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Table 1 Structures, isolations, and/or treatments of Kraft lignin, organosolv lignin, and alkali lignin, and their pyrolytic behaviors

From: A review on lignin pyrolysis: pyrolytic behavior, mechanism, and relevant upgrading for improving process efficiency

Raw material

Isolation

Treatment

Lignin

Lignin properties

Pyrolysis temperature

Pyrolytic property

Refs.

Yield

Major compositions in oils

Commercial Kraft lignin (KL)

N/A

N/A

KL

G/S-type lignin with C = 62.45%, H = 5.28%, N = 0.27%, O = 31.01%, S = 0.16%, ash = 0.83, H/Ceff = 0.63

RT-400–700 °Ca

400 °Ca—gas/oil/char (10/21/69%); 500 °Ca—gas/oil/char (19/33/48%); 600 °Ca—gas/oil/char (24/34/43%); 700 °Ca—gas/oil/char (33/29/38%)

400–700 °Cb (S-type phenols from 58 to 72%, G-type phenols from 18 to 22%)

[188]

Norway spruce (Picea abies)

LignoBoost process

N/A

KL (Lignoboost™ lignin)

G-type lignin with HHV (dry ash free) = 27.1 MJ/kg, HHV (moist) = 18.2 MJ/kg, C = 65.1%, H = 5.8%, N = 0.1%, O = 26.1%, S = 2.5%

RT-500 °Cc

500 °Cc—char (36%)

500 °Cc (guaiacols, catechols, alkylphenols)

[116]

Black liquor of eucalypt Kraft pulping

Acid precipitation

Thermal treatment (175, 200, 225 °C for 30, 90, 150 s)

Thermal-treated KL

KL-200 °C (90 s) (exp.): G/H/S-type lignin with C = 66.30%, H = 5.63%, N = 0.11%, O = 26.07%, S = 1.70%, HHV = 26.52 MJ/kg, soluble lignin = 5.97%, insoluble lignin = 91.41%, sugars = 0.80%, ash = 1.56%

RT-550 °Cc

550 °Cd—char (~ 10%)

225 °Cc (methoxycatechol syringol, 4-methylsyringol)

[189]

Black liquor of poplar Kraft pulping

Acid precipitation

Fractionation by ultrafiltration

KL and F1 (54.3%), F2 (25.9%), F3 (15.4%), F4 (4.4%) fractionated in series by membranes with 10, 5, 1 kDa

KL/F1/F2/F3/F4: G/H/S-type lignin with Mn = 584/1141/703/484 g/mol, Mw = 1507/2640/1119/700 g/mol, Ðe = 2.58/2.31/1.59/1.44, acid-insoluble lignin (AIL) = 76.68/78.41/77.62/75.35/76.56%, acid soluble lignin (ASL) = 5.19/5.31/7.09/7.13/6.97%, total carbohydrates = 4.99/8.11/3.69/0.07/0%, ash = 0.95/1.84/1.19/1.07/1.09%

RT-500, 650, 800 °Cc

750 °Cd—char: KL (35.1%), F1 (33.8%), F2 (25.3%), F3 (31.8%)

500 °Cc: KL, F1, F2, F3 (syringol, 4-methylguaiacol, guaiacol); 650 °Cc: KL (syringol, 4-methylguaiacol, guaiacol), F1 (4-methylguaiacol, guaiacol, 4-vinylguaiacol), F2 (syringol, guaiacol, phenol), F3 (syringol, guaiacol, 4-vinylguaiacol); 800 °Cc: KL (phenol, syringol, toluene), F1 (phenol, 4-methylphenol, 2,4-dimethylphenol), F2 (syringol, guaiacol, 4-vinylguaiacol), F3 (phenol, syringol, 4-vinylguaiacol)

[154]

Black liquor of eucalypt Kraft pulping

Acid precipitation

Fractionation by organic solvents

KL and F1 (59.65%), F2 (28.70%), F3 (10.93%) fractionated in series using ethyl acetate (F1), acetate/petroleum ether (F2), petroleum ether (F3)

KL/F1/F2/F3: G/S-type lignin with Mn = 2033/2872/1611/620 g/mol, Mw = 4664/6158/2397/814 g/mol, Ðe = 2.29/2.14/1.49/1.32, C = 61.30/61.01/62.26/62.49%, H = 5.56/5.59/5.80/5.92%; N = 0.19/0.28/0.01/0.00%, O = 30.81/30.86/29.92/29.91%, S = 2.14/2.26/2.01/1.68%, O/C (mol/mol) = 0.38/0.38/0.36/0.36, H/C (mol/mol) = 1.09/1.10/1.12/1.14, HHV = 24.86/24.80/25.55/25.73 kJ/kg, S/G (unit ratio) = 2.44/2.12/2.32/2.49, β-O-4 = 3.7/12.6/2.8/0%, β–β = 1.2/2.2/0.9/0.3%, β-5 = 5.4/5.5/4.8/4.2%, aliphatic OH = 1.06/1.47/0.84/0.29 mmol/g, total phenolic OH = 3.81/2.51/3.49/4.81 mmol/g, COOH = 0.54/0.49/0.52/0.73 mmol/g, condensed phenolic OH = 0.48/0.35/0.54/0.81 mmol/g, methoxy = 6.86/6.11/6.59/7.19 mmol/g

RT-400, 500, 600 °Cf

600 °Cd—char: KL (40.61%), F1 (38.88%), F2 (33.32%), F3 (18.37%)

400 °Cb, g: KL, F1, F2, F3 (G-/S-type phenols); 500 °Cb, g: KL, F1, F2, F3 (G-/S-type phenols); 600 °Cb, g: KL, F1, F2, F3 (G-/S-/H-type phenols)

[135]

Black liquor of poplar Kraft pulping

Acid precipitation

Fractionation by gradient acid precipitation

KL (extracted under pH = 2) and LpH6 (52.5%), LpH4 (29.7%), LpH2 (17.8%) fractionated in series under pH = 6, 4, 2

KL: G/S/H-type lignin with Mn = 821/1057/703/462 g/mol, Mw = 2118/2399/1057/712 g/mol, Ðe = 2.58/2.27/1.73/1.54, C = 52.89/60.31/60.27/48.42%, H = 4.85/5.28/5.28/3.86%, N = 0.15/0.16/0.30/0.22%, O = 29.51/32.57/32.13/23.61%, S = 12.60/1.76/2.02/23.89%

RT-500, 650, 800 °Cc

750 °Cd—char: KL (35.1%), LpH6 (38.4%), LpH4 (29.1%), LpH2 (26.8%)

500 °Cc: KL, LpH6, LpH4 (syringol, 4-methylguaiacol, guaiacol), LpH2: (syringol, 4-ethylguaiacol, guaiacol); 650 °Cc: KL (syringol, 4-methylguaiacol, guaiacol), LpH6, LpH2 (syringol, 4-ethylguaiacol, guaiacol), LpH4 (3-methoxycatechol, syringol, 4-methylguaiacol); 800 °Cc: KL (phenol, syringol, toluene), LpH6 (acetosyringone, 3-methoxycatechol, phenol), LpH4 (syringol, 4-ethylguaiacol, 4-methylguaiacol), LpH2 (syringol, phenol, guaiacol)

[190]

Commercial alkali lignin (AL)

N/A

N/A

AL

G/H/S-type lignin with C = 55.3%, H = 5.3%, N = 0.1%, O = 35.2%, S = 1.3%, HHV = 20.62 MJ/kg, volatiles = 62.3%, fixed carbon = 34.9%, ash = 2.8%

RT-400, 450, 500 550, 600, 650, 700, 750, 800 °Ca

600 °C–chard (39.0%); 800 °C—chard (40.8%); 400–800 °Ca—gas/oil/char (15/25/65%)

400–800 °Cb (phenol, 2-methylphenol, 4-methylphenol, 4-ethylphenol)

[221]

Commercial alkali lignin

N/A

N/A

AL

G/H/S-type lignin with C = 60.00%, H = 7.18%, N = 0.00%, O = 29.90%, S = 2.92%, HHV = 20.62 MJ/kg, moisture = 6.2%, volatiles = 88.0%, fixed carbon = 9.4%, ash = 2.6%

RT-300, 350, 400, 450 °Ca

300 °Ca—gas/oil/solid (11.8/26.2/62.0%); 350 °Ca—gas/oil/solid (12.7/32.3/55.0%); 400 °Ca—gas/oil/solid (16.5/33.5/50.0%); 450 °Ca—gas/oil/solid (20.9/34.1/45.0%)

300, 350, 400, 450 °Cb (guaiacols, alkyl phenols, catechols)

[204]

Commercial alkali lignin

N/A

N/A

AL

G/H/S-type lignin

40–900 °Cc, i

900 °Cd—char (~ 50%)

300, 500, 900 °Cc (2-methoxy-phenol)

[222]

Commercial alkali lignin

N/A

N/A

AL

G/H-type lignin with aliphatic OH/COOH/phenolic OH/total OH/H (unit)/G (unit) = 2.36/0.38/3.35/6.09/0.27/3.08 mmol/g

RT-400, 500, 600 °Cc

N/A

400 °Cb (no obvious response); 500, 600 °Cb (2-methoxyl-4-methylphenol, acetaldehyde, 2-methoxyl-4-vinylphenol, 2-methoxyl-phenol)

[39]

Black liquor (BL)

Acid precipitation

Fractionation by ultrafiltration

AL, AL-10/5/1 kDa

AL, AL-10/5/1 kDa: G/H-type lignin with Mn = 3284/6076/4045/2616 g/mol, Mw = 7423/12,060/6752/3864 g/mol, Ðe = 2.260/1.985/1.669/1.478, G-type OH = 0.90/1.07/0.86/0.77 mmol/g, H-type OH = 0.22/0.15/0.17/0.30 mmol/g, aliphatic OH = 1.23/1.47/1.06/1.05 mmol/g, condensed phenolic OH = 1.21/1.74/1.17/1.00 mmol/g, COOH = 1.02/1.19/0.74/0.76 mmol/g

RT-400, 600, 800 °Ch

1000 °Cd—char: AL (43.06%), AL-10 kDa (38.42%), AL-5 kDa (39.27%), AL-1 kDa (36.34%)

400 °Cb: AL, AL-10 kDa (guaiacol, 4-methylguaiacol, 4-ethylguaiacol), AL-5 kDa, AL-1 kDa (guaiacol, phenol, 4-methylguaiacol); 600 °Cb: AL, AL-10 kDa, AL-5 kDa (guaiacol, phenol, 4-methylguaiacol), AL-1 kDa (phenol, 4-methylphenol, 3-ethylphenol); 800 °Cb: AL, AL-10 kDa, AL-5 kDa (phenol, indene, naphthalene), AL-1 kDa (1-ethenyl-2-methyl-benzene, indene, naphthalene), (39.27%)

[205]

Corncob residue

Organosolv method (tetrahydrofuran)

N/A

Organosolv lignin (OL)

G/S/H-type lignin with Mn = 1238 g/mol, Mw = 3203 g/mol, Ðe = 2.59

RT-800 °Ca

350 °Ca—gas/oil/char (31.5/16.3/52.2%); 800 °C—chard (36.02%)

350 °Cb (4-vinylphenol, 4-vinylguaiacol, syringol)

[223]

Pine, poplar, bamboo

Organosolv method (dioxane)

N/A

PiL (29.3%), PoL (35.2%), BaL (48.9%)

PiL: G/H-type lignin with Mn = 2580 g/mol, Mw = 9940 g/mol, Ðe = 3.85, β-O-4 (A) = 46.02%, phenylcoumarans (B) = 8.63%, resinol (C) = 5.78%, cinnamyl alcohol end groups (I) = 6.72%, S/G/H (unit) = 0/99.35/0.65%; PoL/BaL: G/S/H-type lignin with Mn = 3540/3420 g/mol, Mw = 13,240/8840 g/mol, Ðe = 3.74/2.58, β-O-4 (A) = 56.31/59.52%, phenylcoumarans (B) = 7.13/5.68%, resinol (C) = 13.56/4.16%, cinnamyl alcohol end groups (I) = 0/0%, S/G/H (unit) = 69.00/30.62/0.38% (60.97/35.79/3.24%)

RT-800 °Ca

800 °Cd—char: PiL (39.33%), PoL (30.19%), BaL (20.71%)

400–600 °Cb: PiL (guaiacol), PoL (phenol), BaL (4-vinylphenol)

[110]

Sugarcane bagasse (BG)

Organosolv method (ethanol)

N/A

BG-Lignin

G/S/H-type lignin with G/S/H (unit ratio) = 0.82/0.02/0.16; moisture = 3.78%, volatiles = 67.34%, fixed carbon = 28.80%, ash = 0.09%, phenolic OH/aliphatic OH = 0.79

RT-400, 500, 600, 700 °Cc

800 °Cd—char (29%)

400 °Cc (2,6-dimethoxy-phenol); 500 °C–600 °Cc (2,6-dimethoxy-4-(2-propenyl)-phenol); 700 °Cc (4-ethyl-phenol)

[216]

Willow biomass

Organosolv method (ethyl acetate-EAC/tetrahydrofuran-THF/γ-butyrolactone-GBL)

N/A

L-EAC (83.8%), THF (92.3%), GBL (72.6%)

L-EAC/L-THF/L-GBL: G-type lignin with C = 65.00/66.25/66.88%, H = 6.26/6.03/6.32%, N = 0.22/0.30/0.21%, O = 28.09/27.00/26.61%, ash = 0.44/0.12/0%, moisture = 4.5/4.0/4.5%

RT-500 °Ca

500 °Ca—gas/oil/char: L-EAC (22.15/34.53/43.32%), L-THF (20.97/35.21/43.83%), L-GBL (21.70/33.55/44.75%)

500 °Cb: L-EAC, L-THF (guaiacol, 4-methylguaiacol), L-GBL (4-methylguaiacol)

[220]

  1. aA fixed bed
  2. bGC/MS and/or GC/FID (gas chromatograph/flame ionization detection)
  3. cPy-GC/MS
  4. dTG-DTG
  5. eDispersity
  6. fU-type tube pyrolysis device
  7. gIn situ FTIR spectroscopy
  8. hTube furnace
  9. iTG–MS (thermogravimetry–mass spectrometry)