Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/013—Preparation of halogenated hydrocarbons by addition of halogens
  • C07C17/04—Preparation of halogenated hydrocarbons by addition of halogens to unsaturated halogenated hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C17/00—Preparation of halogenated hydrocarbons
  • C07C17/25—Preparation of halogenated hydrocarbons by splitting-off hydrogen halides from halogenated hydrocarbons

Definitions

• the present invention relates to a process for producing fluoroolefins or fluorohaloolefins or fluorine-containing olefins, sometimes referred to hereinafter for convenience as fluoroolefins or fluorine-containing olefins, useful as intermediates for making industrial chemicals, in good yield, on an industrial scale and using commercially and readily available starting materials.
• the present invention relates to a process for producing fluoroolefins, for example, 1, 1, 1,3, 3-pentafluoropropene (also designated as "HFC- 1225zc”), by the dehydrohalogenation of a halofluorocarbon, for example, 1-chloro-l, 1,3, 3, 3-pentafluoropropane (also designated as "HCFC-235fa”) which halofluorocarbon can be produced by photochlorinating 1, 1, 3 , 3 , 3-pentafluoropropane (also designated as "HFC-245fa”) .
• a halofluorocarbon for example, 1-chloro-l, 1,3, 3, 3-pentafluoropropane (also designated as "HCFC-235fa") which halofluorocarbon can be produced by photochlorinating 1, 1, 3 , 3 , 3-pentafluoropropane (also designated as "HFC-245fa”) .
• U.S. 5,532,419 discloses a vapor phase catalytic process for the preparation of fluorinated olefins using a chloro- or bromo- halofluorocarbon and HF.
• EP 974571 discloses the preparation of 1,1,1,3- tetrafluoropropene by contacting 1, 1, 1, 3, 3-pentafluoropropane (HFC-245fa) with either an aqueous or alcoholic solution of KOH, NaOH, Ca (OH) _ or Mg (OH) _ or by contact of the HFC-245fa in the vapor phase with a chromium based catalyst at elevated temperature .
• HFC-245fa 1, 1, 1, 3, 3-pentafluoropropane
• the compound of step (A) can be CF 3 CH 2 CF 2 H (a commercially available compound also known as HFC-245fa) or CF 3 CH 2 CF 2 C1, a by-product from the manufacture of HFC-245fa. DETAILED DESCRIPTION
• Fluoroolefins are produced by the process of the present invention by dehydrohalogenating, in the presence of a phase transfer catalyst, a compound of formula (I) comprising contacting the compound of formula (I) with at least one alkali metal hydroxide:
• alkali metal hydroxide is selected from the group consisting of the metals of Group 1 of the Periodic Table of the Elements as shown in Hawley's
• the alkali metal is selected from the group consisting of lithium, sodium and potassium; more preferably, sodium and potassium; most preferably, potassium.
• Useful concentrations of the hydroxide are from about 1 to about 50 wt.%; preferably from about 5 to about 30 wt.%; most preferably from about 10 to about 30 wt.%. While it is possible to use hydroxides other than alkali metal hydroxides, they tend to be less soluble, particular in aqueous systems and are therefore less desirable. For example, hydroxides of the Group 2 metals (e.g., Ca, Mg, and Ba) are of this type; such as magnesium hydroxide.
• the Group 2 metals e.g., Ca, Mg, and Ba
• the molar ratio of hydroxide, preferably alkali metal hydroxide, relative to the amount of CF 3 C(R 1 a R 2 b ) C(R 3 c R 4 a) is from about 1 to about 20; preferably from about 1 to about 15; more preferably from about 1 to about 12; for example, from about 1 to about 10.
• the dehydrohalogenation reaction can be accomplished using an aqueous solution of at least one alkali metal hydroxide, without the need for additional solvent or diluent, other than the water present as a consequence of using aqueous base or alkali metal hydroxide.
• a solvent or diluent can be used if desired for convenience in carrying out the process, e.g., to modify the system viscosity, to act as a preferred phase for reaction by-products, or to increase thermal mass, etc.
• Useful solvents or diluents include those that are not reactive with or negatively impact the equilibrium or kinetics of the process and include alcohols such as methanol and ethanol; ethers such as diethyl ether, dibutyl ether; esters such as methyl acetate, ethyl acetate and the like; linear, branched and cyclic alkanes such as cyclohexane, methylcyclohexane; fluorinated diluents such as perfluoroisopropanol, perfluorotetrahydrofuran; chlorofluorocarbons such as CFC1 2 CF 2 C1, etc.
• phase transfer catalyst is a substance that facilitates the transfer of ionic compounds (e.g., reactants or components) into an organic phase from, e.g., a water phase.
• ionic compounds e.g., reactants or components
• an aqueous or inorganic phase is present as a consequence of the alkali metal hydroxide and an organic phase is present as a result of the fluorocarbon.
• the phase transfer catalyst facilitates the reaction of these dissimilar and incompatible components.
• phase transfer catalysts may function in different ways, their mechanism of action is not determinative of their utility in the present invention provided that the phase transfer catalyst facilitates the dehydrohalogenation reaction based on the identified reactants.
• the phase transfer catalyst can be ionic or neutral and is selected from the group consisting of crown ethers, onium salts, cryptates and polyalkylene glycols and derivatives thereof.
• An effective amount of the phase transfer catalyst should be used in order to effect the desired reaction,- such an amount can be determined by limited experimentation once the reactants, process conditions and phase transfer catalyst are selected.
• the amount of catalyst used relative to the amount of CF 3 C (R ⁇ R 2 ⁇ C (R 3 c R 4 d ) present is from about 0.001 to about 10 mol %; for example from about 0.01 to about 5 mol %; alternatively, for example from about 0.05 to about 5 mol %..
• Crown ethers are cyclic molecules in which ether groups are connected by dimethylene linkages; the compounds form a molecular structure that is believed to be capable of "receiving" or holding the alkali metal ion of the hydroxide and to thereby facilitate the reaction.
• Particularly useful crown ethers include 18-crown-6, especially in combination with potassium hydroxide; 15-crown-5, especially in combination with sodium hydroxide; l2-crown-4, especially in combination with lithium hydroxide.
• Derivatives of the above crown ethers are also useful, e.g., dibenzo-18-crown-6, dicyclohexano-18-crown-6, and dibenzo-24-crown-8 as well as 12-crown-4.
• polyethers particularly useful for alkali metal compounds, and especially for lithium are described in U.S. 4,560,759 which is incorporated herein by reference to the extent permitted.
• Other compounds analogous to the crown ethers and useful for the same purpose are compounds which differ by the replacement of one or more of the oxygen atoms by other kinds of donor atoms, particularly N or S, such as hexamethyl- [14] -4, ll-dieneN 4 .
• Onium salts include quaternary phosphonium salts and quaternary ammonium salts that may be used as the phase transfer catalyst in the process of the present invention; such compounds can be represented by the following formulas II and III:
• each of R 1 , R 2 , R 3 and R 4 which may be the same or different, is an alkyl group, an aryl group or an aralkyl group, and X 1 is a halogen atom.
• these compounds include tetramethylammonium chloride, tetramethylammonium bromide, benzyltriethylammonium chloride, methyltrioctylammonium chloride (available commercially under the brands Aliquat 336 and Adogen 464) , tetra-n-butylammonium chloride, tetra-n-butylammonium bromide, tetra-n- butylammonium hydrogen sulfate, tetra-n-butylphosphonium chloride, tetraphenylphosphonium bromide, tetraphenylphosphonium chloride, triphenylmethylphosphonium bromide and triphenylmethylphosphonium chloride
• benzyltriethylammonium chloride is preferred for use under strongly basic conditions .
• Other useful compounds within this class of compounds include those exhibiting high temperature stabilities (e.g., up to about 200 °C) and including 4- dialkylaminopyridinium salts such as tetraphenylarsonium chloride, bis [tris (dimethyla ino)phosphine] iminium chloride and tetratris [tris (dimethylamino)phosphinimino] phosphonium chloride; the latter two compounds are also reported to be stable in the presence of hot, concentrated sodium hydroxide and, therefore, can be particularly useful.
• Polyalkylene glycol compounds useful as phase transfer catalysts can be represented by the formula:
• R s is an alkylene group
• each of R 6 and R 7 which may be the same or different, is a hydrogen atom, an alkyl group, an aryl group or an aralkyl group
• t is an integer of at least 2.
• Such compounds include, for example glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, diisopropylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and tetramethylene glycol, and monoalkyl ethers such as monomethyl, monoethyl, monopropyl and monobutyl ethers of such glycols, dialkyl ethers such as tetraethylene glycol dimethyl ether and pentaethylene glycol dimethyl ether, phenyl ethers, benzyl ethers, and polyalkylene glycols such as polyethylene glycol (average molecular weight about 300) dimethyl ether, polyethylene glycol (average molecular weight about 300) dibutyl ether, and polyethylene glycol (average molecular weight about 400) dimethyl ether.
• glycols such as diethylene glycol, triethylene glycol,
• Cryptates are another class of compounds useful in the present as phase transfer catalysts. These are three- dimensional polymacrocyclic chelating agents that are formed by joining bridgehead structures with chains that contain properly spaced donor atoms.
• bicyclic molecules that result from joining nitrogen bridgeheads with chains of (-OCH2CH2-) groups as in 2.2.2-cryptate (4,7,13,16,21,24- hexaoxa-1, 10-diasabicyclo- (8.8.8) hexacosane; available under the brand names ryptand 222 and Kryptofix 222) .
• the donor atoms of the bridges may all be 0, N, or S, or the compounds may be mixed donor macrocycles in which the bridge strands contain combinations of such donor atoms.
• phase transfer catalysts from within one of the groups described above may also be useful as well as combinations or mixtures from more than one group, for example, crown ethers and oniums, or from more than two of the groups, e.g., quaternary phosphonium salts and quaternary ammonium salts, and crown ethers and , polyalkylene glycols .
• the reaction is conducted usually at a temperature within the range of from about 0 °C or slightly above to about 80° C, preferably from about 0 °C or slightly above to about 60 °C, more preferably from about 0 °C or slightly above to about 40 °C; for example from about 0 °C to about 25 °C.
• Reference to "slightly above” is intended to mean in the range of from about 1 to about 5 °C and temperatures therein between.
• temperatures below 0 °C can be used, for example from about - 20 °C to about 80 C C; preferably from about -10 °C to about 60 °C; more preferably from about -5 °C to about 40 °C.
• reaction pressure in other words the reaction may be conducted under atmospheric pressure or under an elevated pressure, it may be necessary to operate at elevated pressure if it is desired to maintain the fluorocarbon starting material and the fluoroolefin in the liquid state, at least during the reaction.
• reaction time can vary in accordance with the starting compound CF 3 C (R 1 a R 2 b) C (R 3 c R 4 d ) , as well as the reaction temperature selected and the yield or conversion desired.
• reaction times for reactions conducted at from about 0 °C to about 65 °C, preferably from about 0 to about 25 °C can vary from about 0.1 to about 20 hours; preferably from about 0.1 to about 2.0 hours .
• Y is a hydrogen atom or a halogen atom selected from the group consisting of fluorine, chlorine, bromine or iodine
• X is a hydrogen atom or a halogen atom selected from the group consisting of fluorine, chlorine, bromine or iodine
• the fluorine-containing olefins prepared by the method of this invention are readily removed from the reaction mixture and/or solvent or diluent by phase separation. Depending on the extent of conversion of the starting material, the product can be used directly or further purified by standard distillation techniques. [0025]
• the fluoroolefins obtained by the process of the present invention are useful as monomers for producing fluorine-containing oligomers, homopolymers and copolymers as well as intermediates for other fluorine-containing industrial chemicals.
• Example 3 The reaction of Example 3 was repeated except that the crown ether, 18-crown-6, was not included. Under these conditions, gas chromatographic analysis indicated only the unreacted starting material (CF 3 CH 2 CF 2 C1) .

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• 2001
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