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Патент USA US3096392

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United States Patent 0
Patented July 2, 1963
Any alloy of sodium and potassium is suitable for use
in this invention, and it is preferred to use an alloy that is
liquid at ‘ambient temperature since it is more conveniently
handled, more easily brought into intimate contact with
Oscar L. Wright, McKces Rocks, John Wilson Mausteller, 5 the benzene or benzene fraction, and more adaptable to
Evans City, and Frank J. Vaucheri, Pittsburgh, Pa., as
continuous processing methods. Alloys of sodium and
signors to MSA Research Corporation, Pittsburgh, Pa.
potassium are commercially available at moderate cost.
No Drawing. Filed Apr. 13, 1960, Ser. No. 21,866
The sodium-potassium alloys that are ?uid at normal room
6 Claims. (Cl. 260-674)
temperatures contain between about 35 and 90 potassium.
This invention relates to the puri?cation of hydrocar 10 Neither sodium nor potassium alone are suitable, however,
bons, and more speci?cally to the removal of thiophene
and other impurities from benzene and benzene fractions
since they do not remove a detectable amount of thio
phene even at temperatures substantially above their
melting point.
by treatment with an alloy of alkali metals.
The following examples illustrate the remarkable effect
The main commercial source of benzene is coal; it is
formed by the pyrolysis operation known as coking. A 15 of the use of alloys of alkali metals. Benzene (500 cc.)
containing 300 ppm. thiophene and 2.0 grams of 56%
reasonably pure benzene fraction containing some other
aromatic hydrocarbons, organic sulfur compounds, or
ganic nitrogen compounds, and phenols is separated from
coal gas by well-known methods. Separation and puri?
Keg/14% Na alloy were charged to a 1 liter Morton ?ask
equipped with an agitator, and re?ux condenser.
mixture was agitated at re?ux temperature for one hour,
cation methods have been developed and are generally 20 and the benzene was then distilled and analyzed for thio
phene. Substantially all the thiophene was removed, and
used which successfully remove all of the denaturants ex
the re?ned benzene contained less than 1 ppm. thiophene.
cept thiophene; coke plant benzene generally contains 100
Similar results are obtained using alloys containing from
ppm. or more thiophene. Benzene is also obtained from
about 1 to 99% potassium. However, when 2.6 g. of
petroleum distillate fractions by a process of aromatiza~
tion. The benzene produced by this method is very pure, 25 molten potassium and 500 cc. of benzene containing 300
ppm. thiophene were contacted under identical condi
but generally contains 5-10 p.p.m. of thiophene.
For many purposes it is necessary or desirable to use
tions no thiophene was removed.
Similarly, 10.0 grams
of sodium dispersion (50% in xylene) contacted with
benzene that is substantially thiophene free. The catalytic
500 cc. of benzene under identical conditions removed no
hydrogenation of benzene, for example, requires the use
of catalysts which are poisoned by small amounts of thin 30 detectable amount of thiophene.
The method of this invention may be used equally well
phene or other sulfur compounds.
to purify benzene in which thiophene is the only substan
A number of methotds of purifying benzene and ben
tial impurity and benzene fractions which contain other
zene fractions have been developed which remove some
impurities. If the benzene fractions contain large
thiophene, or can remove substantially all of the thiophene
under special conditions. The most used method is the 35 amounts of other impurities which can easily be separated
acid wash process in which the benzene is intimately con
tacted with concentrated sulfuric acid. The contaminants
by distillation, it is generally more economical to at least
partially remove them by distillation before treatment with
sodium-potassium alloy. To illustrate, most of the water
are decomposed or polymerized and are removed with the
was removed by azeotropic distillation from an acid
acid sludge. ‘In order to obtain the desirable very low
concentration of thiophene, however, a large amount of 40 washed light oil having a composition of about 81% ben
zene, 13% toluene, 2% xylene, 2% other hydrocarbons,
sulfuric acid is required, and the process results in substan
2% H20 and 275 p.p.rn. thiophene. The light oil was
tial losses of benzene and the accumulation of large
reacted with 10.0 g. of 56% Na-44% K alloy (alloy/thic
amounts of useless acid sludge. Other methods such as
phene ratio of 80/1) at re?ux temperature for 15 min
hydrogenation or reaction with sodium at the necessary
utes, and the resultant light oil contained only 0.3 ppm.
high temperature, e.g., about 250° C., require high pres
45 \thiophene. This product can be used directly in applica
sures with the resultant expense and hazard.
tions ‘that are not adversely affected by other hydrocar
It is therefore an object of this invention to provide a
bons, or the mixture may be distilled to separate pure
simple, direct, inexpensive methotd of purifying benzene
thiophene-free benzene. The removal of two percent
and benzene fractions. A further object is to provide a
Water by reaction consumes about 15 grams of alloy, so
method of removing thiophene from benzene and ben
zene fractions that does not require high temperatures or 50 that about 25 g. of alloy is required to purify 500 cc. of
the crude acid-washed light oil. It is generally not eco
pressures. Another object is to provide a method of re
nomical or desirable to remove small or trace amounts of
moving thiophene from benzene or benzene fractions that
distillable impurities from benzene fractions before puri?
minimizes benzene losses. A still further object is to pro
cation by the method of this invention, because their re
vide a method of purifying benzene or benzene fractions
containing thiophene impurity by treatment with an alloy 55 moval by reaction consumes only a small amount of
of alkali metals. Other objects will become apparent
from the following speci?cation and claims.
This invention is based on our discovery that alloys of
About 1.5 parts by weight of alloy are consumed in re
moving 1 part of thiophene, so at least about 1.5 parts
of alloy for each part of thiophene are required to essen
sodium ‘and potassium rapidly and completely remove
thiophene from benzene or benzene fractions at low tem 60 tially remove all the thiophene. The exact mechanism
of the reaction is not known precisely, but virtually all
peratures with the formation of solid products that are
of the sulfur appears in the reaction product as metal sul
easily separable from the benzene.
According to this invention, benzene or a benzene frac
tion containing thiophene impurity is contacted with an
alloy of sodium and potassium in a batch or continuous
manner at a temperature as low as about 50° C.
?des. The organic fragment undoubtedly polymerizes,
because organic tars are found in the organic residue.
Carbon-ates and hydroxides are generally also found in
the residue, re?ecting the almost universal presence of
Water and carbon dioxide in benzene. Additional alloy is
alloy readily reacts with the thiophene impurity to form
a precipitate which is easily separated by decantation, ?l
consumed by other puri?cation reactions when the hen
tration, distillation and other conventional methods. The
zene contains impurities other than thiophene. There
alloy also reacts with other impurities such as carbon di 70 is essentially no loss of benzene due to reaction with the
sul?de, thioethers, Water, carbon dioxide and the like, to
form solid, easily separable products.
It is preferred to use at least about 3 parts alloy to each
ence of the sludge is not detrimental to the puri?cation
reaction, so that it can be removed in any convenient
part thiophene to accomplish rapid removal of the thio
phene and provide alloy for reaction with other trace im
manner at any time.
purities. Even larger excesses of alloy may be used, if
desired, to promote the rate of puri?cation. This is illus
trated by the results of reactions set forth in Table I.
E?ect of NaK/Tlzz'ophene Ratio on Rate 0)‘ Removal
at Reflux Temperature
Other methods of performing a continuous reaction
will be apparent to those familiar with the art. For exam
ple, impure benzene and alloy may be continuously fed
to a reactor maintained below the re?ux temperature, or
at a higher temperature under pressure, so that benzene
is not distilled from the reactor. The reaction mixture
can then be passed to a ?lter separating the sludge from
the puri?ed benzene. The benzene is readily separated
ppm. 'l‘hlophene in Benzene
Time Re
Removal 1
by distillation from any excess or unreacted alloy that
passes the ?lter.
It is generally desirable to use vigorous agitation when
carrying out the puri?cation reaction to promote contact
of the alloy and the benzene. High speed propellors or
Wt. Ratio Thiophene quired for
NaK/Thlo- Renmvctl Complete
in 15
75. 2
84. 4
__________ ._
specially designed dispersing impellors are especially de
sirable. Although increased agitation increases reaction
rate, practical reaction rates can be obtained with mod
20 erate mixing, as with a paddle-type agitator, when mod
erately high proportions of alloy are used; e.g. about 40
1 Puri?ed benzene containing about 0.4 to 0.7 ppm. thlophenc.
1 Couunerclul nitration grade benzene.
parts per part of thiophene. And with even higher pro
portions of alloy, e.g. 100 parts per part of thiophene,
agitation caused by boiling when the reaction is run at
When large excesses of the alloy are used to promote
reaction rate, only a small portion of the alloy is actually
consumed by the puri?cation reaction, and the excess is
e?ux temperature has been found adequate.
readily recoverable for reuse.
According to the provisions of the patent statutes, we
It is generally preferred to use a temperature between
have explained the principle and mode of practicing our
about 60 and 80° C., but higher or lower temperatures
invention, and have described what we now consider to
may be used if desired. At lower temperatures the rate
be its best embodiment. However, it is understood that
of reaction is slower, and below about 50° C. there is 30 within the scope of the following claims the invention
substantially no reaction. At higher temperatures super
may be practiced otherwise than as speci?cally described.
atmospheric pressure is developed by the benzene, and
We claim:
pressure equipment is required. The following reactions
1. A method of purifying benzene that contains thio
illustrate the effect of temperature on the rate of reaction.
phene impurity which comprises contacting said benzene
Benzene containing thiophene (210 ppm. thiophene)
in the liquid phase with an alloy of sodium and potas
sium at a temperature about 50° C. and 80° C., using
at least about 1.5 parts alloy for each part of thiophcne
to be removed, and recovering the puri?ed benzene.
and sufficient 56% K-44% Na alloy to give a 90-100:1
alloy to thiophene ratio were contacted in a Morton ?ask.
After 15 minutes contact at the desired temperature, the
benzene was rapidly distilled from the mixture and anal
2. A method according to claim 1 in which the tem
yzed for thiophene content. Thirteen percent of the 40 perature is between about 60° and the atmospheric pres
thiophene was removed at 50° C.; 30.6% removed at 60°
sure re?ux temperature.
C.; 52.5% removed at 68° C.; and 99.9% removed at
3. A method according to claim 1 in which the benzene
70° C. and higher temperatures. Thus longer reaction
and alloy are contacted with vigorous agitation.
times are required at lower temperatures for complete
4. A method according to claim 1 in which the alloy
removal of the thiophene, e.g. a period of several hours
contains between about 35 and 90% potassium.
is required at 50° C.
5. A method of purifying benzene that contains thio
The method of the invention is particularly adaptable
phene impurity which comprises continuously feeding said
to continuous methods, as is illustrated by the following
benzene and an alloy of sodium and potassium to a con
example. A l~liter Morton ?ask with suitable inlet and
tacting chamber, contacting said alloy and said benzene
outlet connections and equipped with a 4000 rpm. dis
in the liquid phase at a temperature between about 50°
persing impellor was used as a reactor. A charge of 500
C. and 80° C., using at least about 1.5 parts alloy for
m1. of benzene containing 200—300 p.p.m. thiophene and
each part of thiophenc to be removed, and continuously
10 g. of 56% K-44% Na alloy was heated to re?ux and
recovering the resultant puri?ed benzene.
agitated. Forty-two liters of the contaminated benzene
6. A method according to claim 5 in which the alloy
(average thiophene content 265 ppm.) was continuously
contains between about 35 and 90% potassium.
added to the ?ask at a rate of two liters per hour, and
puri?ed benzene Was continuously distilled from the ?ask.
References Cited in the ?le of this patent
An additional 0.5 g. of alloy was added with each liter
of benzene. Each liter of the puri?ed benzene was sam
pled and analyzed for thiophene content; the thiophcne
content ranged from 0.5 to 1.3 ppm. and averaged <1
ppm. for the entire 42 liters. The 42 grams of residue
sludge separated by ?ltration contained sul?des, hydrox
ides, and carbonates of the alkali metals, organic poly
mers, and about 10.5 g. of unreacted alloy.
The pres
Cross _______________ __ May 17,
Williams et al. _______ __ Dec. 19,
Hawkes et al __________ __ Nov. 27,
Berger et al. __________ __ Mar. 1,
Nobis et a] ___________ __ Nov. 15,
Clarke ______________ __ Apr. 11,
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