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using a certied HCl solution and phenolphthalein. The
ꢂ1
concentration of Me -diquat-6 dihydroxide is 0.6 mol L
.
6
Preparation of ZnAPO-ERI-MW and ZnAPO-ERI-CV zeolites
Typically, 0.784 g of boehmite (Catapal® B, 72.6 wt% Al O ,
2
3
ꢂ1
Sasol) was dissolved in a 4.65 g 0.6 mol L aqueous solution
of Me -diquat-6 dihydroxide, and then 1.30 g H PO (85%)
and 0.832 g Zn(NO $6H O were added. The mixture was
6
3
4
3
)
2
2
stirred until a homogeneous solution was obtained. Then
the gel was evaporated under infrared lamp with stirring
until the nal desired water quantity was achieved. The
molar ratio of the nal gel composition was 0.25Zn(NO ) :
3 4
Fig. 4 NH -TPD profiles of AlPO -ERI and ZnAPO-ERI-MW.
3
2
0
.50Al O : 1.0H PO : 0.25Me -diquat-6 : 45H O. If the ratio of
2 3 3 4 6 2
H O/H PO is higher than 45, a dense phase will be formed. The
2
3
4
represents the relative acid-site density or the number of each
precursor gel was loaded in a 100 mL Teon autoclave, which
was then sealed and placed in a microwave oven (Milestone
ETHOS-D). The mixture was heated to the reaction temperature
23–28
acid-site.
For AlPO -ERI, only one desorption peak at 150–
4
ꢁ
250 C is observed, corresponding to the physisorption of NH .
3
ꢁ
However, for ZnAPO-ERI-MW, there are two regions, region-I
of 160 C in 2 min (microwave power was 400 W) and main-
ꢁ
ꢁ
(
150–250 C) and region-II (250–350 C), are observed in its
tained at that temperature for 2 h (microwave power was 200
31
acid proles. These temperature ranges represent weak and W). For comparison, the same reaction mixture was sealed in a
medium acid strength, respectively, which could be attributed 15 mL Teon-lined stainless steel autoclave and heated in a
ꢁ
to the successful substitution of Zn atoms into the alumi- conventional oven at 160 C for 6 days. Aer cooling to room
29,30
nophate lattice.
temperature, the product was obtained by centrifugation, then
washed by distilled water and ethanol and dried at room
temperature. The ZnAPO-ERI samples synthesized under
microwave irradiation method and conventional hydrothermal
method are named as ZnAPO-ERI-MW and ZnAPO-ERI-CV,
In conclusion, thermally-stable zeolite with ERI framework
topology is an important candidate for improving separation
and catalytic processes. Microwave-assisted hydrothermal
synthesis of Zn-containing aluminophosphate ZnAPO-ERI-MW
with ERI-zeotype structure was successfully synthesized by respectively.
0
0
0
using N,N,N,N ,N ,N -hexamethyl-1,6-hexanediammonium as
structure directing agents. Compared to AlPO -ERI and ZnAPO-
4
ERI-CV synthesized under conventional heating process, Acknowledgements
ZnAPO-ERI-MW prepared by microwave radiation exhibits
ꢁ
We thank the State Basic Research Project of China (Grant no.
011CB808703), National Natural Science Foundation of China
(no. 21001050), and the Fundamental Research Funds for the
Central Universities (no. N130305003).
shorter synthesis time, higher thermal stability upon 540
C
2
with the removal of templates, and large surface area with the
2
ꢂ1
3
BET surface area of 648.2 m g . NH -TPD analysis of ZnAPO-
ERI-MW shows that some weak and medium acid sites are
present in the structure, which might contribute to its appli-
cations in adsorption or catalytic processes.
Notes and references
1
N. K. McGuire, C. A. Bateman, C. S. Blackwell, S. T. Wilson
and R. M. Kirchner, Zeolites, 1995, 15, 460.
Experimental
General procedure for the preparation of organic SDA
2
3
J. H. Yu and R. R. Xu, J. Mater. Chem., 2008, 18, 4021.
J. H. Yu and R. R. Xu, Acc. Chem. Res., 2010, 43, 1195.
0
0
0
The organic structure directing agent (SDA) of N,N,N,N ,N ,N -
hexamethyl-1,6-hexanediammonium (Me -diquat-6) cation was
4 Z. P. Wang, J. H. Yu and R. R. Xu, Chem. Soc. Rev., 2012, 41,
1729.
6
prepared by reacting 1,6-dibromohexane (97%, Aldrich) with an
excess of trimethylamine (99%) in ethanol as a solvent with
rapid stirring at room temperature overnight. Then the solvent
was removed by evaporation under vacuum, and the resulting
white solid was washed with diethyl ether until unreacted
amine was completely removed from the product. The
5 K. J. A. Raj and V. R. Vijayaraghavan, Catal. Lett., 2004, 96, 66.
6 P. Concepci ´o n, A. Corma, J. M. L. Nieto and J. P ´e rez-Pariente,
Appl. Catal., A, 1996, 143, 17.
7 D. L. Vanoppen, D. E. De Vos, M. J. Genet, P. G. Rouxhet and
P. A. Jacobs, Angew. Chem., Int. Ed. Engl., 1995, 34, 560.
8 M. P. J. Peeters, M. Busio and P. Leijten, Appl. Catal., A, 1994,
118, 51.
1
13
compound was veried by H and C NMR. The obtained
dibromide salt was converted into the dihydroxide by anion
exchange in distilled water solution using an OH resin. The
9 J. J. Pluth, J. V. Smith and J. M. Bennett, Acta Crystallogr.,
Sect. C: Cryst. Struct. Commun., 1986, 42, 283.
ꢂ
concentrated by rotoevaporation under vacuum with mild 10 S. T. Wilson and E. M. Flanigen, ACS Symp. Ser., 1989, 398,
heating. The nal concentration was determined by titration 329.
49848 | RSC Adv., 2014, 4, 49846–49849
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