Selecting an optimum catalyst for producing para-tert-butylphenol by phenol alkylation with tert-butanol

Article abstract of DOI:10.1134/S096554411708014X

Results of testing various heterogeneous catalysts in the synthesis of p-tert-butylphenol via phenol alkylation with tert-butyl alcohol are presented. It has been shown that all other conditions being equal, zeolite beta produced by the Angarsk catalyst and organic synthesis plant possesses the highest catalytic activity and selectivity for the desired product.

Full text of DOI:10.1134/S096554411708014X

ISSN 0965-5441, Petroleum Chemistry, 2017, Vol. 57, No. 8, pp. 714–717. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.V. Terekhov, L.N. Zanaveskin, S.N. Khadzhiev, 2017, published in Neftekhimiya, 2017, Vol. 57, No. 4, pp. 453–456.
Selecting an Optimum Catalyst for Producing para-tert-Butylphenol
by Phenol Alkylation with tert-Butanol
A. V. Terekhov*, L. N. Zanaveskin, and S. N. Khadzhiev
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia
*e-mail: terekhov.av@ips.ac.ru
Received January 27, 2017
Abstract⎯Results of testing various heterogeneous catalysts in the synthesis of p-tert-butylphenol via phenol
alkylation with tert-butyl alcohol are presented. It has been shown that all other conditions being equal, zeo-
lite beta produced by the Angarsk catalyst and organic synthesis plant possesses the highest catalytic activity
and selectivity for the desired product.
Keywords: phenol, p-tert-butylphenol, alkylation, tert-butyl alcohol, catalyst, zeolite, sulfonated cation
exchanger
DOI: 10.1134/S096554411708014X
p-tert-Butylphenol (PTBP) is used as an interme- advantages. They include comparatively fast deactiva-
diate product in organic synthesis, and the field of its
application is continuously expanding. Phenol–form-
aldehyde resins, antioxidants, rubbers, paints and var-
nishes, and pharmaceuticals are produced on its basis.
In Russia, PTBP is produced by the Novokuibyshevsk
Petrochemical Company via phenol alkylation with
isobutylene. Ion exchange resins including KU-23 and
various Amberlyst brands are used as a catalyst.
Although the process flowchart used provides a quite
tion of the catalysts and the need for their replace-
ment; irrecoverable loss of phenol during catalyst dry-
ing and preparing for unloading; occurrence of the
side reaction of isobutylene polymerization; and, as a
consequence, the formation of toxic wastes which
require disposal.
An alternative to the existing industrial PTBP pro-
duction technology can be a technology based on the
high yield of the desired product, there are some dis- reaction of phenol alkylation with tert-butanol (TBA):
OH
OH
OH
C
+ H2O
CH3
+
CH3
CH3
CH3
CH3
C
CH3
In addition to desired p-tert-butylphenol, small amounts of the o-isomer (OTBP)
OH
OH CH3
C
CH3
OH
C
+ H2O
+
CH3
CH3
CH3
CH3
and 2,4-di-tert-butylphenol (2,4-diTBP)
714

SELECTING AN OPTIMUM CATALYST
715
CH3
C
OH
OH
CH3
OH
C
+ H2O
+
CH3
CH3
CH3
CH3
CH3
CH3
C
CH3
are usually formed in the process.
alyst settling, the reaction mixture was sampled for
analysis of the reaction products.
The products were analyzed by gas–liquid chroma-
tography on a Tsvet-800 chromatograph using a ZB-
WAX capillary column and a flame ionization detec-
tor or a Polisorb-1 packed column and thermal con-
ductivity detector.
Along with the phenol alkylation reactions, the
alcohol dehydration reaction yielding isobutylene
occurs:
OH
CH3
C
CH3
CH3
C
CH2
+ H O
.
2
CH3
CH3
RESULTS AND DISCUSSION
The aim of this study was to select an optimum cat-
alyst for phenol alkylation with tert-butanol that
would have high activity and selectivity for p-tert-
butylphenol.
It is known that irrespective of the type of the
alkylating agent, the mechanism of alkylation includes
the cation formation stage [1]. Therefore, it is possible
to use the same catalysts for both isobutylene and
TBA. Theses are acidic catalysts.
EXPERIMENTAL
In modern technologies for the production of para-
The chemicals used in the study were phenol and substituted phenol alkylation products, heterogeneous
tert-butanol and the catalysts tested were FIBAN K1 catalysts are preferred.
(Institute of Physical and Organic Chemistry,
There is no summarized information in the litera-
Belarus), Amberlyst 35 dry (DOW Chemical),
ture on the basis of which it can be judged whether one
Amberlyst 36 dry (DOW Chemical), KU-2-8 (prelim-
or another heterogeneous catalyst in optimal for phe-
inarily dried with tert-butyl alcohol on a water bath),
nol alkylation with tert-butanol. In particular, it was
zeolite beta CР814Е (Zeolyst International), finely
reported that PTBP is produced with a high yield using
divided zeolite beta (Angarsk catalyst and organic syn-
isobutylene over various sulfonated cation exchangers
thesis plant), and the same zeolite tableted and then
at high temperatures [2]; however, the behavior of sul-
crushed.
fonated cation-exchange resins with respect to TBA
The experiments were performed in a glass reactor
equipped with a reflux condenser, a thermowell, and a
sleeve for catalyst feeding and sampling. The reaction
mixture was agitated using an electrically driven stir-
rer. The reactor was heated using an electric
jacket. The temperature in the reactor was controlled
and measured using a set of instruments including a
TRM-101 single-channel microprocessor-based pro-
grammed temperature meter–regulator and a solid-
state relay.
was not mentioned. A good result on the selectivity for
PTBP over an MCM-22 zeolite and its modifications
was obtained in [3]. There is information about the use
of zirconia- or silica gel-supported tungstophosphoric
heteropoly acid as a catalyst [4]. Of zeolites, H-USY
and H-Beta were tested with tert-butanol [5]; it is the
zeolite H-Beta that was claimed to exhibit the best
PTBP selectivity (81%).
We studied commercial catalysts, sulfonated cat-
ion-exchange resins and zeolites beta, which demon-
strated the best results according to published data.
The reactants were loaded into the reactor in the
following amounts: 60.0 g of phenol and 16.5 g of
TBA. The phenol/TBA molar ratio was 3 : 1. The
reaction mixture was heated to 80–100°С with stir-
ring. The point of catalyst addition in an amount of
1.0 g to the reaction mixture was considered as the
reaction onset time. The catalysts based on FIBAN K-
1 and KU-2-8 sulfonated cation-exchange resin gels
were preliminarily placed in a phenol melt for swelling
over 5 h at 45°C. The reaction time was 2 h. After the
end of the specified period of time, the reactor was
Of the sulfonated cation exchangers, both gelled
(FIBAN К-1 and KU-2-8) and macroporous
(Amberlyst 35 dry and Amberlyst 36 dry) materials
were tested. For comparison, zeolites beta with the
same silica ratio of SiO2/Al2O3 = 25 produced by Zeo-
lyst International (CP814E) and the Angarsk catalyst
plant i were used. The experimental results of catalyst
testing are presented in Table 1.
The experiments were conducted at 80 and 100°C,
cooled to 25°C. After switching the stirrer off and cat- all other conditions being equal, in order to trace the
PETROLEUM CHEMISTRY Vol. 57 No. 8 2017

716
TEREKHOV et al.
Table 1. Experimental data for phenol alkylation with tert-butanol over various catalysts at 80°C
H-Beta
(Angarsk)
tablet.
Amberlyst
A35 Dry
Amberlyst
A36 Dry
H-Beta
(CР814Е)
H-Beta
(Angarsk)
Catalyst
KU2-8 FIBAN К1
Temperature, °C
80
7
80
18
75
33
100
23
80
17
73
21
100
22
80
15
73
32
100
18
80
15
76
35
100
17
80
17
80
35
100
20
100
18
Phenol conversion, %
TBA conversion, %
42
30
94
30
87
86
32
80
37
93
83
35
Selectivity of isobutylene
formation from TBA, %
22
35
PTBP
27
43
2
31
56
6
33
58
10
0
36
51
10
3
38
52
11
0
35
49
10
5
38
52
10
0
83
13
1
90
9
87
12
1
91
9
91
9
OTBP
Selectivity
of phenol
conversion, %
2,4-DiTBP
1
1
1
Phenyl-tert-
28
7
3
0
1
0
0
butyl ether
Yield of PTBP, %
2
6
8
6
8
5
7
12
15
15
18
16
trend in the temperature effect on the yields of all the temperatures leads to the growth in number of Lewis
products.
The sulfonated cation exchanger FIBAN K1 is a
sites and, as a consequence, a decrease in the catalyst
activity and selectivity for PTBP [5].
new material that is a nonwoven polypropylene fiber
with a grafted styrene–divinylbenzene copolymer.
The active sites are the sulfonated polymer. Its activity
turned out to be the highest of all the sulfonated cation
exchangers tested. Most likely, the positive effect in
activity is due to the increased external surface area
provided by the fibrous structure.
Zeolites H-Beta showed high PTBP selectivity
under the experimental conditions. This fact, as well
as a low yield of o- and di-tert-butylphenol under
moderate conditions, can be explained by the struc-
ture of zeolite pores, the radius of which functions as a
molecular sieve (0.67–0.71 nm). Since para-tert-
butylphenol is the least sterically hindered of all the
products (effective width of 0.67 nm), it is toward its
formation that the equilibrium shifts regardless of the
thermodynamic equilibrium.
KU-2-8 was excluded from consideration after the
experiment at 80°C, since it had shown the worst
result. Its activity in comparison to the other catalysts
appeared to be lower by a factor of 2–2.5, and the
PTBP selectivity was about 27%.
As is seen from the data in the Table 1, about one
third of tert-butyl alcohol is converted into isobutylene
over all the catalysts. Moreover, this ratio remains
unchanged with temperature. A portion of isobuty-
lene, depending on the temperature, remains dis-
solved in the reaction mixture, and this part reacts
with phenol to form tert-butylphenols if the reaction
time is prolonged. The other part undergoes transition
to the gas phase. In the case of appropriate organiza-
tion of the reaction stage, this isobutylene can be
effectively used to obtain an additional amount of
PTBP.
It should be noted that all the cation-exchange cat-
alysts including foreign mesoporous Amberlysts A35
and A36 demonstrated low selectivity for the target
product at both 80 and 100°C. The average
OTBP/PTBP ratio is 1.3 : 1. With the increase in the
temperature, some growth in the amount of the para-
substituted product is observed, a change that is con-
sistent with the thermodynamics of the process. How-
ever, to achieve an acceptable result (PTBP selectivity
of about 90%), higher temperatures (140–160°C) are
required. Unfortunately, the catalysts rapidly fail
under these conditions, since cation exchangers of this
kind remain stable only at temperatures of up to 110–
120°C because of their physicochemical properties.
Of all the catalysts considered, zeolite Beta (in
Н-form) (Angarsk catalyst plant) provides the highest
yield of PTBP. A moderate process temperature also
counts in favor of this catalyst because the PTBP
A different result was demonstrated by the experi- selectivity exceeds 90% already at 100°C. Therefore, in
ments with zeolites. During the preparation of the cat- addition to the high yield of the desired product, this
alysts, they were converted from the ammonium into catalyst is characterized by low tarring of the products
the hydrogen form in the temperature range from 100 and insignificant isobutylene polymerization and,
to 450°C. Under such calcination conditions, the hence, a long on-stream time, although this parameter
number of Brønsted acid sites on the zeolite surface should undoubtedly be experimentally tested in fur-
will be as high as possible because calcination at higher ther studies.
PETROLEUM CHEMISTRY
Vol. 57
No. 8
2017

SELECTING AN OPTIMUM CATALYST
717
In the experiments performed, the zeolite catalysts plant) can be used as the catalyst for the industrial pro-
were tested in a finely divided form, so that the reac- cess of p-tert-butylphenol production via phenol
tion proceeded in the kinetic region. However, opera- alkylation with tert-butyl alcohol. The highest selec-
tion with such a finely divided catalyst is fraught with tivity of zeolite beta for the product of interest (above
difficulties of its isolation from the reaction mixture. 90%) at low reaction temperatures (up to 100°C), as
Technologically, it is more -appropriate to run the well as the absence of leaching of the active acidic
process in the fixed-bed mode using large catalyst par- components into the reaction mixture, make it the
ticles. To evaluate the effect of the size of catalyst par- most attractive and promising industrial alkylation
ticles on its activity and product composition, we con- catalyst.
ducted a comparative experiment with Angarsk zeolite
beta tableted and crushed to a particle size of 2–3 mm.
REFERENCES
The experiment was carried out under the same con-
ditions. The result of this experiment is presented in
Table 1.
1. M. B. Smith, March’s Advanced Organic Chemistry:
Reactions, Mechanisms, and Structure (Wiley, Hobo-
ken, NJ, 2013), 7th Ed.
Because of the transition of the process to the
region of internal diffusion in large catalyst particles,
the catalyst activity decreases somewhat (by 7.6% rel-
ative to the conversion over the finely divided cata-
lyst). The selectivity values for all the products
remained at the same level. Therefore, the decrease in
the yield of the desired product with an increase in the
diameter of catalyst particles will be solely due to the
decrease in the catalyst activity.
2. I. O. Voronin, T. N. Nesterova, B. S. Strel’chik, and
E. A. Zhuravskii, Kinet. Catal. 55, 705 (2014).
3. K. Song, J. Guan, S. Wu, et al., Catal. Lett. 126, 333
(2008).
4. H.-L. Hsu and R. Selvin, J. Mater. Sci. Eng. 4 (11), 64
(2010).
5. E. Dumitriu and V. Hulea, J. Catal. 218, 249 (2003).
The results of this study showed that zeolite beta in
the H-form (Angarsk catalyst and organic synthesis
Translated by E. Boltukhina
PETROLEUM CHEMISTRY Vol. 57 No. 8 2017