Zirconia-supported rhenium oxide as an efficient catalyst for the synthesis of biomass-based adipic acid ester

Article abstract of DOI:10.1039/c9cc05413h

Synthesis of adipic acid, a key monomer of nylon-66 and polyurethane, from biomass is highly attractive for establishing green and sustainable chemical processes. Here, we report that zirconia-supported rhenium oxide (ReO_x/ZrO₂) efficiently catalyses the deoxydehydration of cellulose-derived d-glucaric acid, offering adipic acid ester with a yield of 82% by combining with a Pd/C catalyst in subsequent reactions.

Full text of DOI:10.1039/c9cc05413h

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Zirconia-supported rhenium oxide as an efficient catalyst for the
synthesis of biomass-based adipic acid ester†
Received 00th January 20xx,
Accepted 00th January 20xx
Jinchi Lin, Haiyan Song, Xiaoru Shen, Binju Wang, Shunji Xie, Weiping Deng,* Deyin Wu, Qinghong
Zhang, Ye Wang*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Synthesis of adipic acid, a key monomer of nylon-66 and
polyurethane, from biomass is highly attractive for establishing
green and sustainable chemical processes. Here, we report that
zirconia-supported rhenium oxide (ReOx/ZrO2) efficiently catalyses
the deoxydehydration of cellulose-derived D-glucaric acid, offering
adipic acid ester with a yield of 82% by combining with a Pd/C
catalyst in subsequent reactions.
Scheme 1 Conversion of cellulose into adipic acid via D-glucaric acid.
adipic acid could be synthesized by catalytic conversion of
cellulose-derived 5-hydroxymethylfurfural (HMF).6 Another
promising route for adipic acid synthesis from cellulose is via
D-glucaric acid intermediate (Scheme 1). Several studies have
succeeded in converting cellulose or its monomer (D-glucose)
to D-glucaric acid.7 However, the conversion of D-glucaric acid
to adipic acid by removing four hydroxyl groups remains
challenging. Brønsted acids and supported metal nanoparticles
can catalyse the dehydration and hydrogenolysis of alcohols,
but these systems are normally limited to cleaving one C−OH
bond.8 A patent disclosed that hydrogen halide (e.g., HBr or HI)
facilitated the removal of OH groups in glucaric acid in an
organic acid (e.g., acetic acid) solvent and an adipic acid yield
of 89% was achieved by combining HBr with a Pt-Rh catalyst
under H2 at 433 K.9 However, the use of halogen and acid
solvent would cause corrosive and environmental problems,
and would increase the complexity and cost in product
separation. The development of environmental benign
catalytic systems for removal of multiple OH groups is highly
challenging but very attractive for biomass valorisation.
Catalytic deoxydehydration (DODH) is an effective method
to remove two adjacent hydroxyl groups in diols, and the
product is the corresponding alkene. DODH is generally
catalysed by Re-, Mo- and V-based catalysts.10 In particular,
Re-based homogeneous and heterogeneous catalysts have
shown high activity in DODH of polyols, in which the vicinal OH
groups are in cis-form.11,12 For example, mucic acid with two
pairs of cis-diols, which could readily coordinate to Re catalyst,
underwent facile removal of four OH groups, forming muconic
acid, a dicarboxylic acid with conjugate diene.11 On the other
hand, only low efficiencies were obtained for the removal of
Catalytic transformation of renewable biomass into high-value
chemicals is of great importance for establishing sustainable
chemical industry. Because of the high oxygen content (e.g.,
O/C ratio of cellulose is 0.83), lignocellulosic biomass serves as
an ideal feedstock for the synthesis of oxygenated compounds
such as organic acids, many of which are monomers of key
polymers.1 A variety of multi-functional catalysts have been
reported for the conversion of cellulose, the most abundant
component in lignocellulosic biomass, or its derivatives to
hydroxyl acids such as gluconic acid and lactic acid.1-3 However,
few studies have been devoted to the transformation of
cellulose into adipic acid, an important dicarboxylic acid and a
monomer for the production of nylon-66 and polyurethanes.4,5
Currently, the production of adipic acid relies on petroleum
via a route including hydrogenation of benzene to cyclohexane,
selective oxidation of cyclohexane to a mixture of cyclohexanol
and cyclohexanone (KA oil) and subsequent oxidation of KA oil
by concentrated nitric acid. However, this route suffers from
high energy input, low efficiency due to the low cyclohexane
conversion, use of corrosive nitric acid and emission of nitrous
oxide. The catalytic transformation of biomass or its
derivatives into adipic acid would provide a green and
sustainable route for the synthesis of this key monomer of
Nylon-66 and polyurethane. Very recently, we reported that
State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, National Engineering
Laboratory for Green Chemical Productions of Alcohols, Ethers and Esters, College
of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
E-mail: dengwp@xmu.edu.cn; wangye@xmu.edu.cn.
†Electronic Supplementary Information (ESI) available: Experimental & calculation
details and additional data including TPR profiles, XPS spectra, GC-MS results and
IR spectra. See DOI: 10.1039/x0xx00000x
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four OH groups in D-glucaric acid, which contains one pair of ReOx/Al2O3 and ReOx/MgO.
cis-diols and one pair of trans-diols.11
View Article Online
DOI: 10.1039/C9CC05413H
The H2 temperature-programmed reduction (H2-TPR) studies
So far, only a homogeneous KReO4 catalyst in combination revealed that the reducibility of ReOx species changed by
with Pd/C has shown a considerable efficiency for the changing the support (Fig. S1 and Table S1, ESI†). ReOx/ZrO2,
conversion of D-glucaric acid lactone derived from calcium ReOx/TiO2 and ReOx/SiO2 catalysts showed reduction peaks in
glucarate in alcohol to adipate esters in the presence of a range of 610-720 K, whereas the peaks shifted to 700-900 K
various additives (H3PO4 and activated carbon).13 The for ReOx/Al2O3 and ReOx/MgO catalysts. It is likely that ReOx
development of active heterogeneous catalysts for DODH of D- species strongly interact with Al2O3 or MgO via Re-O-Al or Re-
glucaric acid remains challenging. Here, we report an efficient O-Mg bonds,14 decreasing the reducibility of ReOx species.
heterogeneous rhenium oxide-based catalyst for DODH of D- Combining this result with the catalytic behaviors of supported
glucaric acid in butanol solvent, forming alkenyl dicarboxylic ReOx catalysts (Table 1), we speculate that the reducibility of
acid ester. A high yield of adipic acid ester has been achieved ReOx species is a key parameter in determining DODH
by combining subsequent hydrogenation using a Pd/C catalyst. reactions, which may involve the redox of ReOx species (e.g.,
Table 1 shows catalytic performances of V, Mo, W and Re Re(VI)/Re(IV)).11,12 The redox of ReOx species loaded on Al2O3
oxides loaded on ZrO2 as well as
methyltrioxorhenium (CH3ReO3) catalyst for the conversion of leading to low efficiencies of these catalysts in DODH reactions.
D-glucaric acid-1,4-lactone, which is structure-stable The X-ray photoelectron spectroscopy (XPS) studies showed
a homogeneous and MgO becomes not easy due to the strong interaction, thus
a
molecule of D-glucaric acid. All the supported metal oxides that Re species on ReOx/Al2O3 and ReOx/MgO surfaces existed
catalysed the DODH reaction except for the VOx/ZrO2, forming as Re(VII), while those on ReOx/ZrO2, ReOx/TiO2 and ReOx/SiO2
product 1, a five-membered ring lactone with one OH group, surfaces were composed of Re(VI) and a small fraction of
and product 2, dibutyl hexa-2,4-dienedioate, a linear ester Re(IV) (Fig. S2, ESI†). After the catalytic reaction, almost no
with conjugated alkenes. As compared to MoOx/ZrO2 and change in Re oxidation state was observed on the former two
WOx/ZrO2, the ReOx/ZrO2 catalyst showed remarkably higher catalysts, whereas the fraction of Re(IV) increased significantly
activity for the removal of OH groups. The milder reaction on the later three catalysts. This suggests that the redox
temperature (393 K) used in this work probably caused the between Re(VI) and Re(IV) occurs during the reaction on
lower activities of VOx-, MoOx- and WOx-based catalysts, which ReOx/ZrO2, ReOx/TiO2 and ReOx/SiO2 catalysts. Furthermore,
are known to catalyse DODH reactions at higher the ReOx/ZrO2 catalyst exhibited the highest fraction of Re(IV)
temperatures.10b It is of interest that the ReOx/ZrO2 catalyst after the reaction, indicating that ReOx species could facilely
was more efficient than the homogeneous CH3ReO3 catalyst. be reduced on ZrO2 surfaces. The high reducibility of surface
The support played a key role in determining the catalytic ReOx species may contribute to the superior catalytic
behaviour. The ReOx/ZrO2 showed the highest activity, offering performance of the ReOx/ZrO2 catalyst.
product 2 with all OH groups removed with a yield of 41%. The
We performed further studies for the conversion of D-
total yield of DODH products was 93% over this catalyst. The glucaric acid-1,4-lactone using the most efficient ReOx/ZrO2
ReOx/TiO2 and ReOx/SiO2 showed similar performances, which catalyst. The recycling uses of ReOx/ZrO2 showed no significant
were lower than that of ReOx/ZrO2 but higher than those of
changes in the yield of DODH products from the second to the
fifth cycles (Fig. S3, ESI†). The prolonging of reaction time from
24 to 48 h rather decreased the yield of DODH products due to
the polymerization of products 1 and 2 as well as the side
reactions with butanol solvent (Table 1). We designed a DODH-
hydrogenation strategy to enhance the yield of products with
all the OH groups removed (Scheme 2). Because the co-
presence of a hydrogenation catalyst may exert a negative
effect on the performance of ReOx/ZrO2 catalyst (Table S2,
ESI†), the DODH and hydrogenation reactions were conducted
separately. After the conversion of D-glucaric acid-1,4-lactone
Table
1
Catalytic performances of supported rhenium catalysts for the
deoxydehydration of D-glucaric acid-1,4-lactonea
Entry
Catalyst
Yield (%)
Total yield of DODH
products (%)
1
2
1
2
3
CH3ReO3
ReOx/ZrO2
VOx/ZrO2
32
52
0
18
41
0
50
93
0
4
5
6
7
8
9
10b
MoOx/ZrO2
WOx/ZrO2
ReOx/TiO2
ReOx/SiO2
ReOx/Al2O3
ReOx/MgO
ReOx/ZrO2
9.7
2.9
48
43
23
13
39
0
0
9.7
2.9
77
71
44
15
74
29
28
21
2.0
35
Scheme 2 Catalytic deoxydehydration-hydrogenation strategy for the conversion of D-
glucaric acid-1,4-lactone into dibutyl adipate.
a Reaction conditions: D-glucaric acid-1,4-lactone, 0.10 mmol; catalyst, 20 mg; butanol
(BuOH), 5.0 mL; N2, 20 mL/min; reaction temperature, 393 K; reaction time, 24 h.
b
Reaction time, 48 h.
2 |Chem. Commun., 2019, 00, 1-3
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DOI: 10.1039/C9CC05413H
Scheme 3 Proposed reaction scheme for ReOx/ZrO2-catalysed conversion of D-
glucaric acid-1,4-lactone.
at 393 K for 24 h, the solid ReOx/ZrO2 was removed from the Fig. 1 Time course for ReOx/ZrO2-catalysed DODH reaction of D-glucaric acid-1,4-
lactone.
reaction system by filtration. Then, a commercial Pd/C (Pd
loading, 5 wt%) catalyst was added into the system, followed
by hydrogenation under H2 flow (flow rate, 20 mL min-1) at 393
K for 4 h. Products 3 and 4, dibutyl adipate, which is our target
product, were formed. After the removal of Pd/C by filtration,
the ReOx/ZrO2 catalyst was added back into the reaction
system for further conversion of product 3 at 393 K for 24 h,
followed by addition of the Pd/C catalyst for hydrogenation for
4 h under H2 flow. We finally obtained dibutyl adipate (4) with
a yield of 82%. To the best our knowledge, this is highest yield
of adipic acid ester obtained by heterogeneous catalytic
conversion of cellulose derivatives.
DODH products 1 and 2. The relatively higher formation rate of
1 than that of 2 agrees well with that the removal of two OH
groups in a cis-diol is easier. Based on these results, we
propose a possible reaction scheme for the conversion of D-
glucaric acid-1,4-lactone (Scheme 3). In brief, D-glucaric acid-
1,4-lactone first reacts with solvent, butanol, and
an equilibrium of esterification is established among ring-form
(5 and 6) and chain-form products (7). Because of the trans-
diol structure, the OH groups in 5 cannot be easily removed to
form alkenyl product, but 6 and 7 can undergo DODH reactions.
In the presence of ReOx/ZrO2 catalyst, 6 was converted to 1,
and 7 was transformed to 2 via 8. The product 8 also has a pair
of OH groups in trans-diol structure. We speculate that the
removal of the two OH groups from 8 is more feasible than
that from 5. This is because 8 is a chain molecule, in which the
vicinal trans-diol can be transformed to cis-diol by rotation of
the –CH(OH)COOBu group along the C4-C5 axis. The
transformation of trans- to cis- form may need to overcome a
certain energy barrier, leading to a lower formation rate of 2.
How the Re species functions for DODH reactions is a
fundamentally important issue. We performed in-situ Fourier-
transform infrared (FT-IR) spectroscopy studies to gain insights
into the possible interactions between the Re species and
reactants. To simplify the assignment of IR bands and to gain
adequate signal intensity, we chose CH3ReO3 as a model
catalyst and dibutyl tartrate with cis-diol structure as a model
reactant. IR spectra for interactions between CH3ReO3 and
dibutyl tartrate in butanol were displayed in Fig. 2A. No IR
band was observed in a range of 1020-920 cm-1 for dibutyl
tartrate without CH3ReO3 (Fig. 2A, a). The addition of CH3ReO3
into dibutyl tartrate resulted in two bands at ~967 and ~948
cm-1 (Fig. 2A, b-f), which could be assigned to symmetric and
asymmetric stretching vibrations of Re=O bond (Fig. S6, Table
S3, ESI†). The increase in the concentration of CH3ReO3 led to
increased intensities of the two bands. As compared to
CH3ReO3 alone (Fig. 2A, g), the presence of dibutyl tartrate
significantly enhanced the intensity of IR band at 967 cm-1,
whereas the band at 948 cm-1 blue-shifted slightly, indicating
the change in the dipole moment of the Re catalyst. This
suggests the formation of CH3ReO2-diolate complex,15 which
can change the catalyst symmetry, decreasing the differences
in dipole moments of symmetric and asymmetric Re=O
stretching vibrations. Thus, the enhancement in the intensity
of symmetric Re=O stretching vibration and a slight band shift
were observed.
Our control experiments for the conversion of D-glucaric
acid-1,4-lactone without
a catalyst revealed that the
esterification with butanol occurred at 393 K (Fig. S4, ESI†).
Three major esterification products were identified by gas
chromatography-mass spectrometry (GC-MS) with a silylation
method. These products were butyl ester of D-glucaric acid-
1,4-lactone (5), butyl ester of D-glucaric acid-3,6-lactone (6)
and dibutyl ester of D-glucaric acid (7) with a molar ratio of 54:
32: 14 (Scheme 3 and Fig. S5, ESI†). This ratio did not change
upon prolonging the reaction time, suggesting that an
equilibrium was reached among the ring-lactone and chain
esters (Scheme 3). The addition of ReOx/ZrO2 resulted in
product 2, dibutyl hexa-2,4-dienedioate, with a yield of 41%
after a reaction at 393 K for 24 h. As compared to the lower
fraction (14%) of linear esterification product 7 without a
catalyst, the enhanced formation of linear product 2 in the
presence of ReOx/ZrO2 indicates that the esterification
equilibrium is driven to ring-open products by ReOx catalyst.
The change in the product yield with reaction time during
the conversion of D-glucaric acid-1,4-lactone with the
ReOx/ZrO2 catalyst showed that products 5 and 6 were the
major products at a short reaction time (Fig. 1). This indicates
that the esterification occurs at the initial reaction stage. Upon
prolonging the reaction time, the yields of 5 and 6 decreased
and those of 1 and 2 increased. A linear product 8, which
should be derived from 7 through the removal of two vicinal
cis-diols at C2 and C3 positions (Scheme 3), was also formed.
The yield of 8 first increased and then decreased with reaction
time, indicating that it is a reaction intermediate. Our result
suggests that 6 is more reactive than 5 in the DODH reaction.
This can be explained by the fact that the OH groups in a cis-
diol can be removed more readily than those in a tran-diol in
Re-catalysed DODH reactions.10b,10c Product 5 could be
transformed to 6 and 7 through a ring-chain equilibrium
reaction and subsequent conversions of 6 and 7 resulted in
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formation of DODH products.
View Article Online
DOI: 10.1039/C9CC05413H
This work was supported by the National Key R&D program
of China (No. 2018YFB1501602), National Natural Science
Foundation of China (Nos. 21690082, 91545203 and
21473141) and the Fundamental Research Funds for the
Central Universities (No. 20720160029).
Conflicts of interest
Fig. 2 FT-IR spectra at 363 K. (A) Systems composed of dibutyl tartrate and CH3ReO3
with different concentrations in butanol. CH3ReO3 concentration (mmol/L): a, 0; b, 4; c,
8; d, 16; e, 24; f and g, 32. Dibutyl tartrate concentration (mmol/L): a-f, 200; g, 0. (B)
Systems composed of CH3ReO3 (concentration, 32 mmol/L) and different diols
(concentration, 200 mmol/L) in butanol.
There are no conflicts to declare.
Notes and references
Further FT-IR studies for systems composed of CH3ReO3 and
other diols demonstrated that the functional groups in the
diols influenced the IR bands ascribed to the symmetric Re=O
stretching vibration (Fig. 2B). As compared to the electron-
withdrawing groups (e.g., –COOBu in tartrate), the electron-
donating groups such as –CH3 in pinacol and −CH2OCH2– in 1,4-
anhydroerythritol caused the shift of IR band to a lower
wavenumber. This provides further evidence for the formation
of Re-diolate complex in these systems. When the
temperature rose to 393 K, these IR bands disappeared, and
the corresponding alkenes were formed (Fig. S7, ESI†).
Take the DODH of D-glucaric acid-1,4-lactone to product 1 as
an example, we propose a functioning mechanism of Re
species in Scheme 4. As mentioned in Scheme 3, D-glucaric
acid-1,4-lactone is transformed to a cis-diol via esterification
equilibrium in butanol under reaction conditions, and then the
Re species is coordinated by the two vicinal OH groups,
forming a Re-diolate complex. Upon reduction by butanol, the
Re-diolate complex is transformed into an alkene and the Re
catalyst is recovered.
In conclusion, we have discovered that ReOx/ZrO2 is an
efficient catalyst for the deoxydehydration of D-glucaric acid-
1,4-lactone in butanol. The catalyst offers dibutyl hexa-2,4-
dienedioate with a yield of 41% and the total yield of esters
containing alkenyl groups was 93%. The product mixture can
be further converted to butyl adipate with a yield of 82% in the
subsequent hydrogenation reaction in combination with a
Pd/C catalyst. The higher reducibility of ReOx species due to
weaker interactions on ZrO2 is favourable for the removal of
OH groups and the redox of ReOx species may participate in
the deoxydehydration. Re species is believed to be
coordinated by the vicinal OH groups in cis-diol structure,
forming a Re-diolate complex, a key intermediate for the
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Scheme 4 A proposed reaction mechanism for Re-catalysed DODH reaction.
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