A novel route for synthesis of g-butyrolactone through the coupling of
hydrogenation and dehydrogenation
Yu-Lei Zhu, Hong-Wei Xiang, Gui-Sheng Wu, Liang Bai and Yong-Wang Li*
State Key Laboratory of Coal Conversion (SKLCC), Institute of Coal Chemistry, Chinese Academy of
Sciences, P.O. Box 165, Taiyuan 030001, Shanxi, People’s Republic of China. E-mail: ywl@public.ty.sx.cn
Received (in Cambridge, UK) 23rd October 2001, Accepted 11th December 2001
First published as an Advance Article on the web 14th January 2002
A coupling process of the hydrogenation of maleic anhydride
and the dehydrogenation of 1,4-butanediol has been in-
vented for the synthesis of g-butyrolactone over a Cu–Zn
catalyst, realizing optimal hydrogen utilization and better
energy efficiency.
The hydrogenation of MA, the dehydrogenation of BDO and
the coupling process were investigated in a fixed-bed reactor
over a Cu–Zn catalyst, which was prepared by a co-precipitation
method from copper nitrate and zinc nitrate. The reactor (600
mm long, 12 mm i.d.) was packed with 15 g catalyst (20–40
mesh). The reaction system had a buffer tank for collecting the
tail gas and a pump for cycling hydrogen. In the beginning of all
g-Butyrolactone (GBL) is one of the important intermediates in
fine chemical industrial practices, for example, for the synthesis
of pyrrolidone, N-methylpyrrolidone, N-vinylpyrrolidone, her-
bicides, and rubber additives. There are two main routes for the
production of GBL: the catalytic dehydrogenation of 1,4-buta-
nediol (BDO) and the hydrogenation of maleic anhydride (MA).
Both processes are mainly performed typically in multi-tubular
fixed-bed reactors. In particular, the dehydrogenation of BDO is
dominant in commercial applications.1
tests, N
then replaced by 5%H
reduced by increasing the temperature from 25 to 270 °C at a
2
was introduced to purge the reaction system, and was
2
2
/N (v/v) at 1 atm. The catalyst was pre-
2
1
rate of 20 °C h and then keeping it at 270 °C for 2 h. After the
reduction, the reactants were introduced into the reactor.
Hydrogen in tail stream was recycled after the reaction products
had been condensed. The products were collected at an ice trap
and analyzed using a gas chromatograph GC-920 (Shanghai
Analyzer Comp., China) fitted with a FID.
The catalytic hydrogenation of MA or its derivatives such as
maleic acid, succinic anhydride or succinic maleate to GBL has
2–10
frequently been reported in the literature.
The reaction
Table 1 Influence of temperature on MA hydrogenation to GBL
equation of MA hydrogenation to GBL can be represented as
follows:
T/°C
265
270
290
300
100
MA conversion (%)
GBL selectivity (%)
99.5
87.4
100
93.2
100
90.6
(
1)
85.2
Reaction conditions: 1 atm, LHSV = 0.1 h21, H
mol).
2
+MA = 50+1 (mol/
Reaction (1) shows that production of 1 mol GBL requires 1
mol MA and 3 mol H , releasing 211 kJ of heat. Owing to the
2
strong exothermic nature of Reaction (1), it is difficult in the
temperature control of the process, leading to apparent hotspots
typically in a tubular fixed-bed reactor and lowering the
selectivity to the desired product, GBL. In addition, a supply of
hydrogen is needed.
Table 1 shows that the conversion of MA is 100% and that the
selectivity of GBL is > 90% at 270–290 °C.
The dehydrogenation of BDO at different temperatures is
represented in Table 2. It indicates that the conversion of BDO
is > 99.3% and the selectivity for GBL is > 97.6% . In order to
check the thermal equilibrium status of the BDO dehydrogena-
tion reaction [reaction (2)], the experiment under different
hydrogen to BDO ratios was conducted, and the results are
summarized in Table 3. It is clear that the conversion of BDO
can reach 98.2% even under a large hydrogen mol ratio in the
reacting mixture. For all conditions listed in Table 3, it is
The vapor phase catalytic dehydrogenation of BDO to GBL
11–15
has also been described in the literature.
be expressed as follows:
This reaction can
(
2)
It is evident that production of 1 mol GBL requires 1 mol
BDO, releasing 2 mol H and requiring 61.6 kJ of heat. It should
be noted that the reaction is practically irreversible under typical
industrial operating conditions (H +BDO = 15, 1 atm, 200 °C,
2
Table 2 Influence of temperature on BDO dehydrogenation to GBL
2
8
equilibrium constant K
p
= 10 ). Owing to the endothermic
T/°C
190
200
210
230
260
properties of reaction (2), the increase of the LHSV (liquid
hourly space velocity) of BDO is relatively limited by low
external heat supply in a practical reactor. In addition, the
hydrogen released from reaction (2) cannot be used properly in
a single dehydrogenation process.
BDO conversion (%)
GBL selectivity (%)
Reaction conditions: 1 atm, LHSV = 0.5 h21, H
99.3
98.8
99.8
99.6
100
98.3
100
98.1
100
97.6
2
+BDO = 15+1 (mol/
mol).
This work proposes an idea to combine reactions (1) and (2)
in one catalytic process to achieve better thermal balances, the
efficient use of hydrogen, and thus high overall efficiency. The
combined reaction can be expressed as follows:
2
Table 3 Influence of H +BDO ratio on the dehydrogenation of BDO to
GBL
(
3)
2
H +BDO (mol/mol)
10
15
25
45
85
BDO conversion (%)
GBL selectivity (%)
100
97.2
100
97.8 98.0
99.6
99.1
98.2
98.2.
98.8
The above combined system can be practically realized on
the basis of the fact that the hydrogenation of MA and the
dehydrogenation of BDO could be carried out over the same
Cu-based catalyst, and under similar reaction conditions.6
Reaction conditions: 1 atm, LHSV = 0.5 h21, T = 240 °C. Equilibrium
8
constant, K
p
is > 10 under all conditions.
,7,13
2
54
CHEM. COMMUN., 2002, 254–255
This journal is © The Royal Society of Chemistry 2002