US2463903A - Manufacture of gasoline - Google Patents

Description

March 8 1949. H. L. PELZER MANUFACTURE 0F GASOLINE Filed May 25, 1940 H0773/ Pelzer INVENTOR ATTO R N EY5 Patented Mar. 8, 1949 MAN UFACTURE OF GASOLINE Harry L. Pelzer, Houston, Tex., assgnor to Sinclair Reiining Company, New York, N. Y., a

corporation of Maine Application May 25, 1940, Serial No. 337,127

3 Claims. 1

This invention relates to improvements in the manufacture of gasoline from higher boiling hydrocarbon oils by cracking in the presence of dispersed iinely divided argillaceous materials particularly those of high catalytic activity. The invention provides a process whereby a high boiling oil may be converted at a high cracking temperature such that conversion occurs predominantly in the vapor phase such process having several important advantages that may be obtained concomitantly in certain instances and alternatively in others. These advantages include prolongation of the useful period of operation by minimizing deposition of carbonaceous material in the conduit in which the oil is heated to and at a high cracking temperature, improvement in the rate of gasoline production, improvement in the anti-knock value of the gasoline produced, improvement in the gasoline yield, recovery of high overall yields of valuable liquid products uncontaminated with the residue of the argillaceous material, and separate recovery of the spent argillaceous material substantially free from liquid residual products and in a form especially adapted for economic reactivation.

Cracking processes of the type wherein nely divided naturall'` occurring argillaceous materials (e. g., nely divided fullers earth) are dispersed in a owing stream of oil, which is subjected to a cracking temperature under conditions such that liquid phase predominates, have been heretofore proposed` However, such processes are subject to the criticism that gasoline material of relatively low anti-knock value is produced and to the further criticism that the residual oil and the residue of the argillaceous material are discharged from the cracking system as a mixture which makes diflicult a substantially complete separate recovery of either the liquid residual oil uncontaminated with spent argillaceous material or the spent argillaceous material in a form adapted for economic reactivation. In addition rates of gasoline production in such processes are W.

Cracking processes in which high boiling hydrocarbons are vaporized and the vapors are caused to pass through a Xed bed of argillaceous or other catalytic material also have been proposed heretofore. However, such processes are subject to the disadvantage that the usefully active life of the catalytic material is so short and the cost of catalytic material is so high that reactivation at frequent intervals is necessary. This circumstance not only limits the proportion of the total time during which the cracking apparatus is available for producing gasoline but it also requires the provision of complicated and expensive means for reactivating the catalyst bed. Moreover, in processes of this type the ratio of fresh or reactivated catalyst to gasoline, is high. Therefore processes of this type are subject to high plant cost both from the standpoint of high initial cost of the cracking and reactivating equipment and the high cost of its maintenance and operation.

In the practice of my invention I admiX a small proportion of nely divided argillaceous material with a clean high boiling petroleum stock (e. g., a high boiling petroleum distillate) and heat this mixture to and at a high cracking temperature while flowing as a stream at a velocity sufficient to maintain said finely divided material in suspension in said stock for a period of time sumcient to convert a substantial part of said stock into hydrocarbons falling within the, gasoline boiling range. I thereafter separate the resulting hot products into a composite vapor fraction including the desired gasoline material` and a cokey solid residual material comprising the resif due of said argillaceousmaterial. Advantageously the composite vapor fraction is scrubbed with liquid oil in the coke separating zone or subsequent thereto to separate entrained tarry matter and argillaceous material, the liquid mixture obtained by such scrubbing being retained. in or returned to the coke separating zone. The remaining vapors may thereafter be further fractionated to recover gasoline and a clean higher boilingy petroleum stock. The latter may be admixed with fresh finely divided argillaceousV material and further treated as previously described.

The nely divided argillaceous materials. useful in the process of my invention include naturally occurring clays which have a limitedcatalytic action but exert a, preferential` adsorptive power for carbon-forming material, finely divided. fullers earth for example, as well as acid-treated clays. They also include synthetic catalysts of high directive catalytic activity comprising silica and alumina, or silica and: alumina together with other metal oxides such as oxides of zirconium, titanium, and the like, which are commonly used in catalytic cracking processesv of the fixed' bed type.

For use in the process of my invention the argillaceous materials are advantageously reduced to a powder the iineness of whichv may vary from about mesh to an almost. impalpable powder. However, particle sizes larger than 100 mesh may be used so long as the velocity of the oil during the heating operation is high enough to maintain the argillaceous material in a state of dispersion through the oil being treated during its entire passage through the conduit in which the oil is heated. Particle sizes considerably exceeding 100 mesh may be used satisfactorily under appropriate Operating conditions especially when the argillaceous material is of very low apparent density as is the case with many aerogels. The use of larger particle sizes has the advantage that the larger particle sizes may be recovered with less difliculty from entrainment in combustion gasses in which they become dispersed in reactivating operations.

The process of my invention does not require expensive special apparatus and advantageously may be carried out in apparatus similar to that conventionally employed for Combined vapor phase cracking and coking processes with only a minor amount of additional equipment.

The most desirable ratio of dispersed argillaceous material to oil will vary depending upon the nature of the oil to be treated, the particular argillaceous material employed and the desired yield and anti-knock value of the eventual gasoline material. Amounts of nnely divided argillaceous material varying from about l/2 pound per barrel of oil or somewhat less, to more than 12 pounds per barrel of oil, in the mixture as it enters the heating condrit, have been used with considerable success. Dispersion of a very small proportion of the argillaceous material through the oil being treated is effective in substantially eliminating the formation of carbonaceous deposits on the interior surfaces of the heatingr conduit. The adsorptive action of the dispersed argillaceous particles for the more objectionable carbon-forming materials made effective substantially at the point of formation appears in a large measure to be responsible for the substantially complete elimination of carbonaceous deposits in the heating conduit. However, the use of dispersed argillaceous materials in amounts substantially exceeding the minimum amount effective in substantially eliminating the formation of carbonaceous deposits in the heating conduit is advantageous particularly when employing a synthetic vargillaceous material of high catalytic activity, since the additional argillaceous material aids and directs the cracking reaction in producing gasoline material of improved anti-knock value.

The temperatures and pressures useful in the practice of my invention vary with the character of the oil being treated and with the nature of the particular argillaceous material employed as well as with the desired yield and anti-knock value of the eventual gasoline. However, when employing nely-divided synthetic argillaceous materials of high catalytic activity a maximum temperature exceeding 950 F. does not ordinarily increase either the anti-knock value of the eventual gasoline or the gasoline yield. The use of relatively high pressure increases the attainable rate of gasoline production for an apparatus of given size. However, it does not increase the gasoline yield.

My process may be operated as a once-through process or with partial or total recycle of condensed hydrocarbons higher boiling than the desired gasoline. The use of total recycle increases the anti-knock value but reduces the rate of gasoline production. l

By reducing the residual material to a substantially dry coke-like product, including the residuum of the nely divided argillaceous material, hydrocarbons higher boiling than the desired gasoline product may be recovered as a liquid substantially free from suspended matter. At the same time the spent argillaceous material is separately recovered in a form specially adapted for eiiicient reactivation by burning. The ratio of spent catalyst to carbonaceous matter in the coke-like product will vary with the oil being treated and with the method of operation. Using a parafn distillate having a gravity of 28.5 A. P. I., an initial boiling point of 615 F. and about 80% distilling up to 750 F. as a charging stock with total recycle of condensates higher boiling than gasoline and a synthetic argillaceous material comprising silica and 10% alumina, by weight, prepared as hereinafter described in an amount approximating .8% of catalyst on the heater throughput, I have obtained upwards of 70% gasoline having an octane member of 77 as determined by the motor method and a solid residue in which the spent catalyst and carbonaceous matter were presen-t in approximately equal proportions. In this operation there was produced 948 cu. ft. of gas per barrel of gasoline. In another operation conducted in the same apparatus under subs-tantially the same operating conditions and using the same charging stock but with no dispersed catalyst, I obtained a gasoline yield of 64.8%, the produced gasoline having an octane number of 69.1 as determined by the motor method. In this operation there was produced 1475 cu. it. of gas per barrel of gasoline.

An apparatus suitable for carrying out the process of my invention is illustrated, in a conventional diagrammatic manner, in the accompanying drawing, and my invention will be further described in connection therewith.

Referring to the drawing, a clean charging stock, for example paraffin distillate, is supplied from any convenient source of supply through line i to pump 2 by which it is forced through line 3, heat exchanger Il and line 5 to the inlet of the heating conduit. A concentrated slurry of iinely divided argillaceous material in oil is maintained in tank 8. Tank 8 is provided with a suitable mechanical stirring device 9 adapted to prevent settling of the argillaceous material. This concentrated slurry is withdrawn from tank 3 by pump E0 and discharged through line Il into the stream of raw charging stock passing through line 5.

The amount of concentrated slurry supplied in this manner is controlled by regulating the speed of pump l0 so that the mixture eventually entering the heating conduit from line 5 Iwill include the desired predetermined proportion of argillaceous material. The heating conduit in this instance consists of two serially connected coils the first ci which is disposed inv furnace 6 and the second in furnace l. A single furnace may be used although two or more serially connected coils disposed in separate furnaces have the'advantage of permitting better control of the temperature gradient of the oil as it passes through the heating conduit.

The mixture of raw charging stock and iinely divided argillaceous material may be heated in furnace 6 advantageously to 'a temperature of 850-1100 F. and in heater 'l to a temperature of 950 F.-1l.00 In the heater l the oil is maintained at a `,high cracking temperature for a `period of time sufiicient to convert a substantial part of the stock supplied to the heaters into hydrocarbons boiling within the gasoline boiling range. YWhile passing through the heaters 6 and 'I .the velocity of the iiowing stream is maintained at a value high enough to preclude segregation and settling of the dispersed argillaceous material.

The mixture of hot cracked products leaving heater 'I may pass through transfer line I2 and pressure reducing valve i3 to the coking receptacle I4. A by-pass line i5 communicating with valved branch line `Il permits discharge of the hot products from the heater l at points oi progressively increasing elevation as the charge of coky residue accumulates in the coking re,- ceptacle when it is desire-d to minimize the back pressure .on the heating conduit. In coxing receptacle l0, some additional cracking occurs and the mixture discharged from the heater l separates into a composite vapor fraction and a substantially dry coky residue including the resi due of the argillaceous material present in the mixture supplied to the heater E. Such additional conversion as occurs in I :l will be largely thermal in character however unless additionai fresh catalytic material is supplied to receptacle I t. A relatively low pressure, for example, a pressure of 59 pounds per square inch or somewhat less, is maintained with advantage in the coking receptacle it. A pressure of 4430-590 pounds per square inch may if desired be maintained on the oil at the outlet of the heater '1, and this pressure may be reduced at valve i3 (or at the valves in one or more of valved branches It if by-pass line l5 is being used). However, when high pressure is maintained on the heaters to increase the gasoline making capacity of the apparatus by increasing the crack per pass, such an increase usually is accomplished by an increase in the production of gas. Accordingly for maximum anti-knock value with minimum gas production it is usually desirable to maintain in the heating coil only that pressure which is required to overcome the frictional resistance of the heaters and produce the desired ow against the pressure prevailing in the coking receptacle.

In the upper part of the coking receptacle lf2 the temperature of the vapors may approximate 800m-909 F., although optimum gasoline yields usually are obtained when this temperature does not exceed SOW-825 F. These hot vapors are discharged through line I'I to the vapor separator I8.

In the vapor separator I8 high boiling tarry polymers are condensed and separated from the remaining vapors, the latter continuing on from the upper end of the separator I8 through line IS. The intermediate portion of the separator i3 may be provided with baflles 2t while several conventional bubble trays '2l are advantageously provided in the upper portion of this separator to guard against entrainrnent of tarry matter in the vapors leaving through line I9. High boiling polymers accumulating in the lower part of separator i8 are Ydrawn oli through line 22 by pump 23 and this material is returned, in whole or in part, to the upper end of the coking receptacle I4 through line 24 to assist in controlling the vapor temperature at the upper end of the coking receptacle while at the saine time reducing this tarry matter to coke and recovering additional cracking stock therefrom. rIhe tarry liquid thus supplied to the upper end of the coln'ng receptacle performs the further function of assisting to maintain a rliquid layer on the upper surface of the bed of coke accumulating `in I4. 'Thelhot vapors .discharged from transfer iline 't2 4are required to pass through this liquid layer on the upper surface of the accumulating coke bed, thereby separating and retaining in Ythe coking receptacle the rfiner particles of dispersed argillaceous material which lwould otherwise be carried over rto the vapor separator IS by entrainment.

Control of the temperature conditions in the Vapor separator i3 may be maintained by supplying a cooling liquid through the line 25 and branch lines 26 and 2l, by means of `pump 4l. The liquid supplied through branch line 21 washes the baffles 2t and assists in preventing accumulation of particles of tar or Acatalyst that may have escaped precipitation by the scrubbing action in the coking receptacle I4 and the lower part of the vapor separator I8. The temperature of the vapors in the lupper portion of the vapor separator I3 may vary from about 70d" F. to about 800 F. To the extent that high boiling liquid tar accumulates in the lower endof the vapor separator i8 at a rate exceeding that which can be returned to the coking receptacle lli through line 24 and be either reduced to a coky residue or reevaporated therein, such excess tarry matter may be drawn off through valved line Ztl.

Vapcrs discharged from vapor separator I8 through line I9 enter the lower portion of fractionating tower 29 which may be of conventional bubble tower construction. Here the vapors are fractionated so that only those hydrocarbons suitable as components of the desired gasoline product, together with any lower boiling normally gaseous materials, will pass overhead through line St to condenser 3|. The products from condenser 3l discharge into a conventional receiver 32 from the upper end of which gases are vented through line 33. Liquid condensate comprising the desired gasoline material is drawn oi from the lower part of receiver 32 through line 34. A portion of this condensate may be recirculated via line 35, pump 36 and line S'I, to the upper end of the fractionating tower 29 to control the fractionating operation. The temperature prevailing at the upper end of the fractionating tower 29 may approximate 37o-410 F. depending on the desired end point of the final condensate.

Condensate which accumulates in the lower part of the fractionating tower 29 is drawn oi through line 38. The temperature in the lower portion of fractionating tower 29 mayapproximate S40-700 F. This condensate may pass through the heat exchanger d wherein it gives up a part oi its contained heat to the raw charging stock by indirect heat exchange. If desired the requisite cooling in tower 29 may be in part provided by Icy-passing a portion of the raw stock from line 3 to line 5 through exchanger 42. A portion of the condensate drawn oi from tower 29 through line 38, and partially cooled in the heat exchanger il, normally serves as the temperature controlling medium supplied by pump 4I to the vapor separator I8.

That part of the condensate from fractionating tower 29 not returned to the vapor separator I3 by pump 4I may be discharged from the system through line 3S or returned, in whole o1' in part, to the raw feed line I via connection 40 for recirculation through the heating conduit. Discharge of tarry matter from separator I8 and of condensate from fractionating tower 29 through connections 28 and 39, respectively, or either of them, materially increases the gasoline producing capacity of a given cracking unit. However, unless the severity of these conditions in the heater 'l is correspondingly increased, this increase in gasoline producing capacity usually is accompanied by an appreciable reduction in the antiknock value of the gasoline product when discharging from the system relatively light reflux condensate from the bottom of fractionating tower 29. On the other hand discharge from the system of tarry matter drawn off through line 38 has only a slight adverse effect on the octane value of the gasoline, but the resultant increase in gasoline making capacity in this instance is accompanied by a substantial decrease in the gasoline yield.

It will be obvious that more than one coking receptacle may be provided so that the coky deposit may be removed from one receptacle while another is being filled, thus permitting the cracking operation to be carried out as a continuous process. As soon as the operation of one receptacle has been discontinued, it may be steamed out in the usual manner by means of conventional steaming out connections (not shown) whereupon the coking receptacle may be opened and the coky deposit removed. This deposit may be easily removed from the coking receptacle as it is less cohesive than the coke body produced in the usual coking operation. Normally the coky residue resembles a caked powder which may be crushed or disintegrated with little difficulty. The carbon content of the coky residue, including the residue of the spent argillaceous material varies from about 35% to about 50% depending upon the r' temperature maintained in the coking receptacle. As the temperature in the coking receptacle increases the ratio of carbon to spent catalyst normally decreases, other conditions remaining the same.

Specific examples of operations embodying my invention as carried out with particular charging stock in an apparatus of the type illustrated will further exemplify the invention. In the operations comprising each of the following specific examples the charging stock employed was a parain distillate having a gravity of 28.5 A. P. I., an initial boiling point of 615o F. and with 80% distilling off up to 752 F. The catalyst employed in the first of these operations was a synthetic argillaceous material of high catalytic activity composed of 90% silica and 10% alumina by weight prepared by precipitating aqueous sodium silicate with hydrochloric acid in the presence of added sodium chloride, adding aluminum chloride solution and precipitating with ammonium hydroxide, washing, drying at 250 F., crushing and sizing to 100 mesh.

Example No. 1.--A slurry of the iinely divided synthetic catalyst above described in oil was supplied at a rate regulated to maintain approximately .8% catalyst by weight on the oil in the mixture entering the heater 6. The rates of heating in furnaces 6 and 'i were controlled to maintain an oil temperature of 950 F. at the outlet of heater 6 and substantially the same oil temperature at the outlet of heater 1. A temperature of approximately 84.0 F. was maintained in the lower part oi the coking receptacle i4 and a temperature of approximately 810 F. at the upper end thereof. The temperature of the vapor separator i8 was controlled to condense therein only that amount of high boiling material which could be returned to the coking receptacle I4 and reduced to coke therein, no matelrial being drawn off through line 28. This rer--4 quired maintaining a temperature of 705 F. at the upper end of separator I8. Fractionating tower 29 was controlled to condense all hydrocarbons higher boiling than gasoline and all of the resultant condensate was recirculated through heaters 6 and 'I via line 4D, none of this condensate being drawn off through line 34. Fresh oil was supplied at a rate adequate to maintain a constant predetermined rate of heater feed. In this instance the fresh oil amounted to 5.7% of the combined heater feed. Under these conditions of operation a gasoline yield of 70.5%, based on the fresh feed, was obtained. 'I'his gasoline had a gravity of 58.7 A. P. I., a bromine number of 62.5, and an octane number of 77.8 as determined by the motor method. Upon the addition of 3 cc. of tetraethyl lead per gallon the octane number, as determined by the motor method, Was increased to 84.2. The octane number as determined by the research method and without the addition of tetraethyl lead was 90.1. Gas released from the receiver 32 amounted to 948 cu. ft. per barrel of gasoline produced. The carbon f content of the coky residue, comprising the residue of the spent catalyst, deposited in the coldng receptacle I4 was 46%.

Example No. 2.-Using as a raw charge a parafn distillate the same as that used in Example No. 1 and also using the same catalyst in a proportion controlled to maintain the same ratio of catalyst to oil in the heater fed, a second operation was carried out in the same manner except that in the coking receptacle vapor temperatures were increased to 910 F. in the lower part and to 860 F. in the upper part. With this increase in the vapor temperatures in the coking receptacle, the amount of fresh feed required to maintain the same heater throughput exceeded that employed in the operation described in Example No. l by 17.8%, the fresh oil in this instance representing 6.7% of the heater feed. Under these conditions of operation a gasoline yield of 62.8%, based on the fresh oil, was obtained. This gasoline had a gravity of 58.6 A. P. I., a bromine number of 96.7, an octance number of 77.2 determined by the motor method and 90.6 determined by the research method. Upon addition of 3 cc. of tetraethyl lead the octane number as determined by the motor method increased to 81.0. The gas released from receiver 32 amounted to 1605 cu. ft. per barrel of gasoline and the carbon content of the coky residue deposite-d in l0 approximated 35%.

Comparison of the operation of Example No. 2 with the operation of Example No. 1 illustrates the fact that an increase in the temperature of the coking receptacle beyond that employed in the operation of Example No. 1 does not improve the anti-knock Value of the gasoline but that it does improve the throughput and the rate of gasoline production, the increased throughput being accomplished by a substantial sacrice in the gasoline yield and increase in gas production.

Eample No. 3.-A third operation was carried out in the above-described apparatus using the same charging stock, the same catalyst, the same ratio of catalystto heater feed and the same outlet temperatures for heaters 6 and 'l as those employed in the operations of Example No. 1 and Example No. 2. In this third operation the temperatures in the coking receptacle approximated those prevailing in the operation of Example No. 2. In this third operation al1 of the liquid accumulating in the lower part of the vapor sepa- Vrator I8 was returned to the coking receptacle as in the operations of Example 1 and 2 but a part of the condensate accumulating in the fractionating tower 29 was drawn 01T to storage through line 34. The condensate thus drawn off to storage amounted to 12.3% based on the raw charge. In this operation the amount of fresh charge required to maintain the heater feed at the value prevailing in the operations of Examples 1 and 2 showed an increase of 103% over the amount of fresh charge employed in the operation of Example No. 1, and 72.4% over the amount employed in Example No. 2. In this instance the fresh feed amounted to approximately 11.6% of the heater feed. In this operation there was obtained a gasoline yield of 63.2% based on the fresh charge and this gasoline had a gravity of 53.6 A. P. I., an octane number of 72.9 as determined by the motor method and 85.8 as determined by the research method. Upon addition of 3 cc. of tetraethyl lead the octane number as determined by the motor method increased to 80.2. The gas released from receiver 32 amounted to 1060 ou. ft. per barrel of gasoline and the carbon content of the coky residue deposited in receptacle I6 approximated 47.5%. However in the operation of Example No. 3 the gallons of gasoline per pound of catalyst increased to 1.23, as compared to .677 for the operation of Example No. 1 and .710 for the operation of Example No. 2.

Comparison of the operation of Example No. 3 with that of Example No. 2 wherein approximately the same temperature prevailed in the coking receptacle, shows that a marked increase in the permissible charging rate and in the rate of gasoline production results from withdrawing from the cycle a relatively small proportion of the condensate formed in fractionating tower 2S. It also shows that such withdrawal does not materially affect the gasoline yield but that it is acd companied by a marked decrease in the antiknock value of the gasoline and a decrease in the formation of gas.

Example No. 4.-Using as the raw charging oil a paraffin distillate the same as that used in the previous examples, but as the catalyst a contact grade Olmstead earth of 100 mesh and finer, and controlling the proportion of catalyst to oil in the heater feed to maintain. the same ratio as in the operations previously described, a fourth operation was carried out in the same apparatus under substantially the same conditions of operation as those employed in the operation of Example No. 2 except that the amount of fresh feed required to maintain the same heater throughput exceeded that employed in the operation of Example No. 2 by 14.4%, the fresh oil in this instance representing 7.7% of the heater feed. In this fourth operation there was obtained a gasoline yield of 68.4% based on the fresh feed. This gasoline had a gravity of 58.7 A. P. I., a bromine number of 101J and an octane number of 68.8 as determined by the motor method or 81.3 as determined by the research method. Upon the addition of 3 cc. of tetraethyl lead per gallon of gasoline the octane number, as determined by the motor method, increased to 76.7. Gas released from the receiver 32 amounted to 1290 cu. ft. per barrel of gasoline produced. The carbon content of the coky residue, comprising the residue of the spent catalyst, deposited in the coking receptacle I4 approximated 52%. The gasoline produced approximated .887 gallons per pound of catalyst.

Comparison of this operation with an otherwise similar operation employing no catalyst showed 10 that the presence of the dispersed Olmstead earth in the operation of Example No. 4 had no significant eect on the anti-knock value of the gasoline produced but did cause an increase of 5.5% in the gasoline yield, an increase of 17.5% in the permissible charging rate, and an increase of 24% in the rate of gasoline production. In addition it eliminated significant deposition of carbon from the oil in the heating conduits of heaters 6 and 1.

Example No. 5.-Another run was made in the apparatus above described using a synthetic cataiyst containing 85% silica and 15% alumina, by weight. and prepared by the same procedure as that employed in preparing the catalyst used in the operation of Example No. l. A Pennsylvania type gas oil having a gravity of 37.4 A. P. I. was used as raw charging oil. In this operation the catalyst was supplied at a rate regulated to maintain approximately 1.0% catalyst, by weight, on the oil in the mixture entering the heater 6. The rates of heating in the furnaces 6 and I were controlled to maintain an oil temperature of l060 F. at the outlet of the heater 6 and also at the outlet of the heater I. A temperature of approximately 925 F. was maintained in the lower part of the coking receptacle I4. A temperature of approximately 825 F. prevailed at the upper end of the coliing receptacle. The temperature of the vapor separator I8 was controlled to condense therein only that amount of high boiling material which could be returned to the colring receptacle it and reduced to coke therein, no material being drawn olf through line 28. This required maintaining a temperature of about 800 F. at the upper end of separator I8. Fractionating tower 29 was controlled to condense all hydrocarbons higher boiling than gasoline but all of the resultant condensate was drawn off through line 36. No condensate was recirculated through the heaters 5 and 'I, the heater feed consisting exclusively of fresh oil and admixed catalyst. A pressure of 400 lbs. was maintained on the oil at the outlet of the heater 7. This pressure was reduced by regulation of valve I3 so that a pressure of only 50 pounds prevailed in the coking receptacle ifi and subsequent parts of the system. Under these conditions of operation a ygasoline yield of 31%, based on the fresh feed, Was obtained. This gasoline had a gravity of 59.4% A. P. I., a bromine number of 94.5 and an octane number of 74.6, as determined by the motor method, or 86.6, as determined by the research method. Upon addition of 3 cc. of tetraethyl lead per gallon the octane number, as determined by the motor method, increased to 80.7. Gas released from the receiver 82 amounted to 2000 cu. ft. per barrel of gasoline produced. The carbon content of the col/ly residue deposited in the receptacle it approximated 46.5%. In this operation the gasoline produced amounted to 4.6 gallons per pound of catalyst.

It is one of the advantages of the process of my invention that the ratio of catalyst to raw charging stock may be increased to a very high value without raising the ratio of catalyst to oil in the heating conduit to an extent high enough to preclude maintaining the catalyst in suspension. This may be accomplished merely by progressively decreasing the conversion per pass and simultaneously increasing the recycle ratio, while maintaining constant the ratio of catalyst to oil .in the heater feed. This is strikingly illustrated by the fact that in the operation of Example No. 1 the amount of catalyst comprised only .8% by weight on the oil in the mixture 1l entering the heater 6, whereas the fresh oil amounted to only 5.7% of the combined heater feed. Thus the ratio of catalyst to fresh oil substantially exceeded 12%.

As compared to catalytic processes of the fixed bed type the plant costs for carrying out the process of my invention are exceedingly low. Moreover the ratio of high octane gasoline produced to catalyst used is substantially higher in my process.

I claim:

1. In the manufacture of gasoline from higher boiling petroleum oils, the improvement which comprises mixing a small proportion of a finely divided argillaceous material with a high boiling petroleum distillate stock, heating this mixture to and at a high cracking temperature approximating 950-1100 F. while flowing as a stream at a velocity sufficient to maintain said material in suspension in said stock for a period of time sufcient to convert a substantial part of said stock into hydrocarbons of the gasoline boiling range, thereafter in a coke separating zone separating the hot products of said heating into a composite vapor fraction including the gasoline hydrocarbons and a substantially dry coky residual material comprising the residue of said argillaceous material, separately condensing from said composite vapor fraction a first high boiling tarry fraction, a second lower boiling fraction and nally a low boiling gasoline fraction, and returning at least a part of said first high boiling tarry fraction to said coke separating zone.

2. In the manufacture of gasoline from higher boiling petroleum oils, the improvement which comprises mixing a small proportion of a finely divided argillaceous material with a high boiling petroleum distillate stock, heating this mixture to and at a high cracking temperature approximating 950-1100 F. while flowing as a stream at a velocity sufcient to maintain said material in suspension in said stock for a period of time sufficient to convert a substantial part of said stock into hydrocarbons of the gasoline boiling range, thereafter in a coke separating zone separating the hot products of said heating into a composite vapor fraction including the gasoline hydrocarbons and a substantially dry coky residual material comprising the residue of said argillaceous material, separately condensing from said composite vapor fraction a rst high boiling tarry fraction, a second lower boiling fraction and nally a low boiling gasoline fraction, returning at least a part of said first high boiling tarry fraction to said coke separating zone, and returning at least a part of said second lower boiling fraction to the heating operation rst mentioned.

3. In the manufacture of gasoline from higher boiling petroleum oils, the improvement which comprises mixing with a high boiling petroleum distillate stock a small amount of a finely divided synthetic active catalyst comprisingl silica and alumina, heating this mixture to and at a temperature approximating 950 F. While flowing as a stream at a Velocity sufficient to maintain said catalyst in suspension in said stock for a period of time suflicient to convert a substantial part of said stock into hydrocarbons within the gasoline boiling range, thereafter in a coke separating zone maintained at a temperature not substantially exceeding 825 F. separating the hot products of said heating into a composite vapor fraction in cluding the gasoline hydrocarbons and a substantialiy dry coky residual material comprising the residue of said catalyst, separately condensing from said composite vapor fraction a first high boiling tarry fraction, a second lower boiling fraction and finally a low boiling gasoline fraction, returning said first high boiling tarry fraction to said coke separating zone, and returning said second lower boiling fraction to the heating operation rst mentioned.

HARRY L. PELZER.

REFERENCES CITED The following references are of record in the le of this patent: y

UNITED STATES PATENTS Number Name Date 1,827,915 Seguy Oct. 20, 1931 1,860,199 Osterstrom May 24, 1932 1,989,731 Barnes Feb. 5, 1935 2,091,892 Stratford Aug. 31, 1937 2,125,234 Atwell July 26, 1938 2,128,220 Cooke Aug. 30, 1938 2,141,185 Houdry Dec. 27, 1938 2,237,339v De Florez Apr. 8, 1941 2,323,206 De Florez June 29, 1943 FOREIGN PATENTS Number Country Date 411,477 Great Britain June 4, 1934 Certificate of Correction Patent No. 2,463,903. March 8, 1949.

HARRY L. PELZER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 21, for the Word member read number; column 5, line 38, for accomplished read accompanied; column 8, line 32, for fed read feed; line 63, for accomplished read accompanied;

and that the said Letters Patent should be read Wit-h these corrections therein that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 23rd day of August, A. D. 1949.

[SEAL] THOMAS F. MURPHY,

Assistant Gommsoner of Patents.

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