US2319201A - Conversion of hydrocarbon oils - Google Patents

Description

y 1943 I c. H. ANGELL 2,319,201

CONVERSION OF HYDROCARBON OILS Filed llay 9, 1940 REACTI'ON OR TIME FRACTIONATO CHAMBER EPARATING CHAMBER 27 26 I3 f .|4 u l2 com ENSER a: 29 HEATER a. CATALYTIC CRACKING ZONE) 7 f if 9 UNVAPQRIZED I e 4 H AVY E INTER- I 9 l5 IQUID MEDIATE s- -J l0+ l6 l9 FRACTIONS mum I &ONCE USED FRACTION E 4 la CATALYST 37 l coc a mc 2| as o CHARGE 2 I7 22 FRESH olLa. I 23 POWDERED CRACKING CATALYST 6 FRACTION-- 55 55: ATOR so so 57 cognac 67 cu MBER com ENSER v s HEATER a 40 5| sl' 9 THERMAL CRACKING I ZONE 43 .46 a E 1 42- "I f 52 58 saws 48*53' '}59 6| E a 44 HEAVY 62 l uaum INTERMEDIATE FRACTIONS mum ,FRACTIONS v INVENTOR CHARLES H. ANGELL BY [Z ATTORNEY Patented May 18, 1943 CONVERSION OF HYDROCARBON OILS Charles H. Angeli, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 11]., a

corporation of Delaware Application May 9, 1940, Serial No. 334,148

9 Claims. (cums-49) The invention relates to a combination catalytic and thermal cracking operation wherein the fresh charging oil for the process is admixed with relatively small amounts of a cracking catalyst, "in the form of a fine powder dispersed throughout the oil, and is catalytically cracked while intermediate liquid conversion products of the catalytic cracking operation are thermally cracked and thence commingled with catalystcontaining liquid residue derived from the catalytic cracking step to effect appreciable further vaporization of the residue and catalytic cracking of. the residue and thermal conversion products, the vaporous products of the last mentioned cracking and residue-reducing operation being fractionatedv separate from the vaporous products of the first named catalytic cracking operation to separately recover gasoline produced-by catalytic cracking of the charging oil and by subsequent cracking of the intermediate liquid conversion products and the residual oil.

The features and advantages of the invention and various alternative modes of operating of the process provided will be explained in conjunction with the following description of the accompanying diagrammatic drawing which illustrates one specific form of apparatus wherein the improcess provided by the invention may be conducted.

Referring to the drawing, hydrocarbon oil charging stock for the process, which may be any oil amenable to catalytic cracking, is supplied, together with a relatively small percentage of finely divided, solid catalytic material, through line I and valve 2 to pump 3. The small amount of'catalyst employed isdispersed substantially uniformly throughout the oil and, with the small amount and relatively small size catalyst particles employed, the catalyst does not readily settle out during heating. The stream of catalystcontaining charging oil is supplied from pump 3 through line 4 and valve 5 to heating coil 6 disposed in a suitable furnace I.

' Although illustrated in a conventional manner in the drawing, the heater comprising coil 6 and furnace I may advantageously be one of the well known vforms now in common use, wherein heat is transmitted at high rates to the fluid passing through that portion of the coil wherein it attains cracking-temperature, whereby the oil is quickly heated to the required reaction temperature, and, preferably, the oil and dispersed catalyst are then'passed through another portion of the coil, comprising a soaking section, wherein heat is supplied thereto at a rate regulated to maintain the reactants at or near the temperature previously attained for a predetermined time. In this particular instance, however, quick heating of the oil to the required reaction temperature, to minimize thermal cracking, is not so important as in other types of catalytic cracking operations wherein the oil is first heated to cracking temperature in the absence of the catalyst and thereafter contacted with the catalytic material. With the catalyst dispersed throughout the oil supplied to the heating step, catalytic cracking of the oil will occur as soon as it reaches the required temperature for this reaction and,

since this temperature is usually below that re- I quired for active thermal cracking, the latter is inherently less pronounced than in other types of catalytic cracking operations. The method of operation herein provided also obviates the use of expensive heat exchanger type reactors for supplying theendothermic heat of reaction while the previously heated oil is in contactwith the catalyst and, on the other hand, obviates the practice, sometimes employed in other types of operations, of heating the oil alone to well above the temperature required for its catalytic conversion and thereafter contacting the heated oil with the catalyst, in order to'avoid the use of heat exchanger type reactors for the contact plained, or alternatively, the heated products w from coil 6 may, when desired, be directed through line l2 and valve I 3 into reaction chamber M which, although not indicated in the drawing, is preferably well insulated to conserve heat and wherein the catalytic cracking'reaction is allowed to continue at a somewhat reduced temperature for a predetermined time. When reaction chamber I4 is employed, the conversion products and catalyst supplied to'this zone from coil 6 are preferably directed downwardly therethrough and resulting conversion products and catalyst are directed from the lower portion of the chamber through line l5 and valve l6 into line 9 wherein they are cooled to below active cracking temperature and thence supplied to chamber ll.

In the particular case here illustrated, cooling of the conversion products, prior to their introduction into chamber i I, is accomplished as they pass through line 5 by directly commingling a suitable cooling oil therewith, this material being supplied to line 9 through line "and valve la. The cooling oil employed may comprise, for example, regulated quantities or selectedfractions of the intermediate liquid conversion products of either cracking step or regulated quantities of the light distillate product of the catalytic cracking step. Other means, not. illustrated, of accomplishing the desired cooling of the conversion products, such as, for example, a heat exchanger interposed in line 9, wherein useful heat is hecovered from the conversion products by passing the same in indirect heat exchange relation with any desired cooling medium, may be employed within the scope of the invention.

In chamber ll relatively clean vaporous products of the catalytic cracking operation are separated from a liquid residue which comprises high-boiling fractions of the conversion products and includes substantially all of the finely divided catalyst particles. The catalyst containing residual liquid is directed from the lower portion of chamber ll through line l9 and valve 20 to pump 2| and is supplied therefrom through line 22 and valve 23 into the coking zone, which will be later described.

The relatively clean vaporous products of the.

catalytic cracking operation are directed from the upper portion of chamber H through line 24 and valve 25 to fractionator 26 wherein their components boiling within the range of the desired final light distillate product of the catalytic cracking step are separated from their higher boiling components by condensing the latter as reflux condensate.

Fractionated vapors of the desired end-boiling point are removed, together with normally gaseous products of the catalytic cracking operation, from the upper portion 01' fractionator 26 and directed through line 21 and valve 26 to condenser 29 wherefrom the resulting distillate and uncondensed gases pass through line 30 and valve 3| to collection and separation in receiver 32. Distillate collected in receiver 32 is directed therefrom through line 33 and valve 34 to storage or elsewhere, as desired. Uncondensed gases areremoved from the receiver through line 35 and valve 36 to storage or elsewhere, as desired,

this material preferably being supplied to conventional absorption equipment, not illustrated, wherein desired high-boilin components of the normally gaseous products and/or uncondensed normally liquid fractions are recovered therefrom. When desired, regulated quantities of the distillate collected in receiver 32 may be returned by well known means, not illustrated, 'to

the upper portion of fractionator 26 to serve as a cooling and refluxing medium in thi zone.

Intermediate liquid conversion products of the catalytic cracking step, comprising all or selected fractions of the reflux condensate formed in fractionator 26, are directed therefrom through line 31 and valve 38 to pump 39 wherefrom they are supplied through line 40 and valve 4| to thermal cracking treatment in heating coil 42.

Heating coil 42 is disposed in a furnace 43 of any suitable conventional form and the oil passing through the coil is heated to the desired thermal cracking temperature, preferably at a substantial superatmospheric pressure. The resulting. highly heated products are directed, in the case here illustrated, from coil 42 through line 44 and valve 45 into the coking zone. It is also within the scope of the invention to employ a. reaction chamber succeeding heating coil since it is employed to advantage 42, wherein further cracking of all or a portion of the heated products from coil 42 is accomplished prior to their introduction into the coking zone. This reaction chamber, not illustrated, may be of the same general type as chamber l4 and may be connected'with line 44 in the same manner as chamber I 4 is connected with lines 8 and 9.

Although a single coking chamber may be employed, when desired, the coking zone preferably comprises a plurality of chambers (two being illustrated in the drawing) which are alternately operated and cleaned and prepared for further operation in order that the coking step, in common with the rest of the system, may be operated continuously. The catalyst-containing residue from chamber II is contacted with the products of the thermal cracking operation from coil 42 either within or prior to their introduction into the coking zone. To accomplish this, in the particular case here illustrated, a line 46 is provided which connects lines 44 and 22 and from which branch lines 41, 41', 49 and 49', containing the respective valves 48, 48', 56 and 50, communicate with coking chambers. Lines 47 and 49 lead to coking chamber 5| and lines 4'! and 49' lead to coking chamber 5i. Thus, the mixture of catalyst-containing residue and thermal conversion products may be selectively supplied to either the upper, or lower portion of either of the coking chambers or the hot thermal conversion products may be supplied to the lower portion of either of the coking chambers while the catalyst-containing residue from chamber II is supplied to the upper portion of the same chamber. In any case, the catalyst-containing residue is contacted with the hot thermal conversion products, thereby appreciably further vaporized and the heavy non-vaporous compoing oil, considerable catalytic cracking will accompany the coking operation, the catalyst-containing residue commingling with the hotter thermal conversion products to heat the residual oil to a temperature at which the desired further vaporization and further cracking will occur, while the thermal conversion products are also subjected to the action of the catalyst.

The problems encountered in recovering and,

reactivating the relatively small quantities of finely divided catalyst employed in a catalytic cracking operation of the general type described ordinarily makes this procedure too expensive to be justifled on an economic basis. However, the presence of catalyst in the residual oil is detrimental to the use of the latter as fuel oil and must be settled or filtered therefrom. Recycling of the catalyst-containing residue to the catalytic cracking coil, in order to obtain the benefit of any remaining activity in the catalyst, is not a particularly successful expedient, since coking diflicul-' ties will ordinarily be encountered in the heating coil and subsequent equipment. In the present invention these problems are obviated without sacrificing the remaining activity of the catalyst in the coking step and after being thus utilized is largely included with the resulting coke. Its presence in the latter is advantageous in that it will increase spective valves 53 and 53'. v be employed, when desired, as a means of introthe ash content which is ordinarily negligible in petroleum cokes. The ash content imparted to the coke by the catalyst makes it a moreconvenient fuel to use and will materially assist in preventing burned out grates or, when employed as tem, cleaned and prepared for further operation,

while coking continues in another chamber.

Chambers and 5| are provided with drain lines 52 and 52, respectively, containing the re- These lines may also ducing steam, water or other suitable cooling medium into the chamber, after it has been isolated from the rest of the system, in order to hasten cooling and facilitate removal of the coke, which maybe accomplished in any well known manner.

Vaporous products of the coking and catalytic cracking and coking operations which take place in chambers 5| and 5|, are directed therefrom through the respective lines 54 and 54', controlled respectively by valves 55 and 55', and are supplied .through line 56 to fractionator 51. 'Ordinarily, the vapors supplied to fractionator 51 will include some small quantity ofrelatively heavv liquid particles, such as tar and the like, carried over from the coking zone and, preferably, these materials areseparated in the lower portion of column 51 from relatively clean vapors which include substantial quantities of material boiling within the range of gasoline and heavier liquid conversion products, the latter being, condensed in fractionator 51 as reflux condensate.

The heavier liquid fractions are removed fronr line 64 and valve 55 or, preferably, is returnedy through valve 66 in line 63 to further cracking treatment in heating coil 42. Any other desired treatment of all or a portion of the total reflux condensate formed in fractionator 51 or selected fractions thereof is entirely within the scope of the invention. For example, this material may be passed through a separate thermal cracking coil, not illustrated, whereupon resulting products are supplied to the coking zoneor it may, when desired, be returned to heating coil 6 by well known means, not illustrated, for catalytic cracking treatment incommingled state with the charging oil or it may be supplied, after mixing cracking catalyst therewith, to a separate catalytic cracking coil, not shown, wherefrom resulting products are directed to reaction chamber M or to separating chamber coking steps, from. the upper portion of fractionator 51 and directed through line 61 and valve 68 to condenser 59 wherefrom the resulting distil- Fractionated vapors of the desired end-boiling point are removed, together with normally gaseous products of the last described cracking and late anduncondensed gases are directed through line 10 and valve 1| to collection and separation in receiver 12. The distillat cpl l ected in receiver 12, which ordinarily comfl ii's" gasoline of different characteristics from th t recovered in receiver 32, is directed from rece ver 12 through line 13 and valve 14 to storage or elsewhere, as desired. The uncondensed gases, are removed from. receiver 12 through line 15 and valve 16 to storage, suitable absorption equipment, not illustrated, or elsewhere, as desired. When desired regulated quantities of the distillate collected in receiver 12 may be recycled, by well known means not shown, to the upper portion of fractionator 51 to serve as a cooling and refluxing medium in this zone. I

Any solid material in finely divided state which will function to effect catalytic'cracking of the charging oil, when employed in the manner described and relatively in small quantities, may be employed as the cracking catalyst within the scope of the invention. One such material which I have found particularly suitable comprises a substantially impalpable powder consisting essentially of silica and selected metal oxides such as, for example, alumina, thoria, zirconia and titania, alone or in combination. The silica may be precipitated from a sodium silicate solution by acidification and the resulting precipitated fine particles of silica impregnated with the desired metal oxide or oxides derived from the salts of the metal or metals, or the catalyst powder, including the silica and one or more of the metal oxides may be prepared by co-precipitation. No novelty is claimed herein for the particular method of preparing the catalyst powder.

The invention also contemplates the use of certain natural metal silicates in finely ground or pulverized form, such materials being more suitable for one embodiment of the catalytic cracking operation contemplated by the invention than they are for operations in which the cracking catalyst must be reactivated .to make the process economical, since other materials 'will depend upon the composition and the size of the catalyst particles,'as Well as the nature of the v charging oil, and the temperature and pressure conditions utilized. It may range, for example, from 10 to 0.10% by weight of the charging oil. Other conditions being the same, the amount of catalyst required is decreased with a reduction in the particle size of the catalyst. For example, as little as 0.25% of synthetic silicaalumina catalyst prepared as a substantially impalpable powder by precipitation has been successfully employed in cracking paraflinic distillates and even less may quite probably be employed under some conditions.

The operating conditions employed in conducting the process will vary, depending upon the type of charging oil utilized and the nature of the catalyst employed. In cracking predominantly paratfinic distillates, such as Pennsylvania gas-oil, for example, with a synthetically pre pared silica-alumina catalyst powder, such as above mentioned, temperatures of the order of 850 to 1000 F. are preferably employed in the inital catalytic cracking step with superatmospheric pressures of the order of 30 to 150 pounds, or thereabouts, per square inch. The reaction chamber, when utiilzed, is preferably operated at substantially the same pressure as that employed at the outlet of heating coil 6 and, when pressures above 50 pounds, or thereabouts, per

square inch are utilized in the initial catalytic cracking zone, the succeeding separating chamber may, when desired, be operated at a somewhat reduced pressure which preferably is substantially equalized in the succeeding fractionating condensing and collecting equipment. The thermal cracking zone to which intermediate liquid conversion products of the initial catalytic cracking step are supplied preferably utilizes temperatures of the order of 900 to 1000 F., or thereabouts, preferably with a superatmospheric pressure, measured at the outlet of heating coil 42, of the order of 150 to 500 pounds or more per square inch. The coking zone is preferably operated at a superatmospheric pressure of the order .of 30 to 150 pounds, or thereabouts, per square inch. The temperature employed in the coking zone will, of course, depend-upon the temperatures and relative quantities of the catalyst-containing residue and thermal conversion products supplied thereto and will ordinarily be of the order of 800 to 900 F., or thereabouts. Preferably, the pressure employed in the coking'zone is substantially equalized in the succeeding fractionating, condensing and collecting equipment.

As an example of onespecific operation of the process, as it may be conducted in an apparatus such as illustrated and above described, the charging stock is a Pennsylvania gas-oil of approximately 36 A. P. I. gravity to which approximately 0.5% of synthetically prepared aluminasilica powder is added. and substantially unlformly dispersed throughout the oil. The catalyst-containing charge is quickly heated in coil 6 to a temperature of approximately 950 F. and the resulting products, after passing through reaction chamber I 4, are cooled to a temperature of approximately 760 F. and introduced into separating chamber II. A superatmospherlc pressure of approximately 100 pounds per square inch is employed at the outlet of heating coil 6 and at the outlet of chamber l4. The pressure employed in chamber l l is approximately 50 pounds per square inch. Cooling of the conversion prod ucts, prior to their introduction into chamber I l, is accomplished, in part, by the pressure reduction and, in part, by cooling and thence commingling regulated quantities of the intermediate liquid conversion products from fractionator 26 therewith. Fractionator 26, condenser 29 and receiver 32 are operated at substantially the same pressure as that employed in the separating chamber.

The total intermediate liquid conversion products from fractionator 2B are thermally cracked in heating coil 42, the maximum temperature in this zone being approximately 960 F. and the pressure employed at the outlet therefrom being approximately 350 pounds per square inch, superatmospheric.

The coking zone to which catalyst-containlng residue from chamber H and hot thermal conversion products from coil 42 are supplied is operated at a superatmospheric pressure of approximately 80 pounds per square inch, this pressure being substantially equalized in the succeeding fractionating, condensing and collecting equipment. A small quantity of heavy liquid conversion products is removed from the lower portion of fractionating column 51 and the relatively clean intermediate liquid products formed as reflux condensate in this zone are returned to coil 42 for further cracking treatment.

In an operation such as above described, one may expect to obtain approximately 26% of catalytically cracked gasoline having an octane number of approximately 7-8 as determined by the motor method or approximately 89 as determined by the research method. The gasoline produced in the thermal cracking, coking and secondary catalytic cracking steps of the system may amount to approximately 36% based on the charging oil and have an octane number of approximately 70 as determined by the motor method. Additional products ofthe process consist predominantly of low volatile coke, which has an ash content making it suitable for domestic or stoker fuel, normally gaseous fractions, containing over 40% of readily polymerizable olefins, and a relatively small amount of heavy liquid products which latter are recovered as bottoms from fractionator 57.

I claim as my invention:

1. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic cracking in the presence of a cracking-catalyst powder, separating from the resulting conversion products relatively clean vapors and lyst-containing residue, fractionating said vapors to recover good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate, thermally cracking reflux condensate resulting from said fractionation to form additional yields of good antiknock gasoline, commingling resultant heated products with said catalyst-containing residue and reducing the mixture to a relatively dry mass, containing catalyst powder.

2. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic cracking in the presence of a cracking-catalyst powder under catalytic cracking conditions of temperature and pressure, separating from the resulting conversion products relatively clean vapors and a catalyst-containing residue, fractionating said vapors to recover good antiknock'gasoline therefrom and to condense higher boiling components thereof as reflux condensate, thermally cracking reflux condensate resulting from said fractionation in a zone separate from that wherein said catalytic cracking of the first named oil is accomplished to form additional yields of good antiknock gasoline, commingling resultant heated products with said catalyst-containing residue and reducing the mixture to a relatively dry mass, containing catalyst powder, in a zone separate from that; wherein the catalyst-containing residue is separated from the aforementioned vapors.

3. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic a catathermally cracking reflux condensate resulting from said fractionation in avzone separate from that wherein said catalytic cracking of the first named oil is accomplished to form additional yields of good antiknock gasoline, commingling resultant inated products with said catalyst-containing residue and reducing the mixture to a relatively dry mass, containing catalyst powder.

4. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic cracking in the presence of a catalyst capable of promoting the cracking reaction and under conditions at which it is converted to form good antiknock gasoline, said catalyst bein dispersed in the form of a powder throughout a flowing stream of the oil undergoing said heating, separating from the resulting conversion products vapors containing good antiknock gasoline and higher boiling fractions, and a catalyst-containing residue, fractionating the vapors to recover said good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate, thermally cracking reflux con densate resulting from said fractionation in a zone separate from that wherein the first named oil is catalytically cracked, and commingling hot conversion products of the thermal cracking step with said catalyst-containing residue to reduce the latter to a substantially dry mass, containing catalyst powder, in a zone separate from that wherein the catalyst-containing residue is separated from the aforementioned vapors.

5. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic cracking, in the presence of a catalyst capable of promoting the cracking reaction and under conditions at which it is converted to form good antiknock gasoline, said catalyst being dispersed in the form of a powder throughout a flowin stream of the oil undergoing said heating, separati-ng from the resulting conversion products vapors, containing said good antiknock gasoline and higher boiling fractions, and a catalyst-containing residue, fractionating the vapors to recover said good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate, thermally cracking reflux condensate resulting from said fractionation in a zone separate from that wherein the first named oil is catalytically cracked,- co fngling hot conversion products of the thermal cracking step with said catalyst-containing residue to reduce the latter to a substantially dry mass, containing catalyst powder, in a zone separate from that wherein the catalyst-containing residue is separated from the aforementioned vapors and fractionating vaporous products. of the thermal cracking operation and vaporous products of said reducing operation separate from the vaporous products of said catalytic cracking operation to separately recover therefrom additional yields of good antiknock gasoline.

6. A hydrocarbon oil cracking process which comprises, cracking an oil susceptible to catalytic cracking, in the presence of a catalyst capable of promoting the cracking reaction and under con-' vapors, containing said good antiknock gasoline and higher boiling fractions, and a catalyst-containing residue, fractionating the vapors to recover said good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate, thermally cracking reflux con- I catalyst powder, in a zone separate from that wherein the catalyst-containing residue is separated from the aforementioned vapors, fractionating vapors resulting from the thermal cracking and reducing steps to recover additional good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate and returning reflux condensate resulting from the fractionation of said vaporous products of the thermal cracking and reducing steps to the thermal cracking step.

7. A hydrocarbon oil conversion process which comprises, heating a flowing stream of oil susceptible to catalytic cracking'to a temperature at which it is catalytically converted to form good antiknock gasoline, accomplishing said heating and catalytic cracking of the oil in the presence of a. finely divided active cracking catalyst dispersed throughout the stream of oil undergoing treatment, cooling a stream of the resulting conversion I products, including said catalyst, to a temperature at which detrimental further cracking thereof is prevented, separating from the resulting cooled conversion products vapors, which.

comprise said good anti-knock gasoline and higher boiling components, and a residual liquid containing substantially all of the catalyst particles, supplying a catalyst-containing residual oil from the zone of said separation to a coking zone, fractionating said vapors to recover said good antiknock gasoline therefrom and to condense higher boiling components thereof as reflux condensate, heating reflux condensate resulting from said fractionation to a thermal cracking temperature in a zone separate from that wherein the first named oil. is catalytically cracked, introducing resulting highly heated products into the coking zone, therein effecting further catalytic cracking and reduction of the residual oil to an ash-containing coke,-removing resulting vaporous products from the coking zone and separately fractionating the same to recover therefrom additional yields of good antiknock gasoline.

8. A hydrocarbon oil conversion process which comprises, heating a flowing stream of oil susceptible to catalytic cracking to a temperature at which it is catalytically converted to form good antiknock gasoline, accomplishing said heating and catalytic cracking of the oil in the presence of a flnely divided active cracking catalyst dispersed throughout the stream of oil undergoing treatment, cooling a stream of the resulting conversion products, including said catalyst, to a temperatureat which detrimental further cracking thereofis prevented, separating from the resulting cooled conversion products vapors which comprise said good antiknock gasoline and higher boiling components and a residual liquid containing substantially all of the cata- Jecting hydrocarbon oil to catalytic cracking con- 15 ditions in admixturevwith a powdered cracking catalyst, separating the resultant products into vapors and a residual liquid containing the powdered catalyst, fractionating the vapors tocondense heavier fractions thereof, thermally cracking resultant reflux condensate contacting heated products thus formed with said catalyst-containing residual liquid in a vaporizing zone toreffect further vaporization of the residual liquid by the heat of said products, and maintaining said vaporizing zone under catalytic conversion conditions to effect further conversion therein with the aid of said catalyst.

CHARLES H. ANGELL.

Images