Mesoporogen-Free Synthesis of Hierarchical SAPO-34 with Low Template Consumption and Excellent Methanol-to-Olefin Conversion

Article abstract of DOI:10.1002/cssc.201801486

Significant interest has emerged in the development of nanometer-sized and hierarchical silicoaluminophosphate zeolites (SAPO-34) because of their enhanced accessibility and improved catalytic activity for methanol-to-olefin (MTO) conversion. A series of nanometer-sized SAPO-34 catalysts with tunable hierarchical structures was synthesized in a Al₂O₃/H₃PO₄/SiO₂/triethylamine(TEA)/H₂O system by using a mesoporogen-free nanoseed-assisted method. The nanometer-sized hierarchical S_H-3.0 catalyst (TEA/Al₂O₃=3.0) possessed the highest crystallinity, highest abundance of intracrystalline meso-/macropores, and the most suitable acidity among all obtained catalysts, showing the highest ethylene and propylene selectivity of 85.4 %. This is the highest reported selectivity for MTO reactions under similar conditions. Detailed analysis of the coke produced during the reaction revealed that the small-sized methyl-substituted benzene and bulky methyl-substituted pyrene were mainly located inside the crystals instead of on the surface of the crystals, which provided further insight into understanding the deactivation of the SAPO-34 catalyst during MTO reaction. Significantly, the simple and cost-effective synthetic process and superb catalytic performance of the nanometer-sized hierarchical SAPO-34 is promising for their practical large-scale application for MTO conversion.

Full text of DOI:10.1002/cssc.201801486

Accepted Article
Title: Mesoporogen-Free Synthesis of Nano-sized Hierarchical
SAPO-34 Zeolite with Reduced Template Consumption and
Excellent MTO Performance
Authors: Qiming Sun, Ning Wang, Risheng Bai, Guangrui Chen,
Zhiqiang Shi, Yongcun Zou, and Jihong Yu
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To be cited as: ChemSusChem 10.1002/cssc.201801486
Link to VoR: http://dx.doi.org/10.1002/cssc.201801486
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Mesoporogen-Free Synthesis of Nano-sized Hierarchical SAPO-
34 Zeolite with Reduced Template Consumption and Excellent
MTO Performance
Qiming Sun,[a] Ning Wang,[a] Risheng Bai,[a] Guangrui Chen,[a] Zhiqiang Shi,[a] Yongcun Zou,[a] and
Jihong Yu*[a, b]
Abstract: A great interest has emerged in the development of nano-
sized and hierarchical SAPO-34 zeolites because of their enhanced
accessibility and improved catalytic activity in methanol-to-olefin
(MTO) conversions. Here a series of nano-sized SAPO-34 catalysts
with tunable hierarchical structures are synthesized in the system of
Al2O3-H3PO4-SiO2-triethylamine(TEA)-H2O by using a mesoporogen-
free nanoseed-assistant method. The nano-sized hierarchical SH-3.0
catalyst (TEA/Al2O3=3.0) possesses the highest crystallinity,
abundant intracrystalline meso/macropores, and suitable acidity
among all of the obtained catalysts, showing the highest selectivity
of ethylene and propylene up to 85.4%. This value reaches the top
level in MTO reactions ever reported under the similar conditions.
Detailed coke analyses reveal that the small-sized methyl-
substituted benzene and bulky methyl-substituted pyrene are mainly
located inside the crystals instead of on the surface of crystals,
which provides further insight into the understanding of the
deactivation of the SAPO-34 catalyst during MTO reaction.
Significantly, the simple and cost-effective synthetic process and
superb catalytic performance of the nano-sized hierarchical SAPO-
34 promise their practical large-scale application in future MTO units.
can induce a very high selectivity of light olefins in MTO
reactions with complete conversion of methanol.[3] However,
the severe diffusion limitation and rapid coke formation
often lead to the rapid deactivation and unsatisfactory light
olefins selectivity during methanol conversion, which greatly
decreases the economic benefit of commercial MTO
process.[4] Hence, retarding coke deposition rate,
prolonging the catalytic lifetime as well as enhancing the
light olefins selectivity of SAPO-34 catalysts in MTO
reaction are highly desired.
Decreasing the crystal size to nanoscale can effectively
reduce the formation rate of coke deposition and improve
the
catalytic
activity
during
MTO
conversions.
Tetraethylammonium hydroxide (TEAOH) is the most
commonly-used template to synthesize nano-sized SAPO-
34 crystals, but the high prices force researchers to find
other cheaper alternatives.[5] Triethylamine (TEA), as a
cheap and commercially available organic compound, is
also a frequently-used template to generate SAPO-34
catalysts.[3e, 6] However, the large micron-sized crystal and
intergrowth phase of SAPO-34
(CHA)/SAPO-18 (AEI)
usually give rise to the suboptimal MTO catalytic
performance, especially the lower selectivity of ethylene
and propylene. So it is highly desired to synthesize nano-
sized SAPO-34 catalysts in the absence of SAPO-18
impurity using cheap templates.
Introduction
Microporous crystalline zeolites with ordered pore
architectures and uniform channels and/or cavities have
been widely used as the most important solid
heterogeneous catalysts in various industrial processes due
to the excellent shape selectivity and superior thermal and
hydrothermal stability.[1] Silicoaluminophosphate zeolite
SAPO-34 with CHA topological structure has drawn
tremendous attention due to the superior selectivity of light
olefins in methanol-to-olefin (MTO) conversion, which has
proven to be one of the most successful non-petrochemical
routes for the production of light olefins.[2] SAPO-34 zeolite
possesses small three-dimensional 8-ring pore openings
and a large cha cage as well as moderate acidity, which
Besides the reduction of crystal sizes, fabrication of
hierarchically porous structure can also significantly
improve the intercrystalline mass transport efficiency for the
reactant and products as well as enhance the catalytic
activity in MTO reactions.[7] Various methods, such as hard-
templating method,[7f, 7g] soft-templating method,[7d, 7e, 8] and
post-treatment method[9] have been employed to generate
the hierarchical SAPO-34 catalysts. While, these above
approaches not only usually need to add extra
mesoporogen or additionally tedious operation, but also
result in phase separation, poor crystallinity as well as low
stability. Recently, our group developed a novel seed-
assisted method to synthesize nano-sized hierarchical
SAPO-34 catalysts using excess TEA as the template,
which exhibited an excellent selectivity of ethylene plus
propylene (85%).[10] The superfluous consumption of
organic templates undoubtedly brings the increase of
synthetic cost and environmental pollution. So it still needs
to further optimize synthetic conditions and reduce the
consumption of organic templates on the premise of
keeping the excellent MTO catalytic performance.
[a]
Dr. Q. Sun, Dr. N. Wang, R. Bai, G. Chen, Z. Shi, Dr. Y. Zou, Prof. J.
Yu
State Key Laboratory of Inorganic Synthesis and Preparative
Chemistry, College of Chemistry, Jilin University
2699 Qianjin Street, Changchun, 130012, People's Republic of
China
E-mail: jihong@jlu.edu.cn
[b]
Prof. J. Yu
International Center of Future Science, Jilin University
2699 Qianjin Street, Changchun, 130012, People's Republic of
China
In this work, a series of nano-sized hierarchical SAPO-34
catalysts with tunably hierarchical structures and
physicochemical properties were synthesized using
different amounts of TEA as the template by mean of the in-
Supporting information for this article is given via a link at the end of
the document.
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10.1002/cssc.201801486
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situ mesoporogen-free nanoseed-assistant method. The
zeolitic phase and crystallinity, the sizes and distributions of
meso/macropores and the acidity of samples are
significantly subjected to the additions of TEA in the
synthetic gel. Owing to the assistance of seeds, the pure
SAPO-34 catalyst without SAPO-18 and SAPO-5 impurity
can be obtained with a TEA/Al2O3 ratio of 2.0. Significantly,
the nano-sized hierarchical SAPO-34 catalyst synthesized
with a TEA/Al2O3 ratio of 3.0 possesses high crystallinity,
abundant intracrystalline meso/macropores and suitable
acidity, showing the longest catalytic lifetime and highest
selectivity of ethylene plus propylene up to 85.4%, which is
the top level in the MTO reaction ever reported under
similar conditions. As compared with our previous work, the
consumption of organic template was reduced 40
percent.[10] In addition, according to the detailed coke
analyses, we find that the small-sized methyl-substituted
benzene and bulky methyl-substituted pyrene are prone to
be generated inside the channels of crystals instead of on
the outer surface of crystals. Compared to the conventional
microporous catalyst, the hierarchical catalysts are capable
to accommodate more amounts of larger coke species
avoiding rapid deactivation.
The XRD patterns of microporous SM-x and hierarchical SH-x
samples are shown in Figure 1. Without adding seeds, the
SAPO-34 with some impurity of SAPO-18 can be obtained when
the TEA/Al2O3 ratio is more than 2.0. The content of SAPO-18
gradually increases with the decrease of TEA amount. When the
TEA/Al2O3 ratio is less than 2.0, the diffraction peaks of SAPO-5
can be detected. When further decreasing the TEA/Al2O3 ratio
less than 1.2, the pure SAPO-5 zeolite is obtained. In contrast,
introducing the seeds into the synthetic gel is beneficial for the
formation of SAPO-34 zeolite. With the assistance of seeds, the
pure SAPO-34 zeolite can be produced with the TEA/Al2O3 ratio
more than 2.0. The mixed phase of SAPO-34 and SAPO-18 can
be formed with the TEA/Al2O3 ratio of 1.6. When the ratio of
TEA/Al2O3 further decreases to less than 1.6, the SAPO-5
zeolites start to appear.
Results and Discussion
The hierarchical SAPO samples (SH-x) are synthesized by
adding different amounts of TEA as the template together with
some nano-sized seeds. The synthetic gels with molar
compositions of 1.0Al2O3: 1.0P2O5: xTEA: 0.4SiO2: 70H2O: 8.0
wt% Seeds (x = 5.0 ~ 0.2) are crystallized under hydrothermal
conditions at 200 °C for 36 h. The nano-sized seeds are
prepared using the TEAOH as the template. The SAPO-34
seeds have the pure CHA topological structure and nanosheet-
like morphology with the size of about 200 nm (Figure S1 in the
Supporting Information). The microporous SAPO samples (SM-x)
are synthesized with the similar gel compositions of hierarchical
SH-x samples except for the absence of seeds.
Figure 2. SEM images of micron-sized microporous SAPO zeolites (SM-x). a)
SM-0.2, b) SM-0.4, c) SM-0.8, d) SM-1.2, e) SM-1.6, f) SM-2.0, g) SM-3.0, h) SM-
4.0, and i) SM-5.0. The scale bars of all images are 10 μm.
Figure 3. SEM images of nano-sized hierarchical SAPO zeolites (SH-x). a) SH-
0.2, b) SH-0.4, c) SH-0.8, d) SH-1.2, e) SH-1.6, f) SH-2.0, g) SH-3.0, h) SH-4.0,
and i) SH-5.0. The scale bars of images a-d) are 10 μm, and the scale bars of
images e-i) are 2 μm.
Figure 1. XRD patterns of a) micron-sized microporous SAPO zeolites (SM-x)
and b) nano-sized hierarchical SAPO zeolites (SH-x).
SEM images of microporous SAPO zeolites SM-x and
hierarchical SH-x samples are shown in Figures 2 and 3. The
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micron-sized floriated SAPO-5 crystals can be observed in both
of SM-x (x = 0.2 ~ 1.6) and SH-x (x = 0.2 ~ 1.2) samples.
However, for the SAPO-34 crystals, the SH-x (x = 1.6 ~ 5.0)
samples exhibit remarkably reduced crystal sizes (200~800 nm)
as compared with SM-x (x = 2.0 ~ 5.0) samples (~10 μm). TEM
images clearly reveal the presence of mesopores and
macropores with sizes of 20 ~ 150 nm extending along the
nanocrystals of samples SH-4.0, SH-3.0, SH-2.0, and SH-1.6.
Moreover, with the increase of TEA addition, more hierarchical
pores can be formed, and the pore sizes are gradually enlarged
(Figure 4).
uptake near saturation pressure in the isotherms of all
hierarchical SAPO-34 samples can be observed, which can
be attributed to the presence of voids between the nano-
sized crystals stacking and the existence of mesopores
and/or macropores in the hierarchical SAPO-34 crystals.[3h,
11]
This is in accordance with the observation of SEM and
TEM images. Moreover, the nano-sized hierarchical
samples SH-4.0, SH-3.0, SH-2.0, and SH-1.6 exhibit the
increased microporous areas (553-519 m2/g), micropore
volumes (0.26-0.25 cm3/g) and mesopore volumes (0.09-
0.10 cm3/g) as compared with the micron-sized
microporous SAPO-34 sample SM-4.0 (511 m2/g, 0.24
cm3/g, and 0.03 cm3/g). Notably, the hierarchical sample
SH-3.0 shows the highest microporous area (553 m2/g),
indicating the highest crystallinity among all of the samples.
The detailed N2 adsorption-desorption results are
summarized in Table 1. Meanwhile, the pore size
distributions also reveal the existence of hierarchical
porosity in samples SH-4.0, SH-3.0, SH-2.0, and SH-1.6
(Figure 5b).
Figure 4. TEM images of nano-sized hierarchical samples (SH-x). a-c) SH-4.0,
d-f) SH-3.0, g-i) SH-2.0, j-l) SH-1.6. Scale bars: a, d, g, j) 500 nm, b, e, h, k) 200
nm, and c, f, i, l) 100 nm.
The microporous sample SM-4.0 and hierarchical samples
SH-4.0, SH-3.0, SH-2.0, and SH-1.6 display the
characteristics of type-I N2 adsorption-desorption isotherms
(Figure 5a). Compared with sample SM-4.0, an apparent
Figure 5. a) N2 adsorption/desorption, b) Density functional theory pore
size distribution curves of micron-sized microporous (SM-4.0) and nano-
sized hierarchical SAPO-34 (SH-4.0, SH-3.0, SH-2.0, and SH-1.6) samples.
Table 1. Framework composition and porosity of micron-sized microporous SAPO-34 (SM-4.0) and nano-sized hierarchical SAPO-34 (SH-4.0, SH-3.0,
SH-2.0, and SH-1.6) samples.
Molar
Samples
SBET[b] [m2/g]
Smicro[c] [m2/g]
Sext[c] [m2/g]
Vmicro[c] [cm3/g]
Vmeso[d] [cm3/g]
Composition[a]
Al0.48P0.40Si0.12O2
Al0.49P0.40Si0.11O2
Al0.49P0.41Si0.10O2
Al0.49P0.42Si0.09O2
Al0.48P0.43Si0.09O2
SM-4.0
SH-4.0
SH-3.0
SH-2.0
SH-1.6
528
558
566
541
528
511
547
553
528
519
17
11
13
13
9
0.24
0.26
0.26
0.25
0.25
0.03
0.09
0.10
0.09
0.10
[a] Measured by inductively coupled plasma (ICP) spectrometer; [b] SBET (total surface area) is calculated by applying the BET equation using the
linear part (0.05<P/Po<0.30) of the adsorption isotherm; [c] Smicro (micropore area), Sext (external area), and Vmicro (micropore volume) are calculated
using the t-plot method; [d] Vmeso (mesoporous volume) is calculated using the BJH method (from desorption)
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catalyst SM-4.0 (126 min, 79.7%) and other hierarchical
catalysts SH-4.0 (326 min, 84.9%), SH-2.0 (326 min, 82.4%),
and SH-1.6 (306 min, 78.1%). The MTO catalytic
performance of catalyst SH-3.0 is the top level in MTO
reactions ever reported under the similar conditions.[3h, 8a]
More importantly, under the same catalytic condition
(450 °C, WHSV = 4 h-1) compared with our previous work,
the SH-3.0 catalyst possess more than 40% decreased
consumption of organic template and 0.7% enhanced
selectivity of ethylene and propylene (the detailed catalytic
results of our previous work are shown in Table 2 and
Figure S10 in the Supporting Information).[10]
Figure 6. NH3-TPD curves of micron-sized microporous SAPO-34 (SM-
4.0) and nano-sized hierarchical SAPO-34 (SH-4.0, SH-3.0, SH-2.0 and
SH-1.6) samples.
Thermogravimetry (TG) analyses show that the SAPO-34
samples exhibit more weight loss as compared with the
SAPO-5 samples, indicating that more organic templates
are located inside the channels of SAPO-34 (Figures S2
and S3 in the Supporting Information). With the decrease of
organic templates added in the synthetic gel, the SAPO-34
samples show fewer weight losses. Meanwhile, the silicon
contents of samples are gradually reduced along with the
decrease of added templates in the synthetic gels, and the
introduction of seed can further decrease the silicon
contents of samples (Table 1 and S1 in the Supporting
Information). 29Si MAS NMR results reveal that all of the
obtained samples possess the similar local silicon atomic
environments (Figure S4 in the Supporting Information).
The Si(0Si4Al) unit with the peak at ca. -90 ppm as the
main silicon species exits in all of the samples.[12]
Compared with the conventional microporous sample, the
hierarchical samples possess more Si(OAl)n(OH)4-n unit
with the shoulder peak ranging from -80 to -90 ppm
attributed to the breaking of the Si–OH–Al bond, indicating
the existence of defects or/and hierarchical structures. Note
that the difference of Si contents of samples can
considerably affect the acidity of SAPO-34 samples. As
shown in Figure 6, with the decrease of silicon contents, the
acidities of SAPO-34 samples are correspondingly reduced.
The MTO catalytic performances of micron-sized
microporous SAPO-34 (SM-4.0) and nano-sized hierarchical
SAPO-34 (SH-4.0, SH-3.0, SH-2.0, and SH-1.6) samples are
evaluated at 450 °C with a WHSV of 4 h-1 in a fix-bed
reactor. The catalytic lifetime and selectivity of ethylene and
propylene of samples are shown in Figure 7. The detailed
catalytic results and product distribution of samples are
given in Figures S5-S9 in the Supporting Information and
Table 2. Compared to the micron-sized microporous
catalyst SM-4.0, the nano-sized hierarchical catalysts (SH-
4.0, SH-3.0, and SH-2.0) with pure SAPO-34 phase exhibit
Figure 7. a) Lifetimes and b) selectivity of ethylene and propylene over
micron-sized microporous SAPO-34(SM-4.0) and nano-sized hierarchical
SAPO-34 (SH-4.0, SH-3.0, SH-2.0 and SH-1.6) samples. Experimental
conditions: WHSV = 4 h-1, T = 450 °C, catalyst weight = 300 mg.
Compared with the conventional microporous SM-4.0, the
enhanced catalytic property of hierarchical catalysts can be
attributed to the decreased crystal size, high crystallinity of
pure CHA phase, abundant hierarchical structure, and
decreased acidity. Among all of the hierarchical SAPO-34
catalysts, the SH-3.0 exhibits the longest lifetime and
highest selectivity of ethylene and propylene, which can be
mainly attributed to its highest crystallinity, and the suitable
acidity and hierarchal structure. Considering the similar
hierarchical structure and crystallinity with SH-4.0, the
improved catalytic performance of SH-3.0 is mainly
attributed to the decreased acidity, which can restrain the
coke formation rate. In comparison with SH-2.0, the
enhanced catalytic activity of SH-3.0 is mainly ascribed to
the higher crystallinity and larger mesoporous sizes that is
beneficial for the transport of methanol and products. Note
that although possessing the lowest acidity, nano-sized and
hierarchical structure, the SH-1.6 catalyst with mixed phases
of SAPO-34 and SAPO-18 exhibits remarkably decreased
selectivity of ethylene, and the final selectivity of ethylene
and propylene is only 78.1%. This result demonstrates that
more than
a twice prolonged catalytic lifetime and
considerably improved the selectivity of ethylene and
propylene. Notably, the nano-sized hierarchical catalyst SH-
3.0 shows the longest catalytic lifetime of 366 min and the
highest selectivity of ethylene plus propylene up to 85.4%,
which are much higher than those of the microporous
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the SAPO-34 catalyst is beneficial for the formation of light
olefins than the SAPO-18 catalyst, and effectively avoiding
the formation of SAPO-18 impurity in the SAPO-34 catalyst
is of great significance to improve the catalytic performance
in MTO conversion.
and avoiding fast deactivation. When the meso/macropores
in hierarchical SAPO-34 catalysts are filled with cokes, the
deactivation is inevitable due to the inaccessible of the
methanol into the active sites. However, compared with the
microporous counterparts, the hierarchical SAPO-34
catalysts can maximize the use of active sites and possess
the prolonged lifetime and enhanced activity in MTO
reactions.
After MTO reactions, the coke species retained on the
surface and inside the deactivated catalysts are examined
by gas chromatography-mass spectrometer (GC-MS)
analyses. To analyze the coke species on the surface of the
SAPO-34 catalyst, the deactivated SAPO-34 catalyst was
carefully ground for 5 min, and then the solid was extracted
by CH2Cl2. To get the total coke species, the deactivated
catalyst was etched by HF solution for 24 h and then
extracted by CH2Cl2. The total coke species in the samples
are shown in Figure 8a. More bulky cokes such as multi-
methyl-substituted pyrene can be detected within the
deactivated hierarchical SAPO-34 catalysts as compared
with the microporous SAPO-34 catalyst. Interestingly, the
coke species on the surface of both hierarchical and
microporous catalysts are much the same. Multi-methyl-
substituted
naphthalene,
multi-methyl-substituted
anthracene, and pyrene as the main coke species are
located on the surface of catalysts, but few methyl-
substituted benzenes and bulky multi-methyl-substituted
pyrene species can be detected on the surface of catalysts
Figure 8. GC-MS chromatograms of a) total coke species and b) coke
species on the surface in deactivated micron-sized microporous (SM-4.0)
and nano-sized hierarchical SAPO-34 (SH-4.0, SH-3.0, SH-2.0, and SH-
1.6) samples after methanol conversions at 450 °C . c) A schematic of
coke deposition in the deactivated SAPO-34 catalyst. d) TG curves of
deactivated micron-sized microporous (SM-4.0) and nano-sized
hierarchical SAPO-34 (SH-4.0, SH-3.0, SH-2.0, and SH-1.6) samples after
methanol conversions at 450 °C .
(Figure 8b). Figure 8c shows
a schematic of coke
distribution in the deactivated SAPO-34 catalyst. Above
results might shed some light to understand the reason of
deactivation for the SAPO-34 catalyst during the MTO
reaction. In previous work, the methyl-substituted benzene
species are considered as the active intermediates for the
generation of ethylene and propylene.[13] According to the
coke analyses, the reason for the deactivation of
conventional microporous SAPO-34 catalysts is mainly
caused by the blocks on the outer surface, instead of the
absence of active intermediates. Severe coke depositions
on the outer surface of SAPO-34 catalysts lead to
inaccessibility of methanol and active sites or/and active
intermediates inside the catalyst, even though the active
intermediates still exist within the deactivated catalysts; this
is consistent with previous works.[14] Moreover, our
experimental results clearly reveal that the bulky multi-
TG analyses of deactivated catalysts reveal that the
weight loss (20.04 ~ 21.62%) and the decomposition
temperature of cokes (550 ~ 750 ºC) in the hierarchical
catalysts are higher than that in the conventional
microporous catalyst (18.08% and 450 ~ 700 ºC), which
further confirms that more amounts of bulky polycyclic
aromatic hydrocarbon are located inside the hierarchical
catalysts (Figure 8d and Table S2). Significantly, the
hierarchical catalysts SH-3.0 shows the lowest coke
deposition rate of 0.14 mg min-1 among the catalysts, which
is more than twice decrease than that of conventional
microporous SAPO-34 catalyst (0.32 mg min-1) (Table S2 in
the Supporting Information).
methyl-substituted
pyrene
is located
inside
the
intracrystalline hierarchical spaces, which demonstrates
that fabricating hierarchical structure is a powerful approach
to benefit for the interaction between methanol and active
intermediates, accommodating more bulky coke species,
Table 2. MTO results on micron-sized microporous (SM-4.0), nano-sized hierarchical SAPO-34 (SH-4.0, SH-3.0, SH-2.0, and SH-1.6), and counterpart
catalysts.
Lifetime[a]
[min]
126
Selectivity[%]
C3H6
Catalysts
+
=
CH4
1.7
2.2
2.6
3.4
4.0
2.3
C2H4
43.3
50.0
51.3
47.6
43.1
50.1
C2H6
0.8
0.5
0.6
0.5
0.5
0.5
C3H8
3.0
0.7
0.7
0.5
0.9
0.7
C4
10.7
8.4
C5
C2=+C3
79.7
84.9
85.4
82.4
78.1
84.7
SM-4.0
SH-4.0
36.4
34.9
34.1
34.8
35.0
34.6
4.1
3.3
2.9
4.0
5.3
3.4
326
SH-3.0
366
7.8
SH-2.0
326
9.2
SH-1.6
Counterpart[b]
306
11.2
8.4
286
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Reaction conditions: WHSV = 4 h-1, T = 450 °C, catalyst weight = 300 mg.
[a] Lifetime: the reaction duration with > 99.9% methanol conversion. [b] The counterpart catalyst was a nano-sized hierarchical SAPO-34 catalyst
reported in our previous work,[10] which was synthesized with the ratio of TEA/Al2O3 = 4.7.
continuously. Finally, 8.0 wt% of SAPO-34 seed was added into the
mixture and then stirred continuously until the seed was dissolved
completely. The synthetic gel was transferred to a stainless steel
autoclave and heated at 200 °C for 36 h. The as-synthesized solid
Conclusions
In summary,
a facile and cost-effective mesoporogen-free
product was calcined in air at 550 °C for 8 h to remove the template.
Synthesis of micron-sized microporous SAPO-34 zeolites. The
micron-sized microporous SAPO-34 zeolites were synthesized with
the molar compositions of 1.0Al2O3: 1.0P2O5: xTEA: 0.4SiO2:
70H2O (x = 5.0, 4.0, 3.0, 2.5, 2.0, 1.6, 1.2, 0.8, 0.4, and 0.2) under
hydrothermal conditions at 200 °C for 36 h, and the resulting
products were named as SM-x (x meant the molar ratio of
TEA/Al2O3). The synthetic procedure is similar to that of nano-sized
hierarchical SAPO-34 zeolites except for the absence of seeds.
Characterizations. Powder X-ray diffraction patterns recorded on a
Rigaku D-Max 2550 diffractometer using Cu Kα radiation (λ =
0.15418 nm) were used to identify the zeolite phases. The
morphologies of catalysts were measured by transmission electron
microscopy (TEM) (Tecnai F20 electron microscope) and scanning
electron microscopy (SEM) (JSM-6510 (JEOL) electron
microscope). Thermogravimetric (TG) analysis was performed on a
TGA Q500 unit in the air with a heating rate of 10 °C min−1 from
room temperature to 800 °C in air. Chemical compositions of
samples were analyzed by inductively coupled plasma (ICP) using
Perkin-Elmer Optima 3300 DV ICP instrument. The acidity of
samples was measured by ammonia temperature-programmed
desorption of ammonia (NH3-TPD) experiments (Micromeritics
AutoChem II 2920 automated chemisorption analysis unit). N2
method has been developed for the synthesis of nano-sized
SAPO-34 catalysts with tunable hierarchical structures and
physicochemical properties by using TEA as the sole template.
The pure SAPO-34 catalyst without SAPO-18 and SAPO-5
impurity can be obtained with a TEA/Al2O3 ratio as low as 2.0.
Significantly, the nano-sized hierarchical SAPO-34 catalyst with
the lower TEA/Al2O3 ratio of 3.0 shows the excellent selectivity
of ethylene and propylene up to 85.4% due to high crystallinity,
abundant intracrystalline meso/macropores, and suitable acidity.
Such value is among the highest level in the MTO reaction ever
reported under the similar conditions. Detailed coke analyses
reveal that the small-sized methyl-substituted benzene species
and bulky methyl-substituted pyrene are prone to be generated
inside spaces instead of on the surface of catalysts. The above
results reveal that the main reason for the catalyst deactivation
is the blockage of the outer surface of the SAPO-34 catalyst
instead of the lack of active intermediates. Therefore, fabricating
hierarchical structure has proven to be a powerful method to
promote the contact between methanol and active intermediates
as well as avoid fast deactivation. More importantly, the facile
and cost-effective synthetic process and outstanding catalytic
performance of nano-sized hierarchical SAPO-34 zeolite
catalysts promise their practical large-scale application in MTO
units.
adsorption/desorption measurements were carried out on
a
Micromeritics 2020 analyzer at 77.35 K after the samples were
degassed at 350 °C under vacuum. 29Si NMR spectra were
performed on a Bruker AVANCE III 400 WB spectrometer.
Catalytic Tests and Carbon Deposit Analyses. MTO reaction
was performed in a fixed-bed reactor at atmospheric pressure. 300
mg of catalysts (40-60 mesh) were loaded in the quartz reactor (6
mm inner diameter) and activated at 500 °C in an N2 flow (30 mL
min-1) for 1 h before starting each reaction. Then the temperature
was adjusted to reaction temperature (450 °C), and the methanol
was fed by passing the carrier gas (N2, 15 mL/min) through a
saturator containing methanol at 49 °C, which gave a WHSV of 4.0
h-1. The products were analyzed using an online gas
Experimental Section
Chemicals and Materials. Aluminum iso-propoxide (Al(OPri)3, 99.5
wt%, Beijing Reagents Company), pseudoboehmite (Al2O3, 62.5
wt%, Vista), phosphoric acid (H3PO4, 85 wt%, Beijing Chemical
Works), tetraethylammonium hydroxide solution (TEAOH, 35 wt%,
Alfa Aesar), triethylamine (TEA, 99%, Fuyu Company), colloidal
silica (40 wt%, Aldrich), fumed silica (Changling Refining Company),
hydrofluoric acid (HF, 40 wt%, Beijing Chemical Works),
dichloromethane (CH2Cl2, Biaoshiqi Reagents Company).
chromatograph (Agilent GC 7890N), equipped with
a flame
ionization detector (FID) and Plot-Q column (Agilent J&W GC
Columns, HP-PLOT/Q 19091P-Q04, 30 m × 320 µm × 20 µm). The
conversion and selectivity were calculated on the CH2 basis and
dimethyl ether was considered as a reactant in the calculation.
The coke deposition amounts of deactivated SAPO-34 catalysts (the
final methanol conversion decreased to about 60%) after the MTO
reactions were determined by TG analyses. To analyze the coke species
on the surface of the SAPO-34 catalyst, the deactivated SAPO-34
catalysts were carefully ground for 5 min, and then the solid was
extracted by CH2Cl2, the obtained solutions were analyzed by GC-MS
(Thermo Fisher Trace ISQ, equipped with TG-5MS column, 60 m × 320
µm × 25 µm). To determine the total coke species, the deactivated
catalysts were etched by HF solution for 24 h, and then extracted by
CH2Cl2. Subsequently, the obtained solutions were analyzed by GC-MS.
Synthesis of nanosheet-like SAPO-34 zeolite seeds
. The
nanosheet-like SAPO-34 zeolite seeds were synthesized under
conventional hydrothermal conditions from a starting gel with the
molar
composition
of
Al2O3/P2O5/TEAOH/SiO2/H2O
=
1.0/1.2/2.0/0.6/40 as reported in our previous work.[5a]
Synthesis of nano-sized hierarchical SAPO-34 zeolites. The
nano-sized hierarchical SAPO-34 zeolites were synthesized with
the molar compositions of 1.0Al2O3: 1.0P2O5: xTEA: 0.4SiO2:
70H2O: 8.0 wt% Seeds (x = 5.0, 4.0, 3.0, 2.5, 2.0, 1.6, 1.2, 0.8, 0.4,
and 0.2) under hydrothermal conditions at 200 °C for 36 h, and the
resulting products were named as SH-x (x meant the molar ratio of
TEA/Al2O3). Typically, the pseudoboehmite was added into the
mixture of deionized water and phosphoric acid solution, followed
by a continuous stirring for 2 h. Then the TEA was added to the
above mixture. After a continuous stirring for 1 h, the fumed silica
was added into the resultant solution and then stirred for 2 h
Acknowledgements
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10.1002/cssc.201801486
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[4]
[5]
a) K. Hemelsoet, J. Van der Mynsbrugge, K. De Wispelaere, M.
Waroquier, V. Van Speybroeck, Chemphyschem 2013, 14, 1526-1545;
b) J. F. Haw, W. Song, D. M. Marcus, J. B. Nicholas, Acc. Chem. Res.
2003, 36, 317-326; c) W. Dai, G. Wu, L. Li, N. Guan, M. Hunger, ACS
Catal. 2013, 3, 588-596; d) Z. Liu, X. Dong, Y. Zhu, A.-H. Emwas, D.
Zhang, Q. Tian, Y. Han, ACS Catal. 2015, 5, 5837-5845.
This work was supported by the Nation Key Research and
Development Program of China (Grant No. 2016YFB0701100),
National Natural Science Foundation of China (Grant Nos.
21320102001, and 21621001) and the National 111 Project
(B17020).
a) Q. Sun, Y. Ma, N. Wang, X. Li, D. Xi, J. Xu, F. Deng, K. B. Yoon, P.
Oleynikov, O. Terasaki, J. Yu, J. Mater. Chem. A 2014, 2, 17828-
17839; b) Z. Li, J. Martínez-Triguero, J. Yu, A. Corma, J. Catal. 2015,
329, 379-388; c) S. Askari, R. Halladj, Ultrason. Sonochem. 2012, 19,
554-559; d) H. van Heyden, S. Mintova, T. Bein, Chem. Mater. 2008,
20, 2956-2963.
Keywords: heterogeneous catalysis • methanol-to-olefin •
zeolites • SAPO-34 • low template consumption
[1]
a) A. Corma, Chem. Rev. 1997, 97, 2373-2420; b) W. J. Roth, P.
Nachtigall, R. E. Morris, J. Čejka, Chem. Rev. 2014, 114, 4807-4837; c)
J. Čejka, A. Corma, S. I. Zones, Zeolites and catalysis: synthesis
reactions and applications, Wiley-VCH, Weinheim, 2010, pp. 1-881; d)
W. Schwieger, A. G. Machoke, T. Weissenberger, A. Inayat, T. Selvam,
M. Klumpp, A. Inayat, Chem. Soc. Rev. 2016, 45, 3353-3376; e) M.-H.
Sun, S.-Z. Huang, L.-H. Chen, Y. Li, X.-Y. Yang, Z.-Y. Yuan, B.-L. Su,
Chem. Soc. Rev. 2016, 45, 3479-3563; f) D. Verboekend, N. Nuttens, R.
Locus, J. Van Aelst, P. Verolme, J. C. Groen, J. Perez-Ramirez, B. F.
Sels, Chem. Soc. Rev. 2016, 45, 3331-3352; g) Y. Li, L. Li, J. Yu,
Chem 2017, 3, 928-949; h) Q. Sun, N. Wang, Q. Bing, R. Si, J. Liu, R.
Bai, P. Zhang, M. Jia, J. Yu, Chem 2017, 3, 477-493; i) S. Lopez-
Orozco, A. Inayat, A. Schwab, T. Selvam, W. Schwieger, Adv. Mater.
2011, 23, 2602-2615; j) L.-H. Chen, X.-Y. Li, J. C. Rooke, Y.-H. Zhang,
X.-Y. Yang, Y. Tang, F.-S. Xiao, B.-L. Su, J. Mater. Chem. 2012, 22,
17381-17403; k) K. Na, M. Choi, R. Ryoo, Microporous Mesoporous
Mater. 2013, 166, 3-19.
[6]
[7]
a) Y. Li, M. Zhang, D. Wang, F. Wei, Y. Wang, J. Catal. 2014, 311, 281-
287; b) Y. Li, Y. Huang, J. Guo, M. Zhang, D. Wang, F. Wei, Y. Wang,
Catal. Today 2014, 233, 2-7; c) S. H. Jhung, J.-S. Chang, J. S. Hwang,
S.-E. Park, Microporous Mesoporous Mater. 2003, 64, 33-39.
a) M. Hartmann, A. G. Machoke, W. Schwieger, Chem. Soc. Rev. 2016,
45, 3313-3330; b) Q. Sun, N. Wang, D. Xi, M. Yang, J. Yu, Chem.
Commun. 2014, 50, 6502-6505; c) X. Liu, S. Ren, G. Zeng, G. Liu, P.
Wu, G. Wang, X. Chen, Z. Liu, Y. Sun, RSC Adv. 2016, 6, 28787-
28791; d) C. Wang, M. Yang, W. Zhang, X. Su, S. Xu, P. Tian, Z. Liu,
RSC Adv. 2016, 6, 47864-47872; e) F. Wang, L. Sun, C. Chen, Z. Chen,
Z. Zhang, G. Wei, X. Jiang, RSC Adv. 2014, 4, 46093-46096; f) F.
Schmidt, S. Paasch, E. Brunner, S. Kaskel, Microporous Mesoporous
Mater. 2012, 164, 214-221; g) A. Z. Varzaneh, J. Towfighi, S.
Sahebdelfar, Microporous Mesoporous Mater. 2016, 236, 1-12.
a) C. Wang, M. Yang, P. Tian, S. Xu, Y. Yang, D. Wang, Y. Yuan, Z.
Liu, J. Mater. Chem. A 2015, 3, 5608-5616; b) P. Wu, M. Yang, W.
Zhang, S. Xu, P. Guo, P. Tian, Z. Liu, Chem. Commun. 2017, 53, 4985-
4988.
[8]
[9]
[2]
a) C. D. Chang, Catal. Rev. 1984, 26, 323-345; b) P. Tian, Y. X. Wei, M.
Ye, Z. M. Liu, ACS Catal. 2015, 5, 1922-1938; c) J. Zhong, J. Han, Y.
Wei, P. Tian, X. Guo, C. Song, Z. Liu, Catal. Sci. Technol. 2017, 7,
4905-4923; d) Q. Sun, Z. Xie, J. Yu, Natl. Sci. Rev. 2018, 5, 542–558;
e) U. Olsbye, S. Svelle, M. Bjørgen, P. Beato, T. V. W. Janssens, F.
Joensen, S. Bordiga, K. P. Lillerud, Angew. Chem. Int. Ed. 2012, 51,
5810-5831; Angew. Chem. 2012, 124, 5910–5933. f) D. Chen, K.
Moljord, A. Holmen, Microporous Mesoporous Mater. 2012, 164, 239-
250.
a) X. Chen, A. Vicente, Z. Qin, V. Ruaux, J.-P. Gilson, V. Valtchev,
Chem. Commun. 2016, 52, 3512-3515; b) Y. Qiao, M. Yang, B. Gao, L.
Wang, P. Tian, S. Xu, Z. Liu, Chem. Commun. 2016, 52, 5718-5721; c)
Z. Liu, S. Ren, X. Yu, X. Chen, G. Wang, X. Wu, G. Yu, M. Qiu, C.
Yang, Y. Sun, Catal. Sci. Technol. 2018, 8, 423-427.
[10] Q. Sun, N. Wang, R. Bai, X. Chen, J. Yu, J. Mater. Chem. A 2016, 4,
14978-14982.
[3]
a) W. Dai, X. Wang, G. Wu, N. Guan, M. Hunger, L. Li, ACS Catal.
2011, 1, 292-299; b) M. Li, Y. Wang, L. Bai, N. Chang, G. Nan, D. Hu,
Y. Zhang, W. Wei, Appl. Catal. A 2017, 531, 203-211; c) Y. Gao, S.-L.
Chen, Y. Wei, Y. Wang, W. Sun, Y. Cao, P. Zeng, Chem. Eng. J. 2017,
326, 528-539; d) D. Zhao, Y. Zhang, Z. Li, Y. Wang, J. Yu, Chem. Eng.
J. 2017, 323, 295-303; e) J. Zhu, Y. Li, U. Muhammad, D. Wang, Y.
Wang, Chem. Eng. J. 2017, 316, 187-195; f) Q. Sun, N. Wang, G. Guo,
J. Yu, Chem. Commun. 2015, 51, 16397-16400; g) H. Yang, Z. Liu, H.
Gao, Z. Xie, J. Mater. Chem. 2010, 20, 3227-3231; h) Q. Sun, N. Wang,
G. Guo, X. Chen, J. Yu, J. Mater. Chem. A 2015, 3, 19783-19789; i) Y.
Jin, Q. Sun, G. Qi, C. Yang, J. Xu, F. Chen, X. Meng, F. Deng, F.-S.
Xiao, Angew. Chem., Int. Ed. 2013, 52, 9172-9175; Angew. Chem.
2013, 125, 9342–9345 j) G. Guo, Q. Sun, N. Wang, R. Bai, J. Yu,
Chem. Commun. 2018, 54, 3697-3700.
[11] D. Xi, Q. Sun, J. Xu, M. Cho, H. S. Cho, S. Asahina, Y. Li, F. Deng, O.
Terasaki, J. Yu, J. Mater. Chem. A 2014, 2, 17994-18004.
[12] W. Shen, X. Li, Y. Wei, P. Tian, F. Deng, X. Han, X. Bao, Microporous
Mesoporous Mater. 2012, 158, 19-25.
[13] a) W. Song, J. F. Haw, J. B. Nicholas, C. S. Heneghan, J. Am. Chem.
Soc. 2000, 122, 10726-10727; b) E. Borodina, H. Sharbini Harun
Kamaluddin, F. Meirer, M. Mokhtar, A. M. Asiri, S. A. Al-Thabaiti, S. N.
Basahel, J. Ruiz-Martinez, B. M. Weckhuysen, ACS Catal. 2017, 7,
5268-5281.
[14] a) Q. Qian, J. Ruiz-Martínez, M. Mokhtar, A. M. Asiri, S. A. Al-Thabaiti,
S. N. Basahel, B. M. Weckhuysen, ChemCatChem 2014, 6, 772-783;
b) D. Cai, Y. Ma, Y. Hou, Y. Cui, Z. Jia, C. Zhang, Y. Wang, F. Wei,
Catal. Sci. Technol., 2017, 7, 2440–2444.
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Entry for the Table of Contents
FULL PAPER
A
series of nano-sized SAPO-34
Qiming Sun, Ning Wang, Risheng Bai,
Guangrui Chen, Zhiqiang Shi, Yongcun
Zou, and Jihong Yu*
catalysts with tunable hierarchical
structures are synthesized in the
system
triethylamine(TEA)-H2O by using
mesoporogen-free nanoseed-
assistant method. The nano-sized
hierarchical SH-3.0 catalyst
(TEA/Al2O3=3.0) shows the highest
selectivity of ethylene and propylene
up to 85.4%, which reaches the top
level in MTO reactions ever reported
under the similar conditions.
of
Al2O3-H3PO4-SiO2-
Page No. – Page No.
a
Mesoporogen-Free
Synthesis
of
Nano-sized Hierarchical SAPO-34
Zeolite with Reduced Template
Consumption and Excellent MTO
Performance
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