Alkylation of phenol with camphene in the presence of heteropolyacids supported on metal oxides

Article abstract of DOI:10.1134/S0036024413020246

Alkylation of phenol with camphene in the presence of supported heteropolyacids is studied. The main reaction products are found to be phenyl isobornyl ether, 2-isobornylphenol and 2-isocamphylphenol, the ratio between them being determined by the nature of heteropolyacid and carrier (ZrO ₂ or TiO₂).

Full text of DOI:10.1134/S0036024413020246

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2013, Vol. 87, No. 2, pp. 342–344. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © S.A. Popova, A.L. Tarasov, L.M. Kustov, I.Yu. Chukicheva, A.V. Kuchin, 2013, published in Zhurnal Fizicheskoi Khimii, 2013, Vol. 87, No. 2, pp. 350–352.
SHORT
COMMUNICATIONS
Alkylation of Phenol with Camphene in the Presence
of Heteropolyacids Supported on Metal Oxides
,c
S. A. Popovaa, A. L. Tarasovb, L. M. Kustovb , I. Yu. Chukichevaa, and A. V. Kuchina
aInstitute of Chemistry, Komi Research Center, Russian Academy of Sciences, Ural Branch, Syktyvkar, 167610 Russia
bZelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
cFaculty of Chemistry, Moscow State University, Moscow, 119991 Russia
eꢀmails: chukichevaꢀiy@chemi.komisc.ru; lmk@ioc.ac.ru
Received June 13, 2012
Abstract—Alkylation of phenol with camphene in the presence of supported heteropolyacids is studied. The
main reaction products are found to be phenyl isobornyl ether, 2ꢀisobornylphenol and 2ꢀisocamphylphenol,
the ratio between them being determined by the nature of heteropolyacid and carrier (ZrO2 or TiO2).
Keywords: phenol, camphene, Oꢀalkylation, Cꢀalkylation, heteropolyacid, titania, zirconia, catalysis.
DOI: 10.1134/S0036024413020246
INTRODUCTION
isopropyl and secꢀbutyl alcohols were effective in pheꢀ
nol orthoꢀalkylation [9, 10]. The authors argued that
the alkylation does not depend on the specific surface
of the catalyst and is due only to the acidity of the samꢀ
ples. No data on the use of heteropolyacids (HPA) in
the alkylation of phenols with terpenes were found in
the literature.
The alkylation of phenols attracts great interest
among researchers due to the highly valuable properꢀ
ties of synthesis products used in various fields of
industry and medicine. The antioxidative properties
and pharmacological activity of terpenophenols [1, 2],
which open up new prospects for the application of
these compounds on an industrial scale, contribute to
the interest in searching for selective and effective
methods for the alkylation of phenols. The synthesis of
these compounds is based on catalytic alkylation in the
presence of acidic catalysts, for which mineral or
organic acids, metal halides, cation exchange resins,
aluminosilicates and other compounds of acidic charꢀ
acter are usually applied [3–6]. As is well known, some
homogeneous organoaluminum catalysts have high
selectivity in the orthoꢀalkylation reaction of phenols
[3, 6, 7].
It should be noted that supported heteropolyacids
have additional advantages over zeolites. As a rule, the
range of catalytic applications of zeolites is limited to
molecules no more than 1 nm in size, since the dimenꢀ
sions of entrance windows and cavities are usually
0.4–0.65 and 1.0–1.3 nm. By using heteropolyacid
systems supported on sufficiently wideꢀporous supꢀ
ports (ZrO2, TiO2, Al2O3), these limitations are elimiꢀ
nated. Additionally, heteropolyacid systems are distinꢀ
guished by quite high thermal stability and can withꢀ
stand conditions of highꢀtemperature oxidative
regenerations.
Immobilized heteropolyacids have considerable
acidic properties comparable to those of zeolite Hꢀ
forms and of sulfated oxides. Supported heteropolyacꢀ
ids are widely used in a number of syntheses including
the isomerization of hydrocarbons and alkylation. Litꢀ
erature examples of phenol alkylation by means of
heteropolyacids are rather limited. The use of
12ꢀphosphotungstic acid supported on titanium oxide
In this work, the alkylation of phenol
phene in the presence of a number of heteropolyacꢀ
ids with the Keggin structure, H4[SiW12O40] H2O
and H3[PW12O40] H2O, and of H5PW11TiO10 mixed
1 with camꢀ
2
⋅
x
⋅
x
heteropolyacid supported on zirconium and titanium
oxides, is investigated. We studied these catalysts earꢀ
lier in the isomerization of saturated hydrocarbons
[11].
for the alkylation of pꢀcresol with tertꢀbutanol is
known from [8]. The most active catalyst turned out to
be a system of 20% 12ꢀtungstophosphoric acid on TiO2
calcined at 700°C. It promoted the formation of
EXPERIMENTAL
2ꢀtertꢀbutylcresol with a selectivity of 89.5% at a conꢀ
version of 82%.
Samples of H3PW12O40
· xH2O (HPWO) and
H4[SiW12O40] H2O (HSiWO) heteropolyacids
⋅
x
Catalysts based on 12ꢀtungstophosphoric acid supꢀ (Acros Chemical) were used in this work. Samples of
ported on ZrO2 and Al2O3 used to alkylate phenol with H5PW11TiO10 (HPWTiO) was prepared by
342

ALKYLATION OF PHENOL WITH CAMPHENE IN THE PRESENCE
Results from phenol alkylation with camphene
343
Selectivity, %
No.
Catalyst
Т,
°
C
τ
, h
C, %
3a
3b
4a
4b
TP
1
2
3
4
5
HPWO/ZrO2
HSiWO/ZrO2
HPWTiO/ZrO2
HPWO/TiO2
HSiWO/TiO2
100
100
100
100
100
3
4
4
2
3
75
66
61
64
61
46
52
61
10
15
10
13
7
19
15
14
49
46
12
11
8
7
7
5
28
28
16
21
Note: C—phenol conversion; TP states for terpenophenols with other types of terpene substituent.
M.N. Timofeeva (Institute of Catalysis, Russian room temperature. Signals of chloroform were used as
Academy of Sciences, Siberian Branch, Novosibirsk).
our internal standard (δН = 7.26 ppm, δС
=
76.90 ppm). The signals were classified using 13C
NMR spectra registered in JMOD mode. The volatile
reaction products were analyzed by GLC on a Shiꢀ
madzu GCꢀ2010AF apparatus equipped with a flame
ionization detector (carrier gas, helium) on a capillary
ZrO2 was prepared via the calcination of a comꢀ
mercial sample of Zr(OH)4 (Magnesium Electron
Co., grade XZO632/03; S
= 150 m2/g) at 773 K for 2 h
in an air flow. Samples of TiO2 (Degussa Aerolist, S =
260 m2/g) was used in this work.
Supported samples were prepared by the impregnaꢀ
tion of air dried zirconia and titania (at 373 K for 2 h)
with aqueous solutions of corresponding heteropolyꢀ
acids. The content of applied HPA was equal to
20 wt %. The samples were dried at 373 K for 4 h, folꢀ
lowed by calcination in an air flow at 673 K for 2 h.
column HPꢀ1 (Agilent, 60 m
temperature profile, 100–240
×
0.25 mm
; heating, 6 K/min).
×
0.25 m;
µ
°
C
RESULTS AND DISCUSSION
Alkylation was performed at a temperature of
373 K. Phenol and camphene were taken in the ratio
of 1 : 1; the reaction was conducted under stirring for
2–4 h. 1H and 13C NMR spectra of the obtained subꢀ
stances were recorded on a Bruker Avance II 300 specꢀ
The main results from catalyst testing are presented
in the table.
Phenyl isobornyl ether (3a), 2ꢀisobornylphenol
4a), and 2ꢀisocamphylphenol (4b) were isolated as
(
trometer (300 and 75 MHz, respectively) in CDCl3 at the main products (see the reaction scheme below).
OH
OR
OH
R
catalyst
*
*
+
+
,
R =
1
2
3
4
a
b
Alkylation of phenol on catalysts with heteropolyꢀ tion was previously observed for the alkylation of
acids supported on zirconia (table, samples 1–3) proꢀ
ꢀcresol with camphene in the presence of mineral acids
ceeded mainly with the formation of phenyl isobornyl and clays (askanite, montmorillonite KSF) [3, 10].
p
ether, i.e., as Oꢀalkylation (vide supra, 3a) with very
From the obtained data, it follows that the activity
of heteropolyacids both for samples supported on zirꢀ
conia and for systems based on titanium oxide grows in
the series
similar yields (34, 34, and 37%, respectively).
Using the same 12ꢀphosphotungstic and 12ꢀsilicoꢀ
tungstic acids supported on titanium oxide, the reacꢀ
tion proceeded in different directions to form mainly
Cꢀalkylated products. Phenol terpene ethers were
formed in minor amounts. Rather similar results in
terms of yields and process selectivity were obtained
for two catalyst samples (table, samples 4 and 5).
2ꢀIsocamphylphenol (see above, 4b) was obtained
HPWO > HSiWO > HPWTiO.
This series correlates with the order of the acidic
properties of these heteropolyacids and their activity
changing in the reaction of С4–С6ꢀalkane isomerizaꢀ
tion studied in [11].
In accordance with the conclusions drawn in [11],
with selectivities of 49 and 46% at conversion rates of more acidic and more active catalysts are obtained
64 and 61% for 20% HPWO/TiO2 and 20% when zirconia is applied, relative to those obtained by
HSiWO/TiO2, respectively. This direction of alkylaꢀ applying titania.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 87
No. 2 2013

344
POPOVA et al.
The main difference between the catalytic properꢀ
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No. 2 2013