Processes for the manufacture of...

Details Processes for the manufacture of... Processes for the manufacture of...

1999-08-19

2002-04-23

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

C570S165000, C570S166000, C570S168000, C570S176000, C203S067000

Reexamination Certificate

active

06376727

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to fluorine-substituted hydrocarbons, and more particularly to processes for producing CF
3
CH═CF
2
, CF
3
CCl═CF
2
and saturated derivatives thereof such as CF
3
CH
2
CF
3
, CF
3
CH
2
CHF
2
and CF
3
CHFCF
3
, and to compositions comprising the saturated derivatives (e.g., azeotropes of said saturated derivatives with HF and uses of said azeotropes).
BACKGROUND
A number of chlorine-containing halocarbons are considered to be detrimental toward the Earth's ozone layer. There is a world-wide effort to develop materials having lower ozone depletion potential that can serve as effective replacements. For example, the hydrofluorocarbon, 1,1,1,2-tetrafluoro-ethane (HFC-134a) is being used as a replacement for dichlorodifluoromethane (CFC-12) in refrigeration systems. The production of hydrofluorocarbons (i.e., compounds containing only carbon, hydrogen and fluorine), has been the subject of considerable interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishants and power cycle working fluids (see, e.g., PCT International Publication No. WO 93/02150).
SUMMARY OF THE INVENTION
A process is provided in accordance with this invention for producing pentafluoropropenes of the formula CF
3
CX═CF
2
, where X is H or Cl. The process comprises hydrodehalogenating CF
3
CCl
2
CF
3
with hydrogen at an elevated temperature in the vapor phase over a catalyst comprising at least one component selected from the group consisting of elemental metals, metal oxides, metal halides and metal oxyhalides; wherein the metal of said hydrodehalogenation catalyst component is selected from copper, nickel, chromium and mixtures thereof and the halogen of said halides and said oxyhalides is selected from fluorine, chlorine and mixtures thereof.
This invention further provides a process for producing the hydrofluorocarbon CF
3
CHFCF
3
. This process comprises (a) hydrodehalogenating CF
3
CCl
2
CF
3
with hydrogen as indicated above to produce a product comprising CF
3
CCl═CF
2
, CF
3
CH═CF
2
, HCl and HF; and (b) reacting the CF
3
CCl═CF
2
produced in (a) with HF to produce CF
3
CHFCF
3
.
This invention further provides a process for producing the hydrofluorocarbon CF
3
CH
2
CHF
2
. This process comprises (a) hydrodehalogenating CF
3
CCl
2
CF
3
with hydrogen as indicated above to produce a product comprising CF
3
CCl═CF
2
, CF
3
CH═CF
2
, HCl and HF; and (b) reacting at least one of said CF
3
CCl═CF
2
and CF
3
CH═CF
2
produced in (a) in the vapor phase with hydrogen to produce CF
3
CH
2
CHF
2
.
This invention further provides a process for producing CF
3
CH
2
CF
3
. This process comprises (a) hydrodehalogenating CF
3
CCl
2
CF
3
with hydrogen as indicated above to produce a product comprising CF
3
CCl═CF
2
, CF
3
CH═CF
2
, HCl and HF; and (b) reacting the CF
3
CH═CF
2
produced in (a) with HF to produce CF
3
CH
2
CF
3
.
Azeotropic compositions (e.g., an azeotropic composition consisting essentially of from about 29.9 to about 41.3 mole percent HF and from about 70.1 to 58.7 mole percent CF
3
CHFCF
3
) are also provided which comprise CF
3
CHFCF
3
and HF wherein said HF is present in an amount effective to form an azeotropic combination with said CF
3
CHFCF
3
.
The present invention further provides a process for recovering HF from a product mixture comprising HF and CF
3
CHFCF
3
. The process comprises (1) distilling the product mixture to remove all products which have a lower boiling point than the lowest boiling azeotrope containing HF and CF
3
CHFCF
3
; and (2) distilling said azeotrope to recover HF as an azeotropic composition containing HF and CF
3
CHFCF
3
.
This invention further provides a process for producing compositions comprising (c1) a compound selected from the group consisting of CF
3
CHFCF
3
, CF
3
CH
2
CF
3
and CHF
2
CH
2
CF
3
and (c2) at least one saturated compound selected from halogenated hydrocarbons and ethers having the formula:
C
n
H
2n+2−a−b
Cl
a
F
b
O
c
wherein n is an integer from 1 to 4, a is an integer from 0 to 2n+1 b is an integer from 1 to 2n+2−a, and c is 0 or 1, provided that when c is 1 then n is an integer from 2 to 4, and provided that component (c2) does not include the selected component (c1) compound, wherein the molar ratio of component (c2) to component (c1) is between about 1:99 and a molar ratio of HF to component (c1) in an azeotrope or azeotrope-like composition of component (c1) with HF. This process comprises (A) combining (i) said azeotrope or azeotrope-like composition with (ii) at least one fluorination precursor compound, wherein the precursor component (ii) is the fluorination precursor to component (c2); and (B) reacting a sufficient amount of the HF from the azeotrope or azeotrope-like composition (i) with precursor component (ii) to provide a composition containing components (c1) and (c2) in said ratio.
In addition, compositions are provided comprising: (c1) a compound selected from the group consisting of CF
3
CHFCF
3
, CF
3
CH
2
CF
3
and CHF
2
CH
2
CF
3
; and (c2) at least two saturated compounds selected from halogenated hydrocarbons and ethers having the formula:
C
n
H
2n+2−a−b
Cl
a
F
b
O
c
wherein n is an integer from 1 to 4, a is an integer from 0 to 2n+1, b is an integer from 1 to 2n+2−a, and c is 0 or 1, provided that when c is 1 then n is an integer from 2 to 4, provided that component (c2) does not include the selected component (c1) compound and provided that c is 1 for at least one of the component (c2) compounds, wherein the molar ratio of component (c2) to component (c1) is between 1:99 and 41.3:58.7 when component (c1) is CF
3
CHFCF
3
, between 1:99 and 59:41 when component (c1) is CF
3
CH
2
CF
3
, and between 1:99 and 84:16 when component (c1) is CHF
2
CH
2
CF
3
.
DETAILED DESCRIPTION
This invention provides a process for producing 1,1,1,3 3-pentafluoro-propane (i.e., CF
3
CH
2
CHF
2
or HFC-245fa) using 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (i.e., CF
3
CCl
2
CF
3
or CFC-216aa).
The present invention includes the hydrodehalogenation of CFC-216aa in a manner which removes a single fluorine from an end carbon while removing at least one chlorine from the internal carbon to produce CF
3
CCl═CF
2
(CFC-1215xc) and CF
3
CH═CF
2
(HCFC-1225zc). This hydrodehalogenation generally produces a product comprising CF
3
CCl═CF
2
, CF
3
CH═CF
2
, HF and HCl, and involves the use of advantageously catalytic components employing copper, nickel and/or chromium. Suitable components include halides such as CuF, CuCl, CuCl
2
, CuClF, NiF
2
, NiCl
2
, NiClF, CrF
3
, CrCl
3
, CrCl
2
F and CrClF
2
; oxides such as CuO, NiO, and Cr
2
O
3
; and oxyhalides such as copper oxyfluoride and chromium oxyfluoride. Oxyhalides may be produced by conventional procedures such as, for example, halogenation of metal oxides.
The catalysts of this invention may contain other components, some of which are considered to improve the activity and/or longevity of the catalyst composition. Preferred catalysts include catalysts which are promoted with compounds of molybdenum, vanadium, tungsten, silver, iron, potassium, cesium, rubidium, barium or combinations thereof. Also of note are chromium-containing catalysts which further contain zinc and/or aluminum or which comprise copper chromite.
The catalyst may be supported or unsupported. Supports such as metal fluorides, alumina and titania may be advantageously used. Particularly preferred are supports of fluorides of metals of Group IIB, especially calcium. A preferred catalyst consists essentially of copper, nickel and chromium oxides (each of said oxides being preferably present in equimolar quantities) preferably promoted with potassium salt, on calcium fluoride.
An especially preferred catalyst contains proportionally about 1.0 mole CuO, about 0.2 to 1.0 mole NiO, about 1 to 1.2

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