US2168574A - Method of separating wax-containing materials - Google Patents

Description

Patented Aug. 8, 1939 PATENT OFFICE METHOD OF SEPARATING WAX-CONTAIN- ING MATERIALS Dwight B. Mapes and Eddie M. Dons, Tulsa, Okla assignors to Mid-Continent Petroleum Corporation, Tulsa, Okla., a corporation of Delaware No Drawing. Application May 10, 1937, Serial No. 141,860

4 Claims.

This invention relates to methods of separating wax-containing materials, the present application being a continuation in part of an application filed by us on May 20, 1936, Serial No. 80,672.

An object of the invention is toproduce a highly efficient method of separating various wax-containing materials, including lubricating oil stocks,'as well as petrolatum, slack wax and other mixtures containing high and low melting point waxes.

A further object is to produce an economical and entirely feasible method of this kind, without incurring any of the serious undesirable factors involving time, trouble or expense to be expected at one or more stages of an otherwise desirabledewaxin-g process. Actual tests of the invention have shown that it overcomes all of these problems.

More specifically stated, an object is to accomplish the above mentionedresult's in a simple process, while employing a new combination of inexpensive solvents that can be safely used without incurring any serious danger of fire, explosion, or the like, and which cooperate with each other to provide a high filterrate, large yields of the wax or oil, and excellent quality in the resultant products.

With the foregoing and other objects in View, the invention comprises the novel methods hereinafter described to set forth specific examples of the invention. However, it is to be understood that this invention comprehends changes, variations and modifications within the scope of the claims hereunto appended.

Prior to our inventions in this art, it has been customary to employ combinations of radically different solvents, the general rule being to select one solvent having a high solvent power for one of the constituents to be separated, and another solvent having 'a low solvent power for that constituent, but a high solvent power for another constituent. For example, in accordance with the theory generally adhered to in the art, a solvent having a high solvent power for wax may be combined with a substantially different solvent deliberately selected because it has a low solvent power for wax.

Instead of employing such radically different solvents, we prefer to use a combination of solvents of the same general class, and in pr'actice we have found that the particular solvents herein set forth actually produce the entire series of desirable results, despite the similarity in the general nature of the cooperating solvents.

Propyl acetate alone may be used as a dewaxing solvent to produce low cold test lubricating oils, and also to separate the various waxy materials, or to remove oil from such waxy matrials. We have used this single solvent in dewaxing lubricating oil stocks, and for deoiling petrolatum. Propyl acetate has outstanding merit as a simple solvent for work of this kind. Owing to its relatively low cost, we prefer to use isopropyl acetate, instead of the normal propyl acetate.

However, in the preferred form of the invention, we employ a blend of propyl acetate and another fatty acid ester of an aliphatic alcohol, and thereby accomplish important results not obtainable from the propyl acetate alone.

When the propyl acetate contains water, and this may be expected of propyl acetate recovered in the usual manner by distillation in the presence of steam, we have found that certain specific objections appear in the use of this otherwise desirable solvent. In using such propyl acetate as a solvent for deoiling petrolatum, We, found that soft waxes, or gel-like materials of an adhesive nature "are thrown out of solution, resulting in a very undesirable sticky wax cake which adheresto the filter, and that the objectionable oil, etc., can not be washed from this sticky wax. Similar effects were observed in using propyl acetate to dewax lubricating oil stocks containing amorphous wax.

However, by adding amyl acetate to the propyl acetate, we overcome this problem, and produce a very high yield of commercially desirable Wax in the form of a porous hard cake that can be very easily washed on the filter.

Amyl acetate has been previously employed as a dewaxing solvent, but amyl acetate when used alone would result in low filter rates and produce an objectionable bulky and oily wax cake. Amyl acetate alone would be quite unsatisfactory, and not desirable for a commercial process of this kind. Nevertheless, the mixture of propyl acetate and amyl acetate precipitates the wax in a more sharply defined crystalline form, which permits rapid filtration, and the wax cake is more compact and more free of oil. This wax cake is very readily washed to produce a dry cake having a very low oil content.

More specifically stated, as an example of the new process used in deoiling petrolatum, we prepared a solvent composed of "10% isopropyl acetate and 30% technical grade amyl acetate, using five parts of this solvent to one part petrolatum. The solution was heated to about F., then cooled to 76 F. and filtered. The wax cake on the filter was washed with a quantity of solvent equal to .6 to .7 of the volume of the original petrolatum. This resulted in a large yield of the most valuable wax having a high melting point of 160 R, which was about 40% of the original stock.

This combination of propyl acetate and amyl acetate is especially desirable for deoiling petro-' latum, as the petrolatum contains the soft waxes, or gel-like sticky material, most undesirablein' the finished product. Wehave found that-the new combination of solvents is quite selective in holding these adhesive soft waxes in solution, and in producing a high'yield of the hard wax.

The wax thus precipitated'is' quite freenof, said sticky material, and forms a very compact wax cake on the filter. This cake can be readily washed, and easily dischargedfrom' theifilter,

the resultant product being an excellent clean pourpoint oils, the dewaxing may be performed hard wax. 7 a

As another specific example of the invention,

"we will now refer to the dwaxing of a lubri cating oil stock to produce an oil having a low pour point. The solvent was composed of isopropyl acetate "and 10% amyl acetate. The oil stock'was a blendof'40% petroleum residue and 60% distillate having a viscosity of at 210 F. The oil stock was dissolved in this solvent and the solution was chilled and then filtered. The solvents were distilled from the oil in the presence of steam, and usedin subsequent operations. The resultant oil was a finished bright stock having a viscosity of at 210 F. The cloud point of this oil was 20 F.,which shows that all of the wax was removed."

In the foregoing example," the solution was filtered at 10 F;, and the .dewaxed'oil. had a pour point of 5? F." 1" "Actual tests of' the'invention herein disclosed have "positively shown that the new method overcomes all of various serious defects or'objections likelyto arise une'xpectedlyin. processes of this kind, and that it provides an economical and entirely feasible method of accomplishing the several 'results'desired in this artw I V The outstanding results derived from the cooperative action'of propyl acetate'and amyl ace-'- tate are quite apparent in deoiling or dewaxing petroleum stocks containing amorphous wax, and particularly in obtaining the valuable high melting' point wax from petrolatum,-which'involves a number of specific problems not present in the separation-0f paraifin waxes. "Nevertheless, we have .found that the combination of these two solvents is also desirable in separating various stocks containing paraffin waxes, and said solvents can be advantageouslyemployedin purifying slack wax, in lieu of the usual sweating operations. For example, in separating slack wax, using isopropyl acetate and amyl acetate as a combined solvent, we obtained a yield of wax having a melting point of 122 F. amounting to 40% of the original stock, whereas the usual sweating resulted in a 28% yield of wax having the same melting point. By using said combination of solvents we have economically separated the higher melting point waxes from slack wax which are not obtainable by sweating. The proportions of the solvents may be varied as desired, depending upon the stock to be treated .-and the results to be obtained. The propyl acetate is preferably from about 40% to about 90% of the solvent blend, and the dewaxing may be carried out at'high temperatures above 50 F.,

for example, about 75 F. to recover high melting point wax from petrolatum; or in making low at relatively low temperatures. However, the invention is not limited to th'e'spe cific temperature conditionsjnor to the range of proportions specifically mentioned in referring to the solvnt's.

" We claimz' The method 'of separating wax-containing materials derived from petroleum'which com- "prises dissolving said materials in a solvent comprising isopropyl acetate and amyl acetate, cooling the solution to precipitate wax therein, and separating wax from the'cooled'solution.

"2." In' the art'of'sep'arating amorphous wax from petroleum stocks containing said wax and oil, the method of using isopropyl acetate which comprises dissolving said petroleum stocks in a solvent including said isopropyl acetate and amyl acetate, cooling the solution to precipitate wax therein, and separating precipitated wax from the cooled solution. 3-3; The method of separating high melting point Twax from"petroleum stocks containing amorphous wax and oil which comprises dissolving the waxy material'in a solvent including isopropyl'acetate and amyl acetate, cooling the solution to precipitate high melting point wax therein and separating precipitated wax from the cooled solution. a 4. In the art of deoiling petrolatum, the method of using isopropyl acetate which comprises dissolving the petrolatum in a solvent including said isopropyl acetate and. amyl acetate, cooling the solution to precipitate high melting point wax therein, and separating precipitated wax from the cooled solution.

DWIGHT B. MAPES; EDDIE M. DONS.