US2984621A - Color stability of solvent treated oils and waxes derived therefrom - Google Patents

Description

May 16, 1961 R. A. BEHN ETAL 2,984,621

COLOR STABILITY OF SOLVENT TREATED OILS AND WAXES DERIVED THEREF'ROM Filed Sept. 18, 1958 4 Sheets-Sheet 1 Hunsfor .Sondlin w AGENT.

May 16, 1961 R. A. BEHN ETAL 2,984,621

COLOR STABILITY OF SOLVENT TREATED OILS AND WAXES DERIVED THEREFROM Filed Se t. 18. 1958 4 Sheets-Sheet 2 Robert A.Behn Honsford L.Sand|in AGENT:

May 16, 19 R. A. BEHN ETAL COLOR STABILITY OF SOLVENT TREATED OILS AND WAXES DERIVED THEREFROM 4 Sheets-Sheet 3 Filed Sept. 18, 1958 HO'IOQ INLSV m WiSV mmo mdE INVENTORS Robert A.Behn

Honsford L.S dlinl AGENT.

COLOR STABILITY OF SOLVENT TREATED OILS AND WAXES DERIVED THEREFROM Robert A. Bel1n and Hansford L. Sandlin, Beaumont, Tex., assignors, by mesne assignments, to Socony Mobil Oil Company, Inc., New York, N.Y., a corporation of New York Filed Sept. 18, 1958, Ser. No. 761,909 6 Claims. (Cl. 208--370) The present invention relates to the color stability of solvent treated oils and, more particularly, to the color stability of solvent treated lube oils and the paraffin and microcrystalline waxes derived therefrom. The present invention is particularly related to a method for increasing the filtering capacity of a unit for the percolation of solvent treated lube oils and paralfin and microcrystalline waxes.

In the distillation of crude oil to obtain various prod ucts including lubricating oil fractions one of two procedures are generally followed. (1) The crude is dis tilled to obtain gasoline, kerosene, distillate fuel oil, a parafiin lubricating oil fraction, a microcrystalline lubricating oil fraction, and what is known in the art as a short resid, or (2) the fractions through distillate fuel oil are vaporized to leave what is known in the art as a long resid. At this point there is a variation in the further processing which is easily recognized by reference to Figure 4 dependent upon whether the residuum is a short resid or a long resid.

Although solvent treating, dewaxing and percolation of lube oils each is a continuous process the progress of an oil through all three treatments often, and generally, is a discontinuous flow. Thus, while one stock is being solvent treated another stock may be being dewaxed. Consequently, before the second stock can be dewaxed, it is necessary to store the second stock. Frequently, for this and other reasons it is necessary to store stocks for periods up to several days or even two or three weeks or more.

It has been observed that oils darken in storage in an amount sufficient to afiect the capacity of the percolation unit. Consequently, the discovery that the color stability of solvent refined oils is affected by the conditions under which the solvent refined oils are stored and the discovery ofthe conditions under which the color of a solvent refined oil remains substantially constant provides a means for increasing the capacity of a percolation unit as much as 800 percent.

The following discussion in conjunction with the drawings will enable those skilled in the art to understand the present invention. In the following discussion unless specifically noted otherwise, the term solvent refined lube oil or solvent refined lubricating oil includes all products of the steps in process A and process B subsequent to steps 3a and 3b in process A and all steps subsequent to step 2. in process B and includes the microcrystalline wax of steps 5b in both process A and process B (Figure 4).

In the preparation of finished lube oils it is conventional to treat the lube oil fraction with a solvent. One conventional solvent refining treatment comprises treating the oil with two substantially immiscible solvents such as propane and cresylic acid. This is known as the Patent ice Duo-Sol process. Another solvent treatment comprises treating the lube oil fraction with propane to deasphalt the fraction and treating the deasphalted raflinate with furfural. It is also conventional to dewax the rafiinate from any solvent treating process. One of the dewaxing solvents is a mixture of a ketone such as methyl-ethyl ketone and an aromatic solvent such as toluene. The final finishing step is that of percolation through clay such as Attapulgus clay. Often, it not generally, it is necessary to store the treated fraction between successive treatments as between solvent treating and dewaxing and/or between dewaxing and percolating the lube oil fraction. During storage under conditions usually existing the color of the partially treated oil darkens. As is shown in Figure 2 the capacity of a percolation unit is increased if the feed thereto has a lower ASTM color.

Attention is directed to Figure l of the drawings. Figure 1 shows graphically the relation between the darkening of the color of a solvent treated oil and the time in storage at a temperature of F. The lube oil fractions the data for which are plotted in Figure 1 were of the types and treated in the manner indicated in Table I.

The various oils were placed in an oven maintained at 180: (2) F. and the color of a sample of each oil determined at various intervals up to 56 days. It will be observed that although there is not a uniform rate at which the color of the oils darkened nevertheless all of the oils darkened to a commercially unacceptable extent. The initial and final colors for each oil are set forth in Table 11.

TABLE 11 Initial Final 011 N o. Dilute Dilute ASTM ASTM Color Color 1 Dark 3--.- Dark 4 3 t. 0.. 4- Lt. 3 Lt. 4%. 5 Lt. 3%..-. 4%. 6 Lt. 3 Lt. 4.

Attention is now directed to Figure 2. Figure 2 graphically illustrates the relation between the color of the oil to be percolated and the capacity of the percolation unit. Capacity of the percolation unit is not the barrels of oil which can be treated in a unit time but the amount of oil which can be treated before it is necessary to regenerate the clay. When considering the data presented in Figure 2 it is to be observed that the colors are rated on two scales, i.e., one scale is for ASTM color when the sample is not diluted and the other of the sample after dilution in accordance with ASTM test procedure. The latter colors are reported as dilute ASTM. Typical of the reduced capacity of a percolation unit between regenerations of the clay is the number of barrels of lube oil fraction having a light 6 ASTM color which can be filtered between regencrations and the number of barrels of lube oil fraction having a light 4 /2 dilute ASTM color. When both oils are filtered through bauxite at the rate of about 3.8 barrels of oil per hour per 100 cubic feet of clay to. obtain a 7 ASTM color the yield of oil from the 6 ASTM color oil is 124 barrels of oil per ton of clay. On the other hand, when the darker oil is filtered the yield is only 14.barrels per ton. Thus, it is apparent that when percolating a lube oil fraction to a 7 ASTM color product the capacity of the unit between regenerations is increased about 800 percent when the color of the fraction to be filtered is not darker than a light 6 ASTM.

The color of the lube oil fraction to be filtered or percolated through bauxite or clay is adversely aifected by the temperature to which it is subjected during treatment. Thus, in 10 days at 180 F. the color of a solvent treated lube oil fraction will darken from a light 3 to a 3% dilute ASTM and in days to 4 /2 dilute ASTM. On the other hand. at 150 F. the color of the same lube oil fraction will darken from a light 3 dilute ASTM only to a light 3 /2 dilute ASTM color. Thus. the present invention provides for maintaining the solvent treated lube oil fraction at a temperature not greater than about 150 F. during storage before percolation.

A further improvement in color stability is obtained bv control of the gases with which the lube oil fraction is in contact during storage before percolation. Inspection of the curves of Figure 3 makes it manifest that the color of a lube oil fraction darkens much more rapidly when stored in contact with air than when stored in contact with a non-oxidiizng gas such as nitrogen, natural gas or flue gas substantially devoid of oxygen. In fact. curve A in Figure 3 shows that if a lube oil fraction is stored even at 180 F. under a blanket of non-oxidizing gas the color remains substantially constant for at least 32 days.

It has also been discovered that the color of micro crystalline wax admixed with oil, generally known to the art as petrolatum, is improved and stablized when it is necessary to store the petrolatum by storing the petrolatum under a blanket of non-oxidizing gas such as nitrogen, natural gas or flue gas substantially devoid of oxygen even though the petrolatum is stored at 180 F.

5 Solvent refined oil and petrolatum having the physical properties set forth in Table III were stored under blankets of gases having the compositions set forth in Table IV.

1 Oxygen free fiue gas. 2 Fine gas with 0.8% Oxygen.

35 3 Purchased natural gas.

It will be observed that fluegas as usually produced contains an appreciable amount. of oxygen. A typical analysis of flue gas is given here below.

FLUE GAS Volume percent (30 10.1 0 3.5 CO 0 N and other inerts 86.4

The color of the solvent refined oil degraded with time when blanketed by the gases the compositions of which are given in Table IV as shown in Table V.

TABLE V with air, flue gases and natural gas [Stored at F. in sealed 4-02. bottles] Air Flue gas, 0.8 O: Flue Gas, no 0: Natural gas Blanketed Material NPA Dilute N PA Dilute NPA Dilute NPA Dilute NPA NPA NPA NPA Daysstintstorage: D 6 W D 6 3V D 6 3V D 6 3% ar z- 2- g- D. 6 3% D. 7 3% 8- 4- D. 6 3% D. 7 3% D. 8 4- D. 7 D.3% D. 7 D.8% D.8 4- D.7 Dill D.7 D.3% D.8 4- D. 7 D. 3% D. 7 D. 3% D. 8 4- D.7 D. 3% D.7 D.3% D.8 4- D. 7 D. 3% D. 7 D396 1). 8 4- D. 7 D.3% D.7 D.3 D. 8 4- 8- 4- D. 7 4- D. 8 4- D. 8 4- D. 7 4- D. 8 4- TR==Transparent red (darker than 8).

TABLE VI Color stability of petrolaturn from solvent refined lube all (Table IV) blanketed with air and flue gas [Stored at 180 F. in sealed 4-02. bottles] Containing Air no Flue Gas Blanketing Material NPA Dilute NPA Dilute NPA NPA Days in Storage:

Sta t D. 7 3} D. 7 3 7.-- D.8 4- D. 7 3 l4 D.8 4- D.7 3 21.. D3 D4 D. 7 3% 28 TR 95- D7 3% 35.... TR 5- D. 7 D. 3% 42 TR 5- D. 7 D. 3% 49.- TR 5- D. 7 D.3% 66. TR 6- 8- 4- 63-- TR 5- 8- 4- 70-- TR 5+ 8 4 The results set forth in Tables V and VI are summarized in Table VI].

TABLE VII Dilute NPA Color Stock 330 Petrolatum Raffinate Sample Before Storage 3% 3 Sample After Storage for 70 Days at 180 F.,

Blanketed With:

Air TR Dk.5 Flue Gas-No O 4- 4- Flue Gas-0 8% 4- atural G 4- described petrolatum had the physical properties listed in Table VIII.

TABLE VIII Physical properties of microcrystalline waxes Gravity, API 33.2 34.8 34.3 Color, NPA Dilute 5- 4&5- 8%- Viscoslty, SUS 210 F 120 96 Water Content, Wt. Percent Nil Nil Nil The bauxite through which the microcrystalline waxes were percolated had the physical properties given in Table IX.

TABLE IX Physical properties of bauxite:

Density, lbs/ft. 66.3 Volatile matter, wt. percent 0.63

.SCREEN ANALYSIS Screen size: Wt. percent retained 16 0.1 20 0.1

The yields of percolated wax in pounds of wax filtered per ton of bauxite to produce microcrystalline having a color not darker than NPA 5 are given in Table X.

TABLE X Percolation of different color mzcrocrystallme waxes 5--Dilute N PA 4}-Dilute NPA 3V -Dilute NPA Charge Charge harge Filter Com- Filter Filter Yield, Bbls./ poslte Y ield, Composite 1 iold, Composite Ton NPA BblsJIon NPA Color BblsJ'Ion NPA Color Color l5. l3 5- 24. 55 L The data presented in Table X are summarized in Table XI.

Accordingly, the present invention provides a means for increasing the capacity between regenerations of a percolation unit for filtering solvent refined lube oil fractions and waxes obtained therefrom by (1) maintaining the lube oil fraction and the waxes obtained therefrom between treatments or during storage before percolation and after percolation at a temperature not greater than about F.; (2) by blanketing the lube oil fraction between treating steps or during storage before percolation with a non-oxidizing gas such as natural gas, flue gas containing not more than about i percent by volume of oxygen, nitrogen, etc. while maintaining the temperature below about 200 F.; and (3) by maintaining the temperature of a lube oil fraction not higher than 150 F. and blanketing the lube oil fraction with a non-oxidizing gas such as natural gas, flue gas containing not more than about 1 percent by volume of oxygen, nitrogen, etc. As used in the claims, intermediate storage before percolation designates storage between successive treatments as between solvent refining and dewaxing or between dewaxing and percolation.

This application is a continuation-in-part of copending application Serial No. 677,901, filed August 13, 1957.

We claim:

1. In the refining, of a lubricating oil fraction of a mineral oil comprising the steps in succession of (a) solvent extraction, (b) dewaxing, and (c) percolation through clay, wherein a partially refined portion of said fraction is stored following one of said treatments but before percolation through clay, the method of stabilizing the color of said partially refined portion during storage which comprises maintaining said stored portion in a fluid state at a temperature below about 200 F. while under a blanket of non-oxidizing gas.

2. The process according to claim 1 in which the stored portion is a dewaxed raflinate.

3. The method according to claim 1 in which the nonoxidizing 'gas is flue gas substantially devoid of oxygen.

4. The method according to claim 1 in which the stored portion is a solvent extracted lube oil.

5. The method according to claim 1 in which the stored portion is petrolatum.

6-. The method according to claim 1 in which the stored portion is microcrystalline wax.

References Cited in the file of this patent UNITED STATES PATENTS 2,045,160 Moorman et al. June 23, 1936 2,106,071 Stanton Jan. 18, 1938 2,321,459 Chenault et al. June 8, 1943 2,728,716 Watson et al. Dec. 27, 1955 2,862,876 Winberg Dec. 2, 1958

Claims (1)

1. IN THE REFINING OF A LUBRICATING OIL FRACTION OF A MINERAL OIL COMPRISING THE STEPS IN SUCCESSION OF (A) SOLVENT EXTRACTION, (B) DEWAXING, AND (C) PERCOLATION THROUGH CLAY, WHEREIN A PARTIALLY REFINED PORTION OF SAID FRACTION IS STORED FOLLOWING ONE OF SAID TREATMENTS BUT BEFORE PERCOLATION THROUGH CLAY, THE METHOD OF STABILIZING THE COLOR OF SAID PARTIALLY REFINED PORTION DURING STORAGE WHICH COMPRISES MAINTAINING SAID STORED PORTION IN A FLUID STATE AT A TEMPERATURE BELOW ABOUT 200*F. WHILE UNDER A BLANKET OF NON-OXIDIZING GAS.

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