Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B63/00—Purification; Separation; Stabilisation; Use of additives
  • C07B63/04—Use of additives
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C253/00—Preparation of carboxylic acid nitriles
  • C07C253/32—Separation; Purification; Stabilisation; Use of additives
  • C07C253/34—Separation; Purification
• • 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
  • C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
• • 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
  • C07C51/50—Use of additives, e.g. for stabilisation
• • 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

Definitions

• the present invention relates to a process for stabilizing acrylic monomers, in particular acrylic acid, by stabilizers containing a metal sequestering agent.
• phenolic derivatives such as hydroquinone or thiazine derivatives such as phenothiazine are known.
• patent JP 05320205 describes the use of a nitroxide derivative with a metal sequestering agent having a stability constant greater than 10 for Fe complexes under acidic conditions to improve the stability of (meth) acrylic monomers.
• patent JP 05295011 describes the use of one or more phenothiazine compounds (PTZ), aromatic or phenolic amines with a sequestering agent having a stability constant greater than 10 for Fe complexes under acidic conditions.
• PTZ phenothiazine compounds
• aromatic or phenolic amines with a sequestering agent having a stability constant greater than 10 for Fe complexes under acidic conditions.
• EP 048 51 69 discloses polymerization inhibitors comprising one or more stabilizers as well as oxygen.
• these known stabilizations do not completely prevent the formation of polymers during the stages of purification of the acrylic monomers.
• the problem that the invention proposes to solve is therefore to provide a method for stabilizing acrylic monomers having improved stabilizing efficiencies and at the same time making it possible to reduce the corrosion caused by acrylic monomers.
• the object of the invention is therefore to propose a process for stabilizing acrylic monomers, in particular in a distillation column.
• the method for stabilizing acrylic monomers in a distillation column according to the invention comprises the steps of adding at least one stabilizer of acrylic monomers in a total concentration in the liquid phase of between 1 ppm and 5000 ppm, from 1 injection of oxygen into the distillation column with an O 2 / organic vapor molar ratio of between 0.01% and 1%, and the addition of a metal sequestrant at a concentration in the liquid phase of between 0 , 1 ppm and 1000 ppm.
• the stabilizer is chosen from phenolic and thiazine derivatives, transition metal salts and nitroxide derivatives.
• the stabilizer is advantageously chosen from hydroquinone, hydroquinone methyl ether, phenothiazine, methylene blue, copper dibutyldithiocarbamate, manganese acetate, 2,2,6,6 tetramethyl-4-acetoxy- piperidine-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-oxyl, 2,2,6,6-tetramethyl-4-methoxypiperidine-oxyl and mixtures thereof.
• the concentration of the stabilizer in the liquid phase is preferably between 5 ppm and 3000 ppm, preferably between 10 and 1000 ppm.
• the molar ratio between the oxygen injected and the organic vapor is preferably between 0.05% and 0.5%, preferably between 0.1 and 0.25%.
• the metal sequestering agent is advantageously chosen from tetraethylenediaminetetraacetic acid (EDTA), trans-1,2-cyclohexane diamine-tetraacetic acid (CYDTA), diethylenetraiminepentaacetic acid (DTP A), pentasodium salt diethylenetriamine-pentaacetic acid (Na 5 DTPA) as well as their mixtures.
• EDTA tetraethylenediaminetetraacetic acid
• CYDTA trans-1,2-cyclohexane diamine-tetraacetic acid
• DTP A diethylenetraiminepentaacetic acid
• Na 5 DTPA pentasodium salt diethylenetriamine-pentaacetic acid
• the metal sequestrant is present in the liquid phase preferably in a concentration of between 0.5 ppm and 500 ppm, in particular between 5 ppm and 100 ppm.
• the acrylic monomer is chosen from acrylic acid, methacrylic acid, acrylates, methacrylates, acrylonitrile or their mixtures.
• at least two stabilizers are used.
• the following mixtures are particularly preferred: PTZ / HQ / Na 5 DTPA, CB / HA / Na 5 DTPA, CB / PTZ / HQ / Na 5 DTPA, CB / PTZ / HQ / Na 5 DTP A and 4 -OH-TEMPO / EMHQ / Na 5 DTPA.
• metals facilitate redox reactions. Such an effect is for example known for lowering the temperature for generating free radicals in the persulfate / metabisulfite system by adding iron sulfate.
• the problems mentioned are solved according to the invention by adding a stabilizer and a metal sequestrant, and by injecting oxygen into the distillation column.
• the method according to the present invention makes it possible to substantially improve the operating time of a column for distilling a flow based on acrylic monomers and to significantly reduce the corrosion of the industrial tool made of stainless steel.
• acrylic monomers is meant in the present description acrylic acid, methacrylic acid, acrylates, methacrylates as well as acrylonitrile and their mixtures.
• phenolic derivatives such as, for example, hydroquinone, p-methoxyphenol, cresol, phenol, l ' hydroquinone methyl ether, and 2,5-butyl 1 hydroxytoluene.
• Thiazine derivatives such as for example phenothiazine or methylene blue and substituted paraphenylenediamines can also be used.
• transition metal salts such as, for example, copper dimethyl dithiocarbamate, copper diethyldithiocarbamate, copper dibutyldithiocarbamate or the corresponding manganese salts, as well as manganese acetate, are suitable.
• nitroxide derivatives such as for example 2,2,6,6 tetramethyl-4-acetoxy-piperidine-oxyl, 2,2,6,6-tetraméfhyl-4-hydroxypi réelledine -oxyl or 2,2,6,6-tetramethyl-4-methoxypiperidine-oxyl.
• the concentration of stabilizers in the liquid phase is between 1 ppm and 5000 ppm.
• the concentration is between 5, ppm and 3000 ppm, particularly preferred being a concentration between 10 and 1000 ppm.
• the method according to the invention also provides for the injection of oxygen into the distillation column.
• Oxygen improves the effectiveness of stabilizers. It also turns out that it makes it possible to stabilize the gas phase.
• the molar ratio between the oxygen injected into the distillation column and the organic vapor condensed at the head of the column is between 0.01% and 1%. Preferably, the molar ratio is between 0.1% and 0.8%, a ratio between 0.1 and 0.5% being particularly preferred.
• Organic vapor is formed in processes for the purification of substantially the acrylic monomer. Thus, the molar ratio is calculated relative to the vapor pressure of the acrylic monomer under the given temperature and pressure conditions.
• the process according to the invention is also carried out in the presence of a metal sequestering agent.
• a metal sequestering agent can be used for example: tetraethylenediaminetetraacetic acid (EDTA), trans-1, 2-cyclohexane diaminetetraacetic acid (CYDTA) and diethylenetraiminepentaacetic acid (DTP A) and pentasodium salt of l diethylene triaminepentaacetic acid (Na 5 DTPA), Na 5 DTPA being preferred.
• the metal sequestrant is present in the liquid phase in a concentration of between 0.1 ppm and 1000 ppm.
• the sequestering concentration is between 0.5 ppm and 500 ppm, a concentration between 5 ppm and 100 ppm being particularly preferred.
• the simultaneous presence of a stabilizer and a sequestering agent gives rise to a synergistic effect which is manifested by a stabilization efficiency greater than the sum of the effects attributable to the individual components.
• the process according to the present invention is particularly useful on distillation of streams rich in acrylic acid, but it can also be applied with other acrylic monomers.
• the assembly consists of a distillation column equipped with a multikit packing in stainless steel 316, a thermosyphon boiler, surmounted by a swan neck.
• the organic vapors are condensed using a conventional refrigerant. Part of the condensed liquid is recycled to the top of the column after addition of liquid phase stabilizers.
• the distillation is carried out under reduced pressure of approximately 200 mm Hg with a temperature of 105 ° C in the boiler. The distillation is carried out for 6 hours, then the multi-kit filling is dried and weighed.
• the stabilizing efficiency of the mixture studied is evaluated by comparing the mass of polymer formed in the lining. For the tests carried out with 4-OH TEMPO, the duration of the tests was fixed at 3 hours.
• the flux used for all the tests presented consists of crude acrylic acid at 94%. This flow continuously feeds the distillation column with a flow rate of 500 g / h. 445 g / h of distillate and 75 g / h at the bottom are drawn off at the head of the column. The flow rate of organic vapor in the column is 850 g / h. A reflux of 425 g / h is ensured.
• the stabilizers used in the examples are abbreviated as follows: phenothiazine (PTZ), hydroquinone (HQ), copper dibutyldithiocarbamate (CB), 4-hydroxy tetramethyl piperidine N-oxyl (4-OH TEMPO), and hydroquinone methyl ether (EMHQ).
• PTZ phenothiazine
• HQ hydroquinone
• CB copper dibutyldithiocarbamate
• EMHQ 4-hydroxy tetramethyl piperidine N-oxyl
• EMHQ hydroquinone methyl ether
• the stabilizers are combined with one another in the proportions indicated in Table 1 below.
• Oxygen is injected into the distillation column.
• the metal sequestrant is the pentasodium salt of diethylenetriaminepenta-acetic acid (Na 5 DTP A).
• a double jacket heated glass reactor is filled with stabilized acrylic acid and kept at 120 ° C for 72 hours.
• the acrylic acid is fed continuously with a flow rate of 120 ml / h which ensures an average residence time of the acrylic acid in the reactor of 5 hours.
• This same reactor contains elements made of 316L stainless steel, either in the form of 4 rectangular plates of approximately 40 cm 2 , or in the form of 2 spirals of approximately 800 cm 2 .
• the elements have been passivated beforehand. For this, the elements are first degreased with acetone, then oxidized with a fluoro-nitric mixture at 60 ° C for 20 min.
• Bubbling of a nitrogen stream containing 900 molar ppm of oxygen is also ensured in the reactor.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Crystallography & Structural Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Publications (1)

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Citations (6)

Family Cites Families (2)

• 2000
  • 2000-09-29 FR FR0012422A patent/FR2814741B1/fr not_active Expired - Fee Related
• 2001
  • 2001-09-25 KR KR1020037004262A patent/KR100806558B1/ko not_active Expired - Fee Related
  • 2001-09-25 CN CNB018166059A patent/CN1250509C/zh not_active Expired - Fee Related
  • 2001-09-25 EP EP01972199A patent/EP1324969A1/fr not_active Withdrawn
  • 2001-09-25 AU AU2001291986A patent/AU2001291986A1/en not_active Abandoned
  • 2001-09-25 US US10/381,795 patent/US20040011638A1/en not_active Abandoned
  • 2001-09-25 JP JP2002531072A patent/JP2004513089A/ja not_active Withdrawn
  • 2001-09-25 WO PCT/FR2001/002965 patent/WO2002026685A1/fr not_active Ceased

Patent Citations (6)

Non-Patent Citations (2)

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