Recent Development in Chemical Depolymerization of Lignin: A Review

Table 1

Base-calalyzed lignin depolymerization.

Lignin	Base catalyst aqueous solution	Reaction conditions		Major products	Yield	Reference
		𝑇 (°C)	𝑃 (MPa)		wt.%
Steam explosion hemp lignin	5 wt.% NaOH	300–330	3.5	Guaiacol	0.9–2.8	[16]
				Catechol	0.8–3.0
				Vanillin	0.5–0.8
Steam explosion softwood lignin	5 wt.% NaOH	300–330	3.5	Guaiacol	1.2–2.1	[16]
				Catechol	0.1–3.2
				Vanillin	0.3–0.5
Organosolv lignin	2 wt.% NaOH	300	25	Syringol	4.1	[17]
				Hydroxyacetophenone	1.6
				Guaiacol	1.1
Kraft lignin	5 wt.% NaOH	270–315	13	Pyrocatechol	0.5–4.9	[18]
Organosolv olive tree pruning lignin	4 wt.% NaOH, KOH, Ca(OH)2, LiOH, or K2CO3	300	90	Catechol	0.1–2.4	[19]