Supporting information

Efficient and versatile CuNi alloy nanocatalysts for the highly

selective hydrogenation of furfural

Jun Wu a,b, Guang Gao a, Jinlei Li a,b, Peng Sun a, Xiangdong Long a,b and Fuwei Li a,*

a State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute

of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. Chinab University of Chinese Academy of Sciences, Beijing 100039, P. R. China

Corresponding Author

*E-mail: fuweili@licp.cas.cn.

** Corresponding authors. Tel/Fax: +86 931 4968528.E-mail addresses: fuweili@licp.cas.cn.

S1

Table of contents

1. Chemical and reagents

2. Complementary reaction and catalyst characterization results

2.1. Figures

Fig. S1. XRD patterns of (A) the reduced monometallic and bimetallic nanocatalysts: (a)

Cu/MgAlO; (b) Cu7Ni1/MgAlO; (c) Cu3Ni1/MgAlO; (d) CuNi/MgAlO; (e) Cu1Ni3/MgAlO; (f)

Cu1Ni7/MgAlO; (g) Ni/MgAlO and (B) the bimetallic CuNi/MgAlO-T nanocatalysts with

different reduction temperature: (a) CuNi/MgAlO-400; (b) CuNi/MgAlO-500; (c) CuNi/MgAlO-

600; (d) CuNi/MgAlO-650; (e) CuNi/MgAlO-700; (f) CuNi/MgAlO-750.

Fig. S2. Structure characterizations of the bimetallic CuNi/MgAlO-400: (A) HADDF-STEM

image and (B) the corresponding EDS line spectral along the red line in A.

Fig. S3. Effect of base concentration on the selectivity of THFA over the bimetallic CuNi/MgAlO-

T nanocatalysts: (A) CO2-TPD profiles; (B) the correlation between the selectivity of THFA and

the total base concentration.

Fig. S4. XPS spectrum in the Ni 2p region of the monometallic Ni/MgAlO catalyst.

Fig. S5. TEM images of the different bimetallic CuNi nanocatalysts prepared with incipient

wetness impregnation: (A) CuNi/MgAlO-IMP; (B) CuNi/MgO-IMP; (C) CuNi/γ-Al2O3-IMP and

(D) CuNi/SiO2-IMP.

Fig. S6. TEM images of the fresh and spent bimetallic nanocatalysts: (A) Cu1Ni3/MgAlO-fresh;

(B) Cu1Ni3/MgAlO-after five runs; (C) CuNi/MgAlO-fresh; (D) CuNi/MgAlO-after six runs.

Fig. S7. XRD patterns of the fresh and spent bimetallic nanocatalysts: (A) Cu1Ni3/MgAlO; (B)

CuNi/MgAlO.

Fig. S8. O2-TPO profiles of the monometallic and bimetallic nanocatalysts: (a) Cu/MgAlO; (b)

CuNi/MgAlO-400; (c) CuNi/MgAlO-500; (d) CuNi/MgAlO-600; (e) CuNi/MgAlO-650; (f)

CuNi/MgAlO-700; (g) CuNi/MgAlO-750; (h) Ni/MgAlO.

Fig. S9. XPS spectra in the Cu 2p region of the fresh and spent CuNi/MgAlO nanocatalysts.

2.2. Tables

Table S1. The composition of Cu and Ni in the hydrotalcite derived nanocatalysts.

S2

Table S2. The physicochemical properties of bimetallic CuNi/MgAlO-T nanocatalysts with

different reduction temperature.

Table S3. The catalytic performance of monometallic Ni/MgAlO-T with different reduction

temperaturea.

Table S4. Effect of the reaction parameters on the furfural hydrogenation over the bimetallic

CuNi/MgAlO nanocatalysts in ethanola.

Table S5. Effect of surface chemical composition of the bimetallic CuNi/MgAlO-T on the

selectivity of furfural hydrogenation.

Table S6. Effect of solvent on the furfural hydrogenation over the bimetallic CuNi/MgAlO

nanocatalysta.

Table S7. Effect of mixed solvent of methanol and ethanol on furfural hydrogenation over the

bimetallic CuNi/MgAlO nanocatalysta.

Table S8. The leaching of Cu and Ni metals in the bimetallic Cu1Ni3/MgAlO and CuNi/MgAlO

nanocatalysts determined by ICP-AES.

Table S9. Representative works reported in the literatures for the hydrogenation of furfural to

THFA and FOL over different catalysts.

3. References

S3

1. Chemical and reagents

All chemicals are analytical grade and used as received without any further purification, except

furfural was used after distillation, Nickel nitrate (Ni(NO3)2·6H2O), cupric nitrate

(Cu(NO3)2·3H2O), magnesium nitrate (Mg(NO3)2·6H2O), and aluminum nitrate (Al(NO3)2·9H2O)

were purchased from Sinopharm Chemical Reagent Co., Ltd. Zinc. 5% Ru/C, MgO (99.9% metals

basis, 50 nm), γ-Al2O3 (99.9% metals basis, 20 nm), SiO2 (99.8%, 150 m2/g), furfural,

tetrahydrofurfuryl alcohol, furfuryl alcohol, γ-valerolactone, were purchased from Aladdin

Chemistry Co., Ltd. Sodium carbonate, sodium hydroxide, methanol, ethanol and n-propanol,

isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, amyl alcohol, ethyl acetate and cyclohexane

were purchased from Sinopharm Chemical Reagent Co., Ltd and used as received.

S4

2. Complementary reaction and catalyst characterization results

Fig. S1. XRD patterns of (A) the reduced monometallic and bimetallic nanocatalysts: (a)

Cu/MgAlO; (b) Cu7Ni1/MgAlO; (c) Cu3Ni1/MgAlO; (d) CuNi/MgAlO; (e) Cu1Ni3/MgAlO; (f)

Cu1Ni7/MgAlO; (g) Ni/MgAlO and (B) the bimetallic CuNi/MgAlO-T nanocatalysts with

different reduction temperature: (a) CuNi/MgAlO-400; (b) CuNi/MgAlO-500; (c) CuNi/MgAlO-

600; (d) CuNi/MgAlO-650; (e) CuNi/MgAlO-700; (f) CuNi/MgAlO-750.

Crystalline phases: (●) Cu metal, (■) Ni metal, (▽) CuNi alloys, (⊙) MgO-like solid solution.

Fig. S2. Structure characterizations of the bimetallic CuNi/MgAlO-400: (A) HADDF-STEM

image and (B) the corresponding EDS line spectral along the red line in A.

Note: From the EDS line spectral results, we can see similar distribution profiles of the element of

Cu and Ni, indicating the formation of homogeneous CuNi alloys in the CuNi/MgAlO-400.

S5

Fig. S3. Effect of base concentration on the selectivity of THFA over the bimetallic CuNi/MgAlO-

T nanocatalysts: (A) CO2-TPD profiles; (B) the correlation between the selectivity of THFA and

the total base concentration.

Reaction conditions: furfural 5 mmol, ethanol 20 mL, catalyst 0.05 g, 150 °C, 3 h, H2 4 MPa.

Note: Based on the results of CO2-TPD，the total basic concentrations were 2.03 mmol g-1, 1.09

mmol g-1, 0.7 mmol g-1, 0.37 mmol g-1, 0.49 mmol g-1, which were corresponding to the bimetallic

nanocatalysts: CuNi/MgAlO-400, CuNi/MgAlO-500, CuNi/MgAlO-600, CuNi/MgAlO-700,

CuNi/MgAlO-750, respectively. The highest selectivity of THFA was obtained at the total base

concentration of 0.7 mmol g-1 corresponding to the CuNi/MgAlO-600 catalyst. Moreover,

excessive basic concentration could result in side reactions, 6.8%-9.6% yield (GC yield) of 1,2-

pentanediol and 1,5-pentanediol derived from the furan ring opening secondary reaction were

observed over both CuNi/MgAlO-400 and CuNi/MgAlO-500, which might be caused by the high

concentration of basic sites in these two catalysts [1].

S6

Fig. S4. XPS spectrum in the Ni 2p region of the monometallic Ni/MgAlO catalyst.

Note: The XPS result suggested that the nature of metallic Ni species was sensitive to oxygen.

Fig. S5. TEM images of the different bimetallic CuNi nanocatalysts prepared with incipient

wetness impregnation: (A) CuNi/MgAlO-IMP; (B) CuNi/MgO-IMP; (C) CuNi/γ-Al2O3-IMP and

(D) CuNi/SiO2-IMP.

Note: In the TEM images of supported CuNi nanoparticles fabricated by the incipient wet

impregnation method, numerous large nanoparticles were observed, and these catalysts showed

lower catalytic activity for the hydrogenation of furfural to THFA. These results suggest the direct

reduction of as-prepared hydrotalcite precursors is an effective method to obtain high-dispersed

CuNi alloys with high activity and selectivity for the hydrogenation of furfural to THFA.

S7

Fig. S6. TEM images of the fresh and spent bimetallic nanocatalysts: (A) Cu1Ni3/MgAlO-fresh;

(B) Cu1Ni3/MgAlO-after five runs; (C) CuNi/MgAlO-fresh; (D) CuNi/MgAlO-after six runs.

Fig. S7. XRD patterns of the fresh and spent bimetallic nanocatalysts: (A) Cu1Ni3/MgAlO; (B)

CuNi/MgAlO.

S8

Fig. S8. O2-TPO profiles of the monometallic and bimetallic nanocatalysts: (a) Cu/MgAlO; (b)

CuNi/MgAlO-400; (c) CuNi/MgAlO-500; (d) CuNi/MgAlO-600; (e) CuNi/MgAlO-650; (f)

CuNi/MgAlO-700; (g) CuNi/MgAlO-750; (h) Ni/MgAlO.

Note: Based on the O2-TPO profiles, the amount of O2 consumption of the catalysts were:

2.68mmol g-1, 2.01mmol g-1, 2.95mmol g-1, 3.45mmol g-1, 3.92mmol g-1, 4.3mmol g-1, 4.52mmol g-

1, 2.79mmol g-1, which are corresponding to the nanocatalysts: Cu/MgAlO, CuNi/MgAlO-400,

CuNi/MgAlO-500, CuNi/MgAlO-600, CuNi/MgAlO-650, CuNi/MgAlO-700, CuNi/MgAlO-750,

and Ni/MgAlO, respectively.

Fig. S9. XPS spectra in the Cu 2p region of the fresh and spent CuNi/MgAlO nanocatalysts.

S9

Note: The XPS spectra in the Cu 2p region of the CuNi/MgAlO nanocatalysts showed two peaks

with the binding energy of Cu 2p3/2 and Cu 2p1/2 at 932.4ev and 952.3ev, respectively, which

were associated with metallic Cu0 and Cu+ species [2]. Besides, the XPS spectra of the fresh and

spent CuNi/MgAlO catalysts showed a negligible shift in the binding energies in the Cu 2p region,

which indicates the high stability of our bimetallic CuNi nanocatalyst.

Table S1. The composition of Cu and Ni in the hydrotalcite derived nanocatalysts.

Catalyst Cua Nia Cub Nib Bulk Cu/Nia Surface Cu/Nib

(wt %) (wt %) (at %) (at %) (mole ratio) (mole ratio)

Cu/MgAlO 50.94 - 4.10 - - -

Cu7Ni1/MgAlO 38.89 5.00 3.91 0.89 7.100 4.390

Cu3Ni1/MgAlO 35.62 10.88 3.64 1.48 3.026 2.460

Cu1Ni1/MgAlO 26.50 24.00 2.33 2.46 1.021 0.947

Cu1Ni3/MgAlO 15.43 42.73 1.24 3.92 0.333 0.316

Cu1Ni7/MgAlO 5.65 35.69 1.27 4.35 0.146 0.292

Ni/MgAlO - 50.39 - 4.70 - -

a Determined by ICP-AES.

b Determined by XPS.

S10

Tabl

e S2

. The

phy

sico

chem

ical

pro

perti

es o

f bim

etal

lic C

uNi/M

gAlO

-T n

anoc

atal

ysts

with

diff

eren

t red

uctio

n te

mpe

ratu

re.

R. D

.g

Ni(%

)

46 65 73 79 84 86 - 65

a D

eter

min

ed b

y IC

P-A

ES. b

Det

erm

ined

by

N2 p

hysi

sorp

tion.

c Par

ticle

size

cal

cula

ted

from

the

(111

) ref

lect

ion

peak

in X

RD

by

usin

g th

e

Sche

rrer

equ

atio

n. d M

etal

surf

ace

area

det

erm

ined

by

the

TEM

par

ticle

size

. e Pa

rticl

e si

ze d

eter

min

ed fr

om T

EM. f D

ispe

rsio

n ca

lcul

ated

from

the

TEM

par

ticle

siz

e. g R

educ

tion

degr

ee c

alcu

late

d on

the

basi

s of t

he a

mou

nt o

f O2 c

onsu

mpt

ion

in O

2-TPO

and

ass

umed

that

Cu0 +1

/2O

2→C

uO,

Cu(

%)

Ni(%

)61 85 93 99 99 99 67 -

Df

(%)

27.2

25.9

19.9

16.4

5.1

4.7

20.8

9.5

de

(nm

)

3.8

4.0

5.2

6.3

20.3

21.9

4.8

11.0

S TEM

d

(m2 /g

)

88.4

83.9

64.6

53.3

16.5

15.3

69.0

30.6

dc

(nm

)

3.3

3.6

4.4

4.6

5.7

10.0

4.2

7.1

Vpo

reb

(cm

3 /g)

0.75

0.84

0.86

0.69

0.80

0.86

0.63

0.73

d por

eb

(nm

)

11.2

12.3

15.1

13.1

14.7

17.6

12.5

13.6

S BET

b

(m2 /g

)

185

210

172

157

163

137

135

160

AN

ia

(wt %

)

21.8

7

22.9

7

24.0

0

25.0

1

26.0

8

26.8

2

-

50.3

9

Cua

(wt %

)

23.5

7

24.9

8

26.5

0

27.0

3

28.0

2

29.1

3

50.9

4

-

S11

Ni0 +1

/2O

2→N

iO

[3].

Cat

alys

t

CuN

i/MgA

lO-4

00

CuN

i/MgA

lO-5

00

CuN

i/MgA

lO-6

00

CuN

i/MgA

lO-6

50

CuN

i/MgA

lO-7

00

CuN

i/MgA

lO-7

50

Cu/

MgA

lO

Ni/M

gAlO

Table S3. The catalytic performance of monometallic Ni/MgAlO-T with different reduction

temperaturea.

Entry Temperature H2 Pressure Time Conversion Selectivity (%)

(°C) (MPa) (h) (%) FOL THFA Othersi

1 150 4 3 >99 25 65 10

2b 150 4 3 71 80 13 7

3c 150 4 3 >99 38 52 10

a Reaction conditions: furfural 5 mmol, ethanol 20 mL, catalyst (Ni/MgAlO-700) 0.05 g.

b Catalyst (Ni/MgAlO-600), 0.05 g.

c Catalyst (Ni/MgAlO-800), 0.05 g.

Note: According to the TPR profile of NiMgAl-LDH (Fig. 2g), we investigated the effect of

reduction temperature on the catalytic activity of Ni/MgAlO-T and found that the Ni/MgAlO

catalyst reduced at 700 °C showed the best catalytic performance.

S12

Table S4. Effect of the reaction parameters on the furfural hydrogenation over the bimetallic

CuNi/MgAlO nanocatalysts in ethanola.

Entry Temperature H2 Pressure Time Conversion Selectivity (%)

(°C) (MPa) (h) (%) FOL THFA Othersf

1 100 4 3 >99 95 5 0

2 120 4 3 >99 87 13 0

3 140 4 3 >99 14 80 6

4 150 4 3 >99 0 95 5

5 170 4 3 >99 0 87 13

6 150 3 3 >99 34 58 8

7 150 5 3 >99 0 92 8

8 150 4 0.5 >99 76 19 5

9 150 4 1 >99 64 30 6

10 150 4 2 >99 39 53 8

11 150 4 4 >99 0 92 8

12 b 150 4 3 >99 65 29 6

13 c 150 4 3 >99 32 59 9

14 d 150 4 3 >99 0 94 6

15 e 150 4 0.5 77 49 43 8

16 e 150 4 1 92 45 45 10

17 e 150 4 2 >99 38 51 11

18 e 150 4 3 >99 25 65 10

a Reaction conditions: furfural 5 mmol, ethanol 20 mL, catalyst 0.05 g.

b Catalyst 0.03 g.

c Catalyst 0.04 g.

d Catalyst 0.06 g.

e Catalyst (Ni/MgAlO), 0.05 g.

f Others include 1,2-pentanediol, 1,5-pentanediol and other not detected.

S13

Note: As shown in Scheme 1, the transformation of furfural to THFA is a consecutive two-step

hydrogenation process via the FOL intermediate over our bimetallic CuNi nanocatalyst. In

addition, as depicted in Table 2, it can be seen that the TOFC=O values belonging to the

hydrogenation at aldehyde group of furfural to FOL are obviously larger than that of FOL

hydrogenation to THFA (TOFC=C) in all bimetallic nanocatalysts, which indicates that the latter

reaction process of FOL hydrogenation to THFA may be the rate-determining step for the total

hydrogenation of furfural over our bimetallic CuNi nanocatalysts. In the process of investigating

the influence of the amount of catalyst on the catalytic performance under the optimized reaction

temperature, H2 pressure and reaction time (Table S4, entries 4, 12, 13 and 14), a gradual increase

in the amount of catalyst (before getting to the optimized value) in the catalytic tests means that

there exists more catalytically active species which would be beneficial to the step of

hydrogenation of FOL to THFA. Thus the selectivity of furfural hydrogenation is shifted from

FOL to THFA with the increase of catalyst loading to an appropriate value under the optimized

reaction temperature, H2 pressure and reaction time (150 °C, 4 MPa, 3h).

S14

Table S5. Effect of surface chemical composition of the bimetallic CuNi/MgAlO-T on the

selectivity of furfural hydrogenation.

Entry Catalyst Bulk Cu/Nia Surface Cu/Nib Selectivity (%)

(mole ratio) (mole ratio) FOL THFA

1 CuNi/MgAlO-400 0.996 0.615 0 81

2 CuNi/MgAlO-500 1.005 0.825 0 88

3 CuNi/MgAlO-600 1.021 0.947 0 95

4 CuNi/MgAlO-650 0.999 1.105 49 45

5 CuNi/MgAlO-700 0.993 1.271 89 7

6 CuNi/MgAlO-750 1.004 1.538 94 2

a Determined by ICP-AES.

b Determined by XPS.

Reaction conditions: furfural 5 mmol, ethanol 20 mL, catalyst 0.05 g, 150 °C, 3 h, H2 4 MPa.

Note: The surface composition of bimetallic CuNi catalysts varied obviously with the increase of

reduction temperature of hydrotalcite precursor. In the case of CuNi/MgAlO reduced at 600 °C, its

surface Cu/Ni ratio was closed to the bulk one and presented the highest selectivity to THFA. With

the reduction temperature further increased, the surface Cu/Ni ratio were larger than that of bulk

ones, indicating Cu segregated into the nanoparticle surface gradually to form Cu-rich CuNi

alloys. This phenomenon might also explain the gradually enhanced selectivity to FOL in the case

of bimetallic CuNi catalysts reduced by higher temperature (entries 4-6), because the Cu catalytic

sites were believed to be selectively active toward the hydrogenation of aldehyde moiety and inert

for the furan ring activation [4].

Table S6. Effect of solvent on the furfural hydrogenation over the bimetallic CuNi/MgAlO

S15

nanocatalysta.

Entry Solvent Conversion Selectivity (%)

(%) FOL THFA Othersd

1 methanol >99 95 5 0

2 ethanol >99 0 95 0

3 isopropanol >99 0 92 8

4 isobutyl alcohol >99 0 95 5

5 n-propyl alcohol >99 0 90 10

6 n-butyl alcohol >99 0 89 11

7 n-amyl alcohol >99 26 66 8

8 cyclohexane >99 70 26 4

9 ethyl acetate >99 64 30 6

10b methanol >99 94 6 0

11c methanol >99 95 0 5

a Reaction conditions: furfural 5 mmol, solvent 20 mL, catalyst 0.05 g, 150 °C, 3 h, H2 4 MPa.

b Catalyst: Cu1Ni3/MgAlO.

c Catalyst: Cu3Ni1/MgAlO.

d Others include 1,2-pentanediol, 1,5-pentanediol and other not detected.

Note: Based on the above experiment results, solvent has a significant influence on the selectivity

of furfural hydrogenation, especially in the case of methanol. The bimetallic CuNi/MgAlO,

Cu1Ni3/MgAlO and Cu3Ni1/MgAlO catalysts with different chemical compositions all presented

high selectivity to FOL in methanol.

Table S7. Effect of mixed solvent of methanol and ethanol on furfural hydrogenation over the

bimetallic CuNi/MgAlO nanocatalysta.

S16

Entry Solvent Conversion Selectivity (%)

(mL) (%) FOL THFA Othersb

1 0 >99 0 95 5

2 1 >99 12 81 7

3 2.5 >99 31 59 10

4 5 >99 56 35 9

5 10 >99 78 19 3

6 12.5 >99 82 18 0

7 20 >99 95 5 0

a Reaction conditions: furfural 5 mmol, solvent (total volume) 20 mL, catalyst 0.05 g, 150 °C, 3 h,

H2 4 MPa.

b Others include substances not detected. The solvent in the table refers to the volume of methanol.

Note: The selectivity of FOL increased linearly with the volume of methanol elevating in the

mixed solvents, which might suggest methanol suppressed the hydrogenation of furan ring to

some extent [5].

Table S8. The leaching of Cu and Ni metals in the bimetallic Cu1Ni3/MgAlO and CuNi/MgAlO

nanocatalysts determined by ICP-AES.

Catalyst Cu (wt %) Ni (wt %)

Cu1Ni3/MgAlO-600a 15.4 42.7

Cu1Ni3/MgAlO-600b 14.9 41.0

CuNi/MgAlO-600a 26.5 24

CuNi/MgAlO-600c 23.6 20.5

a The fresh catalyst.

b The used catalyst after five runs of reaction.

c The used catalyst after six runs of reaction.

Table S9. Representative works reported in the literatures for the hydrogenation of furfural to

THFA and FOL over different catalysts.

Catalyst Reaction conditions Conversion (%) Selectivity (%) Ref.

S17

The hydrogenation of furfural to THFA

Pd-Ir/SiO2 275 K, 8 MPa H2, 6 h, water >99 94 [6]

Pd-Ni/SiO2 313 K, 8 MPa H2, 2 h, acetic acid-

assisted, water

>99 96 [7]

Pd/MFI 493 K, 500 Psi H2, 5 h, isopropanol 93 67 [8]

Ni/SiO2 413 K, furfural/H2/N2 ratio =

1:36:72, 30 min, 1 atm

>99 94.3 [9]

RuO2 393 K, 4 MPa H2, 1 h, methanol >99 76 [10]

5 wt% Ru/C 393 K, 5 MPa H2, 3 h, methanol >99 59 [10]

3 wt% Pd/C 433 K, 8 MPa H2, 0.5 h, water 98.4 62.1 [11]

Pd-Ir-ReOX/SiO2 323 K, 6 MPa H2, 2 h, water >99 78 [12]

Pt-Li/CoAlO4 413 K, 1.5 MPa H2, 24 h, ethanol >99 31.3 [13]

This study

CuNi/MgAlO

423 K, 4 MPa H2, 3 h,

ethanol

>99 95

The hydrogenation of furfural to FOL

5 wt% Pt/C 458 K, 8 MPa H2, 0.5 h,

n-butanol

99.3 47.9 [14]

Co/SBA-15 423 K, 2 MPa H2, 1.5 h,

ethanol

92 96 [15]

Cu11.2Ni2.4-MgAlO 473 K, 1 MPa H2, 2 h, ethanol 89.9 87 [16]

Ir-ReOX/SiO2 303 K, 0.8 MPa H2, 6h, H2O >99 >99 [17]

Cu-Fe 433 K, 9 MPa H2, 5 h, octane 91 89.5 [18]

This study

CuNi/MgAlO

373 K, 4 MPa H2, 4 h,

methanol

>99 >99

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