The alkylation of naphthalene over one-dimensional fourteen-membered ring zeolites. the influence of zeolite structure and alkylating agent on the selectivity for dialkylnaphthalenes

Article abstract of DOI:10.1246/bcsj.81.1166

The alkylation, i.e., isopropylation, s-butylation, and t-butylation, of naphthalene (NP) was examined over one-dimensional fourteen-membered (14-MR) zeolites: CIT-5 (CF1), UTD-1 (DON), and SSZ-53 (SFH), and compared to the results over H-mordenite (MOR)

Full text of DOI:10.1246/bcsj.81.1166

1166 Bull. Chem. Soc. Jpn. Vol. 81, No. 9, 1166–1174 (2008)
ꢀ 2008 The Chemical Society of Japan
The Alkylation of Naphthalene over One-Dimensional
Fourteen-Membered Ring Zeolites. The Influence of Zeolite Structure
and Alkylating Agent on the Selectivity for Dialkylnaphthalenes
y
ꢀ
Yoshihiro Sugi, Hiroyoshi Maekawa, Hiroaki Naiki, Kenichi Komura, and Yoshihiro Kubota
Department of Materials Science and Technology, Faculty of Engineering, Gifu University, Gifu 501-1193
Received January 16, 2008; E-mail: ysugi@gifu-u.ac.jp
The alkylation, i.e., isopropylation, s-butylation, and t-butylation, of naphthalene (NP) was examined over one-di-
mensional fourteen-membered (14-MR) zeolites: CIT-5 (CFI), UTD-1 (DON), and SSZ-53 (SFH), and compared to the
results over H-mordenite (MOR) to elucidate how zeolite structure and alkylating agent play roles in the shape-
selective catalysis. The ꢀ,ꢀ-selectivities (for ꢀ,ꢀ-dialkylnaphthalene (2,6- and 2,7-dialkylnaphthalenes, ꢀ,ꢀ-DAN))
and the 2,6-selectivities (for 2,6-DAN) were varied with the types of zeolite and of alkylating agent. MOR gave high
ꢀ,ꢀ-selectivities in the all alkylations in the range of 150–300 ꢁC. However, the 14-MR zeolites, CFI, DON, and
SFH, gave much lower ꢀ,ꢀ-selectivities in the isopropylation: bulky and less stable ꢁ,ꢀ- and ꢁ,ꢁ-diisopropylnaphtha-
lenes (ꢁ,ꢀ-DIPN: 1,3-, 1,5-, and 1,7-DIPN); ꢁ,ꢁ-DIPN (1,4- and 1,5-DIPN) were predominantly obtained under kinetic
control at low temperatures, and stable and less bulky ꢀ,ꢀ-DIPN were formed under thermodynamic control at high tem-
peratures. The ꢀ,ꢀ-selectivities were higher than 95% over CFI in the s-butylation, and increased from 50–60% at
150 ꢁC to 75% at 300 ꢁC over DON and SFH, respectively. They were almost 100% in the t-butylation over all zeolites.
The alkylation over MOR occurred with high 2,6-selectivities in the range of 150–250 ꢁC: 60% for the isopropylation,
80% for the s-butylation, and 95% for the t-butylation. CFI, DON, and SFH gave the 2,6-selectivities in the range
of 5–30% in the isopropylation, 65%, 55%, and 50%, respectively, in the s-butylation, and higher than 80% in the
t-butylation. These different features are explained by the discrimination of the least bulky DAN isomers from the other
isomers by steric restriction with the zeolite channels at the transition states: ꢀ,ꢀ-DAN from the DAN isomers, and 2,6-
DAN from ꢀ,ꢀ-DAN. The bulkiness of alkylating agent also enhances the discrimination of the isomers, particularly,
between 2,6- and 2,7-DAN. The ꢀ,ꢀ- and 2,6-selectivities are synergistically governed by the zeolite channel and the
bulkiness of alkylating agents.
Shape-selective catalyses occur by differentiating reactants,
products, and/or reaction intermediates according to their
shape and size in sterically restricted environments of micro-
porous crystals.1–8 The selectivities for products are deter-
mined by molecular size and configuration of the pore-en-
trance and channel, as well as by the characteristics of its cat-
alytic center. Only a reactant molecule, whose dimension is
less than a critical size, can enter into the pore and react at
the catalytic site. Furthermore, only product molecules which
can diffuse out through the pores, will appear in the product.
The selectivity for product isomers is determined by the dis-
crimination of the least bulky isomers with the channels at the
transition states in the alkylation of aromatics: this is so called
‘‘restricted transition-state selectivity’’ as discussed in previous
papers.1 In this mechanism, fitting the transition state of the
least bulky isomer to zeolite channels is an important key
for highly shape-selective catalyses. There are also two other
mechanisms: ‘‘reactant selectivity’’ by the discrimination of
the bulkiness of reactants to enter the zeolite and ‘‘products se-
lectivity’’ by preferential diffusion from the zeolite.1 However,
if the channels are large enough to allow the transition state of
bulky isomers in the channels, the catalyses are governed by
kinetic and/or thermodynamic controls to yield predominantly
bulky isomers at low temperatures, and to yield thermodynam-
ically stable isomers with increasing temperature. These con-
siderations indicate that the discrimination of bulky molecules
from the channels is one of the key factors for shape-selective
catalysis by zeolites, and that it depends on the types of zeolite
and alkylating agent.
The isopropylation of polynuclear hydrocarbons, such as
naphthalene (NP) and biphenyl (BP) is a typical acid-catalyzed
reaction for demonstrating the shape-selective nature of zeo-
lites.4–15 Selective formation of the least bulky 2,6-diisopro-
pylnaphthalene (2,6-DIPN) and 4,40-diisopropylbiphenyl
(4,40-DIPB) is facilitated over zeolites if catalytic sites are ster-
ically restricted in the channels. In previous papers, we and
other workers described that 2,6-DIPN was selectively pro-
duced from NP over dealuminated H-mordenite (MOR).9–15
Catalytically active sites in MOR channels effectively exclude
the transition state of bulky DIPN isomers in the isopropyla-
tion, thus resulting in selective formation of the least bulky
2,6-DIPN.9 These results prompted us to study how the differ-
ence in dimensionality, pore size, and channel structures of
zeolite are related to the catalysis, and how the bulkiness of
alkylating agent influences the transition states to lead to the
shape-selective catalysis in zeolite channels. In previous pa-
y Present address: Department of Materials Science and Engi-
neering, Graduate School of Engineering, Yokohama National
University, Yokohama 240-8501
Published on the web September 11, 2008; doi:10.1246/bcsj.81.1166

Y. Sugi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008) 1167
Table 1. Properties of Zeolites
Pore
Topology entrance
Pore
Cagea) entrance
(MR)
Surface
SiO2
/Al2O3 /m2 gꢃ1
External
Pore
NH3 peak
Acid
Channel
structure
area surface areab) volume temperature amount
Zeolite
(FTC)
(MR)
/nm2
/m2 gꢃ1
35
/mL gꢃ1
0.16
/ꢁC
389
/mmol gꢃ1
0.20
Straight with
8-MR
channels
Slightly
corrugated
Straight
Largely
Mordenite MOR
12
—
0:67 ꢂ 0:72 128
460
CIT-5
CFI
14
14
14
16 0:72 ꢂ 0:75 160
0:70 ꢂ 0:95 200
22 0:65 ꢂ 0:88 64
339
403
385
38
15
83
0.14
0.16
0.11
294
288
316
0.13
0.12
0.26
UTD-1
SSZ-53
DON
SFH
—
corrugated
a) The member of the cages of the zeolites is the maximum size of oxygen rings estimated from data in the reference.26 b) Calculated
from t-plot of N2 adsorption.
ucts were analyzed by using a Gas Chromatograph GC-14A
(Shimadzu Corporation) equipped with TC-17 (25 m ꢂ 0:25 mm;
film thickness: 0.25 mm; GL Sciences) and/or HP-INNOWax
(60 m ꢂ 0:25 mm; film thickness: 0.5 mm; Agilent Technologies)
capillary columns. The products were also identified by using a
Gas Chromatograph-Mass Spectrometer GC-MS 5000 (Shimadzu
Corporation) by using the above columns.
The yields of alkylnaphthalene (AN) and dialkylnaphthalene
(DAN) isomers of each product are calculated on the basis of
the amount of starting NP, and the selectivities for each DAN iso-
mer are expressed based on total amounts of DAN isomers.
DAN in isopropylation, s-butylation, and t-butylation is defined
as DIPN, DSBN, and DTBN, respectively. ꢀ,ꢀ-DAN is defined as
a mixture of 2,6- and 2,7-DAN, ꢁ,ꢀ-DAN as 1,3-, 1,6-, and 1,7-
DAN, and ꢁ,ꢁ-DAN as 1,4- and 1,5-DAN. The ꢀ,ꢀ-, ꢁ,ꢀ-, and
ꢁ,ꢁ-selectivities are defined as the selectivities for ꢀ,ꢀ-, ꢁ,ꢀ-,
and ꢁ,ꢁ-DAN among DAN isomers, respectively. The 2,6- and
2,7-selectivities are the selectivities for 2,6- and 2,7-DAN among
DAN isomers, respectively.
pers, we discussed the alkylation of NP over one-dimensional
12-MR zeolites, MOR, SSZ-24 (AFI), SSZ-55 (ATS), and
SSZ-42 (IFR), and three-dimensional 12-MR zeolites,16 Y-
(FAU), ꢀ-(BEA), and CIT-1 (CON) zeolites by using propene,
1-butene, and 2-methylpropene as alkylating agent,17 and pro-
posed that a controlling factor for shape-selective formation of
ꢀ,ꢀ-dialkylnaphthalenes (ꢀ,ꢀ-DAN) and 2,6-DAN is steric re-
striction of the transition state by zeolite channels.
In this paper, we describe the alkylation, i.e., isopropylation,
s-butylation, and t-butylation of NP, over some recently found
one-dimensional 14-MR zeolites, CIT-5 (CFI) with slightly
corrugated (almost straight) channels, UTD-1 (DON) with
straight channels, and SSZ-53 (SFH) with largely corrugated
channels,18–25 and compared the formation of dialkylnaphtha-
lenes (DAN) to MOR with straight 12-MR channels. The dis-
cussion in this paper is based on the ꢀ,ꢀ-selectivity (selectivity
for ꢀ,ꢀ-DAN (2,6- and 2,7-DAN)) and the 2,6-selectivity (se-
lectivity for 2,6-DAN) among the DAN isomers in order to
focus key factors for controlling the catalysis in sterically re-
stricted environments of zeolites. The abbreviation of zeolites
is expressed by Framework Type Code (FTC) from the IZA
Structure Commission.26 Features on catalytic activities are
shown in Supporting Information.
The catalytic activities based on the yield of alkylated products
are shown in Figures S1–S6 in Supporting Information.
Results and Discussion
The Isopropylation. The isopropylation of NP over MOR,
CFI, DON, and SFH gave mixtures of isopropylnaphthalenes
(IPN), diisopropylnaphthalenes (DIPN), and triisopropylnaph-
thalenes (TriIPN). Catalytic activities increased with tempera-
ture; however, the conversion decreased at higher temperatures
in some cases. The decrease in conversion was accompanied
by a decrease in yield of DIPN and an increase in the yield
of IPN: this is due to de-alkylation of DIPN and IPN (see
Figures S1 and S2 in Supporting Information).
Experimental
Zeolites. CFI, DON, and SFH were synthesized according to
the literature.20,22,24 MOR was obtained from Tosoh Corporation
(SiO2/Al2O3 = 128; TSZ-690HOA). All zeolites were used as
Hþ-form in catalytic alkylation of NP. Table 1 shows typical
properties of zeolites related to the catalysis. Other results on
the characterization of the zeolites used in this work are shown
in our previous paper.27
The influence of reaction temperature on the selectivities for
DIPN isomers in the isopropylation of NP is shown in Figure 1
over MOR and CFI, and in Figure 2 over DON and SFH. The
products consisted of ꢀ,ꢀ-, ꢁ,ꢀ-, and ꢁ,ꢁ-DIPN isomers over
these zeolites, and they varied with the type of zeolite. The
ꢀ,ꢀ-selectivities were over 80–85% in the range of 150–
300 ꢁC in the isopropylation over MOR: the ꢁ,ꢀ- and ꢁ,ꢁ-
selectivities were less than 20%. However, the 14-MR zeolites,
CFI, DON, and SFH, gave much lower ꢀ,ꢀ-selectivities than
MOR. The ꢀ,ꢀ-selectivities over CFI gradually increased with
the increase in reaction temperature from 35% at 150 ꢁC to
65% at 275–300 ꢁC, accompanying the decrease in the ꢁ,ꢀ-
The Alkylation of NP. The alkylation of NP was carried out
in a 100-mL SUS-316 autoclave as described in our previous pa-
pers.16,17 Typical conditions of the isopropylation are: NP 6.42 g
(50 mmol), catalyst 0.25 g, reaction temperature 150–300 ꢁC, and
reaction period 4 h under propene pressure of 0.8 MPa (0.4 MPa
for 1-butene in the s-butylation and for 2-methylpropene in the
t-butylation). An autoclave containing NP and the catalyst was
flushed with nitrogen before heating. After reaching the reaction
temperature, propene was introduced to the autoclave, and the re-
action was started with agitation. The pressure was kept constant
throughout the reaction. After cooling the autoclave, the catalyst
was filtered off, and washed well with toluene. Liquid bulk prod-

1168 Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008)
Alkylation of Naphthalene over 14-MR Zeolites
MOR
CFI
100
100
80
60
40
20
0
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 1. The influence of reaction temperature on the selectivity for DIPN isomers in the isopropylation of NP over MOR
and CFI. Reaction conditions: NP, 50 mmol; catalyst, 0.25 g; temperature, 150–300 ꢁC; propene pressure, 0.8 MPa; period, 4 h.
Legends: : conversion; : 2,6-DIPN; : 2,7-DIPN; : ꢀ,ꢀ-DIPN; : ꢁ,ꢀ-DIPN; : ꢁ,ꢁ-DIPN.
DON
SFH
100
80
60
40
20
0
100
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 2. The influence of reaction temperature on the selectivity for DIPN isomers in the isopropylation of NP over DON and
SFH. Reaction conditions: NP, 50 mmol; catalyst, 0.25 g (DON); NP, 20 mmol; catalyst, 0.1 g (SFH). Other conditions and leg-
ends: see Figure 1.
and ꢁ,ꢁ-selectivities. Principal products over DON and SFH
were ꢁ,ꢀ- and ꢁ,ꢁ-DIPN, particularly at lower temperatures;
however, the ꢀ,ꢀ-selectivities increased with increase in tem-
perature: 5% at 150 ꢁC and 35% at 300 ꢁC for DON and 10% at
150 ꢁC to 25% for SFH at 300 ꢁC The ꢁ,ꢁ-selectivities de-
creased with increase in temperature over DON and SFH;
however, the ꢁ,ꢀ-selectivities remained constant for DON,
and increased for SFH.
The 2,6-selectivities in the isopropylation varied with the
zeolites similarly to ꢀ,ꢀ-selectivities. The 2,6- and 2,7-selec-
tivities over MOR were around 60% and 20% at low and mod-
erate temperatures below 275 ꢁC, respectively, although some
decreases in 2,6-selectivities and increases in 2,7-selectivities
occurred at 300 ꢁC. However, the 2,6-selectivities over the
14-MR zeolites were also much lower than those over MOR.
The 2,6-selectivities for CFI, DON, and SFH were 20%, 5%,
and 10% at 150 ꢁC, and they increased to 40%, 30%, and
25% at 300 ꢁC, respectively.
These results show that the mechanisms of the isopropyla-
tion are different by the type of zeolites, MOR, CFI, DON,
and SFH. MOR was shape selective for the formation of
ꢀ,ꢀ-DIPN; however, the 14-MR zeolites were not. These dif-
ferences are due to steric interaction of DIPN isomers in the
channels, which are invoked by the difference in structures,
such as pore entrance and channel—MOR: 12-MR pore en-
trance (0:67 nm ꢂ 0:72 nm) with straight channels; CFI: 14-

Y. Sugi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008) 1169
MOR
CFI
100
80
60
40
20
0
100
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 3. The influence of reaction temperature on the selectivity for DSBN isomers in the s-butylation of NP over MOR and CFI.
Reaction conditions: NP, 50 mmol; catalyst, 0.25 g (MOR); NP, 25 mmol; catalyst, 0.125 g (CFI); temperature, 150–300 ꢁC; 1-bu-
tene pressure, 0.5 MPa; period, 4 h. Legends: : conversion. : 2,6-DSBN; : 2,7-DSBN; : ꢀ,ꢀ-DSBN; : ꢁ,ꢀ-DSBN;
ꢁ,ꢁ-DSBN.
:
MR pore entrance (0:72 nm ꢂ 0:75 nm) and slightly corrugated
(almost straight) channel with 16-MR cages, DON: 14-MR
pore entrance (0:74 nm ꢂ 0:95 nm) with straight channel, and
SFH: 14-MR pore entrance (0:65 nm ꢂ 0:88 nm) and corrugat-
ed channel with 22-MR cages.26,28 Consequently, the reaction
space in zeolites is in the order: MOR < CFI ꢄ DON <
SFH, and steric restriction in the catalysis increases in the re-
verse order. MOR pores are small enough to discriminate the
less bulky ꢀ,ꢀ-DIPN from other bulky isomers. However, ster-
ic restriction of the channels of 14-MR zeolites is too loose for
shape-selective isopropylation, resulting in the operation of
kinetic and thermodynamic controls. Kinetic control is pre-
dominant at lower temperatures, i.e., a nucleophilic attack of
isopropyl cation to the electron-rich ꢁ-carbon of NP leads to
predominant formation of ꢁ,ꢁ- and ꢁ,ꢀ-DIPN. Thermody-
namic control also operates in the reaction with increase in
temperature, resulting in the predominant formation of less
bulky and stable ꢀ,ꢀ-DIPN.
The 2,6-selectivities also gave the discrimination of 2,6-
DIPN from other bulky isomers, particularly, between 2,6-
and 2,7-DIPN. The difference in steric interaction with the
channels between 2,6- and 2,7-DIPN was invoked by the dif-
ference in the bulkiness between two isomers. The high 2,6-
selectivities only appeared in the isopropylation over MOR,
and 14-MR zeolites, CFI, DON, and SFH, gave lower 2,6-
selectivities. These results mean that CFI, DON, and SFH
cannot discriminate 2,6- and 2,7-DIPN from other bulky
isomers although MOR can discriminate 2,6- and 2,7-DIPN
as previously discussed.10
because the selectivity for 2,6-DIPN in encapsulated products
maintained at around 70% even at 325 ꢁC (data not shown).
The s-Butylation. The influence of reaction temperature
on the s-butylation of NP over CFI, DON, and SFH was exam-
ined in order to know the influence of the bulkiness of alkylat-
ing agent on the catalysis, and compared to the results of
MOR. Similar catalytic activities in the s-butylation were ob-
served as in the isopropylation: s-butylnaphthalenes (SBN)
and di-s-butylnaphthalenes (DSBN) were obtained as princi-
pal products with small amounts of tri-s-butylnaphthalenes
(TriIPN) (see Figures S3 and S4 in Supporting Information).
Figures 3 and 4 show the influence of reaction tempera-
ture on the selectivities for DSBN isomers over MOR, CFI,
DON, and SFH. The ꢀ,ꢀ-selectivities were higher than 90%
for MOR and CFI. However, the ꢀ,ꢀ-selectivities over DON
and SFH were lower than those over MOR and CFI. They in-
creased gradually with increase in temperature: 50% at 150 ꢁC
to 75% at 300 ꢁC for DON and 60% at 150 ꢁC to 75% for SFH
at 300 ꢁC. The increase in the ꢀ,ꢀ-selectivities accompanied
the decrease in the ꢁ,ꢀ-selectivities. These results mean that
MOR and CFI can discriminate effectively ꢀ,ꢀ-DSBN from
other bulky ꢁ,ꢁ- and ꢁ,ꢀ-DSBN isomers by steric interaction
with the channels at their transition states. DON and SFH have
also some shape-selective nature for the formation of ꢀ,ꢀ-
DSBN; however, kinetic control also predominantly operates
at lower temperatures, and the contribution of thermodynamic
control increases with increase in temperature.
The higher ꢀ,ꢀ-selectivities in the s-butylation compared to
the isopropylation are invoked by the difference in the bulki-
ness of isopropyl and s-butyl moieties in DAN isomers. The
differences in the interaction of ꢀ,ꢀ-DSBN with the channels
are enhanced much compared to those of ꢀ,ꢀ-DIPN. Although
molecular diameters of ꢀ,ꢀ-DSBN are almost the same as
those of ꢀ,ꢀ-DIPN, the replacement of isopropyl moieties with
s-butyl ones will enhance the difference in the bulkiness of
The 2,6-selectivities decreased over MOR at high tempera-
tures, accompanying the increase in the 2,7-selectivities; how-
ever, the ꢀ,ꢀ-selectivities remained almost constant. This is
due to the isomerization of 2,6-DIPN to 2,7-DIPN because
the equilibrium mixture contains almost equal amounts of 2,6-
and 2,7-DIPN.17 The isomerization occurs at external acid sites

1170 Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008)
Alkylation of Naphthalene over 14-MR Zeolites
DON
SFH
100
100
80
60
40
20
0
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 4. The influence of reaction temperature on the selectivity for DSBN isomers in the s-butylation of NP over DON and SFH.
Reaction conditions: NP, 25 mmol; catalyst, 0.125 g. Other conditions and legends: see Figure 4.
ꢀ,ꢀ-DSBN from other bulky ꢁ,ꢁ- and ꢁ,ꢀ-DSBN in zeolite
channels. These differences enhance selective formation of
ꢀ,ꢀ-DSBN over these zeolites by the replacement of isopropyl
moieties with s-butyl ones. Thus, ꢁ,ꢀ- and ꢁ,ꢁ-DSBN in the
s-butylation are more easily excluded from the channels than
ꢁ,ꢀ- and ꢁ,ꢁ-DIPN in the isopropylation. These differences
in the channels may result in higher ꢀ,ꢀ-selectivities in the
s-butylation.
The 2,6-selectivities were also around 70–80% among their
isomers in the s-butylation over MOR and CFI as shown in
Figure 3. However, they were around 45–55% in the range
of 150–300 ꢁC over DON and SFH as shown in Figure 4.
The 2,7-selectivities were 5% for DON and 10% for SFH at
150 ꢁC; however, increased to 20% and 25%, respectively at
300 ꢁC. These results mean that channels of MOR and CFI
can discriminate the difference in the size of 2,6- and 2,7-
DSBN. DON and SFH have some shape-selective nature in
the s-butylation at low temperatures, although kinetic control
also operates. However, thermodynamic control enhanced
2,7-selectivities with increase in temperature although the
2,6-selectivities were almost constant. s-Butyl moieties in
DSBN isomers invoke the differences between 2,6- and other
isomers, particularly between 2,6- and 2,7-DSBN, in steric re-
striction with the channels of all zeolites, similarly to the dis-
cussion on ꢀ,ꢀ-selectivities.
amount of tri-t-butylnaphthalenes (TriTBN). However, catalyt-
ic activities were lower than that of the s-butylation and
isopropylation although they increased with temperature (see
Figures S5 and S6 in Supporting Information).
The ꢀ,ꢀ-selectivities were higher than 95% over MOR,
CFI, DON, and SFH in the range of 150–300 ꢁC in the t-butyl-
ation as shown in Figures 5 and 6. These results mean that
these zeolites have channels small enough for the discrimina-
tion of ꢀ,ꢀ-DTBN from other DTBN isomers. The high 2,6-
selectivities were also observed over all zeolites. The 2,6-se-
lectivities were higher than 95% over MOR at low and moder-
ate temperatures although they decreased to 60% at 300 ꢁC.
The 2,6-selectivities at 250 ꢁC were higher than 90% over
MOR and CFI; however, they were around 80% for DON
and SFH. These results indicate that the discrimination of
2,6- and 2,7-DTBN by the channels of DON and SFH is looser
than that by MOR and CFI. The differences are due to struc-
tural differences in channels of the zeolites. Reaction spaces
in DON and SFH are too large for exclusive formation of
2,6-DTBN.
The 2,6-selectivities also decreased at 300 ꢁC in the t-butyl-
ation of NP over MOR, CFI, and SFH accompanying the in-
crease in the 2,7-selectivities; however, the ꢀ,ꢀ-selectivities
almost stayed constant. The decrease in the 2,6-selectivities
is due to the isomerization of 2,6-DTBN to 2,7-DTBN at the
external acid sites similarly to the isomerization of 2,6-DIPN
in the isopropylation and of 2,6-DSBN in the s-butylation.
Shape-Selective Catalysis of the 14-MR Zeolites in the
Alkylation of NP. Catalytic performances of zeolites for
shape-selective catalysis are generally influenced by many fac-
tors.1,2 Some typical factors of zeolites are pore-entrance,
channel, and physical properties, such as crystal size, morphol-
ogy, and density and distribution of active species, which are
also influenced by preparation and post-synthesis methods. Re-
action conditions, such as temperature, pressure, period, and
catalyst amount, also influence catalytic performances. Among
these factors, pore-entrance and channel structures are the
The 2,6-selectivities decreased at 300 ꢁC in the s-butylation
over MOR; however, the ꢀ,ꢀ-selectivities remained almost
constant. This is due to the isomerization of 2,6-DSBN to
2,7-DSBN at external acid sites similarly to the isomerization
of 2,6-DIPN in the isopropylation.
The t-Butylation. Steric restriction among DAN isomers
by zeolite channels is enhanced by the bulkiness of alkylating
agents as discussed in the isopropylation and s-butylation. It is
interesting to know the influence of bulky alkylating agent,
2-methylpropene on the selectivity for DTBN isomers in the
alkylation of NP. The t-butylation gave t-butylnaphthalenes
(TBN) and di-t-butylnaphthalenes (DTBN) with a small

Y. Sugi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008) 1171
MOR
CFI
100
80
60
40
20
0
100
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 5. The influence of reaction temperature on the selectivity for DTBN isomers in the t-butylation of NP over MOR and CFI.
Reaction conditions: NP, 50 mmol; catalyst, 0.25 mg (MOR); NP, 25 mmol; catalyst, 0.125 mg (CFI); temperature, 150–300 ꢁC;
2-methylpropene pressure, 0.5 MPa; period, 4 h. Legends: : conversion; : 2,6-DTBN; : 2,7-DTBN; : ꢀ,ꢀ-DTBN;
ꢁ,ꢀ-DTBN; : ꢁ,ꢁ-DTBN.
:
DON
SFH
100
80
60
40
20
0
100
80
60
40
20
0
130 150
200
250
300 130 150
200
250
300
Reaction temperature /°C
Figure 6. The influence of reaction temperature on the selectivity for DTBN isomers in the t-butylation of NP over DON and SFH.
Reaction conditions: NP, 25 mmol; catalyst, 0.125 g. Other conditions and legends: see Figure 5.
most important keys for controlling shape-selectivity in the
catalysis.1,2
ments: the 2,7-DAN/2,6-DAN ratio should approach unity be-
cause of thermodynamic equilibrium.29
There are two types of selectivities for DAN isomers in the
alkylation of NP: ꢀ,ꢀ-selectivities and 2,6-selectivities. The
ꢀ,ꢀ-selectivities are due to discrimination of less bulky ꢀ,ꢀ-
DAN from bulkier ꢁ,ꢁ- and ꢁ,ꢀ-DAN because sizes of
DAN isomers decrease in the order: ꢁ,ꢁ-DAN > ꢁ,ꢀ-DAN >
ꢀ,ꢀ-DAN. The ꢁ,ꢁ- and ꢁ,ꢀ-selectivities are an index for the
bulky isomers formed principally under kinetic control. The
high ꢀ,ꢀ-selectivities also appeared for stable isomers under
thermodynamic control, which work particularly at higher
temperatures under sterically less restricted reaction environ-
The 2,6-selectivities are due to the discrimination of the
least bulky 2,6-DAN from its DAN isomers, particularly, be-
tween 2,6- and 2,7-DAN, because 2,7-DAN is slightly bulkier
than 2,6-DAN. If the channels are small enough to exclude
bulky isomers by steric limitation of transition states in the
channels, shape selective catalysis occurs to yield less bulky
isomers. However, shape-selective catalysis will not occur if
the channels are large enough for the formation of transition
states for bulkier isomers.
The differences in zeolite structures, particularly, pore-en-

1172 Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008)
Alkylation of Naphthalene over 14-MR Zeolites
Isopropylation
s-Butylation
t-Butylation
100
100
80
60
40
20
0
80
60
40
20
0
MOR CFI DON SFH MOR CFI DON SFH MOR CFI DON SFH
Figure 7. The selectivities for DAN isomers in the alkylation of NP over the zeolites. Reaction conditions: temperature, 250 ꢁC.
Other conditions: see Figures 1–6. Legends: : ꢀ,ꢀ-DAN; : ꢁ,ꢀ-DAN; : ꢁ,ꢁ-DAN; : conversion.
trance and channel also influence the shape-selective nature in
the alkylation as discussed above. The size of pore-entrance of
the zeolites in this study increases in the order: MOR <
CFI ꢄ SFH < DOH.26 However, they have different types
of channels: straight channels for MOR and DON, and corru-
gated channels with 16-MR cage for CFI, which are almost
straight only with small corrugation, and corrugated channels
with 22-MR cage for SFH (see Figure S7 in Supporting Infor-
mation).28 These differences suggest that reaction space in
zeolite channels is in the order: MOR < CFI ꢄ DON ꢄ
SFH, and steric interaction during the catalysis decreases in
the reverse order.
Figure 7 shows the influence of the types of zeolite and al-
kylating agent on the ꢀ,ꢀ-selectivities in the alkylation of NP
at 250 ꢁC. These are typical selectivities of the zeolites for
DAN isomers in the alkylation of NP because DAN isomers
were not significantly isomerized under reaction conditions
at 250 ꢁC.
The ꢀ,ꢀ-selectivities highly depend on the types of zeolite
and alkylating agent. They were enhanced by the bulkiness
of alkylating agents for all zeolites in this study. However,
they were also influenced by reaction space originating from
channel structures. Among zeolites, MOR was the most shape
selective for all alkylating agents in this study. MOR channels
most effectively fit the transition states of the least bulky ꢀ,ꢀ-
DIPN, and they effectively exclude the formation of other
bulky isomers. Among 14-MR zeolites, CFI gave higher
ꢀ,ꢀ-selectivities even in the isopropylation; however, DON
and SFH were not shape selective because their channels are
too large for the discrimination of ꢀ,ꢀ-DIPN from other bulky
isomers. Kinetic and/or thermodynamic controls are key fac-
tors for the isopropylation over DON and SFH as discussed
in previous sections. The increase in the ꢀ,ꢀ-selectivities in
the s-butylation and t-butylation were also observed for 14-
MR one-dimensional zeolites, CFI, DON, and SFH as well
as for MOR. These results mean that shape-selective nature ap-
pears over the 14-MR zeolites in the s-butylation, and these
zeolites are highly shape-selective in the t-butylation. The re-
placement of isopropyl moieties with bulky s-butyl and t-butyl
ones in DAN isomers invokes the difference in the bulkiness of
ꢀ,ꢀ-DAN from other isomers, because the replacement of
bulky alkyl groups increases steric interaction of the DAN iso-
mers with the channels. Particularly, the difference of the bulk-
iness between ꢀ,ꢀ- and ꢁ,ꢀ-DSBN in the s-butylation enhan-
ces the discrimination of less bulky ꢀ,ꢀ-DSBN isomers in the
zeolite channels although effective molecular diameters of
ꢀ,ꢀ-DSBN are almost the same as that of ꢀ,ꢀ-DIPN. t-Butyl
moieties in the DTBN isomers also enhance the ꢀ,ꢀ-selectiv-
ities in the t-butylation. Thus, ꢁ,ꢁ- and ꢁ,ꢀ-DTBN are effec-
tively excluded from the channels by the increase in the
bulkiness of alkylating agents in the order: isopropylation <
s-butylation < t-butylation.
Figure 8 shows the influence of the type of zeolite and
alkylating agent on the 2,6-selectivities at 250 ꢁC. Similar
changes of 2,6-selectivities were observed for ꢀ,ꢀ-selectivities
over MOR, CFI, DON, and SFH. MOR were selective for the
formation of 2,6-DIPN even in the isopropylation, and they in-
creased further in the s-butylation and t-butylation with the in-
crease in the bulkiness of alkylating agents. The bulkiness of
alkylating agents also enhanced the 2,6-selectivities over the
14-MR zeolites. The 2,6-selectivities were much improved
up to 50–60% in the s-butylation, and they were further im-
proved in the t-butylation: 90% for CFI and 80% over DON
and SFH. From these results, it is summarized that high ꢀ,ꢀ-
and 2,6-selectivities are obtained in the channels of the 14-
MR zeolite by the steric interaction by bulky alkylating agents.
The features of the ꢀ,ꢀ-selectivities and the 2,6-selectivities
over one-dimensional 14-MR zeolites, CFI, DON, and SFH,
are different from those over one-dimensional 12-MR zeolites,
MOR, AFI, ATS, and IFR,16 and three-dimensional zeolites,
FAU, BEA, and CON as reported in previous work.17
MOR and AFI gave high ꢀ,ꢀ-selectivities in all alkylations,
by using propene, 1-butene, and 2-methylpropene. However,
the ꢀ,ꢀ-selectivities over ATS and IFR were increased with in-
creasing bulkiness of alkylating agent: 40% for the isopropyla-
tion, 80% for the s-butylation, and almost 100% for the t-bu-
tylation. The ꢀ,ꢀ-selectivities over FAU, BEA, and CON also
increased with increasing the bulkiness of alkylating agents:

Y. Sugi et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008) 1173
t-Butylation
Isopropylation
s-Butylation
100
80
60
40
20
0
MOR CFI DON SFH MOR CFI DON SFH MOR CFI DON SFH
Figure 8. The 2,6- and 2,7-selectivities in the alkylation of NP over the zeolites. Reaction conditions: see Figure 7. Legends:
2,6-DAN; : 2,7-DAN.
:
30–40% in the isopropylation, 75–85% in the s-butylation,
and higher than 95% in the t-butylation, respectively. These
differences in the ꢀ,ꢀ-selectivities are due to synergistic ef-
fects of zeolite channels and bulkiness of alkylating agents
as discussed in previous sections. The precise fitting of the
transition state in the channels is essential for the high ꢀ,ꢀ-
selectivities. The low ꢀ,ꢀ-selectivities are due to kinetic and
thermodynamic controls because the reaction space is large
enough to allow the formation of bulky isomers.
The 2,6-selectivites in the isopropylation were as high as
60% and 50% over MOR and AFI, respectively at 250 ꢁC;
however, they were as high as around 20% over ATS and
IFR. The 2,6-selectivities were as high as 15–25% in the iso-
propylation over FAU, BEA, and CON. The channels of these
zeolites are too large for recognizing the difference between
2,6- and 2,7-DIPN. However, the increase in bulkiness of
alkylating agent enhanced the 2,6-selectivities over all zeolites
including ATS, IFR, DON, and SFH in the s-butylation and
t-butylation. On the other hand, over FAU, BEA, and CON
the increase in the bulkiness of alkylating agent improved both
2,6- and 2,7-selectivities because of the increase in the ꢀ,ꢀ-se-
lectivities: the ratio of 2,7-/2,6-DAN remained low even by
using bulky alkylating agent. Particularly, FAU gave predom-
inantly 2,6-DTBN; however, BEA and CON gave almost equi-
molar mixtures of 2,6- and 2,7-DTBN although ꢀ,ꢀ-DTBN
was formed exclusively: these features are different from
one-dimensional 12- and 14-MR zeolites. Although they can
recognize the differences in ꢀ,ꢀ-DTBN and the other isomers,
the channels of FAU, BEA, and CON are too large for the dis-
crimination of 2,6- and 2,7-DAN, and thermodynamic control
should partly operate at higher temperatures.
for 4,40-dialkylbiphenyl (4,40-DABP) with the increase in the
bulkiness of alkylating agent in the alkylation of BP over
one-dimensional 14-MR zeolites, CFI, DON, and SFH,27 over
one-dimensional 12-MR zeolites, MOR, AFI, ATS, and IFR,30
and over three-dimensional 12-MR zeolites, FAU, BEA, and
CON.31 High selectivities for 4,40-DABP originate from the
discrimination of 4,40-DABP from other isomers, particularly
from 3,40-DABP, at transition states. However, the difference
between 2,6- and 2,7-DAN was small compared to the differ-
ence between 4,40- and 3,40-DABP in the alkylation of BP.
In summary, the results discussed on the alkylation of NP
and BP over the zeolites indicate that the ꢀ,ꢀ- and 2,6-selec-
tivities for DAN isomers and 4,40-selectivities for DABP iso-
mers are synergistically governed by the type of zeolite chan-
nels and bulkiness of alkylating agents.
Conclusion
The selectivities for dialkylnaphthalene (DAN) isomers in
the alkylation, i.e., isopropylation, s-butylation, and t-butyla-
tion of naphthalene (NP) was studied over one-dimensional
14-MR zeolites, CIT-5 (CFI), UTD-1 (DON), and SSZ-53
(SFH), and compared to those over MOR. Two types of selec-
tivity, ꢀ,ꢀ- and 2,6-selectivities were observed in the alkyla-
tion of NP. These selectivities varied with the types of zeolite
and alkylating agent.
The ꢀ,ꢀ-selectivities, which are due to the discrimination of
ꢀ,ꢀ-DAN from their 12 isomers, were higher than 90% in the
isopropylation over MOR; however, those over CFI, DON, and
SFH were much lower than those over MOR: predominant iso-
mers over the 14-MR zeolites were bulky and less stable ꢁ,ꢀ-
DIPN (1,3-, 1,5-, and 1,7-DIPN) and ꢁ,ꢁ-DIPN (1,4- and 1,5-
DIPN) at low temperatures, and the formation of stable ꢀ,ꢀ-
DIPN (2,6- and 2,7-DIPN) increased with increasing tempera-
ture. The ꢀ,ꢀ-selectivities were higher than 95% in the s-bu-
tylation over MOR and CFI. They were lower for DON and
SFH although they increased with an increase in temperature.
The t-butylation gave almost 100% ꢀ,ꢀ-selectivities over all
zeolites. These results suggest the increase in the bulkiness
of alkylating agents enhances steric restriction even over the
From the results of the alkylation of NP over various
zeolites, it is concluded that ꢀ,ꢀ-DAN can be differentiated
from bulky isomers over zeolites with large reaction spaces
in the channels if bulky alkenes are used as alkylating agent,
and that the 2,6-selectivities appear by the discrimination of
small differences in steric interaction among DAN isomers
with zeolite channels.
In previous papers, we found an increase in the selectivities

1174 Bull. Chem. Soc. Jpn. Vol. 81, No. 9 (2008)
Alkylation of Naphthalene over 14-MR Zeolites
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zeolites with large reaction space, resulting in enhancing the
ꢀ,ꢀ-selectivities. Thermodynamic control also possibly partic-
ipates in higher temperatures to increase the ꢀ,ꢀ-selectivities.
The 2,6-selectivities, which are due to the discrimination of
2,6-DAN from other isomers, particularly between 2,6- and
2,7-DAN, increased by using bulkier alkylating agents. They
are higher than 60% in the isopropylation over MOR at mod-
erate temperatures below 275 ꢁC. Low 2,6-selectivities over
CFI, DON, and SFH were observed in the isopropylation;
however, they were enhanced in the s- and t-butylations.
These different features among zeolites are explained by the
discrimination of the least bulky isomers from other bulky iso-
mers at transition states by steric restriction with the zeolite,
where the difference in pore-entrance and channel structures
cause the difference in the isomers: ꢀ,ꢀ-DAN from the
DAN isomers; and 2,6-DAN from ꢀ,ꢀ-DAN. The bulkiness
of alkylating agent also enhances the discrimination of the iso-
mers, particularly, between 2,6- and 2,7-DAN. The ꢀ,ꢀ- and
2,6-selectivities are synergistically governed by the zeolite
channel and the bulkiness of alkylating agents.
13 P. Moreau, C. He, Z. Liu, F. Fajula, J. Mol. Catal. A:
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17 Y. Sugi, H. Maekawa, Y. Hasegawa, H. Naiki, K. Komura,
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A part of this work was financially supported by Grant-
in-Aid for Scientific Research (B) Nos. 16310056 and
19310030, the Japan Society for the Promotion of Science
(JSPS).
21 K. J. Balkus, Jr., M. Biscotto, A. G. Gabrielov, Stud. Surf.
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22 R. F. Lobo, M. Tsapatsis, C. C. Freyhardt, S.
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24 A. Burton, S. Elomari, C.-Y. Chen, R. C. Medrud, I.-Y.
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Supporting Information
Figures S1–S6: The influence of reaction temperature on the
yields of alkylates in the alkylation of NP. Figure S7: Models of
pore-entrances and channels of MOR, CFI, DON, and SFH topol-
ogies. This material is available free of charge on the Web at:
http://www.csj.jp/journals/bcsj/.
25 A. Burton, S. Elomari, C. Y. Chen, T. V. Harris, E. S.
Vittoratos, Stud. Surf. Sci. Catal. 2004, 154, 126.
26 Intern. Zeolite Assoc. http://www.iza-structure.org/
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27 Y. Sugi, H. Maekawa, S. A. R. Mulla, A. Ito, C. Naitoh,
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Bull. Chem. Soc. Jpn. 2007, 80, 1418.
28 The member of the cages of the zeolites is the maximum
size of oxygen rings estimated from the data in the reference.26
29 G. Takeuchi, H. Okazaki, T. Kito, Y. Sugi, T. Matsuzaki,
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