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

Abstract

The invention relates to a method for producing bio-based alpha, beta-unsaturated carboxylic acids from poly (3-hydroxyalkanoate) (P3HA) contained in biomass by extracting said P3HA using a solvent, then separating insoluble organic waste, and then pyrolyzing the P3HA-solvent mixture in the presence of said solvent. The solvent is selected so that it can well dissolve P3HA and does not boil under 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-hydroxyalkanoate) from biomass using a solvent and then pyrolyzing the polymer in the presence of the solvent.

[0002] Existing technologies and technical issues

[0003] The industrial production of α, β-unsaturated carboxylic acids is currently carried out mainly from raw materials of fossil origin. For example, acrylic acid is obtained by oxidation of propylene or methacrylic acid can be obtained by oxidation of isobutylene.

[0004] One possible method to obtain these α, β-unsaturated carboxylic acids is to pyrolyze the corresponding poly(3-hydroxyalkanoate) (P3HA) at temperatures between 150 and 300 °C according to the following reaction:

[0005]

[0006] R1 = H or alkyl, and R2 = H or alkyl; n is a number greater than 30

[0007] If R1=R2=H:

[0008] - Poly(3-hydroxyalkanoate) = poly(3-hydroxypropionate) (P3HP);

[0009] -α, β-unsaturated carboxylic acid = acrylic acid (propenoic acid) (acrylic acid, acrylic acid).

[0010] If R1=methyl and R2=H:

[0011] -Poly (3-hydroxyalkanoate) = poly (3-hydroxyisobutyrate) (P3HiB);

[0012] -α, β-unsaturated carboxylic acid = methacrylic acid (methacrylic acid).

[0013] If R1=H and R2=methyl:

[0014] -Poly (3-hydroxyalkanoate) = poly (3-hydroxybutyrate) (P3HB);

[0015] -α, β-unsaturated carboxylic acid = but-2-enoic acid (crotonic acid).

[0016] If R1=H and R2=ethyl:

[0017] - the poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV);

[0018] -α, β-unsaturated carboxylic acid = pent-2-enoic acid

[0019] These poly(3-hydroxyalkanoates) themselves can be obtained beforehand by chemical conversion of raw materials of fossil origin or by fermentation of biomass.

[0020] There is a strong demand for these α, β-unsaturated carboxylic acids, which are used as monomers for a variety of applications and can be obtained from bio-based raw materials, which come from renewable organic matter (biomass) of biological origin (microorganisms, plants or animals).

[0021] A potential problem with this approach is that the P3HA obtained by fermentation is present inside the cells. Therefore, pyrolysis is performed in the presence of cell membranes, which can lead to reactor clogging or impurities in the final product, or a preliminary P3HA extraction step is required, which can be complex and costly.

[0022] Various solutions have been proposed to this problem.

[0023] Document US9850192 describes a method for producing acrylic acid from genetically modified microbial biomass, which metabolizes glucose or any other renewable raw material to produce poly-3-hydroxypropionate (P3HP) homopolymer or copolymer in microbial cells. The method includes a step of pyrolyzing washed / dried / ground biomass containing P3HP in the presence of a catalyst. The method is effective in producing acrylic acid, but there is a risk that the residue in the reactor after pyrolysis will become mushy and sticky, which may complicate its transfer to industrial scale.

[0024] Another solution is to extract P3HA from biomass using an organic solvent and then pyrolyze it. Document US20150376152 describes the use of an organic solvent (such as 2-butanone) to extract P3HP from biomass in Example 6. The solvent is then removed by distillation, and P3HP is pyrolyzed into acrylic acid.

[0025] The present inventors have now surprisingly found that the procedure for the extraction of P3HA from biomass followed by pyrolysis can be simplified without having to perform an additional step of separating the solvent used to extract the P3HA.

[0026] The present invention therefore aims to provide a simple and easy to implement solution for reducing clogging phenomena and the presence of impurities in the final product, thereby maintaining high reliability and high productivity in the process for producing α, β-unsaturated carboxylic acids from poly(3-hydroxyalkanoates) obtained by fermentation. Summary of the invention

[0027] The proposed technical solution is to extract P3HA from biomass using an organic solvent in which P3HA is highly soluble but whose boiling point is also high enough to allow the P3HA-solvent mixture to be directly subjected to a pyrolysis step without prior removal of the extraction solvent.

[0028] The present invention provides a method for producing a bio-based α, β-unsaturated carboxylic acid, the method comprising the following steps:

[0029] - mixing the biomass comprising poly(3-hydroxyalkanoate) with a solvent capable of dissolving P3HA,

[0030] - separating organic waste (including cell membranes) that are insoluble in the solvent from the P3HA-solvent mixture,

[0031] - subjecting the PHA-solvent mixture to a thermolysis step resulting in obtaining the α, β-unsaturated carboxylic acid on the one hand and the solvent on the other hand.

[0032] According to various embodiments, the method includes the following features and is combined where appropriate. The contents are expressed by weight unless otherwise specified. The numerical ranges include limits.

[0033] According to one embodiment, the poly(3-hydroxyalkanoate) used in the process comprises a single type of 3-hydroxyalkanoate unit, so that the product formed consists of a single α, β-unsaturated carboxylic acid.

[0034] According to one embodiment, the poly(3-hydroxyalkanoate) contains 3-hydroxypropionate units, and at least one of the generated α, β-unsaturated carboxylic acids is acrylic acid.

[0035] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the produced α, β-unsaturated carboxylic acid is acrylic acid.

[0036] According to one embodiment, the poly(3-hydroxyalkanoate) contains 3-hydroxybutyrate units, and at least one of the generated α, β-unsaturated carboxylic acids is crotonic acid.

[0037] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the produced α, β-unsaturated carboxylic acid is crotonic acid.

[0038] According to one embodiment, the poly(3-hydroxyalkanoate) contains 3-hydroxyisobutyrate units, and at least one of the generated α,β-unsaturated carboxylic acids is methacrylic acid.

[0039] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the produced α, β-unsaturated carboxylic acid is methacrylic acid.

[0040] According to one embodiment, the poly(3-hydroxyalkanoate) used in the method comprises a plurality of different 3-hydroxyalkanoate units, so that the formed product consists 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).

[0041] According to one embodiment, the biomass sink is bacteria, yeast, fungi, algae, cyanobacteria or a mixture of two or more of these elements.

[0042] According to one embodiment, the biomass used is pretreated by washing, drying and grinding operations to produce a biomass containing at least 50% by weight of P3HA.

[0043] According to one embodiment, the step of extracting P3HA from biomass with a solvent comprises separating organic waste (eg cell membranes) insoluble in the solvent from the P3HA-solvent mixture, which is achieved by filtration or centrifugation.

[0044] According to one embodiment, the step of extracting P3HA from biomass with a solvent is carried out at a temperature of 20 to 130°C.

[0045] According to one embodiment, the step of extracting P3HA from biomass with a solvent is performed batchwise.

[0046] According to one embodiment, the step of extracting P3HA from biomass with a solvent is performed continuously.

[0047] According to one embodiment, the pyrolysis reaction of P3HA in the form of a solution in a solvent is carried out at a temperature of 130 to 300° C. and a pressure of 1 to 101 kPa (atmospheric pressure).

[0048] 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.

[0049] According to one embodiment, the pyrolysis reaction is carried out in the presence of one or more polymerization inhibitors.

[0050] The polymerization inhibitor used in the process of the present invention is selected from the inhibitors commonly used in the existing industrial processes for producing α, β-unsaturated carboxylic acids. These inhibitors include phenolic 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; nitrogen oxide free radical compounds, such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO); and amino compounds, such as p-phenylenediamine derivatives.

[0051] According to a preferred embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

[0052] According to one embodiment, the pyrolysis reaction of poly(3-hydroxyalkanoate) is carried out batchwise.

[0053] According to one embodiment, the pyrolysis reaction of poly(3-hydroxyalkanoate) is performed continuously.

[0054] According to one embodiment, the method of the present invention comprises condensing the vapor of one or more α, β-unsaturated carboxylic acids obtained by the pyrolysis reaction of poly(3-hydroxyalkanoate) and then performing one or more purification steps. The purification operation may generally include distillation, liquid / liquid extraction, separation using a membrane evaporator, or crystallization.

[0055] According to one embodiment, the method of the invention comprises a step of recovering the solvent used to extract P3HA from the biomass at the end of the pyrolysis step. Advantageously, the solvent can be recycled to the extraction step without distillation.

[0056] The present invention meets the needs expressed in the prior art. It makes it possible to avoid the risk of clogging of the pyrolysis reactor and / or the risk of the presence of impurities originating from the cell membrane in the α, β-unsaturated carboxylic acid final product, without having to perform a step of separating the solvent used to extract P3HA.

[0057] This scheme has two advantages: the energy-consuming distillation of solvent is omitted, and the pyrolysis of P3HA is not carried out in bulk form but in solution form, which reduces the risk of clogging of the pyrolysis reactor.

[0058] The present invention will be described in more detail in the following description. DETAILED DESCRIPTION OF THE INVENTION

[0060] The object of the present invention is to produce biobased α, β-unsaturated carboxylic acids on an industrial scale by pyrolysis of poly(3-hydroxyalkanoates) contained in biomass, while limiting problems of clogging of the pyrolysis reactor and / or the presence of impurities in the final product.

[0061] The present invention aims to provide a method by which the risk of blockage can be reduced or eliminated.

[0062] The present invention is based on the extraction of P3HA from biomass using an organic solvent in which P3HA is highly soluble but whose boiling point is high enough to allow the P3HA-solvent mixture to be directly subjected to a pyrolysis step without prior removal of the extraction solvent.

[0063] The term "biomass" refers to organic matter of plant (including microalgae), animal, bacterial or fungal origin that can be used as a source of bio-based feedstocks, as opposed to feedstocks of fossil origin.

[0064] In the method according to the invention, the first step uses a transgenic host biomass from 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.

[0065] Biomass is obtained by pre-culturing a recombinant host with a renewable feedstock. According to one embodiment, the renewable feedstock is selected from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, ethanol, methanol, glycerol, fatty acids, vegetable oils and biomass-derived syngas or a combination thereof.

[0066] According to one embodiment, the biomass used in the method of the present invention is derived from a bacterial fermentation process of sugars or lipids.

[0067] Depending on the culture conditions and the type of microorganism used, poly(3-hydroxyalkanoate) (P3HA) homopolymers or copolymers having different 3-hydroxyalkanoic acids are formed.

[0068] According to one embodiment, the biomass used is pretreated by washing, drying and grinding operations to produce a biomass containing at least 50% by weight of P3HA.

[0069] According to one embodiment, the solvent used to extract the P3HA present in the biomass is selected from polar organic solvents with a high boiling point so that the solvent does not boil during the pyrolysis step. Examples of such solvents are glycol diethers (glyme types), such as tetraglyme, sulfur-containing sulfoxide or sulfone solvents, such as sulfolane or dimethyl sulfone, carbonate solvents, such as propylene carbonate, or phenolic derivatives, such as p-methoxyphenol (also known as hydroquinone methyl ether or HQME).

[0070] According to one embodiment, the extraction of P3HA present in the biomass is carried out at a temperature ranging from 20 to 130°C.

[0071] According to one embodiment of the invention, the solvent used in the process must be able to dissolve P3HA in a content greater than 5%, preferably greater than 20% by weight of the solution, at the temperature used during the extraction step.

[0072] According to one embodiment, the extraction is followed by a step of separating the P3HA-solvent mixture and organic waste (e.g. cell membranes) that are insoluble in the solvent. Possible methods are filtration or centrifugation.

[0073] According to one embodiment of the present invention, the step of extracting P3HA from biomass with a solvent and the step of separating the P3HA-solvent mixture from organic waste insoluble in the solvent may be performed in batches.

[0074] According to one embodiment of the present invention, the step of extracting P3HA from biomass using a solvent and the step of separating the P3HA-solvent mixture from organic waste insoluble in the solvent may be performed continuously.

[0075] The term "thermolysis" of poly(3-hydroxyalkanoate) (P3HA) means that it is obtained by the action of temperature and chemically decomposes into α,β-unsaturated carboxylic acids. This term is synonymous with thermal decomposition.

[0076] In the process according to the invention, the thermolysis reaction of the poly(3-hydroxyalkanoate)-solvent mixture is carried out at a temperature of 130 to 300° C., preferably 170 to 230° C. and at a pressure of 1 to 101 kPa (atmospheric pressure).

[0077] According to one embodiment of the present invention, the pyrolysis step of the P3HA-solvent mixture can be performed in batches.

[0078] According to one embodiment of the present invention, the thermal decomposition step of the P3HA-solvent mixture can be performed continuously.

[0079] Advantageously, the solvent recovered at the end of the pyrolysis is recycled to the extraction step.

[0080] According to one embodiment of the present invention, the boiling point of the solvent used in the method is greater than 230°C at atmospheric pressure.

[0081] According to one embodiment, the pyrolysis of poly(3-hydroxyalkanoate) is carried out in the absence of a catalyst. The use of a catalyst can accelerate the kinetics of the pyrolysis and / or reduce its temperature. However, the use of a catalyst makes the process more complicated and more difficult to implement on an industrial scale.

[0082] According to one embodiment, the reaction medium in the pyrolysis reactor comprises at least one polymerization inhibitor in an amount ranging from 50 ppm to 5% by weight, in particular from 0.01% to 3% by weight, relative to the weight of the poly(3-hydroxyalkanoate).

[0083] The polymerization inhibitor is selected from inhibitors commonly used in existing industrial processes for producing α, β-unsaturated carboxylic acids. They include phenolic 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; nitrogen oxide free radical compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO); and amino compounds such as p-phenylenediamine derivatives.

[0084] According to one embodiment, the polymerization inhibitor is hydroquinone methyl ether (HQME).

[0085] According to one embodiment, the solvent used to extract the P3HA present in the biomass is hydroquinone methyl ether (HQME) used in molten form. After the step of separating the P3HA-HQME mixture from the insoluble organic waste, the P3HA in solution in the molten HQME is then pyrolyzed under conditions where the HQME is partially volatilized but not boiled, without the addition of supplementary HQME. Thus, the HQME not only acts as an extraction solvent and a pyrolysis solvent at the same time, but also as a partially volatile polymerization inhibitor.

[0086] According to one embodiment, the temperature and pressure conditions in the pyrolysis reactor are selected such that the one or more α, β-unsaturated carboxylic acids formed are in vapor form.

[0087] According to one embodiment, the present invention relates to a method for producing bio-based acrylic acid from P3HP contained in biomass.

[0088] According to one embodiment, the present invention relates to a method for producing bio-based methacrylic acid from P3HiB contained in biomass.

[0089] According to one embodiment, the present invention relates to a method for producing bio-based crotonic acid from P3HB contained in biomass.

[0090] According to one embodiment, the present invention relates to a method for producing an α, β-unsaturated carboxylic acid mixture from P3HA contained in biomass, wherein the P3HA comprises a plurality of different 3-hydroxyalkanoate units.

[0091] According to one embodiment, the method of the present invention comprises a step of condensing the vapor of one or more α, β-unsaturated carboxylic acids obtained by the pyrolysis reaction of poly(3-hydroxyalkanoate), followed by one or more purification steps. The purification operation may generally include distillation, liquid / liquid extraction, separation using a membrane evaporator, or crystallization.

[0092] According to a preferred embodiment, the P3HA contained in the biomass is P3HP, the extraction is carried out using a sulfone solvent, such as sulfolane or dimethyl sulfone, and the pyrolysis step of the P3HP-sulfone solvent mixture is carried out in the presence of hydroquinone methyl ether.

[0093] The following examples illustrate the invention without limiting its scope.

[0094] Experimental Section

[0095] The examples were carried out on a biomass containing 60 wt% P3HP. The α, β-unsaturated carboxylic acid obtained after pyrolysis was acrylic acid (AA).

[0096] The step of extracting P3HP with solvent was carried out by introducing 2 g of the biomass and 20 g of solvent into a glass test tube equipped with a magnetic stirring bar. The medium was placed in an oil bath at 100°C and stirred with a magnetic stirrer for 2 hours. The insoluble organic waste was then separated from the P3HP-solvent mixture by centrifugation.

[0097] The step of pyrolysis of P3HP in solution in a solvent is achieved by placing the medium obtained after the step of separation and extraction of organic waste in a 50 mL two-necked flask; the addition of HQME inhibitor can be carried out. It is equipped with a thermometer on the side neck for monitoring the temperature of the pyrolysis medium and a separation bridge on the upper neck, which leads to a water-cooled side condenser. The condenser leads to a receiver consisting of a 25 mL single-necked flask, cooled by an ice bath. The exhaust device allows the experiments to be carried out under partial vacuum.

[0098] Pyrolysis of biomass in a solvent medium without extraction and prior separation of organic waste

[0099] Experiment 1

[0100] 2 g of biomass containing 60% P3HP (i.e. 1.2 g P3HP) and 20 g of sulfolane were directly introduced into the pyrolysis unit. 0.02 g of HQME was added as a polymerization inhibitor. The pyrolysis reaction was carried out at 200°C and 20 kPa for 4 h. 1.1 g of AA with a purity greater than 90% was collected in the top receiver. The residue in the pyrolysis reactor was almost unusable (the liquid was full of sticky solids).

[0101] Experiment 2

[0102] 2 g of biomass containing 60% P3HP (i.e. 1.2 g P3HP) and 20 g of tetraethylene glycol dimethyl ether were directly introduced into the pyrolysis device. 0.02 g of HQME was added as a polymerization inhibitor. The pyrolysis reaction was carried out at 200°C and 20 kPa for 4 h. 1.1 g of AA with a purity greater than 90% was collected in the receiver at the top. The residue in the pyrolysis reactor was almost unusable (the liquid was full of sticky solids).

[0103] Experiment 3

[0104] 2 g of biomass containing 60% P3HP (i.e. 1.2 g P3HP) and 20 g HQME were directly introduced into the pyrolysis device. The pyrolysis reaction was carried out at 200 ° C and 20 kPa for 4 h. 0.9 g of AA with a purity greater than 90% was collected in the top receiver. The residue in the pyrolysis reactor was almost unusable (the liquid was full of sticky solids).

[0105] Experiment 4

[0106] 2 g of biomass containing 60% P3HP (i.e. 1.2 g P3HP) and 20 g of dimethyl sulfone were directly introduced into the pyrolysis device. The pyrolysis reaction was carried out at 200°C and 20 kPa for 4 h. 1.0 g of AA with a purity greater than 90% was collected in the top receiver. The residue in the pyrolysis reactor was almost unusable (the liquid was full of sticky solids).

[0107] Experiment 5

[0108] 2 g of biomass containing 60% P3HP (i.e. 1.2 g P3HP) and 20 g of propylene carbonate were directly introduced into the pyrolysis device. The pyrolysis reaction was carried out at 200°C and 70 kPa for 4 h. 0.8 g of AA with a purity greater than 90% was collected in the top receiver. The residue in the pyrolysis reactor was almost unusable (the liquid was full of sticky solids).

[0109] Pyrolysis after prior extraction of biomass with methyl isobutyl ketone (MIBK) and separation of organic waste

[0110] Experiment 6

[0111] 2 g of biomass containing 60% P3HP (ie, 1.2 g P3HP) was extracted by 20 g MIBK at 100° C. for 2 h.

[0112] The insoluble organic waste was separated by centrifugation and weighed 1.2 g. Thus, a maximum of 0.8 g of P3HP was extracted into MIBK, i.e. two thirds of the P3HP contained in the biomass.

[0113] The homogeneous P3HP-MIBK mixture was directly introduced into the pyrolysis unit. 0.02 g HQME was added as a polymerization inhibitor. The pyrolysis reaction was carried out at 200° C. and 20 kPa for 4 h. 20.3 g of homogeneous organic medium was collected from the top, which contained 3% (i.e. 0.6 g) of AA in the form of a solution in MIBK. The residue in the pyrolysis reactor was a viscous solid.

[0114] Pyrolysis after prior extraction of the biomass with the solvent of the invention (a good solvent for P3HP that does not boil under pyrolysis conditions)

[0115] Experiment 7

[0116] 2 g of biomass containing 60% P3HP (ie, 1.2 g P3HP) was extracted by 20 g of sulfolane at 100° C. for 2 hours.

[0117] 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, which was probably all the P3HP contained in the biomass.

[0118] The homogeneous P3HP-sulfolane mixture is directly introduced into the pyrolysis unit. 0.02 g 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 AA with a purity greater than 90% is collected in the top receiver. The residue in the pyrolysis reactor is a clear liquid consisting mainly of sulfolane, and it can be recycled to the extraction step.

[0119] Experiment 8

[0120] 2 g of biomass containing 60% P3HP (ie, 1.2 g P3HP) was extracted by 20 g tetraglyme at 100° C. for 2 hours.

[0121] 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, which was probably all the P3HP contained in the biomass.

[0122] The homogenous P3HP-tetraglyme mixture was introduced directly into the pyrolysis unit. 0.02 g HQME was added as a polymerization inhibitor. The pyrolysis reaction was carried out at 200°C and 20 kPa for 4 hours. 1.1 g of AA with a purity greater than 90% was collected in the receiver at the top. The residue in the pyrolysis reactor was a clear liquid consisting mainly of tetraglyme, which could be recycled to the extraction step.

[0123] Experiment 9

[0124] 2 g of biomass containing 60% P3HP (i.e., 1.2 g P3HP) was extracted by 20 g HQME at 100° C. for 2 h.

[0125] Insoluble organic waste was separated by centrifugation and weighed 0.8 g. Thus, a maximum of 1.2 g of P3HP was extracted into the HQME, which was potentially all the P3HP contained in the biomass.

[0126] The homogeneous P3HP-EMHQ mixture is directly introduced into the pyrolysis unit. The pyrolysis reaction is carried out at 200°C and 20 kPa for 4 hours. 0.9 g of AA with a purity greater than 90% is collected in the top receiver. The residue in the pyrolysis reactor is a clear liquid mainly composed of HQME, which can be recycled to the extraction step.

[0127] Experiment 10

[0128] 2 g of biomass containing 60% P3HP (ie, 1.2 g P3HP) was extracted by 20 g of dimethyl sulfone at 115° C. for 2 h.

[0129] 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 dimethyl sulfone, which was probably all the P3HP contained in the biomass.

[0130] The homogeneous P3HP-DMSO mixture was introduced directly into the pyrolysis unit. 0.02 g HQME was added as a polymerization inhibitor. The pyrolysis reaction was carried out at 200 ° C and 20 kPa for 4 h. 1.1 g of AA with a purity greater than 90% was collected in the top receiver. The residue in the pyrolysis reactor was a clear liquid consisting mainly of DMSO, which could be recycled to the extraction step.

[0131] Experiment 11

[0132] 2 g of biomass containing 60% P3HP (ie, 1.2 g P3HP) was extracted by 20 g of propylene carbonate at 100° C. for 2 h.

[0133] 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 propylene carbonate, which was probably all the P3HP contained in the biomass.

[0134] The homogeneous P3HP-propylene carbonate mixture is directly introduced into the pyrolysis unit. 0.02 g 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 greater than 90% is collected in the top receiver. The residue in the pyrolysis reactor is a clear liquid consisting mainly of propylene carbonate, which can be recycled to the extraction step.

Claims

1. A method for producing α, β-unsaturated carboxylic acids from biomass containing poly(3-hydroxyalkanoate) (P3HA), the method comprising the following steps: - extracting P3HA from the biomass using a solvent capable of dissolving P3HA to form a P3HA-solvent mixture, - separating organic waste insoluble in said solvent from the P3HA-solvent mixture, - Pyrolysis of the P3HA-solvent mixture to obtain the α, β-unsaturated carboxylic acid on the one hand and the solvent on the other hand.

2. The method according to claim 1, wherein the biomass used is pre-treated by washing, drying or grinding operations to produce a biomass containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA.

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

4. The method according to any one of the preceding claims, wherein the pyrolysis 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 process according to any one of the preceding claims, wherein the solvent has a boiling point at atmospheric pressure of greater than 230°C.

6. The method according to any one of the preceding claims, wherein the solubility of P3HA in the solvent in the extraction step is greater than 5 wt%, preferably greater than 20 wt%.

7. A method according to any one of the preceding claims, wherein the extraction, separation and pyrolysis steps are each performed batchwise or continuously.

8. A process according to any one of the preceding claims, wherein the thermolysis reaction takes place in the presence of one or more polymerization inhibitors.

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

10. The process according to claim 8, wherein the one or more polymerization inhibitors are compounds selected from phenolic derivatives, phenothiazine derivatives, nitroxide derivatives or p-phenylenediamine derivatives.

11. The method according to any one of claims 8 to 10, wherein one of the polymerization inhibitors is hydroquinone methyl ether (HQME).

12. The process according to any one of claims 1 to 11, wherein the solvent is selected from glycol diethers (glyme types), such as tetraglyme, sulfur-containing organic solvents, such as sulfolane or dimethyl sulfone, or organic carbonates, such as propylene carbonate.

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

14. Process according to any one of the preceding claims, wherein the solvent recovered at the end of the pyrolysis is recycled to the extraction step.

15. The method of any one of the preceding claims, wherein the poly(3-hydroxyalkanoate) contains 3-hydroxypropionate units and at least one of the produced α, β-unsaturated carboxylic acids is acrylic acid.

16. The method of any one of the preceding claims, wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α, β-unsaturated carboxylic acid produced is acrylic acid.

17. The method of any one of claims 1 to 14, wherein the poly(3-hydroxyalkanoate) contains 3-hydroxybutyrate units and at least one of the produced α, β-unsaturated carboxylic acids is crotonic acid.

18. The method of any one of claims 1 to 14 and 17, wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α, β-unsaturated carboxylic acid produced is crotonic acid.

19. The method of any one of claims 1 to 14, wherein the poly(3-hydroxyalkanoate) contains 3-hydroxyisobutyrate units and at least one of the produced α, β-unsaturated carboxylic acids is methacrylic acid.

20. The method of any one of claims 1 to 14 and 19, wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α, β-unsaturated carboxylic acid produced is methacrylic acid.

21. Process for producing an α, β-unsaturated carboxylic acid obtained by the process according to any one of the preceding claims, characterized in that It comprises a step of condensing the product thus obtained, followed by one or more purification steps chosen from distillation, liquid / liquid extraction, separation using a membrane evaporator, or crystallization or a combination of these techniques.

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