Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation

Definitions

• the present invention relates to a process for crystallizing carboxylic acid, more particularly adipic acid and to a process for manufacturing crystallized carboxylic acid, more specifically a process for treating the reaction medium resulting from the direct oxidation of a hydrocarbon to carboxylic acid such as adipic acid, for example.
• Adipic acid is one of the two basic materials in the preparation of polyamides, such as polyamide 6-6, and various other polymers. Polyamide 6-6 applications require very controlled properties from the point of view of chemical, physicochemical composition. To obtain such a polymer, it is necessary to have a very high purity at the monomer stage, such as adipic acid or dicarboxylic acids. Adipic acid is also one of the important raw materials in the manufacture of polyurethanes.
• the impurities which it conceals are obviously different.
• the purification methods generally used are crystallization methods using water as a solvent. Such a process is, for example, described in French patent application No. 2,749,299.
• the known crystallization solvent namely water, does not make it possible to remove certain impurities such as organic impurities, for example.
• One of the aims of the present invention is to provide a process for the crystallization of carboxylic acid and more particularly adipic acid in solvents capable of removing said organic impurities.
• the invention provides a method of crystallization of carboxylic acid, characterized in that said crystallization or recrystallization is carried out in an organic solvent or a mixture of solvents, at least one of which is an organic solvent in which the carboxylic acid has a solubility less than or equal to 15% by weight at a temperature of 20 ° C and in that said solvent is chosen from families of organic compounds comprising ethers, alcohols, ketones, esters, nitriles, amides, sulfoxides, or carbonates and halogenated, nitrated, phosphorous organic solvents as well as in mixtures of organic solvents, the mixture having the solubility properties of the carboxylic acid indicated above, while the solubility of the carboxylic acid in each component or one or more components of the mixture taken individually may not correspond to the solubility ranges indicated above and below.
• the organic solvent is chosen if the solubility of the carboxylic acid in said solvent at a temperature of 100 ° C, or at its boiling point if it is less than 100 ° C , is at least 5% higher than that at 20 ° C in the same solvent, preferably 10% higher.
• the solubility at 100 ° C. must advantageously be at least 15% by weight.
• the carboxylic acids which can advantageously be crystallized by the process of the invention are preferably dicarboxylic acids such as adipic acid, succinic acid, glutaric acid, tere and isophthalic acids.
• the preferred carboxylic acid of the invention is adipic acid.
• solvents suitable for the process of the invention there may be mentioned, by way of example, dioxane 1, 4; diglyme (diethylene glycol dimethyl ether); tetrahydrofuran; aliphatic, cycloaliphatic, aromatic or arylaliphatic ketones such as acetone, methylisobutyl ketone, methyl ethyl ketone, methyl isopropyl ketone, methylphenyl ketone, cyclohexanone; n-butanol; isopropanol; 3-methoxy ethanol; acetonitrile; dimethylformamide; acetamide; dichloromethane; ethyl acetate; 1,2-ethane dichloro; dimethyl sulfoxide; nitromethane; N-methylpyrrolidone, or mixtures thereof.
• dioxane 1, 4 diglyme (diethylene glycol dimethyl ether); tetrahydrofuran
• organic solvents or mixtures of solvents can be used alone or as mixtures with another solvent according to the invention or not. Thus, these organic solvents can be used with water.
• the organic solvent of the invention has a boiling point compatible for carrying out the crystallization under industrially exploitable operating conditions.
• suitable solvents advantageously have a boiling point between 40 ° C and 250 ° C, preferably between 80 ° C and 120 ° C. Crystallization can be carried out at atmospheric pressure or under pressure.
• the solvents suitable for the invention also have and advantageously a certain affinity for water, allowing washing with water of the crystallized adipic acid to remove traces of organic solvent of crystallization.
• the process of the invention is implemented according to the techniques known from the crystallization processes Briefly, this process comprises a step of hot dissolution of the carboxylic acid to be crystallized, then a cooling step after optionally filtration of the hot solution of acid It is also possible to concentrate the hot acid solution before cooling.
• This crystallization can be improved by any known means and in particular by the use of microwaves.
• the present process can be applied to carboxylic acids and more particularly to an acid adipic from various synthesis processes, such as adipic acid from the nitric oxidation of cyclohexanol and / or cyclohexanone, the double hydroxycarbonylation of butadiene or from the direct oxidation of cyclohexane to air
• the process of the invention is particularly applicable to the process of hydroxycarbonylation of butadiene which consists of a first hydroxycarbonylation of butadiene leading to a mixture of pentenoic acids, mainly 3-pentenoic acid, and a second hydroxycarbonylation relating to pentenoic acids obtained in the first reaction and leading to adipic acid also containing a certain amount of 2-methyl-glutanic acid, 2-ethyl-succinic acid, as well as other compounds, already
• This document describes the oxidation of cyclic hydrocarbons to corresponding diacids, in the liquid phase comprising a solvent, using a gas containing oxygen and in the presence of an oxidation catalyst such as a compound of cobalt, said solvent comprising an organic acid having only primary or secondary hydrogen atoms.
• This patent more particularly develops the treatment phases of the final reaction mixture. This treatment consists in separating the diacid formed, by cooling the mixture to cause precipitation.
• This patent more particularly proposes a solution for oxidizing cyclohexane to adipic acid in one step with an industrially acceptable selectivity, but it does not provide a solution applicable industrially to the treatment of the reaction mixture resulting from oxidation, taking into account the separation of the different products and by-products of the reaction, unprocessed products and in particular the recycling of the catalyst.
• Patent EP-A-0 772 581 describes a more complete process for treating the reaction mixture resulting from the direct oxidation of cyclohexane to adipic acid, as well as the recycling of the catalyst.
• the adipic acid is also crystallized from acetic acid which is a corrosive and expensive solvent, require recovery and regeneration operations strongly affecting the general economy of the process for manufacturing adipic acid.
• the crystallization process proposed by the present invention makes it possible to remove most of these organic impurities without requiring the use of a corrosive crystallization solvent such as acetic acid or of additional treatments.
• a corrosive crystallization solvent such as acetic acid or of additional treatments.
• the acid crystallized according to the process of the invention can be more easily purified by a new crystallization in water if this is necessary to reach the high specifications of purity required in the applications of manufacture of the polyamide or polyurethane.
• the invention also relates to a process for the preparation of carboxylic acids by oxidation of a hydrocarbon by direct oxidation and treatment of the reaction medium obtained.
• It relates more particularly to a process for treating the reaction mixture resulting from the direct oxidation of hydrocarbons to carboxylic acid, using in particular molecular oxygen or a gas containing it, in the liquid phase, in a solvent and in the presence of a catalyst dissolved in the reaction medium, characterized in that said process comprises:
• a non-polar upper phase essentially containing the unconverted hydrocarbon
• a polar lower phase essentially comprising the solvent, the acids formed, the catalyst and part of the other reaction products and unprocessed hydrocarbon
• the decantation into two phases of the reaction mixture subjected to the process of the invention essentially depends on the reaction solvent used, the amount of hydrocarbon transformed and the water content in the medium.
• the hydrocarbons which are used as starting substrates in the process of the invention are more particularly alkanes, cycloalkanes and alkyl-aromatic hydrocarbons, having from 3 to 20 carbon atoms.
• cycloalkanes in particular those which have a ring having 5 to 12 carbon atoms, are certainly the most important, because their oxidation leads to dicarboxylic acids.
• hydrocarbon is cyclohexane, the oxidation of which leads to adipic acid, one of the basic compounds of polyamide 6-6 and the most widely used diacids.
• the invention will be very generally described with reference to the treatment of reaction mixtures resulting from the oxidation of cyclohexane to adipic acid, but the process can also be applied to mixtures obtained from the oxidation of other hydrocarbons, and more particularly other cycloalkanes.
• the cyclohexane phase obtained in the possible decantation step is most often reintroduced in a cyclohexane oxidation operation.
• the solvent used in the oxidation of the hydrocarbon is an at least partial solvent for the carboxylic acid whose preparation is targeted.
• This solvent can be very varied in nature insofar as it is not substantially oxidizable under the reaction conditions. It can in particular be chosen from polar protic solvents and polar aprotic solvents.
• polar protic solvents mention may, for example, be made of carboxylic acids having only primary or secondary hydrogen atoms, in particular aliphatic acids having from 1 to 9 carbon atoms, perfluoroalkylcarboxylic acids such as trifluoroacetic acid, , alcohols.
• polar aprotic solvents mention may be made, for example, of lower alkyl esters (preferably an alkyl radical having from 1 to 4 carbon atoms) of carboxylic acids, in particular aliphatic carboxylic acids having from 1 to 9 carbon atoms or perfluoroalkylcarboxylic acids, tetramethylenesulfone (or sulfolane), aliphatic nitriies such as acetonitrile.
• Acetic acid is generally preferred, in particular when the substrate to be oxidized is cyclohexane.
• the catalyst preferably contains cobalt, manganese, a mixture of cobalt with one or more other metals such as manganese, chromium, iron. Zirconium, hafnium, copper, a mixture of manganese with one or more others metals such as chromium, iron, zirconium, hafnium, copper.
• the catalysts comprising either cobalt and chromium, or cobalt, chromium and zirconium, or cobalt and iron, or cobalt and manganese, or cobalt and zirconium and / or hafnium are more particularly suitable.
• This catalyst is used for the oxidation of cyclohexane, in the form of compounds of these metals which are soluble in the reaction medium.
• the reaction mixture to be treated by the process of the invention contains, for information by weight by weight, from 1% to 99% of unconverted hydrocarbon, from 1% to 40% of carboxylic acids formed, from 0.1% to 10% water, from 0.001% to 5% of the metal or metals contained in the catalyst, from 0.1% to 10% of other products of the oxidation reaction, the remainder being constituted by the solvent.
• the distillation stage of the lower phase, or where appropriate of the reaction mixture, is carried out in such a way that most, and as far as possible, all of the unprocessed cyclohexane, which may still be present in this lower phase , or separated from adipic acid.
• the reaction intermediates such as cyclohexanol, cyclohexanone, cyclohexyl acetate, lactones (butyrolactone, essentially valerolactone) are also separated, as well as the solvent, preferably comprising a carboxylic acid.
• the distillation step is generally carried out at a temperature of 25 ° C to 250 ° C and under an absolute pressure between 10 Pa and atmospheric pressure.
• the temperature of the mixture during distillation will be maintained between 70 ° C and 150 ° C.
• the distillation can, if necessary, be carried out in several successive stages, in particular in the preferred mode where it is desired to remove the largest part, for example more than 90% and even more than 99% of the aliphatic carboxylic acid solvent.
• An advantageous variant of the process of the invention consists in the introduction of water vapor into the reaction mixture before or during the distillation step. This operation can better lead to certain compounds present in the mixture subjected to distillation. It can also carry out a partial or complete hydrolysis of the carboxylic esters which can also be found in the mixture to be distilled.
• the distillate obtained in the distillation operation described above comprises the various volatile compounds and water. These volatile compounds are recoverable and are therefore recycled in a new oxidation reaction of cyclohexane, after at least partial elimination of the water, by any known means, in particular by azeotropic distillation.
• an organic solvent or a mixture comprising at least one organic solvent according to the invention is added to the distillation bottom in order to dissolve the adipic acid formed and optionally precipitate the catalysts.
• the amount of solvent added represents from 0.1 to 20 times the weight of the mixture obtained after said distillation. Preferably, the amount of solvent added represents from 0.5 to 10 times this weight.
• This operation therefore consists in hot dissolving adipic acid in the minimum amount of solvent, which optionally makes it possible to separate the catalyst by hot filtration from the solution.
• the crystallization itself is carried out according to the usual techniques, by progressive cooling of the organic solution. Generally, the solution is sown using adipic acid crystals. The adipic acid obtained by this crystallization can then be recrystallized from water, in order to achieve the purity necessary for the main applications where it is used.
• Variants can be produced without departing from the scope of the present invention.
• certain operations can be carried out before the stage of crystallization of adipic acid in an organic solvent.
• an additional oxidation of the intermediate oxidation compounds present in the polar liquid phase after having separated the major part and preferably all of the unconverted cyclohexane and before having separated the other compounds and the solvent.
• carboxylic acid This additional oxidation can be carried out by molecular oxygen or a gas containing it, being catalyzed by the initial catalyst still present in said polar phase, or also using an oxygen donor such as hydrogen peroxide. or an organic hydroperoxide.
• Such additional oxidation is then followed by the total or partial separation of the carboxylic acid solvent, before the stage of crystallization of adipic acid in an organic solvent.
• the adipic acid is crystallized as indicated above.
• the process of the invention can also be completed by a reduction reaction of the reducible impurities possibly present in the technical adipic acid obtained by crystallization from an organic solvent.
• Such a reduction is advantageously hydrogenation by hydrogen, after redissolving the technical adipic acid in a solvent such as water, if necessary in the presence of a hydrogenation catalyst not dissolved in the medium.
• the hydrogenation catalyst is separated from the medium at the end of the reaction.
• recrystallization from water can also be preceded by an oxidizing finish using nitric acid or by a known treatment of adsorption and discoloration, for example using carbon black.
• the process of the invention makes it possible to obtain, in particular, after recrystallization from water, adipic acid which can meet the specifications imposed for its use in the synthesis of polyamide 6-6 or polyurethanes.
• the nitrogen pressure is brought to 20 bars, stirring (1000 rpm) started and the temperature brought to 105 ° C in 20 minutes.
• the nitrogen is then replaced by 20 bars of depleted air (5% oxygen).
• the inlet gas flow rate is adjusted to 250 liters per hour.
• the temperature in the autoclave ranges from 104.9 to 105.1 ° C.
• the content of the decanter is a two-phase mixture.
• the upper, essentially cyclohexane phase which contains little product and cobalt is separated.
• the lower acetic phase (2675 g) contains most of the oxidation and cobalt products.
• the acetic phase is subjected to a first distillation under the following conditions:
• distillation 1 The bottom of distillation 1 is subjected to a new, more thorough distillation intended to remove the volatile organic compounds which it contains by means of an injection of water vapor at 150 ° C. under pressure of 10 kPa.
• a second oxidation mass is carried out according to the same procedure and the same quantities.
• the result obtained after distillation is identical to that indicated in the table above.
• a part (112 g) of the distillation bottom 2 of the oxidation mass 1 is subjected to crystallization in water (250g). The whole is heated to 70 ° C., then is gradually cooled to room temperature
• the cobalt catalyst is found in the water of crystallization and washing.
• Example 3 CRYSTALLIZATION IN ACETONE
• Another part of the distillation bottom 2 of the oxidation mass 1 (225 g) is diluted in 700 ml of acetone and brought to reflux. The organics are dissolved. The undissolved cobalt salts are filtered hot and recovered for recycling.
• the filtrate is gradually cooled to room temperature (around 20 ° C).
• the batches of adipic acid (A) and (B) are subjected to a heating test. This test consists of heating 50 g of each batch at 215 ° C for 205 min, then placing each of them in 415 ml of a 5% aqueous ammonia solution. The absorbance at 454 nm of the solutions of ammonium adipate obtained is then measured.
• the purified adipic acid (B) according to the present invention contains fewer impurities capable of coloring on heating.
• the cobalt catalyst was recovered by hot filtration of the dioxane solution.
• the cobalt catalyst was recovered by hot filtration of the solution in 1 ; acetonitrile.
• Part of the distillation bottom 1 of the oxidation mass 2 (112g) is subjected to crystallization from butyl acetate (250g). The whole is heated to 100 ° C, filtered hot, then is gradually cooled to room temperature After filtration and washing with water, 58 g of crude adipic acid are obtained.
• the batches of adipic acid (A) and (C) to (E) are subjected to a heating test.
• This test consists of heating 50 g of each batch at 215 ° C for 205 min, then placing each of them in 415 ml of a 5% aqueous ammonia solution.
• the absorbance at 454 nm of the solutions of ammonium adipates obtained is then measured.
• adipic acids (B), (C) and (D) purified according to the present invention contain fewer impurities capable of coloring on heating than adipic acid (A), thus demonstrating the effects of this crystallization in an organic solvent. .
• Part of the distillation bottom 2 of the oxidation mass 1 (112 g) is subjected to crystallization from a solvent comprising 6% by volume of dimethylsulfoxide and 94% by volume of butyl acetate (250g). The whole is heated to 100 ° C, filtered hot, then is gradually cooled to room temperature
• crystallization from an organic solvent according to the invention can be carried out on adipic acid crystallized from water.
• This crystallization in an organic solvent can be further supplemented by purification treatments as described above and / or by another crystallization in water.

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• 1999
  • 1999-09-13 TW TW088115740A patent/TW460452B/zh not_active IP Right Cessation
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  • 1999-09-14 WO PCT/FR1999/002181 patent/WO2000015597A1/fr not_active Application Discontinuation
  • 1999-09-14 UA UA2001042573A patent/UA60380C2/uk unknown
  • 1999-09-14 CN CN99812267A patent/CN1323288A/zh active Pending
  • 1999-09-14 US US09/787,127 patent/US6559339B1/en not_active Expired - Fee Related
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