US3507786A

US3507786A - Manufacture of low pour oils by thermal diffusion

Info

Publication number: US3507786A
Application number: US672928A
Authority: US
Inventors: Jack Walker; Lorne William Sproule
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1967-10-04
Filing date: 1967-10-04
Publication date: 1970-04-21
Anticipated expiration: 1987-04-21

Description

United States Patent US. Cl. 208308 14 Claims ABSTRACT OF THE DISCLOSURE The pour point of a hydrocarbon oil is lowered by separating it into fractions by thermal diffusion. Selected fractions are blended to get a lower pour point than the average of the blended fractions.

This application is a continuation of Ser. No. 223,- 811 filed Sept. 14, 1962 and now abandoned.

This invention relates to the preparation of low pour mineral oil fractions. More particularly, this invention relates to a process for obtaining a low pour point oil fraction by subjecting an oil fraction to thermal diffusion to separate it into portions which differ in viscosity and pour point characteristics, and blending the various portions thus obtained. Specifically, this invention relates to improving the low temperature pour point characteristics of an oil fraction by separating the fraction into heart cuts and end cuts by thermal diffusion and blending the heart cuts and end cuts to obtain an overall reduction in the pour point of the feed material.

At present, low pour point oils, for example, to be used as low temperature lubricating oils are prepared by relatively expensive and complicated processes. Low pour point lubricating oils are prepared by a solvent dewaxing process which is carried out at extremely low temperatures. This process requires mixing a waxy oil feed with a dewaxing solvent selective to non-waxy constituents and chilling the mixture to precipitate the wax present. The wax is separated from the chilled oil 'solvent solution by rotary or other type filters. The most widely used commercial processes employ propane or methylethyl ketone as the dewaxing solvents. To obtain extremely low pour point oils, for example, in the range of 70 F., very deep dewaxing at extremely cold temperatures would be required. It is not practical to carry out such deep dewaxing by the presently known commercial processes. There are now requirements for substantial amounts of low pour point specialty oils in the range of 50 to 80 F., pour point for use as low pour point transformer and lubricating oils, in aircraft hydraulic systems, automotive hydraulic systems, and refrigeration systems, etc., which requirements can be met by the present invention.

It is known that hydrocarbon oil fractions which contain molecules differing in their molecular shapes can be separated according to their molecular shapes by subjecting the oils to thermal diffusion. For example, lubrieating oil fractions subjected to thermal diffusion have been qualitatively separated into high viscosity and low viscosity oil fractions. Applicants have now found that by subjectecting mineral oil to thermal diffusion, it may be separated into several fractions and that by blending these fractions in accordance with applicants invention, low pour point oils can be obtained The thermal diffusion separation may be carried out by either a static (i.e. a batch) or continuous process.

The phenomenon known as thermal diffusion occurs when a temperature gradient is established across a fluid 3,507,786 Patented Apr. 21, 1970 mixture and causes differences in concentration to develop between the hot and cold parts of the mixture. An apparatus for this purpose comprises two concentric vertical tubes that form smooth, impervious walls of an annular chamber or thermal diffusion slit. One of the walls is heated and the other is cooled. The distance between the hot and the cold walls is very small and the temperature difference per unit of distance across the thermal diffusion slit is very high. The liquid mixture to be separated is introduced into the annular chamber or slit.

Certain components tend to diffuse toward and concentrate along the hot wall while other components tend to diffuse toward and concentrate along the cold wall. The differences in temperature and liquid density of these concentrations result in convection currents and cause the liquid along the hot wall to rise and the liquid along the cold wall to flow downwardly. From the top of the thermal diffusion slit a fraction of the original mixture enriched in components that diffuse toward the hot wall is recovered from the bottom a fraction enriched in components that diffuse toward the cold wall is recovered.

By constructing a thermal diffusion column with outlet ports evenly spaced along the vertical height of the column for static separations, fractions which vary in viscosity from very low at the top port to very high at the bottom port, can be obtained. These same fractions will vary from a high wax pour point at the top to an intermediate wax pour point in the middle and to a high viscosity pour point at the bottom. When the oil ceases to pour as a result of cooling, the loss of fluidity can be attributed either to a gelling of the wax matrix in which case the pour point is called a wax-pour-point or, alternatively, to an increasing viscosity, in the absence of wax, when it is known as a viscosity pour point. The number of ports will be determined by the height of the column and the degree of separation of a particular feed that is desired. The wax and low viscosity oils accumulate near the top. Oil of intermediate viscosity stays near the center and high viscosity molecules migrate to the bottom of the column.

Because the wax which causes high wax pour point moves toward the top and the molecules of low viscosity index which cause high viscosity pour point move toward the "bottom, the oil near the center of the column has a considerably reduced pour point. It was unexpectedly found that blending of selected fractions separated by thermal diffusion results in an overall reduced pour point for the particular blended fractions.

Apparently, the top high wax pour point fractions and the bottom high viscosity pour point fractions each have constituents which mutually act to reduce the pour point of the other fractions.

In accordance with the present invention, very low pour point oils may be obtained for specialty purposes Without the expense, inconvenience, and difficulties encountered in the conventional dewaxing processes. These low pour point oils are obtained without the requirement of extremely low dewaxing temperatures and with a minimum amount of investment and process costs. Mineral oil fractions, which may be treated in accordance with the present invention can be either naphthenic or paraffinic oils or mixtures thereof. A continuous separation, as well as a batch separation technique may be utilized. Conventional continuous separation thermal diffusion columns normally separate a feed fraction into a top high wax pour point, low viscosity, high viscosity index fraction and a bottom high viscosity pour point, high viscosity, low viscosity index fraction. These two fractions compare somewhat to applicants end cut fractions, i.e. high wax pour point, high viscosity index top fraction, and high viscosity pour point, low viscosity index bottom fraction.

Where the fraction is only separated by thermal diffusion into two fractions, i.e. a top and bottom fraction, there is no low pour point heart cut fraction produced. The conventional continuous thermal diffusion process can, however, be adopted to obtain a low pour point heart cut fraction by subjecting either or both the end cut fractions from the first separation to a second separation in another continuous thermal diffusion column. For example, if the top high wax pour point, high viscosity index fraction is fed to a second thermal diffusion column, it is itself separated into a top and bottom fraction. The top fraction corresponds to applicants top end cut fraction and is still a high wax pour point, high viscosity index fraction, but the bottom fraction is a low wax pour point fraction corresponding to applicants heart cut fraction.

Similarly, the bottom fraction from the first separation can be subjected to a thermal diffusion step and separated into a top and bottom fraction. The top fraction corresponds to applicants low pour point heart cut fraction and the bottom fraction to applicants high viscosity, low viscosity index bottom end cut fraction. By following the above procedure and blending the two heart cut fractions, a separation is obtained whereby the top fraction consists of 25% by volume of the feed, the heart out fraction 50%, and the bottom fraction 25%.

If it is desired to obtain a greater degree of fractionation, any of, or each of the four fractions obtained by the two second thermal diffusion steps, could be subjected to another continuous thermal diffusion step to obtain up to eight separate fractions. Fractions obtained in the above manner can be blended in the same way the fractions obtained in the static (i.e. batch) separations to get blends of improved low pour oils. Obviously, at any stage of separation, a static or batch separation could be substituted for one of the continuous type separations.

In an embodiment of this invention, lubricating oil fractions which have been previously treated to selectively remove aromatic constituents, for example, by phenol extraction, and which have been treated to remove some of the wax components by solvent dewaxing, may be used. The feeds may be deasphalted fractions as well as hydrofined fractions. The feed stocks used will, to a certain extent, determine the final pour points and viscosity of the blended oil fractions which result. Suitable feeds are LCT 5 Base, MCT Base, Solvent 75N, Solvent 100N, which feeds have the following characteristics:

1 Obtained from a naphthenic lube distillate (125/140 LCT Distillate, from T1 102 Crude) by phenol treating and hydrofining.

2 Obtained from a paraffinic (Western Canadian) lube distillate, 155/165 P.D., by phenol treating, dewaxing, and hydrofining.

Various diluents may be added to the feeds subjected to thermal diffusion which aid in increasing the flowability of the feed and/0r increase the separation rate of the dissimilar chemical constituents of the feed undergoing thermal diffusion.

The temperatures for the hot wall and the cold wall are selected to provide a large temperature gradient across the thermal diffusion slit because the rate of separation increases as the difference in temperature per unit of distance across the slit increases. However, temperatures must be chosen that will provide a reasonably large gradient across the slit without either wall temperature being so cold as to make the liquid too viscous, or solid, or so hot as to cause the liquid to decompose or vaporize. In thermal diffusion hot and cold are relative terms. Both the hot and cold walls may be above or below ambient temperature. In fractionating lubricating oils in the boiling range of 550 to 1100 F., a hot wall temperature in the range of to 500 F. and a cold wall temperature in the range of 50 to 150 F. give a suitable balance of the different factors.

The slit width is an important variable in thermal dif fusion. The slit must be narrow so that a high temperature gradient per unit of distance will be obtained but if it is too narrow, the capacity of the unit and hence the maximum feed rate for satisfactory fractionation will be too low. A slit width from about 0.010" to 0.075" can be used.

The feed rate or space velocity of the oil subjected to thermal diffusion depends upon the degree of fractionation that is desired. By feed rate or space velocity, We mean the volume of feed charged per volume of slit capacity per hour. In separating lubricating oils of 55 0-1100 boiling range, we use space velocities of about 0.01 liquid volumes per volume of slit capacity per hour, depending upon the separation desired. Lower space velocity can be used if very careful fractionation is desired and faster rates when the degree of fractionation is not so critical. As is usual in liquid thermal diffusion operations, the feed rate must be low enough to provide non-turbulent flow of liquid in the thermal diffusion slit as turbulent flow will interfere with the diffusion of components toward the hot and cold walls of the apparatus and with the convection currents which cause fractions to migrate toward one end or the other of the apparatus.

Although a vertical concentric type of apparatus was used in the examples, the invention can be carried out in any suitable thermal diffusion apparatus.

Although the examples of this specification describe batch or static thermal diffusion separation, it is within the scope of our invention to employ continuous type thermal diffusion separations.

In the present invention, in order to obtain suitable thermal diffusion cuts, differing in viscosity, wax pour point, and viscosity pour point, a conventional thermal diffusion column is constructed in such a manner that it has several evenly spaced takeoff ports along the vertical height of the column. The number of ports can vary, for example, between about 3 and 30 depending on the height of the column, the number of fractions, and the degree of separation that is desired.

In a specific embodiment of the invention, a thermal diffusion column 6 ft. in height, 0.06 ft. in diameter, and having an annular slit of 0.012 inch, is used. The column has a center feed and 10 takeolf ports evenly spaced from the top to the bottom of the column. The feed to be subjected to thermal diffusion is introduced to the center of the column and equal volumes of separated oil are withdrawn after a suitable period of time from each of the 10 ports. The hot Wall temperature is 260 F. and the cold wall temperature is F.

For ease in discussing the fractions obtained and the various blends, the fractions will be numbered from 1 to 10 starting at the top of the column. Each of the 10 fractions comprised about 10 percent by volume of the feed. Each fraction will have about the same molecular weight and boiling range as the feed. The fractions will, however, differ in viscosity with the highest viscosity index fraction being 1 and decreasing in viscosity to the lowest viscosity index fraction 10. The lowest pour point fractions will generally be 4, 5, or 6.

It was found that fractions 3 to 8, for example, may be blended to obtain fractions comprising 60 percent by volume of the feed and having a pour point approximately the same as that of the lowest pour point fraction 5. It was also found that the end cut high pour point fractions, for example, fractions 1 to 3 and fractions ,8 to 10 may be blended to obtain a blended fraction comprising about 40 percent by volume of the feed and having about the same pour point as the feed and a lower pour point than either of the end cut fractions. The fractions to be blended can be seleced so that a 60 percent by volume heart cut 5 fraction can be obtained having a pour point of 60 F. below the pour point of the feed, and the remaining end cuts blended to have a pour point the same as the feed.,

Apparently the fractions that are blended have constituents which function as pour depressants for each other.

From the above description, it is readily seen that the invention is not related to any particular thermal diffusion apparatus utilized or in any specific operating conditions.

The following data and examples are given in order to specifically illustrate the operation and utility of this invention:

EXAMPLE 1 An LCT 5 Base (phenol treated, hydrofined 5 grade Tia Juana distillate) was subjected to thermal diffusion in a tower 6 ft. tall, having an annular slit of 0.012 inch, a hot wall temperature of 260 F. and a cold wall temperature of 160 F. The feed was separated into 10 fractions at ports evenly spaced from the top to the bottom of the thermal diffusion tower, each fraction comprising about 10 volume percent of the feed. The feed had a viscosity of 133.4 SUS/100 F. and a pour point of 45 F. The viscosity and pour point of the 10 fractions are given in Table I-A.

Heart cut fractions containing between 20 and 60 percent by volume of the feed were made by blending frac-' tions 3 to 8. End cut blends comprising 20 to 40 percent,

by volume of the feed and consisting of fractions 1, 2, 9 and 10 were made by blending these fractions. The viscosities and pour points of the blended heart cuts and end cuts are given in Table I-B:

TABLE I-A.PROPERTIES OF THERMAL DIFFUSION FRACTIONS LOT 5 BASE [Phenol Treated, Hydrofined 5 Grade Tia Juana. Distillate] Feed SUS/IOO F. Pour point, F.

Fraction Number:

TABLE I-B.-PROPERTIES OF BLENDS OF THERMAL DIFFUSION FRACTIONS LOT BASE Yield, Pour Blends of vol. point, fractions percent SUB/100 F. F.

Feed (1-10) 100 133. 4 -45 4, 5 20 94. 3; -52 Heart-Cut Blends #13 7 2g 7 3, 4, 5, 6, 7, 8 60 123. 7 70 l, 2 20 61. 4 +20 Ends Blends 9, 10 20 2,051 +35 1, 2, 9, 10 40 152 25 From the data it can readily be seen that the high wax pour point fractions collect at the top of the column and the high viscosity pour point fractions collect at the bottom of the column. It is also readily apparent that the viscosities increase from the top to the bottom of the column and that the low pour point fractions collect in the middle of the columns. The lowest pour point fraction was taken at port 5 and has a pour point of 75 F. The fraction taken at port 4 has a pour point of 70 F. and the fraction taken at port 6 has a pour point of 50 F. Applicants unexpectedly found that in blending fractions 4, 5, and 6 that there is apparently a mutual pour point depressant effect of fractions 4 and 6 and the resulting blend has a pour point of F., the same as the lowest pour fraction taken at port 5. Even more surprising, a blend of fractions taken at ports 3 to 8, comprising 60 percent by volume of the feed, has a pour point of --70 F., only five degrees higher than the lowest pour point fraction taken at port 5. The results obtained by blending the end cut fractions is even more surprising; whereas end cuts 1 and 2 have a pour point of +20 F. and end cuts 9 and 10 have a pour point of +35 F., a blend of these fourend cuts has a pour point of -25 F.

EXAMPLE 2 TABLE IIA.PROPERTIES OF THERMAL DIFFUSION FRACTIONS MCT 10 BASE Phenol Treated, Dewaxed, Hgdrofined 10 Grade Western Canadian istillatel Feed Pour Point, sue/ F. "F.

Fraction N0.:

TABLE II-B.-PROPERTIES OF BLENDS 0F THERMAL DIFFUSION FRACTIONS MCT 1o BASE Blends of Yield, vol. SUS/lOO Pour fractions percent F. point, F.

Feed (1-10) 100 156. 0 0

Heart-Cut blends .{5, 6, 7 30 167. 8 -65 4, 5,6, 7, s 50 172. 3 65 End blends 1, 2, 3, 9, 1o 50 146.2 +20 The same mutual pour depressant effect appears in blending the heart cuts as well as the end cuts that was exhibited in Example 1. A 50 percent volume heart out exhibited a reduction in pour point of 65 F. A 50 percent blend of the end cuts exhibits only an increase of +20 F. Therefore, with this particular feed and these particular blends, an overall reduction in pour point of the feed was obtained by thermal diffusion.

EXAMPLE 3 A solvent 75 neutral oil was used as the feed. The physical properties of this oil have been previously described. In order to show the effect of the presence of Wax in the feed on the pour points of blends of heart cuts and end cuts, the feed was ketone-dewaxed in a conventional manner to 0 F. pour point oil and -20 F. pour point oil. The solvent 75 neutral having a pour point of 20 F., the oil dewaxed to 0 F., and the oil dewaxed to -20 F, were each subjected to thermal diffusion and each of the feeds separated into tenequal parts. The pour points and viscosities of each of the three feeds and each of the ten fractions separated from each of the three feeds are reported in Table III-A. Heart cuts of different widths were made by reblending contiguous fractions from the central area of the column. Blends including fractions 3 to 8, 4 to 8, and to 9, etc., represent heart cuts. Corresponding end cut blends and specific heart cut blends were made and the properties of the blends reported in Table III-B:

a pour point of -70 F., yet the corresponding end cut blend has a pour point of +20 F. the same as that of the feed from which the heart out was taken. A 40% heart out fraction 5 to 8 shows a pour point of 60 F. and the corresponding end cut fractions, 60%, shows a pour point of F. These blends both have resultant pour points below that of the feed.

TABLE IIIA.VISCOSITIES AND POUR POINTS OF THERMAL DIFFUSION FRACTIONS FROM THE SOLVENT 75 NEUTRAL Solvent 75 Neutral Feed 1 2 3 4 5 6 7 8 9 10 Vise. SUS 100 F 73 2 53. 3 56. 7 59. 3 62 4 67. 7 76. 5 89. 7 123. 2 216. 0 7,128 pour "igour prrt, 17 55 40 15 -12 -22 ;-73 -63 43 150. S 10 77. 2 53. 7 56. 9 6 2 62. 69. 8. 93. Dewaxed m Pom ""'{l our point, rg-.. 0 20 0 0 -20 -45 -75 s0 6 32 isc.S S100 F. 78.1 53.9 57.0 6.l 63.8 69.7 77.8 9.5 ,7 Dewaxed '{Pour point, F 0 0 15 -35 -55 80 --75 --35 15 TABLE IIIB.-VOLUME VISCOSITIES AND POUR POINTS OF THERMAL DIFFUSION FRACTIONS FROM THE SOLVENT 75 NEUTRAL Corresponding Heart-Cut Blends End-Cut Blends Yield, 1 Pour Yield, P ou1 Blends From Fractions of volume, Visc. SUS point, volume, Visc. SUS point, Solvent 75 Neutral percent at 100 F. F percent at 210 F.

20 F. Pour Point:

73. 2 +20 80. 0 20 73. 8 78. 2 30 50 79. 4 +25 96. 0 70 50 67. 5 +20 4 83. 6 -60 60 75. 6 +15 Dewaxed to 0 F. Pour Point:

100(Feed) 77.2 0 1 50(4- 79. 4 81. 6 +10 2 (4-9) 90. 0 -60 40 70. 7 +15 40(5-8) 96. 3 75 60 77. 1 +5 Dewaxed to Pour Point:

100(Feed) 78.1 20 1 60(4-9) 88. 0 40 76. 7 l00 1 Actual fractions used in blends are numbered in parentheses.

From the above data, it is readily apparent that reduc- 40 EXAMPLE 4 ing the pour point of the feed by solvent dewaxing has the largest effect on pour points of fractions near the top of the column. This occurs since wax in the oil causes high wax pour point and the wax concentrates at the top of the column. For example, feed pour points of +20, 0, and 20, respectively, produced top fractions with +55, +25, 0 pour points and center fractions with 70, 75, and F. pour points.

In Table III-B, data from the blends of the fractions show some interesting blending effects. For example, the 20 F. pour point feed shows a 5 to 9, 50% heart cut with TABLE IVA.-VISCOSITIES AND POUR POINTS OF THERMAL SOLVENT NEUTRAL OIL Solvent 100 neutral feed was treated in a similar manner to that of the feed in Example 3. The solvent 100 neutral had a pour point of +l5 F. and was divided into three fractions. The second fraction was solvent dewaxed to 0 F. pour point and the third fraction solvent dewaxed to -20 F. pour point. Each of the three fractions were then submitted to thermal diffusion fractionation which split the feeds into ten equal volume fractions of widely different properties as shown in Table IV-A. Various heart out fractions and the corresponding end cut fractions were blended and the properties of the blends shown in Table IV-B:

SDIFFUSION FRACTIONS FROM THE Solvent 100 Neutral Feed 1 2 a 4 5 6 7 s 0 10 isc.SUS100 108.1 62.1 67.3 74.1 79.3 92.6 108.5 143.5 237.7 500.0 4,132 15F-Pm1rpmnt PourlsxtJliitigogfihfi 15 50 35 10 5 -35 60 60 35 15 +40 ISO. 11.7 62.4 67.8 74.6 70.7 04.0 112.0 152.0 255.7 645.9 5116 Dewaxedto 1;our n 1t, F 0 20 20 0 15 -35 65 65 35 5 '+45 iSC. 100 118.9 64.2 69.8 76.4 82.8 98.6 117.6 161.4 284.3 751.7 5.953 Dewmdt" ""{1ourpoint,F, -20 0 0 -20 -35 -55 -55 -40 0 +50 TABLE IV-B.BLENDS FROM SOLVENT 100 NEUTRAL FRACTIONS Corresponding End-Cut Heart-Cut Blends Blends Yield, Pour Yield, Blends From Fractions of volume Vise. SUS point volume, Vise. SUS Pour Solvent 100 Neutral percent at 100 F. F. percent at 100 F. F.

15 F. Pour point ggtg; 100(Feed) 113. 7 Dcwaxed to 0 F. Pour point 50(4-8) 117. 6 30(5-7) 115. 8 100(Feed) 118. 9 Dewaxed to -20 F. Pour point 50(4-8) 125. 4 30(5-7) 119. 5

1 Actual fractions used in blends are numbered in parentheses.

The same overall improvement in reducing the pour point is evidenced in blending the heart out and end cut fractions from this separation. An interesting blending phenomenon is shown in Table IV-B. In the case of the 20 F. pour point feed, a blend of cuts 4 to 8, 50% heart cut, shows that both the heart cut blend, 78.2 SUS, and the end cut blend, 79.4 SUS, have a higher viscosity than the feed, 73.2 SUS. A blend of the F. pour point S 75N of Table III-B of a 50% heart cut, fractions 4 to 8, has a viscosity of 79.4 SUS and a corresponding end cut blend has a viscosity of 81.6 SUS as compared to the viscosity of the feed of 73.2 SUS. Both these blends show a higher viscosity than the feed material.

EXAMPLE 5 Feed to solvent Feed to thermal dewaxing difiusion Pour point/solid point, F- 0/5 -25/- 30 Yield, wt. percent 91 Viscosity at 100 F., SUS 71. 82 74. 72 Viscosity index 109. 1 103. 0

In the measurement of pour point, the oil samples are cooled at a prescribed rate and the temperature at which oil ceases to flow, as the containing vessel is tipped, is the pour point. Further cooling then results in solidification at a temperature called the solid point. Both temperatures are usually reported simultaneously as pour/ solid, F.

The feed thus produced was subjected to a two-stage static (i.e. batch) thermal diffusion whereby it was separated in the first stage into ten equal portions identified as I-l through I-10. The portions I-1 through I-5 were mixed together and further separated by thermal diffusion in a similar manner in a second stage into equal portions identified as II-l through 11-10.

The pour points of fractions I-1 through I- and 11-1 through 11-10 are given below in Table V-A:

TABLE VA.-TWO-STAGE THERMAL DIFFUSION Stage I Stage II 1 Pour point, Pour point,

Feed traction: Feed fraction:

l The stage two fractions are obtained by mixing the five fractions I-l to I-5 from stage I and subjecting the mixture to thermal diffusion to obtain the ten fractions 11-1 to 11-10 of stage II.

10 Properties of the various blends obtained are shown in Table V-B. From Table V-B, it is seen that two of the blends result in a 94 V.I., F. pour point or better oil with 47.5 and 50% by volume yields.

TABLE V-B.PROPERTIES OF HEART-CUT BLENDS FROM STAGES I AND II Viscosity percent F. S US Pour Fractions in blends V.I. point I, e, 7, s, 1/21-9 1/2.II7, e.g. means that only 50% of the aliquot portion of traction II-7 was included in the blend.

Applicants invention has wide application in the lubricating oil field as well as in any area in which low pour point oils can be used. In accordance with this invention, oils may be subjected to thermal diffusion and separated into equal volume fractions, which fractions may be blended into heart and end cut fractions wherein the heart out fractions have a substantially reduced pour point and the end cut fractions have the same or slightly higher pour point than the feed, but lower than either of the end cut fractions. Blends may also be made which exhibit higher or lower viscosities for the heart cut and/or end cut fraction blends than the viscosity of the feed. Each of the separated fractions and the resulting blends have about the same molecular weight as the feed and about the same volatility as the feed. This invention thus offers a method of making very low pour point oils by either static (i.e. batch) or continuous processes without recourse to deep dewaxing.

What is claimed is:

1. A process for preparing low temperature hydrocarbon oils comprising the steps of (l) separating a phenol treated, S-Grade distillate into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high viscosity index end cut, in a yield of about 30 volume percent, based on the feed, (3) recovering the lower viscosity index fraction as a low-viscosity index end cut, in a yield of about 40 volume percent based on the feed, (4) blending the remaining heart out fractions, in a yield of about 30 volume percent based on the feed, to obtain a hydrocarbon oil product having a pour point of about 10 F. below the average pour point of the heart cut fractions so blended.

2. The method of claim 1 wherein the said high viscosity index end cut is recovered in the yield of about 20 volume percent, based on the feed, the said low viscosity index end cut is recovered in a yield of about 20 volume percent based on feed and said remaining heart out fractions are blended to yield about 60 volume percent, based on feed, of a product having a pour point of at least 10 F. below the average pour point of the blended heart cut fractions.

3. The method of claim 2 wherein the said phenol treated feed has a pour point of about '45 F.

4. A process for preparing low temperature hydrocarbons oil comprising the steps of (l) separating a phenol treated, dewaxed, lO-Grade distillate into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high viscosity index end cut, in a yield of about 30 volume percent based on the feed, '(3) recovering the lower viscosity index fractions as a low viscosity index end cut, in a yield of about 20 volume percent based on feed, (4) blending the remaining heart cut fractions in a yield of about 50 volume percent, based on feed, to obtain a hydrocarbon oil product having a pour point of at least 1 1 F. below the average pour point of the heart out fractions so blended.

5. The method of claim 4 wherein the said phenol treated, dewaxed, IO-Grade distillate has a pour point of about 0 F.

6. A process for preparing low temperature hydrocarbon oils comprising the steps of (l) separating a solvent 75 neutral oil having a pour point of about F. into from 3 to equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut, in a yield of about volume percent, based on the feed, (3) recovering the lower viscosity index fractions as a low viscosity index end cut, in a yield of about 10 volume percent based on feed, (4) blending the remaining heart out fractions to yield about volume percent, based on feed, of a hydrocarbon oil product having a pour point of at least 10 F. below the average pour point of the heart out fraction so blended.

7. A process for preparing low temperature hydrocarbon oils comprising the steps of (1) separating a solvent 75 neutral oil having a pour point of about 0 F. into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut, in a yield of about 30 volume percent based on the feed, 3) recovering the lower viscosity index fractions as a low-viscosity index end cut, in a yield of about 10 volume percent based on feed, (4) blending the remaining heart cut fractions in a yield of about volume percent, based on feed, to obtain a hydrocarbon oil product having a pour point of about 10 F. below the average pour point of the heart out fractions so blended.

8. The method of claim 7 wherein the said high viscosity index end cut is recovered in a yield of about 40 volume percent, based on the feed, the said low viscosity end cut is recovered in a yield of amout 20 volume percent, based on feed, and the said remaining heart out fractions are blended to yield about 40 volume percent based on feed, of a product having a pour point of about 10 F. below the average pour point of the heart out fractions so blended.

9. A process for preparing low temperature hydrocarbon oils comprising the steps of (1) separating a solvent neutral oil having a pour point of about 20 F. into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut, in a yield of about 30 volume percent based on the feed, (3) recovering the lower viscosity index fractions as a low-viscosity index end cut, in a yield of about 10 volume percent based on feed, (4) blending the remaining heart cut fractions in a yield of about 60 volume percent, based on feed, to obtain a hydrocarbon oil product having a pour point of about 10 F. below the average pour point of the heart cut fractions so blended.

10. The method of claim 9 wherein the said high viscosity index end cut is recovered in a yield of about 40 volume percent based on the feed, the said low viscosity index end cut is recovered in a yield of about 20 volume percent, based on feed, and the said remaining heart cut fractions are blended to yield about 40 volume percent based on feed, of a product having a pour point 12 of about 10 F below the average pour point of the heart cut fractions so blended.

11. A process for preparing low temperature hydrocarbon oils comprising the steps of (l) separating a solvent neutral oil having. a pour point of about 15 F..

into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut, in a yield of about 40 volume percent, based on the feed, (3) recovering the lower viscosity index fractions as a low-viscosity index end cut, in a yield of about 10 volume percent based on feed, (4) blending the remaining heart out fractions in a yield of about 50 volume percent, based on feed, to obtain a hydrocarbon oil product having a pour point of about 10 F below the average pour point of the heart out fractions so blended.

12. A process for preparing low temperature hydrocarbon oils comprising the steps of (1) separating a solvent 100 neutral oil having a pour point of about 0 F. into from 3 to 30 equal volume fractions by thermal diffusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut, in a yield of about 30 volume percent based on the feed, (3) recovering the lower viscosity index fractions as a low-viscosity index end cut, in a yield of about 20 volume percent based on feed, (4) blending the remaining heart cut fractions in a yield of about 50 volume percent, based on feed, to obtain a hydrocarbon oil product having a pore point of about 10 F. below the average pour point of the heart out fractions so blended.

13. A process for preparing low temperature hydrocarbon oils comprising the steps of (1) separating a solvent 100 neutral oil having a pour point of about -20 F. into from 3 to 30 equal volume fractions by thermal difmusion, (2) recovering the higher viscosity index fractions as a high-viscosity index end cut,in a yield of about 30 volume percent, based on the feed, (3) recovering the lower viscosity index fractions as a low-viscosity index end cut, in a yield of about 20 volume percent based on feed, (4) blending the remaining heart out fractions in a yield of about 50 volume percent, based on feed, to obtain a hydrocarbon oil product having a pour point of about 10 F. below the average pour point of the heart out fractions so blended.

14. The method of claim 13 wherein the said high viscosity index end cut is recovered in a yield of about 40 volume percent based on the feed, the said low viscosity index end cut is recovered in a yield of about 30 volume percent based on feed and the said remaining heart out fractions are blended to yield about 30 volume percent, based on feed, of a product having a pour point of about 10 F. below the average pour point of the heart cut fraction so blended.

References Cited UNITED STATES PATENTS 3,180,823 4/1965 Stothers et a1.

HERBERT LEVINE, Primary Examiner US. Cl. X.R. 20819, 28