CHEMICAL MODIFIED ZEOLYTHES*
VIORICA POPESCU1, CAMELIA OPREA2, SEMAGHIUL BIRGHILA1
1
Department of Chemistry, Ovidius University, Constanta, Romania
Departement of Physics, Ovidius University, Constanta, Romania
[email protected]
2
Received December 21, 2004
This paper presents a study about the properties of the Na ZSM-5 zeolyth when
the sodium is replaced with Mn, Fe, Mg, Al and Cu.
For obtaining this kind of new zeolythes, the Na ZSM-5 zeolyth was combined
with concentrated boiled CuSO4, MnSO4, FeSO4, MgSO4 and Al2(SO4)3 solutions.
For all these zeolythes have been determined the porous volume, the density
values, the IR spectra, using a Vector 22 Spectrometer in the 4000-400 cm-1 range, and
the conductivities values using a K 610 conductometer.
All the results indicate that the replacing of Na with other metals, determine
modifications on the zeolythes structures.
Key words: zeolyth, Na-ZSM-5, porous volume, K 610 conductometer, Vector 22
spectrometer.
1. INTRODUCTION
The zeolythes are crystalline microporous solids, and have been discovered in
1954. In the beginning they were used like sorbents for the industrial separations, and
for purification. Now, the zeolites are well known like catalysts for many industrial
proceedings.
The general formula for all the zeolythes is:
a M2/nO ; Al2O3 ; n SiO2 ; b H2O
where n ≥2 and M are metals like: Na, Li, K, Ca, [1].
The ZSM-5 is a synthetic zeolyth, with the Si/Al ratio between 12 and 800. It
has a double system of three-dimensional channels, some of them being straights
with a 5,4-5,6 Å span and other being sinuous with a 5,4-5,5 Å span, [2,3,4].
*
Paper presented at the 5th International Balkan Workshop on Applied Physics, 5–7 July
2004, Constanţa, Romania.
Rom. Journ. Phys., Vol. 51, Nos. 1–2, P. 293–297, Bucharest, 2006
294
V. Popescu, C. Oprea, S. Birghila
2
A high number of researches studies the ZSM zeolyth charged with
transitional metals [5,6,7,8] and, in the same way we have obtained five ZSM-5
zeolythes modified by replacing the Na with Mn, Fe, Mg, Al, Cu.
2. EXPERIMENTAL
For obtaining the ZSM-5 catalyst we used the classical method putting
together 2g of silica gel, 2g of alumina and 30 ml of methanol. The mixture was
stirred for about three hours. After that, we added 1 ml of H2SO4 2 N and the
stirring was continued for another three hours. The obtained precipitate was filtered
and washed with hot water. After that, it was calcinated at 105oC for 1.30 hours.
For the preparation of the Na ZSM-5, we prepared an eutectic welt of NaNO3
and KNO3 by mixing a 1:1 molar ratio of NaNO3 and KNO3. The mixture was
warmed till a paste is obtained. This paste is put together with the ZSM-5 zeolyth
and is calcinated for two hours at 400oC.
The next step was to contact the Na ZSM-5 zeolyth with concentrated
solution of CuSO4, MnSO4, FeSO4, MgSO4 and Al2(SO4)3.
After the boiling in the concentrated solutions, the modified zeolythes were
filtered, washed with hot water and dried at 105oC for two hours.
3. RESULTS AND DISCUSSIONS
For analyzing the new zeolythes that we have obtained, we determined the
porous volume, the density, the IR spectra and the conductivity values.
In order to establish the porous volume, the calculation relation is:
Vp =
8V1
, (cm3/g)
G1
where: Vp is porous volume, V1 is water volume and G1 is the catalyst weight.
The results are presented in the Table 1.
Table 1
Porous volume for modified ZSM-5 zeolythes
Zeolyth
Na ZSM-5
Cu ZSM-5
Mn ZSM-5
Fe ZSM-5
Mg ZSM-5
Al ZSM-5
Vp (cm3/g)
5.5
8.64
8.00
8.00
7.36
6.93
3
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Chemical modified zeolythes
One can observe an increase of porous volume for all the modified zeolythes,
the highest value being for the Cu ZSM-5 zeolyth.
We have also determined the density value, using the formula:
ρ=
m1
,
m 2 − m 3 − m1
V1 −
d
where: V1 is the balloon-flask volume, m2 – final weight of the balloon-flask, m3 –
the weight of the empty balloon-flask, m1 – the weight of the catalyst sample and d
– water density at 25 oC.
The density values are presented in Table 2.
Table 2
The density values for the modified zeolythes.
ρ (g/cm3)
2.25
2.04
1.65
1.71
1.21
1.56
Zeolyth
Na ZSM-5
Cu ZSM-5
Mn ZSM-5
Fe ZSM-5
Mg ZSM-5
Al ZSM-5
We can see the decrease of the density values comparing with Na ZSM-5
zeolyth. But from all the modified zeolythes, the highest value is again for the Cu
ZSM-5 zeolyth and the smallest for the Mg ZSM-5 zeolyth.
The IR spectra were platted with a spectrometer Vector 22, in the 400 – 4000
cm-1 range. From these spectra one can observe the existence of the intense peaks
in the specific range for the Cu–O–Al, Mn-O-Al, Fe-O-Al, Mg-O-Al and Al-O-Al
bounds.
In Tables 3, 4 and 5 are presented the most representative values of the IR
spectra.
Table 3
Wavenumbers for the Cu–O–Al, Mn-O-Al, Fe-O-Al, Mg-O-Al and Al-O-Al bounds.
Complexe
Cu–O–Al
Mn-O-Al
Fe-O-Al
Mg-O-Al
Al-O-Al
ν (cm-1)
487.9
465.5
466.3
477.9
464.8
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V. Popescu, C. Oprea, S. Birghila
4
Table 4
The IR spectra values for zeolythes
ν OH (cm-1)
3452.9
3435.4
3486.1
3453.5
Zeolyth
Al ZSM-5
Fe ZSM-5
Cu ZSM-5
Mg ZSM-5
Mn ZSM-5
Table 5
The IR spectra values
ν Al-O-Si (cm-1)
1100.8
1099.0
1108.3
1096.9
1098.2
Zeolyth
Al ZSM-5
Fe ZSM-5
Cu ZSM-5
Mg ZSM-5
Mn ZSM-5
We have also determined the conductivities for all these new zeolythes, using
a K 610 conductometer and these results are presented in Table 6.
Table 6
The values of the conductivities
Zeolyth
Cu ZSM-5
Mn ZSM-5
Fe ZSM-5
Mg ZSM-5
Al ZSM-5
Conductivity (µs/cm)
390
239
174
322
241
The obtained values show the rice of the conductor character for the new
zeolythes and this means that the replacing of the Na with others metallic ions
determine a ricing of the ionic character, the highest value being observed for Cu
ZSM-5 zeolyth.
CONCLUSIONS
We have obtained five ZSM-5 zeolythes modified by the replacement of the
Na from the ZSM-5 zeolyth with Mn, Fe, Mg, Al and Cu.
We have determined the porous volume for all the synthesized zeolythes and
we could observe that the Cu ZSM-5 zeolyth has the highest volume of the porous.
From the density values we can observe that again the Cu ZSM-5 zeolyth
presents the highest value.
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Chemical modified zeolythes
297
From the IR spectra, the presence of the intensive peaks indicates that we
have obtained the supposed compounds.
From the measurements of conductivity, we determine that the highest values
was for the Cu ZSM-5 zeolyth.
In conclusion we have obtained five new modified zeolythes, but from them
the best was the Cu ZSM-5 zeolyth, because of its special characters.
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