Treatment of purified 2,5-furandicarboxylic acid with water and heat

Abstract

1. A thermal treatment of purified 2,5-furandicarboxylic acid (FDCA) to produce a carboxylic acid composition, the method comprising: providing or producing a thermal treatment composition comprising the purified carboxylic acid composition and a water-containing treatment solvent composition; subjecting the thermal treatment composition to an elevated temperature, wherein the FDCA is partially dissolved; and cooling the treated composition to separate at least a portion of the FDCA from the treated composition to obtain the carboxylic acid composition.

Description

[Technical Field]

[0001] The present invention relates to a process for the preparation of carboxylic compositions, the respective carboxylic compositions and starting materials for the preparation of polyalkylene furanoates. [Background technology]

[0002] 2,5-Furandicarboxylic acid (FDCA) is known in the art to be a highly promising building block for replacing petroleum-based monomers in the production of high-performance polymers. In recent years, much attention has been focused on the novel plant-based polyester polyethylene furanoate (PEF), a fully recyclable plastic with superior performance characteristics compared to FDCA and currently widely used petroleum-based plastics. These materials could significantly contribute to reducing dependence on petroleum-based polymers and plastics while enabling more sustainable management of global resources. Therefore, comprehensive research has been conducted in the field to arrive at technologies for producing FDCA and PEF in commercially viable ways, enabling the successful marketing of these promising materials.

[0003] FDCA is typically obtained as a crude carboxylic acid composition by oxidation of molecules containing a furan moiety, such as 5-hydroxymethylfurfural (5-HMF) and the corresponding 5-HMF esters or 5-HMF ethers, and similar starting materials, typically obtained from plant-based sugars, e.g., by dehydration of the sugars. A wide variety of oxidation processes are known in the prior art, including, for example, enzymatic or metal-catalyzed processes.

[0004] One of the most established techniques in the field uses a catalytic system containing cobalt, manganese, and bromine to oxidize compounds containing a furan moiety to FDCA using oxygen or air as an oxidant. Respective methods applicable to a wide variety of starting materials are disclosed, for example, in WO2014 / 014981A1 or WO2011 / 043660A1.

[0005] In most cases, the purity of the crude carboxylic acid composition obtained by the above-mentioned methods is not sufficient to achieve the required degree of purity required for the polymerization of FDCA into PEF or other high-performance polymers. Therefore, purification methods have been developed to further purify the crude carboxylic acid composition and produce a purified carboxylic acid composition. These methods include, for example, hydrogenation, post-oxidation, distillation, recrystallization, or similar methods, often combined with a comprehensive purification scheme that includes multiple steps to wash and isolate the resulting carboxylic acid composition. Exemplary purification methods are disclosed, for example, in WO 2014 / 014981 A1 or WO 2016 / 195499 A1.

[0006] Despite comprehensive efforts to improve existing methods for obtaining sufficiently pure FDCA (sometimes labeled polymer-grade FDCA), the results obtained by known purification methods are often not entirely satisfactory. Prior art methods for purifying crude FDCA often produce good results with respect to 5-formyl-2-furancarboxylic acid (FFCA), a major impurity that is often obtained due to incomplete oxidation of the starting material. However, these methods often do not achieve significant reductions in other common impurities, some of which may be present in significant amounts based on the process used for oxidation. In particular, some prior art methods do not result in significant reductions in the amount of 2-furancarboxylic acid (FCA), the monoacid corresponding to FDCA, which is often produced during oxidation, for example, by decarboxylation of FDCA.

[0007] Furthermore, it has been recognized in the art that solid FDCA particles obtained by prior art purification methods often have less desirable physical and mechanical properties. These properties include, for example, an increased amount of undesirable fines in the solid product, i.e., very small particles often shaped like shards of broken glass, and generally reduced strength of the resulting particles. Other less desirable properties include, for example, agglomeration, which may form during the isolation and drying procedures and result in abnormally large particles. These properties make the particles significantly more difficult and expensive to handle than most common petroleum-based diacids. For example, it is more difficult to inject or feed the solid FDCA product through tubes and pipes. Furthermore, the storage properties of solid FDCA are also less desirable, as the particles often tend to stick together.

[0008] Perhaps one of the most notable drawbacks of less desirable mechanical and physical properties is that it may be less easy to mix solid FDCA with other starting materials and catalysts required to produce the polymer, resulting in a less homogeneous starting mixture with concentration gradients that can adversely affect both the required reaction time and the quality of the resulting polymer.

[0009] The inventors of the present invention believe that the less desirable mechanical and physical properties are due to the particle shape and low strength, as well as the particle size distribution in the resulting purified FDCA composition, which in most cases exhibit plate-like particles with a large amount of fines. To date, no convenient method for efficiently improving the mechanical and physical properties of purified FDCA is known in the art.

[0010] The above-mentioned problems with less than desirable purity and mechanical properties of solid FDCA tend to occur regardless of the starting material used to make the FDCA.

[0011] However, in recent years, it has been discovered that a promising approach to accessing FDCA utilizes significant amounts of 5-HMF ether as the starting material for oxidation. As a result, the crude carboxylic acid compositions obtained from such processes not only contain the free diacid, i.e., FDCA, but also significant amounts of the monoalkyl ester of FDCA, and these processes currently appear to be the most established methods for producing significant amounts of the monomethyl ester of FDCA (FDCA-Me). While each method has several advantages over comparable methods that do not produce the monoalkyl ester of FDCA, the aforementioned drawbacks regarding the purity and mechanical properties of the solid FDCA obtained from these methods are particularly undesirable. The present inventors have now discovered that the monoalkyl ester of FDCA appears to be one of the impurities inadequately removed by many prior art purification methods. As a result, purified FDCA compositions produced using the above-mentioned techniques tend to contain significant amounts of FCA and FDCA-Me, where, in the subsequent polymerization reaction, FCA is a potential end-capping agent and FDCA-Me may produce methanol, which can result in dangerous side reactions. Furthermore, the present inventors have found that the presence of even trace amounts of FDCA-Me can result in mechanical and physical properties of the solid FDCA that are less favorable than those found in purified FDCA compositions that do not contain FDCA-Me. In summary, the deficiencies of the prior art processes described above are particularly evident in processes that include FDCA-Me in the crude and / or purified carboxylic acid composition. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] WO2014 / 014981A1 [Patent Document 2] WO2011 / 043660A1 [Patent Document 3] WO2016 / 195499A1 [Patent Document 4] WO2017 / 003293A1 [Patent Document 5] WO2016195499 [Patent Document 6] WO2016195500 [Patent Document 7] WO2016 / 195500A1 Summary of the Invention [Problem to be solved by the invention]

[0013] In view of the above-mentioned problems, there has been a long-felt need to overcome the respective shortcomings of the prior art processes. An object of the present invention was to provide an improved process that further increases the purity of the resulting carboxylic acid composition, particularly with respect to FCA and / or FDCA-Me impurities. Another object was to provide a process that results in a carboxylic acid composition with good mechanical and physical properties, thus allowing efficient handling of the solid product and favorable behavior of the solid FDCA in subsequent polymerization reactions. A further object of the present invention was to provide a process that can be easily combined with existing oxidation and purification processes and that can be carried out continuously, semi-continuously, or batchwise.

[0014] It would be desirable for the further process steps to be able to be carried out in a resource-efficient manner, and themselves to generate only small amounts of waste. It would also be desirable to provide a method that primarily uses chemical compounds and starting materials that are also utilized in other steps of the remaining manufacturing process, such as oxidation or purification, reducing storage costs and minimizing the amount of different materials that need to be handled in the manufacturing plant.

[0015] Similarly, it is preferable that each method require a limited amount of energy, utilize primarily non-corrosive materials, and be able to operate in a particularly safe manner, minimizing health risks and exposure of hazardous materials to the environment. Aside from the specific efficient purification requirements for FCA and / or FDCA-Me, it is further desirable that the method be able to remove a wide variety of possible impurities and effectively complement prior art purification methods.

[0016] Furthermore, it was an object of the present invention to provide a carboxylic acid composition that not only has high purity but also exhibits favorable physical and / or mechanical properties that allow for its efficient use as a starting material in subsequent polymerization reactions.

[0017] Correspondingly, it was another object of the present invention to provide starting materials for the preparation of polyalkylene furanoates which allow a reduction in reaction times during polymerization and / or which lead to particularly advantageous products. [Means for solving the problem]

[0018] The present inventors have now discovered a method for producing a carboxylic acid composition containing 2,5-furandicarboxylic acid, comprising the steps of: a) providing or producing a crude carboxylic acid composition comprising 2,5-furandicarboxylic acid and 5-formyl-2-furancarboxylic acid; b) purifying the crude carboxylic acid composition to produce a purified carboxylic acid composition comprising 2,5-furandicarboxylic acid, which is preferably at least partially solid, more preferably at least 5% solids, and most preferably at least 80% solids, wherein the purifying comprises: - hydrogenating at least a portion of the 5-formyl-2-furancarboxylic acid; - oxidizing at least a portion of the 5-formyl-2-furancarboxylic acid; - recrystallizing at least a portion of the 2,5-furandicarboxylic acid; and - hydrolyzing the dialkyl ester of 2,5-furandicarboxylic acid and at least one step selected from the group consisting of: c) providing or manufacturing a processing solvent composition comprising greater than 95% by weight, preferably greater than 98% by weight, more preferably greater than 99% by weight water based on the weight of the processing solvent composition; d) providing or manufacturing a thermal treatment composition comprising a purified carboxylic acid composition and a treatment solvent composition; e) subjecting the heat-treated composition to an elevated temperature in the range of 140-200°C for a time in the range of 5-240 minutes to obtain a treated composition, wherein the percentage of dissolved 2,5-furandicarboxylic acid relative to the total amount of 2,5-furandicarboxylic acid is in the range of 10-80%; f) cooling the treated composition to a temperature in the range of 20 to 80°C and separating at least a portion of the 2,5-furandicarboxylic acid from the treated composition to obtain a treated mother liquor containing a carboxylic acid composition and water; The carboxylic acid composition obtainable or obtained by the method is an altered carboxylic acid composition compared to the crude carboxylic acid composition of step a) and the purified carboxylic acid composition of step b). The altered carboxylic acid composition is hereinafter referred to as the carboxylic acid composition.

[0019] The above method provides a further process step in the production of a carboxylic acid composition containing FDCA, which is carried out after both the oxidation and purification steps. The further process step that is part of the present invention is a specific heat treatment, which involves mixing the purified carboxylic acid composition with a processing solvent composition and subjecting it to a heat treatment.

[0020] The heat treatment of the present method is carried out so that a certain percentage of the FDCA is dissolved in the treatment solvent composition during the heat treatment, while the remaining FDCA remains as a solid precipitate. Without wishing to be bound by theory, it is believed that it is the chemical equilibrium and exchange between the dissolved and precipitated FDCA, combined with the extended duration of the heat treatment, that results in the particular advantageous particle shape, increased particle strength, and / or beneficial particle size distribution of the solid FDCA obtained after the heat treatment. Surprisingly, it has been found that the purity of the material obtained by the method using a particular percentage of FDCA that is dissolved during the heat treatment is superior to the purity of material processed by a method in which the FDCA is fully dissolved. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 shows exemplary particles of FDCA obtained by a method according to the present invention without heat treatment, the scale corresponds to 100 μm. [Figure 2] FIG. 1 shows exemplary particles of FDCA obtained by a method according to the present invention without heat treatment, the scale corresponds to 100 μm. [Figure 3] 1 is a diagram showing exemplary particles of FDCA obtained by a method involving heat treatment according to the present invention, the scale corresponds to 100 μm. DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following, the subject matter of the present invention will be considered in more detail and preferred embodiments of the present invention will be disclosed. Thereby, it is particularly preferred to combine two or more preferred embodiments to obtain a particularly preferred embodiment. Correspondingly, the method according to the present invention for defining two or more features of a preferred embodiment of the present invention is particularly preferred.

[0023] The carboxylic acid composition is a carboxylic acid composition that contains a reduced amount of at least one furan-based impurity, i.e., any material having a furan moiety that is not 2,5-furandicarboxylic acid, and / or exhibits improved mechanical and / or physical properties when compared to a purified carboxylic acid composition.

[0024] Step a) of the process according to the present invention is the preparation or production of a crude carboxylic composition containing FDCA and FFCA, i.e., the most important impurities produced during the oxidation of the starting material due to incomplete oxidation. According to the present invention, the crude carboxylic composition may be prepared, for example, obtained from another process or separate facility, or may be produced using one of several methods for obtaining a crude carboxylic composition containing FDCA and FFCA known from the prior art. The process of the present invention is not limited with respect to the oxidation method used to obtain the crude carboxylic composition. However, the crude carboxylic composition is preferably produced by oxidation of a compound having a furan moiety, preferably 5-hydroxymethylfurfural and / or an alkyl ether of 5-hydroxymethylfurfural, with a catalytic system containing cobalt, manganese, and bromine in the presence of a solvent composition containing oxygen as an oxidizing gas, a saturated organic acid solvent having 2 to 6 carbon atoms, and water.

[0025] Step b) of the process of the present invention corresponds to the purification of the crude carboxylic acid composition prepared or produced in step a), resulting in a purified carboxylic acid composition comprising at least partially solid 2,5-furandicarboxylic acid. The process of the present invention comprises at least one purification step selected from the group defined above, which steps correspond to the most important steps of the most well-established purification methods for crude carboxylic acid compositions known in the prior art. Apart from FFCA, other color bodies and impurities, such as so-called heavy furanics, i.e., molecules containing more than one furan moiety, are often also removed during the purification step.

[0026] At least partial hydrogenation of 5-formyl-2-furancarboxylic acid corresponds to purification by hydrogenation based on well-known principles in which several impurities in the crude carboxylic acid composition may be selectively hydrogenated and then separated from the FDCA.

[0027] Within the framework of the present invention, purification by hydrogenation is particularly preferred. Hydrogenation is preferably carried out by contacting the crude carboxylic acid composition with hydrogen in the presence of a hydrogenation solvent and a hydrogenation catalyst that hydrogenates the FDCA into a hydrogenation product, and separating the FDCA from the hydrogenation product. The hydrogenation solvent is preferably water, and the hydrogenation catalyst is preferably palladium on carbon. As a general rule, the hydrogenation catalyst may be selected from a wide variety of available catalysts. Typically, the hydrogenation catalyst comprises one or more metals or metal compounds selected from metals in Groups 8 to 10 of the Periodic Table on a support. Suitable such metals include Pt, Pd, Ru, Rh, Ir, Os, Ni, Co, and mixtures thereof. As is known in the art, such hydrogenation is usually carried out under well-dissolved conditions.

[0028] The step of at least partially oxidizing 5-formyl-2-furancarboxylic acid corresponds to a purification by post-oxidation and is based on the concept that the product of incomplete oxidation, i.e., FFCA, can be oxidized to FDCA in a subsequent oxidation reaction.

[0029] Purification by at least partial recrystallization of the FDCA corresponds to the well-known technique of dissolving the carboxylic acid product in a second solvent and / or changing the solubility of the FDCA in the original solvent by changing the temperature, resulting in dissolution and subsequent precipitation of the desired product.

[0030] Finally, the step of hydrolyzing the dialkyl ester of 2,5-furandicarboxylic acid corresponds to a purification method in which FDCA and / or a monoalkyl ester of FDCA in the crude carboxylic acid composition is esterified with an alcohol to produce a dialkyl ester of 2,5-furandicarboxylic acid (e.g., FDCA-DMe), where the purification is achieved by distillation, recrystallization, or melt crystallization of the resulting composition, and subsequently hydrolyzing the purified dialkyl ester of FDCA to obtain purified FDCA. In other words, the step of hydrolyzing the dialkyl ester of 2,5-furandicarboxylic acid corresponds to forming a dialkyl ester of FDCA from the crude carboxylic acid composition, purifying the dialkyl ester of FDCA, and then hydrolyzing the dialkyl ester of FDCA to obtain FDCA.

[0031] In step c), a processing solvent composition is prepared or manufactured that contains greater than 95% by weight of water based on the weight of the processing solvent composition. The processing solvent composition is a solvent composition that acts as a solvent during the thermal treatment step and as a carrier liquid in the dispersion for the remaining solids. A preferred processing solvent composition comprises a saturated organic acid having 2 to 6 carbon atoms and water.

[0032] It has surprisingly been found that acceptable results can be obtained when the processing solvent composition comprises water as the major component, i.e., greater than 95% by weight of water based on the weight of the processing solvent composition. The use of essentially pure water as the processing solvent composition is preferred because the use of water is relatively inexpensive and allows for a highly sustainable process.

[0033] The processing solvent composition may be obtained by mixing water and another solvent in a different reactor and feeding it to the process of the present invention. However, the processing solvent composition may also be produced within the framework of the process of the present invention. Here, it is particularly preferred to use the solvent composition utilized in purification step b) to produce the processing solvent composition. The production of the processing solvent composition from the solvent used in purification step b) may include all suitable steps to arrive at the processing solvent composition defined above, including filtration, addition of an organic acid solvent having 2 to 6 carbon atoms, addition of water, removal of the organic acid compound, or removal of water.

[0034] In a preferred embodiment, the purified carboxylic acid composition obtained in step b) and at least a portion of the solvent used for purification in step b) are both sent to a heat-treatment reactor, where a saturated organic acid solvent having 2 to 6 carbon atoms and / or water are preferably added as additional solvent or removed to produce the heat-treated composition. The portion of solvent may consist of solvent that remains attached to the solids, for example after a filtration or centrifugation step.

[0035] Step d) involves providing or manufacturing a thermal treatment composition comprising a purified carboxylic acid composition and a processing solvent composition. The thermal treatment composition actually comprises a liquid phase and a solid phase. The purified carboxylic acid composition is obtained from step b). The processing solvent composition is obtained from step c). The thermal treatment composition may be obtained by combining the purified carboxylic acid composition and the processing solvent composition in any manner known to be suitable to those skilled in the art.

[0036] In the context of the present invention, step e) is often called heat treatment or heat treatment step.

[0037] According to the present invention, the heat-treated composition is subjected to an elevated temperature in the range of 140 to 200°C for a time in the range of 5 to 240 minutes. It is essential to the present invention that the percentage of dissolved FDCA relative to the total amount of FDCA is in the range of 10 to 800%. This degree of dissolution is preferably maintained for at least 5 minutes during the entire heat treatment, and the respective amount of dissolved FDCA preferably remains within a given range during the entire 5 to 240 minutes of heat treatment. The percentage of dissolved 2,5-furandicarboxylic acid preferably remains within a given range when averaged over the duration of the heat treatment, provided that the actual value remains within the predetermined range for at least 5 minutes.

[0038] Those skilled in the art can adjust the heat treatment conditions to the desired degree of dissolution and may use the following Table 1, which lists solubility values ​​for FDCA at a given temperature depending on the solvent composition used. These data were generated from experimental values ​​and fitted to an appropriate solubility model. Intermediate values ​​can be obtained by interpolation.

[0039] [Table 1]

[0040] After subjecting the heat-treated composition to an elevated temperature in heat-treatment step e), the treated composition is cooled to a temperature in the range of 20-80°C, thereby reducing the solubility of FDCA in the solvent and causing precipitation of the carboxylic acid composition. The carboxylic acid composition is obtained by separating at least a portion of the solid FDCA from the treated composition, leaving behind a mother liquor containing water.

[0041] The carboxylic acid composition not only exhibits increased purity compared to the purified carboxylic acid composition, but also features solid particles that, unlike the purified carboxylic acid composition, tend to be more spherical rather than exhibiting the undesirable plate-like shape. Similarly, the particle size distribution tends to be more favorable, allowing for easier handling of the solid product. The resulting carboxylic acid composition tends to exhibit very favorable mixing behavior with alkylene glycols, preferably ethylene glycol, and therefore constitutes a very promising starting material for the production of polyalkylene furanoates.

[0042] The above-mentioned heat treatment step used in the process of the present invention may be advantageously incorporated into existing processes for producing carboxylic acid compositions containing FDCA, since the process of the present invention is not limited with respect to the technology used to obtain crude FDCA and can be combined with the most important purification methods known in the prior art.

[0043] It is beneficial for the process solvent composition to include water, as water is one of the most common solvents used in some prior art processes, both in the oxidation reaction and in the purification of crude FDCA, e.g., during hydrogenation or post-oxidation of impurities, which allows for efficient plant management and reduces the need to store additional chemicals, thus reducing storage costs.

[0044] Surprisingly, the method of the present invention allows the aforementioned beneficial effects to be achieved without the need for expensive catalysts or highly corrosive and / or harmful substances, and the surprisingly high suitability of water as the main component of the treatment solvent composition is particularly advantageous. Furthermore, the treatment mother liquor containing water for use in other steps of the method of the present invention can be preferably reused in the oxidation step and / or the purification step and / or the thermal treatment step. This allows for a particularly sustainable method that generates less waste.

[0045] In step b), the process is preferred, which comprises at least two steps selected from the group defined in step b).Furthermore, the process according to the invention is preferred, wherein in step b), the purification comprises hydrogenating at least a portion of the 5-formyl-2-furancarboxylic acid and crystallizing at least a portion of the solid 2,5-furandicarboxylic acid from the hydrogenation reaction mixture.

[0046] Within the framework of the present invention, the expression "at least a part of" preferably means at least 20%, preferably at least 30%, more preferably at least 40%, even more preferably at least 50% and most preferably at least 60%, with respect to concentrations, unless otherwise indicated, these values ​​being given as percentages by weight.

[0047] Preferred is a process according to the invention, wherein the crude carboxylic acid composition and / or the purified carboxylic acid composition comprises a monoalkyl ester of 2,5-furandicarboxylic acid, preferably the monomethyl ester of 2,5-furandicarboxylic acid (FDCA-Me).

[0048] As previously discussed, the preferred method is particularly advantageous due to the fact that the problem underlying the present invention has been found to be particularly pronounced for processes that include a monoalkyl ester of FDCA in the crude carboxylic acid composition and / or the purified carboxylic acid composition. The respective crude carboxylic acid compositions containing a monoalkyl ester of FDCA may be produced, for example, by oxidizing a starting material feed containing an alkyl ether of 5-HMF. Due to the fact that most prior art purification methods are not well suited to completely removing the monoalkyl ester of FDCA from the crude carboxylic acid composition, it is often observed that both the crude carboxylic acid composition and the purified carboxylic acid composition contain a monoalkyl ester of 2,5-furandicarboxylic acid.

[0049] In one of the most mature technologies in the field, the monomethyl ester of FDCA and the monoethyl ester of FDCA are the most important monoalkyl esters of FDCA, and since the monomethyl ester of FDCA is particularly prevalent, the presence of the monomethyl ester of FDCA (FDCA-Me) in the crude carboxylic acid composition and the purified carboxylic acid composition is particularly preferred due to its high industrial importance. As detailed above, when the purified FDCA also contains the monoalkyl ester of FDCA, particularly the monomethyl ester of FDCA, it is often found that the mechanical and physical properties of the solid purified FDCA are less desirable. Without wishing to be bound by any theory, this is believed to be due to the formation of a so-called solid solution of FDCA and FDCA-Me. Surprisingly, the inventors of the present invention have found that the formation of a solid solution of FDCA and FDCA-Me can be very efficiently compensated for and / or prevented by the method of the present invention, which has been shown to be particularly effective both in removing FDCA-Me and in enhancing the physical and mechanical properties of the solid product.

[0050] Preferred is a process according to the invention, wherein step e) is carried out in a reactor pressurized with an inert gas, preferably nitrogen or argon, and / or the heat-treated composition of step e) is agitated, preferably by stirring, at least part of the time, to expose the solid 2,5-furandicarboxylic acid to shear forces.

[0051] It is particularly advantageous to carry out step e) in a reactor pressurized with an inert gas, since this reduces the presence of oxygen or other reactive gaseous compounds in the reactor that may otherwise be present from previous process steps. In these embodiments, the atmosphere in the reactor during operation is primarily composed of an inert gas and vaporized organic acid solvent and / or water. As a result, undesirable side reactions between FDCA and reactive gaseous compounds are inhibited. Therefore, the use of an inert gas allows for a particularly safe process, since the possibility of potentially dangerous side reactions and / or exothermic reactions and / or fires is reduced.

[0052] While the results of the method according to the present invention are often found to be satisfactory by heat-treating the heat-treated composition alone, the inventors have discovered that further agitating the heat-treated composition in step e) and exposing the solid FDCA particles to shear forces can further increase the beneficial effect of the resulting carboxylic acid composition on the mechanical and physical properties of the particles. Without wishing to be bound by any theory, it is believed that agitating the heat-treated composition during heat treatment also enhances the homogeneity of the liquid phase and reduces the concentration gradient of impurities, thereby facilitating both purification and improving the mechanical properties of the resulting particles. Agitation may be achieved by any suitable means known to those skilled in the art, such as stirring the heat-treated composition or utilizing an external pumping loop.

[0053] A method according to the invention is preferred, wherein the heat treatment composition comprises 2,5-furandicarboxylic acid in an amount of 15 to 45% by weight, preferably 20 to 40% by weight, relative to the weight of the heat treatment solvent composition.

[0054] Such a preferred method is advantageous because the desired ratio between dissolved and solid FDCA in step e) can be easily obtained when the respective amount of FDCA is used without the need for high temperatures and with high flexibility regarding the composition of the solvent employed.

[0055] Preferred is a method according to the present invention, wherein the processing solvent composition comprises acetic acid in an amount preferably in the range of 0.05 to 4.5% by weight, preferably 0.1 to 3% by weight, relative to the amount of processing solvent composition.

[0056] When the primary objective is to obtain the highest possible degree of purity and the most advantageous mechanical properties, a respective processing solvent composition containing a specified amount of acetic acid is particularly preferred, as the presence of acetic acid has been found to allow for the best impurity removal.

[0057] As previously discussed, using water as the primary component of the treatment solvent composition surprisingly yields reasonable results in the heat treatment and can be advantageous from the standpoint of cost and sustainability. In particular, heat treatment in water has been found to produce similar particle shapes as heat treatment in organic acids, which in some cases has been found to provide better results in impurity removal, but has other drawbacks, for example, with respect to process sustainability and starting material costs. Furthermore, heat treatment in water has the potential to produce similar product quality, at least in terms of FDCA-Me and FCA content, when process parameters are adjusted (e.g., longer residence time). Without wishing to be bound by any theory, it is believed that at least part of this may be due to the conversion of FDCA-Me to FDCA by hydrolysis. Heat treatments utilizing primarily or exclusively water as the solvent have been found to require higher temperatures or longer residence times in some cases compared to heat treatments in organic acids. Correspondingly, a method in which the heat-treated composition of step e) is subjected to an elevated temperature in the range of 160 to 200°C for a time period in the range of 30 to 240 minutes is preferred.

[0058] Preferred is a process according to the invention, wherein the purified carboxylic acid composition produced in step b) comprises less than 25%, preferably less than 15%, most preferably less than 10% by weight of solvent, based on the weight of the purified carboxylic acid composition.

[0059] Each method is preferred because it may be beneficial to remove a significant amount of the solvent used during purification step b) from the purified carboxylic acid composition, which can then be mixed with the treatment solvent composition to obtain the thermally treated composition (e.g., to keep water from the purification step out of the solvent loop for thermal treatment, which is carried out at a low water content). Each method is particularly beneficial for methods that utilize purification processes that use different solvents, such as aromatics, that may be inconvenient for the thermal treatment step, or that produce significant amounts of soluble by-products and / or impurities that may be removed prior to thermal treatment by intermediate isolation of the purified carboxylic acid.

[0060] The process parameters in steps e) and f) are - exhibits a reduction in mean particle size of less than 35%, preferably less than 25%, between particle size measurements at a dispersion pressure of 0.2 bar and 2 bar; and / or - have a volume average median particle size (d50) in the range of 50 to 300 μm, preferably in the range of 60 to 200 μm The process according to the invention, which is selected to produce particles of 2,5-furandicarboxylic acid, is preferred.

[0061] One of the most beneficial aspects of the method of the present invention is its ability to provide both further purification and enhanced mechanical and physical properties of the resulting product. Surprisingly, this synergistic relationship makes it possible to reliably estimate or predict either purity or mechanical property aspects by measuring and analyzing the respective other parameters. Because the mechanical properties and / or particle size distribution of the product obtained by the method of the present invention can be readily determined in most cases, the preferred method is particularly advantageous because those skilled in the art can monitor the above parameters and predict with great certainty the time required to reach the desired degree of purity without having to perform comprehensive chemical analysis of the product. The respective advantages have been found to be particularly clear for methods involving monoalkyl esters of FDCA. Without wishing to be bound by theory, this is believed to arise from the undesirable effect that the monoalkyl ester of FDCA may, in some cases, have on the mechanical properties and particle size distribution of the resulting product. In other words, the desired particle shape defined by the preferred method has been found to be reached in many cases when the desired degree of purity for FDCA-Me is also obtained.

[0062] Both the average particle size and the volume average median particle size (d50) are parameters well known to those skilled in the art and can be reliably determined. In fact, typical measurements used in the art for determining each parameter are expected to yield at least similar values. Therefore, in the vast majority of cases, the device used to determine the average particle size and the volume average median particle size (d50) is not important. However, in case of doubt, the average particle size and the volume average median particle size (d50) are measured using one of the most common devices for particle size measurement, namely, a laser diffraction particle size analyzer model Mastersizer 3000 manufactured by Malvern Panalytical, with laser obscuration of 1.5%, refractive index of 1.538, and dispersion pressure of 0.2 bar, using the PSD dry method.

[0063] The reduction in mean particle size between particle size measurements at 0.2 bar and 2 bar dispersion pressures is measured on the same material, but on different aliquots (i.e., not subsequent measurements on the same particles). For this, samples are tested using two different levels of air pressure to create particle dispersion. Results using 0.2 bar dispersion pressure are considered the "gentlest," while results using 2 bar dispersion pressure are more aggressive dispersions. This may be used, for example, as a test of particle strength and stability under conditions that may represent stresses experienced during pneumatic conveying operations.

[0064] Preferred is a process according to the present invention, wherein the crude carboxylic acid composition comprises 2-furan carboxylic acid in an amount preferably in the range of 1 to 2000 ppm by mass relative to the mass of the composition, more preferably in an amount in the range of 1 to 1000 ppm by mass relative to the mass of the composition, and wherein the carboxylic acid composition comprises 2-furan carboxylic acid in an amount of 700 ppm by mass or less, more preferably 500 ppm by mass or less.

[0065] As discussed above, FCA is one of the impurities in crude carboxylic acid compositions containing FDCA, and they are often insufficiently removed by prior art purification methods. In particular, FCA is an aromatic carboxylic acid, which is somewhat stable under oxidizing conditions and difficult to remove by oxidation. Furthermore, as an aromatic carboxylic acid, FCA is resistant to hydrogenation under conditions that hydrogenate FDCA but not FDCA, making it difficult to remove by hydrogenation. While FDCA can be esterified to form a diester and then removed by distillation, recrystallization, or melt crystallization, this method is also inappropriate for removing FCA because new FCA is formed when the purified dialkyl ester is hydrolyzed to produce a diacid. Surprisingly, it has been found that the method of the present invention, i.e., a method including thermal treatment, can significantly reduce the amount of FCA in a carboxylic acid composition. The preferred method is particularly advantageous due to its surprisingly high suitability for removing FCA from carboxylic acid compositions containing FDCA. As previously discussed with regard to mechanical and physical properties, it has been surprisingly found that when heat treatment is used for carboxylic compositions containing FCA, it is possible to very reliably estimate or predict whether the mechanical and physical properties of the product will be sufficient from the concentration of FCA in the carboxylic composition. It has been found that carboxylic compositions containing FCA in an amount of 700 ppm by weight or less, preferably 500 ppm by weight or less, relative to the weight of the carboxylic composition, exhibit satisfactory physical and mechanical properties after heat treatment. This is advantageous because, depending on the availability of equipment in the facility, it may be preferable to analyze the chemical composition of the obtained product instead of directly analyzing its mechanical properties.

[0066] the crude carboxylic acid composition comprises 2,5-furandicarboxylic acid in an amount in the range of 90 to 99.5% by mass, preferably in the range of 94 to 99% by mass, based on the mass of the crude carboxylic acid composition; and / or The crude carboxylic acid composition contains 2,5-furandicarboxylic acid in an amount ranging from 90 to 99.5% by mass, preferably from 94 to 99% by mass, based on the total mass of all furanic acids in the crude carboxylic acid composition; and / or the crude carboxylic acid composition contains 5-formyl-2-furancarboxylic acid in an amount in the range of 100 to 3800 ppm by mass, preferably in the range of 150 to 3000 ppm by mass, and more preferably in an amount of 1500 ppm by mass or less, relative to the mass of the crude carboxylic acid composition; and / or The crude carboxylic acid composition is 0.2 to 100% by mass of the crude carboxylic acid composition. 5.0 Preferred is a process comprising the monoalkyl ester of 2,5-furandicarboxylic acid in an amount in the range of % by weight, preferably in an amount in the range of 0.3 to 3% by weight.

[0067] The above-mentioned method is preferred because the heat treatment carried out in such a manner has been found to be particularly effective when used in a process starting from the respective crude carboxylic acid composition. The term furanics is known in the art and describes all compounds containing at least one furan moiety, i.e., a substituted or unsubstituted furan ring. In practice, the most important furanics are typically furan, 5-HMF and its ethers and esters, FCA and its esters, FDCA and its esters, FFCA and its esters, 2,5-diformylfuran, 5-methylfuran-2-carboxylic acid, and dimers of these compounds.

[0068] the purification in step b) comprises hydrogenating at least a portion of the 5-formyl-2-furancarboxylic acid; and / or Preferred is a process according to the invention, wherein the purification in step b) also comprises a step of isolating the purified carboxylic acid composition, wherein the isolation comprises filtering and / or washing and / or drying.

[0069] Thermal treatment has been found to perform particularly well when combined with hydrogenation as a purification method, and therefore both methods are preferred. Purification by hydrogenation is particularly cost-effective and suitable for large product volumes handled in continuous or semi-continuous processes, as well as being highly efficient in removing FDCA from the crude carboxylic acid composition. Hydrogenation as a purification method is also particularly preferred because this method typically utilizes a hydrogenation solvent containing primarily water. Therefore, the hydrogenation solvent composition can often be used as a precursor to the treatment solvent composition utilized during thermal treatment. In most cases, water and / or an organic acid must be added to adjust the desired composition of the treatment solvent composition, but in some cases, at least a portion of the hydrogenation solvent can be used directly as the treatment solvent composition without modification. However, in these cases, it is often preferable to remove at least a portion of the hydrogenation solvent to establish the desired percentage of dissolved FDCA during thermal treatment. For example, a hydrogenation process utilizing fully dissolved conditions can be followed by crystallization using an evaporative crystallizer to remove a portion of the hydrogenation solvent and increase the concentration of FDCA in the process. Other options for partial solvent removal include methods such as decantation, hydrocyclones or clarifiers.

[0070] While the methods of the present invention reliably produce good results in terms of purity and mechanical properties of the carboxylic acid composition, it has been found that it can be particularly beneficial to include an isolation step in which the purified carboxylic acid composition is isolated from other components, such as the solvent used in purification. Such isolation steps typically include filtration and / or washing and / or drying steps. While each method is not usually optimized for cost and / or time efficiency, intermediate isolation of the solid product facilitates purification during heat treatment and allows for tighter control of the composition of the heat-treated composition without having to consider changes in liquid components. Correspondingly, and as noted above, each method is expected to produce one of the highest purities of the carboxylic acid composition.

[0071] the purified carboxylic acid composition contains 2,5-furandicarboxylic acid in an amount in the range of 95 to 99.9% by mass, preferably in the range of 98 to 99.9% by mass, based on the mass of the purified carboxylic acid composition; and / or the purified carboxylic acid composition contains 5-formyl-2-furancarboxylic acid in an amount in the range of 1 to 200 ppm by mass, preferably in the range of 1 to 100 ppm by mass, relative to the mass of the purified carboxylic acid composition; and / or the purified carboxylic acid composition contains a monoalkyl ester of 2,5-furandicarboxylic acid in an amount in the range of 100 to 13,000 ppm by mass, preferably in the range of 200 to 11,000 ppm by mass, relative to the mass of the purified carboxylic acid composition; and / or Preferred is a process according to the invention, wherein the purified carboxylic acid composition comprises 2-furancarboxylic acid in an amount in the range of 1 to 2500 ppm by mass, preferably in an amount in the range of 1 to 1700 ppm by mass, relative to the mass of the purified carboxylic acid composition.

[0072] The heat treatment of the present method has been found to work particularly well with purified carboxylic acid compositions of a given specification, and therefore each method is preferred. While the present method tends to result in an increased degree of product purity and enhanced mechanical and physical properties for a wide variety of purified carboxylic acid compositions studied, in some cases, reduced efficiency has been observed when the overall amount of impurities, particularly the amount of alkyl esters of FDCA and FCA, exceeds a certain threshold. Similar effects have been observed with other purification methods due to the fact that the amount of solvent that can be utilized to dissolve impurities is limited by an inherent feature of the heat treatment, namely, the need for a certain amount of FDCA to remain in the solid phase during the heat treatment.

[0073] Similarly, the heat treatment of the present invention has been found to be less suitable for removing FFCAs, which are also undesirable end-stoppers in polymer-grade FDCAs, and therefore the above method is preferred. Correspondingly, a method in which the purification step b) is carried out so as to remove most of the FFCAs before the heat treatment is preferred. Understanding that the ability of heat treatment to remove FFCAs is relatively low, those skilled in the art can easily adjust the prior art method to produce a purified carboxylic acid composition with the desired amount of FFCAs.

[0074] The temperature in step e) is in the range of 150 to 190°C, preferably in the range of 160 to 190°C. and / or The heat treatment composition of step e) is heated for a period of time ranging from 15 to 120 minutes, preferably from 30 to 90 minutes, most preferably from 0.7 * (220-T / ℃)~3.0 * (220-T / °C) minutes, where T is the temperature in step e). and / or Preferred is a process wherein in step e) the percentage of dissolved 2,5-furandicarboxylic acid relative to the total amount of 2,5-furandicarboxylic acid is in the range of 20-60%, preferably in the range of 30-60%.

[0075] The above method is preferred because it defines the process parameters of the heat treatment that have been found to be most suitable for obtaining the best results for the carboxylic acid composition in terms of both purity and mechanical properties. Here, the temperature range during the heat treatment and the percentage of dissolved FDCA are related by factors that are mainly determined by the composition and amount of the treatment solvent composition. Advantageously, based on screening experiments, a suitable residence time may be given depending on the heat treatment temperature disclosed above.

[0076] The treated composition of step f) is cooled to a temperature in the range of 30 to 80°C, preferably in the range of 40 to 80°C. and / or step f) comprises treating the treatment mother liquor to remove at least a portion of the water from the remaining treated composition; and / or A process according to the invention is preferred, wherein step f) comprises recycling at least a portion of the processing mother liquor to provide the processing solvent composition in step c).

[0077] It may be appreciated that the cooling in step f) is expected to affect the mechanical properties of the resulting product, since a decrease in temperature may reduce the solubility of FDCA in the processing solvent composition, resulting in precipitation of the dissolved FDCA. Correspondingly, those skilled in the art seeking to modify the mechanical properties of carboxylic acid compositions should consider varying the temperature gradient between the heat treatment in step e) and the cooling in step f). It has been found that it can be beneficial if the temperature gradient during step f) is reproducibly controlled and not too steep. It is preferable to cool the processed composition to a temperature well above typical room temperature, between 20 and 25°C. A level of 2530 to 120 K / h is preferred, with cooling rates of up to 600 K / h being quite acceptable. While not wishing to be bound by theory, the inventors believe that the presence of a large solid fraction at the processing temperature reduces the risk of fines formation or spontaneous nucleation that might otherwise be experienced at these relatively high cooling rates. A high cooling rate is advantageous because the thermal stress on the system is not extended longer than necessary to produce the desired processing effect. Excessive thermal stress can result in undesirable reactions, including, for example, color formation. A high cooling rate is advantageously provided by evaporating at least a portion of the solvent, for example by boiling the solvent.

[0078] To increase the sustainability of the thermal treatment process and reduce the amount of waste generated by the method according to the present invention, it is preferable to recycle at least a portion of the treatment mother liquor back into the thermal treatment process. This means that at least a portion of the treatment mother liquor is used as the treatment solvent composition in the thermal treatment of the purified carboxylic acid composition. In this recycle process, it may be important to adjust the solvent composition to account for any changes that may have occurred. For example, if the purified carboxylic acid composition is wet with water, e.g., filtered and washed with water but not dried, water should be incorporated into the mother liquor after the thermal treatment and at least a portion removed from the mother liquor before reuse. In this way, the overall thermal treatment composition can be maintained at a desired concentration level.

[0079] The present invention further relates to a carboxylic acid composition comprising greater than 98% by weight of 2,5-furandicarboxylic acid, based on the weight of the carboxylic acid composition, wherein the carboxylic acid composition particles exhibit a decrease in average particle size of less than 35% between particle size measurements at dispersion pressures of 0.2 bar and 2 bar, the carboxylic acid composition preferably comprising less than 0.1% by weight of a saturated organic acid solvent having 2 to 6 carbon atoms, and the carboxylic acid composition is preferably produced using the method of the present invention.

[0080] Faced with the objective of providing a carboxylic acid composition that has good physical and / or mechanical properties and that can be efficiently processed, for example during storage or transport of the product, the inventors have surprisingly found that the technical problem can be solved by providing said carboxylic acid composition, each parameter being an indication that the particles are suitable for efficient handling and long-term storage, and therefore beneficial.

[0081] The carboxylic compositions of the present invention may be produced using the process of the present invention, in particular by a thermal treatment step of a purified carboxylic composition. Correspondingly, carboxylic compositions produced using the process of the present invention or preferred embodiments of the process of the present invention are preferred.

[0082] The carboxylic acid composition particles have a volume average median particle size (d50) in the range of 50 to 300 μm, preferably in the range of 60 to 200 μm. and / or the carboxylic acid composition particles have a d10 of 20 μm or greater, where d10 is defined as the diameter at which 10% by volume of the particles have a smaller diameter; and / or the carboxylic acid composition particles have a d90 of 400 μm or less, d90 being defined as the diameter at which 90% by volume of the particles have a smaller diameter; and / or Preferred are carboxylic acid compositions according to the invention, in which the ratio of d50 to d10 is in the range of 1 to 3, preferably in the range of 1.5 to 2.5.

[0083] When analyzing those carboxylic composition particles that exhibited the most advantageous mechanical properties, it was found that each carboxylic composition particle tended to exhibit a particular particle size distribution that is believed to be at least partially responsible for the fact that the carboxylic composition particles according to the present invention can be easily injected and pumped through piping, while maintaining their properties even after long-term storage. Furthermore, it was found that these carboxylic composition particles have favorable properties for producing slurries with good stability and good pumping and mixing characteristics.

[0084] the carboxylic acid composition contains a monoalkyl ester of 2,5-furandicarboxylic acid, preferably a monomethyl ester of 2,5-furandicarboxylic acid, in an amount in the range of 200 to 5000 ppm by mass relative to the mass of the carboxylic acid composition; and / or the carboxylic acid composition contains 2-furancarboxylic acid in an amount ranging from 10 to 500 ppm by mass, preferably from 20 to 200 ppm by mass, relative to the carboxylic acid composition; and / or Preferred are carboxylic acid compositions according to the invention, which comprise 5-formyl-2-furancarboxylic acid in an amount ranging from 1 to 100 ppm by weight, preferably from 2 to 50 ppm by weight, and most preferably less than 30 ppm by weight, based on the carboxylic acid composition. Such carboxylic acid compositions are preferred not only because they have particularly favorable mechanical parameters, but also because they contain small amounts of impurities known to have the most detrimental effect on the polymerization behavior of carboxylic acid compositions.

[0085] The present invention also relates to a starting material for the production of polyalkylene furanoate, also called poly(alkylene-2,5-furandicarboxylate), comprising a carboxylic acid composition according to the present invention and an alkylene glycol, preferably ethylene glycol, and a polymerization catalyst, wherein the polyalkylene furanoate is preferably poly(ethylene-2,5-furandicarboxylate).

[0086] The starting materials for the production of polyalkylene furanoates are mixtures of the carboxylic acid composition of the present invention, alkylene glycol, and a typical polymerization catalyst known in the art. Each composition is particularly suitable for use in polymerization reactions leading to polyalkylene furanoates. As discussed above, this is due to the advantageous mechanical and physical properties of the carboxylic acid composition of the present invention, i.e., the carboxylic acid composition obtained by the method of the present invention. The shape and specific particle size distribution of the FDCA particles tend to allow for very efficient mixing with alkylene glycol, even at low molar ratios. In sharp contrast, solid FDCA obtained by prior art purification methods is often found not to form the desired mixture with ethylene glycol at low molar ratios. This poses a significant problem for polymerization processes that produce high-performance polymers of a given composition and therefore cannot be easily adapted to simply increase the molar ratio, allowing for enhanced mixing of the starting materials, or to provide the additional energy required to remove the unwanted excess glycol. As a result, the carboxylic acid compositions of the present invention and their use as starting materials in the polymerization of polyalkylene furanoates are highly advantageous compared to purified carboxylic acid compositions comprising monoalkyl esters of FDCA, particularly because of their manufacturing history, and fulfill a long-felt need.

[0087] The present invention will now be described in more detail using experiments.

[0088] Example A Heat treatment: A1 - Preparation of purified FDCA A crude carboxylic acid composition (cFDCA) containing 2,5-furandicarboxylic acid and 5-formyl-2-furancarboxylic acid was prepared as previously described in accordance with the teachings of WO2017 / 003293A1. This cFDCA was then purified by hydrogenation according to the teachings of WO2016195499 and WO2016195500 to produce purified FDCA, designated hFDCA (for hydrogenated FDCA). To understand the results, it is convenient to analyze the actual composition of the hFDCA.

[0089] Analysis of hFDCA revealed that it contained greater than 98% by weight of 2,5-furandicarboxylic acid (FDCA), with the primary impurities being the monomethyl ester of 2,5-furandicarboxylic acid (FDCA-Me), present at 10,300 ppm by weight, and 2-furancarboxylic acid (FCA), present at 1,680 ppm by weight. These levels of impurities are generally considered less suitable for use in polymer production. In particular, the monoester of FDCA generates methanol during polymer production, which is disadvantageous. The monocarboxylic acid, FCA, has only one polymerization site and is an end-stopper that limits molecular weight growth. Furthermore, FCA is also responsible for color formation.

[0090] A2 - Laboratory equipment for heat treatment Heat treatment tests were carried out in a laboratory autoclave, with heating and cooling carried out through the autoclave wall and an agitator.

[0091] A3 - Comparative Examples 1 and 2 - Dissolution of FDCA Comparative Examples 1 and 2 used 10 wt % hFDCA in water and were heated to 160°C during heat treatment to fully dissolve the FDCA (a small amount of hFDCA is required to allow complete dissolution). This complete dissolution is not consistent with the present invention. The heat-treated composition was then held at the given temperature for 30 minutes. In Comparative Example 1, the sample was then rapidly cooled to 40°C. In Comparative Example 2, the sample was first cooled to 109°C in 15 minutes by evaporating the water using reduced pressure, and then rapidly cooled to 40°C. In each case, the sample was then filtered under vacuum at 40°C, washed with water (1:1 by mass compared to the dried solids), and then dried.

[0092] As shown in the table below, the treatment resulted in a reasonable reduction in the monoester content of the dried FDCA, but the FCA content actually increased compared to the initial feed (indicating further decarboxylation of FDCA / FDCA-Me when processed in water).

[0093] Micrographs revealed that the particles obtained after heat treatment had a "broken glass" appearance with somewhat flattened plates, sharp edges, and a significant level of fines. This particle shape is considered undesirable. Exemplary photographs of the particles obtained in Comparative Example 1 and Comparative Example 2 are shown in Figures 1 and 2, respectively. The photographs were obtained using a Euromex iScope IS.1053-PLPOLRi microscope at 20x magnification.

[0094] [Table 2]

[0095] A4 - Comparative Examples 3 and 4 - Temperature Comparative Examples 3 and 4 were prepared similarly to those described above for Comparative Examples 1 and 2, with process parameters summarized below in Table 2. In both cases, the heating rate was 1.5 K / min until the process temperature (i.e., lower than that defined in the present invention) was reached, which was held for 1 hour, followed by cooling to 40° C. at 1 K / min.

[0096] For ease of understanding, the estimated solubility of FDCA in a given solvent at the process temperature is also presented.

[0097] As shown in Table 2 below, heat treatment with incomplete dissolution at lower temperatures resulted in a reasonable reduction in both the monoester and FCA content of the dried FDCA. However, when comparing Comparative Example 4 with Comparative Examples 1 and 2, the removal efficiency for FCA increases, but the removal efficiency for FDCA-Me decreases.

[0098] Micrographs revealed that the particles obtained after heat treatment had sharp edges and a plate-like appearance, a particle shape that is considered undesirable.

[0099] [Table 3]

[0100] A5 - Examples 1, 2 and 3 Examples 1, 2 and 3 were prepared similarly to those described above for Comparative Examples 1 and 2, with process parameters summarized in Table 3 below. In all cases, the heating rate was 1.5 K / min to reach the process temperature, which was maintained for 1 hour, followed by cooling to 40°C. In Examples 1 and 3, cooling was carried out at a rate of 1 K / min. In Example 2, the sample was first cooled to 107°C in 7 minutes by evaporating the water using reduced pressure, and then cooled to 40°C at a rate of 1 K / min.

[0101] For ease of understanding, the estimated solubility of FDCA in a given solvent at the process temperature is also presented.

[0102] Examples 1 and 2 are not considered to be in accordance with the present invention and are included for comparative purposes only.

[0103] As shown in Table 3 below for Example 3, heat treatment according to the present invention resulted in a significant reduction in both the FDCA-Me and FCA contents of the dried FDCA, which was significantly more pronounced than in Comparative Examples 1-4, indicating that both the temperature and the precise extent of FDCA dissolution are important.

[0104] Furthermore, photomicrographs reveal that the particles obtained after heat treatment have a somewhat smooth and rounded shape and a low level of fines. This particle shape is considered very favorable. An exemplary photograph of the particles obtained in Example 3 is shown in Figure 3. The photograph was taken using a Euromex iScope IS.1053-PLPOLRi microscope at 20x magnification.

[0105] [Table 4]

[0106] Example B particle B1 - Preparation of different FDCA feeds for use in thermal treatment Mixed furanix, containing primarily 5-methoxymethylfurfural (5-HMF ether) and 5-hydroxymethylfurfural (5-HMF), was prepared by acid-catalyzed dehydration of fructose in methanol, followed by partial neutralization of the acid, and recovery of 5-methoxymethylfurfural and 5-hydroxymethylfurfural, according to the teachings of WO 2017 / 003293 A1.

[0107] After recovery, the mixed furanics were fed to an oxidation reactor together with acetic acid (HAc) and a catalyst containing sources of cobalt, manganese, and ionic bromine, in accordance with the teachings of WO 2011 / 043660 A1. The oxidation products were primarily 2,5-furandicarboxylic acid and the monomethyl ester of 2,5-furandicarboxylic acid, along with smaller amounts of 5-formyl-furandicarboxylic acid and trace amounts of other by-products. This corresponds to the crude carboxylic acid composition, hereinafter referred to as cFDCA. It is noted that the use of crude cFDCA allows for particularly good analysis of the effects of the heat treatment of the present invention, since cFDCA has the largest amount of impurities, making the observed effects particularly evident. Therefore, although cFDCA was not subjected to the purification step defined in the method of the present invention, the results obtained below using cFDCA are very important for evaluating the effectiveness of the method of the present invention.

[0108] The crude carboxylic acid composition was further purified by a variety of methods.

[0109] In one purification method, the diacid was esterified with methanol to form the dimethyl ester of 2,5-furandicarboxylic acid, which was purified, then hydrolyzed in the presence of base and re-acidified to form the purified carboxylic acid composition. The corresponding sample is designated eFDCA.

[0110] In another purification method, the crude carboxylic acid composition was purified according to the teachings of WO2016 / 195499A1 and WO2016 / 195500A1 by mixing it with water and hydrogen, heating to dissolve the solids, and then hydrogenating it in a flow system in the presence of a catalyst to form a purified carboxylic acid composition. The corresponding sample is designated as hFDCA.

[0111] Finally, another supply of FDCA was obtained from hydrogenated FDCA (hFDCA), which was thoroughly dissolved and then recrystallized from water. The corresponding sample is designated rFDCA.

[0112] These supplies were analyzed and found to contain the levels of FDCA-Me and FCA shown in the table below (ranges indicate the results of multiple measurements on the same type of sample).

[0113] [Table 5]

[0114] B2-Particle size analysis Samples of FDCA prepared by the various methods described above were subjected to particle size analysis to determine the particle size distribution (PSD) of the samples. Particle size analysis was performed using a Malvern Panalytical Laser Diffraction Particle Size Analyzer, Model Mastersizer 3000. The instrument was used to generate a complete distribution of particle sizes, which were then captured in a summary table along with the well-established d10, d50, and d90 parameters, which represent the volume-average particle size (diameter) cutoffs for 10%, 50%, and 90% of the sample's volume. Additionally, statistics are presented to represent the width of the particle size distribution, reported as the ratio d50 / d10. Large values ​​of this ratio indicate a distribution with particles much smaller than the median, or a significant population of fines, which has been found to be undesirable.

[0115] B3-Stress test In addition to standard particle size analysis, samples were tested using multiple levels of air pressure to create particle dispersion. Results using 0.2 bar dispersion pressure are considered the "gentlest," while results using 2 bar dispersion pressure are more aggressive dispersions. This may be used as a test of particle strength and stability under conditions that may represent, for example, stresses experienced during pneumatic conveying operations. This test is quantitatively shown in the table below as a reduction in d50 when tested at 2.0 bar compared to 0.2 bar.

[0116] B4-Heat Treatment Laboratory Equipment A 5 liter autoclave made from 316L stainless steel was used for the heat treatment and the corresponding crystallization. The system was pressure rated to accommodate the selected temperature and solvent. The vessel was made from 316L stainless steel. Temperature, pressure and shaft speed were recorded. The impeller was an Ekato "Viscoprop", suitable for this purpose.

[0117] B5-Comparative Examples 5~12-Particle size distribution In Comparative Examples 5-12, the respective materials were fully dissolved during heat treatment, then cooled and crystallized according to the details in the table below. In each case, the materials were held at the heat treatment temperature for 30 minutes, then cooled down to 40°C. Comparative Example 7 used a more sophisticated cooling scheme, with a cooling rate of 20 K / h for cooling from 180°C to 140°C, then 40 K / h from 140°C to 100°C, then 60 K / h from 100°C to 40°C.

[0118] The resulting particles were analyzed to determine the particle size distribution, using the ratio d50 / d10 as a measure of the width of the distribution, with large numbers indicating a significant fraction of particles with diameters much smaller than the median.

[0119] [Table 6]

[0120] B6 - Examples 4 to 9 - Particle size distribution The heat treatment for Examples 4-9 was carried out similarly to that described above for Comparative Examples 5-12, with process parameters summarized below in Table 6. For Examples 8 and 9, the heat treatment time was extended to 240 minutes.

[0121] [Table 7]

[0122] Examples 4-9 used lower water concentrations in the treatment solvent composition and are not in accordance with the present invention. However, the inventors observed the above trends even for treatment solvent compositions containing more than 95% water by weight. Therefore, from the data obtained, it can be inferred that heat treatment according to the present invention results in a much more favorable particle size distribution, with a significant reduction in fines, as indicated by a decrease in the d50 / d10 ratio.

[0123] B7 - Comparative Examples 13 and 14 - Particle Strength Comparative Examples 13 and 14 were subjected to heat treatment by obtaining samples of FDCA (hFDCA) purified by hydrogenation and subjecting them to thorough dissolution and controlled crystallization according to the conditions in the following table (Table 8). In each case, the sample was 20 wt % FDCA in water and was heated to 180°C to fully dissolve the hFDCA, then cooled to 40°C.

[0124] These samples were tested to generate particle size distributions at 0.2 bar dispersion pressure and also at 2.0 bar dispersion pressure, and particle strength was tested, with the results shown in Table 7 below.

[0125] [Table 8]

[0126] B8 - Examples 10-12 - Particle Strength: Examples 10-12 were subjected to heat treatment by taking a sample of hydrogenated purified FDCA (hFDCA) and subjecting it to partial dissolution and controlled crystallization according to the conditions in the table below. In each case, the sample was held at the desired temperature for the specified time and then cooled to 40°C.

[0127] These samples were tested to generate particle size distributions at 0.2 bar dispersion pressure and also at 2.0 bar dispersion pressure, and particle strength was tested, with the results shown in Table 8 below.

[0128] [Table 9]

[0129] Examples 10-12 used lower water concentrations in the treatment solvent composition and therefore are not in accordance with the present invention. However, the inventors observed the above trend even for treatment solvent compositions containing more than 95% water by weight. Therefore, from the data obtained, it can be inferred that heat treatment according to the present invention results in much more stable particles after heat treatment, as indicated by the lower percentage reduction in d50 when testing at 2.0 bar compared to 0.2 bar dispersion pressure.

[0130] (Experiment C) Heat Treatment Purified FDCA was prepared by hydrogenation of crude FDCA in water, followed by crystallization, cooling, filtration, and washing with water. The solvent composition was made of acetic acid and water in a 65:35 ratio by mass. For each experiment, 30 grams of FDCA was mixed with 70 grams of solvent. The mixture was heated to the desired temperature in an autoclave and held isothermally for 60 minutes with stirring. The mixture was then rapidly cooled to 40°C and then filtered. The filter cake was washed with solvent, dried, and analyzed for the listed impurities. The results are shown in the table below. The estimated % of total FDCA dissolved at the heat treatment temperature is also shown. The run at 40°C is for comparison and is not in accordance with the present invention.

[0131] [Table 10]

[0132] Examples 13-15 used lower water concentrations in the treatment solvent composition and are therefore not in accordance with the present invention. However, the inventors observed the above trends even for treatment solvent compositions containing more than 95% water by weight. Therefore, from the data obtained, it can be inferred that in heat treatments according to the present invention, the temperature and extent of dissolution are important to the product obtained by the heat treatment, as measured by the relative removal of FDCA-Me and FCA, respectively.

[0133] (Experiment D) Solvent Composition FDCA was prepared by hydrogenation in water, followed by crystallization, cooling, filtration, and washing with water. Solvent compositions were made with different mass ratios of acetic acid and water, as shown in the table. For each experiment, a composition containing 27-30 wt% FDCA was made in the desired solvent. The mixture was heated to 180°C in an autoclave and held isothermally for 60 minutes with stirring. The mixture was then rapidly cooled to 40°C and then filtered. The filter cake was washed with solvent, dried, and analyzed for the impurities reported. The results are shown in Table 10 below. The estimated % of total FDCA dissolved at the heat treatment temperature (180°C) is also reported.

[0134] [Table 11]

[0135] Examples 16-20 used lower water concentrations in the treatment solvent composition and therefore are not in accordance with the present invention. However, the inventors observed the above trends even for treatment solvent compositions containing more than 95% water by mass. Therefore, from the data obtained, it can be inferred that the heat treatment according to the present invention can achieve excellent removal rates of FDCA-Me and FCA for a wide variety of solvent compositions.

[0136] (Experiment E) Crystallization from water after complete dissolution Further comparative experiments were performed with complete dissolution. Mixtures of FDCA made by blending different purified FDCA compositions were prepared to produce samples with variations in FCA and FDCA-Me relative to FDCA. To achieve full dissolution at 140°C, samples were prepared at a total concentration of 4 wt% FDCA. After treatment in water, the samples were cooled to crystallize the FDCA, and the cake was analyzed for purity. The following table shows the results upon recrystallization from water.

[0137] [Table 12]

[0138] From the data, it can be seen that the FCA removal efficiency improves significantly when only limited amounts of FDCA-Me are present. Furthermore, it can be seen that FDCA-Me is not removed by recrystallization from water under these conditions, but is virtually completely reincorporated into the cake. Comparative Experiment 20 approximates the concentrations of FDCA-Me encountered in actual operation, demonstrating removal efficiencies that are often insufficient.

Claims

1. A method for producing a carboxylic acid composition comprising 2,5-furandicarboxylic acid, comprising: a) providing or producing a crude carboxylic acid composition comprising 2,5-furandicarboxylic acid and 5-formyl-2-furancarboxylic acid; b) purifying the crude carboxylic acid composition to produce a purified carboxylic acid composition comprising 2,5-furandicarboxylic acid, wherein the purifying comprises: - hydrogenating at least a portion of the 5-formyl-2-furancarboxylic acid; - oxidizing at least a portion of the 5-formyl-2-furancarboxylic acid; - recrystallizing at least a portion of the 2,5-furandicarboxylic acid; and - hydrolyzing the dialkyl ester of 2,5-furandicarboxylic acid and at least one step selected from the group consisting of: c) providing or manufacturing a processing solvent composition comprising greater than 95% by weight of water based on the weight of the processing solvent composition; d) providing or manufacturing a thermal treatment composition comprising a purified carboxylic acid composition and a treatment solvent composition; e) subjecting the heat-treated composition to an elevated temperature in the range of 140 to 200°C for a time in the range of 5 to 240 minutes to obtain a treated composition, wherein the percentage of dissolved 2,5-furandicarboxylic acid relative to the total amount of 2,5-furandicarboxylic acid is in the range of 10 to 80%; f) cooling the treated composition to a temperature in the range of 20 to 80°C and separating at least a portion of the 2,5-furandicarboxylic acid from the treated composition to obtain a carboxylic acid composition and a treated mother liquor comprising water; A method comprising:

2. 2. The method of claim 1, wherein the crude carboxylic acid composition and / or the purified carboxylic acid composition comprises the monomethyl ester of 2,5-furandicarboxylic acid.

3. step e) is carried out in a reactor pressurized with an inert gas, and / or 3. The method of claim 1 or 2, wherein the heat-treated composition of step e) is agitated for at least a portion of the time to expose the solid 2,5-furandicarboxylic acid to shear forces.

4. the heat treatment composition comprises 2,5-furandicarboxylic acid in an amount of 15 to 45% by weight, based on the weight of the heat treatment composition; and / or the treatment solvent composition comprises acetic acid and water; 4. The method according to any one of claims 1 to 3.

5. The process parameters in steps e) and f) are - exhibit a reduction in mean particle size of less than 35% between particle size measurements at dispersion pressures of 0.2 bar and 2 bar; and / or - having a volume average median particle size (d50) in the range of 50 to 300 μm, 5. The method of claim 1, selected to produce particles of 2,5-furandicarboxylic acid.

6. 6. The process according to any one of claims 1 to 5, wherein the crude carboxylic acid composition comprises 2-furan carboxylic acid in an amount ranging from 1 to 2000 ppm by weight, based on the weight of the composition, and wherein the carboxylic acid composition comprises 2-furan carboxylic acid in an amount of 700 ppm by weight or less.

7. 7. The process of claim 1, wherein the crude carboxylic acid composition comprises the monoalkyl ester of 2,5-furandicarboxylic acid in an amount ranging from 0.2 to 5.0 wt. %, based on the weight of the crude carboxylic acid composition.

8. 8. The method according to claim 1, wherein the purification in step b) comprises hydrogenating at least a portion of the 5-formyl-2-furancarboxylic acid.

9. 9. The method according to claim 1, wherein in step e), the percentage of dissolved 2,5-furandicarboxylic acid relative to the total amount of 2,5-furandicarboxylic acid is in the range of 20 to 60%.

10. the temperature of step e) is in the range of 150 to 190°C, and / or 10. The method of any one of claims 1 to 9, wherein the heat-treated composition of step e) is subjected to elevated temperature for a time in the range of 15 to 120 minutes.

11. 11. The method of any one of claims 1 to 10, wherein the treated composition of step f) is cooled to a temperature in the range of 30 to 80°C.

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