US2162717A - Process of refining cracked petroleum distillates - Google Patents

Description

June 20, 1939 w. T. HANCOCK PROCESS OF REFINING CRACKED PETROLEUM DISTILLATE Filed NOV. l, 1938 Patented June 20, 1939 PATENT OFFICE PROCESS F REFINING CBACKED PETRO- LEUM DISTILLATES .j

William T. Hancochjiong Beach, Calif. l Application November 1, 1938, Serial No. 238,214 '4 Claims. (Cl. 196-147) This invention relates generally to the treatment of cracked petroleum distillate for the pur' pose of removing gum-forming and sulphur-containing compounds, and has for its major object to provide certain improvements in the type of system disclosed in my copending application Serial No. 161,954, led September l, 1937, on Process for refining cracked petroleum distillate.

In accordance with the general method of treating cracked distillate involved in the present system, as well as that of my copending application, the distillate rst is subjected to polymerization by a suitable method, as'by contacting the heated distillate with an adsorptive mal5 terial, and is later admixed with a heated oil such as fuel oil or crude, that is substantially heavier'than the gasoline `fraction of the .pressure distillate mixed therewith. Preferably the oils are mixed under pressure sufficient to main- '20 tain at least the major portidnf the gasoline fraction in liquid phase during the mixing.

Thereafter the gasoline fraction is distilled from the heated heavier oil, either by virtue of pressure reduction and the heat contained in the admixed oils, or by additional heat supplied after the mixing.' By rst subjecting the pressure distillate to polymerization, the gum-forming and sulphur-containing compounds are placed in condition rendering them capable of being re- 3l) moved by the heated heavier oil, apparently by dissolution, although some additional affinity, chemical or physical, is believed to exist between those compounds and the heavier oil.

I have found that in the treatment of many distillates, the percentage removal of gum-forming and sulphur compounds may be materially enhanced by subjecting the polymerized pressure distillate to substantial cooling before the distillate is mixed with the heavier oil. By virtue 40 of the cooling, heavier compounds which it is desired to remove from the' distillate are brought to a denser or more congealed condition, and although the distillate is again heated when admixed with the heavier oil, the ailinity of the 4,-, latter for'the heavy polymerized bodies is increased so that higher percentage of such bodies will remain in the heavier oil after distillation of the gasoline fraction.

When the raw pressure distillate is polymer- 50 ized by contact with adsorptive earth, ordinarily at a temperature well above 200 F., the polymerized distillate is cooled at least 100 F. below the polymerizing temperature, and preferably to substantially atmospheric temperature, i. e., 60-

55 '70 F. As will later appear, I may rapidly chill the oil to any suitable temperature below atmospheric temperature, and thereby subject the distillate to extreme cooling, and further increase the temperature differential between the oils just vprior to mixing.

The invention includes an additional feature in accordance with which the polymerized distillate and heavier oil are maintained, after mixing, in

` an enlarged digesting zone over a period of time sufiicient to eiect complete dissolution of the two 10 oils, one in the other, and to permit maximum absorptionv of the gum-forming and sulphur-containing compounds in the heavier oil.

In the accompanying drawing I have shown diagrammatically and in ilow sheet form, a typi- 1i cal system embodying the invention, and to which reference is now had for more complete description.

It will be understood that the pressure distillate to be treated in the system may be derived from any suitable source for delivery to the polymerizing chamber at proper temperature. For example, pressure distillate may be taken from storage through line I0 and forced by pump I I through theheater I2, in which the oil is heated to a temperature of at least about 200 F., and usually somewhat higher, in the neighborhood of 350 F. or above, depending upon conditions such as the characteristics of the distillate and the polymerizing' method used. Instead of preheat- 30 ing storage pressure distillate, heated distillate may be .taken direct from a cracking plant (not shown) through line I3 connecting with line I4 which delivers the distillate tothe polymerizing chamber l5.

The pressure distillate contains a gasoline fraction and heavier ends, subject to polymerization by any of the known` and suitable methods. By the term polymerization I mean the transformation of hydrocarbons of relatively low molecu- 40 lar weight into hydrocarbons of relatively high molecular weight which, by reason of their higher boiling temperatures and gravities, -are separable from the desirable lighter hydrocarbons. In this respect, the invention is not limited to the use of any particular method of polymerization, and contemplates generally the use of such systems as those employing catalysts such as phosphoric anhydride, or others effecting polymerization by combined high pressure-high temperature treat'- 50 ment of the distillate, or by the use of adsorptive materials such as fullers earth and Muroc clay. Typically, the polymerizing chamber I5 may con.. tain a large body ofadsorptive clay through which the heated pressure distillate passes. while maintained, at least for the most part, in liquid phase, at a temperature above 200 F., and preferably around 350 F. to 375 F. Where other methods of polymerization are used that require the distillate to be heated to temperatures higher than those indicated. it will of course be understood that the distillate may be preheated to whatever temperature is necessary.

Before becoming admixed with .the heated heavier oil, the polymerized pressure distillate leaving chamber I is cooled, or chilled, to a temperature considerably below the temperature maintained for purposes of polymerization. The polymerized distillate may be lcooled by any suitable method, for example, by passing the distillate from line I6 through a cooler I1 to which a suit- 'able cooling medium is supplied. This cooling medium may consist of a heavier oil later to be mixed with the'pressure distillate, delivered to the cooler through line I8 and removed by way of -pipe I9. Where it is desired to chill the distillate to a temperature below the lowest temperature obtainable using the unheated heavier oil as the cooling medium, other cooling or refrigerating fluids such as precooled water, brine or any of the usual refrigerating gases, may be circulated through the cooler via lines 20 and 2|. Using a cold refrigerating medium, theldistillate may be suddenly chilled to low temperatures, around 0 F., or below. In order to maintain the desired temperature diierential between the pressure distillate and heavier oil prior to their mixing' the polymerized pressure distillate will be cooled in the cooler I 'I to a temperature at least substantially 100 F. below the polymerizing temperature of the distillate, and preferably to around atmospheric temperature, or below. As previously indicated, the purpose of subjecting the pressure distillate to a substantial temperature drop is to cause the heavier gum-forming and sulphur-containing compounds to reform, presumably into a denser physical state, so as to be subject to higher percentage removal in the heavier oil.

After leaving the cooler I1, the distillate is discharged through line 22 into a combined mixer and digester 23 comprising an enlarged shell containing staggered baiiies 24, or other suitable means for securing intimate admixture oi.' the oils. The heavier oil to be admixed with the distillate may be obtained from any suitable source, and preferably will consist of fuel oil or crude oil containing fractions heavier than the gasoline fraction in the pressure distillate. As previously explained, the heavier oil may be used as the cooling medium in the cooler I1 and supplied through line I9 to the heater 25, or the oil may be fed directly to the heater through line 26. In heater 25 the `heavier oil is heated to a temperature higher than the normal vaporizing temperature of at least the lighter gasoline fractions in the pressure distillate. VFor example, the oil may leave the heater 25 through line 21 at a temperature above substantially 300 F., and preferably in the neighborhood of from 450 F. to 550 F. or above. In order to eect maximum removal of'gum-forming and sulphur compounds, it is ordinarily advisable to admix with the pressure distillate from two to four times its volume of the heated heavier oil. The oils remain in the enlarged'chamber 23 over a period of time, say in excess of around two minutes, sufficient to permit'maximum dissolution of the-pressure distillate gum-forming and sulphur compounds in the heavier oil. The admixed oils are at the same fractionating column, so as to eiect partial or complete vaporization of the lighter fractions by virtue of the pressure reduction and the heat contained in the oils. 'Ihat is to say, the temperature of the heavier oil may be raised sufficiently in the heater 25, to supply the heat necessary for complete vaporization of the lighter fractions beyond the valve 3l, or in the event of only partial vaporization beyond that point, further heat to complete the vaporization of the lighter fractions may be supplied by suitable means such as a heating coil 32 in the base of the fractionating column.

Any contaminating bodies carried over in the vapor stream leaving the fractionating' column through line 33 may be removed by passing the vapors through column 34 containing adsorptive clay, and the vapors then passed through line 35 for nal fractionation in a second fractionating column 36. Condensate consisting, for example, of kerosene distillate and any heavier fractions present in the clay treated vapors, is removed from fractionating column 36 through line 31, while the vaporized gasoline fraction passes through line I8 to condenser 39, from which the gasoline is taken to receiver 40.

I claim:

1. The process of refining cracked petroleum distillate that includes, subjecting heated cracked distillate containing a gasoline fraction to polymerization by passing the distillate at a temperature of at least about 200 F. but below the temperature of cracking, through a body of adsorptive material, heating an independent heavier oil having a substantially higher boiling range than said gasoline fraction, mixing said distillate after passage through said adsorptive material with a substantially large quantity of the heated heavier oil under pressure suflicient to maintain the major portion of said gasoline constituents of said distillate in liquid phase during the mixing, maintaining the admixed oils in an enlarged digesting zone for a period of at least about two minutes, then reducing the pressure of the mixed oils and vaporizing said gasoline fraction from the heavier oil by virtue of the pressure reduction and heat cantained in the mixed oils, leaving polymerized and sulphur containing constituents o1' the distillate in the unvaporized oil, and condensing the vaporized gasoline fraction.

2. The process of refining cracked petroleum distillate that includes, subjecting heated cracked distillate containing a gasoline fraction to polymerization by passing the distillate at a temperature of at least about 200 F. but below the temperature of cracking, through a body of adsorptive material, heating an independent heavier oil having a substantially higher boiling range than said gasoline fraction, mixing said distillate after passage through said adsorptive maand heat contained in the mixed oils, leaving polymerized and sulphur containing constituents of the distillate in the unvaporized oil, and conv densing the vaporized gasoline fraction.

'Jil

3. The process of refining cracked petroleum distillate that includes, subjecting heated cracked distillate containing a gasoline fraction to polymerization by passing the distillate at a tem-v perature of at least about 200 F. but below the temperature of cracking, through a body of adsorptive material, then cooling the distillate at least about 100 F., heating an independent heavier oil having a substantially higher boiling range than said gasoline fraction, mixing said cooled distillate with a substantially large quantity of the heated heavier oil under pressure sulcient to maintain the major portion of said gasoline constituents of said distillate in liquid phase during the mixing, then reducing the pressure of the mixed oils and vaporizing said gasoline fraction from the heavier oil by virtue of the pressure reduction and heat contained in the mixed oils, leaving polymerized and sulphur containing constituents of the distillate in the unvaporized oil, and condensing the vaporized gasoline fraction.

4. The process of refining cracked petroleum distillate that includes, subjecting heatedcracked distillate containing a gasoline fraction to polymerization by passing the distillate at a temperature of at least about 200 F. but below the temperature of cracking, through a body of adsorptive material, then cooling to at least atmospheric temperature, heating an independent heavier oil having a substantially higher boiling range than said gasoline fraction, mixing said cooled distillate with a substantially large quantity of the heated heavier oil under pressure sufcient to maintain the major portion of said gasoline constituents of said distillate in liquid phase during the mixing, then reducing the pressure of the mixed oils and vaporizing said gasoline fraction from the heavier oil by virtue of the pressure reduction and heat contained in the mixed oils, leaving polymerized and sulphur containing constituents of the distillate in the unvaporized oil, and condensing the vaporized gasoline fraction.

WILLIAM T. HANCOCK.

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