US3119762A

US3119762A - Method of improving microwax quality

Info

Publication number: US3119762A
Application number: US71998A
Authority: US
Inventors: Charles W Siegmund
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1960-11-28
Filing date: 1960-11-28
Publication date: 1964-01-28
Anticipated expiration: 1981-01-28

Description

Jan. 28, 1964 c. w. slEGMuND METHOD or' IMPRovING MIcRowAx QUALITY Filed Nov. 28, 1960 mZON Omo.: mm mm Charles W. Siegmund Inventor By @04% f( Potent A'forneyl United States Patent O 3,119,762 METHOD QF EMPROVHNG MHCROWAX QUALITY Charles W. Siegmund, Morris Plains, NJ., assigner to Esso Research and Engineering Company, a corporation of Delaware Filed Nov. 2S, 1969, Ser. No.. 71,998 Claims. (Ci. 208-27) This invention relates to a process of refining hydrocarbon waxes that are derived from petroleum. More particularly, this invention is concerned with a process of making high molecular weight wax products which have high laminating strength, excellent color, odor, and stability. The present invention is concerned with high molecular weight wax recovered from residual crude oil fractions boiling above about 900 F. These waxes are known as microcrystalline waxes and are used in the manufacture of many products such as food containers, waxed papers and coating materials where it is desired that they be impervious to moisture. Specifically, this invention relates to a process of controlling the asphaltic content of the wax fed to a hydroning unit. Hydroning removes various impurities in the microcrystalline wax which effect properties desired in the end product.

Microcrystalline wax has been made by deasphaltng a residual crude oil to remove substantially all of the asphaltic materials, dewaxing the deasphalted oil to separate the wax from the lighter fraction, deoiling the wax obtained, and contacting the deoiled wax with an absorbent material such as bauxite, alumina, clay, etc., in order to improve odor, color, stability and other properties. It is known that poor color, odor and stability of hydrocarbon waxes are occasioned very often by the presence of polycyclic aromatic oily compounds (asphaltic materials) Within the wax which are not completely removed during the initial deasphalting step. Contacting the wax with bauxite, alumina, clay, etc., removes these materials to some extent. It has, however, been diiiicult to obtain wax products which are completely satisfactory in color, odor, and stability characteristics. It has been known for some time that treating petroleum products with hydrogen improves the odor, stability, and color of the product. However, attempts to hydroiine the deoiled high melting point microcrystalline wax have resulted in short catalyst life and products which did not meet the necessary requirements. Another problem which has prevented full commercial utilization of microcrystalline wax has been the inability to control laminating strength of the product wax and its requisite degree of hardness.

It has now been unexpectedly found that by carefully controlling the conditions in the deoiling zone, and by deasphalting (i.e., a second deasphalting step) the deoiled high melting point micro wax under conditions such that deasphalted wax contains between 3 and 5% of 2 and 3 condensed ring aromatics, that the hydroiining catalyst' is not deactivated, and that microcrystalline wax products of high laminating strength, excellent odor, color, and stability are obtained. It has been found that maintaining the 2 and 3 condensed ring aromatics in the micro wax feed to the hydroning zone below about 5% prevents poisoning of the hydrolining catalyst. However, in order to obtain maximum laminating strength of the microcrystalline wax product, it has been now unexpectedly found that it is necessary to have at least 3% of the 2 and 3 condensed ring aromatics in the deasphalted wax fed to the hydrofining zone.

An object of this invention is to make a microcrystalline wax which has high laminating strength, good color, odor and stability, in high yields, and which process does not cause poisoning of the hydroiining catalyst. Another object of the invention is to provide an improved hydroning process in which the catalyst activity is maintained at a high level, for a heretofore unobtainable length of time.

These and other objects are attained in accordance with the present invention by subjecting a residual crude oil fraction boiling above about 950 F. to a conventional deasphalting treatment, wherein a propane-butane mixture is used as a solvent and deasphalted oil yields of 40 to 50% by volume based on feed are obtained. The deasphalting conditions are such that the maximum amount of deasphalted oil is obtained consistent with the quality of said oil. If the conditions of deasphalting are severe enough to remove substantially all asphaltic materials in the iirst deasphalting step, about 15 to 25% loss in yield of the desired deasphalted oil would result. It is to be remembered that a high yield of deasphalted oil is desired for lube oil manufacture. On the other hand, if too high a yield of deasphalted oil is taken, the deasphalted oil is contaminated with metal contaminants such as vanadium and nickel, andvhas an undesirable amount of asphaltic materials present. The deasphalted oil is then subjected t0 a conventional propane dewaxing step which yields about 25% by volume, based on deasphalted oil, of petrolatum wax (depending on the crude source), and the dewaxed lube oil product is taken olf the top. In one embodiment of the invention where the process is used to make high quality lube oil, as well as high quality microcrystalline wax, it is desirable that the conditions of the initial deasphalting be carried out in such a manner that the maximum yield of deasphalted oil be obtained, consistent with the quality of said oil. The crude petrolatum microcrystalline wax obtained is subjected to a propane deoiling treatment at a temperature of -lO to 1-25 F. to yield 25 to 45% by volume of high melting wax. An oily low melting wax is separated. Although other solvents can be used in this deoiling step, it is desirable for economic reasons to use propane or propane-butane mixture as the deoiling solvent so that all of the solvents used throughout the process will be the same. Obviously, other solvents such as ethane, butane, pentane, and hexane, and mixtures thereof, can be used in the various processes herein described.

Now, in accordance with this invention, the deoiled high boiling microcrystalline wax which contains varying amounts of 2 and 3 condensed ring aromatics is fed to a second deasphalting tower where the conditions of deasphalting are controlled so that the deasphalted micro wax will contain 3 to 5% of 2 and 3 condensed ring aromatics. Within this range, deasphalted wax yields of between 70 to by volume, based on feed to the deasphalting tower, are realized. The deasphalting solvent that is used is propane, or a mixture of propane and butane; however, higher selectivity is obtained with propane. Ratios of propane to wax feed of 10/1 to 15/ 1 can be used. Deasphalting temperatures of to 180 F. can be used. The percentage of 2 and 3 condensed ring aromatics in the product wax is determined by ultraviolet absorption. Deasphalted micro waxes containing 3 to 5% of 2 and 3 condensed ring aromatics are fed at a rate of 0.25 to 1.0 v./v./hr. to a hydroiining zone. The micro wax is hydrofined at a temperature of 400 to 700 F., pressure of 400 to 1200 p.s.i.g. with a treat gas containing 70 to 100% hydrogen which is fed to the hydroining zone at a rate of 400 to 1200 s.c.f./b. Any of the conventional hydroining catalysts may be used; however, cobalt molybdate on alumina is preferred. Products obtained from this process have high laminating strength, good hardness properties, excellent color, stability and odor characteristics. By carefully controlling the percentage of 2 and 3 condensed ring aromatics in the micro wax feed to the hydroning unit, applicant has been able to extend the catalyst life, and has been able to obtain microcrystalline wax of excellent color, odor and stability, high laminating strength,

and desired hardness. An additional advantage obtained is that when the 2 and 3 ring condensed aromatics in the feed to the hydroner are maintained at a concentration of 3 to 5%, the hydroner conditions can be fairly constant, and hydrogen consumption maintained at a minimum.

The attached drawing is a flow diagram of the preferred embodiment of applicants invention.

Various crude residual fractions boiling above 900 F., preferably with initial boiling points of 1050 to 1200" F., can be used in applicants process to make micro waxes of improved quality. The feeds may be selected as to crude source depending on whether or not a lube oil is also to be made or whether only a micro wax is to be made, and depending on the desired qualities of the end product micro wax. Parat'lnic and mixed base residual crudes such as Northern Louisiana, Mississippi, and Panhandle crudes can be used.

The residual crude fraction is deasphalted in a conventional manner to obtain maximum yield of deasphalted oil consistent with quality of said oil. The asphaltic material is precipitated and removed as bottoms. A propane-butane solvent is used in the deasphalting step. Up to 50% butane may be used; however, as the percentage of butane increases, the yield of deasphalted oil increases but the selectivity decreases. The deasphalted oil and solvent are removed overhead. Yields of 40 to 50% by volume of deasphalted oil, based on the crude residuum, are usually obtained.

A conventional propane dewaxing step is used wherein the crude lube oil product is separated from the deasphalted oil and a crude petrolatum wax is precipitated.

The conditions of propane deoiling are carefully controlled as they affect the laminating strength of the micro wax end product. The deoiling is controlled in such a manner that a yield of deoiled wax of to 45% by volume based on feed to the deoiling zone, preferably to and specifically about 35%, is obtained. The deoiling can be carried out at temperatures of -15 to +35 F., although temperatures of about -5 to +5 F. are preferred. Pressure is not critical and is determined by the operating temperature. Ratio of propane solvent to petrolatum wax of 3 to 10 can be used, although a ratio of 6 to 8 is preferred. Control of the percentage yield of deoiled wax is obtained by varying the temperature and the solvent ratio at which the deoiling is carried out. The percentage of oil that remains in a deoiled wax affects the laminating strength of the end product as well as its hardness. To obtain maximum laminating strength having a suitable hardness for most practical uses, a percentage yield of deoiled wax in a range of 25 to 30% by volume is desired when deoiling a typical petrolatum of about 20% oil content. For example, a yield of 28% by volume of deoiled wax from a Panhandle petrolatum resulted in a laminating strength of the end product of 240 grams per inch and of a hardness of 17.8 ACH at F.

The initial deasphalting step was carried out so `that maximum yield of deasphalted oil was obtained consistent with quality of said oil. It is found that the deoiled Wax contains sufficient amounts of 2 and 3 condensed ring aromatics (asphaltic materials) to poison the hydroining catalyst, and prevent effective hydroning of the deoiled wax. Applicant has now found that by carefully controlling the subsequent deasphalting step so that the deasphalted wax contains 3 to 5% of 2 and 3 condensed ring aromatics, the hydrofining catalyst is not poisoned and that microcrystalline wax of high laminating strength is obtained. Propane is used as a deasphalting solvent (in the second deasphalting step) with a ratio of propane to micro wax feed of 3/1 to 15/1, preferably 10/1 to 15/1. The deasphalting is carried out at a temperature of to F., preferably at about 145 to 155 F. The pressure is not critical, except that is should be such that the reactants are maintained in the liquid phase. Deasphalted wax yields of between 70 to 90% by volume have been obtained containing 3 to 5% of 2 and 3 condensed ring aromatics. Preferably, the 2 and 3 condensed ring aromatic concentration shouldbe about 3.5 to 4.5%. The concentration of 2 and 3 condensed ring aromatics pres ent in the deasphalted wax is related to the yield of deasphalted wax.

The deasphalted wax is fed to a hydroning zone at pressures of 400 to 1200 p.s.i.g., preferably at 600 to 1000 p.s.i.g. The percentage of hydrogen in the treat gas is not critical and can vary between 50 and 100%. Temperatures of 400 to 700 F. can be used; however, temperatures of 550 to 650 F. are preferred. The micro wax is fed to the hydroning zone at a rate of 0.25 to 1.0 v./v./hr., preferably a rate of 0.25 to 0.6 v./v./hr. is used. In some instances, depending on the percentage of hydrogen and the pressure, rates of 0.4 to 0.6 v./v./hr. are used. Hydrogen is fed at the rate of 400 s.c.f./b. to 1000 s.c.f./b. Preferably, hydrogen is fed at the rate of 600 to 700 s.c.f./b. and is consumed at a rate of about 25 to 50 s.c.f./b. While hydrolining improves color, odor and stability, it generally effects a reduction in laminating strength, as compared to the deasphalted wax fed to the hydroning unit. Apparently the same reaction that improves the color and stability of the micro wax in changing the chemical nature of the highly cyclic materials remaining also affects the laminating strength. It appears that the microcrystalline materials have some effect, in conjunction with the percentage of oil remaining in the micro wax, on the laminating strength of the end product. Any conventional hydroning catalyst may be used, however, cobalt molybdate on alumina is preferred. The reaction is carried out in the liquid-vapor phase, that is, the reaction is carried out primarily in the liquid phase with some vapor present.

An understanding of various aspects of the invention may be aided by referring to the accompanying drawing and the discussion thereof.

The drawing is a schematic flow diagram showing one arrangement of apparatus which may be used in the practice of one embodiment of the invention. It will be readily appreciated that this drawing is in the nature of a diagram and that numerous pieces of equipment, including pumps, heat exchangers, etc., are not shown. Referring now to the drawing, a crude residual fraction is fed through line 1 to deasphalting tower 2 and subjected to conventional deasphalting treatment. Asphaltic materials are withdrawn from the bottoms through line 4. The deasphalted oil solvent layer is taken overhead through line 5 to stripper 6, wherein the propane solvent is stripped off and recycled through line 7. The deasphalted oil is withdrawn through line 8 and fed to dewaxing zone 9. Dewaxing is carried out in a conventional manner and dewaxed crude lube oil product is removed through line 10. The crude petrolatum micro wax is transferred via line 11 to deoiling zone 12. On entering the deoiling zone, the petrolatum is solvent deoiled to obtain 25 to 45% by volume wax yield which is Withdrawn by line 14 and charged to tower 15. In deasphalting tower 15, the deoiled high melting point wax feed is introduced part way up the tower and flows down through the tower and contacts a rising stream of propane solvent which enters the tower through line 16. As the solvent contacts the feed, the asphalt residue is dissolved out under such conditions that only 3.5 to 4.5% of 2 and 3 condensed ring aromatics remain in the deasphalted wax. The deasphalted wax is removed via line 18 and the propane solvent removed by stripper 19. The stripped solvent is taken overhead and recycled via line 20. The deasphalted wax now contains between 3.5 and 4.5% of 2 and 3 condensed ring aromatics. The stripped wax is fed to the hydroning zone 23 via line 19 at a rate of 0.4 to 0.6 v./v./hr., at a temperature of 550 to 650 F., and at a pressure of about 600 to 1000 p.s.i.g. Hydrogen is fed at a rate of 600 to 700 s.c.f./b. Excess hydrogen is removed by line 24 and recycled to line 22. Microcrystalline wax product is removed via line 2S and taken to storage.

The microcrystalline wax product produced in accordance with applicants invention has high laminating strength, the desired amount of hardness, excellent color, odor and stability characteristics. These make it particularly desirable for use as food wrappings, waxed coated materials which are self-sealing, and various other uses where these particular qualities are desired.

Having described the principal features of the invention, attention is now directed to the following examples which illustrate some of the advantages to be gained by use of this invention.

EXAMPLE 1 A crude Panhandle residual oil fraction is treated in a deasphalting tower in a conventional manner to yield about 45% by volume deasphalted oil. The deasphalted oil is stripped to remove the solvent and is fed to a dewaxing zone where it is dewaxed in a manner known to the art to yield about 27% by volume crude petrolatum micro wax based on the feed to this unit and a crude lube oil fraction. The micro Wax is separated and subjected to a solvent deoiling at a temperature of about 0 F. with a sufficient amount of solvent to yield about 28% by Volume based on micro wax feed of a deoiled high melting micro wax. An oily, low melting wax is also removed from the deoiling zone. In accordance with a specific embodiment of applicants invention, the deoiled high melting wax is fed to a second deasphalting tower with a solvent feed ratio of about 7/1 to 9/1, at a temperature of about 152 F., at about atmospheric pressure to give an 80% by volume yield of deasphalted wax. The wax is analyzed by means of UV absorption and found to contain 3.2% of 2 and 3 condensed ring aromatics. The deasphalted wax, after solvent stripping, is fed to a hydroning zone at a rate of about 0.50 V./ v./hr. at a hydrogen pressure of about 600 p.s.i.g., and at a temperature of 600 F. Hydrogen is fed to the hydroning zone at a rate of about 600 s.c.f./b. The hydroned micro wax product is analyzed and tested and found to have a color of 12 TR, excellent odor and stability, and a laminating strength of about 240 grams per inch.

EXAMPLE 2 Another crude Panhandle residual fraction is processed in a manner similar to Example l, with the exception that a 50% by volume yield of deasphalted oil is taken from the first deasphalting tower, a 30% by volume yield of wax is obtained from the deasphalted oil :fed to the dewaxing zone, and the deoiling step is carried out at about 2 F. and yields 33% of a deoiled high melting point wax. The second deasphalting step is carried out with a solvent to feed ratio of about /1 at a temperature of about 147 F. to yield 70% deasphalted wax. The deasphalted w-ax is analyzed by UV absorption and found to contain 4.2% of 2 and 3 condensed ring aromatics. The propane solvent is stripped from the deasphalted wax and the wax is fed to a hydrofning zone at a rate of 0.38 v./v./hr., under an atmosphere containing 70% hydrogen (the remainder being inert gas) at a pressure of 1000 p.s.i.g., and at a temperature of 550 F. Hydrogen is fed to the hydrofining zone at a rate of about 700 s.c. f./b. It is found that the severity of hydroning apparently has an effect on the laminating strength of the end products. The hydroiined micro wax product is analyzed and has a 12.8 TR color `and a laminating strength of about 220 grams per inch.

EXAMPLE 3 A Panhandle micro wax obtained in accordance with process of Example 2 (this is the product wax obtained after the deoiling treatment) was, for purposes of comparison, hydroined as received and also hydroned in accordance with this invention. The micro wax that was not subjected to the second deasphalting step contained 6.5% of 2 and 3 ring aromatics, and on hydrofining was found to deactivate the catalyst within 24 hours. The hydroning unit was operated at 600 p.s.i.g., 600 F., 70% hydrogen concentration, and a feed rate of micro wax of 0.50 v./v./hr., and hydrogen treat gas of 700 s,c.f./b. Another portion of the Panhandle micro wax, in accordance with applicants invention, was subjected to a second deasphalting step and was `deasphalted to a by volume `deasphalted wax yield. The deasphalted product contained 4.2% of 2 and 3 condensed -ring aromatics and `was hydroined under the same conditions as the first micro Iwax sample. The hydroiining catalyst was used for 500 hours, gave a product of 12| 'T-R, and there was no evidence of catalyst deactivation. The laminating strength of the deasphalted wax was 260 grams per inch. Other deasphalting studies on the same wax showed that deasphalting to a lower yield of micro wax would have given a substantial reduction in vlaminating strength.

The wax used contained no condensed aromatics of 4 rings or higher. These materials, if present, would have been removed either by the rst deasphalting step or by the deasphalting conditions which subsequently reduced the 2 and 3 ring aromatics to about 4%.

EXAMPLE 4 In order to show the effect of the concentration of 2 and 3 condensed ring aromatics on the laminating strength, a Panhandle wax obtained in accordance with the process described in Example 2 was deasphalted under various conditions of severity to obtain different yields of deasphalted Wax and of 2 and 3 condensed ring aromatics. It can readily be seen by Table I below that as the concentration of 2 and 3 condensed ring aromatics decreases, that the laminating strength of the deasphalted wax also decreases.

l Parailns, naphthenes, and one-ring aromatics.

T o obtain a satisfactory micro wax product, it is necessary that the 2 and 3 condensed ring aromatics be between 3 and 5% as a higher concentration deactivates the hydroning catalyst, giving a poor color and other quality characteristics. A lower concentration of 2 and 3 ring aromatics gives a product of Ilow laminating strength. Applicant has found that by carefully controlling the concentration of 2 and 3 ring aromatics in the deasphalted wax, that a wax of maximum laminating strength, excellent color and stability characteristics, :and one which does not deactivate the hydroning catalyst can be obtained.

It is understood that the invention is not to be limited to the specific examples which have been offered merely as illustrations, and that the invention is only to be limited by the :attached claims.

What is claimed is:

l. In the process of making microcrystalline Wax which comprises deasphalting a crude residual oil fraction, dewaxing the deasphalted oil to obtain a lube oil fraction and :a crude petrolatum wax, and deoiling the petrolatum wax, the improvement which comprises subjecting the deoiled wax to a second deasphalting treatment at a temperature of to 155 F. with a propane to feed ratio of about 10/1 to 15/1 to yield 70 to 90% by volume of deasphalted wax which contains 3.5 to 4.5% of 2 and 3 condensed ring aromatics and subjecting said deasphalted wax to 'a catalytic hydroning treatment.

2. The process of claim 1 wherein the deasphalted wax is hydroned at a temperature of 600 to 700 F., pressure of about 600 to 1000 p.s.i.g. in the presence of a treat gas containing 70 to 100% hydrogen with a flow rate of wax feed of 0.25 to 0.60 v./ v./ hr. and a hydrogen feed rate of 600 to 700 s.c.'f./b.

3. In the process of making microcrystalline wax which comprises deasphalting a crude residual oil fraction, dewaxing the deasphalted oil to obtain a lube oil fraction and a crude petrolatum wax, and deoiling the petrolatum wax, the improvement which comprises subjecting the deoiled wax to a second deasphalting step with propane to a feed ratio of about 10/1 to 15/1 to yield deasphalted wax which contains about 3 to 5% of 2 and 3 condensed ring aromatics and subjecting said deasphalted wax to a catalytic hydrofning treatment.

4. The process of claim 3 where the volume of deasphalted wax is 70 to 90%.

5. The process of claim 3 wherein the deasphalted wax is hydroned at a temperature of 600 to 700 F., pressure of about 600 to 1000 p.s.i.g. in the presence of a treat gas containing 70 to 100% hydrogen with a llow rate of wax feed of 0.25 to 0.60 v./v./hr. and a hydrogen feed rate of 600 to 700 s.c.f./b.

References Cited in the le of this patent UNITED STATES PATENTS 2,848,385 Arabian et al Aug. 19, 1958 2,915,448 Annable et a1. Dec. l, 1959 2,956,001 Spars et al. Oct. 11, 1960 3,012,960 An'astasoi Dec. 12, 1961 3,014,002 Beggs Dec. 19, 1961

Claims

1. IN THE PROCESS FOF MAKING MICROCRYSTALLINE WAX WHICH COMPRISES DEASPHALTING A CRUDE RESIDUAL OIL FRACTION, DEWAXING THE DEASPHALTED OIL TO OBTAIN A LUBE OIL FRACTION AND A CRUDE PETROLATUM WAX, AND DEOILING THE PETROLATUM WAX, THE IMPROVEMENT WHICH COMPRISES SUBJECTING THE DEOILED WAX TO A SECOND DEASPHALTING TREATMENT AT A TEMPERATURE OF 145* TO 155*F. WITH A PROPANE TO FEED RATIO OF ABOUT 10/1 TO 15/1 TO YIELD 70 TO 90% BY VOLUME OF DEASPHALTED WAX WHICH CONTAINS 3.5 TO 4.5% OF 2 AND 3 CONDENSED RING AROMATICS AND SUBJECTING SAID DEASPHALTED WAX TO A CATALYTIC HYDROFINING TREATMENT.