US2314561A - Cracking process - Google Patents

Description

March 23, 1943- F. J. SKOWRONSKI CRACKING PROCES S Filed April 5, 1940 NEO? Nanni@ m MUNI Nw.

atente ccc ass Felix J. Skowronski, Colonia, N. J., assigner oi' one-halt to The Winkler-Koch Patent Company, Wichita, Kana., a corporation of Kansas Application April 5, 1940, Serial No. 328,118

1 mslm.

The present invention relates to an improvement in the cracking or conversion of hydrocarbons, specifically for the purpose of producing lower boiling hydrocarbonsfrom higher boiling hydrocarbons.

One of the primary objects of the invention is the employment of a colloidal catalyst; that is to say, a material of catalytic activity which is colloldally dispersed in the oil prior to the cracking operation, the solution or dispersion of which is introduced into the oil during the cracking operation.

Another object of the invention is a cracking system employing colloidal catalytic cracking as its rst step, followed by separation of the resulting cracked products into residuum, vapors of the desired end boiling point, gases, and an intermediate fraction which may be employed as a recycle stock, which latter is cracked separately and noncatalytlcally, the vapors and other products thus produced being commingled and directed into the same vapor-separating, residuum-disposing, and condensing system.

A still further object of the invention is to disperse colloldally a suitable catalytic material, for example aluminum oxide, in the cracking stock-for example, a gas oil-and to inject the resulting dispersion into a soaking section of a tubular cracking system so as to avoid the preliminary heating of the mixture during the early heating stages, some of the oil being heated Yto the desired cracking temperature, gradually having the colloidal dispersion injected into the oil at one or more points of a soaking coil after it has attained the desired cracking temperature or after it has been maintained at said temperature for the necessary time to eiect the desired amount of cracking.

In its preferred embodiment, the colloidal cracking portion of the invention is eected as i a single pass operation vwhile thermal cracking It has already been proposed in the past, in

certain batch operations, to employ colloidal materials such as colloldally dispersed nickel and the material known as colloidal carbon, which however is not truly a colloldally disperslble subguised therefrom in that it employs a really colloidally dispersed catalyst, specically aluminum oxide, although the use of other colloldally dispersible catalytically active materials is to be considered as within the scope and purview of the invention. Such materials may be metallic or inorganic elements or compounds, such as silicon dioxide, magnesium oxide, and metalloorganic compounds capable of decomposing under cracking conditions so as to yield a suiciently dispersed catalytic material.

The particular advantage residing in the em-a ployment of a colloidal catalyst lies in the fact that it presents, for any given weight thereof, the maximum available surface. Calculations will easily prove that a given quam ity of a colloldally dispersed material presents a much greater surface area than a noncolloidal product. Take for example aluminum oxide, which has a specic gravity of 2.2, and reduce it to a very fine powders` Assuming that the resulting particles are spherical and 1,40 micron in diam= eter, it will be fouiid, by making the necessary calculations, that a single particle of this material will weigh 0.000000073'2l gram and that there are 13,564,000 particles in one gram. Therefore one gram of this material will have an available area of 68,182 square millimeters =6.8182 104. Taking the same material but reducing it to colloidal particles the largest of' which can be assumed to be no more than 200 millimicrons in diameter and assuming that the specific gravity is the same, it can soon be ascertained, by making the necessary calculations, that the surface in square millimeters for one gram of this material is equal to l.364 10. The

surface ratio of one gram of colloidal catalyst tol one gram of a noncolloidal catalyst willy show that the colloidal catalyst has over two hundred times the surface for any given weight. Furthermore, from a consideration of the kinetic theory, one may expect an additional advantage of the colloidal catalyst over the noncolloidal catalyst from an increase in the equivalent catalytic surface area as a result of the Brownian movement to which such colloidal rparticles are subject. v

A method of producing an eillcient colloidal catalyst may comprise the following: Alumina may be very finely ground and then put-together with an oil, for example a gas oil-through a suitably constructed colloid mill in order to produce what is usually termed `a colloidal solution rof alumina in the oil. Appropriate amounts of stance. The present invention is to be distin- 55 this solution may then be injected into the main ody of oil which is to be cracked. The amount f catalyst may vary considerably and may range .p to about 200% of the weight oi the oil, but s little as from about 1% to 2% by weight of olloidally dispersed alumina on the weight of he oil to be cracked lwill still be effective.

Perhaps the best way of producing, for instance, olloidal alumina is to employ the Svedberg modication of the Bredig method. `In Svedbergs aD- aratus the distribution is ca 'ed out electrically, )r instance by sparking electrodes, containing a. onducting material and aluminum oxide, under he surface of the oil in which the material is to e dispersed. For example, it has been found oat a satisfactory catalyst for carrying out the resent invention may be produced by forming lectrodes consisting of finely powdered alumium oxide, Ah, and a conducting substance, the lectrodes being in the form of sticks. Two of dese electrodes are immersed in an oil under conltions preventing combustion, whereupon an lectric arc is produced by any of the well-known leans, thus setting up an arc between the elec- .'odes. It is, of course, obvious that the oil must e adequately cooled to prevent its volatilization. s a result of the local heat produced as well as 1e electrical effects, the colloidal dispersion of 1e catalyst, for instance the alumina, in the oil ill form. The spark or arc may be produced by n. induction coil, by means of a low frequency 'ansformen by suitable high potential direct irrent such as from 500 volts and upward, or v means of a low frequency transformer which roduces an air spark gap which is then imressed upon a secondary circuit by means of a. 'ansformer so as to produce a high frequency arc etween the electrodes immersed in the oil. It as been found that in 'general the last mentioned lethod is the most eilicacious. However, the inention is not to be limited by the particular leans forcolloidally dispersing a cracking cata- 'st in oil, for such :methods are Well within the :ill of the trained chemist. As a possible further lternative, the colloidal dispersionfof the cata- 'st may be attained by the employment of a suitole organo-metallic compound, such as one of 1e well-known carbonyl compounds, whereby, at r about at the temperature of cracking, the catatic material will be formed in an effective form. As one exempliilcation of the invention, about or 2% of colloidal alumina may be added to cracking stock such as gas oil, which may then a passed in a single passage through a suitably eated cracking coil which may be heated by rnvection, by radiation, by immersion in a. lolten metal bath, or in any other suitable maner. The conversion is effected under pressure, 1d the resultant cracked products are discharged Lto an environment of lower pressure in which :paration of the formed vapors from the residual quid and of the spent catalyst can be effected. the amount of catalyst is small, it can be al wed to pass into the residuum without any diiiillties being experienced in the further utilizaon thereof. In case of larger amounts, the siduum may 'be ashed or distilled to separate it om the catalyst.

For a more complete understanding of my inintion, reference will now be had to the drawg in which:

Fig. 1 is a diagrammatic representation o-f a 'acking system constructed in accordance with 1e embodiment of this invention; and

Fig. 2 is a diagrammatic sectional view of a cans for producing a colloidal catalyst for use in accordance with one embodiment of this invention.

In its preferred embodiment, the invention may be carried out for example in accordance with the diagrammatically illustrated operation shown in Fig. 1 of the drawing. For example, a suitable raw material such as a 32 A. P. I. East Texas light gas oil may be mixed with from 1% to 2% of colloidal alumina in the following manner: The raw material may be drawn from the storage tank I and directed through the pipe 2, the valve 3 and the line 4 into the colloidal catalyst mixing tank 5. Preferably, a rather heavy colloidal dispersian-let us say, a 10% dispersionmay be made in this mixing tank, or only 2% may be dispersed, in which latter case the oil containing the therein dispersed catalyst maybe drawn through the pipe 6, the valve l, the pipe 8 and the pump 9, by means of which it may be pumped into the inlet of the coil I0 located inthe furnace I I, traversing the entire coil, including the soaking section thereof, designated as I2, issuing from the transfer line I3, and through the pressure reduction valves Il or Il', whence it is directed into the vapor separator I5, in which separation of vapors and gases from the residuum is effected. The residuum is withdrawn through the valve I6, carrying with it the spent catalyst. Further disposal oi' the residuum forms no part of the present invention.

Alternatively, a portion of the raw oil may be drawn throughv the valve Il and the pipe B, being pumped by pump 9 into pipe I0 without any catalyst in it, while a portion containing an appropriate amount of catalyst may be drawn through the valve I8 and pumped by the pump I9 through the line 20 and into the soaking section I2 of the coil within the furnace II, the proportions being so chosen that there will be present in the soaking section the desired amount of catalyst for the cracking of the material passing through the said soaking section of the furnace. thus has complete control of the proportioning of the catalyst and has the choice either of mixing the entire supply of raw material-that is, the gas oil, for example-with the desired amount of catalyst or of producing a more concentrated solution or dispersion of catalyst which is injected into the soaking section I2 of the coil in the furnace I I, while the greater part of the raw material is being pumped into the inlet of the coil I0.

The vapors and gases leaving the vapor separator through thev vapor line 2I are discharged into the bubble tower 22. This bubble tower may be under either atmospheric or greater than atmospheric pressure, but in any event separation is therein effected into vapors of the desired end product and gases which are Withdrawn from the top of the bubble tower in vapor phase, through the vapor line 23, being then directed into the condenser 24, wherein the condensable portions are liquefied to be sent to suitable collecting instrumentalities which need no further description herein, the gas being conducted to any'desired point to be utilized for whatever it may be suitable for.

In the bubble tower a recycle stock of approximately the same specific gravity, or possibly a little lighter, say from 33 to 34 A. P. I., is withdrawn at the bottom through valve 25 and flows through pipe 26 to the recycle pump 21, by means of which it is pumped through the line 28 into the thermal cracking coil 29 located either in furnace I I or a similar separate furnace. In. the coil 29 this recycle stock, without any admixture 'I'he operator of catalyst, is thermally cracked under appropiiate conditions, being discharged from the furnace through the transfer line 30 and the pressure reduction valve 3| which leads into the pipe I3, the eiiluent then being directed from the cracking coil 29 into the same vapor separator I5. It will be noticed that the line 30 is shown as intermediate the valves I4 and I4', this being done in order to give' suiicient latitude to the operation. In other words, the eiliuent from the coil 2 9 may meet the stream in the line I3 at the same pressure that exists in coils I and I2, thus depending upon the pressure reduction valve I4 for the nal reduction in pressure before entering the vapor separator, or by suitable adjustments of the valves I4 and I4' any desired changes in pressure may be maintained.

There is also shown diagrammatically a quench line 32 provided with a suitable control valve 33 through which any desired heavier quench oil may be introduced according to methods well understood in the oil conversion art.

It will thus be seen that in accordance with the example shown in the dtic drawing the original raw material may be subjected to a oncethrough colloidal catalytic cracking procedure. while the recycle stock may be merely thermally cracked. Of course, it is obvious that an entirely separate vapor separation and condensing system may be employed for the cracking of the recycle stock. and such operation is to be construed as within the scope of the present invention.

As examples of the operations of the oncethrough portion of the process-that is to say. the amount of cracking effected in the colloidal catalytic cracking system-the following results are given, without however limiting the invention thereto:

Experiments on East Temas gas oil treated with colloidal catalyst v- Feed stock-32 A. P. I. East Texas light gas oil Catalyst-Colloidal alumina Experiment No.

Ch e:

c. 4100 4010 4150 3800 Grams. 3548 3469 '3591 3289 Catalyst:

Grams (estimated).-. 35 35 72 64 Per emit wt.0n0il.-- 0.99 1.01 2.00 1.95 Coil temperature, F- 800 820 875 850 Coll lsq. In ga. 100 100 100 100 Contact time, secon Y'loil only 20 10 10 20 400 E. P. gasoline,

IMRVP- Cc. 1215 1170 1391 1084 Grams 938. 862.8 1030 795.4 Per cent vol. on

31. 6 29.2 33.5 28.0 Gravity, L P. I. 00. 7 60.4 59. 4 57.8 Octane number,

CFRM 78. 4 80. 8 7S. 6 77. 2

2130 2m 1005 2090 Grams 1830 1966 1707 1786 Per cent vol. on

feed... 51. 9 57. 4 47. 4 55. 0 Aniline pt. F 161 169 165 158 Gravity, P.L 33.2 34.1 31. 4 a4. o Gas, coke and loss (by difference)- Grams. 740 602 802 775 Per cent wt. on

From the above table it will be seen that a comparatively low temperature can be employed for cracking, namely, somewhere between 800 and 900, while obtaining an amount oi cracked material in per cent. of volume upon the feed of roughly 30%, having an A. P. I. gravity close to 60 and an octane ratirg of from 78 to 80, which is an excellent octane rating and makes the product available directly as a motor fuel or as a blending stock. It will be noticed that the characteristics of the cycle oil are also given and that it has an A. P. I. gravity of 34.1. This cycle stock is that which may subequently be passed through the thermal cracking system. The overall results, particularly of the combined processes, substantially as herein illustrated, are excellent. The particular advantage of the present process lies in the fact that it is adaptable to already constructed cracking plants, thereby enabling the use of catalytic cracking without any 'special constructional details and withoutnecessitating expensive catalyst regeneration, which has hitherto been found necessary in order to make catalytic processes commercially successful. The relatively small amount of catalyst required and the fact that it may with substantial impunity be allowed to remain in the residuum makes the process simple and easy to operate. It will also be noticed that the pressure in the once-through process is comparatively low, being on the order ofY about pounds per square inch. This is a. further advantage because it does not require so strongly constructed an apparatus as is usually necessary in carrying out tube cracking noncatalytically.

Referring now to Fig. 2, the colloidal alumina may be formed directly in the oil by means of an electric discharge between two alumina electzodes. The oil is contained in a vessel 40 having a. pair of alumina electrodes 42 and 44 immersed therein. ' I'he electrodes 42 and 44 are supported by clamps 46 and 48 secured to a. standard 50. Current is supplied to the electrodes by the conductors 52 and 54 which may be connected to any suitable ciu'rent source. When the current is applied to the electrodes a spark is formed within the body of oil resulting in. the liberation of colloidal alumina directly therein.

While the invention has been described in connection with colloidal alumina, it is not to be limited thereto, as obviously other materials capable of colloidal dispersion in the oil may be used; and therefore in the claims covering the combined colloidal and thermal cracking processes, no limitations as to the type of catalyst are intended. Thus, the process might be carried out with colloidal nickel, colloidal carbon. or other well-known cracking catalyst. provided oniy that the mme be colloidallydispersed in part or all ofthechargingstock,oratleastinthatpartof the charging Stock that is directed into the soaking section o! the cracking system.

Saving for himself such modincations as lie well within the skill of the oil cracking technologists, the inventor claims:

The process of cracking hydrocarbons which comprises producing an electrical arc between the two aluminum oxide containing electrodes immersedina bodyof aliquid hydrocarbontomoduce a colloidal dispersion of saidoxide in said hydrocarbon', and heating salddispersion to a cracmng temperature.

HELIX J. SKO

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