Gas-solid acetylene dimerization over copper-based catalysts

Article abstract of DOI:10.1039/c9nj02182e

Acetylene dimerization is an important step in an acetylene-based process for chloroprene production, and the traditional catalyst for this transformation is the Nieuwland catalyst in a bubble column reactor. However, the drawbacks of this catalyst are the use of high concentration of a copper reagent, low acetylene conversion and monovinylacetylene (MVA) selectivity, and the difficulty to generate or reuse the catalytic system. Therefore, in this study, we first reported a gas-solid acetylene dimerization reaction by applying copper-supported catalysts, which were prepared via an impregnation technique using CuCl as the precursor. The catalytic activity was examined and discussed in detail by modification of the impregnation solvent, Cu loading amount, reaction temperature, and the acetylene gas hourly space velocity. Under optimal conditions, the catalyst exhibited a maximum acetylene conversion of 48.3% and a monovinylacetylene selectivity of 87.4%. The catalysts were characterized by TGA, XRD, H₂-TPR, TEM, BET, XPS and ICP-AES. Not only the preparation, isolation and recycling of the supported catalyst were easy in the gas-solid reaction, but also the supported catalyst overcame the shortcomings of the liquid phase catalyst. The loss of the Cu active species is concluded to be the main factor causing the decrease in the catalytic activity.

Full text of DOI:10.1039/c9nj02182e

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DOI: 10.1039/C9NJ02182E
Gas-solid acetylene dimerization over copper-based catalysts
a
a
a
a,*
b
a,*
Congcong Li , Juan Luo , Qixia Zhang , Jianwei Xie , Jinli Zhang and Bin Dai
a School of Chemistry and Chemical Engineering/Key Laboratory for Green Processing of Chemical Engineering
of Xinjiang Bingtuan, Shihezi University, Shihezi 832003, China;
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b School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;
* Correspondence: cesxjw@foxmail.com (J. Xie); db_tea@shzu.edu.cn (B. Dai); Tel.: +86-993-205-7213; Fax:
+
86-993-205-7270
Abstract
Acetylene dimerization is an important step in acetylene-based process for
chloroprene production, and the traditional catalyst for this transformation is the
Nieuwland catalyst in a bubble column reactor. However, the drawbacks of this
catalyst are the use of high concentration of copper reagent, low acetylene conversion
and monovinylacetylene (MVA) selectivity, and difficult to generate or reuse the
catalytic system. Therefore, in this study, we firstly reported the gas-solid acetylene
dimerization reaction by applying copper-supported catalysts, which were prepared
via an impregnation technique using CuCl as the precursor. The catalytic activity was
examined and discussed in detail by the modification of impregnation solvent, Cu
loading amount, reaction temperature, as well as the acetylene gas hourly space
velocity. Under the optimal conditions, the catalyst exhibited maximum acetylene
conversion of 48.3% and a selectivity to monovinylacetylene of 87.4%. The catalysts
were characterized by TGA, XRD, H -TPR, TEM, BET, XPS and ICP-AES. Not only
2
the preparation, isolation and recycle of the supported catalyst were easy in gas-solid
reaction, but also supported catalyst overcame the shortcomings of the liquid phase
catalyst. The loss of the Cu active species is concluded to be the main factor causing
the decrease in the catalytic activity.
Keywords: Copper-based catalysts; Gas-solid reaction; Acetylene dimerization
1
. Introduction
Over the past decades, the development and use of catalysts have considerably
progressed, and nearly 80% of the catalyst are used for chemical production [1]. The
dimerization of acetylene is an important industrial process for the output of

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monovinylacetylene (MVA), which is further used to synthesize butan
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chloroprene (CR), styrene and other important chemical products [2,3]. Traditionally,
the process for this transformation is often carried out in a gas-liquid bubble reactor
with Nieuwland catalyst (NC), comprising CuCl, NH
4
Cl or KCl in an aqueous acidic
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solution [4]. Recent studies on gas-liquid NC-catalyzed C
2
H dimerization have
2
focused on the catalyst structure [5,6], reaction mechanism [7], ligand-modified
catalysts [8,9] and co-catalysts [10,11]. And those used for the gas-liquid dimerization
of acetylene is similar to the current industrial process with liquid catalysis [12].
However, a rapid decrease in the catalytic activity related to the considerable
discrepancy in the bubble size and the low gas holdup of the liquid catalytic system
was observed. In addition, the catalyst can be easily wrapped by the polymer from the
side reaction, leading to catalyst deactivation [5]. Simultaneously, the isolation and
recycling of the catalysts were not easy achieved [9], leading to the accumulation of a
large number of copper compounds in the polymer that damages the environment
[4-13]. Although several improvements have been observed for the dimerization of
the C
2
H
2
, limitations of using high concentration of copper reagent, low C
2
H
2
conversion and low MVA selectivity are noted. The comparison of catalytic
performance of the NC or modified NC is shown in Table 1.
Table 1 Research progress on gas-liquid acetylene dimerization
2 2
C H
Reaction
MVA
Catalytic systems
conversion
%)
References
conditions
Selectivity (%)
(
80°C, 105 h-1
25.50
46.90
76.10
78.30
[8]
[9]
NC
NC, N-(2-acetamido)-
iminodiacetic acid-added
0°C, 105 h-1
8
2
+
80°C, 200 h-1
[10]
[4]
Anhydrous NC, Cu -added
38.90
9.60
72.70
88.50
70°C, 140 h-1
NC, HCl-added

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In contrast, a gas-solid reaction exhibits a simple operation, with co
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reaction conditions [15-18]. Moreover, the catalysts of preparation, isolation and
regeneration are facile [19,20]. Hence, a gas-solid metal-based catalyst for the
dimerization of C
2
H is expected, which can not only exhibit high acetylene
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conversion and MVA selectivity but also can efficiently solve the limitations of the
gas-liquid reaction. To the best of our knowledge, the use of metal-supported catalyst
for gas-solid dimerization of acetylene has not been previously investigated. In this
paper, a simple, efficient method for preparing copper-supported catalysts was
reported, which can be sufficiently applied for the dimerization of acetylene. In terms
of selectivity and conversion, results indicated that the efficiency of a gas-solid
catalyst is considerably better than that of a gas-liquid catalyst, and Cu/AC serves as a
metal-supported catalyst for the dimerization of C
2
H , which is environmentally
2
benign and cost-effective.
2
. Experimental
2
.1 Materials and catalyst preparation
Materials: coconut-shell-activated carbon (AC, 60-80 mesh) was purchased from
S. S. Activated Carbon Industry Science and Technology Co., Ltd. CuCl, 1,4-dioxane,
N,N-dimethylformamide (DMF) and EtNH ∙HCl were purchased from Shanghai
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Macklin Biochemical Co., Ltd. Every commercially available materials were used
without any purification.
Catalyst preparation: copper-based catalysts were prepared by impregnation
-1
[
21-24]. Initially, AC was washed with dilute aqueous HCl (1 mol∙L ) at 70°C for 5 h
to remove impurity, and then filtered, washed with distilled water, dried at 150°C for
2 h. Next, 0.625 equivalent of EtNH ∙HCl (based on CuCl) was dissolved in 10 mL
1
2
DMF or a mixture of 1,4-dioxane and DMF at 80°C, followed by the addition of CuCl
and stirring for ~30 min until it dissolved completely. Subsequently, pretreated AC
was added into the above solution mixture and stirred for 120 min until the solution

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was completely impregnated into AC under nitrogen. The mixture was sti
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another 10 h at room temperature, filtered, and dried under vacuum at 80°C for 24 h,
affording the desired catalyst, denoted as Cu/AC. It should be note that the copper
loading was based on metallic copper for the all catalysts.
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.2 Analytical methods and criteria
The gas mixture was injected into the gas chromatography column (Shimadzu,
GC-2014C, GDX-301 and a flame ionization detector) to analyze its composition
every 20 min during the period. The acetylene conversion (X) and selectivity of MVA
S) were utilized as criteria for evaluating the catalytic activity, and they were defined
in the following equation.
X = [(θ + 2θ + 2θ + 3θ
S = [2θ / (θ + 2θ + 2θ + 3θ
where θ , θ , θ , θ , and θ
(
2
3
4
5
)/ (θ
1
+ θ
2
+ 2θ
3
+ 2θ
4
+ 3θ )] × 100%
5
3
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4
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)] × 100%
1
2
3
4
5
represent the volume fractions of acetylene,
acetaldehyde, MVA, 2-chloro-1,3-butadiene and 1,5-hexadien-3-yne (DVA) in the gas
product, respectively.
2.3 Catalyst characterization
Thermogravimetric analysis (TGA) of the sample was carried out using a
NETZSCH STA 449F3 Jupiter instrument coupled to a thermal analyzer. X-ray
diffraction (XRD) pattern was recorded on a Bruker D8 ADVANCE X-ray
diffractometer. Temperature-programmed reduction (TPR) experiment was carried out
on a Micromeritics ASAP 2720 instrument. Transmission electron microscopy (TEM)
image was recorded on a JEM2100F TEM instrument. Brunauer-Emmett-Teller (BET)
was carried out using a Micromeritics ASAP 2020C instrument. X-ray photoelectron
spectroscopy (XPS) was carried out on a Kratos AMICUS spectrometer (Shimadzu,
JP). The absolute content of Cu in all catalysts was measured by inductively coupled
plasma-atomic emission spectrometry (ICP-AES) (710ES, Varian, USA).
2
.4 Catalytic tests

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The catalytic activity was examined at atmospheric pressure in a fi
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microreactor (i.d. 10 mm). Before the reaction, a nitrogen purge pipeline was used 30
min to remove moisture and air from the pipeline (Fig. 1). Simultaneously, the
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temperature was increased to 100°C at a heating rate of 5°C∙min . Then, acetylene
gas, 98.0%) was fed into the filter via calibrated mass flow controllers and into the
fixed-bed microreactor containing 2 mL of the catalysts to achieve a acetylene gas
(
-1
-1
hourly space velocity (C
pressure of the reactants (C
of acetone dissolved in water. Finally, the gas mixture was injected into the gas
2
H
2
GHSV) values of 120 h (C
2
H : 4.0 mLmin ). The
2
2
H ) was maintained at 0.05 Pa for safety. Following, the
2
C
2
H
2
chromatograph (Shimadzu, GC-2014C, GDX-301 and a flame ionization detector) to
analyze its composition.
2 2 2 2 2
Fig. 1. Device diagram of the C H dimerization system: 1 C H ; 2 N ; 3,4 partial pressure valve;
5,6 check valve; 7,8 gas filter; 9,10 mass flow controller; 11 fixed-bed microreactor; 12 H
2
O
solution; 13 Gas Chromatograph (GC-2014C ).
3. Results and discussion
3.1 Catalytic performance for the dimerization of acetylene
3.1.1 Effect of impregnation solvent
Fig. 2 compares the C
solvent. Less than 10% of acetylene conversion was noticed when 1,4-dioxane was
used as the impregnation solvent. Interestingly, the C conversion was significantly
H
2 2
conversion and MVA selectivity under the different
2
H
2
enhanced from 8.8% (in 1,4-dioxane) to 32.5% (in DMF) under the same conditions.
Meanwhile, the MVA selectivity of the Cu/AC (DMF) catalyst exceeded 85% at 10 h

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indeed affects the catalytic performance of Cu/AC catalyst.
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Fig.2. Acetylene conversion (a) and MVA selectivity (b) by using DMF or 1, 4-dioxane as the solo
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impregnation solvents. (Reaction conditions: T = 100 °C; C H GHSV = 120 h )
Fig. 3 shows the catalytic performance of Cu/AC with different
DMF/1,4-dioxane ratios ranging from 2:8 to 8:2, suggesting that the
DMF/1,4-dioxane ratio considerably affects C
increase in the DMF/1,4-dioxane ratios from 2:8 to 5:5 and to 7:3 while
simultaneously maintaining the total solvent volume constant, the C conversion
2
H
2
conversion. Notably, with the
2
H
2
increased from 27% to 35.9% and to 48%, respectively. However, no further
improvement in the catalytic activity was observed, when further increase in the
DMF/1,4-dioxane ratio from 7:3 to 8:2. Hence, the optimal activity for the Cu/AC
catalyst is achieved using DMF/1,4-dioxane ratio of 7:3 as the impregnation solvent.
It is reported that the presence of -CH group in the DMF structure, which can
3

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increase the electron density of the N atom, enhance the coordination ability bDO
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system [10-13]. Therefore, the combination of Figs. 2 and 3 leads to a conclusion that
a mixed solvent may promote the dissolution of cuprous chloride and increase the
electron density of Cu(I); hence, the catalytic activity is greater than others.
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Fig.3. Effect of ratio of DMF/1, 4-dioxane on the catalytic performance of Cu/AC catalyst.
-1
2 2
(Reaction conditions：T= 100°C; C H GHSV= 120 h )
3
.1.2 Effect of Cu loading
After obtaining the optimal impregnation solvent, we next investigated the Cu
loading on the catalytic performance. A series of Cu/AC catalysts with different Cu
loading amounts are prepared, and their catalytic activities are examined under the
same reaction conditions. As shown in Fig. 4 and Table 2, by using 35.0 wt% of the
Cu/AC catalyst, the average conversion of acetylene is 23.6%, and the average
conversion of 35.8% was obtained at a Cu loading amount of 40.0 wt%, which also

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affords an average MVA selectivity of 87.4%. Furthermore, further increasingDOthI:
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C
loading greater than 40.0 wt%, the acetylene initial conversion clearly increased to
0.0%, followed by a rapid decline when the Cu loading amount of 42.5 wt%. One
5
possible reason is that the excess component blocks the pores or causes the
superposition of the active components, leading to low activity [25]. Therefore, with a
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comprehensive consideration of C
2
H conversion, MVA selectivity, and MVA yield,
2
4
0.0 wt% of Cu loading amount of is the best for acetylene dimerization.
Fig. 4 The catalytic performance of Cu/AC catalyst with different loading amount of Cu (Reaction
-1
conditions: T= 100°C; C
2 2
H GHSV= 120 h )
Table 2 The catalytic performance of Cu/AC catalyst with different loading amount of Cu
Cu loading (wt%)
Xaverage (%)
Saverage (%)
Yaverage(%)
3
3
4
5.0
7.5
0.0
23.6
86.8
20.5
28.8
91.1
26.2
35.8
87.4
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28.3 DOI: 10.1039/C9NJ02182E
42.5
5.0
33.6
23.2
84.2
85.1
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19.7
3
.1.3 Effect of the reaction temperature and C
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H GHSV
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0
Fig. 5 Effect of reaction temperature to C
2 2
H dimerization (acetylene conversion (a) and
GHSV= 120 h-1)
H
2
selectivity of MVA (b) ) (Reaction conditions：C
2
Fig. 5 shows the results obtained for the acetylene conversion and MVA
selectivity at reaction temperatures ranging from 80°C to 180°C. As the increase in
the reaction temperature from 80°C to 100°C, the C conversion for the
2
H
2
dimerization of acetylene considerably increased obviously. The Cu/AC catalyst
exhibits a significant initial performance with almost 80% acetylene conversion and
more than 90% MVA selectivity, when the reaction temperature increased to 140°C or
1
80°C, but a sharp decline in its activity occurs after 2h. It is suggested that the

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ults
0.10in39/C9NJ02182E
catalyst is easily activated at high temperature, but high temperature re
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unstable and easy loss of the copper species [26,27]. Therefore, 100°C is the best
reaction temperatures of acetylene dimerization.
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GHSV was tested in the GHSV range between 100 h1
The effect of the C
2
H
2
1
and 140 h (Fig. 6). In general, higher C
2
H
2
GHSV led to a shorter residence time in
conversion as well as an increase of
conversion and MVA selectivity were achieved under
the catalyst, resulting in gradual decrease of C
2
H
2
MVA selectivity. The best C
2
H
2

1
120 h C
2
2
H GHSV.
Fig. 6 Effect of C
2
H
2
GHSV on acetylene dimerization (Reaction conditions: T= 100°C
)
3.2 Catalyst characterization
The catalyst, which exhibiting superior activity and good stability under the

1
optimal conditions: T=100 °C; C
2
H
2
GHSV=120 h ; [Cu] 0.08 mol; [EtNH HCl]
2
0.05 mol and a 10 mL mixed solvent (DMF/1,4-dioxane) volume ratio of 7:3 as the

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impregnation solvents, was characterized by TGA, XRD, H
2
-TPR, TEM, BE
D
T
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X
0.1039/C9NJ02182E
P
S
and ICP-AES.
3
.2.1 Coke deposition on the catalysts
Fig. 7 shows the results obtained from TG analysis of the fresh and used Cu/AC
catalysts. The fresh catalyst exhibited a slight weight loss at a temperature before
1
1
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2
2
2
2
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2
2
2
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1
00°C, corresponding to desorption of adsorbed water [23], while the used catalyst
exhibited a clear weight loss. On the other hand, a weight loss was noticed at
1
00-200°C, corresponding to the volatilization and decomposition of solvent and
cosolvent compounds on the catalyst [13]. The carbon deposition possibly occurred at
200-320°C. When the temperature exceeded 320°C, an obvious weight loss was
observed, mainly related to the combustion of the AC support. Thus, the amount of
coke deposited on the catalyst surface was calculated as 9.13% (Fig. 7) [24,28].
Carbon deposition is a cause of the gradual decrease in catalyst activity.

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Fig. 7 TG and DTG cures of the fresh and used Cu/AC catalysts.
3
.2.2 Catalyst sintering and valence change in the active component during the
dimerization of acetylene
Fig. 8 shows the XRD patterns of all samples, which were recorded to
understand the evolution of the crystal structure in the fresh and used Cu/AC catalysts.
Apart from the amorphous diffraction peaks corresponding to activated carbon [29],
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typical diffraction peaks for Cu
observed at 2θ values of 16.16°, 32.159°, 39.58°, 49.99°, and 53.54° (JCPDS:30-0473)
30], with a small amount of CuCl. In the XRD pattern of the used Cu/AC catalyst,
Cu(111) diffraction peaks corresponding to CuCl (JCPDS:06-0344), with marginal
CuCl , were observed. The results revealed that the valence of Cu changes during the
2
Cl(OH)
3
in the fresh Cu/AC catalyst were clearly
[
2
reaction, which may be one of the causes for the deactivation of the Cu/AC catalyst.
Fig. 8 XRD patterns of the fresh and used Cu/AC catalysts
3
.2.3 H
Fig. 9 shows the TPR spectrum of the Cu/AC catalyst. Two reduction peaks were
noticed for all the Cu-based catalysts, corresponding to the procedure reduction of
2
-TPR results
2+
+
0
Cu →Cu →Cu [31]. Previous studies have reported that the reduction temperature
+
2+
for the Cu species is greater than that for the Cu species [32,33]. Hence, the peaks
observed at 283°C and 398°C for the fresh catalyst are possibly related to the
2
+
+
2+
reduction of Cu and Cu , respectively. And the Cu in fresh catalyst is related to the
+
oxidation of Cu during the catalyst preparation and storage
.
However, the reduction
+
peaks observed at 370°C corresponded to the reduction of the Cu species in the used

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catalyst, while the temperature corresponding to the reduction peak of Cu2 +D OtoI: 10
was 304°C.
+
.1039/C9NJ02182E
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u
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2
Fig. 9 The H -TPR of fresh and used catalyst.
3
.2.4 TEM images and pore structure parameters of catalysts
To observe the dispersion state of the active components in the catalyst, TEM
images of the fresh and used Cu/AC catalysts were recorded (Fig.10). Before the
reaction, the copper species in the small-sized catalyst particles were uniformly
dispersed, with no agglomeration [34]. The particle size of the copper species in the
catalyst became larger, agglomerated, and loss after the reaction, caused decreasing
the catalytic activity. As shown in Table 3, the total pore volumes and surface areas of
2
-1
2
-1
the fresh catalysts rapidly decreased from 1036.00 m g to 256.00 m g after
loading the active Cu species, which due to the heavy load of active Cu species and
the cosolvent fill or block some of AC pores. Combined with TEM and BET data, it
was concluded that poor dispersion of active components, clogging of carrier voids
resulted in low catalyst activity.

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Fig. 10 TEM images of the fresh Cu/AC (a) and used (b) Cu/AC catalysts.
Table 3 Pore structure parameters of catalysts
2
-1
3
-1
S
BET (m g )
Total pore volume (cm g )
Catalysts
Fresh
Used
Fresh
0.54
Used
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AC
1036.00
256.00
—
—
Cu/AC
181.00
0.30
0.10
3.2.5 XPS analysis of the Cu/AC catalyst
XPS analysis was employed to detect the relative content state and valence of the
+
active copper species in the Cu/AC catalysts. Generally, Cu is considered to be the
main active component for the dimerization of acetylene [8,9]. However, gas-liquid
NC-catalyzed studies have reported that Cu2+ also plays a crucial role for the
dimerization of acetylene, and the deactivation of the NC was related to the
+
2+
transformation of Cu to Cu [10]. Hence, the valence state and relative content of
active copper species in the fresh and used Cu/AC catalysts are investigated by XPS.
2
+
The peak observed at 934.2 eV corresponded to the Cu species, and the lower BE
+
peak observed at 932.1 eV corresponded to the presence of the Cu species [35-39]. A
2+
high ratio of the Cu species on the fresh catalyst surface possibly corresponded to
the oxidation occurring during the preparation and/or characterization of the catalyst.
+
However, with the progress of the reaction, the Cu content increased owing to the
+
reduction of acetylene. The peak corresponding to Cu for the fresh and used catalysts
2+
+
shifted possibly because Cu and Cu can convert into each other. Valence changes
for the copper species were speculated to lead to catalyst deactivation.
When the Cu/AC sample was obtained at 100°C, the Cu species predominantly
+
+
comprised Cu (content of ~62.25%) (Table 4). Hence, Cu constitutes the active site
2
+
in the Cu/AC catalyst, but simultaneously, the role of Cu cannot be ignored (Fig.
1).
1
Table 4 Quantification and identification of the Cu species over fresh and used
Cu-based catalysts from XPS data
Catalysts
Cu species (%)
Binding energies (eV)

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DOI: 10.1039/C9NJ02182E
Cu2+
Cu+
Cu2+
Cu
+
Fresh Cu/AC
Used Cu/AC
88.99
37.75
11.01
62.25
934.79
934.78
932.10
932.70
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Fig.11 The Cu2p XPS profiles of the fresh and used catalysts
3.2.6 Possible mechanism on the gas-solid dimerization of C
2
H
2
Based on the experimental results described above and previous reports, [7,
40-42] a possible mechanism of the present gas-solid acetylene dimerization reaction
was proposed in Fig.12. The catalyst was composed of the active copper complex
([Cu(I)
n
Cl
m
]-(m-n) and [Cu(II)
n
Cl
]-(m-2n)) stabilized as the Cu(I) and Cu(II) form and
m
EtNH
2
on the carbon support. First, the active copper species coordinated with C
2
H
2
2
to give C H
2 2
π-complex (I), and then convert the C π-complex into a C
2
H
2
2
H
δ-complex (II) by deprotonation reaction. Subsequently, reaction of II and I formed
the III, followed by protonation to provide IV and MVA, and regenerate active
copper species.

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Fig.12 A possible reaction mechanism for the gas-solid dimerization of acetylene with
copper-based catalysts
3
.2.7 Loss ratio of Cu in Cu-based catalysts
XPS is a surface analysis technology for catalysts. Next, the weight loss ratio of
Cu in the catalyst was examined by ICP-AES analysis.
The adsorption capacity of AC for cuprous chloride is possibly not strong. In
addition, as the cuprous-chloride-containing solution is filtered during catalyst
preparation, the actual load is considerably less than the theoretical load. From Table
5
, the used catalysts exhibited a lower Cu content compared to the fresh catalysts.
With the increase in the reaction time from 0 to 5 h of the catalyst, a Cu loss ratio of
1.88% was attained, corresponding to the fact that the active component does not
1
interact with the support, followed by a dramatic increase with the increase in the
reaction time to greater than 10 h. This result is possibly related to the weakened
interaction of the active component with the carrier as the reaction progresses. For the
used Cu/AC catalyst after 25 h of reaction, the Cu content decreased from an initial
value of 16.41% to 7.41%, with an ~9% reduction. Fig. 13 shows the 25 h stability
test of the Cu/AC catalysts. Hence, the loss of Cu active species is possibly another
main factor causing the decrease in the catalytic activity.

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2
2
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2
2
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3
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Fig.13 Long-term stability test of the CuAC catalysts (Reaction conditions: T= 100°C; C
2 2
H
-
1
GHSV= 120 h )
Table 5 The loss ratio of Cu in catalysts with different reaction time, determined by
ICP-AES.
Catalyst
Cu loading/(wt %)
Time interval Loss ratio of Cu/
%)
(
Cu/AC
Cu/AC-5h
16.41
14.46
14.43
13.53
11.55
7.41
－
－
0-5
11.88
0.21
Cu/AC-10h
Cu/AC-15h
Cu/AC-20h
Cu/AC-25h
. Conclusions
5-10
10-15
15-20
20-25
6.23
14.76
35.84
4
The Cu/AC catalyst was firstly synthesized and evaluated as the catalyst for
gas-solid reaction for dimerization of acetylene. Compared to the traditional
gas-liquid reaction, the copper-based catalyst demonstrates superior activity and
stability with a maximum acetylene conversion of 48.3% and a MVA selectivity of
~
87.4% under optimal conditions. Combining the results from ICP-AES and XPS
analyses, the loss of the Cu active species is concluded to be the main factor causing
the decrease in the catalytic activity. The present work overcomes several drawbacks
of traditional gas-liquid NC-catalyzed acetylene dimerization reaction, render this

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method viable for use in both laboratory research and large industrial pro
D
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: 1
t
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o
1039/C9NJ02182E
n
.
Further investigation involves inhibition of the loss of copper species, exploration of
mechanism and improvement of the catalyst stability is ongoing in our laboratory.
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Acknowledgments: We acknowledge the National Natural Science Foundation of
China (No. 21776179 and 21463021) for their financial support.
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DOI: 10.1039/C9NJ02182E
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A gas-solid acetylene dimerization over copper-based catalysts, with high acetylene conversion
and MVA selectivity and convenient operation, was reported.