Conversion of biomass-derived fatty acids and derivatives into hydrocarbons using a metal-free hydrodeoxygenation process

Article abstract of DOI:10.1039/c5gc00556f

A metal-free hydrodeoxygenation process was developed for the production of hydrocarbons from biomass-derived fatty acids and derivatives. Biomass-derived fatty acids and derivatives were converted to alkanes and alkenes under mild reaction conditions. Furthermore, this catalytic system can also be applied to convert real biomass with satisfactory results.

Full text of DOI:10.1039/c5gc00556f

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: X. Li, R. Shang,
M. Fu and Y. Fu, Green Chem., 2015, DOI: 10.1039/C5GC00556F.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/greenchem

Page 1 of 4
Green Chemistry
View Article Online
DOI: 10.1039/C5GC00556F
Journal Name
RSCPublishing
COMMUNICATION
Conversion of Biomass-derived Fatty Acids and
Derivatives into Hydrocarbons Using a Metal-Free
Hydrodeoxygenation Process
Cite this: DOI: 10.1039/x0xx00000x
a
a
a
*a
Received 00th January 2015,
Accepted 00th January 2015
Xing-Yu Li, Rui Shang, Ming-Chen Fu and Yao Fu
DOI: 10.1039/x0xx00000x
www.rsc.org/
9
A metal-free hydrodeoxygenation process was developed for heterogeneous catalysis. Recently, Vardon et al. reported a route
the production of hydrocarbons from biomass-derived fatty using Pt-Re/C catalyst to convert long chain fatty acid to
1
0
hydrocarbon. Wang et al. accomplished production of long chain
acids and derivatives. Biomass-derived fatty acids and
derivatives were converted to alkane and alkene under mild
reaction conditions. Furthermore, this catalytic system can
also be applied to convert real biomass with satisfactory
result.
hydrocarbon from the aldol condensation product of furfural or 5-
HMF by using a bimetal catalyst, Pt/NbOPO . The method using
heterogeneous catalysis has turned out to be effective. However,
some disadvantages still exist, such as using precious metals (for
instance, Pt) and harsh reaction conditions (300 C).
4
o
The decline of fossil fuel resource and the increasing demand of
energy have stimulated people to search for alternative resources.
Currently, the only known sustainable organic carbon source comes
The homogeneous Lewis acid, trispentafluorophenylborane
(
B(C F ) ), can catalyze reduction reaction in combination with
6 5 3
1
1
1
silane as reductant. This method was first reported by Piers group .
Subsequently, Piers , Yamamoto , and Chandrusekhar et al. apply
this catalysis system to reduction or hydrosilation of ketone,
aldehyde, ether, ester and carboxylic acid . Considering the mild
reaction conditions and low cost of this reduction system, application
of this method to the reduction of biomass evokes the interest of
biomass-chemist recently. Cantat et al. successfully accomplished
C-O bond cleavage of lignin model compounds utilizing B(C F )
from biomass , and biomass is also considered as the only renewable
12
13
14
1
feedstock to obtain liquid fuels . Based on these reasons, utilization
of biomass has attracted increasing attentions. The molecule
structure of biomass-derived fatty acids and derivatives is similar
with the structure of fuel from petrochemical industry. Thus, people
have paid many efforts to convert these biomasses to fuel. Biodiesel,
the first generation of biofuel, is produced by transesterification of
triglyceride (a common biomass-derived fatty acid derivative) and
primary alcohol (mainly methanol). Acid or base homogeneous or
heterogeneous catalysts always play important roles in
15
16
6
5 3
with Et SiH as reducing agent. Gagne et al. reported inspiring work
3
on hydrosilylative reduction of glucose into alkane by using Ir(III)
17
18
2
-4
pincer catalyst . Then, Gagne et al. discovered by replacing Ir(III)
pincer catalyst with B(C , alkane can also be obtained from
transesterification reactions , and lipase catalysis has also been
5
F )
6 5 3
applied to this field . However, the fuels composed of fatty acid
6
glucose under mild conditions. Alkane products from glucose or
glucose-derivatives are mainly hexane or its isomers. For producing
hydrocarbons with different carbon numbers (carbon number>10),
hydrodeoxygenation of biomass-derived carboxylates is a better
choice. Herein, we first-time applied B(C F ) -catalyzed
alkyl esters (FAAEs) have several drawbacks, such as low fluidity ,
6
6
high oxygen content , poor thermal oxidation stability and
2
polymerization of ester fuel molecule . These disadvantages limit the
application of ester biodiesel . To solve these problems, people
6
6
5 3
begin to seek for method that can directly convert biomass,
especially biomass-derived fatty acids and derivatives to
hydrocarbons.
hydrosilylative reduction for the hydrodeoxygenation of biomass-
derived fatty acids and derivatives to produce hydrocarbons. Both
alkane and alkene can be produced in good yields.
Biodiesel usually represents long chain fatty acid methyl ester.
To distinguish the two kinds of fuels, hydrocarbon obtained from
biomass is called green diesel . Some reviews and patents
In the initial studies, the most common triglyceride, tristearin,
2
7
8
was used as model substrate, Et
SiH was chosen as reductant. We
3
tested the reaction using different amount of catalyst.
summarized methods to convert triglyceride to hydrocarbon by
This journal is © The Royal Society of Chemistry 2015
J. Name., 2015, 00, 1-3 |
1

Green Chemistry
Page 2 of 4
View Article Online
COMMUNICATION
DOI: 10.1039/C C00556F
Jou5Grnal Name
mechanism, we speculated whether cheap metal Lewis acid could
also catalyze this reaction. Some metal Lewis acids were tested，
such as (OTf) Zn(II)，(OTf) Fe(II) and AlCl . None of these Lewis-
2
2
3
acid-metal-catalyst was effective even extending the reaction time to
4 h. At last, we studied the necessary reaction time of this reaction
Table 2. Entry 6, Entries 21-23). The result showed 6 h is necessary
2
(
Scheme 1. Conversion of tristearin to octodecane at different amount of to achieve good conversion and yield.
catalyst loading.
When 1 mol% of B(C F ) was used, the yield of target product
6
5 3
Table 2. Yields of alkane under different conditions
octodecane was only 2% (Table 1, Entry 1). Increasing the catalyst
loading to 3 mol% and 5 mol% resulted 40% and 81% yield
respectively (Table 1, Entry 2 and 3). Further increase the catalyst
loading to 10 mol% resulted 95% yield (Table 1, Entry 4).
Prolonging reaction time (from 6 h to 24 h) at the same reaction
conditions in Entry 1 can only increase the yield to 12% (Table 1,
Entry 5). Control experiment without the B(C F ) catalyst showed
a
b
Entry
1
Silane
18 equiv Et
Time
6 h
Solvent
Yield
92
3
SiH
CH
CH
CH
CH
CH
CH
CH
CH
2
2
2
2
2
2
2
2
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
2
2
2
2
2
2
2
2
2
3
18 equiv Et
2
MeSiH
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
6 h
24 h
24 h
24 h
97
--
18 equiv (EtO)
3
SiH
6
5 3
4
18 equiv Ph
2
SiH
2
96
88
91
0
no octodecane was generated (Table 1, Entry 6). Using 5 mol% of
catalyst resulted slightly decreasing of the yield comparing with
using 10 mol% of catalyst (Table 1, Entry 3, Entry 4). Considering
the cost issue of the catalyst, we decide to use 5 mol% of catalyst to
further study this process.
5
18 equiv Et
2
SiH
2
c
6
18 equiv PMHS
7
3 equiv Et
6 equiv Et
3
3
SiH
SiH
Table 1. Conversion of tristearin to octodecane at different catalyst loading
8
52
62
71
88
0
a
b
9
9 equiv Et SiH
2
CH Cl2
3
Entry
Loading
Time
Yield
1
2
3
4
5
6
1 mol%
3 mol%
5 mol%
10 mol%
1 mol%
0
6 h
6 h
6 h
6 h
24 h
6 h
2%
40%
92%
95%
12%
0
10
12 equiv Et
15 equiv Et
3
3
SiH
SiH
CH
2
2
Cl
2
2
1
1
1
1
2
3
CH
Cl
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
18 equiv PMHS
3
CH CN
dioxane
DMF
5
a
6 5 3
B(C F ) as catalyst, 0.1 mmol tristearin, 18 equiv silane, room
b
14
0
temperature. Yields were determined by GC analysis
1
1
1
5
6
7
DMA
0
Next, we tested various factors affecting this proccess, including
different type of silanes, dosage of silanes, solvents and reaction
time.
DMSO
0
cyclohexane
93
0
To study the influence of reaction temperature, we tested reactions
at different temperature. The results show increasing the temperature
decreases the yield of octodecane (see Supporting Information). We
chose ambient temperature as the optimized temperature for this
reaction. Various silanes were tested (Table 2, Entries 1-6). Several
silanes are competent reductant except triethoxysilane (Table 2,
Entry 3). It is worth noting poly(methylhydrosiloxane) (PMHS), a
d
1
8
CH
CH
CH
2
2
2
Cl
2
Cl
2
Cl
2
e
f
1
2
9
0
0
0
2
2
1
2
18 equiv PMHS
18 equiv PMHS
0.2 h
0.5 h
CH
2
2
Cl
2
2
13
28
CH
Cl
1
6
cheap silane used in industry also gave high yield (Table 2, Entry
). Testing the dosage of silane (Table 2, Entry 1, Entries 7-11)
23
18 equiv PMHS
4 h
CH Cl2
60
2
6
a
0
6 6 3
.1 mmol tristearin, 5 mol% B(C F ) as catalyst, 1 mL solvent, room
showed satisfactory yield of octodecane can be got when 18 equiv
silane was used. But when fatty acids and fatty acid methyl esters
were substrates, 9 equiv silane was enough. Entries 12-17 showed
the solvent effect of this reaction. Acetonitrile, dioxane, DMF, DMA
and DMSO are all ineffective as solvent probably due to the poison
of the boron catalyst by their lone pair electron (Entries 12-16).
Except for dichloromethane, cyclohexane also gave good result
b
c
temperature.
poly(methylhydrosiloxane). 5 mol% (OTf)
Yields were determined by GC analysis.
PMHS is
d
e
2
Zn as catalyst. 5 mol%
f
Fe(OTf)
2
as catalyst. 5 mol% AlCl
3
as catalyst
.
A series of biomass-derived fatty acids (Table 3), including lauric
acid (C12), myristic acid (C14), palmitic acid (C16), as well as
stearic acid (C18) were tested under the optimized condition.
Various alkane products can be generated in good yield.
Hydrocarbons with high boiling point, such as hexadecane and
octodecane, were isolated. Unsaturated fatty acid, oleic acid is also
(
Table 2. Entry 17). It should be note for production of fuel, the
alkane product and alkane solvent can be used without extra
separation procedure. To avoid energy-intensive separation steps
after the reaction, cyclohexane can be chosen as solvent for this
1
4, 15
reaction. According to the previous work
, B(C F ) acts as a
6 5 3
Lewis acid catalyst to activate silane in the system. Based on this
2
| J. Name., 2015, 00, 1-3
This journal is © The Royal Society of Chemistry 2015

Page 3 of 4
Journal Name
Green Chemistry
View Article Online
COMMUNICAT56ION
DOI: 10.1039/C5GC005 F
an amenable substrate. 9-octadecene was generated in good yield
with the double bond unreacted.
Glyceride such as laurin and palmitin could be converted to
dodecane and hexadodecane in excellent yield (Table 5).
Considering the advantage of using alkane solvent, we tried all
reactions using cyclohexane as solvent, alkane products of high
yields were also obtained in cyclohexane
Table 3. Conversion of various biomass-derived fatty acids to hydrocarbons
5
mol% B(C6F5)3
O
PMHS, 1 mL solvent
room temperature
6 h
CH3
Table 5. Conversion of glyceride to hydrocarbons
R
R
OH
1
2
1a, R = n-C11H23
1b, R = n-C13H27
1c, R = n-C15H31
1d, R = n-C17H35
2a
2b
2c
2d
O
5 mol% B(C6F5)3
PMHS, 1 mL solvent
room temperature
9-octodecene
7
7
OH
6
h
0%b
8
2
a, C12: dodecane
yield in CH Cl : 99%
yield in cyclohexane: 93%
2c, C16: hexadecane
a
a
b
2
2
yield in CH
2 2
Cl : 92% (74% )
a b
a
2
a, C12: dodecane
yield in CH Cl : 93%
yield in cyclohexane: 92%
2b, C14: tetradecane
a
yield in cyclohexane: 85% (70% )
a
2
2
yield in CH
2 2
Cl : 81%
a
a
yield in cyclohexane: 80%
a
0
.1 mmol substrate, 18 equiv PMHS, room temperature, 1 mL solvent,
b
yields were determined by GC analysis. Isolated yield
2
d, C18: octodecane
a
2
c, C16: hexadecane
a
Applying this conversion to real biomass was also conducted.
yield in CH
yield in cyclohexane: 81% (71% )
2 2
Cl : 84%
a
yield in CH
yield in cyclohexane: 87% (74% )
Cl
2 2
: 83%
19
c
Commercially available colza oil (olein, 55 wt%-65 wt% ) and
a
c
1
9
olive oil (olein, 67 wt% ) gave satisfactory results (mole ratio of
.1 mmol substrate, 9 equiv PMHS, 1 mL solvent, room temperature, yields PMHS and olein is 9:1). We could get 12.7 mg olefin from 40 mg
a
0
b
c
determined by GC analysis. Yield were determined by GC-MS analysis.
Isolated yield
colza oil and 14.3 mg olefin from 40 mg olive oil (detected by GC-
MS, See Supporting Information). It should be pointed out although
commercially available colza oil and olive oil contained small
Meanwhile, we also used corresponding biomass-derived fatty amount of water. Alkane product could be still generated in
acids esters as substrate (Table 4), including methyl laurate, methyl satisfactory yield without pre-dehydration of the biomass oil. This
myristate, .methyl palmitate and methyl stearate. Isolated yields of observation showed the catalytic system can tolerate small amount
1
8
hexadecane and octodecane were also obtained. The yield of alkane of water, which was also confirmed by Gagne’s report . It should
from ester is relatively higher compared with using carboxylic acid. also be noted, by using PMHS as reducing agent, the products could
A possible explanation for this observation is carboxylic anion be easily separated due to the conversion of PMHS to insoluble
14
coordinates with boron atom of the catalyst reduces the activity of residue of siloxane .
the boron catalyst.
Conclusions
Table 4. Conversion of various biomass-derived fatty acids esters to
hydrocarbons
In summary, we report a metal-free method to convert biomass-
derived fatty acids and derivatives to hydrocarbons under mild
condition. By using B(C F ) as catalyst and PHMS as reducing
6
5 3
agent, alkane and alkene were produced in good to excellent yields
under room temperature in alkane solvents. This method is also
proved to be competent for the direct conversion of plant oil to
hydrocarbon, and providing a useful method for upgrading biodiesel
to liquid hydrocarbon fuel.
Notes and references
2
a, C12: dodecane
2b, C14: tetradecane
a
iCHEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui
a
a
yield in CH
yield in cyclohexane: 95%
Cl
2 2
: 99%
2 2
yield in CH Cl : 96%
a
a
Province Key Laboratory of Biomass Clean Energy, Department of
Chemistry, University of Science and Technology of China, Hefei, 23006,
China.
yield in cyclohexane: 90%
2
d, C18: octodecane
a
2
c, C16: hexadecane
a
yield in CH Cl : 97%
yield in cyclohexane: 94% (81% )
2 2
yield in CH
yield in cyclohexane: 88% (78% )
2 2
Cl : 85%
a
a
b
b
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/c000000x/
a
0
.1 mmol substrate, 9 equiv PMHS, 2 mL solvent, room temperature, yields
b
were determined by GC analysis. Isolated yield
This journal is © The Royal Society of Chemistry 2015
J. Name., 2015, 00, 1-3 |
3

Green Chemistry
Page 4 of 4
View Article Online
COMMUNICATION
DOI: 10.1039/C C00556F
Jou5Grnal Name
1
2
3
G. W. Huber, S. Iborra, A. Corma, Chem. Rev. 2006, 106, 4044.
C. Zhao, T. Brück, J. A. Lercher, Green Chem. 2013, 15, 1720.
E. Lotero, Y. J. Liu, D. E. Lopez, K. Suwannakarn, D. A. Bruce, J. G.
Goodwin, Ind. Eng. Chem. Res. 2005, 44, 5353.
4
5
6
7
A. P. Vyas, J. L. Verma, N. Subrahmanyam, Fuel 2010, 89, 1.
T. Tan, J. Lu, K. Nie, L. Deng, F. Wang, Biotechnol.Adv. 2010, 28, 628.
P. Benjumea, J. Agudelo, A. Agudejo, Fuel 2008, 87, 2069.
(a) G. W. Huber, A. Corma, Angew. Chem. Int. Ed. 2007, 46, 7184; (b) M.
J. Climent, A. Corma, S. Iborra, Green Chem. 2014, 16, 516.
8
(a) J. Jakkula, V. Niemi, J. Nikkonen, V.M. Purola, J. Myllyoja, P. Aalto, J.
Lehtonen, V. Alopaeus, US Patent, 2007, 7, 232, 935; (b) W. K. Craig, D.
W. Soveran, US Patent, 1991, 4, 992, 605; (c) A. R. Pinho, M. Silva, A. P.
Silva Neto, J. A. R. Cabral, US Patent, 2009, 7, 540, 952 B2; (d) J. A.
Petri, T. L. Marker, US Patent, 2009, 7, 511, 181 B2.
9
1
D. R. Vardon, B. K. Sharma, H. Jaramillo, D. Kim, J. K. Choe, P. N.
Ciesielski, T. J. Strathmann, Green Chem. 2014, 16, 1507.
0
Q. N. Xia, Q. Cuan, X. H. Liu, X. Q. Gong, G. Z. Lu, Y. Q. Wang, Angew.
Chem. Int. Ed. 2014, 126, 9913.
11
12
13
D. J. Parks, W. E. Piers, J. Am. Chem. Soc. 1996, 118, 9440.
D. J. Parks, J. M. Blackwell, W. E. Piers, J. Org. Chem. 2000, 65, 3090.
(a) V. Gevorgyan, M. Rubin, S. Benson, J. X. Liu, Y. Yamamoto, J. Org.
Chem. 2000, 65, 6; (b) V. Gevorgyan, M. Rubin, J. X. Liu, Y. Yamamoto,
J. Org. Chem. 2001, 66, 1672.
1
4
5
S. Chandrasekhar, C. R. Reddy, B. N. Babu, J. Org. Chem. 2002, 67,
9080.
1
(a) R. D. Nimmagadda, C. McRae, Tetrahedron Letters 2006, 47, 5755;
(
b) R. D. Nimmagadda, C. McRae, Tetrahedron Letters 2006, 47, 3505;
c) M. Tan, Y. Zhang, Tetrahedron Letters 2009, 50, 4912; (d) D. T. Hog,
(
M. Oestreich, Eur. J. Org. Chem. 2009, 5047; (e) D. B
Brookhart, Org. Lett. 2013, 15, 496.
ꢀezier, S. Park, M.
1
6
7
E. Feghali T. Cantat, Chem. Commun. 2014, 50, 862.
1
M. P. McLaughlin, L. L. Adduci, J. J. Becker, M. R. Gagne, J. Am. Chem.
Soc. 2013, 135, 1225.
1
8
9
L. L. Adduci, M. P. McLaughlin, T. A. Bender, J. J. Becker, M. R. Gagne
Angew. Chem. Int. Ed. 2014, 53, 1646.
1
S. Lestari, P. Maki-Arvela, J. Beltramini, G. Q. Max Lu, D. Y. Murzin,
ChemSusChem 2009, 2, 1109.
4
| J. Name., 2015, 00, 1-3
This journal is © The Royal Society of Chemistry 2015