Note: Descriptions are shown in the official language in which they were submitted.
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.
CONVERSION OF OXYGENATED ORGANIC COMPOUNDS
TO FLUOROCARBONS AND ANHYDROUS HYDROGEN FLUORIDE
USING URANI[JM HEXAFLUORIDE
BACKGROUND OF THE INVENTION
Field of the Invention
10 The invention pertains to the fluorination of oxyg~n~ted organic compounds byuranium hexafluoride in the p, ~sence of Group I - m fluorides and transition metal
fluorides to produce hydrogen fluoride, fluorocarbons, and uranium oxyfluorides and
oxides. The fluorocarbons produced are of use as non-ozone depleting refrigerants,
foam blowing agents, and solvents. Anhydrous hydrogen fluoride finds use as a
15 catalyst and as a ch~m:c~l intel...e~ for eA~I"Jle, for production of
chlorofluorocarbons, hydrochlorofluorocarbons, and fluorocarbons incl~ltiing
hydrofluorocarbons.
Description of the Prior Art
20 Uranium hexafluoride (UF6) is a selective and mild fluo~in~ g agent that is in
abundant supply worldwide, for e,~ lc from the appro~i",alely 1.5 billion pounds of
depleted UF6 tailings that are l~ h-ll~ ofthe U.S. isotope enrichment process, and
that await ~Itili7~tinn or disposal around the world. There are no currently available
large-scale methods to directly utilize the fluorine value of the uranium hexafluoride
2S tails while cimlllt~neously red~lçing the hazard of storing UF6 inventories.
It is known in the art to use m~ nesillm or calcium to reduce UF6 and produce
uranium metal and metal fluoride salts having low-level r~dioactive cor~ ;n~ c that
have no significant end-use. This is the so-called Ames process. Alternative methods
30 produce large A.l.O....I~ of uranium oxides and aqueous hydrogen fluoride which is
considered a çh~mic.~l waste product because of a limited commercial market.
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At the same time, new, selective, and less expensive fluorinating agents are needed to
supplement the current fluorination technology that is driving international efforts to
produce fluorine chemicals that do not deplete atmospheric ozone, i.e. having zero
ozone depletion value. The current technology to m~nllf"ctllre hydrochlorofluoro-
5 carbons and fluorocarbons relies on fluormation of chlorinated hydrocarbon feedstocks using hydrogen fluoride (HF) and suitable catalysts. Because of selectivity
problems with this approach, significant amounts of chlorinated by-products are
produced which must either be sold in an increasingly competitive market or
neutralized and disposed as waste.
According to this invention, the problem of red~1cing the hazard of world UF6 tails
inventories might be solved by the use of more ss wasteful fluorinating agents by
capit~li7ing on the fluorine value of UF6 inventories and using the fluol;nat;llg abilities
inherent in UF6. This invention captures the fluorine value in UF6 by using uranium
15 hsx~fllloride to fluorinate o~y~enated organic compounds in the plesel-ce of suitable
metal fluoride salts to produce fluorocarbons. O~y~c;,.aled organic compounds can be
deo~ygena~i~rely fluo~i"aled using uranium h~oY"fl~loride.
There has been a dPmor~ ed need to remove UF6 tails in a cost-effective manner.
20 Uranium hexafluoride has been known for use to fluorinate certain organic chemicals,
principally halo~ ted organic ch~nnic"l~ The literature makes note of several
disclosures which refer to UF6-metli~ted fluorination of organohalides to synth~ci
chlorinated org~nofll.orides. The vapor- and liquid-phase reduction of uranium
h~ fllloride using trichloroethylene to produce uranium tetrafluoride and
25 chlorofluorocarbons is known.
S~hn~llt7 et al [S. African J. Chem. 1992, 45(2/3), 59-62] reported that the reaction
between simple alcohols and uranium hexafluoride in the gas phase produced the
Coll~pOndillg hydrocarbon ethers by dehydrogenation, or fluorocarbons by
30 deoxygenative fluorination. The uranium hexafluoride was converted to uranyl
fluoride, U02F2. EP O 503 792 Al teaches a process for the UF6-me~ ted
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replacement of hydrogen atoms for fluorine atoms in hydrohalocarbons. DE 4328606-
Al teaches the use of UF6 to fluorinate unsaturated hydrocarbons and
chlorohydrocarbons to produce hydrofluorocarbons and hydrochlorofluorocarbons,
respectively, with formation of UF4. US 3,382,049 teaches the reduction of UF6 to
5 UF4 using trichloroethylene to produce the hydrochlorofluorocarbons C2Cl3F3 and
C2C13F2H from the reaction. L.B. Asprey et al. "Fluorination Reactions of UF6"; J.
Fluor. Chem. 1982, 20(2), 277-280 described the reaction of UF6 with alcohols,
aldehydes, ketones, acids, acid halides, ethers, olefins, and alkanes without det~ilçd
accounts of the products obtained or conditions used. Shatolov et al "Use of Uranium
Hexafluoride for making 1,2-Difluorotrichloroethane" Atomnaya Energaya, 1992,
72(2), 192- 195 describe the reaction of UF6 with trichloroethylene to produce
uranium tetrafluoride and l ,2,2-trichloro- 1,2-difluoroethane in 99% yield. Goosen et
al. "Reactions of Uranium Hexafluoride with Organic Substrates" S. Ar. Tydskr.
Chem. 1987; 40(1), 30-34 describes the solution state reactivity of UF6 toward
15 organic compounds such as ketones and hydrocarbons, with no evidence of
deoxygenative fluorination obtained using ad~ none, acetone, cyclohexanone,
bPn7~ldehyde and heptanal. N.G Sçhn~-lt7., et al, "Uranium Fluoride Cht;~ Lry. Part 1.
The Gas Phase Reaction of Uranium Hexafluoride with Alcohols" S. Afr. Chem; 1992,
45(2/3), 59-62 describe the reaction of UF6 with meth~nol, ethanol, trifluoroethanol,
20 l-propanol, and 2-propanol to produce fluolu..l~ ne, dimethyl ether, 1-fluoroethane,
tetrafluoroethane, bis(trifluorun,elllyl)ether, 1-fluolopropane and 2-fluc,lopropane. US
3,235,608 to E.I.du Pont de Nemours & Co (1962) teaches the use of UF6 to
fluorinate "lk~n~ ben_ene and chloroalk~nes in the presence of metal fluoride
catalysts such as calcium fluoride, sodium fluoride, and potassium fluoride.
None of these references teach the metal fluoride catalyzed multiple fluorination of C2
to Cg alcohols, acids, esters, aldehydes and epoxides to produce polyfluorinatedhydrocarbons. Metal fluoride catalysts increase the number of fluorine atoms on
carbon backbones co".p~ed to UF6 alone, thereby increasing the value of the res~llting
30 fluorocarbon. The res-lltin~ uranium oxyfluorides and oxides can be subsequently
converted to stable uranium oxides by known techniques.
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SUMMARY OF THE INVENTION
The invention provides a method of fluorination which comprises reacting UF6 with a
compound selected from the group consisting of C2 to C8 alcohols, acids, esters,S aldehydes and epoxides, wherein the reaction is con~ucted in the presence of afluorination catalyst in an amount sufficient to catalyze the reaction between the UF6
and the alcohol, acid, ester, aldehyde or epoxide.
The invention particularly provides a method of fluorinating an alcohol which
10 comprises reacting UF6 with a C2 to C8 monohydroxyl or polyhydroxyl alcohol,
particularly those which do not form a stable chelate when reacted with UF6, wherein
the reaction is con-iucted in the presence of a fluorination catalyst in an amount
sufficient to catalyze the reaction between the UF6 and the alcohol.
DETAILED DESCRIPTION OF THE PREFER~ED EMBODIMENT
As here~ofore mentioned, the process of the invention fluorinates an alcohol, acid,
ester, aldehyde or epoxide with UF6 in the presellce of a fluorination catalyst. In the
p,efe,led embodiment, the reagent is a C2 to C8 alcohol, C2 to C8 acid, C2 to C820 ester, C2 to Cg aldehyde or C2 to Cg epoxide. In a more pl~Çt;lled embodiment, the
reagent is a C2 to C6 and most preferably a C2 to C4 alcohol, acid, ester, aldehyde or
epoxide. The prert"td reagent acco,ding to this invention include C2 to C8 aliphatic
or aromatic alcohols, acids, esters, aldehydes and epoxides. It is within the
contemrl~tion of this invention that each of these reagents may be unsubstituted or
25 substituted with functional groups which do not materially interfere with the method
which is the subject of the invention. Such substitllterlt~ may include, but are not
limited to, functionalities derived from nitrogen, sulfur and halogens. Such mayinclude, but are not limited to, cyano, nitro, ether, chlorine and bromine groups. Such
pendant groups may or may not take part in the inventive reaction.
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Non-exclusive examples of alcohols suitable for use according to this invention include
primary alcohols such as ethanol and l-propanol, secondary alcohols such as 2-
propanol, tertiary alcohols such as tert-butyl alcohol, ben_ylic alcohols such as benzyl
alcohol, diols such as ethylene glycol and 1,3-propanediol and polyols such as 1,2,4-
5 butanediol. In the most p~ efe~ l ed embodiment, the reagent is a monohydroxyl orpolyl,yd,-)xyl alcohol, incl~ in~ polyols which do not form a stable chelate when
reacted with UF6.
.
Non-exclusive examples of acids suitable for use according to this invention include
alkyl carboxylic acids such as acetic acid and butyric acid, aromatic carboxylic acids
such as benzoic acid and alkyl dicarboxylic acids such as malonic acid.
Non-exclusive examples of esters suitable for use according to this invention include
saturated alkyl carboxylic acid esters such as methyl acetate and ethyl acetate, and aryl
carboxylic acids such as methylb~ .u:.le, ethylben_oate and phenyl benzoate. Primary,
secondary and tertiary esters are useful.
Non-exclusive examples of aldehydes suitable for use acco,ding to this inventioninclude unsaturated alkyl aldehydes such as ~cet~ hyde and butyraldehyde and
aromatic aldehydes such as bçn7~1-1ellyde.
Non-exclusive ~_A~ lcs of epoxides suitable for use according to this invention
include saturated aliphatic epoxides such as ethylene oxide, propylene oxide andcyclohexene oxide as well as aromatic epoxides such as 1,2-epoxyethylben_ene.
Some oxygen co.~ g organic compounds have been found not to function
according to this invention. For example, ethers and ketones such as diethyl ether and
acetone cannot be fluorinated s~ti~f~ctorily by the inventive method. The alcohol, acid,
ester, aldehyde or epoxide is preferably present in a mole ratio of alcohol, acid, ester,
aldehyde or epoxide to UF6 which ranges from about 0.5:1 to about 5:1 or more
,u,e~bly from about 2:1 to about 3:1.
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The reaction is cond-1cted in the presence of a fluorination catalyst to catalyze the
reaction between the UF6 and the alcohol, acid, ester, aldehyde or epoxide. The
- fluorination catalyst is prer~l~bly a Group I, Group II, Group III or transition metal
5 fluoride. ~l~Çelred fluorination catalysts are sodium, pot~c~ m, calcium, magnesium,
chromium and ~Illminllm fluoride with calcium fluoride being most p-~rtlled. Other
fluorination catalysts non-exclusively include Cu(0), BF3, Ag(0)/Cu(O), Au(O)/Cu(O),
FeCl3/C, ~/A12O3, AIF3, CrF3, MllF2; FeF3, CoCl2~ NiF2~ ZrF4, ThF4~ HF/Cr2O3,
HF/CrO3F2, HF/SbCls/C, and HF/SnC14. The fluorination catalyst is present in an
10 amount sufficient to catalyze the reaction between the UF6 and the alcohol, acid, ester,
aldehyde or epoxide. The fluorination catalyst is preferably present in a mole ratio of
UF6 to catalyst ranging from about 1000:1 to about 1:1 or more preferably from about
20:1 to about 1:1.
15 In the prer~l~t;d embodiment, the reaction is con-~ucted at a temperature of from about
15 C to about 800 C, or more plt:rel~bly from about 75 C to about 200 C. In the
pl t;rel I ed embodiment, the reaction is con~l ~cted at a pressure of from about -15 psig
to about 500 psig, or more plerelably from about 50 psig to about 150 psig. In the
prerelled embodiment, the reduction is conducted for from about .1 hours to about 48
20 hours, or more preferably from about 0.5 hours to about 8 hours depending on the
substrate. In a flow confi~.ration, this corresponds to a liquid hourly space velocity
ranging from about 0.02 to about 10 or more preferably from about 0.1 and about 2.
The most advantageous reaction time may be determined by those skilled in the art.
25 In the prerelled embodiment, the reaction is con.lucted in an inert atmosphere such as
nitrogen or argon. The reaction can be con(lucted in a batch mode or continuous
reactor configuration and in gas phase or liquid phase. When con~ucted in a liquid
phase, it may be con~ucted with a suitable solvent which is preferably an excess of the
alcohol, acid, ester, aldehyde or epoxide.
The following non-limiting e,~llples serve to illustrate the invention.
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Example I (Col..par~ e)
Reaction of 2-propanol + CaF2
A 1 0-ml Hoke stainless steel single-neck sample cylinder was charged with 0.1 16 g
(1.5 mmol) calcium fluoride under a nitrogen atmosphere and was ~tt~hed to a
5 stainless steel vacuum manifold equipped with a pressure sensing tr~n~d~lcPn The
reactor was purged with helium three times and evac~l~ted 2-Propanol (1.787 g, 29.7
mmol) that had been previously dried over 3 Angstrom moiecular sieves was vacuumtransferred into the reactor following multiple freeze-pump-thaw cycles. The reactor
was closed, warmed to ambient temperature (22.6C) and re-evacl~ted after cooling
10 to liquid nitrogen tel~-p~- alllre. The reactor was sealed again and warmed to 100C.
Over eight hours the pressure increased from -12 psig to 80 psig (calibrated 0 psig = 1
atm.). The reactor was to cooled ambient te...pe~ re and a residual pressure of 23
psig was noted. The reactor was cooled to liquid nitrogen te...p~ re, evacu~ted~and volatile materials were vacuum ~.~n~r~:..ed into a receiving flask. Analysis by gas
15 chlu...atography indicated only 2-propanol present in the raw reaction mixtures.
Example 2 (Co...pdrali~e)
Reaction of 2-propanol + UF6
A 10-ml Hoke ~Lainless steel single-neck sample cylinder was att~ched to a stainless
20 steel vacuum manifold equipped with a pressure sensing tr~n~d~lcer and was charged
with 1.08 g (3.1 mrnol) uranium heY~fllloride and 0.728 g (12.1 mmol) of 2-propanol
by vacuum .~.srel The reactor was chilled to liquid nitrogen temperature and
evac~l~ted. The reactor was sealed and warmed to 100C. Over eight hours the
pressure increased from -12 psig to 105 psig (calibrated 0 psig = 1 atm). The reactor
25 was cooled to ambient temperature and a residual pressure 29 psig was noted. The
reactor was cooled to liquid nitrogen te...pel~ re, evacu~ted and all volatile materials
were vacuum t-~ r~led into a receiving flask cor.~ ca. 1.5 g. sodium fluoride asa scavenger of hydrogen fluoride. Appro~ lately 1 g methylene chloride was
L-a-,srelled into the product receiving flask to f~cilit~te analysis. Analysis by gas
30 clllomatography, gas cl~o---a~ographic mass spectrometry, and 19F NMR
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spectrometry indicated conversion of 2-propanol to 2-fluoropropane and diisopropyl
ether.
Example 3
5 Reaction of 2-propanol + UF6 + CaF2
A 10-ml Hoke stainless steel single-neck sample cylinder was charged with 0.032 g
(0.4 mrnol) calcium fluoride under an nitrogen atmosphere and was att~ched tO a
stainless steel vacuum manifold equipped with a pressure sensing tr~n.~ducer. The
reactor was evacuated and charged with 2.16 g (6.1 rnmol) uranium hexafluoride and
1.007 g (16.8 mmol) 2-propanol by vacuum Llan~r. The reactor was chilled to liquid
nitrogen temperature and ev~c~ted. The reactor was sealed and warmed to 100C.
Over three hours the pressure increased from 2 psig at ambient temperature to 206
psig (calibrated 0 psig = 1 atm.) then dropped to 114 psig over an additional two
hours. The reactor was cooled to arnbient lelllpelaLure and a residual pressure 31 psig
lS was noted. The reactor was cooled to liquid nitrogen telllpel~Lure7 ev~cu~te~ and all
volatile materials were vacuum ll~n~rellèd into a receiving flask cont~ining ca 1.6 g
sodium fluoride as a scavenger of hydrogen fluoride. A~lu~l~laLely 2 g carbon
tetrachloride was ~r~n~.led into the product receiving flask to f~cilit~te analysis.
Analysis by gas cl"uma~ography, gas cl~.olllaLographic mass spectrometer, and 19F
NMR spe~;~l ullleLly indicated conversion of 2-propanol to 1, I difluoropropdne, 2-
flUOlOpl opane and trace amounts of diisopropyl ether.
Example 4
Reaction of l-propanol + UF6 + CaF2
2S Using the procedure of Example 3, reaction of 0.049 g (0 6 mmol) CaF2 with l .190 g
(19.8 mrnol) 1-propanol and 2.7S g (7.8 rrunol) UF6 produced l-fluolop~ùpane as the
major hydrofluorocarbon with a mixture of 1,1 and 2,2-difluo.ùprùpanes, and dipropyl
ether and trace arnounts of diisopropyl ether present.
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EXAMPLE S (Conl~al~ e~
Reaction of dimethylketone + UF6
The procedure of Example 3 was followed except the re~ct,.nts were 0.406 g (7.0
mmol) dimethyl ketone and 2.44 g (6.9 mmol) UF6 and there was no reactor chal~ g5 with CaF2. No volatile products were observed. This example demonstrates that a
dimethylketone could not be fluorinated s~ticf,.ctorily.
EXAMPLE 6 (Colllpa-~ e)
Reaction of Dimethylketone + UF6 + CaF2
Using the procedure of Example 3, 0.861 g (14 8 mmol) dimethyl ketone reacted with
1.71 g (4.9 mmol) UF6 in the presence of 0.051 g (0.7 mmol) CaF2 with produced no
detect~hle volatile products. This example demonstrates that a dimethylketone could
not be fluorinated s~ti~f~r,torily even in the presence of a fluorination catalyst.
Example 7 (Colll~ald~i~re)
Reaction of 1.3-Propanediol + CaF2
Using the procedure of Fx~mple 1, 0.112 g (1.4 mmol) of CaF2 were reacted with
0.834 g (11.0 mmol) 1,3-plul)allediol and produced no pressure increases and no
detectflkle amounts of volatile materials. This example demonstrates no reactivity
toward r,~leil~m fiuoride.
EXAMPLE 8 (colll~ala~ e)
Reaction of 1.3-Propanediol + UF6
Using the procedure of Example 2, 0.613 g (8.1 mmol) of 1,3-propanediol reacted
with 2.32 g (6.6 mmol) UF6 produced a pressure increase of-12 psig to 54 psig over
eight hours. No volatile materials were detecte~ This example demonstrates the
production of a stable chelate.
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EXAMPLE 9
Reaction of 1.3-Propanediol + UF6 + CaF2
Using the procedure of Example 3, 0.601 g (7.9 mmol) 1,3-propanediol reacted with
2.35 g (6.7 mmol) UF6 in the presence of 0.05 g (0.6 mrnol) CaF2 at 1 00C produced
5 a pressure increase from 12 to 70 psig after 1 hour. Volatile materials were vacuum
transferred from the reaction vessel. Analysis by g.c.m.s. and 19F NMR indicated the
conversion ofthe 1,3-propanediol into a mixture oftetra- and pentafluolopropdl-es, i.e.
1,1,3,3-tetrafluoropl ~pane and 1,1,2,3 ,3-pent~fl-~oropropane.
10 EXAMPLE 10
Reaction of Ethylene oxide + UF6~ 2
Example 3 is repeated except the reaction of ethylene oxide and UF6 in the presence of
a catalytic amount of CaF2 produces 1, l-difluoroethane.
15 EXAMPLE 11
Reaction of Cyclohexene + UF_ + CaF_
Example 3 is repeated except the reaction of cyclohexene -and UF6 in the p,~sence of a
catalytic amount of CaF2 produces 1,1 -difluorocyclohexane.
20 EXAMPLE 12
Reaction of Methylacetate + UF6 + CaF2
Example 3 is repeated except the reaction of methylacetate and UF6 in the presence of
a catalytic amount of CaF2 produces 1,1, I-trifluoroethane.
25 EXAMPLE 13
Reaction of Ethyl benzoate + UF6 + CaF2
Example 3 is repeated except the reaction of ethyl benzoate and UF6 in the presence of
a catalytic amount of CaF2 produces 1, l-trifluoromethylbenzene.
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11
EXA~LE 14
Reaction of Acetic acid + UF6 + CaF2
Example 3 is repeated except the reaction of acetic acid and UF6 in the presence of a
catalytic amount of CaF2 produces 1,1, I-trifluoroethane.
EXAMPLE 15
Reaction of Malonic acid + UF6 + CaF2
Example 3 is repeated except the reaction of malonic acid and UF6 in the presence of a
catalytic amount of CaF2 produces 1,1,1,3,3,3-hexafluoropropane.
EXAMPLE 16
Reaction of ~.et~ldçhyde + UF_ + CaF2
Example 3 is repeated except the reaction of ~cet~ hyde and UF6 in the presence of
a catalytic amount of CaF2 produces 1,1, l-trifluoroethane.
EXA~IPLE 17
Reaction of Bçn7~lrlçhyde + UF6 + CaF2
Example 3 is repeated except the reaction of bç~7~1d~hyde and UF6 in the presence of
a catalytic amount of CaF2 produces 1,1, l-trifluoromethylbenzene.
