Gas-phase hydrogenation of maleic anhydride to γ-butyrolactone at atmospheric pressure over Cu-CeO2-Al2O3 catalyst

Article abstract of DOI:10.1016/j.molcata.2011.01.019

Cu-CeO₂-Al₂O₃ catalyst, prepared by co-precipitation method, was investigated for the gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and the catalyst deactivation was also studied. Effects of catalyst composition, reaction temperature, and liquid hourly space velocity (LHSV) of raw material on the catalytic performance of Cu-CeO₂-Al₂O₃ catalyst were investigated. The catalyst (molar ratio of Cu:Ce:Al = 1:1:2) showed better catalytic performance, in which both the conversion of MA and the selectivity of GBL kept 100% within two hours under the reaction conditions of 6 mL catalyst, 0.1 MPa, 220-280 °C, 30 mL min^-1 H₂, 0.6 h^-1 LHSV of 20 wt.% MA/GBL. As for Cu-CeO₂-Al ₂O₃ catalyst, smaller crystallite size of Cu and higher Cu surface area are favorable to increase its catalytic performance. The deactivation of Cu-CeO₂-Al₂O₃ catalyst is due to formation of the compact wax-like deposition on the catalyst surface, which is probably ascribed to the strong adsorption of succinic anhydride and then polymerization on the catalyst surface. The catalytic performance of the regenerated catalyst can be recovered completely by the regeneration method of N₂-air-H₂ stage treatment.

Full text of DOI:10.1016/j.molcata.2011.01.019

Journal of Molecular Catalysis A: Chemical 337 (2011) 77–81
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Gas-phase hydrogenation of maleic anhydride to ␥-butyrolactone at atmospheric
pressure over Cu–CeO2–Al2O3 catalyst
Yang Yu, Yanglong Guo, Wangcheng Zhan, Yun Guo, Yanqin Wang, Yunsong Wang, Zhigang Zhang,
Guanzhong Lu∗
Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Cu–CeO2–Al2O3 catalyst, prepared by co-precipitation method, was investigated for the gas-phase hydro-
genation of maleic anhydride (MA) to ␥-butyrolactone (GBL) at atmospheric pressure and the catalyst
deactivation was also studied. Effects of catalyst composition, reaction temperature, and liquid hourly
space velocity (LHSV) of raw material on the catalytic performance of Cu–CeO2–Al2O3 catalyst were
investigated. The catalyst (molar ratio of Cu:Ce:Al = 1:1:2) showed better catalytic performance, in which
both the conversion of MA and the selectivity of GBL kept 100% within two hours under the reaction
conditions of 6 mL catalyst, 0.1 MPa, 220–280 ◦C, 30 mL min−1 H2, 0.6 h−1 LHSV of 20 wt.% MA/GBL. As
for Cu–CeO2–Al2O3 catalyst, smaller crystallite size of Cu and higher Cu surface area are favorable to
increase its catalytic performance. The deactivation of Cu–CeO2–Al2O3 catalyst is due to formation of the
compact wax-like deposition on the catalyst surface, which is probably ascribed to the strong adsorp-
tion of succinic anhydride and then polymerization on the catalyst surface. The catalytic performance of
the regenerated catalyst can be recovered completely by the regeneration method of N2–air–H2 stage
treatment.
Received 9 December 2010
Received in revised form 12 January 2011
Accepted 14 January 2011
Available online 27 January 2011
Keywords:
Maleic anhydride
␥-Butyrolactone
Gas-phase hydrogenation
Cu–CeO2–Al2O3 catalyst
Deactivation
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
liquid hourly space velocity (LHSV) of raw material, higher H2/MA
molar ratio, lower selectivity of GBL, and poisonous composition of
␥-Butyrolactone (GBL) is an excellent organic solvent with high
boiling point, and an important intermediate for production of
N-methylpyrrolidone [1] and N-vinylpyrrolidone [2] based on its
unique oxygen-contained five-membered ring structure. In addi-
tion, GBL is preferably used as the cell electrolyte instead of the
strongly corrosion acid liquid [3,4].
GBL is produced by two main processes: dehydrogenation of
1,4-butanediol (BDO) [5] and hydrogenation of maleic anhydride
(MA) [6,7]. The gas-phase catalytic hydrogenation of MA to GBL at
atmospheric pressure has attracted increasing attention because
of the simple process and the low-cost raw material of MA due
to the large-scale industrialization and great improvement of the
technology of oxidation of n-butane to MA. Many studies are
concentrated on enhancing the conversion of MA and the selec-
tivity of GBL, in which some catalysts has been reported, such as
Cu–ZnO–MgO–Cr2O3 [8], Cu–ZnO–Al2O3 [9], Cu–ZnO–TiO2 [10],
Cu–Zn–Cd–Cr [11], Cu–ZnO–CeO2 [12], Cu–ZnO–ZrO2 [13], and
Cu–Pd(Ni)–TiO2–Al2O3 [14]. But there are still some disadvantages
over those catalysts, such as higher reaction temperature, lower
Cr in the catalyst.
As shown in Scheme 1, the catalytic hydrogenation of MA can
produce several products, such as succinic anhydride (SA), GBL,
tetrahydrofuran (THF), BDO and some hydrogenolysis products,
such as propanol, propanoic acid, in which the selectivity of the
target product is a principal criterion for catalyst screening. In
this paper, Cu–CeO2–Al2O3 catalyst, prepared by co-precipitation
method, was investigated for the gas-phase hydrogenation of MA
to GBL and the deactivation of the catalyst was also studied, which
have not yet been reported.
2. Experimental
2.1. Preparation of Cu–CeO2–Al2O3 catalyst
Cu–CeO2–Al2O3 catalyst was prepared by co-precipitation
method with 1.0 mol L−1 Na2CO3 aqueous solution as precip-
itating agent. 0.5 mol L−1 aqueous solution of Cu(NO3)2·3H2O,
Ce(NO3)3·6H2O and Al(NO3)3·9H2O with the given molar ratio, and
the precipitating agent were added dropwise into 200 mL deion-
ized water to keep pH value of the solution at 8–9 under vigorous
stirring. The resultant precipitate was aged under gentle stirring at
room temperature for 3 h and then washed by deionized water with
∗
Corresponding author. Tel.: +86 21 64252923; fax: +86 21 64252923.
E-mail addresses: ylguo@ecust.edu.cn (Y. Guo), gzhlu@ecust.edu.cn (G. Lu).
1381-1169/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2011.01.019

78
Y. Yu et al. / Journal of Molecular Catalysis A: Chemical 337 (2011) 77–81
The specific surface area was measured by nitrogen sorption at
−196 ◦C with BET method on a NOVA 4200e surface area and pore
size analyzer.
TG-DTA profiles were recorded on a PerkinElmer Pyris Diamond
TG-DTA analyzers◦, in which the catalyst was heated programmedly
from 40 ◦C to 800 C at the rate of 10 ◦C min−1 in the atmosphere of
air of 100 mL min−1
.
SEM images were recorded on a JEOL JSM-6360LV scanning elec-
tron microscope.
3. Results and discussion
Scheme 1. The reaction pathway for catalytic hydrogenation of MA.
3.1. Effect of catalyst composition
centrifugation until pH value of the filtrate was 7. After washed
by ethanol for several times, the precipitate was dried at 120 ◦C
overnight, and then calcined in air at 550 ◦Cfor 3 h and 650 ◦Cfor 3 h.
The as-prepared catalyst was pressed and then crushed into 20–40
mesh particles for evaluation of its catalytic performance. The
composition and physicochemical properties of Cu–CeO2–Al2O3
catalysts were shown in Table 1.
Table 2 shows the catalytic performance of Cu–CeO2–Al2O3
catalyst for the gas-phase hydrogenation of MA to GBL at atmo-
spheric pressure. Over CeO2-free catalyst (C1 0 1), the conversion
of MA and the selectivity of GBL were only 70.4% and 64.7%,
respectively, with the selectivity of SA of 21.5% and that of THF
of 13.8% within the first hour. After reaction for 3 h, the conver-
sion of MA and the selectivity of GBL dropped significantly to
50.7% and 50.8%, respectively. Compared with C1 0 1 catalyst, the
catalytic performance was improved greatly with the introduc-
tion of CeO2 into Cu–Al2O3 catalyst, in which the conversion of
MA of 100% and the selectivity of GBL of 100% over C1 2 1 cat-
alyst were achieved within the first hour. Compared with C1 1 1
catalyst, with an increase in Cu content in the catalyst, the cor-
responding catalytic performance dropped significantly and more
SA was formed over C2 1 1 catalyst. With an increase in Al content in
the catalyst, the catalytic performance was improved greatly over
C1 1 2 catalyst, in which both the conversion of MA and the selec-
tivity of GBL kept 100% within two hours. As for the gas-phase
hydrogenation of MA to GBL [8], the multi-component products
are easily formed and hence the design of a new catalyst should
focus on suppressing overhydrogenation and hydrogenolysis of
GBL. As shown in Table 2, except for a small quantity of overhydro-
genation product (THF), no hydrogenolysis products were detected
over Cu–CeO2–Al2O3 catalysts. Therefore Cu–CeO2–Al2O3 catalyst
is very suitable for the gas-phase hydrogenation of MA to GBL at
atmospheric pressure, in which C1 1 2 catalyst shows better catalytic
performance.
2.2. Gas-phase hydrogenation of maleic anhydride
Gas-phase hydrogenation of maleic anhydride to ␥-
butyrolactone over Cu–CeO2–Al2O3 catalyst was investigated
in the quartz tubular fixed-bed reactor (inside diameter = 13 mm,
length = 650 mm) at atmospheric pressure. In
a bottom-up
sequence, the reactor was packed with 1 mL quartz sand pre-
treated at 600 ◦C in air, 6 mL catalyst (height = 45 mm) and then
15 mL pretreated quartz sand for the complete gasification of raw
material (MA dissolved in GBL, 20 wt.%). The catalyst was reduced
in situ by 60 mL min−1 5 vol.% H2/N2 at 380 ◦C for 7 h (designated
as fresh catalyst). Then the temperature was lowered to 220 ◦C,
30 mL min−1 H2 and LHSV of 0.6 h−1 of raw material were fed into
the reactor. The products were collected in the conical beakers
cooled by ice-bath at intervals of 1 h and analyzed by PerkinElmer
Clarus 500 gas chromatograph equipped with a FID detector
and a SE-54 capillary column (25 m × 0.32 mm × 1.0 ␮m). The
temperatures of the injector and the detector were both 220 ◦C,
and the temperature of the column oven was kept at 100 ◦C for
1 min and then increased programmedly from 100 ◦C to 120 ◦C at
the rate of 5 ◦C min−1
.
2.3. Characterization of Cu–CeO2–Al2O3 catalyst
Table 2
Catalytic performance of Cu–CeO2–Al2O3 catalysts for the gas-phase hydrogenation
The powder XRD patterns were recorded on a Bruker AXS D8
Focus diffractometer operated at 40 kV, 40 mA (Cu K˛ radiation,
ꢀ = 0.15406 nm), and the diffraction patterns were taken in the
of MA to GBL at atmospheric pressure.a
Catalysts
Reaction
time (h)
MA conversion (%)
Selectivity (%)
range of 10◦ < 2ꢁ < 80◦ at the scanning rate of 6◦ min−1
.
GBL
64.7
THF
SA
The Cu surface area of Cu–CeO2–Al2O3 catalyst was measured
by N2O chemisorption at 60 ◦C assuming a molar stoichiome-
try of Cu:N2O = 2 and a surface atomic density of 1.46 × 1019 Cu
atoms m−2 [15].
C1 0 1
C1 1 1
C2 1 1
C1 2 1
C1 1 2
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
70.4
66.8
50.7
100.0
98.1
95.0
100.0
90.4
87.7
100.0
99.7
90.8
13.8
9.9
4.6
1.5
–
21.5
29.7
44.6
5.0
9.3
12.9
8.0
16.1
37.1
–
0.6
4.6
–
–
2.0
60.4
50.8
93.5
90.7
87.1
87.1
80.7
61.2
100.0
95.4
92.7
100.0
100.0
97.9
–
Table 1
4.9
3.2
1.7
–
4.0
2.7
–
The composition and physicochemical properties of Cu–CeO2–Al2O3 catalysts.
Catalysts
Molar ratio
SBET (m2 g−1
)
SCu (m2 g−1
)
Crystallite size
of Cu (nm)
Cu
Ce
Al
C1 0 1
C1 1 1
C2 1 1
C1 2 1
C1 1 2
1
1
2
1
1
0
1
1
2
1
1
1
1
1
2
80.1
65.6
50.3
83.7
107.8
19.6
8.9
8.0
12.8
18.7
12
20
27
26
15
100.0
100.0
98.8
–
0.1
a
Reaction conditions: 6 mL catalyst, 220 ◦C, 30 mL min−1 H2, and 0.6 h−1 LHSV of
MA in GBL.

Y. Yu et al. / Journal of Molecular Catalysis A: Chemical 337 (2011) 77–81
79
Table 3
Effect of reaction temperature on the catalytic performance of C1 1 2 catalyst.a
3.3. Effect of LHSV of raw material
Table 4 shows effect of LHSV of raw material on the catalytic
performance of C1 1 2 catalyst at atmospheric pressure. With an
increase in LHSV of raw material, the catalytic performance and
the stability of C1 1 2 catalyst became worse and the selectivity of
SA increased, in which both the conversion of MA and the selectiv-
ity of GBL kept 100% for 7 h at LHSV of 0.2 h−1 and only for 2 h at
LHSV of 0.6 h−1. The increase in LHSV of raw material, which short-
ens the contact time of MA on the surface of the catalyst, increases
the selectivity of SA and thus results in the rapid deactivation of
the catalyst. Therefore lower LHSV of raw material is beneficial to
increase the catalytic performance and the stability of C1 1 2 catalyst.
Reaction
Reaction
time (h)
MA conversion
(%)
Selectivity (%)
temperature (◦C)
GBL
THF
SA
220
240
260
280
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
100.0
100.0
98.8
100.0
100.0
97.9
–
–
0.1
0.1
–
–
–
2.0
7.3
–
89.7
92.6
100.0
100.0
99.6
100.0
100.0
99.3
–
–
0.3
0.2
–
0.4
2.8
–
94.1
97.0
100.0
100.0
100.0
95.2
100.0
100.0
100.0
95.8
100.0
100.0
98.0
–
–
1.5
1.0
–
–
3.0
1.2
0.5
5.7
–
–
1.4
8.6
93.3
3.4. Comparison of catalytic performance of Cu-based catalysts
100.0
100.0
95.6
Cu-based catalyst is preferred for the gas-phase hydrogenation
of MA to GBL, in which some reported catalysts were summarized
in Table 5. As shown in Table 5, the yield of GBL can reach 100%
over Cu–CeO2–Al2O3 and Cu–Pd(Ni)–TiO2–Al2O3 catalysts, which
agrees well with the viewpoint of Herrmann and Emig [16] that the
multistep hydrogenation of MA or SA is stopped at the stage of GBL
and 1,4-butanediol is not formed over zinc-free Cu-based catalysts.
Compared with the reported Cu-based catalysts, Cu–CeO2–Al2O3
(C1 1 2) catalyst without poisonous composition shows better per-
formance, such as higher yield of GBL, lower reaction temperature
and H2/MA molar ratio, and higher LHSV of raw material.
90.2
Reaction conditions: 6 mL catalyst, 0.1 MPa, 30 mL min−1 H2, and 0.6 h−1 LHSV
a
of MA in GBL.
3.2. Effect of reaction temperature
Table 3 shows effect of reaction temperature on the catalytic
performance of C1 1 2 catalyst at atmospheric pressure. Both the
conversion of MA and the selectivity of GBL were 100% within two
hours at 220–280 ◦C. With an increase in reaction temperature, the
decrease in the conversion of MA with the time on stream was
suppressed to some extent; however, the selectivity of GBL pre-
sented a parabola-like type change and reached a maximum at
240 ◦C. Therefore the optimum reaction temperature for the gas-
phase hydrogenation of MA to GBL over C1 1 2 catalyst was 240 ◦C
in terms of the yield of GBL.
3.5. Characterization of Cu–CeO2–Al2O3 catalyst
3.5.1. XRD
Fig. 1 shows XRD patterns of the as-prepared Cu–CeO2–Al2O3
catalysts. The characteristic diffraction peaks of CuO (PDF# 65-
2309) and CeO2 (PDF# 34-0394) can be identified in XRD patterns
Table 4
Effect of LHSV of raw material on the catalytic performance of C1 1 2 catalyst.a
Reaction time (h)
MA conversion (%)
Selectivity (%)
GBL
0.2 (h−1
)
0.4 (h−1
)
0.6 (h−1
)
THF
SA
0.2 (h−1
)
0.4 (h−1
)
0.6 (h−1
)
0.2 (h−1
)
0.4 (h−1
)
0.6 (h−1
)
0.2 (h−1
)
0.4 (h−1
)
0.6 (h−1
)
1
2
3
4
5
6
7
8
9
100.0
100.0
100.0
100.0
100.0
100.0
100.0
100.0
99.5
100.0
100.0
100.0
100.0
100.0
100.0
97.3
92.5
82.5
70.2
100.0
100.0
99.6
94.1
80.4
60.2
46.3
33.2
29.5
28.7
100.0
100.0
100.0
100.0
100.0
100.0
100.0
99.7
100.0
100.0
100.0
100.0
94.2
80.7
71.2
59.7
40.2
100.0
100.0
99.3
97.0
87.3
69.3
57.2
44.7
36.2
22.6
–
–
–
–
–
–
–
0.1
–
–
–
–
–
–
0.8
0.4
0.1
–
–
–
–
–
0.3
0.2
–
–
–
–
–
–
–
–
–
–
–
–
0.2
1.0
8.8
–
–
–
–
5.0
18.9
28.7
40.3
59.8
64.0
–
–
0.4
2.8
12.7
30.7
42.8
55.3
63.8
77.3
99.0
91.2
10
88.2
36.0
–
a
Reaction conditions: 6 mL catalyst, 0.1 MPa, 240 ◦C, and 30 mL min−1 H2.
Table 5
The catalytic performance of Cu-based catalysts for gas-phase hydrogenation of MA to GBL.
Catalysts
Reaction
Reaction
pressure (MPa)
SV of MA
Consecutive
reaction time (h)
H2/MA molar
ratio
Maximum GBL
yield (%)
References
temperature (◦C)
Cu–ZnO–MgO–Cr2O3
Cu–ZnO–Al2O3
Cu–ZnO–TiO2
Cu–ZnO–CdO–Cr2O3
Cu–ZnO–CeO2
Cu–ZnO–ZrO2
245
275
265
245
235
220
220
220
0.1
0.1
0.1
0.1
1.0
1.0
0.1
0.1
0.084a
N/A
N/A
1
N/A
1
1
1
2
121
82.7
96.0
99.2
88.0
91.1
85.0
100.0
100.0
[8]
[9]
0.644a
299
200
299
50
50
32
0.017b
N/A
[10]
[11]
[12]
[13]
[14]
Our work
0.020b
0.020b
0.036b
0.171a/0.143b
Cu–Pd(Ni)–TiO2–Al2O3
Cu–CeO2–Al2O3
9
a
The mass of MA per hour passed through 1 g catalyst (h−1).
b
The mass of MA per hour passed through 1 mL catalyst (g h−1 mL−1).

80
Y. Yu et al. / Journal of Molecular Catalysis A: Chemical 337 (2011) 77–81
at 2ꢁ = 43.3◦, 50.5◦, 74.2◦, corresponding to the crystal planes of
Cu (1 1 1), (2 0 0), (2 2 0), respectively. It indicated that CuO was
reduced completely by 5 vol.% H2/N2 to Cu0 and the state of CeO2
did not change, in which Cu0 is the active site for the gas-phase
hydrogenation of MA to GBL [5,10,12,13]. The characteristic diffrac-
tion peaks of Al2O3 were not observed in Figs. 1 and 2, which
indicated that Al2O3 existed in the amorphous phase in the cat-
alysts.
The crystallite size of Cu was determined by Scherrer formula
with the full peak width at half maximum height of the diffraction
peak of Cu (1 1 1). Based on the diffraction peak of Cu (1 1 1) shown
in Fig. 2, the crystallite size of Cu is shown in Table 1. As shown in
Table 1, with the introduction of CeO2 to Cu–Al2O3 catalyst or with
an increase in Cu content in the catalyst, the crystallite size of Cu
increased, however, with an increase in Al content in the catalyst,
the crystallite size of Cu decreased. As for Cu–CeO2–Al2O3 catalyst,
smaller crystallite size of Cu is favorable to increase its catalytic
performance.
Fig. 1. XRD patterns of the as-prepared Cu–CeO2–Al2O3catalysts.
3.5.2. Nitrogen sorption and N2O chemisorption
The BET specific surface area (SBET) and the Cu surface area
(Scu) of Cu–CeO2–Al2O3 catalysts with different compositions were
shown in Table 1. As shown in Tables 1 and 2, as for Cu–CeO2–Al2O3
catalyst, the variation trend of its catalytic performance was fairly
consistent with that of the corresponding Scu, and higher SBET was
favorable to increase Scu, that is to say, there were more active sites
of Cu0 on the catalyst surface, which resulted in better catalytic
performance.
3.6. Deactivation and regeneration of Cu–CeO2–Al2O3 catalyst
Cu–CeO2–Al2O3 catalyst shows better catalytic performance
for the gas-phase hydrogenation of MA to GBL at atmospheric
pressure, but after reaction for several hours, the catalytic perfor-
mance began to drop obviously. The similar phenomenon was also
observed over Cu/SiO2 catalyst [17]. To investigate the deactivation
of Cu–CeO2–Al2O3 catalyst, the fresh and the used C1 1 2 catalysts
were characterized by SEM, TG-DTA and XRD. The used C1 1 2 cat-
alyst was operated for 10 h under the reaction conditions of 6 mL
catalyst, 0.1 MPa, 240 ◦C, 30 mL min−1 H2, 0.6 h−1 LHSV of MA/GBL.
Fig. 3 shows SEM images of the fresh and the used C1 1 2 cata-
lysts. As shown in Fig. 3, there were many small incompact particles
on the surface of the fresh C1 1 2 catalyst. However, some com-
pact wax-like surface deposition was present on the surface of
the used C1 1 2 catalyst. As shown in Scheme 1, SA was a transi-
tion species in the catalytic hydrogenation of MA to GBL [6]. When
Fig. 2. XRD patterns of the fresh Cu–CeO2–Al2O3 catalysts.
of all catalysts except for C1 0 1 catalyst, in which they located at
2ꢁ = 35.7◦, 38.9◦, 48.9◦, 53.6◦, 58.5◦, 61.73◦, 66.6◦, 68.4◦, 75.5◦ and
28.5◦, 33.1◦, 47.5◦, 56.3◦, 59.1◦, 69.4◦, 76.7◦, 79.1◦, respectively.
Fig. 2 shows XRD patterns of the fresh Cu–CeO2–Al2O3 catalysts.
The characteristic diffraction peaks of CeO2 remained, and the
characteristic diffraction peaks of CuO disappeared, however the
characteristic diffraction peaks of Cu (PDF# 65-9026) appeared
Fig. 3. SEM images of the as-prepared (a) and the used (b) C1 1 2 catalysts.

Y. Yu et al. / Journal of Molecular Catalysis A: Chemical 337 (2011) 77–81
81
Table 6
The catalytic performance of the regenerated and the fresh C1 1 2 catalysts.a
Reaction time (h)
MA conversion (%)
Selectivity (%)
Fresh (F)
Regenerated (R)
GBL
THF
SA
F
R
F
R
F
R
1
2
3
4
100.0
100.0
99.6
100.0
100.0
99.0
100.0
100.0
99.3
100.0
100.0
98.6
–
–
0.3
0.2
–
–
0.1
-
–
–
0.4
2.8
–
–
1.3
3.3
94.1
94.3
97.0
96.7
a
Reaction conditions: 6 mL catalyst, 0.1 MPa, 240 ◦C, 30 mL min−1 H2, and 0.6 h−1 LHSV of MA in GBL.
catalyst for the gas-phase hydrogenation of MA to GBL at atmo-
spheric pressure were investigated. C1 1 2 catalyst shows better
catalytic performance, in which the conversion of MA and the selec-
tivity of GBL were both 100% within two hours under the reaction
conditions of 6 mL catalyst, 220–280 ◦C, 30 mL min−1 H2, 0.6 h−1
LHSV of MA in GBL. Lower LHSV of raw material is beneficial to
increase the catalytic performance and the stability of C1 1 2 catalyst.
Smaller crystallite size of Cu and higher metallic Cu surface area are
favorable to increase the catalytic performance of Cu–CeO2–Al2O3
catalyst. The deactivation of Cu–CeO2–Al2O3 catalyst is due to for-
mation of the compact wax-like surface deposition of the catalyst,
which is probably ascribed to the strong adsorption of SA and then
polymerization on the surfaceofcatalyst. Thecatalytic performance
of the regenerated catalyst can be recovered completely by the
regeneration method of N2–air–H2 stage treatment.
Acknowledgments
Fig. 4. TG-DTA profiles of the used C1 1 2 catalyst.
This project was supported financially by National Basic
Research Program of China (2010CB732300) and Program for New
Century Excellent Talents in University (NCET-09-0343).
Cu–CeO2–Al2O3 catalyst started to deactivate after reaction for sev-
eral hours, both the conversion of MA and the selectivity of GBL
decreased, and the selectivity of SA increased, that is to say, SA could
not be hydrogenated to GBL promptly and was adsorbed strongly
then polymerized on the catalyst surface, which resulted in the fast
deactivation of catalyst.
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Fig. 4 shows TG-DTA profiles of the use C1 1 2 catalyst. As shown
in Fig. 4, the weight loss in the temperature range of 250–450 ◦C was
28.6% with an exothermic peak, which was ascribed to combustion
of the surface depositions of the used C1 1 2 catalyst.
Based on TG-DTA analysis, the used C1 1 2 catalyst was regener-
ated in situ by the N2–air–H2 stage treatment, in which the used
catalyst was purged by 50 mL min−1 N2 at 200 ◦C for 1 h, then cal-
cined in air at 450 ◦C for 4 h and finally reduced by 60 mL min−1
5 vol.% H2/N2 at 380 ◦C for 4 h. The fresh and the regenerated C1 1 2
catalysts were characterized by XRD, in which there was no change
in the characteristic diffraction peaks of Cu and CeO2 and hence
the active sites of Cu0 did not change after regeneration. Table 6
shows the catalytic performance of the regenerated and the fresh
C1 1 2 catalysts. As shown in Table 6, the catalytic performance of
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4. Conclusions
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Effects of catalyst composition, reaction temperature, and LHSV
of raw material on the catalytic performance of Cu–CeO2–Al2O3