US2760904A - Selective use of solvent components in solvent dewaxing - Google Patents

Description

Aug. 28, 1956 L. J. FORD SELECTIVE USE oF soLvENT COMPONENTS 1N soLvENT DEWAXING Filed Dec. 7, 1951 United States Patent SELECTIV E USE F SOLVENT COMPONENTS IN SOLVENT DEWAXIN G Lloyd J. Ford, Baton Rouge, La., assignor to Esso Research and Engineering Company, a corporation of Delaware Application December 7, 1951, Serial No. 260,421

3 Claims. (Cl. 196-18) The present invention is concerne-d with an improved process for the removal of waxy constituents from mineral oils containing the same. The invention is more particularly concerned with a dewaxing operation utilizing two solvents, one of which comprises an anti-wax solvent while the other of which comprises an oil solvent. The present invention is particularly concerned with the use of a solvent mixture in a dewaxing operation comprising a ketone and an aromatic as for example toluene in order to increase dewaxed oil yields and ltering rates. In accordance with the present invention the anti-wax solvent as for example the ketone is incrementally added to the waxy oil during the chilling cycle while the solvent having a solubility for oil is added to the chilled waxy oil in toto at the filtering temperature.

In the rening of hydrocarbon oils such as petroleum oils, it is known to segregate paraffin waxes from socalled paran distillates, waxy lubes and the like. The segregation of these waxes is secured by a number of processes. For example, it is known to chill the selected wax containing oi-l fraction in order to secure crystallization of the wax and then to filter or centrifuge the wax crystals from the oil. It is also known to use various dewaxing solvents such as liquid normally gaseous hydrocarbons, such as propane, as well as, other solvents such as methyl-ethyl ketone and the like. In these dewaxing operations, it is also known to use various filter aids and other agents in order to render the dewaxing and filtering operations more efficient. The wax segregated from the hydrocarbon oil, usually termed slack wax contains from `about to 40% of oil. The oil content and melting point range of this wax maybe reduced if desirable by means of a distillation operation. The slack wax is then handled usually by sweating in a manner to reduce the oil content to less than about 4% by weight. This, crude scale wax, generally has -an oil content of about 2.5% by weight. In order to remove this oil from the wax and to produce a rened wax having an oil content below about .5%, usually below about .3% various pro-l cedures have been proposed and employed.

As pointed out, it is known to employ solvent mixtures wherein one solvent comprises an anti-wax solvent while the other comprises a solvent having a solubility for oil. A solvent mixture of this character for example comprises 60% by volume of methyl-ethyl ketone and 40% by volume of toluene. When utilizing a mixture of this character it has been the practice to add the mixture incrementally to the waxy distillate as it is being chilled. However, t has now been discovered that unexpected desirable results are secured providing the anti-wax solvent is added incrementally and the solvent having a solubility for oily constituents is added in toto at or near the filtering temperature. The process of the present invention may be more readily understood by reference to the drawing illustrating one embodiment of the same.

Referring specically to the drawing, a waxy distillate is introduced into the system by means of feed line 1. The waxy distillate flows serially through chilling zones 2, 3, 4 and 5 wherein the temperature of the waxy distillate is progressively reduced. A typical operation is to introduce the feed oil into the initial chilling zone at a temperature of about 130 F.; to introduce the feed oil into the second chilling zone at a temperature of about F.; to introduce the waxy distillate to the third chilling zone at a temperature of about 60 F.; to introduce the feed oil to the fourth chilling zone a temperature of about 25 F. and to chill the same in the fourth chilling zone to a liltering temperature in the range of from about -10 to }-10 F. The number of the respective chilling zones as well as their arrangement may be varied appreciably and either direct or indirect chilling means utilized. For purposes of illustration it is assumed that the anti-wax solvent comprises methyl-ethyl ketone and that the aromatic solvent having a high solubility for oil comprises toluene. It is also assumed that 3% volumes of total solvent mixture is utilized per volume of waxy oil being dewaxed. The solvent mixture comprises 60% by volume of methyl-ethyl ketone and 40% by volumev of toluene.

The methyl-ethyl ketone is introduced into the system. by means of line 6, and at least a portion of the salmeA passed serially through chilling zones 7, 8, 9 and 10. The: methyl-ethyl ketone in zone 7 is chilled to a temperature: corresponding to the temperature of the waxy distillate: A portion of the methyl-ethyl.

removed from zone 2. ketone is added to the waxy distillate by means of line 11 while the remainder is chilled in zone S to a temperature approximating the temperature of the chilled distillate removed from zone 3. A portion of the methylethyl ketone removed from zone 8 is added to the waxy distillate removed from zone 3 by means of line 12. The remainder of the methyl-ethyl ketone is further chilled in zone 9 to a temperature approximating the temperature of the distillate removed from zone 4. Another portion of the methyl-ethyl ketone removed from zone 9 is added to the distillate removed from zone 4 by means of line 13. The remainder of the methyl-ethyl ketone is chilled in Zone 10 to a temperature approximating the temperature of the waxy ydistillate removed from zone 5 and added to the waxy distillate by means of line 14.

The toluene in accordance with the present invention is introduced into the system by means of line i5, chilled in zone 16 to a temperature approximating the temperature of the cold distillate removed from zone 5 and added to the distillate by means of line 17. The entire mixture comprising oily constituents, crystallized wax constituents, toluene and methyl-ethyl ketone is held at this ltering temperature and passed to liltering zone 18 wherein the solid wax particles are segregated from the oily constituents by any suitable filtering or separation means. The :filtering zone may comprise plate and frame presses, centrifuges or equivalent suitable equipment for the scparation of the precipitated waxy constituents from the oily constituents. The oil and a portion of the solvent is removed from zone 18 by means of line 19 and the wax cake washed with a wash solvent introduced into filtering zone 18 by means of line 20. Slack wax Kand solvent are removed from zone 18 by means of line 21 and passed to a distillation zone'22 wherein'a separation is made between the waxy particles and the solvent, lt is to be understoodnthat other means of separating the solvent from the wax may be utilized if desirable. The wax substantially free of solvent is removed from separation zone 22 by means of line 23 and furtherrened as desired. The solvent mixture comprising methyl-ethyl ketone and toluene is removed overhead from zone 22 by means of line 24 and passed to distillation zone 25.

The oil-solvent mixture removed from filtering zone 18 by means of line 19 is introduced into distillation zone 26 wherein a separation is made between the oily constit uents and the solvent mixture. The oil is removed from Zone 26 by means of line 27 while the solvent mixture is removed overhead by means of line 2S and passed to distillation zone 25. A separation is made in zone 25, which may comprise a distillation zone, between methylethyl ketone which is removed overhead by means of line 29 and the toluene which is removed as a bottoms stream by means of line 30. It is to be understood that ltering zone 18, distillation zones 22, 2S and 26 may comprise any suitable number and arrangement of stages.

The methyl-ethyl ketone removed by means line is preferably recycled to the system and added in increments to fresh, waxy distillate while the toluene is rccyoled and `added in toto at or near the ltering temperature by means of line 17. Fresh methyl-ethyl ketone and toluene may be added as required.

The invention is broadly concerned with a dew ine operation utilizing two solvents, one ot which is characterized by being an anti-wax solvent, while the other is characterized by having a relatively high solubility for oily constituents. Solvents of the anti-wax characteristic, for example, comprise methyl-ethyl ketone, methyl-propyl ketone, acetone and the like, while solvents having a relatively high solubility for oily constituents comprise benzene, toluene and other aromatic solvents. The invention is specically directed to a process wherein the `anti-wax solvent is incrementally added to the waxy distillate it is being chilled to a filtering temperature, while the aromatic solvent is added in toto at or near the filtering temperature. The method of `adding the anti-wax solvent inay be varied appreciably. lt may be added in increments of from two to six and the quantity added as each increment varied appreciably. The amount added at each increment may be equal in volume, or a relatively small amount may be initially added and relativeiy larger amounts added in succeeding stages. For instance, a very satisfactory method of operation is to employ tive chilling stages and to use Iabout 350 volumes of a solvent mixture, comprising 60% by volume of methyi-ethyl ketone and 40% by volume of toluene, per 100 volumes of waxy oil being dewaxed. Under these conditions 30 volumes of methyl-ethyl ketone is added in the rst chilling stage, 30 volumes in the second chilling stage, 60 volumes in the third chilling stage, 90 volumes in the fourth chilling stage and 140 volumes of toluene added at the iltering "-2 temperature.

The process of the present invention may be more fully `appreciated by the following example illustrating the same:

Example Operation Operation I II Filtration Rate., Gal/Hr./Sq. Ft Dewaxed Oil Yield Dewaxed Oil Inspections:

Pour, F Cloud, F

From the above it is apparent that filtering rates are materially increased as well as dewaxed oil yields.

General operating conditions may be varied appreciably. For example, the concentration of the anti-wax solvent may vary from about 50% to 70% by volume while the concentration of the oil solvent may vary from 50% to 30% by volume. The amount of solvent mixture utilized may vary from about .5 to 8 volumes per volume of oil being dewaxed. Preferred ratios are from 3 to 5 volumes of solvent mixture per volume of oil being dewaxed. ln accordance with the present invention, it is also preferred that the temperature of the oil solvent approximate the ltering temperature of the cold waxy distillate. In no instance should the temperature of the oil solvent added to the cold waxy distillate vary greater than about l0-20 degrees.

What is claimed is:

l. The process for the removal of waxy constituents from a a waxy oil containing same by the use of two different solvents, a ketone anti-wax solvent and an aromatic oil solvent, comprising the steps of chilling said waxy oil, adding suicient ketone anti-wax solvent of substantially the same temperature to said waxy oil to precipitate only a portion of said waxy constituents, subsequently further chilling the resulting mixture of waxy oil, precipitated waxy constituents, and ketone anti-wax solvent to a lower temperature, subsequently adding additional ketone anti-Wax solvent of substantially the same temperature as the further-chilled mixture to said furtherohilled mixture to further precipitate said waxy constituents from said oil, adding to the resulting mixture subsequent to the addition of all the ketone anti-wax solvent to be introduced all of said aromatic oil solvent, said aromatic oil solvent being introduced at substantially the same temperature as the mixture to which it is added, and separating the precipitated waxy constituents at substantially the same temperature as said aromatic oil solvent from the resulting mixture of oil, aromatic oil solvent, and ketone anti-wax solvent.

2. The process according to claim l wherein said antiwax solvent is methyl-ethyl ketone and wherein said oil solvent is toluene.

3. The process according to claim 2 wherein from 50- 70 volumes of methyl-ethyl ketone are utilized per 30-50 volumes of toluene and wherein from 2-8 volumes of solvent mixture are utilized per volume of waxy oil being dewaxed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,229,658 Jenkins Jan. 28, 1941 2,274,223 Tuttle Feb. 24, 1942 2,322,438 Henry et al. .lune 22, 1943 2,342,798 Fischer Feb. 29, 1944 2,397,868 Jenkins Apr. 2, i946 2,463,845 Backlund et al. Mar. 8, i949 m nas...

Claims (1)

1. THE PROCESS FOR THE REMOVAL OF WAXY CONSTITUENTS FROM A WAXY OIL CONTAINING SAME BY THE USE OF TWO DIFFERENT SOLVENTS, A KETONE ANTI-WAX SOLVENT AND AN AROMATIC OIL SOLVENT, COMPRISING THE STEPS OF CHILLING SAID WAXY OIL, ADDING SUFFICIENT KETONE ANTI-WAX SOLVENT OF SUBSTANTIALLY THE SAME TEMPERATURE TO SAID WAXY OIL TO PRECIPITATE ONLY A PORTION OF SAID WAXY CONSTITUENTS, SUBSEQUENTLY FURTHER CHILLING THE RESULTING MIXTURE OF WAXY OIL, PRECIPITATED WAXY CONSTITUENTS, AND KETONE ANTI-WAX SOLVENT TO A LOWER TEMPERATURE, SUBSEQUENTLY ADDING ADDITIONAL KETONE ANTI-WAX SOLVENT OF SUBSTANTIALLY THE SAME TEMPERATURE AS THE FURTHER-CHILLED MIXTURE TO SAID FURTHERCHILLED MIXTURE TO FURTHER PRECIPITATE SAID WAXY CONSTITUENTS FROM SAID OIL, ADDING TO THE RESULTING MIXTURE SUBSEQUENT TO THE ADDITION OF ALL THE KETONE ANTI-WAX SOLVENT TO BE INTRODUCED ALL OF SAID AROMATIC OIL SOLVENT, SAID AROMATIC OIL SOLVENT BEING INTRODUCED AT SUBSTANTIALLY THE SAME TEMPERATURE AS THE MIXTURE TO WHICH IT IS ADDED, AND SEPARATING THE PRECIPITATED WAXY CONSTITUENTS AT SUBSTANTIALLY THE SAME TEMPERATURE AS SAID AROMATIC OIL SOLVENT FROM THE RESULTING MIXTURE OF OIL, AROMATIC OIL SOLVENT AND KETONE ANIT-WAX SOLVENT.

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