MÉTODO DE PRODUÇÃO DE ÁCIDOS CARBOXÍLICOS ALPHA,BETA-INSATURADOS DE BASE BIOLÓGICA A PARTIR DE POLI(3-HIDROXIALCANOATO) CONTIDO NA BIOMASSA

Abstract

The present invention relates to a method for producing biobased α-β-unsaturated carboxylic acids from a biomass containing a poly(3-hydroxyalkanoate), comprising the extraction of the poly(3-hydroxyalkanoate), followed by thermolysis of the polymer in the solid or melt state, in the presence of polymerisation inhibitors and in the absence of catalyst, resulting in the production of biobased α-β-unsaturated carboxylic acids.

Description

1 / 23 “METHOD FOR PRODUCING BIOLOGICALLY BASED ALPHA,BETA-UNSATURATED CARBOXYLIC ACIDS FROM POLY(3-HYDROXYALKANOATE) CONTAINED IN BIOMASS” Field of the Technique

[0001] The present invention relates to a process for the production of α,β-unsaturated carboxylic acids of biological origin from a biomass containing a poly(3-hydroxyalkanoate), comprising the extraction of said poly(3-hydroxyalkanoate) in the presence of polymerization inhibitors, followed by thermolysis of said polymer in the solid or molten state, in the absence of a catalyst, leading to the production of α,β-unsaturated carboxylic acids of biological origin. Previous Technique and Problem of the Technique

[0002] α,β-Unsaturated carboxylic acids are currently produced industrially, mainly from fossil-based raw materials. For example, acrylic acid is obtained by the oxidation of propylene, or methacrylic acid can be obtained by the oxidation of isobutylene.

[0003] One possible way to obtain these α,β-unsaturated carboxylic acids is by thermolysis, at temperatures of 150°C to 300°C, of ​​the corresponding poly(3-hydroxyalkanoate) (P3HA), according to the following reaction: Chemistry 1 R1 JR1 Ri = H or alkyl and R2 = H or alkyl; n is a number greater than 30 If R1 = R2 = H: Poly(3-hydroxyalkanoate) = poly(3-hydroxypropionate) Petition 870250084418, dated 09 / 19 / 2025, page 7 / 43 2 / 23 (P3HP); - α,β-unsaturated carboxylic acid = propenoic acid (acrylic acid). If Ri = methyl and R2 = H: - Poly(3-hydroxyalkanoate) = poly(3-hydroxyisobutyrate) (P3HiB); - α,β-unsaturated carboxylic acid = isobutenoic acid (methacrylic acid). If R1 = H and R2 = methyl: - Poly(3-hydroxyalkanoate) = poly(3-hydroxybutyrate) (P3HB); - α,β-unsaturated carboxylic acid = but-2-enoic acid (crotonic acid). If R1 = H and R2 = ethyl: - Poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV); - α,β-unsaturated carboxylic acid = pent-2-enoic acid

[0004] These poly(3-hydroxyalkanoates) can be obtained beforehand by chemical transformations of raw materials of fossil origin, but also by the fermentation of biomass.

[0005] There is a strong market demand for these α,β-unsaturated carboxylic acids, which are used as monomers in numerous applications, obtained from biologically derived raw materials. These biologically derived raw materials are derived from renewable organic matter (biomass) of biological origin (microorganisms, plants or animals).

[0006] A potential problem with this process is that the P3HA obtained by fermentation is present inside the cell. Thermolysis is therefore carried out in the presence of the cell membrane, which causes problems of reactor fouling or impurities in the final product.

[0007] A number of solutions to this problem have been proposed. Petition 870250084418, dated 09 / 19 / 2025, page 8 / 43 3 / 23

[0008] US patent 9850192 describes a process for producing acrylic acid from genetically modified microbial biomass that metabolizes glucose or any other renewable feedstock to produce a poly(3-hydroxypropionate) (P3HP) homopolymer or copolymer inside microbial cells. The process comprises a thermolysis step of the washed / dried / milled biomass containing P3HP in the presence of a catalyst. This process effectively enables the production of acrylic acid by limiting the formation of acrylic acid oligomers, such as acrylic acid dimers, which are spontaneously formed during acrylic acid production. The acrylic acid is recovered in gaseous form and then condensed, while the catalyst and residual biomass mass can be recycled in the process or subjected to thermal regeneration.However, there is a risk that the residue present in the reactor after thermolysis may become pasty and sticky, which could complicate its transfer to an industrial scale. Example 5 and Figure 7 describe how to carry out this invention on an industrial scale. After fermentation, the biomass is washed and dried using an atomizer or a double drum dryer. After the addition of the catalyst, the product is pyrolyzed in a FAST™ reactor at 250-350°C with a residence time between 0.25-1 hour, using an inert gas, such as nitrogen, to send the vapors formed to the purification equipment. The vapor phase is composed of 90% water / organic and 10% inert gas. The gas is then purified, according to the process described in US patent 6646161 or US patent 20120006673, to obtain acrylic acid still containing many impurities.Complete purification is performed using distillation columns, as described in documents US 7332624 and US 7179875, and may also require crystallization operations, as described in documents US 6482981 and US 71798750. Petition 870250084418, dated 09 / 19 / 2025, page 9 / 43 4 / 23

[0009] Another solution consists of initially extracting P3HA from biomass using an organic solvent before subjecting it to thermolysis. US patent 20150376152 describes, in example 6, the extraction of P3HP from biomass using an organic solvent, such as 2-butanone, followed by the production of acrylic acid in three steps: evaporation of the solvent and its condensation in a receiving vessel; thermal degradation of P3HP in the absence of an inhibitor, leading to the production of acrylic acid vapor; and finally, distillation and condensation of the acrylic acid in a receiving vessel containing hydroquinone to prevent the polymerization of the acrylic acid.

[0010] In its application FR 2208914, the applicant company proposes to carry out the thermolysis of P3HA in the absence of a catalyst and in the presence of a polymerization inhibitor; characteristically, the vapor pressure of at least one of the inhibitors at the thermolysis temperature is at least twice the pressure at which the thermolysis is carried out, which has the effect of preventing the formation of polymers in the reactor and also in the gas phase in case of accidental condensation or when acrylic acid vapors condense at the top of the column.

[0011] In its application FR 2208916, the applicant company describes a process using a solvent that allows, from biomass, the selective solubilization of P3HA, the separation of organic debris insoluble in said solvent and then carrying out a thermolysis treatment of P3HA and the solvent medium in the liquid phase in the presence of polymerization inhibitors.

[0012] Document WO 2016 / 039618 describes the thermal degradation of a dry biomass containing poly(3-hydroxybutyrate) to produce crotonic acid. In example 1, it is demonstrated that crotonic acid can be obtained in comparable yields of less than 60% from wet or dry biomass in the absence of a catalyst.

[0013] It has now been discovered that it is possible to simplify the procedure Petition 870250084418, dated 09 / 19 / 2025, page 10 / 43 5 / 23 ment of production of α,β-unsaturated carboxylic acids, carrying out the thermolysis of P3HA in the absence of solvent, after prior extraction of P3HA from the cell membrane and as a mixture with at least one solid-phase polymerization inhibitor, without the use of a catalyst and without the injection of inert gas to drag the vapors out of the reaction zone.

[0014] More precisely, in the absence of a catalyst, it is understood that the thermolysis of PHA in the presence of at least one polymerization inhibitor occurs in the absence of another chemical species that accelerates or redirects the reaction kinetics. Thermolysis, as predicted, is induced only by operating conditions such as temperature, pressure, and residence time.

[0015] In fact, chemical species that lead to different types of catalysis, depending on the nature of the species, are excluded: - Homogeneous catalysis, if the catalyst and reactants form only one phase (often a liquid phase); - heterogeneous catalysis, if the catalyst and reactants form multiple phases (usually a solid catalyst for reactants in the gaseous or liquid phase); - Enzymatic catalysis, if the catalyst is an enzyme, that is, a protein.

[0016] The invention, therefore, proposes to provide a simple and easy-to-implement solution to reduce fouling phenomena and the presence of impurities in the final product, thus maintaining high reliability and increasing productivity in the production processes of α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoates) obtained by fermentation. Summary of the invention

[0017] The present invention relates to a process for producing Petition 870250084418, dated 09 / 19 / 2025, page 11 / 43 6 / 23 tion of a bio-based α,β-unsaturated carboxylic acid from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, the process comprising the following steps: - extraction of poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA; - Evaporation of the solvent to obtain a solid P3HA with a purity of at least 95% by weight; - a mixture of extracted P3HA with at least one solid-state polymerization inhibitor; - subjecting the solid mixture of P3HA-inhibitor to a thermolysis step, resulting, firstly, in the aforementioned α,β-unsaturated carboxylic acid in the vapor phase and, subsequently, in a molten residue; - separation of the two phases formed into a gaseous phase and a solid phase; - purification of the aforementioned gaseous phase to obtain a purified α,β-unsaturated carboxylic acid; - treatment of solid phase waste.

[0018] According to various implementations, the aforementioned process comprises the following characteristics, when appropriate in combination. The indicated contents are expressed by weight, unless otherwise indicated. The limits are included within the indicated value ranges.

[0019] According to one embodiment, the poly(3-hydroxyalkanoate) used in the process comprises a single type of 3-hydroxyalkanoate unit and the product formed is therefore composed of a single α,β-unsaturated carboxylic acid.

[0020] According to one embodiment, poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α,β-unsaturated carboxylic acid produced Petition 870250084418, dated 09 / 19 / 2025, page 12 / 43 7 / 23 zido is acrylic acid.

[0021] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α,β-unsaturated carboxylic acid produced is methacrylic acid.

[0022] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α,β-unsaturated carboxylic acid produced is crotonic acid.

[0023] According to one embodiment, the poly(3-hydroxyalkanoate) used in the process comprises a plurality of different 3-hydroxyalkanoate units and the product formed is therefore composed of a mixture of different α,β-unsaturated carboxylic acids. Examples of P3HA copolymers are poly-3-hydroxybutyrate-co-3hydroxypropionate (poly-3HB-co-3HP) or poly-3-hydroxybutyrate-co-3hydroxyvalerate (poly-3HB-co-3HV).

[0024] According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxypropionate unit and at least one of the α,β-unsaturated carboxylic acids produced is acrylic acid.

[0025] According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxyisobutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is methacrylic acid.

[0026] According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxybutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is crotonic acid.

[0027] According to one embodiment, the host of the biomass is a bacterium, yeast, fungus, alga, cyanobacterium, or a mixture of two or more of these elements.

[0028] Depending on the method, the P3HA used is previously extracted from biomass to produce a solid P3HA with a purity of at least 95%.

[0029] According to one modality, the agreement process Petition 870250084418, dated 09 / 19 / 2025, page 13 / 43 8 / 23 with the invention comprises a condensation step of the vapor of the α,ε-unsaturated carboxylic acid(s) obtained by the thermolysis reaction of poly(3-hydroxyalkanoate), followed by one or more purification steps. The purification operations may generally include distillations, liquid / liquid extractions, separations using a film evaporator or crystallizations.

[0030] According to one embodiment, the process according to the invention comprises a treatment step of said molten residue obtained at the end of thermolysis, for example, by purifying the latter by means of hydrothermal gasification to generate methane.

[0031] The present invention meets a need expressed in the prior art. It avoids the risks of fouling in the thermolysis reactor and / or the presence of impurities in the final product of α,β-unsaturated carboxylic acids from cell membranes, by enabling the obtaining of a gas phase rich in α,β-unsaturated carboxylic acid, also containing polymerization inhibitors and a molten or slightly pasty residue, which can be improved.

[0032] This solution has the advantage of performing the thermolysis of P3HA is available in solid or molten state, which reduces the energy and environmental costs of the process.

[0033] The invention will now be described in more detail in the following description. Detailed description of the invention

[0034] The objective of the invention is to produce bio-based α,β-unsaturated carboxylic acids on an industrial scale by thermolysis of poly(3-hydroxyalkanoate) contained in biomass, while limiting the problems of clogging of the thermolysis reactor and / or the presence of impurities in the final product.

[0035] The term thermolysis of poly(3-hydroxyalkanoate) (P3HA) signifies Petition 870250084418, dated 09 / 19 / 2025, page 14 / 43 9 / 23 signifies its chemical decomposition into α,β-unsaturated carboxylic acid that occurs under the effect of temperature. This term is synonymous with pyrolysis.

[0036] The present invention relates to a process for the production of a bio-based α,β-unsaturated carboxylic acid from biomass containing a poly(3-hydroxyalkanoate) (P3HA) and in the absence of a catalyst, said process comprising the following steps: - extraction of poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA; - Evaporation of the solvent to obtain a solid P3HA with a purity of at least 95% by weight; - a mixture of extracted P3HA with at least one solid-state polymerization inhibitor; - subjecting the aforementioned solid mixture of P3HA inhibitor to a thermolysis step, resulting, firstly, in the aforementioned α,β-unsaturated carboxylic acid in the vapor phase and, subsequently, in a molten residue; - separation of the two phases formed into a gaseous phase and a solid phase; - purification of the aforementioned gas phase to obtain a purified α,β-unsaturated carboxylic acid; - treatment of solid phase waste.

[0037] According to one embodiment, the aforementioned process for the production of an α,β-unsaturated carboxylic acid of biological origin from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) comprises the following steps: - extraction of poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA in a solvolysis reactor; - removal of the cell membrane by liquid separation- Petition 870250084418, dated 09 / 19 / 2025, page 15 / 43 10 / 23 solid; - Evaporation of the solvent to obtain a solid P3HA with a purity of at least 95% by weight in the same reactor; - introduction of P3HA and at least one polymerization inhibitor in a thermolysis reactor; - a mixture of P3HA and at least one polymerization inhibitor in the aforementioned reactor; - thermolysis of this agitated mixture at a specific controlled temperature and pressure in the same reactor, in order to generate a vapor phase and a viscous phase; - Separation of the two phases formed in a gas-liquid separator, resulting in a gaseous phase and a residue; - treatment of the aforementioned waste; - condensation of the gas phase; - Treatment of the condensed phase to obtain the α,β-unsaturated carboxylic acid, using one or more distillation columns, allowing, firstly, the separation of the α,β-unsaturated carboxylic acid from products heavier than these and, secondly, the obtaining of products lighter than these.

[0038] According to one embodiment, the said solvolysis reactor is stirred and heated to a temperature between 20°C and 170°C, preferably from 50°C to 140°C.

[0039] According to one embodiment, the cell membrane is removed by filtration or centrifugation.

[0040] According to one embodiment, the solvent is evaporated by heating under reduced pressure between 3 kPa and 101 kPa, preferably between 20 kPa and 60 kPa, in a temperature range between 50°C and 140°C.

[0041] According to one embodiment, the introduction of P3HA and at least one polymerization inhibitor into the thermolysis reactor is Petition 870250084418, dated 09 / 19 / 2025, page 16 / 43 11 / 23 carried out by means of a pipe or by a screw conveyor.

[0042] Advantageously, the thermolysis reactor is suitable for the treatment of solid, molten or pasty mixtures.

[0043] According to one embodiment, the mixing of P3HA and at least one polymerization inhibitor in the thermolysis reactor is carried out by means of several screw conveyors driven in a cylinder, allowing the mixing of P3HA and at least one inhibitor.

[0044] According to one method, the waste is treated by spreading, combustion or hydrothermal gasification.

[0045] According to one embodiment, condensation of the gas phase is carried out by a system of at least one tubular-type condenser at the thermolysis pressure, cooling it and collecting the resulting liquid phase in an agitated storage tank, optionally with the addition of one or more additional inhibitors.

[0046] According to one embodiment, products heavier than α,β-unsaturated carboxylic acid are recycled upstream of the thermolysis reactor or are mixed with the solid residue resulting from thermolysis.

[0047] According to one embodiment, products lighter than α,β-unsaturated carboxylic acid are benefited by combustion or hydrothermal gasification.

[0048] According to one embodiment, the α,β-unsaturated carboxylic acid obtained is purified by a fractional crystallization operation comprising several separation steps to obtain high-purity α,β-unsaturated carboxylic acid and a residue to be processed as energy or recycled.

[0049] According to one embodiment, the process according to the invention allows the manufacture of various carboxylic acids. Petition 870250084418, dated 09 / 19 / 2025, page 17 / 43 12 / 23 α,β-unsaturated fatty acids of biological origin from poly(3-hydroxyalkanoates) contained in biomass.

[0050] The invention is based on the use of a mixture of P3HA and at least one polymerization inhibitor, using a solids mixing technique and heat treatment of this mixture.

[0051] The term “biomass” means organic matter derived from plants (including microalgae), animals, bacteria or fungi, which can be used as a source of biological raw materials, as opposed to raw materials of fossil origin.

[0052] In the process according to the invention, the first step uses genetically modified host biomass, derived from genetic engineering. According to one embodiment, the host biomass is a bacterium, yeast, fungus, algae, cyanobacteria, or a mixture of two or more of these elements.

[0053] Biomass is obtained by a prior cultivation step of a recombinant host with a renewable feedstock. According to one embodiment, the renewable feedstock is selected from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, ethanol, methanol, glycerol, fatty acids, vegetable oils and biomass-derived synthesis gas or a combination thereof.

[0054] According to one embodiment, the biomass used in the process according to the invention comes from a bacterial fermentation process of sugars or lipids.

[0055] Depending on the growing conditions and the variety of microorganisms used, homopolymers or copolymers of poly(3-hydroxyalkanoate) (P3HA) are formed with different 3-hydroxyalkanoic acid units.

[0056] The biomass used is pre-treated by means of washing, drying or grinding operations to produce a biomass containing at least 30% by weight of P3HA, preferably Petition 870250084418, dated 09 / 19 / 2025, page 18 / 43 13 / 23 at least 50% by weight of P3HA.

[0057] The extraction step of P3HA from biomass with a solvent comprises the separation of organic residues insoluble in said solvent, for example, cell membranes, from the P3HA-solvent mixture, carried out by filtration or centrifugation.

[0058] The extraction step of P3HA from biomass with a solvent occurs at a temperature of 20°C to 130°C.

[0059] According to one modality, the extraction step of P3HA of biomass with a solvent occurs in batches.

[0060] According to a preferred embodiment, the extraction step of P3HA from biomass with a solvent occurs continuously.

[0061] According to one embodiment, the solvent used to extract P3HA from biomass at atmospheric pressure is selected from polar solvents with a boiling point higher than the extraction temperature but lower than the thermolysis temperature. These solvents may be linear or branched alcohols with a carbon number less than or equal to 7, for example, heptanol or n-butanol, linear or branched aldehydes or ketones with a carbon number less than or equal to 7, such as hexanal or butanone, or carboxylic acids with a carbon number less than C4, such as butyric acid.

[0062] The solvent used in the process must be capable of dissolving P3HA at a concentration greater than 5% by weight in the solution, preferably greater than 20%, at the temperature used during the extraction step.

[0063] The solvent is then evaporated to provide a solid P3HA with a purity of at least 95% by weight.

[0064] Depending on the method, evaporation can be carried out under a pressure of 20 kPa to 100 kPa at a temperature between 20°C and 150°C. Petition 870250084418, dated 09 / 19 / 2025, p. 19 / 43 14 / 23

[0065] Solid P3HA is then mixed with at least one polymerization inhibitor chosen from those conventionally used in existing industrial processes for the production of α,β-unsaturated carboxylic acids. These include phenolic derivatives such as hydroquinone (HQ) and its derivatives such as hydroquinone methyl ether (MEHQ), 2,6-di-tert-butyl-4-methylphenol (BHT) or 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazines and their derivatives; nitroxide compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO); and amino compounds such as paraphenylenediamine derivatives.

[0066] According to a preferred embodiment, at least one of said polymerization inhibitors is hydroquinone methyl ether (MEHQ).

[0067] According to one embodiment, the weight content of inhibitor in the mixture with P3HA is between 0.1% and 10%, preferably from 0.4% to 5%.

[0068] According to the invention, the system for feeding the thermolysis reactor with P3HA and at least one polymerization inhibitor can be a pipe, a screw conveyor, a conveyor belt or a hopper, a pneumatic conveyor, a vibratory conveyor or an extruder. In addition, they can be coupled to a dosing device.

[0069] The mixture of P3HA and at least one polymerization inhibitor is then subjected to solid-state or molten thermolysis.

[0070] The mixing step of P3HA and at least one polymerization inhibitor can be carried out in a mixer-conveyor consisting of several screw conveyors driven on a cylinder, or directly in the thermolysis reactor.

[0071] According to one embodiment, the mixing and thermolysis steps are carried out continuously, successively Petition 870250084418, dated 09 / 19 / 2025, page 20 / 43 15 / 23 the mixing on a conveyor belt and the reaction in the thermolysis reactor, or carrying out both operations in the thermolysis reactor.

[0072] Preferably, the thermolysis reactor performs the mixing and the thermolysis reaction.

[0073] Heating of the mixture can be carried out at a temperature between 100°C and a temperature below the auto-ignition temperature of the monomer formed. For acrylic acid, this temperature is 438°C at atmospheric pressure (NF T 20037 standard). Preferably, the heating temperature is between 150°C and 400°C, advantageously between 200°C and 350°C. Heating can be staged, with an initial temperature zone of around 100°C-200°C, which allows liquefying all or part of the mixture, preventing polymerization of the acrylic acid.

[0074] According to one embodiment, the pressure in the thermolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0075] According to one embodiment, the residence time in the thermolysis reactor is between 0.05 h and 1 h, preferably between 0.15 h and 0.5 h.

[0076] According to one embodiment, the apparatus for carrying out the process also comprises a reactor suitable for heating for thermolysis purposes. For example, heating can be carried out by exposing the mixture to microwaves, pulsed electric fields or a preheated inert gas or vapor, with a preheated solid, such as sand, by contact with a hot surface, for example, in an extruder, a screw conveyor, a rotating drum or a plate. The hot surface can be heated by various means: direct electric heating, heating by heat transfer fluid (steam, oil, molten salts).

[0077] According to one embodiment, heat is supplied through Petition 870250084418, dated 09 / 19 / 2025, p. 21 / 43 16 / 23 through a surface heated by a heat transfer fluid and, in particular, molten salts.

[0078] The thermolysis reactor according to the invention may be an extruder or conveyor, a reactor suitable for pyrolysis, for high-temperature pyrolysis, or a fluidized reactor or a reactor suitable for solvolysis, or even a reactor consisting of hollow plates heated by a heat transfer fluid circulating in the plates. However, reactors have been identified that allow for greater gains in the yield of α,β-unsaturated carboxylic acid, such as: a conveyor, an extruder, an extruder-conveyor and / or a set of heating plates.

[0079] According to the invention, the extruder-conveyor is a reactor comprising one or more augers, each driven in a cylinder, notably allowing the mixing of the components introduced into said cylinder. The use of an extruder-conveyor to carry out this P3HA thermolysis process is advantageous from an environmental, safety and process protection standpoint. Specifically, an extruder-conveyor enables the treatment of a molten medium without the need to add solvent to reduce the viscosity of the molten medium. The extruder-conveyor has the advantage of allowing efficient heat transfer from the cylinder to the P3HA inhibitor medium. The extruder can be advantageously replaced by a helical conveyor system along all or part of its length.Advantageously, the system can comprise a combination of a conveyor-type device in the first part, followed by an extruder-type device and a conveyor configured to transport the waste to the outlet. For example, the conveyor could be an Archimedes screw type (endless screw).

[0080] A thermolysis system according to the invention can Petition 870250084418, dated 09 / 19 / 2025, page 22 / 43 17 / 23 comprise an extruder, such as the 200 twin-screw extruder, which comprises an inlet for the solid or previously melted P3HA inhibitor mixture. A twin-screw extruder may be a Clextral extruder. The twin-screw extruder comprises two screws, usually parallel, rotating within a cylinder. Advantageously, the extruder is of a modular nature, i.e., the screw and cylinder are modules assembled in series, the assembly of which can be modified. In the extruder, an external heating means that regulates the cylinder temperature is advantageously configured to, on the one hand, bring the P3HA inhibitor mixture to a molten state and, on the other hand, perform the thermolysis of the P3HA.

[0081] According to another embodiment, the thermolysis system comprises a device consisting of hollow plates, heated by a heat transfer fluid circuit (pressurized steam, oil, molten salts, etc.). During its treatment, the article first advances over plates with increasing temperatures. The residue completes its passage through the reactor by passing over plates that are at a lower temperature, where heat exchange occurs from the residue to the heat transfer fluid. The heat transfer fluid thus heated can then be used to preheat the P3HA-inhibitor mixture that feeds the thermolysis reactor.

[0082] According to one embodiment, the thermolysis system is a mixer-conveyor type device, for example, of the screw conveyor type. This device comprises a reactor in which two screw conveyors operate in opposition. The mixture is heated through the hot wall using a heat transfer fluid, such as steam. The movement of the two screws allows mixing and homogenization of the P3HA and polymerization inhibitor feeds.

[0083] According to one embodiment, the process according to the invention performs the thermolysis of the P3HA-inhibitor mixture by means of a Petition 870250084418, dated 09 / 19 / 2025, page 23 / 43 18 / 23 extruder at a temperature of around 150-400°C.

[0084] In the thermolysis reactor, the P3HA inhibitor mixture is converted, under the action of heat, into gaseous compounds comprising an α,β-unsaturated carboxylic acid.

[0085] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) (P3HP), and the α,β-unsaturated carboxylic acid obtained by the process according to the invention is acrylic acid.

[0086] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutanoate) (P3HiB), and the α,β-unsaturated carboxylic acid obtained by the process according to the invention is methacrylic acid.

[0087] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutanoate) (P3HB), and the α,β-unsaturated carboxylic acid obtained by the process according to the invention is crotonic acid.

[0088] According to one embodiment, the invention relates to a process for producing a mixture of α,β-unsaturated carboxylic acids from a P3HA contained in biomass, comprising a plurality of different 3-hydroxyalkanoate units.

[0089] Gases containing the α,β-unsaturated carboxylic acid(s) can be sent to a cooling system for condensation. The resulting condensate can then be collected in a chamber designed for this purpose. The reactor casing and the chamber are preferably subjected to reduced pressure. The condensation system can be equipped with the injection of one or more inhibitors. To allow the recovery of a purified α,β-unsaturated carboxylic acid, the system may comprise a purification device, for example, one or more distillation columns, or one or more liquid extraction, crystallization, or membrane separation devices.

[0090] The solid waste is then processed, for example, by Petition 870250084418, dated 09 / 19 / 2025, page 24 / 43 19 / 23 hydrothermal seization or in fuel form.

[0091] According to one embodiment, condensation is carried out using one or more tubular or spiral heat exchangers in series.

[0092] According to one embodiment, condensation is carried out by successive pressure adjustments and separation of the resulting gaseous and liquid phases, containing α,β-unsaturated carboxylic acid and contaminants, which can be recycled back to the reactor.

[0093] According to the invention, condensation is carried out by successively adjusting the condensation temperature, placing one or more condensers in series and separating the resulting gaseous and liquid phases, containing α,β-unsaturated carboxylic acid and contaminants, which can be recycled back to the reactor or sent to the purification system.

[0094] According to one embodiment, one or more polymerization inhibitors are added to the condenser.

[0095] According to one embodiment, this condensation can be carried out by placing the α,β-unsaturated carboxylic acid in the gaseous state in contact with the α,β-unsaturated carboxylic acid in the liquid state. This contact operation can be carried out, for example, in a shower-type device, spraying the liquid α,β-unsaturated carboxylic acid into a chamber that collects the α,β-unsaturated carboxylic acid in the gaseous state.

[0096] According to one embodiment, no inhibitor is added to the capacitor.

[0097] According to one embodiment, the residue obtained after the thermolysis stage is processed by hydrothermal gasification.

[0098] According to the method, hydrothermal gasification is carried out at a temperature of 350°C-450°C and a pressure of 25 MPa.

[0099] The examples below illustrate the present invention without, Petition 870250084418, dated 09 / 19 / 2025, page 25 / 43 20 / 23 however, limit its scope. EXPERIMENTAL SECTION

[00100] The examples are performed on biomass containing 60% by weight of poly(3-hydroxypropionate) (P3HP). The α,β-unsaturated carboxylic acid obtained after thermolysis is acrylic acid (AA).

[00101] Biomass containing P3HP is brought into contact with a solvent that solubilizes the P3HP, and then this mixture is treated by centrifugation to separate the insoluble materials (e.g., the cell membrane) from the P3HP-solvent mixture. The solvent is then evaporated under vacuum to recover the solid P3HP.

[00102] Thermolysis is performed by placing solid P3HP (2 g) and the inhibitor (0 or 20 mg of MEHQ or PTZ) in a 50 ml round-bottom flask with two necks, equipped with a magnetic stir bar. The medium is stirred with a magnetic stirrer to spread the inhibitor throughout the solid. This 50 ml round-bottom flask with two necks, containing the medium, is equipped, on the side of the neck, with a thermometer to monitor the temperature of the thermolysis medium and, at the top, with a separating bridge leading to a water-cooled side condenser. The condenser leads to a receiver consisting of a 25 ml single-neck round-bottom flask. An air purge allows the experiment to be performed under partial vacuum.

[00103] At the beginning of the experiment, the system is placed under the desired pressure and the round-bottom flask containing the P3HP inhibitor mixture is then placed in a heating system that allows the desired thermolysis temperature to be established (oil bath or electric heating mantle). The receiver is cooled by an ice bath.

[00104] As soon as the thermolysis reactor reaches more than 170°C, AA vapors are formed, condensing predominantly in the con Petition 870250084418, dated 09 / 19 / 2025, page 26 / 43 21 / 23 side condenser. After 4 hours of heating, the formation of AA vapors in the thermolysis reactor gradually decreases and the experiment is stopped. The consistency of the thermolysis residue is visually assessed at the end of the experiment.

[00105] The results obtained are presented in Table 1.

[00106] Table 1 Test Inhibitor Vapor pressure of inhibitor at 200°C (kPa) Operating pressure (kPa) Thermolysis residue 1 No - 100 Sticky and hard solid 2 No - 55 Sticky and hard solid 3 No - 20 Sticky and hard solid 4 MEHQ 28.5 100 Pasty and viscous solid 5 MEHQ 28.5 55 Pasty and viscous solid 6 MEHQ 28.5 20 Pasty and sticky solid 7 PTZ 0.7 100 Pasty and sticky solid 8 PTZ 0.7 55 Pasty and sticky solid 9 PTZ 0.7 200 Sticky and hard solid

[00107] The results in Table 1 demonstrate that the physical state of the residue depends on the presence of the inhibitor, in particular MEHQ. The addition of the inhibitor allows the residue to become pasty and viscous, while without the addition of the latter it becomes sticky. This change in the consistency of the residue allows for easier extraction when performing continuous thermolysis.

[00108] The tests for examples 10-12 below are performed in the same laboratory, using P3HP purified from biomass, as described above.

[00109] EXAMPLE 10 (comparative): Use of pure P3HP without catalyst and without inhibitor

[00110] 2.05 g of purified P3HP are placed in a flask of Petition 870250084418, dated 09 / 19 / 2025, page 27 / 43 A 22 / 23 round-bottom, two-necked flask of 25 ml capacity equipped with magnetic stirring is used. The round-bottom flask is brought to a pressure of 20 kPa using a diaphragm vacuum pump and then heated to 200°C for 4 h. The vapors generated are condensed in a water-cooled side condenser, yielding 1.41 g of acrylic acid, corresponding to a yield of 68%. The solid obtained after cracking forms a thin layer that remains adhered to the walls of the round-bottom, two-necked flask. This layer is very difficult to remove from the round-bottom, two-necked flask. Solid particles are found in the upper part of the flask and in the side condenser.

[00111] In the absence of a catalyst, the acrylic acid recovery yield is low, on the order of 68%. This low value is consistent with that cited in document WO 2016 / 039618, example 1, in which the thermolysis of PHB leads to the production of 57% crotonic acid. Adding to this low yield is the presence of solid particles that are detrimental to the development of this process.

[00112] EXAMPLE 11 (according to the invention): Use of pure P3HP with the addition of 1% 4-methoxyphenol (MEHQ) without catalyst

[00113] 2.12 g of purified P3HP are placed in a 25 ml two-necked round-bottom flask equipped with magnetic stirring. 0.021 g of MEHQ are added to the round-bottom flask and mixed with the P3HP. The round-bottom flask, equipped with a separating bridge, is subjected to a pressure of 20 kPa by means of a diaphragm vacuum pump. The flask is heated to 200°C for 4 h. The vapors generated are condensed using a water-cooled side condenser to obtain 1.99 g of acrylic acid, which corresponds to a yield of 94%. After cracking, very little solid remains in the round-bottom flask, and this solid is easily removed from the flask by simple scraping. Petition 870250084418, dated 09 / 19 / 2025, page 28 / 43 23 / 23

[00114] EXAMPLE 12 (according to the invention): Use of pure P3HP with the addition of 5% 4-methoxyphenol (MEHQ) without a catalyst.

[00115] 2.12 g of purified P3HP are placed in a 25 ml two-necked round-bottom flask equipped with magnetic stirring. 0.117 g of MEHQ are added to the round-bottom flask and mixed with the P3HP. The round-bottom flask, equipped with a separating bridge, is subjected to a pressure of 20 kPa by means of a diaphragm vacuum pump. The flask is heated to 200°C for 4 h. The vapors generated are condensed using a water-cooled side condenser to obtain 1.85 g of acrylic acid, which corresponds to a yield of 87%. After cracking, very little solid remains in the round-bottom flask, and this solid is easily removed from the flask by simple scraping.

[00116] The yield obtained in examples 11 and 12 is therefore much higher than that reported in example 1 of document WO 2016 / 039618, where thermal degradation also occurs in the absence of a catalyst. Only when thermolysis is carried out in the presence of a catalyst does the yield increase to 86% or 89%, respectively (for examples 2 and 3 of the aforementioned document).

[00117] These examples also show that, in the presence of an inhibitor, in the process according to the invention, the thermolysis yields are very high in the absence of a catalyst and even under more moderate thermal conditions, since this thermolysis is carried out at 200°C (290°C with catalyst in WO 2016 / 039618, example 1). Petition 870250084418, dated 09 / 19 / 2025, page 29 / 43

Claims

1 / 4 CLAIMS 1. Process for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing a poly(3-hydroxyalkanoate) (P3HA) and in the absence of a catalyst, said process characterized by comprising the following steps: - extracting the poly(3-hydroxyalkanoate) from the biomass using a solvent capable of solubilizing the P3HA; - evaporating the solvent to obtain a solid P3HA with a purity of at least 95% by weight; - mixing the extracted P3HA with at least one solid-state polymerization inhibitor; - subjecting said solid mixture of P3HA inhibitor to a thermolysis step, resulting, firstly, in said α,β-unsaturated carboxylic acid in the vapor phase and, secondly, in a molten residue; - separating the two phases formed into a gaseous phase and a solid phase; - purifying said gaseous phase to obtain a purified α,β-unsaturated carboxylic acid; - treat the solid phase residue.

2. Process, according to claim 1, characterized by comprising the following steps: - extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA in a solvolysis reactor; - removing the cell membrane by liquid-solid separation; - evaporating the solvent to obtain a solid P3HA with a purity of at least 95% by weight in the same reactor; - introducing the P3HA and at least one polymerization inhibitor into a thermolysis reactor; - mixing the P3HA and at least one polymerization inhibitor. Petition 870250084418, dated 09 / 19 / 2025, p.30 / 43 2 / 4 tion in the aforementioned reactor; - to thermolyze this agitated mixture at a given temperature and at a controlled pressure in the same reactor or in another reactor of the same type, in order to generate a vapor phase and a viscous phase; - to separate the two phases formed in a gas-liquid separator, resulting in a gaseous phase and a residue; - to treat the aforementioned residue; - to condense the aforementioned gaseous phase; - to treat the condensed phase to obtain the α,β-unsaturated carboxylic acid using one or more distillation columns, allowing, firstly, the separation of the α,β-unsaturated carboxylic acid from products heavier than these and, secondly, to obtain products lighter than these.

3. A process, according to any one of claims 1 and 2, characterized in that the biomass used is pretreated by means of washing, drying or grinding operations to produce a biomass containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

4. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) contains the 3-hydroxypropionate unit and at least one of the α,β-unsaturated carboxylic acids produced is acrylic acid.

5. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α,β-unsaturated carboxylic acid produced is acrylic acid.

6. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) contains the 3-hydroxybutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is crotonic acid. Petition 870250084418, dated 19 / 09 / 2025, page 31 / 43 3 / 4 7. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α,β-unsaturated carboxylic acid produced is crotonic acid.

8. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) contains the 3-hydroxyisobutyrate unit and at least one of the α,β-unsaturated carboxylic acids produced is methacrylic acid.

9. Process, according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α,β-unsaturated carboxylic acid produced is methacrylic acid.

10. Process, according to any of the preceding claims, characterized in that the polymerization inhibitor(s) is / are compound(s) selected from phenol derivatives, phenothiazine derivatives, nitroxide derivatives or para-phenylenediamine derivatives.

11. A process, according to any of the preceding claims, characterized in that at least one of said polymerization inhibitors is hydroquinone methyl ether.

12. A process, according to any of the preceding claims, characterized in that the solvent used to extract the P3HA present in the biomass is selected from polar solvents that have a boiling point higher than the extraction temperature, but lower than the thermolysis temperature.

13. Process, according to any of the preceding claims, characterized in that the thermolysis reactor is selected from: a conveyor, a mixer-conveyor, an extruder, an extruder-conveyor and / or a set of heating plates. Petition 870250084418, dated 19 / 09 / 2025, p. 32 / 43 4 / 4 14. Process according to claim 13, characterized in that the thermolysis reactor is a conveyor extruder having one or more screw conveyors, each driven in a cylinder.

15. Process according to claim 13, characterized in that the thermolysis reactor is a twin-screw extruder.

16. Process according to claim 13, characterized in that the thermolysis reactor is a device consisting of hollow plates heated by a heat transfer fluid circuit.

17. Process according to claim 13, characterized in that the thermolysis reactor is a helical conveyor.

18. Process, according to any of the preceding claims, characterized in that thermolysis is carried out between 150°C and 400°C with a residence time between 0.05 h and 1 h. Petition 870250084418, dated 19 / 09 / 2025, p. 33 / 43