Transformation of methyl laurate into lauryl alcohol over a Ru-Sn-Mo/C catalyst by using zerovalent iron and water as an in situ hydrogen source

Article abstract of DOI:10.1016/j.apcata.2016.05.022

Hydrogenation and hydrogenolysis reactions, which are used in the chemical industry for the synthesis of organic compounds, are very expensive operations because of the need for facilities that can liquefy, transport, and store the hydrogen produced through steam reforming of natural gas. We have therefore developed a novel approach for hydrogenation that does not require the use of high-cost facilities. Using this, zerovalent iron (Fe) and water (H₂O) are introduced as an in situ hydrogen donor system for the transformation of methyl laurate into lauryl alcohol over a Ru-based catalyst. This combination of a Ru-Sn-Mo/C catalyst with a Fe/H₂O system showed significantly higher transformation rates for the conversion of methyl laurate into lauryl alcohol than a conventional reaction system that uses pressurized hydrogen. The reason for this is that the new system produces lauric acid as an intermediate during the reaction, which is more efficiently hydrogenized into lauryl alcohol over the Ru-Sn-Mo/C catalyst. The Fe/H₂O system played two important roles: a hydrogen source for the hydrogenation reaction and a catalyst for the generation of lauric acid by methyl laurate hydrolysis.

Full text of DOI:10.1016/j.apcata.2016.05.022

Accepted Manuscript
Title: Transformation of methyl laurate into lauryl alcohol
over a Ru–Sn–Mo/C catalyst by using zerovalent iron and
water as an in situ hydrogen source
Author: Kunimasa Sagata Mina Hirose Yoshiaki Hirano
Yuichi Kita
PII:
S0926-860X(16)30275-7
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2016.05.022
APCATA 15886
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
10-3-2016
5-5-2016
22-5-2016
Please cite this article as: Kunimasa Sagata, Mina Hirose, Yoshiaki Hirano, Yuichi Kita,
Transformation of methyl laurate into lauryl alcohol over a Ru–Sn–Mo/C catalyst by
using zerovalent iron and water as an in situ hydrogen source, Applied Catalysis A,
General http://dx.doi.org/10.1016/j.apcata.2016.05.022
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Submitted to Applied Catalysis A: General as a research article
Transformation of methyl laurate into lauryl alcohol over a Ru–Sn–
Mo/C catalyst by using zerovalent iron and water as an in situ
hydrogen source
Kunimasa SAGATA, Mina HIROSE, Yoshiaki HIRANO, and Yuichi KITA*
Department of Chemical Science and Engineering, Graduate School of Engineering,
Kobe University, Kobe 657-8501, Japan
* Corresponding author
Yuichi KITA: Department of Chemical Science and Engineering,
Graduate School of Engineering,
Kobe University, Kobe 657-8501, Japan.
Tel. +81-78-803-6244
Fax +81-78-803-6512
E-mail: yuichi_kita@lion.kobe-u.ac.jp
1

Graphical Abstract
Highlights
 We used hydrogen derived from a reaction of zerovalent iron and water as
a novel in-situ hydrogen donor system for the transformation of methyl
laurate into lauryl alcohol over a Ru-based catalyst.
 The Ru-based catalyst with the Fe/H2O system efficiently produced lauryl
alcohol via lauric acid as an intermediate.
 We hope that this Fe/H2O reaction system will encourage the use of more
eco-friendly hydrogenation and hydrogenolysis reaction systems for the
utilization of biomass resources.
2

Abstract
Hydrogenation and hydrogenolysis reactions, which are used in the chemical industry
for the synthesis of organic compounds, are very expensive operations because of the
need for facilities that can liquefy, transport, and store the hydrogen produced through
steam reforming of natural gas. We have therefore developed a novel approach for
hydrogenation that does not require the use of high-cost facilities. Using this, zerovalent
iron (Fe) and water (H2O) are introduced as an in situ hydrogen donor system for the
transformation of methyl laurate into lauryl alcohol over a Ru-based catalyst. This
combination of a Ru–Sn–Mo/C catalyst with a Fe/H2O system showed significantly
higher transformation rates for the conversion of methyl laurate into lauryl alcohol than
a conventional reaction system that uses pressurized hydrogen. The reason for this is
that the new system produces lauric acid as an intermediate during the reaction, which is
more efficiently hydrogenized into lauryl alcohol over the Ru–Sn–Mo/C catalyst. The
Fe/H2O system played two important roles: a hydrogen source for the hydrogenation
reaction and a catalyst for the generation of lauric acid by methyl laurate hydrolysis.
Keywords: Zerovalent iron; Hydrogenation; Hydrolysis; Methyl laurate; Ru catalyst
3

1. Introduction
Hydrogen (H2) is an important chemical feedstock and emerging energy carrier that
is typically produced from hydrocarbon fuels through steam reforming, partial oxidation,
or autothermal reforming. Industrial production of H2 is predominantly dependent on
the steam reforming of methane, the economic viability of which is adversely affected
as the scale of a production plant is decreased [1]. Large plants for hydrogen production
are therefore necessary to ensure the most cost-effective operations. Additionally, as
hydrogen gas needs to be converted into compressed H2 gas or liquid H2 for
transportation and storage purposes, its use can be quite expensive. Indeed, it can cost in
excess of 200 million US dollars to carry out the comprehensive processes of H2
liquefaction (51 tons d-1, 75 million US dollars), transportation (12,000 m3/ship, 82
million US dollars), and storage (3000 m3 plant-1, 54 million US dollars) [2]. Given
these costs, any method that could allow reduction reactions such as hydrogenation and
hydrogenolysis to proceed without the use of expensive hydrogen would be highly
desirable.
Hydrogenation and hydrogenolysis reactions are hugely significant catalytic reactions
that are used in the laboratory and chemical industry for organic synthesis. Recently,
biomass resources, particularly unused biomass such as agricultural residues and forest
4

offcuts, have garnered significant attention as sustainable and renewable raw materials
for the production of chemicals [3–5]. However, the viability of converting biomass
resources into valuable chemicals via hydrogenation and hydrogenolysis reactions
depends on their location characteristics with regards to the scale and ease of biomass
feedstock procurement, hydrogen production and storage capacities, and product
transfer networks. New catalytic procedures that have been explored for hydrogenation
and hydrogenolysis in the absence of any added hydrogen include: aqueous phase
reforming (e.g., C3H8O3 (glycerol) + 3H2O → 3CO2 + 7H2) [6–9], catalytic transfer
hydrogenation (e.g., C3H8O (2-propanol) → C3H6O (acetone) + H2) [10–12], and water
gas shift reactions (CO + H2O = CO2 + H2) [13–15] in which the supply of hydrogen
comes from an in situ source.
It is well known that hydrogen can be produced by chemically reacting metals and
metal oxides such as Fe [16–18], Zn [19,20], W [17], FeO [21], MnO [22], SnO [23],
and Ce2O3 [24] with steam at elevated temperatures. Hydrogenation reactions that
employ a reaction between metals (Al, Fe, Mn, and Zn) and water have also been
investigated for the reduction of many organic and inorganic compounds such as
nitroarenes [25,26], aryl chlorides [27,28], aldehydes [29], biomass-derived glycolides
[30], bio-oil [31], and carbon dioxide [32,33]. To regenerate oxidized metals and metal
5

oxides, the following processes have been proposed as renewable energy sources:
reducing gases from biomass gasification [34], biomass-derived char [35,36], and solar
thermal energy [31,37]. Thus, metal/metal-oxide water systems used as in situ hydrogen
donors can potentially be used for eco-friendly chemical synthesis via hydrogenation
and hydrogenolysis reactions. The zerovalent iron (Fe) and water (H2O) system is
particularly valuable in this regard, because Fe is an abundant and cheap resource that
can be used to produce H2 in accordance with reactions (1) and (2):
(1)
(2)
Fe s  H O g  FeO s  H
g
     


2
2
3FeO s  H O g  Fe O
 
s
 
 H
2
g


 
2
3
4
Here, (s) and (g) represent solids and gases, respectively. The use of H2 derived from
nanoscale Fe and H2O has been investigated for removing contaminants such as
p-nitrophenol [38], trichloroethylene [39], hexachlorobenzene [40], and 4-chlorophenol
[41] from water via catalytic hydrogenation; however, it has not yet been applied to the
production of useful chemicals.
Fatty alcohols derived from renewable resources such as vegetable oils are an
industrially important feedstock for the synthesis of surfactants and plasticizers. Fatty
6

alcohols are produced by the hydrogenation of fatty acid esters, which are obtained by
transesterification of triglycerides using methanol or fatty acids from the hydrolysis of
fats [42]. During the hydrogenation of fatty acids and esters, copper–chromite-based
catalysts are commonly used at high temperatures (250–300 °C) and pressures (20–30
MPa). To date, a large number of heterogeneous catalysts have been investigated based
on noble metals (Ru [43–47], Rh [48], and Pt [49]) or transition metals (Cu [9,50] and
Co [51–53]), and have been shown to exhibit high activity under mild conditions.
In this work, we employed Fe and H2O (Fe/H2O) as an in situ hydrogen donor for the
transformation of methyl laurate into lauryl alcohol over a Ru–Sn–Mo/C catalyst. The
performance of Ru–Sn–Mo/C with this Fe/H2O system was compared to a conventional
reaction system that uses pressurized hydrogen.
2. Experimental
2.1. Catalyst preparation
The Ru–Sn–Mo/C catalyst was prepared by a conventional impregnation method
using aqueous solutions of RuCl3∙nH2O (41.1%, Ru content, Wako Pure Chemical
Industries, Ltd.), SnCl4∙5H2O (100.1%, Wako Pure Chemical Industries, Ltd.), and
(NH4)6Mo7O24∙4H2O (100.7%, Wako Pure Chemical Industries, Ltd.) with activated
7

charcoal (Sigma-Aldrich, Norit SX Ultra). Typically, 316 mg of RuCl3∙nH2O, 222 mg of
SnCl4∙5H2O, and 23 mg of (NH4)6Mo7O24∙4H2O were placed into an evaporating dish,
and 2 g of ultrapure water was added to dissolve the salts. After adding 857 mg of
activated charcoal, the mixture was dried in a water bath at 90 °C while stirring. The
resulting impregnated catalyst was vacuum-dried overnight at 70 °C and the resulting
catalyst was reduced at 350 °C for 1 h under hydrogen (99.999%) at a flow rate of 50
cm3∙min-1.
Oxidized-Fe sample was prepared from 60–80 nm Fe particles (99.9%, 1564 mg,
product number: NM-0029-UP, Ionic Liquids Technologies), H2O (1 g), and tetradecane
(99.7%, 40 mL, Wako Pure Chemical Industries, Ltd.) in a 100 mL Hastelloy C
high-pressure reactor (OM Lab-Tech, MMJ-100). For this, the reactor was first purged
four times with nitrogen, and then heated to 270 °C and held at this temperature for 24 h
at a stirring rate of 1000 rpm. After cooling to room temperature, the oxidized iron was
separated by filtration, washed with acetone, and then vacuum-dried overnight at 70 °C.
2.2. Characterization
To determine the crystalline phase of the catalyst, X-ray powder diffraction (XRD)
analyses were performed using a Rigaku SmartLab diffractometer with CuKα radiation.
X-ray fluorescence (XRF) analyses were also performed to determine composition of
8

the fresh and spent catalyst using a Rigaku ZSX Primus II apparatus with RhKα
radiation. A Brunauer–Emmett–Teller (BET) analysis was conducted to determine the
specific surface area of the catalyst; this was accomplished by using N2 adsorption at
-196 °C with a BEL Japan Bellsorp-mini II instrument. The surface chemical states of
the Ru–Sn–Mo/C were evaluated by X-ray photoelectron spectroscopy (XPS) analyses
(JPS-9000MX, JEOL) with a MgKα excitation source. All binding energy values in the
XPS spectra were referenced to the C 1s line at 285.0 eV.
Temperature programmed desorption (NH3-TPD and CO2-TPD) experiments were
carried out in a flow apparatus with helium as the carrier gas using a MicrotracBEL
BELCAT-A. Prior to these experiments, the samples (0.2 g) were pretreated for 1 h at
300 °C under He (30 cm3·min-1) to remove the adsorbate. Once the samples were cooled
to 100 °C, probe molecules (9.79% NH3/He or 5.02% CO2/He) were introduced into the
reactor until their concentration in the effluent gas was unchanged. The samples were
subsequently flushed at the same temperature for 1 h to remove any physically adsorbed
probe molecules, then heated to 700–750 °C at heating rates of 10 °C·min-1 under
helium flow (30 cm3·min-1). Any desorbed NH3 or CO2 gas was detected by a
quadrupole mass spectrometer.
9

2.3. Hydrogenation of methyl laurate
Methyl laurate (99.4%, 870 mg, Wako Pure Chemical Industries, Ltd.), Ru–Sn–Mo/C
catalyst (43 mg), Fe (28 mmol (1564 mg) of 60–80nm particles without previous
activation), H2O (28–83 mmol), and tetradecane were introduced into a 100 mL
Hastelloy C high pressure reactor. After purging the reactor four times with nitrogen, it
was heated to the required temperature and maintained at that state for 1–24 h. The
stirring rate was adjusted to 1000 rpm. The resulting products were separated by
centrifugation and filtration, and their yields were determined by gas chromatography
on an instrument equipped with a flame ionization detector (Shimadzu, GC-2014) using
anisole as an internal standard. A capillary column (Restek, Stabilwax) was used to
analyze the esters, alcohols, acids, and higher molecular weight hydrocarbons. The
conversion of methyl laurate and yield of product were defined as follows:
nM ethyl laurate , 0  nM ethyl laurate
(3)
(4)
C o n versio n
%


 1 0 0


nM ethyl laurate ,
0
nP roduct
Y ield
%

 100

nM ethyl laurate , 0
Here, nMethyl laurate,0 is the initial molar amount of methyl laurate, nMethyl laurate represents
the molar amount of methyl laurate in the reaction system at the end of the reaction, and
10

nProduct indicates the molar amount of the particular product. The material balance based
on the C12 unit was 100  7% during the transformation of methyl laurate into lauryl
alcohol. Decomposition reactions such as the hydrogenolysis of tetradecane solvent
were not observed under the reaction conditions tested.
3. Results and discussion
3.1. Characterization of Ru-Sn-Mo/C
Information for the Ru–Sn–Mo/C catalyst is listed in Table 1. Note that XPS
measurement of the reduced Ru–Sn–Mo/C was conducted after exposure to air. The
binding energy of Ru 3p3/2 was 462.7 eV, and this value could be ascribed to anhydrous
RuO2 in accordance with the values reported for this species [54–56]. The binding
energies of Sn were 484.7 and 487.1 eV for Sn 3d5/2, suggesting the presence of Sn0 [57]
and Sn4+ [58], respectively. Binding energies for Mo 3d5/2 were observed at 229.2,
232.5, and 236.0 eV, suggesting the presence of MoO2 [59] and MoO3 [60],
respectively.
No detectable diffraction lines for ruthenium-, tin- or molybdenum-related crystallites
species were observed in XRD measurements of the Ru–Sn–Mo/C catalyst, which
suggests that these species can only exist as fine particles below the detectable level of
11

XRD (< 10 nm).
3.2. H2 generation behavior of the Fe/H2O system
Figure 1 shows the H2 pressure observed from the Fe/H2O system at 270 °C over
time. It was confirmed from gas chromatography-thermal conductivity detector
(GC-TCD) measurements that the gaseous product generated was hydrogen. In this
study, a hydrogen pressure of ca. 1.8 MPa was equivalent to approximately 36 mmol of
hydrogen (where the theoretical amount in the Fe and H2O reaction is 3Fe + 4H2O →
Fe3O4 + 4H2). When the reactor was immediately cooled to room temperature after
reaching 270 °C, the observed H2 pressure was 0.4 MPa. A H2 pressure of 0.6 MPa was
achieved after 8 h, after which no further increase in pressure was observed at the end of
24 h. The observed H2 pressure derived from the Fe/H2O system was unchanged in the
presence of Ru–Sn–MoOx/C (data not shown here).
3.3. Transformation of methyl laurate over Ru–Sn–Mo/C with the Fe/H2O system
The transformation of methyl laurate into lauryl alcohol over the Ru–Sn–Mo/C
catalyst with the Fe/H2O system proving an in situ H2 source was compared to the
transformation achieved using a conventional reaction system with pressurized H2.
12

Figure 2 shows the time needed for the transformation of methyl laurate over the Ru–
Sn–Mo/C catalyst with pressurized H2 and the Fe/H2O system. The detected products
consisted of lauryl alcohol, lauric acid, lauryl laurate, undecane, and dodecane, with
similar products having been previously observed in the hydrodeoxygenation of methyl
laurate on silica-supported Ni-Mo phosphides [61]. The proposed reaction pathway is
presented in Scheme 1. Here, methyl laurate is transformed to lauric acid via
hydrogenolysis or hydrolysis, and then successively converted to lauryl alcohol by the
hydrogenation of lauryl aldehyde via the hydrogenolysis of lauric acid. Lauryl laurate is
generated by the esterification of lauric acid and lauryl alcohol, which is an
ester-exchange reaction that occurs very easily without a catalyst [48]. Undecane is
formed by the hydrogenation of undecene via the decarbonylation of lauryl aldehyde,
while dodecane is produced by the hydrogenation of dodecene via the dehydration of
lauryl alcohol.
In the catalytic system with pressurized H2, the lauryl alcohol yield increased almost
linearly over a period of 8 h, but increased only gradually thereafter for a gain of 39% at
the end of 24 h. Moreover, the lauryl laurate yield gradually increased with increasing
reaction time. Conversely, in the catalytic system with Fe/H2O, the lauryl alcohol yield
increased with respect to time for a gain of 61% at the end of 24 h. The yield of lauric
13

acid also increased from 6% at 1 h to 30% at 8 h. Any further reaction, however, led to a
decline in the lauric acid yield. The lauryl laurate yield, on the other hand, gradually
increased with time. These results demonstrate that when used with the Fe/H2O system,
the Ru–Sn–Mo/C catalyst can efficiently hydrogenize methyl laurate during the
production of lauryl alcohol, much unlike the pressurized-H2 system. However, as
shown in Fig. 1, the H2 pressure achieved with the Fe/H2O system (0.6 MPa) was lower
than that for the conventional pressurized-H2 system (1.0 MPa). Given that the
hydrogenation of fatty acid esters generally requires a high H2 pressure for the
production of fatty alcohols [42], it is presumed that the use of Ru–Sn–Mo/C with a
pressurized-H2 system will need a higher H2 pressure to achieve methyl laurate
conversion and lauryl alcohol yields equivalent to those from the use of Ru–Sn–Mo/C
with the Fe/H2O system. Reaction rates for the transformation of methyl laurate to
lauryl alcohol at 15% methyl laurate conversion and turnover frequencies (TOF) based
on the total Ru metal were calculated to be 50 mmol∙gRu.-1∙h-1 and 5 h-1, respectively,
with pressurized H2, and 76 mmol∙ gRu.-1∙h-1 and 8 h-1 with the Fe/H2O system.
Transformation of methyl laurate over the Ru–Sn–Mo/C catalyst with the Fe/H2O
system was performed for varying water contents in the H2O/Fe molar ratio range of
1−3. Figure 3 (a) shows the effect of the molar ratio of H2O to Fe on the transformation
14

of methyl laurate and the amount of H2 generated. When the molar ratio was increased
from 1 to 2, the yield of lauryl alcohol increased from 50 to 61%, the reason for which
was the increase in the amount of H2 generated as the H2O/Fe ratio was increased (Fig.
3). However, increases in the molar ratio from 2 to 3 decreased the lauryl alcohol yield
from 61 to 34%, even though the amount of H2 generated was large. A similar
phenomenon was observed in the catalytic system with pressurized H2 (Fig. 3 (b)). That
is, when the H2O content was increased from 0 to 56 mmol, the lauryl alcohol yield
increased from 40 to 53%. Further increases in H2O addition from 56 to 83 mmol
significantly decreased the lauryl alcohol yield from 53 to 14%, while greatly increasing
the lauric acid yield. While the reasons why the lauryl alcohol yield was decreased by
the high H2O/Fe molar ratio remain unclear, there is a possible explanation for this
phenomenon that involves a change in the active phase. That is, an increase in the
by-product (undecane) yield is indicative of a change in active phase during effective
lauryl alcohol production in the case of H2O/Fe = 3. Indeed Table 2 confirms that the
Sn/Ru atomic ratio in spent Ru–Sn–Mo/C with H2O/Fe = 3 was lower than the Sn/Ru
ratio with H2O/Fe ≤ 2. In the present reaction system, the amount of saturated water
vapor at 270 °C is calculated to be ca. 60 mmol. Consequently, all of the H2O in the
case of H2O/Fe ≤ 2 (H2O ≤ 56 mmol) exists as steam at the reaction temperature used,
15

whereas a portion of the H2O in the case of H2O/Fe = 3 (H2O = 83 mmol) exists as
condensed water in addition to steam. This presence of condensed water might have
caused an accelerated change in the active phase through leaching.
3.4. Roles of the Fe/H2O system during the transformation of methyl laurate
Herein, we investigate the influence of the Fe/H2O system on the transformation of
methyl laurate into lauryl alcohol over a Ru–Sn–Mo/C catalyst. XRD analysis was
performed to examine the changes in crystalline phase during the hydrogenation
reaction. The XRD diffraction patterns obtained are shown in Fig. 4. The fresh Fe
samples provided a strong diffraction line at 44.7° that was assigned to Fe0 (Joint
Committee on Powder Diffraction Standards (JCPDS) file No. 6-0696), as well as broad
lines at 30.1°, 35.5°, and 43.1° that were assigned to Fe3O4 (JCPDS file No. 19-629). A
decrease in the intensity of the diffraction line of Fe0 was observed after the reaction,
whereas the intensity of the Fe3O4 peaks increased. Thus, Fe with H2O largely converted
the crystalline phase to Fe3O4 during the reaction as follows: 3Fe + 4H2O → Fe3O4 +
4H2. However, as previously reported in the literature [62], this Fe/H2O system may
also produce various types of solid iron such as FeO, Fe2O3, and FeOOH in addition to
Fe3O4.
16

To verify that the use of the Ru–Sn–Mo/C catalyst with the Fe/H2O system resulted
in the production of lauric acid during the reaction presented above, methyl laurate was
treated under Fe/H2O and oxidized-Fe/H2O in the absence of Ru–Sn–Mo/C (Table 3).
Both the Fe/H2O and oxidized-Fe/H2O reaction systems achieved effective conversion
of methyl laurate to lauric acid compared with Ru-Sn-Mo/C + H2O system, whereas a
blank test without Fe exhibited only trace amounts of lauric acid. It is well known that
acidic and basic catalysts in the presence of water lead to the hydrolysis of fatty acid
methyl esters [63], and so NH3- and CO2-TPD measurements were conducted to
investigate the acid–base properties of oxidized-Fe samples after reaction in the absence
of Ru–Sn–Mo/C and a methyl laurate substrate. In the NH3- and CO2-TPD profiles of
the oxidized-Fe sample shown in Figure 5, NH3 desorption peaks were observed in the
temperature range of 120–270 °C and 280–400 °C. This suggests that the oxidized-Fe
sample contained weak acidic sites [64]. In the CO2-TPD profile of the oxidized-Fe
sample, on the other hand, at least two kinds of CO2 desorption peaks were detected.
One was observed in the temperature range of 250–400 °C and the other was observed
in the temperature range of 500–730 °C. According to the literature [65,66], the lower
temperature peaks may be assigned to CO2 adsorbed on weak basic sites, while the
peaks at higher temperatures may be assigned to CO2 adsorbed on strong basic sites.
17

These results lead to the assumption that Ru–Sn–Mo/C with the Fe/H2O system
produced lauric acid by hydrolysis over acid–base sites of Fe species.
The hydrogenation reactivity of lauric acid as an intermediate during the
transformation of methyl laurate to lauryl alcohol was compared with that of methyl
laurate. In the results listed in Table 4, it is evident that the catalytic system with
pressurized H2 achieved almost complete conversion of lauric acid, and that the yields
of lauryl alcohol for lauric acid were higher than those for methyl laurate. In the case of
a lauric acid substrate, the lauryl alcohol yields and product distributions were similar in
both catalytic systems. These results indicate that the hydrogenation of lauric acid is
faster than that of methyl laurate, and that the Fe/H2O system does not have a particular
effect in the hydrogenation of lauric acid.
Taking the above experimental results into consideration, the influence of the Fe/H2O
system on the transformation of methyl laurate over the Ru–Sn–Mo/C catalyst was
considered. In addition to the Ru–Sn–Mo/C catalyst, the Fe/H2O system produced a
large amount of lauric acid through the hydrolysis of methyl laurate over Fe species
such as Fe3O4. This lauric acid was efficiently reduced into lauryl alcohol over the Ru–
Sn–Mo/C catalyst via the in situ hydrogen generated from the Fe/H2O reaction, which
resulted in a high lauryl alcohol yield.
18

As can be seen in the experimental results, in addition to not requiring expensive H2
facilities for liquefaction, transportation and storage, our Ru–Sn–Mo/C catalyst with the
Fe/H2O system has been proven to be useful for the transformation of methyl laurate
into lauryl alcohol. Clearly, in order to further develop this Fe/H2O system for
hydrogenation and hydrogenolysis reactions, we need to conduct further studies. In
particular, it would be useful to investigate the reusability of Fe, identify those iron
materials most suitable for highly efficient hydrogen generation, improve the reaction
system in terms of its hydrogen utilization efficiency, and determine the applicability of
this Fe/H2O system to other hydrogenation reactions. Work is also currently underway
to investigate the possibility of magnetically separating the oxidized-iron and
hydrogenation catalyst, with the aim of creating an economical and sustainable process
in which the oxidized-iron is regenerated using biomass waste, and the resulting
reducing gas is used to regenerate the hydrogenation catalyst. If successful, we hope
that this Fe/H2O reaction system can blaze a new path toward the realization of
economical hydrogenation and hydrogenolysis reaction systems.
19

4. Conclusions
We attempted to employ zerovalent iron (Fe) and water (H2O) as an in situ hydrogen
source for the transformation of methyl laurate into lauryl alcohol. The transformation
of methyl laurate over the Ru–Sn–Mo/C catalyst with this Fe/H2O system resulted in a
highly efficient transformation of methyl laurate into lauryl alcohol when compared
with conventional reaction systems that employ pressurized hydrogen. During reaction,
Ru–Sn–Mo/C with Fe/H2O produced lauric acid as an intermediate, which was easily
hydrogenized into lauryl alcohol by the Ru–Sn–Mo/C catalyst. The results obtained
suggest that the Fe/H2O system serves two important functions during the highly
efficient transformation of methyl laurate into lauryl alcohol over the Ru–Sn–Mo/C
catalyst. The first is to provide a hydrogen source for the hydrogenation reaction, while
the second is as a catalyst for the generation of lauric acid by methyl laurate hydrolysis.
Acknowledgements
This work was supported by the Japan Society for the Promotion of Science (JSPS)
KAKENHI program (Grant-in-Aid for Exploratory Research, Grant Number 26620147)
and the Nippon Shokubai Co., Ltd.
20

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Figure captions
Fig. 1. Observed variation in H2 pressure of Fe/H2O system as a function of time at
270 °C. Reaction conditions; Fe = 28 mmol, H2O = 56 mmol, Tetradecane = 40 mL,
Pressure = N2 1.0 MPa, Temperature = 270 °C, and Time = 0–24 h.
27

Fig. 2. Time for hydrogenation of methyl laurate over a Ru–Sn–Mo/C catalyst with (a)
pressurized H2 and (b) the Fe/H2O system. (●) Conversion, (○) lauryl alcohol, (∆) lauric
acid, (□) lauryl laurate, (x) undecane, and (*) dodecane. Reaction conditions; (a) Methyl
laurate = 4 mmol, Ru–Sn–Mo/C = 43 mg, Tetradecane = 40 mL, Pressure = H2 1.0 MPa,
Temperature = 270 °C, and Time = 24 h. (b) Methyl laurate = 4 mmol, Ru–Sn–Mo/C =
43 mg, Fe = 28 mmol, H2O = 56 mmol, Tetradecane = 40 mL, Pressure = N2 1.0 MPa,
Temperature = 270 °C, and Time = 24 h.
28

29