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Патент USA US3029309

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Patented Apr. it?, iii-£32
any given temperature and nitrogen base concentration,
William D. Schaeffer, Pomona, Calif., assignor to Union
Oil Company of California, Los Angeles, Calif., a cor
poration of California
Filed May 3, 1960, Ser. No. 26,489
1S Claims. (Cl. 2611-674)
than can be obtained without the added ammonium salt.
Hence, the efficiency of the Werner complex is materially
increased in terms of pounds of Werner complex required
in the system per pound of feed throughput.
A second difiiculty involved in the foregoing processes
`revolves about the liquid-liquid recovery systems for sepa
rating non-clathrated feed components from the primary
rIhisinvention relates to methods for separating diffi
solvent, and for recovering the clathrated feed component
cultly separable compounds such as isomers, e.g., xylenes 10 by redissolving the clathrate in the primary solvent and
and the like, by selective clathration with heterocyclic
effecting a liquid-liquid phase separation.. Ordinarily, in
nitrogen base Werner complexes. More particularly, the
each of these phase separations, a secondary solvent is
invention is concerned with an improvement in those
employed which is miscible with the feed components,
clathration systems which employ aqueous alkaline sol
immiscible with the primary solvent, and a relatively poor
vent media in the clathration and/or declathration steps, 15 solvent for the heterocyclic base of the Werner complex.
and especially wherein liquid-liquid phase separations are
This materially reduces the loss of heterocyclic base to
relied upon for recovering the respective clathrated and
the product streams, Nevertheless, the heterocyclic-base
non-clathrated feed components from the aqueous alkaline
component of the dissolved Werner complex will still
media. In brief, it has been found that certain disad
distribute itself to some extent between the respective
vantageous features of these aqueous alkaline clathration 20 phases, and hence the raffinate and extract product
systems can be avoided or greatly mitigated by adding to
the aqueous alkaline media a substituted or unsubstituted
ammonium salt which is soluble in the alkaline medium.
The addition of these ammonium salts is found to give
streams will be contaminated to a greater or lesser extent
with the heterocyclic base. The process of this inven
tion provides a means for substantially increasing the se
lectivity of the primary solvent for the heterocyclic base,
several important advantages, principally, (l) an im 25 as opposed to the extract and/or raffinate product streams,
provement in the coefficient of solubility of the 'Werner
and the secondary solvents. This materially decreases
complex in the alkaline solvent media, (2) an improve
the expense and facilities required for recovering hetero
ment in the solvent selectivity of the alkaline solvent for
cyclic base from the extract and raliinate product streams.
the heterocyclic nitrogen base component of the Werner
The metal salt component of the Werner complexes is
complex, thereby reducing the loss of heterocyclic base 30 always a heavy metal salt which, in aqueous alkaline so
to the separated product streams, and (3) elimination of
lutions, will precipitate insoluble metal hydroxide to a
metal hydroxide precipitation in the alkaline system. To
greater or lesser extent. This precipitated metal hy
obtain all of these advantages to the maximum extent,
droxide tends to settle out at various points in the process
the ammonium sait employed should be a salt of the same
and may clog valves, pumps, filters and the like. By add
anion which occurs in the metal salt component of the
ing ammonium salts as described herein, it is found that
Werner complex used, eg., where a Werner complex of
precipitation of metal hydroxide is substantially com
nickel thiocyanate is employed, the preferred ammonium
pletely eliminated.
salt would be a thiocyanate.
Eliminating or minimizing the foregoing ditiiculties
More specifically, the process of this invention is an
constitute the principal objectives of this in
improvement over the basic processes described in my 40 vention, in addition to the overall objective of providing
prior applications, Serial No. 862,223, filed December
28, 1959, and Serial No. 3,058, filed January 18, i960.
Brieiiy, the process of Serial No. 862,223 involves carry
ing out the clathration and declathration steps in aque
or an aqueous volatile amine solu
a Werner complex clathration system which operates
with maximum efficiency and a minimum of expense.
Reference is now made to the accompanying drawing
which is a iiowsheet illustrating more concretely the basic
steps of the process. lIn the clathration step, (I) the
feed mixture is introduced through line 2, and a recycle
solution of Werner complex and ammonium salt dis
tion, while the process of Serial No. 3,058 involves carry
ing out the clathration in an aqueous alkanolarnine so‘ru
tion. While both of these processes offer important ad
solved in the primary solvent is introduced through line
vantages over previously known techniques, they have
4. `Small makeup quantities of ammonium salt, Werner
been found to entail certain diiiiculties. The clathration 50 complex and primary solvent may be admitted through
step is ordinarily effected by iirst dissolving the Werner
lines 6, 8 and 1li respectively. Clathration is effected
complex in the alkaline solvent (hereinafter called the
in this step by agitating the mixture, and either reducing
primary solvent), adding the feed mixture, and then
the temperature or removing sufficient volatile nitrogen
either reducing the temperature or removing volatile nitro
base therefrom, or both, to cause precipitation of the
gen base from the solution, or both, to thereby effect pre 55 solid clathrate. lt is ordinarily preferred to effect the
cipitation of the clathrate. The declathration step is car
clathration at moderate temperatures of about `_10"
ried out by redissolving the separated clathrate in the
-|-70° C., preferably between about 0° and 50° C. The
alkaline solvent at a relatively higher temperature. Un
solid clathrate contains the more readily clathrated com
less a large temperature differential is employed between
ponents of the feed mixture, while the less readily clath
the clathration and declathration steps, or unless substan 60 ratable components will remain dissolved or dispersed
tially all of the ammonia or volatile amine is removed dur
in the primary solvent phase. The resulting slurry is
ing clathration, some Werner complex will remain in solu
then transferred via line 12 .to clathrate separation step
tion throughout, and will not be eifectively utilized. By
II. This may involve a simple filtration, settling, or cen
the process of this invention, a more complete precipita
trifuging, or any other suitable method for separating
tion of Werner complex is obtained during clathration at 65 a liquid phase from a crystalline solid phase. The liquid
contain between about l0% and 90% by weight of nitro
phase from step II is sometimes hereinafter referred to
as mother liquor.
The resulting liquid phase filtrate is then transferred
gen base.
The ratio should be such as to provide the
desired differential solubility of Werner complex therein,
at the respective clathration and declathration tempera
tures. When using ammonia, suitable concentrations
may range between about 10% and 30% by weight in
via line 14 to rafñnate separation step III wherein the
non-clathrated portion of the feed is allowed to stratify
and separate. Normally, at this point, it is preferred
the clathration step and about 0% to 20% in the declath
to add (via line 16) the secondary solvent which pre
ferentially dissolves the non-clat'nratable feed compo
nents, and has a relatively low selectivity for the hetero
ration step. Operative ratios of ethanolamine
cyclic nitrogen base. Where the feed is composed of 10
may range between about 10% and 70% by weight in
aromatic hydrocarbons, the secondary solvent is prefer
ably a parañìnic or naphthenic hydrocarbon such as
pentane, heptane, octane, nonane, or mixed hydrocarbons
both stages.
In all cases, it is preferred to use sutñcient
withdrawn via line I3 and sent to secondary solvent re
covery step IV, which may be for example a fractional
mono-ethanolamine include for example, diethanolamine,
water to render the feed mixture substantially insoluble
in the primary solvent.
such as alkylate fractions. The solution of non-clath
Other alkanolamines which may be used in place of
rated feed components in the secondary solvent is then 15
triethanolamine, Z-amino-n-butanol, 2-amino-2-methyl-l
propanol, Z-methylamino ethanol, Z-ethylamino ethanol,
2-arnino-2-ethyl-L3-propanediol, 2-amino-2-methyl-1,3-
distillation wherein secondary solvent plus any dissolved
heterocyclic base is distilled overhead and returned to
step IV via line 16, and the non-clathrated feed compo
nents are recovered as bottoms via line Z0.
The stripped primary solvent phase from step III
propanediol, and the like. In general any lower alkanol
amine containing from two to about ten carbon atoms,
from one to three amino groups, and from one to three
hydroxyl groups may be employed, including primary,
(sometimes hereinafter referred to as lean mother liquor)
secondary, and tertiary amines. The operative ratios of
is then transferred via line 22 to clathrate dissolving
step V, to which the solid clathrate from step II is also 25 alkanolamine in the primary solvent may vary widely,
e.g., from about 2 percent to 75 percent by weight, the
transferred via line 24. In this dissolving step, the solid
remainder being water. Preferred ratios generally fall
clathrate is redissolved in the primary solvent phase,
Within the range of about l0 percent to 70 percent. The
either by raising the temperature to e.g., 50-l50° C., or
greater the concentration of alkanolamine in the solvent,
by adding more of the volatile amine or ammonia which
was removed in step I, or both. Upon dissolution of 30 the greater will be the solubility of Werner complex and
the clathrate, the clathrated component of the feed ordi
narily forms a separate liquid phase. This two-phase
mixture is then transferred via line 26 to extract sepa
feed mixture therein.
Other volatile bases (boiling below water) which may
be used in place of ammonia include for example, meth
ylarnine, dimethylamine, trimethylamine, methyl-ethyl
ration step VI, wherein the clathrated feed components
are separated by settling and decanting, or any other 35 amine, ethylamine, diethylamine, triethylamine, n-propyl
amine, isopropylamine, n-butylamine, isobutylamine, iso
desired method. Here again, the separation may be
`amylamine, and the like.
facilitated by adding a secondary solvent (via line 23),
In general, any water-soluble nitrogen base having a
which is preferably the same as the secondary solvent ern
dissociation constant greater than about 10-5, and greater
ployed in raffinate separation step III. The solution of
clathrated feed components in the secondary solvent is 40 than the dissociation constant of the heterocyclic base
removed via line 30 and sent to secondary solvent re
covery step VII, which again may be a fractional dis
tillation wherein secondary solvent plus dissolved hereto
cyclic base is distilled overhead and returned to step VI
via line 2S, and the clathrated feed components are
used in the Werner complex, may be used as the alkaline
component of the primary solvent.
The operative ammonium salts which may be used
herein comprise both organic and inorganic s_alts. Suit
able inorganic salts include for example ammonium thio
45 cyanate, ammonium chloride, ammonium sulfate, arn
monium nitrate, and the like. Suitable organic salts in
It is the foregoing extract separation step VI that dif
clude ammonium acetate, ammonium citrate, ammonium'l
fìculty is most often encountered in recovering hetero
oxalate, ammonium glycolate, -ammonium succinate and
cyclic base from the extract product. Since the primary
the like. Suitable substituted ammonium salts include
solvent is rich in dissolved Werner complex at this stage,
the concentration of dissolved heterocyclic base is larger 50 methyl ammonium thiocyanate, dimethyl ammonium'
thiocyanate, ethyl ammonium chloride, ethyl ammonium
than was present in raffinate separation step III. Hence
sulfate, ethanolammonium thiocyanate, ethanolammoni
the product in line 30 is relatively rich in heterocyclic
um chloride, ethanolammonium sulfate, ethanolammoni-V
base. This heterocyclic base is ordinarily recovered by
um cyanate, ethanolammonium cyanide, diethanolammo
azeotropic distillation along with `the secondary solvent.
This is entirely feasible, but sometimes will entail the use r nium thiocyanate, ethanolammonium acetate, and the like.
These salts may be used in proportions ranging between
of excessively large volumes of secondary solvent in
about 1% and 40% by weight of the primary solvent,
order to obtain complete recovery of heterocyclic base.
depending upon relative solubilities. Any amounts are
This problem is greatly alleviated where an ammonium
effective in some degree, and the preferred ratios gener
salt, preferably a thiocyanate, is dissolved in the primary
solvent phase, since this tends to decrease the amount of 60 ally range between about 15% and 30% by weight.
As previously indicated, it is preferred to use an arn
heterocyclic base which is extracted by the secondary
monium salt, the anion of which is the same as the anion
of the metal salt used in the Werner complex. Since the
The primary solvent phase separated in extract sepa
preferred salts in the Werner complexes are the thio
ration step VI contains substantially all of the original
Werner complex and ammonium salt which was used 65 cyanates, it is therefore preferred to use ammonium thio
cyanates. It is further preferred to use an ammonium
in step I. It is hence withdrawn via line 4 and re-V
salt’of the same nitrogen base used in the primary sol
cycled to clathration step I for reuse as above described.
The primary solvents employed herein are made up
vent. Thus, where ethanolamine is used in the primary
of water plus any suitable water-soluble organic or in 70 solvent, the preferred salt would be ethanolammonium
organic nitrogen base which is more strongly basic than
thiocyanate (ethanolammonium thiocyanate is conven
iently prepared by simply boiling an aqueous solution of
the heterocyclic nitrogen base of the Werner complex.
ammonium thiocyanate and ethanolamine, whereby am
The ratio of nitrogen base/water will vary widely de
pending upon the Werner complex used and the partic
monia is continuously volatilized from the mixture).
The Werner-type complexes employed herein are made
ular nitrogen base.' Generally, the primary solvent will
recovered as bo-ttoms via line 32.
up of at least three components. The fundamental unit
is a water-soluble salt of a metal having an atomic num
ber above l2 which is capable of form-ing coordinate
complexes of the Werner type. This includes primarily
the metals of groups iB, IIB, VEB, VHB, and VIH of the
periodic table, such for example as iron, cobalt, nickel,
copper, zinc, cadmium, silver, manganese, chromium,
mercury, and molybdenum. Aluminum may also be used
in some instances. The preferred metals lare those of
atomic numbers 25 to 28 inclusive, i.e., manganese, iron,
cobalt and nickel.
The anion of the metal salt may comprise any acid~
forming negative radical, the salts of which will form
relatively water-insoluble Werner complexes with hetero
cyclic nitrogen bases. The preferred anions are poly
atomic monovalent anions, such as thiocyanate, isothio
cyanate, azide, cyanate, isocyanate and cyanide. Other
operable anions include formate, acetate, propionate, and
the like.
The second major component of the Werner complexes
consists of one or more heterocyclic nitrogen base or
bases, which Vare bound to the central metal atom through
coordinate bonds. The operative complexes are mainly
of the tetra- and hexe-coordinate types, wherein the metal
atom is coordinated with four or six atoms of basic nitro~
gen. The heterocyclic base should be selected so as to
give a maximum selective absorption for the particular
compound which is to be absorbed into the crystal lattice
of the complex. For example, if it is desired to absorb
p-xylene, a very suitable nitrogen base is gamma-picoline. 30
Not all nitrogen bases are equally effective in forming
complexes which will absorb the desired component. For
example, the beta-picoline complex with nickel thio~
cyanate is not as effective as the gamma-picoline complex
for absorbing para-xylene, presumably because of the
steric eiîects of the 3-methyl group. However, the beta
picoline complex may be used advantageously for absorb
ing other compounds. The heterocyclic base should
therefore be selected by a judicious combination of theo
retical reasoning and actual testing of the complexes with 40
the particular mixture to be separated. The over-all
molecular dimensions of the heterocyclic base should pref
erably approximate the molecular size of the compound
wide ,variety of aromatic compounds.
tuted pyridines comprise the following:
4-methyl pyridine
Suitable substi~ Y
4-n-propyl pyridine
4-isopropyl pyridine
4-n-butyl pyridine
4-n-hexyl pyridine
4-vinyl pyridine
4-fluoro pyridine
4-chloro pyridine
4-bromo pyridine
¿1f-hydroxy pyridine
4-hydroxymethyl pyridine
4-methoxy pyridine
4-amino pyridine
Methyl isonicotinate
4~cyano pyridine
4-acetyl pyridine
4-chloromethyl pyridine
S-methyl pyridine
3-ethyl pyridine
3-m-propyl pyridine
3-isopropyl pyridine
3~n-butyl pyridine
3-vinyl pyridine
3~chloro pyridine
« 3-hydroxy pyridine
3-methoxy pyridine
3-ac‘etyl pyridine
3-cyano pyridine
Ethyl nicotinate
3,4-dirnethyl pyridine
3,4-diet'nyl pyridine
S-rnethyl, Ai--ethyl lpyridine
4-methyi, 3-ethyl pyridine
4-methyl, 3«n-hexyl pyridine
4-methyl, S-cyano pyridine
4~chloro, 3-methyl pyridine
¿1f-acetyl, 3-methyl pyridine
Ll-methoxy, 3-ethyl pyridine
`to be absorbed in the complex.
In general, any heterocyclic nitrogen base may be em
Many other similar examples could be cited, as will be
apparent to» those skilled in the `art, and the complexes
ployed which is sufficiently basic to form coordinate
complexes with the abovedescribed salts, but is weaker
may include only one such base, or a mixture of two
or more may be employed, in which case a mixed com«
as a base than the nitrogen base which is to be used in
plex may be formed.
The preferred Werner complexes of monovalent anion
salts of this invention may be designated by the following
general formula:
the primary solvent. This includes monocyclic and poly
cyclic compounds, wherein at least one of the heterocycles ì
contains from one to three hetero-N atoms. ln overall
size, the nitrogen base may contain from three to about
thirty carbon atoms, preferably from four to fifteen. ln
terfering functional groups such as _COOH should be
absent, but other more neutral, relatively non-coordinat
ing functional groups may be present such as halogen,
hydroxyl, nitro, alkoxy, aryloxy, amino, cyano, carbo
alkoxy, alkanoyl, acetyl, etc., provided such functional
wherein X is the metal -atoin as above defined, Z is the
heterocyclic nitrogen base, A is the anion as above defined,
y is a number from 2 to 6, and n is a number from l to 3.
Examples of suitable complexes which may be em
ployed are as follows:
groups are compatible with any functional groups present
in the mixture of compounds to be separated. Examples
of suitable bases include pyridine, substituted pyridines, 60
[CoM-picoline) l,(SCN)2]
[Fe (fy~picoline)4(SCN)2]
[Co (pyridine)4(OCN)2]
[Fe(pyrr01e)4(SCN) 2]
substituted pyrroles, piperidines, substituted piperidines,
and the like.
A particularly preferred class of heterocyclic bases are
the resonance-stabilized bases which contain one to three,
but preferably one, hetero-N atoms. Suitable examples 65
are pyridine, the picolines, pteridine, triazole, quinoline,
the quinaldines, isoquinoline, pyrimidine, pyrazine, pyrid
[Co(fy~picoline)4(CN) 2]
[Ni ('y~picoline ) 4 (NNN) 2]
[Ni ( 4-n-propylpyridine ) 4( SCN ) 2]
[Ni(isoquinoline) 4(SCN)2]
azine, and substituted derivatives of such compounds.
[Ni(4-ethylpyridine) l,(SCN)2]
Of this preferred class, a sub-group which is particularly 70
versatile and useful comprises the substituted pyridines,
and especially the 4-substituted, the 3~substituted, and the
Obviously, many other complexes similar to the above
3,4 disubstituted pyridines. These compounds form rela»
could be employed, not all or" which would give optimum
tively stable Werner complexes capable of selectively
separation of all mixtures but which should be selected
forming clathrates stable at room temperatures with a 75 to meet the specific peculiarities ofthe mixture concerned.
The amount of complex to be employed, relative to the
feed mixture, depends upon its specific capacity for ab
sorbing the particular feed component concerned, and
also upon the proportion of that component present in
may hence be present inthe feed components are as fol«
_CSO-metal, -SR,
the original mixture, as Well as upon the temperature of 5 -CONH2, wherein R is a hydrocarbon radical.
groups of a similar nature may be present.
clathration. The complexes are found in general to be
capable of absorbing between about 5% to 79% by
Examples of mixtures which may be separated herein
weight of absorbable compounds. Optimum eíi‘iciency
include ‘the following, but these examples are by no meansy
may require that more or less than this “stoichiomet'ric”
amount of complex be employed, depending upon its rela
(A) Hydrocarbon mixtures:
o-Ethyl toluene
p~Ethyl toluene
o-Ethyl toluene
m-Ethyl toluene
p-Ethyl toluene
tive capacity for other components in the mixture to be
resolved. In general, the amount of complex to be ern
ployed m-ay vary between about 0.25 and 20 parts by
weight per part of the feed component to be clathrated.
Smaller proportions of complex will generally yield a 15
purer extract, while the larger proportions'result in more
complete recovery of absorbable components from the
m-Ethyl toluene
feed mixture.
The term “clathrating” as used herein is intended to
mean any absorption or adsorption by the herein de
scribed Werner complexes of a sorbable organic com
pound, regardless of the mechanism by which such sorp
tion may take place. The terms “absorbate” or “extract”
refer to the total feed component which is absorbed into
20 Pseudocumene
philic reagents (cf. Remick A. E., Electronic Interpreta
tions of Onganic Chemistry, lohn Wiley, N.Y. 1943).
A wide variety of feed, mixtures may be resolved by
the methods described herein, i.e., substantially any mix
ture of organic compounds wherein the components differ
in molecular configuration, and preferably wherein at
least one component is substantially aromatic in charac
ter. By “substantially aromatic” is meant that at least
about 20% of the carbon atoms in the molecules to be
l-methyl anthracene
30 Prehnitene
' Prehnitene
clathrated are present as digits of an aromatic ring, the
or unsaturated aliphatic side-chains, or saturated or un-
term “aromatic” having the meaning hereinafter specified. 40 Methyl-cyclohexane
Any remaining carbon atoms may be present as saturated
saturated non-aromatic ring systems. Such compounds
may contain a total of from 4 to 60 carbon atoms, pref~
erably from 6 to 20.
A difference in “molecular conliguration,” as referred
to herein, means a difference in molecular size or shape
as a result of dilîerences in (l) the number of atoms per
Diphenyl methane
the clathrate, thus excluding the nitrogen bases, which are 25
bound by coordinate valences. The term “aromatic” is
intended to include all resonance-stabilized, cyclic, un
saturated compounds, which exhibit predominantly sub
stitution rather than addition reactions toward electro
2,3-dimethy1 pentane
Methyl cyclopentane
l-methyl phenanthrene
l-methyl anthracene
2~methyl anthracene
l-methyl naphthalene
2~methyl naphthalene
l-ethyl naphthalene
Z-ethyl naphthalene
p-Di-n-pro-pyl benzene
Hexamethyl benzene
p-Methyl styrene
m-Methyl styrene
p-Methyl styrene
o-Methyl styrene
molecule, and/or (2) the arrangement of atoms within
the respective molecules, and/ or (3) the size of the atoms 50 Chrysene
Methyl cyclopentane
present in the respective molecules.
(B) Hydrocarbon-1101141 ydrocarbon mixtures:
Any number and type of. functional groups may be
present in the feed components, provided that such groups
Z-methyl thiophene »
2,5 -dimethyl furan
are compatible with the Werner complex employed, i.e.,
that such groups do not change the chemical character 55
of the Werner complex. Generally excluded are those
compounds which are either so acidic as to decompose
the Werner complex, or so basic as to displace the hetero
cyclic base from the Werner complex. In general, the
pH of an aqueous mixture of the compounds to be sep
arated should fall between about 4 and the pH of an 60 (C) Non-hydrocarbon mixtures.'
aqueous solution of the heterocyclic base employed in the
o'Methyl toluate
Werner complex. When the compounds are too acidic or
p-Methyl toluate
too basic, it is feasible to prepare neutral derivatives
o-Methyl toluate
thereof, eg., salts, esters, ethers, amides, etc., and then 65 m-Methyl toluate
effect separation of the neutral derivatives.
p-Methyl toluate
m-Methyl toluate
procedures herein described result primarily in chemical
1-nitro naphthalene
decomposition, change, or disruption of the Werner com 70 2~nitro naphthalene
plex, as opposed to the desired clathration, the contact
l-amino naphthalene
Whenever any mixture of compounds is so incompati
ble with the Werner complex that the normal clathration
ing of such lmixtures with the Werner complex is by
delinition excluded from the temi “clathration” as used
herein and in the claims. Functional groups which gen
erally do not disrupt the normal clathration reaction, and 75 Nitro-benzene
p-Amino benzaldehyde
o-Amino benzaldehyde
- 9
o`Phenylene diamine
p-Phenylene diamine
This example illustrates the beneñcial effect of the
added ammonium saltsl in preventing precipitation of
metal hydroxide in the alkaline clathration system. Sev
eral diiîerent clathration solvent compositions containing
dissolved Ni(4-methylpyridine)4(SCN)2 were heated for
various lengths of time and then examined for Ni(OH)2
o-Methyl anisole
p-Methyl anisole
precipitation. The results were as follows:
p-Methyl thiophenol
m-Methyl thiophenol
Sodium p-cresylate
Sodium m-cresylate
Potassium terephthalate
Potassium isophthalate
mis-dimethyl @maine
Dimethyl isophthalate
Dimethyl terephthalate
Dimethyl isophthalate
Dimethyl orthophthalate
Definite pre
55% H2O _______________________ ‘_
0f NMO-Hh
0 30% ethanolamine .............. _.
312 N0 detectable
` 20% ethanolammonium acetate...
54.5% H2O ...................... -
27.7% ethanolamine _____________ _.
17.8%tethenolammonium thiocy~
ana e ......................... __
Substantially equivalent results are obtained when other
aqueous nitrogen base solutions, eg., ammonia, are used
in place of ethanolamine, and when other Werner com#
plexes of transitional metal salts are used, e.g., the cor
responding Werner complexes of cobalt, iron, manganese,
m-Methyl acetanilide
30 etc.
i m-Aminobenzenesulfon
Sodium anthranilate
Picolinic acid
Nicotinic acid
Sodium phthalamate
50% H10 ....................... __
35% ethanolamine .............. _-
Methyl benzoate
Ethyl benzoate
Sodium-l-methyl-4-naphtha- P_Aminobenzenesulfom
lene sulfonate
Sodium-l-methyl»3-naphtha- p-Methyl acetanilide
Heating Heating
Solvent Composition, Wt. percent Tgnòp., Period,
15 65% H2O """""""""""""" “}
Sodium o-toluene sulfonate Methyl salicylate
Sodium p-toluene sulfonate Methyl p-hydroxy bcnzoate
lene sulfonate
Table 1
This example demonstrates the beneficial ettects of the
added ammonium salts on clathration eñiciency, and on
35 selectivity of the primary solvent for the heterocyclic
base component of the Werner complex. In each of the
experiments reported in Table 2, the clathration tech~
nique consisted in dissolving the Werner complex in the
primary solvent at a suitable elevated temperaure of
40 75-90° C., stirring in the feed mixture, and then cool~
ing the mixture to 25° C. to precipitate the clathrate.
About 2 volumes of isooctane per volume of xylenes
It will be noted that some of the foregoing compounds
extracted was then added to facilitate separation of the
are fairly soluble in water, and thus in the primary clath
hydrocarbon phase, and the solid clathrate was filtered
ration solvent. In general this does not affect the 45 otî. The hydrocarbon phase of the filtrate (ratlinate)
clathration step, but may necessitate using different tech
was then separated and analyzed for xylene isomers and
niques for recovering the rañ‘inate and extract products
'y-picoline. The solid clathrate was then redissolved in
from aqueous solution. Conventional techniques such as
the stripped primary solvent at 75~90° C., and the solu
solvent extraction, distillation, fractional crystallization,
tion was extracted with isooctane. The resulting hydro
chemical scavenging, precipitation or the like may be Ul O carbon extract phase was then analyzed for xylene iso~
utilized for this purpose, the choice of the particular
mers and 'y-picoline. The results were as follows:
Table 2
Run N o.
Solvent Comp., Wt.
'y~Pico- Xylene Isomer Distribution
line, Wt.
para meta ortho Et Bz
Feed ______________ _.
1 ............ _
2 ............ _.
FDIÉÉÄÃ ------- ~- {Extraet__-
12.5% RNHsCl lh--- Rnf?nate..
3_¿ __________ __
51.5% IT20 ........ __
MEA ....... _.
Feed .............. ._
Extract--2. s
îtNaHßsoN ß .... _. asfaltate..
6. 5 52. 9 42.1
' Raflinate..
5 3
56.1% 1120....
._. Feed ______________ _. 14. 8`
31.4% NIEA ....... _„ Extract.“
57. 7
94. 5
0. 5
O. 6
0. 3
3. 4
2. 9
3. 4
1, 8
2. 5
47. 2
47. 5
3. 4
sa s
ß MEA=n1onoethanolarnlne
b RNHsCl=ethanolammonlum chloride
° RNHaS CN =ethanolamm0niun1 thiooyanate
method depending upon the particular compounds in- 70 Conditions:
volved, as will be understood by those skilled in the
The following examples are cited to illustrate more
Werner complex/p-xylene (wt. ratio)=l2.0
Solvent/Werner complex (wt. ratio)=3.0
concretely the results obtainable in the practice of this
It isY thus evident that the added ammonium salts have
process, but are not to be construed as limiting in scope. 75 a definite effect of increasing the relative solubility of
l»y-picoline in the primary solvent, thus decreasing loss of
picoline to the raffinate and extract hydrocarbon phases.
solvent comprises ethanolamine, and said ammonium salt
is ethanolammonium thiocyanate.
There is also a definite improvement in clathration ef
5. A process as definedV in claim 1 wherein said pri
mary solvent is aqueous ammonia, and said ammonium
iiciency, as indicated by the higher purity of the raffinate
m-xylene streams in runs Nos. 2 and 3.l While the ab
solute differences in purity may seem small, they are
salt is »ammonium thiocyanate.
relatively quite significant, for as compared to a resolu
tion efficiency' (alpha) of 56.4 in run No. 1, the resolu
feed mixture of organic compounds, the steps which com
prise (1) forming a solution of a heterocyclic nitrogen
tion efficiencies in runs 2 and l-3 were 81.0 and 95.4, re
base Werner complex in an aqueous solution of a lower
6. In a selective cla-thration process for resolving a
spectively. Thisris a reiiecrtion of the lesser solubility 10 alkanolamine and a water-soluble ammonium salt; (2)
mixing the resulting solution with said feed mixture; (3)
of the Werner complex at 25° C. in the modified s01
vents of runs 2 and 3, and thus of its more complete
precipitation and utilization as a clathrate-former.
cooling the resulting mixture to effect precipitation of a
solid clathrate of at least one component of said Vfeed
mixture with said Werner complex; (4) separating said
15 solid clathrate from the liquid phase; (5) recovering the
Other Werner complexes and ammonium salts can be
clathratedV feed component from said clathrate, and (6)
substituted for the ones used in Example II to obtain
recovering the vnon-clathrated feed component from the
resolutions of similar eiiiciency, but wherein isomers other
mother liquor of said clathration step.
than the paraxyiene are sometimes selectively clathrated.
7. A process as defined in claim 6 wherein said non
For example, in treating a xylene mixture containing 20 clathrated feed component is recovered from said liquid
20% p-xylene, 45.5 m-xylene, 19.3% o-xylene and 15.3%
phase «by liquid-liquid phase separation, thereby leaving
ethylbenzene, under conditions described in Example II,
a lean mother liquor.>
the isomers selectively clathrated are as follows:
Tabìe 3
8. A process as defined in claim 7 wherein said clath
rated feed component is recovered by dissolving said solid
25 clathrate in said lean mother liquor and subjecting the
Werner complex
Ammonium salt Selectivity
1. Ni(SCN)r-(3-cyano-pyridine)4 _ _ _
_ _ -_
2. NMSCN)2~(3-amido-pyridine)4._
____ RNHHSCN 1_--- para.
RNHaSCN 1_--.
- RNH3SCN1..__ para.
- k4 - y roxymet y pyri -
RNHSSCN 1...- ortho.
5. Mn (CN)r-(4-ethylpyridine)4 _______ __
RNHSCN _____ __
6. Mn(CNO)a~(4-ethy1pyridine)4 ...... _. RNHsCNO_-___ ortho.
7. Ni(SCN)r~(3 - ethy1-4~methy1 - pyri
8. Ni(S CN)r(4-aeetylpyridine)4 ....... __
NHrSCN _____ __
NHrSCN ..... -_
Et. Bz.
1 R~ethano1 radical.
resulting mixture to liquid-liquid phase separation.
9. A method as defined in claim 6 wherein said al
kanolarnine is mono-ethanolamine.
10. A method as defined in claim 6 wherein said hetero
30 cyclic base is a pyridine ring compound, and wherein
said metal salt is selected from the class consisting of Athe
thiocyanates, isothiocyanates, cyanates, isocyanates, cya
nides and azides of manganese, iron, cobalt «and nickel,
the yanion of said ammonium salt being the same as the
35 anion of said metal salt.
11. A method as defined in claim 6 wherein said
clathrated organic compound is a benzenoid hydrocar
12. A method as defined in claim 6 wherein said
The nickel tetra.=(4-methyl pyridine) dithiocyanate com 40 clathrated compound is p-xylene.
13. A method for resolving a mixture of disubstituted
plex of Example II can also be utilized for the separa
tion of non-hydrocarbon di-substituted benzene isomers.
benzene isomers including a para isomer which com
For example, in utilizing this complex according to the
procedure of Example II, the ortho-, meta- and para
isomers of mixed chloro-toluenes, dichloro benzenes,
Werner complex of a metal salt in an aqueous solution
of a lower alkanolamine and a water-soluble ammonium
prises (1) forming a solution of a lower 4-alkyl pyridine
salt; (2) admixing the resulting solution with said isomer
mixture; (3) cooling the resulting mixture to effect pre
ipitation of a solid clathrate of said para-isomer with
lectively clathrated.
said Werner complex; (4)` separating unclathrated iso
The complexes of the above examples may be em
ployed for effecting separations of other mixtures, and may 50 mers from the resulting mixture; (5) redissolving said
clathrate in lthe remaining aqueous alkanolamine solvent
be interchanged in `the various examples, to effect vary
phase at ya relatively high temperature thereby liberat
ing degrees of resolution. Likewise, many similar com
ing said para-isomer; and (6) separating the enriched
plexes and primary solvents could be substituted for those
para-isomer from the reconstituted Werner complex solu~
set forth in the examples.
The foregoing disclosure of this invention is not to be 55 tion.
toluidines, nitro~toluenes and methyl anisoles are effec
tively resolved, in each case the para-isomer being se
considered as limiting since many variations may be m-ade
14. A method as defined in claim 13 wherein said
resolved is contacted lwith a solution of a heterocyclic
ing p-xylene, which comprises (l) forming a solution
alkanolamine is mono-ethanolamine.
by those skilled in the art without departing from the
15. A method as defined in claim 14 wherein said
scope or spirit of the following claims.
metal salt is a thiocyanat-e of a metal of atomic number
1. In a selective clathration process for the separation 60 25 to 28, and said ammonium salt is ethanolammonium
of organic compounds, wherein the feed mixture to be
16. A process for resolving a xylene mixture includ
nitrogen base Werner complex'dissolved in a primary
of a 4-methyl pyridine Werner complex of a metal salt
solvent comprising an aqueous nitrogen base solution,
in an aqueous solution of a lower alkanolamine and a
wherein clathration is effected by altering the environ
water-soluble ammonium salt; (2) admixing and agitat
ment of said -mixture to effect precipitation of solid
ing the resulting solution with said xylene mixture while
Werner complex clathrate, the improvement which oom
cooling the mixture to effect precipitation of a solid
prises including in said primary solvent a minor propor
clathrate of p-xylene and said Werner complex; (3) add
tion of an added water-soluble ammonium sal-t.
70 ing to the resulting mixture a saturated hydrocarbon; (4)
separating solid clathrate -from the clathration mother
2. A process as defined in claim v1 wherein said am
liquor; (5) separating said mother liquor into a raiiinate
monium salt is ammonium 'thiocyanate
hydrocarbon phase and an aqueous alkanolamine sol
3. A process as defined in claim 1 wherein said am
Y 4 vent phase; (6) distilling said raffinate hydrocarbon phase
monium salt is ethanolammonium thiocyanate.
4. A process `as defined in claim 1 wherein said primary 75 to recover (a) an overhead fraction comprising 4-methyl
pyridine and said saturated hydrocarbon and (b) a higher
boiling fraction comprising raiñnate xylenes; (7) re
cycling said overhead fraction to said step (3); (8) re
dissolving said clathrate in said aqueous allranolamine
17. A method as defined in claim 16 wherein said
alkanolamine is mono-ethanolamine.
18. A method as deñned in claim 17 wherein said
metal salt is a thiocyanate of a metal selected from the
solvent phase at a temperature of `from about 50° to 5 class consisting of manganese, iron, cobalt and nickel,
about 150° C.; (9) adding »to the resulting mixture a
saturated hydrocarbon 'boiling between about 90° and
135 ° C.; (10) separating the resulting mixture into a
Werner complex solution phase and an extract hydro
carbon phase; (l1) distilling said extract hydrocarbon 10
phase to recover (a) an overhead fraction comprising 4
methyl pyridine and said saturated hydrocarbon and (b)
a higher boiling fraction comprising enriched p-Xylene,
and (12) recycling said last-named overhead fraction to
said step (9).
and said ammonium salt is ethanolammonium thio
References Cited in the file of this patent
et al. ________ __ July 2, 1957
_____________ __ July 9, 1957
____________ __ Aug. 26, 1958
____________ __ Mar. 3, 1959
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