Claims
- 1. A catalyst for oxidizing alkali mercaptide compounds to disulfide in an aqueous alkaline solution comprising: a caustic-inert carrier having impregnated thereon a metal compound of tetrapyridinoporphyrazine or substituted derivatives thereof having the structural formula: ##SPC6##
- where M is a metal selected from the group consisting of iron, manganese, chromium, magnesium, copper, nickel, zinc, titanium, hafnium, thorium, tin, lead, columbium, tantalum, antimony, bismuth, molybdenum, palladium, platinum, silver, mercury, vanadium and cobalt, R is selected from the group consisting of hydrogen, methyl, ethyl, propyl, iso-butyl, phenyl, benzyl and napthyl groups, and X is a nitrogen atom, or a carbon atom having one R group attached thereto.
- 2. The catalyst of claim 1 wherein the caustic-inert carrier is granular activated carbon.
- 3. A catalyst for oxidizing alkali mercaptide compounds to disulfides in an aqueous solution, said catalyst comprising a caustic-inert carrier having impregnated thereon a metal-tetrapyridinoporphyrazine compound having the structural formula: ##SPC7##
- where M is a metal selected from the group consisting of cobalt and vanadium.
- 4. The catalyst of claim 3 wherein the caustic-inert carrier is granular activated carbon.
- 5. The catalyst of claim 3 wherein M is cobalt and the caustic-inert carrier is granular activated carbon.
- 6. The catalyst of claim 3 wherein M is vanadium and the caustic-inert carrier is granular activated carbon.
- 7. The catalyst of claim 3 wherein the caustic-inert carrier is granular activated carbon and the compound impregnated thereon is a mixture of cobalt and vanadium compounds of tetrapyridinoporphyrazine.
- 8. The catalyst of claim 3 wherein the concentration of metaltetrapyridinoporphyrazine compound in said catalyst is at least 0.5 percent by weight.
- 9. A method for preparing a catalyst for oxidizing alkali mercaptide compounds in aqueous alkaline solution to disulfide comprising:
- a. dissolving a metal compound selected from the group consisting of cobalt and vanadium tetrapyridinoporphyrazine compounds, and mixtures thereof, in a solvent;
- b. adding a granular adsorbent solid carrier to the solution resulting from (a) and saturating said solid carrier with said solution;
- c. separating said solid carrier from said solution and;
- d. washing said separated solid of (c) with a liquid selected from the group consisting of water, acetone, and mixtures thereof.
- 10. The method of claim 9 wherein said granular solid carrier is selected from the group consisting of silica, alumina, and activated carbon.
- 11. The method of claim 9 wherein said solid carrier is granular activated carbon.
- 12. The method of claim 9 wherein said solvent is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, N,N-dimethyl formamide, N-methyl-2-pyrrolidone, and pyridine.
- 13. The method of claim 9 wherein said metal compound is cobalt tetrapyridinoporphyrazine having the structural formula: ##SPC8##
- 14. The method of claim 13 wherein said solvent is an aqueous solution of sulfuric acid in a concentration of between about 50 and about 96 weight percent of acid.
- 15. The method of claim 9 where said metal compound is vanadium tetrapyridinoporphyrazine having the structural formula: ##SPC9##
- 16. The method of claim 15 wherein said mineral acid is an aqueous solution of sulfuric acid in a concentration of between about 50 and about 96 weight percent acid.
CROSS REFERENCE TO RELATED APPLICATION
This application is a Continuation-in-part of our copending application Ser. No. 395,256, filed Sept. 7, 1973, now U.S. Pat. No. 3,923,645.
This invention relates to a novel method and catalyst for oxidizing to disulfides mercaptans contained in hydrocarbon distillates and mercaptan compounds present in aqueous caustic solutions used to sweeten hydrocarbon distillates.
When hydrocarbon distillates, such as gasoline, naphtha, jet fuel, kerosene, diesel fuel, or fuel oil, contain mercaptans and hydrogen sulfide, they are commonly referred to as sour and usually are unsatisfactory for their intended uses. Mercaptans have a highly offensive odor even in minor concentrations. Their presence in gasoline impairs its susceptibility to octane-improvement through adding compounds such as tetraethyl lead. When mercaptans are combusted they yield undesirable atmospheric contaminants in the form of sulfur oxides.
In present day processes, hydrogen sulfide is first removed from a sour distillate by contacting it with a selective solvent such as monoethanol amine. Subsequently, the mercaptans are removed by contacting the sour distillate with an aqueous alkaline solution (usually sodium hydroxide) thereby converting the mercaptans to water-soluble mercaptides such as sodium mercaptides. The alkaline solution, when separated from the sweetened distillate, retains the alkali mercaptide compounds and is regenerated for recycling to the sweetening process by converting the mercaptides present to disulfides. The conversion or oxidation of the mercaptides to disulfide is extremely slow. Consequently, a catalyst to increase the rate of conversion to disulfides is used. Ordinarily the disulfides formed are then removed from the alkaline solution by extraction with a suitable solvent such as naphtha. In a variation of the basic process, a mixture of distillate, aqueous alkaline solution, and catalyst is contacted with air thereby converting mercaptans present to the disulfides. Sweetened distillate is recovered from the reaction products. These basic processes are sometimes combined in a two-step mercaptan-removal process.
U.S. Pat. No. 2,966,453 discloses a process for oxidizing mercaptans to disulfides with an oxidizing agent (air) in the presence of a metal prophyrin catalyst or metal azoporphyrin catalyst. Metal prophyrins have a structure as follows where M is a metal and R is a substituent group which may be hydrogen, or an alkyl, aryl or other substituent containing up to 30 or more substituent atoms. ##SPC1##
Metal azoporphyrins have the following structure where M is a metal. ##SPC2##
U.S. Pat. Nos. 2,882,224; 2,988,500; 3,108,081; 3,230,180; and 3,148,156, relate to the use of phthalocyanine compounds as a catalyst in the oxidation of mercaptans in alkaline solution. The phthalocyanine compounds have a structural formula as follows where M preferably is cobalt or vanadium. ##SPC3##
Briefly stated our invention comprises in one aspect: (a) a method for oxidizing mercaptides to disulfides by contacting said mercaptides with an oxidizing agent (preferably air) in an aqueous alkaline solution (preferably sodium hydroxide) in the presence of a catalyst comprising a metal complex or metal compound of tetrapyridinoporphyrazine, or a substituted derivative thereof, on an inert granular support; (b) in a second aspect, a method for making one form of the metal-complex catalyst, and in another aspect; (c) the catalyst product resulting by depositing the metal complex on an inert carrier, such as granular activated carbon. In still another aspect our invention comprises an improvement in the technique of preparing the tetrapyridinoporphyrazine metal compound itself wherein the reaction is conducted under pressure in excess of atmospheric.
US Referenced Citations (4)
Continuation in Parts (1)
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Number |
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395256 |
Sep 1973 |
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Patent Grant
3980582
