US2210867A - Manufacture of lubricating oil - Google Patents

Description

- Patented Aug. 6, 1940 OFFICE MANUFACTURE.0FI 1UBRIGATINGOIL Francis X. Govers, Vincennes, Ind., .assignor to Indian Refining Company, Lawrenceville, Ill., a corporation of Maine r N Drawing;

i 1 Claim.

particularly to the manufacture of high viscosity I index, low pour test'lubricating oil from waxbearing mineral oils. The present application is a continuation-in-part of my co-pendin'g application Serial No. 601,888 filed March 29, 1932 for Manufacture Oflubricating oil D#15,143.

In its broadest aspect, the invention contemplates an improved process of treating hydrocarbon oils, particularly parafin-bearing lubricating fractions of petroleum with solvents to selectively produce therefrom low pour .test lubricatingoils characterized by havinga desired vis- 16 cosity temperature relationship and improved lubricating qualities. The invention contemplates a process of manufacturing lubricating oils having a low pour and cloud test, low sulphur content, low Conradson carbon content, a relatively high viscosity index and freefrom bodies of little or no lubricating value.

Low pour test in a lubricating oil denotes an oil, as used inintern'al combustion engines, possessing the characteristics of easy'starting in cold weather and readiness of flow sufficient to respond to methods of circulation so as to immediately reach all parts necessary to be lubricalled. 7 l

The presence of sulphur or sulphur-containing bodies in lubricating oil is objectionable on account of the corrosive eflect 'of'sulphur upon bearing surfaces and other metal portions of the engine. Efiorts to reduce the sulphurcontent of lubricating fractions to a desirable degree by methods ordinarily employed have resulted in an over-refined oil with impaired lubricating value. Lubricating oil having a low Conradson carbon content is desirable since such oilhas little tendency to carbonize in the motor, and suchcar I bon as'may be deposited is of a fiocculent nature,

having little or no tendency to adhere to the piston head or cylinder walls. High Conradson carbon content is characteristic, for example, of residual oils, or oils' not redistilled under low absolute pressure, and is characteristic. of oils having desired high viscosity index, as ordinarily produced heretofore. I l i 1 The viscosity index of a given oil is readily determined by resorting to the method of Deanand Davis, published on pages 618-619 of the 1929 issue of Chemical and Metallurgical Engineering. Lubricating oils of high viscosity in d'ex are characterized by 1 having a relatively narsis Application February "17, 1934, Serial No.'f7-11,735

sessing the desiredviscosity at elevated temperature with no great loss of mobility at very low temperature.

Lubricating oils, as ordinarily made from naphthene-base crudes, have a, low pourvand cloud test, low Conradson carbon content, but have, a low viscosity-index and fairly high sulphur content. On the other hand, lubricating oils, asordinarily made from paraffin-base crudes of the Pennsylvania type, have a high pour and cloud test, high Conradson carbon content and a fairly high sulphur content, depending on the particular crude source. Oils derived from mixed base crudes may fall somewhere between these limits although usually high in sulphur content. Oils of the Pennsylvania type, as well as those derived from mixed base crude sources, are difficult to refine Without undue loss and impairment of their lubricating value. In any case, it is difficult, by methods now employed, to reduce the sulphur content of lubricating oil fractions to the desired point,'regardless of their crude source.

' The generally accepted method, as used in the art of refining petroleum lubricants for the removal of sulphur as Well as other undesired constituents, is by the use of sulphuric acid. Much stress has recently been put on the danger of over-refining due to the use of this method of refining with its consequent impairment of lubricating value due to over-refinement. Sulphur dioxide has been proposed as a substitute in the refining art but the use of this solvent by itself in refining viscous fractions, particularly of the parafiin type, has not been successful from the standpoint of producinga product having the desired high viscosity index, low pour test and other characteristics. 3 v

I have discovered that bythe use of the methods herein disclosed lubricating oils of any desired viscosity index and scale of purification, coupled with low pour test and low cloud test, can be made from mixed-base or paraffin-base crudes, and the oils so produced are characterized further by low Conradson carbon and low sulphur content. The obtaining of oils having these desired qualities does not depend on methodsinvolving redistillation or acid treatment.

1 More specifically the invention comprises mixing with a wax-bearing fraction of a mineral oil a solvent mixture comprising two or more solvent liquids of difiering solvent properties which, in certainratios of one solvent liquid tov other solventfliquids, has substantially complete solventactionon the oil at temperatures of around 100 F. and above and at temperatures of around 0 F. substantially complete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that upon cooling a solution of the mineral oil fraction in such solvent mixture to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid the resulting oil has a cold test of substantially 0 F. or below but which solvent mixture in certain other ratios of one solvent liquid to the other solvent liquids has, at temperatures of 32 F. and below, a selective solubility as between differing viscosity index constituents of the liquid hydrocarbon content. I

The mixture is then chilled to form a precipitate of solid or semi-solid material comprising suspended wax or solid hydrocarbons which are insoluble in, and immiscible with, the solvent mixture. The mother liquor is separated from the cold mixture advantageously by filtration. The separated mass of solid hydrocarbons is then washed free of mother liquor containing dissolved oil by additional quantities of chilled solvent liquid of approximately the same composition as used in the original mix.

A certain portion of the filtrate from this washing operation may be added to the original filtrate, the amount of liquid so added depending on the amount of dissolved oil contained therein. To the original filtrate or mixture of original filtrate and first wash liquor is then added an additional amount of one of the component solvents of the solvent liquid mixture to alter the percentage composition of the components of the solvent mixture in an amount sufiicient to affect the solvent capacity of the solvent mixture and cause a separation between soluble and insoluble constituentsof the hydrocarbons. This mixture is chilled to effect a sharp and rapid separation into two layers, the upper layer containing oils characterized by relatively high viscosity index, and the lower layer containing oils characterized by relatively low viscosity index. The amount and character of the separation is influenced by the amount of alteration in the percentage composition of the components comprising the solvent liquid mixture. 7

' I have found that a suitable solvent liquid mixture may comprise a mixture of liquid sulphur'dioxide and an organic solvent liquid such as benzol or one of its homologs, the most common' of which are toluol and xylol, or a derivative thereof such as monochlorbenzol, or other chlorinated aromatic hydrocarbons such as ehlortoluene. Other solvent liquids may also be employed in conjunction with the sulphur dioxide, as for example, propylene dichloride. The selective solvent action of. a mixture of these solvents upon the various constituents of a hydrocarbon oil fraction is readily altered by varying the proportion of the solvent components of the mixture. I

As an example in carrying out the above invention:

About one part of untreated vacuum distilled wax distillate having a viscosity of 70 Saybolt Universal seconds at 210 F. with a pour test of F. and a sulphur content of about .4%, derived from a semi-paraffin base crude, is mixed with about three parts of a solvent liquid comprising 30% sulphur dioxide and 70% monochlorbenzol, the mixture is chilled to 15 F. to precipitate the. wax-like or solid hydrocarbons and introduced to filtering means described in my co-pending application, Serial No. 585,844, for Method of and apparatus for filtration, filed January 11, 1932, wherein the solid hydrocarbons are separated from the liquid to produce a filter cake.

A wash solvent liquid comprising 30% sulphur dioxide and 70% monochlorbenzol and chilled to 15. F. is introduced to the press to wash out of the filter cake the adhering mother liquor. The first portion of the filtrate resulting from this washing, which may contain a substantial quantity of dissolved oil may be mixed with the original filtrate, While the remaining portion may be used. to mix with and dissolve fresh untreated wax distillate to be treated in the same manner as theoriginal material as above described.

'The slurry remaining in the filter press is then removed and the bulk of the adhering solvent filtered off advantageously by filtering this slurry in a filtermeans such, for example as described in my U. S Patent-No. 1,920,126, for Filtration. The solvent retained in the resulting filter cake is evaporated from the wax and the wax contacted with clay or finished up in the usual nner- The wax in the above example will amount to approximately seven and one-half per cent'of the original wax distillate and after removal of the solvent by evaporation and decolorizing will be white and h ave a melting point, without sweatof about 136 F. i

To the mixture of original filtrate and initial portion of wash liquor is added liquid sulphur dioxide chilled to a temperature of -1( l F. This additional sulphur dioxide should bring the ratio of sulphur dioxide to monochlorbenzol upto'about equal volumes of each.

The mixture is well stirred and allowed to settle and stratify. The top layer willcomprise low gravity, relatively high viscosity index oils, while the lower layer comprises highgravitmlow viscosity index oils.' The oil in the top layer after removal of the' solvent will have a gravity of approximately 27.5 A. 1?. I., a viscosity of fit Saybol't'Universal seconds at-2l0 F. anda viscosity index of approximately 87. The oil in the bottomflayerfafter removal of the solvent, will have a gravity of approximately 13 A. P, 1 a viscosity of approximately 118 Saybolt Universal seconds at 210 E. and a viscosity index below The fraction of relatively high viscosity oilmay be'cont'acted with clay and fiitered, and is then ready for use as a so-called wide cut, or it may be fractionated by vacuum distillation toproduce cuts of narrower distillation range.

On the other hand, this relatively hig viscosity material may be still further'improved or refined by dissolving in monochlorbenzol, cooling the mixture to 0 F. andadding chilled liquid sulphur dioxide in about the "same; proportion as themonochlorbenzol. The mixture is'well stirred, chilled to -10 F. and allowed tosettle. The oil in the top layer, after removal of the solvent, contacting and steaming inth e presence of clay and contact filtering, will havetheffollowchlorbenzol, and chilled to 15" F. toprecipitate the wax-like or solid hydrocarbons. The mixture is filtered and the resulting filter cake washed with the same fresh solvent in the same manner, the initial portion of the wash filtrate being mixed with the original filtrate.

To this mixture of original filtrate and wash liquor is added chilled sulphur dioxide sufficient to give a solvent mixture of sulphur dioxide and 40% monochlorbenzol. The mixture is stirred well, chilled to -10? F. and allowed to settle and stratify.

The separated bottom layer is drawn off, the solvent evaporated and the oil recovered. There will be recovered an oil having a gravity of approximately 12.4 A. P. I. and a viscosity index of approximately 32.

The separated top layer is mixed with a chilled mixture of monochlorbenzol and sulphur dioxide comprising about 40% sulphur-dioxide and 60% monochlorbenzol, well stirred, chilled to -10 F. and allowed to separate. The bottom layer is drawn off, the solvent evaporated and the contained oil contacted at 500 F. with 20 pounds of clay to the barrel. This contacting may be carried out in the presence of steam. The oil and clay mixture is cooled to 350 F. and filtered. The filtered oil will amount to about 73 gallons and have the following approximate characteristics: Gravity 27.5 A. P. I., viscosity 67 Saybolt Universal seconds at 210 F., viscosity index 79 /2, with a pour test of 10 F.

The solvent is evaporated from the separated top layer and the contained oil contacted to 500 F. with 20 pounds of clay to the barrel while steaming. The oil and clay mixture is cooled to 350 F. and filtered. The filtered oil will have the following approximate characteristics: ,Gravity 31.1 A. P. I., viscosity 63 Saybolt Universal seconds at 210 F., viscosity index 102, pour test 5 F., Conradson carbon .012, sulphur .09.

When using propylene dichloride as one of the solvent components, the procedure is substantially similar to that outlined in the foregoing examples except that the proportions of propylene dichloride and sulphur dioxide to each other and to the oil undergoing treatment may diifer considerably. Thus, in the initial treating step for the removal of wax constituents, the wax-bearing oil may be mixed with straight propylene dichloride alone or with a solvent mixture comprising this solvent liquid and not in excess of about l by volume of sulphur dioxide. The resulting cold solution of liquid hydrocarbons in solvent liquid is then mixed with fresh cold sulphur dioxide in an amount, for example, which may be equal to or greater than the propylene dichloride content but usually in excess of about 20% of the solvent mix. This mixture is then chilled to 5 F. or below and settled to form two'layers r in the presence of steam and the clay-contacting sulphur dioxide, the final product is improved color.

When using propylene dichloride and sulphur dioxide as above described, products are obtained having the following characteristics:

The invention is not limited to the production of final products having the particular characteristics of those described above. Products of differing characteristics, as desired, may be prepared by varying the proportions of the-solvent liquids and also the temperatures at which the treating steps are carried out.

Furthermore, the invention is not limited to the treatment of wax distillate such as given in the examples herein but is adapted to the treatment of other parafiin-containing fractions, precipitates or materials somewhat similar in nature derived in various ways from mineral oils.

Thus my invention is applicable to the treatment of hydrogenation products resulting from the hydrogenation of carbonaceous materials, or mineral oils including liquid or solid hydrocarbon fractions derived from mineral oils. Hyrogena: tion products may contain substantial quantities of waxy or paraflin material as well as other constituents of relatively low lubricating value. By treating such products in accordance with my invention, final products of desired characteristics can be obtained.

The invention is not restricted to any particular operating conditions such as that of temperature. or the composition of the solvent mixtures employed since these conditions may advantageously be varied, depending upon the nature of the fraction undergoing treatment as Well as upon the particular characteristics desired in the final product.

It is also contemplated, in many instances, that it may be of advantage to carry on the filtration 1 step in the presence of a comminuted solid filteraid material. Such material may be admixed with the chilled mixture of oil and solvent liquid prior to introduction to the filtering means.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

In the manufacture of lubricating oils of desired high viscosity index from mineral oil containing constituents of relatively low and relatively high viscosity index, the methods of fractionally separating the oil into fractions of differing viscosity index comprising extracting the oil I with liquid sulphur dioxide in the presence of a mono-chlorinated monocyclic aromatic hydrocarbon solvent liquid having substantially less selective action than liquid sulphur dioxide as between relatively high and relatively low viscosity index constituents and in proportions sufiicient to effect the desired degree of selective solvent action upon the oil undergoing treatment.

FRANCIS X. GOVERS.