CLAIMS

1. A process for the depolymerization of lignin, comprising the following steps:

a) Providing a lignin solution or suspension;

b) Bringing the solution or suspension resulting from step a) to a temperature of from 350 to 430°C and to a pressure of at least 220 bar, and maintaining, simultaneously, said pressure and temperature for a time of between 40 and 450 ms, in order to obtain a depolymerized lignin mixture comprising oligomeric and monomeric phenolic compounds;

c) Isolating the oligomeric and monomeric phenolic compounds from the depolymerized lignin mixture.

2. Process according to claim 1 , comprising a preliminary step prior to step a) of preparing a lignin solution or suspension from a lignin product.

3. Process according to claim 2, wherein the lignin product of the preliminary step comprises at most 50% cellulose by weight with respect to the total weight of the lignin product.

4. Process according to any one of claims 2 to 3, wherein the lignin product of the preliminary step comprises at least 10% lignin by weight with respect to the total weight of the lignin product.

5. Process according to any one of claims 1 to 4, wherein the solution or suspension of step a) comprises a base.

6. Process according to claim 5, wherein the base is an alkali metal hydroxide or an alkali metal bicarbonate.

7. Process according to any one of claims 1 to 6, wherein the concentration of lignin in the solution or suspension resulting from step a) is between 10% and 0.1 % by weight with respect to the total weight of the solution or suspension.

8. Process according to any one of claims 1 to 7, wherein the bringing of the solution or suspension resulting from step a) to a temperature of from 350 to 430°C is achieved by adding to said solution or suspension a fluid, wherein the fluid is at a temperature higher than from 350 to 430°C.

9. Process according to any one of claims 1 to 8, wherein the bringing of the solution or suspension resulting from step a) to a temperature of from 350 to 430°C is effected within a time of 10 ms.

10. Process according to any one of claims 1 to 9, wherein immediately after the time of step b) has elapsed, a temperature reduction of between 125 and 300 °C is effected within a time of 1 ms.

1 1. Process according to any one of claims 1 to 10, wherein no metal catalyst is used during steps a) to b).

12. Process according to any one of claims 1 to 1 1 , wherein no capping agent is used during steps a) to b).

13. Process according to any one of claims 1 to 12, wherein the process is a continuous flow process.

14. Process according to any one of claims 1 to 13, wherein step c) comprises:

i. If the depolymerized lignin mixture of step b) does not comprise a first liquid phase and a first solid phase, adding an acid to the depolymerized lignin mixture to obtain a first liquid phase and a first solid phase;

ii. Separating the first solid phase from the first liquid phase, and extracting the first liquid phase with an organic solvent to obtain a final organic phase comprising the oligomeric and monomeric phenolic compounds.

15. Process according to any one of claims 1 to 14, wherein the solution or suspension of step a) is black liquor or a solution or suspension of Kraft lignin.