US1792234A - Process of treating hydrocarbon oil - Google Patents

Description

I"el:.'l0,v 1931. R. E. MANLEY Y PROCESS OF TREATING HYDROCARBON OIL Filed April 15, 1927 By ATTORNEY i Patented Feb. 10, 1931A UNITED STATESI PATENT ol-Fica y ROBERT E. MANLEY, OF PORT ARTHUR, TEXAS, ASSIGNOR TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF TEXAS PROCESS OF TREATING HYDROCABBON OIL Application iiled April 15,

` of the comparatively non-volatile wax in the more viscous residual fraction of the oil. In

order to produce a merchantable grade of.

lubricating oil from such sources it is necessary to remove the greater portion of the wax from the oil and usually it may be said that a small content of paraffin wax, whichv is indicated by a low pour test, renders the lubricating oil more desirable and more val-V uable from a marketing standpoint.

Therefore, in the relining of paraiiin base lubricating oils it is customary to practice dewaxing on a large scale. The usual 'procedure followed in the dewaxing operations is to chill the oil to such an extent that portion of the wax content is precipitated, after which the chilled oil, in which the precipitated wax remains suspended, is passed through a filter or through suitable centrifuge apparatus wherein the oil and wax are ods of dewaxing by chilling and precipitation may be considered eii'ective in producing a pour test in the treated oil suiicient to meetV commercial requirements, they are usually quite expensive, due to the fact that the oil must be chilled to quite a low temperature in order to obtain a fair degree of dewaxing. This is because of the fact that the paraihn wax material contained in the oil is not bodies ranging from those having melting points as high as 160 F. to those melting at below 100 F., these lower melting bodies approaching the oil itself in their characteristics. Therefore, when oil containing disseparated. Although the conventional meth? homogeneous, but consists of hydrocarbon 1927. serial No. 184,176.

solved paraiiin wax is chilled,l the higher melting paraiiin hydrocarbons are easily precipitated in such form as to allow satisfactory separation by filtration whilev on the other hand a much lower temperature is required to precipitate the lower melting paraiiins, and ity is found that when so precipitated uan amorphous mass is formed, which is very dificult to separate by filtration or by other means. p l

My experiments have disclosed the fact that paran wax may bezseparated from viscous hydrocarbon oil with which it is normally associated by means of distillation. Ordinarily the vapor pressures of the solid and semi-solid' paraiins are so nearly the y same as the vapor pressures of the heavier and more viscous hydrocarbon oils with which they are associated that the tweema-` terials distill together without appreciable separation. However, I have discovered that if a more Volatile and wax-free hydrocarbon oil of proper physical characteristics be added to a body of viscous wax-bearing oil and the whole subjected to distillation under proper conditions the more volatile oil may be distilled oli, carrying with it the parattn wax and leaving undistilled the viscous hydrocarbon oil. The less viscous oil, which; for the purpose 0f identification I shall hereinafter term a carrier oil, is desirably waxfree and will normally be of the characteristics of the lighter lubricating oil or gas oil fractions of petroleum, although less volatile than the kerosene fraction. Due to the fact that the lighter gasoil and lubricating oil fractions -of the naphthene base crude petroleums are naturally wax free they are especiallyadapted as carrier oils in the process of dewaxing by distillation.

In its simplest aspect the process may consist of a batch distillation inwhich a viscous tinuously' introduced therein, distillation being maintained at such rate as to cause the carrier oil together' with a portion of the araihn wax .to be continuousl distilled oi rom the viscous oil. It will e understood that thev distillation durin which dewaxing vis effected iscarried on un er conditions that preclude the occurrence of any appreciable decomposition, as such decomposition would materially reduce the quality of the finished dewaxed oil. It is, therefore, preferable that the distillation be carried on with the aid'i'v steam or other suitable vapo-r or gas, or it may be carried out under reduced pressure, and it has been found that distillation under high vacuum not only prevents decomposition but is advantageous in the more complete removal of wax effected. v

The invention is particularly adapted to be used in connection with some of the known processes of dewaxing in which the paraffin wax is lprecipitated-from the oil by cooling. In the process of vdewaxing by distillation the lower melting waxes are more easily removed than those of higher melting points on account of their comparatively greater volatility, while on the other hand, the higher melting waxes are much more easily precipitated upon chilling than are the lower melting waxes. Therefore, a viscous waxcontaining oil which has had a preliminary dewaxing treatment by distillation may be very easily treated by any of the methods involving chilling and precipitation to-yield a completely wax-free oil of very low cold test. A method of cold treating hydrocarliltration. In such a process the comminuted solid material acts as a lter-aid in that it aids the process of filtration by causing the cake of paraiiin wax which is built up on,I the ilter'surface to be porous, thus allowing efficient filtration of the wax from the oil.

. In order that r the invention may be more clearly understood, an example of aifappli-v.

cation thereofgto'fthe dewaxing of a viscous,

. wax-bearing lubricating oil will be described, it being understood that the material used and the conditions described are given only for the purpose of 4illustrating the invention. Eer this illustration a wax-bearing, viscous .lubricating oil of the typergenerally known as cylinder stock will be selected. Such oil will have the approximate physical characteristics indicated by a iiash test of about 525 F., viscosity of about 150 seconds at 210 F. (Saybolt universal), and pour test of about 90 F. The paran wax content of the cylinder stock, as indicated by analysis, is approximately 9 per cent by weight.I

The procedure in dewaxing such an oil by the method involved in the present invention may be as follows: The cylinder stock is placed in a suitable still and is heated to a temperature of approximately 550 to 6000 F., and is maintained at this temperature while a carrier oil consisting of a light asphalt-base lubricating oil of approximatelyA 90 to 100 seconds at 100 F. (Saybolt universal) is continuously introduced into the body of oil in the still. Decomposition of the cylinder 'stock during the heating and distillation is avoided by introducing steam below the surface of the oil in the still, and a pressure less than atmospheric may be maintained upon the still by suitable means. Under the given conditions the less viscous asphalt-base carrier oil is rapidly and continuously distilled from the cylinder stock, carrying with it a portion of the parafiin wax. As the lower melting wax contained in the cylinder stock has a comparatively lower boiling point than the higher melting wax with which it is associated, the portion of wax which distills over with the carrier oil during the earlier stages of the distillation will be of the low melting point variety, and in general, it may be said that as the distillation progresses the wax carried over with the carrier oil increases in melting point and decreases somewhat in the relative quantity distilled. .A y

The distillation of thecarrier oil together with the wax may be continued until a minimum quantity of wax remains in the cylinder stock. However, it has been-found particularly advantageous to carry on the process in such a manner that only about one-third of the wax content of the cylinder stock is distilled oil". Analyses indicate that the greater portion of the lower melting point wax will have been removed at this point and further dewaxing may then be accomplished rapidly and eiiiciently by means of one of the previously known treating processes. Thus, in the example used as an illustration of the invention the cylinder stock. at the be- .;:fginning of the dewaxing operation, has a wax content determined by analysis of approximately 9 per cent. After dewaxing by distillation with the carrier oil has been carried on until the wax content has fallen to 6 per cent, analysis indicates that the bulk of the lower melting wax has been removed.

Thequant-ity of carrier oil which must be distilled from the wax-bearing oil to eecta given degree of dewaxing will vary with the individual characteristics of the waxbearing oil. For example, some wax-bearing oils may contain a much higher melting point wax than others which would require that more carrier oil be distilled to effect the removal of any given percentage of wax. In connection with the example discussed in previous paragraphs, the quantityof carrier oil which may be distilled from the wax-bearing oil to effect the reduction of the wax content from 9% to 6% may be an approximately equal volume of carrier oil.

When the partial dewaxing by-distillation has been effected to the desired degree, that is, when the bulk of the lower melting wax has been removed, the cylinder stock is cooled to about normal temperature after which it is diluted with approximately 50 per cent by volume of petroleum naphtha and the mixture is -then chilled to a sufficiently low temperature to effect precipitation of the remainl ing paraffin'wax. The' temperature at which the oil must be chilled will dependv upon the desired cold test of the finished product but in this particular instance it is found that chilling to a temperature of 25 will be sufficiently low to yield a finished dewaxed cylinder stock which will have a pour test not exceeding` 25 F. After the diluted cylinder stock has been chilled it is thoroughly mixed with a relatively small portion of a comminuted solid material such as diatomaceous earth which will serve the purpose of a filter-aid. The proportion of lter aid material used may be varied over a fairly wide range but an economical and satisfactory y quantity may be about 4 to 6 pounds of filteraid material for each barrel of diluted cylinder stock. The' chilled mixture of diluted oil, precipitated wax, and filter-aid material is then forced through a suitable filter, such for example as a Kelly type pressure filter, where separation of the oil from the wax and the filter-aid material is effected. The diluent may then be separated from the cylinder stock by proper distillation and it will be found that the finished oilwill have a pour test of approximately 25 F. and is substantially wax-free.

Although the dewaxing of a residual cylinder stock has been described for the purpose of illustration, the invention is equall adapted for the dew-axing of distillate oils. For example in the manufacture of high viscosity distillate lubricating oils from paraflin base crude petroleum a distillate fraction having a viscosity of about 300 seconds at 100 F. (Saybolt universal) may be obtained, preferably from a vacuum distillation of the crude petroleum, the constituents of which will range from about 60 to 900 seconds viscosity at 100 F. Such a distillate fraction will contain both-high and low melting paraffin wax, and thedewaxing process carried on in accordance with the present invention may consist in first chilling the oil to about 30 F. then mixing with a small proportion of diatomaceous earth or other suitable filter-aid material and then filtering .off

the precipitated wax and filter-aid material from the oil. Itmay lbe found necessary to dilute the oil with a suitable solvent such as petroleum napt-ha before chilling in order to aid material at about 30 F. effectually removes the higher melting wax and the oil may then be subjected to fractional distillation, preferably under a vacuum, to separate it into its various fractions and at the samev time effect aconcentration of the lower melting wax in certain fractions of the oil. Under the given conditions the lower melting wax remaining in the' oil after the chilling and filtering operation is distilled off with the more volatile fractions of the distillate and it is found that the more viscous fractions of the oil are thus rendered substantially wax-free and of a satisfactoryT low cold test. In such an operation the addition of an extraneous carrier oil to the oil which is to be dewaxed is not required as the lighter fractions of the wax-bearing oil itself, after the higher melting wax has been removed by chilling and filtration, serve as the carrier oil for the removal of the lower meltingwax by distilladerstock, the removal of low melting wax by dlstillation with the carrier oil preceded the chilling and precipitation of the higher melting wax, but in the dewaxing of the distillate oil the'ste of .chilling and precipitating the hlgher me ting wax preceded the removal of the lower melting wax by distillation.

connection with the use of a carrier oil. may be carried on by various methods, perhaps the most simple of which is that described in the fore oing example consisting in mixing the waxcaring oil with the carrier oil and subjecting the mixture to distillation in a y suitable still. However, other methods of procedure may be employed in the practice of the invention audit may be found desir-A able and advantageous to carry on the process of dewaxing in such manner that a body of Wax-bearing oil is maintained at an elevated temperature in a suitable vessel, while vapors of a carrier oil generated in a separate vaporizing apparatus, are continuously introduced into the vessel in contact with the heated body of wax-bearing oil. Thus vapors of the carrier oil carrying with them paraffin wax are continuously evolved from the mass of wax-bearing oil. In such a process it may be found desirable to carry on the contacting of the heated wax-bearing oil withthe vapors of the carrier oil in a suitable apparatus which will produce counter-current flow of loil without the use of an extraneous carrier ,A 1mi The process of dewaxing hydrocarbon oil in the oil and vapors, thereby bringing about more eliicient separation of wax with a given quantity of the carrier oil.

The accompanying drawing illustrates diagrammatically one form of apparatus which may be used for carrying out theprocess of the invention.

' In the apparatus illustrated in the drawing, there is provided a source of wax-bearing oil, such as the tank 11, connected by the line 12 to the pump 13 and thence to the heating coil 14 situated within the furnace 15. The line 16, provided with a valve 17, leads from the heating coil to a distilling vessel 18, which may be of the typeof distilling or fractionating column containing a plurality of trays or plates and generally known as a bubble column.

There is provided also a source of a suitable carrier oil, such as the tank 21, connected by the line 22 to the pump 23, -and Vthence tothe heating coil 24 situated within the furnace 25. The heating coil 24 is connected by means of the line 26, in which is. provided a valve 27, to the distilling vessel 18.

At the bottom of the distilling vessel 18 there is provided a line 31, and valve 32, for the withdrawal of liquid which may collect within the lower portion of thefvessel. A connection 33 is provided with a valve 34 for the introduction of steam within the lower portion of the vessel. A float 35 is provided for indicating the level of liquid collected in the lower portion of the vessel 18,

vte

and this may be connected to the valve 32ste provide automatic regulation of the liquid level. v

In the upper portion of the vessel 18 a cooling coil 41 is provided for the production of such reflux cooling as may be necessary.

lThe vapor line 42 leads from the upper portion ofthe vessel tothe condenser 43 which is connected to the receiving drum 44. From the lower portion of the receivingA d rum 44, the line 45 is provided for withdrawing the liquid condensate which maycollect therein. From the upper portion of the receiving drum 44 a line 46 leads to a vacuum pump 47. The line 46 is also provided with a branch line 48 and valve 49 leading to the atmosphere.

The line 31, from the lower portion of the distilling vessel 18, passes through a suitable cooler 51 and Ithence to a pump 52 connected to a chiller 53, which may be of any of the well-known types suitable for chilling oil to low temperatures. The chiller is connected by means of the line 54 to a filter 55, from which a connection 56 is provided for Withdrawing filtered oil, and also suitable means 57 for withdrawing the filter cake. A line 58 is provided between the cooling coil 51 andthe pump 52, whereby the oil from they vessel 18 may be Withdrawn to storage if desired.

The process of the invention may belopafter which it flows downward over the plates or trays in the vesselunder the influence of gravity. At the same time, carrier oil from thetank 21 is pumped by means of the pump 23 through the heating coil 24 and thence into the distilling vessel 18 at a point lower than that at which the wax-bearing oil is introduced into the vessel. The temperatures at which the wax-bearing oil and the carrier oil are introduced into the distilling vessel 18 are so controlled that a temperature of from 600 to 650 F..is maintained in the pool of oil collected in the bottom of the distilling vessel. The vessel 18 is preferably heavily insulated to avoid a reduction in temperature therein.

Steam is introduced into the lower portion v of the distilling vessel through the connection 33 in such quantity as to provide for a substantially complete volatilization of the carrier oil, whereby theoil withdrawn through the connection 31 will be substantially free from such carrieroil. Cooling may be applied to the upper portion of the Ivessel 18 through the circulation of a cooling medium through the coil 41, although normally this will be unnecessary asv the 'temperature of the wax-bearing oil introduced through the connection 16 may be varied so as to provide the necessary amount of cooling. In any event, the temperature is regulated so as to revent substantial distillation of the waxcaring oil through the vapor line 42 and into the condenser 43.

he rates of introduction of .both carrier and waxfbearing oils are so adjusted that the 'process becomes continuous, withdrawing from the lower portion of the distilling vessel 18 the dewaxed oil, while the vapors passing over through the vapor line 42 consist of the waxing by distillation, after collecting in the lower portion of the distilling vessel 18, is

withdrawn through the line 31 and through the cooling coil 51,. Thereafter, it may be led to storage through the line 58, or may be subjected to chilling and4 filtration. When so processed, the oil is forced by means of the pump 52 through the chiller 53, wherein it is chilled to a temperature suitable for precipitating remaining wax `constituents,

and the chilled oil is then forced through the filter 55, v.wherein the precipitated Wax constituents are separated from the oil. The dewaxed oil is withdrawn from the filter through the line 56 to storage, and the lilter cake 1s discharged from the ilter through the means 57.

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 separating paralin wax from Wax-bearing hydrocarbon lubricating oil which comprises mixing with the waxbearing oil a suitable more volatile carrier oil from an extraneous source, said carrier oil being less volatile than kerosene, and then distilling off thecarrier oil together with the paralin Wax.

2. The process of se arating paraffin wax from wax-bearing hy ocarbon-lubricating oil which comprises mixing with the waxbearing oil a suitable more volatile carrier oil derived from a naphthene base crude-petroleum, said carrier oil being less volatile than kerosene, and then distilling ol the carrier oil together with the parainwax.

3. A process of separating paraiim wax from wax-bearin hydrocarbon lubricating oil which comprises maintainin` la heated body of the wax-bearing oil into w 'ch a suitable more volatile carrier oil from an extra` neous source is continuously introduced, said carrier oil being less volatile than kerosene, and continuously distilling oi the carrier oil together with a portion of the paraffin-wax until the desired quantity of the wax has been removed.

4. The process of separating parain waxoil which comprises mixing the waxbearing oil a suitable more volatile carrier high-melting wax and separating the precipitated wax from the oil.

The process of separating parain wax from Wax-bearing hydrocarbon lubricating oil which comprises passing a stream of heated wax-bearing oil in counter current and in direct contact with the vapors of a suitable carrier oil whereby distillation of

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