US2198575A - Manufacture of lubricating oil - Google Patents

Description

April 23, 1940. F. x, GovERs MANUFACTURE OF 4LUBRIICATING OIL Filed Feb. 27, 1956 ATTORNEY Patented Apr. 23, 1940 Unir-@ED STATES ATENT OFFICE Francis X. Grovers, Vincennes, Ind., assignor'to Indian Refining Company, Lawrenceville, Ill.,

a corporation of Maine Application February 27, 1936, Serial No. 66,053

2 Claims.

This invention relates to the manufacture of lubricating oil from hydrocarbon oils, and more particularly to the manufacture of high viscosity index, low pour test lubricatingA oil from Wax- 5, bearing mineral oils.

This application is a continuation in part of my co-pending application, Serial Number 601,- 888, filed March 29, 1932, for Improvements in manufacture of lubricating oil.

In its broadest aspect, as disclosed in Serial No. 601,888, and also in Serial No. 711,735, a divisional application thereof, filed o-n February 17, 1934, the invention contemplates an improved process of treating hydrocarbon oils, particularly paraf- 1in-bearing lubricating fractions of petroleum with solvents to selectively produce therefrom low pour test lubricating oils characterized by having a desired viscosity temperature relationship and improved lubricating qualities. The in- .Mjvention contemplates a process of manufacturing lubricating oils having a low pour and cloud test, low sulphur content, 10W Conradson 'carbon content, a relatively high viscosity index and free from bodies of little or no lubricating value.

35; Low pour test in a lubricating oil denotes an oil, as used in internal combustion engines, possessing the characteristics of easy starting in cold Weather and readiness of ,ovv sufcient to respond to methods of circulation so as to immegg diately reach all parts necessary to be lubricated.

'I'he presence of sulphur or sulphur-containing bodies in lubricating oil is objectionable on account of the corrosive eiect of sulphur upon bearing surfaces and other metal po-rtions of the 35,2 engine. Efforts to reduce the sulphur content oi lubricating fractions to a desirable degree `by methods ordinarily employed have resulted in an over-reiined oil with impaired lubricating value.

Lubricating oil having a low Conradson carbon ,m content is desirable since such oil has little tendency to carbonize in the motor, and such carbon as may be deposited is of a flocculent nature, having little or no tendency to adhere to the piston head or cylinder Walls. High Conradson carbon 4;, 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.

,-,U The viscosity index of a given oil is readily determined by resorting to the method of Dean and Davis, published on pages 618-519 of the 1929 issue of Chemical and Metallurgical Engineering. Lubricating oils of high viscosity index are 55, characterized byhaving a relatively narrow increase in viscosity with respect to temperature. Such oils have the property of possessing the desired viscosity at elevated temperature with no great loss of mobility at very low temperature.

Lubricating oils, as ordinarily made from naph- 5M thene-base crudes, have a low pour `and cloud test, low Conradson carbon content, but have a low viscosity index and fairly high sulphur content. On the other hand, lubricating oils, as

ordinarily made from paraffin-base crudes of the 10i 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 l5y although usually high in sulphur content. Oils of the Pennsylvania type, as Well as those derived from mixed base crude sources, are difficult to rene Without undue loss and impairment of their lubricative value. In any case, it is diflcult, 201

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 rening with its consequent impairment of lubricating value due to over-renement. Sulphur dioxide has been proposed as a substitute in the refining art but the use of this solvent by itself in rening in viscous fractions, particularly of the parain type, has not been successful from the standpoint of producing a product having the desired high viscosity index, 10W pour test and other characteristics, f

I have discovered that by the 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 paraiiin-base crudes, and the oils so produced are characterized further by low Conradson carbon and 10W sulphur con- 45 tent. The obtaining of oils having these desired qualities does not depend on methods involving redistillation or acid treatment.

More specifically the invention comprises mixing with a Wax-bearingfraction of a mineral oil A a solvent mixturel comrising two or more solvent liquids of different solvent properties which, in certain ratios of one solvent liquid to other solvent liquids, has substantially complete solvent kaction on the oil at temperatures of around 55,

. separation into two layers, the upper layer con- Vthe 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 0f 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.

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 ltration. 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 theflltrate from this washing operation may be added to the original ltrate, the amount of liquid so added depending on the amount of dissolved oil contained therein. 'Io the original ltrate 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 sufdcient to affect the solvent capacity of the solvent mixture and cause a separation between solubler and insoluble constituents of the hydrocarbons. This mixture is chilled to effect a sharp and rapid taining oils characterized by relatively high viscosity index, and the lower layer containingv 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.

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, or a derivative thereof such as monochlorobenzol. 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 alteredby varying the proportion of the solvent components of the mixture.

Instead of sulphur dioxide other 'compounds having a selective solvent action as between relatively low and relatively high viscosity index constituents ofthe oil may be used. Such solvent compounds comprise aniline, benzaldehyde, dichlorethyl ether for example. These compounds may be used with any of the auxiliary solvents mentioned, or with other suitable auxiliary solvents of somewhat similar character, such as ethyl ether and isopropyl ether for example.

As an example in carrying out the above invention: 200 gallons of untreated Vacuum distilled wax distillate having a viscosity of '70 Saybolt Universal seconds at 210 F. with a pour test of 80 F. and a sulphur content of about .4%, de-

rived from a semi-panain base crude, is mixedI with 600 gallons of a solvent liquid comprising 30% sulphur dioxide and 70% monochlorobenzol, the mixture is chilled to- 15 F. to precipitate, the wax-like or solid hydrocarbons and introduced to ltering means described in my application, Serial No. 585,844, now matured into United States Patent No. 2,003,664, for Method of and apparatus for filtration, filed January l1, 1932, wherein the solid hydrocarbons are separated from the liquid to produce a filter cake.

A wash solvent liquid comprising 30% sulphur dioxide and r10% monochlorobenzol 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 oi dissolved oil may be mixed with the original iiltrate, while the remaining portion may be used to mix with and dissolve fresh untreated wax distillate to be treated in the same manner as the original material as above described.

The slurry remaining in the lter press is then removed and the bulk of the .adhering solvent filtered oi advantageously by filtering this slurry in a filter means, such, for example, as described in my application, Serial No. 588,586, now matured I into United States Patent No. 1,920,126, for Filtratiom l'lled January 25, 1932. The solvent retained in the resulting filter cake is evaporated from the wax and the wax contacted with clay or nished up in the usual manner.

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 have a melting point, without sweating, of about 136 F.

To the mixture'of original filtrate and initial portion of wash liquor is added liquid sulphur dioxide chilled to a temperature of 10 F. This additional sulphur dioxide should bring the ratio of sulphur dioxide to monochlorobenzol up to about equal volumesv of each. Y

The mixture is well stirred and allowed to settle and stratify. The top layer will comprise low gravity, relatively high viscosity index oils, while the lower layer comprises high gravity, low viscosity index oils, The oil in the top layer after removal of the solvent will have a gravity ol approximately 27.5 A. P. I., a viscosity of 66 Saybolt Universal seconds at 210 F. and a viscosity index of approximately 87. The oil in the bottom layer, after removal of the solvent, will have a gravity of approximately 13 A. P. I., a viscosity of approximately 118 Saybolt Universal seconds at 210 F. and a viscosity index below 30.

The fraction of relatively high viscosity oil may be contacted with clay and ltered, and is then ready for use as a so-called wide out, or it may be fractionated by vacuum distillation to produce cuts of narrower distillation range.

On the other hand, this relatively high viscosity material may be still further improved or `rened by dissolving in monochlorobenzol, cooling the mixture to 0 F. and adding chilled liquid sulphur dioxide in about the same proportion as the monochlorobenzol. The mixture is well stirred, chilled to 10 F. and allowed to settle.Y

F., viscosity index 95, Conradson carbon .015, and sulphur .1, with a pour test of 5 F.

As an additional example in carrying out the above invention:

Untreated vacuum distilled Wax distillate, similar to that used in the preceding example, is also similarly mixed with sulphur dioxide and monochlorobenzol in the proportion of about 200 gallons of oil to 600 gallons of solvent mixture, and chilled to 15 F. to precipitate the wax-like or solid hydrocarbons. The mixture is ltered and the resulting lter cake washed with the same fresh solvent in the same manner, the initial portion of the wash ltrate being mixed with the original filtrate.

To this mixture of original filtrate and wash liquor is added chilled sulphur dioxide suiiicient to give a solvent mixture of 60% sulphur dioxide and 40%' monochlorobenzol. 'Ihe mixture is stirred Well, chilled to 10 F. and allowed to settle and stratify.

The separated bottom layer is drawn olf, 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 monochlorobenzol and sulphur dioxide comprising about 40% sulphur dioxide and 60% monochlorobenzol, 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 ltered. The ltered 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 791/2, with a pour test of 10 F.

The solvent is evaporated from the separated top layer and the contained oil contacted at 500 F. with 20 pounds of clay to the barrel while steaming. The oil and clay mixture isy cooled to 350 F. and ltered. 'I'he 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 inthe foregoing examples except that the proportions of propylene dichloride and-sulphur dioxide to each other and to the oil undergoing treatment may differ 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 '7l/2% 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. 'Ihis mixture is then chilled to 5 F. or below and settled to form two layers from which the oil is recovered and finished up as has already been described.

The solvent is advantageously removed from the separated oil by evaporation and, in the case of the high-boiling solvent component, under diminished pressure. The evaporation may be High viscos- Low viscosity ity index oil index oil Gravity, A. P. I 28. 5 12. 2 Saybolt Universal viscosity at 210 F.. 65 120. Pour -10 Viscosity index 88 Below 30 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 paraffin-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. Hydrogenation products may contain substantial quantities of waxy or paraiin material as well as other constituents of relatively low lubricating value. By treating such products in accordance with my invention, nal products of desired characteristics can be obtained. f

'I'he invention is not restricted to any particular operating conditions such as that of temperature, or the composition of the solvent mixtures employed since vthese 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 products.

In this connection reference may be made to my U. S. Patent No. 2,158,361 (Serial No. 633,461) and also to my U. S. Patent No. 2,137,218 (Serial No. 648,988), disclosing solvent mixtures which may be employed in the process.

Where the solvent mixtures used comprise a selective solvent such as benzaldehyde or dichlorethyl ether, for example, and a relatively less volatile auxiliary solvent such as benzol, toluol, ethyl ether or light petroleum hydrocarbon, for example, the composition of the solvent mixture, following the removal of the wax, can be altered by vaporizing a portion of the auxiliary solvent. For example, one part wax bearing oil is mixed with four parts of a solvent mixture consisting of 40% dichlorethyl ether and 60% ethyl ether. After chilling to 0 F. and removing the solidified wax, substantially all the ethyl ether is vaporized from the dewaxed solution. The remaining mixture of oil and solvent is thenl cooled and allowed to settle, for example, at a temperature of around 40 F., whereupon the mixture separates into layers.

The accompanying drawing illustrates the carrying out of the process of the invention as above described.

Wax-bearing oil, from a source not shown, is introduced to a mixer I. In this mixer the oil is mixed with a selective solvent, such as sulphur dioxide or benzaldehyde, and a modifying solvent, such as benzol or an aliphatic ether. The oil and solvents are mixed in proportion such that the mixture has the required solvent action as between wax and oil at a temperature of around F. and below.

' This mixture is then passed through a chiller wherein itis chilled to the desired waxing temperature, for example, about F.

The chilled mixture is then conducted to a lter 2 wherein the solid hydrocarbons are del posited in the form of a filter cake. The filter cake is washed with a wash solvent, as already described, and the resulting washed cake is withdrawn from the filter to a wax slurry tank 3.

As previously described, the Wax slurry may be subjected to filtration in another filter 4 for the purpose of removing additional liquid as filtrate.

The remaining wax cake is then drawn off to a still 5 for the recovery therefrom of the retained solvent.

The wax from which the solvent has been removed is withdrawn from the still and is, advantageously, subjected to clay-contacting or other treatment to produce a finished wax.

The filtrate drawn off from the filter 2 comprises the main body of dewaxed oil and may contain some of the wash filtrate-that is, that portion of the wash filtrate which contains substantial amounts of oil.

The remainder of the wash filtrate lean in oil is returned through a pipe 6 to the mixer I for mixing with fresh charge.

The main body of filtrate is conducted through a vpipe I to either a mixer 8 or a still 9, depending upon the nature of the solvent mixture.' Thus, if the modifying solvent is less volatile than the selective solvent component and it is therefore necessary to add additional quantities of the slective solvent in order to alter the solvent composition, the filtrate is passed to the mixer 8. In such case the amount of selective solvent component which is added is sufficient to cause the solvent mixture to exert selective action as between naphthenic and parainic constituents, so that the mixture separates into two liquid phases upon standing. The mixture thus formed in the mixer 8 is drawn off to a separator I0 wherein separation into two liquid phases occurs.

On the other hand, if the modifying solvent is more volatile than the selective solvent component, the solvent composition of the mixture may be altered merely by evaporating a sufficient portion of the modifying solvent from the mixture. In this case the filtrate is conducted to the still 9, as previously indicated, and wherein a portion of the modifying solvent is removed by evaporation.

The unvaporized portion is then withdrawn andr conducted to the separator I0 for separation into two liquid phases.

The upper phase comprises a raffinate phase rich is high viscosity index constituents and is withdrawn from the top of the separator I0 to a still II.

The extract phase rich in low viscosity index constituents is drawn off from the bottom of the separator I0 to a still I2. In the stills II and I2 the solvent liquid is removed from the oil.

The rafnate oil from the still I I may be passed` directly to a clay-contact plant I3 wherein the oil is treated with clay and steam to produce a finished product.

On the other hand, the raffinate oil may be subjected to further solvent fractionation, in which case it is mixed with further solvent in a vessel I4 and from there conducted to a separator I5 for separation into secondary rafnate and extract phases. The secondary raffinate phase is conducted to a still I6 for removal of its solvent content and the resulting raffinate is then conducted to the aforementioned clay-contact plant I3 for final treatment.

It is also contemplated, in many instances, that it may be of advantage to carry on the filtration 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.

In some instances it may be desirable to remove the low viscosity index constituents or a portion thereof, before dewaxing. In that case it is only necessary to mix Athe wax-bearing fraction with the mixture of selective and auxiliary solvent in a proportion such that the mixture has selective action as between the low Viscosity index constituents and the high viscosity index constituents, including paraffin wax. The dissolved phase containing the low viscosity index constituents is removed and the ratio of the solvent liquids in the undissolved phase is altered so as to provide a solvent mixture having selective action as between the high viscosity index oil and solid wax at temperatures of 0 F. l

and below. Upon chilling and filtering to remove the solidified wax, oil of desired pour test and of high viscosity index is obtained.

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:

1. The process of manufacturing high viscosity index lubricating oil having a low pour test from wax-bearing mineral oil which comprises mixing with the oil a solvent liquid mixture composed of a selective solvent and a modifying solvent liquid having substantially no selective action as between constituents of the oil of differing Viscosity indices, and mixed with each other and with the oil in proportions such that at temperatures of around 0 F. the mixture has substantially complete solvent action on the oil, and substantially no solvent action on the wax, chilling the mixture to precipitate wax constituents of the oil, removing the wax thus precipitated, removing from the resulting dewaxed mixture a suitable portion of the modifying solvent to thereby render the remaining solvent liquid selective as between constituents of the oil of differing viscosity indices, and separating from the remaining mixture a fraction of desired viscosity index and low pour test.

2. The process of manufacturing high viscosity index lubricating oil having a low pour test from wax-bearing mineral oil which comprises mixing with the oil a solvent liquid mixture composed of a selective solvent and a relatively more volatile modifying solvent liquid having substantially no selective action as between constituents of the oil of differing viscosity indices, and mixed with each other and with the oil in proportions such that at temperatures of around 0 F. the mixture has substantially complete sol- Vent action on the oil, and substantially no s01- vent action on the Wax, chilling the mixture to precipitate wax constituents of the oil, removing the Wax thus precipitated, vaporizing from the resulting dewaxed mixture a suitable portion of the modifying solvent to thereby render the remaining solvent liquid selective as between constituents of the oil of differing viscosity indices, and separating from the remaining mixture a fraction of desired Viscosity index and 10W 5 pour test.

FRANCIS X. GOVERS.

Images