Combined 1,4-butanediol lactonization and transfer hydrogenation/ hydrogenolysis of furfural-derivatives under continuous flow conditions

Article abstract of DOI:10.1039/c4cy00213j

The oxygen-free lactonization of 1,4-butanediol to γ-butyrolactone coupled with a sequential reductive upgrading of furfural derivatives following a transfer hydrogenation/hydrogenolysis mechanism was studied over AlO _x-supported copper catalysts. The Cu-Al hydrotalcite-like catalyst-precursor was first reduced with H₂, forming dispersed Cu nanoparticles. The catalyst was characterized and tested for the dehydrogenation of various primary and secondary alcohols, optimizing the activation procedure and reaction conditions. Subsequently, the combined transfer hydrogenation/hydrogenolysis to furfural derivatives was investigated. All reactions were performed under continuous flow conditions to increase the space-time yield and the selectivity towards the desired products, as well as to study the catalyst stability.

Full text of DOI:10.1039/c4cy00213j

Catalysis
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Combined 1,4-butanediol lactonization and
transfer hydrogenation/hydrogenolysis of furfural-
Cite this: Catal. Sci. Technol., 2014,
derivatives under continuous flow conditions†
4, 2326
Christof Aellig, Florian Jenny, David Scholz, Patrick Wolf,‡ Isabella Giovinazzo,
Fabian Kollhoff and Ive Hermans‡*
The oxygen-free lactonization of 1,4-butanediol to γ-butyrolactone coupled with a sequential reductive
upgrading of furfural derivatives following a transfer hydrogenation/hydrogenolysis mechanism was
x
studied over AlO -supported copper catalysts. The Cu–Al hydrotalcite-like catalyst-precursor was first
Received 17th February 2014,
Accepted 11th April 2014
reduced with H , forming dispersed Cu nanoparticles. The catalyst was characterized and tested for the
2
dehydrogenation of various primary and secondary alcohols, optimizing the activation procedure and
reaction conditions. Subsequently, the combined transfer hydrogenation/hydrogenolysis to furfural derivatives
was investigated. All reactions were performed under continuous flow conditions to increase the space-time
yield and the selectivity towards the desired products, as well as to study the catalyst stability.
DOI: 10.1039/c4cy00213j
www.rsc.org/catalysis
For the reductive upgrading of HMF, similar noble-metal
catalysts have been used, including Au and Pt catalysts.
Introduction
5
d,6
A key challenge for the chemical industry is the replacement
of the current oil-derived feedstocks with readily available
and preferably renewable raw materials. Furfural and
Usually hydrogenation and hydrogenolysis reactions are
performed under hydrogen pressure. In order to circumvent
the inherent problems associated with H2 (such as storage,
safety and eco-efficiency), other hydrogen sources like
5
-(hydroxymethyl)furfural (HMF), available from the dehydra-
1
5b,j,6b,8
5d
5k,l
tion of biomass-derived sugars, as shown in Scheme 1, are
potential key platform molecules in the manufacturing of
value-added chemicals. 2,5-Bis(hydroxymethyl)furan (BHMF),
obtained by hydrogenation of HMF, is, for instance, used as
an intermediate in the production of polyurethane foams
2-propanol,
formic acid or other alcohols
have
recently gained a lot of attention. In case of alcohols, low-cost
carbonyl compounds (e.g. acetone) are formed that have to be
2
and polyesters. Furfuryl alcohol (FA), the hydrogenation
product of furfural, is widely used in the production of resins
and as an intermediate for various compounds such as vita-
3
min C or lysine. Further hydrogenolysis of FA and BHMF to
methylfuran (MeF) and 2,5-dimethylfuran (DMeF) provides
potential fuel substitutes which have more desirable proper-
4
ties than other bio-fuels such as ethanol. Hydrogenation
and hydrogenolysis of furfural have been extensively investi-
5
a,b
gated with a variety of catalysts, including not only Ru,
5
c,e,7
5d
Pd
and Ir but also promising noble metal-free and
5
e–i
bimetallic catalysts
based on Cu and Ni were reported.
ETH Zurich, Institute for Chemical and Bioengineering, Wolfgang-Pauli-Strasse 10,
8093 Zurich, Switzerland. E-mail: hermans@chem.wisc.edu
†
Electronic supplementary information (ESI) available: Catalyst screening,
Scheme
1
Reductive
upgrading
of
furfural
and
(
S)TEM images, TPR profile and liquid hold-up calculations. See DOI: 10.1039/
c4cy00213j
Current address: University of Wisconsin
Chemistry Department of Chemical and Biological Engineering, 1101
University Ave, Madison WI 53706 USA.
5-(hydroxymethyl)furfural (HMF) to furfuryl alcohol (FA), 2,5-
bis(hydroxymethyl)furan (BHMF), 2-methylfuran (MeF) and 2,5-
dimethylfuran (DMeF) via transfer hydrogenation/hydrogenolysis with
parallel oxygen-free lactonization of 1,4-butanediol (BDO) to
γ-butyrolactone (GBL).
‡
– Madison, Department of
&
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−1
disposed or used elsewhere. Using formic acid as the hydro-
The XRD pattern of a catalyst exposed to H (25 mL min ) at
2
gen donor, CO is co-produced, making it less attractive.
250 °C for 4 hours does not show significant differences to
the XRD pattern of a catalyst reduced for only 45 minutes
(Fig. S7†). This indicates that the crystalline phases of the
catalyst did not significantly change after 45 minutes of
activation.
2
For these reasons, one could envision improving reductive
upgrading by selecting an appropriate renewable hydrogen
source which would yield a valuable side product. The
oxygen-free
1,4-butanediol
(BDO)
lactonization
to
γ-butyrolactone (GBL), a useful intermediate in the synthesis
Catalytic activity studies were performed in a continuous
flow reactor (Scheme S1†), offering several advantages over
batch reactors, such as improved control of reaction parame-
ters, enhanced heat- and mass-transfer, better mixing of the
9
b
of fine chemicals, produces two equivalents of molecular
hydrogen. This makes BDO an excellent hydrogen source,
7
readily available from fermentation of biomass. In the past,
lactonization has been performed with various oxidants and
reactants, shorter reaction times and smaller reactor
9
10
12
catalysts, including some Cu catalysts.
In addition,
Mizugaki et al. reported that copper nanoparticles on AlOx
Cu/AlO ) derived from Cu–Al hydrotalcite (Cu–Al-HT) show
volumes.
Initial catalytic experiments focused on the
1
1
oxygen-free dehydrogenation of alcohols. Although the reac-
(
tion was performed at 16 bar over-pressure, H gas bubbles
x
2
an excellent performance in the hydrogenolysis of glycerol to
,2-propanediol. Prompted by these literature observations,
we decided to investigate transfer hydrogenation/hydrogenolysis
using BDO as the hydrogen donor in the reductive upgrading
were observed at the exit of the reactor. Therefore, the liquid
holdups were calculated using the correlation of Larachi
et al. for trickle bed reactors (see ESI†) in order to accu-
rately determine contact times.
1
1
3
of furfural and HMF with a Cu/AlO catalyst under continuous
flow conditions.
A significantly higher activity was observed when the cata-
lyst was reduced at 250 instead of 200 °C (Fig. S8†). Tempera-
ture Programmed Reduction (TPR) (Fig. S9†) reveals that the
x
2
+
0
Cu -to-Cu reduction only starts at around 200 °C, and this
observation corroborates the working hypothesis that the
active phase of the catalyst consists of dispersed copper
nanoparticles. The dehydrogenation of various primary and
secondary alcohols was investigated and the results are
summarized in Table 1. In the case of benzyl alcohol and
2-heptanol, the catalyst did not only show activity in the
dehydrogenation but also in the hydrogenolysis reaction,
forming toluene and heptane, respectively. In the case of the
conversion of BDO to GBL, the catalyst showed high activity
and selectivity towards the desired lactone product (Fig. 2).
Small quantities of 3-hydroxytetrahydrofuran were detected
by GC-MS, supporting the proposed reaction mechanism in
Scheme 2.
Results and discussion
Catalyst synthesis and activity
Various copper-containing materials were synthesized following
a co-precipitation method as described in the experimental
section. The catalyst composition was initially optimized in
terms of activity and selectivity for the conversion of the
BDO–furfural mixture by screening different supports (Al O ,
SiO and Fe O ) and Cu loadings (see Tables S1 and S2 in the
2 2 3
ESI†). The XRD pattern of the most promising Cu–Al-HT cata-
lyst precursor is characteristic for hydrotalcite-like materials
2
3
(Fig. 1 and S1†). The layered structure of the precursor can
also be observed in an electron micrograph (Fig. S2†).
Reduction of the material under a H2 flow (T ≥ 200 °C)
yielded copper nanoparticles on AlO
x
, as evidenced by using
We emphasize that no activity could be observed in blank
experiments where the reactor was only filled with quartz par-
ticles or an HT support (after thermal activation).
the HAADF-STEM (Fig. S3 and S5†). The XRD pattern shows
the formation of both Cu and Cu O phases (Fig. 1 and S1†).
2
XRD analysis of the spent catalyst (6 hours on stream)
reveals that the Cu O phase completely disappeared and only
2
elemental copper was left. Two additional peaks appeared
(
Fig. 1 and S1†), indicating the formation of crystalline
Table 1 Oxygen-free dehydrogenation of different alcohols to their
corresponding carbonyl compounds and lactonization of BDO to GBL
a
a
Substrate
Product
Conversion /%
Yield /%
b
51
31
2
8
2
6
19
80
c
100
98
Fig. 1 XRD patterns of Cu–Al-HT as prepared, the reduced catalyst
−1
a
−1
(
25 mL min
H
2
flow, 45 min, 250 °C) and the catalyst exposed to the
Solvent: 1,4-dioxane, calcohol: 0.2 mol L p: 16 bar, T: 220 °C,
−1
−1
reaction solution (cBDO: 0.2 mol L , cfurfural: 0.2 mol L , p: 16 bar,
T: 220 °C) for 6 hours.
residence time: 2.7 min, activation T: 250 °C (25 mL min H flow,
45 min). Yield of toluene: 18%. Yield of heptane: 3%.
2
b
c
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with benzaldehyde used as H-acceptor, show clear curvatures
(
Fig. 3). This observation can point towards (i) mass-transfer
limitations at higher temperatures, (ii) a change in the
rate-determining step, or (iii) a rate-determining elementary
reaction step which cannot be expressed by a simple power-
law type model. In contrast, the Arrhenius plots of HMF and
furfural as H-acceptors are perfectly linear (Fig. 3), both
−
1
giving an activation energy of 35 ± 1 kcal mol , suggesting
that the dehydrogenation of BDO to 4-hydroxy-n-butanal is
the rate-determining step (RDS) (Scheme 2). This is
confirmed by the fact that the reaction rate of both BDO and
furfural consumption is first order in BDO (Fig. S10†). At
reaction temperatures below 190 °C, the slopes associated
with pure BDO and the BDO/benzaldehyde transfer-hydrogenation
system are linear, yielding the same activation energy of
Fig. 2 BDO conversion (X) and GBL yield (Y) against contact time
−
1
−1
(
activation T: 250 °C (25 mL min
2
H flow, 45 min), cBDO: 0.2 mol L ,
p: 16 bar, T: 220 °C).
−
1
3
5 ± 1 kcal mol as the BDO/furfural and BDO/HMF systems.
This leads to the assumption that in the 170–190 °C tempera-
ture range, the RDS is the same for all of these systems.
Scheme 2 Proposed mechanism of the oxygen-free lactonization of
Interestingly, at low reaction temperatures, the overall
reaction rate is significantly lower for the BDO/furfural and
BDO/HMF systems than for the BDO and BDO/benzaldehyde
systems, despite our hypothesis of BDO dehydrogenation
being the rate-determining step. One plausible explanation
for this observation could be the strong adsorption of HMF
and furfural to the catalyst, reducing the number of BDO-
dehydrogenation sites, lowering the pre-exponential factor.
In order to test for external mass-transfer limitations (film
diffusion), different reactor lengths were tested, adjusting the
flow rate in a way that the residence time remains constant.
According to film theory, the liquid film around the catalyst
particle gets thinner with increasing flow rate. As a conse-
quence, mass transfer would be enhanced, resulting in an
increase in conversion if this transfer were to be the control-
ling step. Changing the flow rate did however not signifi-
cantly affect the conversion of both BDO and benzaldehyde
BDO to GBL.
1
4
phases of alumina during the reaction. Although there is a
clear difference in activity (Fig. S8†), no significant difference
in the diffractograms of the catalysts activated at 200 °C and
2
50 °C can be observed (Fig. 1 and S1†). However, there is a
difference in the HAADF-STEM images after reaction. The cat-
alyst that was activated at 250 °C showed clearly segregated
Cu nanoparticles with an average particle size of 20–40 nm
(Fig. S6†), whereas the catalyst that was activated at 200 °C
showed a more disperse distribution with large particles up
to 60 nm (Fig. S4†). This difference in the structure of the cat-
alyst probably explains the difference in reactivity (Fig. S8†).
Further increase of the reduction temperature, however, leads
to the formation of larger and less active particles.
Temperature dependence and mass transfer
(
Fig. 4). Therefore, external mass-transfer limitations can be
The Arrhenius plots obtained in the temperature range 170
to 220 °C, based on BDO consumption without acceptor or
excluded. On the other hand, the activation energy above
210 °C clearly decreased to below 10 kcal mol . Since diffusion
−
1
Fig. 3 Arrhenius plots based on BDO consumption of pure BDO, BDO–
benzaldehyde, BDO–HMF and BDO–furfural transfer hydrogenation systems
Fig. 4 Conversion of BDO and benzaldehyde for different column
lengths (6 cm, 10 cm and 15 cm) adjusting the flow rate to keep the
−1
−1
−1
(
activation T: 250 °C (25 mL min
H
2
flow, 45 min), cBDO: 0.2 mol L , cacceptor
:
residence time at 0.26 min (activation T: 250 °C (25 mL min
2
H flow,
−1
−1
−1
0.2 mol L , p: 16 bar, T: 170–220 °C).
45 min), cBDO: 0.2 mol L , cbenzaldehyde: 0.2 mol L , p: 16 bar, T: 220 °C).
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limitations could be excluded, the reaction mechanism is
apparently more complex and cannot be expressed by a simple
power-law type model at higher temperatures. Further kinetic
modeling is required to rationalize these observations.
The same test for external diffusion limitations was
also performed with the BDO–furfural mixture at 220 °C
(Fig. S11†) showing, as expected, no dependence of the
conversion on the flow rate.
Catalyst stability
In order to test the long-term stability of the catalyst, a reac-
tion with the BDO–benzaldehyde mixture was performed at
Fig. 5 Conversion of BDO to GBL and furfural to FA (activation T: 240 °C
−
1
−1
−1
2
20 °C over 24 h. Over the first 12 hours, a slight deactivation
(25 mL min H2 flow, 45 min), cBDO: 0.2 mol L , cfurfural: 0.2 mol L
p: 16 bar, T: 220 °C).
,
could be observed (viz., a decrease of 5% in the BDO conver-
sion and 10% for benzaldehyde; in agreement with the reac-
tion stoichiometry) as shown in Fig. S14.† After 12 hours, the
catalytic performance remained constant and no further
deactivation could be observed. Although several trends
could explain the decrease in conversion over the first
Traces of 2-methylfurfural (MeFF) could be observed at low
residence times using the GC-MS. At higher residence times,
traces of 2,5-dimethyltetrahydrofuran could be detected
(Scheme 3).
1
2 hours, no evidence for significant copper leaching could
be obtained from ICP-OES analysis after digestion of the cata-
lyst. HAADF-STEM analysis reveals an increase in the particle
size (from around 20 nm to 40 nm) of the freshly activated
catalyst at 250 °C and after 6 hours of reaction with the
BDO–furfural mixture (Fig. S5 and S6†). EDXS analysis
At a residence time of 0.6 minutes the hydrogenation of
HMF yields 93% BHMF and 28% GBL at conversions of 94%
and 29% for HMF and BDO, respectively. HMF deoxygenation
results in a 72% yield of DMF at 100% HMF and BDO conver-
sions and a 99% GBL yield after 29 minutes (Fig. 6).
(Fig. S12 and S13†) clearly shows that the carbon content on
the support is significantly higher after reaction. Based on
these observations, we propose that the main reason for the
slight loss in activity is sintering and coking of the catalyst. A
Conclusions
The high oxygen content of biomass-derived platform mole-
cules asks for efficient methods for the reductive upgrading
to chemicals and fuels. After activation of a Cu–Al HT-like
5
% increase in activity could be observed after air calcination
of the used catalyst (after 24 h on stream) at 450 °C, followed
by reactivation under H , indicating that coking is indeed
partially) contributing to deactivation. Although no signifi-
2
precursor under H
at temperatures above 200 °C, Cu nano-
are formed. The present catalyst
2
(
particles dispersed on AlO
x
cant Cu leaching could be observed in the present system, we
emphasize that real biomass streams may contain residual
water from previous processing, and that leaching of Cu
is active not only in the oxygen-free dehydrogenation of alco-
hols to their corresponding carbonyl compounds, but also for
the oxygen-free lactonization of BDO to GBL with parallel
hydrogenation/hydrogenolysis of furfural or HMF. The use of
1
5
could become an issue.
1,4-butanediol as the hydrogen donor has several advantages:
Transfer hydrogenation/hydrogenolysis of furfural and HMF
(i) it can be obtained by fermentation, (ii) it releases two
equivalents of H , and (iii) the product GBL has many appli-
2
The hydrogenation of furfural with BDO yielded 99% FA and
cations and can be further used in the chemical value-chain.
Depending on residence time, FA can be obtained with a
yield of 99%. At longer residence times, MeF and other
5
7% GBL at a residence time of 0.65 minutes under continu-
ous flow conditions (Fig. 5). One can clearly see that FA is
decreasing at residence times higher than 0.5 min due to
hydrogenolysis to MeF and other side reactions like
decarbonylation and ring hydrogenation. The by-products
furan, THF and 2-methyltetrahydrofuran were detected by
GC-MS. Because of the low selectivity towards the desired
MeF product, more focus was put on the selective conversion
of furfural to FA and of BDO to GBL (Fig. 5). When stoichio-
−
1
−1
metric amounts of BDO (0.1 mol L instead of 0.2 mol L )
−
1
were used in combination with furfural (0.2 mol L ), only an
8
1% yield of FA could be obtained at 100% BDO conversion.
The transfer hydrogenation/hydrogenolysis of HMF pro-
ceeds mainly via BHMF, which, subsequently, undergoes
hydrogenolysis via 2-methylfurfuryl alcohol (MFA) to DMeF.
Scheme
3 Reaction network of the transfer hydrogenation/
hydrogenolysis of HMF to BHMF and DMeF.
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99%; 4.96 g, 13.2 mmol) in deionized water (35 mL) and
Na CO (Acros Organics, 99.6; 2.98 g, 28 mmol) in deionized
2
3
water (30 mL) were added dropwise simultaneously to 50 mL
of deionized water in a beaker under vigorous stirring and
the pH was kept constant at 8–9 by adding NaOH (12 g,
0
.3 mol) in deionized water (100 mL). The resulting pale blue
slurry was transferred into a round-bottom flask and aged at
5 °C for two hours. The product was filtrated and washed
6
thoroughly with deionized water and dried at 65 °C in a
vacuum oven for 16 hours. Reduced Cu-loadings were
achieved by reducing the amount of Cu(NO ) ·3H O to 0.5
3
2
2
and 0.25 of the initial amount.
Fig. 6 Conversion of BDO to GBL and HMF to BHMF and DMF
−
1
−1
(
activation T: 250 °C (25 mL min
H
2
flow, 45 min), cBDO: 0.6 mol L
,
−1
Synthesis of Cu/Fe O
cHMF: 0.2 mol L , p: 16 bar, T: 220 °C).
2 3
2 3
Cu/Fe O was prepared according to the above mentioned
procedure by replacing Al(NO ) ·9H O with the correspond-
3
3
2
ring-hydrogenation and decarbonylation products are formed.
In the case of HMF, BHMF can be obtained with a 93% yield at
a residence time of 0.6 min. The subsequent hydrogenolysis of
BHMF yields 72% DMeF after 29 minutes contact time.
The stability of the catalyst is tested over 24 hours showing
that the conversion of both BDO and benzaldehyde slightly
decreases over the first 12 hours, thereafter remaining stable.
The reason for the deactivation can at least partially be attrib-
uted to sintering and coking.
ing amount of Fe(NO
3
)
3
·9H
2
O (Merck, ≥98%).
Synthesis of Cu/SiO
Cu/SiO was prepared according to a literature procedure.
An aqueous solution of NaOH (4 M) was added dropwise to a
solution of Cu(NO ) ·3H O (11.66 g, 48.3 mmol) under vigorous
2
1
6
2
3 2
2
stirring. In the resulting slurry 5.29 g of colloidal silica solution
30% SiO in water, Aldrich) was added. The gel was aged at
(
2
65 °C for two hours. After filtration the product was washed
thoroughly with deionized water and dried in a vacuum oven
at 65 °C for 16 hours.
Experimental section
Quantification of furfural (Sigma-Aldrich, 99%), FA (Aldrich,
9
8%), HMF (Aldrich, ≥99%), BHMF, DMeF (TCI, >98%),
Continuous flow experiments
BDO (ABCR, 99%) and GBL (Acros, 99%) was done with
dodecane (Acros, 99%) as the internal standard and benzal-
dehyde (Acros, >98%), benzyl alcohol (Acros, 99%), heptanal
A tubular reactor (Ø 4.6 mm, Scheme S1†) was packed with a
mixture (void fraction 0.35) of Cu–Al-HT (1.5 g) diluted with
quartz (0.9 g; Ø 0.1–0.2 mm) and attached to a pre-column
(ABCR, 97%), 1-heptanol (ABCR, 99%), 2-heptanone (ABCR,
(
Ø 4.6 mm, length: 10 cm) filled with glass spheres (Ø 0.8 mm).
9
9%) and 2-heptanol (Acros, >99%) with biphenyl (Acros,
The inlet of the reactor was connected to an HPLC pump; the
outlet to a back-pressure regulator. The catalyst was pretreated
9
9%) as the internal standard using a GC-FID equipped with
an HP-FFAP column. 1,4-dioxane (Fluka, ≥99.5%) was used
as the solvent in all experiments.
at 250 °C or 200 °C, under ambient pressure and a constant H
2
−
1
flow (25 ml min ) for 45 min. Prior to pumping the reaction
solvent over the catalyst bed the pressure was increased
to 16 bar H2 pressure with the use of the back-pressure
Synthesis of BHMF
In a solution of HMF (Aldrich-Fine Chemicals, 99%; 2.02 g,
2
regulator. Before starting the reaction, the H -line was closed
1
6 mmol) in dry methanol (ABCR-Chemicals, 99.9; 16 mL),
and the pressure was kept at 16 bar to prevent evaporation of
the solvent.
NaBH (1.21 g, 32 mmol) was slowly added at 273 K under
4
constant stirring. After addition of the reductant, the ice bath
was removed and the solution was stirred at room tempera-
ture for an additional 15 min. The reaction was quenched
with 4 mL deionized water and 5 mL HCl (2 M). The product
was extracted 7 times with 10 mL ethyl acetate and subse-
Catalyst characterization
The copper contents of the untreated, reduced and used cata-
lysts were determined by using an ICP-OES (HORIBA Ultra 2).
The reduced catalyst was prepared according to the
pretreatment procedure described above. For ICP-OES
measurements all samples were calcined in air at 600 °C for
quently dried over MgSO . After filtration the solvent was
4
removed under reduced pressure yielding solid BHMF
(0.65 g, 55%).
5
3
hours and dissolved in aqua regia (37% HCl : 65% HNO3,
: 1). The copper contents were determined to be 65.6 wt%
Synthesis of Cu–Al-HT
(
untreated), 62.6 wt% (reduced at 200 °C), 55.3 wt% (reduced
Solutions of Cu(NO ) ·3H O (Aldrich-Fine Chemicals, 99%;
at 250 °C). Powder X-ray diffraction measurements were
conducted using a PANalytical X'Pert Pro-MPD (CuKα radiation,
3
2
2
6
.04 g, 25 mmol) and Al(NO ) ·9H O (Aldrich-Fine Chemicals,
3 3 2
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X'Celerator linear detector system, 2θ = 10–70°, step size of
8 (a) D. Scholz, C. Aellig and I. Hermans, ChemSusChem,
2014, 7, 268; (b) X. Wang and R. Rinaldi, Energy Environ.
Sci., 2012, 5, 8244.
9 (a) X. Li, Y. Cui, X. Yang, W.-L. Dai and K. Fan, Appl. Catal., A,
2013, 458, 63; (b) J. Huang, W.-L. Dai, H. Li and K. Fan,
J. Catal., 2007, 252, 69; (c) T. Mitsudome, A. Noujima,
T. Mizugaki, K. Jitsukawa and K. Kaneda, Green Chem.,
0.033°, ambient conditions). TEM images of untreated and
STEM images of reduced and used catalysts were recorded
using a Hitachi HD2700CS STEM (aberration-corrected dedi-
cated STEM, cold field-emission source, 200 kV). H -TPR of
2
untreated Cu–Al-HT was performed using a Thermo TPDRO 1100.
2
009, 11, 793; (d) Y. Lin, X. Zhu and Y. Zhou, J. Organomet.
Acknowledgements
Chem., 1992, 429, 269; (e) T. Suzuki, K. Morita, M. Tsuchida
and K. Hiroi, Org. Lett., 2002, 4, 2361; ( f ) T. Baba, K. Kameta,
S. Nishiyama, S. Tsuruya and M. Masai, Bull. Chem. Soc. Jpn.,
Financial support from the Swiss National Science Foundation
(SNSF; project 200021_146661) is gratefully acknowledged. The
1
990, 63, 255; (g) T. Baba, K. Kameta, S. Nishiyama, S. Tsuruya
authors also thank Dr. Frank Krumeich for his help with the
electron microscopy.
and M. Masai, J. Chem. Soc., Chem. Commun., 1989, 1072–1073;
(h) Y. Endo and J.-E. Bäckvall, Chem. – Eur. J., 2011, 17, 12596;
(i) W.-H. Kim, I. S. Park and J. Park, Org. Lett., 2006, 8, 2543;
( j) M. Ito, A. Osaku, A. Shiibashi and T. Ikariya, Org. Lett.,
Notes and references
2
007, 9, 1821; (k) J. Zhang, E. Balaraman, G. Leitus and
1
(a) A. S. Mamman, J. M. Lee, Y. C. Kim, I. T. Hwang,
N. J. Park, Y. K. Hwang, J. S. Chang and J. S. Hwang,
Biofuels, Bioprod. Biorefin., 2008, 2, 438; (b) C. Aellig and
I. Hermans, ChemSusChem, 2012, 5, 1737.
D. Milstein, Organometallics, 2011, 30, 5716; (l) A. Sølvhøj and
R. Madsen, Organometallics, 2011, 30, 6044; (m) K.-N. T. Tseng,
J. W. Kampf and N. K. Szymczak, Organometallics, 2013, 32,
2046; (n) M. C. Bagley, Z. Lin, D. J. Phillips and A. E. Graham,
Tetrahedron Lett., 2009, 50, 6823; (o) T. Morimoto, M. Hirano,
K. Iwasaki and T. Ishikawa, Chem. Lett., 1994, 53; (p)
D. V. Seleznev, L. N. Zorina, V. N. Trifonova, V. V. Zorin and
D. L. Rakhmankulov, Russ. J. Org. Chem., 2002, 38, 1064; (q)
T. R. Beebe, R. Adkins, R. Baldridge, V. Hensley, D. McMillen,
D. Morris, R. Noe, F. W. Ng, G. Powell, C. Spielberger and
M. Stolte, J. Org. Chem., 1985, 50, 3015; (r) S. Kondo,
S. Kawasoe, H. Kunisada and Y. Yuki, Synth. Commun.,
1995, 25, 719; (s) T. Miyazawa and T. Endo, J. Org. Chem.,
1985, 50, 3931; (t) H. Tanaka, Y. Kawakami, K. Goto and
M. Kuroboshi, Tetrahedron Lett., 2001, 42, 445; (u) Y. Ishii,
T. Yoshida, K. Yamawaki and M. Ogawa, J. Org. Chem.,
1988, 53, 5549; (v) K. S. Kim and W. A. Szarek, Carbohydr. Res.,
1982, 104, 328.
2
3
4
W. J. Pentz, GB Patent 2131014, 1984.
A. Corma, S. Iborra and A. Velty, Chem. Rev., 2007, 107, 2411.
W. Chongming, X. Hongming, D. Ritchie, G. Akbar,
M. H. Jose, S. Shijin and M. Xiao, Fuel, 2013, 103, 200.
(a) A. S. Gowda, S. Parkin and F. T. Lapido, Appl. Organomet.
Chem., 2012, 26, 86; (b) Z. Strassberger, M. Mooijman,
E. Ruijter, A. H. Alberts, C. de Graaf, R. V. A. Orru and
G. Rothenberg, Appl. Organomet. Chem., 2010, 24, 142; (c)
J. G. Stevens, R. A. Bourne, M. V. Twigg and M. Poliakoff,
Angew. Chem., 2010, 122, 9040; (d) T. Thananatthanachon
and T. B. Rauchfuss, ChemSusChem, 2010, 3, 1139; (e)
S. Sitthisa and D. E. Resasco, Catal. Lett., 2011, 141, 784; ( f )
M. M. Villaverde, N. M. Bertero, T. F. Garetto and
A. J. Marchi, Catal. Today, 2013, 213, 87; (g) X.-Y. Hao,
W. Zhou, J.-W. Wang, Y.-Q. Zhang and S. Liu, Chem. Lett.,
5
10 (a) D. W. Hwang, P. Kashinathan, J. M. Lee, J. H. Lee, U. Lee,
J.-S. Hwang, Y. K. Hwang and J.-S. Chang, Green Chem.,
2011, 13, 1672; (b) Y.-L. Zhu, H.-W. Xiang, G.-S. Wu, L. Bai and
Y.-W. Li, Chem. Commun., 2002, 254; (c) Y. Mikami, K. Ebata,
T. Mitsudome, T. Mizugaki, K. Jitsukawa and K. Kaneda,
Heterocycles, 2010, 80, 855.
2005, 34, 1000; (h) K. Yan, J. Liao, X. Wu and X. Xie, RSC Adv.,
2013, 3, 3853; (i) H. Luo, H. Li and L. Zhuang, Chem. Lett.,
2001, 404; ( j) M. Chia and J. A. Dumesic, Chem. Commun.,
2011, 47, 12233; (k) L. Bui, H. Luo, W. R. Gunther and
Y. Román-Leshkov, Angew. Chem., Int. Ed., 2013, 52, 8022; (l)
K. Barta, T. D. Matson, M. L. Fettig, S. L. Scott, A. V. Iretskii
and P. C. Ford, Green Chem., 2010, 12, 1640.
11 T. Mizugaki, R. Arundhati, T. Mitsudome, K. Jitsukawa and
K. Kaneda, Chem. Lett., 2013, 42, 729.
6
7
(a) J. Ohyama, A. Esaki, Y. Yamamoto, S. Aral and
A. Satsuma, RSC Adv., 2013, 3, 1033; (b) M. Balakrishnan,
E. R. Sada and A. T. Bell, Green Chem., 2012, 14, 1626; (c)
T. Thananatthanachon and T. B. Rauchfuss, Angew. Chem.,
Int. Ed., 2010, 49, 6616; (d) J. Jae, W. Zheng, R. F. Lobo and
D. G. Vlachos, ChemSusChem, 2013, 6, 1158.
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 and S. Van Dien, Nat. Chem.
Biol., 2011, 7, 445.
12 (a) R. L. Hartman, J. P. McMullen and K. F. Jensen, Angew.
Chem., 2011, 123, 7642; (b) G. Jas and A. Kirschning, Chem. –
Eur. J., 2003, 9, 5708; (c) A. Kirschning, W. Solodenko and
K. Mennecke, Chem. – Eur. J., 2006, 12, 5972.
13 V. V. Rande, R. Chaudhari and P. R. Gunjal, Trickle Bed Reactors,
Reactor Engineering & Applications, Elsevier B.V., Oxford, 2011.
14 P. S. Santos, H. S. Santos and S. P. Toledo, Mat. Res.,
2000, 3, 104.
15 A. M. Henge and C. V. Rode, Green Chem., 2012, 14, 1064.
16 Zhiwei Huang, Fang Cui, Haixiao Kang, Jing Chen,
Xinzhi Zhang and Chungu Xia, Chem. Mater., 2008, 20, 5090.
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