US2586947A - Propane-clay treating - Google Patents

Description

Feb. 26,1952 A. HAYs, JR., ErAL PROFANE-CLAY TREATING Filed Nov. 29, 1949 Y ...www www Il. Il 0 V/ d wm. wm n w am m A. s Nm d B. w G`U$COWJ Wwxzvk .Wmv-YQOR'WQO. Q 8 v m. L R0 vm @WWK .l QN .Mx g .COTQQQW m olmtod IMX wx S EGkm. tc .mv Q N NN \V\ www X23 mm xmms N mm. om IIQM. wok ---Il QQ mum. -l kwh. QMOL xbk mSuQoLQ LowwLQEoo .BCG xv al Ltmbtob *wx ox QQQQkQ mkoxm. .UCB Y Patented Feb. 26, 1952 PROPANE-CLAY TREATING Leonard A. Hays, Jr., Hammond, and Robert B. Selund, Highland, Ind., assignors to Standard Indiana Oil Company, Chicago, Ill., a corporation of Application November 29, 1949, Serial No. 129,918

7 Claims. (Cl. 196-147) This invention relates to the clay treatment of charging stocks particularly of the lubricating oil boiling range in propane solution,` and it pertains more particularly to an improved method and means for treating a propane solution obtained by propane dewaxing of a wax-bearing lubricating oil stock before the propane is removed from the solution. i

Advantages obtainable by theclay contacting of lubricating oil stock in propane solution have long been known (note U. S. 2,215,362) and in commercial operations dewaxed propane-lubrieating oil solutions have been contacted with clay either with or without an intermediate acid treat-y ing in propane solution. It has been the practice, for example, to slurry a contacting clay in a small amount of hot oil from the low pressure propane stripper and inject said slurry to the propane oil solution which is then routed to the high pressure propane recovery tower. Operating difficulties have arisen in such practice because of foaming in the slurrying vessel and because of poorer treating resulting and the production at times of off-,color products. The object of our invention is to provide a method and means for avoiding such operating diiculties and for improving the efliciency and effectiveness of the propane clay treating.

We have found that the activity of solid adsorbents, such as activated clay, in removing color bodies from hydrocarbons of the lubricating voil boiling range is greatly influenced by temperature. At temperatures in the range of .about 60 to 150 F, and in the absence of propane, solid adsorbent is relatively inactive, but at` temperaturesof the order of 200 to 400 F., it is highly active. If active adsorbent clay is contacted with a small portion of hot oil before being contacted with the bulk of an oil to be treated, the clay becomes deactivated by the treating eiect which it exerts on the hot oil and thus becomes too spent for effective decolorization of the larger portion of the oil with which it issubsequently admixed. In practicing our invention, We slurry the solid adsorbent clay in Ia portion of previously treated charging stock which has been freed from propane and cooledto a temperature substantially below 200 F., usually below 175 F. and preferably in the range of 60"r F. to 150 F., then in' timately mix this slurry with a llarge-andv relatively cooler Inass of a'solution of charging Astoel; to be treated dissolved in propaneso thatzthe resulting mixture-will be at a temperature of the order of about l100 F. -After obtaining in imeiemxivr? et, e relatively .19W temp=reture the temperature of the mixture is increased to the extent required for obtaining the desired decolorization. The propane is then sepa-rated from the decolorized charging stock solution and a small fraction of the propane-free decolorized charging stock is cooled to a temperature below about 175 F. and employed for slurrying additional amounts of active solid adsorbent.

The invention is applicable to any lcharging stocks in the lubricating oil boiling range and particularly to stocks in the SAE 10 to SAE 60 range. The invention is particularly applicable to dewaxed lubricating oil stocks which have previously been treated with a selective solvent such as phenol, furfural, dichlor-ethyl ether, etc., and/or has been acid treated. The wax removed from a hydrocarbon of the lubricating oil boiling range may itself be propane-clay treated in accordance with our invention. The invention is also applicable broadly to materials fractionatable by propane and in addition to hydrocarbon oils and waxes, it is applicable to fatty oils and waxes of animal or vegetable source, fatty acids, etc., which are fractionatable by propane in the manner described for example in U. S. 2,383,535.

The propane-clay treatment is preferably effected by initially contacting the charging stock (which has previously been thoroughly mixed with the adsorbent slurry prepared with the cooled slurrying medium) in the presence of a large amount of propane at a temperature of about 200 F then removing the bulk of the propane and finally contacting the charging 'stock in the presence of a small amount of propane at a temperature of the order of about 400 F. vAlternatively, however, the treating may be eiected at other temperatures in the range of about 200 to 400 F. and in the presence of various amounts of propane, the propane to 'charging stock ratio usually being in the range' of about .1:1 to 4:1.

The solid adsorbent may be of any type known to those skilled in the art, such as fullers earth, acid treated clay, such as Filtrol (an acid treated montmorillonite), attapulgus clay, etc., or it mayl be a synthetically prepared adsorbent such as activated alumina orA silica alumina compositions,

all of which are well known to those skilled in the art and require no further detailed descrip.- tion. The particle size of the clay should be sufciently large to enable easy removal by ltra tion, but suflciently 'small to provide maximum surface area and ease of handling, particle sizes usually being in the range of about to'4 400i mesh. The amount of clay will, of course, be de-lpendent upon the nature of the charging stockf and the specifications to be met; for most purposes the clay will be employed at the rate of about .02 to 2 pounds per gallon of charging stock to be treated, about .2 pound per gallon giving excellent results for the clay treating of an SAE 40 Mid-Continent lubricating oil charging stock which has previously been phenol extracted but not acid treated. When the invention is applied to fatty materials, the adsorbent may be vegetable or animal charcoal of the type usualy employed for that purpose.

The invention will be more clearly understood from the following detailed description of a s pecific example which is illustrated in the accompanying drawing which forms a part of this specication and which schematically illustrates a simplied flow diagram of a commercial propane-clay treating plant employing the invention.

Referring to said drawing, a propane-oil solution enters the system from source I and is introduced by line I I to mixer l2. In this example the charging stock is a phenol extracted Mid- Continent distillate which has been dewaxed in a commercial dewaxing plant of the type illustrated in U. S. 2,143,872, the propane solution being withdrawn from the ltrate solution tank of the dewaxing plant and passed throughheat exchangers to bring it to a temperature of approximately 80 F. The oil in this case is an SAE 40 stock diluted with propane to give a propane to oil ratio of about 23:1, the stream consisting of about 1800 barrels per day of oil dissolved in 4200 barrels per day or" propane. The

term propane as used in this specification refers to commercial grades of propane and is intended to include propane which contains minor amounts of other hydrocarbons, such as isobutane, butane, propylene, butylene, etc.

The solid adsorbent in this case is an activated montmorillonite clay, commonly known as Filtrol (specifically, Filtrol X-417) and it is preferably withdrawn from a storage hopper or other source I3 by suction through line I4 to cyclone separator I5, the suction being applied by eductor i5 which withdraws separated gas from a cyclone through line I1 and discharges it through line I8. The solid adsorbent particles may be introduced directly through cyclone dip leg I9 into slurry tank orv if desired it may be discharged into an upper clay hopper (not shown) and introduced therefrom into slurry tank 20 in controlled amounts by a screw conveyor.

The slurrying medium is introduced by line 2| into tank 20 and the adsorbent is thoroughly dispersed in and mixed with the slurrying medium by stirrer 22 driven by motor 23. The temperature at which the slurry is prepared should be as low as feasible; since in this case the liquid slurrying medium is very viscous, the temperature is in the range of about 100 to 150 F. It is important that high temperatures (of the order of 212 to 400 F.) be avoided in the slurry tank because such high temperatures cause foaming dinculties and with some adsorbents liberated water vapors condense and plug or otherwise interfere with the solids inlet portion of the system. Also, we have found that when high temperatures are employed in the slurry tank, the activity of the adsorbent is materially diminished before it even contacts the charging stock to be treated and thereby loses its eiectiveness in obtaining the required decolorization. In other words, the use of relatively low temperatures in the slurrying tank enables the ultimate to those skilled in the art.

attainment of better decolorization with a given amount of adsorbent or the requirement of less adsorbent to meet a given color specication. In this particular example, about 600 pounds per hour of the adsorbent and about 300 gallons per hour of slurrying medium is charged to tank 20.

The slurry from tank 20 is introduced by pump 24 and line 25 to mixer I2 which may be a ballled' chamber such as a knot hole mixer or a stirred mixer or any other type of mixer known The propane-oil solution from line II is preferably cooler than the introduced slurry so that the resulting mixture in this case does not exceed a temperature of about F. This mixture, with the adsorbent intimately dispersed throughout the propane-oil solution, is then passed by line 26 through heat exchanger 21 wherein it is heated by indirect contact with at least a portion of the hot finished product, as will be hereinafter described, and next it is heated with low pressure steam in heater 28 to bring its temperature to about 200 F., at which temperature it is introduced through line 20 at an intermediate point into high pressure tower 30 which operates at a pressure of approximately 250 pounds per square inch. Most of the propane dashes from the introduced mixture and is withdrawn through line SI to the propane condenser and storage tank of the propane dewaxing system. The upper part of tower 30 is provided with a series of baille plates 32, and propane reflux is introduced through line 33 above this baille section of the tower in amounts sufficient to hold the tower top temperature at about F.; `this prevents the carry over oi any oil with the propane discharged through line 3I.

Below the inlet point of line 29, the tower is provided with a total trap-out plate 34 for collecting the liquid slurry which is then passed by pump 35 through one or more reboilers 36 heated with high pressure steam to raise the temperature of the oil slurry to at least about 400 F., at which temperature the slurry is returned through line 31 at a low point' in the tower. Liquid solid adsorbent slurry is withdrawn from the base of tower 30 by line 38 in amounts regulated by valve 39 which in turn is controlled by the liquid level in the lower part of the tower. The withdrawn slurry at a temperature of approximately 400 F. then passes through line 30 or line 38a to the low pressure tower 40 which operates at about atmospheric pressure, from the top of which propane is withdrawn through line 4I to a jet condenser and thence to a compressor in the propane dewaxing plant. A plurality of trays 42 may beA provided in the upper partr of tower 40 and stripping steam is introduced into the tower through lines 43 and 44. Alternately a portion of the steam may be introduced to the tower through line 45. The stripping steam removes all propane from the oil slurry and the hot oil slurry, which is still in the vicinity of about 400 F., is withdrawn through line 45 by pump 41 which is controlled in accordance with the liquid level to be maintained in tower 60.

The bullk of the slurry thus withdrawn by pump 41 is introduced by line 48 to precoated filters 49 for removing the spent adsorbent from the oil, the oil being preferably passed through a blotter press ior insuring the removal of line adsorbent particles. Before or after passing through the blotter press (one of the filters), at least a portion of this hot oil may be employed for supplying the heat in heat exchanger 21.

Spent clay is removed from the filters by line 50. The ltered oil is cooled in cooler 5| and then introduced by line 52 into the proper storage tank 53,54, or 55. One of these storage tanks 55 is preferably set aside for receiving any ltered oil which does not meet color specications and this ltered oil, which has previously been cooled in cooler 5|, may be passed by pump 56 and lines 57 and 2| to slurry tank 20 to supply the required slurrying medium and simultaneously to receive the additional treatment which it may require.

Normally, the slurry medium is obtained by diverting a small fraction of the propane-free, adsorbent-containing oil discharged by pump 41 throughlcooier 58 and lines 59 and 2| to slurry tank 20. The amount of oil so diverted may be of the Yorder of about per cent but the amounts used viria-y vary with the amount of adsorbent being charged. The cooling step in this case is of vital importance since this diverted oil stream mustbe reduced in temperature from about 400 F. to aA temperature less than 200 F. and preferably tov a temperature in the range of about 60 to 150 F., the lower temperature being used with,A

relatively non-viscous oils and the higher temperatures being employed for oils of relatively high Viscosity.

In the above example, we have described the propane adsorbent clay treating of a dewaxed oil solution, the clay contacting being effected ;v

priorl to'propane removal (the high pressure pro-f' pane removal tower and low pressure stripper being in fact a part of the propane dewaxingA system). In other words, the clay contacting stepisL-interposed between the filtering step and the propane removal step in the propane de# waxing system. The ltered wax stream maylikewise be propane-clay treated in the propane dewaxing system between the iiltration step and` the steps of removing propane from the wax.' The invention is not limited, however, to these particular streams or to operation in conjunction with propane dewaxing. It is applicable to other systems of propane fractionation wherein at least one ofthe fractions may be contacted with solid adsorbent prior to the removal of propane there;- from. I Examples of su'ch other systems include the soj-called destearining of animal or vegef. table fats or fatty acids by low temperature pro; pane'f-lr'actionation, and the so-called Solexolf process'pf fractionating animal or vegetable fats or fatty'acids by high temperature propane fraclvtionatin. The term oleaginous may be employedVY to describe the broad class of charging stocks fto which the invention may be employedp# i. e.,yiscous hydrocarbon oils, hydrocarbon waxes ,f fatty oils and waxes of vegetable or animal origin;l '-v and fatty acids derived therefrom.

We claim:

1. .The method of treating with an active solid f adsorbent an oleaginous charging stock in prds pane solution for improving the color of said,- charging stock, which method comprises slurryjv ing said adsorbent in a fraction of previously` treated charging stock which has been freed from il.' propane and cooled to a temperature substan.

tially below 200 F., intimately admixing said slurry with a large mass of a solution of charging stock to be treated dissolved in propane, heating the resulting mixture to a higher temperature 7 in the range of about 200 F. to about 400 F.

effective for obtaining decolorization, separating propane from decolorized charging stock, cooling boiling range.

3. The method of claim l wherein the charging stock is a wax separated from a hydrocarbon of the lubricating oil boiling range.

4. The method of claim 1 wherein the charging stock is a fatty material selected from the class consisting of animal and vegetable waxes.

fatty oils and fatty acids.

5. The method of claim 1 wherein the small fraction of decolorized charging stock employed for slurrying said adsorbent is cooled to a tem- 1 perature in the range of 60 to 150 F. prior to the slurrying step.

6. 'I'he method of claim l wherein the heating is effected by iirst heating the mixture in the presence of a large amount of propane to a temperature of about 200 F., then removing most of the propane and heating the mixture in the presence of a small amount of residual propane'to a temperature of the order of 400 F.

7. The method of adsorbent clay treating a partially rened hydrocarbon charging stock of the lubricating oil boiling range in propane solution, which method comprises slurrying said adsorbent clay in amounts in the range of .02 to 2 pounds per gallon of charging stock in an aliquot fraction of previously treated charging stock which has been freed from propane and cooled to a temperature not substantially higher than 150 F. to obtain a slurry, intimately admixing said slurry with a large and cooler mass of a solution of charging stock to be treated dissolved in at least about two volumes of propane,'heat ing the resulting mixture to a temperature of about 200 F. under a pressure suiiicient to maintain the propane in liquid phase, then separating most of the propane from the heated mixture and heating the residual mixture containing only a small amount of propane to a temperature of approximately 400 F. while at a pressure-ofthe order of about 250 pounds per square inch', then reducing the pressure on the heated solution and stripping it with steam at about 400 F. to remove residual propane, filtering spent adsorbent clay from at least the bulk of the hot stripped oil, cooling at least a small fraction of the hot stripped oil to a temperature in the range of about to 150 F. and employing said cooled fraction for the slurrying of active adsorbent clay.

LEONARD A. HAYS, JR. ROBERT B. SELUND.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,270,214 Adams et al. Jan. 13, 1942 2,273,147 Schumacher et al. Feb. 17, 1942 2,321,459 Chenault et al. June 8, 1943 2,321,460 Chenault et al. June 8, 1943

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