A recyclable heterogeneous-homogeneous-heterogeneous NiO/AlOOH catalysis system for hydrocarboxylation of acetylene to acrylic acid

Article abstract of DOI:10.1039/c9ra09737f

Concerns about the high-valued utilization of coal- A nd natural gas-based acetylene has provided particular impetus for exploration of acrylic acid (AA) production via one-step hydrocarboxylation reaction. Motivated by simple recovery, recycling and reuse of the catalyst, we report a high-performance NiO/AlOOH catalyst with AA space-time-yield of 412 g_AA g_cat.^-1 h^-1, obtainable by a simple incipient wetness impregnation method. Detailed kinetic and controlled experiments confirmed that nickel species on such a solid catalyst provide a heterogeneous-homogeneous-heterogeneous catalytic cycle where the chelates formed between CO and leached nickel act as the active species. The thorough recovery of leached nickel species improves the catalyst stability greatly. These preliminary findings indicate further prospects for new heterogeneous catalyst design in traditional homogeneous catalytic systems.

Full text of DOI:10.1039/c9ra09737f

RSC Advances
View Article Online
View Journal | View Issue
PAPER
A recyclable heterogeneous–homogeneous–
heterogeneous NiO/AlOOH catalysis system for
Cite this: RSC Adv., 2020, 10, 1634
hydrocarboxylation of acetylene to acrylic acid†
ab
a
c
a
a
*
Lifang Yan, Qiaofei Zhang, Binhang Yan and Yi Cheng
*
Yakun Li,
Concerns about the high-valued utilization of coal- and natural gas-based acetylene has provided particular
impetus for exploration of acrylic acid (AA) production via one-step hydrocarboxylation reaction. Motivated
by simple recovery, recycling and reuse of the catalyst, we report a high-performance NiO/AlOOH catalyst
ꢀ1
with AA space-time-yield of 412 gAA gcat.
h
ꢀ1, obtainable by a simple incipient wetness impregnation
method. Detailed kinetic and controlled experiments confirmed that nickel species on such a solid
catalyst provide a heterogeneous–homogeneous–heterogeneous catalytic cycle where the chelates
formed between CO and leached nickel act as the active species. The thorough recovery of leached
nickel species improves the catalyst stability greatly. These preliminary findings indicate further prospects
for new heterogeneous catalyst design in traditional homogeneous catalytic systems.
Received 21st November 2019
Accepted 28th December 2019
DOI: 10.1039/c9ra09737f
rsc.li/rsc-advances
investigated the acetylene carbonylation reaction with the aid of
metal halide/silica gel catalysts in detail, but unfortunately,
1. Introduction
these supported catalysts showed very low AA yield (only 14.2%)
even under optimal conditions.8 Recently, Shi and coworkers
studied the synthesis of AA via hydrocarboxylation of acetylene
over Ni- and Cu-exchanged Y-zeolite with the presence of cupric
salt and nickel salt as promoter respectively.3,9 They found that
the catalytic activity showed a pronounced dependence of the
reaction conditions and Ni2+ and Cu+ ions in the zeolites were
responsible for the catalytic activity, being similar to the
homogeneous catalysts.
Signicantly, question arises simultaneously when using
solid catalysts in the liquid phase (liquid–solid or gas–liquid–
solid system) because the active transition metals may leach
from the catalysts surface into the liquid.10,11 As a consequence,
it is very difficult to clarify the catalytically active species
whether homogeneous or heterogeneous, even if there is only
trance amount of active metals in the liquid.12–14 For example,
the argument about the actual active species (palladium atoms
or complexes in solution,15 or palladium nanoparticles16,17) in
heterogeneous Heck and Suzuki coupling reactions has still
been going on. Up to now, however, there are no data con-
cerning the problem of leaching about heterogeneous catalysts
for the hydrocarboxylation of acetylene and thereby not clear
whether this reaction is homogeneous or heterogeneous.
Correspondingly, it is highly desired not only to develop new
heterogeneous catalysts with excellent performance but also to
clarify the actual active species whether homogeneous or
heterogeneous.
With the depletion of petroleum reserves, it is highly desired to
study sustainable alternatives. Meanwhile, due to the discovery
of huge reserves of shale gas by fracking techniques as well as
the breakthrough development of coal- and natural gas-based
acetylene, the diverse utilization of acetylene to produce high
value-added chemicals has received renewed interest.1,2 As an
ideal atom economy reaction, the one-step hydrocarboxylation
of acetylene to acrylic acid (C2H2 + CO + H2O / C3H4O2)
provides a promising and alternative route to replace the partial
oxidation of propene method, especially in coal- or gas-rich
areas.2,3 However, the commercial production of AA using the
homogeneous NiBr2–CuBr2 catalyst system developed by BASF
Co. remains problematic due to the difficulty in product-catalyst
separation, usage of expensive and sensitive ligands, and cor-
rosivity of acid assistants. Tremendous efforts were made in
recent years to solve these problems, such as new nickel or
palladium complexes,4,5 water-soluble ligands6 and even ligand
free catalyst,7 but the outcomes were still in controversy. Nor-
mally, heterogeneous catalysis is an effective and efficient
method to overcome the above problems due to the facial
separation and recovery of catalysts. Bhattacharyya rstly
aDepartment of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
E-mail: binhangyan@tsinghua.edu.cn; yicheng@tsinghua.edu.cn
bDepartment of Material and Chemical Engineering, Zhengzhou University of Light
Industry, Zhengzhou, Henan 450001, PR China
cCollege of Chemistry, Chemical and Environmental Engineering, Henan University of
In this work, a pseudoboehmite (AlOOH) supported nickel-
based catalyst (denoted as NiO/AlOOH) synthesized by
a simple incipient wetness impregnation was tested. Such
Technology, Zhengzhou, Henan 450001, PR China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra09737f
1634 | RSC Adv., 2020, 10, 1634–1638
This journal is © The Royal Society of Chemistry 2020

View Article Online
Paper
RSC Advances
a caꢀta1lyst showed a high AA space-time-yield (STY) of 412 gAA several times and subsequently pressurized with acetylene to
gcat.
hꢀ1 and AA yield of 65.6%. During the hydro- 0.5 MPa and then to 4.5 MPa of initial total pressure with CO
carboxylation reaction, the dissolution of nickel species was (both controlled by mass owmeter) at room temperature. The
observed due to the induction of CO and CuBr2. The leached molar ratio of CO/C2H2 was 1.75. The reactor was then heated to
nickel species underwent a heterogeneous–homogeneous– 250 ꢁC and kept for 30 min under constant agitation (800 rpm).
heterogeneous catalytic cycle.
Aer reaction, the autoclave was quickly cooled to room
temperature and the tail gas and liquid were collected, calcu-
lated and analyzed. For recycling experiments, the catalyst used
in the previous run was separated by centrifugation and washed
with acetone for several times and reused aer drying in air.
The qualitative and quantitative analysis of the reactants and
products was performed by a Shimadzu GC 2014 gas chro-
matograph equipped with a P–N packed column for identifying
C2H2, C2H4, CO and CO2 and a Stabilwax capillary column for
C2H2, aldehyde, acrylic acid, acetone and tetrahydrofuran
(THF). The conversion of acetylene, selectivity and yield of
acrylic acid and the space time yield (STY) are dened as
follows:
2. Experimental section
2.1 Catalysts preparation
The NiO/AlOOH catalysts were prepared using a simple incip-
ient wetness impregnation by impregnating pseudoboehmite
(AlOOH) with an aqueous solution of nickel nitrate (Ni(NO3)2-
$6H2O) followed by calcining in air at 300 ꢁC for 2 h. Both
AlOOH (purchased from Zibo Jiu Ru Industrial and Trading Co.,
Ltd) and nickel nitrate (purchased from Sinopharm Chemical
Reagent Co., Ltd) were used as received without further puri-
cation or drying. Notably, nickel nitrate was dissolved in an
acetone solution (C3H6O, purchased from Beijing Tong Guang
Fine Chemicals Company).
n0 ꢀ ng ꢀ nl
Conv: ¼
ꢂ 100%
(1)
n0
For comparison, some other supports with high surface area
like silicon dioxide (SiO2, purchased from Sinopharm Chemical
Reagent Co., Ltd), alumina (g-Al2O3, purchased from Sino-
pharm Chemical Reagent Co., Ltd), MCM-41 zeolite (purchased
from Tianjin Nanhua Catalyst Co., Ltd) and Mg–Al layered
double hydroxides (Mg–Al LDHs, purchased from Shanghai
Macklin Reagent Co., Ltd) were also investigated by same
method.
nAA
Y ¼
ꢂ 100%
(2)
n0
S ¼ Y/conv.
wAA
(3)
(4)
STY ¼
ꢂ 100%
wcat: ꢂ t
where n0, molar content of acetylene for feedstock before reac-
tion; ng, molar content of acetylene for tail gas aer reaction; nl,
molar content of acetylene for residue aer reaction; nAA
2.2 Characterization
,
The actual nickel content of NiO/AlOOH catalysts and the nickel
content in residue aer reactions are measured by inductively
coupled plasma-optical emission spectrometry (ICP-OES, Var-
ian Vista RL spectrometer). Specic surface areas of NiO/AlOOH
catalysts are determined by nitrogen adsorption carried out at
77 K on a Quantachrome Autosorb-6B analyzer. The data are
calculated by multipoint BET analysis method in the pressure
range of P/P0 ¼ 0.05–0.30. Prior to the measurement, the
samples are degassed in vacuum at 300 ꢁC for 2 h. X-ray
diffraction (XRD) is performed on a Bruker D8 Advance equip-
ment with Cu Ka radiation (35 kV and 25 mA). 2q scans are run
from 20 to 80 at a rate of 0.5 degree per minute. The spectra are
identied with JCPDS database (Joint Committee of Powder
Diffraction Standards) and the ICSD database (Inorganic Crystal
Structure Database). The morphology of NiO/AlOOH catalysts
are characterized by JEOL JEM2010 high-resolution trans-
mission electron microscopy (HR-TEM) equipped with an
energy dispersive X-ray uorescence spectrometer (EDX).
amount of acrylic acid produced during reaction; WAA, mass of
acrylic acid produced during reaction; Wcat, mass of catalyst for
input before reaction; t, reaction time.
2.4 Kinetic investigation
To explore the nature of catalysis, a detailed kinetic experiment
was carefully conducted. In a typical experiment, known quan-
tities of catalyst powders (0.1 g), CuBr2 (0.12 mM Lꢀ1), H2O (15
mL), and acetone (150 mL) were charged into the stirred pres-
sure reactor. The reactor was rstly ushed with nitrogen for
several times and subsequently pressurized with acetylene to
0.5 MPa and then to 4.5 MPa of initial total pressure with CO
(both controlled by mass owmeter) at room temperature. The
molar ratio of CO/C2H2 was 1.75. The reactor was then heated to
set temperature under constant agitation (800 rpm). Then, the
autoclave was quickly cooled to room temperature and the
liquid was collected and the nickel content was analyzed by ICP
measurement.
2.3 Reactivity tests
3. Results and discussion
The catalytic reactions were carried out in a 0.5 L stainless steel-
316 autoclave reactor with a mechanical stirring device and In general, heterogeneous catalysts are composed of one or
temperature controller. In a typical experiment, known quan- more catalytically active components dispersed on functional
tities of catalyst powders (0.1 g), CuBr2 (0.12 mM Lꢀ1), H2O (15 supports with high surface area, in which the physico-chemical
mL), and acetone (150 mL) were charged into the stirred pres- properties of the supports and catalytic components, as well as
sure reactor. The reactor was rstly ushed with nitrogen for the interaction between them can strongly affect the catalytic
This journal is © The Royal Society of Chemistry 2020
RSC Adv., 2020, 10, 1634–1638 | 1635

View Article Online
RSC Advances
Paper
performance. Therefore the effect of different supports (i.e., much higher than other reported heterogeneous catalysts
SiO2, g-Al2O3, AlOOH, MCM-41 and Mg–Al LDHs) with high (Table S2†).3,9,21 Besides the high activity, stability is another
surface area was investigated and the results were collected in important factor for commercial process. Aer reaction the
Table S1.† Clearly, all the supports except Mg–Al LDHs exhibi- used catalyst was recovered by a simple centrifugal separation
ted similar AA yield while NiO/AlOOH showed highest STY. It is and then tested again without additional treatments.
reported that the abundant hydroxyl groups on the surface of Disappointingly, the performance of recovered NiO/AlOOH
support (e.g., AlOOH) is benecial for the dispersion of active catalyst was poor (Fig. S1†), which may be caused by the
metals, which is crucial in CO coupling reactions.10 leaching of nickel as discussed above. Then, special attention
Furthermore, the hydroxyl groups were also reported to was paid to the nickel leaching phenomenon and the results of
promote the adsorption and activation of CO.18,19 Thus, in the ICP-OES showed that a small amount of nickel ions indeed
following investigations we will focus on discussing the NiO/ existed in the liquid media aer reaction. Next, of tremendous
AlOOH catalyst with 11.5 wt% Ni loading, which was interest is to clarify the following two questions: (a) Whether the
measured by inductively coupled plasma-optical emission catalytically active species are homogeneous or heterogeneous?
spectroscopy.
(b) What is the leaching mechanism and actual active species?
To clarify the catalytically active species are whether homo-
Fig. 1 shows the structural features and morphology of the
NiO/AlOOH catalyst. The as-prepared catalyst presents a specic geneous or heterogeneous, we rstly examined catalytic activity
surface area of 289 m2 gꢀ1 and the hysteresis loop indicates of the ltrate. Aer centrifugal separation, the ltrate, promoter
a mesoporous feature with an average pore diameter of (1.2 mM Lꢀ1 CuBr2) and reaction gases (CO/C2H2 molar ratio of
approximately 6 nm (Fig. 1A). According to the X-ray diffraction 1.75) were charged into the stirred pressure reactor and the
pattern shown in Fig. 1B, the NiO/AlOOH catalyst is dominated result was shown in Fig. S2.† Clearly, the ltrate exhibited even
by the phases of g-AlOOH while no NiO or Ni signals are a little higher catalytic activity than the fresh catalyst, indicating
observed, indicating the high dispersion of NiO or Ni nano- that the reaction was most likely to be homogeneous. Then, we
particles.20 Furthermore, the transmission electron microscopy employed nickel nitrate as nickel resource to test its catalytic
and energy-dispersive X-ray spectroscopy element mappings performance (Fig. S3, details in ESI†). Notably, both the nickel
also reveal the homogeneously dispersed NiO species (Fig. 1C). salt alone and nickel salt with clean AlOOH showed much lower
Unsurprisingly, uniform Ni nanoparticles with an average catalytic activity than the fresh NiO/AlOOH catalyst, suggesting
diameter of 2.5 nm are formed on the NiO/AlOOH sample aer that the actual active species might be nickel complexes rather
ꢁ
pre-reduction in H2 at 400 C for 1 h (Fig. 1D).
than nickel ion. In order to provide more evidence for this
The performance of the NiO/AlOOH catalyst was initially speculation, a detailed kinetic experiment was carefully con-
tested for the hydrocarboxylation of acetylene. As expected, such ducted by correlating the yield of AA and the amount of leached
a catalyst delivered a high acetylene conversion of 76% and AA nickel to the reaction time, which has been reported to be
yield of 65.6% due to the high dispersion of Niꢀs1pecies. The STY a direct and unambiguous method to explore the nature of
was calculated to be as high as 412 gAA gcat. hꢀ1, which is catalysis.10,15,22 As clearly shown in Fig. 2, the whole process can
be divided into three stages. First, large amounts of nickel
species were quickly dissolved from the surface of solid catalyst,
while the yield of AA was very low (less than ꢃ1%) during the
Fig. 1 (A) N2 adsorption/desorption isothermal and Barrett–Joyner–
Halenda (BJH) mesopore size distribution (inset) of the fresh NiO/ Fig. 2 Kinetic investigation and the amount of nickel leaching (XNi) as
AlOOH catalyst. (B) XRD pattern of fresh NiO/AlOOH catalyst with a function of time over the NiO/AlOOH for the hydrocarboxylation of
actual Ni loading of 11.5 wt%. (C) TEM image and EDX element acetylene to AA. Conditions: 150 mL acetone, 15 mL H2O, 1.2 mM Lꢀ1
mappings of the fresh NiO/AlOOH catalyst. (D) TEM image and size CuBr2, 100 mg NiO/AlOOH catalyst, CO/C2H2 molar ratio of 1.75 and
distribution of Ni particles (inset) of the reduced NiO/AlOOH sample.
initial pressure of 4.5 MPa.
1636 | RSC Adv., 2020, 10, 1634–1638
This journal is © The Royal Society of Chemistry 2020

View Article Online
Paper
RSC Advances
heating stage (time of 0–20 min). Second, in the initial reaction and KBr as additives respectively under the atmosphere of CO.
stage (time of 20–25 min) the amount of leached nickel in Interestingly, both Cu2+ and Brꢀ could promote the leaching
solution reached a maximum of ꢃ41% but the reaction rate was process. The nickel content in solution was ꢃ8.9% and ꢃ10.5%
still slow. Aer that (time of 25–47 min), the reaction rate respectively when Cu(NO3)2 and KBr were used, which was
accelerated dramatically accompanied by a gradual decrease of slightly lower than the case of CO–CuBr2 (ꢃ14.5%). As is re-
nickel leaching content in solution which illustrated that the ported, Cu2+ can active acetylene and favor the formation of
leached nickel species re-deposited onto the support. Clearly, alkyneꢀNi-complex intermediates (e.g., CH2]CH–Ni(CO)mLn,
the changes of nickel concentration in solution synchronized L-ligand)9,23,24 while CuBr2 is conducive to high CO solubility.4
with the reaction rates. Third, aer the AA yield reached According to the above results, it can be concluded that only in
a maximum of ꢃ66% (time of 47–150 min), the re-deposition the presence of CO and CuBr2, large amount of nickel species
rate of dissolved nickel species reduced obviously while the would dissolve into the solution.
yield of AA almost remained unchanged. Thus, a reliable
To obtain further insight into the active intermediate
correlation between the yield of AA and leaching content of species, we designed a gas replacement experiment described as
nickel species was obtained. Combined with the results of follows. During stage-1, the same conditions as a normal reac-
ltrate and nickel salt experiments, we believe that the catalytic tion were conducted at rst (as shown in the caption of Fig. 4).
activity originated from the dissolved Ni species, in the form of In order to obtain large amount of leached nickel species, the
nickel complex.
reactor underwent a rapid temperature-rising and -cooling
Furthermore, a series of comparison experiments (ESI† for operation in which the temperature followed the tracks of
details) were designed to further clarify the mechanism of how increasing reaction temperature gradually to 250 ꢁC and
the leaching process took place, with the results as shown in decreasing temperature immediately from 250 ꢁC to room
Fig. 3. Firstly, the effect of gas atmosphere on the nickel temperature. During the stage-2, the reaction gas was replaced
leaching was investigated. The amount of nickel in solution was with N2, N2–C2H2 or CO respectively, with the temperature
very low under different gas atmospheres (i.e., N2, CO or CO– increasing to 250 ꢁC again and keeping for 30 minutes.
C2H2 mixture) without the addition of CuBr2, indicating no According to the ICP results, the content of leached nickel in
obvious phenomenon of nickel leaching. Then, the effect of solution was ꢃ41% at the end of stage-1 while a normal reaction
CuBr2 additive under different gas atmospheres was studied. for 30 minutes led to a nickel amount of ꢃ15.3%. However, the
When CuBr2 was added into the N2–C2H2 mixture, no leaching amount of nickel in solution was very low (<1%) at the end of
enhancement was observed with a nickel content of only stage-2 when the reaction gas was replaced with N2 or N2–C2H2
ꢃ0.5%. As a contrast, the addition of CuBr2 in the presence of (Fig. 4), indicating the leached nickel redeposited onto the solid
CO led to remarkable nickel leaching with the nickel content catalyst. In contrast, nickel leaching was still pronounced in the
increasing from ꢃ1.5% to ꢃ14.5% in the solution. These results case of CO replacement with a nickel content of ꢃ18.3%,
implied that both CO and CuBr2 played a crucial role in the illustrating that the leached nickel species coordinated with CO
leaching process. To further study the doubt that whether Cu2+ to form stable chelates like the form of NiH(CO)mBr.25
or Brꢀ promoted the leaching of nickel, we employed Cu(NO3)2
Fig. 4 Effect of gas replacement on nickel leaching (XNi). Conditions:
(stage-1) 150 mL acetone, 15 mL H2O, 1.2 mM Lꢀ1 CuBr2, 100 mg NiO/
AlOOH catalyst, CO/C2H2 molar ratio of 1.75 and initial pressure of
4.5 MPa, temperature increased to 250 ꢁC and then cooled to room
Fig. 3 Effects of gas atmosphere and additives on nickel leaching (XNi). temperature immediately; (stage-2) gas replacement with N2, N2–
Conditions: 150 mL acetone, 100 mg NiO/AlOOH catalyst, initial C2H2 or CO respectively, initial pressure of 4.5 MPa and temperature
pressure of 4.5 MPa, temperature of 250 ꢁC for 30 minutes.
increased to 250 ꢁC and kept for 30 minutes.
This journal is © The Royal Society of Chemistry 2020
RSC Adv., 2020, 10, 1634–1638 | 1637

View Article Online
RSC Advances
Paper
Combining with the above results of contrast experiments, we
can see that NiO was gradually dissolved from catalyst surface
and then coordinated with CO at the initial stage of the reac-
tion. With the consumption of CO during the reaction, the
leached nickel species redeposited onto solid catalyst again,
which was also demonstrated by the kinetic experiment.
Therefore, we can conclude a heterogeneous-homogeneous-
heterogeneous catalytic cycle for this reaction over the NiO/
AlOOH catalyst. More importantly, the stability of NiO/AlOOH
catalyst was improved signicantly by the means of inert gas
replacement. Aer three recycles, a high acetylene conversion of
82% and AA yield of 46% still can be reached (Fig. S4†). It is
worth noting that the decrease of selectivity of AA is related to
the particle agglomeration during the re-deposition process
(Fig. S5†). Hence, inert gas replacement is a facile and efficient
method to recycle the leached nickel, which delivered useful
reference to the development of new heterogeneous catalysts for
2 H. Schobert, Chem. Rev., 2014, 114, 1743–1760.
3 H. Xie, D. Yi, L. Shi and X. Meng, Chem. Eng. J., 2017, 313,
663–670.
4 C. M. Tang, Y. Zeng, P. Cao, X. G. Yang and G. Y. Wang, Catal.
Lett., 2009, 129, 189–193.
5 C. M. Tang, Y. Zeng, X. G. Yang, Y. C. Lei and G. Y. Wang, J.
Mol. Catal. A: Chem., 2009, 314, 15–20.
6 A. H. M. de Vries, F. J. Parlevliet, L. Schmieder van der
Vondervoort, J. H. M. Mommers, H. J. W. Henderickx,
M. A. M. Walet and J. G. de Vries, Adv. Synth. Catal., 2002,
344, 996–1002.
7 M. Beller, J. G. E. Krauter and A. Zapf, Angew. Chem., Int. Ed.,
1997, 36, 772–774.
8 S. K. Bhattacharyya and A. K. Sen, Ind. Eng. Chem. Process Des.
Dev., 1964, 3, 169–176.
9 T. J. Lin, X. Meng and L. Shi, Appl. Catal., A, 2014, 485, 163–
171.
¨
traditional homogeneous liquid reactions. These preliminary 10 S. S. Soomro, F. L. Ansari, K. Chatziapostolou and K. Kohler,
ndings will open up further prospects for the hydro-
J. Catal., 2010, 273, 138–146.
carboxylation of acetylene to AA.
11 R. A. Sheldon, M. Wallau, I. W. C. E. Arends and
U. Schuchardt, Acc. Chem. Res., 1998, 31, 485–493.
´
12 I. Sadaba, M. L. Granados, A. Riisager and E. Taarning, Green
4. Conclusions
Chem., 2015, 17, 4133–4145.
In summary, a highly active NiO/AlOOH catalyst with AA space-
13 I. W. Davies, L. Matty, D. L. Hughes and P. J. Reider, J. Am.
Chem. Soc., 2001, 123, 10139–10140.
ꢀ1
time-yield of 412 gAA gcat. hꢀ1 was developed for the hydro-
carboxylation of acetylene to AA. During the reaction, large
amount of NiO dissolved from solid catalyst surface into the
solution with the induction of CuBr2 and CO. Detailed kinetic
14 J. A. Widegren, M. A. Bennett and R. G. Finke, J. Am. Chem.
Soc., 2003, 125, 10301–10310.
¨
¨
15 K. Kohler, S. Prockl and W. Kleist, Curr. Org. Chem., 2006, 10,
and controlled experiments conrmed
a heterogeneous–
1585–1601.
homogeneous–heterogeneous catalytic cycle of the nickel
species while the chelates formed between CO and leached
nickel act as the actual active species for the hydrocarboxylation
of acetylene. The recovery of leached nickel onto the solid
catalyst by the means of inert gas replacement can dramatically
improve the stability of NiO/AlOOH catalyst.
16 M. Lamblin, L. Nassar-Hardy, J. C. Hierso, E. Fouquet and
F. X. Felpin, Adv. Synth. Catal., 2010, 352, 33–79.
17 P. J. Ellis, I. J. S. Fairlamb, S. F. J. Hackett, K. Wilson and
A. F. Lee, Angew. Chem., Int. Ed., 2010, 49, 1820–1824.
18 Y. Zhai, D. Pierre, R. Si, W. Deng, P. Ferrin, A. U. Nilekar,
G. Peng, J. A. Herron, D. C. Bell, H. Saltsburg,
M. Mavrikakis and M. Flytzani-Stephanopoulos, Science,
2010, 329, 1633–1636.
Conflicts of interest
19 C. Z. Wang, L. P. Han, Q. F. Zhang, Y. K. Li, G. F. Zhao, Y. Liu
and Y. Lu, Green Chem., 2015, 17, 3762–3765.
There are no conicts to declare.
20 H. M. T Galvis, J. H. Bitter, C. B. Khare, M. Ruitenbeek,
A. I. Dugulan and K. P. de Jong, Science, 2012, 335, 835–838.
21 H. Xie, T. J. Lin, L. Shi and X. Meng, RSC Adv., 2016, 6, 97285–
97292.
Acknowledgements
We gratefully acknowledge the National Natural Science Foun-
dation of China (NSFC) (21776156 and 21707028), China Post-
doctoral Science Foundation (2017M610912) and Research
Fund of Zhengzhou University of Light Industry (2018BSJJ025).
¨
¨
22 S. S. Prockl, W. Kleist, M. A. Gruber and K. Kohler, Angew.
Chem., Int. Ed., 2004, 43, 1881–1882.
23 T. J. Lin, X. Meng and L. Shi, Ind. Eng. Chem. Res., 2013, 52,
14125–14132.
References
24 T. J. Lin, X. Meng and L. Shi, J. Mol. Catal. A: Chem., 2015,
396, 77–83.
25 F. De Angelis and A. Sgamellotti, Organomet, 2000, 19, 4104–
4116.
1 Nexant Incorporation, Multiclient Prospectus-Chemicals from
acetylene
- back to the future?, Nexant, 2007, http://
www.nexant.com/.
1638 | RSC Adv., 2020, 10, 1634–1638
This journal is © The Royal Society of Chemistry 2020