US2244407A

US2244407A - Solvent dewaxing

Info

Publication number: US2244407A
Application number: US291284A
Authority: US
Inventors: Smisloff Walter
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1939-08-22
Filing date: 1939-08-22
Publication date: 1941-06-03
Anticipated expiration: 1958-06-03

Description

June 3, 1941. w. sMlsLoFF SOLVENT DEWAXING Filed Aug. 22, 1939 WALTER SMISLOFF INVENTOR BY j ATTORN YS Patented June 3, 1941 SOLVENT DEWAXING Walter Smisloff, Fishkill, N. Y., assigner to The Texas Company, New York, N. Y., a corporation of Delaware Application August 22, 1939, Serial N0. 291,284

Claims.

'Ihis invention relates to the separation of wax from oil and particularly concerns a method of dewaxing mineral lubricating oil.

Broadly, the invention contemplates a method of separating wax from hydrocarbon oil in the presence of a wax crystal regulator with a dewaxing solvent liquid containing a wax anti-solvent liquid, and wherein the regulator is incorporated in the oil or Wax-bearing mixture in the form of a suspension in a small portion of a mixture of the anti-solvent liquid and water. The mixture of wax-bearing oil, solvent and regulator is chilled to precipitate the wax, which may be removed from the chilled mixture by ltration, centrifuging, or other means. The regulator may be dispersed in the oil or mixture of oil and solvent by heating or soaking or both heating and soaking.

The invention is applicable to dewaxing with selective dewaxing solvent mixtures containing la wax anti-solvent liquid or comprising a mixture of a wax anti-solvent liquid and a solvent liquid for oil. As examples of wax anti-solvent liquids normally liquid ketones, including aliphatic ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl normal butyl ketone, as well as higher molecular Weight ketones, such as dipropyl ketone or mixed ketones, may be mentioned. Other suitable anti-solvents may be used if desired. These anti-solvent liquids are usually employed in conjunction with an oil solvent liquid, such as benzol, and its homologs, or other solvents, such as the low molecular weight aliphatic ethers.

The wax crystal regulating material may be a resinous material, such as that known inthe trade as Plioform. It may comprise montan Wax or the active ingredients thereof, or metallic soaps of the higher fatty acids, such as aluminum stearate. These Wax crystal regulating materials, or dewaxing aids, are generally of the type that form colloidal solutions in benzol and are diiiicultly soluble in dewaxing solvent mixtures, such as a mixture of methyl ethyl ketone and benzol.

The present invention involves dewaxing with a solvent containing a constituent of the character of a ketone with the aid of a Wax crystal regulator of the foregoing character, by a procand from the separated wax by distillation. The bulk of the solvent is distilled from either the oil or the wax, in the absence of steam, so as to recover the solvent in a dry condition. The re- Y maining portion of the solvent, however, is distilled with the aid of steam and during the steam distillation the ketone or other Wax antisolvent liquid of this character tends to form with the water a substantially constant-boiling mixture. i

Consequently, there is produced in the linal stage of the solvent recovery a substantial amount of this constant-boiling mixture which, in the case of methyl ethyl ketone, for example, will comprise a mixture of around 88.6% methyl ethyl ketone and 11.4% Water. This mixture is usually subjected to prolonged settling and recycling through the recovery system.

I have discovered that this constant-boiling mixture, which is substantially free from benzrol,

Vprovides an eiective medium with which to incorporate the wax crystal regulating material in the charge. The regulating material, in a substantially dry powdered form, is mixed with this mixture with suicient agitation to form a suspension and this suspension can then be incorporated in the Wax-bearing mixture prior to chilling, While maintaining the regulator in the desired small particle form and in which form it is most eiectively dispersed in the wax-bearing mixture.

When the material is added in this suspension to the Wax-bearing mixture, agglutination or coagulation into larger particles is greatly reduced. Experiments have indicated that it is desirable to avoid this particle growth on the part of the regulator since the formation of large particles hinders the dispersion of the regulator. Formation of large particles is avoided to a very large extent when the regulating material is added to the Wax-bearing mixture while in the form of a suspension in a mixture of the antisolvent and a small amount of water.

In order to demonstrate the invention more fully reference Will now be made to the accompanying drawing showing a 110W diagram illustrating one method of operating the process.

Wax-bearing oil, from a source not shown, is charged through a pipe l to a charge tank or mixing tank 2. The dewaxing solvent, comprising, for example, a mixture of about 40% methyl ethyl ketone and commercial benzol, is conducted from a tank 3 to the tank 2. The oil and dewaxing solvent are mixed in the proper proportion as, for example, around three or four parts of solvent to one part of oil.

The resulting mixture is forced by a pump 4 through a pipe 5 to a heat exchanger 6. The Wax crystal regulating material, in the form of a suspension, the preparation of which will be described later, is conducted through a pipe 8 communicating with the pipe 5. The regulating material is mixed with the oil in small amount, usually around 0.1 or 0.2% by Weight of the Wax bearing oil.

The heat exchanger 6 may provide a means of heating the mixture where it is desired, for example, to heat the mixture to a temperature of around 1GO-170 F. prior to chilling. Onthe other hand, where such preliminary heating is undesired, the heat exchanger 6 may provide means of preliminarily cooling the mixture.

The Wax bearing mixture is conducted from the heat exchanger 6 to a chiller 9 wherein it isV chilled to a temperaturesuiiciently low to precipitate the wax, and which may be in the range of around 0 F. tok minus 20 F., or even lower, depending upon the pour test desired for the final product.

The chilled mixture is then passed to a filter I0 wherein the precipitated Wax is removed in the form of a iilter cake, which is discharged through a conduit I I, while the resulting dewaxed filtrate is discharged through a conduit I2.

The dewaxed iiltrate is then passed through a heat exchanger or heater I3 to a fractionator I4.

The fractionator I4 may be operated under any desired pressure conditions to removethe bulk of the solvent in the form of a substantially dry vapor or distillate. The vaporized solvent is drawn off through a condenser I5 to the tank 3 previously mentioned.

The unvaporizedportion of the oil and solvent accumulating in the bottom of. the fractionator I4 is drawn oi through a pipe I6 to a steam stripper VI'I. .The steam stripper I1 effects the removal of the remainder of the solvent. The solvent-free oil is drawn oii from the bottom of the stripper, while the vapors lcomprisingsolvent and water are drawn oli" through a condenser'l, wherein they are condensed and the resulting condensate'is conducted to an accumulator I9.

Referring again to'the' wax iilter cake which is drawn off through the conduit I I; as indicated,

this wax cake, comprising a mixtureof wax and solvent, is passed through a heater or heat exchanger to a settling tank 2I.

In the tank 2l, the contents of which are 'inf a warm condition, some stratification occurs with the settling out'of a water layer in the bottom of the tank. v

The upper layer is drawn off through a heat exchanger 22, wherein it is heated prior to introduction to a fractionator 23. In the fractionator 23 the bulk of the solvent associated with the wax is removed in a relatively dry-conditio through a pipe 24.

The remaining mixture of waxv and solvent is then drawn oir through the pipe 24 to a steam.

stripper 25, somewhatsimilar to the stripper VII. Here the remainder of the solvent is stripped in vapor form from the wax and removed through a condenser 26. The resulting condensate is then introduced to the accumulator I9, along with the wet solvent recovered from the dewaxed filtrate. i

In the accumulator I9 stratiiicationinto layers occurs. The upper layer comprises a mix- `ture of solvent and water rich in solvent, and

`composed Yof about 11.4%

this layer is drawn off through pipe 2'I and may be returned directly to the lower portion of the tank 2| for recycling through the recovery system. On the other hand, it may be passed directly to the solvent storage for mixing with fresh charge.

The water layer accumulating in the bottom of the accumulator I9 is siphoned off through a pipe 28 to a receiving drum 29. From there it is passed through a pipe 30 to a stripper 3I, wherein it is subjected to stripping with steam.

The vapor fraction formed in the stripper 3| is drawn off through a condenser 32 and resulting condensate introduced to a receiver 33. This condensate comprises a constant-boiling mixture water and 88.6% methyl ethyl ketone. A portion of it is continuously returned to the top of the stripper 3| as a reux, While the remainder is drawn off through a pipe 34 and, according to the more conventional method of operation, is returned to the lower portion of the tank 2I for recycling through the system, or passed directly to the solvent storage for mixingwith fresh charge.

As indicated, the water layer separating in the bottom of the tank 2I is drawn off through a pipe 35 communicating with the receiving drum 29, previously mentioned, and in this way subjected to further treatment. The water accumulating in the stripper 3| is drawn oiT from the bottom through a pipe 36 and discharged from the system.

In accordance with the present invention all, or a portion of, the constant-boiling mixture is passed through a pipe 31 communicating with a mixing tank 38 for the-preparation of the suspension of wax crystal regulating material.

The wax crystal regulator, as, for example, resinous material, such as P1ioform, `reduced to a relatively dry' powdered form, is stored in a condenser 39, the lower portion of which comthe operation of a control valve 4I in the pipe `37. The suspension is drawn off from the bottom of the mixing tank 38by means of a pump 42, which forces it into 'the pipe 5, which may be provided with suitable means, such as nozzles, for effecting mixing between the suspension and the wax-bearing mixture. Likewise, the operation of the pump 42 may be 'coordinated with that of the pump 4 charging the wax-bearing mixture. f Y

The regulating material may be mixed with the methyl ethyl ketone-water mixture in' the proportion of about one part of regulator to 4rive to fifty parts of ketone-water mixture by weight. Also, if desired, additional methyl ethyl ketone, or other anti-solvent liquid, may beadded directlyto the mixing tank 38.. The anti-solvent liquid added may thus comprise the usual makeup added to the dewaxing system. The addition of liquid in the tank 38 thereby increases the volume of liquid used to produce the dewaxing aid suspension and thus facilitate its incorporation in the wax-bearing mixture, while retaining the particles in a nely-divided state.

It is, of course, contemplated that other forms and arrangement of apparatus, other than those described above, may be employed. Likewise, other operating conditions, such as those pertaining to temperatures and pressures, may be used.

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

I claim:

1. In the dewaxing of Wax bearing oil in the presence of a wax crystal regulator, which is effective in the presence of a small amount of water, with a dewaxing solvent which is subsequently distilled from the dewaxed oil, said solvent containing a Wax anti-solvent liquid, a portion of which during distillation from the oil, in the presence of steam, forms a substantially constant-boiling mixture of anti-solvent and Water, the method of incorporating the regulator in the oil, Which comprises forming a suspension of the regulator in a portion of said constant-boiling mixture and mixing the resulting suspension with the Wax bearing mixture prior to chilling.

2. In the dewaxing of hydrocarbon oil wherein the oil is mixed with a dewaxing solvent, chilled, and the Wax separated from the chilled mixture in the presence of an added Wax crystal regulator, which is eiective in the presence of a small amount of water, the method of adding the regulator to the oil, which comprises mixing the regulator with a substantially constant-boiling mixture of water and a ketone effective as a wax antisolvent component of a dewaxing solvent, and commingling the resulting mixture with the wax bearing oil prior to chilling.

3. In the dewaxing of hydrocarbon oil wherein the oil is mixed with a dewaxing solvent, chilled, and the wax separated from the chilled mixture in the presence of an added wax crystal regulator, which is elective in the presence of a small amount of Water, the method of adding the regulator to the oil, which comprises mixing the regulator with an aliphatic ketone containing a small vamount of water suicient to form with the ketone a constant boiling mixture and incorporating the resulting mixture in the Wax bearing mixture prior to chilling.

4. In the idewaxing of hydrocarbon oil wherein the oil is mixed with a dewaxing solvent, chilled, and the Wax separated from the chilled mixture in the presence of an added Wax crystal regulator, which is effective in the presence of a small amount of water, the method of adding the regulator to the oil comprising adding the regulator in powdered form to methyl ethyl ketone containing around 11% of Water to form a suspension and incorporating said suspension in the wax bearing mixture prior to chilling.

5. In the dewaxing of wax bearing oil wherein the oil is dewaxed in the presence of a wax crystal regulator, which is eilective in the presence of a small amount of water, with a dewaxing solvent, which is subsequently distilled from the dewaxed oil for reuse, said solvent containing a wax antisolvent liquid, a portion of which during distillation from the oil, in the presence of steam, forms a substantially constant-boiling mixture of antisolvent and Water, the method which comprises mixing the Wax bearing oil with the dewaxing solvent, incorporating therein a suspension of a wax crystal regulator in a portion of said constant-boiling mixture, chilling the resulting mixture to precipitate the Wax, and removing the precipitated wax in the presence of the regulator.

6. The method, according to claim 5, in which the wax anti-solvent liquid comprises an aliphatic ketone.

'7. In the dewaxing of wax bearing oil wherein the oil is dewaxed in the presence of a wax crystal regulator, which is effective in the presence of a small amount of water, with a dewaxing solvent, which is subsequently distilled from the dewaxed oil for reuse, said solvent containing a Wax anti-solvent liquid, a portion of Which during distillation from the oil, in the presence of steam, forms a substantially constant-boiling mixture of anti-solvent and water, the steps which comprise mixing the oil with the dewaxing solvent, incorporating in the mixture a suspension of the wax crystal regulator in a portion of said constant-boiling mixture, chilling the resulting mixture to precipitate the wax, removing the wax so precipitated to produce a dewaxed mixture of oil and solvent, distilling the bulk of the solvent from the dewaxed mixture, distilling the remainder of the solvent therefrom in the presence of steam, forming during said steam distillation a constant-boiling mixture of wax anti-solvent liquid and a small amount of Water, and employing said constant-boiling mixture for preparing the suspension of the wax crystal regulator.

8. In the dewaxing of wax bearing mineral oil in the presence of a wax crystal regulator, which is effective in the presence of a small amount of water, with a dewaxing solvent containing a wax anti-solvent, the steps comprising mixing the oil with the dewaxing solvent, forming a suspension of the wax crystal regulator in a constantboiling mixture of wax anti-solvent and water, incorporating said suspension in the Wax bearing mixture, chilling the resulting mixture to precipitate the wax, and removing the precipitated wax in the presence of the added regulator.

9. In the dewaxing of wax-bearing oil wherein the oil is dewaxed in the presence of a wax crystal regulator, which is eiective in the presence of a small amount of water, with a dewaxing solvent, which solvent is subsequently discharged from the dewaxed oil for reuse, said solvent containing a low boiling aliphatic ketone, a portion of which during distillation from the oil, in the presence of steam, forms a substantially constant boiling mixture of ketone and water, the steps which comprise mixing the oil with a dewaxing solvent comprising a mixture in substantial proportions of an aliphatic ketone and an aromatic hydrocarbon selected from the group consisting of benzol and its homologs, incorporating in the mixture a suspension of the wax crystal regulator in a portion of said constant boiling mixture, chilling the resulting mixture to precipitate the wax, removing the wax so precipitated to produce a dewaxed mixture of oil and solvent, dis-q tilling the bulk of the solvent from the dewaxed mixture, distilling the remainder of the solvent therefrom in the presence of steam, forming during said steam distillation a constant boiling mixture of ketone and a small amount of water, and employing said constant boiling mixture for preparing the suspension of the Wax crystal regulator.

10. 'I'he method according to claim 9 in which the aliphatic ketone comprises methyl ethyl ketone and the aromatic hydrocarbon comprises benzol.

WALTER SMISLOFF.