US2076581A - Method of refining gasoline - Google Patents

Description

Patented Apr. 13, 1937 UNITED STATES PATENT OFFICE METHOD OF REFXNING GASOLINE No Drawing. Application February 18, 1933, Serial No. 857,467

15 Claim.

This invention relates to the refining of motor fuels and more particularly to processes for treating motor fuels which contain substituents normally tending to readily discolor and form gum on storage, for the purpose of removing such color-forming and gum-forming constituents.

The motor fuels at present on the market mainly comprise gasolines of various types. Straightrun gasolines which are normally obtained by distilling off the lighter fractions of petroleum comprise mainly saturated hydrocarbons and are rel atively stable. However, they do contain some unstable compounds which apparently oxidize and polymerize on storage to form colored compounds and gummy substances, some of which are insoluble and some of which are soluble but non-volatile. These straight-run gasolines are not, as a general rule, satisfactory for use in the present day types of internal combustion motors.

Accordingly, it is generally the practice to add,

to these straight-run gasolines, unsaturated hydrocarbons, either as such or in the form of cracked gasoline, to increase the efficiency and anti-knock value of the straight-run gasolines.

-35 These additions to the straight-run gasolines generally increase the color-forming and gum-forming constituents thereof. Some of the motor fuels placed on the market consist wholly of cracked gasolines which contain very large proportions of unsaturated compounds. Other motor fuels, such as motor petrol, consist almost entirely of unsaturated hydrocarbons. All of these different types of gasoline tend to discolor and form non-volatile and/or insoluble gummy and resinous products on storage. These gummy and resinous products are extremely objectionable as they tend to clog up the feed lines, cause sticking of the valves, and generally decrease the efficiency of the internal combustion engines in which the motor fuels containing them are employed. I have found that the unsaturated compounds in such motor fuels generally comprise two different types: one type comprises the poly-oleflnes, such as the dienes, naphthenes and the like.

of compounds comprises, as a general rule, the smaller proportion of the unsaturated compounds and tend to readily form gum and colored products which then appear to act as catalysts accelcrating the formation of gum by the other unsaturated constituents, and, being in very small proportions, have but slight anti-knock value. The second class of unsaturated compounds comprises the major portion of the unsaturated constituents of the motor fuels and are composed mainly of the mono-oleflnes. These mono-ole- This class fluoric acid in sufficient amount and over a sufll- 45 fines are comparatively stable and are not readily oxidized and polymerized to form gum and colored products although they will, of course, form such products when stored over long periods of time. Also, these mono-olefines have high anti-knock 5 value and comprise substantially all of the unsaturated compounds which have anti-knock value of any commercial importance.

Accordingly, it has become apractice to treat such motor fuels by various methods in order to 10 remove the color-forming and gum-forming constituents. The most common method at present employed comprises treatment of the motor fuel with sulfuric acid, thereby removing objectionable unsaturated compounds together with benel5 ficial compounds thus, at the same time, greatly reducing the anti-knock value of the motor fuel. These ordinary methods employed for refining motor fuels not only remove the poly-oleflnes, dienes, and naphthenes but also large proportions of the mono-olefines.

An object of the present invention is to provide a process for refining motor fuels which normally tend to form gum and colored products. A further object is to provide a process for treating 25 motor fuels whereby the readily oxidizable and polymerizable constituents which tend to readily form gum on storage are removed from the motor fuels without materially decreasing the antiknock value of the motor fuel. A still further 30 object of this invention comprises a process for treating motor fuels whereby the readily oxidizable. and polymerizable constituents which tend to readily form gum on storage are removed from the motor fuels without removing any substan- 35 tia1 proportion of the mono-olefines or other substituents' having high anti-knock value. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter. 40

These objects may be accomplished in accordance with my invention which comprises treating motor fuels which normally tend to readily form gum and colored products on storage with hydrobe separated from the insoluble gummy substances by decantation. The hydrofluoric acid can be removed from the motor fuel by washing the motor fuel with caustic alkali and then the a motor fuel may be separated from the soluble nonvolatile as well as the insoluble substances by distillation.

The hydrofluoric acid apparently does not materially aflect the mono-oleflnes and other relatlvely stable unsaturated compounds which have high anti-knock value, which mono-oleflnes and desirable unsaturated compounds are retained in the motor fuel. Accordingly, this treatment of the motor fuels with hydrofluoric acid removes substantially all of the substituents which tend to readily form gum and colored products without materially decreasing the anti-knock value of the motor fuel as material amounts of the substituents of the motor fuel which have desirable high 2 anti-knock value are not removed.

In order to more clearly illustrate my invention and the preferred mode of carrying the same into effect and the desirable results obtained 5 thereby, the following examples are given:

Example 1 A sample of highly unsaturated gasoline of known instability toward oxidation was treated with 1% of its weight of anhydrous hydrofluoric acid at room temperature. After the mixture had been allowed to stand for several hours (about 3-4 hours), the free hydrofluoric acid was removed by washing the gasoline with an aqueous solution of sodium hydroxide. The gasoline was then separated from the caustic alkali solution and the precipitated gum and redistilled. Some non-volatile material remained in the still after distillation. Two portions of this treated and distilled gasoline were taken; to one portion 0.005% of catechol, which is a well known gum inhibitor was added, the other portion contained no gum inhibitor. Two samples of ordinary untreated gasoline were taken; to one sample 0.005% of catechol was added while no gum inhibitor was added to the other.

All of these samples or portions were subjected to the "Oxygen bomb test" proposed by Voorhees and Essinger in their paper on Importance and significance of gum in gasoline" in Proc. Am.

Pet. Inst. 10, Sec. II, 169 (1929). This test consists in heating 25 cc. of gum-free unsaturated gasoline under an oxygen atmosphere in a rubber stoppered glass flask at 100 C. The heating period in all tests was 4 hours. After heating, the gasoline was evaporated in an inert atmosphere and the residue of non-volatile matter was weighed. As a result of these tests the sample of gasoline which had been treated with hydrofluoric acid and to which had been added the catechol. formed 17 and 19 mg. of gum per 25 cc. 225mg. of gum per 25 cc. was formed in the sample of gasoline which had not been treated with hydrofluoric acid and which contained catechol. 110 mg. of gum per 25 cc. were formed in the sample of gasoline which had been treated with hydrofluoric acid but to which no catechol had been added while 450 mg. gum per 25 cc. was formed in the untreated gasoline to which no catechol had been added. The octane ratings, determined as described in Chim. and Ind." v01. 25, 1339-47, 1931, of a sample of the gasoline which was treated with hydrofluoric acid but to which no catechol was added was 89 and that of a sample of the gasoline which had not been treated with 75 hydrofluoric acid and to which no catechol had been added was 88.5. The induction periods of the treated and untreated gasoline: were 2% hours and 15 minutes, respectively.

Example 2 A sample of gasoline was treated with hydrofluoric acid and caustic soda as in Example 1. A sample of this treated gasoline and also a sample of the ordinary untreated gasoline were tested for their color stability in the presence of iron. This test consisted of storing gasolines in contact with a strip of rusty and a strip of bright iron in a dark cupboard. The colors of the samples were measured in a Lovibond tintometer before storage and again at the end of 10 and 21 days. The :zzults in units of color are given in the following In the above examples 1% of anhydrous hydrofluoric acid was employed. However, it is not necessary to employ this specific amount of hydrofluoric acid or that the hydrofluoric acid be anhydrous. The concentration and amount of hydrofluoric acid will depend upon and vary with the type of motor fuel treated and the amount of objectionable constituents to be removed. For example, as little as 0.1% or as much as'5% may be employed, if desired. However, for any one gasoline the efllciency of the treatment will be in proportion to the amount of hydrofluoric acid employed and the time required for the most complete removal of the objectionable constituents will vary, inversely with the amount of hydrofluoric acid employed. We have found that in most cases 1-2% of hydrofluoric acid will be most satisfactory for reasons of efficiency and economy, with the hydrofluoric acid maintained in contact with the motor fuel over a period of 3-4 hours. Motor fuels with a lower proportion of unstable components than those employed in the examples have been successfully treated with as little as 0.5% of hydrofluoric acid. If'desired. hydrofluoric acid containing substantial amounts of water may be employed with, however, less emcient removal of the objectionable constituents.

While, in the examples, the motor fuel treated was an unsaturated gasoline, it will be understood that the process of my invention is applicable to all motor fuels containing constituents having a greater degree of instability (or less stable) than mono-oleflnes, for example motor fuels containing poly-olefines, naphthenes and the like.

From the preceding description, it will be apparent that the process of my invention provides a method for the rapid removal of the easily oxidizable and polymerizable constituents of motor fuels without removing the desirable constituents having high anti-knock value. Motor fuels, such as gasolines and the like, obtained by the cracking of petroleum and the like, when treated in accordance with my method, can be employed alone or can be utilized with any proportions of saturated hydrocarbons and thus stable fuels of unprecedently high anti-knock value can be obtained without requiring the use of lead tetra ethyl and the like.

While I have described the preferred form 01 my invention, it will be readily understood by those skilled in the art that many variations and modifications may be made in the method and conditions employed, without departing from the spirit of my invention. Accordingly, the scope of my invention is to be limited solely by the appended claims construed as broadly as is permissible in view of the prior art.

in I claim:

1. The method of refining gasoline containing mono-oieflnes and constituents more easily polymerizable than the mono-oleflnes which comprises contacting the gasoline with substantially l5 anhydrous hydrofluoric acid alone in an amount suflicient to polymerize the more easily polymerizabie constituents, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents 0 is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

2. The method of refining gasoline containing mono-oleflnes and constituents more easily polymerizable than the mono01eflnes which comprises contacting the gasoline with from about 0.1% to about 5% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

3. The method of refining gasoline containing mono-olefines and constituents more easily polymerizabie than the mono-oleflnes which comprises contacting the gasoline with from about 1% to 2% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

4. The method of refining gasoline containing mono-olefines and constituents more easily polymerizable than the mono-oleflnes which comprises contacting the gasoline with substantially anhydrous hydrofluoric acid alone in an amount suflicient to polymerize the more easily polymerlzable constituents, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the moreeasily polymerizable constituents is complete, then washing the gasoline at with aqueous caustic alkali, separating the resulting water solution from the gasoline, and flnally distilling the gasoline.

5. The method of refining gasoline containing mono-oleflnes and constituents more easily polymerizable than the mono-oleflnes which comprises contacting the gasoline with from about 0.1% to about 5% of substantially anhydrous hydrofluoric acid alone maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents is complete, then washing the gasoline with aqueous caustic alkali, separating the resulting water solution from the gasoline, and finally distilling the motor fuel.

7 6. The method of refining gasoline containing mono-olefines and constituents more easily polyrnerizable than the mono-olefines which comprises contacting the gasoline with from about 1% to 2% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization or the more easily polymerizable constituents is complete, then washing the gasoline with aqueous caustic alkali, separating the resulting water solution from the gasoline, and finally distilling the gasoline.

7. The method oi refining cracked gasoline which comprises contacting the gasoline with substantially anhydrous hydrofluoric acid alone in, an amount sufliclent to polymerize the less stable constituents, maintaining the gasoline and hydrofluoric acid in contact until the polymeriza tion of the more easily polymerizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

8. The method oi refining cracked gasoline which comprises contacting the gasoline with from about 0.1% to about 5% ct substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization oi the more easily polymerizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

9. The method of refining cracked gasoline which comprises contacting the gasoline with from about 1% to 2% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymcrization oi the more easily polymerlzable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

10. The method of refining cracked gasoline which comprises contacting the gasoline with substantially anhydrous hydrofluoric acid alone in an amount suflicient to polymerize the less stable constituents, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents is complete, then washing the gasoline with aqueous caustic alkali, separating the resulting water solution from the motor fuel, and finally distilling the gasoline.

11. The method of refining cracked gasoline which comprises contacting the gasoline with from about 0.1% to about 5% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerlzable constituents is complete, then washing the gasoline with aqueous caustic alkali, separating the resulting water solution from the gasoline, and finally distilling the gasoline.

12. The method or reflning cracked gasoline which comprises contacting the gasoline with about 1% to 2% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until the polymerization of the more easily polymerizable constituents is complete, then washing the gasoline with aqueous caustic alkali, separating the resulting water solution from the motor fuel, and finally distilling the gasoline.

13. Motor fuel obtainable by treating gasoline, containing mono-oleflnes and constituents more easily poiymerizable than the mono-oleflnes, with substantially anhydrous hydrofluoric acid alone in an amount sufliclent to polymerize the more easily polymerizable constituents, maintaining the gasoline and hydrofluoric acid in contact until polymerization of the more easily polymerizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

14. Motor fuel obtainable by treating gasoline, containing mono-oleilnes and constituents more 5 easily polymerizabie than the mono-oleflnes, with from about 0.1% to about 5% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until polymerization of the more easily poly- 1o me rizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

'merizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

MORRIS S. KHARASCH.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,581.

April 13, 1937.

MORRIS S. KHARASCH.

It is hereby certified that error a of the above numbered patent requiring first column, line 69, claim 5, and sec 10 and 12, respectively, for said Letters Patent should be correction as follows: Page 3,

therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of June, A. D. 1937.

(Seal) Henry Van Arsdale ppears in the printed specification ond column, lines 44 and 64, claims "motor fuel read gasoline; and that the read with these corrections Acting Commissioner of Patents.

rating the hydrofluoric acid and polymerized constituents from the gasoline.

14. Motor fuel obtainable by treating gasoline, containing mono-oleilnes and constituents more 5 easily polymerizabie than the mono-oleflnes, with from about 0.1% to about 5% of substantially anhydrous hydrofluoric acid alone, maintaining the gasoline and hydrofluoric acid in contact until polymerization of the more easily poly- 1o me rizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

'merizable constituents is complete, and then separating the hydrofluoric acid and polymerized constituents from the gasoline.

MORRIS S. KHARASCH.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,581.

April 13, 1937.

MORRIS S. KHARASCH.

It is hereby certified that error a of the above numbered patent requiring first column, line 69, claim 5, and sec 10 and 12, respectively, for said Letters Patent should be correction as follows: Page 3,

therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of June, A. D. 1937.

(Seal) Henry Van Arsdale ppears in the printed specification ond column, lines 44 and 64, claims "motor fuel read gasoline; and that the read with these corrections Acting Commissioner of Patents.