Table 6 Detailed information of lignin co-pyrolysis

Lignin/low-density polyethylene (LDPE)

HZSM-5

A thermogravimetric analyzer

1. The synergistic effect decreased the starting temperature of pyrolysis and accelerated the decomposition rate

2. The composition of pyrolysis products contained more alkane and aromatic hydrocarbons

800 °C—char: lignin > lignin + LDPE > lignin + LDPE + HZSM-5 > LDPE

Lignin + LDPE + HZSM-5: aromatics, alkane^a

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Lignin/plastics (PS)

Red clay (RC)

A micro reactor

The synergistic effect increased the yield of guaiacol

900 °C^b—char: lignin (14.9%), lignin/PS (6.04%), lignin/PS/RC (33.54%); 500 °C^c—lignin-/PS-/lignin + PS-/lignin + PS + RC-derived compounds: 0.81/6.03/4.67/14.67%

Lignin (guaiacol, 60.41%), lignin/RC (guaiacol, 67.37%), lignin/PS (styrene-C8, 70.22%), lignin/PS/RC (styrene-C8, 86.86%)

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Lignin/phenol–formaldehyde resins (PF)

HZSM-5

A vertical pyrolysis reactor

The synergistic effect improved the yield of aromatic amines

650 °C^c—total compounds/aromatic amines: PF (24.5/14.2%), lignin (7.2/3.7%), lignin/PF = 1/5 (22.0/13.3%)

650 °C^c: lignin (simple phenols, 75.62%, catechols, 14.49%, aromatic hydrocarbon, 9.89%) lignin/PF (simple phenols, 84.16%, dimers, 6.30%, aromatic hydrocarbons, 4.23%), PF (simple phenols, 83.2%, aromatic hydrocarbons, 8.6%, dimers, 6.80%)

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Lignin/spent bleaching clay (BC)

N/A

A fixed-bed reactor system

1. The synergistic effect promoted the production of P-type phenols and aromatic hydrocarbons, and the inhibition of oxygenates species

2. The addition of spent bleaching clay reduced the activation energy and improve the oil quality

550 °C—gas/oil/char: BC (~ 9/25/66%), lignin (~ 34/24/42%), lignin/BC = 1/1 (~ 19/25/57%)

550 °C^c: BC (aliphatic hydrocarbons), lignin (phenols), lignin/BC = 1/1 (H-type phenols)

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Lignin/polyolefins

N/A

A fixed-bed reactor

1. Liquid yield was improved by adding polyolefins due to the formation of lower poly-hydrocarbons derived from polyolefins

2. The yield of gasoline and kerosene was climbed, revealing that lignin pyrolytic products enhanced the cracking of polyethylene (PE) intermediates

3. The rearrangement reactions of polypropylene (PP) intermediates enhanced liquid production via inhibiting the formation of solid

650 °C—gas/liquid/Wax/char: lignin/PE (~ 10/40/25/20%), lignin/PP (~ 10/50/15/20%)

Lignin + PE: hydrocarbons like > C26 and C19-C25, ad diesel (C14–C18)^c; Lignin + PP: hydrocarbons like > C26 and C11–C13, and gasoline (C5–C10)^c

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Lignin/waste cooking oil (WCO)

HZSM-5

A Py-GCMS system

The addition of waste cooking oil in lignin with appropriate catalyst-to-feedstock ratio contributed to high selectivity to aromatics via enhancing alkylation and demethoxylation

823 K^c—feedstock conversion rate: lignin (~ 65%, phenolics, MAHs), WCO (~ 100%, MAHs, PAHs), lignin/WCO = 1/1 (~ 85%, MAHs, PAHs)

823 K^c: lignin (phenolics, MAHs, ~ 65%), lignin/WCO = 1/1 (MAHs, ~ 75%), WCO (MAHs, ~ 60%)

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Lignin/collagen

N/A

An applied test system, Inc. series 3210 vertical tube furnace

1. Collagen addition benefited the formation and evolution of char with abundant oxygenated poly-aromatic structures

2. Collagen addition improved the hydrogen aromaticity index via reducing aromatic substitution and/or facilitating the removal of functional groups

3. Collagen acted as a binder for lignin to form stronger fused framework

600 °C—char: lignin (45.1%), lignin/collagen (45.4–48.4%), collagen (24.9%); 1000 °C—char: lignin (41.8%), lignin/collagen (42.2–43.6%), collagen (22.6%)

600 °C^d—C:O/C:H/C:N (aromatic ratio of char): lignin (3.21/0.90/0), lignin/collagen (3.17/0.84/32.26), collagen (2.32/0.54/3.18)

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Cellulose/lignin/sawdust

N/A

A self-made fixed-bed reactor

1. Interactions between the volatiles generated from cellulose and sawdust promoted oil production

2. Repolymerization happened between light species from cellulose and heavy species from lignin to generate more condensable liquids

3. Interaction between heavy species from lignin and sawdust created more carbonaceous char

500 °C—gas/oil/char: cellulose (28.1/55.6/16.3%), sawdust/cellulose (11.5/71.0/17.5%), sawdust (25.2/50.0/24.8%), lignin (8.5/39.6/51.9%), sawdust/lignin (17.5/41.5/41%)

500 °C^c: lignin (phenols), cellulose (sugars, aldehydes, ketones), sawdust (sugars), sawdust/lignin (phenols, aldehydes, ketones), cellulose/sawdust (aldehydes, ketones), cellulose/lignin (sugars)

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