Liquid-phase dehydration of 1-phenylethanol to styrene over an acidic resin catalyst

Article abstract of DOI:10.5012/bkcs.2011.32.4.1327

Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase with three solid acid catalysts such as H-ZSM-5, H-Y and Amberlyst-15. Amberlyst-15 shows the highest conversion and styrene yield, suggesting the applicability of a resin

Full text of DOI:10.5012/bkcs.2011.32.4.1327

Liquid-phase Dehydration of 1-Phenylethanol to Styrene
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 4 1327
DOI 10.5012/bkcs.2011.32.4.1327
Liquid-phase Dehydration of 1-Phenylethanol to Styrene over an Acidic Resin Catalyst
†
Nazmul Abedin Khan, Jin-Soo Hwang, and Sung Hwa Jhung
*
Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 702-701, Korea
*
E-mail: sung@knu.ac.kr
†
Bio-refinerary Research Center, Korea Research Institute of Chemical Technology, P.O. Box, 107, Yusung,
Daejeon 305-600, Korea
Received January 27, 2011, Accepted March 3, 2011
Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase with three solid acid
catalysts such as H-ZSM-5, H-Y and Amberlyst-15. Amberlyst-15 shows the highest conversion and styrene
yield, suggesting the applicability of a resin catalyst in the dehydration. The good performance of the
Amberlyst-15 may be due to high acid concentration and ready diffusion of reactants and products. A possible
reaction scheme (such as the formation of styrene from diphenylethylether) has also been suggested.
Key Words : Dehydration, 1-Phenylethanol, Amberlyst-15, Liquid-phase, Styrene
18-22
Introduction
widely in acid catalysis.
Moreover, resin catalysts have
the advantage of high concentration of acid sites, easy
1
Dehydration of alcohols has been widely studied and
18
production and low cost. In this work, the dehydration of
used to produce organic olefins, valuable intermediates
because of high activity and functionality. The dehydration
has usually been carried out with acid catalysts such as
mineral acids and solid acids. Various alcohols including
PhE with a resin catalyst (AMB-15) will be discussed. The
catalyst shows not only high activity but also high yield for
ST. Possible reaction scheme from PhE to ST, an intermedi-
ate and a heavy product will also be suggested.
2-6
7,8
9
10
methanol, butanol, hexanol, and glycerol have been
converted into attractive intermediates by using suitable
catalysts.
Experimental
Styrene (ST) is one of the most widely used raw chemicals
for polymers and usually produced with dehydrogenation of
The dehydration of 1-phenylethanol (PhE, 98%, Aldrich)
was carried out in liquid phase using a round bottomed 50
mL three-neck flask equipped with a small rectification
column, and a water cooled condenser attached with a
vacuum pump. An oil bath was employed to maintain the
ethylbenzene (EB) at high temperature by using iron oxide
11,12
catalysts in the presence of superheated steam.
Even
though the direct production of ST from EB is widely used,
the process has a drawback of high energy consumption.
Around 15% of ST is produced by dehydration of 1-
o
reaction temperature of 170 C. The scheme of the reactor is
illustrated in Figure 1.
phenylethanol (PhE) which is obtained from a process called
Three different commercial catalysts (0.1 g each) like H-
13-16
PO/SM (propylene oxide/styrene monomer).
Moreover,
15,16
there was a process
to produce ST by dehydration of PhE
which was obtained from acetophenone. The acetophenone
is usually originated from oxidation of EB.
Dehydration of PhE has been commercially carried out at
o
around 300 C in gas phase in the presence of solid acids like
15,16
titania and alumina.
Recently, liquid-phase dehydration
has been studied using various catalysts like zeolites (H-
13,16
14-16
mordenite
16 17
and H-Y ), alumina, polyoxo-
ZSM-5,
16
16
metallates, and silica-alumina. Liquid-phase dehydration
is very attractive because energy consumption can be
minimized due to low operation temperature. However,
there has been little study to develop suitable acid catalysts
especially solid acid catalysts. Solid acid catalysts are very
promising and important because they are environment-
friendly, recyclable and can be separated easily.
So far, to the best of our knowledge, there has been no
18
report to use a resin catalyst like Amberlyst-15 (AMB-15)
in the dehydration of PhE even though resins have been used
Figure 1. The scheme of the reaction system used in this study.

1328 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 4
Table 1. Textrual properties of the three catalysts
Nazmul Abedin Khan et al.
ZSM-5 (Si/Al=23, Zeolyst), H-Y (Si/Al=15, Zeolyst) and
+
Amberlyst-15 (Aldrich, acid capacity is 4.7 mequiv. H /g)
BET surface area, Total pore volume, Micropore
Catalysts
were used in this study. The surface area and pore volumes
(Table 1) of the catalysts were obtained from nitrogen
adsorption isotherms (shown in Supporting Figure 1). The
pore size distributions (shown in Supporting Figure 2) of the
catalysts were obtained from the nitrogen adsorption-
desorption isotherms. The nitrogen adsorption-desorption
isotherms were obtained using a Micromeritics Tristar II
3020 surface area and porosity analyzer at the temperature of
liquid nitrogen (−196 °C) after evacuation at 200 °C (for H-
ZSM-5 and H-Y) or 110 °C (for AMB-15).
m /g
cm /g
volume, cm /g
H-ZSM-5
H-Y
344
486
45
0.22
0.35
0.30
0.12
0.20
~0
AMB-15
For solvent-free dehydration, the flask was loaded with 15
g of 1-phenylethanol and dipped in the hot oil bath for rapid
heating to the reaction temperature. The dehydration reac-
tion was also carried out in the presence of 1,2-dichloro-
benzene (99%, Samchun Chemical) as a solvent. A mixture
of 5 g of PhE and 25 g of 1,2-dichlorobenzene (o-DCB) was
loaded in the flask and 0.1 g of Amberlyst-15 was used as
the catalyst. The pressure of the reaction system was de-
creased (~0.8 bar) to remove low boiling portion (water and
ST). As the reaction proceeded, distillate fraction containing
water and ST was collected in a vessel. After a fixed reaction
time, the reaction flask was removed from the oil bath and
was allowed to cool down to room temperature. The catalyst
was separated from the residual slurry by centrifugation. The
styrene rich organic phase and residual slurry were mixed
well and analyzed with a FID GC. Products like ST, di-
phenylethylether (DPEE) and heavy products were identi-
fied with authentic samples and GC-MS (Finnigan, MAT-
GCQ).
Results and Discussion
Comparison of Catalysts. Figure 2 compares the perfor-
mance (relative composition of reactant and products) of the
o
three catalysts in the PhE dehydration at 170 C depending
on the reaction time. The conversion, ST selectivity and ST
yield are summarized in Figure 3. As shown in Figures 2 and
3, the PhE converts quite rapidly over the three catalysts.
The performance, especially ST yield, is generally in the
order of AMB-15 > H-ZSM-5 > H-Y (Figure 3(c)), suggest-
ing the applicability of a resin catalyst, AMB-15, in the
dehydration of PhE to ST. To compare precisely the relative
kinetics of PhE dehydration, the conversion of PhE is plotted
to follow the first order kinetics (Figure 4). As illustrated in
−1
Figure 4, the rate constants are kAMB-15 (1.6 × 10 /min) >
−2 −2
kH-Y (5.4 × 10 /min) > kH-ZSM-5 (2.8 × 10 /min).
Medium-pore zeolites, especially small-sized crystals, have
16
shown good performance in the dehydration of PhE. H-
ZSM-5 (Si/Al = 20) has been used in the dehydration to
13
develop a kinetic model. H-mordenite and H-Y have been
16
applied in the dehydration; however, the yield of ST is
poor because large-pore zeolites lead mainly to the diphenyl-
ethylether (DPEE) in a wide range of conversion. Similar to
Figure 2. Changes of the compositions of the reaction system
depending on the reaction time in the presence of three catalysts:
(a) H-ZSM-5; (b) H-Y and (c) AMB-15.
16
a previous work, ST yield over H-Y is low (Figure 3(c))
because of high selectivity to DPEE even though H-Y shows

Liquid-phase Dehydration of 1-Phenylethanol to Styrene
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 4 1329
Figure 4. Plots to show the first order kinetics of the PhE
dehydration with the three catalysts. The kinetic constants are also
shown.
selectivity can be increased up to 85.5% at the conversion of
100% in a selected reaction condition (reaction time: 30
min). The solvent may hinder the formation of heavy
products (HP) because the interaction between ST molecules
can be hindered with dilution (see below).
Therefore, the AMB-15 catalyst shows the best performance
among the three catalysts not only in the conversion but also
in the ST yield, suggesting the potential applications of the
catalyst in the PhE dehydration.
Reaction Scheme and Kinetics Over the AMB-15
Catalyst. The mechanism of the dehydration of PhE over
the acidic catalysts has been described a few times in open
13-17
literatures.
However, there is a disagreement between
13,14
research groups. For example, Bertero et al. and Romanova
et al. have suggested that DPEE can be converted into
17
15,16
ST; however, Lange et al.
obtained from ST.
proposed that DPEE can be
Figure 2 shows the compositions of ST, DPEE and HP,
and suggests that ST and DPEE are primary products and
HP is a secondary product because primary and secondary
products have non-zero and zero initial slopes, respectively.
Interestingly, the concentration of DPEE shows a maximum
and decreases steadily in the case of H-ZSM-5 and AMB-
15, suggesting the DPEE is an intermediate that can be
converted into other products like ST or HP. Moreover, it has
been agreed on that olefins can be obtained from ether in the
3,4
MTO (methanol-to-olefin) process. Therefore, the DPEE,
produced at the early stage of reaction, may be converted
into ST. However, the possibility of DPEE reconversion into
PhE (and finally dehydrated to ST) cannot be ruled out.
The HP concentration increases steadily (Figures 2 and 5)
and ST concentration decreases when HP concentration is
very high (Figure 5). GC-MS analysis shows that the HP is
composed of carbon and hydrogen (chemical formula:
(C6H5)4(CH)6; FW: 386). Therefore, HP may be mainly
obtained from oligomerization of ST. The reaction pathway,
in conclusion, may be summarized as Scheme 1.
Figure 3. (a) PhE conversion, (b) ST selectivity and (c) ST yield at
various reaction times in the presence of three catalysts.
high PhE conversion. H-ZSM-5 has relatively low conver-
sion in a short reaction time even though the ST selectivity is
relatively high.
To increase ST selectivity further with the AMB-15, the
dehydration of PhE was carried out in the presence of a
solvent, 1,2-dichlorobenzene. As shown in Figure 5, the ST

1330 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 4
Nazmul Abedin Khan et al.
because of high concentration of acid sites and ready
diffusion of reactants and products. The ST selectivity can
be increased further when PhE is diluted with a solvent
because the oligomerization of ST may be hindered in low
concentration. The reaction scheme for the dehydration may
be summarized as follows;
− ST and DPEE are primary products and HP is a second-
ary product.
− DPEE, either through PhE or not, may be converted into
ST.
− HP is obtained mainly from ST oligomerization.
Acknowledgments. This study was supported by a grant
(B551179-10-03-00) from the cooperative R&D Program
funded by the Korea Research Council Industrial Science
and Technology, Republic of Korea.
Figure 5. The PhE conversion and selectivities of products with
time in the presence of AMB-15 catalyst when o-DCB was added
as a solvent.
References
1. Molnár, Á.; Bartók, M. Dehydration of Alcohols, In Heterogeneous
Catalysis; Sheldon, R. A., van Bekkum, H., Eds.; Wiley-VCH:
Weinheim, 2001; pp 295-307.
2. Lee, K. Y.; Chae, H.-J.; Jeong, S.-Y.; Seo, G. Appl. Catal. A:
General 2009, 369, 60-66.
3. Chen, D.; Moljord, K.; Fuglerud, T.; Holmen, A. Micropor.
Mesopor. Mater. 1999, 29, 191-203.
4. Lee, Y.-J.; Baek, S.-C.; Jun, K.-W. Appl. Catal. A: General 2007,
329, 130-136.
5. Jun, K.-W.; Lee, H.-S.; Roh, H.-S.; Park, S.-E. Bull. Kor. Chem.
Soc. 2002, 23, 803-806.
Scheme 1
6. Jiang, S.; Hwang, Y. K.; Jhung, S. H.; Chang, J.-S.; Hwang, J.-S.;
Cai, T.; Park, S.-E. Chem. Lett. 2004, 33, 1048-1049.
7. Delsarte, S.; Grange, P. Appl. Catal. A: General 2004, 259, 269-
279.
Figure 4 shows that the kinetic constants for dehydration
decrease in the order of kAMB-15 > kH-Y > kH-ZSM-5, confirming
the rapidest dehydration over the AMB-15 catalyst. It has
8. Macias, O.; Largo, J.; Pesquera, C.; Blanco, C.; Gonzalez, F. Appl.
Catal. A: General 2006, 314, 23-31.
been reported that the dehydration is carried out over an acid
9. Medina, E.; Bringué, R.; Tejero, J.; Iborra, M.; Fité, C. Appl.
Catal. A: General 2010, 374, 41-47.
1,13-17
site of a catalyst.
AMB-15 catalyst has very high acid
+
10. Chai, S.-H.; Wang, H.-P.; Liang, Y.; Xu, B.-Q. Green Chem. 2007,
9, 1130-1136.
concentration (4.7 mequiv. H /g) compared with the zeolites
like H-ZSM-5 and H-Y. It has also been reported that the
yield of ST increases with decreasing the Si/Al ratio (or
11. Chang, J.-S.; Hong, D.-Y.; Vislovskiy, V. P.; Park, S.-E. Catal.
Survey Asia 2007, 11, 59-69.
16
increasing acid concentration) of the H-ZSM-5 catalyst
12. Kochloefl, K.; Muhler, M. Dehydrogenation of ethylbenzene, In
Handbook of Heterogeneous Catalysis; Ertl, G., Knözinger, H.,
Schüth, F., Weitkamp, J., Eds.; 2nd ed.; Wiley-VCH: Weinheim,
2008; 7, 3229-3240.
14
even though high aluminum content of H-mordenite zeolite
is detrimental to the ST production because of difficult diffu-
2
sion. Even though surface area is low (45 m /g, Table 1),
13. Bertero, N. M.; Apesteguía, C. R.; Marchi, A. J. Catal. Commun.
2009, 10, 1339-1344.
18-22
AMB-15 is a macroporous material;
therefore, AMB-15
has the advantage of rapid diffusion of reactants and
products. The pore size distributions of the three catalysts
shown in Supporting Figure 2 also confirm the large pore
size of the AMB-15. Therefore, it can be presumed that a
catalyst having high acid-site concentration and macroporo-
sity such as acidic resins (AMB-15 and AMB-35 etc.) can be
successfully used in the dehydration of PhE.
14. Bertero, N. M.; Apesteguía, C. R.; Marchi, A. J. Catal. Commun.
2008, 10, 261-265.
15. Lange, J.-P.; Otten, V. Ind. Eng. Chem. Res. 2007, 46, 6899-6903.
16. Lange, J.-P.; Otten, V. J. Catal. 2006, 238, 6-12.
17. Romanova, R. G.; Lamberov, A. A.; Shmelev, I. G. Kinetics Catal.
2004, 45, 422-428.
18. Sharma, M. M. Reactive Funct. Polymer 1995, 26, 3-23.
19. Yoon, J. W.; Chang, J.-S.; Lee, H.-D.; Kim, T.-J.; Jhung, S. H. J.
Mol. Catal. A 2006, 260, 181-186.
20. Yoon, J. W.; Jhung, S. H.; Chang, J.-S. Bull. Kor. Chem. Soc.
2008, 29, 339-341.
Conclusions
21. Yoon, J. W.; Jhung, S. H.; Lee, J. S.; Kim, T.-J.; Lee, H.-D.;
Chang. J.-S. Bull. Kor. Chem. Soc. 2008, 29, 57-60.
22. Yoon, J. W.; Jhung, S. H.; Kim, T.-J.; Lee, H.-D.; Jang, N. H.;
Chang, J.-S. Bull. Kor. Chem. Soc. 2007, 28, 2075-2078.
Following conclusions can be derived from the com-
parative study of the dehydration of PhE over the three
catalysts. Resin catalyst such as AMB-15 can be success-
fully applied in the dehydration of PhE to produce ST