Atomic layer deposition of aluminium on anatase: A solid acid catalyst with remarkable performances for alcohol dehydration

Article abstract of DOI:10.1016/j.catcom.2017.05.018

Here we reported the synthesis of Al sites with ultra-high dispersion on anatase by an atomic layer deposition (ALD) method (ALD-Al/TiO₂), which exhibits Br?nsted acidity and satisfactory activity in the dehydration of alcohols, a key step in the deoxygenation of biomass. More importantly, the ALD-Al/TiO₂ catalyst has good stability, which is sintering-resistant and gives constant catalytic performances after treatments at high temperature.

Full text of DOI:10.1016/j.catcom.2017.05.018

Accepted Manuscript
Atomic layer deposition of aluminium on anatase: A solid acid
catalyst with remarkable performances for alcohol dehydration
Yingji Song, Shaodan Xu, Fei Ling, Panpan Tian, Tao Ye, Deqing
Yu, Xuefeng Chu, Yingzi Lin, Xiaotian Yang, Junhong Tang
PII:
DOI:
Reference:
S1566-7367(17)30212-1
doi: 10.1016/j.catcom.2017.05.018
CATCOM 5053
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
9 February 2017
8 May 2017
19 May 2017
Please cite this article as: Yingji Song, Shaodan Xu, Fei Ling, Panpan Tian, Tao Ye,
Deqing Yu, Xuefeng Chu, Yingzi Lin, Xiaotian Yang, Junhong Tang , Atomic layer
deposition of aluminium on anatase: A solid acid catalyst with remarkable performances
for alcohol dehydration. The address for the corresponding author was captured as
affiliation for all authors. Please check if appropriate. Catcom(2017), doi: 10.1016/
j.catcom.2017.05.018
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ACCEPTED MANUSCRIPT
Atomic Layer Deposition of Aluminium on Anatase: A Solid Acid
Catalyst with Remarkable Performances for Alcohol Dehydration
Yingji Song†a, Shaodan Xu†*c, Fei Lingc, Panpan Tianc, Tao Yec, Deqing Yuc, Xuefeng
Chu*a,d, Yingzi Line, Xiaotian Yangd, Junhong Tang*b
a
Department of Basic Science, Jilin Jianzhu University, Changchun 130118, P. R.
China
E-mail: stone2009@126.com
b Department of Environmental Engineering and Science, Hangzhou Dianzi University,
Hangzhou 310018, P. R. China
E-mail: tang_jhjh@163.com
c Zhejiang Institute of Quality Inspection Science, Hangzhou 310018, P. R. China
E-mail: xushaodan6677@126.com
d Jilin Provincial Key Laboratory of Architectural Electricity&Comprehensive Energy
Saving, School of Electrical and Electronic Information Engineering, Jilin Jianzhu
University, Changchun 130118, P. R. China
e
Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin
Jianzhu University, Changchun 130118, P. R. China
AUTHOR INFORMATION
Corresponding Author
* E-mail: stone2009@126.com (X. F. Chu)
* E-mail: tang_jhjh@163.com (J. H. Tang)
* E-mail: xushaodan6677@126.com (S. D. Xu)

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Notes
The authors declare no competing financial interest.
† These authors contributed equally to this work.

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Abstract: Here we reported the synthesis of Al sites with ultra-high dispersion on
anatase by an atomic layer deposition (ALD) method (ALD-Al/TiO2), which exhibits
Brønsted acidity and satisfactory activity in the dehydration of alcohols, a key step in
the deoxygenation of biomass. More importantly, the ALD-Al/TiO2 catalyst has good
stability, which is sintering-resistant and gives constant catalytic performances after
treatments at high temperature.
Keywords: biomass • atomic layer deposition • solid acid catalyst • dehydration

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1. Introduction
Biomass, which is regarded as renewable energy source, has attracted much
attention for producing alternative fuels and fine chemicals [1-4]. Compared with
crude oil, the biomass has high oxygen content, which makes it difficult for directly
using the biomass to partly replace the crude oil feedstocks [5-7]. In order to solve
this problem, upgrading the biomass-based molecules by deoxygenation is critically
important [8-10]. In the deoxygenation process with multiple steps, the acid catalysts
are generally necessary for the cleavage of carbon-oxygen bonds, a key step for the
deoxygenation [11-16]. Therefore, synthesizing efficient acid catalyst is of great
importance for the deoxygenation of biomass-based molecules.
Many homogeneous acids (e.g. H2SO4, HCl) are regarded as active catalysts for
the deoxygenation, but their homogeneous feature creates difficulty in separation and
regeneration from the reaction system [17-20]. Additionally, the corrosivity of these
acids also leads high-cost and environmentally unfriendly problems. The
heterogeneous acids could easily solve the problems of catalyst separation, exhibiting
significant advantages compared with the homogeneous ones. Particularly, the acidic
resins, which are synthesized by functionalizing acidic groups (e.g. -SO3H) on the
mesoporous organic polymers, are attractive because of their Brønsted acidity and
high activity for conversion of bulky molecules. However, the low stability of acidic
resins limited their wide application, especially for the reactions of high temperature
[21-23]. Aluminosilicate zeolites with highly dispersed Al atoms in the silica
framework (e.g. as ZSM-5, Y and Beta), which have significantly higher stability than

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the resins, are regarded as one of the most promising catalysts for biomass
deoxygenation. [24] Nevertheless, for the reaction at high temperature (>200 °C) in
water solvent, the stability of most aluminosilicate zeolites is still unsatisfactory, the
Si-O-Al linkage in the zeolite framework could be destroyed, leading to lose of acid
sites [11]. Additionally, the small micropore size of zeolite also limited their
application in the conversion of bulky molecules. Therefore, development of solid
acid with ultrahigh stability and favorable efficiency is still challenging.
It is generally known that highly dispersed metals (e.g. Al, Zr, Sn) oxides within
several nanometers could efficiently produce rich Brønsted acid sites compared with
the bulky ones [25, 26-37]. In these cases, many methods, such as the impregnating,
grafting, chemical vapor depositing, have been employed for achieving highly
dispersed metal species. However, we have to note that these methods are still
unsatisfactory, where the aggregation of metal species usually occurs, causing the
decreased number of acid centers. Recently, atomic layer deposition (ALD), which is
atom controllable technique through self-limiting binary reactions between gaseous
precursors and the substrate with significant advantages compared with the
conventional chemical vapor deposition (CVD) technique, has been widely used for
synthesizing various metal catalysts with distinguishable catalytic performances
[38-39]. Although much success has been gained in synthesizing metal catalysts by
ALD, to the best of our knowledge, synthesizing solid acids by ALD is rarely
achieved.
Herein, we reported the synthesis of Al sites with ultra-high dispersion on anatase

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by an ALD method. The obtained catalyst, denoted as ALD-Al/TiO2, exhibits
Brønsted acidity and satisfactory activity in the dehydration of alcohols, which is
employed as a model reaction for the deoxygenation of biomass-derived alcohols in
water solvent. Furthermore, by combining ALD-Al/TiO2 with the Pd/C, the mixed
catalysts exhibit good performances in the upgrading of phenolic bio-oil by
hydrodeoxygenation. Moreover, the ALD-Al/TiO2 catalyst has outstanding stability,
which gives constant catalytic performances after harsh treatments.
2. Experimental
2.1 Sample preparation
All reagents were of analytical grade and used as purchased without further
purification. The reference catalysts of H3PO4, H2SO4, and Amberlyst-15 were
commercially obtained from Aladdin Chem. Co.
Synthesis of TiO2. As a typical run, 20 g of tetrabutyl titanate was dropwised into
1 L of water under stirring. Then the mixture was stirred for 5 h at room temperature,
and the white precipitate was separated by centrifugation. After calcining the
precipitate at 600 °C in air, the nanosized TiO2 was obtained.
Synthesis of ALD-Al/TiO2-5C. The ALD experiment was performed on a
LabNano-PE Atomic Layer Deposition System (Ensure Nanotech, China). The Al
species were loaded on TiO2 by using Trimethylaluminum (TMA) and H2O as
precursors of Al and O, respectively. Ultrahigh purity argon was used as carrier gas to
pass through the reactor continuously at a mass flow rate of 15 sccm and a pressure of

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0.4 Torr. Al2O3 coating was performed at 150 °C and the sequence of pulse for one
cycle deposition is H2O (0.02 s)/Ar2(20 s)/TMA(0.02 s)/Ar2(20 s). The samples after
ALD were calcined in oxygen at 400 °C for 1 h. Five cycles were performed for
obtaining enough Al sites.
Synthesis of IM-Al/TiO2. As a typical run, 1 g of TiO2 was dispersed in 30 ml of
Al(NO3)3 solution. After ultrasonic treatment at room temperature for 1 h. the water
was removed under vacuum. After calcining the obtained sample at 500 °C in oxygen
for 3 h, the IM-Al/TiO2 catalyst was obtained.
Synthesis of ZSM-5 zeolite. As a typical run, 3 ml of tetrapropyl ammonium
hydroxide (TPAOH, 30 wt%) and 0.09 g of sodium aluminate (NaAlO2) were added
into 15 ml of water. After stirring at room temperature for 1 h, 7 ml of TEOS was
added and the resulted mixture was stirred for 40 h. Then the gel was transferred into
an autoclave to crystallize at 180 C for 3 days. After filtrating, drying, and calcining
at 550 C for 4 h in oxygen, the ZSM-5 zeolite was obtained.
Synthesis of Al-SBA-15. As a typical run, 1.5 g of P123 and 1.18 g of NaCl were
dissolved in 70 g of water at 40 C. Then, 4.2 g of TEOS was added, and the mixture
was stirred for another 4 h. 10 ml of AlCl3 aqueous solution (0.76 mmol of AlCl3) was
added, and then the mixture was continuously stirred at 40 C for 24 h, and
hydrothermally treated at 90 C for 24 h in an autoclave. After filtrating, washing,
drying, and calcination at 500 C for 4 h in oxygen, Al-SBA-15 with Si/Al atomic
ratio at 55 was finally obtained.
2.2 Sample characterization

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X-ray diffraction (XRD) data were collected on a Rigaku D/MAX 2550
diffractometer with Cu KR radiation (=1.5418 Å). Al loadings were determined by
inductively coupled plasma (ICP) analysis (Perkin-Elmer 3300DV). Nitrogen sorption
isotherms were measured using a Micromeritics ASAP Tristar, the solid samples were
degased at 180 C under vacuum for 14 h before the test. NMR experiments were
performed on a BrukerAscend-500 spectrometer with a 4 mm triple-resonance MAS
probe at a spinning rate of 10 kHz. Prior to the adsorption of the probe molecules, the
acid samples were placed in glass tubes and connected to a vacuum line for
dehydration. The temperature was gradually increased at a rate of 1 °C/min, and the
samples were kept at a final temperature of 400 °C and a pressure below 10-3 Pa over
a period of 10 h and were then cooled. After the samples were cooled to ambient
temperature, a known amount of probe molecule was introduces to the samples. The
samples were frozen by liquid N2, followed by elimination of the physically adsorbed
probing molecules by evacuation at room temperature for 10 min. Finally, the sample
tubes were flame-sealed. The preparation of the acetone adsorbed samples was
performed according to the prior to the NMR experiments. Scanning transmission
electron microscopy and energy dispersive X-ray spectroscopy elemental maps were
collected using a JEOLARM 200F microscope operated at 200 kV. The samples were
ultrasonically dispersed in ethanol and then a drop of the solution was deposited onto
a holey C/Cu grid for STEM characterization and EDX elemental mapping.
Sample Pretreatment for ICP Analysis. The solid samples were dried at 120 °C
under vacuum overnight, then ~15 mg of the sample (the amount was precisely

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measured) was digested in a mixed aqueous solution of HF and HNO3. The
suspension was heated at 100 °C for completely dissolving the sample. Then the
solution was diluted to 100 ml. For each sample, the Al content was tested at least
three times. The Al and Ti content were calculated by the mean value.
The Al content in the solid sample was calculated from the concentration
according to the following equation:
PAl = [(CAl*Vsolution)/W]*100%
Where PAl is the weight percentage of Al in the solid sample, CAl is the
concentration of Al measured by ICP, Vsolution is 100 mL, and W is the amount of solid
sample for preparing the solution.
2.3 Catalytic tests
The dehydration reactions were performed in a 40-mL high-pressure autoclave
with a magnetic stirrer (1100 rpm). The substrate and powder catalyst were mixed in
the reactor, then N2 was introduced and kept at desired pressure. The reaction system
was heated to a given temperature. After the reaction, the product was taken out from
the system and analysed by gas chromatography (Fuli, using a flame ionization
detector) with a flexible quartz capillary column. The recyclability of the catalyst was
tested by separating it from the reaction system by centrifugation, washing with large
quantity of ethanol and drying under vacuum.
3. Results and Discussion
The ALD was carried out in a viscous flow reactor by alternately exposing the

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sample to cycles of trimethylaluminum at room temperature. ALD with 5 cycles were
applied to a nanosized anatase (10-20 nm), followed by calcination at 350 °C in air.
By Inductively Coupled Plasma (ICP) analysis, the Al loading on the final sample
(ALD-Al/TiO2-5C, 5C means 5 ALD cycles in synthesizing the catalyst) was
established to be 2.9%.
Figure S1 shows the XRD patterns of TiO2 and ALD-Al/TiO2-5C, which exhibit
similar peaks assigning to typical anatase structure. Notably, the peaks of Al2O3 are
completely absent in the pattern of ALD-Al/TiO2-5C, suggesting the high dispersion
of Al species. Figure S2 gives the N2 sorption isotherms of ALD-Al/TiO2-5C, which
exhibits significant hysteresis loop at relative pressure of 0.6 to 0.9, indicating the
presence of rich mesoporosity. The surface area and pore size were established at 98
cm2/g and 8.2 nm, respectively. The nanoporous structure of ALD-Al/TiO2-5C should
be favorable for the Al sites accessing to the molecules, because catalysis is well
known as a surface phenomenon.
Electron microscopy images were employed to characterize the Al species on
TiO2. Figure 1a shows high-angle annular dark-field scanning transmission electron
microscopy (HAADF-STEM) by the Z-contrast. This image exhibits aggregation of
nanosized anatase crystals with mesoporosity, in good agreement with the results of
N2 sorption isotherms. Notably, it is difficult to distinguish Al2O3 from TiO2 in the
HAADF-STEM image, which might be due to the high dispersion of Al2O3 on anatase.
EDX mapping analysis could directly observe the Al species. As shown in Figures 1b
and 1c, the distribution of Al element is consistent with that of Ti element, indicating

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the uniform distribution of Al. Although it is difficult to directly observe Al2O3, it is
reasonably to propose that this structure with high Al distribution is favorable to form
small size Al2O3 clusters on TiO2.
The acidity of ALD-Al/TiO2-5C was studied by the TMP-adsorption 31PNMR
spectroscopy, which is a practical technique to characterize the acid strength based on
the host-guest interaction between solid acid and basic probe molecules [40-41]. As
shown in Figure 2, the ALD-Al/TiO2-5C gives two obvious signals at -29 and -3 ppm,
which are assigned to TMP adsorbed at relatively weak and strong acid sites on the
ALD-Al/TiO2-5C. Additionally, the TiO2 support without Al species only gives at
signal at -33 ppm. These results indicate that the weak acid sites are from the TiO2
support (-29 to -33 ppm), while the Al on ALD-Al/TiO2-5C could form strong acid
sites (-3 ppm). It is worth emphasizing that ALD is critically important for creating
the strong acid sites. For example, when Al was loaded on TiO2 by conventional
impregnation method, the obtained sample (IM-Al/TiO2) still exhibits a signal at -33
ppm, the signals of strong acid sites are completely undetectable. This phenomenon is
reasonably attributed to the uniformly distributed Al species on TiO2 by ALD, where
the Al2O3 clusters is favorable to produce rich hydroxyl groups, thus leading to the
formation of strong acid sites.
The investigation on the catalytic performances of ALD-Al/TiO2-5C starts from
the dehydration of cyclohexanol to cyclohexene, which is a key step in the
hydrodeoxygenation of lignin-based phenolic molecules into alkane bio-oils [42-44].
Dehydration of cyclohexanol in water solvent has been regarded as challengeable

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topic. The reaction was carried out at 180 °C in autoclave with high-pressure nitrogen
in water solvent. The catalytic data are shown in Table 1. The TiO2 support without Al
species is inactive for the reaction, giving cyclohexanol conversion lower than 1%
(entry 1). Interestingly, the ALD-Al/TiO2-5C is very active, exhibiting cyclohexanol
conversion at 34.2% with cyclohexene as a sole product (entry 2). In contrast, other
Al-based catalysts of IM-Al/TiO2, γ-Al2O3, AlCl3, and NaAlO2 give very low
conversion (<6.9%, entries 3-6), due to the lack of effective acid sites. When the
reaction temperature decreased to 150 °C, ALD-Al/TiO2-5C still gives cyclohexanol
conversion at 22.4% (entry 7), higher than the homogeneous acids of H3PO4 and
H2SO4 (entries 8-9). In comparison, Amberlyst-15 and Al-SBA-15, two widely used
acid resin catalysts, catalyzed the cyclohexanol conversion at 9.4% and 2.2%,
respectively (entries 10 and 11). Notably, the cyclohexanol conversion over
ALD-Al/TiO2-5C is even comparable to that over ZSM-5 zeolite (22.0%, entry 12).
These results confirmed the high activity of ALD-Al/TiO2-5C in the dehydration of
cyclohexanol. Furthermore, similar results could also be obtained in the dehydration
of cyclopentanol (entries 14-15) and phenylethyl alcohol (entries 16-17), where
ALD-Al/TiO2-5C exhibits much higher activity.
Further study was carried out to understand the stability of ALD-Al/TiO2-5C. By
a calcination treatment at 600 °C for 4 h, which is a harsh condition for most
nanocatalysts, the calcined ALD-Al/TiO2-5C still exhibits uniform distribution of Al,
as confirmed by the electronic microscopy characterization (Figure S3). The
TMP-adsorption 31PNMR spectrum still exhibits the obvious signal at -3 ppm (Figure

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2), assigning to the presence of strong acid sites. In the catalytic dehydration of
cyclohexanol, the calcined ALD-Al/TiO2-5C exhibits similar performances with the
as-synthesized ALD-Al/TiO2-5C catalyst (entry 13, Table 1). These results indicate
the high stability of ALD-Al/TiO2-5C catalyst, therefore, we can reasonably expect a
good recyclability of the catalyst. We verified this by testing the dehydration of
cyclohexanol in water solvent at 180 °C in 12 h to avoid the activity saturation. As
shown in Figure 3, the conversion kept unchanged in a 5-recycle test over
ALD-Al/TiO2-5C, showing excellent recyclability. In contrast, the Amberlyst-15 resin
lost most of the activity in the 2nd run due to its poor thermal stability. ZSM-5 zeolite
exhibit constant conversion in the 4th run, but the conversion obviously decreases in
the 5th run, which might be due to the coke formation blocking the micropores, and
the activity can be regenerated by calcination in oxygen.
Furthermore, we also employed the ALD-Al/TiO2-5C catalyst in the
hydrodeoxygenation of phenolic molecules, which are employed as model bio-oil
molecules. As presented in Table 2, by combining ALD-Al/TiO2-5C with the
commercial Pd/C as bifunctional catalysts, the mixed catalysts exhibit better
performances (higher substrate conversions and higher alkane selectivities) in the
hydrodeoxygenation of phenol and 2,6-dimethoxyphenol to cyclohexane than mixed
catalysts of H3PO4 and Pd/C, which is important process in the upgrading of
biomass-derived pyrolysis oil. All these data confirm the high performance and
potential practical application of ALD-Al/TiO2-5C developed from the ALD method.
4. Conclusion

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In summary, the atomic dispersion of Al species on TiO2 support was achieved
by atomic layer deposition. The obtained catalyst, denoted as ALD-Al/TiO2-5C,
exhibits Brønsted acidity and much higher activity than the conventional Al2O3-based
catalyst in the dehydration of alcohols. More importantly, the ALD-Al/TiO2-5C
exhibit outstanding stability and recyclability. The simple synthesis procedure and
high activity combined with the excellent stability of ALD-Al/TiO2-5C make it
important for potential application. On the other hand, this work also demonstrates a
very unique method for synthesizing solid acids by ALD, which might open a new
route by employing ALD as efficient tools for atomically designing and synthesizing
acid catalysts for biomass conversion in the future.
ASSOCIATED CONTENT
Supporting Information. XRD and N2 sorption are available in Supporting
Information.
Acknowledgements
We gratefully acknowledge the support from National Natural Science
Foundation of China (No. 51672103 and 51272089) and Natural Science Foundation
of Jilin Province Department of Education (No. 2014238 and 2015279).
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Captions
Table 1. Catalytic dehydration of alcohols to olefins over various catalysts in water
solvent.a
Table 2. Catalytic data in hydrodeoxygenation of phenol and 2,6-dimethoxyphenol
over different catalysts.a
Figure 1. (a) HADDF-STEM images of ALD-Al/TiO2-5C. (b, c) Ti, Al elemental
maps by analysing the red-square region in (a).
Figure 2. TMP-adsorption 31P NMR spectra of various samples. The calcined
ALD-Al/TiO2-5C is the sample after calcination treatment at 600 °C for 4 h.
Figure 3. Recyclable tests of various catalysts in the catalytic dehydration of
cyclohexanol. Reaction conditions: 1 mmol of alcohol, 50 mg of catalyst, 5 ml of
water, 3 MPa of N2, reaction time of 12 h.

ACCEPTED MANUSCRIPT
Table 1. Catalytic dehydration of alcohols to olefins over various catalysts in water
solvent.a
Entry
Catalyst
T (°C)
Conversion (%)
Selectivity (%)
C Balanceb (%)
1
2
TiO2
ALD-Al/TiO2-5C
IM-Al/TiO2
γ-Al2O3
180
180
180
180
180
180
150
150
150
150
150
150
180
<1.0
34.2
6.9
--c
>99.0
>99.0
>99.0
96.4
>99.0
>99.0
98.0
3
4
2.1
5
AlCl3
3.9
97.9
6
NaAlO2
<1.0
22.4
1.2
--c
7
ALD-Al/TiO2 -5C
>99.0
69.0
>99.0
d
8
H3PO4
9
H2SO4
Amberlyst-15
Al-SBA-15
ZSM-5
19.9
9.4
97.5
82.1
10
11
12
13
>99.0
>99.0
>99.0
>99.0
>99.0
>99.0
>99.0
>99.0
2.2
22.0
32.1
Calcined
ALD-Al/TiO2 -5Ce
14
15
ALD-Al/TiO2-5C
IM-Al/TiO2
180
180
29.5
1.5
92.3f
--c
95.2

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16
17
ALD-Al/TiO2 -5C
IM-Al/TiO2
180
180
38.8
5.4
>99.0
>99.0
>99.0
>99.0
a Reaction conditions: 1 mmol of alcohol, 50 mg of catalyst, 5 ml of water, 3 MPaof N2, reaction time of 20 h.
b Calculated from thecarbon atoms in the feed and products.
c Undetectable.
d The data are from Ref. [30].
e Thecalcined ALD-Al/TiO2-5C is thesample after calcination treatment at 600 °C for 4 h.
f The by-product is ether.

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Table 2. Catalytic data in hydrodeoxygenation of phenol and 2,6-dimethoxyphenol
over different catalysts.a
Product selectivity (%)b
Conv.
Carbon
balance
(%)
Substrate
Catalyst
(%)
cyclohexane cyclohexanol
cyclohexanone
ALD-Al/TiO2-5
C + Pd/C
H3PO4 + Pd/C
1
2
Phenol
Phenol
>99.5
>99.5
97.0
92.0
3.0
8.0
<1.0
<1.0
>99.5
>99.5
cyclohexane othersc
2,6-dimethoxyphen
ol
2,6-dimethoxyphen
ol
ALD-Al/TiO2-5
C + Pd/C
3
4
90.1
77.2
70.4
55.0
24.0
38.0
93.3d
93.0d
H3PO4 + Pd/C
a Reaction conditions: 150 C, 4 h, 4.0 MP of H2, 50 mg of catalyst, 1 mmol of phenolic molecules,10 ml of water;
b (C atoms in each product/totalC atoms in all products)*100%; c Cyclohexanol-, cyclohexanone-derived
molecules and some others; d The undetected carbon was mainly due to the volatilization of methanol product.

ACCEPTED MANUSCRIPT
(b)
(a)
TiO2(101)
TiO2(101)
2 nm
Ti
(c)
2 nm
Al
Figure 1. (a) HADDF-STEM images of ALD-Al/TiO2-5C. (b, c) Ti, Al elemental
maps by analysing the red-square region in (a).

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IM-Al/TiO2
TiO2
ALD-Al/TiO2-5C
Calcined
ALD-Al/TiO2-5C
Figure 2 TMP-adsorption 31P NMR spectra of various samples. The calcined
ALD-Al/TiO2-5C is the sample after calcination treatment at 600 °C for 4 h.

ACCEPTED MANUSCRIPT
30
25
20
15
10
5
ALD-Al/TiO2-5C
Amberlyst-15
ZSM-5
0
1
2
3
4
5
6
7
Run
Figure 3. Recyclable tests of various catalysts in the catalytic dehydration of cyclohexanol.
Reaction conditions: 1 mmol of alcohol, 50 mg of catalyst, 5 ml of water, 3 MPa of N2, reaction
time of 12 h. The ZSM-5 catalysts were calcined in oxygen at 450 °C for 4 h after the 6th run.

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Research highlights
 Solid acid catalyst ALD-Al/TiO2 is synthesized via atomic layer
deposition (ALD) technique.
 ALD-Al/TiO2 exhibits highly dispersed Al sites with Brønsted
acidity.
 ALD-Al/TiO2 catalysts are efficient for dehydration of alcohols.