A new strategy for the efficient synthesis of 2-methylfuran and γ-butyrolactone

Article abstract of DOI:10.1039/b208849p

A novel process involving the coupling of the hydrogenation of furfural and the dehydrogenation of 1,4-butanediol has been studied in the vapor phase for the synthesis of 2-methylfuran (2-MF) and γ-butyrolactone γ-BL) over the same Cu-based catalyst. It was found that hydrogen and heat energy are utilized with high efficiency in this process.

Full text of DOI:10.1039/b208849p

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A new strategy for the efficient synthesis of 2-methylfuran and
c-butyrolactone
Yu-Lei Zhu,a Hong-Wei Xiang,a Yong-Wang Li,*a Haijun Jiao,ab Gui-Sheng Wu,a
Bing Zhonga and Guang-Qing Guoc
a
L e t t e r
State Key Laboratory of Coal Conversion (SKLCC), Institute of Coal Chemistry,
Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001, P. R. China.
E-mail: ywl@sxicc.ac.cn; Fax: +86 351 405 0320; Tel: +86 351 413 0337
Institut fu¨r Organische Katalyseforschung an der Universita¨t Rostock e.V.,
b
Buchbinderstraße 5-6, 18055, Rostock, Germany
Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
c
Received (in Montpellier, France) 9th September 2002, Accepted 11th November 2002
First published as an Advance Article on the web 24th December 2002
2-MF.3–5 In addition, a supply of hydrogen to the system is
needed.
The catalytic dehydrogenation of BDO to g-BL shown in
eqn. (2) is an endothermic process (61.6 kJ molꢀ1)6–10 and
the oxidative lactonization of diols to g-BL like products has
been reported.11–13 In this reaction, the released hydrogen
cannot be used effectively.
A novel process involving the coupling of the hydrogenation of
furfural and the dehydrogenation of 1,4-butanediol has been
studied in the vapor phase for the synthesis of 2-methylfuran
(2-MF) and c-butyrolactone (c-BL) over the same Cu-based cat-
alyst. It was found that hydrogen and heat energy are utilized
with high efficiency in this process.
The new catalytic process combines reactions (1) and (2)
into one catalytic system to significantly improve the yield of
the catalytic hydrogenation of furfural, as well as leading to
a better thermal balance and the effective usage of hydrogen
through hydrogen transfer between the two reactants. In addi-
tion, this new catalytic process produces two desired products
(2-MF and g-BL) with a substantially increased hydrogenation
yield, while the ‘‘no-hydrogen’’ (with hydrogen recycle but no
hydrogen supply and release) operation also simplifies the
technical procedure.
In this letter, we report a coupled catalytic process through
hydrogen transfer between two reactants, 1,4-butanediol
(BDO) and furfural, to produce two valuable products, 2-
methylfuran (2-MF) and g-butyrolactone (g-BL), in an atom
economic way from the viewpoints of both material and
energy utilization. Catalytic hydrogenation transfer reactions
have been widely investigated in the past, mostly for the reduc-
tion of organic compounds by using a hydrogen donor, which
often leads to undesirable by-products.1 In our coupled hydro-
gen transfer reaction, furfural (hydrogen acceptor) is reduced
by the hydrogen from BDO (hydrogen donor) to form 2-
MF, and at the same time, g-BL is also the desired product
from the BDO dehydrogenation. 2-MF is mainly used for
the synthesis of crysanthemate pesticides, perfume intermedi-
ates and chloroquine lateral chains in medicinal intermediates,
and the major production route is via the catalytic hydrogena-
tion of furfural [eqn. (1)]. g-BL is an important intermediate
for the synthesis of pyrrolidone, N-methylpyrrolidone,
N-vinylpyrrolidone, herbicides and rubber additives, and the
catalytic dehydrogenation of 1,4-butanediol (BDO) to g-BL
is the dominant procedure in commercial applications [eqn.
(2)].2 Both processes are mainly performed in multi-tubular
fixed-bed reactors.
The combined reaction in eqn. (3) shows that producing 1
mol 2-MF and 1 mol g-BL requires 1 mol furfural and 1 mol
BDO, and is exothermic by 80.4 kJ molꢀ1
.
ð3Þ
In addition to the perfect hydrogen mass balance, much easier
temperature control in a practical reactor can also be expected
than in the single furfural hydrogenation process, due to the
lower heat release in the coupled system. In practice, this com-
bined process can be carried out on the basis of the fact that
the hydrogen transfer from BDO (hydrogen donor) to furfural
(hydrogen acceptor) can be carried out over the same Cu–Zn
catalyst and under similar reaction conditions.14,15
ð1Þ
The separate furfural hydrogenation and BDO dehydro-
genation reactions, as well as the coupled process, were carried
out in a fixed-bed reactor over a Cu–Zn catalyst. Table 1
shows that almost complete conversion of furfural can be
achieved over the present Cu-based catalyst. However, the
yield of 2-MF varies substantially with operating temperature,
with the best yield being 88.6% at 212 ꢁC. Scheme 1 shows the
complexity of the hydrogenation of furfural. It is clear that fur-
fural hydrogenation can produce not only the desired product
2-MF but also other by-products, depending on the reaction
ð2Þ
As shown in eqn. (1), the vapor-phase hydrogenation of fur-
fural to 2-MF is exothermic by 142 kJ molꢀ1. Due to the
strongly exothermic nature of this reaction, temperature con-
trol over this process is very difficult and this leads to apparent
hot spots, typically in an industrial tubular fixed-bed reactor,
thus seriously lowering the yield to the desired product,
208
New J. Chem., 2003, 27, 208–210
DOI: 10.1039/b208849p
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2003

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Table 1 Influence of temperature on the hydrogenation of furfural to
Table 2 Influence of temperature on the dehydrogenation of BDO to
g-BL.a
2-MF.a
% Yield
% Yield
T/ꢁC % Furfural conv. 2-MF Ponb Polc MTFd FOLe Other
T/ꢁC
% BDO conv.
g-BL
BuOHb
Other
190
200
212
225
235
99.8
100
75.2
81.5
88.6
85.2
82.7
0.9
4.5
2.7
2.5
2.1
1.5 8.5
4.6 6.7
4.8 3.3
8.7 3.1
11.8 2.7
13.6
2.2
–
0.3
0.5
0.6
0.5
0.7
190
200
210
230
240
99.7
99.9
100
98.8
98.7
98.6
98.3
98.1
0.8
0.9
0.9
1.2
1.3
0.4
0.4
0.5
0.5
0.6
100
100
100
–
100
100
–
a
a
Reaction conditions: atmosphere, LHSV ¼ 0.1 hꢀ1, H2:furfural ¼
Reaction conditions: atmosphere, LHSV ¼ 0.2 hꢀ1, H2:BDO ¼ 15:1
(molar ratio, recycling hydrogen), residence time ¼ 4.5 s. b n-Butanol.
15:1 (molar ratio, recycling hydrogen), residence time ¼ 9.6 s.
b
c
d
Pon ¼ 2-pentanone. Pol ¼ 2-pentanol. MTF ¼ 2-methyl tetra-
e
hydrofuran. FOL ¼ furfuryl alcohol.
of the coupling effect are expected to help explain this
mechanism.
In conclusion, we have demonstrated the feasibility of a
coupled catalytic process, in which hydrogen transfer from
BDO to furfural can be realized to produce 2-MF and g-BL.
Compared to conventional processes, the coupled process in
this work has several advantages, such as improved yield, good
energy efficiency and optimal hydrogen utilization. In addi-
tion, compared with the traditional furfural hydrogenation
process, the coupled process can also be conducted at a lower
reaction temperature (about 10–20 ꢁC less) while leading to
nearly the same efficiency. This shows that the rich activated
hydrogen species on the catalyst surface from BDO dehydro-
genation might promote the furfural hydrogenation reaction.22
The coupled operation leads to other advantages, such as easy
temperature control in a tubular fixed-bed reactor due to the
moderate heat release compared to that of the single furfural
hydrogenation reaction. In addition, the simplified technical
procedure due to a ‘‘no-hydrogen-supply’’ operation shows
improved technology. Further exploration is of both practical
and theoretical importance.
conditions16–20 The non-uniform temperature profile in an
industrial multi-tubular reactor generally lowers the yield of
the desired product (2-MF)16–20 to an extent that much lower
yields are obtained than those in Table 1, for which the experi-
ments were conducted in a laboratory micro-reactor.16–20
The dehydrogenation of BDO at different temperatures is
shown in Table 2. The data indicates that the conversion of
BDO is also nearly complete. Similar to the reported results,21
the yield of the dehydrogenation reaction to g-BL is very high
( > 98%).
The coupled reaction was conducted using the same liquid
hourly space velocity (LHSV), 0.1 hꢀ1, of furfural as that used
in the single hydrogenation reaction test, and a BDO LHSV of
0.1 hꢀ1 was also used to approach the stoichiometry of the
coupled reaction [eqn. (3)]. It was observed that complete con-
version of both furfural and BDO are reached (Table 3), indi-
cating that the conversion efficiency for the hydrogenation of
furfural has been maintained at the same level as in the single
hydrogenation reaction (Table 1) with co-production of
another important product, g-BL through BDO dehydrogena-
tion under the present operating conditions. Moreover, the
coupled reaction has significantly improved the yield, espe-
cially from furfural to 2-MF, compared to those in the indivi-
dual reactions (Table 1). At 210 ꢁC, for example, the yield to
2-MF is raised by about 8%, and that to g-BL is increased
by about 1%. It is also seen that enhancement of the yield of
2-MF at 190 ꢁC is more pronounced, by 15.6%.
Furthermore, the boiling point (at 101.3 kPa) of 2-MF is
63 ꢁC and that of g-BL is 204 ꢁC, leading to easy separation
of the product mixture from the coupled system, meaning less
additional costs in the coupled process for industrial applica-
tions. These advantages may be of great interest for industria-
lization of the coupled synthesis of these two important
products, 2-MF and g-BL.
In order to explain the enhancement in the catalyst perfor-
mance observed in the coupled reaction, we propose that the
activated hydrogen species on the catalyst surface due to
BDO dehydrogenation probably plays an important role in
improving the yield of furfural hydrogenation. In an industrial
process, other factors like an improved temperature profile
along the reactor may further enhance the effect, suggesting
the potential of coupled reactions in practical applications.
Our further systematic investigations on the fundamentals
Experimental
The catalyst mentioned in this study was prepared via the con-
tinuous precipitation method. In this preparation reaction, a
solution of mixed Cu(NO3)2 ꢂ 3H2O and Zn(NO3)2 ꢂ 6H2O salts
(1 M of total metal ions) was used as metal precursors with an
atomic ratio of 1.3:1 (Cu:Zn), with a 1 M Na2CO3 solution
added as the precipitating agent. Precipitation was performed
at 65 ꢁC, and the flow rates of the two solutions were adjusted
to give a constant pH of about 7.5. The precipitate was aged
for about 12 h at room temperature before filtering. The
filtrated cake was washed with deionized water until no Na+
Table 3 Influence of temperature on the coupling of the BDO and
furfural reactions to give g-BL and 2-MF.a
% Conversion
% Furfural
% Yield
2-MFb
T/ꢁC
% BDO
g-BLc
190
200
210
220
230
240
100
100
100
100
100
100
99.8
100
100
100
100
100
90.8
93.4
96.5
95.4
92.8
90.9
99.7
99.6
99.4
99.3
99.4
98.8
a
Reaction conditions: atmosphere, LHSV (furfural + BDO) ¼ 0.2
h
ꢀ1, H2:(BDO + furfural) ¼ 15:1 (molar ratio, recycling hydrogen),
b
BDO:furfural ¼ 1:1 (molar ratio), residence time ¼ 4.7 s. 2-MF
yield ¼ (moles of 2-MF produced) ꢃ 100/(moles of converted fur-
fural). c g-BL yield ¼ (moles of g-BL produced) ꢃ 100/(moles of con-
verted BDO).
Scheme 1
New J. Chem., 2003, 27, 208–210
209

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was detectable in the filtrate and subsequently dried at 110 ꢁC
for 24 h in air atmosphere. The dried catalyst was calcined at
400 ꢁC for 5 h in a furnace. The fresh catalyst was shaped by a
tablet machine and then crushed to 20–40 mesh for the reac-
tion test.
2
F. Othmer, J. I. Kroschwitz, and M. Howe-Grant, in Kirk-
Othmer’s Encyclopedia of Chemical Technology, ed. R. E. Kirk,
John Wiley & Sons, New York, 4th edn., 1991, vol. 1, p. 211.
J. P. Diebold and R. J. Evans, US Pat. 4 764 627, 1988.
P. D. R. Andrew and G. M. Donald, US Pat. 3 020 291, 1962.
R. S. Rao, R. T. K. Baker and M. A. Vannice, Catal. Lett., 1999,
60, 51.
3
4
5
The reaction was carried out in a fixed bed reactor (600 mm,
i.d. 12 mm). The reaction system had a buffer tank for collect-
ing the tail gas and a pump for cycling gas. Fifteen grams of
catalyst was packed. At the beginning of all tests, N2 was intro-
duced to purge the reaction system and then replaced by a gas
mixture containing 3%H2 in N2 at atmosphere pressure. The
catalyst was pre-reduced by increasinꢀg1the temperature from
25 to 250 ꢁC at the rate of 10 ꢁC h and then staying at
250 ꢁC for 5 h. After the reduction, the reactants were intro-
duced into the reactor. The hydrogen in the tail stream was
recycled after the reaction products had been condensed to
keep the proper ratio of hydrogen to the main reactants [fur-
fural, BDO, and (furfural + BDO), respectively]. The compo-
nents in the products collected in the ice trap were identified
with a VG Quattro CG/MS (Fisons VG Biotech, Manchester,
England), and the contents (weight percentages) were deter-
mined by a GC-920 gas chromatograph (Shanghai Analyser
Co., China) with a flame ionization detector (FID).
6
7
F. Rolf and P. Rolf, DE Pat. 19 941 569, 2001.
I. Tatsumi, M. Kaori, S. Sadakatsu, U. Hiroshi and K. Kenji,
Eur. Pat. 523 774, 1993.
H. J. Mercker, F.-F. Pape, J. Simon, A. Henne, M. Hesse, U.
Kohler, R. Dostalek, C. F. Erdbrugger and D. Kratz, US Pat. 5
955 620, 1999.
8
9
T. Baba, K. Kameta, S. Nishiyama, S. Tsuruya and M. Masai,
J. Chem. Soc., Chem. Commun., 1989, 1072.
10 Y.-L. Zhu, H.-W. Xiang, G.-S. Wu, L. Bai and Y.-W. Li, Chem.
Commun., 2002, 254.
11 S. Kondo, M. Ohira, S. Kawasoe, H. Kunisada and Y. Yuki,
J. Org. Chem., 1993, 58, 5003.
12 T. Miyazawa and T. Endo, J. Org. Chem., 1985, 50, 3930.
13 T. R. Beebe, R. Adkins, R. Baldridge, V. Hensley, D. McMillen,
D. Morris, R. Noe, F. W. Ng, G. Powell, C. Spielberger and
M. Stolte, J. Org. Chem., 1987, 52, 5472.
14 J. G. M. Bremner and R. K. F. Keeys, J. Chem. Soc., 1947,
1068.
15 Tatsumi, K. Kenji, S. Sadakatsu and U. Hiroshi, Eur. Pat. 584
408, 1994.
16 N. Merat, C. Godawa and A. Gaset, J. Chem. Tech. Biotechnol.,
1990, 48, 145.
17 S. P. Lee and Y. W. Chen, Ind. Eng. Chem. Res., 1999, 38, 2548.
18 G. Seo and H. Chon, J. Catal., 1981, 67, 424.
19 R. Rao, A. Dandekar, R. T. K. Baker and M. A. Vannice,
J. Catal., 1997, 171, 406.
20 L. Baijun, L. Lianhai, W. Bingchun, C. Tianxi and K. Iwatani,
Appl. Catal. A, 1998, 171, 117.
Acknowledgements
This work was supported by Natural Science Foundation of
China (No.20276077) and Shanxi Natural Science Foundation
(No.20021023).
21 H. J. Mercker, F.-F. Pape, J. Simon, A. Henne, M. Hesse, U.
Kohler, R. Dostalek, C. F. Erdbrugger and D. Kratz, US Pat. 6
093 677, 2000.
22 An alternative explanation could arise from the ‘‘local’’ increment
of the H2 partial pressure (or the H2:furfural molar ratio) on the
catalyst surface, produced by the extra hydrogen evolving from
BDO. We thank one referee for pointing out this possibility.
References
1
(a) R. A. W. Johnstone and A. H. Wilby, Chem. Rev., 1985, 85,
129; (b) G. Zassinovich and G. Mestroni, Chem. Rev., 1992, 92,
1051.
210
New J. Chem., 2003, 27, 208–210