Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C19/00—Acyclic saturated compounds containing halogen atoms
  • C07C19/08—Acyclic saturated compounds containing halogen atoms containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/07—Preparation of halogenated hydrocarbons by addition of hydrogen halides
  • C07C17/087—Preparation of halogenated hydrocarbons by addition of hydrogen halides to unsaturated halogenated hydrocarbons
• • 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

Definitions

• the present invention relates to a process for the production of 1,1,1,2,3,3,3-heptafluoropropane from hexafluoropropene and to a process for the separation of mixtures comprising 1,1,1,2,3,3,3-heptafluoropropane and hydrogen fluoride.
• Hydrofluorocarbons are widely used as replacements for chlorofluorocarbon compounds in a variety of applications. Such applications include use in medical applications, for example as an aerosol propellant, use as a fire suppressant, use in refrigeration applications and in other applications.
• 1,1,1 ,2,3,3,3-heptafluoropropane which is known in the art as Hydrofluorocarbon 227ea and will hereinafter be referred to as "HFC 227ea" for convenience, has zero ozone depletion potential and is particularly beneficial in medical applications in the light of its combination of properties including low toxicity, non-flammability, solvent properties and boiling point.
• hydrofluorocarbons by the hydro fluorination of a fluoroalkene to the corresponding hydrofluoroalkane, optionally in the presence of a catalyst, in the liquid phase or vapour phase.
• Hydrogen fluoride is known for use as a hydro fluorination agent in such hydro fluorination processes.
• HFP hexafluoropropene
• DE 2712732 and GB 902590 disclose the use of a chromium oxyfluoride catalyst and an activated carbon catalyst respectively.
• WO 97/11042 and WO 96/0243 disclose the use of catalysts comprising an organic amine complexed with hydrogen fluoride and certain antimony catalysts respectively.
• the stream comprising the HFC 227ea/hydrogen fluoride azeotrope and the HFP/hydrogen fluoride azeotrope after recovery of a portion of the hydrogen fluoride by distillation, can be water-washed to allow recovery of both a mixture of organic compounds essentially free of hydrogen fluoride and aqueous hydrogen fluoride.
• aqueous hydrogen fluoride generated in this way can be neutralised with caustic solution and/or lime and ultimately disposed of.
• the product stream from the reaction of a fluoroalkene with hydrogen fluoride after recovery of a portion of the hydrogen fluoride by distillation, may be treated with a solution of alkali metal dissolved in anhydrous hydrogen fluoride as described in our patent specification WO 97/13179.
• WO 97/13179 a solution of alkali metal dissolved in anhydrous hydrogen fluoride
• aqueous scrubbing is an effective way of removing hydrogen fluoride from the organic compound(s) after reacting hydrogen fluoride with a haloalkene aqueous scrubbing tends to be expensive in terms of hydrogen fluoride loss from the process.
• reaction product phase-separates in the liquid phase to afford an organic-rich phase, which comprises HFC 227ea and HFP, and a hydrogen fluoride-rich phase.
• the mole fraction of HF to 227ea in the reaction product may be from about 0.1 to 0.9.
• Step C charging the organic-rich phase separated in Step A to a distillation column;
• Step (C) recovering the HFC 227ea and an HF-rich mixture separately from the distillation column in Step (C); and E. recycling the HF-rich mixture recovered from Step D to the reactor.
• the reaction mixture charged to the liquid-phase separator in Step (A) comprises an HFC 227ea/HF azeotrope, or azeotrope-like mixture, and optionally an HFP/HF azeotrope, or azeotrope-like mixture.
• the reaction mixture charged to the liquid-phase separator in Step A may be the mixture arising directly from the reactor in which HFP is reacted with hydrogen fluoride (direct mixture). It is often preferred, however, that the mixture charged to the liquid-phase separator is essentially an HFC 227ea/hydrogen fluoride azeotrope, for example obtained from distillation of the direct mixture.
• HFP facilitates separation of the HFC 227ea/hydrogen fluoride azeotrope into its components.
• the HFP may be introduced into the process according to the present invention at one or more appropriate points. For example, it may be charged to the reactor and/or to the liquid-phase separator in Step A and/or to the distillation column in Step C. Preferably the HFP is added to the liquid phase separator, either directly or mixed with the reaction mixture.
• reaction of HFP with hydrogen fluoride in the process according to the first aspect of the present invention may be carried out in the liquid phase or in the vapour phase.
• Step A is preferably carried out at below ambient temperature, typically at below 30°C.
• Step A is preferably carried out at supra-atmospheric pressure, typically 1-20 bars and preferably about 10 bars.
• the product of the reaction of HFP with hydrogen fluoride is distilled to recover a portion of the hydrogen fluoride therefrom before the mixture comprising HFC 227ea/hydrogen fluoride azeotrope or azeotrope-like mixture thereof, HFP/hydrogen fluoride azeotrope or azeotrope-like mixture thereof, and hydrogen fluoride is charged to the liquid phase separator in Step A.
• the portion of hydrogen fluoride recovered by distillation in a recovery step prior to Step A, where such a recovery step is carried out, is preferably recycled to the reactor vessel.
• HFC 227ea is prepared by reacting HFP with hydrogen fluoride in the process according to the first aspect of the present invention in the liquid phase in the presence of a catalyst, eg TaF 5 , NbF 5 or SbF 5 , it is suitably carried out at a temperature in the range 20 to 200°C, preferably 40 to 120°C and especially 50 to 100°C.
• a catalyst eg TaF 5 , NbF 5 or SbF 5
• the reaction is carried out at superatmospheric pressure such that the reactants are in the liquid phase for sufficient time to react to produce HFC 227ea.
• the pressure is at least 5 bar and more preferably the pressure is 10 to 50 bar.
• the residence time in the reactor in the process according to the first aspect of the present invention is sufficient to permit conversion of HFP feedstock into HFC 227ea.
• the required residence time will be dependent on inter alia the degree of conversion required, the reactant ratio and the reaction conditions.
• the molar ratio of hydrogen fluoride (HF) to HFP fed to the reactor is suitably at least 1:1 and preferably between 1.2 and 10:1. It will be appreciated that where a molar ratio of HF to HFP of 0.1 up to 1:1 is employed the conversion ratio and/or the yield will be lower.
• the molar ratio of HFP to the catalyst is suitably not more than 100:1 and is preferably between 1:1 and 50:1.
• the levels of HF, HFP and catalyst in the process according to the present invention are suitably selected such that the catalyst and reactants are at least largely dissolved in the liquid phase under the reaction conditions employed.
• the process according to the present invention may be operated in batch or continuous mode as desired.
• Semi-batch operation may also be employed in which one or more feedstocks are fed continuously to the process and one or more other feedstocks are fed to the process in batch-wise fashion.
• the process according to the present invention may be carried out in the vapour phase.
• Suitable conditions and catalysts for use in carrying out the process according to the present invention in the vapour phase are more fully described in DE 2712732 and GB 902590 mentioned hereinbefore.
• Figure 1 is a schematic representation of a plant wherein HFP is fed to the liquid-phase separator
• Figure 2 is a schematic representation of a plant wherein HFP is fed to the reactor;
• Figure 3 is a schematic representation of a plant wherein the product of the reaction is fed directly to the liquid-phase separator;
• Figure 4 is a ternary diagram illustrating HFC 227ea, HFP and HF separation.
• feed pipe (1) leads to a reactor (2), which optionally contains a fluorination catalyst.
• Product pipe (3) from the reactor (2) is in fluid-flow communication with a first distillation column (4), which is for example a single stage flash vessel.
• Distillation column (4) is typically operated at a pressure of 12 bars with a bottoms temperature of 100°C and a tops temperature of around 50°C.
• Bottoms pipe (5) from distillation column (4) is in fluid-flow communication with feed-pipe (1).
• Tops line (6) from distillation column (4) is in fluid-flow communication with a liquid-phase separator (7).
• Tops line (8) from the liquid-phase separator (7) is in fluid-flow communication with feed-pipe (1).
• Bottoms line (9) from the liquid-phase separator (7) is in fluid-flow communication with a second distillation column (10), which is for example a packed column.
• Distillation column (10) is typically operated at a pressure of around 12 bars with a tops temperature of 37°C and a bottoms temperature of around 60°C.
• Distillation column (10) is provided with an exit pipe for product (11) and a tops pipe (12).
• tops pipe (12) from distillation column (10) is in fluid flow commumcation with tops line (6) which is provided with a feed-pipe (13).
• tops pipe (12) from distillation column (10) is in fluid flow commumcation with feed-pipe (1) which is provided with feed-pipe (13).
• the reactor (2) is charged through feed pipe (1) with a feed stream containing fresh hydrogen fluoride and recycled hydrogen fluoride (from lines (5) and (8) and, in Figure 2, line (12) ).
• the product from reactor (2) comprising HFC 227ea, hydrogen fluoride and unconverted HFP, often in the form of a ternary azeotrope, travels through product pipe (3) to the first distillation column (4).
• hydrogen fluoride which is recycled via bottoms line (5) to feed pipe (1), is separated from the mixture of HFC 227ea, hydrogen fluoride and unconverted HFP.
• the mixture of HFC 227ea, residual hydrogen fluoride and HFP is fed via tops line (6) from the distillation column (4) to the liquid-phase separator (7).
• the liquid-phase separator (7) is typically operated at 0-20°C to afford better separation.
• HFP is fed via feed line (13) to liquid-phase separator (7).
• HFP is fed via line (13) and feed-pipe (1) to reactor (2).
• an HF-rich phase separates from the organics-rich phase.
• the HF-rich phase is returned via tops-line (8) to feed-pipe (1)
• the organics-rich phase flows via bottoms line (9) to distillation column (10).
• a stream comprising HFP and essentially all the hydrogen fluoride content of the stream entering distillation column (10) via line (9) is removed from the top of distillation column (1Q) via line (12) and the product stream HFC 227ea is removed from the bottom of column (10) via exit pipe (11).
• feed pipe (1) leads to a reactor (2), which optionally contains a fluorination catalyst.
• Line (14) from reactor (2) is provided with a feed line (13) and is in fluid-flow communication with a liquid-phase separator (7).
• Tops line (8) from the liquid-phase separator (7) is in fluid- flow communication with feed-pipe (1).
• Bottoms line (9) from the liquid-phase separator (7) is in fluid-flow communication with a distillation column (10), which is for example a packed column.
• Distillation column (10) is typically operated at a pressure of around 12 bars with a tops temperature of 37°C and a bottoms temperature of around 60°C.
• Distillation column (10) is provided with an exit pipe for product (11) and a tops pipe (12) which is in fluid flow communication with line (14) to liquid-phase separator (7).
• the reactor (2) is charged through feed pipe (1) with a feed stream containing fresh hydrogen fluoride and recycled hydrogen fluoride from line (8).
• the product from reactor (2) comprising HFC 227ea, hydrogen fluoride and unconverted HFP, often in the form of a ternary azeotrope, travels through product pipe (14) to the liquid-phase separator (7).
• HFP is fed via feed line (13) and product pipe (14) to liquid-phase separator (7).
• the liquid-phase separator (7) is typically operated at 0-20°C to afford better separation.
• an HF-rich phase separates from the organics-rich phase.
• the HF-rich phase is returned via tops-line (8) to feed-pipe (1).
• the organics-rich phase flows via bottoms line (9) to distillation column (10).
• a stream comprising HFP and essentially all the hydrogen fluoride content of the stream entering distillation column (10) via line (9) is removed from the top of distillation column (10) via line (12) and returned to the liquid phase separator (7) via line (14).
• the product stream HFC 227ea is removed from the bottom of column (10) via exit pipe (11).
• compositions in the area of the figure designated A phase-separate namely compositions comprising 0.4-0.6 mole % HF, greater than 0.4 mole % HFP and less than 0.6 mole % HFC 227ea.
• a phase-separate namely compositions comprising 0.4-0.6 mole % HF, greater than 0.4 mole % HFP and less than 0.6 mole % HFC 227ea.
• HFC 227ea and HFP were added to HF in a 500 ml whitey bomb cooled in liquid nitrogen.
• the whitey bomb was provided with a double-dip arrangement such that the dip-pipes would sample from the middle of each phase.
• the mixture was allowed to warm to room temperature, agitated, allowed to stand for 2 hours and then analysed.
• the HF phase was analysed for organics by transferring a portion of the HF phase (lOg) to a smaller whitey bomb containing water. It was allowed to stand for 15 minutes then the headspace was analysed by G.C.
• the organics phase was analysed for HF by bubbling a portion of the organics phase through water scrubbers containing fresh de-ionised water and ice. The water was then analysed for fluoride.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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Citations (3)

• 2000
  • 2000-05-15 EP EP00927586A patent/EP1178950A1/en not_active Withdrawn
  • 2000-05-15 JP JP2000618218A patent/JP2002544248A/ja active Pending
  • 2000-05-15 WO PCT/GB2000/001861 patent/WO2000069797A1/en active IP Right Grant
  • 2000-05-15 CA CA002373437A patent/CA2373437A1/en not_active Abandoned
  • 2000-05-15 AU AU45977/00A patent/AU769137B2/en not_active Ceased

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