US2094593A

US2094593A - Method of making high viscosity

Info

Publication number: US2094593A
Authority: US
Publication date: 1937-10-05
Anticipated expiration: 1954-10-05

Description

Patented Oct. 5, 1937 UNITED STATES PATENT OFFICE METHOD OF MAKING HIGH VISCOSITY INDEX LUBRICATING OILS tion of Delaware No Drawing. Original application June 11, 1934,

Serial No. 730,064. Divided and thisapplication October 24, 1936, Serial No. 107,500

9 Claims.

This invention relates to hydrocarbon lubricating 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.

This application is a division of our co-pending application Serial No. 730,064, filed June 11, 1934, but relates more particularly to the production of high viscosity index oils of substantially the same molecular Weight range as that of the initial hydrocarbons from which they are prepared, by operations in which silica gel is utilized as catalyst in the production of the said high viscosity index oils.

As is well known, lubricating oils from Pennsylvania crude oils have higher viscosity indices .than those obtained from Mid-Continent, Gulf or 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, and to 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 lowering the viscosity index of the blend or mix below those of the most superior naturally occurring oils.

We have found that the viscosity ind-ex of the hydrocarbons or series of hydrocarbons in the lubricating oil range of boiling points increases as the structure of the hydrocarbon molecules approaches that of the normal straight chain paraffines, andthat, in fact, the normal straight chain parafiines themselves (for example, the parafiine Waxes) possess apparent viscosity indices far higher than thoseof the most superior parafiine base lubricating oils known.

It is a purpose of the invention to provide hydrocarbon lubricating oils whose molecular structure approaches that of the normal straight chain parafiines and whose viscosity indices approach those of the normal straight chain paraflines 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 invention are produced, generally, by dehydrogenating essentially saturated hydrocarbons of the normal straight chain series, for example, the parafiine waxes, to form olefines and diolefines, and, if desirable, polymerizing the produced olefines and diolefines, wholly or in part, to form higher average molecular weight hydrocarbons of any desired volatility or viscosity range.

The dehydrogenated paraffines (olefines and diolefines) have the same molecular structure, 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. Upon polymerization, 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 parafline 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 at temperatures of 250 F. or higher, however, decomposition of part of the chlorparaifines takes place, and hence are to be avoided. Chlorination catalysts, such as traces of iodine, may be used, but are generally not necessary. Eificient contacting of gas and liquid obviously increases the rate of chlorination.

In the chlorination step, chlorination of all of the parafiine 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-chlor paraffines increase, with respect to monochlorparaffines; moreover, as the proportions of diand higher chlor derivatives increase, the viscosity of the dechlorinated product increases, probably by reason of the greater ease of polymerization of the di-, trl-, etc., olefines produced. Further than this, the viscosity index of the dechlorinated product, whether polymerized to a high or low degree, is lower by reason of the formation of di-, tri-, etc., chlorparaifines, 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 monochlorparaffines will produce hydrocarbons with the longest and most nearly normal straight chains.

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

Un- Chlorinated paraffines mol. chlorinpercent ated Percent chlorine absorbed wax by wax (percent gain in weight upon chlorination) Di- Tri- Higher gg 3. 5 l 72. 5 1l 2. 5 0. 5 52. 5 l9. 5 7. 0 2. 0 34. 0

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 of chlorination may be combined with convenience and high efliciency of wax utilization by chlorinating for a brief period, say to a point when 3-6% by weight of chlorine has been absorbed, on the basis of wax treated, and cooling the partially chlorinated mixture to 70 F. or below. The chlorparaffines, whatever their degree of chlorination, are light mobile liquids at very low temperatures, whereas, as is well known, the paraffine waxes are solid below about 110 F. It has been found that the chlorinated paraifines are excellent crystallizing agents for the unchlorinated waxes, and that the waxes are essentially insoluble in them. By cooling the chlorination mixture to 70 F. or below, very good separation of chlorinated and unchlorinated hydrocarbons may be efiected by the use of a bulk centrifuge without the use of a filter aid, as is invariably necessary in the removal of solid waxes from crude petroleum distillates or residue. In this manner unchlorinated wax, inert in the remaining steps in the process, is prevented from becoming an ingredient of the final oily product; moreover, by return of the wax to the chlorinating step in the process, its utilization is made substantially complete.

For the several reasons advanced above, we prefer that chlorparaffines be produced containing from 13-23% chlorine, on a wax-free basis, and that unchlorinated wax be removed by simple bulk centrifugation and returned for use in a subsequent chlorinating operation. Hereinafter, the terms chlorinated paraflines" and chlorparafiines 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 concerns the color of the finished dechlorinated oils. Lead'or porcelain lined vessels, fittings, etc., are found to have no deleterious effect of this character, and hence are preferred in the construction of the chlorinating apparatus.

The wax-free chlorparaffines are dechlorinated at elevated temperatures with the aid of a dechlorinating 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. Whether polymerization 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 of the use of both nonpolymerizing and polymerizing dechlorination catalysts. Typical of the first class of catalyst (dechlorinating, non-polymerizing) are various of the adsorbent earths,clays of both the fullers 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 conof HCl may conveniently be removed by the use of steam or an inert gas. After HCl 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.

Ezrample 1.A yellow crude scale wax was chlorinated to a chlorine content of 18.6% by weight, on a wax-free basis, and the chlorparafiines separated from unchlorinated wax by bulk centrifuging at 35 F. The fluid chlorparaffines were mixed with 10% by weight of 30-60 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

Viscosity at 100 F 173 secs. Sayboltuniversal Viscosity at 210 F 48 secs. Saybolt universal Viscosity index (Dean 85 Davis) 137 Pour 50 F. Solid 45 F.

Example 2.--A chlorinated parafiine, dewaxed and containing 18.6% chlorine by weight, on a wax-free basis, made by the chlorination of yellow crude scale wax, was mixed with 10% by weight of. an acid-treated 200 meshdecolorizing clay of the montrnorillonite type and heated to 525 F. as rapidly as HCl evolution permitted; it. was held at that temperature until HCl evolution had ceased. Upon cooling somewhat-it was filtered to remove clay. A pale yellow oil with a green bloom was obtained; its characteristics were as follows:

Viscosity at 100 F 144 secs.Saybolt universal Viscosity at 210 F 44 secs. Saybolt universal Viscosity index' 122 Pour"; 60F. Solid 55F.

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

Viscosity at 100 F 151 secs. Saybolt universal Viscosity at 210 F 44 secs. Saybolt universal Viscosity index 113 Pour F. Solid F.

Example 3.--Silica gel, used in the amount and under the conditions detailed in Example 1, above, produced an oil having characteristics identical with those there tabulated.

When using a dechlorination and polymerizing type of catalyst, such as aluminum amalgam or metallic aluminum, the chlorparafiine' is mixed therewith and heated, with agitation, to temperatures between 200and 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. Theresulting oils are darker in color than those prepared with the clay type dechlorinating catalysts; they are of relatively high viscosity, by reason of. the polymerization taking place simultaneously with dechlorination. 1

Example 4.-Substantially wax-free-chlorparaifines containing 21.7% chlorine by weight, made from yellow crude scale wax, were heated with 70.5% 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. forabout 3 hours, by which time dechlorination was-. complete; No sludge, such as is characteristic of the use of anhydrous aluminum chloride, was formed 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: v w

Viscosity at 100 F 690 secs. Saybolt universal Viscosity at 210 F 88 secs. Saybolt universal When dewaxed, this oil had a 0 F. pour point and viscosity index off120. I Y

The aluminum amalgam used above is prepared by contacting aluminum turnings with 5% sodium hydroxide in. the presence of mercury; the sodium hydroxide produces a perf ectly clean surface with which the mercury readily amalgarnates, The amalgam contains about of mercury, by weight; it is'washed free of hydroxide by means of alcohol, and, because of its great reactivity, isladded immediately to th'e chlorparaffine in the .reaction vessel. j

. Example I5.--Wax-free chlorparaifine's containing. 18.6% chlorine were heated with 0.5% by weight of clean aluminum turnings. As the temperature rose, dry HCl gas was bubbled in small amount through the liquid. .At about 200 F. dechlorination commenced, andthe introduction of dry HCl was thereupon discontinued. The 'temperaturewasincreased to 300 F. and held at that point for-about 2 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. separation from the aluminum catalyst and steaming, etc., torernove traces of HCl, had the followingproperties: 1 Viscosity at 100--F 445 secs.Saybolt universal -Viscosity at 210 F 68 secs. Saybolt universal Viscosity index 122 P0ur F. Solid; 60 F.

Example 6.-Metallic aluminum may be used as dechlorinating' and polymerizing catalyst with out the introduction'of HCl to initiate the reaction, as'was exemplified-above (Example 5). In this event, however, higher temperatures must be used and a longer time of heating is required to give equivalent 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 temh peratures, however, excellent'results are obtained, and the following oil,obtained in this manner from a wax-free chlorparafilne containing 15.2% chlorine with the' use of 1% of aluminum by weight, is'typical: r Y Viscosity at 100 F 918 Viscosity at 130 F 432 secs. Saybolt universal Viscosity at 210 F 109 secs. Saybolt universal Viscosity index 126 Pour 65 F.

Solid 60 F.

Anhydrous aluminum chloride is in wide use as a dechlorinating agent,and also as a polymerization catalyst. It functionsin the present dechlorination-reaction is initiated, inuthe latter case,

The resulting oil, after secs. Saybolt universal ination-polymerization reaction to produce satiswith anhydrous HClr As is well known, anhydrous aluminum chloride invariably forms anv like purpose.

In addition to loss in yield of high quality oil through the formation of the typical aluminum chloride'sludge, this catalyst isless' desirable than aluminum 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 required. For example: Wax-freechlorparaffine containing 13.7% chlorine was heated with 5%' by weight of anhydrous aluminum chloride for a total time of 5 hours, the latter 4 of which were at 325 F. After sludge removal, steaming etc.,

and filtration, the produced oil had the following characteristics: I

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 87" Pour 55 F. Solid 1 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 in each case were above 90%, From theabove 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 viscosityof 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 reac- 7 tion 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 paraffine containing 15.6% chlorine by weight, ona wax-free basis, was heated with 10% by. weight of the acidtreated clay. of the montmorillonite type and 0.5% by weightof aluminum, for l hours at 300 F. The temperature was then raised to 500 F. and held there for about 30minutes, by which time dechlorination wascomplete. The reaction mixture was cooled and filtered free of I Reaction time in hours 3 4 Temperature, degrees F 250 250 clay and of aluminum. A light yellowoil with a green bloom was obtained; it had the following characteristics:

Viscosity index 130 Pour 60 F. Solid 55 F.

This oil was dewaxed with liquefied propane as dewaxing diluent, at -40 FL, 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 of Example 7, above, we heat the chlorparaffines with aluminum or aluminum amalgam alone, until'the reaction has proceeded 'sufiiciently to produce an oilof the desired viscosity; without removing any of thereaction products produced by thealuminum 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 ofthe 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 correct selection ofthe chlorine content ofthe chlorinated parafline, 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:

3 4 I 5 250 300 300 300 Chlorine content 12.0%:

ViScOSitY at 210 F 6O 58 65 6O 61 63 Viscosity ind1x 130 137 136 134 122 Chlorine content 18.5%:

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 382 440 354 113 112 113 Viscosity index In these experiments, aluminum amalgam was used as dechlorinating catalyst. t From the results above tabulated it appears hat:

1. The viscosity and viscosity index of the synthetic oil are almost'wholly dependent on the chlorine content of the chlorinated paraffine. The higher the chlorine content, the higher the viscosity and the lower the viscosity index.

2. They reaction time and reaction temperature, within thelimits shown above, have relatively 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 chlorinecontent, the longer the reaction time must be for the reaction to go to completion.

In'blending the high viscosity index oils herein described with oils of low viscosity indeX,-for example, to. improve in this respect the naphthenic or mixed-base naturally occurring 0115;-

Syn- Naph- 50-50 thetio theme n oil blend Viscosity at 100 F 690 687 643 Viscosity at l30 F 324 259 274 Viscosity at 210 F. 88 60 70 Viscosity index 124 25 04 It will be observed that the pour points of several of the oils whose production is described above are higher than is desirable for some lubricating purposes. The pour points of these oils may be lowered by a dewaxing process, as mentioned above in connection with Examples 2 and 4, or, if preferable, by adding small amounts of a specially prepared pour point lowering compound, such as is described, for example in U. S. Patent #1,815,022, issued July 14, 1931, to Garland H. B. Davis. Representative of the results obtained with the use of the Davis compound, identified in the trade as Paraflow, are the following:

Pour Solid Synthetic oil (Example 4, above) 65 F. 60 F. Same, plus 2.0% Paraflow 15 F. 10 F.

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 oil which comprises chlorinating straight chain parafiine hydrocarbons to a chlorine content of between 10 and 25%, on a hydrocarbonfree basis, and dechlorinating the chlorinated hydrocarbons in the presence of silica gel at elevated temperatures.

2. A process of producing a high viscosity index oil which comprises chlorinating straight chain parafiine hydrocarbons to a chlorine content of between 10 and 25%, on a hydrocarbonfree basis, removing unchlorinated hydrocarbons, and dechlorinating the chlorinated hydrocarbons in the presence of silica gel at elevated temperatures.

3. A process of producing a high viscosity index oil which comprises chlorinating straight chain paraffine wax hydrocarbon to a chlorine content of between 10 and 25%, on a hydrocarbon-free basis, cooling the chlorination product to allow unchlorinated wax hydrocarbons to crystallize from produced liquid chlorparaffines, removing crystallized wax hydrocarbons, and dechlorinating the produced chlorparaflines in the presence of silica gel at elevated temperatures.

4. A process of producing a high viscosity index oil which comprises chlorinating straight chain parafiine wax hydrocarbons to a chlorine content of between 13 and 23%, on a hydrocarbon-free basis, cooling the chlorination product to allow unchlorinated wax hydrocarbons to crystallize from produced liquid chlorparamnes, removing crystallized wax hydrocarbons, and dechlorinating the produced chlorparaflines in the presence of silica gel at elevated temperatures.

5. A process of producing a liquid hydrocarbon oil from parafline wax hydrocarbons, comprising chlorinating parafiine wax hydrocarbons at a temperature not above about 250 F., to produce a mixture of mono-, diand tri-chlor derivatives consisting of mono-chlor derivatives in major part, cooling the chlorination product to allow unchlorinated wax hydrocarbons to crystallize from produced. liquid chlorparaffines, removing crystallized wax hydrocarbons, dechlorinating the produced chlorparaifines in the presence of silica.

gel at elevated temperatures, and separating the silica gel from the dechlorinated hydrocarbon oil.

6. A process of producing a liquid hydrocarbon oil from paraffine wax hydrocarbons, comprising chlorinating parafline wax hydrocarbons to a chlorine content of not above about 25% on a hydrocarbon-free basis, at a temperature not above about 250 F., cooling the chlorination product to crystallize unchlorinated wax hydrocarbons from produced liquid chlorparaffines,-removing crystallized wax hydrocarbons, and dechlorinating the produced chlorparaflines in the presence of silica gel at temperatures between about 300 and about 550 F.

7. A process of producing a liquid hydrocarbon oil of high viscosity index and of substantially the molecular weight of the parafiine wax hydrocarbons, comprising passing chlorine gas into a parafiine wax containing hydrocarbon mixture at a temperature between about 110 F. and about 250 F. to produce chlorparafiines containing not above about 25% chlorine on a hydrocarbon-free basis, cooling the mixture containing unchlorinated wax hydrocarbons and produced 'chlorparafiines to a temperature below the crystallizing temperature of the unchlorinated parafiine wax hydrocarbons, separating unchlorinated wax hydrocarbons from the liquid chlorparaflines,

heating the produced chlorparaffines with silica gel to a temperature above about 300 F. to dechlorinate the chlorparafiines without substantial polymerization of the dechlorinated hydrocarbons, and separating the silica gel from the produced dechlorinated liquid hydrocarbon oil.

8. A process of producing synthetic hydrocarbon oils of high viscosity index which comprises chlorinating straight chain parafline hydrocarbons to a chlorine content not above about 25% on a hydrocarbon-free basis, to produce a mixture of mono-, diand tri-chlor derivatives which consist in major part of mono-chlor derivatives, and dechlorinating the produced chlor derivatives with silica gel to produce olefinic hydrocarbons consisting of mono-olefines in major part.

9. A process of producing synthetic hydrocarbon oils of high viscosity index which comprises chlorinating straight chain parafline hydrocarbons to a chlorine content of between about 3% and about 6% by weight, on the basis of the whole hydrocarbon-chlorhydrocarbon reaction mixture, and dechlorinating the produced chlorhydrocarbons with silica gelas dechlorinating catalyst.

ELMSLIE W. GARDINER. JOHN W. GREENE. ARTHUR L. LYMAN.