Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
• • 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
  • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
  • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/52—Esters of acyclic unsaturated carboxylic acids having the esterified carboxyl group bound to an acyclic carbon atom
  • C07C69/533—Monocarboxylic acid esters having only one carbon-to-carbon double bond
  • C07C69/54—Acrylic acid esters; Methacrylic acid esters

Definitions

• the present invention relates to the manufacture of alkyl (meth) acrylates by direct esterification of (meth) acrylic acid with the corresponding alcohol.
• It relates to a process for the purification of C 4 -C 10 alkyl acrylate, in particular of 2-ethylhexyl acrylate, leading to high productivity of a product meeting standards in terms of purity and acidity, under optimized energy conditions.
• esterification of (meth) acrylic acid is a balanced reaction with generation of water which must be removed during the reaction to shift the equilibrium in the direction of the production of the ester (meth ) acrylic.
• AHP presumably forms from AA dimer in the presence of water and on contact with the esterification catalyst. Its formation depends on the reaction operating conditions, the nature of the catalyst used, and the quantity of water present in the reaction medium.
• AA dimers their formation is penalizing on the quantity of heavy by-products to be separated and incinerated, and consequently penalizing for productivity.
• impurities can also form in the case of methacrylic acid, in particular b-hydroxymethylpropionic acid and b-methacryloxypropionic acid.
• PSA pressure sensitive adhesives
• WO 2016/016528 describes operating conditions making it possible to optimize the yield of the reaction and to effectively remove the water produced by the reaction, thus minimizing the side reactions responsible for the formation of acid impurities. and heavy by-products. These operating conditions are based on an excess of alcohol for the esterification reaction and the circulation of a reaction loop comprising only the esterification reactor and a distillation column removing the water produced in the form of a azeotrope with esterifying alcohol. This process results in a purified ester containing low traces of acid-bound impurities.
• EP 2 659 943 describes a configuration of a partition column and its operation to produce a high purity 2-ethylhexyl acrylate.
• this column is complex to manufacture and to operate, it has the advantage of reducing the equipment cost and the energy consumption of the purification process, compared to a conventional installation comprising two distillation columns.
• the question of the stabilization necessary for the proper functioning of the partition column and the problems associated with the separation of AHP forming an azeotrope with 2-ethylhexyl acrylate are not, however, resolved.
• a partition column having a common lower part connected to a single reboiler is used to purify 2-ethylhexyl acrylate or 2-propylheptyl acrylate.
• AHP the issue of the formation of AHP is not addressed.
• the subject of the present invention is therefore a process for the recovery / purification of alkyl acrylate, which is simple to implement, resulting in a product meeting standards in terms of purity with optimized productivity, while limiting the size of the equipment to implement and energy cost.
• the subject of the invention is a process for recovering / purifying a C 4 -C 10 acrylic ester from a crude reaction mixture obtained by direct esterification of acrylic acid with the corresponding alcohol, characterized in that that a stream rich in acidic impurities such as b-hydroxypropionic acid and b-acryloxypropionic acid is withdrawn through a side outlet during the distillation of the crude reaction mixture.
• stream rich in acidic impurities is meant that the bulk of these acidic impurities generated during the esterification reaction is present in the stream which is withdrawn sideways from the distillation column supplied with the crude reaction mixture.
• This stream further comprises the acrylic ester, traces of unreacted reagents and heavy by-products with a higher boiling point than the acrylic ester, as well as traces of water.
• the Applicant has surprisingly found that the profile of the distillation column used to remove the light compounds present in the crude reaction mixture (topping) has a maximum concentration (“concentration belly”) for the acid impurities, which makes it possible to remove said impurities by side draw-off, using a distillation column equipped with a side draw-off.
• the stream rich in acid impurities withdrawn can be in gaseous form or in liquid form, preferably in liquid form.
• the lateral withdrawal is preferably carried out at a level lower than the feed level of the distillation column, which makes it possible to minimize the presence of valuable reagents such as acrylic acid and esterifying alcohol, in the withdrawn stream.
• the stream rich in acidic impurities, withdrawn laterally is subjected to treatment with water, in order to separate said acidic impurities and to recycle the treated stream in the distillation column.
• the treated stream free of most of the acid impurities is recycled to the distillation column.
• the treated stream free of most of the acid impurities can be recycled to the distillation column at a lower level or at a level higher than the side draw-off, preferably it is recycled at a higher level than the side draw-off.
• the treated stream free of most of the acidic impurities is recycled to the distillation column at a level lower than the feed level of the distillation column.
• the process according to the invention is implemented using a purification system comprising at least one distillation column equipped with a side draw-off allowing the separation of most of the acid impurities present in the reaction mixture. gross.
• said distillation column is a topping column separating at the top the light compounds such as the unreacted reagents present in the reaction medium.
• a subject of the invention is also a process for the recovery / purification of a C 4 -C 10 acrylic ester, from a crude reaction mixture obtained by direct esterification of acrylic acid with the corresponding alcohol, comprising at least minus the following steps:
• reaction mixture is subjected to topping in a distillation column equipped with a side draw-off making it possible to obtain:
• the method according to the invention can further comprise a step iii) of treatment of the flow withdrawn laterally:
• the stream rich in acid impurities is subjected to a washing step with an aqueous stream making it possible to obtain after settling,
• an aqueous phase comprising all of the acid impurities which can be sent to a biological treatment station or partly used as an aqueous washing stream, and
• an organic phase comprising the desired ester, heavy by-products and traces of water and reagents, which is recycled at least in part to the topping column.
• the process according to the invention makes it possible to obtain a C 4 -C 10 acrylic ester with a purity greater than or equal to 99.7%, or even greater than 99.8%, and comprising a content of acid impurities (AHP, AA dimer , AA) less than 90 ppm, or even less than 60 ppm.
• the invention leads to optimized productivity while maintaining a moderate energy balance.
• the invention advantageously applies to the production of 2-ethylhexyl acrylate or 2-octyl acrylate, meeting the purity standards required for the production of polymers which can be used, for example, in the field of adhesives or coatings.
• Another object of the invention is a process for producing a C 4 -C 10 acrylic ester free from acid impurities by direct esterification of acrylic acid with the corresponding alcohol comprising the recovery / purification process such as defined above.
• FIG. 1 block diagram of a first purification process according to the prior art.
• FIG. 2 block diagram of a second purification process according to the prior art.
• FIG. 3 block diagram of the process according to the invention.
• the invention is based on the implementation of a purge of a stream rich in acid impurities using a lateral withdrawal preferably fitted to a topping column in a process for purifying a crude reaction mixture. obtained by direct esterification of acrylic acid with a C 4 -C 10 alcohol.
• the esterifying alcohol can be a primary or secondary aliphatic alcohol, comprising a linear or branched alkyl chain comprising from 4 to 10 carbon atoms.
• examples of alcohols include butanol, 2-ethyl hexanol, n-octanol, 2-octanol, n-decanol and 2-propyl heptanol.
• the alcohol is 2-ethyl hexanol or 2-octanol.
• the esterification reaction is generally carried out in a reactor surmounted by a distillation column allowing the water generated by the reaction to be extracted.
• the water of reaction is removed as it forms as an azeotrope with the esterifying alcohol in order to displace the esterification equilibrium.
• the operating conditions of the esterification reaction are not critical, the process according to the invention being able to be applied to the reaction mixture whatever the process for obtaining it.
• the reaction can be carried out in excess of acid or in excess of alcohol, at a temperature generally between 70 ° and 100 ° C, preferably between 75 ° C and 95 ° C.
• the reactor can be a fixed bed reactor or a slurry bed reactor.
• the distillation column, surmounting the reactor is generally packed and it is equipped with an overhead condenser, a settling tank, making it possible to decant the vapors condensed at the top and to separate an organic phase comprising alcohol and traces of ester, which is recycled to the column, and an aqueous phase which is removed.
• the column is generally operated at a pressure ranging from 50 to 70 mm Hg.
• a cationic resin is generally used, preferably a strong cationic resin, for example a strong cationic sulfonated resin of the styrene / divinyl benzene type containing sulfonic groups.
• resins include those marketed under the names ® DIAION PK208 and PK216 from the Mitsubishi company, or those sold under the name LEWATIT ® K2620 or K2621 by Lanxess, or those sold under the name Amberlyst ® A15, A16 or A46 by the Rohm & Haas Company.
• the esterification reaction is generally carried out in the presence of at least one polymerization inhibitor chosen from phenothiazine, hydroquinone (HQ), and its derivatives such as methyl ether of hydroquinone (EMHQ), 2, 6-di-terbutyl-4-methyl phenol (B HT), 2,4-dimethyl-6-terbutyl phenol (Topanol A), salts of thiocarbamic or dithiocarbamic acid, N-oxyl compounds, such as 4 -hydroxy-2,2,6,6-tetramethyl piperidinoxyl (4-OH Tempo), compounds containing nitroso groups, such as N-nitroso phenyl hydroxylamine and its ammonium salts, quinones such as benzoquinone, and amino compounds such as paraphenylenediamine derivatives, at contents in the reaction medium which may be between 50 ppm and 5000 ppm, optionally in the presence of depleted air, but generally at contents of between 150 ppm and 1000 ppm.
• FIG. 1 represents the block diagram of a process for the recovery / purification of an acrylic ester according to the prior art
• the crude reaction mixture (2) leaving the reaction zone (1) is sent to a topping column (3) which separates, at the top, a stream (4) comprising essentially unreacted reactants, and at the bottom, a stream (5) comprising mainly the desired ester with bound impurities to acid and alcohol and heavy by-products.
• Column (3) is for example a column with trays, of the perforated tray type, or with packed.
• the stream (5) is sent to a rectification column (6) leading at the top to a stream (7) of purified ester, and at the bottom to a stream (8) which is concentrated on a film evaporator (9) or distilled in a topping column (not shown) in order to recycle the light compounds (10) present towards the start of the purification section, such as traces of unreacted reagents, and to remove the final residue (11) from heavy products.
• Stream (4) essentially comprises the unreacted reagents, acrylic acid and esterifying alcohol, which are separated from the desired ester due to their lower boiling point. This flow (4), which can be upgraded, is recycled to the reaction.
• FIG. 2 represents the block diagram of a second process for the recovery / purification of an acrylic ester according to the prior art
• washing the reaction mixture (2) with water after topping in the column ( 3) is carried out before separating the impurities and heavy by-products in the rectification column (6).
• the bottom stream (5) from the topping column is subjected to washing with an aqueous stream (20) leading, after settling in a settling tank (12), to an aqueous phase (22) comprising all of the acid impurities as well as to an organic phase (13) comprising the desired ester, heavy by-products and traces of water and acrylic acid.
• the organic phase (13) obtained after washing with water is subjected to a water removal step, by distillation using a distillation column or using a thin film evaporator ( 15), the recovered water (21) being able to be recycled to the washing step.
• the water-free stream (14) is then sent to the last rectification column (6) of the pure ester, with elimination at the bottom of a stream (16) of heavy by-products.
• the distilled product (7) at the top of column (6) is a purified ester containing substantially no more acid impurities.
• a large volume settling tank is needed to treat the entire stream (5), it is necessary to treat part of the washed stream by passing through an evaporator (15).
• This embodiment greatly increases energy consumption and is hardly compatible with an industrial-scale process.
• the invention overcomes the drawbacks of said prior art processes by using a distillation column equipped with a side draw-off as a topping column (3).
• reaction mixture (2) feeds a side-draw topping column (3).
• the internals used for the column (3) can be valve trays or perforated weir trays, or cross-flow trays like Dual Flow, Ripple Trays, Turbo Grid Shell, or ordered packing like structured packing. such as Sulzer's Mellapack 250X.
• the topping column (3) advantageously comprises an equivalent of 10 to 30 theoretical trays, preferably 15 to 20 theoretical stages.
• the feeding of the topping column (3) by the stream (2) is generally carried out at the upper third of this column, preferably between the theoretical plates 3 to 10 counted from the head of the column.
• the column operates with a reflux rate (flow rate of condensed liquid returned to the column / flow rate (4) extracted overhead) advantageously between 1/5 and 1/1, preferably of the order of 1/3.
• Column (3) can operate under vacuum, to minimize thermal exposure of heat-sensitive compounds within the column.
• column (3) operates under a vacuum ranging from 1.333 to 13.332 kPa (10 to 100 mm of Hg).
• the flow (4) at the top of the column (3) essentially comprises the unreacted reagents. This recoverable stream (4) is advantageously recycled to the reaction.
• a stream (31) is withdrawn laterally from the column (3).
• This stream (31) can be in gaseous form or in liquid form, preferably in liquid form.
• the draw-off is placed at a level lower than the level of supply to the column, advantageously between theoretical plates 5 to 15, preferably between 8 and 12 counted from the column head.
• the location of this lateral withdrawal is judiciously chosen so as to maximize the concentration of AHP and that of di-AA while minimizing the presence of valuable reagents (acrylic acid and esterifying alcohol).
• This lateral withdrawal generally comprises the quantity of stabilizers necessary for its operation without fouling. If necessary, in the event of gas phase withdrawal, another stabilizer can also be added.
• 100 to 5000 ppm of polymerization inhibitor is introduced into the purification system according to the process of the invention.
• the polymerization inhibitors employed can be the same as those used to stabilize the esterification reaction.
• the stabilization of the topping column (3) is carried out using a first polymerization inhibitor, preferably injected at the top condenser.
• the acrylic ester as well as the AHP withdrawn laterally from the column as a gas stream or as a liquid stream can be stabilized with a polymerization inhibitor different from the first inhibitor.
• the organic flow (33) can also be stabilized with the first inhibitor before being re-introduced into the topping column.
• the inhibitors it is possible to inject oxygen, air or so-called 7% O 2 depleted air at the bottom of the column (3).
• the quantity of oxygen injected corresponds to a content of 0.2% to 0.5% relative to the quantity of organic vapor in the column.
• the withdrawn stream (31) is sent to a settling tank (30) in which water (32) is added. After cooling to a temperature preferably ranging from 20 ° C to 70 ° C, water (32) is added in a proportion generally between 5 and 50% relative to the flow (31) from the side draw-off.
• the organic phase (33) is reintroduced into column (3), at a level which may be lower or higher than that of the lateral withdrawal, preferably at a level higher than that of the lateral withdrawal, and preferably at a lower level than the feed to the column, in particular between theoretical plates 5 to 15, preferably 7 to 12.
• the aqueous phase (34) comprising most of the Acid impurities can be reused again to wash the stream 31, or sent for treatment to a biological station.
• the stream (5), separated at the bottom of the topping column (3) is sent to a rectification column (6) leading at the top to a stream (7) of purified ester and at the bottom to a stream (8) .
• Column (6) is for example a column with perforated or packed plates.
• the internals used for the column can be valve trays or perforated weir trays, or cross flow trays such as Dual Flow, Ripple Trays, Turbo Grid Shell, or ordered packing such as structured packing such as Mellapack 250X by Sulzer.
• the distillation column (6) advantageously comprises an equivalent of 2 to 15 theoretical stages, preferably 5 to 10 theoretical stages.
• Column (6) operates with a reflux rate (flow rate of condensed liquid returned to the column / flow rate of flow (7)) ranging from 1/5 to 1/1, preferably of the order of 1/2.
• Column (6) can operate under vacuum, to minimize thermal exposure of heat-sensitive compounds within the column.
• column (6) operates under a vacuum ranging from 1.333 to 13.332 kPa (10 to 100 mm of Hg).
• its operating temperature is between 50 ° C and 160 ° C.
• the stream (8) separated at the bottom is concentrated on a scraped film evaporator (9) in order to recycle the light compounds present towards the start of the purification section upstream of the column (3) or of the column (6) and eliminates the residue (11) comprising heavy products.
• the flow (7) at the top of the column (6) consists of the desired ester having as specifications an ester purity greater than 99.7%, a content of acid impurities (AHP + diAA + AA) less than 90 ppm.
• the water content is generally less than 400 ppm.
• Fe stream 2 feed from a topping column (3) of a 2-ethylhexyl acrylate purification process shown in Figure 1, contains 75 ppm AHP in a first test, and 140 ppm d 'AHP in a second trial.
• the energy used in this test at the boiler of columns 3 and 6 and of the evaporator 9 is 2222618 kcal / h.
• Test 2 of Example 1 is reproduced by changing certain operating conditions in order to find a product meeting specifications.
• test 3 the mass flow rate of the stream 4 distilled at the top of the topping column 3 is increased, with the consequence of a drop in the production rate of A2EH (stream 7 at the top of column 6).
• the reboiling rate of the topping column 3 is increased, with the consequence of an increase in the energy consumption of the purification process.
• test 3 The conditions of test 3 lead to a product meeting specifications, with a slightly lower energy consumption (2209593 kcal / h) than test 1. However, a loss in productivity is observed (107 t / d instead of 119 t / d).
• test 4 generate an A2EH that meets specifications and for a productivity equivalent to that of test 1, but with an excess energy consumption of around 10%.
• the flow 5 from the bottom of the topping column 3 is sent to a settling tank 12 and is washed with 20% water at 70 ° C.
• the organic stream 13 is taken up by a film evaporator 15 before being subjected to distillation in column 6: the aqueous stream 22 is sent to biological treatment and the overhead stream 21 from the evaporator is sent back to the feed to the decanter 12.
• the energy cost of this operation is 18% higher than that required for a process without intermediate washing.
• Example 1 (test 2) is reproduced, but in a configuration according to the invention (shown in Figure 3).
• the feed stream (2) contains 140 ppm AHP.
• Stream 31 is withdrawn from plate 26 of column 3 and washed in a settling tank 30 with water 32.
• the organic phase 33 is recycled to plate 22 of column 3 and the aqueous phase 34 is sent for biological treatment.
• the settling in the settling tank 30 is carried out with 20% water relative to the flow 31 at a temperature of 70 ° C.
• Example 4 is reproduced by changing certain operating conditions, with A2EH production maintained at 119T / d and the AHP content in feed stream 2 set at 140 ppm.

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• 2019
  • 2019-05-23 FR FR1905414A patent/FR3096368B1/fr not_active Expired - Fee Related
• 2020
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  • 2020-04-23 CN CN202080038213.7A patent/CN113891874B/zh active Active
  • 2020-04-23 EP EP20734793.1A patent/EP3972953B1/fr active Active
  • 2020-04-23 US US17/612,590 patent/US12122746B2/en active Active
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