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Publication numberUS2729591 A
Publication typeGrant
Publication dateJan 3, 1956
Filing dateJun 20, 1952
Priority dateJul 4, 1951
Also published asDE940005C
Publication numberUS 2729591 A, US 2729591A, US-A-2729591, US2729591 A, US2729591A
InventorsLeonard Denyer Ronald, Sylvia Haresnape Dorothy
Original AssigneeBritish Petroleum Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Sweetening of petroleum oils containing mercaptans with alkali and oxygen and then with alkali, a solutizer and oxygen
US 2729591 A
Abstract  available in
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Description  (OCR text may contain errors)

United States Patent'O SWEETENING OF PETROLEUM OILS CONTAINING MERCAPTANS WITH ALKALI AND OXYGEN AND THEN WITH ALKALI, A SOLUTIZER AND OXYGEN Dorothy Sylvia Haresnape, formerly Macken, and Ronald Leonard Denyer, Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited No Drawing. Application June .20, 1952,.

Serial No. 294,722

Claims priority, application Great Britain July 4, 1951 I 6 Claims. (Cl. 196-29) oils containing mercaptans.

' Among the processes which have been proposed for the removal of mercaptans from petroleum oils is the socalled solutiser process wherein the oils are contacted with an aqueouscaustic alkali solution containing a substance, such as an alkali metal phenolate or isobutyrate, capable of'increasing the solubility of the mercaptans in This inventionrelates to the sweetening of petroleum the caustic solution. The caustic solution is regenerated According to the invention therefore, a process for the sweetening of petroleum oils containing mercaptans, con sists in treating the oils with an aqueous caustic alkali solution containing a substance which is capable of increasing thesolubilityof the inercaptans in the alkali,

solution, in the presence of oxygen or an oxygen-containing gas. The aqueous caustic alkali solution containing the solubility promoter will heerinafter be referred to as the solutiser solution.

The mechanism of the sweetening operation appears to be that the mercaptans first go from the oil phase to the aqueous phase, at which stage both the mercaptan and total sulphur content of the oil are reduced. The mercaptans are oxidised in the aqueous phase, presumably to the insoluble disulphides which then return to the oil phase, thus increasing the sulphur content which gradually returns to its original value while the mercaptan content drops to zero. The caustic solution is thus continuously regenerated so that no separate regeneration process is needed. It is to be understood that the scope of the invention is in no way limited by the above explanation of the mechanism of the reaction.

The treatment of the oil with the solutiser solution may advantageously be carried out in two or more stages, all in the presence of oxygen or an oxygen-containing gas.

It has been found that a considerable conversion of mercaptans to disulphides may be effected by means of an aqueous caustic alkali solution alone, and it is therefore advantageous to treat the oil first with an aqueous caustic alkali solution containing no solubility promoter in the presence of oxygen or an oxygen-containing gas, and then with the solutiser solution likewise in the pres ence of oxygen or an oxygen-containing gas. This method of operation is more economical in the use of solutiser solution and has the further advantage of reducing the time of contact of the oil with th e solutiser solution and thereby considerably improving the colour of the prod uct.

It has been determined that the process of the invention is capable of sweeteninga sour naphtha containing 0.05% by weight mercaptan sulphur. The contact time required is of the order of 20-30 minutes in a two-stage process when giving the naphtha a 50/50 Wash with the solutiser solution. Commercial cresol may conveniently be used as the solubility promoter.

The invention will now be described by way of example asapplied to the continuous sweetening of an unrefined Iranian benzine having a boiling range of l00-150 C and a mercaptan content of 0.05 weight percent.

Two runs were carried out, the first being a treatment with a solutiser solution consisting ofS N NaOH+L5 N cresol and the second with 5. N caustic soda alone. A blanket of oxygen was maintained above the liquid during the whole'of the first run, and the total contact time was initially 30 minutes i. e. 15 in each stage, and was later reduced to 15 minutes and finally to 10 minutes. It was found that with the longer contact times the product was orange in colour probably due: to oxidation products of the cresols. The results of this run are given in the following table and indicate that a contact time of 20-30 minutes is required for a sweet product. The second run using 5 ,N NaOH alone was carried out as a blank experiment; oxygen was again present initially and the total contact time was 30 minutes. For the first 16 hours the product was doctor. negative, but gradually became sour, and finally settled down to a value of 0.002 per cent mercaptan. For the last few hours, the oxygen blanket was replaced by air, the contact time still remaining at 30 minutes. The mercaptan content of the product increased almost immediately, and after 4 hours had reached a value of 0.006 per cent. These results are shown in the table.

TABLE Continuous Z-state washing of unrefined -150 C. Iranian benzine Feedstock:

Conditions:

Rate of feed of spirit... Spirit-reagent ratio Run No M Wash Liquid Contact times:

1st stage 2nd stage Total (J0 at r- 1- cacao Oxygen feed Product from 1st stage:

Mcrcaptan sulphur, wt. percent Product from 2nd stage:

Total sulphur wt. percent. Mereaptan sulphur, wt. percen Acidity ml.N/20 NaOH/lOO ml Exlsteni; Gum mg./l00 ml 2 On On 0. 40 0. 40 trace trace 1 in the absence of a catalyst for the oxidation of mercaptans to disulphides with an aqueous caustic alkali solution containing a substance which is capable of increasing the solubility of the mercaptans in the alkali solution, so as to effect a further conversion of mercaptans into disulphides, and separating a sweetened oil from the caustic alkali solution.

2. A process. of sweetening. a petroleum oil containing mercaptans, which comprises mixing the oil with an aqueous caustic alkali solution in the presence of, free oxygen so as to convert part of said mercaptans into disulphides, separating the oil from, the caustic alkali solution, mixing the separated oil in the presence of free oxy gen but in the absence of a catalyst for the oxidation of mercaptans to disulphides with an aqueous caustic alkali solution containing a commercial cresol capable of increasing the solubility of the mercaptans in the alkali solution, so as to client a turther conversion of mercaptans into disulphides, and separating a sweetened oil from the caustic alkali s lu ion.

3. A process of sweetening a petroleum oil containing mercaptans, which comprises mixing the oil with an aqueous caustic alkali solution in the presence of free oxygen so as to convert part; of said mercaptans into disulphides, separating the oil from the caustic alkali sohu tion, mixing the separated oil in the. presence of free oxygen but in the absence of a. catalyst for the oxidation of mercaptans to disulphides with an aqueous solution consisting of N NaQH+1.5 N commercial cresol so as to effect a further conversion of mercaptans into disulphides, and separating a sweetened oil from the caustic alkali solution.

4. A process of sweetening a sour naphtha Containing more than 0.05%. weight of mercaptan sulphur, which comprises mixing the naphtha with an aqueous caustic alkali solution in the presence of free oxygen so as to convert part of said mercaptans into disulphides, separating from the caustic. alkali solution a naphtha containing not more than 0.05% weight mercaptan sulphur, mixing the separated naphtha in the presence of free oxygen but in the absence of a catalyst for the oxidation of mercaptans to disulphides with an aqueous caustic alkali solution containing a substance which is capable of increasing the solubility of the mercaptans in the alkali solution, so as to effect a further conversion of mercaptans into disulphides, and separating a sweetened oil from the caustic alkali solution.

5. A process of sweetening a sour naphtha containing more than 0.05% weight of mercaptan sulphur, which comprises mixing the naphtha with an aqueous caustic alkali solution in the presence of free oxygen so as to convert part of said mercaptans into disulphides, separating from the caustic alkali solution a naphtha containing not more than 0.05 weight mercaptan sulphur, mixing the separatednaphtha in the presence of free oxygen but in the absence of a catalyst for the oxidation of necrcaptans to disulphides with an aqueous caustic alkali solution containing a commercial cresol capable of increasing the solubility of the mercaptans in the alkali solution, so as to effect a further conversion of mercaptans into disulphides, and separating a sweetened 'oil from the caustic alkali solution.

6. A process of sweetening a sour naphtha containing more than 0.05% weight of mercaptan sulphur, which comprises mixing the napht a with an aqueous caustic alkali solution in the presence of free oxygen so as to convert part of said mercaptans into disulphides, separating from the caustic alkali solution a naphtha containing not more than 0.05% weight mercaptan sulphur, mixing the separated naphtha in the presence of free oxygen but in the absence of a catalyst for the oxidation of mercaptans to disulphides with an aqueous, solution consisting of '5 N NaOH+1.5 N commercial cresol so as to efiect a further conversion of mercaptans into disulphides, and separating a sweetened oil from the caustic alkali solution.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,945 Bolt Jan. 7, 1947 2,427,212 Henderson Sept. 9, 1947 2,474,028 Berger June 21, 1949 2,552,399 Browder' May 8, 1951 2,638,439 Browder et al. May 12, 1953 FOREIGN PATENTS 471,373 Canada Feb. 6, 1951 475,538 Canada July 24, 1951 629,914 Great Britain Sept. 30, 1949

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2413945 *Mar 9, 1944Jan 7, 1947Standard Oil CoTreating petroleum distillates
US2427212 *Dec 2, 1944Sep 9, 1947Pure Oil CoRemoval of peroxides from hydrocarbon oils
US2474028 *Apr 6, 1946Jun 21, 1949Inventors GuildRecovery of phenol salts from aqueous solutions
US2552399 *Feb 19, 1949May 8, 1951Standard Oil Dev CoTreating petroleum distillates
US2638439 *Apr 18, 1951May 12, 1953Standard Oil Dev CoTreatment of petroleum distillates
CA471373A *Feb 6, 1951Pure Oil CoRemoval of acidic sulfur compounds from hydrocarbon oils
CA475538A *Jul 24, 1951Pure Oil CoSweetening of hydrocarbon liquids
GB629914A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3063935 *Sep 1, 1960Nov 13, 1962Shell Oil CoHydrocarbon sweetening process
US4481106 *Dec 5, 1983Nov 6, 1984Uop Inc.Hydrocarbon treating process
Classifications
U.S. Classification208/204, 208/203
International ClassificationC10G27/00, C10G27/04
Cooperative ClassificationC10G27/04
European ClassificationC10G27/04