US1823175A - Art of refining hydrocarbons - Google Patents

Description

Sept' 15; 1931- J. cs STAFFORD ART` OF REFINING- HYDROCARBONS Filed March 50, 1928 Patented Sept. 15,I 1931 f UNITED STATES ,PATENT oF-Fic JAMES G. STAFFORD, F 'WHITING, INDIANA, ASSIGNOR T0 SINCLAIR REFINING C0111- PANY, 0F NEW YORK, N. Y.,

A CORPORATION 0F MAINE ART OF BEFINING HYDROCARBONS Application inea March 3o, 192s. seria No. 26,842.

This invention relates to improvements in refining petroleum distillates. The invention is of special value kand application in the treatment of light cracked petroleum dis- 5 tillates, for example, gasoline to be used for motor fuel, and particularly in the treatment of low boiling distillates produced by vapor phase cracking operations, The invention is also useful inthe treatment of other cracked distillates, such as wax distillate.

Unrefined cracked distillates contain relatively large quantities of unstable unsaturated hydrocarbons which decompose readily on standing or exposure to sunlight with the formation of objectionable gum-like constituents. Low boiling distillates produced by cracking in the va or phase in particular, contain exceptionally large quantities of panied by the removal, together with the more objectionable compounds, of the relatively stable constituents that are. desirable as components of a finished lmotor fuel product.

The present invention provides a novel method of operation whereby even the most highly cracked distillates Lfrom vapor phase cracking operations may be readily converted at small cost with a minimum of equipment and without excessive loss of the material to be treated, into waterfwhite distillate products which are free from disagreeable odor and relatively stable even on prolonged standing or exposure to sunlight.

According to the improved process of the invention, the unrefined distillates to be treated are subjected to an elevated temperature and pressure under non-oxidizing con- (litions in the presence of a finely divided solid adsorbent material, such as fullersy earth, and a stable hydrocarbon liquid capable of acting as a solvent for the gum-like these unstable unsaturated hydrocarbons.-

constituents or higher boiling polymers formed by the resulting reactions.

The refining process of the invention may advantageously be carried out in a continuous manner by flowing a stream of the petroleum distillate to be treated in admixture with a stable hydrocarbon liquid through a body of finely divided fullers earth or similar solid adsorbent material while maintaining the flowing stream of distillate to be treated at temperatures of from about 375 F. or somewhat lower to about 500o F. or'somewhat higher and a pressure at least sufficient to prevent substantial vaporization at the tem-v perature employed, and subsequently separating the treated distillate product from the stable solvent and the dissolved reaction roducts contained therein. Separation o the treated distillate product may be obtained, v

ufor example, by ordinary distillation, at at mospheric pressure, or, the pressure may loe` reduced on the mixture of treated distillate and solvent oil as discharged from the treating operation to eect vaporization of the lower boiling distillate by its contained heat and thereafter separating the desired test distillate by fractional condensation. Y

The exact temperatures and pressures to be most advantageously employed in the treatment of a given distillate will, of course, vary with the character of the distillate to be treated, the kind of solvent oil used, the

nature ofthe solid adsorbent material, the;

degree of refinement desired in the distillate product, the time ofcontact permitted and the yield it is desired to obtain from a given amount of solid adsorbent medium. ln general, increasing either the temperature or pressure tends to increase the rate of the polymerizing reaction. The pressure may, if deslred, be maintained at about the pressure required to prevent substantial vaporization at the temperature employed though higher pressures tend to promote the treatin action and prolong the life off the solid a sorbentmaterial. Fullers earth,.in a finely divided state, maybe satisfactorily employed as the solid adsorbent material in carrying out the process of the invention. Silica gel, activated carbon, bauxite. and similar adsorbent materials may belikewise used to advantage.

Kerosene and gas oil have been satisfactorily employed as stable liquid solvents in carrying out the process of the invention, although l other liquid hydrocarbons substantially stahigher boiling polymers, for example, straight run gasoline, solvent naphtha, pressure still charging stock and the like, may be used to advantage asa diluent. Heavier distillates. such as gas oil, are more readily maintained in liquid state at elevated temperatures and appear to have the greater solvent action. `The heavier solvents have the further vadvantage that they (may be more readily separated by fractional distillation from t e desired test distillate due to the great di erence in their boiling range.

In the treatment of South Texas and Mid- Continent vapor phase cracked distillates usin a blend of 80% of the unreiined crac ed distillate with 20% water-white kerosene and a 60-90 mesh No. 0 Olmstead fullers earth, temperatures of about 380 F. to 500 F. and pressures of 150 to 200 lbs. per square inch have been satisfactorily employed.

The exact relationship between the action of the objectionable unsaturated hydrocarbons contained in unrened highly cracked distillates, the finely divided adsorbent material and the stable liquid solvent in effecting the removal of the former is not clearly understood. It may be that the solid adsorbent material acts directly, to a certain extent, 0n the objectionable unsaturated constituents although in the presence of the stable liquid solvent at elevated temperatures and pressures its'action appears to closelyap' proach that of a true catalyst. In any event,

the combined action of the stable liquid solvent and solid adsorbent material at elevated temperatures and pressures is such that the objectionable constituents may be converted in the liquid phase to higher boiling polymers that may be readily separated from' the desired test distillate by ordinary fractionating operations.

The relationship of the action of the solid i adsorbent material and the stable liquid solvent at elevated temperatures and pressures 'ma be best illustrated by the results of the fo owing s ecific examples:

A 460 end-point vapor' phase cracked South Texas distillate having an. orange color and disagreeable odor was passed oo through a cell containing 60,-90 No. 0 Olmstead fullers earth. The distillate was heated to a temperature of 500 F. andV maintained at a pressure of 150 lbs. per square inch during the treatment. The rate of flow through the treating cell was regulated t0 permit contact of the distillate under treatment with the earth for about one hour. The treatment was discontinued after one gallon of distillate per pound of earth used had been passed through the treating cell and the treated vdistillate redistilled to obtain a 392 F. end-point stock. The redistilled m'aterial was found to'average less than 16 Saybolt color although only one gallon o f material had been treated per pound of earth used.

In another test a mixture consisting of 80% of the same unretinedvapor phase cracked distillate and water-white kerosene was passed through the treating cell under the same conditions employed in the previous test. This time the treatment was continued until more than two gallons per pound of earth used had been passed through the treating cell and was stopped only because of shortage of charging stock. Thev treated material was then redistilled as in the previous test. The redistillation yielded a Saybolt color'motor fuel which had a sweet odor and was stable even on prolonged standing and exposure to sunlight.

In another test a mixture consisting of 80% Mid-Continent va or phase cracked gasoline, having an initial oiling point of about 120 F'. at atmospheric pressure, and 20% waterwhite kerosene was passed throu h the treating cell at a temperature of 380 and pressure of 200 lbs. per square inch. The test was continued until about 4% gallons of oil per pound of earth had been passed tlrough the treating cell. The motor fuel fraction obtained on redistillation of even the last material to pass through the treati' J' el i this test was found to have a 30+ Saybolt color. A sample of the stock used in this test, before treatment, was heatedin a.. autoclave todeterminethe relationship' of the temperature and pressure existing. in the treating cell. The pressure corresponding to the diii'erent temperatures to which the charge of oil was heated in the autoclave are given in the following table:

'Tempera- Pressure tm Lbs. per

aqJn. .l".

25 285 50 332 75 374 100 414 125 450 15o v 474 175 495 m0 519 -225 538 250 558 Since the critical temperature of hydrocar- 4 bon products boiling at= F. at atmospheric pressure is sufliclently high that they will y remain liquid when heated to 380 F. if held at 200 lbs. per square inch ressure it will be evident on inspection of t e relation of the temperature and pressure conditions noted/Nt" in the autoclave treatment that the reactions which took place in the treatin cell in thelast test were accomplished wit all parts of the charge in a liquid condition.

In still another test a mixture consisting of 80% unrefined Mid-Continent vapor phase cracked distillate and 20% water-white kerosene was passed through a treating cell containing a fresh charge of -90 No. 0 Olmstead earth at the same rate as that employed in the previous tests. A temperature of 450 F. and pressure of 150 lbs. per square inch were maintained on the oil during treatment and the operation continued until about 6%: gallons of the vmixture per pound of earth used had passed through the treating cell. The treated distillate was then redistilled as before. The test gasoline so obtained was found to have a 21+ Saybolt color and a sweet odor, and to be substantially stable on standing and exposure to sunlight. The yield of treated test gasoline based on the latter test was found to be approximately 225 barrels perton of fullers earth charged to the treating cell.

In carrying out the processof the invention the polymerization losses will vary considerably with the character of 'the distillate to be treated and the degree of refinement desired in the finished product. In the treatment of a very highly cracked distillate the polymerization losses may, for example, be as high as 10% while in the treatment of cracked disillates from ordinary liquid phase cracking operations, by the process of the present invention, polymerization losses are negligible. In the treatment of very highly cracked distillates the polymerization losses will also vary somewhat during the 'treating operation, being slightly higher during the initial stages when the solid adsorbent material is fresh. In any case, however, substantially' all of the more unstable unsaturatedhydrocarbons suitable as components of a motor fuel remain in the final treated and redistilled'product. The polymerized products may to advantage be subjectedto further cracking treatment and an Vadditional yield of the desired distillate product obtained therefrom and therefore do not represent a true loss comparable to the sludge loss in the usual acid treatment.

The invention will be further described in connection with the accompanying drawings which illustrate one form of apparatus' adapted for carrying out the process of the invention. It will be understood that this more detailed description of the invention isV intended as an exenrplification of the invention and that the process of the invention is not limited-thereto.

Referring to the drawing, the apparatus illustrated comprises a heater-1 and two treating cells 2 and 3, each of which is provided with appropriate ports or removable heads 4the cells, a fractionating tower 4a con- .hot products of combustionthereover from a for supplying and discharging finely divided solid material and with suitable screens to prevent the escape of such solid material fromdenser 5 and a. pump 6 provided with suit- 70 able connections for conveying distillates to be treated through the heater to the treating cells. Cells 2-and 3 are filled with a finely divided solid adsorbent, such as fullers earth or similar adsorbent material. 4 These cells are arranged in duplicate to permit discharging and recharging of one while the oil under treatment is fiowing through the other. The heater lmay be any suitable type of heating element adapted to heat the oil uniformly to the desired temperature during its passage therethrough. For example, the

eating coil 1 may be heated by circulating furnace (not shown). The treating cells 2 85 and 3 and the connections between the heater and the treating cellsmay to advantage be lagged or mildly heated externally to prevent loss ofheat -by radiation during the treating operation. In the apparatus illustrated the pressure onthe treating vcells may be regulated and the rate of fiow of oil through the treating cells controlled by the valves 7, 8 and 9 and the pump 6 so as to maintain any desired pressure on the oil during treatment,v and so that the period of time vover which the oil is in contact with the adsorbent material' is sufficient to effect conversion of the unstable unsaturated hydrocarbons to higher boiling polymers which may be readily separated from the desired test distillate by fractional distillation or condensation. Valved lconnections 10 and 11 are adapted to supply the u nrefined cracked distillate and a. stable liquid solvent in regulated amounts from suitable sources of supply to the pump 6. Following treatment with the solid adsorbent material'the treated mixture may be discharged-directly to the lower end of fractionating tower 4. The pressure on the mixture may be reduced at the valve 7 to effect vaporizat-ion of the lower boiling components thereof by its contained heat and the vapors so generated separated from the higher boiling solvent and dissolved material in the fractlonating tower 4. The treated gasoline product may be taken oil' as vapor from the top of the fractionating tower and condense'd to form the desired test gasoline t product. The heavier solvent oil containing the dissolved higher boiling polymers may be drawn off as a liquid from the bottom of the tower 4 and led to a suitable storage tank or subjected to further treatment. For example, the solvent oil and dissolved constit'- 125 uents may be charged directly while hot to' a pressure still, wherein both the solvent oil and higher boiling polymers may be subjected to further cracking treatment. This method of operation is particularly advantageous when pressure still charging stock is employed as a liquid solvent in the treating operation. The hot treated mixture in the treating cells may, if desired, be drawn off directly through the valved branch connection 12, or through the condenser 5 by means of the by-pass connection 13, the condenser acting as 'a cooler in the latter case to prevent liash evaporation when the pressure is reduced if the treated mixture is to be discharged to a storage tank. If the treated cracked product is to be blended with a straight run gasoline, a portion of the straight-run gasoline may with advantage be used as the stable solvent liquid required inthe treating operation. The treati ed mixture may also be drawn oli through valved branch connection 12 while hot to an ordinary rerun still and redistillation of the cracked treated product carried out in conjunction with distillation of the product with which the test gasoline from the treated mixture is to be blended.

It will be apparent that in carrying out the process of the invention the oil might be passed through a series of cells charged with solid adsorbent material and as the charge in one or more of the cells became exhausted the other charges in the series might be advanced so that the oil discharged from the apparatus will always be last contacted with the1 freshest charge of solid adsorbent mater1a It is one of the advantages of the process of the invention that its simplicity makes it 'Well adapted to continuous operation. The control of the operation involves simply the maintenance of contact between the mixture of unrefined cracked distillate and stable liquid solvent and the solid adsorbent material at an elevated temperature and ressure for a period of time suflicient to e ect'conversion of the desired amount of unstable unsaturated hydrocarbons required in any particular case so that the attention of a skilled operator is, accordingly, not essential.

I claim: j

1. The improvement in the refining of cracked hydrocarbon distillates comprising admixing therewith a liquid hydrocarbon having a higher boiling range than said distillatc, said liquid hydrocarbon being capable of acting as a solvent for the higher boiling reaction products formed in the refining operation and substantially stable under the conditions of the refining operations, and subjecting the mixture in a liquid state to an elevated temperature lower than that at which substantial cracking will occur and simultaneously to an elevated pressure in the presence of a inely divided solid adsorbent material.

2. The improvement in the refining of" cracked hydrocarbon Vdistillates comprising admixing with said cracked distillate a liquid hydrocarbon more stable than said cracked admixing a kerosene-character distillate withv sald cracked distillate, subjecting the mixture to a temperature lower than that at which substantial crackin will occur but in excess of about 375v F. 1n the presence of finely divided fullers earth, and maintaining a superatmospherc pressure in excess of that required to prevent substantial vaporization oi said distillates during the treating operatlon.

4. An improved method of refining cracked hydrocarbon distillates comprisin admixing with said cracked distillate a llqpid hydrocarbon more stable than said crac ed dis.- tillate under the conditions prevailing in the refining operation and capable of acting as a solvent for the khigher boiling reaction products formed during the refining operation and subjecting the mixture in a liquid stateto a temperature lower than that at which substantial cracking will occur but in excess of about 375 F. in the presence of a finely divided solid adsorbent material, and subsequently separatin the treated distillate from the stable liqui solvent and higher boiling reaction products dissolved therein. l

5. The improvement in the refinin of cracked hydrocarbon distillates comprlsing admixing with said cracked distillates a liquid hydrocarbon more stable than the said cracked distillates under the conditions prevailing in the refining operation and capable of acting as a solvent for the higher boiling reaction products formed during the re` fining operation, subjecting the mixture to a temperature of about 375 to 500 F. in the presence of a finely divided solid adsorbent material and maintaining a superatmospheric pressure on the mixture during treatment in excess of that required to prevent `substantial vaporization of said distillate.

6. The improvement in the refnin of cracked hydrocarbon distillates comprlsing admixing with said cracked distillates a hydrocarbon liquid more st-able than the said cracked distillates under the conditions prevailing in the refining operation and capable of acting as a solvent for the higher boiling reaction products formed during the refining operation, subjecting the mixture in a liquid state to a temperature of about 375 to 500 F. in the presence of a finely divided solid adsorbent material, and malntaining a superatmospheric pressure of about -200 lbs. per square inch on' the mixture during the treatment.

7 An improved method of refining low boiling cracked hydrocarbon distillates comprising admixing With said cracked distillates a liquid hydrocarbon more stable than said cracked distillates under the conditions prevailing in the rening operation and capable of acting as a solvent for the higher boiling reaction products formed during the refining operation, passing a st-ream of the mixture in intimate contact With a nely divided solid adsorbent material, maintaining the mixture of low boiling cracked distillates and stable liquid hydrocarbons at a temperature lower than that atV which substantial cracking will occur but in excess of about 375 F. and at a pressure in excess of that required to prevent substantial vaporization at the temperature employed during contact With -said finely divided solid adsorbent material, and subsequently reducing the pressure on the treated mixture to effect vaporization of the low boiling cracked distillates.

In testimony whereof, l have subscribed myname.

JAMES G. STAFFORD.

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