The in situ transformation of the co-product formaldehyde in the reversible hydrolysis of 1,3-dixoane to obtain 1,3-propanediol efficiently

Article abstract of DOI:10.1039/c7gc03692b

Herein, a strategy is developed for efficient production of l,3-propanediol via the hydrolysis of 1,3-dioxane by the in situ transformation of the co-product formaldehyde (HCHO) in the presence of Eu(OH)₃. The reversible hydrolysis reaction is promoted to yield 98% conversion and 99% 1,3-propanediol selectivity. Furthermore, HCHO is converted to formic acid (HCOOH) which could act as an acidic catalyst in the hydrolysis of 1,3-dioxane. The combination of FT-IR and control experiments demonstrates that HCOOH is generated via the hydrolysis of formate species which formed on the surface of Eu(OH)₃.

Full text of DOI:10.1039/c7gc03692b

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The in situ transformation of co-product formaldehyde in the
reversible hydrolysis of 1,3-dixoane to get 1,3-propanediol
efficiently
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a,b
a
a,b
DOI: 10.1039/x0xx00000x
Yehong Wang, Jian Zhang, Zhixin Zhang, Tingting Hou, Chaofeng Zhang, Jinghua An, Feng
a
Wang *
www.rsc.org/
Herein, a strategy is developed for efficient production of l,3- catalysts. When ceria is applied in the hydrolysis of 4-methyl-
propanediol via hydrolysis of 1,3-dioxane by the in situ 1,3-dioxane, the hydrolysis equilibrium is established until
o
transformation of the co-product formaldehyde (HCHO) in the reacted for 12 h at higher temperature (180 C) with 94%
3
presence of Eu(OH) . The reversible hydrolysis reaction is equilibrium conversion, which is relative low and costs long
1
0
promoted to go forward with 98% conversion and 99% 1, 3- times.
propanediol selectivity. Furthermore, HCHO is converted to formic
For liquid-phase reversible reactions, the in situ removal
acid (HCOOH) which could act as a acidic catalyst in the hydrolysis of products is an efficient way to improve the equilibrium
of 1,3-dioxane. The combination of FT-IR and control experiments conversion. In the hydrolysis of 1,3-dioxane catalyzed by acids,
demonstrates that HCOOH is generated via the hydrolysis of 1,3-propanediol is generated with HCHO as co-product
formate species which formed on the surface of Eu(OH)
3
.
(scheme 1). But it is so difficult to remove products in situ from
aqueous media under the reaction conditions due to the
Hydrolysis reactions are greatly significant in both organic
1
2
formation of azeotrope with H O. For this regard, another
-3
chemistry and industrial production.
They are usually
efficient way is to transform the co-product HCHO to promote
the reaction going forward. However, it is still a challenge to
consume the HCHO without causing any interference to 1,3-
propanediol due to the reactivity for both aldehyde and
alcohol in one pot.
catalyzed by homogeneous or heterogeneous acidic catalysts
in aqueous media. As a bi-functional organic compound, 1,3-
propanediol is a high-value specialty chemical and could
potentially be used for many organic synthesis. In particularly,
it can be used as a monomer for polyesters, polyethers and
4
polyurethanes production. Among various methods for the
5
synthesis of 1,3-propanediol, the route via hydrolysis of 1,3-
dioxane is an ideal route, where the 1,3-dioxane could be
, 7
obtained via Prins condensation of ethylene and HCHO.
6
Scheme 1. The synthesis of 1,3-propanediol via the hydrolysis of 1,3-dioxane with
Specifically in recent years, with the developments of the HCHO as co-product.
methanol to olefin (MTO) industrial process and other new
technologies for the conversion of syngas to olefins, great
Herein, a strategy is developed for l,3-propanediol
amounts of ethylene are produced, providing abundant generation via hydrolysis of 1,3-dioxane. As co-product, HCHO
feedstock for Prins condensation to produce 1,3-dioxane.
8
, 9
is converted to HCOOH, which could act as an efficient acid
In the previous study, we have found that ceria could act catalyst in this hydrolysis reaction. The 1,3-dioxane conversion
o
as a water-tolerant Lewis acidic catalyst in hydrolysis of 1,3- reached 98% in 4 h at 180 C with 99% selectivity of 1,3-
1
0
dioxane and its derivatives. However, due to the reversibility propanediol.
of the hydrolysis reaction, the equilibrium conversion of 1,3-
As we known, ceria could act as a acid catalyst with
1
0
dioxane is constant with fixed initial concentration of 1,3- water-tolerant Lewis acidic sites in hydrolysis reactions. It
dioxane and reaction temperature regardless of any acids as inspires us to investigate whether this kind of water-tolerant
Lewis acidic sites exist widely in rare-earth metal oxides.
2 3
During the study, we found that Eu O could catalyze the
hydrolysis of 1,3-dioxane efficiently. The conversion of 1,3-
o
dioxane reached 92% in 4 h at 180 C with > 99% 1,3-
propanediol selectivity (Figure 1a, Conversion A), which is
superior to that of over ceria under the same reaction
conditions (74% conversion with 97% selectivity). Interestingly,
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an induction period about 2 h was observed in the presence of reactant (1,3-dioxane or H
Eu
proceeded slowly with 1,3-dioxane conversion lower than study the effect of 1,3-dioxane. Meanwhile, the Eu(OH)
0%. After another 1 h, the conversion increased quickly and treated with acetonitrile solely was also obtained for
reached 67% and then to 92% in 4 h with > 99% selectivity comparison. These materials after the pre-treatments were
2
O) and product (1,3-propanediol or
2
O
3
. During the induction period, this hydrolysis reaction HCHO). Acetonitrile was used as solvent instead of water when
-NR
3
2
o
(
Figure 1a).
The presence of induction period usually suggests a 2a). There was no obvious improvement for the conversion of
transformation of initial catalyst to the real active species 1,3-dioxane in the presence of Eu(OH) -NR treated in H O or
from reaction 1,3-propanediol. Both conversions were 5%. Little increase of
media at 2 h and 4 h, respectively and marked them as Eu -2 conversion was observed when acetonitrile or acetonitrile
h and Eu -4 h, respectively. XRD analysis illustrated a phase solution of 1,3-dixoxane was applied (8% and 11%,
evolution from the initial Eu to Eu(OH) for both samples respectively). In contrast, the 1,3-dioxane conversion reached
Thus, we deduced that the induction period 18% when treated in HCHO solution (38 wt% HCHO), which is
might arise from the transformation of Eu O to Eu(OH) . To comparable to the used Eu(OH) -NR. A significant dependence
applied in hydrolysis of 1,3-dioxane at 180 C for 2 h (Figure
3
2
1
1, 12
during the reaction.
2 3
We extracted Eu O
2 3
O
2 3
O
2
O
3
3
1
3,14
(Figure1b).
2
3
3
3
exclude the effect of Eu O phase strictly, we then prepared on the amount of HCHO was observed. A decrease of the
2
3
Eu(OH)3 nano-rod [marked as Eu(OH) -NR] via modified HCHO amount (molar ratio of HCHO to Eu from 3:1 to 1:2) led
3
1
5
hydrothermal method (Figure S1) and applied it in the to a increase of 1,3-dioxane conversion. The highest 1,3-
hydrolysis of 1,3-dioxane. The induction period was still dioxane conversion reached 27% with > 99% selectivity when
observed (Figure 1a, Conversion B). It indicates that the real the molar ratio of HCHO to Eu is 1:2 (marked as 1.0 FA-2.0 Eu).
active species is neither Eu O nor Eu(OH) . Furthermore, the Continue to decrease the amount of HCHO (HCHO: Eu=1:4),
2
3
3
length of the introduction period was dependent on the the 1,3-dioxane conversion decreased to 20% (Figure 2a). Then
o
reaction temperatures. It was about 4 h at 150 C. When the material of 1.0 FA-2.0 Eu was used in fresh feed, and the
increasing reaction temperature to 160 °C, it was shortened to hydrolysis reaction proceeded smoothly. The induction period
o
about 0.67 h and then to 0.51 h at 170 C. Continue to increase was eliminated (Figure 2b). For comparison, this reaction did
the temperature to 180 °C, it was shortened to 0.26 h (Figure not proceed in the presence of HCHO without Eu(OH)3
S2).
addition. These results suggest that the real active species is
probably formed with the coexistence of Eu(OH) and HCHO.
3
Conversion A
00
Conversion B
Selectivity
(a)
1
8
6
4
2
0
0
0
0
0
0
2
4
6
Reaction time (h)
(100)
(101)
(
b)
(
110)
(201)
(
211)
(102)
(112)
(302) Eu
(200)
(
111) (210)
2 3
O -4 h
Eu
2
O
3
-2 h
(
222)
(211)
(400)
(440)
(622)
Eu O
2
3
1
0
20
30
40
50
60
70
80
2
theta (degree)
Figure 1. (a) The hydrolysis of 1,3-dioxane carried out in the presence of Eu
2
O
3
or
O 1mL, 180 C. Conversion A
3
O , while Conversion B was the conversion in the
o
Eu(OH)
was obtained in the presence of Eu
presence of Eu(OH) . (b) XRD patterns of Eu
h, which marked as Eu -2 h and Eu -4 h respectively.
3 2
. Eu-based material 0.1 g, 1,3-dioxane 1.5 mmol, H
2
o
3
2 3
O treated in water at 180 C for 2 h and 4
O
2 3
2 3
O
Figure 2. (a) The hydrolysis of 1,3-dioxane carried out in the presence of as-synthesized
Eu(OH)
3 3 3
-NR (as-syn), used Eu(OH) -NR and Eu(OH) -NR treated in solution of 1,3-
We also found that the hydrolysis reaction could carry out
smoothly without induction period in the presence of used
o
propanediol, HCHO, water and acetonitrile solution of 1,3-dioxane at 180 C for 2 h,
-
1
and the concentrations of these solutions were set at 1.5 mol·L . They are described
Eu(OH)
3
-NR which was extracted from the reaction media after in orange. The FA-Eu with various HCHO amounts are marked in blue. Reaction
o
o
conditions: Eu-based material 0.1 g, 1,3-dioxane 1.5 mmol, water 1 mL, 180 C, 1 h. 1,3-
reacting for 7 h at 180 C. The conversion of 1,3-dioxane
reached 18% in the initial 1 h and increased remarkably. It
reveals that the active species is probably formed during the
reaction under the employed conditions. To further investigate
PD: 1,3-propanediol, 1,3-DA: 1,3-dioxane. (b) The hydrolysis of 1,3-dioxane carried out
in the presence of as-synthesized Eu(OH)
3
(Conversion 1) and 1.0 FA-2.0 Eu (Conversion
2
). Reaction condition: Eu-based material 0.1g, 1, 3-dioxane 1.5mmol, water 1mL, 180
o
C, 5 h.
3
the real active species, we pre-treated Eu(OH) -NR with each
2
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To gain a deep understanding of the real active species, active acidic sites for catalyzing the hydrolysis reaction
we investigated the structure of 2.0 Eu-1.0 FA in detail. XRD probably exist in the reaction solution as homogeneous acid.
analysis reveals that the HCHO modification does not lead Control experiment suggests that this is no acidity without
Eu(OH)
that the modification of HCHO probably only occurs on the proposed that the acid is probably formic acid (HCOOH) which
surface of Eu(OH) -NR during the reaction. Then FT-IR was formed via the hydrolysis of formate species on the surface of
applied and the results were shown in Figure 4. According to Eu(OH) . In order to confirm the effect of HCOOH furtherly, we
3 3
to a significant phase change (Figure S3). It indicates Eu(OH) addition or HCHO. Combined the FT-IR results, it is
3
3
the literatures, six types of adsorbed HCHO species have been conducted this reaction with 15 mo% HCOOH addition initially.
confirmed by FT-IR, including: (i) physisorbed HCHO, (ii) The reaction could carry out smoothly without induction
coordinated HCHO, (iii) dioxymethylene, (iv) polyoxymethylene, period (Figure S5). And then we tuned the pH value of reaction
1
0, 16
(
v) formate ions, and (vi) methoxy groups.
3
On both 1.0 FA- media to 5.5 by HCOOH in the absence of Eu(OH) . The
-
.0 Eu sample and used Eu(OH) , the peaks located at 1591 cm conversion achieved 37% in 2 h then 70% in 3 h, which
-1
and 1377 cm are assigned to the vas(COO ) and v
2
1
3
-
-
s
(COO ) of confirmed the catalytic activity of HCOOH. The hydrolysis
1
7, 18
adsorbed formate species (species V), respectively
.
reaction could also proceed in Ar efficiently with 88%
o
Coincidentally, the hydrolysis reaction in the presence of these conversion at 180 C for 3 h, indicating that the oxygen is not
two samples carried out efficiently without induction periods. essential to this system.
In contrast, there is no remarkable peaks assigned to the
adsorbed formate species on as-synthesized Eu(OH) -NR or 1,3-propanediol in the presence of Eu(OH)
Eu(OH) -NR treated in other reagents. In addition, a peak at (Scheme 2a). Firstly, the hydrolysis of 1,3-dioxane carries out
Finally, a reaction route for hydrolysis of 1,3-dioxane to
3
3
is proposed
3
−
1
o
7
06 cm attributed to the O–H bending vibration of Eu–O–H is spontaneously at high temperature (>150 C), generating 1,3-
1
3
-1
observed in all samples. Two peaks located at 1529 cm and propanediol and HCHO (Scheme 2a, step i). The generated
-
1
1
480 cm are attributed to the formation of carbonate ions HCHO adsorbs on Eu(OH)
3
surface, forming formate species
The TG data of (Scheme 2a, step ii), which has been confirmed by XRD and FT-
were collected for IR characterizations. The induction period is probably arisen
comparison (Fig. S4). The weight loss of used Eu(OH) is higher from the accumulation of HCHO and the formation of formate
than fresh Eu(OH) for 1.6 %, which is attributed to the species. Subsequently, formate species hydrolyzes in the
removal of organic species on the surface of used Eu(OH) presence of O, releasing HCOOH, which acts as
probably the formate species. Thus, the catalytic activity is homogeneous acid catalyst in water (Scheme 2a, step iii). This
1
9, 20
3
because of the exposure of Eu(OH) to air.
3 3
both fresh Eu(OH) and used Eu(OH)
3
3
3
,
H
2
probably depend on the formation of formate species.
step is confirmed by the acidity of the reaction solution with
pH = 5.53. At last, the hydrolysis of 1, 3-dixoane carried out
smoothly catalyzed by HCOOH, ending up the induction period
(
(
g)
1529 1480
706
(Scheme 2a, step iv).
(f)
3
While in the presence of used Eu(OH) or Eu-FA samples
e)
(
(
d)
c)
with formate on the surface, the hydrolysis of formate species
carries out in H O directly, generating HCOOH. (Scheme 2b,
step i). Then HCOOH catalyzed the hydrolysis of 1,3-dioxane to
,3-propanediol smoothly and efficiently (Scheme 2b, step ii)
2
(b)
(
a)
1
1
591
1377
which is the reason for the elimination of the induction period.
2
000
1500
1000
-
500
1
Wavenumber (cm )
Figure 4. FT-IR of (a) used Eu(OH)
treated in (b) solution of HCHO (38 wt%), (c) CH
e) solution of 1,3-propanediol, (f) H O.
3
-NR, (g) as-synthesized Eu(OH)
3
-NR and EuOH()
3
3 3
CN solution of 1,3-dioxane, (d) CH CN,
(
2
It is known that the hydrolysis of 1,3-dioxane is usually
catalyzed by acids. Thus, we intend to measure the acidity of
3
formate species on Eu(OH) surface. As useful tools, P MAS
1
3
NMR and pyridine-IR are usually applied in the
1
0, 21-23
characterization of heterogeneous acids.
Firstly, we
3
1
employed P MAS NMR with trimethylphosphine (TMP) as
probe molecule, but no obvious signal assigned to TMP
adsorbed on acidic sites was observed either on 2.0 Eu-1.0 FA
or used Eu(OH) . Then, we tried to apply pyridine-IR to
3
investigate the acidity, but failed again. It suggests that there is
no acidic sites on the surface of solid materials. Interestingly,
the pH value of the reaction media is 5.53, indicating that the
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greatly contribute to the understanding of other reversible
reactions in aqueous reactions.
Acknowledgements
This work was supported by DICP (DICP DMTO201406) and the
"
Strategic Priority Research Program of the Chinese Academy of
Sciences" Grant No.XDB17020300.
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Scheme 2. Proposed reaction routes for hydrolysis of 1, 3-dioxane to 1,3-propanediol
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2
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068.
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o
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1
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2
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vista of real active species generating during the reactions and
4
793.
4
|
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