US2072053A

US2072053A - Purification of naphthenic acids

Info

Publication number: US2072053A
Authority: US
Publication date: 1937-02-23
Anticipated expiration: 1954-02-23

Description

Patented Feb. 23 1937 UNITED STATES PATET OFFICE rnamonrron or minimum: ACIDS Waldersee B. Hendrey, Beacon, N. Y., asslgnor to The Texas Oompany, Ne w York, N. Y., a corporation of Delaware No Drawing. Application April 19, 1933, semi No. 666,844

20 Claims. (Cl. 260-108) form of their alkali metal salts. Inasmuch asthese acids find extended use in the arts, processes have been devised for the recovery and purification of such acids. The methods employed up to the present time however for refining, that is decolorizing said acids, have met with little success since they all fail to reduce the color oi. the acids to a degree necessary to meet the requirements of the arts, such as for instance the grease making industry.

The object of the present invention is to provide a process of producing stable light colored naphthenic acids from vacuum lubricating still residues or bottoms.

In accordance with the present invention these and other objects are attained by'separating the free acids from the still bottoms or residues and then subjecting the acids to a treatment with concentrated sulfuric acid, followed by a vacuum distillation of the naphthenic acids in a still composed of or provided with alining of a material which will not unfavorably influence the color of the acids at the distillation temperature. -Materials which nicely satisfy this requirement are aluminum and alloys or alloy steels containing chromium, and nickel in considerable amount, as, for example, 18% chromium and 8% nickel.

A very peculiar feature of my process is that the acid treatment of the free naphthenic acids unaccompanied by a subsequent vacuum distillation has no marked improving effect upon the color of the acids. Conversely a vacuum distillation without the acid treating step is not efiicacious in permanently lowering the color of the crude naphthenic acids. Light colored acids can be obtained by proper distillation but the-color darkens badly in storage. The color is only removed when the acid treating and distillation.

steps are applied in proper sequence. The par- Y 'ticular reason why this occurs is unknown to me.

which would otherwise become dark after distillaition. This, of course, is only a theory on my part i and hence my disclosure should not be in any way limited in view thereof.

In carrying out my invention, beginning with the crude alkaline still bottoms obtained by redistilling vacuum lubricating distillates from Gulf Coast crude oils over caustic, it is best to first emulsify the bottoms with water and then liberate the free acids from their alkali metal salts by the addition'of a strong mineral acid, such as sulfuric acid, according to the usual practice. The acids can then be drawn off and distilled to leave behind a large quantity of the admixed oil and l other impurities. The distilled crude acids thus obtained can then be submitted to my refining treatment to effect a conversion thereof into water in an emulsifying tank and heated to 150 200 F. In the event that the bottoms are passed 'directly into the emulsifying tank from the still no external-heat is required since the bottoms are at a temperature of 400-600 F'. when they are drawn from the still. The emulsified residue'is then treated with an acid of the nature of sulfuric acid. For instance, one may use any of the ordinary strengths of commercial sulfuric acid or even waste acid. The amount of acid used may vary between 6 to 12% by weight of 98% acid based on anhydrous bottoms. The actual quantity of sulfuric acid used is'dependent on the sodium naphthenate and free alkali content of the bottoms, suflicient sulfuric acid being used to neutralize any .excessalkali and to convert the sodium naphthenate to free acid. The resultant acidified solution is then allowed to settle to permit the free naphthenic acids to separate out. The crude free acids are then pumped oil, a.

product thus being obtained containing about 30% of water. During the settling period the temperature is maintained preferably at 140- 200 F.

The wet acids are then run into a heated insulated tank for further settling in order to reduce the water content in the free naphthenic acids to as low as 540%, The temperature of the solution during this settling operation is also maintained at about -200" F. The settling out of the water from the acid may be expedited naphthas, kerosene, and the like. It is advisable to reduce the water content below this amount if the acids are to be distilled in a batch distillation.' This, however, may be done in the still by a careful regulation of the temperature, the water being reduced to about 2% before distilling.

Considerable time is saved, however, by directly distilling the wet acids of say 5'-l0% water content in a tube still to produce a first distilled naphthenic acid which is relatively dark in color. During this initial distillation the preheater temperature is maintained at approximately 622 F. and the stream temperature at approximately 478 F; at 29 in. mercury vacuum. A distillate is thus obtained comprising from l-4% of naphthas, -40% of naphthenic acids and from 60-74% of very heavy bottoms which may be utilized for fuel or other suitable purposes. The saponification value of the initially distilled naphthenic acid fractions should be as high as possible (e. g. 100 up to about 270) and usually have a viscosity of about 150 Saybolt Universal at 210 F.

The once distilled naphthenic acids are then treated with sulfuric acid. Satisfactory results have been obtained by using approximately 5% by weight of 98% technical sulfuric acid. The solution thus obtained is diluted with a limited amount of water and the sludge permitted to settle. About 20% of water based on the weight of sulfuric acid has been found to give satisfactory sludge coagulation. Most of the sludge can be drawn off from the bottom. The naphthenic acid is then drawn from the top of this settling tank into a washing chamber where the acids are washed with water to remove any excess mineral acid. The number of washes required can be greatly reduced by the early use of a dilute so- 0 dium carbonate solution as a wash.

The washed naphthenic acids are then again vacuum distilled in distilling apparatus fabricated from non-ferrous material or from materials which are resistant to chemical action by the 5' acids. Suitable distilling equipment would comprise a still and fractionating column provided with the usual condensing and cooling coils.

The yield of the naphthenic acids in this distillation ranges from 70% to 90%, depending on 50 the type of charge and also upon the temperature of distillation. The residue is black and may be used as fuel cracking stock or added back to crude naphthenic acids for further treatment. The saponification value of the naphthenic acids 5 remains practically unchanged by the acid treatment. The color of the naphthenic acids, however, is materially lightened. The following table is the result of characteristic tests made on cuts from regular acids and from treated and 60 distilled acids:

70 Obviously manymodifications and variations of the invention, as hereinbefore set ,forth, may

be made without} departing from the spirit and scope thereof, and therefore'only such limitations should be imposed as are indicated in the ap- 75 pended claims.

, 3,072,058 I v I by diluting the solution with lighter oils such The reference to a non-ferrous stillin the appended claims includes the usual distilling apparatus, comprising a still, fractionating column. condensing and cooling means.

I clalmz' l. The process of decolorizing dark colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil which comprises treating said acids with concentrated sulfuric acid and vacuum distilling the so treated acids.

2. The process of decolorizing dark colored naphthenic acids derived from alkaline residues obtainedin the distillation of mineral oil which comprises treating said acids with approximately 5% by weight of 98% technical sulfuric acid and vacuum distilling the so treated acids.

3. The process of decolorizing crude naphthenic acids which comprises treating crude alkali naphthenates to liberate crude naphthenic acids, distilling said crude acids to produce once distilled acids, treating said once distilled acids with concentrated sulfuric acid and then vacuum distilling the so treated once distilled acids.

4. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises treating said residues with i an acid stronger than naphthenic acids to free the naphthenic acids contained therein, distilling the naphthenic acids thus freed to produce once so distilled naphthenic acids, treating said once distilled acids with sulfuric acid and then distilling the so treated once distilled acids.

5. The process of producing light colored naphthenic acids from vacuum lubricating still resi- I dues which comprises treating said residues with a mineral acid to free the naphthenic acids contained therein, distilling. the naphthenic acids thus freed to produce once distilled naphthenic acids, treating the once distilled naphthenic acids with concentrated sulfuric acid and then distilling the so treated once distilled naphthenic acids.

6. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises treating said residues with sulfuric acid to free the naphthenic acids contained therein, vacuum distilling the naphthenic acids thus freed to produce once distilled naphthenic acids, treating said once distilled naphthenic acids with concentratedsulfuric acid and then vacuum distilling the so treated once distilled naphthenic acids in a still formed of a material which will not unfavorably influence the color of the acids at the distillation temperature 7. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises emulsifying said residues, treating said emulsified residues with a mineral acid to free the naphthenic acids contained therein, distilling the naphthenic acids thusfreed to produce once distilled naphthenic acids, treating said once distilled naphthenic acids with concentrated sulfuric acid and then distilling the so treated once distilled naphthenic acids in a still formed of a material which will not unfavorably influence the color of the acids at the distillation temperature.

8. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises emulsifying said residues with water, treating the resultant emulsified solution with a mineral acid to free the naphthenic acids "contained in said residues, permitting the v solution to settle to decrease the water content 7 of said naphthenic acids, distilling said naphthenic acids, treating said distilled naphthenic acids with concentrated sulfuric acid, and distilling the so treated naphthenic acids in a still formed of a material which will not 'unfavorably influence the color of the acids at the distillation temperature.

9. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises emulsifying the residues with water, treating the resultant emulsified solution with a mineral acid to free the naphthenic acids contained therein, permitting the solution to settle to decrease the water content of said naphthenic acids, distilling the said naphthenic acids, treating said distilled naphthenic acids with concentrated sulfuric acid, diluting the resultant solution with water, permitting the diluted solution to settle to separate out the naphthenic acids, washing said naphthenic acids to remove excess mineral acids therefrom, and then vacuum distilling said washed acids in a still formed of a material which will not unfavorably influence the color of the acids at the distillation temperature.

10. The process of producing light colored naphthenic acids from vacuum lubricating still residues which comprises emulsifying the residues with water, treating the resultant emulsified solution with sulfuric acid to free the naphthenic acid contained therein, permitting the solution to settle to decrease the water content of said naphthenic acids, distilling the said naphthenic acids, treating said distilled naphthenic acids with concentrated sulfuric acid, diluting the resultant solution with water, permitting the solution to settle to separate out the naphthenic acids, washing said naphthenic acid with water to remove excess mineral acids therefrom, and then vacuum distilling said washed acids in a still formed of a material which will not unfavorably influence the color of the acids at the distil lation temperature. l 11. The process of decolorizing dark-colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil which comprises preliminarily treating said residues to liberate crude naphthenic acids, removing the liberated acids, treating said acids with concentrated sulphuric acid, and .vacuum distilling the so treated acids in a distilling zone the interior surface of which is formed from material which will not unfavorably influence the color of the acids at the distillation temperature.

'l2.'The process of decolorizing dark colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil, which comprises treating said acids with concentrated sulfuric acid, and distilling the so treated acids.

13. In a process for purifying naphthenic acids contaminated with carbonaceous materials, the steps of contacting said acids with an oxygencontaining, inorganic acid, diluting with water the mixture of naphthenic and oxygen-containing, inorganic acid and separating the naphthenic acids from the resulting coagulated sludge, and distilling the so treated acids. 1

14. In a process for purifying naphthenic acids contaminated with carbonaceous materials, the steps of contacting said acids with an oxygencontaining, inorganic acid, diluting with water the mixture of naphthenic acids and the oxygencontaining, inorganic acid, separating the naphthenic acids from the resulting coagulated sludge, washing the separatednaphthenic acids with a reagent adapted to remove any residual inorganic acidity therefrom, and distilling the so treated acids.

- 15. In a process for purifying naphthenic acids contaminated with carbonaceous materials, the steps of contacting said acids. with an oxygencontaining, inorganic acid, diluting with water the mixture of naphthenic acids and the oxygencontaining, inorganic acid, separating the naphthenic acids from the resulting coagulated sludge, washing the separated naphthenic acids with a reagent adapted to remove any residual inorganic acidity therefrom, distilling the naphthenic acids which are free from inorganic acidity and condensing the overhead product, and distilling the. so treated acids.

16. The process of producing decolorized naphthenic acids from alkaline residue containing sodium naphthenates obtained in the treatment of mineral oil, comprising preliminarily treating said residue to liberate crude naphthenic acids, removing the liberated acids, treating said acids with concentrated. sulphuric acid and distilling the so treated acids.

18. The process of decolorizing dark-colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil, which comprises acid-treating said naphthenic acids with strong acid to remove carbonaceous materials therefrom in the form of a sludge, and distillingthe so treated acids.

19. The process of decolorizing dark-colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil, which comprises acid-treating said naphthenic acids with strong acid to remove carbonaceous materials therefrom in the form of a sludge, removing the resulting sludge, neutralizing the treated naphthenic acids to remove remaining strong acid therefrom, and distilling the so treated acids.

20. The process of decolorizing dark-colored naphthenic acids derived from alkaline residues obtained in the distillation of mineral oil, which comprises treating said acids with concentrated sulphuric acid, removing the resulting sludge, neutralizing the treated naphthenic acids to remove sulphuric acid therefrom, and distilling the so treated acids.

WALDERSEE B. HENDREY.