Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B63/00—Purification; Separation; Stabilisation; Use of additives

Definitions

• the present invention relates to a new process for eliminating polymerization inhibitors from mixtures of monomers, in particular ethylenically unsaturated monomers.
• ethylenic monomers In the polymerization industry for a large number of ethylenic monomers, an important problem relates to the storage and / or transport of these monomers. Indeed, one can observe an uncontrolled spontaneous polymerization of these monomers over time from free radicals.
• polymerization inhibitors can be chosen from: picric acid, nitroaromatics, quinone derivatives (hydroquinone, benzoquinone), naphthols, amines (p-phenylenediamine, phenothiazine), phosphites, p-methoxyphenol, p- tertiobutylcatechol, ...
• the temperature can be raised considerably to cause thermolysis of the inhibitor, but the monomer must have high thermal stability,
• the charge of monomers and inhibitor can be distilled, but the monomer must have good thermal stability, in addition such an operation is difficult to carry out on an industrial scale and the boiling point of the inhibitor is, in many cases, higher than that of the monomer, - the inhibitor can be eliminated by adding a dilute solution, for example sodium hydroxide, the charge of monomers then being washed with water in order to remove all traces of caustic compounds, however, the treatment of liquid effluents also poses industrial problems, - Finally, the inhibitor can be adsorbed using a compound such as alumina, silica gel, activated carbon, calcium oxide, aluminum silicate, talc, sulfates of calcium, magnesium sulphates, copper sulphates, magnesium silicate clays, a resin ... Adsorption is one of the most advantageous methods, because it does not have any of the disadvantages mentioned above. Among the adsorbents used, activated alumina is preferred.
• the object of the present invention is to provide a new alumina for the adsorption of polymerization inhibitors of ethylenically unsaturated monomers having improved adsorption capacities compared to the aluminas of the prior art.
• the invention relates to a process for the adsorption of inhibitors of polymerization of ethylenically unsaturated monomers, in which these inhibitors are brought into contact with an alumina, said alumina being produced by coagulation in drops or by kneading-extrusion.
• the principle of the invention therefore derives from the way in which the alumina has been prepared, particularly with regard to its shaping.
• the purification process according to the invention uses an alumina which can be obtained according to several forms.
• the alumina used can be in the form of alumina beads. These beads result from a shaping by coagulation in drops (or "oil-drop").
• This shaping consists in introducing drops of an aqueous solution based on an aluminum compound into a liquid immiscible with water (petroleum, kerosene, ...) in such a way that the drops form substantially spherical particles, these particles are coagulated simultaneously and / or after spheroidal shaping by a gelling agent.
• the beads are then collected then dried and calcined.
• This type of bead can for example be prepared, according to the process described in patent EP-A-097 539, by coagulation in drops of an aqueous suspension or dispersion of alumina or a solution of a salt basic aluminum in the form of an emulsion consisting of an organic phase, an aqueous phase and a surfactant or an emulsifier.
• Said organic phase may in particular be a hydrocarbon, the surfactant or emulsifier is for example Galoryl EM 10
• These beads can also be prepared according to the process described in patent EP-A-015 801 by mixing at a pH below 7.5 an ultrafine boehmite sol and spheroidal alumina particles, then drop coagulation of this mixture as indicated above, and finally drying and calcination.
• Rotating technology means any device in which agglomeration takes place by contacting and rotating the product to be granulated on itself.
• alumina can also be extruded alumina.
• alumina-based material can also be extruded alumina.
• the starting material can be of very varied nature: it can result from the partial and rapid dehydration of hydrargillite, according to the teaching of the application FR-A-1.108.01 1, or from the precipitation of boehmite alumina, pseudo-boehmite, bayerite or a mixture of these aluminas.
• the alumina can be mixed with additives, such as pore formers.
• the extrudates can be prepared by the preparation process described in US Pat. No. 3,856,708.
• alumina extrudates rather than beads obtained from coagulation in drops.
• extrudates can have all kinds of shapes: full or hollow cylinders, multilobes, ...
• the alumina used in the process according to the invention has a total pore volume (VPT) of at least 0.2 ml / g, preferably of at least 0.3 ml / g.
• VPT total pore volume
• VPT This total pore volume (VPT) is measured as follows. The value of the grain density and of the absolute density is determined, the grain densities (Dg) and absolute (Da) being measured respectively by the mercury and helium picnometry method. And the VPT is then given by the formula:
• aluminas with a particle size of between 0.8 and 10 mm, preferably between 1 and 5 mm, are used.
• the particle size corresponds in the case of shaping by coagulation in drops to the diameter of the beads and in the case of extrudates to the diameter of their cross section.
• the alumina has a specific surface of at least 10 nfVg, or even at least 50 m 2 / g.
• This specific surface is a surface measured by the BET method.
• surface measured by the BET method means the specific surface determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established on the basis of the BRUNAUER - EMMETT - TELLER method described in the periodical "The Journal of the American Society ", __), 309 (1938).
• the method according to the invention uses an alumina comprising at least one compound of an element chosen from alkalis, rare earths and alkaline earths.
• This compound can be an oxide, a hydroxide, a salt or a mixture thereof.
• the hydroxides there may be mentioned, by way of example, in addition to the hydroxides, the sulfates, nitrates, halides, acetates, formates, carbonates and the salts of carboxylic acids.
• the elements chosen from sodium, potassium, lithium, lanthanum and cerium are preferably used.
• the level of alkaline, alkaline-earth or rare earth element is generally at least 5 mmol per 100 g of alumina, preferably at most 400 mmol, even more preferably between 10 and 400 mmol.
• the alkaline element is sodium and its content is between 15 and 300 mmol per 100 g of alumina.
• the deposition of the compound of the doping element on or in alumina can be carried out by any method known to those skilled in the art. It can be carried out, for example, by impregnation of the alumina already prepared with the alkaline elements, of rare earths or alkaline-earth or precursors of these elements, or by mixing of the alkaline elements, of rare earths or alkaline-earth or precursors with alumina during the shaping of these materials. These elements can also be introduced into alumina by coprecipitation of alumina and alkaline, rare earth or alkaline-earth elements or their precursors.
• the alumina used in the process according to the invention is prepared by:
• the impregnation is carried out in a known manner by bringing the alumina into contact with a solution, a sol or a gel comprising at least one alkaline, rare earth or alkaline-earth element in the form of oxide or salt or one of their precursors.
• the operation is generally carried out by soaking the alumina in a determined volume of solution of at least one precursor of an alkaline element, of rare earths or alkaline earth elements.
• solution of a precursor of one of these elements is meant a solution of a salt or compound of the element, or at least one, of the alkaline, rare earth or alkaline-earth elements, these salts and compounds which may be thermally decomposable into oxides.
• the salt concentration of the solution is chosen according to the quantity of element to be deposited on the alumina.
• these elements are deposited by dry impregnation, that is to say that the impregnation is carried out with just the volume of solution necessary for said impregnation, without excess.
• the heat treatment is carried out at a temperature determined as a function either of the temperature of use of the alumina or of the specific surface desired. It may also be possible to carry out a heat treatment to obtain at least partial thermal degradation of the compound, for example in the form of oxide. However, this degradation is not compulsory, and by way of example, it is not necessary in particular when using compounds such as chlorides, nitrates or hydroxides.
• the heat treatment can, for example, be carried out at a temperature between 150 and 1000 ° C, preferably between 300 and 800 ° C.
• the adsorption process according to the invention is suitable when the polymerization inhibitor is chosen, for example, from: picric acid, nitroaromatics, quinone derivatives (hydroquinone, benzoquinone), naphthols, amines (p - phenylenediamine, phenothiazine), phosphites, p-methoxyphenol, p-tertiobutylcatechol. Particularly good results are obtained for the adsorption of p-tertiobutylcatechol.
• the alumina When it comes to purifying an ethylenically unsaturated monomer stabilized by a polymerization inhibitor, the alumina is brought into contact with said mixture of ethylenically unsaturated monomer and inhibitor, for example at room temperature.
• the monomer charge can be based on any type of ethylenically unsaturated monomer such as in particular: styrene, butadiene, isoprene, vinyl chloride, vinylidene chloride, tetrafluoroethylene, trifluorochloroethylene, chloroprene, allyl alcohol, vinyl ether, vinyl ester (acetate vinyl), alkyl acrylates and methacrylates (methacrylate, butylacrylate, ethylacrylate, 2-ethylhexylacrylate, methylmethacrylate, ethyl methacrylate, 2-ethylhexylmethacrylate, ...), acrolein, acrylonitrile, acrylamide, amine vinyl.
• the mixture of ethylenically unsaturated monomer and inhibitor comprises 2 to 2000 ppm by weight per volume of inhibitor, preferably 5 to 1500 ppm.
• the alumina samples tested are pretreated under a stream of nitrogen air at 300 ° C for 2 hours in order to remove any trace of moisture following their storage and in order to be able to compare their effectiveness under identical conditions.
• alumina (dry extract) thus pretreated is introduced into 200 ml of a cyclohexane solution containing 500 or 1000 ppm (w / v) of p-tertiobutylcatechol (TBC).
• TBC p-tertiobutylcatechol
• Alumina 1 Activated Alumina 1, 5/3 marketed by Procatalyse Alumina 2: Spherite 537 marketed by Procatalyse Alumina 3: Spherite 521 E marketed by Procatalyse Alumina 5: Spherite 521 E marketed by Procatalyse
• the alumina samples tested are pretreated under a stream of nitrogen air at 300 ° C for 2 hours in order to remove any trace of moisture following their storage and in order to be able to compare their effectiveness under identical conditions.
• alumina (dry extract) thus pretreated is introduced into 200 ml of a styrene solution containing 500 ppm (w / v) of p-tertiobutylcatechol (TBC).
• TBC p-tertiobutylcatechol
• a commercial alumina is treated with a potassium compound.
• the starting alumina is alumina 5. It intrinsically has a sodium level of 50 ppm.
• This starting alumina is impregnated with potassium at different rates.
• the impregnation is carried out dry using a solution of potassium carbonate.
• the impregnated alumina is then dried overnight at 130 ° C., then calcined at 470 ° C. for 1 hour 30 minutes.
• the alumina samples tested are pretreated under a stream of nitrogen air to

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Catalysts (AREA)
• Polymerisation Methods In General (AREA)
• Paper (AREA)
• Drying Of Gases (AREA)

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• 1997
  • 1997-01-22 FR FR9700625A patent/FR2758554B1/fr not_active Expired - Fee Related
• 1998
  • 1998-01-13 CN CN98802729A patent/CN1248234A/zh active Pending
  • 1998-01-13 WO PCT/FR1998/000053 patent/WO1998032717A1/fr not_active Application Discontinuation
  • 1998-01-13 US US09/341,956 patent/US6174480B1/en not_active Expired - Fee Related
  • 1998-01-13 KR KR1019997006558A patent/KR20000070327A/ko not_active Application Discontinuation
  • 1998-01-13 JP JP10531662A patent/JP2000513007A/ja active Pending
  • 1998-01-13 EP EP98902068A patent/EP0973707A1/fr not_active Withdrawn
  • 1998-01-13 BR BR9806983-7A patent/BR9806983A/pt not_active IP Right Cessation
  • 1998-01-13 AU AU58707/98A patent/AU5870798A/en not_active Abandoned
  • 1998-01-20 TW TW087100707A patent/TW394781B/zh not_active IP Right Cessation
• 1999
  • 1999-07-20 NO NO993555A patent/NO993555L/no not_active Application Discontinuation

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