US2733188A

US2733188A - Process for decolorizing and deodorizing petroleum waxes

Info

Publication number: US2733188A
Authority: US
Publication date: 1956-01-31
Anticipated expiration: 1973-01-31

Description

R. M. BAILLY ETAL File'd Dec. 11 1951 Jan. 31, 1956 PROCESS FOR DECOLORIZING AND DEODORIZING PETROLEUM WAXES PROCESS FR DECLORIZING AND DEoDoRIz- ING PETRoLEUM WAXES Randolph M. Bailly, Little Silver, and Harold F. Hitchcox,

Cranford, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware and odor-stability. Wax has long been one of the most important products properties. Any odor or color in a wax is generally due to the presence of small amounts of impurities. It should same refining techniques. A brief description of the techniques employed in the manufacture of wax will serve to clarify this point and explain the invention. Inasmuch as the manufacture of wax is intimately related with the refining of lubricating 011s, it is felt that a brief discussion of both the processes is necessary to fully show the scope of the present invention.

The waxes present in a petroleum crude oil are con- :entrated in the high boiling distillate fractions and in present to some extent in almost lll types of crude o1l, but are found primarily in the aaraflinic and mixed base crudes. Examples of such :rude oils are the parainic stocks from the Pennsylvania ields such as the Buckeye, Bradford and West Virginia rudes. Examples of mixed base stocks are the East Texas, MidContinent and Panhandle crudes.

The waxy high boiling fractions of a petroleum crude il are separated from the lighter fractions by an initial istillation of the crude known as a topping operation r atmospheric distillation in which the naphtha, kerosene ud lighter fractions are taken olf. The topped crude is ien fed to a vacuum pipe still and il fractions are removed as overhead s1de-stream`and ottoms fractions. The overhead or paratin distillate- 'action usually has a boiling range of about 580 F. to

Sta-fes Patent found Wide application 850 F. and a viscosity of aboutV 80 S. U. S. at 100 The heavy lubricating oil distillate side-stream generally has a boiling range of about 800 F. to 1000 F. and a viscosity of about 50-70 S. U. S. at 210 F. The residuum comprises all of `the hydrocarbons boiling above this point and generally has a viscosity of about 150 to 200 S. U. S. at 210 F. The exact proportion of these three fractions will vary considerably depending upon the parin question, but it is general practice to produce these three fractions.

Each of the lubricating oil fractions described above contains wax which remains in solution at slightly elevated temperatures. If the temperature of any of these fractions is lowered suliciently, however, the wax will oil to take on a gel-like struccondition would be in- It has been found that wax exists in petroleum crude oils in three major crystalline forms. It has further been found that each of these crystalline forms is concentrated comparative ease. The second wax type consists of the semi-crystalline waxes with melting points of about -165 F. which are derived from the heavy lubricating oil distillates. This type has crystals of much smaller size than the lirst type, is more difficult to separate from the oil, and is also more dicult to feline. The third waxes, or petoriginally thought to be amorphous in structure. The petrolatums which melt from about 14S-190 F. are the most diiicult of the wax types to rene. Good odor and color characteristics are especially difficult to obtain in petrolatums as compared to paralin waxes. Furthermore, once good odor and color properties are obtained, it is usually dicult to render these properties stable.

The present invention is primarily concerned with obtaining the process benefits of increased percolation yields and quality advantages of better odor and color characteristics by addition of a wax inhibitor prior to l) percolation or percolation and distillation of refined paraliin waxes and (2) percolation or steaming and percolation of microcrystalline waxes.

The general technique of dewaxing a lubricating oil fraction consists basically in lowering the solubility of the wax in the oil. This can be done by chilling the oil to low temperatures with or without the use of a solvent. The solvents employed for solvent dewaxing at the present time serve three main functions; first, they lower the solubility of the wax in the oil; second, they form a wax precipitate of a structure such that the precipitate can be removed from the oil by filtration means; and third, they lower the viscosity of the oil sufficiently to make rapid filtration possible.

Quite often, the solvents used for dewaxing oils are actually dual solvents inasmuch as combinations of two solvents have been found to fk lfill the three requirements mentioned very satisfactorily. These dual solvents include mixtures of benzene and methyl ethyl ketone, normal propyl ketone, toluene and acetone, and ethylene dichloride. Following dilution with one of these solvent blends, the oil to be dewaxed is chilled by passage through heat exchangers cooled in turn by refrigerants. It should be noted that the solvent can be added to the oil all at once or in increments as the oil is being chilled. One solvent, propane, merits special attention in that the use of an outside refrigerant is dispensed with when this solvent is employed. A propane-oil mixture can be effectively cooled by merely allowing part of the propane to evaporate. This chilling technique is known as autorefrigeration.

Regardless of the type of solvent used, the precipitated wax is separated from the oil and solvent by the use of rotary filters which are a relatively modern development and can be used to filter any of the three types of wax. For the special case of dewaxing paraffin distillates, the well known application of plate and frame presses is satisfactory.

Once the wax has been removed from the oil by one of these separation techniques, the problem then becomes one of reducing the oil content of the wax, purifying it, improving its color and odor, and segregating it into the various melting point grades. The exact manner in which a wax is refined will vary depending upon the type of wax being processed and the equipment available. With crystalline waxes derived from the paraffin distillates, two methods of deoiling are possible: (l) sweating and (2) solvent deoiling. Sweating, which is the older method of the two, consists of cooling the slack wax obtained from the dewaxing operation in tank or pan sweaters and then gradually raising the temperature of the wax cake until the oil and very low melting waxes are removed.

The wax from this ope-ration is known as scale wax and generally contains about 1-6% of oil. The scale wax is then further sweated in a second set of pan sweaters to obtain wax fractions of the required melting point grades with oil contents in the range of 0.1 to 0.5%.

The solvent deoiling method of reducing the oil content of a wax can be used on any of the three crystalline types of wax. It is the only method applicable for the semi-crystalline or micro-crystalline waxes since these types are impossible to deoil by the sweating technique. A wax can be solvent deoiled in one of two ways: first, it can be completely dissolved in from 4 to 14 volumes of a solvent such as methyl ethyl ketone and at a temperature from 20 F. to 70 F. above the dewaxing temperature. The solution is then cooled, the wax re-crystallized and filtered from the solvent. Alternatively, the chilled, solvent-containing wax cake from the dewaxing operation can be repuddled or agitated into a slurry with a lesser amount of cold solvent and then refiltered. Either techniques is very effective in reducing the oil content of any of the three types of wax.

Following the deoiling steps, a crystalline paraffin wax or a semi-crystalline wax will generally contain about 0.1 to 0.5% oil. A microcrystalline wax may contain about 0.5 to 6% oil.

The deoiled waxes are then chemically treated, usually with sulfuric acid, to remove carbonizable substances. This procedure is necessary to insure high purity waxes for the food and drug industry. Mild hydrogenation of wax at about 600 F. and 200 p. s. i. g. has been found to be the equivalent of sulfuric acid treating. Microcrystalline waxes are usually acid treated rather than hydrogenated.

After a wax has been deoiled and chemically treated, two major refining steps remain: (l) separation into the desired melting point grades, and (2) processing to a suitable odor and color. It is these finishing operations with which this invention is primarily concerned.

As described above, the paraffin waxes can be segregated into the various meltingpoint fractions by the sweating technique. All three types can be segregated by frac` tional vacuum distillation, although fractional crystallization may also be employed simultaneously in the solvent deoiling operation. This operation is carried out before the decolorizing or deodorizing step.

The customary method for decolorizing and deodorizing a wax to percolate it through a bed of a color adsorbent material at temperatures sufficient to keep the wax in a fluid state. The adsorbents most generally employed are bauxite, silica gel, and various activated clays. A paraffin or crystalline wax is decolorized by heating it until it becomes fluid, allowing any water to settle out and then passing it through a bed of one of the materials mentioned above. The filtering rate employed is generally about 1/2 to 2 tons of wax per ton of adsorbent per hour and the operating temperature is usually in the range of 160 F. to 200 F. The yield of wax obtained per volume of adsorbent employed will depend upon the color of the feed and the desired color of the products obtained. The paraffin waxes generally are decolorized to a color shade of +30 as determined by the Saybolt chrornometer. Where the feed to the decolorizing operation has -2 Saybolt color, a yield of about 25 tous of wax per ton of adsorbent can be expected. Where the feed has a color rating of about +20 Saybolt, a yield of about 60 tons of decolorized wax per ton of adsorbent is about normal.

Owing to the greater viscosity of the semi-micro waxes and the petrolatums, these wax types are often diluted with a suitable solvent to render their percolation through the adsorbent bed more rapid. One such solvent in general use is a petroleum naphtha which is characterized by a 30G-400 F. boiling range and a relativelyI low aromatic content. A petrolatum may be diluted with 1 to 1.5 volumes of such a naphtha to obtain a satisfactory filtering rate.

The semi-crystalline waxes are essentially light colored and give filter yields of 15-20 tons wax/ton bauxite. However, the petrolatums are very dark in color, and it is often necessary to recycle these materials in the decolorizing step before suitable color ratings can be obtained. With these two stocks, filter rates of about 0.1 ton wax/ton clay/hr. are employed and filter yields of about 1 to 3 tons wax/ ton clay are obtained. Petrolatums having color ratings of about 10 to 14, as determined by the modified Tag-Robinson colorimeter, are satisfactory. Details of the Saybolt and Tag-Robinson methods of color determination are standard tests in the petroleum industry and descriptions of these methods can be found in the New and Revised Tag Manual for Inspectors of ietroleum published by C. J. Tagliabue Manufacturing Company. Y

The odor characteristics of the final waxes are determined as follows: approximately 50 grams of wax and grams of distilled water are heated in a 250 cc. beaker until the water starts to boil. A watch glass covering the beaker is then removed and the vapors over the sample are sniffed by an odor committee having a minimum of three persons. A wax is rated by each committeeman as having: (l) a very faint or lack of odor, (2) an unobgectionable odor, and (3) an objectionable odor.

An average numerical rating of 2.5 or less as satisfactory.

This test is admittedly subject perception of the individuals. For this reason, the men performing the odor test are specially trained for this work and the atmosphere in the test area is kept as odoris regarded to variations in the odor free as possible. The odors of the standard odor wax samples are arrived at by conducting surveys among the various wax consumers. This test has proven to be a reasonably accurate method of predicting the acceptability of a wax by the trade so far as its odor characteristics are concerned.

A second test is performed on waxesto determine their odor and color stability. Inasmuch as the odor of a refined paraflin wax is generally much less stable than its color, this test is specificallyV directed toward the former property. The wax sample to be tested is placed in a glass container and is maintained at a temperature of 200 F. in a constant temperature oven. The amount of time for the wax to develop an objectionable odor, as determined by daily odorrtests, is observed. The length of time a wax must stand up in the stability test to be satisfactory is governed by the application to which a wax is to be put.

Once a wax has been percolated to the required odor and color requirements, an inhibitor is added to stablize the odor and color of the wax. Generally speaking, the inhibitors used for this purpose are chemical anti-oxidants of one type or another. While these inhibitors stabilize -the odor and color of a wax,` their use is subject to a number of restrictions. In the food and pharmaceutical industries, for example, the presence of such inhibitors is a serious matter due to their possible toxicity or taste. For this reason, it is eminently desirable to-produce a Wax which not only has goodcolor and odor, but is also sufficiently stable in these respects to require little or no inhibitor.

The disadvantages of using anti-oxidants to inhibit color and odor degradation can be greatly minimized or completely overcome by means of the invention herein described. In addition, the yields of refined wax are markedly increased. Briefly, this invention consists in adding an anti-oxidant to a wax before it is decolorized and deodorized by percolation through or contacting with an adsorbent such as clay or bauxite. It has been found that wax produced in this manner not only has greatly improved stability, but also that greater yields of wax for given odor and color requirements are thereby obtained. In addition, a further unusual benefit results from this invention in that accepted ultra Violet analytical methods show no trace of inhibitor remaining in a wax after the percolation step. This process then has the very desirable features of producing greater yields of wax possessing good odor and color and also exceptional odor and color stability.

The particular types of inhibitors found to be most effective are the alkyl substituted 2,4,6-phenols in which the alkyl groups in the 2 and 6 positions have from 4 to 8 carbon atoms while the alkyl group in the 4 position has from 1 to 5 carbon atoms. Phenols with tertiary butyl groups in the 2 and 6 positions and a normal alkyl group with from l to 5 carbon atoms in the 4 position are especially effective. 2,6-ditertiary butyl, 4-methyl phenol has proven to be particularly satisfactory for the purposes of this invention.

It will be noted that any odor and color inhibitor conventionally employed in wax should be effective in this process providing it can be removed during the percolation step by the color adsorbents customarily used. Such inhibitors include: 2-tertiary butyl, 4-methoxy phenol, N-lauryl p-amino phenols, 2,2 bis (2-hydroxy, 3-tertiary butyl, 5methyl phenyl) propane and 2,2 bis (2-hydroxy, 3v-tertiary butyl, S-methyl phenyl) propane.

In order to add an anti-oxidant to a Wax, it is preferable that the wax be present generally as a molten liquid. An especially attractive method for incorporating an inhibitor in a wax vis to add it in the form of a wax concentrate. The concentration of inhibitor in any given wax will vary with the nature of the wax. A range of about .O05 to 0.5 wt.% of inhibitor based on the amount of wax being fed to the decoloriziug operation has been found to be sufcient.

As described earlier, it is often necessary to dilute the higher molecular weight waxes such as the petrolatums with 1 to 1.5 volumes of a solvent in order to make percolation of the Wax through a bed of adsorbent a rapid operation. A perfectly satisfactory method for adding the inhibitor in this case is to incorporatevit directly in the solvent stream. It should be noted that following the percolation operation, it is necessary in this procedure to remove the solvent from the wax. This can be done in a conventional flash tower or distillation column.

The process of this invention may best be explained by considering the wax types in two groups, (l) the parafn and semi-crystalline waxes and (2) the micro-crystalline waxes or petrolatums.

Reference to Fig. l will assist in demonstrating the function of the present invention in the conventional process of refining the paraffin and semi-crystalline waxes. As may be seen, a waxy lubricating oil fraction such as a parain distillate or a heavy lubricating oil distillate is diluted with a solvent such as methyl ethyl ketone, propane, toluene and acetone, etc, and dewaxed as in 2 to produce a wax-free oil and a slack wax. In this operation, the oil and solvent mixture is chilled to a temperature low enough to produce the pour point desired in the eventual rened lubricating oil. The temperature of this operation will also vary with the solvent employed, but will generally fall in the range of l0 to 40 F. below the pour point. The solvent to oil ratio can also vary over a wide range depending upon a number of factors, but the solvent to oil ratios usually employed are 3 to 6 by volume. It should be noted that the solvent may be added to the oil in one step or in number of steps while the oil is being chilled.

'I he oil and solvent mixture may be cooled by means of an external refrigerating system through the medium of heat exchangers. Or, in the case where a solvent such as liquid propane is used, the principle of auto-refrigeration can be employed wherein part of the propane is vaporized to cool the remaining liquid by giving up heat to vaporize the propane.

The wax-oil slurry so produced is filtered on a conventional rotary lter such as is common in the petroleum refining industry. The slack Wax from this operation may contain 10 to 30% oil. In order to further reduce the oil content of the slack wax, the wax cake may be washed with additional chilled oil-free solvent before its removal from the ltering element.

For dewaxing paraiiin distillates, plate and frame presses or centrifuges may also be employed if desired. However, these methods are becoming less widely used.

Following the dewaxing operation which produces a dewaxed oil and a wax cake, the wax fraction is deoiled as in (3). Where the solvent deoiling technique is employed, the wax cake is mixed with or dissolved in 4 to 14 volumes of solvent at a temperature above the original dewaxing temperature, is recrystallized by chilling and then reltered. The oil content of a wax deoiled by this method will be generally less than 0.5%.

In the case of a paratin wax, a sweating technique may be used to deoil the wax. In a sweating operation, a parafin wax is separated into (l) foots oil consisting of oil and low melting point waxes, (2) intermediates melting below about 112 F., and (3) scale Wax having an average melting point of about 12S-130 F. The scale wax has an oil content of about 1-6% by weight which is reduced to less than 0.5% oil by resweating. The resweating further serves to separate the wax into the desired melting point grades. Y

Following the solvent deoiling step, a paraiiin or semicrystalline wax is chemically treated with sulfuric acid or hydrogen to reduce its content of carbonizable substances 4. Wax is acid treated with sulfuric acid at a temperature of about 160 to 180 F. and 4 to 30 pounds of acid per gallons of wax. When using hydrogenation, pressures of about 200 p. s. i. and temperatures of about 60G-700 F. are employed. Sweated waxes are usually chemically treated at the scale wax level.

After chemical treatment, a wax is separated into the various melting point grades 5. Vacuum distillation is usually employed for this purpose, but fractional crystaln lization may also be used. Scale Wax from a sweating operation is usually resweated to perform the melting point separation.

The various melting point fractions produced by the distillation step are blended 7 with .005 to 0.5% of an inhibitor of the types described earlier and percolated 8 through beds of color adsorbent at a temperature of about 160-200 F. at feed rates of .l to 2 tons of wax per ton of adsorbent per hour. The inhibitor may be added to a wax as a wax concentrate or in naphtha solution when naphtha is employed as a diluent for the wax.

The adsorbent employed in the percolation step may be one of the conventional materials used for decolorizing wax. These include bauxite, activated charcoal, acidtreated clays, etc. The adsorbent is preferably 10-30 mesh size and should be heat-treated before actual use. When an adsorbent becomes spent, it is reviviiied by washing, steaming and regeneration at 850-l000 F.

Occasionally it may be preferable to add the inhibitor to a wax before the distillation step in which the wax is fractionated into the various melting point grades. As will be shown later, this procedure also results in increased yields of refined wax. One limitation is encountered in this technique, however, in that the inhibitor will generally remain in the bottoms fraction. It becomes necessary, therefore, to still add inhibitor to the distillate fractions before the percolation step for best results.

It will be noted in Figure l that three melting point grades of wax are shown leaving the vacuum distillation and percolation steps. More than three grades are produced, but it is conventional to produce no more than three from a given wax feed stock to the still.

The following example illustrates the manner in which a paran wax may be processed in accordance with the procedure described above.

A waxy paratiin oil was solvent dewaxed t0 a slack wax, solvent deoiled to a refined wax oil content level (less than 0.5% oil), and chemically treated with sulfuric acid for purification purposes.

One portion of the deoiled paraffin wax was distilled into 33% overhead and side stream cuts and 34% bottoms by vacuum fractionation. To another and equal portion of the same wax, 0.01% of a wax anti-oxidant was added (2,6, ditertiary butyl, 4-methyl phenol). This stock was vacuum distilled at the same conditions and yields as the first portion.

The two bottoms fractions from this distillation, each comprising 34% of the feed, were then percolated through freshly burned bauxite to a yield of 10 tons of decolorized wax per ton of bauxite. The bottoms fractions were chosen for this product work-up since these are the most susceptible to odor degradation. In addition, a sample of the uninhibited deoiled paraiiin wax was percolated at a lter yield of 20 tons wax per ton of bauxite without having been distilled.

All three products from this work had a +30 Saybolt color; the odors were as indicated below:

l 54 as much bauxite used per volume of wax as for other two samples.

It is seen from these data that the wax which was not distilled and the 34% botoms cut from the inhibited wax feed stock gave a satisfactory odor after bauxite percolation. The bottoms cut from the uninhibited charge stock did not give an acceptable odor wax and would require additional processing to meet the odor requirements.

It is also interesting that the bauxite percolated product from the 34% bottoms fraction of the inhibited charge stock showed no trace of inhibitor by an ultraviolet analysis procedure for 2,6 ditertiary butyl, 4 methyl phenol. Nevertheless, by the 200 F. storage stability test described earlier, the above product showed an improved heat stability (2 days) as compared to the percolated but undistilled wax 1 day). This increase in heat stability obtained by addition of an inhibitor prior to distillation and percolation is an additional advantage for this invention. The 34% bottoms fraction which contained no inhibitor prior to percolation, of course, was completely unstable since it had an unsatisfactory odor immediately after percolation.

The mirco-crystalline waxes or petrolatums are proceased as shown in Fig. 2. A residuum is first deasphalted as, for example, with liquid propane l. dewaxed 2, solvent deoiled 3 and chemically treated 4 in a manner similar to that described earlier for the paraffin waxes. According to this invention, the deoiled petrolatum is then blended with .O05 to 0.5 of an inhibitor 7 of a type described earlier and percolated or contacted with an adsorbent. The petrolatum is also generally diluted with a solvent as described earlier to increase the filtering rate through the adsorbent.

Occasionally it has been found in deodorizing a petrolatum that it is impossible to remove all of the odors present by merely clay percolating or contacting. ln this case it has been found desirable to steam the petrolatum at a temperature of about ZOO-220 F. before the clay percolation step. In this case, it may prove more advantageous to add the anti-oxidant to the wax before the steaming operation rather than just prior to the percolation step. In either event, the anti-oxidant will be present in the wax as charged to the percolation operation but is completely removed during this step. In general, color and odor stability are more difficult to obtain with d petrolatums than with the paraliin and semi-crystalline waxes. This invention therefore is particularly attractive as a method for improving these characteristics in the petrolatums. It is generally desired that a petrolatum have a light amber color e. g. a Tag-Robinson rating of l0 or better. The following example illustrates how well the process described in this invention is able to meet this requirement and also produce excellent yields.

A deoiled micro-crystalline wax was prepared as shown in Figure 2. A waxy residual oil was propane-deasphaltcd to remove asphalt and resins, and solvent dewaxed to obtain a wax-free lube oil and a petrolatum. The latter was solvent deoiled at a temperature such that the undesirable low melting waxes were discarded with the oil component.

One portion of the deoiled micro-crystalline wax was mixed with 1.5 volumes of petroleum naphtha having a boiling range of SOO-400 F. at atmospheric pressure. This solution was percolated through Attapulgus clay at 200 F. Other percolating temperatures from 160 to 220 F. or clay contacting temperatures from 160 to 550 F. could be employed or the decolorizing step could be carried out with 0-3 volumes of solvent if desired.

Another and equal portion of the same deoiled material was inhibited with 0.01% of 2,6 ditertiary butyl, 4 methyl phenol and percolated in the same manner as the first wax. Filtrate samples from each wax were collected in equal cuts so that the characteristics of the wax produced throughout the iiltrations could be compared. The results on the solvent-free wax fractions are as follows:

It is then solvent i 9 Eect of inhibitor Von odor and color o7 a bright stock petrolatum when percolated at 200 F., without a diluent through activated clay Item Petrolatum With- Petrolatum With out Inhibitor Inhibitor I Odor, Cut N o. 1. Objeetionable.- N ot objectionable. Odor, Cut No. 2. o Do. Odor, Cut No. 3. Not objectionable. Do. Odor, Cut No. 4.. do Do. Odor, Cut No. 5. do T30. Odor, Out No. 6. Objectionable. Do. Odor, Cut No. 7. Not objectionable- D o. Odor, Cut No. B. objectionable Do. Odor, Cut No. 9 ..do.... bDo. Odor, Cut No. 10 do objectionable. Odor, Cut No. 11 do Do. Odor, Cut No. 12 do Do, Odor, Composite Cuts 1-9 do Not obiectionable. Color, Composite Cuts 1-9, 14% 16.

Tag-Robinson? Filter Yield, Tous wax/Ton 2.34 2.38.

Adsorbent.

lInhibitor: .01% 2,6-ditertiary-butyl, 4-1nethyl phenol. 2 Higher numbers denote lighter colors.

It may be seen from this data that the yield of wax having a satisfactory odor was markedly greater in the case where an anti-oxidant was employed during the de odorizing and decolorizing operation. In addition, it may be noted that the color of the wax was also improved to a greater extent as a result of using an anti-oxidant.

In summary, the present invention discloses a process for producing increased yields of hydrocarbon waxes from petroleum crude oils which will have improved color and odor characteristics. A further characteristic of the process lies in the fact that the paraffin and semi-crystalline waxes produced are more heat stable although no inhibitor is present in the final product. While this process is valuable for all the types of waxes derived from petroleum, it has special merit in the refining of petrolatums and for the combined distillation and percolation of paraffin and semi-crystalline waxes.

The nature of the present invention having been thus fully set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. Method for refining a hydrocarbon wax which has been derived from a petroleum crude oil by the conventional steps of dewaxing, deoiling and chemical treating which comprises heating said wax above its melting point, blending said wax with from .005% to 0.5% by weight of a color and odor inhibitor for Wax, percolating the resulting mixture through a bed of an adsorbent at a filter rate of about 1 to 3 tons of Wax per t0n of adsorbent per hour to produce a filter yield of about tons to 30 tons of wax per ton of adsorbent, said percolation being carried out at temperatures of about 160 F. to 200 F.,

10 thereby removing substantially all of said inhibitor from the wax and obtaining an improved yield of wax having satisfactory odor and color.

2. Method for reiining a micro-crystalline wax derived from a petroleum crude oil by the conventional steps of distillation, deasphalting, dewaxing, and deoiling, which comprises heating said wax above its melting point, blending said wax with from .005 to 0.5% by Weight of 2,6- ditertiary butyl, 4-methyl phenol, percolating the resulting mixture through a bed of adsorbent at a filter rate of about 0.5 to 3 tons of wax per ton of adsorbent per hour to produce a filter yield of about 1 to 3 tons of wax per ton of adsorbent, said percolation being carried out at temperatures between to 200 F., thereby removing substantially all of said phenol from said wax and providing an improved yield of wax having satisfactory odor and color.

3. Process as in claim 2 in which said 2,6-ditertiary butyl, 4-methyl phenol is added in naphtha solution.

4. Process as in claim 2 in which said 2,6-ditertiary butyl, 4-methyl phenol is added as a wax concentrate.

5. Method of refining a hydrocarbon wax which has been derived from a waxy petroleum crude oil by the conventional steps of dewaxing, deoiling and chemical treating which comprises melting the wax, blending the melted wax with from 0.005 to 0.5 wt. of a color and odor inhibitor for wax, percolating the resulting blend through a bed of adsorbent thereby removing substantially all of the inhibitor from the wax and obtaining an mproved yield of the wax having a satisfactory odor and color.

6. Method as defined in claim 5 in which the inhibitor is a tri-alkyl phenol.

7. Method as defined in claim 5 in which the inhibitor is an alkyl substituted 2,4,6-phenol.

8. Method as defined in claim 5 in which the inhibitor is 2,6-ditertiary butyl, 4-methyl phenol.

9. Method as defined in claim 5 in which the wax is a micro-crystalline wax.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

5. METHOD OF REFINING A HYDROCARBON WAX WHICH HAS BEEN DERIVED FROM A WAXY PETROLEUM CRUDE OIL BY THE CONVENTIONAL STEPS OF DEWAXING, DEOILING AND CHEMICAL TREATING WHICH COMPRISES MELTING THE WAX, BLENDING THE MELTED WAX WITH FROM 0.005 TO 0.5 WT.% OF A COLOR AND ODOR INHIBITOR FOR WAX, PERCOLATING THE RESULTING BLEND THROUGH A BED OF ADSORBENT THEREBY REMOVING SUBSTANTIALLY ALL OF THE INHIBITOR FROM THE WAX AND OBTAINING AN IMPROVED YIELD OF THE WAX HAVING A SATISFACTORY ODOR AND COLOR.