Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/26—Chromium
• • 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

Definitions

• the present invention relates to a process for the preparation of 1,1,1, 2,3,3, 3-heptafluoropropane from hexafluoropropene, particularly to the process therefor carried out in the vapour phase.
• Hydrofluorocarbons referred to hereinafter for convenience as HFC 's, are widely used as replacements for chlorofluorocarbon compounds. Such uses 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 will be referred to hereinafter for convenience as HFC 227ea, has zero ozone depletion potential and is particularly beneficial in medical propellant applications in the light of its combination of properties including low toxicity, non-flammability, solvent properties and boiling point.
• HFC 227ea It is known in the art to produce HFC 227ea by the hydrofluorination of hexafluoropropene, optionally in the presence of a catalyst, in the liquid phase or vapour phase.
• Hydrogen fluoride is known for use as a hydrofluorination agent in such a hydrofluorination reaction.
• a variety of materials may be employed as catalyst in such a hydrofluorination reaction.
• HFP liquid phase reaction of hexafluoropropene, hereinafter referred to for convenience as HFP, with hydrogen fluoride for the preparation of HFC 227ea
• catalysts in the liquid phase reaction WO 97/11042 and EP 0,634,383 disclose the use of an organic amine complexed with hydrogen fluoride; WO 96/0243 discloses the use of certain antimony catalysts; and EP 0,634,384 discloses the use of a weak ion-exchange resin containing tertiary amine groups.
• GB 902590 discloses the use of an activated carbon catalyst with an at least equimolar gaseous mixture of hydrogen fluoride and HFP, at atmospheric pressure and high temperature; for high yield, the HF.HFP molar ratio is preferably between 1.5:1 and 3:1.
• the use of activated carbon as catalyst in the vapour phase reaction has the drawback that it rapidly becomes deactivated.
• EP 0,562,509 describes a process for reactivating such a carbon catalyst by heating it at 450-900°C in a stream of inert gas or under reduced pressure.
• US 4,158,023 describes the preparation of HFC 227ea as a non-isolated intermediate in the vapour-phase preparation of octafluoropropane from HFP. It discloses the use of a chromium oxyfluoride catalyst in the vapour phase reaction of HFP with hydrogen fluoride for the preparation of HFC 227ea, at 100-350°C, at generally normal pressure and with a low molar ratio of HF:HFP, namely from 1:1 to 3:1.
• a process for the preparation of HFC 227ea by reacting hydrogen fluoride with HFP in the vapour phase over a fluorination catalyst characterised in that the molar ratio of HF:HFP is at least 3.5: 1.
• the molar ratio of HF:HFP is preferably in the range 3.5:1 to 100:1, more preferably in the range 4:1 to 50:1.
• a gaseous mixture of HFP and hydrogen fluoride is passed through a heatable reactor tube containing a hydrofluorination catalyst.
• the reactor tube may be of conventional design made of appropriate material resistant to hydrogen fluoride.
• fluorination catalysts which may be used in the process according to the present invention may be mentioned inter alia (i) fluorination catalysts based on metal oxides/halides or oxyhalides or mixed metal oxides/halides/oxyhalides, for example chromia or alumina; (ii) other metallic oxides/halides/oxyhalides supported on chromia or alumina, for example oxides of zinc, iron, magnesium or nickel; and (iii) metal oxides/halides/oxyhalides, or mixed metal oxides/halides/oxyhalides supported on carbon.
• the fluorination catalyst is dried and subjected to a pretreatment, eg with hydrogen fluoride, prior to use.
• fluorination catalysts are disclosed in our EP 0,502,605 and WO 93/25508, the disclosures in which are incorporated herein by way of reference.
• the metal on which the fluorination catalyst used in the present invention is based is preferably a d- or p-block metal, oxide, fluoride or oxyfluoride thereof, and more preferably chromium, aluminium or a Group Villa metal.
• the catalyst may be compressed into pellets and used in a fixed bed or, alternatively, catalysts of appropriate particle size may be used in a fluidised bed.
• the reaction of HFP with hydrogen fluoride is not equilibrium limited, therefore it is possible to obtain very high conversions per pass, eg 50-100%.
• the reaction of HFP with hydrogen fluoride is significantly exothermic.
• the reaction can be carried out in a cooled reactor, eg a salt-cooled reactor, or in an adiabatic reactor under conditions which moderate the heat generated through formation of HFC 227ea.
• the heat generated can be removed between reactors in a series thereof and/or by use of a diluent in the reaction mixture.
• the reaction according to the present invention is preferably carried out in the presence of a diluent.
• HFP is moderated and we have found that the reaction can be carried out in an adiabatic reactor or series of adiabatic reactors, that is a reactor to which none, or little thermal regulation, ie heating or cooling is required.
• the diluent is preferably a HFC or hydrogen fluoride, more preferably a HFC. However, we do not exclude the possibility that it may be an alternative diluent, eg nitrogen, etc.
• preferred HFC diluents may be mentioned inter alia 1,1,1,2-tetrafluoroethane, pentafluoroethane or preferably HFC 227ea.
• HFC 227ea or hydrogen fluoride as diluent in the reaction facilitates separation of the products at the end of the reaction and allows the use of a simpler separation train and smaller plant.
• the maximum acceptable exotherm across an adiabatic reactor is 50°C and the HF:HFP molar feed ratio is 10:1 we have found that for 50% HFP conversion, 70% HFP conversion and 100% HFP conversion using recycled HFC 227ea as diluent, the relative size of the reactor(s) compared with the use of excess hydrogen fluoride as diluent is about 30%, ie a reduction in reactor size of about 70%.
• the presence of recycled HFC 227ea in the feed to the adiabatic reactor(s) does not adversely affect the conversion of HFP into HFC 227ea since, as mentioned above, the reaction of HFP with hydrogen fluoride is not equilibrium limited. It will be appreciated that use of a low cost adiabatic reactor provides significant capital cost advantage over a salt-cooled reactor employing an internal cooling surface.
• the contact time is typically less than 5 minutes and preferably is 1-5 seconds.
• the process according to the present invention is typically carried out in the temperature range 100-500°C.
• the process according to the present invention is preferably carried out at superatmospheric pressure, for example 2-50 barg, more preferably 5-25 barg. It will be appreciated that where the process is carried out at superatmospheric pressure the productivity of the reactor is increased, smaller-scale plant can be used for the same throughput and less expensive refrigeration can be used in the primary separation stage following the reactor.
• the product stream from the reactor in which HFP is reacted with hydrogen fluoride to prepare HFC 227ea typically contains HFC 227ea, hydrogen fluoride and hexafluoropropene.
• the HFC 227ea may be isolated from unchanged starting materials and by-products using conventional procedures, for example distillation.
• Example 1 The present invention is further illustrated by reference to the following Examples.
• Example 1 The present invention is further illustrated by reference to the following Examples.
• This Example illustrates the advantage of carrying out the reaction of HF with HFP at a high HF:HFP molar ratio, namely 10:1.
• a mixed zinc/chromium oxide fluorination catalyst was charged to a reactor, dried under nitrogen at 200°C for 16 hours and treated with a vapour stream of hydrogen fluoride in nitrogen at 300-380°C for 16 hours.
• the temperature in the reactor was adjusted to give the desired reaction temperature and vapour comprising HFP, hydrogen fluoride and nitrogen in the molar ratio shown in Table 1 was charged to the reactor under atmospheric pressure.
• Example 1 In a Comparative Test, Example 1 was repeated except that a HF:HFP molar ratio of 1 : 1 was used instead of 10: 1.
• CT2 is a Comparative Test.

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• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 1998
  • 1998-07-02 EP EP19980932350 patent/EP1000002A1/de not_active Withdrawn
  • 1998-07-02 JP JP2000505107A patent/JP2001512092A/ja active Pending
  • 1998-07-02 WO PCT/GB1998/001951 patent/WO1999006342A1/en not_active Ceased
  • 1998-07-02 CN CN98809564A patent/CN1271337A/zh active Pending
  • 1998-07-02 AU AU82289/98A patent/AU8228998A/en not_active Abandoned

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