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

Abstract

The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid by thermally decomposing a polymer from biomass containing poly(3-hydroxyalkanoate) or from solid poly(3-hydroxyalkanoate) previously extracted from said biomass in the presence of a polymerization inhibitor, in the absence of a catalyst, to mainly gaseous α,β-unsaturated carboxylic acid, without using an inert gas to promote the evaporation of the acid. More specifically, the present invention describes a step of thermal decomposition of biomass or P3HA, a subsequent purification step to obtain an α,β-unsaturated carboxylic acid, and a recycling step of the intermediate product.

Description

Technical Field

[0001] Technical Field The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid by thermally decomposing a polymer from biomass containing poly(3-hydroxyalkanoate) or from solid poly(3-hydroxyalkanoate) previously extracted from the biomass in the presence of a polymerization inhibitor, in the absence of a catalyst, to mainly gaseous α,β-unsaturated carboxylic acid, without using an inert gas to promote the evaporation of the acid. More specifically, the present invention describes the steps of thermal decomposition of biomass or P3HA, followed by a purification step to obtain α,β-unsaturated carboxylic acid and a recycling step of intermediate products.

Background Art

[0002] Prior Art and Technical Problems α,β-unsaturated carboxylic acids are currently mainly industrially produced from fossil-derived raw materials. For example, acrylic acid can be obtained by the oxidation of propylene, or methacrylic acid can be obtained by the oxidation of isobutylene.

[0003] One possible way to obtain these α,β-unsaturated carboxylic acids is 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

[0004] These poly(3-hydroxyalkanoates) themselves can be obtained in advance not only through the chemical conversion of fossil-derived raw materials, but also through biomass fermentation.

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

[0006] 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-hydroxypropionic acid (P3HP) homopolymers or copolymers within microbial cells. The method includes a step of pyrolysis of washed / dried / ground P3HP-containing biomass in the presence of a catalyst. The acrylic acid is recovered in gaseous form and then condensed, while the catalyst and biomass residue can be recycled back into the process or used for thermal regeneration. However, there is a risk that the residue present in the reactor after pyrolysis may become paste-like and sticky, which could complicate the 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 twin-drum dryer. After the addition of the catalyst, the product is FAST TM The material is thermally decomposed in a reactor at 250°C to 350°C with a residence time of 0.25 to 1 hour, and the resulting vapor is sent to a purification unit using an inert gas such as nitrogen. 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. 6,646,161 or U.S. Patent Application Publication No. 2012 / 0006673 to obtain acrylic acid still containing many impurities. Complete purification is performed using a distillation column as described in U.S. Patent Nos. 7,332,624 and 7,179,875, and crystallization may be required as described in U.S. Patent Nos. 6,482,981 and 7,179,875. The aforementioned documents describe the techniques commonly used to obtain acrylic acid by propylene oxidation.

[0007] U.S. Patent Application Publication No. 2014 / 0018574 describes a method for pyrolysis of P3HA in the presence of a compound containing a catalytic tertiary amine present at a concentration of approximately 0.5% to 4% by weight relative to P3HA. Optionally, one or more inhibitors may be added to P3HA before pyrolysis, preferably at a concentration of 150 ppm to 350 ppm relative to P3HA, in the presence of depleted air (<6% O2) (0107-0108). Furthermore, with respect to the acrylic acid formed during this pyrolysis, no inhibitor (0111) is added during its condensation. Finally, the aforementioned document shows that pyrolysis did not occur at a temperature of 175°C (00143) in the absence of a catalyst.

[0008] When the thermal decomposition of P3HA is carried out in the liquid phase, in the absence of a catalyst or in the presence of an inhibitor, as described in JP2015 / 067567, the reaction is preferably carried out in the presence of an inert gas to evaporate the formed acrylic acid (0031).

[0009] Another solution is to first extract P3HA from the biomass using an organic solvent before subjecting it to thermal decomposition. Example 6 of U.S. Patent Application Publication 2015 / 0376152 describes the production of acrylic acid in which P3HP is extracted from biomass using an organic solvent such as 2-butanone, followed by 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 containing hydroquinone to prevent polymerization of acrylic acid.

[0010] In patent application FR2208914, the applicant company proposes the thermal decomposition of P3HA in the absence of a catalyst and in the presence of a polymerization inhibitor. A key feature is 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, thereby preventing polymer formation in the reactor and in the gas phase in the event of accidental condensation or condensation of acrylic acid vapor at the top of the column.

[0011] In patent application FR2208916, the applicant company describes a method for selectively solubilizing P3HA from biomass using a solvent, separating insoluble organic sediments from the solvent, and performing liquid-phase thermal decomposition in the presence of a polymerization inhibitor.

[0012] International Publication No. 2016 / 039618 describes the thermal decomposition of poly(3-hydroxybutyrate)-containing dry biomass for the production of 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] Currently, it has been discovered that high-purity acrylic acid can be obtained in the absence of a catalyst and without using an inert gas to promote the evaporation of the formed α,β-unsaturated carboxylic acid by combining the thermal decomposition of biomass containing P3HA, or the thermal decomposition of solid P3HA and at least one polymerization inhibitor, with a stepwise thermal decomposition gas condensation system, fractional distillation, and optional crystallization.

[0014] More precisely, the term "in the absence of a catalyst" means that the thermal decomposition of PHA in the presence of at least one polymerization inhibitor occurs in the absence of 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] Therefore, chemical species that produce different types of catalytic activity depending on the properties of the chemical species are excluded: - Homogeneous catalysis: When the catalyst and reagent form only a single (often liquid) phase; - Heterogeneous catalysis: When the catalyst and reagent form multiple phases (generally a solid catalyst for a gaseous or liquid-phase reagent); - Enzyme catalysis: When the catalyst is an enzyme, i.e., a protein.

[0016] The term "in the absence of an inert gas" means that the thermal decomposition of PHA in the presence of at least one polymerization inhibitor is carried out in the absence of the injection of a gas, such as depleted air (<6% O2), which promotes the evaporation of the acid formed and the activation of the inhibitor in the reaction medium.

[0017] Therefore, the present invention proposes to provide a simple and easily implementable solution for obtaining α,β-unsaturated carboxylic acids from biomass containing P3HA or from solid PH3HA by using a pyrolysis reactor combined with an optimized purification process. SUMMARY OF THE INVENTION

[0018] Summary of the Invention The subject of the present invention is a method for producing bio-based α,β-unsaturated carboxylic acids, said method comprising the following steps: - mixing biomass containing poly(3-hydroxyalkanoate) (P3HA) or solid P3HA with at least one polymerization inhibitor in the absence of a catalyst; - subjecting said biomass / inhibitor or P3HA / inhibitor mixture to a pyrolysis step without the addition of an inert gas, to obtain first the α,β-unsaturated carboxylic acid in the vapor phase and second a molten or solid residue; - condensing the gas obtained by pyrolysis in one or more steps and then feeding the obtained pyrolysis gas to a distillation column, - fractionating the pyrolysis gas into an upgraded light product, a heavy product recycled to the pyrolysis reactor, and an α,β-unsaturated carboxylic acid having a purity of more than 98%, which can be crystallized to achieve a purity of more than 99.5%; - treating the solid phase residue and including.

[0019] According to various embodiments, the method comprises, where appropriate, the combination of the following features. The contents described are expressed by weight unless otherwise specified. The ranges of values described include the limit values.

[0020] The term "thermal decomposition" of poly(3-hydroxyalkanoate) (P3HA) means chemical decomposition to α,β-unsaturated carboxylic acids that occurs under the influence of temperature. This term is synonymous with thermal decomposition.

[0021] According to one embodiment, the poly(3-hydroxyalkanoate) used in the method contains one type of 3-hydroxyalkanoate unit, and thus the formed product is composed of a single α,β-unsaturated carboxylic acid.

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

[0023] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate), and the α,β-unsaturated carboxylic acid produced is methacrylic acid.

[0024] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate), and the α,β-unsaturated carboxylic acid produced is crotonic acid.

[0025] According to one embodiment, the poly(3-hydroxyalkanoate) used in the method contains a plurality of different 3-hydroxyalkanoate units, and thus the formed product is 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 (poly-3HB-co-3HV).

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

[0027] According to one embodiment, the poly(3-hydroxyalkanoate) contains a 3-hydroxyisobutyrate unit, and at least one of the α,β-unsaturated carboxylic acids produced is methacrylic acid.

[0028] According to one embodiment, the poly(3-hydroxyalkanoate) contains a 3-hydroxybutyrate unit, and at least one of the α,β-unsaturated carboxylic acids produced is crotonic acid.

[0029] According to one embodiment, the biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or a mixture of two or more of these elements.

[0030] According to one embodiment, the biomass used is pretreated by washing, drying, and crushing operations, resulting in a biomass containing 30% to 90% PHA by weight, with the remainder consisting of cell membranes.

[0031] According to one embodiment, biomass is subjected to a thermal decomposition reaction that occurs in the presence of one or more polymerization inhibitors.

[0032] According to one embodiment, P3HA with a purity exceeding 95% by weight, used in the method according to the present invention, is obtained by extracting P3HA with a solvent, removing the solvent by evaporation, and removing the cell membrane by filtration and centrifugation.

[0033] According to one embodiment, the thermal decomposition reaction occurs in the presence of one or more polymerization inhibitors.

[0034] According to one embodiment, mixing and thermal decomposition are carried out sequentially or simultaneously.

[0035] According to one embodiment, the biomass-containing mixture contains at least 0.01% of one or more polymerization inhibitors and a maximum of 5%, preferably less than 1%, of one or more polymerization inhibitors (by mass).

[0036] According to one embodiment, the mixture containing P3HA contains at least 0.5% of one or more polymerization inhibitors, up to 90% of one or more polymerization inhibitors (by mass), preferably between 20% and 70% of one or more polymerization inhibitors.

[0037] According to one embodiment, the method according to the present invention comprises one or more steps of condensing the vapor of an α,β-unsaturated carboxylic acid (or more types) obtained by a poly(3-hydroxyalkanoate) thermal decomposition reaction.

[0038] According to one embodiment, the obtained condensate can be recycled to a pyrolysis reactor and a separation column.

[0039] According to one embodiment, one or more inhibitors are also injected into the condenser.

[0040] According to one embodiment, no inhibitor is injected into the condenser.

[0041] According to one embodiment, one or more distillation columns can be used to purify α,β-unsaturated carboxylic acids.

[0042] According to one embodiment, the obtained condensate can be subjected to rectification or crystallization treatment before being recycled to a pyrolysis reactor.

[0043] According to one embodiment, the separation column is supplied in the gas phase.

[0044] According to one embodiment, the raw materials at the bottom of the distillation column are recycled to a pyrolysis reactor.

[0045] According to one embodiment, the raw materials at the bottom of the distillation column are subjected to a rectification or crystallization operation before being recycled to a pyrolysis reactor.

[0046] According to one embodiment, the α,β-unsaturated carboxylic acid obtained from the top or side extraction portion has a purity of at least 98% by weight.

[0047] According to one embodiment, this α,β-unsaturated carboxylic acid can also be purified in a subsequent crystallization step.

[0048] According to one embodiment, the purity of the α,β-unsaturated carboxylic acid after crystallization exceeds 99.5% by weight.

[0049] According to one embodiment, the product at the top of the column is sent to a biological purification plant.

[0050] According to one embodiment, these tower top products are upgraded to methane by hydrothermal gasification.

[0051] According to one embodiment, the method according to the present invention includes a step of processing the solid or molten residue at the end of pyrolysis by upgrading it through recycling upstream of the pyrolysis reactor or by external processing such as gasification.

[0052] Other features and advantages of the present invention will be better understood by reading the following detailed description while referring to the attached Figures 1 and 2. [Brief explanation of the drawing]

[0053] [Figure 1] Figure 1 shows a block diagram of the equipment for carrying out the present invention when the method of the present invention is applied to a P3HA / inhibitor mixture. [Figure 2] Figure 1 shows a block diagram of the equipment for carrying out the present invention when the method of the present invention is applied to a biomass / prohibitor mixture. [Modes for carrying out the invention]

[0054] Detailed description of the present invention As an example, the present invention is illustrated by describing a method applicable to poly(3-hydroxypropionate) (P3HP) extracted from cell membranes, or biomass still containing P3HP, that enables obtaining α,β-unsaturated carboxylic acids (in this case, acrylic acid) with a purity exceeding 99.5% by weight.

[0055] This invention is aimed at the industrial-scale production of acrylic acid by the thermal decomposition of poly(3-hydroxypropionate), suppressing the problem of contamination of the thermal decomposition reactor and enabling the production of this acid with a purity of over 98% by weight, and even over 99.5% by weight.

[0056] According to one embodiment, the method for producing bio-based acrylic acid includes the following steps, which can be performed sequentially or simultaneously: - A step of introducing biomass (in powder form) or P3HP and at least one polymerization inhibitor into a mixer (as a solid phase) using a pipe or an endless screw-type conveyor, in the absence of a catalyst. - A step of mixing P3HP or biomass with at least one polymerization inhibitor in a conveyor mixer equipped with multiple endless screws operating within a sheath, or directly in a reactor known as a pyrolysis reactor. - A system suitable for processing molten or paste-like residues, comprising the process of thermally decomposing the mixture at a predetermined temperature and controlled pressure without the injection of an inert gas, thereby generating a vapor phase, a viscous phase, and a solid phase. - The process of separating the two phases formed in a gas / liquid separator. - Processes for treating residues for upgrade by ground spraying, combustion, hydrothermal gasification, or recycling upstream of a pyrolysis reactor. - A process of performing stepwise condensation of the gas phase by controlling the continuous condensation temperature using one or more condensers in series, separating the resulting gas phase containing acrylic acid and contaminants from the liquid phase, which can be returned to the reactor for recycling or sent to a purification system. - A step of obtaining acrylic acid by processing a condensed phase using one or more distillation columns, wherein acrylic acid can be separated from heavier products on the one hand, and lighter products can be produced on the other hand. - A step to purify the obtained acrylic acid by liquid / solid separation methods such as crystallization, or by gas / liquid separation methods such as distillation.

[0057] The present invention is based on using a biomass mixture containing P3HA, or solid P3HA and at least one polymerization inhibitor, by performing a technique of mixing the solids and heat-treating the mixture.

[0058] 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.

[0059] In the method according to the present invention, the first step is to use 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.

[0060] 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.

[0061] According to one embodiment, the biomass used in the method according to the present invention is derived from a process of bacterial fermentation of sugars or lipids.

[0062] Depending on the culture conditions and the type of microorganism used, poly(3-hydroxyalkanoate)(P3HA) homopolymers or copolymers containing different 3-hydroxyalkanoates are formed.

[0063] The method according to the present invention advantageously includes a pre-biomass preparation step of treating biomass by washing, drying and grinding operations to obtain solid biomass (e.g., in powder form) containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

[0064] According to the first embodiment of the present invention shown in Figure 1, flow 1 represents the supply of one or more inhibitors to a pyrolysis reactor. The polymerization inhibitors used in the method of the present invention are selected from inhibitors conventionally used in existing industrial processes for the production of α,β-unsaturated carboxylic acids. These include phenol derivatives, e.g., hydroquinone (HQ) and its derivatives, e.g., hydroquinone methyl ether (HQME), 2,6-di-tert-butyl-4-methylphenol (BHT), or 2,4-dimethyl-6-tert-butylphenol (topanol A); phenothiazines and their derivatives; nitroxide compounds, e.g., 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO); and amino compounds, e.g., para-phenylenediamine derivatives.

[0065] Flow 2 is formed from P3HA pre-extracted from biomass. This is supplied to the pyrolysis reactor via pipes.

[0066] Flows 1 and 2 are supplied to the pyrolysis reactor via pipes, endless screws, conveyor belts or hoppers, air conveyors, vibrating conveyors or extruders. They may also be connected to a weighing device.

[0067] According to a preferred embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

[0068] The mass percentage of the inhibitor in the mixture with P3HA or biomass is at least 0.01% and may be up to 90%; preferably, the inhibitor content in the mixture is 1% to 70%.

[0069] If flow 2 is P3HA extracted from the cell membrane, the pyrolysis reactor is a solvolysis reactor or a melt polycondensation reactor, which is also used to depolymerize the composite material. This reactor is equipped with a heating system and stirring by pumps, and external recirculation via an exchanger or a double-helix belt type magnetic drive shaft.

[0070] According to one embodiment, the temperature inside the pyrolysis reactor is between 20°C and 250°C, preferably between 150°C and 200°C. This temperature can also be controlled by a temperature sensor installed inside the reactor. Such moderate heating allows for the liquefaction of all or part of the mixture while simultaneously preventing the polymerization of α,β-unsaturated carboxylic acids.

[0071] According to one embodiment, the pressure inside the pyrolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0072] According to one embodiment, the residence time in the pyrolysis reactor is between 0.5 hours and 5 hours, preferably between 2 hours and 4 hours.

[0073] All or part of flow 3 exiting the pyrolysis reactor is sent to the upgrade unit or recycled upstream of the pyrolysis reactor.

[0074] Flow 5 is supplied to a first condenser C1, which cools the gas to a temperature at least 20°C below the pyrolysis reactor temperature, producing a liquid flow 12 that can be recycled to the pyrolysis reactor or purified by crystallization (not shown) before being recycled to the pyrolysis reactor. The non-condensable gas discharged from condenser C1 by flow 8 is condensed in condenser C2 at a temperature at least 20°C below the temperature of condenser C1. This temperature is adjusted so that the mass content of the inhibitor in flow 11 is less than 3%.

[0075] The flow 11 may be gaseous or liquid after condensation (not shown) before entering the separation column (COL), thereby enabling the recovery of α,β-unsaturated carboxylic acids with a purity of over 98.5% at a temperature 5°C lower, preferably 10°C lower, than the foaming point of the feed to the separation column.

[0076] Flows 9 and 12 can be recycled in whole or in part to a pyrolysis reactor, or sent to a crystallization vessel (not shown) for separation and purification, thereby obtaining, on the one hand, some heavy impurities and inhibitors that can be recycled to the pyrolysis reactor, and on the other hand, acrylic acid that can be sent to the separation column (COL) feed section.

[0077] Condensers C1 and C2 may also be supplied with a solution of at least one inhibitor dissolved in an α,β-unsaturated carboxylic acid (streams 6 and 7).

[0078] The separation column is equipped with a lateral outlet and has a theoretical number of stages between 10 and 30, preferably between 20 and 25. This single column generally operates under reduced pressure between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

[0079] The separation column can be used for the rectification of mixtures and consists of any type of plate and / or random internal structure and / or structured packing, suitable for the distillation of polymerizable compounds. This can be a conventional distillation column that can include at least one type of packing, e.g., random packing, and / or a combination of sections having random packing and structured packing, and / or plates, e.g., porous plates, fixed valve plates, movable valve plates, bubble plates, or combinations thereof. Preferably, the column is equipped with porous plates.

[0080] The stabilization of the tower (flow 17) is generally carried out using stabilizers well known to those skilled in the art, and optionally by injecting air or oxygen-depleted air (flow 16).

[0081] The tower is supplied with plates in the first quarter of the base of the tower, preferably plates 1 to 7, more preferably plates 3 to 5.

[0082] The light compound-rich stream 4 is distilled at the top of the column and, after condensation, is upgraded by hydrothermal gasification or at a biological treatment plant.

[0083] α,β-unsaturated carboxylic acids with a purity exceeding 98% are withdrawn in liquid or gas phase, preferably between theoretical plates 1-5 located in the first upper third of the separation column, particularly below the top of the column. Preferably, polymer-grade α,β-unsaturated carboxylic acids are withdrawn as liquid phase (flow 18). This flow 18 is further purified by a crystallization operation carried out in a crystallization vessel (CRIS) to achieve a purity of α,β-unsaturated carboxylic acid >99.5% that meets commercial specifications.

[0084] According to one embodiment, this final step to obtain a very high-purity α,β-unsaturated carboxylic acid is carried out by fractional crystallization. This can be carried out in various forms, such as dynamic crystallization, static crystallization, or suspension crystallization.

[0085] According to one embodiment, crystallization is a flow-through membrane process carried out in a multi-tube exchanger; in fact, each tube is continuously supplied with a flow 18, which is a flow of heat transfer fluid, at its top. This operation actually consists of three steps: firstly, crystallization at a controlled temperature of about 14°C in the case of acrylic acid; secondly, dissolution by a stepwise temperature increase of the heat transfer fluid to remove impurities contained in the crystal; and finally, melting by a rapid temperature increase to a temperature above the controlled melting point of the α,β-unsaturated carboxylic acid (about 14°C in the case of acrylic acid), but preferably to less than 35-40°C.

[0086] The feedstock at the bottom of the separation column (COL) is a stream of α,β-unsaturated carboxylic acids containing most of the heavy impurities, and most of the inhibitors are recycled, either all or part, to the pyrolysis reactor.

[0087] In one embodiment, the mass ratio between the lateral draw flow and the tower feed flow is between 60% and 95%, preferably between 75% and 90%.

[0088] In one embodiment, the mass ratio between the bottom withdrawal flow and the tower feed flow is between 5% and 30%, preferably between 5% and 10%.

[0089] According to certain embodiments, the column is equipped with a condenser and an upper liquid feed section (not shown), thereby ensuring reflux of the liquid within the column. The reflux ratio can be defined as the ratio of the recycle flow rate from the top of the column to the separation column (COL) to the side extraction flow rate, and is between 1 and 3, preferably between 1 and 2, for example, equal to 1.2. These conditions make it possible to achieve the best compromise between the size of the column / number of separation stages used and the energy used to ensure efficient distillation.

[0090] According to the second embodiment of the present invention shown in Figure 2, flow 1 represents the supply of one or more inhibitors to the pyrolysis reactor, as described above.

[0091] Flow 2 consists of biomass. It is also supplied to a pyrolysis reactor, which in this case is a paddle dryer type conveyor mixer.

[0092] Flows 1 and 2 are supplied to the pyrolysis reactor via pipes, endless screws, conveyor belts or hoppers, air conveyors, vibrating conveyors or extruders. They may also be connected to a weighing device.

[0093] According to a preferred embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

[0094] The mass percentage of the prohibited agent in the biomass mixture is less than 1%.

[0095] According to one embodiment, the temperature inside the pyrolysis reactor is between 20°C and 250°C, preferably between 150°C and 200°C, and the pressure inside the reactor is between 3kPa and 101kPa, preferably between 15kPa and 40kPa.

[0096] According to one embodiment, the residence time in the reactor is between 0.5 hours and 5 hours, preferably between 2 hours and 4 hours.

[0097] The flow 3, exiting the pyrolysis reactor, is sent, in whole or in part, to equipment for upgrade by combustion, ground spraying, or gasification.

[0098] According to one embodiment, the residue is mixed with the required water and upgraded by hydrothermal gasification.

[0099] Flow 5 is supplied to the first condenser C1, which cools the gas to a temperature below the temperature of the feed plate in the separation column (COL).

[0100] The liquid flow 11 enters the separation column at a temperature 5°C lower, preferably 10°C lower, than the foaming point of the column feed.

[0101] Condenser C1 can also be supplied with a solution (flow 6) of at least one inhibitor dissolved in an α,β-unsaturated carboxylic acid.

[0102] The separation column is equipped with a lateral outlet and has a theoretical number of stages between 10 and 30, preferably between 20 and 25. This single column generally operates under reduced pressure between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

[0103] The separation column can be used for the rectification of mixtures and consists of any type of plate and / or random internal structure and / or structured packing suitable for the distillation of polymerizable compounds. Preferably, the column is equipped with porous plates.

[0104] Stabilization of the tower (flow 17) is generally carried out using stabilizers well known to those skilled in the art, and optionally by injecting air or oxygen-depleted air (flow 16). Side-extracted flows can also be stabilized (not shown).

[0105] The tower is supplied with the first bottom quarter of the tower, preferably plates ranging from 3 to 10, more preferably plates ranging from 4 to 8.

[0106] The light compound-rich stream 4 is distilled at the top of the column and upgraded by hydrothermal gasification or at a biological treatment plant.

[0107] α,β-unsaturated carboxylic acids with a purity exceeding 98% are removed in liquid or gas phase, preferably between theoretical plates 10-20 located in the first bottom quarter of the separation column, particularly below the top of the column. Preferably, polymer-grade α,β-unsaturated carboxylic acids are removed as liquid phase (flow 18). After further cooling, this flow 18 is further purified by a crystallization operation in a crystallization vessel (CRIS) to achieve a purity of α,β-unsaturated carboxylic acid >99.5% that meets commercial specifications.

[0108] This final step, which yields very high-purity α,β-unsaturated carboxylic acids, is carried out by fractional crystallization.

[0109] The feedstock at the bottom of the separation column (COL) is a stream of α,β-unsaturated carboxylic acids containing most of the heavy impurities, and most of the inhibitors are recycled, either all or part, to the pyrolysis reactor.

[0110] In one embodiment, the mass ratio between the lateral draw flow and the tower feed flow is between 60% and 95%, preferably between 75% and 90%.

[0111] In one embodiment, the mass ratio between the bottom withdrawal flow and the tower feed flow is between 5% and 30%, preferably between 5% and 10%.

[0112] According to a particular embodiment, the column COL is equipped with a condenser and an upper liquid supply section (not shown) to ensure reflux of the liquid within the column. The reflux ratio can be defined as the ratio of the recycle flow rate from the top of the column to the separation column (COL) to the lateral extraction flow rate, and is between 1 and 3, preferably between 1 and 2, for example, equal to 1.2.

[0113] The following examples illustrate the present invention, but do not limit its scope. [Examples]

[0114] Experimental items The following abbreviations are used in the table: AA: Acrylic acid ACOH: Acetic acid H2O: Water PTZ: Phenothiazine HQME: Hydroquinone Methyl Ether ACETAL: Acetaldehyde PROH: Propanic acid

[0115] Examples 1-4: The purpose of these laboratory-scale experiments is to observe the viscosity of the residue after the pyrolysis operation and to determine whether this residue can be processed after it leaves the pyrolysis reactor.

[0116] Examples 1-4 were carried out on biomass containing 60% by weight of P3HP. The α,β-unsaturated carboxylic acid obtained after thermal decomposition is acrylic acid (AA).

[0117] The process of mixing biomass containing P3HP with the inhibitor is carried out by introducing 2 g of this biomass and 0 or 20 mg of HQME into a 50 mL two-necked round-bottom flask equipped with a magnetic rod. The medium is stirred using a magnetic stirrer to ensure that the inhibitor is dispersed throughout the solid.

[0118] At the start of the experiment, the system is placed under the desired pressure, and the round-bottom flask containing the biomass is then placed in a heating system (oil bath or electric heating mantle) that can set the desired pyrolysis temperature.

[0119] As soon as the pyrolysis reactor exceeds 170°C, AA vapor is formed and condenses mainly in the side condenser. After 4 hours of heating, the formation of AA vapor in the pyrolysis reactor gradually decreases, and the experiment is stopped. At the end of the experiment, the degree of fouling and the viscosity of the pyrolysis residue are evaluated visually.

[0120] It can be seen that the addition of an inhibitor transforms a very hard solid into a viscous paste-like solid that can be upgraded according to the present invention.

[0121] Table 1 shows the operating conditions for tests 1 to 4. [Table 1]

[0122] The results in Table 1 show that the physical state of the residue depends on the presence of the inhibitor. Adding the inhibitor makes the residue paste-like and viscous, whereas without the inhibitor, the residue is very hard and sticky. This change in the viscosity of the residue facilitates its extraction when thermal decomposition is carried out continuously.

[0123] Thermogravimetric analysis The purpose of this study is to provide information on the operating conditions necessary for the thermal decomposition of P3HA contained in biomass. To better evaluate the degree of thermal decomposition, this study was conducted using P3HP extracted from biomass.

[0124] 10 g of pure P3HP was subjected to thermogravimetric analysis. Thermogravimetric analysis is a technique that measures the change in mass of a sample as a function of time at a given temperature. To do this, 1 g of P3HP was placed on the balance of the instrument while nitrogen was flowing through it for each temperature condition, and the weight loss over time was recorded. It was found that the mass loss becomes significant and rapid above 170°C.

[0125] From a pyrolysis perspective, the least stringent operating conditions for achieving a degree of cracking exceeding 95% are a temperature (T°) of 180°C and a residence time of 3 hours. Table 2 shows the temperature conditions and times required to achieve different degrees of cracking, from 10% to complete cracking. [Table 2]

[0126] The pyrolysis reaction temperature of approximately 180°C in the method according to the present invention is significantly lower than the temperature used in Example 1 of International Publication No. 2016 / 039618.

[0127] The tests in Examples 5–7 below were performed using laboratory equipment. A two-necked round-bottom flask equipped with a magnetic stirrer was used. The side neck of the round-bottom flask was fitted with a thermometer for monitoring the reaction temperature. The top neck of the round-bottom flask was fitted with a separation bridge leading to a water-cooled side condenser, which in turn connected to a receiver consisting of a second 50 ml round-bottom flask. An additional branching line allowed the assembly to be placed under reduced pressure using a diaphragm vacuum pump.

[0128] Example 5 (Comparative): Use of biomass containing 60% P3HP without the addition of an inhibitor, without a catalyst, and in the absence of an inert gas. 2.02 g of biomass containing 60% P3HP is placed in a 25 mL two-neck round-bottom flask equipped with a magnetic stirrer. The round-bottom flask, equipped with a separation bridge, is pressurized to 20 kPa using a diaphragm vacuum pump. The round-bottom flask is heated at 200 °C for 4 hours. The resulting vapor is 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 remains attached to the wall of the two-neck round-bottom flask. It is very difficult to remove from the two-neck round-bottom flask. Solid particles are visible on the neck of the round-bottom flask and on the side condenser.

[0129] Example 6 (according to the present invention): Use of biomass containing 60% P3HP with 5% 4-methoxyphenol (EMHQ) added. 2.19 g of biomass containing 60% P3HP is placed in a 25 mL two-neck round-bottom flask equipped with a magnetic stirrer. 0.117 g of HQME is added to the round-bottom flask and mixed with the biomass. The round-bottom flask, equipped with a separation bridge, is pressurized to 20 kPa using a diaphragm vacuum pump. The round-bottom flask is heated at 200 °C for 4 hours. The resulting vapor is condensed using a water-cooled side condenser to obtain 1.27 g of acrylic acid, corresponding to a yield of 96%. The solid obtained after cracking remains compressed, easily detaches from the wall of the two-neck round-bottom flask, and can be easily crushed with a spatula.

[0130] The results of Example 6 show that when the method according to the present invention is carried out (in the presence of an inhibitor, without a catalyst, and without the addition of an inert gas), the acrylic acid yield reaches 95%, which is higher than the yield obtained in Comparative Example 5. Furthermore, the presence of an inhibitor allows for easy removal of residues.

[0131] Example 7: Method according to the present invention The simulation was performed using Aspen Tech V12.1 software and the Arkema thermodynamic database for the thermal decomposition of P3HA poly(3-hydroxypropionate) (P3HP) to produce acrylic acid (AA) as an α,β-unsaturated carboxylic acid.

[0132] The following is a list of compounds that are thought to represent the gas phase obtained by thermal decomposition without the addition of an inert gas. Percentages are expressed in mass percent.

[0133] Output of the condensation process shown in Figure 1 Table 3 shows the flows entering and leaving condensers C1 and C2 when the supply flow 5 to C1 is at 200°C and 26.7kPa and consists of 30% AA and 70% HQME. C1 partially condenses the gas at 150°C and C2 at 125°C.

[0134] By using a two-stage condenser, acrylic acid with an inhibitor content of 3% (flow 11) can be obtained.

[0135] In the cases studied, flows 6 and 7 were zero. [Table 3]

[0136] The distillation process shown in Figure 1 is performed in the absence of an inert gas. Table 4 shows the flow into and out of the separation column. The column has 25 theoretical plates. The feed is introduced at plate 20, acrylic acid is removed at plate 17, and the light fraction is removed at the top of the column.

[0137] In this simulation, flows 16 and 17 were zero.

[0138] As can be seen from the composition of the extracted stream 18, the purity of the acrylic acid exceeds 98%.

[0139] The recovery rate of acrylic acid in the purification process is 98%. Specifically, only the acrylic acid present in flow 4 will be upgraded during hydrothermal gasification. [Table 4]

[0140] The condensation process shown in Figure 2 is performed in the absence of an inert gas. Table 5 shows the flow entering and leaving condenser C1 when the supply flow 5 to C1 is at 200°C and 26.7kPa and consists of 99% AA and 1% HQME. C1 partially condenses the gas at 80°C. Condensation is completed at 80°C, i.e., a temperature below the foaming point of the column feed plate. [Table 5]

[0141] Distillation process shown in Figure 2 Table 6 shows the flow into and out of the separation column. The column has 25 theoretical plates. The feed is introduced at plate 20, acrylic acid is removed at plate 17, and the light fraction is removed at the top of the column.

[0142] In this simulation, flows 16 and 17 were zero.

[0143] As can be seen from the composition of the extracted stream 18, the purity of the acrylic acid exceeds 98%.

[0144] The recovery rate of acrylic acid in the purification process is 98.3%. Specifically, only the acrylic acid present in flow 4 will be upgraded during hydrothermal gasification. [Table 6]

[0145] Distillation process shown in Figure 2: Influence of lateral extraction in the gas or liquid phase Table 7 shows the flow of lateral extraction in the gas or liquid phase. The column has 25 theoretical plates. The feed is introduced at plate 20, acrylic acid is extracted at plate 17, and the light fraction is removed at the top of the column. In this simulation, flows 16 and 17 were zero. The most preferred configuration for recovering acrylic acid with a purity of over 98% is one with lateral extraction in the liquid phase. [Table 7]

Claims

1. A method for producing bio-based α,β-unsaturated carboxylic acids, comprising the following steps: - A step of mixing biomass or solid P3HA containing poly(3-hydroxyalkanoate) (P3HA) with at least one polymerization inhibitor; - A biomass / inhibitor or P3HA / inhibitor mixture is subjected to a thermal decomposition step without the addition of a catalyst and without the addition of an inert gas, to obtain, firstly, the α,β-unsaturated carboxylic acid in the vapor phase, and secondly, a molten or solid residue; - A process of condensing the gas obtained by pyrolysis in one or more steps, and then supplying the resulting condensed pyrolysis gas to a distillation column; - A process in which pyrolysis gas is fractionated into light products, heavy products recycled to the pyrolysis reactor, and α,β-unsaturated carboxylic acids having a purity of over 98%, and the carboxylic acids can be crystallized to achieve a purity of over 99.5%; - A process for processing solid-phase residue or recycling it to the inlet of a pyrolysis reactor. Methods that include...

2. A method according to claim 1 for producing bio-based acrylic acid, comprising the following steps which can be carried out sequentially or simultaneously: - A step of introducing biomass (in powder form) or P3HP and at least one polymerization inhibitor into a mixer (as a solid phase) using pipes or an endless screw-type conveyor; - A process of mixing P3HP or biomass with at least one polymerization inhibitor in a conveyor mixer equipped with multiple endless screws operating within a sheath, or directly in a reactor known as a pyrolysis reactor; - A system suitable for processing molten or paste-like residues, comprising the process of thermally decomposing the mixture under a predetermined temperature and controlled pressure to generate a vapor phase, a viscous phase, and a solid phase; - A process of separating the two phases formed in a gas / liquid separator; - Processes for treating residues for upgrades through ground spraying, combustion, hydrothermal gasification, or recycling upstream of a pyrolysis reactor; - A process in which the gas phase is condensed stepwise by controlling the continuous condensation temperature using one or more condensers in series, and the resulting gas phase containing acrylic acid and contaminants is separated from the liquid phase, which can be returned to the reactor for recycling or sent to a purification system; - A process for obtaining acrylic acid by processing a condensed phase using one or more distillation columns, wherein acrylic acid can be separated from heavier products on one hand, and lighter products can be produced on the other hand; - A process of purifying the obtained acrylic acid by liquid / solid separation methods such as crystallization, or by gas / liquid separation methods such as distillation. Methods that include...

3. The method according to claim 1 or 2, wherein the biomass to be used is pretreated by washing, drying, or grinding 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) contains a 3-hydroxypropionate unit, and at least one of the α,β-unsaturated carboxylic acids produced 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 α,β-unsaturated carboxylic acid produced 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 α,β-unsaturated carboxylic acids produced 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 α,β-unsaturated carboxylic acid produced is crotonic acid.

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

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

10. The method according to any one of claims 1 to 9, wherein the polymerization inhibitor (multiple types are permitted) is a compound selected from phenol derivatives, phenothiazine derivatives, nitroxide 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 pyrolysis reactor is selected from a conveyor, a conveyor mixer, a dryer, a rotating drum and / or a set of heating plates.

13. The method according to any one of claims 1 to 12, wherein the pyrolysis reactor is a solvolysis reactor or a melt polycondensation reactor that is also used for depolymerizing composite materials.

14. The method according to any one of claims 1 to 13, wherein the thermal decomposition reaction is carried out at a temperature between 150°C and 200°C.

15. The method according to any one of claims 1 to 14, wherein the thermal decomposition reaction is carried out for 2 to 4 hours.

16. The method according to any one of claims 1 to 15, wherein the thermal decomposition reaction is carried out at a pressure between 15 kPa and 40 kPa.

17. The method according to any one of claims 1 to 3, wherein the separation column comprises a lateral extraction section and has a theoretical number of plates between 10 and 30, preferably between 20 and 25.

18. The method according to any one of claims 1 to 3, wherein the separation column operates under reduced pressure, generally between 3 kPa and 30 kPa, preferably between 9 kPa and 20 kPa.

19. The method according to any one of claims 1 to 3, wherein the removal from the separation column is performed in the liquid phase.

20. The method according to claim 12, wherein the mixing and thermal decomposition of biomass and the inhibitor can be carried out continuously or simultaneously.

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