US2072805A - Conversion of hydrocarbons - Google Patents

Description

March 2, 1937. P. H. SULLIVAN CONVERSION OF HYDROCARBONS Filed Oct. 51, 1934 A TTORNEY INVENTOR. P/KE H SULL/W/V Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE Gasoline Products Company,

Inc., Newark,

N. J a corporation of Delaware Application October 31, 1934, Serial No. 750,841

6 Claims.

This invention relates to the conversion of hydrocarbon oils into products suitable for motor fuel and pertains more particularly to a method of treating the lighter gaseous hydrocarbon .5 products resulting from the cracking and distillation of petroleum oils.

One of the principal objects of my invention is to provide a method for treating the lighter gaseous hydrocarbons resulting from the cracking or distillation operation, which is more simple and effective than processes heretofore employed..

Another important object of my invention is to provide a method for treating lighter gaseous 15 hydrocarbons, which can be carried out in more simple and compact equipment.

A further important object of my invention is to provide a process wherein crude petroleum oil may be converted into the maximum amount of 20 motor fuel products having a high anti-knock value.

With the above and other objects in View,

which will become apparent from a more detailed description hereinafter, the invention will 25 be best understood by referring now to the accompanying drawing, which is a schematic illustration of an apparatus suitable for carrying my invention into effect.

Referring now to the drawing, the reference 39 character iii, designates a heating furnace having a heating coil l i into which fresh oil for the process may be introduced through line 52, provided with pump 53. This fresh oil may be from any suitable source, and is preferably a crude 35 petroleum oil of parafinic, asphaltic or mixed base character.

The oil upon passing through the heating coil ll is heated to a distilling temperature for example in the neighborhood of from 550 to 700 F.

40 The oil after passing through heating coil ii is discharged through transfer line i into an intermediate section of a distilling and fractionating tower i5, wherein vapors and liquid products separate. The unvaporized products from the heating coil ii, together with heavy condensate formed in the intermediate zone it of the tower it, are collected in trap-out tray if, located below the point of entry of the fresh charge from heating coil ii and are withdrawn therefrom through line 38.

The product withdrawn from the intermediate trap-out tray l? is preferably passed by means of pump it to a second heating coil 25 located in the heating furnace i9 wherein it is subjected 55 to mild conversion treatment for the purpose of reducing the viscosity thereof without regard to the quantity or character of gasoline constituents which may be formed during the treatment. For example, the charge during its passage through the heating coil 2l may be heated to a temperature ranging from 750 to 850 F., for example, and maintained at this temperature for a period suflicient to convert a relatively high percentage of the original residual charge into gas oil constituents suitable for subsequent 10 cracking under more drastic conditions. The charge passing through the coil is preferably maintained under substantial pressure. For example, the coil outlet pressure may range from 100 to 500 pounds per square inch. v

The hot products, after being subjected to the viscosity breaking treatment within the heating coil 2| is passed through transfer line 22 provided with a pressure reducing valve 23, into the bottom section 24 of the distilling and fractionating tower l5 wherein vapors and heavy unvaporized residual products separate. The unvaporized residual products are withdrawn from the bottom of tower l5 through draw-off line 25 and may be rejected from the system. Vapors 25 liberated in the bottom section 26 of tower l5 pass upwardly through a central vapor passage in trap-out tray i? and are subjected to fractionation in the intermediate section it with the vapors from the fresh charge introduced through 30 line it.

Vapors remaining uncondensed in interme diate section of tower it pass upwardly through a central vapor passage of another trapout tray 28, positioned above the point of introduction of fresh charge through line it, and are subjected to further fractionation in an upper intermediate section 27 of tower E5 to condense a heavier fraction thereof which is suitable for drastic cracking treatment. The temperature at the top of the upper intermediate section 27 is preferably controlled so as to condense hydrocarbons boiling substantially above the normal gasoline range.

Vapors remaining uncondensed in upper intermediate section 2'! pass upwardly through another central vapor passage of another and higher trap-out tray 23 to the top fractionating zone 23 of the tower 25 wherein higher boiling gasoline constituents are condensed For example the top of the tower 35 may be controlled to condense constituents boiling above 250--350 F.

The intermediate fraction collected in trap-out tray 25 is withdrawn from tower 15 through line 311 provided with pump 32, and is introduced into a heating coil 33 located in furnace 34. This fraction upon being passed through the heating coil 33 is heated to a relatively high cracking temperature, so as to convert a high percentage 5 thereof into motor fuel constituents. For example, it may be heated to a temperature of from 900 to 1100 F. or 'more, and the oil may be maintained within the heating coil for a period sufficientto convert from 20 to 40 or more percent into gasoline constituerRs. The oil is preferably maintained at a relatively high pressure during the heating operation, such as, for example, from 500 to 1000 pounds per square inch. The cracked products from the heating coil 33 are passed through line 35, provided with an indirect heat,

exchanger 36, into a separator 31, wherein residual liquid and vapor products separate.

Unvaporized residual products are withdrawn from the bottom of the separator 31 through draw-oif line 38, and are rejected from the system. Vapors liberated in the separator 31 pass overhead through line 39 to a fractionating tower 4|, wherein the higher boiling hydrocarbons are condensed. The temperature at the top of the tower 4| is controlled so as to retain the gasoline constituents in vapor form, and to condense the constituents boiling thereabove. For example, the temperature at the top of the fractionating tower 4| may be controlled so that overhead vapor products have an end point of Vapors remaining uncondensed in the fractionating tower 4| pass overhead through line 42 to a,condenser 43 wherein a final distillate product is liquefied. The products from the condenser 43 then pass to a receiving drum 44, wherein the .gases and distillate separate. A final distillate product is withdrawn from the bottom of receiving drum 44, through line 45.

Gases remaining uncondensed in the condenser 43 pass overhead from receiving drum 44 through line 46 and are treated in a manner hereinafter described.

.Because of the rather drastic cracking con ditions maintained within the heating furnace 34, the gases withdrawn from the receiving drum 44 will contain a relatively large proportion of unsaturated constituents.

The higher boiling gasoline constituents con- 50 densed in the upper end zone 29 of the tower i5 are withdrawn from trap-out tray 28 through line 41, and are passed to a separate reforming coil 48, located in furnace 49, wherein they aresubjected to reforming treatment for the purpose of improving the anti-knock properties thereof. This fraction during its passage through the heating coil 48 is preferably heated to a relatively high reforming temperature. For example, it may be heated to a temperature of the order of 900to 1200 F. The pressure within the heating coil 48 may be maintained relatively low ranging from atmospheric to 100 or 200 pounds per square inch.

.The reformedlproducts from the heating coil 48 pass through line 5|, provided with an indirect heat exchanger 52, and are discharged into a separator 53, wherein liquid residue and vapor products separate. Unvaporized residual products are withdrawn from the bottom of the separator 53through draw-off line 54 and are rejected from the system. Vapors liberated within the separator 53 pass overhead through line 55 to the fractionating tower 4| and are therein subjected to fractionation with the vapor products from the -separ'ator 31. Condensate formed in the fractionating tower 4| is withdrawn from the bottom thereof through line 55 and may be returned by means of line 51, and pump 58, to the inlet side of the heating coil 33., for further. cracking treat- -ment, or it may be withdrawn from the system 5 through line 59 and subjected to separate cracking treatment if desired.

Vapors remaining uncondensed in the combined distilling and fractionating tower I5 pass overhead through line 5| to a condenser 62, wherein l gasoline constituents are liquefied. The liquid and uncondensed gases from the condenser 52 pass to a receiving drum 53 wherein gases and distillates separate. As beforementioned, in accordance with the preferred modeof operation, 1 the .higher boiling gasoline constituents will be condensed in tower l5 and subjected to reforming treatment so that the distillate separated in the receiving drum 63 will comprise principally of the lower boiling gasoline constituents, in which 20 case they will be withdrawn from the receiving drum 63 through line 54 and 65 as a final distillate product.

However, it may be desired to subject the total gasoline fraction to a reforming treatment within 25 the heating coil 48. In accordance with this latter mode of operation, the total gasoline constituents of the charge will pass overhead from the combined distilling and fractionating tower l5, through line 5|, and be condensed in the con- 30 denser coil 62. They distillate separated in the receiving drum 53 will then be passed through line 54 and 55 to the inlet side of the reforming coil 48. When operating in this manner, the trap-out tray 28, located in the top of the com- 35 bined distilling and fractionating tower l5, may be omitted. I

The gases separated in the receiving drum 53 are withdrawn overhead therefrom through line 51. When relatively mild viscosity-breaking con- 40 ditions are maintained within the heating coil 2| located in the furnace l0 so that relatively small amounts of hydrogen and methane are formed during the viscosity-breaking treatment. it is preferred to pass these gases through lines 51. 45 58 and pump 59 to a heating coil '10, located in furnace 1| wherein the gases are subjected to pyrolytic conversion into unsaturated constituents. It may. be preferred, however, particularly when more drastic viscosity-breaking conditions 50 are maintained within the heating coil 2|, located in furnace It, to pass these gases to an apparatus for removing the hydrogen and methane before subjecting the same to pyrolytic conversion. In accordance with the latter procedure the gases 55 from the receiving drum 53 pass through lines 51 and 12 into hydrogen and methane separating towers 13 and 14 wherein the gases are fi'actionjated for removing the hydrogen and methane therefrom as hereinafter described. The hydrogen and methane free gases removed from the top of the fractionating tower 14 through line 15 is returned, via line 15,;tathe inlet side of the heating coil 10 for conve1silinnm unsaturated constituents. These gasesfmayogfitg-n t be com- 05 .bined with other saturated gases rears-the system as hereinafter described.

As before mentioned, the heating furnace 1| is controlled to convert the saturated hydrocarbon gases into unsaturated compounds. For ex- 70 ample, the gases during their passage through the heating coil 10 may be heated to a temperature ranging from 1100 to 1700 F. or higher, while maintained under relatively low pressure, ranging, for example, betweenvatmospheric and 200 75 pounds per square inch. The gases are preferably subjected to a. rapid heating while passing at a. high velocity through the heating coil, and are maintained at conversion temperature for only a. short period such as from one tenth of a second to a second. The velocity of the gases through the heatingcoil may be from 15 to 30 feet per second.

The gases after being subjected to the desired treatment within the heating furnace I0 are passed through line II and are combined in line I8 with gases from the reforming and cracking treatment before described. To this end the line 46 leading from receiving drum 44 and line I! leading from heating coil I0 merge into line I8. The gases resulting from the reforming and cracking treatment will normally contain substantial quantities of unsaturated constituents which can be polymerized without being subjected to pyrolytlc conversion.

The combined stream of gases in line I8 resulting from the gas-pyrolysis in the heating coil I0 and the cracking and reforming treatment in heating coils 33 and 48, respectively, may be- I0. It may be desired, however, to subject these gases to further heating before carrying out the polymerizing reaction.

For example, the combined stream of gases may be passed through lines 18, 8|, 82 and 88 to a heating coil 89 located in the separator 31. thence through line 9I to a second heat-exchange coil 92 located in the separator 53, thence through line 93 to heat exchanger 38 located in transfer line 35, thence through line 05 to heat exchanger 52 located in transfer line 5|, thence through lines 96, 84, pump and lines 86 and 81 to the polymerizing chamber I9. If desired, additional heat may be provided by passing the gases through heating coil 91 located in a separate polymerizing furnace 98. Heat- exchange coils 89 and 92 and heat exchangers 36 and 52 are provided with by-pass lines 99, IOI, I02 and I03, respectively, 50 that one or more of the heat ex changers may be by-passed if .desired.

It is usually preferred, however, to subject the combined gases resulting from the pyrolytlc conversion and from the cracking and reforming treatment to fractionation to remove the hydrogen and methane before subjecting the same to polymerization. In accordance with this latter procedure the combined gases from the line I8 is passed through line I04 provided with a heatexchange coil I05 wherein the gases are cooled, and then through line I 06 provided with pump I 0'! to a fractionating tower I 08.

The temperature and pressure conditions maintained within the fractionating tower I08 is controlled so as to condense all constituents boiling above methane and hydrogen. The uncondens ed hydrogen and methane are withdrawn from the top of fractionating tower I 08 through line I09. Separation of the hydrogen and methane may be aided by introducing a solvent 01' absorbent oil through line III into the top of the fractionating tower I08. This solvent oil may be a relatively heavy hydrocarbon oil such as condensate from the bottom of fractionating tower 4| or the intermediate fractions from trapout trays I1, 26, and 28 of fractionating tower I 5.

The condensate formed in the fractionating tower I08 and unvaporized solvent oil is withdrawn from the bottom of the tower through draw off line I I2, and is introduced into an intermediate section of a second tower II3, wherein it is subjected to distillation and fractionation. A heating coil H4 is provided in the bottom of the tower H3 to supply additional heat for distillation. The tower H3 is heated to a temperature sufficient to distill the absorbed hydrocarbon gases from the solvent oil introduced into the tower I08 through line III. The unvaporized solvent oil is withdrawn from the bottom of tower I I3 through line H4, and again introduced through line II'I into the top of the tower I08. The hydrocarbon vapors liberated from the solvent oil in the fractionating tower I I3 pass overhead through line II5, which connects with line 82 and are subjected to polymerization in chamber I9 after being heated to the desired polymerizing temperature in the heat exchangers 89,

The gases before being passed to the polymerizing chamber I9 are preferably heated to a temperature of the order of 700 to 1000 F. and placed under a relatively high pressure, such as, ifor example, from 500 to 3000 lbs. per square nch.

The gases after being heated to the above mentioned temperature and placed under the desired pressure by the pump 85 are allowed to digest at the above mentioned temperatures and pressure for a period suflicient to polymerize the unsaturated constituents of the gases into higher boiling hydrocarbons suitable for motor fuel. For example, the gases may be allowed to digest in the polymerizing chamber I9 for from, three to thirty minutes. If desired, a suitable polymerizing catalyst su h as clay, may be introduced into the polymerizing chamber I9 to aid in the carrying out of polymerization.

The products from the polymerizing chamber I9, after being subjected to the desired amount of digestion therein, are passed through line IIE, provided with a reducing valve 1, into a combined fractionating and distilling tower II8, wherein liquid and vapor products separate. The fractionating tower H8 is maintained under a pressure materially below that maintained in the polymerizing chamber I9. For example, the pressure may be reduced to from to 300 lbs. per square inch by the reducing valve In. The higher boiling liquid polymers separated in the combined distilling and fractionating tower 8 are withdrawn from the bottom thereof through line H9 and may be rejected from the system, or may be passed to the heating coil 2|, located in furnace I0 by a suitable line (not shown) and subjected to viscosity breaking treatment with the original charge in the manner hereinbefore described.

Vapors liberated in the bottom section of the tower I I8 pass upwardly through a central vapor passage located in the trap-out tray I2I, and are subjected to further fractionation in the upper section of the tower. The temperature of the upper section of the tower II 8 is controlled to condense hydrocarbons boiling above the normal gasoline boiling range. For example, the overhead vapor products may have a 400 F. end point. The condensate fraction formed in the upper section of the tower I I 8 is collected in trapout tray I2I, and is withdrawn therefrom through line I22. This condensate fraction may be passed ing furnace 36, or it may be passed through lines I22, I24 and i8 to the viscosity breaking furnace coil 2|.

Vapors remaining uncondensed in the fractionating and distilling tower H8 pass overhead through line "5 to a condenser I26, wherein a final distillate product is condensed. The products from thecondenser coil I26 then pass to a receiving drum I21, wherein the unpolymerized gases and liquid separate. The liquid is withdrawn as a final distillate through the line I28, and the gases may be removed over-head through 'line I29. The gases from line I29 may be then passed to hydrogen and methane separating towers 13 and 14, which are operated in the same manner as towers I08 and H3 hereinbefore described. If desired, these gases may be rejected from the system through line l3| without further treatment. The gases freed of the hydrogen and methane in towers l3 and 14 are then passed through line I6 to the gas pyrolysis furnace II for conversion into unsaturated compounds.

As illustrated, the gases from the receiving drum I21 may or may not be admixed with gases from line 12 resulting from the stripping or viscosity breaking treatment, before being treated to remove the hydrogen and methane therefrom. In cases where it is desired to remove hydrogen and methane resulting from the initial distilling and viscosity breaking treatment this removal can be advantageously effected in the same equipmentaused to remove hydrogen and methane from the final gases from receiving tank [21.

Although I have described my invention in connection with a specific apparatus, it will be understood that various other types of apparatus may be employed for carrying the invention into effect. For example, I have shown the separate heating coils for heating desired hydrocarbon stocks located in separate heating furnaces, but it will be understood by those skilled in this art that a plurality of said heating coils may be positioned within a single, furnace. For simplicity, I have also shown the fractionating tower l5 and others provided with a plurality of trap-out trays for separating diflerent fractions, with the understanding that these fractions may be collected by separate fractionation in separate towers preferably arranged in series. -It will be further understood that the temperature pressures and time of treatment are not limited to the specific values given herein.

While I have described the preferred embodiment for purposes of illustration, it will be 1111- derstood that my invention embraces such other modifications and variations as come within the spirit and scope thereof, and it is not my intention to dedicate any novel features, or-to unduly limit the-scope of my invention, except as necessary to distinguish from prior art.

I claim:

l. A process for converting hydrocarbon oil into relatively low-boiling hydrocarbon oil suitable for use as motor fuel, which comprises distilling a crude petroleum and fractionating it to separate residual constituents and vapors, subjecting said residual constituents to a mild cracking temperasate to more drastic temperature conditions tocrack the same, fractionating the cracked prodaovasoe ucts to recover a craked gasoline distillate, a gas fraction comprising principally hydrogen and methane, and an intermediate fraction substantially free from hydrogen and methane. subjecting said intermediate fraction to'elevated temperature and superatmospheric pressure effective to polymerize constituents thereof to normally liquid products, fractionating the polymerized products to recover a motor fuel fraction and a heavier reflux, and delivering said reflux to one of the aforementioned cracking operations to crack the same.

combined vapors to condense a clean condensate,

subjecting said clean condensate to more drastic temperature conditions to crack the same, fractionating the cracked products to recover a cracked gasoline distillate, a gas fraction comprising principally hydrogen and methane, and

an intermediate fraction substantially free from hydrogen and methane, subjecting said intermediate fraction to elevated temperature and superatmospheric pressure effective to'polymerize constituents thereof to normally liquid products, fractionating the polymerized products to recover a motor fuel fraction and a heavier reflux, and commingling said reflux with said residual constituents for subjection to said mild cracking temperature.

3. A process for converting hydrocarbon oil into relatively low-boiling hydrocarbon oil suitable for use as motor'fuel, which comprises distilling a crude petroleum and fractionating it to separate residual constituents and vapors, subjecting said residual constituents to a mild cracking temperature, separating the mildly cracked products into tar and vapors, commingling said last-mentioned vapors with vapors from said distilling operation,

'fractionating the combined vapors to condense a gas fraction comprising principally hydrogen and methane, and an intermediate fraction substantiallyfree from hydrogen and methane, subjecting said intermediate fraction to elevated temperature and superatmospheric pressure effective .to polymerize constituents thereof to normally liquid products, fractionating the polymerized products to recover a motor fuel'fraction and a heavier reflux, and commingling said reflux with said clean condensate for-subjection to said more drastic temperature conditions to crack the same.

4. A process for converting hydrocarbon oil into relatively low-boiling hydrocarbon oil suitable for use as motor fuel, which comprises distilling a crude petroleum to separate it into naphtha, a heavier clean condensate and residual constituents, subjecting said residual constituents to a mild cracking temperature under, a high super atmospheric pressure, separating the products to recover gas, naphtha? and a heavier can condensate, subjecting said naphtha and said heavier clean condensate from said distilling and mild cracking operations to more drastic cracking 'aovasos conditions, fractionating the products to separate cracked gases and distillate, collecting gases from the aforementioned operations, fractionating them to remove hydrogen and methane therefrom, subjecting the fractionated gases to elevated temperature and pressure adequate to effect a polymerization of constituents thereof to normally liquid products, fractionating the products to separate a motor fuel fraction and a heavier polymer fraction, and commingling said heavier polymer fraction with said residual constituents for subjection to said mild cracking temperature.

5. A process for converting hydrocarbon oil into relatively low-boiling hydrocarbon oil suitable for use as motor fuel, which comprises distilling a crude petroleum to separate it into naphtha, a heavier clean condensate and residual constituents, subjecting said residual constituents to a mild cracking temperature under a high superatmospheric pressure, separating the products to 'recover gas, naphtha and a heavier clean condensate, subjecting said naphtha and said heavier clean condensate from said distilling and mild cracking operations to more drastic cracking conditions, fractionating the products to. separate cracked gases and distillate, collecting gases from the aforementioned operations, fractionating them to remove hydrogen and methane therefrom, subjecting the fractionated gases to elevated temperature and pressure adequate to ef feet a polymerization of constituents thereof to normally liquid products, fractionating the products to separate a motor fuel fraction and a heavier polymer fraction, and delivering heavier polymer thus obtained to one of the aforementioned cracking operations to crack the same.

6. A process for converting hydrocarbon oil into relatively low-boiling hydrocarbon oil suitable for use as motor fuel, which comprises subject ing heavy hydrocarbon oil to a mild cracking temperature, separating the mildly cracked products into tar and vapors, fractionating said vapors to condense a clean condensate, subjecting said clean condensate to more drastic temperature conditions to crack the same, fractionating the cracked products to recover a cracked gasoline distillate, a gas fraction comprising principally hydrogen and methane, and an intermediate fraction substantially free from hydrogen and methane, subjecting said intermediate fraction to elevated temperature and superatmospheric pressure effective to polymerize constituents thereof to normally liquid products, fractionating the polymerized products to recover a motor fuel fraction and a heavier reflux, and delivering said reflux to one of the aforementioned cracking operations to crack the same.

PIKE H. SULLIVAN.

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