US2038614A - Degumming gasoline and the like - Google Patents

Description

Aprifl 28,1936. D. R. STEVENS ET AL DEGUMMING GASOLINE AND THE LIKE Filed May 5. 1930 Elmo/MM DonaZcLR.STe@ems,

' Willa Lean my W Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE Gruse, Wilkinsburg, Pa., assignors,

by mesne assignments, to Gulf Oil Corporation of Pennsylvania, Pennsylvania Pittsburgh, Pa., a corporation of Application May 3, 1930, Serial No. 449,680 10 Claims. (01. 196-93) This invention relates to degumming gasoline and the like; and it comprises a process wherein a body of liquid gasoline or analogous oil is heated under pressure to a temperature not less than about 700 F. for a period not greater than 30 minutes, the pressure being usually of the order of about 1000 pounds per square inch and being either that developed by heating or by pump pressure, or both; all as more fully hereinafter set forth and as claimed.

In theuse of gasoline from cracking plants an annoying feature is the development of gum on storage. The gasoline as first made contains no actual gum but it does contain bodies which in time, that is in storage or on standing, tend to develop gum; this tendency being aided by the presence of oxygen, that is, by contact with air. It is not practicable to free the gasoline of gum by redistillation. The nature of the gum or of the bodies which yield it is not known, but it is supposed that the gum is formed by the polymerization of diolefins or some other unsaturated bodies, probably assisted by oxidation. Whatever these unsaturated bodies are, they are of the general physical type of gasoline and are useful components of the mixture, provided they do not polymerize to form gum.

We have found that by heating gasoline distillates under pressure for a limited time in the absence of catalysts and of added hydrogen to a temperature considerably in excess of the normal vaporizing temperature,but below a temperature suificiently high to recrack such distillates. The so treated gasoline upon redistillation is found to be permanently substantially free of gum and of the tendency to develop gum on standing. Our invention contemplates treatment of hydrocarbon distillate for a period of time up to fifteen minutes, while maintaining said distillate under a pressure of about one thousand pounds per square inch. This result may be due either to the rearranging of the gum-forming hydrocarbons into more stable forms, or it may be due to the rapid completion of the polymerizing action, thus removing gum and potential gum. There is danger, however, in this reheating, of the polymerization going too far and forming high- .boiling oils from low-boiling oils; this is particutimes of heating are employed, say at moderate temperature. There is further a danger in the opposite direction, in that cracking may occur with the development of gases and some coke from the gasoline. This is particularly true at high temperatures, Both these diificulties should be avoided.

larly true when long We have found that by heating gasoline distillates to a temperature of about 750 F. and holding them under high pressure at this point for about minutes there is substantially no loss in gasoline by cracking and the gasoline is freed of gum and of tendency to develop gum on standing. In the case of gasoline distillates from liquid phase cracking, the optimum temperature seems to be about 790 F. while the dangerous temperature is about 40 degrees higher or 830 F. With gasoline distillates made by a vapor phase operation, the optimum temperature of heating is somewhat lower, being about 770 F. with a danger range again about 40 degrees higher, say, about 810 gasoline and the like materials commercially used, such as the drips from a gas plant handling cracking still gases, at lower limit may be used; about 735 F. For this type of material the dangerous temperature is about 60 degrees higher. In considering the time necessary to effect substantial improvement of the distillate, a distinction must be drawn between preformed gum, that existing in the distillate and remaining after evaporation in an inert atmosphere such as steam, and potential gum, that to be expected after the gasoline has been exposed to oxidation in storage for a prolonged period. This potential gum is determined by a combination of oxidation and evaporation as in the copper dish test or the oxygen gum method of Voorhees and Eisinger, Journal of the Society of Automotive Engineers, 25, 584 (1929). We have found that the preformed gum may be removed very easily; that is, by a short time of exposure to temperatures of the same order as those mentioned above as effective. Even lower temperature may be used. For example, the preformed gum in a liquid phase cracked gasoline was lowered from 37.4.- mg./ co. to 2.6 mg./100 cc. by exposure to a temperature of 660 F. at 500 pounds pressure for six minutes. In a vapor phase cracked gasoline the preformed gum was lowered from 200 mg./ 100 cc. to 6.4 mg./100 cc. by exposure to 660 F. at 500 pounds for six minutes. The potential gum is not sufficiently lowered under these conditions and it is necessary to prolong the time and adjust the temperature as indicated in the preceding paragraph. Conditions suitable for removing potential gum will also remove preformed gum.

By working within the temperature limits indicated, gum and the gum yielding tendency are positively obviated while the losses by polymerization and by cracking are minimized. In other words, by operating within the temperature limits F. With some highly unsaturated I specified the amount of actual gasoline left after treating closely corresponds to the amount of gasoline treated, while gum and gum yielding compounds are obviated. By working at either a higher range of temperature or a lower range of temperature neither result is positively secured. Within the desirable limits, however, the higher the temperature, the less is the time necessary.

We have found portions of gasoline distillates boiling in different temperature ranges may advantageously be treated under somewhat different conditions. For instance, the higher boiling portion of a cracked gasoline distillate (that boiling above 280 F.) may be treated at 790 F., and the lower boiling portion (that boiling below 280 F.) at 750 F., each for 30 minutes under pressure. The treated fractions when mixed, and the resulting gasoline distilled out, yielded a product better as to gum properties than when the whole distillate was treated all at once.

As to the optimum pressure for treatment we have observed that improved gum reduction is obtained as the pressure is raised to about 1000- 1200 pounds, but that above this pressure no substantial further benefit is obtained.

There is some advantage in condensing the reheated material under pressure, this being presumably equivalent to slight extension in time of treating.

In operating under the described invention, any convenient type of apparatus may be employed. With batch operation, autoclaves, boilers and the like may be employed, while in continuous operation liquids to be treated may travel in countercurrent to liquid which has undergone treatment, thereby economizing heat. The particular nature of the apparatus forms no part of the present invention.

Our invention may be described by reference to the accompanying drawing which shows, more or less diagrammatically, an organization of apparatus elements useful for carrying out our process. In this showing:

Fig. 1 is a diagrammatic, elevational view, partly in section, of the complete apparatus required for the conduct of our process, while Fig. 2 is a similar view of the apparatus required in a modification of the later steps of our process.

In the figures like apparatus elements are designated by like reference numerals.

Referring to Fig. 1, element l is a tank acting as a source of supply and containing gasoline distillate from a cracking process, or it may be a tank of finished gasoline which is to be re-treated to reduce its tendency to form and deposit gum. The material to be treated in accordance with my invention is withdrawn from tank I through line 2. It passes through a pump 3 which forces it through line 4 into heating coil 5, this coil being situated in furnace 26. In coil 5 the gasoline is heated to a high temperature, usually from 700 to 800 F., under a pressure which may be of the order of 1000 pounds per square inch. It is held under these temperatures and pressures for a period of time usually less than 30 minutes. After the necessary treatment at high temperature and under high pressure in coil 5, the material may be conveyed through lines 6 and 1 to a condenser 8. Otherwise the heat treatment may be prolonged by passing the hot material from coil 5, through the chamber l9; as described subsequently, prior to condensation. The condensed material fiows through line 9 into iractionator l0 and that sometimes the different.

in this fractionator the desired constituents, having boiling points within the gasoline range, are separated from high boiling point polymerization products and any other high boiling point constituents which leave the fractionator by line 13. The vapors within the gasoline range leave the fractionator through line I2. The necessary heat for the fractionation may be supplied by a steam coil II in the base of the fractionator. The vapors in line l2 pass to a condenser l3, where they are liquefied, and from there pass through line id to a separator l5. The desired stabilized gasoline is withdrawn from separator l5 through line l6, any uncondensed gas is withdrawn from the separator through line I1, and condensed steam is withdrawn from the separator through line l8.

if the time of passage of vapors through coil 5, after attaining the desired temperature, is insufficient to accomplish the desired gum stabilization, the vapors from coil 5 are passed through a large capacity chamber l9 prior to condenser B. Valves are provided on the lines to permit routing the vapors either through line 6 or chamber l9.

Fig. 2 illustrates a later steps in the process of Fig. l and permits a considerable saving in heat as tion in the necessary amounts of steam and cooling water. In this modification the coil 8 is operated as a cooling coil rather than as a total condenser, and at that point the vapors are cooled only to the point necessary to obtain proper fractionation in fractionator Illa. The so cooled stream is delivered through line 9 to a separator 22, where the liquid constituents are separated from the vapor constituents. These two streams are then discharged through lines 23 and 24, respectively, into fractionator "la, the liquid constituents being introduced into the i'ractionator at a higher point than are the vapor constituents.

Gum is highly undesirable in motor fuels, tending to increase carbon deposits, forming gummy deposits on the valves, and in fold, as well as possibly interfering with carburetion. It is therefore highly desirable not only to remove any gum present in gasoline but to treat it so that gum will not form. However, distillates from which gasoline is fractionated may be treated in accordance with our invention-pressure stil distillates, vapor phase distillates and the like, with, not only improvement in such distillates, but with improvement in different fractions obtainable therefrom including gasoline. It is therefore within the purview of our invention to treat such distillates as pressure still distillate, vapor phase distillate, or in fact any distillate containing gum or of a char-* acter likely to form gum as well as to treat gasoline itself.

By the terms cracked gasoline and cracked gasoline distillate employed in the claims we mean a gasoline or a gasoline distillate produced by the cracking of a heavier oil.

What we claim is:

1. In a process of degumming cracked hydrocarbon distillate by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence of catalysts and of added hydrogen to a temperature between 700 and 800 F. for about 6 to 30 minutes while maintaining said distillate under a pressure of about 1000 pounds per square inch, the said cracked the intake manidistillate being of such type as to show substan tially no cracking under the conditions stated.

2. In a process of degumming cracked gasoline distillates by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence'of catalysts and of added hydrogen to a temperature between about 700 and 800 F. for a period sufiicient to effect degumming of the material under treatment but not substantially longer than 30 minutes while maintaining such distillate under a pressure of about 1000 pounds per square inch.

3. In a process of degumming cracked hydro-- carbon distillates by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence of catalysts and of added hydrogen to a temperature of about 750 F. for a period of time suflicient to efiect degumming but not substantially exceeding 30 minutes, while maintaining said distillate under a pressure of about 1000 to 1200 pounds per square inch; the said cracked distillates being of such type as to show substantially no cracking under the conditions stated.

4. In a process of degumming cracked gasoline distillates by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence of catalysts and of added hydrogen to a temperature above 700 F. but not sufiiciently high to re-crack it, for a period of time suflicient to effect degumming but less than 30 minutes, while maintaining said cracked distillate under pressure Within the range of about 1000 to 1200 pounds per square inch.

5. In the process of degumming cracked gasoline distillates by simple heat and pressure treatment, the process which comprises dividing a cracked gasoline distillate into two fractions, one having a higher boiling range than the other, heating said fractions separately in the absence of catalysts and of added hydrogen to temperatures between about 700 and 800 F. under pressures of the order of 1000 to 1200 pounds and for a period of from about 6 to 30 minutes, the higher boiling of the said two fractions being heated to a temperature approximately 40 F. higher than that to which the said lower boiling fraction is heated, and uniting the so-treated fractions.

6. In a process of degumming cracked hydrocarbon distillates by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence of catalysts and of added hydrogen to a temperature between about 700 and 800 F. under pressures of the order of about 1000 to 1200 pounds for a period of time not substantially exceeding 30 minutes but suflicient to efiect degumming, the said cracked distillate being of such type as to show substantially no cracking under the conditions stated.

7. In a process of degumming cracked hydrocarbon distillates by simple heat and pressure treatment, the process which comprises heating such a distillate under pressures of the order of 1000 to 1200 pounds in the absence of catalysts and of added hydrogen to temperatures above 700 F. but insuflicient to cause substantial cracking, for a period of time ranging from about 6 to 30 minutes.

8. In a process of degumming cracked hydrocarbon distillate by simple heat and pressure treatment, the step which comprises heating such a distillate in the absence of catalysts and of added hydrogen to a temperature considerably in excess of the normal vaporizing temperature, but below a temperature sufiiciently high to recrack such distillate, for a period of time not in excess of 30 minutes, while maintaining said distillate under a pressure of about 1000 pounds per square inch.

9. The process of claim 7 wherein agasoline distillate from a liquid phase cracking process is employed and the heating temperature is of the order of 790 F.

10. The process of claim 7 wherein said gasoline distillate is from a vapor phase cracking operation and the heating temperature is of the order of 770 F.

DONALD R. STEVENS. WILLIAM A. GRUSE.

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