Tert-Butylation of toluene with tert-butyl alcohol over immobilized titanium species on the Al-MCM-48

Article abstract of DOI:10.1016/j.molcata.2015.07.001

A series of Ti-Al-M48 (M48 stand for MCM-48) samples with different titanium species loadings were prepared by immobilization method. Their physical chemical properties were characterized by XRD, liquid N₂ adsorption-desorption, Py-IR, NH₃-TPD and UV-vis DRS techniques, and their catalytic performances were investigated in the tert-butylation of toluene with tert-butyl alcohol in a 100 ml stainless steel autoclave equipped with a magnetically driven impeller. The Ti-Al-M48 samples have a large BET surface and ordered mesoporous structure. Although the titanium species loading is the same, the 4% Ti-Al-M48 sample has a larger acid amount than the 4% Ti/Al-M48 sample prepared by impregnation. The Py-IR and UV-vis DRS spectra revealed that the isolated TiO₄ tetrahedra by isomorphous substitution into the Al-M48 network have Lewis acidity. The 4% Ti-Al-M48 has a higher catalytic performance than other samples and the influence of reaction conditions on the tert-butylation of toluene was discussed. The conversion of toluene is 47.5% and the selectivity of p-tert-butyltoluene is 77.2% at the molar ratio of tert-butyl alcohol to toluene 2, the weight ratio of toluene to catalyst 8, reaction temperature 453K and reaction time 4 h. The 4% Ti-Al-M48 sample shows high stability, and toluene conversion 43.7% and p-tert-butyltoluene selectivity 78.4% can be obtained even though after repeated reaction for 3 times.

Full text of DOI:10.1016/j.molcata.2015.07.001

Accepted Manuscript
Title: Tert-butylation of toluene with tert-butyl alcohol over
immobilized titanium species on the Al-MCM-48
Author: Zhiwei Zhou Wei Mao Juan Qin Tianpeng Han
Chaofan Han Wenliang Wu
PII:
S1381-1169(15)30015-7
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2015.07.001
MOLCAA 9551
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
3-2-2015
28-6-2015
2-7-2015
Please cite this article as: Zhiwei Zhou, Wei Mao, Juan Qin, Tianpeng Han, Chaofan
Han, Wenliang Wu, Tert-butylation of toluene with tert-butyl alcohol over immobilized
titanium species on the Al-MCM-48, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2015.07.001
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Tert-butylation of toluene with tert-butyl alcohol over
immobilized titanium species on the Al-MCM-48
Zhiwei Zhoua, Wei Maoa, Juan Qinb, Tianpeng Hana, Chaofan Hana, Wenliang Wu*a
a College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing 210009,
Pepole’s Republic of China
b Technology and Finance Service Center of Jiangsu Province, Productivity Center of Jiangsu
Province, Nanjing 210042, Pepole’s Republic of China
*Corresponding author: Wenliang Wu
Corresponding E-mail address: wwl@njtech.edu.cn
Tel.: +86-025-83587167
Fax: +86-025-83587167

Research highlights:
1. The isolated TiO4 tetrahedra on the Al-MCM-48 were prepared by immobilization.
2. The TiO4 tetrahedra can act as Lewis acid center, which is beneficial to its
application.
3. The Ti-Al-M48 sample was firstly investigated in the tert-butylation of toluene.
4. Catalytic performance of Ti-Al-M48 is much higher than Ti/Al-M48 prepared by
impregnation.
Graphic Abstract:
Al-MCM-48 immobilized titanium species as acid catalysts for the alkylation
reaction of toluene and tert-butyl alcohol.
Abstract: A series of Ti-Al-M48 (M48 stand for MCM-48) samples with different
titanium species loadings were prepared by immobilization method. Their physical
chemical properties were characterized by XRD, liquid N2 adsorption-desorption,
Py-IR, NH3-TPD and UV-vis DRS techniques, and their catalytic performances were
investigated in the tert-butylation of toluene with tert-butyl alcohol in a 100 ml
stainless steel autoclave equipped with a magnetically driven impeller. The

Ti-Al-M48 samples have a large BET surface and ordered mesoporous structure.
Although the titanium species loading is the same, the 4% Ti-Al-M48 sample has a
larger acid amount than the 4% Ti/Al-M48 sample prepared by impregnation. The
Py-IR and UV-vis DRS spectra revealed that the isolated TiO4 tetrahedra by
isomorphous substitution into the Al-M48 network have Lewis acidity. The 4%
Ti-Al-M48 has a higher catalytic performance than other samples and the influence of
reaction conditions on the tert-butylation of toluene was discussed. The conversion of
toluene is 47.5% and the selectivity of p-tert-butyltoluene is 77.2% at the molar ratio
of tert-butyl alcohol to toluene 2, the weight ratio of toluene to catalyst 8, reaction
temperature 453K and reaction time 4 h. The 4% Ti-Al-M48 sample shows high
stability, and toluene conversion 43.7% and p-tert-butyltoluene selectivity 78.4% can
be obtained even though after repeated reaction for 3 times.
Keywords: Lewis acid catalyst, Al-MCM-48, immobilization, TiO4 tetrahedra
1. Introduction
The alkylated products of arenes are of great commercial importance as an
intermediate for the production of specific function materials. All the three isomers of
tert-butyltoluene (TBT) have found for wide applications [1-3]. It is particularly
important that para-tert-butyltoluene (PTBT) can be used for preparing
para-tert-butylbenzaldehyde and para-tert-butylbenzonic acid, which find
applications in production of polyesters, fragrances, resins and pharmaceuticals.
PTBT was industrially obtained by Friedel-Crafts alkylation of toluene with various
alkylation agents, such as tert-butyl chloride, tert-butyl alcohol and isobutylene, when
the HF, H2SO4 or AlCl3 as catalysts [4-5]. However, these catalysts have many
disadvantages, such as recovery difficulty, severe equipment corrosion and
environmental pollution [6]. Some attempts have been developed solid acid catalysts
to avoid these problems, including zeolites and mesoporous materials [7-10]. But the
catalytic performance was limited by the narrow reaction spaces of zeolites.
Meanwhile, water produced by tert-butylation of toluene with tert-butyl alcohol
affected severely the catalytic performance of mesoporous materials, such as

MCM-41 etc. Therefore, the catalytic performance can be promoted by introducing
the hydrophobic substance on the mesoporous materials.
The siliceous mesostructured MCM-48 (M-48) has attracted considerable
attention as catalyst support due to its high surface area and ordered cubic structure
with a uniform and controllable pore size, which contains two independent
three-dimensional pore systems [11-13]. The specific structure has been suggested to
be more advantageous than MCM-41 for catalytic applications because it provides
more favorable mass transfer kinetics [14]. Simultaneously, the catalytic performance
of M-48 can be promoted by importing the aluminum atom into its network because
the acidic properties of M-48 are closely associated to the nature, concentration and
distribution of the aluminum atoms that are attached to or trapped in the network of
pores [9], which is beneficial to its application in the acid catalysis [15-16]. Lewis
acid center is the major active site in the tert-butylation of toluene with tert-butyl
alcohol in our previous report [9]. Some transition metal oxides can work as Lewis
acid catalysts. As a specific transition metal, TiO4 tetrahedra can be formed by
immobilization method [17], which is insoluble in water [18] and Lewis acidity
[19-21]. Therefore, the high catalytic performance of Al-M48 immobilized by
titanium species would potentially acquired in the tert-butylation of toluene with
tert-butyl alcohol. However, the effect of titanium on the Al-M48 surface on their
catalytic performances in the tert-butylation of toluene has not been widely reported
so far.
In this work, a series of Ti-Al-M48 samples were prepared by immobilization
method, and their physical chemical properties were investigated by various
techniques and the influence of reaction conditions on the tert-butylation of toluene
with tert-butyl alcohol was discussed.
2. Experimental Section
2.1 Catalyst Preparation
Mesoporous Al-M48 was synthesized according to the literature using the cetyl
trimethyl ammonium bromide (CTAB) as a structure-directing agent and

tetraethylorthosilicate (TEOS) as silica source. The compositions of initial gel with
molar ratio were as follows [22-23]: 0.05 NaAlO2: 0.65 CTAB: 0.5 NaOH: 1 TEOS:
62 H2O. In a typical procedure, 0.1655 g NaAlO2, 7 g CTAB and 0.6 g NaOH was
respectively added to 40 g distilled water at room temperature. After stirred for 0.5 h,
9 ml TEOS was dropwise added to the mixture and kept for another 0.5 h. The gel
was transferred into a Teflon-lined autoclave and heated at 373 K under autogenous
pressure without agitation for 72 h. Finally the product was collected by filtration,
washed with distilled water and dried at 353 K overnight. In order to remove the
organic template, the sample was obtained by calcination in static air at 823 K for 6h,
and the sample was defined as Al-M48 (Si/Al = 21.7, ICP).
Ti-Al-M48 samples with different titanium species loadings were prepared by a
simple postgrafting method. For example, 1 g Al-M48 was added to a mixture of 29 g
distilled water and 5 g ethanol at room temperature. After stirring for 10 min, a
mixture of 0.17 g tetrabutyl titanate, 0.528 g acetyl acetone and 0.85 g ethanol was
dropwise added to the above mixture and then stirred for 2 h. The solution was heated
at 353 K to dryness, and the material was calcined at 823 K for 4 h. The samples were
defined as n% Ti-Al-M48 (n = the mass ratio of Ti to Al-M48). For comparison, the
sample, defined as n% Ti/Al-M48, was prepared by impregnation under the same
conditions in the absence of acetyl acetone.
2.2. Catalyst Characterization
X-ray powder diffraction (XRD) patterns of the catalysts were obtained on a
Bruker D8 instrument with Ni-filtered Cu Kα radiation (λ=0.154 nm) and operated at
40 kV, 30 mA. The scanning rate was 0.05(º)·s-1 in the 2θ range from 0.7º to 70º.
Nitrogen adsorption-desorption isotherms of samples were measured at 77 K using a
Micromeritics Tristar 3000 system. The surface area was calculated by using the BET
method in the partial pressure (P/P0) range from 0.01 to 0.99. The mesopore size
distribution was obtained from the adsorption branch of the isotherm by using the
BJH adsorption model [24]. Temperature-programmed desorption of ammonia
(NH3-TPD) was carried out in a quartz U-tube reactor, and 300 mg sample was used
for each measurement. The sample was pretreated in the stream at 823 K for 60 min

and then cooled down to 373 K. After that, the NH3/He mixture was switched on for
30 min and then was swept by the stream for 40 min. The temperature was raise from
373 K to 1073 K at a rate 10 K·min-1. The consumption of NH3 in the reactant stream
was recorded by TCD. Fourier transform-infrared spectra of pyridine-adsorbed (Py-IR)
were obtained on the Thermo Nicolet NEXUS spectrometer in KBr pellets. The
sample was pretreated in 10-2 Pa at 573 K for 3 h and then cooled down to room
temperature. After that, pyridine was adsorbed for 2 h and the temperature was raise
to 473 K for 1 h in order to remove the physisorbed pyridine. IR spectra were
measured at room temperature. The Si/Al ratio of Al-M48 was analyzed by
inductively coupled plasma (ICP, Optima 2000 DV, PerkinElmer, USA) after the
sample had been dissolved in HF solution. The Ultraviolet-visible diffuse reflectance
spectroscopy (UV-vis DRS) was measured on a Lambda 950 ultraviolet-visible
spectrophotometer, and the wavelength was in the range from 200 to 600 nm.
2.3 Catalytic reaction
The catalytic tert-butylation of toluene with tert-butyl alcohol was carried out in
a 100 ml stainless steel autoclave equipped with a magnetically driven impeller. 0.2 g
catalyst was added into a mixture of tert-butyl alcohol with toluene (various molar
ratios) using n-hexane as solvent. The reactor was flushed for multiple times with
nitrogen to replace air. Tert-butylation reactions were carried out at the initial pressure
of 1.0 MPa and at a stirring speed 800 r·min-1. Each reaction was carried out at preset
reaction temperatures with various reaction times. At the completion of the reaction,
the reactor was cooled down to room temperature and the reaction mixture was
analyzed on a SP-6890 gas chromatograph equipped with a SE-30 column
(0.25μm×50 m) and a flame ionization detector (FID). The catalytic stability of 4%
Ti-Al-M48 sample was investigated by filtration without any treatment in the next
run.
3. Results and Discussion
3.1. Catalyst characterization

Fig. 1.(A) Low-angle and (B) wide-angle XRD patterns for (a) Al-M48, (b) 2% Ti-Al-M48, (c) 3% Ti-Al-M48, (d)
4% Ti-Al-M48, (e) 5% Ti-Al-M48, and (f) 4% Ti/Al-M48
The XRD patterns of the prepared samples are shown in Fig. 1. It can be seen
from Fig. 1A that the bare Al-M48 sample has well-defined XRD peaks at 2.7° and
3.1°, which is assignable to (221) and (220) reflection [25]. With the titanium species
loading increasing, the intensities of the two peaks decreased because the structure of
Al-M48 was partially destroyed [26]. Compared to the 4% Ti-Al-M48 sample, the
remarkable collapse of the framework of 4% Ti/Al-M48 sample prepared by
impregnation was observed in spite of the titanium species loading is the equal. From
Fig. 1B, it can be concluded that the titanium species were highly dispersed because
of its lack of clear diffractions.
Fig. 2.N2 adsorption-desorption isotherms for (a) Al-M48, (b) 2% Ti-Al-M48, (c) 3% Ti-Al-M48, (d) 4%
Ti-Al-M48, (e) 5% Ti-Al-M48, and (f) 4% Ti/Al-M48
Table 1. Physicochemical Properties of different Ti-Al-M48 samples

SBET
pore diameter
(nm)
pore volume
(cm3/g)
0.78
Samples
(m2/g)
997.88
863.20
783.77
752.68
674.80
701.42
Al-M48
3.56
2% Ti-Al-M48
3% Ti-Al-M48
4% Ti-Al-M48
5% Ti-Al-M48
4% Ti/Al-M48
3.20
0.73
3.14
0.64
2.96
0.61
2.56
0.57
3.01
0.59
N2 adsorption-desorption isotherms of different Al-Ti-M48 samples are shown in
Fig. 2. All these samples have a typical type- N2 adsorption-desorption isotherms
[27], suggesting their mesoporous character. Although the adsorption capacity was
decreased with the titanium species loading increasing, the mesoporous structure of
different Ti-Al-M48 samples kept well. The physicochemical properties of different
Ti-Al-M48 samples are shown in Table 1. It can been seen that the samples have a
large BET surface areas and pore volumes, which is beneficial for its catalytic
application, although there is a decrease in the BET surface areas and pore volumes
with the titanium species loading increasing. The 4% Ti-Al-M48 sample by
immobilization have a larger BET surface area and pore volume than the 4%
Ti/Al-M48 sample by impregnation.
Fig. 3.NH3-TPD curves for (a) Al-M48, (b) 2% Ti-Al-M48, (c) 3% Ti-Al-M48, (d) 4% Ti-Al-M48, (e) 5%
Ti-Al-M48, and (f) 4% Ti/Al-M48
Fig. 3 shows NH3-TPD curves for Al-M48, different Ti-Al-M48 and 4%
Ti/Al-M48 samples. Two ammonia stripping peaks, one at low temperature and

another at high temperature, were observed for all the six samples. Compared to the
Al-M48 sample, the Ti-Al-M48 samples have a lager weak acidity and a smaller
strong acidity. The total acid amount of different Ti-Al-M48 samples increased with
the titanium species loading increasing. The 4% Ti-Al-M48 showed the higher acid
amount than that of 4% Ti/Al-M48 sample although the titanium species loading are
identical.
Fig. 4.FT-IR spectra of pyridine-adsorbed for (a) Al-M48, (b) 2% Ti-Al-M48, (c) 3% Ti-Al-M48,
(d) 4% Ti-Al-M48 after reaction for 3 times, (e) 4% Ti-Al-M48, (f) 5% Ti-Al-M48, and (g) 4% Ti/Al-M48
FT-IR spectra of pyridine-adsorbed for Al-M48, different Ti-Al-M48 and 4%
Ti/Al-M48 samples are shown in Fig. 4. The bands at 1455 cm-1 and 1545 cm-1 could
be assigned to the effects between pyridine and Lewis and Bronsted acid sites,
respectively [28]. From Fig.4, it can be seen that all the samples have Bronsted and
Lewis acid sites. After immobilization of the titanium species, the Bronsted and Lewis
acidity of the Ti-Al-M48 samples have been promoted, which increases with the
titanium species loading increasing. However, compared to the Al-M48 sample, the
Bronsted and Lewis acidity of the 4% Ti/Al-M48 sample decreased. Compared to the
fresh sample (e), the intensity of the bands for 4% Ti-Al-M48 sample after reaction
for 3 times (d) slightly decreased, which suggests that the stability of 4%Ti-Al-M48
sample keeps well.
Fig. 5 shows UV-vis DRS spectra for Ti-Al-M48 with different Ti species

loadings and 4% Ti/Al-M48 samples. It can be seen from Fig.5 that only a band
centered at 220nm can be observed for the 2%Ti-Al-M48 sample, which indicated
that tetrahedrally coordinated Ti species are formed by isopmorphous substitution.
Combined to the results of Py-IR spectra, it suggests that the TiO4 tetrahedral can
improve the Lewis acidity of the Ti-Al-M48 sample, which would be beneficial to its
catalytic activity [18, 29]. With the further increasing of Ti species loading, the
intensity of this band increased and the band would be broader. A new band centered
at 270nm appeared for the 4%Ti-Al-M48 sample, suggesting that the TiO6 octahedra
are formed. A strong and wide absorption band up to 400 nm was present in the 4%
Ti/Al-M48 sample, which indicated that the bulk anatase TiO2 particles were formed
[30].
Fig. 5.UV-vis DRS spectra for (a) 2% Ti-Al-M48, (b) 3% Ti-Al-M48,
(c) 4% Ti-Al-M48, (d) 5% Ti-Al-M48, and (e) 4% Ti/Al-M48
3.2. Comparison of catalytic activities
Table 2. Catalytic performances of different catalysts for the tert-butylation of toluene with tert-butyl alcohol
①
STBT
②
SPTBT
Distribution of TBT / %
Toluene
conversion/%
20.9
Catalysts
/%
/%
OTBT
MTBT
25.7
24.4
20.5
18.8
17.9
25.0
PTBT
72.3
73.4
76.6
77.8
78.2
74.4
DTBT
2.0
Al-M48
0
0
0
0
0
0
98.0
97.8
97.1
96.6
96.1
99.4
73.8
75.1
78.9
80.5
81.4
74.8
2% Ti-Al-M48
3% Ti-Al-M48
4% Ti-Al-M48
5% Ti-Al-M48
4% Ti/Al-M48
21.3
2.2
24.8
2.9
31.8
3.4
28.0
3.9
13.7
0.6
Reaction conditions: W(toluene)/W(Catalyst)=10; Calcination temperature of catalyst 723 K; n(toluene):
n(tert-butanol): n(hexane) = 1: 2: 10; Reaction temperature 453 K; Initial pressure 1.0 MPa; Reaction time 3 h.

①STBT: the molar ratio of mono-tert-butyltoluene to TBT.
②SPTBT: the molar ratio of PTBT to TBT.
Catalytic performances of different catalysts in the tert-butylation of toluene with
tert-butyl alcohol are listed in Table 2. In all cases, the main products are identified as
PTBT and meta-tert-butyltoluene (MTBT). Ortha-tert-butyltoluene (OTBT) was
absence in the reaction products because its formation is hindered by the
ortha-position of methyl and voluminous tert-butyl group. 3, 5-di-tert-butyltoluene
(DTBT), where all tert-butyl groups are in the meta-position, was only be formed due
to the same steric effect [1-2]. It could be found in the reaction products. From Table 2,
it can be seen that with the titanium species loading increasing from 2% to 4%, the
conversion of toluene increased, and then dropped at higher titanium species loading.
The most active catalyst was 4% Ti-Al-M48, giving a toluene conversion of 31.8%,
which may be owing to its appropriate BET surface area, pore volume (Table 1) and
acidity (Fig. 3 and 4), especially the Lewis acidity, although its acid amount is not
highest. When the titanium species loading increased the selectivity of TBT decreased
because the tert-butylation of toluene with tert-butyl alcohol is a continuous reaction.
The selectivity of PTBT increased with the titanium species loading increasing
because its pore diameter slightly decreased probably. However, although the titanium
species loading is the same, the catalytic performance of 4% Ti-Al-M48 sample is
much higher than the 4% Ti/Al-M48 sample, which shows only a toluene conversion
of 13.7%. Because 4% Ti-Al-M48 sample showed the highest catalytic activity, the
following studies on effect of reaction conditions are focused on the catalyst.
3.3. Effect of reaction conditions
3.3.1. Effect of reaction temperature
Table 3. Influence of reaction temperature on the catalytic performance of 4% Ti-Al-M48 sample
Distribution of TBT / %
Reaction
Toluene
conversion/%
12.2
STBT
/%
SPTBT
/%
Temperature /K
MTBT
14.2
PTBT
82.2
77.8
72.2
64.7
DTBT
3.6
433
453
473
493
96.4
96.6
97.0
97.3
85.3
80.5
74.4
66.5
31.8
18.8
3.4
26.5
24.8
3.0
21.1
32.6
2.7
Reaction conditions: W(toluene)/W(Catalyst)=10; Calcination temperature of catalyst 723 K; n(toluene):
n(tert-butyl alcohol) : n(hexane)= 1: 2: 10; Initial pressure 1.0 MPa; Reaction time 3 h.

Table 3 shows the effect of reaction temperature on the tert-butylation of toluene
over 4% Ti-Al-M48. The reaction temperature affects severely on both toluene
conversion and PTBT selectivity. An increase of the reaction temperature to 453 K led
to a significant increase of toluene conversion from 12.2% to 31.8%. With the further
increase of reaction temperature, the conversion of toluene decreased because the
higher temperature causes the dealkylation of TBT probably [9, 28]. A drop of the
selectivity of PTBT is obtained with the reaction temperature increasing, as a result of
the isomerization of PTBT into MTBT, which is more stable at higher temperature.
The selectivity of PTBT is only 66.5% when the reaction temperature reaches up to
493 K.
3.3.2. Effect of the molar ratio of tert-butyl alcohol to toluene
Influence of the molar ratio of tert-butyl alcohol to toluene on the catalytic
performance of 4% Ti-Al-M48 catalyst was shown in Table 4. From Table 4, it can be
seen that the maximum conversion of toluene was 31.8% when the molar ratio of
tert-butyl alcohol to toluene was 2. A negative effect on toluene conversion was found
with the ratio more than 2, which may be owing to oligomerization of the isobutene
formed by intramolecular dehydration of tert-butyl alcohol, carbonization and then
covered the active sites [31]. The selectivity of TBT was declined with the molar ratio
of tert-butyl alcohol to toluene increasing from 1 to 4 because of the incremental
interaction opportunities between TBT and tert-butyl alcohol. However, the
selectivity of PTBT rose slightly, which may be due to depressing of the isomerization
of PTBT to MTBT.
Table 4. Influence of the molar ratio of tert-butyl alcohol to toluene on the catalytic performance of 4% Ti-Al-M48
sample
Distribution of TBT / %
n(tert-butyl alcohol)
Toluene
conversion/%
24.2
STBT
/%
SPTBT
/%
/ n(toluene)
MTBT
22.9
PTBT DTBT
1
2
3
4
75.5
77.7
79.9
81.2
1.6
3.5
4.7
5.9
98.4
96.5
95.3
94.1
76.7
80.5
83.8
86.3
31.8
18.8
26.5
15.4
19.5
12.9
Reaction conditions: W(toluene)/W(Catalyst)=10; Calcination temperature of catalyst 723 K; n(toluene): n(hexane)
= 1: 10; Reaction temperature 453 K; Initial pressure 1.0 MPa; Reaction time 3 h.
3.3.3. Effect of catalyst loading

The liquid phase reaction of tert-butylation of toluene was investigated with
different catalyst loadings in the presence of 4% Ti-Al-M48 sample, and the results
were shown in Table 5. As seen from Table 5, the catalyst loading affected the
conversion and the selectivity of TBT and PTBT greatly. The conversion of toluene
was largely promoted and reached 43.9% when the catalyst loading w (toluene)/ w
(catalyst) increased from 10 to 8. Because the tert-butylation of toluene is a
continuous and reversible reaction, the conversion of toluene kept constant with the
further increase of the catalyst loading. The selectivity of TBT and PTBT decreased
with the catalyst loading increasing, which may be as a result of the dealkylation of
DTBT and the isomerization of PTBT to MTBT [31].
Table 5. Influence of catalyst loading on the catalytic performance of 4% Ti-Al-M48 sample
Distribution of TBT / %
w(toluene)/
w(catalyst)
Toluene
STBT SPTBT
conversion/%
/%
/%
MTBT PTBT DTBT
10
8
31.8
43.9
44.2
44.7
18.7
21.5
25.2
31.0
77.8
74.4
70.2
63.7
3.5
4.1
4.6
5.3
96.5
95.9
95.4
94.7
80.6
77.6
73.6
67.3
6
4
Reaction conditions: Calcination temperature of catalyst 723 K; n(toluene): n(tert-butyl alcohol): n(hexane) = 1: 2:
10; Reaction temperature 453 K; Initial pressure 1.0 MPa; Reaction time 3 h.
3.3.4. Effect of reaction time
The influence of reaction time on the catalytic performance of 4% Ti-Al-M48
sample was examined, and the results are shown in Table 6. It can be seen that the
conversion of toluene increased as the reaction time was prolonged. The conversion
of toluene can reach 47.5% when the reaction time is up to 4 h. Because the
tert-butylation of toluene is a continuous and reversible reaction, the conversion of
toluene kept constant when the reaction time was more than 4 h, which suggests that
the reaction reaches its steady state. The selectivity of TBT and PTBT were declined
when the reaction time was prolonged because of the dealkylation of DTBT [2] and
the isomerization of PTBT to MTBT.
Table 6. Influence of reaction time on the catalytic performance of 4% Ti-Al-M48 sample
Distribution of TBT / %
Reaction
Toluene
conversion/%
35.2
STBT
/%
SPTBT
/%
time/ h
MTBT PTBT DTBT
2
3
17.1
21.5
79.1
74.4
3.8
4.1
96.2
95.9
82.2
77.6
43.9

4
5
6
47.5
47.6
47.5
21.5
24.4
29.4
72.8
69.6
64.4
5.7
6.0
6.2
94.3
94.0
93.8
77.2
74.0
68.7
Reaction conditions: W(toluene)/W(Catalyst)=8; Calcination temperature of catalyst 723 K; n(toluene):
n(tert-butyl alcohol): n(hexane) = 1: 2: 10; Reaction temperature 453 K; Initial pressure 1.0 MPa.
3.3.5. Catalytic stability
The catalytic stability for 4% Ti-Al-M48 sample was investigated, and the results
are listed in Table 7. It can be seen that toluene conversion decreased slightly, and it
can reach to 43.7% after repeated reaction for 3 times, which suggested that the
catalytic stability keeps well. The selectivity of PTBT increases, which may be owing
to oligomerization of the isobutene formed by intramolecular dehydration of tert-butyl
alcohol, carbonization and then blocking the pores probably.
Table 7. Catalytic stability for 4% Ti-Al-M48 sample in the tert-butylation of toluene with tert-butyl alcohol
Distribution of TBT / %
Reaction
Toluene
conversion/%
47.5
STBT
/%
SPTBT
/%
number
MTBT PTBT DTBT
1
2
3
21.5
21.2
20.6
72.8
73.6
74.8
5.7
5.2
4.6
94.3
94.6
95.4
77.2
77.8
78.4
45.9
43.7
Reaction conditions: W(toluene)/W(Catalyst)=8; Calcination temperature of catalyst 723 K; n(toluene):
n(tert-butyl alcohol): n(hexane) = 1: 2: 10; Reaction temperature 453 K; Initial pressure 1.0 MPa.
4. Conclusions
Ti-Al-M48 samples were prepared by immobilization method and investigated in
the tert-butylation of toluene with tert-butyl alcohol. UV-vis DRS spectra revealed
that the TiO4 tetrahedra formed by isomorphous substitution into the Al-M48 network
can offer the Lewis acid center and increase the acid amount, which is beneficial to
the catalytic activity. Compared to the Ti/Al-M48 prepared by impregnation, the
catalytic performance of Ti-Al-M48 is higher in spite of the titanium species is the
same. The reaction condition of tert-butylation of toluene was optimized, and toluene
conversion 47.5% and PTBT selectivity 77.2% can be obtained. The catalytic stability
for 4% Ti-Al-M48 keeps well, and the toluene conversion is 43.7% and PTBT
selectivity is 78.4% after repeated reaction for 3 times. The method can provide a
valuable reference for improving the activity of the M48 sample.

Acknowledgements
This work was supported by Jiangsu Planned Projects for Postdoctoral Research
Funds (1302121C); Open Project of Beijing Key Laboratory for Enze Biomass and
Fine Chemicals; Project Funded by the Priority Academic Program Development of
Jiangsu Higher Education Institutions.
References
[1] D. Mravec, P. Zavadan, A. Kaszonyi, J. Joffre, P. Moreau, Appl. Catal., A: Gen.
257 (2004) 49-55.
[2] M. Selvaraj, T.G. Lee, Microporous Mesoporous Mater. 85 (2005) 59-74.
[3] A. Abbaspourrad, R.J. Kalbasi, F. Zamani, Turk. J. Chem. 34 (2010) 875-885.
[4] S. Kobayashi, K. Manabe, Pure Appl. Chem. 72 (2000) 1373-1380
[5] P.T. Anastas, M.M. Kirchhoff, Acc. Chem. Res. 35 (2002) 686-694.
[6] M. Rueping, B.J. Nachtsheim, Beilstein J. Org. Chem. 6 (2010) 1-24.
[7] M. Selvaraj, S.H. Jeon, J. Han, P.K. Sinha, T.G. Lee, Appl. Catal., A: Gen. 286
(2005) 44-51.
[8] S. Pai, U. Gupta, S. Chilukuri, J. Mol. Catal. A: Chem. 265 (2007) 109-116.
[9] Z. Zhou, W. Wu, J. Wang, C. Zeng, Chin. J. Chem. Eng. 17 (2009) 195-199.
[10] R.J. Balasamy, T. Odedairo, S. Al-Khattaf, Appl. Catal., A: Gen. 409–410 (2011)
223-233.
[11] Fechete, O. Ersen, F. Garin, L. Lazar, A. Rach, Catal. Sci. Technol. 3 (2013)
444-453.
[12] W. Zhao, M. Qin, L. Wang, J. Chu, J. Qu, S. Li, Q. Li, T. Qi, J. Colloid Interface
Sci. 384 (2012) 81-86.
[13] Y. Han, K. Fang, X. Gu, J. Chen, J. Chen, J. Chem. Eng. Data. 57 (2012)
2059-2066.
[14] I. Fechete, B. Donnio, O. Ersen, T. Dintzer, A. Djeddi, F. Garin, Appl. Surf. Sci.
257 (2011) 2791-2800.
[15] K. Venkatachalam, P. Visuvamithiran, B. Sundaravel, Chin. J. Catal. 33 (2012)
478-486

[16] H. Kosslick, G. Lischke, H. Landmesser, B. Parlitz, W. Storek, R. Fricke, J. Catal.
176 (1998) 102-114.
[17] N. Khalili, R. Rahimi, M. Rabbani, Chem. Mon. 144 (2013) 597-603.
[18] K. Nakajima, R. Noma, M. Kitano, M. Hara, J. Phys. Chem. C. 117 (2013)
16028-16033.
[19] S.K. Samantaray, T. Mishra, K.M. Parida, J. Mol. Catal. A: Chem. 156 (2000)
267-274.
[20] S.M. Kumbar, G.V. Shanbhag, F. Lefebvre, S.B. Halligudi, J. Mol. Catal. A:
Chem. 256 (2006) 324-334.
[21] G. Losfeld, V. Escande, P. Vidal de La Blache, L. L’Huillier, C. Grison, Catal.
Today. 189 (2012) 111-116.
[22] M. Thommes, R. Köhn, M. Fröba, Appl. Surf. Sci. 196 (2002) 239-249.
[23] Y. Ding, A. Kong, H. Zhang, H. Shen, Z. Sun, S.D. Huang, Y. Shan, Appl. Catal.,
A: Gen. 455 (2013) 58-64.
[24] F. Liebau, Microporous Mesoporous Mater. 58 (2003) 15-72.
[25] P. Van Der Voort, M. Mathieu, F. Mees, E.F. Vansant, J. Phys. Chem. B. 102
(1998) 8847-8851.
[26] A. Sakthivel, K. Komura, Y. Sugi, Ind. Eng. Chem. Res. 47 (2008) 2538-2544.
[27] K. Schumacher, P.I. Ravikovitch, A. Du Chesne, A.V. Neimark, K.K. Unger,
Langmuir, 16 (2000) 4648-4654.
[28] A. Pruden, M. Suidan, Biodegradation, 15 (2004) 213-227.
[29] T. W. Kim, M. J. Kim, F. Kleitz, M. M. Nair, R. G. Nicolas, K. E. Jeong, H. J.
Chae, C. U. Kim, S. Y. Jeong, Chemcatchem, 4 (2012) 687-697.
[30] H. Shintaku, K. Nakajima, M. Kitano, N. Ichikuni, M. Hara, ACS Catal. 4 (2014)
1198-1204.
[31] C. P. Sebastian, S. Pai, N. Sharanappa, C. V. V. Satyanarayana, J. Mol. Catal. A:
Chem. 223 (2004) 305-311.