Low-Temperature Hydrogenation of CO2 to Methanol over Heterogeneous TiO2-Supported Re Catalysts

Article abstract of DOI:10.1021/acscatal.8b04821

Hydrogenation of carbon dioxide (CO₂) to methanol (MeOH) is an effective strategy for CO₂ utilization. Because of a low equilibrium conversion of CO₂ to MeOH at high temperature, development of efficient catalytic CO₂ hydrogenation processes that operate under low reaction temperature is of extreme importance. Herein, we report that TiO₂-supported Re (Re(1)/TiO₂; Re = 1 wt %) promotes the selective hydrogenation of CO₂ to MeOH (total TON based on Re = 44, MeOH selectivity = 82%) under mild conditions (p_CO2 = 1 MPa; p_H2 = 5 MPa; T = 150 °C). Both in terms of TON and methanol selectivity, the performance of Re(1)/TiO₂ is superior to that of TiO₂ catalysts loaded with other metals and to Re catalysts on other support materials. In addition, our investigations include the reaction mechanism and structure-activity relationship for the catalytic system used in this study, suggesting that relatively reduced Re species (oxidation state: 0-4) of subnanometer size serve as the catalytically active site for the formation of MeOH.

Full text of DOI:10.1021/acscatal.8b04821

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Article
Low-Temperature Hydrogenation of CO2 to Methanol
over Heterogeneous TiO2-Supported Re Catalysts
Kah Wei Ting, Takashi Toyao, S. M. A. Hakim Siddiki, and Ken-Ichi Shimizu
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b04821 • Publication Date (Web): 13 Mar 2019
Downloaded from http://pubs.acs.org on March 14, 2019
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Low-Temperature Hydrogenation of CO to Methanol over
2
Heterogeneous TiO -Supported Re Catalysts
2
†
†,‡
†
†,‡
Kah Wei Ting, Takashi Toyao,* S. M. A. Hakim Siddiki, Ken-ichi Shimizu*
†
Institute for Catalysis, Hokkaido University, N-21, W-10, Sapporo 001-0021, Japan
‡
Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura, Kyoto 615-
520, Japan
8
*Corresponding authors
Takashi Toyao, Ken-ichi Shimizu
E-mail:
toyao@cat.hokudai.ac.jp,
kshimizu@cat.hokudai.ac.jp
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ABSTRACT
Hydrogenation of carbon dioxide (CO
2
) to methanol (MeOH) is an effective strategy for CO
2
utilization. Due to a low equilibrium conversion of CO
development of efficient catalytic CO hydrogenation processes that operate under low reaction
temperature is of extreme importance. Herein, we report that TiO -supported Re (Re(1)/TiO
Re = 1 wt%) promotes the selective hydrogenation of CO to MeOH (total TON based on Re =
4, MeOH selectivity = 82%) under mild conditions (pCO2 = 1 MPa; pH2 = 5 MPa; T = 150 ˚C)
2
to MeOH at high temperature,
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.
Both in terms of TON and methanol selectivity, the performance of Re(1)/TiO
of TiO
2
is superior to that
2
catalysts loaded with other metals and to Re catalysts on other support materials. In
addition, our investigations include the reaction mechanism and structure-activity relationship
for the catalytic system used in this study, suggesting that relatively reduced Re species
(oxidation state: 0-4) of sub-nanometer size serve as the catalytically active site for the formation
of MeOH.
KEYWORDS: CO
2
hydrogenation, methanol synthesis, rhenium, TiO
2
, in situ XAFS, in situ FT-
IR
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. INTRODUCTION
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The growing concern about climate change and the depletion of fossil fuels have
prompted the search for alternative carbon sources for the generation of energy and the
production of chemicals.1–10 Carbon dioxide (CO
), which is regarded to be by far the
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largest contributor to global warming, is a promising prospective for potential applications
as a raw material for the production of fine chemicals.11–19 The direct synthesis of
methanol (MeOH) from the hydrogenation of CO has thus attracted significant interest
2
in the scientific community.20–28 MeOH is used as a precursor for a vast variety of
chemical products, which makes it arguably one of the most important commodity
2
9
30
chemicals. Additionally, MeOH can be used as a fuel. Traditionally, MeOH is almost
exclusively produced from fossil-derived syngas, which primarily consists of CO and H
in addition to small amounts of CO , by employing Cu-based catalysts, typically under
relatively extreme conditions (T > 200 ˚C; p = 5-10 MPa).31 Industrially, the direct
production of MeOH from the hydrogenation of CO has recently been achieved by using
2
2
2
32
similar Cu-based catalysts and reaction conditions. However, this process suffers from
a low equilibrium conversion of CO
since the hydrogenation reaction is exothermic.33,34
Consequently, a lower reaction temperature is more favorable for the formation of MeOH.
Several methods for the low-temperature (T ≤ 150 ˚C) hydrogenation of CO to
afford MeOH over homogeneous catalysts under mild conditions have recently emerged
Table S1).34–46 Although homogeneous catalysts normally exhibit high activity and
2
2
(
operate under mild conditions, they typically suffer from product-separation issues and
usually require additives in order to achieve high catalytic performance. Methods based
on heterogeneous catalysts have also been actively explored recently. However, most
methods hitherto reported suffer from low activity.47–52 Yet some reports on
heterogeneous catalytic systems for the low-temperature hydrogenation of CO to MeOH
2
show high activity.53–57 For instance, Zen and co-workers reported Pt
Co octapods,53
3
5
4
55
Rh75
W
25 nanosheets, and Pt/MoS
Table S1). Carbon-supported Pt Co nanowires (Pt
nanospheres have also been reported recently as active catalysts for the hydrogenation
of CO . These processes represent important contributions to the synthesis of MEOH
2
catalysts that produce MeOH with TON > 2000
(
4
4
Co NWs/C)56 and RhCo porous
5
7
2
under mild conditions. However, in all cases platinum-group metals (PGMs) are
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employed and the preparation of these catalysts is complicated. Yet, catalysts employed
for such selective hydrogenation reactions should be easily accessible. Hence, the
development of versatile heterogeneous catalysts that can be operated under mild
conditions (T ≤ 150 ˚C) is of extreme importance. Moreover, it should be emphasized that
the previous reported studies usually do not mention the formation of byproducts such as
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CO and CH
4
. This is especially problematic for dealing with the hydrogenation of CO ,
2
which usually generates such byproducts to some extent even over homogeneous
catalysts.22
In this study, a Re/TiO
for i) the hydrogenation of carboxylic acid derivatives, ii) the N-methylation of amines
using CO and H , and iii) the N-alkylation of amines with carboxylic acids or esters in the
,58,59 was employed for the hydrogenation of CO
presence of H to MeOH at low
temperature (T = 150 ˚C). A series of Re/TiO catalysts with different Re loadings, which
ensured a wide range of Re dispersion, were prepared and evaluated with respect to their
performance in the hydrogenation of CO . Whereas a Re loading of 5 wt% (Re(5)/TiO )
2
catalyst, which exhibits high activity and product selectivity
2
2
2
2
2
2
2
furnished the best performance in previous studies,58,59 the best performance under the
conditions applied in this study (vide infra) was achieved using a catalyst containing 1
wt% of Re (Re(1)/TiO
that of various other catalysts, including the industrially used methanol synthesis catalyst
Cu/Zn/Al , revealed that Re(1)/TiO surpassed the performance of all the other
catalysts tested.
2
). A comparison of the performance of the Re(1)/TiO catalyst to
2
2
O
3
2
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. EXPERIMENTAL
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Materials and Catalyst Preparation
Inorganic and organic chemicals were obtained from common commercial suppliers. The
obtained reagents were used as received. TiO (ST-01) was purchased from Ishihara Sangyo
Co., Ltd. Its BET (Brunauer-Emmett-Teller) specific surface area is 188 m g and its CO
profile is given in Fig. S1. ZrO (JRC-ZRO-2), MgO (JRC-MGO-3), and SiO -Al (JRC-SAL-2,
Al = 13.75 wt%) were obtained from the Catalysis Society of Japan. Conversely, γ-Al was
prepared by calcination of γ-AlOOH (Catapal B Alumina) obtained from Sasol (T = 900 °C; t = 3
h). CeO was prepared by calcination (T = 600 °C, t = 3 h, in air) of CeO supplied by Daiichi
Kigenso Kagaku Kogyo Co., Ltd (Type A). SiO (Q-10) was supplied by Fuji Silysia Chemical
Ltd. The carbon support (Kishida Chemical) was commercially obtained. SnO was prepared by
calcination (T = 500 °C, t = 3 h) of H SnO (Kojundo Chemical Laboratory Co., Ltd.). HZSM-
:SiO /AI = 22:1 and HY:SiO /AI = 5.5:1 were obtained from TOSOH Co., Ltd. Re and
ReO were purchased from Strem Chemicals Inc. and Hydrus Chemical Inc., respectively.
NH ]ReO and metallic Re were purchased from SigmaAldrich. Cu/Zn/Al (MDC-7; 34 wt%
Cu) was supplied by Clariant Catalysts (Japan).
Precursors for M(1)/TiO (M = 1 wt% Re, Pt, Pd, Rh, Ir, Ru, Ni, Co, Ag, or Cu) and
Re(1)/Support (1 wt% Re; Support = metal oxides, carbon, or zeolites) were prepared by mixing
the support material with the metal sources, i.e., an aqueous solution of [NH ]ReO , nitrates of
Ni, Co, Ag, Cu, RuCl or IrCl ·nH O, or aqueous HNO solutions of Pt(NH
Pd(NH (NO , or Rh(NO . For the preparation of Re/TiO , typically 0.072 g of [NH
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-1
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-TPD
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O
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O
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O
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[
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O
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2
(NO
3 2
) ,
)
3 2
)
3 2
)
3 3
2
4
]ReO
4
were added to a glass vessel (500 mL) containing 100 mL of deionized water ([Re] = 0.0027 M).
After sonication (1 min) to completely dissolve the NH ReO , TiO (4.95 g) was added to the
4
4
2
solution. The mixed solution was then stirred at 200 rpm for 30 min at room temperature.
Subsequently, the solvent of the mixture was evaporated at T = 50 °C, followed by drying in air
(T = 110 °C; t = 12 h). The thus obtained material was calcined (T = 500 °C, t = 3 h, in air). The
individual catalysts were prepared by reducing the individual materials in a quartz vessel (T =
3
-1
5
00 °C, t = 0.5 h) under a flow of H
2
(20 cm min ) prior to each experiment. All other M(1)/TiO
2
catalysts were prepared as described above.
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Characterization of the Catalysts
X-ray diffraction (XRD; Rigaku Miniflex) measurements were conducted using CuK radiation.
Re L -edge X-ray absorption fine structure (XAFS) measurements were performed at the
BL14B2 line (SPring-8) using a Si(111) double crystal monochromator operated at 8 GeV
proposal 2018A1757). Scanning transmission electron microscopy (STEM) images were
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(
recorded on a JEM-ARM200F microscope (JEOL) at an acceleration voltage of 200 kV. The Cs-
corrector CESCOR (CEOS GmbH, Germany) was used in the STEM mode.
FT-IR spectra were measured on a JASCO FT/IR-4200 with a Mercury-Cadmium-
Telluride (MCT) detector. Samples (40 mg) were pressed into self-supporting pellets ( = 2 cm),
which were fitted in the quartz FT-IR cell with CaF
2
windows connected to a gas-flow set up.
Prior to the measurements, the samples were pre-treated (T = 500 °C; t = 0.5 h) under a flow of
-1
-1
H (30 mL min ) and He (50 mL min ), followed by cooling to T = 150 °C under He. Subsequently,
2
-
1
-1
-1
the gas stream containing CO
2
(10 mL min ) and H (30 mL min ) with He (50 mL min ) was
2
introduced to the cell, and the FT-IR measurements were carried out. Spectra were measured
-
1
by accumulating 15 scans (resolution: 4 cm ). A reference spectrum (T = 150 °C; H and He
2
flow) was subtracted from each spectrum.
Catalytic Reactions
The following procedure for the hydrogenation reactions can be considered representative: after
the reduction with H at T = 500 °C (cf. catalyst preparation), the catalyst (0.0054 mmol relative
2
to the Re loading), and a mixture of 1,4-dioxane (1 mL) and n-decane (0.15 mmol) as an internal
3
standard were added to an autoclave (30 cm ). The reaction mixture was stirred magnetically (T
=
150 °C; pCO2 = 1 MPa; pH2 = 5 MPa). MeOH was analyzed using a gas chromatograph with a
+
flame-ionization detector (GC-FID; Shimadzu GC-14B; Ultra ALLOY capillary column UA -1;
Frontier Laboratories Ltd.); while the other products were analyzed using a GC-FID (Shimadzu
GC-2014; Porapak Q column) with a methanizer (Shimadzu MTN-1).
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Catalyst Characterization
Re(1)/TiO
followed by H
electron microscopy (STEM) measurements were carried out in order to characterize Re(1)/TiO
As given in Fig. 1, a XRD pattern of the reduced Re(1)/TiO
that of pristine TiO , while peaks arising from the Re species were not observed. It should be
2
was synthesized using a facile impregnation method employing NH
4
ReO
4
and TiO
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,
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reduction at 500 °C. Powder X-ray diffraction (XRD) and scanning transmission
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.
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catalyst was essentially identical to
2
noted that its structure was confirmed to be anatase. Figure 2 shows the annular bright field
STEM (ABF-STEM) image and high-angle annular dark-field STEM (HAADF-STEM) images of
Re(1)/TiO
sub-nanometer clusters. It is also observed that some Re species exist as single atoms in the
matrix of TiO
.60–62
2
. These images show that the Re loaded on the TiO
2
support forms highly dispersed
2
Figure 1. XRD patterns of a) TiO
2
; b) NH
4
ReO
4
-impregnated TiO
2
calcined at 500 °C in air; c)
after reduction of (b) at 500 °C under H
2
flow (Re(1)/TiO
2
).
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Low-Temperature Hydrogenation of CO
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Hydrogenations of CO
2
were performed in order to screen the catalytic performances of various
catalysts. These reactions were carried out using a catalyst (0.0054 mmol of catalytically active
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metal) in a stainless autoclave (V = 30 cm ; pCO2 = 1 MPa; pH2 = 5 MPa; T = 150 ˚C; t = 24 h)
after pre-treatment of the catalyst under a flow of H
obtained results. Re(1)/TiO afforded a total turnover number (TON) of 44 with 82% MeOH
selectivity (entry 1). As minor byproducts, CO and CH were obtained. In contrast, using TiO
or various other TiO -supported metal catalysts (entries 2-10) did not afford significant amounts
of MeOH. CO and/or CH were produced as the main products over these catalysts. No reaction
occurred when pristine TiO was employed as the catalyst (entry 11). Various supported Re
catalysts were also tested for the direct hydrogenation of CO (entries 12-21). The obtained
2
(T = 500 °C). Table 1 summarizes the
2
4
2
2
4
2
2
total TONs were lower than that for Re(1)/TiO
The industrial Cu-based catalyst Cu/Zn/Al
2
, while the formation of MeOH was not observed.
2
O
3
supplied by Clariant Catalysts (MDC-7; 34 wt%
Cu) was also tested and found to be ineffective under the reaction conditions tested in this study
(entry 22). Moreover, unsupported Re catalysts including metallic Re, NH ReO , ReO , ReO
and Re did not efficiently catalyze the hydrogenation of CO (entries 23-27). It should be
noted here that the catalytic tests were also carried out after a H reduction at 300 °C (Table
S2), given that a H reduction at 500 °C may not be appropriate for some of the catalysts. Still,
it was confirmed that Re(1)/TiO is the most effective catalyst for the direct hydrogenation of CO
to afford MeOH. These results demonstrate that the combination of Re and TiO is particularly
4
4
2
3
,
2
O
7
2
2
19
2
2
2
2
effective for the synthesis of MeOH from the hydrogenation of CO .
2
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catalyzed by a variety of catalysts.a
Table 1. Results of the hydrogenation of CO
2
Selectivity (%)
Entry
Catalyst
Total TON
MeOH
82
<1
<1
<1
<1
<1
<1
<1
-
CO
CH
2
4
1
2
3
4
5
6
7
8
9
1
1
1
1
Re(1)/TiO
2
44
64
21
41
5
3
4
2
<1
<1
<1
8
2
1
16
87
88
100
89
100
100
100
-
Pt(1)/TiO
Pd(1)/TiO
2
13
12
<1
11
<1
<1
<1
-
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Rh(1)/TiO
Ir(1)/TiO
Ru(1)/TiO
2
2
2
Ni(1)/TiO
Co(1)/TiO
2
2
Ag(1)/TiO
Cu(1)/TiO
TiO
Re(1)/ZrO
Re(1)/Al
Re(1)/SiO
Re(1)/Carbon
Re(1)/CeO
Re(1)/MgO
2
0
1
2
3
2
-
-
-
2
-
-
-
2
<1
<1
<1
<1
-
65
9
65
36
-
35
91
35
64
-
2
O
3
14
2
1
1
1
1
1
5
6
7
8
9
1
2
<1
<1
<1
<1
-
-
-
Re(1)/SiO
Re(1)/SnO
2
-Al
2
2
O
3
-
-
-
-
-
-
20
21
Re(1)/HZSM-5(22) 1
Re(1)/HY(5.5) <1
<1
-
92
-
8
-
b
2
2
2
2
2
2
3
4
5
6
Cu/Zn/Al
Metallic Re
2
O
3
<1
<1
2
1
2
-
-
-
c
c
c
c
c
-
-
-
c
NH
ReO
ReO
4
ReO
4
<1
<1
<1
<1
2
4
<1
<1
98
96
100
100
c
2
3
c
c
27
Re
2
O
7
10
aPre-treatment: H
(30 mL min ), 500 ˚C, 0.5 h; reaction conditions: 0.0054 mmol of catalytically
-1
2
active metal, 1,4-dioxane (1 mL), CO
2
(1 MPa), H (5 MPa), 150 ˚C, 24 h; TONs were calculated
2
b
c
based on the total amount of metal atoms used. 34 wt% of Cu. Reactions were carried out
without pre-treatment.
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Mechanistic Study
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The time-course plot of the CO
products (MeOH, CO, and CH
2
hydrogenation reaction shows that the concentration of all the
4
) increases with increasing the reaction time, as given in Fig. 3.
0
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2
3
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It should also be noted that other possible byproducts such as formic acid (HCOOH) and
formaldehyde (HCOH) were not observed when using a GC-FID apparatus equipped with a
methanizer. In order to get further insight into the specifics of the reaction, hydrogenation
reactions employing CO or HCOOH as a starting substrate were carried out (Scheme 1). The
hydrogenation of CO, carried out at lower pressure (0.5 MPa) for safety reasons, hardly
proceeded, whereas that of CO (0.5 MPa) afforded MeOH at a formation rate of 0.8 mmol
2
mmolRe h-1 based on the Re used. This result indicates that the potentially produced CO is not
-1
an intermediate for the formation of MeOH. On the other hand, the reaction of HCOOH afforded
-
MeOH, suggesting that the derivatives of HCOOH (e.g. HCOO ) adsorbed on the catalyst
surface could serve as intermediates for the formation of MeOH. This hypothesis was
corroborated by in-situ FT-IR measurements (Fig. 4). Specifically, the formation of surface
-1
species was investigated at 150 °C under a gas stream containing CO
2
(10 mL min ), H
mL min ), and He (50 mL min ). Note that the measurements were carried out at ambient
pressure. Prior to each measurement, the samples were pre-treated under a flow of H for 0.5 h
indicate the
2
(30
-1
-1
2
-1
at 500 °C. Bands that were clearly observed at 1360 and 1560 cm over Re(1)/TiO
2
formation of HCOO-.21,63 In addition, a band observed at 1130 cm proves the formation of
-1
methoxy species.28 The evolution of several bands in the νCH region (2800-2950 cm ) also
-1
supports the formation of these species.21,28,63 The same features can be seen over pristine TiO
although their intensities are not as high as those for Re(1)/TiO . In contrast, these bands were
negligible for Re(1)/SiO , demonstrating the importance of TiO as a support. We have also
examined the adsorption and activation features of CO , MeOH and HCOOH separately on the
Re(1)/TiO catalyst (Fig. S2). The results are consistent with the discussion described above. It
should be noted that that a CO adsorption experiment was also carried out, albeit that CO did
not adsorb on the Re(1)/TiO catalyst surface. The results obtained from several control
2
,
2
2
2
2
2
2
reactions and in-situ FT-IR studies suggest that the hydrogenation of CO
2
over Re(1)/TiO
2
-
proceeds through the formation of HCOO and methoxy species on the surface to give MeOH.
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Figure 3. Time-course plot of the hydrogenation of CO
2
catalyzed by Re(1)/TiO . Pre-treatment:
2
-1
H
2
(30 mL min ), 500 ˚C, 0.5 h; reaction conditions: 0.0054 mmol Re, 1,4-dioxane (1 mL), CO
2
(1 MPa), H (5 MPa), 150 ˚C.
2
Scheme 1. Hydrogenation of model substrates over Re(1)/TiO
2
. (a) CO , (b) CO, and (c)
2
-1
HCOOH. Pre-treatment: H
2
(30 mL min ), 500 ˚C, 0.5 h; reaction conditions: 0.0054 mmol Re,
1,4-dioxane (1 mL).
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Figure 4. In-situ FT-IR spectra collected at 150 °C under a gas stream that contains CO (10
2
-1
(30 mL min ), and He (50 mL min ). Pre-treatment conditions: H
(30 mL min-1),
-1
-1
mL min ), H
2
2
-1
He (50 mL min ), 500 °C, 0.5 h.
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Structure-Activity Relationship
Subsequently, the hydrogenation of CO
2
was carried out using Re(x)/TiO (x = 0.2, 1.0, 5.0, 10,
2
and 20 wt%) in order to i) determine the optimal Re loading and ii) investigate the effect of the
size of the Re species on the hydrogenation reaction. The corresponding HAADF-STEM images
0
1
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0
for Re(x)/TiO
formation rate and selectivity for MeOH was achieved using Re(1)/TiO
Re loading, the MeOH selectivity is gradually shifting toward CH . This could be attributed to the
fact that larger clusters of Re nanoparticles favor the formation of CH , while isolated atoms
single atoms) of Re mainly seen for Re(x)/TiO with low Re loadings favor the formation of CO.
This notion is in accordance with the results of a previous study on the hydrogenation of CO
2
(x = 0.2, 1, 5, 10, and 20 wt%) are shown in Fig. 5 and Figs. S3-S7. The highest
2
(Fig. 6). With increasing
4
4
(
2
2
64
over Rh/TiO
2
. Moreover, our results indicate that the formation of MeOH should be favored
over Re/TiO
2
given the sub-nanometer size of the Re species. These considerations could
explain why Re(1)/TiO
study.
2
serves as the most effective catalyst for the formation of MeOH in this
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Figure 5. HAADF-STEM images of Re(x)/TiO
2
(x = 0.2, 5, 10, and 20 wt%).
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Figure 6. Effect of the Re loading on the hydrogenation of CO
2
catalyzed by Re(x)/TiO (x = 0.2,
2
-1
1
, 5, 10, and 20 wt%). Pre-treatment: H
2
(30 mL min ), 500 ˚C, 0.5 h; reaction conditions: 0.0054
(5 MPa), 150 ˚C, 24 h.
mmol of Re, 1,4-dioxane (1 mL), CO (1 MPa), H
2
2
Finally, we tested Re(1)/TiO
different temperatures (200, 300, 500, 700, and 900 ˚C), as shown in Fig. 7. The results show
that the best performance is observed for Re(1)/TiO pre-treated at 500 ˚C. X-ray absorption
2
for the hydrogenation of CO
2
after a reduction with H at
2
2
near edge structure (XANES) measurements were measured in order to determine the oxidation
states of Re species, as given in Fig. 8. Note that the XANES spectra were collected at room
temperature without exposure to air after the H
filled with N . Chemical shifts of the binding energy as a function of the reduction temperature
are also plotted. The shifts for reference samples ReO , ReO , and Re metallic powder are
2
reduction by sealing the samples in a glove bag
2
65
3
2
shown with dotted lines. The obtained results suggest that the valence of the Re species
decreases with increasing reduction temperature, which implies that the average oxidation state
of the Re species responsible for the catalytic formation of MeOH should be higher than 0 and
below +4. It is well-known that Re often shows high dispersion on supports, that it is difficult to
be reduced, and exhibits a variety of oxidation states.66-68 These features render research on
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catalytically active Re components highly challenging, and consequently, little is known about
the chemical identity of such catalytically active Re species.69 The precise nature of the
catalytically active Re species remains unknown and the catalyst may contain a variety of Re
species in different oxidation states. At present, we cannot exclude the possibility that these
mixtures of Re species in different oxidation states and the interfaces between them are
necessary for the efficient progression of the reaction. HAADF-STEM measurements suggest
that reduction temperatures beyond 500 ˚C should lead to sintering of the Re species, which
would prevent the formation of MeOH (Figs. 9 and 10).
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0
Figure 7. Effect of the pre-treatment reduction temperature on the CO
2
hydrogenation catalyzed
(30 mL min ), 0.5 h; reaction conditions: 0.0054 mmol
(1 MPa), H (5 MPa), 150 ˚C, 24 h.
-1
by Re(1)/TiO
2
catalysts. Pre-treatment: H
2
of Re, 1,4-dioxane (1 mL), CO
2
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Figure 8. Re L
3
-edge XANES spectra of Re(1)/TiO after temperature-dependent reductions
2
(
left) and the chemical shift of the binding energy as a function of the reduction temperature
right). The samples were treated at 200, 500, or 900 °C under a flow of H . The XANES spectra
(
2
were taken at room temperature without exposure to air after the reduction treatment by sealing
the samples under N
2
.
Figure 9. HAADF-STEM images of Re(1)/TiO
2
after the reduction at 200 °C under a flow of H .
2
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Figure 10. HAADF-STEM images of Re(1)/TiO
2
after the reduction at 900 °C under a flow of H .
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CONCLUSIONS
The hydrogenation of CO
2
was carried out under mild conditions (T < 150 ˚C; pCO2 = 1
catalysts and a series of other
-supported catalysts, oxide-supported, and unsupported Re
catalysts. The highest TON and selectivity for the formation of MeOH was observed for
Re(1)/TiO , i.e., a TiO -supported Re catalyst with a Re loading of 1 wt%. Studies on
MPa; pH2 = 5 MPa) using various heterogeneous Re/TiO
catalysts that includes TiO
2
2
0
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0
2
2
structure-activity relationship indicates that Re species responsible for the catalytic
formation of MeOH should be sub-nanometer size and have oxidation states higher than
0
and below +4.
AUTHOR INFORMATION
Corresponding author
Takashi Toyao, Ken-ichi Shimizu
E-mail: toyao@cat.hokudai.ac.jp, kshimizu@cat.hokudai.ac.jp
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at
http://pubs.acs.org. CO
2
-TPD, FT-IR, and STEM images.
ACKNOWLEDGEMENT
This study was supported financially by KAKENHI grants 17H01341 and 18K14051 from the
JSPS (Japan Society for the Promotion of Science), by MEXT (Japanese Ministry of Education,
Culture, Sports, Science, and Technology) within the projects IRCCS and ESICB, and by JST-
CREST project JPMJCR17J3. The authors thank the technical division of the Institute for
Catalysis (Hokkaido University) for manufacturing experimental equipment, as well as the
technical staff at the Open Facility of Hokkaido University for their help with STEM analyses. X-
ray absorption measurements were carried out at the BL-14B2 beam line of SPring-8 at the
Japan Synchrotron Radiation Research Institute (JASRI; proposal: 2018A1757).
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REFERENCES
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3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
1)
Artz, J.; Müller, T. E.; Thenert, K.; Kleinekorte, J.; Meys, R.; Sternberg, A.; Bardow, A.; Leitner,
W. Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle
Assessment. Chem. Rev. 2018, 118, 434–504.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
(
2)
3)
Fujimoto, K.; Yokota, K. Effective Hydrogenation of Carbon Dioxide with Two-Stage Reaction
System. Chem. Lett. 1991, 20, 559–562.
Xu, Q.; He, D.; Fujiwara, M.; Tanaka, M.; Souma, Y.; Yamanaka, H. Hydrogenation of Carbon
Dioxide over Fe-Cu-Na/Zeolite Composite Catalysts: Na Migration via Solid-Solid Reaction and
Its Effects on the Catalytic Activity. J. Mol. Catal. A Chem. 1998, 136, 161–168.
Motokura, K.; Naijo, M.; Yamaguchi, S.; Miyaji, A.; Baba, T. Silicone Wastes as Reducing Agents
(
4)
for Carbon Dioxide Transformation: Fluoride-Catalyzed Formic Acid Synthesis from CO
2
, H O,
2
and Disilanes. Chem. Lett. 2015, 44, 1464–1466.
(5)
Filonenko, G. A.; Vrijburg, W. L.; Hensen, E. J. M.; Pidko, E. A. On the Activity of Supported Au
Catalysts in the Liquid Phase Hydrogenation of CO to Formates. J. Catal. 2016, 343, 97–105.
Gao, P.; Li, S.; Bu, X.; Dang, S.; Liu, Z.; Wang, H.; Zhong, L.; Qiu, M.; Yang, C.; Cai, J.; Wen,
W.; Sun, Y. Direct Conversion of CO into Liquid Fuels with High Selectivity over a Bifunctional
2
(
6)
2
Catalyst. Nat. Chem. 2017, 9, 1019–1024.
(7)
Kuwahara, Y.; Fujie, Y.; Yamashita, H. Poly(Ethyleneimine)-Tethered Ir Complex Catalyst
Immobilized in Titanate Nanotubes for Hydrogenation of CO to Formic Acid. ChemCatChem
2
2017, 9, 1906–1914.
( Ramirez, A.; Gevers, L.; Bavykina, A.; Ould-Chikh, S.; Gascon, J. Metal Organic Framework-
Derived Iron Catalysts for the Direct Hydrogenation of CO to Short Chain Olefins. ACS Catal.
018, 8, 9174–9182.
( Dang, S.; Gao, P.; Liu, Z.; Chen, X.; Yang, C.; Wang, H.; Zhong, L.; Li, S.; Sun, Y. Role of
Zirconium in Direct CO Hydrogenation to Lower Olefins on Oxide/Zeolite Bifunctional Catalysts.
J. Catal. 2018, 364, 382–393.
(10) Mori, K.; Sano, T.; Kobayashi, H.; Yamashita, H. Surface Engineering of a Supported PdAg
Catalyst for Hydrogenation of CO to Formic Acid: Elucidating the Active Pd Atoms in Alloy
Nanoparticles. J. Am. Chem. Soc. 2018, 140, 8902–8909.
(11) Honda, M.; Kuno, S.; Sonehara, S.; Fujimoto, K.; Suzuki, K.; Nakagawa, Y.; Tomishige, K.
Tandem Carboxylation-Hydration Reaction System from Methanol, CO and Benzonitrile to
8)
2
2
9)
2
2
2
Dimethyl Carbonate and Benzamide Catalyzed by CeO2. ChemCatChem 2011, 3, 365–370.
ACS Paragon Plus Environment
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1

ACS Catalysis
Page 22 of 27
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
12) Wang, W. H.; Himeda, Y.; Muckerman, J. T.; Manbeck, G. F.; Fujita, E. CO
2
Hydrogenation to
Formate and Methanol as an Alternative to Photo- and Electrochemical CO
2
Reduction. Chem.
Rev. 2015, 115, 12936–12973.
(13) Zhu, P.; Sun, J.; Yang, G.; Liu, G.; Zhang, P.; Yoneyama, Y.; Tsubaki, N. Tandem Catalytic
Synthesis of Benzene from CO and H . Catal. Sci. Technol. 2017, 7, 2695–2699.
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
14) Liu, X.; Wang, M.; Zhou, C.; Zhou, W.; Cheng, K.; Kang, J.; Zhang, Q.; Deng, W.; Wang, Y.
Selective Transformation of Carbon Dioxide into Lower Olefins with a Bifunctional Catalyst
Composed of ZnGa
2
O and SAPO-34. Chem. Commun. 2017, 54, 140–143.
4
(15) Toyao, T.; Siddiki, S. M. A. H.; Ishihara, K.; Kon, K.; Onodera, W.; Shimizu, K. Heterogeneous
Platinum Catalysts for Direct Synthesis of Trimethylamine by N-Methylation of Ammonia and Its
Surrogates with CO
2
/H . Chem. Lett. 2017, 46, 68–70.
2
(
16) Mitsudome, T.; Urayama, T.; Fujita, S.; Maeno, Z.; Mizugaki, T.; Jitsukawa, K.; Kaneda, K. A
Titanium Dioxide Supported Gold Nanoparticle Catalyst for the Selective N-Formylation of
Functionalized Amines with Carbon Dioxide and Hydrogen. ChemCatChem 2017, 9, 3632–3636.
17) Li, Y.; Cui, X.; Dong, K.; Junge, K.; Beller, M. Utilization of CO as a C1 Building Block for
(
(
2
Catalytic Methylation Reactions. ACS Catal. 2017, 7, 1077–1086.
18) Tamura, M.; Miura, A.; Gu, Y.; Nakagawa, Y.; Tomishige, K. Selective N-Methylation of Aniline to
N-Methylaniline with CO
017, 46, 1243–1246.
19) Toyao, T.; Hakim Siddiki, S. M. A.; Kon, K.; Shimizu, K. The Catalytic Reduction of Carboxylic
Acid Derivatives and CO by Metal Nanoparticles on Lewis-Acidic Supports. Chem. Rec. 2018,
8, 1374–1393.
2
and H
2
by CeO -Supported Cu Sub-Nanoparticle Catalyst. Chem. Lett.
2
2
(
2
1
(20) Iizuka, T.; Kojima, M.; Tanabe, K. Support Effects in the Formation of Methanol from Carbon
Dioxide and Hydrogen over Rhenium Catalysts. J. Chem. Soc. Chem. Commun. 1983, 638–639.
(
(
21) Xu, Z.; Qian, Z. H.; Tanabe, K.; Hattori, H. Support Effect of Re Catalyst on Methanol Synthesis
From CO and H Under a Pressure of 5-Atm. Bull. Chem. Soc. Jpn. 1991, 64, 1664–1668.
2
2
22) Tominaga, K.; Sasaki, Y.; Kawai, M.; Watanabe, T.; Saito, M. Ruthenium Complex Catalysed
Hydrogenation of Carbon Dioxide to Carbon Monoxide, Methanol and Methane. J. Chem. Soc.
Chem. Commun. 1993, 629–631.
(
23) Álvarez, A.; Bansode, A.; Urakawa, A.; Bavykina, A. V.; Wezendonk, T. A.; Makkee, M.; Gascon,
J.; Kapteijn, F. Challenges in the Greener Production of Formates/Formic Acid, Methanol, and
DME by Heterogeneously Catalyzed CO Hydrogenation Processes. Chem. Rev. 2017, 117,
2
9804–9838.
ACS Paragon Plus Environment
2
2

Page 23 of 27
ACS Catalysis
1
2
3
(
24) Rodriguez, J. A.; Liu, P.; Stacchiola, D. J.; Senanayake, S. D.; White, M. G.; Chen, J. G.
Hydrogenation of CO to Methanol: Importance of Metal-Oxide and Metal-Carbide Interfaces in
the Activation of CO . ACS Catal. 2015, 5, 6696–6706.
(25) Bahruji, H.; Bowker, M.; Hutchings, G.; Dimitratos, N.; Wells, P.; Gibson, E.; Jones, W.; Brookes,
C.; Morgan, D.; Lalev, G. Pd/ZnO Catalysts for Direct CO Hydrogenation to Methanol. J. Catal.
016, 343, 133–146.
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
(
(
(
26) Martin, O.; Martín, A. J.; Mondelli, C.; Mitchell, S.; Segawa, T. F.; Hauert, R.; Drouilly, C.;
Curulla-Ferré, D.; Pérez-Ramírez, J. Indium Oxide as a Superior Catalyst for Methanol Synthesis
by CO
2
Hydrogenation. Angew. Chem. Int. Ed. 2016, 55, 6261–6265.
27) Wang, J.; Li, G.; Li, Z.; Tang, C.; Feng, Z.; An, H.; Liu, H.; Liu, T.; Li, C. A Highly Selective and
Stable ZnO-ZrO
e1701290.
2
Solid Solution Catalyst for CO Hydrogenation to Methanol. Sci. Adv. 2017, 3,
2
28) Larmier, K.; Liao, W. C.; Tada, S.; Lam, E.; Verel, R.; Bansode, A.; Urakawa, A.; Comas-Vives,
A.; Copéret, C. CO -to-Methanol Hydrogenation on Zirconia-Supported Copper Nanoparticles:
2
Reaction Intermediates and the Role of the Metal–Support Interface. Angew. Chem. - Int. Ed.
2017, 56, 2318–2323.
(
(
29) Kattel, S.; Liu, P.; Chen, J. G. Tuning Selectivity of CO Hydrogenation Reactions at the
2
Metal/Oxide Interface. J. Am. Chem. Soc. 2017, 139, 9739–9754.
30) Kar, S.; Kothandaraman, J.; Goeppert, A.; Prakash, G. K. S. Advances in Catalytic
Homogeneous Hydrogenation of Carbon Dioxide to Methanol. J. CO2 Util. 2018, 23, 212–218.
(31) Olah, G. A.; Goeppert, A.; Prakash, G. K. S. Chemical Recycling of Carbon Dioxide to Methanol
and Dimethyl Ether: From Greenhouse Gas to Renewable, Environmentally Carbon Neutral
Fuels and Synthetic Hydrocarbons. J. Org. Chem. 2009, 74, 487–498.
(
32) Saito, M.; Murata, K. Development of High Performance Cu/ZnO-Based Catalysts for Methanol
Synthesis and the Water-Gas Shift Reaction. Catal. Surv. from Asia 2004, 8, 285–294.
33) Gaikwad, R.; Bansode, A.; Urakawa, A. High-Pressure Advantages in Stoichiometric
Hydrogenation of Carbon Dioxide to Methanol. J. Catal. 2016, 343, 127–132.
(
(34) Porosoff, M. D.; Yan, B.; Chen, J. G. Catalytic Reduction of CO
Methanol and Hydrocarbons: Challenges and Opportunities. Energy Environ. Sci. 2016, 9, 62–
3.
2
by H
2
for Synthesis of CO,
7
(
35) Balaraman, E.; Gunanathan, C.; Zhang, J.; Shimon, L. J. W.; Milstein, D. Efficient Hydrogenation
of Organic Carbonates, Carbamates and Formates Indicates Alternative Routes to Methanol
Based on CO
2
and CO. Nat. Chem. 2011, 3, 609–614.
ACS Paragon Plus Environment
2
3

ACS Catalysis
Page 24 of 27
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
(
36) Huff, C. A.; Sanford, M. S. Cascade Catalysis for the Homogeneous Hydrogenation of CO to
2
Methanol. J. Am. Chem. Soc. 2011, 133, 18122–18125.
37) Wesselbaum, S.; Vom Stein, T.; Klankermayer, J.; Leitner, W. Hydrogenation of Carbon Dioxide
to Methanol by Using a Homogeneous Ruthenium-Phosphine Catalyst. Angew. Chem. - Int. Ed.
2
012, 51, 7499–7502.
38) Rezayee, N. M.; Huff, C. A.; Sanford, M. S. Tandem Amine and Ruthenium-Catalyzed
Hydrogenation of CO into Methanol. J. Am. Chem. Soc. 2015, 137, 1028−1031.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
(
2
39) Wesselbaum, S.; Moha, V.; Meuresch, M.; Brosinski, S.; Thenert, K. M.; Kothe, J.; Stein, T. vom;
Englert, U.; Hölscher, M.; Klankermayer, J.; Leitner, W. Hydrogenation of Carbon Dioxide to
Methanol Using a Homogeneous Ruthenium–Triphos Catalyst: From Mechanistic Investigations
to Multiphase Catalysis. Chem. Sci. 2015, 6, 693–704.
(
40) Schneidewind, J.; Adam, R.; Baumann, W.; Jackstell, R.; Beller, M. Low-Temperature
Hydrogenation of Carbon Dioxide to Methanol with a Homogeneous Cobalt Catalyst. Angew.
Chem. - Int. Ed. 2017, 56, 1890 –1893.
(
(
(
41) Kar, S.; Goeppert, A.; Kothandaraman, J.; Prakash, G. K. S. Manganese-Catalyzed Sequential
Hydrogenation of CO to Methanol via Formamide. ACS Catal. 2017, 7, 6347−6351.
2
42) Ribeiro, A. P. C.; Martins, L. M. D. R. S.; Pombeiro, A. J. L. Carbon Dioxide-to-Methanol Single-
Pot Conversion Using a C-Scorpionate Iron(II) Catalyst. Green Chem. 2017, 19, 4811–4815.
43) Everett, M.; Wass, D. F. Highly Productive CO
2
Hydrogenation to Methanol-a Tandem Catalytic
Approach: Via Amide Intermediates. Chem. Commun. 2017, 53, 9502–9504.
(44) Kothandaraman, J.; Goeppert, A.; Czaun, M.; Olah, G. A.; Prakash, G. K. S. Conversion of CO
from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst. J. Am.
Chem. Soc. 2016, 133, 778–781.
2
(
45) Kar, S.; Sen, R.; Goeppert, A.; Prakash, G. K. S. Integrative CO Capture and Hydrogenation to
2
Methanol with Reusable Catalyst and Amine: Toward a Carbon Neutral Methanol Economy. J.
Am. Chem. Soc. 2018, 140, 1580–1583.
(
46) Scharnagl, F.; Hertrich, M.; Neitzel, G.; Jackstell, R.; Beller, M. Homogeneous Catalytic
Hydrogenation of CO to Methanol – Improvements with Tailored Ligands. Adv. Synth. Catal. In
2
Press. doi:10.1002/adsc.201801314.
(
(
47) Zeng, J.; Fujimoto, K.; Tsubaki, N. A New Low-Temperature Synthesis Route of Methanol:
Catalytic Effect of the Alcoholic Solvent. Energy and Fuels 2002, 16, 83–86.
48) Reller, C.; Pöge, M.; Lißner, A.; Mertens, F. O. R. L. Methanol from CO
CO Capture and Hydrogenation in One Process Step. Environ. Sci. Technol. 2014, 48,
4799−14804.
2
by Organo-Cocatalysis:
2
1
ACS Paragon Plus Environment
2
4

Page 25 of 27
ACS Catalysis
1
2
3
(
(
(
49) Chen, Y.; Choi, S.; Thompson, L. T. Low-Temperature CO
a Heterogeneous Cascade Catalytic System. ACS Catal. 2015, 5, 1717−1725.
50) Chen, Y.; Choi, S.; Thompson, L. T. Low Temperature CO Hydrogenation to Alcohols and
Hydrocarbons over Mo C Supported Metal Catalysts. J. Catal. 2016, 343, 147–156.
51) He, Z.; Qian, Q.; Ma, J.; Meng, Q.; Zhou, H.; Song, J.; Liu, Z.; Han, B. Water-Enhanced
Synthesis of Higher Alcohols from CO Hydrogenation over a Pt/Co Catalyst under Milder
Conditions. Angew. Chem. - Int. Ed. 2016, 55, 737–741.
2
Hydrogenation to Liquid Products via
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
3
O
4
(
52) Kothandaraman, J.; Dagle, R. A.; Dagle, V. L.; Davidson, S. D.; Walter, E. D.; Burton, S. D.;
Hoyt, D. W.; Heldebrant, D. J. Condensed-Phase Low Temperature Heterogeneous
Hydrogenation of CO
(53) Khan, M. U.; Wang, L.; Liu, Z.; Gao, Z.; Wang, S.; Li, H.; Zhang, W.; Wang, M.; Wang, Z.; Ma,
C.; Zeng, J. Pt Co Octapods as Superior Catalysts of CO Hydrogenation. Angew. Chem. - Int.
Ed. 2016, 55, 9548 –9552.
2
to Methanol. Catal. Sci. Technol. 2018, 8, 5098–5103.
3
2
(
54) Zhang, W.; Wang, L.; Liu, H.; Hao, Y.; Li, H.; Khan, M. U.; Zeng, J. Integration of Quantum
Confinement and Alloy Effect to Modulate Electronic Properties of RhW Nanocrystals for
Improved Catalytic Performance toward CO
2
Hydrogenation. Nano Lett. 2017, 17, 788−793.
(
55) Li, H.; Wang, L.; Dai, Y.; Pu, Z.; Lao, Z.; Chen, Y.; Wang, M.; Zheng, X.; Zhu, J.; Zhang, W.; Si,
R.; Ma, C.; Zeng, J. Synergetic Interaction between Neighbouring Platinum Monomers in CO
2
Hydrogenation. Nat. Nanotechnol. 2018, 13, 411–417.
(
(
56) Bai, S.; Shao, Q.; Feng, Y.; Bu, L.; Huang, X. Highly Efficient Carbon Dioxide Hydrogenation to
Methanol Catalyzed by Zigzag Platinum–Cobalt Nanowires. Small 2017, 13, 1604311.
57) Zheng, X.; Lin, Y.; Pan, H.; Wu, L.; Zhang, W.; Cao, L.; Zhang, J.; Zheng, L.; Yao, T. Grain
Boundaries Modulating Active Sites in RhCo Porous Nanospheres for Efficient CO
2
Hydrogenation. Nano Res. 2018, 11, 2357–2365.
(
(
58) Toyao, T.; Siddiki, S. M. A. H.; Touchy, A. S.; Onodera, W.; Kon, K.; Morita, Y.; Kamachi, T.;
Yoshizawa, K.; Shimizu, K. TiO -Supported Re as a General and Chemoselective
2
Heterogeneous Catalyst for Hydrogenation of Carboxylic Acids to Alcohols. Chem. - A Eur. J.
2017, 23, 1001–1006.
59) Toyao, T.; Siddiki, S. M. A. H.; Morita, Y.; Kamachi, T.; Touchy, A. S.; Onodera, W.; Kon, K.;
Furukawa, S.; Ariga, H.; Asakura, K.; Yoshizawa, K.; Shimizu, K. Rhenium-Loaded TiO
Highly Versatile and Chemoselective Catalyst for the Hydrogenation of Carboxylic Acid
2
: A
Derivatives and the N-Methylation of Amines Using H
14848–14859.
2
and CO . Chem. - A Eur. J. 2017, 23,
2
ACS Paragon Plus Environment
2
5

ACS Catalysis
Page 26 of 27
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
60) Gates, B. C.; Flytzani-Stephanopoulos, M.; DIxon, D. A.; Katz, A. Atomically Dispersed
Supported Metal Catalysts: Perspectives and Suggestions for Future Research. Catal. Sci.
Technol. 2017, 7, 4259–4275.
(61) Jones, J.; Xiong, H.; DeLaRiva, A. T.; Peterson, E. J.; Pham, H.; Challa, S. R.; Qi, G.; Oh, S.;
Wiebenga, M. H.; Hernández, X. I. P.; Wang, Y.; Datye, A. K. Thermally Stable Single-Atom
Platinum-on-Ceria Catalysts via Atom Trapping. Science 2016, 353, 150–154.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
62) Zhang, Z.; Zhu, Y.; Asakura, H.; Zhang, B.; Zhang, J.; Zhou, M.; Han, Y.; Tanaka, T.; Wang, A.;
Zhang, T.; Yan, N. Thermally Stable Single Atom Pt/m-Al
2
O for Selective Hydrogenation and
3
CO Oxidation. Nat. Commun. 2017, 8, 16100.
(
63) Bobadilla, L. F.; Santos, J. L.; Ivanova, S.; Odriozola, J. A.; Urakawa, A. Unravelling the Role of
Oxygen Vacancies in the Mechanism of the Reverse Water-Gas Shift Reaction by Operando
DRIFTS and Ultraviolet-Visible Spectroscopy. ACS Catal. 2018, 8, 7455−7467.
(
(
64) Matsubu, J. C.; Yang, V. N.; Christopher, P. Isolated Metal Active Site Concentration and
Stability Control Catalytic CO Reduction Selectivity. J. Am. Chem. Soc. 2015, 137, 3076–3084.
2
65) Koso, S.; Watanabe, H.; Okumura, K.; Nakagawa, Y.; Tomishige, K. Stable Low-Valence ReOx
Cluster Attached on Rh Metal Particles Formed by Hydrogen Reduction and Its Formation
Mechanism. J. Phys. Chem. C 2012, 116, 3079−3090.
(
66) Ly, B. K.; Tapin, B.; Aouine, M.; Delichere, P.; Epron, F.; Pinel, C.; Especel, C.; Besson, M.
Insights into the Oxidation State and Location of Rhenium in Re-Pd/TiO Catalysts for Aqueous-
2
Phase Selective Hydrogenation of Succinic Acid to 1,4-Butanediol as a Function of Palladium
and Rhenium Deposition Methods. ChemCatChem 2015, 7, 2161–2178.
(
(
67) Thompson, S. T.; Lamb, H. H. Catalysts for Selective Hydrogenation of Furfural Derived from the
Double Complex Salt [Pd(NH ](ReO on γ-Al . J. Catal. 2017, 350, 111–121.
3
)
4
4
)
2
2
O
3
68) Nakagawa, Y.; Tazawa, S.; Wang, T.; Tamura, M.; Hiyoshi, N.; Okumura, K.; Tomishige, K.
Mechanistic Study of Hydrogen-Driven Deoxydehydration over Ceria-Supported Rhenium
Catalyst Promoted by Au Nanoparticles. ACS Catal. 2018, 8, 584−595.
(
69) Greiner, M. T.; Rocha, T. C. R.; Johnson, B.; Klyushin, A.; Knop-Gericke, A.; Schlögl, R. The
Oxidation of Rhenium and Identification of Rhenium Oxides during Catalytic Partial Oxidation of
Ethylene: An in-Situ Xps Study. Zeitschrift fur Phys. Chemie 2014, 228, 521–541.
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