Dehydration of 1,5-Pentanediol over CeO2-MeOx Catalysts

Article abstract of DOI:10.1002/cctc.201800999

The dehydration reaction of 1,5-pentanediol was performed over CeO₂ and modified CeO₂ (CeO₂?MnO_x, CeO₂?ZnO, CeO₂?MgO, CeO₂?CaO, CeO₂?Na₂O) catalysts in a fixed-bed tubular reactor at 350 °C and an atmospheric pressure. The undoped CeO₂ produced a mixture of the products containing mainly 4-penten-1-ol, 1-pentanol, cyclopentanol, cyclopentanone and tetrahydropyran-2-one from 1,5-pentanediol, while additions of MgO, MnO_x, or ZnO to CeO₂ was found to enhance the overall production rate of unsaturated alcohol. On the other hand, more basic metals like CaO or Na₂O tend to decline the dehydration activity of CeO₂. The porous structure of CeO₂ did not change appreciably with the addition of metal oxides. Temperature programmed desorption of adsorbed CO₂ on an activated catalyst suggest more CO₂ remain on the catalyst surface, particularly CeO₂?CaO and CeO₂?Na₂O indicating that fewer defect sites are only available for reaction. The defect sites or oxygen vacancy on CeO₂ controls both activity and selectivity for the dehydration of 1,5-pentanediol.

Full text of DOI:10.1002/cctc.201800999

Full Papers
DOI: 10.1002/cctc.201800999
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Dehydration of 1,5-Pentanediol over CeO2-MeOx Catalysts
Muthu Kumaran Gnanamani,[a] Michela Martinelli,[a] Sandeep Badoga,[a] Shelley D. Hopps,[a]
and Burtron H. Davis*[a]
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The dehydration reaction of 1,5-pentanediol was performed
over CeO2 and modified CeO2 (CeO2ꢀMnOx, CeO2ꢀZnO,
CeO2ꢀMgO, CeO2ꢀCaO, CeO2ꢀNa2O) catalysts in a fixed-bed
tubular reactor at 3508C and an atmospheric pressure. The
undoped CeO2 produced a mixture of the products containing
mainly 4-penten-1-ol, 1-pentanol, cyclopentanol, cyclopenta-
none and tetrahydropyran-2-one from 1,5-pentanediol, while
additions of MgO, MnOx, or ZnO to CeO2 was found to enhance
the overall production rate of unsaturated alcohol. On the other
hand, more basic metals like CaO or Na2O tend to decline the
dehydration activity of CeO2. The porous structure of CeO2 did
not change appreciably with the addition of metal oxides.
Temperature programmed desorption of adsorbed CO2 on an
activated catalyst suggest more CO2 remain on the catalyst
surface, particularly CeO2ꢀCaO and CeO2ꢀNa2O indicating that
fewer defect sites are only available for reaction. The defect sites
or oxygen vacancy on CeO2 controls both activity and selectivity
for the dehydration of 1,5-pentanediol.
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21 Introduction
22
23 Vapor phase dehydration of diols is catalyzed by various metal
24 oxides that include rare earth oxides.[1–4] Dehydration of diol is
25 an important reaction that generate unsaturated alcohols, a
26 raw material used in the polymer and fine chemicals indus-
27 try.[5–8] In the past, however, selective conversion of the diols
28 into unsaturated alcohol was achieved with 1,3- and 1,4-
29 diols.[9,10] Dehydration of 1,5-pentanediol often producing more
30 cyclized products such as cyclopentanol, tetrahydropyran than
31 the desired product, i.e., unsaturated alcohol using REO’s.
32 Sato[5,11–15] has claimed that rare earth oxides (REO’s) such as
33 CeO2, Tb4O7, ErO2O3, and Yb2O3 were effective on producing
34 unsaturated alcohols from various terminal diols. Regarding 1,5-
35 pentanediol, Sc2O3,[13] Lu2O3, and ScꢀYb mixed oxides[14] have
36 shown a higher activity and more selective to 4-penten-1-ol.
37 CeO2 exhibits the lower activity for dehydration of 1,5-
38 pentanediol in comparison with other diols and moreover the
39 selectivity to 4-penten-1-ol was achieved as high as 25% at
40 4008C.[5]
Scheme 1. Formation of oxygen defect center on CeO2
particles.[12] On the other hand, CeO2 also catalyze side reactions
such as dehydrogenation and/or cyclization producing cyclo-
pentanol, cyclopentanone, and tetrahydropyran-2-one from 1,5-
pentanediol.
In a recent study, we have investigated the effects of
addition of Na on ceria for the conversion of 1,5-pentanediol
and found that Na additions to CeO2 enhanced 4-penten-1-ol
formation from 1,5-pentanediol.[16] The basicity of CeO2 was
found to increase with increasing Na content and this could
eventually affect the formation of defect centers (i.e., oxygen
vacancy and the associated bridged hydroxyl groups) on CeO2
while activation in hydrogen. In the present work, CeO2 is
modified by the addition of different metal oxides with the aim
of altering the basic property and the defect sites of CeO2 to
control both activity and selectivity for dehydration of 1,5-
pentanediol. All catalysts were characterized by X-ray diffraction
(XRD), BET surface area, temperature programmed reduction
(H2-TPR), temperature programmed desorption of CO2 (CO2-
TPD) and attenuated total reflection Fourier transform infrared
(ATR-FTIR) techniques. Our results indicate that the defect sites
are responsible for both activity and the associated side
reactions occur on CeO2 during dehydration of 1,5-pentanediol.
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CeO2 is well-known as a redox catalyst due to its high
42 oxygen storage capacity. The defect centers are produced upon
43 O elimination from CeO2 and re-oxidation by O2 would happen
44 even at room temperature as shown in Scheme 1. This oxygen
45 deficiency can act as an adsorption site for reactants such as
46 CO, H2O and alcohols including diols. Earlier, Sato proposed
47 that Ce cations exposed at an oxygen-defect site of CeO2 (111)
48 surface are the active center for the dehydration of diols.[5] The
49 conversion of diols increases with an increase in the CeO2
50 particle size possibly due to more CeO2 (111) facets on larger
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[a] Dr. M. K. Gnanamani, Dr. M. Martinelli, Dr. S. Badoga, S. D. Hopps,
Results and Discussion
Dr. B. H. Davis
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Center for Applied Energy Research
University of Kentucky
2540 Research Park Dr.
Lexington KY 40511 (USA)
E-mail: burtron.davis@uky.edu
The XRD patterns of CeO2 and modified CeO2 are shown in
Figure 1. All samples show a typical diffraction pattern of
fluorite-like cubic structure of CeO2 as identified using the
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Figure 1. XRD patterns of CeO2 and modified CeO2 catalysts after calcina-
tions at 5008C.
21 standard data JCPDS Card No. 81-0792. For a cubic structure,
22 the lattice constant ‘a’ is evaluated using the relation [Eq. (1)],
23
1=d2 ¼ ðh2 þ k2 þ l2Þ=a2
ð1Þ
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Where, (hkl) are the Miller indices and d is the interplanar
˚
spacing. The lattice parameter of CeO2 was found to be 5.424 A.
The data agree well with those reported in the literature.[17–19]
The addition of MeOx have decreased the lattice parameter of
CeO2 from 5.424 to 5.421 for MnOx, 5.414 for ZnO, 5.408 for
MgO, 5.421 for CaO and 5.417 for Na. This change in the lattice
parameter could be interpreted due to differences in the ionic
radius between CeO2 and MeOx. Here all additives containing
metal cations are smaller in size relative to Ce4+ and thus the
lattice parameter is expected to shrink with the addition of
metal oxides (MnOx, ZnO, MgO, CaO, and Na2O) indicating the
intrusion of metal cations into the lattice of CeO2.
Figure 2. BJH adsorption-desorption isotherms (top) and corresponding BJH
pore size distributions (bottom) of CeO2 and modified CeO2 catalysts
calcined at 5008C.
the addition of MeOx and BJH pore size distributions for CeO2
has been shifted slightly to lower pore diameter as shown in
Figure 2 indicating that MeOx did not affect the porosity of
CeO2.
BET surface area and average pore size distributions for
39 CeO2 and modified CeO2 are shown in Table 1 and Figure 2.
40 Both BET surface area as well as the pore volume of CeO2 were
41 decreased with the addition of MeOx. As seen in Table 1, the
42 surface area for pure CeO2 was 114 m2/g and it was dropped to
43 100 for CeO2ꢀMnOx, 95 for CeO2ꢀZnO, 93 for CeO2ꢀMgO, 92 for
44 CeO2ꢀCaO and 83 for CeO2ꢀNa2O catalysts. The hysteresis
45 corresponds to a type-IV isotherm which remains unaltered by
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The temperature programmed reduction profiles using
hydrogen for various CeO2-based catalysts are shown in
Figure 3. Pure CeO2 shows a typical two peak reduction pattern.
The maxima for the low temperature peak is 4638C correspond-
ing to partial reduction of surface cerium oxide from Ce4+ to
Ce3+ and another peak at 7878C related to the bulk reduction
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Table 1. BET surface area and average pore size of CeO2 and modified CeO2 catalysts.
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Catalyst description
BET surface area
[m2/g]
Single point pore volume[a]
[cm3/g]
BJH pore volume[b]
[cm3/g]
Pore diameter[c]
[nm]
BJH pore diameter[d]
[nm]
CeO2
114
100
95
93
92
0.167
0.149
0.149
0.142
0.130
0.137
0.171
0.153
0.152
0.146
0.133
0.140
5.8
5.9
6.3
6.2
5.6
6.6
4.5
4.6
4.8
4.6
4.4
4.7
CeO2ꢀMnOx
CeO2ꢀZnO
CeO2ꢀMgO
CeO2ꢀCaO
CeO2ꢀNa2O
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[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 nm and 300 nm diameter; [c] Desorption average pore diameter by BET; [d] BJH desorption average pore diameter.
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Figure 4. TPD of CO2 on CeO2 and modified CeO2 catalysts after H2 activation
at 5008C.
Figure 3. H2-TPR patterns of CeO2 and modified CeO2 catalysts.
CeO2ꢀNa2O is relatively low compared to all other catalysts.
Boaro et al.[22] proposed a strong adsorption of CO2 on the
reduced Ce3+ sites. Therefore, one could correlate the amount
of desorbed CO2 to oxygen vacancy sites on a reduced CeO2. In
this case, the addition of more basic metal oxides such as MgO,
CaO and Na2O tend to suppress the oxygen vacancy sites on
CeO2 after activation due to CO2 being desorbed.
20 of CeO2. Doping of various metal oxides was found to shift the
21 reduction temperatures of CeO2. The CeO2ꢀMnOx catalyst
22 displayed a strong TCD response at 2008C which can be
23 assigned to the reduction of manganese oxide from MnOx to
24 Mn3O4 and another peak at 3298C corresponds to the partial
25 reduction of surface cerium oxide along with the reduction of
26 Mn3O4 to MnO. However, the high temperature reduction
27 profile remains unaffected for CeO2 by the addition of MnOx
28 indicating that the presence of manganese improves the
29 reducibility of cerium oxide [20]. Similarly, CeO2ꢀZnO also
30 seems to decrease the reduction temperature of CeO2. The
31 extent of reduction of CeO2 in CeO2ꢀZnO might be higher than
32 CeO2 alone as seen with increase in the intensity of reduction
33 peaks. On the other hand, MgO has shifted the reduction peaks
34 of CeO2 from 463 to 5028C. The intensity of high temperature
35 peak for CeO2 has been reduced significantly. The low temper-
36 ature profile for CeO2ꢀMgO appearing at 4108C can be
37 attributed to CO2 evolution from MgO. Likewise, CaO and Na2O
38 containing CeO2 also show very strong TCD signals between
39 450–4908C correspond to evolved CO2. The H2-TPR reveals that
40 MnOx and ZnO additions have a positive effect on the cerium
41 oxide reduction while MgO, CaO and Na2O tend to suppress it.
ATR-FTIR technique was used to analyze adsorbed CO2 on
calcined samples from atmosphere. The spectrum collected at
room temperature are shown in Figure 5. The pure CeO2 and
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The CO2-TPD profiles of CeO2 and modified CeO2 after
43 activation in hydrogen at 5008C are shown in Figure 4. The
44 pure CeO2 displayed two evident peaks, the first peak was
45 centered at ~110 8C and another with maxima at about 1508C
46 and both are related to a weakly adsorbed CO2 on CeO2. After
47 addition of MeOx to CeO2, the intensity of both peaks dropped
48 and at the same time the high-temperature shoulder at 1758C
49 has been shifted further to a higher value. This reveals that the
50 addition of MeOx could generate more medium strength basic
51 sites. In addition, CeO2ꢀMnOx and CeO2ꢀMgO were shown a
52 broad peak between 300 to 5008C and it could be attributed to
53 the desorption of CO2 from a separate MeOx species. Similarly,
54 CeO2ꢀCaO exhibits multiple high temperature peaks between
55 130 to 3008C. This high temperature peak can be attributed to
56 desorption of the adsorbed CO2 species from separate CaO
57 phase.[21] However, the amount of CO2 desorbed from
Figure 5. ATR-FTIR spectrum of CeO2 and modified CeO2 catalysts.
modified CeO2 catalysts exhibit carbonate bands between 1310
and 1600 cmꢀ1. A shoulder peak at 1630 cmꢀ1 d(HOH) can be
assigned to the bending vibrations of undissociated water
molecule. The addition of MeOx tends to shift carbonate bands
to a higher wavenumber indicating the increased stability of
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carbonate species on modified CeO2 catalysts compared to
pure CeO2. Based on the relative absorptivity, Na-modified CeO2
possess more CO2 meaning that more basic than CeO2ꢀCaO.
The relative basicity of catalysts decrease in the following order:
CeO2ꢀNa2O>CeO2ꢀCaO>CeO2ꢀMgO>CeO2=CeO2ꢀZnO>
CeO2ꢀMnOx. Altogether, CeO2ꢀNa2O is expected to release less
CO2 during activation with hydrogen and form oxygen vacancy
sites on CeO2. If this is the case, CeO2ꢀZnO and CeO2ꢀMnOx
should have higher vacancy sites than pure CeO2 after pretreat-
selectivity to various products obtained for all catalysts are
summarized in Table 2. The selectivity for 4-penten-1-ol on
CeO2ꢀMnOx (17.4%) and CeO2ꢀZnO (18.3%) catalysts is similar
as that of CeO2 (18.1%) but MgO and Na additions tend to
increase the unsaturated alcohol selectivity for CeO2. The
production rate of 4-penten-1-ol as a function of time on-
stream for all catalysts are shown in Figure 7. The production
10 ment and that should be reflected on dehydration activity.
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The conversion of 1,5-pentanediol on CeO2 and modified-
12 CeO2 catalysts are shown in Figure 6. Oure CeO2 shows 40%
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Figure 7. Rate of 4-penten-1-ol formation over CeO2 and modified CeO2
catalysts. Reaction conditions: 3508C, 1 atm, LHSV=0.6 ml/h, carrier gas=H2
(50 sccm), 1.0 g catalyst.
rate of 4-penten-1-ol for CeO2 was 0.28 mmol/h/g catalyst. Due
to a higher conversion, both CeO2ꢀZnO and CeO2ꢀMnOx were
shown a higher productivity compared to CeO2 though the
selectivity to 4-penten-1-ol for all three catalysts were very
close. In this context, Na2O and CaO modified CeO2 was
producing less unsaturated alcohol compared to CeO2 under
similar reaction conditions.
Figure 6. Conversion of 1,5-pentanediol over CeO2 and modified CeO2
catalysts. Reaction conditions: 3508C, 1 atm, LHSV=0.6 ml/h, carrier gas=H2
(50 sccm), 1.0 g catalyst.
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34 conversion of diol that remained more or less the same, while
35 CeO2ꢀMnOx and CeO2ꢀZnO both exhibited a higher conversion
36 (CeO2ꢀMnOx: 48–50% and CeO2ꢀZnO: 60%) than CeO2 and
37 other modified CeO2 catalysts. The conversion of 1,5-pentane-
38 diol decreased in the following order: CeO2ꢀZnO>
39 CeO2ꢀMnOx >CeO2 CeO2ꢀMgO>CeO2ꢀCaO>CeO2ꢀNa2O. The
40
The activity and product selectivity of dehydration of 1,5-
pentanediol were compared for different catalysts using either
H2 or N2 as a carrier gas. Figure 8 shows the ratio of linear
alcohols to the cyclized product for different catalysts. The
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Table 2. Dehydration of 1,5-pentanediol over CeO2 and modified CeO2 catalysts.[a]
Catalyst
Carrier gas
T [8C]
Conv. [%]
Selectivity [%]
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46
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48
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50
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4-P-1-ol
1-P-ol
CyP-ol
CyP-one
THP-2-one
others
CeO2
H2
H2
H2
H2
H2
H2
N2
N2
N2
N2
N2
N2
350
350
350
350
350
350
350
350
350
350
350
350
44.2
50.7
58.4
31.2
18.6
10.8
44.9
37.9
68.4
34.8
22.7
10.0
18.1
17.4
18.3
24.1
16.4
31.5
16.0
3.8
15.3
21.1
16.1
31.0
15.3
13.2
9.8
17.4
16.4
23.9
12.4
6.7
5.3
0.0
19.3
7.0
6.2
0.0
6.3
7.6
12.3
7.0
5.8
0.5
20.7
30.0
13.9
18.8
6.6
26.8
23.8
30.8
23.5
29.5
27.2
22.8
12.0
42.0
18.1
29.4
26.0
13.8
15.6
7.9
9.2
24.9
9.2
15.9
49.8
12.0
14.4
25.0
15.2
CeO2ꢀMnOx
CeO2ꢀZnO
CeO2ꢀMgO
CeO2ꢀCaO
CeO2ꢀNa2O
CeO2
CeO2ꢀMnOx
CeO2ꢀZnO
CeO2ꢀMgO
CeO2ꢀCaO
CeO2ꢀNa2O
8.2
26.6
20.1
12.2
23.0
7.5
6.2
16.4
16.2
19.5
7.8
[a] 4-P-1-ol=4-penten-1-ol; 1-P-ol=1-pentanol; CyP-ol=cyclopentanol; CyP-one=cyclopentanone; THP-2-one=tetrahydropyran-2-one; others=others
included ethanol, 1-propanol, 3,4-dihydropyran, 2-methylcyclopentanone, cyclohexane methanol, 4-penten-1-ol propanoate, valeric acid pentenyl ester,
cyclohexane carboxylic acid cyclohexyl ester, 2,2-dimethyl 3-octanol.
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pentanone, cyclopentanol, tetrahydropyran, tetrahydropyran-2-
one as all these products are thermodynamically favorable
under our reaction conditions. The cyclization of 1,5-pentane-
diol to tetrahydropyran was accompanied by a loss of water
and tetrahydropyran-2-one through H2 elimination. On the
other hand, cyclopentanone could be formed from 1,5-
pentanediol through 4-peneten-ol or 5-hydroxypentanal inter-
mediate as shown in Scheme 2. It is also possible that
cyclopentanone could be formed directly from 1,5-petanediol
on ceria. Addition of basic metals on CeO2 have changed its
reduction and oxygen vacancy sites as inferred from H2-TPR
and CO2-TPD. The vacancy sites on CeO2 decreased with
addition of MgO, CaO or Na2O; on the other hand MnOx and
ZnO promote more oxygen vacancy. Therefore, the dehydration
activity of 1,5-pentanediol for CeO2ꢀMnOx and CeO2ꢀZnO
catalysts are higher than CeO2. Also, irrespective of conversion
levels these catalysts promote not only the dehydration but
also the cyclization route equally. This suggest that addition of
MnOx and ZnO had a positive impact on the activity for
dehydration of 1,5-pentanediol whereas MgO, CaO and Na2O
could potentially impact the adsorption sites of CeO2 for diol.
Figure 8. Effect of carrier gas on the ratio of linear-to-cyclization products
formed from 1,5-pentanediol over CeO2 and modified CeO2 catalysts.
18 carrier gas was found to influence the product selectivity
19 obtained using both CeO2ꢀMnOx and CeO2ꢀZnO catalysts.
20 Overall, hydrogen seems to be a better carrier gas than
21 nitrogen from the selectivity point of view (Table 2). It is noticed
22 that the ratio of linear/cyclized products formed during the
23 dehydration reaction on CeO2ꢀMgO, CeO2ꢀCaO and CeO2ꢀNa2O
24 were well above pure CeO2. The positive effect from H2 on
25 product selectivity could be due to the preference of cerium
26 oxide from oxidation and keeping the cerium in partially
27 reduced state so as to interact with diols.
Conclusions
The addition of MeOx was found to affect both activity and
selectivity of CeO2 for dehydration of 1,5-pentanediol. BET
surface area and pore volume of CeO2 decreased with addition
of MeOx but increased the pore diameter slightly. H2-TPR
reveals that the partial surface reduction of CeO2 enhanced
with addition of ZnO, MnOx, or MgO while CaO and Na2O
additions tend to suppress the conversion. The CO2-TPD infers
that MeOx additions to CeO2 increased the catalyst basicity. The
undoped CeO2 shows dehydration as well as cyclization activity,
28
CeO2 is known to have oxygen vacancy with reduced Ce3+
29 sites after the reduction at higher temperatures.[20] This vacancy
30 site is claimed to be responsible for the activity of dehydration
31 of alcohols. Many suggest that the dissociative adsorption of
32 alcohol is the primary reaction occurs on a vacant site of surface
33 CeO2. As shown in Scheme 2, diol tend to undergo cyclization
34 on CeO2 and form many other side products such as cyclo-
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Scheme 2. Formation of products from dehydration of 1,5-pentanediol on CeO2-based catalysts.
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while MgO, MnOx, and ZnO modified CeO2 increase the
productivity of unsaturated alcohol (i.e., 4-penten-1-ol) from
1,5-pentanediol. The oxygen vacancy was generated on CeO2
by ejecting the adsorbed CO2 from the reduced Ce3+ sites are
potentially the adsorption sites for 1,5-pentanediol. The reac-
tivity of 1,5-pentanediol toward the selective formation of
unsaturated alcohol depend mostly on the neighboring sites
associated with an oxygen vacancy.
Dehydration Activity
The dehydration reaction was carried out using a fixed-bed reactor
at 3508C and atmospheric pressure. Typically, 1.0 g of calcined
catalyst in a powder form (40–100 microns) was loaded into the
reactor. The reactor is a stainless steel tube having a length of
35.6 cm with an internal diameter of 0.9 cm. The total catalyst bed
length is approximately 2.54 cm. The catalyst was pretreated under
flowing H2 (50sccm) at 5008C for 2 h. The catalyst bed temperature
was monitored by a K-type thermocouple (K-type) placed in the
middle of a catalyst bed. The catalyst bed temperature was
decreased to 3508C and 1,5-pentanediol (99.9% Sigma Aldrich) was
fed at the desired flow rate (0.6 ml/h) using a syringe pump and
combined with flowing H2 or N2 (50 sccm). The products were
collected in a trap maintained at 58C. 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 hydrocarbons. The liquid products
condensed in a trap (~58C) were analyzed using an Agilent 7890
gas chromatograph equipped with a DB-5 capillary column and an
FID detector. An appropriate FID response correction factor as
published in the open literature was applied for each component
found in the reaction mixture.[23
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11 Experimental
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13 Catalyst Preparation
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The CeO2 (HSA-10) was obtained commercially from Rhodia. The
material was calcined in a static air flow at 5008C for 4 h. All metal
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nitrates were purchased from Sigma Aldrich (99.9%). An appro-
priate amount of metal nitrate (90Ce:10Me) was dissolved in
deionized water and further added on to the calcined ceria samples
by following the incipient wetness impregnation (IWI) procedure.
The catalysts were dried in an oven at 1008C for 24 h and further
calcined in a muffle furnace at 5008C for 4 h.
Characterization
Acknowledgements
Powder X-ray diffractograms of CeO2 and modified CeO2 catalysts
after calcinations were recorded using a Philips X’Pert diffractom-
eter with monochromatic Cu Ka radiation (l=1.5418). XRD scans
were taken over the range of 2q from 5 to 908. The scanning step
This work was carried out at the CAER was supported by the
Commonwealth of Kentucky.
was 0.0178, and the scan speed was 0.042 sꢀ1
.
BET surface area and porosity characteristics of the calcined
catalysts were measured using a Micromeritics 3-Flex system.
Before performing the test, the temperature was gradually ramped
to 1608C from room temperature and the sample was evacuated at
this temperature for 12 h to approximately 50 mTorr. The BET
surface area, single point pore volume, and single point average
pore diameter were obtained for each sample. The Barrett-Joyner-
Halenda (BJH) method was also used to estimate pore volume and
average pore diameter, as well as to provide pore size distribution
as a function of pore radius.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: CeO2 · metal oxides · basicity · dehydration · 1,5-
pentanediol
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ChemCatChem 2018, 10, 1–8
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Dr. B. H. Davis*
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Dehydration of 1,5-Pentanediol
over CeO2-MeOx Catalysts
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What a site! The defect sites on CeO2
catalyze both dehydration and cycliza-
tion reactions for 1,5-pentanediol. The
addition of MeOx was found to affect
the defect sites formation over CeO2
which greatly impact the activity and
selectivity of dehydration of 1,5-pen-
tanediol. The CO2-TPD and FTIR
analyses indicate more CO2 would
remain on the surfaces of ceria after
MeOx additions. Moderate basicity is
needed for the selective conversion of
1,5-pentanediol to unsaturated
alcohol on ceria.