CA2140292A1 - Separation of tetrafluoroethane isomers - Google Patents
Separation of tetrafluoroethane isomersInfo
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- CA2140292A1 CA2140292A1 CA002140292A CA2140292A CA2140292A1 CA 2140292 A1 CA2140292 A1 CA 2140292A1 CA 002140292 A CA002140292 A CA 002140292A CA 2140292 A CA2140292 A CA 2140292A CA 2140292 A1 CA2140292 A1 CA 2140292A1
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- Canada
- Prior art keywords
- chf2chf2
- hfc
- cf3ch2f
- zeolite
- sorbent
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/389—Separation; Purification; Stabilisation; Use of additives by adsorption on solids
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- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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Abstract
Separation of CF3CH2F and CHF2CHF2 from a mixture thereof is effectively achieved using either inorganic molecular sieves having suitable intermediate electronegativities (compared to Zeolite Na-X) or activated carbon.
Description
~; W094/~2440 ~ 2 g 2 PCT/U~92/0;85t TITLE
SEPARATION OF TETRAELUOROETHANE ISOMERS
EI~L~ QE~ Y~NTIO~
This invention relates to the separation of fluorocarbon products, more particularly to the -separation of the isomers of tetrafluoroethane, CHF2CHF2 (HFC-134) and CF3CH~F ~HFC-134a).
~5~
Isomers of C2H2F4 (HFC-134s) are used as refrigeration fluids for a number of applications.
HFC-134s can also be used as starting materials for producing various other halogenated hydxocarbons.
Products containing isomers of C2H2F4 are produced in various degrees of isomer purity. One method of producing HFC-134s is by the hydrogenolysis of C2Cl2F4 - isomers ~CFC-114s). In the manufacture of C2Cl2F4 by the chlorofluorination of perchloroe~hylene the product typically consists of a mix~ure of the isomers, CClF2CClF2 (CFC-114) and CF3CCl2F (CFC-114a) ~see e.g., U.S. Patent No. 4,605,798). If the CFC-114s are then used to produce CHF2CClF2 (HCFC-124a~, CF3CHClF
(HCF~-124), HFC-13g or HFC-134a by hydrodehalogenation, the products often consist of a mixture of C2HClF4 and C2H2F4 isomers (see e.g., GB 1,578,933).
It has been found that for many applications, the presence of the second isomer of the isomer pair can significantly alter the physical and chemical properties of the desired isomer. For example, variation in the HFC-134~HFC-134a ratio in the product can result in dramatic variability in the thermodynamic properties critical for use in refrigeration applications. For use as a raw material feed, the presence of the unwanted isomer can result in yield loss due to increased side 35 reactions. As a result, there has been a continually ;
.. . . .
W094/02~t~ j P~T/US92/0585~-increasing demand for high isomer purity materials.
Consequently, the separation of HFC-134 isomers represents a significant aspect of preparing these compounds for various applications.
Purification of halogenated hydrocarbon pxoducts has been the subject of considerable research. Of particular interest are the challenges presented in separating desired halogenated hydrocarbon products from materials such as impurities in the starting materials used to produce the ~alogenated hydrocarbon, excess reactants, and reaction by-products and/or reaction co-products which are difficult to remove by standard separation methods such as distillation. Selectivle sorbents such as carbons and zeolites have been proposed for various separations. The effectiveness of separation using such sorbents varies with the chemical components and the sorbents involved. The successful design of sorbent based systems is considered highly dependent upon experimental determination of whether the relative sorbencies of the particular compounds are suitable for such systems.
HFC-134 has a boiling point of -23C and HFC-134a has a boiling point of -26.5C. Distillation is consequently relatively inefficient as a means for separating these two compounds.
SUMMARY OF THE INvE~TION
We have found that mixtures of the isomers of C2H2F4 (i.e., CHF2CHF2 and CF3CH2F) can be substantially separated by using a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves (e.g., zeolitesj having greater intermediate eltectronegativities than Zeolite Na-X, and (ii) activated carbons. The present invention provides a process for separating a mixture of CHF2CHF~ and CF3CH2F
to provide a product wherein the mole ratio of CF3CH2F
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~1~0292 ~ / i .
relative to CHF2CHF2 is increased which comprises contacting said mixture with said sorbent at a temperature within the range of -20C to 300C and a pressure within the range of lQ kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2. A~ a result, the mole ratio of ~1 CF3CH2F to CXF2CHF2 incre3ses (preferably by 25~ or more); and a product wherein the mole ra~io of CF3CH2F
relative to CHF2CHF2 is increased, may thus be recovered.
This invention also provides a process for separating a mixture of C~F2CHF2 and CF3CH2F to provide a product wherein the mole ratio of CHF2CHF2 relative to CF3CH2F is increased which comprises contacting said mixture with said sorbent as described above to remove a substantial amount of the CHF2CHF2, and desorbing sorbed CXF2CHF2 to provide a product which is enriched therewith.
Said process for producing a CF3CH2F enriched product and said process for producing a CHF2CHF2 enriched product may be integrated into an overall process (e.g., a thermal swing cycle process) whereby both of said products are provided. Said process for producing a CF3CH2F enriched product and/or said 9~1TUTE ~ET
: 1 ~ C 2 3 2 /~
process for producing a CHF2CHF2 enriched product may also be used in conjunc~ion with a process for producing HFC-134 and HFC-134a by the hydrogenolysis of CFC-114 and/or CFC-114a.
DETALL~_nE ~L~ ISQY
The present invention,provides for the separation of HFC-134 from HFC-134a. Isomer enriched products are provided in accordance with this invention by contacting a mixt~re of C2H2F4 isomers with a sorbent for CHF2CHF2 ~ , lD selected from the group consisting of acti~ated carbons and certain inorganic molecular sieves at a temperature and pressure suitable for sorption, for a period of time sufficient to remove a substantial amount of said CHF2CHF2. CF3CH2F enriched product is thereby provided using CHF2CHF2 sorption. Where CHF2CHF2 enriched product is desired, the invention also includes a process involving desorbing sorbed CHF2CHF2 to provide a product -which is enriched therewith. The process based upon preferential CHF2CHF2 sorption is particularly useful 0 for purifying CF3CH2F which contains minor amounts of CHF2CHF2. Where the process is used for such puri~ication of CF3CH2F, the isomer mix to be purified by this process generally has a mole ratio of CF3CH2F to CHF2CHF2 of at least about 9:1, preferably at least about 19:1, and most ~referably at least about 99:1.
A mix of the C2H2F4 isomers may result, for example,from a process in~olving the reaction of the ,CFC-114 and~or CF$-114a isomers with hydrogen.
Unreacted starting materials and C2HClF4 isomers may be recycled and reacted further with hydrogen to produce additional C2H2F4. Additional impurities may be present in these products. Distillation is typically used in order to remove impurities such as HCl, HF, under- and , over- chlorinates and fluorinates to produce products that are at least 90% C2H2F4. Separation of C2H2F4 ~rE~
;` W094/02440 ~ ~ i 023 2 PCT/US92/05851 , isomers in accordance with this invention to provide prsducts which are enriched in HFC-134 and/or products which are enriched in HFC-134a then may be advantageously employed. This invention can thus be 5 adapted for use in connection with production of C2H2F
by hydrogenolysis of materials such as C2C12F4 such that after removal of a substantial amount of CHF2CHF2 using the sorbent, either ~i) a product is recovered wherein the mole ratio of CF3CH2F relative to CHF2CHF2 is increased, (ii~ sorbed CHF2C~F2 is desorbed to produce a product wherein the mole ratio of CHF2C~F2 relative to CF3CH2F is increased, or both (i) and ~ii). j Some embodiments of this invention use activated carbon as the sorbent. Commercially available activated carbon may be used. The effectiveness of the process can be influenced by the particular activated carbon employed. Moreover, ~he sorption efficiency and sorption capacity of an activated carbon bed depends - upon the particle size of an activated carbon in a dynamic flow system. Preferably, the activated carbon has a particle size range of from about 4 to 325 mesh ~from about 0.044 to 4.76 millimeters). More preferably, the activated carbon has a particle size range of from about 6 to 100 mesh ~from about 0.149 to 3.36 millimeters). Most preferably, the activated carbon has a particle size range of from about 10 to 30 mesh ~from about 0.595 to 2.00 millimeters).
An activated carbon obtained having a particle size rang~ of about 0.074 x 0.297 millimeters (50 x 200 mesh) is available from the Barneby & Sutcliffe Corp. as Activated Carbon Type UU (natural grain, coconut shell based). An activated carbon having a particle size of 0.595 millimeters x 1.68 millimeters ~12 x 30 mesh) is ~ available from the Calgon Corporation as Calgon ~PL
~bituminous coal based) activated granular carbon. An W094/0~440 ~ 1 4 U 2 9 2 PCT/U592/0~85t _j activated carbon having a particle size range of about 0.450 x 1.68 millimeters (12 x 38 mesh) is available from Barnebey & Sutcliffe Corp. as Barneby & Sutcliffe Corp. Activated Carbon Type PE ~natural grain, coconut S shell carbon). An activated carbon having a particle size range of about 0.297 x 0.841 millimeters (2Q X 50 mesh) is available from Westvaco as Microporous Wood-Base Granular Carbon.
Typically the activated carbon used will have a total content of from about 0.1 to 10 weight percent of alkali and alkaline earth metals selected from lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and/or barium. The alkali and alkaline earth metal content of carbon can be regulated by techniques known in the art. For example, the metal content of carbon can be reduced by acid washing; and the metal content can be increased by standard impregnation techniques. In a preferred embodiment using preferential HFC-134 sorption, the activated carbon contains inherent aikali and/or alkaline earth metal~s) selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, and combinations thereof. Inherent alkali metals (typically Na and~or K) are preferred.
The presence of these metals, particularly as inherent metals in the range of from about 0.5 to 3 percent by weight, is considered to improve the HFC-134 sorption efficiency.
Some embodiments of this invention use inorganic : t , I !
molecular sieves. Molecular sieves are well known in the art and are defined in R. Szostak, Mol~cular Sieves-Principles of Synthesis and Identification, Van Nostrand Reinhold (1989) page 2. The inorganic molecular sieves used for preferentially sorbing HFC-134 in accordance with this invention include various ~1~Q292 ~ /q ~
.
silicates (e.g., titanosilicates and zeolites such as Zeolite Y, Zeolite A, Zeolite ZSM-5, and Zeolite ZSM-8), metalloaluminates and aluminophosphates, as well as other inorganic molecular sieve materials. The molecular sieves useful in the invention will typically have an average pore size of from about 0.~ to 1.5 nm.
The Sanderson electronegati~ity model (see, R. T. Sanderson, I'Chemical Bonds and Bond En~rgyl', 2nd ed., Academic Press, New York, 1976) furnishes a useful method for classifying inorganic molecular sieves based on their chemical composition. In ~ccordance with this invention the preferential sorption of tetrafluoroe~hane isomers by molecular sieves can be correlated with their intermediate electronegativity (i.e., their "Sint") as determined by the Sanderson method based on chemical composition. The Sint for Zeolite Na-X is about 2.38.
Inorganlc molecular sieves with Sints greater than the Sint for Zeolite Na-X ~i.e., more electronegative or more acidic~ may be used in accordance with this invention for increasing the mole ratio of CF3CH2F
relati~e to CHF2CHF2 by remo~ing a substantial amount of CHF2CHF2; and/or for increasing the mole ratio of CHF2CFH2 relati~e to CF3CH2F by desorbing sorbed CHF2CHF2 (i.e., CHF2CHF2 is belie~ed to sorb more strongly than CH2FCF3).
~e~TlTVTE 9~T
~ 1 ~ 0 2 9 2 Example Sint values are provided in Table I.
TABLE I
Intermediate Sanderson Electronegativities for Selected Molecular Sieves olecular Sieve ~in~ !
Na-X 2.38 Ca-A 2.56 Na-Y 2.58 ETS 2.60 H-Y . 2.97 .
Na-ZSM-8 3.00 Generally, for the inorganic molecular sieves, it is desirable to occupy acidic sites of the sie~e material with alkali metal(s) and or alkaline earth metal~s) so long as the intermediate electronegativity remains suitable for the desired separation. In a preferred embodiment using preferential Y.-C-134 sorption the inorganic molecular sieve is a Zeolite Y which contains alkali or alkaline earth metal(s) selected from the group consisting of lithium, sodium, pot~ssium, rubidium, cesium, magnesium, calcium, strontium and CTlTUTE 9t~ET
~?, W094/02440 2 1 4 0 2 g 2 PCT/US92/05851 barium or co~binations thereof. Alkali metals are preferred. It is preferred that alkali metals occupy from about 50% to 100~ of the accessible exchange sites in the zeolite. Particularly preferred zeolite molecular sieves include those having alkali metal to àluminum ratios of about 1:1, or alkaline earth metal to aluminum ratios of about 1:2. ;
Suitable temperature ranges for sorption range from about -20C ~o about 300C. Suitable pressures for sorption range from about 10 kPa to about 3000 kPa.
Contact with sorbent should be sufficient to achieve the desired degree of isomer enrichment.
Preferably, the mole ratio of the enriched isomer to the second isomer is increased by at least about 25%
relati~e to the mole ratio thereof in the initial mixture, most preferably by at least about 50%.
Where the process is used to purify CF3CH2F from a mixture of CF3CH2F and CHF2CHF2 using preferential HFC-134 sorption, preferably at least about 50 mole % of the CHF2C~F2 is removed. A particularly advanta~eous embodiment of this invention involves providing sufficient contact to produce CF3CH2F of at least about 99.99 mole percent purity.
This invention can be practiced with the sorbent contained in a stationary packed bed through which the process stream whose components need separation is passed. Alternatively, it can be practiced with the sorbent applied as a countercurrent moving bed; or with a fluidized bed where thelsorbent itself is moving. It can be applied with the sorbent contained as a stationary packed bed but the process configured as a simulated mo~ing bed, where the point of in~roduction to the bed of the process stream requiring separation is changed, such as may be effected using appropriate switching valves.
., .. . , , , , . - - , :
W094/~2440 , PCT/VS92/0~85 ~
21~0~gZ~' '' o The production of a product enriched with respect to one C2H2F4 isomer may be accompanied by the production of other products which are enriched with regard to the concentration of one or more other components of the S initial mixture. Indeed, a typical process might include both a product which is enriched in CF~CH2F
~e.g., essentially pure CF3CH2F) and another product which is enriched in CHF2CH~2. The production of product enriched in CHF2CXF2 generally involves desorption of CHF2CHF2. In any case, whether or not a CHF2CHF2 enriched product is desired, the sorbent is typically regenerated following CHF2CHF2 removal by desorption of sorbent materials. Desorption of components held by the sorbent may be effected with the sorbent left in place, or the sorbent may be removed and the desorption effected remotely from where the sorption step occurred. These desorbed components may exit the sorbent section in a direction either co-current (in the same direction as the orisinal C2H2F4 mixture feed was fed) or countercurrent (in the opposite direction of the original stream requiring separation). Desorption may be e~fected with or without the use of a supplemental purge liquid or gas flow. Where supplemental purge material is used, it may be a component of the feed, or some appropriate alternative material, such as nitrogen.
Such supplemental purge materials may be fed either co-currently or countercurrently.
In general, desorption can be effected by changing any thermodynamic variable ~which is effecti~e in remo~ing the sorbed components from the sorbent. For example, sorption and desorption may be effected using a thermal swing cycle, ~e.g., where after a period of sorption, the sorbent is heated externally through the wall of the ~essel containing it, and/or by the feeding of a hot liquid or gas into the sorbent, the hot gas ". . - . , . . - . . ~
W094/02440 ~ ~ 4 ~ '~ 9 ~ PCT/US92/05851 heing either one of the component materials or alternative materials). Alternatively, sorbed components can be removed by using a pressure swing cycle or ~acuum swing cycle ~e.g., where after a period S of sorption the pressure is suf~iciently reduced, in some embodiments to a vacuum, such that sorbed components are desorbed). Alternatively, the sorbed components can be removed by use of some type of stripping gas or liguid, fed co-currently or countercurrently to the original process feed material.
The stripping material may be one of the process feed materials or another material such as nitrogen.
One or several beds of sorbent may be used. 'Where several beds are used, they may be combined in series or in parallel. Also, where several beds are used, the separation efficiency may be increased by use of cycling zone sorption, where the pressure and or the temperatures of the beds are alternately raised and lowered as the process stream is passed through.
Practlce of the invention will be further apparent from the following non-limiting Examples.
Metal tubing ~0.l8 inch I.D. x 12 inch, 0.46 cm I.~. x 30.5 cm) was packed with a carbon sorbent and installed in a gas chromatograph with a flame ionization - detector. Helium was fed as a carrier gas at 33 sccm (5.5 x 10-7 m3/s). Samples of the various compounds were then injec~ed into the carrier stream at 200C. The results of these experiments using Barneby & Sutcliffe Type PE (3.75 gj carbon (Carbon A), Westvaco Microporous Wood-Based Granular Carbon ~Carbon B), Barneby &
Sutcliffe Type UU (3.85 g) carbon (Carbon C) and Calgon BPL (2.59g) carbon (Carbon D) are shown in Table l.
These data show that in each case the isomers had W 0 94/02440 ,~ g ~ PCr/US92/05851'~-different retention times, and thus may be separated using the carbons of this Example.
rABLE, 1 Sample Rete~tion Time fmi~l S~paration A 5 6.6 4.0 1.65 0.13% 1.0~%
- 200 4.36 3.16 1.36 0.13% 1.09%
B S 4.22 2.61 1.62 0.58% 75ppm 209 3.32 2.27 1.46 0.58% 75ppm C 200 4.79 3.38 1.42 940ppm 0.93%
D 5 2.32 1.75 1.32 660ppm 650ppm _ _00 2.01 1.59 1.26 _660pum _ 650D m )Volume of gas sample injected ~microliters) ~)134 - C~F2CHF2 )134a ~ ~F3CH2F
~d)Separation Factor - 134 retention time/134a retention time (~)sodium content of carbon in weight percent or parts per million as indicated ~potassium content of carbon in weight percent or parts per million as indicated It is evident from Table 1 that the rela~ive sorption efficiency for HFC-134 is higher in the presence of the alkali metals Na and K.
~MP~ 2 Metal tubing (0.18 inch I.D. x 12 inch, 0.46 cm I.D. x 30.5 cm was packed with a carbon sorbent and installed in a gas chromatograph with a flame ionization detector. The experiment was repeated using the same carbon, but washing it with hydrochloric acid before using it for separations. The sodium content of Westvaco Microporous Wood-Based Granular Carbon (Not Acid-Washed, NAW),was 1.29~. After washing with hydrochloric acid the sodium content was 9 ppm. This carbon was designated Acid-Washed ~AW). Helium was fed as a carrier gas at 33 sccm (5.5 x 10-7 m3~s). Samples of 134 and 134a were then injected into the carrier stream at 200C. The results of these experiments are ~'~ W094/0~0 ~ 1 ~ O ~ 9 2 PCT/US92/05851 shown in Table 2. These data show that a more efficient .
separation was obtained with the carbon containins alkali metal; in this case sodium.
~L~
Retention Time tmin.) Separation Carbon Na Content 134 134a Factor(~) ~AW l.29% lO.67 6.63 l.61 AW 9 ppm 6.2 4.3 _ 1.44 _ )Separation Factor Y 134 retention timeJ134a retention time ~L~ I
A packed tube (2 6 cm x 2 .12 cm I.D) containing Calgon BPL carbon ~46.1 g, 4.8 x 0.59 mm (12 x 30 mesh)) was purged wi~h nitrogen continuously for 24 hours at 2SQC and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% ~FC-134 was then fed to the bed a~ l6~ grams per hour. The results are shown in Table 3.
W0 94/02~40 ~ PCT/US921058 2 9 ~ 14 ~I~
Time 134a 134a 134 o o o - j ~1 0.164 0 0 0.175 0.011 0 ~.
77 0~207 0.043 0 89 0.239 0.075 0.61 100 0.269 0.105 0.88 112 0.301 0.137 O.g6 124 0.334 0.170 1.00 ~)134a in represents the total running sum of the moles ~:E
CF3C~2F fed ~o the column.
~)134a out represents the total running sum of the moles of CF3CH2F exiting the column.
(C~134 out represents the instan~aneou~ concentration of CI~F2CH~2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.% feed (i.e., O.5 would equal a O.5 w~.% HFC-134 concentration in the HFC-134a effluent). A zero i~ less than the detection limit of about 10 ppm.
This example shows that carbon will selectively hold back HFC-134 allowing HFC-134a free of HFC-134 followed by HFC-134a containing reduced HFC-134 concentrations to be obtained.
E~æL~_i A packed tube ~26 cm x 2.12 cm I.D) containing Barneby & Sutcliffe Type PE carbon ~50.3 g) was purged with ni~rogen continuously for 12 hours at 250C and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C.
HFC-139a containing 1 wt% HFC-134 was then fed to the bed at 16.7 grams per hour. The results are shown in .
Table 4.
W O 94~02440 ~ 1 ~ æ ~ ~ PCT/US92/0~851 ~A~LE 4 t Time 134a 134a 134 (min) in(a) out(~) out(C) , - O O O ~ ~
69 0.186 0 0 ~ .
73 0.196 0.010 0 8~ 0.22g 0.043 0 96 ~.258 0.072 0 108 0.291 0.105 0 120 0.323 0.137 0.76 3~ 0.355 0.169 0.94 144 _ 0.387 0.201 1.~0 ~134a in represents the total running sum of the moles of CF3CH2F fed to the column.
t~)134a out represents the total running ~um of the moles of CF~CH2F exiti~g the column.
(C)134 out represents the instantaneous concentration of CHF2CHF2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.% feed (i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration in the HFC-134a efflue~t)~ A zero is less than the detection limut of about 10 ppm.
~I~ :
A pac~ed tube (26 cm x 2.12 cm I.D) containing West~aco Microporous Wood-Based Granular Carbon (46 g) was purged with nitrogen continuously for 12 hours at S 25QC and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% HFC-134 was then fed ~o the bed at 16.6 grams per hour. The results are shown in Table 5.
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s~
,~
: ,t W094/02440 ~ PCT/US92/0~85 ~
TABL~_~
Time134a 134a 134 (min~ ) out~) out~C) i o o o o 74 0 . 199 0 . 003 0 82 0 . 2~1 0 . 025 0 94 0 . 253 0 . 057 0 106 0 . 285 0 . 089 0 118 0 . 317 0 . 121 0 . 16 130 0 . 350 ~ . 154 0 . 65 142 0 .382 0 . 186 0 . 97 155 _ 0 ! 417 0 . 221 _ 1 . 00 (~)134a in represents the total runnin~ ~um of the moles of CF3CH2F fed to the column.
(b)i34a out represents the total running sum of the mole~ of CF3CH2F exiting the column.
~C3134 out represents the instantaneous concentration of CHF2CHF2 - in the CF3~H2F exiting the column, expressed as 3 multiple of the 1 wt.~ feed ~i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration in the HFC-~34a effluent). A zero i~ less than the detection limlt of about 10 ppm.
F~xA~p~E 6 A packed tube ~26 cm x 2.12 cm I.D) containing Westvaco Microporous Wood-Based Granular Carbon (46 g) was purged with nitrogen continuously for 12 hours at 5 250C and at 1 atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% HFC-134 was then fed to the bed at 16.6 grams per hour and at 4.7 atm. (476 kPa). The results are shown in Table 6.
~~~ W094~02440 ~ 1 4 0 2 ~ 2 PCT/US92/05851 ~7 ~;
TA~LE 6 Time 134a 134a 134 (min) in (a) out~b~ out~
~ t - O O O O
54 0.261 0.013 0 0.3125 0.067 0 77 0.373 0.1~5 0 89 0.431 0.183 0 101 0.489 0.241 0.33 113 0.547 0.299 0.47 125 0.605 0.357 0.55 137 0.663 0.415 0.8 t~)134a in represents the total running sum of the moles oi.
CF3CH2F fed to the column.
)134a out represents the total running sum of the moles of CF3CH2F exiting the column.
(C)134 out represents the instantaneous concentration of CHF2~HF2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.~ f~ed ~i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration i~ the HFC-134a effluent). A zero is less than the detection limit of about 10 ppm.
Examples 3 through 6 show that these carbon based sorben~s will selectively sorb HFC-134 allowing HFC-134a free of HFC-134, followed by HFC-134a containing reduced HFC~134 concentration to be 5 obtained. Examples 3 through 6 show that process material other than the componen~s to be separated can be used to strip HFC-134 ~i.e., in this case, nitrogen rather than HFC-134a is used to clear the bed of HFC-134). Also, examples 5 and 6 show that the capacity or 134 increases with pressure, and illustrates the presence of pressure swing adsorption.
EX~PLE 7 This is an example of a thermal swing cycle ~~ alternating a sorption step with a desorption step. The column and carbon pac~ing are the same as that used in Example 4 above. During the sorption step, HFC-134a containing 1 wt % 134 was fed to the packed column at f!
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WO 94/0~0 , . PCT/U~92/0585~
.. . ~ . "
~ 1 4~ ~ 9 2 18 26C and at a feed rate of 16.6 g/hr with a back-pressure se~ting of 1 atmosphere ~101 kPa) in the column. When HFC-134 began to break through at the other end of the column, the flow of feed was stopped, and the ends of the column were sealed. The column was then heated to 150C, and gas was vented from the column in the direction countercurrent to the original direction of feed, to keep the pressure at 1 atmosphere (101 kPa). ~hen the temperature reached 150C, HFC-134a containing less than l ppm of HFC-134 was fed in the direction countercurrent to the original feed to purge the bed, at 16.5 g/hr ,and with a back pressure setting of 1 atmosphere (101 kPa). The column valves were then closed at both ends, and the column cooled to 26C. The cooling of the bed caused a partial vacuum. The pressure was then brought back to 1 atmosphere (101 kPa) using the high HFC-134 content HFC-134a and the cycle was started again. The sorption and desorption steps were then repeated. The results of the second sorption step are shown in Table 7A.
Time Temp HFC-134a HFC-134a HFC-134 ~Min) C in (a) out~) out(C) , 93 26 0.250 0.124 0 117 26 0.315 0.189 0.77 129 26 0.347 0.221 0.87 140 _ 26 0.377 0.251 0.96 ~a)HFC-134a in represents the total running sum of the moles of HFC-134a~ed to~the col~mn. : , ~b)HFC-134a out represents the total running sum of the moles of HFC 134a exiting the column.
)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, expre-~ed aY a multiple of the 1~ feed. A zero is le~s than the detection limit of about 10 ppm.
The results of the desorption step which followed are shown in Table 7B.
1 9 `
~L~ . , Time Temp HFC-134a ~FC-134a HFC-134 ;
(min) ~C in(a) out~b) out(C~ ~
, 0 25 0 ~ 0 7 3S 0 0.049 1.16 12 98 0 0.107 1.~1 24 150 0 0.133 1.63 150 0.032 0.165 1.67 47 150 0.0~2 0.195 1.63 _ 71 150 0.126 0.259 0 _ la)HFC-134a in re~esents ~he total running sum of the mole~ of HFC-134a fed to the column.
FC-134a out repr~ents the total running sum of the mo:Le~ of HFC-134a exiting the column.
~)HFC-134 out repre~ents the instantaneous concentration of the HFC-134 i.n the HFC-134a exiting the column, expre~sed as a multiple o~ the 1~ feed. A zero is less than the detection limit of about 10 ppm.
Initially, no HFC-134a was fed, but HFC-134a and HFC-134 exited the column due to the let down of the pressure as the ~emperature was raised from 26C to 150C. Beginning at 24 minutes, when the temperature reached lS0C, HFC-134a containing less than 1 ppm 134 was fed at 16.5 g/hr. At 71 minutes, the HFC-134a flow was stopped.
This example shows the use of a temperature swing cycle as a process concept to produce both HFC-134-free and HFC-134-reduced HFC-134a.
This is an example of a thermal swing cycle alternating a sorption step with a desorption step. The column and carbon packing were the same as that used in Examples 5 and 6 above. During the sorption step, HFC-134a containing 1 wt % 134 was fed to the packed column at 25C and a 134a feed rate of 16.6 g~hr with a back-pressure setting of 1 atmosphere (101 kPa) in the ~ column. When the outlet HFC-134 concentration matched the inlet concentration, the flow of feed was stopped, .
~i WO 94/0~0 PCT/US92/05851~f'~
2 1 ~ 0 2 9 2 20 and the ends of the column were sealed. The column was then heated to 150C, and gas was vented from the column in the direction countercurren~ to the original direction of feed, to keep the pressure at 1 atmosphere (101 kPa). When the temperature reached 150C, HFC-134a containing less than 1 ppm of HFC-134 was fed in the direction countercurrent to the sriginal feed to purge the bed, at 16.5 g/hr and with a back pressure setting of 1 atmosphere ~101 kPa~. The column valves were then closed at both ends, and cooled to 25C. The cooling of the bed c~used a partial vacuum. The pressure was then brought back to 1 atmosphere (101 kPa) usin~ the hi.gh HFC-134 content HFC-134a and the cycle was started again. The sorption and desorption steps were then repeated.
Tne results of the second sorption step are shown in Table 8A.
Time Temp HFC-134a HFC-134a HFC-134 ~min) C in ~a) out~b) out(c) 29 25 0.140 0 0 73 25 0.353 0.213 0 0.411 0.271 0.25 97 25 0.469 0.329 0.80 _ 100; 25 0.532 0.392 1.00 (a)HFC-134a in repreaents the total running sum of tbe mole~ of HFC-134a fed to the column.
)HFC-134a out represents the total running sum of the moles of HFC-134a exiting the column )HFC-134 out represents the instantaneous concentration of HFC-134 in the HFC-134a exiting the column, expre~-~ed as a multiple of the 1~ feed. A zero is les-~ than the detection lim~t of about 10 ppm.
The results of the desorption step which followed are shown in Table 8B.
~'^WO94/02440 ~ 1 ~ 0 2 3 2 PCT/US92/05851 21' ' ' ~BLE 8B
Time Temp HFC-134a HFC 134a' HFC-134 36 0 0.049 1.09 22 78 0 0.105 1.31 34 ~30 0 0.150 1.54 4~ 150 0.015 0.170 1.65 ~8 150 0.073 0.~2~ 1.59 71 15~ 0.136 0.291 1.56 83 150 0.194 0.349 0.0 _ g5 150 0.252 0.407 _ 0 5a)HFC-134a in represents the total running 3um of the mol~as of XFC-134a fed to the column.
)HFC-134a out represents the total running sum of the mo:Les of HFC-134a exiting t~e column.
)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, expressed a~ a multiple of the 1~ feed. A zero is less than the detec~ion limit of about 10 ppm.
Initially, no HFC-134a was fed, but HFC-134a and HFC-i34 exited the column due to the let down of the pressure as the temperature was raised from 25C to 150C. Beginning at 34 minutes, when the temperature reached 150C, HFC-134a containing less than 1 ppm 134 was fed at 16.5 g/hr. At 95 minutes, the HFC-134a flow was stopped.
This example shows the use of a temperature swing cycle as a process concept to produce both HFC-134-free and HFC-134-red~ced HFC-134a.
~AM~L g Me~al,tubing 0.18" (4.6 mm) I.D. x 2 ft.~0.51 m) was packed with zeolite sorbents as indicated in Table 9, and installed in a gas chromatograph with a flame ionization detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Helium was fed as a carrier gas at 20 sccm ~3.3 x '0-7 m3/s).
Samples ~25 ~L) of HFC-134 and HFC-134a were then ~.. ~ , . .
WO 94/02440 ~ ~ ~ PCT/US9~/05~5 injected into the carrier stream at different temperatures. The resul~s of these experiments are shown in Table 9. Comparison of the 134/134a data for Na-Y and H-Y show a much enhanced separation on the more 5 basic zeolite. , - Zeolite Temperature Retention Times Separation (C) (min) Factor ~
Na-Y 200 408/71.4 5.7 H-Y 100 68.1~46.1 1.5 H-ZSM-sla) 200 470/308 1.5 5A 200 291/about 150 1.9 (a~The flow rate fos the H-ZSM-5 ~un was 35 sccm (5. 8 x 10-7 m3/s ~L~
Metal tubing 0.18" (4.6 mm) I.D. x 2 ft.(0.~1 m) was packed with zeolite sorbents as indicated in Table 10, and installed in a gas chromatograph with a flame ionization detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Helium was fed as a carrier gas at 30 sccm (5.0 x 10-7 m3/s).
Samples (25 to 500 ~L) of HFC-134 and HFC-134a were then injected into the carrier stream at different temperatures. Each test was run in duplicate. Methane (1% in nitrogen) was run as a standard at each temperature. The results of these experiments are shown in Table 10.
;
W094/~2440 ~ PCT/US92/0~8~1 ~
23 I `
~L~
Zeolite Temperature Retention Times Separation .
~C) ~min) Factor .
134/134a Na-Y 230 160/53.2 3.0 -240 128/45.1 2.8 ~50 98.3/36.8 2.7 H-Y 210 2.07/1.19 1.7 220 1.78/1.06 1.7 ~ .
230 l.OlfO.89 1.1 H-ZSM-8 210 110/70.2 1. 6 3 .
220 79.7/51.1 1~6 230 56.7~37.5 1.5 5A 230 74.7/29.4 2.5 240 64.8/24.9 2.6 -EXAMPLr l 1 This is an example of a ~hermal swing cycle with countercurrent purge during desorption. A 1 inch (2.54 cm) diameter tube was packed with 63 grams of the zeolite H-ZSM-5, and purged with nitrogen at 50 psig ~450 kPa). The ni~rogen was then turned off, and the column ed with HFC-134a containing 102 mole % HFC-134 at 60 sccm (1.0 x 10-7 m3/s) and 50 psig ~450 kPa). The results of this test are shown in Table llA.
W094J02440 PCT/US9~/0585 ~
2140~292 24 Time Temp HFC-134 (min) o C out (~) 29 0*
~9 0 ~9 o 29 0.18 100 29 0.34 110 2~ O.S1 ~ , ' *~reakthrough cf HFC-134a occurs.
)HFC-134 out represents the ins~antaneous concentration of ~FC-134 in the HFC-134a exiting t~e column, expr~ aed ~5 a multiple of the original 1% feed. A zero is less than the detection limlt of about 10 ppm.
When the outlet concentration of the 134 matched the inlet concentration, the high 134 concentration 134a flow was stopped and the ends of the column were sealed.
The column was then heated to 150C, and gas was vented S from ~he column in the direction countereurrent to the original direction of feed, to keep the pressure at 1 atmosphere (100 kPa). When the temperature reached 150C, HFC-134a containing less than 1 ppm 134 was fed in the direction countercurrent to the original feed at 50 psig ~450 kPa). The results are summarized in Table 11~}.
'^: W0 94/02440 21~G~2 PCT/US92/058~1 t TABL~
Time Temp HFC-134 (min) ~~ out~') 0 31 1.06 86 1.19 114 1.37 126 1.56 133 1.63 133 1.67 133 1.75 134 1.61 134 1.25 134 0.78 100 134 0.41 1~0 134 0.18 ~a)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, exprec~ed as a multiple of the orlginal 1% feed. A zero is less than the detectlon limit of about 10 ppm.
~AMPLE ~2 This is an example of a thermal swing cycle with countercurrent purge during desorption. A 0.93 inch (2.3S cm) diameter by 12 inch (30.48) long tube was pac~ed with 80 grams of LZ-Y52 zeolite ta Na-Y zeolite), and purged with nitrogen at 50 psig (450 kPa). The nitrogen was then turned off, and the column fed with HFC-134a containing 1.5 mole % HFC-134 at 50 psig . (4S0 kPa) and 30C. The results of this test are shown in Table 12A.
WO 94/02440~ 1 4 ~ ~ 9 2 PCT/U~92/0585 TAB~ 12 HFC-134a HFC 134a HFC-134 O O O
0.~35 0.004 0 O.g58 0.717 0 - 0.965 0.735 0.108 0.987 0.75~ 0.221 1.009 0.781 0.3Q4 1.032 0.8~3 0.379 1.053 0.8~5 0.447 1.071 _ 0.843 0.460 (a)HFC-134a in represents the total running sum of ~he mole~ of ~FC-134a fed to the column.
(~)HFC-134a out represents the total running sum of the mole3 of HFC-134a exitin~ the column.
(C)HFC-134 represents the instantaneous concentration of HFC-134 in the HFC-134a exiting the column, express~d as a mul~i.ple of the 1.54 feed.
When the outlet concentration of the 134 reached 70% of the feed concentration, the high 134 concentration 134a flow was stopped and the column heated to l50~C. The pressure generated from the heating was vented from the column in the direction countercurrent to the original direction of feed.
During the temperature ramp, approximately 0.0514 moles of 134a and 0.0002 moles of 134 were vented. When the temperature reached 150C, HFC-134 free HFC-134a was fed in the direction countercurrent to the original feed at 50 psig (450 kPa) and 150C. The results are summarized in Table 12~.
~'~ W094/02440 ~110 2 3 2 :PCT/US92/05851 ~L~L2~
HFC-134a HFC-134a HFC-134 in~) out~b) out(c) O O O
0.033~ 0.0321 3.26 0.0673 0.0639 3.45 - 0.1010 0.0958 3.48 0.1347 0.1277 3.48 0.1795 0.1702 3.26 0.2118 0.2009 3.05 0.2513 0.238Q 2.4B
_ _ Q.3545 _0.3396 _ 0.58 FC-134a in represents the total running sum of the moles of HFC-134a fed to the column. . :
)HFC-134a out repre~ents the total running ~u~ of the moles of HFC-134a exiting the column.
(C)~FC-134 represents the instantaneous concentration o:E HFC-134 .~ in the HFC-134a exiting the column, expres~ed a~ a multiple of the 1.5~ feed.
EXAM
Metal tubing 0.18" (4.6 mm) I.D. x 2 ft. (0.51 m~
was packed with zeolite sorbents as indicated in Table 13, and in~talled in a gas chromatograph with a flame ionization detector. The columns were heated at 200C in flowing helium for a minimum of 12 hours.
-~ Helium was fed as a carrier gas at 30 sccm (S.0 x 10-7 m3/s). Samples t5 to 25 ~L) of HFC-134 and HFC-134a were then injected into the carrier stream at different ;temperatures. Each test was run in duplicate. Methane - tl% in nitrogen) was run as a standard at each ~- temperature. The results or these experiments are shown - in Table 13. , ; ~
~- ` 2 1 ~ 0 2 3 2 ~L~
Retention Time~
Temperature (m1n) Separation ETS-10~a) 200 262.5/gO.3 2.9 Na-A 200 1.6/G.6 2.7 Clinoptilolite 200 1.0~0.8 1.3 Ferrierite _ 200 0.9/0.5 _ __ _ 1.8 ~)Sodium Pota sium Titanosilicate ~EL~
Metal tubing 0.18" (4.6 mm) I.D. x 4.5 in (11.4 cm) was packed with Zeolite Na-X as indicated in Table 14, and installed in a gas chromatograph with a flame ioni~ation detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Xelium was fed as a carrier gas at 30 sccm (5.0 x 10-7 m3/s).
Samples (25 ~L) of HFC-134 and HFC-134a were then -injected into the carrier stream at different temperatures. Each test was run in duplicate. Methane (1% in nitrogen) was run as a standard at each temperature. The retention times were difficult to ' 15 measure.
Temperature Zeolite ~C) Na-X 200 _ Na-X _ __ 21 Q
The examples serve to illustrate particular embodiments of the invention. The invention is not confined thereto, but embr~ces embodiments which come within the scope of the claims.
~ UTE ~ET
SEPARATION OF TETRAELUOROETHANE ISOMERS
EI~L~ QE~ Y~NTIO~
This invention relates to the separation of fluorocarbon products, more particularly to the -separation of the isomers of tetrafluoroethane, CHF2CHF2 (HFC-134) and CF3CH~F ~HFC-134a).
~5~
Isomers of C2H2F4 (HFC-134s) are used as refrigeration fluids for a number of applications.
HFC-134s can also be used as starting materials for producing various other halogenated hydxocarbons.
Products containing isomers of C2H2F4 are produced in various degrees of isomer purity. One method of producing HFC-134s is by the hydrogenolysis of C2Cl2F4 - isomers ~CFC-114s). In the manufacture of C2Cl2F4 by the chlorofluorination of perchloroe~hylene the product typically consists of a mix~ure of the isomers, CClF2CClF2 (CFC-114) and CF3CCl2F (CFC-114a) ~see e.g., U.S. Patent No. 4,605,798). If the CFC-114s are then used to produce CHF2CClF2 (HCFC-124a~, CF3CHClF
(HCF~-124), HFC-13g or HFC-134a by hydrodehalogenation, the products often consist of a mixture of C2HClF4 and C2H2F4 isomers (see e.g., GB 1,578,933).
It has been found that for many applications, the presence of the second isomer of the isomer pair can significantly alter the physical and chemical properties of the desired isomer. For example, variation in the HFC-134~HFC-134a ratio in the product can result in dramatic variability in the thermodynamic properties critical for use in refrigeration applications. For use as a raw material feed, the presence of the unwanted isomer can result in yield loss due to increased side 35 reactions. As a result, there has been a continually ;
.. . . .
W094/02~t~ j P~T/US92/0585~-increasing demand for high isomer purity materials.
Consequently, the separation of HFC-134 isomers represents a significant aspect of preparing these compounds for various applications.
Purification of halogenated hydrocarbon pxoducts has been the subject of considerable research. Of particular interest are the challenges presented in separating desired halogenated hydrocarbon products from materials such as impurities in the starting materials used to produce the ~alogenated hydrocarbon, excess reactants, and reaction by-products and/or reaction co-products which are difficult to remove by standard separation methods such as distillation. Selectivle sorbents such as carbons and zeolites have been proposed for various separations. The effectiveness of separation using such sorbents varies with the chemical components and the sorbents involved. The successful design of sorbent based systems is considered highly dependent upon experimental determination of whether the relative sorbencies of the particular compounds are suitable for such systems.
HFC-134 has a boiling point of -23C and HFC-134a has a boiling point of -26.5C. Distillation is consequently relatively inefficient as a means for separating these two compounds.
SUMMARY OF THE INvE~TION
We have found that mixtures of the isomers of C2H2F4 (i.e., CHF2CHF2 and CF3CH2F) can be substantially separated by using a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves (e.g., zeolitesj having greater intermediate eltectronegativities than Zeolite Na-X, and (ii) activated carbons. The present invention provides a process for separating a mixture of CHF2CHF~ and CF3CH2F
to provide a product wherein the mole ratio of CF3CH2F
~. t ~ ~ .
~1~0292 ~ / i .
relative to CHF2CHF2 is increased which comprises contacting said mixture with said sorbent at a temperature within the range of -20C to 300C and a pressure within the range of lQ kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2. A~ a result, the mole ratio of ~1 CF3CH2F to CXF2CHF2 incre3ses (preferably by 25~ or more); and a product wherein the mole ra~io of CF3CH2F
relative to CHF2CHF2 is increased, may thus be recovered.
This invention also provides a process for separating a mixture of C~F2CHF2 and CF3CH2F to provide a product wherein the mole ratio of CHF2CHF2 relative to CF3CH2F is increased which comprises contacting said mixture with said sorbent as described above to remove a substantial amount of the CHF2CHF2, and desorbing sorbed CXF2CHF2 to provide a product which is enriched therewith.
Said process for producing a CF3CH2F enriched product and said process for producing a CHF2CHF2 enriched product may be integrated into an overall process (e.g., a thermal swing cycle process) whereby both of said products are provided. Said process for producing a CF3CH2F enriched product and/or said 9~1TUTE ~ET
: 1 ~ C 2 3 2 /~
process for producing a CHF2CHF2 enriched product may also be used in conjunc~ion with a process for producing HFC-134 and HFC-134a by the hydrogenolysis of CFC-114 and/or CFC-114a.
DETALL~_nE ~L~ ISQY
The present invention,provides for the separation of HFC-134 from HFC-134a. Isomer enriched products are provided in accordance with this invention by contacting a mixt~re of C2H2F4 isomers with a sorbent for CHF2CHF2 ~ , lD selected from the group consisting of acti~ated carbons and certain inorganic molecular sieves at a temperature and pressure suitable for sorption, for a period of time sufficient to remove a substantial amount of said CHF2CHF2. CF3CH2F enriched product is thereby provided using CHF2CHF2 sorption. Where CHF2CHF2 enriched product is desired, the invention also includes a process involving desorbing sorbed CHF2CHF2 to provide a product -which is enriched therewith. The process based upon preferential CHF2CHF2 sorption is particularly useful 0 for purifying CF3CH2F which contains minor amounts of CHF2CHF2. Where the process is used for such puri~ication of CF3CH2F, the isomer mix to be purified by this process generally has a mole ratio of CF3CH2F to CHF2CHF2 of at least about 9:1, preferably at least about 19:1, and most ~referably at least about 99:1.
A mix of the C2H2F4 isomers may result, for example,from a process in~olving the reaction of the ,CFC-114 and~or CF$-114a isomers with hydrogen.
Unreacted starting materials and C2HClF4 isomers may be recycled and reacted further with hydrogen to produce additional C2H2F4. Additional impurities may be present in these products. Distillation is typically used in order to remove impurities such as HCl, HF, under- and , over- chlorinates and fluorinates to produce products that are at least 90% C2H2F4. Separation of C2H2F4 ~rE~
;` W094/02440 ~ ~ i 023 2 PCT/US92/05851 , isomers in accordance with this invention to provide prsducts which are enriched in HFC-134 and/or products which are enriched in HFC-134a then may be advantageously employed. This invention can thus be 5 adapted for use in connection with production of C2H2F
by hydrogenolysis of materials such as C2C12F4 such that after removal of a substantial amount of CHF2CHF2 using the sorbent, either ~i) a product is recovered wherein the mole ratio of CF3CH2F relative to CHF2CHF2 is increased, (ii~ sorbed CHF2C~F2 is desorbed to produce a product wherein the mole ratio of CHF2C~F2 relative to CF3CH2F is increased, or both (i) and ~ii). j Some embodiments of this invention use activated carbon as the sorbent. Commercially available activated carbon may be used. The effectiveness of the process can be influenced by the particular activated carbon employed. Moreover, ~he sorption efficiency and sorption capacity of an activated carbon bed depends - upon the particle size of an activated carbon in a dynamic flow system. Preferably, the activated carbon has a particle size range of from about 4 to 325 mesh ~from about 0.044 to 4.76 millimeters). More preferably, the activated carbon has a particle size range of from about 6 to 100 mesh ~from about 0.149 to 3.36 millimeters). Most preferably, the activated carbon has a particle size range of from about 10 to 30 mesh ~from about 0.595 to 2.00 millimeters).
An activated carbon obtained having a particle size rang~ of about 0.074 x 0.297 millimeters (50 x 200 mesh) is available from the Barneby & Sutcliffe Corp. as Activated Carbon Type UU (natural grain, coconut shell based). An activated carbon having a particle size of 0.595 millimeters x 1.68 millimeters ~12 x 30 mesh) is ~ available from the Calgon Corporation as Calgon ~PL
~bituminous coal based) activated granular carbon. An W094/0~440 ~ 1 4 U 2 9 2 PCT/U592/0~85t _j activated carbon having a particle size range of about 0.450 x 1.68 millimeters (12 x 38 mesh) is available from Barnebey & Sutcliffe Corp. as Barneby & Sutcliffe Corp. Activated Carbon Type PE ~natural grain, coconut S shell carbon). An activated carbon having a particle size range of about 0.297 x 0.841 millimeters (2Q X 50 mesh) is available from Westvaco as Microporous Wood-Base Granular Carbon.
Typically the activated carbon used will have a total content of from about 0.1 to 10 weight percent of alkali and alkaline earth metals selected from lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and/or barium. The alkali and alkaline earth metal content of carbon can be regulated by techniques known in the art. For example, the metal content of carbon can be reduced by acid washing; and the metal content can be increased by standard impregnation techniques. In a preferred embodiment using preferential HFC-134 sorption, the activated carbon contains inherent aikali and/or alkaline earth metal~s) selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, and combinations thereof. Inherent alkali metals (typically Na and~or K) are preferred.
The presence of these metals, particularly as inherent metals in the range of from about 0.5 to 3 percent by weight, is considered to improve the HFC-134 sorption efficiency.
Some embodiments of this invention use inorganic : t , I !
molecular sieves. Molecular sieves are well known in the art and are defined in R. Szostak, Mol~cular Sieves-Principles of Synthesis and Identification, Van Nostrand Reinhold (1989) page 2. The inorganic molecular sieves used for preferentially sorbing HFC-134 in accordance with this invention include various ~1~Q292 ~ /q ~
.
silicates (e.g., titanosilicates and zeolites such as Zeolite Y, Zeolite A, Zeolite ZSM-5, and Zeolite ZSM-8), metalloaluminates and aluminophosphates, as well as other inorganic molecular sieve materials. The molecular sieves useful in the invention will typically have an average pore size of from about 0.~ to 1.5 nm.
The Sanderson electronegati~ity model (see, R. T. Sanderson, I'Chemical Bonds and Bond En~rgyl', 2nd ed., Academic Press, New York, 1976) furnishes a useful method for classifying inorganic molecular sieves based on their chemical composition. In ~ccordance with this invention the preferential sorption of tetrafluoroe~hane isomers by molecular sieves can be correlated with their intermediate electronegativity (i.e., their "Sint") as determined by the Sanderson method based on chemical composition. The Sint for Zeolite Na-X is about 2.38.
Inorganlc molecular sieves with Sints greater than the Sint for Zeolite Na-X ~i.e., more electronegative or more acidic~ may be used in accordance with this invention for increasing the mole ratio of CF3CH2F
relati~e to CHF2CHF2 by remo~ing a substantial amount of CHF2CHF2; and/or for increasing the mole ratio of CHF2CFH2 relati~e to CF3CH2F by desorbing sorbed CHF2CHF2 (i.e., CHF2CHF2 is belie~ed to sorb more strongly than CH2FCF3).
~e~TlTVTE 9~T
~ 1 ~ 0 2 9 2 Example Sint values are provided in Table I.
TABLE I
Intermediate Sanderson Electronegativities for Selected Molecular Sieves olecular Sieve ~in~ !
Na-X 2.38 Ca-A 2.56 Na-Y 2.58 ETS 2.60 H-Y . 2.97 .
Na-ZSM-8 3.00 Generally, for the inorganic molecular sieves, it is desirable to occupy acidic sites of the sie~e material with alkali metal(s) and or alkaline earth metal~s) so long as the intermediate electronegativity remains suitable for the desired separation. In a preferred embodiment using preferential Y.-C-134 sorption the inorganic molecular sieve is a Zeolite Y which contains alkali or alkaline earth metal(s) selected from the group consisting of lithium, sodium, pot~ssium, rubidium, cesium, magnesium, calcium, strontium and CTlTUTE 9t~ET
~?, W094/02440 2 1 4 0 2 g 2 PCT/US92/05851 barium or co~binations thereof. Alkali metals are preferred. It is preferred that alkali metals occupy from about 50% to 100~ of the accessible exchange sites in the zeolite. Particularly preferred zeolite molecular sieves include those having alkali metal to àluminum ratios of about 1:1, or alkaline earth metal to aluminum ratios of about 1:2. ;
Suitable temperature ranges for sorption range from about -20C ~o about 300C. Suitable pressures for sorption range from about 10 kPa to about 3000 kPa.
Contact with sorbent should be sufficient to achieve the desired degree of isomer enrichment.
Preferably, the mole ratio of the enriched isomer to the second isomer is increased by at least about 25%
relati~e to the mole ratio thereof in the initial mixture, most preferably by at least about 50%.
Where the process is used to purify CF3CH2F from a mixture of CF3CH2F and CHF2CHF2 using preferential HFC-134 sorption, preferably at least about 50 mole % of the CHF2C~F2 is removed. A particularly advanta~eous embodiment of this invention involves providing sufficient contact to produce CF3CH2F of at least about 99.99 mole percent purity.
This invention can be practiced with the sorbent contained in a stationary packed bed through which the process stream whose components need separation is passed. Alternatively, it can be practiced with the sorbent applied as a countercurrent moving bed; or with a fluidized bed where thelsorbent itself is moving. It can be applied with the sorbent contained as a stationary packed bed but the process configured as a simulated mo~ing bed, where the point of in~roduction to the bed of the process stream requiring separation is changed, such as may be effected using appropriate switching valves.
., .. . , , , , . - - , :
W094/~2440 , PCT/VS92/0~85 ~
21~0~gZ~' '' o The production of a product enriched with respect to one C2H2F4 isomer may be accompanied by the production of other products which are enriched with regard to the concentration of one or more other components of the S initial mixture. Indeed, a typical process might include both a product which is enriched in CF~CH2F
~e.g., essentially pure CF3CH2F) and another product which is enriched in CHF2CH~2. The production of product enriched in CHF2CXF2 generally involves desorption of CHF2CHF2. In any case, whether or not a CHF2CHF2 enriched product is desired, the sorbent is typically regenerated following CHF2CHF2 removal by desorption of sorbent materials. Desorption of components held by the sorbent may be effected with the sorbent left in place, or the sorbent may be removed and the desorption effected remotely from where the sorption step occurred. These desorbed components may exit the sorbent section in a direction either co-current (in the same direction as the orisinal C2H2F4 mixture feed was fed) or countercurrent (in the opposite direction of the original stream requiring separation). Desorption may be e~fected with or without the use of a supplemental purge liquid or gas flow. Where supplemental purge material is used, it may be a component of the feed, or some appropriate alternative material, such as nitrogen.
Such supplemental purge materials may be fed either co-currently or countercurrently.
In general, desorption can be effected by changing any thermodynamic variable ~which is effecti~e in remo~ing the sorbed components from the sorbent. For example, sorption and desorption may be effected using a thermal swing cycle, ~e.g., where after a period of sorption, the sorbent is heated externally through the wall of the ~essel containing it, and/or by the feeding of a hot liquid or gas into the sorbent, the hot gas ". . - . , . . - . . ~
W094/02440 ~ ~ 4 ~ '~ 9 ~ PCT/US92/05851 heing either one of the component materials or alternative materials). Alternatively, sorbed components can be removed by using a pressure swing cycle or ~acuum swing cycle ~e.g., where after a period S of sorption the pressure is suf~iciently reduced, in some embodiments to a vacuum, such that sorbed components are desorbed). Alternatively, the sorbed components can be removed by use of some type of stripping gas or liguid, fed co-currently or countercurrently to the original process feed material.
The stripping material may be one of the process feed materials or another material such as nitrogen.
One or several beds of sorbent may be used. 'Where several beds are used, they may be combined in series or in parallel. Also, where several beds are used, the separation efficiency may be increased by use of cycling zone sorption, where the pressure and or the temperatures of the beds are alternately raised and lowered as the process stream is passed through.
Practlce of the invention will be further apparent from the following non-limiting Examples.
Metal tubing ~0.l8 inch I.D. x 12 inch, 0.46 cm I.~. x 30.5 cm) was packed with a carbon sorbent and installed in a gas chromatograph with a flame ionization - detector. Helium was fed as a carrier gas at 33 sccm (5.5 x 10-7 m3/s). Samples of the various compounds were then injec~ed into the carrier stream at 200C. The results of these experiments using Barneby & Sutcliffe Type PE (3.75 gj carbon (Carbon A), Westvaco Microporous Wood-Based Granular Carbon ~Carbon B), Barneby &
Sutcliffe Type UU (3.85 g) carbon (Carbon C) and Calgon BPL (2.59g) carbon (Carbon D) are shown in Table l.
These data show that in each case the isomers had W 0 94/02440 ,~ g ~ PCr/US92/05851'~-different retention times, and thus may be separated using the carbons of this Example.
rABLE, 1 Sample Rete~tion Time fmi~l S~paration A 5 6.6 4.0 1.65 0.13% 1.0~%
- 200 4.36 3.16 1.36 0.13% 1.09%
B S 4.22 2.61 1.62 0.58% 75ppm 209 3.32 2.27 1.46 0.58% 75ppm C 200 4.79 3.38 1.42 940ppm 0.93%
D 5 2.32 1.75 1.32 660ppm 650ppm _ _00 2.01 1.59 1.26 _660pum _ 650D m )Volume of gas sample injected ~microliters) ~)134 - C~F2CHF2 )134a ~ ~F3CH2F
~d)Separation Factor - 134 retention time/134a retention time (~)sodium content of carbon in weight percent or parts per million as indicated ~potassium content of carbon in weight percent or parts per million as indicated It is evident from Table 1 that the rela~ive sorption efficiency for HFC-134 is higher in the presence of the alkali metals Na and K.
~MP~ 2 Metal tubing (0.18 inch I.D. x 12 inch, 0.46 cm I.D. x 30.5 cm was packed with a carbon sorbent and installed in a gas chromatograph with a flame ionization detector. The experiment was repeated using the same carbon, but washing it with hydrochloric acid before using it for separations. The sodium content of Westvaco Microporous Wood-Based Granular Carbon (Not Acid-Washed, NAW),was 1.29~. After washing with hydrochloric acid the sodium content was 9 ppm. This carbon was designated Acid-Washed ~AW). Helium was fed as a carrier gas at 33 sccm (5.5 x 10-7 m3~s). Samples of 134 and 134a were then injected into the carrier stream at 200C. The results of these experiments are ~'~ W094/0~0 ~ 1 ~ O ~ 9 2 PCT/US92/05851 shown in Table 2. These data show that a more efficient .
separation was obtained with the carbon containins alkali metal; in this case sodium.
~L~
Retention Time tmin.) Separation Carbon Na Content 134 134a Factor(~) ~AW l.29% lO.67 6.63 l.61 AW 9 ppm 6.2 4.3 _ 1.44 _ )Separation Factor Y 134 retention timeJ134a retention time ~L~ I
A packed tube (2 6 cm x 2 .12 cm I.D) containing Calgon BPL carbon ~46.1 g, 4.8 x 0.59 mm (12 x 30 mesh)) was purged wi~h nitrogen continuously for 24 hours at 2SQC and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% ~FC-134 was then fed to the bed a~ l6~ grams per hour. The results are shown in Table 3.
W0 94/02~40 ~ PCT/US921058 2 9 ~ 14 ~I~
Time 134a 134a 134 o o o - j ~1 0.164 0 0 0.175 0.011 0 ~.
77 0~207 0.043 0 89 0.239 0.075 0.61 100 0.269 0.105 0.88 112 0.301 0.137 O.g6 124 0.334 0.170 1.00 ~)134a in represents the total running sum of the moles ~:E
CF3C~2F fed ~o the column.
~)134a out represents the total running sum of the moles of CF3CH2F exiting the column.
(C~134 out represents the instan~aneou~ concentration of CI~F2CH~2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.% feed (i.e., O.5 would equal a O.5 w~.% HFC-134 concentration in the HFC-134a effluent). A zero i~ less than the detection limit of about 10 ppm.
This example shows that carbon will selectively hold back HFC-134 allowing HFC-134a free of HFC-134 followed by HFC-134a containing reduced HFC-134 concentrations to be obtained.
E~æL~_i A packed tube ~26 cm x 2.12 cm I.D) containing Barneby & Sutcliffe Type PE carbon ~50.3 g) was purged with ni~rogen continuously for 12 hours at 250C and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C.
HFC-139a containing 1 wt% HFC-134 was then fed to the bed at 16.7 grams per hour. The results are shown in .
Table 4.
W O 94~02440 ~ 1 ~ æ ~ ~ PCT/US92/0~851 ~A~LE 4 t Time 134a 134a 134 (min) in(a) out(~) out(C) , - O O O ~ ~
69 0.186 0 0 ~ .
73 0.196 0.010 0 8~ 0.22g 0.043 0 96 ~.258 0.072 0 108 0.291 0.105 0 120 0.323 0.137 0.76 3~ 0.355 0.169 0.94 144 _ 0.387 0.201 1.~0 ~134a in represents the total running sum of the moles of CF3CH2F fed to the column.
t~)134a out represents the total running ~um of the moles of CF~CH2F exiti~g the column.
(C)134 out represents the instantaneous concentration of CHF2CHF2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.% feed (i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration in the HFC-134a efflue~t)~ A zero is less than the detection limut of about 10 ppm.
~I~ :
A pac~ed tube (26 cm x 2.12 cm I.D) containing West~aco Microporous Wood-Based Granular Carbon (46 g) was purged with nitrogen continuously for 12 hours at S 25QC and at l atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% HFC-134 was then fed ~o the bed at 16.6 grams per hour. The results are shown in Table 5.
, ':
s~
,~
: ,t W094/02440 ~ PCT/US92/0~85 ~
TABL~_~
Time134a 134a 134 (min~ ) out~) out~C) i o o o o 74 0 . 199 0 . 003 0 82 0 . 2~1 0 . 025 0 94 0 . 253 0 . 057 0 106 0 . 285 0 . 089 0 118 0 . 317 0 . 121 0 . 16 130 0 . 350 ~ . 154 0 . 65 142 0 .382 0 . 186 0 . 97 155 _ 0 ! 417 0 . 221 _ 1 . 00 (~)134a in represents the total runnin~ ~um of the moles of CF3CH2F fed to the column.
(b)i34a out represents the total running sum of the mole~ of CF3CH2F exiting the column.
~C3134 out represents the instantaneous concentration of CHF2CHF2 - in the CF3~H2F exiting the column, expressed as 3 multiple of the 1 wt.~ feed ~i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration in the HFC-~34a effluent). A zero i~ less than the detection limlt of about 10 ppm.
F~xA~p~E 6 A packed tube ~26 cm x 2.12 cm I.D) containing Westvaco Microporous Wood-Based Granular Carbon (46 g) was purged with nitrogen continuously for 12 hours at 5 250C and at 1 atmosphere pressure. While still being purged with nitrogen, the bed was cooled and was maintained at 25C. HFC-134a containing 1 wt% HFC-134 was then fed to the bed at 16.6 grams per hour and at 4.7 atm. (476 kPa). The results are shown in Table 6.
~~~ W094~02440 ~ 1 4 0 2 ~ 2 PCT/US92/05851 ~7 ~;
TA~LE 6 Time 134a 134a 134 (min) in (a) out~b~ out~
~ t - O O O O
54 0.261 0.013 0 0.3125 0.067 0 77 0.373 0.1~5 0 89 0.431 0.183 0 101 0.489 0.241 0.33 113 0.547 0.299 0.47 125 0.605 0.357 0.55 137 0.663 0.415 0.8 t~)134a in represents the total running sum of the moles oi.
CF3CH2F fed to the column.
)134a out represents the total running sum of the moles of CF3CH2F exiting the column.
(C)134 out represents the instantaneous concentration of CHF2~HF2 in the CF3CH2F exiting the column, expressed as a multiple of the 1 wt.~ f~ed ~i.e., 0.5 would equal a 0.5 wt.% HFC-134 concentration i~ the HFC-134a effluent). A zero is less than the detection limit of about 10 ppm.
Examples 3 through 6 show that these carbon based sorben~s will selectively sorb HFC-134 allowing HFC-134a free of HFC-134, followed by HFC-134a containing reduced HFC~134 concentration to be 5 obtained. Examples 3 through 6 show that process material other than the componen~s to be separated can be used to strip HFC-134 ~i.e., in this case, nitrogen rather than HFC-134a is used to clear the bed of HFC-134). Also, examples 5 and 6 show that the capacity or 134 increases with pressure, and illustrates the presence of pressure swing adsorption.
EX~PLE 7 This is an example of a thermal swing cycle ~~ alternating a sorption step with a desorption step. The column and carbon pac~ing are the same as that used in Example 4 above. During the sorption step, HFC-134a containing 1 wt % 134 was fed to the packed column at f!
,, .
q . . .
WO 94/0~0 , . PCT/U~92/0585~
.. . ~ . "
~ 1 4~ ~ 9 2 18 26C and at a feed rate of 16.6 g/hr with a back-pressure se~ting of 1 atmosphere ~101 kPa) in the column. When HFC-134 began to break through at the other end of the column, the flow of feed was stopped, and the ends of the column were sealed. The column was then heated to 150C, and gas was vented from the column in the direction countercurrent to the original direction of feed, to keep the pressure at 1 atmosphere (101 kPa). ~hen the temperature reached 150C, HFC-134a containing less than l ppm of HFC-134 was fed in the direction countercurrent to the original feed to purge the bed, at 16.5 g/hr ,and with a back pressure setting of 1 atmosphere (101 kPa). The column valves were then closed at both ends, and the column cooled to 26C. The cooling of the bed caused a partial vacuum. The pressure was then brought back to 1 atmosphere (101 kPa) using the high HFC-134 content HFC-134a and the cycle was started again. The sorption and desorption steps were then repeated. The results of the second sorption step are shown in Table 7A.
Time Temp HFC-134a HFC-134a HFC-134 ~Min) C in (a) out~) out(C) , 93 26 0.250 0.124 0 117 26 0.315 0.189 0.77 129 26 0.347 0.221 0.87 140 _ 26 0.377 0.251 0.96 ~a)HFC-134a in represents the total running sum of the moles of HFC-134a~ed to~the col~mn. : , ~b)HFC-134a out represents the total running sum of the moles of HFC 134a exiting the column.
)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, expre-~ed aY a multiple of the 1~ feed. A zero is le~s than the detection limit of about 10 ppm.
The results of the desorption step which followed are shown in Table 7B.
1 9 `
~L~ . , Time Temp HFC-134a ~FC-134a HFC-134 ;
(min) ~C in(a) out~b) out(C~ ~
, 0 25 0 ~ 0 7 3S 0 0.049 1.16 12 98 0 0.107 1.~1 24 150 0 0.133 1.63 150 0.032 0.165 1.67 47 150 0.0~2 0.195 1.63 _ 71 150 0.126 0.259 0 _ la)HFC-134a in re~esents ~he total running sum of the mole~ of HFC-134a fed to the column.
FC-134a out repr~ents the total running sum of the mo:Le~ of HFC-134a exiting the column.
~)HFC-134 out repre~ents the instantaneous concentration of the HFC-134 i.n the HFC-134a exiting the column, expre~sed as a multiple o~ the 1~ feed. A zero is less than the detection limit of about 10 ppm.
Initially, no HFC-134a was fed, but HFC-134a and HFC-134 exited the column due to the let down of the pressure as the ~emperature was raised from 26C to 150C. Beginning at 24 minutes, when the temperature reached lS0C, HFC-134a containing less than 1 ppm 134 was fed at 16.5 g/hr. At 71 minutes, the HFC-134a flow was stopped.
This example shows the use of a temperature swing cycle as a process concept to produce both HFC-134-free and HFC-134-reduced HFC-134a.
This is an example of a thermal swing cycle alternating a sorption step with a desorption step. The column and carbon packing were the same as that used in Examples 5 and 6 above. During the sorption step, HFC-134a containing 1 wt % 134 was fed to the packed column at 25C and a 134a feed rate of 16.6 g~hr with a back-pressure setting of 1 atmosphere (101 kPa) in the ~ column. When the outlet HFC-134 concentration matched the inlet concentration, the flow of feed was stopped, .
~i WO 94/0~0 PCT/US92/05851~f'~
2 1 ~ 0 2 9 2 20 and the ends of the column were sealed. The column was then heated to 150C, and gas was vented from the column in the direction countercurren~ to the original direction of feed, to keep the pressure at 1 atmosphere (101 kPa). When the temperature reached 150C, HFC-134a containing less than 1 ppm of HFC-134 was fed in the direction countercurrent to the sriginal feed to purge the bed, at 16.5 g/hr and with a back pressure setting of 1 atmosphere ~101 kPa~. The column valves were then closed at both ends, and cooled to 25C. The cooling of the bed c~used a partial vacuum. The pressure was then brought back to 1 atmosphere (101 kPa) usin~ the hi.gh HFC-134 content HFC-134a and the cycle was started again. The sorption and desorption steps were then repeated.
Tne results of the second sorption step are shown in Table 8A.
Time Temp HFC-134a HFC-134a HFC-134 ~min) C in ~a) out~b) out(c) 29 25 0.140 0 0 73 25 0.353 0.213 0 0.411 0.271 0.25 97 25 0.469 0.329 0.80 _ 100; 25 0.532 0.392 1.00 (a)HFC-134a in repreaents the total running sum of tbe mole~ of HFC-134a fed to the column.
)HFC-134a out represents the total running sum of the moles of HFC-134a exiting the column )HFC-134 out represents the instantaneous concentration of HFC-134 in the HFC-134a exiting the column, expre~-~ed as a multiple of the 1~ feed. A zero is les-~ than the detection lim~t of about 10 ppm.
The results of the desorption step which followed are shown in Table 8B.
~'^WO94/02440 ~ 1 ~ 0 2 3 2 PCT/US92/05851 21' ' ' ~BLE 8B
Time Temp HFC-134a HFC 134a' HFC-134 36 0 0.049 1.09 22 78 0 0.105 1.31 34 ~30 0 0.150 1.54 4~ 150 0.015 0.170 1.65 ~8 150 0.073 0.~2~ 1.59 71 15~ 0.136 0.291 1.56 83 150 0.194 0.349 0.0 _ g5 150 0.252 0.407 _ 0 5a)HFC-134a in represents the total running 3um of the mol~as of XFC-134a fed to the column.
)HFC-134a out represents the total running sum of the mo:Les of HFC-134a exiting t~e column.
)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, expressed a~ a multiple of the 1~ feed. A zero is less than the detec~ion limit of about 10 ppm.
Initially, no HFC-134a was fed, but HFC-134a and HFC-i34 exited the column due to the let down of the pressure as the temperature was raised from 25C to 150C. Beginning at 34 minutes, when the temperature reached 150C, HFC-134a containing less than 1 ppm 134 was fed at 16.5 g/hr. At 95 minutes, the HFC-134a flow was stopped.
This example shows the use of a temperature swing cycle as a process concept to produce both HFC-134-free and HFC-134-red~ced HFC-134a.
~AM~L g Me~al,tubing 0.18" (4.6 mm) I.D. x 2 ft.~0.51 m) was packed with zeolite sorbents as indicated in Table 9, and installed in a gas chromatograph with a flame ionization detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Helium was fed as a carrier gas at 20 sccm ~3.3 x '0-7 m3/s).
Samples ~25 ~L) of HFC-134 and HFC-134a were then ~.. ~ , . .
WO 94/02440 ~ ~ ~ PCT/US9~/05~5 injected into the carrier stream at different temperatures. The resul~s of these experiments are shown in Table 9. Comparison of the 134/134a data for Na-Y and H-Y show a much enhanced separation on the more 5 basic zeolite. , - Zeolite Temperature Retention Times Separation (C) (min) Factor ~
Na-Y 200 408/71.4 5.7 H-Y 100 68.1~46.1 1.5 H-ZSM-sla) 200 470/308 1.5 5A 200 291/about 150 1.9 (a~The flow rate fos the H-ZSM-5 ~un was 35 sccm (5. 8 x 10-7 m3/s ~L~
Metal tubing 0.18" (4.6 mm) I.D. x 2 ft.(0.~1 m) was packed with zeolite sorbents as indicated in Table 10, and installed in a gas chromatograph with a flame ionization detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Helium was fed as a carrier gas at 30 sccm (5.0 x 10-7 m3/s).
Samples (25 to 500 ~L) of HFC-134 and HFC-134a were then injected into the carrier stream at different temperatures. Each test was run in duplicate. Methane (1% in nitrogen) was run as a standard at each temperature. The results of these experiments are shown in Table 10.
;
W094/~2440 ~ PCT/US92/0~8~1 ~
23 I `
~L~
Zeolite Temperature Retention Times Separation .
~C) ~min) Factor .
134/134a Na-Y 230 160/53.2 3.0 -240 128/45.1 2.8 ~50 98.3/36.8 2.7 H-Y 210 2.07/1.19 1.7 220 1.78/1.06 1.7 ~ .
230 l.OlfO.89 1.1 H-ZSM-8 210 110/70.2 1. 6 3 .
220 79.7/51.1 1~6 230 56.7~37.5 1.5 5A 230 74.7/29.4 2.5 240 64.8/24.9 2.6 -EXAMPLr l 1 This is an example of a ~hermal swing cycle with countercurrent purge during desorption. A 1 inch (2.54 cm) diameter tube was packed with 63 grams of the zeolite H-ZSM-5, and purged with nitrogen at 50 psig ~450 kPa). The ni~rogen was then turned off, and the column ed with HFC-134a containing 102 mole % HFC-134 at 60 sccm (1.0 x 10-7 m3/s) and 50 psig ~450 kPa). The results of this test are shown in Table llA.
W094J02440 PCT/US9~/0585 ~
2140~292 24 Time Temp HFC-134 (min) o C out (~) 29 0*
~9 0 ~9 o 29 0.18 100 29 0.34 110 2~ O.S1 ~ , ' *~reakthrough cf HFC-134a occurs.
)HFC-134 out represents the ins~antaneous concentration of ~FC-134 in the HFC-134a exiting t~e column, expr~ aed ~5 a multiple of the original 1% feed. A zero is less than the detection limlt of about 10 ppm.
When the outlet concentration of the 134 matched the inlet concentration, the high 134 concentration 134a flow was stopped and the ends of the column were sealed.
The column was then heated to 150C, and gas was vented S from ~he column in the direction countereurrent to the original direction of feed, to keep the pressure at 1 atmosphere (100 kPa). When the temperature reached 150C, HFC-134a containing less than 1 ppm 134 was fed in the direction countercurrent to the original feed at 50 psig ~450 kPa). The results are summarized in Table 11~}.
'^: W0 94/02440 21~G~2 PCT/US92/058~1 t TABL~
Time Temp HFC-134 (min) ~~ out~') 0 31 1.06 86 1.19 114 1.37 126 1.56 133 1.63 133 1.67 133 1.75 134 1.61 134 1.25 134 0.78 100 134 0.41 1~0 134 0.18 ~a)HFC-134 out represents the instantaneous concentration of the HFC-134 in the HFC-134a exiting the column, exprec~ed as a multiple of the orlginal 1% feed. A zero is less than the detectlon limit of about 10 ppm.
~AMPLE ~2 This is an example of a thermal swing cycle with countercurrent purge during desorption. A 0.93 inch (2.3S cm) diameter by 12 inch (30.48) long tube was pac~ed with 80 grams of LZ-Y52 zeolite ta Na-Y zeolite), and purged with nitrogen at 50 psig (450 kPa). The nitrogen was then turned off, and the column fed with HFC-134a containing 1.5 mole % HFC-134 at 50 psig . (4S0 kPa) and 30C. The results of this test are shown in Table 12A.
WO 94/02440~ 1 4 ~ ~ 9 2 PCT/U~92/0585 TAB~ 12 HFC-134a HFC 134a HFC-134 O O O
0.~35 0.004 0 O.g58 0.717 0 - 0.965 0.735 0.108 0.987 0.75~ 0.221 1.009 0.781 0.3Q4 1.032 0.8~3 0.379 1.053 0.8~5 0.447 1.071 _ 0.843 0.460 (a)HFC-134a in represents the total running sum of ~he mole~ of ~FC-134a fed to the column.
(~)HFC-134a out represents the total running sum of the mole3 of HFC-134a exitin~ the column.
(C)HFC-134 represents the instantaneous concentration of HFC-134 in the HFC-134a exiting the column, express~d as a mul~i.ple of the 1.54 feed.
When the outlet concentration of the 134 reached 70% of the feed concentration, the high 134 concentration 134a flow was stopped and the column heated to l50~C. The pressure generated from the heating was vented from the column in the direction countercurrent to the original direction of feed.
During the temperature ramp, approximately 0.0514 moles of 134a and 0.0002 moles of 134 were vented. When the temperature reached 150C, HFC-134 free HFC-134a was fed in the direction countercurrent to the original feed at 50 psig (450 kPa) and 150C. The results are summarized in Table 12~.
~'~ W094/02440 ~110 2 3 2 :PCT/US92/05851 ~L~L2~
HFC-134a HFC-134a HFC-134 in~) out~b) out(c) O O O
0.033~ 0.0321 3.26 0.0673 0.0639 3.45 - 0.1010 0.0958 3.48 0.1347 0.1277 3.48 0.1795 0.1702 3.26 0.2118 0.2009 3.05 0.2513 0.238Q 2.4B
_ _ Q.3545 _0.3396 _ 0.58 FC-134a in represents the total running sum of the moles of HFC-134a fed to the column. . :
)HFC-134a out repre~ents the total running ~u~ of the moles of HFC-134a exiting the column.
(C)~FC-134 represents the instantaneous concentration o:E HFC-134 .~ in the HFC-134a exiting the column, expres~ed a~ a multiple of the 1.5~ feed.
EXAM
Metal tubing 0.18" (4.6 mm) I.D. x 2 ft. (0.51 m~
was packed with zeolite sorbents as indicated in Table 13, and in~talled in a gas chromatograph with a flame ionization detector. The columns were heated at 200C in flowing helium for a minimum of 12 hours.
-~ Helium was fed as a carrier gas at 30 sccm (S.0 x 10-7 m3/s). Samples t5 to 25 ~L) of HFC-134 and HFC-134a were then injected into the carrier stream at different ;temperatures. Each test was run in duplicate. Methane - tl% in nitrogen) was run as a standard at each ~- temperature. The results or these experiments are shown - in Table 13. , ; ~
~- ` 2 1 ~ 0 2 3 2 ~L~
Retention Time~
Temperature (m1n) Separation ETS-10~a) 200 262.5/gO.3 2.9 Na-A 200 1.6/G.6 2.7 Clinoptilolite 200 1.0~0.8 1.3 Ferrierite _ 200 0.9/0.5 _ __ _ 1.8 ~)Sodium Pota sium Titanosilicate ~EL~
Metal tubing 0.18" (4.6 mm) I.D. x 4.5 in (11.4 cm) was packed with Zeolite Na-X as indicated in Table 14, and installed in a gas chromatograph with a flame ioni~ation detector. The columns were heated at 200C
in flowing helium for a minimum of 12 hours. Xelium was fed as a carrier gas at 30 sccm (5.0 x 10-7 m3/s).
Samples (25 ~L) of HFC-134 and HFC-134a were then -injected into the carrier stream at different temperatures. Each test was run in duplicate. Methane (1% in nitrogen) was run as a standard at each temperature. The retention times were difficult to ' 15 measure.
Temperature Zeolite ~C) Na-X 200 _ Na-X _ __ 21 Q
The examples serve to illustrate particular embodiments of the invention. The invention is not confined thereto, but embr~ces embodiments which come within the scope of the claims.
~ UTE ~ET
Claims (10)
1. A process for separating a mixture of CHF2CHF2 and CF3CH2F to provide a product wherein the mole ratio of CF3CH2F relative to CHF2CHF2 is increased, comprising the step of: contacting said mixture with a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves having intermediate electronegativities greater than the intermediate electronegativity of Zeolite Na-X and (ii) activated carbons, at a temperature within the range of -20°C to 300°C and a pressure within the range of 10 kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2 and increase the mole ratio of CF3CH2F to CHF2CHF2 by at least about 25%
relative to the mole ratio thereof in the initial mixture.
relative to the mole ratio thereof in the initial mixture.
2. The process of Claim 1 wherein the mixture separated has a mole ratio of CF3CH2F to CHF2CHF2 of at least about 9:1 and at least about 50 mole percent of the CHF2CHF2 is removed.
3. The process of Claim 2 wherein a mixture of CF3H2F and CHF2CHF2 is separated to provide CF3CH2F of at least about 99.99 mole percent purity.
4. A process for separating a mixture of CHF2CHF2 and CF3CH2F to provide a product wherein the mole ratio of CHF2CHF2 relative to CF3CH2F is increased comprising the step of: contacting said mixture with a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves having intermediate electronegativities greater than the intermediate electronegativity of Zeolite Na-X and (ii) activated carbons, at a temperature within the range of -20°C to 300°C and a pressure within the range of 10 kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2; and desorbing sorbed CHF2CHF2 to provide a product which is enriched therewith.
5. The process of Claim 1, Claim 2, Claim 3, or Claim 4 wherein the sorbent is a zeolite having an average pore size of from 0.3 to 1.5 nanometers.
6. The process of Claim 1, Claim 2, Claim 3, or Claim 4 wherein the sorbent is a Zeolite Y, a Zeolite A, a Zeolite ZSM-5, or a Zeolite ZSM-8.
7. The process of Claim 1, Claim 2, Claim 3, or Claim 4 wherein the sorbent is an activated carbon.
8. The process of Claim 7 wherein the carbon contains from 0.5 to 3 weight percent inherent metal selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, and combinations thereof.
9. The process of Claim 7 wherein the carbon contains from 0.5 to 3 weight percent of inherent metals selected from the group consisting of sodium, potassium, and combinations thereof.
10. A process for producing C2H2F4 by hydrogenolysis of C2Cl2F4 characterized by the step of:
contacting a mixture of CHF2CHF2 and CF3CH2F produced by said hydrogenolysis with a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves having intermediate electronegativities greater than the intermediate electronegativity of Zeolite Na-X
and (ii) activated carbons, at a temperature within the range of -20°C to 300°C and a pressure within the range of 10 kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2; and either (i) recovering a product wherein the mole ratio of CF3CH2F relative to CHF2CHF2 is increased, (ii) desorbing sorbed CHF2CHF2 to provide a product wherein the mole ratio to CHF2CHF2 relative to CF3CH2F is increased, or both (i) and (ii).
contacting a mixture of CHF2CHF2 and CF3CH2F produced by said hydrogenolysis with a sorbent for CHF2CHF2 selected from the group consisting of (i) inorganic molecular sieves having intermediate electronegativities greater than the intermediate electronegativity of Zeolite Na-X
and (ii) activated carbons, at a temperature within the range of -20°C to 300°C and a pressure within the range of 10 kPa to 3000 kPa and for a period of time sufficient to remove a substantial amount of the CHF2CHF2; and either (i) recovering a product wherein the mole ratio of CF3CH2F relative to CHF2CHF2 is increased, (ii) desorbing sorbed CHF2CHF2 to provide a product wherein the mole ratio to CHF2CHF2 relative to CF3CH2F is increased, or both (i) and (ii).
Priority Applications (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP92916561A EP0649398A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| CA002140292A CA2140292A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| JP6503976A JPH07508994A (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| BR9207152A BR9207152A (en) | 1992-07-17 | 1992-07-17 | Separation processes of a mixture of CHF2CHF2 and CF2 and CF3CH2F and process for the production of C2H2F4 by C2CI2F4 hydrogenolysis |
| PCT/US1992/005851 WO1994002440A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| AU23778/92A AU663515B2 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| ZA935163A ZA935163B (en) | 1992-07-17 | 1993-07-16 | Separation of tetrafluoroethane isomers |
| CN93108891A CN1088903A (en) | 1992-07-17 | 1993-07-17 | The separation of tetrafluoroethane isomers |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002140292A CA2140292A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
| BR9207152A BR9207152A (en) | 1992-07-17 | 1992-07-17 | Separation processes of a mixture of CHF2CHF2 and CF2 and CF3CH2F and process for the production of C2H2F4 by C2CI2F4 hydrogenolysis |
| PCT/US1992/005851 WO1994002440A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2140292A1 true CA2140292A1 (en) | 1994-02-03 |
Family
ID=27160069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002140292A Abandoned CA2140292A1 (en) | 1992-07-17 | 1992-07-17 | Separation of tetrafluoroethane isomers |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0649398A1 (en) |
| JP (1) | JPH07508994A (en) |
| CN (1) | CN1088903A (en) |
| AU (1) | AU663515B2 (en) |
| BR (1) | BR9207152A (en) |
| CA (1) | CA2140292A1 (en) |
| WO (1) | WO1994002440A1 (en) |
| ZA (1) | ZA935163B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5750808A (en) * | 1995-07-11 | 1998-05-12 | E. I. Du Pont De Nemours And Company | Dehydrohalogenation processes |
| JP5427483B2 (en) * | 2009-06-19 | 2014-02-26 | 株式会社化研 | Concentration, elution recovery method, and system of radiotechnetium as a raw material for radiopharmaceuticals and their labeled compounds |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1578933A (en) * | 1977-05-24 | 1980-11-12 | Ici Ltd | Manufacture of halogenated hydrocarbons |
| US4906796A (en) * | 1989-03-08 | 1990-03-06 | Allied Signal Inc. | Process for purifying 1,1,1,2-tetrafluoroethane |
| CA2004709A1 (en) * | 1989-03-23 | 1990-09-23 | Stephen F. Yates | Process for purifying 1,1,1,2-tetrafluoroethane |
| US5087778A (en) * | 1990-04-10 | 1992-02-11 | Allied-Signal Inc. | Regeneration of zeolites used for purifying 1,1,1,2-tetrafluoroethane |
-
1992
- 1992-07-17 BR BR9207152A patent/BR9207152A/en not_active Application Discontinuation
- 1992-07-17 EP EP92916561A patent/EP0649398A1/en not_active Withdrawn
- 1992-07-17 WO PCT/US1992/005851 patent/WO1994002440A1/en not_active Application Discontinuation
- 1992-07-17 AU AU23778/92A patent/AU663515B2/en not_active Ceased
- 1992-07-17 JP JP6503976A patent/JPH07508994A/en active Pending
- 1992-07-17 CA CA002140292A patent/CA2140292A1/en not_active Abandoned
-
1993
- 1993-07-16 ZA ZA935163A patent/ZA935163B/en unknown
- 1993-07-17 CN CN93108891A patent/CN1088903A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| BR9207152A (en) | 1995-12-12 |
| WO1994002440A1 (en) | 1994-02-03 |
| AU2377892A (en) | 1994-02-14 |
| ZA935163B (en) | 1995-01-16 |
| EP0649398A1 (en) | 1995-04-26 |
| AU663515B2 (en) | 1995-10-12 |
| JPH07508994A (en) | 1995-10-05 |
| CN1088903A (en) | 1994-07-06 |
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