lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip
TRANSCRIPT
![Page 1: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/1.jpg)
Isolation of lignin by Organosolv process from
different varieties of rice husk: Understanding
their physical and chemical properties
Sandip Kumar Singh (Ph. D. student)
Research guide: Dr. Paresh Laxmikant Dhepe
Catalysis and Inorganic Chemistry Division
CSIR-National Chemical Laboratory, Pune, India
Tel, +91-20-25902024, Fax. +91-20-2502633,
Email: [email protected]
Websites: http://academic.ncl.res.in/pl.dhepe/group
Keyword: Crop waste, Agricultural waste, Biomass, Rice husk, isolation, extraction,
lignin, organosolv, XRD, SEM, elemental analysis, HSQC NMR, ATR, UV-Vis
![Page 2: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/2.jpg)
Highlights & Keywords
1) Organosolv method used to isolate lignin from 3 rice husk (RH I, RH II & RH III)
to understand properties.
2) XRD analysis proves extracted lignin is not contaminated with polysaccharides.
3) ATR and NMR revealed presence of H, G, S & T substructures in varying
concentrations.
Lignocelluloses, Organosolv isolation, Lignin, Physico-chemical properties, NMR
![Page 3: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/3.jpg)
Elemental analysis of lignocellulosic rice husk
I, II & III, pulps and ORGLs (oven dry basis) Sample name[a] I II III
Elemental analysis Rice Husk (RHs)
(%)
C 36.9 37.7 37.2
H 5.6 5.4 5.7
O[f] 47.7 47.1 47.4
C/O ratio 0.77 0.79 0.78
MMF[b] C6.2H11.3O6 C6.4H11.0O6 C6.3H11.5O6
HHV[c] (±0.02 MJ/kg) 11.94 13.74 12.26
Elemental analysis of pulp (%) C 34.2 33.2 32.6
H 4.5 4.4 4.3
O[f] 51.6 50.5 51.1
C/O ratio 0.66 0.66 0.64
MMF[b] C5.3H8.2O6.0 C5.0H8.0O5.7 C5.0H7.9O6.0
HHV[c] (±0.02 MJ/kg) 7.01 6.00 5.92
Elemental analysis ORGLs (%) C 66.9 68.3 66.7
H 7.9 8.1 7.8
O[f] 25.2 23.7 25.5
C/O ratio 2.65 2.88 2.62
MMF[b] C10.1H12.8O3 C11.5H16.2O3 C10.1H12.8O3
HHV[c] (±0.02 MJ/kg) 29.5 30.52 29.21
DBE[d] 4.7 4.4 4.7
pH[e] 6.31 6.46 6.49
Colour light brown light brown light brown [a]RHs: lignocellulosic rice husks, [b]MMF: monomer molecular formula, [c]HHV: higher heat value, [d]DBE: double
bond equivalence, [e]100 mg sample was suspended in 6 mL millipore water and shaking was done for 5 min. Later
lignin which is insoluble in water was allowed to settle down and then pH was measured. (pH of millipore water
was 6.92 at 25.6 oC) and [f]calculation based on elemental analysis by using (‘O’ wt.%, after ash correction) = 100-
(‘C’ wt.% + ‘H’ wt.%).
![Page 4: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/4.jpg)
Higher heat values and double bond
equivalence
higher heat values (HHVs or also known as calorific value was calculated using
Dulong formula (using equation 1)
𝐻𝐻𝑉 = 0.3383 × 𝐶 + 1.442 × 𝐻 −𝑂
8 (1)
Where C= weight basis % of the carbon, H= weight basis % of the hydrogen
and O= weight basis % of the oxygen.
The double bond equivalence (DBE) number (also known as degree of unsaturation)
calculated for extracted lignin based on equation 2 and considering MMF.
𝐷𝐵𝐸 = 𝐶 −𝐻
2+
𝑁
2+ 1 (2)
Where C, H & N = number of carbon, hydrogen and nitrogen atoms obtained
from the monomer molecular formula.
![Page 5: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/5.jpg)
UV-Visible spectroscopy of the isolated ORGL
samples from three different rice husk
225 250 275 300 325 350 375 400 425 450 475 500 525 550
Non-conjugated phenolic groups
Pi-Pi interaction of aromatic lignin
316
278
230
204
Absorb
ance (
a.u
.)
Wavelength (nm)
(a)
(b)
(c)
290 300 310 320 330 340 350
(c)
(a)
Ab
so
rba
nce
(a.u
.)
(b)
UV-Visible spectra of ORGL samples (a) RH I, (b) RH II and (c) RH III. 1 mg sample was dissolved
in 10 mL methanol solvent.
![Page 6: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/6.jpg)
ATR spectra of isolated ORGL samples
800 1000 1200 1400 1600 1800 2800 3000 3200 3400 3600 3800
91
59
74
84
0
10
36
11
20
11
70
12
20
12
60
13
57
14
22
14
57
15
10
16
00
16
45 17
03
28
53
29
20
33
3017
05
17
10
17
40
Tra
nsm
itta
nce
(%
)
Wavenumber (cm-1
)
(c)
(b)
(a)
ATR spectra of ORGL derived from (a) RH I, (b) RH II and (c) RH III.
![Page 7: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/7.jpg)
ATR band of ORGL derived from RH I, RH II
and RH III samples Bands (cm-1) Assignment ORGLs Band Location (cm-1)
RH I RH II RH III
3400-3300 O-H stretching 3395 (w) 3320 (w) 3350 (w)
2960-2920 C-H asymmetric stretching in methyl and methylene group 2960 (w),
2925 (w)
2960 (w),
2923(s)
2960 (w),
2923 (m)
2850-2830 C-H symmetric stretching in methyl and methylene group 2850 (w) 2850 (s) 2850 (s)
1740-1680 C=O stretching in unconjugated ketone, carbonyl and ester
groups
1700 (w) 1705 (s) 1740 (s),
1710 (w)
1670-1640 C=O stretching in conjugated p-substituted aryl ketones 1650 (s) 1650 (w) 1650 (s)
1610-1590 Aromatic skeleton vibration plus C=O stretching 1600 (s) 1600 (w) 1605 (m)
1515-1505 Aromatic skeleton vibrations 1510 (s) 1510 (s) 1510 (s)
1470-1450 C-H deformation (asymmetric in -CH3 and –CH2-) 1455 (w) 1455 (m) 1455 (s)
1440-1420 Aromatic skeleton vibrations combined with C-H in plane
deformations
1420 (s) 1425 (w) 1425(m)
1370-1350 Aliphatic C-H stretching in CH3 (not –OCH3) and phenolic -O-H 1355 (w) 1370 (m) 1360 (s)
1270-1260 stretching C-H of G units 1260 (s) 1265 (w) 1265 (m)
1230-1210 C-C plus C-O plus C=O stretching (G condensed > G etherified,
typical of G units)
1215 (s) 1230 (w) 1230 (m)
1170-1160 Typical for H, G, S units of lignin 1165 (m) 1170 (w) 1165 (s)
1120-1115 Aromatic C-H in plane deformation 1120 (s) 1120 (m) 1120 (m)
1035-1030 Aromatic C-H in plane deformation (G>S) plus C-O deformation
in primary alcohols plus C=O stretching (unconjugated)
1035 (s) 1035 (s) 1030 (s)
845-830 p- substituted phenolic 835 (s) 830 (w) 835 (m)
Notes: w: weak, m: medium & s: strong band intensities.
![Page 8: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/8.jpg)
1H & 13C NMR of ORGL samples
1H & 13C NMR spectra of ORGL derived from a, b) RH I; c, d) RH II & e, f) RH III. All the spectra
recorded in the DMSO-d6 solvent.
![Page 9: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/9.jpg)
2D HSQC NMR of ORGL samples
HSQC NMR spectra of ORGL derived from a, b) RH I; c, d) RH II & e, f) RH III and main substructure present in
the lignin.
![Page 10: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/10.jpg)
Assignments of 13C/1H HSQC of RH I, RH II
and RH III derived ORGL samples Assignment δC/δH (ppm) ORGLs
RH I RH II RH III
Cβ-Cβ in phenylcoumaran substructures (Bβ) 53.55/3.47 - -
C-H in methoxyls 56.03/3.75 55.95/3.74 56.04/3.76
Cγ-Hγ in cinnamyl alcohol end group (Iγ) 60.07/4.03 59.88/4.026 60.07/4.04
- 60.26/3.6 - -
Cγ-Hγ in β-O-4’ substructures (Aγ) 60.32/3.42 59.97/3.58 59.88/3.49
- - - 62.18/4.12 and 4.25
- 63.86/3.33 - 63.14/3.34
Cγ-Cγ in β-5’ phenylcoumaran substructures (Bγ) 63.04/3.68 - -
- - - 65.06/3.98
- - - 69.09/5.20
Cα-Hα in β-5’ phenylcoumaran substructure (Bα) 87.60/5.46 - -
C8-H8 in tricin (T8) 94.57/6.57 - 94.70/6.57
C6-H6 in tricin (T6) 99.29/6.22 - 99.32/6.22
C2,6-H2,6 in (S) 103.95/6.99 - 103.93/7.00 and
104.44/6.70
- - - 104.60/7.48
- - - 104.60/7.48
C’2,6-H’2,6 in tricin (T’2,6) 104.68/7.34 - 103.93/7.00
C2-H2 in (G) 110.71/6.93 110.36/6.91 110.86/6.92
C3,5-H3,5 in p-hydroxybenzoate (PB3,5) - 115.7/6.62 115.6/6.53
C3,5-H3,5 in (H) 115.7/6.9 115.6/6.92 115.76/6.93
C5-H5 in (G) 115.85/6.77 115.6/6.76 115.76/6.78
C6-H6 in (G) 119.11/6.78 118.92/6.76 119.29/6.78
C2,6-H2,6 in (H) - 128.2/7.22 128.4/7.23
C2,6-H2,6 in p-hydroxybenzoate (PB2,6) - 130.9/7.49 130.5/7.47
Note: (-) not assigned.
![Page 11: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/11.jpg)
Conclusions
In summary, the organosolv lignins (ORGLs), with 12±3% yield and 93±5% mass
balance were isolated from diverse rice husk (RH) substrates using organosolv
procedure (water:ethanol, H2SO4) carried out at 180˚C for 1 h.
In RH I and RH III derived ORGL samples, presence of T units and higher
concentration of G units are evident compared with RH II derived ORGL sample.
In particular, RH III derived ORGL sample has properties and functional groups
similar to both RH I and RH II derived ORGL samples.
![Page 12: Lignin extraction crop waste-biomass-organosolv-characterization-dhepe-ncl-sandip](https://reader034.vdocuments.site/reader034/viewer/2022051520/58a24a6d1a28abe8738b48af/html5/thumbnails/12.jpg)
[1] S.K. Singh, P.L. Dhepe, Isolation of lignin by organosolv process from
different varieties of rice husk: Understanding their physical and chemical
properties, Bioresour. Technol., 221 (2016) 310-317.
[2] http://www.sciencedirect.com/science/article/pii/S0960852416312998
[3] http://academic.ncl.res.in/pl.dhepe/publications
Further reading..!