US2082203A - Methob of making high viscosity - Google Patents

Description

Patented June ,1, 1937 METHOD OF MAKING HIGH VISCOSITY INDEX LUBRICATING OILS Elmslie W. Gardiner,

John W. Greene, and

Arthur L. Lyman, Berkeley, Calif., assignors to Standard Oil Company of California, San Francisco, Caliil., a corporation of Delaware No Drawing. Application June ll, 1934, Serial Nil. 730,064

9 Claims.

This invention relates to hydrocarbon'lubrieating oils which-have extremely fiat viscosity: temperature curves,that is, whose viscosity indices (as defined, for example, by Dean and Davis in Chemical and Metallurgical Engineering, 1929, vol. 36, page 618) are extremely high. The invention also relates to processes for producing hydrocarbon lubricating oils which possess this desired property.

As is well known, lubricating'oils from Pennsylvania crude oils have higher viscosity indices than those obtained from Mid-Continent, Gulfor California crudes, and, in fact, are superior in this respect to lubricating oils obtained from any other naturally occurring crude, oils.

It is a purpose of this invention to provide hydrocarbon lubricating oils possessing considerably higher viscosity indices than those of the most superior naturally occurring oils, andto provide suitable methods of producing them. It is another purpose of the invention to provide lubricating oils of such high viscosity indices that very considerable amounts of low viscosity index oils may be blended or mixed therewith without low- 5 ering the viscosity index of the blend or mix below those of the most superior naturally occurring oils.

We have found that the viscosity index of the hydrocarbons or series of hydrocarbons in the lubricating-oil range of boiling points increases as the structure of the hydrocarbon molecules approaches thatof the normal straight chain parafiines, and that,in fact, the normal straight I It is a purpose of the'invention to provide hydrocarbon lubricating oils whose molecular struc- '40 ture approaches that of the normal straight chain paraifines and whose viscosity indices approach those of the normal straight chain parafiines themselves, but whose fluidity is retained to relatively low temperatures and whose viscosity and boiling points may be of any desired range.

The oils of our inventionare-produced, generally, by 'dehydroge'nating essentially saturated hydrocarbons of the normal straight chain series, for example, the parafline waxes, to form oleflnes and diolefines, and, if desirable, polymerizing the produced oleflnes and'diolefines, wholly or in part, to form higher averagemole'cular weight hydrocarbons of any desired volatility or viscosity range. The dehydrogenated parafilnes (oleflnes and dioleflnes) have the same molecular struceture, so far as length of chain is concerned, as the saturated hydrocarbons from which they are obtained, and moreover, the product is liquid at ordinary temperatures. wholly or in part, branched chains may be introduced, but, due to the length of chain in the hydrocarbons polymerized, all such branched chains in the product are of great length, however far polymerization may be allowed to progress. The produced oils-are. liquid at relatively low temperatures, and possess extremely high viscosity indices, as is exemplified below.

Dehydrogenation of the saturated straight chain hydrocarbons may suitably be brought about by chlorination, followed by dechlorination and the evolution by hydrochloric acid, the latter step taking 'place in the presence of a dechlorination catalyst which may also be a polymerization catalyst, if products of high viscosity are desired.

Although the process as described below is exemplified by the use of parafiine waxes as saturated straight chain hydrocarbons, it will be apparent that the benefits of the invention may be obtained by the use of other hydrocarbon materials, and that the more nearly the original saturated material approaches the single, normal straight chain in molecular structure the greater will be the benefits obtained in the practice of the process.

In the practice of the process:

Parafiine wax (for example, crude scale wax, match wax, Parawax, etc.) is chlorinated by direct contact with chlorine at temperatures of to 210 F. or slightly above. Between these temperatures the rapidity and degree of chlorination of the wax increases with increasing temperature; at temperatures of 250 F. or higher, however, decomposition of part of the chlorparafiines takes place, and hence are to be avoided; Chlorination catalysts, such as traces of iodine, may be used, but are generally not necessary. Efllcient contacting of gas and liquid obviously increases the rate of chlorination.

In the chlorination step, chlorination of all of the parafl'ine hydrocarbons in one operation is impractical, and even undesirable. Thus it has been found that as the degree of chlorination increases, the proportions of diand tri-chlorparaffines increase, with respect to monochlorparafilnes; moreover, as the proportions of diand higher chlor' derivatives increase,-the viscosity of the dechlorina'ted productincreases, probably by reason of the greater ease of 'polymerization of the di tri-, etc., oleflnes produced. Further than this, the viscosity index ofthe dechlorinated Upon polymerization,

product, whether polymerized to a high or low degree, is lower by reason of the formation of di-, .tri-, etc., chlorparafilnes, for, as stated above, the length of chain of the dehydrogenated hydrocarbons has been found to determine in large part the viscosity index of the oil, and it is apparent that the dechlorination of monochlorparafilnes will produce hydrocarbons with the longest and most nearly normal straight chains.

The eflect of increasing degree of chlorination upon the relative proportions of mono-, diand tri-chlorparaflines is brought out thetable below.

- mama-inm ealm g; Chlorinated persfilnesmoL, percent mm wax (percent ess: M... 3333 Mono- Di- Tri- Highnao se as, 1 12.: 0.0 33.5 q n as as as 10.0 sat 10.5 7.0 a0 7 no From a consideration of these data it is apparent that when a product of low viscosity, or a product of high viscosity index (whether of low or high viscosity) is desired, the degree of chlorination should not be high, in any single chlorinating operation.

Low degree or chlorination may be combined with convenience and high efficiency of wax utilization by chlorinating for a brief period, say to a point when 345% by weight of chlorine has been absorbed, on-the basis of wax treated, and cooling the partially chlorinated mixture to 70 F. or below. degree of chlorination, are light mobile liquids at very low temperatures, whereas, as is well known, the parafilne waxes are solid below about 110 F. It has been found that the chlorinated parafilnes are excellent crystallizing agents for the unchlorinated waxes. and that'the waxes areessentially insoluble in them. 'By cooling the chlorination mixture to 70 F. or;beiow, very good separation of chlorinated and unchlorinated hying from 13-23% chlorine, ona wax-free baeis,.

and that unchlorina'ted wax be removed by simple bulk centrifugation and returned for use in a subsequent chlorinating operation. Hereinafter, the terms chlorinated parafllnes" and "chlorparafllnes are to be interpreted on a wax-free basis, that is, after removal of unchlorinated wax.

In effecting chlorination of this type of hydrocarbons, the use of iron reaction vessels, or of ferrous alloy vessels in general, has been found "to produce inferior products, especially as'con-- 'cel'ns the color of the finished dechlorinat'ed oils. Lead or porcelain lined vessels, fittings, etc., are found to have no deleterious efl'ect of this char- 'acter, and hence are preferred in the construction of.the chlorinating apparatus.

The wax-free chlorparafiines are dechlorinated at elevated temperatures with the aid a de- The chiorparafiines, whatever their chlorinating catalyst. Hydrochloric acid is evolved, and olefines, diolefines, etc., depending upon the degree of chlorination (as brought out above), are produced. In the absence of polymerization these hydrocarbons have the same molecular structure as that of the original wax,

namely, single normal straight chains. Whetherpolymerization is or is not allowed to take place, the produced dechlorinated hydrocarbons are entirely of the unsaturated series-olefines, diolefines, etc., and/or their polymers.

The dechlorination catalyst may also be a polymerization catalyst, if products of high viscosity are desired, and there are given hereinbelow examples descriptive ofthe use ofboth non-polymerizing and polymerizing dechlorination catalysts. Typical of the first class of catalyst (dechlorinating, non-polymerizing) are various of the adsorbent earths,--clays ofboth the fuller's earth and bentonite types,--and silica gel. Typical of the second class of catalyst (dechlorinating, polymerizing) are metallic aluminum and aluminum amalgam. Anhydrous aluminum chloride occupies a position intermediate between these two types, so far as polymerization is concerned.

when using the clay or adsorbent earth type of catalyst, the chlorparafiines and clay are heated, with agitation, to'a temperature of 550 ,F., or thereabouts. Hydrochloric acid evolution begins at about 300' I". ahd increases rapidly as the temperature is raised. The reaction is continued until all evolution of H01 has ceased; the last traces of H01 may conveniently be removed by the use of steam or an inert gas. After H01 removal the mixture is allowed to cool somewhat and the clay separated by filtration. The resulting oils are very light in color and possess a green bloom or fluorescence; they are relatively low in viscosity. I

Example L-A yellowcrude scale waxwas chlorinated to a chlorine content of 18.6% by weight, on a wax-free basis, and the chlorparaffines separated from unchlorinated wax by bulk centrifuging at 35 F. The fiuid-chlorparafiines were mixed with 10% by weight of.30-80 mesh Florida clay, such as is used for decolorizing petroleum lubricating oils, and the mixture heated, with agitation, to 500 F. during a period of about 2 hours; the temperature of the mixture was held at 500 F. for 2 hours, by which time .HCl evolution had ceased. The dechlorinated mixture was cooled and filtered free from clay.

There was no oil-insoluble sludge" formed, nor

'did there appear to be any loss of hydrocarbon" material except that held up on the clay. A red oil with a green bloom, having the following characteristics, was obtained:

Viscosityat 100' r.'. 173 Secs. Baybolt Universal Viscosity at 210 1",. 48 Secs. Saybolt Universal Viscosity Index 46' I". I Example z -A chlorinated parafiine, dewa'xed 3m containing 18.6% chlorine by weight, on a.

wax-free basis, made by the chlorination of yelclay of the montmoriilonite type and heated to 525-F. as rapidly as HCl evolution permitted; it

was held at that temperature until H01 evolution had ceased. Upon cooling somewhat it was filtered to remove clay. A pale yellow oil with a its characteristics green bloom was obtained: were as follows:

"Viscosity at 100 F 144 Secs. Saybolt Universal Viscosity at 210 F 44 Secs. Saybolt Universal Viscosity Index 122 Pour F. Solid 557 F.

This oil was dwaxed using four volumes of liquefied butane to one volume of oil, at -40 F. The dewaxed oil had the following characteristics:

Viscosity at 100 F.. 151 Secs. Saybolt Universal Viscosity at 210 F 44 Secs. Saybolt Universal Viscosity Index 113 Pour 01 solid -5 F.

metallic aluminum, the chlor-parafline is mixed therewith and heated, with agitation, totemperatures between 200 and 300 F. Hydrochloric acid evolution begins at about 200 F. and increases rapidly with temperature rise. The reaction is continued until HCl evolution is complete, after which the catalyst is separated and the oil clarified, as before. By reason of the considerable increase in'viscosity attending the use of this type of catalyst, an inert diluent, such as purified (inert) kerosene, may in extreme cases be desirable as a diluent to facilitate handling; the diluent may later be removed, as by ordinary or steam distillation. The resulting oils are darker incolorthan-those prepared with the clay type dechlorinating catalysts; they are of rela-' tively'high viscosity, by reason of the polymerization taking place simultaneously with dechlorination;

Ezample- 4.-Substantially wax-free chlorparamnes containing 21.7% chlorine by weight, made from yellow crude scale waxywas heated with 0.5% by weight of aluminum amalgam,

with agitation. Evolution of HCl began at about 200 F.

The temperature was raised to about 300 F. as rapidly as HCl evolution would permit,

and held at 300 F. for about 3 hours, by which time dechlorlnation was complete. No "sludge, such as is characteristic of the e of anhydrous aluminum chloride, was form with the use of the aluminum amalgam. The! oil was filtered free from aluminum hydroxide] ,after steaming to remove traces of hydrochloric acid. The resulting oil had the following characteristics:

Viscosity at 100 n- 690 Secs. Saybolt Universal Viscosity at 210 F 88 Secs. Saybolt Universal Viscosity Index 137 Pour F. Solid 60 F E:wmple 5.Wax-free chiorparafiines containing 18.6% chlorine were heated with 0.5% by weight of clean aluminum turnings. As the temperature rose, by HG] gas was bubbled in small amount through the liquid. .At about 200 F. dechlorination commenced, and the introduction of dry HCl was thereupon discontinued. The temperature was increased to 300 F. and held at that point for about2 hours, by which time dechlorination was complete. As was noted above, with the use of aluminum amalgam, no "sludge was formed with the use 'of metallic aluminum as catalyst. The resulting oil, after separation from the aluminum catalyst and steaming, etc, to remove traces of HCl, had the following properties:

Viscosity at F;. 445 Secs. Saybolt Universal Viscosity at 210 F 68 Secs. Saybolt Universal Viscosity Index 122 Pour 65 F. Solid 60 F.

Example 6.--Metallic aluminum may be used as dechlorinating and polymerizing catalyst without the introduction of HCl to initiate the reaction, as was exemplified above (Example 5). In this event, however, higher temperatures must to giveequivalent results. Thus, the dechlorination reaction does not begin below about 300 F., and, if the dechlorination is to be completed within 4-5 hours, the reaction temperature should be brought to 400 to 450 F. At these higher temperatures, however, excellent results are obtained, and the following oil, obtained inv this manner from a wax-free chlorparafline' containing 15.2% chlorine with the use of 1% of aluminum by weight, is typical:

Viscosity at 100 F 918 Secs. Saybolt Universal Viscosity at F.-- 432 Secs. Saybolt Universal be used and a longer time of heating is required Viscosity at 210 F 109 Secs. Saybolt Universal- Viscosity index 126 Pour 65 F. Solid. 60 F.

chlorination-polymerization reaction to producesatisfactory high viscosity index oils, but we have found it less desirable than aluminum amalgam, Y

' or metallic aluminum, whether or not the'-de'-- chlorination reaction is initiated, in the latter case, with anhydrous HCl. As is well known, anhydrous aluminum chloride invariably-forms an oil-insoluble sludge" which contains a very considerable amount of hydrocarbon material held in rather loose chemical combination. .'Ihe formation of thissludge decreases'considerably the yield of oil that may be obtained in a reaction such as that here discussed, for, as is well recognized, the hydrocarbons which may be obtained from tlie sludge itself, for example. by decomposition with water, are of inferior quality andrepresent an utter loss except for use as ,a fuel or the like purpose. v

In addition to'loss in yield of high qualityoil through the formation of the typical aluminum chloride sludge, this catalyst is 1cm desirable thanaluminum or aluminum amalgam by reason of its cost and because of the relatively large quantity required. Thus for dechlorination alone (in the absence of polymerization) as much as 5% by weight of anhydrous aluminum chloride. is .75

' in each case were above 90%.

Viscosity at 100 F 97 Secs. Saybolt Universal' Viscosity at 130 F 65 Secs, Saybolt Universal Viscosity at 210 F 39 Secs. Saybolt Universal Viscosity index 8'7 Pour 55 F.

Solid 50 F.

It will be noted that there has been in this instance no appreciable polymerization; to obtain appreciable polymerization, aluminum chloride approaching 10% in amount must be employed, with consequent increase in amount of sludge formed. In the above example, the yield of oil from original wax was 65 per cent by weight; in the preceding examples (Examples 1-6) the yields From the above it will be clear that although anhydrous aluminum chloride may be used as dechlorination and polymerization catalyst (especially the former), the use of aluminum amalgam or of metallic aluminum, the latter either with or without the introduction of HCl to initiate the reaction, is much preferred.

The simultaneous use of both polymerizing (aluminum) and non-polymerizing (clay) type catalysts has been found of advantage, for in this manner the viscosity of the finished oil may be controlled. In the use of the two types of catalysts, aluminum or polymerizing type is allowed to function at relatively low temperatures, for example, 300 F. or thereabouts, until the reaction has proceeded sufficiently to produce oil of the desired viscosity; thereafter, the temperature is raised to a higher point, for example 500 F. or thereabouts, and the non-polymerizing type catalyst allowed to function until dechlorination is complete. The following is an example of this method of operation.

Example 7.Chlorinated parafiine containing 15.6% chlorine by weight, on a wax-free basis,

was heated with 10% by weight of the acidtreated clay of the montmorillonite type and 0.5% by weight of aluminum, for 1 hours at 800 F. The temperature was then raised to 500 I. and held there for about 30 minutes, by which time dechlorination was complete. The reaction mixture was cooled and filtered free of clay and of aluminum. A light yellow oil with a green bloom was obtained; it had the following characteristics:

Viscosity at 100 F 423 Secs. Saybolt Universal Viscosity at 210 1f 70 Secs. Saybolt Universal Viscosity index;-- 130 Pour 60 F. Solid 55 F. I

This oil was dewaxed with liquefied propane as dewaxing diluent, at -40 lit, and an oil was produced with a. cold test'of F., a viscosity of '75 at 210 F. and a viscosity index of 115.

If desired, this use of both polymerizing and non-polymerizing type catalysts may be in partial sequence, rather than simultaneous throughout.

- Thus, in a modification of the sequence of the steps ofiExample 7, above, we heat the chlorparaflins with aluminum or aluminum amalgam alone. until the reaction has proceeded sumciently to produce an oil of the desired viscosity; without removing any of the reaction products produced by the aluminum or aluminum amalgam reaction, other than the produced hydrogen chloride, we then add a non-polymerizing (clay) type catalyst, continuing the heating until dechlorination is complete. The results obtained in using such a sequence of steps are similar to those of Example 7, above, with the advantage that control of the character of the desired end product is in many cases facilitated.

We have found, in general, that the viscosity of the finished oil can be controlled by the correot selection of the chlorine content of the chlorinated paraflin, the time of reaction and the temperature of reaction. The following tabulation will make clear how the practice of our invention may be varied to produce oils, varying viscosity and varying viscosity index:

Reaction time in hours 3 4 3 4 5 Temperature, degrees F- 250 250 250 300 300 300 Chlorine content 12.9%:

Viscosity at 210 F 60 58 65 60 61 63 Viscosity index. 134 139 137 136 134 122 Chlorine content 18.6%:

Viscosity at 210 F 83- 91 115 115 107 80 Viscosity index 131 127 128 125 124 125 Chlorine content 24.1%:

Viscosity at 210 F 382 440 354 Viscosity index 113 112 113 little effect on the viscosity of the synthetic oils,

These two factors control the degree of removal of the chlorine. The temperature must be at least 250 F. for complete dechlorination in a reasonable time. Also the higher the chlorine content, the longer the reaction time must be for the reaction to go to completion.

In blending the hi described with oils f low viscosity index,--for example, to improve in this respect the naphthenic or mixed-base naturally occurring oils,- it is tobe pointed out that the viscosity index (as' defined by Dean and Davis. supra) is not the arithmetic mean of the viscosity indices of the blended 0113, but is in all cases considerably higher. For example, the oil whose preparation was described above in Example 4 was blended with an equal volume of a naphthenic-type lubricating 011 whose viscosity index was 25, by the Dean and Davis method of calculation. The characteristics of the oils and of this 50-50 blend follow: a

s thetio Na hthonic I 50-50blend Pour Solid Synthetic oil (Example 4, above) 65 F. 60 F. Same, plus 2.0 Pareflow't 16 F. 10 F.

hydrocarbon oil which comprises chlorinating' While we have described in detail the character of our invention and given numerous illustrative examples of the preparation of synthetic hydrocarbon oils of high viscosity index, we-have done so by way of illustration and with the intention that no limitation should be imposed upon the invention thereby We claim:

1. A process of producing a high viscosity index lubricating oil which comprises chlorinating straight chain parafiine hydrocarbons to a chlo- I rine content of between 10 and 25% on a hydro-- carbon-free basis, removing unchlcrinated hydrocarbons, dechlorinating the chlorinated hydrocarbons in the presence of a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays, at

elevated temperatures, and separating the catalyst from the dechlorinated hydrocarbon oil.

2. A process of producing a high viscosity index straight chain parafline hydrocarbons to a chicrine content oi! between 10 and 25% on a ,hydrocarbon-free basis, removing unchlorinated hydrocarbons, dechlorinating the chlorinated hydrocarbons in the presence of a fullers earth at elevated temperatures, and separating the fullers earth from the dechlorinated hydrocarbon oil.

3. A process of producing a high viscosity index hydrocarbon oil which comprises chlorinating straight chain parafline hydrocarbons to a chlorine content of between 10% and 25% on. a hydrocarbon-free basis, removing unchlorinated hydrocarbons, dechlorinating the chlorinated Irvdrocarbons inthe presenceof a montmorillonite earthat elevated temperature, and separating the montmorillonite earth from the dechlorinated hydrocarbon oil.

4. A process of producing a liquid hydrocarbon oil from parafiine wax hydrocarbons, comprising chlorinating paraihne wax hydrocarbons at a temperature not above about 250 F., to produce a mixture oi mono-, diand trichlor derivatives consisting o! monochlor derivatives in major part, cooling the-chlorination product to allow unchlorinated wax hydrocarbons to. crystallize from produced liquid chlorparamnes, removing crystallized wax hydrocarbons, and dechlorinating the produced'cmorparaflines inthe presence of a dechlorinating catalyst selected from the group consisting ofiullers earths and the montmorillonite clays at elevated temperatures.

5. A process of producing a liquid hydrocarbon oil from paramne was hydrocarbons, comprising chlorinating parafline wax hydrocarbons to a chlorinecontent of not above about 25% on a hydrocarbon-free basis, at a temperature not above about 25091 F., cooling the chlorination product to crystallize unchlorinated wax hydrocarbons from produced liquidchlorparaflines, re.- moving crystallized wax hydrocarbons, and dechlorinating the produced chlorparaflines in the presence of a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays at temperatures between about 300 and about 550 F.

6. A process of producing a liquid hydrocarbon oil of high viscosity index from parafline wax hydrocarbons, comprising passing chlorine gas into a parafiine wax containing hydrocarbon mixtureat a temperature between about F. and about 250 F. to produce chlorparafilnes containing not above about 25% chlorine, on a hydro carbon-free basis, cooling the mixture containing unchlorinated wax hydrocarbons and produced chlorparafiines to a temperature below the crystallizing temperature of the unchlorinated parafiine waxhydrocarbons, separating unchlorinated wax hydrocarbons from the liquid chlorparaflines, heating the produced chlorparafllnes with a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays to a temperature above about 300 F. to dechlorinate the chlorparafilnes without substantial polymerization of the dechlorinated hydrocarbons, and separating the dechlorination catalyst from the produced dechlorinated liquid hydrocarbon oil.

7. A process of producing synthetic hydrocarbon oils of high viscosity index which comprises chlorinating straight chain paramn hydrocarbons to .a chlorine content not above about 25% on a hydrocarbon-free basis, to produce a mixture'of mono-, diand trichlor derivatives which consist in major part of monochlor derivatives and dechlorinating the produced chlor derivatives with the aid of a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays to produce olefinic hydrocarbons consisting of monoolefines in major part.

8. A process of producing synthetic hydrocarbon oils of high viscosity index which comprises chlorinating straight chain paraflin hydrocare bons to a chlorine content-of between about 3% and about 6% by weight. on the basis of the whole hydrocarbon-chlorhydrocarbon reaction mixture, v

and dechlorinating the produced chlorhydrocarbons with a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays.

9. A process of producing a high viscosity in-' dex lubricating oil which comprises chlorinating straight chain paraflin hydrocarbons to a chicrine content of between 13 and 23 percent, on a hydrocarbon-free basis, removing unchlorinated hydrocarbons, dechlorinating the chlorinated hydrocarbo'ns in the presence of a dechlorinating catalyst selected from the group consisting of fullers earths and the montmorillonite clays, at