US2789081A - Refining mineral oil with molten caustic and adsorbent - Google Patents

Description

April 16, 1957 l. W. MILLS REFINING MINERAL OIL WITH MOLTEN CAUSTIC AND ADSORBENT Crude Nuphthenic Petroleum Gus Oil and Lighter t/m Topping Still Fig. 2

Crude T p e 3 Filed June 2, 1954 Fig Lubricating Oils . l8 l9 Distillation Adsorbem Zone 9 ll FIG 2 Residue Finished Henvy Lubricantuooo- 12,000 BBL/Ton of Adsorbent) ,2? l7 Lubricating Oils, Etc.

l8 Oondensote Containing 26 l-200 PPM of Sodium 24" 29 ;& L Alkali 22 7 .A|kcn so INVENTOR. IVOR W. MILLS IG l I Residue ATTO NEY nited Stats atent 1 REFINING MINERAL OIL WITH MOLTEN CAUSTIC AND ADSORBENT Ivor W. Mills, Glenolden, Pa., assiguor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application June 2, 1954, Serial No. 433,945

5 Claims. (Cl. 196-36) This invention relates to the refining of mineral oil, and more particularly to the improving of certain products obtained in the vapor phase treatment of mineral oil with caustic alkali.

It is known in the art to refine mineral oil, for example lubricating oil, by vaporizing the oil and contacting the vapors with a caustic alkali, for example aqueous caustic soda or potash, molten anhydrous sodium or potassium hydroxide, etc. Such treatment has been employed for example in the refining of naphthenic mineral oils in order to remove naphthenic acids by reaction with sodium hydroxide to form sodium naphthenates in the alkaline treating agent; such sodium naphthenates can be recovered by known methods from the alkaline treating agent to obtain a valuable article of commerce. The mineral oil vapors, after contact with caustic alkali, are generally subjected then to fractionation by known means to obtain various lubricating oil condensates of varying boiling range. These lubricating oils are useful in various applications, and the heaviest of these lubricating oils have ntunerous applications, for example in greases, as electrical oils, gear lubricants, etc.

As previously practiced the vapor phase treatment with caustic alkali has commonly been accomplished in a distillation tower containing a caustic treating section and a fractionating section thereabove. In prior art operation the vapors pass from the uppermost tray or bubble plate in the caustic treating section upwardly into the fractionation section, and means may be provided to avoid entrainment of alkaline material from the caustic treating section. In order to avoid such entrainment a fractionating tray or trays maybe provided between the uppermost tray of the caustic treating section and the tray from which the heaviest lubricant product is removed; alternatively, or in addition, a metal screen of known type may be employed in the tower between the caustic treating section and the fractionation section.

In spite of these precautions, it is not infrequently found that the heaviest lubricant product obtained fromthe fractionation section has unsatisfactory quality from various standpoints, for example poor electrical resistivity. It has been found that such poor properties are attributable to the fact that very small amounts of sodium hydroxide or other alkali-metal containing materials become incorporated in the heaviest lubricant product, having been carried to the fractionation section by entrainment in spite of the precautions taken. It may also be found in some instances that more than one of the heavy lubricant products contains some small amounts of alkali metal compounds; however, it is most frequently the heaviest lubricant product which is thus affected.

The problem of entrainment, and the consequent problem of alkali metal content in the heavy lubricants isv a particularly diflicult one, in view of the various means which have been employed to avoid entrainment, without success in completely avoiding the presence of alkali metal in the heaviest lubricants. Various means which have been employed to avoid entrainment have probably been regarded heretofore as providing substantially com plete prevention of entrainment. However, the presence of small amounts of alkali metal, producing deleterious effects in the heaviest lubricants, indicates that the removal has not been complete by prior art methods.

According to the present invention, heavy lubricants produced by a vapor phase refining with caustic alkali are produced in a manner such that the alkali metal content of the lubricant is well within the limits required for most or all of the uses of such lubricants. Thus the present invention enables the obtaining of an alkali metal content which is satisfactory when the lubricant is used as an electrical oil, the standards being quite strict for such oils since the resistivity of the oil is adversely aiiected by the presence or" alkali metal in the oil.

The treatment according to the invention involves, in one embodiment, the contacting of a heavy lubricant obtained in a vapor phase refining process, which lubricant contains 1 to 200 parts per million of alkali metal in the form of alkali metal compounds, with bauxite under conditions as subsequently specified. It has been found that such contacting is capable of reducing the alkali metal content to a very low level in an operation which provides a very high yield of finished lubricant oil per unit amount of bauxite employed.

The invention will be further described with reference to the attached drawing. Figure 1 illustrates the principal steps involved in a typical embodiment of the process of the invention. Figure 2 illustrates in more detail the steps involving the vapor phase treatment of oil with alkali and fractionation of the treated oil.

Referring to Figure l, a crude naphthenic petroleum is introduced through line 13 into a topping still 10 wherein the gas oil and lighter fractions are distilled from the crude and removed as indicated schematically by line 14. Topped crude is removed from the still through line 15 and introduced into the vapor phase alkali treating zone 11, into which alkali is introduced through line 29, and from which lubricating oil distillates and residue are removed respectively through lines 17 and 16. A heavy lubricating oil fraction, boiling higher than the oils removed as indicated at line 17, is removed through line 13 and introduced into adsorbent treating Zone 12, wherein it is contacted with bauxite in order to remove the small amounts of alkali metal which became incorporated in the heavy lubricant during the treatment in zone ii. The heavy lubricant obtained by the bauxite treatment is removed through line 19. As indicated in the drawing the yields of heavy lubricant obtained are within the range from 1000 to 12,000 barrels of oil per ton of bauxite.

Referring now to Figure 2, the vapor phase alkali treating zone is illustrated in more detail as a distillation tower containing a flash zone 31, an alkali treating zone comprising the trays 20, 21 and 22, an intermediate zone comprising the trays 23 and 25 and the screen 24, and a fractionation section comprisingthe trays 26, 27 and 2S.

Preheated topped crude is introduced through line 15,

30. The vapors rising through the caustic treating section 3 come in contact with the alkali on the trays, and the refining action of the latter takes place. A portion of the alkali removed through line 30 may be subsequently treated by methods known in the art for removal of sodium naphthenates, etc., and a portion of the. alkali removed may be recycled to the caustic treating section through line 29.

The vapors rising above tray 22 pass through tray 23, on which the liquid is primarily oil, and then passes through the screen 24, which may be any suitable type of screen, or demistcr, as known in the art, for minimizing entrainment in distillation towers. The vapors then pass through tray 25, on which the liquid is primarily oil, and then through tray 26 from which the heaviest lubricant product from the fractionation section is removed through line 18.

The lubricant removed through line 18 contains 1 to 200 p. p. m; of sodium which has become incorporated in the lubricant because of entrainment of sodium-containing materials by the oil vapors as they pass from the caustic treating section into the fractionation section. The various sodium-containing materials in the heavy lubricant may include sodium naphthenate, sodium hydroxide, sodium carbonate, etc. The lighter vapors pass upwardly from tray 26 to the other trays of the fractionation section, which may be any suitable number, and as shown in the drawing include trays 27 and 28. From these various additional trays of the fractionation section the lighter lubricating oils are removed through line 17.

The heavy lubricant removed through line 18 is treated, as described in connection with Figure 1, with bauxite in order to remove nearly all of the sodium contained therein.

The following examples illustrate the process of the invention.

7 Example I A process according to the general scheme indicated in Figures 1 and 2 was carried out under the following conditions. T .e bauxite which was employed was a lowiron bauxite containing 75 to 82% alumina, 10 to 14% silica, 2.5 to 3.5% ferric oxide and 3.5 to 4.5% titanium oxide; the bauxite, according to manufacturers specifications, contained 2.9% free moisture (determined by heating to 220 F. for 2 hours) and had an ignition loss after 2 hours at 1800 F. of 5.2%. This bauxite was employed in a bed which was preheated above 220 F. to remove free moisture. A heavy lubricant condensate obtained as indicated in Figure 2 of the drawing was then percolated through the bed in a continuous process running for 15 days. The bauxite employed consisted mainly of particles from 10 to mesh. The sodium content, as determined in the Bcckman flame photometer, of the lubricant prior to treatment with bauxite varied from 16 to 108 p. p. m. during the 15 day period, and the average sodium content was about 55 p. p. m. About 85% of the sodium was present in the form of sodium naphthenate, and 12% as sodium hydroxide, the remainder probably being sodium carbonate. The space rate in the percolation was about 2 volumes of oil per volume of bauxite per hour. The average temperature of the oil upon introduction into the bed was about 480 F. After about 10 days, during which 2500barrels of oil per ton of bauxite had been passed through the bauxite, the sodium content of the bauxite-treated oil was 5 p. p. m., indicating a highly satisfactory removal of sodium from the oil.

Example 11 In an operation generally similar to that described in Example I, a bed of bauxite was employed for a two month period, during which time the sodium content of the heavy lubricant prior to the bauxite treatment was in the neighborhood of 10 p. p. m. throughout the period. The sodium content of the treated oil was approximately 4 l p. p. in. during the two months period, and the yield of oil obtained was in the neighborhood of 10,000 barrels per ton of bauxite.

The treatment according to the invention generally involves only slight, if any, decolorizing of the mineral oil treated, and the adsorbent is generally used for considerably longer periods of time and for treatment of considerably greater amounts of mineral oil than are possible when a decolorizing action is effected. Thus for example in a treatment with bauxite at 550 F., after treatment of 3500 barrels of oil per ton of bauxite, the color of the product was not improved over the color of the charge to the bauxite treatment and was instead very slightly poorer than the initial color.

The temperature of the treatment according to the invention can vary. The temperature should be high enough to obtain a suitabie fluidity of the mineral oil and efiectiyeness of the bauxite, but should not be so high as to cause any substantial cracking of the oil. Temperatures within the approximate range from 350 F. to.600 'F. are generally suitable; preferred temperatures are those in the range from 450 F. to 550 F. Preferred space rates are those in the range from 0.1 to 5 volumes of oil per volume of adsorbent per hour.

A preferred manner of effecting the adsorbent treatment according to the invention is to percolate the liquid mineral oil through a stationary bed of adsorbent particles. in such operation the particle size of the adsorbent should not be so small as to cause a disadvantageously high pressure drop during passage of the oil through the bed. Generally it is preferred that a major proportion of the particles in the bed should be between 10 to 60 mesh in size.

A bauxite containing less than about 10 percent by weight ferric oxide can be advantageously used according to the invention, but bauxite containing greater amounts of ferric oxide, e. g. 14 percent or more, can also be used with entirely satisfactory results.

The bauxite adsorbent, after use in removing alkali metal compounds from oil, can be regenerated for further such use by contact with a acidic regenerating agent, e. g. dilute mineral acid such as hydrochloric acid, sulfuric acid, etc. However the life obtainable without regeneration is quite long, as previously pointed out, and it may be unnecessary or undesirable to regenerate the adsorbent.

The oil treated according to the invention should contain 1 to 200 p. p. m. of alkali metal prior to the adsorbent treatment. Oils containing less than 1 p. p. m. of alkali metal generally do not require any further treatment for removal of alkali metal. Oils containing more than 200 p. p. m. of alkali metal, on the other hand, tend to deactivate the adsorbent too rapidly for satisfactory operation. Therefore the vapor phase alkali treatment prior to the adsorbent treatment should be carried out in such a way as to produce a heavy condensate containing less than 200 p. p. m. alkali metal initially. V

In place of bauxite, activated alumina can be used as adsorbent according to the invention; however, activated alumina has a considerably shorter life than bauxite, since it is more readily deactivated during the treatment.

The treatment according to the invention may'advantageously be applied to oils having S. U. viscosity at 210 F. within the approximate range from 75 to 200 seconds, and preferably from to seconds.

The treatment according to the invention may advantageously be used in cases where the oil is subsequently treated with a catalyst which is subject to poisoning by alkali metal compounds, as in the case of a catalyst comprising molybedenum sulfide or other sulfactive hydrogenation catalyst precipitated on alumina or bauxite, etc. 1

The invention claimed is;

1. Process for refining mineral oil which comprise vaporizing mineral oil; contacting the evolved vapors containing naphthenic acids with molten anhydrous caustic alkali in a contacting zone; passing the contacted vapors from said contacting zone into a fractionating zone; condensing in said fractionating zone as heaviest distillate product a heavy lubricating oil containing 1 to 200 p. p. m. of alkali metal in the form of alkali metal compounds; percolating said heavy lubricating oil at a temperature within the approximate range from 350 F. to 600 F. through a bed of bauxite at a space rate of 0.1 to 5 volumes of oil per volume of bauxite per hour to remove alkali metal compounds from said condensate; and continuing said percolating during a period in which the electrical resistivity of the oil is improved.

independently of color improvement, at least 1000 barrels of condensate being treated per ton of bauxite.

2. Process according to claim 1 wherein said condensate, prior to contacting with bauxite, contains about 5 to 50 p. p. m. or alkali metal.

3. Process according to claim 1 wherein said caustic alkali is caustic soda.

4. Process according to claim 1 wherein said bauxite contains a major proportion of 10 to 60 mesh particles.

5. Process for refining mineral lubricating oil which and at a space rate of 0.1 to 5 volumes of oil per volume of bauxite per hour; and continuing said percolating during a period in which the electrical resistivity of the oil is improved independently of color improvement, 1000 to 12,000 barrels of said heavy lubricant being treated per ton of said bauxite.

References Cited in the file of this patent UNITED STATES PATENTS 1,698,076 Taber Jan. 8, 1929 2,340,939 Davis et a1 Feb. 8, 1944 2,658,027 Hoover Nov. 3, 1953

Claims (1)

1. PROCESS FOR REFINING MINERAL OIL WHICH COMPRISES VAPORIZING MINERAL OIL; CONTACTING THE EVOLVED VAPORS CONTAINING NAPHTHENIC ACIDS WITH MOLTEN ANHYDROUS CAUSTIC ALKALI IN A CONTACTING ZONE; PASSING THE CONTACTED VAPORS FROM SAID CONTACTING ZONE INTO A FRACTIONATING ZONE; CONDENSING IN SAID FRACTIONATING ZONE AS HEAVIEST DISTILLATE PRODUCT A HEAVY LUBRICATING OIL CONTAINING 1 TO 200 P.P. M. OF ALKALI METAL IN THE FORM OF ALKALI METAL COMPOUNDS; PERCOLATING SAID HEAVY LUBRICATING OIL AT A TEMPERATURE WITHIN THE APPROXIMATE RANGE FROM 350*F. TO 600*F. THROUGH A BED OF BAUXITE AT A SPACE RATE OF 0.1 TO 5 VOLUMES OF OIL PER VOLUME OF BAUXITE PER HOUR TO REMOVE ALKALI METAL COMPOUNDS FROM SAID CONDENSATE; AND CONTINUING SAID PERCOLATING DURING A PERIOD IN WHICH THE ELECTRICAL RESISTIVITY OF THE OIL IS IMPROVED INDEPENDENTLY OF COLOR IMPROVEMENT, AT LEAST 1000 BARRELS OF CONDENSATE BEING TREATED PER TON OF BAUXITE.

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