US2660553A - Wax composition and process for producing wax - Google Patents

Description

Nav. 24, 1953 Filed Feb. 23, 1951 Wiliam. TMzoxe/r Bmx/encor @www Patented Nov. 24, 1953 mma WAX COMPOSITION AND PROCESS FOR PRODUCING WAX WilliamV '1`. Knox, Jr., Cranford N. J., assigner to Standard Oil Development Company, a cor-` poration of Delaware Application February 23, 195,1, SeiaNa 212,295,

Claims. l

This invention concerns wax having novel and unusual physical properties derived from a novel combination of processing steps. In accordance with this invention, a uniquely desirable wax is obtained by subjecting the cycle oil obtained from catalytic cracking operations to a solvent extraction operation after which the rafnate of the extraction operation is de-waxed to provide the nal wax product.v The wax thus obtained is characterized by a hardness and flexibility peculiarly adapting the Wax for application in food wrapping services and for other uses.

While wax may be obtainedV in a number of ways following differing processing techniques, at the present time most waxes are obtained by de-waxing distillate fractions of crude oil such as the lubricating oil fraction. It is now generally appreciated that the conventional paraiiin wax obtained from this source is characterized by the presence of hydrocarbons which are predominantly normal paraflins. Vvax obtained by the de-waxing of lubricating oil stocks, presumably by virtue of its hydrocarbon composition, is for many purposes unduly inflexible. High flexibility has been found to be related to good performance of waxes as coating material at low temperatures. Hardness is again an important characteristic governing in part the ability of the wax to withstand rough handling and chipping. Flexibility and hardness control n the permeability characteristics of a waxv coating, since the two properties in combination materially aid in preventing breakage of the wax nlm and the consequent moisture leakage which can occur on breakage. As a result of' these factors, for many applications and in particular for the coating of paper used in packaging food, it is desirable to secure wax having high nexibility while being comparatively hard in nature. It is therefore the principal object of this invention to provide a novel typo of wax having improved properties of hardness and flexibility.

As herein disclosed, a flexible wax having desirable hardness may be obtained by a processing sequence applied to the gas oil fraction of a crude petroleum oil. The gas oil fraction of crude petroleum, boiling in the range of about 700 to i100" F. is iirst subjected to a catalytic cracking operation. The heaviest boiling oil obtained from the catalytic cracking, that is, boiling in the range of about 700 to 1100o F., is then subjected to a treating operation to selectively re,- move the more aromatic constituents. This may be accomplished by a selective absorption process utilizing an absorbent such as silica gel, activated coke., clay', etc. Alternatively, the aromatic constituents. may be, selectively removed by a solvent extraction operation employing a solventwhich selectively removes the aromatics, leaving a raiiinate substantially free of aromatics.. This intermediate product, substantially free of aromatics. is then subjected to a cle-Waxing operation ser as to permit the recovery of wax therefrom.. 1t is thisl wax which has the unusual properties referred to.l

On analysis and by way of a theoretical explanation of what iS. IlVQlVQd. il?l appears. that theV wax obtained from this processing sequence is characterized by hydrQCar-bon constituents which are more cyclic or isoparaiinic in nature than inthe case Qf ordinary conventionally rened wax. The processing sequence followed is of a nature to provide this result. It is significant that waxes obtained by this processing technique are materially d iierent than the naturally occurring; Dalan waxes or microcrystalline waxes. InY effect the processing employed to provide theV waxes of this invention is eective to synthesize a wax differing from normal wax characteristics as a result of the` cracking and aromatic extraction procedures employed.

To fully disclose the nature of this invention and the manner inY which the invention is practiced, reference is made to the, accompanying drawing, illustrating a diagrammatic low plan of the process to be followed in obtaining the novel waxof this invention.

Referring now to the drawing illustrating the entire integral process to be employed, numeral I designates a crude petroleum distillation zone. A crude petroleum oil such asa mixed base crude oil is introduced to: distillation zone i through line 2r. The distillation operation is conducted to permit removal of volatile fractions overhead through line 34 and of heavier boilingy products such as gasoline, kerosene and heating oils through side stream withdrawals 5;, and so on. The heavier boiling fractions having initial boiling rangesof fromSOQ to 1109 F. and higher are withdrawn as a side stream productV through line 7. It is particularlyV contemplated that in the practice of this invention, distillation zone l be of such a nature as to provide a higher boiling fraction boiling in the range of about rco to 1100-o F., preferablyl as obtained by vacuum distillation operations. This fraction is then conducted to a catalytic cracking zone identified by Athe rectangle 8. The cracking operation to be conducted inA renc` 8 isv of any desired type employing a catalyst such as modined natural or synthetic clay or gel type catalysts. Examples of these are montmorillonite clays, silica-alumina, silica-magnesia composites, and other conventional cracking catalysts. The operation may be of a continuous or batch nature employing fixed beds, moving beds, fluidized, or suspensoid systems. The heat required for cracking may be supplied as preheat of processed materials and/or as the sensible heat of exothermically regenerated catalyst or in any other conventional manner. The cracking is carried out at temperatures of about 800 to 1000 F., and pressures of about atmospheric to 25 p. s. i. g., or higher. rIhe total cracked products are removed from cracking Zone 8 and are conducted to a product fractionator 9. Fractionator 9 is operated to remove lighter fractions of the cracked products through overhead IU, side streams Il, I2 and so on. A bottoms product is obtained from fractionator 9 which may be removed through line i4. In the event the cracking operation conducted in zone 8 was of a 'lluidized nature, the material withdrawn through line l will contain a small percentage of catalyst particles carried over from Zone 8. In this case. it is necessary to pass the product stream of line Ill to a settler l5 or otherwise to process the stream to permit separation of the liquid hydrocarbon product from the catalyst. Thus, a clarifled hydrocarbon stream is removed from Zone l5 through line I6. For the purposes of this invention, the bottoms product of fractionator 8, corresponding to the stream of line I4 or i6, boils in the range of about 700 to l100 F. The stream of line i8 is generally called cycle oil. As the name suggests, cycle oil is generally recycled to the cracking zone, as heretofore virtually no other use has been found for this oil. However, it should be appreciated that return of cycle oil to the cracking operation is not particularly desirable. Cycle oil is refractory in nature and constitutes a very poor cracking feed, causing substantial deposition of carbon and coke on the catalyst employed during cracking, As will be appreciated therefore, it is one of the features of this invention to employ cycle oil so as to prevent recycling to a cracking operation and so as to provide valuable products.

As the conduct of the process as described heretofore is well known to the art, no further description of this phase of the process is considered necessary. The cycle oil of line I6, derived as indicated, is then conducted to a zone for the selective removal of aromatic constituents. As formerly suggested, this zone may employ an adsorbent such as silica gel which will selectively adsorb aromatic constituents. The aromatic constituents may be removed by adsorbent treatment in fixed bed or counterow operations as well known to the art. Alternatively, the aromatic constituents may be selectively removed by a solvent extraction operation. It is this specific embodiment of the invention which is illustrated in the drawing. Thus, in order to remove the aromatic constituents by solvent extraction, the stream of line IG is conducted to solvent extraction zone It. Zone I9 may be arranged as a countercurrent liquidliquid contacting tower, if desired, provided with pierced plates, packing, or other means for securing efficient liquid-liquid contacting of the oil and the solvent employed.

As is well known, a variety of solvents may be employed to secure the desired selective removal of aromatic constituents. Thus, for example, sulfur dioxide, phenol, furfural, nitrobenzene, ammonia and other solvents, alone or in conjunction with solvent modifiers, may be employed. While the contacting of the solvent and o1l may be conducted in any desired contacting equipment of a batch or continuous nature, countercurrent treating technique is preferably employed. In such a system, the oil feed of line 1E is introduced to a countercurrent contacting tower le at a point near the bottom thereof. A solvent such as phenol is introduced at an upper portion of the tower through line 20. About a to 350 volume percent treat is used. The oil passes upwardly through the tower while the solvent passes downwardly through the tower, permitting removal from the bottom of the tower of what is known as an extract phase through line 2|. The extract phase will consist principally of the solvent such as phenol together with the constituents selectively extracted from the oil consisting principally of aromatic hydrocarbons. The extract phase may be disposed of as desired. In fact, the hydrocarbons contained in the extract phase are valuable in providing a source of aromatic hydrocarbons suitable for use as plasticizers, iiuxing agents, etc. The material withdrawn from the top of tower I9 through line 22 is known as the raffinate phase and consists principally of the initial oil feed minus the aromatic constituents originally present in the feed, admixed with small proportions of the solvent employed during the contacting. The raffinate phase withdrawn from solvent extraction Zone i9 through line 22 is then passed to dewaxing zone 30. The de-waxing operation conducted in zone 30 may be chosen from any of the conventional de-waxing processes of a nature to reduce the wax content of the hydrocarbon fraction treated to any desired extent. .In general, it is preferred that a solvent de-waxing operation be employed. For example, the hydrocarbon oil of line 22 may be diluted with about 2 to 4 parts per volume with a solvent such as propane or methyl ethyl ketone, including a minor portion of aromatic hydrocarbons such as benzene or toluene if desired. Any aliphatic ketone, or mixtures thereof, having from three to six carbon atoms may be employed as the dewaxing solvent. The mixture of hydrocarbon oil and solvent is then heated suiciently to secure the solution of all wax present. A temperature of about 150 F. is generally suitable. Thereafter, the mixture of oil and solvent is cooled to a temperature of about 25 F. to 40" F., so as to secure the crystallization of the wax present. The chilled mixture of oil, solvent and wax is then ltered to eliminate this wax, permitting removal from zone 3E! of a dewaxed hydrocarbon oil, and permitting removal from zone 3) of a wax product. It may be observed that the dewaxed hydrocarbon oil is a valuable lubricating oil stock characterized by a high viscosity index. Alternatively, if desired, this dewaxed ramnate may be employed as a cracking stock, being well adapted for cracking and being free of the disadvantages characteristic of cycle oil. The wax obtained from the dewaxing zone 30 is suitable for use as the final product of this process. The wax is then subjected to further refining operations such as solvent de-oiling, to reduce' the oil content of the wax, percolation for color and odor improvement, or other conventional finishing processes.

A s a specific example of this invention, a gas oil was subjected to a fluidized catalytic cracking operation. The gas oil boiled in the range of about 650 to 1100 F., and was derived from a mixture of West Texas and similar types of crude oil. The products of the catalytic cracking operation were fractionated and treated to provide a claried cil boiling in the range of 700 to 1100 This clarified oil was then subjected to contact with a selective solvent consisting of phenol containing 7% of water as a solvent modifier. Contact was carried out in a contacting tower providing seven extraction stages'while injecting 2.8% of water at the ram'nate outlet end of the extraction system; a 160% treat of solvent by volume based on the feed was employed. The rafdnate from this extraction operation was topped so as to secure the fraction boiling in the range of 700 to 1100 F.; thereafter the raffinate was dewaxed by mixing the ranate with 300 volume percent of secondary butyl acetate, heating to about 120 F., and cooling to 0 F. The wax thus precipitated was filtered and remixed with 3 volumes of secondary butyl acetate at 0 F., thereafter the wax was filtered from this mixture as the final product.

Data relative to this experiment are given in Table I below, showing the yield and inspections of the diierent products obtained.

TABLE I by holding one end rmly in a vise in a vertical position and displacing the strip with a micrometer at a distance of one inch from the vise jaws until the first sign of a crack appears in the strip. The micrometer extension required is recorded and the thickness of each specimen is measured. Six samples are broken for each thickness determined; three of the samples are broken with the air cooled side facingthe micrometer, and three samples are broken with the water cooled side facing the micrometer. The micrometer extension determined in this test is expressed in thousandths of an inch and is reported as fiexibility.

The hardness test was conduc'ted employing an Abraham consistometer of the nature described in the Chemistry and Technology of Waxes, published by the Reinhold Publishing Company.

In considering the data shown in Table II, it may be noted that the catalytic wax obtained in accordance with this invention is similar to paraffin waxes in melting point and refractive index, but diiers somewhat in viscosity and specie gravity. Most important, however, the wax of this invention is greatly different from parafiin wax in flexibility although having comparable hardness. The fact that the two wax compositions are actually materially different is also borne out by the higher mid-boiling point of the Extraction and dewaxz'ng of catalytic cycle stock l Extrapolated values.

For comparative purposes the corresponding inspections of a conventional refined wax derived from dewaxing of the lubricating oil cut of a crude petroleum oil and of a microcrystalline wax are also given.

wax of this invention 'as compared to conventional rened paraiiin wax.

In comparing the wax of this invention to micro-crystalline wax, it may be noted that the waxes are similar in melting point, oil content TABLE II Catalytic Refined Microcrystalllne Melting point, (ASTM) 134 134435 136 1110 Percent, oil, ASTM 1. 7 0. 3-0. 4 2. 4 1.5 Refractive index at 153 F. (67 C.) l. 433 1. 434-1. 435 1. 442 1. 453 Specific gravity (60 F., 1iquid) 0.818 0.809 0. 842 0. 864 Flexibility at 73 F., 0.001 450 (S6-70 750 750 Abraham hardness at 100 F 19. 4 15-25 10 10 Viscosity at 210o F. (es.) 3. 7 3. 8 6. 6 13. 1 Distillntion at l mm., F

5% at 422 380 t160 495 5 to 95%, F 198 110 160 175 The properties of particular interest reported in Table II are the iiexibility and hardness of the waxes. The flexibility test employed was conducted by forming a wax disc by pouring a weighed sample of wax on the surface of boiling distilled water in a crystallizing dish providing a given surface area. The wax is then allowed to cool for two to three hours and the discs are then cut into strips 3 x 5". The strips are then placed on a smooth brass plate and cooled to 40 F. in a cold room for 16 hours. A Wax strip is broken aecaeec l ing after removal of the aromatic constituents. As emphasized, the wax obtained is unusual as regards its properties of hardness and flexibility, differing materially in these characteristics from waxes obtained by conventional processing.

What is claimed is:

l. A process for producing a moderately hard flexible Wax comprising the steps'of catalytically cracking a gas oil feed stock boiling in the range of about 650-1100 F., fractionating an oil fraction from the cracked products boiling in the range of about 700-1100'J F., selectively removing aromatic compounds from the said oil fraction, and thereafter segregating wax frcm the said fraction remaining after selective removal of aromatic compounds including the step of deoiling the said Wax.

2. The process defined by claim i in whichthe said selective aromatic removal is conducted by solvent extraction.

3. The process dened by claim 1 in which the said selective aromatic removal is conducted by adsorbent treating.

4. 'In the production of wax, the improvement which comprises segregating wax from catalytic cracking cycle stock boiling in the range of about 700 to 1100* F. which has been treated to selectively remove aromatic constituents and deoiling the said segregated Wax.

5. A Wax having a melting point of about 134 F., a refractive index at 153 F. of about 1.43, a specic gravity (liquid at 60 F.) of about 0.82, an Abraham hardness at 100 F. of about 20, a exibility at 73 F. of about 450, and a mid-boiling point at 1 mm. mercury of about 460 F.

WILLIAM 'I'. KNOX, Ja.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,937,518 Henderson et al. Dec. 5, 1933 2,017,432 Bahlke Oct. 15, 1935 2,127,668 Adams et al Aug. 23, 1938 2,378,762 Frey June 19, 1945 2,429,875 Good et al Oct. 28, 1947

Claims (1)

1. A PROCESS FOR PRODUCING A MODERATELY HARD FLEXIBLE WAX COMPRISING THE STEPS OF CATALYTICALLY CRACKING A GAS OIL FEED STOCK BOILING IN THE RANGE OF ABOUT 650-1100* F., FRACTIONATING AN OIL FRACTION FROM THE CRACKED PRODUCTS BOILING IN THE RANGE OF ABOUT 700-1100* F., SELECTIVELY REMOV-

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