A facile strategy for preparation of phosphorus modified HZSM-5 shape-selective catalysts and its performances in disproportionation of toluene

Article abstract of DOI:10.1016/j.catcom.2016.01.027

The phosphorous modified HZSM-5 catalysts were prepared by using phosphoric acid as the precursor with the addition of ethanol during the impregnation process and their shape-selective performances in the synthesis of p-xylene by disproportionation of toluene were investigated. An excellent para-selectivity along with a relatively high catalytic activity was achieved over the phosphorous modified HZSM-5 catalysts. The addition of ethanol during the impregnation process promotes the transition of phosphoric acid to phosphate, which accomplished the cover of the external acid sites and the reserve of the acid sites in the pores of HZSM-5 zeolite after phosphorous modification.

Full text of DOI:10.1016/j.catcom.2016.01.027

A facile strategy for preparation of phosphorus modified HZSM-5 shape-
selective catalysts and its performances in disproportionation of toluene
Na Liu, Xingxing Zhu, Songjie Hua, Dengfeng Guo, Hongyun Yue,
Bing Xue, Yongxin Li
PII:
DOI:
Reference:
S1566-7367(16)30027-9
doi: 10.1016/j.catcom.2016.01.027
CATCOM 4572
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
13 November 2015
19 January 2016
25 January 2016
Please cite this article as: Na Liu, Xingxing Zhu, Songjie Hua, Dengfeng Guo, Hongyun
Yue, Bing Xue, Yongxin Li, A facile strategy for preparation of phosphorus modified
HZSM-5 shape-selective catalysts and its performances in disproportionation of toluene,
Catalysis Communications (2016), doi: 10.1016/j.catcom.2016.01.027
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ACCEPTED MANUSCRIPT
A facile strategy for preparation of phosphorus modified
HZSM-5 shape-selective catalysts and its performances in
disproportionation of toluene
Na Liua, b, Xingxing Zhub, Songjie Huab, Dengfeng Guob, Hongyun Yuec, Bing Xueb *, Yongxin Lib *
a School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
b Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou
213164, China
c School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China
*Corresponding author. Tel: (+86) 519 86330135; Fax: (+86) 519 86330135;
E-mail: xuebing_cn@163.com (Bing Xue), liyxluck@163.com (Yongxin Li)
Abstract: The phosphorous modified HZSM-5 catalysts were prepared by using phosphoric acid
as the precursor with addition of ethanol during the impregnation process and their shape-selective
performances in the synthesis of p-xylene by disproportionation of toluene were investigated. An
excellent para-selectivity along with a relatively high catalytic activity was achieved over the
phosphorous modified HZSM-5 catalysts. The addition of ethanol during the impregnation process
promotes the transition of phosphoric acid to phosphate, which accomplished the cover of the
external acid sites and the reserve of the acid sites in the pores of HZSM-5 zeolite after
phosphorous modification.
Key words: Toluene disproportionation; shape-selective catalysis; phosphorous; HZSM-5
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1. Introduction
p-Xylene, one of the most important aromatic compounds, is widely used as a raw material
for the manufacture of polyesters [1]. ZSM-5 zeolite is the most suitable catalyst for the synthesis
of p-xylene because of its 10-membered ring channel well fitted to the molecular dimensions of
p-xylene [2]. However, in most cases, the concentrations of the xylene isomers produced over
parent ZSM-5 zeolite were close to the thermodynamic equilibrium ratios (23.5% p-xylene, 52.1%
m-xylene and 24.4% o-xylene) [3]. This can be ascribed to the acidic sites on the external surface
of ZSM-5 zeolite, which cause some side reactions and diminish the para-selectivity [4, 5]. To
obtain high para-selectivity, it is necessary to cover the acid sites on the external surface of
zeolites. A number of modification techniques have been reported, such as impregnation of
metallic or non-metallic compounds [6, 7], pre-coking [8], chemical vapor deposition of silica [9]
and chemical liquid deposition of silica [10]. Although chemical vapor deposition of silica or
chemical liquid deposition of silica with simple silica alkoxides, such as tetra-ethyl-orthosilicate
(TEOS), is the usual method for improving para-selectivity of zeolite [11, 12]. However, to obtain
the desired para-selectivity, a long and complicated process is necessary. Pre-coking is often
difficult to control, and needs to be repeated after the recovered zeolite catalysts are regenerated
by calcinations [13]. By comparison, modification of zeolites by coating with metallic or
non-metallic compounds is a convenient approach.
Metal or non-metal oxides could be used to cover the external surface acid sites of zeolite and
achieved an excellent para-selectivity, but this would also block the acid sites in the channels and
then decrease the catalytic activity [14]. To prevent the acidic sites located in the channels of
zeolite from being covered by the metal or non-metal oxide during the impregnation process, we
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have developed a novel method for preparing MgO modified zeolite shape-selective catalysts
using a complexation–impregnation method [15-19]. Furthermore, some borate and phosphate
were also used as the precursor of non-metal oxides for preparing shape-selective catalysts [20,
21]. All these catalysts exhibited exceptional performances in shape-selective catalysis, but the
complicated process or the high cost hampered their practical application in industries. Therefore,
it is imperative to search a more facile and economical strategy for the preparation of
shape-selective catalysts.
Phosphoric acid is the most common precursor for the preparation of phosphorus modified
zeolite shape-selective catalysts [22, 23]. However, the activity of the catalysts always decreased
significantly with increasing the amount of phosphorus. Recently, we found the addition of
ethanol during the preparation of phosphorous modified ZSM-5 shape-selective catalysts by using
phosphoric acid as the precursor could affect the dispersion of phosphoric acid on the surface of
ZSM-5 zeolite, and then influence the structure and acidity of the zeolite. The experimental results
evidenced that the catalytic activity and the shape-selectivity were unambiguously influenced by
the addition of ethanol during the preparation of phosphorous modified ZSM-5 shape-selective
catalysts. In this paper, the role of ethanol in the preparation of phosphorous modified ZSM-5
shape-selective catalysts by using phosphoric acid as the precursor was investigated and a facile
method for the preparation of phosphorous modified zeolite shape-selective catalysts was
suggested.
2. Experimental
2.1 Catalyst preparation
ZSM-5 zeolite (Si/Al=50) was synthesized by hydrothermal crystallization according to an
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established procedure [24]. The NH4+ form of the as synthesized ZSM-5 zeolites was obtained by
ion-exchange with aqueous NH4NO3 solution, and then calcined at 823 K for 3 h. The phosphorus
modified HZSM-5 catalysts was prepared as follows. The phosphoric acid (85% wt.) was
dissolved in anhydrous ethanol. HZSM-5 was impregnated with an ethanol solution containing
phosphoric acid. The mixture was stirred for 1 h and allowed to stand overnight. Afterwards, the
mixture was evaporated in a constant temperature bath at 353 K for 6 h and then dried in an oven
at 383 K for 6 h. Then, the resulting materials were calcined at 823 K for 5 h in an air stream. The
obtained catalyst was denoted as x% P/HZSM-5(E), where the x represented the mass percentage
of phosphorus based on the zeolite. In contrast, phosphorus modified HZSM-5 catalysts were also
prepared by using phosphoric acid aqueous solution as the precursor without the addition of
ethanol, and the samples were denoted as x% P/ZSM-5(H).
2.2 Catalyst characterization
X-ray diffraction (XRD) measurements were conducted using a Rigaku D/max2500PC
diffractometer with Cu Kα (λ=1.54 Å) radiation. N2 adsorption/desorption analyses were obtained
at 77 K using a physical adsorption instrument (Micromeritics ASAP 2020, USA). The
phosphorus contents of the P/HZSM-5(E) samples were obtained using a Panalytical Magix
PW2403 spectrometer (XRF). Sample acidity was measured by NH3 temperature-programmed
desorption (NH3-TPD) using a Quantachrome CHEMBET-3000 instrument. FT-IR spectra of the
samples were recorded using a Bruker FT-IR spectrometer (TENSOR 27) with the KBr pellet
technique. FT-IR spectra with pyridine adsorption were carried out using a Bruker FT-IR
spectrometer (TENSOR 27) together with a high temperature vacuum chamber. Cracking of
1,3,5-triisopropylbenzene (1,3,5-TIPB) and cumene (IPB) was carried out using a fix bed reactor
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at 723 K under N2 flow with a WHSV (weight hourly space velocity) of 1 h-1.
2.3 Disproportionation of toluene
Disproportionation of toluene was carried out in a fixed bed continuous down-flow reactor.
About 3 g of the catalyst (as pellets of 20–40 mesh) was packed in the middle of the reactor and
calcined in a dry nitrogen flow for about 1 h at 673 K before reaction. Toluene was introduced at
the top of the reactor by means of an infusion pump. The products were collected in a ice-cooled
condenser attached to the end of the reactor and analyzed by gas chromatography (GC-2010,
SHIMADZU) using a FFAP capillary column and flame ionization detector.
3. Results and discussion
3.1 Catalytic performances of P/ HZSM-5 catalysts
The catalytic performances of P/HZSM-5(E) and P/ZSM-5(H) catalysts in the synthesis of
p-xylene by disproportionation of toluene were presented in Tables 1 and 2, respectively. As
shown in Table 1, HZSM-5 exhibited the highest conversion of toluene among the investigated
catalysts. However, the selectivity for p-xylene (23.4%) was close to the equilibrium composition
of xylene isomers. After modification by phosphoric acid with the addition of ethanol, the
conversion of toluene over P/HZSM-5(E) catalysts decreased gradually from 56.3% to 22.6% with
increasing the amount of phosphorus to 5.0 %. Notably, a relatively high conversion of toluene
was retained even for 5.0% P/HZSM-5(E) catalyst. Meanwhile, the selectivity for p-xylene over
P/HZSM-5(E) catalysts increased obviously with increasing the amount of phosphorus. The
highest selectivity for p-xylene, about 84.1%, was observed over 5.0% P/HZSM-5(E) catalyst.
The catalytic performances of P/HZSM-5(H) catalysts in disproportionation of toluene differed
from those of P/HZSM-5(E) catalysts. Although the selectivity for p-xylene over P/HZSM-5(H)
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catalysts was also significantly improved with increasing the amount of phosphorus, the catalytic
activities decreased severely, as shown in Table 2. As for 5.0% P/HZSM-5 catalysts, the
conversion of toluene over P/HZSM-5(E) catalyst was markedly higher than those over
P/HZSM-5(H). In particular, only a 6.8% conversion of toluene was acquired over 5.0%
P/HZSM-5(H) catalyst.
3.2 Catalysts characterizations
Fig.S1 shows the XRD patterns of HZSM-5 and P/HZSM-5 catalysts with different
phosphorous loadings. As shown in Fig. S1(A), compared with HZSM-5, no obvious changes in
the position and intensity of peaks belonging to HZSM-5 zeolite were detected in the XRD
patterns of the P/HZSM-5(E) catalysts. This indicated that the structure of HZSM-5 zeolite was
retained without any significant changes after modification with phosphoric acid with the addition
of ethanol. No peaks due to phosphorous compound were observed even for 5.0% P/HZSM-5(E)
catalyst. Similarly, no peaks corresponding to phosphorous compound were detected even for 5.0%
P/HZSM-5(H) catalyst. Careful examination of Fig.S1(B) revealed that the intensities of peaks
belonging to HZSM-5 zeolite in the XRD patterns of P/HZSM-5(H) samples decreased obviously
with increasing in the phosphorous loadings.
The isotherms for HZSM-5 and 5.0% P/HZSM-5 catalysts were displayed in Fig. 1. It can
be seen that all the isotherms of the samples are of type I, showing characteristics of micro-porous
zeolite type materials [25]. This indicated that the main structure of HZSM-5 was retained after
modification with phosphoric acid. The textural parameters of the P/HZSM-5 catalysts were
summarized in Table 3. As shown in Table 3, the BET surface area and the micropore volume of
P/HZSM-5(E) catalysts decreased gradually with increasing the amount of phosphorous. It was
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worth noting that a high BET surface area (273 m2/g) was maintained even for 5.0% P/HZSM-5(E)
catalyst. As shown in Table 3, the BET surface area and the micropore volume of P/HZSM-5(H)
catalysts decreased obviously with increasing the amount of phosphorous. As for 5.0%
P/HZSM-5(H) catalyst, only a BET surface area of 177 m2/ g and a micropore volume of 0.087
cm3/g were observed, which were much lower than that of 5.0% P/HZSM-5(E) catalyst.
The FT-IR spectra of the HZSM-5 and 5.0% P/HZSM-5 catalysts were shown in Fig. 2. The
asymmetric stretching, symmetric stretching and bending vibrations of Si–O–Si were observed at
1100, 800 and 450 cm−1, respectively. The absorptions at 1230 and 550 cm−1 corresponded to the
presence of five-membered ring chains and different ring structures, respectively. These features
were basically identical for the HZSM-5 zeolite [26]. This indicated that the structure of HZSM-5
zeolite was preserved after phosphoric acid modification. Compared with the FT-IR spectrum of
HZSM-5, obvious absorptions at about 1300-1400 cm-1 were presented on the spectra of the 5.0%
P/HZSM-5 catalysts, which was ascribed to the P–O stretching. As reported previously, the
hydroxyl bands observed at 3668 cm-1 were assigned to P-OH groups. This confirmed the
successful loading of phosphorous over the surface of HZSM-5 zeolite [27].
The NH3-TPD profiles of HZSM-5 and 5.0% P/HZSM-5 catalysts are presented in Fig. 3. As
for HZSM-5 zeolite, the strong peak at about 520 K can be associated with the desorption of
physisorbed ammonia and/or ammonia adsorbed on weak acid sites, and the strong peak at about
730 K may be attributed to the desorption of ammonia adsorbed on strong acid sites [28]. It can be
observed that 5.0% P/HZSM-5(E) also exhibited typical double-peak characteristic. However, the
intensities of the two peaks were obviously lower compared with HZSM-5 zeolite. Particularly,
only one peak at about 510 K was observed on the NH3-TPD curve of 5.0% P/HZSM-5(H)
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catalyst. This indicated that the strong acid sites over 5.0% P/HZSM-5(H) had disappeared.
FT-IR spectra with pyridine adsorption of HZSM-5 and P/HZSM-5 catalysts were illustrated
in Fig.4. Pyridine adsorbed on HZSM-5 and the P/HZSM-5 catalysts resulted in the appearance of
bands characteristic of pyridine adsorbed on Brønsted acid sites around 1545 cm-1, on Lewis acid
sites at 1450 cm-1 [29]. It was found that the intensities of the peaks belonging to Brønsted acid
sites and Lewis acid sites both decreased progressively with increasing the amount of phosphorous.
As shown in Fig. 2, the absorptions at about 3668 cm-1 on the spectra of the 5.0% P/HZSM-5
catalysts were ascribed to the P–OH group. However, as for the P/HZSM-5 catalysts, the bands
characteristic of pyridine adsorbed on Brønsted acid sites decreased significantly. This indicated
that the P-OH did not contribute to the Brønsted acid sites of the samples. Furthermore, the
amount of Brønsted acid sites over P/HZSM-5(E) catalysts is higher than that over P/HZSM-5(H)
catalysts with the same phosphorous loadings. This is consistent with the results of NH3-TPD
characterization.
The acidic properties of P/HZSM-5 catalysts were also elucidate by the cracking of
1,3,5-triisopropylbenzene (1,3,5-TIPB) and cumene (IPB) (Table 4). Compared with HZSM-5
zeolite, the conversion of 1,3,5-TIPB and conversion of IPB all decreased over all the P/HZSM-5
catalysts, which corresponded to the decrease in the amount of acid sites after modification of
phosphoric acid. Compared with the 5.0% P/HZSM-5(H) catalyst, the lower conversion of
1,3,5-TIPB and the higher conversion of IPB were observed over 5.0% P/HZSM-5(E) catalyst.
This indicated that most of the acid sites on the external surface of HZSM-5 were covered and
most of the acid sites in the pores of HZSM-5 were retained after modification by phosphoric acid
with the addition of ethanol. Compared with HZSM-5 sample, the much low conversion of
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1,3,5-TIPB over 5.0% P/HZSM-5(E) catalyst indicated that about 90% acid sites on the external
surface of HZSM-5 had been covered.
Based on the evidence presented above, it was speculated that the addition of ethanol during
the impregnation process had a decisive impact on the shape-selective catalytic performances of
the phosphorous modified HZSM-5 catalysts. As reported previously, catalytic synthesis of
p-xylene by toluene disproportionation has been mostly considered as a typical acid-catalyzed
process and p-xylene is obtained as the primary product over the Brønsted acid sites of the catalyst
[30]. Subsequently, isomerization of p-xylene occurred easily over the surface Brønsted acid sites
of zeolite because the meta-isomer has been reported to be thermodynamically more stable than
the other isomers [2]. In order to improve the para-selectivity, it is necessary to cover the acid
sites on the external surface of zeolite. Although an excellent para-selectivity was achieved over
P/HZSM-5(H) catalysts, but the catalytic activity was poor. The results of XRD and N2
adsorption/desorption suggested that the pore structure of HZSM-5 zeolite had been blocked after
phosphoric acid modification. Therefore, the amount of the acid sites, especially for the strong
acid sites, decreased severely. However, as for P/HZSM-5(E) catalysts, a relatively high catalytic
activity along with an outstanding para-selectivity was obtained. This indicated that the cover of
the external acidic sites and the reservation of the acidic sites in the HZSM-5 zeolite channels
were accomplished simultaneously. With the addition of ethanol during the impregnation process,
the molecular of phosphoric acid can react with ethanol to form phosphate, such as ethyl
phosphate (6.9×4.6 Å), diethyl phosphate (9.5×5.6Å) and triethyl phosphate (8.9×8.4 Å) (Scheme
1). These phosphates were mainly restricted on the external surface of HZSM-5 zeolite because of
the large molecular sizes (As shown in Fig. S2). The high micropore volume (Table 3) and the
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high amount of Brønsted acid sites (Fig.4) of P/HZSM-5(E) catalysts could be used to confirm the
explanation mentioned above. Therefore, an excellent shape-selective catalytic performance was
achieved in toluene disproportionation over P/HZSM-5(E) catalysts.
The catalytic performances of P/ZSM-5(E) samples at similar toluene conversion levels by
changing the weight hourly space velocity expressed in terms of gram of feed per gram catalyst
per hour (WHSV) are shown in Table 5. As for HZSM-5 zeolite, conversion of toluene decreased
obviously with increasing the WHSV, while the selectivity for p-xylene was slightly affected. As
for the 2.5% P/ZSM-5(E) samples, the increase in selectivity for p-xylene were also negligible
compared with the decrease in conversion of toluene with increasing the WHSV. It is obvious that
the improvement in selectivity for p-xylene over P/ZSM-5(E) samples should be ascribed to the
modification of phosphorus.
Fig.5 shows the effects of time-on-stream in the synthesis of p-xylene by disproportionation
of toluene over 5.0% P/HZSM-5(E) catalyst. Obviously, the toluene conversion was maintained
above 15% for about 20 h, and then decreased gradually with time-on-stream. The deactivation
can be attributed to coke deposition on the Brønsted-acid sites of the catalyst. The selectivity for
p-xylene was maintained during 28 h on stream.
4. Conclusions
In conclusion, we have developed a very facile and economical strategy for preparation of
phosphorous modified HZSM-5 zeolite shape-selective catalysts by addition of ethanol during the
impregnation process. This novel strategy accomplished the coverage of the external acid sites and
protection of the inner acid sites on zeolite simultaneously. An excellent para-selectivity along
with a high catalytic activity was achieved in the synthesis of p-xylene by disproportionation of
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toluene.
Acknowledgements:
The authors thank the finacial support from the National Natural Science Foundation of
China (21076027), the Natural Science Foundation of Jiangsu College (12KJB530002), and
Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology (BM2012110).
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Figure captions
Fig. 1 N2 adsorption/desorption isotherms of HZSM-5 and P/HZSM-5 samples
Fig. 2 FT-IR spectra of HZSM-5 and P/HZSM-5 samples
Fig. 3 NH3-TPD profiles of HZSM-5 and P/HZSM-5 samples
Fig. 4 FT-IR spectra with pyridine adsorption of HZSM-5 and P/HZSM-5 samples
Fig. 5 Effect of time-on-stream on the synthesis of p-xylene by disproportionation of toluene over
5.0% P/HZSM-5(E) catalyst (temperature=673 K; WHSV=0.8 h-1)
Scheme 1 Reaction of phosphoric acid with ethanol and the deposition of phosphorus on HZSM-5
zeolite
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Fig. 1
180
160
140
120
100
80
HZSM-5
5.0% P/HZSM-5 (E)
5.0% P/HZSM-5 (H)
60
40
20
0
0.0
0.2
0.4
0.6
0.8
1.0
p/p°
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Fig. 2
1.0
0.8
0.6
0.4
0.2
0.0
HZSM-5
5% P/HZSM-5 (E)
5% P/HZSM-5 (H)
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
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Fig. 3
15
12
9
HZSM-5
6
5.0% P/HZSM-5 (E)
5.0% P/HZSM-5 (H)
3
0
500
600
700
800
Temperature (K)
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Fig. 4
0.25
0.20
0.15
0.10
0.05
0.00
0.25
1545
1490
1545
1490
A
B
0.20
0.15
0.10
0.05
0.00
1450
HZSM-5
1450
HZSM-5
2.5% P/HZSM-5(E)
5.0% P/HZSM-5(E)
2.5% P/HZSM-5(H)
5.0% P/HZSM-5(H)
1700
1650
1600
1550
1500
1450
1400
1700
1650
1600
1550
1500
1450
1400
Wavenumber (cm-1
)
Wavenumber (cm-1
)
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Fig.5
40
30
20
10
0
100
Conversion of toluene
Selectivity for p-xylene
95
90
85
80
0
5
10
15
20
25
30
Time-on-stream (h)
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Scheme 1
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Table 1 Catalytic performances of HZSM-5 and P/HZSM-5(E) samplesa
P/HZSM-5(E)
Catalysts
HZSM-5
1.0%
0.94
52.8
39.1
2.5%
3.7%
3.61
36.2
44.0
5.0%
4.86
22.6
47.3
P(wt.%) b
---
2.37
45.9
41.5
56.3
36.7
Conversion of toluene(%)
Xylene selectivity(%)
Xylene isomers(%)
para-xylene
23.4
51.9
24.7
4.8
27.5
48.1
24.4
5.7
47.6
32.4
20.0
9.1
62.0
23.1
14.9
9.9
84.1
9.4
6.5
9.0
meta-xylene
ortho-xylene
Para-xylene yield(%)
a Conditions: temperature=673 K, WHSV=0.8 h-1; bObtained by XRF
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Table 2 Catalytic performances of P/ZSM-5(H) samplesa
P/HZSM-5(H)
Catalysts
1.0%
50.9
37.6
2.5%
3.7%
17.2
42.6
5.0%
6.8
32.5
40.4
Conversion of toluene(%)
Xylene selectivity(%)
Xylene isomers(%)
para-xylene
43.1
23.7
50.4
25.9
4.5
30.6
37.4
32.0
4.0
50.9
19.2
29.9
3.7
89.8
5.5
4.7
2.6
meta-xylene
ortho-xylene
Para-xylene yield(%)
a Conditions: temperature=673 K; WHSV=0.8 h-1
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Table 3 Textural parameters of HZSM-5 and P/HZSM-5(E) samples
Samples
ABET/m2 g-1
AM/m2 g-1
VT/cm3 g-1
VM/cm3 g-1
0.141
374
267
0.245
HZSM-5
336
265
0.194
0.136
1.0% P/HZSM-5(E)
2.5% P/HZSM-5(E)
3.7% P/HZSM-5(E)
5.0% P/HZSM-5(E)
2.5% P/HZSM-5(H)
5.0% P/HZSM-5(H)
311
246
0.186
0.129
282
225
0.172
0.122
273
218
0.166
0.114
248
216
0.149
0.103
177
148
0.103
0.087
ABET – BET surface area; AM – Micropore area; VT – Total pore volume; VM - Micropore volume;
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Table 4 Cracking of 1,3,5-TIPB and IPB over 5.0% P/HZSM-5 catalystsa
Catalysts
Conversion of 1,3,5-TIPB(%)
Conversion of IPB(%)
HZSM-5
23.8
2.7
22.4
16.9
9.7
5.0% P/HZSM-5(E)
5.0% P/HZSM-5(H)
5.2
aConditions: temperature=723 K; WHSV=1.0 h-1
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Table 5 Catalytic performances of P/ZSM-5(E) samples at similar toluene conversion levelsa
P/HZSM-5(E)
Catalysts
HZSM-5
2.5%
2.9
5.0%
0.8
WHSV(h-1)
4.2
23.4
37.5
24.7
43.2
22.6
47.3
Conversion of toluene(%)
Xylene selectivity(%)
Xylene isomers(%)
para-xylene
23.6
49.4
27.0
49.1
29.7
21.2
84.1
9.4
meta-xylene
ortho-xylene
6.5
a Conditions: temperature=673 K
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ACCEPTED MANUSCRIPT
A facile strategy for preparation of phosphorus modified
HZSM-5 shape-selective catalysts and its performances in
disproportionation of toluene
Na Liua, b, Xingxing Zhub, Songjie Huab, Dengfeng Guob, Hongyun Yuec, Bing Xueb *, Yongxin Lib *
a School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
b
Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou
213164, China
c School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China
Graphical abstract
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ACCEPTED MANUSCRIPT
A facile strategy for preparation of phosphorus modified
HZSM-5 shape-selective catalysts and its performances in
disproportionation of toluene
Na Liua, b, Xingxing Zhub, Songjie Huab, Dengfeng Guob, Hongyun Yuec, Bing Xueb *, Yongxin Lib *
a School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
b Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou
213164, China
c School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China
Highlights



Phosphorus modified HZSM-5 prepared by impregnation with addition of ethanol.
Excellent performance was obtained in disproportionation of toluene.
The addition of ethanol promotes the transition of phosphoric acid to phosphate.
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