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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
130oC
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
100oC
110oC
120oC
130oC
140oC
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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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0
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0.015
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1000 1050
1100 1150
1200 1250
Absorbance
Wavenum
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
1059
1072
10901114
1137
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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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2 hours
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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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