Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/62—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/66—Esters of carboxylic acids having esterified carboxylic groups bound to acyclic carbon atoms and having any of the groups OH, O—metal, —CHO, keto, ether, acyloxy, groups, groups, or in the acid moiety
  • C07C69/67—Esters of carboxylic acids having esterified carboxylic groups bound to acyclic carbon atoms and having any of the groups OH, O—metal, —CHO, keto, ether, acyloxy, groups, groups, or in the acid moiety of saturated acids
  • C07C69/675—Esters of carboxylic acids having esterified carboxylic groups bound to acyclic carbon atoms and having any of the groups OH, O—metal, —CHO, keto, ether, acyloxy, groups, groups, or in the acid moiety of saturated acids of saturated hydroxy-carboxylic acids
  • C07C69/68—Lactic acid esters

Definitions

• the present invention relates to a process for preparing ethyl lactate having a purity greater than 97% from lactic acid or a lactic acid composition.
• Ethyl lactate can be used alone or in combination with other solvents, as cleaning and degreasing agents in machine and in non-aqueous medium of solid surfaces such as metal parts, ceramics, glass, plastics having been soiled with oils or greases from machining and / or their temporary protection.
• lactide (IV) does not form.
• the oligomers (II), (III) and / or (V) have been detected for the good reason that industrially, commercial solutions of lactic acid are used.
• lactic acid composition is understood to mean any aqueous solution of lactic acid, whatever its method of production and its characteristics, said solution having a very variable lactic acid purity.
• This transesterification reaction (7) is generally carried out in the presence of basic catalysts, alkyl orthotitanates or complexes based on zirconium. However, it can also occur by heating during the purification of ethyl lactate and, in order to avoid it, the purification is generally carried out under reduced pressure. Thus, the esté ⁇ fic ⁇ tion of lactic acid into ethyl lactate is made more complicated by:
• the esterification reaction medium comprising a mixture of lactic acid, ethanol, lactate ethyl, water and oligomers
• the simplest method is to use the water-ethanol azeotrope.
• the dehydration of the gaseous mixture extracted from the reaction medium is carried out by means of the technique known as PSA "pressure switch adsorption" which consists in carrying out the selective adsorption of water by passing, at a pressure identical to that applied to the esterification reaction medium, the water-ethanol mixture close to the azeotrope in gaseous form through a bed of molecular sieve - adsorption step - then to desorb the water previously adsorbed by lowering the pressure below 300 mbar , and preferably below 100 mbar - desorption step.
• PSA pressure switch adsorption
• the anhydrous ethanol recovered in the adsorption step is advantageously recycled in the esterification reaction medium, while the water-rich phase undergoes distillation in order to recover the pure water and a water azeotrope.
• ethanol which is injected at the top of the distillation column of the gaseous water-ethanol mixture extracted from the reaction medium thus ensuring reflux in said column, not provided with a condenser.
• the reaction is advantageously carried out in the presence of an acid catalyst which is soluble or insoluble in the esterification reaction medium.
• the catalyst according to the invention is used at molar contents ranging from 0.1% to 4% and, preferably, at contents ranging from 0.2% to 3% relative to the 100% lactic acid used. artwork.
• it is possible to operate in a stirred reactor, or according to a so-called fixed bed technology. In the latter case, solid catalysts such as ion exchange resins of the Amberlyst 15 type will be used.
• the initial or initial esterification time can vary widely. It is generally at most equal to 12 hours and, preferably, between 5 and 12 hours.
• the flow of products leaving the esterification reaction medium comprising mainly ethyl lactate and ethanol, as well as traces of water and heavy (oligomers) is subjected to fractional distillation under reduced pressure according to the usual techniques of those skilled in the art.
• the method according to the present invention can be implemented in a device as shown in FIG. 1.
• This device comprises:
• reactor (1) optionally provided with stirring, equipped with temperature probes, lactic acid (2), ethanol (3) and catalyst (4) supplies;
• a PSA device (7) consisting of 2 identical columns (A and B) filled with molecular sieves which operate alternately in adsorption and desorption, said PSA device, supplied in the gas phase of the distillation column (5), via the feed (8) is provided with an outlet (9) connected to the column operating in adsorption allowing the supply of the esterification reactor with ethanol (gas) and an outlet (10) connected to the column operating in desorption allowing a distillation column (11) to be supplied with a water-ethanol mixture; said distillation column (11) is provided with an outlet (12) for discharging water and an outlet (13) for conveying the water-ethanol azeotrope towards the head of the distillation column (5); - an outlet for the esterification products (14) supplying a purification zone (15) from which comes out, via (16) ethanol with water, via (17) pure ethyl lactate and via (18 ) heavy which can be recycled to the esterification reactor after a purge in (19).
• the process according to the present invention applies very
• lactic acid lactic acid compositions Preferably, 87% by weight lactic acid lactic acid compositions will be used.
• the method according to the present invention makes it possible to completely convert the lactic acid of said compositions and to depolymerize the oligomers present in said lactic acid compositions used.
• the ethyl lactate from the esterification reactor contains little water, which makes it easy to purify it.
• the manner of operating according to the present invention also makes it possible to extract from the reaction medium a gaseous phase practically devoid of the ethyl lactate formed.
• a test is carried out in a device as shown in FIG. 1.
• the reactor (1) has a capacity of 21.
• the PSA system (7) consists of 2 identical columns (A and B) filled with NK30, 3A siliporite molecular sieves.
• the distillation column is filled with a Sulzer Ex packing with a diameter equal to 20mm. It has 10 theoretical platforms.
• the esterification of a lactic acid composition is carried out with ethanol, in batch, in the reactor (1). operates at a pressure higher than atmospheric pressure and at a temperature close to 100 ° C.
• the reactor is placed under a pressure of 1.5 bar and then the reaction medium is stirred, which is brought to reflux, which corresponds to a temperature substantially equal to 100 ° C.
• a gaseous mixture comprising water and ethanol is continuously extracted from the reaction medium, by means of the distillation column (5), at a bottom temperature.
• this mixture is dehydrated by sending it to the PSA system (7) which operates under an absolute pressure of 1.5 bar from which exits at (9) pure ethanol which continuously feeds the esterification reaction medium contained in the reactor and in (10) during the desorption step a water-ethanol mixture which is distilled in the distillation column (11) from which emerges in (13) a water-ethanol azeotrope which is directed towards the head of the distillation column (5) thus making it possible to ensure reflux at the head of said distillation column. Water comes out in (12).
• the progress of the reaction is carried out by determining the transformation rate of lactic acid, measured by GC.
• the PSA works identically throughout the manufacturing. Continuous esterification Then, simultaneously, the esterification reaction medium is continuously supplied with: - 87% lactic acid composition,

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2002
  • 2002-12-05 FR FR0215347A patent/FR2848208B1/fr not_active Expired - Fee Related
• 2003
  • 2003-12-05 JP JP2004558174A patent/JP2006509025A/ja active Pending
  • 2003-12-05 KR KR1020057010227A patent/KR100698817B1/ko not_active IP Right Cessation
  • 2003-12-05 WO PCT/FR2003/003599 patent/WO2004052826A2/fr active Application Filing
  • 2003-12-05 US US10/537,150 patent/US7297809B2/en not_active Expired - Fee Related
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  • 2003-12-05 EP EP03796170A patent/EP1581473A2/fr not_active Withdrawn
  • 2003-12-05 CA CA002507916A patent/CA2507916A1/fr not_active Abandoned
  • 2003-12-05 CN CNB2003801049180A patent/CN1326826C/zh not_active Expired - Fee Related
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