SO3H-functionalized acidic ionic liquids as catalysts for the hydrolysis of cellulose

Article abstract of DOI:10.1016/j.carbpol.2012.08.095

The conversion of cellulose into valuable chemicals to deal with the depletion of fossil fuel has got much attention. Completing the hydrolysis of cellulose under mild conditions is the key step. In this study, six kinds of SO₃H-functionalized acidic ionic liquids were used as acid catalyst to promote the hydrolysis of cellulose in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). All of them were efficient for the hydrolysis of cellulose, with the maximum total reducing sugars (TRS) yields over 83% at 100 °C. Acidic ionic liquids with analogous structures showed similar catalytic activities. Triethyl-(3-sulfo-propyl)-ammonium hydrogen sulfate (IL-5 in this study) was the optimum ionic liquid for cellulose hydrolysis, with the maximum TRS yield at 100 °C up to 99% when the dosage used was 0.2 g. In addition, the water in [BMIM]Cl had negative effect on cellulose hydrolysis. Therefore, controlling the content of water in a comparatively low level is quite necessary.

Full text of DOI:10.1016/j.carbpol.2012.08.095

Carbohydrate Polymers 92 (2013) 218–222
Contents lists available at SciVerse ScienceDirect
Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol
SO3H-functionalized acidic ionic liquids as catalysts for the hydrolysis of cellulose
Yuanyuan Liu, Wenwen Xiao, Shuqian Xia∗, Peisheng Ma
Key Laboratory for Green Chemical Technology of State Education Ministry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 July 2012
Received in revised form 20 August 2012
Accepted 25 August 2012
Available online 31 August 2012
The conversion of cellulose into valuable chemicals to deal with the depletion of fossil fuel has got much
attention. Completing the hydrolysis of cellulose under mild conditions is the key step. In this study,
six kinds of SO3H-functionalized acidic ionic liquids were used as acid catalyst to promote the hydroly-
sis of cellulose in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). All of them were efficient for the
hydrolysis of cellulose, with the maximum total reducing sugars (TRS) yields over 83% at 100 ◦C. Acidic
ionic liquids with analogous structures showed similar catalytic activities. Triethyl-(3-sulfo-propyl)-
ammonium hydrogen sulfate (IL-5 in this study) was the optimum ionic liquid for cellulose hydrolysis,
with the maximum TRS yield at 100 ◦C up to 99% when the dosage used was 0.2 g. In addition, the water
in [BMIM]Cl had negative effect on cellulose hydrolysis. Therefore, controlling the content of water in a
comparatively low level is quite necessary.
Keywords:
Cellulose
Hydrolysis
Ionic liquid
Acidic catalysis
© 2012 Elsevier Ltd. All rights reserved.
1. Introduction
of IL, it can be used as the solvent or catalyst. After the disso-
lution of cellulose in ILs, dilute acid, solid acid and cellulase can
In the past decade, more attentions have been paid on the con-
version of renewable biomass into valuable chemicals to deal with
the crisis of fossil fuels. The use of renewable biomass, instead of
fossil fuels, also caters to the concept of green chemistry for the
decrease of exhausting carbon dioxide (Ragauskas et al., 2006; Yat,
Berger, & Shonnard, 2008). To reduce the pressure of the food sup-
ply, inedible cellulose is a promising feedstock. The critical step
is to complete the hydrolysis of cellulose into monosaccharides
(Onda, Ochi, & Kazumichi, 2008). However, the tight hydrogen-
bonding network and van der Waals interactions greatly stabilize
cellulose (Nishiyama, Sugiyama, Chanzy, & Lnagan, 2003), which
makes cellulose recalcitrant to hydrolyze. So a pretreatment pro-
cess to reduce the crystallinity of cellulose is highly required. The
traditional chemical pretreatments include alkali and acid pre-
treatments, organic solvents pretreatment, etc. (Kumar, Barrett,
Delwiche, & Stroeve, 2009). Due to the output of a lot of waste acid
and the emission of volatile organic solvents, all of them are envi-
ronmentally detrimental. Hence, more efficient and environment
friendly pretreatment procedures are required for the conversion
of cellulose to monosaccharides.
be used to promote the hydrolysis of cellulose (Dwiatmoko, Choi,
Suh, Suh, & Kung, 2010; Li, Wang, & Zhao, 2007; Li, Filpponen,
& Argyropoulos, 2010; Rinaldi, Palkovits, & Schuth, 2008; Sievers,
Valenzuela-Olarte, Marzialetti, Agrawal, & Jones, 2009; Watanabe,
2010). Each of the hydrolysis process above has its advantages and
disadvantages. Dilute acid in IL is an efficient system for the hydrol-
ysis of lignocellulosic biomass under mild conditions. However,
the disposal of waste acid remains a difficult task. The depolymer-
ization of cellulose in IL over solid catalysts has been performed
successfully. Unfortunately, excessive catalyst loading is required
and solid catalysts are difficult to be separated from the solid
residues. Although the enzyme hydrolysis can be performed in mild
conditions, the negative effects on enzyme from IL residues cannot
be ignored (Turner, Spear, Huddleston, Holbrey, & Rogers, 2003;
Zhao et al., 2009). In general, these processes above have significant
drawbacks such as corrosion of reactors, difficulty in separation
of catalysts, high loading of catalysts and high cost of enzymes.
Acidic ionic liquid, which combines the advantages of mineral acid
and ionic liquid, can behave as both the solvent and catalyst in the
process of biomass conversion.
Since Swatloski, Spear, Holbrey, and Rogers (2002) showed that
ionic liquid [BMIM]Cl was a powerful solvent for cellulose, up to
25 wt% of cellulose could be dissolved in IL, more attentions have
been paid on the hydrolysis of cellulose using ILs (Fu and Mazza,
2011; Kim, Dwiatmoko, & Choi, 2010). According to the nature
In recent years, many kinds of acidic ionic liquids have been
used as solvent or acid catalyst for the conversion of saccharides
into valuable chemicals. Amarasekara and Owereh (2009) reported
the first application of acidic ionic liquids for the dissolution
and hydrolysis of cellulose under moderate reaction tempera-
tures, and the highest total reducing sugar (TRS) yield of 62% was
attained in 1 h of preheating at 70 ◦C and 30 min of heating at
70 ◦C after adding water. Then the group (Amarasekara and Wiredu,
2011) investigated the hydrolysis of cellulose in dilute aqueous
∗
Corresponding author. Tel.: +86 22 27406974; fax: +86 22 27403389.
E-mail address: shuqianxia@tju.edu.cn (S. Xia).
0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carbpol.2012.08.095

Y. Liu et al. / Carbohydrate Polymers 92 (2013) 218–222
219
a stoichiometric amount of 1-methylimidazole (8.21 g, 0.1 mol) was
added dropwise The mixture was stirred for 3 h at ambient tem-
perature to get the white solid zwitterion. Then the zwitterion
was washed with acetone repeatedly and dried in vacuum for 5 h.
Equimolar amount of concentrated sulfuric acid was added slowly
and the mixture was stirred for 6 h at 80 ◦C to get viscous liquid.
Then the viscous liquid was washed three times with ethyl acetate
and dried in vacuum to form IL-1. Its NMR spectral characteristic
was shown as:
R
N
SO3H
N
SO3H
N
X-
Y-
-
IL-1: R=CH3; X-=HSO4
IL-2: R=CH3; X-=Cl-
-
IL-5:Y-=HSO4
IL-6:Y=Cl-
IL-3: R=CH2=CH; X-=HSO4
IL-4: R=CH2=CH; X-=Cl-
-
1H NMR (300 MHz, D2O): ı 2.039–2.097 (m, 2H), 2.661 (t, 2H),
3.654 (s, 3H), 4.120 (t, 2H), 4.694 (t, 1H), 7.213 (d, 1H), 7.284 (d,
1H), 8.518 (s, 1H).
Fig. 1. Acidic ionic liquids used in this study.
The synthesis of ionic liquids IL-2 to IL-6 followed the same pro-
tocol as was used for the preparation of IL-1. Their NMR spectral
characteristics were shown as follows:
solutions of 1-(1-propylsulfonic)-3-methylimidazolium chloride
([C3SO3Hmim]Cl) and produced TRS yield of 28.5% after heating
at 170 ◦C for 3.0 h. Jiang, Zhu, Ma, Liu, and Han (2011) investi-
gated several kinds of acidic ionic liquids bearing COOH, SO3H
as the catalysts for direct conversion of cellulose to glucose and
5-hydroxymethylfurfural (HMF) in [BMIM]Cl. The acidic ionic liq-
uids functionalized with SO3H greatly increased the reaction rate
of the cellulose hydrolysis, with TRS yields up to 85% in 1 h. Tao,
Song, and Chou (2011a) used the ionic liquid [C4SO3Hmim] HSO4
as the catalyst to dehydration of fructose, high fructose conversion
of 100% with HMF yield of 94.6% was obtained at 120 ◦C for 180 min
reaction time. Then the group (Tao, Song, & Chou, 2011b) chose
sixteen kinds of SO3H-functionalized acidic ionic liquids for the
production of HMF and furfural from cellulose, the results showed
that MnCl2-containing ionic liquids were efficient catalysts for the
selectivities of HMF. Acidic ionic liquid, which combines the advan-
tages of mineral acid and ionic liquid, has higher catalytic activity
for the fracture of glycosidic bonds and can be reused conveniently.
At present, most of the acidic ionic liquids used in the liter-
atures were based on imidazoles and pyridine. In this study, six
kinds of acidic ionic liquids (Fig. 1) based on 1-methylimidazole, 1-
vinylimidazole, triethylamine were applied as catalysts to catalyze
the hydrolysis of microcrystalline cellulose (MCC) in [BMIM]Cl. The
main factors influencing the hydrolysis of cellulose were examined,
involving the hydrolysis temperature, the dosage of acid cata-
lyst, the structure of acidic ionic liquid and the purity of solvent
[BMIM]Cl.
IL-2: 1H NMR (300 MHz, D2O): ı 1.848–1.877 (m, 2H), 2.461 (t,
2H), 3.453 (s, 3H), 3.912 (t, 2H), 4.792 (t, 1H), 7.011 (d,1H), 7.075
(d, 1H), 8.288 (s, 1H).
IL-3: 1H NMR (300 MHz, D2O): ı 2.146–2.175 (m, 2H), 2.747–2.762
(m, 2H), 4.229 (t, 2H), 4.667 (t, 1H), 5.248–5.634 (t, 2H), 6.967 (s,
1H), 7.446 (s, 1H), 7.611 (s, 1H), 8.907 (s, 1H).
IL-4: 1H NMR (300 MHz, D2O): ı 2.114–2.144 (m, 2H), 2.717–2.747
(m, 2H), 4.199 (t, 2H), 4.688 (t, 1H), 5.218–5.606 (t, 2H), 6.939 (s,
1H), 7.417 (s, 1H), 7.585 (s, 1H), 8.878 (s, 1H).
IL-5: 1H NMR (300 MHz, D2O): ı 1.069 (t, 9H), 1.887–1.950 (m, 2H),
2.769 (t, 2H), 3.112 (m, 8H), 4.679 (s, 1H).
IL-6: 1H NMR (300 MHz, D2O): ı 1.035 (t, 9H), 1.852–1.915 (m, 2H),
2.734 (t, 2H), 3.079 (m, 8H), 4.689 (s, 1H).
2.4. Typical procedure for hydrolysis of cellulose into TRS
MCC (0.1 g) in [BMIM]Cl (2.0 g) was heated with stirring at 100 ◦C
to form a transparent solution. Followed by the addition of the
acidic IL and 0.1 ml H2O, the mixture was stirred at a given tem-
perature. At different time intervals, certain amount of sample was
extracted and quenched immediately by 5 ml distilled water. The
supernatant was subjected to TRS analysis.
2.5. Analysis method
2. Materials and methods
The amount of TRS was measured using the DNS method (Miller,
1959). The DNS reagent was prepared according to an IUPAC
method. 1 ml of supernatant was transferred to a test tube, then
3 ml of DNS reagent was added, the resulting solution was heated
at 100 ◦C for 10 min. Then the absorbance was measured at 490 nm
using UV–Vis spectrophotometer. The concentration of the TRS was
calculated by employing a standard curve prepared using glucose.
2.1. Materials
1-Methylimidazole (99.0%) and 1-vinylimidazole were pur-
chased from Yancheng Calechem Co. Ltd. (Jiangsu, China);
triethylamine was purchased from Tianjin chemical reagent com-
pany (Tianjin, China); microcrystalline cellulose (average particle
size 50 ␮m) was purchased from Acros (NJ, USA); 1-chlorobutane
(98%) was purchased from Guangfu Fine Chemical Research Insti-
tute (Tianjin, China).
3. Results and discussion
3.1. The influence of reaction temperature on the hydrolysis of
MCC
2.2. Typical procedure for synthesis of ionic liquids
[BMIM]Cl used for the study was prepared according to
the method described in the literature (Huddleston, Willauer,
Swatloski, Visser, & Rogers, 1998).
The first step of the study was designed to obtain the opti-
mum temperature condition for the hydrolysis of MCC in [BMIM]Cl
with acidic ionic liquid as the catalyst. Most researchers set the
hydrolysis temperature at 100 ◦C. To confirm the effect of hydrol-
ysis temperature on the yield of TRS, we studied the hydrolysis of
MCC at 80 ◦C and 100 ◦C, respectively. Fig. 2 shows the effect of
IL-1 on the TRS yield under different temperatures. Obviously, the
hydrolysis rate at 100 ◦C was higher than the rate at 80 ◦C. 62.49%
of TRS yield was obtained in 1 h at 100 ◦C, while 36.85% of TRS yield
was produced at 80 ◦C. From the tendency of the given curve at
80 ◦C, a maximum TRS yield of ∼67% was achieved after 5 h. The
2.3. Synthesis of SO3H-functionalized ionic liquids
The acidic ionic liquids used in this study were synthe-
sized according to the literatures (Cole et al., 2002; Qian and
Liu, 2011). The acidic ionic liquid IL-1 (1-(1-propylsulfonic)-3-
methylimidazolium hydrogen sulfate) was prepared as follows:
1,3-propanesulfone (12.21 g, 0.1 mol) was dissolved in acetone and

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Y. Liu et al. / Carbohydrate Polymers 92 (2013) 218–222
Fig. 2. TRS yield of cellulose hydrolysis catalyzed by IL-1 at different temperatures
in [BMIM]Cl (0.1 g MCC, 2.0 g [BMIM]Cl, 0.2 g IL-1, 0.1 ml H2O).
Fig. 4. Effect of IL-5 dosage on MCC hydrolysis (0.1 g MCC, 2.0 g [BMIM]Cl, 0.1 ml
H2O, T = 100 ◦C).
IL-5 was chosen as the catalyst to study the effect of IL dosage on
MCC hydrolysis. The amount of IL-5 used was 0.0813 g, 0.2 g, 0.4 g
and 2.0 g, respectively. As it was depicted in Fig. 4, when the dosage
of IL-5 increased from 0.0813 g to 0.20 g, the yield of TRS increased
obviously, from 68% to 99% in 1 h. When the amount increased from
0.2 g to 0.4 g, the TRS yield in 1 h decreased from 99% to 72%. When
the amount of IL-5 was 2.0 g, only 42% of TRS yield was obtained
after 1 h. It also showed that with the reaction time getting longer,
the differences of TRS yields got smaller, which was attributed to
the dehydration of more monosaccharides. In summary, the TRS
yields decreased with the dosage of IL-5 increasing (above 0.2 g)
and the react time prolonging due to the dehydration rate of glu-
cose monomer increasing, which led to less accumulation of TRS
and the increase of dehydration products. In our study, choosing
the amount of IL-5 at 0.2 g was more reasonable.
TRS yields kept nearly constant and had a slowly decrease from
the 8th hour due to the dehydration of glucose. Compared to 80 ◦C,
it only took 1.5 h to reach the peak TRS yield of 88.4% and had a
sharply decline after 2 h at 100 ◦C. In addition, the other five kinds of
acidic ionic liquids followed the similar pattern as IL-1. Fig. 3 shows
the maximum TRS yields of cellulose hydrolysis catalyzed by all the
acidic ionic liquids used in our study. It can be seen that all the acidic
ionic liquids used are effective to promote the hydrolysis of cellu-
lose. The maximum TRS yields at 100 ◦C were all above 83%, much
higher than the TRS yields at 80 ◦C. There is no doubt that reaction
temperature has a great effect on the hydrolysis of cellulose and
the dehydration of glucose. A higher hydrolysis temperature can
shorten the reaction time and get higher TRS yield. Meanwhile, the
degradation of glucose begins earlier, the downward trend curve is
more obvious.
3.2. Effect of the acidic liquid dosage on the hydrolysis of cellulose
3.3. Hydrolysis of MCC with different ionic liquids
The effect of acidic ionic liquid dosage on the hydrolysis of cel-
lulose cannot be ignored. From Fig. 3, we can see that IL-5 is one
of the best catalysts for the hydrolysis of cellulose. In our research,
The acidity and structure of ionic liquids had great effects on
MCC hydrolysis. The acidic liquids used in this study involved three
kinds of cations and two kinds of anions. Fig. 5 shows the hydrolysis
Fig. 3. The maximum TRS yield of MCC hydrolysis catalyzed by kinds of acidic ILs
Fig. 5. Hydrolysis of MCC catalyzed by IL-1, IL-3, and IL-5, respectively (0.1 g MCC,
2.0 g [BMIM]Cl, 0.2 g acidic ionic liquid, 0.1 ml H2O, T = 100 ◦C).
at 80 ◦C and 100 ◦C, respectively.

Y. Liu et al. / Carbohydrate Polymers 92 (2013) 218–222
221
Fig. 7. Effect of H2O added in [BMIM]Cl on the hydrolysis of MCC catalyzed by IL-5.
Fig. 6. Hydrolysis of MCC catalyzed by IL-2, IL-4, and IL-6, respectively (0.1 g MCC,
2.0 g [BMIM]Cl, 0.2 g acidic ionic liquid, 0.1 ml H2O, T = 100 ◦C).
3.4. Effect of the purity of [BMIM]Cl on the hydrolysis of cellulose
of MCC catalyzed by ionic liquids with HSO4− (IL-1, IL-3 and IL-5) at
100 ◦C. As seen in Fig. 5, compared to IL-1 and IL-3, IL-5 performed
steadily well, the TRS yields were above 90% from the reaction time
of 1–2.5 h. The hydrolysis of MCC catalyzed by ionic liquids with
anion Cl− (IL-2, IL-4 and IL-6) were shown in Fig. 6. It showed that
the best result was achieved with IL-2 as the catalyst, and then was
IL-4. There is no doubt that the catalytic activity of acidic ionic liq-
uid is affected by the nature of anion as well as the cation. Fig. 5
showed that IL-1 and IL-3 performed similar TRS yields tendency
due to the same anion and similar cations. There was a decrease
in TRS yields after a maximum yield period. In our study, the acid-
catalyzed hydrolysis of cellulose is a homogeneous reaction and the
conversion rate of cellulose is nearly 100%, in the follow-up stage of
the reaction, the degradation of glucose is the dominant reaction.
The consumption of large amounts of glucose led to the reduction
of TRS. As shown in Fig. 6, compared to the ILs with HSO4− as anion,
the influences of cations on the hydrolysis of MCC were distinctive
for the ILs with Cl− as anion. The hydrolysis curves catalyzed by
IL-2 and IL-4 had analogous tendency due to their same anion (Cl−)
and similar cations. With IL-2 and IL-4 as catalyst, the TRS yields
changed little from 1 h to 4 h. Obviously, the dehydration of glucose
into HMF is relatively slow. It might have great relationship with
the nature of IL-2 and IL-4, such as fewer active acid sites and larger
viscosities. The performance of IL-6 based on triethylamine was dif-
ferent from IL-2 and IL-4, the maximum TRS yield (83.6%) was lower
and the TRS yields decreased sharply after 1 h. We speculated that
less active acid sites caused the lower TRS yield and the lower vis-
cosity of IL-6 led to the sharply decline of TRS yield. In addition, the
different interactions between acidic ionic liquids and solvent IL
might be another critical factor. Although IL-5 had the same cation
with IL-6, IL-5 showed better result, with the TRS yield up to 99% in
1 h at 100 ◦C, which was attributed to more active acid sites accel-
erating the fracture of glycosidic bonds. In summary, for the acidic
ionic liquids used in our study, the structure of ionic liquids had
effects on MCC hydrolysis due to their different acidities, active
acid sites and viscosities. Especially the active acid site and viscos-
ity, both of them greatly affected the catalytic activity of IL. More
active acid sites could accelerate the fracture of glycosidic bonds
and produced more TRS. However, the dehydration of glucose got
faster as well and the TRS yields had a sharply decline. To some
extent, larger viscosity had negative effects on the attacks from
H+ to the ␤-1,4-glycosidic bonds, but the TRS yield could remain
invariable for a long time. All the factors are interactional and the
mechanism is very complicated.
After the dissolution of the cellulose in [BMIM]Cl completely, the
␤-1,4-glycosidic bonds of carbohydrate dissolved in the IL could be
easily attacked by the sulfonic acid groups of the acidic ionic liquids,
which promotes the hydrolysis of cellulose. Impurities in the sol-
vent [BMIM]Cl can impair the dissolution capacity of IL. Considering
the synthesis process and the hygroscopicity of [BMIM]Cl, impuri-
ties in [BMIM]Cl can be residue reactant, side-reaction products or
water. In our study, it was found that the water in [BMIM]Cl had
great effects on the hydrolysis of cellulose. The water in [BMIM]Cl
is a hamper for the dissolution of cellulose in [BMIM]Cl and it has
been shown that 1 wt% of water in [BMIM]Cl is sufficient to pre-
vent cellulose dissolution (Rogers et al., 2002). As it was shown in
Fig. 7, with the increasing of deionized water added in [BMIM]Cl,
the TRS yield declined sharply. 0.0261 g H2O added in [BMIM]Cl
led to the decline of TRS yield from 99% to 27.9%. We speculated
that water impaired the dissolution capacity of IL by forming com-
petitive hydrogen-bonding to the cellulose hydroxyl groups, which
caused the incomplete dissolution of cellulose. When the amount
of H2O added increased to 0.0591 g, only 6% TRS yield was obtained.
In addition, we found that when the cellulose was dissolved in
[BMIM]Cl completely, after adding deionized water and acidic ionic
liquid, a kind of intractable gel might form. This gel was hard to be
broken out. To some extent, increasing the amount of acid cata-
lyst would change the condition, but the TRS yield was quite low.
Binder and Raines (2010) had reported the similar phenomenon
that a 5 wt% solution of cellulose in [EMIM]Cl formed an intractable
gel when the solution was diluted to 10 wt% water. In general, the
water in solvent IL had negative effect on the dissolution of cellulose
and led to the decrease of the ␤-1,4-glycosidic bonds of carbohy-
drate dissolved in the IL. Therefore, strict purification procedures
for [BMIM]Cl are required to ensure the hydrolysis of cellulose
effectively.
4. Conclusions
In this study, six kinds of acidic ionic liquids based on 1-
methylimidazole, 1-vinylimidazole, triethylamine were applied as
catalysts to promote the hydrolysis of MCC in [BMIM]Cl. All of them
were efficient acid catalyst, with the maximum TRS yields over 83%.
Especially the acidic ionic liquid based on triethylamine (IL-5), the
TRS yield in 1 h at 100 ◦C was up to 99% when the dosage of IL-5
was 0.2 g. In addition, the amount of catalyst used had great effect
on the hydrolysis products. When the dosage of acid catalyst was

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Y. Liu et al. / Carbohydrate Polymers 92 (2013) 218–222
higher, the dehydration rate of monosaccharides increased, which
led to less accumulation of TRS and the increase of further dehydra-
tion products. Moreover, the structure of ionic liquids had effects
on MCC hydrolysis due to their different acidities, active acid sites
and viscosities. In addition, it should be noted that the presence
of water in [BMIM]Cl had conspicuous effect on the hydrolysis of
cellulose, 0.0261 g H2O added in [BMIM]Cl led to the decline of TRS
yield from 99% to 27.9%. So strict purification procedures for the
synthesis and recycling of [BMIM]Cl were required.
Kim, S. J., Dwiatmoko, A. A., & Choi, J. W. (2010). Cellulose pretreatment with
1-n-butyl-3-methylimidazolium chloride for solid acid-catalyzed hydrolysis.
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This work was supported by National Natural Science Founda-
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