US2035741A

US2035741A - Of naphthenic acibs

Info

Publication number: US2035741A
Authority: US
Publication date: 1936-03-31
Anticipated expiration: 1953-03-31

Description

Patented Mar. 33, 1936 stares rarer 2&35341 FUBH HCATION' F NAPHTHENIO ACES No Drawing. Application October 2, 1933,

- Serial No. 691,895

1e Claims. (on. eco -s) compounds which are solid or semi-solid at ordinary temperatures. Their viscosity in most in- 5 stances is directly proportional to the viscosity of the-hydrocarbon fractions in which they were originally present. The acidic character of the naphthenic acids is believed to be due to the presence of one or more carboxyl (COOH) groups. 3 Naphthem'c acids, as originally obtained from the alkaline refining wastes of various hydrocarbon fractions including those stated above, possess a dark red to black color and this color subsists whether or not the acids be substantially free from associatedphenolic and hydrocarbon materials. When such acids are distilled, which may or may not be performed under reduced pressure, the overhead product is substantially colorless but it rapidly reverts to a dark amber or black color on standing, thereby rendering the acids unfit for use in many instances where a light colored product is to be used. Therefore, it is desirable to obtain colorless naphthenic acids which do not darken on standing even over a i prolonged period of time and which also possess a bland to sweet odor.

I have discovered that such a decolorization and steady stream, directly into the charge of.

naphthenic acids during the distillation thereof. l By operating in this manner, it is found that not only does the overhead product possess all of the desired characteristics as to odor and color but that these properties are retained even on standing for considerable periods of time.

i The normally gaseous oxidizing agents which- I propose to use in my invention'are gases con-- taining oxygen or which are capable of generating oxygen under the conditions which prevail during the deodorization and decolorization of the naphthenic acids to be hereinafter more fully 5 described. Typical examples of gases which may be employed in my process are: Air, nitrogen peroxide, mixtures of air and nitrogen peroxide, and mixtures of air and hydrocarbon gases or mixtures of oxygen and hydrocarbon gases. When mixtures of oxygen and hydrocarbon gases are employed, the amount of oxygen present should preferably be less than one-half by volume of the total amount of gas used. Thecatalysts which may be used in conjunction with the gaseous oxidizing agents set out above are cupric oxide, manganese dioxide, mercuric oxide, ferric oxide, litharge, etc.. While these oxides are themselves capable of deodorizing and decolorizing naphthenic acids as has been disclosed and claimed in my co-pending application, Serial No. 684,929, they are added in such small amounts that they cannot by themselves be considered to be responsible for the purification of the naphthenic acids. The addition of any of the above-named catalysts appears to bring about a reduction in the time necessary for contact be-, tween the acids and the gaseous oxidizing agent, and therefore may be said to increase the efiiciency of the latter. Only in the case of very dark colored naphthenic acids has any material improvement in the color of the finished product been observed when these catalysts were added. The decolorization and deodorization of the crude or semi-refined naphthenic acids according to my inventionis carried out in the absence of any substantial amounts of water and thus avoids the emulsificationdimculties which arise on treating naphthenic acids with aqueoussolutions of oxidizing agents such as has been done in' the past. Moreover, the introduction of the gaseous oxidizing agent into the still charge does not only agitate the mass to be treated, but also tends to lower the temperature necessary to distil the naphthenic acids overhead and in so doing eliminates any substantial danger of thermal decomposition during the distillation stage. As

the treating agents used in this invention are material which is believed to be due to the treatdrocarbon gas in order to eliminate the admixed asphaltic and carbonaceous materials. The partially purified naphthenic acids are then redis- 'tilled while introducing a current of air or of any of the gaseous oxidizing agents previously enumerated. While this preliminary distillation in the presence of steam or hydrocarbon gas has been found to be helpful in a number of cases, especially where excessive temperatures are to be avoided, it is not considered to be an essential step in the obtainment of the desired results.

Therefore, my invention may be said to reside in a process for deodorizing and decolorizing naphthenic acids which comprises treatment during distillation or heating thereof, with gases containing oxygen or capable of generating oxygen under the conditions prevailing during the aforesaid deodorization and decolorization. My invention also extends. to the employment of small amounts of inorganic oxide catalysts in conjunction with the aforesaid gaseous oxidation agents. In a more limited fashion, my invention relates to the deodorization and decolorization of naphthenic acids by introducing a suitable quantity of air into naphthenic acids while'the same are being heated or distilled for the purpose of obtaining a product of a highly stable color and a bland odor.

Considering, the process in greater detail, a caustic liquor, such as might be obtained by treating crude kerosene or a liquid sulphur dioxide extract thereof, with sodium hydroxide, is neutralized in such a manner that it is only slightly basic toward phenolphthalein. By so operating, the naphthenic acids, in contrast to the phenols, are not liberated from their alkali metal salt but remain as sodium naphthenates. The resulting mixture of sodium naphthenates, phenols, and admixed hydrocarbons is then steam distilled. The sodium naphthenates remain behind in the still and when dissolved in water and treated with sulphuric acid, produce naphthenic acids which contain only very small amounts of phenols and admixed hydrocarbons. These crude naphthenic acidsare of a poor color and contain considerable amounts of insoluble carbonaceous material. They are preferably subjected to a preliminary distillation in the presence of dry steam or some of the normally gaseous hydrocarbons such as ethane or methane, to remove the above-mentioned undesirable fractions. The effect of the introduction of the steam or hydrocarbon gas is to lower the temperature necessary to distil the mixture and thereby avoid any undue cracking and eliminate the necessity of carrying out the distillation under reduced pressure.

The overhead product when first condensed is a clear light yellow liquid but acquires a deep red color so rapidly that in a few hours layers greater than an inch in depth are virtually opaque. Small amounts of water usually come over during the initial stages of the distillation and may be removed by a simple settling or centrifuging process.

The semi-refined naphthenic acids which were condensed as an overhead product are subsequently introduced into a still provided with any suitable meansfor introducing the gaseous oxidation agent during the distillation of the naphthenic acid still charge. If desired, small amounts ofv inorganic oxides such as cupric oxide mospheric pressure until substantially all of the purified naphthenic acids are removed as an overhead product. They are found to be of an excellent color and possess a bland to sweet odor and do not darken on standing even for a period of time as long as six months. In addition, they possess an increased acid number and saponiflcation number and a decreased sulphur content'in comparison with the crude product.

Example 1* A mixture of crude naphthenic acids derived from the caustic liquor obtained in the refining of a kerosene fraction and which has been substantially freed from admixed phenols by careful acidification, steam distillation and acidification of the sodium naphthenate residue as previously described, had the following properties:

Acid number 283 mgs. KOH per gramof substance Saponification number 283 mgs. KOH per gram of substance Specific gravity 0.97 Color Dark brown Sulphur content 0.21%

Boiling range; 480-580" F. Sediment 1 to 2% These acids were subsequently distilled in the presence of small amounts of dry steam or hydrocarbon gas which was introduced into the still during the distillation. The semi-refined naphthenic acids which were condensed as an overhead product had the following properties:

Acid number 284 mgs. KOH per gram of substance Saponification number 286 mgs. KOH per gramofsubstance Specific gravity 0.95 Sulphur content 0.12% Boiling range 480-575" F.

Sediment None 2,085,741 475%. to 565 F. for the finished product which had the following characteristics:

The same amount of semi-refined acids as used in Example 1 was introduced into a still containing 0.05% by weight of cupric oxide and distilled while introducing a slow current of air. The finished product obtained on condensation, had the following properties:

Boiling point range 476 F. to 567 F.

Acid number 288 mgs. KOH per gramofsubstance Saponiflcation number"--. 307 mgs. KOH per gramof substance Specific gravity--. 0.951 Sulphur content 0.07% ColorN.P.A 1 Color N. P. A. after six months standing 1%.;

The amounts of air introduced are of course somewhat dependent upon the particular charge of naphthenic acids to betreated. In general, about 10 to 50 volumes of air (or its equivalents) per volume of naphthenic acids are sufiicient to bring about the desired decolorization and deodorization. The rate of introducing the gaseous oxidizing agents should be such that no frothing over of the still charge may take place. Where continuous distillation is employed, the air or other gaseous oxidizing agent is introduced into the naphthenic acid stream either at the inlet of the heating coil or at the bottom of the flashing chamber or reflux tower. The former is preferred in such cases where the acids do not contain excessive amounts of carbonaceous materials.

Although the above-mentioned process has been more particularly described in connection with naphthenic acids derived from kerosene, it may be equally well carried out in the purifica tion of higher boiling naphthenic acids derived from heavier hydrocarbon frmtions such as stove be considered as limitations thereupon as many variations may be made by those skilled in the art within the scope of the claims appended hereto.

What I claim is:

1. In a process for deodorizing and decolorizing naphthenic acids the step which comprises contacting said acids at temperatures from! 475 F. to 565 F. with oxygen-containing gaseous oxidation agents adapted to impart a light color of high stability and a bland odor to the aforesaid naphthenic acids.

2. A process according to claim 1 in which the oxygen-containing gaseous oxidation agent is introduced during distillation of the naphthenic acids.

3. A process as defined in claim 1 in which the contacting of the naphthenic acids with the gaseous oxidation agents is carried out in the presence of a metal oxide oxidation catalyst capable of increasing the eflicient action of the aforesaid gaseous oxidation agents.

4. A process as defined in claim 1 in which the contacting of the naphthenic acids with the gaseous oxidation agents is carried out-in the presence of metal oxide catalysts capable oi? increasing the efllcient action oi the aforesaid gaseous oxidation agents. 1

5. A process as defined in claim 1 in which the total amount of the gaseous oxidation agents employed is from 10 to 50 times by volume that of the liquid naphthenic acids.

6. In a process for deodorizing and decolorizing naphthenic acids, the step which comrises contacting. said acids at temperatures from 475 F. to 565 F. with air.

7. A process according to claim 6 in which the air is introduced during distillation of the naphthenic acids.

8. A process as defined in claim 6 in which the contacting of the naphthenic acids with air is carried out in the presence of metal oxide catalysts capable of increasing the 'efiicient action thereof.

9. In a process for deodorizing and decolorizing naphthenic acids, the step which comprises contacting said acids at elevated temperatures with nitrogen peroxide. e

10. In a process for deodorizing and decolorizing naphthenic acids, the step which comprises contacting said acids at elevated temperatures with mixtures of air and nitrogen peroxide.

11. A process for deodorizing and decolorizing naphthenic acids which comprises distilling a mixture of crude naphthenic acids to rempve the admixed carbonaceous materials present therein and redistilling the overhead product'so obtained in the presence of an oxygen containing gaseous oxidation agent whereby there is imparted a light color of high stability and a bland odor to the aforesaid naphthenic acids.

12. A process for deodorizing and decolorizing naphthenic acids according to claim 11, in which the oxidation agent used is air.

13. A process for deodorizing and decolorizing naphthenic acids accordingv to claim 11 in which the oxidation agent used is a mixture of air and nitrogen peroxide. Y

14. A process as defined in claim 11 in which the redistillation, of the naphthenic acids with the gaseous oxidation agents is carried out in the presence of metal oxide oxidation catalysts capable of increasing the efiicient action a: the

aforesaid gaseous oxidation agents.

15. A process for obtaining naphthenic acids of a high color stability and a bland odor which comprises extracting a petroleum fraction with alkali, acid treating the resulting extract in such a manner that only the phenols admixed with the alkali salts of the naphthenic acids are liberated, distilling the phenols overhead, liberating the free crude naphthenic acids from the alkali naphthenates remaining in the still after the said distillation for the removal of-the phenols has been completed, distilling. the liberated naphthenic acids to remove the admixed carbonaceous materials present therein and redistilling the so obtained overhead product in the presense of a. gaseous oxidation agent whereby there is imparted a light color. of high stability and a bland odor to the aforementioned naphthenic acids.

16. A process for obtaining naphthenic acids of a high color stability and a bland odor according to claim 15 in which the oxidation agent l0 used is air,

1'7. A process for obtaining naphthenic acids of a high color stability and a bland odor according to claim 15 in which the oxidation agent used is a mixture of air and nitrogen peroxide.

18. A process for deodorizing and decolorizing naphthenic acids with gaseous oxidation agents in the presence oi metal oxide catalysts capable of increasing the eflicient action thereof in which the amount of the catalysts used amounts to approximately .001% to 0.1% of the naphthenic acids undergoing treatment.

FREDERICK J. EWING.