Vapor-phase catalytic dehydration of 1,4-butanediol to 3-buten-1-ol over modified ZrO2 catalysts

Article abstract of DOI:10.1016/j.apcata.2017.01.024

Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over modified ZrO₂catalysts. In the dehydration of 1,4-BDO over monoclinic ZrO₂(m-ZrO₂), an unsaturated alcohol, 3-buten-1-ol (3B1OL), was produced together with tetrahydrofuranand γ-butyrolactone. Among alkaline earth metal oxide modifiers, CaO with an appropriate content significantly enhanced the 3B1OL selectivity of m-ZrO₂. The modification of CaO was more efficient over m-ZrO₂than tetragonal ZrO₂. CO₂-TPD measurements reveal that CaO supported on m-ZrO₂calcined at 800?°C or higher generated new basic sites, which are attributed from Ca-O-Zr hetero-linkages, for the effective formation of 3B1OL from 1,4-BDO. In order to create more Ca-O-Zr hetero-linkages on the m-ZrO₂surface efficiently, additional ZrO₂was loaded on m-ZrO₂together with CaO via a co-impregnation method. At an appropriate weight ratio of CaO/ZrO₂?=?7/2 loaded on m-ZrO₂, both the 1,4-BDO conversion and the 3B1OL selectivity were enhanced greatly. Especially, the 3B1OL selectivity exceeded 90% at 350?°C.

Full text of DOI:10.1016/j.apcata.2017.01.024

Accepted Manuscript
Title: Vapor-phase catalytic dehydration of 1,4-butanediol to
3
-buten-1-ol over modified ZrO catalysts
2
Authors: Hailing Duan, Tomoya Hirota, Shota Ohtsuka,
Yasuhiro Yamada, Satoshi Sato
PII:
S0926-860X(17)30044-3
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2017.01.024
APCATA 16135
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
26-12-2016
23-1-2017
31-1-2017
Please cite this article as: Hailing Duan, Tomoya Hirota, Shota Ohtsuka,
Yasuhiro Yamada, Satoshi Sato, Vapor-phase catalytic dehydration of 1,4-butanediol
to 3-buten-1-ol over modified ZrO2 catalysts, Applied Catalysis A, General
http://dx.doi.org/10.1016/j.apcata.2017.01.024
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.

A revised manuscript for the original paper submitted to the journal of Appl. Catal. A: Gen.
MS#: APCATA-D-16-02325
Vapor-phase catalytic dehydration of 1,4-butanediol to 3-buten-1-ol over
modified ZrO catalysts
2
*
Hailing Duan, Tomoya Hirota, Shota Ohtsuka, Yasuhiro Yamada, Satoshi Sato
Graduate School of Engineering, Chiba University, Yayoi, Inage, Chiba 263-8522, Japan
*
Corresponding author. Tel. +81-43-290-3376; fax: +81-43-290-3401
E-mail address: satoshi@faculty.chiba-u.jp (S. Sato)
1

Graphic abstract
2

Highlights
Vapor-phase dehydration of 1,4-butanediol was studied over modified monoclinic ZrO2.
o
3
-Buten-1-ol was preferentially produced over CaO-modified ZrO catalysts at 350 C.
2
Active sites of Ca-O-Zr hetero-linkage were created efficiently by introducing additional
ZrO together with CaO.
2
Stable catalyitc activity was attained at conversion of 98.3% with the 3-buten-1-ol
selectivity of 86.9%.
The formation of 3-buten-1-ol proceeds via base-acid concerted mechanism.
3

Abstract
Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over
modified ZrO catalysts. In the dehydration of 1,4-BDO over monoclinic ZrO (m-ZrO ), an
2
2
2
unsaturated alcohol, 3-buten-1-ol (3B1OL), was produced together with tetrahydrofuran
THF) and γ-butyrolactone (GBL). Among alkaline earth metal oxide modifiers, CaO with
(
an appropriate content significantly enhanced the 3B1OL selectivity of m-ZrO . The
2
modification of CaO was more efficient over m-ZrO rather than tetragonal ZrO (t-ZrO ).
2
2
2
o
CO -TPD measurements reveal that CaO supported on m-ZrO calcined at 800 C or higher
2
2
generated new basic sites, which are attributed from Ca-O-Zr hetero-linkages, for the
effective formation of 3B1OL from 1,4-BDO. In order to create more Ca-O-Zr
hetero-linkages on the m-ZrO surface efficiently, additional ZrO was loaded on m-ZrO
2
2
2
together with CaO via a co-impregnation method. At an appropriate weight ratio of
CaO/ZrO =7/2 loaded on m-ZrO , both the 1,4-BDO conversion and the 3B1OL selectivity
2
2
o
were enhanced greatly. Especially, the 3B1OL selectivity exceeded 90% at 350 C.
Keywords: 1,4-Butanediol; 3-Buten-1-ol; Dehydration; CaO modifier; m-ZrO support;
2
Co-impregnation.
4

1
. Introduction
A wide variety of chemicals such as tetrahydrofuran, butyrolactone, polybutylene
terephthalate, 1,4-butanediol diglycidyl ether, and poly tetramethylene ether glycol, etc. are
available from 1,4-butanediol (1,4-BDO), which is currently manufactured from fossil-based
feedstocks such as acetylene, propylene, butane, and butadiene. In order to realize the
low-carbon society via diminishing the usage of fossil sources, recently more efforts on the
biomass-derived 1,4-BDO synthesis have been devoted. [1, 2, 3] Thus, the wide application
of the biomass-derived 1,4-butanediol must be developed in the future.
Unsaturated alcohols such as 3B1OL, 2-buten-1-ol, and 3-buten-2-ol are valuable
intermediates for the synthesis of medical drugs, agricultural chemicals and function
polymers [4-8]. As for the selective dehydration of 1,4-BDO to 3B1OL, our group has
previously reported several active catalysts such as CeO [9-12], In O [13, 14], rare earth
2
2
3
metal oxides (REOs) [15-19], ZrO [20], and also ZrO modified with alkali cations [21].
2
2
Oxygen defect sites on the cubic fluorite CeO with (111) facets provide adsorption sites of
2
BDO for the dehydration [3, 9, 22-24].
Bixbyite REOs such as Yb O and Er O have the same crystal structure as In O [13]
2
3
2
3
2
3
and the oxygen defects with exposed rare earth cations on their (222) facets [15-18]. Their
temperature-programmed desorption (TPD) profiles of adsorbed CO and NH indicate that
2
3
only a few weak basic sites and almost no acidic sites are left after being calcined at high
temperatures [25]. However, both the 1,4-BDO conversion and the 3B1OL selectivity were
markedly suppressed by poisoning Er O catalyst with CO carrier gas during the
2
3
2
dehydration, while only the 1,4-BDO conversion decreased in an NH atmosphere [16]. An
3
2
-
H atom at position 2 of 1,4-BDO captured by a basic site (O anion) in addition to the
oxygen atoms in the two OH groups coordinating onto two acidic sites (oxygen vacancies)
should be the most probable adsorption model for the formation of 3B1OL [18]. Then, the H
2
-
atom at position 2 is abstracted by the basic O followed by the abstraction of the OH group
3
+
at position 1 by Er via an acid-base concerted mechanism.
A pure m-ZrO catalyst also provided the acid-base concerted sites for the formation of
2
5

3
B1OL from 1,4-BDO, while 3B1OL and THF competed at a ratio of ca. 1:1 over the
m-ZrO due to its excess acidic sites [19]. In order to adjust the basicity-acidity of ZrO to
2
2
an appropriate balance for the 3B1OL formation, alkali-modified ZrO samples were
2
prepared. The 3B1OL selectivity was greatly enhanced from 45.7% to 71.8% and the side
o
reaction for THF was suppressed at 325 C [20]. Besides, the Yb O supported on m-ZrO
2
3
2
also showed an excellent selectivity to 3B1OL over 80% [21].
O
O
O
HO
HO
+
+
OH
2
+
Zhang et al. introduced Ca into ZrO and generated new medium basic sites on the
2
CaO-modified ZrO catalysts, which enhanced the 3B1OL yield up to 70% in the
2
dehydration of 1,4-BDO, where they used a mixture of t-ZrO and m-ZrO as a support [26,
2
2
2
7]. In contrast, it has been reported that m-ZrO usually performed better than t-ZrO for
2 2
the formation of unsaturated alcohols from butanediols [19-21, 28-30]. Recently, we have
succeeded in modifying m-ZrO with the alkaline earth metal oxides such as CaO, SrO and
2
BaO to generate basic sites efficiently for the dehydration of 2,3-butanediol to 3-buten-2-ol
[
31, 32]. It is confirmed that basic sites with medium strength induced by Ca-O-Zr
hetero-linkage was formed on the m-ZrO surface, where the samples must be calcined at
2
o
8
00 C or higher temperatures [32].
In the present work, we investigated the catalytic activities of CaO/m-ZrO in the
2
dehydration of 1,4-BDO to produce 3B1OL. In the active catalysts, active centers associated
with Ca-O-Zr hetero-linkage were considered to be generated efficiently on m-ZrO surface.
2
In addition, we prepared CaO/m-ZrO catalysts with co-impregnation method in order to
2
create more Ca-O-Zr hetero-linkages efficiently: CaO with additional ZrO was loaded on
2
m-ZrO surface.
2
2
. Experimental
6

2
.1 Catalyst preparation
m-ZrO (RSC-HP) and t-ZrO (Z-3377) were supplied by Daiichi Kigenso Kagaku
2
2
Kogyo Co. Ltd., Japan. SiO (CARIACT Q10) was provided by Fuji Silysia Chemical Ltd.,
2
Japan. TiO (CS-750-24) was supplied by Sakai Chemical Industry Co., Ltd., Japan. Al O
3
2
2
was supplied by Catalysis Society of Japan as a Japan reference catalyst (JRC-ALO-5).
Mg(NO ) ·6H O, Ca(NO ) ·4H O, Sr(NO ) , Ba(NO ) , ZrO(NO ) ·2H O, and 1,4-BDO
3
2
2
3 2
2
3 2
3 2
3 2
2
were purchased from Wako Pure Chemical Industries, Ltd., Japan.
These metal oxides were loaded on the supports by incipient wetness impregnation
method. Each aqueous solution of nitrate with the prescribed amount of metal was
impregnated on either m-ZrO or other supports. Besides, in the co-impregnation of both
2
CaO and ZrO onto m-ZrO , the mixture of their aqueous nitrate solution was used. The
2
2
o
samples loaded with nitrate were dried at 110 C for 12 h and then calcined in air at a
prescribed temperature for 3 h. Hereafter, the ZrO -supported catalysts are expressed as
2
X-MO/ZrO -T, where MO means the alkaline earth metal oxide impregnated on the support
2
ZrO , X is the weight content of MO and T represents the calcination temperature. The
2
samples prepared with the co-impregnation method are also denoted as
X-CaO+Y-ZrO /ZrO -T, in which Y is the weight percentage of loaded ZrO . In addition,
2
2
2
perovskite-type CaZrO was prepared by amorphous citrate process [33] using a mixture of
3
their nitrates and citric acid with the molar ratio Ca: Zr: citric acid=1:1:3 in vacuum at
o
o
o
1
00 C for 2 h and then heated at 180 C for 3 h and finally calcined in air at 800 C h for 3 h.
2
.2 Catalytic reaction
The reaction was carried out in a fixed-bed flow reactor under atmospheric pressure of
3
-1
o
carrier gas (either N or H ) with a flow rate of 30-90 cm min at 300-375 C. A catalyst
2
2
(0.5-1.25 g) was placed on a glass wool as the fixed bed. After the catalyst had been heated
at the prescribed reaction temperature for 1 h, the reactant 1,4-BDO was fed into the reactor
-1
-1
at a liquid feed rate of 1.67 g h (18.6 mmol h ). The contact time, W/F, where W is catalyst
weight and F is the feed rate of 1,4-BDO, was typically 0.30 h at W= 0.5 g. The liquid
7

effluent collected hourly was analyzed by gas chromatography (FID-GC-8A, Shimadzu,
Japan) with a 30-m capillary column (InertCapWAX-HT) and identified by gas
chromatography-mass spectrometry (GCMS-QP5050A, Shimadzu, Japan) with a 30-m
capillary column (DB-WAX). The catalytic activity was stabilized for the initial 5 h, so that
it was evaluated by averaging the conversion and selectivity data of the initial 5 h. Both the
conversion of 1,4-BDO and the selectivity to each product were defined as mol%.
In a poisoning experiment, the catalytic reaction was carried out in a same way as
described above where either CO or NH was mixed with H carrier gas. Total flow rate of
2
3
2
3
-1
3
-1
gas mixture was fixed at 30 cm min , and either CO or NH was flowed at 15 cm min .
2
3
2
.3 Characterization
X-ray diffraction (XRD) patterns were recorded on New D8 ADVANCE (Bruker)
using Cu Kα radiation (λ= 0.154 nm) to identify the crystal structure of each catalyst. The
specific surface area (SA) of catalyst was calculated by the Brunauer-Emmett-Teller (BET)
o
method using the N isotherm at -196 C. In order to estimate the basicity and acidity of the
2
catalysts, TPD profiles of CO and NH were measured by a self-made apparatus using the
2
3
change in the conductivity of the solution, into which the desorbed probe gas bubbled with
N carrier gas [34, 35]. The amounts of basic and acidic sites were estimated from
2
neutralization-titration curves of diluted NaOH and H SO solution, respectively.
2
4
3
. Results
.1. Dehydration of 1,4-BDO over m-ZrO and modified m-ZrO .
3
2
2
In the dehydration of 1,4-BDO, it was confirmed that the main products are 3B1OL,
THF, GBL, 2-buten-1-ol, 1-butanol, and 1,3-butadiene. Table 1 lists the results of catalytic
tests of oxide supports used in this study. Among the supports, m-ZrO showed 33.6%
2
selectivity of 3B1OL, which is consistent with the previous work [19-21]. They, except SiO2,
showed almost full conversion of 1,4-BDO, and high selectivity to THF but rare 3B1OL
except ZrO . This indicates that the acidic oxides such as TiO and Al O are not suitable for
2
2
2
3
8

the formation of 3B1OL. The modification with basic oxide was conducted: 7wt.% CaO was
loaded on these supports. The supports such as SiO , TiO , and Al O are not sensitive to the
2
2
2
3
CaO modifier since they showed no significant changes in the selectivities to THF and
B1OL. The modification, however, affected both t-ZrO and m-ZrO for the selective
3
2
2
production of 3B1OL. Especially, 7-CaO/m-ZrO -800 enhanced the 3B1OL selectivity from
2
3
3.6 to 86.9%, while the 3B1OL selectivity was 68.2% over 7-CaO/t-ZrO -800. However,
2
the loading of CaO onto both t-ZrO and m-ZrO decreased the 1,4-BDO conversion greatly.
2
2
Judging from the high 3B1OL selectivity, we chose m-ZrO as a support in the following
2
study.
Catalytic reaction of 1,4-BDO was also conducted over m-ZrO modified with other
2
alkaline earth metal oxides such as MgO, SrO and BaO at the same mole percentage (Table
1
). The results indicate that these modified m-ZrO enhanced the 3B1OL selectivity but
2
decreased the 1,4-BDO conversion largely. Table 1 also lists the results of catalytic activities
of CaO/m-ZrO with different CaO loadings. At CaO loadings of 5-7 wt.%, high 3B1OL
2
selectivity and relatively high conversion were attained, while excess CaO decreased the
conversion of 1,4-BDO.
Table 2 summarizes the effect of calcination temperature of 7-CaO/m-ZrO on the
2
o
dehydration of 1,4-BDO. In the calcination temperature range of 600-1000 C,
7
-CaO/m-ZrO -900 maintained the conversion at a high level together with high 3B1OL
2
selectivity. The calcination temperature significantly affects the catalytic activity of the
o
resulting CaO/m-ZrO samples. It is noted that 900 C would be needed to construct the
2
active centers on the CaO/m-ZrO but the high temperature decreases the SA. The SA of
2
2
-1
2 -1
7
-CaO/m-ZrO -600 was 44.8 m g , and it decreased to 29.8, 27.7, 23.7, and 14.4 m g after
2
o
calcined at 700, 800, 900, and 1000 C, respectively. The catalytic activity has no correlation
2
-1
with SA of catalyst. In addition, perovskite-type CaZrO with a SA of 7.4 m g showed a
3
low conversion as well as poor selectivity to 3-B1OL.
3
.2 The effects of additional ZrO with CaO via co-impregnation.
2
9

As shown in Table 2, the 3B1OL selectivity has greatly enhanced at high calcination
o
temperatures over 7-CaO/m-ZrO . But we supposed that the calcination at 900 C is too high
2
2
-1
for the catalyst preparation. The SA of as-received m-ZrO was 46.3 m g , and it decreased
2
2
-1
o
to 33.8, 27.8, 17.4, and 12.0 m g after being calcined at 700, 800, 900, and 1000 C,
respectively. This is a disadvantage for high conversion due to the low SA. Thus, in order to
2+
4+
mix Ca effectively with Zr to create Ca-O-Zr hetero-linkage at somewhat high SA, we
also modified m-ZrO2 with CaO and ZrO (the weight rate CaO:ZrO =7:2) via
2
2
o
co-impregnation and calcined at 800 C. The SA of 7-CaO+2-ZrO /m-ZrO -700 was 29.8
2
2
2
-1
2 -1
o
m g , and it decreased to 27.0, 23.5, and 14.2 m g after calcined at 800, 900, and 1000 C,
respectively. The SA values are quite similar to those of 7-CaO/m-ZrO . Table 3 shows the
2
effects of additionally introduced ZrO on the catalytic performances. Additional ZrO
2
2
contents of 1-5 wt.% enhanced both the conversion and the 3B1OL selectivity.
7
1
-CaO+2-ZrO /m-ZrO -800 shows the highest 3B1OL selectivity at a relatively high
2
2
,4-BDO conversion.
Table 4 shows the effect of calcination temperature of 7-CaO+2-ZrO /m-ZrO on their
2
2
catalytic activities. The effect is basically resembled to that of 7-CaO/m-ZrO (Table 2).
2
7
8
-CaO+2-ZrO /m-ZrO shows the highest 3B1OL selectivity at a calcination temperature of
2 2
o
o
00 C: the 3B1OL selectivity exceeded 89% at 800 C, while the 1,4-BDO conversion was
o
2+
4+
maximal at 850 C. By introducing Ca
together with Zr
on to m-ZrO2 of
7
-CaO+2-ZrO /m-ZrO , high 3B1OL selectivity can be activated at a low calcination
2
2
o
o
temperature of 800 C, whereas it is activated at 900 C over 7-CaO/m-ZrO sample.
2
7
3
-CaO+2-ZrO /m-ZrO -800 shows a high 1,4-BDO conversion of 68.2% and the highest
2 2
B1OL selectivity of 89.3%, while 7-CaO/m-ZrO -900 shows the highest 1,4-BDO
2
conversion of 67.1% and a high 3B1OL selectivity of 87.2%.
The effects of reaction temperature were investigated over 7-CaO+2-ZrO /m-ZrO -800
2
2
sample. The product distribution as well as the 1,4-BDO conversion is summarized in Table
S1. The 1,4-BDO conversion increased steeply with increasing reaction temperature while
o
o
the 3B1OL selectivity was maximal at 350 C. At 375 C, the 1,4-BDO conversion reached
1
0

almost a full conversion (98.1%), and the 3B1OL yield exceeded 83%.
Table 5 lists the effects of contact time over 7-CaO/m-ZrO -900, 7-CaO/t-ZrO -800
2
2
and 7-CaO+2-ZrO /m-ZrO -800, which showed the best performance to 3B1OL formation
2
2
in their series. The long contact time gave more chance for the isomerization of 3B1OL to
-buten-1-ol, and resulted in a slight decline of the 3B1OL selectivity. On the other hand,
almost a full conversion is available over the three catalysts at the contact time longer than
.6 h. 7-CaO/t-ZrO -800 showed the 3B1OL yield of 69.9%. The value is consistent with the
2
0
2
yield reported by Zhang et al. [26], who used a mixture of t-ZrO and m-ZrO as a support
2
2
and showed high stability of catalyst. Over the present modified m-ZrO , however, the
2
3
B1OL yield exceeds 85% (Table 5). At a long contact time of 0.60 h, a high 3B1OL yield
of 75.1% was obtained over 7-CaO/m-ZrO -900. The highest 3B1OL yield over 85.9% was
2
obtained over 7-CaO+2-ZrO /m-ZrO -800. Fig. 1 shows the catalytic stability of
2
2
o
7
0
-CaO+2-ZrO /m-ZrO -800 in the dehydration of 1,4-BDO at 350 C and a contact time of
2 2
.60 h. Both the 1,4-BDO conversion (95.2%) and the 3B1OL selectivity (89.3%) were kept
stably with time on stream for 24 h.
3
.3 Effect of carrier gas on the catalytic activity.
The effect of carrier gas on the catalytic activity of 7-CaO+2-ZrO /m-ZrO -800 at
2
2
o
3
50 C is summarized in Table S2. The reactions were conducted in both H and N flow.
2 2
Both the 3B1OL selectivity and the reactant conversion in H carrier gas were higher than
2
those in N . The reason can be deduced to that H carrier gas may reduce the
2
2
dehydrogenation to by-products such as GBL. In addition, the 1,4-BDO conversion was
increased with increase in the flow rate of carrier gas: a high conversion over 80% and a
3
-1
high 3B1OL selectivity over 90% with the carrier gas flow rate faster than 60 cm min at
o
3
50 C. It is reported that there are equilibrium reactions competing between the by-products
and 1,4-BDO [36, 37]. Thus, a high speed of carrier gas changed the partial pressures of
reactant and by-products, and led to the high conversion and the 3B1OL formation rate.
Table 6 shows the poisoning effects of basic and acidic gases in the H carrier gas on
2
11

o
the catalytic activity of m-ZrO2 at 300 C and of 7-CaO/m-ZrO -900 and
2
o
7
-CaO+2-ZrO /m-ZrO -800 at 350 C. Ammonia and carbon dioxide were used as a basic
2
2
and acidic gases. In a pure H flow, m-ZrO produced 3B1OL and THF with the ratio of ca.
2
2
2
5:75. In the addition of NH gas into H flow, the 3B1OL yield was increased 1.5-fold,
3 2
while the THF yield was reduced almost by half. In the addition of CO , the 3B1OL yield
2
was decreased by 20%, while the THF yield was increased by 14%. Over
7
-CaO/m-ZrO -900 and 7-CaO+2-ZrO /m-ZrO -800, the addition of CO gas into H flow
2 2 2 2 2
decreased the 3B1OL yield by 33-42%, while even NH gas decreased the 3B1OL yield by
3
9
-23%. These results present important suggestion to consider the reaction mechanism,
which will be discussed in the following Section 4.3.
3
.4 Characterization of CaO/m-ZrO2.
Fig. 2 shows the XRD patterns of the m-ZrO modified with alkaline earth metal
2
oxides. Monoclinic phase was detected in the samples. In the samples other than m-ZrO2,
-MgO/m-ZrO -800, and 7-CaO/m-ZrO -700, new diffraction patterns assigned to
5
2
2
perovskite compounds such as CaZrO , SrZrO and BaZrO were detected. MgO/m-ZrO
2
3
3
3
samples had only monoclinic phase regardless of calcination temperature without new
diffraction patterns attributed to other crystal phases such as MgZrO3.
In CaO/m-ZrO samples, only m-ZrO phase was detected at a calcination temperature
2
2
o
o
of 700 C while the intensity of diffraction peaks of CaZrO became stronger above 800 C.
3
o
At 900 C, t-ZrO phase appeared together with the decrease in the m-ZrO phase. Besides,
2
2
o
large diffraction peaks assigned to t-ZrO were also observed at 1000 C. It is confirmed that
2
the high calcination temperature induces the transformation of ZrO crystal structure from
2
monoclinic to tetragonal phase. However, the new t-ZrO phase showed no significant
2
effects on the catalytic activity (Table 2).
In the TPD profiles of ammonia adsorbed on t-ZrO and m-ZrO (profiles not shown),
2
2
o
there is only a little difference in their acid properties: small desorption peaks around 150 C
o
and 400 C were observed from the t-ZrO whereas m-ZrO adsorbed no ammonia. Fig. 3a
2
2
1
2

displays the TPD profiles of CO adsorbed on m-ZrO modified with alkaline earth metal
2
2
oxides at the same molar percentage (14.5mol%). With loading of MgO, CaO, SrO and BaO
onto m-ZrO , the peaks present the weak basic sites via the CO -TPD profiles shifted from
2
2
o
o
9
7 (α) to 124 C (α’). Besides, the peaks present the medium basic sites (β) around 320 C
were also detected from all the modified samples while CaO/m-ZrO holds the most CO .
2
2
o
On the other hand, the CO desorption peaks higher than 500 C were also detected from
2
SrO/m-ZrO and BaO/m-ZrO which resulted from the decomposition of SrCO and BaCO ,
2
2
3
3
which may be formed during the storage in an atmosphere at room temperature [38]. A
similar change is also observed in our previous work for the other CaO/m-ZrO with
2
different type of m-ZrO support [31, 32]. The CO -TPD profiles of 7-CaO/m-ZrO -800
2
2
2
shows the most basic sites β. The changes of their base properties affected from CaO content
and calcination temperature are also well accorded with our previous report [31]. Thus, the
TPD profiles are shown in Fig. S1.
3
.5 Characterization of CaO+ZrO /m-ZrO -800.
2 2
Fig. 4a exhibits the XRD pattern of X-CaO+Y-ZrO /m-ZrO -800 samples. In all the
2
2
o
samples, the diffraction peaks at 22.3, 31.8, and 45.4 assigned to CaZrO were observed.
3
However, the strength of the diffraction peaks was weakened gradually with the additional
ZrO , and then grew stronger again at additional ZrO contents higher than 5wt.%. The
2
2
change in the 1,4-BDO conversion (Table 3) seems to be correlated with the variation of
CaZrO with the additional ZrO content. It is suggested that the increase in CaZrO
3
3
2
formation leads to decrease in the amount of active sites since CaZrO was not active for the
3
formation of 3B1OL from 1,4-BDO (Table 2). Therefore, 7-CaO+2-ZrO /m-ZrO -800 with
2
2
the least CaZrO shows the highest 1,4-BDO conversion, as shown in Table 3. Excess
3
additional ZrO resulted in the CaZrO formation and the decrease in both the 1,4-BDO
2
3
conversion and the 3B1OL selectivity. Fig. 4b illustrates the XRD patterns of
o
7
-CaO+2-ZrO /m-ZrO samples with different calcination temperatures. At 700 C, only
2
2
o
o
m-ZrO phase was detected while CaZrO appeared at 800 C or higher. At 900 C, t-ZrO
2
2
3
1
3

o
phase appeared together with decrease in m-ZrO phase. At 1000 C, t-ZrO phase grew
2
2
stronger. There was no significant difference in the XRD profiles between
7
-CaO+2-ZrO /m-ZrO (Fig. 4b) and CaO/m-ZrO samples (Fig. 2).
2 2 2
Fig. 3b depicts the CO -TPD profiles of the 7-CaO+Y-ZrO /m-ZrO -800 samples.
2
2
2
7
-CaO+Y-ZrO /m-ZrO -800 (Y= 0, 1, 2, and 3) samples had α’ and β basic sites. The most α’
2
2
and β basic sites were detected from 7-CaO+2-ZrO /m-ZrO -800, which was quite similar to
2
2
those of 7-CaO/m-ZrO -800.
2
4
. Discussion
4
.1 The active structure for the 3B1OL formation from 1,4-BDO.
Over m-ZrO modified with different alkaline metal oxides, even though the same
2
molar percentage was loaded, the 3B1OL selectivity was enhanced with different levels over
m-ZrO modified with MgO, CaO, SrO, and BaO (Table 1). The formation of perovskite
2
compounds MZrO (M=Ca, Sr, and Ba), but no MgZrO was detected from MgO/ZrO
2
3
3
samples for its instability [38]. The high calcination temperature also makes the intensity of
MZrO (M= Sr and Ba) stronger (profiles not shown) while the intensity of CaZrO was
3
3
weakened and the new peaks assigned to t-ZrO phase appeared. The CaZrO compound
2
3
was tested as catalysts but poor 3B1OL yield was obtained. Thus, MZrO compounds should
3
not be the catalytic active composition for the 3B1OL formation, and the formation of
2
+
CaZrO and t-ZrO wasted Ca cations. Thus, the efficient preparation methods should be
3
2
improved for the more active CaO/ZrO catalysts. As confirmed in our previous work
2
[
31,32] as well as in the work of Zhang’s group [27], the formation of Ca-O-Zr
hetero-linkages occurred via loading appropriate CaO onto ZrO and calcining at a proper
2
2
+
temperature. Excess Ca cations cohered with only a small part of ZrO for MZrO
2
3
compounds and also agglutinated easily for large particles when calcined high temperatures.
2
+
Only a few Ca cations can move into ZrO for the highly dispersed Ca-O-Zr
2
hetero-linkages. Thus, a small part of the Ca-O-Zr hetero-linkages exposed on the surface
and acted as the active sites for the aimed reactions.
1
4

Judging from the results listed in Table 2, we can assume that Ca-O-Zr hetero-linkages
o
are mostly generated at 800 C and the highest 3B1OL selectivity is attained, while
o
unfortunately CaZrO also forms at 800 C and higher. In addition, the Ca-O-Zr
3
o
hetero-linkages in the ZrO bulks were transformed from m-ZrO to t-ZrO at 900 C and
2
2
2
o
then grew to large particles of t-ZrO at 1000 C (Fig. 2). The phenomena that the addition of
2
2
+
either Ca or some other cations stabilizes t-ZrO phase are well known [39-41]. The
2
2
+
formation of CaZrO and t-ZrO wasted Ca and resulted in the decline in the amount of
3
2
active Ca-O-Zr hetero-linkages on the catalyst surface. Especially, the 1,4-BDO conversion
o
decreased at 1000 C (Table 2). In CaO/m-ZrO -800 and CaO/m-ZrO -900, the least
2
2
percentages of CaZrO and t-ZrO must hold the most amount of active Ca-O-Zr
3
2
hetero-linkages. However, the excess CaO over 7wt.% generated more CaZrO , and neither
3
the reactant conversion nor the 3B1OL selectivity were enhanced (Table 1).
In order to increase the active Ca-O-Zr hetero-linkages of CaO/m-ZrO -800, the
2
additional ZrO was also introduced together with CaO via the co-impregnation.
2
7
-CaO+2-ZrO /m-ZrO -800 shows the highest 1,4-BDO conversion of 68.2% and also a
2 2
high 3B1OL selectivity of 89.3% (Table 3). 7-CaO+2-ZrO /m-ZrO -800 shows the weakest
2
2
diffraction peaks assigned to CaZrO while more additional ZrO or excess CaO addition
3
2
would result in the formation of more CaZrO (Fig. 4a). Thus, the most active
3
7
-CaO+2-ZrO /m-ZrO -800 would have the most amount of active Ca-O-Zr
2 2
hetero-linkages.
4
.2 Acid-base concerted mechanism in the dehydration of 1,4-BDO.
It is reasonable that the dehydration of 1,4-BDO to 3B1OL via an acid-base concerted
mechanism via tridentate coordination of 1,4-BDO, in which the basic site for the H atom at
position 2 and the two acid sites for the two OH groups as imaged in our previous work [9,
1
6, 18] as well as the work of Zhang’s group [27]. Scheme 1a illustrates the acid-base
concerted mechanism over m-ZrO to form 3B1Ol form 1,4-BDO. In contrast, the
2
dehydro-cyclization of 1,4-BDO into THF proceeds readily under acidic conditions [42-44]
1
5

or over acidic catalysts [45-48]. Scheme 1b illustrates the acid-base concerted mechanism
over m-ZrO to form THF. It has been also found that dehydrogenation of 1,4-BDO to GBL
2
occurs easily under basic conditions [49]. Thus, balance of the base-acid sites is significant
for the formation of 3B1OL from 1,4-BDO. Among the pure metal oxides listed in Table 1,
only the base-acid bifunctional t-ZrO and m-ZrO can produce 3B1OL. Due to the
2
2
4
+
difference in their crystal structures, the different surface Zr densities of t-ZrO and
2
m-ZrO should affect their base-acid properties. Zhao et al. also demonstrates that the
2
4
+
surface Zr densities of t-ZrO and m-ZrO are approximately 3 times larger than surface
2
2
acid-site densities [50]. Both Brɵnsted and Lewis acid sites exist on the t-ZrO surface while
2
only Lewis acid sites were detected on the m-ZrO surface [50]. Actually, product
2
distribution is different between the two (Table 1). In this study, the surface of m-ZrO -800
2
is poisoned by CO and 3B1OL yield increases in NH atmosphere (Table 6). In NH
3
2
3
atmosphere, it can be said that acid-base balance of m-ZrO is regulated at a suitable extent
2
due to the poisoning the acidic sites of m-ZrO . The surface of 7-CaO/m-ZrO -900 and
2
2
7
-CaO+2-ZrO /m-ZrO -800 are poisoned by both NH and CO (Table 6). This indicates
2 2 3 2
that the surface of pure zirconia is much more acidic whereas 7-CaO/m-ZrO -900 and
2
7
-CaO+2-ZrO /m-ZrO -800 are more basic than m-ZrO .
2 2 2
Modification of m-ZrO with alkaline earth metal oxides changed the m-ZrO structure
2
2
as well as the base-acid properties. In all the modified m-ZrO , the weak basic sites shifting
2
from α to α’ was observed (Fig. 3a). Besides, the peaks assigned to the medium basic sites β
were also detected from all the modified samples. In accordance with the reaction results,
CaO/m-ZrO holds the most α’ and β sites and also showed the best activity for the 3B1OL
2
formation which is also in accordance with our previous work [31, 32]. On the other hand,
the non-active phases CaZrO and t-ZrO also decreased the amount of α’ and β sites. Thus,
3
2
in order to generate more α’ and β sites, crystal structures of the modified m-ZrO should
2
2
+
4+
also be controlled. At an appropriate calcination temperature, the added Ca substitutes Zr
partly in the m-ZrO surface to form the Ca-O-Zr hetero-linkage, and changes the electron
2
density of oxygen anion. These changes also bring in the base-acid sites distribution in
1
6

2
+
4+
2-
strength and amount. The surface Ca and Zr should act as the acid sites and the O
2
-
should be the basic sites. The basic sites α should be generated from the O of
Zr-O-Zr-O-Zr-, which is mainly from the m-ZrO support, and basic sites α’ and β should
-
2
2
-
be generated from the O of hetero-linkages such as -Zr-O-Zr-O-Ca-O-Zr-O-Zr- and
Zr-O-Ca-O-Zr-O-Ca-O-Zr- etc. The new basic sites different in strength should be resulted
-
from the coordination ways of oxygen anions. The basic sites with proper strength should
have priorities for the extraction of the H atom at position 2 of 1,4-BDO. Due to the reported
-1
Gibbs energy for the formation of Ca-OH (-449.2 kJ mol ) [51] lower than that of Zr-OH
-1
2+
4+
(
-378.5 kJ mol ) [52], Ca has superiority to Zr in capturing an OH group of 1,4-BDO.
4
+
2+
Therefore, Zr and Ca of -Ca-O-Zr- should act as the active points for the anchoring
adsorption and extraction of the terminal OH groups of 1,4-BDO, respectively (Scheme 1c).
2
+
It is suggested that medium strength of basic site β induced by the substituted Ca in
m-ZrO is important for the abstraction of H atom from 1,4-BDO.
2
In addition, the additional ZrO content of 2 wt.% together with 7wt.% CaO via
2
co-impregnation enhanced basic sites α’ and β (Fig. 3b) without either generating t-ZrO or
2
increasing CaZrO phase (Fig. 4a). Therefore, the highest 3B1OL yield was obtained over
3
7
-CaO+2-ZrO /m-ZrO -800 catalyst (Tables 2 and 4). This suggests that the additional ZrO
2 2 2
efficiently produce more Ca-O-Zr hetero-linkages on the support to generate more basic
sites α’ and β, and that it prevents from transforming the Ca-O-Zr hetero-linkages to t-ZrO2
and CaZrO phases.
3
5
. Conclusions
Vapor-phase dehydration of 1,4-BDO was investigated over m-ZrO modified with
2
alkaline metal oxides. The 3B1OL formation from 1,4-BDO was enhanced with the m-ZrO2
modified with alkaline metal oxides. In contrast to the modified t-ZrO , which showed a
2
high 1,4-BDO conversion with the 3B1OL selectivity less than 70%, the m-ZrO modified
2
in the same way exhibited a 3B1OL selectivity higher than 90%. Among the alkaline earth
metal oxides, ZrO modified with CaO showed high catalytic activities for the 3B1OL
2
1
7

formation. Especially, 7-CaO/m-ZrO -800 generates the most amount of basic sites α’ and β
2
for the 3B1OL formation. In order to increase the active Ca-O-Zr hetero-linkages for more
sites α’ and β, the additional m-ZrO was also introduced together with CaO via the
2
co-impregnation. The co-addition of CaO and ZrO to m-ZrO enhanced more sites α’ and β
2
2
successfully without generating t-ZrO2 and increasing CaZrO3 phase. Especially,
7
3
-CaO+2-ZrO /m-ZrO -800 shows the highest 1,4-BDO conversion (95.2%) and also a high
2 2
o
B1OL selectivity (89.3%) at 350 C under H carrier gas.
2
References
[
1] H. Yim, R. Haselbeck, W. Niu, C. Pujol-Baxley, A. Burgard, J. Boldt, J. Khandurina, J.D.
Trawick, R.E. Osterhout, R. Stephen, J. Estadilla, S. Teisan, H.B. Schreyer, S. Andrae, T.H. Yang,
S.Y. Lee, M.J. Burk, S.V. Dien, Nat. Chem. Biol.7 (2011) 445-452.
[
[
[
[
2] H. Liu, T. Lu, Metab. Eng. 29 (2015) 135-141.
3] H. Duan, Y. Yamada, S. Sato, Chem. Lett. 45 (2016) 1036-1047.
4] R. Csuk, A. Kern, Tetrahedron 55 (1999) 8409-8422.
5] H. Hagihara, K. Tsuchihara, J. Sugiyama, K. Takeuchi, T. Shiono, J. Polym. Sci. Chem. 42 (2004)
5600-5607.
[
[
[
[
[
[
6] M. Magnin-Lachaux, Z. Tan, B. Liang, E. Negishi, Org. Lett. 6 (2004) 1425-1427.
7] J.S. Yadav, K. Rajasekhar, M.S.R. Murty, Tetrahedron Lett. 46 (2005) 2311-2314.
8] T. Min, B. Yi, P. Zhang, J. Liu, C. Zhang, H. Zhou, Med. Chem. Res. 18 (2009) 495-510.
9] S. Sato, F. Sato, H. Gotoh, Y. Yamada, ACS Catal. 3 (2013) 721-734.
10] S. Sato, R. Takahashi, T. Sodesawa, N. Yamamoto, Catal. Commun. 5 (2004) 397-400.
11] A. Igarashi, N Ichikawa, S. Sato, R. Takahashi, T. Sodesawa, Appl. Catal. A: Gen. 300 (2006)
50-57.
[
[
12] M. Kobune, S. Sato, R. Takahashi, J. Mol. Catal. A: Chem. 279 (2008) 10-19.
13] M. Segawa, S. Sato, M. Kobune, T. Sodesawa, T. Kojima, S. Nishiyama, N. Ishizawa, J. Mol.
Catal. A: Chem. 310 (2009) 166-173.
[
14] R. Takahashi, I. Yamada, A. Iwata, N. Kurahashi, S. Yoshida, S.Sato, Appl. Catal. A: Gen. 383
1
8

(
2010) 134-140.
[
[
15] A. Igarashi, S. Sato, R. Takahashi, T. Sodesawa, M. Kobune, Catal. Commun. 8 (2007) 807-810.
16] S. Sato, R. Takahashi, M. Kobune, H. Inoue, Y. Izawa, H. Ohno, K. Takahashi, Appl. Catal. A:
Gen. 356 (2009) 64-71.
[
[
[
[
[
17] F. Sato, Y. Yamada, S. Sato, Chem. Lett. 41(2012) 593-594.
18] F. Sato, S. Sato, Y.Yamada, M. Nakamura, A. Shiga, Catal. Today 226 (2014) 124-133.
19] N. Yamamoto, S. Sato, R. Takahashi, K. Inui, Catal. Commun. 6 (2005) 480-484.
20] N. Yamamoto, S. Sato, R. Takahashi, K. Inui, J. Mol. Catal. A: Chem. 243 (2006) 52-59.
21] H. Inoue, S. Sato, R. Takahashi, Y. Izawa, H. Ohno, K. Takahashi, Appl. Catal. A: Gen. 352
(
2009) 66-73.
[
[
22] S. Sato, R. Takahashi, T. Sodesawa, N. Honda, J. Mol. Catal. A: Chem. 221 (2004) 177-183.
23] N. Ichikawa, S. Sato, R. Takahashi, T. Sodesawa, H. Fujita, T. Atoguchi, A. Shiga, J. Catal. 239
(
2006) 13-22.
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
24] Y. He, Q. Li, Y. Wang, Y. Zhao, Chin. J. Catal. 31 (2010) 619-622.
25] S. Sato, R. Takahashi, M. Kobune, H. Gotoh, Appl. Catal. A: Gen. 356 (2009) 57-63.
26] Q. Zhang, Y. Zhang, H. Li, C. Gao, Y. Zhao, Appl. Catal. A: Gen. 466 (2013) 233-239.
27] Q. Zhang, Y. Zhang, H. Li, Y. Zhao, M. Ma, Y. Yu, Chin. J. Catal. 34 (2013) 1159-1166.
28] H. Duan, D. Sun, Y. Yamada, S. Sato, Catal. Commun. 48 (2014) 1-4.
29] N. Ichikawa, S. Sato, R. Takahashi, T. Sodesawa, J. Mol. Catal. A: Chem. 256 (2006) 106-112.
30] T. Nozawa, S. Sato, R. Takahashi, Top Catal. 52 (2009) 609-617.
31] H. Duan, Y. Yamada, S. Sato, Appl. Catal. A: Gen. 487 (2014) 226-233.
32] H Duan, Y. Yamada, S. Kubo, S. Sato, Appl. Catal. A: Gen. 530 (2017) 66-74.
33] D.J. Anderton, F.R. Sale, Powder Metallurgy 22 (1979) 14-21.
34] S. Sato, M. Tokumitsu, T. Sodesawa, F. Nozaki, Bull. Chem. Soc. Jpn. 64 (1991) 1005-1007.
35] S. Sato, K. Koizumi, F. Nozaki, J. Catal. 178 (1998) 264-274.
36] C. Ohlinger, B. Kraushaar-Czarnetzki, Chem. Eng. Sci. 58 (2003) 1453-1461.
37] J.H. Schlander, T. Turek, Ind. Eng. Chem. Res. 38 (1999) 1264-1270.
38] K.T. Jacob, Y. Waseda, Metall. Mater. Trans. B 26B (1995) 775-781.
1
9

[
[
[
[
[
[
[
[
[
39] R.B. Heimann, T.A. Vu, J. Mater. Sci. Lett. 16 (1997) 437-439.
40] R. Ramachandra Rao, T.S. Kannan, Mater. Sci. Eng. C 20 (2002) 187-193.
41] D. Lee, D. Kim, D. Cho, J. Mater. Sci. Lett. 17 (1998) 185-187.
42] S.E. Hunter, C.E. Ehrenberger, P.E. Savage, J. Org. Chem. 71 (2006) 6229-6239.
43] T. Richter, H. Vogel, Chem. Eng. Technol. 24 (2001) 340-343.
44] O. Sato, A. Yamaguchi, M. Shirai, Catal. Commun. 68 (2015) 6-10.
45] X. Cao, J. Ren, M. Liu, C. Zhan, B. Xie, Chin. J. Org. Chem. 33 (2013) 1035-1041.
46] A. Takagaki, Catal. Sci. Technol. 6 (2016) 791-799.
47] M. Aghaziarati, M. Kazemeini, M. Soltanieh, S. Sahebdelfar, Ind. Eng. Chem. Res. 46 (2007)
726-733.
[
[
[
[
48] V.M. Shinde, G.N. Patil, A. Katariya, Y.S. Mahajan, Chem. Eng. Process 95 (2015) 241-248.
49] L.P. Kyrides, F.B. Zienty, J. Am. Chem. Soc. 68 (1946) 1385-1385.
50] Y. Zhao, W. Li, M. Zhang, K. Tao, Catal. Commun. 3 (2002) 239-245.
51] D.D. Wagman, W.H. Evans, V.B. Parker, R.H. Schumm, I. Halow, S.M. Bailey, K.L. Churney,
R.L. Nuttall, J. Phys. Chem. Ref. Data 11, Suppl. 2 (1982).
[
52] L. Qiu, D.A. Guzonas, D.G. Webb, J Solution Chem. 38 (2009) 857-867.
2
0

Table 1 Dehydration of 1,4-BDO over several metal oxides and their CaO-modified
samples.
Conversion
Selectivity (mol%)
3B1OL yield
(%)
Catalyst
(mol%)
3B1OL
0
THF
30.0
97.5
98.2
78.8
59.6
65.2
96.7
99.4
6.3
GBL
0
others
70.0
1.8
SiO2
TiO2
0.5
99.2
100
0
0.7
0
0.7
Al O3
0.2
0.1
1.2
0.6
1.2
0.1
0
1.5
0.2
2
t-ZrO2
98.5
98.8
2.5
11.7
33.6
0
7.5
11.6
33.2
0
m-ZrO2
6.3
7
-CaO/SiO -800
33.6
1.7
2
7
-CaO/TiO -800
88.3
100
1.5
1.3
2
7
-CaO/Al O -800
0.1
0.5
0.1
2
3
7
-CaO/t-ZrO -800
48.3
59.4
31.7
26.4
28.4
48.2
53.7
47.6
68.2
86.9
45.4
64.8
54.6
84.4
87.0
86.3
0.9
1.5
0.7
2.1
1.0
0.7
0.6
24.6
3.4
32.9
51.6
16.0
17.1
16.3
40.7
46.7
41.1
2
7
-CaO/m-ZrO -800
8.2
2
5
1
-MgO/m-ZrO -800
50.5
29.1
42.1
13.4
10.3
11.4
3.4
2
3-SrO/m-ZrO -800
0.9
2
1
9-BaO/m-ZrO -800
2.3
2
2
-CaO/m-ZrO -800
1.5
2
5
-CaO/m-ZrO -800
2.1
2
1
0-CaO/m-ZrO -800
0.9
1.4
2
3
o
-1
Catalytic activities are average for 1-5 h. W/F = 0.30 h. Reaction temperature = 350 C. H flow rate = 30 cm min .
2
3
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone. Others include 1-butanol, 2-buten-1-ol, and 1,3-butadiene.
2
1

Table 2 Dehydration of 1,4-BDO over 7-CaO/m-ZrO calcined at different temperatures.
2
Conversion
Selectivity (mol%)
3B1OL yield
(%)
Catalyst
(
mol%)
98.8
39.7
25.1
59.4
67.1
62.6
6.4
3B1OL
33.6
72.5
77.4
86.9
87.2
87.8
31.5
THF
59.6
21.7
15.6
8.2
GBL
0.6
2.3
1.2
1.5
1.1
1.0
1.5
others
6.3
m-ZrO -800
33.2
2
7
7
7
7
-CaO/m-ZrO -600
3.5
28.8
2
-CaO/m-ZrO -700
5.8
19.4
2
-CaO/m-ZrO -800
3.4
51.6
2
-CaO/m-ZrO -900
8.2
3.5
58.5
2
7
-CaO/m-ZrO -1000
7.9
3.3
55.0
2
CaZrO3
58.5
8.5
2.0
3
-
1
Catalytic activities are average for 1-5 h. W/F = 0.3 h. Reaction temperature = 350℃. H flow rate = 30 cm min .
2
3
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone. Others include 1-butanol, 2-buten-1-ol, and 1,3-butadiene.
Table 3 Dehydration of 1,4-BDO over CaO+ZrO /m-ZrO -800 with different CaO and ZrO
2
2
2
contents.
3
B1OL
yield
(%)
Catalyst
Conversion
Selectivity (mol%)
(
mol%)
59.4
64.5
68.2
66.4
60.1
57.2
44.7
44.7
3B1OL
86.9
88.2
89.3
87.6
89.6
89.0
87.1
87.4
THF
8.2
GBL
1.5
0.7
0.8
1.6
0.5
0.5
0.5
0.5
others
3.4
7
-CaO/m-ZrO -800
51.6
56.9
60.9
55.0
53.8
51.0
38.9
39.1
2
7
7
7
7
7
-CaO+1-ZrO /m-ZrO -800
8.6
2.5
2
2
-CaO+2-ZrO /m-ZrO -800
7.3
2.6
2
2
-CaO+3-ZrO /m-ZrO -800
6.4
4.4
2
2
-CaO+5-ZrO /m-ZrO -800
8.4
1.5
2
2
-CaO+7-ZrO /m-ZrO -800
9.0
1.5
2
2
1
1
0-CaO+2-ZrO /m-ZrO -800
11.0
10.4
1.4
2
2
2-CaO+2-ZrO /m-ZrO -800
1.7
2
2
3
-
1
Catalytic activities are average for 1-5 h. W/F = 0.3 h. Reaction temperature = 350℃. H flow rate = 30 cm min .
2
3
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone. Others include 1-butanol, 2-buten-1-ol, and 1,3-butadiene.
2
2

Table 4 Dehydration of 1,4-BDO over 7-CaO+2-ZrO /m-ZrO calcined at different
2
2
temperatures.
3
B1OL
yield
(%)
Conversion
Selectivity (mol%)
Catalyst
(
mol%)
3B1OL
67.0
75.1
82.3
89.3
88.9
88.9
86.9
THF
24.3
16.8
12.6
7.3
GBL
3.7
2.4
1.5
0.8
0.6
0.8
0.5
others
5.0
7
7
7
7
7
7
-CaO+2.0-ZrO /m-ZrO -600
9.7
6.5
2
2
-CaO+2.0-ZrO /m-ZrO -700
21.1
31.9
68.2
68.6
59.7
35.8
5.7
15.9
26.3
60.9
61.0
53.1
31.1
2
2
-CaO+2.0-ZrO /m-ZrO -750
3.6
2
2
-CaO+2.0-ZrO /m-ZrO -800
2.6
2
2
-CaO+2.0-ZrO /m-ZrO -850
7.3
3.2
2
2
-CaO+2.0-ZrO /m-ZrO -900
7.6
2.7
2
2
7
-CaO+2.0-ZrO /m-ZrO -1000
11.1
1.5
2
2
3
-
1
Catalytic activities are average for 1-5 h. W/F = 0.3 h. Reaction temperature = 350℃. H flow rate = 30 cm min .
2
3
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone. Others include 1-butanol, 2-buten-1-ol, and 1,3-butadiene.
2
3

Table 5 Dehydration of 1,4-BDO over the active catalysts with different contact time, W/F.
Selectivity (mol%)
3B1OL
Contact
time (h)
Conversion
Catalyst
yield
(%)
(
mol%)
67.1
93.9
48.3
99.2
68.2
93.6
97.6
98.3
3B1OL
87.2
80.0
68.2
70.2
89.3
89.1
88.0
86.9
THF GBL 2B1OL others
7
-CaO/m-ZrO -900
0.30
8.2
8.9
6.3
4.5
7.3
4.5
5.1
4.6
1.1
1.2
0.9
0.3
0.8
0.6
0.7
0.5
2.2
6.0
1.3
3.9
58.5
75.1
32.9
69.9
60.9
83.4
85.9
2
0
.60
0.30
.60
0.30
7
-CaO/t-ZrO -800
11.2
12.7
1.7
13.4
12.3
0.9
2
0
7
-CaO+2-ZrO /m-ZrO -800
2 2
0
0
0
.45
.60
.75
4.0
1.8
4.1
2.1
5.8
2.7
85.4
3
Catalytic activities are average for 1-5 h. Catalyst weight = 0.5-1.25g. Reaction temperature = 350℃. H flow rate = 30 cm
2
-
1
min .
3
1
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone; 2B1OL, 2-buten-1-ol others include 1-butanol, and
,3-butadiene.
2
4

Table 6 Dehydration of 1,4-BDO over m-ZrO poisoned by either NH or CO carrier gas.
2
3
2
3
B1OL
yield
(%)
Conversion
Selectivity (mol%)
Catalyst
Carrier gas
(
mol%)
42.0
31.5
44.6
82.4
74.2
60.6
84.7
64.3
55.6
3B1OL
25.0
48.0
19.0
87.8
88.1
79.4
88.9
89.8
77.9
THF
74.0
50.6
79.5
5.1
GBL
0.1
0.1
0.2
0.9
0.7
2.5
1.0
0.3
1.8
others
0.9
1.4
1.2
6.2
6.7
4.6
5.4
6.5
5.2
a)
m-ZrO -800
H2
10.5
15.1
8.5
2
b)
H +NH3
2
c)
H +CO2
2
7
-CaO/m-ZrO -900
H2
72.3
65.4
48.1
75.3
57.7
43.3
2
b)
H +NH3
4.5
2
c)
H +CO2
13.5
4.7
2
7
-CaO+2.0-ZrO /m-ZrO -800
H2
2
2
b)
H +NH3
3.4
2
c)
H +CO2
15.1
2
3
-
1
Catalytic activities are average for 1-5 h. W/F = 0.32 h. Reaction temperature = 350℃. H flow rate = 30 cm min .
2
o
a) Reaction temperature = 300 C.
3
-1
3
-1
b) H = 20 cm min + NH = 10 cm min .
2
3
3
-1
3
-1
c) H = 20 cm min + CO = 10 cm min .
2
2
3
B1OL, 3-buten-1-ol; THF, tetrahydrofuran; GBL, γ-butyrolactone. Others include 1-butanol, 2-buten-1-ol, 1,3-butadiene, etc.
2
5

1
00
80
60
40
20
Conv.
3B1OL Selec.
0
10
20
Time on stream / h
Figure 1 Changes in conversion and selectivity to 3B1OL dehydration of 1,4-BDO over
◦
7
-CaO+2-ZrO /m-ZrO -800 with time on stream. Reaction temperature, 350 C; W/F= 0.6 h;
2
2
-1
3
-1
catalyst weight, 1.0 g; feed rate of 1,4-BDO, 18.6 mmol h ; flow rate of H , 30 cm min .
2
2
6

Figure 2 XRD pattern of alkaline metal oxide modified m-ZrO changes with calcination
2
temperature.
2
7

Figure 3 CO -TPD profiles of (a) alkaline earth metal oxide modified m-ZrO and (b)
2
2
7
-CaO+ZrO /m-ZrO -800 with different ZrO contents.
2
2
2
2
8

Figure 4 XRD pattern of (a) CaO+ZrO /m-ZrO at different CaO and ZrO contents and (b)
2
2
2
7
-CaO+2-ZrO /m-ZrO calcined at different temperatures.
2 2
2
9