U.S. patent application number 10/308009 was filed with the patent office on 2003-08-07 for separation of heavy ends from streams of halogenated alkanes.
Invention is credited to Mainz, Eric L., Wilson, Richard L..
Application Number | 20030149316 10/308009 |
Document ID | / |
Family ID | 25478814 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030149316 |
Kind Code |
A1 |
Mainz, Eric L. ; et
al. |
August 7, 2003 |
Separation of heavy ends from streams of halogenated alkanes
Abstract
Provided is a method and system for separating heavy ends from a
halogenated alkane in a waste stream. The method includes: (a)
removing a bottom fraction containing heavy ends from a catalyst
recovery unit and conveying the bottom fraction to a vessel; (b)
introducing steam into the bottom fraction containing heavy ends;
(c) removing a halogenated alkane vapor and a water vapor from the
waste treatment unit; (d) condensing the halogenated alkane and
water vapors; and (e) separating the halogenated alkane phase and
water phase from the heavy ends.
Inventors: |
Mainz, Eric L.; (Goddard,
KS) ; Wilson, Richard L.; (Mulvane, KS) |
Correspondence
Address: |
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
25478814 |
Appl. No.: |
10/308009 |
Filed: |
December 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10308009 |
Dec 3, 2002 |
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09942914 |
Aug 31, 2001 |
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6552238 |
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Current U.S.
Class: |
570/262 |
Current CPC
Class: |
C07C 17/278 20130101;
C07C 17/386 20130101; C07C 17/386 20130101; C07C 17/278 20130101;
C07C 17/383 20130101; C07C 17/38 20130101; C07C 19/01 20130101;
C07C 19/01 20130101; C07C 17/383 20130101; C07C 19/01 20130101 |
Class at
Publication: |
570/262 |
International
Class: |
C07C 017/38 |
Claims
What is claimed is:
1. A method for the separation of heavy ends from a halogenated
alkane stream, comprising: (a) removing a bottom fraction
containing heavy ends from a catalyst recovery unit and conveying
said bottom fraction to a vessel; (b) introducing steam into said
bottom fraction containing heavy ends; (c) removing halogenated
alkane vapor and water vapor from said treatment unit; (d)
condensing said halogenated alkane and water vapors; (e) separating
the halogenated alkane phase from the water phase; and (f) purging
the heavy ends, which remain in the treatment unit either
periodically or continuously.
2. The method for the separation of heavy ends in accordance with
claim 1, further comprising: drying the halogenated alkane
phase.
3. The method for separation of heavy ends in accordance with claim
2, further comprising: processing the halogenated alkane to
manufacture a purified product.
4. The method for the separation of heavy ends in accordance with
claim 1, further comprising: converting said water phase into steam
and reusing said steam to treat a further bottom fraction
containing heavy ends.
5. The method for the separation of heavy ends in accordance with
claim 1, further comprising: removing said bottom fraction
containing heavy ends from said catalyst recovery unit and
conveying a part of said bottom fraction to said vessel.
6. The method for the separation of heavy ends in accordance with
claim 1, wherein said heavy ends is a mixture containing catalyst,
solvent, metal particles, metal chlorides and high boiling
chlorinated by-products.
7. A method for the separation of heavy ends from a halogenated
alkane stream, comprising: (a) removing a bottom fraction
containing heavy ends from a catalyst recovering unit and conveying
said bottom fraction to a vessel; (b) maintaining the temperature
of said vessel above the boiling point of water at a predetermined
pressure; (c) introducing water into said vessel where a portion of
the water is converted into steam and is mixed with said heavy ends
and a portion of unconverted water fluid to form a haloalkane
vapor, and removing a portion of the vapors from the vessel; (d)
condensing said haloalkane mixture and the remaining portion of
steam; and (e) separating a halogenated alkane phase from the water
recovered.
8. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, further comprising:
passing said haloalkane vapor and steam from step (c) through a
column to further fractionate the mixture.
9. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, wherein step (b) is
carried out by: operating said vessel at a pressure in the range of
about 0.1 to 5.0 atmospheres.
10. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, wherein step (b) is
carried out by: operating said vessel at a pressure in the range of
about 0.5 to 1.5 atmospheres.
11. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, wherein step (b) is
carried out by: operating said vessel at a temperature range of
about 40 to 150.degree. C.
12. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, wherein step (b) is
carried out by: operating said vessel at a temperature range of
about 40 to 115.degree. C.
13. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, further comprising:
treating said water which has been recovered to remove or to
neutralize any acidity present.
14. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, further comprising:
recycling the water which has been recovered to treat a further
halogenated alkane stream containing heavy ends.
15. The method for the separation of heavy ends from a halogenated
alkane stream in accordance with claim 7, wherein said halogenated
alkane phase is further treated to manufacture a purified
product.
16. A system for separating heavy ends from a halogenated alkane
stream, comprising: (a) a waste treatment unit for receiving a
bottom fraction containing heavy ends from a catalyst recovery
unit; (b) a steam source for providing steam to said waste
treatment unit to remove a halogenated alkane phase and a water
phase from said waste treatment unit; (c) a condenser for
condensing said halogenated alkane and water phases; and (d) a
vessel for separating the alkane and water phases.
17. A system for separating heavy ends from a halogenated alkane
stream, comprising: (a) a waste treatment unit for receiving a
bottom fraction containing heavy ends from a catalyst recovery
unit; (b) a water source for providing water to said waste
treatment unit, where a portion of the water is converted into
steam and is mixed with said heavy ends and a portion of
unconverted water fluid to form a haloalkane vapor mixture with
steam; (c) a condenser for condensing said haloalkane mixture and
the remainder portion of said steam; and (d) a vessel for and
separating the halogenated alkane phase from the water
recovered.
18. The system for separating heavy ends from a halogenated alkane
stream, further comprising: a column to further fractionate said
haloalkane mixture from step (b).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to methods and systems for the
separation of halogenated alkane streams from heavy ends. In
particular, the invention is directed to the separation of
1,1,1,3,3-pentachloropropane from the heavy ends produced in the
formation of 1,1,1,3,3-pentachloropropane.
[0003] 2. Description of the Related Art
[0004] Fluorocarbon producers have actively pursued the production
of fluorocarbons to replace the banned chlorofluorocarbons (CFC's).
These fluorocarbons will require hydrochlorocarbon feedstocks.
[0005] Several fluorochemical producers have targeted fluorocarbon
1,1,1,3,3-penta-fluoropropane, utilizing
1,1,1,3,3-pentachloropropane as the hydrochlorocarbon feedstock, as
the primary replacement product for foam blowing applications.
Zil'bennan et al. ("Synthesis of liquid telomers of vinyl chloride
with carbon tetrachloride," J. Org. Chem. USSR (English Transl.),
3:2101-2105, 1967) prepared 1,1,1,3,3-pentachloropropa- ne in a 58%
yield by the reaction of carbon tetrachloride (CCl.sub.4) and vinyl
chloride using ferrous chloride tetrahydrate in isopropanol. In
addition, Kotora et. al. ("Addition of tetrachloromethane to
halogenated ethenes catalyzed by transition metal complexes," J.
Mol. Catal., 77(1):51-60, 1992) prepared
1,1,1,3,3-pentachloropropane in high yields using either cuprous
chloride/butylamine or tris(triphenylphosphine)
dichlororuthenium.
[0006] European Patent Application No. 131561 describes a very
general process for the addition of a haloalkane compound to an
alkene or alkyne compound in the presence of iron metal and a
phosphorus (V) compound to form halogenated alkanes. EP 131561 sets
forth several examples of the batch reaction of ethylene and carbon
tetrachloride to produce 1,1,1,3-tetrachloropropane. EP 131561 also
mentions a wide variety of other olefins and alkynes, including
vinyl halides. It states that the batch process could be made
continuous, but does not include any specific information
concerning how this would be carried out.
[0007] U.S. Pat. No. 6,187,978 describes a process based on
Kharasch chemistry where polyhalogenated alkanes and olefins are
reacted in the presence of a transition metal catalyst. The
reaction results in the following Kharasch reaction:
[0008]
CCl.sub.4+CH.sub.2.dbd.CHCl.fwdarw.CHCl.sub.2--CH.sub.2--CCl.sub.3
(1,1,1,3,3-pentachloropropane)
[0009] U.S. patent application Ser. No. 09/671,993, filed Sep. 29,
2000, now allowed, describes a process which includes a reaction
step, a catalyst recovery step, and a process to purify the
haloalkane product. In the process, a portion of the catalyst
stream is withdrawn from the catalyst recovery unit and is disposed
of as a waste stream in order to prevent the build up of unreactive
by-products. The waste stream can contain up to 50 weight percent
of 1,1,1,3,3-pentachloropentane product. Thus, the volume of
product in the waste stream constitutes a significant loss of feed
conversion to the desired product.
[0010] Conventional distillation and even low temperature
distillation of waste streams has resulted in decomposition of both
the 1,1,1,3,3-pentachloropropane product and catalyst components in
the waste stream. Tar-like by-products, which foul the equipment,
for example, are formed. Likewise, treatment of waste streams by
performing a combination of solvent and aqueous extraction is
ineffective and costly. Generally, a primary aqueous extraction is
followed by the addition of non-polar solvents to separate the
waste stream into two phases. These phases can then be further
separated to recover the reactants. However, tests have
demonstrated that extractions through the employment of aqueous, or
aqueous plus inorganic salts and/or acids, or aqueous plus polar
solvents, were ineffective in extracting iron, useful reactants and
products. Aqueous based extractions induce precipitation of solids,
which in turn require increased waste handling and waste disposal
costs.
[0011] To meet the requirements of the fluorocarbon industry of
providing a pure fluorocarbon feedstock at a high yield and to
overcome the disadvantages of the related art, it is an object of
the present invention to provide a novel method for separating
heavy ends from a halogenated stream in a facile and cost-effective
manner.
[0012] It is another object of the invention to recover from the
waste stream a halogenated alkane stream, which contains desirable
halogenated alkane(s) leaving a heavy ends stream that is disposed
of as a waste product. The recovered halogenated alkane stream that
can be further purified to give a product for use as a fluorocarbon
feedstock.
[0013] It is another object of the invention to employ steam in the
separation of the heavy ends from the waste stream and to recover
the steam as a water phase, which will then be utilized to treat
additional waste stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The objects and advantages of the invention will become
apparent from the following detailed description of the preferred
embodiments thereof in connection with the accompanying drawings,
in which:
[0015] FIG. 1 illustrates a schematic diagram of a system that is
used to practice a method for treating a waste stream withdrawn
from the catalyst recovery unit to separate the heavy ends from the
halogenated alkane;
[0016] FIG. 2 illustrates a schematic diagram of a system that is
used to practice a method for treating a waste stream withdrawn
from the catalyst recovery unit to separate the heavy ends from the
halogenated alkane through the further employment of a distillation
column;
[0017] FIG. 3 is a graph illustrating the ratio of the saturated
vapor pressures of HCC240fa to that of HCC470nfaf (i.e., the ratio
of 1,1,1,3,3-pentachloropropane to 1,1,3,3,5,5-hexachloropentane)
as a function of temperature; and
[0018] FIG. 4 is a graph illustrating the ratio of the saturated
vapor pressure of water to that of HCC240fa (i.e.,
1,1,1,3,3-pentachloropropane- ) as a function of temperature.
SUMMARY OF THE INVENTION
[0019] In accordance with the present invention, an innovative
method and system is provided for the separation of heavy ends from
a halogenated alkane in a stream of waste removed from the catalyst
recovery unit.
[0020] In accordance with one aspect of the invention, a method for
separating heavy ends from a halogenated alkane in a waste stream
is provided. The method includes: (a) removing a bottom fraction
containing heavy ends from a catalyst recovery unit and conveying
the bottom fraction to a vessel; (b) introducing steam into the
bottom fraction containing heavy ends;(c) removing a halogenated
alkane vapor and a water vapor from the waste treatment unit; (d)
condensing the halogenated alkane and water vapors; and (e)
separating the halogenated alkane phase and water phase from the
heavy ends.
[0021] In accordance with another aspect of the invention a method
for the separation of heavy ends from a halogenated alkane stream
is provided. The method includes (a) removing a bottom fraction
containing heavy ends from a catalyst recovery unit and conveying
the bottom fraction to a vessel; (b) maintaining the temperature of
the vessel above the boiling point of water and at a predetermined
pressure; (c) introducing water into the vessel where a portion of
the water is converted into steam and is mixed with the heavy ends
and all or a portion of the water is converted into steam and mixes
with the waste stream to form a vapor mixture containing steam and
the haloalkane fraction of the waste stream; (d) condensing the
haloalkane mixture and the steam; (e) separating a halogenated
alkane phase from the water phase; and (f) periodically or
continuously purging a portion of liquid in the bottom of the
vessel.
[0022] In accordance with another aspect of the invention, a system
for separating heavy ends from a halogenated alkane stream is
provided. The system includes (a) a waste treatment unit for
receiving a bottom fraction containing heavy ends from a catalyst
recovery unit; (b) a water source for providing water to the waste
treatment unit, where a portion of the water is converted into
steam and is mixed with the heavy ends to form a water and
halogenated alkane vapor; (c) a condenser for condensing the
haloalkane and water vapor mixture; and (d) separating the
halogenated alkane phase from the water phase.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0023] The invention will now be described with reference to
exemplary embodiments thereof. A first aspect of the invention
relates to a method for the efficient removal/separation of a
haloalkane product from a mixture of catalyst, solvent, metal
particles, metal chlorides and high boiling chlorinated by-products
formed in a Kharasch chemistry type process.
[0024] The separation method of the present invention can be
applied to any haloalkane product manufactured based on Kharasch
chemistry. In a preferred process, a catalyst mixture is employed
to manufacture 1,1,1,3,3-pentachloropropane by the addition
reaction of carbon tetrachloride and vinyl chloride. Particularly,
the catalyst mixture includes tributyl phosphate (TBP), metallic
iron, ferrous chloride and ferric chloride. A system and method for
the manufacture of 1,1,1,3,3-pentachloro-propane based on the
above-described reaction is disclosed in U.S. patent application
Ser. No. 09/671,993, filed Sep. 29, 2000, now allowed, and is
hereby incorporated by reference in its entirety.
[0025] The preferred embodiments are discussed below with reference
to the figures where the same reference numbers denote like
features. In accordance with a preferred embodiment, and as
illustrated in FIG. 1, the system includes a reaction chamber 110,
a catalyst recovery unit 120, a purification unit 150 and a waste
treatment 130. The reaction components (i.e., vinyl chloride,
carbon tetrachloride, tributyl phosphate (TBP), and iron) are
continuously fed into reactor unit 110.
[0026] Reactor unit 110 is agitated to mix the reactor feed and
keep the iron powder suspended. Powdered iron is consumed in
reactor 110, producing ferrous chloride and ferric chloride. These
components (i.e., ferrous chloride and ferric chloride) and TBP
form complexes miscible in reactor contents. These complexes are
catalytic and promote the Kharasch reaction. Side reactions produce
chlorinated hydrocarbon by-products. The major by-products are two
hexachloropentane isomers (e.g., 1,1,1,3,5,5-hexachloropentane and
1,1,3,3,5,5-hexachloropentane).
[0027] Reactor contents are continually withdrawn from the reactor
and routed to the catalyst recovery unit 120. The catalyst recovery
unit 120 distills the reactor effluent into distillate and a bottom
fraction. The distillate fraction, containing unconverted carbon
tetrachloride, unconverted vinyl chloride,
1,1,1,3,3-pentachloropropane, trace light by-products and trace
heavy by-products, is routed to purification unit 150 to further
purify the 1,1,1,3,3-pentachloropropane product.
[0028] The bottom fraction contains ferric chloride, TBP,
1,1,1,3,5,5-hexachloro-pentane, 1,1,3,3,5,5-hexachloropentane, high
boiling point components (hereinafter referred to collectively as
heavy ends) and 1,1,1,3,3-pentachloropropane (hereinafter, referred
to as halogenated alkane). Substantially all catalyst components
remain in the heavy ends. The bottom fraction is continuously drawn
from the catalyst recovery unit 120 in two streams. One stream is
recycled back to the reactor, where ferric chloride and TBP content
resume the roles of catalyst components. The second stream
(hereafter referred to as the waste stream) that would normally be
routed to waste is further processed to separate the heavy ends
from the halogenated alkane. The waste treatment unit 130 receiving
the waste stream is a vessel made of corrosion resistant materials.
Nickel alloys, polytetrafluoroethylene (PTFE), tantalum, and
glass-lined steel, are preferred process wetted materials. Suitable
nickel alloys include Nickel 200, Hastelloy.TM., C-276 and
Monel.TM..
[0029] Water vapor in the form of steam is introduced into waste
treatment unit 130. A mixture of halogenated alkane and steam are
removed from overhead the treatment unit 130 and the mixture is
routed to condenser 140. Therein the mixture is condensed
(re-liquefied) into a halogenated alkane phase and a water phase.
By comparison, the heavy ends remain in waste treatment unit 130.
The water and halogenated alkane phases are separated by methods
known to those skilled in the art. Subsequently, the halogenated
alkane phase is dried. The addition of steam to the heavy ends in
the waste stream does not result in significant hydrolysis of the
heavy ends nor does it form acidic by-products (e.g., HCl). In
fact, the steam effectively stripped the halogenated alkane product
from the heavy ends with very little decomposition of the
product.
[0030] The stripped halogenated alkane product obtained is routed
either to the catalyst recovery unit 120 or the purification unit
150 for further purification and thus reclamation of the product
component of the waste stream. The water component, on the other
hand, can be reintroduced into waste treatment unit 130 in the form
of steam to treat a further waste stream.
[0031] In another preferred embodiment, and as illustrated in FIG.
2, the waste stream is routed from catalyst recovery unit 120 to a
waste treatment unit 130 that is maintained at a temperature above
the boiling point of water. The temperature of waste treatment unit
130 is dependent on the pressure inside the vessel. Thus, the
temperature can be in the range of about 40 to 150.degree. C. and
preferably about 80 to 115.degree. C. The pressure can be in a
range of about 0.1 to 5.0 atmospheres and preferably 0.5 to 1.5
atmospheres.
[0032] A halogenated alkane such as 1,1,1,3,3-pentachloropropane
can be separated from the heavy ends based on the proper selection
of pressure at which the process is conducted. Conducting the
separation process at reduced pressures (i.e., less than ambient)
enhances the separation of 1,1,1,3,3-pentachloropropane from
isomers such as 1,1,1,3,5,5-hexachlorop- entane and
1,1,3,3,5,5-hexachloropentane.
[0033] In particular, as water is introduced into waste treatment
130, steam is formed and commingled with the waste stream and a
portion of the water introduced therein. Steam and halogenated
alkane mixture is removed from overhead the treatment unit 130 and
the mixture is optionally routed to column 160 where the mixture
can be subjected to additional fractionation. The column is
preferably packed with structured packing to provide an adequate
mass transfer and a low pressure drop, thus enhancing contact
between the descending liquid and the rising vapor.
[0034] The rising vapor in column 160 contains steam, halogenated
alkane and low concentrations of other light components. The vapor
is routed to condenser 140, where the mixture is recondensed and
separated into a halogenated alkane phase and a water phase, as
discussed above. The phase-separated water can be reintroduced into
waste treatment unit 130 to treat a further waste stream. However,
the phase-separated water can be first treated to remove or
neutralize any acidity present. Thus, the water used reduces the
volume of waste water produced. On the other hand, as explained
above, the halogenated alkane product can be routed to either the
catalyst recovery unit 120 or the purification unit 150 for further
purification.
[0035] In order to further illustrate the methods in accordance
with the invention, the following examples are given, it being
understood that same are intended only as illustrative and in no
way limiting.
COMPARATIVE EXAMPLES
Comparative Example 1
Extraction of Heavy Ends with Water
[0036] A pilot plant for the production of HCC240fa (i.e.,
1,1,1,3,3-pentachloro-propane) had been running under normal
conditions for several weeks. A sample of the catalyst recovery
unit bottoms material was collected from the HCC240fa pilot plant.
A mixture was prepared by mixing 1.8 ml of the bottom fraction with
1.9 ml of deionized water. When shaken, this mixture formed a
single immobile phase, yellow in color. No free liquid was present,
and the solids adhered to the entire length of the 15-ml centrifuge
tube. After centrifuging the mixture for two minutes, there was 1.6
ml of clear yellow liquid under what appeared to be a single creamy
yellow colored solid phase amounting to about 2.3 ml.
[0037] This upper phase was actually a very thick slurry of solids
in the aqueous phase, but there was almost no freely mobile water
present. The slurry phase was sticky, quite viscous, and adhered to
glass. It is concluded that mixtures of water and bottom fraction
from the 1,1,1,3,3-pentachloropropane process are practically
intractable.
Comparative Example 2
Extraction of Reactor Effluent with Non-polar Solvents
[0038] A sample of reactor effluent from a HCC240fa pilot was used
as feedstock. The main component is HCC240fa. This effluent
contained much smaller amounts of the by-products
1,1,1,3,5,5-hexachloropentane (HCC-470jfdf) and
1,1,3,3,5,5-hexa-chloropentane (HCC-470nfaf).
[0039] Aliquots of this material were mixed with various non-polar
solvents in a 3:5 volume ratio, and then allowed to stand.
Thereafter, the mixtures were immersed in ice water for 20 minutes
and observed again. The results obtained, and shown below in Table
I, indicate that partial separation by this method is possible.
When the reactor effluent was cooled to about 0.degree. C. without
added solvent there was again a separation of phases, with the
lower phase amounting to about 83 vol % of the entire amount. Both
phases contained large amounts of iron, tributylphosphate (TBP) and
HCC-240fa, but the upper phase contained more of the first two
items and less of the latter.
1TABLE I Reactor Effluent Phase Separations Cyclo- Petroleum Butyl
Carbon Halocarbon pentane ether chloride tetrachloride oil Heptane
Room temperature 2-phases Yes Yes No No Yes Yes vol %, bottom 3 6
-- -- 96 4 Ice temperature 2-phases Yes Yes No Yes Yes Yes vol %,
bottom 3 6 -- 96 96 4
Comparative Example 3
Extractions Using Aqueous Solvents Containing Acids or Salts
[0040] The sample of reactor effluent described in Comparative
Example 2, above, was shaken with various aqueous liquids,
including 0.1 Molar (M) HCl, 0.5 M HCl, 1.6 M HCl, 1.9 M
H.sub.2SO.sub.4, 1.9 M H.sub.2SO.sub.4 with 7 M NaCl, 8.5 wt %
H.sub.3PO.sub.4, 24 wt % CaCl.sub.2, 16 wt % CaCl.sub.2 with 0.5 M
NaCl, 1.0 wt % NaCl, 5 wt % Na.sub.2SO.sub.3, 2.5 wt %
(NH.sub.4)H.sub.2PO.sub.4 with 2.5 wt % Na.sub.2SO.sub.3, 5 wt %
KBr, 5 wt % K.sub.2Cr.sub.2O.sub.7, 5 wt % NaHSO.sub.3 (pH=5), 5 wt
% NH.sub.4Cl. In each case, a large amount of solid was formed, so
much so that phase separation was severely hindered.
[0041] None of these methods provided a good way to commercially
separate the iron from the organic layer. In most cases, this is
due to the formation of a large amount of solid, which hinders
phase separation. The solids appeared to be a mixture of iron
compounds with TBP degradation products.
Comparative Example 4
Extractions of Heavy Ends with Aqueous Calcium Chloride and
Non-Polar Solvent
[0042] Perchloroethylene and a catalyst recovery unit bottoms
material (See, Table II below) were mixed in a 4:1 weight ratio,
and then shaken with aqueous 13 wt % calcium chloride solution and
sufficient calcium hydroxide (0.18 grams per gram) to raise the pH
of the aqueous phase to 11. A large amount of solids was formed.
The mixture was centrifuged, and the organic liquid was decanted.
The solids were extracted with perchloroethylene again. After
centrifuging and decanting again, the two perchloroethylene
extracts were combined and analyzed. Fully 30% of the original TBP
and chlorocarbons remained with the solids, presumably in the
liquid adsorbed thereupon. Thus, extraction with perchloroethylene,
calcium hydroxide, and calcium chloride solution resulted in poor
recovery of the chlorocarbons and TBP.
2TABLE II Composition of Bottoms Fraction Component Weight % Carbon
tetrachloride 0.1 HCC-24Of 19.5 HCC-470jfdf 5.8 HCC-470nfaf 4.7
Iron, total, as FeCl.sub.3 29.5 Other Organics 14.0 Phosphorous,
total, as TBP 49.6 TBP, by GC analysis 26.4
Comparative Example 5
Extraction with Hydrochloric Acid and Perchloroethene
[0043] Five (5) grams of bottom fraction material was dissolved in
8.06 grams per-chloroethene. This mixture was extracted six times
with about 2.2 grams of 21.9 wt % hydrochloric acid solution, for a
total of 13.27 grams aqueous extract. Very little solids were
formed. The organic phase remained black; the combined aqueous
phase was bright yellow. All of the original chlorocarbons remained
in the perchloroethene solution, as expected. The aqueous phase
contained 70% of the total iron from the bottom fraction feed, but
only about 1.2% of the total phosphorous.
EXAMPLES OF THE PRESENT INVENTION
Example 1
Steam Stripping of a Bottom Fraction
[0044] A sample of bottom fraction was obtained from the R&D
HCC240fa pilot plant. The heavy ends material contained about 42
weight percent HCC240fa, 45 percent HCC470jfdf plus HCC470nfaf and
the balance being tributylphosphate, iron, phosphorous compounds,
polymeric material and traces of low boiling chlorinated
hydrocarbon compounds. The heavy ends were subjected to batch steam
distillation at ambient pressure, and an average pot liquid
temperature of 106.degree. C. The overhead temperature averaged
99.degree. C. The total amount of water fed was 60 grams, for 52
grams of heavy ends feed.
[0045] The recovery of the HCC240fa content overhead was 98% of
that contained in the feed. The recovery of the HCC470jfdf plus
HCC470nfaf content overhead was about 9%. The recovered steam
distillation bottoms contained virtually all of the
tributylphosphate and 91% of the total HCC470jfdf plus HCC470nfaf
fed. There was no evidence of decomposition.
Example 2
Steam Stripping of a Bottom Fraction
[0046] Lab distilling equipment was set up with a pump to feed
liquid water at a constant rate, using a Snyder floating ball-type
distilling column having three stages. The distillation pot was a
500-ml indented round bottom flask, and the equipment was not
insulated. A sample of a bottom fraction was obtained. The bottom
fraction contained about 40 weight percent HCC240fa, 40 percent
HCC470jfdf plus HCC470nfaf. The balance included tributylphosphate,
iron, phosphorous compounds, polymeric material and traces of low
boiling chlorinated hydrocarbon compounds.
[0047] About 318 grams of this bottom fraction was placed in the
flask and heated, while mixing it vigorously with a shaft driven
stirrer. Water was fed over a period of about 2.2 hours and three
overhead fractions were collected. Thereafter, the water feed was
shut off, heating continued for another 0.8 hour while a rather
large amount of water present in the pot was driven off.
[0048] Taken together, the three overhead fractions contained 93%
of the HCC240fa feed from the bottom fraction, and 8.1% of the
total HCC470jfdf and HCC470nfaf fed. The cumulative ratio of water
overhead to HCC240fa overhead was 13 moles/mole. The cumulative
overhead HCC240fa/HCC470nfaf ratio was 19 moles/mole. The first and
third overhead aqueous layers were further titrated with sodium
hydroxide. They contained less than 19-ppm acid as hydrogen
chloride. The low acidity found surprisingly indicates that very
low levels of hydrolysis and dehydrochlorination occurred during
the steam stripping/separation process.
[0049] These results may be compared to the previous results
wherein both overhead fractions together contained 98% of the
HCC240fa fed, 9% of the two HCC470 isomers fed, and the overhead
water/HCC240fa ratio was 11. The cumulative overhead
HCC240fa/HCC470nfaf ratio was 17 moles/mole.
[0050] The distillation pot, upon cooling, contained two liquid
phases, organic and aqueous, with a trace of solids. The solids
were easily dislodged from the flask walls upon gently shaking the
pot contents. The aqueous phase contained about 10% iron,
presumably as ferric chloride.
Example 3
Steam Stripping of Bottom Fraction
[0051] The equipment described in Example 2, above, was modified by
removing the distillation column and insulating the pot and the
overhead take-off adapter. A sample of bottom fraction was
obtained. The composition of the bottom fraction and the steam
distillation procedure were similar to that described in Example
2.
[0052] About 304 grams of the bottom fraction was placed in the
flask and heated, while mixing it vigorously with a shaft driven
stirrer. A somewhat higher set point was applied to the pot
temperature controller during the water addition. The stirrer
stopped working for a period of about 0.7 hr, during the 2-hour
water addition. Thus, the pot temperature was erratic during that
time. Nevertheless, the experiment was successful in preventing a
build up of a large water phase in the pot during the distillation,
and after the water addition was complete, only 0.1-hour additional
heating sufficed to drive off the excess water. The average pot
temperature during the water addition was about 111.degree. C.,
compared to about 106.degree. C. in Example 2.
[0053] Two overhead fractions were collected. Together, they
contained 93% of the HCC240fa fed, and 11% of the two HCC470
isomers fed. The cumulative overhead water/HCC240fa ratio was 12
moles/mole, almost the same as in Example 2, above. The cumulative
overhead HCC240fa/HCC470nfaf ratio was 13 moles/mole.
[0054] Compared with the two previous experiments, it appears that
relatively more HCC470 isomer was carried out of the pot in this
experiment. While not wishing to be bound by any particular theory,
it is believed that this might be due to the higher average pot
temperature during the current distillation.
[0055] FIG. 3, illustrates that the ratio of the saturated vapor
pressure of HCC240fa to that of HCC470nfaf decreases with
increasing temperature. This ratio, taken together with the liquid
concentrations in the pot, should theoretically determine the
purity of the HCC240fa overhead.
[0056] Based on the findings in Examples 1-3, it was found that if
one wishes to improve the separation between HCC240fa and the
HCC470 isomers, one should operate the steam distillation at lower
pot temperatures, such as by operating at reduced pressure.
However, the ratio of the saturated vapor pressure of water to that
of HCC240fa increases with decreasing temperature. See, FIG. 4.
Thus, more water per pound of HCC240fa stripped would be needed to
operate at a lower temperature.
[0057] Upon review of the results, it can be seen that HCC240fa
halogenated alkane (1,1,1,3,3-pentachloropropane) was surprisingly
separated from the heavy ends in a fast and facile manner.
Moreover, the halogenated alkane recovered was significant.
[0058] While the invention has been described in detail with
reference to specific embodiments thereof, it will be apparent to
those skilled in the art that various changes and modifications can
be made, and equivalents employed, without departing from the scope
of the claims which follow.
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