US2406210A - Method of controlling wax sweating - Google Patents

Description

Patented Aug. 20, 1946 f f UNITED STATES PATENT OFFICE :METHOD OF CONTROLLING W SWEATING Seymour W. Ferris, Mount Holly, N. J., assig'nor to The Atlantic Refining Company, Philadelphia, lra., a corporation of Pennsylvania Application octber 19, 1942, serial No. 462,653

' 7 claims. (c1. 19e-'20) 1 Y The present f'invention relates VVto the sweating of oily wax to reduce the oil content thereof, and relates more particularly to improvements in controlling the sweating of such wax.

An object of this invention is to control wax sweating in such a manner as to produce high yields of wax of reduced oil content without substantial loss of desirable wax in the sweat oil.

` A further object of this invention is the appli-- 'products of reduced oil content. For example,

a commercial product such as scale wax contains from 8% to 10% of oil, whereas fully rened paraflin wax contains less than about 4% ofoil, and high tensile strength parain wax contains less than 1.5% of oil, all of the oil contents being determined by treatment with ethylene dichloride as described more fully hereinafter.

Heretofore, in the sweating of oily wax, it has been very diiicult to judge when the oil has been completely removed, or removed to the desired extent, from the wax remaining in the sweating pans. This diiculty arises from the fact that it is practically impossible to obtain a sample representative of all of thewax remaining in the sweating pans, and in addition, the determination of the oil content of the sweated wax by a selective solvent method is time-consuming. When more than one cycle of sweating is employed for the production of afully sweated wax, there is a greater likelihood that the nal product will be substantially oil-free, but when single cycle sweating is carried out, the determination of the proper time to terminate the sweating becomes more important, since stopping too soon results in incomplete oil removal and low tensile strength, and if each run is carried far enough to insure the lproduction of high tensile strength wax, the average yield of the wax will be reduced.

It has been found that one of the most distinctive properties of a wax is the relationship between its melting point and its refractive index .measured at some temperature above its meltexperimentally sweated wax.

ing point. For convenience, the `melting `point is determined in accordance with A. S. T. M. Method D87-37 Melting point of paraliin wax, and the refractive index is measured at 176 F. in a suitable refractometer.

In accordance with the present invention, use is made of the relationship of the melting point and refractive'index of the sweated wax and the sweat stream in controlling the duration of the sweating operation. More specifically, a sample of an oily wax is experimentally sweated by slowly raising the temperature of the mixture, and successive samples of the material sweated from the mixture, i. e., the sweat stream, are taken. The meltingl point, refractive index, and oil content of each of the samples is determined, and the oil content of the sweated wax may also be determined at each interval at which a sweat stream sample is taken. YFrom the'refractive index-melting point relationship of the sweat stream samples and the oil contents of the sweat stream and sweated wax samples, it is thus possible to determine experi-mentally the point Vat which sweating should be stopped in order to obtain a nal wax having a desired oil content. The results thus determined experimentally for a given wax stock may then be applied directly to the control of a large scale commercial sweating operation. For example, a given wax stock is sweated on large scale and successive sweat stream samples are taken. The melting point and refractive index of each sample is determined as rapidly as the sample is taken from the sweat stream. When the refractive index-melting point relationship of a sweat stream sample is found to correspond to an experimentally determined value indicating a known oil content in the experimentally sweated wax or sweat stream sample, the large scale sweating operation is stopped and the resulting sweated wax will be found to have, substantially the same oil content as the Thus, by simply determining the refractiveindex-melting point relationship of a sweat streamV sample from a commercial sweating oven and comparing it with the refractive index-melting point'relationship of sweat stream samples predetermined experimentally for sweated wax of'known oil content, it isy possible to control closely the large scale sweatingiof wax and to stop the sweating at ex; actly the proper time so that the wax is neither under-sweated nor over-sweated. Since the refractive index and melting point of the sweat `stream samples are easily and rapidly deterthe refractive index and melting point for sweat Manufaturing Company, the aurometer scale being calibrated from zero to 100. The 100 durometer reading indicates no penetration, while thev zero reading indicates complete penetration. Tensile strength of thewax isgiven in lbs/square inch.

stream samples from a commercial slack wax, and the correlation of such -relationship with the oil'k content of the sweat stream samples and of the sweated wax.

Sweat stream Sweated wax Y Hardness R. I., P., Percent` P., Percent Weight per- Tensile 176 F. F. 'o F. oil cent yield strength E 111382 95 `37.5 Y F 1 .4350 99 28 .5 G l .4291 109 14.9 Y:El: 1.4280 115 8.6 126.6 2.0 29.8 I -1 .4273 120 4.1 129 l .0 23 .2 30 0 132 J l .4275 127 .5 1 .1 133 .5 0 .3 6 .3 90 30 378 Referring to the drawing, in which-refractive index is plotted against melting point, the lines AB and CD represent the limits within which lie the majority of the hydrocarbons present in substantially oil-'free waxes. The pure straightchain parain hydrocarbons will be foundV to lie along theline AB, whereas the substantially Voilfree waxes may lie vanywhere within the area defined vby AB and CD. The equation for the line AB is.11.=`1.3950+.000242T, and the equation for the line CD is n=l.3793+.0004T, n being the 'refractive index at 176 F., and T being the A. S. T. M. melting pointfF.

, Upon the drawing is also plotted a curve defined by the points E, F, G, H, I, and J, representing Ythe refractive index-melting point relationships of successive sweat stream samples from an experimentally sweated vheavy paran slack wax having an initial oil content of 33.4% by weight and a melting pointof 106 F. The oil content of the slack wax, aswell asthat of the sweat stream samples and sweated wax, was determined by the following method.

25 grams of oily wax is dissolved in ethylene vdi'chloride 'and made upto 500 cc. at room temperature F.) the solution is then cooled with 4'stirring to 5 F. and filtered at such temperature through rapid filtering qualitativeY filter paper. The wax on the filter is then thoroughly washed f with ethylene dichloride at 5 F., and an aliquot portion of the filtrate cc.) measured at room ene dichloride has been removed, in order to facilitate Vthe removal of the Ylast traces ofthe solvent. IThe oilv residue isweighed and multiplied Referring again to the drawing, the constituents of a hydrocarbon wax, such as asubstantially oil-free parafn Wax, have refractive indexmelting point relationships which f all within Ythe area defined by the lines AB and CD. Liquid constituents of parain distillate, however, Vexhibit relatively high refractive indices, and when the refractive index-'melting point relationship of the first sweat stream sample is found to lie, for example, at point E, it is'mmediately known `that considerable oil is present. When Ythe slackwax is subjected to further sweating, however, the sweat stream shows progressively less oil Vand therefore the points will be found to movev to the left as indicated at F, G, H, and I on the drawing.

rise, due to the increasing melting points, and

inasmuch as such samples areapproaching the composition of substantially pure wax (point J Y'the pointsl will roughlyr parallel the line, 'When 'such condition is reached, the wax remainingin the sweating pans is substantially freeofV oil. For any particular waxstock, it may bedetermined experimentally how close the refractive index-melting pointk value yof the sweat stream must approach the line AB before the 'sweated by a factor to correct forV the aliquot portion of Y the ethylene dichloride filtrate employed. I The corrected value Vis the weight per cent of oil inthe In the following table are given the refractive indices (R. 1.)', melting` points (M. P.)-,- and oil contents for the sweat stream samples E, F, G, H, I, and J as well as the melting points, oil contents, yields, hardness, and tensile Vstrength for the sweated waxes whenthe sweating was stopped at points I-l, I, and J. The hardness was determined b'y means of Aan instrument known as la durometer supplied by the Shore Instrument .wax remaining'inthe pans is of desired quality.

Each wax stock has a particular curve of its own, and the position of the Vcurve on the accompanying drawing may change as either the vboiling range or the sourceof the wax distillate, and therefore the wax stock, varies.

In order to produce from a slack wax stock having an oil content of from 25% to 40% by weight, a commercial grade Vof scale wax having-an oil content of 8% to 10%, it has been found that the refractive index-melting point relationship of the sweat stream should fall. within the limits defined by lines. having the equations n=l.3998-|-.0'G0242T and n=l.l00 3-{-.00O242T.

For the production of a fully. refined pi traii11 V wax the refractive index-melting point relationship of the sweat stream should fall within thevlimits de ned by lines having-the equations I And for the production of high tensile strength wax 'containing less than about 1.5% of oil, and preferably less than 1% of. oil, the refractive index-melting point relationship of the sweat 'stream should fall within the limits defined by lines having the equations n=1.3964-}-.O00242T and n=1.3969+.000242T.

In another aspect of the present invention, it has been found that the refractive index lof the sweat stream is, per se, a'valuable guide in indicating the point at which sweating should be terminated, particularly in the production of waxes of exceedingly low oil content, i. e., less than about 1% by weight of oil. By determining the minimum refractive index of the sweat stream and then terminating sweating when such value is reached, the resulting sweated wax will contain little or no oil. Referring to the draw-v ing, it will be seen that the minimum refractive index of the sweat stream is reached at a point between I and J, and that the oil content of the sweated wax when the sweating was stopped at I was about 1%. By terminating' the sweating at the minimum refractive index between I and J, a somewhat higher yield of low oil content wax would be obtained than by continuing the indices and the melting points of successive sam- I ples of the sweat stream, and terminating the sweating of the wax when a sweat stream sample exhibits a melting point higher than that of the 'preceding sample, and a refractive index at least as great as that of said preceding sample.

2. The method of reducing the oil content of oily Wax, which comprises subjecting said oily wax to sweating, and terminating the sweating of the -wax when the refractive index of the sweat stream attains a minimum value.

3. The method of reducing the oil content of oily Wax, which comprises subjecting said oily wax to sweating, and terminating the sweating of the wax when the relationship between the refractive index at 176 F. and the melting point in F. of at least two successive samples of the sweat stream fall, on a plot of refractive index versus melting point,substantially parallel to the line represented by the equation Where n denotes the refractive index and T denotes melting point in 9F. l

4. The method of reducing the oil content of oily wax, which' comprises subjecting said oily wax to sweating, and terminating the sweating of the wax when the relationship betweenk the refractive index at 176 F. and the melting point in F. of a sweat stream sample falls, on a'plot of refractive index versus melting point, Within the lines defined by the equations n=1.3964-|-0.0G0242T and n=l.4003|-0.000242T, where "nl denotes the refractive index `and T denotes melting point in F. w

5. The method of producing a high tensile wax, which comprises subjecting an oily wax to sweating, and terminating the sweating of the wax when the relationship between the refractive index at 176 F. and the melting point in F, of a sweat stream sample falls, on a plot of refractive index; versus melting point, within the lines defined by the equations and n=1.3969+0.000242T, ywhere. n denotes the refractive index and T denotes melting point in F.

6. The method' of producing a refined wax, which comprises subjecting an oily wax to sweating, and terminating the sweating of the wax when the relationship between the refractive indexat 176 F. and the melting point in F. of a sweat stream sample falls, on a plot of refractive index versus melting point, within the lines den=1.398 3+0.000242T, where n denotes the refractive index and 'I'"` denotes melting point in F.

7. The method of producing scale wax, which comprises subjecting an oily wax to sweating, and terminating the sweating of thewaxwhen the relationship between the refractive index at 176 F. and the melting point in F. of a sweat stream sample falls, von a plot of refractive index versus melting point, within the lines defined 'by the SEYMOUR W. FERRIS.

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