Interfacial Sites in Ag Supported Layered Double Oxide for Dehydrogenation Coupling of Ethanol to n-Butanol

Article abstract of DOI:10.1002/open.202000295

Upgrading of ethanol to n-butanol through dehydrogenation coupling has received increasing attention due to the wide application of n-butanol. But the enhancement of ethanol dehydrogenation and followed coupling to produce high selectivity to n-butanol is still highly desired. Our previous work has reported an acid-base-Ag synergistic catalysis, with Ag particles supported on Mg and Al-containing layered double oxides (Ag/MgAl-LDO). Here, Ag-LDO interfaces have been manipulated for dehydrogenation coupling of ethanol to n-butanol by tailoring the size of Ag particles and the interactions between Ag and LDO. It has been revealed that increasing the population of surface Ag sites at Ag-LDO interfaces promotes not only the dehydrogenation of ethanol to acetaldehyde but also the subsequent aldol condensation of generated acetaldehyde. A selectivity of up to 76 % to n-butanol with an ethanol conversion of 44 % has been achieved on Ag/LDO with abundant interfacial Ag sites, much superior to the state-of-the-art catalysts.

Full text of DOI:10.1002/open.202000295

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
1
2
3
4
5
6
7
8
9
Interfacial Sites in Ag Supported Layered Double Oxide for
Dehydrogenation Coupling of Ethanol to n-Butanol
Jian Zhang, Kai Shi, Yanru Zhu, Zhe An, Wanning Wang, Xiaodan Ma, Xin Shu,
Hongyan Song, Xu Xiang, and Jing He*[a]
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
Upgrading of ethanol to n-butanol through dehydrogenation
coupling has received increasing attention due to the wide
application of n-butanol. But the enhancement of ethanol
dehydrogenation and followed coupling to produce high
selectivity to n-butanol is still highly desired. Our previous work
has reported an acid-base-Ag synergistic catalysis, with Ag
particles supported on Mg and Al-containing layered double
oxides (Ag/MgAl-LDO). Here, Ag-LDO interfaces have been
manipulated for dehydrogenation coupling of ethanol to n-
butanol by tailoring the size of Ag particles and the interactions
between Ag and LDO. It has been revealed that increasing the
population of surface Ag sites at Ag-LDO interfaces promotes
not only the dehydrogenation of ethanol to acetaldehyde but
also the subsequent aldol condensation of generated
acetaldehyde. A selectivity of up to 76% to n-butanol with an
ethanol conversion of 44% has been achieved on Ag/LDO with
abundant interfacial Ag sites, much superior to the state-of-the-
art catalysts.
1. Introduction
catalysts[7a,e,10] have been widely developed in upgrading of
ethanol to n-butanol. Even though excellent performance (>
90% selectivity to n-butanol and >20% conversion of ethanol)
has been achieved in homogeneous systems in a batch reactor
with the addition of extra base (EtONa,[9a,b] nickel or copper
hydroxide complexes[9c]), heterogeneous catalyst, including
solid acids and/or bases (i.e. oxide or mixed oxides,[10a–e] alkali
metal-modified zeolites,[10f] and hydroxyapatite[10g–m]) and sup-
ported metals,[10n–s] for continuously upgrading of ethanol to n-
butanol has been attracting continuous attention due to the
potential industrial application. Incorporation of metals in the
catalytic system allows the reaction to be carried out at lower
temperature with higher ethanol conversion due to the
enhanced ethanol dehydrogenation on the metal sites. Cu-
CeO2/AC affords a selectivity of 40% towards n-butanol with
ethanol conversions of 44–46% at 523 K and 2 MPa N2.[10o]
Encapsulation of Pd into UiO-66 gives a selectivity of 49.9%
toward n-butanol with an ethanol conversion of 50.1%.[10p]
Ethanol dehydrogenation to acetaldehyde is commonly consid-
ered as the rate-determining step in the upgrading of ethanol
to n-butanol.[10n,o,q–s] In our previous work, the dehydrogenation
of ethanol to acetaldehyde has been proposed to be promoted
on the metal-support interfacial sites.[11] Despite this progress,
the metal-support interfaces in the dehydrogenation coupling
of ethanol to n-butanol desire more attention. The develop-
ment of catalyst with tunable interfaces is thus of great
importance to enhance the catalytic performance. We previ-
ously reported an acid-base-Ag synergistical catalyst with Ag
supported on Mg and Al-containing layered double oxides (Ag/
MgAl-LDO), derived from Ag loading Mg and Al-containing
layered double hydroxides (Ag+/MgAl-LDHs). A selectivity of up
to 77% toward n-butanol have been achieved with ethanol
Production of n-butanol has drawn arising attention due to its
wide application as a raw bulk chemical in the manufacture of
chemical products.[1] Also, n-butanol is one of promising
alternatives to gasoline as it has 86% energy density compared
to gasoline and is easier to store due to its water immiscible
nature.[2] Traditionally, n-butanol has been produced through
fossil-based oxo process (hydroformylation of propylene)[3] or
by the fermentation of sugars (acetone-butanol-ethanol
process).[1,4] The increased availability of ethanol from biomass[5]
drives the interest to upgrade ethanol into more valuable
chemicals.[6] Ethanol can undergo CÀ C formation via Guerbet
reaction, offering an economical and sustainable route for n-
butanol production. So far, it has been generally accepted that
the Guerbet reaction involves an aldol-condensation route,[7]
even though some researches support the direct condensation
mechanism.[8] The aldol-condensation route implies ethanol
dehydrogenation to acetaldehyde, aldol condensation of gen-
erated acetaldehyde to crotonaldehyde, and hydrogenation of
crotonaldehyde to 1-butanol through a hydrogen transfer.
In 1901, Guerbet first reported the dehydrogenation cou-
pling of ethanol to n-butanol over barium ethoxide.[7f] Inspired
by Guerbet’s work, both homogeneous[7d,e,9] and heterogeneous
[a] J. Zhang, K. Shi, Dr. Y. Zhu, Prof. Z. An, W. Wang, Dr. X. Ma, Dr. X. Shu,
Prof. Dr. H. Song, Prof. Dr. X. Xiang, Prof. Dr. J. He
State Key Laboratory of Chemical Resource Engineering & Beijing Advanced
Innovation Center for Soft Matter Science and Engineering
Beijing University of Chemical Technology
Box 98, 15 Beisanhuan Donglu
Beijing 100029 (China)
E-mail: jinghe@263.net.cn
°
© 2021 The Authors. Published by Wiley-VCH GmbH. This is an open access
article under the terms of the Creative Commons Attribution Non-Com-
mercial NoDerivs License, which permits use and distribution in any med-
ium, provided the original work is properly cited, the use is non-commercial
and no modifications or adaptations are made.
conversion of 23.2% at 350 C, 0.1 MPa and selectivity of 60%
°
toward n-butanol with ethanol conversion of 45% at 250 C,
2 MPa.[12]
ChemistryOpen 2021, 10, 1–10
1
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
Intrigued by our recent discoveries, Ag-LDO interfaces have
(MgAl-LDO) (JCPDS: 45-0946) and metallic Ag (JCPDS: 04-0783)
are clearly observed for the resulting Ag/Mg4Al-LDO-N-3h and
Ag/Mg4Al-LDO-H-x. The reflections characteristic of Ag particles
become obvious gradually with the thermal treatment time
increasing from 1 h to 5 h under H2 atmosphere (Figure 1B, b–
d). In the TEM images (Figure 1C), Ag particles are observed in a
maximum distribution at 7.4 nm for Ag/MgAl-LDO-N-3h (Fig-
ure 1C, a). But larger Ag particles are observed for Ag/MgAl-
LDO-H-x, the sample prepared by thermal treatment of Ag+/
Mg4Al-LDHs under H2 (Figure 1C, b–d). Increasing thermal
treatment time in H2 obviously results in Ag agglomeration,
with the maximum distribution shifting from 17.9 to 34.1 nm.
The Ag dispersion was determined by HOT as being 17.2%,
8.3%, 5.6%, and 4.3% (Table 1). Each Ag/MgAl-LDO shows a
BET surface area around 90 m2/g (Table 1, entry 1–4).
1
2
3
4
5
6
7
8
9
been manipulated for dehydrogenation coupling of ethanol to
n-butanol in this work. To the best of our knowledge, this is an
original report of interfacial catalysis for upgrading of ethanol
to n-butanol. A n-butanol yield of 39% and a selectivity of 65%
toward n-butanol have been achieved on Ag-MgAl-LDO with
abundant interfacial Ag sites, which is much superior to the
state of art catalysts.[10n–s]
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
2. Results and Discussion
Figure 1 shows the XRD patterns of Mg4Al-LDHs, Ag+/Mg4Al-
LDHs, and Ag/Mg4Al-LDO prepared in this work. For as-prepared
or Ag+ loaded Mg4Al-LDHs, the reflections characteristic of
hydrotalcite-like structure are clearly observed (Figure 1A, a and
b). No phase change occurs in the impregnation of as-prepared
Mg4Al-LDHs with AgNO3 aqueous solution. By thermal treat-
ment of Ag+/Mg4Al-LDHs under either N2 (Figure 1B, a) or H2
(Figure 1B, b–d) atmosphere, both of MgÀ Al mixed oxide
The surface basicity has been determined by CO2-TPD
technique (Figure 2A). On each Ag loaded Mg4Al-LDO, a broad
CO2 desorption is observed in the TPD profiles between 50 and
°
400 C, which can be deconvoluted into three contributions
identified[11,13] as the adsorption of CO2 on weak basic sites at
Figure 1. (A) XRD patterns of (a) Mg4.15Al-LDHs and (b) Ag+/Mg4Al-LDHs; (B) XRD patterns and (C) TEM images, size distribution, and HRTEM images of metallic
Ag nanoparticle of (a) Ag/Mg4Al-LDO-N-3h, (b) Ag/Mg4Al-LDO-H-1h, (c) Ag/Mg4Al-LDO-H-3h, and (d) Ag/Mg4Al-LDO-H-5h.
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
2
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
Table 1. Specific surface area and acid-base properties of Ag supported LDO.
1
2
3
Entry
Samples
SBET
/
DAg
%
/
Basic sites[a]/mmolgÀ 1
Basic density/
Acidic
sites[b]
Acidic
Acid/
Base
AgÀ OÀ Al[c]/
m2 gÀ 1
weak
medium
strong
total
μmolm2
/
density/
%
mmolgÀ 1
μmolm2
4
5
6
7
8
9
1
2
3
4
5
6
Ag/Mg4Al-LDO-N-3h
Ag/Mg4Al-LDO-H-1h
Ag/Mg4Al-LDO-H-3h
Ag/Mg4Al-LDO-H-5h
Ag/Mg4Al-LDO*-N-3h
Ag-Mg4Al-LDO-H-3h
90.2
88.3
87.7
89.8
92.4
89.0
17.2
8.3
5.6
4,3
16.5
61.4
0.16
0.15
0.14
0.17
0.16
0.15
0.07
0.07
0.07
0.07
0.08
0.06
0.21
0.22
0.22
0.21
0.22
0.23
0.44
0.44
0.43
0.45
0.46
0.44
4.88
4.98
4.90
5.01
4.98
4.94
0.25
0.26
0.26
0.27
0.26
0.31
2.77
2.94
2.96
3.01
2.81
3.48
0.57
0.59
0.60
0.60
0.57
0.71
29.5
19.7
11.6
8.7
10.2
39.8
[a] The concentration of weak, medium-strong, and strong basic sites are calculated according to the results of CO2-TPD and the deconvoluted TPD profile in
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 temperature region of 50–400 C. [b] The acidic sites are calculated according to the results of pyridine-FTIR. [c] The AgÀ OÀ Al sites are calculated
according to the results of XPS.
°
°
<170 C, medium-strong basic sites at 170~260 C, and strong
°
basic sites at >260 C. Quantitatively, the total amount and
density of base sites are summarized in Table 1. Similar amount
and density of basic sites are detected on the Ag/Mg4Al-LDO
prepared by thermal treatment of Ag+ loaded Mg4Al-LDHs
under either N2 or H2 (Table 1, entry 1–4). The surface acidity
has been determined by FT-IR spectra of pyridine adsorption
(Figure 2B). On the Ag/Mg4Al-LDO prepared by thermal treat-
ment of Ag+ loaded Mg4Al-LDHs under either N2 or H2
atmosphere, only Lewis acid sites[14] are observed. The total
amount of acid sites shows no marked change with thermal
treatment atmosphere or thermal treatment time (Table 1,
entry 1–4). All samples show similar ratio of acid to base sites
(Table 1, entry 1–4).
Then the Ag/Mg4Al-LDO, with varied Ag particle size while
similar acidic-basic properties, have been applied in the
dehydrogenation coupling of ethanol under ambient pressure
Figure 2. (A) CO2-TPD profiles and (B) FT-IR spectra of pyridine adsorption for
(a) Ag/Mg4Al-LDO-N-3h, (b) Ag/Mg4Al-LDO-H-1h, (c) Ag/Mg4Al-LDO-H-3h,
and (d) Ag/Mg4Al-LDO-H-5h.
°
at 350 C (Table 2 and Figure 3). An ethanol conversion of
32.6% is obtained on Ag/Mg4Al-LDO-N-3h with a selectivity of
61.3% to n-butanol (Table 2, entry 1). Acetaldehyde and acetate
Table 2. Catalytic results for dehydrogenation coupling of ethanol on LDO supported Ag particles.[a]
Entry Catalyst
Con./
%
STC[a]
Sel. in liquid product/mol%
Cin gas
products
Ethyl
ether
acetalde- ethyl
butanal n-
BuOH
i-
n-
others
/
hyde
acetate
hexanol hexanol
mol %
1
2
3
4
5
6
7
8
Ag/Mg4Al-LDO-N3h 32.6
(32.5)
50.8 (50.6)
90.1
9.6
(9.2)
10.7
14.0
(13.5)
14.2
4.1
(4.0)
10.7
1.5
(1.4)
2.6
61.3
(62.1)
54.5
2.1
(2.0)
1.6
3.4
(3.5)
2.1
4.0
(4.3)
3.6
13.8 (14.2)
Ag/Mg4Al-LDO-H-
1h
Ag/Mg4Al-LDO-H-
3h
Ag/Mg4Al-LDO-H-
5h
Ag/Mg4Al-LDO*-N-
3h
27.9
14.5
25.7
(25.5)
17.9
123.0
(122.1)
111.6
11.2
(10.8)
11.5
12.9
(14.3)
15.0
12.1
(12.5)
16.8
2.1
(2.5)
2.8
53.6
(52.5)
47.5
1.7
(1.8)
1.4
2.9
(2.4)
1.7
3.5
(3.2)
3.3
15.8 (16.3)
18.8
21.2
34.4
10.9
14.9
16.7
0.7
52.7
0.8
1.0
2.3
14.3
Ag-Mg4Al-LDO-H-
3h
43.5
(44.1)
64.3
(63.9)
63.2
(62.8)
19.0 (19.2)
11.3
(11.8)
11.3
(11.0)
9.2
1.5
(1.2)
2.5
(2.3)
2.2
(1.8)
1.3
(1.2)
2.9
(2.8)
1.7
(1.8)
0.3
(0.4)
0.3
(0.2)
0.5
(0.4)
75.6
(76.2)
63.4
(63.8)
65.7
(65.6)
2.0
(1.8)
2.5 (2.8) 13.9
6.8
(6.2)
1.2
(1.2)
3.2
(3.1)
2.7
(2.9)
6.4 (5.8)
5.7 (6.2)
6.7 (7.2)
Ag-Mg4Al-LDO-H-
28.1
(27.9)
27.6 (27.4)
3h[c]
(14.0)
14.8
(14.5)
Ag-Mg4Al-LDO-H-
3h[d]
3.2
(3.1)
(9.9)
À 1
°
[a] Conversion and selectivity were obtained at initial point; reaction conditions: 500 mg of catalyst, 350 C, 60 mLmin of N2 (0.1 MPa),
LHSV=6 mL(hgcat)À 1. [b] STC for ethanol conversion was calculated by the mole of ethanol converted on per mole of surface Ag per minute. [c] Conversion
°
and selectivity were obtained at initial point; reaction conditions: 250 C, 2 MPa. [d] Conversion and selectivity were obtained at the steady-state; reaction
conditions: 250 C, 2 MPa. Other products include butyl acetate, ethyl butyrate, 2-ethyl-butanal, hexanal, ethyl 2-ethyl butyrate, butyl butyrate, ethyl caproate,
etc. The data in parentheses are the reproduced experimental data.
°
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
3
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
1
2
3
4
5
6
7
8
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
Figure 3. Stability of (a) Ag/Mg4Al-LDO-N-3h, (b) Ag/Mg4Al-LDO-H-1h, (c) Ag/
Mg4Al-LDO-H-3h, and (d) Ag/Mg4Al-LDO-H-5h. The sphere in dark grey,
square in black, star in red, up triangle in blue, and diamond in olive
represent for ethanol conversion, selectivity to acetaldehyde, diethy ether,
ethyl acetate, and n-butanol, respectively.
Figure 4. FT-IR spectra of ethanol adsorption on (A) Ag/Mg4Al-LDO-N-3h, (B)
Ag/Mg4Al-LDO-H-1h, (C) Ag/Mg4Al-LDO-H-3h, and (D) Ag/Mg4Al-LDO-H-5h at
°
°
°
°
°
°
°
50 C followed by desorption at 100 C, 150 C, 200 C, 250 C, 300 C, 350 C,
°
and 400 C.
have also been produced in a selectivity of 14.0% and 4.1%
(Table 2, entry 1). But an ethanol conversion of 27.9% with a
selectivity of 54.5% to n-butanol and a selectivity of 10.7% to
acetate is obtained on Ag/Mg4Al-LDO-H-1h (Table 2, entry 2).
Further increasing the Ag particle size disfavors not only the
conversion of ethanol but also the formation of n-butanol while
promotes the selectivity to ethyl acetate (Table 2, entry 3–4).
But the site time conversion (STC), determined by ethanol
conversion on per surficial Ag atom, first increases with
increasing Ag particle size from 7.4 nm to 22.9 nm and then
drops slightly with increasing Ag particle size further to 34.1 nm
(Table 2, entry 1–4). No obvious changes are observed in the
selectivity to ethyl ether with the increase in Ag particle size
(Table 2, entry 1–4). 14%–19% of methane and CO2 are
detected in the gaseous products (Table 2, entry 1–4). In our
previous work, the acid-base properties showed clearly influ-
ence on the selectivity to n-butanol.[12] But the great difference
in ethanol conversion and selectivity to n-butanol is supposed
to result from the difference in Ag particle size because the
acid-base properties of the catalysts prepared in this work are
similar. The catalytic results clearly demonstrates that smaller
Ag particles favor the formation of n-butanol. The conversion of
ethanol and the selectivity to n-butanol on each catalyst exhibit
stretching of adsorbed ethoxide at 1099–1077 cmÀ 1 blue shifts
to around 1119–1124 cmÀ 1 since 100 C in each case, and
°
°
eventually vanishes since 250 C for Ag/Mg4Al-LDO-N-3h while
°
300 C for Ag/Mg4Al-LDO-H-1h, Ag/Mg4Al-LDO-H-3h, and Ag/
Mg4Al-LDO-H-5h. The weak band for η1-adsorbed acetaldehyde
slightly increases in intensity with increasing desorption tem-
°
perature in each case and becomes dominant since 150 C for
°
Ag/Mg4Al-LDO-N-3h and 300 C for Ag/Mg4Al-LDO-H-1h, indi-
cating that smaller Ag particles promote the dehydrogenation
of ethanol to acetaldehyde, accounting for the higher con-
version with decreasing Ag particle size (Table 2, entry 1–4). The
bands at 1592–1559 cmÀ 1 and 1416–1443 cmÀ 1 assigned to
acetate,[15] which is formed via coupling of ethanol and
acetaldehyde[16] or Tishchenko-type disproportionation of two
molecules of acetaldehyde,[17] are hardly observed at 50 C on
°
Ag/Mg4Al-LDO-N-3h (Figure 4A) and Ag/Mg4Al-LDO-H-1h (Fig-
ure 4B) while clearly observed on Ag/Mg4Al-LDO-H-3h (Fig-
ure 4C) and Ag/Mg4Al-LDO-H-3h (Figure 4D), demonstrating the
strong ability for acetate formation on larger Ag particles. The
band assigned to acetate at 1559 cmÀ 1 is hardly observed even
at increased desorption temperature for Ag/Mg4Al-LDO-N-3h
°
(Figure 4A), while emerges since 250 C for Ag/Mg4Al-LDO-H-1h
°
no visible change in 12.5 h reaction at 350 C (Figure 3).
(Figure 4B). For Ag/Mg4Al-LDO-H-3h (Figure 4C) and Ag/Mg4Al-
To reveal the role of Ag particle size on dehydrogenation
coupling of ethanol, FT-IR spectra of ethanol adsorption/
desorption were recorded (Figure 4). In addition to the band
assigned[12] to δO-H of un-dissociated ethanol at 1250 cmÀ 1,
2987–2868 cmÀ 1 to CÀ H stretching modes, and 1393–1382 cmÀ 1
to δ modes of À CH3, the bands at 1099–1054 cmÀ 1 assigned to
CÀ O stretching in adsorbed ethoxide and 1617–1604 cmÀ 1 to
η1-adsorbed acetaldehyde have been observed for ethanol
LDO-H-5h (Figure 4D), the bands for acetate are observed at
1559 and 1381 cmÀ 1 since 50 C and become dominant since
°
°
250 C. With increasing Ag particle size, the bands to acetate
not only are observed at lower temperature, but also become
more visible and even dominant in the spectra (Figure 4A–D),
indicating that larger Ag particles favors the formation of
acetate, accounting for the increase in the selectivity to ethyl
acetate. The band at 1456–1451 cmÀ 1 assigned to δ modes of
[12]
°
adsorption at 50 C in each case, indicating that the activation
À CH2 is hardly observed on Ag/Mg4Al-LDO-N-3h (Figure 4A)
of ethanol on Ag/Mg4Al-LDO occurs through the adsorption of
OÀ H bond, affording ethoxide, followed by dehydrogenation to
acetaldehyde. Increasing desorption temperature, the absorp-
and Ag/Mg4Al-LDO-H-1h (Figure 4B), while clearly observed on
Ag/Mg4Al-LDO-H-3h (Figure 4C) and Ag/Mg4Al-LDO-H-5h (Fig-
°
ure 4D) upon adsorption at 50 C and following desorption,
°
tion at 50 C clearly decreases in intensity. The band for CÀ O
consistent with the acetate formation on larger Ag particles.
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
4
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
In our previous work, the introduction of Ag particles
of Ag/Mg4Al-LDO with varied Ag particle size was investigated
by XPS technique (Figure 6). In the Ag 3d5/2 XPS spectra
(Figure 6A), a binding energy at 368.58–368.35 eV assigned[19] to
Ag0 species is clearly observed in each case. Another binding
energy is clearly observed at 371.11 eV for Ag/Mg4Al-LDO-N-3h
(Figure 6A, a). With an increase in Ag particle size, the binding
energy at 371.11 eV shifts to lower value and becomes less
obvious (Figure 6A, b–d). So the binding energy higher than
Ag0, observed in this work, probably originate from the Ag sites
interacting with Mg4Al-LDO surface. In the Al 2p XPS spectra
(Figure 6B), in addition to the binding energy at 74.35–73.95 eV
assigned[20] to MgÀ OÀ Al, another binding energy at 75.43–
74.91 eV is observed in each case. The peak at 75.43–74.91 eV
becomes less obvious with increasing size of Ag particle. In a
previous report on Ag doped alumina, an increase in the
binding energy of Al 2p has been observed due to the
formation of AgÀ OÀ Al chemical bonds.[21] The binding energy
at 75.43–74.91 eV is thus proposed to originate from the Al sites
interacting with Ag particles. In the Mg 1s XPS spectra
(Figure 6C), no obvious change in the binding energy
assigned[22] to MgÀ O-Mg or MgÀ OÀ Al is observed (Figure 6C)
with increasing Ag particle size, further confirming our proposal
that the negatively charged Ag sites originates from Ag
particles interacting with AlÀ O sites rather than MgÀ O sites. The
binding energy of positively charged Ag, such as Ag2O, is lower
than that of Ag0.[19a,c] The binding energy for Ag-O-Mg is also
lower than that for Ag0.[19d] In a previous report on alumina
supported Ag,[19b] the binding energy of Ag at interfacial
AgÀ OÀ Al sites has been verified to be higher than that for Ag0,
which supports our conclusion. In the O 1s spectra (Figure 6D),
three deconvoluted peaks, assigned to absorbed O,[19d] MÀ O
(M=Mg or Al),[19d] and Ag-O,[19c,d] are observed. With the
increase of Ag particle size, the deconvoluted area of Ag-O sites
declines (Figure 6D), consistent with the decrease in the
population of AgÀ OÀ Al sites located at Ag-LDO interface. The
fraction of AgÀ OÀ Al interfacial sites, estimated by the deconvo-
luted area, decreases from 29.5 to 8.7% with Ag particle size
increasing from 7.4 to 34.1 nm (Table 1, entry 1–4).
1
2
3
4
5
6
7
8
9
promoted the aldol condensation of acetaldehyde.[12] The FT-IR
°
spectra of acetaldehyde adsorption at 10 C on Ag particles in
7.4 nm.
(Ag/Mg4Al-LDO-N-3h) and 34.1 nm (Ag/Mg4Al-LDO-H-5h)
were thus recorded (Figure 5). In addition to the bands at
1717 cmÀ 1 assigned[12,18] to ν(C=O), 1463 and 1371 cmÀ 1 as-
signed to δas(CH3) and δs(CH3), and 1583 cmÀ 1 assigned to
νas(OCO) of acetate, the bands at 1337 cmÀ 1 assigned[12,18] to the
δas(CH) of crotonaldehyde and 1272 cmÀ 1 to the δ(C-OH) in
adsorbed 3-hydroxybutanal are also observed in each case. The
intensity of δs(CH3) at 1371 cmÀ 1 is clearly less dominant while
the intensity of δ(CÀ OH) in adsorbed 3-hydroxybutanal at
1272 cmÀ 1 is more dominant on 7.4 nm Ag (Figure 5, a) than on
34.1 nm Ag (Figure 5, b). That indicates small Ag particles favor
the activation of CÀ H of CH3 in acetaldehyde to promote the
aldol condensation, well accounting for the higher selectivity to
n-butanol on smaller Ag particles
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
To make clear the nature of the size effects of Ag particle on
the dehydrogenation coupling of ethanol, the electronic state
°
Figure 5. FT-IR spectra of acetaldehyde adsorption at 10 C on (a) Ag/Mg4Al-
LDO7N-3h and (b) Ag/Mg4Al-LDO-H-5h.
Figure 6. XPS spectra of (A) Ag 3d, (B) Al 2p, (C) Mg 1s, and (D) O 1s for (a) Ag/Mg4Al-LDO-N-3h, (b) Ag/Mg4Al-LDO-H-1h, (c) Ag/Mg4Al-LDO-H-3h, and (d) Ag/
Mg4Al-LDO-H-5h.
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
5
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
To confirm the key role of interfacial AgÀ OÀ Al sites in the
are much lower than that on Ag/Mg4Al-LDO-N-3h, even though
Ag/Mg4Al-LDO*-N-3h and Ag/Mg4Al-LDO-N-3h possess similar
Ag particle size and acidity-basicity properties. Also, the STC on
Ag/Mg4Al-LDO*-N-3h is much lower than that on Ag/Mg4Al-
LDO-N-3h, indicating that the interfacial AgÀ OÀ Al sites also
promote the ethanol conversion. Ag/Mg4Al-LDO*-N-3h affords
similar butanol selectivity to Ag/MgAl-LDO-H-3h due to their
similar concentration of AgÀ OÀ Al sites, clearly confirming the
crucial role of AgÀ OÀ Al sites in dehydrogenation coupling of
ethanol.
1
2
3
4
5
6
7
8
9
dehydrogenation of ethanol to n-butanol, Ag/Mg4Al-LDO*-N-3h
has been prepared for control (Figure 7A). The MgÀ O or AlÀ O in
face centered cubic structure of MgO on the LDO surface, unlike
the MgÀ OH and AlÀ OH in octahedral structure of Mg(OH)2 on
the LDHs surface, provides different chemical environment for
Ag+, which might result in the difference in the formation of
AgÀ OÀ Al sites during topological transformation from Ag+/
LDHs to Ag/LDO. Mg4Al-LDO was first prepared (Figure 7A, a) by
°
thermal treatment of Mg4Al-LDHs under N2 at 400 C for 3 h 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
followed by impregnation of Ag+ (Figure 7A, b). The hydro-
talcite-like structure was regenerated during the impregnation
(Figure 7A, b). Then the regenerated Ag+/Mg4Al-LDHs was re-
Further, Ag-Mg4Al-LDO-H-3h was prepared by thermal treat-
3À
ment of Ag(S2O3)2 intercalated Mg4Al-LDHs (Figure 8A, a)
°
under H2 for 3h at 400 C (Figure 8A, b). HAADF-STEM images
°
calcined under N2 at 400 C for 3 h, producing the Ag/Mg4Al-
show that the cubic Ag particles with maximum distribution at
1.8 nm are located in the interlayer region (Figure 8B-E). Single
Ag atoms are also observed in Ag-Mg4Al-LDO-H-3h (Figure 8E).
Ag-Mg4Al-LDO-H-3h (Table 1, entry 6) displays similar basic
density to all Ag/Mg4Al-LDO, while slightly higher acidic density
than Ag/Mg4Al-LDO (Table 1, entry 1–5). From the XPS spectrum
of Ag3d (Figure 8F), the fraction of AgÀ OÀ Al sites on Ag-Mg4Al-
LDO-H-3h has been estimated as being 39.8% (Table 1, entry 6).
Not surprisingly, a selectivity of 75.6% to n-butanol with an
ethanol conversion of 43.5% has been achieved on Ag-Mg4Al-
LDO-H-3h (Table 2, entry 6), which is higher than all the
selectivity reported till now at an ethanol conversion of >40%.
But only 19.0 minÀ 1 of STC is obtained on Ag-Mg4Al-LDO-H-3h
(Table 2, entry 6). For better comparison, the dehydrogenation
LDO*-N-3h (Figure 7A, c) with a Ag particle size of 7.3 nm at
maximum distribution (Figure 7B). The size distribution of Ag
particle size (Figure 7B) and the acid-base properties (Table 1,
entry 5) on Ag/Mg4Al-LDO*-N-3h are observed to be similar to
those on Ag/Mg4Al-LDO-N-3h. In the XPS spectrum of Ag3d
(Figure 7C), interfacial Ag species is observed. The concentration
of AgÀ OÀ Al sites is estimated as being 10.2% on Ag/Mg4Al-
LDO*-N-3h (Table 1, entry 5), which is much lower than that on
Ag/MgAl-LDO-N-3h and similar to that on Ag/MgAl-LDO-H-3h.
As a result, in the dehydrogenation coupling to butanol, Ag/
Mg4Al-LDO*-N-3h affords an ethanol conversion of 21.2%, with
a
selectivity of 52.7% to n-butanol (Table 2, entry 5).
Acetaldehyde has also been produced in a selectivity of 14.9%
and ethyl acetate in 16.7% (Table 2, entry 5). The conversion of
ethanol and the selectivity to butanol on Ag/Mg4Al-LDO*-N-3h
°
coupling of ethanol has been carried out at 250 C and 2 MPa,
an ethanol conversion of 55–53% with a selectivity of 63–66%
to n-butanol has been achieved (Table 2, entry 7–8), which is
superior to the performance of the state of art catalysts.
Interestingly, a selectivity of about 15% to n-hexanol has been
°
achieved at 250 C and 2 MPa (Table 2, entry 7–8).
Then the catalytic performance was plotted as a function of
the concentration of AgÀ OÀ Al interfacial sites (Figure 9).
Increasing the population of AgÀ OÀ Al interfacial sites promotes
the formation of n-butanol while suppresses the formation of
acetate. Almost no changes in the selectivity to ethyl ether
Figure 7. (A) XRD patterns of (a) Mg4Al-LDO, (b) Ag+/Mg4Al-LDO, and (c) Ag/
Mg4Al-LDO*-N-3h. (B) TEM image and (C) XPS spectrum of Ag 3d for Ag/
Mg4Al-LDO*-N-3h. Insertion in (B) is the size distribution of Ag particles.
Figure 8. (A) XRD patterns of (a) Mg4Al-Ag(S2O3)2-LDHs and (b) Ag-Mg4Al-
LDO-H-3h. (B–C) STEM image in the view of cross section, (D–E) HAADF-
STEM images and (F) XPS spectrum of Ag 3d for Ag-Mg4Al-LDO-H-3h.
Insertion in (D) is the shape simulation for Ag particles.
Figure 9. The selectivity to n-butanol, ethyl ether, acetaldehyde, or ethyl
acetate and the conversion of ethanol as a function of AgÀ OÀ Al
concentration.
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
6
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
have been observed with increasing concentration of AgÀ OÀ Al
interfacial sites (Figure 9). Due to the slightly higher acidic sites,
higher selectivity to n-butanol (75.6%) and lower selectivity to
acetaldehyde (1.5%) than expected have been achieved on Ag-
Mg4Al-LDO-H-3h (Figure 9). These results well verify that the Experimental Section
interfacial AgÀ OÀ Al sites play a key role in promoting the
mechanism for deactivation and development of catalyst with
long-term stability need further investigation.
1
2
3
4
5
6
7
8
9
dehydrogenation coupling of ethanol to n-butanol. But the
correlation between STC and AgÀ OÀ Al interfacial sites is still
ambiguous, even though the results on Ag/Mg4Al-LDO*-N-and
Ag/Mg4Al-LDO-N-3h showed that the AgÀ OÀ Al interfacial sites
promoted the ethanol conversion. This result indicates that
besides the AgÀ OÀ Al interfacial sites, some other factors on the
Ag particle that might affect the ethanol conversion should be
taken into consideration.
The catalytic stability in 50 h has been performed with Ag-
Mg4Al-LDO-H-3h. Satisfactory stability has been observed in
18 h. A slow decrease in the conversion of ethanol was
observed since 18 h and a rapid decrease since 38 h. But the
selectivity to n-butanol was well retained in 38 h (Figure 10).
Carbon deposition or aggregation of Ag particles might be the
reason for the deactivation, which needs further investigation.
Preparation
Mg4Al-LDHs with Mg/Al molar ratio of 4.15 was prepared as
reported in our previous work.[12] Typically, a solution of Mg-
(NO3)2 ·6H2O (0.056 mol) and Al(NO3)3 ·9H2O (0.014 mol) in 200 mL
of deionized water and a solution of NaOH (0.14 mol) and Na2CO3
(0.007 mol) in 200 mL of deionized water were simultaneously
added drop-wise to a four-necked flask containing 200 mL of
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
°
deionized water under constant pH (10.0) at 30 C. The resulting
°
mixture was aged at 85 C for 10 h. Then the solid was filtered,
washed thoroughly with deionized water till the filtrate is neutral,
°
and dried at 60 C. Then the Mg4Al-LDHs was thermally treated of at
400 C for 3h under N2 atmosphere in a rate of 5 CminÀ 1, producing
Mg4Al-LDO.
°
°
1 g of Mg4Al-LDHs was impregnated in 1 mL of AgNO3 (4.2 mmol,
6.6 mg) aqueous solution, producing Ag+/Mg4Al-LDHs with Ag
loading of 0.42 wt%. Ag/Mg4Al-LDO-N-3h was prepared by thermal
+
°
treatment of Ag /Mg4Al-LDHs at 400 C for 3h under N2 atmos-
phere. Unless otherwise indicated, the temperature programmed
from ambient to reduction temperature in a rate of 5 C minÀ 1. Ag
°
3. Conclusions
loading was determined by inductive couple plasma-optical
emission spectroscopy (ICP-OES) as being 0.65 wt%. Ag/Mg4Al-LDO-
H-x was prepared by thermal treatment of Ag+/Mg4Al-LDHs at
In summary, the Ag-LDO interfacial sites have been tuned by
tailoring the size of Ag particles or changing the preparation
method of Ag supported MgAl-LDO. Increasing the interfacial
sites clearly enhances the ethanol conversion and aldol
condensation while suppresses the formation of ethyl acetate,
thus promoting the selectivity to n-butanol. A selectivity of up
to 76% to n-butanol with an ethanol conversion of 44% at
°
400 C for varied time under H2 atmosphere, where x represents
treatment duration. Ag loading was determined by ICP-OES
technique as being in the range of 0.68~0.71 wt%.
Ag+/Mg4Al-LDO with a Ag loading of 0.53 wt% was prepared by
impregnation of 1 g Mg4Al-LDO in 1 mL of AgNO3 (5.3 mmol,
8.4 mg) aqueous solution. Ag/Mg4Al-LDO*-N-3h with a Ag loading
of 0.75 wt% was prepared by thermal treatment of 0.53 wt% Ag+/
°
350 C has been achieved on Ag particles with abundant
interfacial Ag-LDO sites. More interestingly, a selectivity of 15%
°
Mg4Al-LDO at 400 C for 3 h under N2 atmosphere.
Mg4AlÀ Ag(S2O3)2-LDHs was prepared by the reconstruction of
°
to n-hexanol has been achieved at 250 C under 2 MPa.
Mg4Al-LDO in
a Na3Ag(S2O3)2 aqueous solution. Na3Ag(S2O3)2
According to the findings of this work, development of single
atom catalyst might be of great importance to enhance the
upgrading of ethanol to higher alcohols, such as C6-alcohol. The
(0.15 mmol/LAg) was first prepared by mixing Na2S2O3 and AgNO3
solutions.[23] Typically, 150 mg of Na2S2O3 ·5H2O was dissolved in
200 mL of deCO2 and deionized water (Solution A) and 10 mg of
AgNO3 in 200 mL of deCO2 and deionized water (Solution B). Then
Solution B was added drop-by-drop into Solution A with vigorous
stirring, forming Na3Ag(S2O3)2 solution. 1 g of Mg4Al-LDO was
dispersed in 400 mL of the above Na3Ag(S2O3)2 solution and aged
for 24 h at room temperature with slow stirring. All the above
procedures were carried out under N2 atmosphere. The solid was
filtered, washed with deionized water and anhydrous ethanol for
°
several times, and finally dried at 60 C in a vacuum oven, affording
Mg4Al-Ag(S2O3)2-LDHs. Ag-Mg4Al-LDO-H-3h was prepared by ther-
°
mal treatment of Mg4Al-Ag(S2O3)2-LDHs at 400 C for 3h under H2
atmosphere. The Ag loading was determined by ICP-OES method
as being 0.73 wt%.
Characterization
Powder X-ray diffraction (XRD) patterns were recorded on Shimad-
zu XRD-6000 diffractometer operating with Cu Kα radiation (λ=
0.1541) in the range of 3 –80 at a scan rate of 10 minÀ 1. The
quantitation of Ag, Mg, and Al was carried out by ICP-OES on a
Shimadzu ICPS-7500. The low temperature N2 adsorption was
performed on a Micromeritics ASAP 2460 and specific surface area
°
°
°
Figure 10. Long-term stability of Ag-Mg4Al-LDO-H-3h in dehydrogenation
°
coupling of ethanol at 250 C, 2 MPa.
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
7
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
was calculated using Brunauer-Emmett-Teller (BET) method. TEM
and HRTEM images were taken on a Tecnai G2 F30 operating at
300 kV. The high-angle annular dark field (HAADF)-scanning trans-
mission electron microscopic (STEM) images were taken on a JEM-
ARM 200F electron microscope capable of subangstrom resolution.
The Ag dispersion was determined by hydrogen-oxygen titration
(HOT) on a Micrometric ChemiSorb 2920 chemisorption system
showed no change. The spectrum was recorded. For ethanol
adsorption-desorption, the spectrum for background was recorded
1
2
3
4
5
6
7
8
9
°
°
°
°
°
°
°
°
at 400 C, 350 C, 300 C, 250 C, 200 C, 150 C, 100 C, and 50 C in
°
the cooling from 400 to 50 C after the pre-treatment. Subse-
quently, the ethanol was bubbled into the system by Ar
(20 mLminÀ 1) at 50 C for 40 min, and then purged with Ar
°
(20 mLminÀ 1) until the spectra showed no change. The spectrum
°
with a thermal conductivity detector (TCD). 100 mg of Ag loaded
for ethanol adsorption at 50 C was recorded. Then the temperature
was increased to 100 C under Ar with a heating rate of 10 Cmin
and maintained at 100 C for 10 min. The spectrum for ethanol
À 1
À 1
°
°
°
sample was pre-treated at 350 C for 1 h under 20 mLmin of He
°
°
and then cooled to 180 C in the flow of He. Afterwards, O2 pulses
were introduced into the system until saturation and then the
absorbed oxygen was titrated by introducing pulses of H2 at 180 C.
°
desorption at 100 C was recorded. The spectrum for ethanol
°
°
°
°
°
°
°
desorption at 150 C, 200 C, 250 C, 300 C, 350 C, or 400 C was
recorded in the same procedure.
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 Ag dispersion was calculated as follows:
DAg ¼ 2 � amount of consumed H2=Ntotal ðby ICPÞ � 100 %
(1)
Catalytic Tests
The X-ray photoelectron spectra (XPS) were recorded on an AXIS
SUPRA X-ray photoelectron spectrometer equipped with mono-
chromated Al-K X-ray source (1486.6 eV) at a pass energy of 40 eV.
C 1s peak at 284.6 eV was used as a calibration peak. Since the
Auger peak of Mg overlaps with the peak of Ag 3d3/2, the peak for
Ag 3d was obtained by subtracting the Auger peak of Mg from the
original data in this work. The population of AgÀ OÀ Al sites was
calculated as follows:
The dehydrogenation coupling of ethanol was carried out in a
fixed-bed reactor as the procedures described in our previous work
with a stainless steel tubular reactor in an external diameter of
10 mm and a length of 38 cm.[12] Typically, 0.5 g of catalyst (20–
40 mesh) was loaded into the constant temperature zone of the
reactor. Prior to the reaction, the catalyst was pretreated in situ
with N2 (40 mLminÀ 1) at 400 C for 1 h and then cooled to 350 C.
The N2 gas flow was set to 60 mLminÀ 1. The chromatographically
°
°
°
pure ethanol was pumped into a vaporizing chamber (150 C) at a
flow rate of 50 μLminÀ 1, where ethanol vapor and N2 were mixed,
0
AgÀ OÀ Al % ¼ AAgÀ OÀ Al=ðAAgÀ OÀ Al þ AAg Þ � 100 %
(2)
and then into the reaction system. The pipeline behind the reactor
was heated to keep at 200 C. The products were analyzed
quantitatively by GC (Shimadzu, 2014C) with a flame ionization
detector (FID) and a GSBP-INOWAX column (30 m, 0.25 mm inner
diameter). The ethanol conversion and product selectivity were
calculated as follows:
°
where Ai was the deconvoluted area for AgÀ OÀ Al or Ag0.
CO2-temperature programmed desorption (TPD) experiment was
performed on a Micrometric ChemiSorb 2920. Typically, 100 mg of
sample was loaded in a U-type quartz tube reactor and pre-treated
at 400 C for 1 h under He mixture (40 mLminÀ 1). Afterward, the
°
sample was cooled to 50 C in the flow of He (40 mLminÀ 1) and
°
Con:% ¼ ðFinÀ FunreactedÞ=Fin � 100 %
(5)
then CO2 (20 mLminÀ 1) was fed into the reactor until saturation. A
flow of He (40 mLminÀ 1) was subsequently fed for 0.5 h to desorb
weakly physical adsorption. CO2-TPD was carried out under He
Sel:% ¼ Cin specific product=Cin all liquid products � 100 %
(6)
(40 mLminÀ 1) from 50 to 400 C with a temperature-programmed
rate of 10 Cmin
°
wherein, Fin and Funreacted are the moles of initial ethanol and
unreacted ethanol; Cin
moles of carbon in all liquid and gaseous products; Cin
and Cin all liquid products were the moles of carbon in the specific product
and all liquid products. Each catalyst exhibited good stability in a
12.5 h test, showing traceable carbon deposition rate. Therefore,
the carbon balance is close to 100% and the Cin
calculated as follows:
À 1
°
.
were calculated based on the
ethanol reacted
The Fourier-transform infrared spectra (FT-IR) of pyridine,
acetaldehyde, or ethanol adsorption with self-support sample wafer
were recorded on an iS50 FT-IR (NICOLET) spectrometer equipped a
mercury-cadmium-telluride (MCT) detector, with a resolution of
4 cmÀ 1 and 64 scans. The to-be-measured sample was firstly loaded
specific product
% is
gas products
into in-situ IR cell, then pre-treated under Ar (40 mLminÀ 1) at 400 C
°
for 1 h, and cooled in Ar. For pyridine adsorption, the system was
first evacuated and the spectrum for background was recorded at
Cin gas products % ¼ ð1-Cin all liquid products=Cin ethanol reactedÞ � 100 %
(7).
°
50 C. The sample was then exposed to pyridine vapor until
adsorption saturation, and then the adsorbed pyridine was
Mass transfer limitations on Ag/Mg4Al-LDO-N-3h at 623 K, 0.1 MPa
with ethanol conversion of 32% were calculated using the Mears
and Weisz-Prater analyses.[24] Mears Criterion for external diffusion
°
desorbed at 150 C until the spectra showed no change. The
spectrum was recorded. The Lewis and Brønsted acid sites was
quantitatively caculated as following equation:[14]
and Weisz-Prater Criterion for internal diffusion were 1.1×10À 7
<
0.15 and 0.1<1, respectively, suggesting the absence of diffusion
limitation in this work.
CL ¼ 1:41 � r2=w � A1440
(3)
CB ¼ 1:88 � r2=w � A1540
(4)
Acknowledgements
where CL and CB are concentrations of Lewis acid sites and Brønsted
acid sites (μmolgÀ 1), A1440 and A1540 are integrated areas of the
bands at 1440 and 1540 cmÀ 1, r is the wafer radius (cm), and w is
the wafer weight (g). For acetaldehyde adsorption, the system was
first evacuated and the spectrum for background was recorded at
This work is sponsored by the National Key R&D Program of China
(2017YFA0206804), NSFC (21521005), and the Fundamental
Research Funds for Chinese Central Universities (XK1802-6).
°
10 C. The sample was then exposed to acetaldehyde vapor until
adsorption saturation, and then purged with Ar until the spectra
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
8
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/open.202000295
ChemistryOpen
2016, 6, 939–948; k) T. Moteki, D. W. Flaherty, ACS Catal. 2016, 6, 4170–
Conflict of Interest
1
2
3
4
5
6
7
8
9
4183; l) S. Ogo, A. Onda, Y. Iwasa, K. Hara, A. Fukuoka, K. Yanagisawa, J.
Catal. 2012, 296, 24–30; m) M. B. Osman, J. M. Krafft, C. Thomas, T.
Yoshioka, J. Kubo, G. Costentin, ChemCatChem 2019, 11, 1765–1778;
n) J. Pang, M. Zheng, L. He, L. Li, X. Pan, A. Wang, X. Wang, T. Zhang, J.
Catal. 2016, 344, 184–193; o) D. Jiang, X. Wu, J. Mao, J. Ni, X. Li, Chem.
Commun. 2016, 52, 13749–13752; p) D. Jiang, G. Fang, Y. Tong, X. Wu, Y.
Wang, D. Hong, W. Leng, Z. Liang, P. Tu, L. Liu, K. Xu, J. Ni, X. Li, ACS
Catal. 2018, 8, 11973–11978; q) X. Wu, G. Fang, Z. Liang, W. Leng, K. Xu,
D. Jiang, J. Ni, X. Li, Catal. Commun. 2017, 100, 15–18; r) P. A. Kots, A. V.
Zabilska, Y. V. Grigor’ev, I. I. Ivanova, Petrol. Chem. 2019, 59, 925–934;
s) C. Lopez-Olmos, A. Guerrero-Ruiz, I. Rodríguez-Ramos, Catal. Today
2019, https://doi.org/10.1016/j.cattod.2019.1005.1058.
The authors declare no conflict of interest.
Keywords: Ag particle size
dehydrogenation coupling · ethanol · interfacial sites
·
Ag supported LDO
·
[1] B. Ndaba, I. Chiyanzu, S. Marx, Biotechnol. Rep. 2015, 8, 1–9.
[2] a) W. R. d. S. Trindade, R. G. d. Santos, Renewable Sustainable Energy Rev.
2017, 69, 642–651; b) C. Jin, M. Yao, H. Liu, C.-f. F. Lee, J. Ji, Renewable
Sustainable Energy Rev. 2011, 15, 4080–4106.
[3] U. C. Corp, GB, GB815566A, 1957.
[4] a) W. Charles, GB, GB191504845A, 1915; b) N. P. Nguyen, C. Raynaud, I.
Meynial-Salles, P. Soucaille, Nat. Commun. 2018, 9, 3682.
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
[11] a) J. Zhang, Z. An, Y. Zhu, X. Shu, H. Song, Y. Jiang, W. Wang, X. Xiang, L.
Xu, J. He, ACS Catal. 2019, 9, 11438–11446; b) J. Zhang, W. Yan, Z. An, H.
Song, J. He, ACS Sustainable Chem. Eng. 2018, 6, 7313–7324.
[12] J. Zhang, K. Shi, Z. An, Y. Zhu, X. Shu, H. Song, X. Xiang, J. He, Ind. Eng.
Chem. Res. 2020, 59, 3342–3350.
[13] O. D. Pavel, D. Tichit, I. C. Marcu, Appl. Clay Sci. 2012, 61, 52–58.
[14] C. A. Emeis, J. Catal. 1993, 141, 347–354.
[15] J. V. Ochoa, C. Trevisanut, J. M. M. Millet, G. Busca, F. Cavani, J. Phys.
Chem. C 2013, 117, 23908–23918.
[16] M. Nielsen, H. Junge, A. Kammer, M. Beller, Angew. Chem. Int. Ed. 2012,
[5] G. W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106, 4044–4098.
[6] J. Sun, Y. Wang, ACS Catal. 2014, 4, 1078–1090.
[7] a) J. T. Kozlowski, R. J. Davis, ACS Catal. 2013, 3, 1588–1600; b) D.
Gabriëls, W. Y. Hernández, B. Sels, P. V. D. Voort, A. Verberckmoes, Catal.
Sci. Technol. 2015, 5, 3876–3902; c) A. Galadima, O. Muraza, Ind. Eng.
Chem. Res. 2015, 54, 7181–7194; d) H. Aitchison, R. L. Wingad, D. F.
Wass, ACS Catal. 2016, 6, 7125–7132; e) X. Wu, G. Fang, Y. Tong, D.
Jiang, Z. Liang, W. Leng, L. Liu, P. Tu, H. Wang, J. Ni, X. Li, ChemSusChem
2018, 11, 71–85; f) M. Guerbet, J. Chem. Soc. Abstr. 1901, 80, I625.
[8] a) A. Ndou, Appl. Catal. A 2003, 251, 337–345; b) T. Tsuchida, S. Sakuma,
T. Takeguchi, W. Ueda, Ind. Eng. Chem. Res. 2006, 45, 8634–8642; c) J.
Scalbert, F. Thibault-Starzyk, R. Jacquot, D. Morvan, F. Meunier, J. Catal.
2014, 311, 28–32.
[9] a) G. R. Dowson, M. F. Haddow, J. Lee, R. L. Wingad, D. F. Wass, Angew.
Chem. Int. Ed. 2013, 52, 9005–9008; Angew. Chem. 2013, 125, 9175–
9178; b) S. Fu, Z. Shao, Y. Wang, Q. Liu, J. Am. Chem. Soc. 2017, 139,
11941–11948; c) S. Chakraborty, P. E. Piszel, C. E. Hayes, R. T. Baker, W. D.
Jones, J. Am. Chem. Soc. 2015, 137, 14264–14267.
[10] a) J. I. D. Cosimo, C. R. Apesteguía, M. J. L. Ginés, E. Iglesia, J. Catal. 2000,
190, 261–275; b) M. León, E. Díaz, S. Ordóñez, Catal. Today 2011, 164,
436–442; c) D. L. Carvalho, R. R. de Avillez, M. T. Rodrigues, L. E. P.
Borges, L. G. Appel, Appl. Catal. A 2012, 415–416, 96–100; d) T. W. Birky,
J. T. Kozlowski, R. J. Davis, J. Catal. 2013, 298, 130–137; e) S. Hanspal,
Z. D. Young, H. Shou, R. J. Davis, ACS Catal. 2015, 5, 1737–1746; f) C.
Yang, Z. Meng, J. Catal. 1993, 142, 37–44; g) T. Tsuchida, J. Kubo, T.
Yoshioka, S. Sakuma, T. Takeguchi, W. Ueda, J. Catal. 2008, 259, 183–
189; h) S. Ogo, A. Onda, K. Yanagisawa, Appl. Catal. A 2011, 402, 188–
195; i) T. Tsuchida, S. Sakuma, T. Takeguchi, W. Ueda, Ind. Eng. Chem.
Res. 2006, 45, 8634–8642; j) C. R. Ho, S. Shylesh, A. T. Bell, ACS Catal.
51, 5711–5713.
[17] H. Horino, T. Ito, A. Yamamoto, Chem. Lett. 1978, 1, 17–20.
[18] A. K. P. Mann, Z. Wu, F. C. Calaza, S. H. Overbury, ACS Catal. 2014, 4,
2437–2448.
[19] a) E. Sekera, J. Cavataioa, E. Gularia, P. Lorpongpaiboonb, S. Osuwan,
Appl. Catal. A 1999, 183, 121–134; b) X. She, M. Flytzani-Stephanopoulos,
J. Catal. 2006, 237, 79–93; c) V. K. Kaushik, J. Electron. Spectros. Relat.
Phenomena 1991, 56, 273–277; d) Y. Cai, D. Wu, X. Zhu, W. Wang, F. Tan,
J. Chen, X. Qiao, X. Qiu, Ceram. Int. 2017, 43, 1066–1072.
[20] Y. Kameshima, A. Yasumori, K. Okada, Surf. Sci. Soc. Jpn. 2000, 21, 481–
487.
[21] D. Zou, X. Chen, E. Drioli, X. Ke, M. Qiu, Y. Fan, J. Membr. Sci. 2020, 593.
[22] a) S. Ardizzone, C. L. Bianchi, M. Fadoni, B. Vercelli, Appl. Surf. Sci. 1997,
119, 253–259; b) J. S. Corneille, J.-W. He, D. W. Goodman, Surf. Sci. 1994,
306, 269–278.
[23] M. S. Bhadraver, Bull. Chem. Soc. Jpn. 1962, 35, 1939–1941.
[24] a) D. E. Mears, Ind. Eng. Chem. Process Des. Dev. 1971, 10, 541–547;
b) P. B. Weisz, C. D. Prater, Adv. Catal. 1954, 6, 143–196.
Manuscript received: October 30, 2020
Revised manuscript received: January 7, 2021
ChemistryOpen 2021, 10, 1–10
www.chemistryopen.org
9
© 2021 The Authors. Published by Wiley-VCH GmbH
��
These are not the final page numbers!

FULL PAPERS
1
2
3
4
5
6
7
8
9
Synergistic Catalysis: Upgrading of
ethanol to n-butanol through dehy-
drogenation coupling provides a sus-
tainable way for n-butanol produc-
tion. But high selectivity to n-butanol
is still desirable. In this work, Ag-LDO
interfaces have been manipulated for
dehydrogenation coupling of
ethanol to n-butanol by tailoring the
size of Ag particles and the interac-
tions between Ag and LDO. Increas-
ing the population of interfacial Ag
sites promotes not only the dehydro-
genation of ethanol to acetaldehyde
but also the subsequent aldol con-
densation. A selectivity of up to 76%
to n-butanol with an ethanol conver-
sion of 44% has been achieved on
Ag/LDO with abundant interfacial Ag
sites.
J. Zhang, K. Shi, Dr. Y. Zhu, Prof. Z. An,
W. Wang, Dr. X. Ma, Dr. X. Shu,
Prof. Dr. H. Song, Prof. Dr. X. Xiang,
Prof. Dr. J. He*
1 – 10
Interfacial Sites in Ag Supported
Layered Double Oxide for Dehydro-
genation Coupling of Ethanol to n-
Butanol
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