CA1123359A

CA1123359A - Process for treating a sour petroleum distillate

Info

Publication number: CA1123359A
Application number: CA322,100A
Authority: CA
Inventors: David H.J. Carlson; James R. Deering
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 1978-06-01
Filing date: 1979-02-22
Publication date: 1982-05-11
Also published as: GB2027049B; DE2908417C2; GB2027049A; ES478531A2; JPS5811471B2; IT7921259A0; FR2427377A2; DE2908417A1; IT1165010B; JPS54157104A; FR2427377B2

Abstract

PROCESS FOR TREATING A SOUR PETROLEUM DISTILLATE

ABSTRACT

A process for treating a mercaptan-containing sour petroleum distillate is disclosed. The process comprises contacting said distillate with a supported metal phthalo-cyanine catalyst in the presence of an alkaline reagent at oxidation conditions, said catalyst having been prepared by impregnating said phthalocyanine on a solid adsorptive support from an aqueous solution or dispersion of said phthalocyanine containing from about 5 to about 50 wt. ppm.
morpholine.

Description

~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.

3~9 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 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 ~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 Mercaptan SulE~lr, wt. ppm.
Catalyst Catalyst Catalyst Catalyst Catalyst Time, min. A B C D E
0~07 407 407 407 407 Mercaptan Sulfur, wt. ppm.
Catalyst Catalys-t Catalyst Cataiys-t Catalyst Time, min. A B C D E

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 ~ 11

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 reagent at oxidation conditions, said catalyst having been prepared by impregnating said phthalocyanine on a solid adsorptive support from an aqueous impregnating solution or dispersion of said metal phthalocyanine containing from 5 to 50 wt.
ppm. morpholine.

2. The process of Claim 1 wherein said solid adsorptive support is impregnated with from 0.1 to 10 wt. %
metal phthalocyanine from said impregnating solution.

3. The process of Claim 1 wherein said metal phthalocyanine is a cobalt phthalocyanine.

4. The process of Claim 1, 2 or 3 wherein said metal phthalocyanine is a sulfonated derivative of a cobalt phthalocyanine.

5. The process of Claim 1, 2 or 3 wherein said metal phthalocyanine is a cobalt phthalocyanine mono-sulfonate.

6. The process of Claim 1, 2 or 3 wherein said metal phthalocyanine is a cobalt phthalocyanine disulfonate.

7. The process of Claim 1 wherein said metal phthalocyanine is a vanadium phthalocyanine.

8. The process of Claim 1, 2 or 3 wherein said solid adsorptive support is a charcoal.

sb/?
14 .

9. The process of Claim 1, 2 or 3 wherein said solid adsorptive support is an activated charcoal.

10. The process of Claim 1, 2 or 3 wherein said alkaline reagent is an alkali metal hydroxide in from a 2 to a 30 wt. % aqueous solution.

11. The process of Claim 1, 2 or 3 wherein said alkaline reagent is sodium hydroxide in from a 2 to a 30 wt. % aqueous solution.