Hydrogenation and Hydrolysis of Furfural to Furfuryl Alcohol

Subscriber access provided by Washington University | Libraries

Applied Chemistry

Hydrogenation and Hydrolysis of Furfural to Furfuryl Alcohol, Cyclopentanone and Cyclopentanol with a Heterogeneous Copper Catalyst in Water Xuyang Zhou, Zhipeng Feng, Wanwan Guo, Junmei Liu, Ruyue Li, Rizhi Chen, and Jun Huang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b06217 • Publication Date (Web): 21 Feb 2019 Downloaded from http://pubs.acs.org on February 27, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29 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

Industrial & Engineering Chemistry Research

Hydrogenation and Hydrolysis of Furfural to Furfuryl Alcohol, Cyclopentanone and Cyclopentanol with a Heterogeneous Copper Catalyst in Water Xuyang Zhou, Zhipeng Feng, Wanwan Guo, Junmei Liu, Ruyue Li, Rizhi Chen, and Jun Huang*

*State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, China E-mail: [email protected]

ACS Paragon Plus Environment

1

Industrial & Engineering Chemistry Research 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

Page 2 of 29

ABSTRACT: The selectivity of hydrogenation of furfural can be tuned to furfuryl alcohol, cyclopentanone and cyclopentanol by tuning the reaction conditions with a Cu catalyst. Catalysed by Cu0.4Mg5.6Al2, furfural can be hydrogenated and dehydrated smoothly to furfuryl alcohol, cyclopentanone and cyclopentanol in high yields respectively. At 110 °C and under 2.0 MPa H2 pressure, furfuryl alcohol can be obtained in 99.5% yield. Moreover, the Cu0.4Mg5.6Al2 catalysed hydrogenation of furfural in water gave cyclopentanol in 98.6% yield. Additionally, cyclopentanone can also be obtained in 98.1% yield. The catalyst Cu0.4Mg5.6Al2 can be reused several times with only slightly deactivation. Additionally, the hydrogenation of furfural gave well to excellent yield of cyclopentanol in high concentration (15-30 wt % solution of furfural in water), which


2

Page 3 of 29 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


improved the practicability and efficiency of the process. The hydrogenation of furfural is high efficient, practical and green process of biomass application. KEYWORDS: Furfural, Hydrogenation, Copper, Cyclopentanone, Cyclopentanol

INTRODUCTION


3


Page 4 of 29

The demand for alternative energy sources is growing rapidly as the amount of global fossil fuels declining.1 Biomass conversion to value-added products is highly important in academic and industrial application. It is of great significance to develop sustainable chemical industry by utilizing renewable biomass replacing the fossil fuels to produce chemicals in the future.2 In the industry, furfural is produced from agricultural raw materials rich in pentosans, such as straw, corn cob, oat hull and bagasse.3 The catalytic hydrogenation of furfural is an important reaction which can obtain furfuryl alcohol,

tetrahydrofuran

methanol,

2-methylfuran,

2-methyltetrahydrofuran

and

pentanediol.4 The aqueous phase hydrogenative condensation of furfural is particularly attractive, which can produce cyclopentanone and cyclopentanol.5 Cyclopentanol is widely used in the production of pharmaceuticals, dyes and fragrances, as well as solvents for preparation of pharmaceuticals and fragrances.4 Cyclopentanone can be used in synthetic drugs, insecticides, rubber chemicals, herbicides and fragrances.6 In addition, cyclopentanone can dissolve various resins and is therefore widely used as a solvent in the electronics industry.4 Conventional cyclopentanone synthesis methods are pyrolysis of adipic acid and its derivatives and oxidation of cyclopentene.7-9 The


4

Page 5 of 29 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


reaction conditions are harsh and the process is cumbersome. At present, cyclopentanone is in great demand, but it still relies on the preparation of fossil-based raw materials.10

The Hronec group introduced the direct conversion of furfural to cyclopentanone firstly, but the selectivity was not good, and many by-products were formed.11-12 Cyclopentanone, cyclopentanol, furfuryl alcohol and tetrahydrofurfuryl alcohol were formed. At present, a large number of catalysts based on Pd, Pt, Ru, Au, Co and Ni have been studied for the selective hydrogenation of furfural to cyclopentanone.5-6, 11-14 To promote the open of the furfural cycle, acidic supports were usually used for the catalysts11-12 and then the carbon balance was not 100% and some coking may be formed. Thus, it is still highly desirable to develop inexpensive catalysts for the selective hydrogenation of furfural under mild conditions.

Recently, we have reported the hydrogenation of nitroaromatics, and the reductive amination of aldehydes and ketones with amines and nitroaromatics under H2 by Rh15, Co16, Ir17 catalysts, and amines can be obtained efficiently. And we also tried to study


5


Page 6 of 29

the hydrogenation/ dehydration of biomass to high value-added products. Here we report Cu catalysts on basic supports as catalysts for the tuneable and selective hydrogenation of furfural to furfuryl alcohol, cyclopentanol and cyclopentanone respectively in high yields in water by controlling the reaction conditions (Scheme 1).

O

OH

>99% O

O

>98%

>98%

OH

O

Scheme 1. The Cu catalysed selective hydrolysis to furfuryl alcohol cyclopentanone and cyclopentanol.

RESULTS AND DISCUSSION

To avoid the coking of furfural, we tried to use basic supports to replace acidic supports to improve the carbon balance. Since the formation of furfuryl alcohol without methylfuran before the opening of furan cycle is important, Cu catalyst is a suitable choice for the hydrogenation of furfural to cyclopentanone and cyclopentanol. Thus,


6

Page 7 of 29 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


partial Cu substituted hydrotalcites (Mg/Al) were designed as the catalysts precursors for active Cu catalysts. Catalysts precursors (before reducing) P-Cu0.4Mg5.6Al2, PCu0.8Mg5.2Al2 and P-Cu1.2Mg4.8Al2 were characterized by XRD, and the spectra are shown as Figure 1 a-c. We found that the P-Cu0.4Mg5.6Al2 has characteristic diffraction peaks of hydrotalcite and crystallized well by comparing with the standard card of hydrotalcite Mg6Al2(OH)16CO3 (JCPDS NO.20-0658).18 The results indicate that Cu2+ replaces part of Mg2+ in the P-Cu0.4Mg5.6Al2, which is due to that Cu2+ (0.73 A) and Mg2+ ion (0.72 A) have similar ion radius.19 When the content of Cu increases, the PCu0.8Mg5.2Al2 and P-Cu1.2Mg4.8Al2 have a peak at 35.5 o respectively, which is CuO formed on the surface mixed with the crystal structure. We can image that the partial of the Cu2+ replaced Mg2+ in the hydrotalcite structure, and the rest of Cu2+ converted to CuO on the hydrotalcite surface. After nitrogen calcination and hydrogen reduction, the XRD spectra of Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2 catalysts are also presented as Figure 1 d-f. In catalyst Cu0.4Mg5.6Al2 (Figure 1, d), the weakened peaks of hydrotalcite can be found and no Cu peak is detected which implied that Cu particles are quite small in the hydrotalcite structure and the structure is stable. When the content


7


Page 8 of 29

of Cu increases, peaks of Cu at 50.3o, 74o are found in catalysts Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2, which means that the CuO on the hydrotalcite surface were reduced to Cu particles. Reducing the Cu substituted Mg/Al hydrotalcites afforded uniformly dispersed copper catalysts with large surface area, strong alkalinity and high stability.

Figure 1. XRD patterns of the as-synthesized (a) P-Cu0.4Mg5.6Al2, (b) P-Cu0.8Mg5.2Al2 and (c) P-Cu1.2Mg4.8Al2, and the reduced (d) Cu0.4Mg5.6Al2, (e) Cu0.8Mg5.2Al2 and (f) Cu1.2Mg4.8Al2.

The nitrogen adsorption-desorption curves were presented in Figure S1 for Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2 and Cu/HT. According to the IPUAC


8

Page 9 of 29 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


classification, they are all type II adsorption isotherms and type H3 hysteresis loops, which indicates that the pore structure of the catalyst is irregular. This is because that slit pore channels formed due to the aggregation of plate-like layers. From the nitrogen adsorption-desorption curves of Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2 and Cu/HT in Figure S1, we can see that they have similar hysteresis loops but with hysteresis ring closure points at relative pressures of 0.70, 0.76, 0.80 and 0.86 respectively, which indicated that they have similar pore structures. The BJH pore structures were also shown in Figure S2, and the specific surface, pore volume, and pore size of Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2, and Cu/HT were presented in Table 1. There are two forms of pore size in the catalysts Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2, and with the Cu content increased, the pore size of the catalyst increased. The Cu0.4Mg5.6Al2 has the highest specific surface area of 119.84 m2/g. With increasing of Cu content, the specific BET surface area of the samples decreased and pore volume increased slightly, and the average pore size increased. The Cu/HT prepared by the impregnation method has a specific surface area of 49.35 m2/g.


9


Page 10 of 29

Catalysts Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2 and Cu/HT were also characterized by scanning electron microscopy (SEM), and the SEM images were shown in Figure S3. With increasing of the Cu content, the Cu particles on the surface of the catalyst increased, which is consistent with the results of XRD results from the Figure 1.

Table 1. The specific surface, pore volume, and pore size of Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2, and Cu/HT after reduction. Catalyst

Surface area

Pore

Average pore diameter

(m2/g)

volume(cm3/g)

(nm)

Cu0.4Mg5.6Al2

119.84

0.52

17.41

Cu0.8Mg5.2Al2

109.86

0.57

20.73

Cu1.2Mg4.8Al2

100.28

0.57

22.81

Cu/HT

49.35

0.40

32.35

The TEM images of catalysts Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2 and Cu/HT were shown in Figure 2 respectively. It can be seen that there is no obvious separated Cu particles on the surface of Cu0.4Mg5.6Al2, and the Cu particle size is below 2 nm dispersed well in the MgAlOx support (Figure 2, a). The Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2


10

Page 11 of 29 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


have a small amount of independent Cu particles on the surface. This is because partial of the Cu2+ replaced Mg2+ in the hydrotalcite structure, and the Cu particles formed from the CuO on the hydrotalcite surface. When Cu2+ in the hydrotalcite structure was reduced to Cu, Cu was dispersed well in hydrotalcite structure. But when CuO on the surface of hydrotalcite was reduced to Cu, bigger Cu particles were supported on hydrotalcite. And the results were consistent with the XRD analysis results. But in the Cu/HT (Cu supported on the prepared HT) catalyst, biger Cu particles (about 20 nm) reduced from CuO on the surface were supported on hydrotalcite(Figure 2, d).

Figure 2. The TEM images of: (a) Cu0.4Mg5.6Al2 (b) Cu0.8Mg5.2Al2 (c) Cu1.2Mg4.8Al2 (d) Cu/HT.


11


Page 12 of 29

The Cu0.4Mg5.6Al2 was also studied by TGA (thermogravimetry analysis), and the TGA curve was shown in Figure S4. There is about 14% weight loss from 110°C to 240°C, which is due to the loss of adsorbed water. There is a further loss of about 15% weight from 260°C to 420 °C, which is due to the release of crystal water and CO2 decomposed from the Cu0.4Mg5.6Al2 catalyst. To investigate the Cu state of the catalysts, XPS spectra of the Cu0.4Mg5.6Al2, Cu0.8Mg5.2Al2, Cu1.2Mg4.8Al2 and Cu/HT were shown in Figure S5. According to the XPS spectra analysis, the peak at about 933 eV represents the presence of Cu0, and the peak at 935.6 eV was corresponding to Cu2+. In addition, the peak at 943.3 eV also indicates the presence of Cu2+.20-22 The relative atomic concentrations of each element on the surface of catalysts measured by the XPS are shown in Table S1. We compared these results with the atomic concentrations measured by EDS, and the atomic concentrations are in agreement roughly with the results by EDS (Table S2). In order to further identify copper in different valence states, we also obtained the Auger peak spectra of copper in the catalysts in the Figure S6. Figure S7 shows summary spectra of catalysts measured by the XPS and Figure S8 shows the energy spectra of different catalysts. The proportions of each Cu-species on


12

Page 13 of 29 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


the surface of catalysts are shown in the Table S3. Based on these results, the Cu state in the Cu catalysts is mainly as Cu0, and some Cu+ and Cu2+ species were on the surface of the Cu catalysts. Besides, Cu2+ in the catalyst Cu0.4Mg5.6Al2 was reduced at about 175-245 °C, which also can be found in the H2-TPR (H2 Temperature Programmed Reduction) curve (Figure S9).

The hydrogenation of furfural

The hydrogenation of furfural to cyclopentanol was tested to optimize the catalysts firstly, and the results were summarized in Table 2. Additionally, the optimization of reaction temperature, H2 pressure and reaction time was summarized in Table S4 and S5. The Cu0.4Mg5.6Al2 showed the best selectivity to cyclopentanol, and the yield of cyclopentanol was up to 98.6% at 190 °C under 2.0 MPa H2 in water in 12 hours (Table 2, entry 1). The yields of cyclopentanol were 97.9% and 85.1% with Cu0.8Mg5.2Al2 and Cu1.2Mg4.8Al2 catalysts respectively under similar reaction conditions (Table 2, entries 2, 3). The hydrogenation of furfural gave cyclopentanol in 72.9% yield with Cu/HT catalyst(Table 2, entry 4). When the support was replaced by activated carbon, the yield


13


Page 14 of 29

of cyclopentanol was only 1.2 % using Cu/C as catalyst, but cyclopentanone was obtained in 92.1% yield(Table 2, entry 5). With Co/HT catalyst, cyclopentanone can be obtained in 15.1% yield without cyclopentanol(Table 2, entry 6). No cyclopentanol was obtained without catalyst (Table 2, entry 7).

Table 2. The hydrogenation of furfural to cyclopentanol with different catalysts.a Entry

Catalyst

Conversion

Yield b(%)

TOF（h-1）d

(%)

a

Carbon balance (%)

1

Cu0.4Mg5.6Al2

100

98.6

1.4

100

2

Cu0.8Mg5.2Al2

100

97.9

0.9

100

3

Cu1.2Mg4.8Al2

100

85.1

0.6

100

4

Cu/HT

99.2

72.9

1.0

100

5

Cu/C

99.1

1.2c

--

--

6

Co/HT

17.1

0

--

--

7

no

1.3

0

--

--

Reaction conditions: 1.0 mmol furfural, 2.0 mL water, under 2.0 MPa H2. The reaction

was carried out at 190 °C for 12 h. b GC yields. c 92% of cyclopentanone formed. d TOF = ((mol of cyclopentanol )/(mol of Cu))/(reaction time).


14

Page 15 of 29 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


With the optimized reaction temperature and pressure, the curve of cyclopentanol yield against the reaction time was studied, and the results were shown in Figure 3. The furfural decreased rapidly, and cyclopentanol and cyclopentanone formed mainly in the first 3 hours. The yield of cyclopentanol gradually increased with the decreasing of cyclopentanone in the following 9 hours. And finally, cyclopentanol was obtained in 98.6% yield. Moreover, from the temperature effect curve of the hydrogenation of furfural (Table S4), we can see furfuryl alcohol was obtained in 98.7% yield at 110 °C under 2.0 MPa H2. At 130 °C, cyclopentanone and cyclopentanol begin to appear, which indicated that the hydrolysis of furfuryl alcohol can be performed at high temperature (above 130 °C) in aqueous phase. Low H2 pressure is beneficial for the formation of cyclopentanone, as cyclopentanone can be hydrogenated to cyclopentanol under high H2 pressure (Table S5). These results implied that furfuryl alcohol, cyclopentanone and cyclopentanol can be obtained respectively by tuning the reaction temperature and H2 pressure.


15


100

80

Content (%)

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

Page 16 of 29

cyclopentanol cyclopentanone furfuryl alcohol furfural

60

40

20

0

0

3

6

9

12

Time (h)

Figure 3. The hydrogenation process of fufural to cyclopentanol on reaction time; reaction conditions: 1.0 mmol furfural, 2.0 mL water and 64 mg Cu0.4Mg5.6Al2 (Cu 6.0 mol %), at 190 °C, under 2.0 MPa H2. The hydrogenation of furfural to furfuryl alcohol was performed with the Cu0.4Mg5.6Al2 catalyst in water, and the reaction conditions were optimized and the results were summarized in Table S6. Furfuryl alcohol can be obtained in high yield under mild conditions. With the optimized reaction temperature and H2 pressure, the curve of the furfuryl alcohol yield on the reaction time was drawn as Figure 4. Furfuryl alcohol increased gradually with the decreasing of furfural. And furfuryl alcohol can be obtained in 99.5% yield at 110 °C under 2.0 MPa in 2.5 h.


16

Page 17 of 29

100

furfuryl alcohol furfural

80

Content (%)

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


60

40

20

0 0.0

0.5

1.0

1.5

2.0

2.5

Time (h)

Figure 4. The hydrogenation process of fufural to furfuryl alcohol on reaction time; reaction conditions: 1.0 mmol furfural, 2.0 mL water and 64 mg Cu0.4Mg5.6Al2 (Cu 6.0 mol %), at 110 °C, under 2.0 MPa H2. Afterwards, the hydrogenation of furfural to cyclopentanone was performed with the Cu0.4Mg5.6Al2 catalyst in water, and the reaction conditions were optimized (Table S7and Table S8). The process of the hydrogenation of furfural to cyclopentanone can be seen in Figure 5 with the optimized reaction temperature and H2 pressure in water (at 180 °C, under 0.2 MPa H2). Cyclopentanone increased rapidly with the decreasing of furfural in first 4 hours. Only trace of furfuryl alcohol can be detected. Cyclopentanone can be obtained in 98.1% yield till the 5th hour. Subsequently, the cyclopentanone was hydrogenated to cyclopentanol slowly. The results indicate that furfural is hydrogenated


17


to form furfuryl alcohol, cyclopentanone, and cyclopentanol successively in aqueous phase.

100

80

Content (%)

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

Page 18 of 29

cyclopentanol cyclopentanone furfuryl alcohol furfural

60

40

20

0

0

3

4

5

6

7

Time (h)

Figure 5. The hydrogenation process of fufural to cyclopentanone on reaction time; reaction conditions: 1.0 mmol furfural, 2.0 mL water and 64 mg Cu0.4Mg5.6Al2 (Cu 6.0 mol %), at 180 °C, under 0.2 MPa H2. The Cu0.4Mg5.6Al2 catalyst reusability was tested for the hydrogenation of furfural to cyclopentanone (180 °C, 0.2 MPa H2, 5 hours) and the results were shown as Figure 6. The Cu0.4Mg5.6Al2 catalyst was easily recycled by filtration and reused for the next reaction cycle. The Cu0.4Mg5.6Al2 catalyst can be reused at least 5 times with only slightly deactivation of activity (Figure 6). The filtrate was detected by ICP-OES (inductively coupled plasma optical emission spectroscopy with detection limitation 7 ppb) after removal of the Cu0.4Mg5.6Al2 catalyst by filtration. No Cu was detected in the


18

Page 19 of 29

filtrate, and the filtrate was not active anymore for the hydrogenation of furfural, which indicated that no Cu was leaked into the reaction mixture.

Conversion Yield

100

80

Percentage (%)

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


60

40

20

0 1

2

3

4

5

Run number

Figure 6. The reusability of the Cu0.4Mg5.6Al2 catalyst for the hydrogenation of furfural to cyclopentanone. To study the practical application of the Cu0.4Mg5.6Al2 catalyst, we performed the hydrogenation of furfural to cyclopentanol with high concentration, and the results are shown in Table 3. The hydrogenation of furfural gave well to excellent yield of cyclopentanol in high concentration (15-30 wt % solution of furfural in water). Starting with a 20 wt% furfural solution in water, cyclopentanol was obtained in 97.1% yield at 190 °C under 3.0 MPa H2 pressure (Table 3). Since the Cu0.4Mg5.6Al2 catalyst is basic, we did not find any coke formation in the reaction system, although coke is easily


19


Page 20 of 29

formed from furfural in acid or neutral conditions. Owning to synergistic effect of the high activity and selectivity of Cu, basic supports and aqueous system, furfural can converted to furfuryl alcohol, cyclopentanone and cyclopentanol cleanly without any coke formation.

Based on the results above, we proposed the pathway of the hydrogenation of the furfural to furfuryl alcohol, cyclopentanone and cyclopentanol (Scheme 2). Furfural is hydrogenated to furfuryl alcohol firstly under mild conditions with Cu0.4Mg5.6Al2 catalyst. And then the furfuryl alcohol is hydrolyzed to compound A in water. Subsequently, compound B formed through dehydration/ hydrogenation/ dehydration. Finally, cyclopentanone and cyclopentanol are formed through compound B. Although we did not detected the compound A, trace amounts of the compound B can be detected when the reaction was not completed. The dehydration and hydrogenation (of compound A and B) are rapid at the high temperature and under H2 pressure.

Table 3. The hydrogenation of furfural to cyclopentanol with high concentration a Concentration (wt%)

Conversion (%)

Yieldf (%)


20

Page 21 of 29 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


a

15b

100

73.3

30c

100

62.1

20d

100

78.4

20e

100

97.1

Reaction conditions: Substrate / Catalyst = 1.5 (wt / wt); at 190 °C; under 2.0 MPa H2

pressure; for 12 hours. b furfural, 300 mg; water, 1.7 mL; Cu0.4Mg5.6Al2, 200 mg (Cu 6.0 mol %);

c

furfural, 600 mg; water, 1.4 mL; Cu0.4Mg5.6Al2, 400 mg (Cu 6.0 mol %);

d

furfural, 400 mg; water, 1.6 mL; Cu0.4Mg5.6Al2, 267 mg (Cu 6.0 mol%), under 2.5 MPa H2 pressure; for 17 hours. e furfural, 400 mg; water, 1.6 mL; Cu0.4Mg5.6Al2, 267 mg (Cu 6.0 mol %), under 3.0 MPa H2 pressure; for 23 hours. f GC Yields.

O

O H2/Cu

OH

O

OH

O O A +H2 /-H2O Base

O H2

O + H2

OH

B

Scheme 2. Possible pathway of the hydrogenation of furfural to furfuryl alcohol, cyclopentanone and cyclopentanol.

CONCLUSION


21


Page 22 of 29

In conclusion, highly selective and tuneable hydrogenation process of furfural to furfuryl alcohol, cyclopentanone and cyclopentanol was demonstrated in water. Catalysed by the Cu/basic catalyst Cu0.4Mg5.6Al2, furfural can be hydrogenated and dehydrated smoothly to furfuryl alcohol, cyclopentanone and cyclopentanol respectively in high yield. The catalyst Cu0.4Mg5.6Al2 can be reused several times with only slightly deactivation. Moreover, the hydrogenation of furfural gave well to excellent yield of cyclopentanol with high concentration (15-30 wt % solution of furfural in water), which improved the practicability and efficiency of the process. The hydrogenation of furfural is highly efficient, practical and green process of biomass application to high value-added products. We believe the process can be applied for the production of furfuryl alcohol, cyclopentanone and cyclopentanol respectively in near futhure.

EXPERIMENTAL SECTION

Catalysts CuxMgyAlz were prepared using coprecipitation (Cu: Mg: Al molar ratios of 0.4:5.6:2, 0.8:5.2:2 and 1.5:4.5:2).23 Typically, Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, Al(NO3)3·9H2O were dissolved in 400 mL water, in which (Cu2+ + Mg2+ + Al3+) = 0.2


22

Page 23 of 29 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


mol/L and Al3+ / (Cu2++Mg2+ + Al3+) = 0.25. The solution was recorded as solution A. The 0.25 mol/L of Na2CO3, 0.8 mol/L NaOH was prepared and recorded as solution B (400 mL). Solution A was slowly added to solution B by stirring at room temperature within 2 hours. The mixed solution was stirring at 110 °C for 12 hours. Then the solution was filtered and washed with water until the pH reached about 7. The filtered powder was then dried in a vacuum oven at 80 °C for 12 hours to obtain a catalyst precursor PCuxMgyAlz. The catalyst precursor was heated to 300 °C under nitrogen atmosphere for 4 h. It was then reduced under hydrogen atmosphere at 300 °C for 2 h. The catalyst CuxMgyAlz was obtained after naturally cooling to room temperature.

The Cu/HT, Cu/C and Co/HT were prepared by impregnation. The certain amount of Cu(NO3)2·3H2O was dissolved in water, then hydrotalcite (Mg: Al=3) was added to the solution, and the round bottom flask was transferred to an oil bath at 40 °C and stirred for 4 h. Dropwisely the 1.0 M NaOH solution was added to a round bottom flask until pH reached 11 with stirring for another 1 h. Then the powder was filtered and washed with water to pH 7, and then dried in a vacuum oven at 80 °C for 12 hours. The powder was


23


Page 24 of 29

heated to 300 °C in 1 h and kept at 300 °C for 4 h in a tube furnace under a nitrogen atmosphere. It was then reduced under hydrogen at 300 °C for 2 h. The catalyst Cu/HT was obtained after naturally cooling to room temperature. Catalysts Cu/C and Co/HT were also prepared similarly. (The loading of Cu is consistent with Cu0.4Mg5.6Al2.).

Hydrogenation of furfural to furfuryl alcohol 1 mmol furfural, 2.0 mL water and 64 mg (6.0 mol %) of catalyst were added to a 50 mL stainless steel autoclave. The autoclave was filled with 2.0 MPa of hydrogen after exchanged the air 3 times with H2 and heated to 110 °C for 2.5 hours. After the reaction was completed, the autoclave was cooled to room temperature. Finally, reaction mixture was determined by gas chromatography. Hydrogenation of furfural to cyclopentanone 1 mmol furfural, 2.0 mL water and 64 mg (6.0 mol %) of catalyst were added to a 50 mL stainless steel autoclave. The autoclave was filled with 0.2 MPa of hydrogen after exchanged the air 3 times with H2 and heated to 180 °C for 5 hours. After the reaction was completed, the autoclave was cooled to room temperature. Finally, reaction mixture was determined by gas chromatography. Hydrogenation of furfural to cyclopentanol 1 mmol furfural, 2.0 mL water and 64 mg (6.0 mol %) of catalyst were added to a 50 mL stainless steel autoclave. The autoclave was filled with 2.0 MPa of hydrogen after exchanged the air 3 times with H2 and heated to 190 °C for 12 hours. After the reaction was completed, the autoclave was cooled to room temperature. Finally, reaction mixture was determined by gas chromatography.


24

Page 25 of 29 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


ASSOCIATED CONTENT

Supporting Information.

General Methods and Reagents; N2 adsorption isotherm, BJH curves , SEM images ,TG-MS curves ,XPS spectra and H2-TPR profiles of catalysts ; detailed data of reaction results.

AUTHOR INFORMATION

Corresponding Author *E-mile: [email protected]

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (grant No. 21676140), the fund from the State Key Laboratory of Materials-Oriented Chemical Engineering (grant ZK201711).


25


Page 26 of 29

REFERENCES (1)

Fang, R.; Liu, H.; Luque, R.; Li, Y., Efficient and selective hydrogenation of

biomass-derived furfural to cyclopentanone using Ru catalysts. Green Chem. 2015, 17 (8), 4183-4188. (2)

Yang, Y.; Ma, J.; Jia, X.; Du, Z.; Duan, Y.; Xu, J., Aqueous phase hydrogenation

of furfural to tetrahydrofurfuryl alcohol on alkaline earth metal modified Ni/Al2O3. RSC

Adv. 2016, 6 (56), 51221-51228. (3)

Zeitsch, K. J., The chemistry and technology of furfural and its many by-

products;Elsevier: 2000. (4)

Li, X. L.; Deng, J.; Shi, J.; Pan, T.; Yu, C. G.; Xu, H. J.; Fu, Y., Selective

conversion of furfural to cyclopentanone or cyclopentanol using different preparation methods of Cu–Co catalysts. Green Chem. 2015, 17 (2), 1038-1046. (5)

Zhang, G. S.; Zhu, M. M.; Zhang, Q.; Liu, Y. M.; He, H. Y.; Cao, Y., Towards

quantitative and scalable transformation of furfural to cyclopentanone with supported gold catalysts. Green Chem. 2016, 18 (7), 2155-2164. (6)

Yang, Y.; Du, Z.; Huang, Y.; Lu, F.; Wang, F.; Gao, J.; Xu, J.,Conversion of

furfural into cyclopentanone over Ni–Cu bimetallic catalysts. Green Chem. 2013, 15 (7), 1932-1940. (7)

Renz, M., Ketonization of Carboxylic Acids by Decarboxylation: Mechanism and

Scope. Eur. J. Org. Chem. 2005, (6), 979-988. (8)

Dubkov, K.; Panov, G.; Starokon, E.; Parmon, V., Non-catalytic liquid phase

oxidation of alkenes with nitrous oxide. React.Kinet.Catal.Lett. 2002, 77 (1), 197-205. (9)

Marquie, J.; Laporterie, A.; Dubac, J.; Roques, N., Graphite-supported

ketodecarboxylation of carboxylic diacids. Synlett 2001, 4, 493-496. (10)

Ramos, R.; Grigoropoulos, A.; Perret, N.; Marco Zanella, M.; Katsoulidis,

A.;Manning, T. D.; Claridge,J. and Rosseinsky, M., Selective conversion of 5hydroxymethylfurfural to cyclopentanone derivatives over Cu-Al2O3 and Co–Al2O3 catalysts in water. Green Chem. 2017, 19, 1701-1713. (11)

Hronec, M.; Fulajtarová, K., Selective transformation of furfural to

cyclopentanone. Catal. Commun. 2012, 24, 100-104.


26

Page 27 of 29 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


(12)

Hronec, M.; Fulajtarová, K.; Liptaj, T., Effect of catalyst and solvent on the furan

ring rearrangement to cyclopentanone. Appl. Catal. A 2012, 437-438, 104-111. (13)

Dohade, M.; Dhepe, P. L., Efficient method for cyclopentanone synthesis from

furfural: understanding the role of solvents and solubility in a bimetallic catalytic system.

Catal. Sci.Technol. 2018. (14)

Gong, W.; Chen, C.; Zhang, H.; Wang, G.; Zhao, H., Highly dispersed Co and Ni

nanoparticles encapsulated in N-doped carbon nanotubes as efficient catalysts for the reduction of unsaturated oxygen compounds in aqueous phase. Catal. Sci. Technol. 2018. (15)

Huang, L.; Luo, P.; Pei, W.; Liu, X.; Wang, Y.; Wang, J.; Xing, W.; Huang, J.,

Selective Hydrogenation of Nitroarenes and Olefins over Rhodium Nanoparticles on Hydroxyapatite. Adv. Synth. Catal. 2012, 354 (14-15), 2689-2694. (16)

Mao, F.; Sui, D.; Qi, Z.; Fan, H.; Chen, R.; Huang, J., Heterogeneous cobalt

catalysts for reductive amination with H2: general synthesis of secondary and tertiary amines. RSC Adv. 2016, 6 (96), 94068-94073. (17)

Sui, D.; Mao, F.; Fan, H,; Qi, Z.; Huang, J., General reductive amination of

aldehydes and ketones with amines and nitroaromatics under H2 by recyclable Iridium catalysts. Chinese J. Chem. 2017, 35 (9), 1371–1377. (18)

Cruz, I.; Ribeiro, N.; Aranda, D.; Souza, M., Hydrogen production by aqueous-

phase reforming of ethanol over nickel catalysts prepared from hydrotalcite precursors.

Catal. Commun. 2008, 9 (15), 2606-2611. (19)

Kannan, S.; Dubey, A.; Knozinger, H., Synthesis and characterization of CuMgAl

ternary hydrotalcites as catalysts for the hydroxylation of phenol. J. Catal. 2005, 231 (2), 381-392. (20)

Hronec, M.; Fulajtárová, K.; Vávra, I.; Soták, T.; Dobročka, E.; Mičušík, M.,

Carbon supported Pd–Cu catalysts for highly selective rearrangement of furfural to cyclopentanone. Appl. Catal. B 2016, 181, 210-219. (21)

Tian, H.; Zhang, X.; Scott, J.; Ng, C.; Amal, R., TiO2-supported copper

nanoparticles prepared via ion exchange for photocatalytic hydrogen production. J.

Mater. Chem. A 2014, 2 (18), 6432-6438.


27


(22)

Page 28 of 29

Crivello, M.; Pérez, C.; Herrero, E.; Ghione, G.; Casuscelli, S.; Rodríguez-

Castellón, E., Characterization of Al-Cu and Al-Cu-Mg mixed oxides and their catalytic activity in dehydrogenation of 2-octanol. Catal. Today 2005, 107-108, 215-222. (23)

Yuan, Z.; Wang, L.; Wang, J.; Xia, S.; Chen, P.; Hou, Z.; Zheng, X.,

Hydrogenolysis of glycerol over homogenously dispersed copper on solid base catalysts. Appl.Catal.B 2011, 101 (3-4), 431-440.


28

Page 29 of 29 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


For Table of Contents Only

OH

O

>99%

O O

>98%

>98% O OH

The selectivity of hydrogenation of furfural can be tuned to furfuryl alcohol, cyclopentanone and cyclopentanol by tuning the reaction conditions with a Cu catalyst. Furfuryl alcohol, cyclopentanone and cyclopentanol can be obtained in high yields respectively catalysed by the Cu/basic catalyst Cu0.4Mg5.6Al2.


29

Hydrogenation and Hydrolysis of Furfural to Furfuryl Alcohol

Recommend Documents