US2853480A - Method of sulfochlorinating dialkyl polysulfide-olefin mixtures - Google Patents

Description

I ganic derivatives.

United States Patent METHOD OF SULFOCHLORINATING DIALKYL POLYSULFIDE-OL-EFIN MIXTURES Albert W. Lindert, iflomewood, Ill., assignor to Standard .011 Company, Chicago, 111., a corporation of Indiana No Drawing. Application May 28, 1954 Serial No. 433,297

4 Claims. (Cl. 260--139) The present invention relates to an improved method for preparing stable sulfur and chlorine-containing or- In particular, it relates to the treatment of crude mixtures of low flash point dialkyl polysulfides with a sulfur chloride and 'water to produce stable high flash point materials containing increased amounts of sulfur and chlorine.

The use of sulfur-containing materials, chlorine-contaming materials, and sulfochlorinated materials in cutting oils and gear lubricants for the purpose of imparting extreme pressure properties is well known. And it is rather well established that the sulfur in these sulfurcontaining additives reacts at elevated temperatures with iron-to form ironsulfide, which in turn acts as a lubricant preventing seizure or welding of the metal surfaces, and reducing friction. Various techniques have been suggested for preparing sulfur-containing organic compounds as well as the materials containing both sulfur and chlorine for purposes of this type. Thus, various hydro- :carbon and fatty materials have been sulfurized, sulfochlorinated and/or phospho-rized by the action of substances such as sulfur, the sulfur chlorides, the phosphorus sulfides, etc. and combinations of these. Early in the art, sulfurized mineral oils .and sulfurized :fatty oils were employed for extreme pressure use in gear lubricants and as additives to .cutting oils, but these materials were deficient in at least two important respects, viz. a low sulfur content and a very dark or black appearance.

More recently, the art has described the ,use of various organic polysulfides for the above mentioned purposes. These materials are substantially lighter in color and permit the introduction of a relatively larger amount of combined sulfur than with sulfurized mineral oils and sulfurized fatty oils. However, such polysulfides often have an undesirably low fiash point as a result of the presence of certain amounts of'unsulfurized hydrocarbons carried over from an early step in the synthesis of the polysulfides. And the art has taught that it is desirable to strip the lower boiling materials out of the polysulfides in order to raise the flash point. As a result of such stripping step, although the net sulfur content of the stripped material is somewhat higher than the unstripped, a substantial loss of potentially valuable material occurs as a result of the light ends being removed. And it is a principal object of this invention to avoid any such loss of valuable material by eliminating the stripping step and raising the flash point of the mixture by the sulfochlorination of the crude polysulfides. This and other objects and advantages of the present invention will be apparent from the ensuing description.

In accordance with the present invention, it has been found that the loss in yield resulting from stripping of low flash point crude polysulfides can be avoided, that materials containing not only an increased amount of sulfur but also a substantial amount of desirable chlorine may .be prepared, and that the resulting product while very stable under storage conditions, readily gives off sulfur and chlorine under extreme pressure or temperature "ice conditions to contribute to the lubrication of metal surfaces. Thus, it has been found that if crude alkyl polysulfides, of the type hereinafter described in greater detail, are treated with a sulfur chloride in the presence of an effective amount of water, a product containing a substantial quantity of stable sulfur and chlorine may be prepared. Carrying out the reaction in the presence of water results in products of substantially improved color over similar products. The products have .proven to be excellent as extreme pressure additives.

The crude alkyl polysulfides which are treated with a sulfur chloride in accordance herewith are preferably prepared by sulfurizing a suitable mercaptan with sulfur in the presence of a basic catalyst. Polysulfides prepared by sulfurizing a dialkyl disulfide are likewise suitable. U..S. 2,237,625 and U. S. 2,237,627 are examples of these respective polysulfide preparation methods. .The crude alkyl polysulfides, however prepared (this invention not being limited to any particular method of preparing the same), are treated according to the present invention with from about 5 to 50 volume percent, preferably 10 to 30 volume percent of a sulfur chloride, in the presence of from about 1 to about 50 volume percent, preferably 5 to 25 volume percent of added water at a temperature in the range of from about F. to 150 F. and preferably from about F. to about .125 F. Although the use of greater amounts of water is not detrimental to the color of the product, removal of excess water from the final product is a problem which can be readily avoided by operating within the above range.

As indicated above, the present invention is applicable to crude polysulfides comprising a predominant amount of dialkyl polysulfides and a lesser amount of unreacted olefins or other hydrocarbon constituents. In accordance herewith, the term crude polysulfides shall refer to a product comprising at least about 70% by weight of dialkyl polysulfides and the remainder comprising essen tially a lower boiling hydrocarbon material such as the olefinic constituents from which the mercaptans or disulfides employed in the polysulfide synthesis had been derived. The percentage of the polysulfides in the crude mixture may often be higher than about 70% and it should be understood that the present invention is equally applicable to crude mixtures containing as little as ,5 to 10% low boiling material and even less.

In conducting the reaction of sulfur chloride with the alkyl polysulfides, ,it is preferred to add the :sulfur chloride and water simultaneously, although separately, to the alkyl When the reaction is complete, it is necessary to raise the temperature of the reaction mixture .to drive off the water. It has been found that treatment .of an alkyl polysulfide in this manner results in a product retaining good color when heated to temperatures substantially higher than those to which ordinary sulfurized materials may be heated. Likewise, storage at subzero temperatures has established the excellent stability of the products prepared in accordance herewith.

The presence of a phosphorous sulfide during the sulfochlorination of the crude polysulfide appears to contribute to the stability .of the resulting product in preventing loss of sulfur and evolution of HCl. Moreover, a minor amount of phosphorus may thus be introduced into the product. Phosphorus sulfides such as P 8 P 8 P 8 P 5 and preferably the later, may be employed. These may be employed in amounts of from about '1 to 15% by weight. v

The treatment of polysulfides may also be carried out by adding the sulfur chloride to a mixture of polysulfide and water, or the polysulfide may be added to the sulfur chloride and water. In the former case, the sulfur chloride is added slowly, while in the latter, specialprecaudrocarbon solvent, i. e., boiling below about 36Q- 370 F.

tion should be taken to provide adequate cooling because the action is particularly vigorous. The present invention may also be carried out by adding water to the mixture of sulfur chloride and polysulfide; however, in this case, the product is darker than that usually obtained by other techniques. In accordance with the preferred method of operation, incremental addition of sulfur chloride, permitting each ingredient thereof to react with the polysulfide, is desirable. And it has been found especially desirable to add an anti-foam agent such as a silicone polymer or other suitable material to prevent undue turbulence and foaming of the reaction mixture.

The sulfur chloride employed in accordance herewith may be any of the usual sulfur chlorides such as sulfur monochloride (S Cl sulfur dichloride (SCl or mixtures thereof and preferably sulfur monochloride.

The product obtained in the manner described contains some so-called corrosive sulfur and chlorine, and for uses wherein the presence of corrosive sulfur and chlorine is not detrimental or objectionable the product obtained in the sulfurization reaction can be used as such, after neutralization with an alkaline reagent such as an alkali metal or alkaline earth oxide, hydroxide, or carbonate, for example NaOH, Na CO CaO, K CO etc. The aikaline reagent is preferably added in solid form, although solutions thereof can be used. The neutralized product can then be taken up in a low boiling hydrocarbon solvent, preferably aliphatic hydrocarbon, such as hexane, naphtha, etc. separated from the hydrocarbon insoluble products and recovered by evaporation or distillation of the solvent. With low molecular weight polysulfides, the addition of solvent is unnecessary; the neutralized material being simply decanted and filtered.

If the presence of corrosive sulfur is objectionable or detrimental to the intended use of the sulfurized product, the latter can be freed of the corrosive sulfur by subjecting the same to a so-called deactivation step. To obtain a non-corrosive product the sulfurized product, either after neutralization as above described or without prior neutralization, is refluxed with a solution containing about 5% to about 50% of an alkali metal sulfide, such as sodium sulfide or an alkali hydroxide such as sodium hydroxide; a low molecular weight aliphatic alcohol, such as isopropyl alcohol, ethyl alcohol, butyl alcohol, and the like, and water. Whereas the use of alcohol is desirable, it is not essential. The solution is refluxed for a period of from about one hour to about five hours, and preferably for about three hours. A suitable deactivating solution is one containing about 18 grams of anhydrous sodium sulfide, 34 cubic centimeters of isopropyl alcohol, and 100 cubic centimeters of water for each 100 grams of the sulfurized product. Deactivation of a previously neutralized sulfurized product can be accomplished by refluxing the entire neutralized reaction mass with the alcoholic solution of the alkali metal sulfide or hydroxide without separating the neutralized hydrocarbon soluble fractions from the insoluble fractions. After refluxing for the desired period, approximately an equal volume of a low boiling hydrocarbon solvent, such as hexane or a low boiling naphtha such as a petroleum naphtha boiling below about 360 F., is added, if necessary, to the refluxed solution and the mixture allowed to settle for several hours to permit stratification into two distinct layers, the upper containing the deactivated sulfurized product. The deactivated product is washed free of alkali and recovered by distilling off the hydrocarbon diluent or by other suitable means. The deactivation step also removes chlorine from the sulfurized product, the extent of dechloriuation being dependent upon the amount of deactivator, i. e., Na S or NaOH.

To control the rate of reaction, it is often desirable to dilute the polysulfides with a diluent such as a substantially saturated hydrocarbon solvent, for example, a petroleum naphtha, hexane or other relatively low-boiling hythis is particularly desirable with the heavier polysulfides. Where it is not essential that the diluent or solvent be removed from the sulfurized product, higher boiling material, such as a viscous hydrocarbon oil, can be used as the diluent.

The present invention is applicable to the treatment of crude polysulfides of the type referred to above and will be particularly described with respect to the treatment of crude polysulfides produced from mercaptans derived from olefins by reaction with H 8. It is understood, of course, that mercaptans derived from other sources may also be converted to dialkyl polysulfides. And the present invention is broadly applicable to the sulfochlorination of any crude mixture of polysulfides and constituents of the type defined, however obtained. Thus, mercaptans derived from petroleum, e. g. by extraction, may be converted to polysulfides in accordance with the above mentioned technique but ordinarily such mercaptans would not be mixed to any substantial extent with lower boiling constituents and would not require the treatment herein described. Various mercaptans and particularly tertiary alkyl mercaptans may be readily prepared by the action of hydrogen sulfide on the corresponding olefin, e. g. diisobutylene, in the presence of a non-oxidizing acid catalyst, such as alkane sulfonic acid, at atmospheric pressure and at a temperature of about 30 C. Temperatures below about 60 C. are preferred for this reaction. The reaction of hydrogen sulfide and an olefin in accordance with such a process is described in detail in U. S. 2,615,786. Mercaptans prepared by reacting hydrogen sulfide with the same olefin in the presence of a free radical initiator may, of course, be employed in accordance herewith; U. S. 2,411,983 describes such a reaction. Such reactions are well known to those skilled in the art, and as indicated above, the methods, per se, of preparing mercaptans or polysulfides is not a part of the present invention. For purposes of preparing a material useful as an extreme pressure additive for gear lubricants or cutting oils, alkyl mercaptans containing from about 3 to about 20 carbon atoms and preferably from about 6 to about 12 carbon atoms, should be employed, but it should be understood that the method of the present invention is applicable to mercaptans of much higher molecular weight as well as those containing less than 3 carbon atoms. Inasmuch as a polysulfide prepared from a particular mercaptan contains twice as many carbon atoms as the original mercaptan, it is apparent that for purposes of preparing an extreme pressure additive for lubricants, the polysulfides treated in accordance herewith should contain from about 6 to about 40 carbon atoms and preferably from about 12 to about 24 carbon atoms per molecule. These polysulfides may be di-, tri-, tetra-, penta-, hexaor higher.

Typical examples of di-alkyl polysulfides which may be employed in accordance herewith (without in any way limiting the invention to those enumerated) are: dipropyl disulfide, dipropyl trisulfide, diamyl disulfide, dihexyl tri sulfide, dioctyl tetrasulfide, dinonyl trisulfide, dilauryl disulfide, dioctadecyl trisulfide, etc. Assymetrical dialkyl polysulfides such as butyl heptyl trisulfide, dodecyl octyl disulfide, etc. may, of course, be employed in accordance herewith.

For purposes of illustration and not of limitation, there are given below several examples of the method of raising the flash point of crude polysulfides without reducing the yield and at the same time producing products containing desirable amounts of chlorine. In each of the following examples the crude polysulfides employed had a weight loss of 11% upon stripping to an acceptable flash point. The advantage of saving this ll% of ordinarly lost material will be apparent from the following examples.

EXAMPLE 1 Two hundred. grams of crude dodecyl polysulfide (prepared from, commercial grade dodecyl mercaptan purchased from Phillips Petroleum Co. Chemical Products Division) containing 30.46 total sulfur (1.40% of which was free sulfur) and having a viscosity of 353 SSU at 100 and a flash point of 310 F. was treated for 3 hours at a temperature from 78 to 89 F. with 50 grams of S Cl The product was then treated with.30 grams of NaCO to neturalize any undesirable acidic components and then dissolved in hexane to facilitate desalting. The hexane was thereafter evaporated and the resulting product contained 36.50% total sulfur (6.08% of which was free sulfur), 2.33% combined chlorine, and had a viscosity of 1159 SSU at 100 F. and a flash point of 330 F. The product was very dark and when diluted with an oil of 2-NPA color in amount suflicient to give a 2% added sulfur in the oil composition, gave a 33 /2 NPA color. Such color is too dark for commercial application.

EXAMPLE 2 Two hundred grams of the same crude dodecyl polysulfide employed in Example 1 was treated for three hours at temperatures in the range of 78 to 98 F. with 50 grams of S Cl and grams of water. After the product was freed of water by raising its temperature to about 260 F., it was treated with 30 grams of NaCO to neturalize any undesirable acidic components and then dissolved in hexane to permit ready desalting. The hexane was thereafter evaporated to give a product analyzing 36.7% total sulfur (comprising 2.78-free sulfur) and 1.56 combined chlorine. The product when diluted with oil as per Example 1 had an NPA color of 2-296.

. EXAMPLE 3 In a manner identical with that of Example 2, 200

grams of the same dodecyl polysulfide was treated with 50 grams of S Cl in the presence of 10 grams of water and 10 grams of P S free of water, neutralized and desalted. The resulting product contained 37.5% total sulfur, of which 3.80% was free sulfur, and 0.97% chlorine. Upon dilution with petroleum oil as in the foregoing examples, the color of the oil containing 2% added sulfur was 22 /2 NPA.

Table 1 indicates the improved yield of high sulfur E. P. agent obtainable from a given quantity of crude polysulfide by using the present invention. Thus, instead of losing upwards of of the total sulfurized material because of the necessity for adjusting the flash point, it is now possible to raise the flash point and at the same time end up with a substantially larger amount of useful l The product (A) was treated with 16% by volume of $2011 in the resence of 5% P285 by weight and 5% by volume of water for several ours at a temperature of from 77104 F. after which the water was removed at a higher temperature the product neutralized with NaOOg and desalted, all in accordance with t e illustrative examples set forth above.

stantially reducing the yield, of crude alkyl polysulfide mixtures comprising at least about 70% by weight of dialkyl polysulfides and a lower boiling hydrocarbon material comprising olefinic constituents from which the raw materials employed in the polysulfide synthesis have been derived, which method comprises sulfochlorinating said crude alkyl polysulfide mixture with from about 10% to about 25% by volume of a sulfur chloride in the presence of from about 1% to about 50% by volume of water at a temperature in the range from about F. to about F.

2. The method of claim 1 wherein an amount of phosphorus sulfide, not in excess of 15% by weight, is present in the reaction zone.

3. The method of claim 1 wherein the sulfur chloride is sgclg. I

4. A method of sulfochlorinating a crude polysulfide mixture comprising at least about 70% by weight of dialkyl polysulfides and a lower boiling hydrocarbon material comprising olefinic constituents from which the raw materials employed in the polysulflde synthesis have been derived, which method comprises contacting said crude alkyl polysulfide mixture with from about 10% to about 25% by volume of S Cl and from about 1% to about 15% by weight of a phosphorus sulfide in the presence of from about 1% to about 50% by volume of water at a temperature in the range of from about 80 F. to about 150' F.

References Cited in the file of this patent UNITED STATES PATENTS 2,237,625 01in Apr. 8, 1941 2,237,627 Olin Apr. 8, 1941 2,405,607 Rogers Aug. 13, 1946 2,405,608 Rogers Aug. 13, 1946 2,516,119 Hersh July 25, 1950 2,727,030 Beretvas Dec. 13, 1955

Claims (1)

1. A METHOD OF INCREASING THE FLASH POINT, WITHOUT SUBSTANTIALLY REDUCING THE YEILD, OF CRUDE ALKYL POLYSULFIDE MIXTURES COMPRISING AT LEAST ABOUT 70% BY WEIGHT OF DIALKYL POLYSULFIDES AND A LOWER BOILING HYDROCARBON MATERIAL COMPRISING OLEFINIC CONSTITUENTS FROM WHICH THE RAW MATERIALS EMPLOYED IN THE POLYSULFIDE SYNTHESIS HAVE BEEN DERIVED, WHICH METHOD COMPRISES SULFOCHLORINATING SAID CRUDE ALKYL POLYSULFIDE MIXTURE WITH FROM ABOUT 10% TO ABOUT 25% BY VOLUME OF A SULFUR CHLORIDE IN THE PRESENCE OF FROM ABOUT 1% TO ABOUT 50% BY VOLUME OF WATER AT A TEMPERATURE IN THE RANGE FROM ABOUT 80*F. TO ABOUT 150*F.