Process for manufacturing esters by reaction between an alcohol and a carboxylic acid in the presence of an enzymatic catalyst in a biphasic medium in the form of a Pickering emulsion

Abstract

A process for manufacturing esters by reacting a first reagent selected from an alcohol or a carboxylic acid contained in an aqueous solution with at least a second reagent selected from a carboxylic acid or an alcohol in the presence of an enzymatic catalyst, characterized in that the reaction mixture is in the form of a Pickering emulsion comprising at least one water phase and one oil phase, said oil phase comprising at least one extraction solvent.

Description

Title of the invention: Process for manufacturing esters by reaction between an alcohol and a carboxylic acid in the presence of an enzymatic catalyst in a biphasic medium in the form of a Pickering emulsion technical field

[0001] The present invention relates to the field of manufacturing esters preferably bio-based used in particular in the field of cosmetics, fragrances, lubricants, emulsifiers, glues, varnishes and biofuels by reaction between an alcohol and a carboxylic acid in the presence of an enzymatic catalyst in a biphasic medium in the form of a Pickering emulsion. State of the art

[0002] The market for esters is very vast since these compounds are used in many fields such as biofuels, lubricants, emulsifiers, fragrances, complexing agents, synthesis intermediates, particularly for biodegradable polymers, adhesives, printing inks, paints, varnishes...

[0003] In a context of strong demand for bio-based products with a low environmental impact, ester manufacturers are increasingly seeking to source bio-based reagents, i.e., those derived from renewable resources, for their production. It is known that an ester can be manufactured from an alcohol and a carboxylic acid. At least one of the two reagents must therefore be bio-based to meet this demand.

[0004] These compounds can be obtained from biomass by fermentation, by oxidation (for carboxylic acids) of carbohydrates derived from biomass (cellulose, glucose, and glycerol), or by any process known to those skilled in the art. However, unlike the petrochemical industry, the processes used lead to solutions that are dilute or even highly dilute in water. Yet, conventional ester manufacturing processes use highly concentrated or pure reagents containing as little water as possible. Indeed, it is known to those skilled in the art that the presence of water is strongly detrimental to the esterification reaction. Therefore, processes for separating these reagents must be used to purify them. However, these processes have an energy cost that significantly increases the carbon footprint of the final product. Examples include vaporization, distillation or membrane separation processes (see patents US8906204B2, US11471786B2 and US10961489B2).There are also liquid-liquid extraction processes, but they do not allow... to extract 100% of the compound of interest (see patent application US2013 / 0149757) especially if the compound is very diluted in water.

[0005] Van Den Berg et al. (Van Den Berg, C., et al. Biotechnol Bioeng (2013), 110(1), 137-142) propose reacting butanol formed by fermentation with butyric acid, both of which are diluted in water, using an enzymatic catalyst in aqueous solution and extracting the ester formed, butyl butyrate, into an oil phase such as hexadecane. However, the contact surface area between the oil and water phases is small in this implementation, which significantly slows down ester extraction and thus the esterification reaction.

[0006] Patent CN114606222 describes a process for reacting methanol in aqueous solution with lauric acid contained in an oil phase, in the presence of a biocatalyst. A Pickering emulsion is prepared to stabilize the emulsion and promote the exchange between the two phases. In this case, the methanol is in very high excess to convert as much lauric acid as possible. The methanol is therefore highly concentrated in the water (15% to 50% wt.). As this concentration is problematic for the enzyme used, the enzyme had to be encapsulated beforehand, and it is the capsules containing the enzyme that are used to prepare the Pickering emulsion. Given the size of the capsules, the size of the water phase droplets dispersed in the oil phase is particularly large (150 pm to 650 pm), i.e. one to two orders of magnitude higher than what could be achieved with a Pickering emulsion not constrained by the encapsulation of the enzyme.Since the exchange surface area between the two phases is inversely proportional to the size of the droplets, the exchange surface area is reduced in this case, thus hindering the transfer of molecules between the phases. Object of the invention.

[0007] The applicant has developed a process for manufacturing esters by reacting an alcohol with a carboxylic acid in the presence of an enzymatic catalyst in a biphasic medium in the form of a Pickering emulsion, enabling the synthesis of esters with optimized yields and rates from alcohols and / or carboxylic acids present in dilute aqueous solutions. This is particularly true when the alcohols and / or carboxylic acids are bio-based.

[0008] The present invention therefore has the advantage of implementing a process for manufacturing esters from reagents diluted in water without requiring prior purification or concentration of the reagents. The biocatalyst (enzymatic catalyst) used in the invention also allows the carboxylic acid to react with the alcohol in a dilute medium where a chemical catalyst would not have allowed the esterification reaction to occur. Furthermore, in the process of manufacturing a bio-ester, replacing a chemical catalyst with a biocatalyst represents an additional advantage, especially since the temperatures involved are... The work involved is much less in this case, thus reducing the carbon footprint of the process.

[0009] The use of an emulsion according to the invention further allows the ester to be extracted from the oil phase as it is formed. Since the esterification reaction is an equilibrium reaction, that is to say, not a complete one, the transfer of the ester into the oil phase shifts the equilibrium in the direction favorable to ester production.

[0010] The use of a Pickering emulsion according to the invention makes it possible to optimize the emulsion by developing a large exchange surface between the two phases, which strongly promotes the extraction of the ester.

[0011] This large exchange surface area offers an additional advantage if one of the two reactants is introduced into the oil phase to promote its transfer from the oil phase to the water phase, where the reaction takes place in the presence of the biocatalyst. This is the case, for example, with fatty carboxylic acids and fatty alcohols, which have sufficiently long carbon chains to considerably reduce their solubility in water. They are then solubilized in the oil phase. The Pickering emulsion allows their reaction in water despite their low solubility. The large exchange surface area generated between the two liquid phases compensates for this low solubility, and the microreactors created by the Pickering emulsion promote the reaction kinetics.

[0012] The Pickering emulsion also eliminates the need for vigorous agitation, which is traditionally required to transfer a molecule between two liquid phases, thus reducing the energy demand of the process. The Pickering emulsion produces an emulsion that remains stable after its creation; it is no longer necessary to supply energy to maintain the two liquid phases in contact.

[0013] Pickering emulsions therefore also allow continuous implementation with, for example, continuous reagent addition in the continuous phase and / or continuous withdrawal of the continuous phase to separate the reaction products.

[0014] Pickering emulsions have the additional advantage over a surfactant-stabilized emulsion of not using products that may have an impact on the environment and of using solids that are easily separable from liquids.

[0015] The present invention relates to a process for manufacturing an ester from a first reagent chosen from an alcohol or a carboxylic acid in aqueous solution, comprising the following steps:

[0016] a) an esterification reaction is carried out on a reaction mixture in the form of an oil-in-water or water-in-oil Pickering emulsion to form an ester in the oil phase, said reaction mixture being obtained according to the following steps:

[0017] a) a two-phase mixture comprising at least one water phase and one oil phase is formed by contacting an aqueous solution comprising said first reagent, at least one second reagent chosen from a carboxylic acid or an alcohol, at least one enzymatic catalyst, at least one organic extraction solvent and solid particles;

[0018] a2) the biphasic mixture obtained in step a1 is emulsified to form a reaction mixture in the form of a Pickering oil-in-water or water-in-oil emulsion; said reaction mixture comprising:

[0019] -either droplets of said oil phase stabilized by said solid particles in said water phase;

[0020] -either droplets of said water phase stabilized by said solid particles in said oil phase;

[0021] b) the ester formed in step a) is recovered in the oil phase.

[0022] Advantageously, the first reactant contained in said aqueous solution is an alcohol, and the second reactant is a carboxylic acid.

[0023] Advantageously, the first reactant contained in said aqueous solution is a carboxylic acid and the second reactant is an alcohol.

[0024] Advantageously, the concentration of first reactant in said aqueous solution is between 0.001 mol / L and 0.4 mol / L when said first reactant is an alcohol, and between 0.001 mol / L and 2 mol / L when said first reactant is a carboxylic acid.

[0025] Advantageously, the molar ratio between said second reactant and said first reactant is between 1 and 10.

[0026] Advantageously, said first reagent chosen from said alcohol or said carboxylic acid is of bio-based origin.

[0027] Advantageously, the enzymatic catalyst added in step a1) is chosen from lipases of microbial or plant origin.

[0028] Preferably, the enzymatic catalyst added in step a1) is chosen from lipase B of Candida antarctica, lipase of Candida rugosa, or lipase of Rhizomucor miehei.

[0029] Advantageously, the pH of the water phase is less than 7.

[0030] Advantageously, the solid particles added in step a1) are chosen from solid particles of silica, clay, or natural or synthetic polymers.

[0031] Advantageously, the droplet size of the Pickering emulsion obtained at the end of step a) is between 1 pm and 140 pm.

[0032] Advantageously, the temperature of the esterification reaction in step a) is between 10°C and 90°C.

[0033] Advantageously, the mass concentration of solid particles added in step a1) is between 0.1% weight and 10% weight relative to the total weight of said two-phase mixture.

[0034] Advantageously, the reaction mixture obtained at the end of step a) is a Pickering water-in-oil emulsion.

[0035] Advantageously, a step a') of production of said first reagent chosen from said alcohol or said carboxylic acid in aqueous solution is carried out in combination with step a). Detailed description of the invention Definitions

[0036] The term “biomass” means all organic matter of plant or animal origin, but also any derived product or liquid effluent resulting from its mechanical, thermochemical, enzymatic or fermentation processes, as well as mixtures thereof.

[0037] The term “bio-based” or “renewable” means that the material / product / compound it describes is derived from biomass. In the text, the prefix “Bio” may also be used before the type of compound to characterize its bio-based nature: for example, bio-methanol, bio-ethanol, bio-butanol, bio-isobutanol, bio-acrylic acid, bio-ester. Pickering's emulsion and emulsion#:

[0038] An emulsion is a heterogeneous medium formed by the dispersion of one liquid in another liquid. Emulsions are generally stabilized by surfactants due to their amphiphilic properties.

[0039] Emulsions can also be stabilized with solid particles; this is called a Pickering emulsion.

[0040] Pickering emulsions are indeed liquid / liquid dispersions stabilized by solid nanoparticles or aggregates of nanoparticles that accumulate at the interface between the two immiscible liquids (generally water and oil) and prevent coalescence (see, for example, Pickering, SU (1907). J. Chem. Soc. Trans. 91, 2001-2021). In fact, the solid particles used to make Pickering emulsions are capable of adhering irreversibly to the interface between the two liquids, resulting in much more effective emulsion stabilization than the adsorption of surfactants (see, for example, Aveyard, R., Binks, BP, and Clint, JH (2003); Adv. Colloid Interface Sci. 100, 503-546). The direction of the emulsion (water in oil or oil in water) is determined by the preferential wettability of the solid particles towards one or the other phase.In fact, the liquid that is most wetting towards the solid particles will constitute the continuous phase of the emulsion, and the one that is least wetting will constitute the dispersed phase (see, for example, the publication Binks, B., and Lumsdon, S. (2000. Langmuir 16, 8622-8631).

[0041] Pickering emulsions have the advantage of promoting the transfer of mass between the two liquid phases. Indeed, to ensure the transfer of a molecule between two liquid phases, it is necessary to create a large exchange surface between the two liquids.

[0042] An “emulsifier” is a compound or substance that acts as a stabilizer for emulsions, preventing liquids from separating.

[0043] A "hydrophobic" molecule or part of a molecule is a molecule that is repelled by a mass of water and other polar substances.

[0044] A "hydrophilic" molecule or part of a molecule is a molecule that tends to interact with or be dissolved by water and other polar substances.

[0045] “Amphiphile” is a term describing a chemical compound comprising both hydrophilic and hydrophobic properties.

[0046] Sizes of solid particles and droplets:

[0047] Solid particle size: The solid particles according to the invention can be of various shapes and sizes, for example from a few nanometers to a few microns, or even tens of microns, in the form of substantially spherical or non-spherical beads (FB de Carvalho-Guimarães, K Leal Correa, T Pereira de Souza, JR Rodriguez Amado, RM Ribeiro-Costa and JO Carréra Silva-Junior (2022) A Review of Pickering Emulsions: Perspectives and Applications, Pharmaceuticals, 15, 1413. https: / / doi.org / 10.3390 / phl5111413). The shape can be substantially spherical, or in the form of a rod, ellipsoid, needle, spindle, nanofibril, nanocage, plate, nanotube, nanocube, etc. (Li W, Jiao B, Li S, Faisal S, Shi A, Fu W, Chen Y and Wang Q (2022) Recent Advances on Pickering Emulsions Stabilized by Diverse Edible Particles: Stability Mechanism and Applications. Front. Nutr. 9:864943. doi: 10.3389 / fnut.2022.864943).The size can vary enormously, from a few nanometers to a few tens of microns. The size obviously depends on the morphology of the solid particles involved. It is generally determined by scanning and transmission electron microscopy. It is easy to define for spherical particles (diameter), and more difficult for solid particles whose shape deviates from sphericity (plates, rods, ellipsoids, needles, etc.). In these cases, two characteristic sizes are usually specified: the smallest and the longest. Another difficulty is related to the spontaneous formation of aggregates between the elementary solid particles. A distinction is then made between the size of the elementary solid particles and the size of the aggregates. For example, the commercial silica Aerosil R972 is a mixture of elementary solid particles between 5 nm and 50 nm with aggregates of average size on the order of 250 nm.

[0048] Droplet size: Droplet size means the largest dimension of the droplets measured by optical microscopy (in particular by Olympus BX51 with analysIS software for image analysis). Solubility

[0049] Solubility refers to the ability of a substance, called the solute, to dissolve in another substance, called the solvent. Depending on the solubility value, a mass fraction (expressed as a percentage) of the substance is dissolved in the solvent.

[0050] In the case of a liquid / liquid biphasic medium, we speak of the affinity of a substance for a phase, when this substance solubilizes with a mass fraction greater than 50% in this phase, the complement to 100% is found in the other phase.

[0051] The invention relates to a process for manufacturing an ester from a first reagent chosen from an alcohol or a carboxylic acid in aqueous solution comprising the following steps:

[0052] a) an esterification reaction is carried out on a reaction mixture in the form of an oil-in-water or water-in-oil Pickering emulsion to form an ester in the oil phase, said reaction mixture being obtained according to the following steps:

[0053] a) a biphasic mixture comprising at least one water phase and one oil phase is formed by bringing into contact an aqueous solution comprising said first reagent, at least one second reagent chosen from a carboxylic acid or an alcohol, at least one enzymatic catalyst, at least one organic extraction solvent and solid particles;

[0054] a2) the biphasic mixture obtained in step a1 is emulsified to form a reaction mixture in the form of a Pickering oil-in-water or water-in-oil emulsion; said reaction mixture comprising:

[0055] -either droplets of said oil phase stabilized by said solid particles in said water phase;

[0056] -either droplets of said water phase stabilized by said solid particles in said oil phase;

[0057] b) the ester formed in step a) is recovered in the oil phase.

[0058] Step a') (optional) Step of producing the first reagent chosen from an alcohol or a carboxylic acid in aqueous solution

[0059] The first reagent chosen from an alcohol or a carboxylic acid can be obtained from biomass by fermentation and / or chemically according to several processes.

[0060] Examples include biorefinery processes for producing alcohols and carboxylic acids, as described by Laurent, P. et al., Biorefining, a promising alternative to petrochemistry, Biotechnology, Agronomy, Society and Environment, 2022, 15(4), 597-610; and by Takkellapati, S. et al., An overview of biorefinery-derived platform Chemicals from a cellulose and hemicellulose biorefinery, Clean Technologies and Environmental Policy, 2018, 20(7), 1615-1630 or as described in patent FR2923840.

[0061] We can also cite the biomass transformation processes described by Straathof, AJJ et al., Transformation of biomass into commodity Chemicals using enzymes or cells, Chem. Rev., 2014, 114, 1871-1908.

[0062] In particular, alcohols produced by fermentation processes (e.g., isopropanol and n-butanol) are among the most promising substitutes for petrochemical derivatives. ABE (Acetone-Butanol-Ethanol) fermentation, carried out by microorganisms belonging to the genus Clostridium, is one of the oldest fermentations to have been industrialized and has since been extensively studied. More recently, IBE (Isopropanol-Butanol-Ethanol) fermentation, which produces a mixture of isopropanol, butanol, and ethanol and is also carried out by microorganisms belonging to the genus Clostridium, has been the subject of fairly recent studies (Dos Santos Vieira et al., Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation, Bioresource Technology, 2019, 287, 121425).Regarding the fermentation method used in this type of process, batch production has been studied for ABE and IBE fermentations (see, for example, Jones DT, Woods DR, Acetone-Butanol Fermentation Revisited, Microbiol. Rew., 1986, 50(4), 484-524). Continuous processes have also been studied, initially with cells suspended in a homogeneous reactor. Improvements to continuous processes have subsequently been proposed by increasing the retention of microbial biomass in the bioreactor, notably by using cells immobilized on a substrate, and / or by using cell recycling with retention by means of filter membranes (Dos Santos Vieira et al., Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation, Bioresource Technology, 2019, 287,121425).

[0063] Carboxylic acids can be obtained from fermentation processes using different types of biomass.

[0064] One can cite in particular the conversion of carbohydrates (sugars, glucose, fructose, sucrose...) by fermentation which leads to acetic, succinic, lactic, itaconic, citric and gluconic acids as described by Lopez-Garzon CS (Lopez-Garzon, CS et al, Recovery of carboxylic acids produced by fermentation, Biotechnology Advances, 2014, 32, 873-904).

[0065] We can also cite Abrodo PA et al., Fatty acid composition of cider obtained either by traditional or controlled fermentation, Food Chemistry, 2005, 92, 183-187; and Serra, S. et al., Microbial Fermentation of the Water-Soluble Fraction of Brewers' Spent Grain for the Production of High-Value Fatty Acids, Fermentation, 2023, 9, 1008.

[0066] Carboxylic acids can also be obtained chemically from biomass. These can be carbohydrates derived from lignocellulosic biomass, including cellulose, glucose, fructose, or glycerol. The various routes for producing acids from biomass are well described by Deng W. et al., Production of organic acids from biomass resources, Current Opinion in Green and Sustainable Chemistry, 2016, 2, 54-58; and Li S. et al., Catalytic transformation of cellulose and its derivatives into functionalized organic acids, ChemSusChem, 2018, 11(13), 1995-2028; and Wang M. et al., Sustainable productions of organic acids and their derivatives from biomass via selective oxidation cleavage of CC bond, ACS Catalysis, 2018, 8(3), 2129-2165.

[0067] We can also cite in particular the oxidation of cellulose according to Wang F. et al., One-pot hydrothermal conversion of cellulose into organic acids with CuO as an oxidant, Industrial & Engineering Chemistry Research, 2014, 53(19), 7939-7946; and Jiang, Z. et al, Metal-oxide-catalyzed efficient conversion of cellulose to oxalic acid in alkaline solution under low oxygen pressure, ACS Sustainable Chemistry & Engineering, 2016, 4(1), 305-311.

[0068] One can cite the case of the oxidation of glucose, as for example according to Tang Z. et al., Transformation of cellulose and its derived carbohydrates into formic and lactic acids catalyzedby vanadyl cations, ChemSusChem, 2014, 7(6), 1557-1567.

[0069] We can also cite the case of the oxidation of glycerol, as described in patent application WO2014199256, which leads to oxalic acid, formic acid and alpha-hydroxy acids such as lactic acid, glycolic acid, glyceric acid and tartronic acid.

[0070] Carboxylic acids can also be obtained by hydrolysis or saponification of vegetable or animal oils according to a process described by BANCOURT, H., Saponification, Tech. Ingé., 1991, J5810, 1-6 or SPITZ, L., Soap Technology for the 1990s, ed. SPITZ, L. AOCS Press, Champaign, Illinois. 1991, or SPITZ, L., Soaps and Detergents: A Theoretical and Practical Review, ed. SPITZ, L. AOCS Press. 1996, or WOOLLATT, E., The Manufacture of Soaps, Other Detergents and Glycerin. Ellis Horwood Limited. 1985.

[0071] Step a) a reaction mixture is prepared in the form of a Pickering emulsion.

[0072] The invention aims to form an ester from a first reagent chosen from an alcohol or a carboxylic acid diluted in an aqueous solution, by adding to this aqueous solution a second reagent chosen from a carboxylic acid or an alcohol and an enzymatic catalyst. Since the ester is insoluble in the aqueous solution, the invention utilizes the immiscibility properties between the aqueous solution containing the first reactant and the ester produced to promote the shift of the reaction towards the formation of the ester by preparing a biphasic mixture, notably with the addition of an organic solvent, in the form of a Pickering emulsion.

[0073] Pickering emulsions are liquid-liquid dispersions (water / oil phase) stabilized by solid particles or aggregates of solid particles that accumulate at the interface between the two immiscible liquids and prevent coalescence. The direction of the emulsion (water-in-oil or oil-in-water) is determined by the preferential wettability of the solid particles towards one or the other phase. In fact, the liquid with the highest wetting power towards the solid particles will constitute the continuous phase of the emulsion, and the one with the lowest wetting power will constitute the dispersed phase. The direction of the emulsion will therefore depend on the nature of the solid particles, the organic extraction solvent, the water phase, and the reactants (alcohol and carboxylic acid). Step al) preparation of a biphasic mixture.

[0074] Said aqueous solution comprising said first reagent chosen from said alcohol or said carboxylic acid, at least one second reagent chosen from a carboxylic acid or an alcohol, at least one enzymatic catalyst, at least one organic extraction solvent and solid particles are brought into contact.

[0075] When all these species are brought into contact, a two-phase mixture comprising a water phase and an oil phase is formed. The different species distribute themselves between these two phases according to their affinity for one or the other phase. The exact composition of the different phases depends on the properties of each species present in the mixture. Aqueous solution#containing the first reactant:

[0076] Said aqueous solution comprises at least the first reagent chosen from said alcohol or said carboxylic acid.

[0077] According to one embodiment of the invention, the aqueous solution comprises the first reagent in the form of micelles. This is then referred to as a micellar aqueous solution. This is the case, for example, with micellar solutions obtained by hydrolysis or saponification of vegetable oils. The fatty acid molecules thus obtained form micelles in solution in water.

[0078] If the first reactant is an alcohol, its concentration in the aqueous solution is between 0.001 mol / L and 3 mol / L, preferably between 0.001 mol / L and 2 mol / L, preferably between 0.001 and 1 mol / L and preferably between 0.001 and 0.4 mol / L.

[0079] If the first reactant is a carboxylic acid, its concentration in the aqueous solution is between 0.001 mol / L and 3 mol / L, preferably between 0.001 mol / L and 2 mol / L.

[0080] Said alcohol and said carboxylic acid are described below. Second reagent#:

[0081] The second reagent is chosen from a carboxylic acid or an alcohol. Said alcohol and said carboxylic acid are described below. It may be soluble in the water phase or in the oil phase.

[0082] The molar ratio between the second reagent chosen from said carboxylic acid or said alcohol and the first reagent chosen from said alcohol or said carboxylic acid contained in the aqueous solution is greater than or equal to 1, preferably between 1 and 10 and most preferably between 1 and 5. According to a variant of the invention, said alcohol comprises several alcohol functional groups and / or said carboxylic acid comprises several carboxylic acid functional groups. In this case, the molar ratio between said alcohol and said carboxylic acid will be adjusted by a person skilled in the art according to the number of functional groups they wish to react.

[0083] When the first reactant in the aqueous solution is an alcohol, a carboxylic acid will be added as the second reactant to carry out the esterification reaction.

[0084] According to one embodiment of the invention, the second reactant is already present in the aqueous solution. This may be the case, for example, when the second reactant is formed at the same time as the first reactant. This may be the case in a fermentation process. Alcohol#:

[0085] Depending on the circumstances, said alcohol is either the first reactant contained in the aqueous solution or the second reactant added to said aqueous solution to carry out the esterification reaction.

[0086] Said alcohol according to the invention is any hydrocarbon compound comprising at least one alcohol functional group. The alcohol according to the invention preferably comprises a linear or non-linear, saturated or unsaturated, cyclic or non-cyclic, aromatic or non-aromatic carbon chain, comprising or not heteroatoms, preferably comprising 1 to 40 carbon atoms and possibly comprising other chemical functional groups. It may or may not be bio-based, derived or not from biomass such as cellulose, a sugar, a sterol, an alcohol formed by fermentation, or obtained or not by processing a bio-based product.

[0087] Without being exhaustive, the alcohol may be chosen from at least one of the following compounds: methanol, ethanol, 1-propanol, 2-propanol (or isopropanol), 1-butanol, 2-butanol, 2-methyl-1-propanol, tert-butanol, 3-hydroxybutanone (or acetoin), 1-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 1-heptanol (or n-heptanol), 2-octanol, 1-dodecanol (or lauryl alcohol), 1-tetradecanol (or myristyl alcohol), 1-hexadecanol (or cetyl alcohol), 1-octadecanol (or stearic alcohol), cis-9-octadecen-l-ol (or octadecenol or oleyl alcohol), 1,2-ethanediol (or ethylene glycol), 1,2-propanediol (or propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, glycerol, trimethylolproprane, pentaerythritol, sorbitol, xylitol, glucose, fructose, 5-hydroxymethylfurfural (5-HMF), furfuryl alcohol, a phenol, a polyphenol.

[0088] According to one embodiment of the invention, the molecule carries both a carboxylic acid function and an alcohol function and can be selected from lactic acid, glycolic acid, glyceric acid, tartronic acid, malic acid, citric acid, gluconic acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid, 5-hydroxypentanoic acid, glyceric acid, ascorbic acid, 2-keto-L-gulonic acid, 2-hydroxyisobutyric acid, and glucosaminic acid. In this case, the molecule can be said first reactant and / or said second reactant.

[0089] Alcohols can be used alone or in mixtures.

[0090] According to a particular embodiment of the invention, said alcohol is of bio-based origin.

[0091] According to a particular embodiment of the invention, said alcohol is derived from an aqueous fermentation juice. In this case, the alcohols are used purified or unpurified. Thus, the fermentation alcohols are diluted in water with a concentration that varies according to their formation process. Carboxylic acid#:

[0092] Depending on the circumstances, said carboxylic acid is either the first reactant contained in the aqueous solution or the second reactant added to said aqueous solution to carry out the esterification reaction.

[0093] Said carboxylic acid according to the invention is any hydrocarbon compound comprising at least one carboxylic acid functional group. The carboxylic acid according to the invention preferably comprises a linear or non-linear, saturated or unsaturated, cyclic or non-cyclic, aromatic or non-aromatic carbon chain, comprising or not heteroatoms, preferably comprising 1 to 40 carbon atoms and possibly comprising other chemical functional groups. It may or may not be bio-based, derived from biomass, from the processing of a vegetable or animal oil, from fermentation, particularly of sugars, obtained by pressing biomass, or obtained by processing a bio-based product, for example, by oxidation of an alcohol. It may be in its acidic (or protonated) form or in the form of a salt, for example, an alkali or alkaline earth metal salt or an ammonium salt.Without being exhaustive, the carboxylic acid can be chosen from at least one of the following compounds: formic acid, acetic acid, propanoic acid (or propionic acid), butanoic acid (or butyric acid), isobutyric acid, . pentanoic acid (or valeric acid), isovaleric acid, hexanoic acid (or caproic acid), n-heptanoic acid, myristic acid, levulinic acid, behenic acid, gadoleic acid, succinic acid, adipic acid, glutaric acid, citric acid, aconitic acid, itaconic acid, palmitic acid, oleic acid, fumaric acid, glycolic acid, glyceric acid, tartronic acid, stearic acid, palmitoleic acid, linoleic acid, alinolenic acid, erucic acid, petroselinic acid, gondoic acid, sterculic acid, dihydrosterculic acid, calendic acid, α-eleostearic acid, punicic acid, eicosapentaenoic acid, docosahexaenoic acid, 10-undecenoic acid, ricinoleic acid, malic acid, gluconic acid, 3-hydroxypropionic acid, glyceric acid, ascorbic acid, glucosaminic acid, pyruvic acid, lactic acid, glycolic acid,Glyceric acid, tartronic acid, malic acid, citric acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid, 5-hydroxypentanoic acid, glyceric acid, ascorbic acid, acrylic acid, methacrylic acid, 2,5-furandicarboxylic acid, 2-keto-L-gulonic acid, 2-hydroxyisobutyric acid, benzoic acid, and glucosamine.

[0094] According to one embodiment of the invention, the molecule carries both a carboxylic acid function and an alcohol function and can be selected from lactic acid, glycolic acid, glyceric acid, tartronic acid, malic acid, citric acid, gluconic acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid, 5-hydroxypentanoic acid, glyceric acid, ascorbic acid, 2-keto-L-gulonic acid, 2-hydroxyisobutyric acid, and glucosaminic acid. In this case, the molecule can be said first reactant and / or said second reactant.

[0095] According to a particular embodiment of the invention, said carboxylic acid is of bio-based origin. Solid particles

[0096] The solid particles can be hydrophilic, hydrophobic or amphiphilic. Preferably the solid particles are amphiphilic.

[0097] They can be modified to change their surface properties (in particular to modify their wettability). They can be of a single type, or be used in a mixture of several types of solid particles (in terms of size, shape and wettability).

[0098] Optionally, at least one surfactant may be added to the solid particles. This surfactant (or each of them if a mixture of surfactants is used) may be anionic, cationic, non-ionic, or amphoteric.

[0099] According to the invention, the solid particles can thus be chosen from: solid silica particles, preferably at least partially functionalized by hydrophobic hydrocarbon groups, solid clay particles, preferably at least partially modified with organic or amphiphilic molecules, magnetic particles, in particular Fe3O4, carbon nanotubes, solid particles of graphene oxides, solid particles of synthetic polymers, such as polyethylene glycol (PEG), polystyrene (PS), polylactic acid (PLA), polycaprolactone (PCL), or solid latex particles, solid particles of material of natural origin preferably selected from hydroxyapatite, chitosan, cyclodextrin, dextran, solid particles in the form of cellulose nanocrystals or nanofibers, solid particles of biological material, in particular food grade, preferably selected from starch, zein, soy protein, bacteria and yeasts.

[0100] The size can vary enormously, from a few nanometers to a few tens of microns. The size obviously depends on the morphology of the solid particles involved. It is generally determined by scanning and transmission electron microscopy. It is easy to define for spherical solid particles (diameter), and more difficult for solid particles whose shape deviates from sphericity (plates, rods, ellipsoids, needles, etc.). In these cases, two characteristic sizes are generally distinguished: the smallest and the longest. Another difficulty is related to the spontaneous formation of aggregates between the elementary solid particles. A distinction is then made between the size of the elementary solid particles and the size of the aggregates. For example, the commercial silica Aerosil R972 is a mixture of elementary solid particles between 5 nm and 50 nm with aggregates of average size on the order of 250 nm.

[0101] In a particular embodiment of the invention, the solid particles are nanometric, with an average size between 1 nm and 500 nm, preferably between 5 nm and 300 nm.

[0102] The content of solid particles relative to the weight of the biphasic reaction mixture obtained at the end of step a) is between 0.1% wt to 10% wt, in particular between 1% wt to 5% wt, and preferably between 0.5% wt and 2% wt of solid particles relative to the weight of said biphasic reaction mixture obtained at the end of step a).

[0103] The ratio between the largest dimension of the droplets and the largest dimension of the solid particles is preferably at least 100. (The largest dimension is understood to be the diameter when the solid particles are substantially spherical). They are located at the interface of the water / oil emulsion droplets. The enzymatic catalyst

[0104] The enzymatic catalyst is chosen from lipases of animal, microbial or plant origin.

[0105] Different types of lipases can be used according to the invention. Without this being exhaustive, we will cite the lipases produced by Humicola lanuginosa, Rhizopus delemar, Geotrichum candidum, Rhizomucor miehei (Mucor miehei), Pseudomonas glumae, Candida rugosa (C. cylindraceae), Candida antarctica, Chromobacterium viscosum, Rhizopus arrhizus, Yarrowia lipolytica, Pseudomonas, Hansenula, Bacillus, Aspergillus, wheat germ, horse or bovine pancreas.

[0106] Preferably, the enzymatic catalyst is Candida antarctica lipase B, Candida rugosa lipase, or Rhizomucor miehei lipase. Preferably, Candida antarctica lipase B.

[0107] The enzymes may be commercially available or manufactured using techniques known to those skilled in the art. They are presented either as a dilute solution or immobilized by grafting or adsorption onto solid particles to facilitate their recovery. Those skilled in the art will adjust the quantity of enzyme according to its nature, reactivity, and dilution ratio if the enzyme is in solution, or the amount of immobilized enzyme if the enzyme is supported on solid particles.

[0108] According to one embodiment of the invention, the enzyme is immobilized on the solid particles, which makes it easy to recover the enzyme by filtration and reuse it (Yin, Chengmei, et al. "Pickering emulsion biocatalysis: Bridging interfacial design with enzymatic reactions." Biotechnology Advances (2024): 108338).

[0109] The enzyme can be immobilized by any method known to those skilled in the art. Classically, enzyme immobilization can be physical (adsorption, trapping) or chemical (chemical grafting).

[0110] In the so-called physical method, there can be different types of interaction between the enzyme and the solid particle: hydrogen bonds, electrostatic forces, or hydrophobic interactions. The enzyme is immobilized by simply bringing it into contact with the solid particle. Preferably, the solid particle is rich in hydrophobic functions to immobilize the enzyme.

[0111] In the so-called chemical method, a chemical bond is formed between the enzyme and the solid particle. To achieve this, the surface of the solid particles can be modified by bifunctional agents that bridge the enzyme and the solid particle by reacting on one side with the enzyme and on the other with the solid particle. The bifunctional agents can be any compound well known to those skilled in the art, such as epichlorohydrin, glutaraldehyde, glyoxal, paraformaldehyde, carbodiimide, or ethylenediamine. The bifunctional agents can react with the chemical functions of the enzyme, such as a alcohol, thiol, or amine group. The most common method is to react an amine group of the enzyme. In this case, it is common to also introduce an amine group onto the surface of the solid particle and to use glutaraldehyde, which will create a bridge between an amine group of the enzyme and an amine group of the solid particle.

[0112] According to a particular embodiment of the invention, the solid particles on which the enzyme is immobilized are amphiphilic solid particles, that is to say, comprising on their surface at least one hydrophilic function and at least one hydrophobic function. Organic extraction solvent:

[0113] The organic extraction solvent constitutes at least one of the compounds in the oil phase of the emulsion. It allows the extraction of the ester produced by the esterification reaction.

[0114] The organic extraction solvent can be any liquid immiscible with the aqueous solution.

[0115] A person skilled in the art may preferentially choose an organic solvent with a high partition coefficient for the ester produced and not exhibiting toxicity to the enzyme.

[0116] In one or more particular embodiments of the invention, the organic solvent can be chosen from vegetable or animal oils, fatty acid esters of natural or non-natural origin, ethers, alkyl glycerol ethers, glycol ethers and hydrocarbons or mixtures of hydrocarbons, branched or unbranched, aromatic or non-aromatic, which may contain other compounds (for example in the case of petroleum cuts or any mixture of hydrocarbons from petroleum refining).

[0117] Without being exhaustive, the organic solvent may be chosen from at least one of the following compounds: hexane, heptane, octane, decane, dodecane, hexadecane, cyclohexane, methylcyclohexane, toluene, paraxylene, metaxylene, orthoxylene, ethylbenzene, limonene, cyclopentyl methyl ether, diphenyl ether, methyl soyate, methyl or ethyl esters of rapeseed oil, palm oil, jatropha oil, olive oil, sesame oil, peanut oil, corn oil, poppy seed oil, safflower oil, soybean oil, sunflower seed oil, used oils or animal fats.

[0118] In one or more particular embodiments of the invention, the organic solvent may be the same compound as the product of the esterification reaction according to the invention.

[0119] In one or more particular embodiments of the invention, the solvent is one of the reactants of the esterification reaction (either said alcohol or said carboxylic acid) if it is liquid under the conditions of implementation of the invention and is not miscible with the aqueous solution.

[0120] In one or more particular embodiments of the invention, the organic solvent has a higher boiling point than the ester formed in order to promote the separation of the ester from the organic extraction solvent by distillation.

[0121] In one or more particular embodiments of the invention, the organic solvent has a lower boiling point than the ester formed in order to promote the separation of the solvent by distillation and recovery of the ester in the distillation residue.

[0122] In one or more particular embodiments of the invention, the organic solvent is chosen to be used in a mixture with the ester formed according to the invention, thus not requiring any further separation step of the ester and the organic solvent. The phases present at stage a)

[0123] At least said aqueous solution comprising said first reagent chosen from said alcohol or said carboxylic acid, said second reagent chosen from a carboxylic acid or an alcohol, said enzymatic catalyst, said organic extraction solvent, solid particles are brought into contact.

[0124] When all these species are brought into contact, a two-phase mixture comprising at least one water phase and one oil phase is formed. The different species distribute themselves between these two phases according to their affinity for one or the other of the phases.

[0125] The exact composition of the different phases depends on the properties of each species present in the mixture and evolves during the process.

[0126] After contacting all the species, the water phase comprises at least water and at least a fraction of the first reagent chosen from said alcohol or said carboxylic acid. Depending on the affinity of the first reagent initially in the aqueous solution for the oil phase, a portion may dissolve in the oil phase upon contact with the oil phase. The water phase comprises between 40% and 100% by mass of said first reagent, and the oil phase comprises between 0% and 60% by mass of said first reagent. It is understood that the mass fraction of the first reagent dissolved in the water phase and the mass fraction of the first reagent dissolved in the oil phase represent 100% of the mass of the first reagent.

[0127] Preferably, said first reagent has a greater affinity for the water phase. The water phase comprises a mass fraction greater than or equal to 50% of said first reagent. The oil phase comprises a mass fraction less than 50% of said first reagent.

[0128] Depending on the affinity of the second reactant for the water phase, the water phase also comprises a mass fraction of said second reactant between 0 and 100% relative to the total mass of the second reactant chosen from said carboxylic acid or The alcohol and the oil phase comprise between 0 and 100% of the second reactant relative to the total mass of the second reactant. It is understood that the mass fraction of the second reactant dissolved in the water phase and the mass fraction of the second reactant dissolved in the oil phase represent 100% of the total mass of the second reactant.

[0129] The oil phase comprises at least the organic extraction solvent.

[0130] During the esterification reaction, the composition of the oil phase changes, in particular the ester produced by the esterification reaction passes into the oil phase.

[0131] At the end of the esterification reaction (step a), said water phase has become depleted in first reactant and the oil phase has become enriched in ester.

[0132] The solid particles are at the interface between the two phases.

[0133] If the enzymatic catalyst is not immobilized on the solid particles, the water phase also contains the enzymatic catalyst.

[0134] The volume fraction of the water phase in the two-phase reaction mixture prepared in step a1) is between 10% by volume and 90% by volume, preferably between 40% by volume and 60% by volume of the water phase relative to the total volume of said reaction mixture. This volume fraction changes during the process.

[0135] The pH of the water phase depends on the nature of the enzymatic catalyst, the solid particles, and the nature of the reagents and extraction solvent. Those skilled in the art can adjust the pH by acidifying or alkalizing the medium to ensure optimal enzyme function. Preferably, the pH is less than 7 or greater than 8, preferably less than 7.

[0136] The process according to the invention can be implemented in several embodiments depending on the method of obtaining the reagents and their hydrophilic or hydrophobic character.

[0137] According to a first embodiment of the invention, solid particles, an enzymatic catalyst, and an oil phase comprising an organic extraction solvent are brought into contact with a water phase comprising an alcohol (first reactant) in aqueous solution, to which a carboxylic acid (second reactant) is added, having a greater affinity for the water phase than for the oil phase. In this case, the mass fraction of the carboxylic acid in the water phase is greater than 50% relative to the total mass of carboxylic acid. The mass fraction of the carboxylic acid in the oil phase is less than 50% relative to the total mass of carboxylic acid.

[0138] According to a second embodiment of the invention, solid particles, an enzymatic catalyst and an oil phase comprising an organic extraction solvent are brought into the presence of a water phase, comprising a carboxylic acid (first reactant) in aqueous solution, and to which is added an alcohol (second reactant) having a greater affinity for the water phase than for the oil phase.

[0139] In this case, the mass fraction of alcohol in the water phase is greater than 50% relative to the total mass of alcohol. The mass fraction of alcohol in the oil phase is less than 50% relative to the total mass of alcohol.

[0140] According to a third embodiment of the invention, solid particles, an enzymatic catalyst, and an oil phase comprising an organic extraction solvent are brought into contact with a water phase comprising an alcohol (first reactant) in aqueous solution. A carboxylic acid (second reactant) having a greater affinity for the oil phase than for the water phase is added. In this case, the mass fraction of the carboxylic acid in the oil phase is greater than 50% relative to the total mass of carboxylic acid. The mass fraction of the carboxylic acid in the water phase is less than 50% relative to the total mass of carboxylic acid. In this embodiment of the invention, the carboxylic acid is preferably dissolved in the oil phase before the two phases are brought into contact.

[0141] According to a fourth embodiment of the invention, solid particles, an enzymatic catalyst, and an oil phase comprising an organic extraction solvent are brought into contact with a water phase comprising a carboxylic acid (first reactant) in aqueous solution. An alcohol (second reactant) having a greater affinity for the oil phase than for the water phase is added. In this case, the mass fraction of the alcohol in the oil phase is greater than 50% relative to the total mass of alcohol. The mass fraction of the alcohol in the water phase is less than 50% relative to the total mass of alcohol. In this embodiment of the invention, the alcohol is preferably dissolved in the oil phase before the two phases are brought into contact. Step a2) formation of a Pickering emulsion.

[0142] Said biphasic mixture obtained in step a1) is emulsified to form a reaction mixture in the form of an oil-in-water or water-in-oil Pickering emulsion; said reaction mixture comprising at least droplets stabilized by said solid particles in said water phase or said oil phase.

[0143] Emulsification transforms the biphasic mixture obtained in step a1a) into droplets dispersed in the continuous phase, forming a Pickering emulsion. The largest droplet size is between 1 pm and 1000 pm, preferably between 1 pm and 140 pm, preferably between 2 pm and 100 pm, and in particular between 10 pm and 50 pm. It should be noted that the droplet size is measured by optical microscopy (in particular using an Olympus BX51 with AnalySIS software for image analysis).

[0144] The emulsification of the two-phase medium is carried out by any type of system supplying energy to generate the emulsification known to those skilled in the art. Without this To be exhaustive, examples include rotor-stator type tools, propeller agitators, static mixers, colloid mills, membrane systems, ultrasonic stirring, and microfluidic systems. The principle of these mixers is described, for example, in the Techniques de l'Ingénieur dossier J2153V1: Emulsification Processes - Equipment Techniques, by M. Poux and JP Canselier, 10 / 06 / 2004. A microfluidic system is described, for example, in the Techniques de l'Ingénieur dossier J8010V1: Microfluidics and Formulation - Emulsions and Complex Colloidal Systems, by V. Nardello-Rataj and JF Ontiveros, 10 / 05 / 2019.

[0145] In a particular embodiment of the invention, emulsification is carried out using a rotor-stator system of the type of the system marketed under the name Ultra-Turrax.

[0146] The direction of the emulsion depends on the nature of the particles, the solvent, the water phase, and the reactants (alcohol and carboxylic acid).

[0147] In a particular embodiment of the invention, the Pickering emulsion is a water-in-oil emulsion. The droplets, which comprise the water phase including at least water and at least a fraction of the first reagent selected from said alcohol or said carboxylic acid, are stabilized by the solid particles in the oil phase including at least the extraction solvent and the ester formed by the esterification reaction. The second reagent is partitioned between the oil phase and the water phase according to its affinity for these phases. The enzymatic catalyst is either in the water phase or immobilized on the solid particles, depending on its nature.

[0148] In another particular embodiment of the invention, the Pickering emulsion is an oil-in-water emulsion. The droplets, which comprise the oil phase including at least the extraction solvent and the ester formed by the esterification reaction, are stabilized by solid particles in the water phase, which includes at least water and at least a fraction of the first reagent selected from said alcohol or said carboxylic acid. The second reagent is distributed between the oil and water phases according to its affinity for these phases. The enzymatic catalyst is either in the water phase or immobilized on the solid particles, depending on its nature. Esterification reaction

[0149] The esterification reaction of step a) is carried out at a temperature between 10°C and 90°C to form said ester. Preferably, the temperature is between 20°C and 60°C, most preferably between 25°C and 50°C, and most preferably between 35°C and 45°C.

[0150] The pressure is between atmospheric pressure and 0.3 MPa absolute.

[0151] The esterification reaction is written:

[0152] R1-OH+ R2-COOH ~ R2-COO-R1 + H2O

[0153] The reaction is in equilibrium and releases water. The ester, which is sparingly soluble in water, is extracted into the oil phase, while the water formed is extracted into the water phase. The removal of one of the reaction products by transfer from one phase to another shifts the reaction towards the formation of ester.

[0154] At the end of step a) of esterification, said water phase has become depleted in first reactant and the oil phase has become enriched in ester.

[0155] A person skilled in the art may use different implementations of this reaction. The reaction may be carried out with or without agitation.

[0156] In a particular embodiment of the invention the reaction is conducted in a closed system (or batch).

[0157] In another particular embodiment of the invention, the reaction is conducted in an open (or continuous) system with continuous withdrawal of a fraction of the oil phase from the water-in-oil Pickering emulsion. The withdrawal of a fraction of the oil phase is sent to an ester separation step from the oil phase (step b2), and then the withdrawal of the ester-depleted oil phase is returned to step a).

[0158] In another particular embodiment of the invention, the reaction is carried out in an open (or continuous) system with additions of aqueous solution containing the first reagent selected from said alcohol or said carboxylic acid, to the Pickering oil-in-water emulsion. According to this embodiment of the invention, a portion of the water phase can be withdrawn to control the ratio between the water and oil phases. According to this embodiment of the invention, an enzymatic catalyst can be added. This embodiment of the invention can be implemented in combination with the process for producing said first reagent selected from said alcohol or said carboxylic acid in the aqueous solution (step a'), with or without withdrawal and reinjection of the water phase depleted of the first reagent in the production step a') of said first reagent.This embodiment of the invention is particularly suited to the use of an enzymatic catalyst immobilized on solid particles.

[0159] In one or more particular embodiments of the invention, additions of a second reagent chosen from said alcohol or said carboxylic acid can be made, continuously or not, preferably via the continuous phase.

[0160] The duration of the reaction in closed mode or the liquid flow rate in open mode depends on the operating conditions and the reactivity of the enzymatic catalyst. It will be adjusted by a person skilled in the art to obtain the desired ester yield in a desired time.

[0161] In one or more particular embodiments of the invention, the optional step a') of producing said first reagent chosen from said alcohol or said carboxylic acid, may be carried out in combination with step a).

[0162] This implementation has the advantage of promoting the production of said alcohol or carboxylic acid by extracting it as it is produced. This is particularly true when said alcohol or carboxylic acid is produced by fermentation or by an equilibrium reaction such as, for example, the hydrolysis of an ester, such as the esters contained in vegetable and animal oils. Indeed, it is known to those skilled in the art that fermentation slows down as the content of fermentation products in the medium increases in the case of alcohol production (Lim, J. et al., Mathematical Modeling of Acetone-Butanol-Ethanol Fermentation with Simultaneous Utilization of Glucose and Xylose by Recombinant Clostridium acetobutylicum, Energy Fuels, 2019, 33, 8620-8631) and in the case of carboxylic acid production (Joglekar, HG et al.(Comparative assessment of downstream processing options for lactic acid, Separation and Purification Technology, 2006, 52(1), 1-17). Therefore, their extraction as they are produced prevents slowing down fermentation. Similarly, it is known to those skilled in the art that extracting a product from an equilibrium reaction, such as the hydrolysis of an ester, shifts the equilibrium towards the formation of that product. Combining step a') with steps a) and b) can be carried out in various ways, such as those described in US patents 2014 / 0178529 A1, US 9517985 B2, US 2010 / 0143993 A1, and US 8614077 B2, as well as by Woodley JM et al. Future directions for in-situ product removal (ISPR), J Chem Technol Biotechnol., 2008, 83,121-123. .

[0163] Step b) Recovery of the ester formed in the oil phase

[0164] The step of recovering the ester formed in the oil phase advantageously takes place in two steps:

[0165] -Step bl) Separation of said oil phase from said water phase;

[0166] -Step b2) Separation of the ester in said oil phase;

[0167] Step bl) Separation of said oil phase from said water phase;

[0168] The two phases, oil and water, are separated. To do this, the Pickering emulsion is broken to separate the two liquid phases. The Pickering emulsion can be broken using various mechanical or physicochemical methods. The principles used for destabilizing these systems are very well described in the journal article by C. P. Whitby and E. J. Wanless (2016), "Controlling Pickering Emulsion Destabilization: A Route to Fabricating New Materials by Phase Inversion," Materials, 9, 626; doi:10.3390 / ma9080626. It is possible to break the emulsion by applying an external force that causes the interfacial film to rupture and the droplets to coalesce, such as a shear, compression, or centrifugal force. Another method is to add a chemical that, by transferring from the continuous phase to the dispersed phase, destabilizes the interfacial film formed by the particles. This causes the droplets to coalesce, thus breaking the emulsion. In the specific case of magnetic particles, a magnetic field can be used to destabilize the emulsion. It is also possible to break the emulsion by modifying the wettability of the particles to detach them from the interface and carry them into the continuous or dispersed phase. This can be done by adding a surfactant, which will adsorb onto the particles and change their wettability, or by modifying the pH in the case of pH-sensitive particles (such as proteins), or by modifying the temperature in the case of heat-sensitive particles. All the different mechanisms described above can also be combined (addition of a surfactant and shearing, modification of pH and centrifugation; these two examples are not exhaustive).

[0169] In a particular embodiment of the invention, the solid particles are removed from the reaction mixture using any solid / liquid separation technique such as filtration, centrifugation or a combination of separation methods.

[0170] Once the emulsion has been broken, the two phases can be recovered separately, for example in a decanter.

[0171] According to one embodiment of the invention, the oil phase is washed with salt water to extract any compounds other than the ester, thereby facilitating the separation of the ester from the oil phase and its constituents. The nature and salt concentration of said salt water will be adjusted by those skilled in the art to optimize the efficiency and selectivity of this washing. For example, saturated alkali or alkaline earth metal chlorides may be chosen.

[0172] According to one embodiment of the invention, any compounds in the oil phase other than said ester are adsorbed onto a solid by contacting the oil phase with that solid. Those skilled in the art will choose the adsorbent solid according to the nature of said compounds to be extracted.

[0173] According to one embodiment of the invention, the water phase is returned to step a).

[0174] According to one embodiment of the invention, the water phase is returned to step a').

[0175] Step b2) Separation of the ester in said oil phase;

[0176] The ester is then separated from the oil phase recovered in step bl) to recover said ester and an oil phase depleted in ester. Said oil phase depleted comprises at least the organic solvent.

[0177] Any method known to those skilled in the art can then be used to separate the ester dissolved in the oil phase. The ester can be separated by liquid-liquid extraction, precipitation, membrane separation, or distillation. Preferably, the ester is separated by distillation.

[0178] According to one embodiment of the invention, the organic solvent has a higher boiling point than the ester formed in order to promote the separation of the ester from the organic extraction solvent by distillation.

[0179] According to one embodiment of the invention, the organic solvent has a lower boiling point than the ester formed in order to promote the separation of the solvent by distillation and recovery of the ester in the distillation residue.

[0180] According to one embodiment of the invention, the organic solvent is chosen to be used in a mixture with the ester formed according to the invention, thus requiring no further separation step of the ester and the organic solvent.

[0181] According to one embodiment of the invention, the organic solvent is the same molecule as the ester formed according to the invention, thus requiring no further separation step of the ester and the organic solvent.

[0182] According to one embodiment of the invention, the ester-depleted oil phase is returned to step a). Examples

[0183] Examples 1 to 11 describe the esterification reaction between two reactants (alcohol and carboxylic acid) present in the water phase under different conditions. Examples 12 to 15 describe the esterification reaction between two reactants, one present in the water phase (alcohol) and the other in the oil phase (carboxylic acid). In all examples, the amount of ester formed is determined by analyzing a sample of the supernatant oil phase by gas chromatography on an Agilent 7890 instrument equipped with an HP-lms column and using hexadecane as an internal standard. The conversion rate of 1-butanol after one hour and six hours is given in Table 1. It is calculated by dividing the amount of ester formed by the initial amount of 1-butanol.

[0184] Example 1 (not in accordance with the invention): biphasic mixture without biocatalyst (no Pickering emulsion)

[0185] 600 mL of water containing 0.1 mol / L of 1-butanol and 0.1 mol / L of butyric acid and 600 mL of n-dodecane are stirred at 40°C at 500 rpm for 6 hours using a magnetic stir bar. The initial pH of the water phase is 2.7. 1-Butanol reacts with butyric acid to form an ester, butyl butyrate, which is extracted in the oil phase containing n-dodecane.

[0186] Example 2 (not in accordance with the invention): biphasic mixture with biocatalyst (no Pickering emulsion)

[0187] The protocol is the same as in Example 1 with the addition of 1.8 mL of the commercial Lipase B Candida antarctica (CaLB) solution reference L3170-50ML supplied by Sigma-Aldrich.

[0188] Example 3 (not in accordance with the invention): biphasic mixture with biocatalyst and with adjustment of the initial pH to 4 (no Pickering emulsion)

[0189] The protocol is the same as in example 2 with adjustment of the initial pH of the water phase to 4 by addition of potassium.

[0190] Example 4 (not in accordance with the invention): biphasic mixture with biocatalyst and with adjustment of the initial pH to 4.5 (no Pickering emulsion)

[0191] The protocol is the same as in example 2 with adjustment of the initial pH of the water phase to 4.5 by addition of potassium.

[0192] Example 5 (not in accordance with the invention): Pickering emulsion water-in-oil without biocatalyst

[0193] 10.5 g of Aerosil® R972 supplied by Evonik, 600 mL of water containing 0.1 mol / L of 1-Butanol, 0.1 mol / L butyric acid, and 600 mL of n-dodecane are emulsified using an Ultra-Turrax for 10 minutes at 13,500 rpm to form a Pickering emulsion. The droplet size is between 10 and 50 µm. The Pickering emulsion is heated to 40°C and stirred at 500 rpm for 6 hours using a magnetic stir bar. The initial pH of the water phase is 2.7. 1-Butanol reacts with butyric acid to form an ester, butyl butyrate, which is extracted in the oil phase containing n-dodecane.

[0194] Example 6 (according to the invention): Pickering water-in-oil emulsion with biocatalyst

[0195] 10.5 g of Aerosil® R972 supplied by Evonik, 600 mL of water containing 0.1 mol / L of 1- Butanol and 0.1 mol / L butyric acid, 1.8 mL of the commercial Candida antarctica Lipase B (CaLB) solution, reference L3170-50 mL, supplied by Sigma-Aldrich, and 600 mL of n-dodecane are emulsified using an Ultra-Turrax for 10 minutes at 13,500 rpm to form a Pickering emulsion. The droplet size is between 10 and 50 µm. The initial pH of the water phase is 2.7. 1-Butanol reacts with butyric acid to form an ester, butyl butyrate, which is extracted in the oil phase containing n-dodecane.

[0196] Example 7 (according to the invention): Pickering water-in-oil emulsion with biocatalyst and with initial pH adjustment to 4

[0197] The protocol is the same as in example 6 with adjustment of the initial pH of the water phase to 4 by addition of potassium.

[0198] Example 8 (according to the invention): Pickering water-in-oil emulsion with biocatalyst and with initial pH adjustment to 4.5

[0199] The protocol is the same as in example 6 with adjustment of the initial pH of the water phase to 4.5 by addition of potassium.

[0200] Example 9 (according to the invention): Pickering oil-in-water emulsion with biocatalyst and with initial pH adjustment to 4.5

[0201] 10.5 g of Aerosil® R816 supplied by Evonik, 600 mL of water containing 0.1 mol / L of 1- 1-Butanol and 0.1 mol / L butyric acid, 1.8 mL of the commercial Candida antarctica Lipase B (CaLB) solution, reference L3170-50 mL, supplied by Sigma-Aldrich, and 600 mL of n-dodecane are emulsified using an Ultra-Turrax for 10 minutes at 13,500 rpm to form a Pickering emulsion. The droplet size is between 10 and 40 µm. The initial pH of the water phase is adjusted to 4.5 by adding potassium hydroxide. 1-Butanol reacts with butyric acid to form an ester, butyl butyrate, which is extracted into the oil phase containing n-dodecane. To collect the oil phase and determine the amount of ester formed, the oil and water phases are separated by centrifugation at 5,000 rpm for 30 minutes.

[0202] Example 10 (not in accordance with the invention): biphasic mixture with biocatalyst, excess butyric acid and with adjustment of the initial pH to 4 (no Pickering emulsion)

[0203] The protocol is the same as in example 3, introducing 0.3 mol / L of butyric acid into the water phase instead of 0.1 mol / L.

[0204] Example 11 (according to the invention): Pickering water-in-oil emulsion with biocatalyst, excess butyric acid and with initial pH adjustment to 4

[0205] The protocol is the same as in example 7, introducing 0.3 mol / L of butyric acid into the water phase instead of 0.1 mol / L.

[0206] Example 12 (not in accordance with the invention): biphasic mixture containing hexanoic acid with biocatalyst (not Pickering emulsion)

[0207] 600 mL of water containing 0.1 mol / L of 1-butanol, 1.8 mL of the commercial solution Lipase B Candida antarctica (CaLB) reference L3170-50ML supplied by Sigma-Aldrich and 600 mL of n-dodecane containing 0.1 mol / L hexanoic acid are stirred at 40°C at 500 rpm for 6 hours using a magnetic stir bar. The initial pH of the water phase is 6. 1-Butanol reacts with hexanoic acid to form an ester, butyl hexanoate, which is extracted in the oil phase containing n-dodecane.

[0208] Example 13 (according to the invention): Pickering water-in-oil emulsion containing hexanoic acid with biocatalyst

[0209] 10.5 g of Aerosil® R972 supplied by Evonik, 600 mL of water containing 0.1 mol / L of 1-Butanol, 1.8 mL of the commercial Candida antarctica Lipase B (CaLB) solution, reference L3170-50ML, supplied by Sigma-Aldrich, and 600 mL of n-dodecane containing 0.1 mol / L hexanoic acid are emulsified using an Ultra-Turrax for 10 minutes at 13,500 rpm to form a Pickering emulsion. The droplet size is between 10 and 50 µm. The initial pH of the water phase is 6. 1-Butanol reacts with hexanoic acid to form an ester, butyl hexanoate, which is extracted in the oil phase containing n-dodecane.

[0210] Example 14 (not in accordance with the invention): biphasic mixture containing palmitic acid with biocatalyst (not Pickering emulsion)

[0211] 600 mL of water containing 0.1 mol / L of 1-butanol, 1.8 mL of the commercial solution Lipase B Candida antarctica (CaLB) reference L3170-50ML supplied by Sigma-Aldrich and 600 mL of n-dodecane containing 0.1 mol / L palmitic acid are stirred at 40°C at 500 rpm for 6 hours using a magnetic stir bar. The initial pH of the water phase is 6. 1-Butanol reacts with palmitic acid to form an ester, butyl palmitate, which is extracted in the oil phase containing n-dodecane.

[0212] Example 15 (according to the invention): Pickering water-in-oil emulsion containing palmitic acid with biocatalyst

[0213] 10.5 g of Aerosil® R972 supplied by Evonik, 600 mL of water containing 0.1 mol / L of 1-Butanol, 1.8 mL of the commercial Candida antarctica Lipase B (CaLB) solution, reference L3170-50ML, supplied by Sigma-Aldrich, and 600 mL of n-dodecane containing 0.1 mol / L palmitic acid are emulsified using an Ultra-Turrax for 10 minutes at 13,500 rpm, followed by Pickering emulsification. The droplet size is between 10 and 50 µm. The initial pH of the aqueous phase is 6. 1-Butanol reacts with palmitic acid to form an ester, butyl palmitate, which is extracted in the oil phase containing n-dodecane.

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[0215] Examples 1 to 11 describe the esterification reaction between two reactants present in the water phase under different conditions. Example 1 shows first of all that without the biocatalyst, there is no reaction between the alcohol and the carboxylic acid under the conditions of the study, even in the case of the Pickering emulsion (comparative example 5). Comparative examples 2, 3, and 4 show that in the presence of a In a stirred two-phase biocatalyst without a Pickering emulsion, the conversions of alcohol and carboxylic acid to ester are low after one hour of reaction. Conversely, Examples 6, 7, and 8 of the invention show ester conversion rates in water-in-oil Pickering emulsion after one hour that are significantly higher than those obtained in a two-phase medium (a gain of approximately a factor of 4) and are still higher after six hours. Examples 1 to 8 thus clearly demonstrate that the combination of a biocatalyst and a Pickering emulsion enables the fastest conversion kinetics of alcohol and carboxylic acid to ester for a given pH. These examples also show that performance increases as the pH becomes increasingly acidic within the studied range. Example 9 according to the invention confirms the maintenance of the advantage of the invention in the case of a Pickering oil-in-water emulsion.Example 11 according to the invention shows that an excess of carboxylic acid relative to the alcohol increases the conversion to ester and the kinetics, which is much higher than in comparative example 10 in stirred biphasic medium without Pickering emulsion.

[0216] Examples 13 and 15 according to the invention and comparative examples 12 and 14 employ carboxylic acids, which are introduced into the oil phase due to their significantly greater solubility in the oil phase than in the water phase. It is further demonstrated that the implementation according to the invention results in a considerable increase in ester conversion, as evidenced by the values ​​obtained after one hour of reaction. This confirms that the invention works equally well whether both reactants are in the water phase or whether one reactant is in the water phase and the other in the oil phase.

[0217] The examples also show that conversions to esters can be excellent for pH values ​​below 7.

Claims

Demands

1. A process for manufacturing an ester from a first reagent selected from an alcohol or a carboxylic acid in aqueous solution comprising the following steps: a) an esterification reaction is carried out on a reaction mixture in the form of an oil-in-water or water-in-oil Pickering emulsion to form an ester in the oil phase, said reaction mixture being obtained according to the following steps: a1) a two-phase mixture is formed comprising at least a water phase and an oil phase, by contacting an aqueous solution comprising said first reagent, at least a second reagent selected from a carboxylic acid or an alcohol, at least one enzymatic catalyst, at least one organic extraction solvent and solid particles; a2) said two-phase mixture obtained in step a1) is emulsified to form a reaction mixture in the form of an oil-in-water or water-in-oil Pickering emulsion;said reaction mixture comprising: -either droplets of said oil phase stabilized by said solid particles in said water phase; -or droplets of said water phase stabilized by said solid particles in said oil phase; b) the ester formed in step a) is recovered in the oil phase.

2. A process according to claim 1, wherein the first reactant contained in said aqueous solution is an alcohol, and the second reactant is a carboxylic acid.

3. A process according to claim 1, wherein the first reactant contained in said aqueous solution is a carboxylic acid and the second reactant is an alcohol.

4. A process according to any one of the preceding claims, wherein the concentration of first reactant in said aqueous solution is between 0.001 mol / L and 0.4 mol / L when said first reactant is an alcohol, and between 0.001 mol / L and 2 mol / L when said first reactant is a carboxylic acid.

5. A method according to any one of the preceding claims, wherein the molar ratio between said second reactant and said first reactant is between 1 and 10.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15. A process according to any one of the preceding claims, wherein said first reagent selected from said alcohol or said carboxylic acid is of bio-based origin. A method according to any one of the preceding claims, wherein the enzymatic catalyst added in step a1) is selected from lipases of microbial or plant origin. A method according to any one of the preceding claims, wherein the enzymatic catalyst added in step a1a) is selected from lipase B of Candida antarctica, lipase of Candida rugosa, or lipase of Rhizomucor miehei. A process according to any one of the preceding claims, wherein the pH of the water phase is less than 7. A method according to any one of the preceding claims, wherein the solid particles added in step a1a) are selected from particles of silica, clay, or natural or synthetic polymers. A method according to any one of the preceding claims, wherein the droplet size of the Pickering emulsion obtained at the end of step a) is between 1 pm and 140 pm. A process according to any one of the preceding claims, wherein the temperature of the esterification reaction in step a) is between 10°C and 90°C. A process according to any one of the preceding claims, wherein the mass concentration of solid particles added in step a1) is between 0.1% weight and 10% weight relative to the total weight of said two-phase mixture. A process according to claim 1, wherein the reaction mixture obtained at the end of step a) is a Pickering water-in-oil emulsion. A process according to any one of the preceding claims, wherein a step a') of producing said first reagent selected from said alcohol or said carboxylic acid in aqueous solution is carried out in combination with step a).