Note: Descriptions are shown in the official language in which they were submitted.
~233~i9
PROCESS FOR TREATING A SOUR PET~O~EUM DISTILLATE
SPECIFICATION
Processes for -the treatment of sour petroleum
dis-tillates, wherein the distillate is passed in contac-t
with a supported metal phthalocyanine catalyst, are widely
practiced in the petroleum refining industry. The treat-
ing process is typically designed to eEfect the catalytic
oxidation of offensive mercaptans contained in a sour
petroleum distillate, thereby converting said mercaptans
to innocuous disulfides -- a process commonly referred to
as sweetening. The oxidizing agent is most often air which
is admixed with the distillate to be treated, and the alkaline
reagent is most often an aqueous caustic solution charged
continuously to the process, or lntermittently as required.
Gasoline, including natural, straight-run and cracked gasoline,
is one of the most frequently treated petroleum distillates.
Others include the normally gaseous petroleum fractions as
well as naphtha, kerosene, jet fuel and lube oil.
In the preparation of a supported methal phthalo-
cyanine catalyst, it is the practice to adsorb the metal
~ phthalocyanine on an adsorptive support from an alcoholic
solution and/or dispersion thereof. Methanolic solutions
and/or dispersions have heretofore provided a most active
catalytic composite. However, methanol has become increas-
ingly objectionable in that it is relatively expensive,
toxic and difficult to dispose of.
-2-
~:lZ33~9
It has now been found that when the metal ph-tahlo-
cyanine is impregnated on said solid support from a common
aqueous solution and/or dispersion of said metal ph-thalo-
- cyanine and morpholine, a catalytic composite of improved
activity results. Thus, the present invention embodies a
process for treating a mercaptan-containing sour petroleum
distillate which comprises contacting said distillate with a
supported metal phthalocyanine catalyst in the presence of
an alkaline reagen-t at oxidation conditions, said catalyst
having been prepared by impregnating said phthalocyanine on
a solid adsorptive support fron~ an aqueous impregnating
solution or dispersion of said phthalocyanine containing
from 5 to 50 wt. ppm~ morpholine.
Another embodimen-t of this invention concerns a
process which comprises treating said distillate in contact
with a supported metal phthalocyanine catalyst in the presence
of an aqueous alkali metal hydroxide solution and air, said
catalyst having been prepared by impregnating a cobalt phthalo-
cyanine on a charcoal support from an aqueous impregnating
solution or dispersion oE said phthalocyanine containing
from 5 to 50 wt. ppm. morpholine.
One of the preferred embodiments of this invention
relates to a process for treating a mercaptan-containing sour
petroleum distillate which comprises contacting said distillate
with a supported metal phthalocyanine catalyst in the presence
of an aqueous sodium hydroxide solution and air, said catalyst
having been prepared by impregnating from 0.1 to 10 wt. ~
cobalt phthalocyanine monosulfonate on an activated charcoal
support from an aqueous solution or dispersion of said phthalo-
~cyanine containing from 5 to 50 ppm. morpholine.
--3--
3~9
The solid adsorbent supports herein contemplated
include the various solid adsorbent materials in general
use as catalyst supports. 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 adsor-
bent capacity, and generally defined as activated charcoal.
Said adsorbent materials also include the naturally occurrin~
clays and silicates, for example, diatomaceous earth, fuller's
earth, kieselguhr, attapulgus 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 stabili-ty and to conditions of its intended
use. For example, in the treatment of a sour pe-troleum dis-
tilla~e, the solid adsorbent material should not only be
insoluble in, and otherwise inert to, the petroleum distillate
at conditions existing in the treating zone, but also to the
aqueous caustic solution typically admixed with the distillate.
Charcoal, and particularly activated charcoal, is preferred
because of its capacity for metal phthalocyanine and because
of its stability under treating conditions. ~owever, it should
be observed that the method of this invention is also appli-
cable to the preparation of a metal phthalocyanine composited
~13LZ~3~
with any of the other well-known solid adsorbent ma-terials,
particularly the refractory inorganic oxides.
The catalytic composite of this inven-tion may com-
prise any of the various metal phthalocyanines heretofore
disclosed as useful to catalyze the sweetening process, for
example molybdenum, manganese, iron, cobalt, nickel, platinum,
palladium, copper, silver, zinc and tin phthalocyanine.
Cobalt phthalocyanine and vanadium phthalocyanine are par-
ticularly preferred metal phthalocyanines. The me-tal phthalo-
cyanine is preferably employed herein as a derivative thereo~,
the commercially available sulfonated derivatives, for example,
cobalt phthalocyanine monosulfonate, cobalt phthalocyanine
disulfonate, or mixtures thereof, being particuarly preferred.
The sul~onated derivatives may be prepared, ~or example, by
reacting cobalt, vanadium, or other metal phthalocyanine with
fuming sulfuric acid. While the sulfonated derivatives are
preferred, it is understood that other derivatives, particu-
larly the carboxylated derivatives, may be employed. The
carboxylated derivatives are readily prepared by reactiny
the metal phthalocyanine with phos~ene in the presence of
alumium chloride. ITI the latter reaction, the acid chloride
is formed and may be converted to the desired carboxylated
derivative by conventional hydrolysis.
Pursuant to the present invention, the metal phthalo-
cyanine is impregnated on the solid adsorptive support from
- an aqueous solution and/or dispersion of said metal phthalo-
cyanine, said solution further containing from 5 to 50 wt.
ppm. morpholine (tetrahydro-1,4-isooxazine~. Morpholine,
335~
heretofore recogni~ed as an efEective corrosion or oxidation
inhibitor, has now been found to be a surprisingly effective
promoter for the me-tal phthalocyanine -- catalyzed oxidati~n
of mercaptans contained in a sour petroleum distillate.
Morpholine concentrations in excess of 50 wt. ppm. tend to
become less effective, and the metal phthalocyanine is
preferably impregnated on the solid adsorptive support from .
an impregnating solution containing from 5 to 50 wt. ppm.
morpholine.
The adsorbent support can be impregnated with the
aqueous me-tal phthalocyanine solution-dispersion in any
conventional or otherwise convenient manner. In general,
the support, in the form of spheres, pills, pellets, granules
or other particles of uniform or irregular sha~e, is dipped,
soaked, suspended, or otherwise immersed in the described
aqueous dispersion, where the aqueous dispersion may be
sprayed onto, poured over, or otherwise contacted with the
adsorbent support. In any case, the excess solution is
separated and the resulting composite allowed to dry und~r
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.
It is generally preferably to adsorb as much metal
phthalocyanine on the adsorbent support as will form a stable
catalytic composite -- generally up to 25 wt. ~, although a
lesser amount in the range of from 0.1 to 10 wt. % affords
a suitably active catalytic composite. One suitable and
. . .
335~
convenient me-thod comprises predisposincJ the solid support
in a distillate treatin~ zone or cha~ber as a fixed bed, and
~assing the aqueous metal phthalocyanine solution-dispersion
through the bed in order to form the catalytic composite in
situ. This methoa allows the aqueous solu-tion-dispersion
to be recycled one or more times to achieve a desired con-
centration of a metal phthalocyanine on the adsorbent sup-
port. In still another method, the adsorbent support may
be predisposed in said treating chamber and the chamber
thereafter filled with the aqueous metal phthalocyanine
solution-dispersion to soak the support for a predetermined
period, thereby ~orming the catalytic compos te in situ~
In the sweetening process herein contemplated,
offensive mercap-tans contained in a sour petroleum distillate
are oxidized to form innocuous disulfides in the presence
of an alkaline reagent. The catalytic composite is typically
initially saturated with the alkaline reagent, and the alkaline
reagent thereafter admixed, at least intermitten-tly, with
the sour petroleum distillate passed in contac-t with the
catalytic composite to maintain a desired alkaline reagent
concentration thereon. While any suitable alkaline reagent
may be employed, an alkali metal hydroxide in aqueous solution,
for example, an aqueous solution of sodium hydroxide or po-
tassium hydroxide, is most often preferred. The solution
2S may further comprise a solubilizer to promote mercaptan
solubility, for example, alcohol, and especially methanol,
ethanol, n-propanol and isopropanol, and also phenols and
cresols. A particularly preferred alkaline reagent is a
~l~2~35~
caustic solution comprising ~rom 2 to 30 wt. ~ sodium hy-
droxide. The solubilizer, when employed, is preferably
methanol, and the alkaline solu-tion may suitably comprise
from 2 to 100 vol. ~ thereo~. While sodium hydroxide and
the potassium hydroxide consti-tute the preferred alkaline
reagents, others including lithium hydroxide, rubidium hy-
droxide and cesium hydroxide, are also suitably employed.
The sweetening process is usually effected at
ambien-t temperature conditions, although elevated tempera-
tures generally not in excess of 150~C. may be used. The
process may be effected at a pressure of up to 69 atmospheres,
although atmospheric, or substan-tially atmospheric, pres-
sures are entirely suitable. Contact times e~uivalent to a
liquid hourly space velocity of from 1 to 100 are effective
to achieve a desired reduction in the mercaptan content of
a sour petroleum distillatè, an optimum contact time being
dependent on the size of the treating zone, the quantity of
catalyst contained therein, and the sour petroleum distillate
being treated.
As previously sta-ted, sweetening of the sour petro-
leum distillate is effected by oxidizing the ~ercaptan con-
tents thereof to disulfides. Accordingly, the process is
effected in the presence of an oxidizing agent, preferably
air, although oxygen or other oxygen-containin~ agents may
be employed. The mixture of petroleum distilla-te, alkaline
reagent and oxidizing agent can be passed upwardly or down-
wardly through a catalyst bed. In some cases, the air may
be passed countercurrent to the petroleum ais-tillate. In
~233~
still other cases, the petroleum distillate and alkaline
reagent may be introducea separately into the trea-ting zone.
The catalytic composite prepared in accordance
t~ith the method o~ this invention is both ac-tive and stable.
Accordingly, the cataly-tic composite may be employed in a
fixed bed for the treatment of large volume of sour petro-
leum distillate. Although the metal phthalocyanine is some-
what soluble in alkaline solution, it is nevertheless re-
tained on the solid adsorbent support. However, in the
event that any of the me-tal phthalocyanine is leached from
the support, or otherwise carried away in the alkaline solu-
tion, it may be readily recycled in said solution for reuse
in the sweetening process. However, it is in some cases
desirable to introduce additional metal phthalocyanine for
adsorption on the solid suppor-t in the manner herein described.
The sour petroleum distillates vary widely in com-
position depending on the source of the petroleum from which
the distillate was derived, the boiling range of the dis-
tillate, and possibly the methods of processing the petroleum
to produce the distillate. The supported metal phthalocyanine
catalyst is particularly adapted to the treatment of petro-
leum dis-tillates boiling in excess of about 135C., for ex-
ample, kerosene, jet fuel, fuel oil and naphtha, in a fixed
bed treating system. These higher boiling distillates sen-
erally contain the more difficul-tly oxidiæable mercaptans,
i.e., the caustic insoluble, highly hindered, branched chain
and aromatic thiols -- especially the higher molecular weight
tertiary and polyfunctional mercaptans. Al-though the supported
3359
catalyst of this invention is particularly applicable to
the heavier petroleum dis-tillates, it is also useful for
the treatment of the lower boiling distillates such as the
natural, straight run and the cracked gasolines.
The following examples are presented in illustra-
tion of certain preferred embodiments of this invention and
are not intended as an undue limitation on the generally
broad scope of the invention as se-t out in the appended
claims.
EXA~IPLE I
.
In the preparation of a supported metal phthalo-
cyanine catalyst in accordance with the method oE this in-
vention, activated adsorp-tive charcoal particles we~e im-
pregna-ted with a common aqueous dispersion-solution of cobalt
phthalocyanine monosulfonate and morpholine. The dispersion-
solution was prepared by c~iluting a 0.31 ml. sample of an
aqueous morpholine solution containing about 2000 wt. ppm.
morpholine, the sample being diluted to 25 ml. with water.
To this 25 ml. solu-tion was added 150 mg. of cobalt phthalo-
cyanine monosulfonate, ancl the mixture was stirred to orm
a slurry. The slurry was then further diluted by the addition
of 100 ml. of water -to provide an impregnating dispersion-
solution, hereinafter referred to as solution, containing
about 5 wt. ppm. morpholine, and the solution further stirred
for about 5 minutes. About 100 cc of the charcoal particles,
having an average bulk density of about 0.25 gm/cc and a par-
ticle size in the 10 x 30 mesh range, were then immersed in
the impregnating solution. The solution was stirred in contact
--10--
~233~i9
with -the particles For about 5 minutes, and then maintained
in contact with the particles under quiescent conditions
for about 1 hour. The impregna-ting solu-tion was thereaf-ter
evaporated to dryness in contact with the particles over
a steam bath, and the impregnated particles subsequently
oven-dried at about 100C~ for 1 hour. The ca-talytic com-
posite thus prepared is hereinafter referred to as Catalyst
A. Catalysts hereinafter referred tQ as B, C and D were
similarly prepared except that the impregnating solution
contained 10, 16 and 2000 ppm. morpholine respectively.
EXAMPLE II
In this example, the activated charcoal-supported
cobalt phthalocyanine catalyst of Example I was prepared
substantially as described except that the cobalt phthalo-
cyanine was adsorbed or impregnated on the activa-ted char-
coal support from a methanolic dispersion thereof in accor-
dance with prior art practices. Thus, 150 mg. of cobalt
phthalocyanine monosulfonate was admixed with 50 ml. of
methanol and stirred for about 5 minutes. The resulting
dispersion was then further diluted to 300 ml. with methanol
with an additional 5 minutes o~ stirring. About 100 cc o~
the activated charcoal particles were immersed in the methanol
dispersion, and the dispersion was stirred in contact with
the particles for about 5 minutes and then maintained in con-
tact with the particles for 1 hour under quie~cent conditions.
The methanolic dispersion was thereafter evaporated to dry-
ness over a steam bath in contact with the charcoal particles,
and the resulting impregnated particles were subsequently
--11-- ,
~l~Z3359
oven dried at 100C. for 1 hour. The supported catalyst of
this example is hereinafter referred to as Ca-talys-t E.
The ca-talysts thus prepared were subjected to a
comparative evaluation test. The test was effected in an
air a-tmosphere at ambient conditions of temperature and
pressure. In each case, 13.3 cc of catalyst wetted with
5 cc of aqueous sodium hydroxide (pH 14) and 100 cc of a
sour kerosene were contained in a closed glass vessel in-
serted in a mechanical shaking device. The reaction mix-
ture was shaken in contact with the catalyst for about a
30 minute period after which the kerosene was analy~ed for
residual mercaptan sulfur. The catalysts were each evaluated
with respect to a sour Xerosene containin~ 164, 407 and 832
wt. ppm. mercaptan sulfur. The resul-ts appear in Table I
below.
TABLE I
Mercaptan Sulfur, wt. ppm.
Catalyst Catalyst Ca-talyst Catalyst Catalyst
Time, min.A B C _ D E
0164 164 16~ 16~ 164
6 5 6 - 8
Mercaptan SulE~lr, wt. ppm.
Catalyst Catalyst Catalyst Catalyst Catalyst
Time, min. A B C D E
0~07 407 407 407 407
12 6 9 30 19
Mercaptan Sulfur, wt. ppm.
Catalyst Catalys-t Catalyst Cataiys-t Catalyst
Time, min. A B C D E
0832 832 832 832 832
- 120 22 15 15 33 20
335~3
EX~IPLE III
_ _ _
A catalyst prepared substan-tially in accordance
with the preparation of Catalys-t B was subjected to a com-
parative evaluation test relative to a catalyst prepared
in accordance with the prior art preparation of Ca-talyst ~.
In each case, 100 cc of the catalyst was disposed as a fixed
bed in a vertical glass tubular reactor maintained at ambient
temperature conditions -- about 23~C. Prior to the start
of each test, the catalyst bed was washed with 10 baumé
aqueous sodium hydroxide solution. Air was charged to the
system through a rotameter a-t about 100 cc per,hour and
admixed with the sour kerosene feed stock, The mixture was
processed downwardly through the catalyst bed at a liquid
hourly space velocity of about 1 over a 20 hour period.
The reactor effluent was monitored and analyzed periodically
for mercaptan sulfur. The results are set out in Table II
below.
TABLE II
Mercaptan Sulfur, wt. ppm
Time, hrs. Catalyst B Catalyst E
0 448 ~8
1 4 - 5
6 8
~ 11
8 14
9 17
-13-
