US2360622A - Method of producing aviation gasoline - Google Patents

Description

oct. 17, 1944. B E ROETHEL, 2,360,622

METHOD OF PRODUCING AVIATION GASOLINE METHOD OF PRODUCING AVIATION GASOLINE Filed April 50, 1943 2 Sheets-Sheet 2 jfja y CATALYST 'n ,93

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GAS OIL Patented Oct. 17, 194.4

METHOD OF RODUCING AVIATION SOLINE Bruno E. Roetheli, Cranford, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application April 30, 1943, Serial No. 485,129

(Cl. 19E-53) 6 Claims.

The present invention relates to improvements in the production of aviation gasoline and has for its main object the production of a maximum quantity of high octane number gasoline from a crude petroleum oil.

The main object of this invention is to treat, in an integrated process, a crude petroleum oil to produce, by destructive hydrogenation of the kerosene or light gas oil fraction of the crude oil, and by catalytic cracking of the heavier gas oil, followed by separate fractionation of the products of both processes, blends of certain components of the hydrogenated and cracked products yielding an aviation base fuel of superior quality.

In explanation of the preceding object, it is pointed out that the fraction of the hydrogenated product boiling up to about 200 F. and the fraction of the catalytically cracked product boiling from about 200 to 350 F. form a blend of superior anti-detonation qualities. On the other hand, the fraction of the hydrogenated product boiling above about 200 F. and the fraction of the catalytically cracked products boiling below about 200 F. do notpossess good anti-detonation characteristics.

Another object of my invention is to utilize, for producing alkylate, the olefins and isoparafiins lproduced in the system for blending with the aviation base stocks produced by hydrogenation and catalytic cracking, and also to employ the formed isopentane as a blending agent.

Other and further objects of my invention will appear from the following description and claims.

For a better understanding of my invention reference is male to the accompanying drawings in which I hav shown in Fig. I diagrammatically, a preferred modication of my invention;

and in Fig. II, I have shown a cracking vessel f and means for feeding catalyst and oil thereto.

Referring in detail to the drawings, a crude petroleum oil, preferably one which is highly naphthenic, is introduced into the system through line I and is then heated in a red coil 3 to a temperature of from 8Go-900 F., whereupon it is discharged through line into a fractionating column I0. From fractionating column I0 I recover as bottoms through line I2 a heavy residual reduced crude, this reduced crude amounting to about 1020% by volume of the orginal feed. The reduced crude recovered through line i2 may be withdrawn from the present system and subjected to coking or viscosity reducing to produce further quantities of gas oil, or it may be subjected to cracking as will subsequently more fully appear hereinafter.- Overhead through line I5 I recover normally gaseous components and virgin naphtha. A kerosene or light gas oil fraction boiling say from S-600 F. is withdrawn from the fractionating column I0 through line I6 and thence after suitable heating is subjected to destructive hydrogenation in a system which I have designated as I8. The hydrogenation is preferably carried out by heating the oil" to a temperature of around '700 F. and conducting it to a, hydrogenation zone containing a catalyst such as tungsten sulfide, iron sulfide, molybdenum sulfide or the like, supported on activated alumina or activated clay. The oil is fed to the reaction zone at a rate of 0.5to 2.0 volumes of oil per volume of catalyst per hour. Hydrogen in the amount of SOOO-20,000 cu. ft. per barrel of oil is also fed to the hydrogenation reactor and a pressure of from -1000 atmospheres lis imposed u-pon the hydrogenation system, whereupon the kerosene fraction undergoes destructive hydrogenation to form fractions of gasoline boiling range and other products.

The products of the hydrogenation step are passed through line 20 into a fractionating column 25 where they are subjected to fractionation as follows: First, a heavy bottoms fraction is withdrawn through line 301and it may be recycled through line 32 to a second hydrogenation unit 35, operated similarly in all respects to hydrogenator I8 and thereafter the hydrogenation products from this second hydrogenation zone are returned through line 40 to fractionator 25, or the heavy bottoms fraction may be discharged into line I'I leading to a cracker, as will appear presently. Second, a heavy naphtha boiling from about 200 to 400 F. or higher is withdrawnl from fractionator 25 through line 21. The fraction does not possess suiiiciently high anti-detonation quality to make it a desirable aviation fuel, but it is satisfactory for use as an automotive fuel andmay be blended with other constituents of gasoline to make a finished product of suitable boiling range and volatility. Third, the most important fraction, from the standpoint of this process is recovered from fractionator 25 through line 2B. This fraction boils up to 200 F. and contains the saturated hydrocarbons above the Cs fraction. It possesses a high octane number and hence forms a valuable component of aviation gasoline. y Finally, from the fractionator 25, I recover separately through line 28 C5 hydrocarbons including isopentane which may bev added to aviation gasoline to increase volatility and also through` line 3l a C4 fraction containing isobutane, which isobutane may be alkylated with the olefins formed in other parts of the present system. The disposition and use of the C5 and C4 hydrocarbons will be explained subsequently herein. Methane, ethane, propane, etc., are rejected from the system through pipe 29. The separation of the C1 to C5 hydrocarbons is merely indicated in the drawings diagrammatically for purposes of simplicity of explanation, but the expert will understand that actually additional distillation towers (not shown) will be required to effect the indicated separation by conventional means.

Referring again to fractionator |0, a heavy gas oil, that is a gas oil boiling from 60G-800 F., is withdrawn from the fractionator through line and thence subjected to a catalytic cracking operation in a unit 50. The details of operation of the unit'50 will be described in more detail hereinafter. Suiilce it to say for the moment, that oil is cracked and the cracked products are Withdrawn from the unit 50 and discharged through line 52 into a fractionator 55 where they are subjected to fractionation. From fractionator 55 agasoline fraction is Withdrawn through line 58 and subjected to a second stage of catalytic cracking in a unit 59. The cracked products from the second stage are withdrawn through line 62 and discharged into a fractionator 10. From fractionator there is recovered through line 1| a motor gasoline fraction, through line 13 a heavy naphtha fraction, through line 14 a motor gasoline bottoms product, and through line 12 a naphtha boiling in the aviation range which is combined with the lighter (lower boiling) aviation base stock recovered through line 26 from fractionator 25, which latter fractionator contained the products resulting from the hydrogenation of the kerosene or light gas oil. Now the naphtha recovered through line I2 boils from about 200 to 350 F. and is superior in octane number to the' fraction boiling up to 200 F. Hence by combining the fraction in 26 from the hydrogenation unit with the fraction in 12 from the cracking steps, I secu-re a blended base aviation gasoline of very high octane number, and as stated thisV feature of producing and combining the specified components goes to the hearth of this invention;

From fractionator 55 as indicated in Fig. I, there is also obtained a cycle stock through line 60 which may be recycled through line 6| or line 64, respectively, to the first or second stage of cracking or to the hydrogenation stage. A por-- tion of this fraction may be rejected from the system. Also from fractionator 55, C4 olenic hydrocarbons, maybe recoveredand alkylated with an isoparaii'n in known manner. Lighter hydrocarbons may be rejected from the system, as indicated. The separation of C5 and lighter hydrocarbons is effected in known manner.

I have described thus far, a method of producing an aviation base stock from a crude petroleum oil and it involved separating from the crude oil, a light gas oil (or kerosene) and subjecting that light gas oil to destructive hydrogenation to form a component of the aviation base gasoline boiling up to 200 F.; also separating from the crude oil, a heavier gas oil which is cracked to form cracked gasoline, which cracked gasoline is recracked catalytically', and from this recracked gasoline, the heavier ends, i. e., the 200 to 350 F. fraction is recovered from the second stage of cracking and blended with the naphtha boiling up to 200 F. produced from the hydrogenated kerosene or light gas oil.

Referring now to Fig. II, I shall describe in detail a fluid catalyst cracking operation. The unit 50 of Fig. I comprises in a preferred modification, shown in Fig. II, the following essential apparatus; first, a feed means standpipe |00 is in communication with an elevated hopper 99 containing the cracking catalyst inthe form of a powder having an average particle size of aroundA 300 mesh, although it may vary from 20D-400 mesh. I'his catalyst may be removed from standpipe |00 and discharged into a line |02 Where it is mixed with the heavier gas oil from line Il and fractionator I0, after the said gasoil has been heated in a furnace or fired coil |04 to a temperature of around 850 to 1000 F. The vaporized gas oil is withdrawn from the fired coil |04 through line |06 and discharged into the pipe |02 containing catalyst (as described above) and thereafter the mixture is discharged into a cracking vessel 50 wherein the superficial'velocity of the vapors is regulated or controlled within the limits of 0.5 to 6 ft. per second, preferably 1. to 2 ft. per second, so as to form within reactor 50 a. dense, turbulent, fiuidized mass of catalyst intermixed with the vapors. It should be pointed out that in order to aid in the fiuidization of the catalyst descending through standpipe |00, a plurality of gas taps |05 are provided at spaced points in the standpipe through which some gaseous material (e. g., normally gaseous hydrocarbons) may be forced into the standpipe so as to cause the fluidization of the catalyst therein, this gas ascending at a relatively low velocity, say 2-3 ft. per second, and effecting the fluidization of the catalyst and rendering it capable of flowing freely, like water, through the system in the manner indicated.

Withinthe reactor 50 the temperature is from S50-1000 F., the concentration of catalyst being -such that the iluidized mass weighs from 15-25 lbs. per cu. ft., and a pressure of 0 to 15 lbs. per square inch above atmospheric is maintained within the reactor.` The residence time is such that the vapors reside in the reaction zone for 10-40 seconds.

The vapors pass upwardly into a suitable separating device ||2 which is herein shown to be a section of greater diameter than the lower portion of the reactor. The catalyst entering therein reverses vdirection and gravitates towards the catalyst in the "main body of the reactor and the vapors are therefore depleted considerably of catalyst, the separation being induced or caused by the fact that the linear velocity of the gases in the disengaging chamber ||2 is reduced by the increased diameter to the order of 1/2 ft. per second. The catalyst is continuouslyv withdrawn from, reactor 50 through line H4, and this catalyst may `be regenerated by burning off its contaminants with air, in apparatus not shown, and thence returned to feed hopper 99. The details of regeneration of the catalyst are Well known to the art and need not be discussed herein, but preferably the catalyst is regenerated in the form of a uidizedfmass of catalyst in an oxygen containing gas, having approximately the same density as the mixture of catalyst and vapor in the reaction zone and formed in a similar manner, viz. by controlling the velocity of the gas inthe regenerator within the limits heretofore prescribed for the vapors in the reactor. The vapors are withdrawn through line 52, as indicated in Fig. I. and they may be treated as hereinbefore described. It should be pointed out of course that it may be desirable to insert in line 52 dust separators, cyclone separators, electrical precipitators, and the like to separate the last traces of catalyst.

The second stage cracking'unit 59 may be of the same construction and operated in the same manner as 50 illustrated in Fig. II, and it is deemed unnecessary to repeat the description. Suiflce it to say that the gasoline is heated and passed through unit 59 at a temperature of from 850-1000 F. in the presence of an active cracking catalyst. The cracking catalyst used in my process may be an acid treated clay of the bentonitic or montmorillonitetype, but preferably it is a mixed or plural gel containing alumina or magnesia and silicia. For example, an` excellent catalyst containing to 20% by'weight alumina. the remainder silica gel may be employed.

During the operations which I have described various quantities of gas are produced. For example, there is recovered from fractionating column 25 an overhead fraction containing C4, C5 and lighter hydrocarbons, that is, methane, ethane, propane, etc. The C4 fraction containing high percentages of isobutane is preferably passed through ,line 3| and subjected to alkylation with propylene, butylene or pentylene from towers 55 and 'I0 in the presence of sulfuric acid at temperatures around 30 F., in known manner, in a unit which I have designated 'I5 to produce an alkylate product, which alkylate product may be blended with the base gasoline components in lines 26 and 12 in the ratio of say 60-90 volume per cent of the base gasoline and the remainder the alkylation product. By thus combining the products in the manner indicated, I am enabled to produce a finished aviation gasoline approaching an octane number of 100 without lead, and by adding 4 cc. of. lead tetraethyl per gallon I am able to produce an aviation gasoline having an octane number considerably in excess of 100 and exhibiting good rich mixture characteristics. Also, it is pointed out that the C5 hydrocarbons contain some isopentane which may be blended into the alkylate product for the purpose of increasing volatility and forming with the other components an aviation gasoline of proper volatility and boiling range.

Another modification of my invention includes discharging the reduced crude in line I2 through a line I9 into the first stage of cracking in a unit such as 50, provided with conduit means adapted to permit injection of liquid oil. This oil may be injected in liquid form through pipe 5I directly into the cracking unit 50 Where it contacts the catalyst which may have a temperature of around 1000* F.v where it is discharged into the cracking unit directly from regeneration. In other words,

. if the fouled catalyst withdrawn through line I I4 (Fig. 2) from crackingvessel 50 is regenerated, its temperature as it leaves the regenerator may be about 1000 F. or even higher, say 1100a F. If this hot catalyst is directly returned uncooled to the cracking zone and mixed with reduced crude recovered from column I 0 at a temperature of say 400-600 F. in the ratio of 20-40 lbs. oi' catalyst per pound of oil, then the hot catalyst heats the oil to cracking temperatures and thus obviates the necessity of using a'furnace to heat the reduced crude. In like manner the heavy gas oil in line I1 may bypass furnace |04 (Fig. 2) and be directly injected into the cracking retort 50, if the catalyst to oil ratio is of the order indicated.

It can be seen therefore from the foregoing description of my invention that it involves primarily the destructive hydrogenation of light gas oil from a crude oil to form a light aviation base component, and the catalytic cracking of a heavy gas oil from said crude' oil, the recracking catalytically of the gasoline produced in the first stage of cracking, and the fractionation of the recracked product to form a heavier aviation base component which is blended with the said lig-ht aviation base component from the hydrogenated kerosene fraction. The C4 isoparaiiln hydrocarbon and the C3, C4 and C5 oleflns produced in the process, are alkylated to form an alkylated product which is blended with the isopentanes formed in the process and further blended with the above aviation base components to form a high quality aviation gasoline. vIn the drawings I have shown by means of dotted lines alternative procedures. 'Ihus referring to fractionator I0 I may recover a mixed gas oil fraction through line 2I as a single stream and catalytically crack it rather than to separate the gas oil into a lighter fraction for destructive hydrogenation, cracking only the heavier fraction.

Further, the C4 cut or fraction from fractionators 25 and 10 is rich 'in isobutane, while the C4 fraction from thev first stage of cracking recovered from fractionator 55 is rich in butylenes.

Hence, the alkylation step of my process may be,l

' heavier gas oil from said distillation zone, subjecting the light gas oil to destructive hydrogenation, fractionating the hydrogenation products to recover a base gasoline component boiling up to 200 F., subjecting the heavierv gas oil to catalytic cracking, fractionating the products to recover a cracked gasoline, recracking the cracked gasoline catalytically, fractionating the products, recovering a component boiling from about 200 to 825 F., and blending the gasoline component from the destructive hydrogenation process with the recracked cracked gasoline to form an aviation gasoline.

2. The process of claim 1 in which isoparaftins formed during the hydrogenation are recovered during the fractionation of the hydrogenation products, in which olefins formed during the catalytic 'cracking are recovered by fractionation of the products of the cracking operation, in which the said isoparailns are alkylated with the said olefins to form an alkyate of gasoline boiling range and in which the said alkylate is blended with the said selected components of the hydrogenation and catalytic cracking to form aviation gasoline yof superior quality.

3. A process of producing aviation base gasoline which comprises destructively hydrogenating the light gas oil of a naphthenic crude petrostructive hydrogenation step is eiIected in the presence of a hydrogenation catalyst.

5. The method of claim 3 in which the cracking steps are performed in the presence o! a synthetic gel catalyst.

6. 'I'he method of claim 3 including the alkylation of isoparaflins produce in the process with oleiins similarly produced and the addition of the alkvlate to the base gasoline.

BRUNO E. ROETHELI.

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