US2358921A - Dewaxing wax-bearing oil - Google Patents

Description

Patented Sept. 26, 1944 William P. Gee, Plainfield, N. J., assignor to Texaco Development Corporation, New York, N. Y., a corporation of'Delaware No Drawing. Application December 13 1941, Serial No. 422,879

7 Claims. (Cl. 196-18) This invention relates to dewaxing wax-bearing oil and particularly to dewaxing oil with a selective solvent mixture composed of a wax antisolvent liquid and an oil solvent liquid.

The invention broadly contemplates dewaxing,

wax-bearing oil with a selective dewaxing solvent mixture composed in part of a hydrocarbon mixture consisting mainly of naphthene, paraflin, aromatic and oxygenated hydrocarbons.

'More particularly it contemplates dewaxing with a dewaxing solvent liquid mixture composed of a. wax antisolvent liquid and an oil solvent liquid in which the oil solvent component comprises at least in part a hydrocarbon mixture of naphthene, parafiin, aromatic and oxygenated hydrocarbons. Advantageously this hydrocarbon mixture comprises a synthetic hydrocarbon mixture composed of a major proportion of naphthene, paraflin and aromatic hydrocarbons and a minor proportion of oxygenated hydrocarbons which are substantially completely soluble in a saturated aqueous solution of sodium bisulfite at room temperature.

It is already known in the art to dewax waxbearing oils such as mineral lubricating oils with selective solvents and. with selective solvent mixtures which consist of a mixture of a wax antisolvent liquid such as a low boiling aliphatic ketone and an oil solvent liquid such a benzol and toluol. For example, Govers Patent 1,802,942 discloses dewaxing wax-bearing mineral lubricatoil with a mixture of acetone and benzol, while Govers Patent 2,061,541 discloses dewaxin .such oil with a mixture of a ketone, benzol and toluol, the toluol amounting to about to 30% of the mixture; In this latter case the toluol serves to increase the solvent action of the selective solvent mixture upon the oil constitutents of the wax-bearing mixture so as to prevent oil separation at dewaxing temperatures of minus .F. and'below.

The present invention involves dewaxing with a selective solvent mixture of the foregoing type in which the oil solvent component of the solvent I fiXture consists. essentially} or. in part, of a hydrocarbon mixture containing little or notoluol. A'hydrocarbon mixture which has been'fo'und particularly effective for. this purpose is that knownfin the trade asNotol. In; a co ce w h thi -inv n io W xrb i g oil is dewaxed with adewaxing solvent mixture com risin an hat c keto s o oth r sui a le wax ntisolven liq id and a d a bon mixture su has Notc advan a eo l the dew xin .so ventliquid may co prise a mi t e oi ketone and benzol containing a substantial proportion of Notol, th benzol component being either pure or commercial benzol. In such case the Notol may be substituted for the toluol component of the ketone-benzol-tolu'ol dewaxing sol- Vent mixture referred to in the foregoing Govers Patent 2,061,541.

The hydrocarbon mixture known in the trade as Notol has an A. P. I. gravity of about 43 to 44 and has an initial boiling point of about 160 F. and an end boiling point of about 300 F. by the A. S. T. M. method of distillation. The approximate composition of this hydrocarbon mixture is as follows:

Per cent by volume Benzene 8.4 Toluene l 10.5 Xylene and higher l 32.5' Naphthenes 10.9 Parafiins; 23.3 Oxygenated hydrocarbons. r 9.4

The oxygenated hydrocarbons comprise alcohols, ketones and aldehydessubstantially completely soluble at about F. in aqueous sodium bisulfite solution consisting of water saturated with NaHSOs at about 70 F. The hydrocarbon mixture has a bromine number less than 1 so that it is substantially free from olefins.

A hydrocarbon mixture of the foregoing character and composition has a relatively low content of toluene and this is a. desirable attribute where the supply of toluene available for industrial solvent uses is scarce or costly. It has also been found that in the case of some wax-bearing oils the foregoing hydrocarbon mixture possesses unexpected advantages as the oil solvent component of a selective .dewaxing solvent mixture.

in some cases when dewaxing with a solvent mixture comprising methylethyl ketone and the foregoing synthetic hydrocarbon mixture employing a continuous rotary filter a higher filtration rate is realized and in addition a smaller volume of wash solvent is required to wash the resulting filter cake of wax. Moreover, these advantages are realized without any apparent reduction in the yield of dewaxed oil.

The following .data indicate the results obtainable in dewaxing mineral lubricating oil stocks with a selective solvent comprising a mixture of methylethyl ketone, commercial benzol and toluol on the one hand, and with a mixture of methylethyl ketone, commercial bB l QI and Notol on theother hand.

Example 1 In this example a steam refined cylinder stock having an A. P. I. gravity of about 24.5, a Saybolt Universal viscosity at 210 F. of about 161 and a pour point of plus 25 F. was mixed with the solvent liquid in the proportion of 4 parts of solvent to 1 part of oil by volume. This mixture was chilled and filtered at a dewaxing temperature of about minus 12 F. The solvent was removed from the resulting filtrate of dewaxed oil and the dewaxed oil was found to have a pour test of about F. In the run with toluol as thethird component of the solvent, the solvent liquid conof Notol, the ketone or wax antisolvent constitusisted of 37% methylethyl ketone, 47.25% commercial benzol and 15.75% toluol. In the companion run the solvent mixture consisted of the same proportions of methylethyl ketone and ben-.

zol but contained 15.75% of Notol.

The following is a tabulation of the results obtained as applied to dewaxing on a continuous rotary vacuum filter of the drum type operating so as to maintain a two-minute cycle.

A B Third component of solvent Wash Cycle W. F. 0. Wash Cycle W. F. O.

ratio rate yield ratio rate yield Toluol 0 8. 68 84. 4 0. 75 '8. 95 86. 9 Notol 0 .8. 75 85. 6 0. 63 9. '56 87. 4

The first pair'of runs (A) were made without washing the filter cake and 'as indicated',"the cycle rate, namely, gallons of Wax-free oil per square foot of filtering surface per hour is slightly greater when using the solvent containing Notol and in addition the yield of wax-free oil (W. F. 0.) expressed as volume per cent basis wax-bearingoil charge is slightly greater. 'In the second pairof Example 2 In this examplev a wax distillate having an A. P. Lgravity of about 25.4, a Saybolt Universal viscosity of 52.6 .at 2.10 F. and a pour point of plus 85 F. was mixed with the solvent liquid in the proportion of 3-volumes of solvent to 1 volume of wax distillate. .The resulting mixture was chilled and filtered at a temperature of minus F. obtaining in each case an oil having a pour test of about 0 F. The solvent composition in each instance was similar to that employed in Example 1, obtaining the following results when operating with a filtercycle of one minute.

As in the case of Example 1 a slightly higher cycle rate with a smaller wash ratio was permitted in the run with solvent containing Notol,

ent of the mixture may range from about 30 to 60% by volume, the remainder being Notol. When a three-component dewaxing mixture, namely,

wax antisolvent, benzol and Notol, is employed the composition may also range from about 30 to 60% ketone or wax antisolvent liquid, the re: mainder being a mixture of commercial benzol and Notol, the Notol comprising from 10 to 50% of this benzol-Notol mixture.

It is contemplated that the solvent mixture of this invention may be employed for separatin solid hydrocarbons from various hydrocarbon mixtures of wax concentrates derived from different sources including petroleum, vegetable and animal sources.

Obviously many modifications and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated by the appended claims.

I claim: I

1. In the separation of wax from wax-bearing oil wherein the wax-bearing oil is mixed with a dewa'xing solvent mixture c'omprisinga wax antisolvent and an oil solvent mixed in proportion with each other and with the oil such that the solvent mixture exerts selective action as between wax and oil at reduced temperature, the method which comprises mixing the wax-bearing oil with a dewaxing solvent composed of about 30 to 60% wax antisolvent liquid, the remainder to 44 and comprising mainly naphthene, 'paraflin,

aromatic and a substantial proportion 'of1oXy-. genated hydrocarbons which are completely soluble in aqueous sodium bisulfite solution consisting of water saturated with NaHSOa at about 70 F., chilling the mixture of wax-bearing oil and solvent liquid to a temperature at which wax constituents are solidified, separating solidifled wax from the chilled mixture and recovering the solvent liquid from the resulting dewaxed oil.

2. In the dewaxing of wax-bearing oil wherein the oil is mixed with a dewaxing solvent mixture comprising a wax antisolvent and an oil solvent mixed in proportion with each other and with the oil .such that thesolvent mixture exerts slective action as between wax and oil at the de- Waxing temperature, the method which comprises mixing the wax-bearing oil with a dewaxing solvent composedof a wax antisolvent'and an oil solvent, said oil solvent comprising a hydrocarbon mixture boiling in the range about to 300 F. and containing about 51% aromatic hydrocarbons, 10.9% naphthene hydrocarbons, 28.3% parafiin hydrocarbons and 9.*i% oxygenated hydrocarbons, chilling the mixture or oil and while obtaining substantially the sameoraslightly L6 solvent liquid. to a dewaxing temperature at which wax constituents are solidified, separating solidified wax from the chilled mixture and recovering the solvent liquid from the resulting dewaxed oil.

3. The method according to claim 1 in which the wax antisolvent liquid comprises a low boiling aliphatic ketone.

4. The method according to claim 2 in which the wax antisolvent liquid comprises a low boiling aliphatic ketone.

5. In the separation of wax from wax-bearing oil wherein the wax-bearing oil is mixed with a dewaxing solvent mixture comprisinga wax antisolvent and an oil solvent mixed in proportion with each other and with the oil such that the solvent mixture exerts selective action as between wax and oil at reduced temperature, the method which comprises mixing the wax-bearing oil with a dewaxing solvent composed of about 30 to 60% wax antisolvent, the remainder being an oil solvent composed of a mixture of commercial benzol and a hydrocarbon mixture boiling in the range about 160 to 300 F., said hydrocarbon mixture comprising to 50% of said remainder and having an A. P. I. gravity of about 43 to 44 and comprising mainly naphthene, paraflin, aromatic and a substantial proportion of oxygenated hydrocarbons which are completely soluble in aqueous sodium bisulfite solution consisting of water 80% saturated with NaHSOa at about 70 F., chilling the mixture of oil and solvent liquid to dewaxing temperature at which wax constituents are solidified, separating solidifled wax from the chilled mixture and recovering the solvent liquid from the resulting dewaxed oil.

6. The method according to claim 5 in which the hydrocarbon mixture boiling in the range about 160 to 300 F. contains about 51% aromatic hydrocarbons, 10.9% naphthene hydrocarbons,

28.3% paraffin hydrocarbons and 9.4% oxygenated hydrocarbons, said oxygenated hydrocarbons being substantially completely soluble in a saturated aqueous sodium bisulfite solution at about room temperature.

7. In the separation of wax from wax-bearing oil wherein the wax-bearing oil is mixed with a dewaxing solvent mixture comprising a wax antisolvent and an oil solvent mixed in proportion with each other and with the oil such that the solvent mixture exerts selective action as between wax and oil at reduced temperature, the method which comprises mixing wax-bearing oil with a dewaxing solvent composed of an oxygenated hydrocarbon wax. antisolvent liquid, the remainder being an oil solvent, said oil solvent consisting essentially of a hydrocarbon mixture substantially free from olefins, having an initial boiling point of about 160 F. with an end boiling point of about 300 F., and an A. P. I. gravity of about 43 to 44 and comprising a mixture of naphthene, paraffins, aromatic,- and oxygenated hydrocarbons, said oxygenated hydrocarbons being completely soluble in aqueous sodium bi-sulfite solution consisting of water, 80 per cent saturated with NaHSOz, at about F., chilling the mixture of wax-bearing oil and solvent liquid at a temperature to which wax constituents are solidified, separating solidified wax from the chilled mixture and. rcovering the solvent liquid from the resulting dewaxed oil.

WILLIAM F. GEE.