US3536461A - Hydrotreated and raw shale oils of lowered pour points with longchain esters of styrene and maleic anhydride polymers - Google Patents

Description

United States Patent O Int. Cl. C101 1/16 US. Cl. 44-62 12 Claims ABSTRACT OF THE DISCLOSURE The pour point of shale oils is reduced by the addition of novel pour point depressant compositions comprising, as the effective additive, long chain C C fatty alkanol esters of polymers of styrene and maleic anhydride. In cluded are mixtures of C C fatty alkanol esters of polymers of styrene and maleic anhydride which are particularly effective for lowering the pour point of raw shale oils. Also included is the octandecanol esters of polymers of styrene and maleic anhydride which is highly effective for lowering the pour point of hydrotreated shale oils, but is not effective for lowering the pour point of raw shale oils.

This invention relates to novel pour point depressant compositions and their use. More particularly, this invention relates to a method for lowering the pour point of shale oils by chemical additives, to novel pour point depressant compositions for shale oils and to shale oils of lowered pour point containing novel pour point depressant additives or compositions.

One of the serious problems associated with shale oils is their high natural pour points, approximately 7095 to 100 F. To aid pipeline pumpability of shale oils, it is desirable to reduce the pour point. While heat treating, such as hydrogenation-hydrocracking, of shale oil can be employed to reduce pour point, this reduction is at the expense of liquid oil yield.

Thus chemical additives which are effective to lower the pour point of shale oils are highly desirable and useful. However, many pour point depressants which heretofore have been used to control the pour point of middle distillate fuels and lubricants have been found to be either ineffective or show only slight improvement in lowering the pour point of shale oils.

It has now been found that certain long chain fatty alcohol esters of polymers of styrene and maleic anhydride are effective pour point depressants in shale oils. These esters are polymers of styrene and maleic anhydride esterified with a long chain fatty alkanol of 18 to 22 carbon atoms, preferably of 18 carbons, and mixtures of 20-22 carbons.

In raw shale oil, the C C esters from long chain fatty alcohols within the range of 20 to 22 carbon atoms or mixtures thereof, are particularly effective and preferred. However in hydrotreated shale oil, with a slightly lower pour point than raw shale oil, the C ester from octadecanol is the particularly effective pour point depressant at low concentrations and is preferred. While the higher esters C C are effective to lower the pour point of both raw and hydrotreated shale oil, the C ester is effective to lower the pour point only in shale oil which has been at least mildly hydrotreated.

These long chain fatty alcohol esters of styrene and maleic anhydride polymers are generally prepared in or added to a mineral base oil of lubricating viscosity for ease of handling and ready addition to the shale oils.

3,536,461 Patented Oct. 27, 1970 Thus the pour point depressant compositions can comprise a mineral base oil of lubricating viscosity containing the ester in substantial proportion, such as about 10% to about 50% and up to or more by weight. The mineral base oil can be solvent extracted or solvent refined oils obtained in accordance with conventional methods of solvent refining lubricating oils. Frequently, the viscosity of these mineral oils will be about 20 to 250 SUS at 210 F. However the esters can be prepared in other solvents or without solvent and the esters thus prepared without solvent can be directly added to shale oils to effect lowering of the pour point. The esters and the mineral base oil containing the esters can be incorporated into the shale oils merely by admixture or in any other conventional manner used for incorporating an additive into oils. If desired the esters and the mineral base oil containing the esters can be added to and dis solved in the shale oils at a mildly elevated temperature.

Styrene and maleic anhydride can be polymerized to form polymers for use in this invention by conventional polymerization methods. Solution polymerization methods can be employed where the monomers are polymerized in a suitable solvent using as a polymerization catalyst a free-radical catalyst, such as a peroxide, preferably benzoyl peroxide, dicumyl peroxide or an alkyl peroxy dicarbonate, at a temperature of about 75 to 300 C. or more. Suitable solvents include the aromatic hydrocarbon solvents, such as cumene, p-cymene, xylene, toluene, etc. Other suitable solvents are the ketones, such as methylethylketone. A preferred manner of carrying out the polymerization is by what is known as incremental feed addition. By this method the monomers and catalysts are first dissolved in a portion of the solvent in which the polymerization is to be conducted and the resulting solution fed in increments into a reactor containing solvent heated to reaction temperature, usually the reflux temperature of the mixture.

When an aromatic solvent is employed as the solvent for the polymeriaztion, the formation of the polymer causes a heterogeneous system, the polymer layer being the heavier layer and recoverable by merely decanting the upper aromatic solvent layer and drying. On the other hand, when a ketone is the solvent, the formed copolymer is usually soluble in the solvent media so that recovery of the product necessitates a solvent-stripping operation. The polymer contains a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 to 4:1 depending on the molar proportions of the monomers employed in the polymerization. e average molecular weight of the polymers can be about 500 to 5000, preferably 500 up to 2000, and more preferably within the range of about 500 to about 1600. The polymers containing a molar ratio of styrent to maleic anhydride of about 1:1 are most preferred.

The polymers of styrene and maleic anhydride can be esterified with the C to C long chain fatty alcohols or their mixtures in a conventional manner. These long chain fatty alcohols include octadecanol, eicosanol, docosanol and other straight chain, especially l-alkanols, of 18 to 22 carbon atoms. It is often convenient to use mixtures of these long chain fatty alkanols, such as the C to C alkanols, to produce esters of polymers of styrent and maleic anhydride useful as shale oil pour point depressants of this invention.

Usually stoichiometric amounts or an excess of the long chain fatty alkanol is employed in the esterification. The use of acidic catalysts, e.g., HCl, H p-toluene sulfonic acid, etc. increase the efficiency of the esterification. It has been found that esters having lower acid values or numbers, as given in mg. KOH/gm. sample, have significantly improved effectiveness as pour point depressants in shale oils. Esters having acid values or acid numbers of less than about 75 or even less than about 60 are desirable and those of less than about 35, based on 100% of polymer ester concentration, give maximum efficiency as pour poont depressants in shale oils, particularly with the octadecyl ester for use as a pour point depressant of hydrotreated shale oil. However, esters of higher acid number can be used, although not as effectively.

In accordance with this invention, pour points of shale oils are lowered by adding thereto a small amount, effective to lower the pour point of the shale oil, of a polymer of styrene and maleic anhydride esterified with the long chain fatty alcohol. Effective amounts of the esterified polymer to lower the pour point of shale oils are often within the range of about .01 to 2% by weight of the shale oil and preferably are within the range of about .05 to 0.5% by weight. Thus ray shale oils containing a small amount as a pour point depressant of the Cgo-Czg esters, and hydrotreated shale oils containing a small amount of the C -C esters, and preferably the C esters, have their normal pour points lowered. Raw shale oils have an API gravity generally of about 25 and often of about 15 percent N generally of about 1.5+ and often of about 4+; percent C residue generally of about 3+ and often of about viscosity at 122 F., kinematic, c.s. generally of about and often of about Hydrotreated shale oils have an API gravity generally of at least about 30 and often of at least about percent N generally of less than about 1% and often less than about 20 p.p.m.; percent C residue generally of less than about 0.05 and often less than about 0.005; viscosity at 122 F., kinematic, c.s. of generally less than about 5 and often of less than about 2.

It has also been found that esters of this invention, particularly the C20-C2g mixed esters, are excellent dspersants which do not separate from shale oil and that no pour point regeneration is apparent. Thus the pour point depression of saile oil according to this invention is substantially permanent, i.e., pour points of shale oils containing the pour point depressants of this invention do not appear to increase with time.

The following examples illustrate various embodiments of this invention and include preferred embodiments thereof.

EXAMPLE I The C -C ester of a polymer of styrene and maleic anhydride in which the mole ratio of polymerized styrene to polymerized maleic anhydride is 1:1 is prepared as follows:

Into a 2 liter 3-necked round bottom flask equipped with stirrer and Water trap, are mixed 80 gms. (0.4 mole equivalent of the styrene and maleic anhydride polymer) and 312 gms. (1.0 mole) of a mixture of C and C fatty alcohols, together with 392 gms. solvent treated lubricating mineral base oil of 155-165 sec. Sayboldt viscosity at 100 F. and 30 ml. toluene. Two grams p-toluene sulfonic acid are used to catalyze the reaction. Reflux temperature is held at 180 C. for 2.5 hours to remove 8 ml. H O, the theoretical amount for complete esterification. 'Ihe toluene is distilled from solution and the residue is allowed to cool. This preparation, a mixture of the C and C esters of the styrene and maleic anhydride polymer in the mineral oil of lubricating viscosity is used as a pour point depressant without any further purification. It contains by weight of the ester as the active pour point depressant ingredient. Its physical properties are r1 0.86, acid number 15.3, mol. Weight (osmometer) 563.

Samples for pour point determinations are prepared by adding Weighed amounts of the pour point depressant composition into known amounts of shale oil. Pour points are obtained using standard ASTM procedures.

The following tabulation shows the reduction in pour point of a raw shale oil obtained with various weight per- 4 cent of the above pour point depressant composition, i.e., the mineral base oil containing 50% by weight of the ester.

Additive concentration (Wt. percent) Pour point F.) of raw shale oil lldditive is 50 (wt) percent of active polymer ester.

EXAMPLE II The C C ester of a polymer of styrene and maleic anhydride in which the mole ratio of polymerized styrene to polymerized maleic anhydride is 1:1 and the molecular weight in 1063 (osmometry) is prepared as follows:

Into a three liter, four necked flask equipped with motor stirrer, thermometer, water trap and condenser is placed 1 moie (312 grams) of a mixture of C and C fatty alcohols, 392 grams of mineral base oil of lubricating viscosity, 2 grams toluene sulfonic acid, 30 grams of toluene and 0.4 mole gms.) of styrene and maleic anhydride polymer. The mixture is heated with stirring to 180 F. reflux and held for 2.5 hours. The water of reaction is distilled off with toluene and the remaining toluene striped off. The product is a wax slurry, a 50% by Weight mixture of the C and C esters of the styrene and maleic anhydride polymer in the mineral base oil of lubricating viscosity. This pour point depressant composition having an acid number of 15.3 and specific density 0.86 is effective in reducing the pour point of various raw shale oils as shown in the following tabulation.

Pour Point, F.

Shale O il Two raw shale oils, No. 1 and No. 2 with 7% naphtha containing 0.1 weight percent of the pour point depressant of Example II dissolved therein at elevated temperatures (160 F.) were allowed to cold soak for five hours at 40 F. After this soaking period the samples were centrifuged at 4000 r.p.m. for thirty minutes. The spun samples were separated and pour point determinations were made on both the top and bottom portions. After the spinning period none of the treated samples showed separation or sludging in the bottom of the tube, indicating complete dispersion. Similar samples of the untreated oils spun at 4000 r.p.m. for thirty minutes gave in the bottom of the tube 3.0% sludge for No. 1 shale oil and 1.5% sludge for No. 2 shale oil plus 7% naphtha. Because of the high pour point of the untreated samples,

EXAMPLE 1v Example II is repeated without the mineral base oil at a temperature of 180 F. for 2 hours and there is obtained a polymer of styrene and maleic anhydride esterified with the mixture of C and C alkanols. This ester has an acid number of 15.3 and at a 0.5 wt. percent concentration in raw shale oil lowers the pour point from the natural pour point of 85 F. to F. At the same concentration of 0.5 wt. percent in hydrotreated shale oil, the pour point of 70 F. is lowered to F.

The procedure of Example II is repeated using 0.075 mole of the styrene and maleic anhydride polymer and 0.150 mole of eicosanol in 62 grams of mineral base oil and 0.5 grams of p-toluene sulfonic acid. The reaction temperature of 120 C. is maintained for 6 hours. There is obtained the eicosanol ester of styrene and maleic anhydride polymer in mineral base oil. This pour point depressant composition has an acid number of 10.6 and at a 0.5 wt. percent concentration in raw shale oil lowers the natural pour point of 85 F. to 15 F. At the same concentration of 0.5% weight concentration in hydrotreated shale oil the pour point of 70 F. is lowered to 15 F.

The procedure of Example II is repeated using 0.15 mole of the styrene and maleic anhydride polymer and 0.3 mole of eicosanol in 133 grams of mineral base oil with no catalyst. The reaction temperature of 220 C. is maintained for 1 hour. There is obtained the eicosanol ester of styrene and maleic anhydride polymer in mineral base oil. This pour point depressant composition has an acid number of 27.2 and at a 0.5 wt. percent concentration lowers the pour point of hydrotreated shale oil from 70 F. to 35 F. but it not effective in raw shale oil.

The procedure of Example II is repeated using 0.2 mole of a styrene and maleic anhydride polymer having a 1:1 mole ratio of polymerized styrene to polymerized maleic anhydride with a molecular weight of approximately 1600. There is used 0.5 mole of the mixed C and C alcohols in 500 grams of mineral base oil with 1 gram of p-toluene sulfonic acid. The reaction temperature of 175 C. is maintained for 30 minutes. There is obtained the C C ester of the polymer in mineral base oil which has an acid number of 35.5. This pour point depressant composition at 0.5 wt. percent concentration in raw shale oil lowers its natural pour point of 85 F. to 15 F. and at the same concentration of 0.5 wt. percent in hydrotreated shale oil, it lowers the pour point of 70 F. to 15 F.

EXAMPLE V The octadecyl ester of styrene and maleic anhydride polymer is prepared as follows:

'Into a 4 necked, 3 liter fluted round bottom fiask equipped with stirrer, thermometer, water trap and nitrogen inlet is placed 270 grams (1 mole) of l-octadecanol and 350 grams of mineral base oil of lubricating viscosity (150 SUS at 100 F., 95 VI). By use of a heating mantle the l-octadecanol is melted and the solution is heated to 100 C. To this liquid is added 0.5 g. ptoluene sulfonic acid and 101 grams (0.5 moles) of a styrene and maleic anhydride polymer having a 1:1 mole ratio of polymerized styrene to polymerized maleic anhydride and an average molecular weight of about 700. The solution is blanketed with nitrogen and heated to 170 C. i5, held for 1.5 hours and allowed to cool. Five mls. of water are collected in the water trap. Infrared analysis indicates an ester with a small amount of anhydride present. Upon cooling, there is obtained a semi-solid, waxy slurry. This product, the octadecyl ester of styrene and maleic anhydride polymer in mineral base oil is used as a pour point depressant. The acid number of the approximately 50% slurry is 13.8.

The following tabulation shows the reduction in pour point of a hydrotreated shale oil obtained with this pour point depressant composition having approximately 50% by weight of the octadecyl ester of styrene and maleic anhydride in mineral base oil.

Additive concentration wt. Pour point F.) of

percent: hydrotreated shale oil None +75 0.06 +35 0.13 +35 0.25 +30 0.50 +15 1.0 +5 2.0 5

EXAMPLE VI Using the procedure of Example V, 0.5 mole of a polymer of styrene and maleic anhydride of 1:1 mole ratio and having an average molecular weight of about 1600 is esterified with 1 mole of l-octadecanol in 371 grams of mineral base oil with 2 grams of p-toluene sulfonic acid at a reaction temperature of 210 C. for 2 hours. The 50% by weight of the octadecyl ester in the mineral base oil has an acid number of 16.8. This pour point depression composition in 0.5 wt. percent concentration reduces the pour point of a severely hydrotreated shale oil from 30 F. to 5 EXAMPLE VII The use of an acidic catalyst and a solvent in the esterification improves the esterification process as shown by the lower acid number values obtained in esterifying the styrene and maleic anhydride polymer of Example V with n-octadecanol under various conditions as tabulated in preparations 1 to 4 below:

These pour point depressant compositions are used in 0.5% wt. concentration in hydrogenated shale oil having a pour point of 70 F. and the following tabulation of results is obtained showing that the esters having lower acid numbers produce greater pour point depressions:

Hydrogenated shale oil containmg 0.5 wt. percent depressant composition N0. 1 No. 2 No.3 No. 4

Pour point, F +5 0 10 55 Acid No. of ester based on concentration of polymer ester 18 28 43 It should be noted that the acid number determined on a 50% concentration of polymer ester in mineral base oil must be doubled to obtain the acid number of the polymer ester which is given on a basis of 100% concentration.

It is claimed:

1. A shale oil composition of lowered pour point comprising a hydrotreated shale oil having incorporated therein a small amount, effective to lower the pour point of said hydrotreated shale oil, of an ester of a styrene and maleic anhydride polymer and an alcohol selected from the group consisting of long chain fatty alkanols of 18 to 22 carbon atoms and mixtures thereof, said polymer prior to esterification containing a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 to 4:1 and having an average molecular weight within the range of about 500 to 5000, said hydrotreated shale oil having an API gravity of at least about 30; nitrogen content of less than about 1%; percent carbon residue of less than about 0.05; and kinematic viscosity at 122 F. of less than about 5 cs.

2. A shale oil composition of claim 1 wherein said polymer prior to esterification contains a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 and has an average molecular weight within the range of about 500 to 2000.

3. A shale oil composition of claim 1 wherein said polymer of styrene and maleic anhydride is esterified with l-octadecanol.

4. A shale oil composition of lowered pour point comprising a hydrotreated shale oil having incorporated therein a small amount, effective to lower the pour point of said hydrotreated shale oil, of an ester of a styrene and maleic anhydride polymer and l-octadecanol, said polymer prior to esterification containing a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 and having an average molecular weight Within the range of about 500 to 2000, said hydrotreated shale oil having an API gravity of at least about 30; nitrogen content of less than about 1%; percent carbon residue of less than about 0.05; and kinematic viscosity at 122 F. of less than about 5 cs.

5. A shale oil composition of claim 4 wherein said esterified polymer has an acid number of less than about 35, based on 100 of polymer ester concentration, and is about .05 to 0.5% by weight of said hydrotreated shale oil.

6. A shale oil composition of lowered pour point comprising a raw shale oil having incorporated therein a small amount, effective to lower the pour point of said raw shale oil, of an ester of a styrene and maleic anhydride polymer and an alcohol selected from the group consisting of long chain fatty alkanols of to 22 carbon atoms and mixtures thereof with the proviso that when said alkanol has 20 carbon atoms, said esterified polymer has an acid number of less than about 35, based on 100% of polymer ester concentration, said polymer prior to esterification containing a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 to 4:1 and having an average molecular weight within the range of about 500 to 5000.

7. A shale oil composition of claim 6 wherein said polymer prior to esterification contains a molar ratio of polymerized styrene to polymerized maleic anhydrided of about 1:1 and has an average molecular weight within the range of about 500 to 2000.

8. A shale oil composition of claim 6 wherein said polymer of styrene and maleic anhydride is esterified with a mixture of long chain fatty alkanols of 20 and 22 carbon atoms.

9. A shale oil composition of lowered pour point comprising a raw shale oil having incorporated therein a small amount, effective to lower the pour point of said raw shale oil, of an ester of a styrene and maleic anhydride polymer and a mixture of long chain fatty alkanols of 20 and 22 carbon atoms, said polymer prior to esterification containing a molar ratio of polymerized styrene to polymerized maleic anhydride of about 1:1 and having an average molecular weight within the range of about 500 to 2000.

10. A shale oil composition of claim 9 wherein said esterified polymer has an acid number of less than about 75, based on of polymer ester concentration, and is about .01 to 2% by weight of said raw shale oil.

11. A shale oil composition of claim 9 wherein said esterified polymer has an acid number of less than about 35, based on 100% of polymer ester concentration, and is about .05 to 0.5% by Weight of said raw shale oil.

12. A shale oil composition of claim 7 wherein said polymer of styrene and maleic anhydride is esterified with a long chain fatty alkanol of 20 carbon atoms and has an acid number of less than about 35, based on 100% of polymer ester concentration.

References Cited UNITED STATES PATENTS 4/1961 Hollyday et al. 25256 OTHER REFERENCES DANIEL E. WYMAN, Primary Examiner MRS. Y. H. SMITH, Assistant Examiner US. Cl. X.R.