Effects of acid-modified HBEA zeolites on thiophene acylation and the origin of deactivation of zeolites

Article abstract of DOI:10.1016/j.apcata.2014.05.028

The liquid phase Friedel-Crafts acylation of thiophene with acetic anhydride over HBEA zeolites modified by hydrochloric, nitric, and acetic acid was investigated in a trickle bed reactor. The catalytic stability of the HBEA zeolite was doubled after treatment with the hydrochloric and nitric acids due to the increase of the ratio of Broensted to Lewis acid sites, the surface area, and the average pore diameter. The deactivated zeolites can be regenerated by calcination in a muffle furnace and the superior reusability of the zeolite HBEA was demonstrated after nine cycles. Moreover, the carbon deposit was proved to be one of the main reasons for the deactivation by using ¹³C NMR MAS, ²⁷Al NMR MAS, and TGA.

Full text of DOI:10.1016/j.apcata.2014.05.028

Accepted Manuscript
Title: Effects of acid-modified HBEA zeolites on thiophene
acylation and the origin of deactivation of zeolites
Author: Zhihua Chen Yuefei Feng Tianxia Tong Aiwu Zeng
PII:
S0926-860X(14)00362-7
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2014.05.028
APCATA 14848
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Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
22-3-2014
25-5-2014
26-5-2014
Please cite this article as: Z. Chen, Y. Feng, T. Tong, A. Zeng, Effects of acid-modified
HBEA zeolites on thiophene acylation and the origin of deactivation of zeolites, Applied
Catalysis A, General (2014), http://dx.doi.org/10.1016/j.apcata.2014.05.028
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Effects of acid-modified HBEA zeolites on thiophene acylation and
the origin of deactivation of zeolites
*
Zhihua Chen, Yuefei Feng, Tianxia Tong, Aiwu Zeng
State Key Laboratory of Chemical Engineering, Tianjin University, School of Chemical Engineering and Technology,
Tianjin 300072, P.R. China.
Highlights
■
■
■
First repot on thiophene acylation over acid-modified HBEA zeolite.
Discussion about origin of deactivation of zeolite on thiophene acylation.
Use of green renewable technology that can potentially be industrialized.
Abstract: The liquid phase Friedel-Crafts acylation of thiophene with acetic anhydride over
HBEA zeolites modified by hydrochloric, nitric, and acetic acid was investigated in a trickle bed
reactor. The catalytic stability of the HBEA zeolite was doubled after treatment with the
hydrochloric and nitric acids due to the increase of the ratio of Broensted to Lewis acid sites, the
surface area, and the average pore diameter. The deactivated zeolites can be regenerated by
calcination in a muffle furnace and the superior reusability of the zeolite HBEA was demonstrated
after nine cycles. Moreover, the carbon deposit was proved to be one of the main reasons for the
13
27
deactivation by using C NMR MAS, Al NMR MAS, and TGA.
Keywords: Friedel-Crafts acylation; Zeolite; Thiophene; Modification; Deactivation
1
. Introduction
Friedel-Crafts acylation is an important reaction for synthesizing aromatic ketones, which are
[
1-6]
the key intermediates in the production of valuable industrial and fine chemicals
, such as
[
7,8]
[8]
[8]
pharmaceuticals , insecticides , plasticizers, dyes and perfumes. Traditionally, the catalysts
used in the Friedel-Crafts acylation are Lewis acid (e.g. metal halides) or Broensted acid (e.g.
[
9,10]
[2]
H
2
SO
4
, HCl, HF ). However, a number of problems including the disposal of spent catalysts,
[1,11]
corrosion, toxicity and product isolation, are involved
.
In view of the disadvantages of the conventional catalysts, the development of eco-friendly
catalytic routes for various organic transformations has become an ongoing interest of catalytic
[
12,13]
[14,15,16]
researchers
. Considerable efforts have been made to develop zeolites, such as ZSM-5
,
*
Corresponding author. Tel: +86-022-27404732；Fax：+86-022-27404496
E-mail address: awzeng@tju.edu.cn; xiaofeng.xiaoyu@163.com
1
Page 1 of 17

[2,4,17,18]
[18,19,20]
[21]
Hβ
, and HY
for the acylation reaction. Harvey et al. reported H-Beta exhibited
highly active catalyst for the acylation of anisole by acetic anhydride and phenyl acetyl chloride.
Mild liquid-phase Friedel-Crafts acylation of heteroaromatic compounds such as thiophene,
[
22]
pyrroles and furans over zeolite beta were studied by Alvaro et al. , and the beta zeolites were
also found to have high catalytic activity in the acylation of thiophene in micro-reactor without
solvent. In addition, indium modified zeolite beta has provided a way to obtain a good yield in the
acylation of pyrroles. On the other hand, the study on the nature of active sites of zeolites was still
[
23]
in grope. Reddy et al. found the Friedel-Crafts acylation of furan and pyrrole was more active
on Broensted acid sites. However, there was a correlation between the initial rates of reaction and
[24]
the number of Lewis acid sites but not Broensted acid sites
.
What is also worth noticing is that modifications of zeolites are essential for obtaining higher
catalytic stability and activity in the reaction process. Dealumination was one of the modifications
used for promoting the performance of zeolites, which was obtained via hydrolysis of Al-O-Si
[
25,26]
[27]
bonds by organic acids, such as oxalic acid and citric acid
. Zhao et al. reported that the
beta zeolite modified with hydrochloric acid exhibited the most active performance and best
catalytic stability in the anisole acetylation. However, the study of the effects of the modified
zeolites with acids on the acylation of heteroaromatic compounds in a fixed bed reactor was
scarcely seen.
In this paper, HBEA zeolites modified by typical simple organic acid (acetic acid) and
inorganic acids (hydrochloric and nitric acid) were first investigated in Friedel-Crafts acylation of
thiophene in a trickle bed reactor. The thiophene used in this work was distinguished from the
general one due to its particular source of being purified from the by-products of coal coking
process, and herein it was named as coking thiophene. In China, over 21,500 tons of coking
thiophene could be get as a by-product from the industry of coal coking per year, and that is ten
times than the amount of synthetic thiophene. Moreover, almost all coking thiophene was wrecked
into pollutions. It is very urgent to find a solution to utilize the coking thiophene. Therefore, the
aim of this paper was to provide an efficient approach to change coking thiophene into
pharmaceutical intermediate 2-acetyl thiophene. And an attempt was made to analyze the effects
of modified HBEA zeolites with its acids on the structure, acidity, catalytic stability and the origin
of deactivation of zeolite HBEA was discussed as well.
2. Experimental
2
.1 Materials
Thiophene (96%) was provided by Qiaoyou Chemical Co., Ltd and it contains impurities
such as propionitrile (approximately 4%), trace of benzene and furan. Various acids, acetic
anhydride (>99%) and tetraethyl ammonium hydroxide (TEAOH) were purchased from Aladdin
reagent Co., Ltd. The commercial aluminosilicate was purchased from Nankai University Catalyst
Co., Ltd. All materials were used without further purification.
2
.2 Catalyst Preparation
[
28]
The HBEA sample was made according to the method reported by Matsukata et al. . 50 g
2
Page 2 of 17

HBEA (Si/Al=27.6) were subjected to acid treatments by stirring with 1.0 mol/L hydrochloric,
nitric and acetic acid at 100 °C for 12 h, respectively. The acid-treated zeolites were washed by
deionized water until the solution reached neutral, then dried at 120 °C for 2 h. After that, the
zeolites were calcined at 450 °C for 5 h. The treated zeolites were named HA-BEA, NA-BEA and
AC-BEA, respectively.
2 3
Each 10 g powder of HBEA, HA-BEA, NA-BEA and AC-BEA were mixed with 3 g Al O
and 4 g nitric acid solution (10 wt%) into homogenate and then extruded and cut into short
cylinder within 4 mm in length and 3 mm in diameter. The granular zeolites were dried at 120 °C
for 2 h, and then calcined at 450 °C for 5 h in a muffle furnace.
2
.3 Catalyst Characterization
X-ray diffraction (XRD) analysis was recorded on a Bruker D8-S4 with Cu Kα radiation,
scanning from 5° to 50° (2 θ) range with a scanning rate of 5.21 °/min. The voltage and current
used were 40 kV and 40 mA, respectively.
The bulk Si/Al molar ratios of the samples were determined by XRF. The BET surface area
and total pore volume were determined using a Micromeritics ASAP2020 volumetric instrument at
-
196 °C using nitrogen adsorption isotherms. The pore size was determined by Horvath-Kawazoe
method.
The acidity of all the zeolite samples was determined by the pyridine adsorption-desorption
method performing on a Nicolet 750 infrared spectrometer coupled to a conventional high vacuum
system. The samples were calcined at 450 °C for 120 min in an in situ IR gas cell under vacuum
prior to pyridine adsorption. Then the temperature was cooled down to 90 °C. Pyridine was
adsorbed for 30 min and then the physisorption pyridine was evacuated at 200 °C and 350 °C for
2
0 min, respectively. The IR spectra were obtained at 200 °C and 350 °C.
13
27
13
27
C-NMR and Al-NMR spectra were recorded on a Varian Infinity plus NMR ( C, Al 300
MHz) spectrometer in order to investigate the kind of carbon deposit and the form of aluminum.
The scanning frequency was 75.4 MHz and pulse delay was 5.0 second. Chemical shifts (δ) were
reported in ppm on behalf of the kind of carbon deposit and the form of aluminum, respectively.
A PerkinElmer Diamond TG/DTA instrument was used to obtain TG/DTG profiles. For
clarity, the differential TG curve (DTG) was presented. Each time, appropriate 10 mg of the
−1
samples were heated at a heating rate of 20 °C·min .
2
.4 Catalytic Reaction
The acylation reactions were carried out in a trickle bed reactor (Fig. 1) made of glass (inner
diameter 10 mm) at 80 °C under atmospheric pressure. The catalyst (6.2 g) was preheated for 2 h
at 200 °C in a drying oven before the reaction, and then placed in the center zone of the reactor.
The reactants of thiophene and acetic anhydride mixture with a molar ratio of 1:2 were fed into the
reactor by a metering pump, at a flow rate of 0.05 ml/min. Products were taken in regular intervals
and analyzed by gas chromatography (Agilent 7890A) equipped with a FID detector using 30 m
column of DB-17MS.
The organic compounds retained on the external zeolite surface and in the micropores were
recovered at the end of the experiment. For that, the used catalyst underwent a double-extraction
3
Page 3 of 17

[29]
methodology according to the description by Rohan and the remaining organic materials were
analyzed by GC-MS. We found side products containing 3-acetylthiophene (0.1~0.3% relative to
2
-acetylthiophene) and others (<0.01%) such as 1-(thien-2-yl)-1,3-butanedione and
-(thien-2-yl)-1-propanone.
1
Since acetic anhydride was in excess, and the product isomer was hardly found by the
spectral in comparison with the authentic samples, that is to say, the selectivity of the
-acetylthiophene was approximately 100%. The conversion of thiophene was calculated by
2
%
Thiophene(feed) − %Thiophene(product)
XThiophene
=
×100
%Thiophene(feed)
After the first cycle, the catalysts were collected together and dried at 120 °C for 2 h, then
calcined at 450 °C for 5 h in a muffle furnace. Catalytic behavior of regenerated zeolite was
investigated under the same conditions. The tests were repeated for nine times.
3
. Results and discussion
3
.1 Characterization of zeolites
XRD patterns of all zeolite HBEA samples are shown in Fig. 2. All of them showed that the
reflections at 7.8° and 22.5°, typical of zeolite HBEA structure even after the acid modifications,
indicating that the acid-treatment did not change the zeolite structure, and there were no other
visible peaks can be observed. The modified zeolite samples all existed relatively high
crystallinity as Table 1 showed. Table 1 also illustrates that the ratios of Si/Al of the zeolites
HBEA, AC-BEA, HA-BEA and NA-BEA were 27.6, 33.7, 62.3 and 89.8, respectively, suggesting
that the dealuminized extent of HBEA zeolite increased significantly after inorganic acid (HCl and
HNO
3 3
) treatments but slightly after organic acid (CH COOH) treatment.
Table 2 shows that the total BET surface areas and average pore diameters of NA-BEA and
HA-BEA were larger than those of HBEA and AC-BEA, with NA-BEA having the largest surface
area and HA-BEA having the largest average pore diameter. These results might be explained by
[27]
the extent of dealumination of the zeolites after acid modification which can be confirmed by
Si/Al ratio shown in Table 1.
The FT-IR spectra of the parent and acid-modified HBEA zeolites adsorbed pyridine probe
-
1
molecule are compared in Fig. 3. Band at 3744 cm in Fig. 3A is assigned to silanol groups,
[
30]
characteristic of terminating silanols . Compared with HBEA, the band of terminating silanols at
-
1
3
744 cm increased its intensity substantially for HA-BEA and NA-BEA, while there was only a
little increase for AC-BEA. The information of Broensted and Lewis acid sites can be gained by
-
1
the pyridine-IR spectra shown in Fig. 3B. Bands at 1545 and 1455 cm can be ascribed to
+
pyridinium ions (PyH , Broensted acid site) and coordinative bound pyridine (PyL, Lewis acid
[
27,30-33]
-1
site), respectively
. The band at 1489 cm was associated with adsorption on both Broensted
[
31]
and Lewis acid sites . A reliable assessment of the concentration of surface acid sites can be
[
32]
calculated by the integrated peak area , and the results of Py-IR analysis of different samples are
listed in Table 3. In comparison with unmodified HBEA zeolite, it is clear to see that acid-treated
ones contained more Broensted acid sites, and the number of Lewis acid sites decreased
remarkably after modifications except AC-BEA zeolite. Therefore, it can be concluded that the
4
Page 4 of 17

hydrochloric acid and nitric acid treatments are able to etch most Lewis acid sites on or near the
external surface but acetic acid treatment is not. This is validated by the absorbance fluctuation
-
1
appeared at band 3744 cm . Moreover, the ratios of Broensted to Lewis acid site (B/L ratio) of
HA-BEA and NA-BEA are far more than those of HBEA and AC-BEA zeolites.
3
.2 Catalytic stability of the zeolites
The catalytic stability for the conversion of thiophene into 2-acetylthiophene has been
investigated in a trickle bed reactor using the HBEA zeolites with and without modification. It is
obviously observed that HA-BEA and NA-BEA zeolites exhibited higher catalytic stability than
the parent HBEA and AC-BEA zeolites as shown in Fig. 4. In the presence of parent HBEA zeolite,
the conversion of thiophene could keep up to 90% within 2510 min, which is similar to that of
AC-BEA zeolite. The zeolites HA-BEA and NA-BEA maintained 4847 min and 5332 min
respectively, and the highest conversion was found to be 99.9% at 200 min for both of them. In
addition, the conversions with AC-BEA and parent HBEA zeolites decreased sharply after 820
min, while HA-BEA and NA-BEA still showed relatively higher conversion (>97%) after 3000
[4]
min. This distinction is in good agreement with results reported by Heinichen and Holderich . Fig.
and Table 1 indicate that the catalytic stability went up when increasing the ratio of Si/Al in a
4
certain range. Besides, combining with Table 2, it can be clearly seen that higher catalytic stability
of the catalyst are related to larger external surface area and average pore diameter, which could
be conductive to the diffusion of the product.
Herein the performance of zeolites characterized in this work were compared with those of
[
34]
the best-performing ones reported by Kantam et al. . Better results (conversion of thiophene
reached 91% and selectivity of 2-acetyl thiophene was 70% after 3 h) were got when using
microcrystalline beta zeolite (particle size of 1~10 μm). Though there existing a huge difference in
reactive mode between current work described above (continuous mode) and that in the literature
(
batch mode, in a flask), it can obviously reveal the superiorities of acylation reaction in
continuous mode (conversion of thiophene was up to 90% within 5332 min and selectivity of
-acetyl thiophene was close to 100%) under the similar conditions (80 °C, thiophene/acetic
anhydride molar ratio=1:2).
2
3
.3 Effects of the zeolites modified with acids
It is well known that Friedel-Crafts acylation reaction over zeolites is catalyzed on the
Broensted or Lewis acid sites, this makes no essential difference with the general catalytic
mechanism of traditional Broensted or Lewis acid to some extent. The acidic properties of zeolites
are closely linked to the quantity, nature, and distribution of the aluminum atoms attached to or
trapped in pores and cavities of zeolites. Broensted acid sites have external –OH groups, while the
3+
[35]
Lewis sites are exposed three-fold coordinated Al ions
.
Zeolites HBEA treated by acids exhibited different catalytic stabilities in acylation of
thiophene (Fig. 4). Among these zeolites, NA-BEA and HA-BEA gave higher catalytic stability,
while AC-BEA and HBEA were less effective. It was of interest to see that catalytic stability
increased with the increase of the ratio of Si/Al without a linear relationship (Table 1), which was
[
36]
due to the different levels of dealumination by acids. Donk et al. reported a mild acid-leaching
5
Page 5 of 17

step using either inorganic acids or organic acid, improved the porous properties by dissolving the
extraframework material. However, during the severe treatment with strong inorganic acids,
aluminum is removed from the framework. And similar conclusions have been obtained by other
[
37,38]
groups
. In this work, hydrochloric acid and nitric acid treatments were more intense than
acetic acid treatment, which may remove additional framework aluminum species. Structural
characteristics of zeolites can be significantly affected by acid-modification. Though all of the
zeolites possessed high crystallinity (Fig. 2 and Table 1), the XRD patterns at 7.8°and 22.5°of
NA-BEA and HA-BEA zeolites were stronger than those of AC-BEA and HBEA, which may
favor the acylation reaction. In addition, NA-BEA and HA-BEA zeolites had larger external
surface area and average pore diameter (Table 2), because of the removal of most extra-framework
aluminum through hydrochloric acid and nitric acid treatments and hence the formation of some
intergranular pore or new unchoked channels. It should be noticed that all the acid treatments are
mild so that the integrity of the zeolite crystal would not be destroyed. And the channels were
unchoked in the gentle acid treatments, which may contribute to maintain high zeolite
crystallinity.
The increase of external surface area and average pore diameter were not only conductive to
better distribution of acid sites on zeolites surface, as well as fully diffusion of reactants and
products. Besides, external surface areas of NA-BEA and HA-BEA zeolites augmented visibly
compared with HBEA, but not the internal. Hence, it seems that the external surface is primarily
active catalytically. It has been reported that Broensted acid sites present both on the internal and
[39,40]
external surface, while Lewis acid sites are predominantly presents on the internal surface
.
Thus, possessing large external surface may contribute to adding Broensted acidity, which is
beneficial to the acylation reactions.
Combined with Fig. 4, the correlation of catalytic stability with acidity reveals that the ratio
of Broensted to Lewis acid sites seems to be of great importance for the acylation reaction (Table
3
). That is NA-BEA and HA-BEA zeolites with more Broensted but less Lewis acid sites exhibited
higher stability, while AC-BEA with both large Broensted and Lewis acid sites displayed
unsatisfactory results. With further analysis of the ratio of Broensted to Lewis acid sites for HBEA
(0.71~0.64), AC-BEA (0.95~0.91), HA-BEA (4.07~4.23) and NA-BEA (4.32~4.46)，which is
highly consistent with the acylation results ranked by catalytic stability as follows
NA− BEA ≈ HA− BEA ? AC − BEA ≈ HBEA
The reasons may be that some Broensted acid sites which were covered by neutral or
non-acidic amorphous substance on the external surface would be exposed through the
hydrochloric and nitric acid treatments, and most extra-framework aluminum which represents
[
41]
Lewis acid sites was etched simultaneously , resulting in producing more Broensted acid sites
but less Lewis acid sites, with higher ratio of Si/Al. With regard to acetic acid, a kind of weak
organic acid, probably due to the gentle treatment, only some amorphous substance was removed,
resulting in the release of Broensted acid sites which were covered before. Therefore, the number
of Broensted acid sites increased but the number of Lewis acid sites was nearly unchanged, that is,
[
42]
the total amount of acid sites of HBEA increased. Canizares and Carrero
reported that
extra-framework aluminum could decrease the accessibility of active sites to reactant molecules,
which reduces the contact time but favors the formation of by-products. Thus, hydrochloric and
nitric acid treatments could enhance the catalytic stability of the catalysts, but acetic acid
treatment could not.
6
Page 6 of 17

To summarize, the dealuminated catalysts with a higher ratio of Broensted to Lewis acid sites
have lower acid site density (and higher acid strength) and exhibit higher catalytic stability. Hence,
it can be proposed that acid treatment affects the coordination state of aluminum and therefore
change the number and type of acid sites. And an ideal catalyst with an outstanding activity and
stability may not possess Broensted acid sites as much as possible but a high ratio of Broensted to
Lewis acid sites, as well as a large external surface area and average pore diameter.
3
.4 Regeneration and reusability of the zeolites
Reusability of HBEA, AC-BEA, HA-BEA and NA-BEA zeolites was investigated and the
results are given in Table 4. The regenerated zeolites almost displayed the same trend profiles with
the reactive time and performances as their origins. In this paper, the catalyst was regarded as
deactivation when the conversion of thiophene was below 90%.
Table.4 also shows that the zeolites HBEA before and after modification could be regenerated
and recycled through calcination at high temperature. The average lifetime of HBEA was kept at
2
911 min before the deactivated point during the nine times reaction processes, and 6.2 g HBEA
zeolite help to produce 1310 g primary products, such as 2-acetyl thiophene, acetic acid, etc. That
is to say, the treated capacity of the parent zeolite was up to 211 g, which was roughly equal to the
capacity of AC-BEA zeolite (3061 min, 222 g). As expected, the average lifetime and treated
capacity of HA-BEA (4863 min, 353 g) and NA-BEA (4893 min, 356 g) zeolites were better than
those of the parent zeolite HBEA and AC-BEA.
It indicates that the activity and stability of the zeolite can be regenerated efficiently and
satisfactorily, which means that most of the acid sites can be regenerated to its original states.
Therefore, the zeolites HBEA are expected to replace the traditional Lewis acid and Broensted
acid catalysts to solve the manufacturing and environmental problems.
3
.5 The origin of deactivation
1
3
In order to study the reasons for deactivation of zeolites, the analytical methods of the
C
27
MAS NMR, Al MAS NMR and TGA were taken.
13
The C MAS NMR spectra of the deactivated and regenerated zeolites are shown in Fig. 5.
[43]
13
Derouane et al. first studied the formation and stability of coke deposits by the method of
C
MAS NMR during the conversion reaction of methanol to hydrocarbons. Carbon deposit mainly
includes fat carbon, olefin carbon, aromatic carbon and poly aromatic carbon, etc. The peak signal
of fat carbon is between 10 ppm and 40 ppm, the signal between 125 ppm and 145 ppm belong to
aromatic carbon, while between 130 ppm and 200 ppm was the characteristic signal of poly
aromatic. For the deactivated zeolites, the carbon deposit in the channel and surface was very
severe, which mainly consisted of fat hydrocarbon, cyclic compound and aromatic oligomers. It
was clearly exhibited that there was no carbon depositing on the surface and inside channel for the
regenerated samples, which meant the organics accumulated in zeolites were basically removed
through regeneration in a muffle furnace. As a consequence, the HBEA zeolite can be reused in
the acylation of thiophene.
27
The influence of carbon deposit on zeolites framework could be characterized by Al MAS
NMR. The state of aluminum framework changed when the zeolites channel was filled with
7
Page 7 of 17

carbon deposit. There are two peaks in Fig. 6 corresponding to tetrahedral and octahedral Al
[
44]
sites in the range of -10 to 40 and 40 to 80 ppm, respectively. The tetrahedral Al concentration
tended to decrease on the deactivated zeolite compared to the regenerated and the parent ones,
while the octahedral Al concentration kept constant. This indicated that the change of tetrahedral
Al results from the adsorption of carbon deposit in the zeolites. Besides, the tetrahedral Al
represents Broensted acid sites, while the octahedral Al is on behalf of Lewis acid sites. Therefore,
Fig. 6 may indicate that the Broensted acid is responsible for the Friedel-Crafts acylation reaction
of thiophene with acetic anhydride.
TGA (Thermogravimetric Analysis) was employed to investigate the amount of carbon
deposit in the surface and channel of the zeolites. As shown in Fig. 7, both of the samples had a
peak of weight loss in the range of 50~150 °C mainly caused by surface moisture adsorbed from
air, hydrated water and adsorbed organic with low boiling point in the reaction process. There was
no weight loss for the regenerated zeolite over 150 °C, but the peaks of weight loss existed in the
range of 200~300 °C and 350~400 °C for the deactivated zeolite. At the range of 200~300 °C, the
peak of deactivated zeolite represented the high boiling point organic, such as 2-acetyl thiophene,
while at the range of 350~400 °C, the peak represents the oligomers, such as poly thiophene, poly
[44]
propionitrile, poly 2-acetyl thiophene, et al. Besides, Chica et al.
reported that thiophene
oligomers formed during adsorption and their size depended on spatial constraints within zeolite
channels, and moreover oligomerization occured on Broensted acid sites at 90 °C. Fig.7 shows
that the carbon deposit from deactivated zeolite mainly focused on the range of 200~300 °C, about
1
1.7% weight loss in this scope and 1.8% in the range of 350~400 °C. In summary, the carbon
deposit rate of the regenerated zeolite was zero, while the number for deactivated zeolite was up to
3.5%.
1
4
. Conclusions
The catalytic stability of zeolite HBEA in trickle bed reactor can be greatly improved by
dealumination through various acids treatments, especially by hydrochloric and nitric acid. It is
found that the ratio of Broensted to Lewis acid sites, external surface area and average pore
diameter play important roles in the significant increase of catalytic stability. And HBEA zeolites
still exhibit excellent reusability even after eight cycles. The main reason for deactivation is the
carbon deposit through the comparison between the deactivated and regenerated zeolites.
Acknowledgements
This work is supplied by The National Key Technology R&D Program of China
(
2007BAB24B05) and Shanxi Qiaoyou Chemical Co. Ltd.
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10
Page 10 of 17

Figure Captions
Fig.1. Acylation of thiophene in trickle bed reactor apparatus diagram.
Fig.2. XRD patterns of the parent and acid-modified HBEA zeolites.
Fig.3. FTIR spectra of pyridine-adsorbed parent and acid-modified HBEA zeolites (Pyridine
adsorption at 90 °C and desorption at 200 °C).
Fig.4. Catalytic stability tests for acylation of thiophene with acetic anhydride over the parent and
acid-modified HBEA zeolites in a trickle bed reactor (experimental conditions: 80 °C,
thiophene/acetic anhydride molar ratio=1:2, 6.2 g of catalyst).
13
Fig.5. C MAS NMR of the deactivated and regenerated samples
27
Fig.6. Al MAS NMR of the parent, deactivated and regenerated samples
Fig.7. TG/DTG curves of the deactivated and regenerated samples
Table Captions
Table 1 Properties of XRD on the parent and acid-modified HBEA zeolites.
Table 2 BET surface area, micropore volume and average pore diameter of the parent and
acid-modified HBEA zeolites.
Table 3 Result of IR spectra of Py adsorbed on the parent and acid-modified HBEA zeolites after
desorption at different desorption temperatures.
Table 4 Results of the treated capacity of the parent and acid-modified HBEA zeolites.
11
Page 11 of 17

Fig.1
Fig.2
HBEA
NA-BEA
HA-BEA
AC-BEA
40
5
10
15
20
25
30
35
45
50
2-Theta (degree)
12
Page 12 of 17

Fig.3
Fig.4
100
HBEA
99
98
97
96
95
94
93
92
91
90
NA-BEA
HA-BEA
AC-BEA
500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500
Time on stream / min
Fig.5
13
Page 13 of 17

Deactivated zeolite
Regenerated zeolite
350 300 250 200 150 100 50 0 -50 -100-150
ppm
Fig.6
Deactivated zeolite
Regenerated zeolite
Parent zeolite
300 250 200 150 100 50
0 -50 -100-150-200-250
ppm
Fig.7
14
Page 14 of 17

15
Page 15 of 17

Table 1 Properties of XRD on the parent zeolite HBEA and modified with various acids.
a
b
Catalyst Bulk Si/Al ratio
XRD crystallinity (%)
HBEA
27.6
33.7
62.3
89.8
100
99
AC-BEA
HA-BEA
NA-BEA
99
99
a
b
Determined by XRF; XRD signal 2θ=7.8°, and 22.5°.
Table 2 BET surface area, micropore volume and average pore diameter of zeolite HBEA and modified zeolite
HBEA with various acids.
a
2
c
Surface Area (m /g)
Micropore
Micropore Pore
Average Pore Diameter
(nm)
Sample
b
3
Volume (cm /g)
Total
External
HBEA
542
558
585
597
449
425
419
432
93
0.209
0.198
0.194
0.201
0.56
0.59
0.74
0.66
AC-BEA
HA-BEA
NA-BEA
133
166
165
a
b
c
Surface area determined by the BET method;
Micropore pore volume determined by the t-plot method;
Micropore diameter determined by Horvath-Kawazoe method.
Table 3 Result of IR spectra of Py adsorbed on the zeolite HBEA and modified zeolite HBEA with acid after
desorption at different desorption temperatures.
2
00 °C
350 °C
L acid site
a
a
Sample
B acid site
L acid site
(mmol/g)
0.331
B/C
B acid site
(mmol/g)
0.228
B/C
(mmol/g)
(mmol/g)
0.252
HBEA
0.334
0.71
0.95
4.07
4.32
0.64
0.91
4.23
4.46
AC-BEA
HA-BEA
0.517
0.384
0.398
0.306
0.502
0.087
0.396
0.066
NA-BEA
0.571
0.093
0.472
0.074
a
B/C: the ration of B acid site to L acid site.
16
Page 16 of 17

Table 4 Results of the treated capacity of the parent zeolite HBEA and modified zeolite with various acids.
The amount of
initial
product / g
125.5
107.1
149.1
152.2
151.2
155.8
145.8
176.2
147.1
--/ 1310
132.8
145.7
172.1
196.8
149.5
155.1
149.9
129.3
146.5
--/ 1378
242.6
286.2
295.1
273.1
232.0
260.6
190.7
205.5
204.9
--/ 2191
267.2
275.7
260.8
253.8
242.2
240.4
225.2
229.2
212.3
--/ 2207
The treated
Regeneration
time
Deactivated
point
Catalyst
Lifetime /
min
Catalyst
HBEA
capacity
of catalyst /g
20.2
dosage / g
0
1
2
3
4
5
6
7
8
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
2510
2139
2981
3042
3024
3117
2916
3523
2943
2911 /--
2655
2913
3439
3935
2990
3100
3000
2586
2930
3061 /--
4847
5705
5899
5447
4641
5212
3813
4110
4097
4863 /--
5332
5508
5212
5075
4824
4788
4483
4574
4244
4893 /--
17.3
24.0
24.5
24.4
25.1
23.5
28.4
23.7
Average / Total
--/ 211
21.4
AC-BEA
0
1
2
3
4
5
6
7
8
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
23.5
27.8
31.7
24.1
25.0
24.2
20.9
23.6
Average / Total
--/ 222
39.1
HA-BEA
0
1
2
3
4
5
6
7
8
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
46.2
47.6
44.0
37.4
42.0
30.8
33.1
33.0
Average / Total
--/ 353
43.1
NA-BEA
0
1
2
3
4
5
6
7
8
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
90.0%
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
6.2
44.5
42.1
40.9
39.1
38.8
36.3
37.0
34.2
Average / Total
--/ 356
17
Page 17 of 17