PROCESSO DE FABRICAÇÃO DE ÁCIDOS CARBOXÍLICOS ALFA-BETA INSATURADOS DE ORIGEM BIOLÓGICA A PARTIR DE POLI(3-HIDROXIALCANOATO)

Abstract

The present invention relates to a process for producing biobased α,β-unsaturated carboxylic acids from biomass containing a poly(3-hydroxyalkanoate), or from a solid poly(3-hydroxyalkanoate) previously extracted from this biomass in the presence of polymerization inhibitors, by thermolysis of said polymer, in the absence of a catalyst, predominantly to α,β-unsaturated carboxylic acid in gaseous form without using an inert gas to facilitate the evaporation of this acid. This invention more precisely describes the step of thermolysis of the biomass or of P3HA, then the purification steps making it possible to obtain the α,β-unsaturated carboxylic acid and the recycling of the intermediate products.

Description

1 / 28 “PROCESS FOR MANUFACTURING ALPHA-BETA UNSATURATED CARBOXYLIC ACIDS OF BIOLOGICAL ORIGIN FROM POLY(3-HYDROXYALKANOATE) Technical field

[001] The present invention relates to a process for manufacturing α-β unsaturated carboxylic acids of biological origin from biomass containing a poly(3-hydroxyalkanoate), or from a solid poly(3-hydroxyalkanoate) previously extracted from this biomass in the presence of polymerization inhibitors, by thermolysis of said polymer, in the absence of a catalyst, mainly in gaseous α-β unsaturated carboxylic acid without using an inert gas to facilitate the evaporation of this acid. This invention describes more precisely the thermolysis step of the biomass or P3HA, then the purification steps that allow obtaining the α-β unsaturated carboxylic acid and recycling of the intermediate products. Previous technique and technical problem

[002] The industrial production of α-β unsaturated carboxylic acids is currently primarily made from raw materials of fossil origin. For example, acrylic acid is obtained by oxidizing propylene, or methacrylic acid can be obtained by oxidizing isobutylene.

[003] One of the possible routes to obtain these α-β unsaturated carboxylic acids is the thermolysis at temperatures of 150 to 300°C of the corresponding poly(3-hydroxyalkanoates) (P3HA), according to the following reaction: (Quim 1) Petition 870250084836, dated 09 / 19 / 2025, page 8 / 53 2 / 28 Ri = H or alkyl and R2 = H or alkyl; n is a number greater than 30 Si Ri = R2 = H: - poly(3-hydroxyalkanoate) = poly(3-hydroxypropionate) (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). Si R3 = H and R2 = methyl - poly(3-hydroxyalkanoate) = poly(3-hydroxybutyrate) (P3HB). - α-β unsaturated carboxylic acid = but-2-enoic acid (crotonic acid). Si Ri = H and R2 = ethyl: - poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV); - α-β unsaturated carboxylic acid = pent-2-enoic acid

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

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

[006] US patent 9850192 describes a process for producing acrylic acid from a genetically modified microbial biomass that metabolizes glucose or any other renewable feedstock to produce a homopolymer or copolymer. Petition 870250084836, dated 09 / 19 / 2025, page 9 / 53 3 / 28 of poly-3-hydroxypropionate (P3HP) inside microbial cells. The process comprises a thermolysis step of washed / dried / crushed biomass containing P3HP, in the presence of a catalyst. Acrylic acid is recovered in gaseous form, then condensed, while the catalyst, as well as the residual biomass mass, can be recycled in the process subjected to thermal regeneration. However, the risk is that the residue present in the reactor after thermolysis is pasty and sticky, which could complicate its transition to 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, i.e., a double drum dryer.After the addition of the catalyst, the product is pyrolyzed in a FAST™ reactor at 250°C-350°C with a residence time of 0.25–1 hour, using an inert gas such as nitrogen to send the vapors formed to purification equipment. The vapor phase is composed of 90% organic / water and 10% inert gas. The gas is then purified, following the process described in US patent 6646161 or US patent 20120006673, to obtain acrylic acid containing even more impurities. Complete purification is carried out using distillation columns, as described in US patents 7332624 and 7179875, and may also require crystallization operations, as described in US patents 6482981 and 71798750. These documents describe techniques commonly used to obtain acrylic acid by propylene oxidation.

[007] Document US2014 / 0018574 describes a process for the thermolysis of P3HA in the presence of a compound comprising a tertiary amine acting as a catalyst, present in a concentration of approximately 0.5% to 4% by weight relative to P3HA. Optionally, one or more inhibitors may be added to the Petition 870250084836, dated 09 / 19 / 2025, page 10 / 53 4 / 28 P3HA before performing thermolysis preferably in a proportion of 150 ppm to 350 ppm in relation to P3HA in the presence of depleted air (<6% O2) (0107-0108). Furthermore, regarding acrylic acid formed during this thermolysis, no inhibitor (0111) is added during its condensation. Finally, this document shows that at a temperature of 175°C (0010143) and in the absence of a catalyst, the thermolysis was inoperative.

[008] When the thermolysis of P3HA is carried out in the liquid phase as in document JP 2015607567, in the absence or presence of a catalyst and in the absence of an inhibitor, this reaction is preferably carried out in the presence of an inert gas to evaporate the acrylic acid formed (0031).

[009] Another solution consists of extracting P3HA from the biomass beforehand with the aid of an organic solvent before carrying out its thermolysis. Document US 2015376152 describes, in example 6, the extraction of P3HP from biomass with the aid of an organic solvent, such as 2-butanone, then obtaining acrylic acid in three steps: evaporation of the solvent and condensation of the latter in a receiving vessel; thermal degradation of P3HP in the absence of an inhibitor leading to the obtaining 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 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, as well as in the gas phase in case of accidental condensation or at the moment of condensation of acrylic acid vapors at the top of the column. Petition 870250084836, dated 09 / 19 / 2025, page 11 / 53 5 / 28

[0011] In its patent application FR 2208916, the applicant company describes a process that uses a solvent that allows the selective solubilization of P3HA from biomass, separating the insoluble organic debris from said solvent, to perform a liquid-phase thermolysis treatment 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 shown 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 found that it is possible to obtain high-purity acrylic acid by combining the thermolysis of biomass containing P3HA, or the thermolysis of solid P3HA and at least one polymerization inhibitor, a staged condensation system of thermolysis gas, fractional distillation and possibly crystallization, in the absence of a catalyst and without using an inert gas to favor the evaporation of the α-β unsaturated carboxylic acid formed.

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

[0015] Chemical species that lead to different types of catalysis depending on the nature of the species are indeed excluded: - Homogeneous catalysis, if the catalyst and reactants form only one phase (often liquid); - Heterogeneous catalysis, if the catalyst and reactants form multiple phases (generally, a solid catalyst for reactants in the gaseous or liquid phase); Petition 870250084836, dated 09 / 19 / 2025, page 12 / 53 6 / 28 Enzymatic catalysis occurs when the catalyst is an enzyme, that is, a protein.

[0016] The expression “in the absence of inert gas” means that the thermolysis of PHA, in the presence of at least one polymerization inhibitor, takes place in the absence of gas injection, such as depleted air (<6%O2), which facilitates the evaporation of the acid formed and generally facilitates the activation of inhibitors in the reaction medium.

[0017] Consequently, the invention proposes to provide a simple and easy-to-implement solution, allowing the obtaining of α-β unsaturated carboxylic acids from biomass containing P3HA, or from solid PH3HA, using a thermolysis reactor coupled to an optimized purification process. Summary of the invention

[0018] The present invention relates to a process for manufacturing an α-β unsaturated carboxylic acid of biological origin, said process comprising the following steps: - mixing a biomass containing a poly(3-hydroxyalkanoate) (P3HA), or solid P3HA, with at least one polymerization inhibitor in the absence of a catalyst; - subjecting said biomass-inhibitor mixture or P3HA inhibitor to a thermolysis step that leads to obtaining, on the one hand, said unsaturated α-β carboxylic acid in vapor form and, on the other hand, a molten or solid residue, without the addition of an inert gas; - to condense, in one or more stages, the gases from thermolysis, then feed a distillation column with the thermolysis gases obtained, - to fractionate thermolysis gases into beneficiated light products, heavy products recycled in the thermolysis reactor, and unsaturated α-β carboxylic acid with a purity greater than 98%, which can be crystallized to achieve a purity > 99.5%, Petition 870250084836, dated 09 / 19 / 2025, page 13 / 53 7 / 28 - treat the waste in its solid phase.

[0019] According to various modalities, the said process comprises the following characteristics, combined if necessary. The indicated contents are expressed by weight, unless otherwise indicated. The indicated value ranges include the limits.

[0020] The term “thermolysis” of poly(3-hydroxyalkanoate) (P3HA) means its chemical decomposition into α-β unsaturated carboxylic acid obtained under the effect of temperature. This term is synonymous with pyrolysis.

[0021] According to one embodiment, the poly(3-hydroxyalkanoate) used in the process comprises only one type of 3-hydroxyalkanoate motif and the product formed is therefore composed of a single α-β unsaturated carboxylic acid.

[0022] According to one embodiment, the poly(3-hydroxyalkanoate) is the poly(*3-hydroxyisobutyrate) 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 several different 3-hydroxyalkanoate motifs 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-3-hydroxypropionate (poly-3HB-co-3HP) or poly-3-hydroxybutyrate-co-3-hydroxyvalerate (poly3HB-co-3HV).

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

[0026] According to one embodiment, poly(3-hydroxyal Petition 870250084836, dated 09 / 19 / 2025, page 14 / 53 8 / 28 canoatao) contains the 3-hydroxybutyrate motif 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, a yeast, a mushroom, an alga, a cyanobacterium, or a mixture of two or more of these elements.

[0028] According to one embodiment, the biomass used is pre-treated by washing, drying and grinding operations, to yield a biomass containing 30% to 90% by weight of PHA, the remainder being made up of the cell membrane.

[0029] According to one embodiment, biomass is subjected to a thermolysis reaction, which occurs in the presence of one or more polymerization inhibitors.

[0030] According to one embodiment, the P3HA with a purity greater than 95% by weight, used in the process according to the invention, comes from the extraction of P3HA by a solvent, evaporation of the latter and elimination of the cell membrane by filtration and centrifugation.

[0031] According to one embodiment, the thermolysis reaction occurs in the presence of one or more polymerization inhibitors.

[0032] According to one embodiment, mixing and thermolysis are carried out continuously in successive stages or simultaneously.

[0033] According to one embodiment, the mixture comprising the biomass comprises at least 0.01% of one or more polymerization inhibitors up to 5% and preferably less than 1% of one or more polymerization inhibitors (mass percentages).

[0034] According to one embodiment, the mixture comprising P3HA comprises at least 0.5% of one or more polymerization inhibitors to 90% of one or more polymerization inhibitors (mass percentages) and preferably between 20% and 70% of one or more polymerization inhibitors. Petition 870250084836, dated 09 / 19 / 2025, page 15 / 53 9 / 28

[0035] According to one embodiment, the process according to the invention comprises one to several steps of condensation of the vapors of the α-β unsaturated carboxylic acid(s) obtained by the thermolysis reaction of poly(3-hydroxyalkanoate).

[0036] According to one embodiment, the condensates obtained can be recycled back into the thermolysis reactor and into the separation column.

[0037] According to one embodiment, one or more inhibitors are injected equally into the capacitors.

[0038] According to one embodiment, no inhibitors are injected into the capacitors.

[0039] According to one embodiment, one or more distillation columns can be used to purify the α-β unsaturated carboxylic acid.

[0040] According to one embodiment, the condensates obtained can be subjected to a rectification or crystallization treatment before being recycled to the thermolysis reactor.

[0041] According to one embodiment, the feed to the separation column is carried out in the gas phase.

[0042] According to one embodiment, the foot of the distillation column is recycled to the thermolysis reactor.

[0043] According to one embodiment, the foot of the separation column is subjected to a rectification or crystallization operation before being recycled to the thermolysis reactor.

[0044] According to one embodiment, the unsaturated α-β carboxylic acid obtained from the top or side discharge to a purity of at least 98% by weight.

[0045] According to one embodiment, this α-β unsaturated carboxylic acid can be further purified in a subsequent crystallization step. Petition 870250084836, dated 09 / 19 / 2025, page 16 / 53 10 / 28

[0046] According to one embodiment, the purity of the α-β unsaturated carboxylic acid after crystallization is greater than 99.5% by weight.

[0047] According to one embodiment, the top-of-column products are sent to a biological purification station.

[0048] According to one embodiment, these top-of-column products are beneficiated into methane by hydrothermal gasification.

[0049] According to one embodiment, the process according to the invention comprises a solid or molten waste treatment step at the end of thermolysis, benefiting the latter by upstream recycling of the thermolysis reactor or by external treatment such as gasification.

[0050] Other features and advantages of the invention will become clearer when reading the detailed description below, with reference to the attached figures 1 and 2.

[0051] Figure 1 represents the schematic of an installation for carrying out the process according to the invention, when it is applied to a P3HA - inhibitor mixture.

[0052] Figure 2 represents the schematic of a setup for carrying out the process according to the invention, when it is applied to a biomass-inhibitor mixture. Detailed description of the invention

[0053] By way of example, the illustration of the invention will be carried out by describing the process applied to poly(3-hydroxypropionate) (P3HP) extracted from the cell membrane, or to biomass still containing P3HP, allowing to obtain α-β unsaturated carboxylic acid (in this case, acrylic acid) having a purity greater than 99.5% by weight.

[0054] The invention aims to produce acrylic acid on an industrial scale by thermolysis of poly(3-hydroxypropionate), limiting the problems of clogging of the thermolysis reactor and allowing this acid to be obtained with a purity >98% or even >99.5% by weight. Petition 870250084836, dated 09 / 19 / 2025, page 17 / 53 11 / 28

[0055] According to one embodiment, the said process for obtaining acrylic acid of biological origin contains the following steps, which may be carried out sequentially or simultaneously: - introduction of biomass (in powder form) or P3HP and at least one polymerization inhibitor, in the absence of a catalyst, into a mixer (in solid phase) by means of a conduit or a screw conveyor; - Mixing of P3HP or biomass and at least one polymerization inhibitor in a conveyor mixer comprising several screw conveyors, driven in a sheath furnace or directly into the reactor called a thermolysis reactor; - thermolysis of this mixture at a given temperature and controlled pressure in a system adapted to the treatment of molten or pasty residue, to generate a vapor phase and a viscous or even solid phase without the injection of an inert gas; - separation of the two phases formed in a gas-liquid separator; - treatment of the residue for beneficiation by spreading, combustion or hydrothermal gasification or by recycling upstream of the thermolysis reactor; - Staged condensation of the gas phase is achieved by adjusting successive condensation temperatures by placing one or more condensers in series and separating the resulting gaseous and liquid phases, which contain acrylic acid and contaminants that can be recycled back into the reactor or sent to the purification system; - treatment of the condensed phase to obtain acrylic acid by using one or more distillation columns, allowing, on the one hand, the separation of acrylic acid from products heavier than Petition 870250084836, dated 09 / 19 / 2025, page 18 / 53 12 / 28 the latter and, on the other hand, obtain products that are lighter than the latter; - purification of acrylic acid obtained by a liquid / solid separation method such as crystallization or by a gas / liquid separation method such as distillation.

[0056] The invention is based on the use of a biomass mixture containing a P3HA, or solid P3HA, and at least one polymerization inhibitor using a solids mixing technology and heat treatment of this mixture.

[0057] The term “biomass” means organic matter of plant (including microalgae), animal, bacterial or fungal (mushrooms) origin, usable as a source of biological raw materials, as opposed to raw materials of fossil origin.

[0058] In the process according to the invention, the first step uses genetically modified host biomass, obtained through genetic engineering. According to one embodiment, the host biomass is a bacterium, a yeast, a mushroom, an alga, a cyanobacterium, or a mixture of two or more of these elements.

[0059] Biomass is obtained by a prior culture step of a recombinant host with a feedstock chosen from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, ethanol, methanol, glycerol, fatty acids, vegetable oils and synthesis gas derived from biomass or a combination thereof.

[0060] According to one embodiment, the biomass used in the process according to the invention comes from a bacterial fermentation process of sugars or lipids.

[0061] Depending on the culture conditions and the variety of microorganism used, poly(3-hydroxyalkanoates) (P3HA) homo- or copolymers are formed with different 3-hydroxyalkanoic acids. Petition 870250084836, dated 09 / 19 / 2025, page 19 / 53 13 / 28

[0062] The process according to the invention advantageously comprises a prior biomass preparation step, wherein the latter is treated by washing, drying and grinding operations, to yield a solid biomass (e.g., in powder form) containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

[0063] According to a first embodiment of the invention represented in Figure 1, flow 1 represents the input of one or more inhibitors into the thermolysis reactor. The polymerization inhibitors used in the process according to the invention are chosen from among the inhibitors classically used in existing industrial processes for the production of α-β unsaturated carboxylic acids. The latter comprise phenolic derivatives such as hydroquinone (HQ) and its derivatives such as hydroquinone methyl ether (EMHQ), 2,6-di-tert-butyl-4-methylphenol (BHT) or 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazines and their derivatives; nigrox compounds such as 4-hydroxy-2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO); and amine compounds such as paraphenylenediamine derivatives.

[0064] Stream 2 consists of P3HA extracted from biomass. It feeds the thermolysis reactor via a conduit.

[0065] Stream 1 and stream 2 are carried to the thermolysis reactor by a conduit, a screw conveyor, a conveyor belt or a hopper, a pneumatic conveyor, a vibratory conveyor, an extruder. In addition, they can be coupled to a dosing device.

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

[0067] The mass proportion of inhibitor in the mixture with P3HA or with biomass is at least 0.01% and can reach 90%; preferably Petition 870250084836, dated 09 / 19 / 2025, page 20 / 53 14 / 28 ence, the inhibitor content in said mixture is from 1% to 70% by weight.

[0068] When stream 2 is P3HA extracted from its cell membrane, the thermolysis reactor is a solvolysis reactor used equally for depolymerizing composites or a molten medium polycondensation type reactor. This reactor is equipped with a heating system and agitation by a pump and external recirculation through a heat exchanger or a fine helical double magnetic drive shaft.

[0069] According to one embodiment, the temperature in the thermolysis reactor is between 20°C and 250°C, preferably 150°C to 200°C. This temperature can also be controlled by means of temperature sensors placed in the reactor. Such moderate heating allows the mixture to be liquefied, totally or partially, avoiding the polymerization of the α-β carboxylic acid.

[0070] According to one embodiment, the pressure in the thermolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0071] According to one embodiment, the residence time in the thermolysis reactor is between 0.5 h and 5 h, preferably between 2 h and 4 h.

[0072] Stream 3 at the outlet of the thermolysis reactor is sent, in whole or in part, to a beneficiation unit or recycled upstream of the thermolysis reactor.

[0073] Stream 5 feeds a first capacitor C1 which will cool the gases to a temperature at least 20°C lower than the temperature of the thermolysis reactor and regenerate a liquid stream 12 which is recycled to the thermolysis reactor or which may be purified by crystallization (not shown) before recycling to the thermolysis reactor. The non-condensed gases exiting this condenser C1 by stream 8 are condensed in a condenser C2 at a temperature Petition 870250084836, dated 09 / 19 / 2025, p. 21 / 53 15 / 28 temperature lower by at least 20°C than that of capacitor Cl1. This temperature is adjusted so that the mass content of inhibitor in flux 11 is less than 3%.

[0074] Stream 11 can be gaseous or liquid after condensation (not shown) before entering the separation column (COL) which will allow recovery of unsaturated α-β carboxylic acid with a purity greater than 98.5% at a temperature below 5°C, preferably 10°C below the bubble point of the feed to this separation column.

[0075] Streams 9 and 12 can be recycled, in whole or in part, to the thermolysis reactor or sent to a crystallizer (not shown) to be separated and purified in order to obtain, on the one hand, the heavy impurities and the inhibitor that can be recycled to the thermolysis reactor and, on the other hand, the acrylic acid that can be sent to the feed of the separation column (COL).

[0076] Capacitors C1 and C2 can be powered equally by a solution of at least one inhibitor in solution in the unsaturated α-β carboxylic acid (flows 6 and 7).

[0077] The separation column is equipped with a side bleed and comprises a theoretical number of trays between 10 and 30, preferably between 20 and 25. This single column operates under a reduced pressure generally between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

[0078] The separation column consists of any type of tray and / or random internals and / or structured fittings available for the rectification of mixtures and adapted to the distillation of polymerizable compounds. It may be a classic distillation column, comprising at least one fitting, such as, for example, a random fitting and / or a combination of sections fitted with random and structured fittings, and / or trays. Petition 870250084836, dated 09 / 19 / 2025, page 22 / 53 16 / 28 such as, for example, perforated trays, fixed valve trays, movable valve trays, cap trays, or combinations thereof. Preferably, the column is fitted with perforated trays.

[0079] Column stabilization (flow 17) is generally carried out with the aid of stabilizers well known to a technician in the field, possibly with injection of air or oxygen-depleted air (flow 16).

[0080] The column feed is carried out in the first quarter of the column base, preferably at the level of a tray that runs from trays 1 to 7, preferably from trays 3 to 5.

[0081] Stream 4, rich in light compounds, is distilled at the top of the column and beneficiated by hydrothermal gasification or in a biological treatment plant after condensation.

[0082] Unsaturated α-β carboxylic acid having a purity >90% is withdrawn in liquid or gas phase, preferably in the first third of the top of the separation column, in particular between theoretical trays 1 to 5, trays located below the top of the column. Preferably, polymer-grade unsaturated α-β carboxylic acid is withdrawn in liquid phase (flow 18). This flow 18 can be further purified by a crystallization operation carried out in the crystallizer (CRIS), to achieve an α-β unsaturated carboxylic acid purity > 99.5% and compatible with commercial specifications.

[0083] According to one embodiment, this last operation, which allows obtaining α-β unsaturated carboxylic acid of very high purity, is carried out by fractional crystallization. The latter can be performed in different ways: dynamic crystallization, static crystallization, or suspension crystallization.

[0084] According to one embodiment, crystallization is a falling film, operated in a multitubular exchanger; in practice, each Petition 870250084836, dated 09 / 19 / 2025, page 23 / 53 Tube 17 / 28 is continuously fed by flow 18 at the top, a refrigerant fluid flow. This operation actually comprises 3 stages: first, crystallization at a controlled temperature of around 14°C, for example, for acrylic acid; then, desudation by a progressive temperature increase of the refrigerant fluid to eliminate impurities included in the crystals; and finally, the controlled melting of the α-β unsaturated carboxylic acid (around 14°C for acrylic acid), but preferably below 35-40°C.

[0085] The foot of the separation column (COL) is a stream of α-β unsaturated carboxylic acid comprising the essential heavy impurities and a large proportion of the inhibitor recycled, in whole or in part, to the thermolysis reactor.

[0086] According to one embodiment, the mass ratio between the flow withdrawn at the base and the column feed flow is between 5% and 30%, preferably between 5% and 10%.

[0087] According to one embodiment, the column is equipped with a condenser and a liquid feed at the top (not shown), which assumes a liquid reflux in the column. The reflux ratio, which can be defined as the recycling rate from the top of the column to the separation column (COL) relative to that of the side withdrawal, is between 1 and 3, preferably between 1 and 3, for example, it is equal to 1.2. These conditions allow for the best compromise between the column size / number of separation stages to be used and the energy to be used to ensure effective distillation.

[0088] According to an embodiment of the invention represented in figure 2, flow 1 represents the input of one or more inhibitors into the thermolysis reactor, as described above.

[0089] Stream 2 consists of biomass. It also feeds the pyrolysis reactor, which in this case is a trans mixer. Petition 870250084836, dated 09 / 19 / 2025, page 24 / 53 18 / 28 paddle dryer type carrier.

[0090] Streams 1 and 2 are carried to the thermolysis reactor by a conduit, a screw conveyor, a conveyor belt or a hopper, a pneumatic conveyor, a vibratory conveyor, an extruder. In addition, they may be coupled to a metering device.

[0091] According to a preferred embodiment, at least one of said polymerization inhibitors is hydroquinone methyl ether (HME).

[0092] The mass proportion of inhibitor in the mixture with biomass is less than 1%.

[0093] According to one embodiment, the temperature in the thermolysis reactor is between 20°C and 250°C, preferably 150°C and -200°C, and the pressure in the reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0094] According to one embodiment, the residence time in the reactor is between 0.5 h and 5 h, preferably between 2 h and 4 h.

[0095] Stream 3 at the outlet of the thermolysis reactor is sent, in whole or in part, to a beneficiation unit, by combustion, spreading or gasification.

[0096] According to one embodiment, the residue is mixed with the required water and processed by hydrothermal gasification.

[0097] Stream 5 feeds a first condenser C1, which will cool the gas to a temperature below the temperature of the feed tray in the separation column (COL).

[0098] The liquid stream 11 enters the separation column at a temperature below 5°, preferably 10°C below the bubble point of the column feed.

[0099] Capacitor C1 can also be powered by Petition 870250084836, dated 09 / 19 / 2025, page 25 / 53 19 / 28 a solution of at least one inhibitor in solution in the α-β unsaturated carboxylic acid (stream 6).

[00100] The separation column is equipped with a side bleed and comprises a theoretical number of trays between 10 and 30, preferably between 20 and 25. This single column operates under reduced pressure, generally between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

[00101] The separation column consists of any type of trays and / or random internals and / or structured fittings, available for the rectification of mixtures and adapted to the distillation of polymerizable compounds. Preferably, the column is equipped with perforated trays.

[00102] Column stabilization (flow 17) is generally performed with the aid of stabilizers well known to a technician in the field, possibly with air injection or oxygen-depleted air (flow 16). Side bleed flow can be stabilized similarly (not shown).

[00103] The column feed is carried out in the first quarter of the column base, preferably at the level of a tray that runs from trays 3 to 10, preferably from trays 4 to 8.

[00104] Stream 4, rich in light compounds, is distilled at the top of the column and beneficiated by hydrothermal gasification or in the biological station after condensation.

[00105] Unsaturated α-β carboxylic acid having a purity > 98% withdrawn in liquid or gas phase, preferably in the first quarter of the bottom of the separation column, in particular between theoretical trays 10 to 20, trays located below the top of the column. Preferably, polymer-grade unsaturated α-β carboxylic acid is withdrawn in liquid phase (flow 18). After further cooling, this flow 18 can be further purified earlier by an operation Petition 870250084836, dated 09 / 19 / 2025, page 26 / 53 20 / 28 crystallization in a crystallizer (CRIS) to achieve a purity in α-β unsaturated carboxylic acid >99.5% and compatible with commercial specifications.

[00106] At the base of the separation column (COL) a stream of unsaturated α-β carboxylic acid comprising the essential heavy impurities and a large proportion of the inhibitor is recycled, in whole or in part, to the thermolysis reactor.

[00107] According to one embodiment, the mass ratio between the laterally withdrawn flow and the column feed flow is between 60 and 95%, preferably between 75% and 90%.

[00108] According to one embodiment, the mass ratio between the flow withdrawn at the base and the column feed flow is between 5% and 30%, preferably between 5% and 10%.

[00109] According to a particular embodiment, COL is equipped with a condenser and a liquid feed at the top (not shown), which ensures a liquid reflux in the column. The reflux ratio, which can be defined as the recycling rate from the column head to the separation column (COL) relative to that of side withdrawal, is between 1 and 3, preferably between 1 and 2, for example, it is equal to 1.2.

[00110] The examples below illustrate the present invention without, however, limiting its scope. EXPERIMENTAL PART

[00111] The following abbreviations are used in the tables: AA: acrylic acid ACOH: acetic acid H2O: water PTZ: phenothiazine EMHQ: hydroquinone methyl ether ACETAL: acetaldehyde Petition 870250084836, dated 09 / 19 / 2025, page 27 / 53 21 / 28 PROH: propanoic acid

[00112] Examples 1-4: This laboratory-scale experiment aims to observe the consistency of the residue after a thermolysis operation to determine if it can be handled after exiting the thermolysis reactor.

[00113] Examples 1-4: are performed on biomass containing 60% by weight of P3HP.

[00114] The α-β unsaturated carboxylic acid obtained after thermolysis is acrylic acid (AA).

[00115] The mixing step of the biomass containing P3HP with the inhibitor is carried out by introducing 2 g of this biomass and 0 or 20 mg of EMHQ into a 50 mL bicol flask equipped with a magnetized stir bar. The medium is stirred with the aid of a magnetic stirrer to distribute the inhibitor in the solid.

[00116] At the beginning of the experiment, the system is placed under the desired pressure, then the flask containing the biomass is placed in a heating system that allows the desired thermolysis temperature to be established (oil bath or electric heating flask).

[00117] As soon as the thermolysis reactor reaches more than 170°C, the formation of AA vapors is observed, which condense mainly in the side condenser. After 4 h of heating, the formation of AA vapors in the thermolysis reactor decreases, and then the experiment is stopped. The state of fat content as well as the consistency of the thermolysis residue are visually assessed at the end of the experiment.

[00118] It is observed that the addition of the inhibitor allows a very hard solid to be transformed into a viscous, pasty solid, which could be used in the invention.

[00119] The operating conditions for tests 1-4 are shown in Table 1. Petition 870250084836, dated 09 / 19 / 2025, p. 28 / 53 22 / 28 Table 1 Test Inhibitor Operating pressure (kPa) Thermolysis residue 1 EMHQ 100 Viscous pasty solid 2 EMHQ 55 Viscous pasty solid 3 EMHQ 20 Viscous pasty solid 4 NO 100 Viscous pasty solid

[00120] The results in Table 1 show that the physical state of the residue is dependent on the presence of the inhibitor. The addition of inhibitor allows the residue to become pasty and viscous, whereas it was very hard and sticky without the addition of the inhibitor. The change in consistency of the residue allows for easier extraction when performing continuous thermolysis. Thermogravimetric analysis test

[00121] This test aims to inform us about the operational conditions necessary to carry out the thermolysis of P3HA contained in biomass. To better evaluate the thermolysis rate, this test is performed with P3HP extracted from biomass.

[00122] 10g of pure P3HP were subjected to thermogravimetric analysis. This thermogravimetric analysis is a technique that consists of measuring the mass variation of a sample as a function of time, for a given temperature. To do this, for each temperature condition, 1g of P3HP is placed on the balance of the apparatus under nitrogen scanning and the weight loss over time is then recorded. It is found that the mass loss becomes significant and rapid from 170°C.

[00123] From a thermolysis point of view, the least severe operating conditions would be: a temperature of 180°C for a residence time of 3h, to obtain a cracking rate greater than 95%. Table 2 indicates the temperature conditions and times required to obtain different cracking rates, from 10% to complete cracking. Petition 870250084836, dated 09 / 19 / 2025, p. 29 / 53 23 / 28 Table 2 Time required for: 10% cracking 50% cracking Complete cracking (>95%) 120°C >24h >24h >24h 130°C 14h >24h >24h 140°C 6h 24h >24h 150°C 2h 8h 15h 160°C 1h30 6h 10h 170°C 1h 4h 8h 180°C 45min 2h 3h 190°C 30min 1h15 1h45 200°C <30min 45min 1h 210°C <30min 40min 50min 220°C <30min 35min 40min

[00124] The thermolysis reaction temperature of around 180°C in the process according to the invention is significantly lower than that used in example 1 of document WO 2016 / 039618.

[00125] The tests in examples 5-7 below are carried out in a laboratory setup. A bicol flask equipped with magnetic stirring was used. The side neck of the flask is fitted with a thermometer to monitor the reaction temperature. The top neck of the flask is fitted with a separating bridge leading to a water-cooled side condenser, itself carrying a recipe consisting of a second 50 mL flask. An additional point allows for the setup to be operated at reduced pressure thanks to a diaphragm vacuum pump. EXAMPLE 5 (comparative): Use of a biomass containing 60% P3HP without the addition of an inhibitor, without a catalyst, and in the absence of inert gas.

[00126] 2.02 g of biomass containing 60% P3HP are placed Petition 870250084836, dated 09 / 19 / 2025, page 30 / 53 24 / 28 in a 25 ml bicol flask equipped with magnetic stirring. The flask, fitted with a separating bridge, is placed at 10 kPa pressure using a diaphragm vacuum pump. The flask is heated to 200°C for 4 hours. The generated vapors are condensed using a water-cooled side condenser to obtain 1.06 g of acrylic acid, corresponding to an 87% yield. The solid obtained after cracking adheres to the walls of the bicol flask. It is very difficult to remove from the bicol flask. EXAMPLE 6 (according to the invention): use of a biomass containing 60% P3HP with the addition of 5% 4-methoxyphenol (EMHQ)

[00127] 2.29 g of biomass containing 60% P3HP are placed in a 25 ml bicol flask equipped with magnetic stirring. 0.117 g of EMHQ are added to the flask and mixed with the biomass. The flask, equipped with a separating bridge, is placed at 20 kPa pressure using a diaphragm vacuum pump. The flask is heated to 200°C for 4 h. The generated vapors are condensed using a water-cooled side condenser to obtain 1.27 g of acrylic acid, which corresponds to a 96% yield. The solid obtained after cracking remains compact and detaches easily from the walls of the bicol flask and breaks easily with a spatula.

[00128] The results of example 6 show that, when the process is carried out according to the invention (in the presence of an inhibitor, without a catalyst, without the addition of inert gas), the yield of acrylic acid reaches 95%, higher than that obtained in comparative example 5. Furthermore, the presence of the inhibitor allows for the easy elimination of the residue. Example 7: Processes according to the invention

[00129] Simulations were performed on the case of the thermolysis of P3HA poly(3-hydroxypropionate) (P3HP) giving the α-β unsaturated carboxylic acid of acrylic acid (AA) as the carboxylic acid, using the Aspen software. Petition 870250084836, dated 09 / 19 / 2025, page 31 / 53 25 / 28 Tech V12.1 and the Arkema thermodynamic databases.

[00130] The compounds taken into account to represent the gas phase from thermolysis, without the addition of an inert gas, are listed below. The percentages are expressed as mass percent. Condensation process output following figure 1

[00131] Table 3 shows the flows entering and exiting condensers C1 and C2 when the feed to C1 and flow 5 consists of 30% AA and 70% EMHQ at 200°C and 26.7 kPa. C1 partially condenses the gases at 150°C and C2 at 125°C.

[00132] The use of two stepped condensers allows obtaining an acrylic acid (flow 11) with an inhibitor content of 3%.

[00133] In the case studied, flows 6 and 7 were zero. Table 3 FLOW 5 12 8 9 11 Temperature Pressure °C 200.00 150.00 150.00 125.00 125.00 kPa 27 27 27 27 27 Total mass flow rate kg / h 100.00 79.50 20.50 4.96 15.54 AA flow rate kg / h 30.00 12.99 17.01 1.97 15.04 EMHQ flow rate kg / h 70.00 66.52 3.48 2.98 0.50 Mass fraction AA 0.30 0.16 0.83 0.40 0.97 EMHQ 0.70 0.84 0.17 0.60 0.03 Distillation process following Figure 1 in the absence of an inert gas.

[00134] Table 4 shows the flows entering and exiting the separation column. This comprises 25 theoretical stages. Feeding is done in tray 20, acrylic acid removal is done in tray 17, and light particles are eliminated at the top of the column. In this simulation, flows 16 and 17 were zero.

[00135] The acrylic acid recovery balance for purification is 98%. In fact, only the acrylic acid present in stream 4 will be processed in hydrothermal gasification. Petition 870250084836, dated 09 / 19 / 2025, page 32 / 53 26 / 28 Table 4 Flow Rate 11 15 4 18 Temperature °C 50 110 30 90 Pressure kPa 200.00 20.00 20.00 20.00 Mass Flow Rate Kg / h 100.00 6.00 10.00 84.00 FORMALDEHYDE Kg / h 1.32 0.00 1.31 0.01 ACETAL Kg / h 0.04 0.00 0.03 0.00 ACRO Kg / h 0.00 0.00 0.00 0.00 H2O Kg / h 4.87 0.00 4.56 0.31 ACOH Kg / h 3.15 0.00 2.19 0.95 AA Kg / h 87.42 3.06 1.90 82.46 PROH Kg / h 0.28 0.02 0.00 0.26 EMHQ Kg / h 2.92 2.92 0.00 0.00 Mass fractions FORMOL 0.01 0.00 0.13 0.000 ACETAL 0.00 0.00 0.00 0.000 H2O 0.05 0.00 0.46 0.004 ACOH 0.03 0.00 0.22 0.011 AA 0.87 0.51 0.19 0.982 PROH 0.00 0.00 0.00 0.003 EMHQ 0.03 0.49 0.00 0.000 Condensation process following Table 2 in the absence of an inert gas.

[00136] Table 5 shows the flows entering and leaving capacitor C1 when the C1 feed flux 5 consists of 99% AA and 1% EMHQ at 200°C and 26.7 kPa. C1 partially condenses the gases at 80°C. Condensation is complete at 80°C, i.e., a temperature below the bubble point of the column feed tray. Table 5 Flow 5 11 Temperature Pressure °C kPa 200 27 90 27 Mass flow rate kg / h 100 100 AA kg / h 99 99 EMHQ kg / h 1 1 Mass fractions AA 0.99 0.99 EMHQ 0.01 0.01 Petition 870250084836, dated 09 / 19 / 2025, page 33 / 53 27 / 28 Distillation process following figure 2

[00137] Table 6 shows the flows entering and exiting the separation column. This comprises 25 theoretical stages. Feeding is done in tray 20, acrylic acid removal is done in tray 17, and light particles are eliminated at the top of the column. In this simulation, flows 16 and 17 were zero.

[00138] As shown by the composition of the withdrawal flux 18, the acrylic acid has a purity greater than 98%.

[00139] The acrylic acid recovery balance for purification is 98.3%. In fact, only the acrylic acid present in stream 4 will be processed in hydrothermal gasification. Table 6 Flow Units 11 4 15 18 Temperature °C 50 30 98 90 Pressure kPa 200 20 20 20 Mass flow rate kg / h 100.00 10.00 6.00 84.00 FORMOL kg / h 1.35 1.34 0.00 0.01 ACETAL kg / h 0.04 0.04 0.00 0.00 H2O kg / h 4.97 4.65 0.00 0.31 ACOH kg / h 3.21 2.24 0.00 0.97 AA kg / h 89.15 1.73 4.98 82.45 PROH kg / h 0.29 0.00 0.03 0.26 EMHQ kg / h 0.99 0.00 0.99 0.00 Mass fractions: FORMAL 0.014 0.134 0.000 0.000 ACETAL 0.000 0.004 0.000 0.000 H2O 0.050 0.465 0.000 0.004 ACOH 0.032 0.224 0.000 0.011 AA 0.892 0.173 0.829 0.982 PROH 0.003 0.000 0.005 0.003 EMHQ 0.010 0.000 0.166 0.000 Distillation process as shown in Figure 2: effect of a side-by-side withdrawal in the gas or liquid phase. Petition 870250084836, dated 09 / 19 / 2025, pp. 34 / 53 28 / 28

[00140] Table 7 presents the gas-phase or liquid-phase side removal flows. The column comprises 25 theoretical stages. Feeding is done in tray 20, acrylic acid removal is done in tray 17, and light is removed at the top of the column. In this simulation, flows 16 and 17 were zero; the most favorable configuration for recovering acrylic acid with a purity >98% is the one with liquid-phase side removal. Table 7 Flow Rate Units LIQUID PHASE GAS PHASE Temperature °C 90 91 Pressure kPa 20 20 Mass Flow Rate kg / h 84.00 84.00 FORMALDEHYDE kg / h 0.01 0.44 ACETAL kg / h 0.00 0.01 H2O kg / h 0.31 1.78 ACOH kg / h 0.97 1.58 AA kg / h 82.45 79.93 PROH kg / h 0.26 0.26 EMHQ kg / h 0.00 0.00 Mass fractions: FORMOL 0.000 0.01 ACETAL 0.000 0.00 H2OO 0.004 0.02 ACOH 0.011 0.02 AA 0.982 0.95 PROH 0.003 0.00 EMHQ 0.000 0.00 Petition 870250084836, dated 09 / 19 / 2025, page 35 / 53

Claims

1 / 5 CLAIMS 1. A manufacturing process for an unsaturated α-β carboxylic acid of biological origin, characterized in that said process comprises the following steps: - mixing a biomass containing a poly(3-hydroxyalkanoate) (P3HA), or a solid P3HA, with at least one polymerization inhibitor; - subjecting said biomass / inhibitor or P3HA / inhibitor mixture, without the addition of a catalyst and without the addition of inert gas, to a thermolysis step that leads to obtaining, on the one hand, said unsaturated α-β carboxylic acid in the vapor phase and, on the other hand, a molten, solid or liquid residue;- To condense, in one or more stages, the gases from thermolysis, then feed a distillation column with the condensed thermolysis gases obtained; - To fractionate the thermolysis gases into light products, recycled heavy products from the thermolysis reactor, and unsaturated αβ carboxylic acid with a purity greater than 98%, which can be crystallized to achieve a purity greater than 99.5%; - To treat the residue in solid phase or recycle it at the inlet of the thermolysis reactor.

2. Process according to claim 1, characterized in that obtaining acrylic acid of biological origin comprises the following steps, which may be carried out sequentially or simultaneously: - introducing biomass (in powder form) or P3HP and at least one polymerization inhibitor into a mixer (in solid phase) by means of a conduit or a screw conveyor; - mixing the P3HP or biomass and at least one polymerization inhibitor in a mixer conveyor comprising several screws driven in a sheath or directly in a reactor called a thermolysis reactor; - thermolysis of this mixture at a given temperature and at a controlled pressure in a system adapted to the treatment of molten or pasty residue, to generate a vapor phase and a viscous phase, or even a solid phase; - separating the two phases formed in a gas / liquid separator;- Treat the residue for beneficiation by spreading, combustion, hydrothermal gasification, or recycling upstream of the pyrolysis reactor; - Condense the gaseous phase in stages by adjusting the condensation temperature successively by placing one or more condensers in series and separating the resulting gaseous and liquid phases containing acrylic acid and contaminants, which can be recycled back into the reactor or sent to the purification system; - Treat the condensed phase to obtain acrylic acid using one or more distillation columns, allowing, on the one hand, the separation of acrylic acid from products heavier than the latter and, on the other hand, the obtaining of products lighter than the latter; - Purify the acrylic acid obtained by a liquid / solid separation method, such as crystallization, or by a gas / liquid separation method, such as distillation.

3. Process according to any one of claims 1 to 2, characterized in that the biomass used is previously treated by washing, drying or shredding operations, to lead to a biomass containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA. Petition 870250084836, dated 19 / 09 / 2025, page 37 / 53 3 / 5 4. Process according to any one of claims 1 to 3, characterized in that the poly(3-hydroxyalkanoate) contains the 3-hydroxypropionate motif 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 motif and at least one of the α-β unsaturated carboxylic acids produced is crotonic acid.

7. Process according to any one of claims 1 to 3, characterized in that the poly(3-hydroxycycloanoate) 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 motif 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. A process according to any one of the preceding claims, characterized in that the polymerization inhibitor(s) are compounds selected from phenolic derivatives, phenothiazine derivatives, nitroxide derivatives, or paraphenylenediamine derivatives.

11. Process in accordance with any of the preceding claims, characterized in that at least one of said polymerization inhibitors is hydroquinone methyl ether.

12. Process according to any of the preceding claims, characterized in that the thermolysis reactor is chosen from among: a conveyor, a conveyor mixer, a dryer, a rotating drum and / or a set of heating plates.

13. Process according to any of the preceding claims, characterized in that the thermolysis reactor is a solvolysis reactor, also used to depolymerize composites, or a molten polycondensation type reactor.

14. Process according to any of the preceding claims, characterized in that the thermolysis reaction is carried out at a temperature between 150°C and 200°C.

15. A process according to any one of the preceding claims, characterized in that the thermolysis reaction is carried out for two to four hours.

16. Process according to any of the preceding claims, characterized in that the thermolysis reaction is carried out at a pressure between 15 kPa and 40 kPa.

17. Process according to any one of claims 1 to 3, characterized in that the separation column is equipped with a side withdrawal and comprises a theoretical number of trays between 10 and 30, preferably between 20 and 25.

18. Process according to any one of claims 1 to 3, characterized in that the separation column operates under a reduced pressure, generally between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

19. Process in accordance with any of the claims Petition 870250084836, dated 09 / 19 / 2025, page 39 / 53 5 / 5 tions 1 to 3, characterized by the fact that the removal of the separation column is carried out in liquid phase.

20. Process according to claim 12, characterized in that the mixing of the biomass and the inhibitor and the thermolysis can be carried out consecutively or simultaneously. Petition 870250084836, dated 09 / 19 / 2025, pp. 40 / 53

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