Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported ZnO Catalysts: Influence of Support Crystallite Size

Article abstract of DOI:10.1002/cjoc.202000042

The ZnO catalysts supported on Silicalite-1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7 μm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N₂ adsorption, SEM, TEM-EDX, DRIFT spectra and NH₃-TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO₂ was investigated. The catalytic activity is strongly dependent on the crystallite size of Silicalite-1 support. The ZnO/S-1-0.35 catalyst with ca. 0.35 μm crystallite size displays the highest activity, affording an initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well as the largest amount of nest silanols possessed by the S-1-0.35 support.

Full text of DOI:10.1002/cjoc.202000042

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Accepted Article
Title: Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported ZnO
Catalysts: Influence of Support Crystallite Size
Authors: Yajun Luo, Chunling Wei, Changxi Miao,* Yinghong Yue, Weiming Hua,*
and Zi Gao
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Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported
ZnO Catalysts: Influence of Support Crystallite Size
Yajun Luo,a Chunling Wei,b Changxi Miao,*,b Yinghong Yue, a Weiming Hua,*,a and Zi Gaoa
a Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai 200438, China
b Shanghai Research Institute of Petrochemical Technology SINOPEC, Shanghai 201208, China
Cite this paper: Chin. J. Chem. 2020, 38, XXX—XXX. DOI: 10.1002/cjoc.202000XXX
Summary of main observation and conclusion The ZnO catalysts supported on Silicalite-1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7
µm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, SEM, TEM-EDX,
DRIFT spectra and NH3-TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO2 was investigated. The catalytic activity is strongly
dependent on the crystallite size of Silicalite-1 support. The ZnO/S-1-0.35 catalyst with ca. 0.35 µm crystallite size displays the highest activity, affording an
initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well
as the largest amount of nest silanols possessed by the S-1-0.35 support.
content.[24] Inspired by this finding, in the present work we first re-
port the influence of Silicalite-1 crystallite size on the catalytic per-
Background and Originality Content
With the depletion of fossil resources, the development of pro-
formance of ZnO/Silicalite-1 catalysts for isobutane dehydrogena-
cesses that specifically facilitate the conversion of hydrocarbons
tion assisted by CO2. The reasons for the different activities exhib-
can be established as an improvement in the use of these resources.
ited by these catalysts were discussed in terms of both acidity and
Two major ways to produce isobutene, i.e. naphtha steam cracking
silanol groups.
and fluidized catalytic cracking, strongly reply on petroleum re-
source. With the growing demand for isobutene, which is regarded
Results and Discussion
Catalyst characterization
as an important feedstock for the manufacture of value-added
−
chemicals,[1 3] a lot of attention has been paid to the process of cat-
alytic dehydrogenation of isobutane.
The XRD patterns of the ZnO catalysts supported on Silicalite-1
In recent years, the use of CO2 as a soft oxidant for the selective
zeolites with different crystallite sizes are depicted in Figure 1. All
dehydrogenation of light alkanes into their corresponding alkenes
catalysts display MFI structure with the characteristic diffraction
−
has received much attention.[4 12] Compared with employing O2 as
peaks at 2θ = 8.0o, 8.9o, 23.1o, 23.3o and 24.0o.[12,25] No reflections
an oxidant, CO2 has obvious advantages such as improving the se-
corresponding to crystalline ZnO can be observed, indicating that
zinc oxide is well dispersed on the four Silicalite-1 supports. The
lectivity toward targeted olefins and decreasing CO2 emissions.[13]
−
[15 17]
Several types of catalysts such as Cr2O3,[11,14] V2O5
and
SEM images of the Silicalite-1 supports (Figure S1) show that S-1-
0.08, S-1-0.35 and S-1-1 samples display approximately sphere-like
morphology with crystallite sizes of around 0.08, 0.35 and 1 µm,
respectively, whereas the S-1-1.7 sample shows coffin-like mor-
phology with ca. 1.7 µm in width. The homogeneous distribution
of the Zn element on the four Silicalite-1 supports is demonstrated
by HAADF STEM mapping (Figure S2), which is in accordance with
the XRD result.
V−Mg−O [18,19] have been explored for isobutane dehydrogenation
with carbon dioxide. The catalytic activity is strongly dependent on
the catalyst support. γ-Al2O3,[15,19] SiO2,[15,19] active carbon
(AC),[14,15,19] mesoporous SiO2 molecular sieve (e.g. SBA-15)
[11,17]
are generally chosen as the supports to prepared the supported
catalysts. However, the application of this technology is still chal-
lenged by the low activity and fast catalyst deactivation.
Silicalite-1 is an aluminum-free crystalline zeolite with MFI top-
ological framework. The presence of Si atom defective sites in their
lattice can impose the formation of acid centers (silanol groups),
which have been reported as active catalysts for the Beckmann re-
−
[20 22]
arrangement
as well as the etherification of 5-hydroxyme-
thyl-2-furfural.[23] More recently, we have found that the ZnO cata-
lyst supported on Silicalite-1 zeolite exhibits a superior catalytic
performance for CO2 assisted dehydrogenation of isobutane, which
is far more active than SBA-15-supported one with the same Zn
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(0.192−0.371 mmol/g). This implies that the acid sites present on
the catalysts are mainly originated from the dispersed zinc oxide
species. Metal species can interact with the alumina or silica sup-
port by consuming the exposed support-OH groups, thus modifying
the acidic properties of the support.[26,27]
Figure 1 XRD patterns of the catalysts. (a) ZnO/S-1-0.08, (b)
ZnO/S-1-0.35, (c) ZnO/S-1-1, (d) ZnO/S-1-1.7.
Table 1 Physico-chemical properties of the samples
Vmicroa/(cm3/g)
Vmeso/(cm3/g)
A3490/A3739
8.4
c
Sample
S-1-0.08
SBET/(m2/g)
385
Vtotalb/(cm3/g)
0.32
Acid amount/(mmol/g)
0.18
0.14
0.0445
0.371
1.0
ZnO/S-1-0.08
S-1-0.35
354
0.17
0.18
0.16
0.17
0.16
0.16
0.16
0.11
0.12
0.09
0.10
0.06
0.08
0.06
0.28
16.0
3.9
379
0.30
0.0387
0.314
ZnO/S-1-0.35
S-1-1
340
0.25
8.1
369
0.27
0.0182
0.231
0.3
ZnO/S-1-1
S-1-1.7
334
0.22
5.6
356
0.24
0.0108
0.192
0.2
ZnO/S-1-1.7
321
0.22
a Calculated by the t-plot method. b Total pore volume adsorbed at P/P0 = 0.99. c A3490 and A3739 are the peak area of nest silanols
−
−
1
1
(3490 cm ) and isolated silanols (3739 cm ), respectively.
The textural properties of the Silicalite-1 supports and Sili-
calite-1-supported zinc oxide catalysts are presented in Table 1.
The BET surface areas and mesopore volumes (contribution from
intercrystalline voids) of the Silicalite-1 supports increase slightly
with the decrease of crystallite size, which diminish somewhat af-
ter the impregnation of zinc oxide (5% Zn). The micropore volumes
of the Silicalite-1 supports are almost unchanged upon the intro-
duction of ZnO.
The amount of acid sites on the ZnO/S-1 catalysts with differ-
ent crystallite sizes was measured by the NH3-TPD method, and the
result is given in Figure 2 and Table 1. Two desorption peaks on the
TPD profiles of all supported zinc oxide catalysts can be found. The
low temperature peaks are located at ca. 166 oC and the high tem-
o
perature shoulders are centered at around 324 C, which corre-
spond to the acid sites of weak and moderate strength, respec-
tively. The total acid amount of the catalysts increases in the order
of ZnO/S-1-1.7 < ZnO/S-1-1 < ZnO/S-1-0.35 < ZnO/S-1-0.08 (Table
1). It is clear in Table 1 that the Silicalite-1 supports possess a small
number of acid sites (0.0108−0.0445 mmol/g), and their acidities
are improved substantially after supporting zinc oxide
Figure 2 NH3-TPD profiles of the catalysts. (a) ZnO/S-1-0.08, (b)
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Running title
Chin. J. Chem.
ZnO/S-1-0.35, (c) ZnO/S-1-1, (d) ZnO/S-1-1.7.
o
According to the literature,[27,28] the weight loss below 100 C
o
and between 100 and 200 C was attributed to the elimination of
physically and chemically adsorbed water, respectively, while the
o
weight loss above 200 C was assigned to the dehydroxylation by
condensation of silanols. Based on the TG result, the amount of si-
lanols on the four Silicalite-1 supports is 1.05, 1.21, 1.54 and 1.61
mmol/g for S-1-1.7, S-1-1, S-1-0.35 and S-1-0.08, respectively,
which increases with decreasing the crystallite size. Higher amount
of silanols on the Silicalite-1 support would favor the dispersion of
supported metal oxide species,[27] thus leading to a higher amount
of acid sites on the Silicalite-1-supported ZnO catalyst, as evi-
denced in Figure 3.
Figure 3 Relationship between the acidity of the Silicalite-1-sup-
ported ZnO catalysts and the amount of silanols on the Silicalite-1
supports () as well as between the initial activity and acidity of
the catalysts ().
DRIFT spectra were investigated to get a deep understanding
of hydroxyl groups on the Silicalite-1 supports with different crys-
tallite sizes, and the result is shown in Figure 4A. Three types of
−OH groups can be found. The intense and sharp peak at 3739 cm−
1
is assigned to isolated silanol groups located on the external sur-
face, and the small peak at 3686 cm−1 is ascribed to vicinal silanol
−
32]
groups located inside the micropores.[20,29,30
The strong broad
peak at around 3490 cm− is generally attributed to nest silanol
groups that comprise a number of silanol groups interacting
through extended hydrogen bonding.[20,32] Such nest silanol groups
generally appear at crystal steps or extended defects.[31,33] It is
1
clear in Figure 4A that the intensity of the peak at ca. 3490 cm−
1
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First author et al.
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Figure 4 DRIFT spectra of the Silicalite-1 supports (A) and Silicalite-1-supported ZnO catalysts (B). (a) S-1-0.08, (b) S-1-0.35, (c) S-1-
1, (d) S-1-1.7, (e) ZnO/S-1-0.08, (f) ZnO/S-1-0.35, (g) ZnO/S-1-1, (f) ZnO/S-1-1.7.
Figure 5 Conversion of isobutane (A) and selectivity to isobutene (B) as a function of reaction time for the Silicalite-1-supported
ZnO catalysts. () ZnO/S-1-0.08, () ZnO/S-1-0.35, () ZnO/S-1-1, () ZnO/S-1-1.7.
−
1
decreases in the order of S-1-0.35 > S-1-0.08 ≈ S-1-1 > S-1-1.7, sug-
gesting that S-1-0.35 possesses the largest amount of nest silanols.
The TG and IR results reveal that the total amount of silanols as
well as silanol distribution on these Silicalite-1 supports are differ-
ent from each other, albeit they have the same topology and simi-
lar texture properties. As seen from Figure 4B, after supporting ZnO
on Silicalite-1 (5% Zn), there is an obvious decrease in the intensity
of three bands, especially the band at 3490 cm , which is due to
the interaction of Zn species with the support−OH groups.[29,34] This
is indicative of a decrease in the number of silanol groups via con-
suming the exposed hydroxyl groups. As presented in Table 1, the
peak area ratio of nest silanol groups (3490 cm ) to isolated silanol
−
1
ones (3739 cm ) is 8.4, 16.0, 8.1 and 5.6 for S-1-0.08, S-1-0.35, S-
1-1 and S-1-1.7, respectively, which declines to 1.0, 3.9, 0.3 and 0.2,
respectively. The above findings imply that Zn species primarily in-
teract with nest silanol groups. Note that after supporting ZnO, the
peak intensity of the left nest silanols on the Silicalite-1 supports
diminishes in the order of ZnO/S-1-0.35 > ZnO/S-1-0.08 > ZnO/S-1-
1 ≈ ZnO/S-1-1.7 (Figure 4B), indicating that ZnO/S-1-0.35 has the
highest amount of the left nest silanols.
−
1
Catalytic performance
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Running title
Chin. J. Chem.
Table 2 Reaction data of the Silicalite-1-supported ZnO catalystsa
Conversion/%
i-C4H10 CO2
46.7(44.3) 8.4(5.5)
51.0(49.0) 10.1(7.2) 74.5(79.4) 2.5(1.8) 0.4(0.2) 0.1(0.1) 6.2(4.8) 0.8(0.5) 15.5(13.2)
Selectivity/%
i-C4H8
yield/%
35.3(36.2)
38.0(38.9)
33.8(34.2)
29.2(30.2)
Catalyst
b
i-C4H8
CH4
C2H4
C2H6
C3H6
C3H8
C4H8
ZnO/S-1-0.08
ZnO/S-1-0.35
ZnO/S-1-1
75.6(81.7) 2.3(1.6) 0.3(0.1) 0.1(0.1) 5.7(4.3) 0.7(0.3) 15.3(11.9)
43.5(41.4) 7.6(4.6)
37.2(36.4) 5.1(2.7)
77.7(82.6) 2.1(1.6) 0.3(0.1) 0(0) 5.1(4.1) 0.6(0.4) 14.2(11.2)
78.5(83.0) 1.9(1.4) 0.3(0.1) 0(0) 4.9(4.0) 0.6(0.3) 13.8(11.2)
ZnO/S-1-1.7
a The values outside and inside the bracket are the data obtained at 10 min and 360 min, respectively.
b 1-Butene, cis-2-butene and trans-2-butene.
The dehydrogenation of isobutane to isobutene assisted by
CO2 over the Silicalite-1-supported ZnO catalysts was investigated
at 570 C. The result is shown in Figure 5 and Table 2. The major
ZnO/S-1-0.08 catalyst displays lower activity than ZnO/S-1-0.35, al-
beit the former catalyst has more acid sites than the latter one. This
can be interpreted as follows. S-1-0.35 and ZnO/S-1-0.35 have
more nest silanols than S-1-0.08 and ZnO/S-1-0.08, respectively
(Figure 4). The acid strength of nest silanols is stronger than iso-
lated ones.[20,22] The activation energy of one-step elimination re-
action (Eq. (2)) is strongly dependent on the relative position of
[Zn–i-C4H9]+ and framework attached H+ ions. Therefore, the resid-
ual acidic −OH groups on the catalyst, especially the residual nest
silanols owing to their stronger acid strength, which are close to
the [Zn–i-C4H9]+ species can promote the regeneration of the active
sites, thereby leading to an increase in the catalytic activity.[24,35,36]
It is thus concluded that the highest activity observed for the
ZnO/S-1-0.35 catalyst can be attributed to a higher amount of acid
sites present on this catalyst as well as the largest amount of nest
silanols possessed by the S-1-0.35 support.
The catalytic performance of our catalysts (ZnO/S-1) in this
work is compared with the performance of other catalysts re-
ported in the literature. Table S1 lists the conversion, selectivity
and space-time yield of isobutene, together with the reaction con-
ditions. In fact, it is not appropriate to compare the catalytic activ-
ity because of the different reaction conditions. As far as the space-
time yield of isobutene is concerned, our catalysts are obviously
more active than the supported Cr-based, V-based and V-Mg-O
catalysts. Furthermore, the ZnO/S-1 catalysts display higher stabil-
ity.
o
hydrocarbon product is isobutene, and the minor hydrocarbon
products comprise methane, ethane, ethylene, propane, propyl-
ene and butenes (excluding isobutene). The catalytic activity
strongly depends on the crystallite size of Silicalite-1 support. As
the crystallite size decreases from 1.7 µm to 0.35 µm, the initial
conversion of isobutane on the ZnO/S-1 catalysts increases evi-
dently from 37.2% to 51.0%. A further decrease in the crystallite
size of Silicalite-1 support to 0.08 µm results in a decrease in the
initial isobutane conversion to 46.7%. In general, the ZnO/S-1 cat-
alyst with higher activity displays lower isobutene selectivity (Fig-
ure 5B). The ZnO catalyst supported on Silicalite-1 with ca. 0.35 µm
crystallite size exhibits the highest activity, giving an initial isobu-
tane conversion of 51.0% and 74.5% isobutene selectivity. As
shown in Table 2, the ZnO/S-1-0.35 catalyst displays the highest
isobutene yield. It should be pointed out that under the same re-
action conditions the isobutane conversion on the Silicalite-1 sup-
ports is below 3%, which indicates that the dispersed zinc oxide
species on the Silicalite-1 supports are the active sites for the de-
hydrogenation reaction.
According to the DFT calculations, the reaction pathway of
ethane dehydrogenation over the Zn/ZSM-5 catalyst was proposed
by Pidko and van Santen.[35] We think that isobutane dehydrogena-
tion over the ZnO/Silicalite-1 catalyst could follow the same mech-
anism (Scheme S1).[24] Isobutane is dissociatively adsorbed on the
zinc oxide sites (i.e. acidic sites) in the initial step (Eq. (1)). In the
following step, the resulting product decomposes via one-step
elimination, thus generating isobutene and H2 (Eq. (2)). Based on
this reaction mechanism, one would expect that the ZnO/S-1 cata-
lyst having a higher amount of dispersed zinc oxide (i.e. more acid
sites) exhibits higher catalytic activity. Note that the acid sites pre-
sent on the ZnO/S-1 catalysts are mainly contributed from the dis-
persed zinc oxide species, as revealed by the NH3-TPD result. This
speculation is further corroborated by a good correlation between
the initial activity of the ZnO/S-1 catalysts (ZnO/S-1-1.7, ZnO/S-1-1
and ZnO/S-1-0.35) and acid amount of these catalysts (Figure 3). In
our recent work we have also demonstrated the excellent correla-
tion between the catalytic activity for CO2-assisted isobutane de-
hydrogenation over the ZnO/S-1-0.35 catalysts with different Zn
contents and acid amount of these catalysts.[24] Nevertheless, the
Conclusions
The Silicalite-1-supported ZnO catalysts with 5% Zn were pre-
pared by an incipient wetness method. The XRD and HAADF STEM
mapping results reveal the homogeneous distribution of the Zn el-
ement on the Silicalite-1 supports with different crystallite sizes
(0.08, 0.35, 1 and 1.7 µm, respectively). The amount of silanols on
the four Silicalite-1 supports determined by TG increases with de-
creasing the crystallite size, thus favoring the dispersion of sup-
ported zinc oxide species. As a result, a higher amount of acid sites
are achieved on the Silicalite-1-supported ZnO catalyst. The ZnO/S-
1-0.35 catalyst with ca. 0.35 µm crystallite size exhibits the highest
activity for CO2-assisted isobutane dehydrogenation, giving an ini-
tial isobutane conversion of 51.0% and 74.5% isobutene selectivity.
This can be accounted for by both a higher amount of acid sites
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First author et al.
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present on this catalyst and the largest amount of nest silanols pos-
sessed by the S-1-0.35 support.
Fourier transform (DRIFT) spectra were obtained on a Nicolet 6700
spectrometer equipped with an MCT detector cooled by liquid N2.
The DRIFT cell was fitted with CaF2 windows and a heating cartridge.
o
The samples were pretreated in a He flow (30 mL/min) at 450 C
Experimental
Preparation of catalyst
for 1 h, and cooled to 300 oC under flowing He. DRIFT spectra were
−
1
o
collected at 300 C under flowing He with a resolution of 4 cm
and accumulation of 128 scans.
Submicron and micrometer Silicalite-1 zeolites were synthe-
sized according to the literature.[37] Typically, tetrapropylammo-
nium hydroxide (TPAOH, 25 wt% aqueous solution), tetraethyl or-
thosilicate (TEOS) and distilled deionized water were mixed with
stirring at room temperature to form a clear gel with a molar com-
position of mTPAOH : 25SiO2 : 480H2O (where m = 3, 6 and 9, re-
spectively). The gel was stirred for additional 4 h to ensure the
complete hydrolysis of TEOS. Then it was transferred to an auto-
clave and crystallized at 170 oC for 72 h. The as-synthesized precip-
itate was washed with deionized water, dried at 100 oC overnight,
Activity measurement
Catalytic tests for isobutane dehydrogenation to isobutene as-
sisted by CO2 were performed at 570 oC in a fixed-bed flow micro-
reactor at atmospheric pressure.[39] The catalyst load was 0.1 g
(40–60 mesh), and it was pretreated at 570 oC for 1 h in a N2 flow
prior to the reaction. The gas reactant contained 50 vol.% CO2 and
50 vol.% isobutane. The flow rate of isobutane was 2.9 mL/min,
corresponding to the weight hourly space velocity (WHSV) of 4.1
−
1
o
h . The hydrocarbon products were analyzed using an on-line gas
chromatograph (GC) equipped with a FID and a HP-AL/S capillary
column (50 m × 0.53 mm × 15 µm). CO and CO2 were analyzed on-
line by another GC equipped with a TCD and a 2-m packed column
of carbon molecular sieve 601.
and calcined in air at 550 C for 4 h. The resultant Silicalite-1 zeo-
lites are labelled as S-1-x (where x = 1.7, 1 and 0.35 represent the
crystallite size of ca. 1.7, 1 and 0.35 μm corresponding to m = 3, 6
and 9, respectively). To prepare nanosize Silicalite-1 zeolite, TPAOH,
TEOS and distilled deionized water were mixed under stirring at
room temperature to get a clear solution, followed by being stirred
at 80 oC for 24 h to form a gel with a molar composition of 1TPAOH :
4SiO2 : 32H2O. Then the gel was transferred to an autoclave and
crystallized at 170 oC for 24 h, followed by the same treatment as
the above Silicalite-1 zeolites. The obtained Silicalite-1 is labelled
as S-1-0.08, where 0.08 represents the crystallite size of ca. 0.08
μm
The supported ZnO catalysts were prepared by impregnating
an aqueous solution of Zn(NO3)2•6H2O on Silicalite-1 zeolites with
different crystallite sizes via an incipient wetness method. The im-
pregnated samples were dried at 100 oC overnight and calcined at
600 oC for 6 h in air to obtain the ZnO/S-1-x catalysts. The weight
content of Zn in all catalysts was 5%.
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2020xxxxx.
Acknowledgement
This work was supported by the National Key R&D Program of
China (2017YFB0602200), the National Natural Science Foundation
of China (91645201), the Science and Technology Commission of
Shanghai Municipality (19DZ2270100) and the Shanghai Research
Institute of Petrochemical Technology SINOPEC (19ZC06070005).
Catalyst characterization
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Chin. J. Chem. 2020, 38, XXX－XXX
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First author et al.
Report
Luo, Y. J.; Miao, C. X.; Yue, Y. H.; Yang, W. M.; Hua, W. M.; Gao, Z.
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
Chromium oxide supported on Silicalite-1 zeolite as a novel efficient
catalyst for dehydrogenation of isobutane assisted by CO2. Catalysts
2019, 9, 1040.
(The following will be filled in by the editorial staff)
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Entry for the Table of Contents
Page No.
Isobutane Dehydrogenation Assisted by CO2
over Silicalite-1-Supported ZnO Catalysts: Influ-
ence of Support Crystallite Size
The ZnO catalyst supported on Silicalite-1 with ca. 0.35 µm crystallite size exhibits the highest activ-
ity for CO2-assisted isobutane dehydrogenation, which can be attributed to both a higher amount of
acid sites present on this catalyst and the largest amount of nest silanols possessed by the Silicalite-
1 support.
Yajun Luo, Chunling Wei, Changxi Miao,* Ying-
hong Yue, Weiming Hua,* and Zi Gao
Chin. J. Chem. 2018, template© 2018 SIOC, CAS, Shanghai,
&
WILEY-VCH Verlag GmbH
&
Co. KGaA, Wein-
heim
This article is protected by copyright. All rights reserved.