A catalyst for one-step isoparaffin production via fischer-tropsch synthesis: Growth of a H-mordenite shell encapsulating a fused iron core

Article abstract of DOI:10.1002/cctc.201300336

Fused iron (FI), is a general Fischer-Tropsch synthesis (FTS) catalyst and can be used to convert syngas (CO+H₂) into normal hydrocarbons. The syntheses of HZSM-5 or H-β zeolite-shell encapsulated catalysts for FTS have been reported previously, however, conventional zeolite-shell synthesis generally employs an organic template, which is neither economic nor environmentally benign. Here we report the synthesis, without using an organic template, of a millimeter-sized defect-free capsule catalyst covered by a MOR zeolite shell (thickness of 23μm) on FI pellets. The capsule catalyst (HMOR/FI) exhibited excellent performance for FTS, greatly increasing the selectivity of middle isoparaffins. Compared with the pure FI catalyst, the CO conversion of the HMOR/FI capsule catalyst increased remarkably and the iso/n ratio was almost 8times that of the pure FI catalyst. This report provides an effective route to synthesize a capsule catalyst, which can reduce costs effectively and is also more environmentally benign than the current conventional zeolite-shell synthesis. Capsule catalyst: A H-mordenite (HMOR) zeolite shell is directly synthesized, without an organic template, on a silicalite-1 coated fused iron catalyst. When applied to Fischer-Tropsch synthesis (FTS), the selectivity of the prepared capsule catalyst to middle isoparaffins is significantly better than a physical mixture catalyst.

Full text of DOI:10.1002/cctc.201300336

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DOI: 10.1002/cctc.201300336
A Catalyst for One-step Isoparaffin Production via Fischer–
Tropsch Synthesis: Growth of a H-Mordenite Shell
Encapsulating a Fused Iron Core
[
a, b]
[b]
[c]
[b]
[a]
Qihang Lin,
Guohui Yang, Xiaonian Li, Yoshiharu Yoneyama, Huilin Wan,* and
[b]
Noritatsu Tsubaki*
Fused iron (FI), is a general Fischer–Tropsch synthesis (FTS) cat-
23 mm) on FI pellets. The capsule catalyst (HMOR/FI) exhibited
excellent performance for FTS, greatly increasing the selectivity
of middle isoparaffins. Compared with the pure FI catalyst, the
CO conversion of the HMOR/FI capsule catalyst increased re-
markably and the iso/n ratio was almost 8 times that of the
pure FI catalyst. This report provides an effective route to syn-
thesize a capsule catalyst, which can reduce costs effectively
and is also more environmentally benign than the current con-
ventional zeolite-shell synthesis.
alyst and can be used to convert syngas (CO+H ) into normal
2
hydrocarbons. The syntheses of HZSM-5 or H-b zeolite-shell en-
capsulated catalysts for FTS have been reported previously,
however, conventional zeolite-shell synthesis generally em-
ploys an organic template, which is neither economic nor envi-
ronmentally benign. Here we report the synthesis, without
using an organic template, of a millimeter-sized defect-free
capsule catalyst covered by a MOR zeolite shell (thickness of
Introduction
A wide range of Fischer–Tropsch synthesis (FTS) hydrocarbon
low-molecular hydrocarbons in high temperature Fischer–
Tropsch (HTFT) reactions, also its methane selectivity does not
increase as drastically with increasing temperature, as com-
products, which are converted from syngas (CO+H ), can be
2
[
1]
[2]
adjusted by controlling reaction conditions and catalysts. In
conventional FTS, products obey the Anderson–Schultz–Flory
[4]
pared to Co-based catalysts. Most of zeolites are synthesized
in a basic environment, so the fused iron (FI) catalyst core is
suitable for zeolite-shell synthesis because of its strong me-
chanical resistance and reliable anticorrosion properties com-
pared with other Fe-based catalysts prepared by impregnated
or precipitated methods.
(ASF) distribution, which is hard to break without introducing
other active sites. Zeolite shells not only provide acidic sites for
further hydrocracking and isomerization of FTS hydrocarbons,
but they also suppress chain growth, owing to their unique
pore and channel structure. The capsule catalyst, where acidic
zeolite shell enwraps a Fe- or Co-based FTS catalyst core, is
more beneficial to directly produce middle isoparaffins from
Zeolites are usually prepared by two methods. One is the
template method, in situ direct hydrothermal synthesis using
the alkyl base as a template. The as-synthesized zeolite should
be treated carefully to remove template in the calcination
step, otherwise the pores will be enlarged and result in col-
lapse. The advantages of template method are avoiding impur-
ities effectively and convenience. Our group has successfully
prepared H-b/Co/Al O and HZSM-5/Fe capsule catalyst for the
[
3]
syngas than a physical mixture catalyst. More attention is
paid to Fe-based catalysts because of their ability to synthesize
[a] Q. Lin, Prof. H. Wan
State Key Laboratory of Physical Chemistry of Solid Surfaces
National Engineering Laboratory for Green Chemical Production
of Alcohols, Ethers and Esters, Department of Chemistry, College
of Chemistry and Chemical Engineering
Xiamen University
2
3
one-step synthesis of gasoline-range hydrocarbons from
syngas, and limited the hydrocarbon distribution to less than
[3a,b]
C12.
Zong and co-workers have prepared a R-Fe@ HZSM-5
Xiamen 361005 (P.R. China)
Fax: (+86)592-218-6569
E-mail: hlwan@xmu.edu.cn
catalyst by using porous Raney FeAl as the core to investigate
[5]
FTS performance. Another method is the seed-assisted
method, in which a zeolite matrix is induced by a zeolite
[
b] Q. Lin, G. Yang, Y. Yoneyama, Prof. N. Tsubaki
Department of Applied Chemistry, School of Engineering
University of Toyama
[6]
seed. Many zeolites have been synthesized by this method;
[6b]
G. Majano et al. has synthesized ZSM-5,
and Y. Kamimura
Gofuku 3190, Toyama 930-8555 (Japan)
Fax: (+81)076-445-6846
E-mail: tsubaki@eng.u-toyama.ac.jp
et al. has developed a seed-assisted method to synthesize sev-
[7]
[8]
eral zeolites, such as beta and ZSM-12. It is possible to syn-
thesize a zeolite shell by both of these routes. However, so far,
only few zeolites such as Silicalite-1 and ZSM-5 are reported to
[
c] Prof. X. Li
Institute of Industrial Catalysis
Zhejiang University of Technology
Hangzhou, Zhejiang 310032 (P.R. China)
[3c,9]
be able to be synthesized as shell onto the substrate.
In
the present study, the HMOR zeolite shell is directly synthe-
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201300336.
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sized, without using an organic template, on the silicalite-1 zeo-
lite decorated FI catalyst.
BET surface areas measurements
In general, bifunctional catalyst Pt/HMOR is typically applied
in a reaction of hydroisomerization of normal paraffins to
The specific surface areas of FI catalyst, HMOR and HMOR/FI
were measured by a NOVA 2200e surface area analyzer. The FI
catalyst, with its composition listed in Table 1, exhibited an
almost nonporous structure, and its specific surface area was
[10]
branched isomers in the petroleum refining industry.
This
catalyst provides two active centers: hydrogenation sites and
acidic sites. The metal phase forms olefinic intermediates,
which can also be produced directly from syngas under FTS
conditions. The zeolite phase forms carbenium ions to imple-
ment hydrocracking and the isomerization reaction for which
2
À1
2
À1
only 3.2 m g , whereas that of HMOR was 367.9 m g . As
both FI and HMOR were contributors to the HMOR/FI surface
area, 96 wt% FI and 4 wt% HMOR result in 3.2ꢁ0.96+367.9ꢁ
2
À1
0.04=17.8 m g , which matched accurately with the mea-
2
À1
H is available from syngas. Compared to H-b zeolite, HMOR
2
sured data (17.8 m g ).
zeolite has more steric hindrance to restrain the diffusion of
gaseous molecules. When heavy molecular hydrocarbons stay
in channel for a longer time, the hydrocarbons will undergo re-
arrangement and hydrocracking process on strong acidic sites.
Herein, the HMOR zeolite shell is selected as a shell to conduct
isomerization and hydrocracking of FTS normal hydrocarbons
Table 1. Surface EDS analysis results of FI.
[
a]
Catalyst
Atomic ratio [%]
Fe
Ca
K
Al
Si
FI
96.4
0.8
0.6
1.1
0.1
(
diesel), to obtain isoparaffin, premium gasoline, directly from
syngas.
Fused iron (FI) catalyst has a low surface area and lacks large
[
a] Oxygen is not included.
amounts of surface hydroxyl groups. Based on this meaning,
modifying the surface of FI is a key point. Taking the physically
adhesive (PA) method, the FI surface adsorbs silicalite-1 zeolite
via small amounts of organic adhesive, such as 3-aminopropyl-
Temperature programmed desorption of ammonia
NH -TPD)
(
3
NH -TPD experiment was applied to detect acidic sites of
3
[
11]
trimethoxysilane (AP-TMS). MOR zeolite bulk can be synthe-
HMOR zeolite and capsule catalyst. The NH desorption profile
3
[
12]
sized without a template. Under our synthesis conditions,
the MOR zeolite shell is obtained successfully. This is the first
time a MOR shell has been used to enwrap a FTS catalyst, en-
larging the MOR zeolite as a shell candidate in the FTS cata-
lysts field.
of HMOR/FI was similar to that of HMOR, but shifted slightly to
lower temperature as displayed in Figure 2. Both of the two
profiles were evidently divided into low-temperature (LT,
<2508C) and high-temperature (HT,>2508C) regions. In gen-
eral, the LT peak was assigned to weakly adsorbed ammonia,
likely those that are hydrogen bonded, and the HT peak was
[13]
ascribed to strong acidic sites. The amount of acidic sites
À1
concentration for HMOR was calculated to be 2.1 mmolg
,
HMOR
À1
Results and discussion
and
for
HMOR/FI
0.072 mmolgcat
(equivalent
to
À1
1
.8 mmolgHMOR,capsule ). The loss of acidic sites was caused by
XRD analysis
the formation of Si-OH-Al bonds, which tightly anchored the
surface of FI core catalyst and the inner side of zeolite shell,
unlike conventional zeolite powder. In addition, potassium
may migrate from the bulk of FI to the boundary of HMOR
under the air calcination procedure, further neutralizing the
No template was needed in the zeolite-shell synthesis process
here. As seen in Figure 1a and b, the FI exhibited Fe1 O pat-
Àx
tern, while Silicalite-1 zeolite was synthesized successfully. The
pure MOR zeolite was confirmed by XRD as presented in Fig-
ure 1c. As shown in Figure 1d, both HMOR peaks and Fe cata-
lyst peaks were confirmed, proving the effectiveness of this
kind of catalyst preparation method.
[14]
acidic sites, as illustrated by X. Y. Gwagwa et al. This linkage
Figure 1. XRD patterns of a) Pure FI, b) Silicalite-1, c) HMOR, and d) HMOR/FI.
Figure 2. The NH
3
-TPD profiles of a) Pure FI, b) Silicalite-1/FI, c) HMOR, and
(
! Fe1ÀxO, * Mordenite).
d) HMOR/FI.
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between core and shell might also weaken the acidic site
strength of HMOR/FI, making both the HT and LT peak temper-
The physically adhesive (PA) method was applied here to re-
place the conventional direct template synthesis, as in
Scheme 1. The remaining AP-TMS/EtOH and Silicalite-1/EtOH
could be reused, which could reduce the energy consumption
and environmental pollution. The silicalite-1 layer provided Si-
OH to stick zeolite shell. Consequently, without pre-treatment
by silicalite-1, the MOR shell could not form, owing to the ab-
sence of Al-OH and Si-OH groups.
ature profiles of NH -TPD of HMOR/FI lower than those of
3
HMOR.
SEM-EDS measurements
In our experiments, pure fused iron exhibited a flat surface as
shown in Figure 3a. As presented by our previous reports, the
hydrothermal synthesis of HZSM-5/Fe needed to be performed
twice in succession by direct template synthesis to activate the
Pure HMOR zeolite was synthesized as shown in Figure 3d.
There was an isolated, discrete ellipsoidal phase formed by this
new template-free method. The surface of HMOR/FI shown in
Figure 4a exhibited compact and integral phase. From the sur-
face element analysis by EDS as shown in Figure 4b, no Fe
signal was detected. It is clear that MOR shell without cracks or
pinholes was synthesized on the FI core according to the de-
signed route. The EDS linear scan image in Figure 4c and Fig-
ure 4d indicated that the thickness of HMOR shell was about
[
3a]
FI surface hydroxyl groups.
The lack of surface hydroxyl
groups retarded the zeolite-shell synthesis rate and made the
zeolite shell enwrap FI loosely. The SEM image in Figure 3b ex-
hibited homogeneous cubic Silicalite-1 particles (mean size of
about 0.55 mm), without the core catalyst.
23 mm. An EDS linear scan, parallel to the MOR shell, was also
displayed in Figure 4e, where the Si/Al molar ratio line from
EDS analysis was stable, indicating an integral and continuous
shell. Si/Al ratio of 6.3 as in Figure 4 f was considerably less
than its preparation recipe value of 14.2, which showed that
the Al ion behaved as preferential adsorption in the hydrother-
mal process. Meanwhile, the introduction of Al brought more
acidic sites and promoted the hydrocracking and isomerization
reaction in our modified FTS reaction with the aid of H from
2
syngas.
Catalytic performances for one-step isoparaffin synthesis via
FTS from syngas
The catalytic reaction performances of FI, Silicalite-1/FI,
HMOR+FI and HMOR/FI were compared in Table 2. The pure
FI catalyst, with the chemical composition in Table 1, exhibited
CO conversion of 19.0%. The activity of Silicalite-1/FI was
Figure 3. The surface of a) Pure FI, b) Silicalite-1 zeolite, c) Silicalite-1 coated
FI, and d) Pure HMOR. Scale bars=10 mm (a,d), 5 mm (b,c).
21.4%, slightly higher than that of pure FI. Probably the sur-
face decoration with silicate group and followed silicalite-1 ad-
sorbing brought higher hydrogen availability, thus promoting
For the seed-assisted synthesis of a zeolite separation mem-
brane, it is necessary to polish the negatively charged sub-
strates, such as porous stainless steel, alumina, and silica, with
positive organic adhesive, such as 3-aminopropyl-trimethoxysi-
lane (AP-TMS) or 3-chloropropyl-trimethoxysilane (CP-TMS).
The polished surface adsorbs the zeolite seed with the nega-
tive charge for the following zeolite growth from the seeded
surface under synthesis environment. Based on this design, Sili-
calite-1 zeolite was attached to
[15]
the CO conversion as proved by previous researchers. Physi-
cal mixture catalyst increased CO conversion to 26.5%, and
HMOR/FI capsule catalyst presented the highest CO conversion
[16]
of 47.5%. As discussed by A. Martꢂnez et al., the intimacy
degree between two component catalysts is important to tune
reaction performance. Here, physical mixture catalyst was pre-
pared by mixing pre-pelletized bodies of FI and zeolite. Since
the FI surface via AP-TMS organ-
ic adhesive to form an oval mor-
phology (axis size 160ꢁ460 nm)
as shown in Figure 3c. In con-
trast, CP-TMS was not used here
owing to its harmful deactiva-
tion effect on FTS by halogen el-
ements. The surface Al-OH or Si-
OH groups of modified FI were
considered as active species for
the following zeolite growth.
Scheme 1. The schematic image about the synthesis procedure of HMOR/FI capsule catalyst without template.
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No noticeable variation was observed during repeated experi-
ments of capsule catalysts, as shown in Table S1 in the Sup-
porting Information, guaranteeing that the proposed new cat-
alytic reaction were repeatable.
Physical mixtures of conventional FTS catalysts and acidic
zeolite are widely studied and can increase selectivity to
middle isoparaffins. After FTS the products go on to react with
the zeolite. The zeolite provides acidic sites for hydrocracking
and isomerization of these normal hydrocarbon products in
succession. For a physical mixture catalyst the zeolite and the
FTS catalyst are randomly distributed. Coupling the two reac-
tions between FTS and hydrocracking/isomerization is
a random process for this catalyst. For a capsule catalyst, how-
ever, linear hydrocarbons formed in the core (FTS catalyst)
must diffuse through the acidic zeolite shell. This process
greatly increases the collision possibility between linear hydro-
carbons and acidic sites in zeolite, therefore the capsule cata-
lyst exhibit higher selectivity to middle isoparaffins than a phys-
ical mixture catalyst, as compared in Figure 5 and Table 2.
Normal hydrocarbons without branches could enter the zeo-
lite membrane from the inner side smoothly, being cracked
and isomerized to form shorter isoparaffins on the acidic sites
at the inner wall of zeolite channels. The escaped isoparaffins
with their branched structure and related steric impediment
could not return to the original capsule catalyst covered by
zeolite membrane; also was impossible to enter the other
neighboring capsule catalysts. By this molecular-shape-selec-
tive property, the capsule catalyst realized extremely high iso-
paraffin selectivity. The ratio of isoparaffins to normal paraffins
Figure 4. a) HMOR/FI surface image, b) HMOR/FI surface EDS analysis,
c,e) HMOR/FI cross-sectional images, and d,f) EDS analysis across the line of
c and e. Scale bars=5 mm (a), 30 mm (c,e).
(
iso/n) on the FI catalyst was only 0.11. From Table 2, the iso/n
the FI was a nonporous catalyst, the heavy FTS hydrocarbons
mostly accumulated on its surface. HMOR zeolite hydro-
cracked/isomerized the heavy hydrocarbons when they dif-
fused from the FI. Therefore, the combined processes en-
hanced the total catalytic activity, as the removal of heavy hy-
drocarbons on the catalyst surface could increase syngas diffu-
sion rate. It is interesting that the CO conversion of the capsule
catalyst was higher than that of the physical mixture, partly be-
cause the intimate contact of acidic zeolite to core catalyst
could decompose waxy hydrocarbons accumulation layer at
the surface more efficiently than what happened in the physi-
cal mixture, accelerating the reactant diffusion and adsorption.
ratio of physical mixture catalyst increased to 0.37, while the
capsule catalyst exhibited the best iso/n ratio as high as 0.87.
Meanwhile, branched hydrocarbons are more stable than
linear hydrocarbons. The interconversion between them may
be available to partly promote the iso/n ratio. In physical mix-
ture or capsule catalysts, the reaction heat brought from exo-
thermic FTS reaction was in situ utilized by endothermic hydro-
cracking of linear FTS hydrocarbons in succession, avoiding the
“hot spot” formation efficiently. Therefore, the selectivity of
methane could be suppressed by the coexisting HMOR zeolite
compared to pure FI. Meanwhile, CO was unrestricted for mix-
ture catalyst, but it was limited by the intrapellet diffusion re-
strictions for capsule catalyst. These restrictions
could lead to a hydrogen-rich environment in the
Table 2. FTS performances of various catalysts.
core section of capsule catalyst, which favors the for-
[
a]
Catalysts
CO Conv.
%]
Sel. [%]
Hydrocarbon Sel. [%]
Iso/n
(nꢀ4)
0.11
0.09
0.37
0.87
mation of CH . Based on the above factors, we dem-
4
[
b]
=
[c]
[
CH
4
CO
2
C
n
C
C
iso
C
12+
onstrated that the CH selectivity of mixture catalyst
4
[
d]
FI
Silicalite-1/FI
19.0
21.4
26.5
47.5
19.4
19.9
14.6
16.0
36.7
37.0
37.2
30.5
51.1
52.5
47.6
45.0
45.9
45.0
42.7
40.8
3.0
2.5
9.7
1.8
2.1
0.6
0.5
was lower than that of others.
[
e]
[f]
HMOR+FI
HMOR/FI
[
g]
14.2
Conclusions
[
1
a] FTS reaction conditions
0 gFI hmol , TOS=20 h. [b] The calculation of CH
:
0.5 g,
H
2
/CO=1/1, 1.0 MPa, 3008C,
WFI/F(CO+H2) =
After being coated by silicalite-1 via AP-TMS, the
MOR/FI capsule catalyst could be synthesized with-
out a template. In FTS, the catalyst not only greatly
increased CO conversion, but also enhanced the iso/
n ratio significantly, owing the proximity of the FI
core to the HMOR zeolite membrane. The excellent
À1
4
selectivity was based on all the
hydrocarbons. [c] iso/n was the ratio of iso-paraffin to n-paraffin with carbon number
more than 3. [d] Fused iron was denoted as FI. [e] Silicalite-1 was attached on the sur-
face of FI via AP-TMS. [f] Physical mixture of FI and HMOR zeolite. [g] Capsule catalyst
with HMOR zeolite as shell and FI as core and this result was the mean value of re-
peated experiments.
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Experimental Section
Preparation of HMOR/FI capsule catalyst
First, as in Scheme 1, the Silicalite-1 zeolite was prepared with pre-
cursor molar ratio of tetraethyl orthosilicate/tetrapropylammonium
hydroxide/EtOH/H O of 1:0.25:4:60. This precursor was stirred for
2
6
h to obtain a homogenous solution. The solution was then trans-
ferred to a Teflon-lined stainless steel autoclave and crystallization
was conducted in the hydrothermal synthesis equipment at 1808C
for 24 h (DRM-420DA, Hiro Company, Japan). The synthesized silica-
lite-1 was centrifuged with water until neutral pH was achieved,
followed by suspension in EtOH to prepare 0.3 wt% Silicalite-1/
EtOH solution. The fused iron (FI) catalyst (Nanjing Chemical Plant,
[17]
0
.85–1.70 mm), was prepared as reported previously,
was im-
mersed in the prepared 1.88 vol.% 3-aminopropyl-trimethoxysi-
lane/EtOH (AP-TMS, 95%, Kanto Chem. Co.) solution in a Teflon
container. It was subjected to hydrothermal treatment at 1008C for
4
h under a rotation of 2 rpm. After washing the unattached AP-
TMS with ethanol, the modified FI pellet was immersed in 0.3 wt%
Silicalite-1/EtOH solution in a Teflon container for another 4 h. Fi-
nally, the excessive silicalite-1 zeolite was washed out with water.
The modified FI was used as core catalyst, denoted as
Silicalite-1/FI.
For the successive zeolite-shell synthesis, NaOH, NaAlO (Wako Co.)
2
and fumed silica (Sigma–Aldrich) were used as starting materials
for MOR. The MOR precursor solution with a molar composition of
Na O/Al O /SiO /H O, 6.25:0.88:25:1168, was stirred in a Teflon con-
2
2
3
2
2
tainer for 6 h. The modified FI core was then added into the MOR
precursor solution in the Teflon container and crystallization pro-
cess was conducted at 1808C for 48 h under 2 rpm, as illustrated
in Scheme 1. After zeolite-shell synthesis, the particle was separat-
ed, washed with water until neutral pH, and dried at 608C for 12 h.
Then, the obtained Na-MOR/FI was exchanged with 0.5m NH NO
4
3
solution at 808C for 9 h, followed by washing with water several
times. The as-prepared capsule catalyst was dried at 608C for 12 h
and calcined at 5008C for 5 h. This catalyst was denoted as HMOR/
FI. The HMOR zeolite weight percent of catalyst was 4 wt% and Na
signal was not detected by EDS.
Preparation of HMOR zeolite and physical mixture catalyst
The HMOR zeolite powder was synthesized by using the same
method as the shell synthesis as above, but without a core. NaOH,
NaAlO (Wako Co.) and fumed silica (Sigma–Aldrich) were used as
2
starting materials. The MOR precursor solution with a molar com-
position of Na O/Al O /SiO /H O, 6.25:0.88:25:1168, was stirred in
2
2
3
2
2
a Teflon container for 6 h. Then, the MOR precursor solution was
put into the Teflon container, and crystallization process was con-
ducted at 1808C for 48 h under 2 rpm. After synthesis, the powder
was separated, washed with water until neutral pH, and dried at
Figure 5. The product distribution of a) Pure FI, b) Silicalite-1/FI,
c) HMOR+FI, and d) HMOR/FI.
6
0
08C for 12 h. Then, the obtained Na-MOR was exchanged with
.5m NH NO solution at 808C for 9 h, followed by washing with
increase in reaction performance by the MOR/FI capsule cata-
lyst over the physical mixture was attributed to the confine-
ment effect of the core–shell structure of the capsule catalyst
and the shape-selective property of zeolite membrane. This
new catalyst preparation method reduced the cost and em-
phasized a more benign process than the conventional tem-
plate method.
4
3
water several times. The catalyst was dried at 608C for 12 h and
calcined at 5008C in air under static condition using a muffle fur-
nace for 5 h. The obtained powder was granulated into 0.85–
1
.7 mm, and then the HMOR zeolite was mixed with 0.85–1.7 mm
FI. The HMOR weight percent of physical mixture catalyst was also
4 wt%, the equivalent weight percent as that of the capsule cata-
lyst. The physical mixture catalyst was denoted as HMOR+FI.
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Catalyst characterization
Keywords: Fischer–Tropsch synthesis · iron · isoparaffin · MOR
capsule catalyst · zeolite synthesis
The phase structures of the catalysts were measured by X-ray dif-
fraction (XRD) by using a Rigaku RINT2400 diffractometer with CuKa
radiation (l=0.154 nm) in the range of 2q angels 2–808. Opera-
tions were performed at 40 kV and 40 mA.
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Temperature programmed desorption of ammonia (NH -TPD)
3
measurements were performed by using a BELCAT-B-TT (BEL,
Japan) instrument. 30 mg sample was pretreated with Ar gas flow
at 1508C for 1 h. After temperature was cooled down to 808C, the
gas was switched to a NH -He mixture (5 vol.% NH , 20 sccm) for
3
3
3
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4
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3
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This work was financially supported by JST-CREST and NEDO,
Japan. Financial aid from JX (Nippon Oil) Co. Ltd was also ac-
knowledged. Qihang Lin thanks the China Scholarship Council
Received: May 2, 2013
Revised: June 12, 2013
(CSC) for financial support.
Published online on July 16, 2013
ꢀ
2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 2013, 5, 3101 – 3106 3106