US2528785A - Mineral oil compositions containing alkyl aminobenzothiophenes - Google Patents

Description

Patented Nov. 7, 1950 MINERAL OIL COMPOSITIONS CONTAINING ALKYL AMINOBENZOTHIOPHENES E '1 Frederick P. Richter and Everett W. Fuller, Woodbury, N.

J., ass'ignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application September 26, 1947,

' Serial No. 776,426

Claims. I

This invention relates primarily to lubricating oils, improved as to stability, by the addition dibenzothiophenes. In a somewhat broader sense, this invention also includes lubricating oils improved as to stability, by the addition thereto of a small proportion of an aminodibenzothiophene or a mixture of aminodibenzothiophenes or of a mixture of alkyl-substituted aminodibenzothiophenes andaminodibenzothiophenes.

Apparently, alkylaminodibenzothiophenes were unknown prior to this invention, and this invention therefore includes, as new compositions of matter, alkylaminodibenzothiophenes and mixtures thereof, and a method of producing them.

The preparation of 2-amino and'2,8-diaminodibenzothiophene has been described in the chemical literature. No reference has been found in the literature to the preparation of alkylaminodibenzothiophenes and no reference has covered that both aminodibenzothiophenes and alkylaminodibenzothiophenes, when added to lubricating oils in relatively small proportions, efllciently stabilize those oils against oxidation at elevated temperatures.

For the purposes of this invention, the alkylamincdibenzothiophenes, and mixtures thereof,

- are preferred because of their increased solubility in oils. The unsubstituted aminodibenzothiophenes, and mixtures thereof, are less soluble in oil, but are sufllciently soluble so that they can be used.

Preparation of alkyl aminodibenzothiophenes Aminodibenzothiophenesmay beprepared as indicated in the literature, from dibenzothiophene which has been frequently referred to in the earlier literature as diphenylenesulfide. Dibenzothiophene is conveniently and cheaply available. Its formula is commonlyindicated as follows (using the ofllcial system of numbering adopted by Chemical Abstracts in 1937):

The sulfur atom of dibenzothiophene is not as reactive as the sulfur atom in alkyl sulfides, but

thereto of a small proportion of 'an alkylaminodibenzothiophene or a mixture of alkylamino- 2 on the other hand appears to be somewhat more reactive than the sulfur atom in unsubstituted thiophena- It can be progressively oxidized-to a sulfoxide and a sulfone without cleavage. Dibenzothiophene undergoes the usual aromatic substitution reactions, such as nitration, halogenation, alkylation, sulfonation, and the like.

According to this invention, it has been found that aminodibenzothiophenes are only slightly soluble in petroleum oils and, therefore, while aminodibenzothiophene can be prepared by nitrating dibenzothiophene and reducing the nitrate groups to amine groups, it is preferable to first alkylate the dibenzothiophene and thereafter nitrate the alkyldibenzothiophene and then reduce the nitrate groups to form amino groups. This results in the production of an alkylaminodibenzothiophene. 1

By the process of alkylating, nitrating, and then reducing the nitrate groups to amino groups, an alkylaminodibenzothiophene or a mixture of a1kylaminodibenzothiophenes may be produced, in which there are one, two, or more, alkyl substituents, and one, two, or more, amino groups.

Conveniently, dibenzothiophene may be so treated that the average dibenzothiophene molecule will receive about two alkyl substituents and about two amino groups. In such a treatment, it seems likely that the alkyl substituents will attach themselves in the threeand seven-positions, and the amino groups will be attached to the twoand eight-positions. The composition that results from such a reaction, however, is probably not a single, uniform compound,'but rather a mixture of compounds in which the positions and numbers of the substituents vary from molecule to molecule. No attempt, as yet, has been made to .separate individual, distinct, compounds from the compositions .produced by the reactions which have been mentioned hereinbefore.

In a general way, the reactions described above may be illustrated as follows:

In the formula R is used to represent an alkyl radical and X to represent a halogen atom. As shown the dibenzothiophene nucleus receives two alkyl substituents in the threeand'seven-positions and two amino substituents in the twoand eight-positions. It is to be understood, however, that, within the scope of this invention, the nucleus may receive any number of alkyl substituents from zero to seven, arranged in any manner upon the nucleus. It is preferred, however, that there shall be at. least one and not more than four alkyl substituents.

It is also to be understood that the nucleus may, similarly, receive any number of amino substituents from one to eight, in any arrangement. Again, however, it is preferred that the number of amino substituents be no greater than four, and at least one is essential.

In ordinary substitution reactions, such as bromination, nitration, or sulfonation, the entering group or groups generally occupy the twoand/or eight-positions. In substitution reactions involving electron-dificient catalysts, such as aluminum chloride, the orientation of the entering group or groups is not known with certainty. It is believed, however, that the entering groups usually attach themselves to the nucleus in the threeand/or seven-positions. This reasoning leads to a conclusion that a diallnvldiaminodibenzothiophene, produced as above, would normally be a 2,8-dinitro,3,7-dialkyldibenzothiophene. It appears, however, that a variety of isomeric alkyldibenzothiophenes are formed at the same time.

Reactants The primary reactant in the preparation of aminodibenzothiophenes or alkylaminodibenzothiophenes or mixtures thereof, will normally be dibenzothiophene.- The purity of this material is not especially critical, and a commercial grade of the material, containing the usual impurities, may be used. The dibenzothiophene may be alkylated with either alkyl halides or oleflns, or even alcohols. Some branching of the alkyl chain is permissible. The halogen or hydroxy group may be attached to a secondary or tertiary carbon atom and the olefin linkage may occur at some other than the alpha position, as will be indicated by the specific examples in which tertiary amyl chloride was used.

The number of carbon atoms, or the chain length of the alkyl compounds is not highly critical but, in general, it has been found that alkyl substituents containing less than four carbon atoms are undesirable because they do not sufliciently increase the solubility of the final compound in lubricating oil. Alkyl substituents ranging in carbon content from at least four carbon atoms to not more than about twentyfour carbon atoms, or mixtures of alkyl substituents containing an average number of carbon atoms in this range, are preferred as they make the final compounds satisfactorily oil soluble. Any of the common alkylation catalysts, such as anhydrous aluminum chloride or boron trifluoride etherate, may be used. Anhydrous aluminum chloride is preferable because it is readily available, convenient, and in general gives excellent results.

The nitration can be effected with concentrated nitric acid (specific gravity 1 42) either alone or in conjunction with concentrated sulfuric acid (specific gravity 1.84). Alternatively, a nitrate salt, such as sodium or potassium nitrate, may be used with concentrated sulfuric acid, thus generating the nitric acid in situ. Fuming nitric acid, specific gravity 1.59 to 1.60, may be used either alone or with sulfuric acid.

All of these agents tend to oxidize dibenzothiophene to the corresponding sulfoxide or sulfone. Because of this, it has been found preferable to accomplish the nitration in the presence of a dehydrating agent, such as acetic anhydride, or a mixture of acetic acid and acetic anhydride. When fuming nitric acid was used in acetic acidacetic anhydride solvent, the reaction proceeded smoothly and no tarry by-products were formed. It is probable that an acetyl nitrate intermediate functioned as the actual nitrating agent under these conditions.

Reaction conditions The alkylation reaction may be accomplished under a relatively wide variety of conditions, similar to those given in the literature for the alkylation of aromatic compounds. Preferably, an alkyl chloride is used as the alkylating agent and anhydrous aluminum chloride is used as the catalyst. By adjustment of proportions, a monoalkylated, dialkylated, or polyalkyiated product can be produced. Preferably, about 0.05 to 0.10 mols of catalyst per mol of alkyl halide are used. At these catalyst concentrations, the evolution of hydrogen chloride is rapid and there is practically no tarry material formed. Higher concentrations of catalyst are wasteful and lead to the formation of tarry by-products. The temperature is adjusted to produce the desired alkylation without the production of an excessive amount of by-products. Generally, temperatures in the neighborhood of 0 C. to 50 C. are preferred, although somewhat higher temperatures may be used.

The nitration preferably is performed at from about 20 C. to about 40 C. It can be performed at temperatures as low as 0 C. or even below, but at temperatures below 0 C., it occurs rather slowly even with fuming nitric acid. At temperatures above about 40 0., oxidation and degradation reactions begin to occur at a substantial rate which increases rapidly with increased temperatures. At 20 C. to 40 0., usingfuming nitric acid, the nitration reaction is usually complete within about six to eight hours.

For mononitration, it has been found preferable to employ 1.00 to 1.05 mols of nitric acid per mol of alkyldibenzothiophene. For dinitration, it has been found preferable to employ 2.00 to 2.10 mols of nitric acid per mol of alkyldibenzothiophene. Any large excess of nitric acid will result in the formation of higher nitration products and possible oxidation.

The reduction of the nitro compounds to amines may be effected in a variety of ways as will be apparent to those skilled in the art. It hasbeen found preferable to employ an active metal such as tin, zinc, or iron, and a nonoxidizing inorganic acid, preferably aqueous hydrochloric acid. In order to insure complete reduction to the final amino stage, it is preferable to use the metallic reducing agent in excess.

Oil base and also concentrates of aminodibenzothiophenes;

alkylaminodibenzothiophenes v and mixtures thereof in lubricating oil.

The lubricating oil compositions included within the scope of this invention comprise not only lubrication improvers, other stabilizing agents,

viscosity index improvers, detergents, rust inhibitors and any other additive or additives which it may be found desirable to add. Preferably, the aminodibenzothiophen'e or alkylaminodibenzothiophenes of this invention are incorporated in lubricating oils in amounts ranging from 0.1% to 2%. In some cases amounts as low as 0.01% are sumcient and in others amounts as high as .10%'may be found desirable. The lubricating oil base will normally be a mineral lubricating oil derived from petroleum and of the type used in the lubrication of turbines and internal combustion engines. However, the

aminodibenzothiophens and alkylaminodibenzothiophenes described above, may advantageously be incorporated in petroleum products ranging-all the way from gasoline and kerosene to petrolatum and petroleum wax. They may also be incorporated in corresponding synthetic products derived from animal or vegetable sources, or other min eral sources than petroleum.

The concentrates prepared in accordance with this invention are mixtures of the aminodibenzothiophenes and alkylaminodibenzothiophenes of this invention with oils or oily materialscompatible with the oilsor oily materials in which the products are finally to be incorporated. In the concentrates. the amount of the dibenzothio phene products may reach 50% or even higher, although it is generally preferred, because of their solubility, to use not more than 25% of the EXAIWPLEI A sample of 2.8-diaminodibenzothophene was prepared according to a method described in the literature. The product consisted of yellow crystals which melted at 17'7-178 C. with decomposition. The material was tested for antioxidant activity as follows: a saturated solution of the pure compound at room temperature was prepared using as the solvent a mixture consisting of per cent of xylene and 90 per cent of a highly-refined oil suitable for use in transformers which had been prepared by treating a Coastal distillate with 40 pounds of 98 per cent sulfuric acid and 180 pounds of 103 per cent oleum per barrel, followed by washing and clay percolation. It had a specific gravity of 0.871, a

hash point of 310 F. and a S. U. viscosity of 69 seconds at 100 F. This type of oil tends to form acidic products on oxidation. It was. tested-by heating samples to 120 C. and bubbling oxygen through them for 70 hours. The acids thus formed were determined by titrating with alcoholic potassium hydroxide. Results are expressed as neutralization numbers (N. N.) which Test specimen N. N. Oil-xylene mixture 24.7

Oil-xylene mixture saturated with 2,8-diaminodibenzothiophene 10.5 EXAMPLE r1 Alkylation of dibenzothiophene. Preparation of isomeric di-tertiaryamyl dibenzothiophene A solution consisting of 92 parts of crystallized dibenzothiophene (M. P. 99 C.) in 200 parts of carbon disulfide was treated with 10 parts of anhydrous aluminum chloride in a reactor equipped with a water-cooled return condenser protected against atmospheric moisture, a thermometer and agitator. At room temperature (20-25 C.) 106.6 parts of tertiary amyl chloride (B. P. 84-86 C.) were added dropwise over a period of 1.5 hours. Hydrogen chloride gas was evolved in large amounts. After the addition of alkyl chloride was complete, the reaction mixture was stirred at a temperature of 20-25". C. for an additional three hours.

The reaction mixture was treated with 200 parts of ice and then with 200 parts of cold 20 per cent aqueous hydrochloric acid. The aqueous layer was discarded and the carbon disulflde solution was washed with water until neutral. After drying over anhydrous calcium sulfate and filtering, the carbon disulfide was distilled off and'the residue distilled in vacuo. There were thus obtained 148 parts of isomeric ditertiaryamyldbenzothiophenesboiling over a range of 200-232 C. and having a sulfur content of 9.5 per cent. Calculated sulfur for di-tertiaryamyldibenzothiophene is 9.9 per cent. A fraction boiling at 200-220 C. was used in the following preparations.

Nitration of iii-tertiary-amyldibenzothiophene A solution consisting of 16 parts of isomeric ditertiaryamyldibenzothiophene in 20 parts of glacial acetic acid and 10 parts of acetic anhydride was treated slowly with 3.5 parts of per cent fuming nitric acid at a temperature of 20-40 C. The mixture was stirred for 6 hours at 20-40 C. to complete the react on. The nitration product was then poured onto parts of cracked ice and the resulting mixture was extracted with benzene. The benzene solution was washed with water until neutral, dried over an inertsolid dehydrating agent and the benzene removed by distillation. The residue consisted of 18 parts of a substantially mono-nitroditertiary-amyldibenzothiophene.

In the same manner as above, except that '7 parts of 90 per cent fuming nitric acid were used instead of 3.5 parts, there was obtained a subs'tantially di nitro-ditertiaryamyldibenzothiophene.

, Reduction of nitro-ditertiary-amyldibenzothiophenes An intimate mixture consisting of 16 parts of the substantially mononitro-ditertiary-amyldi- 75 benzothiophene prepared above and 19 parts of droxide and extracted with benzene. After drying over solid potassium hydroxide the filtered solution was distilled to remove the benzene. The residue consisted of 14 parts of a dark, viscous liquid which did not crystallize upon cooling in ice. It consisted substantially of a monoamino di tertiary-amyldibenzothiophene and was found to contain 9.50 per cent sulfur. Calculated for C22H29NS: sulfur=9.46 per cent.

In a manner similar to that described above, except that 38 parts of tin and 50 parts of concentrated hydrochloric acid were used, a substantially diamino-ditertiary-amyldibenzothiophene was prepared. Sulfur found, 9.00 per cent. Calculated for CzzHaoNzS: sulfur=9.06 per cent.

The amino-alkyldibenzothiophenes thus prepared were tested in accordance with the procedure given in Example I, except that the test fluids were prepared by dissolving the compound in question directly in the oils without the use of xylene. The tests were made at concentrations of 1.0 to 0.5%. The value for the blank oil is given in order that the large improvement in stability toward oxidation can be more readily EXAMPLE III (Corrosion test) The oil used in this test was a solvent-refined addition agent is run simultaneously with a blank, and the loss in weight of the bearing section in the inhibited oil can thus be compared directly with the loss in weight of the bearing section in the blank. The results obtained with the typical reaction products contemplated herein are given in the following table:

It is thus seen that these amino-alkyldibenzothiophenes completely inhibit corrosion of the bearing metal surface.

EXAMPIE IV A solvent-refined oil consisting of a distillate 7 from a Rodessa crude which had been refined with furfural, dewaxed and filtered was used in this test. It had a specific gravity of 0.856, a flash point of 420 F. and a Saybolt universal viscosity oi. 151 seconds at F.

The test involved maintaining a 25 cc. sample of the oil (or oil blend) at a temperature of 200 F. with 5 liters of air per hour bubbling therethrough. Each sample contained 24 inches of No. 18 gauge copper wire and approximately one gram of iron in the form of small nails, and 2 cc. of distilled water were added each day. The samples were tested after varying intervals for acidity, color and sludge, and the results for the blank oil and blends of the same containing the compounds herein contemplated are shown in Table III.

Table III Compound Blend Time Color N. N. Sludge Hours Ma.

Mouoaminoditertiaryamyldibenzothiophene. 0.3% in oil 163 16. 0+ 0. 01+ 6+ Do do 329 65.0 2.3 9+ Diaminoditertiaryamyldlbenzo nnhen do 168 25. 0+ 0. 01+ 5+ D0... (in 334 40.0 0.10 3+ Do... do 502 55.0 2.10 11+ Blank oil 46 8. 5 0. 7 2

55 EXAMPLE V S. A. E. 20 grade motor oil, which is normally corrosive to bearing metals having the corrosionsusceptibility of cadmium-silver alloys. The oil was tested by placing a section of a bearing containing a cadmium-silver alloy surface and weighing about 6 grams in a sample of the oil (or oil blend) and heating the oil sample to a temperature of 175 C. for a period of 22 hours while bubbling a stream of air therethrough against the surface of the hearing. The loss in weight of the bearing as a result of this treatment measures the amount of corrosion that has taken place. A sample of the oil containing the The oil described in the previous example was used in this test. It is characteristic of this oil to deteriorate in color and form acidic products when subject to contact with air at elevated temperatures. The test used, known as the Brown- Boveri turbine oil test, involves heating a test sample of the oil in the presence of a piece of copper foil at a temperature of C. in air for 72 hours, after which the color and neutralization number (N. N.) are determined as indicative of the extent to which the oil is afiected by oxidation.

. The results oi the tests of both Examples IV and V indicate that the amino alkyldibenzothiophenes are particularly effective in improving the stability of solvent-refined oils toward oxidation, as shown by the high reduction in acidity and the greatly improved color.

What is claimed is: a

' 1. A mineral lubricating oil containing a minor proportion, suflicient to improve the stability of said .oil against oxidation, of a material selected from the group consisting oi alkyl 2-monoamin0- dibenzothiophenes, alkyl 8-monoaminodibenzothiophenes, and alkyl 2,8-diaminodibenzothiophenes, in which the alkyl radicals contain not less than four but not more than twenty-tour carbon atoms and are connected to carbon atoms of the dibenzothiophene nucleus.

2. A mineral lubricating oil containing trom about 0.01% to about 10% oi! a material selected from the group consisting of alkyl 2-monoaminodibenzothiophenes, alkyl a-monoaminodibenzothiophenes, and alkyl 2,8-diaminodibenzothiophenes, in which the alkyl radicals contain not less than four but not more than twenty-four carbon atoms and are connected to carbon atoms of the dibenzothiophene nucleus.

3. A mineral lubricating oil containing from 10 about 0.1% to about 2.0% of 2-monoaminoditertiaryamyldibenzothiophene.

4. A mineral lubricating oil containing from about 0.1% to about 2.0% o! 8-monoaminoditertiaryamyldibenzothiophene.

5. A mineral lubricating oil containing from about 0.1% to about 2.0% of 2,8-diaminoditertiaryamyldibenzothiophene.

. FREDERICK P. RICHTER.

EVEREI'I' W. FULIER.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,471,150 Dziewonski Oct. 16, 1923 2,154,096 Loane Apr. 11, 1939 2,290,316 Cook July 21, 1942 2,308,690 Hughes Jan. 19, 1943' 2,361,904 Wilson Oct. 31, 1944 2,438,955 Tryon Apr. 6, 1948 FOREIGN PATENTS Number Country Date 330,833 Germany Dec. 20, 1920

Claims (1)

1. A MINERAL LUBRICATING OIL CONTAINING A MINOR PROPORTION, SUFFICIENT TO IMPROVE THE STABILITY OF SAID OIL AGAINST OXIDATION, OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKYL 2-MONOAMINODIBENZOTHIOPHENES, ALKYL 8-MONOAMINODIBENZOTHIOPHENES, AND ALKYL 2,8-DIAMINODIBENZOTHIOPHENES, IN WHICH THE ALKYL RADICALS CONTAIN NOT LESS THAN FOUR BUT NOT MORE THAN TWENTY-FOUR CARBON ATOMS AND ARE CONNECTED TO CARBON ATOMS OF THE DIBENZOTHIOPHENE NUCLEUS.