Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Reexamination Certificate
2001-11-27
2003-04-22
Siegel, Alan (Department: 1621)
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
C570S176000
Reexamination Certificate
active
06551469
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for producing hydrochlorofluorocarbons (i.e., compounds that contain only hydrogen, fluorine, chlorine and carbon atoms, HCFCs) that are useful for producing fluorine-containing olefins, which are themselves useful as intermediates for making industrial chemicals, including polymers. HCFCs can also be used in place of chlorofluorocarbons, (i.e., compounds that contain only carbon, chlorine and fluorine atoms, CFCs) since the latter have been implicated in the depletion of stratospheric ozone and HCFCs are believed to contribute less to such depletion. More particularly, the present invention relates to a process for producing 1-chloro-1,1,3,3,3-pentafluoropropane or CF
3
CH
2
CF
2
Cl (also designated “HCFC-235fa”), by photochlorinating 1,1,1,3,3-pentafluoropropane, or CF
3
CH
2
CHF
2
, (also designated “HFC-245fa”).
U.S. Pat. No. 6,187,976 B1 describes the preparation of 1-chloro-1,1,3,3,3-pentafluoropropane by reacting, in the liquid or vapor phase, CCl
3
CH
2
CCl
3
with hydrogen fluoride in the presence of a fluorination catalyst.
The production of CF
3
CH
2
CF
2
Cl occurs as an intermediate during the production of CF
3
CH
2
CHF
2
, as described in U.S. Pat. No. 5,728,904, incorporated herein by reference to the extent permitted. That method involves conversion of CCl
3
CH
2
CCl
3
to CF
3
CH
2
CF
2
Cl by reaction with HF in the presence of a fluorination catalyst, selected from TiCl
4
, SnCl
4
or mixtures thereof.
The UV catalyzed reaction of CF
3
CH
2
CHF
2
and chlorine to produce CF
3
CH
2
CF
2
Cl is described by J. Chen et al., J. Phys. Chem. A, 1997, 101, 2648-2653, 2649. The reaction was carried out in the absence of oxygen and using a mixture of CF
3
CH
2
CF
2
H at a concentration range of 0.4-0.7 Torr and Cl
2
at a concentration range of 3-4 Torr; the overall system diluted in 700 Torr of helium. The corresponding molar ratio of chlorine to CF
3
CH
2
CHF
2
for this system ranged from 4.3 to 10:1. In this highly dilute, inert environment (at most, the reactants represented only 0.7% of the overall composition), it is said that the primary reaction products were CF
3
CH
2
CF
2
Cl and HCl. The conditions and process described, while suitable for academic research, are not amenable to scale-up and industrial use.
While the photochlorination of fluorine-containing hydrocarbons is described in the patent literature, it is in connection with the purification of 1,1,1,3,3-pentafluoropropane, HFC-245fa, by chlorinating olefinic impurities, U.S. Pat. Nos. 6,077,982 and 5,951,830; and the production of HCFCs (and HFCs), wherein the HCFC compounds contained more than one chlorine atom, U.S. Pat. Nos. 5,421,971 and 4,060,469. In particular, U.S. Pat. No. 6,077,982 discloses that the amount of chlorine added relative to the unsaturated impurity present can range from about 1 to 1.5 times the concentration of the unsaturated impurity (col. 3, lines 4-6) and the concentration of the unsaturated species is from about 300-20,000 wt. ppm (col. 2, lines 55-56). Based on these values, the maximum ratio of chlorine to HFC-245fa disclosed in this patent is about 0.1. While the patent discloses that increasing the amount of chlorine relative to the amount of impurity improves its chlorination and ultimate removal, the increase is within the scope of the range disclosed and there is no recognition that further increases run the risk of chlorinating or over-chlorinating the primary product, HFC-245fa. In fact, chlorination of HFC-245fa is contrary to the objectives of this patent.
There is a continuing need for the production of HFC-235fa, a useful industrial chemical, using a controlled process that produces little or no undesirable by-products.
SUMMARY OF THE INVENTION
A process for preparing 1-chloro-1,1,3,3,3-pentafluoropropane, CF
3
CH
2
CF
2
Cl, comprising contacting in a reaction zone in the substantial absence of oxygen reactants comprising chlorine and 1,1,1,3,3-pentafluoropropane, CF
3
CH
2
CHF
2
, and subjecting the reactants to actinic radiation, wherein: (A) inert gas is present at a concentration equal to or less than 5 wt. % of the total weight of said reactants; and (B) the concentration of chlorinated product produced having greater than one chlorine present in the molecule is less than or equal to about 10 wt. %.
DETAILED DESCRIPTION
As used herein, “actinic radiation” means light irradiation of sufficient intensity and at appropriate wavelengths, including ultraviolet and visible light, but preferably wavelengths shorter than those of visible light, such that the radiation causes photochemical effects, especially including chemical reaction between chlorine and 1,1,1,3,3-pentafluoropropane.
Various methods for producing 1,1,1,3,3-pentafluoropropane or HFC-245fa are described in U.S. Pat. Nos. 5,710,352; 5,969,198; and 6,023,004. Another method, described in U.S. Pat. No. 5,728,904, is said to be economical, amenable to large scale application and uses readily available raw materials. The process of that patent uses three steps, as follows: 1) formation of CCl
3
CH
2
CCl
3
by the reaction of CCl
4
with vinylidene chloride; 2) conversion of CCl
3
CH
2
CCl
3
to CF
3
CH
2
CF
2
Cl by reaction with HF in the presence of a fluorination catalyst, selected from TiCl
4
, SnCl
4
or mixtures thereof; and 3) reduction of CF
3
CH
2
CF
2
Cl to CF
3
CH
2
CF
2
H. The disclosures of each of these four patents are incorporated herein to the extent permitted. Commercial quantities of CF
3
CH
2
CHF
2
, or HFC-245fa, also are available from Honeywell International Inc., Morristown, N.J. for use as a reactant in the present process.
The preferred reaction of the present process between HFC-245fa and chlorine in the presence of actinic radiation causes substitution of a covalently bonded hydrogen atom in the substrate molecule by chlorine, as represented by the following equation:
CF
3
CH
2
CHF
2
+Cl
2
→CF
3
CH
2
CF
2
Cl+HCl
Undesirable multichlorinated byproducts include, for example, 1,1,1,3,3-pentafluoro-2,2,3-trichloropropane, CF
3
CCl
2
CF
2
Cl, and CF
3
CHClCF
2
Cl.
The apparatus used for photochlorination can be any suitable reactor capable of containing the reactants at the temperature and pressure during the photochlorination reaction and also containing an appropriate actinic radiation source or sufficiently transparent to actinic radiation in the desired wavelength range. For example, the reactor can be constructed of suitably corrosion-resistant metal, metal lined with glass or plastic, or glass, in other words a material suitably resistant to the corrosive effects of chlorine, and include a well, for example a quartz well, in which a light source is located. Alternatively, the reactor can be constructed of glass and the light source can be external to the reaction zone, but irradiating the reaction zone or focused thereon. Preferably, the reactor includes means to mix or stir reactants in the liquid and/or vapor phase and at least one condenser or cold trap in order to control the reactants and reaction products. The apparatus preferably includes at least one inlet for the reactants and at least one outlet for the reaction by-products. For example, multiple inlets are provided, one for HFC-245fa and one for chlorine. A suitable reactor consists of a glass reactor, of appropriate size for producing the quantities of product desired, equipped with a condenser or cold trap, a magnetic stirrer, and fitted with a water cooled, quartz immersion well for placement of a 450 watt, quartz, medium pressure, mercury vapor lamp, e.g., providing radiation at about 200-400 nm, and having an inlet for the introduction of chlorine and an outlet for gaseous products. Such an apparatus, having a capacity of 1 liter, is available from Ace Glass Co., Vineland, N.J. In addition, the
Kirk-Othmer Encyclopedia of Chemical Technology
, Vol. 17, pages 545-555 (3d ed. 1982) contains a general description of the types of light sources and reactors that may be used; this portion of the reference is incorporated herein to the
Bradley David E.
Cheney Martin E.
Demmin Timothy R.
Nair Haridasan K.
Nalewajek David
Chess Deborah M.
Honeywell International
Siegel Alan
Szuch Collen D.
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