Acetylene hydrochlorination over bimetallic Ru-based catalysts

Article abstract of DOI:10.1039/c3ra42867b

Ruthenium-based catalysts including monometallic Ru, bimetallic Ru-Cu and Ru-Co were prepared using spheric active carbon (SAC) as the support, and their catalytic performance was assessed for the acetylene hydrochlorination reaction, characterized by BET, TG, TEM, TPR and XPS. It is suggested that using cobalt as the additive can significantly enhance the catalytic activity of the Ru/SAC catalyst for the acetylene hydrochlorination reaction. Over the 1%Ru1Co3/SAC catalyst the acetylene conversion is maintained above 95% with 48 h on stream under reaction conditions of 170 °C, C₂H₂ hourly space velocity = 180 h^-1 and the feed HCl/C₂H₂ volume ratio = 1.1; while the addition of copper results in a lower acetylene conversion. It is illustrated that the cobalt additive can greatly influence the amount of ruthenium species involved in RuO₂, Ru⁰, RuO_x and RuCl₃ in the catalyst, which results in good catalytic activity and capability to inhibit coking of the 1%Ru1Co3/SAC catalyst. The optimal 1%Ru1Co3/SAC catalyst is a promising non-mercuric catalyst for PVC manufacture, with the advantages of both good stability and low cost. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra42867b

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Acetylene hydrochlorination over bimetallic Ru-based
catalysts†
Cite this: DOI: 10.1039/c3ra42867b
a
a
a
Jinli Zhang,ab Wei Sheng, Cuili Guo and Wei Li
*
Ruthenium-based catalysts including monometallic Ru, bimetallic Ru–Cu and Ru–Co were prepared using
spheric active carbon (SAC) as the support, and their catalytic performance was assessed for the acetylene
hydrochlorination reaction, characterized by BET, TG, TEM, TPR and XPS. It is suggested that using cobalt as
the additive can significantly enhance the catalytic activity of the Ru/SAC catalyst for the acetylene
hydrochlorination reaction. Over the 1%Ru1Co3/SAC catalyst the acetylene conversion is maintained
above 95% with 48 h on stream under reaction conditions of 170 ꢀC, C2H2 hourly space velocity ¼ 180
hꢁ1 and the feed HCl/C2H2 volume ratio ¼ 1.1; while the addition of copper results in a lower acetylene
conversion. It is illustrated that the cobalt additive can greatly influence the amount of ruthenium
species involved in RuO2, Ru0, RuOx and RuCl3 in the catalyst, which results in good catalytic activity and
capability to inhibit coking of the 1%Ru1Co3/SAC catalyst. The optimal 1%Ru1Co3/SAC catalyst is a
promising non-mercuric catalyst for PVC manufacture, with the advantages of both good stability and
low cost.
Received 9th June 2013
Accepted 19th August 2013
DOI: 10.1039/c3ra42867b
www.rsc.org/advances
acetylene hydrochlorination reaction. Hutchings and co-workers4,5
performed the pioneer work on developing Au-based catalysts for
1. Introduction
Hydrochlorination of acetylene is one of the important reaction
pathways to produce vinyl chloride, particularly in Chinese
regions enriched with coal, which can be used as the monomer to
manufacture polyvinyl chloride (PVC),1,2 the third most widely
produced plastic that is suitable for a wide variety of applications
including pipes, clothing, electric wires, portable electronic
accessories, ceiling tiles, etc. The current industrial catalyst for
acetylene hydrochlorination reaction is mercuric chloride sup-
ported on activated-carbon. Mercuric chloride is highly toxic and
cumulative in the environment, hence, the UN Environment
Programme's Governing Council has imposed a global crack-
down agreement on the use of the poisonous pollutant mercury
since 2009.3 Being unable to use mercuric chloride catalysts has
created a bottleneck in current industrial processes that produce
vinyl chloride monomers through the acetylene hydro-
chlorination reaction. It is therefore urgent to explore new green
catalysts for acetylene hydrochlorination to replace the poisonous
mercuric chloride, in order to promote the global green economy
and a sustainable crisis-free future.
acetylene hydrochlorination, and found that the initial catalytic
activity of a gold catalyst was higher than that of a mercuric
chloride catalyst, whereas the stability of the gold catalyst was
poor, as was the platinum and palladium catalysts. Zhang et al.6
studied the deactivation mechanism of a gold catalyst in the
acetylene hydrochlorination reaction using a density functional
theory method, and disclosed that the intermediate chlorovinyl
was difficult to be desorbed from AuCl3 so as to inhibit the co-
adsorption of the reactant HCl and C2H2 on the gold active sites,
resulting in a decrease of catalytic activity. Conte7 et al. studied the
effect of the second metal additive on the catalytic activity of the
gold catalyst, and concluded that a higher conversion was
obtained over Au–Rh catalysts while the addition of Pd, iron Pt can
slightly enhance the initial catalytic activity of Au/C catalysts. In
addition, Wang et al.8 optimized the acetylene hydrochlorination
reaction over bimetallic Au–Cu/C catalysts and obtained an acet-
ylene conversion of 99.5% at 200 h on stream under conditions of
160 ꢀC, C2H2 gas hourly space velocity (GHSV) ¼ 50 hꢁ1 and a feed
HCl/C2H2 volume ratio ¼ 1.15. Recently, under higher C2H2 GHSV
of 360 hꢁ1 an acetylene conversion of 91.6% was obtained over
bimetallic Au–Co(III) catalysts during a 50 h reaction at 150 ꢀC and
the feed HCl/C2H2 volume ratio ¼ 1.15.9 It is suggested that the
catalytic activity of gold catalysts can be signicantly enhanced by
screening proper second metal additives.
Noble metal catalysts involving Au, Pt, Pd, etc. have been
intensively studied as a promising alternative to catalyze the
aKey Laboratory for Green Chemical Technology MOE, Key Laboratory of Systems
Bioengineering MOE, Tianjin University, Tianjin 300072, People's Republic of
China. E-mail: liwei@tju.edu.cn
As well as these noble metals, some non-noble metals have
also been studied as potential catalysts for the acetylene
hydrochlorination reaction. For example, Zhou et al.10 reported
that over bimetallic phosphates of Cu and Bi supported on SiO2
bSchool of Chemistry and Chemical Engineering, Shihezi University, Xinjiang, Shihezi,
832000, People's Republic of China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c3ra42867b
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ꢀ
the initial acetylene conversion of 85% was obtained at 200 C porosity analyzer. The samples were rst degassed at 150 ꢀC for
and C2H2 GHSV ¼ 360 hꢁ1. A Chinese patent11 suggested that 6 h and analyzed via liquid nitrogen adsorption–desorption at
the monometallic Ru catalyst showed high catalytic activity for ꢁ196 ꢀC.
acetylene hydrochlorination with no detailed reaction condi-
A thermogravimetric analysis (TGA) of the samples was
tions. Recently Zhu et al.12 reported that the calculated activa- performed using a NETZSCH STA 449 F3 Jupiterꢀ thermogra-
tion barrier for the acetylene hydrochlorination is 16.3, 11.9, vimetric-differential scanning calorimetry (TG-DSC) simulta-
and 9.1 kcal molꢁ1 over HgCl2, AuCl3 and RuCl3, respectively, neous thermal analyzer in an air atmosphere at a ow rate of 30
indicating that RuCl3 is probably a good catalyst for the acety- ml minꢁ1. The temperature was increased from 50 ꢀC to 900 ꢀC
ꢁ1
ꢀ
lene hydrochlorination reaction.
at a rate of 10 C min
.
Enlightened by the positive effects of copper and cobalt ions
Samples for examination by transmission electron micros-
on the catalytic activity of gold catalysts, in this paper, we study copy (TEM) were prepared by dispersing the catalyst powder in
the catalytic performance of bimetallic Ru-based catalysts for the ethanol, then allowing a drop of the suspension to evaporate on
acetylene hydrochlorination reaction, using Cu(II) and Co(III) as a holey carbon lm supported by a 300-mesh copper TEM grid.
the additive. Through characterization by BET, TG, TEM, TPR and Bright-eld and annular dark-eld (ADF) imaging experiments
XPS, it is indicated that adding cobalt or copper can signicantly were carried out using a JEM2100F TEM and an FEI Titan 80-300
inuence the catalytic species of ruthenium, and over 1%Ru1Co3/ TEM/STEM equipped with CEOS spherical aberration corrector,
SAC catalyst the acetylene conversion maintains aboveꢁ915% with respectively.
48 h on stream under 170 ꢀC and C2H2 GHSV ¼ 180 h
.
Temperature-programmed reduction (TPR) experiments
were performed in a micro-ow reactor fed with a 10.0% H2–Ar
mixture owing at a rate of 50 ml minꢁ1. The weight of the
tested samples was 100 mg. Prior to each test, the samples were
2. Experimental
2.1 Catalyst preparation
ꢀ
treated with N2 gas at 60 C for 30 min. The temperature was
then increased from 60 to 910 ꢀC at a rate of 10 C minꢁ1. The
ꢀ
The sphere activated carbon (SAC) support (20–40 mesh) was
rst treated with a 1 mol Lꢁ1 HCl aqueous solution at 70 ꢀC for
5 h to remove impurities, followed by washing with tri-distilled
hydrogen consumption was measured using
conductivity detector (TCD).
a thermal
ꢀ
X-ray photoelectron spectroscopy (XPS) spectra were recor-
ded using a Kratos Axis Ultra DLD spectrometer employing a
monochromated Al-Ka X-ray source (hn ¼ 1486.6 eV), hybrid
(magnetic/electrostatic) optics and a multi-channel plate and
delay line detector (DLD). All XPS spectra were recorded using
an aperture slot of 300 ꢂ 700 microns, survey spectra were
recorded with a pass energy of 80 eV, and high resolution
spectra with a pass energy of 40 eV. In order to subtract the
surface charging effect, the C1s peak has been xed at a binding
energy of 284.6 eV.
water to a neutral pH and then being dessicated at 150 C for
20 h. A RuCl3 aqueous solution was added quantitatively into
ꢀ
the cleaned SAC support at 60 C under stirring for 16 h, the
obtained mixture was dessicated at 150 ꢀC for 18 h so as to
prepare the monometallic Ru/SAC catalysts. When CuCl2 was
added into the RuCl3 aqueous solution with a certain molar
ratio of Ru/Cu, the bimetallic Ru–Cu/SAC catalysts can be
prepared through a procedure similar to that above.
To prepare the bimetallic Ru–Co/SAC catalysts, we rst
produced Co(III) species using the precursor of CoCl2 as below.
0.0577 g of CoCl2 and 0.0382 g of NH4Cl were dissolved in 2 ml
water and mixed with 0.01 g of cleaned SAC, followed by adding
2 ml of concentrated ammonia at room temperature. Then 2 ml
of 6% H2O2 were added dropwise into the above mixture at 10 ꢀC,
2.3 Catalytic performance tests
Catalytic performances of monometallic and bimetallic Ru-
based catalysts were assessed with a C2H2/HCl feed volumetric
ꢀ
aer incubating at 60 C for 20 min 1 ml of concentrated HCl
ratio of 1 : 1.1 and the GHSV (C2H2) of 180 hꢁ1 at 170 C. The
ꢀ
solution was input at 2 ꢀC, so as to obtain the catalytic species of
Co(III). Using the mixture solution of such Co(III) species and
RuCl3 to impregnate the cleaned SAC support, bimetallic Ru–Co/
SAC catalysts can be produced through the above preparation
procedure.
catalytic performance tests were conducted in a xed-bed ow
microreactor (i.d.10 mm). The reactor temperature was regu-
lated using an AI-808FX5 temperature controller from the
Yudian Automation Technology liability company (Xiamen,
China). A pipeline was purged with nitrogen before the reaction
to remove water and air in the system. C2H2 (30 ml minꢁ1) and
HCl (33 ml minꢁ1) were then fed through the lter (to remove
trace impurities) via calibrated mass ow controllers to a heated
reactor containing 10 ml of the catalyst. The effect of the
external diffusion was eliminated at the C2H2 ow rate range of
25–100 ml minꢁ1. The reaction rate was not limited by the
internal mass transport within the 0.180–0.900 mm grain size
range; thus the reaction was not affected by the internal and
external diffusion. The pressure of the reactants, both HCl and
In order to make the discussion clear, the catalysts was named
in terms of the catalytic components, the molar ratio of the two
metallic components as well as the content of ruthenium, e.g.,
0.1%Ru/SAC indicates the monometallic ruthenium catalysts
with the ruthenium content of 0.1 wt%, while 0.1%Ru1Co1/SAC
indicates the bimetallic ruthenium–cobalt catalysts with the
ruthenium content of 0.1 wt% and the Ru/Co molar ratio of 1 : 1.
2.2 Catalyst characterization
Low-temperature N2 adsorption–desorption experiments were C2H2, was in the 1.1–1.2 bar range, which was chosen both for
conducted using a Micromeritics ASAP 2020C surface area and safety reasons and to test the catalyst under mild conditions.7,13
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The exit gas mixture was passed through an absorption bottle
containing NaOH and then sent into a Beifen3420A chromato-
graph for analysis.
3. Results and discussion
3.1 Catalytic performance for acetylene hydrochlorination
Fig. 1 shows the catalytic performance of a monometallic cata-
lyst involving monometallic Ru, Cu, Co for acetylene hydro-
chlorination at 170 ꢀC and C2H2 GHSV of 180 hꢁ1. Over 1%Ru/
SAC the acetylene conversion is stable at 91% during a 48 h
reaction, while the selectivity to vinyl chloride (VCM) increases
slightly from the initial 96.8% to 99.3% at 48 h. For the
monometallic copper catalyst 5%Cu/SAC, the acetylene
conversion is 40% at a reaction time of 48 h, while over cobalt
catalyst 1.5%Co/SAC the acetylene conversion is as low as 2%,
even lower than that over the lone SAC support (14%). However,
the selectivities to VCM over copper, cobalt and the lone SAC
support are all equal to 100%.
In order to improve the selectivity to VCM but also the
economical efficiency of the Ru catalysts, we studied the effects
of copper or cobalt additives on the catalytic performance of
0.1%Ru catalysts. As shown in Fig. 2a1 and a2, the acetylene
conversion over bimetallic Ru–Cu catalysts, with the Ru/Cu
molar ratio from 1 : 0.5, 1 : 1 to 1 : 3, is lower than that over a
monometallic Ru catalyst. As the Ru/Cu molar ratio equals 1 : 1,
the acetylene conversion over 0.1%Ru1Cu1/SAC is close to that
over 0.1%Ru/SAC catalyst. Meanwhile, the selectivities to VCM
over these bimetallic Ru–Cu catalysts is somewhat higher than
that over the 0.1%Ru/SAC catalyst within the rst 10 h of the
reaction, aer 10 h the selectivities to VCM show little depen-
dence on the copper additives.
In the case of bimetallic Ru–Co catalysts, as shown in
Fig. 2b1 and b2, the acetylene conversion over 0.1%Ru1Co1/SAC
is 80% at the reaction time of 48 h, approximate to that over
0.1%Ru/SAC; whereas over 0.1%Ru1Co3/SAC the acetylene
conversion is signicantly higher than that over 0.1%Ru1Co1/
SAC. With much higher cobalt content, the incremental extent
of the acetylene conversion tends to be lower, i.e., over 0.1%
Ru1Co5/SAC the acetylene conversion reaches 89% aer a
reaction time of 48 h, only a little higher than 87% over 0.1%
Ru1Co3/SAC. On the other hand, the selectivity to VCM over
0.1%Ru1Co3/SAC is about 99.7% aer a reaction time of 48 h,
which is the highest among these Ru–Co catalysts.
Fig. 2 The acetylene conversion (a1) and the selectivity to VCM (a2) over
bimetallic Ru–Cu catalysts, and those over Ru–Co catalysts (b1) and (b2) with the
ruthenium content of 0.1%. Reaction conditions are: temperature (T) ¼ 170 ꢀC,
C2H2 GHSV ¼ 180 hꢁ1, vHCl/v
¼ 1.1.
C2H2
Further Fig. 3 compares the catalytic performance of Ru–Cu
and Ru–Co under the optimal metallic molar ratio with higher
ruthenium content of 1 wt%. The acetylene conversion over 1%
Ru1Cu1/SAC catalyst is 69% at the reaction time of 48 h, lower
than 89% of 1%Ru/SAC catalyst; while over 1%Ru1Co3/SAC
catalyst the acetylene conversion maintains above 95% with 48
h on stream, and the selectivity to VCM is 100% over 1%
Ru1Co3/SAC catalyst. It is suggested that there exists a synergic
effect between ruthenium and cobalt catalytic species, which
can signicantly enhance the catalytic activity of Ru/SAC cata-
lyst for the acetylene hydrochlorination reaction.
3.2 Catalyst texture properties
Fig. 4a shows the N2 adsorption–desorption isotherms of the
fresh 1%Ru, 1%Ru1Cu1, and 1%Ru1Co3 catalysts. For the SAC
support alone, it shows a type-I adsorption isotherm, due to the
existence of a large number of micropores.14–16 For the mono-
metallic Ru and bimetallic Ru–Cu, and Ru–Co catalysts, similar
adsorption isotherms are exhibited; and the pore size distri-
butions of these Ru-based catalysts are approximate to that of
the support (Fig. 4b).
Fig. 1 The acetylene conversion (a) and the selectivity to VCM (b) over mono-
metallic Ru, Cu, Co catalysts. Reaction conditions are: temperature (T) ¼ 170 ꢀC,
C2H2 GHSV ¼ 180 hꢁ1, vHCl/vC H ¼ 1.1.
Fig. 3 (a) The acetylene conversion and (b) the selectivity to VCM over 1%Ru,
1%Ru1Cu1, and 1%Ru1Co3 catalysts. Reaction conditions are: temperature (T) ¼
170 ꢀC, C2H2 GHSV ¼ 180 hꢁ1, vHCl/vC H ¼ 1.1.
2
2
2
2
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Fig. 4 N2 adsorption–desorption isotherms (a) and corresponding pore size
distribution (b) of the support SAC, the fresh 1%Ru/SAC, 1%Ru1Cu1/SAC, and
1%Ru1Co3/SAC samples.
Table 1 lists the specic surface area, the pore volume and the
average pore diameter of the fresh Ru-based catalysts. It is indi-
cated that with the dopant of 1 wt% Ru the specic surface area
decreases from 1339 m2 gꢁ1 to 847.1 m2 gꢁ1, the total pore volume
decreases from 0.666 cm3 gꢁ1 to 0.437 cm3 gꢁ1, while the average
pore diameter changes a little. As for the bimetallic 1%Ru1Cu1
and 1%Ru1Co3 catalysts, the specic surface area and the total
pore volume are a little higher than those of the monometallic Ru-
catalysts but lower than those of the support SAC.
Fig. 5 shows TEM images of the fresh and used 1%Ru-based
catalysts aer a 48 h reaction. For the monometallic 1%Ru/SAC
(Fig. 5a and b) and the bimetallic 1%Ru1Cu1/SAC catalysts
(Fig. 5c and d), the coverage density of black dots are obviously
increased aer a 48 h reaction. However, for the used 1%
Ru1Co3/SAC catalysts black dots appear sparsely aer a 48 h
reaction, even less than those in the fresh 1%Ru1Co3/SAC
catalysts (Fig. 5e and f).
Thermal gravimetric (TG) analyses were performed to
compare the differences between the fresh and used catalysts
aer different reaction times. In the case of the monometallic
Ru/SAC catalyst, the slight mass loss before 150 ꢀC is due to the
desiccation of adsorbed water, the rapid mass loss above 370 ꢀC
is caused by the burning of the SAC support (Fig. 6a), hence it is
the mass loss in the temperature range of 150–370 ꢀC that
reects the variation on the catalyst surfaces potentially caused
by coking during the acetylene hydrochlorination reaction. For
the fresh 1%Ru/SAC catalyst, the mass loss is 2.57% in the
temperature range of 150–370 ꢀC, while the used 1%Ru/SAC
aer reaction times of 12 h, 24 h, 36 h and 48 h show a mass loss
of 7.88%, 8.27%, 8.67% and 8.80% respectively (Table S1 in the
ESI†). Similarly for the bimetallic 1%Ru1Cu1/SAC catalyst rapid
Fig. 5 TEM images of fresh and used Ru-based catalysts. (a) Fresh 1%Ru/SAC, (b)
used 1%Ru/SAC, (c) fresh 1%Ru1Cu1/SAC, (d) used 1%Ru1Cu1/SAC, (e) fresh 1%
Ru1Co3/SAC, (f) used 1%Ru1Co3/SAC.
8.01%, 8.82%, 9.55% and 9.55%, respectively aer reaction
times of 12 h, 24 h, 36 h and 48 h (Table S2 in the ESI†).
It is worth mentioning that the TG curves for 1%Ru1Co3/SAC
are different from those of 1%Ru/SAC and 1%Ru1Cu1/SAC. As
shown in Fig. 6c, the mass loss of 1%Ru1Co3/SAC can be clas-
sied into four temperature periods, including the little mass loss
before 200 ꢀC due to the desiccation of adsorbed water, the mass
loss in the temperature range of 200–325 ꢀC caused by the
decomposition of cobalt compounds, the mass loss in the range
ꢀ
ꢀ
mass loss occurs above 370 C (Fig. 6b); the mass loss for the
of 325–400 C due to potential coking on the surfaces, and the
rapid mass loss above 400 ꢀC caused by the burning of SAC
support. For the fresh 1%Ru1Co3/SAC the mass loss in the range
of 200–325 ꢀC is 11.83%; whereas aer reaction times of 12 h, 24
h, 36 h and 48 h, the mass loss in the range of 200–325 ꢀC
decreases gradually to 8.24%. The mass loss in the range of 325–
400 ꢀC is 0.31% for the fresh 1%Ru1Co3/SAC, and 3.03%, 3.56%,
3.77% and 4.19% for the used 1%Ru1Co3/SAC aer reaction
times of 12 h, 24 h, 36 h and 48 h (Table S3 in the ESI†).
fresh 1%Ru1Cu1/SAC catalyst is 1.95% in the range of 150–
ꢀ
370 C, and for the used 1%Ru1Cu1/SAC shows a mass loss of
Table 1 Pore structure parameters of fresh 1%Ru/SAC, 1%Ru1Cu1/SAC and 1%
Ru1Co3/SAC samples
SBET
Total pore volume
Average pore
diameter (nm)
Catalyst
(m2 gꢁ1
)
(cm3 gꢁ1
)
Table 2 lists the coke content over the used 1%Ru/SAC, 1%
Ru1Cu1/SAC and 1%Ru1Co3/SAC, calculated by the difference of
the mass loss between the fresh and used catalysts in the special
temperature range reecting the coke deposition. It is indicated
SAC
1339
847.1
983.5
935.1
0.666
0.437
0.491
0.468
0.503
0.498
0.528
0.503
1%Ru/SAC
1%Ru1Cu1/SAC
1%Ru1Co3/SAC
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Fig. 6 (a) TGA and DTG curves of the fresh and used catalysts of 1%Ru/SAC and (a-1) the magnified view, (b) 1%Ru1Cu1/SAC and (c) 1%Ru1Co3/SAC.
that aer a 48 h reaction time the coke content is 6.23% over the Ru1Cu1/SAC, the prominent peak is at 212 ꢀC due to the
used 1%Ru/SAC catalyst, 7.6% over the used 1%Ru1Cu1/SAC, and reduction of the Ru cation species, accompanied by a shoulder
3.88% over the used 1%Ru1Co3/SAC. It is suggested that cobalt peak at 251 ꢀC that is due to the reduction of Cu2+ to Cu1+
0
additives can reduce the coking deposition on ruthenium cata- without the inuence of Cu1+ to Cu at 436 C (the location of
ꢀ
lysts, whereas copper additives increase the coking amount.
the black arrow),21,23 as reected by the TPR prole of the
monometallic Cu/SAC catalysts. As for the fresh 1%Ru1Co3/
SAC catalysts, the TPR prole shows a small shoulder band at
280 ꢀC, a sharp peak at 315 ꢀC, as well as a broad band around
3.3 Catalytic species of Ru catalysts
TPR proles of the fresh and used 1%Ru/SAC, 1%Ru1Co3/SAC, 459 ꢀC. The peak around 459 ꢀC is due to the reduction of
1%Ru1Cu1/SAC catalysts disclose that the copper and cobalt cobalt ions(II) into cobalt atoms, compared with the TPR of the
additives greatly affect the reducibility of ruthenium catalysts, monometallic Co/SAC. The peak around 280–315 ꢀC is attrib-
as well as the variation of ruthenium species aer a 48 h uted to the reduction of ruthenium ions including RuCl3 and
reaction. As shown in Fig. 7, for the support SAC, only a broad ruthenium species with the valence higher than 4.24
ꢀ
H2 consumption zone from 600 to 900 C appears, which is a Comparing with the fresh 1%Ru/SAC, there appears a clear
consequence of methanation reactions of carbon and H2 at the shi of H2 consumption zone for the fresh 1%Ru1Cu1/SAC,
carbon surface.17,18 For the fresh 1%Ru/SAC catalyst the TPR and even a signicant shi for the fresh 1%Ru1Co3/SAC,
prole shows a broad band around 189 ꢀC tandem with 220 ꢀC, which suggests that strong interactions occur between RuCl3
which corresponds to the reduction peaks of RuCl3 and RuO2, and Co(NH3)6Cl3 or CuCl2, and the reducibility of these Ru-
respectively.19–21 Previously the complete reduction of unsup- based catalysts decreases in the order: 1%Ru1Cu1/SAC > 1%
ported RuCl3 was reported as 160 ꢀC.22 For the fresh 1% Ru/SAC > 1%Ru1Co3/SAC.
Table 2 Coke content of different reaction time of catalysts under different temperature ranges
Catalyst
Coke (%)
Catalyst
Coke (%)
Catalyst
Coke (%)
Fresh 1%Ru/SAC
0
Fresh 1%Ru1Cu1/SAC
0
Fresh 1%Ru1Co3/SAC
0
Used 1%Ru/SAC-12h
Used 1%Ru/SAC-24h
Used 1%Ru/SAC-36h
Used 1%Ru/SAC-48h
5.31
5.7
6.1
6.23
Used 1%Ru1Cu1/SAC-12h
Used 1%Ru1Cu1/SAC-24h
Used 1%Ru1Cu1/SAC-36h
Used 1%Ru1Cu1/SAC-48h
6.06
6.87
7.6
7.6
Used 1%Ru1Co3/SAC-12h
Used 1%Ru1Co3/SAC-24h
Used 1%Ru1Co3/SAC-36h
Used 1%Ru1Co3/SAC-48h
2.72
3.25
3.46
3.88
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deconvolution of the XPS spectra (Fig. S1 in the ESI†). For the
fresh 1%Ru/SAC catalyst, there appears Ru0 appears at 460.8 eV,
RuCl3 at 463.3 eV and RuO2 at 465.6 eV, with the content of
these ruthenium species decreasing in the order of RuCl3
>
RuO2 > Ru0. In the case of the fresh 1%Ru1Cu1/SAC, there exists
the ruthenium species with the binding energy at 460.5 eV,
463.0 eV, 465.0 eV and 466.9 eV, attributed respectively to Ru0,
RuCl3, RuO2, and RuOx that is due to the ruthenium valence
higher than 4.19,26–28 As for the fresh 1%Ru1Co3/SAC there exist
Ru0 species at 460.1 eV, RuCl3 at 463.0 eV, and RuO2 at 463.2 eV.
All the fresh catalysts show the most abundant species of RuCl3,
followed by the species of RuO2.
As listed in Table 3, the amounts of ruthenium species in the
used catalysts differ greatly from those in the fresh ones. For the
1%Ru/SAC catalysts, aer a 48 h reaction, the amounts of RuO2
increased from 23.7% to 40.8% and Ru0 from 5.3% to 6.2%,
while the contents of RuCl3 decreased from 71.0% to 53.0%. For
the 1%Ru1Cu1/SAC catalysts, aer 48 h, the contents of Ru0,
RuCl3 and RuO2 decrease slightly whereas the amount of RuOx
increased from 6.4% to 14.9%. For the 1%Ru1Co3/SAC catalyst,
aer 48 h, the content of Ru0 increased from 18.6% to 23.3%,
and RuO2 from 20.5% to 50.8%, whereas RuCl3 decreased from
60.9% to 14.5%. In addition RuOx species appears at 465.3 eV
(11.5%) for the used 1%Ru1Co3/SAC catalyst. Combined with
the good catalytic activity and the coking inhibition capability of
the 1%Ru1Co3/SAC catalyst (as shown in Fig. 3 and Table 2), it
is illustrated that the cobalt additive greatly inuences the
amount of ruthenium species involving RuO2, Ru0, RuOx and
RuCl3 in the catalyst, however, a detailed investigation of the
reaction mechanism is still needed to make it clear which
Fig. 7 H2-TPR profiles of the fresh and used 1%Ru/SAC, 1%Ru1Cu1/SAC and
1%Ru1Co3/SAC, as well as those of the blank SAC support, Co/SAC and Cu/SAC
samples.
The TPR proles of used 1%Ru/SAC, 1%Ru1Cu1/SAC cata-
lysts show a degree of band shi, compared with each indi-
vidual fresh catalyst. For the used 1%Ru/SAC catalyst, the
ꢀ
prominent peak shis to 315 C, suggesting the formation of
higher valent ruthenium species aer a 48 h reaction. For the
used 1%Ru1Cu1/SAC, the peak is about 290 ꢀC. Whereas for the
used 1%Ru1Co3/SAC, the TPR prole shows a broad band at
300 ꢀC, with the curve shape quite different from that of the
fresh catalyst. In combination with the TG analyses (Fig. 6), it is
conrmed that the decomposition of cobalt compounds occurs
as well as the formation of organometallic complexes involving
Ru and Co in the 1%Ru1Co3/SAC catalyst during acetylene
hydrochlorination. The reason for the signicant variations of
TPR proles for these Ru-based catalysts can be deduced further
by using XPS spectra.
XPS spectra were measured to study the valence variations of
the ruthenium species for the catalysts of 1%Ru/SAC, 1%
Ru1Cu1/SAC and 1%Ru1Co3/SAC. The deconvolution of the
Ru3p prole was adopted to discriminate between the ruthe-
nium species, because the overlapping of C1s signals makes it
difficult to unequivocally determin the Ru3d signals.25,26 Table 3
lists the binding energy and relative content of the Ru species in
the fresh and in the used catalysts respectively, based on the
ruthenium
species
is
predominant
to
acetylene
hydrochlorination.
4. Conclusions
For the acetylene hydrochlorination reaction, over the 1%Ru/
SAC catalyst the acetylene conversion is 91% with 48 h on
stream under conditions of 170 ꢀC, C2H2 hourly space velocity ¼
180 hꢁ1 and a feed HCl/C2H2 volume ratio ¼ 1.1. The addition of
cobalt can signicantly enhance the catalytic activity of the Ru/
SAC catalyst, over the 1%Ru1Co3/SAC catalyst and the acetylene
conversion is maintained above 95% with 48 h on stream; while
the addition of copper results in a lower acetylene conversion.
Based on the deconvolution of the XPS spectra, it is illustrated
that the cobalt additive greatly inuences the amount of
Table 3 The relative content and binding energy of Ru species in the fresh and used catalysts
XPS analysis, eV (area%)
Sample
Ru0
RuCl3
RuO2
RuOx
Fresh 1%Ru/SAC
460.8(5.3)
460.5(7.6)
460.1(18.6)
460.8(6.2)
458.9(4.9)
458.8(23.2)
463.3(71.0)
463.0(54.5)
463.0(60.9)
462.7(53.0)
461.4(52.9)
461.7(14.5)
465.6(23.7)
465.0(31.5)
465.9(20.5)
464.9(40.8)
463.5(27.3)
463.8(50.8)
—
Fresh 1%Ru1Cu1/SAC
Fresh 1%Ru1Co3/SAC
Used 1%Ru/SAC
Used 1%Ru1Cu1/SAC
Used 1%Ru1Co3/SAC
466.9(6.4)
—
—
464.1(14.9)
465.3(11.5)
RSC Adv.
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Acknowledgements
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Research Program of China (2012CB720300), the NSFC
Science Press, Beijing, 2009.
(21176174), and the Program for Changjiang Scholars and 17 P. D. Zgolicz, J. P. Stassi, M. J. Yanez, O. A. Scelza and S. R. de
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