Metal-reinforced sulfonic-acid-modified zirconia for the removal of trace olefins from aromatics

Article abstract of DOI:10.1002/jccs.201900507

Metal-reinforced sulfonic-acid-modified zirconia catalysts were successfully prepared and used to remove trace olefins from aromatics in a fixed-bed reactor. Catalysts were characterized by ICP-OES, N₂ adsorption–desorption, X-ray diffraction, thermogravimetric analysis (TGA), and pyridine-FTIR spectroscopy. Different metals and calcination temperatures had great influence on the catalytic activity. Alumina-reinforced sulfated zirconia exhibited outstanding catalytic performance, stable regeneration activity, and giant surface area, and are promising in industrial catalysis. TGA showed that the decomposition of methyl could be attributed to Br?nsted acid sites, and pyridine-FTIR spectroscopy proved the weak Br?nsted sites on these synthesized metal-reinforced sulfated zirconia. Also, a relation between the reaction rate and weak Br?nsted acid density is proposed.

Full text of DOI:10.1002/jccs.201900507

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Received: 27 November 2019
DOI: 10.1002/jccs.201900507
Revised: 22 March 2020
Accepted: 23 March 2020
A R T I C L E
Metal-reinforced sulfonic-acid-modified zirconia for the
removal of trace olefins from aromatics
Decun Kong1 | Qian Peng1
Xiude Hu2 | Naiwang Liu1
| Li Shi1 | Xin Wang1 | Xuan Meng1
|
1International Joint Research Center of
Green Energy Chemical Engineering, East
China University of Science and
Abstract
Metal-reinforced sulfonic-acid-modified zirconia catalysts were successfully
prepared and used to remove trace olefins from aromatics in a fixed-bed reac-
tor. Catalysts were characterized by ICP-OES, N2 adsorption–desorption, X-ray
diffraction, thermogravimetric analysis (TGA), and pyridine-FTIR spectros-
copy. Different metals and calcination temperatures had great influence on the
catalytic activity. Alumina-reinforced sulfated zirconia exhibited outstanding
catalytic performance, stable regeneration activity, and giant surface area, and
are promising in industrial catalysis. TGA showed that the decomposition of
methyl could be attributed to Brønsted acid sites, and pyridine-FTIR spectros-
copy proved the weak Brønsted sites on these synthesized metal-reinforced sul-
fated zirconia. Also, a relation between the reaction rate and weak Brønsted
acid density is proposed.
Technology, Shanghai, China
2State Key Laboratory of High-efficiency
Utilization of Coal and Green Chemical
Engineering, Ningxia University,
Yinchuan, China
Correspondence
Naiwang Liu, International Joint
Research Center of Green Energy
Chemical Engineering, East China
University of Science and Technology,
Shanghai 200237, China.
Email: liunw@ecust.edu.cn
Funding information
China Postdoctoral Science Foundation,
Grant/Award Number: NO.2017M621389;
Explore and Research Foundation for
Youth Scholars of Ministry of Education of
China, Grant/Award Number: NO.
222201814011; National Natural Science
Foundation of China, Grant/Award
Number: NO.21808054; Open Project
Program of State Key Laboratory of High-
efficiency Utilization of Coal and Green
Chemical Engineering, Ningxia
K E Y W O R D S
alkylation, brønsted acid, catalysis, sulfated zirconia
University, Grant/Award Number:
2020-KF-38; Science and Technology
Commission of Shanghai Municipality,
Grant/Award Number: Sailing Program
18YF1406300
1 | INTRODUCTION
produce polyester fibers, polyester sheets, and polyester
containers. Polyester fiber is currently the largest syn-
Paraxylene (PX) is the fundamental chemical intermedi-
ate used to synthesize terephthalic acid and further in the
synthesis of polyester resins, such as ethylene terephthal-
ate and butylene glycol ester, which are widely used to
thetic fiber to be used as raw material for paints, dyes,
and pesticides. However, aromatics produced from gaso-
line cracking and catalytic reforming of naphtha usually
contain trace olefins. These trace olefins are more active
© 2020 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J Chin Chem Soc. 2020;1–10.
http://www.jccs.wiley-vch.de
1

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2
KONG ET AL.
than aromatics and have adverse effects on subsequent
applications. Therefore, it is necessary to remove trace
olefins from aromatics. At present, the most common
method is clay treatment.1 Activated clay has various
merits such as low cost and outstanding absorption prop-
erties. However, it is impossible to recycle it due to its
poor thermal stability. The normal treatment of
deactivated clay is landfill, which brings out many envi-
ronmental problems.
badly needed. Considering that methanesulfonic acid
(MSA) is more environmentally friendly and biodegrad-
able, it has been widely applied in the electroplating
industry,25 the production of linear alkylbenzenes,26 and
the Fries rearrangement of phenyl acetate for the paracet-
amol process.27 Zhang et al.25 used MSA as a Brønsted
acidic ionic liquid for the esterification of alcohols, with
good conversion rates and high selectivity. Rackemann
et al.28 found that MSA could catalyze the conversion of
glucose and xylose mixtures to levulinic acid and furfural.
So, MSA is suitable for acid regulation. Inspired by this,
aluminum methosulfate/SiO2 was used to remove trace
olefins from aromatics.29
The mechanism of removing trace olefins can be elab-
orated as follows:
In this work, MSA was chosen to prepare the impreg-
nating solution; Al, Zn, and Cu were designed as the
bridge to link MSA and zirconia. The synthesized catalyst
could be characterized by its renewability, environmental
friendliness, high reaction rate, weak Brønsted acid den-
sity, and deducibility of the Zr–O–M–O–S bond from the
relation between the reaction rate and the weak Brønsted
acid density.
Because of the alkylation mechanism, clay modified
with Lewis acids such as AlCl3 and ZnCl2 has demon-
strated excellent catalytic performance in this reaction.2
Besides, modified MCM-22,3 USY,4 and ionic liquids5,6
were also used to remove trace olefins from aromatics.
Actually, Lewis-acid-dominating catalysts and Brønsted-
acid-dominating catalysts can all be applied to this
reaction.
In the case of Brønsted-acid-dominating catalysts,
Awate et al.7 synthesized zirconia-pillared montmorillon-
ite and found that the Brønsted acid sites played a major
role in alkylation. Guerra et al.8 investigated different
clays intercalated with zirconium acetate solutions and
found that the Zr/clay ratio affected the activity and
selectivity of olefins with longer hydrocarbon chains.
Faghihian et al.9 studied acid-activated Al-pillared ben-
tonite and argued that this catalyst showed higher sur-
face, activity, and selectivity.
2 | RESULTS AND DISCUSSION
2.1 | Catalytic activity of different
catalysts
Figure 1 shows the catalytic activity of different catalysts
in the alkylation of olefins with aromatics. The initial
reaction rate of activated clay was high (Figure 1a), with
an also apparent deactivation rate. The excellent
Zeolites with specific acidity and porous structures
have been widely applied in catalysis and separation pro-
cesses, such as Y,10–12 MCM,13,14 SBA-15,15 and β zeo-
lites16 in the alkylation of aromatics with olefins. Zhao
et al.10–12 studied various reaction parameters in detail
and proposed a possible mechanism for the alkylation on
zeolites. But the rapid deactivation and high cost
restricted their application and promotion.
400
(a)
(b)
300
200
100
0
AlMSZ-923
Molecular sieve
Activated clay
AlMSZ-923
ZnMSZ-923
CuMSZ-923
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
400
300
200
100
0
(c)
(d)
In recent years, solid superacids, especially sulfated
zirconia, have been widely used in alkylation,17,18
AlMSZ-923
isomerization,19–21 esterification,22 and dehydration.23
A
AlMSZ-923R1
AlMSZ-923R2
AlMSZ-923R3
AlMSZ-823
ZnMSZ-823
CuMSZ-823
novel one-step solvent-free method to synthesize sulfated
zirconia was reported by Liu et al.24 However, due to the
weak bond between the sulfate groups and zirconia and
the few active sites on the zirconia surface, the catalytic
activity of this sulfated zirconia was unsatisfactory.
Besides, sulfuric acid would inevitably corrode the equip-
ment during the preparation of sulfated zirconia and is
often accompanied by water pollution, soil acidification,
acid rain, and so on. Thus, a substitute for sulfuric acid is
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
Time (h)
FIGURE 1 Catalytic activity of different catalysts. (a) The
catalytic activity of AlMSZ-923,molecular sieve and activated clay.
(b) The effect of different metalon catalytic activity (calcined at
923K). (c) The effect of different metalon catalytic activity (calcined
at 823K). (d) The repeatability of AlMSZ-923

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KONG ET AL.
3
performance of the activated clay in the first hour could
be attributed to the strong adsorption property of the
clay, but the adsorption capacity saturated with time.
Therefore, for activated clay, it was appropriate to
describe the olefin removal rate by the adsorption rate.29
From 2 to 6 hr, the reaction rate of HY zeolite decreased
rapidly. During the reaction, the deposited carbon in the
micropores covered the active acid sites of HY zeolite,
which could account for the evident deactivation.4
Two conclusions could be drawn from Figure 1b,c.
First, the most important factor that affected the catalytic
activity was the type of metal; AlMSZ showed the best
catalytic performance, followed by ZnMSZ, but CuMSZ
had little catalytic activity for this reaction. Second, the
calcination temperature showed different effects on the
catalysts; AlMSZ-923 had a better catalytic activity than
AlMSZ-823, and the deactivation rate of AlMSZ-923 was
lower than that of AlMSZ-823. However, the calcination
temperature had the opposite effects on ZnMSZ: the reac-
tion rate of ZnMSZ-923 was only half of ZnMSZ-823 after
4 hr. The reusability of AlMSZ-923 is shown in Figure 1d.
AlMSZ-923-Rn (n = 1, 2, 3) denotes the regenerated
cycles of the deactivated AlMSZ-923. Even after regenera-
tion (calcination at 823 K in air atmosphere for 2 hr) for
three times, the reaction rate of AlMSZ-923 was still high.
Thus, the outstanding catalytic performance, recoverabil-
ity, and reusability of AlMSZ-923 make it a promising
candidate to facilitate the development of favorable and
waste-free processes in removing olefins from aromatics.
calcined at 823 K, these three catalysts had similar specific
surface area, pore size, and pore volume, but the introduc-
tion of sulfur was found to slow down the decrease in sur-
face area.30 However, when the calcination temperature
was raised to 923 K, AlMSZ-923 still possessed excellent
surface area due to the formation of the Zr–O–Al bond,
which is considered to increase the surface area of zirconia
with aluminum combining with more sulfur, while the
surface area of ZnMSZ-923 and CuMSZ-923 decreased to
45 and 40 m2/g. The sharp decrease in the surface area of
ZnMSZ-923 may lead to decreased conversion of ZnMSZ-
823. Meanwhile, the calcination temperature of 923 K
might result in the sintering of catalysts, which would
damage their structure and increase the pore diameter and
dispersibility of the active ingredients.
As shown in Figure 2, the N2 adsorption–desorption
isotherms of AlMSZ-923 correspond to type IV of the
IUPAC classification characteristics of mesoporous solids
with low contribution of microporosity, as indicated by
the low amount of nitrogen adsorbed at low and high rel-
ative pressures.
2.2.2 | Characterization by X-ray
diffraction
Figure 3 displays the X-ray diffraction (XRD) patterns of
the catalysts, and Table 2 reports the proportion of the
different phases. Because the calcination temperature of
the catalysts was below 923 K, it was impossible to form
the cubic phase. The catalysts exhibited the diffraction
peaks of the tetragonal ZrO2 phase (t-ZrO2) and the
monoclinic ZrO2 phase (m-ZrO2),31 as shown in Figure 3.
According to the ICDD PDF card, the diffraction peaks of
t-ZrO2 are at 2θ ≈ 30.27, 35.24, 50.70, and 60.19ꢀ, while
those of m-ZrO2 are at 2θ ≈ 24.06, 28.19, 31.48, and
34.17ꢀ. No peaks associated with oxides of aluminum,
zinc, or copper were observed, possibly because those
particles were well distributed.25
2.2 | Structure and composition
characterization
2.2.1 | Characterization of pore structure
and element content
Table 1 lists the surface area, pore diameter, pore volume,
and element content of the different catalysts. When
TABLE 1
Surface areas and pore volumes of different samples
Sample
Surface area (m2/g)
Pore diameter (nm)
Pore volume (cm3/g)
Composition
AlMSZ-923
ZnMSZ-923
CuMSZ-923
AlMSZ-823
ZnMSZ-823
CuMSZ-823
ZrO2-823
144
45
5.63
11.32
12.95
4.10
0.20
0.13
0.13
0.18
0.17
0.17
0.16
0.13
ZrO2ꢁ0.05Al2O3ꢁ0.06SO3
—
40
ZrO2ꢁ0.09CuOꢁ0.07SO3
—
173
163
169
70
4.20
ZrO2ꢁ0.05ZnOꢁ0.08SO3
—
4.12
8.97
—
ZrO2-923
25
21.10

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4
KONG ET AL.
In the absence of sulfate groups, the crystal phases in
zirconia were almost all monoclinic.17 After the introduc-
tion of sulfate species, the content of m-ZrO2 decreased
and that of t-ZrO2 increased. As shown in Table 2, the
proportion of t-ZrO2 exceeded 50%, and the ratio of t-
ZrO2 in ZnMSZ-823 and CuMSZ-923 reached 95%. Also,
different calcination temperatures showed different
effects on the catalyst phases. For AlMSZ-923 and
AlMSZ-823, the increase in calcination temperature gen-
erated weak effects on the phase; the t-ZrO2 phase of
AlMSZ-923 was only 4% higher than that of AlMSZ-823.
Based on the studies of sulfated zirconia, t-ZrO2 was con-
sidered beneficial for the reaction in removing trace ole-
fins from aromatics.32,33 For ZnMSZ, the increase of
calcination temperature caused the decrease of t-ZrO2 in
these catalysts, and the calcination temperature of 823 K
was better, as the excessively high calcination tempera-
ture had a giant influence on the crystal form of the cata-
lyst. Taking ZnMSZ-923 for example, the catalyst
particles were large and likely to be sintered; meanwhile,
some active centers and sulfur components for stabilizing
the t-ZrO2 phase were destroyed, leading to a greatly
reduced proportion of t-ZrO2. The proportion of t-ZrO2 in
CuMSZ was ~100%; however, the reaction rate of this cat-
alyst was very low. The addition of copper ion was bene-
ficial for stabilizing the tetragonal form, which was
similar to that of yttria-stabilized zirconia.34 Several fac-
tors affect the catalytic activity, such as the surface area,
calcination temperature, and surface acidity. To figure
out the relationship between the structure and reaction,
thermal and acidity analyses were necessary.
0.06
140
0.05
0.04
120
0.03
0.02
100
Adsorption
Desorption
0.01
0.00
80
1
10
100
1000
Pore Diameter (nm)
60
40
20
0
-20
0.0
0.2
0.4
0.6
0.8
1.0
Relative Pressure (P/P0)
FIGURE 2 Adsorption and desorption curves and pore size
distribution of AlMSZ-923
■
■
♦
m-ZrO2
t-ZrO2
■
■
♦
♦
♦
■
AlMSZ-923
AlMSZ-823
ZnMSZ-923
ZnMSZ-823
CuMSZ-923
CuMSZ-823
ZrO2
2.2.3 | Characterization of thermal
analysis
10
20
30
40
50
60
70
80
2θ (°)
Calcination temperature is a vital parameter in the cata-
lyst preparation process, and thermal stability is also an
important condition for industrial application.35 When
setting the calcination temperature, the thermal decom-
position temperature of the active component is essential.
FIGURE 3 XRD patterns of the catalysts
Thermogravimetry/differential
thermal
analysis
(TG/DTA) curves of the active components (aluminum
methane sulfonate, zinc methane sulfonate, and copper
methane sulfonate), catalysts, and carriers are given in
Figure 4, and the related mass losses are given in Table 3.
It can be seen from the Figure 4a that AlMS has two
stages of weight loss. From the thermal characterization
of AlMS, there were mainly four weight loss peaks during
dehydration.29,36 The first weight loss of AlMS can be
attributed to the loss of water adsorbed on the samples.
The second weight loss started at 643 K and ended at
773 K, which was attributed to the decomposition of the
TABLE 2
Phase proportion in catalysts
Sample
t-ZrO2
0.57
0.53
0.66
0.96
0.95
0.72
0
m-ZrO2
AlMSZ-923
AlMSZ-823
ZnMSZ-923
ZnMSZ-823
CuMSZ-923
CuMSZ-823
ZrO2
0.43
0.47
0.34
0.04
0.05
0.28
1