US2064506A - Dewaxing lubricating oil - Google Patents

Description

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Original Filed March 7, 1934 2 Shee ts-Sheet 1 Char/xs C. 7wnz INVENTOR ATTORNEY Dec.`15,1936` c. c. 'rowNE l 2,064,506

DEWAXING LUBRICATING OIL Original Filed March '7, 1934 2 Sheets-Sheet 2 /f/:s ArroRNEY Patented Dec. l5, 193@ DEWAXHNG LUBRIICATHNG @lIlL @riginal application March 7, 1931i, Serial No.

Divided and this application @ctober 24, 1934, Seriali N0. 749,69

5 Claims. (Cl. 19d-19) This invention relates to dewaxing of mineral lubricating oils, and particularly to the dewaxing of such oils with the aid of a wax crystal modifying material.

One of the objects of the invention is to provide a method of dewaxing a Wax bearing oil by the employment of a wax crystal modifying material obtained from the pyrclysis` of normally gaseous hydrocarbons, such as fixed refinery gases or oil gas from cracking stills.

This is a division of my co-pending application Serial No. 714,360, led March 7, 1934, wherein is disclosed and claimed the method of lowering pour point and imparting bloom to a mineral lubricating oil by addition of materials described herein, as Well as the resulting products produced thereby.

It has heretofore been suggested that a wax crystal modifying material for facilitating dewaxing of mineral oils can be prepared from the residuum of distillation of a petroleum oil. However, this has necessitated the employment, as starting materials, of mineral oils which could otherwise be used for the preparation of more valuable products. Furthermore, this has necessitated special distillation equipment and processing, in order to produce a wax crystal modifying material of acceptable character.

I have discovered that a very satisfactory wax crystal modifying material of this character may be prepared from hydrocarbon gases, such as oil gas from cracking stills, or other waste gases from oil refineries. Other hydrocarbongases of a similar nature, such as natural gases, fixed gases from the stabilization of natural gasoline, storage relief gases, as Well as individual constituents thereof including propane, butane, etc., and mixtures thereof, may be employed for this purpose.

According to the present invention, the hydrocarbon gases are subjected to high temperature polymerization in a cracking still. This may be accomplished in connection with a plant for the manufacture of benzol and its homologues from hydrocarbon gases by polymerization thereof, in accordance with my Patent No. 1,943,246, dated January 9, i934. High temperature pyrolysis has the usual significance of this term in the art,-namely, a pyrolyss in which the gases are passed through a heating coil or Zone at a temperature in excess of 1150 F., and generally at temperatures varying between 1150* F.2000 F. Known types of catalysts may be employed, either as porous catalysts within the heating tubes, or as materials constituting the heating tubes. The

gases may be maintained at substantially atmospheric pressure, or they may be passed through the heating coil under superatmospheric pressure varying up to 500 lbs. per sq. in. or higher. The polymerized gases are then passed to a cooling zone, such as a water cooled condenser, where the temperature is controlled to separate primarily high boiling constituents, mainly above the boiling points of benzol and homologous hydrocarbons of the benzene series. In this manner. there is condensed a liquid fraction comprising a heavy black oil. Depending upon the temperature of condensation, this material will usually comprise a small proportion of benzol and naphthalene in admixture with a tarry residue. The latter is found to be highly concen trated in wax crystal modifying material. The condensate oil may be mixed directly with a wax bearing oil which is to be dewaxed; or a concentrated extract of the wax crystal modifying material may be obtained from the condensate oil by suitable methods, such as distillation or solvent extraction, and the concentrated extract then added to the wax bearing oil.

Referring to the drawings, Fig. l is a flow sheet of the process of dewaxing in accordance with the present invention; and

Fig. 2 is a diagrammatic view of apparatus for preparing the wax crystal modifying material used in the dewaxing process of this invention.

Referring to Fig. 2, I@ indicates a cracking furnace containing a coil II through which the hydrocarbon gas Is passed and heated to a high temperature such as ordinarily used in gas pyrolysis operations. The products of pyrolysis are discharged into a water cooled. condenser I2, to which cooling water is supplied by line I3 and discharged by line Il. The products pass upwardly through tubes I5 of the condenser, uncondensed gases escaping by pipe I6 leading to a fractionating tower Il where various lower boiling constituents, including benzol, may be separated. The gas outlet temperature of the condenser IR is preferably controlled to about 400 F. or above. so that mainly high boiling constituents are condensed therein. These constituents form a black oil which runs down the tubes I5, accumulating in the lower portion of the condenser, and discharging by the line 2l). Although normally solid compounds are present in this oil,

the liquid constituents maintain them in solution,

4I, to which is added a dewaxing solvent from tank 42. The wax bearing oil mix is then passed through chilling coils 43. Filter aid, prepared in the form of a slurry, may be added from tank 44 by line 45 to the wax bearing oil mix in mixer 4l prior to chilling, or by line 46 to the chilled mix subsequent to passage thereof through the chiller.

AThe chilled mix is then filtered on filter 41, the

wax and filter aid being discharged at 48, and the lfiltrate oil passing to a solvent stripper 49. In the stripper, the solvent is removed and returned by line 50 to the solvent storage 42, and the wax free oil is passed to tankage 5l.

This condensed oil may be added directly to a wax bearing oil to facilitate dewaxing thereof. Or, ifdesired, the condensed oil maybe treated or purified prior to use, such as by simple filtration, or by heating/in contact with an adsorbent material followed by filtration, or by acid treatment or other conventional treatments employed in the refining of petroleum oils. This is indicated in the drawings, in which the pipe 20 discharges into a refining tank 2| to which suitable chemical may be introduced by pipe 22. If de sired the oil may be treated to prepare a `concentrate therefrom; as it is found that the wax crystal modifying materials in the oil consist mainly of high boiling constituents which remain in the tarry residue resulting from reducing the oil by distillation, or are dissolved from the oil or residue by solvent extraction. However, it is not necessary that any of these refining or concentrating treatments be employed, as the condensate recovered from condenser l2 may be employed directly for dewaxing.

The condensate, whether treated .or not in the 'refining tank 2|, is passed by une 24 to either valve controlled line 25 leading to receiver 26, or valve controlled line 21 leading to receiver 28. From the receivers 26 and 28, the oil or' concentrate is passed by lines 29 and 30 respectively to a mixing tank 32, to which the wax bearing oil d to be treated is admitted by line 33. The mixed oil and dewaxing aid is then passed by line 35 to storage tank 36, from which it is withdrawn by line 31 to suitable chillers and dewaxing equipment.

As a specific example of the preparation of a dewaxing aid of the present invention, an oilgas obtained from vapor phase cracking stills, is `passed through a. silica tube 20 mm. in diameter by 48 in. in length at thel rate of 0.6 cu. ft. per hour, the tube being maintained at a temperature of 14501500 F. Issuing vapors are cooled in a water cooled condenser having a vapor outlet temperature of approximately 450 F. A black condensate oil is thereby obtained in the amount o f approximately cc. per 4 to 5 cu. ft. of gas tmfated.

The addition of. a small proportion of the heavy condensate, or extracts thereof, to a wax bearing oil, is found to modify wax crystal formation upon chillinglof the oil to thereby facilitate separation of the wax `from the oil by centrifuging or cold settling. It is also found that the addition of a wax crystal modifying material of. this character to a wax bearing oil results in substantially increasing filtration rates, where the wax is separated from the chilled oil by filtration.

The employment of products of the present invention .along with a solvent in which both the solid and normally liquid constituents are soluble at elevated'temperatures of the order of 100 F. or above, and in which the normally liquid constituents are soluble but the normally solid constituents or waxes are substantially completely insoluble at lowered temperatures of the order of 0 F. to 20 F., is found particularly beneficial. Various solvents of this character may be employed, such for example, as acetone, ethylene dichloride, methyl ethyl ketone, liquid sulphur dioxide, naphtha, propyl alcohol and the like. Mixtures of. such selective and non-selective solvent liquids are also satisfactory. For example, a very suitable solvent mixture capable of servl0 ing as a dewaxing solvent consists of acetone and benzol, for instance in the proportions of 35%, acetone and 65%l benzol. Another very suitable solvent mixture, particularly for the dewaxing of residual oils, consists of about ZES-35% acetone, 15 47-57% benzol and 15-18% toluol.

By way of example, a proportion of from 1 to 10% by weight of the heavy condensation product obtained from the pyrolysis of oil gas. as described above, may be added to a wax bearing lubricating oil fraction, together with a sol-- vent mixture of 35% acetone and 65% of benzol in the proportions of one part of oil to three parts of the acetone-benzol mixture. The oil is then chilled to a temperature of around 0 to -10 F. and subjected to settling at this temperature. The wax constituents settle rapidly from the mixture, the supernatant liquid layer of oil and solvent may be drawn off, and the solvent removed therefrom by distillation. According to another method of operation, the chilled mixture may be subjected to centrifuging with satisfactory separation of the wax from the oil. In still another method of operation, the chilled mixture may be subjected to dewaxing by pressure filtration, and the filtering rates be mark-A edly increased over the rates obtained when the condensation product of the present invention is not added. Where a solvent mixture of the character of acetone-benzol or acetone-benzoltoluol is employed, the resulting wax free oil is found to have a pour test of around 0 F. when chilled only to about 0 F. or slightly below.

Very satisfactory results are also secured by` adding to th'e wax bearing oil a filter aid material, such as an acid treated clay or fullers earth. 'I'his is found beneiicial'when used in conjunction with the'wax crystal modifying material and also with the solvent or solvent mixture.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made withoutv 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 method of dewaxing a mineral wax bearing oil, which comprises mixing with the oil a fraction boiling above 450 F. recovered from the high temperature pyrolysis of a normally gasmodifying wax crystal formation upon chilling of the oil, chilling the mixture to precipitate the wax, and separating the wax from the oil.

2. The method of dewaxing a mineral wax bearing oil, which comprises mixing wit-i the oil a fraction boiling above 450 F. recovered from the high temperature pyrolysis of a normally gaseous hydrocarbon and having the property of modifying wax crystal formation upon chilling of the oil such as to increase the filtration rates thereof, chilling the mixture to precipitate the wax, and separating the wax from the oil by filtration.

3. The method of dewaxing a wax bearing oil,

which comprises mixing with the oil a solvent selective between the normally liquid and normally solid constituents of the oil and in which the normally liquid constituents aresoluble at lowered temperatures while the normally solid constituents are substantially insoluble, together with a fraction boiling above 450 F. recovered from the high temperature pyrolysis of a normally gaseous hydrocarbon and which has the property of modifying wax crystal formation upon chilling of the oil, chilling the mixture to precipitate the wax', separating the wax from the oil, and recovering the solvent from the dewaxed oil.

4. The method of dewaxing a wax bearing oil, comprising mixing" with the oil a solvent mixture comprising acetone and benzol, together with a fraction boiling above 450 F. recovered from the high temperature pyrolysis of a normally gaseous hydrocarbon and which has the property of modifying wax crystal formation upon chilling of the oil, chilling the mixture to precipitate the wax, and separating the wax from the oil.

5. The method of dewaxing a wax bearing oil, comprising mixing with the oil a filter aid material and a fraction boiling above 450 F. recovered from the high temperature pyrolysis of ,a normally gaseous hydrocarbon and which has the property of modifying wax crystal formation upon chilling of the oil, chilling the mixture to precipitate the wax in the presence of the iilter aid material, and separating the wax and iilter aid material from the oil.

CHARLES c. ToWNE.

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