Supplementary Information for“Equilibrating metal-oxide cluster
ensembles for oxidation reactions using oxygen in water”
Nature 414, 191
Contents:
1. Preparation and characterization of M7[Al3W10O38] (M = Li+, Na+, K+).
2. Synthesis and composition of equilibrated cluster ensembles optimized for
delignification of wood-pulp samples.
3. Papermaking properties of POM delignified commercial pulp samples.
4. Pulp washing: Analysis of POM delignified fiber samples.
5. Determination of CO2 evolved during oxidative mineralization of solubilized
lignin and polysaccharide fragments.
6. Measurements, control experiments and methods used in mass-balance
calculation of theoretical CO2 values.
1. M7[Al3W10O38] (M = Li+, Na+, K+).
Step 1. Preparation of K6[Al2W11O39]. K9[AlW11O39]13H2O (Weinstock, I. A.,
Cowan, J. J., Barbuzzi, E. M. G., Zeng, H. & Hill, C. L. J. Am. Chem. Soc. 121, 4608-4617
(1999)), (50.18 g, 15.48 mmol) was slurried in 150 mL of water. The solution was then
stirred and heated to 60 C using an oil bath. A solution of AlCl36H2O (15.48 mmol in
10 mL of water) was then added over 4 h, during which time the suspended material
dissolved. The solution was then stirred for an additional 30 min. and stored at 0 C
overnight to give a colorless crystalline solid. The solid was collected by filtration and
washed several times with cold water.
Yield 18.06 g (36%; mixture of positional
isomers). Anal. Calcd (found) for K6[Al2W11O39]16H2O: H, 1.0 (0.87); W 62.75 (62.75);
Al 1.67 (1.58); K 7.23 (7.28).
27Al
NMR (D2O, ppm):  74.0 (1/2 = 85.6 Hz), 8.5 (1/2 =
289 Hz). IR (KBr, cm-1): 947, 877, 800, 764, 742, 686, 530, 495, 472. Step 2. Preparation
of M7[Al3W10O38]. K6[Al2W11O39]16H2O (13.60g, 4.29 mmol) was dissolved in 20 mL of
2
water in a 100-mL round bottom flask and heated with stirring to 85 C using an oil
bath. KOH (36.5 mmol in 2 mL of water) was added dropwise; the pH was kept below
10.5. The solution was cooled to room temperature, after which a white precipitate was
collected by filtration and washed with cold water. Yield 5.64 g (86.6% based on the 2:1
stoichiometric hydrolysis and rearrangement of [Al2W11O39]6- to positional isomers of
[Al3W10O38]7-). Anal. Calcd (found) for K7[Al3W10O38]14H2O: H, 0.92 (1.06); W 60.21
(60.28); Al 2.65 (3.10); K 8.96 (9.02).
27Al
NMR (D2O, ppm):  74.9 (tetrahedrally
coordinated central Al atom, relative intensity 1), 13.7 (octahedrally coordinated
addendum Al atoms, relative intensity 2). IR (KBr, cm-1): 939, 790, 756, 740, 698, 530,
499. K7[Al3W10O38]14H2O (10 g, 3.27 mmol) was dissolved in 25mL of water and passed
through a Na+ charged cation-exchange column (ca. 100 mL column of amberlite IR-120
(plus); 1.9 meq/mL). The resultant solution of the more soluble Na 7[Al3W10O38] was
evaporated to dryness:
27Al
NMR (D2O, ppm):  75.1 (1/2 = 176.6 Hz, relative
intensity 1), 13.8 (1/2 = 1787 Hz, relative intensity 2). High resolution
183W
NMR
spectra were obtained using concentrated solutions of the highly soluble Li + salt,
prepared by addition of LiClO4 to a slurry of Na7[Al3W10O38] in D2O and filtration of
NaClO4.
183W
NMR Li7[Al3W10O38] (D2O, ppm):  -88.7, -117.9, -138.3, -139.9, -174.3, -
179.6, -227.2, -232.7 ppm.
2.
Synthesis and composition of equilibrated cluster ensembles optimized for
delignification of wood-pulp samples.
Optimized systems include equilibrated ensembles of Si(IV), 0.9 V(IV), 1.0
Mo(VI) and 10.1 W(VI) in the indicated molar ratios (1.0:0.9:1.0:10.1) and in which the
dominant specie(s) are Keggin anion(s) of the formula [SiVMoW10O40]5- and/or
[SiVW11O40]5-. Further modification of this system involves partial replacement of some
3
of the W by 0.05 to 0.10 molar equivalents of Mn(III). Inclusion of Mn dramatically
increases the rate of reoxidation of the reduced solution by O2. One of these (Si, V, Mo,
W in molar ratios 1.0:0.9:1.0:10.1) has been scaled up (20 L reactions) to provide
kilogram quantities of delignified industrial fiber samples. Detailed description of the
species present in these optimized and complex systems (each contain structural and
positional isomers of the dominant specie and are additionally complicated by the
presence of Mn in several paramagnetic valence states) and of the reactions that occur
during
delignification
and
POM
reoxidation/lignin
mineralization,
although
extraordinarily difficult, is in progress.
Preparation of 15 L of a 0.5 M (i.e., 0.5 M Si(IV)) equilibrated solutions in
which the dominant specie(s) are Keggin anion(s) of the formula [SiVMoW10O40]5and/or [SiVW11O40]5- designated (based on molar ratios of cations present) as
“Na6.9SiV0.9Mo1.0W10.1”. The following are weighed and mixed as solids: 1.0 eq. (993.1
g) Na2SiO3 (anhydrous, 92.2%), 4.9 eq. (1,500.0 g) NaOH (98%), 0.45 eq. (618.8 g) V2O5
(99.2%), 1.0 eq. (1,090.5 g) MoO3 (99%) and 10.1 eq. (17,583.7 g) WO3 (99.88%). Use of an
experimentally determined “density factor” of 0.422 indicates that a 0.5 M solution has a
density of 2.185 g/ml a total weight of 32,773 g. To achieve this, 10,980 g of water need
to be added to the precursors mixture. About 90% of the water is placed in the reactor
vessel. The mixed dry solids are poured into the reactor vessel with periodic mixing
and adequate ventilation. The heats of solution of the NaOH and Na2SiO3 as well as the
initial reaction are exothermic and can result in a boil-over if the solids are added too
rapidly. The reactor vessel is sealed and heated to 200 ºC for 3 hours under 100 psi
4
(cold) of O2 with continuous rapid stirring (about 500 rpm). The reactor is then cooled.
If necessary, any residual solids are allowed to settle overnight; the solution is then
decanted and filtered. Prior to use in delignification, the solution is treated with ozone
in a glass vessel and concentrated to about 0.6 M (density 2.422). When combined with
pulp for use in delignification, water in the pulp fibers contributes to give a final
concentration of 0.5 M.
Preparation of 250 ml of a 0.5 M (i.e., 0.5 M Si(IV)) optimized equilibrated
POM solution designated (based on the molar ratios of cations present) as
“Na6.5SiV0.9Mn0.1W10Mo”. Combination of the oxides of the d- and p-group cations
indicated in Table S1 below with 6.5 equivalents of NaOH gives a self buffering POM
solution with an appropriate pH value (5-6). The molar quantities indicated in the
Table S1 below were added to 188 ml H2O in a 600 ml reactor equipped with standard
stirring. Oxygen (200 - 250 psi) was added and the mixture stirred (1000 rpm) while
heated to 200 ºC for 5 hours, then cooled, vented, opened and the solution filtered. This
gives solutions with densities of about 2.2 g/ml and pH values in the range of 5-6.
Table S1. Starting materials for synthesis of optimized POM solution.
WO3
MoO3
Na2SiO3
V2O5
NaOH
MnO2*
moles
1.250
0.1250
0.1250
0.005625 0.5625
0.01250
equivalents 10.00
1.000
1.000
0.4500
4.500
0.1000
* The manganese dioxide used was activated grade; during synthesis, Mn(IV) is
reduced (most probably by water) to Mn(III).
5
3. Papermaking properties of POM delignified commercial pulp samples.
The data presented below are early results. It is likely that better properties will be
achieved when the procedures are fully optimized.
Comparison of POM delignified pulp with commercial pulp delignified using a
totally chlorine-free (TCF) manufacturing process.
Softwood furnish, pulped using the kraft (alkaline sulfide) process
Starting pulp for lab study: Post 1st O2 stage
Bleaching Sequence:
Mill: OOZPQP (O-oxygen, Z-ozone, P-alkaline hydrogen peroxide, Q-chelation)
Lab: (POM)P
POM solution used: equilibrated ensemble of 1.0 Si(IV), 0.9 V(IV), 1.0 Mo(VI) and 10.1
W(VI) in the indicated molar ratios (1.0:0.9:1.0:10.1) and 0.5 M in Si(IV) and in which the
dominant specie(s) are Keggin anion(s) of the formula [SiVMoW10O40]5- and/or
[SiVW11O40]5- (see item 2. above).
POM bleaching conditions:
20-liter reaction vessel
3% pulp consistency
135° C for 1.5 hours
Initial pH 5.5, final pH 5.8
H2O2: 2% on pulp, 90° C for 5 hours, pH 12.3
Pulp Properties
POM delignification followed by alkaline hydrogen peroxide brightening was found to
be approximately 50% more selective than OOZPQP as shown in the Table S2. Higher
selectivity is beneficial because it indicates that the POMs oxidatively depolymerize and
solubilize residual kraft lignin with less degradative (oxidative) damage to cellulose.
Higher selectivity results in higher yield and a stronger pulp.
Table S2. Pulp properties
6
Kappa(1)
Viscosity(2)
Selectivity (k/v)
Post 1st O2 Stage
13.1
28.2
---
OOZPQP
4.2
16.1
0.74
(POM)P
~0
17.0
1.17
(1) Kappa 1.5, (2) Viscosity 1.0
Paper Properties - Handsheet Test Results
Freeness
The (POM)P pulp required slightly more refining than the commercially bleached pulp
to develop equivalent Canadian Standard Freeness (CSF).
PFI Revolutions (300 CSF)
POM
Mill
8400
7700
Tear Index
At 317 CSF, the (POM)P pulp had a tear index of 11.9 mN-m2/g (standard deviation, SD
= 2.1) while the tear index of the TCF mill bleached pulp was 13.5 mN-m2/g (SD = 1.3).
This difference was not significant.
Tensile Strength
Breaking length and tensile index were slightly lower for the (POM)P pulp when
compared at 317 CSF. The difference was not significant at the 95% confidence interval.
Tensile Index
(kN-m/g)
(POM)P
Mill – TCF
0.0847 (SD = 0.0045)
0.0887 (0.0046)
Breaking Length
(km)
8.6 (0.4)
9.0 (0.5)
Burst Index
When compared at 317 CSF, the (POM)P pulp was found to be slightly weaker in burst
than the mill pulp [7.7 kPa-m2/g (SD = 0.3) vs. 7.9 kPa-m2/g (SD = 0.3), respectively].
This difference was not significant.
MIT Fold
7
The (POM)P pulp had slightly higher folding endurance than the TCF pulp at 317 CSF
[2396 folds (SD = 395) vs. 2282 (SD = 297), respectively]. This difference was not
significant.
Relative to a commercial TCF pulp (OOZPQP):
1. POM delignification followed by alkaline hydrogen peroxide brightening was more
selective.
2. (POM)P pulp required slightly more refining to achieve a given freeness.
3. At equal freeness, (POM)P pulp had slightly lower tear, tensile, burst and higher
fold. These were not significant differences (95% CI).
4. A POM delignification stage has the potential to replace the OZP stages.
In this study the (POM)P pulp brightness was significantly higher than the commercial
pulp (81.4 vs. 72.0, respectively). It is expected that the mechanical strength properties
of the (POM)P pulp would be superior to those of the TCF pulp if the comparison was
done at equal brightness. This work is in progress.
Comparison of POM delignified pulp with commercial pulp delignified using a
elemental chlorine-free (ECF) manufacturing process.
Softwood furnish, pulped using the kraft (alkaline sulfide) process
Starting pulp for lab study: Brownstock
Bleaching Sequence:
Mill: ODEop (O-oxygen, D-chlorine dioxide, Eop- alkaline extraction with oxygen and
hydrogen peroxide)
Lab: (POM)P
POM solution used: equilibrated ensemble of 1.0 Si(IV), 0.9 V(IV), 1.0 Mo(VI) and 10.1
W(VI) in the indicated molar ratios (1.0:0.9:1.0:10.1) and 0.5 M in Si(IV) and in which the
dominant specie(s) are Keggin anion(s) of the formula [SiVMoW10O40]5- and/or
[SiVW11O40]5- (see item 2. above).
POM bleaching conditions:
20-liter reaction vessel
3% pulp consistency
140° C for 1.25 hours
Initial pH 5.5, final pH 6.1
8
Pulp Properties
POM delignification was found to be more selective than ODE as shown in the Table S3.
Data show pulps delignified to closely similar lignin-content (kappa number) values.
Table S3. Pulp properties
Kappa(1)
Viscosity(2)
Selectivity (k/v)
Brownstock
32.3
24.2
---
ODEop
3.5
15.8
3.4
POM
4.4
18.1
4.6
(1) Kappa 1.5, (2) Viscosity 1.0
Paper Properties - Handsheet Test Results
Freeness
The initial freeness of the POM bleached pulp was higher (720 vs. 695). This pulp
required more refining than the commercially bleached pulp to develop equivalent
freeness.
PFI Revolutions (500 CSF)
POM
Mill
5000
4000
Tear Index
The unrefined POM bleached pulp had lower tear strength than the commercial pulp.
Upon refining the tear strength of the POM pulp increased and exceeded that of the mill
bleached pulp.
Tear Index [4-ply, lbs-f/basis weight (45 lbs/ream)]
@5000 PFI Rev.
@500 CSF
@Equal Tensile (8.5 km)
POM
Mill
1.51
1.26
1.50
1.20
1.5
1.4
9
Tear at 85 mullen was approximately 5% higher for the POM bleached pulp.
Tensile Strength
Tensile strength as measured by breaking length was slightly lower for the POM
bleached pulp when compared at equal refining or equal freeness.
Breaking Length (km)
@5000 PFI Rev.
@500 CSF
POM
Mill
8.2
8.9
8.0
8.4
Burst
When compared at equal refining or equal freeness, the POM bleached pulp was
slightly weaker in burst than the mill pulp.
Burst (psi)
@5000 PFI Rev.
@500 CSF
POM
Mill
150
165
140
145
Relative to a mill ECF pulp (ODEop):
1. POM delignification was more selective.
2. POM pulp required slightly more refining to achieve a given freeness.
3. At equal freeness or at equal refining, POM pulp had higher tear, lower tensile and
lower burst.
4. POM pulp had slightly higher tear @ 85 mullen.
Caustic extraction after POM delignification has been found to have a beneficial effect
on pulp and paper properties. Following extraction, brightness increased 15% and
strength properties improved (5% increases were seen in tensile, breaking length, and
burst. Tear was not affected). In the follow-up study, the POM bleached pulp will be
extracted prior to comparison with similarly treated control pulp. It is anticipated that
the properties of the POM bleached pulp will exceed those of the commercial ECF pulp.
This work is in progress.
4. Pulp washing: Analysis of POM delignified fiber samples.
10
In a preliminary washing study, 0.12 ppm V and 4.0 ppm W were detected in
fibers after delignification by 0.05 M K5[SiVW11O40] (3% csc, 0.2 M pH 7 potassium
phosphate buffer), washing (two applications of 100 C water at 3% pulp consistency)
and alkali extraction (2% pulp consistency, 1% NaOH, 85 C, a standard industry
practice) followed by a final room-temperature rinse by water at 3X dilution. Although
obtained using starting concentrations of 0.05 M, this early result is significant because
the potassium salts used were less soluble than the sodium counter-cation systems
reported here. In addition, reaction of K5[SiVW11O40] at pH 7 in phosphate resulted in
the formation of relatively insoluble lacunary salts, K9[SiVW10O39]. Importantly, recent
data show that removal of V and W by washing alone (prior to alkali extraction) of
pulps treated with 0.5 M equilibrating (sodium counter-cation) solutions is diffusion
controlled at medium pulp consistency (i.e., pre-alkali extraction metal-cation contents
were ca. 50-150 ppm in W, in-line with theoretical diffusion-controlled water
displacement values and similar to the pre-alkali extraction values from the earlier
work using 0.05 M K5[SiVW11O40]). Alkali extraction and trace-metal analysis of the
alkali-extracted pulps is in progress.
The earlier obtained values (0.12 ppm V and 4.0 ppm W) are comparable to
naturally occurring levels in the environment and to those reported in selected food
items (e.g., 0.001 ppm V in drinking water and 0.99 ppm V in black pepper (Myron, D.
R., Givand, S. H. & Nielsen, F. H. Vanadium content of selected foods as determined by
flameless atomic absorption spectroscopy. J. Agric. Food Chem. 25, 297-299 (1977)) and
0.04 ppm W in grains and 0.35 ppm W in coconuts (Kletzin, A. & Adams, M. W. W.
Tungsten in biological systems. FEMS Microbiol. Rev. 18, 5-63 (1996)). Vanadium is
postulated to be an essential nutrient and is present in popular multiple vitamin
formulations.
Most diets supply from 10 to 30 g V per day (Nielsen, F. H. in
Vanadium Compounds, Chemistry, Biochemistry and Therapeutic Applications, A. S.
Tracey and D C. Crans, Eds. (American Chemical Society Symposium Series 711,
11
Washington, D. C. 1999) chap. 23). Natural dietary intake of W is estimated at 8-13 g
per day (Kletzin, A. & Adams, M. W. W. Tungsten in biological systems. FEMS
Microbiol. Rev. 18, 5-63 (1996)).
The low levels of V and W (0.12 and 4.0 ppm,
respectively) found in POM treated pulp fibers are comparable to the levels of inorganic
elements present in native wood, which correlate with location and include 0.01 to 10
ppm levels of Ba, V, Mo, Co and Pb among numerous others (Young, H. E. & Guinn, V.
P. Chemical elements in complete mature trees of seven species in Maine. Tappi J. 49,
190-197 (1966)), are far below those of many trace metals added to paper as impurities
in natural clay (aluminosilicate) fillers (3-120 ppm each of Ba, Ni, Cr, Pb, Sn, Zn, Mo,
Co, in natural kaolin, which constitutes 20-30% by weight of many papers; data from
the Thiele Kaolin Company, Sandersville, GA, USA), and orders of magnitude below
those of Ti(IV) added as TiO2, an opacification agent, and Al(III) (in clay fillers).
Containerboard (heavy paper) used for applications involving food packaging or
processing are always coated with wax or with synthetic polymers such as polyethylene
to prevent contact between food and the pulp fibers and associated additives or
impurities. According to guidelines established by the Conference of Northeastern
Governors (CONEG) to which many U.S. manufacturers conform, coffee filters
(typically made from unbleached or bleached kraft pulps) must contain less than 100
ppm total of four toxic heavy metals (these are the only ones included in the
Guidelines): Cd, Pb, Hg and hexavalent Cr.
5. Determination of CO2 evolved during oxidative mineralization of solubilized
lignin and polysaccharide fragments.
Each experimental CO2 value was determined using a quantitative Ba(OH)2
solution according to the reaction shown in equation (1), followed by titrametric
determination of the Ba(OH)2 thus consumed.
12
CO2 + Ba(OH)2 (aq)  BaCO3(solid) + H2O
(1)
Analyses were conducted on the head space gases formed during each of the ten
reoxidation/oxidative mineralization steps. The Parr reactor was connected through a
teflon tube to two columns in series each filled with 200 mL of 0.058 N Ba(OH) 2. A few
drops of isopropanol were added to ensure formation of a homogeneous fine-foam that
provided effective mass transfer of CO2 (small gas bubbles in the foam) into the
Ba(OH)2 solution. A flow of Ar (10 psi) was passed through the Parr reactor in order to
ensure that the CO2-rich head-space gases were effectively removed, and a 10-mm Hg
(aspirator) vacuum was applied to the outlet side of the columns to avoid backflow of
atmospheric CO2 into the system. It is important during this operation to carefully
check the outlet pressure of the Ar gas (at the cylinder regulator). If this pressure is too
high, the integrity of the columns could be disrupted. The operation was carried out for
1 h in order to ensure that all the CO2 in the head space was transferred into the
Ba(OH)2 column. At room temperature at neutral pH, the solubility of CO2 in water is
sufficiently high that exhaustive efforts must be taken to ensure mass-transfer of the
dissolved gas into the headspace and subsequently into the Ba(OH)2 solution.
To
accomplish this, a steel reflux condenser was inserted between the Parr reactor and the
Ba(OH)2 column, the reactor was heated to 100 C, and Ar was passed gently through
the refluxing system. The operation was stopped after ca. 30 min at which time the
consumption of CO2 by reaction with Ba(OH)2 (observed as precipitation of BaCO3) had
clearly stopped.
The supernatant from the Ba(OH)2 column was titrated to a
phenolphthalein endpoint using 0.101 N HCl.
The titrations were performed in
triplicate and average values are reported in Table S4.
13
6. Measurements, control experiments and methods used in mass-balance calculation
of theoretical CO2 values.
Theoretical CO2 values were calculated by mass balance from decreases in lignin
content and changes in pulp mass.
Lignin content was determined after each
delignification step using a standard method (Useful method um-246; Technical
Association of the Pulp and Paper Industry (TAPPI) Useful Test Methods 1991, TAPPI
Press, Atlanta, GA, 1991, p. 43).
In the 10-cycle experiment, fiber samples were
removed for lignin analysis after each delignification step. Because the final lignin
content in each case was small, relatively large amounts of the pulp were required for
accurate lignin analysis, leaving insufficient quantities for equally accurate overall fiberyield determinations. Therefore, in order to obtain highly accurate values of changes in
total
fiber
mass
during
delignification,
the
first
5
delignification/oxidative
mineralization cycles reported in Figs. 2 and 3 were repeated in their entirety under
conditions identical to those used in the 10-cycle experiment. This repetition of the first
5 cycles was carried out solely for the purpose of obtaining accurate yield data. The
yields of the entire fiber masses collected after the delignification steps of each of these 5
cycles were then determined. Data demonstrating that the 5 cycles carried out for the
purpose of obtaining fiber-yield measurements were identical to those used to obtain
lignin content data was provided by measurement of solution densities and pH values
before and after each delignification reaction, by measurement of %-reduction of the
POM solution after each delignification reaction (Table S5) and by 51V and 27Al NMR.
14
Fiber-mass yields. The fiber-yield determinations were carried out as follows.
First, four identical untreated pulp samples (from red and jack pine, 5% lignin by
weight; ca. 2.5 g in each sample) were carefully weighed, oven dried to constant weight,
and the water content determined by difference. The average of the four water-content
values (all within 2% of one another) was used to calculate the %-moisture and thus dry
mass of the untreated fibers. The moisture-content value was then used to calculate the
actual dry masses of the pulp samples used in the 5 delignification reactions in the 5
cycles. After each of these 5 delignification reactions, the pulp fibers were washed
thoroughly with water and the entire fiber mass dried to constant weight (Table S5).
Mass-balance calculations. The difference between changes in lignin mass and
in total fiber mass were assigned to dissolution of polysaccharide components of the
predominantly cellulose fibers as follows:
Mass of lignin removed =
[dry-fiber mass  weight-% lignin]o  [dry-fiber mass  weight-% lignin]f
(2)
Mass of dissolved polysaccharides =
[(dry-fiber mass)o – (dry-fiber mass)f]  (mass of lignin removed)
(3)
The results (changes in mass of lignin and of polysaccharides) are reported in Table S6.
15
Calculation of the theoretical CO2 values is based on the following equations (4-7). For
CO2 attributed to mineralization of lignin, the formula weight (FW = 196 amu) of a
typical -O-4 linked coniferyl alcohol (CA) monomer unit was used:
(C10H12O4)n + 11 O2  10 CO2 + 6 H2O
(4)
For CO2 attributed to mineralization of dissolved polysaccharides, the formula weight
of a glucose monomer of cellulose (FW = 162 amu) was used:
(C6H10O5)n + 6 O2  6 CO2 + 5 H2O
(5)
Evaluating the results from equations (2) and (3) using equations (4) and (5) finally
gives the mass of CO2 (MW = 44.01) from lignin and polysaccharide respectively:
Mass of CO2 derived from lignin =
[(mass of lignin removed)/196]  44.01(10 mol CO2/mol of CA)
(6)
Mass of CO2 derived from polysaccharides =
[(mass of dissolved polysaccharides/162)  44.01(6 mol CO2/mol of glucose)
(7)
16
Summation of the CO2 values from equations (6) and (7) gives the theoretical CO2
values reported in Figure 2 and here in Table S6.
The error bars assigned to the theoretical CO2 values in Figure 2b (6.3%) were
determined from variability in yield and lignin-content data. Uncertainties associated
with experimental data (5%) are minimum values based on titrations of Ba(OH)2
solutions. Due to removal of solution for analysis after each step, the volume of POM
solution decreased slightly over the 10-cycles (Tables S5 and S6). However, the massbalance measurements and calculations made it possible to determine the
concentrations of organic compounds dissolved during each delignification reaction.
Thus, theoretical and experimental CO2 data are reported in reference to the specific
solution volumes present during oxidative mineralization. Accordingly, all CO2 values
in Tables S4 and S6 and in Figure 2b are reported in units of mg/L of POM solution.
Table S4.
CO2 Evolved in Each Mineralization Step of the 10-cycle Experiment
Summarized in Figure 2a.
Cycle Vol. of HCl
Avg. Final conc.
CO2
Conc.
(0.101 N; mLb ) (mL) of Ba(OH)2 (mg/L) (Al(III))
Final
Red.
pH
of POM
M)
(M)
(%)
14.7
1
15.7
14.6
0.03709
920
0.5
7.65
13.3
14.5
0.03664
940
0.5
7.66
13.7
13.4
14.5
2
14.7
17
14.3
14.4
3
15.0
14.2
0.03595
970
0.5
7.65
14.6
14.3
0.03625
957
0.5
7.66
14.5
14.5
0.03661
941
0.5
7.65
14.8
14.7
0.03714
918
0.5
7.67
14.0
14.7
0.03718
916
0.5
7.66
14.0
14.9
0.03761
897
0.5
7.66
14.8
14.9
0.03755
900
0.5
7.66
14.5
14.9
0.03766
895
0.5
7.67
14.7
13.2
15.1
4
14.7
13.1
14.5
5
14.5
14.5
15.0
6
14.4
14.7
14.8
7
15.1
14.2
15.4
8
15.0
14.3
14.9
9
14.9
14.9
15.0
10
15.0
14.7
a The initial pH of the solution used in the 10-cycle experiment was 7.30.
18
b
After each mineralization reaction, three 20 mL aliquots of the Ba(OH)2 solution were
titrated using 0.101 N HCl.
Table S5. Fiber-Mass Yields.
Cycle Solution Dry fiber mass (g)
volume
Initial
Final
Yield
Conc.
Final
Reduction
(%)
(Al(III))
pH
of POM
M)
(mL)
(%)
1
250
2.50
2.37
94.8
0.50
7.52
14.0
2
246
2.46
2.37
96.3
0.50
7.45
13.0
3
244
2.44
2.34
95.9
0.50
7.65
14.0
4
241
2.41
2.31
95.9
0.50
7.60
14.0
5
237
2.37
2.26
95.4
0.50
7.60
14.0
a The initial pH of the solution used in the 5-cycle experiment was 7.30.
Table S6. Changes in Mass of Lignin and Polysaccharide Components and
CO2 Evolved During Oxidative Mineralization in the 10-cycle experiment.
Cycle
Solution Initial
volume
dry fiber
(mL)
mass (g)
1
250
2.50
2
242
3
Change in mass (mg)
Lignin
Poly-
Total CO2
Total CO2
Experimental Theoretical
saccharide (mg/L)
(mg/L)
79.67
6.17
920
830
2.40
74.00
12.06
940
840
235
2.30
68.58
16.38
970
835
4
230
2.30
68.06
15.28
957
840
5
225
2.20
72.25
13.30
941
890
6
217
2.17
68.10
13.30
918
875
7
210
2.10
69.47
10.61
916
900
19
8
201
2.00
64.57
11.83
897
890
9
195
1.90
66.12
8.92
900
910
10
187
1.87
62.12
9.03
895
900