Preparation of the Ru/HZSM-5 catalyst and its catalytic performance for the 2-pentanone hydrodeoxygenation reaction

Article abstract of DOI:10.1039/d1nj03504e

Levulinic acid is an ideal model compound for complex oxygenated components in bio-oil. To assist the understanding of its hydrodeoxygenation (HDO) performance, it is necessary to investigate separately the HDO property of the ketonic carbonyl group and carboxyl group. Herein, 2-pentanone was selected as a model to study the HDO property of the ketonic carbonyl group. The Ru/HZSM-5 catalyst was prepared by an excessive impregnation method and its structure and acidity were characterized by H₂-TPR, NH₃-TPD, HRTEM, SEAD, Py-IR, TG-DSC, and ICP analyses. The effect of preparation conditions on the catalytic performance of Ru/HZSM-5 was studied; the suitable preparation conditions were determined as follows: a calcination temperature of 450 °C, a calcination time of 3 h, a reduction temperature of 350 °C, and a reduction time of 4 h. The catalytic performance of Ru/HZSM-5 for the 2-pentanone HDO reaction was evaluated; pentane selectivity of 77.7% at a 2-pentanone conversion of 91.8% was achieved under the conditions of a reaction pressure of 5 MPa, a reaction temperature of 190 °C, a catalyst amount of 6 wt% and a reaction time of 6 h. 2-Pentanone HDO follows the reaction path of 2-pentanone hydrogenation to 2-pentanol and then 2-pentanol dehydration and hydrogenation to the target product pentane. The acidity of the catalyst plays a certain role in influencing its catalytic performance: Lewis acid sites show high activity for activating C-O bonds and Br?nsted acid sites are the key to accelerate the further dehydration of 2-pentanol and hydrogenation to alkanes.

Full text of DOI:10.1039/d1nj03504e

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Preparation of Ru/HZSM-5 catalyst and its catalytic
performance for 2-pentanone hydrodeoxygenation reaction
Received 00th April 2021
Accepted 00th April 2021
a
a
a
a
a
Xi Xi , Ye Yang , Hualiang An* , Xinqiang Zhao* and Yanji Wang
DOI: 10.1039/x0xx00000x
Levulinic acid is an ideal model compound of the complex oxygenated components in bio-oil. To assist the understanding of
its hydrodeoxygenation (HDO) performance, it is necessary to investigate separately the HDO property of ketonic carbonyl
group and carboxyl group. Herein 2-pentanone was selected as a model to study the HDO property of ketonic carbonyl
group. The Ru/HZSM-5 catalyst was prepared by an excessive impregnation method and its structure and acidity were
2 3
characterized by H -TPR, NH -TPD, HRTEM, SEAD, Py-IR, TG-DSC, and ICP analyses. The effect of preparation
conditions on the catalytic performance of Ru/HZSM-5 was studied; the suitable preparation conditions were determined as
follows: a calcination temperature of 450°C, a calcination time of 3 h, a reduction temperature of 350°C, and a reduction
time of 4 h. The catalytic performance of Ru/HZSM-5 for 2-pentanone HDO reaction was evaluated; pentane selectivity of
7
7.7% at a 2-pentanone conversion of 91.8% was received under the conditions of a reaction pressure of 5 MPa, a reaction
temperature of 190 °C, a catalyst amount of 6 wt.% and a reaction time of 6 h. 2-Pentanone HDO follows the reaction path
of 2-pentanone hydrogenation to 2-pentanol and then 2-pentanol dehydration and hydrogenation to the target product
pentane. The acidity of the catalyst plays a certain role in influencing its catalytic performance: Lewis acid sites have high
activity for activating C=O bond and Brφnsted acid sites are the key to accelerate the further dehydration of 2-pentanol and
hydrogenation to alkanes.
.
6,7. Among
2
metals can activate both oxygenated compounds and H
Introduction
the noble metals, Ru shows outstanding hydrogenation activity and
selectivity. Li 8 explored the catalytic properties of Ru/NCNT
Environmental pollution and energy shortage are two major
obstacles to the development of our society. The rapid consumption
of fossil fuels has aroused global concern about energy
sustainability. It is urgent to explore renewable energy and new
2 2
(nitrogen-modified carbon nanotubes), Ru/Al O3, Ru/SiO2, Ru/TiO
and Ru/C for stearic acid HDO reaction and found that C17 alkane
yield of 86.8% could be reached at a complete conversion of stearic
emissions 1,2. Bio-oil is one of
acid over the Ru/NCNT catalyst under the H
25°C and 4 h. This proves that Ru/NCNT can selectively break C-
O bond in the HDO reaction. Wang et al 7 studied the catalytic
performance of Ru/AC, Ru/AC-SO H (sulfonated activated carbon)
and Ru/SiO for acetophenone HDO reaction and found that the
conversion of acetophenone respectively reached 53%, 65% and
00% over the three catalysts at H pressure of 3 MPa, 150 °C and 3
h. The selectivity of the deoxygenated product was up to 90% over
Ru/AC-SO H while it was less than 15% over Ru/AC and Ru/SiO
2
pressure of 4 MPa,
energy sources with low NO and SO
x x
2
the renewable energy sources. Although it has low emission and
good biodegradability, it suffers from some disadvantages such as
poor chemical stability, low enthalpy of combustion and high
viscosity due to the existence of a large number of oxygen-
containing groups such as aldehydes, furans, phenols, ketones, etc. 3
3
2
1
2
Hydrodeoxygenation (HDO) can effectively reduce the oxygen
content of bio-oil 4 and improve its combustion performance. The
3
2
.
core of the research on bio-oil HDO is still the development of high-
performance catalyst. In order to ensure the excellent HDO
performance of catalyst, it is necessary for the catalyst to possess
good activation and adsorption ability for "C-O" and "C=O" bonds
This shows that the selectivity of deoxygenation is related to the
acidity of catalyst and strong acidic sites are beneficial to the
deoxygenation of acetophenone and its intermediates. HZSM-5 is
widely used as a solid acid catalyst and an acidic support with good
5
and high dissociation ability for "H-H" bond . Supported noble
9
thermal stability . Based on the synergy between the acidic sites of
metals have been proved to be efficient HDO catalysts because noble
support and the active metal components, a bifunctional catalyst
could improve the catalytic activity for HDO reaction 10. Therefore,
a. Hebei Provincial Key Lab of Green Chemical Technology and Efficient Energy
Saving, National Local Joint Laboratory of Energy-saving Process Integration and
Resource Utilization in Chemical Industry, School of Chemical Engineering and
Technology, Hebei University of Technology,
some researchers prepared bifunctional HZSM-5 supported metal
catalysts and obtained good results. Lange et al 11 realized the
selective deoxygenation of γ-valerolactone (GVL) to valerate with a
Tianjin, 300130, P. R. China
selectivity more than 90% using Pt/HZSM-5 catalyst. The work of
Chen et al12 showed that Ru/HZSM-5 had good catalytic
Email: zhaoxq@hebut.edu.cn; anhl@hebut.edu.cn
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See performance for the deoxidation of bio-oil and the yield of
DOI: 10.1039/x0xx00000x
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deoxidation products was over 80% at a conversion of as high as
Catalytic activity evaluation. The Ru/HZSM-5 catalyVsietw(A3r.t5iclegO) nalninde
1
00%. Kumar et al 13 used Ni/HZSM-5 catalyst for stearic acid HDO 2-pentanone (35 g) were charged in an auDtoOcIl:a1v0e.10a3n9d/Df1lNusJh0e3d50b4Ey
and the yield of complete deoxidation products reached 61.6%. Cao hydrogen for three times. The temperature of the autoclave was
et al 14 explored the catalytic performance of Co/HZSM-22 for elevated while stirring and hydrogen was introduced after the
palmitic acid HDO reaction and obtained C16 isomeric alkane required reaction temperature was reached. After the completion of
selectivity of 73.4% with a complete conversion of palmitic acid.
reaction, the autoclave was cooled to room temperature and the
Levulinic acid (LA) is one of the twelve biomass platform chemicals composition of the product liquid was analysed by Shimadzu GC-
recognized by the US National Renewable Energy Laboratory and 2018 gas chromatograph equipped with a flame ionization detector
one of the new top ten platform chemicals for biorefined and A KB-1 capillary column. The column temperature was
carbohydrates 15,16. In view of the fact that LA molecule contains two controlled by a temperature program: started at an initial temperature
functional groups, ketonic carbonyl and carboxyl group, it is suitably of 50 °C and kept for 2 min, elevated at a ramp of 1 °C/min to 53 °C,
used as a model compound of the complex oxygenated components then at a rate of 15 °C/min to 85 °C, finally at a 3 °C/min to 200 °C
in bio-oil. In order to understand the HDO reaction of bio-oil, the and kept for 5 min. The composition was quantitatively calculated
HDO reaction of LA should be studied17-22. It is helpful to separately by the internal standard method using cyclohexanol as the internal
investigate the HDO property of ketonic carbonyl group and standard.
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carboxyl group for understanding the HDO reaction of LA. This
paper focused on the HDO property of ketonic carbonyl group. With
Results and discussion
2
-pentanone as the model compound of ketonic carbonyl group, the
catalytic performance of Ru-based catalyst was evaluated. In Catalyst screening. Several HZSM-5 supported metal catalysts
combination the characterization of HRTEM, SEAD, NH -TPD, H
were prepared and their performances for 2-pentanone HDO were
TPR, Py-IR, TG-DSC with activity evaluation, the structure-activity investigated and the results are listed in Table 1. As shown in Table
relationship of the catalyst was clarified and the HDO reaction SI-1, the loadings of all metals measured by ICP are basically
pathway of ketonic carbonyl group was explored, laying a
foundation for clarifying the HDO reaction of LA.
3
2
-
consistent with the results calculated theoretically. HZSM-5 was
chosen as the support due to its good acid catalytic performance. The
conversion of 2-pentanone decreased in the following order:
Ru/HZSM-5>Pt/HZSM-5>Ir/HZSM-5>Co/HZSM-5>Ni/HZSM-
>Pd/HZSM-5>Cu/HZSM-5; pentane yield reduced according to the
following order: Pt/HZSM-5>Ru/HZSM-5>Co/HZSM-5>Ir/HZSM-
>Ni/HZSM-5>Pd/HZSM-5>Cu/HZSM-5. As a result, the activity
Experimental
5
Catalyst preparation. The supported Ru catalyst was prepared by
an excessive impregnation method. HZSM-5 sample (industrial
grade, The Catalyst Factory of Nankai University) was calcined at
5
of the supported noble metal catalysts except Pd/HZSM-5 was
higher than that of the supported non-noble metal catalysts. Among
them, the catalytic activity of Ru/HZSM-5 was the most outstanding,
with the highest conversion of 67.5% and pentane selectivity of
5
50 °C for 3 h in a muffle furnace. A certain amount of RuCl3·xH
AR, Sinopharm Chemical Reagent Co., Ltd.) was dissolved in 50
mL deionized water. The aqueous solution of RuCl and 4 g of the
2
O
(
3
4
9.9%. Zhang et al. 23 also found that Ru was more active than Pd
calcinated HZSM-5 sample were poured into a rotary bottle and
ultrasonically stirred for 60 min and evaporated 90 min at 70 °C to
remove moisture. Then the resulting solid was dried at 110 °C for 12
h and calcinated at 550°C for 4 h. Finally, a reduction at 450°C for 4
h in the atmosphere of H
Ru/HZSM-5 catalyst.
Catalyst characterization. The acid type of sample was analysed
by FT-IR on a NICOLET Nexus-470 Fourier infrared spectrometer
using pyridine as a probe molecule. The transmission electron
microscopy (HRTEM) and selected area electron diffraction
and Pt, mainly because Ru had higher hydrogenolysis activity.
Although the selectivity of Ru to the target product was slightly
lower than that of Pt, Ru/HZSM-5 has higher potential application
value considering their prices 1.
2 2
:N =40:60 was conducted to afford the
Table 1 Screening of catalysts
Catalyst
X
MPK/%
30.3
65.1
60.8
67.5
49.9
54.3
24.8
Y
Pentane
%
Y
MPA/%
0.13
4.0
S
Pentane/%
SMPA/%
Pd/HZSM-5
Pt/HZSM-5
Ir/HZSM-5
Ru/HZSM-5
Ni/HZSM-5
Co/HZSM-5
Cu/HZSM-5
1.3
4.3
0.4
34.2
26.8
33.7
24.8
30.0
0.03
52.5
44.1
49.9
49.7
55.2
0.1
6.1
21.0
1.1
21.0
1.6
(
SAED) were taken by TECNAI G2 F20 field emission
transmission electron microscope with an acceleration voltage of
00 kV. The XRD patterns of the catalyst samples were recorded on
4.5
9.0
10.2
0
18.8
0
2
a Rigaku D/MAX-2500 X-ray diffractometer using CuKα radiation
as an X-ray source in a scanning range from 2θ=10 to 90° by a step
of 6°/min. The specific surface area and pore structure of the catalyst
samples were measured on an ASAP 2020 M+C specific surface and
porosity analyser. The Thermal Gravimetric analysis of the catalyst
samples were performed on the Perkin elmer-7 thermogravimetric
analyser (TGA). The content of metal component in the catalyst
samples was measured by inductively coupled plasma atomic
The loading of noble metal was 2 wt.% and that of non-noble metal was 5
wt.%. The Si/Al ratio of HZSM-5 was 21. Reaction conditions: P=3 MPa, t=6
h, T=190 °C. MPK: 2-pentanone; MPA: 2-pentanol. X: conversion; S:
selectivity; Y: yield.
The effect of Si/Al ratio of HZSM-5 on the catalytic performance of
Ru/HZSM-5 was investigated and the result is shown in Table 2.
With an increase of Si/Al ratio the selectivity of pentane and the
conversion of 2-pentanone decreased gradually due to a decrease in
the acidity of Ru/HZSM-5 . In addition, the selectivity of 2-pentanol
and the conversion of 2-pentanone increased obviously while the
emission spectrometry (ICP-AES) on an Optima 7300
spectrometer of PerkinElmer.
V
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| J. Name., 2012, 00, 1-3
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selectivity of pentane sharply decreased when TiO
were separately used in place of HZSM-5, indicating that Brφnsted
acid sites has an important influence on improving pentane
selectivity. By comparing the catalysis of Ru/TiO
2
, SiO
2
and ZrO
2
g
View Article Online
DOI: 10.1039/D1NJ03504E
2 2
, Ru/SiO and
Ru/ZrO , it was found that the yield of 2-pentanol over the catalyst
2
0.01
0.00
mainly composed of Lewis acid sites was about 50~70 times higher
than that over Ru/HZSM-5 catalyst but the yield of pentane was less
than 5%. This indicates that Lewis acid sites favour the
hydrogenation of C=O bond but disfavour the successive
100
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350
T/C
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Fig. 1 NH
catalysts with different Si/Al ratios (a: Si/Al ratios 21; b: Si/Al ratios 60; c:
Si/Al ratios 130; d: Si/Al ratios 360; e: Ru/TiO ; f: Ru/SiO ; g: Ru/ZrO
3 2 2 2
-TPD profiles of Ru/TiO , Ru/SiO , Ru/ZrO and Ru/HZSM-5
dehydration. On further analysis of the catalysis of Ru/TiO
2
,
2
2
2
)
Ru/SiO , Ru/ZrO and Ru/HZSM-5 with different Si/Al ratios, it can
2
2
To further explain the experimental results, NH
catalysts listed in Table 2 were carried out and the results are shown
in Figure 1. From the change of NH -TPD curves, three NH
desorption peaks can be observed separately at different temperature
region for Ru/HZSM-5(21). NH desorption peaks can be observed
3
-TPD analyses of all
be concluded that Lewis acid sites play an important role for
activating C=O bond and Brφnsted acid sites are the key to
accelerate the further dehydration of R-OH to alkane. Taking
pentane selectivity as the evaluation target, HZSM-5 with a Si/Al
ratio of 21 was determined as the suitable support.
3
3
3
only at low temperature region and medium temperature region for
other catalysts. The specific analysis data are shown in Table SI-2.
The desorption peak of NH -TPD began to shift to low temperature
3
with an increase of Si/Al ratio, indicating that the higher Si/Al ratio
is, the weaker the acid strength is. According to Table SI-2 and
Figure 1, it can be concluded that the acid amount of Ru/HZSM-5
with different Si/Al ratios decreased in the following order:
Table 2 Effect of Si/Al ratio on catalytic performance of Ru/HZSM-5
X
MPK
/
Y
Pentane
/
Y
MPA
S /
MPA
Catalyst
S
Pentane/%
%
%
/%
%
Ru/HZSM-5(21)
67.5
65.6
33.7
23.8
1.1
0.9
49.9
36.3
1.6
1.4
Ru/HZSM-5(61)
Ru/HZSM-
6
5
1.5
1.4
18.2
9.2
0.4
0.3
29.6
17.9
0.7
0.6
5
(130)
Ru/HZSM-
(360)
Ru/TiO
Ru/SiO
Ru/ZrO
Ru/HZSM-5(21)
Ru/HZSM-5(360). Among the other three Lewis acid catalysts, the
acid amount of Ru/TiO is the largest and that of Ru/SiO is the
>
Ru/HZSM-5(61)
>
Ru/HZSM-5(130)
>
5
2
2
2
88.1
88.7
88.5
0.1
3.7
0.3
77.3
49.4
75.9
0.1
4.2
0.3
87.7
55.7
85.8
smallest. The change tendency of acid strength of all catalysts is
consistent with that of acid amount.
2
To prove the influence of different kinds of acidic sites on the
catalytic performance for HDO reaction of 2-pentanone, Py-IR
analyses of Ru/HZSM-5 catalysts with different Si/Al ratios and
other catalysts listed in Table 2 were carried out and the results are
shown in Figure SI-1. The absorption peak at 1540 cm-1 belongs to
Brφnsted acid sites, the absorption peak at 1480 cm-1 can be
attributed to both Brφnsted acid sites and Lewis acid sites, and the
absorption peak at 1450 cm-1 belongs to Lewis acid sites 24. With an
increase of Si/Al ratio, the absorption peak intensity of Brφnsted-
Lewis acid sites, Lewis acid sites and Brφnsted acid sites all showed
a significant downward trend. This shows that the smaller the Si/Al
ratio, the stronger the acidity, in consistency with the analysis results
of NH -TPD. There is only Lewis acid sites but no Brφnsted acid
sites in SiO , TiO and ZrO . These bands around 1600 cm−1are also
ascribed to pyridine adsorbed on Lewis acid sites and can be taken as
a measure of the Lewis acid strength 25. In this work, the bands at
around 1596 cm may be arisen from the hydrogen bonded pyridine
2
Reaction conditions: P=3 MPa, t=6 h, T=190 °C. MPK: 2-pentanone; MPA:
-pentanol. S: selectivity; Y: yield; X: conversion.
2
0.06
0.06
0.05
0.04
0.03
0.02
0.01
0.00
a
b
d
f
0.05
0.04
0.03
0.02
0
.01
.00
0
100
150
200
250
300
350
100
150
200
250
300
350
T/C
T/C
0.06
0.05
0.04
0.03
0.02
0.01
0.00
0.06
0.05
0.04
0.03
0.02
0.01
0.00
c
3
2
2
2
−1
or the weak-medium Lewis acid sites. The bands at around 1606
100
150
200
250
300
350
100
150
200
250
300
350
−
1
T/C
T/C
cm may be due to medium-strong Lewis acid sites. Combined with
the activity evaluation data, it is further proved that Brφnsted acid
sites are the key to complete HDO reaction of 2-pentanone.
0.06
0.05
0.04
0.06
e
0.05
0.04
0.03
0.02
0.01
0.00
Effect of preparation conditions on catalytic performance of
Ru/HZSM-5. The effect of preparation conditions on the catalytic
performance of Ru/HZSM-5 is summarized in Table 3. With an
increase of calcination temperature, both the conversion of 2-
pentanone and the selectivity of pentane decreased slightly. Using
MDI Jade5.0 software to analyse the average grain size of the XRD
measurement data of the catalyst samples calcined at different
temperatures, the change of the crystal grains with the calcining
0.03
0.02
0.01
0.00
100
150
200
250
300
350
100
150
200
250
300
350
T/C
T/C
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temperature is shown in Figure SI-2. It can be seen that the crystal et al 27. To further confirm the presence of Ru parVtiiecwleAsr,ticale hOinglihne-
grains gradually increased as the calcination temperature increased. resolution transmission analysis of Ru/HZSMDO-5I: w10a.1s0p39e/rDfo1rNmJ0e3d50an4Ed
Below the calcination temperature of 500 ℃, the crystal grains the results are shown in Figure 2. TEM images at different scales
increased slowly, and when the calcination temperature was above revealed the growth of well dispersed Ru nanoparticles. The rod-like
5
00 ℃, the crystal grains increased rapidly with the increase of the Ru particles with a length of about 66 nm and a width of about 15
calcination temperature. This is also one of the reasons why the nm were observed and Ru particles uniformly existed on the surface
conversion of 2-pentanone began to decrease when the calcination of HZSM-5 in Figure 2(b). Figure 2(C) showed lattice fringe with
temperature exceeded 500 ℃. At a calcination temperature of 450 inter-planar spacing 0.21 nm corresponding to [101] plane of
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
°
C, the selectivity and yield of pentane reached their maxima, 36.1% ruthenium. The uniform spacing throughout the nanoparticle
and 51.0% respectively. The XRD characterization results of suggested single crystalline nature of the particle. The SAED ring
Ru/HZSM-5 at different calcination temperatures in Figure SI-3 pattern indexing prove that the rod-like particles are Ru (0) phase
showed only the diffraction peak of HZSM-5 at 2θ = 10~55°. structure. With the prolongation of calcination time, the yield of
Moreover, the structure of HZSM-5 retained its original MFI pentane and the conversion of 2-pentanone firstly increased
topology 26 and was not affected by the change of calcination gradually and then levelled off. When the calcination time was 3 h,
temperature. Due to small loading of Ru (only 2 wt.%) and high the conversion of 2-pentanone reached the maximum of 70.5%, and
dispersion on the support surface, no diffraction peaks of Ru was the selectivity and yield of pentane reached the maximum of 51.8%
observed in XRD patterns. These experimental results are similar to and 36.5%, respectively.
those obtained for Ru/H-Beta catalyst characterized by XRD by Yao
Table 3 Influence of preparation conditions
Calcination conditions
Reduction conditions
Yield/%
Selectivity/%
Pentane
Entry
XMPK/%
o
o
Temp/ C
400
450
500
550
600
450
450
450
450
450
450
450
450
450
450
Time/h
Temp/ C
450
450
450
450
450
450
450
450
300
350
400
350
350
350
350
Time/h
Pentane
35.3
36.1
35.8
33.2
30.8
28.4
30.6
36.5
41.9
45.9
39.1
40.0
40.8
40.3
47.8
MPA
1.3
0.8
0.7
1.1
0.6
1.0
1.8
0.3
0.7
0.8
1.2
0.6
0.9
1.7
0.5
MPA
1.8
1.1
1.0
1.6
0.9
1.7
2.8
0.4
1.0
1.1
1.7
0.8
1.2
2.3
0.6
1
2
4
4
4
4
4
1
2
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
4
1
2
3
5
71.1
70.8
70.5
69.9
66.8
59.0
64.1
70.5
72.7
75.4
72.4
74.7
74.8
75.2
80.8
49.6
51.0
50.8
47.5
46.1
48.1
47.7
51.8
57.6
60.9
54.0
53.5
54.5
53.6
59.2
3
4
5
6
7
8
9
10
11
12
13
14
15
Reaction conditions: P=3 MPa; t=6 h; T=190 °C; MPA: 2-pentanol; MPK: 2-pentanone; X: conversion;
In the investigated temperature range, the selectivity of pentane and
the conversion of 2-pentanone first increased and then decreased
with an increase of reduction temperature. At 350 °C, pentane
selectivity and the conversion of 2-pentanone reached their maxima,
60.9% and 75.4% respectively, indicating that Ru/HZSM-5 reduced
at 350 °C had higher catalytic performance. However, with an
extension of reduction time, the conversion of 2-pentanone gradually
increased. The yield and selectivity of pentane did not increase much
at the reduction time of 4 h and 5 h. This shows that the metal oxide
had been completely reduced at the reduction time of 4 h. H
analysis results of RuO /HZSM-5 calcined at 450 °C are shown in
Figure 3. The reduction peak at 89 °C~104.7 °C can be attributed to
2
-TPR
2
the reduction of RuO
2
→RuO, the reduction peak at 142 °C can be
0
attributed to the reduction of RuO→Ru , and the reduction peak at
350.3 °C can be attributed to the reduction of Ru species which is
difficult to be reduced. The different interactions between Ru and
HZSM-5 affects the reduction of Ru species. To sum up, different
Ru oxides can be completely reduced at 350 °C. The measured
2
Fig. 2 HRTEM micrograph (a-c) and SAED pattern (d) of Ru/HZSM-5
results of H -TPR are consistent with the experimental results.
calcinated at 450 °C
4
| J. Name., 2012, 00, 1-3
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The reaction (I) is exothermic. King et al 28 did not observe the
View Article Online
intermediate 2-pentene when exploring theDOHI:D10O.10r3e9a/cDt1iNonJ03o5f043E-
pentanone, indicating that the olefin intermediate was easily
hydrogenated. Similarly, we did not find the olefin intermediate in
reaction (II) either. Therefore, the dehydration of 2-pentanol in
reaction (II) is a rate-controlling step. Since dehydration is
endothermic reaction, the higher the reaction temperature is, the
more favourable it is for dehydration reaction. However, higher
temperature is unfavourable for the hydrogenation reaction (I). As
the first step in the whole reaction process, the higher the reaction
temperature is, the more unfavourable it is to the conversion of 2-
pentanone, limiting the formation of intermediate 2-pentanol and its
dehydration. At relatively high temperature, the selectivity of
pentane was not improved obviously, further indicating that the
dehydration of 2-pentanol was limited by the hydrogenation of 2-
pentanone. Resende et al. 29 thermodynamically analysed gas-phase
phenol HDO reaction and found that the optimal conditions for
product formation were intermediate temperature and higher
hydrogen/phenol ratio. This is similar to the effect of reaction
temperature on the HDO reaction of 2-pentanone in this study. Tieuli
et al. 30 also believed that higher temperature would promote
intermolecular polymerization and decrease the deoxygenation
activity of catalyst, also leading to a decrease of 2-pentanone
conversion and pentane selectivity. With prolonging reaction time
and increasing hydrogen pressure, the conversion of 2-pentanone
increased continuously while the selectivity of pentane first
increased and then decreased. When the hydrogen pressure increased
from 5 MPa to 6 MPa, the selectivity of pentane declined and the
yield of pentane levelled off although the conversion of 2-pentanone
continued to increase. This indicated that 2-pentanone HDO to
pentane reached equilibrium at a hydrogen pressure of 5 MPa. When
the reaction time was extended to 8 h, the selectivity and yield of 2-
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
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4
5
6
7
8
9
0
Fig. 3 H
2
-TPR curve of RuO
2
/HZSM-5 obtained at calcination temperature of
450 °C
Ru/HZSM-5 catalysed HDO reaction of 2-pentanone. Using
Ru/HZSM-5 catalyst prepared under the suitable conditions, the
effects of reaction time, hydrogen pressure, reaction temperature and
catalyst amount on 2-pentanone HDO reaction performance
investigated and the results are shown in Table 4. With an increase
of catalyst amount, the yield and selectivity of pentane first
increased, reached their maximum of 52.7% and 64.0%, and then
levelled off. It is worth noting that the selectivity of 2-pentanol
decreased obviously when the catalyst amount increased to 6 wt.%.
This indicated that an increase of catalyst amount enhanced the
number of acidic sites and hydrogenation active sites and thus
promoted the dehydration of 2-pentanol and hydrogenation of 2-
pentanone. With an elevation of reaction temperature, the conversion
of 2-pentanone gradually decreased while the selectivity and yield of
pentane first increased and then decreased. The highest conversion
of 2-pentanone could be reached to 99.5% at 150 °C. However, the
selectivity of pentane and the conversion of 2-pentanone decreased
in the range of 210 °C~230 °C. This is mainly affected by the
thermodynamics of reaction. The HDO of 2-pentanone can be
simplified as hydrogenation of 2-pentanone (I) and then dehydration
of 2-pentanol and finally hydrogenation (II).
pentanol increased slightly while the yield and selectivity of pentane
decreased. Yu et al. 36 thoughts that too long a reaction time was not
conducive to the main reaction but more favourable for side-
reactions. Because of long-term contact with solid acid, the reactants
are more prone to side-reactions such as polycondensation.
Therefore, the appropriate reaction conditions for the 2-pentanone
HDO are as follows: a catalyst amount of 6 wt.%, a reaction time of
h, a reaction pressure of 5 MPa and a reaction temperature of 190
°C. Under these conditions, the conversion of 2-pentanone was
1.8% and the selectivity of pentane was 77.7%.
O
OH
+ H2
6
(I)
k1
A
B
9
OH
-
H O&+H
2
2
(II)
k2
B
C
Table 4 Influence of reaction conditions
Reaction conditions
Yield/%
Selectivity/%
Entry
X
MPK/%
o
Catalyst amount/wt.%
Temp/ C
P(H2)/MPa
Time/h
Pentane
27.9
52.7
50.7
50.6
20.9
27.2
18.1
11.3
3.1
MPA
28.2
2.1
Pentane
MPA
34.6
2.6
1
2
3
4
5
6
7
8
9
4
6
190
190
190
190
150
170
210
230
190
3
3
3
3
3
3
3
3
1
6
6
6
6
6
6
6
6
6
81.6
82.3
79.6
80.2
99.5
98.9
44.8
40.9
23.8
34.2
64.0
63.7
63.1
21.0
27.5
40.4
27.6
13.0
8
0.6
0.8
10
6
0.8
1.0
51
51.3
44.6
0.9
6
44.1
0.4
6
6
0.2
0.5
6
0.1
0.4
This journal is © The Royal Society of Chemistry 20xx
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View Article Online
DOI: 10.1039/D1NJ03504E
86.1
91.8
99.4
91.4
91.9
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68.9
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72.7
74.5
73.9
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MPK: 2-pentanone; MPA: 2-pentanol; X: conversion;
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Reusability of Ru/HZSM-5 catalyst. After the completion of
reaction, Ru/HZSM-5 catalyst was separated from the product liquid
by centrifugation. The recovered catalyst was washed with
anhydrous ethanol for 3 times, dried at 110 °C overnight, calcined at
Run
1
Ru content/wt.%
2.0
2.0
1.9
1.3
1.0
2
3
4
5
50 °C for 3 h, and reused in the HDO reaction of 2-pentanone. The
5
results are shown in Figure 4. After the catalyst was reused two
times, the activity of Ru/HZSM-5 catalyst did not decline; the
conversion of 2-pentanone, the yield and selectivity of pentane
Conclusions
remained basically unchanged. After repeated use for 3 times, the To HDO reaction of 2-pentanone which contains a keto
yield of pentane decreased slightly, and the conversion of 2- carbonyl group proceeds easily. The main reaction path is via
pentanone had no obvious change but the yield of 2-pentanol the hydrogenation of 2-pentanone to 2-pentanol, and then the
increased significantly, possibly due to carbon deposition on the dehydration and hydrogenation of 2-pentanol to pentane. The
surface of Ru/HZSM-5 catalyst. Figure SI-4 shows the TG-DSC effect of reaction temperature and hydrogen pressure is
plots of the used sample of Ru/HZSM-5(21). An endothermic stage significant; a moderate reaction temperature and higher
was observed which occurred in the range of 350 °C to 550 °C with hydrogen pressure are more suitable for 2-pentanone HDO
a weight loss of about 15%, being attributed to the combustion of process. Lewis acid sites play an important role for activating
carbonaceous substances. These results indicated the absorbed C=O bond and Brφnsted acid sites are the key to accelerate the
carbonaceous substances could be removed by calcination at 550 °C further dehydration of 2-pentanol to pentane. Among a series of
and further confirmed the carbonaceous deposition on the surface of HZSM-5 supported metal catalysts, Ru/HZSM-5 showed the
the catalyst being the main reason for the deactivation of the catalyst. highest catalytic performance. The suitable preparation
However, the conversion of 2-pentanone decreased after repeated conditions for Ru/HZSM-5 with Si/Al=21 was as follows: a
use for 4 times, suggesting the decrease of hydrogenation activity of
Ru/HZSM-5 catalyst due to the loss of Ru.
calcination temperature of 450 °C, a calcination time of 3 h, a
reduction temperature of 350 °C and a reduction time of 4 h.
Under the appropriate conditions of a catalyst amount of 6
wt.%, a reaction time of 6 h, a reaction pressure of 5 MPa and a
reaction temperature of 190 °C, the conversion of 2-pentanone
was 91.8%
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by National Natural Science
Foundation of China (Grant No. 21476058), Natural Science
Foundation of Tianjin (Grant No. 16JCQNJC06100), Basic
Research Program of Hebei Province for Natural Science
Foundation and Key Basic Research Project (18964308D) and
Key Project of Hebei Province Natural Science Foundation
Fig. 4 Reusability of Ru/HZSM-5
In order to further analyze the reason for Ru/HZSM-5 deactivation, (B2020202048).
an ICP analysis was carried out and the results are shown in Table 5.
It was found that metal Ru could stably exist on the surface of
HZSM-5 after repeated use twice. With an increase of reuse times,
the content of metal Ru significantly decreased, leading to a decline
in the activity of catalyst, being consistent with the experimental
data in Table 5.
Table 5 ICP measurement results of Ru content in Ru/HZSM-5 catalyst
before and after use
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Journal Name
Svenum, J. Walmsley, C. Detavernier, H. Poelman, and J.
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