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A facile synthesis for zeolite ZSM-5 by the template hexamethyleneimine by facile MW aging and it's application in ethanol to olefin and aromatics conversion.
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5/28/2018 Synthesis of ZSM-5 with hexamethylineimine
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ByImteaz AhmedPhD candidate
Green Nanomaterials Research Center& Dept. of Chemistry
Kyungpook National UniversityRepublic of Korea
5/28/2018 Synthesis of ZSM-5 with hexamethylineimine
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IntroductionExperimental
Results and discussion
Summary
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Introduction
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Zeolite ZSM-5 with an MFI structure is one of
the most widely used and studied structures
because of its special pore structure, good
stability and high acidity.
Especially, ZSM-5 has been very widely used
in various chemical industries for acid
catalyses.
So far, ZSM-5 has been prepared with tetra-n-
propyl ammonium hydroxide (TPAOH) as a
templating molecule (template) or structure-
directing agent. However, the cost of TPAOH
is very high.
Pore structure of ZSM-5
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In this study, the facile synthesis of ZSM-5 from
gels using a HMI template under varying reaction
conditions (such as Al2O3/SiO2, HMI/SiO2and H2O/
SiO2ratios, pHs, reaction times, etc.) was reported.
Especially the effects of MW aging were shown forthe synthesis of ZSM-5 from gels containing the
HMI template.
The obtained ZSM-5 was used in the dehydration of
simple alcohols such as ethanol and n-butanol, and
the results were also compared with those obtainedwith a commercial ZSM-5 zeolite in order to
estimate the potential applications of the produced
ZSM-5 zeolite.
3 dimensional structure of
ZSM-5
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7
15.1 g TEOS was hydrolyzed in
13.7 mL 0.3 M aqueous
solution of HCL at room temp.
for 2 h to get the gel mixture.
An aqueous solution was
obtained by mixing NaAlO2,
NaOH, hexamethylen eimine
(HMI) and water.
the above two solutions were placed in MW at 60 oC for 1
h to give the final synthesis gel mixture. The composition
of the gel was: SiO2 : X NaOH : Y AlO2: Z HMI : 20 H2O.
+
Finally, the slurry was transferred to a Teflon-lined stainless steel
autoclave and left to crystallize statically at 150 C. Products from the
synthesis were separated by centrifugation, followed with washing
with deionized water and air-drying at 100 C.
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XRD:
Bruker D2 Phaser
SEM:
Hitachi, S-4300
N2 ads.: Micromeritics,
Tristar II 3020
pH:
Horiba pH meter F-51
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N2
M.F.C
Feed
F.I.D
200
200
ReactionTemp. :
200450
Flow diagram of the processes Equipment used for the processes
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Results and discussion
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Sample
Synthesis conditions Textural properties
MW aging
temp.
[oC]
Synthesis
time
[d]
HMI/SiO2
ratio
H2O/SiO
2
ratio
BET
surface area
[m2/g]
Micropore
volume
[cm3/g]
Total pore
volume
[cm3/g]
A 30 3 0.6 20 248 0.09 0.14
B 60 3 0.6 20 333 0.13 0.23
C 90 5 0.6 20 308 0.11 0.19
D 120 5 0.6 20 292 0.11 0.18
E 60 3 1.2 20 312 0.12 0.19
F 60 3 0.6 12 325 0.12 0.20
Comm. - - - - 360 0.16 0.28
MW aging time was 1 h and the synthesis temp. was
175 oC. SiO2 to Al2O3molar ratio was taken as 60.
Typical composition: SiO2: 0.017 Al2O3: 0.075
Na2O: 0.6 HMI : 20 H2O0.0 0.2 0.4 0.6 0.8 1.0
0
30
60
90
120
A
B
C
D
E
F
Comm.
Quantityadsorbed(cm
3/g)
Relative pressure (P/Po)
N2adsorption isotherms
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0 20 40 60 80 100 1200.00
0.25
0.50
0.75
1.00
Relativecrystallinity
Time (h)
(b)
5 10 15 20 25 300
5000
10000
15000
20000
25000
(a)
Calculated
Intensity(a.u.)
2 theta (deg)
96 h
72 h
48 h
36 h
24 h
18 h
6 h12 h
XRD patterns Relative crystallization curve
The XRD patterns matched nicely with those of the ZSM-5 (MFI) structure,suggesting that ZSM-5 zeolite can be obtained from the HMI template under suitable
conditions.
The X-ray crystallinity of the ZSM-5 increased with the reaction time up to 72 h and
there was no change in the XRD pattern with further increase in time up to 96 h.
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5 10 15 20 25 300
1500
3000
4500
After 3 dIntensity(a.u.)
2 theta (degree)
After 7 d
(c)
5 10 15 20 25 300
2000
4000
6000
8000
After 7 d
After 3 d
Intensity(a.u.)
2 theta (degree)
(a)
5 10 15 20 25 300
1000
2000
3000
4000
After 3 d
After 7 d *
*
*
**
**
(b)
Intensity(a.u.)
2 theta (degree)
*
5 10 15 20 25 300
300
600
900
1200
(d)
Intensity(a.u.
)
2 theta (degree)
After 7 d
After 3 d
Only MW aging was very effective in the ZSM-5
synthesis up to 4 d (after 7 d, an unknown impurity phase
was observed);
Aging under conventional heating was not efficient (aging
by conventional heating at 60 oC and aging at room
temperature led to amorphous materials and MFI/MOR
mixed zeolites (after 7 d), respectively)
Syntheses without aging led only to amorphous materials.
MW, 60 oC, 1 h Stirred, 25 oC, 20 h Stirred, 60 oC, 20 h
Without significant aging
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5 10 15 20 25 30 35 400
5000
10000
15000
20000
25000SiO
2/Al
2O
3= 80
SiO2/Al
2O
3= 60
SiO2/Al
2O
3= 40
SiO2/Al
2O
3= 20
SiO2/Al
2O
3= 10
Intensity
(a.u.)
2 theta (degree)
ZSM-5 was obtained from gels with a
SiO2/Al2O3 ratio of 40 60. A
SiO2/Al2O3 ratio of 80 or 10 leads to
an amorphous phase.
Zeolite gmelinite (GME structure) was
obtained at a SiO2/Al2O3ratio of 20.
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10 15 20 25 300
4000
8000
12000
16000
H2O / SiO
2= 12
H2O / SiO2= 16
H2O / SiO
2= 20
H2O / SiO
2= 60
Intensity(a.u.)
2 theta (degree)
(a)
10 15 20 25 300
10000
20000
30000
40000
HMI / SiO2= 1.2
HMI / SiO2= 0.6
HMI / SiO2= 0.3
Intensity(a.u.)
2 theta (degree)
(b)
Effect of water content Effect of HMI content
A very diluted precursor (H2O/SiO2=60) led to amorphous materials, and a ZSM-5
with low crystallinity was obtained with precursors having a low HMI content
(HMI/SiO2=0.3).
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5 10 15 20 25 300
5000
10000
15000
20000
Intensity(a.u.)
2 theta (degree)
pH 9.8
pH 11.5
pH 12.3
pH 12.8
pH 13.5
the pH of the precursor was also very important
for the crystallization of ZSM-5 zeolites.
A pH of 12.8 was the optimum basicity for the
synthesis.
Higher and lower pH led to poor crystallinity
and amorphous (or dense-phase) materials,
respectively.
Even though the synthesis condition is quitenarrow, highly porous ZSM-5 can be
synthesized.
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10 20 300
2500
5000
7500
10000
240 min
120 min
60 min
30 min
10 min
Intensity(a.u.)
2 theta (degree)
A long or short aging time (at 60 oC) was not
effective for the crystallization of ZSM-5, and
60 min were the optimum duration for aging.
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5 10 15 20 25 300
7000
14000
21000
28000
30oC
60oC
90oC
120oC
Intensity(a.u.)
2 theta (degree)
(b)
5 10 15 20 25 300
5000
10000
15000
20000
30oC
60 oC
90oC
120oC
Intensity(a.u.)
2 theta (degree)
(a)
The crystallinity of the zeolite decreased as the aging temperature increased
above 60 oC.
The optimum aging temperature was 60 oC because a low temperature of 30oC was also not effective to produce highly crystalline ZSM-5.
3 d synthesis 5 d synthesis
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100 200 300 400 500
H-ZSM-5 (HMI)
H-ZSM-5 (comm.)
Intensity(a.u.)
Temp. (oC)
synthesis temp. = 175 oC,
Synthesis time = 3 d,
SiO2/Al2O3= 60.
The ammonia-TPD, confirms the acid strength and
acid concentration of H-ZSM-5(HMI) obtained with
the HMI template are very similar to those of a
commercial ZSM-5 zeolite (H-ZSM-5(Comm.)).
Moreover, the synthesized H-ZSM-5(HMI) has not
only weak but also strong acid sites. Therefore, the
ZSM-5(HMI) can be used in various acid-catalyzed
reactions.
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Ethanol 250 ~ 400 oC
N2pretreatment,
Feed = 0.1 cc/h,
Catalyst = 0.2g,
WHSV = 0.3
Temp.
Selectivity (mol %)
C2 C3 C4C5
/C6+
Benz
ene
Tolue
ne
Ethylbe
nzene
Xyle
ne
Cum
eneC9
+
250 oC 92.7 0.9 2.3 2.1 - - 0.2 0.4 0.1 1.1
400 oC 14.8 13.3 5.6 4.1 1.0 9.1 2.1 18.8 5.4 25.8
At the low temperature of 250 oC, ethanol is converted mainly into ethylene
through a dehydration reaction, similar to reported results.
Not only olefins but also aromatics such as xylenes and toluene were obtained
at 400o
C with the zeolite.
Aromatics are produced because of aromatization of the formed ethylene or
olefins. Therefore, the results of the ethanol conversion show the acidity of the
ZSM-5(HMI), in agreement with the ammonia TPD result.
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Temp. Zeolite
Selectivity (mol %)
C2 C3 C4C5
/C6+
Benz
ene
Tolu
ene
Ethy
lben
zene
Xyl
ene
Cu
me
ne
C9+
250 oC
H-ZSM-
5(Comm.) 0.1 0.9 79.3 6.4 1.2 2.9 0.3 2.3 2.8 3.9
H-ZSM-5(HMI) 0 1.2 94.8 0.5 0.2 1.5 0.1 1.1 0.2 0.1
400 oC
H-ZSM-
5(Comm.)8.6 16.3 8.8 7.3 1.2 13.3 1.5
20.
34.5 18.2
H-ZSM-5(HMI) 9.0 27.4 7.2 2.6 3.5 21.6 1.217.
22.8 7.4
Butanol 200 ~ 400 oC
N2pretreatment,Feed = 0.1 cc/h,
Catalyst = 0.2g,
WHSV = 0.3
HMI ZSM-5 (60), at 12 h
Temp. ZeoliteC
4
1-B T-2-B C-2-B
250 oCH-ZSM-5(Commercial) 14.9 53.3 31.8
H-ZSM-5(HMI) 16.6 50.9 32.6
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4 6 8 10 12
0
20
40
60
80
100
Conversion&
selectivity
Time (hr)
Conversion
C3
C4
C5C6
Aromatics
4 6 8 10 12
0
20
40
60
80
100
Conversion&
selectivity
Time (hr)
Conversion
C3
C4
C5C6
Aromatics
H-ZSM-5 (HMI) H-ZSM-5 (Comm.)
The two zeolites produced mainly butenes at 250 oC and the conversions, irrespective of
the zeolites, were very stable up to 12 h at that temperature.
The selectivity for butenes such as 1-butene, cis-2-butene and trans-2-butene did not
remarkably depend on the catalysts (Table 3).
The selectivity for butenes over H-ZSM-5(HMI) was higher than that over H-ZSM-
5(Comm.)
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10 m 1.0 m
H-ZSM-5 (HMI) H-ZSM-5 (comm.)
Higher crystal size was obtained for H-ZSM-5 synthesized from HMI.
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Commercially valuable ZSM-5 zeolite can be produced from gels containing HMI asan inexpensive template.
For the successful synthesis, selected conditions should be followed. Some of them
are strict aging under MW irradiation (60 oC for 1 h), a SiO2/Al2O3ratio of 40-60, pH of
~ 12.8 and so on.
When the aging time under MW was too long or too short, or when the aging
temperature was too high, only amorphous phase was produced.
The synthesized ZSM-5 was converted into H-ZSM-5 by ion exchange and could be
used in acid-catalyzed reactions because of the acidic property of the obtained H-ZSM-5.
The H-ZSM-5 produced by the HMI template was comparable to the commercial H-
ZSM-5 in TPD patterns and in its performance of dehydrating simple alcohols.
It can be concluded that the produced H-ZSM-5 can be used in various acid-catalyzed
reactions.
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Thank you for your kind attention