US3422161A - Unsymmetrical dialkylbenzene mixtures - Google Patents

Description

United States Patent 3,422,161 UNSYMMETRICAL DIALKYLBENZENE MIXTURES Joe B. Lavigne, Oakland, and Mack F. Hughes, Albany,

Califl, assignors to Chevron Research Company, San

Francisco, Calif., a corporation of Delaware No Drawing. Filed Sept. 16, 1966, Ser. No. 579,814 US. Cl. 260-668 11 Claims Int. Cl. C07c 15/04 ABSTRACT OF THE DISCLOSURE Unsymmetrical dialkylbenzene mixtures having an average molecular weight in the range 300-500 and in which the alkyl groups contain from 4 to 21 carbon atoms, and are dissimilar in that one is a branched chain, the other is a straight chain and for the mixture the average carbon atom content of the two types varies by at least 4.

This invention relates to a novel dialkylbenzene mixture. More particularly, it relates to unsymmetrical dialkylbenzene mixtures having a two-fold asymmetry in that (1) the benzene contains two different types of alkyl group constituents, and (2) there is a substantial average molecular weight difference as between the alkyl types constituting the mixture. Still more particularly, it relates to dialkylbenzene mixtures especially useful for the production of lubricating oil additives.

-Dialkylbenzenes have long been known and used for the production of heavy duty detergents useful in the mechanical arts. With each succeeding year in the advancing technology, the demand for substantial improvements in the performance of mechanical systems is a constant problem. [Improved performance on the part of mechanical systems in general also engenders corresponding requirements for improved performance on the part of adjuvants associated with these systems. This circumstance is especially experienced in the case of internal combustion engines in regard to crankcase lubricant additives. Higher work loads, higher power output requirements and the like mean increased severity of the operating conditions. Particularly severe conditions are encountered in diesel engine operations. In service the lubricating oil deteriorates and forms harmful deposits on piston rings, lands and skirts.

It has now been found that manifold improvements over prior art means for reducing harmful depositions can be obtained in the case of crankcase lubricants and in their ability to minimize harmful deposits on piston surfaces by the use of unsymmetrical dialkylbenzene sulfonate detergent additives in which the dialkylbenzene functionality of the detergent is a mixture of dialkylbenzenes having an average molecular weight in the range 300-500 molecular weight units, in which the alkyl substituents of the benzene ring contain from 4 to 21 carbon atoms, in which one of the alkyl groups attached to the benzene ring is a straight chain radical and the other a branched chain alkyl radical having on the average at least one branch for every two carbon atoms along the chain and in which the carbon atom content of the alkyl types in the dialkylbenzene mixture varies, the average carbon atom content of the aforementioned two types differing by at least four carbon atoms. The unique dialkylbenzenes of the present invention yield heavy duty detergents which are surprisingly superior to conventional additives as known in the art. Comparative performance of the instant novel additives under severe test conditions have demonstrated as much as a sixtyfold and higher reduction in harmful deposit accumulation on critical piston surfaces.

In a preferred embodiment of the invention, a monoalkyl polypropylbenzene fraction having a boiling point 3,422,161 Patented Jan. 14, 1969 range of about 3l8-478 F. (ASTM D 447), containing from 4 to 9 carbon atoms and an average molecular weight of about 167 is alkylated with a substantially straightchain C -C cracked-wax tat-olefin. The molecular weight of the dialkylbenzene mixture has an average value in the range 400-410.

The dialkylbenzenes of the present invention desirably have average molecular weights in excess of about 300. On the other hand, dialkylbenzenes having average molecular weights substantially in excess of about 500 are not particularly economical, at least for the preparation of dialkylbenzene sulfonate lubricating oil additives. Dialkylbenzenes having average molecular weight values in the range 350-450 are preferred. In view of the above molecular weight requirement, the alkyl substituents useful for the preparation of the instant dialkylbenzenes will have in general from 4 to about 21 carbon atoms. In each mol of the dialkylbenzene mixture there is desirably a range of carbon atom values for each alkyl chain type, i.e., straight and branched chains.

In addition to the above noted alkyl chain-type differentiation, and the described carbon atom range feature for these chain types, an especially desirable and contributory feature of the present dialkylbenzene mixtures is a mass imbalance in the subject dialkylbenzene mixtures as between the alkyl chain types. This is conveniently described in terms of an average carbon atom content difference for the chains. That is, the average carbon atom content of the straight chain alkyl substituents of the dialkylbenzene mixture less that for the branched chain substituents or vice 'versa, should be at least 4. This difference may be as much as 10 and higher, possibly as much as 15 for useful dialkylbenzene mixtures depending upon the particular use intended.

The foregoing alkyl mass imbalance is preferably and conveniently obtained in practice by using a combination of a lower alkyl alkylation agent, i.e., a fraction in the range C -C and an upper alkyl alkylation agent, i.e., a fraction in the range C C Starting from benzene and the desired alkylation agents, the instant dialkylbenzene mixtures must be prepared in a two-stage process. In the preferred method benzene is alkylated using a Friedel-Crafts catalyst, such as HF or aluminum chloride. At temperatures in the range from about 40 F. to about 200 F. benzene, the HF catalyst, and preferably the alkylating agent having the lower average carbon atom content are reacted. The branched chain alkylations usually are accomplished at the lower reaction temperatures, while the straight chain alkylations usually require higher reaction temperatures. The product is fractionally distilled to remove unreacted benzene, and light ends. Next, the resulting monoalkylbenzene is alkylated by reaction with the desired second type alkylation agent, i.e., straight or branched chain, as the case may be, using HF catalyst. The crude dialkylbenzene product is similarly fractionated in a distillation in which unreacted monoalkylbenzene is removed as a forerun fraction, and a minor amount of high boiling by-product is rejected, if desired. In general, the dialkylbenzene mixtures of the invention have boiling points greater than 400 F. at 10 mm. of Hg pressure (i.e., ASTM D 1160).

The subject dialkylbenzene mixtures can be prepared from a variety of alkylation agents including alcohols, alkyl halides, ethers and the like, providing, of course, that the required alkyl chain type and a suitable carbon number range is used. In the alkylations, catalysts other than 'Friedel-Crafts catalysts are useful; these include sulfuric acid, phosphoric acid, and the like. The reaction combination of alkenes and hydrogen fluoride as described above is preferred for practical reasons.

The branched-chain alkyls are preferably derived from propylene polymers of suitable molecular weight range,

3 that is, the propylene dimer, trimer, tetramer, pentamer and higher poly-propylenes. Copolymers, such as propene-butene, propene-ethene, etc., are also useful. At least one branch for every two carbon atoms along the chain appears to provide a sufiicient branching-ratio.

The straight chain alkyls are preferably derived from cracked petroleum wax alkene fractions. They may also be l-alkene mixtures or internal alkene mixtures as from isomerized l-alkenes or from dehydrochlorination of chloroparafilns, deyhydration of alcohols, or parafiin dehydrogenation. Mixtures of olefins containing alkane may be used because the alkanes are in general inert diluents.

The subject dialkylbenzenes have characteristic infrared spectra absorbances at 830 cmf 708 cm. and at 722 cm. (0.037 mm. cell and 0.0325 mm. ref. cell). The degree of the absorbance at 830 cm.- varies depending upon the para-isomer content (in general in the range 85 to 30 mol percent); the absorbance at 708 cm? varies depending upon the meta-isomer content (in general in the range 15 to 70 mol percent). The absorbance at 722 cm? varies depending upon the number of methylene groups in the straight chain alkyl group.

A minor amount of monoalkylbenzene may be present in the product depending upon the relative etficiency of the second alkylation and the subsequent fractionation. This impurity is characterizable by infrared absorbance at 700 cm? and 760 cmr When there is some monoalkylbenzene impurity in the desired dialkylbenzene, the average molecular weight value is, of course, an apparent Value. So long as this average molecular weight value is in the range specified, i.e., 300-500 units, the subject dialkylbenzenes are particularly useful as described below. Hence larger amounts of monoalkylbenzene, possibly as much as 20 mol percent, can be tolerated where the side chain is long.

The variation in meta-para-isomer distribution is a function of the particular FriedebCrafts catalyst, of the alkylation conditions, and of the alkyl group combination used. Hydrogen fluoride is a particularly satisfactory catalyst.

The following examples further illustrate the invention.

EXAMPLE 1 Short branched chain-long straight chain dialkylbenzene (A) Benzene was alkylated using a tetramer polypropene fraction and HF alkylation catalyst, a reaction temperature of about 65 F, and efficient mixing. The hydrocarbon phase was separated, washed and fractionated. The lower alkyl fraction (boiling point range 318 F. to 478 F., ASTM D 447 distillation) was collected as feed for the second stage alkylation by a straight chain alkene. The average molecular weight of the above branched chain alkylbenzene was 164. This corresponds to an average of 6 carbon atoms per alkyl group in the mixture. The overall alkyl carbon atom content corresponding to the above boiling point range is the C -C range.

Using the above branched-chain monoalkylbenzene and a substantially straight-chain (I -C l-alkene fraction obtained from cracked wax, and hydrogen fluoride catalyst, the desired dialkylbenzene was produced in a stirred, continuous reactor. The l-alkene feed had the following characteristics:

Average mol Weight 268 Average number of carbon atoms per alkyl group 19 Olefin distribution, weight percent:

C 2 C 22 C 39 C20 32 C21 Reaction conditions:

LHSV 2 Temperature, F. Monoalkylbenzene to a-olefin, mol ratio 2-1 Hydrocarbon to HP ratio, volume 2.3-1

After reaction the settled product was separated into an upper organic phase and a lower HF acid phase. The crude dialkylbenzene organic phase was washed and then fractionated by distillation. A minor amount of forecut, mainly monoalkylbenzene, was collected up to an overhead temperature of about 450 F. at 10 mm. Hg. The balance of the distillate was the desired product, and had an average molecular weight of about 405. The difference between the average carbon atom content of the alkyl-chain types was about 13.

EXAMPLE 2 Long branched chain-short straight chain dialkylbenzene (B) As in Example 1 a dialkylbenzene was prepared using a polypropylbenzene as the branched-chain monoalkylbenzene (boiling point range 475-620 F., average molecular weight about 260 and average number of carbon atoms in the branched chain of 13 In the second stage alkylation, a mixture of C -C cracked-wax-a-olefin of the composition:

Olefin Weight percent 0 20 c, 17 c 18 c, 23 c 22 was used. The resulting reaction mixture was topped. The desired dialkylbenzene had a boiling point greater than 405 F. at 10 mm. of Hg pressure and an average molecular weight of about 392. The average alkyl-type carbon atom difference was about 5.

EXAMPLE 3 Short branched chain-wide range long straight chain dialkylhenzene (C) A mixed alkyl-type dialkylbenzene was prepared as in Example 1, except that a Wider range straight-chain 1alkene, i.e., C14-C21 range, was used.

The dialkylbenzenes prepared as in Examples 1-3, inclusive, were tested by the preparation of sulfonate detergent-type additives for use in crankcase lubricating oil compositions. These lube oil compositions were subjeoted to the severe Caterpillar l-G conditions (MIL-L- 45119). Straight chain-branch chain dialkylbenzene sulfonate modified crankcase lubricating oil performance was outstanding.

The dialkylbenzenes of this invention are readily converted to useful lube oil sulfonate additives. The sulfonation can be accomplished using conventional sulfonation procedures and agents including oleum, chlorosulfonic acid, sulfur trioxide (complexed or thin film dilution techniques and the like as described in the art) and the like. In the following example, oleum is employed.

EXAMPLE 4 Sulfonate additive preparation The dialkylbenzene prepared as in Example 1 was charged to a stirred reaction vessel fitted for temperature control along with a neutral oil which was substantially free of sulfonatable material. The volume ratio of the reactants was 3% to 4, respectively, and to this mixture was added over a period of several hours 2 volumes of 25% oleum. The reaction temperature was maintained at about 100 F. Two phases developed in the settled reaction mixture, the lower being a spent mineral acid phase and the upper being the desired sulfonic acid phase.

The separated sulfonie acid-oil mixture was then neutralized with one volume of 50% aqueous caustic diluted with 15 volumes of aqueous Z-butanol. During the neutralization the temperature was maintained below about 110 F., and after completion thereof the neutral solution was heated and maintained at 140 F. during .a second phase separation- Two phases developed, a lower brine alcohol solution and an upper neutral alcohol-sodium sulfonate solution.

The neutral alcohol-sodium sulfonate phase was metathesized using concentrated sodium chloride brine to produce the desired neutral calcium chloride brine to produce the desired neutral calcium dialkylbenzene sulfonate. The latter was water washed and steam stripped to remove alcohol during which operation calcium oxide was incorporated in the neutral sulfonate, thereby converting it to the desired overbased lube oil additive. The resulting basic calcium sulfonate in neutral oil contained about 42 mol percent excess of base expressed as calcium.

EXAMPLE 5 Sulfonate additive preparation A charge of 137 g. of dialkylbenzene (Example 2 product) 110 g. of neutral oil having 130 SSU viscosity at 100 F. was introduced into a stirred reactor fitted for temperature control. Over a period of 40 minutes and while maintaining the reaction temperature at 105 F., 181 g. of 25% oleum was fed into the charge. The resulting product mixture separated, after standing for 16 hours, into two homogeneous phases, a lower acid phase which was discarded, and an upper sulfonic acid-oil phase. The latter was neutralized with 35 g. of 50% sodium hydroxide in aqueous 2-butanol and maintaind at 150 F. for two hours while phase separation took place. The upper phase, oil, and the lower phase, brine, were discarded. The middle phase contained sodium dialkylbenzene sulfonate which was converted to the overbased (30 mol percent excess of calcium) calcium sulfonate salt by metathesis using concentrated calcium chloride brine. Neutral oil (130 SSU viscosity) was added.

ENGINE TESTS Lube oil compositions were then compared by engine testing under Caterpillar l-G conditions (MIL-L-45l19). The tests ran for 480 hours, and the data are tabulated below. The compositions tested varied only in the metal sulfonate used. In Test No. 1 the sulfonate of Example 4 was used. In Test No. 2 a commercially available calcium sulfonate was used. In Test No. 3 a straight chain dialkylbenzene was used (see below).

In each case the base oil used was a solvent refined mid-continent SAE 30 parafiinic base oil. The test composition contained 150 millimols of total calcium per kilogram of finished oil composition (mM./kg.), the millimol content being based on the metal of the additives. These included an excess of about 38 mol percent calcium over and above that required to neutralize the sulfonic acids. The compositions contained in addition 94 mM./kg. of an overbased sulfurized carbonated calcium alkyl phenate, and an average of 12 carbon atoms in the alkyl group derived from polypropylene; 10 rnM./kg. of zinc 0,0-di(alkylphenyl) phosphorodiothioate (alkyl group being polypropylene averaging 14 carbon atoms); and 0.001%, by weight, of a silicone foam inhibitor.

Land deposits 2 Groove deposits 1 l Equals percent filling by deposit. 7 Values range from 0 (clean) to 800 (black).

equal. length, the dialkylbenzenes having an average molecular weight of 371.

The sulfonate in Test No. 3 was derived from a mixture of a dialkylbenzene of about 400 in melocular weight and 500 neutral oil. The dialkylbenzene was obtained from the alkylation of benzene with straight chain alkylating agent to produce linear alkylbenzene detergent for household use. The total carbons in the alkyl groups averaged :23 and the alkyl chains were of approximately equal length.

It will be noted that Test No. 1 using the metal sulfonates of the present invention gives superior results over sulfonates derived from known synthetic hydrocarbons. Use of the present sulfonates causes less deposit formation on piston lands, in the first groove, and also significantly in the second groove.

In addition to the foregoing Caterpillar test, the subject dialkylbenzene sulfonates were similarly compounded in crankcase lube oil compositions which were tested in preliminary engine screening tests. In every case the nstant unique branched-straight chain dialkylbenzene sulfonates were superior to conventional materials.

The foregoing tests demonstrate that the performance of crankcase lubricating oil compositions is markedly improved by the addition of minor amounts of unsymmetrical straight chain-branched chain dialkylbenzene sulfonate mixtures as described. Thus the above noted modification of base oils of lubricating oil viscosity in general is contemplated within the inventive concept, such compositions comprising an oil of lubricating oil viscosity and, in an amount eifective to inhibit deposit formation, the metal sulfonate salt herein described. In general, the amount of sulfonate salt present in the composition can range from 0.1% to 70%, by weight, based on finished composition. When the composition is used in an internal combustion engine, it will usually comprise a major proportion of oil of lubricating oil viscosity, and a minor, but eifective amount to inhibit deposit formation by the oil, of the metal sulfonate salt. A suitable amount for this purpose ranges from about 0.1% to 10%, preferably 1 to 5%, by weight, based on the finished composition. Because of their excellent solubility in oils, concentrates in oil of the contemplated alkaline earth (i.e., atomic number greater than 4 and less than 57) metal sulfonates are also within the purview of the invention. When forming concentrates, the metal sulfonate salt content can range from about 20 to 70%, by weight, based on the finished composition.

The lubricating oil compositions containing the sulfonates of the present invention may, and usually, contain other components as is known in the art. These other components include viscosity index improving agents, other detergents, oxidation inhibitors, foam inhibitors, extreme pressure agents, thickening agents, and pour point depressants.

Lubricating oils which are suitable as base oils for the compositions of this invention include a wide variety of oils, such as naphthenic base, parafiin base, and mixed base petroleum oils; lubricating oils derived from coal products; synthetic oils, e.g., alkylene polymers, such as the polymers of propylene and butylene and mixtures thereof; alkylene oxide polymers; dicarboxylic acid esters; liquid esters of acids of phosphorus; aromatic type base oils; and polymers of silicon. In general, satisfactory oils have a viscosity of 20 to SSU at 210 F.

As the range of embodiments of this invention is wide, and many may appear to be widely diiferent, yet not depart from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof, except as defined in the appended claims.-

We claim:

1. A dialkylbenzene mixture having an average molecular weight in the range of 300-500 molecular weight units wherein the alkyl substituents of said mixture contain from 4 to 21 carbon atoms; wherein for each of said dialkylbenzenes one of said alkyls has a straight chain and the other a branched chain having on the average at least one branch per every two carbon atoms along the chain; wherein the carbon atom content of the alkyl types in said dialkylbenzene mixture varies and wherein the average carbon atom content of said alkyl types, straight and branched, differ by at least 4.

2. The dialkylbenzene mixture as in claim 1 wherein said branched alkyls are derived from propylene polymerization.

3. The dialkylbenzene mixture as in claim 2 wherein said branched chain alkyls are lower alkyls and said straight chain alkyls are upper alkyls.

4. The dialkylbenzene mixture as in claim 2 wherein said branched chain alkyls are upper alkyls and said straight chain alkyls are lower alkyls.

5. The dialkylbenzene mixture as in claim 3 wherein said branched chain alkyls contain from about 4 to 9 carbon atoms and contain an average carbon atom content of about 6 and said straight chain alkyls contain from about 17 to 21 carbon atoms and have an average carbon atom content of about 19.

6. The dialkylbenzene mixture as in claim 4 wherein said branched chain alkyls contain an average carbon atom content in the range -0 and said straight chain alkyls are a mixture of C -C cracked-wax alkyls having an average carbon atom content of about 8-10.

7. The composition as in claim 1 wherein said dialkylbenzene average molecular weight is in the range 350- 450.

8. The dialkylbenzene mixture as in claim 1 wherein said branched chain alkyl group is a polypropylene group and wherein said straight chain alkyl group is a crackedwax a-olefin group.

9. The mixture as in claim v1 wherein said straight chain alkyl groups are cracked-wax straight chain groups containing from 17 to 21, inclusive, carbon atoms per group and have on the average about 19 carbon atoms; and wherein said branched'chain alkyl groups have an average molecular weight of about 87 and contain on the average about 6 carbon ato'ms.

10. The mixture as in claim 1 wherein said straight chain alkyl groups are cracked-wax straight-chain groups containing from 6 to 10, inclusive, carbon atoms per group; and wherein said branched chain alkyl groups have an average molecular weight of about 183; and wherein the average alkyl-type carbon atom difference is about 5. v

11. The mixture as in claim 1 wherein said straight chain alkyl groups contain from 14 to 21, inclusive, carbon atoms; and wherein said branched chain alkyl groups have an average molecular weight of about 87, and contain on the average about 6 carbon atoms.

References Cited UNITED STATES PATENTS 12/1952 Van Battum 260-671 3/1965 Pappas et al 260-671 US. Cl. X.R.