Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H3PWI2040.
React. Kinet. Catal. Lett., Vol. 46, No. i, 17-23 (1992)
ALKYLATION OF p-SUBSTITUTED PHENOLS BY HETEROPOLY ACIDS I.V. Kozhevnikov, A.I. Ts~zganok, M.N. Timofeeva, S.M. Kulikov and V.N. Sidelnikov Institute of Catalysis, Novosibirsk 630090, USSR
Received: April 24, 1991 Accepted: June 25. 1991
Liquid-phase alkylation of p-tert-butylphenol
(TBP)
and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids and 25~ H3PWI2040/SiO 2 at 100-150 ~
(HPA) H3PWI2040 provides high
yields of mono- and disubstituted products. HPAs are more active than H2SO 4, easily separated from the reaction mixture and can be used repeatedly.
AnK~nnposaH~e n a p a - T p e T - S y T n n r one~HHaMH ~ 0 e H a H n X n O p ~ O M
(TB@) ~ napa-Kpesona
B ~M~KO~ ~a3e B HpMcyTCTBHH
TBep~IX FeTepononHKHCn0T (FnK) H3PW12040 ~ 25% H3PW12040/ SiO 2 HpM ]00-]50Oc ~aeT c BDICOK~M BblXO~0M MOHO- H ~M3aMe~eHHNe Hpo~yKTbl.
FII~ aKTHBHee, qeM H2S04, neP~o OT-
~eZ~DTCS OT peSHHHOHHO~ MaCCbl M MOPyT ~51TB HCHO~SSOBaHbl ~OBTOpHO.
Heteropoly acids have been extensively used as catalysts for organic synthesis butylphenol
[13. We have studied alkylation of p-tert-
(TBP) by olefins and benzyl chloride
(BzCl) into
2,6-dialkyl derivatives of TBP in the presence of H3PWI2040 and 25% H3PWI2040/SiO 2. Experiments have also been carried out to study alkylation of p-cresol by isobutylene over HPA. Alkylation of aromatic hydrocarbons in the presence of HPA has been reported
previously [2,3].
Akad~miai Kiad6,
Budapest
KOZHEVNIKOV et al, : HETEROPOLY ACIDS
EXPERIMENTAL Chemical water. 04-6
grade H 3 P W I 2 0 4 0 - 1 5
25% H 3 P W I 2 0 4 0 / S i O 2 was p r e p a r e d
silica
by a w a t e r
gel
(surface
solution
area and p a r t i c l e 0.2 mm,
to GLC data.
Freshly
Analytical
further
Alkylation
lution
distilled
was c a r r i e d
increased
The surface
344 m2/g and
prepared
were
0.1-
through
heat-
contained
and b e n z y l
solvents
or heptane
(50 h -1)
according chloride
were
used w i t h o u t
was a n a l y z e d
RESULTS
stirring,
~
~
the m o l t e n
by GLC.
Products
mixture
= 3:1.5
passing
containing mixture.
identified
was
then
was stirred
alkylated
= i:i.i,
p-cresol
were
slowly, agent was
The t e m p e r a t u r e
was
(300
TBP or its so-
Then very
h. p - C r e s o l
by a C H 3 C I 3 / H 2 0
at TBP/olefin
intensive
an a l k y l a t i n g
and the r e a c t i o n
and p - c r e s o l / o l e f i n
reactor under
to m o l t e n
at 100-110
for 0.5-7.0
through
treated
was added
~
its p o l y m e r i z a t i o n .
to 130-150
at 90 ~
ate was
out in a glass
of 1 h, under
temperature
butylene
at
by isoisobutyl-
HPA.
Organic
Alkyllayer
by MS-GLC.
AND D I S C U S S I O N
HPAs
are known
by olefins
to be effective [2,3].
to 2 , 6 - d i a l k y l p h e n o l s . of TBP is more cyclohexene,
l-hexene,
m a i n products yield b a s e d styrene.
But this
catalysts reaction
We have e s t a b l i s h e d
selective
ence of bulk HPA
(Table
styrene
(i wt.%
for a l k y l a t i o n
has
that the a l k y l a t i o n
i) . The r e a c t i o n and benzyl
on TBP)
takes
It yields
The most
selective
of
low s e l e c t i v i t y of TBP with
chloride
place
in the pres-
at 110-150 ~
are 2 , 6 - d i a l k y l - 4 - t e r t - b u t y l p h e n o l s
on TBP.
at 100% c o n v e r s i o n
18
olefins
grade
of IKT-
1.2 cm3/g)
respectively,
and 100-150
The catalyst
to e l i m i n a t e
phenol
HPAs were
substance,
or c h e m i c a l
in decane
over a p e r i o d
ene
in air~
were
for 2 h. TBP and p - c r e s o l
= 1:2.7 mol/l
stirring.
added
pore volume
purification.
and T B P / B z C I
this
Anhydrous
at 220 ~
from
via i m p r e g n a t i o n
360 m2/g,
of HPA and then dried
and 99% for the main
used.
rpm)
area
size of the c a t a l y s t
respectively.
ing in v a c u u m 99.5%
H20 was r e c r y s t a l l i z e d
with
is the reaction
Its
63-90% with
90% 2 , 6 - b i s ( l - p h e n y l e t h y l ) - 4 - t e r t - b u t y l p h e n o l of TBP
(100-110
~
1 h) . In the case of ~-
KOZHEVNIKOV et al. : HETEROPOLY ACIDS
methylstyrene
the predominant
reaction
is monoalkylation
70% yield of 2-cumyl-4-tert-butylphenol. produces
2-hexyl-4-tert-butylphenol
and 2,6-dihexyl-butylphenol,
consisting of two isomers with different yl group.
The yield of 2,6-dialkyl
when the reaction and decane.
is carried out in solvents
increases
of the hex-
of TBP rises
such as heptane
if the HCI formed is removed
the system by an argon flow. zation of olefins,
The side reactions
dealkylation
If after TBP alkylation o-xylene at ~rH/TBP = 5:1 2,6-dialkylphenols
separating
structures
derivatives
In the case of BzCI the yield of 2,6-dibenzyl-4-
tert-butylphenol
system,
with
Reaction with 1-hexe-
(mol/mol),
of phenols.
hydrocarbon,
e.g.,
is added to the reaction
can be obtained
2,6-dialkyl-4-tert-butylphenol.
the tert-butyl
are oligomeri-
and transalkylation
an aromatic
from
in situ without The displacement
group takes place quantitatively
according
of
to
the equation
0
R,~R
+
The dealkylation the tert-butyl
~-~R
proceeds
smoothly
with cyclohexane
alkylation.
in the presence
dicyclohexylphenol
easily separated
synthesis.
Me
after olefin intro-
Thus the reaction of TBP
of o-xylene
(Table i). This method
of 2,6-dialkylphenols
ates of organic
R +
even if the acceptor of
group is added immediately
duction prior to complete
preparation
e
~Me
yields
77% of 2,6-
is convenient
that are valuable
for the
intermedi-
Both bulk and supported HPAs are
from the reaction mixture
and can be used re-
peatedly. Apparently, heterogeneous
TBP alkylation
process,
the reaction system.
in the presence
of HPAs is a
since HPAs are practically
The activities
insoluble
of crystalohydrates,
in
e~g.
19
KOZHEVNIKOV
et al. : H E T E R O P O L Y
ACIDS
0 0 -M 0
q~ 0
tY
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p~
kl~
kO
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tY
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r
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+
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o
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0 0
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J
lm
K O Z H E V N I K O V et al.: HETEROPOLY ACIDS
L) 0
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o~
.IJ 4a
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0 ,--t
I o
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L~ .~ ~
r~
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il
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m
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on
0
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0
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n~ CO
t.~ 0
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2~L
KOZHEVNIKOV et al. : HETEROPOLY ACIDS
H 3 P W I 2 0 4 0 - 1 5 H 2 0 , and of a n h y d r o u s
HPAs
are close.
catalyst
25% H 3 P W I 2 0 4 0 / S i O 2 is less active
I g HPA.
This
ton centers
of HPA when
into a c c o u n t tically 1%
can be due to a decrease
that
(the surface
one a c c e s s i b l e magnitude
[5], whereas
is -100 ~2
on SiO 2 [4].
acidic
center
centers
in u n s u p p o r t e d
[5]),
of pro-
Taking are prac-
H P A only about
and the c r o s s - s e c t i o n
the a c t i v i t y
can be higher
of bulk HPA per
by two orders
of
than that of 25% H P A / S i O 2.
HPA is m u c h more ble
it is supported
area of HPA is i-5 m2/g
of a HPA m o l e c u l e
than bulk HPA per
in the s t r e n g t h
in 25% H P A / S i O 2 all acidic
accessible
The s u p p o r t e d
2), w h i c h
active
than H2SO 4 in TBP a l k y l a t i o n
can be due to its stronger
into account
the n u m b e r
be s u g g e s t e d
to be by 4 orders
accessible
proton
of a c c e s s i b l e
of m a g n i t u d e
velocity
[13.
centers, more
Taking HPA can
active
per one
(i.i mol,
space
than H2SO 4 in this reaction. Table
Alkylation
acidity
acidic
(Ta-
of p - c r e s o l 50 h -1)
(i mol)
2
by isobutylene
in the presence
of H 3 P W I 2 0 4 0 " I 5
H20 and
H2SO 4 at 90 ~
HPk
Catalyst
Time
(wt.%)
(h)
(0.i)
4
5
80
15
5
Ii
77
12
95% H2SO 4 (2.0)
Alkylation selectively groups.
Composition p-cresol
of p - c r e s o l
by i s o b u t y l e n e
in the o r t h o - p o s i t i o n
The HPA is insoluble
heterogeneously. and H2SO 4 under
Data
conditions
reaction
providing
2-tert-butyl-4-methylphenol s o l / C 4 H 8 > 1 the m a i n p r o d u c t
22
without
in p-cresol
for this
are shown
(mol.%)
2-tert-butyl-4-methylphenol
2,6-di-ter~ butyl-4-met~ ylphenol
over HPA takes migration
place
of alkyl
and a p p a r e n t l y
reacts
in the p r e s e n c e
of HPA
predominant in Table
formation
of
2. With p - c r e s o l
is 2 , 6 - d i t e r t - b u t y l - 4 - m e t h y l p h e -
KOZHEVNIKOV et alo : HETEROPOLY ACIDS nol) ~ C o n c e n t r a t i o n s their m i n i m a l This permits
values,
at which
us to compare
count the number by 4 orders
of HPA and H2SO 4 are taken the r e a c t i o n
of m a g n i t u d e
proceeds
their a c t i v i t i e s .
of a c c e s s i b l e
protons,
higher
to be close
Taking
smoothly. into ac-
the a c t i v i t y
compared
to
of HPA is
to H2SO 4 than in the
case of TBP alkylation. The authors ance
are thankful
to A.P.
Krysin
for his a s s i s t -
in our study.
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23
