US2013198A - Gum inhibitor - Google Patents

Description

Patented Sept. 3, 1935 UNITED STATES- :PATENT OFFICE GUM mnmrroa Arthur L. Blount, Palos Vcrdcs Estate's. Galif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application August 21, 1933,

. g Serial No. 686,071

24 Claims. (Cl. 44- 9) The present invention relates to a process and means for the protection of liquid hydrocarbon products against the formation of soluble and insoluble gummy products. More particularly does it relate'to a new and useful series of compounds which, when added to various liquid hydrocarbons tend to prevent or substantially inh hibit the formation of the above mentioned gums during storage or use. This invention is a continnation in part of my application, Serial Number 685,079, filed August 14, 1933.

Liquid hydrocarbons, produced on a'commercial scale, and particularly those prepared from crude petroleum oils by any of the well known processes of distillation, cracking or solvent extraction, possess on standing a tendency to form gummy and resinous substances. This is particularly the case with those light motor fuels which are produced by subjecting various petroleum fractions to any of the well known cracking processes, and which as a result thereof contain varying percentages of' highly unsaturated compounds. Unrefined hydrocarbon fractions, obtained by the more recent methods of vapor phase cracking are known to contain as high as 15 to 20% of these highly unsaturated bodies. Although the exact chemical composition of these unsaturated bodies has not yet been completely determined, it is believed that they consist principally of diolefines and other higher oleflnic hydrocarbons. These compounds possess a high degree of residual afiinity and in the presence of air are capable of being oxidized, which ultimately results,in the formation of a series ,of products some of which are resinous or gummy. This reaction is believed to be catalyzed by the presence of sunlight, although" considerable gum formation has been detected in hydrocarbons which were stored in the dark. The rate of oxidation in general is believed to be directly proportional to the degree of unsaturation of the particular compounds.

1% has been customary to treat crude hydrocarbon fractions obtained from petroleum oils,

5o ers earth or aluminum chloride,

The treatment of some of the more volatile hydrocarbon fractions such as motor fuels with sulphuric acid has not proved to be entirely satisfactory largely on account of more or less severe losses of both material and anti-knock value. It is a known fact that many of these highly unsaturated bodies possess more or less excellent anti-knock properties and their retention in the motor fuel would be desirable, were it not for the fact that they are responsible for the ultimate formation gums. The vapor -phase clay treatment, while tending to produce a polymerization of the unsaturates and allowing for the removal of the polymerized product, is characterized by a low yield, while the vapor phase aluminum chloride treatment of the lighter hydrocarbon fractions does not always produce desirable results and also produces motor fuels 'of a relatively low anti-knock value.

While the customary methods employed in the purification of crude hydrocarbon fractions may be so modified as to remove the major portion of these unsaturated bodies, it is found that such procedures are costly and destructive as to antiknock properties. Vast ,amounts of refining chemicals are to be used in such cases and in many instances valuable constituents are recombustion engine or the internal combustion engine itself.

retion and'sticking valves may be directly at- Many cases of ineificient carbutributed to the presence of gums.

It is, therefore, considered desirable to inhibit the formation of these soluble and insoluble gums and resins and simultaneously to improve the quality of the hydrocarbon and to eliminate the above mentioned difiiculties arising out of the formation of these undesirable compounds in the hydrocarbons during storage or use;

By my invention, to be hereinafter more fully described, the usual purification processes ineluding those set out above, may be entirely eliminated or else substantially reduced in intensity without detracting from the quality of the-liquid hydrocarbon. Another one of the essential features which distinguish the present invention from any of the known processes of treating hydrocarbon fractions is that only small amounts or none at all of the potential gum forming constituents are removed by filtration or decantation' as is the case where liquid hydrocarbons are treated with large proportions of acids, alkalies or various salt solutions.

I have discovered that the organic compounds of the normally non-gaseous elements of the fifth group of the periodic system and more particularly the organic oxides of antimony and arsenic exhibit excellent gum inhibiting properties. When these organic oxides are added in small amounts to the various hydrocarbon fractions which contain easily oxidizable bodies, gum for- -mation during storage thereof is markedly retarded. Thus, a cracked hydrocarbon fraction which may become contaminated with gums even after a few hours, is rendered stable by the addition of these compounds. The amounts of the gum inhibiting agents which are added to the various hydrocarbon fractions are very small and will not effect the volatility or the burning power or the viscosity thereof to any noticeable degree. They range from 0.001% to 0.1% or higher depending upon the nature of the inhibitor and the tendency of the material to form gums. In many instances the customary sulphuric acid and alkali treatments may be entirely eliminated or else substantially reduced by the addition of these compounds. which is a blend of a cracked and a straight run stock, I may add my inhibitor directly to the cracked component without having to subject it to a treatment with acid and alkali, and then blend it with the straight run fraction. It is, however, deemed desirable first to subject the particular hydrocarbon fraction, to which the inhibitors are to be added, to a treatment with sodium plumbite or an equivalent agent, to render it negative toward the so-called doctor test. Moreover, by the use of these inhibitors in a motor fuel, all of the desirable unsaturated compounds of good anti-knock properties may be retained therein and at the same time any gum forming tendency is substantially inhibited.

Hence, it is an object of my invention to provide a process for obtaining high grade liquid hydrocarbons with the minimum amount of labor and cost of refining chemicals.

It is another object of my invention to provide a process for the treatment of hydrocarbon fractions which are subject to the formation of gums and resins on exposure to light and air, or during storage, whereby these harmful defects are prevent or inhibited to a substantial extent.

It is another object of my invention to provide a process for treating liquid hydrocarbons whereby a substantial amount of unsaturated bodies 7 Thus, in the case of a gasolineinvention further resides in the addition of these oxides to crude hydrocarbon fractions containing large amounts of easily oxidizable bodies without previously subjecting these fractions to any process whereby the said bodies might be wholly or partially removed as an independent process. My invention also resides in the use as gum inhibitors of any and all of the specific organic oxides hereinafter more fully disclosed. As the inhibition of gum formation is closely associated with the absence of substances which are capable of acting as oxidizing agents, I prefer to use metallic oxides in which the valence of the metallic elements is less than their maximum of five. Although the specific metallic oxides which I propose to use as gum inhibitors contain an oxygen atom in the molecule, they do not act as oxidizing agents as far as the inhibition of gum is concerned.

Amongst the organic oxides of antimony and arsenic which may be employed as gum inhibitors are the following.

(1) Organic oxides of arsenic containing an unsubstituted phenyl group such as phenyl arsine oxide,

as well as organic oxides of arsenic containing an alkyl substituted phenyl group such as xylyl arsine oxide (which may be readily prepared from commercial xylidine which usually contains all possible isomers), 2,3 dimethylphenylarsine oxide 2,4 dimethylphenylarsine oxide 2,5 dimethylphenylarsine oxide 2,6 dimethylphenylarsine oxide 3,4 dimethyphenylarsine oxide mC-QAFO 3,5 dimethylphenylarsine oxide C II:

2 methylphenylarsine oxide 3 methylphenylarsine oxide 4 methylphenylarsine oxide and organic oxides of arsenic having an alkoxy group in the para position.

(2) Organic oxides of antimony containing an unsubstituted phenyl group such as phenylstibine oxide organic oxides of antimony containing an alkyl substituted phenyl group such as, xylystibine oxide (which may be readily prepared from commercial xylidine which usually contains all possible isomers) as well as all other stibine oxides corresponding to the arsine oxides enumerated above.

The most effective members of this class of organic oxides are those having no substituent in the benzene ring such as phenylarsine oxide or phenylstibine' oxide and those having a substituentin the benzene ring in a para position with respect to the metallic oxide radical (i. e. in the 4 position) especially 4 methyl phenyl arsine oxide and paraethoxy phenylarsine oxide or. the corresponding stibine oxides. These specifically mentioned compounds are especially effective in inhibiting gum formation as may be seen from the examples hereinafter described. The character and the position of the substituent on the benzene nucleus influence to some extent the effectiveness and the persistence of the efiectiveness of the various arsine or stibine oxides. Thus, while paraethoxyphenylarsine oxide is particularly effective initially, it does not exert its protecting influence for as long a period of time as 2,4 and 2,5-dimethylphenylarsine oxide which are not quite as eifective in inhibiting gum formation immediately after addition to the hydrocarbon fractions but continue to exert their influence for periods of time of six months or longer.

The above mentioned compounds as wellas the other members of. the class to which they belong,

all exhibit the desired characteristicsof good gum inhibitors. They are soluble in most liquid hydrocarbons, they are all fairly strong reducing agents, their solubility in oil is greater than that in water, although traces of water in a hydrocarbon fraction will not cause them to separate out, and they do not form colored substances upon reaction with air or the unstable materials in the gasoline or other liquid hydrocarbon fractions. Although certain members of this class of inhibitors may exhibit better inhibiting tendencies and greater stability in one hydrocarbon'fraction over another, they nevertheless reduce the possibility of gum formation in all kinds of liquid hydrocarbons amount thereof to the stock to be treated in order to obtain the desired concentration of the inhibitor in the treated stock. Or, the total amount of any inhibitor may be added directly to the stock and complete solution thereof brought about by means of suitable agitation.

The following examples are illustrative of the invention herein disclosed:

Example 1 A crude pressure distillate of the gasoline type which had a copper dish gum content of 200 milligrams per 100 cc. was mixed with 0.003%, 0.005%, 0.010%, and 0.015% of phenyl arsine oxide. The gum content decrea"ed in the manner shown in the following table:

Copper dish gum content Original sample 200 mgs. per 100 cc. Original sample plus 0.003%

of phenyl arsine oxide Original sample plus 0.005% of phenyl arsine oxide Original sample plus 0.010% of phenyl arsine oxide Original sample plus 0.015% of phenyl arsine oxide 60 mgs. per 100 cc.

40 mgs. per 100 cc.

20 mgs. per 100 cc.

18 mgs. per 100 cc.

Example 2 oxide 25 mgs. per 100 cc.

Example 3 Samples of a pressure distillate of the gasoline type which showed a copper dish content of 130 mgs. per 100 cc. were admixed with 0.001%, 0.002%, and 0.003% of paraethoxyphenylarsine oxide respectively. The copper dish gum content decreased as follows:

Copper dish gum content Original sample 130 mgs. per 100 cc.

Original sample plus 0.001% of paraethoxyphenylarsine oxide Original sample plus 0.002%

of paraethoxyphenylarsine oxide mgs. per cc.

30 mgs. per 100 cc.

Original sample plus 0.003%

of paraethoxyphenylarsine oxide Example 4 A pressure distillate of the gasoline type had an initial copper dish gum content of 872 milligrams per 100 cubic centimeters. samples of this gasoline were added 0.020% and 0.025% of 2,4 dimethylp'henylarsine oxide. The gum content decreased asfollows:

, Copper dish gum content Original sample 872 mgs. per 100 '00. Original sample plus 0.020%

of 2,4 dimethylphenylarsine oxide 371 mgs. per 100 cc. Original sample plus 0.025% of 2,4 dimethylphenylarsine oxide 255 mgs. per 100cc.

5 mgs. per 100 cc.

30 mgs. per 100 cc.

To 100 cc. I

Emample 5 To the same pressure distillate of Example 4 were added 0.015% and 0.025% of 2,5 dimethylphenylarsine oxide with the following results:

The value for the copper dish gum content of the various liquid hydrocarbons given in the above examples have not been corrected for any amounts of the gum inhibitor which might be present in the copper dish after the test has been completed so that the actual amounts of gums present are believed to be somewhat lower than indicated.

The copper dish gum test herein referred to has been described on page 96 of the U. S. Bureau of Mines Technical Paper 323B, revised Oct. 21, 1927.

This invention is not restricted to any specific example described therein, the examples being merely illustrative of the generic invention herein disclosed and many variations may be made within the scope of the appended claims.

I claim:

1. In a process for preventing gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage the step of adding thereto organic oxides of the type R-M=O, wherein R is an aryl or alkoxy-substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five, said oxides being adapted to prevent the formation of the aforesaid gums.

2. In a process for inhibiting gum formation in a blend of cracked and straight run gasoline the step of dissolving therein small amounts of organic oxides of the type RM=O, wherein R is an aryl or alkoxy-substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five, said oxides being adapted to prevent the formation of the aforesaid gums.

3. In a process for preventing gum formation in untreated hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage the step of adding thereto organic oxides of the type R-M==O wherein R is an aryl or alkoxy-substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five, said oxides being adapted to prevent the formation of the aforesaid gums.

4. In a process for inhibiting gum formation in motor fuels containing hydrocarbons which normally develop gum during the usual conditions of storage, the step of adding thereto small amounts of paraethoxyphenylarsine oxide.

5. In a process for inhibiting gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage, the step of adding thereto small amounts of 2.4 dimethylphenylarsine oxide.

6. In a process for inhibiting gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage, the step of adding thereto small amounts of 2.5 dimethylphenylarsine oxide.

'7. In a process for preventing gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage the step of adding thereto between 0.1% and 0.001% of organic oxides of the type RM=O wherein R is an aryl or alkoxy substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five.

8. In a process for inhibiting gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage, the step of adding thereto between 0.1% and 0.001% of paraethoxyphenylarsine oxide.

9. In a process for inhibiting gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage, the step of adding thereto between 0.1% and 0.001% of 2.4 dimethylphenylarsine oxide.

10. In a process for inhibiting gum formation in hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage, the step of adding thereto between O.1% and 0.001% of 2.5 dimethylphenylarsine oxide.

11. A process as in claim 3 in which M is arsenic.

12. Low boilng petroleum fractions which normally develop gum during the usual conditions of storage and containing small amounts of organic oxides of the type RM=O, wherein R. is an aryl or alkoxy-substituted aryl group and M representsa metal of the class consisting of arsenic and antimony having a valency of less than five, said oxides being adapted to prevent the formation of the aforesaid gums.

13. Low boiling cracked petroleum fractions otherwise capable of forming gums and/or resinous substances and containing organic oxides of the type RM=O, wherein R is an aryl or alkoxy-substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five, said oxides being adapted to prevent the formation of the aforesaid gums.

14. Motor fuels containing hydrocarbons which normally develop gum during the usual conditions of storage and containing between 0.1% and 0.001% of organic oxides of the type R-M=O wherein R is an aryl or alkoxy substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five.

15. Motor fuels containing hydrocarbons which normally develop gum during the usual conditions of storage and containing organic oxides of the type RM=O wherein R is an aryl or alkoxy substituted aryl group and M represents a metal of the class consisting of arsenic and antimony having a valency of less than five.

16. Motor fuels containing hydrocarbons which normally develop gum during the usual conditions of storage and containing a small proportion of paraethoxyphenylarsine oxide.

17. Motor fuels containing hydrocarbon which normally develop gum during the usual conditions of storage and containing a small proportion of 2.4 dimethylphenylarsine oxide. i

18. Motor fuels containing hydrocarbons which normally develop gum during the usua conditions of storage and containing a small proportion of 2.5 dimethylphenylarsine oxide.

19. A product as defined in claim 12 in which M is arsenic having a. valency of three.

20. Hydrocarbon-containing motor fuels which normally develop gum during the usual condi- 5 tions of storage and containing from 0.001% to 0.1% of paraethoxyphenylarsine oxide.

21. Hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage and containing from 0.001% to 0.1%

10 of 2.4 dimethylphenylarsine oxide.

22. Hydrocarbon-containing motor fuels which normally develop gum during the usual conditions of storage and containing from 0.001% to 0.1% of 2.5 dimethylphenylarsine oxide.

23. A process according to claim 1 in which M is arsenic.

24. A product as defined in claim 13 wherein the petroleum fraction treated is cracked gasoline and wherein M is arsenic having a valency of three.

ARTHUR L. BLOUNT.