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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:rajendra@iitrpr.ac.in

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.

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Fig. S4 TEM image of CePO4 heat-treated at 773 K.

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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.

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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.

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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.

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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.

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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.