WO2003002245A1 - Reactor for heterogeneous catalytic reactions and method using said reactor - Google Patents

Abstract

The invention relates to the implementation of heterogeneous catalytic reactions in a moving-bed reactor. Expansion volumes for the catalyst are provided in the defining walls of the catalyst bed, said volumes being easily created by means of at least two graduated conical-or polygonal-frustrum-shaped walls. Said implementation reduces the catalyst abrasion and avoids damaging the catalyst screens.

Description

Reactor for heterogeneous catalytic reactions and processes using this reactor

description

The present invention relates to a reactor for heterogeneous catalytic reactions and a method using this reactor. In particular, the present invention relates to a radial flow reactor for heterogeneous catalytic reactions, a reactor in which the catalyst is moved through the reaction zone (so-called “moving bed reactor”), and heterogeneously catalyzed gas phase reactions, in particular processes carried out adiabatically, and an adiabatic process for the dehydrogenation of hydrocarbons using such a moving bed reactor.

Reactors and especially moving bed reactors for heterogeneous catalytic reactions are known. Moving bed reactors are used primarily in those processes in which the catalytic properties of the catalyst deteriorate significantly (for example loss of activity and / or selectivity) in a comparatively short time. The catalyst is introduced into the moving bed reactor, where it is moved through the reaction zone and catalyzes the reaction carried out in the reactor, with its catalytic properties deteriorating. The catalyst is removed from the reactor at the outlet thereof. If possible in individual cases, its initial good catalytic properties are advantageously restored by regeneration, whereupon the catalyst can be reintroduced into the moving bed reactor.

The term “moving bed reactor” is also used in the context of this invention to delimit fluidized bed reactors (“fluidized bed reactor”). A fluidized bed reactor is to be understood as a reactor in which comparatively finely divided catalyst is fluidized by the fluid reaction medium, that is to say it moves with and through the reaction medium. The solid and the gaseous or liquid contents of a fluidized bed reactor ideally each have the residence time distribution in an ideal stirred tank, and ideally the content of each individual volume element of the reaction zone is composed completely identically. In the case of a moving bed reactor, on the other hand, the movements or flows of the solid, generally lumpy catalyst and the fluid reaction medium are essentially decoupled. The catalyst is moved through the reactor, for example by gravity within one of for the reaction medium-permeable walls of a limited vertical container or on a horizontal motor-driven belt that is permeable to the reaction medium. In a moving bed reactor, the catalyst ideally moves through the reactor with the residence time characteristic in an ideal flow tube. The reaction medium flows through the catalyst, it is normally not significantly moved by this flow. Both a stirred tank residence time characteristic and a flow tube residence time characteristic can be technically implemented for the reaction medium in the moving bed reactor.

The advantage of moving bed reactors is that even if the catalyst has to be regenerated regularly and comparatively frequently, the reaction itself can be carried out continuously. If the same reaction was carried out on the same catalyst in a conventional fixed bed reactor, the reaction for the regeneration would instead have to be interrupted regularly and comparatively frequently. However, moving bed reactors have to be operated with catalysts which can withstand the mechanical stresses in the moving bed and are generally operated adiabatically since the arrangement of cooling or heating devices in the moving catalyst bed would in most cases hinder or even prevent the movement of the catalyst.

Reactions that are typically carried out in moving bed reactors are mostly those in which the catalyst gradually loses its activity due to the formation of deposits thereon. For example, undesirable side reactions on the catalyst can form substances which are not volatile under the reaction conditions and therefore collect on the catalyst or in its pore system and gradually block its catalytically active centers. The catalyst is deactivated.

Examples of such reactions are the catalytic dehydrogenation of alkanes to olefins and the reforming of hydrocarbons, in each of which the catalyst is deactivated by coke deposits.

US-A-5, 406, 014 contains an overview of various technical processes for the catalytic dehydrogenation of alkanes and teaches measures to overcome the material corrosion problems in the reactor which occur with such processes. Figure 1 shows a simplified longitudinal section through a basic design of a known moving bed reactor for heterogeneously catalyzed gas phase reactions, as is disclosed, for example, in addition to the use of such a reactor for reforming reactions in US Pat. No. 3,647,680. The catalyst is located in a catalyst bed 5 in the form of a hollow cylinder, which is delimited by two nested, cylindrical perforated catalyst baskets 10 and 20 (boundary walls of the catalyst bed are usually referred to as "catalyst baskets" or "screens") of different diameters. The lumpy catalyst moves through gravity from top to bottom through the catalyst bed 5 due to its flowability, is removed from it at one or more outlets (two outlets 4 and 4 'are shown), fed to regeneration, and regenerated catalyst is at the top one or more inlets (two inlets 2 and 2 'are shown) again abandoned. The two catalyst baskets are located within a cylindrical reactor delimited by a reactor wall 30, so that a cylindrical cavity is delimited inside and from the inner catalyst basket and a further hollow cylindrical cavity is delimited from and between the inner wall of the reactor and the outer catalyst basket. The reaction medium enters the reactor at an inlet 1, flows radially through the catalyst bed 5 from one of these cavities into the other, and leaves the reactor at the outlet 3. Alternatively, the reaction medium can also enter the reactor at 3 and leave it at 1; in one case the gas flow is centrifugal and in the other centripetal.

US-A-3, 647, 680 also teaches that multi-stage reactor cascades can be used through which the catalyst and reaction medium are passed step by step. US-A-3, 978, 150 and US-A-4, 869, 808 teach the use of moving bed reactors of this type for the dehydrogenation of alkanes. US-A-5,209, 908 and US-A-5, 366,704 disclose a variant of the basic design of moving bed reactors in which the outer boundary of the approximately hollow cylindrical catalyst bed is formed by the inner wall of the reactor. In this design, the reaction gas mixture is removed or supplied through gas collection tubes of approximately semi-cylindrical shape, which are guided along the inner wall of the reactor through the catalyst bed.

A general problem when carrying out reactions in moving bed reactors is catalyst abrasion, which not only leads to catalyst losses and material abrasion, but also to blockage of the comparatively fine perforations in the catalyst baskets with catalyst particles which are present in these Forations can also catalyze undesirable reactions (eg coke formation, reactor fouling). This is particularly serious in the case of reactions with a strong exotherm, in particular in the case of adiabatic reaction control, since temperature fluctuations, especially when the reactor is started up or shut down, which cannot be compensated for by cooling or heating devices, and the associated thermal expansion and contraction of the catalyst and the Catalyst baskets - especially due to different expansion or contraction of the inner and outer basket, which mostly do not have the same temperature or experience the same temperature jumps - considerable mechanical loads occur in the catalyst bed and between the catalyst and catalyst baskets. On the one hand, this causes the catalyst to be ground, so to speak, and catalyst abrasion occurs. On the other hand, the high pressure on the catalyst baskets can also cause considerable damage to the catalyst baskets. This effect also occurs in fixed bed reactors of a comparable design. The object of the present invention is therefore to find a reactor in which the mechanical loads on the catalyst and catalyst baskets are reduced, in particular by temperature fluctuations.

Accordingly, a reactor for heterogeneous catalytic reactions has been found, which is characterized in that expansion volumes for the catalyst are set up in at least one catalyst basket. Methods for carrying out chemical reactions using the reactor according to the invention have also been found.

In the reactor according to the invention, the catalyst can escape into the expansion volumes under mechanical stress, which is caused, for example, by thermal stress. As a result, the pressure on the catalyst and the catalyst baskets that builds up in the catalyst bed is at least partially reduced, which reduces the mechanical load on the catalyst and, consequently, the catalyst wear. This results in less catalyst loss and clogging of perforations in the catalyst baskets is also reduced; damage to the catalyst baskets is also avoided.

Expansion spaces for the catalyst in the catalyst baskets can be set up in a very simple manner by attaching at least one hollow body, but preferably a large number of hollow bodies distributed over the entire area of the catalyst basket, to the catalyst basket on the side facing away from the catalyst bed, but with an open passage to the catalyst bed that they are partially empty during normal operation of the reactor, so they are not automatically filled by the catalyst due to gravity. For this purpose, the hollow bodies have volume elements which are spatially above that part of their volume which is filled with catalyst in normal operation. The catalyst always takes up a finite part of the volume of these hollow bodies, since it slides into the hollow body with its specific angle of repose from the upper edge of the passage in the catalyst basket which leads to the hollow body. (The angle of repose α of the catalytic converter is the angle between the conical surface of a cone of free material which is filled up freely on a flat base surface from the catalyst particles and the flat base surface. The angle of repose is substance-specific and can be measured very easily.) The hollow bodies are preferably shaped in such a way that when the volume between the catalyst baskets expands, the catalyst completely or at least partially slides back out of the expansion space into the actual catalyst bed (ie the volume filled with catalyst during normal operation of the reactor).

The total volume of the hollow bodies, which is not filled with catalyst in normal operation, is normally dimensioned in such a way that it is at least as large as the volume decrease of the actual catalyst bed with the greatest expected temperature jump downwards.

The hollow bodies are either permeable to the reaction gas mixture or not. Provided that they are dimensioned large enough so that no catalyst can slip out of the hollow bodies even in the event of a strong volume contraction of the catalyst bed, or alternatively devices are provided in the reactor for collecting such "overflowed" catalyst, the hollow bodies can be open at the top.

Examples of such hollow bodies are tubes or boxes attached to the catalyst basket with an open passage to the catalyst bed, preferably horizontally or diagonally upwards. A further embodiment is horizontal, completely or partially circumferential cutouts in the catalyst basket, in front of which profiles are placed in the manner of a balcony, preferably with a floor inclined towards the catalyst bed, which provide the expansion space but prevent the catalyst from flowing out freely ,

In general, the diameters or the smallest distances between the boundaries of these open passages are greater than four times, preferably at least ten times the largest main dimension of a single catalyst particle. With spherical catalyst particles with a diameter of 2 to 3 mm, for example, the smallest open passage of 30 mm or 60 mm can be selected.

In a preferred embodiment, at least one boundary of the catalyst bed is formed by at least two staggered conical or polygonal-shaped walls, between which there is an open passage. Preferably more than two such frusto-conical staggered walls are used, between each of which there is an open passage. The design principles for this preferred embodiment are described in detail below, but the principles apply equally to the general case of catalyst baskets with expansion volumes.

Figure 2 shows a simplified longitudinal section through a reactor according to the invention in a basic design with several - not necessarily drawn to scale - frustoconical staggered walls (e.g. 40, 40 '), which except for the inner catalyst basket with the known reactor shown in Figure 1 is identical; the same reference numerals designate identical parts of the reactors shown. A moving bed reactor is shown, but the principle according to the invention also applies to fixed bed reactors of the same type, but in which there are no outlets and inlets for the catalyst which is continuously moved by the reactor. Figure 3 shows an equally simplified longitudinal section through another embodiment of the reactor according to the invention, in which the reaction gas mixture is introduced at the bottom of the reactor.

The inner boundary of the catalyst bed, that is to say the inner catalyst basket, in the illustrated reactor according to the invention is formed by staggered conical or truncated-polygonal walls 40 (hereinafter referred to simply as "cones" or in the majority "cones"). In the context of this invention, “polygon stump” is understood to mean a three-dimensional geometric body which has a polygon with three or more corners as the base surface and whose tip lying outside the base surface is cut off. A "triangular stump" is accordingly a tetrahedral stump, a "quadrangular stump" a pyramid stump, etc., and a truncated cone with its circular base corresponds to a polygonal stump with an infinite number of corners.

The cones 40 are permeable or impermeable to the reaction medium. Permeability is achieved, if desired, through perforations or openings in the walls of the cones 40, for example through slits, perforations or holes. The size of the perforations or openings in the cone walls is so chosen that catalyst particles can not pass through, preferably the largest clear width of the openings is at most half as large as the smallest main dimension (the expansion of a geometric body in one of three perpendicular spatial directions) of a single particle of the particle-shaped catalyst used (e.g. Diameter for spherical or strand-shaped particles or height for catalyst tablets). The cones are preferably impermeable to the reaction medium; in this way the reaction medium between the cones is led into and / or out of the catalyst bed. In this embodiment, there are no perforations or slots that can clog with catalyst abrasion, which completely prevents the clogging problem.

The outer catalyst basket can also be designed in a completely analogous manner with expansion volumes. In particular and preferably, like the inner catalyst basket, it can be designed in the form of at least two staggered cones. It is also possible to use only one catalyst basket, designed according to the invention, and to either introduce the reaction gas mixture into the catalyst bed or withdraw it from it through perforated hollow bodies such as, for example, tubes which are located in the catalyst bed.

The cones are arranged in the reactor in such a way that for cones which serve to limit the catalyst bed inwards, the smaller opening points upwards and for cones which serve to limit the catalyst bed to the outside the larger opening points upwards. They are arranged in stages. A staggered arrangement is to be understood as an arrangement in which the upper edge of a cone is arranged at least as high below or within the cone above that the catalyst located in the catalyst bed does not flow continuously over this upper edge. In individual cases, this depends on the distance from the upper and lower edge and the angle of repose α of the catalyst used for the reaction carried out in the reactor. Strictly speaking: The upper edge of the lower cone 40 'must lie at least at the level of the lateral surface of an imaginary cone standing on the tip, which lies all around on the lower edge of the upper cone 40 and an angle of 90 ° between the cone shell and the central cone axis. α has. For polygon stumps, the cone standing on the tip includes the points on the base surface of the polygon stump that correspond to the smallest possible diameter of this base surface of the polygon stump. If the upper edge of the lower cone 40 'were lower, catalyst would continuously flow over this upper edge into the central interior or flow around the outer annulus of the reactor, which in general removes it undesirably from the reaction.

The upper edge of each cone (with the exception of the uppermost one) is preferably at least at the level of the lower edge of the cone above it. In a particularly preferred embodiment, the upper edge of each cone (with the exception of the uppermost one) lies above the height of the lower edge of the cone lying above it, so there is a certain height overlap of the cones.

In general, it does not interfere with the operation of the reactor according to the invention if, in certain operating states - for example when the reactor is being heated - a certain amount of catalyst flows over the top edge of individual or all cones into the central interior of the reactor. The lower boundary 50 of the central interior can be designed as a cone with the tip facing upwards, the base of which adjoins the upper edge of the lowest cone, as a result of which catalyst overflowing further up is returned to the cavity between the lowest and the second lowest cone, approximately as is shown in Figure 3. In the embodiment shown in Figure 3, however, this cone is provided with an opening for the reaction gas mixture, which, of course, is closed by the cone tip when the reaction gas mixture is introduced elsewhere into the reactor. It is also possible to design the lower limit 50 as a cone standing on the tip, at the tip of which the overflowed catalyst is removed analogously to the catalyst outlets 4 4 '; if necessary, an analogous construction for the outer annular space of the reactor around the outer catalyst basket is also to be provided. In these cases, the lower limit 50 can also be arranged below the upper edge of the lowest cone.

The length of the cones (i.e. the height of the truncated cone or n-corner), the height overlap of the cones, the cone angle K (the cone angle is the angle that the corresponding truncated cone shell forms with the central axis of the truncated cone, or the largest analogue angle of a polygonal stump) of the cones and, associated with this, their upper and lower opening cross sections and the spacing of the cones from one another are selected such that the catalyst used for the reaction carried out in the reactor with the temperature increases occurring during this reaction (normal operation, start-up and shutdown) and in the event of malfunctions) has a sufficient expansion volume in the open passages between the cones, without overflowing over the upper edges of the cones, and so that the catalyst with corresponding temperature fluctuations can flow into the expansion volume and flow back out of it.

The length of the cones and thus also their number is chosen so that a sufficient number of openings between two cones is available for the expansion of the catalyst. A catalyst which has a high internal friction of the catalyst particles (i.e. a high friction of the particles against one another) requires a higher number of passes between individual cones, that is also a higher number of cones, compared to a catalyst which has a low internal friction. The minimum number of cones required in a catalyst basket is two. In general, however, a large number of cones are used for a typical reactor basket of an industrial reactor, for example at least 10, preferably at least 50, and particularly preferably at least 100 cones.

The length of the cones also results from the desired thickness of the catalyst bed: A catalyst bed that is the same thickness over the entire height of the reactor requires cones that are exactly aligned in the reactor axis. If the cones are to be aligned exactly, their length is automatically determined by the selected cone angle and the selected height overlap. However, it is also possible to change the thickness of the catalyst bed in the reactor according to the invention as a function of the reactor height. This is achieved in a simple manner by appropriate choice of the cone length and therefore cones which are not exactly aligned. The pressure drop and the residence time of the reaction gas mixture in the catalyst bed can thus be changed in a simple manner as a function of the vertical position of the relevant point in the catalyst bed. In a moving bed reactor according to the invention, it can be advantageous to make a lower region of the catalyst bed thicker at the lower end of the reactor in order to compensate for a loss of activity of the catalyst over its residence time in the reactor by a longer residence time of the reaction gas mixture in this lower region of the catalyst bed.

The height overlap of the cones essentially determines the available expansion space, which is equal to the sum of all volume elements, each from the level of the upper edge of a cone lying below, but overlapping with the cone above, the level of the lower edge of the cone above and the between cone lateral surfaces lying at these planes are formed, plus the sum of those volume elements which, below the plane of the lower edge of the cone above, due to the angle of repose α different from 0 of the catalytic converter remain free of catalyst. The total expansion space should be at least as large as the difference between the volume expansion of the catalyst in the reactor and the actual catalyst bed at the greatest temperature increase that occurs during operation of the reactor (including start-up and shutdown as well as malfunctions), but also at least as large as the difference of Volume contraction of the catalyst bed and the catalyst located in the reactor at the greatest temperature drop occurring during operation of the reactor (including start-up and shutdown as well as malfunctions). The expansion volume is preferably chosen to be somewhat larger, for example at least 1.5 times or at least twice these differences in volume expansion or contraction. Too high an expansion volume is technically not a disadvantage, but enlarges the reactor unnecessarily and is therefore not desirable from an economic point of view.

The cone angle K is chosen so that the catalyst can slide on the cone. In principle, the same problem arises when determining the cone angle for the reactor according to the invention as when designing an outlet funnel for a solid silo, from which the stored solid is to be emptied in the mass flow and not in the core flow: the cone angle K is chosen such that the catalyst flows out of the mass flow on the cone, that is to say catalyst particles which are in direct contact with a cone do not have significantly longer dwell times in the reactor than catalyst particles in the middle of the catalyst bed. The solution to such design tasks is state of the art (see, for example, L. ter Borg: "Influence of the wall material on the leakage behavior of bulk materials from silos", Chem. Ing. Techn. 58 (1986) 588-590; AC McLean: "Empirical Critical Flow Factor Equations ", Bulk Solids Handling 6 (1986) 779-782 and AW Jenike:" Gravity Flow of Bulk Solids ", Univ. Utah Eng. Exp. Station Bull-, 108, Salt Lake City / Utah 1961). Es However, when applying the design rules known for silo discharge funnels to cones in the reactor according to the invention, it should be noted that a cone in the inner catalyst basket of a reactor according to the invention is upside down relative to an outlet funnel of a silo, and the catalyst moves away from the central axis of the cone does not slip towards it as in a silo discharge funnel. The angle of inclination of a silo discharge funnel towards the vertical, usually referred to as θ in the relevant literature, thus corresponds to the cone wi n K of a cone in the outer catalyst basket of a reactor according to the invention, while the cone angle K of a cone in the inner catalyst basket of a reactor according to the invention is accordingly (180 ° - θ). The angle of inclination θp _rak i _{sch to be used} in practice of a silo discharge funnel equivalent to a cone in the reactor according to the invention, which corresponds to the angle K or (180 ° -K) of an outer or inner cone in the reactor according to the invention, respectively, becomes at most as large as the limit value chosen for the angle θ at which the transition between mass flow and core flow takes place when the catalyst used flows out through this silo outlet funnel, which is equivalent to a cone. Preferably, the angle θ is selected to be smaller at least 3 ° _prakt than this critical angle i _sch. This critical angle in turn depends on the so-called wall friction angle ς and the so-called effective friction angle φ _e . For the catalyst used and the material used for the cones, these two angles are substance-specific quantities that depend on the internal friction and the wall friction of the catalyst and are determined experimentally in a simple manner (see ter Borg; McLean, Jenike, Ie). Accordingly, in the reactor according to the invention, the cone angle K of a cone in the outer catalyst basket is chosen such as the angle θ _{pr kt} i _sch , and the cone angle K of a cone in the inner catalyst basket is selected as the angle (180 ° - θ _practically ).

Typically, the cone angle is at most 30 °, for catalysts with very high internal friction and / or wall friction also at most 20 ° or at most 15 °. It is not necessary that the cone angle as a function of the cone length is constant (ie, the cones can certainly have individual sections with a larger or smaller cone angle, that is to say, in turn, be composed of individual truncated cones or polygonal stumps with different cone angles) in this In this case, however, the largest available cone angle is chosen at least so small that the catalytic converter can slip out of the cone.

The upper and lower opening cross sections of the cones result on the one hand from the selected cone lengths, the selected cone angles and the selected height overlap of the cones and on the other hand are determined by the chosen reactor diameter, more precisely, by the chosen diameter of the central reactor interior and / or the outer annulus of the reactor determined around the outer catalyst basket. In general, this central interior and / or the outer annulus are chosen not larger than is necessary for the structure for fastening and arranging the cones of the inner and / or outer catalyst baskets and necessary maintenance work (driving on the reactor), since an unnecessarily large reactor is sufficient is not desirable for economic reasons. In the normal case, it can be assumed that a lower volume for distributing or collecting the reaction medium of the central reactor interior or of the outer annulus would be necessary as these mechanical and maintenance requirements correspond, but sometimes reaction-technical requirements for the geometry of the catalyst bed or requirements, the distribution or collection of the reaction medium, the minimum sizes of the reactor interior and / or the outer annulus establish. Likewise, the size of the central interior can be determined by a maximum possible construction height of the reactor with a quantity of catalyst determined by the desired capacity of the reactor and a maximum thickness of the catalyst bed determined for reaction reasons, so that the necessary volume of the catalyst bed can only be achieved with a sufficiently large diameter of the catalyst baskets can be achieved, determined. This is of no importance for the mode of operation of the invention.

The open passages between the cones, that is to say the smallest distances between two adjacent cones, are selected such that the catalyst particles can escape into these open passages or flow back out of them when the catalyst volume expands or contracts. In general, the open passageways are larger than four times, preferably at least ten times the largest major dimension of a single catalyst particle. For spherical catalyst particles with a diameter of 2 to 3 mm, for example, a cone spacing of 30 mm or 60 mm can be selected.

The parameters required for determining the length and height overlap of the cones, the cone angle and the spacing of the cones from one another are determined using simple routine tests with the catalyst used for the reaction to be carried out (in the case of supported catalysts, the support without active composition is normally sufficient for these tests, since this determines the bulk properties of the catalyst). In particular, the angle of repose of a catalyst cone and the angle θ _pract i _{sc of} the catalyst on the material selected for the cones are to be determined or determined, and by measuring or calculating the thermal expansion or contraction of the catalyst and the volume change of the catalyst bed in the expected ones Jumps in temperature the necessary expansion volume.

The design principles listed can also be applied in a completely analogous manner to the outer catalyst basket. In general, at least in the case of moving bed reactors, it will suffice if the catalyst bed, that is to say either the inner or the outer catalyst basket, is limited according to the invention. If both the inner and the outer catalyst basket according to the invention are carried out, there is a considerably higher expansion volume and twice the number of open passages for the catalyst available with the same overall height of the reactor than with only one catalyst basket designed according to the invention; in some cases - especially with fixed bed reactors - the reactor can therefore be made more compact with two catalyst baskets designed according to the invention than with only one:

The cones are produced using methods customary in reactor construction from materials customary in reactor construction, preferably from one

Material that is sufficiently corrosion-resistant under reaction conditions. For example, sheets are deformed to form the cones. If the sheets are to be permeable to the reaction medium, they are provided with slots, perforations or holes, for example by punching. Alternatively, wire nets can also be used, or rods can be attached in parallel to at least two carrier rings of different diameters. The individual cones are attached to a suitable support structure, for example on several vertical supports which are distributed in the central reactor interior along the inner opening of the cones, or correspondingly outside the outer catalyst basket along the outer opening of the cones and, if necessary, the cones additionally support with struts. Such installation constructions in reactors are easy to carry out for any person skilled in the art.

The thickness of the catalyst bed, which generally corresponds to the distance between the two catalyst baskets, is chosen so that the reaction gas mixture experiences the selected (ie, the desired or the tolerable) pressure loss when it passes through the catalyst bed. Another boundary condition which the reactor according to the invention in turn has in common with solid silos (see above) is that the catalyst flows in a mass flow between the inner and the outer catalyst basket. The known design principles for solid silos, here for the minimum discharge opening of a silo, can also be transferred here. In general, the smallest distance between the inner and the outer catalyst basket is at least four times, preferably at least ten times the largest main dimension of a single catalyst particle. Typically, however, to keep the overall height of the reactor within the range, a distance of at least one hundred times the largest main dimension of a single catalyst particle is used. In the case of spherical catalyst particles with a diameter of 2 to 3 mm, for example, a distance between the catalyst baskets of 300 mm is selected. The mixing of catalyst particles that are located in the catalyst bed near or between the cones. to improve those inside the catalyst bed and thus macroscopically standardize the catalyst, it may be useful to provide internals that promote this mixing; this is also well known from solid silos.

The height of the catalyst bed is chosen so that, given the thickness of the catalyst bed in the reactor, there is at least sufficient amount of catalyst available for the desired capacity of the reactor and the desired degree of conversion in the reactor. As already mentioned, the thickness of the catalyst bed can be varied over its height.

The reactor according to the invention is suitable for carrying out heterogeneously catalyzed reactions, equally for carrying out heterogeneously catalyzed reactions in the liquid phase, the gas phase, or the mixed liquid and gas phase. The reactor according to the invention is particularly suitable for carrying out heterogeneously catalyzed gas phase reactions. The particular advantages of the reactor according to the invention occur in particular in reactions with a high degree of heat and in reactions which are carried out at comparatively high temperatures. The reactor according to the invention in its embodiment is very particularly suitable as a moving bed reactor for carrying out heterogeneously catalyzed gas-phase reactions such as the reforming of hydrocarbons or the dehydrogenation of alkane hydrocarbons such as propane, butane, pentane, octane or ethylbenzene or hydrocarbon mixtures to give the corresponding alkenes or alkene mixtures.

To carry out a process according to the invention using the reactor according to the invention, the catalyst is filled into the catalyst bed and the feed mixture is passed at one or more inlet ports either into the central interior of the reactor or the exterior between the outer catalyst basket and the reactor wall. The feed mixture flows radially from the inside to the outside of the catalyst bed or from the outside in, and the product mixture, if the feed mixture has been passed from the inside to the outside, from the outside space between the outer catalyst basket and the reactor wall, or, if the feed mixture has passed from the outside to the inside was removed from the central reactor interior via one or more outlet ports. The lumpy catalyst used for the reaction is arranged in the catalyst bed. If the reactor is operated as a moving bed reactor, catalyst is removed from the reactor at the bottom of the catalyst bed from one or more catalyst outlet ports. At the top of the catalyst bed, one or more catalyst inlet ports in the same amount as that taken out below was filled into the catalyst bed. The catalyst moves from top to bottom through the reactor by gravity. The removal and the addition can be in individual portions, at certain time intervals or as required, for. B. when falling below a certain minimum activity, or continuously. The catalyst removed below is usually either regenerated or used in a further reactor in a multi-stage reactor cascade, in individual cases, for example if it can no longer be regenerated, it must also be disposed of. The average residence time of the catalyst in the reactor is set via the amount of catalyst withdrawn per unit of time. This average residence time is selected such that the catalytic properties of the catalyst filling are overall above satisfactory, reaction-specific values. If, for example, the activity of the catalyst deteriorates with its residence time, the residence time is adjusted so that the desired minimum conversion is achieved in the reactor at the reaction temperature used.

The process according to the invention for carrying out chemical reactions thus differs from known, comparable designs in known reactors, but without expansion spaces for the catalyst, processes carried out by the construction according to the invention of a catalyst basket or both catalyst baskets in the reactor used. Measures for carrying out the method according to the invention are therefore known, for example from the prior art documents cited herein, to which reference is hereby expressly made.

Preferred chemical reactions which are carried out with the process according to the invention in the reactor according to the invention are the dehydrogenation of hydrocarbons, the generation of synthesis gas and the reforming of hydrocarbons, in particular:

The catalytic dehydrogenation of propane to propene, for example with those from US-A-3, 584, 060, US-A-3, 878,131, US-A-4, 438, 288, US-A-4, 595, 673 , US-A-4, 716,143 or US-A-4, 827, 072 known or any other suitable catalyst and

• The catalytic dehydrogenation of ethylbenzene to styrene. Example: Determination of the length and height overlap of the cones, the cone angle and the distance of the cones with a model apparatus

Figures 4 and 5 represent a simple model arrangement for experimental testing of the selected parameters (length and height overlap of the cones, cone angle K, distance of the cones from one another, material). Figure 4 shows a section through a cuboid-shaped container (400 * 300 * 2019 mm ) with a floor discharge funnel (total height 2318 mm), which is made of the material chosen for the cones (here as example V2A steel). A slider is attached to the floor (not shown). One wall of this box, as shown in Figure 4 and is also evident in the front view of Figure 5, is formed by rectangular (300 * 170 mm) sheets arranged in the manner of a blind. The positions of the top and bottom edge of these sheets are given in Figure 4 in millimeters, measured from the top edge of the container. The angle between the sheet and the vertical (which corresponds to the cone angle) was 15 °, and the smallest distance between the sheets (which corresponds to the open passage between the cones) was 30 mm.

A solid porous aluminosilicate in the form of spheres with a diameter of 2 to 3 mm, an angle of repose of 17 ° and a slip angle on an inclined plane made of V2A steel was placed in this container with the slide closed up to the height of the upper edge of the discharge funnel as a model substance 10 ° (a commercially available so-called "molecular sieve"). A pressure sensor (water-filled fabric bag with hose) was placed in the middle of the device, and further molecular sieves were filled into the device in portions of 3-4 kg Build-up pressure was measured by means of the pressure sensor, which initially rose with the fill level, but reached a maximum value of 240 mm water column at a fill level of approximately 1000 mm, which remained constant even at higher fill levels due to the internal friction of the solid spheres Filling levels between the sheets arranged in the manner of blinds were 0-1 mm, measured in each case from the lower edge of the sheet, and showed no dependence on the height.

In a further experiment without a pressure sensor, solids were removed from the device in portions of approx. 3 kg on the slide and refilled at the top. The solid was completely circulated in this way, without showing a level dependence of the fill levels between the sheet-like arranged sheets. The corresponding parameters for the cones can be checked and optimized in a simple manner by changing the length of these sheets arranged in the manner of a blind, their angle of inclination, their number and their spacing from one another.

Claims

claims 1. Reactor for heterogeneous catalytic reactions, characterized in that expansion volumes for the catalyst are set up in at least one catalyst basket. 2. Reactor according to claim 1, characterized in that at least one boundary of the catalyst bed is formed by at least two staggered conical or truncated polygonal walls, between which there is at least one open passage. 3. Reactor according to claim 2, characterized in that the staggered walls are frustoconical. 4. Reactor according to claim 2, characterized in that the walls themselves are impermeable to the reaction medium. 5. Reactor according to one of claims 1 or 2, characterized in that the heterogeneous catalyst is moved through the reactor. 6. A process for carrying out heterogeneous catalytic chemical reactions, characterized in that it is carried out in the reactor defined in claim 1. 7. The method according to claim 6, characterized in that propane is dehydrated to propene. 8. The method according to claim 6, characterized in that dehydrogenated ethylbenzene to styrene. Sign.