US2432537A

US2432537A - Production of motor fuels

Info

Publication number: US2432537A
Application number: US572494A
Authority: US
Inventors: Roger H Newton
Original assignee: Houdry Process Corp
Current assignee: Houdry Process Corp
Priority date: 1945-01-12
Filing date: 1945-01-12
Publication date: 1947-12-16
Anticipated expiration: 1964-12-16

Description

Dec. 16, 1947a Filed Jan. 12, 1945 R. H. NEWTON PRODUCTION OF MOTOR FUELS 2 Sheets-Sheet l CHARGE ATTORNEY Dec. 16, 1.947.

R. H. NEWTON PRODUCTION OF MOTOR FUELS Filed` Jan. 12., 1945 2 Sheets-Sheet 2 Patented Dec. 16,A 1947 UNITED STATES PATENT OFFICE PRODUCTION F MOTOR FUELS Roger H. Newton, Bowling Green, Pa., assignor to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware Application January 12, 1945, Serial No. 572,494

9 Claims.

This invention relates to the catalytic conversion of hydrocarbons for the production of motor fuels including aviation base stock of superior quality.

One object of the invention is to improve acid heat of motor fuels, thereby to enhance lead susceptibility of the same and to obtain better leaded octane ratings which will be reflected in both the 1C and 3-C tests for aviation fuels. Another object is to insure the production of non-corrosive motor fuels directly from cracking operations. Another object is to effect the above improvements in either one-pass or two-pass operations. Still another object is to utilize as part of the charge toa catalytic zone hydrocarbon material which during reaction will produce heat thereby supplying at least a portion of the heat necessary for the conversion or transformation of the remainder of the charge. Other objects will be apparent from the detailed description which follows.

The discovery has been made that the above objects can be attained by sending into a catalytic zone, along with the fresh charge to be converted, normally liquid low boiling unsaturated hydrocarbons, specifically C5 unsaturates with or without Cs unsaturates, and even at times some C7 unsaturates. The unsaturatesthus charged may be in whole or in part recycle material from a previous reaction in the same catalytic zone, or may come from an extraneous source. In general in a catalytic cracking operation the higher boiling the charge, the greater the quantity of olens or unsaturates that are formed in the C5 and Cs cuts. For example with a light gas oil charge, of the order of 20 to 25% of the C5 and C6 cuts in the cracked product Will be unsaturates; and When the charge is heavy gas oil the percentage of unsaturates in the said cuts may run up to 60%. The adverse effect of such a quantity of unsaturates on acid heat and lead susceptibility is only too apparent when it is realized that the C5 and Cs cuts normally amount to something like 50 to 55% of aviation base stock.

In accordance with the present invention it is advantageous to recirculate or recycle in the cracking zone C5 and Cs unsaturates when the production of the latter is 20% of such cuts or whenever sucient of such unsaturates can be segregated so as to make up at least 5% of the gas oil or other charge to the cracking zone. C5 and/or Cs unsaturates should be recycled or recirculated through the cracking zone in such amount that the nal product cuts of C5s and 2 Cs contain not more than 10% of olens or unsaturates; for best results, however, the operation should be conducted so as to reduce the olen content of the Css and Ces in the nal product to about 3%.

In order to illustrate the invention and the manner of its use concrete embodiments of the invention are shown in the accompanying drawings Which are entirely schematic in character and in which:`

Fig. 1 is a diagrammatic view of a single pass operation; and

Fig. 2 is a similar view of a two pass operation.

In Fig. 1 preheated fresh charge, such as gas oil is admitted by line I to a catalytic cracking Zone 2 containing one or more catalytic reactors of any desired type and the products of the cracking operation are fractionated in fraction ator 3, the overhead from which, containing cracked gas and gasoline, is led through cooler 4 and separator 5 to effect division into Wet gas and condensed gasoline fractions leaving separator 5 by lines 6 and 1, respectively. The Wet gas fraction, which may contain parafns and olens up to and including a part of the Css, then passes through a gas plant of any desired type indicated schematically by compressor 8, cooler 9 and knock-out drums I0. For production of motor fuels of the aviation type, the Cds and lighter are preferably withdrawn from the gas plant as by line Il, the higher boiling cornponents of the Wet gas, which may contain up to 50% olens of 5 and 6 carbon atoms, being Withdrawn by line I2 as a liquid stream, all or a portion of which may be led directly back to the catalytic cracking zone by lines I3, I4 and I. Through control of the temperatures and pressures obtaining in cooler Il and separator 5 any desired portion of the C5 and Ce olens in the cracked products may be returned to the cracking zone. In the catalytic cracking zone 2 and C5 and Cs fractions so circulated have their olenic content reduced to an extent controlled by regulation of the proportion of the total quantity of liquid in line I2 which is Withdrawn as product, as for example, by line I5 and thence through the depentanizer 2l and line 23. As the ratio of recirculated to Withdrawn material is increased the concentration in the latter of stable, high anti-knock components, such as isopentane, increases, especially When the catalytic material `utilized in the cracking zone is capable of promoting polymerization and selective cracking reactions, among which are activated hydrosilicates of alumina and synthetic blends of silica and alumina, silica and zirconia, alumina and zirconia, or any desired combination of them. Thus, the system disclosed may be operated to produce a stream of pure or substantially pure iso-pentane, or, alternatively, a motor or aviation fuel in which the C components are composed practically entirely of this compound.

To effect withdrawal of iso-pentane concentrate or gasoline containing the same, the isopentane concentrate in line I5 may be combined with the condensed gasoline in line l, the combined streams debutanized in debutanizer I6 and the resulting debutanized gasoline withdrawn from the system by lines I'I andk I8. If desired, this gasoline may be fractionated in de-isopentanizer I9 to remove any desired part of the isopentane concentrate by line 20 for use as a blending agent for high quality fuels. Y

When gas plant condensate is sent by lines I2 and I5 to combine with condensed gasoline in line 'I, recirculation of the light olen containing stream to the cracking zone 2 may be eected by subjecting the deisopentanized gasoline n line I3 to depentanization or de-hexanization in a suitable fractionator 2 I the overhead from which comprising C5 of C5 and Ce hydrocarbons may be led by line 22 to line I4 and thence to the catalytic cracking zone 2, thus supplementing or replacing the stream of light material in line I3. Whether recirculation is through line I3 or not, any small amounts of normal pentane that may remain in the C5 fraction after recirculation may be withdrawn from the system as by use of a suitable withdrawal line, such as line 23. In the event substantially all the C5 fraction is passed to the gas plant through line 6 and condensate issuing from the gas plant by line I2 is processed in debutanizer I6, deisopentanizer I9, and depentanizer 2|, the stream withdrawn in line 23 may be substantially pure normal pentane and the recycle stream in line I4 substantially isopentane free.

The produce from a normal single pass operation, which includes the bottoms from the gas separator line 'I and from the gas plant line I2 is usually,T corrosive to copper dish, and often requires further treatment to produce a satisfactory aviation fuel. By complete recirculation of the gas plant bottoms through lines I2, I3 and ifi, the corrosion materials are removed and the products obtained from line I8 and the naphtha sidestream from fractionator 3 are non-corrosive and may be used directly in the i'inal motor fuel products.

Fig. 2 illustrates a two-pass operation to produce very high quality fuels, for example base for combat grade aviation gasoline, which operation permits the use in the second catalytic pass of the comparatively severe operating conditions which affect beneficially the composition of the heavier portions of the iirst pass gasoline with a minimum of coke production. In this operation all or a part of the olefin rich light material, such as the C5 fraction from the rst pass cracking, is charged back to the rst pass cracking zone. The olefin rich fraction is shown as being obtained by de-isopentanizing the heavy eliluent of the gas plant and is the bottoms from the deisopentanizing fractionator I9 which may be returned to the first pass cracking by line 24. The wet gas from both rst and second pass operations comprise the feed to the gas plant G-I, although separate gas plants may be used if desired. The second pass charge is composed essentially of Cs-lhydrocarbons obtained for example 4 by de-pentanizing in depentanizer 5b liquid products from separator 5 resulting from the condensation of light overhead material from the primary fractionator 3 and combining the resulting de-pentanized material in line 26 with the motor naphtha fraction withdrawn from fractionator 3 through line 25, the resulting motor gasoline being fed to the second pass catalytic cracking zone through line 21. A part of the recrculated material in line 24 may be diverted through line 28 and into line 21 for charging to the second pass. By operating in this manner, full advantage may be taken of the very highly selective reactions which take place in 'second` pass cracking under the comparatively severe conditions which are preferred with a charge containing only a small proportion of low boiling olens. rl'he reaction produces from olenic Cs charge a C5 fraction highly concentrated in isopentane and practically free of pentenes and normal pentane. For this reason the C5 content of the second pass product may be left in the final gasoline fraction, as for example by subjecting the condensed gasoline merely to debutanization in a suitable fractionator 29 and Withdravving the bottoms from the latter as final product.

Even in two pass operation the product from normal procedures, consisting of condensed gasoline from the gas separator and condensed C5 fraction from the gas plant is frequently suinciently corrosive to copper dish to require secondary treatment. However, when the wet gas from second pass is processed in the manner shown in Fig. 2 wherein the C5 portion of this gas is recovered as isopentane concentrate in line 2@ and as a concentrate of higher boiling material in line 24 with all of the latter being returned to the cracking zone or zones, the nal product consisting of 05+ aviation base from debutanzer tower 29 and isopentane concentrate from line 20 is non-corrosive and suitable for blending directly to the highest grades of aviation fuel.

The polymerization or other reaction which removes or converts in the cracking zone to more stable form the olens contained in the recycled or recirculated streams produces heat in the catalytic zone, thus supplying at least a part of the heat needed to crack the fresh charge. This eiect is of particular Value when the catalytic cracking Zones have moving catalyst reactors, for the exothermic heat of reaction of the olens tends to reduce the quantity of heat input to the reactor from other sources as in the fresh charge and/or in regenerated or recirculated catalyst. Thus the point of admission of the oleiinic stream may be selected to produce this heat at the most advantageous point or points in a moving catalyst reactor, as for example at or near the level of admission of the cracking stock or of regenerated or reheated catalyst. However, this production of heat is advantageous regardless of whether the catalytic reactors in the cracking Zones are of the fixed bed, moving bed, or fluid types.

For purposes of supplying more exothermic heat of reaction in the cracking zone, the recycled olenic feed may be augmented by olens obtained from a source other than the eiiluent from the catalytic cracking zone itself, as for example propylenes, butylenes, pentenes and/or hexenes obtained from a cracking unit which produces highly olenic material, such as a thermal cracker. In such event the additional feed may be admitted at a suitable point in the system, as at 30a to line M (Fig. 1) or at 30h to line 24 (Fig. 2).

Certain of the important advantages of the invention can be realized when the operation is conducted to produce motor fuel of the motor gasoline type rather than aviation gasoline, in which event the recirculated material rich in unsaturates may include butylenes. The gas plant would then be operated in normal manner for rejection of Cas and lighter in the dry gas stream.

The following example illustrates use of the invention in a single pass operation as in Fig. 1:

A long gas oil boiling in the range of 440 to 900 F. was fed to a catalytic cracking zone containing active synthetic silica-alumina catalyst of about 35 activity index and maintained at average temperature of about 835 F., the pressure of the oil feed being pounds per square inch gauge and the space rate (liquid volume of oil per volume of catalystper hour) being 1.0. The nshed aviation gasoline base separated from the cracked products amounted to about by volume of the gas oil charge.` This aviation base had an acid heat of the order of 135 F., and 1-C and B-C octane ratings (4.6 cc. of tetraethyl lead added) of about 88.5 and approximately S 95 ZW-l respectively. (In the expression reference is made to a blend of 95% Standard Reference Fuel S having 100 octane by the 3-C method of test, and 5% Standard Reference Fuel M having O octane by that method.) When there was added to the gas oil charge light olefin containing condensate composed essentially of C5 and Cs hydrocarbons obtained by compression and cooling of the wet gas from the cracking operation, the resulting base stock exhibited reduced acid heat of about 100 F. and l-C and 3-C octane ratings (4.6 cc. of tetraethyl lead added) of about 90 and (98% Fuel S and 2% Fuel M) respectively. These results were obtained after recirculation equilibrium had been reached, at which point the quantity of C5 and C6 hydrocarbons recharged to the catalyst was equivalent to about 8 to 10% of the gas oil charge.

In the two pass operation it is desirable to utilize, in second pass, synthetic cracking catalysts of high activity (at least 40 activity index) and in general more severe operating conditions, such as higher temperature or higher pressure or lower feed rate or a combination of these factors, in order to produce aromatics. This can be done Without excessively heavy coke deposit on the catalyst since the unsaturates have already been substantially removed or converted in the rst pass.

The cut of C5 and Ce unsaturates to be recycled in the cracking zone is usually within the boiling range of about 80 to 150 F. but the range may extend higher, as to 185 F., when some C7 unsaturates are included, or extend lower if C4 unsaturates are included.

I claim as my invention:

1. Process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons which comprises subjecting the charge under cracking conditions to the action of cracking catalyst in a cracking zone, separating from the resulting cracked product a fraction rich in isopentane and a fraction rich in pentenes, and recirculating through said cracking zone along with the fresh charge the pentene rich fraction in order to reduce the quantity of Cs unsaturates in the nal motor fuel product.

2. Process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons in a two pass operation which comprises sending the charge under cracking conditions into a first catalytic cracking zone, separating depentanized gasoline and naphtha from the efuent of said rst cracking zone, and sending the same under cracking conditions at least as severe as in said first zone into a second catalytic cracking zone, separating an aviation base product from the effluent of said second cracking zone, combining the Wet gas from both cracking zones, separating a normally liquid fraction containing C5 unsaturates from said wet gas, and adding at least a part of said fraction to the charge to one of said cracking Zones.

3. Process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons in a two pass operation which comprises sending the charge under cracking conditions into a first catalytic cracking zone, separating depentanized gasoline and naphtha from the eiiluent of said rst cracking zone and sending the same under cracking conditions at least as severe as in said first zone into a second catalytic cracking zone, separating an aviation base product from the eliluent of said second cracking zone, combining wet gas containing C5 hydrocarbons from both cracking Zones, separating xed gas and a fraction rich in isopentane from said wet gas, and adding at least a part of the remainder of the wet gas including Cs unsaturates to the charge to said first cracking zone.

4. Process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons in a two pass operation which comprises sending the charge under cracking condition into a rst catalytic cracking zone, separating depentanized gasoline and naphtha from the el'luent of said rst cracking zone and sending the same under cracking conditions at least as severe as in said first zone into a second catalytic cracking zone, separating an aviation base product from the eiiluent of said second cracking Zone, combining the wet gas from both cracking zones, separating said wet gas into a C4 and lighter fraction, a fraction rich in isopentane, and a fraction containing C5 unsaturates, and adding at least a part of said last named fraction to the charge to said nrst cracking zone.

5. Process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons in a two pass operation Which comprises sending the charge under cracking condition into a rst catalytic cracking zone, separating depentanized gasoline and naphtha from the eflluent of said first cracking zone and sending the same under cracking conditions at least as severe as in said first zone into a second catalytic cracking zone, separating an aviation base product from the eflluent of said second cracking zone, combining the Wet gas from both cracking Zones, separating said Wet gas into a C4 and lighter fraction, a fraction rich in isopentane, and a fraction containing C5 unsaturates, and adding at least a part of said last named fraction to the charge to both said first and said second cracking zones.

6. Process of making motor fuels of improved quality and lead susceptibility from .higher boiling hydrocarbons in a two pass operation which comprises sending the charge under cracking condition into a first catalytic cracking zone, separating depentanized gasoline and naphtha from the effluent of said first cracking zone and sending the same under cracking conditions at least as severe as in said first zone into a second catalytic cracking zone, separating an aviation base product from the eiiluent of said second cracking Zone, separating from the wet gas from said cracking Zones a normally liquid light fraction containing C unsaturates and recirculating said fraction through one of said cracking zones to be converted to more saturated and more stable hydrocarbons and to insure that the said aviation base product from said second cracking zone is free of components corrosive to copper dish.

7. The process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons which comprises subjecting the charge under cracking conditions to the action of a cracking and polymerizing catalyst in a cracking zone, separating from resulting cracked products an essentially C5 fraction rich in isopentane and an essentially C5 plus Cs fraction rich in olenes, and recirculating said C5 plus Ce fraction with the fresh charge through said cracking zone to increase the concentration of isopentane and to decrease the concentration of oleiines in the products therefrom.

8. The process of making motor fuels of improved quality and lead susceptibility from higher boiling hydrocarbons which comprises subjecting the charge under cracking conditions in a cracking zone to the action of cracking catalyst, separating products of the cracking operation into a wet gas fraction containing pentanes and pentenes and a gasoline fraction, separating Cis and lighter from said wet gas fraction to leave a normally liquid fraction containing Css,

separating said normally liquid fraction into a fraction rich in isopentane and a fraction rich in pentenes, and recycling the latter through said cracking zone along with the charge thereto, whereby the distillate products of said cracking zone are relatively free of pentenes and relatively concentrated in isopentane.

9. In making motor fuels of improved quality and lead susceptibility, the process comprising subjecting cracking stock under cracking conditions in a cracking zone to the action of cracking catalyst, separating the products of cracking into a Ci and lighter fraction, and a gasoline fraction containing C5 and Ce olenes and isopentanes, separating a fraction rich in isopentane from said gasoline fraction, separating from the remainder of the gasoline fraction a light normally liquid fraction rich in olenes, and recirculating said last named fraction to said cracking Zone for conversion simultaneously with said cracking stock to produce isopentane and to reduce the quantity of light olenes in the iinal motor fuel product.

ROGER H. NEWTON.

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

UNITED STATES PATENTS Number Name Date 2,251,571 Howard Aug. 9, 1941 2,273,089 Carpenter Feb. 17, 1942 2,309,137 Peterkin Jan. 26, 1943 2,353,490 Noorduyn July 11, 1944 2,358,149 Cooke Sept. 12, 1944 2,358,888 Thomas Sept. 26, 1944 2,360,622 Roetheli Oct. 17, 1944 2,361,611 DOuville et al. Oct. 31, 1944 2,374,095 Helmers Apr. 17, 1945 2,282,855 Egloi May 12, 1942 2,346,642 Babcock et al Apr. 18, 1944