US3598739A - Synthetic hydrocarbon lubricating composition - Google Patents

Abstract

THIS DISCLOSURE CONCERNS A SYNTHETIC HYDROCARBON LUBRICATING COMPOSITION, HAVING GOOD VISCOSITY PROPERTIES AND EXCELLENT POUR POINT PROPERTIES, WHICH CONSISTS ESSENTIALLY OF A MIXTURE OF DIALKYLBENZENES AND ALKYL-SUBSTITUTED TETRAHYDRONAPHTHALENES, PREFERABLY TRIALKYL-SUBSITUTED TETRAHYDRONATPHTHALENES. AN IMPORTANT ASPECT OF THE DISCLOSURE IS THE FEATURE THAT THE POUR POINT OF DIALKYLBENZENE CAN BE LOWERED BY INCORPORATING THEREIN ALKYLSUBSTITUTED TETRAHYDRONAPHTHALENES.

Description

United States Patent 01 fice 3,598,739 Patented Aug. 10, 1971 3,598,739 SYNTHETIC HYDROCARBON LUBRICATING COMPOSITION Roy C. Sias, Ponca City, Okla, assignor to Continental Oil Company, Ponea City, Okla. N Drawing. Filed Feb. 20, 1969, Ser. No. 801,190 Int. Cl, Cm N16 US. Cl. 25259 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND Various petroleum fractions have been used as lubricants for many years. While the petroleum-derived lubricants have been satisfactory for most uses, there are fields of use, as for example, jet engine lubricants and arctic oils, wherein the requirements render the conventional petroleum-derived lubricants either unsatisfactory or of marginal utility. In an attempt to solve this problem, synthetic lubricants (for example, diesters) have been developed having improved viscosity and pour point properties. Unfortunately, however, the synthetic lubricants of the prior art have been relatively expensive.

In an effort to provide lower-cost, high-quality synthetic lubricants, work has been directed to synthetic hydrocarbons. For example, Pappas and Kant in US. 3,173,965 teach that dialkylbenzenes have properties which render them useful as lubricants. In addition, Becraft and Durr, in US. 3,288,176, teach that a bottoms fraction of the product resulting from the condensation of a substantially straight chain paraflinic hydrocarbon, containing in the range of about 8 to about 18 carbon atoms, with an aromatic hydrocarbon, has properties which render it particularly useful as a lubricant.

Applicant has discovered that the pour point of dialkylbenzenes can be lowered by incorporating therein alkyl-substituted tetrahydronaphthalenes, preferably trialkyl-substituted tetrahydronaphthalenes.

PRIOR ART The most pertinent prior art is believed to be US. Pats. 3,173,965 and 3,288,176, referred to above.

With regard to 3,288,176 read in its entirety the patent teaches that tetrahydronaphthalenes are undesirable and contain no recognition that the presence of tetrahydronaphthalenes improves the pour point. Moreover it does not recognize the presence of trialkyl-substituted tetrahydronaphthalenes.

BRIEF SUMMARY OF THE INVENTION Broadly stated, the present invention relates to a synthetic hydrocarbon lubricating composition consisting essentially of about 1 part dialkylbenzenes and from about 0.25 to about 1.6 parts alkyl-substituted tetrahydronaphthalenes, said composition containing less than 0.10 part of diphenylalkanes per part of dialkylbenzenes and having a pour point of at least 50 F.

In a preferred embodiment of this aspect of my invention, the composition contains an intentionally added amount, sufficient to lower the pour point of the composition by at least 5 F., of alkyl-substituted tetrahydronaphthalenes. The intentionally added amount is from about 0.05 to about 1 part per part of said dialkylbenzenes.

In another aspect the present invention relates to a process for lowering the pour point of asynthetic hydrocarbon lubricating composition containing at least 55 percent, preferably at least 70 percent, by volume, dialkylbenzenes, which comprises incorporating therein from about 0.25 to about 1.6 parts alkyl-substituted tetrahydronaphthalenes per part of dialkylbenzenes.

Preferably, the alkyl-substituted tetrahydronaphthalenes are trialkyl-substituted tetrahydronaphthalenes.

DETAILED DESCRIPTION Components of the composition The major components of the composition of my invention are dialkylbenzenes and alkyl-substituted tetrahydronaphthalenes. The dialkylbenzenes can be represented by the formula wherein R is a straight-chain alkyl group containing from about 10 to about 18 carbon atoms. The alkyl group is attached to the benzene ring through an internal carbon atom.

The alkyl-substituted tetrahydronaphthalenes can be represented by the formula Rap wherein R and R contain from 1 to about 16 carbon atoms each, with the sum of R and R being from about 9 to about 17. Both R and R, are straight-chain alkyl groups.

The trialkyl-substituted tetrahydronaphthalenes, which are preferred, can be represented by the formula wherein R and R contain from 1 to about 13 carbon atoms each, with the sum of R and R being from about 6 to about 14, and R and R contain from 1 to about 16 carbon atoms, each wtih the sum of R and R being from about 9 to about 17. The alkyl groups, R R R and R are straight chain. For example, a C-11 trialkyl-substituted tetrahydronaphthalene would be represented by the formula wherein R and R would have a total of 7 carbon atoms with R or R having at least a methyl group, and wherein the sum of R and R, is 10. R and R, can contain from 1 to 9 carbon atoms each.

wherein the I OHR grouping is the same as in the trialkyl-substituted tetrahydronaphthalenes.

For reason of simplicity, the above-described dialkylbenzenes, alkyl-substituted tetrahydronaphthalenes and trialkyl-substituted tetrahydronaphthalenes are often referred to as DAB, ATHN and 'ITHN, respectively, hereinafter.

Since mixtures of ATHN and 'ITHN are suitable in the composition of my invention, the term ATHN is generic and includes mixtures of ATHN and TTHN.

As indicated hereinbefore, addition of the ATHN to the DAB provides a reduction in the pour point of the resulting composition. Plotting the relative amounts of the ATHN and DAB against the pour point usually shows that a small amount of ATHN has a pronounced efl ect, producing a sharp upward break in the curve. Moreover, the curve produces a peak, which may be either sharp or relatively broad, after which a downward break results in the curve, thereby indicating that the ATHN actually increases the pour point. The effectiveness of the ATHN on lowering the pour point of the DAB varies, depending on the particular composition of the ATHN and the DAB.

Suitably, the composition of my invention contains from about 0.25 to about 1.6 parts by volume ATHN per part of DAB. Preferably, the compositions contain from about 0.30 to about 0.80 part by volume ATHN per part of DAB.

In one embodiment, the composition of my invention contains an intentionally added amount, sufiicient to lower the pour point at least 5", preferably at least F., of ATHN. The intentionally added amount is from about 0.05 to about 1 part by volume, preferably from about 0.10 to about 0.80 part by volume ATHN per part DAB.

While DAB and ATHN are the essential materials of the composition of my invention, other materials can be present. Usually, the other materials are by-products of the processess of producing the essential materials.

One of the non-essential materials is diphenylalkanes (DPA). At one time these materials were believed to be beneficial in synthetic hydrocarbon lubricants in that they produced a lower pour point. It now appears that the DPA reduced the pour point by dilution rather than by depression, as is the case with the ATHN and TTHN. These diphenylalkanes are present in an amount of less than 0.10 part by volume, preferably less than 0.05 part by volume, per part of DAB. Typically, the DPA which are present are represented by the formula where the sum of R R and R is from about 8 to about 16 carbon atoms and R and R is at least a methyl group.

Other materials which can be present, even though they are not desirable, include monoalkylbenzenes and miscellaneous condensed alkyl aromatic compounds. These materials are present in less than about 0.25 part by volume, preferably less than about 0.10 part by volume, per part of DAB.

Properties of the compositions The compositions of my invention have excellent (i.e. very low pour points, excellent (i.e. very high) viscosity indexes, good flash points and acceptable 40 F. viscosities. For example, the compositions suitably have a pour point of less than 50 F., preferably less than -60 F., and more preferably less than F. In addition, the composition suitably has a viscosity index of at least 90, preferably at least and more preferably at least 110. Moreover, the compositions have a flash point of at least 400 F. and a 40 F. viscosity of less than 20,000 cs.

Preparation of the composition The following description describes a particularly suitable process for preparing the composition.

The dialkylbenzenes are prepared by disproportionating monalkylbenzenes or by alkylating monoalkylbenzenes with an olefin or a chlorinated paraffin of suitable carbon content. Since disproportionation of monoalkylbenzenes provides a suitable dialkylbenzene product, this process will be described in detail.

A suitable monoalkylbenzene fraction for the disproportionation reaction is prepared by alkylating benzene with a mixture of substantially monohalogenated parafiins, containing 10 to 15 carbon atoms, using a Friedel- Crafts catalyst. One such method is described in detail in US. Pat. No. 3,316,294 which is made a part of this disclosure.

Briefly, US. 3,316,294 relates to a process of preparing a detergent alkylate, wherein the process comprises the following steps, broadly stated: (a) separating a fraction of substantially straight-chain C C hydrocarbons from a petroleum distillate substantially free of olefins and containing said straight-chain hydrocarbons together with non-straight chain hydrocarbons, (b) chlorinating said fraction to the extent whereby between abonut l0 and about 35 mole percent of the straightchain hydrocarbons present are substantially only monochlorinated, and (c) alkylating an aromatic compound, e.g. benzene, with the chlorination product of step (b) in the presence of an alkylation catalyst.

Disproportionation of the mono-n-alkylbenzenes to di-n-alkylbenzenes is conducted using a Friedel-Crafts catalyst. The term Friedel-Crafts catalyst is well understood in the art and refers, generally, to materials such as the aluminum halides, boron trifluoride, boron trichloride, antimony chlorides, stannic chloride, zinc chloride, and mercuric chloride. Preferably, the Friedel-Crafts catalyst is aluminum chloride or aluminum bromide. The more preferred catalyst is aluminum chloride, which also includes in situ prepared aluminum chloride, or, in other words, the reaction product of aluminum metal and hydrogen chloride.

In some cases it is desirable to use a proton-donor promoter with the Friedel-Crafts catalyst. Suitable promoters include any material which, when added to the catalyst, yields a proton. Preferred promoters are hydrogen chloride and water. The amount of promoter is typically about 4 weight percent based on the weight of the catalyst employed.

Preferably, the catalyst is added to the reaction mixture after the mono-n-alkylbenzenes are brought to within the correct temperature range, which will be described below. The amount of the catalyst which is used can vary from about 0.1 weight percent to about 10 weight percent based on the mono-n-alkylbenzene starting material. Preferably, the amount of catalyst is from about 0.5 Weight percent to about 3 Weight percent.

The disproportionation process, suitably, is conducted at a temperature of from about 20 C. to about 130 C. tained at temperatures between about 60 C. and C., used, preferably the amount of catalyst is from about 1 to about 2 Weight percent.

Following the reaction, the reaction mass is distilled in order to remove the benzene, parafiins and unreacted mono-n-alkylbenzenes. The desired disproportionation product is the bottoms fraction with a distillation cut point of 197 C. at 5 mm. Hg. In other words the desired product distills above 197 C. at 5 mm. Hg.

While we have described in detail the process conditions for the disproportionation reaction, the disproportionation process is not part of our invention. This process is disclosed and claimed in application Ser. No. 529; 284, filed Feb. 23, 1966, having the same assignee as the present application.

The disproportionate product contains at least 55 percent by volume, more usually at least 70 percent by volume, dialkylbenzenes. It has a viscosity index (IOU-210 F. basis) of from about 105 to about 120 and a pour point of from about -55 to about 70 F. The disproportionate product usually contains a small amount of TTHN. The amount of TTHN varies with the disproportionation conditions and the amount of dialkyl-substituted tetrahydronaphthalenes in the monoalkylbenzene disproportionation charge. By careful selection of disproportionation conditions a disproportionated product can be prepared containing as much as 30% by volume (mass spectral analysis) TTHN. In instances where it is desired to have a product having a pour point of less than about 55 F. and a high flash point (over 450 F.) disproportionation conditions are selected which produce a product containing less than about 20% TTHN. Then additional TTHN is added in an amount sufficient to lower the pour point.

The benefits of my invention (i.e. the effect of ATHN on lowering the pour point of dialkylbenzene compositions) will be readily apparent to those skilled in this art. For example, as indicated above, the emphasis in the preparation of the dialkylbenzenes can be to produce a product which is strong in properties other than pour point. Then, the desired pour point can be attained by simply adding the ATHN 0r TTHN to the dialkylbenzenes.

The alkyl-substituted tetrahydronaphthalenes are prepared by alkylating tetrahydronaphthalene with an olefin or a chlorinated paraflin having the desired chain length. The trialkyl-substituted tetrahydronaphthalenes are prepared in a similar manner using dialkyl-substituted tetrahydronaphthalenes. The dialkyl-substituted tetrahydronaphthalenes can be obtained by careful fractionation of the product prepared by the process described by U.S. 3,316,294, described hereinbefore. Alternatively, the trialkyl-substituted tetrahydronaphthalenes can be obtained by careful fractionation of the disproportionated product. The first described procedure of preparing the trialkylsubstituted tetrahydronaphthalenes is preferred since in effect the value of the dialkyl-substituted tetrahydronaphthalenes is increased by conversion to the trialkylsubstituted tetrahydronaphthalenes.

The non-essential components of the composition (diphenylalkanes, monoalkylbenzenes, and miscellaneous condensed alkyl aromatic compounds) are by-products of the process of manufacturing the composition, which has been described herein.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

EXAMPLE 1 (A) Preparation of the dialkylbenzenes The dialkylbenzenes were prepared by disproportionation of a topped monoalkylbenzene fraction prepared by the process of U.S. Pat. No. 3,316,294. The monoalkylbenzenes had the following carbon content of the alkyl groups C-12less than 5 percent by volume C121030 percent S13--30 min. percent C14-20 min. percent C14-less than 5 percent An overhead fraction was then obtained using a cut-point of 182 C. at 5 mm. Hg pressure. This 80% overhead fraction was the material disproportionated.

Prior to disproportionation the charge stock was pretreated with AlCl as follows:

1100 grams of alkylate (80% overhead material) was contacted with 11.0 grams of anhydrous AlCl at 60 C. for 30 minutes. The reaction mass was allowed to cool and settle for 1% hours to separate the sludge. There was obtained 1086 grams of pretreated alkylate and 25 grams of sludge.

Disproportionation procedure Charge:

1000 g. pretreated alkylate (described above) 10.0 g. anhydrous A1Cl 0.4 ml. H O

Procedure:

The pretreated alkylate was added to a reaction flask. While stirring the admixture, heat was applied until the temperature of the admixture rose to 60 C. At this point the AlCl and H 0 were added. The reaction mass Was heated to -l03 C. and held there for one hour. The admixture was then allowed to cool and settle. There was obtained 980.1 grams of crude alkylate and 30.8 grams of a sludge.

The crude alkylate was washed with deionized water,, followed by a wash with a 5% NaOH solution, and then again ashed with Water. From this treatment, there was obtained 962 grams of crude alkylate.

The crude alkylate Was then subjected to a distillation taking the benzene, parafiin, and monoalkylbenzene fractions overhead. The cut-point for the monoalkylbenzenebottoms fraction was 197 C. at 5 mm. Hg.

The bottoms fraction (which was the dialkylbenzene fraction) was then treated with Filtrol clay. The yield of treated bottoms fraction was 235.9 grams.

The properties of the bottoms framtion (DAB) are shown in Table I.

(B) Preparation of trialkyl-substituted tetrahydronaphthalenes (TTHN) Volume percent C tetrahydronaphthalenes 89 C tetrahydronaphthalenes 2 C alkylbenzene 5 Naphthalene 2 Other 2 The properties of the product (TTHN) are shown in Table I.

(C) Blends of trialkyl-substituted tetrahydronaphthalenes and dialkylbenzenes In order to determine the effect on pour point, blends of TTHN and DAB were prepared, using the abovedescribed fractions. The blends contained, 5, l0 and 20 weight percent TTHN fraction, with the remainder being DAB fractions.

7 The pour points of the 100 percent DAB fraction, 100 percent TTHN fraction and the various blends are shown below:

Pour point, F.

100% DAB fraction 60 100% TTHN fraction 55 Blend A -65 95% DAB fraction 5% TTHN fraction Blend B 65 90% DAB fraction 10% TTHN fraction Blend C -55 80% DAB fraction 20% TTHN fraction The physical properties and complete data for the various blends are shown in Table I.

TABLE I 100% 100% Blend DAB TTHN fraction fraction A 113 O TTHN fraction, wt.

percent 5. D 10. 20. 0 DAB fraction, wt. percent; 95. 0 00.0 80. 0

l), 526 '95, 759 10, T94 11, 500 13, 308 30. 86 67. 72 32. 02 B3. 02 v.35. 54 5. 35 8. 00 5. 38 ii. 48 5. 69 ill) 91 113 l14 110 Your point, F 60 55 -65 -65 55 Mass spectraanalysis,

vol, percent:

DAB 78. 0 5. 7 T4. 1 F0. 8 TTHN .16. U 68. 3 19. 4 L21. 9 27. 0 DPA 0.5 10.0 1.0 111.5 12.4 Indenes 2. 0 l2. 4 5 i3. 0 4. l Mi c. compounds 2. 7 3.6 2. 8 8 2. 9 Ratio DAB/TTHN 11/0. 21 11/12. 0 1/0. 26 11/0. 31 11/043 8 DAB fraction, 100 percent TTHN fraction and the various blends are shown below:

Pour point, F.

80% DAB fraction TTHN fraction Blend E 60 15% DAB fraction TTHN fraction Blend F 60 70% DAB fraction 130%TTHN fraction Blend G 55 65% DAB fraction 35% TTHN fraction The physical properties and complete data for the various blends are shown in Table II.

TABLE 11 100 ID AB Blend Blend Blend Blond Blend Blend Blend traction A B C F TTHN f action wt. rcei t 1.7.0 10.0 15. 0 20.0 25.0 30.0 35. 0 r De 1 9;. 0 so. 0 s5. 0 80.0 75. o 70.0 65. o

DAB fraction. Wt. percent Viscosity, cps. at-

Mlsc. compounds Ratio DEA/TTHN 1 Calculated from 100 percent DAB fraction and 100 percent TTHN fraction.

2 Contains 13.4 percent trialkylbenzene, no mono.

EXAMPLE 2 The dialkylbenzenes used in this example were prepared by disproportionation, using the same procedure as in Example 1. The material subjected to disproportionation differed slightly from that in Example 1. In this example the charge alkylate was the monalkylbenzene fraction without any overhead distillation (in other words, the monoalkylbenzene fraction per se was used).

The properties of the DAB fraction (bottoms) are shown in Table 11 following.

The TTHN fraction used in this example was the same as in Example 1.

In order to determine the effect on pour point, blends of TTHN fraction and the DAB fraction of this example were prepared. The blends contained 5, 10, 15, 20, 25, 30 and 35 weight percent TTHN fraction with the remainder being DAB fraction. The pour points of the 100 percent EXAMPLE 3 This example shows the effect on pour point of blending a C TTHN with a C DAB. (By C TTHN is meant one wherein the grouping R CI-I-R has a total of 13 carbon atoms.)

The C TTHN was prepared by alkylating dialkyltetrahydronaphthalene with a C olefin.

The C DAB was prepared by disproportionation of pure tetradecylbenzene.

The analyses on the C TTHN and C DAB are shown in Table IV.

Various blends were prepared of the two materials. The effect on pour point and other pertinent information on these blends are shown in Table III.

EXAMPLE 4 This example shows the effect on pour point of blending a C13 or a C11 a C12 The C TTHN was the same as in Example 3.

The C TTHN was prepared by alkylating dialkyltetrahydronaphthalene with a C chlorinated parafiin.

The C DAB was prepared by alkylating a narrow cut of -75 F., which is 5 lower than that for 100% DAB Fraction and 25 lower than that for 100% TTHN Fraction. Also, in Example 4 compositions containing 0.69 and 1.32 parts C TTHN per part of C DAB had a C C monoalkylbenzene with a C C chlorinated 5 pour point of 75 R, which is 5 lower than that for n-paraflin. (Both materials had a predominance of C 100% DAB Fraction and lower than that for 100% The analyses on the C TTHN, C TTHN, and C TTHN Fraction. DAB are shown in Table IV. In Example 5 compositions containing 0.75 and 1.40 Various blends were prepared of the materials. The parts TTHN per part of DAB had a pour point of 70 effect on pour point and other pertinent information on 10 R, which is lower than that for 100% DAB Fraction these blends are shown in Table III. and 10 lower than that for 100% TTHN Fraction.

Since addition of an optimum amount of TTHN to the EXAMPLE 5 DAB produces a composition having a lower pour point This examples shows the effect of blending a C TTHN than either alone, and particularly lower than the TTHN with a C DAB. 15 alone, it appears that synergistic effect is present.

The C TTHN was the same as in Example 4. What is considered new and inventive in the present The C DAB was prepared by first alkylating benzene invention is defined in the hereunto appended claims, it with a chlorinated C n-paraflin to produce a C -monobeing understood, of course, that equivalents known to alkylbenzene. The latter material was then disproporthose skilled in the art are to be construed as within the tionated to prepare the C DAB. 0 scope of the invention.

The analyses on the C TTHN and C DAB are shown What is claimed is: in Table IV. 1. A synthetic hydrocarbon lubricating composition Various blends were prepared of the two materials. The consisting essentially of about 1 part by volume dialkyleffect on pour point and other pertinent information are benzenes, the alkyl groups of which are straight-chain and shown in Table III. contain from about 10 to about 16 carbon atoms each TABLE III Wt. Mass spectral analyses, vol. percent Pour percent 2 Ratio TTHN 1 point, Example N0. DAB TTHN in blend DAB TTHN DPA Misc. DAB/TTHN DPA/Mlsc 10. 0 3 20. o so. 2 10. 3 0. 7 2. 8 1/0. 20 0. 01/0. 04 13 30.0 72.3 23.4 0.6 3. 7 1/0. 32 0.01/0. 05 40. 0 -55 54. 3 30. 0 0. 5 4. 5 1/0. 48 0. 01/0. 07 45. 0 50. 3 34. 1 0. 6 5. 0 1/0. 57 0. 01/0. 08

10. 0 75 54. 4 35. 1 0. 5 10. 0 1/0. 54 0. 01/0. 18 c 25. 0 75 4s. 2 41. 5 0. 5 10. 0 1/0. 86 0. 01 0. 21 35. 0 75 43. 9 45. 6 0. 5 10. 0 1/1. 01 0. 01/0. 23 4 (3-12 40.0 *70 41.8 47.7 0.5 10.0 1/1. 14 0. 01/0. 24 10. 0 -75 53. 1 36.6 0. 5 9. 8 1/0. 50 0. 01/0. 19 on 25.0 -75 35. 0 75 38.8 51. 3 o. 5 9. 4 1/1. 32 0. 01/0. 24 4o. 0 65 35. 9 54. 3 0. 5 9. 3 1/1. 51 0. 01/0. 25

1 Fraction. 2 Calculated from analysis of DAB and TTHN materials used to prepare blends.

TABLE IV Pour Mass spectral analyses, vol. percent Ratio Example Alkyl point, Number Type material chain Method of preparation F DAB TTHN B DPA Misc. DAB/TTHN DPA/Miso.

3 DAB fraction C14 Disproportionation. -40 96.3 2.0 0.7 1.0 1/0.02 001/001 4 do 01g Alkylation 70 58.8 30.7 0.5 10.0 1/0. 52 0, 01 0, 17 33nd 4 TTHN fraction-.." C15 do 50 16.2 73.4 0.5 9.9 1/4.5 0. 03/0. 51 5 DAB fraction C13 Disproporticnation. 50 76. 2 19. 3 1.1 3. 4 1/0. 25 0. 01/0. 05 5 TTHN fraction"... C11 Alkylation 1.0 89.6 0.5 3.3 1 55 03 52 4 Includes trace amounts of indanes. b Average.

A study of the data presented in the foregoing tables indicates the following:

In Example 1 compositions containing 0.26 and 0.31 part TTHN per part DAB had a pour point of R, which is 5 lower than that for 100% DAB Fraction and 10 lower than that for 100% TTHN Fraction.

and an added amount, sufiicient to lower the pour point of said dialkylbenzenes by at least 5 F., of alkyl-substituted tetrahydronaphthalenes, the total amount of said alkyl-substituted tetrahydronaphthalenes being from about 0.25 to about 1.6 parts by volume per part of said dialkylbenzenes, the added amount being from about 0.05 to about 1 part by volume per part of said dialkylbenzenes, said alkyl-substituted tetrahydronaphthalenes being represented by the formula wherein A is hydrogen or a straight-chain alkyl group containing from 1 to about 13 carbon atoms, characterized in that when both A substituents are alkyl groups the total number of carbon atoms in both of the alkyl groups is from about 6 to about 14 and wherein R and R contain from 1 to about 16 carbon atoms each, with the sum of R and R being from about 9 to about 17, said composition containing less than 0.10 part by volume of diphenylalkanes per part of said dialkylbenzenes and having a pour point of below about 50 F.

2. The composition of claim 1 wherein the alkyl-substituted tetrahydronaphthalenes are trialkyl-substituted tetrahydronaphthalenes, which are represented by the formula wherein R and R are straight chain alkyl groups containing from 1 to about 13 carbon atoms each, with the sum of R and R being from about 6 to about 14, R and R are straight chain alkyl groups containing from 1 to about 16 carbon atoms each, with the sum of R and R being from about 9 to about 17.

3. The composition of claim 2 wherein (1) it contains from about 0.30 to about 0.80 part by volume trialkylsubstituded tetrahydronaphthalenes per part of dialkylbenzenes and (2) has a pour point of at least --60 F.

4. The composition of claim 3 wherein the added amount of trialkyl-substituted tetrahydronaphthalenes is from about 0.10 to about 0.80 part per part of dialkylbenzenes.

5. The composition of claim 4 wherein the added amount of trialkyl-substituted tetrahydronaphthalenes is suflicient to lower the pour point of the dialkylbenzenes by at least 10 F.

6. The composition of claim 5 characterized further in that it has a pour point of at least 75 F.

References Cited UNITED STATES PATENTS 3,173,965 13/ 1965 Pappas et al 25259X 3,288,716 11/ 1966 Becraft et al. 252-59 FOREIGN PATENTS 510,952 8/ 1939 Great Britain 252-59 DANIEL 1E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner UNITED STATES PATENT (WHEEL CERTIFICATE OF CORRECTION Patent No. 5 59 ,759 Dated August 10 1371 Inventofls) Roy C Sias It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 6, "asynthetic" should be --a synthetic". Column 2, line 56, "wtih" should be --wjth--.

Column line 39, "abonut" should be "about".

Column l, line 72, after 130C, insert -S1'nce maximum yields of the di-n-alkylbenzenes are oh-.

Column 4, line 7'}, after 120C, insert --these temperatures are preferred. The most preferred temperature is about 80C. When this temperature f s-.

Column line 5, "8-13" should be --Cl3-. Column L3, line 553, 'ashed" should be -washod-. Column J, line 47, frnmti on" should he --fracti n-.

Tahle II, under Blend 1.5, latio DAB/TTHN, 1/0. 21 rhonld he --1/o.27--.

Column 9, line 14, "examples" should be --example--.

Signed and sealed this 31st day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTPSCHALK Attestlng Officer Commissioner of Patents