Synergistic effect for selective hydrodeoxygenation of anisole over Cu-ReOx/SiO2

Article abstract of DOI:10.1016/j.cattod.2020.04.034

Selective hydrodeoxygenation (HDO) of lignin derived oxygenated aromatic compounds has great significance for lignin utilization and chemicals production. Hereby, bifunctional catalysts of Cu-MO_x/SiO₂ (M = Re, Mo or W) were prepared to study the synergistic effect of Cu and MO_x on the performance of anisole HDO. Characterizations indicated that Cu interacted strongly with the second metal species. As a result, more efficient sites exposed on catalysts surface, and metal dispersion and surface properties both were improved. Besides, adsorption strength for both oxygen atom and aromatic ring in reactant were all adjusted due to Cu-MO_x interaction. Bimetallic catalyst Cu-ReO_x/SiO₂ showed the highest HDO activity, while Cu-MoO_x/SiO₂ and Cu-WO_x/SiO₂ both preferred transmethylation because of their prominent acid properties. The Cu-ReO_x composition was found to evidently affect the anisole conversion and selectivity of benzene, toluene and xylene (BTX). The highest BTX yield of 50.5 % could be achieved when Cu/Re ratio was 3.

Full text of DOI:10.1016/j.cattod.2020.04.034

Catalysis Today xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Catalysis Today
journal homepage: www.elsevier.com/locate/cattod
Synergistic effect for selective hydrodeoxygenation of anisole over Cu-ReOx/
SiO2
Xiaofei Wang , Wei Zhou , Yue Wanga,b,*, Shouying Huanga,b, Yujun Zhao , Shengping Wang ,
Xinbin Ma
a
a
a
a
a
a,b,
*
Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Centre of Chemical Science and Engineering, School of Chemical
Engineering and Technology, Tianjin University, Tianjin, 300072, China
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou, 350207, China
b
A R T I C L E I N F O
A B S T R A C T
Keywords:
Selective hydrodeoxygenation (HDO) of lignin derived oxygenated aromatic compounds has great significance
Anisole
for lignin utilization and chemicals production. Hereby, bifunctional catalysts of Cu-MO /SiO (M = Re, Mo or
W) were prepared to study the synergistic effect of Cu and MO on the performance of anisole HDO.
x
Characterizations indicated that Cu interacted strongly with the second metal species. As a result, more efficient
sites exposed on catalysts surface, and metal dispersion and surface properties both were improved. Besides,
x
2
Hydrodeoxygenation
Transmethylation
Bimetallic catalyst
x
adsorption strength for both oxygen atom and aromatic ring in reactant were all adjusted due to Cu-MO in-
teraction. Bimetallic catalyst Cu-ReO
x
/SiO
2
showed the highest HDO activity, while Cu-MoO
x
/SiO
2
and Cu-
WO /SiO both preferred transmethylation because of their prominent acid properties. The Cu-ReO
x
2
x
composi-
tion was found to evidently affect the anisole conversion and selectivity of benzene, toluene and xylene (BTX).
The highest BTX yield of 50.5 % could be achieved when Cu/Re ratio was 3.
1. Introduction
(eOH) are the most abundant functional groups in pyrolysis oil, phenol
and anisole are often chosen as model molecules [15].
Bioenergy, an environment friendly and renewable natural energy
A wide range of metallic catalysts have been studied in hydro-
deoxygenation of oxygenated aromatic compounds derived from lignin.
Noble metallic catalysts are the most efficient choice in this reaction
system due to their high activity and stability [16,17]. However, noble
metal catalysts caused saturated hydrogenation of aromatic ring easily,
resulting in generation of cycloalkanes and alkanes, etc. In order to
obtain aromatic hydrocarbon, base metallic catalysts such as Ni, Co
have been more frequently investigated because of their low cost, high
availability and moderate hydrogenation capacity. Ni and Co active
sites have been reported by previous literatures to exhibit satisfied
performance in HDO for oxygenated aromatic compounds. But they
preferentially interact with aromatic ring to produce hydrogenation
products such as cyclohexane, cyclohexanol under high temperature
derived from biomass, has attracted more and more attention from
various fields [1–3]. Among the bioresources, lignin is one constituent
of lignocellulose, and its content is only inferior to cellulose inside plant
(
constituting 15–35 wt. % of dry biomass) [4]. Besides, lignin is the
only renewable carbon source containing rich aromatic structures in
nature [5]. It is an important source to produce chemicals and trans-
portation fuel.
Fast pyrolysis [6,7] was reported to be maturely applied in lignin
depolymerization to produce bio-oil containing complex oxygenated
aromatic compounds. However, pyrolysis oil could not be used directly
because of its high oxygen and water content, which could lead to
following poor properties: low energy density, high viscosity and cor-
rosivity, thermally and chemical unstability, and immiscibility with the
fossil fuels [8,9]. Catalytic hydrodeoxygenation is one of the most cri-
tical upgrading methods to convert pyrolysis oil to deoxygenated pro-
ducts, such as alkane and aromatic hydrocarbon [9–14]. For laboratory
research, model compound representative in pyrolysis oil was usually
and H
favorable choice for hydrogenation of carbonyl and alcohol compounds
because of its high H activation capacity and inactivation for CeC
2
pressure [18–20]. On the other hand, metal Cu was reported as a
2
bonds hydrogenolysis [21–27]. Therefore, it is regarded potential in
promoting selective HDO for oxygenated aromatic compounds derived
from lignin.
3
applied for HDO study. Considering methoxyl (eOCH ) and hydroxyl
⁎
Corresponding authors at: Key Laboratory for Green Chemical Technology of Ministry of Education, Collaborative Innovation Centre of Chemical Science and
Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
E-mail addresses: yuewang@tju.edu.cn (Y. Wang), xbma@tju.edu.cn (X. Ma).
https://doi.org/10.1016/j.cattod.2020.04.034
Received 16 January 2020; Received in revised form 1 April 2020; Accepted 14 April 2020
0920-5861/ © 2020 Elsevier B.V. All rights reserved.
Please cite this article as: Xiaofei Wang, et al., Catalysis Today, https://doi.org/10.1016/j.cattod.2020.04.034

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
Besides the active metals mentioned above, the existence of Mo, Fe,
preparation, the powder samples were pressure into tablets and trans-
ferred into in situ reduction cell. The samples were firstly reduced at
350 °C for 1 h, and then cooled to 50 °C in vacuum. A background
spectrum was recorded after vacuumization for 30 min. Then, pyridine
was injected (3 μL per injection) into reaction cell with the flow of He
until adsorption saturation. The physical adsorption of pyridine was
removed through vacuumization for 30 min. Subsequently, a tempera-
ture programmed desorption (TPD) from 50 °C to 400 °C was conducted
with a heating rate of 3 °C/min, during which the spectra were con-
Re, W and some other oxophilic species in catalysts are more effective
for cleaving CaromeO bonds due to their nature affinity for oxygen or
coordinatively unsaturated metallic sites [28–36]. Moreover, acid sites
produced from coordinatively unsaturated metallic sites may also pro-
mote transalkylation on aromatic rings, which is beneficial for carbon
utilization [37,38]. Normally, both hydrogen dissociating sites and
oxophilic centers are expected for bifunctional HDO catalyst at the
same time, respectively responsible for hydrogenation (or hydro-
genolysis) and deoxygenation [39–42]. The balance between two active
sites in catalysts dominate the overall selectivity in the HDO of oxy-
genated aromatic compounds. Bimetallic catalysts, combining reducible
and oxophilic metal, have been identified as a promising choice in
hydrodeoxygenation reaction [43–45].
−
1
tinuously collected. All spectra were collected at a resolution of 4 cm
.
CO-FTIR was conducted on the same equipment as above. And all
pretreatments were also consistent with above operation. The back-
ground spectrum was collected at 30 °C in vacuum atmosphere. And
then, CO was introduced continuously into reaction cell for 30 min.
After adsorption saturation, the IR spectra were continuously collected
during the vacuumization process until the peak area was no longer
changing.
The H -TPR was conducted on Micromeritics Autochem Ⅱ 2920
2
instrument equipped with a thermal conductivity detector (TCD).
Sample (50 mg) was loaded into a quartz tube, following by dehy-
In this work, anisole, abundantly existing in bio-oil with typical
AReOeCH group [4,46], was selected as the probe molecule to study
3
C
HDO performance on Cu-based bimetallic catalysts. To promote HDO
activity, oxophilic metals Re, Mo and W were added to cooperate with
metal Cu in bimetallic catalysts. It was found the enhanced HDO ac-
tivity of anisole can be attributed to the improved metal dispersion and
surface properties of catalysts caused by synergistic effect between Cu
and oxophilic additives.
drating treatment for 1 h in N
cooled down to 50 °C and baseline was stable in 10 vol. % H
(
2
atmosphere. After the temperature
/N
60 mL/min), the sample was heated from 50 °C to 800 °C with a
2
2
2. Experimental
2
heating rate of 10 °C/min, and the H consuming signal was collected
by TCD detector.
2
.1. Catalyst preparation
The CO-TPD was conducted on the same equipment as above.
Sample (100 mg) was first reduced in situ at 350 °C for 1 h, then purged
with He for 1 h. After the temperature cooling down to room tem-
perature, the sample adsorbed CO for 30 min. Gas flow of He was used
to purge the CO weekly adsorbed on the surface of sample at 50 °C for
1 h until the baseline was stable. Finally, the sample was heated from
50 °C to 800 °C with a heat rate of 10 °C/min, and the CO signal was
recorded by TCD detector.
Cu-ReO
prepared by the method of incipient wetness co-impregnation. For Cu-
ReO /SiO example, Cu (NO ·3H O together with NH ReO (Cu
loading was 10 wt. % in all catalysts, Cu/Re molar ratio were ranging
from 5:1 to 1:1) were firstly uniformly dissolved in 4 mL distilled water.
x 2 x 2 x 2
/SiO , Cu-MoO /SiO and Cu-WO /SiO catalysts were all
x
2
3
)
2
2
4
4
2
Then 2 g commercial SiO was impregnated by above solution. After
drying at room temperature for 24 h and 110 °C for 12 h, the obtained
samples were calcinated at 500 °C for 4 h in flowing air. The precursors
The XPS and XAES were both measured on Perkin Elmer PHI 1600
ESCA with Al Kα laser resource (hν = 1486.6 eV) to get the information
of metals states on catalysts surface. All powder samples were reduced
ex situ at 350 °C and sealed in a glovebox (Mikrouna, Super 1220/750/
900). The samples were transferred into the measurement chamber
rapidly for vacuum degassing treatment and testing. The binding en-
ergy was calibrated by introducing C1s peak at 284.6 eV.
The product Benzene and reactant anisole were separately selected
as probe molecule for TPD characterization to analyze their adsorption
state on catalysts surface. And the test was conducted on a chemi-
sorption equipment with a flame ionization detector (FID). Sample
were reduced in H
characterizations. The reduced catalysts are all marked as nCu-MO
SiO (n means the molar ratio of Cu/M). Bimetallic Cu-MoO /SiO and
Cu-WO /SiO were also prepared as the same method, and the Cu/Mo
and Cu/W molar ratio were maintained at 2. Monometallic catalyst of
Cu/SiO and ReO /SiO were prepared as the same method, where Cu
and Re loadings were both 10 wt. %.
2
atmosphere at 350 °C before activity tests and
x
/
2
x
2
x
2
2
x
2
2.2. Catalyst characterization
(
200 mg) was loaded and reduced in situ at 350 °C for 1 h, then purged
with N (30 mL/min) for 1 h. Benzene was separately injected into the
sample tube in continuous N flow at 90 °C while anisole was injected at
160 °C, which were a little higher than their boiling points. After the
adsorption was saturated, N flow (30 mL/min) kept purging for 1 h to
To get the information of specific surface area and pore structure of
2
the catalyst, N
2
physical adsorption experiments were performed on a
2
Micromeritics Tristar 3000. The catalyst (70 mg) was prepared and
subjected to dehydration treatment at 200 °C for 4 h before the test.
Finally, the isothermal adsorption-desorption curve was obtained at
2
make the baseline stable enough. Finally, the sample was heated to
600 °C with a rate of 10 °C/min to get the FID signal.
−
2
196 °C in N atmosphere. The specific surface area and pore size
distribution were calculated through Brunauer-Emmett-Teller (BET)
and Barrett-Joyner-Halenda (BJH) method, respectively.
2.3. Catalyst test
The X-ray diffraction (XRD) was used to determine the catalysts
crystal structure on a Bruker D8-Focus with a Cu Kα radiation
The activity tests were carried out on a 100 mL stainless autoclave
with mechanical stirrer. Before test, catalysts were ex situ reduced at
(
λ = 1.54 Å). And all samples were scanned in the 2θ range from 10° to
90° with a scanning rate of 8°/min. Scherrer Formula was used to cal-
350 °C for 3 h and passivated by 1.0 vol. % O
1 g reactant (anisole), 20 g solvent (octane) and 150 mg catalyst were
put into the reactor. Before 2 MPa H was pressured for reaction, the
sealed reactor was purged with H for several times at room tempera-
2
/Ar for 1 h. For each test,
culate the crystal particle size.
Transmission electron microscopy (TEM) images and elements dis-
tribution analysis were obtained on JEM-2100 F (JEOL, 200 kV)
equipped with energy-dispersive spectroscopy (EDS) system. Before the
test, the reduced powder samples were dispersed in ethanol through
sonication and impregnated on copper grids. The metal particle sizes
were also measured from TEM images.
2
2
ture. Then the reactor was heated to 320 °C to conduct the reaction with
a continuous stirring of 600 rpm. The reactor was cooled to room
temperature after the reaction time was over, and liquid product was
collected through filtration before quantitative analysis by gas chro-
matography (GC, Agilent Micro 4890) equipped with a FID detector and
a DB-FFAP column (Agilent, 30 m × 320 μm × 1.0 μm). The qualitative
The test of in situ Fourier transform infrared spectra (FTIR) of
pyridine was conducted on Thermo Nicolet 6700. For samples
2

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
only metal Cu but also silica due to its oxophilicity [33], which supports
the above conclusion. Both 2Cu-MoO
fuzzy particles (flocculent structure) in TEM pictures, probably because
that unreduced MoO and WO clusters coated Cu particles.
Fig. 3 shows the H -TPR results for Cu/SiO and 2Cu-MO
M = Re, Mo and W). There is mainly one reduction peak at 240 °C with
a shoulder at around 270 °C on Cu/SiO , respectively assigned to re-
duction of bulk CuO and copper silicate [48]. For 2Cu-MO /SiO , H
consumption peaks lie in a relatively wide temperature range, involving
the reduction of Cu species, synchronous reduction of Cu and MO or
isolated MO . Re, Mo and W addition shift the Cu reduction peak to
x 2 x 2
/SiO and 2Cu-WO /SiO present
x
x
2
2
x 2
/SiO
(
2
x
2
2
x
x
higher temperature because of the interaction between Cu and the
second metal species. The reduction peak at around 300 °C on 2Cu-
ReO /SiO appears to be stronger and narrower compared with the
x 2
other catalysts, which suggests the mono-structure and more strong
interaction between Cu and Re. There is no obvious reduction peak at
temperature higher than 400 °C on 2Cu-ReO
appears at high temperature on 2Cu-MoO /SiO
WO /SiO (∼600 °C), which is consistent with that in published reports
49–51]. Combining the integral results of H -TPR curves in Table S1,
ReO species has a greater reduction degree at current reaction condi-
tions than MoO and WO species.
x
/SiO
2
, while a broad peak
(∼680 °C) and 2Cu-
x
2
x
2
[
2
x
2 x 2
Fig. 1. XRD patterns of reduced Cu/SiO and 2Cu-MO /SiO (M = Re, Mo and
W).
x
x
It is well known that acid property has great influence for reaction
routes and products distribution [52,53]. To explore the acid properties
results were got on gas chromatograph-mass spectrometer (GC–MS,
Agilent 7890B-5977A) with HP-INNOWax column
30 m × 250 μm × 0.5 μm).
The results of anisole conversion and products selectivity were
calculated by the following formulas (where n represent the moles of a
certain component):
of Cu/SiO2 and 2Cu-MO /SiO2 (M = Re, Mo and W), pyridine was se-
x
a
lected as a probe molecule for FTIR-TPD analysis, because it has a si-
(
milar molecular size with anisole [54]. As the results shown in Fig. 4,
Lewis acid is found as the major acid site for all samples. Only a weak
−1
peak assigned to Brönsted acid appeared at 1540 cm
on 2Cu-MoOx/
SiO , which stems from the surface hydroxyls introduced by MoO .
2
x
−1
As the Py-IR-TPD spectra show, Lewis acid amount at 1450 cm
Conversion (X, %) = (nAnisole,consumed/nAnisole, input) × 100 %;
varies among different catalysts. And the desorption curves, which
Selectivity (S
i
, %) =n
i
/(nAnisole, consumed) × 100 %;
present the integral area changing with temperature, reveal the total
Lewis acid amount as following range: 2Cu-MoO
x
/SiO
2
(4.6) > 2Cu-
Yields (Y ) = X × S
represents the total deoxygenated products yield).
i
i
×100 % (Note: Hydrodeoxygenation yield (YHDO)
ReO /SiO (3.3) ≈ 2Cu-WO /SiO (3.2) > Cu/SiO
x
2
x
2
2
(0.9). In addition,
the derivative analysis of desorption curves shows the pyridine deso-
rption rate over temperature. All catalysts show more than one acid
centers. The amount ratios of relative weak and stronger acid (written
as W/S) were calculated based on the desorbed pyridine amount (with a
boundary of 250 °C), respectively were 3.4, 4.7, 3.2 and 2.8 for Cu/
3. Results and discussion
3
3
.1. Effect of MO in Cu-based bimetallic catalyst
x
SiO
them, 2Cu-ReO
WO /SiO has stronger acid as its main acid sites.
2
, 2Cu-ReO
x
/SiO
2
, 2Cu-MoO
x 2 x 2
/SiO and 2Cu-WO /SiO . Among
x
/SiO
2
has the highest percent of weak acid, while 2Cu-
.1.1. Characterizations of Cu-MO
As XRD patterns shown in Fig. 1, Cu characteristic peaks evidently
x
/SiO
2
x
2
0
0
exist in all reduced catalysts. And Cu diffraction peaks become broader
x 2
3.1.2. HDO performance of Cu-MO /SiO
and weaker with a second metal insertion, the result suggests that MO
x
Anisole was selected as a model compound to test the catalysts
performance. As shown in Fig. 5, anisole conversion of 10.4 % with 1.0
addition improve metal Cu dispersion. Average Cu0 crystalline sizes
calculated by Scherrer equation are 12.9, 7.1 and 8.9 nm respectively
2
% BTX yield and 6.6 % deoxygenation yield was obtained over Cu/SiO .
After Re, Mo and W addition, the anisole conversion reached 98.3 %,
58.0 % and 74.4 % respectively. The highest BTX and hydro-
0
on Cu/SiO
peak appears on the curve of 2Cu-ReO
phase Re (101) at 42.9° partially overlaps with Cu (111) at 43.3°. The
situation turns to be different for 2Cu-MoO /SiO and 2Cu-WO /SiO
2
, 2Cu-MoO
x
/SiO
2
and 2Cu-WO
x
/SiO
2
. Re characteristic
x
2
/SiO with its main crystalline
deoxygenation yield were both achieved on 2Cu-ReO
with those on 2Cu-MoO /SiO , 2Cu-WO /SiO and Cu/SiO
attributed to the excellent oxophilic capacity of Re species [55,56] and
the strong interaction between Cu and ReO . However, the products
distribution in Fig. 5 shows various trends on different catalysts. Phe-
nols and cyclohexane are main products on Cu/SiO with respective
selectivity of 36.2 % and 39.6 %, and BTX selectivity is only 12.1 %.
2Cu-ReO /SiO had BTX and cyclohexane as its main products with
selectivity of 35.3 % and 47.3 %, respectively. And almost no oxyge-
nated products were produced on 2Cu-ReO /SiO . For both 2Cu-MoO
SiO and 2Cu-WO /SiO , phenols are the main products with selectivity
of 44.9 % and 44.0 %, confirming the lower deoxygenation capacity
compared with 2Cu-ReO /SiO
x
/SiO
2
compared
x
2
x
2
,
x
2
x
2
2
. It could be
0
0
where no Mo or W characteristic peaks is found because Mo and W
species are more difficult to be reduced to metallic state in catalysts
x
[
37,47]. Metal oxide phases ReO
are almost invisible in XRD patterns due to their high dispersion. Be-
sides, Cu O characteristic peaks are found to be more intense on 2Cu-
ReO /SiO . It indicates that the crystallinity of Cu O was improved
under the interaction of Cu with ReO species.
TEM images of reduced Cu/SiO , 2Cu-ReO
and 2Cu-WO /SiO are presented in Fig. 2. Bimetallic samples have
smaller metal particles compared with Cu/SiO , which is in good
agreement with above XRD results. Especially for 2Cu-ReO /SiO
x x x
, MoO and WO characteristic peaks
2
2
x
2
2
x
2
x
2
x
/SiO
2
, 2Cu-MoO
x
/SiO
2
x
2
x
/
x
2
2
x
2
2
x
2
,
x
2
.
much smaller metal particles (∼ 5.8 nm) were found to distribute
evenly on support. The textural properties results are summarized in
Table S2. It has been reported that metal Re interacts strongly with not
Besides hydrogen activation and oxygen affinity capacity, acid
property is also an important factor for catalytic performance.
Appropriate acid strength and amount are beneficial for deoxygenation
3

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
2 x 2
Fig. 2. TEM images of reduced Cu/SiO and 2Cu-MO /SiO (M = Re, Mo or W).
much higher level at 28.8 % and 41.6 % respectively. According to the
above FTIR-TPD of pyridine result, the W/S ratio decreased in the
following
order: 2Cu-ReO
x 2 2 x
/SiO > Cu/SiO > 2Cu-MoO /
SiO > 2Cu-WO
2
x
/SiO , just opposite to the methyl-products se-
2
lectivity. C. Ranga et al. reported that phenol intermediate can dis-
sociate and adsorb strongly on the stronger acid sites to facilitate the
methylation process [59]. The higher percent of strong acid, the more
favorable for transmethylation. On the other hand, methyl-phenols and
methyl-anisoles are the main transmethylation products on 2Cu-MoO
SiO , while more methyl-benzenes and methyl-phenols are formed on
Cu-WO /SiO . The different methyl-products distribution confirms the
disparate role of MO in Cu-MO /SiO
x
/
2
2
x
2
x
x
2
.
Considering the differences on product distribution, the bimetallic
catalysts were evaluated for different reaction time to further verify the
reaction routes. The 2Cu-ReO
SiO activity results are respectively shown in Fig. 6(a)–(c). Anisole
conversion and hydrodeoxygenation yield both gradually increased
with reaction time on all catalysts. And 2Cu-ReO /SiO always had the
highest conversion (69.9 %–98.3 %) and HDO yield (69.7 %–98.3 %).
BTX yield on 2Cu-ReO /SiO also appears to be much higher than the
other two catalysts, and the maximum is 38.5 % at 2 h.
For 2Cu-ReO /SiO at initial reaction stage (0.5 h), benzene and
x 2 x 2 x
/SiO , 2Cu-MoO /SiO and 2Cu-WO /
2
x
2
x
2
2 x 2
Fig. 3. TPR profiles of reduced Cu/SiO and 2Cu-MO /SiO (M = Re, Mo and
W).
x
2
cyclohexane are the two dominant products with selectivity of 51.6 %
and 39.9 %, respectively. As reaction time prolonged, benzene se-
lectivity gradually decreased to 34.6 % while cyclohexane selectivity
showed an opposite trend with a maximum value of 47.3 % at 4 h.
as well as transmethylation [37,52,53,57,58]. Table 1 presents the
methyl-transfer products distribution on Cu/SiO and 2Cu-MO /SiO
M = Re, Mo, and W). Obviously, there are almost no methyl-transfer
products on Cu/SiO and 2Cu-ReO /SiO . The selectivity of total me-
thyl-transfer products on 2Cu-MoO /SiO and 2Cu-WO /SiO reach
2
x
2
(
However, phenol is the main product on both 2Cu-MoO
x 2
/SiO and 2Cu-
2
x
2
WO /SiO with selectivity of 54.5 % and 52.3 % at 0.5 h, and decreased
x
2
x
2
x
2
4

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
2 x 2
Fig. 4. In-situ Py-IR-TPD spectra and acid desorption or desorption rate curves related to temperature for Cu/SiO and 2Cu-MO /SiO (M = Re, Mo and W; the FTIR-
TPD spectra have the same Z axis range).
5

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
Fig. 5. Catalytic activity of anisole HDO on Cu/SiO
2
and 2Cu-MO
x
/SiO
2
(M = Re, Mo and W). (Reaction conditions: anisole = 1.0 g, octane = 20 g, initial H
2
pressure = 2.0 MPa, reaction temperature = 320 °C, reaction time = 4 h, catalyst loading = 150 mg.).
Table 1
3.2.1. Characterizations of Cu-ReO
In order to study the reduction capacity of Cu/SiO
Cu-ReO /SiO , H
Fig. 7. Reduction peak on 5Cu-ReO
shifts slightly to higher temperature compared with that of Cu/SiO
attributed to the simultaneous reduction of Cu and Re species. More-
x
interaction
Methyl-transfer products selectivity on Cu/SiO
Mo and W). (Reaction conditions: anisole = 1.0 g, octane = 20 g, initial H
pressure = 2.0 MPa, reaction temperature = 320 °C, reaction time = 4 h, cata-
lyst loading = 150 mg.).
2
and 2Cu-MO
x
/SiO
2
(M = Re,
and bimetallic
2
2
x
2
2
-TPR was conducted, and the results are shown in
/SiO located at 268 °C, which
, is
x
2
2
Catalyst
Methyl-
benzenes /%
Methyl-
phenols /%
Methyl-
anisoles /%
Total methyl-
products /%
º
x 2
over, the shoulder peak at 248 C on 5Cu-ReO /SiO indicates the re-
duction of isolated Cu particles. With Re content increasing, the main
reduction peak shifts to higher temperature followed by a slight de-
Cu/SiO
2
1.0
0.7
1.9
7.4
0
0
13.2
18.4
0
0
8.4
6.1
1.0
0.7
28.8
41.6
Cu
2
Cu
2
Cu
2
ReO
MoO
WO /SiO
x
/SiO
2
x
/SiO
2
crease. The reduction peak on 3Cu-ReO
temperature of 280 °C, and appears to be sharper and more intense. It
means there is a stronger interaction between Cu and ReO on 3Cu-
ReO /SiO . When Cu/Re molar ratio is less than 3:1, a shoulder peak
appears at ∼310 °C, which is assigned to the reduction of agglomerated
Re particle. ReO species were enhanced to be reduced in Cu-ReO /SiO
with appropriate Cu/Re ratio, which is also consistent with the results
of integral analysis of H -TPR in Table S1.
Fig. 8 shows wide angle XRD results (a) and partial enlarged pat-
terns (b) of nCu-ReO /SiO . For Cu/SiO , there are three characteristic
peaks for Cu located at 43.3°, 50.4°and 74.1°, represent Cu (111), Cu
200) and Cu (220) respectively. No evident shift for Cu diffraction
x 2
/SiO present at a higher
x
2
x
MNT_ELSEVIER_JOURNAL_CATTOD_12813_110
x
2
gradually to 31.6 % and 25.6 % at 4 h respectively. For 2Cu-MoO
SiO , the selectivity of methyl-products, mainly methyl-phenols and
methyl-anisoles, increased at the expense of phenol and anisole. And on
Cu-WO /SiO , cyclohexane selectivity gradually increased. The pro-
x
/
x
x
2
2
2
2
x
2
cess of transmethylation and hydrogenation of aromatic rings both
proved to be enhanced with reaction time. On the other hand, the total
methyl-products selectivity at 0.5 h was respectively 4 % and 41 % on
x
2
2
(
peaks is observed after the addition of Re, which means there is no alloy
formed. In the range of Cu/Re molar ratio from 5:1 to 3:1, the Cu (111)
diffraction peak turns to be broad and weak due to the promoting effect
2
%
Cu-MoO
x 2 x 2
/SiO and 2Cu-WO /SiO , and respectively changed to 23.5
and 31.9 % after 4 h. The changes indicated the properties of MO
x
affect initial rate of transmethylation.
x
of ReO . Diffraction peak for Re species was negligible when Cu/Re
Based on above discussion, the reaction pathways on the Cu-MO
x
/
molar ratio was higher than 3, because of the high Re species disper-
sion. When the Re content was further increased, the diffraction peak of
Re (101) at 42.9° appeared. It indicates that excessive Re agglomerates
SiO
phenol was detected, direct demethoxylation of anisole to benzene was
regarded as the dominant route for benzene production on 2Cu-ReO
SiO . And cyclohexane, as a major by-product, was coming from ben-
zene ring hydrogenation on all catalysts. Transmethylation reaction
happened mainly on 2Cu-MoO /SiO and 2Cu-WO /SiO with more
2
(M = Re, Mo or W) are presumed as Scheme 1. Considering little
x
/
into isolated Re particles, in accordance with above H
The TEM images of nCu-ReO /SiO are shown in Fig. 9. Cu/SiO
owns large and uniform particle size of 13 nm. With more Re addition,
metal particle size is firstly reduced to 5 nm on 3Cu-ReO /SiO , and
then goes up to 8.8 nm on 1Cu-ReO /SiO . This result further proved
2
-TPR results.
2
x
2
2
x
2
x
2
acid sites. Notably, there is no methanol detected in products, it is
supposed that methanol hydrogenolysis happened with high tempera-
x
2
x
2
that moderate amount of Re is beneficial to improve metal dispersion,
while Re particles agglomerate on bimetallic catalysts with Cu/Re
molar ratio less than 3:1. To further explore the distribution of Cu and
ture and H
2
pressure [60].
3.2. Cu-ReO
x
synergistic effect for anisole HDO
x 2
Re species in metal particles, STEM-EDS of reduced 3Cu-ReO /SiO was
also tested as shown in Fig. S1. EDS mapping and line-scanning results
show Cu and Re distribute evenly, which is in line with previous report
According to the above results, Re species was selected as the ad-
ditive to Cu/SiO to further improve BTX yield. Interaction between Cu
and ReO was also comprehensively explored through adjusting Cu/Re
molar ratio.
2
that metal Cu owns high affinity to Re surface [61]. In addition, N
physical adsorption results (shown in Table S3) also agrees well with
2
x
6

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
Fig. 6. Catalytic performance of (a) 2Cu-ReO
x
/SiO
2
(b) 2Cu-MoO
x
/SiO
2
and (c) 2Cu-WO
x
/SiO
2
for anisole conversion for different reaction time. (Reaction con-
ditions: anisole = 1.0 g, octane = 20 g, initial H
2
pressure = 2.0 MPa, reaction temperature = 320 °C, catalyst loading = 150 mg.).
above conclusion.
Fig. 10 reveals the XPS results of Cu 2p3/2, Re 4f and XAES spectra
of Cu LMM for nCu-ReO /SiO . Spectrum of Cu 2p in Fig. S2 shows two
x
2
peaks respectively locate at ∼932.6 eV (2p3/2) and ∼952.6 eV (2p1/2),
the absence of satellite peak at ∼944 eV confirms the complete re-
duction of CuO to Cu0 or Cu . For nCu-ReO
+
/SiO
, the Cu binding
x
2
energy (BE) shifts slightly to higher value of 932.8 eV on 2Cu-ReO
SiO and 1Cu-ReO /SiO compared with that on Cu/SiO (Cu 2p3/2 at
32.6 eV). This BE shift for Cu 2p proves that electrons are transferred
x
/
2
x
2
2
9
from Cu to Re.
Spectra of Re 4f present only one broad peak ranging from 35.0 eV
0
4+
6+
7+
to 55.0 eV, which was fitted to covers Re , Re , Re
cies (Re0 4f7/2 BE was fixed at 40.4 eV) in Fig. 11(b). However, the Re
5/2 and Re 4f7/2 partially overlapped for each doublet, they were
and Re
spe-
x 2
Scheme 1. Anisole conversion network on 2Cu-MO /SiO (M = Re, Mo, W).
4f
fitted based on the fixed relative intensity (area ratio = 3:4) and se-
paration (2.4 eV). The relative amount of Cu0 and Cu+ was also ana-
lyzed by XAES of Cu LMM in Fig. 10(c). Table S4 summarizes dis-
tribution of different oxidation states of Cu and Re species and the
reduction degree calculated from fitting results. Both Cu and Re species
show the higher reduction degree among bimetallic Cu-ReO /SiO . It
x 2
means that moderate amount of Re promotes metal sites exposing on
surface and decrease the interaction of Cu and support because of more
and more Cu-ReO
leads to lower reduction degrees than the value on Cu/SiO
SiO
x
sites formation. However, Cu-ReO
x
sites formation
2
and ReO /
x
2
.
Fig. 11 presents the in-situ CO-FTIR and CO-TPD profiles of nCu-
ReO /SiO . CO-FTIR spectra show a peak located in the range of 2120
2140 cm
adsorbed CO on Cu. The CO adsorption on ReO
about 10 wt %) is almost invisible because of the low adsorption ca-
pacity for CO on Re surface [33,62,63]. For bimetallic Cu-ReO /SiO
the adsorption capacity is gradually improved when Re content in-
crease, and the most intense peak appears on 1Cu-ReO /SiO . Besides,
on Cu/SiO to
, and a further shift happens from 5Cu-
x
2
−
1
∼
for bimetallic Cu-ReO
x
/SiO
2
, which belongs to linear-
/SiO (Re loading is
x
2
x
2
,
x
2
−1
the adsorption band blue-shifts from 2120 cm
130 cm
2
−1
2
on 5Cu-ReO
to 1Cu-ReO
x
/SiO
/SiO
2
2 2 x 2
Fig. 7. H -TPR profiles of precursors Cu/SiO and nCu-ReO /SiO .
−
1
ReO /SiO
x
2
x
2
(2136 cm ). The result indicates that
7

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
x 2
Fig. 8. XRD patterns of (a) reduced nCu-ReO /SiO and (b) partial enlarged spectra.
interaction between Cu and ReO
Re.
x
lead to an electron transfer from Cu to
to CO-adsorbing on Cu species strongly interacted with ReO
the intensity and position of peak 3 are both improved with Re content
increasing, especially for 2Cu-ReO /SiO and 1Cu-ReO /SiO with
much higher Re content than the others (including ReO /SiO ).
Similarly, there also appears a small shoulder peak on 2Cu-ReO /SiO
and 1Cu-ReO /SiO2 in CO-FTIR. Therefore, the high Re loading and
x
. However,
For Cu/SiO
2
, there is only one CO adsorption peak (peak 1) at about
x
2
x
2
138 °C. With Re addition, another two peaks (peak 2 and peak 3)
x
2
emerge at higher temperature. And peaks shift to higher temperature
with Re content increasing, especially for peak 3. Peak 1 is pointed as
the weak adsorption of CO on Cu, as well as a little amount of physical
adsorption. Considering the intensity of Peak 2 has no liner relationship
with Cu/Re molar ratio changing from 3:1 to 1:1, this peak is assigned
x
2
x
particle aggregation are thought to cause a little of CO adsorption in
peak 3.
Fig. 9. TEM images and metal particle size distribution of reduced nCu-ReO
ReO /SiO , (f) 1Cu-ReO /SiO ).
x 2 2 x 2 x 2 x 2
/SiO ((a) Cu/SiO , (b) 5Cu-ReO /SiO , (c) 4Cu-ReO /SiO , (d) 3Cu-ReO /SiO , (e) 2Cu-
x
2
x
2
8

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
x 2
Fig. 10. XPS spectra of Cu 2p3/2 (a), XPS spectra of Re 4f (b) and XAES spectra of Cu LMM (c) for nCu-ReO /SiO .
3
.2.2. Anisole and benzene TPD (ANI-TPD and BEN-TPD)
In order to further reveal the reaction mechanism of anisole HDO to
indicates that Cu-ReO
capable for adsorbing anisole. As a selective hydrodeoxygenation pro-
duct, benzene adsorbed less on Cu/SiO and ReO /SiO , and its ad-
sorption amount slightly increase with Cu/Re molar ratio decreasing.
There appears another benzene adsorption peak appeared during 400
x
synergistic sites make catalysts surfaces more
benzene, anisole and benzene were selected as probe molecules for
TPD. As shown in Fig. 12, anisole adsorption amount on both Cu/SiO
and ReO /SiO show to be much lower than nCu-ReO /SiO . Even on
Cu-ReO /SiO , the adsorption amount is far greater than the sum
amount on Cu/SiO and ReO /SiO . The adsorption amount on bime-
tallic Cu-ReO /SiO gradually increased with more Re addition. It
2
x
2
2
x
2
x
2
5
x
2
∼ 500 °C on Cu/SiO
sorption capacity [64], the peak at high temperature is assigned to the
benzene adsorbed on Cu interacted with support. However, Cu-ReO
x
2
. Considering the isolated Cu almost has no ad-
2
x
2
x
2
x 2
Fig. 11. CO-FTIR (a) and CO-TPD (b) spectra of reduced nCu-ReO /SiO .
9

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
Fig. 12. Probe molecule of anisole and benzene temperature-programed desorption on nCu-ReO
x
/SiO
2
. (adsorption temperature: anisole at 90 °C and 160 °C re-
spectively.).
interaction decreased the interaction of Cu and support, which leads to
a decline of benzene adsorption strength. Appropriate Cu-ReO inter-
action is beneficial for both anisole adsorption and benzene desorption,
or esters [27], but is almost inert for deoxygenation in oxygenated
aromatic compounds [64]. And Re is widely recognized as an oxophilic
metal in oxygenated aromatic compounds HDO process [65–68].
x
and BTX selectivity was increased as a result.
Herein, Cu-ReO
x
sites formation provs to be beneficial for decreasing Cu
or ReO ensemble effect and modifying electronic properties, which
x
could enhance selective HDO activity and reduce side reaction such as
aromatic rings hydrogenation.
3
.2.3. HDO performance of nCu-ReO
The catalytic performance results for anisole HDO on nCu-ReO
are shown in Fig. 13. Anisole conversion and deoxygenation yield
x 2
/SiO
x
/
Cyclohexane, as the main side product, shows almost an opposite
change compared with benzene, which indicates it is the further hy-
drogenation product from benzene. Anyway, cyclohexane selectivity
always keeps high above 30 % even when the anisole conversion is very
low. This is ascribed to the nature properties of Cu species. And cy-
clohexane selectivity further increases with Cu/Re ratio changing from
SiO
2
is significantly enhanced with Re addition, and the products composi-
tion changed obviously as well.
BTX (mainly benzene) yield and selectivity both show an increase
from Cu/Re = 1:0 to 3:1 followed by a drop from Cu/Re = 3:1 to 0:1.
The highest BTX selectivity of 58.2 % and yield of 50.5 % appear both
on 3Cu-ReO
teraction. Considering above ANI-TPD and BEN-TPD results, synergistic
effect of Cu-ReO sites modified the surface properties for molecule
adsorption, leading to both higher activity and BTX selectivity.
According to previous literature, Cu has excellent H activation capa-
city and hydrogenation ability for CeO and C]O bond in fatty alcohols
3:1 to 1:1 due to more Re particles agglomerating on Cu. Interaction
x 2 x
/SiO , which proves to obtain the strongest Cu-ReO in-
between Cu and ReO also turns to be weak when excess ReO ag-
x
x
glomerating on Cu, which is consistent with the rising metal particle
size on surface. Besides, according to previous reports [69–71], the
saturated hydrogenation of aromatic rings was a structure sensitive
process. Hydrogenation prefer to occur on larger metal particles. It is
x
2
worth noting that the other products produced on nCu-ReO
x
/SiO
2
contain mainly C-C hydrogenolysis products and a little oligomer.
4. Conclusion
Introduction of appropriate amount of ReO
x
to Cu/SiO
2
remarkably
improved metal distribution and interaction between Cu and ReO
most Cu-ReO synergistic sites were exposed on the surface of 3Cu-
, which gave the best HDO performance. However, excess
x
, the
x
ReO
ReO
ReO
x
x
x
/SiO
2
led to poor metal dispersion and weak interaction between Cu and
. In addition to geometric interaction, electronic interaction was
presented as electron transferring from Cu to Re based on XPS and CO-
FTIR results. Both geometric and electronic interaction between Cu and
Re species seemed to be beneficial for modifying the adsorption states
of molecules on metal surface, which realized higher selective HDO.
The performance of Cu /SiO
ophilic metal species addition. The anisole HDO activity, deoxygena-
tion selectivity and BTX selectivity showed higher value on Cu-ReO
SiO than Cu-MoO /SiO and Cu-WO /SiO . Anisole conversion was
2
was promoted remarkably with ox-
x
/
2
x
2
x
2
gradually improved with Re adding, and almost near to 100 % when
Cu/Re molar ratio is 1:1. And the highest BTX yield (50.5 %) was ob-
tained on 3Cu-ReO /SiO .
x 2
Fig. 13. Catalytic performance of Cu-ReO
x 2
/SiO with different Cu/Re molar
ratio. (Reaction conditions: anisole = 1.0 g, octane = 20 g, initial
pressure = 2.0 MPa, reaction temperature = 320 °C, reaction time = 4 h, cata-
lyst loading = 150 mg.).
H
2
CRediT authorship contribution statement
Xiaofei Wang: Conceptualization, Methodology, Investigation,
10

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
Writing - original draft. Wei Zhou: Conceptualization, Methodology.
Yue Wang: Methodology, Resources, Writing - review & editing.
Shouying Huang: Methodology, Resources. Yujun Zhao:
Methodology, Resources. Shengping Wang: Methodology. Xinbin Ma:
Conceptualization, Methodology, Supervision, Resources, Project ad-
ministration, Writing - review & editing.
model compound over supported Ni and Co catalysts: effect of metal and support
properties, Catal. Today 243 (2015) 163–172.
19] Y. Zheng, N. Zhao, J. Chen, Enhanced direct deoxygenation of anisole to benzene on
SiO -supported Ni-Ga alloy and intermetallic compound, Appl. Catal. B Environ.
2
250 (2019) 280–291.
2
20] X. Wang, J. Chen, Effects of indium on Ni/SiO catalytic performance in hydro-
deoxygenation of anisole as model bio-oil compound: suppression of benzene ring
hydrogenation and C–C bond hydrogenolysis, Chin. J. Catal. 38 (2017) 1818–1830.
21] R.P. Ye, L. Lin, C.C. Chen, J.X. Yang, F. Li, X. Zhang, D.J. Li, Y.Y. Qin, Z. Zhou,
[
[
[
Declaration of Competing Interest
2
Y.G. Yao, Synthesis of Robust MOF-derived Cu/SiO catalyst with low copper
loading via sol - gel method for the dimethyl oxalate hydrogenation reaction, ACS
Catal. 8 (2018) 3382–3394.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
[22] H. Yue, Y. Zhao, S. Zhao, B. Wang, X. Ma, J. Gong, A copper-phyllosilicate core-
sheath nanoreactor for carbon–oxygen hydrogenolysis reactions, Nat. Commun. 4
(2013) 2339.
[
23] D. Yao, Y. Wang, Y. Li, Y. Zhao, J. Lv, X. Ma, A high-performance nanoreactor for
carbon–oxygen bond hydrogenation reactions achieved by the morphology of na-
notube-assembled hollow spheres, ACS Catal. 8 (2018) 1218–1226.
Acknowledgement
[
24] E.S. Vasiliadou, T.M. Eggenhuisen, P. Munnik, P.E.D. Jongh, K.P.D. Jong,
2
A.A. Lemonidou, Synthesis and performance of highly dispersed Cu/SiO catalysts
The work was supported by National Natural Science Foundation of
China (21938008).
for the hydrogenolysis of glycerol, Appl. Catal. B Environ. 145 (2014) 108–119.
25] E.S. Vasiliadou, A.A. Lemonidou, Kinetic study of liquid-phase glycerol hydro-
[
2
genolysis over Cu/SiO catalyst, Chem. Eng. J. 231 (2013) 103–112.
[
26] B. Li, L. Li, H. Sun, C. Zhao, Selective deoxygenation of aqueous furfural to 2-me-
0
Appendix A. Supplementary data
thylfuran over Cu /Cu O· SiO sites via a copper phyllosilicate precursor without
2
2
extraneous gas, ACS Sustain. Chem. Eng. 6 (2018) 12096–12103.
27] Y. Wang, Y. Shen, Y. Zhao, J. Lv, S. Wang, X. Ma, Insight into the balancing effect of
active Cu species for hydrogenation of carbon–oxygen bonds, ACS Catal. 5 (2015)
6200–6208.
[
[
[
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.cattod.2020.04.034.
28] I.T. Ghampson, G. Pecchi, J.L.G. Fierro, A. Videla, N. Escalona, Catalytic hydro-
x 2 x 2
deoxygenation of anisole over Re-MoO /TiO and Re-VO /TiO catalysts, Appl.
Catal. B Environ. 208 (2017) 60–74.
29] P. Sirous-Rezaei, J. Jae, J.M. Ha, C.H. Ko, J.M. Kim, J.K. Jeon, Y.K. Park, Mild
References
[
1] D.A. Ruddy, J.A. Schaidle, J.R. Ferrell lii, J. Wang, L. Moens, J.E. Hensley, Recent
advances in heterogeneous catalysts for bio-oil upgrading via “ex situ catalytic fast
pyrolysis”: catalyst development through the study of model compounds, Green
Chem. 16 (2014) 454–490.
hydrodeoxygenation of phenolic lignin model compounds over a FeReO /ZrO
catalyst: zirconia and rhenium oxide as efficient dehydration promoters, Green
Chem. 20 (2018) 1472–1483.
x
2
[30] Y. Takeda, Y. Nakagawa, K. Tomishige, Selective hydrogenation of higher saturated
[2] M. He, Y. Sun, B. Han, Green carbon science: scientific basis for integrating carbon
resource processing, utilization, and recycling, Angew. Chemie Int. Ed. English 52
x 2
carboxylic acids to alcohols using a ReO –Pd/SiO catalyst, Catal. Sci. Technol. 2
(2012) 2221–2223.
(
2013) 9620–9633.
[31] Y. Amada, H. Watanabe, M. Tamura, Y. Nakagawa, K. Okumura, K. Tomishige,
Structure of ReO Clusters attached on the Ir metal surface in Ir–ReO /SiO for the
hydrogenolysis reaction, J. Phys. Chem. C 116 (2012) 23503–23514.
[32] F. Yang, H. Wang, J. Han, Q. Ge, X. Zhu, Influence of Re addition to Ni/SiO
on the reaction network and deactivation during hydrodeoxygenation of m-cresol,
Catal. Today (2018).
[33] F. Yang, D. Liu, H. Wang, X. Liu, J. Han, Q. Ge, X. Zhu, Geometric and electronic
effects of bimetallic Ni–Re catalysts for selective deoxygenation of m-cresol to to-
luene, J. Catal. 349 (2017) 84–97.
[34] A.J. Hensley, Y. Wang, D. Mei, J.S. McEwen, Mechanistic effects of water on the Fe-
catalyzed hydrodeoxygenation of phenol. The role of Brønsted acid sites, ACS Catal.
8 (2018) 2200–2208.
[35] S. Song, J. Zhang, G. Gözaydın, N. Yan, Production of terephthalic acid from corn
stover lignin, Angew. Chemie Int. Ed. English 131 (2019) 4988–4991.
[36] S. Song, J. Zhang, N. Yan, Support effects in the de-methoxylation of lignin
monomer 4-propylguaiacol over molybdenum-based catalysts, Fuel Process.
Technol. 199 (2020) 106224.
[
3] M. Besson, P. Gallezot, C. Pinel, Conversion of biomass into chemicals over metal
x
x
2
catalysts, Chem. Rev. 114 (2013) 1827–1870.
[
4] J.J. Zhang, B. Fidalgo, D.K. Shen, X.L. Zhang, S. Gu, Mechanism of hydro-
deoxygenation (HDO) in anisole decomposition over metal loaded Bronsted acid
sites: density Functional Theory (DFT) study, Mol. Catal. 454 (2018) 30–37.
5] W.J. Liu, H. Jiang, H.Q. Yu, Thermochemical conversion of lignin to functional
materials: a review and future directions, Green Chem. 17 (2015) 4888–4907.
6] A.A. Boateng, C.A. Mullen, N. Goldberg, K.B. Hicks, H.J.G. Jung, J.F.S. Lamb,
Production of bio-oil from alfalfa stems by fluidized-bed fast pyrolysis, Ind. Eng.
Chem. Res. 47 (2008) 4115–4122.
7] D.M. Alonso, S.G. Wettstein, J.A. Dumesic, Bimetallic catalysts for upgrading of
biomass to fuels and chemicals, Chem. Soc. Rev. 41 (2012) 8075–8098.
8] S.A. Khromova, A.A. Smirnov, O.A. Bulavchenko, A.A. Saraev, V.V. Kaichev,
S.I. Reshetnikov, V.A. Yakovlev, Anisole hydrodeoxygenation over Ni–Cu bimetallic
catalysts: the effect of Ni/Cu ratio on selectivity, Appl. Catal. A Gen. 470 (2014)
2
catalyst
[
[
[
[
2
61–270.
[
9] M. Saidi, F. Samimi, D. Karimipourfard, T. Nimmanwudipong, B.C. Gates,
M.R. Rahimpour, Upgrading of lignin-derived bio-oils by catalytic hydro-
deoxygenation, Energ. Environ. Sci. 7 (2014) 103–129.
[37] A. Robinson, G.A. Ferguson, J.R. Gallagher, S. Cheah, G.T. Beckham, J.A. Schaidle,
J.E. Hensley, J.W. Medlin, Enhanced hydrodeoxygenation of m-cresol over bime-
tallic Pt–Mo catalysts through an oxophilic metal-induced tautomerization
pathway, ACS Catal. 6 (2016) 4356–4368.
[38] J. Sun, A.M. Karim, H. Zhang, L. Kovarik, X.S. Li, A.J. Hensley, J.S. Mcewen,
Y. Wang, Carbon-supported bimetallic Pd–Fe catalysts for vapor-phase hydro-
deoxygenation of guaiacol, J. Catal. 306 (2013) 47–57.
[
10] H. Ohta, K. Yamamoto, M. Hayashi, G. Hamasaka, Y. Uozumi, Y. Watanabe, Low
temperature hydrodeoxygenation of phenols under ambient hydrogen pressure to
form cyclohexanes catalysed by Pt nanoparticles supported on H-ZSM-5, Chem.
Commun. 51 (2015) 17000–17003.
[
11] Y.C. Shi, E.H. Xing, K.J. Wu, J.L. Wang, M.D. Yang, Y.L. Wu, Recent progress on
upgrading of bio-oil to hydrocarbons over metal/zeolite bifunctional catalysts,
Catal. Sci. Technol. 7 (2017) 2385–2415.
[39] K.L. Deutsch, B.H. Shanks, Hydrodeoxygenation of lignin model compounds over a
copper chromite catalyst, Appl. Catal. A Gen. 447 (2012) 144–150.
[40] L. Nie, P.M. de Souza, F.B. Noronha, W. An, T. Sooknoi, D.E. Resasco, Selective
conversion of m-cresol to toluene over bimetallic Ni–Fe catalysts, J. Mol. Catal. A
Chem. 388 (2014) 47–55.
[
12] L. Wang, J. Zhang, X.F. Yi, A.M. Zheng, F. Deng, C.Y. Chen, Y.Y. Ji, F.J. Liu,
X.J. Meng, F.S. Xiao, Mesoporous ZSM-5 zeolite-supported Ru nanoparticles as
highly efficient catalysts for upgrading phenolic biomolecules, ACS Catal. 5 (2015)
[41] K.L. Li, R.J. Wang, J.X. Chen, Hydrodeoxygenation of anisole over silica-supported
2
727–2734.
2
Ni P, MoP, and NiMoP catalysts, Energ. Fuel. 25 (2011) 854–863.
[
13] S. De, B. Saha, R. Luque, Hydrodeoxygenation processes: advances on catalytic
transformations of biomass-derived platform chemicals into hydrocarbon fuels,
Bioresour. Technol. Rep. 178 (2015) 108–118.
14] C. Li, X. Zhao, A. Wang, G.W. Huber, T. Zhang, Catalytic transformation of lignin for
the production of chemicals and fuels, Chem. Rev. 115 (2015) 11559–11624.
15] A. Sanna, T.P. Vispute, G.W. Huber, Hydrodeoxygenation of the aqueous fraction of
bio-oil with Ru/C and Pt/C catalysts, Appl. Catal. B Environ. 165 (2015) 446–456.
16] H. Duan, J.C. Liu, M. Xu, Y. Zhao, X.L. Ma, J. Dong, X. Zheng, J. Zheng, C.S. Allen,
M. Danaie, Molecular nitrogen promotes catalytic hydrodeoxygenation, Nat. Catal.
[42] A.M. Robinson, J.E. Hensley, J.W. Medlin, Bifunctional catalysts for upgrading of
biomass-derived oxygenates: a review, ACS Catal. 6 (2016) 5026–5043.
[43] M. Chia, Y.J. Pagán-Torres, D. Hibbitts, Q. Tan, H.N. Pham, A.K. Datye, M. Neurock,
R.J. Davis, J.A. Dumesic, Selective hydrogenolysis of polyols and cyclic ethers over
bifunctional surface sites on rhodium–rhenium catalysts, J. Am. Chem. Soc. 133
(2011) 12675–12689.
[44] S. Koso, I. Furikado, A. Shimao, T. Miyazawa, K. Kunimori, K. Tomishige,
Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol,
Chem. Commun. (2009) 2035–2037.
[
[
[
2
(2019) 1–10.
[45] S. Koso, H. Watanabe, K. Okumura, Y. Nakagawa, K. Tomishige, Comparative study
[
17] W. Mu, H. Ben, X. Du, X. Zhang, F. Hu, W. Liu, A.J. Ragauskas, Y. Deng, Noble metal
catalyzed aqueous phase hydrogenation and hydrodeoxygenation of lignin-derived
pyrolysis oil and related model compounds, Bioresour. Technol. Rep. 173 (2014)
x x 2
of Rh–MoO and Rh–ReO supported on SiO for the hydrogenolysis of ethers and
polyols, Appl. Catal. B Environ. 111 (2012) 27–37.
[46] S.J. Hurff, M.T.J.I. Klein, Reaction pathway analysis of thermal and catalytic lignin
fragmentation by use of model compounds, Ind. Eng. Chem. fund. 22 (1983)
426–430.
6
–10.
[
18] T.M. Sankaranarayanan, A. Berenguer, C. Ochoa-Hernandez, I. Moreno, P. Jana,
J.M. Coronado, D.P. Serrano, P. Pizarro, Hydrodeoxygenation of anisole as bio-oil
[47] C. Wang, A.V. Mironenko, A. Raizada, T. Chen, X. Mao, A. Padmanabhan,
11

X. Wang, et al.
Catalysis Today xxx (xxxx) xxx–xxx
D.G. Vlachos, R.J. Gorte, J.M. Vohs, Mechanistic study of the direct hydro-
deoxygenation of m-cresol over WO -decorated Pt/C catalysts, ACS Catal. 8 (2018)
749–7759.
[59] C. Ranga, V.I. Alexiadis, J. Lauwaert, R. Lødeng, J.W. Thybaut, Effect of Co in-
corporation and support selection on deoxygenation selectivity and stability of (Co)
Mo catalysts in anisole HDO, Appl. Catal. A Gen. 571 (2019) 61–70.
[60] J. Zhang, Catalytic transfer hydrogenolysis as an efficient route in cleavage of lignin
and model compounds, Green Energ. Environ. 3 (2018) 328–334.
[61] R. Wagner, D. Schlatterbeck, K. Christmann, The interaction of copper with a
rhenium (0001) surface: structure, energetics, and growth modes, Surf. Sci. 440
(1999) 231–251.
x
7
[
48] C.H. Zhou, K. Deng, M. Di Serio, S. Xiao, D.S. Tong, L. Li, C.X. Lin, J. Beltramini,
H. Zhang, W.H. Yu, Cleaner hydrothermal hydrogenolysis of glycerol to 1,2-pro-
panediol over Cu/oxide catalysts without addition of external hydrogen, Mol Catal.
4
32 (2017) 274–284.
[
49] K. Leiva, N. Martinez, C. Sepulveda, R. García, C.A. Jiménez, D. Laurenti, M. Vrinat,
C. Geantet, J.L.G. Fierro, I.T. Ghampson, Hydrodeoxygenation of 2-methoxyphenol
[62] E.L. Kunkes, D.A. Simonetti, J.A. Dumesic, W.D. Pyrz, L.E. Murillo, J.G. Chen,
D.J. Buttrey, The role of rhenium in the conversion of glycerol to synthesis gas over
carbon supported platinum–rhenium catalysts, J. Catal. 260 (2008) 164–177.
[63] M.S. Nacheff, L.S. Kraus, M. Ichikawa, B.M. Huffman, J.B. Butt, W.M.H. Sachtler,
over different Re active phases supported on SiO
2015) 71–79.
2
catalysts, Appl. Catal. A Gen. 490
(
[
[
[
[
[
50] M. Shetty, K. Murugappan, T. Prasomsri, W.H. Green, Y. Román-Leshkov, Reactivity
and stability investigation of supported molybdenum oxide catalysts for the hy-
drodeoxygenation (HDO) of m-cresol, J. Catal. 331 (2015) 86–97.
0
4+
2 3 2 3
Characterization and catalytic function of Re and Re in ReAl O and PtReAl O
catalysts, J. Catal. 106 (2016) 263–272.
51] M.A. Banares, L.J. Alemany, M. Lopez, Partial oxidation of methane to for-
maldehyde on silica-supported transition metal oxide catalysts, Catal. Today 33
[64] A. Bjelic, M. Grilc, M. Hus, B. Likozar, Hydrogenation and hydrodeoxygenation of
aromatic lignin monomers over Cu/C, Ni/C, Pd/C, Pt/C, Rh/C and Ru/C catalysts:
mechanisms, reaction micro-kinetic modelling and quantitative structure-activity
relationships, Chem. Eng. J. 359 (2019) 305–320.
(1997) 73–83.
52] X.W. Xu, E.C. Jiang, Z.Y. Li, Y. Sun, BTX from anisole by hydrodeoxygenation and
transalkylation at ambient pressure with zeolite catalysts, Fuel 221 (2018)
[65] H. Ohta, B. Feng, H. Kobayashi, K. Hara, A. Fukuoka, Selective hydrodeoxygenation
4
40–446.
of lignin-related 4-propylphenol into n -propylbenzene in water by Pt-Re/ZrO
2
catalysts, Catal. Today 234 (2014) 139–144.
[66] S.H. Hakim, C. Sener, A.C. Alba-Rubio, T.M. Gostanian, B.J. O’Neill, F.H. Ribeiro,
J.T. Miller, J.A. Dumesic, Synthesis of supported bimetallic nanoparticles with
controlled size and composition distributions for active site elucidation, J. Catal.
328 (2015) 75–90.
53] G.S. Foo, A.K. Rogers, M.M. Yung, C. Sievers, Steric effect and evolution of surface
species in the hydrodeoxygenation of bio-oil model compounds over Pt/HBEA, ACS
Catal. 6 (2016) 1292–1307.
54] C.J. Baranowski, A.M. Bahmanpour, F. Héroguel, J.S. Luterbacher, O. Kröcher,
Prominent role of mesopore surface area and external acid sites for the synthesis of
polyoxymethylene dimethyl ethers (OME) on a hierarchical H-ZSM-5 zeolite, Catal.
Sci. Technol. 9 (2019) 366–376.
[67] I.T. Ghampson, C. Sepulveda, R. Garcia, J.L.G. Fierro, N. Escalona, Carbon nano-
x
fiber-supported ReO catalysts for the hydrodeoxygenation of lignin-derived com-
[55] S.T. Thompson, H.H. Lamb, Vapor-phase hydrodeoxygenation of guaiacol over
pounds, Catal. Sci. Technol. 6 (2016) 4356–4369.
carbon-supported Pd, Re and PdRe catalysts, Appl. Catal. A Gen. 563 (2018)
[68] N. Ota, M. Tamura, Y. Nakagawa, K. Okumura, K. Tomishige, Performance, struc-
1
05–117.
ture, and mechanism of ReO
x 2
–Pd/CeO catalyst for simultaneous removal of vicinal
[
56] J. Hu, S.H. Zhang, R. Xiao, X.X. Jiang, Y.J. Wang, Y.H. Sun, P. Lu, Catalytic transfer
hydrogenolysis of lignin into monophenols over platinum-rhenium supported on
titanium dioxide using isopropanol as in situ hydrogen source, Bioresour. Technol.
Rep. 279 (2019) 228–233.
OH groups with H , ACS Catal. 6 (2016) 3213–3226.
2
[69] C. Newman, X. Zhou, B. Goundie, I.T. Ghampson, B.G. Frederick, Effects of support
identity and metal dispersion in supported ruthenium hydrodeoxygenation cata-
lysts, Appl. Catal. A Gen. 477 (2014) 64–74.
[57] X.W. Xu, E.C. Jiang, Y.H. Du, B.S. Li, BTX from the gas-phase hydrodeoxygenation
[70] F. Yang, N.J. Libretto, M.R. Komarneni, W. Zhou, J.T. Miller, X. Zhu, D.E. Resasco,
and transmethylation of guaiacol at room pressure, Renew. Energ. 96 (2016)
Enhancement of m-cresol hydrodeoxygenation selectivity on Ni catalysts by surface
4
58–468.
x
decoration of MoO species, ACS Catal. 9 (2019) 7791–7800.
[
58] P.M. de Souza, R.C. Rabelo-Neto, L.E. Borges, G. Jacobs, B.H. Davis, D.E. Resasco,
F.B. Noronha, Hydrodeoxygenation of phenol over Pd catalysts. Effect of support on
reaction mechanism and catalyst deactivation, ACS Catal. 7 (2017) 2058–2073.
[71] P.M. Mortensen, J.D. Grunwaldt, P.A. Jensen, A.D. Jensen, Influence on nickel
2
particle size on the hydrodeoxygenation of phenol over Ni/SiO , Catal. Today 259
(2016) 277–284.
12