US2538066A - Manufacture of lubricating oil - Google Patents

Description

Jan 16, 1951 T. J. WALSH ETAL MANUFACTURE oF LUBRICATING oIL Filed De'c. 3, 1946 Patented Jan. 16, 1951 2,538,066 MANUFACTURE 0F LUBRICATING OIL Thomas J. Walsh,

Shaker Heights, Godfrey L. Ladd, Toledo, and Donald W.

Heil, Cleveland,

Ohio, assignors `to The Standard Oil Company,

Cleveland, Ohio, a corporation .of Ohio Application December 3, 1946, Serial No. 713,710

The present invention relates to the manufac ture of lubricating oil and more particularly to new and improved methods for refining petroleum lubricating distillates to produce lubricating oils of high quality.

Petroleum lubricating distillates are fractions having a relatively wide boiling range and as usually fractionated contain some gas oil, various lubricating oils or blending stocks and wax. 'Close fractionation might be employed to separate the gas oil fromthe lubricating oils and wax, but some of the lubricating fractions and waxes distill in the same range and must be separated from each other by methods other than distillation. Since the presence `of gas oil helps inthe separation of the wax from the lubricating oil, it is the usual practice to fractionate the lubricating distillate with some gas oil in it.

The lubricating oils or blending stocks in the fraction are separable into cuts including the light or pale oils which are relatively lnon-viscous and the heavier or viscous machinery oils. These lubricating oils or blending `stocks may be used `as such or blended to give a lubricating oil of 'conventional viscosity.

In refining petroleum lubricating distillates, :it has been customary, heretofore, first to re- :move the wax from the fraction such as by chilling and filtering, and then to fractionate the dewaxed oil at atmospheric pressure to remove the gas oil and to form lubricating oil blending-stocks of various viscosities, a practice known as rerunning. The fractions thus separated by the re- `running, comprising a group of lubricating blending stocks, are then separately treated with c.

sulphuric acid to iremove undesirable components in lubricating oil. Following .the acid treatment, each acid-treated oil stock is separately neutralized, e. g., with an `alkaline material or preferably by contacting with clay.

The method outlined brieiy above is disadvantageous in several `material respects. In ithe rst place, it necessitates a large amount of tankage or equipment for acid and/0r lclay treating the several lubricating oil blending stocks produced in the rerunning operation. Also, we have found that itproduces only a small yield of heavy neutral oils because of the .loss in viscosity yresulting .from the separate treatment of the several stocks. Further, clay contacting the stocks as a `final stage gives the Vproduct a somewhat objectionable odor. The :slack wax from the lpressing `operation alsohas a poorcolor. resulting Vin a more dimcult sweat 1 lClaim. (Cl. IE6-19) 'v make the products unmarlietable.

step without any cracking are of ing operation and subsequent loss in yield of crude vscale wax.

In an effort to overcome the deficiencies of the method described above, it has been proposed to treat the lubricating stock with acid. and/or clay and then rerun the treated stock in the usual manner to separate the several lubricating oil blending stock fractions. However, it was found that with this method of operation `there appears to be some cracking of the heavier fractions, resulting in the production of lighter materials as well as olenic and unstable compounds which adversely affect the color and odor of the blending stocks produced to suchan extent as to This method has not found favor in commercial operations. In fact, the art has been careful to avoid operations wherein the rerunning vstep is the last or final treating and separation step.

The objects achieved in accordance with the invention include the provision of an advantageous method of refining and separating waxcontaining lubricating distillates whereby lubricating oil blending lstocks or fractions are separated after the entire fraction, before or after dewaxing, has been acid rened; the provision of a method of separating lubricating oil fractions directly from dewaxed and acid vrefined lubricating distillate by distillation under a reduced pressure; and other objects which will become apparent as details and embodiments of the invention are set forth hereinafter.

In accordance with our invention, we propose to rerun the lubricating distillate fraction under reduced pressure after carrying out the treating operation with sulphuric acid and/or clay. In this way, it is possible to distill olf the several lubricating oil blending stock fractions as a final of the heavier fractions and without adversely affecting the odor and color of the lubricating oil stocks obtained.

By virtue of this novel procedure only a minimum amount of tankage equipment is required for the acid treating operations since the entire oil fraction, either with or without the Wax therein, is treated as a unit instead `of treating Vthe several lubricating stocks obtained after ,rerunning', as ,in the prior art. This is a vmarked advantage from the equipment cost and upkeep viewpoint. There is also greater ease in separating and disposing of the acid sludge. Further, the iinished lubricating oil blending stocks good color and odor andare ready to be packaged and sold directly or `blended as they come-from athe `rerunning unit. This isdesirablc from the operation viewpoint since it gives better control of the viscosity of the final product.

In one embodiment of the invention, we iirst subject the petroleum lubricating distillate to be refined to a dewaxing operation in which wax is removed from the initial fraction in any conventional manner, such as by chilling and filtering. It may or may not be desirable to have a solvent present depending on the amount and character of the wax present in the initial fraction. The dewaxed oil is then subjected to treatment with sulfuric acid and/or clay and the refined oil is fed to the rerunning unit where the several lubricating oil blending stocks are separated as a final step. if gas oil is present as a solvent in the initial fraction and is separated in the rerunning operation, it may be recycled to the dewaxing plant. y

In another embodiment of the invention, the paraiiin lubricating fraction is first treated with 'sulphuric acid and/or clay and the refined` fraction is dewaxed in any conventional manner. The dewaxed oil is then rerun to produce the desired lubricating oil blending stocks as a final step. As in the foregoing embodiment, if one vof the rerun fractions comprises gas oil which has been used as a solvent, this may be recycled to the dewaxing plant prior to the dewaxing operation.

The invention may be better understood from the following detailed description taken Vin conjunction with the accompanying` drawings, in which:

Figure l a flow sheet of the successive steps followed in a method for manufacturing lubricating oil blending stocks according to the invention; and

Figure 2 is a iiow sheet of a modified method for producing lubricating oil blending stocks in accordance with the invention.

The starting materials used in the methods described as illustrative of the present invention is a paraffin distillate comprising a crude petroleum fraction boiling higher than gas oil. It is usually a wide cut and may include a certain amount of gas oil in addition to various lubricatingoil blending stocks, wax, etc.

In'the embodiment illustrated in Figure 1 of the drawings, the lubricating distillate starting material is first fed to a pressing plant where slack wax is taken ofi by chilling and pressing. In order to facilitate the pressing operation, it is desirable to have a suitable petroleum product, such as gas oil, for example, in the fraction. This may be contained in the fraction as it is initially separated, or it may be obtained subsequently from the rerunning operation as described in greater detail hereinafter. The charge should preferably contain about 5 to 35 per cent by volume of gas oil based on the total mixture, and the fraction should be slowly chilled down to about 19 to +20 F.

lThe chilled mixture is then filtered in theusual manner. The slack Wax is taken off and is fed to a sweating plant Where oil is separated from the solidified Wax by gradually raising the'temperature of the Wax cake and allowing the'oil'to drip from the wax crystals in the conventional manner. The Foots oil is drained off and collected and used for special purposes or added to th'e pressed oil, leaving the crude scale wax which may be subsequently refined, if desired.

"if The. entire quantity of pressed oil from the pressing plant is' then fed tof the acid refining plant where it is irsttreated with sulphuric' acid,

for example, for the purpose of removing undesirable components. The acid sludge obtained in the treating operation is then separated and the rened oil is subsequently treated with a suitable alkaline material, and/or preferably contacted with clay, for the purpose of neutralizing the acid in the charge. The expression acid relining as used herein includes the treatment with acid followed by treatment with an alkaline material such as clay, if this is required. The details of the acid treating operation are known to the art and usually about 1 to 100 pounds sulphuric acid is used per barrel of oil, followed by neutralization with approximately 3 to 90 pounds of absorbent clay per barrel of oil. The clay and the oil are separated by filtration and the refined oil is conducted to a rerunning unit Where the several lubricating oil blending stock fractions are distilled off under vacuum as a final step. Preferably, the rerunning operation is carried out under a vacuum of less than `E300 mm. Hg., preferably 50 to 150 mm. Hg, absolute pressure.

As indicated above, the lubricating distillate starting material usually includes gas oil as one of its components. In the rerunning operation the gas oil is one of the fractions distilled olf, and it may be fed back to the pressing plant, thus providing for the dilution of the charge prior to the pressing operation. If this is done, it will not be necessary to include as much gas oil in the initial fraction, In order to inject the gas oil into the system, at the start of the process, it can be added from an outside source or can be included in the lubricating distillate feed for a time sufficient to build up a required amount of recycle between the rerunning and pressing operations.

If the gas oil is recycled from the rerunning unit to the pressing plant it is necessarily subjected to repeated treatment with sulphuric acid and/or clay along with the rest of the paraffin distillate charge. Consequently, it continues to use up the acid because retreatment continues t take oli more and more of the gas oil components and reduce it in volume to a total of 5D per cent before becoming a stable white gas oil capable of being continuously recycled without further loss under the circumstances, and considering the cost of recycling equipment, it may be more economical not to recycle gas oil.

The lubricating oil blending stock fractions obtained from the rerunning operation will include a light oil having a viscosity of about SSUv' at F. and heavier oils of 150, 200 and ranging up to viscosities of 300 or even 400 SSU at 100 F.

The refining of lubricating oils in accordance with the novel methodoutlined above hasbeen found to result in a very considerable simplification of refinery operations with a corresponding reduction of tankage requirements and elimination of lag in processing. Further, the finished oils are characterized by improved odor and color. Only one ,acid treating step is necessary, and this is always the same and is applied to the same kind vof material as distinguished from the variations -when the Whole oil is treated in accordance with the invention, the viscosity of the oil and sludge is lower than was formerly the case with the heavy oil treating operations, and separation and disposal is easier. It has also been found that less caustic is required for neutralizing the acid sludge.

In the alternative embodiment of the process, the lubricating distillate starting material may rst be treated with sulphuric acid and/or clay and then subjected to the pressing operation, as shown in greater detail in Figure 2. In addition to the advantages described heretofore, this alternative embodiment also results in improved color and an increased yield of the crude scale wax produced from the slack wax obtained from the pressing plant because the Wax has been acid treated before pressing. Further, we have noted an improvement in the pressability of lubricating distillate stocks so that heavier lubricating distillates can be processed in accordance with the method, resulting in greater yield of viscous oils from the charge.

This modication is especially advantageous Where it is desired to recycle gas oil from the rerunning unit to the pressing unit to dilute the charge prior to the pressing operation. Since the acid treating operation is carried out prior to the pressing operation in the modication illustrated in Figure 2, the recycled gas oil is not subjected to re-treatment.

In this embodiment, a further saving is obtained if the gas oil in the lubricating distillate is removed (stripped) prior to the sulpnuric acid treating step. This cuts down the consumption of treating agent and increases the amount of blending stock which may be produced from a plant of any given size.

While several representative embodiments have been described in detail herein, the invention is not intended to be limited thereto but is susceptible of numerous changes in form and detail within the scope of the appended claim.

We claim:

A method of producing lubricating oil blending stocks from a lubricating distillate fraction including both the light or pale oils which are relatively non-viscous and the heavier or viscous machinery oils, which comprises dewaxing the oil in the presence of a recycled acid-treated gas oil, and then acid rening said lubricating distillate fraction in the presence of about 5 to 35% of said acid-treated gas oil, and then subjecting the de- Waxed and acid-rened stock to distillation under a reduced pressure as a final step to separate it into a plurality of dewaxed and acid-refined lubricating oil blending stocks and acid-treated gas oil, and recycling said acid-treated gas oil to said dewaxing step.

THOMAS J. WALSH. GODFREY L. LADD. DONALD W. HEIL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,327,184 Von Groeling Jan. 6, 1920 1,388,832 Cobb Aug. 23, 1921 1,559,981 Petty 1 Nov. 3, 1925 1,802,942 Govers Apr. 28, 1931 1,947,817 Wallis Feb. 20, 1934 2,057,923 Slater Oct. 20, 1936. 2,103,898 Fellows Dec. 28, 1937 2,117,984 Richardson et al. May 17, 1938 2,142,359 Lederer et al Jan. 3, 1939

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