High-Performance Catalysts Derived from Cupric Subcarbonate for Selective Hydrogenation of Acetylene in an Ethylene Stream

Article abstract of DOI:10.1002/ejic.202001073

A high-performance base metal catalyst for acetylene selective hydrogenation was prepared from cupric subcarbonate (Cu₂(OH)₂CO₃) by thermal treatment with an acetylene-containing gas followed by hydrogen reduction. The characterization results revealed that the copper catalyst was composed of interstitial copper carbide (Cu_xC) and metal Cu, which were embedded in porous carbon matrix. The Cu_xC crystallites, which showed outstanding hydrogenation activity, were derived from the hydrogen reduction of copper (II) acetylide (CuC₂) which was generated from the reaction between acetylene and Cu₂(OH)₂CO₃. The Cu particles and porous carbon were generated from the unavoidable thermal decomposition of CuC₂. The prepared Cu-derived catalyst completely removed the acetylene impurity in an ethylene stream with a very low over-hydrogenation selectivity at 110 °C and atmospheric pressure. No obvious deactivation was observed in a 180-h test run. In the Cu-derived catalyst, Cu_xC served as the catalytic site for H₂ dissociation, Cu mainly functioned as the site for selective hydrogenation of acetylene, whereas the porous carbon matrix posed a steric hindrance effect on the chain growth of linear hydrocarbons so as to suppress the undesired oligomerization.

Full text of DOI:10.1002/ejic.202001073

Full Papers
doi.org/10.1002/ejic.202001073
1
2
3
4
5
6
7
8
9
High-Performance Catalysts Derived from Cupric
Subcarbonate for Selective Hydrogenation of Acetylene in
an Ethylene Stream
Chenyang Lu,[a] Aonan Zeng,[a] Yao Wang,*[a, b] and Anjie Wang*[a, b]
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
A high-performance base metal catalyst for acetylene selective
hydrogenation was prepared from cupric subcarbonate
(Cu2(OH)2CO3) by thermal treatment with an acetylene-contain-
ing gas followed by hydrogen reduction. The characterization
results revealed that the copper catalyst was composed of
interstitial copper carbide (CuxC) and metal Cu, which were
embedded in porous carbon matrix. The CuxC crystallites, which
showed outstanding hydrogenation activity, were derived from
the hydrogen reduction of copper (II) acetylide (CuC2) which
was generated from the reaction between acetylene and
Cu2(OH)2CO3. The Cu particles and porous carbon were
generated from the unavoidable thermal decomposition of
CuC2. The prepared Cu-derived catalyst completely removed
the acetylene impurity in an ethylene stream with a very low
°
over-hydrogenation selectivity at 110 C and atmospheric
pressure. No obvious deactivation was observed in a 180-h test
run. In the Cu-derived catalyst, CuxC served as the catalytic site
for H2 dissociation, Cu mainly functioned as the site for selective
hydrogenation of acetylene, whereas the porous carbon matrix
posed a steric hindrance effect on the chain growth of linear
hydrocarbons so as to suppress the undesired oligomerization.
Introduction
lysts deactivate quickly during the acetylene hydrogenation
due to the vigorous formation of oligomers.[32,33] In addition, Fe-
based,[34,35] Cu-based[36–38] and CeO2-based[39–41] catalysts were
also reported to perform well in selective hydrogenation of
acetylene. For example, Cu catalysts were intrinsically selective
to alkene in alkyne hydrogenation due to the marked difference
of adsorption energy between alkyne and the corresponding
alkene.[7,42,43] However, Cu catalysts are much less active than Pd
catalysts in hydrogenation, and, as a result, the selective
hydrogenation of acetylene over Cu catalysts often takes place
at higher temperatures. Acetylene is prone to oligomerize to
produce green oil at high temperatures, and the oligomers will
foul the catalyst surface, thus leading to rapid catalyst
deactivation.[7,44] Bridier et al[45] reported that CO-modified Cu-
based catalyst displayed an enhanced propene selectivity and
suppressed the formation of oligomers. They proposed that the
addition of CO altered the surface structure of Cu irreversibly,
resulting in smaller Cu ensembles and minimizing the CÀ C
coupling reaction. Another effective approach to suppressing
the formation of oligomers is to lower the reaction temperature.
McCue et al.[46] and Kyriakou[47] reported that the Pd-promoted
Cu catalysts exhibited outstanding performance in selective
hydrogenation of acetylene at low temperatures, by taking
advantage of the high ethylene selectivity of Cu and the high
activity of Pd.
Ethylene is mainly produced by naphtha cracking and is used as
a basic petrochemical raw material for synthetic resins, such as
polyethylene. For polymer-grade ethylene, acetylene impurity
must be reduced below an acceptable level (5 ppm) to protect
the downstream polymerization catalyst and to avoid ungraded
polymer products.[1–4] In industry, the preferred method of
removing the acetylene impurity in ethylene stream is by
selective hydrogenation of acetylene to ethylene product.[5,6]
The most commonly used catalyst is the low-surface-area
alumina-supported Pd catalyst modified by Ag.[7,8] In addition,
Ga,[9–11] Zn,[12–14] Au,[15–17] Cu,[18–21] and In[22,23] are also used as the
promoters. Recently, Liu et al.[24,25] and McCue et al.[26] reported
that palladium sulfide and palladium phosphides exhibited
excellent ethylene selectivity at complete acetylene conversion
°
above 125 C. In general, one major disadvantage associated
with precious metal catalysts is the high cost.
Ni-based catalysts have been extensively explored for
replacing supported Pd catalysts.[27–31] However, Ni-based cata-
[a] C. Lu, A. Zeng, Prof. Y. Wang, Prof. A. Wang
State Key Laboratory of Fine Chemicals
School of Chemical Engineering
Dalian University of Technology
Dalian 116024, P. R. China
E-mail: wangyao@dlut.edu.cn
In our previous investigation, a new interstitial copper
carbide (CuxC) was synthesized by reducing copper (I) acetylide
ajwang@dlut.edu.cn
http://faculty.dlut.edu.cn/1991011025/en/index.htm
http://faculty.dlut.edu.cn/1988011014/en/index/777137/list/index.htm
[b] Prof. Y. Wang, Prof. A. Wang
[48]
°
(Cu2C2) in H2 at 180 C. The DFT calculation results indicated
that the CuxC was more active than the Cu catalyst in H2
dissociation. The Cu2O-derived catalyst, consisting of CuxC and
Cu, was remarkably active, selective, and stable in acetylene
selective hydrogenation in an ethylene stream. In the present
work, Cu2(OH)2CO3 was used to prepare the catalysts for
Liaoning Key Laboratory of Petrochemical Technology and Equipment
Dalian University of Technology
Dalian 116024, P. R. China
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejic.202001073
Eur. J. Inorg. Chem. 2021, 997–1004
997
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
°
°
selective acetylene hydrogenation using the same method. The
obtained catalysts were characterized and tested in selective
hydrogenation of acetylene in ethylene stream. In addition, the
stability of the catalyst was investigated.
45 and 65 C). At higher temperatures (45 and 65 C), the well
resolved diffraction peaks characteristic of Cu2(OH)2CO3 (JCPDS
No. 76-0660) were detected in the XRD patterns, and no other
1
2
3
4
5
6
7
8
9
°
crystal phase was detectable. At 25 C, no distinct diffraction
peaks were detected, probably because the crystallite size of
Cu2(OH)2CO3 was below the detection limit or the sample was
amorphous. The HRTEM image (Figure 1e) shows that the
Cu2(OH)2CO3 sample synthesized at 25 C consisted of nanosized
polycrystallites (2~4 nm) with various orientations, suggesting
that highly dispersed crystallites of Cu2(OH)2CO3 were obtained
Results and Discussion
°
Synthesis of Cu2(OH)2CO3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
°
The catalyst precursor Cu2(OH)2CO3 was synthesized by a
precipitation method. The effect of synthesis temperature on
the morphology and structure of the synthesized Cu2(OH)2CO3
was investigated. The SEM observation (Figure 1a–c) revealed
that the particle size of Cu2(OH)2CO3 increased with temper-
ature. The morphology of Cu2(OH)2CO3 changed from an
aggregation of nanoparticles (~25 nm) to bundles of rectangu-
lar pillars, accordingly. Figure 1d shows the XRD patterns of the
Cu2(OH)2CO3 samples synthesized at different temperatures (25,
at 25 C. The lattice fringes with d-spacing of 0.262, 0.252, 0.247
and 0.228 nm corresponded to the (121), (240), (201) and (221)
planes of Cu2(OH)2CO3, respectively. Figure 1f presents the N2
adsorption and desorption isotherms and the BET specific
surface areas of the three Cu2(OH)2CO3 samples. With increasing
synthesis temperature, the specific surface area decreased from
67 to 10 and to 4 m2 gÀ 1. It demonstrates that the synthesis
temperature significantly affected the morphology and disper-
sion of the synthesized Cu2(OH)2CO3.
°
°
°
Figure 1. SEM images of the Cu2(OH)2CO3 samples synthesized at (a1, a2) 25 C, (b1, b2) 45 C and (c1, c2) 65 C. (d) XRD patterns of Cu2(OH)2CO3 synthesized
at different temperatures. (e) HRTEM image of Cu2(OH)2CO3 synthesized at 25 C. (f) N2 adsorption-desorption isotherms and specific surface areas of
°
°
°
°
Cu2(OH)2CO3 samples synthesized at various temperatures (25 C, 45 C and 65 C.).
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
998
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
The Cu2(OH)2CO3 samples synthesized at different temper-
atures were used as the precursors to prepare selective hydro-
genation catalysts. The preparation procedure mainly includes
two steps: (1) thermal treatment with an acetylene-containing
CuxC phase with high hydrogenation activity. Therefore, the
1
2
3
4
5
6
7
8
9
°
Cu2(OH)2CO3 sample synthesized at 25 C was used to prepare
the acetylene hydrogenation catalyst in the following inves-
tigation.
°
°
gas at 120 C, and (2) hydrogen reduction at 150 C. Figure 2
compares the catalytic performance of the three prepared
catalysts in selective hydrogenation of acetylene in an ethylene
stream. The catalyst prepared from the Cu2(OH)2CO3 sample
Characterization of Cu2(OH)2CO3-derived catalysts
°
synthesized at 25 C exhibited the highest activity, achieving
100% acetylene conversion with 17% ethane selectivity at
The XRD pattern of Cu2(OH)2CO3(T120-R150) (Figure 3a) indi-
cated that all the diffraction peaks characteristic of Cu2(OH)2CO3
disappeared after the thermal treatment and the subsequent H2
reduction. In contrast, four new peaks were detected. Among
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
°
120 C and atmospheric pressure. The better catalyst activity
might be related to the smaller particle size, higher dispersion
and surface area of the Cu2(OH)2CO3 precursor synthesized at
low temperatures, leading to the formation of highly dispersed
°
them, the sharp peaks at 2θ=43.3, 50.4 and 74.1 were ascribed
to the (111), (200) and (220) planes of metallic Cu (PDF 04-
°
0836). The broad diffraction peak at 2θ=37.2 was identical to
that of the (0001) plane of CuxC reported in our previous
investigation,[48] indicating the formation of the interstitial
copper carbide (CuxC) phase in Cu2(OH)2CO3(T120-R150). The
weak and broad diffraction peak indicates the CuxC phase was
highly dispersed in the catalyst. Figure 3b illustrates the HRTEM
image of Cu2(OH)2CO3(T120-R150). In accordance with the XRD
characterization, two types of crystal phases were observed.
The lattice fringe of 0.181 nm was assigned to the (200) plane
of metal Cu. The lattice fringe of 0.238 nm corresponded to the
°
diffraction peak at 2θ=37.2 in the XRD pattern of
Cu2(OH)2CO3(T120-R150).
Figure 2. (a) Acetylene conversion and (b) ethane selectivity as a function of
reaction temperature in acetylene selective hydrogenation on the catalysts
from Cu2(OH)2CO3 samples synthesized at different temperatures. The
Cu2(OH)2CO3 samples were treated with an acetylene-containing gas at
The XPS spectra of Cu2(OH)2CO3(T120-R150) are shown in
Figure 4. The absence of the Cu 2p3/2 peak at 934.6 eV and the
satellite peak at around 945 eV of Cu2+ (Figure 4a) indicates
that no Cu2+ species was present in the catalyst.[37] In addition
to the Cu 2p3/2 peak at 932.1 eV attributed to Cu+/Cu0, the peak
at 932.8 eV located between that of Cu2+ and that of Cu+/Cu0
was linked to a CuÀ C bond in CuxC.[37,48,50] The Cu species in
CuxC has a partial positive charge (δ+) due to an electron
density transfer from Cu to C.[51] In the Cu LMM spectrum
(Figure 4b), the peak could be deconvoluted to two peaks at
918.6 and 917.2 eV. The one at 918.6 eV was attributed to Cu0,
and the other one at 917.2 eV, situated between Cu+ (916.8 eV)
and Cu0 (918.6 eV), could be ascribed to the Cuδ+ species in
CuxC.[48] In the C 1s spectrum, a shoulder peak at 283.8 eV
indicated the formation of the interstitial carbide.[48,50]
°
°
120 C and subsequently reduced in H2 at 150 C.
Figure 3. (a) XRD pattern and (b) HRTEM image of Cu2(OH)2CO3(T120-R150)
°
prepared from Cu2(OH)2CO3 obtained at 25 C.
Figure 4. (a) Cu 2p, (b) Cu LMM and (c) C 1s XPS spectra of Cu2(OH)2CO3(T120-R150).
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
999
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
The N2 adsorption-desorption isotherms and BET specific
surface areas of Cu2(OH)2CO3, Cu2(OH)2CO3(T120) and
Cu2(OH)2CO3(T120-R150) are shown in Figure S1. When
Cu2(OH)2CO3 was treated with the acetylene-containing gas, the
specific surface area increased from 67 to 91 m2 gÀ 1. The
subsequent hydrogen reduction led to a significant increase of
the specific surface area (164 m2/g). When Cu2(OH)2CO3(T120-
R150) was treated in a 1.5 M HNO3 solution at room temper-
ature, the copper species were dissolved in the solution, and
the specific surface area of the remaining material was
pattern of Cu2(OH)2CO3(T120-R150). It suggests that CuxC was
1
2
3
4
5
6
7
8
9
2+
°
produced by H2 reduction of CuC2 at 150 C, reducing Cu in
CuC2 to Cuδ+ in CuxC. In parallel, metal Cu and carbon material
were produced by decomposition of CuC2 because of its
considerably low thermal stability. It is, therefore, proposed that
the formation of CuxC in Cu2(OH)2CO3-derived catalyst involves
the following two steps: (1) CuC2 is produced by the reaction of
Cu2(OH)2CO3 with acetylene, (2) the resultant CuC2 is reduced in
hydrogen to generate CuxC.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
538 m2 gÀ 1 (Figure S2). After the treatment, the
D band
(1360 cmÀ 1) and G band (1560 cmÀ 1) were detectable in the
Raman spectrum (Figure S3). It suggests that a porous carbon
matrix was present in the catalyst. It seems that the
Cu2(OH)2CO3-derived catalyst consisted of CuxC and Cu particles
which were wrapped in a porous carbon matrix.
Catalytic performance
It is known that Cu catalysts show outstanding selectivity to
ethenes in selective hydrogenation of ethynes.[42,43] However,
due to the low H2 dissociation ability of Cu catalyst, Pd was
often added to enhance the dissociation of H2 at low
temperatures.[46,47] On the other hand, interstitial transition
metal carbides were reported to exhibit significantly higher
activity in many hydrogenation reactions than their correspond-
ing parent metals.[53–55] Recently, we reported that CuxC
exhibited considerably higher hydrogenation ability than the
Cu catalyst.[48]
Our previous study indicated that CuxC was obtained by H2
reduction of copper (I) acetylide (Cu2C2).[48] It was reported that
Cu2(OH)2CO3 reacts with acetylene readily to form copper (II)
acetylide (CuC2).[52] It is therefore inferred that the copper (II)
acetylide (CuC2) was the precursor or intermediate in the
formation of CuxC.
A small amount of bulk CuC2 was synthesized from
°
Cu2(OH)2CO3 and then thermally treated at 150 C in hydrogen
Cu2(OH)2CO3(T140-R150) was tested in the selective hydro-
genation of acetylene in excess ethylene in the temperature of
to obtain CuC2(R150). HRTEM image of CuC2(R150) (Figure 5a)
displayed that two types of lattice spacings corresponding to
CuxC and Cu were observed. In the XRD pattern of CuC2(R150)
(Figure 5b), three strong diffraction peaks at 2θ=43.3, 50.4 and
°
90–120 C at atmospheric pressure, in comparison with the Cu
catalyst obtained from the same precursor by hydrogen
reduction (Figure 6a). Cu2(OH)2CO3(T140-R150) displayed an
outstanding hydrogenation activity in the temperature range of
°
74.1 , which were attributed to metal Cu, and a weak peak
°
ascribed to CuxC, were detected, identical to the peaks in the
90–120 C, whereas the Cu catalyst showed extremely low
hydrogenation activity in the same temperature range. In
general, Cu catalysts showed marked hydrogenation activity
°
above 150 C (Table S1). With increasing the hydrogenation
temperature, the acetylene conversion increased monotonically
°
and reached 100% above 110 C. Simultaneously, the ethane
selectivity, a measure of the undesired over-hydrogenation
increased with temperature. When acetylene was completely
°
removed at 110 C, the selectivity to ethane was around 20%.
°
When the temperature was raised to 120 C, the selectivity to
ethane was still below 40%. In our previous investigation, the
DFT calculation results illustrated that the CuxC was in
accordance with Cu3C(0001) in a rhombohedra-centered hex-
Figure 5. (a) HRTEM image and (b) XRD pattern of CuC2(R150).
Figure 6. Acetylene conversion and ethane selectivity as a function of (a) reaction temperature, (b) H2/C2H2 ratio and (c) time on stream in acetylene
hydrogenation over Cu2(OH)2CO3(T140-R150).
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
1000
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
agonal structure, and H2 preferably adsorbed on Cu3C(0001).[48]
Effect of acetylene treatment conditions
1
2
3
4
5
6
7
8
9
Additionally, the dissociation energy of H2 on Cu3C(0001) was
significantly lower than on Cu(111). In addition, the ethylene
hydrogenation activity (Figure S4) on CuC2(R150) composed of
CuxC and Cu is markedly higher than that on CuC2(v150) which
was decomposed to C and Cu.[52] On the other hand, the energy
barriers for acetylene hydrogenation to vinylidene and then to
ethylene over Cu3C(0001) were considerably higher than on
Cu(111), suggesting that the Cu phase provides the main sites
for acetylene hydrogenation. In the selective hydrogenation of
acetylene over Cu2(OH)2CO3(T140-R150), CuxC lowered the
energy barrier of H2 dissociation and served as the site for H2
dissociation at low temperature, and majority of the generated
hydrogen atom spilt over to the Cu surface where acetylene
was selectively hydrogenated to produce ethylene.
In industry, the ratio of hydrogen to acetylene (H2/C2H2) is
strictly monitored when supported Pd catalysts are used to
remove acetylene impurity in ethylene.[56] High H2/C2H2 ratio
often leads to the formation of unselective palladium hydride
phase and thus to over-hydrogenation,[8,57,58] resulting in a net
ethylene loss and increasing the risk of a thermal runaway due
to the high exothermicity of ethylene hydrogenation. Low H2/
C2H2 ratio decreases acetylene conversion, and facilitates the
oligomerization to yield green oil which fouls the catalyst. The
effect of H2/C2H2 ratio on the performance of Cu2(OH)2CO3(T140-
During the preparation of the hydrogenation catalyst, both the
acetylene treatment and subsequent H2 reduction significantly
affect the contents and dispersion of CuxC crystallites. The effect
of the acetylene treatment temperature (120–180 C) on the
hydrogenation performance of the catalyst reduced in H2 at
°
°
150 C is shown in Figure 7. Acetylene was completely con-
°
verted at 110 C and atmospheric pressure over Cu-
(OH)2CO3(T140-R150) and Cu(OH)2CO3(T160-R150), with ethane
selectivities of 21% and 18%. The acetylene conversions over
Cu(OH)2CO3(T120-R150) and Cu(OH)2CO3(T180-R150) were 70%
and 61%, respectively. Acetylene conversion increased with
reaction temperature, and complete acetylene conversion was
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
°
achieved above 120 C for each catalyst. Cu(OH)2CO3(T140-R150)
exhibited the highest acetylene conversion. In the TG-DSC curve
of bulk CuC2 (Figure S5), an exothermic peak appeared above
°
160 C, indicating that CuC2 decomposed considerably to Cu
°
and carbon above 160 C. As a result, vigorous decomposition
°
of the generated CuC2 above 160 C reduced formation of CuxC
active phase and enhanced the production of Cu and carbon,
whereas low reaction rate at 120 C yield less amount of CuC2.
The effect of acetylene treatment time is shown in Figure 8.
The acetylene treatment time had a strong impact on the
activity of the resultant catalyst. The optimal treatment time at
°
°
°
R150) was investigated in the range of 6–15 at 120 C and
140 C was 2 h. CuC2, which is the intermediate for the
atmospheric pressure (Figure 6b). Acetylene conversion was
kept constant at 100%, while the ethane selectivity increased
from 10% to 39% when the H2/C2H2 ratio increased from 6 to
15. The wide operation window of H2/C2H2 ratio is favorable not
only for the reactor operation, but also for the flexible choice of
the front-end and the tail-end hydrogenation processes.
production of CuxC, is thermally unstable, and prolonged
treatment time led to enhanced decomposition of the in situ
generated CuC2.
It is apparent that H2 reduction of the in situ formed CuC2
was accompanied by the simultaneous decomposition of CuC2.
Fast deactivation of copper catalysts was observed in alkyne
hydrogenation due to the buildup of oligomers below
[7,45]
°
160 C.
Meanwhile, copper is often reported as the catalyst
for the synthesis of carbon nanofibers by using acetylene as the
gas source.[59,60] The carbon nanofibers from acetylene polymer-
ization are accumulated on the catalyst surface and also
deactivate the catalyst in acetylene hydrogenation. Therefore,
the catalyst stability is of paramount importance for selective
hydrogenation of acetylene on copper-based catalysts. Fig-
ure 6c demonstrated that Cu2(OH)2CO3(T140-R150) was stable in
Figure 7. (a) Acetylene conversion and (b) ethane selectivity as a function of
reaction temperature over the Cu(OH)2CO3(TxÀ R150) catalysts.
°
the selective acetylene hydrogenation at 110 C for 180 h, with
complete acetylene conversion and 16% ethane selectivity. The
high stability of Cu2(OH)2CO3(T140-R150) might be associated
with the low reaction temperature. It was reported that the
core-shell Pd@carbon nanoparticles supported on carbon nano-
tubes (Pd@C/CNTs) showed excellent stability in acetylene
hydrogenation.[61] The formation of the porous carbon matrix in
Cu2(OH)2CO3(T140-R150) might pose steric hindrance to the
chain growth of linear hydrocarbons, thus suppressing the
undesired oligomerization and polymerization.
Figure 8. (a) Acetylene conversion and (b) ethane selectivity as a function of
reaction temperature over Cu(OH)2CO3(T140-R150) catalysts treated with
acetylene-containing gas for different times at 140 C.
°
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
1001
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
As a result, the subsequent H2 reduction determines the
matrix. The obtained catalyst was highly active, selective and
stable in acetylene hydrogenation at low temperatures (~
1
2
3
4
5
6
7
8
9
amount of generated CuxC active phase and thus the hydro-
genation activity of the obtained catalysts. The effect of
reduction temperature on the performance of the prepared
catalyst in selective hydrogenation of acetylene is shown in
Figure 9. Acetylene conversion and ethane selectivity increased
with reaction temperature, and complete acetylene conversion
°
120 C). The Cu phase was the main site for acetylene hydro-
genation, and the CuxC phase served as the catalytic sites for H2
dissociation. In contrast to the high sensitivity to H2/C2H2 for Pd-
based catalysts, the ethane selectivity on the prepared catalyst
was not dramatically affected by the H2/C2H2 ratio in the feed in
the presence of large excess ethylene. As a result, the new
catalyst could be used for both the front-end hydrogenation
process and the tail-end hydrogenation process without adding
CO as a selectivity enhancer. The high stability of the catalyst
might be ascribed to the lowered reaction temperature as well
as to the formation of a porous carbon matrix which suppressed
the chain growth of linear hydrocarbons by a steric hindrance
effect.
°
was achieved at 120 C for each catalyst. The reduction below
°
180 C resulted in highly active catalyst for acetylene hydro-
°
genation, achieving 100% acetylene conversion at 110 C and
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
atmospheric pressure. When Cu(OH)2CO3(T140) was reduced at
210 C, the acetylene conversion was around 80% under the
same conditions. Reduction at higher temperature enhanced
the parallel decomposition of CuC2, leading to decreased
formation of CuxC. The lower activity of the catalyst reduced at
°
°
130 C might be linked to the lower reduction rate of CuC2. The
effect of reduction time on the performance of the catalyst is
presented in Figure 10. It is shown that the reduction time had Experimental Section
a minor effect on the activity of the catalysts, probably due to
the fast rate in reduction and thermal decomposition of CuC2 at
Chemicals and Materials
°
180 C.
Cu(NO3)2 ·3H2O, Na2CO3 and ethanol were purchased from Sino-
pharm Chemical Reagent Co., Ltd, China, and used without further
purification. Hydrogen gas and ethylene were from Dalian Guangm-
ing Gas Co., China. The acetylene-containing gas (0.50% C2H2 and
99.50% Ar) for the thermal treatment and the hydrogenation feed
(0.80% CH4, 0.50% C2H2, and 98.70% C2H4) were provided by Dalian
Guangming Gas Co., China.
Conclusions
A non-precious metal catalyst for selective hydrogenation of
acetylene in excess ethylene was prepared from Cu(OH)2CO3
through thermal treatment with acetylene and subsequent H2
reduction. The catalyst was composed of CuxC and Cu
crystallites which were highly dispersed in a porous carbon
Preparation of catalysts
Cu2(OH)2CO3 was synthesized by
a fast-precipitation method
according to the literature.[49] 200 mL Na2CO3 solution (0.1 molLÀ 1
)
was poured into 200 ml Cu(NO3)2 solution (0.1 molLÀ 1) at different
°
temperatures (25, 45 and 65 C) and stirred for 30 min. Then the
precipitate was collected through filtration, washed with deionized
water and ethanol for several times, and dried in a vacuum oven at
°
30 C for 12 h.
The catalysts were prepared as follows. The Cu2(OH)2CO3 sample
was heated from room À t1emperature to the thermal treatment
°
temperature at 3 Cmin and kept for 2 h in an acetylene-
containing gas (0.50% C2H2 and 99.50% Ar) at 30 mlminÀ 1, then
cooled down to room temperature. The obtained sample was
denoted as Cu2(OH)2CO3(Tx), where x represents the thermal
treatment temperature. Then Cu2(OH)2CO3(Tx) was reduced in
50 mlminÀ 1 H2 at a set temperature for 3 h with a heating rate of
Figure 9. (a) Acetylene conversion and (b) ethane selectivity as a function of
reaction temperature over the Cu(OH)2CO3(T140-Ry) catalysts reduced at
different temperatures.
3 CminÀ 1. The resultant hydrogenation catalyst was denoted as
°
Cu2(OH)2CO3(TxÀ Ry), where y represents the reduction temperature.
For comparison, a Cu catalyst was prepared from the Cu2(OH)2CO3
°
°
sample synthesized at 25 C by hydrogen reduction at 400 C and
atmospheric pressure for 6 h
Bulk CuC2 was prepared as follows. Cu2(OH)2CO3 was dissolved in
ammonia solution (12.5%) at room temperature. Ar was bubbled
into the blue solution at 50 mlminÀ 1 for 30 min. Subsequently, a
mixture gas (10.0% C2H2 in Ar at 50 mlminÀ 1) was bubbled for 5 h.
The bulk copper (II) acetylide (CuC2) was obtained by centrifugation
and washed with deionized water and ethanol for several times,
and then kept in water (CAUTION: Dry CuC2 is highly explosive.).
The obtained CuC2 was heated in H2 (50 mlminÀ 1) or in vacuum at
°
150 C for 3 h, and the resultant materials were denoted as
Figure 10. (a) Acetylene conversion and (b) ethane selectivity as a function
of reaction temperature over the Cu(OH)2CO3(T140-R180) catalysts reduced
CuC2(R150) and CuC2(v150), respectively.
°
at 180 C for different times.
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
1002
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
[1] H. M. Torres Galvis, K. P. de Jong, ACS Catal. 2013, 3, 2130–2149.
Catalyst Characterization
1
2
3
4
5
6
7
8
9
[2] L. Zhang, M. Zhou, A. Wang, T. Zhang, Chem. Rev. 2020, 120, 683–733.
[3] J. Gislason, W. Xia, H. Sellers, J. Phys. Chem. A 2002, 106, 767–774.
[4] M. R. Rahimpour, O. Dehghani, M. R. Gholipour, M. S. Shokrollahi Yan-
cheshmeh, S. Seifzadeh Haghighi, A. Shariati, Chem. Eng. J. 2012, 198–
199, 491–502.
Powder X-ray diffraction (XRD) patterns were collected on a Rigaku
SmartLab diffractometer with Cu Kα radiation at a scanning rate of
°
°
°
8 /min between 20 and 80 . The tube voltage and current were
40 kV and 100 mA, respectively. Scanning electron microscope
(SEM) observation was conducted on
[5] S. A. Nikolaev, L. N. Zanaveskin, V. V. Smirnov, V. A. Averyanov, K. L.
Zanaveskin, Russ. Chem. Rev. 2009, 78, 231–247.
a SU8220 instrument
operated with a beam energy of 5.0 kV. Transmission electron
microscopy (TEM) observation was performed on a FEI Tecnai G2
F30 microscope operated at 300 kV. Raman spectrum was recorded
using a Thermo Scientific DXR Raman instrument with a 532 nm
laser beam as the excitation source. TG-DSC curves were measured
on TGAÀ 1Q50 in N2 flow at 50 mlminÀ 1 with a heating rate of
[6] A. Borodziński, G. C. Bond, Catal. Rev. 2006, 48, 91–144.
[7] B. Bridier, N. López, J. Pérez-Ramírez, J. Catal. 2010, 269, 80–92.
[8] F. Studt, F. Abild-Pedersen, T. Bligaard, R. Z. Sorensen, C. H. Christensen,
J. K. Norskov, Angew. Chem. Int. Ed. 2008, 47, 9299–9302; Angew. Chem.
2008, 120, 9439–9442.
[9] L. Ding, H. Yi, W. Zhang, R. You, T. Cao, J. Yang, J. Lu, W. Huang, ACS
Catal. 2016, 6, 3700–3707.
[10] M. Krajčí, J. Hafner, J. Catal. 2014, 312, 232–248.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
°
°
3 Cmin . Nitrogen sorption isotherms were measured at À 196 C
on Micromeritics Tristar II 3020 instrument. The specific surface
areas was calculated according to the Brunauer-Emmett-Teller (BET)
method.
[11] A. Ota, J. Kröhnert, G. Weinberg, I. Kasatkin, E. L. Kunkes, D. Ferri, F.
Girgsdies, N. Hamilton, M. Armbrüster, R. Schlögl, M. Behrens, ACS Catal.
2014, 4, 2048–2059.
[12] L. Yang, Y. Guo, J. Long, L. Xia, D. Li, J. Xiao, H. Liu, Chem. Commun.
2019, 55, 14693–14696.
Catalytic performance
[13] M. Hu, S. Zhao, S. Liu, C. Chen, W. Chen, W. Zhu, C. Liang, W. Cheong, Y.
Wang, Y. Yu, Q. Peng, K. Zhou, J. Li, Y. Li, Adv. Mater. 2018, 30, 1801878.
[14] M. W. Tew, H. Emerich, J. A. van Bokhoven, J. Phys. Chem. C 2011, 115,
8457–8465.
[15] B. Pongthawornsakun, O. Mekasuwandumrong, F. J. C. Santos Aires, R.
Büchel, A. Baiker, S. E. Pratsinis, J. Panpranot, Appl. Catal. A 2018, 549, 1–
7.
[16] C. Ma, Y. Du, J. Feng, X. Cao, J. Yang, D. Li, J. Catal. 2014, 317, 263–271.
[17] Y. Zhang, W. Diao, C. T. Williams, J. R. Monnier, Appl. Catal. A 2014, 469,
419–426.
[18] C. M. Kruppe, J. D. Krooswyk, M. Trenary, ACS Catal. 2017, 7, 8042–8049.
[19] S. K. Kim, J. H. Lee, I. Y. Ahn, W. Kim, S. H. Moon, Appl. Catal. A 2011, 401,
12–19.
The selective hydrogenation of acetylene in ethylene stream was
performed at atmospheric pressure in a quartz tube fixed-bed
reactor (10 mm i.d.). Cu2(OH)2CO3 sample (0.1 g) was mixed with
quartz sands (0.6 g, 60–80 mesh), and sandwiched in the middle of
the reactor. The acetylene hydrogenation catalyst was prepared
in situ, prior to selective hydrogenation.
The acetylene hydrogenation reaction was performed in the
temperature range of 90–120 C with a mixture gas of 93% feed
°
gas and 7% H2. The total flow was 10 ml/min. The outlet gas
composition was analyzed by an online gas chromatography (GC
A90, ECHROM) equipped with an FID detector and a capillary
column (Agilent HP-AL/S, 30 m×0.535 mm×15.00 μm). Methane
was used as the internal standard for GC analysis. Because it is
extremely difficult to determine the increment of ethylene in the
presence of over 90% ethylene, the selectivity to undesired ethane
was used to measure the selectivity of the catalyst. Acetylene
conversion and ethane selectivity were calculated as follows
(Equation 1 and Equation 2).
[20] L. Guczi, Z. Schay, G. Stefler, L. F. Liotta, G. Deganello, A. M. Venezia, J.
Catal. 1999, 182, 456–462.
[21] G. X. Pei, X. Y. Liu, X. Yang, L. Zhang, A. Wang, L. Li, H. Wang, X. Wang, T.
Zhang, ACS Catal. 2017, 7, 1491–1500.
[22] Y. Cao, Z. Sui, Y. Zhu, X. Zhou, D. Chen, ACS Catal. 2017, 7, 7835–7846.
[23] Y. Luo, S. Alarcón Villaseca, M. Friedrich, D. Teschner, A. Knop-Gericke,
M. Armbrüster, J. Catal. 2016, 338, 265–272.
[24] Y. Liu, A. J. McCue, C. Miao, J. Feng, D. Li, J. A. Anderson, J. Catal. 2018,
364, 406–414.
[25] Y. Liu, A. J. McCue, J. Feng, S. Guan, D. Li, J. A. Anderson, J. Catal. 2018,
364, 204–215.
[26] A. J. McCue, A. Guerrero-Ruiz, I. Rodríguez-Ramos, J. A. Anderson, J.
Catal. 2016, 340, 10–16.
[27] M. Hu, W. Yang, S. Liu, W. Zhu, Y. Li, B. Hu, Z. Chen, R. Shen, W. Cheong,
Y. Wang, K. Zhou, Q. Peng, C. Chen, Y. Li, Chem. Sci. 2019, 10, 614–619.
[28] Y. Chai, G. Wu, X. Liu, Y. Ren, W. Dai, C. Wang, Z. Xie, N. Guan, L. Li, J.
Am. Chem. Soc. 2019, 141, 9920–9927.
[29] Y. Liu, X. Liu, Q. Feng, D. He, L. Zhang, C. Lian, R. Shen, G. Zhao, Y. Ji, D.
Wang, G. Zhou, Y. Li, Adv. Mater. 2016, 28, 4747–4754.
[30] C. S. Spanjers, R. S. Sim, N. P. Sturgis, B. Kabius, R. M. Rioux, ACS Catal.
2015, 5, 3304–3315.
(1)
(2)
Acknowledgements
[31] F. Studt, F. Abild-Pedersen, T. Bligaard, R. Z. Sorensen, C. H. Christensen,
The work is supported by the Natural Science Foundation of China
(21972014, 21473017, U1508205), the Fundamental Research
Funds for the Central Universities (DUT19GJ205), and International
S&T Cooperation Program of China (2016YFE0109800).
J. K. Norskov, Science 2008, 320, 1320–1322.
[32] Y. Liu, J. Zhao, J. Feng, Y. He, Y. Du, D. Li, J. Catal. 2018, 359, 251–260.
[33] J. C. Rodrıguez, A. J. Marchi, A. Borgna, A. Monzón, J. Catal. 1997, 171,
268–278.
[34] M. Tejeda-Serrano, M. Mon, B. Ross, F. Gonell, J. Ferrando-Soria, A.
Corma, A. Leyva-Pérez, D. Armentano, E. Pardo, J. Am. Chem. Soc. 2018,
140, 8827–8832.
[35] M. Armbrüster, K. Kovnir, M. Friedrich, D. Teschner, G. Wowsnick, M.
Hahne, P. Gille, L. Szentmiklósi, M. Feuerbacher, M. Heggen, F. Girgsdies,
D. Rosenthal, R. Schlögl, Y. Grin, Nat. Mater. 2012, 11, 690–693.
[36] X. Shi, Y. Lin, L. Huang, Z. Sun, Y. Yang, X. Zhou, E. Vovk, X. Liu, X.
Huang, M. Sun, S. Wei, J. Lu, ACS Catal. 2020, 10, 3495–3504.
[37] F. Huang, Y. Deng, Y. Chen, X. Cai, M. Peng, Z. Jia, J. Xie, D. Xiao, X. Wen,
N. Wang, Z. Jiang, H. Liu, D. Ma, Nat. Commun. 2019, 10, 4431.
[38] B. Bridier, J. Pérez-Ramírez, J. Am. Chem. Soc. 2010, 132, 4321–4327.
[39] T. Cao, R. You, X. Zhang, S. Chen, D. Li, Z. Zhang, W. Huang, Phys. Chem.
Chem. Phys. 2018, 20, 9659–9670.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: Copper
·
Copper carbide
·
Ethylene
·
Hydrogenation · Heterogeneous catalysis
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
1003
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejic.202001073
[40] K. Werner, X. Weng, F. Calaza, M. Sterrer, T. Kropp, J. Paier, J. Sauer, M.
[51] J. Tian, Q. Liu, N. Cheng, A. M. Asiri, X. Sun, Angew. Chem. Int. Ed. 2014,
53, 9577–9581; Angew. Chem. 2014, 126, 9731–9735.
[52] V. F. Brameld, M. T. Clark, A. P. Seyfang, J. Soc. Chem. Ind. 1947, 66, 346–
1
2
3
Wilde, K. Fukutani, S. Shaikhutdinov, H. Freund, J. Am. Chem. Soc. 2017,
139, 17608–17616.
[41] G. Vilé, S. Colussi, F. Krumeich, A. Trovarelli, J. Pérez-Ramírez, Angew.
Chem. Int. Ed. 2014, 53, 12069–12072; Angew. Chem. 2014, 126, 12265–
12268.
353.
[53] A. Morato, C. Alonso, F. Medina, P. Salagre, J. E. Sueiras, R. Terrado, A.
Giralt, Appl. Catal. B 1999, 23, 175–185.
4
[54] J. S. Lee, M. H. Yeom, K. Y. Park, I. Nam, J. S. Chung, Y. G. Kim, S. H.
Moon, J. Catal. 1991, 128, 126–136.
[42] Z. J. Zhao, J. Zhao, X. Chang, S. Zha, L. Zeng, J. Gong, AIChE J. 2019, 65,
1059–1066.
[43] B. Bridier, N. Lopez, J. Pérez-Ramírez, Dalton Trans. 2010, 39, 8412–8419.
[44] M. R. Stammbach, D. J. Thomas, D. L. Trimm, M. S. Wainwright, Appl.
Catal. 1990, 58, 209–217.
[45] B. Bridier, M. A. G. Hevia, N. López, J. Pérez-Ramírez, J. Catal. 2011, 278,
167–172.
[46] A. J. McCue, C. J. McRitchie, A. M. Shepherd, J. A. Anderson, J. Catal.
2014, 319, 127–135.
5
6
7
8
[55] M. Saito, R. B. Anderson, J. Catal. 1981, 67, 296–302.
[56] M. L. Derrien, in Catalytic Hydrogenation Studies in Surface Science and
Catalysis (Ed.: L. Cerveny), Elsevier, Amsterdam, 1986, pp. 613–625.
[57] Á. Molnár, A. Sárkány, M. Varga, J. Mol. Catal. A 2001, 173, 185–221.
[58] D. Teschner, J. Borsodi, A. Wootsch, Z. Révay, M. Hävecker, A. Knop-
Gericke, S. D. Jackson, R. Schlögl, Science 2008, 320, 86–89.
[59] X. Ren, H. Zhang, Z. Cui, Mater. Res. Bull. 2007, 42, 2202–2210.
[60] Y. Qin, Z. Zhang, Z. Cui, Carbon 2004, 42, 1917–1922.
[61] L. Zhang, Y. Ding, K. Wu, Y. Niu, J. Luo, X. Yang, B. Zhang, D. Su,
Nanoscale 2017, 9, 14317–14321.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
[47] G. Kyriakou, M. B. Boucher, A. D. Jewell, E. A. Lewis, T. J. Lawton, A. E.
Baber, H. L. Tierney, M. Flytzani-Stephanopoulos, E. C. Sykes, Science
2012, 335, 1209–1212.
[48] C. Lu, Y. Wang, R. Zhang, B. Wang, A. Wang, ACS Appl. Mater. Interfaces
2020, 12, 46027–46036.
[49] J. Sun, Y. Jia, Y. Jing, Y. Yao, J. Ma, F. Gao, C. Xia, J. Nanosci. Nanotechnol.
2009, 9, 5903–5909.
Manuscript received: November 25, 2020
Revised manuscript received: January 12, 2021
Accepted manuscript online: January 14, 2021
[50] S. Kim, Y. Son, K. Choi, S. I. Kim, Y. Son, J. Park, J. H. Lee, J. Jang,
ChemSusChem 2018, 11, 4203–4208.
Eur. J. Inorg. Chem. 2021, 997–1004
www.eurjic.org
1004
© 2021 Wiley-VCH GmbH