Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the selective oxidation
of non-paraffinic hydrocarbons. More particularly, this
invention relates to the selective oxidation of aromatic
- compounds, particularly aromatic hydrocarbons includiny
aliphatic-substituted aromatic hydrocarbons, e.g. alkyl-
substituted aromatic hydrocarbons~and polycyclic aromatic
hydrocarbons.
;~ It is known that ruthenium tetroxide is a powerful
oxidizing agent, see U.S. Patents 3,409,649 (1968) and
~10 3,479,403 (1969), also J.O.C. 33, 1959 (1968), the article
by J. ~. Caputo ot al, olltitled "Synthesis and Ionization
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Constants of meta- and para-substituted cis-3-Phenylcyclo-
butanecarboxylic Acids" and Tetrahedron Letters- 47, 4729
(1967), the article by J. A. Caputo et al, entitled "The
Oxidation of Cyclobutanols and Aromatic Rings with
Ruthenium Tetroxide".
It is known that saturated aliphatic or paraffinic
hydrocarbons, particularly n-paraffinic hydrocarbons, such
as liquid n-paraffinic hydrocarbons having a carbon content
up to C23, such as in the range C7-C18, are useful as sub-
strates or feedstock for the production of a single cell
protein (SCP) involving the growth of selective microorganisms
on such substrates, see Hydrocarbon Processing, pages 104-108,
March 1969.
! I
In the utilization of paraffinic hydrocarbons as
a substrate for the growth of microorganisms for the produc-
:.; tion of SCP, it is desirable that the paraffinic hydrocarbons
. so employed be substantially free of non-paraffinic hydro-
carbons, particularly with respect to being substantially
free of aromatic compounds, such as aromatic hydrocarbons,
or have an aromaticcompound or non-paraffinic hydrocarbon
content such that the growth of the microorganisms is not
~¦ inhibited and/or the SCP material produced is readily har-
vested and is free of any undesirable materials, such as
aromatic compounds.
It is an object of this invention to provide a
method for the selective oxidation of one hydrocarbon type
ovcr anothcr hyclL-ocarbon type.
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It is another object of this invention to provide
a method for the separation of non-aliphatic and/or non-
saturated hydrocarbons, particularly aromatic hydrocarbons,
from saturated aliphatic hydrocarbons.
How these and other objects of this invention
are achieved will become apparent in the light of the
accompanying disclosure and with reference to the accompany-
ing drawing wherein is illustrated a process flow scheme
in accordance with this invention for the removal of aromatic
hydrocarbons from an n-paraffinic hydrocarbon stream.
In accordance with this invention, it has been
disco~ered that a high oxidation state ruthenium species,
i.e. higher than ruthenium dioxide, is useful as an oxidiz-
ing agent for the selective oxidation of non-aliphatic
and/or non-saturated hydrocarbons, particularly aromatic
compounds, such as aromatic hydrocarbons, in the presence
of saturated aliphatic hydrocarbons, such as n-paraffins.
The aromatic compounds, e.g. aromatic hydrocarbons which
may be present as an undesirable component in an aliphatic
paraffinic hydrocarbon stream, such as n-paraffinic hydro-
carbon-containing stream, are removed during or after
oxidation.
More specifically, in accordance with one embodiment
of the practices of this invention a stream, such as a hydro-
carbon stream containing saturated aliphatic hydrocarbons
together with non-saturated and/or non-aliphatic compounds,
e.g. hydrocarbons, particularly aromatic compounds, such as
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aromatic hydrocarbons, is contacted with a mixture comprising
a low oxidation state ruthenium species, e.g. ruthenium
dioxide, and an aqueous hypochlorite solution, such as an
aqueous sodium hypochlorite solution. The ruthenium species,
e.g. ruthenium dioxide, in the presence of the aqueous hypo-
chlorite solution is converted to a higher oxidation state
ruthenium species. In turn, the higher oxidation state
ruthenium species selectively oxidizes those compounds other
than the saturated aliphatic hydrocarbons, such as the
aromatic compounds and aromatic hydrocarbons, with the re-
sulting conversion of the aromatic compounds and aromatic
hydrocarbons to compounds which are readily removable, such
as carbon dioxide and/or water-soluble oxygenated derivatives.
More than one higher oxidation state ruthenium species, such
as ruthenates, perruthenates and mixtures thereof, may be
present or employed in the practices of this invention.
In the above-described treatment, aliphatic
paraffinic hydrocarbons, particularly the n-paraffins, are
refractory and are not, or tend not to be, oxidized, with
the result that the non-aliphatic and/or non-saturated
compounds, e.g. aromatic hydrocarbons, present along with the
saturated aliphatic or paraffinic hydrocarbons are selectively
oxidized. In the above-described operation involving selective
oxidation of the non-aliphatic and/or non-saturated compounds
in the presence of the paraffinic hydrocarbons, particularly
n-paraffinic hydrocarbons, the high oxidation state ruthenium
species which is derived from the admixture of a low oxidation
state ruthenium species, such as Ru02, and aqueous hypochlorite
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solution, is reconverted to the corresponding low oxidation
state ruthenium species, such as Ru02, which, in turn, is
reoxidized in the presence of the aqueous hypochlorite solu-
tion to additional higher oxidation state ruthenium species
which is again utilized as the active oxidizing agent for
the selective oxidation of the above mentioned compounds in
the presence of the paraffinic hydrocarbons. Accordingly,
only a small or catalytic amount of the low oxidation state
ruthenium species, such as Ru02, need be present along with
the aqueous hypochlorite solution in the practices of this
invention. As indicated, the ruthenium dioxide is present
in small, catalytically effective amounts; however, the
aqueous hypochlorite solution is employed in substantially
stoichiometric amounts relative to the compounds, e.g.
aromatic hydrocarbons, undergoing oxidation; usually
desirably the hypochlorite is present or utilized in
stoichiometric excess.
.
The overall chemical reaction sequence in accordance
with the practices of this invention may be exemplified as
set forth hereinbelow:
n-paraffinic n-paraffins + C02
and aromatic + (Ru02 + NaOCl ~ Ru04 + NaCl) ~ + water-soluble
hydrocarbons oxygenated compounds
Aromatic compounds and hydrocarbons which are
selectively oxidized include the substituted monocyclic
aromatic compounds and hydrocarbons, such as the aliphatic-
substituted benzenes, e.g. alkyl-substituted benzenes, the
alkenyl-substituted benzenes, the polycyclic aromatic com-
pounds and hydrocarbons including the fused polycyclic or
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polynuclear aromatic compounds and hydrocarbons and
derivatives, e.g. naphthalene, anthracene and phenanthrene,
and the unfused polynuclear aromatic compounds, such as the
biphenyls, and the corresponding aliphatic hydrocarbon.
substituted polycyclic or polynuclear aromatic hydrocarbons.
- Of special interest would be those aromatic compounds and
hydrocarbons which have a boiling point in the boiling point
range of aliphatic paraffinic hydrocarbons having a carbon
atom content in the range of about C6 to about C23, more or
less. Of special interest would be those aromatic hydro-
carbons which have a boiling point in the boiling point
range of the C7-C18 normal paraffinic hydrocarbons.
.,
The saturated or paraffinic aliphatic hydrocarbons,
which are refractory to oxidation in the practices of this,~
invention, include, as indicated hereinabove, the aliphatic
paraffinic hydrocarbons, particularly the n-paraffinic hydro-
carbons or n-alkanes. Saturated aliphatic hydrocarbons having
a carbon content in the range from about C6 up to about C23
containing in admixture therewith minor amounts of other non-
saturated and/or non-aliphatic hydrocarbons which may also
possess the same above-mentioned carbon content, e.g. aromatic
hydrocarbons, usually below about 10% by weight, e.g. in the
range 0.001 to about 2-5% by weight, are usefully treated in
accordance with the practices of this invention.
The saturated aliphatic hydrocarbons, useful for
the treatment in accordance with the practices of this inven-
tion, include the normally liquid saturated aliphatic hydro-
carbons, particularly the normally liquid n-paraffinic or
straight chain paraffinic hydrocarbons, i.e. such hydrocarbons
:
;` having a melting point up to about 100C., more or less,
such as a melting point in the range about -100 to about
75C
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-~ As indicated hereinabove, in the practices of
this invention the oxidation of the non-aliphatic and/or
non-saturated compounds, such as aromatic hydrocarbons, in
the presence of saturated aliphatic hydrocarbons, such as
the n-paraffinic hydrocarbons, is carried out by employing
as the oxidizing agent a mixture of one or more ruthenium
species or compound of a relatively low oxidation state,
such as ruthenium dioxide, and an aqueous hypochlorite solu-
tion. The aqueous hypochlorite solution, as also indicated
hereinabove, may comprise an aqueous alkali metal hypo-
chlorite solution, such as aqueous sodium hypochlorite,
aqueous potassium hypochlorite or mixtures thereof, or may
comprise an aqueous alkaline earth me*al hypochlorite, such
as calcium hypochlorite, or mixtures thereof or with an
aqueous alkali metal hypochlorite. Mixtures of one or more
of the above-described hypochlorites, including hypochlorous
acid, are useful in the practices of this invention. It is
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preferred, however, to employ aqueous sodium hypochlorite,
such as an aqueous sodium hypochlorite solution having a
concentration in the range of about 0.1 to about 15-20~ by
weight and at a suitable pH, such as a pH in the range from
about 5 to about 11. The above-indicated hypochlorite solu-
tion concentration range and pH would encompass suitable
aqueous hypochlorite solutions derived from hypochlorites
other than sodium hypochlorite and mentioned hereinabove.
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The ruthenium species, such as ruthenium dioxide,
employed in combination with an aqueous hypochlorite solu-
tion is preferably finely divided. Initially, if desired
and as indicated hereinabove, instead of ruthenium dioxide
other ruthenium species, organic or inorganic, might be
employed. Specifically, any organic or inorganic ruthenium
salt which has an anion which does not retard the formation
of the desired higher oxidation state ruthenium species
oxidizing agent in the presence of hypochlorite solution
would be useful, such as ruthenium halides, e.g. ruthenium
trichloride. The above-identified patents, U.S. 3,409,649
and U.S. 3,479,403, contain a listing of ruthenium compounds,
other than ruthenium dioxide, which are useful in the
selective oxidation operation in accordance with this
invention.
The selective oxidation reaction involving contact
between the saturated aliphatic (straight chain paraffinic)
hydrocarbon stream to be treated and purified and the aqueous
hypochlorite solution is conveniently carried out at ambient
pressure, although subatmospheric or superatmospheric pressures
may be employed during the reaction. The reaction is also
conveniently carried out at ambient temperatures, such as a
temperature at which the hydrocarbons undergoing treatment are
maintained in liquid phase, such as a temperature of about
15-30C., more or less. If desired~ a lower reaction or con-
tacting temperature, such as a temperature as low as about
10C. or lower, or a higher reaction or contacting temperature
as high as 75C. or higher, might be employed depending upon
the makeup of the hydrocarbons undergoing treatment and the
makeup of the hypochlorite solution employed in combination
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with the ruthenium species or compound for effecting the
selective oxidation of the non-aliphatic, non-saturated
hydrocarbons. The reaction should desirably be carried out
under conditions such that intimate contact is effected
between the hydrocarbons in the liquid phase with the
selective oxidizing system comprising the ruthenium species
or compound (ruthenium dioxide) and the hypochlorite. In
general, however, any suitable, practical operating tempera-
ture may be employed in the practice of this invention.
A suitable technique for effecting reaction between
the hydrocarbon stream undergoing treatment and the ruthenium-
hypochlorite oxidizing system would involve the addition of
the hydrocarbons and the ruthenium-hypochlorite oxidizing
system to a reactor while the resulting reaction admixture is
vigorously agitated. In this operation, only a small catalytic
amount of the ruthenium component of the oxidizing system need
be employed. The hypochlorite component of the oxidizing
system, as indicated hereinabove, can be added continuously
or intermittently or substantially all at one time. Since
the ruthenium component need only be employed in small
catalytic amounts and the higher oxidation state ruthenium
active oxidizing agent is regenerated during the reaction in
the presence of the hypochlorite, the reaction is essentially
controlled by the amount of hypochlorite added or present
during the reaction. If a stoichiometric amount of hypochlorite,
e.g. sodium hypochlorite, is added relative to the compounds
or hydrocarbons yndergoing oxidation, upon completion of the
reaction the added hypochlorite should be converted to the
corresponding salt, such as sodium hypochlorite to sodium
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chloride, and the ruthenium compound employed, such as
ruthenium dioxide, would appear as a solid, finely divided
ruthenium dioxide.
The contacting of the hydrocarbon stream with the
ruthenium-hypochlorite oxidizing system may be carried out
in a batch, single-step contacting operation or in a con-
current contacting operation or a countercurrent contacting
operation, such as in a tower packed with a permeable mass
of solid contact material. In general, any suitable means
or technique for effecting liquid-liquid and/or liquid
solids contact would be suitable for use in the practices
of this invention.
Upon completion of the reaction with resulting
conversion of the contaminating materials to be removed,
such as aromatic hydrocarbons, to innocuous products or
products which are readily removed, such as carbon dioxide
or water-soluble oxygenated compounds, the resulting reac-
tion admixture would be recovered and segregated. The
resulting treated hydrocarbons in the reaction mixture,
now comprising substantially only saturated aliphatic hydro-
carbons, e.g. n-paraffinic hydrocarbons, are withdrawn as
product after settling or separation from the aqueous phase,
such as the aqueous phase containing also the aqueous hypo-
chlorite or the depleted aqueous hypochlorite, i.e. sodium
chloride derived from sodium hypochlorite and the ruthenium
species or compound employed, e.g. finely divided solid
ruthenium dioxide. This aqueous phase containing aqueous
sodium chloride and finely divided ruthenium dioxide is then
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further treated, such as by filtration, for the removal
of the solid ruthenium dioxide which could be returned to
the reactor for contact with additional aqueous hypochlorite
to react or treat additional hydrocarbons in accordance
with the practices of this invention. The remaining segre-
gated or separated aqueous phase, which would contain, for
example, sodium chloride and water-soluble oxygenated
derivatives of the hydrocarbons undergoing oxidation, could
then be separately treated for the recovery of any values
therefrom.
Reference is now made to the drawing which
schematically illustrates one embodiment of the practices
of this invention directed to the selective oxidation of
aromatic hydrocarbons in the presence of n-paraffins.
As illustrated in the drawing, an aromatic hydro-
carbon-containing n-paraffin stream from a suitable source,
not shown, is supplied via line 10 to reactor 11 wherein it
is intimately mixed, employing agitator 12, with an admixture
of ruthenium dioxide supplied from a suitable source, not
shown, via line 14 with aqueous hypochlorite solution, such
as an aqueous sodium hypochlorite solution supplied from a
suitable source, not shown, via line 15, the resulting admix-
ture of ruthenium dioxide and aqueous sodium hypochlorite
being supplied to reactor 11 via line 16 for reaction with
the aromatic hydrocarbons within reactor 11. Vent line 18
is provided in the upper portion of reactor 11 to avoid any
undue pressure build-up within reactor 11.
There is withdrawn from the bottom of reactor 11 via
line 19 a reaction admixture comprising the n-paraffinic hydro-
carbons, ruthenium dioxide and depleted aqueous hypochlorite
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(sodium chloride). This reaction admlxture is supplied
via line 19 to oil-water separator 20 wherein, upon settling,
the resulting treated hydrocarbons, now comprising substan-
tially only n-paraffins, substantially free of aromatic
hydrocarbons, are removed from the upper portion of separator
20 via line 21. An aqueous phase comprising finely divided
ruthenium dioxide and sodium chloride is recovered from
the bottcm of aeparator 20 via line 22 and passed to
ruthenium dioxide separator or filter 24 from which the
ruthenium dioxide is separated and recovered via line 25.
The resulting. recovered ruthenium dioxide is recycled via
lines 25, 15 and 16 to reactor 11 along with additional
fresh aqueous sodium hypochlorite supplied to reactor 11 in
combination with the ruthenium dioxide via lines 15 and 16.
There is withdrawn from ruthenium dioxide separator
or filter 24 a separated aqueous phase or filtrate via line
26 comprising the depleted aqueous sodium hypochlorite
solution (now aqueous sodium chloride) along with any water-
soluble oxygenated compounds produced within reactor 11 by
the selective oxidation of the aromatic hydrocarbons by the
ruthenium tetroxide which is generated within reactor 11
by the combination of ruthenium dioxide and aqueous sodium
hypochlorite.
The above-described embodiment in the practice
of this invention made with reference to the drawing is
particularly applicable to a batch operation or process for
.removal of contaminating materials from an n-paraffinic
hydrocarbon stream.
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The following is an example of one embodiment
(batch process) of the practices of this invention for the
removal of aromatic hydrocarbons from an n-paraffinic hydro-
carbon stream, the n-paraffinic hydrocarbons being comprised
of n-paraffins having a carbon atom content (per molecule)
in the range from about C8 to about C16 and containing a
minor amount of aromatic hydrocarbons in the range of about
0.01-0.5 to about 2.5% by weight of the stream. The
n-paraffinic hydrocarbon stream in the amount of about 50
barrels (U.S.) is introduced into a reactor where it is mixed
vigorously with an aqueous admixture comprising ruthenium
dioxide and aqueous sodium hypochlorite. The aqueous sodium
hypochlorite is added in an amount in stoichiometric excess
relative to the aromatic hydrocarbons to be oxidized and
removed. The added aqueous sodium hypochlorite solution
conveniently has a concentration of about 5% by weight sodium
hypochlorite and is at a pH of about 9.5. As indicated,
finely divided ruthenium dioxide is added in a small amount,
about 0.5-10 pounds, more or less, along with the aqueous
hypochlorite solution to contact the hydrocarbons within the
reactor.
The reactants supplied to the reactor and the
resulting reaction admixture during the oxidation reaction
(selective oxidation of the aromatic hydrocarbons) are
usually at about ambient temperature or slightly more or
less than ambient temperature, such as in the range of
10-50C., more or less, depending upon the amount of aromatic
hydrocarbons in the hydrocarbon stream undergoing reaction and
the temperature of the reactants supplied to the reactor.
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Carbon dioxide formed due to oxidation of the aromatic hydro-
carbons along with other gases or vapors which might be formed
are vented upon the reactor.
Upon completion of the reaction which is carried
out with vigorous agitation, usually after contacting the
reaction mixture for a short period of time, about five
minutes to about one hour, the resulting reaction mixture is
withdrawn and the hydrocarbon phase separated from the
aqueous phase. The resulting separated hydrocarbon phase
now has a substantially reduced aromatic hydrocarbon content.
The aqueous phase containing sodium hypochlorite solution and
the ruthenium oxidizing species is treated with sufficient
reducing agent, e.g. methanol, to reduce the ruthenium
oxidizing species to ruthenium dioxide and the sodium hypo-
chlorite to sodium chloride. The resulting admixture is
filtered for the removal of ruthenium dioxide which can be
returned to contact additional hydrocarbons for the oxidation
of aromatic hydrocarbons along with added additional aqueous
sodium hypochlorite.
In this example or embodiment of the practices
of this invention, the treatment of the aromatic-containing
hydrocarbon stream, which is comprised predominantly of
n-paraffinic hydrocarbons, is carried out batchwise, i.e.
all the reactants, preferably in the desired amount, are added
at substantially the same time to the reactor. If desirable
or preferred, upon the addition of the hydrocarbons to be
treated substantially all of the ruthenium dioxide can be
added directly thereto separately or in admixture with the
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aqueous sodium hypochlorite solution which could be then
added gradually continuously or intermittently for a period
of time until the desired stoichiometric excess amount of
aqueous hypochlorite has been added, effective, in combina-
tion with ruthenium dioxide, to complete the oxidation of
the aromatic hydrocarbons. If desired, instead of adding
the hydrocarbons to be treated all at once or batchwise,
the hydrocarbons may be added over a period of time, inter-
mittently or continuously, to an admixture of ruthenium
dioxide and aqueous sodium hypochlorite. Under such con-
ditions, the aromatic hydrocarbons in the n-paraffinic
hydrocarbon stream would be rapidly oxidized.
Obviously, many variations of the above and other
techniques for bringing the reactants together for effecting
the oxidation of the undesirable contaminating components
are suitable in the practices of this invention. In the
practice of this invention, as indicated hereinabove, it is
desirable to add only sufficient aqueous hypochlorite solu-
tion to generate the powerful active high oxidation state
ruthenium species oxidizing agent, e.g. ruthenium tetroxide,
and to replenish the same until the contaminants in the
n-paraffinic hydrocarbon stream undergoing treatment have
been removed by oxidation or converted to readily removable
water-soluble oxygenated compounds.
Although in the practices of this invention
ruthenium dioxide is the preferred low oxidation state
ruthenium compound or species employed in association with
the aqueous hypochlorite solution, e.g. aqueous sodium
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hypochlorite, for the production of a relatively high oxida-
tion state ruthenium compound or species, as indicated
hereinabove, other ruthenium compounds or species are also
usefully employed in association with the a~ueous hypochlorite
solution for the production of the higher oxidation state
ruthenium species. Other suitable ruthenium compounds include
the ruthenium halides, e.g. ruthenium trichloride, and other
inorganic ruthenium salts, as well as the ruthenium salts
of fatty acids, such as the C2 and higher fatty acids,
ruthenium acetate, ruthenium propionate and ruthenium butyrate.
For a larger listing of suitable ruthenium compounds includ-
ing ruthenium-containing chelates useful in the practices of
this invention, see U.S. 3,409,649 as mentioned hereinabove.
Although emphasis has been placed on the selective
oxidation of aromatic hydrocarbons in the presence of
saturated aliphatic hydrocarbons in the practices of this
invention, compounds other than saturated aliphatic compounds
or, more particularly, organic compounds other than saturated
aliphatic hydrocarbons, are also suitably removed by selective
oxidation in accordance with the practices of this invention.
For example, compounds other than saturated aliphatic hydro-
carbons which would appear to be selectively oxidized in
accordance with the practices of this invention in the presence
of saturated aliphatic hydrocarbons, particularly n-paraffinic
hydrocarbons, include aromatic compounds, substituted aromatic
hydrocarbons, unsaturated aliphatic compounds, including
unsaturated aliphatic hydrocarbons, cycloaliphatic compounds,
including cycloaliphatic hydrocarbons, saturated or unsaturated.
In general, the practices of this invention are particularly
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applicable for the removal by selective oxidation of con-
taminating compounds in the presence of saturated aliphatic
compounds, particularly n-paraffinic hydrocarbons.
As will be apparent to those skilled in the art
in the light of the foregoing disclosure, many modifications,
alterations and substitutions are possible in the practice
of this invention without departing from the spirit or
scope thereof.
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