US2246654A - Hydrocarbon conversion system - Google Patents

Description

June 24, 1941. M. H. ARvl-:soN

HYDROCARBON CONVERSION SYSTEM 5 Sheets-Sheet l v Filed Dec. 30, 1939 INVENToR /lam'lwrp/eswz ATTORNE June 24, 1941. M. H. ARvEsoN HYDROCARBON CONVERSION SYSTEM Filed Dec. so, 1939 3 sheets-sheet 2 M. H. ARVESON HYDROCARBON CONVERSIO SYSTEM l June-24, 1941.

` Filed Dc. 50, 1939 5 Sheets-Sheet 3 Mazzi/Me( jNvENToR Q/D M ATTQRBZY Patented June V24, 1941 mmnocaaon coNvEnsIoN sY-s'rEM i Maurice H. Arveson, Flossmoor, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application December 3o, 1939, serial No. 311,886

(cl. 19e-52) 16 Claims.

tofore been of two types: (1) the stationary or hxed bed type, and (2) the moving bed or contin` nous type.' The object of my invention is to provide a new type of catalytic systemwhichwill avoid the disadvantages of both previous types lwhile retaining advantages of both.

Fixed bed catalyst systems lare exemplied by i,

the so-called Houdry plants wherein nested periorated tubes are imbedded throughout the catalyst mass for charging and withdrawing gases and vapors to and from said mass. The cost of such a reactor is enormous and it requires an cxhorbitantly large number of valves most of which must be automatically operated. AWhen used for catalytic cracking the on-stream period is only a matter of minutes and the catalyst is regenerated in situ, the regener-ation usually requiring two or 'three times as long as the onstream period. `Wide temperature ranges are involved in going over from on-stream to regeneration and from regeneration bach to on-stream periods, thus placing a severe mechanical strain on the apparatus structure and :making it im possible to obtain uniform reaction conditions during the on-stream catalytic conversion period.

-jcct of my invention is to provide a system which will avoid the diculties hereinabove enumerated and the many other difficultiesk which are inherent in xed bed catalyst conversion operations.

In moving -bed operationsv the catalyst itself flows through the reaction chamber eitherconcurrent with or countercurrent to the flow of hydrocarbon vapors undergoing conversion and the spent `catalyst material is regenerated outside of the conversion zone and then returned for further use. In this system the temperature and lpressure conditions in the conversion zone are maintained constant, and the conversion is continuous under substantially optimum conditions so that maximum product quality and maximum yields are obtainable. In such' systems, however, the problem of regulating catalyst flow through the tubes has not ybeen and perhaps cannot he satisfactorily-solved. If any particular tube discharges too rapidly or for some other reason is emptied it forms a bypass through which the hydrocarbons flow without coming in contact with the catalyst material. If catalyst material becomes stagnant there is a tendency for coke formation and tube plugging which may require removing the entire tube. An object of my invention is to avoid these and the many other inherent disadvantages of continuous or, moving bed catalyst systems while at the same time retaining the advantages of said systems.

A further object of the invention is to provide an 1in-proved catalytic reactor with positive means for renewing catalyst therein (i. e, discharging spent catalyst therefrom and adding fresh catalyst thereto) without interrupting the ow of hydrocarbon vapors through the reactor, without permitting the by--passing of hydrocarbon vapors through empty tubes and without requiring tne regulation of catalyst flow through the tubes. A turtner object is to avoid catalyst abra-n sion and disintegration which has heretofore been caused by means tor regulating catalyst ow; in

other words, it is my obJect to reduce to a minimum the production oi' catalyst rines and the loss o1 catalyst from this and other sources.

A rurtner object is to provide an improved catalytic conversion system which will operate under substantially constant conditions of temperature and pressure and produce maximum yields oi' high quality motor fuel with minimum losses to gas and coke. A further object is to provide improved means for preventing incoming catalyst from being fouled -by carbon deposits resulting Irom contact of hydrocarbon vapors with catalyst prior to the introduction Vof the catalyst into the conversion tubes. A further object is to provide an improved means for distributing catalyst material in reaction tubes or beds. A further object is to provide improved means .for discharging catalyst `from a catalyst bed while the reactor is onstream. A 'further object is to provide method and means for completely emptying one section of a reactor and then lling that section of the reactor With catalyst without disturbing other catalyst sections and Without permitting any appreciable flow of gases or vapors through the tube during the emptying step, while empty, and during the filling step. Other objects of the invention will be more fully understood as the following detailed description thereof proceeds.

I have discovered that the advantages of moving bed catalyst systems may be obtained without the inherent disadvantages of said systems by dispensing entirely with the regulating means heretofore employed for controlling the rate of catalyst flow through the reactor, stopping the vapor flow through each tube when the catalyst therein becomes spent, completely discharging the catalyst therefrom Without permitting vapor flow therethrough, filling the tube with fresh catalyst while it remains effectively cut out of the system and then passing hydrocarbons through the tube until the catalyst therein becomes spent once more.

Although the invention is subject to various forms and modifications I prefer to employ a cylindrical chamber provided with a plurality of catalyst tubes or sectors which may be surrounded by a heat exchange medium. A rotating upper member seals the ends of the tubes which are being emptied, charges fresh catalyst into the empty tube sector or cell and prevents the introduced hydrocarbons from contacting freshly introduced catalyst prior to the actual placement of the catalyst in the tubes. A lower rotating member holds the catalyst in those tubes through which'hydrocarbon vapors are beingpassed, permits the discharge of catalyst materials which have become spent, and seals the lower ends of the tubes which are empty or which are being filled with catalyst material. These upper and lower members are rotated in unison either continuously or intermittently so that the catalyst in each tube is on-stream for a time sufficient for its maximum effectiveness, then completely emptied of spent catalyst material, recharged with fresh catalyst material and returned to on-stream position. The invention will be more readily understood from the following detailed description read in conjunction with the accompanying drawings wherein similar parts are designated by like reference characters in the several figures and wherein,

Figure 1 is a vertical cross section of a simplified form of my improved catalytic reactor shown in conjunction with a schematic flow diagram ofl other parts of the conversion system;

Figure 2 is an enlarged vertical section of the reactor shown in Figure 1;

Figure 3 is a horizontal cross section taken along 'the line 3-3 of Figure 2;

Figure 4 is a cross section through the reactorv taken along the line 4-4 of Figure 2;

Figure 5 is a detail cross section of the grating nlustrated in Figure 4;

Figure 6 is a section taken along the line 4,-4 of Figure 2 showing a modified lower plate structure for use with hinged screens;

Figure 7 is a detail section taken along the lines 1-1 of Figure 6;

Figure 8 is a detail section taken along the lines 8-8 of Figure 6;

Figure 9 is a detail section taken along the lines 9-9 of Figure 6;

Figure 10 is a detail section taken along the lines III-I0 of Figure 6;

Figure 1l is a detail section taken along the lines II-II of Figure 6;

Figure l2 is a detail cross section along the sheet I'I.

Figures 13 and 14 are detail sections similar to Figures 9 and l0 wherein a cam surface coacts with a lug on the hinged screen frame for positioning the latter, and

Figures 15 and 16 show a modification of the structure shown in Figures 11 and 12, wherein a vertically movable closure plate is held against the lower end of the tubes by pivoted'weights.

While the invention is applicable to innumerable hydrocarbon conversion processes it will be described in connection with a catalytic cracking process vfor converting gas oil to high quality motor fuel. The catalyst for such a process is preferably of the silica alumina type and it may consist essentially of natural clay such as bentonite which has been acid-treated or otherwise activated to remove objectionable impurities (an example of which is acid-treated bentonite commercially marketed as Super Filtrol) Alternatively, the catalyst may consist essentially of siilca gel with a metal oxide associated therewith or deposited thereon; a preferred catalyst of this type is silica gel having about 15% to 25% of alumina deposited thereon by impregnation, adsorption, coprecipitation or other known means. Oxides of other metals such as thorium, magnesium, copper, nickel, manganese, titanium, beryllium, cerium, zirconium, boron, etc. may be used with or in place of alumina.

For hydrogenation, dehydrogenation, reforming and aromatization the catalysts are preferably Group VI metal oxides deposited on alumina, although other metal oxides such as vanadium oxide, cerium oxide, etc. may be used. For polymerization the catalyst may consist of kieselguhr impregnated with phosphoric acid or it may comprise copper pyrophosp-hate on activated carbon. For isomerization or desulfurization the catalyst may be bauxite, active alumina, activated clays, etc. The catalysts per se form no part of the present invention and they will not be described in further detail. It should Ibe understood, however, that any type of catalyst may be used which will effect the desired conversion and the catalyst may be in granular, molded, pelleted, extruded or any other form. Preferably the catalyst particles are of fairly uniform size, although the particle size may range from about 1 inch to about 200 mesh.

Referring to Figures 1 and 2 of the drawings, gas oil is forced by pump I0 through coils II of pipe still I2 and introducedby transfer line I3 into the upper part of reactor I4. In this reactor there are a plurality of substantially vertical tubes I5 with their upper ends welded to tube sheet I6 and their lower ends welded to tube The space in the reactor vessel which is outside of the tubes and which is bounded by 4,tube sheets I6 and I1 may contain any heating fluid such as flue gases, fused salts, mercury, diphenyl, etc. introduced through line I8 and withdrawn through line I9. 'Ihe temperature of the catalyst in tubes I5 may be about 800 to 1000 F., preferably about 900 F., and the space velocity of hydrocarbon vapors through the catalyst tubes is about 0.2 to 4.0, preferably about 1, volumes of charging stock (liquid basis) per volume of catalyst space per hour. The pressure in the reactor is about atmospheric to pounds per square inch, preferably about 25 to 50 pounds per square inch. 'Ihe details of the reactor per are withdrawn through line 21.

Spent catalyst is withdrawn from the base of reactor it through sealed hopper 28 and returned` by line 29 to any suitable system 30 for stripping hydrocarbons out of the catalyst, re-

generating the spent catalyst and removing oxyl gen from the regenerated catalyst. The removal oi hydrocarbons from the catalyst or purging may be effected by stripping with steam, a hydrocarbon gas or any other suitable inert gas, or it may be effected by the use of a vacuum. The

Y regeneration may be effected in a burner utilizing recirculated due gas as illustrated in Wilson Patent No. 1,520,493. Preferably the regeneration is effected under a pressure oi about to 125 pounds per square inch since such pressure lowers the lrindling point of the carboriaceous material in the catalyst and makes possible the use oi larger amounts of recirculated Yilue gas (for absorbing and withdrawingthe heat oi regeneration) without unduly increasing the velocity oi the gases dowing through the regeneration system. Regeneration may likewise be eiiected in a louvered type continuous system described and claimed in my copending application Serial No. 309,448. Since regeneration per se forms no part ci the present invention it will not be described in further detail. The regenerated catalyst which is preferably at a temperature of about 850 to 900 F. is returned by line .ill to seal hopper 32 from which it is introduced intel reactor i4.

Referring more specifically to the reactor structure, the catalyst from hopper 32 discharges through valved conduit 33 into the rotating feeder pipe 3d, the upper part of which is formed into a curved annular ange 35 rotating in and closely fitting against the inner curved bearing surface of member 36 which may be the lower end oi conduit 33 or a separate element welded to thetop of chamber I4. Packing material 31, such as asbestos, held by bolted plate 38 helps to maintain the vapor seal and hold curved ange 55 against bearing 36 while permitting the rotation of feeder 34 around a vertical axis.

The lower discharge end of feeder pipe 34 is welded to a rotating disk plate 39 which is centered by central bearing member 40. Plate 39 has holes 4i under feeder tube 34 through which catalyst may flow from feeder pipe 34 into tubes tween the ends of these slots andthe other side of the juncture withieeder 34, plate 39 is provided with imperiorate portion 45. This portion oi the plate acts as a seal for tube ends during the discharge of spent catalyst from the tubes.

The lower part of rotatable plate 39 is machined to give'a fairly tight fit with the upper ends oi the tubes. This plate is rotated by pinion wheel 46 mounted on shaft 41 extending through packing gland 48 and driven by beveled gear 49 meshing with beveled gear 50 which in turn is xed to shaft 5I driven by any suitable motor not shown. Idling plnions 52 hold the plate in place during its rotation, pinions and 52 meshing with ring gear or rack 53.

In the position illustrated in Figure 3 and with plate 39 moving counterclockwise in the direcl tion of the arrow the catalyst material from feeder '34 is viilling the Vtubes through openings 4Iin zone A; the tubes in zone B are empty, the-tubes in zone C are discharging spent catalyst and the tubes in zone D are on-stream. As the plate continues to rotate the tubes in zone 4A will go on-stream, the tubes in zoneB will be iilled, the tubes in zone C* will be in the neutral zone and the next tubes in succession will be emptied. This operation will be more fully understood after the description of the catalyst discharge means.

Adjacent and bearing against the bottom ot tubes I5 is another rotatable plate 54 (see Figure 4) which is imperforate in zones .A and B, provided with somewhat horizontal elongated apertures 55 in zone C and provided with recesses 55 in zone D. The recesses may be in the form of apertures or annular slots, the preferred structure being a wedge-shaped grating, as indicated'by Figure 5. The function oi these slots, apertures or similar structures is to form a support for catalyst material in the tubes and to permit the dow or hydrocarbon vapors from the tubes to the lower part oi the reaction chamber. The wedge-shaped structure illustrated in Figure 5 is effective for preventing the clogging of the grating structure with catalyst particles.

The outer edge of plate 5t is provided with the beveled gear or annular rack 5l driven by pinion 58 mounted on shaft 59 extending through packing gland 50 and carrying a beveled gear 6I meshing with beveled gear 52 keyed to shaft 5i. Idling pinion supports 53 cooperate with pinion 5,8 in supporting plate 54 and holding it in place to maintain a close fit between the upper part of the plate and the lower ends oi tubes I5.

As plate 54 is rotated in the indicated counterclockwise direction it will be seen that the upper ends of thetubes in zones A and E are sealed while the tubes in zone C are discharging spent catalyst through apertures 55, all ofthe remaining tubes being on-stream withV vapors flowing through the grating or the annular slots 55. The irnperforate` section of plate 54 which is in zones .A and B seals the lower ends of the tubes which are being filled and the tubes which have lust been emptied. This imperforate section extends for suiiicient area to'prevent any overlapping of tubes which are being filled and emptied respectively. While the tubes in zone C are being emptied through slots 55 the `upper ends of those tubes are sealed by the imperforate portion 45 of upper plate 39. Thus all tubes which are not actually on-stream are effectively sealed against the passage of hydrocarbon vapors therethrough. It will be understood, of course, that plates 35 and 54 are rotated together at the same speed, either continuously or intermittently. I prefer to allow suillcient registrationoi? the apertures 55 at the lower ends of the tubes to completely discharge the catalyst from said tubes but it should be understood that a more rapid rotation of the plates may effect only partial removal of the catalyst from the tubes.

` To center plate 54 and hold Vit snugly against the lower ends oi tubes I5 I provide shaft 54 ber is illustrated in Figures 6 to'16. inclusive, and

while this form is slightly more complicated than the form hereinabove described it offers the further advantage of preventing abrasion and catalyst disintegration due to the shearing effect of the rotating grating under the catalyst tubes. In this preferred modification the upper plate and catalyst distributing mechanism may be as previously described, but instead of employing a simplev plate with perforations or grooves, as illustrated in Figure 4, I employ a hinged screen at the base of each tube with means for holding these screens snugly against the ends of the tubes while the tubes are on-stream, means for permitting the screens to pivot on their hinge for discharging spent catalyst and means for sealing the tubes prior to and during the catalyst charging step.

Referring to Figure 6, I provide a plate 10 which is supported and rotated in exactly the same manner as plate 54 hereinabove described. This plate contains an imperforate section 1I illustrated in zones A and B. It contains a plurality of concentric slots 12 which may extend approximately 270 around the plate and which slots are similar to slots 43 and 44 in plate 39. The width of these slots is approximately equal to the inside diameter of the tubes or, more exactly speaking, to the inside diameter of the screen supports as will be hereinafter described. In zone C I increase the width of the slots to make them wider than the outside diameter of the screen supports, thus providing tube dumping apertures 13 which are equivalent in function to the apertures 55 of plate 54.

Referring to Figures 7 to 12, Iprovide each tube I with an annular screen support 14 which fits snugly against the lower end of the tube.

This annular screen support is secured to one side of hinge 15, the other side of the hinge being secured to tube sheet I1 or to the lower end of the tube itself by a suitable bracket 16. Annular screen support 14 carries a screen or grating 11 for supporting catalyst material in tubes I5 while permitting the flow of vapors therethrough.

In zone D the annular screen support 14 is held against the end of tube I5 by bearing surfaces 18 on plate 10 on both sides of slot 12. Thus as plate rotates in a'counter-clockwise direction there is no abrasion of catalyst material against the rotating plate but merely a sliding contact between the rotating plate and the annular screen support. When zone C reaches each particular screen support bearing 18 is discontinued and the enlarged slot opening permits the screen support to pivot downwardly on its hinge as shown in Figure 9. Thus in zone C the spent catalyst may be discharged from the' tube.

As the plate continues to rotate the screen support is forced back into position against the lower end of the tube by surface 19 on the imperforate section 1I of plate 10 so that when zones B and A are under the tubes this imperforate section 1I of plate 10 effectively seals the lower ends of the tubes and prevents gases and vapors from iiowing into or out of said tubes. This position of the tubes is shown in Figures 11 and 12. While the tubes are thus sealed and catalyst screen supports are supported and sealed by imperforate plate 'section 1I the tubes are recharged with fresh catalyst as hereinabove described. On continued rotation of the plate the screen supports are held in place by bearing surfaces 18 while hydrocarbons pass through the catalyst through slot 12.

Instead of supporting the edges of annular screen supports 14 on 'bearing surfaces 18 I may make the slots 12 slightly greater in width than the outside diameter of screen supports 14 and I may provide the screen supports with lugs 88 as illustrated in Figures 13 to 16. These lugs slide on bearing surfaces 18 in zone D but in zone C there is a cam-like depression 8I in bearing surface 18 which permits the screen support to pivot on its hinge and discharge spent catalyst.

`Cam surface 82 forces the screen support back against the lower ends of the tubes in the saine manner :that inclined surface 19 repositions the screen supports.

Instead of employing a Y simple imperforate plate section 1I I may provide zones A and B with annular slots or recesses 83 provided with annular plates 84 machined to t snugly against the lower surfaces of annular screen supports 14 and to seal the same. Plates 84 are preferably provided with inclined surfaces 85 which serve somewhat the same function as inclined surfaces 19 and 82. These plates may be held tightly against the annular screen support 14 by means of weights 86 mounted on the ends of bars 81 which are pivoted on pins 88 and pivotally connected to the lower part of plates 84 by connection 89. By making the distance between weight 86 and pivot 88 materially longer than the distance between pivot 88 and connection 89 the desired leverage may be obtained for exerting sumcient upward pressure against plate 84 to effectively seal .the lower ends of tubes I5 against both the Weight of catalyst and pressure.

In all of the modifications hereinabove described it will be seen that I have provided means for emptying and refilling tubes in a reaction chamber Without permitting or at least reducing to a very minimum the entrance of hydrocarbon vapors into said tubes during and between said filling and emptying steps. It will be noted that I have avoided the necessity of controlling or regulating the continuous flow of catalyst material through the catalyst tubes and at the same time I have obtained all of the advantages of the continuous moving bed catalyst system. In the modiiication described in Figures 6 to 16 I uhave provided means for preventing catalyst abrasion. In short I have obtained all of the advantages of continuous operation Without the inherent dimculties of that system and at the same time I have obtained the.advantages without the disadvantages of a xed bed catalyst system.

To positively insure against leakage of hydrocarbon vapors into feeder pipe 34 or into the sealed hc'ppers, an inert gas may be introduced thereinto Ithrough lines 90, 9|, 92 etc. to maintain the necessary pressure.

My invention is not limited to the particular structure or to the particular modifications herein disclosed since many alternative structures and modifications of the invention will be apparent to those skilled in the art from the above description. The word tube" or tubesy in the followamasar. 5

ing claims are hereby defined to include not only circular conduits but conduits of any other contou in other words, a tube is a conduit which may be alternately iilied -with catalyst at one end and from which catalyst may be discharged at the other.

I claim: Y

l. In a catalytic hydrocarbon conversion system comprising a catalytic reaction chamber containing a plurality of tubes adapted to contain catalyst, the method of eiecting continuous operation, which method comprises periodically emptying catalyst from at least one of said tubes while other of said tubes remain on-stream, charging iresh catalyst into said emptied tube while other of said tubes remain ori-stream and preventing the by-passing of hydrocarbon Va'- pors through said Itube while it is empty and while catalyst material is being discharged therefrom and charged thereto.

2. The method or effecting continuous catalytic conversion which comprises mounting a plurality oi catalyst tubes in a reaction chamber, maintaining certain of said tubes full oi catalyst while other ci said tubes are being emptied and lilled with catalyst material, preventing the pas- `sage or vapors through each tube while it is empty and while it is being emptied and filled, removing spent catalyst material from the reaction acne without interrupting the iiow or hydrocarbon vapors in said cone, and introducing catalyst to said reaction none without interrupting :the ilow oi hydrocarbon vapors in said zone.

3. The process oi claim 2 wherein catalyst introduced into the system is kept out of contact with hydrocarbon vapors until it is positioned in said tubes.

i. The method of renewing catalyst in one of a plurality oi tubes adapted to contain catalyst without interrupting the flow oi hydrocarbons through other of said tubes, which method comprises enclosing a plurality of tubes in a catalytic reaction chamber, sealing the top of one of said tubes .and opening the bottom thereof to permit the discharge of `spent catalyst therefrom' in a catalyst discharge zone, sealing the bottom of said tube while catalyst is vbeing introduced into the top thereof in a catalyst charging zone and l spacing the discharge zone sufiiciently far from the charging zone to prevent the simultaneous charging and discharging of said catalyst tube. 5. The method of claim 4 which includes the further step of maintaining a positive inert gas pressure in the catalyst charging zone suiiicient to prevent leakage of hydrocarbons thereinto.

6. In a catalytic conversion system a catalyst reactor chamber, a plurality of tubes adapted to contain catalyst substantially vertically mounted in said chamber, means for selectively introducing catalyst into the top of at least one of said tubes while the top of at least one of said tubes is closed and the top of at least one of said tubes is open to the flow of hydrocarbon vapors, means for removing catalyst from the base of one of said tubes while the top of said tube is closed, means for closing the bottom of said tube while it is `being charged with fresh catalyst and means for holding catalyst in the tube while permitting' the flow of hydrocarbon vapors therethrough. l

'7. The apparatus of claim 6 which includes means in said reactor chamber for maintaining catalyst out of contact with vapors until said catalyst is deposited in said tubes.

3. In a catalytic conversion system a plurality of substantially vertical. concentrically arranged tubes adapted to contain catalyst, an upper plate containing an imperforate section, a catalyst distributing section and a slotted section, a. lower plate containing a catalyst discharge section, a tube sealing'section and a slotted section for the passage oi hydrocarbon vapors therethrough. means for simultaneously rotating both of said plates and for maintaining the imperforate and sealing section oi the upper plate closely against the upper end oi' each tube while it is being emptied and for maintaining the tube sealing section of the lower plate closely against the lower end of each tube While it is being filled. v

9. In catalytic conversion apparatus a plurality of tubes adapted to contain catalyst, a closed catalyst chamber surrounding said tubes, screen supports hinged adjacent the lower ends of said tubes, means for periodically holding said supports against said lower tube ends, means "for periodically moving said holding means out of holding position so that said hinged supports may swing away from said tube ends, and means for periodically sealing said tube ends against the flow of hydrocarbon vapors.

lil. In catalytic conversion apparatus compris ing a closed catalyst reaction chamber containing a plurality oi tubes adapted to contain catalyst and an apertured element relatively movable with respect to the lower end ,oi said tubes, means including a movably mounted screen support at the base ci each tube for, keeping the catalyst out of contact with the movable element while the catalyst is on-stream, means ior successively aligning the aperture oi s'aid element with each screen support so that it may move away from the tube for discharging catalyst from said tube, and means for moving the screen support back to its original position after catalyst has been discharged from said tube.

1l. The apparatus of claim 10 which includes means for sealing the lower ends ci the tubes after catalyst has been discharged therefrom.

12. In catalytic conversion apparatus, a reactor chamber, a plurality of tubes adapted to contain catalyst therein, means for continuously introducing hot vapors into the reactor chamber and withdrawing reaction products therefrom, means for introducing catalyst vmaterial into said chamber without interrupting the conversion therein while preventing the escape of vapors through the catalyst inlet, means for maintaining the top of each tube closed while said tube is being emptied, means for maintaining at least one end of each tube closed While the tube is empty, means for maintaining the bottom of each tube closed while the tube is being filled, means for holding the catalyst in each tube while vapors are passed therethrough, and means for removing spent catalyst from the reactor chamber while preventing the escape of gas therewith.

13. The apparatus of claim 12 wherein the means for maintaining at least one end oi the tube ends .closed comprises an imperforate portion of a rotatable plate.

14. The apparatus of claim l2 wherein the means for maintaining at least one of the tube contain .catalyst in said chamber, means for l vapors through the tube which is being discharged, means for withdrawing spent catalyst from the reaction chamber without permitting f the escape of substantial amounts of hydrocarbon vapors, and means for introducing catalyst to the reaction chamber without permitting the escape of substantial amounts or hydrocarbon vapors at the point of catalyst introduction.

16. In catalytic conversion apparatus, a catalytic reaction chamber, a plurality of tubes adapted to contain catalyst in said reaction chamber, closure means at the -top and bottom of said tubes and means for operating said closure means whereby each tube is closed at its lower end while catalyst is being charged thereto, each tube is closedl at its upper end when catalyst is discharged therefrom and each tube is open at both ends for the passage of hydrocarbon vapors therethrough while the tube is on-stream.

MAURICE H. ARVESON.

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