Activated-carbon-supported gold-cesium(I) as highly effective catalysts for hydrochlorination of acetylene to vinyl chloride

Article abstract of DOI:10.1002/cplu.201402176

The synthesis of vinyl chloride from acetylene by hydrochlorination has gained tremendous interest in coal-based chemistry. Bimetallic gold-cesium(I)/activated carbon (Au-Cs^I/AC) catalysts were found to have a higher catalytic activity and stability for acetylene hydrochlorination when compared with gold catalysts. Over 1Au-4Cs^I/AC catalysts, the maximum conversion of acetylene was 94% and there was only 5% C₂H₂ conversion loss after 50 h of running time. Moreover, the 1Au-4Cs^I/AC catalyst delivered a stable performance during a 500 h test with the conversion of acetylene and the selectivity of vinyl chloride reaching more than 99.8 and 99.9 %, respectively. Temperature-programmed reduction of H₂, temperature-programmed desorption of C₂H₂, and X-ray photoelectron spectroscopy techniques were further applied to detect structural information on the Au-Cs^I/AC catalysts. Additives of CsCl indeed stabilized the catalytically active Au³⁺ species and inhibited the reduction of Au³⁺ to Au⁰, thereby improving the activity and long-term stability of gold-based catalysts.

Full text of DOI:10.1002/cplu.201402176

DOI: 10.1002/cplu.201402176
Full Papers
Activated-Carbon-Supported Gold–Cesium(I) as Highly
Effective Catalysts for Hydrochlorination of Acetylene to
Vinyl Chloride
Jia Zhao, Jiangtao Xu, Jinhui Xu, Jun Ni, Tongtong Zhang, Xiaoliang Xu, and Xiaonian Li*[a]
The synthesis of vinyl chloride from acetylene by hydrochlori-
nation has gained tremendous interest in coal-based chemistry.
Bimetallic gold–cesium(I)/activated carbon (AuꢀCsI/AC) cata-
lysts were found to have a higher catalytic activity and stability
for acetylene hydrochlorination when compared with gold cat-
alysts. Over 1Auꢀ4CsI/AC catalysts, the maximum conversion
of acetylene was 94% and there was only 5% C2H2 conversion
loss after 50 h of running time. Moreover, the 1Auꢀ4CsI/AC
catalyst delivered a stable performance during a 500 h test
with the conversion of acetylene and the selectivity of vinyl
chloride reaching more than 99.8 and 99.9%, respectively. Tem-
perature-programmed reduction of H2, temperature-pro-
grammed desorption of C2H2, and X-ray photoelectron spec-
troscopy techniques were further applied to detect structural
information on the AuꢀCsI/AC catalysts. Additives of CsCl
indeed stabilized the catalytically active Au3+ species and in-
hibited the reduction of Au3+ to Au0, thereby improving the
activity and long-term stability of gold-based catalysts.
Introduction
Vinyl chloride monomer (VCM) is an important chemical mate-
rial and intermediate commonly used in the production of
polyvinyl chloride (PVC).[1] Acetylene hydrochlorination is an
important coal-based route for the industrial production of
VCM following the reaction C2H2 +HCl!CH2 =CHCl (~H=
ꢀ124.8 kJmolꢀ1).[2] One of the advantages of using this route is
related to its economic benefit compared with the oxychlorina-
tion reaction based on petroleum. In addition, the energy
structure of China, with huge coal reserves, also means that
acetylene hydrochlorination is a very in-demand reaction; how-
ever, it is restricted by the toxicity and volatility of mercury
chloride used as a common catalyst for industrial acetylene hy-
drochlorination.[3] Therefore, extensive efforts have been made
to explore non-mercury catalysts as alternatives for acetylene
hydrochlorination.[4] The pioneering study by Hutchings and
co-workers revealed that gold in the Au3+ state demonstrated
unique catalysis in the gas-phase hydrochlorination of acety-
lene to form vinyl chloride.[2a,4a,c,5] Subsequently, AuCl3 species
supported on different carbon materials were demonstrated to
be the most active catalyst for the hydrochlorination of acety-
lene.[6] Despite these impressive results, the high standard elec-
trode potential of Au3+ may result in active species being
readily reduced to Au0 under the reaction conditions, and con-
sequently, losing activity.[2a,7] Therefore, extensive efforts have
to be made to improve the stability of AuCl3 catalysts for acet-
ylene hydrochlorination.
acetylene hydrochlorination. Among them, bimetallic support-
ed gold catalysts showed particularly promising results.[6,8] For
example, Dai et al. reported a supported gold–lanthanum cata-
lyst on pitch-based spherical activated carbon (SAC), which
was highly stable for the gas-phase hydrochlorination of acety-
lene, and they suggested that the addition of lanthanum to
gold could weaken the occurrence of coke deposition and in-
hibit the valence change of gold to improve the stability of
the catalyst.[6a] Wang et al. evaluated the catalytic activity and
stability of AuꢀCu/C and Au/C catalysts for the gas-phase cata-
lytic hydrochlorination of acetylene, and observed greater sta-
bility of AuꢀCu/C than that of Au/C.[6b] Research by Zhang
et al. indicated that the additives of cobalt(III), cobalt(II), and
lanthanum(III) could greatly inhibit the occurrence of coke
deposition on the catalyst surface, and also inhibit catalyst sin-
tering, thereby improving the long-term stability of gold-
based/SAC catalysts.[8c] In general, gold alloyed with other
metals did not significantly increase the activity. Furthermore,
if the activity was increased, the catalyst deactivated much
more rapidly.
Herein, a series of gold–cesium(I)/activated carbon (AuꢀCsI/
AC) catalysts were carefully investigated to show the benefits
of CsCl promotion of AC supporting gold catalysts for acety-
lene hydrochlorination. Notably, AuꢀCsI/AC catalysts showed
much higher catalytic activities than those of 1Au/AC catalysts.
The best catalytic performance was obtained over 1Auꢀ4CsI/
AC catalysts with an acetylene conversion of 93% and only 5%
C2H2 conversion loss after 50 h under the reaction conditions
of temperature 1808C and C2H2 gas hourly space velocity
(GHSV) of 740 hꢀ1. The influences of CsCl doping on the redox,
adsorption, and electronic properties of the AuꢀCsI/AC cata-
lysts were investigated by temperature-programmed reduction
(TPR), temperature-programmed desorption (TPD) and X-ray
The design of catalysts has, so far, been the main tool em-
ployed to attain the required level of catalytic performance for
[a] Dr. J. Zhao, J. Xu, J. Xu, J. Ni, T. Zhang, X. Xu, Prof. Dr. X. Li
College Of Chemical Engineering
Zhejiang University of Technology
Hangzhou, Zhejiang 310014 (P. R. China)
E-mail: xnli@zjut.edu.cn
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photoelectron spectroscopy (XPS) techniques. AuꢀCsI/AC
proved to be effective catalysts for the hydrochlorination of
acetylene.
promoted the initial catalytic activity of the 1Au/AC catalyst
and significantly enhanced the catalyst stability. In particular,
the 1Auꢀ4CsI/AC catalyst displayed optimal catalytic stability
for the hydrochlorination of acetylene with only 5% C2H2 con-
version loss after 50 h, as shown in Figure 1. These results
show that an increase in the CsCl content is effective in the in-
crease of hydrochlorination stability without significant loss of
catalytic activity. It should be highlighted that, for all tests per-
formed and reported in the current study, the selectivity to
VCM was virtually 100% with only trace amounts (<0.1%) of
1,2-dichlorethane and chlorinated oligomers observed.
Results and Discussion
The time course for gas-phase hydrochlorination of acetylene
over 1Au/AC is presented in Figure 1. Similar profiles obtained
The long-term stability, in particular, at elevated tempera-
tures, is crucial for the industrial application of hydrochlorina-
tion. To further demonstrate the superior performance of Auꢀ
CsI/AC, we chose to use 1Auꢀ4CsI/AC to investigate the stabili-
ty of the catalysts for the acetylene hydrochlorination reaction.
The catalytic results are shown in Figure 2. As expected, the
1Auꢀ4CsI/AC catalyst showed excellent stability under the re-
Figure 1. Catalytic performance of AuꢀCsI/AC catalysts. Reaction conditions:
T=1808C, C2H2 GHSV=740 hꢀ1, feed volume ratio V(HCl)/V(C2H2)=1.2.
over AuꢀCsI/AC catalysts are also shown in Figure 1. For mono-
metallic catalyst 1Au/AC, the maximum acetylene conversion
is 84% during a reaction time of 50 h, whereas over 1Auꢀ2CsI/
AC catalyst the acetylene conversion is 94% during a reaction
time of 5 h, which is 10% higher than that of 1Au/AC catalysts.
With a much higher cesium(I) content, the incremental extent
of the acetylene conversion tends to be higher. However, if the
loading amount of CsCl was more than 2 wt%, the positive
effect of increasing activity was barely obtained. The turnover
frequency (TOF) values of 1Au/AC, 1Auꢀ0.5CsI/AC, 1Auꢀ1CsI/
AC, 1Auꢀ2CsI/AC, and 1Auꢀ4CsI/AC were determined to be
0.24, 0.25, 0.26, 0.27, and 0.27 sꢀ1, respectively, and the value
was slightly higher than that of the Au/C catalysts reported by
Hutchings et al., though a lower amount of Au3+ was obtained
in this study than those obtained by Hutchings.[9] These results
show that the coexistence of CsCl species with Au/AC is effec-
tive in increasing the activity of the catalysts.
Figure 2. Long-term stability test of 1Auꢀ4CsI/AC. Reaction conditions:
T=1808C, C2H2 GHSV=50 hꢀ1, feed volume ratio V(HCl)/V(C2H2)=1.2.
action conditions of 1808C and C2H2 GSHV of 50 hꢀ1. The cata-
lyst 1Auꢀ4CsI/AC showed more than 99.8% conversion of
C2H2 and more than 99.9% selectivity to VCM without any de-
cline during a 500 h test, as demonstrated in Figure 2. The re-
sults indicated that the bimetallic 1Auꢀ4CsI/AC catalyst could
give favorable activity and stability. Because reports on long-
life non-mercuric catalysts are scare, the bimetallic AuꢀCsI cata-
lysts may be promising in future applications.
Controlled tests for the AC support without gold showed
that the activity of the 4CsI/AC catalyst was identical to that of
the support. The activity of AC can arise from the presence of
trace amounts of K+ and Al3+ in the carbon matrix because
these metals can display some activity in the hydrochlorination
reaction of acetylene.[4b] Compared with three AuꢀCsI/AC bi-
metallic catalysts, monometallic 1Au/AC catalyst shows a signif-
icant rate of deactivation. The acetylene conversion of 1Au/AC
catalyst decreased from 84 to 53% after 50 h; this indicated
that the 1Au/AC catalyst had low catalyst stability under these
reaction conditions. Surprisingly, the presence of CsCl species
TPR is a useful characterization technique for the analysis of
the catalysts reported herein because it is able to provide in-
formation on the quantification of the bulk Au3+ amount and
the changes in the carbon support matrix. Figure 3 presents
the H2-TPR profiles of 4CsI/AC, 1Au/AC, and AuꢀCsI/AC cata-
lysts. For the 4CsI/AC catalyst, a maximum hydrogen consump-
tion peak at approximately 7008C, which can be attributed to
the reduction of the surface groups of AC, is observed. It
should be noted that cesium(I) species cannot be reduced by
hydrogen. The TPR profiles of fresh gold catalyst and bimetallic
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formed, the gold metal loading should be considered as equal
to the nominal amount of metal impregnated onto the sup-
port. Thus, the increase in Au3+ could be explained by the in-
creasing CsI content in the samples; Au particles preferentially
exist in the Au3+ state. This also shows that, if the amount of
Au3+ increases (in the range of 16.2 to 26.8), the activity also
increases. It is worth noting that, in a previous study,[12] materi-
al prepared at 1108C in the presence of aqua regia presented
higher amounts of Au3+ than those in the present study; this
could be attributed to the drying process employed, which
was under vacuum, rather than air drying used in this study.
However, if the amount of Au3+ increases further, no actual
gain in activity is obtained. According to Hutchings et al., in-
creasing amounts of Au3+, which are clearly needed for the re-
action, will not further increase the activity after exceeding
a given threshold.[9] By using TPR determinations, the optimal
Au3+ amount would be approximately 30%, and excess
amounts would not affect the reactivity of the catalyst.[13] This
was explained by the existence of active sites at the Au/C in-
terface, and not just by the presence of Au3+ species on top of
the Au nanoparticles.[9,12] It also can be seen that, as the addi-
tive amount of CsI increases, a positive shift of the reduction
band of Au3+ occurs. This shows the existence of interactions
between the gold and cesium(I) species. The reduction behav-
ior of Au3+ is affected by AuꢀCsI interactions. The presence of
CsCl makes it difficult to reduce Au3+ species. Therefore, these
results indicate that a synergistic effect between Au and CsI
exists in AuꢀCsI/AC catalysts. It is reasonable to conclude that
the addition of CsCl can stabilize the catalytic active Au3+ spe-
cies and inhibit the reduction of Au3+ into Au0 during the
preparation process.
Figure 3. H2-TPR profiles of samples a) 4CsI/AC, b) 1Au/AC, c) 1Auꢀ0.5CsI/
AC, d) 1Auꢀ1CsI/AC, e) 1Auꢀ2CsI/AC, and f) 1Auꢀ4CsI/AC.
gold–cesium(I) catalysts are different when compared with
that of 4CsI/AC, which has two hydrogen uptake bands. The
band between 250 and 3508C is the one associated with the
reduction of Au3+ [10]
whereas the other band between 450
,
and 8008C is associated with the reduction of carbon function-
al groups, such as carboxyl, phenol, ether, and lactone
groups.[11]
Additionally, it can be seen that the area of the Au3+ band
increases as the cesium(I) content increases. The area of the
bands is related to the amount of Au3+ present in the samples.
By comparing the thermal conductivity detector (TCD) signals
with that of a standard, the fractions of Au3+ species in these
fresh catalysts can be estimated. It is worth mentioning that
the relative amount of Au3+ in AuꢀCsI/AC catalysts increases
as the CsI content increases (Figure 4). By analyzing the
amount of Au3+ for the fresh 1Au/AC catalyst and the AuꢀCsI/
AC catalyst, the Au3+ content increased from approximately
16.2% to 21.1, 26.8, 35.9, and 46.8%, respectively, for CsI con-
tents from 0, 0.5, 1, 2, to 4. Owing to the catalyst preparation
procedure, which, after impregnation with the same gold load-
ing, no filtering of the carbon or catalyst washing was per-
TPD is an effective technique that provides a direct compari-
son of the adsorption and activation of reactants on different
catalysts. Specifically, the desorption temperature in the TPD
profiles reflects the binding strength of the adsorbed species;
the catalyst surface and peak area correlate with the amount
of active species. Figure 5 presents the C2H2-TPD profiles for
AC, 1Au/AC, and bimetallic AuꢀCsI/AC catalysts with various
Figure 5. TPD profiles of acetylene on different samples: a) AC (support),
b) 1Au/AC, c) 1Auꢀ0.5CsI/AC, d) 1Auꢀ1CsI/AC, e) 1Auꢀ2CsI/AC, and f) 1Auꢀ
4CsI/AC.
Figure 4. The proportional content of Au3+ species for 1Au/AC and AuꢀCsI/
AC catalysts prepared with different CsI content.
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CsI contents. AC shows a weak desorption peak at approxi-
mately 1158C, which is related to acetylene desorption from
the support. After the deposition of 1 wt% gold onto the AC
support, a new C2H2 desorption peak appears at 2528C. Be-
cause there is no desorption peak below 1808C, only C2H2 de-
sorption at a higher temperature is considered. Interestingly,
the relative content of C2H2 desorption in the AuꢀCsI/AC bi-
metallic catalysts increases monotonically with CsI content
(Figure 5), which indicates that the quantity of active Au3+ spe-
cies increases with CsI content. Because the areas of C2H2-TPD
peaks can be correlated with the amounts of active species, an
increase in the amount of active sites is evidenced by the in-
crease in C2H2 desorption. Taking both C2H2-TPD and H2-TPR
measurements into account, we can confirm that not only the
amounts of Au3+ active species increase as the CsI content in-
creases, but they can also be accessible for acetylene adsorp-
tion. In addition, it is known that weakly bound species have
a lower activation energy for desorption and will therefore un-
dergo desorption at a lower temperature. Thus, the shift in the
higher C2H2 desorption temperature to lower temperature may
be attributed to the interaction between Au and Cs+ in bimet-
allic catalysts, resulting in different C2H2 chemisorption
strengths and further catalytic properties than those of mono-
metallic 1Au/AC
Because previous literature studies ascribed the activity of
the catalyst to the presence of Au3+ species and postulated
that they were the active sites,[2,4a,5a,b,13] XPS was used to inves-
tigate the valence-state changes of the surface of the Au nano-
particles and the relative amount of active Au3+ in 1Au/AC
and bimetallic 1Auꢀ4CsI/AC catalysts before and after the re-
action. More than one gold species was evident, and thus,
curve fitting was employed to determine the ratio of each spe-
cies (Figure 6). Owing to the reduction property of carbon to-
wards Au3+, there is a large amount of Au0 in both fresh 1Au/
AC and 1Auꢀ4CsI/AC catalysts. In fresh 1Au/AC and 1Auꢀ
4CsI/AC catalysts, the relative content of Au3+ is 11.0 and
35.8%, respectively, which is slightly lower than the H2-TPR re-
sults.
For one reason, the Au3+ amounts obtained by XPS are
lower than those obtained by H2-TPR can be ascribed to the
former being a surface method, whereas the latter is a bulk
technique. For another reason, XPS is known to cause chemical
and structural changes within several investigated mole-
cules.[14] The technique has been reported to result in the re-
duction of metal ions by ion, electron, and photon bombard-
Figure 6. XPS spectrum and simulation for the samples a) fresh 1Au/AC catalyst, b) used 1Au/AC catalyst, c) fresh 1Auꢀ4CsI/AC catalyst, and d) used 1Auꢀ
4CsI/AC catalyst.
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ment, referred to as “radiation-induced damage” during analy-
sis. For example, Karadas et al. published an overview of the
HAuCl4 photoreduction process from Au3+ to Au0 when ex-
posed to 1253.6 eV MgKa (non-monochromatized) radiation.[15]
Together with further contributions from Ozkaraoglu et al.,[16]
Karadas and co-workers showed that the disappearance of
Au3+ peaks in the XPS spectra occurred through first-order ki-
netics, but at differing rates. In view of this, it is reasonable
that the Au3+ content obtained by XPS is always lower than
those obtained by TPR. It should also be stressed that some
small metallic gold clusters (Au0) are also formed in the fresh
gold–base catalyst (Figure 6). However, the Au0 species are in-
active and are not involved in the reaction.[9] In addition, the
higher content of Au3+ in 1Auꢀ4CsI/AC also illustrated that
the existence of CsCl inhibited the reduction of Au3+ into Au0
in the preparation process. Under the reaction conditions,
Au3+ is reduced into Au0, which contributes to the deactiva-
tion of the gold catalyst. In the case of the 1Au/AC catalyst
after the reaction, only 6.3% of Au3+ species are present,
which demonstrates that a reduction and/or agglomeration of
Au3+ species occurs in the reaction process. On the contrary,
there is a considerable amount of Au3+ (26.3%) in the used
1Auꢀ4CsI/AC catalyst, which indicates that the addition of
CsCl indeed inhibits the reduction of Au3+ to Au0.
used catalysts can be estimated. After the reaction, the Au3+
content of the 1Au/AC catalyst reduces to about 7.6%. On the
contrary, after the addition of CsI to the Au catalyst, the Au3+
content of the 1Auꢀ4CsI/AC catalyst only reduces to about
32.1%, which further confirms that the addition of CsCl is pref-
erential to stabilize catalytic active Au3+ species and inhibit
the reduction of Au3+ to Au0 in gold–base/AC catalysts during
the reaction process.
Conclusion
Bimetallic AuꢀCsI/AC catalysts with varying weight ratios of
CsI/Au from 0.5 to 4 exhibited remarkably higher catalytic ac-
tivity and stability than that of a monometallic 1Au/AC catalyst
in the hydrochlorination of acetylene. The addition of the
second metal component allowed catalysts to be prepared
with Au3+ abundance on the catalyst surface. Catalytic tests of
acetylene hydrochlorination showed a dramatic increase in the
activity to vinyl chloride when the CsI/Au weight ratio in-
creased from zero to two, with no further improvement in ac-
tivity. The catalytic stability could be further enhanced upon in-
creasing the weight ratio from two to four. It was indicated
that the addition of CsCl was preferential to stabilize the cata-
lytically active Au3+ species and inhibit the reduction of Au3+
to Au0 in both the preparation and reaction process for gold-
based/AC catalysts, thereby improving the activity and long-
term stability of the gold-based catalysts. Clarification of the in-
fluence of the addition of CsCl on stabilizing the catalytically
active Au3+ species requires a further detailed investigation,
which is currently underway in our laboratory.
The Au3+ content after the reaction was also determined for
1Au/AC and 1Auꢀ4CsI/AC catalysts by means of TPR. Figure 7
Experimental Section
Catalyst preparation
A commercially available AC, NORIT ROX 0.8 (pellets of 0.8 mm in
diameter and 5 mm long), was selected for the preparation of the
support. The AC was first pretreated with HNO3 (65 wt%) at room
temperature for 1 h to remove Na, Fe, and Al contaminants. The
pretreated AC was filtered, washed with deionized water until
pH 7, and then dried at 1108C for 12 h.
Figure 7. TPR intensities for the reduction of Au3+ species for used 1Au/AC
(a) and 1Auꢀ4CsI/AC (b) catalysts.
Bimetallic AuꢀCsI/AC catalysts were prepared by using an incipient
wetness impregnation technique. The Au and CsI precursors,
HAuCl4·4H2O (assay: 48%) and CsCl (99.9 wt%) powder, were first
dissolved in aqua regia and the solution was added dropwise to
the pretreated AC support with agitated stirring (dropwise addition
of the solution to the support with stirring and then the addition
of a second drop of solution after the first liquid was completely
dispersed into the support). After the solution was homogeneously
mixed with the support, the system was aged at 408C for 4 h, fol-
lowed by drying at 1108C in air for 12 h before use. Au loading in
all catalysts was fixed at 1.0 wt% at various Au/CsI ratios (wt/wt),
namely, 1:0.5, 1:1, 1:2, and 1:4, and were denoted as 1Auꢀ0.5CsI/
AC, 1Auꢀ1CsI/AC, 1Auꢀ2CsI/AC, and 1Auꢀ4CsI/AC, respectively.
The same procedure was also followed to prepare the correspond-
ing 1Au/AC (1.0 wt% Au loading) and 4CsI/AC (4.0 wt% CsI load-
ing) catalysts for comparison.
shows the TPR profiles for the 1Au/AC and 1Auꢀ4CsI/AC cata-
lysts after the reaction. It is clear from TPR analysis of the
1Auꢀ4CsI/AC catalyst that the low-temperature reduction
peak, which is characteristic of Au3+, can be clearly observed;
this indicates that CsI exerts a negative influence on the ease
of Au3+ reduction, which occurs during the reaction process.
As in the case of 1Au/AC, the reduction peak of Au3+ to Au0 is
evidently decreased compared with that of the fresh one,
which shows a higher degree of Au3+ reduction to Au0 during
acetylene hydrochlorination. Also, by comparing the TCD sig-
nals with a standard, the fractions of Au3+ species in these
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Catalyst characterization
al Basic Research Program of China (973 Program;
no. 2011CB710800), the Qianjiang Talent Project in Zhejiang Prov-
ince (no. QJD1302011), and the Scientific Research Fund of Zhe-
jiang Provincial Education Department (no. Y201328681) are
gratefully acknowledged.
XPS analysis was performed by using a Kratos AXIS Ultra DLD spec-
trometer with
a monochromatized aluminum X-ray source
(1486.6 eV) and a pass energy of 40 eV. The pressure in the sample
analysis chamber was lower than 6ꢁ10ꢀ9 torr during data acquisi-
tion. The C 1s peak at 284.8 eV, which arose from adventitious
carbon, was taken as a reference to correct surface-charging ef-
fects. This reference gave binding energy values with a precision of
ꢁ0.02 eV.
Keywords: cesium · gold · hydrochlorination · metal–metal
interactions · supported catalysts
TPD experiments were performed in a tubular quartz reactor. The
samples (75 mg) were first treated in situ at 1808C for 0.5 h by
using pure C2H2 and then the sample was swept with pure Ar at
a flow rate of 30 mLminꢀ1 for 1 h to remove physisorbed and/or
weakly bound species. TPD was performed by heating the sample
from room temperature to 5508C at a ramp rate of 108Cminꢀ1 in
pure Ar, and the TPD spectra were recorded by using a quadrupole
mass spectrometer (QMS 200 Omnistar).
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TPR experiments were performed in the same apparatus as that
used for the TPD experiments. The weight of the tested samples
was 75 mg. The temperature was linearly increased from 30 to
8508C at a rate of 108Cminꢀ1, under a flow of hydrogen (5% in Ar,
40 cm3 minꢀ1). The hydrogen consumption was measured by using
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Catalyst tests
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Catalysts were tested for acetylene hydrochlorination in a fixed-
bed glass microreactor (i.d. 10 mm). Acetylene (5 mLminꢀ1, 1 bar)
and hydrogen chloride (6 mLminꢀ1, 1 bar) were fed by means of
a mixing vessel through calibrated mass flow controllers to
a heated glass reactor containing catalyst (200 mg), with a total
C2H2 GHSV of 740 hꢀ1. A reaction temperature of 1808C was
chosen; blank tests with an empty reactor filled with quartz wool
did not reveal any catalytic activity, and quartz sand was used to
extend the bed length, above and below the catalyst itself, sepa-
rated by quartz wool. The gas-phase products were first passed
through an absorption bottle containing a solution of NaOH and
then analyzed online by means of a GC equipped with a flame ion-
ization detector (FID). Chromatographic separation and identifica-
tion of the products was performed by using a Porapak N packed
column (6 ftꢁ1/800 stainless steel). The long-term stability experi-
ments were performed in the same apparatus under reaction con-
ditions of 1808C and C2H2 GSHV of 50 hꢀ1
.
Received: June 12, 2014
Published online on September 18, 2014
Acknowledgements
Financial support from the National Natural Science Foundation
of China (NSFC; grant nos. 20976164, and 21303163), the Nation-
ChemPlusChem 2015, 80, 196 – 201
www.chempluschem.org
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