BRPI0814196B1 - Process to perform an endothermic reaction, reactor to perform the process and its use - Google Patents

Description

Report of the Invention Patent for "PROCESS FOR CARRYING OUT AN ENDOTHERMIC REACTION, REACTOR FOR CARRYING OUT THE PROCESS AND ITS USE". The present invention relates to a process for performing an endothermic reaction in a reactor containing catalyst tubes, the catalyst tubes containing a catalyst that promotes the endothermic reaction. DE-10229661-A describes a process for the dehydrogenation of alkanes, which is an example of an endothermic equilibrium reaction. This document describes a process in which pipes containing a catalyst are heated by burners positioned between the pipes. By controlling the heat produced by the burners, a desired temperature profile along the length of the tubes is considered to be imposed to achieve a continuous high rate of selectivity and conversion. However, no concrete description is provided of how much this should be done in practice. Additionally, the use of burners in the vicinity of the catalyst pipes causes radiant heating of the pipes, which can give rise to hot spots, requiring high cost high temperature resistant pipe material and causing local coke formation which will require frequent catalyst regeneration which may lead to clogging of the pipes. As an additional problem associated with high local temperature, additional unwanted side reactions may occur. The object of the present invention is to provide a process for performing an endothermic equilibrium reaction that produces a favorable temperature profile along the reaction tubes, preventing local hot spots. The objective is achieved according to the invention in that the process comprises the steps of bringing the catalyst contained in the catalyst tubes into contact with a feed stream passing through the channels from an inlet end to an outlet end. , of contacting an external surface of the catalyst tubes with a flow of a heating medium having an initial heating temperature and flowing co-simultaneously with the feed stream to heat the surface by convection, of mixing at least part of the medium. after contacting the catalyst tubes with a strong heating medium flow having a higher initial temperature than the initial heating temperature to form the cosimultaneous heating medium having the initial heating temperature.

By using convective pipe heating in combination with partial recirculation of the heating medium, an initial heating temperature can be guaranteed which is below a maximum level so that common and lower cost materials such as stainless steel can be used for the pipes. The present process allows the control of the flow rate and the initial heating temperature of the heating medium independently, so that the temperature profile along the pipes can be very precisely controlled. In addition, said flow rate and said initial heating temperature in combination with tube dimensions may be chosen such that an axial temperature profile along the tubes can be achieved. The catalyst contained in the catalyst tubes is contacted with a feed stream passing through the tubes from an inlet end to an outlet end. With the path through the tubes, the feed will be converted to the desired product.

Preferably, the feed stream is subjected to a critical pressure drop at the inlet end of each tube. This prevents different rates of feed flow through different tubes. Lower flow rates in some tubes will cause higher temperatures in these tubes, potentially even unwanted high temperatures causing catalyst degradation and unwanted side reactions in these tubes. Coke formation is one of these unwanted side reactions and will additionally slow down the flow rate and ultimately cause the tube to clog.

Process-applicable catalysts according to the invention are essentially particulate catalysts, which are preferably present as a layer in the tubes. Thereafter, it will be assumed that the reactor tubes run vertically and the cosine simultaneous flows of feeds and the heating medium flow upwards from the bottom, indicated as bottom or inlet, to the top of the tubes, top or outlet. . It is also possible to carry out the process of the invention with said flows running co-simultaneous in a downward direction or to apply a reactor in which the tubes run horizontally or at an angle to the horizontal plane. The initial heating temperature of the heating medium is considerably higher than the temperature of the feed entering the catalyst tubes. The enthalpy of the heating medium will be sufficient to compensate for the heat consumed by the endothermic feed reaction and to heat the feed / product mixture in the tubes. The temperature difference between the heating medium and the tube contents is the driving force for this heat exchange. This difference will decrease along the inlet to outlet pipes and so that the heat transfer rate will decrease from inlet to outlet. Since the remaining amount of unconverted power will also decrease from input to output, less compensation heat is also required. Preferably, the flow rate and the initial temperature of the heating medium are chosen such that the temperature of the tube contents decreases along the bottom to top tube and more preferably is chosen such that said temperature. continuously increase along the tubes. The flow rate and the initial temperature of the heating medium will be chosen such that the temperature of the tube walls and the tube contents at its outlet end remain below a temperature where product feeding or decomposition may occur, coke formation and other unwanted side reactions.

In the process according to the invention, the reaction at the inlet of the pipes will run at a high rate due to the presence of the highest amount of unconverted feed. The high initial temperature of the heating medium will compensate for the heat consumed and even raise the temperature of the tube contents. Due to the additional continuous heating over the length of the tube, the reaction strictly follows the increasing equilibrium conversion, resulting in the high feed conversion at the outlet end. The higher temperature the catalyst can withstand, in fact, is the main limiting factor in achieving full conversion. In the present process, the main part of the feed is already converted to relatively low temperature and the selectivity of the reaction appeared to be high.

Also with a suitable choice of initial heating temperature and flow rate, a situation can be achieved in which the temperature of the pipe walls is approximately constant over most of its length.

Preferably, the feeds are preheated to a minimum temperature necessary for the catalyst to be active before being in contact with the catalyst. This temperature causes the reaction to start already running at a high rate at the inlet end, the rate being driven by the distance to equilibrium at the control temperature and with less risk of unwanted side reactions than at a higher inlet temperature. . With the upward movement, the feed temperature, gradually mixed with a larger amount of product formed, and the catalyst will increase by heat exchange with the heating medium, this temperature rise favoring the reaction rate even as where the reaction was considered to follow the increasing equilibrium conversion with increasing temperature, giving an optimal total conversion.

It has been found that the conversion efficiency of the process may even be enhanced when bottom-to-top catalyst tubes are filled with layers of at least two different catalysts, where the nearest bottom catalyst is selected for its relatively high activity, whereas a relatively lower temperature resistance or a relatively low level of another temperature dependent catalyst property may be accepted, and the nearest top catalyst is selected for its relatively high temperature resistance or a relatively high level of another temperature property. temperature-dependent catalyst, while relatively lower activity may be accepted. If more than two catalyst layers are used, the temperature resistance or level of another temperature-dependent catalyst property of the layers will increase from bottom to top, if some decreases in their bottom-to-top activity are inevitable. This allows optimal use of the temperature controlled profile along the pipes, obtaining the highest possible conversion and possibly also selectivity. Relativity is used here with respect to adjacent layers. The controlled temperature range over the pipes allows the application of heat sensitive catalysts in the process according to the invention. Everywhere the process according to the invention protects the high catalytic activity for a long period.

To improve the conversion selectivity and catalyst life cycle, the feed stream may be diluted with an inert gas, for example carbon dioxide, nitrogen or steam, steam being preferred. If diluted, the dilution rate will depend on the reaction performed on the tubes and in practice will range from 0.1 or 2 to 12 mmol inert gas per mol feed.

It is also possible to add from 0.01 to 1 mol of H2 per mol per mol feed instead of an inert gas, for example when the catalyst used is not compatible with inert gases. The heating medium, which flows along the pipes, will transfer heat to the pipe walls, which in turn will transfer heat to the catalyst and the feed. When this flow of heating medium reaches the top of the tubes, it will have been cooled from the initial heating temperature to a lower temperature. As described later, some of the heat energy still present in the medium may be used to generate steam or for other process heat integration purposes, which will cool the medium further. At least part of the cooled medium will be recirculated to control the initial heating temperature of the heating medium. This can be done by mixing the newly generated heating medium, for example flue gas from a burner or strong steam. This strong medium will generally have a higher temperature than the initial heating temperature. By mixing it with a controlled amount of the heating medium, which has been cooled by being brought into contact with the catalyst tubes, and optionally also by an additional heat exchange, for example to generate steam, the medium Strong cosimultaneous heat is formed having the desired initial heating temperature.

Another way to achieve the desired initial heating temperature, applicable when strong heating medium is generated by a burner, is to apply the cooled heating medium recirculated through the burner to mix it with the flue gas immediately. when it is generated by combustion. The strong heating medium may be steam, but preferably the strong heating medium consists of flue gases from a burner, for example a gas or oil burner. The amount of flue gas produced by such a burner can be easily controlled, which allows for versatility in the ratio of strong heating medium to recirculated cooled heating medium in order to obtain the heating medium with the desired initial heating temperature and temperature. flow rate for contact with catalyst tubes again. The process according to the invention allows the temperature to be maintained over the entire length of the pipes between a maximum temperature where catalyst degradation and undesirable side reactions can occur and a minimum temperature required for the reaction to run at an acceptable speed. .

In the process according to the invention the amount of hot burner gases and the amount of cooler recirculated consumed heating medium can be independently controlled. This provides great versatility in both the flow rate and the initial temperature of the heating medium independently, allowing control of the heat exchange profile over the length of the catalyst tubes over a wide range. In the known process, the relationship between fuel gas and combustion air is the only control parameter. This only allows for limited variation in flow rate and temperature, as variation in the amount of air is restricted by the minimum amount of oxygen required to burn the fuel gas.

In the process according to the invention, no radiant heating of the catalyst tubes by the burner will be permitted by the proper positioning of the burners with respect to the catalyst tubes, by the positioning of shields between the burner flames and the catalyst tubes, by the isolation of the burners. catalyst tubes at the points exposed to radiation, or by combinations of these measures. The heating of the catalyst tubes then occurs through convective heating only.

The tubes in the reactor may be conventional reforming tubes as known from DE-A-10229661. Such tubes may be applied as catalyst tubes in the process according to the invention, preventing radiant heating and its associated problems. However, they do have a serious exchange in catalyst volume and transfer properties. To prevent unwanted radial temperature gradients, their diameter should be relatively small. This will require a large number of tubes to obtain a desired catalyst volume. Also, catalyst replacement is a tedious process.

These and other problems associated with known tubular reactors have been found to be solved in a preferred embodiment of the process according to the invention by applying a panel reactor as described below. The process according to the invention is suitable for carrying out endothermic reactions. Examples of this type of reaction that can be performed with favorable results with this process include endothermic equilibrium reactions, for example dehydrogenation of C2 -C6 alkanes to olefins (eg ethylene, propylene and isobutylene), dehydrogenation of mixtures of C 2 -C 6 alkanes and olefins to diolefins (eg, butadiene and isoprene), dehydrogenation of ethylbenzene to styrene and non-oxidative dehydrogenations of alcohols to aldehydes (eg methanol to formaldehyde and ethanol to acetaldehyde) and carboxylic acid dehydrations C2 to Cs to their intramolecular anhydrides, and irreversible reactions, for example, higher olefin catalytic cracking to lower oleofine content.

One reaction which has proved very suitable to be carried out with the process according to the invention is the dehydrogenation reaction of a hydrocarbon with one or more saturated carbon bonds, in particular a C2 -C8 alkane such as ethane, propane, (iso) butane, (iso) pentane, hexane, heptane and octane, and ethylbenzene. These reactions run with a higher conversion at higher reaction temperatures. The maximum allowable reaction temperature is limited by the catalyst which may decompose or lose its activity at high temperature. In practice, temperatures of about 500 to 750 ° C are applied, thus benefiting most from the continuous heat supply by the heating medium over the entire length of the reaction tubes. Higher temperatures may be used when available catalysts allow it. The execution of the process according to the invention imposes specific requirements on the reactor. Accordingly, the invention further relates to a reactor for performing an endo-thermal equilibrium reaction process comprising a heat supply section containing a heat supply means, the heat supply section communicating with one end. of a reactor section, the reactor section containing catalyst tubes and having an outlet end communicating with a head space section, the catalyst tubes being protected from heat radiation by the heat generating means, the reactor additionally comprising a recirculation section that connects the head space section to the heat supply section. The reactor comprises a heat supply section. In this section, the heating medium flow is prepared to supply the required heat to the catalyst tubes. The heat supply means may comprise one or more burners for generating flue gas. These means may also be a steam inlet of suitable temperature. Additionally, this section contains, as a connection to the recirculation section, an input for the recirculated consumed heating medium. The recirculated heating medium inlet may be connected to the heat supply section in a downstream position from the burner or steam inlet. It can also be connected so close to the burner so that the heating medium immediately mixes with the strong combustion gas. The heat supply section communicates with an inlet end of a descending reactor section. Communication here indicates that there is an open connection for the heating medium flow. At the same time, the catalyst tubes are protected from radiant heating by the heat generating means. Radiant heating of the catalyst tubes can produce local hot spots that should be avoided. To achieve this protection, an optically closed path from the burner flames to the catalyst tubes may be provided. For this purpose, the heat supply section and the reactor section may be positioned at a certain angle, preferably by a 90 ° bend, or baffles may be provided between the heat supply and reactor section, leaving a pathway. to the heating medium, but blocking any direct optical path to the burner radiation catalyst tube. Another way to prevent radiant heating of the catalyst tubes is to thermally insulate those parts of the catalyst tubes that face the burner flames. The reactor additionally comprises a reaction section. This reaction section contains reactor tubes to be filled with catalyst particles that can promote the endothermic reaction to be conducted in the reactor. Reactor tubes generally run parallel to a length axis of the reactor and generally also in a substantially vertical direction.

A known concept for such reactor tubes is the known multitubular reactor, which comprises a bundle of parallel tubes. Each tube is individually connected to a feed line that provides a feed stream for a product line to remove formed product from the reactor for further processing. The reaction section may further comprise a means for creating a desired flow pattern of the heating medium along the catalyst tubes, for example in the form of baffles. The reactor according to the invention has an inlet end connected to and communicating with the heat generation section through which the heating medium can enter the reaction section for heating the catalyst tubes. The reactor section also has an outlet end positioned opposite the inlet end beyond and upstream of the catalyst tubes connecting the reactor section to a head space section. The head space section is designed to collect the consumed heating medium, that is, the heating medium after it has passed and left the reactor section. It may contain heat exchange equipment to further divert heat from the heating medium consumed, for example to generate steam or to preheat the feed. The head space section has at least one connection to a recirculation section. This recirculation section connects the head space section to the heat supply section. It may comprise a means for controlling the amount and temperature of the consumed heating medium to be supplied to a heating section inlet. The head space section may additionally comprise an outlet for the consumed heating medium that is not recirculated to the reactor heating section. This output can be connected to the equipment to additionally benefit from the thermal energy still remaining in the consumed heating medium.

Preferably, the heat supply means is at least one burner. The temperature of the flue gas heating medium is then controlled either by mixing the flue gas with the recirculated consumed heating medium of the chiller or by feeding the recirculated consumed heating medium in such proximity to the burner flame that the flue gas will be diluted and cooled immediately. In the latter case also the NOx content of the flue gas heating medium may be reduced. The ratio of recirculated heating medium to high flue gas will be chosen to obtain the heating medium having the desired temperature and flow rate. In practice, ratios of 90% 10% to 10% - 90% will apply. The reactor will further comprise means for distributing the feed to the catalyst tubes and for collecting the formed product from the tubes. It may also comprise a means for evenly distributing the heating medium over the reactor tubes to prevent local hot or cold regions in the reactor. The reactor will also comprise a means for supplying a feed stream to the reaction tubes, connected to an external supply line, and a means for conducting a mixed feed product stream from the reaction tubes, connected to a line. of product.

In a preferred embodiment, the product line and feed line are connected to a heat exchanger for heat exchange between the feed stream and the higher temperature product stream. This construction has the advantage that the temperature of the feed stream will remain in a safe range preventing coke formation and other unwanted side reactions.

Preferably, the reactor according to the invention comprises reactor panels comprising channels acting as catalyst tubes.

In this case, the reactor additionally comprises a feed line and a product line and the reactor section contains reactor panels, each reactor panel comprising a feed collector, a product collector and adjacent channels, each channel having a length, which runs from an input end to an output end, and where the input ends are directly connected to and open to the power manifold and the output ends are directly connected to and open to the product manifold, and wherein the feed manifold has at least one connection to a supply line and the product manifold has at least one connection to a product line and in which part of at least one of the manifolds, the feed manifold or the manifold product is detachable giving access to the ends of the channel.

The panels in the reactor will be positioned between the inlet end and the outlet end of the reactor reaction section and can be separately and easily exchanged, the panels allowing great versatility in dimensions and giving great flexibility in applying heating media to obtain desired temperature profiles along catalyst tubes.

Instead of a single tube bundle as in the known multitubular reactor, the required reaction volume can be constructed from numerous reactor panels, each featuring a power inlet and a power outlet for multiple channels rather than for each. single tube and being easier to handle, maintain and replace the catalyst. Increasing reaction volume does not require the connection of more and more single tubes to the supply and product lines, but can simply be achieved by adding more panels or other panels.

The reactor channels are manually connected. In this way they form a unit having a higher stiffness against curvature that allows a panel to hang on the reactor, only supported at an upper end.

The inlet ends of the channels are directly connected to and directly open to the feed manifold, which should be understood to be an open connection through which feed manifold reagents can enter the channels, the end channel inlet being visible from inside the collector. It should be understood directly, therefore, as containing no intermediate construction elements such as siphon tubes, bellows, tubes and the like, but only a direct connection medium such as bolted flanges and welds.

Preferably, the inlet end of each catalyst tube is provided with a flow restricting means suitable for imposing an almost critical pressure drop on a feed stream entering the tube. This will ensure a constant feed flow rate to the channels even when the channels do not have exactly the same pressure drop. The difference in pressure drop may occur due to differences in catalyst filling or packing within considerable ranges and may also occur during coke operation. Almost critical pressure drop is defined as the pressure drop that causes the flow rate to be at least 50%, preferably at least 70, more preferably at least 80% of the critical flow rate. The reactor may additionally contain shielding means to prevent direct exposure of the panels to the reactor walls which may cause temperature differences between the panels closest to the walls and other panels. These shielding means may then be temperature controlled separately from the other panels. An example of such shielding means are panels such as those containing the catalyst but not containing the catalyst and being internally cooled.

Additional details, specifications, alternative and preferred embodiments and advantages of panels with means for providing catalyst channels are described in the publication based on copending EP Priority Document No. 07013192.5, the contents of which are incorporated herein by reference.

At least one of the collectors, the feed collector or the product collector, is completely or partially detachable, thus giving access to the ends of the channel.

A partially detachable collector may comprise an opening locked by a detachable part. The part may be hinged to a collector edge that may be brought into an open position or may be a loose part that may be attached to and removed from the opening. The part must be gas and liquid tight, pluggable to the manifold and preferably also easily removable. The connection can be established by pinning the detachable part to the manifold, but the part can also be welded to the manifold and grounded along the weld line to detach the part.

After detaching the detachable part, the opening gives access to the ends of the channel. This allows for easy emptying, cleaning and refilling of the channels. Preferably, such an opening is present in both the feed collector and the product collector. This allows the channels to be emptied through one collector, the positioning of the panel such that this collector is in a lower position than the other collector, and the refilling of the channels from above through the other collector, keeping the panels in the same position. The opening may be present in a collector wall facing the ends of the channels or in a wall normal to the length direction of the channels. The foregoing embodiment of these two is preferred as conferring the easiest access.

The channels preferably are arranged at most in two rows, each row defining a flat or curved plane, the planes running substantially parallel. In this way the panels remain thin in a first dimension and provide a large area for heat exchange with respect to their volume. Preferably, the channels are arranged in a straight or curved row to fit the shape of the reactor housing into which the panels will be placed. The feed and product collectors then follow the shape of the channel row. In this way the panels are flattened and, when arranged in parallel at a suitable distance in the reactor, the channels can be easily accessed by a heating medium that flows into the space between the panels, allowing precise temperature control of the channels over their lengths. . The panel can be constructed simply and economically, for example from basic elements such as pipes, bent plates, fittings, sheets and construction techniques commonly known as welding, bolt joints and others.

Preferably, the reactor according to the invention contains reactor panels, the reactor panel being composed of a first and a second parallel plate bounded by a first pair of substantially parallel outer edges and a second pair of outer edges that connect the edges of the first pair, wherein at least the first plate comprises alternating flat connecting strips and channel recesses having an inlet end and an outlet end, the strips and recesses running normal to the first pair of edges in the wherein the plates are connected to each other at least along the second pair of outer edges and the connecting strips, combining the channel recesses of the first plate and the turned part of the second plate in the channels, the panel additionally comprising a feed manifold, a product collector and adjacent channels, each channel having a length running from an inlet end to an outlet end, and where the input ends are directly connected to and open to the power manifold and the output ends are directly connected to and open to the product manifold and where the power manifold has at least one connection to one supply line and the product collector has at least one connection to a product line and in which part of at least one collector, the feed collector or the product collector is detachable, giving access to the ends of the channel.

The channels are present as a combination of a channel recess of one plate and the opposite part of the other plate. This part may be a channel recess, a flat strip or another flat part of that other plate.

The channels are intended to be filled with catalyst particles such that voids running along the entire length of the channel are prevented as much as possible. In this way, fluid entering the channels at the inlet end is prevented from reaching the outlet end without being sufficiently in contact with the catalyst and remaining unreacted. Although the cross section of the channels may have any shape, for the above reason, the cross section of the channels preferably has a smooth and even shape without sharp angles. Examples of such shapes are circular, elliptical or polygonal shapes with rounded edges.

The building elements that make up the panels must consist of materials that match the reaction and process conditions and components to which they will be exposed. Known materials for use under chemical reaction conditions are metal, metal alloys and ceramic materials. It is also known in the art to apply backing layers. One skilled in the art will be able to select the appropriate materials for their intended use. Preferably, the material shows sufficient heat conductivity.

The dimensions of the panels are mainly determined by the length and number of the channels. These values may vary widely, depending on the type of reaction, production capacity, size and type of catalyst for which it is intended. Since a major advantage of the panel is its modular character, each panel can be considerably smaller in size than a single tube multitubular bundle required in a reactor for the same reaction and having the same production capacity as a corresponding large amount of panels. The cross-sectional area of the channels will depend on the catalyst type and reaction. The more endothermic the reaction runs, the smaller this area will have to be to prevent a non-homogeneous reaction profile, in particular large radial temperature gradients, in the catalyst layer and to ensure sufficient heat transport from the catalyst layer to or of the canal walls. In practice, said area will be between 5 and 300 cm2. Preferably, the area is less than 200,100 or even 50 cm 2.

More critical than the channel area is the smallest linear dimension of a channel cross section. Preferably, the shortest linear distance from any point of the channel cross-sectional area to the channel wall is at most 3.5 cm. More preferably, this distance is at most 2.5 cm. The shape of the channels can be circular, ellipsoidal or other smooth and regular shapes without sharp corners.

The channels do not have to be too flat in shape to allow the desired flow within it. For this purpose, as a rule of thumb, the longest of all shorter linear distances should preferably be at least 1 cm when a solid catalyst is used and at least 2 mm when a gaseous catalyst is used. The length of the channels may vary within wide limits, the upper length being potentially restricted by pressure drop over the length of the channel. This pressure drop may also depend on the type and density of the catalyst layer. Suitable lengths will range from 0.5 to 10 meters. The wall thickness of the channels, this thickness being the thickness of the plates in case the panel is constructed of two parallel plates, will be sufficient to withstand mechanical forces exerted on it, for example by differences in pressure, gravity or mounting activities. . At the upper limit, the thickness will be substantially limited for panels according to the invention composed of two parallel plates by the requirement that the plates may be formed by common techniques. The practical thickness may range from 0.5 to 5 mm.

Correspondingly, the dimension of the panel will be determined by the sum of the dimensions of the composition parts. As an example, this dimension in the channel length direction will be at least equal to the channel length plus the height of the feed and product manifolds in that direction. Also, the thickness of the panel that is its normal dimension to the channel length direction will be at least equal to the channel diameter in that direction plus the channel wall thickness and the thickness of any sheets on the outer surface.

This panel can be constructed easily and with high versatility by known techniques, for example for the manufacture of central heating radiator panels or in the automotive industry. The formation of metal plates in the desired shape and profile, for example by hot pressing, allows to produce plates having complex shape and profile patterns. In another suitable process for constructing this panel, known as hydraulic cold pressing, two flat plates are welded together at the edge position and at all other positions where the plates will be connected to the panel to be formed and applying hydraulic pressure between the two. plates in order to inflate the non-welded parts to the required channels and manifolds.

Additional details, specifications, alternative and preferred embodiments and advantages of these panels as a means for providing catalyst channels are also described in the publication based on copending EP priority document No. 07013192.5, the contents of which are incorporated herein by reference.

Also the reactor according to the invention offers great versatility with respect to heat exchange properties. The relative position and distance of the panels can be freely chosen allowing to create an ideal and effective heat exchange flow between the panels and the heating medium. Thus, the reactor according to the invention has the advantage that no deflector is required to create a desired heating medium flow pattern in the reaction section along the panels. As an additional advantage of the reactor according to the invention, in case of channel obstruction, leakage and other incidents, only the panel involved has to be removed from the reactor and replaced or simply eliminated before production can be resumed. Catalyst repair or replacement can be done by off-line panel while production is continued. In the known reactor comprising a single tube bundle, production is stopped until catalyst repair or replacement is completed. In order to allow easy removal of the panels, the reactor part above the reaction section is preferably at least partially detachable.

Preferably, the panel connection to the power line is flexible in that differences in thermal expansion between the panels and the power line connection can be absorbed, thus minimizing stresses. Constructive elements for achieving this flexibility are known in the art and, as an example, it may be mentioned that the feed line contains a pigtail shaped tube piece or a bellows shaped connecting piece.

Panels will generally be positioned vertically in the reactor. The channels then run substantially vertically and the collectors will run essentially horizontally. The panels will generally be arranged in parallel at a distance from each other. This distance may depend on the flow rate of heating medium designed for the required heat transfer and may range from 1 mm to 3 cm. Larger distances are possible, but have proven to be less efficient for heat exchange and also require a higher heating medium flow. The distance between the panels indicated herein is the shortest normal distance between two adjacent parallel panels, measured between the channel of one panel to the opposite channel or strip of the adjacent panel.

The panels can be mounted inside the reactor supported by but not attached to the reactor housing constructive elements. The reactor housing is the total of the building element that shields the room's internal reactor volume and will have the normal and known properties of a reactor housing adapted to match reaction control and heat exchange conditions. In particular, the housing comprises at least the heat generation section, the reactor section and the head space section.

Preferably, the panels may move relative to the housing upon retraction or expansion. This prevents thermal stresses from occurring between the panels and the housing.

Preferably, the panels are hung only at their largest end. This allows thermal expansion or shrinkage of the panels, only causing minimal stresses that extend the operating life and reliability of the panels, and thus of the reactor as a whole. The invention further relates to the use of the reactor according to the invention to conduct the process according to the invention.

In particular, the invention relates to the use of the reactor according to the invention, comprising reactor panels of the construction described for the dehydrogenation reaction of a saturated hydrocarbon or ethylbenzene, in particular of C2 -C8 alkanes. The invention will be further explained by the following drawings. In these drawings: Figure 1 is a cross section of a first embodiment of the reactor according to the invention containing tubes, such as reactor tubes; Figure 2 is a cross section of a second reactor embodiment according to the invention containing reactor panels; Figure 3 is a cross section of a third reactor embodiment according to the invention containing reactor panels; Figure 4 is a graph showing the temperature profiles of the heating medium, wall and feed / product flow along the reactor length; and Figure 5 is a graph showing the equilibrium conversion line and the effective conversion line in a reactor catalyst tube according to the invention.

Figures 1, 2 and 3 show a reactor having reactor wall 4. The reactor comprises a heat supply section 6, an input end 8 for reaction section 10, an output end 12 of reaction section 10, a head space section 14 and a recirculation section 16, comprising ducts 18 and 20 and the compressor 22.

In Figure 1, reaction section 10 contains reactor tubes 24 at the inlet end of the reaction section connected to feed line 26 and at its opposite end to production line 28.

In Figures 1, 2 and 3, heat supply section 6 is positioned at an angle of 90 ° to reaction section 10. This construction protects the reactor tubes from heat radiation generated by heat generating means 30. Heat generating means 30, in this embodiment, is a burner connected to a fuel inlet 32 and a combustion air inlet 34. The head space section 14 is connected to the used heating medium outlet 36 which leads to an external heat recovery section (not shown). It is also connected to duct 18 of recirculation section 16, which in turn is connected to compressor 22. The output of compressor 22 is connected by duct 20 to heat generation section 6, where the recirculated medium will be mixed with the strong heating medium produced.

In Figure 2, item 40 is a reactor panel, viewed from a front side, which is freely hung from reaction section 10 with its product manifold 44 resting on the support protrusions 46 attached to reactor wall 4 Supply manifold 48 is connected to supply line 26 and product manifold 44 is connected to product line 28. Panel 40 comprises catalyst channels 50. Duct 20 is introduced into heat generation section 6 through bottom of the burner 30, thus allowing mixing of the recirculated used heating medium with the strong heating medium immediately upon generation of the latter. Numbers not mentioned have specifically the same meaning as in Figure 1.

In Figure 3, the heat generation section 6 is positioned vertically below the reaction section 10. In the reaction section 10, numerous reactor panels 40 are located, viewed separately. The bottom of the feed manifolds 48 of the reactor panels 40 is lined with layers 52 of heat insulating material to protect the burner facing portions of the panels 30 from the heat radiation of that burner 30, here an arrangement of small burners. Numbers specifically not mentioned have the same meaning as in Figure 1. Figure 4, where the X axis indicates the relative length of the input end reactor (0) to the output end (1) and the Y axis indicates the temperature. in ° C, shows three temperature profiles from the inlet to the outlet end of the reaction zone in a reactor as described in Figure 3, where the propane to propylene catalyzed dehydrogenation reaction is conducted under the conditions as described in Example 1. Line 70 shows the temperature profile of the heating medium as it flows from the input side of the reaction section to the output side of it and is cooled as it transfers heat to the heating channels. catalyst. Line 72 shows the corresponding temperature profile for the wall of the catalyst channels that absorb the heat from the heating medium flowing therethrough. Curve 72 shows the temperature rise that results from heat absorption from the heating medium and heat transfer to the feed / product flow in the catalyst tubes. Line 74 shows the corresponding temperature profile for the feed / tube contents resulting from the heat transfer by the wall of the catalyst channels and the heat consumed by the endothermic reaction in the catalyst channels. Wall temperature shows a very moderate variation in pipe length that prevents thermal and mechanical stress in reactor construction and prevents local hot spots.

In Figure 5, where the X axis indicates the temperature in ° C and the Y axis indicates the conversion, line 76 is the equilibrium conversion line of the propane to propylene dehydrogenation reaction. Line 78 shows the effective conversion along the length of the catalyst channels from the inlet end to the outlet end of the reaction section as a function of increasing feed / conversion flow temperature (according to line 74 of Figure 4). In the first quarter of the temperature range, the conversion is mainly driven by the large amount of unconverted power present, and in the last quarter, the highest temperature is the main drive force. As a total result, almost equilibrium conversion at the highest temperature is achieved. Maximum conversion is restricted by the maximum allowable temperature in view of catalyst degeneration or unwanted side reactions. The invention will be explained by, but not limited to, the following examples.

Example 1: Propane Dehydrogenation In a reactor, as shown in Figure 3, where the catalyst channels of the reactor panels are filled with an alumina conductor Pt / Sn as catalyst, the propane is dehydrogenated in propylene.

A vapor and propane mixture (3.5 mol / mol vapor-propane ratio) having a temperature of 550 ° C and a pressure of 0.25 MPa is supplied to the LHSV reactor panel feed manifolds of 1, 5 m3 propane / m3 cat h. After passing through the catalyst tubes, the feed / product effluent mixture has a temperature of 630 degrees and a pressure of 0.15 MPa. The heating medium is supplied to the inlet end of the reaction section with a temperature of 1000 ° C. After passing the reaction section, the heating medium used has a temperature of 715 ° C. The catalyst channel wall temperature at the inlet end is 565 ° C, at the outlet end 635 ° C. Propane conversion makes up 72% and propylene direction selectivity makes up 89%.

Claims (11)

Process for performing an endothermic reaction in a reactor containing catalyst tubes, catalyst tubes containing a catalyst that promotes the endothermic reaction, the process comprising the steps of: a. contacting the catalyst contained in the catalyst tubes with a feed stream passing through the channels from an inlet end to an outlet end, b. contacting an external surface of the catalyst tubes with a flow of a heating medium having an initial heating temperature and flowing co-simultaneously with the feed stream to heat the surface by convection, c. mix at least part of the heating medium after contacting the catalyst tubes with a strong heating medium flow having a higher initial temperature than the initial heating temperature to form the cos simultaneous heating medium having the initial heating temperature. Process according to Claim 1, characterized in that the feed stream is subjected to a critical pressure drop at the inlet end of each channel. Process according to Claim 1 or 2, characterized in that the strong heating means are flue gases from a burner. Process according to any one of claims 1 to 3, characterized in that the endothermic equilibrium reaction is a dehydrogenation reaction. Process according to Claim 4, characterized in that the dehydrogenation reaction is carried out in a hydrocarbon, preferably a C 2 -C 6 alkane or olefin or ethylbenzene. 6. Reactor for performing an endothermic reaction process, characterized in that it comprises a heat supply section containing a heat supply means, the heat supply section communicating with an inlet end of a reactor section, the reactor section containing catalyst tubes and having an outlet end communicating with a head space section, the catalyst tubes being protected from heat radiation from the heat generating means, the reactor further comprising a recirculation section. connecting the head space section to the heat supply section, the heating of the catalytic pipes only by convection heating, Reactor according to claim 6, characterized in that the heat supply means comprises at least one burner, Reactor according to claim 6 or 7, characterized in that it further comprises a feed line and a product line and in which the reactor section contains reactor panels, each reactor panel comprising a feed manifold. , a product manifold and adjacent channels, each channel having a length, which runs from an inlet end to an outlet end, and wherein the inlet ends are directly connected to and open to the feed manifold and the output ends are directly connected to and open to the product manifold where the power manifold has at least one connection to a power line and the product collector has at least one connection to a product line and to which part of at least one collector, the feed collector or product collector, is detachable, giving access to the ends of the channel. Reactor according to any one of claims 6 to 8, characterized in that the inlet end of each catalyst tube is provided with a suitable flow restricting means to impose a critical pressure drop on a feed stream that is in enter the tube, Use of the reactor as defined in any one of claims 6 to 9, characterized in that it is for conducting the process as defined in any one of claims 1 to 5. Use of the reactor as defined in claim 8 or 9, characterized in that it is for conducting the process as defined in one of claims 4 or 5.