US2270072A - Hydrocarbon conversion - Google Patents

Description

Jan E. H. HYDHOCARBON CONVERSION Filed Sept. 8, 1959 Patented Jan. 1 3, 1942.

HYDROCARBON CONVERSION Edwin H. McGrew, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, El., a corporation of Delaware Application september 8, i939, serial No. 293,895

5 Claims.

This invention relates to the production of a motor gasoline of relatively low olefin content, high octane rating, and relatively low potential gum content, which due to its relatively high degree of saturation, is useful as aviation gas-' crude and reflux condensate, thermal reforming.

treatment of a relatively light hydrocarbon oil,

such as, for example, gasoline, naphtha, or.

kerosene, high temperature catalytic cracking treatment of an intermediate oil,such as, for example, kerosene or gas oil, common fractionation of the conversion products from the thermal cracking and reforming treatments, and the high tially atmospheric to 200 pounds or more per square inch in the presence of a catalyst of essentially the same composition as that employed in the high temperature catalytic cracking treatment and the reaction is essentially that of hydrogen transfer.

It has been found that when mixtures of olefin-containing gasolines produced by either temperature catalytic cracking treatment and,

low temperature catalytic conversion treatment of the distillate and light reflux condensate.

formed and separated therein.

The term thermal cracking treatment as used throughout the specification and claims refers to the conversion of -heavxr hydrocarbons into lighter hydrocarbons by heat and pressure, and in all instances involves the scission of carbon to carbon bonds. The term thermal reforming treatment on the other hand, refers to the treatment of relatively light hydrocarbons to im- ,prove their octane rating and may involve the scission of carbon to carbon bonds, the scission of carbon to hydrogen bonds, cyclization and many other reactions of lesser importance. The term high temperature catalytic cracking treatment refers to the treatment of hydrocarbon oils in the presence of catalytcally active massesat temperatures ranging, for example, from 800 to 1200 F. and at pressures varying from substantially atmospheric to 200 pounds or more per square inch to effect substantial conversion to l gasoline boiling range hydrocarbons, and ordinarily involves the scission of carbon .to carbonl non-catalytic or catalytic methods and a relatively heavy hydrocarbon oil, such as intermediate conversion products from a non-catalytic cracking treatment or from a once-through catalytic cracking treatment, are subjected to contact with a catalyst essentially the same composition asthat employed in the catalytic cracking treatment but at lower space velocities and lower temperatures, a substantially saturated.

gasoline product is obtained. Whereas, inhigh temperature catalytic cracking treatments temperatures of the order of 800 to 1200 F. are employed with pressures of from substantially atmospheric to 200 pounds or more per square inch with space velocities of from 2 to 6 volumes of hydrocarbon material per volume of catalyst per hour, in the low temperature' treatment temperatures of the order of 500 to 900 F.A are employed with pressures of from substantially atmospheric to 200 pounds or more per square inch and with space velocities of from .5 to 2.

'I'he hydrogen content of the intermediate conversion products from a non-catalytic cracking treatment is ordinarily high as compared to vthat of the intermediate conversion products from a catalytic cracking treatment when `recycle operation is employed in both cases, and therefore the intermediate conversion products from the non-catalytic cracking treatment are preferred as the hydrogen donor. On the other hand, the hydrogen content of the intermediate conversion products formed in a once-through catalytic cracking treatment is also high, and this material may be employed as the hydrogen donor in the low temperature catalytic conversion treatment.

The reaction involved in low temperature catalytic conversion is essentially one of transferring hydrogen from the heavier hydrocarbons to the lighter olefinic hydrocarbons to convert the latter to parainic hydrocarbons, although cracking, cyclizatlon, and isomerization reactions may also be involved. It is believed that in low temperature catalytic conversion treatment saturated hydrocarbons and particularly the naphthenic hydrocarbons of the recycle oil actas hy?,

the gasoline, while the oleflnic hydrocarbons become saturated to form paraflinic hydrocarbons and the naphthenic hydrocarbons are converted to aromatic hydrocarbons., Various other reactions, such as, for example, dehydrogenation and cyclization of an aliphatic hydrocarbon to form an aromatic hydrocarbon with the formation of two or three molecules of hydrogen which attach to the unsaturated oleiinic hydrocarbons may also take place. However, since the invention is concerned primarily with a process in which the various reactions may be conducted, further discussion with regard to the chemical reactions which may possibly be involved is unnecessary for a full understanding of the invention which is to be vdescribed later in more detail.

In one specific embodiment the invention comprises subjecting combined feed comprising heavy reflux condensate, formed as hereinafter described, and a relatively heavy hydrocarbon oil to thermal cracking treatment in a heating coil and communicating reaction chamber, concurrently therewith subjecting a relatively light hydrocarbon oil to thermal reforming treatment, simultaneously in another step subjecting an intermediate oil to high-temperature catalytic cracking treatment in a heating coil and communicating high temperature catalytic reactor, commingling the conversion products from the three treatments and introducing the mixture to a vaporizing and separating chamber to separate a non-vaporous liquid residue from the vaporous conversion products, recovering the former, fractionating said vaporous conversion products to form light and heavy reflux condensate and to separate fractionated vapors boiling in the range of gasoline, subjecting the heavy reilux condensate to thermal cracking treatment, as previously described, cooling and condensing said' fractionated vapors, separating the resulting distillate and gas and recovering the latter, commingling said distillate with the light reflux condensate, heating the mixture and subjecting the heated oil to contact with a cracking catalyst in the low temperature catalytic reactor, fractionating the conversion products from said low temperature catalytic reactor to form reflux condensate and to separate vapors boiling in the range of gasoline, subjecting said reflux condensate to thermal cracking treatment in commingled state with said heavy reflux condensate, formed as previously described, cooling aand condensing said vapors and recovering the resulting distillate and gas as products of the process.

The accompanying diagrammatic drawing shows in conventional side elevation one specific form of the apparatus in which the object of the invention may be accomplished. It is to be understood, however, that the invention is not limited to the use of the specific form of apparatus herein shown and that various departures may be made therefrom without deviating from the spirit of the invention.

Referring now to the drawing, a relatively heavy hydrocarbon oil, such as, for example, a topped or reduced crude oil is introduced through line I and valve 2 to pump 3, which discharges through line 4 and valve 5, said heavy oil commingling with heavy reflux condensate, formed as hereinafter described, and the combined feed introduced to heating coil 6. The oil in passing through heating coil 6 is raised to the desired cracking temperature which may range, for example, from 850 to 1000 F. and is maintained at this temperature for a sufcient period of time to effect substantial thermal cracking thereof, heat being supplied from furnace 1. The hot conversion products leaving heating coil 6 at a superatmospheric pressure ranging, for example, from 200 to 600 pounds or more per square inch, are directed through line 8 and valve 9 into reaction chamber I0 wherein they are subjected to prolonged conversion at the cracking temperature. Reaction chamber I0 is preferablyoperated at a superatmospheric pressure substantially the same as that employed on the outlet of heating coil 6 and is preferable insulated to reduce radiation losses therefrom, although no insulation is shown in the drawing. The vaporous and liquid conversion products leaving chamber I0 are directed through line II and valve I2 into vaporizing and separating chamber I3 for treatment as hereinafter described.

In addition to the thermal cracking treatment of a heavy hydrocarbon oil, the invention also proposes to thermally reform a relatively light hydrocarbon oil, such as gasoline, naphtha,'or kerosene, or any mixture thereof, and to catalytically crack an intermediate oil at relatively high temperatures to produce more valuable products than either of the two last mentioned charging stocks. The use of either of these operations is optional and may depend upon the amount of high octane substantially saturated motor fuel desired, which may vary for each specific case. In accordance with the objects of the invention, however, since both thermal reforming and high temperature catalytic cracking yield a gasoline product rich in olefinic hydrocarbons and since the objective in all cases is to treat each hydrocarbon oil under the optimum conditions for the production of motor fuel, such operations may be conveniently employed in combination with a thermal cracking treatment and the gasolines produced in al1 cases subjected to low temperature catalytic conversion treatment to produce a substantially saturated motor fuel.

Thermal reforming treatment, in the case here illustrated, may be accomplished by introducing a relatively light hydrocarbon oil, such as, for example, gasoline, naphtha, or kerosene, or any mixture thereof, through line I4 and valve I5 to pump I 6, which dischargesI through line ll and valve i8 into heating coil I9. The oil in passing through heating coil I9 is subjected to thermal reforming treatment at a temperature ranging, for example, from 950 to 1050 F. by means of heat supplied from furnace 20. The conversion products leaving heating coil I9 at a pressure ranging, for example, from 500 to 1200 pounds per square inch are directed through line 2l and valve 22 into line Il where they commingle with the vaporous and liquid conversion products from reaction chamber I0.

The high temperature catalytic cracking treatment may be accomplished by introducing an intermediate oil, such as kerosene, or gas-oil, or any mixture thereof, through line 23 and valve 24 to pump 25, which discharges through line 26 and valve 2l into heating coil 28. The oil in passing through heating coil 28 is substantially completely vaporized and raised to the desired temperature, which may range, for example, from 800 to 1200 F. without substantial pyrolytic cracking thereof by means of heat supplied from furnace 29. The heated vapors leaving heating coil 28 at a pressure ranging, for example, from substantially atmospheric to 200 pounds or more per square inch are directed through line 30 and ,ferred to above.

be prepared by precipitating silica from a solution disposed therein while maintaining the hydrocarbon vapors at substantially the same temperature as that employed on the outlet of the heating coil by means of heat supplied from an external source.

The preferred cracking catalysts for use in the present process consists in general of a precipitated alumina hydrogel and/or zirconia hydrogel composited with silica hydrogel, the gel composite being washed, dried, formed into particles and calcined to produce a catalytic mass. It is not intended, however, that the process should be limited to these particular catalysts, for other catalysts, such as, for example, the hydrosilicates of alumina, acid treated clays, and the like, may be used within the broad scope of. the invention,

In the following specification and claims the terms silica, alumina, silica-zirconia, and silicaalumina-zirconia masses are used in the broad sense to designate the synthetic composites re- The preferred catalysts may as a hydrogel within or upon'which the alumina and/or zirconia. are deposited also by precipitaactors are segregated from the balance for the purpose of reactivation. y

Although the reactor described above constitutes the preferred type of reactor, it is not intended that the invention should be limited in this respect, for various other types of reactors, known to those in the art, may be substituted therefor without departing from the broad scope of the invention.

The conversion products leave reactor 32 by way of line 33 and a portion'or all are directed the conversion products from heating coil I9 in line -I I for treatment as hereinafter described.

Vaporizing and separating chamber i3 is preferably operated at a reduced pressure relative to that employed in either of the three conversion treatments or at substantially the same pressure tion as hydrogels. The silica hydrogel may coni veniently be prepared by acidifying an aqueous solution of sodium silicate by the addition of a 5 required amount of hydrochloric acid. After precipitating, the silica gel is preferably washed until substantially free-from alkali metal salts. The Washed silica hydrogel is then suspended in a solution of alumina and/or zirconium salts and an alkaline precipitant, such as ammonium hydroxide, lammonium carbonate or ammonium sulfide added to the solution to precipitateA which may be ground and pelleted or sized to" produce particles of catalyst after which the catalyst particles are calcined at a temperature in the approximate range of 1000 to 1500 F. Various other procedures, such as, for example,

vco-precipitation of the hydrated gels may be eml ployed, when desired, to produce the preferred catalyst.

Reactor 32 is preferably of the type which employs a plurality of relatively small diameter reactor tubes containing the desired catalyst, the tubes being confined within an enclosed zone tov which heat from an external source may be sup- The vapors introduced to fractlonator di are subgasoline.

plied for the purpose of maintaining the ref means, not shown, may be employed for reactivat` ing the catalyst disposed within the various reactors during the period those particular reas that lemployed in the high temperature catalytic cracking treatment in reactor 32 when low pressures are employed therein, and it may range,

for example, from 25 to 250 pounds or more per square inch. The liquid conversion-products introduced in commingled state withthe vaporous conversion products in chamber I3 are subjected to substantial further vaporization therein to form a non-vaporous liquid residue which is4 withdrawn from chamber I3 by way of line 3l` and valve 38, cooled and subjected to any dejected to fractionation therein to form light and heavy reflux condensate and to separate fractionated vapors which may, comprise gasoline boiling range hydrocarbons or may, when desired, include hydrocarbons boiling above the range of The heavy reflux condensate is directed through line d2 and valve B3 to pump da, which discharges through line d5 and valve 66 into line d where said heavy reflux condensate commingles with the heavy oil to form combined feed and said combined feed thereafter subjected to thermal cracking treatment, as` previously described. f

Fractionated vapors separated inv fractionator il are directed from the upper portion thereof through line 41 and valve 48 to cooling and conf densation in condenser '59. The distillate in condenser 39, together with undissolved and uncondensed gases, is directed through line 50 and valve 5I into receiver 52 wherein said distillate is separatedA from the undissolved and uncondensed gases, the latter being withdrawn from receiver 52 by way of vline 53 and valve 53 and recovered or subjected to any desired further treatment. A portion of the distillate collected and separate in receiver 52 may be returned to the upper portion of' fractionator 5I by well known means, not shown, as a refluxing and cooling medium. A portion or all of the remaining distillate in receiver 52 may be withdrawn therefrom by Way of line 55 and valve 56and recovered as a product of the process. Preferably, however, the remaining lboiling range hydrocarbons.

distillate in receiver 52 is directed through line 5l and valve 58 to pump 59, which discharges through line 60 and valve 6l into line 65 for treatment as hereinafter described.

Light reflux condensate from fractionator il is directed through line 62 and valve 63 to pump 513, which discharges through line 65 and valve 66 and said light reflux condensate commingled with the distillate removed from receiver 52, as previously described, the mixture thereafter being supplied to heating coil 61.

The mixture of oil introduced to heating coil 61 is raised to a temperature in the range of 500 to 900 F. without substantial pyrolytic cracking thereof by means of heat supplied from furnace 69. The heated oil leaving heating coil 61 at a pressure ranging, for example, from substantially l atmospheric to 200 pounds or more per square inch is directed through line E9 and valve 19 into reactor 1| where it is subjected to contact with a cracking catalyst while maintaining the oil at substantially the same temperature as that employed on the outlet of heating coil 61. The catalyst employed in reactor 1l may be of the same composition as that employed and described in connection with reactor 32. The low and high temperature catalytic conversion reactions diier essentially with respect to temperature and contact times employed, the reaction in reactor 32 being carried out at a'relatively high temperature and short contact time, whereas the reaction in reactor 1l is carried out at a lower temperature and at a longer contact time. Reactors 32 and 1| may be essentially of the same design, however, as was previously .I

mentioned, various other types of reactors may be employed to accomplish the desired results.

The conversion products leaving reactor 1I are directed through line 12 and valve 13 into fractionator 14 which is maintained at substantially the same or at a reduced pressure vrelative to that employed on the outlet of reactorY 1I. The conversion products introduced to fractionator 14 are subjected to fractionation therein to form reflux condensate and to separate the gasoline Reflux condensate formed in fractionator 14, which in this stage of the process containsy relatively large amounts of aromatic hydrocarbons, is preferably subjected to thermal cracking treatment and this may be accomplished by directing the same through line 15 and valve 16 to pump 11, which discharges through line 18 and valve 19 into line 45 where said reflux condensate commingles with the heavy reflux condensate fromfractionator 4l, the mixture thereafter being subjected to the same treatment as that performed on the heavy reflux condensate, as previously described.

Fractionated vapors fromfractionator 14 are directed through line 80 and valve 8l to cooling and condensation in condenser 82. Distillate, together with undissolved and uncondensed gas- :es in condenser 82, is directed through line 83 and valve 84 to collection and separation in receiver 85. Normally gaseous hydrocarbons collected and separated in receiver 85 are directed from the upper portion thereof through line 8G and valve 81 to storage or to any desired further treatment. A portion of the distillate collected in the lower portion of receiver 85 may be returned to the upper portion of fractionator 14 by well known means, not shown, as a refluxing and cooling medium therein. The balance of the distillate collected in receiver 85 is removed therefrom by way of line 88 and valve 89 and recovered as a product of the process.

In carrying out one specic operation of the process illustrated and above described, the conditions employedand results obtained were approximately as follows:

A A. P. I. gravity mid-continent yreduced crude oil was commingled with heavy reflux condensate, formed as hereinafter described, and the mixture subjected to thermal cracking treatment in the heating coil and communicating reaction chamber at a temperature of 930 F. and under a superatmospheric pressure of 300 pounds per square inch.

AIn another step of the process a 53 A. P. I. gravity straight-run gasoline fraction was subjected to thermal reforming treatment in a heating coil at a temperature of 1010 F. and under a superatmospheric pressure of 750 pounds per square inch.

In another step of the process a 35 A. P. I. gravity straight-run gas-oil fraction was vaporized and heated to a temperature of 950 F. and the resulting vapors subjected to contact with a silicaalumina-zirconia catalyst under a superatmospheric pressure of approximately 60 pounds per square inch while maintaining the vapors in the catalytic zone at a cracking temperature.

The conversion products from the thermal cracking and reforming treatments and the catalytic cracking treatment were commingled and the mixture introduced to a vaporizing and separating chamber maintained under a superatmospheric pressure of 50 pounds per square inch. The liquid conversion products introduced to the vaporizing and separating chamber were subjected to substantial further vaporization to form a non-vaporous liquid residue and the latter, corresponding to approximately 25.3% of the total charge, recovered as a product of the process.

The vapors from the vaporizing and separating chamber were fractionated to form light and heavy reflux condensates and to separate vapors boiling below 400 F. The heavy reflux condensate was subjected to conversion, as previously described. The fractionated vapors were subjected to cooling and condensation and the resulting distillate and gas collected and separated.

The 400 end point distillate recovered was commingled with the light reux condensate, the mixture heated to a temperature of 750 F. and thereafter subjected to contact with a silica-alumina-zirconia catalyst at' a pressure of approximately pounds per square inch while maintaining the temperature of the materials undergoingconversion at substantially that at which they were discharged from the heating coil. The conversion products from the low temperature catalytic treatment were fractionated to form reflux condensate, which was supplied to the thermal cracking treatment, and to separate fractionated vapors boiling below 300 F. which were cooled, condensed, and recovered as a product of the process.

The above described operation, based on a total feed, distributed approximately as follows:

44% reduced crude, 22% straight-run gasoline, and 34% gas-oil resulted in a yield of approximately 63.5% of 300 end point gasoline having an octane number of 74 and a bromine number of 9. With the addition of 6 cc. of tetraethyl lead the octane rating was raised to 96. In addition, normally gaseous hydrocarbons were obtained, corresponding to approximately 100% minus the yield of gasoline and liquid residue, which contained a high percentage of polymerizable oleiins.v

I claim as my invention:

v1. The process of converting hydrocarbons, which comprises subjecting combined feed comprising a relatively heavy hydrocarbon oil and reflux condensates, formed as hereinafter described, to thermal cracking treatment, concurrently therewith subjecting a relatively light hydrocarbon oil to thermal reforming treatment and an intermediate oil to high temperature catalytic cracking treatment, commingling the conversion products from said thermal cracking and reforming treatments and from said high temperature catalytic cracking treatment, supplying the mixture to a vaporizing and separating zone to separate non-vaporous liquid residue'which is recovered as a product of the process from the vaporous conversion products, fractionating said vaporous conversion products to form light and heavy reflux condensate and to separate vapors boiling in the range of gasoline, supplying said heavy reflux condensate to treatment as aforesaid, cooling and condensing said vaporsand recovering the resulting distillate and gas, commingling said distillate with the light refluxcondensate and subjecting the mixture to low temperature catalytic treatment, fractionating the conversion products from said low temperature catalytic treatment to form reflux condensate and to separate fractionated, vapors, supplying said reflux condensate to said thermal cracking treatucts of the process. l

2. The process of. converting hydrocarbons,

which comprises subjecting combined feed comprising a relatively heavy` hydrocarbon oil and reflux condensates, formed as4 hereinafter de-`v scribed, to thermal cracking treatment, concurrently therewith subjecting a relatively light hydrocarbon .oil to thermal reforming treatment and an intermediate oil to high temperature catalytic cracking treatment, commingling the conversion products from said thermal cracking treatment and said thermal reforming treatments and supplying the mixture toa vaporizing and separating chamber to separate a non-va- `the mixture to low temperature catalytic treatmen-t, fractionating the conversion products from said low temperature catalytic treatment to form reflux and to separate fractionatedvapors. 'supplying said reux condensate to said thermal cracking treatment for treatment as` aforesaid, cooling and condensing said fractionated vapors and recovering the resulting distillate and gas as products of the process. 3. The5 process of converting hydrocarbons, which comprises subjecting combined feed comreflux condensates, formed as hereinafter described, to thermal cracking treatment, concurrently therewith subjecting a relatively light hydrocarbon oil to thermal reforming treatment and an intermediate oil to high temperature catalytic cracking treatment in the presence of a silicaalumina catalyst, commingling the conversion products from said thermal cracking and reforming treatments and from said high temperature catalytic cracking treatment, supplying the mixture-to a vaporizing and separating zone to separate non-vaporous liquid residue which is recovered as a product of the process from the vaporous conversion products, fractionating saidl vaporous conversion products to form light and heavy reflux condensate and to separate vapors boiling in the range of gasoline, supplying said -heavy reux condensate to said thermal cracking ment in the presence of a catalyst of `essentially I the same composition as hereinbefore set forth,

., fractionating the/conversion products from said low temperaturecatalytic treatment to form re-i flux condensate and to separate fractionated vapors, supplying said reux condensate to said thermal cracking treatment for treatment as aforesaid, cooling and condensing said fractionated vaporsfand recovering the resulting distillate and gas as products of the process.-

4. The process of converting hydrocarbons, which comprises subjecting combined feed comprising a relatively heavy hydrocarbon oil and reflux condensates, formed as hereinafter described, to thermal cracking treatment at a temperature of from 850 to 1000" F. and under asuperatmospheric pressure of from 200 to 600 pounds per square inch, concurrently therewith subjecting a relatively light hydrocarbon Oil to thermal reforming treatment at atemperature of from 950 to 1050 F. and at a pressure of from 50 to 200 pounds per square inch, and an intermediate oil to high temperature catalytic cracking treatment in 'the presencel of a silica-zirconia catalyst at a temperature of from 800 to 12009 F. and under a pressure of from substantially atmospheric to 200 pounds per square inch, commingling the conversion products ,from said 'thermal cracking and reforming treatments and from said high temperature catalytic cracking treatment, supplying the mixture to a vaporizing and separating zone to separate non-vaporous liquid residue which is recovered as a product of the process from the vheavy reflux condensate to said thermal cracking treatment for treatment as aforesaid,cool ing and condensing said vapors and recovering the resulting distillate and gas, commingling said distillate with the light reflux condensate and subjecting the mixture to low temperature catav lytic treatment inthe presence of a catalyst of es- ,prisinga relatively heavy hydrocarbon oil and sentially the same composition as that hereinbefore set forth at a temperature offrom 500 to 900 F. and at a pressure of from substantially atmospheric to 200 pounds per square inch, fractionating the conversion products from said low temperature catalytic treatment to form reux condensate and to separate fractionated vapors, supplying said reflux condensate to said thermal cracking treatment for treatment as aforesaid, cooling and condensing said fractionated vapors and recovering the resulting distillate and gas as products of the process.

5. The process of converting hydrocarbons, which comprises subjecting combined feed cornprising a relatively heavy hydrocarbon oil and reflux condensates, formed as hereinafter described, to thermal cracking treatment at a temperature of from 850 to 1000 F. and under a superatmospheric pressure of from 200 to 600 pounds per squareinch, concurrently therewith subjecting a relatively light hydrocarbon oil to thermal reforming treatment at a temperature of from 950 to 1050 F. and at a pressure of from 50 to 200 pounds per square inch. and an intermediate oil to high temperature catalytic cracking treatment in the presence of a catalyst consisting essentially of silica composited with alumina and zirconia, at a temperature of from 800 to l200 F. and at a pressure of from substantially atmospheric to 200 pounds per square inch, commingling the conversion products from said thermal cracking and reforming treatments and from said high temperature catalytic cracking treatment, supplying the mixture to a vaporizing and separating zone to separate non-vaporous liquid residue which is recovered as a product of the process from the vaporous conversion products, fractionating said vaporous conversion products to form light and heavy reflux condensate and to separate vapors boiling in the range of gasoline, supplying said heavy reilux condensate to said thermal cracking treatment for treatment as aforesaid, cooling and condensing said vapors and recovering the resulting distillate and gas, commingling said distillate with the light reiiuX condensate and subjecting the mixture to low temperature catalytic treatment in the presence of a catalyst of essentially the same composition as that hereinbefore set forth at a temperature of from 500 to 900 F. and at a pressure of from substantially atmospheric to 200 pounds per square inch, fractionating the conversion products from said low temperature catalytic treatment, to form reflux condensate and to separate fractionated vapors, supplying said reflux condensate to said thermal cracking treatment for treatment as aforesaid, cooling and condensing said fractionated vapors and recovering the resulting distillate and gas as products of the process.

EDWIN H. MCGREW.

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