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

Abstract

The present invention relates to a method for producing biobased α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoates) (P3HA) contained in biomass by extracting the P3HA with a solvent, followed by separation of the insoluble organic waste, and then pyrolyzing the P3HA / solvent mixture in the presence of a solvent. The solvent is selected to provide good solubility for the P3HA and not boil under the pyrolysis conditions.

Description

[Technical Field]

[0001] The present invention relates to a method for producing bio-based α,β-unsaturated carboxylic acids by extracting poly(3-hydroxyalkanoates) from biomass with a solvent, followed by pyrolysis of the polymer in the presence of the solvent.

[0002] Prior art and issues α,β-Unsaturated carboxylic acids are nowadays produced industrially mainly from raw materials of fossil origin: for example, acrylic acid can be obtained by oxidation of propylene, or methacrylic acid can be obtained by oxidation of isobutylene.

[0003] One method to obtain these α,β-unsaturated carboxylic acids is by pyrolysis of the corresponding poly(3-hydroxyalkanoates) (P3HA) at temperatures between 150 and 300°C according to the following reaction: TIFF2025527926000001.tif28170R1=H or alkyl and R2=H or alkyl; n is a number greater than 30; If R1=R2=H, · Poly(3-hydroxyalkanoate) = poly(3-hydroxypropionate) (P3HP); ·α,β-Unsaturated carboxylic acid = propenoic acid (acrylic acid). If R1=methyl and R2=H, then · Poly(3-hydroxyalkanoate) = Poly(3-hydroxyisobutyrate) (P3HiB); ·α,β-unsaturated carboxylic acid = isobutenoic acid (methacrylic acid). If R1=H and R2=methyl, then · Poly(3-hydroxyalkanoate) = Poly(3-hydroxybutyrate) (P3HB); ·α,β-Unsaturated carboxylic acid = but-2-enoic acid (crotonic acid). If R1=H and R2=ethyl, then · Poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV); ·α,β-Unsaturated carboxylic acid = Pent-2-enoic acid.

[0004] These poly(3-hydroxyalkanoates) themselves have previously been obtained by chemical conversion of fossil-derived raw materials and by fermentation of biomass.

[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 biobased feedstocks, which are derived from renewable organic matter (biomass) of biological origin (microorganisms, plants, or animals).

[0006] A potential problem with such a process is that the P3HA obtained by fermentation is intracellular, so pyrolysis takes place in the presence of cell membranes, which can lead to problems with reactor clogging or impurities in the final product, or requires a preliminary P3HA extraction step, which can be complex and expensive.

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

[0008] U.S. Patent No. 9,850,192 (US 9,850,192) describes a process for producing acrylic acid from genetically modified microbial biomass that metabolizes glucose or other renewable feedstocks, producing a homopolymer or copolymer of poly-3-hydroxypropionate (P3HP) within the microbial cells. The process involves pyrolyzing washed, dried, and ground P3HP-containing biomass in the presence of a catalyst. While this process can effectively produce acrylic acid, there is a risk that the residue remaining in the reactor after pyrolysis will be pasty and sticky, which can complicate the transition to an industrial scale.

[0009] Another solution is to first extract P3HA from the biomass using an organic solvent before subjecting it to pyrolysis. U.S. Patent Application Publication No. 20150376152 (US 20150376152) describes in Example 6 the use of an organic solvent such as 2-butanone to extract P3HP from biomass. The solvent is then removed by distillation before pyrolyzing the P3HP to acrylic acid.

[0010] The inventors have surprisingly discovered that it is possible to simplify the procedure for extraction from biomass and subsequent pyrolysis of P3HA without the additional step of separating the solvent used to extract P3HA.

[0011] The present invention therefore proposes to provide a simple and easily implementable solution for reducing clogging phenomena and the presence of impurities in the final product, thereby maintaining high reliability and improved productivity in processes for producing α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoates) obtained by fermentation.

[0012] Summary of the Invention The proposed technical solution is to use an organic solvent to extract P3HA from biomass, in which P3HA is highly soluble, but whose boiling point is high enough that a pyrolysis step can be carried out directly on this P3HA / solvent mixture without first removing the extraction solvent.

[0013] According to the present invention, there is provided a method for producing a bio-based α,β-unsaturated carboxylic acid, the method comprising the steps of: mixing a biomass containing poly(3-hydroxyalkanoate) with a solvent capable of solubilizing P3HA; separating the solvent-insoluble organic waste, including cell membranes, from the P3HA / solvent mixture; subjecting said PHA / solvent mixture to a pyrolysis step to provide firstly said α,β-unsaturated carboxylic acid and secondly said solvent. Includes:

[0014] According to various embodiments, the method includes the following features in combination, where appropriate: Descriptions are by weight unless otherwise stated, and stated ranges of values ​​include the extreme values.

[0015] According to one embodiment, the poly(3-hydroxyalkanoate) used in the present method contains one type of 3-hydroxyalkanoate unit, so that the product formed is composed of one α,β-unsaturated carboxylic acid.

[0016] According to one embodiment, the poly(3-hydroxyalkanoate) comprises 3-hydroxypropionic acid units and at least one of the α,β-unsaturated carboxylic acids produced is acrylic acid.

[0017] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α,β-unsaturated carboxylic acid produced is acrylic acid.

[0018] According to one embodiment, the poly(3-hydroxyalkanoate) comprises 3-hydroxybutyrate units and at least one of the α,β-unsaturated carboxylic acids produced is crotonic acid.

[0019] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α,β-unsaturated carboxylic acid produced is crotonic acid.

[0020] According to one embodiment, the poly(3-hydroxyalkanoate) comprises 3-hydroxyisobutyrate units and at least one of the α,β-unsaturated carboxylic acids produced is methacrylic 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) used in the present method comprises a plurality of different 3-hydroxyalkanoate units, such that the resulting 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-3-hydroxybutyrate-co-3-hydroxyvalerate (poly-3-HB-co-3HV).

[0023] In one embodiment, the biomass host is a bacterium, yeast, fungus, algae, cyanobacteria, or a mixture of two or more of these elements.

[0024] According to one embodiment, the biomass used is pretreated by washing, drying and grinding operations to result in a biomass containing at least 50% by weight of P3HA.

[0025] According to one embodiment, the step of extracting P3HA from biomass with a solvent includes separating organic waste that is insoluble in the solvent, such as cell membranes, from the P3HA / solvent mixture, which is accomplished by filtration or centrifugation.

[0026] According to one embodiment, the step of extracting P3HA from biomass with a solvent occurs at a temperature of 20-130°C.

[0027] According to one embodiment, the step of extracting P3HA from biomass with a solvent occurs batchwise.

[0028] According to one embodiment, the step of extracting P3HA from the biomass with a solvent occurs continuously.

[0029] According to one embodiment, the thermal decomposition reaction of P3HA in solution in a solvent occurs at a temperature of 130-300° C. and a pressure of 1-101 kPa (atmospheric pressure).

[0030] According to one embodiment, the solvent used to extract the P3HA present in the biomass has a boiling point such that it does not boil under the temperature and pressure conditions of the pyrolysis reaction.

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

[0032] The polymerization inhibitor used in the method according to the present invention is selected from inhibitors conventionally used in existing industrial processes for producing α,β-unsaturated carboxylic acids. Such inhibitors include phenol derivatives, such as hydroquinone (HQ) and its derivatives, such as hydroquinone methyl ether (HQME), 2,6-di-tert-butyl-4-methylphenol (BHT), or 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazine and its derivatives; nitroxide compounds, such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO); and amino compounds, such as paraphenylenediamine derivatives.

[0033] According to one embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

[0034] According to one embodiment, the pyrolysis reaction of poly(3-hydroxyalkanoates) occurs batchwise.

[0035] According to one embodiment, the pyrolysis reaction of poly(3-hydroxyalkanoate) occurs continuously.

[0036] According to one embodiment, the method of the present invention comprises a step of condensing the vapors of one or more α,β-unsaturated carboxylic acids obtained by the pyrolysis of poly(3-hydroxyalkanoates), followed by one or more purification steps, which typically involve distillation, liquid-solid extraction, separation using a thin-film evaporator, or recrystallization.

[0037] According to one embodiment, the method according to the invention comprises, at the end of the pyrolysis step, a step of recycling the solvent used to extract P3HA from the biomass, which is advantageous if the solvent can be recycled to the extraction step without the need for distillation.

[0038] The present invention fulfills the needs expressed in the prior art by eliminating the step of separating the solvent used for the extraction of P3HA, thereby avoiding the risk of clogging the pyrolysis reactor and / or the risk of the end product α,β-unsaturated carboxylic acid containing impurities originating from cell membranes.

[0039] This solution has two advantages: it eliminates the need for energy-intensive solvent evaporation, and the pyrolysis of P3HA is carried out in solution rather than in bulk, reducing the risk of clogging the pyrolysis reactor.

[0040] The invention is described in more detail below.

[0041] Detailed Description of the Invention The object of the present invention is to produce bio-based α,β-unsaturated carboxylic acids on an industrial scale by pyrolysis of poly(3-hydroxyalkanoates) contained in biomass, while limiting problems due to clogging of the pyrolysis reactor and / or the presence of impurities in the final product.

[0042] It is proposed according to the invention to provide a method which makes it possible to reduce or eliminate this risk of clogging.

[0043] The present invention is based on the use of organic solvents to extract P3HA from biomass, solvents in which P3HA is highly soluble and which have a boiling point high enough that a pyrolysis step can be carried out directly on this P3HA / solvent mixture without first removing the extraction solvent.

[0044] "Biomass" means organic matter derived from plants (including microalgae), animals, bacteria, or fungi that can be used as a source of bio-based feedstock, as opposed to fossil-derived feedstock.

[0045] In the method according to the invention, in the first step, a genetically modified host biomass derived from genetic engineering is used. According to one embodiment, the biomass host is a bacterium, yeast, fungus, algae, cyanobacteria, or a mixture of two or more of these elements.

[0046] The biomass is obtained by a previous step of culturing the recombinant host on renewable feedstocks, which according to one embodiment are selected from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, ethanol, methanol, glycerol, fatty acids, vegetable oils and biomass-derived syngas, or combinations thereof.

[0047] According to one embodiment, the biomass used in the method according to the invention comes from a process of bacterial fermentation of sugars or lipids.

[0048] Depending on the culture conditions and the type of microorganism used, homopolymers of poly(3-hydroxyalkanoate) (P3HA) or copolymers of poly(3-hydroxyalkanoate) (P3HA) with 3-hydroxyalkanoic acids other than poly(3-hydroxyalkanoate) (P3HA) are formed.

[0049] According to one embodiment, the biomass used is pretreated by washing, drying and grinding operations to result in a biomass containing at least 50% by weight of P3HA.

[0050] According to one embodiment, the solvent used to extract the P3HA present in the biomass is selected from polar organic solvents with a boiling point high enough that the solvent does not boil during the pyrolysis process. Examples of such solvents are glycol diethers (glymes) such as tetraglyme, sulfur-containing sulfoxide or sulfone solvents such as sulfolane or dimethyl sulfone, carbonate solvents such as propylene carbonate, or phenol derivatives such as para-methoxyphenol (also called hydroquinone methyl ether or HQME).

[0051] According to one embodiment, the extraction of the P3HA present in the biomass occurs at a temperature between 20 and 130°C.

[0052] According to one embodiment, the solvent used in the method must be capable of solubilizing P3HA at a content of more than 5% by weight in solution, preferably more than 20% by weight, at the temperature used during the extraction step.

[0053] According to one embodiment, extraction is followed by a step of separating the P3HA / solvent mixture from organic waste insoluble in the solvent, such as cell membranes, possible methods being filtration or centrifugation.

[0054] According to one embodiment of the present invention, the steps of extracting P3HA from biomass with a solvent and separating the P3HA / solvent mixture from the solvent-insoluble organic waste may be carried out batchwise.

[0055] According to one embodiment, the steps of extracting P3HA from biomass with a solvent and separating the P3HA / solvent mixture from organic waste that is insoluble in the solvent may be performed continuously.

[0056] The term "pyrolysis" of poly(3-hydroxyalkanoates) (P3HA) refers to the chemical decomposition into α,β-unsaturated carboxylic acids that occurs under the influence of temperature. This term is synonymous with high-temperature pyrolysis.

[0057] In the method of the present invention, the thermal decomposition reaction of the poly(3-hydroxyalkanoate) / solvent mixture occurs at a temperature of 130 to 300°C, preferably 170 to 230°C, and a pressure of 1 to 101 kPa (atmospheric pressure).

[0058] According to one embodiment of the present invention, the step of pyrolyzing the P3HA / solvent mixture may be carried out batchwise.

[0059] According to one embodiment of the present invention, the step of pyrolyzing the P3HA / solvent mixture may be carried out continuously.

[0060] The solvent recovered at the end of pyrolysis is advantageously recycled to the extraction step.

[0061] According to one embodiment of the invention, the solvent used in the process has a boiling point above 230° C. at atmospheric pressure.

[0062] According to one embodiment, the pyrolysis of poly(3-hydroxyalkanoate) occurs in the absence of a catalyst. The use of a catalyst can accelerate the pyrolysis rate and / or lower the pyrolysis temperature. However, the use of a catalyst makes the process more complicated and more difficult to implement on an industrial scale.

[0063] According to one embodiment, the reaction medium in the pyrolysis reactor comprises at least one polymerization inhibitor, in particular in a proportion of 50 ppm to 5% by weight, in particular 0.01% to 3% by weight, relative to the weight of poly(3-hydroxyalkanoate).

[0064] The polymerization inhibitor is selected from inhibitors conventionally used in existing industrial processes for producing α,β-unsaturated carboxylic acids, including phenol derivatives such as hydroquinone (HQ) and its derivatives, such as hydroquinone methyl ether (HQME), 2,6-di-tert-butyl-4-methylphenol (BHT), or 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazine and its derivatives; nitroxide 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 one embodiment, the polymerization inhibitor is hydroquinone methyl ether (HQME).

[0066] According to a specific embodiment, the solvent used to extract the P3HA present in the biomass is hydroquinone methyl ether (HQME), used in molten form. After separating the P3HA / HQME mixture from the insoluble organic waste, the P3HA in solution in the molten HQME is pyrolyzed under conditions where the HQME is partially volatile but not boiling, without the addition of additional HQME. Thus, the HQME simultaneously functions not only as an extraction solvent and pyrolysis solvent, but also as a partially volatile polymerization inhibitor.

[0067] According to one embodiment, the temperature and pressure conditions in the pyrolysis reactor are selected so that the α,β-unsaturated carboxylic acid or acids formed are in vapor form.

[0068] According to one embodiment, the present invention relates to a method for producing bio-based acrylic acid from P3HP contained in biomass.

[0069] According to one embodiment, the present invention relates to a method for producing bio-based methacrylic acid from P3HiB contained in biomass.

[0070] According to one embodiment, the present invention relates to a method for producing bio-based crotonic acid from P3HB contained in biomass.

[0071] According to one embodiment, the present invention relates to a method for producing a mixture of α,β-unsaturated carboxylic acids from P3HA (containing a plurality of different 3-hydroxyalkanoate units) contained in biomass.

[0072] According to one embodiment, the method according to the invention comprises a step of condensing the vapors of one or more α,β-unsaturated carboxylic acids obtained by the pyrolysis of poly(3-hydroxyalkanoates), followed by one or more purification steps, which generally involve distillation, liquid-liquid extraction, separation using a thin-film evaporator, or recrystallization.

[0073] According to a preferred embodiment, the P3HA contained in the biomass is P3HP, extraction is carried out using a sulfone-based solvent (e.g., sulfolane or dimethyl sulfone), and the step of pyrolyzing the P3HP / sulfone solvent mixture is carried out in the presence of hydroquinone methyl ether.

[0074] The following examples are intended to illustrate the present invention without limiting its scope.

[0075] Experimental Department This example is carried out on biomass containing 60% by weight of P3HP. The α,β-unsaturated carboxylic acid obtained after pyrolysis is acrylic acid (AA).

[0076] The P3HP extraction process is carried out by placing 2 g of this biomass and 20 g of solvent in a glass test tube equipped with a magnetic stir bar. The medium is placed in an oil bath at 100°C and stirred for 2 hours using the magnetic stirrer. The insoluble organic waste is then separated from the P3HP / solvent mixture by centrifugation.

[0077] The pyrolysis of P3HP in solution in a solvent is carried out by placing the medium obtained after the extraction and separation of the organic waste in a 50 mL two-neck flask. The addition of an HQME inhibitor can be performed. The side neck of the flask is equipped with a thermometer to monitor the temperature of the pyrolysis medium, and the upper neck of the flask is equipped with a separating bridge that leads to a water-cooled side condenser. The condenser is connected to a receiver consisting of a 25 mL one-neck flask cooled in an ice bath. An air bleed allows the experiment to be carried out under partial vacuum.

[0078] Pyrolysis of biomass in solvent medium without extraction and prior separation of organic waste

[0079] Experiment 1 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) and 20 g of sulfolane are introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.1 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is barely processable (a liquid filled with sticky solids).

[0080] Experiment 2 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) and 20 g of tetraglyme are introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200 °C and 20 kPa for 4 hours. 1.1 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is barely processable (a liquid filled with sticky solids).

[0081] Experiment 3 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) and 20 g of HQME are introduced directly into the pyrolysis assembly. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 0.9 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is barely processable (a liquid filled with sticky solids).

[0082] Experiment 4 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) and 20 g of dimethyl sulfone are introduced directly into the pyrolysis assembly. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.0 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is barely processable (a liquid filled with sticky solids).

[0083] Experiment 5 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) and 20 g of propylene carbonate are introduced directly into the pyrolysis assembly. The pyrolysis reaction is carried out at 200°C and 70 kPa for 4 hours. 0.8 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is barely processable (a liquid filled with sticky solids).

[0084] Pre-extraction of biomass with methyl isobutyl ketone (MIBK) followed by pyrolysis and separation of organic waste

[0085] Experiment 6 2 g of biomass containing 60% P3HP (ie, 1.2 g of P3HP) is extracted with 20 g of MIBK at 100° C. for 2 hours.

[0086] The insoluble organic waste was separated by centrifugation and weighed 1.2 g, so that a maximum of 0.8 g of P3HP was extracted into MIBK, i.e., two-thirds of the P3HP contained in the biomass was extracted.

[0087] The homogeneous P3HP / MIBK mixture is introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 20.3 g of a homogeneous organic medium containing 3% (i.e., 0.6 g) of AA dissolved in MIBK is recovered overhead. The residue in the pyrolysis reactor is a sticky solid.

[0088] Pre-extraction of biomass with solvent followed by pyrolysis according to the present invention (a good solvent for P3HP that does not boil under pyrolysis conditions)

[0089] Experiment 7 2 g of biomass containing 60% P3HP (ie, 1.2 g of P3HP) is extracted with 20 g of sulfolane at 100° C. for 2 hours.

[0090] The insoluble organic waste was separated by centrifugation and weighed 0.8 g. Thus, a maximum of 1.2 g of P3HP was extracted into sulfolane, i.e., all of the P3HP contained in the biomass could be extracted.

[0091] The homogeneous P3HP / sulfolane mixture is introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.1 g of AA with a purity of over 90% is recovered in the upper receiver. The residue in the pyrolysis reactor is a clear liquid consisting essentially of sulfolane, which can be recycled to the extraction process.

[0092] Experiment 8 2 g of biomass containing 60% P3HP (ie 1.2 g of P3HP) is extracted with 20 g of tetraglyme at 100° C. for 2 hours.

[0093] The insoluble organic waste was separated by centrifugation and weighed 0.8 g. Thus, a maximum of 1.2 g of P3HP was extracted into tetraglyme, i.e., all of the P3HP contained in the biomass could be extracted.

[0094] The homogeneous P3HP / tetraglyme mixture is introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.1 g of AA with a purity of over 90% is recovered in the upper receiver. The residue in the pyrolysis reactor is a clear liquid consisting essentially of tetraglyme, which can be recycled to the extraction process.

[0095] Experiment 9 2 g of biomass containing 60% P3HP (i.e., 1.2 g of P3HP) is extracted with 20 g of HQME at 100° C. for 2 hours.

[0096] The insoluble organic waste was separated by centrifugation and weighed 0.8 g, so a maximum of 1.2 g of P3HP was extracted into HQME, i.e., all of the P3HP contained in the biomass could be extracted.

[0097] The homogeneous P3HP / EMHQ mixture is introduced directly into the pyrolysis assembly. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 0.9 g of AA with a purity of over 90% is recovered in the upper receiver. The residue in the pyrolysis reactor is a clear liquid consisting essentially of HQME, which can be recycled to the extraction process.

[0098] Experiment 10 2 g of biomass containing 60% P3HP (ie, 1.2 g of P3HP) is extracted with 20 g of dimethyl sulfone at 115° C. for 2 hours.

[0099] The insoluble organic waste was separated by centrifugation and weighed 0.8 g. Therefore, a maximum of 1.2 g of P3HP was extracted into dimethyl sulfone, i.e., all of the P3HP contained in the biomass could be extracted.

[0100] The homogeneous P3HP / dimethyl sulfone mixture is introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.1 g of AA with a purity of over 90% is recovered in the upper receiver. The residue in the pyrolysis reactor is a clear liquid consisting essentially of dimethyl sulfone, which can be recycled to the extraction process.

[0101] Experiment 11 2 g of biomass containing 60% P3HP (ie, 1.2 g of P3HP) is extracted with 20 g of propylene carbonate at 100° C. for 2 hours.

[0102] The insoluble organic waste was separated by centrifugation and weighed 0.8 g. Therefore, a maximum of 1.2 g of P3HP was extracted into propylene carbonate, i.e., all of the P3HP contained in the biomass could be extracted.

[0103] The homogeneous P3HP / propylene carbonate mixture is introduced directly into the pyrolysis assembly. 0.02 g of HQME is added as a polymerization inhibitor. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 1.0 g of AA with a purity of over 90% is collected in the upper receiver. The residue in the pyrolysis reactor is a clear liquid consisting essentially of propylene carbonate, which can be recycled to the extraction process.

Claims

1. A method for producing α,β-unsaturated carboxylic acids from biomass containing poly(3-hydroxyalkanoate) (P3HA), comprising the following steps: - A step of extracting P3HA from biomass using a solvent capable of solubilizing P3HA, and forming a P3HA / solvent mixture. - A step of separating organic waste that is insoluble in the solvent from the P3HA / solvent mixture. - A step of thermally decomposing the P3HA / solvent mixture to obtain the α,β-unsaturated carboxylic acid first, and the solvent second. Methods that include...

2. The method according to claim 1, 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.

3. The method according to claim 1, wherein the extraction is performed at a temperature between 20 and 130°C.

4. The method according to claim 1, wherein the thermal decomposition is carried out at a temperature between 130 and 300°C, preferably between 170 and 230°C, and at a pressure between 1 and 101 kPa (atmospheric pressure), preferably between 10 and 101 kPa (atmospheric pressure).

5. The method according to claim 1, wherein the solvent has a boiling point greater than 230°C at atmospheric pressure.

6. The method according to claim 1, wherein the solubility of P3HA in the solvent during the extraction step is greater than 5% by weight, preferably greater than 20% by weight.

7. The method according to claim 1, wherein the steps of extraction, separation, and thermal decomposition are each performed in a batch or continuously.

8. The method according to claim 1, wherein the thermal decomposition reaction occurs in the presence of one or more polymerization inhibitors.

9. The method according to claim 8, wherein the content of the inhibitor is in the range of 50 ppm to 5% by weight, particularly 0.01% to 3% by weight, relative to the weight of poly(3-hydroxyalkanoate).

10. The method according to claim 8, wherein one or more polymerization inhibitors are compounds selected from phenol derivatives, phenothiazine derivatives, nitroxide derivatives, or paraphenylenediamine derivatives.

11. The method according to claim 8, wherein one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

12. The method according to claim 1, wherein the solvent is selected from glycol diether (glycol), for example tetraglycol, sulfur-containing organic solvent, for example sulfolane or dimethyl sulfone, or organic carbonate, for example propylene carbonate.

13. The method according to claim 8, wherein the solvent is itself a polymerization inhibitor, and preferably the solvent is hydroquinone methyl ether (HQME) in molten form.

14. The method according to claim 1, wherein the solvent recovered at the end of the thermal decomposition is recycled to the extraction step.

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

16. The method according to claim 1, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α,β-unsaturated carboxylic acid produced is acrylic acid.

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

18. The method according to claim 1, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α,β-unsaturated carboxylic acid produced is crotonic acid.

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

20. The method according to claim 1, wherein poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α,β-unsaturated carboxylic acid produced is methacrylic acid.

21. A method for producing an α,β-unsaturated carboxylic acid obtained according to claim 1, comprising a step of condensing the product thus obtained, and subsequently comprising one or more purification steps selected from distillation, liquid-liquid extraction, separation using a thin-film evaporator, or recrystallization, or a combination thereof.