US2248357A - Hydrocarbon conversion - Google Patents

Description

July 8, 1941. E. R. KANHOFER HYDROCARBON couvERsION Filed July 31. 1939 FRACTIONATOR CONDENSERr-QO FRACTIONATOR REACT? i FURNACE,69

INVENTOR ELMER R. KANHOFER Patented July 8, 1941 UNITED STATE 5 PATENT YoFFlcE I HYDROCARBON CONVERSION Elmer R. Kanhofer, Chicago, 111., assignor to Unlveral Oil Products Company, Chicago, 111., acorporation of Delaware Application July 31; 1939, seramazsmsi 2 Claims.

This invention relates to a process'which involves a series of concomitant steps wherein hydrocarbon oils are converted into substantial yields of high octane rating gasoline having a relatively low olefin'content and improved prop-.

catalytic cracking treatment of the reformed andcracked gasoline in commingled state with the straight-run gas-oil fraction, fractionation of the conversion products from the low temperature catalytic cracking treatment to separate the gasoline boiling range hydrocarbons from the higher boiling hydrocarbons, recovery of the former, and

range of gas-oil, and a heavy fraction containing hydrocarbons boiling above said intermediate fraction, commingling said heavy fraction with reflux condensate, formed as hereinafter described,

and subjecting the mixture to thermal cracking treatment in a heating coil and communicating reaction chamber, simultaneously subjecting said light fraction to thermal reforming treatment in a heating coil, commingling the conversion products from the thermal cracking and thermal-re-' forming treatments and supplying the mixture to a'vaporizer and separator wherein non-vaporous liquid residue is separated from the vaporous conversion products, recovering the former, supplying said vaporous conversion products to a fractionating zone to separate fractionated vathe return of the latter to the thermal cracking treatment.

The term thermal cracking as used throughout the specification and claims refers to the treatment of a hydrocarbon oil boiling above the range of gasoline under elevated temperatures and pressures whereby to effect substantial conversion into gasoline boiling range hydrocarbons;

' whereas the term thermal reforming treatment refers to the treatment of gasoline boiling range hydrocarbons under elevated temperatures and pressures to effect substantial conversion of the parafllnic hydrocarbons into olefinic hydrocarbons without materially altering the boiling range. The term low temperature catalytic cracking treatment refers to the treatment of a 1 mixture of hydrocarbon oil containing the gasoline from the thermal cracking treatments and an added saturated hydrocarbon oil in the presence of a cracking catalyst at a temperature in the range of 500 to 800 F., but preferably from 700 to 800 F. and at a pressure ranging, for example, from substantially atmospheric to 200 pounds or more per square inch whereby to increase the degree of saturation of the olefinic hydrocarbons subjected to treatment and at the same time'efiect some cracking of the heavier hydrocarbons.

In one specific embodiment the invention comprises fractionally distilling a wide. boiling range hydrocarbon oil to separate a light fraction consisting essentially of hydrocarbons boiling in the range of gasoline, an intermediate fraction consisting essentially of hydrocarbons boiling in the pors boiling in the range of gasoline from the heavier hydrocarbons. condensing the latter as reflux condensate in'the fractionating zone and supplying it tovthe heating coil, as previously described, cooling and condensing said fractionated vapors to formdistillate and gas, recovering the latter, commingling said distillate with said intermediate fraction, separated as aforementimed, and passing the mixture in the heated state in contact with a cracking catalyst in a relatively low temperature catalyticcracking zone whereby to increase the degree of saturation of the olefinic hydrocarbons contained in the mixture in addition to cracking some of the heavier hydrocarbons, fractionating the conversion products from the low temperature cracking zone to separate fractionated vapors boiling in the range of gasoline from the higher boiling hydrocarbons, recovering the former, condensing the latter in the fractionating zone as reflux condensate, and returning it to the thermal cracking treatment.

In the thermal cracking and reforming processes, gasoline is produced which contains high percentages of olefinic hydrocarbons which, although-tending to increase its octane rating, are responsible for the poorer susceptibility of the gasoline to added antiknocking agents, such as tetraethyl lead, and in addition are responsible for the poorer storage stability because of gum formation as compared to a gasoline which is predominantly paraflinic and/or aromatic in character. It has been found that if the gasoline produced in the thermal cracking treatments is commingled with a saturated hydrocarbon oil and the mixture subjected to contact with a catalyst mass, to be described more fully later, at a temperature in therange of. 600 to 900 1?. for a longer period of time than that ordinarily employed in catalytic cracking treatments, a gasoline product is obtained, composed primarily of paraflinic and aromatic hydrocarbons, which has a relatively high octane rating, low potential gum content, and a good susceptibility to antiknocking agents, whereby it is possible with the addition of relatively small amounts of tetraethyl lead to obtain a gasoline suitable for aviation purposes.

It is believed that in the low temperature catalytic cracking treatment, as described. above, that a portion of the hydrogen from the saturated hydrocarbons, and particularly the naphthenic hydrocarbons, is transferred to the oleflnichydrocarbons formed in the thermal cracking treatment, whereby the olefinic hydrocarbons become saturated to form paramnic hydrocarbons and the naphthenic hydrocarbons are converted to aromatic hydrocarbons.

Various other reactions, such as, for example, dehydrogenation and cyciization of an aliphatic hydrocarbon to form an aromatic hydrocarbon with the formation of 2 or 3 molecules of hydrogen which attach to the unreacted oleflnic hydrocarbons. may also take place. A further discussion in connection with what may possibly take place is unnecessary since the invention does not concern itself with the chemistry of the various reactions but is concerned with the process for producing the desired result.

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 that the invention is not limited to the use of the specific form of apparatus herein disclosed and that various modifications of the process herein described may be made without departing from the broad scope of the invention.

Referring now to the drawing, the charging stock for the process, comprising a wide boiling' range hydrocarbon oil, such as crude oil, is introduced through line I and valve 2 to fractionator 3, which is operated at a pressure ranging, for example, from to 100 pounds or more per square inch, wherein the oil is subjected to fractional distillation to separate a light fraction consisting essentially of gasoline boiling range hydrocarbons, an intermediate fraction consisting essentially of hydrocarbons boiling in the range of gas-oil, and a heavy fraction containing hydrocarbons boiling above said intermediate fraction. The light fraction withdrawn in the vaporous state from fractionator 3 is directed through line 4 and valve 5 into condenser 6 wherein the vapors are subjected to cooling and condensation. The resulting distillate and gas from condenser 6 is directed through line I and valve 8 into receiver 9 wherein undissolved and uncondensed gases are separated from the condensed light fraction. Gases collected and separated in receiver 9 are directed from the upper portion thereof through line l0 and valve II to collection and storage or disposed of in any suitable manner. When desired, fractionator 3 may be operated so that the light fraction contains only the lower boiling hydrocarbons in the gasoline boiling range, such as, for example, those boiling below 275 F., in which case this iraction may be recovered as a product of the process, and the higher boiling hydrocarbons in fraction contains not only gasoline boiling range hydrocarbons but also naphtha and kerosene.

Aportion of the light distillate fraction collected and separated in receiver 3 may be returned to the upper portion of fractionator 3 by well known means not shown as the refluxing and cooling medium. When 'fractionator 3 is operated so that the light fraction contains only the lower boiling hydrocarbons in the gasoline boiling range, the same may be recovered from receiver 9 as a product of the process by way of line-H2 and valve l3. On the other hand, when fractionator 3 is operated so that the light fraction contains all of the gasoline boiling range hydrocarbons and in addition, when desired, naphtha and kerosene, this fraction may be directed from receiver 3 through line II and valve ii to pump Ii. Pump l3 discharges through line I1 and, when desired, all or a portion of the light fraction from line l'l may be directed through line "and valve is into line ii, for use as subsequently described. However, the preferred method is to direct the light fraction in line l'l through line 23 into heating coil 2i. The light fraction introduced to heating coil 2| is subjected to thermal reforming treatment therein at a temperature ranging, for example, from 900 to 1050 F. by means of heat supplied from furnace 22, whereby to effect substantial conversion to oleflnic and aromatic hydrocarbons and possibly some isomerization without materially altering its boiling range. The conversion products leaving heating coil II, at a superatmospheric pressure in the range of 600 to 1200 pounds or more per square inch, are directed through line 23 and valve 24 into line 43 wherein the gasoline boiling range would be withdrawn from fractionator 3 in commingled state with the intermediate fraction. On the other hand, fractionator 3 may also be operated so that the light they commingled with other conversion products, formed as hereinafter described. 7

-The heavy fraction from fractionator 3 is direct'ed through line 25 and valve 25 to pump 21, which discharges through line 28, whereupon said heavy fraction may be directed, when desired, through line 23 and valve 30 into line 36 where it commingles with reflux condensate, formed as hereinafter described, to form a combined feed. However, the preferred method is to direct said heavy fraction through valve 3| into fractionator 32 where it commingles with vaporous conversion products, formed as hereinafter described, and'the mixture fractionated to separate fractionated vapors boiling in the range of gasoline from the higher boiling fractions of the conversion products and said heavy fraction, the higher boiling fractions ofthe conversion products being condensed as reflux condensate commingling with said heavy fraction to form a combined feed. The combined feed is directed through line 33 and valve 34 to pump 35, which discharges through line- 36 and valve 31 into heating coil 38. The oil in passing through heating coil 38 is subjected to a cracking temperature ranging, for example, from 850 to 1000' F. by means of heat supplied from furnace 39. The heated oil is discharged from heating coil 38 under a superatmospheric pressure ranging, for example, from 200 to 600 pounds or more per square inch and is directed through line 40 and valve ll into reaction chamber 42 wherein the oil is subjected to prolonged conversion in passing through reaction chamber 42.

Reaction chamber 42 is preferably maintained at substantially the same pressure as that emplOyed on the outlet of heating coil 38 and is preferably insulated to reduce radiation losses and recovered as a product of the process.

therefrom, although no insulation is shown in the drawing.

The vaporous'and liquid conversion products leaving reaction chamber 42 are directed through line 43 and valve 44, commingled with the conversion products from the reforming treatment, as previously described, and the mixture introduced to vaporizer and separator 45.

Valve 44 is preferably a pressure control valve by means of which a substantial super-atmospheric pressure is maintained on heating coil 38 and communicating reaction chamber 42 and in addition permits a substantial reduction in pressure on the downstream side of the valve.

Vaporizer and separator 45 is preferably maintained at a substantially reduced pressure relative to that employed in reaction chamber 42, ranging, for example, from 25 to 200 pounds or more per square inch whereby the liquid conversion products introduced thereto undergo substantial further vaporization to form a nonvaporous liquid residue. The non-vaporous liquid residue is withdrawn from vaporizer and separator 45 by way of line 48 and valve 41, cooled The vaporous conversion products, together with the vapors evolved in vaporizer and separator 45, are directed through line 48 and valve 49 into fractionator 32, for treatment as previously described.

Th fractionated vapors separated in fractionator 32 are directed through line 50 and valve to cooler and condenser 52 wherein the normally liquid hydrocarbons are condensed as a gasoline distillate. The distillate, together with the undissolved and uncondensed gases leaving condenser 52, is directed through line 53 and valve 54 into receiver 55 wherein the distillate and gases are collected and separated. The normally gaseous hydrocarbons collected-and separated in receiver 55 are directed through line 56 and valve 51 to storage or to further treatment as desired. A portion of the distillate collected and separated in receiver 55 may be returned to the upper portion of fractionator 32, by well known means not shown, for refluxing and cooling the upper portion thereof.

The intermediate fraction from fractionator 3 is directed through line-58 and valve 59 to pump 60, which discharges through linetl and valve 62, after which it may be commingled with a portion or all of the straight-run gasoline introduced by way of line l8 and valve !9, as previously described, this mixture or only the intermediate fraction being commingled with the bal-- ance of the distillate separated in receiver 55and removed therefrom by way of line 63, valve 64, pump 65, line 66, and valve 67 and the final mixture introduced to heating coil 68. The oil in passing through heating coil 68 is raised to the desired temperature, whichmay range, for example, from 500 to 800 F., by means of heat supplied from furnace 69. The heated hydrocarbon oil leaving heating coil 68 at a pressure whereby to reduce to a substantial degree theamount of olefinic hydrocarbons present in the feed introduced thereto and to eflect some cracking of the higher boiling hydrocarbons.

The preferred cracking catalysts for use in the present process consist 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. vIt is not intended, however, that the process should be limited to these particular catalysts, for other catalysts, such as, for example, the hYdIOSfli? cates 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 referred to above. The preferred catalysts may be prepared by precipitating silica from a solution as a hydrogel within or upon which the alumina and/0r zirconia are deposited also by precipitation as hydrogels. The silica hydrogel may conveniently be prepared by acidifying an aqueous solution of sodium 'silicateby the addition of a 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 am- 'monium hydroxide, ammonium carbonate or ammonium sulfide added to the solution to precipitate aluminum and/or zirconium hydrogels. The final precipitate, comprising essentially hydrated silica and hydrated alumina and/or zirconia, is washed to substantially completely remove water soluble materials and dried at about 300 F. to produce a rather crumbly and granular material 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, co-precipitation of the hydrated gels may be employed, when desired, to produce the preferred catalyst.

Reactor l2 is preferably of the type which employs a plurality of relatively small diameter re actor tubes containing the desired catalyst, the

tubes being confined within an enclosed zone to which heat from an external source may be supplied for the purpose of maintaining the reactants at the desired temperature during the conversion reaction. In addition, slnce relatively short periods of operation are employed in catalytic cracking because of the rather rapid deposition of carbon upon the surface and within the pores of the catalyst particles which necessitates frequent reactivation, it is preferred that a plurality of reactors be employed, although only one is shown in the drawing, in order that one or more may be segregated and the catalysts disposed therein subjected to reactivation while conversion of the hydrocarbon vapors is being accomplished in the other or others. Suitable means, not shown,'may be employedfor reacti-' vating the catalyst disposed within the various reactors during the period those particular reactors are segregated from the balance for the purpose of reactivation.

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 leaving reactor 12 are directed through line 13, and when they contain non-vaporous liquid residue they may be introduced to separator 14 by way of line 15 and valve 16 wherein said non-vaporous liquid residue is removed from the vaporous conversion products and the former withdrawn from separator 14 by way of line H and valve 18 and recovered as a product of the process. The vaporous conversion products, in this case, are directed through line 19 and valve 80 into line I3. However, when the conversion products contain little or no non-vaporous liquid residue,

separator I4 may be by-passed by closing valves 16 and BB in lines 15 and 19, respectively, and the conversion products in line 13 directed through valve 8|. products in line 13 are introduced to fractionator 82 wherein fractionated vapors boiling in the range of gasoline are separated from the higher boiling hydrocarbons, the latter being condensed as reflux condensate in this zone. The reflux condensate collected in fractionator 82 is directed through line 83 and valve 84 to pump 85,

which discharges through line 88 and valve 81 into line 36 where it commingles with the combined feed from fractionator 32. It is thereafter subjected to conversion in heating coil 38, as previously described. The fractionated vapors are directed from the upper portion of fractionator 82 through line 88 and valve 89 to cooler and condenser 90. The distillate leaving condenser 90, together with undissolved and uncondensed gases, is directed through line 8| and valve 92 into receiver 83 wherein the undissolved and uncondensed gases are separated from the distillate. The gases collected and separated in receiver 93 are directed from the upper portion thereof through line 84 and valve 95 to storage or, when desired, to further treatment. A portion of the distillate collected in the lower portion of receiver 88 is returned to the upper portion of fractionator 82, by well known means not shown, as a refluxing and cooling medium therein. The balance of the distillate collected in receiver 83, containing predominantly parafiinic and aromatic hydrocarbons, is directed through line-96 and valve 91 to storage or to further treatment as desired.

An example of one specific operation of the process as it may be accomplished in an apparatus such as illustrated and above described to accomplish the desired results is approximately as follows:

The charging stock, a 36 A. P. I. gravity Mid- Continent crude oil was subjected to fractionation under a superatmospheric pressure of pounds per square inch to separate a light fraction having an end boiling point of 475 F. from the higher boiling hydrocarbons, an intermediate fraction'haying an end boiling point of 750 F.,

and a reduced crude fraction containing the hydrocarbons boiling above said intermediate fraction. The light fraction was subjected to cooling and condensation and the resulting distillate and gas collected and separated.

The light distillate fraction was subjected to thermal reforming treatment at a temperature of 1020 F. and under a superatmospheric pressure of 750 pounds per square inch, the resulting In any case, the conversion 20 conversion products, formed as hereinafter described.

The reduced crude fraction was introduced to a fractionator operated at a pressure of 75 pounds per square inch, commingled with thermally cracked vaporous conversion products, introduced as hereinafter described, and the mixture fractionated to separate fractionated vapors having an end boiling point of 400 F. from the higher boiling hydrocarbons, the higher jected to thermal cracking treatment in a heating coil and communicating reaction chamber at a temperature of 930 F. and under a superatmospheric pressure of approximately 250 pounds per square inch. The resulting conversion products from this treatment were commingled with the conversion products from the thermal reforming treatment and the mixture introduced to a vaporizer and separator operated -at a superatmospheric pressure of approximately 5 80 pounds per square inch wherein the liquid conversion products were subjected to substantial further vaporization to form a non-vaporous liquid residue which was recovered as a product of the process. The vaporous conversion prod- 0 ucts introduced to the vaporizer and separator,

together with the vapors formed therein, were introduced to the fractionator for,treatment, as previously described.

Fractionated vapors, formed as previously described, were subjected to cooling and condensation and the resulting distillate and gas collected and separated. The normally gaseous hydrocarbons were recovered as a product of the process. The 400 end point thermally cracked and reformed distillate was commingled with the velocity of l and under a superatmospheric pressure of 100 pounds per square inch. The conversion products from this operation were introduced to a fractionator operated at a superatmospheric pressure of 40 pounds per square inch to separate fractionated vapors having a 300 end point from the higher boiling hydrocarbons. The latter were condensed as reflux condensate in the fr'actionating zone and returned to the thermal cracking treatment. The 300 end point fractionated vapors were subjected to cooling and condensation and the resulting distillate and gas collected and separated and recovered as products of the process.

This operation yielded approximately 55%. of

o 300 end point gasoline having a bromine number 1 knock value, a heavy residual fraction and an intermediate predominantly saturated fraction, thermally reforming said light fraction and thermally cracking said residual fraction, separating cracked gasoline from the products of conversion products commingling with other the thermal cracking, supplying resultant formed and cracked gasoline products to a catalytic conversion zone containing a cracking catalyst, subjecting said gasoline products to the action of said catalyst at a temperature in the approximate range of 500 to 800 F. and in admixture with a quantity of said intermediate fraction and for a contact time suificient to saturate at least the major portion of the olefin content of said gasoline products, and fractionating and condensing the resultant vaporous conversion products.

' 2. A process for producing motor fuel of high octane rating and low olefin content which comprises fractionally distilling crude petroleum and separatingtherefrom a light straight-run fracline products to a catalytic conversion zone containing a cracking catalyst, subjecting said gasoline products to the action of said catalyst at a temperature in the approximate range of 500 to 800 F. and in admixture with a quantity of said heavier fraction and for a contact time sufiicient to saturate at least the major portion of the olefin content of said gasoline products,

and fraction'ating and condensing the resultant vaporous conversion products;

-ELMER R. KANHOFER.

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