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Electronic Supplementary Information

Revisiting the Brønsted acid catalysed hydrolysis kinetics of polymeric

carbohydrates in ionic liquids by in-situ ATR-FTIR spectroscopy

Andreas J. Kunov-Kruse, Anders Riisager, Shunmugavel Saravanamurugan, Rolf W. Berg , Steffen B. Kristensen, and Rasmus Fehrmann

Contents

Determination of Hydrolysis Rates ...........................................................................................................................2

Interpretation of IR Spectra ................................................................................................................................... 12

HPLC Analysis ......................................................................................................................................................... 14

Determination of HMF Formation Rates ............................................................................................................... 15

Supporting IR Spectral Data ................................................................................................................................... 19

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Figure S1 - Areas of the 1157 cm-1 band during hydrolysis of cellulose with sulfuric acid. Points with circles are those included in the determination of the first order rate. 10 wt.% cellulose, 1 equivalent of water and 1.7 wt.% H2SO4 in [BDMIm]Cl.

Determination of Hydrolysis Rates

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Figure S2 - Areas of the 1157 cm-1 band during hydrolysis of cellobiose with sulfuric acid. Points with

circles are those included in the determination of the first order rate. 10.6 wt.% cellobiose, 1

equivalent of water and 1.7 wt.% H2SO4 in [BDMIm]Cl.

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Figure S3 - Top: Decrease in the integrated band intensity of the 1155 cm-1 band of the glucoside bond during

acid catalyzed hydrolysis of cellulose(left) and cellobiose(right) at 120 oC in [BDMIM]Cl. The points surrounded

by circles marks the pointes used for determination of the initial rates.

Bottom: The decrease fits 1st order kinetics until late in the experiments. This apparent deviation is most probable

due to overlap with levulinic acid band that has a relatively strong absorption band at 1165 cm-1. At very high con-versions the band of the glucoside bond is very weak and the small amounts of levulinic acid formed from HMF

rehydration seem to disturb the monitoring slightly.

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Figure S4: Initial(black) and pseudo steady state(red) spectra during hydrolysis of cellulose in [BDMIM]Cl with H2SO4.

90oC

100oC

110oC

120oC

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140oC

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Figure S5: Initial(black) and pseudo steady state(red) spectra during hydrolysis of cellobiose in [BDMIM]Cl with H2SO4.

90oC

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Cellulose

Temperature Rate

(Absorbance s-1) Standard deviation

(Absorbance s-1) Standard deviation

(%)

90 -1.26e-5 4.0e-7 3.1

100 -2.18e-5 4.9e-7 2.2

110 -6.03e-5 1.7e-6 2.8

120 -1.37e-4 2.2e-6 1.6

130 -2.50e-4 4.8e-6 1.9

140 -4.94e-4 9.0e-6 1.8

Cellobiose

Temperature Rate

(Absorbance s-1) Standard deviation

(Absorbance s-1) Standard deviation

(%)

90 -3.08e-5 6.43e-7 2.1

100 -6.76e-5 1.21e-6 1.8

110 -1.09e-4 4.87e-6 4.5

120 -1.87e-4 3.22e-6 1.7

130 -2.84e-4 9.71e-6 3.4

140 -4.94e-4 9.00e-6 1.8

Table S1 – Rates of cellulose and cellobiose hydrolysis determined from the area of the 1155 cm-1 band in the

deconvoluted spectra. Standard deviations are determined corresponding to a confidence interval of 0.95

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Figure S8 – Initial development of the 1072 and 1059 cm-1 bands during hydrolysis of cellulose at 120oC

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bers cm−1

Figure S9 − C

omparison betw

een difference spectra obtained during cellobiose hydrolysis and glucose conversion using sulfuric acid catalyst at 120 C

.

1156 cm−1

1142 cm−1

10.5 wt%

cellobiose,1.7wt%

H2 S

O4 , [B

DM

IM]C

l at 120oC

in 90 min

10 wt%

glucose,1.7wt%

H2 S

O4 , [B

DM

IM]C

l at 120oC

in 120 min

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Cellulose

Calculated cm-1 Observed cm-1 Interpretation

974 975 Symmetric C-O-C glycoside stretch

995 994 C-C stretching + acetal C-O stretching

1021 1017 C-O stretching

1029 acetal C-O stretching (ring) inside cellulose chain

1042 1041 C6-O6 stretching, O-H bending

1061 1059 acetal C-O stretching

1071 1072 C-C stretching, C-H bending

1094 1090 Various C-O and C-C stretching

1101 1114 C-H stretching, O-C-O stretching

1110 various C-C stretching

1127-1537 1137 C-H and O-H bending + C-C stretching

1157 1157 Anti-symmetric glycoside C-O-C stretch

1180 1182 no IR active modes

Glucose

Calculated cm-1 Observed cm-1 interpretation

987 975 C3-C4 stetching,C1-O1 stretching+ O-H bending

1000 994 C3-C4 stetching,C1-O1 stretching+ O-H bending

1013 1017 C-6-O6 strethcing+C1-C2stretching + O-H bending

1037 1041 C6-O6 strethcing, OH bending

1056 1059 C6-C5-C4 stretching, C5-O stretching, O-H bending

1066 1072 O-C4-C3 antisymmetric stretching,O3-H bending

1083

C5-O, stretching, C3-O stretching, C2-C3-C4 stretching, varios OH bend

1095 1090 varios C-C stretching and C-H/OH bending

1098 1114 varios C-C stretching and C-H/OH bending

1112 1116 C5-O ,C4-O, C1-O stretching, C-H bend, OH bend

1148 1137 C1-O stretching, OH-bending

- 1157 no IR active modes modes

1173 1182 C-H bending

Table S2 – Interpretation of the difference spectra during hydrolysis in the region 1180-975 cm-1. The reported calculated values are scaled with a factor of 0.978.

Interpretation of IR Spectra

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1,4-β-cellopentose

1,4-β-cellotetraose

1,4-β-cellotriose

1,4-β-cellobiose

Glucose

Figure S10 - Structures of 1,4-β-cellopentose, 1,4-β-cellotetraose, 1,4-β-cellotriose, 1,4-β-cellobiose and glucose optimized using Daussian09 B3LYP/6-311+G(d,p).

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Figure S11 – High-Performance Liquid Chromatography of samples after hydrolysis of cellulose in micro reactor at 100 and 120 oC, respectively. Sample composition: 10 wt.% cellulose, 1 equivalent of water and 1.7 wt.% H2SO4 in [BDMIm]Cl in 0.7 mL d6-DMSO.

HPLC Analysis

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Determination of HMF Formation Rates

Figure S12 - Initial rates of HMF formation during cellulose hydrolysis using 10 wt.% cellulose and 1.7 wt.%

sulfuric acid in [BDMIM]Cl

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Figure S13 – Initial rates of HMF formation during cellobiose hydrolysis using 10.5 wt.% cellobiose and 1.7 wt.%

sulfuric acid in [BDMIM]Cl

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Figure S14 - Top: Formation of HMF expressed as growth*of the 1669 cm-1 band during acid cata-lyzed hydrolysis of cellulose(left) and cellobiose(right) at 120 oC in [BDMIM]Cl. The point surrounded by circles show the points used for determination of the initial pseudo zero-order rate. Bottom: Shows natural logarithm to the change in the 1669 cm-1 band during hydrolysis of cellulose and cellobiose* *(If I0 expresses the absolute value of area of the initial difference spectrum and I(t) the band area of each of the later difference spectra at a given time, then the growth of HMF was expressed as IHMF(t) = |I(t)-I0|. For the first order dependency plots I(t) was used)

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Table S3 – Initial rates of HMF formation as absorbance s-1 during cellulose and cellobiose hydrolysis

determined from the area of the 1669 cm-1 band in the deconvoluted spectra. Standard deviations are

determined corresponding to a confidence interval of 0.95.

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Figure S15 - Corrected ATR-FTIR spectra of 10 wt.% cellulose solutions in [BMIM]Cl and [BDMIM]Cl and the

pure ionic liquids at 120oC

Supporting IR Spectral Data

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Figure S16 - Experimental spectra compared to calculated spectra of cellotetraose. The top is solid

microcrystalline Avicel cellulose powder. In the middle a difference spectrum showing 10 wt.% avicel cellulose

in [BDMIM]Cl at 120oC, where a spectrum of the pure ionic liquid was subtracted.

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Figure S17: Typical deconvolution of in−situ ATR−FTIR difference spectra during cellulose hydrolysis at 120 oC with H2SO4

876898932957

974

995

1021

1041

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1072

10901114

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ModelObserved

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Figure S18: Room temperature ATR−FTIR Spectra of Solid Cellulose Oligomers and Glucose

Avicel Cellulose

1,4−β−Cellohexaose

1,4−β−Cellopentose

1,4−β−Cellotetraose

1,4−β−Cellotriose

1,4−β−Cellobiose

Glucose

Free

δ

C1−

O1−

H

ν C−O

−Cas

ym.

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Figure S19: Calculated IR spectra of glucose and cellulose oligomers

GlucoseCellobioseCellotriose

CellotetraoseCellotetraose

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Figure S20− In−situ ATR−FTIR spectra during cellulose hydrolysis at 120 oC with H2SO4

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Figure S21 In−situ ATR−FTIR spectra during cellulose hydrolysis at 120 o C with H2SO4.

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Figure S22 :In−situ ATR−FTIR difference spectra during cellulose hydrolysis at 120 oC with H2SO4. Substracted spectrum corresponds to red spectrum in figure S20-S21

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