Dehydration of 1,5-Pentanediol over Na-Doped CeO2 Catalysts

Article abstract of DOI:10.1002/cctc.201701420

The effects of CeO₂ doped with Na on the dehydration of 1,5-pentanediol were studied by using a fixed-bed reactor at two different temperatures (350 and 400 °C) and atmospheric pressure. For characterization, BET surface area, hydrogen temperature-programmed reduction, CO₂ temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy techniques were utilized. The conversion of the diol on CeO₂ was found to depend on Na loading. The selectivity to the desired product (i.e., unsaturated alcohol) increased and the selectivity to undesired products (i.e., tetrahydropyran, tetrahydropyran-2-one, cyclopentanol and cylopentanone) decreased with increasing Na content on CeO₂. The basicity of hydroxyl groups or surface oxygen on CeO₂ was altered with the addition of Na, and controlled the dehydration reaction pathway.

Full text of DOI:10.1002/cctc.201701420

DOI: 10.1002/cctc.201701420
Full Papers
Dehydration of 1,5-Pentanediol over Na-Doped CeO2
Catalysts
Muthu Kumaran Gnanamani,[a] Gary Jacobs,[a, b] Michela Martinelli,[a] Wilson D. Shafer,[a, c]
Shelley D. Hopps,[a] Gerald A. Thomas,[a] and Burtron H. Davis*[a]
The effects of CeO2 doped with Na on the dehydration of 1,5-
pentanediol were studied by using a fixed-bed reactor at two
different temperatures (350 and 4008C) and atmospheric pres-
sure. For characterization, BET surface area, hydrogen tempera-
ture-programmed reduction, CO2 temperature-programmed
desorption, and diffuse reflectance infrared Fourier transform
spectroscopy techniques were utilized. The conversion of the
diol on CeO2 was found to depend on Na loading. The selectiv-
ity to the desired product (i.e., unsaturated alcohol) increased
and the selectivity to undesired products (i.e., tetrahydropyran,
tetrahydropyran-2-one, cyclopentanol and cylopentanone) de-
creased with increasing Na content on CeO2. The basicity of
hydroxyl groups or surface oxygen on CeO2 was altered with
the addition of Na, and controlled the dehydration reaction
pathway.
Introduction
Cerium oxide (CeO2, ceria) is known for its excellent redox
property, and is useful for many applications, including the
three-way catalyst for auto exhaust cleanup.[1] The high oxygen
storage capacity of ceria results from its rich density of oxygen
vacancies. Likewise, the acid–base properties of ceria can cata-
lyze transformations of a variety of organic molecules, includ-
ing reactions such as dehydration, dehydrogenation, dimeriza-
tion of alcohols, and condensation of aldehydes.[2–10]
selectivity to unsaturated alcohols was not defined. Igarashi
et al. have shown that the selectivity for unsaturated alcohol
from diol is influenced by the nature of the crystalline planes
present on the surface of ceria after calcination at various tem-
peratures.[15] In this regard, CeO2 {111} facets become predomi-
nant on the larger particles and are active for the formation of
unsaturated alcohols, whereas CeO2 {100} and {110} facets are
more exposed on the smaller ceria particles and catalyze side
reactions, such as cracking and cyclization.[15]
The conversion of pentanediol into value-added products is
becoming increasingly important because of its abundance de-
rived mainly from the biomass-based building block, furfural.[11]
One of the promising targets is the selective conversion of 1,5-
pentanediol into 4-penten-1-ol, as it is one of the raw materials
used to produce polymers.[12] The Sato group[13–19] has worked
on the dehydration of diols over various rare earth oxides, and
these authors found that the dehydration selectivity to unsatu-
rated alcohol from 1,5-pentanediol on ceria remains lower in
comparison with other diols, although the reason for such low
Another factor to be considered regarding the catalysis of
ceria is the presence of defect sites. Diols are adsorbed on
defect sites on ceria; however, the defect sites are nonuniform
and sites located on different exposed planes have different re-
activity. In this regard, Wu et al. recently showed that rod-
shaped ceria has a greater number of defect sites than cubic
and octahedral geometries.[20] Not only do defect sites change
with the geometric structure of ceria, but the acid–base prop-
erties are altered as well. Kobune et al. observed that dehydra-
tion of 1,3- and 1,4-butanediol to unsaturated alcohol on ceria
is a structure-sensitive reaction the activity of which increases
with increasing particle size of ceria.[4] Previously, we reported
that Ga- and In-modified ceria displayed higher reactivity for
dehydration of 1,5-pentanediol in comparison with ceria;
moreover, the product spectrum shifted towards greater cycli-
zation and cracking relative to dehydration. This was attributed
to differences in the shape of ceria as well as the intrinsic activ-
ity of Ga and In.[21] In the current contribution, the acid–base
property of ceria was modified by the addition of Na. Tempera-
ture-programmed desorption (TPD) of CO2 and diffuse reflec-
tance infrared Fourier transform spectroscopy (DRIFTS) tech-
niques were employed to investigate the basic properties of
the catalysts. The activity and selectivity for dehydration of 1,5-
pentanediol were correlated with the defect sites present on
the surface of ceria.
[a] Dr. M. K. Gnanamani, Dr. G. Jacobs, Dr. M. Martinelli, Dr. W. D. Shafer,
S. D. Hopps, G. A. Thomas, Dr. B. H. Davis
Center for Applied Energy Research
University of Kentucky
2540 Research Park Drive, Lexington, KY 40511 (USA)
E-mail: burtron.davis@uky.edu
[b] Dr. G. Jacobs
University of Texas at San Antonio
Chemical Engineering Program, Department of Biomedical Engineering
UTSA Circle, San Antonio, TX 78249 (USA)
[c] Dr. W. D. Shafer
Natural Science and Allied Health Department
Asbury University
Wilmore, KY 40390 (USA)
Supporting information and the ORCID identification number(s) for the
author(s) of this article can be found under https://doi.org/10.1002/
cctc.201701420.
ChemCatChem 2018, 10, 1 – 8
1
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Results and Discussion
The amount of Na present in ceria and Na-doped ceria was
measured experimentally by using inductively coupled plasma
optical emission spectroscopy (ICP–OES) and the data are
shown in Table S1 in the Supporting Information. The estimat-
ed values are in close agreement with the theoretical values
calculated for all catalysts based on molecular formulae of
NaCeO2 except 0.08Na0.92Ce and 0.10Na0.90Ce catalysts, for
which both were on the low side. Notably, even undoped ceria
has a slight percentage of Na (0.22 wt%). As expected, data
presented in Table S1 clearly show an increasing trend of Na
content in the ceria samples studied. The surface areas and
pore-size distributions of ceria and Na-doped ceria catalysts
are shown in Table 1. The surface area of the calcined ceria
Figure 1. TPR profiles of CeO2 and Na-doped CeO2 catalysts: (a) CeO2,
(b) 0.01Na0.99Ce, (c) 0.02Na0.98Ce, (d) 0.05Na0.95Ce, (e) 0.08Na0.92Ce,
(f) 0.1Na0.9Ce.
Table 1. BET surface area and average pore size
Catalyst
description
BET
S.A.
[m2 gÀ1
Pore volume
Pore diameter
8508C for all catalysts. The first reduction peak is generally as-
sociated with the partial reduction (e.g., surface shell reduc-
tion) of ceria from Ce4+ to Ce3+ and the second peak is attrib-
Single-point[a]
BJH[b]
BET[c]
[nm]
BJH[d]
[nm]
]
[cm3 gÀ1
]
[cm3 gÀ1
]
CeO2
114
112
112
100
88
0.167
0.164
0.164
0.149
0.141
0.137
0.171
0.169
0.168
0.153
0.144
0.140
5.8
5.8
5.8
5.9
6.3
6.6
4.5
4.5
4.5
4.6
4.8
4.7
uted to bulk reduction of ceria from Ce4+ to Ce3+ [22]
The
.
0.01Na0.99Ce
0.02Na0.98Ce
0.05Na0.95Ce
0.08Na0.92Ce
0.1Na0.9Ce
former may involve removal of surface-capping oxygen atoms
resulting in oxygen vacancy defects[22] and/or the formation of
bridging OH groups, either from dissociative adsorption of hy-
drogen or formation of water and subsequent dissociation of
water at the oxygen vacancy; ample evidence for the latter
viewpoint has been provided by infrared spectroscopy experi-
ments.[23,24] Note that replacing two surface O atoms by OH
groups is accompanied by a change in oxidation state of asso-
ciated Ce atoms from Ce4+ to Ce3+. Addition of Na to ceria up
to 0.02 caused a shift in the reduction peaks to higher temper-
ature. Further addition of Na (i.e., >0.02) to ceria resulted in a
sharpening of the reduction peak associated with surface shell
reduction. A likely explanation is that Na increases the basicity
of the catalyst, resulting in greater stability of carbonate, as ob-
served with low-temperature water-gas shift catalysts contain-
ing alkali metals.[25] From investigations of the reduction of
ceria by using X-ray absorption near-edge spectroscopy
(XANES) and DRIFTS, it is well known that upon surface shell
reduction of ceria, decomposition of surface carbonate also
occurs, with the formation of bridging OH groups.[21,22,26–29] The
shift in reduction peaks to higher temperature upon Na addi-
tion indicates that the reduction process associated with the
ceria surface is hampered by the presence of Na. Possible ex-
planations include (1) Na hindering the hydrogen dissociative
adsorption mechanism, attributed to a decreasing probability
for the formation of adjacent bridging OH groups because of
the presence of Na on the surface, and (2) Na increasing the
stability of surface carbonate because of the increased surface
basicity.
83
[a] Single-point pore volume obtained from single-point desorption total
volume of pores at P/Po =0.99. [b] BJH desorption cumulative volume of
pores between 1.7 and 300 nm diameter. [c] Desorption average pore di-
ameter by BET. [d] BJH desorption average pore diameter.
was 114 m2 gÀ1, and Na addition did not introduce any noticea-
ble changes up to a Na content of 0.02. A systematic decreas-
ing trend in BET surface area and pore volume was observed
with further increases in Na content up to 0.1. The N2 adsorp-
tion–desorption isotherms for ceria and various Na-doped
ceria catalysts were measured at the boiling temperature of
liquid nitrogen (À1968C) and are shown in Figure S1 in the
Supporting Information. All samples show a typical type IV iso-
therm with hysteresis, which is a characteristic of mesopores.
The BJH analysis infers that ceria possesses a narrow pore size
distribution and the pore sizes range from 2.5 to 7.0 nm. The
addition of Na to ceria was found to decrease both single-
point as well as the BJH pore volumes. The results suggest
that partial blockage in the pores of ceria occurred upon addi-
tion of Na above a certain level, which may have occurred
during calcination. The XRD patterns of ceria and Na-doped
ceria catalysts calcined at 5008C are shown in Figure S2. The
patterns are indexed to the cubic fluorite structure of ceria.
The estimated crystallite sizes for various catalysts are 9.0–
9.3 nm. This indicates that there are no significant differences
in the phases of ceria formed with addition of Na.
The CO2-TPD profiles of ceria and Na-doped ceria (i.e., after
reduction at 5008C under flowing H2 followed by the adsorp-
tion of CO2 at 308C) are shown in Figure 2. Pure ceria dis-
played multiple peaks in the temperature range of 60–2008C.
The low-temperature peak at ꢀ608C corresponds to the de-
The hydrogen temperature-programmed reduction (H2-TPR)
profiles of the calcined sample of ceria and Na-doped ceria cat-
alysts are depicted in Figure 1. A typical two-peak reduction
pattern is observed between 300 and 5008C and 650 and
&
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
2
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
Figure 2. TPD profiles of CO2 of CeO2 and Na-doped CeO2 catalysts after re-
duction under flowing H2 (50 cm3 minÀ1) at 5008C for 2 h.
sorption of physically adsorbed CO2 on ceria.[30] The multiple
peaks between 100 to 2008C indicate the presence of basic
sites of varying strengths on activated ceria. In general, the
basic sites on ceria are attributed to the presence of hydroxyl
groups and/or oxy anions associated with the partially reduced
ceria sites (CeÀOH or Ce3+ÀOÀ). The addition of Na on ceria
was found to suppress the overall intensity of the thermal con-
ductivity detector (TCD) signal. This suggests that Na ions
might undergo exchange with protons associated with hydrox-
yl groups on ceria and this could eventually have altered the
adsorption property of CO2. Gaillard found a single desorption
peak between 130 and 1808C from CO2-TPD over ceria and the
author attributed this to both mono- and bidentate carbonate
species.[31] In our case, the presence of Na has made the de-
composition of carbonate become more difficult on ceria.
DRIFTS spectra of ceria and Na-doped ceria after pre-treat-
ment conditions are shown in Figure 3. Ceria is known to
adsorb CO2 from the atmosphere and forms various carbonate
species (e.g., bicarbonate, bridged carbonate, bidentate car-
bonate, monodentate carbonate) depending on the nature of
the adsorption sites.[20] The DRIFTS spectra, as shown in
Figure 3 in the region between 1200 and 1600 cmÀ1, are as-
signed to the vibrations of various carbonate species. The in-
tensities of the peaks (1350 cmÀ1 and 1450 cmÀ1) increase with
increasing Na content on ceria up to 0.05, with a further in-
crease in Na causing the merging of the two peaks into a
single peak with a relatively higher intensity. This shows that
the amount of CO2 left over on ceria after activation depends
on the net Na content in the catalyst. Under the reducing envi-
ronment, CO2 was likely bound to hydroxyl groups as well as
coordinatively unsaturated oxygen vacancy sites on ceria, and,
therefore, the number of sites available on ceria for adsorption
of diols was diminished. This is reflected in the DRIFTS results
over the hydroxyl region for various reduced catalysts. There
are at least two major types of OH groups present on the sur-
face of reduced ceria. They are type I terminal OH groups
(3700–3720 cmÀ1) and lower wavenumber type II bridging OH
Figure 3. DRIFTS images for the CeO2 and Na-doped CeO2 catalysts after re-
duced under flowing H2/He at 5008C. The difference spectra were made by
using KBr as a background. (top, carbonate region; bottom, hydroxyl
region).
groups (Scheme 1) with the main
band associated with Ce3+ defects
located in the 3630–3660 cmÀ1.[27,32]
In our case, the peak intensity of
type II bridging OH groups re-
mained more or less the same with
the addition of Na on ceria up to
0.05, and further addition resulted
Scheme 1. Formation of
type II bridging OH groups
associated with defect sites
in a steep decrease in the intensity.
This suggests that Na primarily tar-
geted the negatively charged oxy-
anion species initially and then re-
on ceria.
placed the protons associated with hydroxyl groups on ceria.
The dehydration of 1,5-pentanediol was compared for vari-
ous catalysts at two different temperatures (350 and 4008C).
The effect of Na addition to ceria for the conversion of 1,5-
pentanediol at 3508C is shown in Figure 4. All catalysts exhibit-
ed a relatively stable conversion. A systematic decrease in con-
version of diol was observed with the addition of Na on ceria.
Both CeO2 and 0.01Na0.99Ce catalyst samples displayed similar
conversions (ꢀ45–48%), whereas the 0.02Na0.98Ce sample
had a lower conversion of ꢀ32%. The samples having higher
Na content (i.e., 0.05Na0.95Ce, 0.08Na0.92Ce, and 0.1Na0.90Ce)
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
3
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 5. Effect of Na content in CeO2 on the conversion and the product se-
Figure 4. Conversion of 1,5-pentanediol over CeO2 and Na-doped CeO2 cata-
lysts. Reaction conditions: 3508C, 1 atm, 0.6 mLhÀ1 of 1,5-pentanediol,
lectivity for the dehydration reaction of 1,5-pentanediol. Reaction condi-
tions: 3508C, 1 atm, 0.6 mLhÀ1 of 1,5-pentanediol, H2 =50 cm3 minÀ1
.
H2 =50 cm3 minÀ1
.
exhibited much lower conversion. The selectivity to 4-penten-
1-ol and 1-pentanol plotted against Na content are shown in
Figure 5. The selectivity to the desired product (i.e., 4-penten-
1-ol) increased with Na content and, at the same time, increas-
ing Na content tended to decrease the conversion of diols for
ceria. The CO2-TPD and DRIFTS studies indicate that Na altered
the acid–base characteristics of ceria, which could play an im-
portant role in the activity and the selectivity of the dehydra-
tion reaction. The selectivities of CeO2 and various Na-doped
CeO2 catalysts were compared at similar conversion levels so
that the effect of conversion on selectivity could be ruled out.
In this regard, the data in Figure 6 and Table 2 reveal an in-
creasing trend of selectivity to 4-penten-1-ol and 1-pentanol
from 12.2 and 22.2% for ceria to 34.5 and 28.2% for
0.1Na0.9Ce, respectively. In contrast, selectivity to the cyclized
products such as tetrahydropyran (THP) derivatives, cyclopen-
tanol, and cyclopentanone decreased. This suggests that Na
addition to ceria influences the reaction pathways for 1,5-pen-
tanediol.
Figure 6. Effect of Na content in CeO2 on the product distribution for the
dehydration of 1,5-pentanediol at similar conversion levels. Reaction condi-
tions: 4008C, 1 atm, 0.6–1.8 mLhÀ1 of 1,5-pentanediol, H2 =50 cm3 minÀ1
.
CyP-ol, cyclopentanol; CyP-one, cyclopentanone; THP, tetrahydropyran.
The adsorption of 1,5-pentanediol may take place on the
surface of reduced ceria. Depending upon the nature of sites,
as shown in Scheme 2, the reactant undergoes dehydration
and forms unsaturated alcohols or it might be involved in cyc-
lization that leads to tetrahydropyran (THP), tetrahydropyran-2-
one (THP-2-one), cyclopentanol, or cyclopentanone formation.
It is reported that either the acid–base property or the surface
Table 2. Dehydration of 1,5-pentanediol on CeO2 and Na-doped CeO2 catalysts.
Description
Calcination
temp. [8C]
Conversion of
1,5-pentanediol [%][a]
Product distributions [%]
4-penten-1-ol
1-pentanol
Cyclopentanol
Cyclopentanone
THP derivatives[b]
Others[c]
CeO2
500
500
500
500
500
500
65.6
48
51.7
51.3
48.5
49.4
12.2
22.2
18.7
28.2
31.3
34.5
22.2
16.5
20.2
24.1
27.0
28.2
3.8
0
16.2
0
1.4
1.5
31.5
31.3
14.7
24.7
20
8.9
26
21.1
20.2
16.2
12.6
21.4
4
9.1
2.8
4.1
3.2
0.01Na0.99Ce
0.02Na0.98Ce
0.05Na0.95Ce
0.08Na0.92Ce
0.1Na0.9Ce
20
[a] Reaction conditions: 4008C, 1 atm, 0.6–1.8 mLhÀ1 of 1,5-pentanediol, H2 =50 cm3 minÀ1; [b] THP derivatives include tetrahydropyran, tetrahydropyran-2-
one; [c] others include ethanol, acetone, 1-propanol, pentanal, cyclohexanone, cyclohexanemethanol, 4-penten-1-ol propanoate, valeric acid pentenyl
ester.
&
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
4
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
4008C and atmospheric pressure either by flowing
H2 or N2 (50 sccm) along with 1,5-pentanediol. For
CeO2, higher calcination temperature (8008C) result-
ed in a positive effect on the conversion of 1,5-pen-
tanediol whereas the selectivity for 4-penten-1-ol
and 1-pentanol did not vary significantly with calci-
nation temperature. However, THP formation de-
creased but cyclopentanone content increased with
increasing calcination temperature. On the other
hand, the 0.1Na0.9Ce catalyst exhibited decreasing
conversion of 1,5-pentanediol with increasing calci-
nation temperature from 500 to 8008C. Moreover,
the selectivity to 4-penten-1-ol was diminished in
the presence of flowing H2 from 34.5 to 20.8% with
increasing calcination temperature, and, consequent-
ly, 1-pentanol selectivity increased from 28.2 to
Scheme 2. Formation of various products from the dehydration of 1,5-pentanediol over
CeO2 and Na-doped CeO2 catalysts.
34.9%.
A
similar trend was observed using
0.1Na0.9Ce catalyst in N2 atmosphere. The results in-
dicate that lower calcination temperature favors the
geometry of rare earth oxides affects the formation of cyclic
ethers from the dehydration of 1,4-butanediol.[33] A recent
report suggests that a strong adsorptive interaction between
the catalyst and reactant would be favorable for the formation
of unsaturated alcohols from the corresponding diols.[34] In our
study, Na addition appears to increase the surface basicity of
ceria resulting in a decrease in the dehydration activity owing
to a loss in active sites (both oxygen vacancy sites as well as
basic hydroxyl groups) and a change in the selectivity from cy-
clized product to the desired product (i.e., unsaturated alco-
hol). This is manifested by the nature of the neighboring sites
associated with oxygen vacancy sites on ceria. Thus, the addi-
tion of Na provides ceria with a controlled environment that
prevents THP formation from 1,5-pentanediol. A study on the
effect of other alkali and alkali earth metals added to ceria for
the dehydration of 1,5-pentanediol is in progress. This further
enhances the understanding of the mechanisms of various
products formed from 1,5-penetanediol over ceria and its inter-
relation to acid–base properties.
formation of desired product (i.e., 4-penten-ol) from 1,5-penta-
nediol using 0.1Na0.9Ce. The higher activity has been reported
with increasing calcination temperature of CeO2 for dehydra-
tion of 1,3- and 1,4-butanediols.[4,35] In the present study, the
use of H2 instead of N2 along with reactant provided a positive
effect both on conversion as well as selectivity towards unsatu-
rated alcohol.
Conclusions
Vapor-phase catalytic dehydration of 1,5-pentanediol was in-
vestigated over ceria and Na-modified ceria catalysts. The addi-
tion of Na to ceria was found to enhance the selectivity to un-
saturated alcohol (i.e., 4-penten-1-ol) at similar conversion
levels and to suppress the selectivity to cyclized products such
as tetrahydropyran, tetrahydropyran-2-one, cyclopentanol, and
cyclopentanone from 1,5-pentanediol. Temperature-pro-
grammed reduction profiles indicate that the partial reduction
of surface ceria was hampered with addition of Na. Diffuse re-
flectance infrared Fourier transform spectra and CO2 tempera-
ture-programmed desorption profiles of the activated catalysts
revealed that the basicity of Na-doped ceria was higher than
that of the undoped catalyst. The addition of Na on ceria re-
The effect of calcination temperature on ceria and Na-doped
ceria catalysts was investigated for the dehydration of 1,5-pen-
tanediol, and the data collected after 3 h of time on-stream are
shown in Table 3. The dehydration reaction was performed at
Table 3. Effect of the carrier gas on the dehydration of 1,5-pentanediol over CeO2 and 0.1Na0.99Ce at different calcination temperatures.
Description Carrier Calcination Time on Conversion of
Product distributions [%]
gas
temp. [8C] stream [h] 1,5-pentanediol [%][a] 4-penten-1-ol 1-pentanol Cyclopentanol Cyclopentanone THP derivatives[b] Others[c]
CeO2
H2
H2
N2
N2
500
800
500
800
500
800
500
800
3
3.5
3
3
2.5
3
65.6
74.4
62.4
72.4
49.4
26.4
39
12.2
12
11
22.2
22.1
21.4
21
28.2
34.9
26.9
30.3
3.8
0.2
3.6
0.7
1.5
3.5
2
31.5
41.2
35.4
43.4
20
14.1
17.9
17.6
8.9
4.7
8.9
21.4
19.8
19.7
23.1
3.2
13.5
16.1
20.7
9
2.8
0.1Na0.9Ce H2
34.5
20.8
29
12.6
13.2
8.1
H2
N2
N2
2
3
25.7
16.5
3.8
11.1
[a] Reaction conditions: 4008C, 1 atm, feed rate of 1,5-pentanediol (1.2 mLhÀ1 for CeO2 and 0.6 mLhÀ1 for 0.1Na0.9Ce), H2 or N2 =50 cm3 minÀ1); [b] THP
derivatives include tetrahydropyran, tetrahydropyran-2-one; [c] others include ethanol, acetone, 1-propanol, pentanal, cyclohexanone, cyclohexanemetha-
nol, 4-penten-1-ol propanoate, valeric acid pentenyl ester.
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
5
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
rate of 6.88CminÀ1. DRIFTS spectra of samples were recorded using
a Nicolet Nexus 870 spectrometer equipped with a deuterated tri-
glycine sulfate and thermoelectrically cooled (DTGS–TEC) detector.
A thermo spectra–tech cell capable of high-pressure/high-tempera-
ture operation and fitted with ZnSe windows served as the cham-
ber for in situ reduction treatments. Scans were taken before and
after reduction in 100 cm3 minÀ1 of H2/He at 5008C at a resolution
of 4 cmÀ1 to give a data spacing of 1.928 cmÀ1. The difference
spectra were made using KBr as the background.
duces both the density of reduced defect centers (i.e., oxygen
vacancies and associated bridging hydroxyl groups) which ad-
versely affects the activity of ceria for the dehydration of 1,5-
pentanediol but, on the other hand, promotes the selectivity
to desired products. The higher calcination temperature of
CeO2 favors higher activity for the dehydration of 1,5-pentane-
diol whereas low calcination temperature shifts the selectivity
for 0.1Na0.9Ce catalyst more towards unsaturated alcohols.
Experimental Section
Dehydration activity
The dehydration reaction was performed by using a fixed-bed re-
actor in the temperature range between 350 and 4008C and at-
mospheric pressure. Typically, the calcined catalyst (1.0 g) in a
powder form (40–100 mm) was loaded into the reactor. The reactor
was a stainless-steel tube having a length of 35.6 cm with an inter-
nal diameter of 0.9 cm. The toal catalyst bed length was approxi-
mately 2.54 cm. The catalyst was pretreated under flowing H2
(50 cm3 minÀ1) at 5008C for 2 h. The catalyst-bed temperature was
monitored by a movable thermocouple (K-type) housed in a ther-
mowell. The catalyst-bed temperature was decreased to the de-
sired reaction temperature (350–4008C) and 1,5-pentanediol
(99.9% Sigma Aldrich) was fed at the desired flow rate by using a
syringe pump and combined with flowing H2 or N2 (50 cm3 minÀ1).
The products were collected in a trap maintained at room temper-
ature. The effluent gases were collected in a Tedlar gas bag during
various time intervals and analyzed using a micro GC (HP quad
series gas analyzer) to identify the formation, if any, of lower hy-
drocarbons. The liquid products condensed at room temperature
were analyzed by using an Agilent 7890 gas chromatograph
equipped with a DB-5 capillary column and a flame ionization de-
tector (FID). An appropriate FID response correction factor as pub-
lished in the open literature was applied for each component
found in the reaction mixture.[36]
Catalyst preparation
The ceria utilized in this study was HSA-10 Rhodia CeO2. The mate-
rial was calcined in static air at 5008C for 4 h and further used for
loading Na to different levels. An appropriate amount of Na
(atomic fractions, 0.01Na0.99Ce, 0.02Na0.98Ce, 0.05Na0.95Ce,
0.08Na0.92Ce, 0.1Na0.9Ce) was introduced into ceria in the form of
aqueous sodium nitrate (99.999% Sigma Aldrich) solution by fol-
lowing the incipient wetness impregnation (IWI) procedure. The re-
sulting solid was then dried in an oven at 1008C for 24 h and fur-
ther calcined in a muffle furnace at 500 or 8008C for 4 h.
Characterization
Elemental analysis of Na present in all catalyst samples was deter-
mined by ICP–OES using a Varian 720-ES analyzer. The materials
were dissolved in a perchloric/nitric acid mixture and the emission
spectra of dissolved species were compared to those of a series of
standard solutions of known concentrations. Specific surface areas
of calcined catalysts were measured by the BET method using a
Micromeritics 3-Flex system. Before performing the test, the tem-
perature was gradually increased to 1608C, and the sample was
evacuated at the same temperature for 12 h to a pressure of
6.67 Pa. The BET surface area, single-point pore volume, and single-
point average pore diameter were obtained. The Barrett–Joyner–
Halenda (BJH) method was used to estimate pore volume, pore di-
ameter, and pore-size distribution as a function of pore radius.
Powder X-ray diffractograms of the calcined catalysts were record-
ed using a Philips X’Pert diffractometer with monochromatic CuKa
radiation (l=1.5418). XRD scans were taken over the range of 2q
from 10–908. The scanning step was 0.01, the scan speed was
0.0025 sÀ1, and the scan time was 4 s. The crystallite sizes of ceria
were determined using the Scherrer equation, B=Kl/Lcosq (in
which B stands for peak width, K is a constant (0.94), l equals to
0.154 ꢁ, and L is the mean size of ordered crystalline domains. TPR
profiles for catalyst samples were recorded using a Zeton-Altamira
AMI-200 unit, which makes use of a thermal conductivity detector
(TCD). Typically, a 200 mg quantitiy of the sample was first subject-
Acknowledgements
The work performed at the CAER was supported by the Common-
wealth of Kentucky.
Conflict of interest
The authors declare no conflict of interest.
Keywords: alcohols · basicity · cerium · doping · olefination
ed to a heat treatment at 3508C in a flow of pure Ar (30 cm3 minÀ1
)
[1] A. Trovarelli, Catal. Rev. Sci. Eng. 1996, 38, 439–520.
[2] S. Sato, F. Sato, H. Totoh, Y. Yamada, ACS Catal. 2013, 3, 721–734.
[3] D. Haffad, A. Chambellan, J. C. Lavalley, J. Mol. Catal. A 2001, 168, 153–
164.
[4] M. Kobune, S. Sato, R. Takahashi, J. Mol. Catal. A 2008, 279, 10–19.
[5] S. Sato, R. Takahashi, N. Yamamoto, E. Kaneko, H. Inoue, Appl. Catal. A
2008, 334, 84–91.
[6] B. M. Reddy, G. K. Reddy, L. Katta, J. Mol. Catal. A 2010, 319, 52–57.
[7] B. M. Reddy, P. Lakshmanan, P. Bharali, P. Saikia, J. Mol. Catal. A 2006,
258, 355–360.
[8] M. G. Cutrufello, I. Ferino, E. Rombi, V. Solinas, G. Colon, J. A. Navio,
React. Kinet. Catal. Lett. 2003, 79, 93–99.
to remove residual water from the sample. The sample tempera-
ture was then cooled to 508C before the start of the TPR experi-
ment. TPR was performed by using a 10%H2/Ar mixture referenced
to Ar at a flow rate of 30 cm3 minÀ1. The sample was heated to
8008C at a ramp rate of 108CminÀ1. The TPD of adsorbed CO2 was
examined by using an in-house system consisting of a furnace ca-
pable of operating at temperatures of up to 12008C, along with a
TCD. Prior to TPD, the samples were pretreated at 5008C in flowing
H2 (50 cm3 minÀ1) for 2 h. The samples were then saturated with
pure CO2 at 308C for 1 h and subsequently flushed with He to
remove the physisorbed CO2. The CO2-TPD was performed by
using He and the temperature was increased to 8508C at a ramp
[9] A. K. P. Mann, Z. Wu, F. C. Calaza, S. H. Overbury, ACS Catal. 2014, 4,
2437–2448.
&
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
6
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
[10] H. Idriss, C. Diagne, J. P. Hindermann, A. Kiennemann, M. A. Barteau, J.
Catal. 1995, 155, 219–237.
[25] H. N. Evin, G. Jacobs, J. Ruiz-Martinez, G. A. Thomas, B. H. Davis, Catal.
Lett. 2008, 120, 166–178.
[26] J. El Fallah, S. Boujani, H. Dexpert, A. Kiennemann, J. Majerus, O. Touret,
F. Villain, F. Le Normand, J. Phys. Chem. 1994, 98, 5522–5533.
[27] A. Laachir, V. Perrichon, A. Badri, J. Lamotte, E. Catherine, J. C. Lavalley,
J. El Fallah, L. Hilaire, F. Le Normand, E. Quemere, G. N. Sauvion, O.
Touret, J. Chem. Soc. Faraday Trans. 1991, 87, 1601.
[28] G. Jacobs, S. Ricote, P. M. Patterson, U. M. Graham, A. Dozier, S. Khalid,
E. Rhodus, B. H. Davis, Appl. Catal. A 2005, 292, 229–243.
[29] G. Jacobs, L. Williams, U. Graham, D. Sparks, B. H. Davis, J. Phys. Chem. B
2003, 107, 10398–10404.
[11] R. Mariscal, P. Maireles-Torres, M. Ojeda, I. Sadaba, M. L. Granados,
Energy Environ. Sci. 2016, 9, 1144–1189.
[12] W. Wang, L. Hou, S. Luo, G. Zheng, H. Wang, Macromol. Chem. Phys.
2013, 214, 2245–2249.
[13] M. Segawa, S. Sato, M. Kobune, T. Sodesawa, T. Kojima, S. Nishiyama, N.
Ishizawa, J. Mol. Catal. A 2009, 310, 166–173.
[14] H. Gotoh, Y. Yamada, S. Sato, Appl. Catal. A 2010, 377, 92–98.
[15] A. Igarashi, N. Ichikawa, S. Sato, R. Takahashi, T. Sodesawa, Appl. Catal. A
2006, 300, 50–57.
[30] X. Jiao, L. Li, N. Zhao, F. Xiao, W. Wei, Energy Fuels 2013, 27, 5407–5415.
[31] F. Gaillard, Catal. Lett. 2004, 95, 23–29.
[16] S. Sato, R. Takahashi, M. Kobune, H. Inoue, Y. Izawa, H. Ohno, K. Takaha-
shi, Appl. Catal. A 2009, 356, 64–71.
[32] A. Badri, C. Binet, J. C. Lavalley, J. Chem. Soc. Faraday Trans. 1996, 92,
4669–4673.
[17] N. Ichikawa, S. Sato, R. Takahashi, T. Sodesawa, H. Fujita, T. Atoguchi, A.
Shiga, J. Catal. 2006, 239, 13–22.
[33] S. Sato, R. Takahashi, T. Sodesawa, A. Igarashi, H. Inoue, Appl. Catal. A
2007, 328, 109–116.
[34] H. Duan, M. Unno, Y. Yamada, S. Sato, Appl. Catal. A 2017, 546, 96–102.
[35] S. Sato, R. Takahashi, T. Sodesawa, N. Honda, H. Shimizu, Catal.
Commun. 2003, 4, 77–81.
[18] F. Sato, H. Okazaki, S. Sato, Appl. Catal. A 2012, 419–420, 41–48.
[19] F. Sato, S. Sato, Catal. Commun. 2012, 27, 129–133.
[20] Z. Wu, A. K. P. Mann, M. Li, S. H. Overbury, J. Phys. Chem. C 2015, 119,
7340–7350.
[21] M. K. Gnanamani, G. Jacobs, W. D. Shafer, S. D. Hopps, B. H. Davis, Chem-
istrySelect 2017, 2, 4150–4156.
[36] W. A. Dietz, J. Gas Chromatogr. 1967, 5, 68–71.
[22] H. C. Yao, Y. F. Y. Yao, J. Catal. 1984, 86, 254–265.
[23] C. Binet, M. Daturi, J. C. Lavalley, Catal. Today 1999, 50, 207–225.
[24] G. Jacobs, U. M. Graham, E. Chenu, P. M. Patterson, A. Dozier, B. H.
Davis, J. Catal. 2005, 229, 499–512.
Manuscript received: August 31, 2017
Revised manuscript received: November 8, 2017
Version of record online: && &&, 0000
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
7
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

FULL PAPERS
M. K. Gnanamani, G. Jacobs,
M. Martinelli, W. D. Shafer, S. D. Hopps,
G. A. Thomas, B. H. Davis*
On a sodium basis: Na-doped ceria
converts 1.5-pentanediol more selective-
ly to unsaturated alcohol than undoped
ceria. The basicity of catalysts deter-
mines the reaction pathway. Oxygen va-
cancies on the surface of ceria are the
primary adsorption sites for alcohols.
&& – &&
Dehydration of 1,5-Pentanediol over
Na-Doped CeO2 Catalysts
&
ChemCatChem 2018, 10, 1 – 8
www.chemcatchem.org
8
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!