A unique nickel-base nitrogen-oxygen bidentate ligand catalyst for carbonylation of acetylene to acrylic acid

Article abstract of DOI:10.1016/j.mcat.2019.02.015

A nickel-base nitrogen-oxygen bidentate ligand catalyst was prepared in-situ via the complexation method. Our results show that the ligand with nickel can form a chelate catalyst possessing a ring structure, which exhibits good catalytic performance in the carbonylation reaction of acetylene to acrylic acid (AA). Furthermore, we discovered that, under our optimized conditions, when 8-hydroxyquinoline (HQ) is used as the ligand [c(Ni(OAc)₂·4H₂O) = 15 × 10^?6 mol L^?1, n(HQ):n(Ni(OAc)₂·4H₂O) = 1:1, V(H₂O) = 7 mL], 70.1% conversion of acetylene and 92.4% the selectivity of AA is achieved at 200 °C with 8.0 MPa pressure for 30 min. Compared to traditional acetylene carbonylation catalysts and nickel-base phosphine ligand homogeneous complex catalysts, our catalytic system has unique advantages, including no copper, no halogen and no carbon deposition generated during the reaction process. It displays high selectivity and no corrosion of equipment, suggesting that this catalytic system possesses future industrial applications.

Full text of DOI:10.1016/j.mcat.2019.02.015

MolecularCatalysis468(2019)57–61
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
A unique nickel-base nitrogen-oxygen bidentate ligand catalyst for
carbonylation of acetylene to acrylic acid
⁎
Long Cuia,b,c, Xiangui Yanga,b, Yi Zenga, Yuntang Chenc, Gongying Wanga,b,
a Chengdu Organic Chemistry CO. LTD, (Chengdu Institute of Organic Chemistry), Chinese Academy of Sciences, 610041, Chengdu, PR China
b Graduate University of Chinese Academy of Sciences, 100039, Beijing, PR China
c The Isotope Institute Ltd, Henan Academy of Sciences, 450015, Zhengzhou, Henan, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Carbonylation
Acrylic acid
Nickel acetate
8-Hydroxyquinoline
A nickel-base nitrogen-oxygen bidentate ligand catalyst was prepared in-situ via the complexation method. Our
results show that the ligand with nickel can form a chelate catalyst possessing a ring structure, which exhibits
good catalytic performance in the carbonylation reaction of acetylene to acrylic acid (AA). Furthermore, we
discovered that, under our optimized conditions, when 8-hydroxyquinoline (HQ) is used as the ligand [c(Ni
(OAc)2·4H2O) = 15 × 10−6 mol L−1, n(HQ):n(Ni(OAc)2·4H2O) = 1:1, V(H2O) = 7 mL], 70.1% conversion of
acetylene and 92.4% the selectivity of AA is achieved at 200 °C with 8.0 MPa pressure for 30 min. Compared to
traditional acetylene carbonylation catalysts and nickel-base phosphine ligand homogeneous complex catalysts,
our catalytic system has unique advantages, including no copper, no halogen and no carbon deposition gener-
ated during the reaction process. It displays high selectivity and no corrosion of equipment, suggesting that this
catalytic system possesses future industrial applications.
1. Introduction
weak acidic salts of nickel such as NiX2, nickel acetate and nickel
naphthenate were studied. However, their catalytic activity is greatly
Acrylic acid is a highly important and widely used chemical mate-
rial, for water-borne coatings, polymer materials and as a dispersion
agent [1]. Due to increased demand of absorbent resins in recent years,
acrylic acid has been of growing interest. Acrylic acid is produced using
numerous techniques which include the ketene method, acetylene
carbonylation, oxidation of propane, oxidation of propylene, dehydra-
tion of glycerol oxidation, and dehydration of lactic acid. Un-
fortunately, due to their environmentally unfriendly synthetic pro-
cesses, these methodologies have yet to be adapted into industry. At
present, the partial oxidation of propylene and carbonylation of acet-
ylene are the preferred routes for acrylic acid preparation. However,
depletion of the world’s oil has provoked a rapid increase in production
costs of acrylic acid prepared via the oxidation of propylene. In the case
of acetylene, generated from calcium carbide and carbon monoxide for
the synthesis of acrylic acid, it belongs to the atomic economic reactions
and plays a crucial role in the full utilization of resources. Therefore, it
is an effective way in compensating for petrochemical raw materials
shortage [2].
reduced, which can be overcome with the addition of copper and acid
additives to the reaction system [3–6]. This type of approach is widely
used in industrial production, but the catalytic system possesses some
disadvantages, such as carbon deposition during the reaction process,
low selectivity to acrylic acid, and corrosion of equipment.
In order to solve these problems, homogeneous complex catalyst
systems were developed, as well as phosphine ligand based complexes.
To date, numerous reports have investigated phosphine ligand based
nickel complexes that display good catalytic activities [7–11]. Fur-
thermore, in our previous work, nickel salts and triphenylphosphine are
used as catalysts for acrylic acid synthesis, giving 90% selectivity under
optimal conditions [12]. Palladium salts with diphenyl-2-pyridylpho-
sphine ligands are also examined for methyl acrylate preparation, re-
sulting in 99.7% selectivity under mild conditions [13,14].
Importantly, all the above mentioned homogeneous catalysts bear
halogen and acidic proton moieties, which are seriously corrosion to
equipment. The presence of copper ions can intensify acetylene dec-
arburization and polymerization of acetylene and acrylic acid. These
issues must be addressed before considering any industrial application
by developing a novel catalyst without copper, halogen, and protonic
Initially, a nickel carbonyl catalyst was used for the carbonylation of
acetylene to acrylic acid, but because of the catalysts high toxicity,
⁎ Corresponding author at: Chengdu Organic Chemistry CO. LTD, (Chengdu Institute of Organic Chemistry), Chinese Academy of Sciences, 610041, Chengdu, PR
China.
E-mail address: gywang@cioc.ac.cn (G. Wang).
https://doi.org/10.1016/j.mcat.2019.02.015
Received 29 November 2018; Received in revised form 24 January 2019; Accepted 15 February 2019
2468-8231/©2019ElsevierB.V.Allrightsreserved.

L. Cui, et al.
MolecularCatalysis468(2019)57–61
acid groups. Due to the strong coordination ability of nitrogen ligands,
they are ideal for incorporation into nickel based systems to catalyze
the carbonylation of acetylene. Furthermore, considering the stability
of nitrogen bound ligands, the catalytic system of other carbonylation
reactions is used as reference [15–18]. Herein, a series of N-ligands
with nickel salt are studied for the carbonylation of acetylene. We found
that the prepared catalysts, consisting of a nitrogen-oxygen bidentate
ligand and nickel salt, display enhanced catalytic performance under
optimized conditions, compared with traditional nickel based systems.
A plausible reaction mechanism is also proposed.
is also inactive (entry 5). Hence, both the presence and position of the
hydroxyl group is vital for catalytic performance.
The effect of pyridine ligands on the carbonylation reaction is cor-
respondingly summarized in Table 1 (entry 6–11). When 2-(hydro-
xymethyl)pyridine or 2-picolinic acid derivative are employed as the
ligand, good catalytic activity is observed, with 81.2% and 57% se-
lectivity of AA and 63.9% and 72.6% conversion of acetylene, respec-
tively (entry 9 and 11). In this case hydroxypyridine ligands, the hy-
droxyl group position did not have a substantial influence on the
catalytic activity, however, the overall catalytic affect is not satisfactory
(entry 6–8). In the comparison of HQ, 2-(hydroxymethyl)pyridine and
2-picolinic acid chemical structures, a common characteristic is de-
tected. All nitrogen atoms are equal distance from the hydroxyl group
(two carbon atoms), creating a stable chelate ring structure (Scheme 1)
with the nickel salt, resulting in excellent catalytic effect (Scheme 2).
According to reports the key step in the acetylene carbonylation
mechanism is the transition of carbonyl complexes adsorbed acetylene
to acyl complexes via CO insertion reaction [19]. During the carbony-
lation process, L1 and L2 are substituted by carbonyl forming carbonyl
complexes in CO atmosphere, upon adsorbing acetylene alkynes com-
plexes are generated, and after the CO insertion reaction they transform
to acyl complexes. When nitrogen-oxygen bidentate chelates are used as
catalysts, the substituents on the ligands affect the electron cloud
density on Ni through the five-membered ring. This eventually reg-
ulates the strength of C–O bonds and those complexes that can facilitate
the conversion of carbonyl to acyl complexes exhibit enhanced catalytic
activity. The experimental results show that catalyst activity is in the
following order: HQ > 2-picolinic acid > 2-hydroxymethyl pyridine.
Therefore, when N and O are close to the electron-absorbing or aro-
matic groups, they are beneficial to the conversion of carbonyl to acyl
complexes.
2. Experimental
2.1. Chemical reagents
All preparations were performed under laboratory atmosphere. All
reagents and solvents employed were commercially available, of ana-
lytical grade and used without further purification. CO (> 98%) and
C2H2 (> 99.95%) were purchased from the Southwest Research &
Design Institute of the Chemical Industry.
2.2. General procedure
Tetrahydrofuran (60 mL), the specified amount of water and cata-
lyst were charged into a 100 mL high pressure reactor and purged three
times with N2. The specified amount of acetylene was dissolved in the
solution with stirring for 20 min. The reactor was then pressurized with
CO to 6.2 MPa. The reaction was carried out at 200 °C and 8.0 MPa,
1000 rpm stirring speed for the specified time, followed by water bath
cooling of the reaction system to room temperature. The gases and li-
quid solution were analyzed by GC with TCD and FID, respectively.
However, other hydroxyl-substituted quinolones are inactive,
whereas hydroxyl-substituted pyridines have certain activity, this may
be attributed to the spatial structure. Ni can complex to N on one
pyridine ligand and O on the other simultaneously. However, the de-
scribed intermolecular coordinated complex is not as stable as the in-
tramolecular ring structure, which shows moderate catalytic activity.
Correspondingly, intermolecular coordination complex formation is
impossible between Ni and 2,4-dihydroxyquinoline, because the qui-
noline ring is relatively larger, resulting in low catalytic activity.
Among the examined ligands, optimal catalytic performance is ob-
tained when HQ is used as the ligand. Therefore, the catalytic perfor-
mance of Ni(OAc)2-HQ was investigated, and the process conditions
optimized.
2.3. Preparation of NiQ2
0.25 g Ni(OAc)2·4H2O and 0.30 g 8-Hydroxyquinoline (HQ) were
dissolved in 100 mL ethanol solution, respectively. The ethanol solution
with HQ was added to the ethanol solution of nickel acetate, stirred for
20 min at 60 °C, filtered while hot, washed and dried, and then 8-hy-
droxyquinoline nickel complex (NiQ2) was obtained.
2.4. Product analysis
Tail gas was analyzed by GC-3000B gas chromatography, using N2
as the carrier gas with a TDX-01 Aglient's (1 m × 2 mm, I.D.) chroma-
tographic column. Column temperature: 130 °C, TCD temperature:
140 °C, vaporizing chamber temperature: 140 °C, current bridge cur-
3.2. Effect of the preparation method on catalytic performance
rent: 120 mA, signal polarity: +, carrier gas flow rate: 65 mL·min−1
.
Kettle liquid was analyzed by SC-14B gas chromatograph. Nitrogen
was the carrier gas, with a hydrogen flame detector, and DB-FFAP
Aglient's (60 m × 0.34 mm × 0.5 μm) chromatographic column.
Temperature programmed retention: initial temperature 40 °C 2.5 min,
40 °C–220 °C/min. The detector temperature: 240 °C, the gasification
chamber temperature: 240 °C.
Table 2 shows that the catalyst, which has 1:1 M ratio of ligand: Ni
prepared in-situ (entry 2), has an 84.5% increase in selectivity com-
pared with NiQ2 (entry 4). When the molar ratio of ligand: Ni is
2:1(entry 3), the amount of AE increases, and the selectivity of AA re-
duces to ca. 5%. Importantly, the ligands can effectively prevent the
formation of carbon deposits.
Furthermore, Table 2 compares catalysts bereft of ligands, with HQ
and Ni(OAc)2·4H2O prepared in-situ and complexes prepared out-situ,
catalyst AA selectivity increases of AA from 62.3% to 84.5%, the con-
version of acetylene increases from 45.7% to 64%. This substantial
increase is observed especially in the case of HQ and Ni(OAc)2·4H2O
prepared together in-situ, which allows for reduction in the amount of
ligand and AE, enhancing the selectivity of acrylic acid. Importantly,
this has great significance in the promotion of further applications of
acetylene as well as decreasing catalyst production costs in industrial.
3. Results and discussion
3.1. Effect of different ligands
The effect of quinolone ligands on the carbonylation reaction is
summarized in Table 1 (entry 1–5). Optimum activity is obtained for
the catalyst bearing HQ ligand, displaying 84.5% acrylic acid selectivity
and 64.5% conversion of acetylene (entry 2). When the hydroxyl group
of HQ ligand is replaced with an amino electron donating group (8-
aminoquinoline) (entry 4) or nitro electron withdrawing group (8-ni-
troquinoline) (entry 3) rendered the catalyst inactive. Moreover, when
the position of the hydroxyl group is changed on quinolone the catalyst
3.3. Effect of Ni(OAc)2·4H2O concentrations
As shown in Fig. 1, the carbonylation reaction is inactive without
58

L. Cui, et al.
MolecularCatalysis468(2019)57–61
Table 1
Catalytic performance of Ni(OAc)2·4H2O with different ligands.
Entry
Ligand (HL)
Conversion of acetylene/%
Selectivity/%
AA
Acetone
Acetaldehyde
Acetic acid
Dimer
AE
1
2
–
45.7
64.5
62.3
84.5
4.9
2.6
12.9
3.4
15.2
2.7
3.4
5.6
0.4
1.0
3
4
5
7.8
2.9
28.7
22.9
21.8
37.9
30.1
28.7
29.8
23.7
22.5
0.0
0.0
0.0
0.4
0.4
0.5
9.8
19.4
24.4
10.3
6
7
8
37.2
40
53.4
54.9
50.7
10.5
9.8
13.9
12.9
14.2
10.9
10.2
11.2
2.4
2.3
2.5
5.2
4.9
5.4
36.4
10.8
9
57
72.6
37.3
3.9
5.2
4.1
6.3
0.6
5.7
6.5
10
15.1
14.8
19.6
15.4
11
63.9
81.2
2.6
4.6
2.7
5.7
0.4
Reaction conditions: n(Ni(OAc)2·4H2O) = 0.001 mol, n(ligand) = 0.001 mol, V(THF) = 60 mL, V(H2O) = 5 mL,
r = 1000 rpm, t = 30 min.
m (C2H2) = 4 g, P = 8.0 MPa, T = 200 °C,
3.5. Effect of H2O
In the studied reaction, water is both raw material and a composi-
tion of mixed solvent with tetrahydrofuran, which absorbs acetylene
and CO, followed by the carbonylation reaction in the liquid phase. The
amount of water effects the relative concentration of raw materials and
polarity of the solution, which influences acetylene and CO con-
centration in the liquid phase, and the reaction rate. The effect of water
on the reaction is shown in Fig. 3. When 4 mL of water is used, which is
in stoichiometric ratio with acetylene, the conversion of acetylene and
selectivity of acrylic acid are rather low at 65.9% and 70%, respec-
tively. An increase in water to 7 mL resulted in 70.1% conversion and
92.4% selectivity. Excess water promotes the reaction with acetylene,
and the increase in by-product acetaldehyde production. Hence, the
addition of 10 mL of water reduced the selectivity to acrylic acid to
83.1%.
Scheme 1. Structural formula of nickel-based nitrogen-oxygen bidentate che-
late.
catalyst, generating 9.8% acetylene via decarburization reaction, and
producing a large amount of carbon deposition. When the concentra-
tion of catalyst (n(HQ): N(Ni(OAc)2·4H2O) = 1:1) is increased to
8 × 10−6 mol L−1, the conversion of acetylene and selectivity of acrylic
acid shows a significant increase to 65.6% and 83.1%, respectively.
When the concentration is further increased to 15 × 10−6 mol·L-1, the
conversion and selectivity are 70.1% and 92.4%, respectively. Above
this concentration, the conversion slowly increases to 72.5%, but the
selectivity is greatly reduced to 81.3%, due to the occurrence of side
reactions.
3.6. Effect of reaction time
3.4. Effect of the amount of ligand
Effect of reaction time is shown in Fig. 4, the conversion of acet-
ylene and selectivity of acrylic acid are 65.4% and 86%, respectively, at
20 min. The yield of acrylic acid is 56.2%, which shows that the cata-
lytic activity is high. When the reaction is conducted for 30 min, the
selectivity reaches a maximum of 92.4%, and conversion of 70.1%.
Prolongation of the reaction time did not significantly increase acet-
ylene conversion rate, but increases the amount of side reactions whilst
decreasing the selectivity to 82.1%. Therefore, the optimal reaction
time is 30 min.
The effect of the amount of HQ on the carbonylation reaction is
shown in Fig. 2. The conversion of acetylene is very low without HQ,
only 55.3%. Increasing the concentration of HQ, the selectivity of ac-
rylic acid increases rapidly. When the ratio of n(HQ)/n(Ni(OAc)2·4H2O)
is ca. 1.0, the selectivity of acrylic acid is 92.3%. HQ, an amphoteric
compound, can undergo esterification with acrylic acid, whereas ex-
cessive HQ reduces the selectivity of acrylic acid.
59

L. Cui, et al.
MolecularCatalysis468(2019)57–61
Fig. 1. Effect of catalyst concentrations on the carbonylation reaction.
Reaction conditions: n(ligand): n(Ni(OAc)2·4H2O) = 1:1, V(THF) = 60 mL, V
(H2O) = 5 mL, m(C2H2) = 4 g, P = 8.0 MPa, T = 200 °C, r = 1000 rpm,
t = 30 min.
Fig. 2. Effect of the amount of HQ on the carbonylation reaction.
Reaction conditions: n(Ni(OAc)2·4H2O) = 0.001 mol, V(THF) = 60 mL,
(H2O) = 5 mL, m(C2H2) = 4 g, P = 8.0 MPa, T = 200 °C, r = 1000 rpm,
t = 30 min.
Scheme 2. Proposed catalytic mechanism of acetylene carbonylation to AA
catalyzed by Ni-HQ.
V
Table 2
Effect of the preparation method on catalytic performance.
acetylene with carbon monoxide, the following mechanism is proposed
[19–22]:
Entry Catalyst
Conversion of
acetylene/%
Selectivity/%
Carbon
deposition
Under the reaction conditions, Ni(OAc)2 forms a chelate with HQ
acetic acid nickel chelate with HQ, and freed protons (1). Chelation in
CO atmosphere (2) removes acetate ions formed HQ nickel carbonyl
complexes, generating a ring shaped nickel hydride complexes active
component in part of the proton acid (3). The complex adsorbs acet-
ylene and undergoes additional reactions (4), followed by the insertion
reaction of carbonyl complexes, allowing the acyl complexes to trans-
form to the acyl complex. The acyl complex with one part of CO as
ligand forms acrylic acid in the presence of water (8). At the same time,
the catalyst is reduced to the ring nickel metal hydride complexes active
components. Step (3) is the key step in the catalytic cycle, while step
(6) is the rate-determining step.
AA
AE
1
2
3
4
aNi(OAc)2·4H2O
45.7
62.3
84.5
78.7
79.8
–
Yes
No
No
No
bNi(OAc)2·4H2O,HQ 64.5
1.0
5.2
4.6
cNi(OAc)2·4H2O,HQ 63.7
dNiQ2
63.9
Reaction conditions: V(THF) = 60 mL, V(H2O) = 5 mL, m(C2H2) = 4 g,
P = 8.0 MPa, T = 200 °C, r = 1000 rpm, t = 45 min.
a
n(Ni(OAc)2·4H2O) = 0.001 mol.
n(Ni(OAc)2·4H2O) = 0.001 mol, n(HQ) = 0.001 mol.
n(Ni(OAc)2·4H2O) = 0.001 mol, n(HQ) = 0.002 mol.
n(NiQ2) = 0.001 mol.
b
c
d
3.7. Reaction mechanism
4. Conclusions
On the basis of the above experiments and reported mechanisms of
nickel or palladium catalyzed hydroesterification of methylacetylene or
Herein, we found that nitrogen ligands containing a hydroxyl group
and a lone pair of electrons on the aromatic ring generates a ring
60

L. Cui, et al.
MolecularCatalysis468(2019)57–61
[2] X.M. Zhang, X. Zhou, Chin. J. Chem. Eng. 20 (2012) 399–402.
[3] W. Reppe, US Pat. Appl., US 2883418, 1959.
[4] S.K. Bhattacharyya, A.K. Sen, Ind. Eng. Chem. Proc. Des. Dev. 3 (1964) 169–176.
[5] T. Lin, H. Xie, X. Meng, L. Shi, Catal. Commun. 68 (2015) 88–92.
[6] D.K. Dutta, B. Deb, G.X. Hua, J.D. Woollins, J. Mol. Catal. A: Chem. 353 (2012)
7–12.
[7] W.R. Proops, US Pat. Appl., US 2967884, 1961.
[8] W. Reppe, US Pat. Appl., US 2925436, 1960.
[9] T.J. Lin, X. Meng, S. Li, J. Mol. Catal. A: Chem. 396 (2015) 77–83.
[10] P.P. Sarmah, D.K. Dutta, J. Mol. Catal. A: Chem. 372 (2013) 1–5.
[11] C.M. Tang, Y. Zeng, P. Cao, X.G. Yang, G. Wang, Catal. Lett. 129 (2009) 189–193.
[12] L. Cui, X. Zhou, X.G. Yang, Y. Zeng, X.J. Chen, Z.Y. Deng, G.Y. Wang, Chin. J. Inorg.
Chem. 30 (2014) 1600–1608.
[13] C.M. Tang, Y. Zeng, X.G. Yang, Y.C. Lei, G.Y. Wang, J. Mol. Catal. A: Chem. 314
(2009) 15–20.
[14] C.M. Tang, X.L. Li, G.Y. Wang, Korean J. Chem. Eng. 29 (2012) 1700–1707.
[15] J. Peng, Y. Geng, H. Yang, W. He, Z. Wei, J. Yang, C. Guo, Mol. Catal. 432 (2017)
37–46.
[16] Y. Xie, Y. Huang, C. Wu, W. Yuan, Y. Xia, X. Liu, H. Wang, Mol. Catal. 452 (2018)
20–27.
[17] X. Yang, Y. Hu, H. Bai, M. Feng, Z. Yan, S. Cao, B. Yang, Mol. Catal. 457 (2018) 1–7.
[18] D. Sun, A. Ohkubo, K. Asami, T. Katori, Y. Yamada, S. Sato, Mol. Catal. 437 (2017)
105–113.
[19] F. De Angelis, A. Sgamellotti, N. Re, Organometallics 19 (2000) 4104–4116.
[20] X.G. Yang, J.Q. Zhang, Z.T. Liu, et al., Appl. Catal. A-Gen. 173 (1998) 11–17.
[21] E. Drent, P. Arnoldy, P.H.M. Budzelaar, J. Organomet. Chem. 455 (1993) 247–253.
[22] Samuel Quinetro-Duque, Katrin Marie Dyballa, Ivana Fleischer, Tetrahedron Lett.
56 (2015) 2634–2650.
Fig. 3. Effect of H2O on the carbonylation reaction.
Reaction conditions: n(Ni(OAc)2·4H2O) = 0.001 mol, n(ligand) = 0.001 mol, m
(C2H2) = 4 g, P = 8.0 MPa, T = 200 °C, r = 1000 rpm, t = 30 min.
Fig. 4. Effect of reaction time on the carbonylation reaction.
Reaction conditions: n(Ni(OAc)2·4H2O) = 0.001 mol, n(ligand) = 0.001 mol, V
(THF) = 60 mL, V(H2O) = 5 mL, m(C2H2) = 4 g, P = 8.0 MPa, T = 200 °C,
r = 1000 rpm.
complex with nickel salt, resulting in good catalytic activities. Catalysts
bearing 8-hydroxyquinoline as the ligand display good catalytic activity
and higher acrylic acid selectivity. Importantly, the catalytic system has
no copper, no halogen, no need for acidic protons and no carbon de-
position occurring during the reaction process. Our approach has suc-
cessfully solved the problems of the traditional acetylene carbonylation
catalyst and phosphine ligand homogeneous complex catalysts, whilst
maintaining excellent catalytic efficiency for the carbonylation of
acetylene to acrylic acid, making it suitable for industrial production.
References
[1] V.H. Rane, U. Rodemerck, M. Baerns, J. Mol. Catal. A: Chem. 245 (2006) 161–166.
61