Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/38—Separation; Purification; Stabilisation; Use of additives
  • C07C17/42—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/38—Separation; Purification; Stabilisation; Use of additives
  • C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
  • C07C17/386—Separation; Purification; Stabilisation; Use of additives by distillation with auxiliary compounds

Definitions

• the present invention relates to a method of manufacture of a hydrofluoroalkane and a stabilized hydrofluoroalkane.
• Hydrofluoroalkanes can be used, for example, as a blowing agent for polyurethane foams or as a constituent of solvent compositions.
• Patent application EP-A-0564036 generally envisages the stabilization of hydrofluoroalkanes with, preferably, amylene and describes stabilization during distillation of 1,1-dichloro-1-fluoroethane (HCFC-141b) against its dehydrochlorination with this compound.
• hydrofluoroalkanes notably by (hydro)fluorination of a chlorinated precursor
• olefinic impurities is often observed, which formation is associated at least partially with dehydrofluorination of the hydrofluoroalkane, for example during purification operations such as distillation.
• the invention relates to a method of manufacture of a hydrofluoroalkane comprising the use of a Lewis base as stabilizer of the hydrofluoroalkane.
• “method of manufacture” relates in particular to stages of purification of a hydrofluoroalkane, said hydrofluoroalkane resulting for example from a stage of synthesis by hydrofluorination of a suitable precursor for example saturated or unsaturated, chlorinated or chlorofluorinated precursors.
• the Lewis base often contains at least one heteroatom and is preferably selected from alcohols, amines, amides, nitriles and phosphorus-containing compounds.
• An aliphatic alcohol in particular unsubstituted, selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and the pentanols is more particularly preferred.
• N-propanol and/or isopropanol, in particular isopropanol is quite particularly preferred.
• the alcohol is a polyol, preferably a diol.
• Ethylene glycol is preferred as diol.
• amines that can be used as Lewis base mention may be made of the aliphatic amines or the aromatic amines.
• the aliphatic amines the primary amines, the secondary amines and the tertiary amines are to be mentioned in particular.
• the alkanolamines, the alkylamines such as for example ethanolamine, n-butylamine, tert-butylamine, n-propylamine, isopropylamine, benzylamine, hexamethylene diamine, diethylamine, triethylamine or aromatic amines such as pyridine or aniline are used as amine.
• nitriles propionitrile and adiponitrile are preferred.
• amides that can be used as Lewis base mention may be made of the linear amides such as N,N-dimethylacetamide and N,N-dimethylformamide and cyclic amides such as N-methylpyrrolidone. Mention may also be made of hexamethylphosphoramide.
• trialkylphosphine oxides that can be used, mention may be notably made of the compounds of formula (R1R2R3)PO, in which R1, R2 and R3 represent identical or different C3-C10 alkyl groups, preferably linear.
• R1, R2 and R3 represent identical or different C3-C10 alkyl groups, preferably linear.
• the following are used in particular: tri(n-butyl)phosphine oxide, tri(n-hexyl)phosphine oxide, tri(n-octyl)phosphine oxide, n-octyldi(n-hexyl)-phosphine oxide and n-hexyldi(n-octyl)phosphine oxide and mixtures thereof.
• trialkyl phosphates mention may notably be made of the compounds of formula (RO) 3 PO, in which R represents a C3-C10 alkyl group, preferably linear. Tributyl phosphate is used in particular.
• the Lewis base does not form an azeotrope with the hydrofluoroalkane. This makes it possible to improve the overall economics of the method since the Lewis base can be separated easily and reused without formation of undesirable azeotropic fractions of hydrofluoroalkane containing substantial amounts of Lewis base.
• the hydrofluoroalkane generally contains at least one Lewis acid, in particular iron compounds, more particularly ferric chloride.
• the content of Lewis acid in the hydrofluoroalkane is generally from 0.1 to 500 and more often from 1 to 100 mg/kg of hydrofluoroalkane.
• the stabilized hydrofluoroalkane is generally subjected to a temperature from 50 to 200° C., for example during a purification treatment.
• the Lewis base is preferably employed during purification of the hydrofluoroalkane, in particular during a distillation stage.
• a particular embodiment of the method according to the invention comprises at least one stage of distillation of the stabilized hydrofluoroalkane.
• the method according to the invention comprises at least two stages of distillation of the stabilized hydrofluoroalkane, one intended to remove “light” impurities and the other intended to remove “heavy” impurities.
• the Lewis base is preferably added to the hydrofluoroalkane before it is subjected to distillation. It can also be added in a distillation column.
• Hydrofluoroalkane is intended to denote an alkane consisting of atoms of carbon, hydrogen and fluorine.
• the hydrofluoroalkane is often selected from 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3,3-hexafluoropropane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,3,3-pentafluorobutane and 1,1,1,2,3,4,4,5,5,5-decafluoropentane.
• it is selected from 1,1,1,3,3-pentafluoropropane and 1,1,1,3,3-pentafluorobutane.
• 1,1,1,3,3-pentafluorobutane is more particularly preferred.
• the invention also relates to a stabilized hydrofluoroalkane containing from 1 to 500 mg/kg of a Lewis base. It was found that the stated content of Lewis base in the hydrofluoroalkane makes it possible to minimize its potential dehydrofluorination, for example during its use or its storage.
• the 1,1,1,3,3-pentafluorobutane (without isopropanol) feeding the first distillation contained between 10 and 20 mg/kg of olefins.
• ferric chlorides at concentrations between 20 and 300 mg/kg
• degradation of the 1,1,1,3,3-pentafluorobutane was observed.
• the latter was characterized by re-formation of olefins, the concentrations of which were from 40 to 60 mg/kg at discharge from the second distillation.

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Citations (4)

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• 2004
  • 2004-01-30 FR FR0400921A patent/FR2865731B1/fr not_active Expired - Fee Related
• 2005
  • 2005-01-18 EP EP05000864.8A patent/EP1559702B1/de not_active Not-in-force
  • 2005-01-18 ES ES05000864.8T patent/ES2550216T3/es active Active
  • 2005-01-19 US US11/039,599 patent/US20050171391A1/en not_active Abandoned
  • 2005-01-27 JP JP2005019833A patent/JP4763299B2/ja not_active Expired - Fee Related
  • 2005-01-28 CN CN2005100063853A patent/CN1680230B/zh active Active
• 2006
  • 2006-05-02 US US11/416,000 patent/US7253327B2/en active Active

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