US3846092A - Crude oils and fuel oils of improved pour point depressant and flowability properties - Google Patents

Abstract

1. PETROLEUM CRUDE OIL AND FUEL OIL COMPOSITIONS HAVING IMPROVED POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURES, COMPRISING A PETROLEUM OIL OF THE GROUP CONSISTING OF A CRUDE OIL AND A FUEL OIL NORMALLY HAVING UNDESIRABLE POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURE, AND FROM ABOUT 0.001% TO ABOUT 5% OF A HYDROLYZED COPOLYMER OF ETHYLENE AND A VINYL ESTER OF A LOWER ALKYL FATTY ACID HAVING UP TO FIVE CARBON ATOMS, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 500 TO ABOUT 30,000, AND CONTAINING ABOUT 10-90% ETHYLENE AND ABOUT 90-10% OF SAID VINYL ESTER, SAID COPOLYMER BEING HYDROLYZED TO THE EXTEND OFF HYDROLYZING FROM ABOUT 10% TO ABOUT 90% OF THE ESTER UNITS OF SAID COPOLYMER.

Description

United States Patent 3,846,092 CRUDE OILS AND FUEL OILS OF IMPROVED POUR POINT DEPRESSANT AND FLOWABILITY PROPERTIES Peter G. Pappas, Downers Grove, Walter C. Edmisten, Olympia Fields, and Hobe Schroeder von Levern, Downers Grove, Ill., assiguors to Standard Oil Company, Chicago, Ill. No Drawing. Filed Mar. 21, 1973, Ser. No. 343,286

Int. Cl. C101 1/16 U.S. Cl. 44-62 8 Claims ABSTRACT OF THE DISCLOSURE Hydrocarbon fuel oils having improved pour and flowability characteristics at temperatures at which such characteristics of such fuel oils are adversely affected, are obtained by incorporating in such hydrocarbon fuel oils small amounts, i.e., from about 0.001% to about preferably from about 0.0025% to about 1.0%, of a A BACKGROUND OF THE INVENTION In the storage, transportation and use of hydrocarbon fuel oils, problems associated with the pour point of such fuels have been long recognized. The pour point of an oil is defined as the lowest temperature at which the oil will flow when chilled without disturbance under specified conditions. Pour point problems arise through the formation of solid or semi-solid waxy particles in the fuel oil, e.g., distillate fuel oils, such as heating oils, diesel oils, turbo-jet fuels and the like, when such fuel oils are subjected to low temperatures in storage. A related problem also exists in respect of hydrocarbon resid fuel oils and waxy crude oils, in which the waxy components of such oils adversely affect the flowability and/or pumpability of the oil under low temperature conditions.

The formation of such solid or semi-solid waxy particles in fuel oils and in waxy crude oils at temperatures just below their pour point causes serious distribution and/or operating difficulties. For example, the distribution of such oils by pumping is rendered difiicult or impossible at temperatures below the pour point of the oil; also, the flow of the oil at such temperatures through filters in heating systems cannot be maintained, resulting in the failure of the equipment to function. The formation of solid or semi-solid Waxy particles in wax-containing crude oils gives rise to difficulties in the movement of such crude oils through pipelines at low ambient temperatures.

In respect of fuel oils, the aforementioned problems have been in part remedied by lowering the end points of oils used for blending heating and diesel oils. It has also been suggested that the fuel oils, particularly distillate fuel oils, may be dewaxed such as by urea dewaxing. However, readjustment of end points causes a loss of valuable product as blending material for fuel oil stocks; also, dewaxing operations are costly.

Another approach in overcoming the problem has been to attempt to find a pour point depressant which will lower the pour point of the fuel oil or crude oil as is known to be done in lowering the pour point of lubricating oils. However, materials which are effective in lowering the pour point of lubricating oils are ineffective as pour point depressants for fuel oils or crude oils.

Recently, certain products have been made which provide pour point depressant properties in certain fuel oils, particularly the distillate fuel oils. However, while such pour point depressant additives may be effective in socalled distillate fuel oils, they generally are not sufficiently effective in resid fuel oils or in waxy crude oils. U.S. Pat. 3,048,479 issued Aug. 7, 1962 to S. Ilnyckyj et al., discloses copolymers of ethylene and vinyl acetate as pour point depressants for middle distillates; however, such copolymers are not sufiiciently effective in resid fuel oils or in crude oils. Other patents in the field of such copolymers are illustrated by U.S. 2,499,723; U.S. 2,654,188; U.S. 3,093,723; U.S. 3,126,364; U.S. 3,236,612 and others.

The state of the art is further illustrated by the following patents: U.S. 3,447,915 issued to B. Otto, June 3, 1969, teaches the use of terpolymers of ethylene, propylene and an alkyl ester of acrylic acid or methacrylic acid as pour point depressors in fuel oils. The pour point depressants and flow improvers disclosed in U.S. 3,467,597, issued to N. Tunkel et al., Sept. 16, 1969, are terpolymers of ethylene, vinyl esters, e.g. vinyl acetate, and a monoolefinically unsaturated polymerizable compound grafted with ethylene. U.S. Pat. 3,679,380 issued July 25, 1972 to C. Biswell et al. discloses middle distillate fuel compositions containing a copolymer of ethylene, propylene and 1,4-hexadiene as pour point depressants. To facilitate the movement of waxy crude oil through pipelines, U.S. Pat. 3,675,671 issued July 11, 1972 to W. Sweeny et al., discloses such crude oils with a low pour crude oil and a copolymer of ethylene and a vinyl fatty acid ester, such as vinyl acetate.

We have found that by the hydrolysis of copolymers of ethylene and a vinyl ester of fatty acids of up to 5- carbon atoms, the products obtained are effective pour point depressants for hydrocarbon distillate and resid fuel oils, and are also effective in improving the flowability and pumpability of such fuel oils as well as wax-containing crude oils. The hydrolysis, by alcoholysis or by saponification, of copolymers of ethylene and vinyl esters is disclosed in such prior art as U.S. Pats. 3,344,129; 3,386,978; 3,560,318; 3,560,461; 3,562,234, and others. Such art neither teaches nor suggests the use of such products as pour point depressants or flow improvers in hydrocarbon fuel oils and/ or waxy petroleum crude oils.

SUMMARY OF THE INVENTION In accordance with the present invention, additives for fuel oils and crude oils which are effective in lowering the pour point and in improving the flowability and/ or pumpability of such oils at low temperatures, i.e., at temperatures at or below which the waxy components thereof start to become semi-solid or solid, are obtained by hydrolyzing copolymers of ethylene and a vinyl ester of an alkyl fatty acid having up to about five carbon atoms, which copolymers have an average molecular Weight of from about 500 to about 30,000, preferably from about 700 to about 10,000, and contain from about 10% to about preferably from about 25% to about 40% vinyl ester units. The hydrolysis of such copolymers is conducted under conditions which will effect the hydrolysis of from about 10% to about 90%, preferably from about 40% to about 70% of the vinyl ester units of the copolymer.

Preparation of the copolymer Methods of preparing the starting copolymer of ethylene and the vinyl ester, e.g., the vinyl acetate, are well known in the art. Such copolymers can be produced by the copolymerization of ethylene with the vinyl ester under pressure at elevated temperatures, i.e. from about 280 F. to about 350 F. in the presence of a free radical catalyst, such as a peroxy compound. Processes for the preparation of such copolymers are described in US. Pats. 2,396,785 and 3,048,479.

In US. Pat. 3,048,479, ethylene vinyl acetate polymers are prepared in a benzene solution using di-tertiary-butylperoxide, as the catalyst, at a temperature of 280-340 F and at a pressure of 7002,000 pounds. After purging the reactor with nitrogen and ethylene, the vinyl acetate, solvent and catalyst are introduced into the reactor, the sufficient ethylene charged to the reactor to yield the desired pressure at the reaction temperature. Additional ethylene is added during the polymerization to maintain the desired pressure in the reactor. The polymerization is considered complete, when a pressure drop of less than 50 p.s.i.g. per hour is observed, The product is then stripped free under vacuum of solids and unreacted vinyl acetate.

Preparation of hydrolyzed copolymer The said copolymers may be hydrolyzed by alcoholysis or by saponification. Such methods are well known in the art, as exemplified by U.S. lPats. Nos. 3,344,129; 3,386,978; 3,560,318; 3,560,461; 3,562,234 and others. Illustrative of a method of hydrolyzing the ethylene-vinyl ester copolymer is the following: The hydrolysis of the copolymer is carried out under anhydrous conditions by heating the copolymer, preferably diluted to about 2060%, in an inert diluent or solvent, such as for example, kerosene, naphtha, etc., or an aromatic hydrocarbon solvent, e.g. toluene, to reflux temperature while purging with dry nitrogen or other inert gas, then cooling down to a temperature of from about 120 C. to about 50 C., preferably 70 C., while continuing blowing with the inert gas, such as nitrogen. From about 0.23 to about 1 mole, based on the copolymer, of an anhydrus lower alkanol, e.g. methanol, ethanol, are added, and the reaction temperature raised to reflux temperature. At this point there is rapidly added as the catalyst from about 0.005 to about 0.1 mole of sodium methoxide or sodium ethoxide (depending upon the alkanol employed). The catalyst can be used in solutions of from about 0.1 N to about 10 N, preferably about 1 N. After the catalyst has been added the reaction mixture temperature is raised to reflux temperature, and maintained at such temperature for about 0.1-3 hours, preferably about 1 hour, while stirring the reaction mass. At

the end of the reaction period the reaction is quenched by adding to the reactor from about 0.005 to about 0.1 mole of the lower alkyl fatty acid corresponding to the vinyl ester, e.g. acetic acid when the vinyl ester is vinyl acetate, and the reaction mass stirred for about 5-10 minutes. The quenched reaction mixture is then heated to a temperature of about 120 C.150 C. to strip off volatiles, such as alkanol, alkyl ester of the lower fatty acid, and diluent or solvent light ends.

The hydrolyzed copolymers of the present invention are effective in petroleum distillate and residual fuel oils, and in petroleum crude oils. The fuel oil, such as for example, heavy industrial residual fuels, e.g. Bunker C fuel, and crude oils. The fuel oil may be virgin or cracked petroleum stock, or mixtures thereof, boiling in the range of from about 200 F. to about 750 F., and preferably in the range of about 350 F. to 750 F. The fuel oil may contain other additives such as, for example, rust inhibitors, corrosion inhibitors, antitoxidants, detergents etc.

The additives of the present invention are used in the fuel oils and crude oils in amounts of from about 0.001% to about 5%, preferably from about 0.0025% to about 1.0%. The additives, may for convenience, be prepared as addition agent concentrates. Accordingly, the hydrolyzed copolymer may be dissolved in a suitable organic solvent therefor in amounts greater than 5% and preferably about 2575%. The solvent in such concentrate preferably has a distillation range of from about F. to about 700 F. The organic solvents are hydrocarbon solvents, for example, petroleum fractions such as naphtha, kerosene, heater oil, and the like; aromatic hydrocarbons such as benzene, xylene, and toluene, or paraffinic hydrocarbons such as hexane, pentane, etc. The solvents employed should, of course, be selected with regard to possible beneficial or adverse effects it may have on the final fuel oil composition. Thus, the solvent used should preferably burn without leaving an objectionable residue, and should be noncorrosive with regard to metals.

PREFERRED EMBODIMENT OF THE INVENTION The examples given below are illustrative of the preferred embodiment of the present invention. In each of the described examples, the ethylene-vinyl acetate copolymer hydrolyzed by alcoholysis or by saponification was a copolymer having an average molecular weight of about 2,400, and containing about 32% vinyl acetate units.

The hydrolysis of the ethylene-vinyl acetate copolymer is illustrated by the following examples:

EXAMPLE 1 Ethanol-Sodium Ethoxide Method 3,180 grams of 52% ethylene-vinyl acetate copolymer solution in kerosene was heated to C. and purged with nitrogen. The solution was then cooled to 78 C., nitrogen purging discontinued, and the cooled solution treated with 1,600 grams of absolute ethanol. The reaction mixture was heated to reflux temperature, ml. of a 1.0 N. sodium ethoxide in ethanol added and the reaction mixture maintained at reflux temperature for one hour. The reaction mass was then quenched with 10 ml. of glacial acetic acid, and the mixture then stripped to 120 C. The recovered product as 61% hydrolyzed, that is 61% of the ester units of the ethylene-vinyl acetate copolymer were hydrolyzed. The degree of hydrolysis was measured by gas chromatography (GC), which measures the amount of ethyl acetate formed as byproduct.

EXAMPLE II Ethanol-Sodium Methoxide Method 500 grams of a 60% ethylene-vinyl acetate copolymer solution in kerosene was heated to 120 C. and purged with nitrogen to remove any moisture present. The solution was then cooled to 70 C., nitrogen purging stopped, and the cooled solution treated with 55 grams of ethanol (denatured with benzene) and the mixture heated to reflux temperature, i.e. about 82 C. The mixture at reflux temperature was then treated with 7.9 ml. of 4.55 N sodium methoxide in ethanol, and the reaction mixture maintained at reflux temperature for one hour. The re action was then quenched with 2 ml. of glacial acetic acid, and stripped of volatiles at 120 C. Gas chromatography analysis showed the recovered product to be 57% hydrolyzed.

EXAMPLE III Methanol-Sodium Methoxide Method 100 grams of a 52% ethylene-vinyl acetate copolymer solution in kerosene was heated to 120 C. in a pressure reactor flask while purging with nitrogen to remove any moisture. The solution was then cooled to 60 0., treated with 10 grams of methanol and heated to 100 C.; the pressure in the reactor reaching about 45 p.s.i. 7.5 ml. of sodium methoxide (1 N) was injected into the reaction mixture, and the mixture maintained at 100 C. for one hour. The reaction was then quenched with 2 ml. of glacial acetic acid, cooled to room temperature, the pressure-released, and the volatiles stripped off by heating to 120 C. The recovered product was 80% hydrolyzed.

" Saponification Method 300 grams of a 60% ethylene-vinyl acetate copolymer solution in kerosene was heated to 100 C. The solution was then treated with 11 grams of sodium hydroxide dissolved in 30 ml. water, and the mixture maintained at reflux temperature (108-110 C.) for three hours. The heated reaction mixture was then treated with 8 'ml. 12 N HCl. The resultant acidic solution was heated to 150 C. to distill off the water present in the product. The recovered product was 38% hydrolyzed.

EXAMPLE V Ethanol-Sodium Hydroxide Method 500 grams of a 60% ethylene-vinyl acetate copolymer solution in kerosene and 50 grams of ethanol were heated to reflux temperature. To the refluxing solution was added 50 ml. of 1 N NaOH and the mixture maintained at reflux temperature for four hours. The solution was then treated with ml. of 12 N HCl, and stripped of volatiles at 150 C. The removed product was 11% hydrolyzed.

The effectiveness of the hydrolyzed ethylene-vinyl acetate copolymer in improving the pour and flowability or pumpability characteristics of fuel oils and of crude oils is demonstrated by the data in the following tables.

The effectiveness as pour depressors of the hydrolyzed ethylene-vinyl acetate copolymer with varying degrees of hydrolysis, in concentrations of 0.1%, in different resid fuel oils is demonstrated by the data in Table I.

TABLE I Degree of Pour point, F. hydrolysis, Sample number percent Resid. A Resid. B Resid. C

The effectiveness of the hydrolyzed ethylene-vinyl acetate copolymer with varying degrees of hydrolysis, in concentrations of 0.1%, as flowability or pumpability improvers in resid fuel oils is demonstrated by the data in Table II. These data were obtained by the method of the Institute of Petroleum identified as IP 230 titled Pumpability Test for Industrial Fuel Oils. Briefly, in this test a sample of the fuel oil, preheated if necessary, to a temperature not exceeding 180 F. to make it fluid, is poured into the cup of a Ferranti portable viscometer. This is immersed in a bath at 180 F. for 20 minutes, and then transferred to a bath at a predetermined temperature. After 15 minutes the viscometer is started at a rate of shear of 9.7 sec.- After a further 5 minutes the bath is cooled at 1 F./min. The temperature at which apparent viscosities of 6 poise and 25 poise are obtained are determined. This test gives the minimum storage and handling temperatures which would ensure that the oil is usable in normal oil-fired installations.

TABLE II Resid. A, Resid. B, Degree of temperature, F. temperature, F. hydrolysis, Sample number percent 6 poise 25 poise 6 poise 25 poise The effectiveness of the hydrolyzed ethylene-vinyl acetate copolymer as pour point depressors in crude oils is shown by the data in the following Table III.

TABLE III Pour point, F., crude oil Concena Hydrolysis, tration, Brut Brut Sample number percent percent Arzew Nigerian Control +16 -10 1 0.1 52 60 0 0.1 +16 -10 Percentages given herein and in the appended claims are weight percentages unless otherwise stated.

Although the present invention has been described with reference to certain specific preferred embodiments thereof, the invention is not limited thereto, but includes withinits scope such modifications and variations as some within the scope and spirit of the appended claims.

We claim:

1. Petroleum crude oil and fuel oil compositions having improved pour and flowability characteristics at low temperatures, comprising a petroleum oil of the group consisting of a crude oil and a fuel oil normally having undesirable pour and flowability characteristics at low temperatures, and from about 0.001% to about 5% of a hydrolyzed copolymer of ethylene and a vinyl ester of a lower alkyl fatty acid having up to about five carbon atoms, said copolymer having an average molecular weight of from about 500 to about 30,000, and containing about 1090% ethylene and about l0% of said vinyl ester, said copolymer being hydrolyzed to the extent of hydrolyzing from about 10% to about 90% of the ester units of said copolymer.

2. Petroleum crude oil and fuel oil compositions as described in Claim 1, wherein the vinyl ester is vinyl acetate.

3. Petroleum crude oil and fuel oil compositions as described in Claim 1, wherein the fuel oil is a residual fuel oil.

4. A petroleum fuel oil composition having improved pour and flowability characteristics, at low temperatures, comprising a major proportion of a petroleum fuel oil normally having undesirable pour and flowability characteristics at low temperatures and from about 0.0025 to about 1.0% of a hydrolyzed copolymer of ethylene and vinyl acetate, said copolymer having an average molecular weight of from about 700 to about 10,000, and containing about 6075% ethylene and about 40-25% vinyl acetate, said copolymer being hydrolyzed to the extent of hydrolyzing from about 30% to about 70% of the acetate units of said copolymer.

5. A fuel oil composition as described in Claim 4, wherein the petroleum fuel oil is a residual fuel oil.

6. A fuel oil composition as described in Claim 4, wherein the petroleum fuel oil is a distillate fuel oil.

7. A petroleum crude oil composition, comprising a major proportion of a waxy petroleum crude oil normally having undesirable flowability characteristics at low temperature, and from about 0.0025% to about 1.0% of a hydrolyzed copolymer of ethylene and vinyl acetate, said copolymer having an average molecular weight of from about 700 to about 10,000, and containing about 6075% ethylene and about 4025% vinyl acetate, said copolymer being hydrolyzed to the extent of hydrolyzing from about 30 %to about 70% of the acetate units of said copolymer.

8. A concentrate composition for addition to petroleum crude oils and petroleum fuel oils to improve the pour and flowability of such oils at low temperatures, said concentrate comprising essentially a hydrocarbon solvent boiling at a temperature in the range of from about F. to about 700 F., and more than 5% of the hydrolyzed copolymer defined in Claim 1, said concentrate being capable of dilution with petroleum crude oils and with petroleum fuel oils, normally having undersirable pour 7 8 and flowabiity characteristics at low temperatures, to pro- 3,560,461 2/ 1971 Y'onezu' et a1. 26087.3 duce crude oil and fuel oil compositions containing from 3,567,639 3/1971 Aaron et a1. 4462 about 0.001% to about 5% of said hydrolyzed co- 3,776,247 3 C f r 'et a1. 4462 1 v 1 p0 ymer References Cited 5 PATRICK P. GARVIN, Primary Examiner i UNITED STATES PATENTS Y. H. SMITH, Assistant Examiner 3,344,129 9/1967 Bestian et a1 260-873 CL "fwd 3,386,978 6/1968 Salyer 26087.3 44 70

Claims (1)

1. PETROLEUM CRUDE OIL AND FUEL OIL COMPOSITIONS HAVING IMPROVED POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURES, COMPRISING A PETROLEUM OIL OF THE GROUP CONSISTING OF A CRUDE OIL AND A FUEL OIL NORMALLY HAVING UNDESIRABLE POUR AND FLOWABILITY CHARACTERISTICS AT LOW TEMPERATURE, AND FROM ABOUT 0.001% TO ABOUT 5% OF A HYDROLYZED COPOLYMER OF ETHYLENE AND A VINYL ESTER OF A LOWER ALKYL FATTY ACID HAVING UP TO FIVE CARBON ATOMS, SAID COPOLYMER HAVING AN AVERAGE MOLECULAR WEIGHT OF FROM ABOUT 500 TO ABOUT 30,000, AND CONTAINING ABOUT 10-90% ETHYLENE AND ABOUT 90-10% OF SAID VINYL ESTER, SAID COPOLYMER BEING HYDROLYZED TO THE EXTEND OFF HYDROLYZING FROM ABOUT 10% TO ABOUT 90% OF THE ESTER UNITS OF SAID COPOLYMER.