US3145161A - Preparation of electrical and refrigerator oils - Google Patents

Description

United States Patent 3,145,161 PREFPARATEUN (3F ELECTRTCAL AND REEEELQEERATUR @iilLS Frank E. Anderson, Springfield, and ivor W. Mills, Glenolden, Pan, assignors to Sun Company, Philadelphia, li es, a corporation of New Jersey No Drawing. Filed Nov. 26, 11962, Ser. No. 244L146 12 (Claims. (Ci. ass-e75 This invention relates to the preparation of electrical oils and refrigerator oils having a high oxidation resistance and a high degree of inertness to Freon type refrigerants.

In the use of electrical oils such as transformer oils, cable oils, and the like it is important that the oil have a high resistance to oxidation in order to avoid the formation and accumulation of sludge-like deposits Within the equipment. In addition, in a refrigeration system using a Freon type refrigerant such as Freon-12 (dichlorodifluoromethane) it is important that the refrigerator oil be inert to the refrigerant because any reaction between the oil and refrigerant produces highly corrosive hydrochloric acid. Consequently, a method of preparing electrical oils of high oxidation stability and refrigerator oils of a high degere of inertness to Freon type refrigerants is highly desirable.

A commonly used test for determining the oxidation stability of electrical oils is known as the Doble Oxidation Test. This procedure has been described in ASTM Standards on Electrical Insulating Liquids and Gases,

pages 307-313, December 1959, under the title Suggested Method of Test for Oxidation Characteristics of Mineral Transformer Oil. It involves bubbling air through a known amount of the oil held at a temperature of 95 C. in the presence of copper and iron and making two types of tests daily on small samples of the oil. One type of test is an acidity measurement. The other is a precipitation test in which one volume of the oil is diluted with five volumes of pentane, the mixture is allowed to stand at least eight hours and the presence or absence of a sludge precipitate is noted. The end point of the Doble test is taken as the number of days of oxidation either before the acidity of the oil reaches 0.25 mg. of KOH per gram or before a positive precipitation test for sludge is obtained.

A procedure used to obtain a measure of the inertness of refrigerator oils to Freon type refrigerants is known as the Continental Oxidation Test. This procedure is described at pages 314-317 in ASTM Standr r ards on Electrical Insulating Liquids and Gases, Decemoer 1959. Results of this test are expressed in terms of hours before a given amount of oxygen absorption has occurred under certain oxidation conditions. It should be noted that while the oxidation stability per se of refrigerator oils is not overly important, since such oils are usually used in closed systems which contain no oxygen, the oxidation stability of refrigerator oils has been traditionally regarded by commercial users of such oils as a measure of the inertness of such oils to Freon type refrigerants. Oils having improved oxidation stability have traditionally been found to have improved inertness to Freon type refrigerants.

Another procedure used to determine the reactivity of refrigerator oils with Freon type refrigerants is known as the Sealed Tube Test and is described in Refrigerating Engineering, July 1952, at pages 737-742. The procedure involves placing equal volumes of the oil and refrigerant, usually Freon-l2, and a small strip each of copper and iron in a glass tube which is then evacuated, sealed, and held at 347 F. As the oil and refrigerant react, the mixture becomes progressively darker. The

ddidddihi end point of the test is taken as the number of days before the mixture becomes black.

A conventional procedure for refining oils to make electrical or refrigerator oils involves a preliminary solvent extraction such as extraction with furfural, treatment of the resulting raffinate with concentrated sulfuric acid typically in amount of 5-30 lbs./bbl. and then treatment with adsorptive clay typically in amount of 20-40 lbs./bbl. This procedure, however, often does not produce an oil having satisfactory oxidation resistance or satisfactory inertness to Freon type refrigerants. Hence a more effective treatment is needed.

A method has now been found by which electrical oils of outstanding oxidation stability and refrigerator oils of outstanding inertness to Freon type refrigerants can be prepared. The method comprises the steps of (1) treating the charge oil with concentrated sulfuric acid, (2) neutralizing the acid treated oil, (3) contacting the neutralized oil with copper, and (4) treating the acid treated, neutralized, copper contacted oil with adsorptive clay.

Before describing the invention in detail it is desirable to briefly discuss known methods of treating mineral oils. The literature and patent art abound with suggested methods for treating petroleum fractions with copper. These methods are generally directed to the removal of sulfur compounds from petroleum fractions, and the methods arose many years ago when sulfur compounds were first recognized as generally undesirable constituents of most petroleum fractions. However, when these known methods are applied to the preparation of refrigerator oils and electrical oils such as transformer oils, there is little if any improvement in the oil, either with respect to sulfur content or with respect to oxidation resistance and inertness to Freon type refrigerants. The lack of improvement in sulfur content is due to the fact that electrical and refrigerator oil charge stocks have invariably already been treated with sulfuric acid and hence contain either essentially no sulfur or an amount of sulfur which is so small that no further reduction is effected by the known copper treating procedures. The reason why known copper treating procedures fail to effect any improvement in either the oxidation resistance of electrical oils or the inertness of refrigerator oils to Freon type refrigerants is that the known procedures do not contain the precise conditions necessary to effect such improvement.

According to the present invention, electrical oils of outstanding resistance to oxidation and refrigerator oils of outstanding inertness to Freon type refrigerants are obtained by a treating procedure which comprises:

(1) Treating the charge oil with 5-30 lbs. per barrel of concentrated sulfuric acid.

(2) Neutralizing the acid treated charge oil.

(3) Contacting the acid treated, neutralized charge oil in liquid phase with 0.3-5 .0%, preferably (Hi-3.0% metallic, i.e., elemental, copper at a temperature of -5O0 E, preferably -350 E, the copper being deposited on an inert support and the contacting being by the contact technique as opposed to the percolation technique.

(4) Treating the sulfuric acid treated, neutralized, cop per contacted charge oil with 1-40 lbs. per barrel of adsorptive clay.

The charge oils of the invention are conventional electrical and refrigerator oil charge stocks. They are mineral distillate oils, usually naphthenic distillate oils obtained from Coastal crudes, and they have viscosity-gravity constants in the range of 0.84 to 6.92. which corresponds to aromatic contents generally in the range of 15-65% by weight. The viscosity, boiling range, and other physical properties of the charge oils will vary depending upon the ultimate use of the final oil product.

For example, a transformer oil charge stock will usually have an S.U.S. viscosity at 100 F. in the range of 50-65 while a refrigerator oil charge stock will usually have an S.U.S. viscosity at 100 F. in the range of 100-700. However, it is characteristic of all the charge oils of the invention that they have viscosity-gravity constants in the range of 0.84 to 0.92. In some cases the charge oil will have been subjected to a preliminary extraction with a solvent such as furfural, but this is not necessary to the operability of the invention.

As described, the charge oil is initially treated with sulfuric acid. The sulfuric acid should be concentrated, i.e., 90l00%, and should be used in the amount of 30, preferably 10, pounds of acid per barrel of oil (1 bbl.=42 gallons). Conventional sulfuric acid treating temperatures of 70200 F. are satisfactory for the present purpose. The acid treatment of the oil is conveniently carried out by adding the prescribed amount of acid to the oil in a tank equipped with an agitator. Upon adding the acid to the oil, essentialy two liquid phases result. One is an acid phase, the other is an oil phase. In addition, some sludge usually forms by reaction of the acid with the oil. After mixing for, say, 30 minutes, the agitation is stopped and the phases are allowed to separate. The acid and sludge settle to the bottom of the tank, the oil phase remains on the surface and is then separated by, for example, decanting.

It should be noted that the amount of sulfuric acid specified above, i.e., 5-30 lbs./bbl., is a relatively light acid treatment and will effect essentially no change in the viscosity'gravity constant of the charge oil. in other words, the viscosity-gravity constant of the acid treated oil is essentially the same as that of the charge oil. Similarly, the next step of the invention, i.e., neutralization, also results in essentially no change in the viscosity-gravity constant of the charge oil.

The acid treated oil is next neutralized, i.e., the acidity which is present in the oil after the sulfuric acid treatment is eliminated. Even after the sulfuric acid phase is separated from the acid treated oil, there is some acidity present in the oil which must be neutralized if the subsequent treatment with copper is to be efiective. The neutralization of the acid treated oil can be done in any convenient manner. One method is to treat the acid treated oil with an adsorptive clay. Any conventional adsorptivc clay such as fullers earth and the like can be used. Generally 5-40 lbs. clay per barrel of oil will be sutlicient to effect neutralization. Conventional clay treating temperatures of 150 to 300 F., preferably 210 to 250 F, are satisfactory for the present purpose. The clay treatment can be by the contact or percolation method. Thus the clay can be added to a tank containing the acid treated oil, the mixture agitated, and the clay then separated from the oil by filtration. Alternatively the oil can be passed through a column containing the clay.

Alternatively, the acid treated oil can be neutralized by washing with an alkaline material, caustic soda (NaOl-l) being the preferred material for economic reasons. in most cases, neutralization of the acid-treated oil can be effected by Washing the oil with 5%, by volume of the oil, of 5 Be. NaOl-l. Excess NaOl-l can then be removed by washing the oil one or more times with water. The result is an oil which is usually slightly basic but such basicity is unimportant for the present purpose. The important quality of the oil resulting from this neutralization step, and the meaning of neutralization as herein used, is that it has no acidity, as determined by pH, titration with KOH, or the like.

The acid treated, neutralized oil is next treated with copper. There are several essential conditions involved in the copper treating step and each must be observed if the beneficial results of the invention are to be obtained.

One essential feature is that the copper used as copper metal, i.e., elemental copper. Copper salts, whether they be cupric or cuprous salts, have been found to be inoperable for the present purpose.

Another essential feature is that the copper is deposited on an inert support. Merely treating the oil with copper metal alone, in conjunction with the other treatments herein specified, will not give the beneficial results of the invention. The support is described as inert because it undergoes essentially no reaction with either the oil or with the copper under the conditions of the treatment. Examples of suitable inert supports are silica gel, silica, montmorillonite, and other clays, pumice, bauxite, and the like. Silica gel is preferred.

The copper can be deposited on the inert support by any convenient method. One method is to impregnate the support with a solution of a copper salt, oxidize the copper salt to copper oxide, and then reduce the copper oxide to copper metal by heating in an atmosphere of hydrogen. For example, the support is impregnated with copper acetate and is then heated to and held at, say 700 F. in an atmosphere of air for, say, l0-20 hours. The resulting copper oxide is then held at, say, 700 F. for, say, l5 hours in an atmosphere of hydrogen. In some cases it will be desirable to repeat the deposition procedure in order to obtain the desired amount of copper on the support.

The amount of copper deposited on the support can vary over wide limits and will depend upon such factors as the surface area of the carrier, the amount of carrier which it is desired to use, and the like. Generally the amount of copper will be 1 to 300% by weight of the support.

in the treatment of the acid treated oil with the copper, it is an essential feature that the treatment be by the contact technique in contradistinction to the percolation technique. In petroleum refining these two terms,

. c.g., contact and percolation, relate to methods of treatin" a liquid with a solid and each term has a conven tional, well-known connotation. In the percolation method of treating a liquid with a solid, the liquid is pumped or otherwise caused to flow through a bed of particles of the solid. The solid is in a relatively fine state of division in order to maximize the amount of solid exposed to the liquid. in this type of treatment the solid particles remain substantially fixed in position, their only motion being that created by the inherent turbulence of the flowing liquid. An example of the percolation technique involves the use of a cylindrical column filled with particles of the solid and fitted at each end with a screen of appropriate mesh to prevent the escape of the solid particles from the column. The liquid to be treated is pumped into the bottom (or the top) of the column and is allowed to how, i.e., percolate through the bed of solid particles.

In the contact method of treating a liquid with a solid, the particles of solid are thoroughly dispersed in the liquid by some means of agitation which may be, for example, a motor driven paddle type agitator, air sparging, or the like. Usually the dispersion is carried out in a conventional mixing tank. After mixing, the solid particles are separated from the liquid. The separation is most commonly eiiccted by filtration although other methods can be employed in some cases. Thus, if the solid is substantially more dense than the liquid, the solid can be separated by settling and decantaion. From the above it is apparent that the significant difference between the contact and percolation method is that in the former some positive method of dispersing the solid in the liquid is utilized.

As described hereinbefore, the beneficial results of the invention are not obtained unless the treatment of the oil with the copper is by the contact method as opposed to the percolation method. Although the reason therefore is not definitely known, it has nevertheless been found that when the acid treated neutralized oil is precolated through a bed of copper deposited on an inert carrier,

the final oil does not have outstanding resistance to oxidation and outstanding inertness to Freon type refrigerants. The oil is substantially inferior to an oil which has been prepared in the same manner except that the copper treating step is by the contact method.

In order to determine the reason for this unusual result, several possible explanations were investigated. One explanation is that when the copper and acid treated oil are mechanically agitated in a tank, i.e., when the contact method is employed, oxidizing conditions are inherently present because of the surrounding atmosphere of air and the tendency of any mechanical agitation to inject surrounding air into the liquid being mixed. Conversely, oxidizing conditions would not be present when percolating the oil through copper in a closed column. However, this explanation is not satisfactory, for when the acid treated oil is agitated with the copper in a tank maintained in an atmosphere of nitrogen, the final oil still has the same outstanding properties. Hence, oxidizing conditions during the copper treating step are not the explanation nor are they essential to the operability of the invention.

Another possible explanation is that the percolation method of treating an oil with copper does not provide the same intimate, efficient, thorough mixing of the oil with the copper that the contact method provides. However, even when the rate at which the oil is percolated through a bed of copper is substantially reduced, in order to increase the residence time, there is little improvement in the oxidation resistance or inertness to Freon type refrigerants of the final oil. For example, when the contact method is used, a one hour residence time of copper in the oil is more than sufficient to provide an oil of out standing properties. When the percolation" method is used, a residence time as high as 4 hours results in essentially no improvement. If efficiency of mixing was the responsible factor, it would be expected that the percolation method would result in at least some significant improvement. This has not, however, been found to be the case.

As used in the appended claims with reference to treating an oil with copper, the term contact is limited to its specialized meaning as defined above and as conven tionally used in the petroleum refining art.

The amount of copper that should be used in the copper treating step is 03-50%, preferably 0.73.0%, based on the weight of the acid treated oil and not including the support on which the copper is carried.

The temperature at which the copper is contacted with the oil should be at least 100 F. and can be as high as 500 F. Preferably, however, the temperature is in the range of 150 F. to 350 F. The duration of the copper treatment will vary depending upon such factors as the temperature selected, the degree of dispersion of the copper in the oil, and the like but will generally be of the order of minutes to 3 hours.

It is another essential feature of the copper treating step that it is a liquid phase treatment. Treating the oil in the vapor phase with copper has been found inoperable for the present purpose. Consequently, for whatever temperature is selected for the copper treating step sufii cient pressure should be employed to maintain the oil in the liquid phase.

The removal of the copper from the copper treated oil can be effected in any of several ways. Where it is desired to reuse the copper, it is preferably separated by, for example, filtration prior to the clay treatment step. This is not necessary, however, for the clay treatmen step itself will remove the copper from the oil.

The acid treated, neutralized, copper contacted oil is next treated with adsorptive clay. Any conventional ad sorptive clay such as fullers earth and the like can be used. The amount of clay used should be in the range of 1 to 40 lbs. of clay per barrel of oil. Conventional clay treating temperatures of 150 to 300 F, preferably 210 to 250 F., are satisfactory for the present purpose. Unlike the copper treatment, the clay treatment can be by the contact method or the percolation method. Thus the clay can be added to a tank containing the oil, the mixture agitated, and the clay then separated from the oil by filtration. Alternatively the oil can be passed through a column containing the clay.

The following examples illustrate the invention more specifically.

EXAMPLE I A commercial silica gel was thoroughly mixed with a 9.6 percent by weight aqueous copper acetate solution in weight ratio of 55 parts solution to 44 parts gel. The wet gel was then placed in an oven and held at about 750 F. for 16 hours while purging the oven with air. Next the gel was held at about 600 F. for 1 hour while purging the oven with hydrogen. At the end of this period the gel was removed and identified as copper metal on silica gel. The gel analyzed 39 percent by weight copper metal.

EXAMPLE H The charge oil was a naphthenic distillate stock suitable for electrical transformer use. The oil initially had the following properties: A.P.l. gravity=24.4; flash point :380 E; fire point=310 F; S.U.S. viscosity at F.=55.3; S.U.S. viscosity at 210 13:33.6; viscosity' gravity constant=0.88; and sulfur content=0.2 percent.

The above oil was first extracted with furfural using only enough furfural to yield 95 percent rafilnate. The viscosity-gravity constant of the ratfinate oil was 0.87. The raflinate oil was treated at F. with 20 lbs./bbl. of 99 percent sulfuric acid. The acid-treated oil was mixed at 210 F. with 35 lbs./bbl. of fullers earth after which the clay was separated by filtration. The clay treated oil had a Doble life of 2 days and was identified as Oil A. Oil A had a sulfur content of 0.1 percent and an acidity of 0 mg. KOH per gm. of oil.

EXAMPLE Ill A portion of Oil A of Example ll was charged to a tank equipped with an agitator and maintained in an atmosphere of nitrogen. Next, 1 percent, as copper, based on weight of oil, of the copper metal on silica. gel prepared in Example I was charged to the tank. The mixture was heated to and held at F. for one hour after which the copper on silica gel was separated by filtration through a millipore filter which had a cellulose filter medium. The filtrate oil was mixed at 210 F. with 5 lbs./bbl. fullers earth, after which the clay was removed by filtration through paper. The finished oil had a Doble life of 6 days. These results show that treating an electrical oil according to the invention effects a substantial improvement in the oxidation stability of such an oil. The sui fur content of the finished oil was 0.1 percent.

EXAMPLE IV In this example the copper treating step was by the percolation technique. The percolation column was a 17 /2-inch length of glass pipe wrapped with heating tape. The column was positioned vertically and the bottom of the column fitted with a 60 mesh screen. Two inches of glass wool were packed on top of the screen. The next 13 /2 inches of the column was packed with a known amount of the copper metal on silica gel prepared in Example I. The final 2 inches of the column was packed with glass wool. A portion of Oil A prepared in Example H was heated to 175 F. and caused to flow downwardly through the column. The column temperature was maintained at 175 F. with the heating tape. The flow rate Was adjusted so that the residence time or" the oil in the bed of copper metal on silica gel was 2 hours. The oil that discharged from the bottom of the column, i.e., the efiluent oil, was collected until the amount collected was 100 times the weight of copper in the bed. The oil collected was thus treated with 1 percent copper, based on ale-5,161

7 the weight of the oil, for 2 hours. The collected oil was mixed at 210 F. with lbs./bbl. of fullers-earth after which the clay was removed by filtration through paper.

EXAMPLE V1 To another portion of Oil A obtained in Example II was added 1 percent by weight, based on the oil, of finely divided copper metal. The copper was not supported on an inert carrier. The copper metal had a particle size of 100 percent through 200 mesh Tyler Standard Screen. The oil-copper metal mixture was held at 175 EXAMPLE VII The charge oil was another oil suitable for electrical transformer use. The oil initially had the following properties: ARI. gravity:25.2; flash point=305; fire point=335; S.U;S. viscosity at 100 F.=58.4; S.U.S. viscosity at 210 F.:34.2; viscosity-gravity constant=0.90; sulfur content=0.12 percent.

The above charge oil, not solvent extracted, was acidtreated by the same procedure as in Example ii. The acid-treated oil Was neutralized by Washing with 5. percent by volume of oil, 5 es. NaCH and was then washed with 4 volumes of water per volume of oil to remove excess NaOH. The neutralized oil was identified as Oil of 0 mg. KOH/gm. or oil, and a Doble life of 3 days.

The finished oil had a Doble life of 7 days. content of the finished oil was 0.05%.

EXAMPLE X Another portion of Oil B obtained in Example V II was treated by the same procedure as in Example III except that the final clay treating step was omitted. In other words, the copper contacted oil was filtered through a rnillipore filter. The filtrate oil had a Doble life of 3 days. This result shows, in conjunction with the result of Example TX, the necessity of the final clay treating step.

EXAMPLE XI The charge oil was a napththenic distillate oil suitable for preparation of refrigerator oils. The oil had the following properties: A.P.li. gravity=19.5; flash point=330 1 pour point=- E; S.U.S. viscosity at 100 F. :167; S.U.S. viscosity at 210 F.:46; viscosity-gravity constant:0.90; sulfur content:0.3 percent.

The above charge oil was treated at 125 F. with 10 lbs/bbl. of 93% sulfuric acid. The acid treated oil was then mixed at 210 F. with 20 lbs./bbl. of fullers earth after which the clay was separated by filtration. The sulfur content and acidity of the clay treated oil were 0.07% and 0 mg. KOH/gm. of oil respectively. The clay treated oil had a Continental Oxidation life of 10 hours and a Sealed Tube life (using Freon-12 as the refrigerant) of 45 days. The clay treated oil was identified as Oil C.

The sulfur EXAMPLE XII A portion of Oil C obtained in Example XI was treated by the same procedure as in Example III. The finished oil had a Continental Oxidation life of 20 hours and a Sealed Tube life (using Freon-12 as the refrigerant) of '75 days. The sulfur content of the finished oil was 0.07 percent. These data show that treating the oil by the method of the invention substantially improves the inertness of the oil to Freon-type refrigerants.

The results of the Examples ll-XII above are summarized in Table 1 below. In order to facilitate comparison of the results, the three different charge oils used are designated as Charge Oils 1, 2, and 3.

Table I Treating Stops Results Charge Copper Example Oil Sulfuric Clay Doble Conti- Sealed Acid, Method of Treat- Lite mental Tube lbs./bbl. Neutralization Form of Method of Time ment, (Days) Life Life Copper Treatment (hrs) lbs./bbl. (Hours) (Days) It 1 20 Clay No Cooper Treatment None 2 II 1 20 Copper Metal ontact 1 5 6 on Silica Gel. IV T 1 2O 1o Percolation.-. 2 5 3 V 1 20 d0 4 5 3 VI 1 20 Copper Metal 1 5 3 (No support). VII 2 20 NaOH and Water... No Copper Treatment N one 3 VIII 2 20 do No C0 per Treatment 5 3 IX 2 20 do Copper Metal Contact 1 5 7 on Silica Gel. 2 20 .do .do .Jlc 1 None 8 3 10 No Go per Treatment 10 5 3 10 Copper Metal Contact 1 20 75 on 1Silica Ge EXAMPLE Vill A portion of Gil l3 obtained in Example Vii was mixed at 210 F. with 5 lbs./bbl. of fullers earth after which the clay was separated by filtration through paper. The filtrate oil had a Doble life of 3 days.

EXAMPLE TX Another portion of Oil B obtained in Example VII was treated by the same procedure as in Example ill.

It is apparent from the data contained in Table Ithat the oxidation resistance of electrical oils and the inertness to Freon-type refrigerants of refrigerator oils are very substantially improved by treating such oils bythe method of the invention. It is also apparent that deviations from the method will result in no such improvement.

We claim:

1. Method of preparing electrical and refrigerator oils comprising the steps of (1) treating a mineral distillate oil having a viscosity-gravity constant in the range of 0.84 to 0.92 with -30 pounds of concentrated sulfuric acid per barrel of oil, said treating being at a temperature in the range of 70-200 F., (2) neutralizing the acidtreated oil, (3) contacting the acid-treated, neutralized oil in liquid phase at a temperature in the range of 100 F. to 500 F. with 0.3-5.0 percent by Weight of copper metal based on the oil, said copper metal being deposited on an inert support, and (4) treating the acid-treated, neutralized, copper contacted oil with adsorptive clay.

2. Method according to claim 1 wherein the amount of copper metal is 0.7-3.0 percent.

3. Method according to claim 1 wherein said temperature in step (3) is in the range of 150350 F.

4. Method according to claim 1 wherein said support is silica gel.

5. Method according to claim 1 wherein said neutralization is by treating the acid-treated oil with adsorptive clay.

6. Method according to claim 1 wherein said neutralization is by treating the acid-treated oil with aqueous sodium hydroxide.

7. Method according to claim 1 wherein said adsorptive clay in step (4) is used in amount of 1-40 lbs. clay per barrel of oil.

8. Method of preparing electrical and refrigerator oils comprising the steps of (1) admixing, with agitation and at a temperature in the range of 100-500 F., a mineral distillate oil which has been treated with 5-30 lbs./bbl. of concentrated sulfuric acid at a temperature in the range of -200 R, which has been neutralized after said sulfuric acid treatment, and which has a viscosity-gravity constant in the range of 0.84 to 0.92 with copper metal, said copper metal being deposited on an inert support and the amount of said copper metal being 0.3-5.0 percent by weight based on the oil, whereby a copper-treated mineral. distillate oil is obtained; (2) treating said coppertreated mineral distillate oil with 1-40 lbs./bbl. adsorptive clay and (3) recovering an oil of improved oxidation resistance.

9. Method according to claim 8 wherein the amount of copper metal is 0.7-3.0 percent.

10. Method according to claim 8 wherein said admixing is at a temperature in the range of -350 F.

11. Method according to claim 8 in which the oil recovered in step (3) has approximately the same sulfur content as said mineral distillate oil prior to copper treat ment.

12. Method according to claim 8 wherein said support is silica gel.

References Cited in the file of this patent UNITED STATES PATENTS Colin Nov. 5, 1901 Von Fuchs et a1 Mar. 17, 1942 OTHER REFERENCES

Claims (1)

1. METHOD OF PREPARING ELECTIRCAL AND REFRIGERATOR OILS COMPRISING THE STEPS OF (1) TRATING A MINERAL DISTILLATE OIL HAVING A VISCOSITY-GRAVITY CONSTANT IN THE RANGE OF 0.84 TO 0.92 WITH 5-30 POUNDS OF CONCENTRATED SULFURIC ACID PER BARREL OF OIL, SAID TREATING BEING AT A TEMPERATURE IN THE RANGE OF 70*-200*F., (2) NEUTRALIZING THE ACIDTREATED OIL, (3) CONTACTING THE ACID-TREATED, NEUTRALIZED OIL IN LIQUID PHASE AT A TEMPERATURE IN THE RANGE OF 100* F. TO 500*F. WITH 0.3-5.0 PERCENT BY WEIGHT OF COPPER METAL BASED ON THE OIL, SAID COPPER METAL BEING DEPOSITED ON AN INERT SUPPORT, AND (4) TREATING THE ACID-TREATED, NEUTRALIZED, COPPER CONTACTED OIL WITH ADSORPTIVE CLAY.