Table 3.

Performance of niobium-based catalysts for conversion of lignin into different products—from 2010 up to date.

Entry	Catalyst	Solvent	t (h)	T (°C)	Product	C (%)	S (%)	Y (%)	Experimental Conditions	Ref.
1	4 wt% Co@Nb2O5@Fe3O4	Water	6	180	C20–C28 and C29–C37 fragments	53	96	51	10 atm H2; 0.01 g catalyst, 0.4 g lignin, 5 mL solvent	[95]
2	Fe3O4@Nb2O5@Co@Re	Water	6	180	C29–C37 fragments	~85	~100	85	0.02 g catalyst, 0.01 g lignin, 2.5 mL H2O, 10 bar H2	[116]
3	Nb2O5/Ru	Water/cyclohexane	20	250	C7–C9 arenes	99	88	87	0.1 g lignin, 0.2 g catalyst, 10 mL H2O, 5 mL cyclohexane, 0.5 MPa H2	[118]
4	Nb2O5/Ru	Water	20	250	C7–C9 arenes	~50	95	~50	0.1 g enzymatic lignin, 0.2 g catalyst, 15 mL H2O, initial H2 pressure of 0.7 MPa	[126]
5	Nb2O5/Ru	Water/cyclohexane	20	250	C7–C9 arenes	38	86	33 (wt.%)	lignin oil (0.1 g, birch wood), 2% Ru/Nb2O5 (0.2 g), iPrOH (1.0 g), H2O (14 mL), cyclohexane (5 mL), 20 h	[119]
6	Nb2O5/Ru	Water	20	250	C7–C9 arenes	32 wt.%	71 wt.%	23 wt.%	0.1 g of birch lignin, 0.2 g catalyst, 15 mL water, 0.7 MPa H2, 2 wt% Ru	[121]
7	Zr-doped NbOPO4/Ni	C10	5.5	220	oxygen-free aromatics	84	62	52	8 wt% diaryl ether in 20 mL C10, 0.1 g catalyst, 0.5 MPa, 700 rpm	[120]
8	Nb2O5	-	2	60	-	45	-	-	Catalyst loading: 1 g catalyst/1 g switchgrass	[127]
9	NbN	Supercritical ethanol	1	340	Aromatic monomer	-	-	17 (wt.%)	200 mg catalyst, 400 mg lignin, 20 mL solvent, 10 bar H2.	[122]
10	CH2Cl2-modified Nb2O5/Ru	Water	20	250	Indane and its derivatives	34	70	24 (wt.%)	0.10 g catalyst, 0.10 g lignin-oil, 15 mL water, 0.5 MPa H2, 700 rpm	[123]
11	Nb2O5	Water	2	90	vanillin	-	-	-	0.50 g catalyst, 100 mL water, 8 g lignin, 150 rpm. Produced vanillin = 137 mg L−1	[124]
12	Ni0.92Nb0.08O	C10	2	200	cyclohexane	>99	100	-	0.1g Ni0.92Nb0.08 catalyst, 8 wt% substrate, 20 mL C10, 3 MPa, 700 rpm	[125]
13	Pd/Nb2O5/SiO2	Cyclohexane	24	170	cyclohexane	100	98	98	catalyst (0.2 g), diphenil ether (0.2 g), cyclohexane (6.46 g), 2.5 MPa H2	[128]
14	Nb2O5	Water	5	60	monomeric phenolic compounds			47 wt.%	0.2–1 g lignin/g peracetic acid; 10 wt% Nb2O5	[129]
15	Pt/NbOPO4	Cyclohexane	20	190	alkylcyclohexanes	-	-	36	0.4 g of birch sawdust, 0.4 g of catalyst, and 6.46 g of cyclohexane, and 5 MPa H2	[98]