Note: Descriptions are shown in the official language in which they were submitted.
l~ Z4223
SPECIFICATION
This invention relates to a catalytic composite
particularly adapted to the conversion of difficultly
oxidizable mercaptans contained in a sour petroleum distillate.
Processes for the treatment of sour petroleum distillates
wherein the distillate is treated in contact with an oxidation
catalyst in the preeence of an oxidizing agent at alkaline
reaction conditions have become well known and widely practiced
in the petroleum refining industry. Said processe are typi-
cally designed to effect the oxidation of offensive mercaptanscontained in a sour petroleum distillate with the formation of
innocuous disulfide~--a proces~ commonly referred to as
sweetening. Depending on the source of the pe~roleum from
which the sour distillate was derived, the boiling range of
~the distillate itself, and pos3ibly the method of processing
the petroleum to produce the distillate, the distillates vary
widely with respect to the concentration, molecular weight
and complexity of the mercaptans contained therein, and the
sweetening process will vary accordingly.
One such process relates to olefin-containing
petroleum distillates. When said distillates are required
to be maintained in storage for any length of time, they
advantageously contain an oxidation i~nhibitor to obviate
gum fermation. The inhibitor is typically an oil-soluble
phenylenediamine. When the olefin-containing distillates
further contain a relatively small concentration of the more
:*~
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readily oxidizable mercaptans, the phenylenediamine acts as
a homogeneous oxygen transfer agent and, in the presence of
an alkaline reagent, promotes the oxidation of mercaptans
and the formation of disulfides. It i8 to be noted that at
least one-third of the mercaptans are consumed by interaction
with the olefin content of the sour distillate. The process is
commonly referred to as inhibitor sweetening. The homogeneous
phenylenediamine is not recoverable but is expended in the
sweetening process, and as the amount of the phenylenediamine
required to effect an economical rate of oxidation becomes
exce~sive, the process becomes ineffective as a sweetening
process and resort must be had to other means. It i8 known
that inhibitor sweetening, which is essentially a batch type of
process more suited to the treatment of sour distillates in
storage, functions only with respect to olefin-containing dis-
tillates--the olefin being essential to the inhibitor sweetening
process. Over a period of time, usually measured in hours or
days, the stored distillate may become sweetened depending
on the complexity and the concentration of the mercaptans con-
tained therein. While certain quaternary ammonium halides havebeen used in conjunction with the homogeneous phenylenediamine
catalyst to accelerate the sweetening process as shown in
U.S. Patent No. 3,164,544, the process remains subject to the
general limitations of inhibitor ~weetening. Thus, inhibitor
sweetening is generally ineffective with respect to sour
petroleum distillates containing mercaptans other than primary
and secondary mercaptans, and increasingly ineffective with
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respect to petroleum di3tillates conta~ning ln excess of
about 150 ppm. mercaptan sulfur.
Sour petroleum di~tillates that do not re~pond to
inhibitor sweetening, i.e., those containing the higher
molecular weight and/or more complex mercaptans, or higher
mercaptan concentrations, are commonly treated in contact with
a heterogenous metal phthalocyanine catalyst dispersed in an
aqueous caustic solution to yield a ~sweetened pr~uct.
The sour distillate and the catalyst-containing aqueous caustic
solution provide a liquid-liquid ~ystem wherein mercaptans are
converted to disulfides at the interface of the immer~ible
solutions in the presence of an oxidizing agent--u~ually air.
This liquid-liquid system is invariably employed in a con-
tinuous type of operation requiring a substantially lesser
contact time than re~uired of inhibitor sweetening. The
metal phthalocyanine catalyst, which i~ recovered and recycled
for continuous use, is not limited to use in conjunction with
an olefin-containing petroleum distillate, but is equally
effective with regard to olefin-free di~tillates to provide
a doctor sweet product.
Certain of the higher boiling 30ur petroleum dis-
tillates, generally boiling in excess of about 135C~
contain highly hindered branched chain and aromatic thiols,
and/or higher molecular weight tertiary and polyfunctional
mercaptans, which are at most only partially soluble in the
catalyst-containing caustic solution of the liquid-liquid
treating system. Sour petroleum distillates containing these
3L~Z~Z3
more difficultly oxidizable mercaptans are more effectively
treated in contact with a metal phthalocyanine cataly~t dis-
posed or impregnated on a high Qurface area adsorptive support
or carrier material-~u~ually an activated charcoal. The
distillate is treated in contact with the supported metal
phthalocyanine catalyst at oxidation conditions in the presence
of an alkaline reagent. One such process is described in
U.S. Patent No. 2,988,500~ The oxidizing agent is most often
air admixed with the distillate to be treated, and the alkaline
reagent is most often an aqueous caustic solution charged
continuously to the process or intermitten~ly as required to
maintain the catalyst in a caustic-wetted state.
It is an object of this invention to present a novel
catalytic composite particularly useful in the treatment of
sour petroleum distillates containing the more difficultly
oxidizable mercaptans.
In one of its broad aspects, the present invention
embodies a catalytic composite comprising a metal chelate mer-
captan oxidation catalyst and a quaternary ammonium compound im-
pregnated on a solid adsorptive support, said quaternary ammoniumcompound being represented by the structural formula
Rl
, 2 X
R
wherein R is a hydrocarbon radical containing up to
20 carbon atoms and selected from the group consisting of
alkyl, cycloalkyl, aryl, alkaryl and aralkyl, Rl is a
3L~2~223
substantially straight-chain alkyl radical containing from
5 to 20 carbon atoms, R2 is selected from the group con-
sisting of aryl, alkaryl and aralkyl, and X is an anion
selected from the group consisting of chloride, bromide,
iodide, fluoride, nitrate, nitrite, sulfate, phosphate,
acetate, citrate, tartrate and hydroxide.
The metal chelate mercaptan oxidation catalyst
employed as a component of the catalytic composite of this
invention can be any of the various metal chelates known to
the treating art as effective to catalyze the oxidation of
mercaptans contained in a sour petroleum distillate with
the formation of polysulfide oxidation products. Said che-
lates include the metal compounds of tetrapyridinoporphyrazine
described in U.S. Patent No. 3,980,582, e.g., cobalt tetra~
pyridinoporphyrazine; porphyrin and metaloporphyrin catalysts
as described in U.S. Patent No. 2,966,453, e.g., cobalt tetra-
phenylporphrin sulfonate; corriniod catalysts as described in
U.S. Patent No. 3,252,892, e.g., cobalt corrin sulfonate; and
chelate organometallic catalysts such as described in U.S.
Patent No. 2,918,426, e.g., the condensation product of a~
aminophenol and a metal of Group VIII. Metal phthalocyanines
are a preferred class of metal chelate mercaptan oxidation
catalysts.
The metal phthalocyanines employed as a mercaptan
oxidation catalyst generally include magnesium phthalocyanine,
titanium phthalocyanine, hafnium phthalocyanine, vanadium
phthalocyanine, tantalum phthalocyanine, molybdenum phthalo-
cyanine, manganese phthalocyanine, iron phthalocyanine, cobalt
phthalocyanine, nickel phthalocyanine, platinum phthalocyanine~
palladium phthalocyanine, copper phthalocyanine, silver phthalo-
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cyanine, zinc phthalocyanine and tin phthalocyanine. Cobalt
phthalocyanine and vanadium phthalocyanine are particularly
preferred. The metal phthalocyanine is most frequently em-
ployed as a derivative thereof, the commercially available
sulfonated derivatives, e.g., cobalt phthalocyanine monosul-
fonate, cobalt phthalocyanine disulfonate or a mixture the~e-
of being particularly preferred. The sulfonated derivatives
may be prepared, for example, by reacting cobalt, vanadium
or other metal phthalocyanine with fuming sulfuric acid.
While the sulfonated derivatives are preferred, it is under-
stood that other derivatives, particularly the carboxylated
derivatives, may be employed. The carboxylated derivatives
are readily prepared by the action of trichloroacetic acid
on the metal phthalocyanine.
The quaternary ammonium compound component of the
catalytic composite of this invention is represented by the
structural formula
R
l +
R - N - R2 X
R
wherein R is a hydrocarbon radical containing up to 20 car-
bon atoms and selected from the group consisting of alkyl,
cycloalkyl, aryl, alkaryl and aralkyl, Rl is a ~ubstantially
straight chain alkyl radical containing from 5 to 20 carbon
atoms, R2 is selected from the group consising of aryl,
alkaryl and aralkyl and X is an anion selected from the
group consisting of halide, nitrate, nitrite, sulfate, phos-
phate, acetate, citrate, tartrate and hydroxide. Rl is
~P2~2Z3
is preferably an alkyl radical containing from 12 to 18 car-
bon atoms, R2 is preferably benzyl, and ~ is preferably
chloride or hydroxide. Preferred quaternary ammonium com-
pounds thus include quaternary ammonium chlorides and
quaternary ammonium hydroxides such as benzyldimethyldodecyl-
ammonium chloride, benzyldimethyltetradecylammonium chloride,
benzyldimethyLhexadecylammonium chloride, benzyldimethyloctade-
cylammonium chloride, benæyldimethyldodecylammonium hydroxide,
benzyldimethyltetradecylammonium hydroxide, benzyldimethyl-
hexadecylammonium hydroxide, benzyldimethyloctadecylammonium
hydroxide, and the like. Other suitable quaternary ammonium
compounds include phenyldialkylpentylammonium chloride,
phenyldialkylhexylammonium chloride, phenyldialkyloctylammonium
chloride, phenyldialkyldecylammonium chloride, phenyldialkyl-
dodecylammonium chloride, phenyldialkyltetradecylammonium
chloride, phenyldialkylhexadecylammonium chloride, phenyldi-
alkyloctadecylammonium chloride, phenyldialkyleicosylammonium
chloride, naphthyldialkylpentylammonium chloride, naphthyldi-
alkylhexylammonium chloride, naphthyldialkyloctylammonium
chloride, naphthyldialkyldecylammonium chloride, naphthyldi-
alkyldodecylammonium chloride, naphthyldialkyltetradecyl-
ammonium chloride, naphthyldialkylhexadecylammonium chloride,
naphthyldialkyloctadecylammonium chloride, benzyldialkylpentyl-
ammonium chloride, benzyldialkylhexylammonium chloride, benzyl-
dialkyloctylammonium chloride, benzyldialkyldecylammonium
chloride, benzyldialkyleicosylammonium chloride, tolyldialkyl-
pentylammonium chloride, tolyldialkylhexylammonium chloride,
tolyldialkyloctylammonium chloride, tolyldialkyldecylammonium
- ~Z4ZZ3
chloride, tolyldialkyldodecylammonium chloride, tolyldialkyl-
tetradecylammonium chloride, tolyldialkylhexadecylammonium
chloride, tolyldialkyloctadecylammonium chloride, tolyldi-
alkyleicosylammonium chloride, diphenylalkylpentylammonium
chloride, diphenylalkylhexylammonium chloride, diphenylalkyl-
octylammonium chloride, diphenylalkyldecylammonium chloride,
diphenylalkyldodecylammonium chloride, dipphenylalkyltetra-
decylammonium chloride, diphenylalkylhexadecylammonium chloride,
diphenylalkyloctadecylammonium chloride and diphenylalkyleicosyl-
ammonium chloride, ~ well as the corres-
ponding fluoride, bromide, iodide, sulfate, nitrate, nitrite,
phosphate, acetate, citrate, tartrate and hydroxide compounds,
wherein the alkyl radical is selected from the group consisting
of methyl, ethyl and propyl.
The preferred benzyldimethylalkylammonium chlorides
are commercially available from the Mason Chemical Company
-y under the tradename Maquats. However, said benzyldimethyl-
alkylammonium chlorides can be prepared by initially reacting
ammonia and a Cl~-C18 carboxylic acid in contact with silica
gel at about 500C. to form a C12-C18 nitrile. The nitrile
is then reduced with hydrogen in contact with a nickel cat-
alyst at about 140C. The resulting C12-C18 am~ne is separated
from the reaction mixture and reacted with a 2 molar exce~s of
methyl chloride. After neutralization of the reaction mixture,
the amine is further reacted with 1 mole equivalent of benzyl
chloride to yield the desired benzyldimethylalkylammonium chloride.
The methyl chloride as well as the benzyl chloride, is suitably
reacted with the amine in methanolic solution at a temperature
~L~Z4Z23
of about 150C. The product can be used as is or further
treated over activated charcoal to remove impurities.
The solid adsorbent support or carrier material em-
ployed herein can be any of the well known solid adsorbent
materials generally utilized as a catalyst support or carrier
material. Preferred adsorbent materials include the various
charcoals produced by the destructive distillation of wood,
peat, lignite, nutshells, bones, and other carbonaceous matter,
and preferably such charcoals as have been heat treated or
chemically treated or both, to form a highly porous particle
structure of increased adsorbent capacity, and generally de-
fined as activated carbon or charcoal. Said adsorbent mate-
rials also include the naturally occurring clays and silicates,
e.g., diatomaceous earth, fuller's earth, kieselguhr, attapul-
gus clay, feldspar, montmorillonite, halloysite and kaolin,
and also the naturally occurring or synthetically prepared
refractory inorganic oxides such as alumina, silica, zirconia,
thoria and boria, or combinations thereof like silica-alumina,
silica-zirconia and alumina-zirconia. Any particular solid
adsorbent material is selected with regard to its stability
under conditions of its intended use. For example, in the
treatment of a sour petroleum distillate heretofore described,
the solid adsorbent carrier material should be insoluble in,
and otherwise inert to, the petroleum distillate at the alka-
line reaction conditions existing in the treating zone. In
the latter case, charcoal, and particularly, activated charcoal,
is preferred because of its capacity for metal phthalocyanine,
and because ~f its stability under treating conditions.
--10--
- ~24;~23
The quaternary ammonium compounds of this invention,
as well as the metal chelate mercaptan oxidation catalyst,
particularly the metal phthalocyanines, are readily adsorbed
on the solid adsorbent support. The quaternary ammonium salt
may comprise up to 50 wt. % of the catalytic composite. In
the sweetening process herein contemplated, the quaternary
ammonium salt will suitably comprise from 1 to 50 wt. %, and
preferably from 5 to 35 wt. % of the said composite. In
general, up to about 25 wt. % metal phthalocyanine can be
adsorbed on the solid adsorbent support and still form a
stable catalytic composite. A lesser amount in the range of
from 0.1 to 10 wt. % generally forms a suitabl~ active cata-
lytic composite, with a range of 0.1 to 2.0 wt. % generally
being preferred. The activity advantage derived from metal
phthalocyanine concentrations in excess of 2 wt. ~ has not
heretofore warranted use of higher concentrations. However,
in view of the significant increase in activity derived from
the use of the quaternary ammonium salt of this invention in
conjunction with minimal metal phthalocyanine concentrations,
it is contemplated that the higher concentration will become
effective to promote a further increase in the rate of mercap-
tan oxidation, particularly with regard to the hard to treat
sour petroleum distillates.
The quaternary ammonium compound and the metal chelate
components can be impregnated on the solid adsorbent support
in any conventional or otherwise convenient manner, and said
components can be impregnated on said support simultaneously
1~242Z3
from a common aqueous or alcoholic solution and/or dispersion
thereof, or separately and in any desired sequence. The
impregnation process can be effected utilizing oonventional
techni~ues whereby the support in the form of spheres, pills,
pellets, granules or other particles of uniform or irregular
size or shape, is soaked, suspended, dipped one or more times,
or otherwise immersed in an aqueous or alcoholic impregnating
solution and/or dispersion to adsorb a given quantity of the
ammonium compound and metal chelate components thereon. One
preferred method involves the use of a steam-jacketed rotary
dryer. The adsorbent support i5 immersed in the impregnating
solution and/or dispersion contained in the dryer and the sup-
port is tumbled therein by the rotating motion of the dryer.
Evaporation of the solution in contact with the tumbling sup-
port is expedited by applying steam to the dryer jacket. In
any case, the resulting composite is allowed to dry under
ambient temperature conditions, or dried at an elevated tem-
perature in an oven, or in a flow of hot gases, or in any
other suitable manner.
An alternative and convenient method for adsorbing
the ammonium compound and metal chelate components on the solid
adsorbent support comprises predisposing the support in a
sour petroleum distillate treating zone or chamber as a fixed
bed and passing the ammonium compound-metal chelate impreg-
nating solution and/or dispersion through the bed in order to
form the catalytic composite in situ. This method allows
the solution and/or dispersion to be recycled one or more
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times to achieve a desired concentration of the ammonium
compound and metal chelate components on the adsorbent sup-
port. In still another alternative method, the adsorbent
may be predisposed in said treating zone or chamber, and the
5- zone or chamher thereafter filled with the impregnating solu-
tion and/or dispersion to soak the support for a predetermined
period.
In the process of sweetening a sour petroleum dis-
tillate, it has heretofore been the practice to oxidize the
mercaptans contained therein in the presence of an alkaline
reagent. A supported mercaptan oxidation catalyst is typi-
cally initially saturated with the alkaline reagent, and the
alkaline reagent thereafter passed in contact with the catalyst
bed, continuously or intermittently as required, admixed with
the sour petroleum distillate. Any suitable alkaline reagent
may be employed. An alkaline metal hydroxide in aqueous solu-
tion, e.g., sodium hydroxide in aqueous solution, is most
often employed. The solution may further comprise a solubilizer
to promote mercaptan solubility, e.g., alcohol, and especially
methanol, ethanol, n-propanol or isopropanol, and also phenols
or cresols. A particularly preferred alkaline reagent is an
aqueous caustic solution comprising from 2 to 30 wt. % sodium
hydroxide. The solubilizer, when amployed, is preferably
methanol, and the alkaline solution may suitably comprise from
2 to 100 vol. % thereof. Sodium hydroxide and potassium
hydroxide constitute the preferred alkaline reagents, others
including lithium hydroxide, rubidium hydroxide and cesium
.
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~L~242Z3
hydroxide are also suitably employed. When the catalytic
composite of the present invention comprises a quaternary
ammonium hydroxide component, those distillates containing the
more readily oxidized mercaptans can be treated in the absence
of added alkaline reagent.
The process of this invention can be effected in
accordance with prior art treating conditions. The process
is usually effected at ambient temperature conditions, although
higher temperatures up to about 105C. are suitably employed.
Pressures of up to 69 atmospheres are operable, although atmo-
spheric or substantially atmospheric pressures are entirely
suitable. Contact times equivalent to a liquid hourly space
velocity of from 0.5 to 10 or more are effective to achieve a
desired reduction in the mercaptan content of a sour petroleum
distillate, an optimum contact time being dependent on the size
of the treating zone, the quantity of catalyst contained therein,
and the character of the distillate being treated.
As previously stated, sweetening of the sour petro-
leum distillate is effected by oxidizing the mercaptan content
thereof to disulfides. Accordingly, the procesq is effected
in the presence of an oxidizing agent, preferably air, although
oxygen or other oxygen-containing gas may be employed. The
sour petroleum distillate may be passed upwardly or downwardly
through the catalyst bed. The sour petroleum distillate may
contain sufficient entrained air, but generally added air is
admixed with the distillate and charged to the treating zone
concurrently therewith. In some cases, it may be of advantage
-14-
~2~2Z3
to charge the air separately to the treating zone and counter-
current to the distillate separately charged thereto.
The catalytic composite of this invention is both
active and stable. Accordingly, the composite can be used
in a fixed bed to treat large volumes of sour petroleum dis-
tillates, especially those distillates containing the more
difficultly oxidizable mercaptans. As heretofore mentioned,
the quaternary ammonium compound and metal phthalocyanine com-
ponents of the catalytic composite of this invention are readily
adsorbed on the solid adsorbent support component thereo~.
Thus, any of the said quaternary ammonium compound or metal
phthalocyanine components which may in time be leached from
the support and carried away in the reactant stream can be
easily restored to the catalytic composite in situ by intro-
ducing either or both of said components to the sweetening
process, for example, in admixture with an alkaline reagent,
to be adsorbed on the solid adsorbent support in the treating
zone.
The following examples are presented in illustration
of one preferred embodiment of this invention and are not in-
tended as an undue limitation on the generally broad scope
of the invention as set out in the appended claims.
EXAMPLE
_ _
In the preparation of the catalytic composite of this
invention, an impregnating solution and/or dispersion was formu-
lated by adding 0.75 gms of cobalt phthalocyanine monosulfonate
and 23.5 gms of a 50% alcoholic solu~ion of dimethylbenzyl-
4223
alkylammonium chloride to 250 ml of deionized water in a
rotary steam evaporatorO The benzyldimethylalkylammonium
chloride consisted of benzyldimethyldodecylammonium chloride
(61%), benzyldimethyltetradecylammonium chloride (23~),
benzyldimethylhexadecylammonium chloride (11%), and benzyldi-
methyloctadecylammonium chloride. 250 cc o~ 10 x 30 mesh
activated charcoal particles were immersed in the impregnating
solution and tumbled therein for 1 hour by the rotating mo-
tion of the evaporator. Steam was thereafter applied to the
evaporator jacket, and the impregnating solution was evapor~
ated to dryness in contact with the tumbling charcoal par-
ticles over a one hour period.
The catalytic composite thus prepared, hereinafter
referred to as Catalyst A, was subjected to a comparative
evaluation test relative to a "standard" catalyst. The
"standard" catalyst, hereinafter referred to as Catalyst B,
was prepared substantially as described but without the ben-
zyldimethylalkylammonium chloride component.
The comparative evaluation test consisted in process-
ing a sour kerosene downflow through 100 cc of catalyst dis-
posed as a fixed bed in a vertical tubular reactor. The
kerosene was charged at an LHSV of 0.5 under 3.4 atmospheres
of air -- sufficient to provide about 1.5 times the stoichio-
metric amount of oxygen required to oxidize the mercaptans
contained in the kerosene. In each case, the catalyst bed
was initially wetted with 10 cc of an 8% aqueous sodium
hydroxide solution, 10 cc of said solution being subsequently
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~1~4ZZ3
charged to the catalyst bed at 12 hour intervals admixed with
the kerosene charged thereto. The treated kero6ene, which
initially contained 533 ppm mercaptan sulfur, was analyzed
periodically for mercaptan sulfur. The mercaptan sulfur con-
tent of the treated kerosene was plotted against the hours on
stream to provide a curve from which the data set out in the
table below was derived.
TABLE
Time, hrs. Merca tan Sulfur, wt.
- P ppm.
v Catalyst A Catalyst B
36
100 9 31
150 11
200 11 31
250 11 31
