Hidrodesoxigenação de compostos derivados de lignocelulose

Prévia do material em texto

Catalysis
Science &
Technology
PAPER
Cite this: DOI: 10.1039/c9cy02367d
Received 23rd November 2019,
Accepted 9th January 2020
DOI: 10.1039/c9cy02367d
rsc.li/catalysis
Hydrodeoxygenation of lignocellulose-derived
oxygenates to diesel or jet fuel range alkanes
under mild conditions†
Kui Li,a Feng Zhou,b Xiaohao Liu,c Huixia Ma,b Jin Deng, a
Guangyue Xua and Ying Zhang *ad
Hydrodeoxygenation (HDO) of lignocellulose-derived oxygenates to diesel or jet fuel range C8–C18 alkanes
usually requires harsh reaction conditions. A fairly mild (160 °C, 4 MPa H2) one-pot catalytic HDO system
based on Ru/HAP combined with the HZSM-5 catalyst was developed, and a series of diesel or jet fuel
range alkanes (C8–C18), including straight, branched, and cyclic alkanes, were obtained from nine
complicated lignocellulose-derived oxygenates with a desired yield. Ru/HAP was characterized by a series
of analyses, indicating that the electron donor effect of HAP led to the generation of highly dispersed
electron-rich Ru, which demonstrated stronger hydrogen activation and hydrogenolysis ability.
Introduction
Diesel (C9–C21 hydrocarbons)1 and jet fuel (C8–C16
hydrocarbons)2 are two important transportation fuels.
Currently, they are produced mainly from non-renewable
petroleum, which causes a lot of environmental issues.
Therefore, as a promising renewable route, the synthesis of
diesel or jet fuel range alkanes from lignocellulose-derived
platform compounds has been extensively studied since the
pioneering work conducted by the groups of Dumesic,3,4
Huber5,6 and Corma.7,8 Most of the reported studies about
this route could be summarized as follows: first, a C–C
bond coupling reaction of lignocellulose-derived platform
compounds was carried out to obtain the condensation
intermediates with a longer carbon chain; subsequently,
alkanes were obtained by HDO of the condensation products.
The latter step is still challenging due to the requirement of
high temperature and H2 pressure, which leads to high
energy consumption, equipment and operation costs and
safety risks.
Currently, various types of catalytic systems were
established for HDO of complicated lignocellulose-derived
oxygenates to alkanes, which are summarized in Table 1. In
the recent work of Li's group, Pd-based bimetallic catalysts
were used for HDO of a C10 oxygenate at 350 °C and 6 MPa
H2, and high quality alkanes were obtained
9,10 (Table 1, entry
1). In the previous reports of Zou's group11 and Ma's group,12
Pd/Hβ and Pd/C + ZrP catalysts were employed for preparing
branched cycloalkanes at temperatures above 280 °C (Table 1
, entries 2 and 3). Wang's group13 found that the Pd/NbOPO4
catalyst could catalyze a C15 oxygenate into branched long-
chain alkanes at 220 °C and 6 MPa H2 (Table 1, entry 4).
However, the cost of the NbOPO4 carrier was high and the
synthetic process was complex. Catalysts such as Pt/ZrP,1
Pd/C + HfIJOTf)4,
14 Pd/NbOPO4,
15 Ir–ReOX/SiO2,
16 Ni/Hβ,17
Ni/HZSM-5 (ref. 18) and Ni/ZrO2–SiO2 (ref. 19) have also
been developed for branched alkane production from
trifurylmethane. High temperatures or pressures were
required in most cases. It is highly desirable to develop
catalysts with high activity for HDO, which are expected to
be able to catalyze oxygenates into alkanes under mild
conditions.
Hydroxyapatite (HAP) is a calcium orthophosphate with
the apatite structure, in which Ca2+ sites are surrounded by a
PO4
3− tetrahedron parallel to the hexagonal axis. Owing to
multiple functionalities including ion-exchange ability,
adsorption capacity, and adjustable weak acid–base
properties, HAP has aroused great interest especially in the
field of heterogeneous catalysis, such as cross-coupling
Catal. Sci. Technol.This journal is © The Royal Society of Chemistry 2020
a CAS Key Lab of Urban Pollutant Conversion, Department of Applied Chemistry,
University of Science and Technology of China, Hefei 230026, China.
E-mail: zhzhying@ustc.edu.cn
b Fushun Research Institute of Petroleum and Petrochemicals, SINOPEC, Fushun,
113001, China
c CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy
Conversion, Chinese Academy of Sciences, Guangzhou 510640, China
dDalian National Laboratory for Clean Energy, 457 Zhongshan Rd., Dalian
116011, China
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c9cy02367d
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
View Journal
http://crossmark.crossref.org/dialog/?doi=10.1039/c9cy02367d&domain=pdf&date_stamp=2020-01-23
http://orcid.org/0000-0003-0272-1031
http://orcid.org/0000-0003-2519-7359
https://doi.org/10.1039/c9cy02367d
https://pubs.rsc.org/en/journals/journal/CY
Catal. Sci. Technol. This journal is © The Royal Society of Chemistry 2020
reactions,20 condensation reactions,21,22 alcohol selective
oxidation reactions,23,24 dehydration reactions25 and (de)
hydrogenation reactions.26–32 As a kind of multifunctional
metal catalysts, Ru-based catalysts have been widely used in
various fields of biomass conversion.33–40
In this work, a highly dispersed Ru/HAP catalyst was
employed together with zeolite HZSM-5 for one-pot HDO of a
series of complicated lignocellulose-derived oxygenates under
relatively mild conditions to obtain diesel or jet fuel range
alkanes (C8–C18). Ru/HAP was characterized by high-
resolution transmission electron microscopy (HRTEM), X-ray
diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and
temperature-programmed desorption of ammonia (NH3-TPD).
The HDO pathway was also investigated.
Experimental section
Materials and chemicals
Hydroxyapatite (HAP, ≥97%), 5-methylfurfural (98%),
levulinic acid (99.0%), ethyl levulinate (>98.0%),
2-methylfuran (98%), manganeseIJIII) oxide (Mn2O3, 98%),
ruthenium chloride hydrate (RuCl3·XH2O, 38.0–42.0% Ru
basis), ruthenium on carbon (5% Ru/C) and C8–C18 alkane
standard samples (≥99.5%) were purchased from Aladdin
Chemistry Co., Ltd. Cyclohexane (AR), methanol (AR), acetone
(AR), furfural (AR), benzaldehyde (AR), cyclopentanone (AR),
cyclohexanone (AR), hydrochloric acid (AR) and sodium
hydroxide (AR) were purchased from Sinopharm Chemical
Reagent Co., Ltd. Alpha-angelica lactone was purchased from
Shanghai Bide Pharmatech Co., Ltd. HZSM-5 zeolites with
different Si/Al ratios (Si/Al = 25, 50 and 80) were purchased
from the Catalyst Plant of Nankai University. Chloroform-D
was purchased from Qingdao Tenglong Weibo Technology
Co., Ltd. Dimethyl sulfoxide-D6 was purchased from
Cambridge Isotope Laboratories, Inc. 5-Hydroxymethylfurfural
was supplied by Hefei Leaf Energy Biotechnology Co., Ltd.
Furfural was purified by vacuum distillation and stored at
−15 °C. Other reagents were used without any pretreatment.
Catalyst preparation
The Ru/HAP catalyst was prepared by the wetness
impregnation method. The standard preparation procedure
is described below: 1.00 g of HAP carrier was added into 100
mL of acetone in a round-bottom flask equipped with a reflux
condenser and stirred at 55 °C. After that, 81.4 mg of RuCl3
·XH2O was dissolved in 15 mL of acetone and then added to
the above suspension dropwise. After stirring for 24 h,
acetone was removed by rotary evaporation and dried at 40
°C overnight. The catalyst precursor was reduced in a 10%/
90% H2/N2 flow (100 mL min
−1) at 280 °C (1 °C min−1) for 3
h. The actual ruthenium loading of the catalyst is 2.3% on
the basis of ICP analysis. The preparation method of the Ru/
HZSM-5 (Si/Al = 50) catalyst is similar to that of Ru/HAP, but
the carrier is different.
Catalyst characterization
The morphology of the catalysts was observed on a JEOL
JEM-2200FS analytical HRTEM system combined with a 200
kV field emission gun (FEG) and an in-column energy filter
(Omega Filter). The samples were suspended in ethanol.
Powder XRD patterns were obtained on a Rigaku D/max2500
VL/PC X-ray diffractometer (Rigaku Corporation,Tokyo,
Japan) using a Cu Kα radiation source (λ = 1.54056 Å) at 40
kV and 40 mA. XPS analysis was carried out on a VG MultiLab
2000 spectrometer (Thermo Electron Corporation) with Al Kα
radiation (1486.92 eV) as the excitation source (300 W). The
binding energies of recorded XPS spectra were calibrated
Table 1 Previous reports on HDO of complicated lignocellulose-derived oxygenates to alkanes
Entry Substrates Catalysts Conditions Alkane yields Ref.
1 Step 1: Pd/C Step 1: 160 °C, 4 MPa H2 C9–C10: 96% 9
Step 2: Pd–FeOX/SiO2 Step 2: 350 °C, 6 MPa H2
Step 1: Pd/C Step 1: 160 °C, 4 MPa H2 C8–C10: 94.9% 10
Step 2: Pd–Cu/SiO2 Step 2: 350 °C, 6 MPa H2
2 Pd/Hβ 280 °C, 8 MPa H2, 24 h C7–C15: 92.1% (Sel.) 11
Pd/C + ZrP 300 °C, 4 MPa H2, 3 h C13–C15: 70% 12
3 Pd/Hβ 280 °C, 8 MPa H2, 24 h C7–C18: 92.8% (Sel.) 11
Pd/C + ZrP 300 °C, 4 MPa H2, 3 h C13–C18: 43% 12
4 Pd/NbOPO4 220 °C, 6 MPa H2, 24 h C14–C15: 97.0% 13
5 Pt/ZrP 350 °C, H2: 60 mL min
−1 C9–C15: 94% 1
Pd/C + HfIJOTf)4 225 °C, 5 MPa H2, 24 h C9–C15: 97% 14
Pd/NbOPO4 200 °C, 4 MPa H2, 12 h C10–C15: 89.1% 15
Ir–ReOX/SiO2 170 °C, 5 MPa H2, 12 h C8–C15: 91% 16
Ni/Hβ 260 °C, 6 MPa H2 C9–C15: ∼70% 17
Ni/HZSM-5 260 °C, 6 MPa H2 C9–C15: 70.4% 18
Ni/ZrO2–ZrO2 280 °C, 5 MPa H2 C8–C15: 83% 19
Catalysis Science & TechnologyPaper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol.This journal is © The Royal Society of Chemistry 2020
versus the C 1s signal at 284.6 eV. Temperature-programmed
desorption of ammonia (NH3-TPD) analyses were conducted
in a home-built reactor system coupled to a gas
chromatograph with a thermal conductivity detector (TCD).
Before the NH3-TPD tests, the samples (100 mg) were
pretreated in an Ar flow at 500 °C for 60 min. After cooling
down to 40 °C, ammonia adsorption was carried out at 40 °C
for 60 min. Then, the physisorbed ammonia was removed by
purging with Ar at 40 °C for 60 min. Subsequently, the
temperature was increased to 500 °C at a heating rate of 10
°C min−1 in an Ar flow. Differential scanning calorimetry-
thermogravimetry analysis (DSC-TGA) was performed with an
SDT Q600V20.9 Build 20 in air from 40 °C to 800 °C using a
10 °C min−1 ramp rate. The composition of the Ru/HAP
catalyst was analyzed with atomic emission spectroscopy on
an Optima 7300DV inductively coupled plasma atomic
emission spectrometer (ICP-AES, PerkinElmer, Inc., USA).
The sample treatment procedure was as follows: 5 mL of
hydrochloric acid was added to a 10 mL round-bottom flask
containing 50 mg of catalyst and stirred at 80 °C for 24 h.
The mixture was then diluted to 25 mL in a volumetric flask.
Catalyst tests
The catalytic reactions were performed in a 25 mL stainless
steel autoclave equipped with a mechanical stirrer, a pressure
gauge, and automatic temperature control apparatus. In a
typical experiment, 100 mg feedstock, 100 mg Ru/HAP (2.3
wt% Ru in Ru/HAP), 100 mg HZSM-5 and 10 mL cyclohexane
were added to the reactor. The reactor was sealed, purged five
times with H2, and then pressurized with H2 to a set point.
The reactor was then heated to the desired temperature with
continuous stirring at 600 rpm to eliminate diffusion effects.
After the reaction, the reactor was cooled to ambient
temperature and a certain amount of internal standard
substance was added. The liquid product was transferred
with 20 mL of cyclohexane and the catalyst was separated by
centrifugation. The liquid products were identified using a
gas chromatography (Agilent 7890A)-mass spectrometry
detector (Agilent 5975C with a triple-axis detector) with a DB-
5MS column (30 m × 0.250 mm × 0.25 μm). The column
temperature was increased from 50 to 280 °C at a ramp rate
of 5 °C min−1 and held for 20 min. The liquid products were
quantified using a gas chromatograph (GC, Kexiao 1690) with
an HP-5 capillary column (30 m × 0.320 mm × 0.25 μm). The
column temperature was increased from 50 to 280 °C at a
ramp rate of 5 °C min−1 and held for 20 min. Bicyclohexane,
nonane and hexadecane were used as internal standards to
quantify the products. Specifically, bicyclohexane was used to
quantify the HDO products of compounds 1A, 2A, 3A and 4A;
hexadecane was used to quantify the HDO products of
compounds 5A, 6A and 9A. Nonane was used to quantify the
HDO products of compounds 7A and 8A. The conversion and
yield were calculated as follows:
Conv: mol%ð Þ ¼ 1 − moles of feedstock after reaction
moles of feedstock before reaction
� �
× 100%
Yield mol%ð Þ ¼ moles of each product
moles of feedstock before reaction
× 100%
During the catalyst stability test, the catalyst was
separated by centrifugation and washed three times with
dichloromethane followed by washing three times with
cyclohexane. After that, the catalyst was used for the next run
directly or characterized after drying at 80 °C.
Results and discussion
Initially, a C10 oxygenate (3-(furan-2-ylmethylene)-5-
methylfuran-2IJ3H)-one, i.e., compound 1A in Scheme 1) was
chosen as a model compound which could be synthesized by
aldol condensation of furfural41 and α-angelica lactone42,43
(ESI†). Both of them are important lignocellulosic platform
molecules.41–43 Complete HDO of 1A to alkanes requires
hydrogenation of the carbon–carbon double bonds and
hydrogenolysis of the lactone and tetrahydrofuran rings. Ru/
HAP was used as the catalyst for the HDO of 1A and 36.6%
C8–C10 alkanes were obtained at 180 °C and 4 MPa H2 in
cyclohexane (Table 2, entry 1). As shown in Fig. 1, other
products in the HDO of 1A over Ru/HAP were mainly
tetrahydrofuran compounds and alcohols. No product with a
lactone ring was detected. According to previous
reports,11,44,45 zeolites have been a favoured catalyst for HDO
of biomass-derived compounds via dehydration because of
their excellent acid properties. We also synthesized a Ru/
HZSM-5 (Si/Al = 50) catalyst for HDO of 1A (Table 2, entry 2).
No alkanes were found but several oxygenated intermediates
were detected. It was noted that all of these intermediates
have a lactone ring structure and some of the tetrahydrofuran
rings were opened (Fig. 1). For comparison, Ru/C, a
commercial catalyst, was employed under the same
conditions (Table 2, entry 3). No alkane was found but an
oxygenated intermediate was detected, which came from the
hydrogenation of the carbon–carbon double bonds of 1A
(Fig. 1). Based on the above results, all of the three Ru-based
catalysts exhibited excellent hydrogenation activity for
carbon–carbon double bonds. However, they showed a
significant difference in the hydrogenolysis of the lactone
rings and tetrahydrofuran rings. Ru/HAP exhibited high
hydrogenolysis activity and opened all of the lactone rings
and some of the tetrahydrofuran rings. Ru/HZSM-5 showed a
certain hydrogenolysis activity and opened some of the
Scheme 1 One-pot hydrodeoxygenation of compound 1A to C8–C10
alkanes under mild conditions.
Catalysis Science & Technology Paper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol. This journal is © The Royal Society of Chemistry 2020
tetrahydrofuran rings, which should have benefitted from the
acid sites of HZSM-5.14 The hydrogenolysis activity of Ru/C
was weak and could not open either lactone rings or
tetrahydrofuran rings.
Based on a previous study and the above results, acidic
HZSM-5 can help the cleavage of the ether bond in
tetrahydrofuran rings and dehydration of hydroxyl groups.46
HZSM-5 zeolites with different Si/Al ratios (25, 50 and 80)
were physically mixed with Ru/HAP to promote the ring
opening reaction of tetrahydrofuran and dehydration of
alcohols. Generally, the acidity (acid amount and strength)
of HZSM-5 decreases as the Si/Al ratio increases.47 As
shown in Table 2, entries4–6, the presence of HZSM-5
increased the total yield of C8–C10 alkanes to various
degrees. HZSM-5 with Si/Al lower than or equal to 50 that
possesses an appropriately high acid amount and acid
strength led to a significant increase of total alkane yield.
In contrast, the promotion by HZSM-5 (80) with a lower
acid amount and weak acidity was limited. The change in
product distribution could be seen from Fig. 1. When Ru/
HAP was used alone, compounds with a tetrahydrofuran
ring and a small amount of alcohols were present in the
product. However, when HZSM-5 (50) was added
concomitantly, the tetrahydrofuran compounds and
alcohols were almost completely converted. HZSM-5 (50)
was also physically mixed with Ru/HZSM-5 (50) and Ru/C
for the HDO of 1A, respectively. For the former (Table 2,
entry 7), a little amount of alkanes was generated, and the
other products were two kinds of lactone compounds with
alkyl groups (Fig. 1). For the latter (Table 2, entry 8), a
small amount of products with an opened tetrahydrofuran
ring was detected. These results demonstrated that the Ru-
based catalysts exhibited high activity for hydrogenation of
carbon–carbon double bonds. Ru/HAP showed high activity
for hydrogenolysis of the lactone ring and a certain activity
for hydrogenolysis of the tetrahydrofuran ring, and HZSM-5
with the desired acidity was conducive to tetrahydrofuran
ring opening and dehydration.
Table 2 HDO of 1A over different catalysts
Entry Catalyst
Alkane yields/%
C8 C9 C10 Total
1 Ru/HAP 12.8 16.2 7.6 36.6
2 Ru/HZSM-5 (50) 0.0 0.0 0.0 0.0
3 Ru/C 0.0 0.0 0.0 0.0
4 Ru/HAP + HZSM-5 (25) 19.6 43.1 27.8 90.5
5 Ru/HAP + HZSM-5 (50) 18.6 43.8 29.5 91.9
6 Ru/HAP + HZSM-5 (80) 7.1 25.9 20.7 53.7
7 Ru/HZSM-5 (50) + HZSM-5 (50) 1.3 2.1 3.7 7.1
8 Ru/C + HZSM-5 (50) 0.0 0.0 0.0 0.0
Reaction conditions: 100 mg of 1A, 100 mg of Ru-based catalyst, 100 mg of HZSM-5, 10 mL cyclohexane, 180 °C, 4 MPa H2, 10 h and 600 rpm.
Conversion is 100% in all cases. Other products could be seen in Fig. 1.
Fig. 1 The comparison of gas chromatograms of HDO of 1A with different catalysts. Reaction conditions: 100 mg of 1A, 100 mg of Ru-based
catalyst, 100 mg of HZSM-5, 10 mL cyclohexane, 180 °C, 4 MPa H2, 10 h and 600 rpm.
Catalysis Science & TechnologyPaper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol.This journal is © The Royal Society of Chemistry 2020
A series of experiments were carried out to investigate the
effects of reaction temperature and hydrogen pressure on the
HDO of 1A over the Ru/HAP + HZSM-5 (50) co-catalyst. The
temperature effect on HDO of 1A is shown in Fig. 2(a). When
the reaction was performed at 150 °C, only 18.8% yield of
C8–C10 alkanes was acquired. Significant improvement of
the C8–C10 alkane yield could be seen when the reaction
temperature was raised to 160 °C, which indicated that a
sufficiently high temperature was necessary to overcome the
energy barrier in the HDO process. The total yield of C8–C10
alkanes reached maximum (91.9%) at 180 °C. However, when
the temperature was further increased to 190 °C, the total
alkane yield decreased slightly. The change in product
distribution was even more remarkable, in which the C8
alkanes increased accompanied by the C9 and C10 alkanes
decreasing. High temperature promoted decarbonylation,
decarboxylation and hydrocracking of branched alkyl groups
and these could be restrained at lower temperature.
The effect of initial hydrogen pressure on HDO of 1A is
shown in Fig. 2(b). When the hydrogen pressure was 2
MPa, only 41.4% yield of C8–C10 alkanes was obtained
where C8 and C9 alkanes were the main products. The
total yield of C8–C10 alkanes was increased greatly as the
hydrogen pressure rose from 2 MPa to 4 MPa, which
promoted the production of C9 and C10 alkanes. When the
hydrogen pressure was increased further to 5 MPa, there
was no significant increase of total alkane yield. This
meant that a 4 MPa hydrogen pressure was suitable for
HDO of 1A and this pressure was chosen for the following
research.
The effect of reaction time on HDO of 1A over Ru/HAP +
HZSM-5 (50) was studied at 180 °C and 160 °C, respectively.
When the reaction was conducted at 180 °C (Fig. 2c), 27.4%
yield of C8–C10 alkanes were acquired in the initial 2 h, with
100% conversion. As the reaction time was increased to 4 h,
the total yield of C8–C10 alkanes reached 80.4%, which far
beyond twice the total alkane yield obtained in the first 2 h,
indicating that the partially saturated oxygenated
intermediates were further converted to alkanes in the HDO
process. The maximal yield (93.8%) was achieved at 15 h.
When the reaction time was extended to 24 h, the total yield
of C8–C10 alkanes decreased slightly, which could be due to
the hydrocracking of branched alkyl groups at high
temperature.
To get further insight into the reaction pathways, the HDO
of 1A at 160 °C with different times was carried out as well.
Compared with the case at 180 °C, the lower temperature led
to a slower HDO rate. As shown in Fig. 2(d), only 14.0% C8–
C10 alkanes were acquired in the initial 5 h, and other
products mainly consisted of tetrahydrofuran compounds,
lactone compounds and a dialkyl tetrahydropyran, as shown
in Fig. 3. It was noted that 2,4-dipropyltetrahydrofuran and
2-methyl-6-propyltetrahydropyran were generated from the
HDO of 1A. As the reaction time was prolonged to 10 h, a
large proportion of the oxygen-containing intermediates were
converted, and the total yield of C8–C10 alkanes reached
80.2%, which took only 4 h at 180 °C. When the reaction
time was continuously extended to 24 h, the total yield of
C8–C10 alkanes kept increasing slowly and finally reached
90.7%. The decrease of total alkane production rate could be
Fig. 2 The conversion and product distribution of HDO of 1A as a function of (a) temperature, (b) pressure and (c) and (d) time. Reaction
conditions: 100 mg of 1A, 100 mg of Ru/HAP catalyst (Ru/1A = 2.3%), 100 mg of HZSM-5 (50), 10 mL cyclohexane, 600 rpm, (a) 4 MPa H2, 10 h, (b)
180 °C, 10 h, (c) 180 °C, 4 MPa H2, (d) 160 °C, 4 MPa H2.
Catalysis Science & Technology Paper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol. This journal is © The Royal Society of Chemistry 2020
the result of the decrease of the residual intermediate
concentration. By comparing the distribution of alkane
products at different temperatures, it could be found that C9
alkanes were the most abundant products in both cases. The
C10 alkane yield at low temperature was higher than that at
high temperature, while the C8 alkane yield exhibited the
opposite trend. From the perspective of atom economy and
environmental friendliness, low temperature was better than
high temperature, but the conversion efficiency was the
opposite.
Based on the detailed studies of product change over
reaction time (Fig. 3), possible reaction pathways over the
Ru/HAP + HZSM-5 (50) co-catalyst are proposed, as shown in
Scheme 2. First, 1A is converted into 1B rapidly by
hydrogenation of the four carbon–carbon double bonds.
Then, the following conversion process can be generally
divided into three pathways, in which pathway 1 and pathway
2 are the primary pathways. In pathway 1, 1B is first
converted to the tetrahydrofuran compounds via
hydrogenolysis of the lactone ring. Then, alkanes are formed
by tetrahydrofuran ring opening, dehydration and
hydrogenation. The main difference between pathway 2 and
pathway 1 is the hydrogenolysis sequence of the two cyclic
structures of 1B. In pathway 2, 1B is initially converted into
lactones followed by hydrogenolysis of the lactone ring,
dehydration and hydrogenation, and the relevant alkanes are
acquired.Pathway 3 is a special side reaction process in HDO
of 1A. Small amounts of diols (2-propyl-1,4-heptanediol and
2,6-nonanediol) are generated from the hydrogenolysis of the
lactone ring and tetrahydrofuran ring of 1B followed by
dehydration and decarbonylation, respectively. They are
unstable under acidic conditions and easily
dehydrated to 2,4-dipropyltetrahydrofuran and 2-methyl-6-
Fig. 3 The comparison of the gas chromatograms of HDO of 1A at 160 °C at different times. Reaction conditions: 100 mg of 1A, 100 mg of Ru/
HAP catalyst (Ru/1A = 2.3%), 100 mg of HZSM-5 (50), 10 mL cyclohexane, 160 °C, 4 MPa H2 and 600 rpm. “0 h” means that the heating was
stopped immediately when the reactor was heated to 160 °C.
Scheme 2 Possible reaction pathways for HDO of 1A with the Ru/
HAP + HZSM-5 (50) co-catalyst.
Catalysis Science & TechnologyPaper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol.This journal is © The Royal Society of Chemistry 2020
propyltetrahydropyran. After hydrogenolysis, dehydration and
hydrogenation, the relevant alkanes are obtained.
To figure out the reason for the different hydrogenolysis
activities of the three Ru-based catalysts, HRTEM, XRD, XPS
and NH3-TPD characterization were conducted. The
morphology and metal dispersion of Ru-based catalysts were
characterized by HRTEM. As shown in Fig. 4(a–c), the
undersized Ru nanoclusters are highly dispersed on the HAP
carrier. The average Ru particle size of the Ru/HAP catalyst
was approximately 1.3 nm estimated from randomly selected
particles in HRTEM analysis. The Ru nanoclusters in Ru/
HZSM-5 were quite dispersive as well and the average Ru
particle size was about 2.6 nm. For Ru/C, it could be clearly
seen that relatively large Ru particles were distributed on
activated carbon, and the average Ru particle size was about
5.1 nm.
The powder XRD patterns are shown in Fig. 4(d). The
diffraction spectrum of Ru/HAP was similar to that of pure
HAP, which indicated that Ru did not change the bulk crystal
structure of HAP. No diffraction peak of Ru particles for all
the three catalysts appeared by comparing the diffraction
spectra of the catalysts with that of Ru0 (JCPDS no. 06-0663),
also indicating that Ru nanoparticles were well dispersed.
The highly dispersed Ru nanoparticles anchored on the HAP
surface provided more metal active sites, which could be an
important reason for Ru/HAP having better hydrogen
activation ability.
The chemical state of the Ru-based catalysts was
investigated by XPS. Due to the overlap of Ru 3d with the C
1s region in all cases (Fig. S1, ESI†), the Ru 3p orbital level
was employed. According to Fig. 4(e), the binding energy
peaks for Ru 3p3/2 of Ru/HAP, Ru/HZSM-5 and Ru/C were at
462.7 eV, 463.1 eV and 463.0 eV, respectively. The lower
binding energy of Ru in Ru/HAP could be due to the electron
donor effect of HAP, which increased the electron density of
Ru.28,32 According to previous studies,32 the active Ru with a
higher electron density led to better hydrogen activation
ability. The outstanding hydrogen activation ability of Ru/
HAP led to high activity for lactone ring hydrogenolysis.
According to the results shown in Fig. 1, Ru/HZSM-5 had
no lactone ring hydrogenolysis ability but displayed good
tetrahydrofuran ring hydrogenolysis and dehydration activity,
which could be attributed to the acidity of the catalyst.14,46
NH3-TPD analyses of the Ru-based catalysts were carried out
(Fig. 5). It could be seen that Ru/HZSM-5 has abundant weak
and medium strong acid sites. Ru/HAP showed a certain
amount of weak and medium strong acid sites. Ru/C has a
little of weak acid sites. These rationalized the phenomenon
Fig. 4 Characterization of Ru-based catalysts. HRTEM images of (a) Ru/HAP, (b) Ru/HZSM-5 (50) and (c) Ru/C; (d) powder XRD patterns; (e) XPS
spectra of the Ru 3p3/2 region.
Catalysis Science & Technology Paper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol. This journal is © The Royal Society of Chemistry 2020
that Ru/HZSM-5 showed better ability for tetrahydrofuran
ring hydrogenolysis and dehydration than Ru/HAP, and Ru/C
was ineffective.
Eight more complicated oxygenates were synthesized with
common lignocellulosic platform molecules, including
furfural,41 α-angelica lactone,42,43 5-hydroxymethylfurfural,48
benzaldehyde,49 levulinic acid,50 cyclopentanone,51
5-methylfurfural,52 cyclohexanone28,53 and 2-methylfuran.54
The detailed information of preparation, characterization
and conversion of these oxygenates are presented in the ESI.†
These oxygenates were deemed as promising alternatives for
the large-scale production of diesel or jet fuel and therefore
were widely studied. The reaction was conducted at 160 °C
and 4 MPa H2 for 24 h without further optimization
(Table 3). Compounds 2A and 3A were the condensation
products of α-angelica lactone with 5-HMF and
benzaldehyde, respectively. By conducting the HDO of 2A, the
total alkane yield was 78.9%. 92.7% branched cycloalkanes
could be obtained when 3A was employed as the substrate.
Compounds 4A and 5A were derived from the aldol
condensation of levulinic acid and furfural via the
α-carbanion generated from levulinic acid attacking the
aldehyde group of furfural. The total alkane yields of HDO of
4A and 5A were 87.8% and 74.5%, respectively. Compounds
6A, 7A and 8A were three oxygenates derived from the aldol
condensation of cyclic ketones and furanaldehydes. Multiple
branched cycloalkanes could be obtained with comparable
yield. Particularly, the total alkane yield of HDO of 7A
reached up to 91.1%. Compound 9A could be synthesized by
the acid catalyzed hydroxylation/alkylation reaction of
furfural and 2-methylfuran. When the HDO of 9A was
performed, 69.7% total alkane yield could be achieved.
Although the reaction conditions were adopted from those of
substrate 1A without further optimization, the above results
indicated that the Ru/HAP + HZSM-5 co-catalyst exhibited the
desired activity in the HDO of a wide range of complicated
lignocellulose-derived oxygenates. The alkanes synthesized
above included straight, branched, and cyclic alkanes and
Fig. 5 NH3-TPD characterization of Ru-based catalysts.
Table 3 HDO of other lignocellulose-derived oxygenates
Entry Oxygenates
Alkane yields/%
C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 Total
2A 7.1 30.9 33.9 7.0 — — — — — — — 78.9
3A 1.3 1.6 0.9 55.5 33.4 — — — — — — 92.7
4A 36.5 40.6 10.7 — — — — — — — — 87.8
5A 0.3 0.5 1.4 0.5 3.0 18.3 32.8 17.7 — — — 74.5
6A — 0.2 0.1 — — 28.7 32.6 16.3 — — — 77.9
7A — — 0.2 — 6.8 — 0.7 0.9 2.1 1.5 78.9 91.1
8A — — 0.1 0.5 1.2 — 4.8 22.3 28.1 11.4 4.5 72.9
9A — 2.7 11.8 10.4 — 1.4 12.2 31.2 — — — 69.7
Reaction conditions: 100 mg of substrate, 100 mg of Ru/HAP catalyst (Ru/substrate = 2.3%), 100 mg of HZSM-5 (50), 10 mL cyclohexane, 160
°C, 4 MPa H2, 24 h and 600 rpm.
Catalysis Science & TechnologyPaper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol.This journal is © The Royal Society of Chemistry 2020
the carbon atom number of these alkanes ranged from 8 to
18. They could be employed as diesel or jet fuel. As a
potential application, the Ru/HAP based catalyst could be
used for converting various kinds of biomass-based
oxygenates into high quality fuels.
The stability and recyclability of the Ru/HAP + HZSM-5
catalyst were investigated (Table S3†). It could be found that
deactivation occurred when the catalyst was subjected to a
second run (Table S3,† entries a1 anda2), in which only a
trace amount of alkanes was produced and the product is
mainly oxygenated intermediates. If fresh HZSM-5 was added
to the used catalyst and tested for a second run (Table S3,†
entries b1 and b2), only a slight decrease of alkane yield was
observed. Therefore, it was HZSM-5 that has a tendency to
deactivate during the reaction. ICP-AES and TEM analysis
indicated no significant Ru leaching or Ru nanoparticle
agglomeration after HDO (Fig. S2†). The XRD patterns of the
catalyst before and after use are shown in Fig. S3.† It could
be found that the diffraction peak intensities of HZSM-5
(such as those at 2θ = 5–10° and 23–25°) weakened while
those of Ru/HAP (such as those at 2θ = 31–35° and 38–41°)
were nearly unchanged. DSC-TGA was conducted on the fresh
and used catalysts (Ru/HAP + HZSM-5) and substrate 1A (Fig.
S4†). Comparing the heat flow curves of the fresh and used
catalysts, it could be found that the latter had a distinct
exothermic peak. Since the peak was in a low temperature
range (200–340 °C), the temperature is not high enough to
oxidize carbon deposits under normal conditions. The peak
could be attributed to the thermal effect of unstable
oligomers deposited in the catalysts, especially in the pores
of acidic HZSM-5. The formation of oligomers which may
cover the acid sites of HZSM-5 as well as the structure change
of HZSM-5 (XRD result) led to the catalyst deactivation.
Conclusions
In this work, a highly dispersed Ru/HAP catalyst was
prepared. It exhibited high hydrogenolysis activity compared
with the other two Ru-based catalysts (Ru/C and Ru/HZSM-5)
in the HDO process of 3-(furan-2-ylmethylene)-5-methylfuran-
2IJ3H)-one (1A). When the acidic HZSM-5 catalyst was mixed
with Ru/HAP, the HDO of 1A was significantly promoted.
Both temperature and initial hydrogen pressure affected the
product distribution significantly. By tracking the product
change with time, the possible reaction pathway was also
proposed. Characterization indicated that the electron donor
effect of HAP led to the generation of highly dispersed
electron-rich Ru, which demonstrated stronger hydrogen
activation and hydrogenolysis ability. The Ru/HAP + HZSM-5
co-catalyst was applied to one-pot HDO of nine complicated
lignocellulose-derived oxygenates. Under mild conditions
(160 °C and 4 MPa H2), a series of diesel or jet fuel range
alkanes (C8–C18), including straight, branched, and cyclic
alkanes, were obtained with the desired yield. This work
provided an efficient way for liquid fuel production from
lignocellulose-derived oxygenates. Further work regarding the
synthesis of more stable and efficient acidic catalysts
combined with Ru/HAP is ongoing in our group.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was financially supported by the National Key R&D
Program of China (2018YFB1501502), the NSFC (51876200)
and the DNL Cooperation Fund, CAS (DNL180301).
References
1 G. Li, N. Li, Z. Wang, C. Li, A. Wang, X. Wang, Y. Cong and
T. Zhang, ChemSusChem, 2012, 5, 1958–1966.
2 B. G. Harvey and R. L. Quintana, Energy Environ. Sci.,
2010, 3, 352–357.
3 G. W. Huber, J. N. Chheda, C. J. Barrett and J. A. Dumesic,
Science, 2005, 308, 1446–1450.
4 J. Q. Bond, D. M. Alonso, D. Wang, R. M. West and J. A.
Dumesic, Science, 2010, 327, 1110–1114.
5 R. Xing, A. V. Subrahmanyam, H. Olcay, W. Qi, G. P. van
Walsum, H. Pendse and G. W. Huber, Green Chem., 2010, 12,
1933–1946.
6 H. Olcay, A. V. Subrahmanyam, R. Xing, J. Lajoie, J. A.
Dumesic and G. W. Huber, Energy Environ. Sci., 2013, 6,
205–216.
7 A. Corma, O. de la Torre, M. Renz and N. Villandier, Angew.
Chem., Int. Ed., 2011, 50, 2375–2378.
8 A. Corma, O. de la Torre and M. Renz, Energy Environ. Sci.,
2012, 5, 6328–6344.
9 J. Xu, N. Li, X. Yang, G. Li, A. Wang, Y. Cong, X. Wang and T.
Zhang, ACS Catal., 2017, 7, 5880–5886.
10 J. Xu, L. Li, G. Li, A. Wang, Y. Cong, X. Wang and N. Li, ACS
Sustainable Chem. Eng., 2018, 6, 6126–6134.
11 Q. Deng, J. Xu, P. Han, L. Pan, L. Wang, X. Zhang and J.-J.
Zou, Fuel Process. Technol., 2016, 148, 361–366.
12 Q. Liu, C. Zhang, N. Shi, X. Zhang, C. Wang and L. Ma, RSC
Adv., 2018, 8, 13686–13696.
13 C. Li, D. Ding, Q. Xia, X. Liu and Y. Wang, ChemSusChem,
2016, 9, 1712–1718.
14 S. Dutta and B. Saha, ACS Catal., 2017, 7, 5491–5499.
15 Q. Xia, Y. Xia, J. Xi, X. Liu, Y. Zhang, Y. Guo and Y. Wang,
ChemSusChem, 2017, 10, 747–753.
16 S. Liu, S. Dutta, W. Zheng, N. S. Gould, Z. Cheng, B. Xu,
B. Saha and D. G. Vlachos, ChemSusChem, 2017, 10,
3225–3234.
17 G. Li, N. Li, J. Yang, L. Li, A. Wang, X. Wang, Y. Cong and T.
Zhang, Green Chem., 2014, 16, 594–599.
18 S. Li, N. Li, G. Li, L. Li, A. Wang, Y. Cong, X. Wang and T.
Zhang, Green Chem., 2015, 17, 3644–3652.
19 T. Wang, K. Li, Q. Liu, Q. Zhang, S. Qiu, J. Long, L. Chen, L.
Ma and Q. Zhang, Appl. Energy, 2014, 136, 775–780.
20 H. Sun, F. Z. Su, J. Ni, Y. Cao, H. Y. He and K. N. Fan, Angew.
Chem., Int. Ed., 2009, 48, 4390–4393.
Catalysis Science & Technology Paper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
Catal. Sci. Technol. This journal is © The Royal Society of Chemistry 2020
21 S. Sebti, R. Tahir, R. Nazih, A. Saber and S. Boulaajaj, Appl.
Catal., A, 2002, 228, 155–159.
22 M. Gruselle, T. Kanger, R. Thouvenot, A. Flambard, K. Kriis,
V. Mikli, R. Traksmaa, B. Maaten and K. Tõnsuaadu, ACS
Catal., 2011, 1, 1729–1733.
23 K. Yamaguchi, K. Mori, T. Mizugaki, K. Ebitani and K.
Kaneda, J. Am. Chem. Soc., 2000, 122, 7144–7145.
24 K. Mori, K. Yamaguchi, T. Hara, T. Mizugaki, K. Ebitani
and K. Kaneda, J. Am. Chem. Soc., 2002, 124,
11572–11573.
25 B. Yan, L.-Z. Tao, Y. Liang and B.-Q. Xu, ACS Catal., 2014, 4,
1931–1943.
26 M. Khachani, M. Kacimi, A. Ensuque, J.-Y. Piquemal, C.
Connan, F. Bozon-Verduraz and M. Ziyad, Appl. Catal., A,
2010, 388, 113–123.
27 P. Zhang, T. Wu, T. Jiang, W. Wang, H. Liu, H. Fan, Z. Zhang
and B. Han, Green Chem., 2013, 15, 152–159.
28 G. Xu, J. Guo, Y. Zhang, Y. Fu, J. Chen, L. Ma and Q. Guo,
ChemCatChem, 2015, 7, 2485–2492.
29 C. Li, G. Xu, X. Liu, Y. Zhang and Y. Fu, Ind. Eng. Chem. Res.,
2017, 56, 8843–8849.
30 G. Xu, Y. Zhang, Y. Fu and Q. Guo, ACS Catal., 2017, 7,
1158–1169.
31 W. Jia, G. Xu, X. Liu, F. Zhou, H. Ma, Y. Zhang and Y. Fu,
Energy Fuels, 2018, 32, 8438–8446.
32 M. Hua, J. Song, C. Xie, H. Wu, Y. Hu, X. Huang and B. Han,
Green Chem., 2019, 21, 5073–5079.
33 A. Fukuoka and P. L. Dhepe, Angew. Chem., Int. Ed., 2006, 45,
5161–5163.
34 C. Luo, S. Wang and H. Liu, Angew. Chem., Int. Ed., 2007, 46,
7636–7639.
35 J.-H. Guo, G.-Y. Xu, F. Shen, Y. Fu, Y. Zhang and Q.-X. Guo,
Green Chem., 2015, 17, 2888–2895.
36 B. Op de Beeck, M. Dusselier, J. Geboers, J. Holsbeek, E.
Morré, S. Oswald, L. Giebeler and B. F. Sels, Energy Environ.
Sci., 2015, 8, 230–240.
37 Z. Luo, Y. Wang, M. He and C. Zhao, Green Chem., 2016, 18,
433–441.
38 G.-Y. Xu, J.-H. Guo, Y.-C. Qu, Y. Zhang, Y. Fu and Q.-X. Guo,
Green Chem., 2016, 18, 5510–5517.
39 L. Dong, L. Lin, X. Han, X. Si, X. Liu, Y. Guo, F. Lu, S. Rudić,
S. F. Parker, S. Yang and Y. Wang, Chem, 2019, 5, 1521–1536.
40 G. Li, B. Hou, A. Wang, X. Xin, Y. Cong, X. Wang, N. Li and
T. Zhang, Angew. Chem., Int. Ed., 2019, 58, 12154–12158.
41 R. Mariscal, P. Maireles-Torres, M. Ojeda, I. Sádaba and M.
López Granados, Energy Environ. Sci., 2016, 9, 1144–1189.
42 S. G. Wettstein, D. M. Alonso, Y. Chong and J. A. Dumesic,
Energy Environ. Sci., 2012, 5, 8199–8203.
43 M. Mascal, S. Dutta and I. Gandarias, Angew. Chem., Int. Ed.,
2014, 53, 1854–1857.
44 C. Zhao and J. A. Lercher, Angew. Chem., Int. Ed., 2012, 51,
5935–5940.
45 P. Han, G. Nie, J. Xie, X.-t.-f. E, L. Pan, X. Zhang and J.-J.
Zou, Fuel Process. Technol., 2017, 163, 45–50.
46 N. Li and G. W. Huber, J. Catal., 2010, 270, 48–59.
47 L. Xu, Y. Jiang, Q. Yao, Z. Han, Y. Zhang, Y. Fu, Q. Guo and
G. W. Huber, Green Chem., 2015,17, 1281–1290.
48 R. J. van Putten, J. C. van der Waal, E. de Jong, C. B.
Rasrendra, H. J. Heeres and J. G. de Vries, Chem. Rev.,
2013, 113, 1499–1597.
49 Z.-Z. Zhou, M. Liu and C.-J. Li, ACS Catal., 2017, 7,
3344–3348.
50 R. Weingarten, W. C. Conner and G. W. Huber, Energy
Environ. Sci., 2012, 5, 7559–7574.
51 Y. Yang, Z. Du, Y. Huang, F. Lu, F. Wang, J. Gao and J. Xu,
Green Chem., 2013, 15, 1932–1940.
52 Y. Peng, X. Li, T. Gao, T. Li and W. Yang, Green Chem.,
2019, 21, 4169–4177.
53 F. Liu, Q. Liu, A. Wang and T. Zhang, ACS Sustainable Chem.
Eng., 2016, 4, 3850–3856.
54 Y. Shi, Y. Zhu, Y. Yang, Y.-W. Li and H. Jiao, ACS Catal.,
2015, 5, 4020–4032.
Catalysis Science & TechnologyPaper
Pu
bl
is
he
d 
on
 0
9 
Ja
nu
ar
y 
20
20
. D
ow
nl
oa
de
d 
by
 U
N
IV
E
R
SI
T
E
 P
A
R
IS
 S
U
D
 o
n 
1/
25
/2
02
0 
12
:0
5:
38
 P
M
. 
View Article Online
https://doi.org/10.1039/c9cy02367d
	crossmark: