US1806570A - Dew axing oil - Google Patents

Description

PaTtented May 19, 193i AUONITEVD STATES PATENT OFFICES LEO I). JONES, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE SHABPLES SPECIALTY COMPANY, DELAWARE No Drawing. Application filed May 25,

This invention relates to the removal of wax from oil, and while the invention is of general application it is particularly well suited to the removal of wax from petroleum products in the manufacture of lubricating and other de waxed oils.

Lighter fractions .of petroleum oil, such as lighter lubricating-oil stocks, distilled from petroleum after the removal of gas, naphtha,

1 burning oil and gas oil therefrom, may contain wax that is crystalline in nature when precipitated by chilling a diluted body of the oil, or such lighter fractions and even heavier fractions may be subjected to cracking distillation with the result that the wax precipitat ed in a diluted body of the oil by chilling is crystalline in nature when so precipitated.

Such crystalline wax may be removed from the oil by chilling the oil and then removing the precipitated wax by filter-pressing the oil through cloth such as duck.

The residue obtained by steam distillation of petroleum, such as steam refined cylinder stock, contains, when properly prepared, only 2 wax that is amorphous in nature when properly precipitated. Such wax can be removed from oil conveniently and economically by the centrifugal process of Patent No. 1,351,265

, issued to P. T. Sharples, August 3.1, 1920. Such wax may also be removed from steam refinedcylinder stock to some extent: by the so-called cold-settling process. It cannot be removed from oil by filter-pressing because it clogs the filters now employed.

In the usual operations performed in refining petroleum, bOdies of oil occur or result which contain wax of such nature that when it is precipitated by chilling of a diluted body ofthe oil, even when great ca'reis exercised in the chillin operation, it cannot be removed from the oilby filter-pressing through canvas or by cold-settling. It is sometimes difficult to remove wax from such oils by centrifugal processes; and if removal of wax from such oils is accomplished centrifugally, the success of the centrifugal de-waxing operation is usually due to the employment of special methods forming the subject matter of other applications for patents which have- 5 been filed by me. Examples of oils con- PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF DEWAXING OIL 1928. Serial No. 280,658.

taining such wax are petroleum fractions of intermediate viscosity and boiling point and mixtures of oil containing wa'x that tends to be crystalline when precipitated bychilling with oil containing wax that is amorphous when precipitated by proper chilling; The wax contained in such oils of intermediate viscosity may be said to be in an intermediate state.

Formerly oil that contains wax of such a nature that it cannot be removed from the oil, even when great care is exercised in the diluting and in the manner of chilling in precipitating the wax, either by filter-pressing through the duck employed in such operations or by coldsettling, was subjected to cracking distillation before de-waxing. The wax in the oil was thereby converted into wax that. would precipitate in a crystalline form, and it existed in that state in the distillate; but While cracking distillation brought the wax to a form in which it can be removed conveniently and economically, there was considerable loss due to incidental conversion of lubricating oil into non-lubrieating oil such as gas oil. In some cases oil 1 containing wax which cannot be removed by filter-pressing or cold-settling even when carefully precipitated, was'de-waxed by diluting the oil and then adding paper pulp thereto and then chilling and filter-pressing through cloth. It has also been suggested that kiesel-guhr or fullers earth be used for the purpose of similarly gaining the same result that follows from adding paper pulp prior to'de-waxing.- However, the addition of such a foreign substance, commonly called a'filter-aid, is objectionable because it increases the amount of refrigeration neces sary and the foreign substance must be removed from the wax separated from the oil, such removal often requiring troublesome and expensive operations such as extracting Wax with naphtha from filter-aid.

- In accordance with this invention the oil that is to be de-waxed is diluted with a solvent such as naphtha or other suitable liquid and then properly chilled Without shock, as by chilling itin accordance with my P atent No. 1,558,619 issued October 27th,

1925, and then the wax, which will usually be precipitated in comparatively coarse particles, will be removed from the oil by a filtering medium capable of filtering the precipitated wax from the diluted oil without that clogging which occurs when an attempt is made to remove amorphous or intermediate wax by means of a filter consisting of the duck that is commonly used in removal of crystalline wax-precipitates by filter-pressing. In accordance with this invention such a filtering medium will consist of or have a surface consisting of fibers that are flexible or elastic and are loosely felted or matted and which may in some cases be capable of being compressed into a closer felting or matting by the pressure of a substance being filtered. A specific example of such a filtering medium is the material commonly used for woolen blankets, or the woven-felt blankets used in paper machines, such as, for instance, a woolen fabric with a loose twill weave having about twenty-five threads to the inch in each direction and woven from sheeps wool, 'one oriboth sides of the final woven fabric being teasled to form a mat of lose fibers thereon.

In the practice of this invention suction may advantageously be employed in the filtering operation, preferably having the oil pass through the filtering medium from that side thereof which is formed'into a mat of loose fibers, because the layer of wax held back by the filtering medium may be separated readily from the medium by discontinuing the suction and applying air or other gas pressure to the opposite side of the filtering medium. It appears that when use is made, in the practice of this invention, of a fabric having a mat of fibers on the surface upon which the cake of wax is formed, although I do not intend to be bound by any theory, an application of suction causes the fibers to mat or compress and form an effective filtering surface which expands or loosens up when air or gas pressure is applied to the side of the fabric opposite to the side carrying the cake of wax and thereby facilitates the removal of the cake of wax from the filtering medium. In any event the use of a filtering medium of coarse mesh in accordance with this invention, and particularly the use of a woolen filtering medium of the character above described, prevents that clogging of the filter which occurs when there is introduced into a common filter-press embodying canvas cloth, an oil that contains precipitated wax that is amorphous or of such nature that it cannot be removed by either cold-settling or filter-pressing. And, the use of a woolen filtering medium in accordance with this invention facilitates the removal of the cake of wax from the filtering medium, the cake being removable therefrom with slight scraping of the medium.

In the practice of this invention the diluting of the oil prior to chilling may be carried out with any suitable solvent and for this purpose 65 Baum naphtha may be used and a sufficient quantity of solvent is added to insure that there is sufiicient space in the resulting mixture for the formation of separate wax crystals without such crowding as would promote coalescence. A mixture of which 65% is naphthamay beemployed. Ofcourse, the specific gravity and the proportion of naphtha employed may be varied to suit variations in the properties of the oil that is to be de-waxed.

In the chilling operation the temperature of the mixture is reduced until the desired degree of wax precipitation has occurred, a temperature of 10 F, to 15 F. usually being sufiiciently low.

Substantially all mixtures of wax and oil may be de-waxed in accordance with this invention including distillates and residues, but the practice of this invention is particularly advantageous in the de-waxing of oils in which the wax is of such nature that when it is precipitated by chilling it cannot be removed either by cold-settling or by filterpressing. Examples of the oil last referred to, it being understood that this invention is not limited to the examples given but that the examples are given for the purpose of making clear the character of wax that has been referred to as wax in an intermediate state, are

A. That fraction obtained from a typical Pennsylvania crude petroleum by steam dlstillation which begins at seconds universal Saybolt viscosity at F. and ends when the residue has a gravity of 27 Banm or has a fire test of 600 F.

B. That fraction obtained from a. typical mid-continent crude petroleum by steam (lIS- tillation which begins when the oil in the steam has a viscosity of 80 seconds universal Saybolt viscosity at 100 F. and extends to a point at which the residue is a 600 F. fire test cylinder stock.

0. That fraction obtained from a typical mid-continent or Pennsylvania crude petroleum by steam distillation, and which consists of a residue having a flash point of 300 F. to 400 F.

Also there are the heterogeneous mixtures of oil, made accidentally or intentionally, in which the Wax precipitated by chillin the oil after dilution cannot be removed by 'lterpressing or cold-settling or simple centrifugal methods.

Asan illustrative procedure in the prac-- tice of this invention the oil to be de-waxed may be diluted with naphtha and then chilled until the desired wax precipitation has been effected, and then the resulting mixture may be filtered with the aid of suction until a suitable cake of wax is formed on one side of the filtering medium, and then gas or air pressure may be applied to the other side of the filtering medium to loosen the cake from the medium and facilitate its'removal therefrom by scrapin There are many types of apparatus available for supporting a suitable filtering medium in such a manner that a cake is formed on the medium by suction and then loosened therefrom by air or gas pressure. In one type of such apparatus, commonly known as the Oliver States Patent No. 1,659,699, the desired filtering medium is supported on a rotating drum that is partly immersed in the mixture to be filtered and the interior of which is divided into a plurality of compartments which are so connected to sources of suction and pressure by valves that are operated upon rotation of the drum that the compartments covered by filtering medium that is immersed and by a major portion of the filtering medium that is not immersed are sub jected to vacuum and the compartments covered by the remaining part of the filtering medium that is not immersed are subjected to pressure. In such a device a scraper acts upon that part of the filtering medium which is subjected to pressure acting from within the drum.

In the practice of this invention the fibers employed may be wool, cotton, steel, ramie. asbestos, or other fibers suitable to removal of wax or wax-like substances from animal, vegetable or mineral oils in accordance with this invention. Improved results are to be expected from the selection of fibers that will not be caused to adhere or firmly compact under the influence of the materials with which the fibers are contacted in the filtering operation.

I claim:

1. In the dewaxing of oil that contains wax which when precipitated by temperature reduction is too amorphous for removal from the oil by common filter pressing with duck filters, the steps comprising diluting the oil with 'a solt'ent,-reducing the temperature of the resulting mixture and thereby precipitating wax therein, and then filtering the diluted oil through a body of interlaced and unwoven wooli'fibers and thereby removing precipitated wax therefrom.

1 2. Inthe dewaxing of oil that contains wax which when precipitated by temperature reduction is too amorphous for removal from the oil by common filter pressing with duck filters, the steps comprising diluting the oil with a solvent, reducing the temperature of the resulting mixture and thereby precipitating wax therein, and then filtering the diluted oil through a body of looselyjmatted itatedwax therefrom;

resilient fibers and therebyremqviri'g precip- .3. In thedewaxing of oil by diluting the drum filter, as exemplified in United.

oil, reducing the temperature of the resultresilient fibers and thereby removing precipitated wax from the oil.

5. In the dewaxing of oil by diluting the oil, reducing the temperature of the resulting mixture to effect precipitation of wax, and removing the precipitated wax by filtration, the steps comprising filtering the chilled mixture containing precipitated wax through a mass of loosely felted fibers with the aid of suction, and then subjecting the cake of wax formed 011 one side of the filtering medium to gas pressure acting from the opposite side of the filtering medium and thereby loosening the cake of wax from the filtering medium.

In testimony whereof, I have signed my name to this specification.

, LEO D. JONES.

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