CA1124223A

CA1124223A - Catalytic composite particularly useful for the oxidation of mercaptans contained in a sour petroleum distillate

Info

Publication number: CA1124223A
Application number: CA330,581A
Authority: CA
Inventors: Robert R. Frame
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 1978-07-24
Filing date: 1979-06-26
Publication date: 1982-05-25
Also published as: SE7906183L; FR2433974A2; NO792430L; DK310279A; GB2027359A; DE2927685A1; NO160493B; IT7924574A0; ES482760A2; SU1095873A3; PH14933A; ATA501079A; MX154990A; BR7904695A; GB2027359B; IT1122275B; FR2433974B2; RO77061A; SE436696B; YU179179A

Abstract

ABSTRACT
A catalytic composite comprising a metal chelate mercaptan oxidation catalyst and a quaternary ammonoium com-pound impregnated on a solid adsorptive support is disclosed.
The quaternary ammonium compound is represented by the struc-tual formula

Description

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 :*~

~124ZZ3 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 ~.Z4ZZ3 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-~242Z3 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
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.

- ~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 ~Z~Z%3 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 .

~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 ~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-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 ~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

Claims

I CLAIM AS MY INVENTION:

1. A catalytic composite comprising a metal chelate mercaptan oxidation catalyst and a quaternary ammonium com-pound impregnated on a solid adsorptive support, said quater-nary ammonium compound being represented by the structural formula wherein R is a hydrocarbon radical containing up to 20 carbon atoms and selected from the group consisting of alkyl, cyclo-alkyl, aryl, alkaryl and aralkyl, R1 is a substantially straight chain alkyl radical containing from 5 to 20 carbon atoms, R2 is selected from the group consisting 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.

2. The catalytic composite of Claim 1 wherein said quaternary ammonium compound comprises from 1 to 50 wt. % of said catalytic composite.

3. The catalytic composite of Claim 1 or 2 wherein said quaternary ammonium compound comprises from 5 to 35 wt. % of said catalytic composite.

4. The catalytic composite of claim 1 or 2, wherein R1 is a substantially straight chain alkyl radical containing from 12 to 18 carbon atoms.

5. The catalytic composite of claim 1 or 2, wherein R2 is benzyl.

6. The catalytic composite of claim 1, wherein said quaternary ammonium compound is a quaternary ammonium halide.

7. The catalytic composite of claim 6, wherein said quaternary ammonium compound is a quaternary ammonium chloride.

8. The catalytic composite of claim 7, wherein said quaternary ammonium chloride is selected from the group con-sisting of benzyldimethyldodecylammonium chloride, benzyldi-methyltetradecylammonium chloride, benzyldimethylhexadecyl-ammonium chloride and benzyldimethyloctadecylammonium chloride.

9. The catalytic composite of claim 1 wherein said quaternary ammonium compound is a quaternary ammonium hydroxide.

10. The catalytic composite of claim 9, wherein said quaternary ammonium hydroxide is selected from the group con-sisting of benzyldimethyldodecylammonium hydroxide, benzyldi-methyltetradecylammonium hydroxide, benzyldimethylhexadecyl-ammonium hydroxide and benzyldimethyloctadecylammonium hydroxide.

11. The catalytic composite of claim 1, 2 or 6, wherein said solid adsorptive support is an activated charcoal.

12. The catalytic composite of claim 1, wherein said metal chelate mercaptan oxidation catalyst is a metal phthalocyanine.

13. The catalytic composite of claim 1, wherein said metal chelate mercaptan oxidation catalyst comprises from 0.1 to 10 wt. % of said catalytic composite.

14. The catalytic composite of claim 1, 12 or 13, wherein said metal chelate mercaptan oxidation catalyst comprises from 0.1 to 2 wt. % of said catalytic composite.

15. The catalytic composite of claim 1, 12 or 13, wherein said metal chelate mercaptan oxidation catalyst is a vanadium phthalocyanine.

16. The catalytic composite of claim 1, 12 or 13, wherein said metal chelate mercaptan oxidation catalyst is a cobalt phthalocyanine.

17. The catalytic composite of claim 1, 12 or 13, wherein said metal chelate mercaptan oxidation catalyst is cobalt phthalocyanine monosulfonate.