Method for producing bio-based α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) contained in biomass

Abstract

The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate), the method comprising extracting the poly(3-hydroxyalkanoate), and subsequently thermally decomposing the polymer in a solid or molten state in the presence of a polymerization inhibitor and in the absence of a catalyst to produce a bio-based α,β-unsaturated carboxylic acid.

Description

Technical Field

[0001] Technical field The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate), the method comprising extracting poly(3-hydroxyalkanoate) in the presence of a polymerization inhibitor and subsequently thermally decomposing the polymer in a solid or molten state in the absence of a catalyst to produce a bio-based α,β-unsaturated carboxylic acid.

Background Art

[0002] Conventional technologies and technical challenges α,β-unsaturated carboxylic acids are currently mainly industrially produced from fossil-derived raw materials. For example, acrylic acid is obtained by the oxidation of propylene, and methacrylic acid is obtained by the oxidation of isobutylene.

[0003] One method for obtaining these α,β-unsaturated carboxylic acids is to thermally decompose the corresponding poly(3-hydroxyalkanoate) (P3HA) at a temperature of 150°C to 300°C according to the following reaction. [Chemical Formula 1] TIFF2026513836000001.tif31170R1 is H or alkyl, R2 is H or alkyl, and n is a number greater than 30. When R1 = R2 = H: - Poly(3-hydroxyalkanoate) = Poly(3-hydroxypropionate) (P3HP) - α,β-unsaturated carboxylic acid = Propene acid (acrylic acid). When R1 = methyl and R2 = H: - Poly(3-hydroxyalkanoate) = Poly(3-hydroxyisobutyrate) (P3HiB) - α,β-unsaturated carboxylic acid = Isobutene acid (methacrylic acid). When R1 = H and R2 = methyl: - Poly(3-hydroxyalkanoate) = poly(3-hydroxybutyrate) (P3HB) - α,β-unsaturated carboxylic acid = buta-2-enoic acid (crotonic acid). When 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) themselves can be obtained not only through the chemical transformation of fossil-derived raw materials, but also through biomass fermentation.

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

[0006] A potential problem in this process is that the P3HA obtained through fermentation is present within the cells. Therefore, thermal decomposition takes place in the presence of the cell membrane, leading to problems such as reactor contamination and the presence of impurities in the final product.

[0007] Numerous solutions have been proposed to this problem.

[0008] U.S. Patent No. 9,850,192 describes a method for producing acrylic acid from genetically modified microbial biomass that metabolizes glucose or other renewable raw materials to produce poly-3-hydroxypropionate (P3HP) homopolymers or copolymers within microbial cells. The process includes a step of thermally decomposing the washed / dried / ground P3HP-containing biomass in the presence of a catalyst. This method makes it possible to produce acrylic acid while limiting the formation of acrylic acid oligomers, such as acrylic acid dimers, which are naturally formed during acrylic acid production. The acrylic acid is recovered in gaseous form and then condensed, but the catalyst and biomass residue can be reused in the method or thermally regenerated. However, the residue present in the reactor after thermal decomposition may become paste-like and sticky, potentially making it difficult to transition to industrial scale. Example 5 and Figure 7 illustrate a method for carrying out the present invention on an industrial scale. After fermentation, the biomass is washed and dried using an atomizer or double drum dryer. After the catalyst is added, the product is thermally decomposed at 250-350°C in a FAST™ reactor with an inert gas such as nitrogen for a residence time of 0.25-1 hour, and the resulting vapor is sent to a purification unit. The vapor phase consists of 90% organic matter / water and 10% inert gas. The gas is then purified according to the method described in U.S. Patent No. 6646161 or U.S. Patent No. 20120006673 to obtain acrylic acid still containing many impurities. Complete purification is carried out using a distillation column as described in U.S. Patent Nos. 7332624 and 7179875, and crystallization operations may also be required as described in U.S. Patent Nos. 6482981 and 71798750.

[0009] Another solution involves first extracting P3HA from biomass using an organic solvent, followed by thermal decomposition. Example 6 of U.S. Patent No. 20150376152 describes a method for extracting P3HP from biomass using an organic solvent such as 2-butanone, and then producing acrylic acid in the following three steps: evaporating the solvent and condensing it in a receptor; thermally decomposing the P3HP in the absence of an inhibitor to produce acrylic acid vapor; and finally, distilling and condensing the acrylic acid in a receptor to which hydroquinone has been added to prevent polymerization of acrylic acid.

[0010] In those applications, French Patent No. 2208914, the applicant proposes the thermal decomposition of P3HA in the presence of a polymerization inhibitor without the presence of a catalyst, characterized in that the vapor pressure of at least one inhibitor at the thermal decomposition temperature is at least twice the pressure at which the thermal decomposition takes place, which has the effect of preventing polymer formation in the reactor and in the gas phase in the event of accidental condensation or when acrylic acid vapor condenses at the top of the column.

[0011] In those applications, French Patent No. 2208916, it is described that P3HA is selectively solubilized starting from biomass, organic residues insoluble in the solvent are separated, and then the P3HA and solvent medium in the liquid phase are subjected to thermal decomposition in the presence of a polymerization inhibitor.

[0012] International Publication No. 2016 / 039618 describes a method for pyrolysis of dry biomass containing poly(3-hydroxybutyrate) to produce crotonic acid. Example 1 shows that crotonic acid can be obtained from wet or dry biomass in equivalent yields of less than 60% in the absence of a catalyst.

[0013] It has now been discovered that the procedure for producing α,β-unsaturated carboxylic acids can be simplified by pre-extracting P3HA from the cell membrane and then performing thermal decomposition of P3HA without a catalyst, without injecting an inert gas to remove vapor from the reaction area, and without solvent, as a mixture with at least one solid-phase polymerization inhibitor.

[0014] More precisely, "in the absence of a catalyst" is understood to mean that the thermal decomposition of PHA in the presence of at least one polymerization inhibitor occurs in the absence of any other chemical species that would accelerate or redirect the reaction rate. The assumed thermal decomposition is induced solely by operating conditions such as temperature, pressure, and residence time.

[0015] What is actually excluded are chemical species that produce different types of catalytic activity depending on the nature of the species. - Homogeneous catalysis, where the catalyst and reactants form only one phase (often a liquid phase); - Heterogeneous catalysts where the catalyst and reactants form multiple phases (usually solid catalysts for reactants in the gas or liquid phase); - When the catalyst is an enzyme, i.e., a protein, it is called an enzyme catalyst.

[0016] Therefore, the present invention proposes to provide a simple and easily implementable solution for a method of producing α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) obtained by fermentation, which reduces contamination phenomena and the presence of impurities in the final product, while maintaining high reliability and improved productivity. [Overview of the project]

[0017] Summary of the Invention The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, the method comprising the following steps: - A step of extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA, - To obtain solid P3HA having a purity of at least 95% by weight, the process involves evaporating the solvent, - A step of mixing the extracted P3HA with at least one polymerization inhibitor in a solid state, - A step of subjecting the P3HA-preventing agent solid mixture to a thermal decomposition step, as a result of which, first, an α,β-unsaturated carboxylic acid is formed in the vapor phase and, second, a molten residue is formed, the step of subjecting the P3HA-preventing agent mixture to a thermal decomposition step - A step of separating the two formed phases into a gas phase and a solid phase - A step of purifying the gas phase in order to obtain a purified α,β-unsaturated carboxylic acid - A step of treating the solid phase residue

[0018] According to various implementations, the method optionally comprises the following features in combination. The contents shown are expressed in weight unless otherwise specified. The ranges of the values shown include limitations.

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

[0020] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate), and the α,β-unsaturated carboxylic acid produced 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 method comprises a plurality of different 3-hydroxyalkanoate units, and therefore the product formed consists 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-hydroxypropionate-co-3-hydroxyvalerate (poly-3HB-co-3HV).

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

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

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

[0027] According to one embodiment, the biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or a mixture of two or more of these elements.

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

[0029] According to one embodiment, the method according to the present invention comprises a thermal decomposition reaction of poly(3-hydroxyalkanoate), followed by one or more purification steps. The purification steps typically include distillation, liquid / liquid extraction, separation using a membrane evaporator, or crystallization.

[0030] According to one embodiment, the method according to the present invention includes a step of processing the molten residue obtained at the end of the thermal decomposition, for example, a step of upgrading the latter by hydrothermal gasification to obtain methane.

[0031] This invention satisfies the needs expressed in the prior art. It makes it possible to obtain a gas phase rich in α,β-unsaturated carboxylic acids and a polymerization inhibitor, as well as a molten or slightly paste-like residue that can be improved in quality, thereby preventing contamination of the pyrolysis reactor and / or the presence of impurities in the final α,β-unsaturated carboxylic acid product originating from cell membranes.

[0032] This solution has the advantage of being able to perform the thermal decomposition of P3HA in a solid or molten state, reducing the energy and environmental costs of the process.

[0033] The present invention will be described in more detail below. [Modes for carrying out the invention]

[0034] Detailed description of the invention The objective of the present invention is to produce bio-based α,β-unsaturated carboxylic acids on an industrial scale by thermal decomposition of poly(3-hydroxyalkanoate) contained in biomass, while limiting the problem of clogging of the thermal decomposition reactor and / or the presence of impurities in the final product. The term "thermal decomposition" of poly(3-hydroxyalkanoate) (P3HA) refers to the chemical decomposition into α,β-unsaturated carboxylic acids that occurs under the influence of temperature. This term is synonymous with thermal decomposition.

[0035] The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, the method comprising the following steps: - A step of extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA, - To obtain solid P3HA having a purity of at least 95% by weight, the process involves evaporating the solvent, - A step of mixing the extracted P3HA with at least one polymerization inhibitor in a solid state, - A step of subjecting a P3HA-inhibiting agent solid mixture to a thermal decomposition step, wherein, as a result, firstly, the α,β-unsaturated carboxylic acid is generated in the vapor phase, and secondly, a molten residue is generated, - A step of separating the two formed phases into a gas phase and a solid phase, - A step of purifying the gas phase in order to obtain purified α,β-unsaturated carboxylic acid, - A process for processing solid-phase residue.

[0036] According to one embodiment, the method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) includes the following steps: - A step of extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA in a solvent decomposition reactor, - A step to remove the cell membrane by liquid-solid separation, - To obtain solid P3HA having a purity of at least 95% by weight, the process involves evaporating the solvent in the same reactor, - Introducing P3HA and at least one polymerization inhibitor into the pyrolysis reactor, - A step of mixing P3HA and at least one polymerization inhibitor in the reactor, - In order to generate a vapor phase and a viscous phase, the process involves thermally decomposing the stirred mixture in the same reactor at a given temperature and controlled pressure, - A step of separating the two phases formed in a gas-liquid separator in order to obtain the gas phase and the residue, - A step of processing the aforementioned residue, - The process of condensing the gas phase, - A step of obtaining α,β-unsaturated carboxylic acids using one to several distillation columns, and treating the condensed phase in order to, firstly, enable the separation of the α,β-unsaturated carboxylic acids from heavier products, and secondly, enable the acquisition of products lighter than the α,β-unsaturated carboxylic acids.

[0037] According to one embodiment, the solvent decomposition reactor is stirred and heated to a temperature between 20°C and 170°C, preferably 50°C to 140°C.

[0038] According to one embodiment, the cell membrane is removed by filtration or centrifugation.

[0039] According to one embodiment, the solvent is evaporated and removed 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.

[0040] According to one embodiment, the introduction of P3HA and at least one polymerization inhibitor into the pyrolysis reactor is carried out by a pipe or an endless screw-type conveyor.

[0041] Advantageously, the pyrolysis reactor is suitable for processing solids, molten materials, or paste-like mixtures.

[0042] According to one embodiment, the mixing of P3HA and at least one polymerization inhibitor in the pyrolysis reactor is carried out by a plurality of endless screws operating in a barrel, enabling the mixing of P3HA and at least one inhibitor.

[0043] According to one embodiment, the residue is treated by ground spraying, combustion, or modification by hydrothermal gasification.

[0044] According to one embodiment, the condensation of the gas phase is carried out by a system of at least one tubular condenser type condenser at the pressure of the pyrolysis, the pyrolysis is cooled and the resulting liquid phase is collected in a stirred storage tank, and the addition of one or more additional inhibitors is optionally performed.

[0045] According to one embodiment, the product, which is heavier than the α,β-unsaturated carboxylic acid, is recycled upstream of the pyrolysis reactor or mixed with the solid residue resulting from the pyrolysis.

[0046] According to one embodiment, the product, which is lighter than an α,β-unsaturated carboxylic acid, is improved in quality by combustion or hydrothermal gasification.

[0047] According to one embodiment, the obtained α,β-unsaturated carboxylic acid is purified by a fractional crystallization process including several separation steps to obtain high-purity α,β-unsaturated carboxylic acid and a residue that is upgraded as energy.

[0048] According to one embodiment, the method of the present invention makes it possible to produce several bio-based α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) contained in biomass.

[0049] This invention is based on using a mixture of P3HA and at least one polymerization inhibitor by performing a technique of mixing solids and heat-treating the mixture.

[0050] The term "biomass" refers to organic matter derived from plants (including microalgae), animals, bacteria, or fungi that can be used as a source of bio-based raw materials, in contrast to fossil-derived raw materials.

[0051] In the method according to the present invention, the first step uses genetically modified host biomass obtained by genetic engineering. According to one embodiment, the biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or a mixture of two or more of these elements.

[0052] Biomass is obtained by a preliminary step of culturing a recombinant host using renewable raw materials. According to one embodiment, the renewable raw materials are 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.

[0053] According to one embodiment, the biomass used in the method of the present invention is obtained from a process of bacterial fermentation of sugars or lipids.

[0054] Depending on the culture conditions and the type of microorganism used, poly(3-hydroxyalkanoate) (P3HA) homopolymers or copolymers containing different 3-hydroxyanoalkanoate units are formed.

[0055] The biomass used is pre-treated by washing, drying, or grinding to obtain biomass containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

[0056] The step of extracting P3HA from biomass using a solvent includes separating organic waste insoluble in the solvent, such as cell membranes, from the P3HA-solvent mixture by filtration or centrifugation.

[0057] The process of extracting P3HA from biomass using a solvent is carried out at temperatures between 20°C and 130°C.

[0058] According to one embodiment, the process of extracting P3HA from biomass using a solvent is carried out in a batch manner.

[0059] According to a preferred embodiment, the step of extracting P3HA from biomass using a solvent is carried out continuously.

[0060] According to one embodiment, the solvent used to extract P3HA present in biomass under atmospheric pressure is selected from polar solvents having a boiling point higher than the extraction temperature but lower than the thermal decomposition temperature. These solvents may be linear or branched alcohols with 7 or fewer carbon atoms, such as heptanol or n-butanol; linear or branched aldehydes or ketones with 7 or fewer carbon atoms, such as hexanal or butanone; or carboxylic acids having fewer than 4 carbon atoms, such as butyric acid.

[0061] The solvent used in this process must be able to dissolve P3HA at a concentration of 5% or more, preferably more than 20%, of the weight of the solution at the temperature used during the extraction process.

[0062] Next, the solvent is evaporated to obtain solid P3HA having a purity of at least 95% by weight.

[0063] Depending on the embodiment, evaporation can be carried out at a pressure of 20 kPa to 100 kPa and a temperature between 20°C and 150°C.

[0064] Next, the solid P3HA is mixed with at least one polymerization inhibitor selected from inhibitors conventionally used in existing industrial processes for the production of α,β-unsaturated carboxylic acids. These include phenol derivatives such as hydroquinone (HQ) and their derivatives such as hydroquinone methyl ether (MEHQ), 2,6-di-tert-butyl-4-methylphenol (BHT), and 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazines and their derivatives; nitrous oxide compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO); and amino compounds such as paraphenylenediamine derivatives.

[0065] According to a preferred embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (MEHQ).

[0066] According to one embodiment, the weight content of the inhibitor in the mixture with P3HA is between 0.1% and 10%, preferably 0.4% to 5%.

[0067] According to the present invention, the system for supplying P3HA and at least one polymerization inhibitor to a pyrolysis reactor may be a pipe, an endless screw, a conveyor belt or hopper, an air conveyor, a vibrating conveyor or an extruder. Furthermore, it may be coupled with a measuring device.

[0068] Next, a mixture of P3HA and at least one polymerization inhibitor is thermally decomposed in a solid or molten state.

[0069] The step of mixing P3HA with at least one polymerization inhibitor can be carried out in a mixer conveyor equipped with multiple endless screws operating within a barrel, or directly in a pyrolysis reactor.

[0070] According to one embodiment, the mixing step and the pyrolysis step are carried out continuously by performing conveyor mixing and pyrolysis reactions in succession, or by performing these two operations in a pyrolysis reactor.

[0071] Preferably, the pyrolysis reactor carries out the mixing and pyrolysis reactions. The mixture can be heated at a temperature between 100°C and a temperature lower than the self-ignition temperature of the formed monomer. In the case of acrylic acid, this temperature is 438°C at atmospheric pressure (NF T 20037 standard). The heating temperature is preferably between 150°C and 400°C, and particularly between 200°C and 350°C. Heating can be carried out in stages, with the first temperature zone being around 100°C to 200°C, which allows for the liquefaction of all or part of the mixture while avoiding polymerization of acrylic acid.

[0072] According to one embodiment, the pressure inside the pyrolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0073] According to one embodiment, the residence time in the pyrolysis reactor is between 0.05 hours and 1 hour, preferably between 0.15 hours and 0.5 hours.

[0074] According to one embodiment, the apparatus for carrying out this process also includes a reactor suitable for heating for the purpose of thermal decomposition. For example, heating can be carried out by exposing the mixture to microwaves, pulsed electric fields, or preheated inert gases or vapors, or preheated solids such as sand, or by bringing it into contact with a high-temperature surface such as an extruder, screw conveyor, rotating drum, or platen. The high-temperature surface can be heated in various ways, such as by direct electric heating or by heating with a heat transfer fluid (steam, oil, molten salt).

[0075] According to one embodiment, heat is supplied through a heat transfer fluid, particularly a molten salt, which heats a high-temperature surface.

[0076] The pyrolysis reactor according to the present invention may be an extruder or conveyor, a reactor suitable for pyrolysis, a reactor suitable for high-temperature pyrolysis, a fluidized reactor, a reactor suitable for solvent decomposition, or a reactor consisting of a hollow plate heated by a heat transfer fluid circulating within the plate. However, reactors that can further increase the yield of α,β-unsaturated carboxylic acids have been identified, such as a conveyor, an extruder, an extruder conveyor, and / or a set of heating plates.

[0077] According to the present invention, the extruder conveyor is a reactor equipped with one or more endless screws operating within a barrel, and in particular, enables mixing of the components introduced into the barrel. Using an extruder conveyor to carry out this P3HA pyrolysis process is advantageous in terms of the process's environmental, security, and safety. In particular, using an extruder conveyor allows the molten medium to be processed without the need to add solvent to reduce the viscosity of the molten medium. The extruder conveyor has the advantage of enabling efficient heat transfer from the barrel to the P3HA inhibitor medium. It is preferable to replace the extruder with a screw conveyor system over its entire length or in part. Advantageously, the system may include a combination of a conveyor-type device in a first part, followed by an extruder-type device, and a conveyor configured to transport the residue to the outlet. For example, the conveyor can be of the "Archimedean screw" (endless screw) type.

[0078] The pyrolysis system according to the present invention may include an extruder, such as a twin-screw extruder 200, which has an inlet for a solid or pre-molten P3HA inhibitor mixture. A cleextral extruder is a possible twin-screw extruder. A twin-screw extruder consists of two screws, usually arranged in parallel, that rotate in a barrel. Advantageously, the extruder is modular, i.e., the screws and barrel are assembled in series as modules, and the assembly is changeable. In the extruder, an external heating means for regulating the barrel temperature is advantageously configured to, on the one hand, molten the P3HA inhibitor mixture, and on the other hand, to perform the pyrolysis of P3HA.

[0079] According to another embodiment, the pyrolysis system comprises a device consisting of hollow plates heated by a heat transfer fluid (such as pressurized steam, oil, or molten salt). During the process, the material first moves across plates where the temperature rises. The residue then passes over plates at a lower temperature and through the reactor, where heat exchange from the residue to the heat transfer fluid takes place. The heat transfer fluid thus heated can be used to preheat the P3HA-inhibitor mixture supplied to the pyrolysis reactor.

[0080] According to one embodiment, the pyrolysis system is a mixer conveyor type, such as a screw conveyor type device. This device consists of a reactor in which two endless screws move in opposite directions. The mixture is heated through a high-temperature wall using a heat transfer fluid such as steam. The movement of the two screws can mix and homogenize the feed of P3HA and polymerization inhibitor.

[0081] According to one embodiment, the method according to the present invention involves using an extruder to perform thermal decomposition of the P3HA inhibitor mixture at a temperature of about 150 to 400°C.

[0082] In the pyrolysis reactor, the P3HA inhibitor mixture is converted into a gaseous compound containing α,β-unsaturated carboxylic acid by the action of heat.

[0083] According to one embodiment, poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) (P3HP), and the α,β-unsaturated carboxylic acid obtained by the method of the present invention is acrylic acid.

[0084] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutanoate) (P3HiB), and the α,β-unsaturated carboxylic acid obtained by the method of the present invention is methacrylic acid.

[0085] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutanoate) (P3HB), and the α,β-unsaturated carboxylic acid obtained by the method of the present invention is acrylic acid.

[0086] According to one embodiment, the present invention relates to a method for producing a mixture of α,β-unsaturated carboxylic acids containing a plurality of different 3-hydroxyalkanoate units from P3HA contained in biomass.

[0087] The gas containing the α,β-unsaturated carboxylic acid can be sent to a cooling system for condensation. The resulting condensate is collected in a chamber designed for this purpose. The reactor enclosure and chamber are preferably placed under reduced pressure. The condensation system may be equipped with injection of one or more inhibitors. To enable the recovery of the purified α,β-unsaturated carboxylic acid, the system may include purification equipment such as one or more distillation columns or one or more liquid extraction, crystallization, or membrane separation devices.

[0088] Subsequently, the solid residue is improved, for example, through hydrothermal gasification or as fuel.

[0089] According to one embodiment, condensation is carried out using one or more tubular or helical heat exchangers in series.

[0090] According to one embodiment, condensation is carried out by continuous pressure adjustment and separation of the resulting gas phase and liquid phase (containing α,β-unsaturated carboxylic acids and contaminants that can be returned to the reactor for reuse).

[0091] According to the present invention, condensation is carried out by continuous condensation temperature control performed by arranging one or more condensers in series, and by separation of the resulting gas phase and liquid phase, which contain α,β-unsaturated carboxylic acids and contaminants, and these contaminants can be returned to the reactor for reuse or sent to a purification system.

[0092] According to one embodiment, one or more polymerization inhibitors are added to the condenser.

[0093] According to one embodiment, this condensation can be carried out by contacting a gaseous α,β-unsaturated carboxylic acid with a liquid α,β-unsaturated carboxylic acid. This contact operation can be carried out, for example, by spraying a liquid α,β-unsaturated carboxylic acid into a chamber using a shower-type device and collecting the α,β-unsaturated carboxylic acid in a gaseous state.

[0094] According to one embodiment, no inhibitor is added to the condenser.

[0095] According to one embodiment, the residue obtained after the pyrolysis process is upgraded by hydrothermal gasification.

[0096] In this embodiment, hydrothermal gasification is performed at a temperature of 350°C to 450°C and a pressure of 25 MPa.

[0097] The following examples illustrate the present invention, but do not limit its scope. [Examples]

[0098] Experiment Section The examples are carried out on biomass containing 60% by weight of poly(3-hydroxypropionate) (P3HP). The α,β-unsaturated carboxylic acid obtained after thermal decomposition is acrylic acid (AA).

[0099] Biomass containing P3HP is brought into contact with a solvent that solubilizes P3HP, and then the mixture is centrifuged to separate insoluble substances (e.g., cell membranes) from the P3HP solvent mixture. Next, the solvent is evaporated under vacuum to recover the solid P3HP.

[0100] Pyrolysis is performed by placing solid P3HP (2g) and an inhibitor (0 or 20mg of MEHQ or PTZ) in a 50ml two-neck round-bottom flask equipped with a bar magnet. The medium is stirred using a magnetic stirrer to ensure the inhibitor is evenly distributed throughout the solid. This 50ml two-neck round-bottom flask containing the medium is equipped with a thermometer on the side neck for monitoring the temperature of the pyrolysis medium, and a separation bridge on the top neck that connects to a water-cooled side condenser. The condenser is connected to a receiver consisting of a 25ml one-neck round-bottom flask. An air bleed allows the experiment to be performed under partial vacuum conditions.

[0101] At the start of the experiment, the system is placed under the desired pressure, and a round-bottom flask containing the P3HP inhibitor mixture is placed in the heating system (oil bath or electric heating mantle) to establish the desired thermal decomposition temperature. The receptor is cooled in an ice bath.

[0102] As soon as the temperature of the pyrolysis reactor exceeds 170°C, AA vapor is generated and mainly condenses in the side condenser. After 4 hours of heating, the generation of AA vapor in the pyrolysis reactor gradually decreases, and the experiment is stopped. At the end of the experiment, the viscosity of the pyrolysis residue is visually evaluated.

[0103] The results obtained are shown in Table 1. [Table 1] TIFF2026513836000002.tif100170

[0104] The results in Table 1 show that the physical state of the residue, particularly in MEHQ, depends on the presence of the inhibitor. When the inhibitor is added, the residue becomes paste-like and viscous, while when the inhibitor is not added, the residue remains sticky. This change in the viscosity of the residue facilitates its extraction during continuous thermal decomposition.

[0105] The following examples 10-12 are performed in the same laboratory assembly, using P3HP purified from biomass as described above.

[0106] Example 10 (Comparative): Use of pure P3HP without catalysts and inhibitors 2.05 g of purified P3HP is placed in a 25 ml two-neck round-bottom flask equipped with a magnetic stirrer. The round-bottom flask is pressurized to 20 kPa using a diaphragm vacuum pump and heated at 200 °C for 4 hours. The resulting vapor is condensed using a water-cooled side condenser to obtain 1.41 g of acrylic acid, which corresponds to a yield of 68%. The solid obtained after decomposition forms a thin layer that remains attached to the walls of the two-neck round-bottom flask. The formed layer is very difficult to remove from the two-neck round-bottom flask. Solid particles are present in the condensers at the top and sides of the flask.

[0107] In the absence of a catalyst, the recovery rate of acrylic acid is low, at approximately 68%. This low value is consistent with the value described in Example 1 of International Publication No. 2016 / 039618, which states that 57% crotonic acid is produced by the thermal decomposition of PHB. In addition to this low yield, solid particles are present that negatively impact the development of this process.

[0108] Example 11 (according to the present invention): Use of pure P3HP with 1% 4-methoxyphenol (MEHQ) added without catalyst. 2.12 g of purified P3HP is placed in a 25 ml two-necked round-bottom flask equipped with a magnetic stirrer. 0.021 g of MEHQ is added to the round-bottom flask and mixed with the biomass. The round-bottom flask, equipped with a separation bridge, is placed to a pressure of 20 kPa by a diaphragm vacuum pump. The flask is heated at 200 °C for 4 hours. The resulting vapor is condensed using a water-cooled side condenser to obtain 1.99 g of acrylic acid, which corresponds to a yield of 94%.

[0109] After cracking, very little solid material remains in the round-bottom flask, and this solid material can be easily removed by simply scraping it off.

[0110] Example 12 (according to the present invention): Use of pure P3HP with 5% 4-methoxyphenol (MEHQ) added without catalyst. 2.12 g of purified P3HP is placed in a 25 ml two-necked round-bottom flask equipped with a magnetic stirrer. 0.117 g of MEHQ is added to the round-bottom flask and mixed with the biomass. The round-bottom flask, equipped with a separation bridge, is placed to a pressure of 20 kPa by a diaphragm vacuum pump. The flask is heated at 200 °C for 4 hours. The resulting vapor is condensed using a water-cooled side condenser to obtain 1.85 g of acrylic acid, which corresponds to a yield of 87%.

[0111] After cracking, very little solid material remains in the round-bottom flask, and this solid material can be easily removed by simply scraping it off.

[0112] Therefore, the yields obtained in Examples 11 and 12 are much higher than the yield reported in Example 1 of the literature, International Publication No. 2016 / 039618, where the pyrolysis occurs in the absence of a catalyst. The yields increase to 86% and 89%, respectively, only when the pyrolysis is carried out in the presence of a catalyst (Examples 2 and 3 of the above-mentioned literature).

[0113] These examples also demonstrate that, in the presence of an inhibitor, the pyrolysis in the method according to the present invention is carried out at 200°C (290°C with a catalyst in Example 1 of International Publication No. 2016 / 039618), and therefore, even in the absence of a catalyst and under milder thermal conditions, the pyrolysis yield is very high.

Claims

1. A method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, - A step of extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA, - A step of evaporating the solvent to obtain solid P3HA having a purity of at least 95% by weight, - A step of mixing the extracted P3HA with at least one polymerization inhibitor in a solid state, - A step of subjecting a P3HA-inhibiting agent solid mixture to a thermal decomposition step, wherein, as a result, firstly, α,β-unsaturated carboxylic acid is generated in the vapor phase, and secondly, a molten residue is generated, - A process of separating the two formed phases into a gas phase and a solid phase, - A step of purifying the gas phase in order to obtain purified α,β-unsaturated carboxylic acid, - Process for processing solid-phase residues and A method that includes this.

2. The following steps: - A step of extracting poly(3-hydroxyalkanoate) from biomass using a solvent capable of solubilizing P3HA in a solvent decomposition reactor, - A step to remove the cell membrane by liquid-solid separation, - The process involves evaporating the solvent in the same reactor to obtain solid P3HA having a purity of at least 95% by weight, - Introducing P3HA and at least one polymerization inhibitor into the pyrolysis reactor, - A step of mixing P3HA and at least one polymerization inhibitor in the reactor, - A step of thermally decomposing this stirred mixture at a given temperature and controlled pressure in the same reactor or another reactor of the same type to produce a vapor phase and a viscous phase, - A separation step in which two phases formed in a gas-liquid separator are separated, resulting in a gas phase and a residue. - A process for processing the aforementioned residue, - A step of condensing the aforementioned gas phase, - A step to obtain α,β-unsaturated carboxylic acids using one to several distillation columns, and to first enable the separation of α,β-unsaturated carboxylic acids from heavier products, and second enable the acquisition of products lighter than α,β-unsaturated carboxylic acids, by treating the condensed phase. The method according to claim 1, including the method described in claim 1.

3. The method according to claim 1 or 2, wherein the biomass used is pretreated by washing, drying, or grinding in order to obtain biomass containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

4. The method according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) comprises a 3-hydroxypropionate unit, and at least one of the resulting α,β-unsaturated carboxylic acids is acrylic acid.

5. The method according to any one of claims 1 to 3, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the resulting α,β-unsaturated carboxylic acid is acrylic acid.

6. The method according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) contains a 3-hydroxybutyrate unit, and at least one of the resulting α,β-unsaturated carboxylic acids is crotonic acid.

7. The method according to any one of claims 1 to 3, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the resulting α,β-unsaturated carboxylic acid is crotonic acid.

8. The method according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) comprises a 3-hydroxyisobutyrate unit, and at least one of the resulting α,β-unsaturated carboxylic acids is methacrylic acid.

9. The method according to any one of claims 1 to 3, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the resulting α,β-unsaturated carboxylic acid is methacrylic acid.

10. The method according to any one of claims 1 to 9, wherein the polymerization inhibitor is a compound selected from phenol derivatives, phenothiazine derivatives, nitric oxide derivatives, or paraphenylenediamine derivatives.

11. The method according to any one of claims 1 to 10, wherein at least one of the polymerization inhibitors is hydroquinone methyl ether.

12. The method according to any one of claims 1 to 11, wherein the solvent used to extract P3HA present in biomass is selected from polar solvents having a boiling point higher than the extraction temperature but lower than the thermal decomposition temperature.

13. The method according to any one of claims 1 to 12, wherein the pyrolysis reactor is selected from a set of conveyors, mixer conveyors, extruders, extruder conveyors and / or heating plates.

14. The method according to claim 13, wherein the pyrolysis reactor is an extruder conveyor having one or more endless screws, each operating within a barrel.

15. The method according to claim 13, wherein the pyrolysis reactor is a twin-screw extruder.

16. The method according to claim 13, wherein the pyrolysis reactor is an apparatus comprising a hollow plate heated by a heat transfer fluid circuit.

17. The method according to claim 13, wherein the pyrolysis reactor is a screw conveyor.

18. The method according to any one of claims 1 to 17, wherein the thermal decomposition is carried out at a temperature between 150°C and 400°C with a residence time between 0.05 hours and 1 hour.

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