Synergistic Interaction within Bifunctional Ruthenium Nanoparticle/SILP Catalysts for the Selective Hydrodeoxygenation of Phenols

Article abstract of DOI:10.1002/anie.201508513

Ruthenium nanoparticles immobilized on acid-functionalized supported ionic liquid phases (Ru NPs@SILPs) act as efficient bifunctional catalysts in the hydrodeoxygenation of phenolic substrates under batch and continuous flow conditions. A synergistic interaction between the metal sites and acid groups within the bifunctional catalyst leads to enhanced catalytic activities for the overall transformation as compared to the individual steps catalyzed by the separate catalytic functionalities.

Full text of DOI:10.1002/anie.201508513

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Angewandte
Communications
International Edition: DOI: 10.1002/anie.201508513
German Edition: DOI: 10.1002/ange.201508513
Bifunctional Catalysts
Synergistic Interaction within Bifunctional Ruthenium Nanoparticle/
SILP Catalysts for the Selective Hydrodeoxygenation of Phenols
Kylie L. Luska, Pedro Migowski, Sami El Sayed, and Walter Leitner*
Abstract: Ruthenium nanoparticles immobilized on acid-
functionalized supported ionic liquid phases (RuNPs@SILPs)
act as efficient bifunctional catalysts in the hydrodeoxygena-
tion of phenolic substrates under batch and continuous flow
conditions. A synergistic interaction between the metal sites
and acid groups within the bifunctional catalyst leads to
enhanced catalytic activities for the overall transformation as
compared to the individual steps catalyzed by the separate
catalytic functionalities.
a network of metal- and acid-catalyzed reactions, in which the
removal of oxygenated moieties involves the acid and metal
components working independently (for example, metal-
catalyzed hydrogenation coupled with acid-catalyzed dehy-
dration) and/or cooperatively (for example, hydrogenolysis
catalyzed by both metal and acid components of the bifunc-
tional catalyst). Despite the growing number of bifunctional
catalysts, a detailed analysis of the individual and combined
action of the two catalytic moieties to control the reaction
network is seldom available making the rational design of
such materials still challenging.
In our present work, we describe the application of
a bifunctional catalyst composed of nanoparticles immobi-
lized on a supported ionic liquid phase (NP@SILP) in the
hydrodeoxygenation of phenols. A synergistic relationship
between the metal and acid components can be tuned through
the molecular, bottom-up synthesis of the materials to
provide an enhanced catalytic performance for the overall
transformation as compared to the individual steps catalyzed
by the separate catalytic functionalities.
L
ignocellulosic materials are a potential renewable feed-
stock for the manufacture of chemicals and fuels in the
chemical industry as they represent a non-edible resource that
can be produced in short timeframes and on large scales.[1]
Much progress has been made toward the production of
various classes of value-added products (for example, ethers,
alcohols, and alkanes) from pentose- and hexose-derived
platform chemicals;[2–4] however, valorization of the lignin
fraction remains a significant challenge.[5] As such, a signifi-
cant amount of research has focused on the development of
homogeneous-[6] and heterogeneous-based[7] catalytic strat-
egies towards the production of chemicals and fuels from
lignin.
The general design of these bifunctional metal NP@SILP
catalysts is based on a molecular approach to assemble the
individual components onto solid materials in a flexible and
controlled manner (Figure 1).[11] The support is synthesized by
One strategy towards the utilization of lignin involves
depolymerization into oligomeric and monomeric aromatic
components (primarily substituted phenols), followed by
deoxygenation of the phenolic intermediates to arenes and
cycloalkanes.[8] Although high yields of monomeric phenols
can be obtained by the depolymerization of lignin using
pyrolysis, hydrogenolysis, or hydrolysis,[9] the subsequent
hydrodeoxygenation of these substrates using conventional
CoMo and NiMo sulfide catalysts suffers from sulfur con-
tamination of the product and catalyst deactivation.[8] Novel
deoxygenation catalysts have been developed in which the
combination of an acid (for example, a Lewis or Brønsted
acid) and a metal catalyst (such as commercial heterogeneous
catalysts or metal nanoparticles), defined herein as a bifunc-
tional catalyst, has shown significant potential for the hydro-
deoxygenation of phenols.[10] This transformation comprises
Figure 1. Bifunctional catalysts, composed of Ru nanoparticles and an
acid-functionalized supported ionic liquid phase (RuNPs@SILP),
employed for the hydrodeoxygenation of phenolic substrates.
R=CH2SO3H (IL 1), R=CH3 (IL 2).
[*] Dr. K. L. Luska, Dr. P. Migowski, S. El Sayed, Prof. Dr. W. Leitner
Institut für Technische und Makromolekulare Chemie (ITMC)
RWTH Aachen University
tethering functionalized and/or nonfunctionalized imidazo-
lium-based ionic liquids (ILs) onto silica,[12] in which the
degree of functionality on the support can be tuned through
the ratio of functionalized to nonfunctionalized imidazolium
units.[3b] Even though these surface layers are of course no
longer true “liquid phases”, the materials are generally
referred to as supported ionic liquid phases (SILPs).[13] The
Worringerweg 1, 52074 Aachen (Germany)
E-mail: leitner@itmc.rwth-aachen.de
Prof. Dr. W. Leitner
Max-Planck-Institut für Kohlenforschung
45470 Mülheim an der Ruhr (Germany)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201508513.
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IL-like structure of the surface layer provides a stabilizing
environment for metal nanoparticles[14] formed from organo-
metallic precursors in a controlled chemical reaction. This
approach combines the molecular diversity of the IL-like
structures with the catalytic activity of metal nanoparticles.[11]
For deoxygenation processes required in selective biomass
conversion, the combination of acidic functionalities with Ru
metal NPs is particularly attractive.[3,4,10c,15]
RuNPs@SILPs were first investigated for the hydrode-
oxygenation of phenol under batch conditions, in which
a series of bifunctional catalysts were examined (Table 1).
Table 1: Hydrodeoxygenation of phenol using RuNPs@SILP.[a]
Entry Catalyst
Conversion [%]
Product Yield [%][b]
Ketone Alcohol Alkene Alkane
1
RuNPs@
SILP-0.33
RuNPs@
SILP-0.66
RuNPs@
SILP-1.00
RuNPs@
SILP-1.00
RuNPs@IL
93
33
3
51
73
59
5
0
0
0
0
0
9
Acidic SILPs were synthesized according to a modified
literature procedure[3b] and involved the condensation of
a sulfonic acid functionalized IL [1-(4-sulfobutyl)-3-(3-tri-
ethoxysilylpropyl)-imidazolium]NTf2 (IL 1), and a nonfunc-
tionalized IL [1-butyl-3-(3-triethoxysilylpropyl)imidazo-
lium]NTf2 (IL 2), with dehydroxylated SiO2. The combination
of an acid-functionalized IL 1 and a nonfunctionalized IL 2
allowed for control of the quantity of grafted sulfonic acid
moieties (defined as SILP acidity or acid loading =
IL 1/[IL 1 + IL 2]; see Table S1 in the Supporting Informa-
tion). RuNPs were synthesized and immobilized onto SILPs
(RuNPs@SILP) by means of wet impregnation of the SILP
with a solution of [Ru(2-methylallyl)2)cod)] (cod = 1,5-cyclo-
octadiene), followed by reduction of the dried SILP under an
atmosphere of H2. Characterization of the RuNPs@SILPs
using scanning transmission electron microscopy (STEM)
showed the production of small and well-dispersed RuNPs
(1.6–1.9 nm). A Ru loading of 0.23 wt% was determined for
the bifunctional catalysts using inductively coupled plasma
atomic adsorption spectroscopy (ICP-AAS; see the Support-
ing Information for full synthetic and characterization
details).
2
>99
>99
>99
62
24
41
95
32
3
0
4[c]
5[d]
0
19
11
[a] Reaction conditions: RuNPs@SILP (75 mg, 0.0024 mmol Ru), sub-
strate (6.0 mmol, 2500 equiv), decalin (1 mL), H2 (120 bar), 2 h, 1508C.
[b] Determined by GC using hexadecane as an internal standard.
[c] Substrate (2.4 mmol, 1000 equiv), 16 h, 1758C. [d] RuNPs stabilized
in [1-butyl-3-(4-sulfobutyl)imidazolium]NTf2: [Ru] (0.0024 mmol Ru), IL
(0.051 mmol).
The acid loading of the SILP was varied between 0.33 and 1.00
and was shown to influence both the catalytic activity and
selectivity of the bifunctional catalysts. Under standard
conditions (2500 equiv phenol, 1508C, 120 bar H2, 2 h),
RuNPs@SILP-0.33 did not achieve full phenol conversion
(Table 1, entry 1), whereas an increased SILP acidity pro-
vided
quant-
RuNPs@SILPs were investigated as bifunctional catalysts
for the hydrodeoxygenation of phenol, where the reaction
pathway involves a series of metal- and acid-catalyzed
reactions as outlined in Scheme 1. Aromatic hydrogenation
itative conversions of phenol for RuNPs@SILP-0.66 and
RuNPs@SILP-1.00 (Table 1, entries 2 and 3). In terms of the
catalytic selectivity, higher acid loadings of the SILP shifted
the product selectivity away from the alcohol and more
toward the deoxygenated product cyclohexane (Table 1,
entries 1–3). A yield of more than 95% of cyclohexane was
achieved using RuNPs@SILP-1.00 at 1758C (Table 1,
entry 4). The hydrodeoxygenation of phenol was also per-
formed using an unsupported bifunctional catalyst in which
RuNPs were immobilized in a homogeneous sulfonic acid
functionalized IL [1-butyl-3-(4-sulfobutyl)imidazolium]NTf2
(RuNPs@IL).[3a] The catalytic activity of RuNPs@IL was
significantly decreased in comparison to SILP-based bifunc-
tional catalysts (Table 1, entry 5) because the colloidal
RuNPs were unstable under catalytic conditions leading to
precipitation of bulk metal from the IL phase during the
reaction (Figure S6). Thus, the immobilization of IL 1 onto
SiO2 provided improved NP stability, probably through the
combination of electrosteric stabilization of the IL and steric
protection provided by the inert support material.[16]
Scheme 1. Reaction pathway for the hydrodeoxygenation of phenol
catalyzed by RuNPs@SILP.
of phenol is catalyzed by RuNPs to cyclohexanone and
further to cyclohexanol. Dehydration of cyclohexanol by the
acidic SILP yields cyclohexene, and subsequent hydrogena-
tion involving RuNPs provides the saturated product cyclo-
hexane. Integration of the RuNPs onto a sulfonic acid
functionalized SILP to form a bifunctional catalyst was
anticipated to allow for this reaction cascade to be carried
out in a single-pot reaction and under continuous flow
conditions.
The hydrodeoxygenation of phenol was investigated
under continuous flow conditions using the most active
bifunctional catalyst RuNPs@SILP-1.00.
A solution of
phenol (0.05m in decalin) was passed over a cartridge
packed with RuNPs@SILP-1.00 using a H-Cube Pro (a
continuous flow reactor), where the influence of the reaction
temperature, substrate flow, and H2 flow on the catalytic
activity and selectivity was investigated (Table S3). At a sub-
strate flow rate of 0.3 mLminÀ1 (residence time = 2.00 min),
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a reaction temperature of 1358C or more was required to
achieve quantitative conversion of phenol. Under these
conditions, an increased temperature (1508C) provided
higher quantities of the deoxygenated products cyclohexene
and cyclohexane (> 99% conversion, 56% deoxygenation
product yield). Increased substrate flows led to full conver-
sion of phenol between 0.3 and 0.9 mLminÀ1 (residence
time = 2.00 and 0.67 min, respectively). However, under these
conditions the alkane yield decreased from 52% to 28%
whereas the alkene yield doubled from 4% to 8%. The H2
flow rate did not have a significant influence on the catalytic
behavior of the bifunctional catalyst.
From this parameter screening, conditions were selected
that provided a mixture of hydrogenation and deoxygen-
ation products to evaluate the long-term behavior of
RuNPs@SILP-1.00 (T= 1508C, substrate flow rate =
0.3 mLminÀ1, H2 flow rate = 60 NmLminÀ1, t = 4 h; Figure 2,
Table S4). The hydrogenation of phenol catalyzed by RuNPs
occurred rapidly under continuous flow conditions to give
quantitative conversion over 240 minutes time-on-stream. A
largely constant amount of the primary hydrogenation
products cyclohexanone (6–9%) and cyclohexanol (34–
39%) was detected throughout the reaction. The total yield
of deoxygenated products was also consistent (55–60%) over
the course of the reaction. The composition of the alkene/
alkane mixture, however, changed during time-on-stream as
the yield of cyclohexene increased from 6% to 30%, while
concomitantly that of cyclohexane decreased from 51% to
30%.
Analysis of RuNP@SILP-1.00 after catalysis did not show
significant growth or aggregation of the RuNPs by STEM
(1.80 Æ 0.3 nm; Figure S5), ICP measurements did not evi-
dence any leaching of Ru or the IL, and changes to the
textural properties were not detected by BET surface-area
analysis (Table S5). As the RuNP@SILP bifunctional cata-
lysts appear to be quite stable materials under continuous
flow conditions, we set out to determine the activity of each of
the individual reaction steps to identify the reason for
a change in the product selectivity.
Figure 2. Hydrodeoxygenation of phenol (0.05m in decalin,
0.3 mLminÀ1) using RuNPs@SILP-1.00 (550 mg, 0.0176 mmol Ru)
under continuous flow conditions at 1508C and 80 bar H2 (gas flow
rate under standard conditions=60 NmL minÀ1).
1.00), in which reaction rates (r) were derived from the
consumption of the substrates. The hydrogenation of phenol
(Àrphenol) to the primary hydrogenation products cyclohexa-
none and cyclohexanol catalyzed by RuNPs@SILP-0.00 had
a reaction rate of 1.74m hÀ1 (Table 2, Entry 1a), in which
negligible quantities of cyclohexane (< 1%) were produced in
the absence of an acid catalyst. Dehydration of cyclohexanol
(-ralcohol) using SILP-1.00 provided cyclohexene with a rate of
0.02m hÀ1 and the subsequent hydrogenation of cyclohexene
(-ralkene) catalyzed by RuNPs@SILP-0.00 yielded cyclohexane
at a rate of 20.7m hÀ1 (Table 2, Entries 1b and 1c). From these
kinetic experiments, the rate-limiting elementary reaction
was determined to be the acid-catalyzed dehydration of
cyclohexanol, which was about 87 and 1035 times slower than
Using two separate materials, one
containing the acid moiety and one
Table 2: Reaction rates for the hydrodeoxygenation of phenol using SILP-based catalysts.[a]
comprising the metal functionality,
kinetic parameters for the elemen-
tary reactions involved in the reac-
tion sequence leading to hydro-
deoxygenation of phenol were
determined.
Reaction
Catalyst
Reaction rates [mhÀ1 [b]
]
The reaction rates for the ele-
mentary reactions involved in the
phenol hydrodeoxygenation path-
way were determined for SILP-
based catalysts, where pseudo
zero-order kinetics were detected
during the initial stages of the
reactions (Table 2; Figure S2).
First, the elementary reactions
were investigated using the individ-
ual metal- (RuNPs@SILP-0.00) and
1) Elementary Reactions:
a) Phenol hydrogenation
b) Cyclohexanol dehydration
c) Cyclohexene hydrogenation
RuNPs@SILP-0.00
SILP-1.00
RuNPs@SILP-0.00
Àrphenol =1.74
Àralcohol =0.02
Àralkene =20.7
2) Tandem/Integrated Reactions:
a) Physical mixture
RuNPs@SILP-0.00
+SILP-1.00
RuNPs@SILP-1.00
Àrphenol =0.73
+rtotal =0.07
Àrphenol =1.62
+rtotal =0.47
b) Bifunctional catalyst
[a] Reaction conditions: RuNPs@SILP (225 mg, 0.0072 mmol Ru), substrate (18.0 mmol, 2500 equiv),
decalin (3 mL), H2 (120 bar), 1258C. [b] Determined by GC using hexadecane as an internal standard
acid-based components (SILP- during the first 2 h of reaction.
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Table 3: Deoxygenation of phenolic derivatives using RuNPs@SILP-
the metal-catalyzed hydrogenation of phenol and cyclohex-
ene, respectively. These results provided evidence on the
behavior of the bifunctional catalyst under continuous flow
conditions (Figure 2), in which changes in the product
selectivity were likely caused by a decrease in the reaction
rate of the slowest step in this transformation, that is, the
dehydration of cyclohexanol. Due to the lack of back mixing
under continuous flow conditions, a decreased cyclohexanol
dehydration rate led to a shorter retention time of the
intermediate cyclohexene for the subsequent hydrogenation
to cyclohexane. As the catalyst materials were found to be
quite stable under catalytic conditions, the reason for
a decreased dehydration rate may result from the accumu-
lation of water formed during the reaction within the catalyst
bed.
1.00.[a]
Product Yield (%)[b]
Alcohol
Entry
Substrate
Ether
Alkane
1
–
–
0
>99
2[c]
21
14
3
1
76
81
3
Kinetic experiments were also performed for the tandem
reaction employing a physical mixture of the individual metal-
and acid-based catalysts, RuNPs@SILP-0.00 and SILP-1.00,
and for the integrated reaction using the bifunctional catalyst
RuNPs@SILP-1.00. The hydrodeoxygenation of phenol cata-
lyzed by the physical mixture had a reaction rate of 0.73m hÀ1
for the consumption of phenol, probably reflecting the
dilution of the metal catalyst with unloaded support
(Table 2, entry 2a). In comparison, the conversion of phenol
catalyzed by RuNPs@SILP-1.00 had a reaction rate of
1.62m hÀ1 (Table 2, entry 2b), which was more than twice
the rate of the physical mixture and similar to the phenol
hydrogenation in the absence of acid. Most significantly, the
overall reaction rate towards the production of cyclohexane
(+ rtotal) was significantly improved for the bifunctional
catalyst, as the rate was almost seven times higher than that
for the physical mixture (0.47 versus 0.07m hÀ1, respectively).
These results show that immobilization of the metal and acid
species within the RuNP@SILP bifunctional catalysts leads to
a synergistic interaction between the two catalytic compo-
nents. According to this data, the effect largely results from an
increase of the dehydration rate which may be due to the fact
that the substrate for this step is formed from the hydro-
genation of phenol, in close proximity to the acidic site.
Next, the performance of the bifunctional catalyst in the
hydrodeoxygenation of substituted phenolic substrates was
investigated (Table 3). Alkyl substitution of phenol did not
affect the reaction as quantitative hydrodeoxygenation of
p-cresol (4-methylphenol) to methylcyclohexane was ach-
ieved at 1758C (Table 3, entry 1). The bifunctional catalysts
also tolerated ether substitution of the phenolic ring as the
deoxygenation of anisole (methoxybenzene) to cyclohexane
was achieved in high yields (Table 3, entry 2). Deoxygenation
of di- and trisubstituted phenols, guaiacol (2-methoxyphenol)
and creosol (2-methoxy-4-methylphenol), was effectively
catalyzed by RuNPs@SILP-1.00 leading to yields of more
than 77% for the cyclohexane products (Table 3, entries 3
and 4). Thus, the close contact between the metal and acid
sites within the RuNP@SILP bifunctional catalysts also
facilitates the hydrogenolysis of ether moieties, wherein the
deoxygenation of ether-substituted phenols involves a series
of dehydration, hydrogenation, and hydrogenolysis reactions.
The reaction network for the deoxygenation of ether-
substituted phenols catalyzed by RuNPs@SILP is outlined in
4
18
4
77
[a] Reaction conditions: RuNPs@SILP-1.00 (75 mg, 0.0024 mmol Ru),
substrate (2.4 mmol, 1000 equiv), decalin (1 mL), H2 (120 bar), 16 h,
1758C. [b] Conversion >99%, determined by GC using hexadecane as
an internal standard. [c] Substrate (1.2 mmol, 500 equiv).
Scheme 2. Reaction network for the deoxygenation of substituted
phenols catalyzed by RuNPs@SILP. Note: each reaction step requires
the RuNP@SILP-1.00 catalyst and H2 as reagents, which have been
omitted here for clarity.
Scheme 2. Aromatic hydrogenation of the phenolic ring yields
methoxycyclohexanols, which can be deoxygenated to cyclo-
hexanol through three possible pathways: 1) hydrogenolysis
of the methoxy group to produce 1,2-cyclohexanediols and
subsequent dehydration/hydrogenation to cyclohexanols;
2) direct hydrogenolysis of the methoxy group to form
cyclohexanols; and 3) dehydration/hydrogenation of the hy-
droxy group to yield methoxycyclohexanes and successive
hydrogenolysis of the methoxy group to cyclohexanols.
Dehydration/hydrogenation of the intermediate cyclohexa-
nols allows for the complete deoxygenation to form cyclo-
hexanes. GC analysis of the reactions mixtures allowed for
a discrimination between the possible deoxygenation path-
ways (Table S2). For the deoxygenation of guaiacol (1508C,
120 bar H2, 6 h), the major intermediates formed were 2-
methoxycyclohexanol (25%) and cyclohexanol (27%), the
minor species were 1,2-cyclohexanediol (4%) and methox-
ycyclohexane (4%), and MeOH was not produced. Compa-
rable intermediates were formed during the deoxygenation of
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autoclave. After purging the autoclave with H2, the reaction mixture
was stirred at 1508C in an aluminum heating block under 120 bar H2
(pressurized to 100 bar H2 at RT). Once the reaction was finished, the
reactor was cooled in an ice bath, carefully vented, and the reaction
mixture was analyzed by GC using hexadecane as an internal
standard.
creosol as 2-methoxy-4-methylcyclohexanol (31%) and 4-
methylcyclohexanol (35%) were the predominate intermedi-
ates, while low concentrations of 4-methyl-1,2-cyclohexane-
diol (6%) and 1-methoxy-3-methylcyclohexane (3%) were
formed. As such, RuNPs@SILP catalyzed the deoxygenation
of substituted phenols through pathways 1 and 3 (Scheme 2)
involving the hydrogenolysis of the methoxy group into an
alcohol intermediate and methane, followed by the dehydra-
tion/hydrogenation of the hydroxy group (or vice versa). The
direct hydrogenolysis of the methoxy group from the
cyclohexane ring (pathway 2) was not a preferred deoxyge-
nation route, as methanol was not formed during these
reactions. Therefore, RuNP@SILP bifunctional catalysts
operate through pathways 1 and 3 to achieve the deoxygena-
tion of ether-substituted phenols. These competing pathways
operate simultaneously and are the rate-determining step in
this transformation.
Continuous flow conditions: A 70 mm CatCart was filled with
RuNPs@SILP-1.00 (540 mg, 0.0173 mmol Ru) and placed into a flow
reactor (H-Cube Pro). Prior to catalysis, the catalyst was heated at
1008C under a flow of decalin (0.3 mLminÀ1) and H2 (80 bar; gas flow
rate under standard conditions = 60 NmLminÀ1) for 30 min. The
substrate solution (0.05m phenol in decalin) was introduced into the
system with a flow of H2 (80 bar) and the reaction parameters
(temperature = 110–1508C, substrate flow = 0.3–0.9 mLminÀ1
, H2
flow rate = 60–90 NmLminÀ1) were varied. The system was allowed
to equilibrate under the desired reaction conditions for 20 min before
approximately 6 mL of reaction solution was collected. The reaction
mixture was analyzed by GC using hexadecane as an internal
standard.
In summary, the hydrodeoxygenation of phenolic sub-
strates was achieved using bifunctional catalysts composed of
ruthenium nanoparticles immobilized on an acid-functional-
ized supported ionic liquid phase. RuNPs@SILPs possessed
high catalytic activities and selectivities for the hydrodeoxy-
genation of phenol to cyclohexene and cyclohexane under
batch and continuous flow conditions, in which modulation of
the SILP acidity allowed for control of the bifunctional
catalyst properties. Kinetic determination of the elementary
and tandem reaction rates involved in phenol hydrodeoxyge-
nation was accomplished by using the individual metal- or
acid-based catalytic materials, or by employing a physical
mixture of the metal and acid components. In comparison,
RuNPs@SILP-1.00 showed superior hydrogenation and
deoxygenation activities resulting from intimate contact
between the metal and acid components within the bifunc-
tional catalyst. This cooperative effect provided active
catalysts for the deoxygenation of ether-substituted phenols
as model compounds for lignin cleavage products. The
favored pathway for this reaction involved the hydrogenolysis
of ether moieties to cyclohexanol intermediates and dehy-
dration/hydrogenation of hydroxy groups to cycloalkane
products. The possibility to control this synergistic interaction
may have widespread implications within the field of biomass
conversion, as bifunctional catalysis has been a popular
strategy to find selective pathways in the complex networks of
acid- and metal-catalyzed reactions involved in the deoxyge-
nation of bio-based substrates.[4] Further studies within our
group will involve catalytic tests to determine whether
RuNP@SILP catalysts provide enhanced deoxygenation
rates for other classes of renewable feedstocks. Additionally,
mechanistic investigations will be undertaken to identify the
nature of this synergistic effect.
Acknowledgements
This work was performed as a part of the Cluster of
Excellence “Tailor-Made Fuels from Biomass”, which is
funded by the Excellence Initiative of the German federal
and state governments to promote science and research at
German universities. Additional support by the the European
Union (Marie Curie ITN “SuBiCat” PITN-GA-2013–607044)
is gratefully acknowledged. The authors would like to thank
Karl-Josef Vaeßen (ITMC, RWTH Aachen University) for
N2(g) adsorption measurements, Bernd Spliethoff and Hans-
Josef Bongard (Max-Planck-Institut für Kohlenforschung) for
TEM and STEM analyses, and Dr. Nils Theyssen (Max-
Planck-Institut für Kohlenforschung) for his generous sup-
port. K.L.L. would like to thank Deutscher Akademischer
Austaush Dienst (DAAD) for financial support. P. M. would
like to thank the Alexander von Humboldt Foundation for
funding.
Keywords: bifunctional catalysts · biomass conversion ·
kinetics · lignin · ruthenium
How to cite: Angew. Chem. Int. Ed. 2015, 54, 15750–15755
Angew. Chem. 2015, 127, 15976–15981
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reported.[3b] Full experimental and characterization data are provided
in the Supporting Information.
Batch conditions: In a typical experiment, RuNPs@SILP (75 mg,
0.0024 mmol Ru), phenol (6.0 mmol, 2500 equiv), and decalin (1 mL)
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Received: September 11, 2015
Published online: November 5, 2015
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