US2348459A - Process for producing oils with low pour points - Google Patents

Description

May 9, 1944. 2,348,459

` PROCESS FOR PRODUCING OILS WITH LOW POUR POINTS B.` ENGEL Filed Dec. 51. 193s Y mf fm Mm W4 r 5,.

M f W4 Patented May 9, 1944 PROCESS FOR PRoDUoING oiLs wrrn Low POUR Poms Bruno Engel, Appelviken, Sweden, assigner to Aktiebolaget Separator-Nobel, Stockholm, Sweden, a corporation of Sweden Application December 31, 1938, Serial No. 248,874

In Germany January 4, 1938 s claims. (ci. 19e-1s) In the dewaxing of oils and tars as Well as their distillation and transformation products it is generally desirable that the dewaxed oil should have as low a pour point and as nat a temperature-viscosity curve as possible. In order to remove the wax from the said products, they are diluted by adding agreater or lesser amount of a solvent and are then chilled,y whereupon the solid wax precipitated at the low temperature is removed by means of filters, presses, centrifuges or the like.

In such processes the refrigerating energy required for the chilling is of great economic importance. It is therefore desirable to use as small on amount as possible of such solvents by which is obtained an oil whose pour point is scarcely higher than the dewaxing temperature. This requirement'is fullled only by solvents of the type which have a marked selectivity relative to the groups of hydrocarbons contained in the oils, such as parafnic and naphthenic and aro.- matic compounds."

The greater the selectivity of the solvent, the higher the temperature which may be used for the removal of a given amount of solid wax and for obtaining a given pour point. On the other hand, if a solvent without selective effect is used, the dewaxing must be effected at a comparatively A low temperature if the same pour point is to be secured.

For instance, to produce an oil having a pour point of 15 C; from a Roumanian mineral oil` distillate by means of dewaxing, it is necessary to cool to at least 40"C, if non-selective solvents,

such as propane, butane or naphtha, are used, f

whilea-'temperatureof only 15 to 17 C.l is suiiicient if a selective solvent, such as dichlorethane, is used. In the latter case the amount of solvent required is also substantially smaller than in the former. v

If paran base oils are treated, the selective qualities of the solvents have, of course, prac-V tically no disadvantageous effect on the viscositytemperature curve. But with mixed base oils, and to a still highervdegree with asphalt base oils, the

selectivity may cause disadvantages, as the highly polymeric hydrocarbons, such as resins, asphalts, etc., are precipitated in more or less colloidal form and make the removal of the wax more diiicult, the yield thereby often being considerably reduced. In order to avoid this, aromatic hydrocarbons, such as benzene, toluene, are in many cases added as so-called oil-dissolving agents to the ordinary dewaxing agents.

As a further disadvantageous phenomenon, it

may be mentioned that besides the solid waxprecipitated at the given temperature, valuable parafnous hydrocarbons, which are liquid at ordinary temperature, are precipitated orenclosed in the solid phase, which entails not only areduction in yield of oil but also a very considerable reduction of the viscosityrindex of the dewaxed oil.

This phenomenon, which is particularly conspicuous in connection with mixed base oils, may make it impossible to obtain a given low pour point with the aid of selective dewaxing gents. If, for instance, it is desirable to obtain a 4pour point of 20 C., it would be necessary to treat the oil with a suitable wax precipitating agent at a temperature between 15 and 20 C. Within this temperature range and with the kinds ofoils mentioned above, the selectivity is so high that a considerable proportion of the valuable parafiincus lubricatingoil constituents are enclosed in the precipitated solid wax, with a resultant reduction not onlyin yield but'also in the viscosity index. If, on the other hand, the dewaxing is carried out' at a comparatively high temperature, for instance above 15 C., the solubility of the crystalline wax is too high, and the oils obtained have a pour point considerably higher than that required. I

It has now been found that these objections can be avoidedby eifecting the dewaxing with the aid of selective wax precipitating agents in two or more stages. AA selective separation 'of the solid and fluid Wax particles from the other groups of hydrocarbons is rst effected. ThenV a separation at higher temperature of the mixture of wax hydrocarbons into solid crystalline wax and uid lubricating 'oil" particles is'eiecte'd. Finally, the uid parainic hydrocarbons obtained in the second separation are, allor partly, kadded to the primary oil (hereinafter called ex-- tract) obtained in the rst separation.

By this process `thel following advantages are obtained:

1. Only the solid hydrocarbons, which increase the pour point of the oil, are separated as the nal wax product. They are obtainedin very pure form.

2. By adding the uid Wax hydrocarbons to the primary oil, not only lubricating oils with a paraffinic pour point, but also lubricants with a dat viscosity-temperature curve, are obtained.

3. It is allowable to keep in solution or to bring into solution a relatively great proportion of the soft wax, possibly allthe soft waxes', which, as is Well known, substantially raise the viscosity ndex, without substantially point.

If the first separating stage is carried out at a comparatively low temperature, the obtained extract is a concentrate of viscosity bearers rich in aromatics, which renders diicult the precipitation of. soft wax, etc., in the same manner as takes place on addition of so-called pour point reducers. Consequently the second separating stage, that is, the division into solid wax and par-v alinic lubricating oil components, can be carried out at comparatively high temperatures. By mixing the extract from the rst stage with the fluid hydrocarbons liberated from the hard wax, the pour point of the hydrocarbons is substantially lowered, and simultaneously the viscosity index of the dewaxed primary oil or extract and the total yield of oil are considerably raised.

This process is advantageously carried out in continuous operation in centrifuges, as indicated in the following example.

100 kg. of a Roumanian heavy distillate are mixed with 200 kg. dichlorethane and centrifuged at ,-2G C. Thereby are obtained 64 kg. mixture of dewaxed oil and solvent as well as 236 kg. mixture of solid wax hydrocarbons and enclosed therein fluid wax hydrocarbons with solvent. From 64 kg. dewaxed oil and solvent, lli kg. eX- trac are obtained by distillation. The 236 kg. wax and solvent are now heated under stirring to from to +5 C. and are again subjected to continuous centrifugation. There are thereby obtained 80 kg. petrolatum consisting of 38 kg. hard wax and 42 kg. dichlorethane, aswell as 1,56 kg. mixture of fluid wax hydrocarbons containing -108 kg. dichlorethane and 48kg. oil. The latter is mixed with the originally obtained 14 kg. extract As a final product there are obtained a total of 62% oil with a pour point of -20 C. and a viscosity index of 86, and 38% wax having a melting point of 66 C.

In ythe drawing, which is a diagrammatic View of an apparatus for carrying out the above described example process: a is a tank for blending the distillate with the selective solvent; b, c, c, chillers; d a centrifugal separator in which is separated the primary dewaxed oil dissolved in a minor proportion of the solvent from the mixture of solid and fluid hydrocarbons (theprimary wax) and the bulk of the solvent; c a still for distilling off the solvent (whichA is returned to the solvent storage tank .f through line g) from the extract; h a heat exchanger whereraising the pour Ain the temperature of the diluted primary wax is raised, usually Vfrom 20 to 25 C., to obtain a mixture of solid crystalline wax and a solution of fluid wax hydrocarbons and solvent, i the centrifuge in which the solid crystalline wax and some of the solvent are separated from the solution of uid parainicv oil and the remainder of the solvent; Ic the still in which the solvent is separated from the said parafnic oil; m the still in which the solvent is separated from the hard wax; n the return line for distilled solvent from still k to the solvent storage tankconveniently through line Q1 o the return line for distilled solvent from still m to the solvent storage tank; and p aline through which a small proportion of the non-parainic oil may be added to the oil to be dewaxed prior to chilling, as hereinafter described.

If the process is carried out in only one stage with the same quantity of the same solvent at for instance -|-5 C.. the major portion of the valuable viscosity bearers, that is, those substances lthe viscosity index.

which according to the method above described are obtained as extract in the rst stage, remain in the said petrolatum owing to the unsatisfactory selectivity at the temperature indicated. In this way not only a wax of inferior quality is obtained but also a reduced yield of low quality oil having a pour point 0i +5" C. due to lack of extract substances by which the pour point is lowered.

It is true that it is possible to obtain a sufficient concentration of extract substances in the dewaxed oil to ensure the desired pour point by substantially increasing the amount of solvent, using in this case, for instance, a tenfold quantity, which can also be deduced by means of the laws of the solubility. However, the use of large amounts of solvent not only entails considerable economic disadvantages owing to the high re- Afrigerating and distilling energy utilized for the solvent, but a considerable dissolution of solid wax hydrocarbons also results, which in turn raises the pour point of the oil considerably.

The selective effect of the dewaxing agents herein considered may also be utilized for obtaining substances which have the same qualities as the so-called pour point reducers sold in the open market. It has been found, in connection with the dewaxing of (particularly) mixed base oils or distillates with, for instance, dichloretnane, dichlorethylene, methylenechloride, trichlorethane, and less desirably, tetrachlorethylene and carbontetrachl-oride, and with mixtures of the same with ketones, alcohols, `ethers, esters, etc. at low temperatures, for instance, below w20" C., that extracts are obtained of which small amounts suice to reduce the pour point of oils 10 to 20 or more degrees, without having any practically unfavorable influence on the viscosity index.

The lower the separating temperature used -for obtaining the natural pour point reducer, the

lower the yield, but also the higher the concentration and consequently the effect.

If, for instance, a Roumanian overhead distillate is treated with the same volume of dichlorethane at 30 C., about 15%l extract of high viscosity is obtained. If now only 3% extract is added to a gas oil having a pour point of +6 C. and a viscosity of 1.82 E. at 20 C. and a viscosity index of 90, the pour point ofthe gas oil is lowered to 12 C., without changing If the same treatment of the overhead is carried out at 40 C., it is true that only about 10% extract is obtained, but to obtain the low pour point referred to above with the same gas oil it is now necessary to add only 1%. With increasing amounts of extract the pour point is, of course, further lowered.

The amount of natural pour point reducer to be added is generally so small that a harmful iniiuence on the color of the oils treated therewith need not be feared. If necessary, the pour point reducer may be made lighter in color by chemical or physical rening, for instance, with fullers earth in benzine solution yor the like.

vWhile the natural pour point reducers thus obtained have the same effect in regard to the lowering of the pour point and the maintenance of the viscosity index as the articial ones which may be obtained, for instance, by condensation of naphthalene, anthracene, etc., with chlorinated wax according to the method Friedl-Crafts, they offer the following considerable advantages over the latter products.

, 1. They are natural products and therefore it is in many cases' unnecessary 'toadd 'a lforeign oiltoagivenoil. 'r i i' rlTheir rproduction is not dependent on special chemical and expensive reaction processes.

3. They can be obtained in more or less high hconcentration by using suitable selective solvents in connection with several dewaxing'processes, and can then be addedto a parafinous oil as pour point reducer. Possibly they can -be obtained in comparatively low concentrationat the stage dewaxing according to the method described above; and after the division of the wax hydrocarbons into solid and fluid particles, they can again be added to the latter.

4. While the artici'al pour point reducers hardly influence the cloud point, the natural reducers cause a lowering of the same.

The natural pour point reducers may also beM obtained by first liberating the oil at low tem-iA perature with the aid of a non-selective solventy from the crystalline hard wax, whereupon the treatment with the selective agent is effected.

The natural pour point reducers produced acl.

cording to the process described above Imay be added to the oils to be dewaxed also prior to the chilling to low temperature or the removal of the wax, respectively, in order to obtain a better,v

the less it dissolves the paranic compounds on i the-other hand; naphtha, propane and similar light hydrocarbon oil fractions are not selective" solvents, as their temperature-solubility-curves for paraiflnic compounds do not essentially differ from their temperature-solubility-curves for non-parailnic compounds. The following solvents may be mentioned as examples of selective solvents: chlorinated hydrocarbons, alcohols, ketones, aldehydes, esters and the like, separate or in mixtures, but of course the method is not restricted to the use of these solvents and mixtures. However, it is to Ibe understood that by a selective solvent is meant to include only those solvents whose temperature-solubility curve for parafiinic compounds differs so substantially from their temperature-solubility curve for nonfparainic compounds that they are relatively good solvents for the naphthenic and/or aromatic compounds and relatively poor solvents for the paraflinic compounds. Of such solvents, those whose sole or main constituent is a chlorinated hydrocarbon, of which a number of ex amples are hereinbefore given, offer distinct advantages.

What I claim and desire to protect by Letters Patent is:

1. The process of treating wax-bearing hydro-y carbon oils to obtain therefrom oils having low. pour points and good viscosity-temperature characteristics, which comprises adding to the voil a solvent selective non-parainic hydrocarfbon and cooling to a temperature adapted to pre;- cipitate solid wax and iluid paraiinic hydrocarbons and centrifugally separating the sam'e with a major proportion of the solvent from the of the mixture of solid wax parainic hydrocarbons and solvent to form a mixture of solid crys talline wax and a solution "of solvent and parafflnic oil and at that temperature separating the' last named solution, containing the major part of the solvent of said mixture, from the said solid crystalline wax and such minor part of the solvent as is carried oiT with the wax.

2. The process set forth in claim 1 in which substantially all the solvent present in the second specied `separating step is that which is added thereto preparatory to the first specified separat' ing step.

3. The process set forth in 'claiml in which the said selective solvent comprises a chlorinated hydrocarbon.

4. The process set forth in claim 1 in which the temperature to which the solution is chilled preparatory to the specified centrifugal separation is not substantially above 15 C. and in which the temperature to'which the mixture of solid wax, paraiiinic hydrocarbons and solventI separated inthe said centrifugal separation is heated preparatory to the second specified separation is not substantially less than 20 C. above the temperature to which it waschilled preparatory to the first specied separation.

5. The process set forth in claim l in which the temperature to which the` solution is chilled preparatory to the specified centrifugal separation is not substantially above -15 C. and in which the temperature to which the mixture of solid wax, parafnic hydrocarbons and solvent separated in the said centrifugal separation is heated preparatory to the second specified separation is approximately 20-25" C. above the temperat'ure to which it was chilled preparatory to the first specified separation.

6. The process of treating wax-bearing hydrocarbon oils to' obtain therefrom oils having low pour points and good viscosity-temperature characteristics, which comprises adding to the oil a solvent selective for non-parafiinic hydrocar-bons and cooling to a temperature adapted to precipitate solid wax and fluid parafnic hydrocarbons and centrifugally separating the same with a major proportion of the solvent from the oil and a. minor proportion oi" the solvent to thereby produce a solution of a non-paralnic low pour-point, low cloud-point-reducing extract and a minor proportion of the solvent, subsequently substantially raising the temperature of the mixture of solid wax parainic hydrocarbons and solvent to form a mixture of solid crystalline wax and a solution of solvent and paraiiinic oil and at that temperature separating the last named solution, containing the major part of the solvent of said mixture, from the said solid crystalline wax and such minor part of the solvent as is carried 01T with the wax, and adding said non-paranic extract in small proportions to said wax-bearing starting oil to thereby obtain a better crystallization of wax and increase the yield of oil.

7. The process of treating wax-bearing hydrocarbon oil to obtain therefrom oils having low pour points and good viscosity-temperature characteristics, which comprises adding to the waxbearing hydrocarbon oil a solvent selective for non-parainic hydrocarbons Vand cooling to a temperature adapted to precipitate solid wax enclosing therein fluid parafiinic hydrocarbons and subjecting the same to such centrifugal operation as to separately discharge two constituents, namely, a constituent which consists of a. solution of oil and solvent containing such minor proportion of the solvent that the oil in the solution isa non-parafnic low pour-point, low cloudpoint-reducing extract and a constituentwhich is Va mixture of said solid wax and a solution comprising the remaining major proportion of the solvent and an oil which is a fluid mainly parainic oil, and subsequently substantially raising the temperature of said mixture to render a part of said solid Wax fluid to thereby form a mixture'v ofsolid crystalline wax and a solution of solvent and oil which is mainly parainic and 10 tain the desired product.

at that temperature separating the last named solution, containing the major part of the s01- vent, lfrom the solid crystalline wax and such minor part of the solvent as is retained with the wax.

8. The process set forth in claim '7, followed by separation of said extract and said fluid mainly paraflinic oil from their respective solvents and mixing said extract and oil to thereby ob- BRUNO ENGEL- GERTIFI CA TE OF C ORREC TION Patent No. 2,948,159. May 9, 19h14.

y BRUNO ENGEL.

It is herebyr certified that error appears in theprinted specification of the above numbered patent requiring correction asifollows: Page 5, first column, line 59, before "what I claimrl insert the following paragraph --1 do not herein Claim the addition to the feed stock and solvent blended therewith of a portion of the solvent extract, asthe same is included in the subject matter of a pending application filed by me November, 19h42, Serial No. i-hlhu;

and that the said Letters Patent should be read with this correction-there.- in that the semeV may conform to the record of the case in the Patent Office.

lsigned and sealed this 29th day of August, A. D. 19th.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFICATE OF C ORRECTI ON Patent No. 2,5Ly8,u59. may 9, 191m.

BRUNO ENGEL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, lines 65 and 66, claim 1 for the words "non-paraffinic hydrocarbon read --for non-paraffinie hydrocarbons-H; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the .case in the Patent Office.

signed and sealed this 27th day of June, A. Demut.

Leslie Frazer (Seal) Y Acting` Commissioner Aof Patents

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