US2982715A

US2982715A - Separation of normal paraffin wax from lubricating oil utilizing molecular sieve

Info

Publication number: US2982715A
Application number: US714594A
Authority: US
Inventors: John W Gibson
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1958-02-11
Filing date: 1958-02-11
Publication date: 1961-05-02
Anticipated expiration: 1978-05-02
Also published as: FR1227293A

Description

J. w. GIBSON 2,982,715 SEPARATION OF NORMAL PARAFFIN WAX FROM LUBRICATING May 2, 1961 OIL UTILIZING MOLECULAR SIEVE 2 Sheets-Sheet 1 Filed Feb. 11, 1958 zo L E22 REGENERATOR WASTE GAS OIL PRODUCT FIG. I

INVENTOR:

JOHN W. GIBSON BY: fil X 8 HIS ATTORNEY y 1961 J. w. GIBSON 2,982,715

SEPARATION OF NORMAL PARAFFIN WAX FROM LUBRICATING OIL UTILIZING MOLECULAR SIEVE Filed Feb. 11, 1958 2 Sheets-Sheet 2 POUR POINT,

IO 20 3O 4O 50 TOTAL OIL RECOVERED, BY WEIGHT OF MOLECULAR SIEVE FIG. 2

INVENTOR:

JOHN W. GIBSON BY: M a 3 HIS ATTORNEY United States Patent JohnW. Gibson, Oakland, Calif., assignor to Shell Oil Company, a corporation of Delaware Filed Feb. 11, 1958, Ser. No. 714,594

8 Claims. (Cl. 208-26) This invention relates to a process for treating waxy oils. improved process for removing waxy normal parafiins from hydrocarbon oils and to the improved dewaxed oils produced in this manner.

It is an object of this invention to provide an improved process for the dewaxing of oils, particularly petroleum oils. Another object of this invention is to provide a process for the dewaxing of oils which avoids the necessity of using refrigeration. It is an important object of this invention to provide methods for utilizing molecular sieve sorbents in the dewaxing of waxy oils. It is a further object to provide an efficient method for dewaxing distillate oils of relatively low wax content. It is a specific object to provide a method for substantially lowering the pour point of lubricating oils. Further specific objects are to provide a method for removing normal waxes from lubricating oils to make them susceptible to still further substantial pour point lowering by means of pour depressants, and to provide a method for substantially lowering the cloud point of previously dewaxed lubricating oils. vide oils substantially free of normal waxy parafiins and exceptionally susceptible to pour depressants.

Other objects will become apparent from the following description of the invention, which is made in part with reference to the drawing, wherein Figure 1 is a schematic representation of a preferred 7 mode of carrying out the process of this invention, and

Figure 2 is a graphic representation of the pour point lowering obtained in treating oils with molecular sieves.

A number of processes have been developed for removing paraffin wax from hydrocarbon oils and particularly from distillates. All of these processes are based on separating the wax in crystalline form while retaining the oil as a liquid. Pressing to remove paraffin wax from distillates and sweating the resultant slack wax are two of the oldest processes in the petroleum industry. Solvent dewaxing of distillates has more recently come into wide commercial use. All of the processes. which are in commercial operation for dewaxing of hydrocarbon oils require substantial refrigeration. For example, it has been estimated that the cost of refrigeration in most solvent dewaxingprocedures constitutes approximately 60% of the total dewaxing expense.

In particular, the dewaxing of petroleum fractions having a low wax content by conventional refrigerating methods is highly inefficient in that a high proportion of the wax removed must be recycled to the system ahead of the separation area in order that a filter cake having satisfactory properties may be built up. For example, in dewaxing fractions having wax contents of about 6% or lower, it has been found necessary to recycle as much as 95% of the wax separated. Such operations are obviously inefficient and costly and should be avoided if it is possible to do so.

It is well known that certain zeolites have the characteristics of selectively sorbing normal paraflinhydrocar- More particularly the invention is directed to an It is a further object to pro- 2,982,715 Patented May 2, 1961 bus. These zeolites are commonly known as molecular sieves. They will be described in more detail hereinafter. The molecular sieves which have the characteristic of selectively sorbing normal hydrocarbons or hydrocarbon derivatives are characterized byan essentially uniform pore diameter of about five Angstrom units.

Although it has been known for a long time that molecular sieves of about five Angstrom units pore diameter selectively sorb normal parafiins it was also known that the rate of sorption of hydrocarbons in molecular sieves decreases with increasing molecular weight. No successful use of molecular sieves in separating waxy par'afiins has been reported in the literature to date.

The current state of the art in this field is summarized in a paper by Guyer et al., Helvetica Chimica Acta, 40, 1603 (October 1957) at page 1604, as follows:

Among the crystalline zeolites, chabazite, which permits the separation of normal from branched hydrocarbons, has been studied most extensively. In 1956, Brook and coworkers succeeded in synthesizing a crystalline zeolite with a more open structure than chabazite. This synthetic zeolite type A made it possible to sorb straight chains up to tetradecane, whereas chabazite had sorbed normal hydrocarbons only to a chain length of C (Quotation translated.)

It has now been found that five-Angstrom molecular sieves can be employed to remove waxy normal paraflins from hydrocarbon oils by carrying out the contact at least partly in liquid phase at a temperature between 300 and 500 C. It has been found that waxy normal paraflins can beseparated by sorption in molecular sieves in a batch process, although this operation is not generally practical for commercial use. It has been further found that'a separation of some degree of utility can be obtained by carrying out the sorption in a conventional chromatographic column in liquid phase. Most importantly, it has been found that a greatly superior method for dewaxing of waxy oils consists in passing the waxy oil downwardly through a bed of stationary granules of five Angstrom molecular sieve sorbent while also passing downwardly through the bed of sorbent simultaneously with the oil a stream of gas or vapor sufficient to force the oil to flow through said bed of granules in the form of a film on the surface of the granules rather than in the form of a column of liquid filling the total void spaces. By operating according to this improved method, the dewaxing of oils can be carried out utilizing sorbent granules of substantially larger size than required in the chromatographic method and at a substantially greater rate of oil flow through a given column per unit time, while at the same time obtaining the benefit of an unexpected and surprisingly greater efiiciency of separation of waxy constituents from the oil.

It has also been found that Oils dewaxed by contact with molecular sieves are more sensitive to pour point depressants than oils which have been dewaxed to an equal or lower pour point by conventional methods.

Zeolites suitable for use as molecular sieves in this invention are characterized by rigid three-dimensional anionic networks with intra-crystalline interstitial channels whose narrowest cross section has an effective, essentially uniform diameter of about five Angstrom units. Molecular sieve zeolites are described, for example, in a paper entitled Zeolites as Absorbents and Molecular Sieves by R. M. Barrer, Annular Reports on the Progress of Chemistry for 1944, Vol. 61, pp. 31-46, London (1945) and in US. Patent 2,306,610 to Barrer. More recently, certain synthetic molecular sieves have become commercially available from Linde Company, a division of Union Carbide Corporation.

The five-Angstrom molecular sieves are those minerals classified by Barrer as Class I minerals, including chabazite, gmelinite and phacolite as well as a synthetic zeolite BaAlz Show "H2O A preferred five-Angstrom molecular sieve is that designated A by Linde Company; it is reported to have the average composition 0.25Na O-0.75CaO-1.00Al O -2.0SiO

The crystals of MS-SA are cubic with unit cells measuring on an edge approximately 12.26 Angstrom units and are characterized by an essentially uniform pore diameter of about five Angstrom units. The synthetic zeolite of type A is described in detail in papers by Breck et al. in Journal of the American Chemical Society, 78, 5963-71 (1956) and Reed et al., ibid., 5972-77. The particular type A sieve which has the above formula and a 5 Angstrom pore diameter is referred to by the authors as calcium exchanged type A. v

The pure zeolitic molecular sieves, particularly the synthetic ones, generally are produced in the form of soft, powdery masses of small crystals. For use in commercial processes these zeolite crystals may be composited with binder materials, e.g., clays, alumina or other materials, to form stronger, more attrition-resistant particles. Such molecular sieve composites are suitable for use in this invention.

For use in conventional chromatographic separation with a liquid-filled bed of sorbent, the molecular sieve composite is suitably used in the form of finely divided particles having a distribution in the range between 14 and 200 mesh, e.g., from 20 to 170 mesh.

In the preferred trickle phase mode of operating the process of this invention, the molecular sieve is preferably used as a composite in the form ofpellets or irregularly shaped particles having an average diameter in the range from $4 to A inch or more. It is preferable in this mode to have a contact mass of essentially uniform particle size. In any event, a mixture of widely different particle sizes should be avoided in order to prevent close packing of the sorbent particles in the column, unless the sorbent bed is classified.

In the process of this invention the oil is contacted with the sorbent in the form of a fixed foraminous bed. By a fixed bed is meant a bed in which the particles of the solid are stationary, as distinguished from a bed in which the solid is agitated, e.g., by paddles, force of fluid flow, or the like. It is to be understood, however, that the bed may be a so-called moving bed, i.e., a bed which is substantially fixed but is slowly replaced by the continuous or intermittent addition of increments of fresh sorbent to one end and the withdrawal of a like amount of sorbentfrom the other end.

In the preferred trickle phase mode of the process according to this invention, liquid oil is contacted with molecular sieve sorbent in the presence of an inert vapor or gas. Inert gases are those which react neither with the oil being treated nor with the sorbent at the conditions prevailing in the contact zone., Suitable inert gases or vapors are nitrogen, hydrogen, CO and the light hydrocarbon gases, e.g., methane, ethane, and propane.

It is .within the scope of this invention to process an oil which contains a fraction that vaporizes at the temperature and pressure maintained in the sorption zone. The vapors liberated may be light hydrocarbons or they may be hydrocarbons in the gasoline or kerosene boiling range.

In one particular modification of the process, a waxy oil, which also contains asphaltic constituents, is first deasphalted by means of liquid propane in a conventional propane deasphalting operation and the deasphalted oil, still containing a substantial proportion of propane, is charged to the ,sorption zone containing molecular sieve after having been heated to the desired temperature at a sufficiently low pressure to vaporize at least a substantial part of the propane contained in the oil.

In order for the contact to be carried out at a satisfactory rate, the temperature in the sorption Zone should be at least about 300 C. Although temperatures as high as 600 C. will not destroy the sorptive characteristics of the molecular sieve, temperatures of 450 C. and higher tend to cause the decomposition of the contacted oil. Temperatures in the range between 300 and 400 C. are generally preferred. Temperatures up to 500 C. are useful with some oils.

The pressure employed in the contacting step may be subatmospheric, atmospheric or superatmospheric. Pressures in the range from 0.1 to atmospheres absolute may be employed; lower pressures in this range are preferred. For practical reasons, pressures between 1 and 10 atmospheres absolute are most suitable.

The rate at which the oil is contacted with the sorbent is conveniently expressed as the liquid hourly space velocity (LHSV), calculated on the bulk volume of the sorbent mass. Suitable rates in the trickle phase operation are in the range from /2 to 4 volumes of oil per volume of contact mass per hour (v./v./hr.). The range from /2 to l v./v./hr. is preferred. A higher rate may be employed so long as the oil effluent still is free of normal paraflins to the desired degree. Lower rates may be employed if desired, but are not required as long as the normal paraflin removal is suificiently complete. In the chromatographic liquid phase method, lower rates are generally required, e.g., from 0.1 to 1 v./v./hr.

The ratio of inert gas to charge oil in trickle phase operation is suitably in the range of from 250 to 1000 cubic feet of gas per barrel of oil (c.f./b.), the gas volume being measured at standard temperature and pressure. The gas-to-oil ratio may be as low as 50 c.f./b., so long as it is sufiicient to maintain vapor in the voids between sorbent particles, thus keeping the liquid flowing in a thin film over the. sorbent particles. Higher ratios than 1000 may also be employed if desired.

When the feed oil contains a lighter component which is partly vaporized at the contact conditions, it is only necessary that the total ratio of gaseous fluid to liquid he sufiicient to maintain vapor in the voids between particles. As little as 10% of the total feed oil may remain in liquid phase.

Since molecular sieve sorbent is relatively expensive and its capacity for the sorption of normal paraflins-is limited, it eventually becomes necessary to regenerate the bed of sorbent. Several suitable methods for regenerating molecular sieves are known and others may be devised.

In one suitable method, an oxygencontaining gas, e.g., air, suitably at essentially atmospheric pressure, is passed through the sorbent bed to burn ed the sorbed wax. The temperature during this regeneration is preferably maintained between 400 and 550 C. The heat generated in this manner may be employed in the process, e.g., to heat the oil being charged to another contact bed then onstream in the dewaxing step.

When wax, removed from oil in the process of this invention, is .not of the type which is suitable for sale as a parafl'in wax of commerce, it has generally only fuel value and burning it from the sorbent bed does not represent an economic penalty, particularly since only a relatively small quantity is usually involved.

Instead of removing the sorbed wax by burning, it may be desorbed and recovered by passing through the sorbent bed a liquid normal hydrocarbon of lower molecular weight in the manner described in copending patent application Serial No. 648,506, filed March 26, 1957, now abandoned.

Figure 1 of the drawing is a schematic representation of the preferred mode of carrying out the process of this invention. The process is illustrated using two alternating fixed bed contacting vessels 11 and 12. One of these vessels is on-stream while the other is regenerated or is being refilled. Further equipment shown is a heater 14,

other necessary equipment will be readily apparent to the person skilled in the art. For the sake of illustration, contact vessel 11 is considered to be on-stream while vessel 12 is being regenerated.

A waxy oil feed enters through line 16, is preheated in heat exchanger 18 by contact with waste gas from the regeneration, further heated in heater 14, and then passes to vessel 11 through

lines

19 and 20 in which valve 21 is open. At the same time inert gas, heated in heater 14, passes into vessel 11 from line 28 through line 22 in which valve 24 is open. All of this inert gas may be gas which enters the system through line 25 containing heat exchanger 26. For reasons of economy it is preferred, however, to recover inert gas from product separator 15 and recirculate it through line 29 containing pump 30.

During the period that vesselllis in sorption service,

valve 34 in line 32 and valve 60 in line 65 are closed. The former line connects with the air supply for regeneration, and the latter provides for removal of regeneration waste gas.

Vessel 11 is a vertically disposed cylindrical vessel of suitable dimensions to handle the required volume of oil and gas and withstand the working conditions of temperature and pressure. It is provided with a suitable perforated plate 35 near the bottom to support the stationary bed of sorbent 37. In order to decrease the weight of sorbent on this support it may be desirable to provide one or more additional supports higher up in the vessel. The vessel is also provided with a suitable means at the top for distributing the incoming oil over the upper surface of the sorbent. In the illustrated vessel, a spray cone 36 is provided for the purpose. Other suitable means may be used.

The bed of sorbent which substantially fills the contact vessel has a ratio of length to diameter of at least 5:1 and. I

preferably above 10:1. That part of the liquid oil which flows down through the vessel near the wall is less effi-- ciently contacted. In order to correct this deficiency the vessel is preferably provided with a suitable means for directing the liquid flow near the wall inwardly toward the center of the bed. In the illustrated vessel, short A number of open-ended pipes 39 extend 'fromthe: troughs downwardly and inwardly towards the. center of the bed of sorbent.

and then flows through pipes 39 to a point near the center of the bed.

Inertgas is introduced simultaneously with the oil into the top of the contact vessel. The gas entering the vessel through line 22 passes downwardly through the bed of 55 sorbent in contact with the oil. The mixture of gas and liquid oil is removed from the bottom of the vessel by line 40 in which valve 41 is open. The mixture then passes through line 42 and line 43 containing cooler 44 and thence to separator 15 in which all liquid product is 0 withdrawn through line 45 and inert gas is withdrawn through line 29 and recycled by pump 30 or removed through line 46.

Although this is not illustrated, the cooling medium in cooler 44 may suitably be the oil being charged to the system through line 16.

While vessel 11 is in sorption service, vessel 12, which is suitably constructed like vessel 11, is being regenerated.

Valve 51 in line 50 and valve 54 in line 52 are closed since they connect respectively to

lines

19 and 28 which 7 beginning of the regeneration to lowerthe concentration 45 troughs 38 are attached to the wall at spacedint'er'vals.

of oxygen in the regenerating gas. If the inert gas in line 28 is non-combustible, this may be done by partly opening valve 54 in inert gas line 52 until the desired mixture is obtained. The oxygen serves to burn off any unremoved oil and sorbed waxy parafiins from the sorbent contact mass in vessel 12. The resulting gas mixture passes out of the vessel through lines 61 and 64. The waste gas from the regeneration cycle is suitably used as a heating medium in

exchangers

56, 18 and 26, and is then removed from the system for discard or for further use as desired. If the inert gas is to be used for further contact with molecular sieve, means are provided for first removing moisture from the gas.

The end of the useful sorption cycle is suitably determined by monitoring the pour point of the oil leaving the sorbent vessel. When a oil of known characteristics is treated, the amount of the oil that can be charged per cycle may also be predetermined by routine tests. After the desired amount of oil has been contacted, valve 21 is closed to shut ofl? further oil flow to vessel 11 and valve 24 is suitably maintained open for a somewhatgreater period of time to permit removal of any physically held oil from the sorbent. Valve 41 is then closed and valve 66 is opened. Valve 24 may be closed or partly closed as A so-called 100 distillate from a mixture of East Texas and Louisiana crudes was selected to determine whether five-Angstrom molecular sieves could be usefully employed for lowering the pour point of waxy oils.

'A 100 distillate is a fraction which yields a finished oil having aviscosity of 100 SSU at 100 F. The waxy distillate had an average molecular weight of 339, a viscosity of 9.15 centistokes (cs.) at 130 F. and of 3.51 cs. at 210 F. and a pour point of F; This oil had been solvent-extracted to remove constituents of low viscosity index,

In Run No. 1, 20 grams of this oil was placed in a I fl a In operation, the liquid oil descgndaml 7 ask nd admixed with grams of L1nde MS-5A 1n the ing near the wall of the vessel collects in the troughs 33 .51).

form of 20170 mesh particles containing 20% clay binder. The flask containing the mixture of sorbent and oil washeated to 300 C. and maintained at that temperature with occasionalshaking, for about 50 minutes and then allowed to cool. The material in the flask at that time had the appearance of dry molecular sieve par ticles. This material was then extracted with boiling liquid methylcyclopentane (MCP) which dissolved the oil adhering to the sieve particles without removing the n-paraflins contained in the sieve. The MCP solution was removed and flash distilled, leaving the dewaxed oil as residue. It was found that the pour point of the oil had beenlowered from 80 to 25 F. by this method. This result was reproducible.

EXAMPLE II To develop a more practical method than that described in Example I, a'chromatographic column of about 10 to 1 length-to-diameter ratio was prepared. This column could be externally heated and maintained at a desired temperature. Run No. 2 was carried out by filling this column with 20-170 mesh particles of Linde MS-SA containing 20% clay binder, maintaining the column at a temperature of 300? C. and adding the same feed oil as used in Example I dropwise to the column at arate of about 2 v./v./hr., based on bulk volume of sorbent. The oil passed through and out of the column.

Efiluent oil was collected and successive cuts tested to determine their pour points. The amount of dewaxed oil recovered is reported as percent by weight, based on the amount of sorbent.

Table I shows the pour point of the last increment recovered up to a given oil throughput. The first cut actually measured represented 2.5% of oil, based on sorbent, and had -a pour point of 25 F. In the next cut the pour point increased to 30 F., stayed there until about 25% of oil was recovered and then gradually increased further. These results are plotted as curve A of Figure 2.

Run No. 3 was carried out in essentially the same man ner as Run No. 2 and with the same feed, but using instead of the 20-170 mesh sorbent a 14-30 mesh distribution. In this case the first two cuts, representing 2.3 and 4.8% of oil based on sorbent, had a pour point of 20 F.;' in the later part of the run the pour point increased somewhat more rapidly than in Run No. 2.

Run No. 4 Was carried out in a manner similar to Runs Nos. 2 and 3 and with the same feed oil but at a lower feed rate and employing the sorbent in the form of -inch pellets of Linde MS-SA composite containing 20% clay binder. This run resulted in poor dewaxing. The results of this run are shown in Table I and plotted By comparing the results-of Runs Nos. 5 and 6 with Runs Nos. 2-4 in Table I, or by comparing curve C with curves A and B in Figure 2 it is seen that the trickle phase technique of Runs Nos. 5 and 6 leads to a much more complete and clean-cut dewaxing than the chromatographic or batch techniques. The oil recovered throughout the major portion of Runs Nos. 5 and 6 had a pour point to degrees lower than even the first cuts recovered in Runs Nos. 2-4 or the oil produced by the batch technique of Example I.

EXAMPLE IV In studying the effect of temperature in chromatographic operation, a run was carried out according to the manner of Run No. 2 of Example II, but maintaining the column jacket at the temperature of saturated atmospheric steam, i.e., about 212 F., instead of 300 C. There was only a very slight lowering of the pour point observed, the first small cut of oil having a pour point of 55 F.; at 11% oil recovery, based on. sorbent, the pour point had risen to 70 F.

EXAMPLE v To study the effect of temperature in trickle phase operation, Run No. 8 was made in the same manner as Runs Nos. 5 and 6 were carried out in accordance with the process of this invention in which a liquid film is maintained on the sorbent particles and vapor in the void spaces between particles. The feed oil was the same as employed in previous runs. These runs were carried out in identical manner except that the rate of gas flow in Run No. 5 was 600 c.f./b. and in Run No. 6, 1500 c.f./b.

A column of 18.721 length-to-diameter ratio was packed with A -inch pellets of Linde MS-SA molecular sieve composite containing 20% clay binder. The column was placed in a heater which maintained it at the desired temperature. The temperature in various parts of the bed and at various parts of the run varied between 375 and 425 C. The liquid feed and nitrogen were passed to the top of the column at the stated rates; oil was collected from the effluent and recovered increments of oil were tested for pour point. The results are shown in Table I.

The results of Runs Nos. 5 and 6 were sufiiciently close to be represented as a single curve, which is shown as curve C in Figure 2.

as curve B of Figure 2. Run No. 5 of Example III but maintaining a tempera- Table 1 Run No 2 3 4 5 6 7 Method Chromatographic Trickle Phase Sorbent Linde MS-5A Particle Size 20-170 1430 1/16 1/16 1/16" 1/16" mesh mesh pellets pellets pellets pellets Temperature, C 300 300 295-345 375-425 375425 350-375 Liquid Hourly Space Velocity. 1-2 1-2 0. 4 1 1 1 Gas Rate, c.f./b 600 1, 500 600 POUR POINT, F.

Feed 80 8O 80 80 80 80 Dggvaxed Oil, percent Wt. of

EXAMPLE III ture of 350375 C. instead of 375.425 C. The first increment of 5% Wt. of oil, based on sieve, had a pour point of -10 F.; the next increments up to about 15%, had pour points of 0 and the increment at 22% had a pour point of 15 F. The run was discontinued at this point for reasons not pertinent here.

In this case, dropping the temperature from the range of 375 -425 C. to 350-375 C. had the effect of permitting production of dewaxed oil of even lower pour point than oilproduced in Run No. 5.

EXAMPLE VI Run No. 9 was carried out in the manner of Runs Nos. 5 and 6 of Example III, but employing as oil feed a 100 waxy distillate from a Mid-Continent crude having a pour point of F., an average molecular weight of 347, and a viscosity at F. of 4.451 cs. The contact temperature was 350375 C. and the nitrogen flow rate 540 c.f./b. The first cut of about 5% by weight, based on sorbent, had a pour point of 0 F.; cuts up to 22% had a pour point of 5 R; up to 66% a pour point of 15 F.; and at 77% a pour point of 20 F.; from then on, the pour point rose steadily, reaching 55 F., at 101%.

9 EXAMPLE VII Run No. 10 was carried out in the manner of Runs Nos. and 6 of Example III, using as feed a 100 waxy distillate obtained from a crude from the Four Corners area. The run was carried out at a temperature of 325- 380 C. and with a feed space rate of 0.75 LHSV, a nitrogen flow rate of 600 c.f./b., but otherwise in the same manner as Runs Nos. 5 and 6. In this run, the cumulative oil recovered up to 63% by weight, based on sorbent, had a pour point of 5 F. compared with the feed pour point of' 80 F.

EXAMPLE VIII Runs Nos. 11-13 were carried out in the manner of Runs Nos. 5 and 6 of Example III, but employing as feed oil a heavier oil than had been employed in the previous runs, namely a so-called medium distillate or 250 waxy distillate. The distillate in this'case was from a California crude, and had a pour point of 70 F. Run No. 11 was carried out at a temperature of 350375 C., Run No. 12 at 335355 C., and Run No. 13 at 300380 C. In Run No. 11, over 390% of oil, based on sorbent, was recovered, having a cumulative pour point of 20 F. In Run No. 12, over 250% of oil, based on sorbent, was recovered, having a cumulative pour point of 20-30 F.; and in Run No. 13, over 200% of oil was recovered having a cumulative pour point between 20 and 30 F. v

EXAMPLE IX 7 Run No. 14 was carried out in the manner of Runs Nos. 5 and 6 of Example III, but employing as feed a 250 waxy distillate from a Mid-Continent crude. The feed oil had a molecular weight of 391 and a viscosity at 100 F. of 7.35 cs., and had a pour point of 75 F. Over 200% by weight of oil, based on sorbent, was recovered before the pour point began to rise appreciably; the average pour point of this recovered oil was 25-35 F.

EXAMPLE X Run No. 15 was carried out'in the manner of Run No. of Example VII, employing as feed oil a 250 waxy distillate from a Canadian crude. The distillate had an average molecular weight of 424, a viscosity at 100 F. of 6.52 cs., and a pour point of 110 F. The run was carried out at a temperature of from 320-380 C.; 9% of dewaxed oil, based on sorbent, was recovered, having a pour point of about 35 F. 4

It is well known in the dewaxing art that the pour point of oils containing only a relatively small proportion of wax can in some cases be substantially suppressed by adding a small amount of a pour depressant. A number of dilferent chemicals have been found to be suitable pour depressants and several are sold on a commercial basis.

The residual wax in oils in which the prior workers used pour depressants has been largely normal paraffin wax. It was, therefore, not to be expected that pour depressants would be very effective in oils dewaxed by molecular sieves. It has now been found that pour depressants are even more effective in the case of oils from which the waxy normal paraflins have been substantially completely removed by dewaxing in accordance with this invention than in conventionally dewaxed oils.

EXAMPLE XI The efiectiveness of adding 0.5% by weight of a commercial pour depressant of the polyalkylmethacrylate type, known as Acryloid 1-50, to various oils treated in accordance with this invention is illustrated by the following data:

A composite of 11 cuts of oil recovered from Run No. 2 of Example II had a pour point of +30 F. Addition of pour depressant reduced this to F.

In Run No. 5 of Example 1H, addition of pour de- '10 pressant to the first cut of product, which had a pour point of +5 F., reduced it to 35 F. The pour point of the second cut, which was +15 F., was also reduced to 35 F. by addition of pour depressant. The pour point of a composite sample was reduced from to Adding pour depressant to a composite sample of product oil from Run No. 10 of Example VII reduced the pour point from +5 to 45" F.

Adding pour depressant to a composite sample of product oil from Run No. 11 of Example VIII reduced the pour point from 20 to 30 F.

Similarly good results are obtained by employing other pour depressants of the polyallylmethacrylate type, or alkylated polycyclic aromatics of the Paraflow type.

EXAMPLE XII A sample of neutral oil, produced in commercial operation by solvent extracting and solvent dewaxing a 100 distillate from a Mid-Continent crude had a pour point of +10 F.'which was lowered to 30 F. by adding 0.5 wt. of Acryloid 150. To obtain the same low pour point of 30 F. by addition of the same amount of pour depressant to an oil dewaxed by contact with molecular sieve, it was only necessary to dewax to a pour point of +15 F.

EXAMPLE XIII In the dewaxing of bright stocks by means of molecular sieve, it was found that the treated oil, at low temperatureshad a smooth homogeneous appearance compared with a grainy appearance of the untreated oil. The pour point of bright stock is'not, generally, significant because of the viscous nature of these oils. "The following data illustrate, however,'that the blending of molecular sieve-dewaxed bright stock in neutral oils'produces oils of significantly lowered pour point and further show that these oils are more responsive to pour depressant than oils blended using commercially dewaxed bright stock.

With a commercially produced 250 neutral oil from a Mid-Continent crude were blended in one case 6% 'wt. of a commercially produced bright stock which had been deasphalted, solvent-extracted and dewaxed by conventional methods, and in another case 6% wt. of a similar bright stock which had been deasphalted and solventextracted by conventional methods and dewaxed according to this invention. The following data were obtained.

Pour Point, F.

Conventional Dewaxed Bright Stock Bright Stock Dewaxed by Molecular Sieve Blend of:

250StNeIutra1+Oonventional Dewaxed Bright 250 Neutral-l-Waxy Bright Stock +40 +20 250 Neutral+Bright Stock Dewaxe by lecular Sieve +25 20 The oils which can be treated in accordance with the invention are oils containing waxy normal paraflins. Waxy normal paraflins are those of 20 or more carbon atoms per molecule. The process is particularly suitable for treatment of distillate oils but may also be used in treating residual oils. The oil feed to this process may first be deasphalted by known methods; if necessary; it is also possible to deasphalt oil after treatment with molecular sieve.

It is preferred to treat oils in which the ratio of normal to non-normal waxy compounds is relatively high, i.e., those oils in which normals constitute 50 to 100% of the waxy materials. It is also preferred to treat oils 11 containing a relatively low concentration of total waxy material, e.g., uptogabout 25% by weight of the oil, preferably not over by weight, and most preferably not over 2% by weight.

A particularly suitable method of utilizing the process of this invention is in combination with solvent dewaxing. The conventional solvent dewaxing processes require substantial refrigeration in order to produce lubricating oils of satisfactory pour point and cloud point. By utilizing the process of this invention it is possible to partially dewax a lubricating oil with a solvent such as a mixture of an aromatic and methylethyl ketone at ambient temperatures to substantially reduce the wax content and thereafter reduce the pour point and cloud point of the oil to the required low value by removing normal parafiins from the oil by contact with molecular sieve sorbent as described.

I claim as my invention:

1. A process for separating waxy normal parafiins from a lubricating oil which comprises passing a stream of said oil as a liquid film under trickle phase contacting conditions downwardly through a foraminous bed of stationary granules of a molecular sieve sorbent having an essentially uniform pore diameter of about five Angstrom units maintained at a temperature in the range from about 300 to 500 C., simultaneously passing downwardly through said bed an inert fluid in vapor phase at a rate of at least 50 c.f./b., whereby the pore volume between granules is filled with vapors permitting only a film of the oil to contact the granules and withdrawing an oil of lowered normal parafiin content from said bed.

2. A process according to claim 1 wherein said waxy oil is a distillate lubricating oil fraction.

3. A process according to claim 1 wherein said waxy oil is a solvent extracted distillate lubricating oil fraction and said oil of lowered normal parafiin content is a neutral oil.

4. A process according to claim 1 wherein said waxy oil is a partially solvent-dewaxed lubricating oil fraction.

5. A process according to claim 1 wherein said waxy 12 oil is a deasphalted bright stock and said temperature is in the range from 350 to 450 C.

6. A process according to claim 1 wherein said waxy oil is passed throughsaid sorbent bed at a liquid hourly space velocity of from /2 to 2 v./v./hr. and said inert fluid at a rate of from 250 to 1000 c.f./b.

7. A process according to claim 1 in which said foraminous bed is composed of particles of a composite of calcium exchanged type A zeolite, having an essentially uniform particle size in the range from to A inch diameter.

8. A process for producing a lubricating oil of low pour point from an oil containing predominantly normal parafiins as wax constituents which comprises passing a stream of said oil in liquid phase under trickle phase contacting conditions downwardly through a foraminous bed of stationary granules of a molecular sieve sorbent having an essentially uniform pore diameter of about five Angstrom units maintained at a temperature in the range from 350 to 450 C., simultaneously passing downwardly through said bed an inert fluid in vapor phase at a rate of at least c.f./ b. whereby the pore volume between granules is filled with vapors permitting only a film of the oil to contact the granules, and withdrawing an oil of substantially lowered pour point from said bed.

References Cited in the file of this patent UNITED STATES PATENTS 2,091,627 Bruson Aug. 31, 1937 2,436,565 Gillett Feb. 24, 1950 2,522,426 Black Sept. 12, 1950 2,574,434 Greentree et al. Nov. 6, 1951 2,809,152 Weeks Oct. 8, 1957 2,818,137 Richmond et al. Dec. 31, 1957 2,818,455 Ballard et al. Dec. 31, 1957 2,834,429 Kinsella et al. May 13, 1958 2,859,257 Hess et al. Nov. 4, 1958 2,886,522 Cooper et al. May 12, 1959 2,889,893 Hess et al. June 9, 1959

Claims

1. A PROCESS FOR SEPARATING WAXY NORMAL PARAFFINS FROM A LUBRICATING OIL WHICH COMPRISES PASSING A STREAM OF SAID OIL AS A LIQUID FILM UNDER TRICKLE PHASE CONTACTING CONDITIONS DOWNWARDLY THROUGH A FORAMINOUS BED OF STATIONARY GRANULES OF A MOLECULAR SIEVE SORBENT HAVING AN ESSENTIALLY UNIFORM PORE DIAMETER OF ABOUT FIVE ANGSTROM UNITS MAINTAINED AT A TEMPERATURE IN THE RANGE FROM ABOUT 300* TO 500* C., SIMULTANEOUSLY PASSING DOWNWARDLY THROUGH SAID BED AN INERT FLUID IN VAPOR PHASE AT A RATE OF AT LEAST 50 CF./B., WHEREBY THE PORE VOLUME BETWEEN GRANULES IS FILLED WITH VAPORS PERMITTING ONLY A FILM OF THE OIL TO CONTACT THE GRANULES AND WITHDRAWING AN OIL OF LOWERED NORMAL PARAFFIN CONTENT FROM SAID BED.