METHOD FOR PRODUCING BIOBASED ALPHA-BETA-UNSATURATED CARBOXYLIC ACIDS FROM POLY(3-HYDROXYALKANOATE) CONTAINED IN BIOMASS

1 . A process for producing α,β-unsaturated carboxylic acids from biomass containing poly(3-hydroxyalkanoate) (P3HA), said process comprising the steps of:

extracting P3HA from the biomass with a solvent capable of solubilizing P3HA to form a P3HA-solvent mixture,

separating organic waste insoluble in said solvent from the P3HA-solvent mixture,

thermolyzing said P3HA-solvent mixture to obtain said α,β-unsaturated carboxylic acid and recover said solvent.

2 . The process as claimed in claim 1 , wherein the biomass is pretreated by means of washing, drying or milling operations until the biomass contains at least 30% by weight of P3HA.

3 . The process as claimed in claim 1 , wherein the extracting is carried out at a temperature of between 20° C. and 130° C.

4 . The process as claimed in claim 1 , wherein the thermolyzing is carried out at a temperature of between 130° C. and 300° C., and at a pressure of between 1 kPa and 101 kPa (atmospheric pressure).

5 . The process as claimed in claim 1 , wherein the solvent has a boiling temperature at atmospheric pressure of greater than 230° C.

6 . The process as claimed in claim 1 , wherein solubility of the P3HA in the solvent in the extracting step is greater than 5% by weight.

7 . The process as claimed in claim 1 , wherein said extracting, separating and thermolyzing are each performed batchwise or continuously.

8 . The process as claimed in claim 1 , wherein said thermolyzing takes place in the presence of one or more polymerization inhibitors.

9 . The process as claimed in claim 8 , wherein an amount of the one or more polymerization inhibitors ranges from 0.005% to 5% by weight relative to a weight of the poly(3-hydroxyalkanoate).

10 . The process as claimed in claim 8 , wherein the one or more polymerization inhibitors are selected from phenol derivatives, phenothiazine derivatives, nitroxide derivatives or para-phenylenediamine derivatives.

11 . The process as claimed in claim 8 , wherein said one or more polymerization inhibitors is hydroquinone methyl ether (HQME).

12 . The process as claimed in claim 1 , wherein the solvent is selected from glycol diethers (glymes), sulfur-containing organic solvents, or organic carbonates.

13 . The process as claimed in claim 8 , wherein the solvent is itself a polymerization inhibitor.

14 . The process as claimed in claim 1 , further comprising recycling the solvent recovered from the thermolyzing step to the extracting step.

15 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) contains a 3-hydroxypropionate unit and at least one of the α,β-unsaturated carboxylic acids produced is acrylic acid.

16 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α,β-unsaturated carboxylic acid produced is acrylic acid.

17 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) contains a 3-hydroxybutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is crotonic acid.

18 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α,β-unsaturated carboxylic acid produced is crotonic acid.

19 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) contains a 3-hydroxyisobutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is methacrylic acid.

20 . The process as claimed in claim 1 , wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α,β-unsaturated carboxylic acid produced is methacrylic acid.

21 . A process for producing α,β-unsaturated carboxylic acids according to claim 1 , further comprising a step of condensing the produced α,β-unsaturated carboxylic acids, followed by one or more purification steps selected from distillation, liquid/liquid extraction, separation using a film evaporator, or crystallization, or a combination of these techniques.