US2564071A

US2564071A - Refining oils

Info

Publication number: US2564071A
Application number: US681123A
Authority: US
Inventors: Arthur P Lien; Bernard L Evering; Frank W Hacckl
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1946-07-02
Filing date: 1946-07-02
Publication date: 1951-08-14
Anticipated expiration: 1968-08-14

Description

Aug. 14, 1951 A P. LIEN ETAL REFINING OILS Filed July 2, 1946 *SSS atentecl ug. 14, 195i REFINING OILS Arthur P. Lien, Hammond, Ind., Bernard L. Evering, Chicago, Ill., and Frank W. Haeckl, Detroit, Mich., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application July 2, 1946, Serial No. 681,123

14 Claims. 1

'I'his invention relates to a novel process of treating hydrocarbon oils. More particularly it relates to a novel process for refining hydrocarbon oil-s to remove non-hydrocarbon components such as water, inorganic salts, compounds of oxygen, ni-trogen and, especially, sulfur and the like. The application of the process of the present invention to hydrocarbon lubricating oil stocks leads to the lproduction of high viscosity index (V. I.) lubricating oils containing substantially no inorganic components and a reduced or negligible content of low V. I. aromatic hydrocarbons.

It 'is known to renehydrocarb-on oils -by treatment with liquid hydrogen fluoride, as described, for example in British Patent 292,932. It is also known -to refine hydrocarbon oils with solutions of BFa in liquid hydrouoric acid, as described for `example in United States Letters Patent 2,343,841. However, the prior art processes suffer from certain disadvantages. We have discovered that unexpected advantages and results can be obtained by treating hydrocarbon oils in sequence with hydrogen fluoride and with liquid HF-BFs.

lWe have found that liquid hydrogen fluoride has a relatively limited capacity to increase the visc'osity index of any given lubricating oil stock; Also, although liquid hydrogen fluoride is a fairly eflicient -solvent for sulfur compounds contained in hydrocarbon oils, it appears that certain sulfur compounds such as high molecular weight mercaptans, for example n-dodecyl mercap-tan, exhibit little or n'o solubility in liquid hydrogen iluoride at ambient temperatures.

Although liquid ELF-BFE; is an extremely active desulfurizing agent for hydrocarbon oils, the BFa componentl thereof is quite expensive and is readily1 converted by water to inactive BFS hydrates from which the BFa can be recovered only indirectly and at great expense and difiiculty. Since most unrened hydrocarbon oils normally contain a not inconsiderable quantity of water, the direct application of liquid HF-BFs thereto is unduly expensive and must be preceded by a dehydration operation which adds to the expense of the rening process. Most hydrocarbon oils contain some sulfur compounds which are readily removable by less powerful re'agents than liquid HF-BFa and at considerably less expense. It is, therefore, desirable, in view of the high relative cost -of liquid I-l'F-BF3, to segregate readily removvable sulfur compounds from hydrocarbon oils by a less expensive reagent and to reserve the employment of liquid IIE-EP3 for difficul'tly removable sulfur compounds.

In the treatment of hydrocarbon lubricating oil stocks vfor the purpose, inter alia, of increasing viscosity index, the direct application of liquid HF-BFs to the stock causes very substantial treating losses due in part to the fact that the HF-BFa or the HF-Bli's extract exhibits undesirable solvent capacity for high V. I. paratnic componen-ts 2 of lubricating oil stocks. application of liquid HF-Bl's to lubricating oil stocks leads not only to aggravated losses due to excessive extraction, but also to -products of lower viscosity index than those which can be obtained by the pro-cess of this invention, as will be described hereinafter.

We have found that the treatment of hydrocarbon oils with hydrogen fluoride followed by treatment of the resultant partially refined oils with liquid HF-BFa avoids the disadvantages associated with the employment of these treating agents alone.

It is an object of this invention to provide a novel process for the treatment of hydrocarbon" oils, which process comprises contacting said olS with hydrogen fluoride, separating .partially refined hydrocarbon oils from the products of the hydrogen fluoride treatment and thereafter con# and nitrogen from hydrocarbon oils, in which process a hydrocarbon oil containing lone or more of the aforesaid undesirable constituents is intermingled or contacted with liquid hydrogen fluoride, the resultant mixture is then separated into two liquid layers, viz. a partially rened hydrocarbon oil layer and a hydrogen fluoride extract layer which contains impurities removed from the hydrocarbon cil, and the partially rei-ined hydrocarbon oil is thereafter intermingled wi-th liquid HF-BFs to effect the substantially complete removal of impurities.

A further object of this invention is to provide a process for treating hydrocarbon lubricating oil stocks in lsequence with liquid hydrogen fluoride and liquid HF-Bls to Produce lubricating oils of higher viscosity index than could be obtained by the application of either reagent alone, which process is accompanied by unexpectedly low treating losses.

An additional object of this invention is to provide a process for refining hydrocarbon oils with liquid HF-BFa in the presence of low-boiling saturated hydrocarbons, whereby cracking of said hydrocarbon oils is inhibited or substantiall eliminated. q

In the first stage of the process of this invention the hydrocarbon charging stock is partially ref-ined by being intimately contacted with hydrogen fluoride. The general temperature range within which contacting with hydrogen fluoride is feasible lies between about 0 F. and about 450 F. Ordinarily, it is desirable to effect contacting under suiiicient pressure to maintain both the hydrocarbon ycharging stock and most, if not substantially all, of the hydrogen fluoride in the liq- As a result, the direct uid phase. However, this is not to be taken as the invariable rule, for there are some instances in which hydrogen fluoride vapor may be applied to a liquid or liquefied hydrocarbon charging stock to effect partial refining thereof. For example, We have observed that if hydrogen fluoride vapors are passed into a sulfur-containing hydrocarbon oil, the oil absorbs hydrogen fluoride and, in time, a liquid layer containing hydrogen fluoride and sulfur compounds settles from the oil, leaving a supernatant rainate oil of reduced sulfur content.

As will be shown hereinafter, contacting of a hydrocarbon oil with liquid hydrogen fluoride at temperatures above about 200 F. results in appreciable cracking, as evidenced by the production of hydrocarbons boiling below the initial boiling point of the charging stock. It is believed that when the extent of cracking is limited, for example to about 2O weight per cent of the charging stock or less, the low V. I. constituents of the oil are selectively cracked. Cracking is accompanied by condensation oi low V. I. aromatic hydrocarbons having relatively low solubility in liquid I-IF to polynuclear aromatic hydrocarbons whichV are readily soluble in liquid HF and are therefore extracted by the HF. Cracking of the low V. I. constituents of hydrocarbon oils is accelerated by the concurrent employment of temperatures between about 200 F. and about 450 F., preferably between about 300 F. and about 450 and relatively large volumes of hydrogen fluoride, e. g., 50, 100 or even 200 volume per cent or more of liquid hydrogen Afluoride based on the volume of the hydrocarbon charging stock.

The quantity of hydrogen fluoride which will be applied in the first step of our process will be dependent to some degree on the nature of the hydrocarbon charging stock and on the degree of refining which is being sought. However, a generally applicable range comprises a liquid hydrogen `fluoride volume between about 5 per cent and about 100 per cent, based on the volume of the hydrocarbon charging stock being treated, although an even larger volume of hydrogen fluoride, e. g., 200 volume per cent, may sometimes be desirable.

The contacting between the hydrogen fluoride and hydrogen charging stock may be effected in conventional equipment constructed of hydro gen uoride-resistant materials. As a 'general rule, hydrocarbons are substantially immiscible with liquid hydrogen fluoride and are of lower density. Accordingly, liquid hydrogen fluoride lends itself readily to counterow contacting with hydrocarbon oils. Ordinarily, contacting .between the hydrogen fluoride and the hydrocarbon charging stock may be effected by counterflowing the charging stock and liquid hydrogen fluoride in a tube or tower which may, if desired, be packed with hydrogen iiuoride-resistant spacing materials to cause intimateoontacting between the two-streams. The contacting tower may be operated in such fashion that it contains a major amount of hydrogen uoride or of the hydrocarbon charging stock. When the contacting tower is operated rich in hydrogen fluoride, the hydrocarbon charging stock may be introduced into the liquid hydrogen uoride phase and will ascend therethrough and will ultimately leave the contacting tower at or about its top. In this case the hydrogen fluoride phase becomes rich in extracted materials, e. g.,`.sulfur compounds and/or low V. I. 'aromatic hydrocarbons, and the extract layer itself can operate as a solvent to promote better refining of the charging stock.

It should be understood that the process of this invention is not limited to particular meansor methods for eiecting contact between hydrogen fluoride and the hydrocarbon charging stock. Other methods of contacting than those described above may be employed, such as concurrent flow of charging stock and hydrogen fluoride, mechanical stirring, orifice mixing and settling, etc. Regardless of the method of contacting, a multiplicity of contactor's maybe employed.

The efficiency of contacting and of the subsequent separation of extract and rafinate layers is markedly alected by the viscosity of the hy' drocarbon charging stock. It is desirable, especially when viscous hydrocarbon oils are employed as charging stock, to add diluents such as light hydrocarbons to reduce the viscosity. These diluents serve not only to improve the efficiency of the rst stage contacting and separation operations, but serve additionally to repress excessive cracking of the charging stock in the second stage of the process of this invention. The diluents which are employed may be .recovered from the refined charging stocks and recycled. Itv may be desirable to employ as a diluent a crude light hydrocarbon stock, e. g., a sulfur-containing naphtha which may itself-.be refined concurrently with the refining of a more Viscous 'hyl-vA drocarbon charging stock.

The time of contacting will depend to some extent on the other reaction variables which are employed, the nature of the hydrocarbon charging stock and the degree of refining sought to be eiected. Ordinarily, we may employ contacting periods between about l and about 360 minutes or even more, if desired. In order to repress excessive cracking which might otherwise ensue at temperatures aboveabout 200 F., especially when relatively large hydrogen fluoride1oil ratios are employed, it is desirable to limit the contacting to a period less than about 180 minutes, preferably between about 5 and about 150 minutes.

In a preferred mode of operation the hydrocarbon charging stock is subjected to a prelim.- inary treatment with 5 or more volume per cent of liquid hydrogen fluoride at ambient temperatures, e. g. about 50 F. about 100 F., to remove readily extractable materials. Following the extraction operation, a raffinate consisting of par'- tially reiined oil is separated from extractI phase comprising extracted materials dissolved in or combined with liquid hydrogen fluoride. The raffinate may then be contacted with liquid H-F-BFa, upon which a vpartial pressure of BF; is superimposed but is preferably first contacted with liquid hydrogen uoride at elevated temperatures between about 200 F. and about 450 F. in order to eiect further refining, conversion and selective cracking of low V. I. constituents of the charging stock. The treatment at ele'- vated temperature is followed by a contacting-or settling period with liquid hydrogen fluoride lat ambient temperatures. If desired, the elevated T. operating conditions in the hydrogen fluoride treating stage to obtain a very substantial increase in the viscosity index of the charging stock, e. g. to employ temperatures .between abou; 200 F. and about 450 F. concurrently with the employment of about 50 volume per cent or more of 'hydrogen fluoride, based on the volume of hydrocarbon charging stock.

Upon completion of the contacting of hydrogen fluoride and the hydrocarbon charging stock, the resultant mixture or emulsion is separated into a partially refined hydrocarbon oil and a liquid hydrogen fluoride extract layer. Where contacting between hydrogen fluoride and oil has been effected at high temperatures, e. g. 200 F. or more, the hydrogen fluoride may be distilled or flashed from the contacting mixture and this -hydrogen fluoride may thereafter be recovered by condensation. This method of hydrogen fluoride removal, however, necessitates the subsequent extraction of the partially refined or converted hydrocarbon oil with 5 to 100 volume per cent or more of liquid hydrogen fluoride to remove the conversion products formed in the oil, preferably at ambient temperatures of 100 F. or less, e. g. room temperature. Hydrogen fluoride may be recovered from the extract phase by conventional methods, such as distillation, and reused. There is no necessity i" or removing small amounts of dissolved or suspended hydrogen fluoride from the partially refined hydrocarbon oil, as this oil will be subjected in the second stage of our process to contacting with liquid HF-BF.

Ordinarily, upon completion of the contacting operation between the hydrogen fluoride and hydrocarbon oil, the resultant mixture or emulsion is-brought to a temperature such that the hydrogen fluoride and partially refined oil can be readily separated as distinct liquid phases by settling, centrifuging or similar operations. Usually temperatures below about 150 F. are used in the separation step and it is desirable to effect separation at about room temperature. In order to facilitate the separation, especially where viscous hydrocarbon oils are involved, it is desirable to add a light liquid or liquefied hydrocarbon diluent to the mixture of oil and hydrogen fluoride, e. g., propane, butane, pentane, parafilnic or cycloparafnic naphthas or the like.

Following the separation operation, the diluent can be removed from the partially refined oil, usually simply by distillation. However, it is desirable to retain a hydrocarbon diluent in the partially rened oil throughout the second stage treatment of the oil with liquid HE-BF3. HF-BFa is a much more powerful cracking catalyst than hydrogen fluoride alone under similar conditions and the inclusion of light parafnic hydrocarbons, either formed in the hydrogen fluoride contacting operation or added to the partially refined oil, in the oil being contacted with HF-BFa tends to repress excessive cracking thereof.

YIn the second stage of our process, the partially refined hydrocarbon oil derived from the first stage, with or without complete separation of the hydrogen fluoride therefrom, is contacted with liquid IdF-BF2. in quantity sufficient to form a distinct liquid phase under the contacting conditions. The amount and composition of the liquid HF-BFa which are employed will be dependent upon the extent of refining sought to be effected. Generally, we may employ between about 5 and about 100 per cent by volume of liquid HF-BFa, based on the volume of oil being contacted therewith, although the employment of even larger volumes of liquid HF-BFs may sometimes be *del sirable. The BFs concentration in the liquid HF-BFsmay vary between about 1 and about 200 per cent by weight, based on the weight of hydrogen fluoride. We prefer to employ between about 10 and about 60 per cent by weight of BFs.- based on the weight of hydrogen fluoride, andhave carried on desirable operations with between about l5 and about 25 per cent by weight of BFa.

A wide range of temperatures is available forv effecting the refining of hydrocarbon oils with liquid HF-BFs, viz. temperatures between about 30 F, and about 350 F.` However, liquid HF-BFa is a powerful cracking catalyst and is capable of effecting a considerable amount of conversionof hydrocarbon lubricating oil stocks to lower boiling hydrocarbons even at room temperature. Since uncontrolled cracking of the partially refined oil charged to the second step of our process tends to reduce the yield of finished oil, we prefer to employ temperatures below about 100 F particularly temperatures between about F. and about 80 F., during the contacting thereof with liquid HF-BFa.

Suflicient pressure is maintained on the contacting mixture in the second stage of our process to obtain essentially liquid phase contacting. However, BFS is extremely volatile and, depending upon the temperature and the BF3 concentration in the liquid contacting mixture, considerable BFS pressure may be generatedin the contacting zone. l

We may employ contact times between about 1 and about 180 minutes in the second stage contactiig operation, preferably between about 5 and about 120 minutes. When liquid HF-BF; is employed at preferred temperatures falling beto employ contact times between about 5 and s, about 120 minutes.

By the inclusion of cracked hydrocarbon prodinvention, by the deliberate addition of low boiling hydrocarbons to the charging stock, or both, by maintaining temperatures below about 100 F., by employing between about 10 and about 60 per cent by weight of BFs based on the Weight of hydrogen uoride and by limiting the duration of contacting, cracking of the charging stock may be inhibited or satisfactorily controlled in the second stage operation of our process to yield refined oils of high viscosity index in good yields.

The contacting methods and equipment employed in the second stage of our process are essentially the same as those employed in the first stage. Because of the relatively high volatility of BFs, it will be desirable to employ equipment capable of withstanding moderate pressures, even when the temperature employed in the second stage is 100 F. or less.

If the second stage contacting operation has been effected at temperatures substantially above 100 F., the contacting mixture is preferably cooled to a temperature below 100 F. before effecting separation of refined oil and liquid HF-BF3 therefrom. In a preferred method of operation', the second stage contacting mixture is cooled to a temperature between about 0 F. and about F. and the cooled mixture is then centrifuged or allowed to stratify under the influence of gravity into two liquid layers of different density, viz. an HF-BFs extract layer containing materials extracted from the oil and a supernatantraiiinate. The HF-BFav can be recovered from the extract layer by conventional" ammi methods, e. g., distillation, and reused in the contacting operation.

Hydrogen fluoride and BFa may conveniently be recovered from the railinate layer by stripping with heat, with or without the aid of stripping agents. These stripping agents may be any inert gas, hydrocarbon gas or Vaporized light liquid. Alternatively, HF-BFa may be removed from the rafnate by passage thereof in contact with metal fluoride salts such as NaF CaFz or the like, optionally supported upon spacing materials such as activated alumina or carbon. Metal fluoride salts combine with hydrogen fluoride and BFs to form complex salts from which the adsorbed or reacted hydrogen fluoride and BFS can be recovered by heating. Fluoride impurities may also be removed from the rafllnate by washing with water or dilute alkalies, treatment with sulfuric acid, or passage of the raffinate over dehydrogenating metal oxides, e. g., chromium oxide supported on alumina, bauxite, etc.

The rened oil may be clayed, acid-treated or, if oils of special properties are desired, may be further extracted with conventional solvents such as Chlorex (B,B-dichlorodiethyl ether), phenol, furfural, nitrobenzene or the like. It is usually desirable to adjust the initial boiling point of the refined oil by distillation.

In order to illustrate the novel two-stage treating process of this invention, reference is made to the accompanying flow diagram which is a schematic representation of one embodiment.

By way of example and not with the intention of limiting the invention, the processing of a hydrocarbon lubricating oil stock to improve V. I.

will be described. By the operation of the twostage process of this invention on lubricating oil stocks sulfur, oxygen and nitrogen compounds and water are removed from the stock, together with low V. I. constituents. A hydrocarbon lubricating oil stock from the source I is passed by pump II into heat exchanger I2 wherein it is brought to the desired temperature, which may be thev processing temperature employed in the hydrogen fluoride contacting zone. From heat exchanger I2 the charging stock passes through line I3 into a hydrogen fluoride contacting zone I4, which has been schematically represented inthe form of a tower, although it will be readily understood that other contacting means, as indicated above, may be employed instead. Contacting tower I4 may be provided with mechanical agitating means (not shown). In order to facilitate contacting and the subsequent settling operation, it is desirable to add a light hydrocarbon diluent to the charging stock by means of valved line I3A. Suitable light hydrocarbon diluents include liquid propane, butanes, pentanes, hexanes, saturated naphthas and the like. In tower I 4 the charging stock is intimately contacted with liquid hydrogen iluoride in quantity sufficient atlleast to maintain a .distinct liquid phase under the contacting conditions, viz., usually between about 5 and about 100 per cent by volume of liquid hydrogen fluoride, based on the volume of charging stock. Ordinarily it is preferred to use commercial, substantially anhydrous hydrogen fluoride. The hydrogen fluoride .enters the contacting tower through line I5 or through lines I5 and I6. If desired, liquid hydrogen iluoride may be introduced into the tower at a number of other vertically spaced points. As shown, the charging stock is introduced at a low point in the contacting tower, preferably below the level of the hydrogen fluoride extract phase, with the result 8 that the hydrogen fluoride is used Very efciently, since the extract is presented for further Contact with additional charging stock which is thereby extratced to some extent and at the same time strips occluded paraffinic materials from the extract. If desired, tower Ill may be partially or substantially completely packed with spacing materials which are resistant to the action of the mixture being contacted.

Although temperature between about 0 F. and about 450 F. may be employed in contacting tower I4, it may be desirable to use temperatures between about 200 F. and about 450 F. Sufficient pressure will be maintained in the contacting tower to maintain essentially liquid phase contacting conditions. Depending on the nature of the charging stock, the extent of V. I. improvement which is sought and the temperature employed, the time of contact in tower I4 may vary between about 1 and about 360 minutes. We prefer to eiTect a very substantial increase in the V. I. of the lubricating oil stock in tower I4 and to this end we prefer to employ temperatures between about 200 F. and about 450 F. therein and contact times between about 5 and about 180 minutes. Under these conditions partial selective cracking and extraction of low V. I. constituents of the charging stock are effected; far greater increases in V. I. are obtained under these conditions than are obtainable at temperatures below 200 F. The temperature in contacting tower I4 may be controlled by controlling the temperatures of the charging stock and hydrogen fluoride streams introduced therein and, if desired, by additional temperature adjusting means such as heating and cooling jackets or coils (not shown).

A partially rened lubricating oil stock passes overhead from contacting tower I4 through line I7, pressure-reducing valve I8 and thence to heat exchanger I9 wherein its temperature is suitably adjusted to maintain a desired temperature in settler 2l. From heat exchanger I9, the oil passes through line 20 to settler ZI. It is desirable to employ settling temperatures below about 150 F., preferably below about 100 F., e. g. about F. in settler 2l. A light hydrocarbon diluent may be introduced into settler 2I through

lines

22 and 20, in lieu of or in addition to the diluent which may be introduced into contacting tower I4 through line I3A. In settler 2| the mixture of hydrocarbons and liquid hydrogen fluoride derived from contacting tower I4 is allowed to stratify under the influence of gravity into two liquid layers. The more dense liquid hydrogen iluoride layer is withdrawn from settler 2I through line 23 and forced by pump 24 into valved line I6 and/or valved line 25 to line I5 for recycle to contacting tower I4.

The lighter, partially refined hydrocarbon oil layer flows over weir 26 and is removed from settler 2| through line 27, Ywhence it is forced vby pump 28 into the second stage contacting zone. It is not necessary to strip the small proportion of hydrogen fluoride dissolved or dispersed in this oil, usually between about 0.5 and 2 weight per cent hydrogen fluoride, before subjecting the oil to the second stage treating operation of this invention. Settler 2l is provided with a lvalved vent line 21A through which light hydrocarbon gases which may be produced by cracking in tower I4 or by partial vaporization of light hydrocarbon diluents introduced into the system at line I3A and 22 may be separated. Light gasese removed through line 27A usually containsome hydrogen fluoride which may be recovered by absorption, as will be described hereinafter.

In contacting tower I4 there is formed an extract phase comprising water, compounds of oxygen, sulfur and nitrogen, and low V. I. materials which have Irbeen removed from the hydrocarbon charging stock, dissolved in liquid hydrogen iluoride. The extract layer is withdrawn from the bottom of contacting tower 4 through valved line 29 and is introduced into a stripping zone 30 to remove hydrogen fluoride which is present in the extract layer in the free state or in loose chemical combination with the extracted materials. Stripper 30 can be operated at temperatures between about 100 F. and about 190 F., preferably about 100 F. to about 160 F. at pressures between about 5 and about 50 p. s. i. g., preferably at about atmospheric pressure. Under these vconditions free or loosely bound hydrogen fluoride is vaporized from the extract layer and passes from the top of stripper 30 through line 3|, valved line 32 and condenser 33 toithe hydrogen fluoride storage tank 34.

The denuded extract layer which contains somehydrogen iluoride in firm combination, apparently in chemical combination, is withdrawn from the bottom of stripper 30 through valved line 35 and is passed into hydrogen uoride regeneration zone 36. In the regeneration zone, the denuded extract is subjected to temperatures between about 200 F. and about 500 F., preferably about 250 F. to about 350 F. at about atmospheric pressure, although if desired, somewhat higher pressures may be employed. Under these conditions, tarry extract materials are'partially decomposed to regenerate hydrogen fluoride which vaporizes and passes overhead from the regeneration zone through line 31, whence it may be passed into line 32. Extract materials are removed from regeneration zone through valved line 38.

Hydrocarbon charging stocks usually contain Small, but nonetheless appreciable amounts of water which are absorbed by the liquid hydrogen fluoride in contacting tower I4 and, because of the repeated (recycle) use of hydrogen fluoride, tend to concentrate in and dilute the hydrogen fluoride. Consequently, it is necessary intermittently or continuously to subject a portion of the hydrogen uorde to dehydration. This may be done by passing hydrogen fluoride vapors from lines 3| and 31 through valved line 39 into an azeotropic distillation tower 4l] wherein a maximum boiling hydrogen fluoride-water azeotrope is separated as a liquid phase from substantially anhydrous hydrogen'fluoride vapors which pass overhead through lines 4| and 42 to hydrogen fluoride storage tank 34. The liquid hydrogen fluoride-water azeotrope is withdrawn from tower 40 through valved line 43 and may be removed from the system. Anhydrous hydrogen uoride may be regenerated from this azeotrope by known methods, for example by treatment with fluosulfonic acid. Also the hydrogen fluoride-water azeotrope, which`is still an active dehydrating agent, may be contacted with the charging stock which is introduced into contacting tower |4 in order to dry the same.

Referring now to the schematic representation of the second stage treating operation of the process of this invention, partially refined oil derived from the rst stage treating operation is transferred from settler 2| into line 21 and zone which, like the first stage contacting zone, is represented in the form of a vertical tower. Tower 45 may be unpacked or partially or wholly packed with solid spacing materials resistant to the action of the mixture being contacted. The oil -is preferably introduced below the level of the extract phase in tower 45. Liquid I-IF-BFs is introduced into tower 45 at a plurality of vertically spaced points through

lines

46, 41 and 48. Fresh anhydrous HF may be introduced into tower 45 by

lines

93, 93' and 46. In tower 45 the oil and liquid HF-BF3 streams are intimately contacted and counterflowed. A substantial amount of the BFa is introduced by line 48 to tower 45.

A temperature between about 30 F. and

about 350 F., is maintained in tower 45. The contacting temperature may -be controlled by controlling the temperatures of the various streams which are introduced into tower 45 and/or by temperature-control jackets or coils (not shown). Because of the capacity of liquid HF-BFa to induce catalytic cracking of hydrocarbons at relatively low temperatures, we prefer to employ a contacting temperature below about 100 F., preferably between about 40 and about F., in tower 45. Sufficient pressure is maintained in tower 45 to obtain essentially liquid phase contacting conditions, although a considerable BFs vapor pressure, e. g., about p. s. i. or even more, is permissible. The quantity of I-IF-BFa which is lintroduced into tower 45 is suilicient to develop and maintain a distinct liquid I-IF-BFs extract phase in the lower portion of the tower, the solute of said extract phase comprising low V. I. constituents derived from the oil being processed, sulfur compounds and the like.

The time of contact will be dependent upon other reaction variables which are selected and upon the extent of relining and V. I. improvement sought to be elected. Ordinarily the oil is contacted for a period of time between about 1 and forced by pump 28 through heat exchanger 44 about minutes.

Upon completion of the contacting operation relined oil containing dissolved and dispersed hydrogen fluoride and BFa ilows overhead from tower 45 through line 49 and pressure reducing valve 50 into heat exchanger 5|. In heat exchanger 5| the rened oil stream is cooled to a suitable settling temperature and is then passed into settler 52, which is depicted as an inclined gravity settler, although it should be understood that equivalent means such as centrifuges may be used. In settler 52 a. lower layer of liquid hydrogen lluoride containing dissolved boron fluoride settles out and is removed for recycle to tower 45 by line 41 and pump 41A. Refined oil, which is of lower specic gravity than the liquid hydrofluoric acid solution flows over weir 53 into the upper portion of settler 52. Settler 52 is provided with a valved vent line 54 through which BFL usually contaminated with low boiling diluent hydrocarbons such as methane, ethane, propane, etc. derived from cracking or introduced into tower 45 as diluents, can be vented. It is desirable to recover BF3 from the low boiling hydrocarbon gases which are vented by line 54, suitably by the employment of an absorption operation which will be described hereinafter. Refined oil passes from settler 52 through valved line 55 into BFa stripping tower 56 provided with a heating coil 51 and a dephlegmating coil 58. In tower 56, BF3 and small amounts of low boiling hydrocarbons vaporizefrom the rened oil to pass overhead through line 59, whence BFa can be recycled to tower 45 through valved line 48. In order to prevent the accumulation of inert gases in the contacting system it is desirable intermittently or continuously to divert a portion of the gas stream passing through line 59 through valved line 60 for recycle (by lines not shown) to the BFs absorber 9D. The refined' oil which contains small amounts of dissolved or dispersed hydrogen fluoride, and possibly low boiling hydrocarbons boiling at room temperature or higher at atmospheric pressure, is transferred from stripper 56 by valved line 6| and pump 52 into a hydrogen fluoride stripping tower 63 provided with heating coil 64 and dephlegmating coil 65. In tower 53, the hydrogen fluoride is stripped from the refined oil usually as an azeotrope with low boiling hydrocarbons and passes overhead through line 66 and condenser 61 into settler 68, wherein a lower liquid hydrogen fluoride layer forms and is removed by valved line 69 for recycle to hydrogen fluoride storage tank 34 (by lines not shown). Light hydrocarbons are removed from settler 68 by valved line 'l0 and may, if desired, be recycled as a diluent through lines ISA or 22. Gases may be vented from settler 63 through valved line 1|. A rened oil which is essentially free of all but traces of fluorides is removed from the hydrogen fluoride stripper 53 through valved line 12 and may be subjected to such after-treatment as may be desired.

The liquid HF-BF3 extract phase which settles to the lower portion of tower 45 is withdrawn through valved line I3 and passed into extract stripper '54. In stripper 14 dissolved and loosely bound HF and BFa are vaporized by the application of heat, for example through heating coil 15, and pass overhead through line '16. Suitable temperatures for use in stripper 'i4 are about 100 F. to about 190 F., preferably between about 100 and 160 F. The partially denuded extract is removed from the base of stripper 'I4 through valved line I1 and is forced by pump 'I8 into regenerator 'I9 provided with a heating coil 80 or other heating means. In regenerator 19 the extract is subjected to temperatures sufcient to release hydrogen fluoride and BFS which are firmly, probably chemically, bound to the materials extracted from the hydrocarbon oil which was processed in tower 45. The liberated hydrogen fluoride and boron fluoride leave regenerator I9 by valved line 8|. 'I'he hydrogen fluoride and BF3 in lines 15 and 8| can be passed through valved line 82 into fractionator 83 wherein liquid hydrogen lluoride is separated as bottoms and transferred through valved line 84, pump 85 and

lines

42 and 32 to hydrogen fluoride storage tank 34. BFE-containing gases leave tower 83 through valved line 8S and may be recycled to tower 45 via line 48, together with fresh BFS which is introduced into the system Via valved line 81. All or part of the BFS may be diverted from line 66 through valved line 88 and cooler 89 for passage to absorber 90.

Hydrogen fluoride and BF3 from lines 1E and 8| may be passed through valved line 9| for recycle to tower 45 through line 48. All or part of the stream passing through line 9| may be diverted through valved line 92 into line 88 for passage to absorber 90. In absorber 90, BFS-containing streams derived from various points in the treating system (for example in lines 54, 76, 3| and 86), more or less contaminated with low boiling hydrocarbons,

are subjected to absorption in liquid hydrogen fluoride. For this purpose liquid hydrogen fluo# ride, which is introduced into storage tank 34 through line 93, is passed through valved line 94 and cooler 95 into the upper portion of absorber 90. Suitable operating conditions in the absorber are temperatures between about 40 and about F. and pressures between about 10 and about 500 p. s. i. The cold, liquid hydrogen fluoride selectively absorbs the BF: from the BEE-containing gas streams and a solution of BFs in liquid hydrogen uoride is withdrawn from the base of absorber 96 through valved line 96, whence it may be recycled by pump 91 in line 98 to valved line 99, pump |00 and heat exchanger |0i to line 46 for recycle to tower 45. In order to adjust the HFzBFa ratio of the stream in line 99, liquid hydrogen fluoride may be admitted therelnto from storage tank 34 and line S4. Part or all of the HF-BF3 solution withdrawn from the base of absorber 90 may be passed by lines (not shown) to the HF-BFa fractionator B3. Unabsorbed gases such as methane, ethane, propane, etc. are vented from the top of absorber 90 through valved line |02 and may be removed from the system or recycled, wholly or in part, as diluents through lines ISA and/or 22.

Following are examples of the application'of the process of this invention to Mid-Continent lubricating oil stocks of S. A. E. 20 and 50 grades. In the runs presented hereinafter the oil to be rened and liquid hydrogen fluoride or liquid I-IF-BFS were intermittently contacted in a carbon steel stirring bomb whose contents were agitated at about 1725 R. P. M. by a mechanical stirrer. The bomb was provided with a bleed-off tube terminating at a point well above the level of liquid hydrogen fluoride or HF-BFa, allowing ready removal of supernatant raffinate from the lower extract phase. In all runs on S. A. E. 20 grade stock, the hydrogen fluoride Was employed in the amount of 515 cc. per liter of oil. In the runs on the S. A. E. 50 grade stock, a solution containing '70 volume per cent of the oil in normal pentane was prepared and the solution was treated with hydrogen fluoride in the amount of 515 cc. per liteiof oil and, where indicated, with BF: in addition. Where no amount of BFs is indicated in the following table, the oil was contacted with hydrogen fluoride alone. The S. A. E. 20 lubricating oil stock which was charged contained about 0.66 weight per cent sulfur in the form of various organic sulfur compounds and the S. A. E. 50 grade lubricating oil stock contained 0.71 per cent by weight of sulfur. As a result of our treating process, substantially all the sulfur was removed from these oils.

In the following table, runs entitled A and B or A, B and C denote sequential treatments of the charging stock and the rafnate or rafllnates produced therefrom, the hydrogen fluoride:charging stock volume ratio being maintained constant throughout the series of refining operations. Where sequential operations were ellected upon the oils, cracked products were not removed between the treating steps.

The amounts of cracked products were determined by Vacuum distillation of a sample of the refined oil to remove hydrocarbons boiling below the initial boiling point of the charging stock. It is well-known that the cracking of high molecular weight hydrocarbons always produces both lower boiling and higher boiling hydrocarbons than the charging stock. It will be apparent 13 therefore, that the amount of cracking was actually greater than the figures in the following table indicate.

' Where treating operations were effected at temperatures above room temperature, upon completion of contacting, the contacting mixture was allowed to cool to room temperature and stirred for 30 minutes at about 1725 R.. P. M. at that temperature before allowing the contacting mixture to stratify into raffinate and extract layers.

An inspection of run l of the table shows that treatment of the charging stock with liquid HF-BFa at about room temperature produced a surprising amount of cracking, viz. nominally 7.4 weight per cent on the charging stock, and that the relatively low V. I. of 92 was obtained at the relatively high treating loss of 54.1 per cent based on the weight of the charging stock. The specific dispersion of the product, being below 100, indicates substantially complete removal of aromatic hydrocarbons from the charging stock. From this run it appears that IIE-Elib is an extremely good solvent for aromatic hydrocarbons. It appears, however, that the aromatics react to form an HF-BFa-aromatic complex which exhibits solvent capacity for some of the relatively high V. I. constituents of the charging stock. Although we do not choose to be bound by this theory, it`deserves some confidence because of the experimentally observed high treating loss and because, as will be brought out more fully hereinafter, hydrogen fluoride pre-treatment at 212 F. or 330 F. to remove the bulk of the aromatics tained in run 2 but that this loss was oilset by a substantial gain in V. I., from 95.4 in run 2 to 98.6 in run 3. The combination of hydrogen fluoride treatment at room temperature and at 330 F. to yield an oil having a V. I. of 94.7, as shown in runs 3A and 3B represents about the maximum V. I. which we have been able to obtain by hydrogen uoride treatment alone of this particular charging stock.

It will be apparent from the runs discussed above that the combination of hydrogen fluoride and HTF-BFs treatment of the hydrocarbon'lubricating oil stock produced an unpredictable and unexpected result, viz. a high V. I. product which could not be obtained with either hydrogen fluoride treatment alone or with HF-BFx treatment alone. Moreover, this result was obtained at no expense in the yield of finished product; rather, the combination treating process produced an increased yield of higher V. I. oil. It will be noted that the specific dispersions of the products of runs 2 and 3 indicate that substantially complete removal of aromatics from the charging stock was eiected by the treatments. This fact coupled with the fact of far lower treating losses than the one obtained in run 1 indicates that in run 1 the HF-BF-aromatic complex apparently retained solvent properties for high V. I. parafnic constituents of the oil.

Run 4 indicates that our novel combination treating process can be applied to S. A. E. grade oil to produce high V. I. products withou exaggerated treating losses.

Table Cumulative Treat V V C 1 S ing LosCs, lVt. Per Yield BF Time, Tem is, is, oor, pcc. yen Ru N0 glia. Hrs. m5 100 r 210 F. V' L N. P. A im D42 Disp. y Total VJCltf Extraction Cracking REFINING OF MID-CONTINENT S. A. E. 20 GRADE LUBRICATING OIL STOCK 594 60.4 55.5 8 1.5087 0.914 131 321 52.9 92.0 114-2 1.4761 0.860 99 46.7 7.4 54.1 48.7 427 56.3 76.7 4-41/ 1.4942 0.890 119 17. 2 3.3 20.5 81.6 312 52.8 05.4 l-ll/ 1.4782 0.865 A 100 35.4 5. 7 41.1 62.2 15.0 15.0 86.5 317 53.0 94.7 4 1,4840 0.874 107 25.7 12. 7 38.4 64.5 281 51.4 98.6 295-3 1.4764 0.859 98 31.7 13.3 45.0 58.6

REFINING OF MID-CONTINENT S. A. E. 50 GRADE LUBRICATING OIL STOCK Feed 4,006 149. 0 52. 1 A l 80 2,115 118. 6 75. 6 3 212 l, 855 112. 9 79. 7 1t 76 947 85.0 94.0

from the charging stock resulted in much lower treating losses for a given extent of the V. I. improve'ment.

An inspection of run 2 in the above table shows that treatment of the charging stock with liquid hydrogen uoride at 212 F. followed by low temperature treatment of the resultant raflinate with liquid 11F-BFS resulted in the relatively low total loss of 41.1.weight per cent and the relatively high V. I. of 95.4, as compared with the results obtained in run 1.

In run 3 the charging stock was extracted with liquid hydrogen fluoride at room temperature, the resultant raffinate was treated with liquid hydrogen fluoride at 330 F., followed by a contacting and separation period at about room temperature, and the resultant raffinate was then treated at room temperature with liquid 11F-BFS. It will be noted that this three-stage treatment resulted in a slightly increased treating loss over that ob- The application of the process of this invention to the manufacture of high V. I. lubricating oils has been emphasized. However, the process is far more generally applicable, for example, for the relining of diverse crude liquid hydrocarbons Such as are obtainable from petroleum by fractionation or conversion, from shale oil, coal or coal ltar hydrogenation, and the like. Suitable hydrocarbon charging stocks which may be processed in accordance with this invention include naphthas, kerosenes, Diesel oils, gas oils, furnace oils, range oils and the like. Our process is, in fact, generally applicable to the refinement of hydrocarbon oils containing one or more of the following: unsaturates, aromatics, compounds of oxygen, nitrogen or sulfur.

An especially advantageous application of the processof this invention, in additionto its application to the rening of hydrocarbon lubricating oil stocks, can be made to white oil or mineral oil stocks.

Another especially advantageous application of our process may be made to sulfur-containing oils, especially to relatively heavy oils such as furnace oils. If doctor-sweet products are desired-oxidizing agents such as SO2, S03, oxygen, airy Ditrogen oxides, nitric acid and the like may be introduced into the rst stage contacting zone wherein liquid hydrogen fluoride and oil are intimately commingled.

A substantial proportion of the sulfur in hydrocarbon oils can be eliminated as hydrogen sulde by treating such oils concurrently with liquid hydrogen fluoride and hydrogen. A hydrogen partial pressure between about 50 and about 3000 p. s. i. g., preferably about 200 to about 2000, may be employed. Increased hydrogenation may be effected by employing a nickel liner in tower I4. When hydrogen is employed, we prefer to use temperatures between about 150 F. and about 500 F. preferably about 250 F. to about 400 F.

We claim;

l. The process for refining a hydrocarbon lubricating oil stock having a specific dispersion in Substantial excess of 100, which process cornprises contacting said stock with about 50 per Vcent by volume of liquid hydrogen iiuoride, based on the volume of said stock, at a temperature of about 200 F. under pressure suflicient to maintain the liquid phase, for a period of time sufficient to' effect a substantial increase in the viscosity index of said stock, cooling the resultant mixture of liquid hydrogen liuoride and lubricating oil stock to a temperature below about .100 F., separating a partially reiined lubricating oil stock and a liquid hydrogen fluoride-containing phase, thereafter contacting said partially refined lubricating oil stock with liquid hydrogen fluoride-boron iiuoride containing between about 10 per cent and about 60 per cent by Weight of boron fluoride, based on the weight of the hydrogen fluoride, at a temperature between about 40 F. and about 80 F. under a pressure sufiicient to maintain the liquid phase, the quantity of hydrogen fluoride-boron iiuoride being sufficient at least to form a distinct liquid phase under the contacting conditions, and separating a refined hydrocarbon oil having a speciiic dispersion not in excess of about 100 hydrogen iiuoride-boron fluoride from the resultant mixture.

2. The process for refining a hydrocarbon 1ubricating oil stock having a specific dispersion in substantial excess of 100, which process comprises contacting said stock with about 50 per cent by volume of liquid hydrogen fluoride, based on the volume of said stock, at a temperature of about 330 F. under pressure sufficient to maintain the liquid phase, for a period of time suliicient to effect a substantial increase in the viscosity index of said stock, cooling the resultant mixture of liquid hydrogen fluoride and lubricating oil stock to a temperature below about 100 F., separating a partially rened lubricating oil stock and a liquid hydrogen fluoride-containing phase, thereafter contacting said partially refined lubricating oil stock with liquid hydrogen fluoride-boron fluoride containing between about 10 per cent and about 60 per cent by weight of boron fluoride, based on the weight of the hydrogen fluoride, at a temperature between about 40 F. and about 80 EF. under pressure sufficient to maintain the liquid phase, the quantity of hydrogen iiuoride-boron fluoride being suiiicient at least to form a distinct liquid phase under the contacting conditions, and sepcifc dispersion not in excess of about 100 hydrogen iiuoride-boron fluoride from the resultant mixture.

3. A process of refining a hydrocarbon lubricating oil stock having a specific dispersion in substantial excess of 100, which process comprises contacting said stock with liquid hydrogen fluoride at a temperature between about 50 F. and about F. under pressure suiiicient to maintain the liquid phase, the quantity of hydrogen iiuoride being at least sufficient to form a distinct liquid phase` under the contacting conditions, separating the resultant mixture into a liquid hydrogen fluoride-containing phase and a first raffinate lubricating oil stock having a specific dispersion in substantial excess of 100, thereafter contacting said first raiiinate lubricating oil stock with liquid hydrogen iiuoride at a temperature between about 200 F. and about 450 F. under a pressure sufficient to maintain the liquid phase, cooling the resultantmixture to a temperature between about 50 F. and about 100 F. and then separating the same into a liquid hydrogen fluoride-containing phase and a second raffinate lubricating oil stock having a specific dispersion in excess of 100, contacting said second rafnate lubricating oil stock with liquid hydrogen fluorideboron fluoride at a temperature between about 50 F. and about 100 F., under pressurelsuflicient to maintain the liquid phase, the quantity of said liquid hydrogen fluoride-boron fluoride being sufcient at least to form a distinct liquid phase under the contacting conditions, and separating a refined lubricating oil having a specic dispersion not in excess of 100 and a liquid phase comprising principally hydrogen fluoride-boron iiuoride from the resultant mixture.

4. A process for refining a hydrocarbon lubricating oil stock having specific dispersion in substantial excess of 100, which process comprises contacting said stock with between about 50 and about 200 percent by Volume of liquid hydrogen fluoride at a temperature between about 200 F. and about 450 F. under pressure suiiicient to maintain the liquid phase, separating the resultant mixture at a temperature between about 75 F. and about 150 F. into a liquid phase comprising principally hydrogen fluoride and a second liquid phase consisting essentially of a, partially refined lubricating oil stock having a speci'iic dispersion less than the specic dispersion of said hydrocarbon lubricating oil stock but in excess of 100, thereafter contacting the partially refined stock with between about 5 and about 100 volume percent of liquid hydrogen fluoride-boron iiuoride containing between about 10 and about 60 percent by weight of boron iiuoride at a temperature between about 40 F. and about 80 F. under pressure suiiicient to maintain the liquid phase, and separating from the resultant mixture a refined lubricating oil having a specific dispersion not in excess of about 100 and hydrogen fluoride-boron fluoride.

ARTHUR P. LIEN.

BERNARD L. EVERING.

FRANK W. HAECKL.

REFERENCES CITED The following references are of record in the nle of this patent:

UNITED STATES PATENTS Number Name Date 2,343,744 Burk Mar. 7, 1944 2,343,841 Burk Mar. 7, 1944 2,378,762 Frey June 19, 1945 2,405,995 Burk Aug. 20, 1946 Certiicate of Correction Patent No. 2,564,071 August 14, 1951 ARTHUR P. LIEN ET AL.

It is hereby certified that error appears in the printed Specification of the above numbered patent requiring correction as follows:

Column 3, line 49, for hydrogen read hydrocarbon; column 4, line 49, before about insert to; column 5, line 55, for HE-EP3 read [YF-B173; column 8, line 4, for extratced read etmoted; line 74, for gasese read gases;

columns

13 and 14, in the table, under the heading nD20, opposite Run No. 3B for 1,4840 read 1.4840; under the same heading, opposite Run No. 4A for 1,5083 read 1.5033; same column, opposite Run No. 4B for 1,5022 read 1.5022; same column, opposite Run 4C for 1,4820 read 1.4820; same table, under the heading D420 opposite Run No. 4B for 0,894 read 0.894; same column, opposite Run No. 4C for 0,867 read 0.867 column 15,

lines

48 and 75, respectively, after 100 insert ami a Zz'quz'd phase containing;

and that the said Letters Patent should be read as corrected above, so that the same mayr conform to the record of the case in the Patent Oilice.

Signed and sealed this 20th day of November, A. D. 1951.

THOMAS F. MURPHY,

Assistant Uommz'sszoner of Patents.

Claims

1. THE PROCESS FOR REFINING A HYDROCABON LUBRICATING OIL STOCK HAVING A SPECIFIC DISPERSION INN SUBSTANTIAL EXCESS OF 100, WHICH PROCESS COMPRISES CONTACTING SAID STOCK WITH ABOUT 50 PER CENT BY VOLUME OF LIQUID HYDROGEN FLUORIDE, BASED ON THE VOLUME OF SAID STOCK, AT A TEMPERATURE OF ABOUT 200* F. UNDER PRESSURE SUFFICIENT TO MAINTAIN THE LIQUID PHASE, FOR A PERIOPD OF TIME SUFFICIENT TO EFFECT A SUBSTANTIAL INCREASE IN THE VISCOSITY INDEX OF SAID STOCK, COOLING THE RESULTANT MIXTURE OF LIQUID HYDROGEN FLUORIDE AND LUBRICATING OIL STOCK TO A TEMPERATURE BELOW ABOUT 100* F., SEPARATING A PARTIALLY REFINED LUBRICATING OIL STOCK AND A LIQUID HYDROGEN FLUORIDE-CONTAINING PHASE, THEREAFTER CONTACTING SAID PARTIALLY REFINED LUBRICATING OIL STOCK WITH LIQUID HYDROGEN FLUORIDE-BORON FLUORIDE CONTAINING BETWEEN ABOUT 10 PER CENT AND ABOUT 60 PER CENT BY WEIGHT OF BORON FLUORIDE, BASED ON THE WEIGHT OF THE HYDROGEN FLUORIDE, AT A TEMPERATURE BETWEEN ABOUT 40* F. AND ABOUT 80* F. UNDER A PRESSURE SUFFICIENT TO MAINTAIN THE LIQUID PHASE, THE QUANTITY OF HYDROGEN FLUORIDE-BORON FLUORIDE BEING SUFFICIENT AT LEAST TO FORM A DISTINCT LIQUID PHASE UNDER THE CONTACTING CONDITIONS, AND SEPARATING A REFINED HYDROCARBON OIL HAVING A SPECIFIC DISPERSION NOT IN EXCESS OF ABOUT 100 HYDROGEN FLUORIDE-BORN FLUORIDE FROM THE RESULTANT MIXTURE.