US2141623A - Method of refining paraffin base oils - Google Patents

Description

Patented Dec. 27, 1938 UNITED STATES METHOD OF REFINING PARAFFIN BASE OILS V Victor-I. Downey, Lakewood, Ohio, assignor to National Refining Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application April 22, 1937, Serial No. 138,365

8 Claims.

This invention relates to petroleum oil refining and more particularly to an improved method of producing so-called bright stock from paraffin base oils such as Pennsylvania crude.

Bright stock is the name given to a product which results when crude oil is so refined that it is freed of undesirable light ends and paraffin waxes and then filtered to a bright color. Bright stock is used in larger quantities, when blended with other oils, to produce the various grades of lubricating oils used in internal combustion engines and the like. The so-called paraffin base oils, of which Pennsylvania grade crude oil is an example, difier from the mixed base oils such as come from the Mid-Continent oil fields in that the parafiin base oils do not contain sufficient quantities of certain unsaturated hydrocarbons or asphaltic substances, which are normally contained in the Mid-Continent oils, to permit of 20 the economic use of the sulphuric acid de-Waxing treatment.

V In the production of bright stock it has heretofore been common practice to produce steam refined or cylinder stock by distilling crude oil to drive off the lighter portions and then process- 25 ing such cylinder stock to remove the wax contained therein. Among the de-waxing processes which have been employed are various procedures including centrifugal separating, chilling and precipitating the Wax by gravity settling. A particularly successful process, as far as the Mid- Continent type oils are concerned, is described and claimed in the Setzler and McDonald Patent No. 1,791,329 in which cylinder stock containing amorphous wax is suitably diluted, chilled to a temperature below 40 F., subjected to the action of sulphuric acid and the mixture agitated whereupon a sludge is formed by the acid and the undesired wax removed from the oil with the sludge by gravity separation.

The Setzler and McDonald process, however, has not been available for the production of bright stock from parafiin base oils of the Pennsylvania type because the Pennsylvania oils do not contain enough of the unsaturated hydrocarbons or asphaltic substances which apparently are necessary in appreciable amounts to cause the sulphuric acid effectively to remove the wax from the chilled oil.

In a co-pending application of Morace B. Setzler, Serial No. 747,421, filed October 8, 1934, a method of de-waxing, de-colorizing and raising the viscosity index of bright stock made from paraffin base oils is disclosed. This method contemplates the addition of a residuum of mixed base oil from a Mid-Continent crude to- Pennsylvania steam refined stock, diluting with naphtha or light hydrocarbon fractions, and then chilling and treating this mixture with sulphuric acid to cause the wax to settle out with the sludge,

The present invention may be considered to be an improvement on the method described and claimed in the said co-pending Setzler application, and it is among the objects of the present invention to provide a method of producing bright stock from paraflin base or Pennsylvania steam refined stock without the addition to the oil of any foreign asphaltic materials, such as the residuum from Mid-Continent crude.

Other objects of my invention are: the provision of an improved method of producing, at reduced cost and with greater yield than with previous processes, a superior bright stock for lubricating purposes from Pennsylvania type crudes containing little or no unsaturated hydrocarbons or asphaltic substances; to provide a method of refining Pennsylvania or the like crude oils by which bright stock can be produced which is substantially free from waxor Waxy constituents, which has a low pour test and which has a low viscosity in relation to its flash test; to provide a method of producing high grade bright stock from Pennsylvania or the like oils which is susceptible of accurate control and is readily adaptable for use with difierent kinds or grades of parafiin base oils.

My invention contemplates the creation of certain unsaturated hydrocarbons or reactive substances in steam refined or cylinder stock made from Pennsylvania or similar type crude oil, which unsaturated hydrocarbons or reactive substances are created from and within the original oil itself and without the addition to or contamination of the oil with any foreign'material not derived from Pennsylvania crude. I have found that when a paraffin base crude is subjected to distillation to remove the lighter fractions and is either simultaneously or thereafter subjected to a relatively slight degree of cracking, sufiicient merely to create within the body of the oil an amount of unsaturated or reactive ,material suficient to cause the later sulphuric acid treatment effectively to remove the undesired waxes, the' so processed steam refined or cylinder stock may be readily de-waxed and converted into a superior quality bright stock by the Setzler and McDonald process of Patent No. 1,791,329, referred to above.

As a general outline of the procedure which has been found to result in the successful production of a very high grade of, bright stock, a Pennsylvania oil can be distilled in a batch still at a temperature of approximately 650 F. and the oil stripped with steam until it reaches approximately the following specifications:

Viscosity at 210 F. by the Saybolt Universal viscosimeter, 150 seconds. 7

Flash, Cleveland open cup. 550 F.

When the material in the still reaches the above specifications steam is shut off from the still and the oil allowed to decompose or crack for a period of time (usually about 4 hours for Pennsylvania crude) sufficient to reduce the viscosity of the oil with accompanying formation of the desired unsaturates or reactive substances in the oil. At the end of the cracking'step the viscosity may be reduced to approximately 135 seconds at 210 F. and this reduction of viscosity may be used as an indication of when the oil has been cracked enough to give the desired results' This material is then cooled to below about 150 F. and may be mixed with an approximately equal volume of a light fraction such as gasoline, naphtha, or kerosene and the mixture then further cooled to a temperature of approximately zero degrees Fahrenheit or below and treated with sulphuric acid to convert the unsaturated'hydrocarbons or reactive material created in the oil, by the slight cracking, into a sludge which is efiective in precipitating out or removing the wax in the oil. The clear de-waxed oil is removed and freed of acid by neutralization with a suitable alkali or adsorbent agent such as fullers earth, heated to distill off the gasoline or other light fractions which were added and then filtered if necessary, the resulting product'being high grade bright stock.

A more specific description of a procedure which has been followed in a regular commercial run of a batch of paraffin base Pennsylvania crude oil follows.

It will be understood that my process may be advantageously used with any Pennsylvania grade crude oil which is acceptable to the Pennsylvania Grade Crude Oil Association.

The crude oil processed was from the Ohio- West Virginia field and before treating had a gravity of 44 to 45 A. P. I. scale.

A charge of 335 50-gallon barrels of this oil was pumped into a regular batchstill and after heating until reaching a temperature of 160 F., live or open steam was started into the body of the oil in the still and continued for approximately 36 hours until the desired distillation was completed. When this point was reached oil in the still had been raised to a temperature of 625 F., and had an A. P. I. gravity of about 25 and a viscosity of 154 seconds at 210 F., Saybolt Universal. The operator then started to check the flow of steam to the still and after two hours it was entirely shut off from the still. During this period and for about two hours longer the temperature of the oil was allowed to rise to between 640 F. to 650 F. and during this time the slight cracking required to form the desired unsaturates or reactive substances in the oil occurred.

Of the 335 barrels charged into the still ap proximately 14% or 47 barrels of steam refined stock remained after the distillation was completed and the steam removed. After the cracking period approximately 12.24% or 41 barrels remained. During the four hour cracking period the flash point of the oil decreased from approximately 550 F. to 500 F. and the viscosity dropped from 154 at 210 F. .to 134 at 210 F., S. U.

The processed steam refined stock was then sent to a storage tank, along with other batches of similarly treated oil, from which required amounts were withdrawn as desired for blending and further treatment. In the particular blending operation being described approximately 246 barrels of steam refined stock from the'storage tank, which had been processed substantially as described above, were blended with 254 barrels of a heavy (564 gravity A. P. I.) naphtha. The complete blending of this .batch was finished in six hours and the total blended mixture of 500 barrels tested as follows:

Viscosity at 100 F., S. U 54 Gravity 385 A. P. I. Solid point minus 35 F.

After the solution was blended it was chilled in a Carbondale chiller apparatus. I have found that satisfactory results may be obtained by chilling the oil to a temperature of 10 to -15 F. The chilled oil was pumped into a treating chamber after which 98% sulphuric acid was pumped into thechamber while the oil was being agitated with air. During the violent agitation of the oil and sulphuric acid a sludge was created which after about six hours dropped out of the solution and the batch was allowed to settle for approximately six hours longer at which time a substantially complete separation of sludge from wax-freed oil is obtained. The sludge was then removed from the chamber for use as fuel in the burners of the plant boilers. The treated oil was then suitably neutralized with fullers earth or other suitable adsorbent or alkali; distilled to remove the naphtha or other light fractions which had been added and then filtered to put in proper condition for marketing.

Although I have described my procedure. as carried out in a batch still it will be understood by those-skilled in the art that it might be carried out in a pipe still and fractionating tower by controlling the steam in the fractionating tower to give the desired cracking efiect after the distillation has been completed. Also, any desired type of chilling and agitating apparatus may be used.

The finished bright stock tested as follows: Gravity (approximately). 26 A. I. 1.

Flash (approximatelypflm 540 141, Cleveland open cup Fire (approximately) 615 R, Cleveland open cup Viscosity (approxnnately) 125-135 at 210 F., S U.

Pour (approximately) 2o 1 A. 5. T. M, Viscosityindex 100 minimum Carbon residue 1.5 percent maximum (,olor (approximately) 6, A. S. T. M.

As will be understood the above properties may be varied in processing to give the desired commercial product.

By subjecting a paraffin base steam refined or cylinder stock to a certain relatively slight but definite amount 'of cracking, I believe that unsaturated hydrocarbons are formed in the oil which make possible the successful removal of wax by chilling and sulphuric acid treatment. It is understood, and will be evident from the above outlined procedure, that the cracking step is not suificient to seriously reduce the quantity or" bright stock which is obtained from the steam refined stock.

The resulting bright stock, if desired, can be blended with other suitable oils to make up the various standard grades of lubricating oil. I have found that, for internal combustion lubrication particularly, oil made by my improved process has certain definite advantages over oils made by other processes, such as the process of the Setzler application above noted, in which foreign unsaturates or reactive compounds are added to a paraffin base oil in order to possible the sulphuric acid treatment for separation of Wax therefrom. It is my opinion, based on my tests and the successful commercial operation of my process, that mystep of "relatively slight cracking creates in the oil certain unsaturates or reactive substances which are later removed in the sulphuric acid treatment with the wax sludge. If the oil to which my process is applicable was not so subjected to this slight cracking it would, in some measure, be subjected to such action in use in an internal combustion engine. This cracking in the engine of oil which has not been processed by my method results in the creation in the oil of substances Which render it a poorer lubricant and which decrease its life and lubricating qualities and result in increased oil consumption. In other words, my slight cracking step results in an oil which is less susceptible to decomposition and sludging in use in an engine. My preliminary slight cracking breaks down the portions of the oil which would otherwise be broken down in operation in the engine and would then remain in the oil to the detriment thereof. I have disclosed herein a method of producing my improved product by a simple and practical procedure.

Although I have described in detail a specific procedure which has been commercially used in refining a particular Pennsylvania oil in accordance with my method, it will be understood by those skilled in the art that the time and temperature factors noted in the outlined procedure may be departed from and varied in accordance with the particular material being treated and in accordance with the product which is to be I obtained. I, therefore, do not wish to be limited to the specific procedures outlined herein but claim as my invention all embodiments thereof coming within the scope of the appended claims.

I claim:

1. The method of refining parafiin base oils, containing insufficient asphaltic material for satisfactory acid de-waxing treatment, to form substantially wax free bright stock which includes the steps of producing a steam refined or cylinder stock from the paraffin base oil, cracking said steam refined or cylinder stock whereby the viscosity of the oil is reduced and a small amount of unsaturated asphaltic hydrocarbon or reactive substances are created from and in the steam refined or cylinder stock, diluting said steam refined or cylinder stock containing said unsaturated hydrocarbons or reactive substances with a lighter oil, chilling said diluted mixture to a temperature below F., and subjecting said chilled mixture to the action of sulphuric acid whereby the mixture may be approximately freed from the wax content thereof.

2. A method of removing wax from paraffin base oils which includes the steps of distilling the oil to produce a cylinder stock having a viscosity of between approximately 140 and 160 seconds at 210 F., S. U., subjecting such cylinder stock to a slight cracking whereby the viscosity of the oil is reduced to between 130 and 140 seconds at 210 F., S. U., chilling the cracked oil to a temperature below 40 F., agitating and subjecting the chilled oil to the action of sulphuric acid until a sludge is created in the oil, and separating the oil from the sludge.

3. A method of refining Pennsylvania grade crude oil to produce high grade bright stock which includes the steps of distilling the crude oil to produce cylinder stock, cracking said cylinder stock under such time and temperature conditions as to reduce the viscosity thereof between 10 and 20 seconds at 210 F. as measured by the Saybolt Universal viscosimeter, and cooling and agitating the cracked oil with sulphuric acid.

4. In the production of bright stock from paraflin base oils having a deficiency of the unsaturates or reactive substances necessary to effect de-wam'ng by chilling and mixing with sulphuric acid, the steps of distilling the oil to produce cylinder stock, and subjecting the cylinder stock to cracking whereby the viscosity of the oil is reduced and sufficient unsaturates or reactive substances are formed from and in the oil to permit of de-Waxing by chilling and mixing with sulphuric acid.

5. A method of producing a lubricating oil which includes the steps of subjecting a Pennsylvania grade crude oil to distillation until its viscosity at 210 F. as measured by the Saybolt Universal viscosimeter is between 130 and 230 seconds, heating the oil at between 620 F. and 680 F. for a period of from two to six hours whereby a slight cracking of the oil is effected, the viscosity of the oil is reduced and unsaturates or reactive substances are created from and in the oil, cooling the cracked oil to a temperature below about 150 F. and blending it with about an equal quantity of a light petroleum fraction such'as gasoline or naphtha, further cooling said blended oil to a temperature of below 40 F., treating said cooled blend with sulphuric acid whereby a sludge is formed which includes the unsaturates or reactive substances created in the oil by the cracking step, separating the oil and sludge, neutralizing the oil, and distilling off the light fraction.

6. A method of producing lubricating oil which includes the steps of subjecting a Pennsylvania grade crude oil to a slight cracking whereby the viscosity of the oil is reduced and unsaturates or reactive substances are created from and in the oil, chilling and then mixing the oil containing such unsaturates or reactive substances with sulphuric acid and agitating the mixture whereby a sludge is formed of the acid, wax contained in the oil, and the unsaturates or reactive substances, and separating said oil and sludge.

7. In the production of an improved lubricating oil from Pennsylvania grade crude oil, the steps of reducing the viscosity of the oil and creating unsaturates or reactive substances of the type described from and in the oil by slightly cracking the oil, and removing the so created unsaturates or reactive substances along with undesirable wax contained in the crude oil by chilling and then mixing the oil with sulphuric acid to form a sludge containing the undesirable materials and then separating the oil from the sludge.

8. In the production of an improved lubricating oil from Pennsylvania grade crude oil, the steps of reducing the viscosity of the oil and creating unsaturates or reactive substances of the typedescribed from and in the oil by slightly cracking the oil, and removing the so created unsaturates or reactive substances along with undesirable wax contained in the crude oil by chilling and then mixing the oil with sulphuric acid to form a sludge containing the undesirable materials, separating the oilfrom the sludge, and blending the oil so produced with other oils to produce the various commercial grades of lubricating ils.

VICTOR I. DOWNEY.