US2726988A

US2726988A - Solvent dewaxing process

Info

Publication number: US2726988A
Application number: US308324A
Authority: US
Inventors: Robert A Macke
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1952-09-08
Filing date: 1952-09-08
Publication date: 1955-12-13
Anticipated expiration: 1972-12-13

Description

Dec. 13, 1955 R. A. MACKE soLvENT DEWAXING PROCESS Filed Sept. 8. 1952 INVENTOR. Roberf A. Macke'l BY Uu-4 a,

United States Patent O 2,726,988 SOLVENT DEWAXING PROCESS Robert A. Macke, Baytown, Tex., assignor, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N. J., a corporation of Delaware Application September 8, 1952, Serial No. 308,324 9 Claims. (Cl. 196-18) The present invention is directed to a solvent dewaxing process. More particularly, the present invention is directed to a solvent dewaxing process in which a solvent mixture of a ketone and a low boiling aromatic hydrocarbon is employed. In its more specific aspects, the invention is directed to a process in which a solvent mixture of a ketone and a low boiling aromatic may be employed to dewax a plurality of waxy oils.

The present invention may be briefly described as involving a method for dewaxing a waxy oil with a solvent comprising a mixture of a ketone and a low boiling aromatic hydrocarbon in which the ketone and aromatic hydrocarbon are proportioned to provide a solvent which with said oil has a miscibility temperature corresponding to the proportion of ketone and aromatic in said mixture, the particular feature of the invention being adding to the solvent mixture an amount of water sulicient to adjust the miscibility temperature of the mixture to a miscibility temperature corresponding to a solvent having a ratio of ketone to aromatic greater than that of the solvent mixture. The solvent mixture of ketone and aromatic to which water has been added is then employed to dewax a waxy oil.

The present invention also contemplates the dewaxing of a plurality of waxy oils having dilerent miscibility temperatures with a solvent mixture of a ketone and a low A boiling aromatic hydrocarbon in which the ratio of ketone to aromatic hydrocarbons in the solvent mixture is maintained substantially unchanged. In my invention the solvent mixture of a substantially constant ratio of ketone to aromatic hydrocarbon is employed to dewax a rst of said oils having a miscibility temperature corresponding to the ratio of ketone and aromatic therein and following thereafter employing the same solvent mixture to dewax a second of said oils having a different miscibility temperature by adding to said solvent mixture a sutlicient amount of water to adjust the miscibility temperature of the solvent mixture to the miscibility temperature correspending to that of the second of said oils. The second of said oils is then dewaxed with the solvent mixture to which water has been added. A third of the oils may also be dewaxed by adding further amounts of water to the solvent mixture to which Water has been added to adjust further the miscibility temperature to that corresponding to the miscibility temperature of the third of the oils. The process may be repeated by adding water to adjust further the amount of water in the solvent mixture to correspond to oils having different miscibility temperatures.

The ketone employed in the practice of the present invention may be any one of a large class of aliphatic ke tones, such as illustrated by acetone, diethyl ketone, methylethyl ketone, dipropyl ketone, dibutyl ketone, diamyl ketone, methylpropyl ketone, ethylpropyl ketone, methylbutyl ketones, ethylbutyl ketone, propylbutyl ketones and many others of the same homologous series. I prefer to use methylethyl ketone because of its availability and further because it gives improved results.

The low boiling aromatic hydrocarbon employed in the practice of the present invention may be any one of a large' number of low boiling aromatic hydrocarbons, such as benzene, toluene, xylene, propyl benzene, tn'methyl benzene, tettamethyl benzene and the like. It will be preferred, however, to use as the low boiling aromatic hydrocarbon either benzene and/ or toluene with the latter preferred of the two.

The ratio of the ketone to the low boiling aromatic hydrocarbon may range rather widely; however, a ratio of ketone to low boiling aromatic hydrocarbon in the range from about 3.0 to 9.5:7.0 to 0.5 will ordinarily be employed. In short, a solvent mixture of methylethyl ketone of 58% methylethyl ketone and 42% of toluene will give satisfactory results. Other concentrations such as 75% methylethyl ketone and 25% of toluene may also be used.

The amount of water employed in the practice of the present invention will be that amount required to adjust the miscibility temperature of the solvent oil mixture to a miscibility temperature corresponding to that of the oil being dewaxed. The amount of water added will usually be in the range from about 0.6% to about 2.5% by volume, For example, if it is desired to filter an oil to dewax it at 17 F., a solvent mixture of 75% methylethyl ketone and 25% toluene may be employed which with the oil gives a miscibility temperature of 17 F. Another oil having a miscibility temperature of 5 F.

may be dewaxed by iiltration employing the same solvent but with 1% of water added to it.

The invention will be further illustrated by reference to the drawing in which the single ligure is a ilow diagram of a preferred mode.

Referring nowv to the drawing,

numerals

11, 12 and 13 designate, respectively, storage tanks for feed stocks which are identified as feed stocks A, B, and

C. Storage tanks

11, 12 and 13 are'connected to a charge line 14 by a manifold 15 containing

control valves

16, 17 and 18. By suitable manipulation of

valves

16, 17, and 18 it is possible to charge either feed stocks A, B, or C to the system. For purposes of this description, it will be assurned that feed stock A will be charged into the system and in this instance valve 16 is opened and Valves 17 and 18 are closed, allowing the feed stock A to how into manifold 15 and then into line 14 which introduces feed stock A into a chilling zone 19. Chilling zone 19 may be a plurality of Chillers of the well-known type employed in the dewaxing art. The oil is introduced into chiller 19 at a temperature of about 150 F. and prior to introduction into chilling zone 19 has admixed with it about 1 volume of a so-called Wet solvent introduced by line 20 from a source which will be described further. The adrnixture of wet solvent and oil is chilled in chilling vone 19 to a temperature corresponding approximately to the miscibility temperature of the oil with the particular methylethyl ketone solvent to be used. It may be assumed that this particular4 oil will require a solvent of 75% methylethyl ketone and 25 toluene. In this event, the oil will be chilled to a temperature of approximately 15 F. or somewhat lower. The chilled oil issues from chiller 19 by line 21 which serves to discharge the oil into filtering zone 22 which may be a plurality of rotary iilters which are also well known to the art. Prior to discharge into the iiltering zone 22, the chilled oil and solvent in line 21 had admixed with it from line 23 approximately 1 volume of a so-called dry solvent, the source of which will be described in detail hereinafter. In filtering zone 22 the oil which has wax crystals contained in it as a result of the chilling operation is subjected to filtration to remove the wax. As a result of the chilling operation in chilling zone 19 the wet solvent hasv its water content reduced by virtue of the fact that the chilling operation causes the Water to form ice crystals which are removed with the wax.

ln the filtering zone 22 the wax cake which forms on the rotary filter is washed with quantities of the dry solvent which is introduced into the filtering zone 22 by line 24 from a source which will be described further and has Vadditional amounts of' solvent introduced to it by lineY 24. VIt is possible to control 'the water lcontent of the solvent by controlling the solvent content of the wax stream in scroll 29. Thus the higher the solvent content of the waxthe more water is carried out with the wax to the recovery system and into the recovered solvent. Ilr

it is desired to reduce the water coment ofthe recovered solvent, the quantity of the solvent introduced to the wax scrollV may be likewise reduced 'which-'will control the water content. In any event, the wax and solvent from Vscroll 29 is discharged by line 30 intol a wax decanter In wax decanter 31 there exists two phases, a wax Y 31. plus solvent phase and a water plus solvent phase; the latter. being heavier than the wax is Withdrawn from the bottom of wax decanter 31 by line 32 yand discharged thereby into a solvent stripper 33 wherein temperature and pressure conditions are adjusted by a .heating Vmeans illustrated by steam coil 34 to allow -a vseparation to be 'made between the solvent and the water, the latter being withdrawn from the system by line 35 while the wet solvent is withdrawn overhead by line 36 as a solvent-Water azeotrope.

The dewaxed oil which is withdrawnfromtiltering zone 22 by line 27 is discharged therebyfinto 'evaporator 28 which is exemplified by a heating means illustrated by a steam coil 37. Conditions of `temperature and vpressure are adjusted in the evaporator 28 to fallow removal "as an overhead fraction by linev 39'the drly solvent which is discharged thereby into dry solvent storage facilities 40 'from which the dry solvent is withdrawn by line 24, containing a chilling means 41, for introduction into line 21 and into filtering zone' 22 and scroll 29 as has been described. The oil from whichsolvent has been 'substantially removed is withdrawn from the bottom ofthe evaporator 28 by line 42 and introduced thereby Yinto adewaxed oil stripper 43 wherein the remainder of the'fsolvent not removed in evaporator 28 is stripped from the dewaxed oil by introduction of open steam by line 44. The steam serves to remove the solvent not removed in evaporator 28 as an overhead by line 45 which admixes with the solvent-water a'zeotrope in line 36 and the two discharged into .de'canterY 31. The-dewaxed' oil is removed from stripper 43 by line 46 for use as a lubricant or to be .further processed.

The wax plus solvent lmixture indecanter 31 .is withdrawn therefrom by Yline, 47 'and isintrodueed thereby into evaporator 48 which, like evaporator 28, is provided with 4 solvent adrnixed with the feed stock A by line 20 in line 14 is obtained. Y

The wax from which substantially all of the solvent has been removed in evaporator 48 is withdrawn from stripper 48 by line 51a and isA introduced thereby into a wax stripper 52 which, by introduction of open steam by line 53, is stripped of the remaining solvent not removed Y.

in stripper 48. The. stripping steam condensate containing solvent from stripper 52 is discharged'from stripper 52 by line 54 into decanter 31. The wax is removed'from wax stripper 52 by line 55 and may then be further refined for employment as wax in various operations in whichpetroleum waxes are put.

From the foregoing brief description of the ow through a dewaxingv plant employing a methylethyl ketone-toluene solvent mixture, it may' be seen that the amount of water in the solvent may be controlled Vby controlling the amount of solvent introduced into the wax scroll by line 24.

When the dry solvent facilities 40 become lled, an overow line 56 is provided which allows the dry solvent-to be introduced in with Vthe wet solvent.

In accordance with my invention it is possible to employ in such a system as has been described one solvent havingA a substantially constant ratio of ketone to low boiling aromatic hydrocarbon such as rnethylethyll ketone and 25%V toluene and to adjust the solvent to characteristics of other feed stocks; thus feed stock B may be dewaxed at 0 F. and it would be desirable to use the same solvent as employed with feed stock A. However, feed stock B actually would require a solvent containingl 81% methylethyl ketone and 19% of toluene. Since'it' is impractical to provide facilities for solvents 'of varyingratios 'in-my invention, I adjust the water content of the solvent mixture for the filtering temperal"ture required for feed stock B over that of feed stock A. Thus, I increase for feed stock B the water content of lthe solvent from 0.4% to 0.75% and I can thereby in- 'crease the miscibility temperature from the figure of -l5 to about 5 F. This allows me to process feed 'stock B through the system as has been described for 'feed stock A and get highly beneficial results.

Likewise, for feed stock C I can further adjust the water contentfof the solvent and dewax `feed stock C at 'invention results in a substantially improved lter rate.

-Inother words, in practicing my' invention I am able to 'increase the filter rate as gallons of derwaxed oil per "square '-fo'ot of .lter surface Vper hour over that of `a Asolvent mixture whose Watercontent has not been adjusted lin accordance with the present invention.

The invention will be illustrated further by the following table of data which show the effect of the amount of water in the solvent on the -lter rate and the miscibility temperature for varying concentrations of methylethyl ketone with toluene and benzene.

Table l Solvent Composition Y Percent Oil Solvent Pme Pent Filter Filter Miseibnity iiertiirit P t P t vgalm lil (iii in mi sub* Temp e y eroen ercen o ven Y ax Ethyl Toluene Benzenei `mergence F. .Ketone B 39 3 D 36 3.6 3.7 -42 iss a9 Y aus as L0 v1o 2s sa 39 v;; 8; 1.15 a 9 4a v.10 es 2931s, 2.25 o a4 4.o -140 -27 68 29.75. V2.225' 0.6 34 5.3 33 -lU 75 $.25. 1.75 A0 32 5.9 29 -14 l Gallons dewaxgd WsqJtJhr-.at Calcnlatediorplant type lter..

annexes It wlll be noted from the above data that the same iilter rate was obtained when using a solvent containing 58% methylethyl ketone with 0.6% water as with 68% methylethyl ketone with no water. It may also-be seen that similar iilter rates were obtained for a solvent containing 58% methylethyl ketone with 1.15% water and a solvent containing 68% methylethyl ketone with 0.6% Water. In short, these data show that I may simply, by adjusting the water content of the solvent, provide a solvent having different characteristics without having to increase the methylethyl ketone content.

Since in commercial operations the solvent composition employed in a commercial plant is usually fixed by the feed stock requiring the minimum methylethyl ketone content, it is necessary to dewax other stocks with solvents containing much less methylethyl ketone than could be tolerated. This results in a loss of lter rate which decreases the plant throughput. In my invention this is compensated for by adding water to the solvent to permit operations closer to the miscibility temperature for the particular stock being dewaxed and yet result in a higher lter rate than could be obtained heretofore. For example, in one commercial operation the three stocks employed are a phenol ranate of a lubricating oil fraction, a light motor oil and a neutral oil. Miscibility temperature relationships for these stocks are presented in the following table:

For a solvent containing 0.6% water the phenol ratiinate limits the methylethyl ketone content of the solvent to 59%. 'Ihus it is necessary, in accordance with the practice of the prior art, to dewax the light motor oil and a neutral oil with this solvent composition. In my invention, however, by adding water to the solvent an increased iilter rate can be obtained on light motor oil and neutral oil with no loss in dewaxed oil yield.

This latter may be illustrated by the data in the following Table III wherein a solvent having a composition of 75% methylethyl ketone and 25% toluene was employed to dewax a neutral oil.

Table III Solvent Composition Percent Filter Rate Percent Water fylrslbutg Gals/sq. l Methyl- Percent Added p" ft./hr.

Ethyl Toluene Ketone It will be noted that an increase of 25% in iilter ratel has been effected by adjusting the water content of the solvent.

From the foregoing description and data, it will be seen that my invention is susceptible to many modifications. In short, I may choose to dewax an oil with a solvent having a ratio of ketone to low boiling aromatic such that it would oridinarily be unsuitable for dewaxing said oil but I can make it suitable for best results and obtain increased filter rates by adding a sullcient amount of water to adjust the solvent/oil miscibility temperature at which filtration is to be conducted. Also I can employ in a commercial unit one solvent composition and yet get the benefits of varying solvent compositions by adjusting the water content of the solvent.

While in the description of my invention, taken with the ow sheet, I have shown water being added by the steam introduced into the system and the water content of the solvent controlled by the amount of solvent introduced into the wax scroll, I need not restrict myself to this specific mode but I may use a simpliied operation and add water to the solvent as required. However, in any commercial operation I should prefer to add the water as steam used for stripping and to adjust the water content as has been described. v

In the specication the terms wet and dry solvent have been used. Actually the term dry solvent is relative and the solvent so designated may contain an amount of water. Usually the amount of Water contained in the dry solvent will be in the range from 0.1% to 0.8%. The wet solvent will contain an amount of water in the range from 0.3% to 2.0%.

In the practice of the present invention it will be desirable to employ in the chilling zone 19 a temperature in the range from -i-l25 to 20 F.

In the filtering zone 22 the temperature will depend on the temperature to which the oil has been chilled in chilling zone 19 but the iiltering temperature should correspond approximately to 1 to 10 F. above the miscibility temperature of the oil and solvent. For usual lubricating oil fractions this temperature for conducting the filtering operation, will be in the range from +20 to 20 F.

The amount of wet solvent employed for admixture with the oil to be dewaxed will be in the range from 0.21 volume to 4.0 volumes of solvent to one volume of waxy oil while the amount of dry solvent used will range from 0 volume to4.0 volumes.

The temperatures employed in the evaporators and in the several strippers will depend on the particular solvent being used in the operation.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Pateut is:

l. A method for dewaxing a waxing oil with a solvent comprising a' mixture of one single ketone and a low boiling aromatic hydrocarbon in which the ketone and aromatic hydrocarbon are proportioned to provide a solvent having a miscibility temperature with a first waxy oil corresponding to the proportion of said ketone and aromatic in said mixture, which comprises adding to said solvent mixture an amount of water sufficient to adjust the miscibility temperature of the mixture to a miscibility temperature of about 5 F. corresponding to a solvent having a ratio of ketoneto aromatic greater than that of the solvent mixture, and then employing said solvent to which water is added in dewaxing a second waxy oil at a temperature of about 0 F.

2. A method for dewaxing a waxy oil with a solvent comprising a mixture of one single ketone and a low boiling aromatic hydrocarbon in which the ketone and aromatic hydrocarbon are proportioned in a ratio in the range from 3.0 to 9.5:7.0 to 0.5 to provide a solvent having a miscibility temperature with a rst waxy oil corresponding to the proportion of said ketone and aromatic in said mixture, which comprises adding to said solvent mixture an amount of water in the range from about 0.6% to about 2.5% by volume sufticient to adjust the miscibility temperature of the mixture to a miscibility temperature of about -5 F. corresponding to a solvent having a ratio of ketone to aromatic greater than that of the solvent mixture, and then employing said solvent to which water is added in dewaxing a second waxy oil at a temperature of about 0 F.

3. A method for dewaxing a waxy oil with a solvent comprising a mixture of methylethyl ketone only and 7 toluene-in which the ketone and aromatic hydrocarbon are proportioned to provide a solvent `having-a miscibility temperature with .a'rst Vwaxy oil corresponding Yto the proportion of said ketone. and aromatic in said lmixture, which 4comprises adding to said solvent mixture an amount of Water suiicient to adjust the miscibility 'temperature of the mixture to a nl'iscibility temperature of about YF. corresponding to a solvent havinga ratio of ketone to aromatic greater than that of the solvent mixture, and'then employing said solvent to which'water is added in dewaxing a second Ywaxy oil at a temperature 4. A method in accordance with claim 3 .in which the methylethyl ketone and toluene are proportioned in a ration the range from 3f() to"9.5:'7.0 tor`0Q5vand the amount ofrwateris in the range from about. 0.6% to about 2.5% by volume.

5. A method for dewaxing a plurality of waxy oils having differentl rniscibiiityV temperatures with -a solventV mixture of one single'ketone and a lowboiling aromatic hydrocarbon in which the ratio of .ketone to aromatic hydrocarbon in the solventmixture -is maintained substantially constant, the steps o`fdewaxing a first of 'said oils with said solvent mixture at a temperature of Vabout 15 F. and corresponding approximately to a miscibility temperature of the 'first of said oils with vsaid solvent mixture, adding lto said'solvent mixture an amount of water suicient to adjust the mis'cibility temperature of the solvent mixture to a miscibility temperature of about 5 F. corresponding approximately to .that of a second of said oils, and dewaxing at least the second of said oils at about 0 F.4 with said solvent mixture to which water has been-added;

6. Ameihod for devvaxing a plurality of'waxy oils having diierent miscibility temperatures withV a .solvent mix- Y ture of one single ketone and a low vboiling aromatic hydrocarbon in which the ratio of ketone to aromatic hydrocarbon in the solvent mixture is maintained substantially constant, the steps of dewaxing a tirst of said oils with said solvent mixture at a temperature of .about 15 F. and corresponding approximately .to aimiscibility ten1- perature ofthe first of said oils with said solvent mixture, adding to said solvent mixture an amount of water vsuicient to adjust the miscibility vtemperature of the solvent mixture to a miscibility temperature of about 5 yF. and corresponding approximately to that of a second Vof said oils, dewaxing thegsecond of said oils at a temperature of about 0 F. with said solvent mixture to whichwater has been added,1adding to said solvent to which .water has beenaddedvstill a furtheramount amount of watersuicient to .adjust the miscibility temperature of -the solvent .mixture to a .misci'oility temperature .corresponding approximately 4to that .of Va third of.. said oils, V.and dewaxing .the .third or" said oils 'with said-solvent mixture to which.

said amounts or waterhave-been added.

7. A method for dewaxing a Iplurality of waxy 'oils .8 having different misciblity'temperatures with a vsolvent mixture Yof 'one single ketone'and a low boiling aromatic hydrocarbon in which the ratio Aof ketone to aromatic hydrocarbon inthe solvent mixture -is maintained substantially constant, -the steps of dewaxing va first Yof -said .oils

with said solvent mixture at a temperature of about 15 F. and corresponding approximataely to-a-miscibility temperature of .therst of said-oils with said solvent mixture, addingto said .solvent :mixture an vamount of Water-in the range vfrom about 0.6% to about 2.5% vby volume suicient to raise the miscib'ility temperature of. the solvent mixture to a miscibilty .temperature of about 5 Ffand corresponding approximately to that of a second of said oils, anddewaxingat least Ythe second ofsaid oils at about 0 F. with said .solventmixture to which water has been added. e

S. vA method ltor dewaxing a plurality of waxy .oils having different miscibility .temperatures with a solvent mixture ofmethylethyl ketone and toluene in which the ratio .of meth-ylethyl fketone to toluene in the solvent mixture is maintained substantially constant, the lsteps of dewaxing 1a first of said oils with said solvent mixturerat a temperature-o -about 15 Foand corresponding approximately to a' miscibilit-y temperature of the rst of said oils with saidisolvent mixture,` separating said'solvent mixture-from the first of said oils, adding to said-solvent mixture an amount of water sufficient to adjust the miscibility temperature of the solvent mixture to a miscibility temperature ot about 5 F. and corresponding approximately to that of a second of said oils, dewaxing the second otsaidzoils at .'abou't 0 F. with said solvent mixture to which water has been vadded, separating said solvent mixture Tto 4which -water `has been added from the second of said oils, adding to said separated solvent to which water has been vadded still a further amount of water suicient to adjust Ythe miscibility temperature of the solvent mixture to a miscibility temperature corresponding approximately to that of a third of said oils,

References Cited vin the tile of this patent UNITED STATES PATENTS` l,669,151 Wagner `May 8, 1928 2,478,456 Boudreaux et al. Aug. 9, 1949 2,550,058 -Ge'e Apr.l 24, 1951 2,584,966 Reeves Y. ...Feb..-5, 1952 Pokorny let al. Sept. 7, 1954

Claims

1. A METHOD FOR DEWAXING A WAXING OIL WITH A SOLVENT COMPRISING A MIXTURE OF ONE SINGLE KETONE AND A LOW BOILING AROMATIC HYDROCARBON IN WHICH THE KETONE AND AROMATIC HYDROCARBON ARE PROPORTIONED TO PROVIDE A SOLVENT HAVING A MISCIBILITY TEMPERATURE WITH A FIRST WAXY OIL CORRESPONDING TO THE PROPORTION OF SAID KETONE AND AROMATIC IN SAID MIXTURE, WHICH COMPRISES ADDING TO SAID SOLVENT MIXTURE AN AMOUNT OF WATER SUFFICIENT TO ADJUST THE MISCIBILITY TEMPERATURE OF THE MIXTURE TO A MISCIBILITY TEMPERATURE OF ABOUT -5* F. CORRESPONDING TO A SOLVENT HAVING A RATIO OF KETONE TO AROMATIC GREATER THAN THAT OF THE SOLVENT MIXTURE, AND THEN EMPLOYING SAID SOLVENT TO WHICH WATER IS ADDED IN DEWAXING A SECOND WAXY OIL AT A TEMPERATURE OF ABOUT 0* F.