On the Reactivity of Dihydro-p-coumaryl Alcohol towards Reductive Processes Catalyzed by Raney Nickel

Article abstract of DOI:10.1002/cctc.201601590

There are several established approaches for the reductive fractionation of lignocellulose (e.g., “catalytic upstream biorefining” and “lignin-first” approaches) that lead to a lignin oil product that is composed primarily of dihydro-p-monolignols [e.g., 4-(3-hydroxypropyl)-2-methoxyphenol and 4-(3-hydroxypropyl)-2,6-dimethoxyphenol]. Although effective catalytic methods have been developed to perform reductive or deoxygenative processes on the lignin oil, the influence of the 3-hydroxypropyl substituent on catalyst activity has previously been overlooked. Herein, to better understand the reactivity of the depolymerized lignin oil obtained from catalytic upstream biorefining processes, dihydro-p-coumaryl alcohol was selected as a model compound. Hydrogenation of this species in the presence of Raney Ni with molecular hydrogen led to ring saturation (100 % selectivity) in the absence of hydrodeoxygenation, whereas under hydrogen-transfer conditions with 2-propanol, hydrogenation occurred (≈55 % selectivity) simultaneously with hydrodeoxygenation (≈40 % selectivity). In a broader context, this study sheds light not only on the reactivity of dihydro-p-monolignols but also on the intricacies of the catalytic upstream biorefining reaction network in which these species are revealed to be key intermediates in the formation of less-functionalized p-alkylphenols.

Full text of DOI:10.1002/cctc.201601590

Accepted Article
Title: On the reactivity of dehydro-p-coumaryl alcohol towards reductive
processes catalyzed by Raney Ni
Authors: Gaetano Calvaruso, Jorge Augusto Burak, Matthew Clough,
Marco Kennema, Fabian Meemken, and Roberto Rinaldi
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201601590
Link to VoR: http://dx.doi.org/10.1002/cctc.201601590
A Journal of
www.chemcatchem.org

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
On the reactivity of dehydro-p-coumaryl alcohol towards reduc-
tive processes catalyzed by Raney Ni
Gaetano Calvaruso,[a] Jorge Augusto Burak,[a] Matthew T. Clough,[a] Marco Kennema,[a] Fabian
Meemken,[b] and Roberto Rinaldi*,[c]
Abstract: There are several established approaches for the reductive
fractionation of lignocellulose (e.g. ‘catalytic upstream biorefining’ –
CUB, or ‘lignin-first’ approaches) that render a lignin oil product com-
posed primarily of dehydro-p-monolignols (e.g. 4-(3-hydroxypropyl)-
2-methoxyphenol, 4-(3-hydroxypropyl)-2,6-dimethoxyphenol). Alt-
hough effective catalytic methods have been developed in order to
perform reductive or deoxygenative processes on the lignin oil, the
influence of the 3-hydroxypropyl substituent on catalyst activity has
previously been overlooked. Herein, to better understand the reactiv-
ity of the depolymerized lignin oil obtained from catalytic upstream bi-
orefining processes, dehydro-p-coumaryl alcohol is selected as a
model compound. Hydrogenation of this species in the presence of
Raney Ni with molecular hydrogen leads to ring saturation (100% se-
lectivity) in the absence of hydrodeoxygenation, whereas under hy-
drogen transfer conditions with 2-propanol, hydrogenation occurs (ca.
55% selectivity) simultaneously with hydrodeoxygenation (ca. 40%
selectivity). In a broader context, this study sheds light not only on the
reactivity of dehydro-p-monolignols but also on the intricacies of the
CUB reaction network in which these species are revealed to be key
intermediates in the formation of less functionalized p-alkylphenols.
monophenolic products obtained by H-transfer CUB in the pres-
ence of Raney Ni, two major products — dihydro-p-sinapyl alco-
hol (1, Fig. 1) and dihydro-p-coniferyl alcohol (2, Fig. 1) — are
obtained from the biorefining of hardwoods. Understandably, the
CUB of softwoods generates 2 as the major product.
Products 1 and 2 incorporate three classes of oxygenated
functional group, namely: (i) the phenolic –OH substituent; (ii) the
methoxy group(s) ortho to the phenolic –OH group, and; (iii) the
primary alcohol at the γ-position of the propyl sidechain. While
catalytic transformations of model compounds entailing the first
two functional groups (e.g. guaiacol derivatives) have been the
motivation for numerous insightful studies in catalysis for lignin
valorization,[1b, 6] little is known about the conversion of 1 or 2 in
the presence of a heterogeneous catalyst. Our previous studies
revealed that the hydrogenation activity of Raney Ni is
dramatically inhibited by using primary alcohols as reaction sol-
vents.[7] Among the main reasons accounting for this observation,
the high affinity of primary alcohols towards the catalyst surface
seems to be the factor responsible for the decreased performance
of Raney Ni in these solvents.[7-8] Therefore, it is to be expected
that conversion of dehydro-p-monolignols would be hindered by
the presence of the γ-CH2OH group.
Undoubtedly, lignin constitutes the primary renewable source of
bulk and specialty aromatic chemicals.[1] Recently, several cata-
lytic routes have been developed to convert lignocellulosic bio-
mass into a mixture of compounds that show potential to replace
petroleum-based raw materials.[2] In this context, the emerging
field of ‘catalytic upstream biorefining’ (CUB, sometimes referred
to as ‘reductive fractionation’ or the ‘lignin-first’ approach) has at-
tracted increasing attention.[1a, 3] CUB encompasses processes
for plant biomass deconstruction through the early-stage catalytic
conversion of lignin (ECCL) by the action of a hydrogenation cat-
alyst.[1a] In our CUB process, based on the ECCL of lignin by hy-
drogen-transfer (H-transfer) reactions catalyzed by Raney Ni, the
lignin fraction is isolated as a viscous oil.[4] This lignin stream is
rich in monophenolic species (< 65%). Notably, the type of func-
tional groups on the propyl sidechain of the monophenolic com-
pounds depends both on the selected catalyst and the hydrogen
source employed in the process.[4a, 5] Furthermore, the lignin oil
also contains dimers and low-molecular-weight lignin oligomers
(Mw < 1,000 Da), as minor products (> 35%). Amid the
Figure 1 The two most abundant phenolic products present in lignin oils ob-
tained from H-transfer CUB processes performed in the presence of Raney Ni
and 2-propanol (H-donor and component of the liquor) – dehydro-p-sinapyl al-
cohol (1) and dehydro-p-coniferyl alcohol (2) – alongside model compound de-
hydro-p-coumaryl alcohol (3).
In this communication, we explore the effect of the γ-CH2OH
substituent on the reactivity of dehydro-p-coumaryl alcohol (3,
corresponding to lignin H-units) in reductive processes catalyzed
by Raney Ni, under H2 pressure, as well as under H-transfer con-
ditions solely using 2-propanol (2-PrOH) as the H-donor. The rea-
son underlining the choice of 3 (instead of 1 or 2) is the absence
of labile methoxy groups as a substituent on the phenolic ring. In
the presence of Raney Ni using 2-PrOH as the solvent and H-
donor, o-methoxyphenols easily undergo demethoxylation via H-
transfer processes, releasing MeOH. In the reaction medium, the
presence of MeOH perturbs the H-transfer reactions and may bias
the results regarding the precise effect of the γ-CH2OH group
upon substrate reactivity. Using compound 3 as a model, the spe-
cific influence of the γ-CH2OH substituent may, therefore, be pin-
pointed specifically without the interference of MeOH.
[a]
[b]
[c]
G. Calvaruso, J. A. Burak, M. T. Clough, M. Kennema
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz
1, 45470 Mülheim an der Ruhr (Germany)
F. Meemken
Department of Chemistry and Applied Biosciences, ETH Zürich,
8093 Zürich (Switzerland)
R. Rinaldi
Department of Chemical Engineering, Imperial College London,
South Kensington Campus, SW7 2AZ London (UK)
E-mail: rrinaldi@ic.ac.uk
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
Table 1 summarizes the product distributions for hydrogenation
of 3, with H2 gas, and through H-transfer reactions using 2-PrOH
as the sole H-source.
Table 1. Catalytic reduction of dehydro-p-coumaryl alcohol, 3, using H2 gas,
and via H-transfer reactions using 2-PrOH as an H-donor.
Figure 2 Schematic representation of proposed interaction motifs of dehydro-
p-coumaryl alcohol with an idealized Ni surface: (A) an adsorption complex
involving interactions of the phenolic –OH group and ring with the surface; (B)
an adsorption complex established via the interactions of the γ-CH2OH alcohol
group in addition to the phenolic –OH group and ring with the surface.
Entry
H-source
Catalyst
amount
(g)
T
(°C)
t
Conv.
(%)
Selectivity (%)
(h)
4
5
-
6
-
1[a]
2[b]
3[b]
5 MPa H2
2-PrOH
2-PrOH
0.1
0.1
1.0
90
80
80
2.5
3
25
5
100
58
35
32
7
9
3
78
56
Reaction conditions: [a] substrate (3 mmol), solvent (2-PrOH, 15 mL), stirring rate: 300
rpm; [b] substrate (2 mmol), solvent and H-donor (2-PrOH, 8 mL), stirring rate: 800 rpm.
Scheme 1 Comparison of product selectivity obtained from the H-transfer reac-
tion of 3-phenylpropan-1-ol. Reaction conditions: 3-phenylpropanol (2 mmol);
Raney Ni (1 g); 2-PrOH (7 mL, H-donor); 80 °C; 800 rpm; 3 h.
In the presence of H2, the substrate underwent hydrogenation
selectively to render the diol 4-(3-hydroxypropyl)cyclohexan-1-ol
(4) as the product (entry 1). In the absence of H2, the conversion
fell from 25% to just 5% (entry 2). Surprisingly when 2-PrOH was
used as the sole H-source, the diol 4 was no longer the exclusive
product, but 4-propylphenol (5) and 4-ethylphenol (6) were also
present in the product mixture in high concentrations (entry 2). To
achieve a higher conversion in the H-transfer reaction, the loading
of Raney Ni was increased (from 0.1 to 1 g, entry 3). Under this
condition, a 78% conversion at 80 °C was achieved after 3 h.
However, the reaction selectivity remained unchanged regardless
of the catalyst amount present in the reaction (entries 2 and 3).
This result clearly indicates that products 4, 5 and 6 are formed
by parallel reactions. The parallel reactions are proposed to be a
consequence of the formation of distinct adsorption complexes of
3 on the surface of Raney Ni. From the current experimental evi-
dence, one population of the adsorbed molecules appears to in-
teract with the surface via the formation of a phenolate surface
species (Fig. 2a), involving the interactions of both phenolic –OH
substituent and aromatic ring with the surface. In agreement with
a previous report,[9] the planar adsorption of phenol on the Ni sur-
face favors hydrogenation. Therefore, this surface species (Fig.
2a) undergoes hydrogenation, yielding 4 as the product. Hypo-
thetically, the other population of adsorbed molecules interacts
with the surface through the formation of an alkoxide species in-
volving the γ-CH2OH group in addition to the phenolate interaction
(Fig. 2b). Indeed, adsorption on the nickel surface brings about
dehydrogenation of methanol to coadsorbed methoxy (CH3O) and
hydrogen species.10
Scheme 2 Hydrogenation of hydrocinnamaldehyde with 2-PrOH. Reaction con-
ditions: hydrocinnamaldehyde (2 mmol); Raney Ni (1 g); 2-PrOH (7 mL); 80 °C;
800 rpm; 3 h.
Under the same reaction conditions, the conversion of 3-phe-
nylpropanol (70%) was slightly lower than that of 3 (78%). Sur-
prisingly, the conversion of 3-phenylpropanol afforded a yield of
arene products twice as high as that obtained from the conversion
of 3. In particular, n-propylbenzene accounted for 72% of the
product mixture obtained from 3-phenylpropanol. For both reac-
tions, the accumulation of arenes in the reaction mixture agrees
well with previous results demonstrating that aromatic hydrocar-
bons are far less reactive than phenols with respect to ring satu-
ration via transfer hydrogenation.[8] Hence, if the tendency to-
wards hydrogenation of the aromatic ring is decreased from 3 to
3-phenylpropanol, the rate of the deoxygenation of the propyl
chain is increased. As a result, deoxygenation occurs with the for-
mation of a high yield of n-propylbenzene and a lower quantity of
ethylbenzene. As evidenced by several studies, the interaction
between Ni surfaces and primary –OH alcohol groups is stronger
than that of Raney Ni and secondary alcohols.[7-8] In this manner,
the γ-CH2OH group could also serve as a source of hydrogen for
H-transfer processes.
To better understand the reactivity of the γ-CH2OH substituent
in conjunction with aromatic moieties, another model compound,
3-phenylpropanol, was investigated with respect to transfer hy-
drogenation. The overall conversion and product distribution is
shown in Scheme 1, compared against the results of the reaction
involving phenolic analog 3.
Taking this hypothesis into account, we chose to perform an
additional catalytic experiment on hydrocinnamaldehyde. This
model compound corresponds to an intermediate that may be
postulated to exist on the Raney Ni surface via the donation of
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
two H atoms from 3-phenylpropanol to the surface. The overall
conversion and product distribution are shown in Scheme 2.
Hydrocinnamaldehyde was converted in 90% yield, affording the
primary products 3-phenylpropanol (43%) and ethylbenzene
(20%). Notably, the mass balance was not fully closed. Only ca.
65% of the starting carbon could be accounted for in the products.
Condensation reactions could explain this observation, because
such high Mw-products would not be identifiable by GC-MS/FID.
Figure 3 displays the ATR-IR spectra of strongly adsorbed
species at the catalytic solid-liquid interface at 25 °C. A decrease
in signal intensity of the characteristic vibration bands of 2-PrOH
was caused by the presence of MeOH in the solution. Conversely,
Figure 3b shows that the signal intensities of the characteristic vi-
bration bands of phenol were not affected by the presence of
MeOH. These observations demonstrate that MeOH can displace
2-PrOH from the Raney Ni surface, whereas MeOH and phenol
can co-adsorb without affecting the populations of one another on
the surface.
Hydrogenation and elimination reactions of the aldehyde
group were found to proceed as parallel processes (Scheme 2).
However, hydrogenation of the carbonyl group was favored over
the deoxygenation process via elimination of the aldehydic group.
In light of the current results, the adsorption complex ‘B,' as
proposed in Figure 2, seems to be a plausible proposition of the
Notably, selectivity toward n-propylbenzene was relatively low (ca. interactions of 3 occurring at the catalytic solid-liquid interface un-
2%). This result clearly demonstrates that the formation of
ethylbenzene from 3-phenylpropanol (Scheme 1) occurs via de-
hydrogenation of the primary alcohol, forming an aldehyde inter-
mediate, which decomposes into ethylbenzene. It can generally
be stated that hydrogen has an influence on the reaction path-
way.[10] It is here shown that in the absence of the hydrogen pres-
sure, hydrogenation of the aromatic ring becoming less favorable,
and deoxygenation becomes increasingly significant.
der the absence of an H2 pressure. Notably, the current results
demonstrate that interaction of the γ-CH2OH substituent does not
depend upon interactions of the phenolic/aromatic ring with the
surface. The catalytic results showing that the γ-CH2OH group
undergoes dehydrogenation, forming an intermediate aldehyde,
corroborate with the preferential interactions established between
a primary alcohol group and the Raney Ni surface, which largely
compete with those interactions established between 2-PrOH and
the catalytic surface.
Although this pathway is plausible, further reaction of the al-
dehyde to the corresponding carboxylic acid, and subsequently
decarboxylation of the carboxylic acid may also lead to the ethyl-
substituted cyclic compounds.[11] However, in a previous study,
we found that benzoic acid is readily and quantitatively converted
into cyclohexanecarboxylic acid in the presence of Raney Ni/2-
PrOH at 80 °C, within 3 h.[8] In comparison, benzaldehyde exhibits
a similar pattern of reactivity to that of hydrocinnamaldehyde, that
is, hydrogenation of the aldehyde substituent, rendering benzyl
alcohol, taking place in parallel with the hydrodeoxygenation of
benzaldehyde to toluene.[8] Therefore, as no carboxylic acid was
detected in the product mixture arising from the conversion of
hydrocinnamaldehyde, its further dehydrogenation generating hy-
drocinnamic acid seems not to occur under the reaction condi-
tions. Cracking of the alkyl chain could also, in principle, lead to
the formation of the p-ethyl derivative. However, such a cracking
reaction is only reported to occur at higher temperatures (over
200 °C).[12] Moreover, the reactions of various alkylated phenols
on Raney Ni, with 2-PrOH as a hydrogen source at 80 °C (same
condition of reaction as for the hydrogenation of 3),[8] do not lead
to any detected products derived from cracking of the alkyl chain.
In an attempt to establish a rank of interaction strengths of 2-
PrOH (H-donor), methanol (a model of the γ-CH2OH group in 3),
and phenol with the Raney Ni surface, competitive adsorptions of
2-PrOH vs. MeOH and phenol vs. MeOH at the catalytic solid-
liquid interface were evaluated (25 °C), by using an Attenuated
Total Reflection–Infrared (ATR-IR) spectroscopy setup. In these
experiments, a film of Raney Ni was deposited on a ZnSe crystal
under an argon atmosphere. A background spectrum was
collected under a flow of cyclohexane. In sequence, the catalyst
was flushed with a 5 mM solution of 2-PrOH in cyclohexane or a
1 mM solution of phenol in cyclohexane. To remove dissolved-
phase species, the cell was flushed again with cyclohexane, and
the spectrum was collected. Finally, in each experiment, the initial
solution was then exchanged with an analogous solution contain-
ing an additional 2 mM MeOH (in the case of 2-PrOH) or 1 mM
MeOH (in the case of phenol), and the spectra were collected af-
ter flushing the catalyst bed with cyclohexane.
Figure 3 Competitive adsorption of a) 2-PrOH vs. MeOH, and; b) phenol and
MeOH on the surface of Raney Ni at 25 °C. Blue arrows indicate a decrease in
the signal intensity of the characteristic bands of adsorbed 2-PrOH at the cata-
lytic solid-liquid interface.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
From the observations of this study, the three parallel reaction
processes occurring for dehydro-p-coumaryl alcohol, using 2-
PrOH as the H-donor and solvent in the presence of Raney Ni,
can be summarized in Scheme 3. In process (A), saturation of the
phenolic ring is achieved. This pathway predominates under H-
transfer conditions but is not exclusively followed (56% selectivity
to diol). By contrast, under H2 pressure, this reaction brings about
100% selectively to the diol product. Under both conditions, the
diol 4 cannot undergo a further transformation in the presence of
Raney Ni. Processes (B) and (C) are parallel reactions occurring
only under H-transfer conditions. Through pathway (B), the C–O
bond of the γ-CH2OH group is hydrogenolyzed, leading to the for-
mation of 4-propylphenol at a selectivity of 32%. In turn, the reac-
tion process (C) is a competing reaction, forming an aldehyde in-
termediate via dehydrogenation of dehydro-p-coumaryl alcohol,
and subsequent elimination of the aldehyde group, most likely as
formaldehyde.
new directions for the valorization of the lignin oil obtained from
CUB processes. As several CUB processes produce dehydro-p-
monolignols as major products, the selective hydrogenation of
these intermediates to the corresponding diols could well hold the
key to obtaining lignin-derived long-chain diol monomers as re-
placements for petroleum-derived 1,6-hexanediol, employed on
the large-scale production of polyesters.
Clearly, the suppression of reaction processes (B) and (C)
when the reaction is carried out under H2 pressure reveals that
even under low-severity conditions (e.g. 5 MPa H2 at 90 °C), the
surface chemistry of Raney Ni can be substantially altered. As
revealed by Ni X-ray Photoelectron Spectroscopy (XPS)
experiments (Figure 4), the surface of freshly synthesized Raney
Ni shows at least three major Ni surface species: Ni(0) at 852.6
eV, Ni(II)-OH at 855.8 eV, and an unassigned species at a higher
binding energy (857 eV, most likely related to NiOx(OH)y
species).[13] Our results suggest that the proportion of these spe-
cies may vary substantially under H2 pressure at temperatures as
low as 90 °C. Moreover, the accumulation of 4-alkylphenols in the
product mixture is a key feature starkly contrasting to our previous
studies, which demonstrated that 4-propylphenol fully converts
into 4-propylcyclohexanol under low-severity conditions.[8] The
current results also suggest that, when reacted in a system
composed of 2-PrOH/Raney Ni, the substrate 3 not only inhibits
the activity of Raney Ni towards the saturation of the phenolic ring
but also seems to modify the surface structure of Raney Ni,
making it no longer active for the catalytic processes leading to
the hydrogenation of the phenolic ring by H-transfer processes at
temperatures as low as 80 °C.
Scheme 3 Reaction processes resulting in the conversion of dehydro-p-
coumaryl alcohol in the presence of Raney Ni and 2-PrOH (as the solvent and
H-donor).
In the broader context of heterogeneous catalysis, the confir-
mation of these hypotheses would reveal a somehow surprising
feature of Raney Ni. As well-known from the experience of sup-
ported Ni catalyst preparation, Ni(II) reduction to Ni(0) species
usually takes places at temperatures higher than 200 °C, for Ni(II)
supported on activated carbon or inorganic carriers.[14] Accord-
ingly, the ease of reduction of the Raney Ni surface, as revealed
by the change of selectivity to the exclusive saturation of the phe-
nolic ring, seems to be a feature of Raney Ni distinguishing it from
supported Ni catalysts.
Figure 4 X-ray Photoelectron Spectroscopy spectrum of a freshly prepared
sample of Raney Ni.
In summary, dehydro-p-coumaryl alcohol exhibits distinctly differ-
ent reactivity patterns toward reductive processes catalyzed by
Raney Ni, when performed under H-transfer conditions or H2
pressure. Evident lines of investigation for the future are high-
pressure XPS, XANES and XRD studies under operando condi-
tions to lend insight into the functionality of the surface structure
of the real Raney Ni catalyst. Nonetheless, the current results
clarify the origin of C7-C9-alkylphenols formed as minor products
in the CUB process based on H-transfer ECCL in the presence of
Raney Ni. In a broader context, the current results also point out
Experimental Section
Chemicals
2-Propanol (99.8%), dehydro-p-coumaryl alcohol (99%), n-hexadecane
(99%), Raney Ni 2800, 3-phenylpropanol (Aldrich, 98%), and hydrocin-
namaldehyde (>95%) were purchased from Aldrich and used as received.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
Hydrogenation of dehydro-p-coumaryl alcohol with H2
Acknowledgements
Dehydro-p-coumaryl alcohol (2.9 mmol), hexadecane (internal standard
for GC, 0.78 mmol), Raney Ni 2800 (dry 100 mg, pre-dried under reductive
pressure using Schlenk techniques), and 2-PrOH as the solvent (15 mL)
were placed in a batch reactor (30 mL) under an argon atmosphere (glove
box). After purging the reactor with H2, the reaction vessel was loaded with
5 MPa H2 (measured at 25 °C). The reaction temperature was increased
from r.t. to 90 °C at a rate of 7 °C min-1, and was then maintained at 90 °C
for 2.5 h, applying overhead mechanical stirring throughout (300 rpm).
This work was performed as part of the Cluster of Excellence “Tai-
lor-Made Fuels from Biomass.”
Keywords: lignin • Raney Ni • catalytic upstream biorefining •
hydrodeoxygenation • hydrogen transfer
[1]
a) R. Rinaldi, R. Jastrzebski, M. T. Clough, J. Ralph, M. Kennema, P. C.
A. Bruijnincx, B. M. Weckhuysen, Angew. Chem. Int. Ed. 2016, 55, 8164-
8215; b) C. Li, X. Zhao, A. Wang, G. W. Huber, T. Zhang, Chem. Rev.
2015, 115, 11559-11624; c) M. Zaheer, R. Kempe, ACS Catal. 2015, 5,
1675-1684.
Hydrogen transfer reaction of dehydro-p-coumaryl alcohol, 3-
phenylpropanol, and hydrocinnamaldehyde with 2-PrOH
[2]
[3]
[4]
a) M. Grilc, B. Likozar, J. Levec, ChemCatChem 2016, 8, 180-191; b) M.
Grilc, B. Likozar, J. Levec, Biomass and Bioenergy 2014, 63, 300-312.
a) P. Ferrini, C. A. Rezende, R. Rinaldi, ChemSusChem 2016; b) M. V.
Galkin, J. S. M. Samec, ChemSusChem 2016, 9, 1544-1558.
a) P. Ferrini, R. Rinaldi, Angew. Chem. Int. Ed. 2014, 53, 8634-8639; b)
C. Chesi, I. B. D. de Castro, M. T. Clough, P. Ferrini, R. Rinaldi,
ChemCatChem 2016, 8, 2079-2088; c) J. Chen, F. Lu, X. Si, X. Nie, J.
Chen, R. Lu, J. Xu, ChemSusChem 2016, n/a-n/a.
Dehydro-p-coumaryl alcohol, 3-phenylpropanol or hydrocinnamaldehyde
(2.1 mmol), n-hexadecane (internal standard for GC, 0.8 mmol), Raney Ni
2800 (1 g, wet), solvent (7 mL) and a magnetic stirrer bar were placed in
a glass vial (20 mL). The vial was flushed with argon and then tightly closed.
The experiment was performed at 80 °C under magnetic stirring (800 rpm)
in a stainless steel heating block for 3 h.
GC-MS/FID analysis
[5]
a) S. Van den Bosch, W. Schutyser, S. F. Koelewijn, T. Renders, C. M.
Courtin, B. F. Sels, Chemical Communications 2015, 51, 13158-13161;
b) T. Parsell, S. Yohe, J. Degenstein, T. Jarrell, I. Klein, E. Gencer, B.
Hewetson, M. Hurt, J. I. Kim, H. Choudhari, B. Saha, R. Meilan, N. Mosier,
F. Ribeiro, W. N. Delgass, C. Chapple, H. I. Kenttamaa, R. Agrawal, M.
M. Abu-Omar, Green Chem. 2015, 17, 1492-1499; c) I. Klein, B. Saha,
M. M. Abu-Omar, Catal. Sci. Technol. 2015, 5, 3242-3245; d) M. V. Gal-
kin, J. S. M. Samec, ChemSusChem 2014, 7, 2154-2158.
The samples were analyzed by GC using a Shimadzu QP2010 Plus gas
chromatograph, equipped with a ZB-1HT Inferno column (30 m, 0.25 mm
ID, df 0.25 µm). The injector temperature was 300 °C. The temperature
program started at 40 °C for one minute. Next, the temperature was
increased at 8 °C min–1 to 140 °C, then increased at 20 °C min–1 to 180 °C
and then again raised at 30 °C min–1 before reaching an isothermal step
at 340 °C for 5 min. The compounds were identified by comparing the EI-
MS spectra with the MS libraries NIST 08, NIST 08s, and Wiley 9. Quanti-
fication was performed using the response of the FID.
[6]
a) L. Nie, P. M. de Souza, F. B. Noronha, W. An, T. Sooknoi, D. E. Re-
sasco, Journal of Molecular Catalysis A: Chemical 2014, 388–389, 47-
55; b) Y. Yoon, R. Rousseau, R. S. Weber, D. Mei, J. A. Lercher, J. of
Am. Chem. Soc. 2014, 136, 10287-10298; c) D. Verboekend, Y. Liao, W.
Schutyser, B. F. Sels, Green Chem. 2016, 18, 297-306; d) B. Güvenatam,
O. Kurşun, E. H. J. Heeres, E. A. Pidko, E. J. M. Hensen, Catal. Today
2014, 233, 83-91; e) M. Zaheer, R. Kempe, ACS Catal. 2015, 5, 1675-
1684.
In situ ATR-IR spectroscopic measurements
The in situ ATR-IR spectroscopic measurements were performed using a
custom-built set-up.[15] A thin film of Raney Ni was deposited onto a ZnSe
crystal in a custom built mini glove-box by shaking a hexane solution con-
taining Raney Ni and pouring the suspension into a form as described in
Ref. [15]. The film was then sealed into the ATR-IR spectroscopic flow-
through cell under an argon atmosphere and was transferred to the con-
tinuous flow set-up.[15] The argon was removed from the cell with a cyclo-
hexane solution at a flow rate of 0.5 mL min–1, after which the flow rate
was increased to 2.7 mL min–1. A background spectrum was collected un-
der a convective flow of cyclohexane at a flow rate of 2.7 mL min–1. For
the adsorption experiments, the film was treated with a 1 mM phenol solu-
tion (5 mM in the case of 2-PrOH) in cyclohexane. The cell was again
flushed with cyclohexane, removing the dissolved-phase of phenol and
leaving only the strongly adsorbed species, which could not be removed
by a convective flow of cyclohexane. In each experiment, the initial solution
was then exchanged with an analogous solution containing an additional
2 mM MeOH (in the case of 2-PrOH) or 1 mM MeOH (in the case of phenol),
and the spectra were collected after flushing the catalyst bed with cyclo-
hexane.
[7]
[8]
[9]
X. Y. Wang, R. Rinaldi, ChemSusChem 2012, 5, 1455-1466.
X. Wang, R. Rinaldi, Energy Environ. Sci. 2012, 5, 8244-8260.
J. Zhong, J. Chen, L. Chen, Catal. Sci. Technol. 2014, 4, 3555-3569.
[10] B. Rozmysłowicz, P. Mäki-Arvela, A. Tokarev, A.-R. Leino, K. Eränen, D.
Y. Murzin, Ind. Eng. Chem. Res. 2012, 51, 8922-8927.
[11] J. Wu, J. Shi, J. Fu, J. A. Leidl, Z. Hou, X. Lu, Sci. Rep. 2016, 6, 27820.
[12] M. Grilc, B. Likozar, J. Levec, Appl. Catal. B: Environ. 2014, 150–151,
275-287.
[13] a) H. Lei, Z. Song, X. Bao, X. Mu, B. Zong, E. Min, Surf. Interface Anal.
2001, 32, 210-213; b) E. S. Shpiro, G. N. Baeva, A. B. Fasman, K. M.
Minachev, React. Kinet. Catal. Lett. 1986, 32, 499-504.
[14] a) C. Li, Y.-W. Chen, Thermochim. Acta 1995, 256, 457-465; b) X. Wang,
R. Rinaldi, Catal. Today 2016, 269, 48-55; c) R. Rinaldi, A. d. M. Porcari,
T. C. R. Rocha, W. H. Cassinelli, R. U. Ribeiro, J. M. C. Bueno, D.
Zanchet, J. Mol. Catal. A: Chem. 2009, 301, 11-17.
[15] F. Meemken, P. Muller, K. Hungerbuhler, A. Baiker, Rev. Sci. Instrum.
2014, 85, 084101.
XPS analysis of Raney Ni
In a glove-box under argon atmosphere, the dry Raney Ni powder was
distributed uniformly on a carbon tape fixed on an XPS sample holder for
air-sensitive samples. The holder was closed and transferred to the XPS
pre-chamber. XPS analysis was performed using a ‘Kratos His’ spectrom-
eter with a hemispherical analyzer. The monochromatized AlKα X-ray
source (E =1486.6 eV) was operated at 15 kV and 15 mA. For the narrow
scans, an analyzer pass energy of 40 eV was applied. The hybrid mode
was used as the lens mode. The base pressure during the experiment in
the analysis chamber was 4.10-7 Pa. To account for charging effects, the
spectra were referred against C1s at 284.5 eV.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601590
ChemCatChem
COMMUNICATION
COMMUNICATION
Fifty shades of green. The advent of
catalytic upstream biorefining has
made available new platform chemi-
cals from lignin. In this communica-
tion, the reactivity of dehydro-p-
Gaetano Calvaruso, Jorge Augusto
Burak, Matthew T. Clough, Marco
Kennema, Fabian Meemken, and
Roberto Rinaldi*
Page No. – Page No.
coumaryl alcohol is explored in reduc-
tive processes catalyzed by Raney Ni,
under H2 pressure as well as under H-
transfer conditions. Under H2 pres-
sure, Raney Ni is a selective hydro-
genation catalyst. However, under H-
transfer conditions, the catalyst also
produces 4-alkylphenols.
On the reactivity of dehydro-p-
coumaryl alcohol towards reductive
processes catalyzed by Raney Ni
This article is protected by copyright. All rights reserved.