US1901240A - Method of dewaxing oils - Google Patents

Description

Patented Mar. 14,- 1933 UNITED STATES PATENT OFFICE 'ALERED HENRIKSEN, F PONCA CITY, OKLAHOMA, ASSIGNOR TO CONTINENTAL OIL I COMPANY, OF PONCA CITY, OKLAHOMA, A CORPORATION OF DELAWARE METHOD OF DEWAXING OILS No Drawing.

a continuous centrifuge process.

In the production of lubricating oils, one 'of the troublesome group of compounds en'- countered is the waxes. These waxes'vary from low melting point amorphous wax to highlmelting crystalline Wax-and are com- Lubricating pounds of the paraffin series. I oils to be used at low temperatures must have these waxes removed in order to obtain free movement of the lubricating medium; moreover, the waxes themselves are of very poor lubricating value and act as a detriment to the lubricating qualities of the oil. High wax content oils, being solid at relatively high temperatures, give considerable trouble in refining practice because they cannot be pumped or require heated tanks for cold weather storage.

Oil refiners have developed three general methods of wax separation:

-l. Lubricating stock dilution with naphtha, chilling and pressing.

2. Lubricating stock dilution with naphtha, chilling and cold settling. 3. Lubricating stock dilution with naph tha, chilling and centrifuging.

These general methods have taken on various modifications in an effort to solvethe dewaxing problem.

A brief outline of the refinery practice on parafiin base crudes will show the essentials of Wax separation methods. The-ordinary break-up of crude in the "refinery is: 1,'

naphtha; 2, kerosene; 3, gas oil; 4, wax distillate; 5, residue-steam refined cylindertemperature, rate of distillation, amount of steam, etc. are regulated to prevent injury of the residue. 'The Wax distillate is removed at as low still temperature as pos sible, using large amounts of steam. This gives the crystalline waxes in the overhead Application filed January 18, 1930. Serial No. 421,815,

wax distillate and the amorphous waxes in r the residue.

' The amount of crystalline-amorphous wax separation depends on the nature-of the crude and control of the refining process. The wax distillate is either chilled and pressed directly or given a heating treatment with a small amount of steam, called cracking wax distillate, then chilled and cold pressed. I

The steamrefined cylinder stock requires other treatment to obtain high class lubricating oil price. This further refining includes acid treating and/or clay treating, which treating causes the waxes to be less soluble and a higher pour point results on the finished stock. For example, a steam refined stock may have a 40 F. pour point before treating with acid and/or clay for color and removal of impurities, and an 80 F. pour point after treatment.

It is, therefore, necessary to dewax the finished oil. Ifthe stock is diluted with naphtha and chilled, the wax crystals will form and settle to the bottom of the container. This is a very slow'pnocess requiring severaldays for completion, and gives a rather poor separation and a large loss of stock in the settled wax solvent solution. The chilling is done slowly at the top of the container and the wax crystals start flowing to the bottom, care being taken that no external agitation is obtained; therefore, the process could not be continuous. This process maybe more successfully operated if a heavy finely divided substance, that is wax .adherent, is 'added'to give'a greater gravity difference between the oil and the wax.

chilling, the wax separates from the oil and is held by the finely divided solid material suspended in the oil;'alsothe finely divided material forms a mat with the wax and aids in holding the wax from assing through the filter cloth. After the 'lter has been in operation for a short period, the finely divided solid and wax form such a thick bed on the filter cloth that the process must be stopped and the filter cloth cleaned. This process is a batch process and the regular required cleaning of the filter cloth is costly and cuts down the unit volume throughput. To process an oil by this method, the wax must be in a specific form. Some oils will not give up their wax by this process.

When a lubricating stock is diluted with naphtha and chilled, the wax crystals that separate out have a slightly higher specific gravity than the solvent oil mixture. Advantage is taken of this characteristic in wax removal by high speed centrifuge. I The wax bodies are thrown out by'the centrifugal action into the outer compartment of a special apparatus from which they are removed by a warmer solution. The partly dewaxed lube oil stocknaphtha solution passes onup and out of the centrifuge. The density of the wax is so near that of the mother liquorthat separation of wax is rather poor. Under the best operating conditions, one obtains a pour point on the finished oil of about 35 F to 40 F. higher than the temperature at which the solution goes to the centrifuge.

To dewax stocks with the centrifuge, they I must be very carefully blended to the proper gravity with the solvent used. Another disadvantage of this process is the time and required regularity of cooling. After the careful blending, the solution must be chilled at a slow rate requiring, as a rule, nearly twenty four hours for chilling; the chilling rate usually is from 3 F. to 6 F. per hour, depending on the stock, solvent and result required.

Some stocks cannot be dewaxed by the centrifuge process, 'even though all known disturbing factors are controlled.

The present invention provides an improved method of separation of wax from cold' type stock mixtures, or from crude petrolatum stock produced by present dewaxing methods, or form other fractions from which separation of wax is desired. Objects of the present invention are:

1. More nearly complete wax separation by centrifugal action.

2. Wax removal in centrifuge with the aid of collodial substances in the stock naphtha solution.

3. Continuous wax removal in the centri- 4. Continuous wax removal in the centrifuge by' the addition of bituminous colloidal centrifuge aids.

5. Centrifugal continuous wax removal using substances capable of forming a dispersoid in the solvent used.

6. Wax removal which allows the shockchilling of the stock naptha solution without the detrimental effects obtained in other methods by shock-chilling.

In the operation of this method, the stock to be dewaxed is diluted with a suitable solvent, such as naphtha, any of the heavy alcohols, benzol, acetone and similar organic solvents, or any other solvent which will give a wax-solution density differential, and remain liquid at the temperatures used. To this solution is added a substance which will give a colloidal solution. Such substances as bitumen, Grahamite and the like, which are not soluble or are only partly soluble in the solution, are desirable. This material may be added before chilling, during chilling, or after the chilling period. In actual practice the most satisfactory method for adding the centrifuging aid to the oil to be treated is to preparethe colloidal solution of the centrifuging aid in a suitable medium and add the colloidal solution at any point in the chilling process prior to centrifuging.

ferent from the diluent used for the oil.

The chilled stock-naphtha blend with the centrifuge aid added is now charged to'the centrifuge where the wax and centrifuge aid are easily thrown out of the oil naphtha solution. The nature of the centrifuge aid allows it to be easily washed out of the centrifuge with the wax without obstructing or clogging the system.- This advantage is not present in finely divided or inorganic pulverized solids which would not flow from a high speed centrifuge. As in other centrifugal processes, the de-waxed stock-solvent' solution is drawn off the top of the centrifuge from which the de-waxed tha being the class of substances intermediate between asphalt and petroleum.

The definition of the term centrifuge-aid is apparent from the context ofthespecification. The term centrifuge-aid is used to include substances which allow better operation of the centrifuge, substances which in any way The solvent in 'which the colloidal solute is converted to a colloidal solution may be the same or dif alter the nature of the wax particles and more easily precipitated at the temperatures and dilutionsused.

In the application of the process many comparisons of the merits of our process and the other type processes have been made. For example, two stocks can be chosen, one of which may be de-waxed at the centrifuge and not de-waxed by the cold pressing with filter-aid process; the other being de-waxed by the cold pressing with a filter-aid process and not de-waxed at thecentrifuge. By conditioning these two stocks for my process, that is, by adding a centrifuge-aid, I can de-wax both at the centrifuge.

Numerous colloidal agents have been found that have given satisfactory commercial results. In the practice of this process it has been found that the centrifuge-aid required for de-waxing one stock may be found in another stockwhich is to be de-waxed and in such cases the centrifuge-aid naturally existing in one stockmay be utilized by blending with the other.

The material or centrifuge-aid thought to be bitumen or the constitutents thereof may be:

(a) Naturally present in the oil or its residues to be processed;

(6) Present in excess of requirement in one stock and deficient in another, so blended will give proper percentage;

(0) A product of addition.

An example of (a) is as follows: A cylinder stock produced from Tonkawa crude after acid treating and neutralizing was dissolved or blended in the proportion of 2 parts naphtha to 1 part oil, chilled to minus 15 F. and centrifuged, giving good wax separation and a finished oil having pour test of 15 F. The above indicates that. oil from this source contains at least sufiicient centrifuge-aid to give satisfactory wax separation.

An example of (b) is a cylinder stock made by distillation overhead from dark .of this overhead distillate Mid-Continent oil was blended with 3parts of the Tonkawa cylinder stock or flux from this cylinder stock in smaller quantities mentioned under (a) and the mixture blended, .chilled and centrifuged as above, there was asatisfactory wax separation with a resulting pour test on the finished-oil of 20 F. A residue,

flux or extract from distillation of some oils contain the centrifuge aid contemplated herein.

The following examples, which include examples of (c), are not to be considered a limitation of the invention, it being understood that these are just a few examples given to make clear the operation of the process. Some of the examples also disclose the-use of a bitumen in combination with petrolatum. Example 1 Overhead lube treated with 30# sulfuric acid per barrel and 15% clay showing on the treated oil Gravity Vicos ity Pour point Gn Fl. Fr. Vis. Pour pt. Color 23.7 490 F. 565 F. 80 100 F. 2-Tag.Robinson was blended with 68.5% of 57 .4 gravity naphtha, to which was added 0.025% California bitumen and 2% petrolatum. This was chilled at 6 F. per hour to minus 40 F. and gave at the centrifuge after finishing a lubricating stock of pour point 8 F., filtered through clay 200 bbls/ton.

Gr. F1. Fr. Vis. Pour point Color 22.0 500 580 90 7 F. 1% T.R

Example 3 A commercial product known as Grahamite to an amount of 0.1% was used with success lowering the pour point on the finished oil 50 F. By use of 0.1% Grahamite and 2% petrolatum, the pour point was lowered on the'finished stock 65 F.

Example 4 A treated overhead lube stock was diluted,

chilled and centrifuged yielding a finished stock of 44 F. pour point. The centrifuged stock was blended with 56.9% of 54.6 gravity naphtha and 0.2% Montan wax, chilled at 6 F. per hour to F.; then centrifuged yielding a finished product of F. pour point; operating same as above with the addition of 0.05% bitumen gave a finished product of 15 F. pour point.

By extensive actual tests, I have found that any bituminous substance that is not soluble or partly soluble at centrifuging temperatures used proves satisfactory in the operation of this process. I have further found that substances which give a dispersoid solution of naptha and lubricating oil understood that this proves satisfactory. I believe that the dispersoid gives a nucleus around which the wax gathers, forming a body of greater density than the solutionfrom which the Wax came. The centrifuge can then make a better a separation. It is to be clearly patent is independent of any theory oifered.

I claim as my invention:

1. A method for removing wax from waxcontaining oils comprising the steps of adding a suitable solvent and a colloidal asphaltite, chilling the mixture to the desired temperature, and subjecting the chilled mixture to a centrifugal action.

2. A method for removing wax from W axcontaining'oilscomprising the steps of adding a suitable solvent and Grahamite, chilling the mixture to the desired temperature and subjecting the chilled mixture to a centrifugal action.v

3. A method ing a suitable solvent and amixture of Grahamite and petrolatum, chilling the resulting mixture to the desired temperature, and subjecting the chilled mixture to a centrifugal action.

4. A method for removing wax from waxcontaining oils comprising the steps of adding a suitable solvent and on asphaltite capable of forming a dispersoid in the solution, chilling the mixture to the desired temperature and subjecting the chilled oil to a centrifugal action. a

In testimony whereof I aflix my signature.

ALFRED HENRIKSEN.

for removing wax from waxcontamlng olls comprising the steps of add-.