Method for producing biobased alpha-beta-unsaturated carboxylic acids from poly(3-hydroxyalkanoate) contained in biomass

Abstract

The present invention relates to a method for producing biobased α-β-unsaturated carboxylic acids from a biomass containing a poly(3-hydroxyalkanoate), comprising a step of thermolysis of the biomass, in the presence of polymerisation inhibitors and in the absence of catalyst, followed by a plurality of steps resulting in the production of α-β-unsaturated carboxylic acids.

Description

[0001]Title: PROCESS FOR PRODUCING BIOSOURCED α-β UNSATURATED CARBOXYLIC ACIDS FROM POLY(3-HYDROXYALKANOATE) CONTAINED IN BIOMASS Technical field The present invention relates to a process for producing biosourced α-β unsaturated carboxylic acids from a biomass containing a poly(3-hydroxyalkanoate) in the presence of polymerization inhibitors, comprising a step of thermolysis of said biomass, in the absence of a catalyst, followed by several steps leading to the production of α-β unsaturated carboxylic acids. Prior art and technical problem The industrial production of α-β unsaturated carboxylic acids is currently mainly carried out 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.One possible way to obtain these α-β unsaturated carboxylic acids is the thermolysis at temperatures of 150 to 300°C of the corresponding poly(3-hydroxyalkanoates) (P3HA), according to the following reaction: [Chem 1]. R1= 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); - Unsaturated α-β carboxylic acid = propenoic acid (acrylic acid). If R1= methyl and R2= H: - Poly(3-hydroxyalkanoate) = poly(3-hydroxyisobutyrate) (P3HiB); - Unsaturated α-β carboxylic acid = isobutenoic acid (methacrylic acid). If R1= H and R2= methyl: - Poly(3-hydroxyalkanoate) = poly(3-hydroxybutyrate) (P3HB); - Unsaturated α-β carboxylic acid = but-2-enoic acid (crotonic acid). If R1=H and R2 = ethyl: - Poly(3-hydroxyalkanoate) is poly(3-hydroxyvalerate) (P3HV); - Unsaturated α-β carboxylic acid = pent-2-enoic acid These poly(3-hydroxyalkanoates) can themselves be previously obtained by chemical transformations of raw materials of fossil origin, but also by fermentation of biomass.There is a strong market demand for these α-β unsaturated carboxylic acids, used as monomers in many applications, to be obtained from bio-based raw materials. These bio-based raw materials are derived from renewable organic matter (biomass) of biological origin (microorganisms, plants or animals). A potential problem with such a process is that the P3HA obtained by fermentation is present inside the cell. Thermolysis is therefore carried out in the presence of the cell membrane, which poses problems of reactor fouling or the presence of impurities in the final product. Several solutions have been proposed to solve this problem.US 9850192 describes a process for the production of acrylic acid from genetically modified microbial biomass metabolizing glucose or any other renewable raw material, to produce a homopolymer or copolymer of poly-3-hydroxypropionate (P3HP) inside microbial cells. Said process comprises a step of thermolysis of the washed / dried / ground biomass containing P3HP, in the presence of a catalyst. This process effectively makes it possible to produce acrylic acid while limiting the formation of oligomers of the latter such as the dimer of acrylic acid which is spontaneously formed during the production of acrylic acid. The acrylic acid is recovered in gaseous form and then condensed, while the catalyst as well as the residual mass of biomass can be recycled in the process or subjected to thermal regeneration.However, there is a risk that the residue present in the reactor after thermolysis will be pasty and sticky, which could make it difficult to scale up to industrial scale. Example 5 and Figure 7 describe how to implement this invention on an industrial scale. After fermentation, the biomass is washed and dried using an atomizer or a double-drum dryer. After adding the catalyst, the product is pyrolyzed in a FAST reactor. TMat 250-350 °C with a residence time of between 0.25-1 hour using an inert gas such as nitrogen to send the vapors formed to the purification equipment. The vapor phase is composed of 90% organic / water and 10% inert gas. The gas is then purified, following the process described in document US 6646161 or in document US 20120006673, to obtain acrylic acid still containing many impurities. Complete purification is carried out using distillation columns, as described in documents US 7332624 and US 7179875, and may also require crystallization operations, as described in documents US 6482981 and US 71798750. Another solution consists of first extracting the P3HA from the biomass using an organic solvent before carrying out its thermolysis.Document US 20150376152 describes in Example 6 the extraction of P3HP from biomass, using an organic solvent, such as 2-butanone, then obtaining acrylic acid in three stages: evaporation of the solvent and condensation of the latter in a receiving pot; thermal degradation of the P3HP in the absence of inhibitor leading to obtaining acrylic acid vapor, and finally distillation and condensation of the acrylic acid in a receiving pot containing hydroquinone to avoid polymerization of the acrylic acid.In its application FR 2208914, the applicant company proposes to carry out the thermolysis of P3HA in the absence of a catalyst and in the presence of a polymerization inhibitor; typically, the vapor pressure is less than twice the vapor pressure of one of the inhibitors at the thermolysis temperature, which has the effect of avoiding the formation of polymers in the reactor as well as in the gas phase in the event of accidental condensation or at the time of condensation of acrylic acid vapors at the top of the column. In its application FR 2208916, the applicant company describes a process using a solvent which makes it possible to selectively solubilize P3HA from the biomass, to separate the insoluble organic detritus from said solvent, to carry out a thermolysis treatment in the liquid phase in the presence of polymerization inhibitors.WO 2016 / 039618 describes the thermal degradation of dry biomass containing poly(3-hydroxybutyrate) to produce crotonic acid. In Example 1, it is shown that crotonic acid can be obtained with comparable yields of less than 60% from wet or dry biomass, in the absence of a catalyst. It has now been discovered that it is possible to simplify the procedure for manufacturing α-β unsaturated carboxylic acids, by carrying out the thermolysis operation of P3HA directly on biomass in a mixture with at least one polymerization inhibitor, without performing any prior separation of the cell membrane, without using a solvent to carry out the thermolysis, without using a catalyst, and without injecting inert gas to entrain the vapors out of the reaction zone.More precisely, "in the absence of a catalyst" means that the thermolysis of PHA in the presence of at least one polymerization inhibitor occurs in the absence of another chemical species that accelerates or redirects the kinetics of the reaction. Thermolysis as envisaged is only induced by operating conditions such as temperature, pressure and residence time. Chemical species that lead to different types of catalysis depending on the nature of the species are excluded: - homogeneous catalysis, if the catalyst and the reactants form only one phase (often liquid); - heterogeneous catalysis, if the catalyst and the reactants form several phases (generally a solid catalyst for reactants in the gas or liquid phase); - enzymatic catalysis, if the catalyst is an enzyme, i.e. a protein.Accordingly, the invention proposes to provide a simple and easy-to-implement solution for reducing fouling phenomena and the presence of impurities in the final product, and thus maintaining high reliability and high productivity in processes for manufacturing α-β unsaturated carboxylic acids from poly(3-hydroxyalkanoates) obtained by fermentation.Summary of the invention The subject of the present invention is a process for manufacturing a biosourced α-β unsaturated carboxylic acid from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, said process comprising the following steps: - mixing said biomass with at least one polymerization inhibitor; - subjecting said biomass-inhibitor mixture to a thermolysis step leading to obtaining, on the one hand, said α-β unsaturated carboxylic acid in vapor phase, and on the other hand, a solid residue; - separating the two phases formed into a gas phase and a solid phase; - purifying said gas phase to obtain a purified α-β unsaturated carboxylic acid; - treating the residue in solid phase. According to various embodiments, said process comprises the following characteristics, where appropriate combined. The contents indicated are expressed by weight, unless otherwise indicated.Within the ranges of values ​​indicated, the limits are included. According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises a single type of 3-hydroxyalkanoate units and the product formed is therefore composed of a single α-β unsaturated carboxylic acid. According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxypropionate) and the α-β unsaturated carboxylic acid produced is acrylic acid. According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate) and the α-β unsaturated carboxylic acid produced is crotonic acid. According to one embodiment, the poly(3-hydroxyalkanoate) is poly(3-hydroxyisobutyrate) and the α-β unsaturated carboxylic acid produced is methacrylic acid.According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises several different 3-hydroxyalkanoate units and the product formed is therefore 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). According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxypropionate unit and at least one of the α-β unsaturated carboxylic acids produced is acrylic acid. According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxybutyrate unit and at least one of the α-β unsaturated carboxylic acids produced is crotonic acid. According to one embodiment, the poly(3-hydroxyalkanoate) contains the 3-hydroxyisobutyrate unit and at least one of the α-β unsaturated carboxylic acids produced is methacrylic acid.According to one embodiment, the host of the biomass is a bacterium, a yeast, a fungus, an algae, a cyanobacteria or a mixture of two or more of these elements. The biomass is subjected to a thermolysis reaction, which takes place in the presence of one or more polymerization inhibitors. According to one reaction mode, the biomass is intimately mixed with one or more polymerization inhibitors before thermolysis. According to one embodiment, the method according to the invention comprises a step of condensation of the vapors of the unsaturated α-β carboxylic acid(s) obtained by the thermolysis reaction of the biomass, followed by one or more purification steps. The purification operations may generally comprise distillations, liquid / liquid extractions, separations using a film evaporator, or crystallizations.According to one embodiment, the method according to the invention comprises a step of treating said residue obtained at the end of thermolysis, for example by upgrading the latter by hydrothermal gasification into methane. The present invention meets the need expressed in the state of the art. It makes it possible to prevent the risks of fouling of the thermolysis reactor and of the gas phase in the event of accidental condensation by making it possible to obtain a gas phase rich in one or more unsaturated α-β carboxylic acids and also containing polymerization inhibitors as well as a solid residue which can be upgraded. This solution has two advantages: it saves the distillation of the solvent, which is energy-intensive, and the thermolysis of the P3HA contained in the biomass is carried out in the solid state, and not in solution, which reduces the energy and environmental cost of the process. The invention will now be described in more detail in the description which follows.Detailed description of the invention The invention aims to produce bio-sourced α-β unsaturated carboxylic acids on an industrial scale by thermolysis of poly(3-hydroxyalkanoates) contained in biomass, while limiting the problems of fouling of the thermolysis reactor and / or the presence of impurities in the final product. The term "thermolysis" of poly(3-hydroxyalkanoate) (P3HA) means its chemical decomposition into unsaturated α-β carboxylic acid obtained under the effect of temperature. This term is synonymous with pyrolysis.The present invention relates to a process for manufacturing bio-sourced α-β unsaturated carboxylic acids from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) in the absence of a catalyst, said process comprising the following steps: - mixing said biomass with at least one polymerization inhibitor, in the solid state; - subjecting said biomass-inhibitor mixture to a thermolysis step leading to obtaining, on the one hand, said α-β unsaturated carboxylic acid in the vapor phase, and on the other hand, a solid residue; - separating the two phases formed into a gas phase and a solid phase; - purifying said gas phase to obtain a purified α-β unsaturated carboxylic acid; - treating the residue in the solid phase.According to one embodiment, said method for manufacturing bio-sourced α-β unsaturated carboxylic acids from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) comprises the following steps: - Introduction of the biomass (in powder form) and at least one polymerization inhibitor into a mixer (in solid phase) by means of a pipe or by a conveyor of the screw type. - Mixing of the biomass and at least one polymerization inhibitor in a conveyor mixer comprising several screw screws operated in a barrel or directly in a reactor called a thermolysis reactor. - Thermolysis of this mixture at a given temperature and at a controlled pressure in a system adapted to the treatment of the molten or pasty residue in order to generate a vapor phase and a pasty and / or solid phase. - Separation of the two phases formed in a gas-liquid separator.- Treatment of the residue for recovery by spreading, by combustion or by hydrothermal gasification - Condensation of the gaseous phase carried out by a successive condensation temperature adjustment by placing in series one or more condensers and separation of the gaseous and liquid phases obtained containing unsaturated α-β carboxylic acid and contaminants which can be recycled again in the reactor or sent to the purification system. - Treatment of the condensed phase to obtain the unsaturated α-β carboxylic acid by the implementation of one or more distillation columns allowing, on the one hand, to separate the unsaturated α-β carboxylic acid from products heavier than the latter, and on the other hand to obtain products lighter than the latter. - Purification of the unsaturated α-β carboxylic acid obtained by a liquid / solid separation method such as crystallization or by a gas / liquid separation method such as distillation.The invention is based on the use of a biomass mixture containing a P3HA and at least one polymerization inhibitor by implementing a technology for mixing solids and heat treatment of this mixture. The term "biomass" means an organic material of plant (including microalgae), animal, bacterial or fungal (fungi) origin, usable as a source of biosourced raw materials, as opposed to raw materials of fossil origin. In the method according to the invention, the first step uses genetically modified host biomass, resulting from genetic engineering. According to one embodiment, the host of the biomass is a bacterium, a yeast, a fungus, an algae, a cyanobacteria or a mixture of two or more of these elements. The biomass is obtained by a prior step of culturing a recombinant host with a renewable raw material.According to one embodiment, the renewable raw material is selected from glucose, fructose, sucrose, arabinose, maltose, lactose, xylose, ethanol, methanol, glycerol, fatty acids, vegetable oils and syngas derived from biomass or a combination thereof. According to one embodiment, the biomass used in the method according to the invention comes from a bacterial fermentation process of sugars or lipids. Depending on the culture conditions and the variety of the microorganism used, poly(3-hydroxyalkanoates) (P3HA) homo- or copolymers with different 3-hydroxyalkanoic acids are formed.The process according to the invention advantageously comprises a preliminary step of preparing the biomass, where the latter is treated by washing, drying and grinding operations, to produce a solid biomass (for example, in powder form) containing at least 30% by weight of P3HA, preferably at least 50% by weight of P3HA. The biomass is mixed with at least one polymerization inhibitor chosen from the inhibitors conventionally used in existing industrial processes for the production of unsaturated α-β carboxylic acids. These include phenolic derivatives such as hydroquinone (HQ) and its derivatives such as hydroquinone methyl ether (EMHQ), 2,6-di-terbutyl-4-methyl phenol (BHT) or 2,4-dimethyl-6-terbutyl phenol (Topanol A); phenothiazine and its derivatives; nitroxide compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO); and amine compounds such as paraphenylenediamine derivatives.According to a preferred embodiment, at least one of said polymerization inhibitors is hydroquinone methyl ether (HMEQ). According to one embodiment, the mass content of inhibitor in the mixture is between 0.1% and 10%, preferably 1% to 5%. According to one embodiment, the mixing and thermolysis steps are carried out continuously. The mixture of biomass and at least one polymerization inhibitor is then subjected to thermolysis in the solid or partially molten state. The thermolysis of the biomass-inhibitor mixture is carried out under temperature and pressure conditions allowing the chemical decomposition of P3HA and the generation of one or more α-β unsaturated carboxylic acids in the gaseous state.According to one embodiment, the system for feeding the biomass and at least one polymerization inhibitor may be a pipe, a screw, a conveyor belt or a hopper, a pneumatic conveyor, a vibrating conveyor, an extruder. In addition, they may be coupled to a metering device. The system according to the invention for heating the biomass-inhibitor mixture also comprises a reactor adapted for heating for the thermolysis of P3HA. For example, the heating may be carried out by exposing the mixture to microwaves, pulsed electric fields or preheated water vapor or inert gas, by a preheated solid such as sand, by contact with a hot surface such as in an extruder, a screw conveyor, a rotating drum or a tray.The hot surface can be heated by different means: direct electric heating, heating by heat transfer fluid (steam, oil or molten salts). According to one embodiment, the heat supply is made through a hot surface heated by a heat transfer fluid and in particular pressurized steam. The reactor can be a conveyor but also any type of dryer known to those skilled in the art, described for example on the site:. According to one embodiment, said reactor is a reactor suitable for pyrolysis, for high-temperature pyrolysis, or a fluidized reactor or a reactor suitable for solvolysis or a reactor consisting of hollow plates heated by a heat transfer fluid circulating in the plates. However, reactors have been identified which allow higher yield gains in acrylic acid, such as: a conveyor, a rotating drum and / or a set of heating plates. According to one embodiment, said reactor is a conveyor mixer type device, for example of the propeller dryer type (Paddle Dryer). This device comprises a reactor in which rotating propellers or blades are arranged. The propeller makes it possible to mix and homogenize the arrivals of biomass and polymerization inhibitor. This conveyor mixer also has the advantage of allowing the treatment of large quantities of mixture.It also allows good heat transfer between the wall and the mixture. Such a device is usually used at an average temperature to dry a solid, but in the context of the invention, by increasing the temperature, it is possible to carry out thermolysis. According to one embodiment, said reactor is a conveyor mixer type device, for example of the screw conveyor type. This device comprises a reactor in which two endless screws operate in opposition. The heating of the mixture is done through the hot wall using a heat transfer fluid, such as water vapor. The movement of the two screws makes it possible to mix and homogenize the biomass and polymerization inhibitor arrivals, then by increasing the temperature to carry out thermolysis. According to one embodiment, the temperature in the thermolysis reactor is between 100°C and 250°C, preferably between 150°C and 200°C to allow the thermolysis of P3HA.This temperature can also be controlled by means of temperature sensors placed in the mixer. Such moderate heating makes it possible to liquefy all or part of the mixture, while avoiding the polymerization of the unsaturated α-β carboxylic acid. According to one embodiment, the pressure in the thermolysis reactor is between 3 kPa and 101 kPa, preferably between 15 kPa and 40 kPa. According to one embodiment, the residence time in the thermolysis reactor is between 0.5 h and 5 h, preferably between 2-4 h. The mixing between the biomass and the inhibitor, and the thermolysis reaction can be carried out consecutively or simultaneously. In the thermolysis reactor, the biomass-inhibitor mixture is, under the action of heat, transformed into gaseous compounds comprising one or more unsaturated α-β carboxylic acids.In one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises a single type of 3-hydroxyalkanoate units and the product formed is therefore composed of a single α-β unsaturated carboxylic acid. In one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxypropionate) and the α-β unsaturated carboxylic acid produced is acrylic acid. In one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxybutyrate) and the α-β unsaturated carboxylic acid produced is crotonic acid. In one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass is poly(3-hydroxyisobutyrate) and the α-β unsaturated carboxylic acid produced is methacrylic acid.According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass comprises several different 3-hydroxyalkanoate units and the product formed is therefore 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). According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains the 3-hydroxypropionate unit and at least one of the α-β unsaturated carboxylic acids produced is acrylic acid. According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains the 3-hydroxybutyrate unit and at least one of the α-β unsaturated carboxylic acids produced is crotonic acid.According to one embodiment, the poly(3-hydroxyalkanoate) contained in the biomass contains the 3-hydroxyisobutyrate unit and at least one of the α-β unsaturated carboxylic acids produced is methacrylic acid. According to one embodiment, the method according to the invention allows the production of several biosourced α-β unsaturated carboxylic acids from the poly(3-hydroxyalkanoate) contained in the biomass. The gases containing the α-β unsaturated carboxylic acid(s) can be directed to a cooling system in order to be condensed. The condensate obtained can then be collected in a chamber provided for this purpose. The reactor enclosure as well as the chamber are preferably under negative pressure. The condensation system can be equipped with an injection of one or more inhibitors.In order to enable the recovery of one or more purified α-β unsaturated carboxylic acids, the system may comprise a purification device, for example one or more distillation columns, one or more liquid extraction, crystallization or membrane separation equipment. The solid residue is then recovered, for example by hydrothermal gasification or in the form of energy by combustion. According to one embodiment, the condensation is carried out by successive pressure adjustment and separation of the gaseous and liquid phases obtained containing α-β unsaturated carboxylic acid and contaminants which can be recycled back into the reactor.According to the invention, the condensation is carried out by adjusting the successive condensation temperature by placing one or more tubular or spiral condensers in series and separating the resulting gaseous and liquid phases containing unsaturated α-β carboxylic acid and contaminants which can be recycled back into the reactor or sent to the purification system. According to one embodiment, one or more polymerization inhibitors are added to the condenser. According to one embodiment, no inhibitor is added to the condenser. According to one embodiment, this condensation can be carried out by bringing the unsaturated α-β carboxylic acid in the gaseous state into contact with one or more unsaturated α-β carboxylic acids in the liquid state.This contacting can for example be carried out in a shower-type device, by spraying one or more liquid α-β unsaturated carboxylic acids into an enclosure collecting these α-β unsaturated carboxylic acids in the gaseous state. According to one embodiment, the condensation of the gaseous phase is carried out by a system of at least one condenser of the tubular condenser type at the thermolysis pressure, by cooling it and collecting the liquid phase obtained in a stirred storage tank, with optionally the addition of one or more additional inhibitors. According to one embodiment, said products heavier than the α-β unsaturated carboxylic acid are recycled upstream of the thermolysis reactor, or are mixed with the solid residue resulting from the thermolysis. According to one embodiment, said products lighter than the α-β unsaturated carboxylic acid are recovered by combustion or gasification.According to one embodiment, the residue obtained after the thermolysis step is recovered by hydrothermal gasification. According to the embodiment, the hydrothermal gasification is carried out at a temperature of 350°C-450°C and a pressure of 25 MPa. According to one embodiment, the unsaturated α-β carboxylic acid obtained is purified by a fractional crystallization operation comprising several separation stages to obtain high-purity unsaturated α-β carboxylic acid and a residue to be recovered as energy. The examples below illustrate the present invention without, however, limiting its scope. EXPERIMENTAL PART Example 1: This laboratory-scale experiment aims to observe the consistency of the residue after a thermolysis operation to determine whether it can be handled after leaving the thermolysis reactor. Examples 1-4 are carried out on biomass containing 60% by weight of P3HP.The unsaturated α-β carboxylic acid obtained after thermolysis is acrylic acid (AA). The step of mixing the biomass containing P3HP with the inhibitor is carried out by introducing 2 g of this biomass and 0 or 20 mg of EMHQ or in a 50 mL two-necked flask equipped with a magnetic bar. The medium is stirred using a magnetic stirrer in order to distribute the inhibitor in the solid. At the beginning of the experiment, the system is placed under the desired pressure and then the flask containing the biomass is placed in a heating system to establish the desired thermolysis temperature (oil bath or electric heating mantle). As soon as the thermolysis reactor reaches more than 170 °C, the formation of AA vapors is observed, which condense mainly in the lateral condenser. After 4 hours of heating, the formation of AA vapors in the thermolysis reactor diminishes and the experiment is then stopped.The fouling state and the consistency of the thermolysis residue are judged visually at the end of the experiment. It is noted that the addition of the inhibitor makes it possible to transform a very hard solid into a pasty and sticky solid which can be used in the invention. The operating conditions of tests 1-4 are shown in Table 1. [Table 1] Test Inhibitor Operating pressure (kPa) Thermolysis residue 1 EMHQ 100 Viscous pasty solid 2 EMHQ 55 Viscous pasty solid 3 EMHQ 20 Viscous pasty solid 4 NON 100 Very hard and sticky solid The results in Table 1 highlight that the physical state of the residue is dependent on the presence of the inhibitor. The addition of inhibitor allows the residue to become pasty and viscous, whereas it was very hard and sticky without the addition of the latter. This change in the consistency of the residue allows for easier extraction of the latter when continuous thermolysis is required.Thermogravimetric Analysis Test This test aims to provide information on the operating conditions necessary to achieve the thermolysis of P3HA contained in biomass. In order to best assess the thermolysis rate, this test is carried out with P3HP extracted from biomass. 10 g of pure P3HP were subjected to thermogravimetric analysis. This thermogravimetric analysis is a technique that consists of measuring the variation in mass of a sample as a function of time, for a given temperature. To do this, for each temperature condition, 1 g of P3HP is placed on the scale of the device under nitrogen flushing and the weight loss over time is then recorded. It is noted that the loss of mass becomes significant and rapid from 170°C. From a thermolysis point of view, the least severe operating conditions would be: T° of 180°C for a residence time of 3 hours, to obtain a cracking rate greater than 95%.Table 2 shows the temperature conditions and times required to achieve different cracking rates, from 10% to complete cracking. [Table 2] Time required for: T 10% cracking 50% cracking Complete cracking (>95%) 120°C >24h >24h >24h 130°C 14h >24h >24h 140°C 6h 24h >24h 150°C 2h 8h 15h 160°C 1h30 6h 10h 170°C 1h 4h 8h 180°C 45min 2h 3h 190°C 30min 1h15 1h45 200°C <30min 45min 1h 210°C <30min 40min 50min 220°C <30min 35min 40min The temperature of the thermolysis reaction around 180°C in the process according to the invention is significantly smaller than that used in Example 1 of document WO2016 / 039618. The tests of the following Examples 5-7 are carried out in a laboratory setup. A two-necked flask equipped with magnetic stirring was used. The side neck of the flask is equipped with a thermometer to monitor the reaction temperature.The upper neck of the flask is equipped with a separation bridge leading to a water-cooled side condenser, which in turn leads to a recipe consisting of a second 50 mL flask. An additional tapping allows the assembly to be put under reduced pressure using a membrane vacuum pump. EXAMPLE 5 (comparative): Use of a biomass containing 60% P3HP without the addition of inhibitor and without catalyst 2.02 g of biomass containing 60% P3HP are placed in a 25 mL two-necked flask equipped with magnetic stirring. The flask equipped with a separation bridge is placed at 20 kPa pressure using a membrane vacuum pump. The flask is heated to 200°C for 4 hours. The vapors generated are condensed using a water-cooled side condenser to obtain 1.06 g of acrylic acid, which corresponds to an 87% yield. The solid obtained after cracking remains stuck to the walls of the two-necked flask. It is very difficult to remove from the two-necked flask.Solid particles are found in the head of the flask and on the side condenser. EXAMPLE 6 (according to the invention): Use of a biomass containing 60% P3HP with the addition of 1% 4-methoxyphenol (EMHQ) without catalyst 2.11 g of biomass containing 60% P3HP are placed in a 25 ml two-necked flask equipped with magnetic stirring. 0.021 g of EMHQ are added to the flask and mixed with the biomass. The flask equipped with a separation bridge is placed at 20 kPa pressure using a membrane vacuum pump. The flask is heated to 200°C for 4 hours. The vapors generated are condensed using a water-cooled side condenser to obtain 1.21 g of acrylic acid, which corresponds to a 95% yield. The solid obtained after cracking remains compact and easily detaches from the walls of the two-necked flask. This solid breaks easily with a spatula.EXAMPLE 7 (according to the invention): Use of a biomass containing 60% P3HP with the addition of 5% 4-methoxyphenol (EMHQ) 2.19 g of biomass containing 60% P3HP are placed in a 25 ml two-necked flask equipped with magnetic stirring. 0.117 g of EMHQ are added to the flask and mixed with the biomass. The flask equipped with a separation bridge is placed at 20 kPa pressure using a membrane vacuum pump. The flask is heated to 200°C for 4 hours. The vapors generated are condensed using a water-cooled side condenser to obtain 1.27 g of acrylic acid, which corresponds to a 96% yield. The solid obtained after cracking remains compact and is easily detached from the walls of the two-necked flask and easily broken with a spatula.The results of Examples 6 and 7 show that, when the process according to the invention is carried out (in the presence of an inhibitor and without a catalyst), the yield of acrylic acid reaches 95%, higher than that obtained in Comparative Example 5. In addition, the presence of the inhibitor makes it possible to easily eliminate the residue.

Claims

CLAIMS 1. Process for manufacturing a bio-sourced α-β unsaturated carboxylic acid from a biomass containing a poly(3-hydroxyalkanoate) (P3HA) and in the absence of a catalyst, said process comprising the following steps: - mixing said biomass with at least one polymerization inhibitor, in the solid state; - subjecting said biomass-inhibitor mixture to a thermolysis step leading to obtaining, on the one hand, said α-β unsaturated carboxylic acid in vapor phase, and on the other hand, a solid residue; - separating the two phases formed into a gas phase and a solid phase; - purifying said gas phase to obtain a purified α-β unsaturated carboxylic acid; - treating the residue in solid phase. 2.Method according to claim 1, comprising the following steps: - Introduction of the biomass (in powder form) and at least one polymerization inhibitor into a mixer (in solid phase) by means of a pipe or by a conveyor of the screw type. - Mixing of the biomass and at least one polymerization inhibitor in a conveyor mixer comprising several screw screws operated in a barrel or directly in a reactor called a thermolysis reactor. - Thermolysis of this mixture at a given temperature and at a controlled pressure in a system adapted to the treatment of the molten or pasty residue in order to generate a vapor phase and a pasty and / or solid phase. - Separation of the two phases formed in a gas-liquid separator. - Treatment of the residue for recovery by spreading, by combustion or by hydrothermal gasification.- Condensation of the gas phase carried out by adjusting the successive condensation temperature by placing one or more condensers in series and separating the gas and liquid phases obtained containing carboxylic acid. α-β unsaturated carboxylic acid and contaminants which can be recycled back into the reactor or sent to the purification system. - Treatment of the condensed phase to obtain the α-β unsaturated carboxylic acid by using one or more distillation columns allowing, on the one hand, to separate the α-β unsaturated carboxylic acid from products heavier than the latter, and on the other hand to obtain products lighter than the latter. - Purification of the α-β unsaturated carboxylic acid obtained by a liquid / solid separation method such as crystallization or by a gas / liquid separation method such as distillation.

3. Method according to one of claims 1 or 2, in which the biomass used is pretreated 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. 4.A method according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) contains the 3-hydroxypropionate unit and at least one of the α-β unsaturated carboxylic acids produced is acrylic acid.

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

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

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

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

10. A process according to any one of the preceding claims, wherein the polymerization inhibitor(s) are compounds selected from phenolic derivatives, phenothiazine derivatives, nitroxide derivatives or paraphenylenediamine derivatives.

11. A process according to any one of the preceding claims, wherein at least one of said polymerization inhibitors is hydroquinone methyl ether.

12. A process according to any one of the preceding claims, wherein the thermolysis reactor is selected from: a conveyor, a conveyor mixer, a dryer, a rotating drum and / or a set of heating plates. 13.A method according to any one of the preceding claims, wherein the thermolysis reaction is carried out at a temperature between 150°C and 200°C.

14. A method according to any one of the preceding claims, wherein the thermolysis reaction is carried out for two to four hours.

15. A method according to any one of the preceding claims, wherein the thermolysis reaction is carried out at a pressure between 15kPa and 40kPa.

16. A method according to claim 12, wherein the thermolysis reactor is a conveyor mixer type device, for example of the propeller dryer type.

17. A method according to claim 12, wherein the thermolysis reactor is a device consisting of hollow plates, heated by a heat transfer fluid circuit.

18. A method according to claim 12, wherein the thermolysis reactor is a screw conveyor.

19. The method of claim 12, wherein the mixing between the biomass and the inhibitor and the thermolysis can be carried out consecutively or simultaneously.

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