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portant monomer for the production of synthetic rubber. We
explored a number of Lewis acidic (Sn- and Zr-Beta) and
hybrid (containing both Lewis and Brønsted acid sites) Zn con-
taining zeolites and found that the hybrid materials are more
active and selective. Zn containing H-ZSM-5 was the optimal
catalyst of those investigated exhibiting high activity and se-
lectivity to the target product; 3-buten-1-ol. Zn containing H-
beta is active but not selective, since it catalyzes a series of un-
desired reaction steps, mainly involving 3-buten-1-ol sequential
reactions to form C-5 compounds. Zn addition favors both ac-
tivity and 3-buten-1-ol selectivity however, the catalytically
active site is the Brønsted acid sites. An optimum Brønsted
acid site density is essential to achieve high activity and 3-
buten-1-ol selectivity and to suppress undesired side reactions.
beta samples. In situ Fourier transform infrared (FTIR) spectra were
obtained on an Agilent Cary 660 FTIR Spectrometer equipped with
a MCT detector (128 scans at a spectral resolution of 2 cm ) with
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1
a homemade in situ transmission cell. A vacuum level of <1.3ꢂ
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1
0
MPa in the transmission cell was reached through a vacuum
manifold, which is connected to a mechanical pump and a diffu-
sion pump. A self-standing zeolite wafer was loaded to a custom-
made sample holder, followed by annealing at 723 K under
vacuum to completely remove adsorbed water. After cooling to
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323 K, ca. 1.3ꢂ10 MPa of deuterated acetonitrile (CD CN) was in-
3
troduced to the transmission cell via the vacuum manifold, and IR
spectra were collected in the process of heating the zeolite wafer
to 723 K.
Catalyst evaluation
The reaction of formaldehyde with propylene was carried out in a
50 mL batch reactor (Parr Instrument Company) under magnetic
stirring. Temperature controlled with a band heater and a control-
ler (Dwyer Instruments, Inc.). In a typical experiment, the reactor
was loaded with required amounts of the reactants (propylene=
Experimental Section
Catalyst Preparation
Zn containing zeolites: A series of zinc-containing zeolites were
prepared by ion exchange from commercially available samples.
The parent zeolites were: ferrierite (CP914C, Si/Al=10, Zeolyst In-
0
.75 MPa and paraformaldehyde=0.1 g) in the presence of a sol-
vent (1,4-dioxane=20 mL) and an appropriate amount of catalyst
0.25 g). Reaction temperature was set constant at 423 K unless
+
(
ternational, H form obtained after calcination at 773 K for 20 h
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otherwise stated. After reaction, the reactor was cooled down
using an ice bath. The gas phase was collected using a gas bag
and liquid phase was collected after catalyst separation using filtra-
tion. The gas phase was analyzed using an Agilent 7890A gas chro-
matographer equipped with an HP-PLOT Q column (30 m length
and 0.53 mm diameter) and an FID detector. The liquid phase was
analyzed using an Agilent 7890B gas chromatographer equipped
with an Innowax column (30 m length and 0.25 mm diameter) and
an FID detector as well. Liquid products were also identified with
gas chromatography (GC)-mass spectroscopy (MS) with a Shimadzu
GC-2010 having the same Innowax column and being coupled
with a GC-MS-QP2010 PLUS. Reaction products were quantified
using multi-point calibration curves. Conversion of formaldehyde
was calculated based on products and reaction stoichiometry
using the equation:
under 100 mLmin air flow), H-SSZ-13 (Si/Al=12) synthesized
+
using a protocol reported elsewhere, H form of the zeolite used
[25]
for ion-exchange, ZSM-5 (CBV 2314 and CBV 5524G, Si/Al=11.5
+
and 25, Zeolyst International, H form obtained after calcination at
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73 K for 20 h under 100 mLmin air flow), and beta (CP814E*, Si/
+
Al=12.5, Zeolyst International H form obtained after calcination
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1
at 773 K for 20 h under 100 mLmin air flow,). Ion-exchange was
performed at 343 K for 5.5 h using an aqueous solution of 0.005m
Zn(NO ) ·6H O (Sigma Aldrich), the ratio of zeolite mass per
3
2
2
volume of solution was 1 g per 100 mL. The exchanged sample
was then dried overnight at 383 K and finally calcined at 773 K
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under 100 mLmin air for 20 h. One sodium-containing sample
was prepared by impregnation of the ion-exchanged Zn/H-ZSM-5
(
(
H-ZSM-5 Si/Al=11.5 nominal) with an aqueous solution of NaNO3
Sigma Aldrich). Two samples of zinc-containing H-ZSM-5 (Si/Al=
1
1.5) were prepared using the dry impregnation method. Theoreti-
moles of CH O converted to all products
cal Zn/Al ratios were 0.5 and 1.0. For 1 g of zeolite, 0.4 mL of DI
H O was used to dissolve the required amount of Zn(NO ) ·6H O.
2
Conv: ¼
moles of CH O initially loaded
2
2
3 2
2
The zinc precursor was dropwise added to H-ZSM-5. The samples
were dried overnight at 383 K and finally calcined at 773 K under
Selectivity was carbon-based excluding side products such as
methanol and 2-propanol formed via formaldehyde and propylene
through independent side reactions; these reactions were however
only observed with beta zeolite (see Results and Discussion for
more details).
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1
00 mLmin air for 20 h.
Sn-beta and Zr-Beta: Zr-beta and Sn-beta were synthesized
[26,27]
according to protocols described previously.
moles of C in product i
C-based selectivity ¼
Analytical Section
moles of C in all products
Nitrogen physisorption was performed in a Micromeritics 3Flex
system at 77 K to determine the micropore volume using the t-
plot method. Samples were degassed overnight at 523 K and back-
filled with dry nitrogen prior to analysis. Scanning electron micros-
copy images were recorded on a JEOL JSM 7400F at 10 mA. X-ray
diffraction (XRD) patterns were collected using a Bruker D8 diffrac-
tometer with CuKa radiation. The diffraction pattern was collected
for 2 s at each increment of 0.028 between 5 and 508. X-ray fluores-
cence (XRF) using a Rigaku WDXRF was used for elemental analysis
of the Zn containing samples. Coupled plasma-atomic emission
spectroscopy (ICP-AES) analysis was performed by Galbraith Labo-
ratories (Knoxville, TN) to determine Zr and Sn content of the final
The heterocycle compounds are abbreviated as follows: 1,3-Diox-
ane, 4-methyl- is abbreviated as m-dioxane, tetrahydro-4H-pyran-4-
ol is abbreviated as oxan-4-ol and 5,6-dihydro-2H-pyran is abbrevi-
ated as 2H-pyran.
Acknowledgements
We are grateful to Dr. W. Zheng for his help with Scanning elec-
tron microscopy. Research was supported as part of the Catalysis
Center for Energy Innovation, an Energy Frontier Research Center
&
ChemCatChem 2017, 9, 1 – 10
8
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