US2622094A - Method of purifying a lubricating oil feedstock with zinc halides - Google Patents

Description

Patented Dec. 16, 1952 METHOD OF PURIFYING A LUBRICATING OIL FEEDSTOCK WITH ZINC HALIDES,

Thomas F. Rutledge, New

Castle, Del., and

Francis M. Seger, Pitman, N. 'J., assignors to Socony-Vacuum Oil Company, Incorporated, a

corporation of New York No Drawing. Application March 11, 1949, Serial No. 81,013

3 Claims.

This invention has to do with the preparation of synthetic lubricants from normal, alpha monoolefins and, more particularly, has to do with the preparation of lubricants from certain complex mixtures containing such olefins.

As described in several related and co-pending applications, identified hereinafter, it has been found that normal, alpha mono-olefins of varied chain length can be converted to excellent synthetic lubricants. High viscosity indices, low pour points and/ or superior stability characterize these lubricants. Not only have the individual normal, alpha mono-olefins proven of value in this regard, but mixtures of the same have been found to be satisfactory. In addition, complex mixtures containing substantial proportions of these olefins have been found to be suitable starting materials. A source for the complex mixtures containing these olefins is the Fischer-Tropsch process and related processes. As is Well known in the art the Fischer-Tropsch process involves reaction of carbon monoxide and hydrogen in the presence of cobalt or chemically related catalysts, whereupon hydrocarbons, including olefins and paraflins, and oxygen-containing compounds are formed. When iron catalysts are used in place of cobalt, and/or when larger carbon monoxide to hydrogen ratios are used, larger quantities of oxygen-containing compounds are generally formed.

While the foregoing complex mixtures are converted to synthetic lubricants of low pour point, high viscosity index and good stability, as described in the applications referred to above, cer-' tain constituents therein are deleterious in reducing the yield and/or quality of the lubricants. Undesirable constituents include non-primary olefins, aromatics, naphthenes and parafiins; oxygen-containing compounds; suspended material, particularly metallic catalysts and their compounds. With regard to quality of the lubricants, it has been found that considerable color characterizes the lubricants. This is a serious shortcoming inasmuch as the highly colored lubricants generally do not respond to conventional procedures, namely, filtration, adsorption, etc., for removing color bodies. In addition, the carbon residue values of the lubricants are relatively high. A further shortcoming, traceable to constituents of the complex olefinic charge stocks, is that the viscosity indices of the lubricants generally fall below those of the lubricants formed from individual normal, alpha mono-olefins. Still another undesirable feature is in the relatively low response of the lubricants to inhibitors, particularly oxidation inhibitors. This is well illuscomprising an oil-soluble, p'ho'sphoru'sand "sulfur-containing reaction product of plnene and phosphorus pentasulfide, which is described in detail in Patent No. 2,416,281 and in copending application Serial No. 482,482, filed April 9,1943.

It has now been found that synthetic lubricants of good color and. low carbon residues can be obtained by treating the foregoing complex olefin charge stocks with zinc chloride, distilling off the olefinic material from the resultant mixture and converting the olefinic material to synthetic lubricants by the procedures described in the following copending applications.

In copending application Serial No. 761,716, filed July 17, 1947, now abandoned in favor of application Serial No. 104,932, filed July 15, 1949, which matured into U. S. Letters Patent No. 2,500,166, issued March 14, 1950, it has been shown that normal, alpha mono-olefins having six to twelve carbon atoms per molecule form synthetic lubricants when heated at 500-750 F. in the absence of a catalyst (particularly of the Friedel- Crafts type). At temperatures of the order of 700-900 F., the use of a gas such as hydrogen, carbon monoxide and mixtures of such gases, with the aforesaid mono-olefins makes possible the formation of synthetic lubricants in substantial yield. This is described in copending application Serial Number 6,814, filed February 6, 1948, now Patent No. 2,500,159, issued March 14, 1950. The aforesaid mono-olefins are also converted to synthetic lubricants when contacted with lead tetra-acetate at elevated temperatures, particularly 400-700 as explained in copending application Serial Number 44,403, filed August 14, 1948, now Patent No. 2,500,161, issued March 14, 1950. Another related development involves condensation, at 500-750 11, of an olefin mixture comprising a short chain, mono-olefin of two to six carbon atoms and a long chain normal, alpha mono-olefin of ten to thirty carbon atoms; the mean carbon chain length is maintained Within the range of six to twelve carbon atoms by proper proportioning of the clefins. This is described in copending application Serial Number 47,556 filed September 2, 1948, now Patent No. 2,500,162 issued March 14, 1950.

Polymerization of the aforesaid mono-olefins of six to fourteen carbon atoms per molecule, in the presence of a paraffin at temperatures in excess of 700 F., forms the subject matter of copending application Serial No. 86,384, filed April 8, 1949, now Patent No. 2,500,165 issued March 14, 1950. Mcnocyclic aromatics and/or naphthenes may be used in this polymerization, in place of the paraffin, as shown in copendingapplicationSerial No. 88,895, filed April 21, 1949, now

Patent No. 2,500,244 issued March 14, 1950. Polymerization of said mono-olefins may also'be accomplished at temperatures within the range 550-750" F. by using small amounts of sulfur, selenium and/or tellurium; this is described in copending application Serial No. 63,204, filed December 2, 1948, now Patent No. 2,500,164 issued March 14, 1950. At temperatures of the order of SOD-750 F., small amounts of phosphorus sulfides affect the polymerization of the aforesaidmonoolefins; this is described in copending application Serial No. 57,421, filed October 29, 1948, now Patent No. 2,500,163 issued March 14,1950. 7

A catalytic conversion of normal, alpha monoolefins having from five to eighteen carbon atoms to synthetic lubricants is described in copending application Serial No. 776,428, filed September 26, 1947, now abandoned; the catalysts used are silica-alumina composites.

Styrene also reacts with the aforesaid monoolefins, at temperatures from about 500 F. to about 700 F. with the formation of synthetic lubricants, as shown in copending application Serial No. 6,993, filed February 7, 1948, now Patent No. 2,500,160 issued March 14, 1950. Conjugated hydrocarbons and sulfur react with normal, alpha mono-olefins having from about five to about eighteen carbon atoms to form lubricants; copending application Serial No. 33,438, filed June 16, 1948, now Patent No. 2,500,167 issued March 14, 1950. A related development involves reaction of conjugated hydrocarbons, phosphorus sulfides and the corresponding mono-olefins of six to fourteen carbon atoms, as shown in copending application Serial No. 64,904, filed December 11, 1948, now Patent No. 2,500,247 issued March 14, 1950. Still another related development is that wherein lubricants are formed by reaction of vinyl-substituted aromatic compounds, thiols and normal, alpha mono-olefins, described in copending application Serial No. 97,921, filed June 8, 1949, now Patent No. 2,500,672 issued March 14, 1950.

In copending application Serial No. 673,892, filed June 1, 1946,, now Patent No. 2,551,638, issued May 8, 1951, it is shown that normal, alpha mono-olefins having from about seven to about twelve carbon atoms per molecule react with organic peroxides at 120-570 F. to form synthetic lubricants. With the corresponding mono-olefins of six to eighteen carbon chain length, organic peroxides and halogenatedolefins are reacted at 120-570 F. with the formationof lubricants; Serial No. 776,427, filed September 26, 1947, now Patent No. 2,551,640, issued May 8, 1951. As a related development, organic peroxides, conjugated hydrocarbons and the aforesaid mono-olefins of from five to eighteen carbon atoms are reacted at 120570 F. to form lubricants; Serial No. 53,372, filed October 7, 1948, now Patent No. 2,551,641, issued May 8, 1951. Organic peroxides, aromatic hydrocarbons and said mono-olefins of six to fourteen carbons also react to form lubricants, as described in copending application Serial No. 72,744 filed January 25, 1949, now Patent No. 2,551,642, issued May 8, 1951. Certain heterocyclic compounds may be used in place of the aromatic hydrocarbons in the last-mentioned development; this is explained in copending application Serial No. 83,772 filed March 26, 1949. Lubricantsof high viscosity are formed by reacting the aforesaid mono-olefins of six to fourteen carbon atoms with certain unsaturated esters and organic peroxides; copending application Serial No. 72,745 filed September 23, 1949, now Patent No. 2,551,643 issuedMay 8, 1951.

Normal, alpha mono-olefins also react with olefinic mono-oxides and -,sulfides at 500-700 F. to form lubricants, as explained in copending application Serial No. 750,170, filed May 23, 1947, now Patent No. 2,486,441 issued November 1, 1949.

It is to be understood, therefore, that the treated, complex olefinic charge may be converted to synthetic lubricants by any of the foregoing conversion procedures shown in the aboveidentified applications.

ZINC CHLORIDE: TREAT As indicated above, zinc chloride is used in treating the complex olefinic charge stock. Zinc fluoride, bromide and iodide are of the same chemical class as the chloride and may be used herein; however, in view of the much lower cost and greater availability of the chloride, the latter is most advantageous herein. The chloride is preferably used in anhydrous form, although satisfactory results are also obtained with a chloride containing some Water. In fact, aqueous solutions of zinc chloride are suitable such as a saturated solution at C. containing 615 grams ZnClZ per 100 parts of water; but, ordinarily, the water is removed by distillation in the treating procedure and is therefore not desired in the charge.

The amount of zinc chloride may be varied widely, depending upon the form of the chloride, the particular olefinic charge stock and the treating conditions. Quantities from about 0.5 per cent to 20 per cent or more of chloride, by weight, based upon the quantity of olefinic charge stock, are employed.

Treating temperatures may be varied considerably. Preferred, though, are temperatures of reflux of the olefinic charge, either at atmospheric, reduced or elevated pressure. Reflux temperatures make possible removal of any water of reaction, causing a more favorable equilibrium in various condensation and/or polymerization reactions catalyzed or induced by the solid acidic treating agent. Whatever the reaction mechanism, however, the olefinic content of the charge is not affected appreciably.

It will be clear that the zinc chloride treatment may be carried out in batch operation, as in a reaction vessel equipped with suitable distillation equipment. For example, the olefinic charge may be slowly distilled over the chloride, or may be heated with said compound for a longer period, e. g., several hours, and then flash distilled. It is also to be understood that the treat may be carried out in continuous operation, in which case the chloride and the olefinic charge stock may flow in concurrent or counter-current relationship to each other in a reaction vessel. It is preferred that the chloride be in finelydivided form in such operations. In all cases, agitation of the olefinic material and treatin agent, or other means for providing intimate contact, is recommended.

Following treatment of the complex olefinic charge with zinc chloride, the treated charge is dis-tilled. This distillation removes any reaction pro-ducts which may dissolve in the excess hydrocarbon present. The distillate is a material containing purified and concentrated olefins, particularly normal, alpha mono-rolefins. The distillate fraction boiling from about 100 F. to about 600 F.. and boiling predominantly within the range -500 F., is taken overhead.

7 It will. be apparent from the discussionof the zinc chloride treat and from the earlier discussion of the conversion processes contemplated herein that the treated olefinic charge stocks should contain normal, alpha mono-olefins havally not improved. Aluminum chloride, which has been used considerably in hydrocarbon treatments, has proven to be undesirable in the procedure contemplated herein. As demonstrated ing from about six to twelve, fourteen or eighteen 5 hereinafter, A1013 does not improve the color or carbon atoms depending upon the conversion carbon residue values, but actually has a deleprocedure. Accordingly, the predominant porterious effect. Ferric chloride, too, is of little tion of the treated olefinic mixture should boil value. above about 145 F., the boiling point of n-hexene-l, with the maximum boiling point of the 10 EXAMPLES treated mixture being not substantially greater The following specific examples serve to illusthan the boiling point of a normal, alpha monotrate, and not limit, the invention. In all examolefin of fourteen, sixteen or eighteen carbon ples, the olefin charge stocks used were obtained atoms. It will also be apparent that the boiling from Fischer-Tropsch reactions wherein iron range of the untreated olefinic mixture may be catalysts were used. In Examples I-X, the considerablywider than that of the treated mixcharge stock had a boiling range of 200-300 F., a ture which is converted in the aforesaid procespecific gravity of 0.7559, and contained a predures. The minimum boiling point may be well dominant quantity of normal, alpha mono-olebelow that of the distillate fraction to be confins of seven to nine carbon atoms; in Examples verted, and the maximum boiling point of the un- XI-XIV, the stock had a boiling range of 300-450 treated mixture may be somewhat higher than F., a specific gravity of 0.8003, and the mono-olesaid distillate fraction. With regard to the unfins were mainly of nine to twelve carbon atoms; treated mixture, it is generally advisable to suband in Examples XV-XVI, the boiling range was ject the crude olefinic mixture from the Fischer- 150-5l0 F., specific gravity, 0.7766, and the num- Tropsch process to a preliminary distillation, ber of carbon atoms of said mono-olefins was prior to the zinc chloride treat. In this distillafrom six to fourteen. The quantity of charge tion, gross contaminants such as iron particles stock in each example was 500 parts by weight. and high boiling waxy materials are removed, In the examples wherein a metal halide was and a distillate fraction of the selected boiling used, the olefinic charge and the halide were range is taken. mixed and the charge refluxed at atmospheric While filtration of the charge, prior to distilressure for 1-4 hours, except as indicated otherlation, is not essential, it is a desirable procedure. Wise. The mixture 'was vigorously stirred during With filtration, any occluded solid particles are refluxing and the refluxing was accompanied by removed. water removal. The residual halide was removed In contrast to the zinc chloride treat and its by filtration and the filtrate was distilled. The infiuence upon the synthetic lubricants formed distillate was then converted to a synthetic lubrifrom the treated stocks are treatments with other cant when heated in a bomb, at 625 or 650 F. as metal halides. Calcium chloride, for example, indicated, for ten hours in an atmosphere of nihas been found to be of little or no value in such trogen, as described in detail in said copending a treat. While some improvement in viscosity 40 application Serial No. 761,716. index may be realized when calcium chloride is Pertinent data for the examples are set forth used, carbon residue and color values are generin Table I.

TABLE I Pretreatment of olefinic charge stocks with metal halides Run N0 I II -III Iv v VI VII vnr Bgilling range ofstock used, 200-300 200-300 200-300--.. 200-300.--- 200-300 200-300 200-300 200-300 Pretreatment Filtered Distilled only. CaOlz-l-HCI A1013 (1%) A1013 only. (1%)- (1%)- Temperature, C 110 29 (liq.). Time, hours l. 2. Water removed, parts 4.0 None by weight. Redistillation,F 200-290.-.- 200-294."- 200-300 200-280 200-300 200-302 Distillate color W.white Yel1ow. Pale yellow Pale yellow- Pale yellow. Yellow Material balance:

Redisttilled charge, per- 70.0 89.0 80.0 79.0 89.0 02.0 Dfs ta iltlationresiduapen 12.8 6.05 2.4 5.2 7.8 4.8. 'i liosse ercentun 11.2 4.95 17.0 15.8 3.2 33.2. Distillate inspections:

Bromi(1i1)e number (Nor- 99.9 97.7 104.8 100.7 99.5 102.4. sggcfitcgmvt 0.7491. 0.7515. 0.8348 0.7519 01519.1"--. 0.7511 Conversion:

Marxsimum pressure Oil yield, wt. percent of treated hydrocol charge. Residual oil:

Color, lovibond Carbon residue, Ramsottom. Specific gravity.-- Pour point, F"... K. V., centistokes a 210F Viscosity index 1 Abnormal losses in bomb.

TABLE IContinued Pretreatment of olefim'c charge stocks with metal halides Run No IX X XI XII XIII XIV XV XVI Boiling range of stock used, 200-300---- 200-300-.-- 300-450 300-450 300450 300450 150-509.- 150-509. Pretreatment Fe???) BEE-$33711) Reiiluzxed and ZnClz(1%).. ZnOlz(2%).. FeCh(1%). None Z1101: (1%).

Temperature,0 1101..." 29 (111 5... 176.7 (liq)- 149 117 (1lq.)-- 176.7 (liq.)- Time,hours 1 1 2 4. Water removed, parts 2.9 None- 1.0.

byweight. Redistillation, F 200-300.--. 200-310 300-421 Distillate color W.'white W.white Yellow Material balance:

Rcdisttllled charge, per- 89.0. 86.0 87.4

cen Distillation residue, per- 5.0 5.4 9.65

cen Total losses, percent. 6.0 8.6 2.95 Distillate inspections:

Bromidn)e number (Nor- 1019..-... 101.0 73.4

woo Specific gravity 0.7519.-- 0.7479--- 0.8003 Conversion:

Maximum pressure 1,650 1,450 300 (PSI). Oil yield, wt. percent 18.5 16 34.1

of treated hydrocol charge. Residual oil:

Color, lovibond l4 7. Carbon residue, Rams- 0.09 0.04. bottom. I

Specific gravity 0.8458. 0.8628. Pour point, F (-30.

K. V., centistokes at- Viscosity index 105 .3.

2 Slow distillation over solid ZnClz, variable temperature.

Considering the foregoing data for Examples I-IV, it will be noted that the sequence of zinc chloride treat, distillation and conversion of dis tillate make possible the production of a superior lubricant. The example, the viscosity index values (V. I.) of the lubricants identified as Examples III and IV are 104 and 99, respectively; Whereas, the V. I., of Examples I and II are only 92 and 96, respectively. In this connection, it should .be noted that V. I. values are accurate to about 12% (this includes normal variation in polymerization step, etc). The data also reveal a substantial color improvement, 1.2 and 5.0 for the oils of Examples I11 and IV, respectively, compared with 48 and 13, respectively, for the oils of Examples I and II. Substantial reduction in carbon residue is also shown by Examples III and IV.

The effect of other metal halides is shown by Examples V-X. Calcium chloride is shown in Examples V and VI, demonstrating improvement in V. I. but less desirable color and carbon residue values. Examples VII and VIII reveal that aluminum chloride may have an adverse efiect or an improving effect upon V. I., but greatly depreciates the color and carbon residue values. Ferric chloride is shown in Example IX; no improvement in carbon residue is realized and there is but slight improvement in V. I.

Examples XI-XIV involve a different fraction of olefinic stock, with the results similar in character to those of Examples I-X.

The value of slowly distilling an olefinic charge stock over zinc chloride is shown by Examples XV and XVI.

It is to be understood that the foregoing specific treating conditions and examples serve to illustrate the invention, for it will be apparent to those skilled in the art that modification and variations thereof may be used. It is to be under-' stood, therefore, that such modifications and variations fall within the scope of the appended claims, and that the invention is to be construed broadly in the light of the language of the claims.

We claim:

1. The process for preparing a synthetic lubricant having good color, low carbon residue and high viscosity index, which comprises: contacting with a zinc halide an olefim'c charge stock obtained by a Fischer-Tropsch reaction, a sub stantial portion of said stock boiling within the range of about F. to about 500 F.; distilling said treated stock and collecting an olefinic distillate boiling predominantly within the range of about 150 F. to about 500 F.; and converting said distillate into said synthetic lubricant.

2. The process of claim 1 wherein the halide-is zinc chloride.

3. The process of claim 1 wherein the distillate is converted into said synthetic lubricant by heating the same at a temperature of about 625 F. for about ten'hours.

THOMAS F. RUTLEDGE. FRANCIS M. SEGER.

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

UNITED STATES PATENTS I Heinrich et a1. May 9, 1950

Claims (1)

1. THE PROCESS FOR PREPARING A SYNTHETIC LUBRICANT HAVING GOOD COLOR, LOW CARBON RESIDUE AND HIGH VISCOSITY INDEX, WHICH COMPRISES: CONTACTING WITH A ZINC HALIDE AN OLEFINIC CHARGE STOCK OBTAINED BY A FISCHER-TROPSCH REACTION, A SUBSTANTIAL PORTION OF SAID STOCK BOILING WITHIN THE RANGE OF ABOUT 150* F. TO ABOUT 500* F.; DISTILLING SAID TREATED STOCK AND COLLECTING AN OLEFINIC DISTILLATE BOILING PREDOMINANTLY WITHIN THE RANGE OF ABOUT 150* F. TO ABOUT 500* F.; AND CONVERTING SAID DISTILLATE INTO SAID SYNTHETIC LUBRICANT.