US2345128A - Conversion of hydrocarbons - Google Patents

Description

Filed Aug. 7, 1942 kan;

III'.

KARL J. KoRPl INVENTOR Patented Mar. 28, 1944 CONVERSION OF HYDROCARBONS Karl J. Kor-pi, Beacon, N.

Texas Company, tion of Delaware Y., assignor to The New York, N. Y., a corpora- Application August 7, 1942, Serial No. 453,976

` (ci. 19a-s2) 8 Claims.

This invention relates to the conversion of hydrocarbons and has to do particularly with conversion into lower boiling products such as gasoline in the presence of a catalyst.

In accordance with the invention the hydrocarbon feed oil is subjected while at elevated temperature to the action of a cracking catalyst which is in a high state of activity such that substantial conversion of feed hydrocarbons into gasoline hydrocarbons occurs. The catalyst is not maintained in contact with feed oil undergoing conversion suillciently long to become completely spent or even substantially spent. Instead, the partially spent catalyst still of relatively high activity is employed as a reforming catalyst under substantially diiferent operating conditions to treat the gasoline hydrocarbons formed by cracking during contact between feed oil and the catalyst in its more active state.

'I'he term reforming is used in a generic sense as involving reactions of isomerization and polymerization, as well as hydrogen transfer wherein naphthene hydrocarbons are converted to aromatics and hydrogen and the resulting hydrogen is utilized to combine with olens formed from the conversion of other constituents of the hydrocarbon mixture undergoing treatment.

More specifically the invention comprises cracking higher boiling hydrocarbons such as kerosene, gas oil and the like by the action of an active cracking catalyst at a temperature above about 900 F. and which may range from about 1000 to 1200" F. The heated oil in vapor phase and under low pressure is maintained in brief contact with the catalyst, as forexample, for about a second or less, the total time that the catalyst is maintained in contact with hydrocarbons under these conditions of high temperature being in the range about 1 to 2 minutes and not in excess of about 5 minutes. The catalyst is thus only partially spent so far as concerns its effectiveness as a cracking catalyst.

The hydrocarbon products of the conversion reaction are fractionated to remove gasoline hydrocarbons or a fraction consisting essentially of gasoline hydrocarbons. This gasoline, or any desired portion thereof, is separately subjectedV to the action oi the partially spent catalyst under less drastic temperature conditions so as to eifect reforming of the gasoline hydrocarbons. The partially spent catalyst is employed directly in the reforming step without an intervening reactivation to remove carbonaceous and other material adhering to it as it issues from the cracking operation.

This reforming treatment is advantageously effected at a temperature ranging from 700 to 900 F. with a contact time between hydrocarbons and catalyst of about 1 to 20 seconds In this case. the total time that the catalyst is maintained in contact with gasoline hydrocarbons undergoing treatment ranges from about 5 to 30 minutes.

Substantially atmospheric pressure may pre` vail in both conversion operations although pressures substantially below atmospheric may be used.

The process is advaantageously practiced by employing a finely divided or powdered type of catalyst which is passed from the cracking reaction to the reforming or secondary reaction zone in substantially continuous iiow. In such type of operation fresh or freshly regenerated catalyst and feed hydrocarbon are charged continuously to a cracking reaction zone, the powdered catalyst being suspended in the body of hydrocarbon vapor passing through the reaction zone, or if desired being in the form of a. moving bed.

The catalyst' is .continuously withdrawn from the cracking reaction zone so that the residence time of the catalyst within the reaction zone will not exceed several minutes. The withdrawn catalyst, without reactivation, is passed to the reforming reaction zone, wherein it may be employed in substantially the same manner as in the cracking reaction zone. The catalyst is continuously drawn off from the reforming reaction zone and passed to regenerating means whereinthe carbonaceous deposit upon the catalyst is removed by burning under properly controlled conditions so as not to injure 'the particle structure or in other words, .so as to avoid destroying its catalytic activity.

The catalyst may be either a naturally occur ring or synthetic adsorbent solid material. Silicious adsorbent material such as active clays and zeolites are contemplated. Activated clays useful for this purpose include acid treated bentonites. such as Filtrol. Synthetic catalysts of inorganic gel-type such as alumina-silica, with or without the addition of metal oxides such as zirconium or molybdenum oxide, may be used. In general a catalyst is employed which is stable at high temperatures, of the order of 1400 to 1600*I F. as determined by calcining in a munie furnace at that temperature, and which is a measure or indication of the ability of the catalyst to maintain its activity under the customary temperatures of reactivation in the range 1100 to 1400 F. It is preferred to employ a catalyst which is substantially free from alkali and alkali-earth metals.

It is thought that catalytic cracking involves adsorption of a molecular lm of hydrocarbon on the active centers of the catalyst followed by desorption of this film accompanied by cracking. The heat of adsorption of the oil on the catalyst provides energy of activation. The indications are that adsorption with its activating influence precedes cracking.

The initially adsorbed nlm on the catalyst proceeds to crack, polymerize and form carbon. It appears that the molecular weight of the adsorbed film decreases with increasing temperature, approaching that of carbon as a limit in the neighborhood of 950 F. and above. The molecular weight also increases with the residence time .of the catalyst in the reaction zone. Moreover, the cracking or desorption pressure apparently decreases rapidly as catalyst residence time is lengthened and also as pressure is applied.

Accordingly, the present invention involves effecting the cracking step under high temperature and low pressure with relatively short exposure of both oil and catalyst to the conversion conditions so as to reduce the molecular weight of the adsorbed film and thereby secure a high conversion to high grade gasoline with reduction in carbon formation. yThe use of a high velocity of inert carrier gasthrough the reaction zone may be resorted to as a means of reducing the effective pressure.

By operating with a short catalyst residence time within the reaction zone the catalyst is at a high average level of activity during the entire period that it is within the reaction zone and this is advantageous from the standpoint of producing high octane gasoline having a high lead susceptibilty. It appears that catalytic conversion under these conditions favors the hydrogen transfer reaction to which reference has already been made.

As already mentioned the second or reforming step of the process is also carried out under conditions to favor the further extension of the hydrogen transfer reaction. 'The reforming operation also eii'ects polymerization of unsaturated constituents of the gasoline which would otherwise result in increasing the acid heat value of the final product. In addition, the reforming operation involves increasing the branched chain character of aliphatic hydrocarbons including both olefins and parafllns. The product obtained is of increased octane value and possesses greater lead susceptibility.

Reference will now be made to the accompanying drawing illustrating diagrammatically one method by which the invention may be practiced.

Feed oil such as gas oil is drawn from a source not shown and conducted through a pipe I to a heater 2 wherein the oil is rapidly heated to a cracking temperature but without substantial cracking occurring. This temperature may be in the range 900 and above and may, for example, be 1000 to 1200 F.

The heated oil vapors are conducted through a pipe 3 to a reactor l wherein the hydrocarbon vapors are subjected to the action of a catalyst. It is desirable that pyrolytic cracking be substantially avoided prior to contact between the hy.

drocarbons and the catalyst.

The reactor 4 is advantageously of the type in which a powdered type of catalyst is employed vusing a high ratio of catalyst to hydrocarbon as, for example, up to to 15 parts by weight of catalyst to 1 part of feed hydrocarbon.

A relatively large mass of catalyst may be maintained in the form of a fluid suspension within the reactor.

'Ihe catalyst powder may be introduced from a conduit 5 to the reactor along with the feed hydrocarbon stream using the hydrocarbons as an injecting medium. Catalyst is continuously removed from the reactor. The bulk of it may be discharged from the bottom of the reactor I through a conduit 6 or instead, the bulk of it may be discharged along with the hydrocarbon vapors through a conduit 1, depending upon the conditions of operation employed. Catalyst may be discharged simultaneously through both conduits 6 and 1.

By operating with a high velocity of hydrocarbon and catalyst powder through the reactor so that substantially all of the catalyst is carried out through the conduit 1, the residence time of thecatalyst within the reactor Acan be maintained knot in excess of about 2 to v5 minutes, while the residence Atime of the hydrocarbon vapors within the reactor will be materially less, in the order of 1 or 2 seconds.

'Ihe eilluent stream of hydrocarbons and catalyst is discharged through the conduitl'l to av separator 8 providing means for separating the entrained catalyst from the `hydrocarbon vapors..

The hydrocarbon vapors comprising gaseous hydrocarbons, gasoline hydrocarbons and higher boiling hydrocarbons are conducted from' the separator through a conduit 9 leading to a fractionator I0. l

The fractionator I0 is advantageously operated so as to separate gasoline and lighter hydrocarbons from the higher boiling hydrocarbons which latter are discharged from the -bottom thereof through a conduit II. The gasoline and lighter hydrocarbons are removed as a distillate through the conduit I2 leading to a second fractionator or stabilizer I3 wherein gaseous hydrocarbons are removed as an overhead fraction through a conduit I4 while the gasoline hydro.

carbon fraction is removed from the lower portion of the fractionator I3 through a conduit Ila.

If desired, the fractionation in the fractionator I3 may be omitted; in which case the distillate passing through the conduit I2 will be bypassed through a branch conduit I5 leading to a heater or heat exchanger I6.

The gasoline hydrocarbons leaving the heater I6 advantageously in vapor form and heated to the desired temperature are passed through a conduit I1. The' conduit I1 communicates with a conduit I8 aording communication between the separator 8 and the lower portion of a reactor I9 wherein the gasoline hydrocarbons are subjected Thus, the gasolineV to the reforming reaction. hydrocarbons together with partially spent catalyst from the separator 8 are continuously passed to the reactor I9. v f

The partially spent-catalyst withdrawnv from` the separator 8 may be at sufilciently high tem-V perature so that it is unnecesssary to add heat to the gasoline hydrocarbons passingto the reactor I9. In such case the previously mentioned heater I6 may be bypassed as indicated in the drawing. If necessary a portion of the hydrocarbons may bypass the heater I6 in order to Acontrol the temperature maintained .in the reactor- I9, Which. y

the range about' temperature is advantageously in 700 to 900 F. f

The reactor I9 may be similar in design and operation to the reactor 4except that the conditionsz'of -iiow 'therethrough are such as to maintain the desired conditions of catalyst and hydrocarbon residence time-wlthin the reaction zone. Thus, the catalyst and hydrocarbons may remain in contact within Ithe reactor for a period of 1 to 20 seconds' while the residence time of the catalyst may rangefrom to 30 minutes.

:,:The eiliuent hydrocarbons together with entrained catalyst powder are removed from the top of the reactor through a conduit leading to a separator 2| substantially similar to the separator 8 previously referredto. The hydrocarbons substantially free from catalyst powder lareconducted from the separator 2| lthrough a conduit 22 leading toa fractionator 23. The fractionator 23 may be operated so as to effect fractionation into any desired number of fractions. For example, a distillate fraction consisting essentially of gaseous hydrocarbons may be removed and discharged through a conduit 24 while a `gasoline fraction `vmay be-separated and discharged throughA a conduit 25, the higher boiling hydrocarbons being discharged from the lower portion of the fractionator through a conduit 26.

That portion of the catalyst separated in the separator 2| may be recycled through the reactor |l-ll and in such case it is passedthrouglrsI conduit 21 which communicates with the previously mentioned conduit i8. Instead of recycling this catalyst to the reactor i9 it may be drawn off and reactivated following which it can be recycled to the reactor 4.

U'lhe spent catalyst discharged from the reactor IB either through conduit4 21 andibranch conduit 28 or through conduit 29, is passed to a reactivation unit wherein the carbonaceous deposit upon the catalyst particles is removed by burning. Since the reactivation of conversioncatalysts o f this type is`no w well understood itis deemed unnecessary to describethe operation of the reactivation unit 30 in detail. Y

` The reactivated catalyst is passed from the unit 30 through the previously mentioned conduit 5 by which means it is returned to the reactor 4 for contact with the fresh feed oil.

.As already intimated in the operation of the reactor 4 some or substantially all of the catalyst may be discharged through the conduit 6. In this case the partially spent catalyst may pass from the conduit 6 through a branch conduit 3| which communicates with the previously mentioned conduit I8 and in this Way is conveyed to the reactor I9.

In the event that all of the partially spent catalyst drawn olf from the reactor 4 is not passed to the reactor I9 the remainder may then be passed directly to the reactivation unit 30.

While mention has been made of using reactors in which the catalyst is employed in a suspended form, nevertheless it is contemplated that other types of reactors may be employed as, for example, wherein the catalyst passes through the reactor in the form of a continuously moving bed. In such case the catalyst bed may move either countercurrently to or concurrently with the stream of hydrocarbons undergoing conversion.

Vertical reaction vessels may be employed in which both hydrocarbon vapors and catalyst particles pass downwardly through the vessel in concurrent flow. On the other hand, the arrangement may be such that the catalyst particles ilow or pass through the reactor in a vertical direction while the hydrocarbons ilow in a horizontal or substantially horizontal direction. By proper selection of the rate and direction of flow of hydrocarbons and catalyst, as well as shape and dimensions of the reaction vessel, the desired conditions of hydrocarbon and catalyst residence times may be maintained.

Both the cracking and reforming reactions may be carried out in-the presence of added gaseous hydrocarbons including hydrogen and hydrogen-'containingl gases such as methane, ethane, etc. Also if desired the gaseous fractions removed from the fractionators Il and. 23 may be recycled through the reactors 4 and I9 for the purpose of supplying the added gaseous agents or diluents.

The addition of these and other gaseous agents is beneficial in aiding volatilization of heavy polymer material which otherwise tends to remain adhering to the catalyst and is ultimately converted to carbonaceous deposit.

Other agents useful in displacing carbonforming bodies fromthe catalyst or in inhibiting their deposition thereon may include carbon monoxide, carbon dioxide, sulfur dioxide, carbonyl suliide, metal carbonyls, etc.

Obviously many modiiicatons and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as 4are indicated inthe appended claims.

I claim:

1. A process for the catalytic conversion `of hydrocarbons to produce gasoline which comprises passing feed oil higher boiling than gasoline to a catalytic reaction zone, subjecting the oil therein to the action of an active cracking catalyst in solid granular form under conditions of elevated temperature such that substantial conversion of higher boiling hydrocarbons into gasoline hydrocarbons occurs. obtaining from said catalytic cracking reaction a cracked hydrocarbon mixture containing gasoline hydrocarbons and hydrocarbons higher boiling than gasoline, also obtaining from said reaction partially spent cata.- lyst which has been in contact with feed oil in said reaction zone for not in excess of about 5 minutes between reactivations and which is at elevated temperature, separating gasoline hydrocarbons i'rom said hydrocarbon mixture and separately subjecting said gasoline hydrocarbons to the action oi' said partially spent catalyst, without intervening reactivation and without substantial cooling of the catalyst under less drastic temperature conditions than prevail in the cracking zone such that substantial reforming of the gasoline hydrocarbons is secured.

2. A process for the catahrtic conversion of hydrocarbons to produce gasoline which comprises passing feed oil higher boiling than gasoline to a catalytic reaction zone, subjecting the oil therein to the action of an active cracking catalyst in solid granular form under conditions of elevated temperature such that substantial conversion of higher boiling hydrocarbons into gasoline hydrocarbons occurs, obtaining from said catalytic cracking reaction a cracked hydrocarbon mixture containing gasoline hydrocarbons and hydrocarbons higher boiling than gasoline. also obtaining from said reaction partially spent catalyst which has been in contact with feed oil in said reaction zone for not in excess ot about 5 minutes between reactivations and which is at elevated temperature, .separating gasoline hydrocarbons from said hydrocarbonmixture, separately subjecting said gasoline hydrocarbons to the action of said partially spent catalyst, without intervening reactivation and without substantial cooling of the catalyst, under less drastic temperature conditions than prevail in the cracking zone such that substantial reforming of the gasoline hydrocarbons is secured, withdrawing catalyst used in said reforming, reactivating said withdrawn catalystv and recycling reactivated catalyst to the cracking reaction zone.

3. The method according to claim 1 in which the cracking reaction is effected at a temperature in the range 900 to 1200 F. and the reforming reaction is carried out at a temperature in the range about 700 to 900 F.

4. A continuous process for the catalytic conversion of hydrocarbons which comprises passing a stream of feed-hydrocarbon higher boiling than gasoline to a cracking reaction zone, passing an active cracking catalyst in solid granular form to said zone, subjecting the feed hydrocarbon to brief contact with said catalyst within the reaction zone such that substantial conversion of higher boiling hydrocarbons into gasoline hydrocarbons occurs, continuously removing the partially spent catalyst and reacted hydrocarbons from said zone, said removed catalyst having been in contact with feed oil in the reaction zone for 'not in excess of about 5 minutes between reactivations and being at an elevated temperature, separating gasoline hydrocarbons from said reacted hydrocarbons, passing said gasoline hydrocarbons through a reforming zone, subjecting the gasoline hydrocarbons` therein to the action of said partially spent catalyst, without intervening reactivation4 and without substantial cooling of the catalyst under less drastic temperature conditions than prevail in the cracking zone such that substantial reforming of the gasoline hydrocarbons is secured and withdrawing converted gasoline hydrocarbons and spent catalyst from the reforming reaction zone.

5. The method according to' claim 4 in which the cracking reaction is effected at a temperature in the range about 900 to 1200 F. and the reforming reaction is effected at a temperature in the range about '100 to 900 F.

6. A continuous process for the catalytic conversion of hydrocarbons which comprises passing a stream of feed hydrocarbon higher boiling than gasoline to a cracking reaction zone, passing an active cracking catalyst in solid granular form to said zone, maintaining hydrocarbons and catalyst within the reaction zone at a temperature in the range about 900 to 1200 F., the time of contact between hydrocarbons and catalyst being of the order of about one second, removing partially spent catalyst and reacted hydrocarbon mixture from said zone, said removed catalyst having been in contact with feed oil in the reaction zone for not in excess of about 5 minutes betweanreactivations and being at an elevated temperature separating gasoline hydrocarbons from said hydrocarbon mixture, passing said gasoline hydrocarbons to a reforming zone, passing said partially spent catalyst without intervening reactivation and without substantial reduction in temperature to said reforming zone, maintaining the gasoline hydrocarbons and partially spent catalyst within the reaction zone at a temperature in the range about '100 to 900 F., the time of contact between gasoline hydrocarbons and catalyst being in the range about l to 20 seconds and withdrawing converted gasoline hydrocarbons andspent catalyst from the reforming reaction zone.

7. The method according to claim 6 in which the spent catalyst withdrawn from the reforming zone is reactivated and recycled at least in part to the cracking zone.

8. 'I'he method according to claim` 6 in which the residence time of the catalyst in the cracking reaction zone is about 1 to 2 minutes and the residence time of the partially spent catalyst in the reforming zone is in the range about 5 to 30 minutes.

KARL J. KORPI.

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