Enhancing the Antioxidant Activity of Technical Lignins by Combining Solvent Fractionation and Ionic-Liquid Treatment

Article abstract of DOI:10.1002/cssc.201901916

A grass soda technical lignin (PB1000) underwent a process combining solvent fractionation and treatment with an ionic liquid (IL), and a comprehensive investigation of the structural modifications was performed by using high-performance size-exclusion ch

Full text of DOI:10.1002/cssc.201901916

Accepted Article
Title: Enhancing the antioxidant activity of technical lignins by
combining solvent fractionation and ionic liquid treatment
Authors: amel majira, blandine godon, laurence foulon, jacinta van
der putten, laurent cézard, marina thierry, florian pion, anne
bado-nilles, pascal pandard, thangavelu jayabalan, Véronique
Aguié-Béghin, Paul-Henri Ducrot, catherine lapierre, guy
marlair, richard J.A. Gosselink, stephanie baumberger, and
betty cottyn
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To be cited as: ChemSusChem 10.1002/cssc.201901916
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10.1002/cssc.201901916
ChemSusChem
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Enhancing the antioxidant activity of technical lignins by
combining solvent fractionation and ionic liquid treatment
A. Majira,[a] B. Godon,[b] L. Foulon,[b] J.C. van der Putten,[c] L. Cézard,[a] M. Thierry,[a] F. Pion,[a] A. Bado-
Nilles,[d] P. Pandard,[d] T. Jayabalan,[d] V. Aguié-Béghin,[b] P.H. Ducrot,[a] C. Lapierre,[a] G. Marlair,[d]
R.J.A. Gosselink,[c] S. Baumberger,*[a] B. Cottyn*[a]
Abstract: A grass soda technical lignin (PB1000) underwent a
process combining solvent-fractionation and treatment with an ionic
liquid (IL), and a comprehensive investigation of the structural
modifications was performed using HPSEC, 31P NMR, thioacidolysis
and GC-MS. Three fractions with distinct reactivity were recovered
from successive ethyl acetate (EA), butanone (MEK) and methanol
(MeOH) extractions. In parallel, a fraction deprived of EA extractives
was obtained. The samples were treated with methyl imidazolium
bromide [HMIM]Br using either conventional heating (CH) or
microwave irradiation (MW). The treatment allowed to solubilise 28%
of the EA insoluble fraction and yielded additional free phenols in all
biomass are in particular potential alternatives to synthetic
commercial antioxidants like Bisphenol A and t-butylated
hydroxytoluene (BHT)2. Among them ferulic acid is already known
for its potential regarding various applications 3 but its low
availability from plant sources might hinder industrial
developments. As polymer of phenyl propanoids representing up
1
to 30% of the plant biomass, lignins represent one of the major
4
potential sources of biobased phenolics.
Moreover, the
valorisation of technical lignins generated as industrial by-
products would increase the sustainability of lignocellulose-based
biorefineries.5
the fractions, as
a
consequence of depolymerisation and
demethylation. The gain of the combined process in terms of
antioxidant properties was demonstrated through DPPH● radical
scavenging test. Integrating further IL safety-related data and
environmental considerations, this study paves the way for the
sustainable production of phenolic oligomers competing with
commercial antioxidants.
Various strategies driven by the green chemistry principles have
been designed to convert technical lignins into functional
molecules or assemblies while mitigating their variability
processing from botanical origin and transformations during
industrial treatments.6 These strategies include fractionation and
depolymerisation. Fractionation can be performed by ultrafiltration,
potentially directly integrated into the pulping process, 7 or by
solvent extraction, which is advantageously performed at ambient
temperature and pressure and does not require specific
equipment.8 On the other hand, among the depolymerisation
strategies (thermochemical, biological or chemo-catalytic)9, the
recently reported implementation of methyl imidazolium bromide
ionic liquid (IL) [HMIM]Br provides a way to produce lignin
oligomers with increased free phenol content (PhOH) and
decreased polymerisation degree, as a consequence of the
selective cleavage of aryl-alkyl ether bonds (Figure 1). 10 In
particular, it was shown to generate new phenol groups from the
methoxy groups of lignin syringyl and guaiacyl units. Such
phenolic oligomers have a great potential as antioxidant additives
for the formulation of materials, since they are likely to combine
miscibility in the polymer matrix and limited migration towards the
environment due to their oligomeric structure.11,12 Despite this
potential, the process has, until now, only been applied to lignin
models and the antioxidant properties of the oligomers had not
been assessed yet. Advantages of using [HMIM]Br for the
transformation of lignins are foreseen to potentially ensure the
homogeneity of the reaction medium, to avoid the use of
additional chemical reagents and to perform the reaction in mild
conditions (T<110°C, time<40min) compared to most lignin
catalytic conversion processes. Moreover, in this context of use,
this ionic liquid can be recycled. All these advantages also a priori
render the process attractive from an environmental point of view.
However, the sustainability assessment of the process requires
further health and safety information on [HMIM]Br which had not
been provided so far. The present paper aims at assessing the
Introduction
The industry is more and more demanding of biobased phenolic
compounds, to be used as building blocks for polymer synthesis
or valued for their antiradical activity, especially in the field of
polymers, materials and cosmetics. Phenolics derived from plant
[a]
[b]
A. Majira, L. Cézard, M. Thierry, Dr. F. Pion, Dr. P.H. Ducrot, Prof.
C. Lapierre, Prof. S. Baumberger, Dr. B. Cottyn
Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS,
Université Paris-Saclay, 78000 Versailles, France.
E-mail: betty.cottyn@inra.fr and
stephanie.baumberger@agroparistech.fr
B. Godon, L. Foulon, Dr. V. Aguié-Béghin
FARE Laboratory, Fractionnement des AgroRessources et
Environnement, INRA Université de Reims Champagne Ardenne,
F-51100 Reims, France.
[c]
[d]
J.C. van der Putten, Dr. R.J.A.Gosselink
Wageningen Food and Biobased Research
6708 WG Wageningen, The Netherlands
Dr. A. Bado-Nilles, Dr. P. Pandard, T. Jayabalan, Dr. G. Marlair
Institut National de l'Environnement Industriel et des Risques
(INERIS), Parc Technologique Alata, BP2, 60550 Verneuil-en-
Halatte, France
Supporting information for this article is given via a link at the end of the
document.
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10.1002/cssc.201901916
ChemSusChem
FULL PAPER
possibility to transfer the IL newly-developed process10 to Results and Discussion
technical lignin fractions. The objective was to recover antioxidant
extracts soluble in ethyl acetate (EA), one of the conventional
solvents recommended for their relatively limited health hazard
and environmental footprint as assessed from HSE criteria
compiled from various sources.13 EA was selected here in order
to separate extractives from the IL/water layer. Since alkali grass
lignin Protobind 1000 (PB1000) from GreenValue LLC is available
at industrial scale and is already known for its antioxidant
properties,14 it was selected as starting material for this study.
This lignin was subjected to a three-step semi-continuous solvent
fractionation process in order to recover three structurally distinct
soluble fractions (F1-F3). In parallel, the same lignin sample was
submitted to an extensive EA washing to recover a EA insoluble
residue (F4) and validate the possibility of recovering soluble
compounds through chemical treatment of this fraction. PB1000
and the four fractions were submitted to the previously optimized
IL-treatment using microwave-irradiation (MW) or conventional
heating (CH) as heating process. The advantage of microwave-
irradiation was the short reaction time (10 s), whereas the
conventional heating was used to generate more severe
modifications relevant to investigate structure-properties
relationships. The phenolic monomers and oligomers were
extracted from the reaction media with EA and the ethyl acetate
extracts (EAE) were analysed by chromatographic and
spectroscopic methods in order to assess the efficiency of the
conversion, elucidate mechanisms and identify molecules of
interest for further developments. The antioxidant properties of
PB1000 and the EAE as well as those of the insoluble residues
recovered from the most drastic process (CH, 40 min) were
assessed through DPPH● radical scavenging test. The half-max-
effective concentration EC50 was used as criteria to compare the
performance of the different samples. The study demonstrates
the technical advantage of implementing the [HMIM]Br-based
treatment in a cascading approach combining fractionation and
depolymerisation. In addition, sustainability considerations of the
process are further discussed according to safety data obtained
on the IL.
1.
Recovery of different PB1000 fractions and their
contrasted reactivity towards [HMIM]Br-treatments
PB1000 fractionation
PB1000 was fractionated at a semi pilot scale (1 kg dry powder)
through a semi-continuous process intended for future industrial
development.8 This process consisted in a 3-step sequential
extraction with solvents of increasing polarity (Figure 2) and
yielded 31% wt. for the EA-soluble fraction F1, 19% wt. for the
MEK-soluble fraction F2, and 23% for the MeOH-soluble fraction
F3. Since F2 and F3 contained residual EA-soluble compounds
(37 and 7% respectively), PB1000 was also submitted, at lab
scale (g), to a drastic extensive washing with EA yielding an EA-
insoluble fraction F4 (50% of the weight of the starting PB1000)
subsequently used only to validate the depolymerisation process.
Figure 2. Fractionation scheme of PB1000 by sequential extraction with (EA)
ethyl acetate, (MEK) butanone, and (MeOH) methanol, and recovery yields (%
wt./PB1000) of the fractions (F1-F4).
One main characteristic of these set of four fractions was the
increasing proportion of lignin inter unit aryl-alkyl -0-4 linkages
content from F1 to F4, as reflected by the increasing thioacidolysis
yields (Table 1).15 Since our previous study carried out on dioxan-
isolated model lignins showed the -0-4 linkages to be the most
privileged target of the IL treatment allowing partial
depolymerisation,10 these fractions were thus expected to show
increasing reactivity towards the IL-treatment.
Table 1. Thioacidolysis yield of PB1000 and its fractions.
Samples
PB1000
F1
Thioacidolysis yield (µmol g-1)
83
32
F2
96
F3
F4
166
197
Figure 1. Model for the chemical structure of lignin showing the G and S
phenylpropane units linked together by interunit labile aryl-alkyl ether bonds (-
O-4) and resistant bonds (5-5, 10
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In order to determine the influence of structural variations on the
efficiency of the depolymerisation process, PB1000 and its four
derived fractions were subjected to heating treatments in
[HMIM]Br, either under microwave irradiation (MW, 10 s, 110°C)
or under conventional heating (CH, 110°C, 20 or 40 min). In line
with the objective of the treatment to recover EA-soluble
functional extracts, the efficiency of the treatments was assessed
on the base of the recovery yields of the EAE after treatment and
the characteristics of the extracts, selecting average molar
masses and PhOH as major criteria for further applications (Table
2). Moreover, to estimate the solubility gain, the proportion of EAE
soluble compounds with respect to the total products recovered
was calculated and compared to the EA solubility of the initial
sample (Figure 3).
Table 2. Yields and characteristics of the EAE recovered after treatment by
[HMIM]Br ((-MW) microwave irradiation, (-CH20) conventional heating 20
min, (-CH40) conventional heating 40 min) compared to the initial sample
PB1000 and its fractions F1-F4.
Samples
EAE yields[a]
(%)
PhOH[b]
Molar mass averages[c]
(Mn, Mw, g.mol-1) and
polydispersity (PD)
(mmol g-1)
/starting /PB1000
fraction
Mn
Mw
PD
PB1000
Initial
MW
56
36
45
29
56
36
45
29
2.68
4.55
3.95
4.22
1015
580
606
802
1260
814
843
936
1.2
1.4
1.4
1.2
CH20
CH40
F1
Initial
MW
100
72
31
22
18
18
3.88
4.43
5.45
6.62
896
805
664
680
1089
1190
882
1.2
1.5
1.3
1.3
CH20
CH40
F2
59
59
876
Initial
MW
37
28
26
16
7
5
5
3
2.76
4.14
5.74
8.27
914
978
700
676
1085
1407
935
1.4
1.4
1.3
1.3
CH20
CH40
F3
872
Figure 3. EA soluble compounds proportion (% wt.) of the initial samples
(PB1000 and its fractions F1-F4) and the reaction products recovered upon
[HMIM]Br treatments with (MW) microwave, (CH20) conventional heating 20
min, and (CH40) conventional heating 40 min. Values after treatments are
calculated based on the EA extract (EAE) and EA extraction residues (EAR)
recovery yields.
Initial
MW
7
21
9
2
5
2
2
1.18
2.78
961
851
752
709
1212
1140
945
1.3
1.3
1.3
1.3
CH20
CH40
F4
7.26
7
11.94
937
Effect of the [HMIM]Br treatments on the recovery of EAE
Initial
MW
0
15
5
0
8
2
3
1.59
6.25
3.96
4.64
1165
865
867
971
1856
1144
1153
1282
1.6
1.3
1.3
1.3
As a consequence of the fractionation process, the four fractions
exhibited initial contrasted solubility in EA: F1 was 100% EA
soluble, whereas F4 was poorly soluble and F2 and F3 only
partially (37 and 7%, respectively). The [HMIM]Br treatments
induced a decrease of the proportion of EA soluble compounds of
all the samples, except for F3 and F4 which exhibited on the
contrary an increase. The highest effect of the [HMIM]Br
treatment was observed for F4 in the MW conditions. Indeed, 15%
of this insoluble fraction could be solubilized and 28% of the
products formed was soluble. The EAE represented 8% of
PB1000. Three-fold- and twice lower solubility were observed in
CH20 and CH40 conditions, respectively.
CH20
CH40
7
[a] EAE recovery yields expressed with respect to the mass of sample
treated by [HMIM]Br (/ starting fraction) and to the mass of PB1000 submitted
to fractionation before treatment (/ PB1000); [b] determination by 31P NMR
after phosphorylation in pyridine/deuterated chloroform of the whole initial
samples and of the EAE recovered after IL treatment; [c] HPSEC
determination after dissolution-filtration in THF of the EAE recovered before
and after IL treatment (values given for PB1000 and F4 before treatment
correspond to the whole samples).
In contrast, the treatment of the totally soluble fraction F1 led to
the decrease of the solubility with production of insoluble material
(16 to 40% depending on the treatment). The maximum solubility
decrease was observed with the CH conditions, indicating that
these conditions potentially favored recondensation reactions of
the EA soluble compounds due to a longer reaction time. In the
case of the only partially EA soluble fractions F2 and F3 two
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10.1002/cssc.201901916
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contrasted behavior was observed: F2 behavior similar to F1 with
a solubility decrease enhanced in CH conditions, and F3 behavior
similar to F4 with solubility increase (up to 19% solubility increase)
in MW. The EAE recovered from F3 accounted for 21% of the
fraction and 5% of PB1000. The treatment of PB1000 without any
previous fractionation led to an intermediate behavior with a
solubility decrease observed only in the most severe conditions
CH40. In conclusion, the [HMIM]Br treatments could produce EA-
soluble compounds from fractions showing poor initial EA-
solubility, and the presence of EA-soluble compounds in the initial
sample led to an apparent decrease in EA-solubility most
probably due to recondensation reactions favored by CH
conditions.
Besides initial EA-solubility, the fraction dependent effect of
[HMIM]Br treatments on the amount of EAE recovered could be
related to the fraction’s structural differences in terms of -O-4
bonds content. Indeed, in the case of F1 and F2, exhibiting the
lowest amount of -O-4 bonds according to thioacidolysis yields,
the proportion of EA soluble compounds in the reaction mixtures
after treatment decreased, whereas in the case of F3 and mainly
F4, this proportion significantly increased: the results are in
agreement with our previously reported statements and suggest
that -O-4 linkages are effectively the most privileged targets of
the IL treatment. This also demonstrates that the efficiency of the
depolymerisation process is able to counterbalance the effect of
recondensation reactions, occurring during the treatment and that
may be particularly important in the case of long reaction times
(CH compared to MW).
Evidences of demethylation and depolymerisation upon
[HMIM]Br treatment
GC-MS analysis was performed to investigate the phenolic
monomers present in the EAE (Supplementary information S1). It
revealed the presence of a mixture of compounds (phenolic acids,
ketones and aldehydes accounting in total for 1.2% of PB1000) in
F1, the absence of monomeric compounds in F2 and F3 before
treatment, and the formation of new compounds for all the
fractions after treatment. The chromatograms of the EAE
recovered after treatment revealed the presence of phenolic
monomers diagnostic of demethylation (all fractions) and/or
depolymerisation (F2 and F3). In F1 the treatment led to the total
conversion of acetosyringone, the major EAE phenolic monomer
before treatment, into its once- and twice-demethylated
counterparts (1-(3,4-dihydroxy-5-methoxyphenyl)-ethan-1-one C
and 1-(3,4,5-trihydroxyphenyl)-ethan1-one D) and to the
disappearance of all the other phenolic extractives, most probably
involved in recondensation reactions. In F2 and F3 the treatment
led to the production of two ketones A and B previously identified
as acidolysis ketones from experiments on lignin models.10 In F2
only the demethylated form B was detected whereas in F3 both
were formed. The analysis of the thioacidolysis products also
indicated that demethylation took place within lignin units linked
through -0-4 bonds (Supplementary information S2). Indeed,
catechol,
5-hydroxyguaiacyl,
and
3,4,5-trihydroxyphenyl
thioethylated derivatives were detected after thioacidolysis of all
the treated samples. The proportion of these demethylated units
was higher in the CH-treated samples, with an increased effect
for 40 min. An important feature arising from these results is that
demethylation and depolymerisation through the cleavage of -O-
4 bonds seem to be concomitant but independent processes.
Both the demethylation and depolymerisation reactions
diagnosed herein allow the appearance of new phenolic groups
initially involved in ether bonds and could thus account for the
increase of PhOH evidenced further.
In all cases, and whatever the treatment, the yield of the reaction
was good but never reached 100% due to losses of compounds,
mainly volatiles (not identified nor quantified) during the reaction
and soluble and insoluble compounds during the separation
process (precipitation of the products and removal of the water/IL
layer).
Molar mass distribution of the EAE
Whatever the sample, the weight-average molar mass (Mw) of the
EAE, before or after treatment, did not exceed 2000 g mol-1,
indicating that the EAE were essentially composed of oligomers
(less than 10 phenylpropane units). Nevertheless, some
variations in molar distribution appeared between the samples
upon treatments. Increasing EAE average molar masses was
observed from F1 to F3, in agreement with the use of solvent with
increasing polarities for PB1000 fractionation process.16,17 The
effect of the [HMIM]Br treatment on the molar masses depended
on the fraction and conditions used. In the case of F3, all the
treatments induced a decrease in average molar masses with an
increasing effect from MW to CH20 and CH40. For F1 and F2 a
decrease in the molar mass was only observed in CH conditions
and the use of MW by contrast led to a slight increase. In the case
of F4, the EAE produced by the treatments exhibited molar
masses 1.4- to 1.6-fold lower than that of the initial F4 insoluble
fraction, and of the same range as the non-modified EAE of the
other fractions. A slight increase was observed in the CH
conditions. This result supported the hypothesis that
recondensation reactions were favored by the CH conditions.
PhOH functionality gained by IL-treatment combined with EA
extraction
In order to assess the functionality gained through IL treatment
combined with subsequent extraction, the PhOH of the EAE after
treatment were compared to the initial PhOH of the samples. As
shown by the higher PhOH of F1 (the PB1000 EA soluble fraction)
compared to PB1000, EA extraction alone provided a way to
recover compounds with higher functionality. However, this
functionality was even higher when the IL treatment was applied
before recovery of the EAE (3.95-11.94 versus 3.88 mmol g-1),
except for F3-MW (2.78 mmol g-1). Moreover, whatever the
sample and the conditions, the [HMIM]Br treatment led to an
increase of PhOH compared to the starting sample. This effect
increased from F1 to F3, for which a maximum 10-fold increase
was obtained (Table 2). In the case of F3, the increase in PhOH
was concomitant to the decrease in average molar masses,
suggesting that the treatment induced the cleavage of ether
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10.1002/cssc.201901916
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bonds with subsequent release of phenol groups, as previously
demonstrated on lignin models.10
2.
Interest of the products of fractionation and [HMIM]Br
treatment as potential antioxidants
The PhOH enrichment (PhOH, mmol g-1) through IL treatment
and subsequent EA extraction increased with the thioacidolysis
yield of the initial fraction, whatever the treatment (Figure 4). This
was consistent with the major contribution of depolymerisation
reactions through -O-4 bonds cleavage to the formation of new
phenol groups. However, PB1000 and its residual F4 fraction did
not followed the same tendency as the other three fractions. In
particular, their PhOH upon CH treatments were lower than
expected from the behavior of these fractions. This suggested that
a higher proportion of phenols formed by depolymerisation were
present in the EA insoluble residues compared to the other
fractions. Moreover, the weak differences in terms of mass
distribution, and in fact the unclear correlation between
thioacidolysis yield of the starting fraction and the Mw of the
obtained EAE, once more indicated that in the case of fractions
for which the depolymerisation process could be highly efficient
(F3 or F4), recondensation reactions also occur. Interestingly,
these recondensations reactions seemed not to impact the global
PhOH. This could be also a proof of synergy between both
demethylation and depolymerisation processes. In all cases, the
efficiency of the treatment conditions in terms of phenols
production was increased from MW to CH20 and CH40. As a
major feature, the [HMIM]Br treatments was shown to induce an
increase of PhOH, that may be the consequence of both
depolymerisation and transformation of methoxy groups into
phenol ones.
Antioxidant properties (AOP) of the phenolic monomers
compared to reference antioxidants
The main phenolic monomers detected in the EAE after treatment,
namely acidolysis ketones (compounds A and B, Figure 5) and
acetosyringone demethylated once or twice (compounds C and D,
Figure 5) were tested for their DPPH● radical scavenging capacity
according to a test previously used to compare the AOP of lignin
models and technical lignins.14 EC50 (concentration of tested
sample necessary to reduce 50% of the radicals) was used for
this comparison.
Figure 5. Structures of phenolic compounds compared for their radical
scavenging activity: (A-D) compounds detected by GC-MS in the EAE
after IL treatment of PB1000 fractions, (ferulic acid, coniferyl alcohol, p-
coumaryl alcohol) lignin model compounds referred as monolignols, and
(BHT), a commercial antioxidant.
A, B, C and D showed higher AOP (EC50 lower than 0.2 g L-1)
than the other lignin model compounds tested (ferulic acid,
coniferyl alcohol and p-coumaryl alcohol) (Figure 6). The lowest
EC50 was reached with the twice-demethylated acetosyringone
(compound D) four times lower than that of ferulic acid (0.21 g L-
1), which is a reference for natural antioxidants. The radical
scavenging capacity of lignins, and phenolics in general, relies on
the ability of phenols to trap free radicals in the medium after the
loss of a proton18 followed by the stabilization of this radical by
mesomerism. The best performance of compounds C and D is
consistent with the presence of highly electron withdrawing group
conjugated to the aromatic ring and to the presence several
phenols carried by adjacent carbons.19
Figure 4. Enrichment in PhOH upon (green) MW-, (blue) CH20- , and (red)
CH40- [HMIM]Br treatments (difference between the EAE PhOH content after
treatment and the initial PhOH content of the sample) as a function of the
thioacidolysis yield of the initial samples () PB1000, and its fractions () F1,
() F2, () F3 and () F4.
In order to assess the effect of the PhOH increase on the
antioxidant properties, the EAE showing the highest PhOH (CH40
samples) were selected for the further radical scavenging tests.
The corresponding EA insoluble residues were also tested in view
of a potential use of all the fractions of PB1000.
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Table 3. DPPH● radical scavenging capacity (EC50) of PB1000, its fractions
(F1-F3) and their reaction products ((EAE) EA extracts and (EAR) EA
extraction residues) recovered upon [HMIM]Br IL treatment with
conventional heating during 40 min.
Samples
EC50 (g L-1)
EAE
Untreated
EAR
PB1000
F1
F2
0.40 ± 0.01
0.27 ± 0.03
0.27 ± 0.01
0.38 ± 0.03
-
-
0.11 ± 0.00
0.11 ± 0.00
0.33 ± 0.01
0.42 ± 0.08
0.15 ± 0.01
0.17 ± 0.01
F3
Benefit of combining fractionation and IL treatment
Figure 6. DPPH● radical scavenging capacity of phenolic compounds
Thanks to PB1000 fractionation and the subsequent IL
treatment of the fractions a set of functional antioxidant
products with distinct characteristics was generated. The
mapping of the different samples according to their antioxidant
property (EC50), molar mass distribution (Mn, Mw), and
phenolic content (PhOH) (Figure 7) highlights that the EAE
recovered after IL treatment of the fractions combined several
advantages: lower molar masses (Mn ~700 g mol- 1), higher
PhOH (6-12 mmol g-1) and higher radical scavenging activity
(EC50=0.10-0.17 g L-1).
produced by IL treatment of PB1000 fractions (compounds
A-D)
compared to monolignols and a commercial synthetic antioxidant (BHT).
error < 1%.
Interestingly, all the compounds tested were competitive with a
commercial antioxidant like BHT (EC50=0.19 g L-1).Thus, these
compounds might be advantageously purified or synthetised and
used as antioxidant for commercial applications. However, in
order to avoid costly purification steps and take profit of possible
synergies between phenolic compounds, the AOP of the mixtures
of products recovered from the treatments (EAE and EA
extraction residues) was considered.
Moreover, it shows that the molar mass differences between
the fractions were leveled by the IL treatment. These
characteristics make them good candidates as antioxidant
ingredients for the formulation of plastics or cosmetics or for
the synthesis of new bio-based polymers and multi-functional
molecules. Based on these results, an integrated process
could be proposed and its sustainability was discussed.
AOP of the EAE and EA extraction residues compared to
PB1000 and its fractions
All the fractions (F1-F3) and the products recovered from the
CH40 IL treatment of these fractions exhibited DPPH● radical
scavenging capacity similar or higher than that of the PB1000
reference sample, according to EC50 (Table 3). Concerning the
untreated fractions, the results are in accordance with previous
studies on the fractionation of other technical lignins (organosolv
lignin BIOLIGNINTM and LignoBoost kraft lignins), showing the
general higher radical scavenging activity of the EA soluble
fraction compared to the other ones. 20 The IL treatment of the
fractions led to the production of EAE with enhanced radical
scavenging activity compared to PB1000 and the fraction
considered. This enhancement could be explained by the
increased of PhOH after treatment and the presence of the highly
antioxidant phenolic monomers in EAE. In addition, the EA
extraction residues (EAR) also exhibited interesting higher activity
than their corresponding starting fraction, except for F1. In the
case of F3, the AOP of the insoluble residue was even twice better
than the EAE, which confirmed that some neo-formed phenol
groups were carried by some compounds of higher molar mass
insoluble in EA after treatment. According to the EC50, F2
appeared as the most interesting fraction with respect to the
production of antioxidant through IL treatment, since the radical
scavenging activity of both the EA- soluble and insoluble fraction
after treatment were the best.
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10.1002/cssc.201901916
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FULL PAPER
cases, the demethylation and depolymerisation induced by the
treatment is beneficial. To design a cascade approach and
preliminary assess its sustainability, it is necessary to consider
the technical performances of the products but also the recovery
yields and safety aspects.
Recovery yields and technical gain
The process proposed in Figure 8 allows the production of a total
of 67.7% of products with enhanced antioxidant activity compared
to PB1000, including 35.5% EA-soluble oligomers enriched in
PhOH. In order to optimize the gain in AOP and PhOH, the IL
treatment conditions selected are the most drastic ones
(conventional heating, 40 min), which on contrary do not favor the
formation of soluble material. However, since the insoluble
products exhibit high antioxidant properties, they could be
advantageously incorporated directly as filler in plastics or
functionalized by grafting of the PhOH. In the first step of the
process, a functional fraction is directly obtained from PB1000 by
EA extraction. In the second step, the residue is submitted to a
MEK extraction combined with IL treatment of the extract to
recover both EA-soluble and –insoluble highly antioxidant
products. In the last stage, the MEK extraction residue undergoes
a MeOH extraction combined with IL treatment to recover EA
soluble oligomers highly enriched in phenol groups together with
antioxidant insoluble compounds. Due to its lowest content in
lower-molar-mass phenolic extractives, the final residue of the
process might find applications for instance as filler in materials.21
Figure 8. Scheme of a process proposal yielding 35.5% of EA soluble
products (F1, EAE2, EA3) and 29.2% EA insoluble products (EAR2,
EAR3) showing a gain in terms of antioxidant property (AOP=1/EC50) and
free PhOH content compared to the starting material.
Figure 7. Mapping of PB1000 and its products according to (A) EC50 and
PhOH content, (B) EC50 and Mn, and (C) EC50 and Mw: (black) starting
PB1000 sample, (blue) PB1000 fractions, (green) ethyl acetate extracts
(EAE) recovered after [HMIM]Br treatment with conventional heating
during 40 min (CH40).
Safety and environment related aspects and further
sustainability considerations
3.
Towards a sustainable cascade integrated process
Sustainability assessment of the developed value chain was
further examined for physico-chemical hazards and
environmental impacts potentially arising from the key chemicals
involved. With regard to the fire hazard, the two main critical
points of the process in terms of safety are the use of organic
solvents (EA, MEK, and MeOH) for the extraction steps and the
Taken together, the results showed that IL treatment could be
advantageously applied to lignin fractions for different purposes:
production of competitive antioxidant extracts, increase of lignin
free phenol content, partial dissolution of insoluble residues. In all
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10.1002/cssc.201901916
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Union between 1 and 10 tons per year) and immunotoxicity tests
on the three-spined stickleback (Gasterosteus aculeatus). The
results (Table 5) showed that [HMIM]Br has a low the toxicity for
D. magna and P. subcapitata (EC50>100 mg L-1). No
biodegradation was observed in the manometric respirometry
test, leading to conclude that [HMIM]Br is not-rapidly
biodegradable. These results are consistent with those already
obtained on compounds of the imidazolium family which
demonstrate that the toxicity increases, and the biodegradability
is enhanced with the length of side alkyl chain. The fish
use of a new ionic liquid ([HMIM]Br). Of course, the well-
established flammability of mentioned solvents has to be handled
from supply to process end-use, which leads in this particular
context to limited issues according to mild operations conditions.
Despite their flammability properties, such materials remain still
recommendable as extraction solvents, with regard to HSE
criteria taken into consideration with some prioritising rules.22 In
particular, these substances are not mentioned in any list of the
EU REACH regulation designating substances of particular
concern due to their adverse health or environmental impacts. A
summary of results pertaining to physical hazards potentially
associated to the use of [HMIMBr] is provided in Table 4.
immunotoxicity tests indicated that [HMIM]Br has low
toxic
effects on the stickleback splenocytes by inducing necrosis, likely
due to the bromine anion associated to the imidazolium-based
cation of [HMIM]Br. Recyclability of [HMIM]Br was already
examined in our previous study. It was concluded that 75% of
clean IL can be recovered at the end of the treatment and could
be used again for similar reactions for several cycles.10 All these
results bring a contribution to safe-by-design biorefinery involving
the studied value chain.
Moreover, EA and MeOH could potentially be substituted by
biobased recommended alternatives, bio ethyl lactate and bio
ethanol, respectively (this latter one being nowadays totally bio-
sourced). MEK, if not so easily substituted, and although having
some toxicity hazard, might at least be produced from biomass in
the future, in a cost-effective way as an intermediate to
biobutanol.23
Table 5. Overview of the results obtained for the methyl-imidazolium
bromide [HMIM]Br.
Classification for
aquatic
environmental
hazards
Test
Results
Table 4. Data summary pertaining to fire and corrosivity to metal hazards.
EA
easy
medium
MeOH
easy
moderate
MEK
easy
large
[HMIM] Br
Very difficult
Very low
Daphnia
immobilization test
(OECD 202)
magna
Ignitability
Heat Release
Rate
EC50 48h: 414 mg L-1
(352 – 477 mg L-1)[a]
Not classified for
acute aquatic
hazard
NOEC[b] 72h: 62.5 mg L-1
EC10 72h: 227 mg L-1
(209 – 242 mg L-1)
EC50 72h: 346 mg L-1
(327 – 361 mg L-1)
Algal growth
Fire
none
none
none
Very
inhibition test
Pseudokirchneriella
subcapitata,
retardancy
Fire induced
toxicity
significant
COx
emissions
in fire
COx
emissions
in fire
COx
emissions
in fire
COx,
HCN
from
(OECD 201)
unexpected
fire conditions
Significant for
neat IL and IL
Not readily
biodegradable.
Further
Corrosivity to
metals (C and
stainless steel
nd
nd
nd
with
10%
Manometric
respirometry
(OECD 301F)
investigation is
needed to
conclude on the
classification for
the long-term
aquatic hazard
No biodegradation
observed
added water
test
Also often considered as green solvents per se, ionic liquids
remain controversial for safety issues24 and chiefly require a
case-by-case analysis in the context of use, since safety
assessments are not based only on intrinsic properties, but
essentially on apparatus and testing procedure dependent
Fish innate immune
responses
(Gasterosteus
aculeatus)
Stimulate immune
responses
Cytotoxic effect
[c]
-
properties (flash point, thermal stability, metal corrosivity).25
A
[a] 95% confidence interval;[b] No Observed Effect Concentration;[c]
not relevant
preliminary assessment of [HMIM]Br safety profile has been
performed and is provided herein (with technical details in
Supplementary information S3), integrating both physico-
chemical hazard (fire, corrosivity to metals) and eco-toxicological
properties of the IL, in line with REACH regulation safety data
needed for future registration. This study also provides new
insights regarding [HMIM]Br thermal stability and fire behavior,
showing in particular a remarkable resistance to ignition and a
flame retardancy property. A first order evaluation of the
corrosivity potential of the neat IL has indicated that further
investigation on the matter will be required for the appropriate
selection of the reactor material owing to practical conditions of
used of the IL.
Conclusions
The possibility to transfer the [HMIM]Br treatment to technical
lignins was demonstrated, using PB1000 as commercial
reference sample. Safety assessment of [HMIM]Br highlighted the
effective flame retardant property of this IL and provided data on
its eco-toxicological footprint, not departing from other ILs of the
imidazolium family useful for future REACH registration. The
treatment induced both depolymerisation and demethylation of
lignin, leading to the formation of additional free phenols. Based
on these results and after checking that similar effects were
obtained with other commercial technical lignins including Kraft
Regarding the environmental properties of the IL,26 the selected
test battery includes the tests required by annex VII of the REACH
regulation (substance manufactured or imported into European
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10.1002/cssc.201901916
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extracts were concentrated under reduced pressure and the final solvent
was removed by vacuum drying. The residual lignin fraction was collected
and dried at maximum temperature of 40°C.
lignin (data not shown), an integrated cascade process combining
IL treatment and solvent extractions was designed so as to
optimize the recovery yield of EA soluble extracts with enhanced
performance compared to the technical lignin. The first step
directly provides a functional EA extract, while the second and
third steps combine extractions with IL treatment to further
improve functionalities for applications as antioxidant or building
blocks. Indeed, the extracts consisted of free-phenol rich
oligomers with antioxidant properties favorably competing with
ferulic acid and BHT. Besides their high antiradical activity, these
extracts have the advantage to show standardized average molar
masses (872-937 g mol-1), low polydispersity (1.2-1.3) and high
free phenol content (up to 11.9 mmol g-1), which provides
opportunities of green bio-based innovation in plastics and
cosmetics formulation.
EA solubility test. Lignin solubility was determined gravimetrically by
dispersing 100 mg of lignin in 10 mL of EA (room temperature, 30 min),
then centrifuging the suspension (20°C, 20 min, 4000g) and drying the
solid residue at 40 °C for 48 h. Solubility was determined in duplicate,
based on the amount of solid residue.
[HMIM]Br treatments
Whatever the treatment, the IL was vacuum-dried at RT before use.
Treatment with microwave irradiation. MW irradiation experiments were
conducted in an Anton Paar Monowave 300 instrument. The sample (200
mg) and [HMIM]Br (2 g) were placed in an Anton Paar 30 mL reaction tube
equipped with a magnetic stirrer. The mixture was irradiated with P=300
W, Tmax=110 °C, ramp 30 s, hold 10 s, with full air cooling and stirring. At
the end of the reaction, the solid residue was filtered, washed with water
(20 mL) and EA (20 mL). The filtrate was recovered, the layers were
separated and the aqueous layer was extracted with EA (2x20 mL). The
combined EA extracts were dried over MgSO4 and concentrated under
reduced pressure bellow 35°C. The crude soluble mixture was analyzed
by 31P NMR, HPSEC, and thioacidolysis.
Experimental Section
General materials and methods
Technical grass (mixed wheat straw/Sarkanda grass) alkali lignin
PROTOBIND 1000 (PB1000) was purchased from GreenValue LLC
(USA).27 Ionic liquid [HMIM]Br was synthesised following a previously
reported procedure. 28 Ethyl acetate was purchased from Carlo Erba
Reagents (France) and used as received. All other reagents, compounds
A (ref 410659) and B (ref 796883), were purchased from Sigma-Aldrich
Chemical Co. (USA) and were used as received.
Treatment of lignin upon conventional heating. The sample (200 mg) and
[HMIM]Br (2 g) were placed into an Ace pressure tube equipped with a
magnetic stirrer under an inert atmosphere, flushed with Ar. The tube was
closed and the mixture was stirred in an oil bath at 110 °C. After 20 or 40
min, the solid residue was filtered and the same downstream procedure as
for MW irradiation was applied to the solid residue and the filtrate.
TLC experiments were performed on an aluminium strip coated with Silica
Gel 60 F254 from Macherey-Nagel, revealed under UV-light (254 nm), then
in the presence of a 5% w/w ethanolic solution of phosphomolybdic acid.
Evaporations were conducted under reduced pressure at temperatures
below 35°C unless otherwise stated. Column chromatography (CC) was
carried out with an automated flash chromatography PuriFlash system and
Synthetic procedure for compounds C and D
Acetosyringone (500 mg, 2.5 mmol) and [HMIM]Br (2.5 g, 6 equivalents)
were placed in an Anton Paar 30 mL reaction tube equipped with a
magnetic stirrer. The mixture was irradiated with P=300 W, Tmax=110 °C,
ramp 30 s, hold 10 s, with full air cooling and stirring. At the end of the
reaction, water (20 mL) and EA (20 mL) were added. The layers were
separated and the aqueous layer was extracted with EA (2x20 mL). The
combined EA extracts were dried over MgSO4 and concentrated under
reduced pressure bellow 35°C. The crude mixture was purified by flash
column chromatography (eluted with 50 to 100% ethyl acetate in
pre-packed INTERCHIM PF-30SI-HP (30 μm silica gel) columns. 1H, 13
C
spectra were recorded in CD3OD at 400, 100 MHz respectively on a Bruker
Ascend 400 MHz instrument. Chemical shifts are reported in parts per
million relative to internal references (solvent signal).
Lignin fractionation and EA solubility test
EA extraction (1). PB1000 (1 kg) was fractionated by a three-step
sequential solvent extraction process, according to a previously published
approach.8 The following solvents were used sequentially in a semi-
continuous process: ethyl acetate (EA); 2-butanone (MEK); methanol.
Lignin was loaded in the first solvent in the glass column. After settlement,
EA was pumped by the HPLC pump at a flow rate of 2-4 mL.min-1 in the
column. The solubilized fraction was collected at different heights in the
column. The solvent was removed via vacuum evaporation and the final
solvent was removed by vacuum drying. The recovered solvent was re-
used in the process. When the concentration of solubilized lignin was very
low, the second solvent was added by the pump in the column. For each
solvent the procedure was repeated till after 3 solvent extractions, the
residual lignin fraction was collected from the column. This fraction was
dried at maximum temperature of 40°C.
cyclohexane) to yield 63
methoxyphenyl)-ethan-1-one) and 26
trihydroxyphenyl)-ethan-1-one). The products were characterized by NMR
(Supplementary information S4).
%
of product
C
(1-(3,4-dihydroxy-5-
(1-(3,4,5-
%
of product
D
Compound C: Rf = 0.34 (cyclohexane/ethyl acetate 1:1). 1H NMR (400
MHz, CD3OD, 25°C): H 2.53 (s, 3H, CH3), 3.91 (s, 3H, CH3O), 7.19 (m,
2H, H2 and H6). 13C NMR (100 MHz, CD3OD, 25°C): C 24.9 (CH3), 55.3
(CH3O), 103.6, 110.2 (C2, C6), 127.9, 139.9, 144.9, 147.9 (4*Cq), 198.3
(CO).
Compound D: Rf = 0.23 (cyclohexane/ethyl acetate 1:1). 1H NMR (400
MHz, CD3OD, 25°C): H 2.48 (s, 3H, CH3), 7.05 (s, 2H, H2 and H6). 13C
NMR (100 MHz, CD3OD, 25°C): C 24.8 (CH3), 107.89 (C2, C6), 128.0,
139.1, 145.2 (4*Cq), 198.4 (CO).
EA extraction (2). PB1000 (6.5 g) was dissolved in 250 mL EA, the mixture
was stirred at room temperature during 30 minutes. The resulting solid
residue was filtered and the filtrate was recovered. The procedure was
repeated 9 times to obtain an exhaustive extraction. The combined EA
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Chemical analysis of lignin and lignin-derived products
assessed from the apparent molar masses determined by a calibration
curve based on polyethylene oxide standards (Igepal, Aldrich) and lignin
model dimers.33
GC-MS analysis. 20 L of EA solutions (1 mg mL-1) previously dried on
sodium sulfate were silylated with 100 L of bistrimethylsilyl-
trifluoroacetamide (BSTFA) and 10 L of GC-grade pyridine. The silylation
was completed within a few minutes at room temperature. GC-MS
analyses were performed in splitless mode on an Agilent 7890A gas
chromatograph coupled to an Agilent 5977B mass spectrometer, with a
poly(dimethylsiloxane) column (30 m × 0.25 mm; Rxi-5Sil, RESTEK),
working in the temperature program mode from 70 to 330 °C at +30°C min-
1, during 20 min, with helium as carrier gas. The chromatographic system
was combined to a quadrupole mass spectrometer operating with electron
impact ionisation (70 eV) and positive mode detection, with a source at
230°C and an interface at 300°C, and with a 50 to 800 m/z scanning
range.29
Assessment of antioxidant properties
Preparation of the solutions. A lignin sample was weighed in a 2 mL
microfuge tube and the solvent (90/10 v/v dioxane/water mixture) was
added in order to obtain concentrations between 0.1 and 0.5 mg mL−1. The
dispersion was homogenized using a vortex (Heidolph TOP-MIX 94323,
Fisher Scientific Bioblock, Vaulx Milieu, France) for 30 s at 20 000 Hz. The
resulting solutions were tested for their radical scavenging activity.
Measurement of the free radical scavenging activity by DPPH• test.
The free radical scavenging activity of the samples was evaluated by
measuring their reactivity toward the stable free radical DPPH• according
to a published method.14 In a quartz cuvette, 77 μL of the sample
dioxane/water solution was added to 3 mL of a 6 × 10−5 mol L−1 DPPH●
solution, prepared daily in absolute ethanol. The absorbance at 515 nm of
each sample was monitored using an UV− visible double-beam
spectrophotometer (Shigematsu Scientific Instrument, USA), until
reaching a plateau. A blank was prepared under the same conditions,
using 77 μL of solvent instead of the sample solution. All kinetics were
obtained from at least six solutions, prepared from three different lignin
preparations. The kinetics of disappearance of DPPH● was obtained by
calculating at each time the difference between the absorbance of the
blank solution and the absorbance of the sample. When the absorbance
reached a plateau, the percentage of residual DPPH● was calculated and
plotted vs the concentration of soluble lignin in the sample tested. The
concentration of antioxidant extract needed to reduce 50% of the initial
DPPH● (noted EC50, with EC standing for efficient concentration) was
determined from this linear curve.
Quantitative 31P NMR and samples preparation. Derivatisation of the
samples
with
2-chloro-4,4’,5,5’-tetramethyl-1,3,2-dioxaphospholane
(TMDP, Sigma-Aldrich, France) was performed according to a reported
procedure.30 Lignin samples (20 mg) were dissolved in 400 L of a mixture
of anhydrous pyridine and deuterated chloroform (1.6:1 v/v). Then was
added 150 L of a solution containing cyclohexanol (6 mg mL-1) and
chromium(III)acetylacetonate (3.6 mg mL-1), which served as internal
standard and relaxation reagent respectively and 75 L of TMDP. NMR
spectra were acquired without proton decoupling in CDCl3 at 162 MHz, on
a Bruker Ascend 400 MHz spectrometer. A total of 128 scans were
acquired with a delay time of 6 s between two successive pulses. The
spectra were processed using Topspin 3.1. All chemical shifts were
reported in parts per million relative to the product of phosphorylated
cyclohexanol (internal standard), which has been observed to give a
doublet at 145.1 ppm. The content in hydroxyl groups (in mmol g-1) was
calculated on the basis of the integration of the phosphorylated
cyclohexanol signal and by integration of the following spectral regions:
aliphatic hydroxyls (150.8–146.4 ppm), condensed phenolic units (145.8-
143.8 ppm; 142.2-140.2 ppm), syringyl phenolic hydroxyls (143.8-142.2
ppm), guaiacyl phenolic hydroxyls (140.2–138.2), p-hydroxyphenyl
phenolic hydroxyls (138.2–137.0 ppm), and carboxylic acids (136.6-133.6
ppm).
Safety assessment of [HMIM]Br
Overall multicriteria safety analysis has been inspired by the global
strategy developed by some of the authors of this manuscript for greener
use of ionic liquids in general, as exemplified by Eshetu et al.34 in the case
of energy storage in electrochemical devices.
Thioacidolysis. Thioacidolysis of lignins (5 mg) was carried out according
to literature published protocol,31 using heneicosane (C21H44, Fluka) as
internal standard (IS). Lignin-derived p-hydroxyphenyl (H), guaiacyl (G),
and syringyl (S) thioacidolysis monomers were analyzed as their
trimethylsilyl derivatives by a gas chromatography−mass spectrometry
Fire hazard: examined by fire calorimetry testing based on the use of the
most polyvalent fire calorimeter designated as the Fire Propagation
Apparatus, following ISO 12136. See also ESI for further details on
procedures and complementary details on achieved experimental data.
(GC-MS) instrument (Saturn 2100, Varian) equipped with
a
poly(dimethylsiloxane) column (30 m × 0.25 mm; SPB-1, Supelco) and
using the following heating program: 40 to 180 °C at 30 °C min−1, then 180
to 260 °C at 2 °C min−1. The mass spectrometer was an ion trap with an
ionization energy of 70 eV and positive mode detection. The determination
of the thioethylated H, G, and S monomers was performed from ion
chromatograms reconstructed at m/z 239, 269, and 299, respectively, as
compared to the IS signal measured from the ion chromatogram
reconstructed at m/z (57 + 71 + 85). The molar yield of the detected
thioethylated monomers was calculated on the basis of the Klason lignin
content of the sample, determined according to a published procedure.32
Corrosivity screening tests: carbon and stainless-steel specimen, partially
immerged in plastic cells containing neat IL and IL added with 10% water,
following home-made procedure (exposure in an oven regulated at 100°C
during 8 days): mass loss determined before and after exposure with
calibrated balance, inspired from procedure developed for IL corrosivity
assessment by German ILs producer IO-LI-TEC.
Ecotoxicity tests. Ecotoxicity tests required by annex VII of the REACH
regulation (substance manufactured or imported into European Union
between 1 and 10 tons per year) have been performed. They are
presented briefly in Table 6. In addition to these regulatory tests, fish
immunomarker tests were conducted to study possible long-term effects
on aquatic ecosystems. Their protocol is detailed in a previous paper.26
Molar Mass distribution. The apparent number-average- (Mn) and the
weight-average- (Mw) molar mass of the samples were estimated by high-
performance size-exclusion chromatography (HPSEC) using a styrene -
divinylbenzene PL-gel column (Polymer Laboratories, 5 µm, 100 Å, 600
mm x 7.5 mm I.D.) with photodiode array detector (Dionex Ultimate 3000
UV/vis detector) set at 280 nm, and using BHT-stabilized THF (1 mL min−1
)
as eluent. The samples were solubilized in THF and filtered on PTFE
membrane (0.45 μm) before injection. The molar mass averages were
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Table 6. Summary of the ecotoxicity tests performed on [HMIM]Br.
Organisms
Test method
Effect
Endpoints
Expression
of results
Test
duration
NOEC
EC10
Micro-algae
OECD 201,
2011
Chronic
Acute
Growth
Mobility
72 hours
Pseudokirchneriella subcapitata
EC50
Micro-crustaceans
OECD 202,
2004
EC50
48 hours
28 days
Daphnia magna
Ready
OECD 301F,
1992
Oxygen
consumption
%
Activated sludge receiving predominantly domestic sewage
biodegradation
Biodegradability
A. Bado-Nilles, P. Pandard, T. Jayabalan and G. Marlair
performed the safety related analysis of [HMIM]Br and contributed
to the selection of process conditions.
P.-H. Ducrot contributed to the design of the IL route for lignin
conversion and to the elucidation of reaction mechanisms.
Acknowledgements
C. Lapierre performed the analysis of lignin extractives and
contributed to the identification of lignin demethylation and
depolymerisation products by mass spectrometry.
The authors would like to acknowledge Emmanuel Magnier and
Bruce Pégot (Université de Versailles St-Quentin, ILV, UMR
CNRS 8180) for their scientific support in the development of the
[HMIM]Br treatment, Franck Flécheux and Jean-Baptiste Mathieu
(LEREM) for the corrosivity-to-metal tests, and the IJPB Institute
Plant Observatory chemistry and metabolism platform for access
to the Agilent GC-MS system. The IJPB benefits from the support
of the LabEx Saclay Plant Sciences-SPS (ANR-10-LABX-552
0040-SPS). This publication is a part of Zelcor project that has
received funding from the Bio Based Industry Joint Undertaking
under the European Union's Horizon 2020 research and
innovation programme under grant agreement No 720303.
B. Godon, L. Foulon and V. Aguié-Béghin conceived, performed
and analysed the measure of antioxidant activity of the raw and
derivated lignin samples.
J.C. van der Putten performed the semi-continuous fractionation
processes and characterised lignin fraction F1-F3.
R.J.A. Gosselink coordinated the semi-continuous fractionation
process implemented on PB1000 and provided the characterised
lignin fractions F1-F3.
Authors contributions
S. Baumberger coordinated the study within the framework of
Zelcor project and designed the cascade process.
A. Majira synthetised the model compounds, performed the
31PNMR analyses of the raw and derivated lignin samples and
provided technical support for the experiments with [HMIM]Br.
B. Cottyn designed the [HMIM]Br process, implemented it to
PB1000 and its fractions and coordinated the analysis of the lignin
raw material and derivatives.
L. Cézard performed the thioacidolysis analysis of the raw and
derivated lignin samples.
All the authors participated in the scientific discussions, red and
approved the final manuscript.
M. Thierry contributed to the optimisation of the IL-treatment and
investigated the effect of the treatment on PB1000, in the
framework of her MSc thesis.
Keywords: lignins • biorefinery • green chemistry • antioxidant •
ionic liquid
F. Pion prepared PB1000 fraction F4 at lab scale and contributed
to the design of the integrated cascade process.
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Entry for the Table of Contents
FULL PAPER
A. Majira, B. Godon, L. Foulon, J.C. van
der Putten, L. Cézard, M. Thierry, F.
Pion, A. Bado-Nilles, P. Pandard, T.
Jayabalan, V. Aguié-Béghin, P.H.
Ducrot, C. Lapierre, G. Marlair, R.J.A.
Gosselink, S. Baumberger,* B. Cottyn*
A
cascade biorefinery process is
presented. Upgrading of technical
lignins and sustainable production of
phenolic oligomers of interest as
substitutes
for
commercial
antioxidants.
Page No. – Page No.
((Insert TOC Graphic here: max.
width: 5.5 cm; max. height: 5.0 cm))
Enhancing the antioxidant activity of
technical lignins by combining
solvent fractionation and ionic liquid
treatment
[1]
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Polym. J. 2015, 63, 186-193; c) L. Hollande, A.S. Jaufurally, P.H. Ducrot, F. Allais, RSC Advances 2016, 6, 44297-44304; d) A.F. Reano, F. Pion, S.
Domenek, P.H. Ducrot, F. Allais, Green Chem. 2016, 18, 3334-3345; e) M. Janvier, L. Hollande, A.S. Jaufurally, M. Pernes, R. Menard, M. Grimaldi, J.
Beaugrand, P. Balaguer, P.H. Ducrot, F. Allais, ChemSusChem 2017, 10, 738-746; f) F. Pion, A.F. Reano, P.H. Ducrot, F. Allais, RSC Advances, 2013, 3,
8988-8997.
[2]
[3]
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