Transformation of γ-valerolactone into 1,4-pentanediol and 2-methyltetrahydrofuran over Zn-promoted Cu/Al2O3catalysts

Article abstract of DOI:10.1039/d0cy00801j

The transformation of γ-valerolactone (GVL) into 1,4-pentanediol (1,4-PDO) and 2-methyltetra-hydrofuran (2-MTHF) in the presence of H2, one of the useful biomass conversion and utilization processes, was investigated with monometallic Cu/Al2O3 and bimetallic ZnCu/Al2O3 catalysts. A 10 wt% Cu-loaded monometallic catalyst produced 1,4-PDO and 2-MTHF in comparable quantities at a medium conversion (～50%). When Zn was added in a range of Zn/Cu molar ratios of up to 2, in contrast, the catalysts yielded 1,4-PDO in a high selectivity of about 97% at low and high conversion levels. In addition, the 1,4-PDO selectivity over the ZnCu/Al2O3 catalysts remained almost unchanged during recycled runs. That is, the addition of Zn to Cu/Al2O3 switched the product selectivity and improved the catalyst stability and reusability. Furthermore, the physicochemical properties of the catalysts were characterized by several methods including XRD, TEM, TPR, XPS, FTIR of adsorbed pyridine, and so on. On the basis of those results, the relationships between the catalytic performance (activity, selectivity, and reusability) and the catalyst structural features were discussed.

Full text of DOI:10.1039/d0cy00801j

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DOI: 10.1039/D0CY00801J.
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PAPER
Chaoqiu Chen, Yong Qin et al.
Highly dispersed Pt nanoparticles supported on carbon
nanotubes produced by atomic layer deposition for hydrogen
generation from hydrolysis of ammonia borane
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Transformation of γ-valerolactone to
1
,4-pentanediol and 2-methyltetrahydrofuran
over Zn-promoted Cu/Al O catalyst
2
3
Qiang Liua,b,c, Zhenbo Zhao , Masahiko Arai , Chao Zhang*a,c, Ke Liua,b,c, Ruhui Shia,c,
b
a,c
a,c
a,c
a,c
a,c
Peixuan Wu , Zhuangqing Wang , Weiwei Lin , Haiyang Cheng , and Fengyu
Zhao*a,c
a
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied
Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
b
School of Chemistry and Life Science, Changchun University of Technology,
Changchun 130022, PR China
c
Jilin Province Key Laboratory of Green Chemistry and Process, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
*Corresponding author, Tel:+86-431-85262454; Fax: +86-431-85262454;
E-mail address: czhang@ciac.ac.cn, zhaofy@ciac.ac.cn
ABSTRACT
The transformation of γ-valerolactone (GVL) to 1,4-pentanediol (1,4-PDO) and 2-methyltetra-
hydrofuran (2-MTHF) in the presence of H , one of useful biomass conversion and utilization
2
processes, was investigated with monometallic Cu/Al O and bimetallic ZnCu/Al O catalysts.
2
3
2
3
A 10 wt.-% Cu-loaded monometallic catalyst produced 1,4-PDO and 2-MTHF in comparable
quantities at a medium conversion (~ 50%). When Zn was added in a range of Zn/Cu molar
ratio of up to 2, in contrast, the catalysts yielded 1,4-PDO in a high selectivity of about 97% at
low and high conversion levels. In addition, the 1,4-PDO selectivity over the ZnCu/Al O
2
3
catalysts remained almost unchanged during recycled runs. That is, the addition of Zn to
Cu/Al O switched the product selectivity and improved the catalyst stability and reusability.
2
3
Furthermore, the physicochemical properties of the catalysts were characterized by several
methods including XRD, TEM, TPR, XPS, FTIR of adsorbed pyridine, and so on. On the basis
of those results, the relationships between the catalytic performance (activity, selectivity,
1

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reusability) and the catalyst structural features were discussed.
Keywords:
Biomass conversion, Copper catalyst, Zinc additive, γ-Valerolactone, 1, 4-Pentanediol,
2
-Methyltetrahydrofuran
1
. Introduction
Lignocellulosic biomass, a renewable carbon resource, has attracted much attention in the
past few decades owing to its potential applications in the synthesis of fine chemicals and fuels.
Catalytic hydrogenation of biomass is one of the most efficient and environmental-friendly
ways to remove oxygen atoms and improve its practical values. Levulinic acid (LA) is one of
the most studied platform molecules derived from cellulose, which is considered as an
important C5 resource. It can be converted to γ-valerolactone (GVL) via hydrogenation over Pt,
1
-6
Ru, Ni, Pd, Ir, and other catalysts under mild reaction conditions . Hydrogenation of GVL can
produce value-added chemicals, such as 1,4-pentanediol (1,4-PDO) and
-methyltetrahydrofuran (2-MTHF). 1,4-PDO is a useful monomer for the production of
polyesters and an intermediate for the synthesis of fragrances, lubricants, and others 7-11 while
-MTHF is a promising biofuel or fuel additive for currently used gasoline because of its
favorable features similar to gasoline12-15
1,4-PDO is produced via the
hydrogenation/hydrogenolysis of GVL over several monometallic Cu catalysts supported on
2
2
.
1
6-20
ZnO, MgO, ZrO , and other oxide materials
but a high Cu loading of > 20% is often used to
2
obtain a satisfactory performance (activity, selectivity, stability, and reusability). 2-MTHF is
2
1
22
also produced from GVL (or LA) via 1,4-PDO over bimetallic CuNi catalysts on Al O , SiO ,
2
3
2
2
3
and CuNi/Al O -ZrO . A good 2-MTHF yield of 64% was obtained with CuNi/Al O (Cu
2
3
2
2
3
2
1
loading 35 w%, Ni/Cu = 2 in mole) in the reaction of GVL at a temperature of 230 ºC .
Moreover, a higher Cu loading of 72 wt% was used in the Cu/SiO , with which 2-MTHF was
2
o
22
produced with a yield of 89% at 265 C . Those results indicate that Cu is a promising active
component for the selective production of either 1,4-PDO or 2-MTHF from GVL. It is an
important and challenging task, therefore, to prepare a Cu-based catalyst with less metal loading
but the high-performance for the target reactions of biomass conversion.
Considering the above-mentioned results, the present authors has prepared a series of
Zn-promoted Cu catalysts (Zn Cu/Al O ) and investigated their catalytic performances for the
x
2
3
transformation of GVL to 1,4-PDO and 2-MTHF in the presence of H . The catalysts were
2
prepared by successive impregnation of Cu (first) and Zn (second) on -Al O support, in which
2
3
the amount of Cu loaded was fixed to 10 wt.-% (mass of Cu against mass of Al O ) and that of
2
3
2

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Zn was varied in a range of Zn/Cu molar ratio of 0 ~ 2. The results obtained show that the
catalytic performance depends significantly on the Zn/Cu ratio: it is interesting that the main
product changed from 2-MTHF with monometallic Cu/Al O catalyst to 1,4-PDO with
2
3
ZnCu/Al O ones, and the high 1,4-PDO selectivity over the ZnCu/Al O catalysts could remain
2
3
2
3
during the course of either a single reaction run up to the end of reaction or repeated runs in
catalyst recycling test. It was reported in the literature that CuO/ZnO/Al O mixed oxides were
2
3
one of the most attractive heterogeneous catalysts in biomass conversion24, 25, methanol
synthesis26, 27, water-gas shift reaction28, 29, and synthesis of dimethyl ether30, 31. However, there
still remain some controversy and unclear points about the catalysis of those Cu-based catalysts
including the structure of active Cu sites, the roles of Zn species, and the surface acidity, and so
on. In the present work, the bulk and surface physicochemical properties of the catalysts were
examined by TPR, TPD, pyridine-FTIR, XRD, TEM, XPS and the parameters/variables
determining their catalytic performance (activity, selectivity, reusability) were discussed.
2
. Experimental
2
.1. Catalyst preparation
Monometallic (Cu) and bimetallic (ZnCu) catalysts supported on -Al O were prepared by
2
3
incipient wetness method. For the former, Cu(NO ) •3H O (Shanghai Macklin Biochemical Co.,
3
2
2
analytical grade) was dissolved in 4ꢀmL deionized water and then the solution was gradually
dropped into a beaker containing 1 g of γ-Al O while being stirred, in which the support was
2
3
prepared by calcining a pseudo-boemite (Zibo Senchi Fine Chem.) at 800 ºC for 4 h. The slurry
obtained was dried at 80ꢀ°C overnight and calcined at 450 °C for 3 h in air. The sample so
prepared was reduced with 10% H (Juyang Gas Co., 99.999%) in Ar (Juyang Gas Co.,
2
9
9.999%) at 250 °C for 2 h before activity measurement. For the latter bimetallic catalysts, a
given amount of Zn(NO ) •6H O (Guangdong Xilong Chem. Co., analytical grade) was
3
2
2
dissolved in 4 mL deionized water and the solution was gradually dropped into a beaker
containing the calcined (unreduced) Cu/Al O sample while being stirred. Then, the mixture
2
3
was dried at 80 °C overnight, calcined at 300 °C for 3 h in air, and reduced with H at 280 °C
2
for 2 h. The Cu loading was fixed to 10% (Cu/Al O in weight) while the Zn loading was varied
2
3
in a range of Zn/Cu (molar ratio), x, of 0 ~ 2. In the following, the catalysts are denoted as
Zn Cu/Al O . The BET surface areas of the precursor boemite and -Al O support prepared
x
2
3
2
3
2
-1
2
-1
were 325 m g and 259 m g , respectively. The metal loading in the catalysts so prepared was
measured by ICP-OES on a Thermo iCAP 6300 spectrometer. The results measured are
presented in Table S1 of Supporting Information (SI).
3

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2
.2. Activity measurement
The catalytic performance of Cu/Al O and ZnCu/Al O catalysts was examined in the
2
3
2
3
transformation of GVL to 1,4-PDO and 2-MTHF in the presence of H in a solvent of
2
1
,4-dioxane. The reagents of GVL, 1,4-PDO, 2-MTHF, and 1,4-dioxane were purchased from
Shanghai Aladdin Biochemical Technology Co., which were of analytical grade and used with
no further pretreatment. The reaction runs were conducted in a 50 mL stainless steel autoclave
with a stirring speed of 600 rpm with a magnetic stirrer. For a typical reaction, 2 mmol GVL,
1
00 mg catalyst, and 10 mL 1,4-dioxane were introduced into the autoclave. The reactor was
flushed by atmospheric H for 5 times, pressurized with H to 4 MPa, and then heated to 200 °C
2
2
while being stirred at 200 rpm. When the reaction temperature reached 200 °C in 45 min, the
stirring rate was raised to 600 rpm. After a certain period of reaction, the reactor was cooled to
room temperature by immersing in an ice water bath and the solid materials were separated
from the liquid phase by centrifugation. The liquid phase was analyzed with a gas
chromatograph (Shimadzu, 14C) equipped with a capillary column (Restek Stabilwax 30 m ×
0
.53 mm × 1 μm,) and a flame ionization detector (FID) using biphenyl as internal standard.
The conversion was determined by 1- (the amount of substrate unreacted) / (the initial amount
of substrate loaded) and the product selectivity by (the amount (mole) of a product) / (the
amount (mole) of substrate reacted).
2
.3. Catalyst characterization
The bulk and surface properties of the catalysts prepared were characterized by different
methods. Powder X-ray diffraction (XRD) patterns were obtained using a Bruker D8 Advance
X-ray powder diffraction instrument with a Cu–Kα radiation ( = 0.154 nm, 40 kV, 10 mA,) in
−
1
a 2θ range of 10–80° with a scan speed of 1° min . Transmission electron microscopy (TEM)
images were taken using a field emission FEI Tecnai G2 F20 instrument operated at an
accelerating voltage of 200ꢀkV. Temperature programmed reduction (TPR) profiles were
measured on Micromeritics AutoChem II 2920. A sample (50 mg) was treated by Ar at 150 ºC
for 0.5 h to remove residual water and cool to room temperature. Then, the sample was heated at
-1
-1
1
0 °C min to 900 C in a stream of H (10%) in Ar at a rate of 50 mL min . The amount of H
2 2
consumed was measured by a thermal conductivity detector.
X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES)
measurements were carried on VG Microtech 3000 Multilab without sputtering. The quantity of
copper species exposed on the surface of Cu/Al O and ZnCu/Al O catalysts was measured by
2
3
2
3
4

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N O oxidation and H reduction using a Micromeritics AutoChem II 2920 apparatus . A
2
2
-1
calcined catalyst sample was pretreated in a 20% O /N stream at 30 mL min for 20 min at
2
2
-1
4
00°C. After cooled to 50 °C, the sample was treated by pure Ar (30 mL min ) for 30 min at
-1
this temperature. The sample was then reduced by a 10% H /Ar (30 mL min ) for 1 h at the
2
desired temperature of 250 °C for monometallic Cu/Al O and 280 °C for bimetallic
2
3
2
+
0
ZnCu/Al O with a heating rate of 5 °C (first reduction of Cu (CuO) to Cu ). The sample was
2
3
-1
cooled to 50 °C and treated by pure Ar (30 mL min ) for 30 min to remove residual physisorbed
0
hydrogen species. The surface copper species (Cu ) were partially oxidized at this temperature
-1
+
-1
by 20% N O/Ar (30 mL min ) to Cu (Cu O). After the treatment with Ar (30 mL min ) for 30
2
2
-1
min, the sample was reduced again by the 10% H /Ar stream at 30 mL min (second reduction
2
+
0
of Cu (Cu O to Cu ). The amounts of H consumed in the first and second reduction processes
2
2
were measured by a thermal conductive detector for determining the amount of surface exposed
0
Cu species of the catalysts.
The acid properties on the surface of catalysts were measured by FTIR spectroscopy for
3
3
pyridine adsorbed thereon with a PE Frontier FT-IR spectrometer . A catalyst sample was
−
2
pressed into a self-supported wafer (ca.10 mg cm ) and pretreated in an in-situ IR cell at
−
2
3
50 °C for 2 h under vacuum (10 Pa) prior to pyridine adsorption. The cell was cooled to room
temperature and the background spectrum was collected. Pyridine vapor was introduced into the
cell and the sample was exposed to the pyridine for 30 min. After physicsorbed pyridine was
-2
removed by dynamic evacuation at 10 Pa and at room temperature for 30 min, the spectra of
chemisorbed pyridine were collected at different temperatures.
3
. Results and discussion
3
.1. Catalytic performance
The activity of the catalysts prepared was tested for the transformation of GVL in the
presence of 4 MPa H at 200 ºC. Under the reaction conditions used, 1,4-PDO and
2
2
-MTHF were produced and no other products were detected to form. Table 1 shows
the results of reactions in 10 min and 120 min over different catalysts. A conversion of
2% and a selectivity of 46% to 1,4-PDO was obtained in 10 min over monometallic
Cu/Al O catalyst (entry 1). A catalyst of Zn/Al O (15% Zn loading) was found to be
5
2
3
2
3
not active and give no any reaction produces. It is interesting that the addition of
inactive Zn species to Cu/Al O significantly changed the product selectivity. When a
2
3
small amount of Zn was added (Zn/Cu = 0.5 in molar ratio), 1,4-PDO selectivity
increased to 87% (entry 2) and it further increased up to 98% with an increase of
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Zn/Cu to 1.0 (entry 3). The 1,4-PDO selectivity did not change so much when more Zn
species was added up to Zn/Cu = 2 (entries 4, 5). In contrast, the total conversion
presented a slightly decrease with the addition of Zn (entries 1 - 5), which may be
0
ascribed to the decrease of the surface active Cu species with increasing the amount of
Zn in the ZnCu/Al O catalysts. Similar effects of the Zn addition on the product
2
3
selectivity and the total conversion were observed when reaction time was extended to
1
20 min (entries 6-10). The average reaction rate per a surface zero-valent copper atom
0
(
Cu ) was calculated from the conversion in 10 min and the number of these exposed
0
Cu atoms determined by N O titration (described later). Table 1 shows that the average
2
-1
rates so calculated are 66, 76, 74, 89 and 165 h for the catalysts of Cu/Al O and
2
3
Zn Cu/Al O , Zn Cu/Al O and Zn Cu/Al O , respectively. Evidently, the presence
1
.0
2
3
1.5
2
3
2.0
2
3
of Zn species in the copper catalyst enhanced its catalytic activity, especially for those
with a larger Zn/Cu ratio of 1.5 and 2 (entries 4, 5). As shown below the amount of
0
exposed Cu species was decreased by the addition of Zn, suggesting the surface active
sites were not only the zero-valent copper species but also some new active species
formed with the addition of Zn, such as ZnCu alloys.
2 3
Table 1 Results of GVL transformation over Zn-modified and -unmodified Cu/Al O catalysts
OH
O
O
O
OH +
GVL
1,4-PDO
2-MTHF
Catalyst a
Entry
Conversion
Selectivity (%)
Average reaction rate
b
-
1
(
%)
1,4-PDO
46
2-MTHF
54
(h )
66
76
74
89
165
--
1
2
Cu/Al
2
O
3
(9.9 wt. %)
52
50
46
42
52
91
92
91
91
90
Zn0.5Cu/Al
Zn1.0Cu/Al
Zn1.5Cu/Al
Zn2.0Cu/Al
2
2
2
2
O
3
3
3
3
(9.5 wt. %)
(8.4 wt. %)
(7.9 wt. %)
(6.6 wt. %)
87
98
97
97
19
75
94
97
97
13
2
3
O
O
O
4
3
5
3
6 c
7 c
8 c
9 c
Cu/Al
2
O
3
(9.9 wt. %)
81
25
6
Zn0.5Cu/Al
Zn1.0Cu/Al
Zn1.5Cu/Al
Zn2.0Cu/Al
2
2
2
2
O
3
3
3
3
(9.5 wt. %)
(8.4 wt. %)
(7.9 wt. %)
(6.6 wt. %)
--
O
O
O
--
3
--
1
0 c
3
--
6

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2
Reaction conditions: 0.1 g catalyst, 10.0 mL 1,4-dioxane, 2.0 mmol GVL, 200℃, 4 MPa H , 10 min.
2 3
a. Al O -supported catalysts. Figures in parentheses indicate the true Cu loading measured by ICP.
b. Average reaction rate was calculated by the moles of GVL converted within 10 min with per mole of
0
0
surface Cu active sites. The number of exposed Cu atoms was determined by N
2
O adsorption.
c. Reaction time 120 min.
3
3
.2. Catalyst characterization
.2.1. Bulk properties
H -TPR was conducted to examine and compare the reducibility of metal species in
2
different catalysts. Figure 1 shows the results with the calcined Cu/Al O , Zn/Al O and
2
3
2
3
ZnCu/Al O catalysts. For Cu/Al O , a single H consumption peak was observed at
2
3
2
3
2
about 165 ºC for the reduction of the surface CuO species. For Zn/Al O , a broad H
2
2
3
consumption peak appeared at 250 ºC - 350 ºC, probably due to the reduction of ZnO
species. When Zn was added to Cu/Al O , the H consumption occurred in a
2
3
2
temperature range of around 170 ºC and 260 ºC and the reduction temperature of CuO
was increased due to the interactions between CuO and ZnO species. The H2
consumption peak at higher temperatures may be attributed to the reduction of CuO
strongly contacted with Zn, which produced a ZnCu alloy34, 35. The quantity of H2
consumption for different samples were estimated from H -TPR results and summarized
2
in Table 2. It increased with the increase in the amount of Zn and it was larger than the
theoretical value calculated from the complete reduction of all supported CuO species to
0
Cu . Therefore, a part of ZnO should be reduced in ZnCu/Al O catalysts, forming a
2
3
ZnCu alloy34-38, which will be further confirmed by TEM and Zn LMM X-ray excited
Auger spectroscopy spectra later.
7

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Figure 1. H -TPR profiles of Cu/Al O , Zn/Al O and Zn Cu/Al O catalysts.
2
2
3
2
3
x
2
3
Table 2. H Consumption of different samples on the H -TPR.
2
2
Entry
Catalyst
Cu content
Theoretical
Actual
Actual/Theo
a
b
c
H consumption
H consumption
retical H2
consumption
ratio
2
2
(
wt. %)
(mmol/g)
(mmol/g)
1
2
3
4
Cu/Al O
9.9
9.5
8.4
7.9
6.6
1.55
1.48
1.31
1.23
1.03
1.09
1.21
1.56
1.57
1.30
0.70
2
3
Zn Cu/Al O
0.82
0
.5
2
3
3
3
3
Zn Cu/Al O
1.19
1
.0
2
Zn Cu/Al O
1.28
1
.5
2
5
Zn Cu/Al O
1.26
2
.0
2
a.
Cu weight concentration was determined by ICP.
b.
c.
2+
0
Theoretical H consumption for the reduction of all Cu to Cu .
2
Actual H consumption obtained by H -TPR.
2
2
Figure 2 gives XRD patterns of support and reduced monometallic and bimetallic
catalysts. The Cu-loaded catalysts did not show the diffraction patterns of CuO, which
was detected for the corresponding calcined catalysts (Fig. S1), but the diffraction peaks
due to copper metal at 43.3º, 50.4º and 74.2º were detected. These diffraction peaks
became stronger and sharper on the addition of Zn in the range of Zn/Cu of 0 ~ 1.5,
0
indicating that the CuO was reduced completely to Cu and the metal particle size
increased. The average copper metal particle size was 19, 25, 26, 22 and 23 nm for
8

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Cu/Al O , Zn Cu/Al O , Zn Cu/Al O , Zn Cu/Al O , and Zn Cu/Al O
3,
2
3
0.5
2
3
1.0
2
3
1.5
2
3
2.0
2
respectively, as determined by the diffraction peak broadening via the Debye-Scherrer
equation. In addition, there were no obvious diffractions of Zn species for the
Zn Cu/Al O samples with Zn/Cu of 0 ~ 1.5. While, for the sample loaded with a larger
x
2
3
amount of Zn (Zn/Cu = 2), the diffractions due to ZnO at 31.8º, 34.4º, 36.3º, 47.6º, 56.7º,
2.9º, 68.0º and 69.1º were found, which suggested that ZnO species still remained on
6
the surface of catalyst.
TEM images of the selected two reduced Cu/Al O and Zn Cu/Al O catalysts are
2
3
1.5
2
3
shown in Figure 3. For the Cu/Al O catalyst, the copper metal particles were dispersed
2
3
on the surface of support, and the lattice of CuO (002) and Cu (111) plane was detected
with an interlayer spacing of 0.252 and 0.209 nm, respectively (Figure 3B). While, for
the Zn Cu/Al O catalyst, the metal particles were dispersed finely on the support
1
.5
2
3
(
Figure 3D). The state of distribution of elements over the surface of Zn Cu/Al O
1.5 2 3
catalyst was recorded by HAADF-STEM and EDX analysis. The results are shown in
Figure 4. It was observed that some Zn species closely presented to the copper particles,
and the ZnCu alloy was likely to form in the catalyst, while the others were dispersed on
the support solely probably with ZnO species.
x
Figure 2. XRD patterns of the calcinedγ-Al O support and reduced Cu/Al O and
2
3
2
3
Zn Cu/Al O catalysts.
x
2
3
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Figure 3. TEM and HRTEM images of as-reduced Cu/Al O (A, B) and Zn Cu/Al O
3
2
3
1.5
2
catalysts (C, D), respectively. The inset in D is an enlarged image of a single
nanoparticle.
Figure 4. HAADF-STEM image (A) and EDX elemental maps of Cu (B), O (C), Zn
(
D), mixture of Cu and Zn (E), and mixture of Cu, Zn, and O (F) for Zn Cu/Al O
1.5 2 3
catalyst.
1
0

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3
.2.2. Surface properties
The amount of zero-valent copper Cu species exposed on the surface of catalysts was
3
2
measured by N O titration . As shown in Table 3, it was 0.94 mmol/g for
2
cat
Zn-unloaded Cu/Al O catalyst (entry 1) and it decreased by the addition of Zn (entries
2
3
2
-5). When Zn/Cu was 1.5, for example, it was deceased by 40% to 0.56 mmol/gcat
0
(
entry 4). The decrease of the exposed Cu species could be explained by the changes of
the metal particle size and/or the coverage with Zn additive. As described earlier,
however, the size of metal particles did not change with the amount of Zn species added
0
so much. Using the amount of surface Cu species so determined, the average rate of
0
GVL transformation per surface Cu atom in 10 min was calculated. It was higher for
Zn-promoted Zn Cu/Al O catalysts compared to Cu/Al O one (entries 1-5). Figure 5
x
2
3
2
3
0
gives the changes of the surface Cu concentration and the average reaction rate against
0
the Zn/Cu ratio in the Cu/Al O and Zn Cu/Al O catalysts. Although the Cu
2
3
x
2
3
concentration was decreased, the specific reaction rate was enhanced. The main
0
catalytically active species are copper atoms (Cu ). So, the results of Figure 5 indicate
0
the existence of other active copper species in addition to Cu in the Zn-promoted
catalysts, which should be those in ZnCu alloy.
0
Table 3. The amount of exposed Cu species determined by N O titration
2
0
Amount of exposed Exposed Cu against
Average reaction
rate c
Catalyst a
0
Entry
Cu species
the total loaded
copper species
mmol/gCu) b
0.94
-1
(
(%)
61
53
56
46
37
(h )
1
2
3
4
5
Cu/Al O
66
76
2
3
Zn Cu/Al O
0.78
0
.5
2
3
3
3
3
Zn Cu/Al O
0.74
74
1
.0
2
Zn Cu/Al O
0.56
89
1
.5
2
Zn Cu/Al O
0.38
165
2
.0
2
a. Copper loading: 10 wt.-% (weight of Cu against weight of Al O ).
2
3
0
b. Amount of Cu species per 1 g of copper loaded.
c. Determined using the reaction data in 10 min (Table 1).
1
1

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DOI: 10.1039/D0CY00801J
0
0
Figure 5. The changes of exposed Cu concentration and Cu -based average reaction
rate as a function of Zn/Cu molar ratio.
Figure 6 shows the Cu 2p XPS results of the reduced Cu/Al O and Zn Cu/Al O
2
3
x
2
3
0
1
catalysts. The binding energy (BE) at around 933.1eV can be assigned to the Cu or Cu
0
+
specie, because the BE of Cu and Cu cannot be distinguished on the basis of Cu 2p
signal (Figure 6 A). These two copper species cannot be confirmed by Auger Cu LMM
as well due to weak signal. A peak at around 934.3 eV together with a satellite peak
around 940-945 eV indicated the presence of CuO in the catalysts39-42, which are much
2
+
obvious in the Cu/Al O and Zn Cu/Al O catalysts, indicating more Cu species
2
3
0.5
2
3
0
coexisted with Cu on them. The Cu 2p peak gradually shifted to lower binding
3
/2
energy and the satellite peak related to Cu2+ species decreased with the increasing Zn
content disappeared when Zn/Cu ratio is 1 or larger, suggesting that the presence of Zn
4
3
could promote the reduction of Cu species .
For the Zn 2p XPS spectra (Figure 6B), the BE shifted slightly to higher value,
suggesting that the electron transfer should occur from zinc species to copper ones. The
2
+
results of Zn LMM Auger (Figure 6C) BE at around 499 eV was assigned to Zn and
0
44
0
4
96.2 eV to Zn species , confirming the metallic Zn species of Zn existed somewhat
in the reduced catalysts which is in agreement with the TPR and XRD results. With the
0
increase of Zn content in the catalysts, surface Zn species increased accordingly. These
results further confirmed that ZnCu alloy was formed with the addition of Zn, and the
amount of ZnCu alloy increased with increasing of the ratio of Zn/Cu.
1
2

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DOI: 10.1039/D0CY00801J
Figure 6. (A) Cu 2p XPS spectra; (B) Zn 2p XPS spectra of the reduced Cu/Al O ,
2
3
Zn Cu/Al O , Zn Cu/Al O , Zn Cu/Al O and Zn Cu/Al O catalysts; (C) Zn
0
.5
2
3
1.0
2
3
1.5
2
3
2.0
2
3
LMM XAES spectra of the reduced Cu/Al O , Zn Cu/Al O , Zn Cu/Al O ,
2
3
0.5
2
3
1.0
2
3
Zn Cu/Al O and Zn Cu/Al O catalysts.
1
.5
2
3
2.0
2
3
3
.2.3. Surface acidity
The surface acidity of catalysts was examined by FTIR of pyridine adsorbed thereon
Figure 7A). The FTIR spectra were collected after the adsorption of pyridine at room
(
temperature and the subsequent evacuation at 200 ºC. Four absorption bands were
observed for all the catalysts examined, which are attributed to pyridine molecules
-1
adsorbed on Lewis acid sites (~1450, ~1495, ~1575, ~1612 cm ) and those at Brønsted
-1 45, 46
-1
-1
acid sites (~1490 cm )
. The absorption bands of I (1450 cm ) and IV (1612 cm )
1
3

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D4 5O I: 10.1039/D0CY00801J
are often used to estimate the total amount and strength of Lewis acid sites . These
absorption bands became weaker with the addition of Zn to Cu/Al O . Figure 7B gives
2
3
the plots of the amount of Lewis acid sites and the 1,4-PDO selectivity in the GVL
transformation against the Zn/Cu ratio in the catalysts. A relationship is seen that the
1
,4-PDO selectivity increases (the 2-MTHF selectivity decreases) while the amount of
Lewis acid sites is decreased by the addition of Zn. That is, the Zn additive decreased
the quantity of surface Lewis acid sites and then promoted the formation of 1,4-PDO
than 2-MTHF. However, for the Zn Cu/Al O catalyst, a slight increase of peak IV
2
.0
2
3
were observed with respect to Zn Cu/Al O , while the total acid sites still presented a
1
.5
2
3
little decrease.
Figure 7. (A) In-situ FTIR spectra of pyridine chemisorbed on (a) Cu/Al O , (b)
2
3
Zn Cu/Al O , (c) Zn Cu/Al O , (d) Zn Cu/Al O , and (e) Zn Cu/Al O catalysts;
0
.5
2
3
1.0
2
3
1.5
2
3
2.0
2
3
(
B) Amount of acid sites and 1,4-PDO selectivity in GVL transformation against the
Zn/Cu molar ratio in the catalysts. Reaction conditions: 0.1 g catalyst, 10.0
mL1,4-dioxane, 2.0 mmol GVL, 200℃, 4 MPa H , 12 h.
2
3
.3 Active sites and reaction pathway
Based on the above-mentioned results of GVL transformation and catalyst
characterization by several methods, it was concluded that the specific reaction rate was
enhanced with the addition of Zn to Cu/Al O catalyst, and the ZnCu alloy species were
2
3
0
formed in these Zn Cu/Al O catalysts; the amount of Cu on the surface of catalysts
x
2
3
decreased, and the amount of ZnCu alloy increased with increasing amount of Zn.
0
Therefore, it was demonstrated that the metallic Cu and ZnCu alloy were the active
species on the surface of ZnCu/Al O catalysts.
2
3
1
4

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DOI: 10.1039/D0CY00801J
Moreover, the selectivity to 1,4-PDO was improved significantly with addition of Zn
to Cu/Al O catalyst. Figure 8 compares the change of the 1,4-PDO selectivity with
2
3
total conversion (time-conversion cures are presented in Figure S2). For Zn-unmodified
Cu/Al O catalyst, the selectivity to 1,4-PDO largely decreased during reaction
2
3
(correspondingly, the selectivity to 2-MTHF increased), while the decrease of
selectivity to 1,4-PDO became slower over the Zn Cu/Al O catalysts.
x
2
3
Figure 8. The change of product selectivity with total conversion in the GVL
transformation over Cu/Al O , Zn Cu/Al O , Zn Cu/Al O , Zn Cu/Al O , and
2
3
0.5
2
3
1.0
2
3
1.5
2
3
Zn Cu/Al O catalysts. The data were collected at reaction time of 1/6, 1, 2, and 12 h,
2
.0
2
3
respectively. Reaction conditions: 0.1 g catalyst, 10.0 mL1,4-dioxane, 2.0 mmol GVL,
2
00℃, 4 MPa H2.
The selectivity to 1,4-PDO decreased while that to 2-MTHF increased with reaction
time (Figure S2). Thus, it is likely that the 2-MTHF was formed from 1,4-PDO over the
Cu/Al O and Zn Cu/Al O catalysts but the transformation of 1,4-PDO to 2-MTHF
2
3
x
2
3
may be suppressed to larger extent by the addition of more amount of Zn species.
Herein, control reactions using 1,4-PDO as a starting reactant were carried out with
Al O alone, Cu/Al O , and Zn Cu/Al O , and the results obtained are shown in Table
2
3
2
3
1.5
2
3
4
. A 35% conversion was obtained with Al O support alone, while a larger conversion
2 3
of 60% over Cu/Al O catalyst in 20 min (entries 1, 2). However, by contrast, the same
2
3
transformation was much slower with Zn Cu/Al O catalyst, in which the conversion
1
.5
2
3
was only 17% with extending the reaction time to 120 min (entry 3), in which 2-MTHF
was still the main product although a minor amount of GVL was detected (entry 3). It
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5

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DOI: 10.1039/D0CY00801J
was reported that 2-MTHF could be formed through cyclodehydration of 1,4-PDO in
the presence of Lewis acids47, 48. Compared with Cu/Al O , less and weaker Lewis acid
2
3
sites exist on the surface of Zn Cu/Al O (Figure 5) and thus the transformation of
1
.5
2
3
1
,4-PDO to 2-MTHF promoted by the surface Lewis acid sites was prohibited. That is,
as shown in Scheme 1, GVL transforms to 1,4-PDO through hydrogenation and then to
-MTHF by dehydrogenation49, 50
2
.
Table 4. Results of the reaction of 1, 4-PDO to 2-MTHF over different catalysts
Entry
Catalyst
Time (min)
Conversion (%)
1
2
3
Al
2
O
3
20
20
35
60
17
Cu/Al
2
O
3
Zn1.5Cu/Al
2
O
3
120
2
Reaction conditions: 0.1 g catalyst, 10.0 mL1,4-dioxane, 2.0 mmol 1,4-PDO, 200℃, 4 MPa H , 10 min.
Scheme 1. Reaction pathways of GVL hydrogenation to 1,4-PDO and 2-MTHF.
3
.4 Catalyst stability
Furthermore, the catalyst reusability was examined with the two selected Cu/Al O
2
3
and Zn Cu/Al O catalysts. For the reusability test, the catalyst was centrifuged and
1
.5
2
3
separated from the reaction mixture after the first run, washed with 1,4-dioxane three
times and then transferred to the reactor for the next run under the same reaction
conditions. Figure 9 shows the recycling results over the Cu/Al O and Zn Cu/Al O
3
2
3
1,5
2
catalysts. For the former catalyst, the conversion decreased from 98% to 50%, the
selectivity to 2-MTHF decreased, that to 1,4-PDO increased during the five repeated
runs. For the latter, in contrast, the conversion changed only marginally and the high
1
,4-PDO selectivity remained unchanged. These results indicated that the addition of Zn
improves the stability of the catalyst. Generally, the deactivation of supported metal
catalysts usually results from the leaching or oxidation of surface active species, and/or
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6

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carbon depositions51-55. The ICP results indicated that the leaching of copper was
DOI: 10.1039/D0CY00801J
negligible for the Cu/Al O catalyst (Table S2). Besides, TGA showed very similar
2
3
weight loss patterns for both the catalysts, which were due to the adsorbed water and
surface hydroxyl groups (Figure S3). The carbon balances over the tested catalysts are
higher than 95%. Therefore, the metal leaching and carbon deposition are not
responsible for the significant activity loss of the Cu/Al O catalyst.
2
3
Figure 9. The recycling results for the catalysts: (A) Cu/Al O , (B) Zn Cu/Al O .
2
3
1.5
2
3
Reaction Conditions: 0.1 g catalyst, 10.0 mL1,4-dioxane, 2.0 mmol GVL, 200 ℃ , 4
MPa H . Reaction time: Cu/Al O catalyst was 3 h and Zn Cu/Al O catalyst was 2 h.
2
2
3
1.5
2
3
In addition, the fresh and recycled catalysts were examined by XRD and TEM. The
diffraction peak of both the Cu/Al O and Zn Cu/Al O intensity became weaker after
2
3
1.5
2
3
used , indicating both the crystallinity and particle sizes changed during reaction (Figure
0
1
0 and Figure S4 ). For the used Cu/Al O almost no diffraction peaks of Cu can be
2
3,
detected and a new diffraction related to Al(OH) was found (JCPDF:330018). But, for
3
0
the used Zn Cu/Al O , Cu was still found in addition to Al(OH) . These changes were
1
.5
2
3
3
further confirmed by XPS and Zn LMM Auger spectra.
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Figure 10. XRD patterns of the fresh and used Cu/Al O and Zn Cu/Al O catalysts.
2
3
1.5
2
3
As shown in Figure 11, the chemical states of Cu, Zn and Al of the used Cu/Al O
2
3
catalyst were different from those of the fresh one. The Cu 2p3/2 peak was observed at a
2
+
0
.8 eV higher BE value with a wide satellite peak of Cu , indicating the partial
0
oxidation of Cu during the recycling. The state of Al 2p also changed very largely. By
contrast, the Cu 2p3/2 and Al 2p BE changed very slightly and the satellite peak of Cu2+
0
2+
was still not unremarkable for the used Zn Cu/Al O catalyst. Besides, the Zn /Zn
1
.5
2
3
remained almost unchanged on the repeated runs from the Auger results of Zn. Thus,
the surface metallic states like Cu and ZnCu changed slightly for the Zn Cu/Al O in
1
.5
2
3
the recycled runs, but very remarkable for the Zn-unloaded Cu/Al O catalyst.
2
3
Therefore, it is concluded that the Zn Cu/Al O catalyst was more stable and
1
.5
2
3
recyclable than Cu/Al O one in the present GVL transformation. One reason is that the
2
3
presence of ZnCu alloy makes the catalyst stronger against the oxidation of the Cu0
0
during the catalyst handling and reaction processes. Besides, the Cu active sites in the
Cu/Al O catalyst were covered by the Al(OH) formed and this is another reason for its
2
3
3
deactivation. But Al(OH) was less likely to form on the Zn Cu/Al O catalyst，as it
3
1.5
2
3
yielded less water (via dehydration product of 1,4-PDO) to react with Al O . Therefore,
2
3
the Zn Cu/Al O catalyst presented high stability in the present reaction as the
1
.5
2
3
0
existence of ZnCu alloy active species, prohibiting the oxidation of Cu and the
formation of Al(OH)3.
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8

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Figure 11. (A) Cu 2p, (B) Al 2p XPS and (C) Zn LMM Auger spectra of the fresh and
used Cu/Al O and Zn Cu/Al O catalysts.
2
3
1.5
2
3
4
. Conclusions
A series of Zn-promoted Cu/Al O catalysts have been fabricated and their catalytic
2
3
performances were compared with those of Cu/Al O for the selective hydrogenolysis
2
3
hydrogenation of GVL, which is an important reaction in biomass conversion. Under
the reaction conditions, 1,4-PDO and 2-MTHF are produced and the product selectivity
can be controlled by adjusting Zn/Cu ratio in the ZnCu/Al O catalysts, for which the
2
3
Cu loading is 15 wt.-%. It is interesting that the selectivity to 1,4-PDO was only 46%
with Cu/Al O catalyst at 52% conversion, but it increased with the Zn/Cu ratio and
2
3
reached to above 98% when Zn/Cu was 1.5. The catalyst stability was also improved
largely with the addition of Zn; Zn Cu/Al O could be recycled for 10 times with very
1
.5
2
3
less loss in the activity and selectivity. It was demonstrated that the ZnCu alloy and Zn0
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were formed on the ZnCu/Al O catalysts and the ZnCu alloy was more active than the
2
3
0
0
2+
Cu species and could suppress the oxidation of Cu to Cu species during the reaction.
Moreover, the presence of Zn species also reduced the surface Lewis acid sites and so
the dehydration of 1,4-PDO to 2-MTHF was suppressed, leading to the selective
0
production of 1,4-PDO. The Zn additive prohibits the oxidation of Cu and the change
of Al O to Al(OH) , which are responsible for the improved stability of Zn Cu/Al O
3
2
3
3
1.5
2
catalyst.
Acknowledgment
This work is financially supported by the National Natural Science Foundation of China
21872134), National Program on Key Research Project (2016YFA0602900),
(
International Cooperation Project of Jilin Province (20170414012GH), and CAS
President’s International Fellowship Initiative (PIFI) 2018CV0012, Chinese Academy
of Science.
Author contributions
Dr Chao Zhang proposed the central idea, Mr. Qiang Liu did all the experiments, Mr.
Qiang Liu, Dr. Chao Zhang, Prof. Masahiko Arai, and Prof. Fengyu Zhao analyzed the
data and organized the paper, Prof. Zhenbo Zhao gave constructive suggestions for the
research, Miss Ke Liu, Miss Ruhui Shi, Mr. Peixuan Wu, Mr. Zhuangqing Wang, Dr.
Weiwei Lin and Dr. Haiyang Cheng also discussed this work.
References
1.
2.
3.
4.
5.
P. P. Upare, J.-M. Lee, D. W. Hwang, S. B. Halligudi, Y. K. Hwang and J.-S.
Chang, Journal of Industrial and Engineering Chemistry, 2011, 17, 287-292.
O. Mamun, M. Saleheen, J. Q. Bond and A. Heyden, Journal of Catalysis, 2019,
3
79, 164-179.
B. P. Pinto, A. L. L. Fortuna, C. P. Cardoso and C. J. A. Mota, Catalysis Letters,
017, 147, 751-757.
W. Li, J.-H. Xie, H. Lin and Q.-L. Zhou, Green Chemistry, 2012, 14,
388-2390.
2
2
B. Banerjee, R. Singuru, S. K. Kundu, K. Dhanalaxmi, L. Bai, Y. Zhao, B. M.
Reddy, A. Bhaumik and J. Mondal, Catalysis Science & Technology, 2016, 6,
5
102-5115.
6
.
H.-J. Feng, X.-C. Li, H. Qian, Y.-F. Zhang, D.-H. Zhang, D. Zhao, S.-G. Hong
and N. Zhang, Green Chemistry, 2019, 21, 1743-1756.
2
0

Page 21 of 24
Catalysis Science & Technology
View Article Online
DOI: 10.1039/D0CY00801J
7
8
.
.
Y. C. Ahn and J. Han, Bioresour Technology, 2017, 245, 442-448.
D. M. Alonso, S. G. Wettstein and J. A. Dumesic, Green Chemistry, 2013, 15,
84.
5
9
1
1
1
.
L. Corbel-Demailly, B. K. Ly, D. P. Minh, B. Tapin and C. Pinel,
ChemSusChem, 2013, 6, 2388-2395.
0.
1.
2.
H. Mehdi, V. Fábos, R. Tuba, A. Bodor, L. T. Mika and I. T. Horváth, Topics in
Catalysis, 2008, 48, 49-54.
M. Pagliaro, R. Ciriminna, H. Kimura, M. Rossi and C. Della Pina, Angewandte
Chemie International Edition, 2007, 46, 4434-4440.
J. P. Lange, R. Price, P. M. Ayoub, J. Louis and H. Gosselink, Angewandte
Chemie International Edition, 2010, 49, 4479-4483.
1
1
3.
4.
M. J. Climent, A. Corma and S. Iborra, Green Chemistry, 2014, 16, 516-547.
I. Obregón, I. Gandarias, M. G. Al-Shaal, C. Mevissen and R. Palkovits,
ChemSusChem, 2016, 9, 2488-2495.
15.
16.
17.
18.
V. Pace, D. P. Hoyos, L. Castoldi, D. P. D. d. María and A. R. Alcantara,
ChemSusChem, 2012, 5, 1369-1379.
D. Sun, T. Saito, Y. Yamada, X. Chen and S. Sato, Applied Catalysis A:
General, 2017, 542, 289-295.
X.-J. Zhai, C. Li, X. Di, D.-d. Yin and C.-h. Liang, Journal of Fuel Chemistry &
Technology, 2017, 45, 537-546.
X. Du, Q. Bi, Y. Liu, Y. Cao, H. He and K. Fan, Green Chemistry, 2012, 14,
9
35-939.
1
2
9.
0.
J. Wu, G. Gao, P. Sun, X. Long and F. Li, ACS Catalysis, 2017, 7, 7890-7901.
J. Wu, G. Gao, Y. Li, P. Sun, J. Wang and F. Li, Applied Catalysis B:
Environmental, 2019, 245, 251-261.
21.
22.
23.
24.
25.
I. Obregón, I. Gandarias, A. Ocio, I. García-García, N. Alvarez de Eulate and P.
L. Arias, Applied Catalysis B: Environmental, 2017, 210, 328-341.
P. P. Upare, J. M. Lee, Y. K. Hwang, D. W. Hwang, J. H. Lee, S. B. Halligudi,
J. S. Hwang and J. S. Chang, ChemSusChem, 2011, 4, 1749-1752.
Z. Xie, B. Chen, H. Wu, M. Liu, H. Liu, J. Zhang, G. Yang and B. Han, Green
Chemistry, 2019, 21, 606-613.
C. Zhang, Z. Huo, D. Ren, Z. Song, Y. Liu, F. Jin and W. Zhou, Journal of
Energy Chemistry, 2019, 32, 189-197.
H. Niu, J. Luo, C. Li, B. Wang and C. Liang, Industrial & Engineering
Chemistry Research, 2019, 58, 6298-6308.
2
1

Catalysis Science & Technology
Page 22 of 24
View Article Online
DOI: 10.1039/D0CY00801J
2
6.
M. Behrens, F. Studt, I. Kasatkin, S. Kuhl, M. Havecker, F. Abild-Pedersen, S.
Zander, F. Girgsdies, P. Kurr, B. L. Kniep, M. Tovar, R. W. Fischer, J. K.
Norskov and R. Schlogl, Science, 2012, 336, 893-897.
27.
28.
29.
30.
31.
32.
F. Zhang, Y. Liu, X. Xu, P. Yang, P. Miao, Y. Zhang and Q. Sun, Fuel
Processing Technology, 2018, 178, 148-155.
P. Kowalik, W. a. Próchniak, M. Konkol and T. Borowiecki, Applied Catalysis
A: General, 2012, 423-424, 15-20.
D. Li, S. Xu, Y. Cai, C. Chen, Y. Zhan and L. Jiang, Industrial & Engineering
Chemistry Research, 2017, 56, 3175-3183.
S.-C. Baek, S.-H. Kang, J. W. Bae, Y.-J. Lee, D.-H. Lee and K.-Y. Lee, Energy
&
Fuels, 2011, 25, 2438-2443.
H. Ham, S. W. Baek, C. H. Shin and J. W. Bae, ACS Catalysis, 2018, 9,
79-690.
O. F. G. E.D. Guerreiro, G. Larsen, L.A. Arrúa, Applied Catalysis A: General,
000, 204, 33–48.
6
2
3
3
3.
4.
E. P. Parry, Journal of Catalysis, 1963, 2, 371-379.
S. Kuld, C. Conradsen, P. G. Moses, I. Chorkendorff and J. Sehested,
Angewandte Chemie International Edition, 2014, 53, 5941-5945.
S. Kuld, M. Thorhauge, H. Falsig, C. F. Elkjaer, S. Helveg, I. Chorkendorff and
J. Sehested, Science, 2016, 352, 969-974.
35.
36.
37.
38.
39.
Y. Kanai, T. Watanabe, T. Fujitani, M. Saito, J. Nakamura and T. Uchijima,
Catalysis Letters, 1994, 27, 67-78.
C. Tisseraud, C. Comminges, T. Belin, H. Ahouari, A. Soualah, Y. Pouilloux
and A. Le Valant, Journal of Catalysis, 2015, 330, 533-544.
A. L. Valant, C. Comminges, C. Tisseraud, C. Canaff, L. Pinard and Y.
Pouilloux, Journal of Catalysis, 2015, 324, 41-49.
J. M. Camposmartin, A. Guerreroruiz and J. L. G. Fierro, Journal of Catalysis,
1
995, 156, 208-218.
4
4
0.
1.
T. H. Fleisch and R. L. Mieville, Journal of Catalysis, 1984, 90, 165-172.
S. D. Jones, L. M. Neal and H. E. Hagelin-Weaver, Applied Catalysis B:
Environmental, 2008, 84, 631-642.
42.
43.
44.
Melián-Cabrera, L. Granados, Terreros and Fierro, Catalysis Today, 1998, 45,
2
51-256.
M. C. Annesini, R. Lavecchia, L. Marrelli, M. Lojacono and P. Porta, Solid State
Ionics, 1993, 63-65, 281-288.
L. Gang, Z. Liang, Z. Zhijian, T. Hao, W. Tengfang and G. Jinlong, ACS
Catalysis, 2016, 6, 2158−2162.
2
2

Page 23 of 24
Catalysis Science & Technology
View Article Online
DOI: 10.1039/D0CY00801J
45.
46.
47.
A. Flura, F. Can, X. Courtois, S. Royer and D. Duprez, Applied Catalysis B:
Environmental, 2012, 126, 275-289.
Y. Shao, K. Sun, Q. Li, Q. Liu, S. Zhang, Q. Liu, G. Hu and X. Hu, Green
Chemistry, 2019, 21, 4499-4511.
M. L. Mihailović, S. Gojković and Ž. Čeković, Journal of the Chemical Society,
Perkin Transactions 1, 1972, 1, 2460-2464.
4
4
8.
9.
Á. Molnár, K. Felföldi and M. Bartók, Tetrahedron, 1981, 37, 2149-2151.
J. J. Bozell, L. Moens, D. C. Elliott, Y. Wang, G. G. Neuenscwander, S. W.
Fitzpatrick, R. J. Bilski and J. L. Jarnefeld, Resources Conservation &
Recycling, 2000, 28, 227-239.
5
5
5
5
5
5
0.
1.
2.
3.
4.
5.
R. V. Christian, H. D. Brown and R. M. Hixon, Journal of the American
Chemical Society, 1947, 69, 1961-1963.
I. Sádaba, M. López Granados, A. Riisager and E. Taarning, Green Chemistry,
2
015, 17, 4133-4145.
D. Wang, Y. Han, Y. Tan and N. Tsubaki, Fuel Processing Technology, 2009,
0, 446-451.
9
B. Liang, J. Ma, X. Su, C. Yang, H. Duan, H. Zhou, S. Deng, L. Li and Y.
Huang, Industrial & Engineering Chemistry Research, 2019, 58, 9030-9037.
G. Zhang, J. Yan, J. Wang, D. Jia, H. Zheng and Z. Li, Applied Surface Science,
2
018, 455, 696-704.
C. X. Chen, C.-H. Xu, L.-R. Feng, F.-L. Qiu and J.-S. Suo, Journal of Molecular
Catalysis A Chemical, 2006, 252, 171-175.
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Catalysis Science & Technology
Page 24 of 24
View Article Online
DOI: 10.1039/D0CY00801J
TOC
The presence of Zn can promote the activity and stability as well as adjust the product
selectivity, due to the appearance of new active species, which modified the surface
composition and thus prohibited the cyclodehydration of 1,4-PDO and surface change of
ZnCu/Al O catalyst during the reaction.
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