 °C for 60 min
(10 °C/min) under He flow, then cooled and saturated with
ammonia at 150 °C for 30 min. The samples were purged with
He (30 mL/min) for 30 min and measurements of the desorbed
NH3 were performed from 100 to 700 °C (10 °C/min) under a
He flow (30 mL/min). The TGA were recorded on a Q500 SDT
thermogravimetric analyzer. In a typical measurement, a small
amount (10–20 mg) of sample was heated in an Al2O3 crucible
from ambient temperature to 800 °C at a heating rate of 10
°C/min under a stream of air at a constant flow rate of 100
mL/min.
The primary amine n‐butylamine (BA) has been used to
synthesize
lamellar
AlPO‐kanemite
[21].
Lamellar
AlPO‐kanemite can be transformed to SAPO‐34 by adding a
silica source and hexamethyleneimine (HMI) into the synthetic
system under hydrothermal conditions [22]. SAPO‐34 is
co‐templated by HMI and BA and pure SAPO‐34 is synthesized
in over a relatively narrow range of the SiO2/Al2O3 molar ratio
in the initial gel [22]. To the best of our knowledge, there is no
report on the synthesis of SAPO‐34 with a single BA template.
In this paper, we report the synthesis, characterization, and
catalytic application of SAPO‐34 with BA as a template for the
first time. The importance of initial silica amount and crystalli‐
zation temperature on the SAPO‐34 synthesized was investi‐
gated. The hydrothermal crystallization process at two differ‐
ent crystallization temperatures was examined in order to bet‐
ter understand/control the synthesis system with a BA tem‐
plate. The physicochemical properties of the BA‐templated
SAPO‐34 were characterized with powder X‐ray diffraction
(XRD), X‐ray fluorescence (XRF), scanning electron microscopy
(SEM), nuclear magnetic resonance (NMR), thermogravime‐
try‐differential thermal analysis (TG‐DTA), ammonia tempera‐
ture‐programmed desorption (NH3‐TPD) and N2 physisorption.
The catalytic performance of the samples was tested in the
methanol amination reaction.
2. Experimental
2.3. Catalyst evaluation
2.1. Synthesis
The methanol amination reaction was carried out with a
fixed‐bed quartz tubular reactor at atmospheric pressure. Typ‐
ically, 300 mg of calcined SAPO‐34 sample (40–60 mesh) was
loaded in the reactor and activated under a He flow at 500 °C
for 1 h, then the reactor was cooled to the reaction temperature
(350 °C). The reaction was carried out by feeding the reactor
with a 2:1 mixture (on mole basis) of ammonia and methanol
diluted in helium. Methanol was fed into the reactor by passing
the carrier gas (He, 25.3 mL/min) through a methanol satura‐
tor maintained at 10 °C. The weight hourly space velocity
(WHSV) of methanol was 0.813 h−1. The products were ana‐
lyzed by an online gas chromatograph (Agilent GC 7890N)
equipped with a flame ionization detector and CP‐Volamine
column.
Organic amines used as templates in the syntheses were
n‐butylamine (BA, 99.5 wt%), n‐propylamine (PA, 99.5 wt%),
and cyclohexylamine (CyHA, 99.5 wt%). Pseudoboehmite (67.5
wt%), phosphoric acid (85 wt%), silica sol (31 wt%), tetraethyl
orthosilicate (TEOS), and fume silica were used as inorganic
precursors.
A typical hydrothermal synthesis procedure was as follows:
the organic amine, Si source, pseudoboehmite, phosphoric acid
and distilled water were added sequentially into a stainless
steel autoclave. The typical molar composition of the gel was
2.0BA:0.8SiO2:1.0Al2O3:0.8P2O5:50H2O. The mixture was stirred
until homogeneous, the autoclave sealed quickly and placed in
a rotation oven. The gel was heated to the desired temperature
under rotation and held for a certain time. After crystallization,
the as‐synthesized sample was obtained by centrifugal separa‐
tion, washing and drying in air at 120 °C. The catalyst was pre‐
pared by heating the sample in air at 600 °C for 2 h in a muf‐
fle furnace to remove the organic template.
3. Results and discussion
3.1. Effect of synthesis conditions
3.1.1. Effect of silica amount and silica source
2.2. Characterization
The effect of the initial silica amount on the SAPO‐34 syn‐
thesis using silica sol as the Si source was investigated by fixing
the other synthetic conditions. Table 1 shows the detailed gel
compositions, crystallization conditions and product composi‐
The XRD data was recorded on a PANalytical X’Pert PRO
X‐ray diffractometer with Cu Kα radiation (λ = 1.54059 Å) op‐

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Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
Table 1
Influence of silica amount and silica source on SAPO‐34 synthesis.
Sample
Silica source
—
n*
Product
kanemite
SAPO‐34 + kanemite
SAPO‐34 + kanemite
SAPO‐34
Yield (%)
95
Product composition
—
0
1
2
3
4
5
6
7
8
9
10
0.0
0.2
0.4
0.6
0.8
1.2
1.4
1.6
0.8
0.8
1.4
silica sol
silica sol
silica sol
silica sol
silica sol
silica sol
silica sol
TEOS
91
Si0.039Al0.525P0.436
Si0.098Al0.508P0.394
Si0.161Al0.492P0.347
Si0.207Al0.472P0.321
Si0.244Al0.453P0.303
Si0.266Al0.441P0.293
Si0..300Al0.420P0.280
Si0.198Al0.477P0.325
Si0.200Al0.445P0.335
Si0.293Al0.430P0.277
89
82
83
83
84
86
SAPO‐34
SAPO‐34
SAPO‐34
SAPO‐34 + amorphous SiO2
SAPO‐34
82
83
83
fume silica
fume silica
SAPO‐34
SAPO‐34
* SiO2/Al2O3 molar ratio in the initial gel. All the syntheses were carried out at 200 °C for 24 h under rotation. Initial molar compositions were as fol‐
lows: BA:Al2O3:P2O5:SiO2:H2O = 2.0:1.0:0.8:n:50.
tions. Figs. 1 and 2 display the XRD patterns and SEM images of
the as‐synthesized samples. Lamellar material AlPO‐kanemite
was obtained as the only product when a silica source was
omitted in the initial gel. After inclusion of a small amount of
silica sol, SAPO‐34 starts to appear and gradually becomes the
dominant product with increasing amounts of silica at the
expense of AlPO‐kanemite, suggesting the positive effect of
silica on inhibiting the formation of lamellar material and facil‐
itating the generation of SAPO‐34. Pure SAPO‐34 was obtained
once the silica amount reached 0.6 equivalents relative to the
pseudoboehmite or higher. However, greater Si amounts in the
initial gel (n = 1.6) resulted in the presence of an amorphous
phase because of the unreacted silica residues, implying the
capacity limitation of silica incorporation into the framework of
BA‐templated SAPO‐34. The solid yields and elemental compo‐
sitions of the samples are shown in Table 1. All samples tem‐
plated by BA have high solid yields of > 80%. SAPO‐34 products
synthesized under hydrothermal conditions have characteris‐
tically high silica content, with Si molar concentration varying
from 0.161 to 0.266. The SEM image of Sample 4 shows rhom‐
bohedra crystals with a size range of about 5–10 μm (Fig. 1).
The effect of the Si source on the syntheses was also inves‐
tigated. Both fumed silica and TEOS gave similar synthetic re‐
sults as silica sol. SAPO‐34 synthesized with fumed silica has
relatively high Si content (Table 1) and small crystal sizes (Fig.
1) as compared with SAPO‐34 prepared with the other two
silica sources.
0
4
8
10
15
22
21
20
15
12
11
10
8
12
21
6
4
2
23
0
10
20
30
2/(o )
40
50
Fig. 1. XRD patterns of the as‐synthesized samples.
Fig. 2. SEM images of the as‐synthesized samples.

Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
577
Table 2
Influence of crystallization temperature on SAPO‐34 synthesis.
Sample
11
n *
T (°C)
240
240
240
240
240
240
240
160
160
160
t (h)
24
3
Product
dense phase
SAPO‐34
Yield (%)
50
Product composition
—
0.0
0.2
0.4
0.6
0.8
1.2
1.4
0.4
0.8
1.2
12
52
Si0.089Al0.537P0.374
Si0.106Al0.501P0.393
Si0.153Al0.480P0.367
Si0.189Al0.463P0.348
Si0.245Al0.432P0.323
Si0.308Al0.400P0.292
—
13
8
SAPO‐34
74
14
24
24
24
24
48
48
48
SAPO‐34
83
15
SAPO‐34
84
16
SAPO‐34
84
17
SAPO‐34 + amorphous SiO2
kanemite
86
18
93
19
kanemite
94
—
20
kanemite
94
—
* SiO2/Al2O3 molar ratio in the initial gel. Initial molar compositions were as follows: BA:Al2O3:P2O5:SiO2:H2O = 2.0:1.0:0.8:n:50. Silica sol was used as
the Si source.
3.1.2. Effect of crystallization temperature
3.2. Crystallization process of BA‐templated SAPO‐34
The effect of crystallization temperature on the syntheses
was investigated (Table 2). Only AlPO‐kanemite was obtained
at 160 °C, even with a high silica feed. Raising the crystalliza‐
tion temperature to 240 °C in the absence of silica formed a
dense phase instead of AlPO‐kanemite. Pure SAPO‐34 was
readily produced when the SiO2/Al2O3 molar ratio in the initial
gel was increased to 0.2 or higher. This is very different from
the syntheses at relatively low temperatures, as no molecular
sieve products formed at 160 °C and higher Si content in the
initial gel was required to achieve pure SAPO‐34 at 200 °C. The
results are reasonable considering that lamellar materials gen‐
erally have worse thermal stability than SAPO molecular sieves
and higher crystallization temperatures impose negative effects
on lamellar material formation. Crystallization temperature
may be used to tune/optimize the crystal phase, especially for
systems where lamellar material is an impurity.
Table 2 lists the elemental compositions of the products.
The Si content in SAPO‐34 synthesized at 240 °C varied from
0.089 to 0.245, which is a wider range than that of SAPO‐34
synthesized at 200 °C. The SEM images of selected samples are
given in Fig. 2. The samples present rhombohedra morphology
with crystal sizes of 4–6 μm, which are a little smaller than
those obtained at 200 °C.
The crystallization processes of BA‐templated SAPO‐34 at
200 and 240 °C were examined based on the synthetic systems
of Samples 4 and 15, respectively. Table 3 shows the detailed
information about the product phases, elemental compositions,
and solid yields. Fig. 3 displays the SEM images of the
as‐synthesized samples.
Just lamellar AlPO‐kanemite was generated first for the
synthesis at200 °C at the beginning of crystallization (1 h). The
high solid yield of 60% suggests rapid and facile formation of
lamellar material. The diffraction peaks arising from
AlPO‐kanemite become stronger after crystallization for 3 h.
SAPO‐34 begins to appear and the solid yield increased to 85%.
Subsequently, SAPO‐34 became the major phase at the expense
of AlPO‐kanemite. Only minor kanemite was detected after 5 h
crystallization time and the relative crystallinity of the SAPO‐34
reached 78%. Extending the crystallization time further gave
pure SAPO‐34 and the relative crystallinity increased until the
end of the crystallization. The silicon content in the products
rises continuously throughout the crystallization process (Ta‐
ble 3), which is consistent with our previous studies [7] and
suggests the relatively slow reaction rate with the Si source as
compared with Al and P sources.
According to the above results, the crystallization process at
Table 3
Crystallization processes of Samples 4 and 15.
Sample
4‐1h
4‐3h
4‐5h
4‐12h
4
15‐0h
15‐1h
15‐3h
15‐8h
15
t (h)
1
3
Product
kanemite
Kanemite + SAPO‐34
SAPO‐34 + kanemite
SAPO‐34
R (%) *
—
—
Yield (%)
60
Product composition
—
85
Si0.131Al0.511P0.358
Si0.174Al0.496P0.330
Si0.192Al0.483P0.325
Si0.207Al0.472P0.321
—
Si0.142Al0.489P0.369
Si0.172Al0.470P0.358
Si0.178Al0.467P0.355
Si0.189Al0.463P0.348
5
78
87
100
—
83
100
100
100
81
82
83
26
81
83
12
24
0
1
3
SAPO‐34
amorphous
SAPO‐34
SAPO‐34
8
24
SAPO‐34
SAPO‐34
83
84
* Relative crystallinities calculated based on the intensity of the two strongest peaks (2θ = 9.5° and 20.5°) in the XRD patterns of the samples.

578
Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
Table 4
4‐1h
4‐3h
4‐5h
4‐12h
15‐0h
Aminothermal synthesis of CHA‐type SAPO molecular sieves using BA,
CHyA and PA systems.
Product
composition
T
t
Yield
(%)
Sample
Template
Product
(°C) (h)
21
22
23
PA
BA
CyHA
240 24 SAPO‐34 68 Si0.281Al0.460P0.259
240 SAPO‐34 86 Si0.201Al0.465P0.334
240 24 SAPO‐44 90 Si0.211Al0449P0.340
8
The initial molar compositions were as follows: 7R:0.8SiO2:
1.0Al2O3:0.8P2O5:15H2O. TEOS was used as the Si source.
15‐1h
15‐3h
15‐8h
of inorganic raw materials and their fast crystallization to
SAPO‐34.
3.3. Aminothermal synthesis of SAPO‐34 based on three
primary amines
We recently reported [8,11] aminothermal synthesis as a
method to synthesize SAPO molecular sieves, in which organic
amines are used as both a solvent and template. The amino‐
thermal method has shown some advantages including high
yield and good methanol‐to‐olefins catalytic performance of the
products [11,23]. Primary amines, including BA, PA, CyHA and
1,2‐ethylenediamine (EDA), always lead to the formation of
lamellar materials at 200 °C with the aminothermal synthesis
method [9]. Herein, we investigated conducting the synthesis at
the elevated temperature of 240 °C with three primary amines
(BA, PA and CyHA) employed as the solvent and template. High
temperature effectively inhibited the formation of lamellar
materials and facilitated the synthesis of pure chabazite
(CHA)‐type SAPO products (Table 4), similar to those produced
by the hydrothermal synthesis process. PA is a novel template
for the synthesis of SAPO‐34 (Figs. 1 and 2). From the ele‐
mental composition of the samples determined by XRF (Table
4), SAPO‐34‐PA possesses higher silicon content than
SAPO‐34‐BA and SAPO‐44‐CyHA synthesized with the same
initial molar composition. This is likely an effect of the smaller
molecule size of PA.
Fig. 3. SEM images of samples synthesized with different crystallization
times. Left: based on the synthetic system of Sample 4 (200 °C); Right:
based on the synthetic system of Sample 15 (240 °C).
200 °C can be established. AlPO‐kanemite forms quickly in the
initial stage of the crystallization because of its simple lamellar
structure. Subsequently, SAPO‐34 appears as a second phase
with the participation of silica. SAPO‐34 materials have higher
thermodynamic stability than kanemite and the SAPO‐34
products have more opportunity to survive in the synthetic gel.
The growth of SAPO‐34 may cause changes to gel pH and com‐
position [18], which further prompt the dissolution of
kanemite. Finally, SAPO‐34 becomes the only product.
Only a small amount of amorphous materials was observed
at t = 0 h in the product formed at 240 °C. Heating the gel for 1
h formed pure SAPO‐34 with high crystallinity (83%) and solid
yield (81%). The relative crystallinity of the SAPO‐34 product
reached 100% after 3 h and maintained at this level until the
end of the crystallization, indicating a fast crystallization rate at
high temperature. Kanemite or other lamellar materials were
not detected throughout the crystallization process, which con‐
firms the suppression of the generation of lamellar phase at
high temperatures. The Si content in the product also shows an
increasing trend with time, consistent with the findings of the
crystallization process at 200 °C. The above phenomena indi‐
cate that the crystallization process at 240 °C is simple as com‐
pared with that at 200 °C, which consisted of initial dissolution
3.4. Physiochemical properties of SAPO‐34 templated by BA
The textural properties of Samples 4, 15 and 22 were char‐
acterized by nitrogen physisorption (Table 5). All of the sam‐
ples have typical type I isotherms. The BET surface area and
micropore volume of Sample 4 are 585 m2/g and 0.27 cm3/g,
respectively. The values of samples 15 and 22 are close to those
of sample 4, confirming the good crystallinity and porosity of
Table 5
Textural properties of Samples 4, 15 and 22.
a
b
c
d
e
ABET
Amic
Aext
Vmic
(cm3/g)
Vmeso
(cm3/g)
Sample
(m2/g)
(m2/g)
(m2/g)
4
15
22
585
574
592
576
566
585
9
8
7
0.27
0.27
0.28
0.00
0.01
0.02
a BET surface area. b t‐plot micropore surface area. c t‐plot external sur‐
face area. d t‐plot micropore volume. e BJH adsorption volume.

Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
579
-90
(b)
(a)
4
CH3-CH2-CH2-CH2-NH2
4
3
2
1
3
2
1
-94
-99
-105
-109
-60
(d)
-70
-80
-90
-100
-110
-120
-130
-40
-20
0
20
40
60
80
100
 (29Si)
 (13C)
(c)
40
20
0
-20
-40
-60
-80
150
100
50
0
-50
-100
(31P)
(27Al)
Fig. 4. 13C (a), 29Si (b), 27Al (c) and 31P (d) MAS NMR spectra of Sample 4.
the samples.
Table 6. TG result shows that Sample 4 has three weight loss
stages (I, II, III) in the range of 30–800 °C. The first weight loss
stage at 50–200 °C is an endothermic process attributed to
water desorption from the sample. The second and third
weight loss stages between 200 and 700 °C are strongly exo‐
thermic processes attributed to the combustion decomposition
of the template and organic residue, respectively. There is no
weight loss and exothermic peak associated with structural
collapse until 800 °C, suggesting high thermal stability of
SAPO‐34 templated by BA. Samples 15 and 22 have TG curves
similar to that of Sample 4, and the results of weight loss are
listed in Table 6. The number of template molecules per CHA
cage were calculated based on the elemental composition and
topological structure of SAPO‐34, with 1.88, 1.75 and 1.84 BA
molecules for Samples 4, 15 and 22, respectively. These values
are similar, suggesting little effect from crystallization temper‐
ature and synthetic method on the inclusion of the organic
amine in SAPO‐34. The BA number per cage, which is higher
A 13C MAS NMR spectrum was recorded to verify the exact
template species occluded in Sample 4 (Fig. 4). The spectrum
exhibits four symmetrical peaks between 50 and 10 ppm,
which can be ascribed to the carbon atom directly attached to
the nitrogen atoms (C1) and the other three conjoint carbon
atoms in the BA molecules, respectively. This result is in good
agreement with previous literature [24] and implies that BA
remains intact in the SAPO‐34 crystals.
The TG‐DTA curve of Sample 4 is shown in Fig. 5 and the
corresponding weight loss of each stage are summarized in
102
100
98
96
94
92
90
88
86
84
82
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
Table 6
Thermal analysis results of Samples 4, 15 and 22.
Weight loss (wt%)
Sample
Template per cage
I
II + III
4
15
22
0.9
2.0
1.8
15.8
14.7
15.3
1.88
1.75
1.84
100 200 300 400 500 600 700 800
Temperature (oC)
Fig. 5. TG‐DTA curve of Sample 4.

580
Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
desorbed from weak and strong acid sites, respectively. Alt‐
hough both samples have a similar Si content, their acidic
properties are different, which is possibly because of the dif‐
ferent Si distribution (Si coordination environment) in the
crystals [26,27]. Sample 15, which was synthesized at 240 °C,
possesses less acidity than the sample synthesized at 200 °C,
demonstrating that the crystallization conditions may exert
influence on the acidic properties (Si distribution) of the sam‐
ples.
Sample 4
Sample 15
3.5. Catalytic performance
100
200
300
400
500
600
700
Temperature (oC)
Monomethylamine (MMA) and dimethylamine (DMA) are
important intermediates in chemical industries. These com‐
pounds are mainly produced by the methanol amination reac‐
tion with amorphous acidic oxide (Al2O3 or SiO2‐Al2O3) as the
catalyst at 390–430 °C and ~20 atm. Trimethylamine (TMA) is
the predominant product because of thermodynamic equilib‐
rium during the process. Small pore molecular sieves with
eight‐membered rings are promising catalysts for the methanol
amination reaction to improve the selectivity for MMA and
DMA [28,29].
Fig. 6. NH3‐TPD curves of Samples 4 and 15.
than that of tetraethylammonium hydroxide (TEAOH) [13] and
close to diethylamine (DEA) [17], is reasonable considering the
small molecule size of BA. The high number of BA molecules
per cage also explains the easy production of SAPO‐34‐BA with
higher Si content, because the organic amine can compensate
for a more negative framework charge and thus prompt higher
Si incorporation [25].
The catalytic performance of the BA‐templated SAPO‐34
samples were evaluated in the methanol amination reaction.
The steady‐state reaction data obtained with Samples 4 and 15
as catalyst at different reaction temperatures were determined
after 170 min on stream and listed in Table 7. The dominant
amination products were MMA and DMA for both catalysts, and
only small amounts of TMA were generated. A higher methanol
conversion and lower selectivity for MMA plus DMA was ob‐
served for Sample 4 compared with Sample 15 at each reaction
temperature. This is possibly because Sample 4 has larger acid
sites, which promote the acid catalyzed conversion of reactants
and further methylation of products in the methanol amination
reaction. The selectivity of MMA plus DMA in the three me‐
thylamine products over Sample 15 at 330 °C was 90.77%.
Methanol conversion was greatly improved by raising the reac‐
tion temperature to 350 °C, and the selectivity for DMA and
TMA increased, implying an enhancement of the methylation
degree. The (MMA + DMA) selectivity in the three methyla‐
mines presents a slight decline as compared with the results at
330 °C. However, the (MMA + DMA) selectivity in all products is
higher than that at 330 °C because of the decrease of dimethyl
ether (DME) in the products. Methanol conversion exceeded
80% by further raising the reaction temperature to 380 °C. The
(MMA + DMA) selectivity drops under these conditions, but is
The 29Si, 27Al and 31P MAS NMR spectra were obtained to
investigate the local atomic coordination environments in the
as‐synthesized Sample 4. The 29Si spectrum is complex because
of the high silica content of Sample 4, which consists of five
peaks ranging from −91 to −110 ppm corresponding to
Si(OSi)n(OAl)(4–n) (n = 0–4) species, respectively (Fig. 4). The
strong peak at −91 ppm suggests a dominant occupation of
Si(4Al) species in the framework, which is consistent with the
higher BA molecule number per cage in the SAPO‐34 crystals
revealed by TG analysis. This structure can compensate more
framework charge and thus facilitate the existence of more
single Si(4Al) environments.
The 27Al MAS NMR spectrum of Sample 4 displays two peaks
centered at around 37 and 9 ppm. The strong resonance at high
field should arise from a tetrahedral Al species, and the weak
one is attributed to penta‐coordinated Al formed by an addi‐
tional interaction of one water or template molecule with the
framework aluminum. Only one strong resonance peak at 30
ppm can be observed in the 31P spectrum, suggesting a pre‐
dominant P(4Al) environment in the framework.
The acidic properties of Samples 4 and 15 were investigated
by NH3‐TPD. There are two desorption peaks at about 190–200
and 450–470 °C for the samples (Fig. 6), corresponding to NH3
Table 7
Reaction results for methylamines synthesis using Samples 4 and 15 at TOS = 170 mina.
Selectivity(wt%)
TMA MMA + DMA
Sample
T (°C)
Conversion (%)
Sel(MMA + DMA) b (wt%)
MMA
34.66
29.54
39.02
34.20
26.78
DMA
42.63
47.07
43.86
48.93
54.73
DME
6.20
4.81
8.12
6.09
3.84
CH4
0.37
0.26
0.57
0.38
0.20
4
4
15
15
15
330
350
330
350
380
51.19
71.46
34.43
51.07
82.00
16.15
18.32
8.43
77.29
76.61
82.88
83.13
81.51
82.72
80.70
90.77
88.88
84.94
10.40
14.46
a NH3/CH3OH molar ratio = 2/1, WHSV = 0.813 h−1. b (MMA + DMA) selectivity in the three methylamine products.

Yuyan Qiao et al. / Chinese Journal of Catalysis 38 (2017) 574–582
581
sults. Only lamellar AlPO‐kanemite was obtained at 160 °C.
Pure SAPO‐34 was synthesized using a higher silica feeding
amount at 200 °C. Investigation of the crystallization process
revealed that AlPO‐kanemite is generated as an intermediate,
which transforms to SAPO‐34 under the assistance/participant
of silica. SAPO‐34 was synthesized with a wider range of silica
content by further increasing the crystallization temperature to
240 °C, showing that higher temperature can effectively sup‐
press the generation of lamellar materials. Unlike the crystalli‐
zation process at 200 °C, no AlPO‐kanemite intermediate was
observed at 240 °C and SAPO‐34 crystallizes directly from the
amorphous gel. We successfully synthesized CHA‐SAPO prod‐
ucts at 240 °C by the aminothermal method and found PA a
suitable template for the synthesis of SAPO‐34. The
BA‐templated SAPO‐34 has good crystallinity, high thermal
stability and high Si(4Al) content in the framework because of
the small size of BA. The as‐synthesized SAPO‐34 shows excel‐
lent shape‐selective catalytic performance in the methanol
amination reaction with high methanol conversion and good
selectivity for MMA and DMA, implying that the BA‐templated
SAPO‐34 has potential as a catalyst for the synthesis of me‐
thylamines.
100
90
80
70
60
50
40
30
20
10
0
CH3OH
MMA
CH4
DMA
DME
TMA
0
50
100
Time (min)
150
200
Fig. 7. Methanol conversion and product selectivity in the methanol
amination reaction on Sample 15 at 350 °C (NH3/CH3OH molar ratio =
2/1, WHSV = 0.813 h−1).
still maintained at a high level (> 80%). These results suggest
that Sample 15 has excellent shape‐selective catalytic effect
because of the 8‐membered windows in the structure of
SAPO‐34 and its suitable acidic properties. Fig. 7 shows the
methanol conversion and selectivity of all products with time
using Sample 15 at 350 °C. Methanol conversion and the selec‐
tivities of all products are stable in the tested reaction time of
193 min. These preliminary results demonstrate that
BA‐templated SAPO‐34 can be an excellent catalyst for the
synthesis of methylamines.
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Graphical Abstract
Chin. J. Catal., 2017, 38: 574–582 doi: 10.1016/S1872‐2067(17)62775‐X
SAPO‐34 synthesized with n‐butylamine as a template and its catalytic application in the methanol amination reaction
Yuyan Qiao, Pengfei Wu, Xiao Xiang, Miao Yang, Quanyi Wang, Peng Tian*, Zhongmin Liu*
Dalian Institute of Chemical Physics, Chinese Academy of Sciences;University of Chinese Academy of Sciences
n‐Butylamine was used as a template to synthesize SAPO‐34 with excellent shape‐selective catalytic performance in the methanol amina‐
tion reaction.

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