Recent Development in Chemical Depolymerization of Lignin: A Review

Table 3

Metallic catalyzed lignin depolymerization.

Lignin	Catalyst	Reaction conditions		Major products	Yield	Reference
		𝑇 (°C)	𝑃 (MPa)
Kraft lignin	(1) Si-Al catalyst/H2O/butanol	200–350	1.1–23	Phenols	6.5	[22]
	(2) ZrO2-Al2O3-FeO𝑥	300
Organosolv switchgrass lignin	16 wt.% formic acid	350		4-Propylguaiacol	7.8	[23]
	4 wt.% Pt/C			4-Methylguaiacol	5.0
	80 wt.% ethanol
Acidic hydrolysis spruce lignin	4.4 wt.% formic acid	300	9.6	Guaiacol	2.0	[24]
	0.15 wt.% Pd catalyst			Pyrocatechol	1.8
	0.94 wt.% Nafion SAC-13			Resorcinol	0.5
Enzymatic hydrolysis spruce lignin	4.4 wt.% formic acid	300	9.6	Guaiacol	1.7	[24]
	0.15 Pd catalyst			Pyrocatechol	1.3
	0.94 wt.% Nafion SAC-13			Resorcinol	1.0
Kraft spruce lignin	4.4 wt.% formic acid	300	9.6	Guaiacol	4.7	[24]
	0.15 wt.% Pd catalyst			Pyrocatechol	4.9
	0.94 wt.% Nafion SAC-13			Resorcinol	1.2
Lignosulfonate	Ni/C, NiLa/C, NiPt/C, NiCu/C, NiPd/C, and NiCe/C	200	5	Guaiacol	10	[25]
Birch sawdust lignin	Ni/C	200		Propenylguaiacol	12	[26]
				Propenylsyringol	36
Enzymatic hydrolysis corn stalk lignin	Pt/C, Pd/C, Ru/C	200–250	1–6	4-Ethylphenol	0.13–3.1	[27]
				4-Ethylguaicol	0.06–1.4
Organosolv olive tree pruning lignin	Ni, Pd, Pt, or Ru supported by mesoporous Al-SBA-15	140		Diethyl phthalate	1.1	[28]
Guaiacyl dehydrogenation oligomers	K10 montmorillonite clay (Al2O3-4SiO2-𝑥H2O)/HCl	100		Low-molecular weight products	—	[29]