supporting informationhigh purity n2 gas (99.99%, gc grade) was used as the carrier gas with a flow...
TRANSCRIPT
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Supporting Information
CePO4, a multi-functional catalyst for carbohydrate biomass conversion: Production of 5-hydroxymethylfurfural, 2,5-diformylfuran, and -valerolactone
Abhinav Kumar and Rajendra Srivastava*
Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar-140001, India
Corresponding author Email:[email protected]
Electronic Supplementary Material (ESI) for Sustainable Energy & Fuels.This journal is © The Royal Society of Chemistry 2019
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Synthesis of CePO4
CePO4 was synthesized by following the reported procedure.43 In a synthesis procedure, P123
(1 g), H3PO4 (10 mmol), and water (15 g) were charged into a polypropylene bottle and
agitated with a magnetic stirrer at ambient temperature for 2 h. Then CeCl3.7H2O (10 mmol)
dissolved in 5 g water was slowly added to the above solution under stirring condition and
stirring was continued for another 3 h. Then, the above white gel was subjected to
hydrothermal treatment in an oven at 373 K for 72 h. The white precipitate of CePO4 was
recovered by centrifugation at 8000 rpm and washing three times with distilled water
followed by drying in an oven at 343 K for 12 h.
Synthesis procedure of CePO4 decorated H-Beta nanocomposites (CePO4@H-Beta)
To obtain CePO4@H-Beta nanocomposite, CePO4 and H-Beta zeolite was mixed by grinding
in a mortar and pestle. Ethanol was added during mixing to make the mixture homogeneous
and mixture was grinded until complete removal of ethanol, which became powder again.
Finally, the powder mixture was heated at 473 K for 2 h and then calcined at 773 K for 12 h
to obtain the material. Three nanocomposites with 20, 30, and 40 % weight ratio of CePO4
were synthesize and designated as CePO4(20%)@H-Beta, CePO4(30%)@H-Beta, and
CePO4(40%)@H-Beta respectively.
Catalyst characterizationThe materials were characterized by X-ray diffraction (XRD) analysis using a RIGAKU
Mini-flex diffractometer in 2θ range of 5-70o with Cu kα (λ = 0.154 nm) radiation. The
specific surface area and porous nature of the synthesized materials were analysed using N2
sorption measurements on a Quantachrome Instrument, Autosorb-IQ, USA. Before analysis,
the samples were degassed at 423 K for 5 h in the degassing port. The surface area was
measure in the relative pressure range of 0.05 to 0.3 using Brunauer-Emmett-Teller (BET)
equation. The distribution of pores was calculated using Barrett-Joyner-Halenda (BJH)
method. The morphologies and microstructures of the synthesized materials were analysed
using Field Emission Scanning Electron Microscopy (FE-SEM), Nova Nano SEM-450, JFEI,
USA and high-resolution transmission electron microscope (HR-TEM) operated at an
accelerating voltage of 300 KV (Tecnai G2, F30) at SAIF centre, IIT Bombay. The
compositions of the various elements present in the material were calculated using energy
dispersive X-ray spectroscopy (EDX). The X-Ray photoelectron spectroscopy (XPS) analysis
was carried out on a PHI 5000 VersaProbeII XPS system (ULVAC-PHI, INC, Japan) with a
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microfocussed (100 m, 25 W, 15 kV) monochromatic Al-K source. A Bruker Tensor-II F-
27 instrument with Pt-ATR assembly was used for Fourier transform-Infra red (FT-IR)
analysis. The estimation of the nature of acid sites present in the materials were carry out on
the same FT-IR instrument using pyridine as a probe molecule. The total acidity
measurement of the materials was carried out using NH3 temperature programmed desorption
(NH3-TPD) technique on a Quantachrome, CHEMBETTM TPR/TPD instrument. Before NH3-
TPD analysis, the sample was preheated at 423 K at a heating rate of 10 deg/min under a
continuous He gas flow for 30 min. Then, after cooling to 323 K, NH3 was allowed to adsorb
on the sample for 1 h. After adsorption, the excess or physically adsorbed NH3 was removed
by flushing He gas (50 mL/min) for 30 min. Finally, the temperature controlled device (TCD)
device became on and the temperature was ramped from 323-873 K at a rate of 10 deg/min.
Catalytic reaction Procedure
Conversion of carbohydrates into HMF
The reaction was performed in a Teflon lined 15 mL autoclave. In a typical reaction,
carbohydrate (100 mg), catalyst (50 mg), and solvent (4 mL) were charged in the autoclave.
The solvent was a mixture of aqueous phase (saturated NaCl solution) and diglyme in a
volume ratio of 1:3. The autoclave was heated to 413 K in an oil bath with a vigorous stirring
for the required period of time. The starting time of the reaction was recorded when the
temperature of the oil bath was reached to 413 K and stirring was started at the same time.
After completion of the reaction, the autoclave was allowed to cool down naturally to room
temperature. The catalyst was removed from the reaction mixture by centrifugation. The
recovered catalyst was washed three times with water, followed by acetone and dried in an
oven at 343 K for 12 h, followed by activation at 673 K for 1 h. Carbohydrate conversion and
HMF selectivity were based on 1H NMR investigation. The carbohydrate conversion and
HMF selectivity were obtained by analyzing the crude reaction mixture using 1H NMR (Jeol,
400 MHz) in DMSO-d6. Analytical method for the determination of HMF yield is given
below.
Analytic methods for the determination of yield using 1H NMRConversion of carbohydrates to 5-HMF and formic acid were monitored using 1H NMR. 1H
NMR was recorded at a regular interval by following a reported procedure.10 A small portion
of the reaction mixture was centrifuged at regular time interval to remove the catalyst, and
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then few-drops of reaction mixture was transferred to NMR tube, and diluted with DMSO-
D6. One illustrative example is given below for the quantification of HMF yield using 1H
NMR.
When sucrose was taken as starting material, HMF as the product and sucrose conversion is
defined as follows:
Sucrose (C12H22O11) HMF (C6H6O2)
No. of hydrogen= 22 No. of hydrogen= (6) x (3.67)
= 22
Areas under the peak correspond to chemical shift value for sucrose (ppm) based on proton
content.
Say, area under the peaks correspond to sucrose = y
And area under the peaks correspond to HMF = w. factor = (w) x (3.67) = z
% Unreacted sucrose = [y/(y+z)] X 100
Sucrose conversion (%) = [100- y/(y+z)].
HMF selectivity (%) = [HMF (product) i.e area under the peaks correspond to HMF
protons]/[Total product formed (area under the peaks based on proton content of all products)
x 100.
HMF yield (%) = [Sucrose conversion (%) x (%) HMF selectivity]/100
Oxidation of HMF to DFF
The DFF was prepared from HMF oxidation using CePO4 as the catalyst by using similar
reaction setup describe in our previous report.11 In brief, in a 25 mL round bottom flask,
connected to a water condenser, HMF (0.5 mmol), DMSO (5 mL), and catalyst (50 mg) were
heated at 413 K in a preheated oil bath and stirring was continued during the reaction. The
reaction was performed under a continuous bubbling of molecular oxygen (10 mL/min). On
completion of the reaction, the reaction mixture was centrifuged for catalyst removal. For
recyclability test, the catalyst was washed three times with water, followed by acetone and
dried at 343 K for 12 h, followed by activation at 473 K for 1 h. The reaction mixture was
poured in water and the extraction of the reactants and products were carried out by the
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addition of ethyl acetate. The reaction mixture was extracted three times and the ethyl acetate
portions were combined and evaporated using rota-evaporator. The concentrated reaction
mixture was diluted with 2 mL of ethyl acetate and then analyzed with gas chromatography
(GC) (Yonglin; 6100; GC column: BP-5; 30 m×0.25 mm×0.25μm) fitted with FID detector.
High purity N2 gas (99.99%, GC grade) was used as the carrier gas with a flow rate of 10
ml/min whereas H2 (99.99%, GC grade) and Air (99.99%, GC grade) were used as ignition
gases. The injector and detector temperature were set at 553 K. GC column oven temperature
was programmed as follows: Initial temperature = 353 K, hold time = 2 min followed by
temperature ramping to final temperature of 573 K with a ramp rate of 10 K/min. 0.4 L of
sample was injected for the analysis. The calibration curves were constructed for pure HMF
and DFF (diluted in ethyl acetate) for the determination of HMF conversion and DFF
selectivity. Products were also confirmed using GC-MS (Shimadzu GCMS-QP 2010 Ultra;
Rtx-5 Sil Ms; 30 m × 0.25 mm × 0.25 μm) and 1H NMR.1H NMR of DFF in DMSO-d6: 9.75 (s, 2H, -CHO), 7.60 (s, 2H, olefin protons)
Catalytic transfer-hydrogenation of LA into GVL
The transfer hydrogenation reaction was carried out in a Teflon-lined autoclave, charged with
LA (1mmol), 2-propanol (6 mL), and catalyst (100 mg, pre-treated at 773 K for 5 h) and
heated at 413 K in an oil bath for the desired period of time. After completion of the reaction,
the stirring was stopped and the autoclave was allowed to cool to room temperature naturally.
On completion of the reaction, the reaction mixture was centrifuged for catalyst removal. For
recyclability test, the catalyst was washed three times with 2-propanol, followed by acetone
and dried at 343 K for 12 h, followed by activation at 673 K for 1 h. The reaction mixture
was directly analyzed with gas chromatography (GC) (Yonglin; 6100; GC column: BP-5; 30
m×0.25 mm×0.25μm) fitted with FID detector. High purity N2 gas (99.99%, GC grade) was
used as the carrier gas with a flow rate of 10 ml/min whereas H2 (99.99%, GC grade) and Air
(99.99%, GC grade) were used as ignition gases. The injector and detector temperature were
set at 553 K. GC column oven temperature was programmed as follows: Initial temperature
= 353 K, hold time = 2 min followed by temperature ramping to final temperature of 573 K
with a ramp rate of 10 K/min. 0.4 L of sample was injected for the analysis. The calibration
curves were constructed for pure LA and GVL (diluted in 2-propanol) for the determination
of LA conversion and GVL selectivity. Products were also confirmed using GC-MS
(Shimadzu GCMS-QP 2010 Ultra; Rtx-5 Sil Ms; 30 m × 0.25 mm × 0.25 μm).
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Table S1. Crystallite size of various materials prepared in this study.
Sr. No.
Catalyst Mean crystallite sizea (nm)
1 H-Beta (before heat treatment) 8.762 H-Beta (after heat treatment at 773 K) 9.033 CePO4(before heat treatment) 24.964 CePO4- (after heat treatment at 773 K) 22.335 CePO4(30%)@H-Beta
(before heat treatment)H-Beta- 9.29CePO4- 23.14
6 CePO4(30%)@H-Beta (after heat treatment at 773 K)
H-Beta- 8.42 CePO4- 21.49
a Calculated using Scherrer formula.
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10 20 30 40 50 60 70
CePO4
CePO4-heat treated
Inte
nsity
(a.u
.)
2 (Degree)Fig. S1 XRD patterns of CePO4 and CePO4-heat treated at 773 K.
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0 30 60 90 120 150 1800.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035 H-Beta CePO4(20%)@H-Beta CePO4(30%)@H-Beta CePO4(40%)@H-Beta
dV
/dD
(mL/
g nm
)
Pore diameter (nm)
0.0 0.2 0.4 0.6 0.8 1.00
30
60
90
120
150
180
210
0 50 100 150
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
Amou
nt a
dsor
bed
(cc/g
)
Relative pressure (P/P0)
CePO4
dV
/dD
(mL/
g nm
)
Pore diameter (nm)
0.0 0.2 0.4 0.6 0.8 1.00
20
40
60
80
100
120
140
160
0 50 100 150
0.000
0.001
0.002
0.003
0.004
0.005
0.006
Amou
nt a
dsor
bed
(cc/g
)
Relative pressure (P/P0)
CePO4-heat treated
dV/d
D (m
L/g
nm)
Pore diameter (nm)
32.2 nm17.6 nm
(b) (c)(a)
0.0 0.2 0.4 0.6 0.8 1.00
100
200
300
400
500
600
3 6 9 12 15 18
0.005
0.010
0.015
0.020
0.025
0.030
0.035
Amou
nt a
dsor
bed
(cc/g
)
Relative pressure (P/P0)
H-Beta CePO4(20%)@H-Beta CePO4(30%)@H-Beta CePO4(40%)@H-Beta
dV/d
D (m
L/g
nm)
Pore diameter (nm)
(e)(d)
0 2 4 6 8 10 12 14 16 18 200.000
0.001
0.002
0.003
0.004
0.005
0.006
0.007
dV/d
D (m
L/g
nm)
Pore diameter (nm)
CePO4
Fig. S2 (a) N2-adsorption isotherm of CePO4 (Inset shows the BJH pore size distributions),
(b) BJH pore size distribution of CePO4 in the range of 2-20 nm, (c) N2-adsorption isotherm
of CePO4 treated at 773 K (Inset shows the BJH pore size distribution), (d) N2-adsorption
isotherm of H-Beta, CePO4(20%)@H-Beta, CePO4(30%)@H-Beta, and CePO4(40%)@H-
Beta (Inset shows the BJH pore size distribution in the range of 2-20 nm), and (e) BJH pore
size distribution of materials shown in Fig. d in the range of 2-180 nm.
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10 15 20 25 30 35 400
2
4
6
8
10
12
14
16
18
Freq
uenc
y
Diameter (nm)
Nanorods Diameter Distributionean = 22.8 nm, = 5.89 nm
50 100 150 200 250 3000
2
4
6
8
10
Fr
eque
ncy
Length (nm)
Nanorods Length Distribution Mean = 150.5 nm, = 55.0 nm (a) (b)
Energy (eV)
OCe P
Pt
Ce
(C)
Fig. S3 Distributions of (a) length and (b) diameter of CePO4 nanorods, (c) EDAX profile for CePO4.
10
Fig. S4 TEM image of CePO4 heat-treated at 773 K.
11
1800 1600 1400 1200 1000 800 600 400
422568
524
462
537572
613
1066
1628
Tran
smitt
ance
(a.u
.)
Wavenumber (cm-1)
1010 955
(b)
(c)
(d)
(e)
(a)
Fig. S5 FT-IR spectra of (a) CePO4, (b) H-Beta, (c) CePO4(20%)@H-Beta, (d)
CePO4(30%)@H-Beta, and (e) CePO4(40%)@H-Beta.
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1560 1520 1480 1440 1400
Tran
smitt
ance
(%)
Wavenumber (cm-1)
CePO4 H-Beta
LL+BB
1546 1490 1444
1560 1520 1480 1440 1400
15461490
1444
Tran
smitt
ance
(%)
Wavenumber (cm-1)
H-Beta CePO4(30%)@H-Beta
LL+BB
1560 1520 1480 1440 1400
1546
14901444
L+BB
Tran
smitt
ance
(%)
Wavenumber (cm-1)
CePO4 CePO4-heat treated
L
(a) (b) (c)
Fig. S6 Pyridine IR spectra of (a) CePO4 & CePO4 heat-treated at 773 K, (b) H-Beta & CePO4(30%)@H-Beta, and (c) comparative PY-IR spectra of CePO4 & H-Beta.
13
4.04.24.44.64.85.05.25.45.65.86.06.26.46.66.87.07.27.47.67.88.08.28.48.68.89.09.29.49.69.8f1 (ppm)
O O O
O O
CH2OH CH2OH CH2OH
OH
OH
OH
OH
OH
OH
OH
OH
n
CePO4(20%)@H-Beta
CePO4(30%)@H-Beta
CePO4(40%)@H-Beta HMFFormic acid
Fig. S7 1H NMR spectra for the conversion of starch into HMF over CePO4(20%)@H-Beta, CePO4(30%)@H-Beta, and CePO4(40%)@H-Beta nanocomposite.
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Photographs taken after each step in the sucrose to HMF conversion
Reaction mixturewithout catalyst
Reaction mixturewith catalyst
Reaction mixtureBefore centrifugation
Reaction mixtureafter catalyst removal
by centrifugation
Reaction mixtureWith MIBK
Before reaction After reaction
Reaction mixtureWith MIBK/H2O
mixture
CatalystRecovered and
activated catalyst
Fig. S8 Photographs recorded after each steps of the sucrose to HMF conversion using CePO4(30%)@H-Beta catalyst.
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0102030405060708090
100
6 12 18 24
DFF
Yie
ld (%
)
Reaction Time (h)
DFF
0102030405060708090
100
10 20 30 40 50 60
DFF
Yie
ld (%
)
Catalyst amount (mg)
DFF
(b)
(c)
0102030405060708090
100
373 383 393 403 413 423
DFF
Yie
ld (%
)
Temperature (K)
DFF(a)
0102030405060708090
100
5 10 15 20
DFF
Yie
ld (%
)
O2 flow rate (mL/min)
DFF(d)
Fig. S9 Optimization of reaction parameters (a) temperature, (b) catalyst amount, (c) reaction time, and (d) O2 flow rate for the selective conversion of HMF into DFF over CePO4.
16
0
20
40
60
80
100
120
1 2 3 4
DFF
Yie
ld (%
)
Cycle number
DFF(a)
0102030405060708090
100
0 6 12 18 24H
MF
Con
vers
ion
(%)
Time (h)
Catalyst removed after 4 h
Catalyst removed after 6 h
With Catalyst
(b)
Fig. S10 (a) Catalyst recyclability and (b) leaching behaviour of CePO4 for the conversion of HMF into DFF.
17
10 20 30 40 50 60 70
CePO4- recycled
CePO4
2 (Degree)
Inte
nsity
(a.u
.)
Fig. S11 XRD patterns of the fresh and recycled catalysts recovered after the HMF oxidation.
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Glucose Fructose Catalyst
H
C
C
O
C
H OH
Ce
O OO
OP
O
HO H
C
C
OH
OH
Ce
O OO
OP
O
HO H
C
C
HOH
OCe
O OO
OP
HO
O
Ce
O OO
OP
O
HO
C
C
HHO
OHH
CH2OH
OHH
C
C
C
HHO
OHH
CH2OH
OHH
C
C
C
HHO
OHH
CH2OH
OHH
C
C
C
HHO
OHH
CH2OH
OHH
C O
OH
H
H
Scheme S1 Plausible reaction pathways for the isomerisation of glucose to fructose over
CePO4 catalyst.
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-H2O
-H2O
-H2O
Tautomerization EnolKeto
HMF
O
O
O
O
OCH2OH
OH
OHOH
CH2OH
OH
OH
CH2OH
OH
OHOH
n
OOH
OH
OH
OHOH O
OH
HOHO
OHHO
OHO
OHO
OH
OOH
HOH
OHHO
HO
OOH
HO
OHO
HH
OHO
O
OH
OOHO
OHO
O
OH
H
B = Brönsted acid sitesL = Lewis acid sites
Scheme S2 Plausible reaction pathways for the transformation of starch into HMF.
20
OO
H2O
O
O
HO
OH
CeO
P O CeO
OH
O
H
Ce
OP
O
Ce
OHO
CeO
PO Ce
O
O
O
HCe OP
OCe
O
OH
O
O
OH
O
H
Ce
O P
O Ce
O
HOO
O
OH
H
O
H
Ce
O
P
O
Ce
OHO
O
O
HOH
O
O
O
OH
H
OH
O
OH
OH
O
O
O
H
CeO
PO Ce
O
OH
OH
Role of L-SitesRole of B-Sites
Role of L & B-Sites
GVLIsopropyl 4-oxopentonoate
ester
Scheme S3 Plausible reaction pathways for the transformation of LA into GVL. Where B is the Brönsted acid sites and L is the Lewis acid sites present in the catalyst.