GB1585064A - Oxidation of sulphur-containing compounds - Google Patents

Description

(54) OXIDATION OF SULPHUR-CONTAINING COMPOUNDS (71) We, UOP INC, a corporation organized under the laws of the State of Delaware United States of America, of Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines, Illinois, United States of America, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The oxidation of various oxidizable sulphurcontaining compounds is well-known in the prior art. The oxidation reactions known in the art are mainly directed to the oxidation of mercaptans to disulphides and the oxidation of hydrogen sulphide to sulphur. Various modes of operation have been set forth: however, most generally the oxidation reactions have been performed catalytically in an alkaline environment. It has been shown that various catalysts can be utilised in the oxidation reactions, the most notable consisting of different metal chelates such as metal phthalocyanines.

The metal phthalocyanine catalysts disclosed have included cobalt phthalocyanine, vanadium phthalocyanine, iron phthalocyanine, copper phthalo cyanine, nickel phthalocyanine, molyb denum phthalocyanine chromium phthalocyanine, tungsten phthalocyanine, magnesium phthalocyanine, platinum phthalocyanine, hafnium phthalocyanine and palladium phthalocyanine. Further, the catalysts of the prior art have been shown to be used in an aqueous liquid-liquid form or in a solid form dispersed on a solid support.

The prior art has also disclosed the use of poly metalo phthalocyanines in the oxidation reactions. For example, U.S. Patent No.

3,565,959 teaches the use of, inter alia, poly iron-manganese phthalocyanine in a process for oxidising mercaptans to disulphides.

In accordance with the present invention we have discovered that a catalyst system comprising a mixture of a Group VIIB phthalocyanine and a Group VIII phthalocyanine can be utilised with advantage in the oxidation of sulphur-containing compounds. Many sulphurcontaining compounds, especially mercaptans and hydrogen sulphide, which are formed in many industrial processes or occur naturally in crude oil, must be converted to other compounds before disposal as a result of environmental considerations. For example, hydrogen sulphide has a high oxygen demand and accordingly will deprive marine life and other living organisms of oxygen needed for survival. Also, most mercaptan compounds possess a pungent odour which is harmful and displeasing to the surrounding environment.

Previous metal phthalocyanine catalyst systems set forth in the prior art possess problems of hydrogen peroxide production which causes overoxidation of the oxidizable sulphurcontaining compounds. The overoxidation of the sulphur-containing compounds presents problems of colour generation, which is highly undesirable in the treatment of petroleum charge stocks, and of consumption of caustic or ammonia, which is normally utilised in the oxidation of both mercaptans and hydrogen sulphide. We have found that the utilisation of a catalyst system according to the present invention will greatly reduce the production of hydrogen peroxide, and therefore the overoxidation of the entire system. The reduction in overoxidation will reduce or eliminate side oxidation products which would otherwise create consumption of caustic and colour form ation within the recovered charge stock. The utilisation of the present invention will also allow the refiner or manufacturer a catalytic treating method which is more economically feasible as a result of the eradication of any necessary subsequent treatment steps to remove colour-generating compounds and the extended "use time" for the caustic medium of the various treatment processes. The new catalyst system according to the present invention also creates new combinations as a result of the two component system, therefore, different impreg nation and dispersal effects can further be studied to maximise catalytic treatment conditions.

According to the invention there is provided a process for the oxidation of an oxidizable sulphur-containing compound, which comprises treating the sulphur-containing compound with an oxygen-containing gas in a medium possessing a pH of from 8 to 14 in the presence of a catalyst system comprising a Group VIIB metal phthalocyanine and a Group VIII metal phthalocyanine at oxidation conditions, and recovering the resulting oxidized sulphurcontaining compound.

The oxidation conditions used in the process of the present invention generally include a temperature of from 0 to 5000C, preferably from 500C to 4000C, and a pressure from 1 to 100 atmospheres.

The sulphur-containing compounds which can be oxidized by the process of the present invention may be present in a pure form or they may be intermixed in a petroleum charge stock, an aqueous stream or an alkali-aqueous stream. The sulphur-containing compounds in a petroleum charge stock may be present as natural mercaptans in a crude oil charge stock in its natural condition. Such mercaptans will in general possess 1 to 19 carbon atoms. Other mercaptans which may also be present include aromatic mercaptans such as thiphenol and substituted thiophenols. It is also contemplated within the scope of this invention that the sulphur-containing compound may comprise or consist of hydrogen sulphide, e.g. dissolved in an aqueous or an aqueous-alkaline solution.

Specific mercaptans which are converted to disulphide material by the oxidation process of this invention include methylmercaptan, ethyl mercaptan,propyl mercaptan, various mercaptobenzothiazoles, hydroxy mercaptans such as mercaptoethanol, cysteine, and aromatic mercaptans such as thiophenol, methyl-substituted thiophenol isomers, ethyl-substituted thiophenol isomers and propyl-substituted thiophenol isomers.

The catalyst system according to the invention suitably contains from 1 to 6 moles of the Group VIIB metal phthalocyanine per mole of the Group VIII metal phthalocyanine. The total catalyst system may be present in a weight percent relative to the entire reaction system of from 0.0001 to 10 weight percent. The Group VIIB metal phthalocyanine can be, for example, manganese phthalocyanine and rhenium phthalocyanine, and the phthalocyanine compounds may be present in a sulphonated or a carboxylated state. For example, the Group VIIB metal phthalocyanine may comprise the monosulphonate, the disulphonate, the trisulphonate, the tetrasulphonate, or the carboxylate. The Group VIII metal phthalocyanine compounds are cobalt phthalocyanine, iron phthalocyanine, nickel phthalocyanine, palladium phthalocyanine, rhodium phthalocyanine, ruthenium phthalocyanine, osmium phthalocyanine, iridium phthalocyanine and platinum phthalocyanine, and these Group VIII metal phthalocyanines may also be carboxylated or sulphonated. The catalyst comprising the Group VIIB metal phthalocyanine and Group VIII metal phthalocyanine may also be present in the form of polymers of phthalocyanine. For example, the catalyst system may comprise either a polymer or monomer of manganese phthalocyanine tetrasulphonate together with either a polymer or monomer of cobalt phthalocyanine tetrasul phonate - In preferred embodiments of this invention the catalyst system comprising the Group VIIB metal phthalocyanine and Group VIII metal phthalocyanine is present in either an aqueous or liquid-liquid form or the catalyst system is dispersed on a solid support such as alumina, silica, magnesia, thallia, zirconia, carbon, charcoal, Y-alumina, mordenite or faujasite. The solid supports may be impregnated with reduced forms of the phthalocyanine compounds.

The process of the present invention is effected in a medium possessing a pH in a range of from 8 to 14. The appropriate pH can be supplied to the medium by any alkaline material such as sodium hydroxide, potassiumiydrox- ide, ammonia, pyridine, piperidine, picoline, lutidine, quinoline, pyrrole, indole, carbazole, acridine, diethylamine, triethylamine or any suitable quaternary ammonium compound such as tetrabutyl ammonium hydroxide, tetraamyl ammonium hydroxide, tetrapropyl ammonium methoxide or tetraamyl ammonium methoxide, however, the preferred alkaline materials are either sodium hydroxide or ammonia, sodium hydroxide being preferred when mercaptan removal is effected and ammonia being preferred when hydrogen sulphide removal is effected. As hereinbefore set forth, the pH range of the medium is from 8 to 14. The preferred pH range is 9 to 13. For example, when sodium hydroxide is utilised to provide the treatment medium pH for the present invention, a pH of from 11 to 13 will usually exist within the treatment system. However, when ammonia is used a pH of from 9 to 13 will usually be present in the treatment system. It should also be noted that a treatment medium possessing a pH in the range of from 8 to 14 must be present in any system in which the catalyst is dispersed upon an inert support. The treatment medium may be present in the solid support system as a result either of a continual flow over the solid support or of an intermittent contact between the treatment medium and the solid support.

Treatment of the charge stock containing the sulphur-containing compounds may be effected in any suitable manner and may be in a batch or continuous type process. The batch or continuous type process may both comprise either a solid bed treating process or a liquid-liquid treating process. In a batch process a charge stock containing an oxidizable sulphur-containing compound is introduced into an oxidation zone containing a catalytic system according to the present invention and a treatment medium possessing a pH in the range of from 8 to 14, and air is introduced therein or passed therethrough. Preferably, the oxidation zone is equipped with suitable stirrers or other mixing device to obtain intimate mixing. In a continuous process the treatment medium may contain the catalytic system according to the present invention and both of them may be passed countercurrently or concurrently with the charge stock containing the sulphur-containing compounds in the presence of a continuous stream of air or oxygen. In a mixed type process the oxidation zone contains the treatment medium and phthalocyanine catalyst system, and the charge stock and air are passed continuously therethrough and removed, generally from the upper portion of the oxidation zone. In cases of treating charge stocks containing mercaptan compounds, the resultant disulphide oxidation products may be recovered directly from the resulting oxidation zone effluent by any method known in the art or the disulphides may be allowed to continue through other petroleum process treating units as a harmless sulphurcontaining compound which is eventually recovered, i.e. separated. In the case in which the charge stock comprises hydrogen sulphide, the resulting sulphur product may be separated by any method known to the art and utilised in the chemical industry as a pure sulphur compound.

The following Examples, some of which are included purely for comparison, illustrate the conduct of the oxidation step and the benefits of the use of the special catalyst system. In each Example the pH was in the range from 8 to 14.

EXAMPLE I (Comparative) In this example 0.98 grams of thiophenol, 50 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and 0.008 grams of cobalt phthalocyanine tetrasulphonate were placed in a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxygen uptake measurement is defined as the amount of oxygen consumed in the oxidation of the thiophenol. The desired effect is to minimise the quantity of oxygen uptake, thereby indicating the diminishment of the quantity of hydrogen peroxide (which is a partial reduction product of oxygen and is responsible for overoxidation). The potassium cyanide was added because the amount:of hydrogen peroxide is maximise when the cyanide ion is present. In this manner, it is easier to compare small increments of hydrogen peroxide formation. The flask was maintained at a temperature of 20CC and a pressure of 1 atmosphere as afforded by the introduction of oxygen to the oxidation flask for a period of time comprising 19 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptaken being 80.5 ml/ gram of thiophenol at standard pressure and temperature.

EXAMPLE II (Comparative) In this example 0.73 grams of thiophenol, 50 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and 0.034 grams of cobalt phthalocyanine tetrasulphonate were placed in a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measure ment. The flask was maintained at a tempera ture of 20"C and a pressure of 1 atmosphere as afforded by the introduction of oxygen to the oxidation flask for a period of time comprising 13 minutes, which was the approximate 100% oxidation time. The oxygen uptake was mea sured at the end of this period of time, said oxygen uptake being 71.8 ml/grams of thio phenol at standard pressure and temperature.

EXAMPLE III In this example 1.00 grams of thiophenol, 50 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and a catalyst system comprising 0.008 grams of cobalt phthalocyanine tetrasulphonate and 0.026 grams of manganese phthalocyanine tetrasulphonate (a 3:1 mole ratio of manganese species to cobalt species) was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxygen uptake is defined as set forth in Example I. The oxidation flask was maintained at the conditions of pressure and temperature of Examples land II for a period of time comprising 15 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptake being 42.2 ml/gram of thiophenol at standard pressure and tempera ture.

The unexpected results of the present inven tion may be cogently seen in a comparison of Example III with Examples I and II. In Example III a catalyst system comprising a Group VIIB metal phthalocyanine and a Group VIII metal phthalocyanine was utilized in comparison to the Group VIII metal phthalocyanine of Exam ples I and II. The result of the different catalyst system in Example III was the oxygen uptake of only 42.2 ml/gram of thiophenol at STP in comparison with the oxygen uptake of 80.5 ml/gram of thiophenol at STP of Example I and the 7,1.8 ml/gram of thiophenol at STP of Example II. The difference in the respective numbers shows that less overoxidation occurred in Example III, since substantially less hydro gen peroxide was present than in the Examples I and II, which utilized a catalyst known in the art.

EXAMPLE IV In this example 1.11 grams of thiophenol, 50 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and a catalyst system comprising 0.008 grams of cobalt phthalocyanine tetrasulphonate and 0.008 grams of manganese phthalocyanine tetrasulphone (a 1:1 mole ratio of the manganese species to the cobalt species) was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxidation flask was maintained at the conditions of pressure and temperature of Examples I, II and III for a period of time comprising 17 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptake being 50A ml/gram of thiophenol at standard pressure and temperature.

It should be noted that in comparison of Example IV to Example III that the amount of hydrogen peroxide was increased with the change from the 3:1 metal species ratio to the 1:1 metal species ratio. However, in the comparison of Example IV to-Examples I and II it can be seen that the amount of oxygen uptake, or hydrogen peroxide formation, the relative value was still decreased using the 1:1 metal species ratio in contrast to the known catalytic metals of Examples I and II which shown an oxygen uptake of 80.5 ml/gram of thiophenol at STP for Example I and 71.8 ml/gram of thiophenol at STP for Example II.

EXAMPLE V In this example 1.50 grams of thiophenol, 50 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and a catalyst system comprising 0.014 grams of cobalt phthalocyanine tetrasulphonate and 0.007 grams of manganese phthalocyanine disulphonate (a 2:1 mole ratio of cobalt species to the manganese species) was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. It should be noted in this experiment that a disulphonate of one metal of the two-component system is utilized in conjunction with a tetrasulphonated metal of the twocomponent system in contrast to the previous examples which have all compared the metal tetrasulphonates in combination with each other. The oxidation flask was maintained at a temperature of 20"C. and a pressure of 1 atmosphere as afforded by the introduction of oxygen to the oxidation flask for a period of time comprising 23 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptake being 53.5 ml/ gram of thiophenol at STP.

It should be noted that a comparison of Example V with Examples I and II show a decrease in the hydrogen peroxide formed (lower oxygen uptake values) utilizing the Group VIIB metal disulphonaye in conjunction with the Group VIII metal tetrasulphonate (cobalt phthalocyanine tetrasulphonate), which was previously known in the art.

EXAMPLE VI (Comparative) In this example 1.54 grams of thiophenol, 20 ml of isooctane, 50 ml of 8% sodium hydroxide, and 0.05 grams of cobalt phthalocyanide tetrasulphonate dispersed on 50.00 grams of Nuchar WA (a charcoal compound produced under the trademark Nuchar WA) was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxidation flask was maintained at conditions of 20 C. and a pressure of 1 atmosphere for a period of time comprising 30 minutes, which was the approximate 100% oxidation time.

The oxygen uptake at the end of this period of time was measured, said oxygen uptake being 62.7 ml/gram of thiophenol at STP.

It should be noted that this example is included within the specification to show the increased advantage of treating a sulphurcontaining compound with the bimetallic catalyst system of Example VII, this example, Example VI, utilizing only the monometallic catalyst system which was previously known in the art.

EXAMPLE VII In this example 1.53 grams of thiophenol, 20 ml of isooctane, 50 ml of 8% sodium hydroxide, 0.008 grams of potassium cyanide and a catalyst system comprising 0.90 grams of manganese phthalocyanine tetrasulphonate and 0.16 grams of cobalt phthalocyanine tetrasulphonate dispersed on 45.00 grams of charcoal was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxidation flask was maintained at the conditions of temperature and pressure of experiment VI for a period of time comprising 42.5 minutes which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptake being 48.0 ml/gram of thiophenol at STP.

It should be noted that a comparison of Example VI with Example VII will show a decrease in the amount of oxygen uptake from 62.7 ml/gram of thiophenol at STP of Example VI to the 48.0 ml/gram of thiophenol at STP oxygen uptake of Example VII. The decrease in the oxygen uptake as hereinbefore set forth indicates the lower amount of hydrogen peroxide present in Example VII, thereby alleviating problems of caustic use and colour generation.

EXAMPLE VIII In this example 1.66 grams of methyl mer captan, 0.010 grams of potassium cyanide in a vaporous phase and a catalyst comprising 0.50 grams of rhenium phthalocyanine disulphonate and 0.50 grams of ruthenium phthalocyanine tetrasulphonate dispersed on 25.6 grams of alumina is added to a 100 ml-round bottom flask containing a medium comprising tetrabutyl ammonium hydroxide, a magnetic stirrer and a means of air entry and air uptake measurement. The oxidation flask is maintained at oxidation conditions of 1500 C. and a pressure of 5 atmospheres as afforded by the introduction of air to the reaction system for a period of time comprising 15 minutes, which is the approximate 100% oxidation time of the methyl mercaptan. The air uptake is measured at the end of this period of time, said air uptake being equal to an amount less than that of a controlled standardized example utilizing only the rhenium phthalocyanine disulphonate.

EXAMPLE IX (Comparative) In this example 0.52 grams of sodium sulphide, 50 ml of 4% sodium hydroxide and 0.10 grams of cobalt phthalocyanine tetrasulphonate was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxidation flask was maintained at oxidation conditions of 200C. and a pressure of 1 atmosphere as afforded by the introduction of oxygen to the reaction system for a period of time comprising approximately 130 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this time, said oxygen uptake being 183.0 ml/gram sulphide at STP. It should be noted that the purpose of this example was to compare monometallic catalyst system known to the art of this example with the hereinafter set forth Example X which discloses the unexpected utilizing the two-component catalyst system.

EXAMPLE X In this sample 0.53 grams of sodium sulphide, which was partially converted to hydrogen sulphide before oxidation, 50 ml of 4% sodium hydroxide, 0.10 grams of cobalt phthalocyanine tetrasulphonate and 0.30 grams of manganese phthalocyanine tetrasulphonate (a 3:1 mole ratio of manganese species to cobalt species) was added to a 100 ml-round bottom flask containing a magnetic stirrer and a means of oxygen entry and uptake measurement. The oxidation flask was maintained at the same physical conditions of Example IX for a period of time comprising 125 minutes, which was the approximate 100% oxidation time. The oxygen uptake was measured at the end of this period of time, said oxygen uptake being 157.0 ml /gram sulphide at STP.

It can be seen as a comparison of Examples IX and X that the catalyst system of the present invention provided unexpected results in the fact that less oxygen uptake was recorded utilizing the two-component catalyst systems.

However, it should be noted that in the case of the hydrogen sulphide the decreased amount of oxygen uptake does not mean less formation of hydrogen peroxide as in the case of the oxidation of the thiophenol or mercaptan compound. The smaller the oxygen uptake of the example, the smaller the quantity of thiosulphate production from the oxidation of the sodium sulphide and the more sulphur.

EXAMPLE XI In this example a catalyst comprising 1.1 grams of manganese phthalocyanine tetrasulphonate and 0.15 grams of cobalt phthalocyanine tetrasulphonate on 45 grams of Dacro 12 x 20 (a tradename for an activated charcoal compound sold under the name Darco 12 x 20) was prepared and utilized for the oxidation of a charge stock comprising a liquid feed of 5.63 grams of sulphur as ammonium sulphide per hour (this sulphur being derived from hydrogen sulphide), and 0.73 grams of ammonium thiosulphate per hour for a total of 6.36 grams of sulphur per hour. The temperature was maintained at 52 C. and the pressure was maintained at 5 atmospheres, circulation of charge was at a liquid hourly space velocity (LHSV) of 1.0 with a 90% stoichiometric quantity of air. The resultant oxidation product was recovered, analyzed and found to contain only 0.72 grams of sulphur as ammonium thiosulphate, said result being unexpected in the fact that an experiment utilizing a catalyst known to the art would have resulted in the conversion of 7-1 4% of the ammonium sulphide to ammonium thiosulphate. The oxidation product also indicates a 69.6 percent conversion of ammonium sulphide to ammonium polysulphide. It can be seen from the treatment of the two-component catalytic system of the present invention that the amount of thiosulphate compound was drastically reduced in the presence of the novel catalyst system of the present invention.

EXAMPLE XII In this example a comparison is made between a poly metalo phthalocyanine catalyst made in accordance with the teaching of U.S.

Patent No. 3,565,959 and the present catalyst system which comprises a mixture of two mono metallic phthalocyanines.

A polyiron-manganese phthalocyanine catalyst was prepared by admixing and reacting 0.1 mole of pyromellitic acid with 1.0 mole of urea, 0.025 mole of ferric chloride and 0.075 mole of manganese dichloride, the reaction mixture being heated at 160 C. for 2 hours substantially in accordance with the method of 3,565,959. The manganese dichloride and ferric chloride were employed in a 3:1 mole ratio to provide a polyiron-manganese phthalo cyanine catalyst containing manganese and iron in substantially the same mole ratio as employed in the catalyst system of the present invention. In addition, a catalyst system was prepared pursuant to our method as described in the present specification. Thus, .0081 grams of sulphonated manganese phthalocyanine was admixed with .0240 grams of sulphonated iron phthalocyanine to provide a mixture of said phthalocyanines in substantially a 3:1 mole ratio.

The last described iron phthalocyaninemanganese phthalocyanine system, and the first described poly-iron-manganese phthalocyanine catalyst of 3,565,959, were subjected to a comparative evaluation with respect to the overoxidation tendencies of the catalyst by the method described in the present specification.

This method determines how much side-product hydrogen peroxide is formed while oxidizing a small charge of thiophenol to diphenyl disulphide. It also determines to what extent the thiophenol is overoxidized. Basically, the method consists of measuring the total oxygen uptake during the thiophenol oxidation. Thus, in each case, 1.25 grams of thiophenol, 20 milliliters of isooctane, 50 milliliters of 8% sodium hydroxide, 0.008 grams of potassium cyanide, and 0.034 grams of catalyst were placed in a 100 milliliter round bottomed flask containing a magnetic stirrer and a means of oxygen entry and measurement of oxygen uptake. The flask was maintained at a temperature of 200C. and at a pressure of 1 atmosphere as afforded by the introduction of oxygen to the oxidation flask until oxidation is completed. The oxygen uptake was measured at the end of the period required to effect 100% oxidation of the thiophenol, the oxygen uptake being 62 milliliters per gram with respect to the catalyst of U.S. Patent No. 3,565,959, and 53.5 milliliters per gram with respect to our catalyst, indicating substantial overoxidation by the 3,565,959 catalyst as compared to our catalyst.

This example, therefore, clearly demonstrates an improvement achieved by the use of the present invention as compared with procedure according to U.S. Patent No. 3,565,959, particularly as evidenced by the better selectivity with respect to the oxidation of sulphurcontaining compounds to minimize overoxidation to hydrogen peroxide and the resultant formation of undesirable side products.

WHAT WE CLAIM IS: 1. A process for the oxidation of an oxidizable sulphur-containing compound, which comprises treating the sulphur-containing compound with an oxygen-containing gas in a medium possessing a pH of from 8 to 14 in the presence of a catalyst system comprising a Group VIIB metal phthalocyanine and a Group VIII metal phthalocyanine at oxidation conditions, and recovering the resulting oxidized sulphurcontaining compound.

2. A process as claimed in claim 1 wherein the oxidation conditions include a temperature of from 0" to 5000C. and a pressure of from 1 to 100 atmospheres.

3. A process as claimed in claim 1 or 2 wherein the catalyst system comprises from 1 to 6 mol of the Group VIIB metal phthalocyanine per mol of the Group VIII metal phthalocyanine.

4. A process as claimed in any of claims 1 to 3 wherein the sulphur-containing compound is a mercaptan.

5. A process as claimed in claim 4 wherein the mercaptan is selected from methyl mercaptan, propyl mercaptan

Claims (16)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   first described poly-iron-manganese phthalocyanine catalyst of 3,565,959, were subjected to a comparative evaluation with respect to the overoxidation tendencies of the catalyst by the method described in the present specification.

   This method determines how much side-product hydrogen peroxide is formed while oxidizing a small charge of thiophenol to diphenyl disulphide. It also determines to what extent the thiophenol is overoxidized. Basically, the method consists of measuring the total oxygen uptake during the thiophenol oxidation. Thus, in each case, 1.25 grams of thiophenol, 20 milliliters of isooctane, 50 milliliters of 8% sodium hydroxide, 0.008 grams of potassium cyanide, and 0.034 grams of catalyst were placed in a 100 milliliter round bottomed flask containing a magnetic stirrer and a means of oxygen entry and measurement of oxygen uptake. The flask was maintained at a temperature of 200C. and at a pressure of 1 atmosphere as afforded by the introduction of oxygen to the oxidation flask until oxidation is completed. The oxygen uptake was measured at the end of the period required to effect 100% oxidation of the thiophenol, the oxygen uptake being 62 milliliters per gram with respect to the catalyst of U.S. Patent No. 3,565,959, and 53.5 milliliters per gram with respect to our catalyst, indicating substantial overoxidation by the 3,565,959 catalyst as compared to our catalyst.

   This example, therefore, clearly demonstrates an improvement achieved by the use of the present invention as compared with procedure according to U.S. Patent No. 3,565,959, particularly as evidenced by the better selectivity with respect to the oxidation of sulphurcontaining compounds to minimize overoxidation to hydrogen peroxide and the resultant formation of undesirable side products.

   WHAT WE CLAIM IS: 1. A process for the oxidation of an oxidizable sulphur-containing compound, which comprises treating the sulphur-containing compound with an oxygen-containing gas in a medium possessing a pH of from 8 to 14 in the presence of a catalyst system comprising a Group VIIB metal phthalocyanine and a Group VIII metal phthalocyanine at oxidation conditions, and recovering the resulting oxidized sulphurcontaining compound.
2. 2. A process as claimed in claim 1 wherein the oxidation conditions include a temperature of from 0" to 5000C. and a pressure of from 1 to 100 atmospheres.
3. 3. A process as claimed in claim 1 or 2 wherein the catalyst system comprises from 1 to 6 mol of the Group VIIB metal phthalocyanine per mol of the Group VIII metal phthalocyanine.
4. 4. A process as claimed in any of claims 1 to 3 wherein the sulphur-containing compound is a mercaptan.
5. 5. A process as claimed in claim 4 wherein the mercaptan is selected from methyl mercaptan, propyl mercaptan and thiophenol.
6. 6. A process as claimed in any of claims 1 to 3 wherein the sulphur-containing compound is hydrogen sulphide.
7. 7. A process as claimed in any of claims 1 to 6 wherein the oxygen-containing gas is oxygen or air.
8. 8. A process as claimed in any of claims 1 to 7. wherein the Group VIIB metal is manganese or rehnium.
9. 9. A process as claimed in any of claims 1 to 8 wherein the Group VIII metal is selected from ruthenium, iridium, cobalt, nickel and iron.
10. 10. A process as claimed in any of claims 1 to 9 wherein the catalyst system is dispersed on a solid support.
11. 11. A process as claimed in claim 10 wherein the solid support is carbon of Y-alumina.
12. 12. A process as claimed in any of claims 1 to 11 wherein the medium contains sodium hydroxide or a quaternary ammonium compound - to provide a pH of from 8 to 14.
13. 13. A process as claimed in any claims 1 to 12 wherein the sulphur-containing compound is present in a petroleum charge stock or an aqueous or aqueous-alkaline stream.
14. 14. A process as claimed in claim 13 as appendent to any of claims 1 to 5 or 7 to 12 wherein the sulphur-containing compound is one or more natural mercaptans naturally present in a crude oil charge stock and said mercaptan(s) are oxidized in a petroleum charge stock to form sulphide material.
15. 15. A process as claimed in claim 1 wherein the oxidation is carried out substantially as hereinbefore described or illustrated in any of the foregoing Examples III to V, VII, VIII or X to XII.
16. 16. An oxidised sulfur-containing compound when obtained by the process of any of claims 1 to 15.