US2353399A - Manufacture of gasoline - Google Patents

Description

July 11, 1944. E. c. HERTHEL MANUFACTURE OF GASOLINE 'Filed May 25, 1940 NVENTOR gene C. #efie @fm fm ATTO R N EY5 Patented July 1l, 1944 2,353,399 MANUFACTUBE or GAsoLmE Eugene C. Herthel, Flossmoor, Ill., assignor to Sinclair Rcilninsr Compann New York, N. Y.; a

corporation of Maine Application May 25, 1940, serial No. 337,238

2 claims. (ci. 19o-5o) This invention relates to improvements in the manufacture of gasoline of high anti-knock value by cracking petroleum stocks of lower anti-knock value in the presence of nely divideddispersed argillaceous materials which possess high adsorptive capacity and aid or direct the cracking reaction by catalysis. In particular the invention is concerned with improvements in that type of process in which a vhydrocarbon stock a major portion of which boils within the boiling range oi' gasoline is subjected to that type of cracking commonly known as reforming whereby a substantial part of said stock is converted into gasoline material of improved anti-knock value.

Several methods for producing gasoline material of high anti-knock value, from high boiling petroleum stocks and from low boiling stocks of lesser anti-knock value, have been heretofore produced and used commercially to a considerable extent. However, such proposals have not been entirely satisfactory for a number of reasons. For example, it has been proposed to produce gasoline of high anti-knock value directly from high boiling petroleum stocks, such as gas oil and reduced crude, by severe thermal cracking. However, such operations invariably are accompanied by excessively high gas losses although such high gas losses are readily avoided in thermal cracking processes producing gasoline material of moderate or relatively low anti-knock value.

It has likewise been proposed to produce gasoline of high anti-knock value directly from high boiling petroleum stocks by thermal cracking aided by catalysis, in processes wherein the high boiling stock is vaporized and the-vapors passed at a cracking temperature through a bed of catalytically active material. However, the active catalysts lemployed in such processes are costly and their efliciency active life is so short that regeneration of the catalyst bed at very short intervals is essential. The cost of such regeneration both from the standpoint of the initial cost of the equipment involved and its maintenance, the cost of carrying out the regenerating operation itself, vand the limitations imposed on the useful operating time of the converting processes proper, all involve handicaps of major importance with respect to processes of this type.

A third proposal has involved thermally converting, or reforming, relatively low boiling stocks,

a major part of which boils within the boiling range of gasoline, under severe cracking conditions. According to this proposal the low boiling charging material for the reforming operation may be either a distillate obtained from virgin stock or the crude product of the ordinary thermal cracking process carried out to produce gasoline material of relatively low anti-knock value. Operations of this type have been subject to serious limitations in continuity, due to the deposition from the oil of heat insulating material on the interior surfaces of the conduit wherein the stock is heated to and at the cracking temperature, with resultant overheating of the walls of the conduit frequently accompanied by coke formation. The adverse eiect of the deposition of such heat insulating materials is much more pronounced and more difficult to avoid in operations of this type than when cracking higher boiling materials such as gas oil.

I have devised a process by which the objectionable features of each of these prior proposals are substantially eliminated and several important additional advantages are derived. In the practice of my invention I admix a small proportion of a nnely divided'argillaceous material with a petroleum stock, a major part of which boils within the boiling range of gasoline, and heat this mixture to and at a high cracking temperature while flowing as al stream at a sumcient velocity to maintain said finely divided material'in suspension in said stock, for a period of time sumcient to reform a substantialpart of. said stock to produce gasoline material of improved antiknock value. 'Thereafter I separate a vapor fraction comprising said gasoline material from the resulting residual material comprising the residue of said nely divided argillaceous material. The residual material may be drawn oil from the initial separating zone as a fluid mixture including the residue of the finely divided argillaceous material. Alternatively :the residual material comprising the residueof the finely divided argillaceous material may be reduced in the initial vapor separating zone to a dry or substantially dry coke-like residue.

I employ as said petroleum stock a petroleum distillate of the requisite boiling characteristics produced by thermal cracking without catalysis. The boiling characteristics of this stock may be such that about 40% or somewhat less will distill oil Iunder superatmospheric pressure at temperatures up to 420 F. although stocks falling entirely within the gasoline boiling range may also be treated with advantage.

The iinely divided argillaceo s materials useful in the process of my invention include naturally occurring clays which have a limited catalytic action but exert a marked preferential adsorptive power for carbon forming materials, iinely divided fullers earth for example, as well as acid treated clays. I'hey 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, chromium, and the like, which are commonly used in catalytic cracking processes of thexed bed type.

For use in the process of my invention the argillaceous materials are advantageously reduced to a powder the i'lneness of which may vary from about 100 mesh to an almost impalpable powder. However, particle sizes larger than 100 mesh may be used so long as the velocity of the oil is high enough to maintain the argillaceous material in a state of dispersion through the ol being treated during its entire passage through the heating conduit. 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 particles may be recovered with less dilculty from entrainment in combustion gases in which they become dispersed in regenerating 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 vapor phase cracking processes or for combined vapor phase cracking and coking processes with only a :minor amount of additional equipment. The temperatures and pressures useful in the practice of my invention may be similar to those employed in conventional thermal reforming operations. For example the mixture of oil and dispersed argillaceous material may be heated in the heating conduit to a temperature of 1050-1100 F. vunder a pressure of from 400-500 pounds per square inch. However, with synthetic argillaceous materials of high catalytic activity the optimum temperature may be as low as 950 F. The use of high pressures promotes increased capacity with a given apparatus but tends to limit the antiknock value obtainable with moderate temperatures. Therefore, when using synthetic catalysts of high reforming activity and relatively low temperatures pressures as low as 50 pounds per square inch or somewhat less may be used with advantage.

The 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 anti-knock value of the eventual gasoline material. Amounts of nely dividedv argillaceous material varying from l/A, 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 conduit, have been used with considerable success. Dispersion of a very small proportion of the argillaceous material through the oil being treated is effective in eliminating, or substantially reducing. the formation of heat insulating deposits on the interior surfaces of the heating conduit. The adsorptive action of the dispersed argillaceous particles for the more objectionable carbon-forming materials, e. g., tarry matter and polymers of high molecular weight, made effective substantially at the point of formation, appears in a large measure to be responsible for the elimination of heat insulating 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 heat insulating deposits in the heating conduit is advantageous particularly when employing synthetic argillaceous material of high catalytic activity, since the additional argilla.

ceous material aids and directs the reforming reaction in producing gasoline material of improved anti-knock value.

In the process of my invention the effectiveness of the dispersed argillaceous material is promoted rather than impaired by the volatile character of the charging stock, since with charging stocks initially containing substantial proportions of high boiling hydrocarbons of high molecular weight the useful adsorptive capacity of the dispersed material is more rapidly exceeded and its catalytic action is masked to a greater extent by the larger quantity of adsorbed tarry matter.

By reducing the residual material' to a substantially dry cokey product including the residue "of the nely divided argillaceous matter, any

insumciently cracked high boiling hydrocarbons may be recovered as a liquid -substantially free from suspended matter, while the spent argillaceous material is recovered in a form especially adapted for eilcient reactivation by burning. Moreover, the proportion of carbonaceous matter and vaporizable hydrocarbons present in the coke-like residue is so low that when using inexpensive naturally occurring argillaceous materials in my process, reactivation oi' the spent argillaceous material ceases tovbe a matter of economic necessity. Expensive regenerating equipment and the cost of regenerating operations may be dispensed with entirely in such instances.

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 raw gasoline stock, or raw stock containing gasoline, is supplied from any convenient source of supply through line l to pump 2 by which it is forced through line 3, heat exchanger 4 and line 5 to the inlet of the heating conduit. A concentrated slurry of finely 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 8 by pump I0 and discharged through line Il into the siigeasm of raw charging stock passing through l e The amount of concentrated slurry supplied in this manner is controlled by regulating the speed of pump I0 so that the mixture eventually entering the heating conduit from line 5 will include the desired predetermined proportion of argillaceous material. 'I'he heating conduit in this instance consists of two serially connected Acoils the rst of which is disposed in furnace 6 and the second in furnace 1. A single furnace may be used although 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 finely divided argillaceous material may be heated in the heater 6 advantageously to a temperature of 850 -1100 F. andin the heater 1 to a temperature of 950-1100 F. In the heater 1 the oil is maintained at a high cracking temperature for a period of time sufiicient to reform a substantial part of said stock to produce gasoline material of improved anti-knock value. While passing through the heaters 6 and 1 the velocity of the flowing 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 passes through transfer line l2 and pressure reducing valve I3 to receptacle Il which may function either as' a coking receptacle or merely as a vapor.- liquid separator. A by-pass line I communieating with valved branch lines I9 permits discharge of the products from the heater 'I at points of progressively increasing elevation when receptacle I4 is being used as a coke separating chamber and it is desired to minimize the back pressure on the heating conduit. In receptacle I4 the material discharged from the heater 'I separates into a vapor fraction and a residue including the residue of the argillaceous material present in the mixture supplied to heater 9. A relatively low pressure, for example, a pressure of 50 pounds per square inch or somewhat less is maintained in receptacle I4. A pressure of 40G-500 pounds per square inch may 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 I9 if by-pass line I5 is being used). Vapors lib'- erated in receptacle I4 are discharged through line I1 to the scrubbing tower I8. The liquid residue which accumulates in receptacle I4, when the temperature prevailing therein is insulicient for reduction to coke, may be drawn off through valved line 42 together with the dispersed residue of the argillaceous material.

In the scrubbing tower I 8 high boiling tarry polymers are condensed and separated from the remaining vapors which continue on from the upper end of tower I8 through line I9. The intermediate portion of the scrubbing tower I8 may be provided with bailles while several conven. tional bubble trays 2| are advantageously provided in the upper portion to guard against entrainment of tarry matter in the vapors leaving .this tower through line I9. High boiling polymers accumulating in the lower part of scrubbing tower I8 are drawn off through line 22by pump 23 and this material is returned, in whole or'in part, to the upper end of receptacle I4 through line 24 to control the temperature of the initial vapor `separating zone. ,A When receptacle I4 is being operated as a coking receptacle, the tarry liquid thus supplied through line 24 performs the further function of assisting to maintain a liquid layer on the upper surface of the accumulating bed of coke. The hot vapors discharged from transfer line I2 are required to pass through this liquid layer on the upper surface of the accumulating coke bed, thereby separating and retaining in the coking receptacle the finer particles of dispersed argillaceous material which would otherwise be carried over to the scrubbing tower I8 by entrainment. When the chamber I4 is being operated as a coking receptacle, the temperature of the vapors in the upper part of this chamber may approximate BOW-825 F. Control of the temperature conditions in the scrubbing tower I8 may be maintained by supplying a cooling liquid through line 25, and branch lines 26 and 21,. by means of pump 4I. The temperature in the lower portion of the tower I8 may be varied from 650 F. to as high as 770 F.

while the temperature in the upper portion may be varied from about 550 F. to 740 F. To the extent that high boiling tarry condensate accumulates in the lower end of tower I8 at a rate exceeding that which can be returned to receptacle I4 through line 24, and be either reduced to a cokey residue or reevaporated therein, such excess tarry condensate may be drawn off through valved line 28. Alternatively this condensate'may be returned to chamber I4 to assist in providing the requisite additional cooling and -III to assist in ushing out spent argillaceous material through discharge line 42 when receptacle I4 is toA function merely 'as a vapor separator. When it is desired that the receptacle I4 function merely as a vapor separator an oil temperature not exceeding about 750 F. should be maintained in the lower end o! receptacle I4 while the oil vapor temperature at the upper end should not exceed about 725 F.

Vapors discharged from scrubbing tower I8 through line I9 enter. the lower end of frac'- tionating 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 fraction, together with any lower boiling. normally gaseous materials, will pass overhead through line 39 to condenser 3 I. The products from condenser 3| 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 of high anti-knock value is drawn oil 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 31, to the upper end of fractionating tower 29 to control the fractionating operation. j The condensate which accumulates in the lower part of fractionating tower 29 is drawn off through line 39. This condensate may pass through the heat exchanger 4 wherein it gives up part of its contained heat to the raw gasoline stock by indirect heat exchange. The temperature prevailing at the upper end of the fractionating tower 29 may approximate V350-410 F., depending on the desired end point of the nal condensate. The temperature in the lower portion of this tower may vary from 500 F. to about 620 F. A portion of the condensate drawn oi from tower 29 through line 38 and partially cooled in the heat exchanger 4 normally serves as the ternperature controlling medium supplied by pump 4I to the scrubbing tower I8.

That part of the condensate from fractionat ing tower 29 not returned to the scrubbing tower I8'by pump 4I may be` discharged from the system through line 39 or returned, in whole or in part, to the raw feed line I via connection 40 for recirculation through the heating conduit.

. Discharge of tarry matter from receptacle I4 through connection 42, of tarry condensate from scrubbing tower I8 through line 28, and of intermediate condensate from fractionating tower 29 through line 39 al1 have the effect of increasing the capacity of a given reforming unit but this increase in capacity is accompanied by a decrease in the maximum ultimate gasoline yield obtainable. Discharge of relatively volatile condensate from fractionating tower 29 through line 39 also has the effect of reducing the anti-knock value of the final product attainable with moderately severe heater conditions. This adverse effect on the anti-knock value of the nal product can be counteracted by increasing the severity of the heater conditions although such increase is usually accompanied by an increase in the production of gas. On the other hand the discharge of heavy tarry matter in limited quantities from v apor separator I4 or scrubbing tower I8 appears to have no significant adverse eifect on the antiknock value of the nal product.

It will be obvious that more than one coking receptacle may be provided so that the cokey deposit may be removed from one receptacle while another is being iilled, thus also permitting the coking modication of my reforming 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 coklng receptacle may be opened and the cokey 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 cokey residue resembles a caked powder which may be crushed or disintegrated with little difficulty.

A specific example of an operation embodying my invention as carried out with a particular charging stock in an apparatus of the type illustrated will further exemplify the invention: Using as the raw charging stock a distillate obtained from a paraine base c rude by moderately severe thermal cracking of the gas oil fraction, the distillate having an initial boiling point of 250 F. and with 60% and 90% distilling of! up to 420 F. and 470 F., respectively; and as the reforming catalyst a synthetic argillaceous material composed of 85% silica and 15% 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, the illustrated apparatus may be operated in accordance with my invention in the following manner: A slurry of the raw charging oil and nely divided silica alumina catalyst above described is supplied at a rate regulated to maintain a ratio of 2.3 pounds of catalyst per barrel of oil in the mixture entering the heater 6. The rates of heating in furnaces 6 and 1 are controlled to maintain an oil temperature of 1050 F. at the outlet of the heater 6 and substantially the same oil temperature at the outlet of heater 1. An oil vapor temperature of 810 F. is maintained at the vapor outlet of receptacle I4. A pressure of 50 pounds per square inch is maintained ln receptacle I4, while a pressure of 400 pounds per square inch is maintained at theoutlet of the heater 1 by regulation of valve I3. All of the condensate from the scrubbing tower I8 is returned to receptacle I4 through line 24 and all of the condensate from the fractionating tower 29 not used in controlling the head temperature of the scrubbing tower I8 is recycled through the heaters 6 and 1 in admixture with the raw stock. Operating in the manner and under the conditions .lust described, there is produced approximately 80% of gasoline based on the raw charge. The gasoline thus produced will have an octane value of 77 as determined by the motor method. A solid cokey residue including the residue of the spent catalyst will deposit in receptacle I4 and this residue will contain about 35% carbon.

It will be apparent that in carrying out the process of my invention 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 ari extent high enough to preclude maintaining the catalyst in suspension, merely by progressively decreasing the conversion per pass and simultaneously increasing the recycle ratio. When using an active reforming catalyst and maintaining the heater temperature, pressure and crack per pass at a value limited to maintain gas production at a minimum, an increase in the ratio of catalyst to oil increases the anti-knock value of the iinal product up to a point where an apparent antiknock ceiling is reached. 'I'his appears to have been reached when the octane value approximates 'J7-78 as determined by the motor method.

As compared to catalytic processes of the fixed bed type, the plant costs for carrying outthe process of my invention are exceedingly low. Moreover, the ratio of high octane gasoline produced to catalyst used is higher. Furthermore the ratios of high octane gasoline produced to vcoke formed and to catalyst used are higher in my process than those attainable by catalytic cracking of higher boiling oils such as gas oil.,

The higher -gasoline yields per pound of catalyst involve a decrease in catalyst regenerating diiiiculties and costs.

I claim:

l. In the manufacture of gasoline of high antiknock value, the improvement which comprises mixing a small proportion of a nely-divided argillaceous material with a petroleum stock produced by thermal cracking without catalysis the major portion of which boils within the boiling range of gasoline, heating this mixture to and at a high cracking temperature approximating 950- 1l00 F. and under a pressure not substantially exceeding 500 pounds per square inch while owing as a stream of sufficient velocity to maintain said argillaceous material in suspension in said stock for a period of time suflicient to reform a substantial part of said stock to produce a gasoline material of improved anti-knock value, thereafter separating a vapor fraction comprising said gasoline material from the resulting re-A sidual material comprising the residue of said argillaceous material, and limiting the maximum value of the crack per pass and the minimum value of the ratio of argillaceous material to oil in the mixture supplied to said heating to produce a gasoline product having an octane number approximating '77 as determined by the motor method.

2. In the. manufacture of gasoline of high antiknock value, the improvement which comprises mixing a small proportion of a finely-divided adsorptive catalyst with a petroleum stock produced by thermal cracking without catalysis the major portion of which boils within the boiling range of gasoline, heating this mixture to and at a high cracking temperature approximating 950- 1100 F. and under a pressure not substantially exceeding 500 pounds per square inch while ilowing as a stream of sufficient Velocity to maintain said catalyst in suspension in said stock for a period of time sufficient to reforma substantial part of said stock to produce a gasoline material of improved anti-knock value, thereafter separating a vapor fraction comprising said gasoline material from the resulting residual material comprising the residue of said catalyst, and limiting the maximum value of the crack per pass and the minimum value of the ratio of catalyst to oil in the mixture supplied to said heating to produce a gasoline product having an octane number approximating 77 as determined by the motor method.

EUGENE C. HERTHEL.

Images