Continuous flow process for the synthesis of polyol esters

Abstract

The present invention relates to a process for synthesizing a final composition comprising at least one polyol ester and a carboxylic acid using an exothermic acylation reaction from an initial mixture comprising at least two liquid and immiscible starting reagents which are a polyol and an acid anhydride, characterized in that it is carried out in continuous flow in a mechanical mixer comprising at least one mixing chamber, the process comprising the following successive steps: (A) the separate introduction and at room temperature of said at least two starting reagents into the mixer to form said initial mixture, (B) the mixing in said mechanical mixer of said initial mixture for a residence time of less than or equal to 1 hour; (C) the recovery at the outlet of the mixer of said final composition. Figure for abstract: no Figure

Description

Title of the invention: Process for the synthesis of polyol esters in continuous flow Technical field of the invention

[0001] The present invention relates to a process for the synthesis of polyol esters. In particular, the present invention relates to a process for the manufacture of polyol esters, carried out within a continuous flow mechanical mixer, such as for example a three-dimensional mill with or without microbeads, of an initial mixture comprising at least two liquid reactants, generally immiscible, which are a polyol and an organic acid anhydride. State of the art

[0002] As is known, polyol esters can be used in many fields.

[0003] For example, triacetin is a triester of glycerol and acetic acid and can be used both in the food field as a food additive for its humectant property (number E1518) or in fuels as an adjuvant to reduce knocking and improve resistance to cold. It can also be used in the field of medicines as an excipient.

[0004] Currently, triacetin is generally synthesized on an industrial scale by exothermic acylation of glycerol by acetic anhydride using basic or acid catalysis under batch conditions. Leonardo N. Silva's publication "Catalytic acetylation of glycerol with acetic anhydride" from Elsevier in March 2010 describes the synthesis of glycerol acetylation with acetic anhydride using different solid catalysts in batch mode. The results of this publication indicate that at 60°C, zeolite beta and montmorillonite K-10 showed 100% triacetin selectivity within 20 minutes, with a molar ratio of 4:1. Amberlyst-15 acid resin produced 100% triacetin after 80 minutes, while niobium phosphate gave diacetin and triacetin with 53% and 47% selectivity, respectively.Thus, this publication demonstrates that all catalysts were more selective for triacetin than the uncatalyzed reaction. However, the exothermicity of the reaction makes its solvent-free batch synthesis dangerous on an industrial scale.

[0005] Triacetin can also be obtained by a mixture of acetic acid / acetic anhydride at high temperature in a continuous flow. US 4,381,407 describes a process for the manufacture of triacetin by reacting glycerol with acetic acid and acetic anhydride at high temperature and optionally in the presence of catalysts. This process is characterized in that it reacts the reaction partners together in a continuous countercurrent mode of operation, by passing liquid glycerol into an esterification column comprising a multiplicity of trays, under a pressure of 0.2 to 30 bar and at a temperature of 100 to 250°C, in the opposite direction to an ascending stream of superheated acetic acid vapor, the residence time of the liquid reaction mixture being at least one hour, and by adding to the descending reaction mixture, when it reaches an OH number of less than 600, on the appropriate tray of the reaction column or in a correspondingly adapted post-reactor, acetic anhydride in a quantity sufficient for the water dissolved at this point in the liquid reaction phase to be converted quantitatively into acetic acid and for the mono- and diacetin present to be able to react quantitatively into triacetin.

[0006] The limitations of this continuous flow process using acetic anhydride / self-generated acetic acid lie in its complicated and sensitive implementation in order to control the synthesis in the different zones of the process (zone 1 of first acetylation by acetic acid at high temperature, zone 2 of complete acetylation by acetic anhydride generating acetic acid at high temperature, zone 3 of separation of triacetin and acetic acid returned to zone 1). In addition, the entire device constitutes a large volume and must be maintained at high temperature. The patent describing the invention dates from 1980 and does not provide information on actual experimental implementation and analyses.

[0007] Thus, due to the immiscible nature of the glycerol / acetic anhydride mixture, the implementation of a simple and economical continuous process remains difficult.

[0008] There is therefore a need in the state of the art for new processes for manufacturing polyol esters in continuous mode, preferably industrially exploitable, and which are alternatives to or improved compared to known processes.

[0009] The object of the present invention is therefore to provide a process for the continuous manufacture of polyol esters, which at least partially avoids the aforementioned drawbacks. In particular, the object of the present invention is to provide a new process for the continuous manufacture of polyol esters, which is industrially exploitable (i.e.: good productivity), while not requiring excessive heating and / or an excessively long reaction time. Presentation of the invention

[0010] To this end, the present invention provides a process for synthesizing a final composition comprising at least one polyol ester and a carboxylic acid implementing an exothermic acylation reaction from an initial mixture comprising at least two liquid starting reagents, preferably immiscible, which are a polyol and an acid anhydride, characterized in that it is carried out in continuous flow in a mechanical mixer comprising at least one mixing chamber (such as a mechanical mixing chamber), the method comprising the following successive steps:

[0011] (A) the separate introduction and at room temperature of said at least two reagents starting, in the mixer to form said initial mixture,

[0012] (B) mixing in said mechanical mixer said initial mixture for a time stay of less than or equal to 1 hour;

[0013] (C) the recovery at the outlet of the mixer of said final composition.

[0014] As will be demonstrated in the experimental tests below, the process of the invention using a particular mechanical mixer, such as a three-dimensional mill with or without microbeads, makes it possible to continuously manufacture a polyol ester, such as triacetin, with a yield generally greater than or equal to 80% and in particular greater than or equal to 99% and this in a very short period of time.

[0015] The method according to the invention also has the advantages of having a very low cost price (the raw materials used are in fact widely available, non-polluting and inexpensive) and of having both excellent reproducibility and excellent productivity, which further sets it apart from the methods described in the prior arts.

[0016] Furthermore, despite the numerous researches conducted on the synthesis of polyol esters, such as triacetin, none have suggested the above-mentioned process and in particular a step of intense mixing in a mechanical mixer from the starting reactants which are liquid and, preferably, immiscible.

[0017] Other non-limiting and advantageous characteristics of the process for synthesizing polyol esters in accordance with the invention, taken individually or in all technically possible combinations, are as follows:

[0018] - the polyol is chosen from the group consisting of: glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol and other liquid glycerol oligomers or a mixture thereof;

[0019] - the acid anhydride corresponds to the following general formula: smb. [Chem. 1] RR

[0020] where R is chosen from: a linear or branched alkyl group comprising from 1 to 17 carbon atoms, preferably R is chosen from a methyl, pentyl or heptyl group and typically, R is a methyl group; - the molar ratio of acid anhydride to the number of hydroxyl groups within the polyol in the initial mixture is less than or equal to 10, preferably less than or equal to 6 and in particular less than or equal to 1.1, without ever being less than 1; during the mixing step (B), the residence time of the initial mixture within the mechanical mixer is less than or equal to 50 minutes, in particular ranging from 30 seconds to 40 minutes and typically ranging from 1 minute to 30 minutes; said at least one acid anhydride is introduced into said mixer at a flow rate of at least 6 mmol / min, preferably ranging from 6 to 200 mmol / min, and typically ranging from 9.3 mmol / min to 100 mmol / min; said at least one polyol is introduced into the mixer at a flow rate of at least 2 mmol / min, preferably ranging from 2 to 70 mmol / min, in particular from 3 mmol / min to 55 mmol / min and typically from 3 mmol / min to 10 mmol / min; the initial mixture comprises at least one catalyst; said at least one catalyst is an acid catalyst or a basic catalyst; the acid catalyst is selected from one or more of the following compounds acetic acid (AcOH), sulfuric acid (H2SO4), cobalt (II) sulfate heptahydrate (CoSO4.7H2O), zinc chloride (ZnCl2), copper sulfate dihydrate (CuCl2.2H2O), iron II chloride tetrahydrate (FeCl2.4H2O), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2) and is preferably sulfuric acid (H2SO4), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2), in which the basic catalyst is chosen from one or more of the following compounds: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate. wherein the mixing step (B) is carried out without external heat input, the temperature within the mixing chamber being at least 20°C and preferably ranging from 20°C to 150°C due to the exothermicity of the synthesis reaction; the initial mixture does not include a catalyst; during the mixing step (B), an external heat supply is made, so as to obtain a temperature within the mixing chamber which is at least 80°C, preferably which ranges from 100°C to 200°C, in particular from 110°C to 150°C and typically from 120°C to 140°C; the mechanical mixer is chosen from a three-dimensional mill with or without balls; said three-dimensional mill with or without balls comprises at least: • a generally cylindrical mixing chamber extending along a longitudinal axis XX, said mixing chamber comprising at a first end at least one inlet serving to introduce said starting reagents and at a second end, an outlet capable of discharging said final composition formed in said mixing chamber; and • a stirring system, arranged in the mixing chamber, comprising at least one rod or elongated coil extending along the longitudinal axis XX, said stirring system being capable of mixing said starting reagents; - the stirring system has a rotation speed ranging from 0.01 m / s to 20 m / s, preferably from 4 m / s to 18 m / s and typically from 6 m / s to 11 m / s; - the conversion into polyol ester at the end of step (C) is greater than or equal to 70%, better still greater than or equal to 80%;

[0021] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The invention will be better understood and other aims, details, characteristics and advantages thereof will appear more clearly on reading the following description of exemplary embodiments, with reference to the appended figures in which:

[0023] [Fig-1] represents a sectional view, along a sectional plane passing through the longitudinal axis XX, of a three-dimensional grinder according to a first embodiment of the invention comprising in particular an induction heating device;

[0024] [Fig.2] represents, according to sectional planes passing through the longitudinal axis XX and through the axis AA, different variants of embodiment of three-dimensional mills according to the invention each comprising a heating device and at least one agitator possibly supporting another mixing member: (a) the agitator comprises several other mixing members in accordance with the mill of [Fig.l], (b) the agitator also comprises fingers capable of cooperating with the other mixing members and (c) the agitator does not comprise mixing members and fingers. A°) Definition

[0025] In the present invention, unless otherwise specified, the term "comprising" and its derivatives should be understood as non-limiting and not excluding the presence of other components or steps. In certain particular embodiments, the term "comprising" may be understood as "consisting essentially of" or "consisting of".

[0026] For the remainder of the description, unless otherwise specified, the indication of an interval of values ​​"from X to Y" or "between X and Y", in the present invention, is understood as including the values ​​X and Y.

[0027] By "alkyl group" according to the invention, we mean a linear or branched saturated hydrocarbon group comprising (unless otherwise stated) from 1 to 17 carbon atoms (Ci to C17), more preferably from 1 to 11 carbon atoms (Ci to Cn), in particular from 1 to 7 carbon atoms (Ci to C7), and typically from 1 to 5 carbon atoms (Ci to C5). Among the examples of alkyl groups according to the invention, we can notably mention the methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, pentyl and heptyl groups.

[0028] According to the invention, "residence time" means the time in seconds, minutes or hours during which the initial mixture is maintained within the mixing chamber of the mechanical mixer. In general, the residence time corresponds to the reaction time allowing the synthesis into polyol esters with preferably a conversion of at least 75%, in particular at least 80% and typically at least 90%, or even better at least 99%.

[0029] According to the invention, “continuous reaction” means a synthesis reaction carried out in a device crossed by a reaction mixture in continuous flow.

[0030] Conversion to polyol ester estimated by proton and carbon NMR analysis.

[0031] Hereinafter, “mixing” means intense mixing and adequate dispersion of the starting reagents so as to obtain, at the outlet of the mechanical mixer, a final composition which is homogeneous.

[0032] “Ambient temperature” means the temperature of the room where the mechanical mixer; this generally varies from 19°C to 35°C, typically from 20°C to 25°C. B°) Synthesis process Bl The stages of synthesis

[0033] The inventors have focused on developing a new process for the continuous synthesis of polyol esters that is simple and economical. In particular, the inventors have focused on developing a new process for the synthesis of polyol esters that is suitable for being implemented on an industrial scale, that has good yields, that is easy to implement and that can be carried out in a relatively short time, while not requiring the use of high temperatures.

[0034] Thus, the present invention relates to a process for synthesizing a final composition comprising at least one polyol ester and a carboxylic acid implementing an exothermic acylation reaction from an initial mixture comprising at least two liquid, preferably immiscible, starting reactants which are a polyol and an acid anhydride,

[0035] characterized in that it is carried out in continuous flow in a mechanical mixer comprising at least one mixing chamber,

[0036] the method comprising the following successive steps:

[0037] (A) the separate introduction and at room temperature of said at least two reagents starting in the mixer to form said initial mixture,

[0038] (B) mixing in said mechanical mixer said initial mixture for a time stay of less than or equal to 1 hour;

[0039] (C) the recovery at the outlet of the mixer of said final composition.

[0040] As mentioned above, due to the generally immiscible nature of the starting reagents composed of a polyol, such as glycerol, with an acetic anhydride, the implementation of a simple and economical continuous synthesis process remained difficult. Furthermore, the exothermicity of the reaction made this synthesis in batch mode without solvent according to the methods of the prior art dangerous on an industrial scale. The inventors have now discovered, surprisingly and unexpectedly, that the use of a mechanical mixer, such as a three-dimensional mill with or without microbeads usually used to reduce the particle diameter of a powder, removes the barrier of both the miscibility of the starting reagents and the exothermicity of the reaction in order to be able to provide a synthesis process in continuous mode.

[0041] Preferably, the mechanical mixer is chosen from: a three-dimensional mill with or without balls or any other equivalent tubular mixer incorporating within it a stirring system, such as an elongated rod or a coil also of elongated shape.

[0042] In particular, the polyol ester synthesis reaction can be summarized as follows:

[0043] [Chem.2] OO ...... O J ---------------------------------------------r R '0' 'R / O. \ + ” HO h your eonte » 7 rrpely&î

[0044] In general, the polyol is selected from the group consisting of: glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol and other liquid glycerol oligomers or a mixture thereof. In general, the polyol is immiscible with the acid anhydride and may be glycerol, diglycerol and triglycerol or a mixture thereof. Preferably, the polyol is selected from glycerol.

[0045] Generally, acetic anhydride has the following general formula: [Chem. 1]

[0046] where R is chosen from: a linear or branched alkyl group comprising from 1 to 17 carbon atoms, preferably, R is chosen from a methyl, pentyl or heptyl group and typically, R is in particular a methyl group.

[0047] Thus, the method according to the invention can allow the synthesis of triacetin according to the following reaction: [Chem. 3]

[0048] However, the method of the invention is not limited to the synthesis of triacetin. Thus, other polyol esters can be synthesized like those shown in Table 1 below:

[0049] [Tables 1] Compound Chemical formula Triacetin (ie: 1,3-diacetyloxypr Po opan-2-yl acetate) O" Ô Ô Glyceryl trihexanoate (CAS 621-70-5) A o G XX À A ' 0 T ~ oo Glyceryl trioctanoate (CAS 538-23-8) Ao P Û ô Ethylene glycol diacetate (CAS 111-55-7) bb O---\ Ethylene glycol dihexanoate A® bb ox Al; Ethylene glycol dioctanoate QA xx CvH^' 'O' Y" ' " Ô Propylene glycol diacetate O a Propylene glycol dihexanoate ox OY p ô Propylene glycol dioctanoate CZH« 0 C / H15 Zx Ô 1,3 diacetoxypropane Ô ô Diglycerol tetraacetate (oxybis(propane-3,l,2 -triyl) tetraacetate) (CAS 92373-24-5) Q 0 .A^^xx 0. YUTQ 0 Q ZW A'-q Diglycerol tetrahexanoate Y AO / ao \ < j « y O ÿ OAAX Diglycerol tetraoctanoate (CAS 1821681-44-0) 9 9 Cj-HY Y VAns§ A?0 gty Pentaacetate (((2-acetoxypropane-1,3-diyl)bi s(oxy))bis(propane-3,l,2-triyl) tetraacetate) of triglycerol 0- P cy QQQ Aq z^o

[0050] According to a characteristic of the invention, the molar ratio of acid anhydride to the number of hydroxyl groups within the polyol in the initial mixture is lower or equal to 10, preferably less than or equal to 6 and in particular less than or equal to 1.1, without ever being less than 1.

[0051] According to the invention, "a molar ratio of acid anhydride to the number of hydroxyl groups within the polyol in the initial mixture is less than or equal to 10" includes the following values ​​and all intervals between these values: 10; 9; 8; 7; 6; 5; 4; 3; 2; 1.5; 1.4; 1.3; 1.2; 1.1; 1.0.

[0052] In general, the synthesis reaction is carried out continuously and rapidly, namely the residence time of the initial mixture within the mechanical mixer is less than or equal to 1 hour, typically less than or equal to 50 minutes, in particular ranging from 30 seconds to 40 minutes and typically ranging from 1 minute to 30 minutes.

[0053] According to the invention, “a residence time less than or equal to 1 hour” includes the following values ​​and all intervals between these values ​​(in minutes): 60; 55; 50; 45; 40; 35; 30; 25; 20; 15; 10; 9; 8; 7; 6; 5; 4; 3; 2; 1.

[0054] In general and in particular when the mechanical mixer is chosen from a three-dimensional mill with or without microbeads or any type of equivalent mechanical mixer having a longitudinal mixing chamber within which a stirring system is arranged, the residence time is linked to the flow rate of introduction of the starting reagents and to the actual volume within the mixing chamber (i.e.: the actual volume corresponding to the volume of the mixing chamber deduced from the apparent volume of the grinding balls when these are present).

[0055] Thus, according to a characteristic of the invention, the acid anhydride is introduced into said mechanical mixer at a flow rate of at least 6 mmol / min, preferably ranging from 6 to 200 mmol / min, in particular ranging from 9 mmol / min to 170 mmol / min and typically ranging from 9 mmol / min to 100 mmol / min.

[0056] According to the invention, "a flow rate of at least 6 mmol / min" includes the following values ​​and all intervals between these values ​​(in mmol / min): 6; 7; 8; 9; 10; 11; 12; 13; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60; 65; 70; 75; 80; 85; 90; 95; 100; 120; 130; 140; 150; 160; 170; 180; 190; 200; 210; 220; etc.

[0057] Thus, in general, the acid anhydride is introduced into said mechanical mixer at a flow rate of at least 1 mL / min, preferably ranging from 2 to 20 mL / min, and typically ranging from 3 mL / min to 15 mL / min.

[0058] According to another characteristic of the invention, said at least one polyol is introduced into the mechanical mixer at a flow rate of at least 2 mmol / min, preferably ranging from 2 to 70 mmol / min, in particular ranging from 3 mmol / min to 55 mmol / min and typically from 3 mmol / min to 10 mmol / min.

[0059] Also, according to the invention “a flow rate of at least 2 mmol / min” includes the following values ​​and all intervals between these values ​​(in mmol / min): 2; 2.5; 3; 3.5; 4; 4.5; 5; 5.5; 6; 6.5; 7; 7.5; 8; 8.5; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 25; 30; 35; 40; 45; 50; 55; 60; 65; 70; 75; 80; 85; etc.

[0060] Thus, in general, said at least one polyol is introduced into the mechanical mixer at a flow rate of at least 0.2 mL / min, preferably ranging from 0.25 to 10 mL / min, and typically from 0.4 mL / min to 7 mL / min.

[0061] According to a first embodiment, the initial mixture comprises at least one catalyst.

[0062] In general, said at least one catalyst is an acid catalyst or a basic catalyst.

[0063] In particular, the acid catalyst may be chosen from one or more of the following compounds: acetic acid (AcOH), sulfuric acid (H2SO4), cobalt (II) sulfate heptahydrate (CoSO4.7H2O), zinc chloride (ZnCl2), copper sulfate dihydrate (CuC12.2H2O), iron II chloride tetrahydrate (FeCl2.4H2O), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2) and is preferably sulfuric acid (H2SO4), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2).

[0064] The basic catalyst can be chosen from one or more of the following compounds: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate.

[0065] According to this embodiment, the mixing step (B) can be carried out with or without external heat input, namely without an integrated heating system or at least connected to the mechanical mixer. When the mixing step (B) is carried out without external heat input, the temperature within the mixing chamber is at least 20°C and preferably ranges from 20°C to 180°C, in particular from 50°C to 170°C, and typically from 80°C to 150°C, such as 130°C. This is due to the exothermicity of the synthesis reaction. When the mixing step (B) is carried out with external heat input, the temperature within the mixing chamber is typically at least 50°C, preferably 100°C to 200°C, in particular 110°C to 150°C, and typically 120°C to 140°C.

[0066] According to the invention, "a temperature of at least 20°C" includes the following values ​​and all intervals between these values ​​(in °C): 20; 30; 40; 50; 60; 70; 80; 90; 100; 110; 120; 130; 140; 150; 160; 170; 180; 190; 200; 210; etc.

[0067] According to a second embodiment, the initial mixture does not comprise a catalyst.

[0068] In general, in this case, during the mixing step (B), an external heat supply is made, so as to obtain a temperature within the mixing chamber which is at least 50°C, preferably which ranges from 80°C to 200°C, and in particular from 100°C to 140°C.

[0069] According to the invention, “a temperature of at least 50°C” includes the following values ​​and all intervals between these values ​​(in °C): 50; 60; 70; 80; 90; 100; 110; 120; 130; 140; 150; 160; 170; 180; 190; 200; 210; etc.

[0070] To better understand the process which is the subject of the invention, a planetary ball mill, as well as a three-dimensional microbead mill capable of allowing the synthesis of polyol esters according to the invention, and thus forming part of the invention, will be described below.

[0071] B.2 Three-dimensional mill with or without grinding balls

[0072] This embodiment will be described with reference to [Fig. 1] and 2.

[0073] As illustrated in Figures 1 and 2, the three-dimensional grinder 100 comprises at least one stationary grinding chamber 1 having a wall 7 of generally cylindrical shape which envelops an interior 8.

[0074] The wall 7 extends along a longitudinal axis XX, advantageously horizontal.

[0075] This stationary mixing chamber 1 is configured to receive and mix at least the starting reactants, namely the polyol, the acid anhydride and, if applicable, the catalyst. In general, if it is present, the catalyst is premixed with the polyol. In particular, the polyol and the acid anhydride are introduced into the mixing chamber 1 separately since they are very reactive.

[0076] According to a characteristic of the invention, the stationary mixing chamber 1 does not comprise a grinding body 6.

[0077] According to another characteristic of the invention which will be described in more detail below, the stationary mixing chamber 1 is partially filled with at least grinding bodies 6, such as beads / microbeads 6 which will allow the grinding and mixing of the starting reagents in an intense and efficient manner.

[0078] The stationary chamber 1 comprises, at a first end 2 (upstream), an inlet 4 which opens into the stationary mixing chamber 1 and which is used to introduce the starting reagent(s). This inlet 4 can also be used to introduce the microbeads 6 before the mill 100 is used. As will be seen below, the size and nature of the microbeads 6 can vary slightly.

[0079] The mixing chamber 1 comprises, at a second end 3 (downstream), an outlet 5 which leads outwards and which is configured to discharge the final composition formed in the stationary mixing chamber 1.

[0080] The outlet 5 generally comprises a separation means (not shown), such as a sieve or a grid, adapted to evacuate only the final composition and consequently to retain the microbeads 6 when the grinder 100 is in operation.

[0081] In particular, the inlet 4 is generally connected to at least two pumps, for example peristaltic (not shown). These pumps make it possible to bring the starting reagents into the stationary mixing chamber 1.

[0082] Each starting reagent may, for example, be contained in a container, such as a tank. The pump also makes it possible, during operation of the three-dimensional mill 100, to supply each starting reagent with a certain flow rate which is adjustable, hereinafter called “passage flow rate”. This passage flow rate also forms a current in the stationary chamber 1 making it possible to drive the starting reagents from the inlet 4 to the outlet 5.

[0083] The three-dimensional mill 100 also comprises an agitator 10 which comprises an elongated rod 11 along the longitudinal axis XX and which extends mainly around the first end 2 to beyond the second end 3 of the stationary chamber 1.

[0084] This elongated rod 11 advantageously extends coaxially to the aforementioned longitudinal axis XX.

[0085] This agitator 10 is in particular capable of pivoting so as to set in motion, in addition to the aforementioned flow rate, the assembly comprising grinding bodies 6 and starting reagents.

[0086] In particular, the agitator 10 is configured to rotate on itself, along the longitudinal axis XX, via an elongated rod 11 (or rotating shaft), to impart within the stationary chamber 1 a swirling movement to the initial mixture and thus carry out intense mixing between this initial mixture and the microbeads 6 present in the chamber 1 along the internal surface of the wall 7 of this chamber 1.

[0087] Alternatively, the agitator 10 may be in the form of an elongated coil (i.e.: the elongated rod 11 is coated with a grinding element which extends along the rod 11 in a helical manner).

[0088] In particular, the stirrer 10 via its elongated rod 11 can have a rotation speed greater than or equal to 100 revolutions per minute, advantageously greater than or equal to 1000 revolutions per minute (rpm), preferably greater than or equal to 2000 revolutions per minute and typically greater than or equal to 2500 revolutions per minute.

[0089] For the purposes of the invention, “a rotational speed greater than or equal to 100” includes the following values: 100; 150; 200; 250; 300; 350; 400; 450; 500; 550; 600; 650; 700; 750; 800; 850; 900; 950; 1000; 1100; 1200; 1300; 1400; 1500; 1600; 1700; 1800; 1900; 2000; 2100; 2200; 2300; 2400; 2500; 2600; 2700; 2800; 2900; 3000; 3100; 3200; 3300; 3400; 3500; 3600; 3700; 3800; 3900; 4000, 4500; 5000; 5500; 6000; etc., or any intervals between these values.

[0090] In particular, the rotation speed of the agitator 10 is greater than or equal to 1500 rpm, advantageously greater than or equal to 1600 rpm, in particular greater than or equal to 1800 rpm and typically greater than or equal to 2400 rpm.

[0091] In general, the agitator 10 has a rotation speed ranging for example from 1500 rpm to 5000 rpm, in particular from 1550 rpm to 4500 rpm, preferably from 1600 rpm to 4000 rpm and typically from 2400 to 3200 rpm.

[0092] Preferably, the peripheral speed of the stirrer is greater than or equal to 6 m / s, in particular greater than or equal to 8 m / s. According to the invention, a peripheral speed of the stirrer greater than or equal to 6 m / s comprises the following values ​​or any interval between these values: 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20, etc. In general, the peripheral speed of the stirrer ranges from 7 m / s to 20 m / s, preferably from 8 m / s to 16 m / s. By "peripheral speed of the stirrer" is meant the rotational speed multiplied by the circumference of the stirrer disc.

[0093] The rotation speed will be adapted by the person skilled in the art depending on the three-dimensional grinder used (laboratory grinder or industrial grinder).

[0094] For example, a three-dimensional mill marketed by the company WAB (Willy A. Bachofen SARL) of the AP05 type has an agitator with the following characteristics: for a frequency of 80 Hz, a speed in revolutions per minute of 4800 and a peripheral speed in m / s of 16.0; while a mill of the AP2 type, for a frequency of 70.8 Hz, has a speed in revolutions per minute of 2730 and a peripheral speed in m / s of 16.0. In order to improve this mixing, the agitator 10, just like the internal surface of the internal wall 7 of the chamber 1, can have various possible configurations shown for example in [Fig.2].

[0095] According to a first configuration illustrated in figure 2a, the agitator 10 comprises, along its elongated rod 11, “rotating” mixing members 22, 26, arranged perpendicular to the latter.

[0096] As will be described below, a mixing member 22 (called “first mixing member”) may also correspond to a susceptor of the heating means 20 according to the invention and is thus different from the other mixing members 26 (called “other mixing members”).

[0097] This first mixing member 22, as well as the other mixing members 26, may correspond to the mixing members described in document US 5,597,126.

[0098] In particular, they may comprise at least two circular discs parallel to each other, configured to set the grinding bodies 6 (microbeads) in motion.

[0099] The number of these mixing members 22, 26 within the mixing chamber 1 can vary from 2 to 8, preferably from 2 to 5.

[0100] These mixing members 22, 26 make it possible, on the one hand, to improve the mixing / grinding of the starting reagents and / or the starting composition by further stirring the microbeads 6 and, on the other hand, to accelerate the reaction time.

[0101] According to a second configuration illustrated in figure 2b, the agitator 10 can also comprise, along its rod 11, one or more “rotating” mixing members 22, 26 which are furthermore capable of cooperating with “fixed” fingers 28, arranged perpendicularly to the internal wall 7 of the chamber 1.

[0102] A finger 28 is in particular in the form of a ring which extends perpendicularly from the wall 7.

[0103] For this configuration, the mixing members 22, 26 and the fingers 28 are arranged in a staggered manner, namely the mixing members 22, 26 and the fingers 28 are arranged alternately in the chamber 1.

[0104] The fingers 28 thus form counter-fingers, each arranged between two mixing members 22, 26.

[0105] Furthermore, the thickness of the rod 11 is increased compared to the previous configuration (figure 2a) so that the periphery of the mixing members 22, 26 is close to the internal wall 7 and that of the fingers 28 is close to the periphery of the rod of the agitator 10.

[0106] Thus, in this configuration, the volume of the chamber is reduced compared to the previous configuration, consequently allowing better mixing between the starting reagents and / or the starting composition, the microbeads 6 and the internal wall 7 of the chamber 1.

[0107] According to a third configuration the volume of the chamber 1 can be further reduced as illustrated in figure 2c.

[0108] According to this embodiment, the stirrer 10 has an external diameter slightly smaller than the internal diameter of the chamber 1, thus forming an annular chamber 12 of small volume arranged between the external wall of the stirrer 10 and the internal wall 7 of the chamber 1. The microbeads (not shown) are arranged in this annular chamber 12. During the operation of this third configuration, the starting reagents and / or the starting composition are / is introduced through the inlet 4 with a certain flow rate, which will then travel through the annular chamber 12 to the outlet 5, while being stirred by the microbeads 6.

[0109] The geometry of the mixing chamber 1 and the agitator 10 may be adjusted by a person skilled in the art depending on the desired yield, as well as the desired reaction time. For example, it is also possible for the mixing chamber 1 to comprise an accelerator in order to improve the mixing / grinding of the initial mixture. Since this accelerator is known to a person skilled in the art, it will not be detailed below.

[0110] In general, the stationary chamber has a diameter of 75 mm to 300 mm for a length of 80 mm to 900 mm and an agitator 10 having a size ranging from 65 mm to 260 mm. Thus, the volume of the mixing chamber can vary from 0.35 L to 600 L, preferably from 0.35 L to 400 L, and typically from 0.35 L to 62 L.

[0111] For the purposes of the invention, “a volume of the stationary chamber 1 ranging from 0.35 L to 600 L” includes the following values: 0.35; 0.5; 0.8; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60; 65; 70; 80; 85; 90; 100; 110; 120; 130; 140; 150; 160; 170; 180; 190; 200; 210; 220; 230; 240; 250; 260; 270; 280; 290; 300; 350; 400; 450; 500; 550; 600, or any intervals between these values.

[0112] Preferably, the microbeads 6 housed in the mixing chamber 3 of the mill 1 during its operation are substantially spherical in shape and have an average diameter less than or equal to 5 mm, generally ranging from 0.05 mm to 4 mm, preferably from 0.2 to 3 mm, in particular from 0.3 to 2 mm, and typically of the order of 0.5 to 1 mm. Preferably, the diameter of the microbeads is less than or equal to 1 mm and is typically of the order of 0.05 mm to 1 mm.

[0113] They are preferably chosen from microbeads having a high hardness and relatively good resistance to abrasion.

[0114] In particular, the microbeads 6 have a Vickers hardness measured according to standard EN ISO 6507-1 (2005) greater than or equal to 900 HV1, preferably ranging from 900 HV1 to 1600 HV1, typically ranging from 1000 to 1400 HV1 and in particular ranging from 110 to 1300 HV1.

[0115] For the purposes of the invention, “a Vickers hardness greater than or equal to 900 HV1” includes the following values: 900; 910; 920; 930; 940; 950; 960; 970; 980; 990; 1000; 1010; 1020; 1030; 1040; 1050; 1060; 1070; 1080; 1090; 1000; 1110; 1120; 1130; 1140; 1150; 1160; 1170; 1180; 1190; 1200; 1300; 1400; 1500; 1600; 1700; etc., or any intervals between these values.

[0116] Advantageously, they have a high actual density. In general, the microbeads according to the invention have an actual density greater than or equal to 2 g / cm3, in particular ranging from 2 to 15 g / cm3, preferably from 3 to 12 g / cm3, and typically from 4 to 10 g / cm3.

[0117] Thus, the microbeads according to the invention may be ceramic microbeads (zirconium oxide ZrO2, zirconium silicate ZrSiO4); steel microbeads, tungsten carbide microbeads, glass microbeads or one of their combinations.

[0118] Preferably, the microbeads are made of ceramic because they do not generate pollution through their wear.

[0119] In particular, the microbeads are made of zirconium oxide.

[0120] Optionally, the zirconium oxide microbeads may be stabilized by another oxide, such as cerium oxide, yttrium oxide and / or silicon.

[0121] As examples, the following compositions, summarized in Table 2 below, are suitable for forming the microbeads according to the invention:

[0122] [Tables2] Composition of microbeads Hardness HV1 Actual density (g / cm3) Manufacturer Cerium oxide stabilized zirconium oxide microbeads 80% ZrO2 20% 1180 >6.10 Saint-Gobain or EIP (Rr.ûicerpx® Zû Cd.r) Yttrium stabilized zirconium oxide microbeads 95% ZrCo <5% AI2O3 Remainder: Y2O3 1250 >5.95 EIP (PlQAeiW® 40 (Y)) Yttrium and silicon stabilized zirconium oxide microbeads: 78%ZrO2, 12% SiO2. 5% AI2O3 and 4% Y2O3 > 700 >4.80 Saint-Gobain (ER120 CMarŒôBeadsl Zirconium silicate microbeads ZrSiO4 >800 >6.5 Saint-Gobain Glass microbeads 500 > 3.76 - Steel microbeads 700 > 7.7 -

[0123] Generally, the microbeads 6 suitable for the invention are not made of glass or exclusively made of glass.

[0124] In particular, the microbeads 6 represent, in volume, relative to the total volume of the stationary chamber 2 from 50% to 85%, preferably from 55% to 70%.

[0125] For the purposes of the invention, “a volume of 50 to 85%” includes the following values: 50; 55; 60; 65; 70; 75; 80; 85; etc., or any intervals between these values.

[0126] According to one embodiment, the polyol ester synthesis reaction does not require heat input, i.e. does not require a heating system (included or not within the mill).

[0127] According to another embodiment, the polyol ester synthesis reaction requires a heat input. According to this method, the three-dimensional mill may comprise a heating device outside or inside and preferably inside the mixing chamber. Such a mill incorporating a heating device will be briefly described below with reference to [Fig.l]

[0128] During the mixing step (B), the starting reagents are heated within the three-dimensional microbead mill which comprises at least one device for heating, preferably at least one induction heating device 20. This embodiment has the advantage of a more precise reaction temperature, regardless of the flow rate or temperature of the starting reactants at the inlet of the mill (better heating of the flow forming the initial mixture). For example and as shown in [Fig.l], the induction heating device(s) 20 are integrated inside the stationary mixing chamber 1 and make it possible to heat at least one zone of said stationary mixing chamber 1. According to a characteristic of the invention, the induction heating device(s) 20 are located at the inlet of the chamber 1, i.e. around the first end 2 so as to be able to heat the initial mixture flow (starting reactants) as soon as it is introduced and consequently allow and / or activate the chemical synthesis of the polyol esters.

[0129] According to a preferred embodiment of the invention, the induction heating device 20 is carried by at least a part of said stirrer 10, allowing the induction heating device 20 to be set into rotary movement around the longitudinal axis XX.

[0130] Generally, the induction heating device 20 comprises:

[0131] - at least one inductor 21, capable of generating a magnetic field, and

[0132] - at least one susceptor 22, electrically conductive, which is coupled to said inductor 21 and which is capable of being heated by it 21.

[0133] In particular, the inductor 21 is a coil or a solenoid having turns which surround a part of said rod 11 of the stirrer 10, advantageously an upstream section located on the side of the first end 2 as shown in [Fig.l]. The inductor 21 is in particular capable of generating a magnetic field which will allow the heating of the conductive materials in its environment, and in particular the susceptor 22 to which it is coupled. Indeed, the susceptor 22, which is electrically conductive, is capable of capturing the magnetic field emitted by the inductor. The coil and susceptor assembly can be rotated by the rod 11.

[0134] The other mixing members 26 which are different from the first mixing member 22, namely they are not necessarily electrically conductive, may in particular be made of chrome cast iron or zirconium oxide type ceramic.

[0135] Referring to [Fig.l], this first mixing member 22 generally comprises a base secured to the rod 11 of the stirrer 10. Preferably, the inductor 21 is installed at the level of this base.

[0136] Generally, the induction heating device 20 is connected to an alternating electric current generator arranged outside said mixing chamber 1 by means of at least one current supply means 27 which is coaxial with the rod 11 of the stirrer 10. In particular, the generator may have a power ranging from 5 to 15KW and preferably 10 kW with a frequency varying for example from 17 to 200 kHz. It comprises a capacity box which can be in parallel or in series. For example, an ID Partner series generator reference 1X3600 model PO8010 is suitable for producing the crusher according to the invention.

[0137] In general, the stationary mixing chamber 1 incorporates a magnetic screen 23 arranged between said inductor 21 and said rod 11 of the stirrer 10, so as to direct the heating towards the initial mixture. Indeed, it may be that the stirrer 10 or its rod 11 is made of electrically conductive material and thus, in order to avoid any overheating of the stirrer 10, it is preferable to protect the stirrer 10 or at least the rod part 11 which is surrounded by the inductor 21. This magnetic screen 23 also has the advantage of directing the magnetic field emitted by the coil 21 to the first mixing member 22 so that all the power is concentrated outside the inductor and in particular is not directed towards the rod 11. Thus the heating zone is restricted to the outer periphery of the rod 11 and particularly concentrated on the first mixing member 22.

[0138] Such a grinder incorporating a heating device is notably described in application FR 18 54592.

[0139] By way of example, the three-dimensional liquid-phase microbead mill suitable for carrying out the method according to the invention may correspond to mills marketed by the WAB companies, Dyno-Mill range: DYN0®-MILL Research Lab (Willy A. Bachofen AG, Switzerland) and DYN0®-MILL Multi Lab (Willy A. Bachofen AG, Switzerland) instrument equipped with ECM and KD accelerators, NETZCH or Alpine Hosokawa, for example, Agitated Media Mill AHM or to these types of mills in which a heating device as described above has been integrated.

[0140] Alternatively, a continuous IMR mixer marketed for example by the company PARIMIX is suitable for forming a three-dimensional grinder without grinding bodies (i.e.: the stirring system comprises an axis on which one or more blades extend, extending helically along the axis).

[0141] The process for synthesizing polyol ester according to the invention will now be described more explicitly below according to this embodiment using a three-dimensional microbead mill.

[0142] Thus, advantageously, the manufacture of polyol ester according to the invention can comprise a prior step of preparing a first polyol mixture with, where appropriate, the catalyst. Indeed, it is generally easier from a practical point of view to prepare this first mixture comprising the various starting reagents in the desired proportions.

[0143] Then, the starting reactants (namely, the polyol, if applicable the catalyst or the first polyol + catalyst mixture and the acid anhydride) are introduced separately at the inlet 4 into the mixing chamber 1 via peristaltic pumps and thus form the initial mixture. The different reactants can be introduced according to a controlled flow rate, as mentioned above in paragraph B1

[0144] Once the starting reagents are introduced into chamber 1, the mixing step (B) begins.

[0145] Under the effect of the current created by the flow rate, the initial mixture travels through the stationary chamber 1 from the inlet 4 to the outlet 5, while being set in motion by the agitator 10 which allows intense mixing of this mixture with the microbeads and, where appropriate, with the discs 22; 26, the fingers 28, etc., along the internal wall of the chamber 1.

[0146] The rotation speed of the agitator may for example vary from 10 to 150 Pi rad / s, preferably from 40 to 100 and in particular from 60 to 70 Pi rad / s and is in particular at least 60 Pi rad / s such as 63 Pi rad / s.

[0147] According to the invention, a rotation speed ranging from 10 to 150 Pi rad / s comprises the following values ​​and all intervals between these values: 10; 20; 30; 40; 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100; 110; 120; 130; 140; 150.

[0148] The residence time of the initial mixture is less than or equal to 1 hour. Preferably, the residence time in the mill is less than or equal to less than or equal to 50 minutes, in particular ranging from 30 seconds to 40 minutes and typically ranging from 1 minute to 30 minutes.

[0149] As mentioned above, the residence time is inherent to the actual volume of the stationary chamber 1 as well as the flow rate. For example, if the volume of the grinding chamber is 309 mL and 80% of the volume is taken up by the beads, then the actual volume of the grinding chamber is 61.8 mL. If the flow rate of the reactant is 30 L / h (or 30,000 mL / 3600 seconds), then the residence time will be 7.4 seconds ([61.8 x 3600] / 30000). Therefore, the residence time can be advantageously adjusted, for example by controlling the bulk density of the microbeads, as well as the flow rate.

[0150] The term "apparent volume" means the volume of the microbeads including the interstitial air between the beads. The apparent density is the ratio between the mass of the microbeads and the apparent volume. Preferably, the apparent volume of the microbeads ranges from 250 mL to 450 mL, preferably from 300 mL to 400 mL and is typically from 330 mL to 360 mL. This apparent volume of the microbeads is suitable for example for a three-dimensional mill comprising a stationary chamber 1 of 500 mL.

[0151] Furthermore, by varying the flow rate, the synthesis of polyol esters can be improved.

[0152] Preferably, the pressure during the stirring step (B) ranges from 0.05 to 20 MPa, preferably from 0.08 to 0.5 MPa and is typically of the order of 0.1 MPa.

[0153] The brewing step (B) is carried out in continuous mode.

[0154] Indeed, the inventors noticed that a single pass through the microbead mill, despite a relatively short residence time, made it possible to obtain at the outlet 5 a final composition comprising a conversion rate into polyol ester greater than or equal to 80%, or even 100%.

[0155] As mentioned above, this mixing step (B) takes place at room temperature, generally greater than or equal to 25°C due to the exothermicity of the reaction. An external heating device can however be added in order to better control the temperature and the latter is necessary if the initial mixture does not include a catalyst.

[0156] Once the mixing step (B) has been carried out, the final composition is recovered at the outlet 5 of the grinder 100. This final composition may include traces of the starting reagents which have not reacted, such as for example the catalyst or even a by-product such as a carboxylic acid.

[0157] The process according to the invention makes it possible to obtain a yield of polyol ester greater than or equal to 80%, preferably greater than or equal to 85% and in particular greater than or equal to 90%. In general, the process according to the invention makes it possible to obtain a yield of polyol ester greater than or equal to 99% (optimized experimental conditions).

[0158] In a known manner, the polyol ester may be separated from the reaction medium (from the starting reagents and / or from the by-products formed and, where appropriate, from the catalyst) by methods well known to those skilled in the art. These methods may be, for example, by liquid / liquid extraction, by ethyl acetate and water followed by a vacuum evaporation step.

[0159] The polyol ester may also be purified if necessary by techniques also well known to those skilled in the art, such as by distillation.

[0160] Obviously, the process parameters (concentration of the starting reactants, flow rate, etc.) can be optimized in order to obtain a continuous synthesis of polyol ester, i.e. in a single pass. For example, the use of a lower flow rate makes it possible to increase, for example, the residence time of the starting reactants in the mixing chamber and thus to increase the yield / conversion rate in a single pass. EXAMPLES

[0161] The description of the tests below is given as a purely illustrative and non-limiting example.

[0162] Example A: Synthesis of triacetin according to the invention in a three-dimensional mill in the presence of microbeads Mill according to the invention

[0163] The tests were carried out in a Dynomill WAB Research Lab three-dimensional microbead mill from Willy A. Bachofen AG (WAB) of 80mL, which contains 44mL of microbeads. The device does not include a heating device.

[0164] The microbeads are made of zirconium oxide and have a diameter of 0.7mm.

[0165] The mixing chamber of the grinder has a capacity of 80 mL and is filled, in volume, relative to its total volume of 44 mL with the microbeads described above.

[0166] In operation, the microbeads are stirred by a stirrer at a rotation speed which can vary depending on the examples from 4.6 to 11 m / s. The stirrer further comprises a zirconia oxide accelerator.

[0167] The starting reagents (glycerol, acetic anhydride and a catalyst) are introduced into the mill according to the experimental conditions set out in the table below. In particular, the glycerol was previously mixed with the catalyst, then this mixture was introduced into the mill at a precise flow rate using a peristaltic pump. Similarly, the acetic anhydride was introduced into the mill at a precise flow rate using a high-flow HPLC pump. The outlets of the two pumps are connected via a T-fitting before the mill inlet. A total flow rate is calculated as follows: glycerol flow rate + acetic anhydride flow rate.

[0168] The samples recovered at the outlet of the crusher are analyzed by proton NMR in deuterated DMSO.

[0169] Reaction conditions used and results (Tables 3 and 4):

[0170] [Tables3] Ex. Mol% Glycerol flow rate (mL / Min) Anhydride flow rate (mL / Min) Early flow rate (mL / Min) Residence time (min) Agitator rotation speed (m / s) T° (°C) at mill outlet Ex.l Fe(OTf)2 1 mol% 0.25 1.05 1.3 28 11 70 Ex.2 Fe(OTf)2 1 mol% 0.25 1.05 1.3 28 4.6 63 Ex.3 Fe(OTf)2 1 mol% 0.5 2.1 2.6 14 4.6 59 Ex.4 Fe(OTf)2 0.5 mol% 0.5 2.1 2.6 14 11 50 Ex.5 H2SO4 1 mol% 0.5 2.1 2.6 14 4.6 70 Ex.6 H2SO4 1 mol% 0.25 1.05 1.3 28 4.6 70 Ex.7 FeCl3.6H2 O 1 mol% 0.25 1.05 1.3 28 4.6 50

[0171] [Tables4] Ex. Yield % (triacetin) Productivity Kg / h Volumetric productivity Kg / h / L Ex.l 100 0.045 1.25 Ex.2 100 0.045 1.25 Ex.3 97 0.086 2.40 Ex.4 89 0.016 0.45 Ex.5 100 0.084 2.30 Ex.6 100 0.045 1.2 Ex.7 71 0.010 0.38

[0172] Example B: Synthesis of triacetin according to the invention in a three-dimensional mill without microbeads

[0173] Example A above is reproduced, except that the mill did not include grinding balls.

[0174] The conditions and results are as follows (Tables 5 and 6):

[0175] [Tables5] Ex. Mol% Glycerol flow rate (mL / Min) Anhydride flow rate (mL / Min) Early flow rate (mL / Min) Residence time (min) Agitator rotation speed (m / s) T° (°C) at mill outlet Ex.8 FeOTf2 1 mol% 0.5 2 2.5 32 11 - Ex.9 H2SO4 0.5 2 2.5 32 11 - 1 mol% Ex.10 H2SO4 1 mol% 3.75 15 18.75 4 11 100

[0176] [Tableauxô] Ex. Yield % (triacetin) Productivity Kg / h Volumetric productivity Kg / h / L Ex.8 100 0.09 1.10 Ex.9 100 0.09 1.10 Ex.10 100 0.068 8.44

[0177] This shows that the three-dimensional mill alone, i.e. in the absence of the microbeads, is effective for the homogenization / reaction of glycerol and acetic anhydride. Without being bound by any theory, it would seem that in the particular case of glycerol and acetic anhydride, the beads could hinder homogenization due to the formation of glycerol / zirconia agglutinates and the passage of acetic anhydride through the preferential pathway.

[0178] Example C: Synthesis of polyol acetates according to the invention in a three-dimensional mill with heating device without the use of catalyst

[0179] The tests were carried out in a WAB IMPACT three-dimensional mill from Willy A. Bachofen AG (WAB) of 500mL without microbeads. The device includes an induction heating device.

[0180] In operation, the agitator has a rotation speed which can vary according to the examples from 4.6 to 11 m / s. The agitator further comprises an accelerator made of a chrome-reinforced alloy. The target temperature is 135°C.

[0181] The starting reagents (glycerol, acetic anhydride) are introduced into the mill according to the experimental conditions stated in the table below. In particular, glycerol was introduced into the mill at a precise flow rate using a peristaltic pump. Similarly, acetic anhydride was introduced into the reactor at a precise flow rate using a peristaltic pump as well. The outlets of the two pumps are connected via a T-fitting before the mill inlet. A total flow rate is calculated as follows: glycerol flow rate + acid anhydride flow rate.

[0182] The samples recovered at the outlet of the crusher are analyzed by proton NMR in deuterated DMSO.

[0183] Reaction conditions used and results (Tables 7 and 8):

[0184] [Tables7] Ex. Flow Rate Flow Rate Total Dwell Time Rotation Speed ​​Glycerol Anhydride (mL / Min) or agitator (mL / Min) (mL / Min) (min) (m / s) Ex.ll 13.6 65 79 6.4 10 Ex.12 6.8 32.5 39 13 10 Ex.13 4.5 22 26.5 19 10

[0185] [Tables8] Ex. Glycerol conversion (%) Monoacetin composition (ml and m2) (%) Diacetin composition (dl2 and dl3) (%) Triacetin composition (%) Ex.ll 99 8% 51 40 Ex.12 100 8% 40% 52% Ex.13 100 0% 30% 70%

[0186] By varying the residence time, it is possible to modulate the mono, di and tri acetate composition of the mixture. Example D#: Synthesis of other polyol acetates

[0187] For this test, the procedure is identical to that of Example B (three-dimensional ball mill) except that the polyol used is glycerol dimer. The catalyst used is sulfuric acid and the acid anhydride is acetic anhydride.

[0188] The experimental conditions, as well as the results, are illustrated in Tables 9 and 10 below.

[0189] [Tables9] Ex. Mol% Diglycerol flow rate (mL / Min) Anhydride flow rate (mL / Min) Early flow rate (mL / Min) Residence time (min) Agitator rotation speed (m / s) T° (°C) at mill outlet Ex.14 H2SO4 1 mol% 4.6 14.4 19 4 11 100

[0190] [TableauxlO] Ex. Yield % (diglycerol tetraacetate) Productivity Kg / h Volumetric productivity Kg / h / L Ex.14 100 0.09 1.10

[0191] Example E: Synthesis of polyol hexanoates

[0192] Example C is reproduced, except that the anhydride used is hexanoic anhydride. The polyol used is glycerol.

[0193] Reaction conditions used and results (Tables 11 and 12):

[0194] [T ables 11] Ex. Glycerol flow rate (mL / Min) Anhydride flow rate (mL / Min) Total flow rate (mL / Min) Residence time (min) Stirrer rotation speed (m / s) Ex.15 4.4 49 53 10 10 Ex.16 1.7 16.5 18 28 10

[0195] [Tablesl2] Ex. Conversion of gly cerol (%) Composition in mo nohexanoin (ml and m2) (%) Composition in dihe xanoin (dl2 and dl3) (%) Composition in tria hexanoin (%) Ex.15 97 18.5 40 40 Ex.16 97 11 30 56

Claims

Claims

1. Process for synthesizing a final composition comprising at least one polyol ester and a carboxylic acid implementing an exothermic acylation reaction from an initial mixture comprising at least two liquid starting reagents, preferably immiscible, which are a polyol and an acid anhydride, characterized in that it is carried out in continuous flow in a mechanical mixer comprising at least one mixing chamber, the process comprising the following successive steps: (A) the separate introduction and at room temperature of said at least two starting reagents into the mixer to form said initial mixture, (B) the mixing in said mechanical mixer of said initial mixture for a residence time less than or equal to 1 hour; (C) the recovery at the outlet of the mixer of said final composition.

2. The synthesis process of claim 1, wherein the polyol is selected from the group consisting of: glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol and other liquid glycerol oligomers or a mixture thereof.

3. A synthesis process according to claim 1 or 2, wherein the acid anhydride corresponds to the following general formula: p 0 [Chem. 1] 1 AR"' O'' "R where R is selected from: a linear or branched alkyl group comprising from 1 to 17 carbon atoms, preferably, R is selected from a methyl, pentyl or heptyl group and typically, R is a methyl group.

4. Process according to any one of the preceding claims, in which the molar ratio of acid anhydride to the number of hydroxyl groups within the polyol in the initial mixture is less than or equal to 10, preferably less than or equal to 6 and in particular less than or equal to 1.1, without ever being less than 1.

5. A method according to any preceding claim, wherein in the mixing step (B), the residence time of the initial mixture within the mechanical mixer is less than or equal to 50 minutes, in particular ranges from 30 seconds to 40 minutes and typically ranges from 1 minute to 30 minutes.

6. Synthesis process according to one of the preceding claims, in which the initial mixture comprises at least one catalyst.

7. The synthesis process of claim 6, wherein said at least one catalyst is an acid catalyst or a basic catalyst.

8. Synthesis process according to claim 7, wherein - the acid catalyst is selected from one or more of the following compounds: acetic acid (AcOH), sulfuric acid (H2SO4), cobalt (II) sulfate heptahydrate (CoSO4.7H2O), zinc chloride (ZnCl2), copper sulfate dihydrate (CuC12.2H2O), iron II chloride tetrahydrate (FeCl2.4H2O), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2) and is preferably sulfuric acid (H2SO4), iron II chloride hexahydrate (FeCl3.6H2O), iron II triflate (FeOTf2), - wherein the basic catalyst is selected from one or more of the following compounds: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate.

9. A synthesis method according to any one of the preceding claims 1 to 8, wherein the mixing step (B) is carried out without the supply of external heat, the temperature within the mixing chamber being at least 20°C and preferably ranging from 20°C to 150°C due to the exothermicity of the synthesis reaction.

10. A synthesis process according to any one of the preceding claims 1 to 5, wherein the initial mixture does not comprise a catalyst.

11. Synthesis method according to any one of claims 1 to 8 and 10, wherein during the mixing step (B), an external heat supply is carried out, so as to obtain a temperature within the mixing chamber which is at least 80°C, preferably which ranges from 100°C to 200°C and in particular from 110°C to 150°C.

12. Method according to any one of the preceding claims, in which the mechanical mixer is chosen from: a three-dimensional mill with or without balls.

13.

14. The method of claim 12, wherein said three-dimensional mill with or without balls comprises at least: - a generally cylindrical mixing chamber extending along a longitudinal axis XX, said mixing chamber comprising at a first end at least one inlet serving to introduce said starting reagents and at a second end, an outlet capable of discharging said final composition formed in said mixing chamber; and - a stirring system, arranged in the mixing chamber, comprising at least one rod or elongated coil extending along the longitudinal axis XX, said stirring system being capable of mixing said starting reagents. The method of claim 13, wherein the stirring system has a rotation speed ranging from 0.01 m / s to 20 m / s, preferably from 4 m / s to 18 m / s and typically from 6 m / s to 11 m / s.

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