Ag-Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorination of 1,2-dichloroethane towards ethylene

Article abstract of DOI:10.1016/j.catcom.2015.06.009

Dealuminated form of BEA zeolite with Si/Al ratio of 1500 was used for the synthesis of Ag_2.0SiBEA, Ni_2.0SiBEA and Ag_2.0Ni_2.0SiBEA by two-step postsynthesis method. The calcination of zeolite samples led to the formation of well dispersed isolated mononuclear Ag(I) and Ag_n^{δ +} clusters and a pseudo-tetrahedral Ni(II), incorporated in BEA framework as evidenced by DR UV-vis investigations. The treatment of samples in flowing 10% H₂/Ar stream gave small (average 3.1 nm) and well dispersed metal nanoparticles. Reduced catalysts were investigated in 1,2-dichloroethane hydrodechlorination at atmospheric pressure, at low reaction temperature (523 K) with ～ 100% of selectivity to ethylene, desired product of the reaction.

Full text of DOI:10.1016/j.catcom.2015.06.009

Ag-Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorination
of 1,2-dichloroethane towards ethylene
´
A. Srebowata, I. Zielin´ska, R. Baran, G. Słowik, S. Dzwigaj
PII:
DOI:
Reference:
S1566-7367(15)00237-X
doi: 10.1016/j.catcom.2015.06.009
CATCOM 4359
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
22 April 2015
9 June 2015
10 June 2015
´
Please cite this article as: A. Srebowata, I. Zielin´ska, R. Baran, G. Slꢀowik, S.
Dzwigaj, Ag-Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorina-
tion of 1,2-dichloroethane towards ethylene, Catalysis Communications (2015), doi:
10.1016/j.catcom.2015.06.009
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ACCEPTED MANUSCRIPT
Ag-Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorination of 1,2-
dichloroethane towards ethylene
A. Śrębowata1,*, I. Zielińska1, R. Baran2,3,4, G. Słowik5 and S. Dzwigaj3,4*
1Institute of Physical Chemistry, PAS, Kasprzaka 44/52, PL-01224 Warszawa, Poland,
2AGH University of Science and Technology al. A. Mickiewicza 30, 30-059 Krakow, Poland
3Sorbonne Universités, UPMC Univ Paris 06, UMR 7197, Laboratoire de Réactivité de
Surface, F-75005, Paris, France
4CNRS, UMR 7197, Laboratoire de Réactivité de Surface, F-75005, Paris, France
5Faculty of Chemistry, Department of Chemical Technology, Maria Curie – Skłodowska
University, Plac Marii Curie – Skłodowskiej 3, PL-20-031 Lublin, Poland
Figures: 5
Keywords: Ag, Ni, BEA, 1,2-dichloroethane, ethylene, hydrodechlorination
*Corresponding authors
Anna Srebowata, E-mail:
asrebowata@ichf.edu.pl,
Tel. 48 1 22 343 3320
Stanislaw Dzwigaj, E-mail : stanislaw.dzwigaj@upmc.fr, Fax : 33 1 44 27 21 13
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Abstract
Dealuminated form of BEA zeolite with Si/Al ratio of 1500 was used for synthesis
Ag2.0SiBEA, Ni2.0SiBEA and Ag2.0Ni2.0SiBEA by two-step postsynthesis method. The
calcination of zeolite samples led to formation of well dispersed isolated mononuclear Ag(I)
δ+
and Agn clusters and a pseudo-tetrahedral Ni(II), incorporated in BEA framework as
evidenced by DR UV-vis investigations. The treatment of samples in flowing 10 % H2/Ar
stream gave small (average 3.1 nm) and well dispersed metals nanoparticles. Reduced
catalysts were investigated in 1,2-dichloroethane hydrodechlorination at atmospheric
pressure, at low reaction temperature (523 K) with ~100% of selectivity to ethylene, desired
product of the reaction.
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Introduction
The stability, activity and high selectivity toward desired product are the key factors for
the design and preparation of catalysts for hydrodechlorination (HDC) and the essential issue
for the industrial application of this technology [1,2]. Therefore, the finding of effective
methods of synthesis HDC catalysts is still under investigation. Hydrodechlorination is known
as structural sensitive reaction, but among the researchers opinions are divided on the effect of
metal(s) dispersion and metal particle size on this process. Some of the scientists claim that
higher metal particles size and smaller dispersion play the crucial role in activity and stability
of HDC catalysts [3,4]. On the other hand, some of the literature data clearly show the
beneficial role of excellent dispersed very small metal particles in hydrodechlorination
process [5]. Our recent studies on nickel containing beta zeolite in conversion of 1,2-
dichloroethane brightly demonstrated the high stability, and high selectivity of very small
(~1,5 nm) nickel particles size [5]. In spite of earlier reports [6,7] the small metal particles did
not deactivate during reaction and they are resistant to sintering [5]. As we have earlier shown
[8] the application of dealuminated SiBEA zeolite with vacant T-atom sites played an
important role on the formation stable, active and selective catalysts. Very interesting results
were obtained also for bimetallic Cu-Ni systems prepared by two-step postsynthesis method
[9] that consist, in the first step, dealumination of BEA zeolite by treatment with nitric acid
and then, in the second step, incorporation of metal into the framework of BEA zeolite by
their reaction with silanol groups of vacant T-atom sites of resulted SiBEA zeolite. The
reduction of well dispersed metal species with H2 led to formation of small metal
nanoparticles in extra-framework position. Careful investigations have shown very good
activity of bimetallic Cu-Ni zeolite catalysts containing small and well dispersed Ni(0) and
Cu(0) nanoparticles in hydrodechlorination of 1,2-dichloroethane and high selectivity to
ethylene [9]. Inspired by our earlier work [9,10] we would like to investigate the effect of
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two-step postsynthesis method of preparation on catalytic properties of silver and nickel
loaded BEA zeolite in hydrodechlorination of 1,2-dichloroethane. Until now only the addition
of silver to Pd in HDC of 1,2-dichloroethane were successfully investigated [11,12]. Addition
of silver to palladium containing catalysts has reduced strong hydrogenating properties of
palladium and led to increasing of the selectivity to ethylene (desired product 1,2-DCA HDC).
Therefore, we have expected to observe the same phenomenon in the case of Ag-Ni system.
1
Experimental
1.1 Catalysts preparation
A tetraethylammonium BEA (TEABEA) (Si/Al = 17) zeolite provided by RIPP (China)
was calcined for 15 h at 823 K to remove template. Organic-free BEA zeolite was separated
into two portions. The first, portion of 2 g of TEABEA was treated with 200 ml of 13 mol ∙ L-
1
nitric acid solution (353 K, 4 h) to obtain dealuminated SiBEA zeolite and then washed
several times with distilled water and dried at 363 K overnight. Results of chemical analysis
indicate that only traces of Al remain in SiBEA after nitric acid treatment with Si/Al ratio of
1500.
AgxSiBEA (x = 2 Ag wt %), NixSiBEA (x = 2 Ni wt %) or AgxNiySiBEA (x = 2 Ag wt %
and y = 2 Ni wt %) were prepared by co-impregnation of 2 g of SiBEA with Ag(NO3)2 · 6H2O
or Ni(NO3)2 · 6H2O and Ag(NO3)2 · 6H2O solutions, respectively, with appropriate
concentration of Ag and Ni. Firstly, all suspensions were stirred for 24 h at 298 K in excess
solvent using 200 mL of the precursor solutions. Then, the suspensions were stirred in rot-
evaporator under vacuum of a water pump for 2 h in air at 333 K until complete evaporation
of water. The catalysts obtained in this ways are labeled Ag2.0SiBEA, Ni2.0SiBEA and
Ag2.0Ni2.0SiBEA. All these materials were calcined in static air at 773 K for 3 h and labeled
C-Ag2.0SiBEA, C-Ni2.0SiBEA and C-Ag2.0Ni2.0SiBEA, respectively. Then, a portion of these
materials were reduced at 873 K for 3 h in flowing 10 % H2/Ar to obtain red-C-Ag2.0SiBEA,
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red-C-Ni2.0SiBEA and red-C-Ag2.0Ni2.0SiBEA, where C - stands for calcined and red - for
reduced. These catalysts after kinetic run were labeled with additional prefix spent-, as spent-
red-C-Ag2.0SiBEA, spent-red-C-Ni2.0SiBEA and spent-red-C-Ag2.0Ni2.0SiBEA.
1.2 Catalyst characterization
Chemical analysis was performed at room temperature on SPECTRO X-Lab Pro
apparatus.
DR UV–vis spectra were recorded at ambient atmosphere on a Cary 5000 Varian
spectrometer equipped with a double integrator with polytetrafluoroethylene as reference.
Temperature – programmed reduction (TPR) for both of the catalysts, after calcination
step, were carried out using the glass-flow system. TPR runs were performed in flowing 10 %
H2/Ar (25 cm3 min-1), ramping the temperature at 10 K min-1 and using a Gow-Mac thermal
conductivity detector (TCD). Injections of known amounts of hydrogen into the hydrogen–
argon flow were provided for calibration (before and after each TPR run).
Chemisorption measurements of H2 and CO using a conventional static method were
carried out with a Micromeritics ASAP 2020 Chem instrument. Prior to chemisorption
measurement 0.1 g of C-Ag2.0Ni2.0SiBEA were reduced in flowing 10%H2/Ar (25 cm3 min-1),
ramping the temperature from room to 873 K (at 10 K min-1) and kept at 873 K for 3 h. Then
the catalysts were cooled down to the room temperature and connected with ASAP 2020
instrument. Next, the samples were heated in flowing He at 383 K for 30 min with an
additional evacuation for 10 min. At this temperature, the helium flow was switched for the
hydrogen flow and the temperature increased (10 K min-1) to 653 K and the samples were
reduced for 120 min, subsequently outgassed for 30 min, and finally cooled to 343 K with 30
min evacuation. The hydrogen adsorption isotherm was established. After evacuation at 343
K, a second H2 isotherm was performed. The gas uptake was obtained by extrapolating to zero
pressure the linear portion of the isotherm above the saturation pressure. The first hydrogen
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isotherm provided the sum of the reversibly and irreversibly adsorbed hydrogen while the
second isotherm represented only the reversibly adsorbed hydrogen. The amount of
chemisorbed hydrogen was given by the difference. After the second isotherm, the same
sample was heated in H2 at 653K and outgassed at this temperature for 30 min. Then, the H2
flow was switched for He and the sample was cooled down to the temperature 298 K with
additional 10 minutes evacuation. CO adsorption isotherm was measured at room temperature
and was established similarly like in the case of hydrogen adsorption procedure. The metal
dispersion (D, in %), and metal particle size (d, in nm) were determined from both the H2 and
CO chemisorption data, assuming that H/Nis ratio equals 1 [13,14] and CO/Ni equals 0,5 at
room temperature. [15,16].
TEM studies for the catalysts after reduction step were carried out using JEOL JEM-
100CXII electron microscope operated at an acceleration voltage of 100 keV. The samples
were prepared by their dispersing in pure alcohol using ultrasonic cleaner and putting a drop
of this suspension on carbon films on copper grids. Independent STEM and HRTEM
experiments were carried out on the electron microscope Titan G2 60-300 kV FEI Company,
equipped with: field emission gun (FEG), monochromator, three condenser lenses system, the
objective lens system, image correction (Cs-corrector), HAADF detector and EDS
spectrometer (Energy Dispersive X -Ray Spectroscopy) EDAX Company with detector
Si(Li). Microscopic studies of the catalysts were carried out at an accelerating voltage of the
electron beam equal to 300 kV. The mapping was carried out in the STEM mode by collecting
point by point of EDS spectrum of each of the corresponding pixels in the map. The collected
maps were presented in the form of a matrix of pixels with the color mapped significant
element and the intensity corresponding to the percentage of the element.
X-ray driffractograms (XRD) for red-C-Ag2.0SiBEA, red-C-Ag2.0Ni2.0SiBEA and spent-
red-C-AgxSiBEA, spent-red-C-AgxNiySiBEA were recorded on Geigerflex Rigaku-Denki
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(Japan) diffractometer with nickel filtered and CuKα radiation. Data acquisitions for sample
after reduction step and after kinetic run were recorded in the 2θ range of 5 - 90º with step of
0.02º.
1.3 Catalysts activity measurements
The reactions of hydrodechlorination of 1,2-dichloroethane (1,2-DCE, HPLC grade,
99.8% pure from Sigma–Aldrich, Germany) were carried out at atmospheric pressure, in a
glass flow reactor equipped with fritted disk to place a catalyst charge. Prior to reaction, 0.2 g
of the catalyst, after calcination step at 773 K, was reduced in flowing 10 % H2/Ar (25 cm3
min-1), ramping the temperature from room temperature to 873 K (10 K min-1) and kept at 873
K for 3 h. After this time, the catalysts were cooled to 523 K, then contacted with the flowing
reaction mixture (H2 + Ar + 1,2-DCA) of 2.86 × 10−5 mol s−1 (42 cm3 min-1) The contact time
was of 0.7 s and the space velocity (SV) of 0.0035 (m3 kg−1 s−1). 1,2-DCE was provided from
a saturator kept at 273 K to give the partial pressure of 1,2-dichloroethane of 2.9 kPa. The
partial pressure ratio pH2/p1,2-DCE was 1:1. The flows of H2 and Ar, were fixed by using
Bronkhorst Hi-Tec mass flow controllers. The reaction was followed by gas chromatography,
using a HP5890 series II gas chromatograph with FID, a 5 % Fluorcol/Carbopack B column
(10 ft) from Supelco. The results of GC analysis were elaborated using HP Chemstation. The
total FID signal from the first two analyses was similar to that observed in subsequent GC
analyses.
2. Results and discussion
2.1. Diffuse reflectance UV–vis investigation
In the DR UV-vis spectrum of C-Ni2.0SiBEA (Fig. 1) the bands at 460 and 555 nm are
related to Ni(II) in tetrahedral or strongly distorted tetrahedral coordination and correspond to
oxygen–tetrahedral Ni(II) charge transfer transitions [17,18]. DR-UV vis spectrum of C-
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Ag2.0SiBEA (Fig. 1) contains characteristic band at 214 nm, strongly related to the charge
transfer transition between 4d10 and 4d95s1 level of highly dispersed mononuclear Ag(I), in
line with earlier reports for Ag-MFI, Ag+/ZSM-5 and AgBEA zeolites, or Ag/Al2O3, [18-22].
Additionally, presence of the bands at 265 and 420 nm in the case of C-Ag2.0SiBEA may be
δ+
the consequence of partial reduction and agglomeration of Ag+ to Agn clusters under
calcination condition and the presence of silver nanoparticles.
For C-Ag2.0Ni2.0SiBEA (Fig. 1) the band at 214 nm related to the charge transfer transition
between 4d10 and 4d95s1 level of highly dispersed mononuclear Ag(I) is present as well as the
δ+
band at 265 nm attributed to Agn clusters. In addition, the bands present between 450–635
nm may be related to Ni(II) in tetrahedral and pseudo-tetrahedral coordination and correspond
to oxygen–tetrahedral Ni(II) charge transfer transition [17,18] indicating that nickel in C-
Ag2.0Ni2.0SiBEA is mainly present as pseudo-tetrahedral isolated centers.
2.2. Temperature – programmed reduction results
Temperature-programmed reduction experiments were carried out to determine the
reducibility of silver and silver and nickel in C-Ag2.0SiBEA and C-Ag2.0Ni2.0SiBEA zeolites,
respectively. As shown in Fig. 2 TPR profile for C-Ag2.0SiBEA contains four reduction
peaks. The low intense reduction peaks at 312 and 363 K could be assigned to reduction of
well dispersed silver oxides, in agreement with earlier works on silver based catalysts [23,24].
Two reduction peaks at 645 and 744 K may be attributed to reduction of excellent dispersed
silver species, most probably present C-Ag2.0SiBEA as mononuclear isolated Ag(I).
The TPR pattern of C-Ni2.0SiBEA (Fig. 2) contains three peaks present at 730, 650
and 845 K. The main signals at 730 K and 845 K suggests that nickel in C-Ni2.0SiBEA is well
dispersed as two kinds of isolated Ni(II) pseudo-tetrahedral species, strongly bound to SiBEA
matrix [25,26]. Appearance of reduction peak at 650 K may be explained by the presence in
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C-Ni2.0SiBEA small amount of octahedral Ni(II) species, easier reduced to Ni(0) than pseudo-
tetrahedral Ni(II) one.
In TPR pattern of C-Ag2.0Ni2.0SiBEA five peaks are present. The signals in the range
of 618 – 672 K are due to the presence of nickel species in pseudo-tetrahedral coordination.
The shift of the peaks to lower temperatures than that observed for C-Ni2.0SiBEA in our
earlier work [9], may be caused by present of silver species, that slightly change of nickel
environment and/or lead to formation of silver-nickel alloys. The presence of the TPR peaks
corresponding to reduction of well dispersed silver oxides at higher temperature (352 and 390
K) than those observed for C-Ag2.0SiBEA, suggests also about the interaction between silver
and nickel in C-Ag2.0Ni2.0SiBEA. Moreover, the reduction peak observed for C-
Ag2.0Ni2.0SiBEA at 744 K confirms that in this sample isolated mononuclear Ag(I) are
present.
2.3. TEM investigation
Transmission electron microscopy images of red-C-Ag2.0SiBEA and red-C-
Ag2.0Ni2.0SiBEA are shown in Fig. 3a. Both, TEM images and histograms show rather
uniform distribution of metallic nanoparticles for both red-C-Ag2.0SiBEA and red-C-
Ag2.0Ni2.0SiBEA with the vast amount of average nanoparticles size of 2-3 nm and 3-4 nm,
respectively. In relation to our earlier studies concerning red-C-Cu2.0Ni2.0SiBEA [10] in
hydrodechlorination of 1,2-dichloroethane, very small nanoparticles size obtained for
bimetallic Ag-Ni catalyst could suggest that two-step postsynthesis method used for
preparation of red-C-Ag2.0Ni2.0SiBEA allowed to formation rather separate Ag(0) and Ni(0)
nanoparticles than bimetallic alloys.
To confirm this statement the independent STEM and HRTEM experiments were
realised. They confirmed our suppositions. Fig. 3b shows the typical STEM image and EDS-
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elemental mapping of Ag (violet) and Ni (orange) for red-C-Ag2.0Ni2.0SiBEA. HRTEM
images reveal rather uniform distribution of silver and nickel nanoparticles for red-C-
Ag2.0Ni2.0SiBEA zeolite with average metals particles size of 3.1 nm. Bimetallic Ag-Ni
catalyst contains separately located and very small (~1.5 nm) Ni nanoparticles and bigger
silver nanoparticles located in the direct vicinity with nickel. This phenomenon could confirm
the partial formation of Ag-Ni alloys.
2.4. Chemisorption results
Chemisorption measurements of H2 and CO using a conventional static method were
effective way to determine dispersion of nickel in red-C-Ag2.0Ni2.0SiBEA. For bimetallic Ag-
Ni sample rather high nickel dispersion was measured (30.0 % from H2 adsorption and 37.4%
from CO adsorption). The lower adsorption capability for bimetallic Ag-Ni catalyst than for
monometallic nickel sample (55 % from H2 adsorption and 60% from CO adsorption [5])
confirms the formation of Ag-Ni alloys. According to literature [16] very high compatibility
of the results obtained by H2 and CO chemisorption was observed.
2.5 Catalytic activity of Ag-Ni catalysts
Figure 4 shows the time on stream behaviour of red-C-Ag2.0Ni2.0SiBEA catalyst in
comparison with the results obtained for monometallic silver and monometallic nickel
samples. Red-C-Ag2.0SiBEA exhibits approximately halved lower activity in
hydrodechlorination of 1,2-dichloroethane than monometallic nickel and bimetallic Ag-Ni
material. However, as we reported in our recent work [5], SiBEA zeolite is practically
inactive in reaction condition, so it is worth noting that the measurable activity of
monometallic silver in 1,2-dichloroethane HDC (~ 4 % of conversion) is rather unique.
Earlier studies on silver catalysts in hydrodechlorination have shown that independently on
the synthesis method (conventional impregnation [27], sol – gel method [28] or
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photodeposition [29] and regardless of the kind of the support (C, SiO2 and TiO2) [27-29].
only negligible 1,2-dichloroethane conversion was identified for monometallic silver
catalysts, or silver catalysts were completely inactive in hydrodechlorination. This
phenomenon was ascribed to the rapid and irreversible deactivation of Ag sites by chlorine
during the HDC process. The measurable activity obtained for red-C-Ag2.0SiBEA could be the
effect application of two-step postsynthesis procedure as the method of synthesis very small
silver particles capable to promote electron transfer from metal to the support. The similar
phenomenon was observed for very small Pd particles in hydrodechlorination of
chlorobenzene [30]. The crucial role in activity of red-C-Ag2.0SiBEA plays also the
dealuminated form of BEA zeolite as the support for Ag species. This zeolite obtained by
dealumination of parent BEA material contains vacancies, which may be the cause of
formation of electron deficient Ag species, similarly like in case Au/Fe2O3 in
δ+
hydrodechlorination of 2,4-dichlorophenol [31]. The cationic Ag and/or Agn clusters thus
formed are resistant to deactivation by adsorbed chlorine and well-dispersed red-C-
Ag2.0SiBEA zeolite catalyst remains active during the reaction.
On the other hand red-C-Ni2.0SiBEA exhibits approximately two times higher activity
than silver catalyst and ~ 90 % of selectivity towards ethylene – desired product of
hydrodechlorination of 1,2-dichloroethene (Fig. 4). Whereas red-C-Ag2.0Ni2.0SiBEA shows
only slightly lower activity than red-C-Ni2.0SiBEA, (Fig. 4). So, the addition of nickel to Ag
plays the beneficial major role in increasing of red-C-Ag2.0Ni2.0SiBEA activity, while
maintaining 100% selectivity to ethylene.
Due to the fact that both nickel and silver nanoparticles supported on dealuminated
form of BEA are active in 1,2-DCE HDC, and both of them show very high selectivity toward
desired product, we suppose that Ni(0) can plays dual role in red-C-Ag2.0Ni2.0SiBEA zeolite
during conversion of 1,2-DCE to ethylene. So, it probably serves as the hydrogen source (in
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the case of Ag(0)-Ni(0) alloys) and as separately located nickel active sites in reaction with
1,2-dichloroethane.
According to the results of the calculations published by Pirard at al. [28]
hydrodechlorination of 1,2-dichloroethane correspond to a Langmuir–Hinshelwood model
including two types of active sites. It could mean that hydrodechlorination of 1,2-
dichloroethane into ethylene on red-C-Ag2.0Ni2.0SiBEA zeolite occurs both on Ag(0) and
Ni(0) sites through dissociative adsorption with successive breaking of the two C–Cl bonds
and desorption of ethylene. However, reaction on Ag(0), independently on used support,
usually leads to irreversible adsorption on chlorine atoms. Therefore, in practice, the activity
of monometallic silver has been never observed. So Therefore, the presence of Ni(0) as the
source of the atomic hydrogen in Ag-Ni alloys could prevent deactivation of Ag(0) sites. It
means that the simultaneously introduction of silver and nickel ions in dealuminated BEA
structure in the second step of postsynthesis procedure allows obtaining after reduction of
bimetallic Ag-Ni catalyst with well dispersed, separated Ag(0) and Ni(0) nanoparticles and
Ag-Ni alloys that have higher selectivity to ethylene than monometallic nickel catalyst.
2.6. X-ray diffraction investigation
The XRD patterns of red-C-Ag2.0SiBEA and red-C-Ag2.0Ni2.0SiBEA (Fig.5) are
typical of BEA structure as was observed earlier [5], so the incorporation of nickel and silver
into zeolite structure did not damage the BEA matrix. The absence of diffraction lines of Ni
and NiO in bimetallic sample indicates a good dispersion of nickel species, what is in
agreement with our earlier studies [5,10]. On the other hand, the presence of diffraction lines
characteristic for Ag(0) in red-C-Ag2.0SiBEA and red-C-Ag2.0Ni2.0SiBEA (Fig.5 circles)
indicates the average silver diameter based on (1 1 1) XRD line broadening as 6 nm.
Moreover, comparative study between XRD results obtained for red-C-Ag2.0SiBEA,
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red-C-Ag2.0Ni2.0SiBEA, spent-red-C-Ag2.0SiBEA and spent-red-C-Ag2.0Ni2.0SiBEA have
shown that AgCl is formed on both catalysts under reaction conditions (Fig. 5 – triangles)
with average AgCl diameter based on (0 0 2) XRD line broadening - 9 nm. It should be
stressed that, in case of spent-red-C-Ag2.0Ni2.0SiBEA there has been only partial
transformation of Ag(0) into AgCl. This phenomenon may confirm that coexistence of Ag(0)
and Ni(0) in red-C-Ag2.0Ni2.0SiBEA catalyst partially blocks deactivation of Ag(0) by
chlorine species. On the other hand, the formation of significant amounts of AgCl during
HDC reaction could suggest about confirms the presence in red-C-Ag2.0Ni2.0SiBEA of both
separately located Ni(0) and Ag(0) nanoparticles and Ag-Ni alloys.
Conclusions
The two-step postsynthesis method used for catalyst preparation is an excellent way to
obtain Ag-Ni zeolite materials with high level of metal dispersion and good catalytic
properties.
Both, red-C-Ag2.0SiBEA and red-C-Ag2.0Ni2.0SiBEA catalysts are active in
hydrodechlorination of 1,2-dichloroethane with 100 % of selectivity toward ethylene –
desired product of the reaction.
Addition of nickel to silver catalyst leads to increasing of the overall conversion in
HDC and protects silver species against irreversible adsorption chlorine species and formation
of AgCl.
Acknowledgements
Project funded by the Foundation for Polish Science, POMOST/2011-4/11 co-financed by the
EU European Regional Development Fund (AŚ, IZ, SD). Special thanks for Sandra Casale
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from Laboratoire de Réactivité de Surface, Sorbonne Universités, UPMC Univ Paris 06 for
TEM measurements. Special thanks for Dmytro Lisovytskiy from Institute of Physical
Chemistry, PAS for XRD measurements.
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Figure captions:
Figure 1. DR UV-vis spectra recorded at ambient atmosphere of C-Ni2.0SiBEA, C-
Ag2.0SiBEA and C-Ag2.0Ni2.0SiBEA zeolites.
Figure 2. Temperature - programmed reduction profiles of C-Ni2.0SiBEA, C-Ag2.0SiBEA and
C-Ag2.0Ni2.0SiBEA zeolites.
Figure 3a. TEM images and metal nanoparticle size distribution of red-C-Ag2.0SiBEA and
red-C-Ag2.0Ni2.0SiBEA zeolite catalysts.
Figure 3b. STEM images and EDS-elemental mapping of Ag (violet) and Ni (orange) for red-
C-Ag2.0Ni2.0SiBEA
Figure 4. Time on stream behavior of red-C-Ni2.0SiBEA red-C-Ag2.0SiBEA and red-C-
Ag2.0Ni2.0SiBEA zeolite catalysts in hydrodechlorination of 1,2-dichloroethane at 523 K:
overall conversion and ethylene selectivity.
Figure 5. XRD results for red-C-Ag2.0SiBEA, red-C-Ag2.0Ni2.0SiBEA, spent-red-C-
Ag2.0SiBEA and spent-red-C-Ag2.0Ni2.0SiBEA zeolite catalysts (circles – Ag(0) triangles –
AgCl).
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214
265
214
265
C-Ag Ni SiBEA
2.0
2.0
650
555
460
420
C-Ag SiBEA
2.0
C-Ni SiBEA
2.0
555
460
200
300
400
500
600
700
800
Wevelength (nm)
Figure 1
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Figure 2
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45
40
33,7
35
30
25
18,9
18,6
20
15
10
5
12,8
4,8
3,6
2,8
1,8
1,3
0,8
0,5
0,3
0,3
0,0
0,0
0
35
30
25
20
15
10
5
30,8
24,5
9,3
6,6
6,0
4,0
4,0
3,4
2,6
2,6
2,4
1,6
0,8
0,6 0,6
0
Figure 3a
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Ag
Ni
Ag+Ni
Figure 3b
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Figure 4
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Figure 5
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Graphical Abstract
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Highlights
 Two-step postsynthesis method allowed to obtain catalysts with high metal
dispersion.
 HRTEM of Ag-Ni catalyst distinguished separately Ni(0) and Ag(0)
nanoparticles.
 Ag-Ni-containing catalyst is active in HDC of 1,2-dichloroethane
 Red-C-AgSiBEA and red-C-AgNiSiBEA catalysts showed 100 % selectivity
toward ethylene.
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