US2310710A - Inhibitor for gasoline - Google Patents

Description

Patented Feb. 9, 1943 ITOR ron GASOLINE Robert H. Rosenwald and Joseph A. Chenicek, Re

Chicago, IlL, assignors to Universal Oil Prodnets Company, Chicago, 111., a corporation of Delaware Reissued I 5, 39 June 6, 1950 No Drawing. Application September 18, 1939, Serial No. 295,476

18 Claims.

This invention relates to a method for stabilizing olefin-containing hydrocarbon oils, and more particularly, cracked gasolines of the petroleum origin. However, gasolines from other sources, such as coal tar, shale oil, etc., may be also treat ed according to the present invention, as may those made by polymerization of olefins, reforming of naphthas, etc.

More specifically, the invention concerns a method for stabilizing olefin-containing gasolines during storage in respect to their valuable properties such as color and anti-knock value and low gum content which tend to depreciate because of the action of oxygen upon theoleflns in said gasolines.

The cracking and reforming processes which are employed to produce additional yields of gasoline from heavy hydrocarbonaceous oils, or to increase the antiknock properties of naphthas and straight-run gasolines, produce motor fuels having substantial concentrations of unsaturated hydrocarbons, particularly mono-olefins and dicleflns. These olefinic hydrocarbons tend to form peroxides and gums when stored in the presence of oxygen. The use of inhibitors to prevent such reactions has been practiced, and many types of compounds have been suggested for this purpose, including aminophenols, wood tar fractions, polyhydroxy phenols, etc.

In one specific embodiment, the present invention comprises the treatment of unstable olefin-containing gasolines to preserve their valuable properties in respect to gum content, color and antiknock value by adding thereto minor quantities of 2-alkyl-4-alkoxyphenols of the general structure wherein R. comprises any alkyl group and OR is an alkoxy group wherein R is of the same or different molecular weight and structure than R.

The properties desirable in a gasoline gum inhibitor are as follows:

a. Solubility in the gasoline to a degree in excess of the maximum concentration in which it is likely to be used.

h. High degree of potency so that relatively small concentrations can be used.

c. Insolubility or relatively low solubility in water or aqueous alkaline or acidic solutions with which the gasoline is likely to come in contact.

:1. Either normally liquid or having a high degree of solubility in a non-aqueous, gasolinemisci-ble solvent thus increasing the ease of handling and addition to the gasoline.

e. Non-reactive with tanks, fittings, lines, engine parts, etc., with which the gasoline is likely to come in contact.

j. Of light color, and imparting or developing no objectionable color or odor to the gasoline when added, or during storage.

The inhibitors of the present invention to a large extent fulfil these requirements.

The degree of insolubility of an inhibitor in water or caustic solutions is of particular importance since gasoline storage tanks generally contain water which is alkaline in reaction. If the inhibitor is soluble in the water layer, it is partially removed from the gasoline and thus its effect is greatly reduced. The present type of compound has been found to be practically in soluble in water and in slightly removable from gasoline by contact with dilute alkaline solutions.

The compounds of the present invention are useful for preventing the deterioration of gasoline, but diiierent individual compounds of the same type are not necessarily exact equivalents.

The alkyl groups substituted in the ring may comprise any alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, t-butyl, amyl, isoamyl, secondary amyl, etc. Of these groups, the t-alkyl groups appear to 'be more efiective in contributing to the inhibitor potency of the resultant compound than do those groups of lower molecular weight, for example methyl and ethyl groups. Likewise, the groups of higher molecular weight contribute to other desirable properties of the inhibitor such as decreasing the solubility of the resulting compound in aqueous solutions. The substituent group is preferably in the position ortho to the hydroxyl group. Some compounds having alkyl groups in the meta position may also have inhibiting value.

We have found that when the alkoxy or ether group is in the -positlon, compounds having greater inhibitor potency are available than when this group is in any other position in the substituted phenol. The alkyl group of this alkoxy substituent may comprise for example ethyl, methyl, propyl, isopropyl, 'butyl, isobutyl, secondary butyl, t-butyl, amyl, isoamyl, secondary most cases to be but lows:

Hydroqulnone =0.00 Hydroquinone monoimothylethenfltil 110G015: mcoQon CzHs 1H5 2-othylhydroquinone=0.35 2 ethyl-4-mothoxyphenol=2.39

In this case, the inhibitor potencies of the various compounds listed as given by the numerical values, were measured by means of the oxygen bomb induction period test, and the inhibitor potencies are reported as "inhibitor ratio. The inhibitor ratio is defined as the ratio of the increase in induction period of a given gasoline by a given percentage of unknown inhibitor to the induction period increase with a like quantity of a standard commercial gum inhibitor. Thus the' values as reported are direct ratios of inhibitor potency as compared with a widely used commercial gum inhibitor. From the illustration it will be noted that hydroquinone and ethylhydroquinone have little or no inhibitor value compared with the commercial inhibitor. The monomethyl ether of hydroquinone has a considerable potency, being 1.69 times as efiective as the commercial inhibitor. The substitution of an ethyl group in the position ortho to the hydroxyl group (2-ethyl-4-methoxyphenol) increases the inhibitor ratio to an even greater extent, so that the resulting 2-ethyl-4-methoxyphenol is 2.39 times as effective as the commercial inhibitor.

The alkyl substituents may be introduced into the aromatic nucleus in a number of ways. one of these consists in alkylating a hydroquinone ether by contacting it at a temperature 01' -80 C. with the alcohol corresponding to the group to be substituted, using phosphoric acid as the catalyst. The reaction mixture is stirred continuously until the reaction is complete. The mixture is then washed with water to remove remaining acid and is extracted with 10% sodium hydroxide solution to remove the unreacted hydroqulnone ether. The insoluble portion is distilled under reduced pressure and the resulting compound may be further purified by recrystallization.

The term stabilizing gasoline as used herein is intended to mean the prevention of deterioration of the gasoline in so far as its desirable properties of storage stability, color, antilrnock value,

'etc., are concerned.

The following example still further illustrates the benefits and usefulness of the present type of inhibitor. This example is given to demonstrate the usefulness and practicability of our invention, but should not be construed as limiting it to the exact compounds illustrated therein. As in the foregoing, the inhibiting value in so far as the stabilization of gasoline is concerned is reported in terms of inhibitor ratio compared with a commercially used gum inhibitor.

In the following table are shown a number of representative compounds of the present invention together with their inhibitor ratios:

TABLE I Inhibitor ratios of 2-aZkyl-4-alkozyphenols in 0.05% concentration Compound Structural iormnla ga? Commercial inhibitor 1.00

2-ethyl-4-methoxyphenol. HOQO CH; 2. 39

2-ethyl-4-eihoxyphen0l H090 01H. aaa

Z-allyl-i-mathoxyphenol HO-Q-O 03, 2.19

Hr- C H=C H:

2-propyl-4-mothoxyphenol HOQ-O CH: 2. 30

2-tert-butyl-i-methoxyphenol.. HOQO on. a. m

2-tert-butyl-4-athoxyphenol HOQO 01H} 4.40

2tert-butyl-t-lsopropoxyphenol.. HOQ o-omom). a as aeromo 3 Compound Structural formula Inhibitor ratio fi-tert-butyl-i-isobutoxyphenol. HOQO CHr-CH (CH 2. 78

Z-t-amyl-i-mcthoxyphenol H0 0 CH 3.

t-CaHn The results show that the compounds listed are specially effective inhibitors as compared to a commercial gum inhibitor when used in equal weights. They are not, however, exactly equivalent since the specific efiects of different groups in the alkoxy or in the ortho ring substituted positions may be quite different. Thus it will be seen that an ethyl or methyl group in the alkom group is more efiective than other alkyl groups tried. on the other hand, the substitution of a t-butyl group in the aromatic ring greatly increases the inhibitor potency of the resultant compound.

The effectiveness is further illustrated by the quantities. In all cases, the color of the resulting gasoline was equal to or better than that of the gasoline inhibited with a commercial inhibitor.

It has been our observation in the laboratory that the inhibitors of this invention are comparatively stable insofar as color is concerned when exposed to air. One of the disadvantages of many commercial inhibitors is that they develop color rapidly when exposed to air. The stable character of the present inhibitors may therefore be considered an advantage.

We claim as our invention:

1. A process for stabilizing olefin-containing hydrocarbon oils in regard to their desirable data presented in Table II. properties which comprises adding to said oils TABLE II Oxygen bomb induction Per cent removed Mg dish gum .Pcriod by- Inhibitor Orig Water Caustic orl Water Caustic Water Caustic wash wash wash wash wash Wash Blank gasoline 127 138 184 90 80 75 Commercial inhibitor 4 24 180 310 260 100 18 89 Z-tert-butyl-t-mcthoxyphenol- 8 7 9 305 310 295 0 0 2tert-butyl-4-ethoxyphcnol 7 9 10 310 336 330 0 0 2-tert-butyl-4-isogropoxyphenol 15 15 17 290 295 280 0 0 2-tert-butyl-4-iso utoxyphenol.-. 16 24 19 310 300 295 0 0 Z-ethyl-i-mcthoxyphcnoL 37 64 19 300 300 145 0 67 2-ethyl-t-ethoxy 13 .19 28 290 300 180 0 47 Hydroquinune monoethyl ether 32 38 104 310 280 100 9 89 Hydroquinone mouo-isopropyl ether 27 44 115 280 270 90 0 92 the gasoline was inhibited with a sumcient quantity of each inhibitor to produce apprommately the same induction period. Hydroquinone monoethylether and monoiso-propylether are included in. the list for purposes of comparison. The percentage of inhibitor removed by water or caustic is calculated from the per cent decrease in induction period after the sample has been washed with water or with caustic solution. It will be noted that the compounds of the present invention are less soluble in water than the commercial inhibitor or hydroquinone monoethylether. Moreover, these compounds are less soluble in dilute caustic solution that the monoalkylethers or the commercial gum inhibitor. It will be noted also that the t-butyl group as the ring substituent reduces the alkali solubility of the compounds to a greater extent than does an ethyl group in the same position. It will also be observed that the compounds of the present invention have practically no detrimental efiect on the color or color stability of the gasoline when added in these a minor portion of a compound having the general structure wherein R and R comprise alkyl groups.

3. A process for stabilizing cracked gasoline against deterioration of its valuable properties which comprises adding to said gasoline a minor portion of a compound of the following general formula:

wherein R is a t-allryl group and R is an allryl group.

i. A process for stabilizing olefin-containing gasoline against deterioration of its valuable properties which comprises adding to said gasoline a minor portion of a compound of the following general formula:

wherein R and R are t-alkyl groups.

6. A process for stabilizing olefin-containing gasoline against deterioration of its valuable properties which comprises adding to said gasoline a minor portion of a 2-alkyl-4-alkoxyphenol.

7. An inhibitor for cracked gasoline which comprises essentially a compound having the general formula:

wherein R and R are alkyl groups.

8. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula:

wherein R is an alkyl group and R is a difierent alkyl group.

aaiwrio a. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula on i l R R! wherein R comprises a t-allryl group and R an alkyl group.

10. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula on B R! wherein R is a t-butyl and R is an alkyl group. 11. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula on i R R! wherein R and R are t-alkyl groups.

12. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula on R R! wherein R is an alkyl group and R is a t-alkyl group.

13. An inhibitor for olefin-containing gasoline which comprises essentially a compound having the general formula wherein R is a t-alkyl group and R is a t-butyl group.

14. Motor fuel comprising oleflnic gasoline and a relatively small amount of a 2-alkyl-4-alkoxyphenol.

15. Motor fuel comprising olefinic gasoline and a relatively small amount of a 2-t-alkyl-4- alkoxyphenol.

16. Motor fuel comprising oleflnic gasoline and o, rollotively small amount of a compound having 18. An inhibitor comprising a. compound havibho general formula, ing the general formula on on wherein R is an alkyl group of at least 3 carbon 10 wherein R is an alkyl group of at least 3 carbon atoms and R is an alkyl group of less than 3 atoms and R is an alkyl group of less than 3 corbon atoms. carbon atoms.

17. inhibitor comprising a 2-a1ky1-4-a1koxy- ROBERT H. ROSENWALD. phenol. JOSEPH A. CHENICEK.