US1813642A - Process of purifying petroleum products - Google Patents

Description

' No Drawing.

UNETE PATENT A oFFicE;

HER-SCHEL G. SMITH, OF PORT ARTHUR, TEXAS, ASSIGNOR TO GULF REFINING- COM- PA'NY, OE PITTSBURGH,\?ENNSYLVANIA, A CORPORATION OF TEXAS PROCESS OF. PURIFYING PETROLEUM PRODUCTS Application filed June 16,

- ing with weak sulfuric acid solution, drying and brightening, filtering through clay, fire and steam reduction, and final clay treatment; the melting point of the final product in the case of petrolatum usually being adjusted by an addition of an oil produced by treatment in the way described; all as more fully hereinafter set forthandclaimed.

" It is desirable to be able to produce white I and light colored petrolatum completely devoid of taste and odor. The same considerations apply in the case of heavy oils used for medicinal and/or technical purposes. Various market grades of petrolatum are recognized differing mainly in color, snow white, lily white, amber, etc. and in melting point. With all these grades, absence of taste and odor and unchangeability by exposure to light and air are extremely desirable and are difficult to secure in full measure by current methods. The tendency to alter with age is more or less parallel with the iodin number; the greater the iodin number, the greater the alterability. Little of the petrolatum on the market has an iodin number under 10. Waxes of the nature of those impart-' ing the. jell-like characteristics to petrolatum are contained in undistilled heavy residual oils or cylinder stock and such oils are an or dinary source of petrolatum stock, From such oils petrolatum'of commercial grades can be made by tedious and expensive filtration methods involving many repeated treatments with active decolorizing agents such as bone black, decolorizing carbon, bauxite, fullersearth, etc. In order to abbreviate and 1926. Serial No. 116,461.

cheapen the manufacture of petrolatum, va-

and with the large amounts of strong acid required, the effects of the refining operation are usually negative. Any advantage secured by the purifying action of the acid on petrolatum stock is counterbalanced by development of fixed'brown colors which are difiicult, and sometimes impossible, to remove by subsequent filtering operations so as to secure any profitable yield of finished petrolatum of the desired light color and odorless and tasteless characteristics. Other drawbacks of the acid refining process are a tendency to burn the oil and to add organic compounds of sulfuricv acid to the stock being treated, suchcompounds being extremely refractory as regards subsequent processes of purification or de colorization. With the employment of aluminum chlorid at the proper stage in the se-. quence of operat1ons,'thcse difiiculties are greatly reduced, as the action of the aluminum chlorid is to remove as a heavy tarry sludge the heavy undesirable constituents without adding to the oil being treated highly colored products which cannot readily be removed at later stages. In addition, aluminum chlorid is a far more potent agent for removing the undesirable compounds, such as the resinous coloring matters, than is sulfuric acid, as a given Weight of aluminum chlorid applied at the proper stage has been found to be as much as ten times as effective as a like weight of concentrated sulfuric acid, even filming sulfuric acid. In other words, it is very difficult to secure a profitable yield of petrolatum of colorless, odorless andtasteless characteristics by means of a sulfuric acid treatment followed by filtering operations, while satisfactory yields can readilybe secured with the employment of a treatment wita aluminum chlorid in place of the sulfuric acid. Much the same considerations applyto the manufacture of'heavy oils, or oils of high viscosity, for medicinal or technical uses. These are enerally made from a lubricating oil distillate subjected to a drastic refining or purification in much the same way as is used with petrolatum. Processes of producing medicinal oil with the aid of aluminum chlorid are described and claimed by McAfee in his Patent No. 1,277,329, whereon the pres ent invention in some of its aspects may be regarded as animprovementu I have discovered that T can produce petrolatum and heavy white oils of the desired grades in a simple, easy and economic way utilizing the purifying action of aluminum chlorid, by a certain succession of treatment steps; the products having a Hanus iodin number, or value, much below that usual in commercial petrolatum and white oil. Usually this number is not greater than l or 2, while many of the so-called white grades now being marketed have iodin numbers of around 15. While this succession of steps may be applied to petrolatum stock of other origins with advantageous results, I find the best results are obtained with a stock produced in a certain particular way. By this method a relatively highmelting petrola-tum may be purified to the extent desired and its melting point finally adjusted to that of the market grade desired by. a suitable addition of lubricating oil distillate which has been treated in the same way; White oil. I

In this way of making a suitable petrolatum stock, acid treated crude oil is reduced in a still in the usual way, using fire and steam, with the production of the usual distillates and of a residual reduced oil or cylinder stock bottomsof about 24 B. Heavy ends resulting from ire-reduction of the distillates may be, and often are, returned for admixture withmylinder stock. It is then diluted with naphtha for conveniencein han dling and filtering. The amount of naphtha used may range from 1.5 to 2 parts by volume for each volume of oil. The diluted cylinder stock is given a clay treatment being thin enough to permit easy treatment with fullers earth. The mixture is next chilled to freeze outsolidifiable constituents. A temperature of 10 F. is convenient. The wax is next separated fromthe chilled oil by settling or, and more conveniently, by'the use ofa centrifugal of the general type used in creameries. The liquid etlluent is not here further interesting. This liquid efiuent contains most of the naphtha used for" dilution, but some remains in the wax settlin'gs or concentrate. The concentrate, or setthngs, comlng from the centrifugal or the settler is reduced to expel the naphtha in a suitable still using fire and steam. This reduction gives a petrolatum terse ea stock advantageous for use in the present process. Typical properties of the stock are as follows: a specific gravity of about 0.910 at F; a gravity of 35.1 B. at 140 F.; a fiash point of 500 F; a melting point of 136F.; and a Saybolt viscosity at 210 F. of 85. The physical properties of the stock will vary within reasonably wide limits, being influenced by variations in the nature and proportions of both the wax and the oil present. While I find most advantageous a petrolatum stock made in this way, other petrolatum stocks of similar characteristics may be used.

Tn practicing the present process, the petrolatum stock is placed in a suitable apparatus provided with stirring means and is treated by adding a relatively largeamount of anhydrous and active aluminum chlorid. The addition maybe, and advantageously is, as high as 10-to 20 per cent by weight. The two materials are stirred together energeticallyat a temperature sufiicient to keep the petrolatum stock in a molten condition, this temperature being somewhere above 140 F. and below 250 F. A temperature of 175 F. is often desirable. After agitation has con 7 tinned for an hour or so, the contents of the treatment vessel are allowed to become quiescent to deposit a sludge of a mixture and/or a combination of aluminum chlorid with undesirable hydrocarbons, and this is removed. Thereupon a fresh charge of active aluminum chlorid is added and treatment resumed and so on as many times as may be deemed necessary. Ordinarily with the usual grades of petrolatum stock I find it desirable to repeat the treatments five or six times using 10 per cent or more of aluminum chlorid each time. Half as many treatments with twice as much aluminum chlorid each time may be used. The aluminum chlorid employed forfeits but little of its activity in this operation and may be afterwards employed elsewhere in lieu of fresh aluminum chlorid; for example in methods of making gasoline and kerosene. It is separated from the treated oil as a sludgecarrying a considerable amount of heavy hydrocarbons. Where the sludge is used for making gasoline and kerosene this hydrocarbon content is also utilized. It is possible. to have the charges of aluminum chlorid used methodically in counter-order; so that absolutely fresh aluminum chlorid meets oil which has already been treated several times While aluminum chlorid which has been used several times is used on new oil. However, for the bestresults, I do not recommend this, providing the remaining activity of the aluminum chlorid, that has been employed, can be utilized for other operations as indicated above, such as the production of 'asoline. I find it better to use fresh highly active aluminum chlorid in each stage of treatment; and at most ll reuse only the final charge of aluminum chlorid in the first down with the oil in the usual Way. A

further continuance of treatment with the chlorid is damaging since it results in the production of low boiling oils at the'expense of yields of the desired petrolatum or white oil on account of the resolution of the heavy hydrocarbons into 'those of lower molecular weight as a result of the activity of aluminum chlorid in this direction. As the present process designs the production of heavy products as free as may be from volatile bodies, this is undesirable. The oil at this stage is a brownish red and carries more or less aluminum chlorid (or its compounds) in solution. If directly washed with water to remove this chlorid, there usually is produced an emulsion which is very difficult-to break or to resolve into a solution of aluminum chlorid and a Water-free oil. I attribute this'tendency to form a fixed emulsion to theocclusion of water in the oil. In this emulsion there appears to remain a small portion of aluminum chlorid or compounds which cannot readily be reached by the water employed for washing. It is not diflicult to remove the water from this emulsion by heating it, the water being driven off as steam, but, unfortunately, the remaining small amounts of aluminum chlorid and its compounds then tend to impart an undesirable amount of fixed color to the treated oil stock. As a result, this stock does not respond satisfactorily to the finishing operation of'clay filtering, or the like. I therefore find it best to wash the reddish brown oil with dilute sulfuric acid, say 5 per cent strength; the acid being at a temperature near its boiling point; say around 200 F. Weak sulfuric acid, unlike water, is capable of removing residual aluminum chlorid, or aluminum chlorid compounds, Without damaging the oil. The oil and acid are vigorously agitated together inthe usual ways; advantageously eitherby an air or open steam blast. About one part by volume of acid may be used for two parts of oil. The oil after being washed with hot dilute sulfuric acid may be washed with water to remove tracesof acid and other compounds, and then'dried. To this end the acidwater is withdrawn, hot water is added and withdrawn, and the warm oil then air blown until it is dried and brightened. The oil is then filtered through fullers earth, passing a la ge volume of Oll through a small weight of'the earth; this treatment being carried out to remove any residual products coming from the aluminum chlorid treatment ted to reduction in a still using fire and steam for the purpose of removing light petroleum hydrocarbons and any other compoundsof low volatility. In case I do not filter the washed aluminum chlorid treated oil through clay before the fire and steam reduction, I find that the remaining traces of aluminum chlorid and various undesirable compounds that would remain in the Washed oil tend to impart a fixed color to the stock upon heating it in a still. lVhile acid purified oils are apt to discolor in reduction, this does not occur to any extent with oil treated by the present process, which usually has a grayish, opalescent appearance. The reduced oil product is once more submitted to a clay treatment, preferably by filtering through a bed of clay, and the filtered product is a finishedcommercial petrolatum; The melting or solidi- .fying point of the clayed product'may .be

adjusted by addition of white oil before or after claying.

In making white oil for medicinal and/or technical purposes the same general procedure is followed save that a highgrade lubricating distillate is used in lieu of petrolatum stock. Advantageously thisvdistillate is from Texas coastal crudes. An uncracked lubricatin distillate of this type having a viscosity FSaybolt) at F. of from 500 to 1000 and a gravity of 19 td20 B. is suitable. However, at times it is desirable to employ parafiin lubricating oil stocks of similar viscosities.

As an additional step in the process for refining a white oil, it has been found advantageous to interpose between the washing of the aluminum chlorid treated" oil and the filtering through clay which precedes the final fire and steam reduction a treatment of the dry washed oil with from 10 to 40 pounds of fuming sulfuric acid per barrel ofthe oil in order to remove coloring matter remaining in the oil at'this point. The net result of this additional treatment is to effect a much larger clay filter yield of the finished white oil in the final filtering operation. This acid treatment at this point cannot be carried out satisfactorily on the petrolatum stock itself, or usually upon any heavy oil of like viscosity which has been secured from a residual stock that has not been distilled from the crude. The same difiiculties, to a lesser extent, are encountered for the petrolatum stock at this stage that are encountered when attempting to refine the stock with sulfuric acid treatments without treatments with aluminum chlorid. However, a distilled heavy lubricating oil stock after refining with aluminum chlorid can be treated with sulfuric acid in certain amounts without the formation of compounds which cannot be re- I the original reduced crude oil.

moved by the usual washing procedure. For this reason, it often appears desirable treat the lubricating oil stock as a matter of economy, and this additional step often justifies the separate processing of petrolatum stool; and the white oil to be employed up to this point. From this stage on, the two c '1 be mixed to effect a lowering of the point of the petrolatum to the desired one, and the remainder of the operation can be conducted on the mixture. In other words, the mixture can be then passed throu h clay; the light fractions which impart taste to a petrolatum distilled oil; and the :cduced' stock subjected to a final finishing procedure by filtering through clay.

In a specific embodiment of the present invention, a reduced parafiin crude oil was acid treated, using 1 pound of 98 per cent sulfuric acid per gallon of the reduced crude and was then reduced in a fire heated still, using injected steam. Various light and heavy cuts were sent over leaving a residual oil of the nature of cylinder stock bottoms. This formed 34.1 per cent by volume of the original reduced crudeoil and was of 24.4 gravity with a viscosity at 210 F. of 120. One part by volume of this material was thinned down with 1.65 parts by volume ofuncrached crude naphtha and the mixture subjected to a treatment with fullers earth,- using about 1 ton of 16-30 mesh earth for 25 barrels of "cylinder stock in the mixture. The filtered mixture of naphtha and oil was cooled by means of an appropriate apparatus, being agitated occasionally, that is about every half hour, during the chilling.

The temperature was brought down to l F. The chilled mixture was then introduced into a rapidly rotating centrifugal where it was separated into liquid and solid components. The temperature at the point of discharge from centrifugal was about +5 F. The naphtha was distilled from the clear liquid discharged from the centrifugal so as to secure cylinderstock; this cylinder stock amounting to 26.0 per cent by volume of The waxbearing discharge containedsome naphtha which was distilled off with fire and steam, so as to secure a residue of petrolatum stock. This particular petrolatum stock amounted to 5.4 per cent of the original reducedcrude oil and had a gravity in the melted state of 35. Be. at 140 F., a viscosity at 210 F. of 90, and a melting point (Saybolt) of 140 F.

stirred together at a temperature somewhat above the melting point or the petrolatum; this temperature in this case being F. After stirring for 2 hours the agitator was stopped and a sludge of aluminum chlorid withdrawn at the bottom. This aluminum chlorid had lost but a portion of its activity and it was well adapted for subsequent use in the manufacture of gasoline. To the oncetreated oil in the agitating apparatus was added another charge of a like amount of fresh aluminum chlorid, namely 1.46 pounds per gallon and stirring.- and separation re peated. Finally a third addition of aluminum chlorid, also 1. 16 pounds per gallon was made. After separation of this last sludge the volume amounted to 62 per cent of the volume of the original petrolatum stock. The treated petrolatum stock was next charged into a tank and stirred with about half its volume of :4 per cent sulfuric acid, open steam being blown in for the sake of agitation and to bring the temperature to a point ust below 212 F.

The hotacid was allowed to settle out and withdrawn and a charge of hot water added to the sour oil, the mixture being blown with steam as before. The hot water was allowed to settle out and the oil brightened and dried by a current of hot air. The washed petrolat-um stock amounted to 58.9 per cent. To it was added a certain amount of white oil; the amount so added depending upon the particular melting point desired in the final product.

The mixture of white oil and petrolatum was filtered hot through clay. V In this particular instance there was added to the petro- This petrolatum stock was then treated by the process of the present invention. It was rharged into a-stirring apparatus where there was added a large amount of fresh and active anhydrous aluminum chlorid. In this particular work the amount of aluminum chlorid latum stock about 3 times its volume of white oil and the material recovered after the clay treatment had a melting point (Saybolt) of 106 F. This mixture was placed in a still and submitted to reduction with fire and steam, giving a reduced productwith a melting point of 110. The reduced product was given a finishing filtration with clay. The first portions through the clay ave an excellent yield of material. After tion, the melting pointwas adjusted to the desired degree by additions of white oil made as previously described. Excellent yields of high grade materials were produced.

In making white oil for medicinal and technical uses and for blending with petrolatum, a suitable lubricating oil after proper preliminary purification is submitted to repeated treatments with large charges of alu-' minum chlorid in theway described :to'r petrolatum, treatment being discontinued when the oil nolonger responds to form a heavy sludge; The oil is then washed with hot dilute sulfuric acid, water washed, and dried. At this point, a treatment with fuming acid at a temperature of around F. isa-pplied at times, followed by washing and drying. The oil, whether treated With acid at this stage or not, is then passed through clay and given a reduction with fire and steam as a preliminary to final clay finishing.

Petrolatum and white oil made as described, in addition to their tasteless and odorless characteristics, are distinguished by the practical absence of fixed carbon; of charred or carbon residue left after heating. Petrolatum made by the present process frequently develops 0.04 per cent or less; and white oil, 0.01 per cent or less. The process may be applied to lubricating oils in which freedom from fixed carbon is a particularly valuable characteristic. In using the pres ent process with lubricating oils, however, as a rule the treatment with aluminum chlorid does not need to be so drastic; the process being carried only to-the point where the carbon residue is reduced, as shown by tests, as low as may be desired. Lubricating oils free of fixed carbon, or substantiallyso, can be made bythe use of the described process upon a variety of oils. The process is particularly applicable to the treatment of dewaxed oil from the acid treated reduced crude previously described. On the other hand, if applied before de-waxing, the process yields both'purified petrolatum and lubricating oil as finished products. Lubri- 'c'ating oils freed from carbon in the present manner are particularly advantageous foraviation motor lubrication and other exacting work. They are suitable for admixture in small amounts (say from 1 to 3 per cent by volume) with motor fuel in making compound gasoline for aviation motors and army tank and'tractor motors.

What I claim is 1. Inthe final purification of petroleum products to remove taste and odor, the process which comprises repeatedly warming such a product with a plurality of portions of fresh and active aluminum'chlorid with intermediate separation of sludge, heating the treated material with dilute solution of sulfuric acid, washing with water and drying.

2. In the purification of petrolatum stock,

the process which comprises treatii g such stock at a temperature sufficient to melt it, with a plurality of portions of active alumiduction with fire and steam and repeating the clay treatment.

4. In the manufacture of petrolatum of HERSGHEL G. SMITH.

num chlorid with intermediate removal of sludge, washing the stock with a hot dilute solution of sulfuric acid, washing and dry- 3. In the manufacture of petrolatum from petrolatum stock, the process which comprises treating such a stock a plurality of separation of sludge, washing out residual aluminum chlorid with dilute sulfuruic acid,

drying, filtering with clay, submitting to re-.

times with successive portions bf highly ac-. tive aluminum chlorid with intermediate