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

Abstract

The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate), and comprises a step of thermally decomposing the biomass in the presence of a polymerization inhibitor and in the absence of a catalyst, and a plurality of steps leading to the production of the α,β-unsaturated carboxylic acid.

Description

Technical Field

[0001] Technical field The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) in the presence of a polymerization inhibitor, including a step of pyrolyzing the biomass in the absence of a catalyst and several subsequent steps leading to the production of the α,β-unsaturated carboxylic acid.

Background Art

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

[0003] One method for obtaining these α,β-unsaturated carboxylic acids is to pyrolyze the corresponding poly(3-hydroxyalkanoate) (P3HA) at a temperature of 150°C to 300°C according to the following reaction.

[0004] [Chemical Formula 1] TIFF2026513797000001.tif30170R1 = H or alkyl, R2 = H or alkyl, and n is a number greater than 30. When R1 = R2 = H: - Poly(3-hydroxyalkanoate) = Poly(3-hydroxypropionate) (P3HP) - α,β-unsaturated carboxylic acid = Propene acid (acrylic acid). When R1 = methyl and R2 = H: - Poly(3-hydroxyalkanoate) = Poly(3-hydroxyisobutyrate) (P3HiB) - α,β-unsaturated carboxylic acid = Isobutene acid (methacrylic acid). When R1 = H and R2 = methyl: - Poly(3-hydroxyalkanoate) = poly(3-hydroxybutyrate) (P3HB) - α,β-unsaturated carboxylic acid = buta-2-enoic acid (crotonic acid). When R1=H and R2=ethyl: - Poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV). - α,β-unsaturated carboxylic acid = pent-2-enoic acid

[0005] These poly(3-hydroxyalkanoates) themselves can be obtained not only through the chemical transformation of fossil-derived raw materials, but also through biomass fermentation.

[0006] There is a strong market demand for obtaining these α,β-unsaturated carboxylic acids, which are used as monomers in many applications, from bio-based raw materials. These bio-based raw materials are obtained from renewable organic matter (biomass) of biological origin (microorganisms, plants, or animals).

[0007] A potential problem in this process is that the P3HA obtained through fermentation is present within the cells. Therefore, thermal decomposition takes place in the presence of the cell membrane, leading to problems such as reactor contamination and the presence of impurities in the final product.

[0008] Numerous solutions have been proposed to this problem.

[0009] U.S. Patent No. 9,850,192 describes a method for producing acrylic acid from genetically modified microbial biomass that metabolizes glucose or other renewable raw materials to produce poly-3-hydroxypropionate (P3HP) homopolymers or copolymers within microbial cells. The process includes a step of thermally decomposing the washed / dried / ground P3HP-containing biomass in the presence of a catalyst. This method makes it possible to produce acrylic acid while limiting the formation of acrylic acid oligomers, such as acrylic acid dimers, which are naturally formed during acrylic acid production. The acrylic acid is recovered in gaseous form and then condensed, but the catalyst and biomass residue can be reused in the method or thermally regenerated. However, the residue present in the reactor after thermal decomposition may become paste-like and sticky, potentially making it difficult to transition to industrial scale. Example 5 and Figure 7 illustrate a method for carrying out the present invention on an industrial scale. After fermentation, the biomass is washed and dried using an atomizer or double drum dryer. After the catalyst is added, the product is thermally decomposed at 250-350°C in a FAST™ reactor with an inert gas such as nitrogen for a residence time of 0.25-1 hour, and the resulting vapor is sent to a purification apparatus. The vapor phase consists of 90% organic matter / water and 10% inert gas. The gas is then purified according to the method described in U.S. Patent No. 6646161 or U.S. Patent No. 20120006673 to obtain acrylic acid still containing many impurities. Complete purification is carried out using a distillation column as described in U.S. Patent Nos. 7332624 and 7179875, and crystallization operations may be required as described in U.S. Patent Nos. 6482981 and 71798750.

[0010] Another solution involves first extracting P3HA from biomass using an organic solvent, followed by thermal decomposition. Example 6 of U.S. Patent No. 20150376152 describes a method for extracting P3HP from biomass using an organic solvent such as 2-butanone, and then producing acrylic acid in the following three steps: evaporating the solvent and condensing it in a receptor; thermally decomposing the P3HP in the absence of an inhibitor to produce acrylic acid vapor; and finally, distilling and condensing the acrylic acid in a receptor to which hydroquinone has been added to prevent polymerization of acrylic acid.

[0011] In those applications, French Patent No. 2208914, the applicant proposed the thermal decomposition of P3HA in the presence of a polymerization inhibitor without the presence of a catalyst, characterized in that the vapor pressure at the thermal decomposition temperature is less than twice the vapor pressure of either inhibitor, thereby preventing the formation of polymers in the reactor and in the gas phase in the event of accidental condensation or when acrylic acid vapor condenses at the top of the column.

[0012] In those applications, French Patent No. 2208916, a method is described using a solvent that allows for the selective solubilization of P3HA starting from biomass, the separation of organic residues insoluble in the solvent, and thermal decomposition in the liquid phase in the presence of a polymerization inhibitor.

[0013] International Publication No. 2016 / 039618 describes a method for pyrolysis of dry biomass containing poly(3-hydroxybutyrate) to produce crotonic acid. Example 1 shows that crotonic acid can be obtained from wet or dry biomass in equivalent yields of less than 60% in the absence of a catalyst.

[0014] It has been found that the procedure for producing α,β-unsaturated carboxylic acids can be simplified by directly performing the P3HA pyrolysis operation on biomass mixed with at least one polymerization inhibitor, without pre-separating the cell membrane, without requiring a solvent for pyrolysis, without using a catalyst, and without injecting an inert gas to remove vapor from the reaction area.

[0015] More precisely, "in the absence of a catalyst" is understood to mean that the thermal decomposition of PHA in the presence of at least one polymerization inhibitor occurs in the absence of any other chemical species that would accelerate or redirect the reaction rate. The assumed thermal decomposition is induced solely by operating conditions such as temperature, pressure, and residence time.

[0016] What is actually excluded are chemical species that produce different types of catalytic activity depending on the nature of the species. - Homogeneous catalysis, where the catalyst and reactants form only one phase (often a liquid phase); - Heterogeneous catalysts where the catalyst and reactants form multiple phases (usually solid catalysts for reactants in the gas or liquid phase); - When the catalyst is an enzyme, i.e., a protein, it is called an enzyme catalyst.

[0017] Therefore, the present invention proposes to provide a simple and easily implementable solution for a method of producing α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) obtained by fermentation, which reduces contamination phenomena and the presence of impurities in the final product, while maintaining high reliability and improved productivity. [Overview of the project]

[0018] Summary of the Invention The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, the method comprising the following steps: - A step of mixing the biomass with at least one polymerization inhibitor, - A step of subjecting the biomass-preventive solid mixture to a thermal decomposition step, wherein, as a result, firstly, the α,β-unsaturated carboxylic acid is produced in the vapor phase, and secondly, a solid residue is produced, - A step of separating the two formed phases into a gas phase and a solid phase, - a step of purifying the gas phase to obtain a purified α,β-unsaturated carboxylic acid; - a step of treating the solid-phase residue

[0019] According to various embodiments, the method optionally comprises the following features in combination. The contents shown are expressed in weight unless otherwise specified; the ranges of the values shown include limitations

[0020] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains a single type of 3-hydroxyalkanoate unit, and thus the product formed is composed of a single α,β-unsaturated carboxylic acid.

[0021] According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate), and the α,β-unsaturated carboxylic acid produced is acrylic acid.

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

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

[0024] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains a plurality of different 3-hydroxyalkanoate units, and thus the product formed is composed of a mixture of different α,β-unsaturated carboxylic acids. Examples of P3HA copolymers include poly-3-hydroxybutyrate-co-3-hydroxypropionate, poly-3-hydroxybutyrate-co-3-hydroxyvalerate (poly-3-HB-co-3HV).

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

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

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

[0028] According to one embodiment, the biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or a mixture of two or more of these elements.

[0029] The biomass is subjected to a thermal decomposition reaction that occurs in the presence of one or more polymerization inhibitors.

[0030] According to one reaction mode, the biomass is thoroughly mixed with one or more polymerization inhibitors before thermal decomposition.

[0031] According to one embodiment, the method according to the present invention comprises a step of condensing the vapor of an α,β-unsaturated carboxylic acid obtained by a biomass pyrolysis reaction, and one or more subsequent purification steps. The purification steps typically include distillation, liquid / liquid extraction, separation using a membrane evaporator, or crystallization.

[0032] According to one embodiment, the method according to the present invention includes a step of processing the residue obtained at the end of the thermal decomposition, for example, a step of upgrading the latter by hydrothermal gasification to obtain methane.

[0033] This invention satisfies the needs expressed in the prior art. This prevents the risk of contamination of the pyrolysis reactor and gas phase in the event of accidental condensation, while simultaneously obtaining a gas phase rich in one or more α,β-unsaturated carboxylic acids, polymerization inhibitors, and solid residues that can improve quality.

[0034] This solution has two advantages: it eliminates the need for energy-intensive solvent distillation, and reduces process energy and environmental costs because the P3HA in the biomass is thermally decomposed in a solid state rather than a solution.

[0035] The present invention will be described in more detail below. [Modes for carrying out the invention]

[0036] Detailed description of the invention The objective of the present invention is to produce bio-based α,β-unsaturated carboxylic acids on an industrial scale by thermal decomposition of poly(3-hydroxyalkanoate) contained in biomass, while limiting the problem of fouling in the thermal decomposition reactor and / or the presence of impurities in the final product.

[0037] The term "thermal decomposition" of poly(3-hydroxyalkanoate) (P3HA) refers to the chemical decomposition into α,β-unsaturated carboxylic acids that occurs under the influence of temperature. This term is synonymous with thermal decomposition.

[0038] The present invention relates to a method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, the method comprising the following steps: - A step of mixing the biomass with at least one polymerization inhibitor in a solid state, - A step of subjecting the biomass-preventive solid mixture to a thermal decomposition step, wherein, as a result, firstly, the α,β-unsaturated carboxylic acid is produced in the vapor phase, and secondly, a solid residue is produced, - A step of separating the two formed phases into a gas phase and a solid phase, - A step of purifying the gas phase in order to obtain purified α,β-unsaturated carboxylic acid, - A process for processing solid-phase residue.

[0039] According to one embodiment, the method for producing a bio-based α,β-unsaturated carboxylic acid from biomass containing poly(3-hydroxyalkanoate) (P3HA) includes the following steps: - A step of introducing biomass (in powder form) and at least one polymerization inhibitor into a (solid phase) mixer by pipe or endless screw type conveyor, - A step of mixing biomass and 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 step of thermally decomposing this mixture at a given temperature and controlled pressure in a system suitable for processing molten or paste-like residues in order to produce a vapor phase and a paste-like and / or solid phase, - A process of separating the two phases formed in a gas-liquid separator, - A process of treating the residue for upgrade purposes by land spraying, combustion, or hydrothermal gasification, - A process of condensing a gas phase by sequentially adjusting the condensation temperature, wherein one or more condensers are installed in series, and the resulting gas phase containing an α,β-unsaturated carboxylic acid and contaminants that can be returned to the reactor for reuse or sent to a purification system is separated from the liquid phase, and the process of condensing a gas phase is carried out by this separation. - A step of treating the condensed phase to obtain α,β-unsaturated carboxylic acids using one to several distillation columns, firstly, to enable the separation of α,β-unsaturated carboxylic acids from heavier products, and secondly, to enable the acquisition of products lighter than α,β-unsaturated carboxylic acids. - A step to purify the obtained α,β-unsaturated carboxylic acid by a liquid-solid separation method such as crystallization, or a gas-liquid separation method such as distillation. Includes.

[0040] The present invention is based on using a biomass mixture containing P3HA and at least one polymerization inhibitor by performing a technique of mixing solids and heat-treating the mixture.

[0041] 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.

[0042] In the method according to the present invention, the first step uses genetically modified host biomass obtained by genetic engineering. According to one embodiment, the biomass host is bacteria, yeast, fungi, algae, cyanobacteria, or a mixture of two or more of these elements.

[0043] 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.

[0044] According to one embodiment, the biomass used in the method of the present invention is obtained from a process of bacterial fermentation of sugars or lipids.

[0045] Depending on the culture conditions and the type of microorganism used, poly(3-hydroxyalkanoate)(P3HA) homopolymers or copolymers containing different 3-hydroxyanoalkanoates are formed.

[0046] 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.

[0047] Next, the biomass is mixed with at least one polymerization inhibitor selected from inhibitors conventionally used in existing industrial processes for the production of α,β-unsaturated carboxylic acids. These include phenol derivatives such as hydroquinone (HQ) and their derivatives such as hydroquinone methyl ether (MEHQ), 2,6-di-tert-butyl-4-methylphenol (BHT), and 2,4-dimethyl-6-tert-butylphenol (Topanol A); phenothiazines and their derivatives; nitroxide compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO); and amino compounds such as paraphenylenediamine derivatives.

[0048] According to a preferred embodiment, at least one of the polymerization inhibitors is hydroquinone methyl ether (MEHQ).

[0049] According to one embodiment, the weight content of the inhibitor in the mixture is between 0.1% and 10%, preferably 1% to 5%.

[0050] According to one embodiment, the mixing step and the pyrolysis step are performed in succession.

[0051] Next, the mixture of biomass and at least one polymerization inhibitor is thermally decomposed in a solid or partially molten state.

[0052] The thermal decomposition of the biomass-preventive mixture is carried out under temperature and pressure conditions that allow for the chemical decomposition of P3HA and the production of one or more α,β-unsaturated carboxylic acids in a gaseous state.

[0053] According to one embodiment, the system for supplying biomass and at least one polymerization inhibitor may be a pipe, an endless screw, a conveyor belt or hopper, an air conveyor, a vibrating conveyor, or an extruder. Furthermore, it may be coupled with a measuring device.

[0054] The system for heating the biomass-preventive mixture according to the present invention also includes a reactor suitable for heating for the purpose of thermal decomposition of P3HA. For example, heating can be carried out by exposing the mixture to microwaves, pulsed electric fields, or preheated inert gas or steam, or preheated solids such as sand, or by bringing it into contact with a high-temperature surface such as an extruder, screw conveyor, rotating drum, or platen. The high-temperature surface can be heated in various ways, such as by direct electric heating or by heating with a heat transfer fluid (steam, oil, molten salt).

[0055] According to one embodiment, heat is supplied through a high-temperature surface heated by a heat transfer fluid, particularly pressurized steam.

[0056] The reactor may be a conveyor, or any type of dryer known to those skilled in the art, as described, for example, on the following website. https: / / www.techniques-ingenieur.fr / base-documentaire / 42665210-production-des-medicaments-industrialisation / download / j2455 / sechage-industriel.html

[0057] According to one embodiment, the reactor is a reactor suitable for thermal decomposition, a reactor suitable for high-temperature thermal decomposition, a fluidized reactor, a reactor suitable for solvent decomposition, or a reactor consisting of a hollow plate heated by a heat transfer fluid circulating within the plate. However, reactors that can further increase the yield of acrylic acid have been identified, such as conveyors, rotating drums, and sets of heated plates.

[0058] According to one embodiment, the reactor is a mixer conveyor type, such as a paddle dryer type device. This device consists of a reactor on which rotating blades or paddles are arranged. The paddles make it possible to mix and homogenize the input materials of biomass and polymerization inhibitor. This mixer conveyor also has the advantage of being able to process large quantities of mixture. It also allows for good heat transfer between the wall and the mixture. Such devices are usually used at moderate temperatures to dry solids, but in the context of the present invention, it is possible to perform thermal decomposition by increasing the temperature.

[0059] According to one embodiment, the reactor is a mixer conveyor type, such as a screw conveyor type device. This device consists of a reactor in which two endless screws move in opposite directions. The mixture is heated through a high-temperature wall using a heat transfer fluid such as steam. The movement of the two screws mixes and homogenizes the input biomass and polymerization inhibitor, and then the temperature can be raised to perform thermal decomposition.

[0060] According to one embodiment, in order to enable the thermal decomposition of P3HA, the temperature in the pyrolysis reactor is between 100°C and 250°C, preferably between 150°C and 200°C. This temperature can also be monitored by a temperature sensor placed in the mixer. Such moderate heating allows all or part of the mixture to liquefy while preventing polymerization of the α,β-saturated carboxylic acid.

[0061] According to one embodiment, the pressure inside the pyrolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa.

[0062] 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.

[0063] The mixing of biomass and the inhibitor, and the thermal decomposition reaction, can be carried out continuously or simultaneously.

[0064] In a pyrolysis reactor, a mixture of biomass and an inhibitor is converted by heat into a gaseous compound containing one or more α,β-unsaturated carboxylic acids.

[0065] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises a single type of 3-hydroxyalkanoate unit, and therefore the resulting product consists of a single α,β-unsaturated carboxylic acid.

[0066] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxypropionate), and the resulting α,β-unsaturated carboxylic acid is acrylic acid.

[0067] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxybutyrate), and the resulting α,β-unsaturated carboxylic acid is crotonic acid.

[0068] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxyisobutyrate), and the resulting α,β-unsaturated carboxylic acid is methacrylic acid.

[0069] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises multiple different 3-hydroxyalkanoate units, and therefore the resulting product consists of a mixture of different α,β-unsaturated carboxylic acids. Examples of P3HA copolymers include poly-3-hydroxybutyrate-co-3-hydroxypropionate and poly-3-hydroxybutyrate-co-3-hydroxyvalerate (poly-3-HB-co-3HV).

[0070] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains 3-hydroxypropionate units, and at least one of the resulting α,β-unsaturated carboxylic acids is acrylic acid.

[0071] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains a 3-hydroxybutyrate unit, and at least one of the resulting α,β-unsaturated carboxylic acids is crotonic acid.

[0072] According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains a 3-hydroxyisobutyrate unit, and at least one of the resulting α,β-unsaturated carboxylic acids is methacrylic acid.

[0073] According to one embodiment, the method of the present invention makes it possible to produce several bio-based α,β-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) contained in biomass.

[0074] The gas containing the α,β-unsaturated carboxylic acid can be sent to a cooling system for condensation. The resulting condensate is collected in a chamber designed for this purpose. The reactor enclosure and chamber are preferably placed under reduced pressure. The condensation system may be equipped with injection of one or more inhibitors. To enable the recovery of one or more purified α,β-unsaturated carboxylic acids, the system may include purification equipment such as one or more distillation columns or one or more liquid extraction, crystallization, or membrane separation devices.

[0075] Subsequently, the solid residue is upgraded in the form of energy, for example, by hydrothermal gasification or by combustion.

[0076] According to one embodiment, condensation is carried out by continuous pressure adjustment and separation of the resulting gas phase and liquid phase (containing α,β-unsaturated carboxylic acids and contaminants that can be returned to the reactor for reuse).

[0077] According to the present invention, condensation is carried out by continuous condensation temperature control, which is performed by arranging one or more tubular or helical condensers in series, and by separation of the resulting gas phase and liquid phase, which contain α,β-unsaturated carboxylic acids and contaminants, and these contaminants can be returned to the reactor for reuse or sent to a purification system.

[0078] According to one embodiment, one or more polymerization inhibitors are added to the condenser.

[0079] According to one embodiment, no inhibitor is added to the condenser.

[0080] According to one embodiment, this condensation can be carried out by contacting a gaseous α,β-unsaturated carboxylic acid with one or more liquid α,β-unsaturated carboxylic acids. This contact operation can be carried out, for example, by spraying one or more liquid α,β-unsaturated carboxylic acids into a chamber using a shower-type device and collecting these α,β-unsaturated carboxylic acids in a gaseous state.

[0081] According to one embodiment, the condensation of the gas phase is carried out by a system of at least one tubular condenser type condenser at the pressure of the pyrolysis, the pyrolysis is cooled and the resulting liquid phase is collected in a stirred storage tank, and the addition of one or more additional inhibitors is optionally performed.

[0082] According to one embodiment, the product, which is heavier than the α,β-unsaturated carboxylic acid, is recycled upstream of the pyrolysis reactor or mixed with the solid residue resulting from the pyrolysis.

[0083] According to one embodiment, the product, which is lighter than an α,β-unsaturated carboxylic acid, is improved in quality by combustion or gasification.

[0084] According to one embodiment, the residue obtained after the pyrolysis process is upgraded by hydrothermal gasification.

[0085] In this embodiment, hydrothermal gasification is performed at a temperature of 350°C to 450°C and a pressure of 25 MPa.

[0086] According to one embodiment, the obtained α,β-unsaturated carboxylic acid is purified by a fractional crystallization process including several separation steps to obtain high-purity α,β-unsaturated carboxylic acid and a residue that is upgraded as energy.

[0087] The following examples illustrate the present invention, but do not limit its scope. [Examples]

[0088] Experiment Section Example 1: The purpose of this laboratory-scale experiment is to observe the viscosity of the residue after the pyrolysis operation and to determine whether it can be processed after being removed from the pyrolysis reactor.

[0089] 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).

[0090] 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 MEHQ into a 50 ml two-necked round-bottom flask equipped with a bar magnet. The medium is stirred using a magnetic stirrer to ensure that the inhibitor is distributed throughout the solid.

[0091] At the start of the experiment, the system is placed under the desired pressure, and a round-bottom flask containing biomass is placed in the heating system (oil bath or electric heating mantle) to establish the desired pyrolysis temperature.

[0092] As soon as the temperature of the pyrolysis reactor exceeds 170°C, AA vapor is generated and mainly condenses in the side condenser. After 4 hours of heating, the generation of AA vapor in the pyrolysis reactor gradually decreases, and the experiment is stopped. At the end of the experiment, the degree of fouling and the viscosity of the pyrolysis residue are visually evaluated.

[0093] It has been found that by adding an inhibitor, a very hard solid can be converted into a paste-like, sticky solid, thus upgrading the quality in this invention.

[0094] Table 1 shows the operating process conditions for Tests 1-4.

[0095] [Table 1] TIFF2026513797000002.tif43170

[0096] The results in Table 1 show that the physical state of the residue depends on the presence of the inhibitor. When the inhibitor is added, the residue becomes paste-like and viscous, but when the inhibitor is not added, 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.

[0097] Thermogravimetric analysis The purpose of this study is to provide information on the operating conditions necessary to perform the thermal decomposition of P3HA contained in biomass. To better evaluate the degree of thermal decomposition, this study was performed using P3HP extracted from biomass.

[0098] 10 g of pure P3HP was subjected to thermogravimetric analysis. Thermogravimetric analysis is a technique that measures the change in mass of a sample at a given temperature as a function of time. To do this, 1 g of P3HP is placed on the balance of the instrument while nitrogen is flowing through it at each temperature condition, and the weight loss over time is recorded. It is known that the mass loss becomes significant and rapid above 170°C.

[0099] From a thermal decomposition perspective, the mildest operating conditions are as follows: a residence time of 3 hours at 180°C with a T° of over 95% cracking can be obtained. Table 2 shows the temperature conditions and times required to obtain various degrees of cracking, from 10% to complete cracking.

[0100] [Table 2] TIFF2026513797000003.tif73170

[0101] 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. The tests in Examples 5-7 below will be performed in a laboratory environment.

[0102] A two-necked round-bottom flask equipped with a magnetic stirrer was used. A thermometer for monitoring the reaction temperature was mounted on the side neck of the round-bottom flask. The top neck of the round-bottom flask was equipped with a separation bridge that led 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 pressurized with a diaphragm vacuum pump.

[0103] Example 5 (Comparative): Use of biomass containing 60% P3HP without the addition of inhibitors and catalysts. 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 placed under a pressure of 20 kPa by 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, which corresponds to a yield of 87%. The solid obtained after decomposition remains attached to the walls of the two-neck round-bottom flask. It is very difficult to remove from the two-neck round-bottom flask. The solid particles are located in the top and side condensers of the round-bottom flask.

[0104] Example 6 (according to the present invention): Use of biomass containing 60% P3HP by adding 1% 4-methoxyphenol (MEHQ) without a catalyst. 2.11 g of biomass containing 60% P3HP is placed in a 25 ml two-neck round-bottom flask equipped with a magnetic stirrer. 0.021 g of MEHQ is added to the round-bottom flask and mixed with the biomass. The round-bottom flask, equipped with a separation bridge, is placed under a pressure of 20 kPa by 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 1.21 g of acrylic acid, which corresponds to a yield of 95%. The solid obtained after decomposition remains compact and easily detaches from the wall of the two-neck round-bottom flask. This solid can be easily crushed with a spatula.

[0105] Example 7 (according to the present invention): Use of biomass containing 60% P3HP with 5% 4-methoxyphenol (MEHQ) 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 MEHQ is added to the round-bottom flask and mixed with the biomass. The round-bottom flask, equipped with a separation bridge, is placed under a pressure of 20 kPa by 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, which corresponds to a yield of 96%. The solid obtained after decomposition remains compact, easily detaches from the wall of the two-neck round-bottom flask, and can be easily crushed with a spatula.

[0106] The results of Examples 6 and 7 show that when the method according to the present invention (in the presence of an inhibitor, without a catalyst) is carried out, the yield of acrylic acid reaches 95%, which is higher than the value obtained in Comparative Example 5. Furthermore, the presence of an inhibitor allows for easy removal of residues.

Claims

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

2. - A step of introducing biomass (in powder form) and at least one polymerization inhibitor into a (solid phase) mixer by pipe or endless screw type conveyor, - A step of mixing biomass and 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 step of thermally decomposing this mixture at a given temperature and controlled pressure in a system suitable for processing molten or paste-like residues in order to produce a vapor phase and a paste-like and / or solid phase, - A process of separating the two phases formed in the gas-liquid separator, - A process to treat the residue for upgrade purposes by land spraying, combustion, or hydrothermal gasification, - A process of condensing a gas phase, which is carried out by sequentially adjusting the condensation temperature, wherein the sequential adjustment of the condensation temperature is carried out by separating the resulting gas phase from the liquid phase, which contains an α,β-unsaturated carboxylic acid and contaminants that can be returned to the reactor for reuse or sent to a purification system, by installing one or more condensers in series. - A step of treating the condensed phase to obtain α,β-unsaturated carboxylic acids using one to several distillation columns, firstly, to enable the separation of α,β-unsaturated carboxylic acids from heavier products, and secondly, to enable the acquisition of products lighter than α,β-unsaturated carboxylic acids. - A step of purifying the obtained α,β-unsaturated carboxylic acid by a liquid-solid separation method such as crystallization, or a gas-liquid separation method such as distillation. The method according to claim 1, including the method described in claim 1.

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

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

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

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

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

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

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

10. The method according to any one of claims 1 to 9, wherein the polymerization inhibitor is a compound selected from phenol derivatives, phenothiazine derivatives, 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 set of conveyors, mixer conveyors, dryers, rotating drums and / or heating plates.

13. The method according to any one of claims 1 to 12, wherein the thermal decomposition reaction is carried out at a temperature between 150°C and 200°C.

14. The method according to any one of claims 1 to 13, wherein the thermal decomposition reaction is carried out for 2 to 4 hours.

15. The method according to any one of claims 1 to 14, wherein the thermal decomposition reaction is carried out at a pressure between 15 kPa and 40 kPa.

16. The method according to claim 12, wherein the pyrolysis reactor is a mixer conveyor type, for example, a paddle dryer type device.

17. The method according to claim 12, wherein the pyrolysis reactor is a device comprising a hollow plate heated by a heat transfer fluid circuit.

18. The method according to claim 12, wherein the pyrolysis reactor is a screw conveyor.

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

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