Selective hydrogenation of maleic anhydride over Pd/Al2O3 catalysts prepared via colloid deposition

Article abstract of DOI:10.1007/s12039-013-0542-3

Pd/Al₂O₃ catalysts were prepared via colloid deposition and the performance of the catalysts was examined in the selective hydrogenation of maleic anhydride to succinic anhydride. When the reaction was carried on in a batch system with 1,4-dioxane as the solvent (353 K and 1.0 MPa), high conversion of maleic anhydride (>98%) and high selectivity (>99%) for succinic anhydride were observed after 5 h. The as-prepared Pd/Al₂O₃ catalyst also showed excellent performance in solvent-free system and fixed-bed systems. The maleic anhydride (MA) conversion was greater than 98%, and high selectivity (>99%) for succinic anhydride was obtained after 1600 h in a fixed bed reacter. The results showed that the activity of the Pd/Al₂O₃ catalysts was excellent due to its high active surface area. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s12039-013-0542-3

c
J. Chem. Sci. Vol. 126, No. 1, January 2014, pp. 141–145. ꢀ Indian Academy of Sciences.
Selective hydrogenation of maleic anhydride over Pd/Al2O3 catalysts
prepared via colloid deposition
HONGJING YUANa, CHUNLEI ZHANGb, WEITAO HUOa, CHUNLI NINGb,
YONG TANGb, YI ZHANGb, DEQUAN CONGa, WENXIANG ZHANGa,
JIAHUAN LUOc, SU LIa and ZHENLU WANGa,∗
aKey Laboratory of Surface and Interface Chemistry of Jilin Province, College of Chemistry,
Jilin University, Qianjin Road 2699, Changchun 130012, PR China
bShanghai Huayi (Group) Company Technology Research Institute, Longwu Road 4600,
Shanghai 200241, PR China
cState Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry,
Jilin University, Qianjin Road 2699, Changchun 130012, PR China
e-mail: wzl@jlu.edu.cn
MS received 21 September 2013; revised 23 October 2013; accepted 24 October 2013
Abstract. Pd/Al2O3 catalysts were prepared via colloid deposition and the performance of the catalysts was
examined in the selective hydrogenation of maleic anhydride to succinic anhydride. When the reaction was
carried on in a batch system with 1,4-dioxane as the solvent (353 K and 1.0 MPa), high conversion of maleic
anhydride (>98%) and high selectivity (>99%) for succinic anhydride were observed after 5 h. The as-prepared
Pd/Al2O3 catalyst also showed excellent performance in solvent-free system and fixed-bed systems. The maleic
anhydride (MA) conversion was greater than 98%, and high selectivity (>99%) for succinic anhydride was
obtained after 1600 h in a fixed bed reacter. The results showed that the activity of the Pd/Al2O3 catalysts was
excellent due to its high active surface area.
Keywords. Pd/Al2O3 catalyst; maleic anhydride; selective hydrogenation; succinic anhydride.
1. Introduction
were achieved at an H2 pressure of 4 MPa and reaction
temperature of 473 K.10
The hydrogenation of maleic anhydride (MA) has
attracted a significant amount of attention because the
majority of its reaction products, including succinic
anhydride (SA), γ -butyrolactone (GBL), tetrahydro-
furan (THF) and 1,4-butanediol (BDO), are widely
used in industrial applications.1,2 In particular, SA is
widely used in the manufacturing of polymeric mate-
rials, pharmaceuticals, agrochemicals, dyes, surface-
active agents, organic flame retardant materials and
fragrances.3
In the literature, different types of catalysts, includ-
ing noble and non-noble metals, have been used for
the hydrogenation of MA with different solvents in
the liquid and gas phases.4–6 Various products, includ-
ing GBL, THF, BDO and butyric acid were obtained,
depending on the catalysts and reaction conditions.6–9
For example, when Pd/C was used as a catalyst in the
hydrogenation of MA in supercritical carbon dioxide,
97.3% selectivity for GBL and 100% conversion of MA
Several catalysts have been investigated in the hydro-
genation of MA to SA. For example, when RhCl(PPh3)3
was used as a catalyst in the liquid phase hydrogena-
tion of MA in ethylene glycol dimethylether, 99% con-
version of MA and 100% SA selectivity to SA were
achieved under the optimal reaction conditions.11 To
avoid the high cost of separating the solvent from the
reaction mixture, solvent-free hydrogenation of MA
has been carried out using metallic nickel catalyst.12
Several catalysts have been investigated in fixed bed
reactors, which are suitable for sequential production
processes used in commercial procedures. For exam-
ple, Ni/SiO2, Co/SiO2 and Cu/SiO2 1,13 have been used
as catalysts in the hydrogenation of MA in a fixed bed
reactor. However, partial deactivation occurred due to
the deposition of carbonaceous species on the metal-
lic phase. Although nickel–platinum catalysts are often
used in the hydrogenation of MA, the addition of Pt
increases the stability of the catalyst. Moreover, only a
4% loss of reaction activity was observed after 120 h.3
Noble catalysts, especially Pd-based catalysts, have
shown excellent catalytic performance in hydrogenation
∗For correspondence
141

142
Hongjing Yuan et al.
reactions.14–16 Several groups, including ours, have to a position of 284.6 eV. The palladium content in the
demonstrated that colloid-deposition methods are effi- prepared catalysts were determined using inductively
cient procedures for the preparation of highly dispersed, coupled plasma-optical emission spectrometry (ICP-
supported noble metal catalysts.17–22 In the present OES), in a Perkin-Elmer Optima 3300DV ICP-OES
study, Pd/Al2O3 was prepared by the colloid-deposition spectrometry.
method, and the catalytic performance of the resulting
The surface area of Pd26 was calculated basing on
materials was investigated in the selective hydrogena- the surface concentration of Pd determined by XPS
tion of MA to SA in both a batch and fixed bed sys- and the BET surface area, assuming that the atomic
tem. The physical–chemical properties of the Pd/Al2O3 cross sections are 0.059 nm2 for Pd, 0.054 nm2 for O2−
catalysts were determined to correlate the catalytic and 0.01 nm2 for Al3+, which were calculated from the
performance and characteristics of the catalysts.
atomic and ionic radii; the surface of Pd (SPd) is calcu-
lated by the equation: SPd = SBET×αPd×cPd/(αPd×cPd +
αAl×cAl + cO), where SBET is BET surface area, αPd and
αM are the atomic ratios of Pd/O and Al/O, cPd, cAl, and
cO are the cross sections.
2. Experimental
2.1 Catalyst preparation
Supported Pd/Al2O3 catalysts were prepared using the
colloid-deposition method, according to the previously
described procedure.23,24
2.3 Catalytic evaluation
Selective hydrogenation of MA to SA was carried on
both in batch system and fixed bed system.
Typically,
poly(N-vinyl-2-pyrrolidone)-protected
(PVP) and Na2PdCl4 (100 mL, 1.6 mM) were generated
from of PVP, PdCl2, NaCl and ethylene glycol. Sub-
sequently, an ethylene glycol solution of NaOH was
added, and the colour of the resulting mixture turned
brown. After stirring for 2 h, Al2O3 and distilled water
were added, and the mixture was heated to 353 K until
the total deposition of Pd colloids occurred. After the
deposition process, the material was washed with dis-
tilled water to obtain the separated solid. The product
was dried at 373 K for 6 h and was reduced with H2/Ar
at 573 K for 2 h prior to use. The obtained catalyst was
labelled as CD-Pd/Al2O3.21,22
To compare, 1 wt% Pd/Al2O3 catalyst was prepared
by impregnation method.25 After the impregnation step,
the catalyst was dried at 373 K for 6 h, and then reduced
with H2/Ar at 573 K for 2 h before used, the obtained
catalyst was recorded as IM-Pd/Al2O3.
In batch system, the reaction was performed in a
100 mL stainless steel autoclave. For the solvent sys-
tem, the vessel was charged with MA (75 mmol), 1, 4-
dioxane (50 ml) and catalyst (0.1 g, containing 8.5*10−3
mmol Pd), while for the solvent-free system, the ves-
sel was charged with MA (75 mmol) and catalyst
(0.1 g, containing 8.5*10−3 mmol Pd). After purged
with hydrogen three times to remove the air, the reac-
tor was pressured up to certain pressure. Under string at
800 rpm, the reaction was heated to certain temperature
and carried out for certain time.
Fixed bed system was conducted in a stainless fixed
tube at 0.2 MPa H2 pressure. About 1.0 g catalyst (con-
taining 8.5*10−2 mmol Pd) was packed into the centre
of the tubular reactor. After the reactor was heated to
373 K at the flow of H2, the reactant which consisted of
a solution of MA in GBL (22 wt%) was injected simul-
taneity. The H2 flow was controlled with H2/MA =
21.4 (molar ratio). The weight hourly space velocity
(WHSV) has been maintained at 0.61 h−1.
2.2 Catalyst characterization
The X-ray diffraction (XRD) analysis of the catalysts
were carried out using a D/Max-rA X-ray diffractome-
ter operated at 30 kV and 40 mA employing nickel-
filtered Cu Kα radiation. Transmission electron micro-
scopic (TEM) images were obtained using H8100-IV
electron microscopic operated at 200 kV. BET surface
areas of catalysts were calculated according to the
nitrogen adsorption isotherm at 77 K measured in a
micromeritics ASAP2010 apparatus. The X-ray photo-
electron spectra (XPS) measurements were carried out
on an ESCALAB250 X-ray photoelectron spectrome-
All the collected products were analysed in a gas
chromatograph (BEIFEN GC model 3420A) equipped
with a flame ionization detector (FID) and a capillary
Carbowax20000 column. The calculated method of MA
conversion and selectivity to the products in fixed bed
system was according to the literature.9,27
3. Results and discussion
3.1 Characterization of Pd/Al2O3 catalysts
ter, using Al Kα radiation as the excitation source. The The XRD patterns of Al2O3 and Pd/Al2O3 catalysts
XPS spectra were corrected by adjusting the C 1speak prepared according to different methods are presented

Selective hydrogenation of maleic anhydride
143
size of the Pd cluster was 6–10 nm (figure 2C), which
indicated that the Pd particles in the IM Pd/Al2O3
catalyst were highly aggregated. Many studies have
reported the aggregation of pure palladium catalysts
prepared by the impregnation method.2,30–32 The results
of the current study showed that the CD-Pd/Al2O3
catalyst presented better Pd dispersion than the IM-
Pd/Al2O3 catalyst, which was consistent with the XRD
results.
The textural properties of the Pd/Al2O3 catalysts
are presented in table 1. N2 adsorption was used to
investigate the specific surface area of the Al2O3 sup-
port, IM-Pd/Al2O3 catalyst and CD-Pd/Al2O3 catalyst.
The Al2O3 support did not show significant changes
after the addition of Pd. Furthermore, the ICP results
revealed that the Pd content of the IM-Pd/Al2O3 cata-
lyst and CD-Pd/Al2O3 catalyst was similar. The Pd sur-
face area was calculated as demonstrated previously,
and the results are also shown in table 1. The Pd surface
area on the CD-Pd/Al2O3 catalyst was 3.7 times greater
than that of the IM-Pd/Al2O3 catalyst, likely due to the
formation of small Pd particles.2,33
Figure 1. XRD patterns of (a) Al2O3 support; (b) IM-
Pd/Al2O3; (c) CD-Pd/Al2O3 catalyst.
in figure 1. The Pd diffraction peak appeared at approx-
imately 2θ = 40.1◦, 46.8◦ and 68.2◦.28,29 As shown in
the figure, for the CD-Pd/Al2O3 catalyst, only the char-
acteristic peaks of the Al2O3 support were observed,
indicating that Pd was highly dispersed on the cata-
3.2 Catalytic performance
lyst. Compared to the CD-Pd/Al2O3 catalyst, a weak Figure 3 presents the catalytic performance of the CD-
diffraction peak at 2θ = 40.1◦ was observed on the IM- Pd/Al2O3 catalyst and the IM-Pd/Al2O3 catalyst in the
Pd/Al2O3 catalyst, suggesting that Pd dispersion was liquid phase hydrogenation of maleic anhydride. As
relatively poor.
shown in the figure, when the reaction was carried out
Figure 2 shows the TEM images of Pd colloids at 353 K and 1.0 MPa of H2 pressure in 1,4-dioxane,
(figure 2A) and CD-Pd/Al2O3 (figure 2B) and IM- both catalysts showed high selectivity (>99%) for SA
Pd/Al2O3 catalysts (figure 2 C). The Pd clusters in the (results not shown). The activity over CD-Pd/Al2O3
native solution were uniform spheres with particle sizes was significantly higher than that over IM-Pd/Al2O3.
ranging from 1.5 to 3 nm (figure 2A). Compared to col- After 2 h, 56% MA conversion was obtained over the
loidal Pd particles, significant differences in the particle CD-Pd/Al2O3 catalyst, while only 15% MA conversion
sizes of the CD-Pd/Al2O3 catalyst were not observed, was attained over the IM-Pd/Al2O3 catalyst.
and the average size was approximately 1.5–3 nm
These results indicated that Pd/Al2O3 catalysts pre-
(figure 2B). For the IM-Pd/Al2O3 catalyst, the particle pared by the colloid deposition method were more
(A)
(B)
(C)
Figure 2. TEM images of (A): Pd colloid; (B): IM-Pd/Al2O3; (C) CD-Pd/Al2O3 catalyst.

144
Hongjing Yuan et al.
Table 1. Some textural properties of Pd/Al2O3 catalysts.
Pd content SBET Pd surface area Pd dispersity Pd particle size
TOF
Catalysts
(wt.%) m2/g
m2/g
on surface (%)a
(nm)b
(mmol/hm2·Pd)
Al2O3
IM-Pd/Al2O3
CD-Pd/Al2O3
–
115
109
126
–
0.6
2.2
–
0.47
1.09
–
–
94
95
0.91
0.89c
0.87d
6–10
1.5–3
aDefined by SPd/SBET
bFrom TEM
cBefore reaction
dAfter reaction for 1600 h
Figure 4. Effect of pressure on hydrogenation of MA over
CD-Pd/Al2O3 catalyst. Reaction conditions: T = 353 K,
P = 1.0 MPa, catalyst: 0.1 g, MA = 7.35 g.
Figure 3. Liquid–phase selective hydrogenation of MA
used catalysts prepared via different methods. Reaction con-
dition: T = 353 K, P = 1.0 MPa, catalyst: 0.1 g, MA = 7.35 g,
1, 4-dioxane = 50 mL.
active than catalysts prepared by the impregnation
method, whereas the similar TOF results implied
that both catalysts exhibited similar intrinsic activities
(table 1). Thus, the higher activity of Pd/Al2O3 cata-
lysts prepared by the colloid deposition method was
attributed to its higher active surface area.
In order to avoid the cost of separating the sol-
vent from the reaction mixture, the reaction was car-
ried out without a solvent. The effect of the pressure
on the catalytic performance of the CD-Pd/Al2O3 cata-
lyst was also investigated (figure 4). When the reac-
tion was carried out at 403 K for 4.5 h at 0.5, 0.8, 1.0
and 1.5 MPa, the conversion of MA was 25%, 51%,
99.8% and 99.9%, respectively. In the studied pressure
range, the activity increased with an increase in pres-
sure; however, differences in the selectivity for SA were
not observed.
Compared to batch systems, fixed bed systems are
Figure 5. Time on steam of MA hydrogenation over
more convenient for commercialization because they CD-Pd/Al2O3 catalyst in fixed bed.

Selective hydrogenation of maleic anhydride
145
are suitable for sequential production, and the distribu-
tion of products is stable. To examine the stability of
the catalyst in fixed bed systems, the catalytic perfor-
mance of CD-Pd/Al2O3 in a fixed bed was investigated
at 373 K and 0.2 MPa (figure 5). The CD-Pd/Al2O3
catalyst showed excellent catalytic performance in the
hydrogenation of MA in a fixed bed system, and both
the MA conversion and SA selectivity were greater than
98%. What need to notice was that deactivation was not
observed when the reaction was carried out for 1600 h,
The ICP results revealed that the Pd loading did not
have obviously change after reaction for 1600 h, indi-
cating that the Pd species were not leaching the support.
So, it can be stated that CD-Pd/Al2O3 catalyst was a
highly stable catalyst for this reaction at this condition.
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4. Conclusions
Pd/Al2O3 catalysts prepared by the colloid depo-
sition method showed remarkable catalytic perfor-
mance in the selective hydrogenation of MA to SA in
batch and fixed bed systems and showed significantly
higher activity than Pd/Al2O3 catalysts prepared by
the impregnation method. When the reaction was car-
ried out on Pd/Al2O3 catalysts prepared by the col-
loid deposition method in 1,4-dioxane at 353 K and
1.0 MPa of H2 pressure, the conversion and SA selec-
tivity were greater than 99% after 5 h. The catalyst also
showed excellent performance in solvent-free batch
systems and fixed bed systems. Moreover, the MA con-
version did not decrease significantly after 1600 h in a
fixed bed system. These results demonstrated that CD-
Pd/Al2O3 catalysts prepared by the colloid deposition
method are high-performance catalysts for the selective
hydrogenation of MA to SA.
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This work was supported by the Technology Institute
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