Iron-containing graphite as a Friedel-Crafts alkylation catalyst

Article abstract of DOI:10.1006/jcat.2001.3240

The activity of iron-containing graphites for the Friedel-Crafts reaction of phenol with tert-butyl halides was studied. The reaction of phenol with either different tert-butyl halides or tert-butyl alcohol on iron-containing graphite was conducted in a benzene solvent for 4 hr at 50°C. The Friedel-Crafts reaction of phenol with tert-butyl halides on graphite was in the following order: iodide > bromide > chloride. tert-Butyl iodide was the most active in the Friedel-Crafts of phenol in the presence of graphite, whereas it was the least reactive in the presence of AlCl₃. AlCl₃ was very highly active in phenol, while graphite was mildly reactive in phenol. The presence of iron accelerated the reaction of phenol with the tert-butyl halide on graphite to produced p-tert-butylphenol as the main product. The distance between the layers of graphite increased in the presence of both tert-butyl bromide and iron, but not in the presence of either the iron or tert-butyl bromide. tert-Butyl halide was first adsorbed on graphite and then dissociated to form tert-butyl and halogen ions. The Friedel-Crafts alkylation of phenol on graphite was accompanied by isomerization and dealkylation.

Full text of DOI:10.1006/jcat.2001.3240

Journal of Catalysis 201, 105–112 (2001)
doi:10.1006/jcat.2001.3240, available online at http://www.idealibrary.com on
Iron-Containing Graphite as a Friedel-Crafts Alkylation Catalyst
,1
Masatoshi Nagai,
Takeshi Yoda, Shinzo Omi, and Mistuo Kodomari†
Graduate School of Bio-applications and Systems Engineering, Tokyo University of Agriculture and Technology, 2-24 Nakamachi, Koganei, Tokyo
184-8588, Japan; and †Department of Industrial Chemistry, Shibaura Technological University, 3-9 Shibaura, Minato, Tokyo 108-8548, Japan
Received January 15, 2001; revised March 29, 2001; accepted March 29, 2001; published online May 31, 2001
were reported as a Brønsted catalyst instead of AlCl3. In the
case of clays, Fe- and Zn-modified montmorillonite (12–14)
and smectites (15) catalyzed the Friedel-Crafts alkylation.
On the other hand, graphite behaves like a Lewis acid and
is characteristic of a layered structure. Intercalation com-
pounds with many compounds in the layers are used to ob-
tain special properties. Graphite can be easily recovered by
simple filtration after the reaction and is reused without loss
ofactivity. Also, the processavailable with the graphite does
not produce waste acid liquids. Although graphite intercala-
tion compounds have been studied extensively (16–26), few
studies have been reported concerning utilization as cata-
lysts: graphites (27, 28) and FeCl3- and AlCl3-graphites (29,
30) were reported to catalyze the Friedel-Crafts as a Lewis
acid. Graphite-sulfuric acid (31) was reported to be active
for the isomerization of trimethylbenzenes and graphite-
potassium and lithium in THF for anionic polymerization
of lactones (32). In this study, the purpose of the present
paper is to facilitate the alkylation of phenol with tert-butyl
bromide on iron-containing graphite, to determine the pro-
moting effect of iron on the reaction, and to compare it
with the reaction in the presence of AlCl3. The relationship
among the surface and bulk properties of iron-containing
graphite and the catalytic activity and selectivity of three
kinds of tert-butyl halides (Cl, Br, and I) and the stage
structure of the iron-containing graphite with tert-butyl bro-
mide in the reaction were studied. The mechanism for the
Friedel-Crafts reaction of phenol with tert-butyl bromide
on the iron-containing graphite was also examined.
The activity of iron-containing graphites for the Friedel-Crafts
reaction of phenol with tert-butyl halides was studied. Graphites
were characterized by XRD and XPS. The reaction of phenol
with either various tert-butyl halides or tert-butyl alcohol on iron-
containing graphite was performed in a benzene solvent for 4 h at
50 C. The conversion and yield of the reaction on iron-containing
graphite decreased in the order, tert-butyl iodide, tert-butyl
bromide, and tert-butyl chloride, whereas for AlCl3, tert-butyl
chloride was the most reactive while tert-butyl iodide was the least.
Activated charcoal was not reactive. The presence of iron acceler-
ated the reaction of phenol with the tert-butyl halide on graphite
to yield p-tert-butylphenol as the main product. The presence of
both tert-butyl bromide and iron increased the distance between
the layers of graphite but not in the presence of either the iron or
tert-butyl bromide. tert-Butyl halide was first adsorbed on graphite
and then dissociated to form tert-butyl and halogen ions. The peak
˚
was observed at d = 11.9 A in the XRD pattern of the graphite
after the reaction in which the high purity graphite was treated
with tert-butyl halide and iron in phenol. This is probably due to
the mixture of phenol with tert-butyl ion and iron inserted into the
c
layers of graphite to form a two-stage structure.
2001 Academic Press
INTRODUCTION
The Friedel-Crafts reaction is known to be an important
method of introducing alkyl and acyl groups into aromatic
compounds. Aluminum chloride, in general, is the most
widely used catalyst for this reaction, but it is not easily
recovered. Wastes containing aluminum chloride stain the
equipment and are discharged to produce a large amount
of toxic acidic fluids. Acid solids have been proposed as
suitable catalysts for resolving these problems. Zeolites (1,
2), ZSM-5 (3, 4), mesoporous silica (5), and alumina (6)
catalyzed the shape-selective alkylation of benzene, phe-
nol, and naphthalene with formaldehyde and tert-butyl and
benzyl compounds. Furthermore, the acylation of anisole,
benzene, and p-xylene over heteropolyacids (7), sulfated
zirconia catalysts (8), Nafion/silica (9), and ZSM-5 (10, 11)
EXPERIMENTAL
Catalysts and Reagents
Phenol, o-tert-butylphenol, benzene (Kishida Chemical,
specific grade), Fe2O3, and FeCl3 (specific grade) were used
without purification. Synthetic graphite (Aldrich) (ALG),
produced from petroleum pitch and tars, was mainly used.
The other graphites also used for comparison included syn-
thetic graphite (Kishida Chemical; C, 99.9% ; Fe, 300 ppm;
other metals, 5 ppm) (KIG), mineral graphite (Kishida
Chemical, 78% ), high purity graphite (Tokai Carbon Co; C,
1 To whom correspondence should be addressed. Fax: +81-42-3887060.
E-mail: mnagai@cc.tuat.ac.jp.
105
0021-9517/01 $35.00
c
Copyright
2001 by Academic Press
All rights of reproduction in any form reserved.

106
NAGAI ET AL.
˚
99.99% ) (HPG), activated charcoal (Merck), and fullerene and 20 mA ( = 1.5418 A) with a scanning speed of 2
1
(Matsubo, a mixture of C60 and C70). Aluminum chloride, (2 ) min from 5 to 120 . The peaks in the spectra were
the tert-butyl halides (chloride, bromide, and iodine), and identified using JPCD cards. The XRD measurements were
tert-butyl alcohol (Kishida Chemical) were also used with- performed in order to determine the stage structure of the
out purification.
graphites after the reaction with the halides, the wetted
graphite, and the HPG treated with tert-butyl bromide and
iron: (Treatment A) the wetted graphite was separated after
the mixture of tert-butyl halide (bromide, iodide, or chlo-
ride) and ALG in the benzene solution was stirred at 50 C
for 2 h. (Treatment B) The wetted ALG graphite was sepa-
rated after bromine (2 ml) was added to the ALG graphite
(0.2 g) and sealed in a vial for 2 h. (Treatment C) The HPG
graphite was mixed with phenol and tert-butyl bromide in
the presence and absence of iron.
The surface areas of the graphites were measured at
78 K by nitrogen adsorption using a BET apparatus (Om-
nisorp, 100CX) after evacuation at 473 K and 1 Pa for 2 h.
X-ray photoelectron spectroscopy was carried out using a
Shimadzu ESCA 3200 photoelectron spectrometer with Mg
K radiation (1253.6 eV, 8 kV, and 30 mA). The sample was
mounted on a holder with silver collodion. Argon etch-
ing was done for 5 min before the XPS measurement. The
atomic ratios of the XPS O 1s/C 1s and Fe 2p/C 1s on
graphite were calculated by
Equipment and Procedure
The reaction was carried out in a 50-ml round-bottom
flask in a water bath, provided with a magnetic stirrer, a
thermocouple, and a reflux condenser connected to a 10%
aqueous solution of sodium hydrate to absorb acidic gas
formed during the reaction. The temperature in the water
bath was controlled by a thermocouple at 50 C. For each
conventional reaction, 8 mmol of phenol and tert-butyl bro-
mide and 4 g of graphite in 20 ml of benzene were simul-
taneously mixed and stirred at 50 C for 4 h. The reaction
was monitored using a syringe (0.1 ml) every 30 min by gas
chromatography. In order to study the preferential adsorp-
tion of tert-butyl bromide on iron-containing graphite, the
following two reaction procedures were used: (Method A)
The flask was charged with ALG, tert-butyl bromide, and
benzene and then stirred at 50 C for 1 h before the phenol
was added. (Method B) The flask was charged with ALG,
phenol, and benzene and then stirred at 50 C for 1 h be-
fore the tert-butyl bromide was added. Furthermore, tert-
butyl halide (bromide, chloride, or iodine) (2 mmol) was
added to the mixture of phenol (5 ml) with ALG at 20 C
for 1 h. For the reaction with AlCl3 instead of ALG, the
reaction products were extracted with diethyl ether after
the reaction. For the promoting effect of iron on the reac-
tion, Fe2O3 (0.004, 0.008, and 0.016 g) and FeCl3 (0.008 g)
were added to the mixture solution. The reaction prod-
ucts were analyzed using a Shimadzu GC-14B gas chro-
matograph equipped with flame ionization using an HR-
1 capillary column. o-tert-Butylphenol, p-tert-butylphenol,
bromophenol, and 2,4-di-tert-butylphenol were quantita-
tively analyzed using calibration curves. For the reaction
with AlCl3, the analysis was done using an internal stan-
dard method (naphthalene) after extraction of the reaction
mixture with diethyl ether. The reaction products were also
identified with a Hewlett-Packard 5890 gas chromatograph
coupled to a Jeol Automass System III mass spectrometer.
(peak area) (sensitivity factor for atoms including
apparatus factor)
in the spectra of carbon, oxygen, and iron in the graphites
fitted into XPS C 1s (282–294 eV (33)), O 1s (528–540 eV),
and Fe 2p (707–730 eV, a broad peak at 711.0 eV (Fe2O3)),
respectively.
RESULTS AND DISCUSSION
Activation of tert-Butyl Bromide on Graphite
The Friedel-Crafts reaction of phenol with tert-butyl
bromide on ALG is shown in Fig. 1A (Method A). Af-
ter tert-butyl bromide and ALG were added to benzene
solvent and stirred for 1 h, phenol was then introduced
into the benzene solution. The reaction products were
immediately observed after the phenol addition and p-
tert-butylphenol together with small amounts of o-tert-
butylphenol and 2,4-di-tert-butylphenol. The concentra-
tion of o-tert-butylphenol reached a maximum at 60 min
and then slowly decreased. The formation of 2,4-di-tert-
butylphenol gradually increased and reached a steady state
after 120 min. The yield of the three compounds was 59% .
The same trend was observed for KIG and mineral graphite.
However, when phenol and ALG were first mixed in ben-
zene for 1 h before addition of the tert-butyl bromide, an
The GC was equipped with a 2 m
fused-silica precolumn and a 30 m
capillary column. Conversion (% ) is given as the conversion
of the feed (phenol or o-tert-butylphenol) into the products
(o- and p-tert-butylphenols).
0.53 mm deactivated
0.32 mm J&W DB-1
Characterization of Graphite
Crystallographic identification of the graphites was per- induction period was observed for the formation of the re-
formed using powder X-ray diffraction with Ni-filtered action products in Fig. 1B (Method B). No reaction prod-
CuK radiation (XRD, a Rigaku X-ray diffractometer uct was observed for 20 min after the reaction, although
(RAD-IIC)). The X-ray diffraction was collected at 30 kV the conversion was about 10% . This is probably due to the

FRIEDEL-CRAFTS CATALYST
107
Iron-Promoted Graphite
The reaction of phenol with tert-butyl bromide in the
presence of various graphites is shown in Table 1. The re-
sults for the activated charcoal and fullerene are given for
comparison. The conversion over ALG was 60% with a
59% yield. The ALG graphite was more reactive with p-
tert-butylphenol and in a higher yield than AlCl3. The other
materials such as activated charcoal and HPG had no yield
with small conversion. Fullerene did not exhibit any activ-
ity for the reaction. These observations are due to only the
physical adsorption of phenol on the surface of graphite
without the reaction. Furthermore, the conversion on the
graphites and activated charcoal did not depend on the sur-
face area of the samples as shown in Table 1.
The ALG graphite originallycontained an amount ofiron
compared to the other graphites, while no iron wasobserved
in the activated charcoal listed in Table 2. The relationship
between the concentration of p-tert-butylphenol formed at
4 h and the ratio of iron to carbon (XPS Fe 2p/C 1s atomic
ratio) for various graphites is shown in Fig. 2A. The con-
centration of p-tert-butylphenol significantly increased with
the increasing Fe 2p/C 1s ratio. The ALG graphite with the
Fe 2p/C 1s ratio of 0.012 had a large concentration of p-tert-
butylphenol. A low concentration of the reaction product
was formed for KIG and HPG. No reaction occurred in the
presence of activated charcoal with added iron. This result
showed that the activity of the graphites was related to the
TABLE 1
Friedel-Crafts Alkylation of Phenol in the Presence of Various
Graphites, Fullerene, Activated Charcoal, and AlCl3
Selectivityd (% )
Surface area Conversiona–c Yield
1
Graphite
Synthesis
(m2 g
)
(% )
(% )
a
b
c
11
60
59
3
95
2
graphite, ALG
Synthesis
graphite, KIG
Mineral graphite
Highly pure
FIG. 1. (A) The addition of phenol after tert-butyl bromide and ALG
graphite were mixed and stirred in benzene for 1 h. (B) The addition of
tert-butyl bromide after phenol and ALG graphite were added and stirred
in benzene for 1 h.
8
40a
24
8
85
7
1
18
60a
22a
41
Trace
9
—
80
100
11
—
graphite, HPG
Fullerene
adsorption of phenol on ALG without the reaction tak-
ing place. The reaction products were observed in simi-
lar amounts after 20 min. This observation suggested that
tert-butyl bromide was displaced by some portion of the
adsorbed phenol on ALG for some time (induction time)
and reacted with the other adsorbed phenol. The induction
time was probably the time when tert-butyl bromide was
adsorbed on the graphite and then activated. Because no
induction time was observed on the addition of phenol after
mixing with tert-butyl bromide and with ALG, the reaction
of phenol with tert-butyl bromide did not occur until the
tert-butyl bromide had been adsorbed on the graphite.
0.5
0
0
Trace
53
—
—
2
—
100
96
—
—
2
(C60 + C70
Activated
charcoal
)
768
—
50b
89c
e
AlCl3
a,b
The difference in conversion and yield was approximately the per-
centage of the feed amount adsorbed on the agraphites (about 20% of
b
phenol) and activated charcoal (50% ).
c The difference was the percentage of unknown products.
d (a) o-tert-Butylphenol, (b) p-tert-butylphenol, and (c) c2,4-di-tert-
butylphenol were produced in the reaction.
e Reaction conditions: phenol (2 mmol), tert-butyl bromide (2 mmol),
AlCl3 (0.1 g), nitrobenzene (35) (5 ml) at 20 C.

108
NAGAI ET AL.
TABLE 2
selectivity of 45% for p-tert-butylphenol, although the con-
version was 15% without any yield at 4 h. The conversion of
57% corresponded to the consumed amount of 4.4 mmol
for the tert-butyl reagents. This value suggested that this
amount (0.4 mmol) of tert-butyl alcohol did react during
the reaction. Note that all the reactions with tert-butyl al-
cohol did not occur on the graphite. On the other hand, the
reactivity of the tert-butyl halides toward phenol in the pres-
ence of AlCl3 decreased in the following order: tert-butyl
chloride, tert-butyl bromide, and tert-butyl iodide. This re-
activity order of the tert-butyl halides in the presence of
AlCl3 is different from that in the presence of ALG.
Contents of Iron and Oxygen in the Graphites and Activated
Charcoal from XPS Measurement
Atomic ratio
Sample
O 1s/C 1s
Fe 2p/C 1s
Synthetic graphite (ALG)
Synthetic graphite (KIG)
Mineral graphite
Highly pure graphite (HPG)
Activated charcoal
0.150
0.036
0.181
0.203
0.435
0.0117
0.0010
0.0022
0.0009
0
iron content. In order to determine the promoting effect
of iron oxide (and chloride) on the reaction of phenol with
tert-butyl bromide, the addition of Fe2O3 to the solution in
the presence of HPG is shown in Fig. 2B. The conversion
increased with increasing Fe2O3 addition. A small amount
of Fe2O3 (0.008 g) increased the p-tert-butylphenol concen-
tration by twice that in the absence of Fe2O3. The addi-
tion of Fe2O3 tremendously shortened the induction time.
The reaction occurred on graphite in the presence of both
Fe2O3 and tert-butyl bromide. Furthermore, the addition
of FeCl3 to the reaction for HPG exhibited a conversion
of 50% at 10 h, and the conversion was similar to that in
the presence of Fe2O3. The two compounds exhibited the
same promoting effect on the reaction of phenol. In the
presence of Fe2O3, tert-butyl bromide was dissociated on
graphite to form tert-butyl and bromine ions. The latter ion
was likely to be associated with iron probably to form FeBr2
and FeBr3 (17, 24) in the layers of graphite. The tert-butyl
ion reacted with phenol during the exposure to graphite.
Hydrogen bromide formed during the reaction generates a
Lewis acid which was inserted into the graphite layers.
Reaction of Phenol with tert-Butyl Halides and Alcohol
on Graphites and Aluminum Halides
The reaction of phenol with three alkyl halides and tert-
butyl alcohol in the presence of ALG is shown in Table 3.
Aluminum halides were also used in the reaction of phe-
nol instead of ALG for comparison. For the reaction with
tert-butyl iodide, the conversion was 80% at 4 h with the se-
lectivity of p-tert-butylphenol at 64% . The reaction reached
a steady state 7 h after the reaction started. For tert-butyl
bromide, the conversion was 60% at 4 h. However, in the
case of tert-butyl chloride, the reaction products appeared
after 6 h and the conversion at 12 h was 64% . These results
showed that tert-butyl iodide was the most active of the
three halides with a good selectivity of p-tert-butylphenol.
tert-Butyl bromide as the reactant had a good yield but the
chloride was the worst. On the contrary, very little reaction
took place with tert-butyl alcohol. For the mixture of tert-
butyl bromide (4 mmol) and tert-butyl alcohol (4 mmol),
FIG. 2. (A) Relationship between the XPS Fe/C ratio of the various
graphites and the concentration of reaction products for 4 h run. (a) ALG,
(b) KIG, (c) mineral graphite, and (d) HPG. (B) The addition of Fe2O3 to
the conversion was 57% at 10 h (recovery of 43% ) with a HPG in the reaction of phenol.

FRIEDEL-CRAFTS CATALYST
109
TABLE 3
absence of tert-butyl bromide, 2,4-di-tert-butylphenol was
formed after the tert-butyl bromide addition. Furthermore,
p-tert-butylphenol and phenol were observed 90 min after
the addition. Because this reaction with tert-butyl bromide
did not take place in the absence of ALG, tert-butyl bro-
mide was dissociated to yield tert-butyl and bromine ions
on graphite. o-tert-Butylphenol reacted with the tert-butyl
ion to yield 2,4-di-tert-butylphenol. Also, o-tert-butylphenol
was isomerized to p-tert-butylphenol and dealkylated to
phenol with low selectivities. Therefore, the conversion re-
action of phenol into o- and p-tert-butylphenol with tert-
butyl bromide and the alkylation of o,p-tert-butylphenol to
2,4-di-tert-butylphenol were reversible.
Friedel-Crafts Alkylation of Phenol with Various tert-Butyl
Halides and Alcohol
Selectivityd (% )
tert-Butyl
halides and Time Conversiona–c Yield
Catalyst
alcohol
(h)
(% )
(% )
a
b
c
Graphitee
Cl
Br
I
OH
Cl
Br
I
12
4
4
4
1
64a
60
80b
15a
99c
89c
77c
41
59
46
0
65
53
33
16
3
11
—
1
61
94
64
—
95
96
75
23
2
25
—
4
f
AlCl3
1
1
2
8
2
17
a,b The difference in conversion and yield was approximately 20% of
phenol adsorbed on the graphites. For btert-butyl iodide, about 15% of the
feed amount was converted to unknown products.
Reactivity of Iron-Containing Graphite and AlCl3
The tert-butyl iodide and bromide were very reactive with
phenol in the presence of ALG and the reaction reached
a steady state at 4 h. However, tert-butyl chloride was less
c The difference was the percentage of unknown products.
d (a) o-tert-Butylphenol, (b) p-tert-butylphenol, and (c) 2,4-di-tert-
butylphenol were produced in the reaction.
e Reaction conditions: phenol (8 mmol), tert-butyl halide (8 mmol), active and the reaction products were less after more than
ALG graphite (4 g), and benzene (20 ml) at 50 C.
a 6-h reaction. An induction time was required to form
p-tert-butylphenol after the addition of phenol (Method
A). The formation of p-tert-butylphenol in the reaction of
f Reaction conditions: phenol (2 mmol), tert-butyl halide (2 mmol),
AlCl3 (0.1 g), nitrobenzene (35) (5 ml), and benzene (20 ml) at 20 C.
phenol with tert-butyl halide decreased with the decreas-
ing bond dissociation energy (C–Cl, 330; C–Br, 263; C–I,
209 kJ mol 1) (34). tert-Butyl iodide with the smallest bond
dissociation energy was then the most reactive toward phe-
nol on ALG. FeCl3 can also insert into graphite (17, 18,
20–22, 29) but tert-butyl chloride was much less active in
the Friedel-Crafts reaction of phenol. tert-Butyl bromide
was first dissociated to form tert-butyl and bromine ions
on graphite. The tert-butyl ion reacted with phenol while
the bromine ion was associated with the iron. The reaction
took place in the layers of graphite based on the carbocation
mechanism as follows.
Reaction of o-tert-Butylphenol
The reaction of o-tert-butylphenol with tert-butyl bro-
mide in the presence of ALG is shown in Fig. 3. Although
the reaction of o-tert-butylphenol did not occur in the
On the other hand, the reactivity of the tert-butyl halides
in the presence of AlCl3 decreased in the order: chloride >
bromide > iodide. The mechanism for the Friedel-Crafts
with AlCl3 is well known and fully established. This order
of reactivity corresponded to the electronegativity of the
halogen (Cl, 3.16; Br, 2.96; I, 2.66). The carbon and halogen
atoms of the tert-butyl halides were distorted and charged
+
as
and ; respectively. Therefore, the negative charge
was dislocated on the halogen (X) and decreased as fol-
lows: chlorine > bromine > iodine. tert-Butyl chloride was
the most reactive with AlCl3 to form a complex (AlCl3X –
R+) that acted as an electron acceptor. This reaction was
favorable for producing p-tert-butylphenol, because the
FIG. 3. Change in reaction products with reaction time during the
alkylation of o-tert-butylphenol at 50 C. (a) o-tert-Butylphenol and ALG
graphite in benzene. (b) o-tert-Butylphenol, o-tert-butyl bromide, and
ALG graphite in benzene.

110
NAGAI ET AL.
tert-butyl halides have larger distorted charges and were
coordinated to form a complex with AlCl3. When tert-
butylalcohol was used as the tert-butyl agent, it was hard
to react on ALG, because graphite probably showed no
Brønsted acid characteristics. However, because the reac-
tion took place with tert-butyl bromide in the mixture of
tert-butyl bromide and tert-butyl alcohol, the hydrogen bro-
mide that formed during the reaction reacted with tert-butyl
alcohol to form the tert-butyl carbocation. The tert-butyl ion
was finally reacted with phenol to form tert-butyl phenol in
the mixture of the alkyl halide and tert-butyl alcohol on
graphite.
Stage Structure of Graphites and Friedel-Crafts Mechanism
The graphites layered with bromine and iron bromide
are reported to be in a second stage structure (16, 17, 19,
20, 22–24). A model of the stage structure of bromine ion
insertion is shown in Fig. 4. The distance (d0) between the
˚
graphite layers is 3.35 A before the reaction. The relation-
ship between the stage structure and the layer distance is
as follows:
Ic = d1 + (n 1) d0,
[1]
where Ic is the distance in the stage cycle, d1 is the layer
distance of the graphite between the layers containing com-
pounds, and n is the stage number. The XRD patterns of the
ALG treated under the various conditions and the treated
HPG are shown in Table 4 and Fig. 5. The peak at d1 =
FIG. 5. XRD patterns of active charcoal and the graphites samples af-
ter the reaction and under various treatment conditions. (a) ALG graphite
before reaction, (b) ALG graphite after reaction, (c) ALG graphite treated
with tert-butyl bromide, (d) HPG graphite treated with tert-butyl bromide
and Fe2O3, and (e) (lower) XRD spectrum of graphite (lattice constant,
˚
11.9 A (2 = 7.40 ) was observed together with the char-
acteristic peaks for the ALG after the reaction (Fig. 5b)
and the HPG treated with Fe2O3 and tert-butyl bromide
(Treatment C). The peak was observed for the wet ALG
˚
˚
d = 3.35 A) and (upper) the layer-inserted graphite (d = 4.10 A) simulated
but disappeared for the dry ALG. No peaks appeared with using Cerius2.
tert-butyl chloride. The untreated ALG showed no enlarge-
ment of the layer distance and exhibited a strong peak at
˚
2
= 26.48 (d0 = 3.35 A; see d0 in Eq. [1]) together with
small peaks of 2 = 42.4 (100), 44.50 (101), 54.56 (004),
and 77.50 (110) as shown in Fig. 5a. The distance (d1) be-
˚
tween the layers increased to 6.98 A after insertion of the
bromine ion into the layers (Treatment B). Bromine ion
was inserted into the layered carbons in the stage structures.
˚
d1=7.02 (2 = 12.6 and 6.98 A (2 = 12.7 ) were observed
for the ALG treated with tert-butyl bromide (Treatment A)
(Fig. 5c) and for the ALG treated with bromine (Treatment
˚
B), respectively. These values of 7.02 and 6.98 A were close
˚
to d1 (7.04 A) of the bromine inserted in the graphite in the
FIG. 4. Stage structure of graphite intercalation with bromine.

FRIEDEL-CRAFTS CATALYST
111
TABLE 4
XRD Results of Iron-Containing Graphite Samples after the Reaction and under Various
Treatment Conditions
Treatment (A)a,c
Treatment (C)e,f
Fe2O3, tert-Butyl
bromide
After
reactiona,b
tert-Butyl
bromide
tert-Butyl
tert-Butyl
Treatment (B)a,d
Bromine
iodine
chloride
˚
Inserted layer d1/A
Graphite phase(002) d3/A
11.9
3.35
15.25
7.02
3.35
10.37
9.46
3.35
12.81
—
3.36
—
6.98
3.36
10.25
11.7e (11.9)f
3.36 (3.35)
15.06 (15.25)
˚
˚
Ic/A
a Before reaction: ALG, phase (002); ASTM card, 2 = 26.48 , d = 3.35 A.
˚
˚
b
Phenol, tert-butyl halide, benzene, and ALG at 50 C for 2 h. d1 = 11.9 A (2 = 7.40 ).
c tert-Butyl halide, benzene, and ALG at 50 C for 2 h.
d ALG in bromine solution in a vial for 2 h.
e,f
Phenol, tert-butyl bromide, benzene, HPG, and 0.008 g Fe2O3 at 50 C for 2e(5)f h. HPG alone (002): d0 = 3.35 A;
˚
no change in graphite distance was observed in the absence of Fe2O3 or tert-butyl bromide.
literature (18, 22, 23). No peak at 2 = 7.40 was observed tivated charcoal contained several kinds of carbonaceous
for the HPG with tert-butyl bromide in the absence of iron, carbon species and oxygen-containing groups such as hy-
but the peak was obtained for the treated HPG for 2 and droxyl, carbonyl, and carboxyl groups (33). The activated
5 h (Treatment C) (Fig. 5d). The presence of both tert-butyl charcoal was not active in the Friedel-Crafts reaction; there-
bromide and iron increased the distance between the lay- fore, these functional groups did not affect the reaction, but
ers of HPG but not in the presence of either the iron or the the rich -electron carbons of the graphite were responsible
tert-butyl bromide. Because ALG was likely to contain iron for the adsorption and dissociation of the tert-butyl halide
as Fe2O3 but not as FeBr3 (Br was not detected by XPS), on graphite and the reaction with phenol.
the Fe2O3 was converted to FeBr3 in the presence of hy-
The mechanism for the Friedel-Crafts reaction of phe-
drogen bromide formed in the reaction of phenol with tert- nol with tert-butyl bromide on graphite proceeded in sev-
butyl ion. Furthermore, a new peak at 2 = 13.0 appeared eral steps as shown in Fig. 6. tert-Butyl bromide was first
when the distance of the carbon layer increased from 3.35 adsorbed on graphite and dissociated to tert-butyl and
˚
to 4.10 A (only two carbon layers), according to the Cerius2
program (Fig. 5e). From the results, the appearance of the
˚
peak at d1 = 11.9 A was due to the wet ALG containing tert-
butyl, bromine ions, iron, phenol, and benzene. tert-Butyl
halide was first adsorbed and dissociated to tert-butyl and
halogen ions on the graphite. The dissociated tert-butyl ion
entered into the layers of graphite in the presence of iron.
˚
The increased layers (d1 = 11.9 A) are due to the reaction of
phenol with tert-butyl ion in the presence of iron in the lay-
ers similar to the insertion of biphenyl and tetrahydrofuran
with potassium in the graphite layer (25). Thus, the peak at
˚
d1 = 11.9 A is due to the reaction of phenol with tert-butyl
ion which was inserted with iron into the layer of graphite.
Another possibility would be that the bromine ion entered
˚
the layers of graphite, because d1 (11.9 A) in this reaction is
˚
˚
approximately 9.9 A (FeBr2; 9.55 A for FeBr3 (17, 24)). The
layered compound was formed in the two-stage structure.
In addition, a new peak was not observed in the presence of
tert-butyl chloride but formed in the presence of tert-butyl
iodide, and the graphite assumed the second stage struc-
˚
ture (d1 = 9.46 A). Also, it is reasonable that the d1 value of
tert-butyl iodide was greater than that of tert-butyl bromide
because of the larger iodine ion. Furthermore, activated
charcoal exhibited no peaks except for the broad peaks at
2 equal to about 20 , even in the presence of iron. The ac-
FIG. 6. Reaction mechanism for the Friedel-Crafts of phenol with
tert-butyl bromide in the presence of iron-containing graphite.

112
NAGAI ET AL.
bromine ions during the initial stage of the reaction. Fe2O3
or iron bromide (formed with hydrogen bromide) assisted
the removalofa bromine ion from tert-butylbromide (prob-
ably as a complex of the iron bromide) in the layers of
graphite. The tert-butyl ions were inserted into the layers of
graphite and reacted at the para position of the phenol to
yield p-tert-butylphenol, while the bromine ion reacted with
the hydrogen of tert-butylphenol to yield hydrogen bromide
in the graphite.
7. Izumi, Y., Onaka, M., and Urabe, K., Appl. Catal. A 132, 127 (1995).
8. Quaschning, V., Deutsch, J., Druska, P., Niclas, H.-J., and Kemnitz, E.,
J. Catal. 177, 164 (1998).
9. Heidekum, A., Hamm, M. A., and Hoelderich, F., J. Catal. 188, 230
(1999).
10. Reddy, P. R., Subrahmanyam, M., and Kumari, V. D., Catal. Lett. 61,
207 (1999).
11. Wang, Q. L., Ma, Y., Ji, X., Yan, H., and Qiu, Q., J. Chem. Soc., Chem.
Commun. 2307 (1995).
12. Cativiela, C., Garcia, J. I., Garcia-Matres, M., Mayoral, J. A., Figueras,
F., Fraile, J. M., Cseri, T., and Chiche, B., Appl. Catal. A 123, 273
(1995).
13. Clark, J. H., Kybett, A. P., Macquarrie, D. J., Barlow, J., and Landon,
P. , J. Chem. Soc., Chem. Commun., 1353 (1989).
14. Laszlo, P., and Mathy, A., Helv. Chim. Acta 70, 577 (1987).
15. (a) Izumi, Y., Urabe, K., and Onaka, M., Catal. Surveys from Jpn.
1, 17 (1997); (b) Urabe, K., Hisada, M., and Izumi, Y., Abstracts, 7th
Int. Symp. on Relation between Homogeneous and Heterogeneous
Catalysis, Tokyo, p. 437, 1992.
CONCLUSIONS
The Friedel-Crafts reaction of phenol with tert-butyl
halides on graphite decreased in the following order: iodide,
bromide, and chloride. tert-Butyl iodide was the most active
in the Friedel-Crafts of phenol in the presence of graphite,
whereas it was the least reactive in the presence of AlCl3.
Aluminum chloride was very highly active in phenol, while
graphite was mildly reactive in phenol. The reaction did not
occur until after the induction time when tert-butyl bromide
was adsorbed and dissociated into tert-butyl and bromine
ions on graphite. Bromide and iodide were readily inserted
into the layered carbons of graphite, while chlorine was
inserted with difficulty, and therefore hardly reacted with
phenol. Fe2O3 or iron bromide formed during the reaction
promoted the removal of bromine ion from tert-butyl bro-
mide and the insertion of tert-butyl ion into the layers of
the graphite. Phenol with tert-butyl ion in the presence of
iron entered the layers of graphite in the two-stage struc-
tures. The Friedel-Crafts alkylation of phenol on graphite
is accompanied by isomerization and dealkylation.
16. Kagan, H. B., Chemtech 510 (1976).
17. Stumpp, E., Mater. Sci. Eng. 31, 53 (1977).
18. Herein, D., Braun, T., and Schlo¨gl, R., Carbon 35, 17 (1997).
19. Mordkovich, V. Z., Synthetic Metals 63, 1 (1994).
20. Dresselhaus, M. S., and Dresselhaus, G., Adv. Phys. 30, 139 (1981).
21. Inagaki, M., and Ohira, M., Carbon 31, 777 (1993).
22. Takahashi, Y., in “New Development of Applied Carbon Material
Technology” (Japanese) (M. Inagaki, Ed.), pp. 93–115. Jisk., Tokyo,
1988.
23. Sasa, T., Takahashi, Y., and Mukaibo, T., Carbon 9, 407 (1971).
24. Stahl, V. H., Z. Anorg. Allg. Chem. 428, 269 (1977).
25. Beguin, F., Setton, R., Hamwi, A., and Touzain, P., Mater. Sci. Eng. 40,
167 (1979).
26. Herein, D., Braun, T., and Schlo¨gl, R., Mol. Cryst. Liq. Cryst. 245,
189 (1994).
27. Kodomari, M., Suzuki, Y., and Yoshida, K., J. Chem. Soc., Chem. Com-
mun. 1569, 1957 (1997).
28. Suzuki, Y., Kodomari, M., and Matushima, M., Chem. Lett., 319
(1998).
REFERENCES
29. Go¨ndo¨s, G., and Kapocsi, I., J. Phys. Chem. Solid 57, 855 (1996).
30. Lalancette, J.-M., Fournier, M.-J., and Thiffault, R., Can. J. Chem. 52,
589 (1974).
1. Armengol, E., Corma, A., Garc´ıa, H., and Primo, J., Appl. Catal. A
149, 411 (1997).
31. Tsuchiya, S., Fujii, K., Mitsuno, T., Sakata, Y., and Imamura, H., Bull.
Chem. Soc. Jpn. 64, 1011 (1991).
2. Miller, J. M., Goodchild, M., Lakshmi, J. L., Wails, D., and Hartman,
J. S., Catal. Lett. 63, 199 (1999).
32. Rashkov, I., Panayotov, I., and Gitsov, I., Poly. Bull. 4, 97 (1981).
33. Wild, U., Pfa¨nder, N., and Schlo¨gl, R., Fresenius,’ J. Anal. Chem. 357,
420 (1997).
3. Wu, X., and Anthony, R. G., J. Catal. 252, 112 (1999).
4. Choudhary, V. R., Jana, S. K., and Kiran, B. P., Catal. Lett. 59, 217
(1999).
34. McMurry, J., “Organic Chemistry,” 5th ed. Brooks/Cole, CA, 2000.
35. Pivsa-Art, S., Okuro, K., Miura, M., Murata, S., and Nomura, M.,
J. Chem. Soc.,Perkin. Trans. I, 1703 (1994).
5. Jun, S., and Ryoo, R., J. Catal. 195, 237 (2000).
6. Kamitori, Y., Hojo, M., Matsuda, R., Izumi, T., and Tsukamoto, S.,
J. Org. Chem. 49, 4165 (1984).