Highly Selective and Efficient Rearrangement of Biomass-Derived

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Highly Selective and Efficient Rearrangement of Biomass-derived Furfural to Cyclopentanone over Interface-active Ru/CNTs Catalyst in Water Yanhua Liu, Zhihao Chen, Xiaofeng Wang, Yu Liang, Xiaomin Yang, and Zichen Wang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b02080 • Publication Date (Web): 28 Oct 2016 Downloaded from http://pubs.acs.org on October 31, 2016

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ACS Sustainable Chemistry & Engineering

Highly

Selective

Biomass-derived

and

Efficient

Furfural

to

Rearrangement Cyclopentanone

of over

Interface-active Ru/CNTs Catalyst in Water Yanhua Liu,† Zhihao Chen,† Xiaofeng Wang,‡ Yu Liang,† Xiaomin Yang,*, †and Zichen Wang† †

College of Chemistry, Jilin University, Changchun 130012, China.

‡

State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry,

Jilin University, Changchun, 130012, China.

1

ACS Paragon Plus Environment


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ABSTRACT: Biomass-derived furfural was efficiently converted to valuable cyclopentanone over interface-active Ru/CNTs catalyst in water. The effect of reaction conditions, including furfural concentration, reaction temperature, hydrogen pressure, speed of stirring and reaction time, on the catalytic performance of Ru/CNTs has been studied in detail. The furfural conversion of 99% and cyclopentanone selectivity of 91% were efficiently achieved at very low concentration of Ru/CNTs catalyst (0.26 wt% Ru) under mild reaction conditions (1 MPa H2, 160 oC, 500 rpm). Possible reaction pathways of furfural transformation over Ru/CNTs nanoparticles in water are proposed. KEYWORDS: Carbon nanotube, Ruthenium nanoparticles, Furfural, Ring rearrangement, Cyclopentanone.

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INTRODUCTION Catalytic conversion of renewable biomass resources, as feed stock for the

chemical industry, becomes more and more important because of the urgent demand of sustainable and clean fuels and chemicals.1-4 Furfural can be produced from renewable biomass resources by acid-catalyzed dehydration of pentose, which has the potential to be a sustainable substitute for building blocks derived from petrochemical in the production of fuels and fine chemicals.5, 6 Catalytic hydrogenation of furfural is an important reaction since it allows obtaining products such as furfuryl alcohol, tetrahydrofurfurylalcohol, 2-methylfuran, and cyclopentanone.7 Due to the wide variety of available hydrogenation products of furfural, it is one of the most important themes to design catalysts that are highly selective to the desired products. Cyclopentanone is a versatile fine chemical intermediate. It can be used for the synthesis of pharmaceuticals, fungicides, rubber chemicals, and flavour and fragrance chemicals. Traditionally, cyclopentanone can be prepared by the catalytic liquid phase oxidation of cyclopentene with nitrous oxide

8

or vapour-phase cyclization of 1,

6-hexanediol 9 or adipic acid esters 10. However, petroleum-based products are used as feed stocks in all these processes. Recently, furfural was proved to be a good feedstock to synthesize cyclopentanone,11-19 which has the potential to replace unsustainable fossil fuel. Furfural is the product of acid catalyzed dehydration of pentose proceeding in water. The process of furfural separation from the formed aqueous solutions increases its cost of production. Therefore, it is highly beneficial to use furfural aqueous solution 3



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as feedstock for preparation of chemicals and fuels. This will significantly reduce the energy needed for furfural production. Recently, Hronec et al. reported new methods of rearrangement reaction of furfural 11-13 and furfuryl alcohol 20 to cyclopentanone in aqueous media. They found that some metal catalysts (e.g. Pt/C, Pd-Cu/C, and Ni-based catalysts) had good performance in the selective synthesis of cyclopentanone from furfural or furfuryl alcohol in aqueous solution. In other reports, Ni–Cu/SBA-15,14 Cu–Co,15 CuZnAl,16 and CuNiAl hydrotalcite type catalysts,17 Ru/MIL-101,18 and Au/TiO219 were also used as efficient catalysts for the furfural rearrangement to cyclopentanone in aqueous solution. In addition, aqueous-phase catalytic hydrogenation of furfural to cyclopentanol over Ni/CNTs and Cu-Mg-Al hydrotalcites derived catalysts were reported by Xiao group.21, 22 Although some pioneering work has been done in this area, the study is still in its infancy. Gas−water−solid multiphase catalysis reactions often suffer from low catalytic efficiency because of the low solubility of gases in water and the mass-transfer resistances between multiphase interfaces.23,

24

How to obtain high

reaction efficiency for gas−water−solid multiphase catalysis reactions remains a challenge.25 To some degree, this can be done by raising reaction pressure (e.g. 3-8 MPa) and impeller speed (e.g. 1200-1500 rpm), which will require severe operating conditions. Therefore, developing highly efficient and selective interface-active catalysts in water under mild reaction conditions for furfural rearrangement is still a much-sought-after goal. Carbon nanotubes (CNTs) have potential application in catalysis due to their unique 4


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electron conductivity, thermal stability, and high mechanical strength etc.26-34 Compared with traditional catalyst supports, CNTs have high external surface area and aspect ratio, which significantly increase the contact surface between the reactants and active sites of catalysts, and greatly minimize the diffusion limitations. These features make CNTs very attractive as catalyst supports in liquid phase reactions.35-40 It has been found that CNT supported metal nanoparticles show excellent activity, selectivity, and stability in some redox reactions, which are greatly enhanced and quickened by water.35-37 Therefore, we have the immense interest to explore the novel catalytic properties of CNT supported metal nanoparticles for biomass-derived platform molecule transformations in gas−water−solid multiphase catalysis reaction system. Herein, we have investigated the catalytic conversion of biomass-derived furfural to cyclopentanone in aqueous phase, applying CNT supported Ru nanoparticles as catalyst. The main objective was to develop novel and efficient interface-active catalyst for furfural rearrangement to cyclopentanone in aqueous phase. Various experimental parameters such as furfural concentration, reaction temperature, hydrogen pressure, speed of stirring and reaction time were studied in detail, aiming to optimize the reaction conditions and to elucidate the reaction pathways of furfural transformation over Ru/CNTs catalysts in aqueous phase.

EXPERIMENTAL Materials and Reagents. CNTs with a main range of diameter of 30–50 nm, a

length of 1–2 µm, and a N2 surface area of 151 m2/g were purchased from Shenzhen 5



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Nanotech Port Co., Ltd. (Shenzhen, China). Furfural before experiments was purified by vacuum distillation and stored at -15 oC. All reagents used in this work were of analytical grade. Catalyst Preparation and Characterization. The Ru/CNT catalyst with a metal loading of 6.0 wt% was made via a wetness impregnation method.35,

36

The

preparation procedure is as following. The oxidized CNTs (1 g) were impregnated in an aqueous solution of RuCl3 (40 mL, 0.10 mol/L) under ultrasonic conditions for 30 min, and then the mixture was incubated at room temperature for 12 h. The CNT-supported RuCl3 sample was dried at 110 °C for 12 h under vacuum, and reduced at 400 °C in flowing hydrogen for 2 h, and then cooled to room temperature in N2, obtaining 6.0 wt% Ru/CNT catalyst. For the recycling experiments, the separated Ru/CNTs catalyst was washed first with ethanol, and then with water. Thereafter it was dried at 100 ◦C for 8 h under vacuum. Before recycling, the obtained catalyst was reduced at 400 °C in flowing hydrogen for 2 h, and then cooled to room temperature in an inert atmosphere. The crystalline structure of Ru/CNTs was analyzed by powder X-ray diffraction (XRD, D/MAX-2550) using Cu-Kα radiation with a scanning rate of 2o min−1. Transmission electron microscopy (TEM) examination was conducted using a JEM-2100F equipped with a CCD camera operated at 200 kV. X-ray photoelectron spectroscopy (XPS) was performed on a Thermo ESCALAB 250 system with Mg Kα source (1254.6 eV). The XPS spectrum was calibrated by adjusting the position of the C 1s peak to 284.6 eV. The temperature-programmed desorption of ammonia 6


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(NH3-TPD) experiment was performed using a Micromeritics AutoChem II 2920 automated chemisorption analysis unit with a thermal conductivity detector (TCD) under helium flow. NH3 was adsorbed at 50 oC for 1 h after pretreatment at 300 oC for 1 h in a He stream. After the adsorption, the reactor was purged with He for 1 h at 50 o

C. For the desorption measurement, the Ru/CNTs sample was heated from 50 oC to

500 oC at a rate of 10 K min-1 in a He stream. Furfural Hydrogenation. The selective hydrogenation of furfural was performed in a 100 mL autoclave under stirring. For a typical run, the reaction was carried out with 0.46 g furfural, 0.020 g 6 wt% Ru/CNTs, 40 mL water as solvent, and 1 MPa H2 at 160 °C for 5 h. After each reaction, the catalyst particles were separated from the solution by centrifugation. The liquid phase products were collected, then extracted by ethylacetate, and subsequently analyzed and identified by means of GC (2014C, SHIMADZU) and GC-MS (QP 2010 Plus, SHIMADZU) as well as by comparison with the retention times of the respective standards in GC traces. A HP-INNOWAX capillary column (30 m × 0.32 mm × 0.25 µm) was used for the separation of reaction mixtures. The quantitative determination of the reaction products was carried out by area normalization method and external standard method. All results were evaluated on the basis of the amount of furfural. The conversion of furfural (mol%), the selectivity (mol%) of main products, and carbon balance were calculated as following. Conversion = (1-Moles of furfural/Moles of furfural loaded initially) × 100% Selectivity of product = (Moles of product/Moles of furfural converted) × 100% 7



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Carbon balance = (Moles of products/Moles of furfural converted) × 100%

RESULTS AND DISCUSSION XRD patterns of CNTs and 6.0 wt% Ru/CNTs are shown in Figure 1. For CNTs,

there exists a symmetrical and sharp graphite 0 0 2 peak at 26o, and a broad graphite 1 0 0 peak at 42o. The average interlayer spacing was calculated to be 0.33 nm.41 The layered structure of CNTs was reported to be favorable for the transfer of electrons and for a close interaction between the metal and support by intercalation.42 For 6.0 wt% Ru/CNTs catalyst, no diffraction peak related to metallic Ru is detected (Figure 1), which implies that Ru nanoparticles are of nanometer scale. Typical TEM images and the particle size distribution of the 6.0 wt% Ru/CNTs catalyst are shown in Figure 2, which shows that the Ru nanoparticles with an average size of 2.74 nm are highly dispersed on the surface of CNTs. Figure 3 shows the XPS spectra of the Ru 3p for the 6.0 wt% Ru/CNTs catalyst. Peaks at about 462 eV and 485 eV are attributed to Ru 3p3/2 and Ru 3p1/2, respectively. The XPS spectra indicate that the chemical state of Ru on the surface of Ru/CNTs is metallic. Most of the oxygen-containing functional groups like carboxyl and hydroxyl groups on CNT surface are acidic sites, which are capable of adsorbing basic molecules like NH3. Therefore, the desorption of pre-adsorbed NH3 can be used to characterize the surface acidic sites on CNTs.43,

44

NH3-TPD profile of 6.0 wt%

Ru/CNTs catalyst is shown in Figure 4. The main ammonia TPD peak appeared at about 150-200 oC (Figure 4), indicating that most of the ammonia molecules are weakly chemisorbed. Most of the acidic groups act as primary adsorption centers, 8


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which bind additional ammonia molecules weakly through hydrogen bonds.43-45 The signal at temperature above 300 oC originates from the decomposition of the surface functional groups of CNTs.43 According to TPD-NH3 measurement, the acidity of the catalyst is 991 µmol/g. The aqueous phase hydrogenation of biomass-derived furfural was used to explore the catalytic performance of the Ru/CNTs catalyst. The effect of reaction temperature on the catalytic performance of Ru/CNTs for the selective hydrogenation of furfural is shown in Run 1-3, Table 1. Results show that reaction temperature has significant effect on the selectivity of cyclopentanone. At 160 °C, the selectivity of cyclopentanone is the highest compared with that at 140 °C and 150 °C, which reveals that 160 °C is an appropriate temperature for the furfural rearrangement to cyclopentanone. The effect of speed of stirring on the catalytic performance of Ru/CNTs for the selective hydrogenation of furfural was also studied, as shown in Run 3 and 4, Table 1. With the increase of stirring speed from 500 to 800 rpm, the over-hydrogenation of cyclopentanone to cyclopentanol is promoted, which causes the decrease of the selectivity of cyclopentanone and the corresponding increase of the selectivity of cyclopentanol. The effect of reaction pressure on the catalytic performance of Ru/CNTs for the selective hydrogenation of furfural was investigated, as shown in Run 3 and 5, Table 1. With the increase of hydrogen pressure from 1 to 2 MPa, the selectivity of cyclopentanone decreases from 59% to 0% and meanwhile the selectivity of 9



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cyclopentanol, tetrahydrofurfuryl alcohol and 1, 2-pentanediol increases obviously. The cumutive selectivity of cyclopentanone and cyclopentanol decreases from 90% to 70% when the hydrogen pressure increases from 1 MPa to 2 MPa, which reveals that higher hydrogen pressure is not beneficial for the ring-rearrangement of furfural to cyclopentanone and cyclopentanol over Ru/CNTs in aqueous phase. According to our experimental results, the optimum reaction conditions are as follows: the reaction temperature is 160 °C, the reaction pressure is 1 MPa, and the speed of stirring is 500 rpm. To explore the reaction pathway of furfural hydrogenation, the evolution of reactant and products with reaction time was studied under the above mentioned optimal reaction conditions, as shown in Table 2. The conversion of furfural increases gradually in the 1 h of reaction and it reaches 100% at 2 h. The selectivity of furfuryl alcohol and 2-pentenoic acid decreases gradually in the 1 h. The selectivity of cyclopentanol and tetrahydrofurfuryl alcohol (THFAL) increases gradually. The selectivity of cyclopentanone increases in the 1 h of reaction and then it decreases. According to experimental results and the literature, furfuryl alcohol is an intermediate product and subsequently it is consumed by further hydrogenation to form THFAL, and THFAL to hydrogenalysis to form 1, 2-pentanediol, and by rearrangement to form cyclopentanone and cyclopentanol. It should be noted that the cumulative yield of cyclopentanone and cyclopentanol increases from 49 mol% to 91 mol% with prolong of the reaction time from 0.5 h to 3 h. However, the molar ratio of cyclopentanone to cyclopentanol increases in 1 h, and decreases afterwards. Therefore, high yield and selectivity of cyclopentanone can be 10


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achieved by controlling the reaction time. Effect of solvents on the catalytic activity of Ru/CNTs for the furfural hydrogenation is shown in Table 3. Results show that the highest conversion and selectivity of cyclopentanone are achieved using water as reaction solvent. When CH2Cl2 or ethanol was used as reaction solvent, the furfural rearrangement product of cyclopentanone or cyclopentanol appears, respectively. It should be noted that specified contents of water are in the used dichloromethane and ethanol. For example, the content of water is usually about 0.24% in CH2Cl2 at 20 °C. So, this content of water can influence the rearrangement reaction, i. e. the rearrangement reaction is influenced not only by the acidity of the catalyst but also water in the reaction system. Similarly, in the case of ethanol the content of water is even significantly higher. According to our experimental results and the literature data, possible reaction pathways for the furfural transformation over Ru/CNTs nanoparticles in water are proposed and shown in Scheme 1. The dominant reaction pathway is furfural rearrangement to cyclopentanone (reaction 3, Scheme 1). The first stage of this pathway is the Ru/CNTs catalyzed hydrogenation of furfural to furfuryl alcohol. Then the rearrangement of the furan ring of furfuryl alcohol happens to form an intermediate (*) catalyzed by acid catalyst (H3O+), which may originate from water by self-dissociation according to Hronec’ reports together with the acidic groups on CNTs.

11-13, 20

And then this intermediate species (*) are converted by consecutive

reaction to cyclopentanone over Ru/CNTs catalyst. According to the literature, the intermediate (*) could be 4-hydroxy-2-cyclopentenone.11, 11


13, 14, 46

Meanwhile,


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tetrahydrofurfuryl alcohol (THFA) is produced by total hydrogenation of furfural via furfuryl alcohol over Ru/CNTs catalyst in water (reaction 1, Scheme 1). 1, 2-pentanediol was detected under some reaction conditions, which may be formed via the furfuryl alcohol hydrogenolysis (reaction 2, Scheme 1).47,

48

In water furfuryl

alcohol can be also converted to levulinic acid in the presence of acid catalyst (H3O+).11,

13

Then levulinic acid is converted to 2-pentenoic acid by consecutive

hydrogenation, dehydration, and rearrangement reaction in the presence of Ru/CNTs (reaction 4, Scheme 1). In our case, levulinic acid was not detected, but smaller amount of 2-pentenoic acid was detected under some special reaction conditions. In addition, in the presence of acid catalyst furfuryl alcohol dissolved in water may undergo condensation and oligomerization reactions to give some undesired byproduct.49, 50 To investigate the application potential of the production of cyclopentanone derived from biomass feedstock, the effect of furfural concentration on the catalytic activity of Ru/CNTs was studied, as shown in Table 4. A low concentration of furfural aqueous solution was preferred in reported works to reduce the carbon loss.11, 12, 14 Therefore, the studied furfural concentration was 0.84 ~ 2.42 wt% in our research. With the increase of the furfural concentration, the selective rearrangement of furfural to cyclopentanone can be tuned through varying hydrogen pressure and reaction time. High yield and selectivity of cyclopentanone still obtain. The furfural conversion of 99% and cyclopentanone selectivity of 91% were efficiently achieved using only 0.26 wt% of Ru with respect to furfural under mild reaction conditions (1 MPa H2, 160 oC, 12


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500 rpm). The knowledge of this dependence offers us the possibility to achieve very high yields of cyclopentanone from aqueous solutions of furfural with different concentrations at relatively low hydrogen pressure and speed of stirring compared with the literatures. According to literatures, the main reason of carbon loss comes from the resinification of furfural or furfuryl alcohol.11-14 Unlike furfural and furfuryl alcohol, cyclopentanone and cyclopentanol are much more stable in hot water. Once cyclopentanone and cyclopentanol were formed, the carbon loss would be reduced. A higher concentration of furfural would lead to higher carbon loss due to resinification.11-14 To reduce the carbon loss, a low concentration of furfural aqueous solution was preferred in reported works. Moreover, the total selectivity of cyclopentanone and cyclopentanol is 82%~95% in our research. Therefore, we can infer that the carbon loss is low. To prove this inference, the quantitative determination of C balance was carried out by external standard method, taking Run 2 in Table 4 as example. The C balance is 94%. To test the stability of the Ru/CNTs catalyst, the recycling experiments were performed. When the Ru/CNTs catalyst was repeated 3 times for the furfural hydrogenation reaction, the furfural conversion of 83% and cyclopentanone selectivity of 95% were achieved. The slight decrease of the yield of cyclopentanone may be due to the leaching of Ru particles during the reaction and/or the catalyst recycling processes. Another possible reason is the aggregation of the Ru particles during the reaction and/or the catalyst regeneration processes. The mechanism of the 13



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deactivation and regeneration of catalyst will be carried out in our further studies.

CONCLUSIONS In this contribution, carbon nanotube-supported Ru nanoparticles have been

demonstrated to be a novel and efficient interface-active catalyst for furfural rearrangement to cyclopentanone in aqueous phase. Results show that the selective rearrangement of furfural can be tuned through controlling the furfural concentration, reaction temperature, hydrogen pressure, speed of stirring, and reaction time. Under relative mild reaction conditions (1 MPa H2, 160 oC, 500 rpm), 99% conversion of furfural and 91% selectivity of cyclopentanone were efficiently obtained after 5 h of reaction at very low concentration of Ru/CNTs catalyst (0.26 wt% Ru with respect to furfural). Possible reaction pathways of furfural transformation over Ru/CNTs catalyst in water are also proposed.

ASSOCIATED CONTENT

Supporting Information Oxidation of CNTs, SEM images of CNTs and 6.0 wt% Ru/CNTs.

AUTHOR INFORMATION

Corresponding Author * E-mail: [email protected].

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the ﬁnal version of the manuscript. Notes 14


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The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work was partly supported by the National Nature Science Foundation of

China (No. 51502108), the Research Fund for the Doctoral Program of Higher Education of China (No. 20130061120018), the Development Project of Science and Technology of Jilin Province, China (No. 20150520016JH), the Foundation of Jilin Provence Development and Reform Commission, China (No. 2014N145) and the China Postdoctoral Science Foundation (No. 2013M540242). We thank Dr. Qiming Sun at State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, China for his kind help in the experiment and helpful discussions.

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FIGURE CAPTIONS: Figure 1. XRD patterns of CNTs and 6.0 wt% Ru/CNTs. Figure 2. TEM images and particle size distribution of 6.0 wt% Ru/CNTs. Figure 3. XPS spectra of Ru 3p for 6 wt% Ru/CNTs catalyst. Figure 4. NH3-TPD profile of 6.0 wt% Ru/CNTs catalyst.

23


Ru/CNTs

Page 24 of 33

Graphite (110)

Graphite (004)

Graphite (100)

Graphite (002)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Intensity (a.u.)


CNTs

10

20

30

40

50

60

70

80

2 Theta (deg.) Figure 1. XRD patterns of CNTs and 6.0 wt% Ru/CNTs.

24


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


30 25

Frequency (%)

Page 25 of 33

20 15 10 5 0 1

2

3

4

5

6

Particle Size (nm)

Figure 2. TEM images and particle size distribution of 6.0 wt% Ru/CNTs.

25



Ru 3p Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

460

465

470

475

480

485

490

Binding Energy (eV)

Figure 3. XPS spectra of Ru 3p for 6 wt% Ru/CNTs catalyst.

26


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Intensity (a.u.)

Page 27 of 33

50

100

150

200

250

300

350

400

450

500

o

Temperature ( C)

Figure 4. NH3-TPD profile of 6.0 wt% Ru/CNTs catalyst.

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Scheme 1. Proposed reaction pathways for the furfural transformation over Ru/CNTs catalyst in water. (*) denotes intermediate species of furan ring rearrangement. Cat. represents Ru/CNTs catalyst.

28


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Table 1. Effects of reaction temperature, hydrogen pressure, and speed of stirring on the catalytic performance of Ru/CNTs for the furfural hydrogenation. Sel./%

R/ Run

Con./%

T/℃

OH

rpm

CH2OH

Other

COOH

OH

O

OH

a

O

1a

140

500

99.7

9

2

1

50

30

8

2a

150

500

100

8

2

0

63

21

6

3a

160

500

100

6

1

0

31

59

3

4a

160

800

100

7

1

0

68

18

6

5b

160

500

100

15

4

1

70

0

10

Reaction conditions: 6 wt% Ru/CNTs (20 mg), furfural (0.34 g), solvent (H2O: 40 mL), p (H2)=1

MPa, 3 h. b

Reaction conditions: 6 wt% Ru/CNTs (20 mg), furfural (0.34g), solvent (H2O: 40 mL), p (H2)=2

MPa, 3 h.

29



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Page 30 of 33

Table 2. Effects of reaction time on conversion and selectivity for the furfural hydrogenation.a Sel./% t/h

Con./% OH

CH2OH

CH2OH

O

Other

COOH

OH

O

OH

O

0.5

73

21

3

0

9

2

65

0

1

94

10

4

0

4

2

80

0

2

100

0

6

1

0

28

63

2

3

100

0

6

1

0

31

59

3

a

Reaction conditions: 6 wt% Ru/CNTs (20 mg), furfural (0.34 g), solvent (H2O: 40 mL), p (H2)=1

MPa, 160 oC, 500 rpm.

30


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Table 3. Effect of solvents on the catalytic activity of Ru/CNTs for the furfural hydrogenation. Sel./% Run

Solvent

Con./% CH2OH

CH2OH O

O

OH

O

1

CH2Cl2

2

0

34

0

66

2

water

99

0

5

4

91

3

ethanol

51

57

0

43

0

Reaction conditions: 6 wt% Ru/CNTs (20 mg), furfural (0.45 g), solvent (40 mL), p (H2)=1 MPa, 160 oC, 5 h, 500 rpm.

31



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Page 32 of 33

Table 4. Effect of furfural concentration on the catalytic activity of Ru/CNTs for the furfural hydrogenation. Sel./% Run

Cfurfural/wt%

Con./% CH2OH

CH2OH

O

COOH

O

OH

a

O

1a

0.84

94

10

4

4

2

80

2b

1.14

99

0

5

0

4

91

3c

1.67

89

3

8

2

4

83

4d

2.42

86

1

9

0

3

87

Reaction conditions: 6 wt% Ru/CNTs (20 mg), solvent (H2O: 40 mL), p (H2)=1 MPa, 160 oC, 1 h,

500 rpm. b


500 rpm. c


500 rpm. d

Reaction conditions: 6 wt% Ru/CNTs (20 mg)，solvent (H2O: 40 mL), p (H2)=2 MPa, 160 oC, 5 h,

500 rpm.

32


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Highly

Selective

Biomass-derived

and

Efficient

Furfural

to

Rearrangement Cyclopentanone

of over

Interface-active Ru/CNTs Catalyst in Water Yanhua Liu, Zhihao Chen, Xiaofeng Wang, Yu Liang, Xiaomin Yang,* and Zichen Wang

The furfural conversion of 99% and cyclopentanone selectivity of 91% were efficiently achieved over interface-active Ru/CNTs catalyst in water under mild reaction conditions.


Highly Selective and Efficient Rearrangement of Biomass-Derived

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