Hydrogenation of maleic anhydride to succinic anhydride over nickel/clay catalysts

Article abstract of DOI:10.1007/s11243-012-9648-6

Hydrogenation of maleic anhydride (MA) to succinic anhydride (SA) over Ni/clay catalysts prepared by an impregnation method has been studied at different temperatures, Ni contents, pressures and weighted hourly space velocity (WHSV). The catalytic activity was greatly influenced by the temperature, Ni content, WHSV and pressure. A 97.1 % MA conversion with 99.6 % selectivity to SA was obtained over 5 %wt catalyst at 180 °C and at a pressure of 1 MPa H2. The catalysts were characterized by an array of techniques, including X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR) and thermogravimetric analysis (TGA). XRD and TPR studies showed that nickel was present as Ni2? species on the support. Increasing the calcination temperature up to 650 °C led to the destruction of the support structure, as observed by TGA, while a calcination temperature of 550 °C gave the best results. Catalyst deactivation studies showed that the catalyst has a long lifetime, the yield of SA remaining better than 90 % even after a reaction time of 60 h. Studies on the catalyst induction showed that the presence or absence of an induction period was determined by the type of hydrogenation catalyst. Springer Science+Business Media Dordrecht 2012.

Full text of DOI:10.1007/s11243-012-9648-6

Transition Met Chem
DOI 10.1007/s11243-012-9648-6
Hydrogenation of maleic anhydride to succinic anhydride
over nickel/clay catalysts
•
Shaofei Guo Weiping Tian Li Shi
•
Received: 9 July 2012 / Accepted: 12 September 2012
Ó Springer Science+Business Media Dordrecht 2012
Abstract Hydrogenation of maleic anhydride (MA) to
succinic anhydride (SA) over Ni/clay catalysts prepared by
an impregnation method has been studied at different
temperatures, Ni contents, pressures and weighted hourly
space velocity (WHSV). The catalytic activity was greatly
influenced by the temperature, Ni content, WHSV and
pressure. A 97.1 % MA conversion with 99.6 % selectivity
to SA was obtained over 5 %wt catalyst at 180 °C and at a
pressure of 1 MPa H2. The catalysts were characterized by an
array of techniques, including X-ray diffraction (XRD), H2
temperature-programmed reduction (TPR) and thermogravi-
metric analysis (TGA). XRD and TPR studies showed that
nickel was present as Ni2? species on the support. Increasing
the calcination temperature up to 650 °C led to the destruction
of the support structure, as observed by TGA, while a calci-
nation temperature of 550 °C gave the best results. Catalyst
deactivation studies showed that the catalyst has a long life-
time, the yield of SA remaining better than 90 % even after a
reaction time of 60 h. Studies on the catalyst induction
showed that the presence or absence of an induction period
was determined by the type of hydrogenation catalyst.
succinic anhydride (SA), c-butyrolactone (GBL), 1,4-
butanediol (BDO) and tetrahydrofuran (THF), are impor-
tant chemicals in the food, pharmaceuticals and textile
industries [1–5]. The reaction pathway for the hydrogena-
tion of MA to BDO and THF is illustrated in Fig. 1 [6–8].
In this process, both hydrogenation and hydrogenolysis
reactions are involved.
These compounds are mainly produced by four indus-
trial processes: (1) the Reppe process, based on acetylene–
formaldehyde condensation; (2) the Arco process, based on
isomerization of propylene oxide to allyl alcohol and
subsequent hydroformylation; (3) the Mitsubishi Kasei
process (MKC), based on 1,3-butadiene diacetoxylation;
and (4) the Davy McKee process based on hydrogenation
of diethyl or dimethyl maleates [3]. However, each of these
processes has some disadvantages. The Reppe process uses
acetylene and formaldehyde as starting materials, plus
severe reaction conditions (140–280 bar, 250–350 °C) [9].
The Davy McKee process needs two different reactors,
catalysts and reaction conditions [10].
In principle, hydrogenation of MA is the most direct,
environmentally benign, and economic way to produce SA.
Because of MA’s ready availability and low price, which
became possible by the construction of large fluid bed
plants, according to Alusuisse–Lumnus and BP/UCB
technologies, MA may be considered as a good feedstock
[2, 3].
Introduction
Hydrogenation of maleic anhydride (MA) is an important
industrial chemical process, the products of which, such as
Hydrogenation of MA over different noble metal and
copper-based catalysts in both vapor and liquid phases has
been reported [11–17]. However, these catalysts are
expensive and are susceptible to deactivation, as the coke
deposition must still be resolved, so it is necessary to
explore highly active catalysts which can work under much
milder reaction pressures or use less expensive metals, if
possible. We have studied Ni/HY-Al2O3 catalysts for
S. Guo ꢀ W. Tian ꢀ L. Shi (&)
The State Key Laboratory of Chemical Engineering, East China
University of Science and Technology, Shanghai 200237,
People’s Republic of China
e-mail: yyshi@ecust.edu.cn
123

Transition Met Chem
maleic acid
O
succinic acid
O
Ni(NO3)2ꢀ6H2O (0.852 mol/L analytical grade) at room
temperature and left to stand for 12 h. After the impreg-
nation step, all the catalysts were dried at 120 °C overnight
and then calcined in air at different temperatures (250, 350,
450, 550 or 650 °C) for 3 h and allowed to cool to room
temperature. The amount of clay and Ni precursor was
varied to obtain catalysts with different nickel contents. For
example, 5 %wt Ni/clay requires 5 ml of the normal
aqueous solution of Ni(NO3)2ꢀ6H2O and 4.75 g of the
support.
HO
1,4-butanediol
HO
OH
OH
O
O
maleic anhydride
succinic anhydride
γ
-butyrolactone
tetrahydrofuran
O
O
O
O
O
O
O
O
O
butyric acid
n-butanol
propionic acid
n-propanol
Catalyst characterization
Fig. 1 Reaction scheme of hydrogenation of maleic anhydride (MA)
In situ X-ray diffraction patterns during reduction of the
catalysts were obtained with a Bruker D8 Advance X-ray
diffractometer equipped with an atmosphere and tempera-
ture control stage using CuKa radiation operated at 40 kV
and 100 mA. The powder diffraction patterns were recor-
ded in the 2h range from 10° to 80°.
Temperature-programmed reduction (TPR) with H2 was
carried out on Auto Chem 2910 (Micromeritics) instru-
ment. In a typical experiment, 0.050 g of calcined catalyst
was exposed to a reducing gas consisting of 5.0 vol % H2
in argon with a temperature ramp from ambient to 800 °C
at a heating rate of 10 °C/min.
hydrogenation of MA to SA. Over 5 %wt of Ni/Al2O3-HY
catalyst, a SA yield of 95 % was obtained under the opti-
mized reaction conditions [reaction temperature = 190 °C;
reaction pressure = 1 MPa; weighted hourly space velocity
(WHSV) = 2 h-1 MA] [18]. These results show that
nickel-based systems are good alternatives to noble metal
hydrogenation catalysts. Therefore, in this work, an
inexpensive Ni-loaded clay-based catalyst was chosen to
investigate MA hydrogenation. For the most active catalyst,
a systematic study of the reaction system, including the
influence of temperature, Ni content, pressure and WHSV,
has been carried out. Moreover, catalyst deactivation and
induction period have been investigated. Compared with the
Ni/HY-Al2O3 catalyst for hydrogenation of MA, higher
yield of SA and longer stream time were obtained for the
Ni/clay catalyst at a greater WHSV and lower reaction
temperature.
The thermogravimetric analysis (TGA) was carried out
in air using a Dupont thermo-balance. In these experi-
ments, the sample temperature was increased from
40 to 700 °C with a heating rate of 10 °C/min.
Catalytic tests
The reaction was performed in a fixed-bed reactor operated
in the down-flow mode. The temperature of the reactor was
controlled using a PID controller. The temperature of the
catalyst bed was measured using a Ni–Cr–Ni thermocou-
ple. Isothermal operating conditions were maintained by a
cooling coil inside the reactor and an electrical heating
jacket covering the outer side of the reactor wall. The
pipings of the system were heated with three independent
heating sets. The reactant was a solution of MA in
c-butyrolactone (22 wt%), which was transported into the
reactor with a micro-syringe pump. For each experiment,
1 g of unreduced catalyst (20–40 mesh) was loaded into the
reactor. The catalyst was reduced in situ at a pressure of
1 MPa with H2 (flow rate 32 cm3/min) for 2 h. The prod-
ucts were analyzed using an Agilent 6,890 N gas chro-
matograph (flame ionization detector, HP-5 column,
30 m 9 5 mm 9 0.25 lm) and confirmed by gas GC–MS.
MA conversion and selectivity to the product i was
calculated according to the following equations:
Experimental
Catalysts preparation
The support was prepared via the kneading method, using
clay. The clay was obtained from Yongsheng catalyst plant
(Linan China). The elemental analysis (mass %) showed the
composition of the clay to be SiO2: 67.8; Al2O3: 16.3;
Fe2O3: 4.0; MgO: 1.7; CaO: 1.1; TiO2: 0.4; Na2O: 0.9;
K2O: 1.6 %. First, the clay was shaped with normal aqueous
solutions of HNO3 (10 %wt) and dried at 120 °C overnight
and then calcined in air at 550 °C. After the calcination, the
clay was cooled to room temperature and then crushed and
sieved to a particle size between 0.38 and 0.83 mm.
The monometallic nickel catalysts (Ni supported on
clay) were prepared by impregnation of the support with an
aqueous solution of nickel nitrate hexahydrate. First, the
support was impregnated in normal aqueous solutions of
123

Transition Met Chem
MAin ꢁ MAout
XMA ð%Þ ¼
Si ð%Þ ¼
ꢂ 100
ꢂ 100;
ð1Þ
ð2Þ
MAin
Producti;out
MAin ꢁ MAout
where MAin, MAout and Producti,out represent the concen-
trations of reactant or products entering (in) or leaving
(out) the reactor, respectively.
Results and discussion
XRD analysis
XRD patterns (Fig. 2) of all the catalyst samples examined
at the big angle showed the characteristic peaks for NiO
species at 2h = 37.25, 43.28, 62.88, 75.41 and 79.41°
corresponding to the planes (1 1 1), (2 0 0), (2 2 0), (3 1 1)
and (2 2 2) of cubic NiO species, respectively. For the
peaks at 2h = 37.25 and 62.88°, the diffraction intensity
was clearly enhanced with Ni loading of around 7 %wt.
With further increase in nickel content, the diffraction peak
intensities increased without any other visible change. This
suggests the presence of NiO when the loading of nickel is
more than 7 %, but there are no other kinds of Ni oxides or
elemental Ni present.
0
200
400
600
800
Temperature(
)
Fig. 3 TPR profiles of the 5 %wt Ni/clay (calcined in air at 550 °C)
catalyst
assigned to the Ni2? of the NiO species interacting with the
support and other than Ni silicate/aluminate peak, since the
reduction peak of Ni silicate/aluminate would appear at
higher temperature [16]. The peak at Tmax = 730 °C may
be due to the formation of amorphous Ni silicate/aluminate
species.
Thermogravimetric analysis
Temperature-programmed reduction of 5 %wt Ni/clay
TGA of the dried sample was performed at a range of
temperatures from 40 to 700 °C. The TGA curves are
illustrated in Fig. 4. These curves show that the removal of
physisorbed water was complete by 150 °C. The weight
loss and the derived weight observed in the temperature
range of 250–450 °C can be attributed to the decomposi-
tion of nitrates entrapped in the narrow pores of the Ni
The TPR profiles of the samples are presented in Fig. 3.
The peak with Tmax at 370°C can be attributed to the
reduction of NiO particles with no interaction with the
support [19]. The peak with Tmax at around 550 °C can be
NiO
0.14
0
0.12
Weight Loss
Deriv/Weight
2
0.10
0.08
4
20%
7%
0.06
6
0.04
5%
3%
0.02
0.00
8
10
20
30
40
50
60
70
80
90
10
0
100
200
300
400
500
600
700
800
2θ(derees)
Temperature (
)
Fig. 2 X-ray diffraction pattern of calcined Ni/clay (calcined in air at
550 °C) samples with different Ni loadings
Fig. 4 TGA analysis of the of 5 %wt Ni/clay catalyst
123

Transition Met Chem
98
97
96
95
94
93
92
containing xero- and aerogels [20]. Consistent with Fig. 2,
the Ni(NO3)2ꢀ6H2O should be decomposed to NiO in the
temperature range of 250–450 °C. Finally, the weight loss
observed at temperatures higher than 550 °C can be
attributed to the removal of structural water from the
support.
Effect of reduction and calcination temperatures
The catalysts were reduced for 2 h in H2 flow at a range of
temperatures from 250 to 450 °C. The effect of reduction
temperature on the conversion of MA and selectivity for
SA is shown in Fig. 5. Both the MA conversion and SA
selectivity increased rapidly when the temperature was
increased from 250 to 350 °C. Though higher temperatures
gave a small further increase in conversion of the MA, the
selectivity for SA was decreased.
200
300
400
500
600
700
Calcination temperature (
)
Fig. 6 Hydrogenation of maleic anhydride over 5 %wt Ni/clay:
effect of calcined temperature. Reaction conditions: reduction tem-
perature = 350 °C, WHSV = 4 h-1 MA, reaction temperature =
180 °C, reaction pressure = 1 MPa, H2 flow = 50 ml/min
Catalysts calcined at a temperatures ranging from 250 to
650 °C were used to investigate the effect of calcination
temperature on the conversion of MA, and the results are
shown in Fig. 6. The selectivity for SA was proximity 100 %
in the catalyst activity tests, so it is understandable that the
conversion of MA could be evidence for the activity of
the catalyst. In Fig. 6, the conversion of MA increased as the
calcination temperature increased, achieving maximum con-
version at 550 °C, and then decreased rapidly. As mentioned
above, Ni(NO3)2ꢀ6H2O should be decomposed to NiO in the
temperature range of 250–450 °C. With the calcination
temperature increasing from 250 to 550 °C, more
Ni(NO3)2ꢀ6H2O would be decomposed to NiO; hence, more
NiO could be reduced to Ni. Therefore, samples with high
calcination temperature would be more active than samples
with low calcination temperature. The conversion of MA
ranged from 96.1 to 97.1 % as the calcination temperature
increased from 250 to 550 °C. When the calcination tem-
perature reached 650 °C, the conversion of MA was drasti-
cally decreased, as a result of the removal of structural water
from the support and the resulting collapse of the support
structure. The TGA results showed clearly that loss of
structural water from the support occurred at temperatures
higher than 550 °C.
As the calcination temperature was increased from 250
to 550 °C, conversion of MA only increased by about 1 %.
So, in view of its lower energy consumption, we concen-
trated on the catalyst calcined at 250 °C. Figure 7 shows
that the catalyst was not very active at the beginning of the
100
90
80
70
60
50
40
100
90
80
70
60
50
40
100
90
80
70
60
50
100
90
80
70
60
50
Conversion of MA
Selectivity of SA
Conversion of MA
Selectivity of SA
0
1
2
3
4
5
6
7
8
9
250
300
350
400
450
Reaction time (h)
Reduction temperature (
)
Fig. 7 Hydrogenation of MA over 5 %wt Ni/clay calcined at 250 °C:
time-on-stream study. Reaction conditions: reduction temperature =
350 °C, WHSV = 4 h-1 MA, reaction temperature = 180 °C, reac-
tion pressure = 1 MPa, H2 flow = 50 ml/min. Catalyst calcined at
250 °C
Fig. 5 Hydrogenation of MA over 5wt % Ni/clay: effect of reduction
temperature. Reaction conditions: calcination temperature = 550 °C,
WHSV = 4 h-1 MA, reaction temperature = 200 °C, reaction pres-
sure = 1 MPa, H2 flow = 50 ml/min
123

Transition Met Chem
test, but after 1.5 h, the conversion of MA increased to
96 %. However, the conversion rate was only stable up to
5.5 h, and the conversion decreased from 96 to 50 % for
longer reaction times. Compared with Fig. 9 which shows
the time-on-stream of the catalyst calcined at 550 °C, the
catalyst calcined at 250 °C is less active.
In general, the calcination temperature has a strong
influence on the catalytic activity and stability. Calcination
at low temperature (250 °C) is not effective due to the
lower concentration of NiO. Conversely, high calcination
temperatures (650 °C) cause low MA conversion due to
damage to the structure of the support.
Table 2 Effect of reaction pressure
P (MPa)
Conversion
of maleic
anhydride (%)
Selectivity (%)
Yield (%)
SA
SA
GBL
0
11.70
85.45
97.14
98.52
100
100
0
11.70
85.45
96.70
96.23
0.5
1
0
99.55
97.68
0.45
2.32
1.5
Reaction conditions: reduction temperature = 350 °C, calcination
temperature = 550 °C, WHSV = 4 h-1 MA, reaction tempera-
ture = 180 °C, H2 flow = 50 ml/min, catalyst: 5 %wt Ni/clay
good SA yields. The effect of H2 pressure on the MA
hydrogenation (Table 2) shows that 97.1 % MA conversion
with 99.6 % selectivity to SA could be obtained at 180 °C
and a pressure of 1 MPa H2. Product conversion, however,
varied significantly with changes in pressure (Table 2).
Thus, the conversion of MA increased from 11.7 to 98.5 % as
the reaction pressure increased from 0 to 1.5 MPa, while the
SA selectivity decreased with increasing H2 pressure,
because of over-hydrogenation. The yield of SA increased as
the reaction pressure increased up to a maximum at 1 MPa,
then decreased. Hence, control of the reaction pressure could
be used to regulate the desired product as well the product
distribution between SA and GBL.
Effect of Ni content
The conversion of MA increased with increasing Ni content
(Table 1). No significant amounts of over-hydrogenated
or hydrogenolysis products such as tetrahydrofuran,
1,4-butanediol or propionic acid were observed in this study.
The major products were SA and GBL. Since GBL forms
via the hydrogenation of SA [21], it is reasonable that the
yield of SA can be used to estimate the activity of the cat-
alyst. The conversion of MA was 93.2 % when the Ni
content was 3 %, increasing to 99.2 % when the Ni content
was increased to 20 %. However, the yield of SA as well as
the selectivity for SA increased as the Ni increased,
achieving maximum yield at 5 %wt Ni content, then
decreasing. This decrease is due to over-hydrogenation. As
mentioned above, Ni0 is the active species in the hydroge-
nation reaction. Therefore, samples with high nickel (after
NiO reduction) content would be more active than samples
with low nickel content, resulting in a decrease in the
selectivity for SA. The XRD results clearly show that the
relative concentration of free NiO increases with Ni loading.
The effects of different reaction temperatures on the
performance of the catalyst are shown in Table 3. Reaction
temperature proved to be critical in obtaining good SA
yields. As is seen in Table 3, MA conversion increased with
increasing temperature. Both the yield and the selectivity of
SA increased as the reaction temperature increased, reaching
a maximum at 180 °C, then decreased. Thus, the yield is
affected not only by manipulating the temperature, but also
by varying the hydrogen pressure and Ni content.
Effect of pressure and temperature
Effect of weighted hourly space velocity
Different reactions were carried out at a pressure of
0–1.5 MPa (Table 2). Pressure was critical in obtaining
The hydrogenation of MA was carried out at 180 °C with
WHSV varying from 2 to 6 h-1 (Fig. 8). As the WHSV
Table 1 Effect of Ni content
Table 3 Effect of reaction temperature
Ni content
(%wt)
Conversion
of maleic
anhydride (%)
Selectivity (%)
Yield (%)
SA
T (°C)
Conversion
of maleic
anhydride (%)
Selectivity (%)
Yield (%)
SA
SA
GBL
SA
GBL
3
93.17
97.14
97.64
98.13
99.20
96.61
99.55
96.89
95.25
80.52
3.39
0.45
3.11
4.75
9.48
90.01
96.70
94.60
93.46
79.87
150
180
190
200
93.83
97.14
97.26
97.46
83.51
99.55
99.29
98.91
16.49
0.45
0.71
1.09
78.36
96.70
96.57
96.40
5
7
10
20
Reaction conditions: reduction temperature = 350 °C, calcination
temperature = 550 °C, WHSV = 4 h-1 MA, reaction pressur-
e = 1 MPa, H2 flow = 50 ml/min. Catalyst: 5 %wt Ni/clay
Reaction conditions: reduction temperature = 350 °C, calcination
temperature = 550 °C, WHSV = 4 h-1 MA, reaction tempera-
ture = 180 °C, H2 flow = 50 ml/min
123

Transition Met Chem
101
100
99
98
97
96
95
94
93
92
91
90
89
101
100
99
98
97
96
95
94
93
92
91
90
89
100
95
90
85
80
75
70
Conversion of MA
Yield of SA
0
10
20
30
40
50
60
70
2
3
4
5
6
Reaction time(h)
WHSV(h-1)
Fig. 9 Hydrogenation of MA over 5 %wt Ni/clay: time-on-stream
study. Reaction conditions: reduction temperature = 350 °C, calci-
nation temperature = 550 °C, WHSV = 4 h-1 MA, reaction tem-
perature = 180 °C, reaction pressure = 1 MPa, H2 flow =
50 ml/min
Fig. 8 Hydrogenation of MA over 5 %wt Ni/clay: effect of WHSV.
Reaction conditions: reduction temperature = 350 °C, calcination
temperature = 550 °C, reaction temperature = 180 °C, reaction
pressure = 1 MPa, H2 flow = 50 ml/min
increased, the conversion of MA decreased; in addition, as
the WHSV increased, the yield of SA fell exponentially.
The conversion decreased from 97.1 % at 4 h-1 to 93.6 %
at 6 h-1, while the yield of SA decreased from 96.7 to
93.6 % during this period.
70
(a)
(b)
60
50
25
Stability and reusability of the catalyst
To study the stability and reusability of the catalyst, three
identical experiments were performed using of 5 %wt
Ni/clay for 4 h. Table 4 shows that the conversion of MA
was 97.1, 98.4 and 97.1 %, respectively. The results indi-
cate that the catalyst has high stability and reusability for
hydrogenation of MA to SA.
20
15
0
1
2
3
4
Reaction Time (h)
Fig. 10 Hydrogenation of MA over 5 %wt Ni/clay and 0.5 %wt Pt/
clay. Reaction conditions: reduction temperature = 350 °C, calcina-
tion temperature = 550 °C, reaction temperature = 180 °C, reaction
pressure = 1 MPa, H2 flow = 50 ml/min. a Reduction time = 5 h,
WHSV = 8 h-1 MA. b Reduction time = 2 h, WHSV = 4 h-1 MA
Time-on-stream study
From the above preliminary studies, the optimum reaction
parameters were chosen as: reduction temperature, 350 °C;
calcination temperature, 550 °C; reaction temperature,
180 °C; reaction pressure, 1 MPa; WHSV, 4 h-1 MA.
Time-on-stream studies showed that the catalyst is not very
active at the beginning of the test, but after an induction
period of about 3 h, the yield raises steeply to 97.8 %
(Fig. 9). The yield of MA declined slowly as the reaction
proceeded, but was still higher than 90 % even after a
reaction time of 60 h.
Table 4 Stability and reusability of 5 %wt Ni/clay
The number
of reactions
Conversion
of MA (%)
Selectivity
of SA (%)
Yield
of SA (%)
Figure 8 reveals that the catalyst is not very active at the
beginning of the test, but after an induction period of about
3 h, the yield raises steeply to 97.8 %. In order to find the
reasons for this phenomenon, we increased the reduction
time from 2 to 5 h to see whether inadequate reduction was
responsible for the induction period. The results shown in
Fig. 10a show that the induction period was not eliminated
No. 1
No. 2
No. 3
97.14
98.41
97.06
99.55
97.14
99.67
96.70
95.60
96.74
Reaction conditions: reduction temperature = 350 °C, WHSV =
4 h-1 MA, calcination temperature = 550 °C, reaction temperature
= 180 °C, reaction pressure = 1 MPa, H2 flow = 50 ml/min
123

Transition Met Chem
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shown in Fig. 10b. This catalyst is active at the beginning
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presence of an induction period is determined by the type
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In summary, hydrogenation of MA to SA over Ni/clay
impregnated catalysts has been studied under a range of
conditions. Catalytic activity was greatly influenced by the
temperature, Ni content, WHSV and pressure. Nickel was
present in the ?2 state, as NiO on the catalyst. There was
no elemental nickel or Ni2O3 in the unreduced samples.
The catalyst calcined at 550 °C gave the best catalytic
performance, since most of the Ni(NO3)2ꢀ6H2O was
decomposed to NiO but the support structure remained
intact. Catalyst deactivation studies showed that the cata-
lyst has a long lifetime, the yield of MA remaining higher
than 90 % even after a reaction time of 60 h.
20. Bourikas K, Kordulis C, Lycourghiotis A (2006) Catal Rev
48:363
21. Messori M, Vaccari A (1994) J Catal 150:177
Using 5 %wt Ni/clay, 97.1 % conversion for MA and
99.6 % selectivity for SA were obtained for MA hydro-
genation at a reaction temperature of 180 °C and WHSV of
4 h-1 under 1 MPa pressure.
123