Selective hydrodeoxygenation of 5-hydroxy-2(5H)-furanone to γ-butyrolactone over Pt/mesoporous solid acid bifunctional catalyst

Article abstract of DOI:10.1039/c7ra03205f

Selective hydrodeoxygenation of 5-hydroxy-2(5H)-furanone (HFO) derived from furfural oxidation to γ-butyrolactone (GBL) provides a sustainable alternative to the petroleum-based process for γ-butyrolactone production. Furfural is first converted to HFO through selective photocatalytic oxidation by using air oxygen as the oxidant (yield: 85.0%). HFO is further converted to GBL through hydrodeoxygenation over noble-metal nanoparticles on mesoporous Nb-Zr mixed oxides. The conversion of HFO to GBL involves two reactions: hydrogenation catalyzed by active metal and dehydration over mesoporous solid acids. The catalytic properties of M/Nb-Zr mixed oxides (M = Pt, Ir, Ru, Rh and Pd) are related to the composition of support and active metal. The incorporation of zirconia into matrixes improves the thermal stability of mesoporous mixed oxides and increases the amounts of surface acid, which contributes to its catalytic selectivity to GBL. Pt/Nb₅Zr₅-550 exhibited the best catalytic performances with 97.3% selectivity of GBL at full conversion. The excellent performance can be correlated with the cooperative effect between active metal species and acid sites. The Pt-solid acid bifunctional catalysts show superior catalytic performance compared with conventional catalysts, such as Pt/H-ZSM-5, Pt/C, Rh/C or Pd/C. An overall GBL yield of 82.7% from furfural was obtained.

Full text of DOI:10.1039/c7ra03205f

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Selective hydrodeoxygenation of 5-hydroxy-2(5H)-
furanone to g-butyrolactone over Pt/mesoporous
solid acid bifunctional catalyst†
Cite this: RSC Adv., 2017, 7, 21145
Bingfeng Chen,
Fengbo Li* and Guoqing Yuan*
Selective hydrodeoxygenation of 5-hydroxy-2(5H)-furanone (HFO) derived from furfural oxidation to g-
butyrolactone (GBL) provides sustainable alternative to the petroleum-based process for g-
a
butyrolactone production. Furfural is first converted to HFO through selective photocatalytic oxidation
by using air oxygen as the oxidant (yield: 85.0%). HFO is further converted to GBL through
hydrodeoxygenation over noble-metal nanoparticles on mesoporous Nb–Zr mixed oxides. The
conversion of HFO to GBL involves two reactions: hydrogenation catalyzed by active metal and
dehydration over mesoporous solid acids. The catalytic properties of M/Nb–Zr mixed oxides (M ¼ Pt, Ir,
Ru, Rh and Pd) are related to the composition of support and active metal. The incorporation of zirconia
into matrixes improves the thermal stability of mesoporous mixed oxides and increases the amounts of
5 5
surface acid, which contributes to its catalytic selectivity to GBL. Pt/Nb Zr -550 exhibited the best
Received 18th March 2017
Accepted 5th April 2017
catalytic performances with 97.3% selectivity of GBL at full conversion. The excellent performance can
be correlated with the cooperative effect between active metal species and acid sites. The Pt-solid acid
bifunctional catalysts show superior catalytic performance compared with conventional catalysts, such
as Pt/H-ZSM-5, Pt/C, Rh/C or Pd/C. An overall GBL yield of 82.7% from furfural was obtained.
DOI: 10.1039/c7ra03205f
rsc.li/rsc-advances
as a feedstock molecule for the production of GBL through
tetrahydrofuran (THF) as an intermediate. Several homo-
1
. Introduction
g-Butyrolactone (GBL) is considered as an important C4 feed- geneous or heterogeneous catalysts have been attempted to
14–17
stock, which can be used as the main intermediate for the oxidation of tetrahydrofuran to GBL.
Sooknoi et al. have
synthesis of pyrrolidone and pyrrolidone-derivatives, pharma- applied the thermally treated iron-containing clay catalyst to
1
,2
ceuticals, agrochemicals and rubber additives. It can also be convert THF into GBL with H
2
O
2
as the oxidant and the best
18
used as an eco-friendly solvent or extraction agent in petroleum yield of GBL was only 16.6%. This conversion has some
processing and textile industries. There are several approaches drawbacks, such as multiple-step reactions (including decar-
3
for GBL production, such as hydrogenation of maleic anhy- bonylation, hydrogenation and oxidation), low efficiency, and
4,5
3,6,7
dride, dehydrocyclization of 1,4-butanediol (BDO),
hydrogenation of succinic acid or dialkyl succinate.
and a large investment in equipment. Maleic acid and succinic acid
The can also be produced through the selective oxidation of furfural
8
–11
former two methods are based heavily on fossil fuel resources and further hydrogenation of them leads to the formation of
and the last one is derived from succinic acid produced through GBL. There are many catalytic systems for furfural oxidation,
1
2
19
20
fermentation of sugars and starches. However, the fermenta- such as H
3
PMo12
O
40/Cu(NO
,
3
)
2
,
H
5
PV
2
Mo10
O
40/Cu(CF
3
SO
3
)
2
,
21
22
23
tion process shows the low productivity. More efficient Amberlyst-15/H
2
O
2
titanium silicalite, and VO
x
/Al
2
O
3
.
processes based on biomass resources attract great attention Homogeneous catalysts show relatively poor selectivity and the
during developing novel catalytic pathway for GBL production. separation of the products and the catalysts poses a great
Furfural is the most important platform chemical, which is problem in practical operation. Heterogeneous processes of
produced from hemicelluloses through dehydration with an furfural oxidation require high reaction temperature and short
13
annual production of 5 million tons. Furfural can be applied contact time and the main drawback is the inevitable thermal
24
polymerization of furfural under reaction conditions.
In our work, a sustainable catalytic process for GBL
Beijing National Laboratory of Molecular Science, Key Laboratory of Green Printing, production from furfural is steadily developed via a novel
Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
intermediate: 5-hydroxy-2(5H)-furanone (HFO), as illustrated in
Scheme 1. Furfural is rst converted to HFO through selective
photocatalytic oxidation by using air oxygen as the oxidant. HFO
is further converted to GBL through hydrodeoxygenation over
E-mail: li@iccas.ac.cn; yuangq@iccas.ac.cn; Fax: +86-10-62559373; Tel: +86-10-
6
†
1
2634920
Electronic supplementary information (ESI) available. See DOI:
0.1039/c7ra03205f
This journal is © The Royal Society of Chemistry 2017
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with different compositions were synthesized by adjusting the
proportions of Zr(OBu) and NbCl (the total Nb–Zr molar is 6
4
5
mmol). The so template F127 can be replaced by P123.
The supported bifunctional catalysts were prepared by a wet
impregnation method. The as-synthesized mesoporous mixed
oxides (Nb10ꢀxZr
lated amount Nb10ꢀxZr
concentration aqueous solution of metal precursors (such as
PtCl , H IrCl , RuCl , RhCl and PdCl (CH CN) ) and kept in
x
-T) were used as support materials. The calcu-
x
-T was impregnated with a certain
H
2
6
2
6
3
3
2
3
2
an oven at 383 K overnight. Then these solids were calcinated at
ꢁ
4
00 C in air for 3.0 h. These catalysts were activated under diluted
Scheme 1 Catalytic conversion of furfural into g-butyrolactone.
ꢁ
hydrogen ow (H /Ar: 10%) at 400 C for 2.0 h before catalytic
2
tests. The loading amount of metal is stated as 2 wt%. The metal
loadings quoted were conrmed by the ICP-AES elemental anal-
ysis. They are in good agreement with the preparation stoichi-
ometries since the preparations did not involve operations such
as ltration and washing which could cause metal loss.
a bifunctional catalyst under mild conditions. The catalyst is
prepared by supporting noble-metal nanoparticles on meso-
porous Nb–Zr mixed oxides that are synthesized through
a modied evaporation-induced self-assemble (EISA) approach.
The physicochemical properties of these materials are
detailedly investigated and the reaction conditions of g-butyr-
olactone production are optimized. The conversion of HFO to
GBL involves two reactions: hydrogenation and dehydration.
These reactions can be integrated over one catalyst with
bifunctional active sites: Pt nanoparticles for hydrogenation
and mesoporous solid acids for dehydration. To the best our
knowledge, it is the rst time that 5-hydroxy-2(5H)-furanone
derived from furfural oxidation is smoothly converted into g-
butyrolactone through catalytic hydrodeoxygenation.
Pt/Al O and Pt/HZSM-5 catalysts were also prepared by the
2
3
wet impregnation method. The specied preparation processes
of these catalysts were similar to the above-mentioned procedure.
2.3 Materials characterization
Powder X-ray diffraction (XRD) patterns were measured on
a Rigaku Rotaex diffractometer equipped with a rotating
anode and a Cu-Ka radiation source (40 kV, 200 MA; l ¼ 1.54056
˚
A). Nitrogen adsorption–desorption analysis was carried out at
77 K on a Quadrasorb SI-MP adsorption analyzer. Before the
adsorption analysis, the samples were outgassed under
ꢁ
a vacuum at 300 C in the port of the adsorption analyzer.
2
. Experimental
Inductive coupling plasma emission spectrometer (ICP-OES)
analysis was conducted on the Varian 710 ICP-OES with ICP
2.1 Chemicals
Triblock copolymer Pluronic P123 (Mw ¼ 5800, EO PO EO ) Expert II soware. XPS data were obtained with an
2
0
70
20
and Pluronic F127 (Mw ¼ 12 600, EO106PO70EO106) were ESCALab220i-XL electron spectrometer from VG Scientic using
purchased from Sigma Aldrich Crop. NbCl5, Zr(OBu)
(80% w/w 300 W Al-Ka radiations. The base pressure was approximately 3
in 1-butanol), H PtCl , H IrCl , RuCl , RhCl and PdCl
CN)
were purchased from Alfa Aesar. Furfural, rose bengal, line at 284.8 eV from adventitious carbon. The Eclipse V2.1 data
4
ꢀ
9
2
6
2
6
3
3
2
(CH
3
-
ꢂ 10 mbar. The binding energies were referenced to the C 1s
2
methanol, 1-propanol, chloroform, dioxane and THF were ob- analysis soware supplied by the VG ESCA-Lab200I-XL instru-
tained from Aladdin Reagent Limited Company (Shanghai, ment manufacturer was used to manipulate the acquired
China). Pd(10 wt%)/C, Rh(5 wt%)/C, Pt(5 wt%)/C, Al O and spectra. Transmission electron microscopy (TEM) was per-
2
3
ZSM-5 were provided by Strem. All chemicals were used as formed on a JEOL 2010 TEM equipped with an attachment for
received. Furfural was used aer vacuum distillation.
local energy dispersion analysis (EDX). The accelerating voltage
was 200 kV, and the spot size was 1 nm. High-angle annular
dark eld scanning transmission microscopy (HAADF-STEM)
was performed on the mesoporous Nb–Zr mixed oxide with
JEOL JEM-2100F microscope in a scanning transmission elec-
2.2 Catalysts preparation
Mesoporous Nb –ZrO mixed oxides (Nb10ꢀxZr -T, x is the
2
O
5
2
x
Zr/(Nb + Zr) mole ratio and T is the calcination temperature),
were synthesized through a modied evaporation-induced self-
assemble (EISA) approach. During a typical preparation proce-
tron microscopy (STEM) mode operated at 200 kV. The NH
3
temperature programmed desorption (NH -TPD) experiments
3
were carried out using a Autochem 2910 (Micromeritics) surface
analyzer quipped with a TCD detector.
dure of Nb
g) by ultrasonic dispersion. Zr(OBu)
butanol) and NbCl (3.0 mmol) were added to the mixture under
stirring. The mixture was stirred vigorously for 2 h at room
temperature and then 0.54 g H O was added. Aer being further Furfural was converted into 5-hydroxy-2(5H)-furanone (HFO)
stirred for 1.0 h, the mixture was transferred to Petri dishes to through photocatalytic oxidation with rose bengal. This method
5 5
Zr -550, F127 (1.0 g) was dissolved in 1-propanol (10.0
4
(3.0 mmol, 80% w/w in 1-
5
2.4 Catalytic reactions
2
ꢁ
25
undergo the slow EISA process at 40 C for 4–6 days. The as- has been reported by Gollnick, K. A solution consisting of
ꢁ
synthesized xerogel was calcined at 550 C for 4.0 h in air to furfural (18.5 ml, 0.223 mol) and rose bengal (0.455 g) in
remove the structure-directing agents. Mesoporous Nb–Zr oxides methanol (115 ml) was bubbled oxygen gas and the mixed
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solution was irradiated Ace medium-pressure Hg lamp (PLS- present of long-range ordered mesostructures in these
26,27
LAM500, 500 W, PerfectLight. Crop.) in Pyrex photochemical composite oxides.
The wide-angle X-ray diffraction (WXRD)
reactor for 15 h. The as-synthesized 5-hydroxy-2(5H)-furanone patterns of the as-prepared mesoporous oxides are shown in
was recrystallized in chloroform (yield: 85.0%).
Fig. S1.† When the Zr content is between 0 and 40 mol%, these
ꢁ
The catalytic transformation of 5-hydroxy-2(5H)-furanone samples exhibited two broad peaks in the 2q range of 20–40
ꢁ
(HFO) into g-butyrolactone was carried out in a 100 ml stainless and 40–65 , indicating that these mesoporous oxides mainly
autoclave equipped with a pressure gauge, a magnetic stirrer, exist in amorphous states. The diffraction lines of tetragonal
ꢁ
ꢁ
and an electric temperature controller. The catalyst (50 mg), ZrO
dioxane (5 ml) and HFO (0.5 g) were introduced into the auto- (PDF#50–1089).
clave, which then underwent several cycles of ushing with H2 The chemical composition of mesoporous Nb–Zr mixed
ow to drive off the air in the autoclave. Aer pressurizing with oxides shows many inuences on their porosity properties. It is
2
were observed at 2q ¼ 30.2 and 50.2 in the Nb
5 5
Zr -550

H to 5.0 MPa, the reactor was heated to a certain temperature difficult for pure niobium oxide to prepare mesoporous struc-
2
under stirring for several hours. At the end of reaction, the tures through EISA. The presence of zirconium facilitates
autoclave was cooled to ambient temperature and slowly dep- development of mesoporous structures (Fig. 2a). Nitrogen
ressurized. The conversion and product composition were adsorption–desorption isotherms exhibit type-IV curves
0
analyzed by GC and GC-MS and chlorobenzene was used as an (Fig. 2b). There are hysteresis loops at relative pressure (p/p ) of
external standard. GC was performed on a GC-2014 (SHI- 0.6–0.9, which are attributed to capillary condensation within
MADZU) equipped with a high-temperature capillary column the mesopore structure. Pure niobium oxide shows no character
(
MXT-1, 30 m, 0.25 mm ID) and a FID detector. GC-MS was of the mesopore structure. Nb Zr -550 sample has the highest
5
ꢀ1
5
2
performed on a GCT Premier/Waters instrument equipped with BET surface area (206.4 m g ). According to BJH analysis,
a capillary column (DB-5MS/J&W Scientic, 30 m, 0.25 mm ID). these composite oxides showed uniform-sized mesopores. The
Identication of main products was based on GC-MS as well as average pore diameter changes from 12.2 nm to 5.6 nm with the
by comparison with authentic samples. The product distribu- increase of the Zr proportion (Fig. 2c). As shown in the TEM
tion was shown on the mole basis.
images (Fig. 3), Nb10ꢀxZr
x
-550 (x ¼ 1–5) materials show hexag-
onally ordered mesoporous structures. These results are
consistent with their SXRD patterns and nitrogen adsorption–
desorption isotherms. However, pure niobium oxide sample
shows a disordered wormhole-like structure (Fig. 3f).
3. Results and discussion
3.1 Physicochemical properties of mesoporous solid acid
catalysts
x
Table 1 summarizes porosity properties of Nb10ꢀxZr -550
samples. The average pore sizes of Nb–Zr mixed oxides decrease
aer Zr incorporation, but the specic surface area values
increase with the addition of zirconium. The presence of
zirconia is benecial for maintaining the mesoporous frame-
Two structure-directing agents (P123 and F127) are attempted
to prepare mesoporous solid acids. As revealed in Fig. 1, F127 is
a more efficient template molecule than P123 to fabricate
mesoporous Nb–Zr mixed oxides. The sample from P123 shows
ꢁ
work. Kondo et al. has reported that mesoporous Zr Nb O was
6 2 17
a weak peak around 1 . However, the materials based on F127
prepared using P123 as template, the BET surface area of this
exhibit well-ordered mesostructures. Therefore, F127 was
chosed as so template for further investigations. As shown by
the small-angle powder X-ray diffraction patterns (SXRD), there
2
ꢀ1
ꢁ
material was 178 m g at 350 C calcination temperature and
2
ꢀ1
ꢁ
then substantially decreased to 58 m g at 720 C calcination
28
ꢁ
temperature. STEM and EDS analysis is used to investigate the
elemental composition and the distribution of the elements in
the mixed oxide. As shown in Fig. 4, the element mapping of the
Nb and Zr reveals that niobium and zirconium are homoge-
neously distributed in the mesoporous frameworks. According
to the energy dispersive X-ray spectroscopy (EDS), the atomic
ratio of Nb to Zr is 1.06, which is consistent with ICP data.
is a strong peak around 0.9 , which is indexed as (100) reection
of the two-dimensional (2D) (P6mm) hexagonal mesostructure.
ꢁ
Another peak appears around 1.4–1.7 , which reveals the
The characterization of acid catalysts with NH
3
-TPD analysis
gives an estimation of the total acidity and strength in gas
phase. NH
3
-TPD curves can be roughly divided into four regions
ꢁ
(Fig. 5). The low temperature region from 100 to 350 C is
usually attributed to weak acidic sites. The second region in the
ꢁ
range of 350 to 450 C can be appointed as medium strong
ꢁ
acidic sites, and the region of 450–600 C can be assigned to
ꢁ
strong acidic sites. The weak peak around 700 C might be
3
caused by NH desorption from superacid sites. The total
acidity per gram of catalyst gives the following order: Nb
5
Zr
-550
5
-
ꢀ
1
ꢀ1
4
50 (0.61 mmol g ) > Nb
5
Zr
5
-550 (0.52 mmol g ) > Nb
7
Zr
3
ꢀ1
ꢀ1
(0.35 mmol g ) > Nb-550 (0.11 mmol g ). Compared with pure
5 5
Fig. 1 Small-angle XRD patterns of Nb Zr -550 sample by using
different templates.
niobium oxide, the mesoporous Nb–Zr mixed oxides contain
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Fig. 3 TEM images of the mesoporous Nb10ꢀxZr
F127: (a) Nb Zr , (b) Nb Zr , (c) Nb Zr , (d) Nb Zr
scale bar: 50 nm).
x
-550 samples using
, (e) Nb Zr , (f) Nb
2 9 1
5
5
6
4
7
3
8
(
The precursors of metal nanoparticles are introduced by
a wet impregnation and supporting catalysts are reduced under
diluted hydrogen ow. Fig. 6a shows the HRTEM image of
supported Pt nanoparticles. The lattice spaces of the Pt nano-
particles are 0.229 nm and 0.198 nm, which corresponds to the
Fig. 2 (a) Small-angle XRD patterns of Nb10ꢀxZr
x
-550 samples with
sorption
-550 samples using F127. (c) Pore size
distribution curves of the Nb10ꢀxZr -550 samples using F127.
(111) and (200) planes of Pt crystal. X-ray photoemission spec-
different ratio of niobium to zirconium using F127. (b) N
2
troscopy (XPS) measurement is performed to investigate the
surface chemical composition and chemical states. The XPS
survey spectrum of the supporting catalyst reveals the presence
of carbon, zirconium, niobium, platinum and oxygen (Fig. 6b).
The binding energies of Nb 3d5/2 and 3d3/2 were 207.3 eV and
isotherms of the Nb10ꢀxZr
x
x
32
more weak and strong acid sites. It has been suggested that the 210.0 eV, which are indexed to Nb O (Fig. S2b†). The Zr 3d
2
5
formation of M -O-M hetero-linkages in binary complex oxides XPS spectrum shows two peaks of 182.4 eV (3d5/2) and 184.8 eV
1
2
can lead to the non-uniformity of the charge distribution due to (3d3/2) (Fig. S2a†). This indicates Zr species are in Zr(IV) oxida-
33
the difference for electro negativity and subsequently generate tion state. The insert of Fig. 6b shows Pt 4f peaks. The binding
29
new acid sites. Moreover, the total acidity increases upon energy of Pt 4f7/2 is around 70.7 eV and Pt 4f5/2 is at 74.0 eV,
zirconia incorporation is in line with the increase of BET surface which is indexed to zero-valent platinum species.
area except Nb
5 5 5 5
Zr -450. Although Nb Zr -450 contains higher
amount of the surface acid sites than Nb Zr -550, higher calci-
nation temperature will lead to removing the weak acid sites. It
has been reported that the decrease of acid sites and acid
5
5
3
.2 Catalytic performance in sustainable production of g-
butyrolactone from a renewable feedstock molecule
strength upon increasing calcination temperature was observed Furfural is converted into 5-hydroxy-2(5H)-furanone (HFO)
30,31
in mesoporous Ti–W oxides and Nb
2
O
5
catalysts.
through photocatalytic oxidation and subsequently HFO is
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x
Table 1 Porosity properties of the Nb10ꢀxZr -550 samples using F127
SXRD
Nitrogen adsorption and desorption data
ꢁ
a
b
2
ꢀ1
c
d
3
ꢀ1
Samples
Nb-550
2q ( )
d-spacing (100) (nm)
Specic surface area (m g
)
Pore size (nm)
Pore volume (cm g )
—
—
60.0
184.2
190.9
190.5
161.6
206.4
156.9
12.21
7.88
7.87
6.57
5.66
5.61
4.88
0.27
0.36
0.38
0.33
0.23
0.30
0.19
Nb
Nb
Nb
Nb
Nb
Nb
9
8
7
6
5
5
Zr
1
Zr
2
Zr
3
Zr
4
Zr
5
Zr
5
-550
-550
-550
-550
-550
-450
0.84
0.86
0.89
0.91
0.98
1.01
10.53
10.22
9.91
9.63
8.95
8.66
a
b
d-spacing is calculated from the (100) diffraction peak in small-angle XRD patterns. Surface area is calculated by the Brunauer–Emmett–Teller
c
0
d
(BET) method. Total pore volume (V
p
) is determined by using the adsorption branch of the N
2
isotherm at P/P ¼ 0.99. Average pore diameter (D
p
)
2
is determined from the local maximum of the BJH distribution of pore diameters obtained in the adsorption branch of the N isotherm.
Fig. 4 HAADF-STEM image (a) and the corresponding elemental
mapping images of the mesoporous Nb
b) elemental mapping of Zr; (c) elemental mapping of Nb; (d)
elemental mapping of O (scale bar: 100 nm).
5 5
Zr -550 sample using F127:
(
5 5
Fig. 6 (a) TEM image of Pt/Nb Zr -550 catalyst. (b) XPS survey spec-
trum of Pt/Nb Zr -550 catalyst (the insert is Pt XPS peaks).
5
5
converted into GBL (Scheme 1). There are two types of reactions
during conversion of HFO to GBL: hydrogenation and dehy-
dration. Supported Group VIII metal nanoparticles act as the
catalytic active sites for hydrogenation, and mesoporous solid
acids have two functions: the catalyst support and acidic cata-
lytic sites for dehydration. Based on this bifunctional catalytic
surface, these reactions are integrated over one catalyst through
one-pot model. Screening experiment results about catalytic
activity are summarized in Table 2. Various active metals are
tested for HFO conversion. M/Nb Zr -550 catalysts (M ¼ Ru, Pd,
5
5
Pt, Rh, Ir) have been investigated under typical reaction condi-
tions (entry 2–6 in Table 2). Supported Ru and Rh catalysts
have excellent selectivity of GBL (100%). However, the HFO
3 x
Fig. 5 NH -TPD curves of Nb10ꢀxZr mixed oxides using F127.
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conversions are relatively low (52.2% and 36.2%). Pd/Nb
5
Zr
5
-
23.8% (Table 3). Pt/C gave the 100% selectivity of GBL with the
5
50 and Ir/Nb Zr -550 catalysts show middle catalytic perfor- HFO conversion of 58.6%. Pt/H-ZSM-5 also showed the excellent
5 5
mances. Pt/Nb Zr -550 is the best catalyst and GBL yield selectivity of GBL, but the conversion was 60.2%. It is worth
5
5
reached 97.3%.
The compositions of Nb–Zr mixed oxides can exert inu- oxides showed much higher catalytic activity than the conven-
ences on the catalytic performances. Nb Zr -550 was tested as tional platinum catalyst supported on H-ZSM-5. Therefore, Pt/
the blank sample and it shows no activity (entry 1 in Table 2). Pt/ Nb Zr -550 showed superior catalytic performance in this
Nb-550 achieved the 91.3% selectivity of GBL with full conver- reaction.
sion of HFO. The main by-product was tetrahydrofuran (selec- GBL production from HFO involves multi-step consecutive
noting that the Pt supported on the mesoporous Nb–Zr mixed
5
5
5
5
tivity: 8.7%). Aer the introduction of Zirconia into support, the reactions. The GBL formation is attributed to the cooperative
GBL selectivity increased with the percentage of ZrO in the effects between active metal and acidic sites. Supported Pt
2
mixed oxides. Pt/Nb Zr -550 exhibited excellent performance. species catalyze the hydrogenation of C]C bond of HFO and 5-
5
5
The selectivity of GBL reached 97.3% under the total conversion hydroxydihydrofuran-2(3H)-one (HDFO) is formed (Scheme 1).
of HFO. According to NH -TPD analysis, the total acidity of the
mixed oxide increases with the ZrO content. These results
indicate that the acid properties of support are benecial to
improve the catalytic selectivity. Pt/Nb Zr -450 gave a high
3
2
5
5
selectivity of HFO, but the HFO conversion decreased to 95.7%.
Although Nb Zr -450 has higher total acidity than Nb Zr -550,
5
5
5
5
the BET surface area of the former is smaller than that of the
latter. High BET surface area facilitates the mass trans-
portation. Several commercial hydrogenation catalysts were
tested for HFO conversion. Pd/C and Rh/C showed low perfor-
mances for HFO conversion, and the GBL yield were 58.1% and
Table 2 Screening experimental results of catalytic conversion of
HFO to GBL
Selectivity (%)
a
Entry
Catalyst
Conversion (%)
GBL
Others
1
2
3
4
5
6
7
8
9
Nb
Ru/Nb
Pd/Nb
Ir/Nb Zr
Rh/Nb Zr
5
Zr
5
-550
—
—
—
—
5
Zr
Zr
5
-550
-550
52.2
73.4
63.7
36.2
100
100
100
95.7
100
96.7
95.7
100
97.3
95.7
91.3
97.7
5
5
3.3
4.3
—
2.7
4.3
8.7
2.3
5
5
-550
-550
5
5
Pt/Nb
Pt/Nb
5
Zr
Zr
5
-550
-550
7
3
Pt/Nb-550
Pt/Nb Zr -450
5
5
a
Reaction condition: 0.5 g HFO, 50 mg catalyst, 5 ml dioxane, 5 MPa H
40 C/8 h.
2
,
ꢁ
1
Table
3 Results of the conversion of HFO over hydrogenation
catalysts
Selectivity (%)
a
b
Entry
Catalyst
Conversion (%)
GBL
Others
1
2
3
4
5
Rh(5 wt%)/C
Pt(5 wt%)/C
Pd(10 wt%)/C
Pt(2 wt%)/HZSM-5
Pt(2 wt%)/Nb
23.8
58.6
60.8
60.2
100
100
100
95.5
100
97.3
—
—
4.5
—
2.7
5
Zr
5
-550
Fig. 7 (a) The effects of reaction temperature on HFO conversion and
GBL selectivity. (b) HFO conversion and GBL selectivity related to the
a
Reaction condition: 0.5 g HFO, certain amount of catalyst, 5 ml
ꢁ
b
dioxane, 5 MPa H
different catalyst was similar.
2
, 140 C/8 h. The used amount of active metal in elevation of hydrogen pressure. (c) The effects of reaction time on
HFO conversion and GBL selectivity.
21150 | RSC Adv., 2017, 7, 21145–21152
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GBL from HDFO proceeds via dehydration catalyzed by acid work provides a novel and eco-friendly pathway to produce high
sites of mesoporous solid acid sites and subsequent hydroge- valued-added g-butyrolactone from renewable resources.
nation of double carbon bonds over supported Pt nanoparticles.
During these processes, the main by-products are THF and
butyric acid, which are resulted from further hydrogenation of
Acknowledgements
GBL. Excellent GBL selectivity reveals that the side reactions are This work was supported by the National Natural Science Foun-
inhibited over the metal–acid bifunctional catalyst through dation of China (NSFC, No. 21403248; 21174148, 21101161).
selecting proper acidic support and active metals.
The reaction condition was further optimized with Pt/
Notes and references
Nb Zr -550. The effects of reaction temperature on HFO
5
5
ꢁ
ꢁ
conversion are investigated from 100 C to 180 C (Fig. 7a). HFO
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