US2871184A - Process for the production of gasoline from petroleum residues - Google Patents

Description

Jan. 27, 1959 KUNREUTHER PROCESS FOR THE PRODUCTION OF GASOLINE FROM PETROLEUM RESIDUES Filed June 28, 1955 250mm l@ m35 Emi DZQOmm OP INVENTORI R E H. I ww m/W Kl KV m m nm F.

HIS ATTORNEY United States Patent PROCESS FOR THE PRODUCTION OF GASOLINE FROM PETROLEUM RESIDUES Frederick Kunreuther, HoustonTex., assigner to Shell Development Company, New York, N. Y., a corporation of Delaware Application June 28, 1955, SerialNo. 518,467

4 Claims. (Cl. 208-55) This invention relates to a process for the cracking of residue type hydrocarbon oils to gasoline and related products. y f

By residue type hydrocarbon oils ismeant the residues remaining after removing lighter distillable material from petroleum and hydrocarbon oils of similar nature regardless of origin. Such oils are characterized by containing appreciable amounts -of material which cannot be distilled in conventional fractionating equipment. They normally contain appreciable amounts of asphaltenes and resins and have rather high Conradson carbon values. Typical of the materials in question are the residue fractions known in the reiineries as long residue and asher pitch.

It is well known that residue type hydrocarbon oils produce inordinate amounts of coke if it is attempted to convert them'to gasoline by the process known as catalytic cracking. The coke yield is not only high initially but increases as such oils are processed due to contamination of the catalyst with traces of potent carbon forming metals such as iron, nickel, Vanadium, copper, chromium, etc. which are invariably present in such residue oils and accumulate on the catalyst during the cracking operation. It is therefore the practice to first treat such oils in various ways to produce therefrom feed stocks more amenable to the catalytic cracking process. One such method is known as catalytic decarbonization. In this process the residual oil is first treated with a solid material of relatively low catalytic activity such as spent cracking catalyst, clay, bauxite or the like under low severity cracking conditions. A large part of the materials which tend to form coke are coked along with most of the detrimental metal components. The overhead product is essentially a substantially clean, lightly cracked gas oil containing little if any gasoline which is then catalytically cracked in a separate unit in the conventional manner. This process has never been used commercially because of its high cost, and particularly the very large capital expenditure required for the plant which in fact is considerably larger and more costly than the catalytic cracking plant itself. Also the amount of heat generated by the combustion of the large amount of coke produced is so large that it cannot profitably be used in the refinery.

Another method which is presently coming kinto commercial use involves the production of a relatively clean,

lightly cracked gas oil feed for the catalytic cracking process by the process known as iluid coking. In this process, a separatecoking plant similar to the catalytic cracking plant in complexity and size is required in addition to the conventional catalytic cracking plant. The two units are distinct, separate units separately operated. Although the cost is here again 4quite large the process has the advantage that a substantial part of the'coke may be withdrawn and recovered as such instead of having to burn it.

It has recently been found that considerably improved l F. in the riser reactor.

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results may be obtained Vin catalytic cracking of various hydrocarbon oils if the catalytic cracking operation is carried out in stages under certain properly controlled conditions. One of these conditions is the use of higher than normal temperatures. When using the fluidized catalyst technique, the major part of the heat required in the cracking reactor is supplied by the sensible heat of the circulated hot regenerated catalyst. The use of high temperatures then requires the use of relatively high'catalyst to oil ratios (i. e., weight ratio of catalyst to oil entering and leaving the reaction zone). This is undesirable since it tends to lower the selectivity of the cracking to gasoline and increases the capital and operating expenses.

An object of the present invention is to provide a process retaining the advantages of catalytic decarbonization, fluid coking and staged catalytic cracking while avoiding the undesirable features of the lirst two and allowing the third to be carried out at high temperatures in one or all stages with reasonably low catalyst to oil ratios. v

The process ofthe invention will be best understood from the accompanying drawing in which a plant arranged to operate according to the principles of this invention is illustrated semi-diagrammatically.

Referring to the drawing, a fluidized bed of coke particles 1 is maintained in a coke heater 2. The coke which is in the form of particles ranging in size from the very inest particles up to several lor even several hundred microns diameter may be derived solely from the oil in the processing or may be in part derived from a separatesource such as a separate grinder, pulverizer or the like.

y The heater 2 is similar in design to a iluidized catalyst regenerator. Thus, coke is cycled to the heater by line 3. Air is introduced by line 4- connected to a suitable airy distributor. v Flue gas is removed by vent line 5. Excess coke may be withdrawn by line 6 to maintain any desired inventory of coke in the system.

The fluidized bed of coke is maintained at a temperature between about 1100 and 1500o F. by control of the air used for its partial combustion. The air introduced also maintains the bed of coke in a iluidized condition. Y

Hot finely divided coke from the heater is continuously withdrawn by line 7 at a rate controlled by valve 8. This hot coke is passed to a coker 9 a thermal riser reactor) wherein it contacts and heats the residual gas yintroduced by line 10`- The amount of coke is regulated to provide a temperature in the range of 1000 to 4'1400 Due to the narrow cylindrical shape of the riser reactor the linear velocity therein is uniformly high. The residence time therein is very short and the coke is maintained in free suspension, i. el, there is no fluid bed of coke. The hydrocarbon vapors Lcontaining suspended coke particles are passed from the riser reactor to a cyclone separator wherein the major part of the coke is separated. The separated coke is returned to the coke heater by line 3. Under these conditions the residual oilis subjected to va high temperature for a very short time. For each individual oil the conditions are adjusted in` the known manner within the stated limits to maintain the coke substantially dry and free owing.

In this stage of the process the residual oil is converted to distillable heavy oil with little conversion to gasfor gasoline. However, some gasoline production is not harmful since the gasoline so produced is highly The separators 11 effect only a partial separation of the suspended coke. The major part of the coke particles, and particularly the larger particles, is separated from the vapors and returned to the coke bed by line v3. Super-heated steam may be injected by line. 12 to aid in transferring the coke. A part of the coke consisting .mainly of the smaller particles passes out through the separator 11 with the eliiuent vapors into transfer line 13'. In order to prevent coking of the transfer line 13 super-heated steam is advisably injected by line 14.

The suspension of coke in oil vapors in transfer line 13 is passed without cooling to a first stage riser reactor 15 which in the case illustrated is an extension of line 13. Relatively clean distillate cracking stock may also be charged if desired to the rst stage riser reactor by line 16. Used and partially spent (i. e. carbonized) cracking catalyst withdrawn from the second stage catalytic cracking reactor 17 is introduced by line 18 into the riser reactor wherein it mixes with the suspension of coke in the heavy oil vapors and the vapors of any added distillate feed stock. The resulting suspension of crackingv catalyst and coke in the oil vapor is catalytically cracked during the rapid passage up through the relatively long narrow reactor 15 of substantially uniform diameter. In this reactor the solids are again freely suspended and there is no fluid catalyst bed. The amount of catalyst introduced by line 18 is adjusted to give a temperature between about 900 and ll00 F. The depth of conversion in this case is adjusted to 25 to 60% depending upon the particular oil treated and the amount land character of the cracking catalyst used.

The product of the first catalytic cracking stage containing suspended particles of coke and cracking catalyst is passed to a separatonstripper 19. Here the solids are separated from the oil vapor by a cyclone separator. The separation is essentially complete and only a small amount of solids passes out with the product to the iirst stage fr-actionator (not shown). The solid material which passes out through the cyclone separator may be recovered from the bottom product of the fractionator. lt is `ordinarily discarded. The hydrocarbon product from the rst stage cracking is separated in the rst stage fractionator (not shown) into gasoline an-d lighter products and a heavier clean oil which is cracked in the second catalytic cracking stage of the process. Thus, this clean oil from the first stage cracking is introduced by line 20 into the second stage reactor 17. This second stage catalytic reactor, which may be of conventional design, is operated yat a temperature between about 900- 1000 F. Hot freshly regenerated catalyst is supplied from the regenerator 22 by line 21. The overhead product is separately fractionated in a second stage fractionator (not shown) to separate the gasoline and lighter products.

Referring back to the separator-stripper 19, the solid separated bythe cyclone separator and collected in the stripper consists of a mixture of cracking catalyst and ne coke particles. This mixture after being stripped with steam introduced by line 23 passes by line 24 to the regenerator 22. The combustion gas passing up through the bed of catalyst in the regenerator tends to separate and carry in suspension the small coke particles. These particles are not lonly lighter in density than the catalyst but are also reduced in size in the regeneration Zone by partial combustion. Thus, although considerable amounts of coke are introduced into the regeneration zone by line 24, the catalyst bed in the regenerator contains only a very low percentage of coke particles.

In the described operation the hot freshly regenerated catalyst flows counter-current, so to speak, to the oil to be cracked, i. e., it is used first in the second stage catalytic cracking zone and then in the iirst stage catalytic cracking zone. When employing this sequence, the temperature in the first stage catalytic cracking zone normal` ly is considerably below that in the second stage catalytic cracking zone. In the described operation, however, the first stage catalytic cracking may be effected at the higher temperature. Thus, in the process of the present invention the tirst stage catalytic cracking zone is carried out at `a temperature at least as-high and preferably higher than that in the second stage catalytic cracking zone. This is possible in the present case due to the high heat content of the oil vapors containing suspended coke transferred directly from the riser coker to the riser-type first stage catalytic cracking reactor.

The inclusion of coke from a coking zone to the catalytic cracking would normally be considered undesirable and would be avoided since the coke contains the major part `of the metal contaminants found in such residual oils. However, in the system described it is only the smaller particles of coke that are so transferred. These are further reduced in size by combustion in the regeneration zone and their residue containing the contaminants is largely carried out of the system in suspension in the regenerator flue gas. Thus, the contaminants carried into the catalyst cracking section with the .coke are largely eliminated.

In a typical case the process is used to produce gasoline from a so-called long residue produced by topping petroleum to remove the straight-run gasoline and some other straight-run products boiling up to about 550 F. The coke in the coke heater consists of particles ranging Vin size from about l to about 1,000 microns diameter and is maintained at a temperature of about 1209 F. by partial combustion. This hot `coke is fed to the tubular pitch coker at a rate of about 60 tons per minute. The long residueat a temperature of about 480 F. is introduced at the bottom of the pitch coker to mix with the incoming heated coke. The temperature in the pitch coker is about 1050o F. 'and the residence time therein is about 1.2 seconds. In this operation only a minor amount of gasoline is produced and this gasoline is not separated. The vaporized oil carrying approximately 7,000 pounds per hour of line coke particles is transferred directly to the first stage catalytic cracking reactor` where it is catalytically cracked at about 1011 F. This cracking is effected with approximately 32 tons per minute of cracking catalyst which is fed to the first stage catalytic cracking reactor from the second stage catalytic crack ing reactor. In this case the `catalyst Withdrawn from the second stage catalytic cracking reactor at a temperature of about 1000 F. serves as a coolant rather than a4 heat carrier. Approximately 7000 pounds of coke per hour is transferred withv the twice used catalyst to the rcgenerator. The gasoline from the first stage catalytic cracking step is fractionated from the residue and the residue consisting of a partially cracked catalytically cracked gas oil is separately cracked in the second stage catalytic cracking zone at a temperature of about l000 F. The first stage catalytic cracking conversion is about 40% and the remaining .conversion effected in the second stage brings the total conversion to. about 74% without recycle of catalytically cracked gas oil. if second stage catalytically cracked `gas oil is recycled the total conversion is even higher.

If the long residue were catalytically cracked `directly in the catalytic cracking unit to the same total conversion the amount of coke to be burned would be about 78,000 pounds per hour. 1n the described system, it is lonly about 30,000 pounds penhour.

-I claim as my invention.:

l. Process for the production of gasoline from residual oils which -comprises contacting a residual oil with hot finely divided ycoke particles under conditions to suspend the coke particles in the oil vapors without a pseudo liquid coke phase and to give a resulting .temperature between 1000 and 1400 F., centrifugally` separating the major ypart; Vof the suspended lCoke particles IOIIl the suspension after a very short contact time, suspending used and partially carbonized nely divided cracking catalyst in the remaining suspension of coke particles in oil vapors in an amount to give a resulting temperature between 900 and 1100 F. and contacting the suspendedv catalyst with the oil vapors in the absence of a pseudo liquid catalyst phase for a short time suliicient to afford a conversion between and 60%, centrifugally separating suspended coke and catalyst particles from the oil vapors after said short time of contact and passing the separated catalyst and coke mixture to a iiuidized catalyst regeneration zone, separating gasoline from the last said oil vapors and catalytically cracking the remaining oil in a separate catalytic cracking reaction zone at a ternperature between about 900 and 1000 F. with less carbonized cracking catalyst from said regeneration zone, separately removing gasoline from the product of said separate reaction zone, and passing carbonized and partially spent finely divided cracking catalyst from said separate reaction zone to said suspension of coke in oil vapors as aforesaid.

2. Process for the production of gasoline from residual oils which comprises contactinga residual oil with hot iinely divided coke particles under conditions to suspend the coke particles in the oil vapors without a pseudo liquid coke phase and to give a resulting temperature between 1000 and 1400 F., centrifugally separating the major part of the suspended coke particles from the suspension after a very short contact time, suspending partially carbonized and partially cooled nely divided cracking catalyst in the remaining hotter suspension of coke particles in oil vapors in an amount to 'give a resulting temperature between 900 and 1100 F. and contacting the suspended catalyst with the oil vapors at said temperature in the absence of a pseudo liquid catalyst phase for a short time sufficient to alford a iirst stage conversion between 25 and 60%, centrifugally separating suspended coke and catalyst particles from the oil vapors after said short time of contact and passing the separated mixture of catalyst and coke to a uidized catalyst regeneration zone, separating gasoline from the last said oil vapors and catalytically cracking the remaining `oil in a separate catalytic cracking reaction zone at a temperature between about 900 and 1000 F., but below that for said iirst stage conversion, with less carbonized cracking catalyst from said regeneration zone, separately removing gasoline from the product of said separate reaction zone, and passing used and partially carbonized iinely divided cracking catalyst from said separate reaction zone to said hotter suspension of coke in oil vapors as aforesaid.

3. Process for the cracking of residual oils which comprises contacting a residual oil with hot nely divided coke particles under conditions to freely suspend the coke particles in the oil vapors at avtemperature between 1000 and 1400" F., centrifugally separating part of the suspended coke particles from the suspension after a very short contact time, suspending cooled partially carbonized tinely divided cracking catalyst in the remainil f) ing still hot suspension of coke particles in oil vapors in an amount to give a lower resulting temperature between 900 and l100 F. and contacting the suspended catalyst with the oil vapors at said temperature in the absence of a pseudo liquid catalyst phase for a short time sufficient to afford a limited conversion between 25 and centrifugally separating suspended coke and catalyst particles from the oil vapors after said short time of contact and passing the separated catalyst and `coke mixture to a fluidized catalyst regeneration zone,

separating gasoline from the last said oil vapors and catalytically cracking the remaining oil in a separate catalytic cracking reaction zone at `a lower temperature between about 900 and l000 F. with less carbonized "i cracking catalyst from said regeneration zone separately removing gasoline from the product of said separate reaction zone, and passing used and partially carbonized iinely divided cracking catalyst from said separate reaction zone to said suspension of coke in oil vapors as aforesaid.

4. Process for the production of gasoline from residual oils which comprises contacting a residual oil with hot coke particles of from about 1 to 1000 microns diameter under conditions to suspend all the coke particles in the oil vapors without -a pseudo liquid coke phase and to give a resulting temperature of about 1050 F., centrifugally separating the major part of the suspended coke particles from the suspension after a very short contact time of about 1.2 seconds, suspending used and partially spent finely divided cracking catalyst in the remaining suspension of coke particles in -oil vapors in an amount to give a resulting temperature of about 1010 F. and contacting the suspended catalyst with the oil vapors in the absence of a pseudo liquid catalyst phase for a short time suiiicient to afford a conversion of about 40%, centrifugally separating suspended coke and catalyst particles from the oil vapors after said short time of contact and passing the separated mixture of catalyst and coke particles to a iuidized catalyst regeneration zone, separating gasoline from the last said oil vapors and catalytically cracking the remaining oil in a separate catalytic cracking reaction zone at a temperature of about 1000 F. with hot freshly regenerated cracking catalyst from said regeneration zone, separately removing gasoline from the product of said separate reaction zone, and passing used and partially spent finely divided cracking catalyst at said temperature of about 1000 F. from said separate reaction zone to said suspension of coke in oil vapors as aforesaid.

References Cited in the le of this patent UNITED STATES PATENTS Great Britain May 26,

Claims (1)

1. PROCESS FOR THE PRODUCTION OF GASOLINE FROM REDIDUAL OILS WHICH COMPRISES CONTACTING A RESIDUAL OIL WITH HOT FINELY DIVIDED COKE PARTICLED UNDER CONDITIONS TO SUSPEND THE COKE PARTICLES IN THE OIL VAPORS WITHOUT A PSEUDO LIQUID COKE PHASE AND TO GIVE A RESULTING TEMPERATURES BETWEEN 1000 AND 1400''F., CENTRIFUGALLY SEPARATING THE MAJOR PART OF THE SUSPENDED COKE PARTICLES FROM THE SUSPENSION AFTER A VERY SHORT CONTANT TIME, SUSPENDING USED AND PARTIALLY CARBONIZED FINELY DIVIDED CRACKING CATALYST IN THE REMAINING SUSPENSION OF COKE PARTICLES IN OIL VAPORS IN AN AMOUNT TO GIVE RESULTING TEMPERATURE BETWEEN 900 AND 1100''F. AND CONTACTING THE SUSPENDED CATALYST WITH THE OIL VAPORS IN THE ABSENCE OF A PSEUDO LIQUID CATALYST PHASE FOR A SHORT TIME SUFFICIET TO AFFORD A CONVERSION BETWEEN 25 AND 60%, CENTRIFUGALLY SEPARATING SUSPENDED COKE AND CATALYST PARTICLES FROM THE OIL VAPORS AFTER SAID SHORT TIME OF CONTACT AND PASSING THE SEPARATED CATALYST AND COKE MIXTURE TO A FLUIDIZED CATALYST REGENERATION ZONE, SEPARATING GASOLINE FROM THE LAST SAID OIL IN VAPORS AND CATALYTICALLY CRACKING THE REMAINING OIL IN A SEPARATE CATALYTIC CRACKING REACTION ZONE AT A TEMPERATURE BETWEEN ABOUT 900 AND 100''F. WITH LESS CARBONIZED CRACKING CATALYST FROM SAID REGENERATION ZONE, SEPARELY REMOVING GASOLINE FROM THE PRODUCT OF SAID SEPARATE REACTION ZONE, AND PASSING CARBONIZED AND PARTIALLY SPENT FINELY DIVIDED CRACKING CATALYST FROM SAID SEPARATE REACTION ZONE TO SAID SUSPENSION OF COKE IN OIL VAPORS AS AFORESAID.

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