Hydrodeoxygenation of Fatty Acids, Triglycerides, and Ketones to Liquid Alkanes by a Pt–MoOx/TiO2 Catalyst

Article abstract of DOI:10.1002/cctc.201700219

Various supported metal catalysts are screened for hydrogenation of lauric acid and 2-octanone as model reactions for the transformation of biomass-derived oxygenates to liquid alkanes (biofuels) in a batch reactor under solvent-free conditions. Among the catalysts tested, Pt and MoO_x co-loaded on TiO₂ (Pt–MoO_x/TiO₂) shows the highest yields of n-alkanes for both of the reactions. Pt–MoO_x/TiO₂ selectively catalyzes the hydrodeoxygenation of various fatty acids and triglycerides to n-alkanes without C?C bond cleavage under 50 bar H₂ and shows higher turnover numbers than the catalysts in the literature. Pt–MoO_x/TiO₂ is effective also for the hydrodeoxygenation of various ketones to the corresponding alkanes. In situ IR study of the reaction of adsorbed acetone under H₂ suggests that the high activity of Pt–MoO_x/TiO₂ is attributed to the cooperation between Pt and Lewis acid sites of the MoO_x/TiO₂ support.

Full text of DOI:10.1002/cctc.201700219

Accepted Article
Title: Hydrodeoxygenation of Fatty Acids, Triglycerides, and Ketones to
Liquid Alkanes by Pt-MoOx/TiO2 Catalyst
Authors: Ken-ichi Shimizu, Takashi Toyao, Wataru Onodera, Kenichi
Kon, and S. M. A. H. Siddiki
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To be cited as: ChemCatChem 10.1002/cctc.201700219
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10.1002/cctc.201700219
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Hydrodeoxygenation of Fatty Acids, Triglycerides, and Ketones
to Liquid Alkanes by Pt-MoOx/TiO2 Catalyst
Kenichi Kon, [a] Takashi Toyao,[a,b] Wataru Onodera,[a] S. M. A. H. Siddiki,[a] Ken-ichi Shimizu*[a,b]
based catalysts.[20-23] Recently, we have developed Pt and MoOx
Abstract: Various supported metal catalysts are screened for
hydrogenation of lauric acid and 2-octanone as model reactions
co-loaded TiO2 (Pt-MoOx/TiO2) as a generally effective catalyst
for hydrogenation of amides, CO2 and sulfoxides.[26-28] We report
for the transformation of biomass-derived oxygenates to liquid
herein that Pt-MoOx/TiO2 is a more efficient catalyst than
alkanes (biofuels) in a batch reactor under solvent-free conditions.
Among the catalysts tested, Pt and MoOx co-loaded TiO2 (Pt-
Pt/Nb2O5 for the selective hydrodeoxygenation of various fatty
acids and triglycerides to n-alkanes with the same chain length as
MoOx/TiO2) shows the highest yields of n-alkanes for both of the
reactions. Pt-MoOx/TiO2 selectively catalyzes the
the substrates in a batch reactor. Kinetic and control experiments
are carried out to show a reaction pathway.
Hydrodeoxygenation of ketones to alkanes is also an important
reaction in the production of biofuels[1,29-35] as well as in organic
synthesis.[36] In this paper we report that Pt-MoOx/TiO2 shows
high activity than various supported metal catalysts for a model
hydrodeoxygenation of 2-octanone. We show substrate scope
and mechanistic studies to demonstrate the catalytic performance
and to discuss a possible role of Mon+ Lewis acid sites. It should
be noted that spectroscopic characterization results of Pt-
MoOx/TiO2 have been shown in our previous papers, [26-28] so the
structure and acidity of the catalyst are not discussed in this paper.
hydrodeoxygenation of various fatty acids and triglycerides to n-
alkanes without C-C bond cleavage under 50 bar H2 and shows
higher turnover number than the catalysts in the literature. Pt-
MoOx/TiO2 is effective also for hydrodeoxygenation of various
ketones to the corresponding alkanes. In situ IR study for the
reaction of adsorbed acetone under H2 suggests that the high
activity of Pt-MoOx/TiO2 is attributed to the cooperation between
Pt and Lewis acid site of the MoOx/TiO2 support.
Introduction
Results and Discussion
Catalytic hydrogenation of biomass-derived oxygenates to
liquid alkanes has been attracted much attention in view of the
biomass conversion to fuels.[1-5] Triglycerides and fatty acids from
microalgae and jatropha are considered as promising candidates
of renewable resources of the biofuels. Hydrogenation of
triglycerides and fatty acids reduces their high-oxygen content
and produce higher alkanes suitable as diesel fuel. Among the
Hydrodeoxygenation of Lauric Acid
In our previous study of hydrogenation of lauric acid,
[18]
we
showed a catalyst screening study for hydrogenation of neat lauric
acid under 8 bar H2 at 180 ˚C for 4 h using various catalyst
containing 1 mol% of the active metal with respect to lauric acid.
Under the condition, Pt/Nb2O5 showed the highest yield of n-
dodecane.[18] Here, we tested various catalyst for hydrogenation
of neat lauric acid under 8 bar H2 at 180 ˚C for 3 h using smaller
amount of the catalyst (0.5 mol%). As listed in Table 1, Pt-
MoOx/TiO2 showed the highest conversion of lauric acid (100%)
and the highest yield of n-dodecane (86%). Pt/Nb2O5 showed
19% yield of n-dodecane, and other catalysts including Pt/TiO2,
Pt/SiO2 and various metals (Pd, Rh, Ru, Ni, Cu) on the MoOx/TiO2
support showed low yields (0-3%) of n-dodecane.
three
deoxygenation
methods
of
fatty
acids,[2,3]
hydrodeoxygenation, producing hydrocarbons without C-C
cleavage of the fatty acid, is more atom-efficient than the other
methods (decarbonylation, decarboxylation) with C-C cleavage of
the fatty acid. In the previous studies, most of the supported metal
catalysts, such as supported Pt, Pd, Ru, Rh, Fe and Ni catalysts,
suffer from high selectivity to decarbonylation or decarboxylation
products rather than hydrodeoxygenation products even under
H2.[6-14] Few catalysts, including Ni-loaded Hβ zeolite,[16] Pt-
Re/ZSM-5,[17] Pt/Nb2O5,[18] Pd/Nb2O5/SiO2,[19] tungsten- or
Figure 1 shows the time course of the reaction by Pt-MoOx/TiO2
under the conditions in Table 1. The profile shows a typical pattern
of a consecutive pathway; 1-dodecanol and dodecyl dodecanoate
are first produced and are then consumed to yield n-dodecane.
Table 2 compares the results for hydrogenation of possible
intermediates (1-dodecanol, 1-dodecanal, dodecyl dodecanoate)
and lauric acid under the same conditions. The yield of n-
dodecane from these oxygenates changed in the following order:
1-dodecanol (89%) > 1-dodecanal (71%) >> lauric acid (26%) >
dodecyl dodecanoate (6%). Note that lauric acid underwent
esterification with 1-dodecanol in the absence of catalysts gave
dodecyl dodecanoate in 63% yield. These results suggest the
reaction pathway in Figure 1. Hydrogenation of lauric acid yields
1-dodecanol (via 1-dodecanal), which is then hydrogenated to n-
dodecane. 1-Dodecanol can also undergo thermal esterification
with lauric acid to give dodecyl dodecanoate which is then
hydrogenated to n-dodecane via 1-dodecanol. The hydrogenation
of 1-dodecanol did not yield dodecene. The reaction of 1-
dodecanol by Pt-MoOx/TiO2 under 1 atm N2 for 1 h gave only 17%
[24]
molybdenum-based
catalysts,[20-23]
Ni-Mo/Al2O3
and
hydrodesulfurization catalysts[25] (sulfided NiMo oxides), catalyze
the selective hydrodeoxygenation of fatty acids under pressured
H2. However, most of these systems have some drawbacks such
as decarbonylation and cracking as side reactions and necessity
of high catalyst loading or, in other word, low turnover number
(TON). In our previous study,[18] we reported that Pt/Nb2O5
showed 60 times higher TON for hydrodeoxygenation of a fatty
acid than Ni-loaded Hβ zeolite[16] and tungsten- or molybdenum-
[a]
[b]
Dr. K. Kon, Dr. T. Toyao, W. Onodera, Prof. Dr. K. Shimizu
Institute for Catalysis, Hokkaido University, N-21, W-10, Sapporo
(Japan)
E-mail: kshimizu@cat.hokudai.ac.jp
Dr. T. Toyao, Prof. Dr. K. Shimizu
Elements Strategy Initiative for Catalysis and Batteries, Kyoto
University, Katsura, Kyoto 615-8520 (Japan)
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10.1002/cctc.201700219
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FULL PAPER
yield of dodecene. These results exclude a possible route to
alkane via dehydration of alcohol to alkene[16] and its
hydrogenation as the main pathway in this system. The pathway
Table 2. Hydrodeoxygenation of lauric acid and possible
in Scheme
1
is basically consistent with those for
[18]
intermediates by Pt-MoOx/TiO2.[a]
hydrodeoxygenation of fatty acids by Ni/Hβ[16] and Pt/Nb2O5
catalysts. The hydrogenation rate of dodecyl dodecanoate for Pt-
MoOx/TiO2 is 1.5 times higher than that of Pt/Nb2O5,[18] which is
consistent with the higher catalytic performance of the former
catalyst in Table 1.
Conv.
[%]
71
71
89
Yield [%]
Substrate
dodecane dodecanol ester[b]
Lauric acid
1-Dodecanal
1-Dodecanol
Dodecyl
26
71
89
20
0
0
20
0
0
7
6
0
-
dodecanoate
Table 1. Catalyst screening for hydrogenation of lauric acid.[a]
[a] 1 mmol substrate, 0.5 mol% Pt catalyst, 180 °C, 8 bar H2, 1
h
Catalyst
Conv.
[%]
100
34
Yield [%]
dodecane dodecanol ester [b]
[b] Dodecyl dodecanoate.
Pt-MoOX/TiO2
Pt/TiO2
Pt/Nb2O5
86
3
2
5
8
17
68
0
98
0
19
0
11
0
Pt/SiO2
Pd-MoOX/TiO2
Rh-MoOX/TiO2
Ru-MoOX/TiO2
Ni-MoOX/TiO2
Cu-MoOX/TiO2
23
30
50
5
0
1
1
0
2
4
32
0
0
16
20
3
3
0
Hydrodeoxygenation of Fatty Acids and Triglycerides
To study the stability, efficiency and general applicability of our
method, we studied the substrate scope for the
hydrodeoxygenation of various biomass-derived fatty acids and
triglycerides using small amount of Pt-MoOx/TiO2 (0.1 or 0.5
mol%) in the neat conditions under 50 bar H2 (Table 3). After 48
h of the reaction with 0.1 mol% of the catalyst at 230 °C, stearic,
palmitic, myristic, and lauric acid were selectively transformed to
the corresponding hydrodeoxygenation products, linear alkanes
without losing the carbon atoms of the fatty acid. The yields of the
main products were 98-99%, while by-products due to
decarbonylation, cracking, and partial deoxygenation reactions
were not detected by GC analyses. The TON of Pt-MoOx/TiO2 for
30
1
[a] 1 mmol lauric acid, 0.5 mol% metal (Pt) catalyst, 180 °C, 8
bar H2, 3 h.
[b] Dodecyl dodecanoate.
the hydrodeoxygenation of palmitic acid (990) is higher than those
[18]
of Pt/Nb2O5 (450)
and Pd/Nb2O5/SiO2 (10)[19] under similar
conditions in a batch reactor. The present method is effective also
for the hydrodeoxygenation of triglycerides. Hydrogenation of
trilaurin with 0.5 mol% of the Pt-MoOx/TiO2 catalyst (with respect
to carboxyl groups in the substrate) resulted in 93% yield of n-
dodecane. Under the same conditions, tristearin was also
hydrogenated to give n-octadecane in 89% yield, corresponding
to the TON of 178. This TON is higher than those of Pt/Nb2O5 (93)
[18] and Pd/Nb2O5/SiO2 (8).[19]
100
lauric acid
n-dodecane
80
60
40
Table 3. Pt-MoOX/TiO2-catalyzed hydrodeoxygenation of fatty
acids.[a]
Pt
[mol%]
0.1
T
fatty acids
products
Yield [%]
[°C]
230
230
230
230
250
250
Stearic acid
Palmitic acid
Myristic acid
Lauric acid
Trilaurin[b]
n-C18H38
n-C16H34
n-C14H30
n-C12H26
n-C12H26
n-C18H38
98
99
99
99
93
89
0.1
0.1
0.1
1-dodecanol
20
0.5
0.5
dodecyl dodecanoate
Tristearin[b]
[a] Reaction conditions: fatty acids (1 mmol), 50 bar H2, 48 h.
2
4
6
0
t [h]
[b] 0.33 mmol triglycerides, 0.5 mol% Pt with respect to carboxyl
groups.
Figure 1. Time course of the reaction of lauric acid by Pt-
MoOx/TiO2 under the conditions in Table 1. A reaction pathway is
shown on the figure.
Hydrodeoxygenation of 2-Octanone
Next, we studied an extension of our catalytic method to
hydrodeoxygenation of ketones. Adopting the hydrogenation of 2-
octanone under 8 bar H2 at 150 ˚C for 1 h as a model reaction, we
performed catalyst screening. Table 4 lists the conversion of 2-
octanone and yields of n-octane and 2-octanol. Among the
catalysts tested, Pt-MoOx/TiO2 showed the highest yield of the
hydrodeoxygenation product, n-octane (40%) with 40% yield of 2-
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octanol. The other bimetallic Pt catalysts, Pt-VOx/TiO2 Pt-
MoOx/Al2O3 and Pt-MoOx/SiO2, showed high conversion and
relatively high yields of n-octane (30-34%) with 2-octanol as a
major product. Pt-based monometallic catalysts, such as
Pt/Nb2O5 Pt/TiO2 and Pt/SiO2 showed low yields of n-octane (0-
5%). MoOx/TiO2-supported Pd, Ru, Rh, Cu, and Ni catalysts
showed low yields (0-18%) of n-octane.
Table 5. Hydrodeoxygenation of ketones by Pt-MoOX/TiO2.
Figure 2 shows the time course of the hydrogenation of 2-
octanone by Pt-MoOx/TiO2 under the conditions in Table 4. The
profile is characteristic to a consecutive reaction; 2-octanol is first
produced which is then converted to n-octane. The final yield of
n-octane was 98%, and the GC-MS analysis showed no
byproducts. The yield (64%) of n-octane for hydrogenation of 2-
octanol, eqn. (1), was higher than that for 2-octanone (40%). This
indicates that the initial step is slower than the second step.
Yield
[%]
Entry
Substrate
Product
1
2
95
93
O
O
3
4
97
88
O
O
5[a]
93
Table 4. Hydrodeoxygenation of 2-octanone with 5 wt% metal-
loaded catalysts.
6
7
70
90
O
O
Conv.
[%]
84
99
99
99
87
75
99
99
80
93
90
99
8
Yield [%]
O
Entry
Catalysts
n-octane
2-octanol
8
94
1
2
3
4
5
6
7
8
9
10
11
12
13
Pt-MoOx/TiO2
Pt-VOx/TiO2
Pt-MoOx/Al2O3
Pt-MoOx/SiO2
Pt/Nb2O5
Pt/TiO2
Pt/Al2O3
Pt/CeO2
Pt/SiO2
Pd-MoOx/TiO2
Ru-MoOx/TiO2
Rh-MoOx/TiO2
Cu-MoOx/TiO2
40
30
34
30
0
0
5
2
0
18
17
13
0
40
58
55
63
55
36
65
70
80
60
56
86
[a] 36 h
With the most effective catalyst, we tested hydrogenation of
ketones with different structures. Table 5 shows the yields of the
hydrodeoxygenation product (alkanes) for the reaction of the
ketones under 8 bar H2 at 200 ˚C for 24 h with small amount (0.1
mol%) of the Pt-MoOx/TiO2 catalyst. Linear and cyclic aliphatic
ketones (entries 1-6) underwent selective hydrodeoxygenation
with good to high yields (70-97%) of alkanes. Relatively low yield
(70%) for the reaction of norbornanone may be due to steric
hindrance. The olefinic and aromatic functional groups in 2-
cyclohexen-1-one and acetophenone were also hydrogenated
(entries 7,8). As shown in eqn. (2), the hydrogenation of 7.3 mmol
2-octanone with only 0.03 mol% of the Pt-MoOx/TiO2 catalyst for
48 h resulted in 70% yield of n-octane, corresponding to the
turnover number (TON) of 2300.
0
100
2-octanone
n-octane
80
60
40
20
2-octanol
Possible role of MoOX
Finally, we discuss the reason of the higher activity of Pt-
MoOx/TiO2 than the comparative catalysts (Pt/TiO2 and Pt/Al2O3)
for the hydrodeoxygenation of ketones (Table 4). In our previous
IR study of the pyridine adsorbed on these catalysts, we showed
that Pt-MoOx/TiO2, Pt/TiO2 and Pt/Al2O3 were Lewis acidic due to
the exposed cations on the support surface.[26] Also, we reported
that the C=O stretching band in the IR spectrum of the acetone
coordinated to the Mon+ Lewis acid sites on Pt-MoOx/TiO2 was
observed at lower wavenumber than Pt/TiO2 and Pt/Al2O3.[27] The
10
t [h]
20
0
Figure 2. Time-conversion profile for hydrogenation of 2-
octanone 1a by Pt-MoOx/TiO2 under the conditions in Table 4.
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IR spectra of acetone on these catalysts are shown in Figure 3A;
the spectra at t = 0 s are due to the acetone adsorbed on the
catalyst at 40 °C after adsorption of acetone followed by purging
with He flow for 10 min. The C=O stretching band of acetone for
Pt-MoOx/TiO2 is at lower wavenumber (1690 cm-1) than those for
Pt/TiO2 (1709 cm-1) and Pt/Al2O3 (1703 cm-1), which indicates that
the Lewis acid sites on Pt-MoOx/TiO2 weakens the C=O bond
strength more effectively than those on Pt/TiO2 and Pt/Al2O3.[27]
Then, we studied the reactivity of the acetone on these catalysts
under 1 atm H2. After the observation of these spectra (at t = 0 s
in Figure 3A), the flowing gas was switched from He to H2, and
the time-dependence of the IR spectra were monitored. Figure 3B
shows the time course of the relative amount of the adsorbed
acetone (area of the C=O stretching band). On the other hand the
gas was switched to H2, the acetone adsorbed on Pt-MoOx/TiO2
were completely consumed within 100 s. Whereas, those on
Pt/TiO2 and Pt/Al2O3 were relatively stable and were observed
even after 300 s. Taking into account the well-established fact that
dissociation of H2 on Pt surfaces is fast process, the result
indicates that the rate of hydrogen transfer from Pt surface to the
acetone on the Lewis acid sites of the supports depend strongly
on the support materials; the rate for Pt-MoOx/TiO2 is faster than
those for Pt/TiO2 and Pt/Al2O3. On the basis of the result, we
propose the catalytic mechanism shown in the scheme in Figure
3. The carbonyl group of the acetone undergoes activation by the
surfaces Lewis acids on MoOx/TiO2. On the other hand, Pt
surface dissociates H2 to give hydrogen atoms which then react
with the activated acetone. The Lewis acid activation of the
ketones is responsible to the support specific activity of the
present catalytic system.
The reaction under neat conditions with small amount of the
catalyst (0.1 or 0.5 mol%) results in 89-99% yields of the
corresponding n-alkanes without C-C bond cleavage. This
catalytic system shows higher TON than the reported catalysts for
the hydrodeoxygenation of fatty acids or triglycerides. Pt-
MoOx/TiO2 is also effective for hydrodeoxygenation of various
ketones to the corresponding alkanes. On the basis of the
mechanistic study for the hydrogenation of acetone, the high
activity of Pt-MoOx/TiO2 is attributed to the cooperation between
Pt and Lewis acid site of MoOx/TiO2, in which Pt acts as H2-
dissociation sites and the C=O bond of the coordinated ketones
is weakened by the Lewis acid site.
Experimental Section
General
The GC (Shimadzu GC-2014) and GCMS (Shimadzu GCMS-
QP2010) analyses were carried out with Ultra ALLOY capillary
column UA+-1 (Frontier Laboratories Ltd.) using nitrogen and He
as the carrier gas.
Commercially available organic compounds (from Tokyo
Chemical Industry or Kanto Chemical) were used without further
purification. Trilaurin (>98% purity) and tristearin (>80% purity),
purchased from Tokyo Chemical Industry, contain the
corresponding diglycerides and monoglycerides as impurities.
We estimated the contents of fatty acids in these commercial
trilaurin (97%) and tristearin (94%) by hydrolysis of the
triglycerides; the products (lauric acid and stearic acid) of the
hydrolysis reactions in eqn. (3) and (4) were isolated and
characterized by 1H- and 13C-NMR analyses.
A
B
1690
He
H2
0.2
Pt-MoOX/TiO2
Pt-MoOX/TiO2
0 s
30 s
300 s
Catalyst preparation
1709
TiO2 (JRC-TIO-4, 50 m2 g-1) and CeO2 (JRC-CEO-3) were
supplied from Catalysis Society of Japan. SiO2 (Q-10, 300 m2 g-1)
was kindly supplied by Fuji Silysia Chemical Ltd. γ-Al2O3 was
prepared by calcination (900 °C, 3 h) of boehmite (Catapal B
Alumina, Sasol). Nb2O5 was prepared by calcination (500 °C, 3 h)
of Nb2O5∙nH2O, kindly supplied by CBMM.
5.0
Pt/TiO2
0 s
30 s
Pt/Al2O3
Pt/TiO2
1703
300 s
Pt/Al2O3
0 s
30 s
300 s
Precursors of M1-MoOX/TiO2 (M1 = 5 wt% Pt, Pd, Rh, Ru, Ni,
Cu; 7 wt% Mo), Pt-VOX/TiO2, Pt-MoOX/Al2O3, and Pt-MoOX/SiO2
were prepared by a sequential impregnation method. M1 sources
were aqueous HNO3 solution of Pt(NH3)2(NO3)2, Rh(NO3)3,
Pd(NH3)2(NO3)2 and aqueous solution of RuCl3 and nitrates (Ni,
Cu). Mo and V sources were (NH4)6Mo7O24·4H2O and NH4VO3.
Loading of Pt (or M1) and Mo (or V) were 5 wt% and 7 wt%. For
the preparation of Pt-MoOx/TiO2 (5 wt% Pt, 7 wt% Mo) as an
example, 5 g of TiO2, 0.88 mmol (NH4)6Mo7O244H2O, and 50 mL
water were mixed. Then, the mixture was evaporated to dryness
at 50 °C, followed by drying at 90 °C (12 h) and by calcination in
air at 500 °C (3 h) to yield MoO3-loaded TiO2 (MoO3/TiO2).
MoO3/TiO2 (or other supports) and aqueous HNO3 solution of
Pt(NH3)2(NO3)2 were mixed, evaporated, dried at 90 °C to yield a
Pt(II)-loaded precursor. Before the catalytic experiment, all of the
1750 1700 1650 1600
Wavenumber [cm -1
0
100
t [s]
200
300
]
Figure 3. (A) IR spectra of acetone adsorbed on Pt-MoOx/TiO2
and Pt/TiO2 as a function of the time in flow of H2 at 40 °C and (B)
area of C=O bands due to the adsorbed acetone on () Pt-
MoOx/TiO2, (▲) Pt/TiO2 and () Pt/Al2O3 vs the time.
Conclusions
We have found that Pt-MoOx/TiO2 is effective heterogeneous
catalyst for hydrodeoxygenation of fatty acids and triglycerides.
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catalysts were prepared by pre-reduction of the precursor in a
Pyrex tube under flowing H2 (20 cm3 min-1) at 300 °C for 0.5 h.
The Pt-MoOx/TiO2 catalyst was used as the standard catalyst.
Detailed characterization results including temperature-
programmed reduction under H2 flow (H2-TPR) have been
reported in our previous studies.[26-28]
In situ IR experiment
In situ IR spectra were recorded at 40 °C using a JASCO FT/IR-
4200 with an MCT detector. The catalyst powder was pressed into
a 30 mg wafer ( = 2 cm) which was placed in the quartz IR cell
(CaF2 windows) connected to a conventional flow reaction system.
The catalysts in situ pre-reduced under H2 (20 cm3 min-1, 300 °C,
0.5 h) was cooled to 40 °C in a flow of He. Then, a reference
spectrum of the catalyst in He was taken at 40 °C. Then, 1 μL of
liquid acetone was injected into the He flow preheated at 200 °C,
followed by He purge (600 s). Then the flowing gas was switched
to H2 (20 cm3 min-1). IR spectra of acetone adsorbed on the
catalyst were measured as a function of the time of H2 flowing.
Typical procedures of catalytic reactions
The hydrogenation of fatty acids and triglycerides were carried out
as follows. After the pre-reduction, the catalyst in the closed Pyrex
tube sealed with a septum inlet was cooled to room temperature
under H2, followed injection of n-hexadecane (0.2 mmol) to the
reduced catalyst powder in the tube through the septum inlet.
Then, the septum was removed under air, and 1 mmol fatty acids
(or 0.33 mmol triglycerides) and magnetic stirrer were put in the
tube, followed by inserting the tube inside stainless autoclave (14
cm3). After being sealed, the reactor was charged with H2 (8 or 50
bar). The reactor was heated at 180-250 ˚C under stirring (500
rpm). After a certain period of time, the reactor was cooled
followed by adding 2-propanol (6 cm3) to the mixture, the
conversion and yields of products were determined by GC using
n-hexadecane as an internal standard. The products were
identified by GC-MS equipped with the same column as GC and
by comparison with commercially available products. The
hydrogenation of ketones was carried out by the similar method
using n-dodecane (0.2 mmol) as an internal standard. Note that
the carbon balance for some of the catalysts in Table 1, 2, and 4
are below 100% due to the short reaction time which is suitable
to the comparison of the catalytic activity. The carbon balance
was >90% at longer reaction time, but the condition was not
suitable to the kinetic analysis.
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific Research
on Innovative Areas "Nano Informatics" (25106010) from JSPS
and a MEXT program "Elements Strategy Initiative to Form Core
Research Center". The authors thank the technical division of
Institute for Catalysis, Hokkaido University, for their help in
building the experimental equipment.
Keywords: hydrodeoxygenation • fatty acids • triglycerides •
ketones • platinum
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10.1002/cctc.201700219
ChemCatChem
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Kenichi Kon, Takashi Toyao, Wataru
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Hydrodeoxygenation of Fatty Acids,
Triglycerides and Ketones to Liquid
Alkanes by Pt-MoOx/TiO2 Catalyst
Pt-MoOx/TiO2 catalyst shows high activity for selective hydrodeoxygenation of fatty
acids, triglycerides and ketones under solvent-free conditions to give n-alkanes
without C-C bond cleavage. H2 is dissociated by Pt sites and the C=O group
coordinated to the Mon+ site undergoes Lewis acid activation.
This article is protected by copyright. All rights reserved.