US1784525A - Method of dewaxing petroleum oil - Google Patents

Description

De. 9, 1930. L. D. JoNEs 'I ETHOD OF D EWXING PETROLEUM'OIL Filed oct. 7, 1925 INVENTOR ATTORNEY illy Patented Dec. 9, 1930 UNITED. STATES PATENT OFFICE-r` LEO D. JONES, AOF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE SHARPLES p SPECIALTY COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OFv DELAWARE Application led October 7, 1925.

My invention relates to a process of refining petroleum, and particularly to the relining of that part of crude petroleum which remains after gas, naphtha and burning oils have been distilled olf, such part of vthe petroleum, formerly called tar, being-herein referred to as long residuum of petroleum, and to the refining of certain distillates of such' residuum. The term long residuum is intended to mean a still residue which in-l cludes a larger percentage of the crude oil than would be contained in cylinder stock residuum made from the same crude, and in general includes most of the lubricating content of the oil. v

It is an object of my invention -to provide a process whereby viscous lubricating oils of f low cold test are efciently and economically produced from long residuum of petroleum anddistillates of such residuum thatA contain nonressable waX, contain oil of low speci c gravity and low boiling point, and have a low flash point, e. g., a flash point lower than 450 F. Oils that contain nonpressable Wax are oils from which the contained wax cannot be removed to a satisfactory degree in a single operation by precipitating the wax therein by chilling and then pressing the 0il"through pervious material while the wax is held back by the pervious material, although a fraction may be taken from such oils by distillation from which wax may be removed to a satisfactory degree by chilling and pressing. The wax in such' a fraction is light wax ('i. e., of lower boiling point than other wax in the oil) and is the wax hereinafter referred to as light wax.

y,In the removal of non-pressable wax from oil it yhas formerly been the practice to purify or decolorize the oil, before dewaxing it, by treatment with acid or clay or both with the intended purpose of rendering the removal of wax more complete and for the purpose of decolorizing the oil.

example oils having a dash point belowT 450- METHOD OF DEWAXING PETROLEUM OIL This prac tice, wherein the oil was purified before being dewaXed, worked satisfactorily with Serial No. 61,125.

F., difficulty was encountered in securing a desired degree of wax removal as the light wax was not removed with the result that the cold test of the oil was unsatisfactory and in fractionation of the dewaxed oil light wax' accumulated in the viscous neutral fraction giving that product a higher cold test than the cold test of the viscousxfraction or bright stock residue although it is desirablev that the viscous neutral fraction have as low ,a cold test as possible. If o-il that contains non-pressable wax is'purified by acid treatment or by clay treatment or by both of such treatments to such an extent that it meets commercial requirements as to color and purity for a red or yellow oil, and if such oil is in a diluted state either as a result of the presence of gas oil in it or as a result of the addition of naphtha, and'if the diluted oil is then chilled to precipitate the wax, then some of the wax may float on the solution and therefore pass out with the oil in dewax- K lmay be effected, in accordance with my invention, to a satisfactorily complete degree.. The separation of wax precipitated by dilution and chilling of such wax-bearing oil may be carried out centrifugally. References to hard asphalt herein refer to .asphalt which is precipitated when the oil is eXtensively diluted with light naphtha and which if then compressed together forms a brittle cake and which impairs centrifugal dewax- I ing by producing hard accumulations within the centrifugal bowl. A. reference herein to impurities other than hard asphalt or' to impurities that may readily'be removed by o moved by clay treatment have not as yet,

although decolorizing by clay treatment is old in lthe art, been identified chemically and it is not knownwhat other changes and removals occur in such decolorizing. It has been common practice to so purif the long residuum or a distillate thereo prior to dewaxin and the above described difficulties obtain in the dewaxing. But, in accordance with this invention a residuum or aY distillate thereof that is made from waxf bearing crude petroleum by steam distillay tion and merely substantially freed of hard asphalt, is' diluted and chilled and the wax is precipitated in a form in which it may be separated from the oil' by subsidence, and

ysgreeo particularly by centrifugal separation. In other words 'I have discovered that if oil containing light wax also contains a sufficient quantity of such impurities as are above mentioned, the light wax passes from the oil,'rparticularly in a centrifugal dewaxing operation, in the same manner that heavywax present passes from the oil and in the same manner that the wax passes from dec'olorizedsteam refined cylinder stock. In other words I have discovered that if oil contains light wax and also contains a sufficient quantity of such im urities as are above mentioned, chilling o the oil to a suiiiciently low degree will eiect such precipitation that the wax may be removed to a satisfactorily complete degree by a suitable wax'removing operation. I have also discovered that a portion of the im urities that are present-pass from the oil'wit the waxes, that the ratio of impuritiessoA removed with the wax to the v'total impurities present before wax removal is at least as eat as the ratio of removed Wax to the original mixture of oil andl wax, and that the im urities that so pass out withthe waxes are t ose impurities that are diiiicult to remove from the oil insubsequent purification as with clay, in lthat it is these impurities which use up the purifying property of a large portion of the cla that is used. `he long residuumv of some .petroleums -A naturally contains those impurities which when present will insure a satisfactory de- `the long residuum is 'dewaxed.

The long residuum of other petroleums will fbe found to contain a small amount of asphalt. In other words the long residuum of some petroleums will contain impurities other removal of non-pressable wax whenI than those that may readily be removed by clay treatment and which will interfere with the operation of my process. Such excessive 4impurities include what is commonly termed hard asphalt. I have discovered that if long residuum containing such impurities is given a mild acid treatmentl that will leave in the long residuum such impurities as may be removed readily by clay treatment, dewaxing of the resulting product is satisfactorily accomplished. Objectionable asphalt is aspedes the discharge from the centrifugal bowl of the wax separated therein. The identificaand are (b) most readily (i. e., most economtion of the particular impurities ofhoil that are referred to herein may be further facilitated by a consideration of a long residuum of Waxbearing oil which is produced by steam distillation and which contains enough hard asphalt to produce an *appreciable` precipitate upon extensible dilution of the residuum with light naphtha. While such asphalt might be removed by clay treatment of the residuum it is more economical, and it is usual, to remove such asphalt by mild acid treatment, but thi` impurities remaining after such mild acid treatment are removed economically, and for that reason readily, byclay treatment. The mild acid treatment effectively reduces the hard as halt content of the residuum and althoug the operation is old the impurities removed in such treatment have 'not been chemically identified and its not known what 'changes and removals occur other than reduction of the hard asphalt content. Therefore, im urities other than those that may readily i. e., economically) be removed by clay treatment are those impurities which are removed by the preliminary mild acid treatment and they include hard asphalt.

The long residuum of still other petroleums will be found to contain more asphalt than' can be economicallyI removed by acid treati ment for the purpose of bringing the oil to a condition wherein dewaxing in accordance with my processie satisfactorily carried out. I have discovered that such long residuum may be brought to a condition wherein it may be dewaxed satisfactorily in accordance with my process, by distillation that is so carried out that substantially all of the lubrieating content of the long residuum is dis- -tilled over without cracking and a sutlicient quantity of impurities ofthe character above mentioned is distilledover into the distillate.

lSuch distillation may becxsteam distillation llO at atmospheric pressure or .vacuum distillation or a combination of both. The distillate so produced is then treated in accordance with my invention. Distillates from pipe stills lhavealso been satisfactorily treated in ac- 'dewaxing of the resulting product is satisfactorily accomplished in accordance with my invention.

If the stock that is to be treated in accordance with my invention, regardless of Whether it is a distillate ora long residuum of petroleum, does not contain va sufiicient quantity of impurities to insure, as above set forth, that non-pressable wax will be removed from the oil to a sufciently complete degree, impurities may be brought into the stock that is to be deWaxed by blending such' distillate or long residuum that is lacking inimpurities. with other products containing an excess ot such impurities other than hard asphalt.

Regardless of Whether the product that is to be devvaxed contains the necessary impurities naturally or by blending, and regardless of Whether the product that is to be deyvaxed has been brought to the proper condition by vacid treatment or by non-cracking distillation as above described, -the product that is to be dewaxed possesses` in any casesubstantially the same characteristics. I A product that is to be deWaxed and which contains enough of such impurities that dewaxing may be satisfactorily effected in accordance with my invention Will be herein referredto as dewaxing stock regardless of Whether it was obtained naturally, by blending, by .ac id treatment or' other purification or by distillation. n

In -carrying out my process crude oil 1s distilled Without cracking to remove the gas, naphtha and burning oil. If the long residuum thus obtainedor a. desired distillate thereof contains the impurities designated as desirable above, such stock then constitutes a de'waxing stock.` If the long residuum thus obtained or a desired vdistillate thereof does not contain the impurities designated above as desirable, such stock is brought bythe appropriate application of the steps of my -invention above set forth, to a condition wherein it constitutes a devvaxlng stock.

A feature of this invention is that by the steps leading toits formation or by blending,

a long residuum or 'a distillate is obtained or formed that contains impurities that naturally occur in such distillates or residues and that are most readily or economically removable by clay treatment, and the presence of such impurities causes the wax as a whole that is precipitated by chilling to be of such specific avity and such character or degree' of plasticity that it may be removed by subsidence, and particularly by centrifugal de- Waxing. While the impurities other than hard asphalt may affect the specific gravity of the precipitated Wax they nevertheless tend to cause precipitated Wax to be amor phous in form and they may therefore be said to constitute an amorphizing agent.

If the long residuum (such as long residuum of Cabin Creek crude-oil) or a' distillate thereof does not contain a sufficient concentration of impurities other than hard asphalt, to render the precipitated Wax readily removable in a single operation, when that residuum or distillate is produced in the most desirable Way, or if more extended dis-y tillation for the purpose of carrying such impurities into the devvaxingl stock is im! practical or would produce an oil of undesirable viscosity, impurities may be added by blending with the dewaxing stock oil products containing such impurities in excess, as above suggested, and either containing or free of wax. However, in some cases such i blending would be excessive and impair the efliciency of the dewaxing plant, as in the case of a distillate taken'for the purpose of. producing a non-viscous lubricating oil, and in such cases the process of my copending application Ser. No. 147,383,1iled November 9, 1926, may be advantageously employed, that process involving the addition of distinctly amorphous Wax, or of petroleum products containing such Wax, either free of or containing amorphizing impurities.

In carrying out my invention the deWaX- ing stock, after its temperature is reduced.; to about 120o F. if\-previous treatment has raised its temperature above that point, is

diluted with about 55% to 65%, e. g., 62%, s of straight cut naphtha having a .specific gravity of approximately 62 B. and the mixture is heated to about 100 F. to effect complete solution of the contained Wax.

-This mixture is then gradually cooled and.

`to P. T. Sharples, No. 1,232,104, the oil and Wax being continuously and separately discharged. The naphtha is removed from the dewaxedoil and the remaining product \is distillate, and, provided the dewaxing stock contains sufliciently viscous material, cylinder stockresldue. Both the non-viscous oil vand the viscous neutral oil will be of light color 'andl will have a cold test below 25 F. and may be regarded as finished lubrieating products. The cylinder stock will contain all of the impurities present in the dewaxing stock except those removed in the dewaxing operation'and will vbe of dark color.

If desired, this cylinder stock may be made into a bright stock by clay treatment and will then have a cold test of 20o F. or lower.

As one alternative the de-waxed oil, e. g., the oil discharged from the centrifugemay be treated with or filtered through clay before fractionation. This clay treatment or filtration may be carried out either before or after the naphtha is removed. In this case" the product may. then be fractionated, as by steam distillation. The products of this procedure will include vnon-viscous oil, viscous neutral oil and, provided the dewaxing stock contains sufficiently viscous material, bright stock residue. The non-viscous oil, viscous neutral oil and any bright stock residue will have the same properties as the similar products produced in accordance with the above described procedure wherein the clay treatment was limited tok the cylinder stock in which all ofthe impurities were concentrated by distillation.

As` another alternative the oil discharged from the centrifugal separator may be treated with or filtered through clay and -freed of the diluting naphtha by steam distillation, by whichever order of procedure is most convenient, and the resulting light colored low cold test product maybe used as afinished lubricant or as blending stock. "L

An important advantage of my invention resides in the fact that I am thereby enabled to more v completely remove non-pressable wax, including light 'wax that is in itself pressable, from oils of low flash test with the result that I am enabled to dewax, particularly by a centrifugal process, all of .the lubricating content of crude petroleum and .to obtain not only lubricating oils of -low cold test but to obtain a greater proportionate yiel-d of such oil. Previous processes for the dewaxing of oils containing non-pressable wax have been of two kinds. In one such process the wax was removed by filter pressing and in that case preliminary cracking -to the mixture of Wax and oil.

treatment was necessary but that converted a large proportion of the lubricating content of the oil into non-lubricating products. In the other of such processes the amorphous wax was removed without change of) state by centrifugal dewa-Xing'of previously purified or decolorized stock. I obtain substantially three times as much viscous neutral oil as is obtained by such processes wherein cracking distillation is restorted to for the purpose of bringing the wax into a form inl which it is removable by a 'filter pressing'. Such previous centrifugal processes have not atta-ined the improvement in cold test that results from centrifugally dewaXing the oil, in accordance with my invention, without previously decolorizing'the oil. Thus the final product attained by the practice of my invention will have a cold test of 25 F. or lower even though the dewaxing stock was of low fiash test whereas previous centrifugal rocesses when applied to dewaxing stock o low flash test produced a final product having a cold test of 50 F. or higher.

Another important advantage of my invention resides in the fact that when'wax isv removed from dewaxing stock before decolorization of the dewaxing stock, impurities that are of such character that they are the most difficult to remove from the oil will `pass from the oil when the oil is diluted and fraction, 15% to 30% in most'cases, of the original dewaxing stock, and as above stated the ratio of impurities removed with the wax to the total impurities of the dewaxing stock is at least as great as the ratio of wax But the wax may, without application of decolorizing treatment thereto, be converted and the total cost of decolorization is accordingly reduced. The separated" wax although it contains the impurities left in it in the practice of my invention, may be subjected to a cracking distillation andthe distillate then filter-pressed and sweated in order to produce paraffine, the color being concentrated in the still bottoms. Or such separated wax may be used as a pressure still stock for the production of naphtha. If the dewaxed product is separately, i. e., after dewaxing, decolorized by treatment with clay an advantage is gained in the fact that itis easier to pass the dewaxed product through the clay than it is to pass a wax-containing product through the clay.

Another important advantage of my invention resides in the fact that my process is extremely fiexible with respect to the final a great 'variety of straight run viscous neu-l tral oils-can be produced that have ayvide range of flash tests Yand that have viscosities up to as high as one thousand seconds Saybolt at 1000]?.

Another important advantage of my invention resides in the fact that in dealing with Wax-bearing crudes containing a very large proportion of asphalt a .distillate may be produced by distillation vwhich may be satisfactorily deWaXed by my process and from Which .may be obtained cylinder stock or bright stock which cannot be obtained from these crudes by any other process and from which a much higher yield `of viscous neutral can be obtained than by the customary process involving cracking distillation of the crude and filter pressing to remove the wax.

From the foregoing it is apparent that lin the practice of my invention lubricating oils of loW cold test and comprising an exceptionally large proportion of viscous neutral oil and which are freed in the dewaxing operation of impurities that are the most diiiicult to remove may be obtained from dewaXing stock consisting of long residuum or a distillate that naturally contains certain impurities or that is prepared from long residuum or distillate by blending with products that contain desired impurities or that areprepared by simple operations from long residuum or distillate containing asphalt.

In the practice of this invention one feature is that the oil is brought to a condition which causes all of the Wax precipitated therein by reduction of temperature to be in that amorphous state in which it can be removed from the oil by processes suitable to the removal 5071 therefrom of precipitated amorphous Wax, in spite of the fact that the Wax in the oil is of such character that if theV oil Were in some other condition some of the Wax present would precipitate in crystalline form. That condition is arrived at in accordance With the' talline form. In the claims a statement that the precipitated Wax is in that amorphous state in which it is removable by processes suitable to removal of precipitated amorphous wax means ,that all of the precipitated Wax is so homogeneous and plastic that it is removable by such processes and remains in that condition until it is removed. Also, a

reference herein tov oil that contains crystalline Wax is intended as a reference either to oil which contains an insufficient quantity of amorphizing impurities to cause all of the precipitated Wax to be in such amorphous state-or is free of such impurities and which will upon reduction of temperature produce a Wax precipitate of which some part iscrystalline; or to oil which may or may not contain a quantity of such impurities sufficient to cause all of the Wax precipitated therein by reduction of temperature to be in such amorc-l phous state but which if first freed of such impurities in Whole or in substantial part, as

by such treatment as Iwould bring the oil to commercially desired color, Will upon reduction of temperature produce a Wax precipitate of which some part is crystalline; or to oil which may or may not contain a quantity of such impurities suicient to cause all of the wax precipitated therein by reduction of temperature to be in such amorphous state but which by non-cracking distillation Will produce an initial distillate that Will upon reduction of temperature produce a Wax precipitate of which some part wis crystalline. In short, oil that contains crystalline Wax is oil from which Wax can be recovered that is in lnon-plastic crystals (even though the oil in-4 long residuum contains so much asphalt that it is' desirable for economical reasons to produce the devvaXing stock by distillation of the long residuum and some hard asphalt or still residue is carried over into the distillate, it may be desirable to subject the distillate to a slight acid treatment to eliminate such hard asphalt or still residue priorto dewaxing. While I prefer, in the practice of my invention to separate centrifugally the precipitated Wax and the impurities that pass lout with it I do not limit my invention to that method of separation in every case; and in this conl\nection I consider that ani-tr known method of separating precipitated fw'aX from .the oil so long as non-pressable Wax and impurities other than hard asphalt or such impurities as may readily be removed by clay treatment gal dewaxing operations, such for example as the use of an auxiliary or carrier liquid Within the centrifugalbowl. The chilling step of the dewaxing operation may also be modified inknown respects.

The claims of this application are directed broadly to the ensuring of the presence in crystalline-waX-containin oil, prior to the deWa-xing of such oil and y addition thereto or otherwise and for the urpose of assisting` in dewaxing such' .crystal ine-WaxLcontaining oil, of amorphizing ,impurities of petroleum, and specifically to the ensuring of the presence in such oil in such manner and for such purpose of impurities other than hard asphalt and which naturally occur in petroleum oil and are commonly removed therefrom by extensive acid treatment or by extensive clay treatment; and to the dewaxing of oil containing such impurities. My copending application Serial No. 147,383, filed November 8th, 1926 is directed broadly to the regulating of the condition of crystalline-WaX-containing oil to the end that wax precipitated therein may be separated therefrom by methods suitable to the removal of precipitated amorphous wax, and broadly to the addition to crystalline-Wax-containing oil, for that purpose, of amorphizing substances, and specifically to the use "of such amorphizing substances as amorphous Wax alone or amorphous Wax together'with'-amor phizing impurities of which the use is claimed herein, and which are impurities other than hard asphalt which naturally occur in petroleum oil. A reference in the claims hereof to amorphizing impurities is intended as a reference to those impurities otherthan hard asphalt which naturally occur in petroleum oil and possess the property of causing crystalline wax toprecipitate in amorphous form, andis not intended to include wax that occurs in petroleum.

Having thus describedmy invention, what I claim as new and desire to secure by Letters Patent is: t l

1. The method of dewaxing the residuum remaining after the distillation of gas, naphtha and burning oils from Wax-bearing petroleum, which comprises subjecting the residuum to such acid treatment as will substantially remove hard asphalt therefrom While leaving therein other impurities' and thereby producing dewaxing stock, and then dewaxing the dewaxing stock Whilel it contains said other impurities by methods suitable to the removal of precipitated amorphous wax. y

' 2. The method of dewaxing the residuum remaining after the distillation of gas, naphtha and burning oil from wax bearing petroleum, which comprises substantially removing hard asphalt from the residuum While leaving other impurities and non-pressable Wax therein and thereby producing de. Waxing stock, and then dewaxing the dewaxing stock containing said other impurities b methods suitable to the removal of precipitated amorphous Wax.

3.v In the treatment of petroleum, the method of dewaxing petroleum products containing crystalline wax and amorphous wax which comprises forminga mixture of the oil containing crystalline wax and amorphous Wax with amorphizing impurities causing Wax precipitated' from the mixture by chill.-

ving to possess suiiicient plasticity and high enough specific gravity to be separable from the oil by centrifugal separation, -precipitat ing the Wax by chilling and centrifugally separating the oil and wax.

4. In the refining of petroleum, the method of removing waxY from petroleum oils containing crystallinewax and amorphous waxI which comprises forming a mixture of such oil and substancescommonly removed from petroleum oil by extensive acid treatment kor clay treatment, precipitating the Wax by chilling of such mixture and centrifugally separating the wax and oil.

y 5. In the refining of petroleum, the method of removing Wax from petroleum oils `containing crystalline Wax and amorphous wax Which comprises so regulating the condition of the mixture of oil and wax with respect to the amount and character of amorphizing impurities that the wax, upon precipitation by chilling y, after dilution,.is in a -state in which it is ,capable of being removed' from the oil by centrifugal separation, recipitating the Wax by chilling, and centri ugally separating the wax and oil.

6. In the dewaxing of petroleum oil that contains crystalline wax and amorphous waxthe step comprising reducing the temperature of the Oil and removing the wax which precipitates in amorphous form, while thel oil contains those impurities which naturally occur in petroleum oil and which cause all of the wax precipitated in the oil by reduction of temperature to be in an amorphous state.

be in that plastic state in which it is removable by processes suitable to the removal of precipitated amorphous Wax.

8. In the devvaxing of petroleum oil that contains amorphous Wax and also crystalline Wax the steps comprising reducing the temperature of the oil While it contains amorphizing impurities that naturally occur in petroleum oils Which cause all of the precipitated Wax to be in amorphous form, and centrifugally separating the precipitated Wax.

9. In the dewaxing of petroleum oil that contains amorphous Wax and also crystalline Wax, the steps comprising subjecting the oil to common purification continued to a point at which substantially the only impurities that remain in the oil and affect precipitation of waxupon reduction of temperature thereof are those impurities which cause Wax precipitated by reduction of temperature to be in amorphous form, reducing the temperature of the oil While it contains suiiicient of such impurities to cause all of the p recipitated Wax to be in amorphous form, and removing the 'precipitated Wax -by methods suitable to the removal of precipitated amorphous wax. A

10. In the dewaxing of petroleum oil containing crystalline Wax, amorphous Wax and impurities that occur in petroleum yand impair `the precipitation of Wax therein upon reduction of temperature thereof, the steps comprising removing such impurities by common purification methods, then reducing the temperature of the oil While it contains suiicient amorphizing impurities that occur in petroleum oil to cause all of the Wax precipitated by such reduction of temperature to be in amorphous form, and removing the precipitated Wax by methods suitable to the removal of precipitated amorphous Wax.

.11. In the deWaXing of petroleum oil that contains amorphous wax and crystalline Wax, the steps comprising producing a mixture of such oil and impurities that naturally occur in petroleum oil and which cause Wax precipitated from such oil to be all in an amorphous state, reducing the temperature of the resultant mixture While it contains suiicientof such impurities to cau-se all Wax precipitated as a result of the reduction in temperature to be in an amorphous state, and removing the precipitated wax by methods suitable to the removalof precipitated amorphous wax.

12.. .In the dewaxing of petroleum oil that contains amorphous Wax and crystalline wax, the steps comprising adding to such oil` in such quantity as to cause all Wax precipitated therein by reduction of temperature thereof to be amorphousin form, impurities that naturally occur in petroleum oil and which have the property of causing Wax precipitated in such oil to be amorphous in form, reducing the temperature of the resulting mixture and thereby precipitating Wax therein in amorphous form, and removing the Wax by methods suitable'to the" removal of precipitated amorphous wax.

13. In the treatment of "long residuum of petroleum remaining after distilling off gas, naphtha and burning oils from wax-containing crude petroleum and containing amorphous wax, crystalline Wax, hard asphalt and other impurities naturally occurring in petroleum, the steps comprising subjecting such long residuum to non-cracking distillation and thereby producing a distillate having a lower content of'hard asphalt than the long residuum and containing suiicient of such other impurities to cause all Wax precipitated in the distillateupon reduction 'of temperature thereof, to be in amorphous form, and reducing the temperature of the distillate and thereby yprecipitating Wax therein.

14. In the devva-Xing of petroleum oil that contains amorphous Wfaxjand crystalline waxl and impurities which naturally occur in petroleum and are other than those impurities which occur in petroleum and cause wax precipitated in the oil by reduction `of temperature to be in an amorphous state, the steps comprising subjecting such oil to such acid l treatment as will substantially remove said impurities contained therein, and then reducing the temperature of the resulting oil while l it contains, insuch quantities as to cause all wax precipitated therein by reduction of temperature thereof 'to be in amorphous form, impurities that naturally occur in petroleum oil and cause all of the Wax precipitatedtherein by reduction of temperature to be in an'amorphous state. l

15. In the dewaxing of petroleum'oil containing crystalline waX, amorphous wax, hard asphalt, and amorphizing impurities naturally occurring` in petroleum, the steps comprising subjecting such oil to non-cracking distillation and thereby producing a distillate having a lower content of hard asphalt than the original oil and containing suflicient of said amorphizing impurities to cause all of the Wax precipitated in the distillate upon reduction of temperature thereof to be in amorphous `form, subjecting the distillate to mild acid treatment to remove asphaltic impurities that interfere with precipitation of wax inthe distillate, and reducing the temperature of the acid-treated distillate and" thereby precipitating` WaX therein. 1 16; In the dewaxing of petroleum oil con-l taining wax the steps comprising reducing.`

the temperature, and thereby precipitating Wax therein, of petroleum o il which contains wax and is substantially free of hard asphalt and contains, in a concentration suiicient to cause the oil tobe of undesirably dark color and. insufficient to impair substantially the precipitation of Wax therein by reduction of temperature .and in such cbncentration that Wax precipitated therein by the reduction of temperature is all removable from the oil by continuous centrifugal separation, impurities that naturally occur in petroleum oil and 'are removable therefrom by clay strong acid treatment or both of such treatments, and removing the precipitated Wax from the oil, together with such of said impurities as accompany the wax removed from the oil, While the oil is at reduced temperature by methods suitable tothe removal of precipitated amorphous wax, and thereafter subjecting the residual dewaxed oil to treatment suitable to the removal therefrom of said impurities which remain therein to produce dewaxed oil of desired lighter color.

In rtestimony whereof, I have signed my vname to this specification.

LEO D., JONES.

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