WO2014108351A1

WO2014108351A1 - Device and method for the continuous reaction of liquids with gases

Info

Publication number: WO2014108351A1
Application number: PCT/EP2014/050043
Authority: WO
Inventors: Oliver Bey; Christian Kunkelmann; Roland Bauer; Patrick HÜBLER; Peter Zehner
Original assignee: Basf Se
Priority date: 2013-01-11
Filing date: 2014-01-03
Publication date: 2014-07-17

Abstract

The invention relates to a device of the loop-Venturi reactor type for the continuous reaction of liquids with gases, in particular for hydrogenation, oxidation or acetylation, e.g. for the production of diaminotoluene by the hydrogenation of dinitrotoluol. The invention also relates to a method for the continuous reaction of liquid reactants with gaseous reactants in the device. The device according to the invention comprises one or more eductors, each of which has a diffuser.

Description

Description: The present invention relates to a loop venturi type reactor for the continuous reaction of liquids with gases, in particular for hydrogenations, oxidations or acetylations, e.g. for the preparation of toluenediamine by hydrogenation of dinitrotoluene and a process for the continuous reaction of liquid reactants with gaseous reactants in the device. The device according to the invention comprises one or more ejectors, each comprising a diffuser.

In many chemical processes, gas-liquid mass transfer and heat removal performance are the rate-limiting steps. Thus, in the customary production of aromatic mono- and / or polyamines by reaction of the corresponding nitro compounds with hydrogen, a considerable amount of heat is released. The same applies to many other hydrogenations, oxidations or acetylations. Measures for improving the heat removal performance are known per se from the prior art.

In EP-A-634 391 a process for the hydrogenation of aromatic polynitro compounds is described, in which a loop Venturi reactor is used with an ejector (loop reactor with Venturi nozzle). The process is based on special conditions such as the exact circulation volume ratio, the energy input, a precisely adjusted hydrogen volume flow, which on the one hand by-products should be avoided and on the other hand, the heat released can be used to generate steam. In this method, due to the location of a heat exchanger to remove the heat of reaction outside the loop reactor, in the ejector and in the reactor to local overheating with immediate onset of side reactions such as nuclear hydrogenation, hydrogenolytic cleavage or formation of high molecular weight, tarry products, the catalyst surface prove, come. In addition, in the reactor volume outside the ejector, a bubble column characteristic which is pure with respect to the flow and residence time behavior sets in, in which random small and large-scale vortices with comparatively low mass transfer performance occur. A substantial improvement in the hydrogenation yield, the hydrogenation selectivity and the space-time yield is thus hardly achieved in this process. In addition, the catalyst is subjected to high mechanical stresses by pumping the entire reaction mixture, which in turn leads to a reduced service life of the catalyst.

As a reactor particularly suitable for the removal of the heat of reaction, therefore, WO 00/35852 has proposed a reactor with internal and external circulation flow (so-called internal and external loop), which is designed as a vertically upright apparatus, with a propulsion jet nozzle at its upper end, via which in the upper region of the reactor the reaction mixture withdrawn from the reactor sump is injected via the external loop, and which then flows into a central insertion tube, which is arranged in the longitudinal direction of the reactor, flows through this from top to bottom and in an inter- NEN loop movement outside the insert tube again flows upwards. For the removal of the heat of reaction field tubes are proposed in the reactor interior.

Field tube heat exchanger denote in a known manner heat exchangers having a bundle of parallel double-walled tubes, said projecting into the reactor chamber ends of the outer tubes closed and the corresponding ends of the inner tubes are open, such that the cooling medium via a arranged outside the reactor chamber feed space into the inner tubes flows in and flows out through the space between the inner and outer tubes and a discharge space. They are characterized by a high ratio of heat exchanger surface to volume of the reaction space and are thus particularly suitable for removing the released heat of reaction.

EP-A 1 140349 discloses a reactor for gas-liquid or gas-liquid-solid reactions in hochzylindrisch design with a arranged in the upper reactor region, downwardly directed jet nozzle through which the reactants and the reaction mixture are fed and with a trigger in the lower reactor region over which the reaction mixture is taken and fed via an external circuit by means of a pump of the jet nozzle again. In the reactor, a concentric draft tube is arranged which extends substantially the entire length of the reactor except for the reactor ends and has a cross-sectional area in the range of one-tenth to one-half of the cross-sectional area of the reactor.

However, it has been found that in the prior art reactors, especially in the flow below the internal loop at the transition to the external loop, d. H. near the reactor exit, increased levels of nitroaromatics may occur.

The above-mentioned prior art reactors and related processes have the particular disadvantage that, in a design for large recirculated volumes, they cause short-circuit currents which undesirably cause the flow from the reactor to flow into the external circulating flow, without a flow for to have completed the implementation necessary route in the reactor. As a result, the concentration of the liquid reactant does not drop sufficiently before it leaves the reactor.

A high efficiency of the internal circulation flow is an important prerequisite for setting a high product concentration and a low educt concentration when removing the reaction medium from the reactor. An essential prerequisite is an efficient mixing of the multiphase reaction medium in the ejector, in particular an improvement of the mass transfer at the phase interface. However, the known from the prior art reactors have improvements in terms of the efficiency of the internal circulation flow. This limits the space-time yield. It was the object of the present invention to avoid the aforementioned disadvantages. In particular, a device for carrying out gas-liquid reactions should be found which is suitable for particularly large amounts of heat and for high space-time yields.

This object is achieved by a device for the continuous reaction of liquids with gases, in particular for the production of toluylenediamine by hydrogenation of dinitotoluene, comprising

a vertically extended reactor in which there is a reaction space, at least one heat exchanger arranged inside the reactor,

at least one inlet for feeding the cooling medium into the heat exchanger,

at least one outlet for removing the cooling medium from the heat exchanger,

at least one inlet for feeding the gaseous reactant into the reaction space,

at least one inlet for feeding the liquid reactant into the reaction space,

at least one mixing chamber,

at least one downwardly directed propulsion jet nozzle for introduction of the reaction medium, the outlet of which is arranged above the at least one mixing chamber and which is in fluid communication with the reaction space,

- At least one outlet for removing the reaction medium from the reactor, and

at least one means disposed below the heat exchanger and below the mixing chamber for deflecting the reaction medium flowing downwards through the mixing chamber in such a way that the reaction medium flows upwards again through the heat exchanger,

characterized in that the mixing chamber or the mixing chambers are connected at their lower end in each case with a diffuser.

This object is also achieved by a process for the continuous reaction of liquid reactants with gaseous reactants in the aforementioned device.

The reactor of the device according to the invention comprises a delimited space (defined by a container) and is designed to allow specific reactions to proceed and control under defined conditions. The term "reactor" includes all areas within the delimited space, ie the reaction space, the gas space and the space occupied by the cooling medium (cooling area). A vertically expanded reactor is understood to mean a reactor which has a greater extent in the vertical direction (longitudinal direction of the reactor) than in the horizontal direction (transverse direction of the reactor). The reactor is vertically upright during operation. Under "in operation" is to be understood when carrying out the method according to the invention.

In the context of the present invention, the designations above, below, beside, above and below refer to the vertical direction (longitudinal direction) of the reactor, i. H. they refer to a broad arrangement. The reaction space of the reactor is the space within the reactor intended to receive the reaction medium and thus comprises all areas within the reactor which are in fluid communication with the reaction medium during operation.

Fluid communication is the spatial connection within the reactor of any two sites or elements through which a fluid, so in particular the reaction medium or the cooling medium, can pass from one point or from one element to another or to the other element.

In particular, a reaction space identifies a region within the reactor in which the reaction takes place during operation and in which means for cooling are provided. As a result, the reaction in the reaction space can proceed essentially without significant temperature changes, ie. H. essentially isothermal.

Preferably, the mixing chamber is formed by a cylindrical insert tube. A diffuser is characterized by an extension, preferably a funnel-shaped extension, of the cross-section opposite the mixing chamber. According to the invention, the at least one mixing chamber is connected at the lower end in each case with a diffuser. By this is meant in particular that the diffuser and mixing chamber are physically connected to each other, i. immediately adjacent to each other and thus form a single entity.

When using a diffuser, an improvement in mass transfer occurs at the phase interface by utilizing the kinetic energy of a high velocity liquid jet to aspirate and disperse the gas phase. Due to the high energy input in the ejector high turbulence and high shear forces generated with the result that the gas is dispersed in the form of very small bubbles, d. H. that a very high volume-specific gas-liquid interface is generated. Overall, the function of the diffuser is to increase the efficiency of the internal circulation flow.

Heat exchanger is a means for transferring heat to a cooling medium in order to dissipate released heat of reaction. As heat exchangers are basically different types into consideration, provided they have the required heat transfer surface. preferred Heat exchangers are shell-and-tube heat exchangers, plate heat exchangers, field tube heat exchangers and tube coil heat exchangers.

The heat exchanger is located within the reactor and requires the heat transfer surface between the reaction space and the cooling area. Preferably, the heat exchanger comprises heat exchanger tubes and is in particular a shell-and-tube heat exchanger.

Heat exchanger tubes are at the ends provided with openings hollow body, which are in particular elongated, d. H. have a greater length than an inner diameter. In particular, the ratio of length to inner diameter is at least 10, preferably at least 20, particularly preferably at least 50, in particular at least 100. The heat exchanger tubes also delimit the reaction medium from the cooling medium and allow the transfer of heat between the two media. Preferably, the cross-section of the tubes is substantially circular. However, it is basically possible to deviate from the circular shape in order to realize special flow guides.

The diameter of a single heat exchanger tube is preferably from 10 to 100 mm, in particular from 20 to 50 mm. The heat exchanger tubes are preferably mounted vertically in the reactor, d. H. in the longitudinal direction of the reactor.

For the purposes of the present invention, tube bundles are understood to mean at least two heat exchanger tubes arranged in parallel. Tube bundles are particularly suitable for the absorption of large amounts of heat. The skilled person selects the number of heat exchanger tubes in the tube bundle corresponding to the necessary heat transfer surface based on the volume of the reaction space. The number of heat exchanger tubes in the reactor is preferably at least 100, in particular at least 200, preferably at least 300, very particularly preferably at least 500. In addition, the number of heat exchanger tubes in the reactor is preferably at most 10,000, in particular at most 7,000, particularly preferably at most 5,000, very particularly preferably at most 4,000.

The tube bundle is preferably mounted within the vertically extended reactor around the at least one mixing chamber and around the at least one diffuser (ie the tube bundle completely surrounds the mixing chamber and the diffuser in the vertical direction) and preferably occupies at least 20 area%, in particular at least 30 areas -%, more preferably at least 40 areas. %, most preferably at least 50 area% of the inner horizontal cross-section of the reactor.

The number of tubes in the tube bundle is preferably from 100 to 10,000, particularly preferably from 500 to 5,000. The skilled person selects the number, length and diameter of the heat exchanger tubes in particular as a function of the per unit time and per volume expectant heat of reaction, which determines the temperature difference and heat transfer surface required for heat dissipation.

The ratio of the number of heat exchanger tubes to the number of ejectors in the reactor is preferably at least 100, in particular at least 200, more preferably at least 500. The said ratio of heat exchanger tubes to ejector is preferably at most 10,000, in particular at most 7,500, particularly preferably at most 5,000. By the aforementioned measures in relation to the number of heat exchanger tubes in the reactor ensures that the internal circulation flow is in fluid communication with a plurality of heat exchanger tubes. In the range of the above-mentioned conditions, a favorable internal circulation flow is achieved during operation and at the same time a high amount of heat is transferred.

In a particularly preferred embodiment, the area surrounding the heat exchanger tubes is in fluid communication with the inlet for supplying the cooling medium and the outlet for removing the cooling medium, and the inner area of the heat exchanger tubes forms part of the reaction space and communicates with the at least one propulsion jet nozzle and the outlet Removal of the reaction medium from the reactor in fluid communication.

The heat exchanger tubes are in such a way in particular in fluid communication with the at least one propulsion jet nozzle and the outlet for removing the reaction medium from the reactor, that in operation the reaction mixture first the propulsion jet nozzle, then the mixing chamber and the diffuser, then the heat exchanger tubes and finally the outlet for removing the Reaction medium flows through the reactor.

In this particularly preferred embodiment, the reactor is designed so that in operation, the cooling medium surrounds the heat exchanger tubes and the reaction medium flows through the interior of the heat exchanger tubes. The term reaction medium characterizes the mixture of the educts and products in the reactor, ie the educts, the reacting mixture and / or the reaction product. The reaction medium is in particular a multiphase mixture of reaction liquid, dispersed gas and optionally suspended solid catalyst. This is achieved in this particularly preferred embodiment in that the area surrounding the heat exchanger tubes is in fluid communication with the inlet for supplying the cooling medium and the outlet for removing the cooling medium, so that during operation of the reactor the heat exchanger tubes are surrounded by the cooling medium. At the same time, the inner region of the heat exchanger tubes is a component of the reaction space and is in fluid communication with the at least one propulsion jet nozzle and the at least one outlet for removing the reaction medium, so that during operation of the reactor, the reaction medium flows through the heat exchanger tubes on the inside. In this particularly preferred embodiment, the region surrounding the heat exchanger tubes is thus connected to the inlet for supplying the cooling medium and the outlet for removing the cooling medium so that the heat transfer tube is surrounded by the cooling medium during operation of the reactor. In this particularly preferred embodiment, therefore, the inner region of the heat exchanger tubes is thus connected to the propulsion jet nozzles and the outlet for removing the reaction medium so that during operation of the reactor, the reaction medium flows through the heat exchanger tubes inside. As a result, local temperature increases are avoided at large amounts of heat released and the space utilization of the reactor volume and the heat dissipation and the residence time distribution in the reactor optimized. In particular, such a large number can be realized to each other located in close proximity heat exchanger tubes without (see, for example, when using field pipes) to narrowed flow paths between the tubes, which would otherwise lead to local Termperaturerhöhungen by spatially inhomogeneous heat transfer.

The heat transfer area, based on the reaction volume, is preferably from 20 to 400 m ² / m ³ , in particular from 25 to 300 m ² / m ³ , particularly preferably from 40 to 100 m ² / m ³ .

In operation, the device according to the invention additionally comprises at least one gas space in the upper region of the reactor. The gas space in the upper region of the reactor is the space inside the reactor, which is arranged above the liquid level of the reaction medium. Accordingly, the gas space is filled during operation with the gaseous reactants and possibly inert gas.

The device according to the invention also comprises at least one inlet for supplying the cooling medium into the heat exchanger.

In the context of the present invention, inlet means any means provided for the inlet of the corresponding medium. Accordingly, the term "outlet" in the context of the present invention means any means provided for the outlet of the corresponding medium. The aforementioned means may be in particular openings, pipes, valves or nozzles.

The device according to the invention also comprises at least one outlet for removing the cooling medium from the heat exchanger. The inlet for supplying the cooling medium in the heat exchanger is preferably mounted in the lower region of the reactor, in the vertical direction above the lower end of the reaction space and below the outlet for the removal of the cooling medium. In this case, the cooling medium flows in the heat exchanger from bottom to top. The outlet is preferably mounted in the vertical direction at the level below the upper end of the reaction space. The device according to the invention additionally comprises at least one inlet for feeding the gaseous reactant into the reactor. Preferably, the inlet for supplying the gaseous reactant in the vertical direction at height below the heat exchanger, but above the means for deflecting the flowing down through the mixing chamber reaction medium is mounted. Since the said deflection takes place in such a way that the reaction medium flows upwards again through the heat exchanger, an internal circulation flow results during operation of the device, which is why it is also possible to speak of a deflection of an internal circulation flow.

By mounting underneath the heat exchanger, it is possible to minimize the energy consumption for introducing the gaseous reactant, since the internal circulation flow can be optimally utilized for the mixing and additionally reinforced by the buoyancy.

In order to achieve a rapid and uniform mixing of the reaction medium in operation, it is advantageous for the gaseous reactants in a horizontal cross section of the reaction space below the heat exchanger tubes to a part, preferably at least 50%, in particular at least 70%, particularly preferably at least 80% to distribute the cross-sectional area. Basically, this is any means suitable, which has sufficient and suitably arranged outlet openings. Of importance is also the cross section of the outlet opening. In this regard, advantageous outlet openings are with a diameter of 1 to 20 mm, in particular from 3 to 10 mm. In this regard, a speed in the outlet openings of 5 to 300 m / s, in particular from 10 to 200 m / s is also advantageous. Because of the use of a tube bundle as a heat exchanger, a specific embodiment adapted to the heat exchanger is preferred, since the reaction medium is in operation in the inner region of the tubes.

In an alternative embodiment, the entry of the gaseous reactant takes place from above, ie the inlet for supplying the gaseous reactant is located above the heat exchanger, preferably in the gas space. The disadvantage here is that more energy must be expended in order to introduce the gaseous reactant. It is advantageous, however, that the uniform distribution of the gaseous reactant in the reaction space is particularly easy. However, the above-described supply below the lower end of the heat exchanger tubes and above the means for reversing the internal circulation flow is preferred. In a particularly preferred alternative embodiment, in addition to the aforementioned embodiment of the supply above the heat exchanger, a further inlet for supplying the gaseous reactant below the lower end of the heat exchanger tubes and above the means for reversing the internal circulation flow is provided. This makes it possible to realize a simple distribution of the gaseous reactant with little energy expenditure for the feed.

The device according to the invention additionally comprises at least one inlet for feeding the liquid reactant into the reactor. Preferably, the at least one inlet for supplying the liquid reactant is at least one pipe mounted above the mixing chamber, in particular in the gas space. In an alternative embodiment, a fluid nozzle may be used. The inlet for the liquid reactant is preferably mounted in close proximity to the propulsion jet nozzle. As a result, a faster and more complete mixing of the liquid reactant with the reaction medium is possible.

The liquid reactant feed may be cooled to the inlet, preferably within the reactor, to prevent overheating of thermally sensitive reactants. This is particularly advantageous in the hydrogenation of dinitrotoluene. In this case, the temperature is controlled at temperatures of 60 to 150 ° C, preferably from 70 to 1 10 ° C. Particularly preferably, the feeding of the dinitrotoluene is surrounded by two mutually adjacent jacket tubes: In the inner jacket tube, the cooling medium flows to the tip of the feeder and back to the outside in the outer jacket tube. Preferably, the inlet of the liquid reactant is such that there is no immediate proximity to the reaction medium during operation.

The device according to the invention also comprises at least one downwardly directed propulsion jet nozzle, which is arranged vertically in the gas space of the reactor. By attaching downwards, it is possible to automatically, d. H. through the Treibstrahldüse to suck the gaseous reactants in the gas space. The motive jet nozzle is operated with liquid (the reaction medium) and is thus a liquid nozzle.

The propulsion jet nozzle or the propulsion jet nozzles can each be configured as a single-hole nozzle or as a multi-hole nozzle. A one-hole nozzle has a nozzle bottom with exactly one opening, the so-called mouth. A multi-hole nozzle accordingly has a nozzle lower side with a plurality of openings.

A one-hole nozzle is easy to manufacture. A multi-hole nozzle allows a particularly effective suction of the gaseous reactants, so that the liquid level can be kept at a minimum distance to the propulsion jet nozzle. If the different orifices of a multi-hole nozzle are arranged on different horizontal planes, the liquid level can be held particularly stably at a minimum distance to the jet nozzle. Multi-hole nozzles with a round cross-section of the openings and a diameter of the openings of 5 to 100 mm, preferably from 10 to 80 mm, particularly preferably from 20 to 50 mm are particularly advantageous. In a particularly preferred embodiment, the single-hole nozzle or the multi-hole nozzle does not comprise rotationally symmetrical openings, in particular star-shaped or annular cross-sections. Cross-shaped or slotted openings may also be advantageous. Of importance for such deviating from the circular embodiments is that the hydraulic diameter is reduced compared to a rotationally symmetrical opening. The hydraulic diameter is understood to be four times the cross-sectional area of the opening divided by the circumference of the opening. Hydraulic diameters of 5 to 100 mm, preferably 10 to 80 mm, particularly preferably 20 to 50 mm, of each opening are advantageously used. An embodiment of the propulsion jet nozzle or the propulsion jet nozzles as Mehrlochdüse is particularly preferred.

Each propulsion jet nozzle is arranged in the vertical direction above a mixing chamber. In a preferred embodiment, each propulsion jet nozzle is assigned its own mixing chamber, more preferably multi-hole nozzles being used.

In the mixing chamber, pulse exchange occurs during operation of the present invention.

The propulsion jet nozzle is preferably mounted so that, in use, the lower end of the nozzle is spaced from the surface of the reaction medium by 0 to 10 times the diameter of the propulsion jet nozzle, preferably 0.5 to 2 times. This achieves an optimum suction effect with respect to the gaseous reactant.

In an alternative embodiment, the propulsion jet nozzle dips into the liquid through the gas-liquid phase separation mirror to a certain extent of its overall length. The gas entry then takes place only via the fresh gas supply below the heat exchanger.

In order to further improve the mixing between the reactants and the reaction medium, at least one inlet for the liquid reactant per propulsion jet nozzle can be provided.

The device according to the invention also comprises at least one outlet for removing the reaction medium from the reactor. The outlet for removing the reaction medium from the reactor is preferably attached to the lower end of the reactor. In a preferred embodiment, the outlet is below the means for reversing the internal circulation flow. As a result, the outlet is preferably out of the internal circulation flow during operation. The removal of the reaction medium from the internal circulation flow is through another means to be distinguished from the outlet for removal from the reactor.

Of importance here is the manner of removal of the reaction medium from the internal circulation flow before the reaction medium is removed from the reactor. The removal of the reaction medium from the internal circulation flow is preferably carried out immediately before the inlet for the liquid reactant. This achieves that the reaction product is taken from the internal circulation flow at a point where there is maximum conversion with respect to the liquid reactant.

Preferably, the removal of the reaction medium from the internal circulation flow thus takes place in the immediate vicinity of the inlet for the supply of the liquid reactant. Thus, it is preferred that the reaction medium, after being withdrawn from the internal circulation flow, flows down a layer along the outer wall of the reactor before being withdrawn from the reactor. Particularly preferably, the reaction medium in this case flows down through the interior of heat exchanger tubes arranged in the outer region of the reaction space and is thus further cooled on this route.

In an alternative embodiment, the outlet for removing the reaction medium from the reactor is in the upper region of the reactor. In this embodiment, the outlet for removing the reaction medium from the reactor is in close proximity to the removal of the reaction medium from the internal circulation flow.

The outlet for removing the reaction medium from the reactor and the at least one propulsion jet nozzle for introducing the reaction medium are in fluid communication with each other during operation of the device according to the invention via an external circuit. In a further alternative embodiment, the removal of the reaction medium from the internal circulation flow takes place in the lower region of the reactor and then flows past the means for reversing the internal circulation flow, where it is withdrawn from the reactor and fed to the external circulation flow (ie Pump flow is sucked in). However, this embodiment is less preferable.

In operation of the device according to the invention at least one pump is arranged in the external circuit, which forms the fluid connection between the outlet for removing the reaction medium from the reactor and the at least one propulsion jet nozzle, so that the reaction medium is pumped from the outlet for removal from the reactor to the propulsion jet nozzle becomes. The device according to the invention therefore preferably comprises at least one pump, which is arranged in an external circuit and which has the outlet for removal. me fluid of the reaction medium from the reactor with the at least one propulsion jet nozzle connects. Thus, the energy input for the external circulation flow through at least one pump, which is why one can speak of a pump current here. The internal circulation flow is driven by the propulsion jet nozzle, which is why one can speak here of an intake flow.

Each mixing chamber forms with the above-arranged propulsion jet nozzle or propulsion jet nozzles a jet pump, which is referred to as an ejector. The ejector further comprises according to the invention a diffuser which is connected to the lower end of the mixing chamber.

The mixing chamber is formed in a preferred embodiment of a plug-in tube.

According to the invention, the mixing chamber or the mixing chambers are each connected at the lower end thereof to a diffuser. In the vertical direction below the diffuser is in a preferred embodiment, a cylindrical extension of the diffuser in the form of a tube with a constant diameter.

In a particularly preferred embodiment, correspondingly comprises an ejector arranged in propulsion jet direction from top to bottom, which is formed by one or more propulsion jet nozzles, a mixing chamber, optionally diffuser and possibly further cylindrical sections, below the propulsion jet nozzles at least 3 sections: an upper section, which has a substantially circular cross-section with the diameter d1, a diffuser as a central portion, whose cross-section widens from top to bottom with respect to the top portion, and a bottom portion, which has a substantially circular cross-section with the diameter d2, where d2 > d1.

In a preferred embodiment, the plug-in tube as a mixing chamber at the upper end of a rounded inlet, d. H. the plug-in tube has a slight widening of the inner diameter in the region of the upper end. This leads to an improved absorption effect with respect to the reaction medium while avoiding flow losses.

In a preferred embodiment, multiple ejectors are used. As a result, the mixing of the educt streams is accelerated. In addition, this embodiment is particularly efficient in combination with the cross-flow filtration below, since this leads to a pre-distribution of currents. The individual tubes of this pre-distribution can thus be advantageously connected to a propulsion jet nozzle.

In principle, the mixing length required for a sufficient mixture is generally five to ten times the diameter of the mixing chamber. Thus, in the case of several ejectors, the overall efficiency of the mixing increases, that is to say, the sufficient mixing occurs more quickly in the flow. The direct gas entry through the propulsion jet nozzle is also improved by increasing the contact area between the gas and the liquid. In a further embodiment, the propulsion jet nozzle, which is arranged in the upper region of the reactor, is designed as an annular gap nozzle, and the gaseous reactant, preferably hydrogen, is passed into the reactor via an annular gap on the outer wall of the propulsion jet nozzle designed as a two-jet nozzle.

In order to set an internal circulation flow during operation of the reactor, means are provided which deflect the flow laterally below the heat exchanger, resulting in an internal circulation flow in the reactor.

Accordingly, the device according to the invention comprises at least one means for deflecting the internal circulation flow, wherein the at least one means is mounted within the reactor and below the heat exchanger. Preferably, the means for deflecting the flow of the reaction medium is a deflection trough.

A deflection tank is characterized in that it comprises a surface oriented transversely of the reactor and a lateral border extending in the longitudinal direction of the reactor, which faces upwards, ie. pointing in the direction of the ejector. In an alternative embodiment, the means for deflecting the flow of the reaction medium is a baffle plate. A baffle plate is characterized in that it has a transversely oriented surface of the reactor and no lateral, extending in the longitudinal direction of the reactor border. A deflection tank is preferred. This makes it possible to avoid short-circuit currents in the lower region of the reactor and to set particularly low possible product concentrations at the outlet for removing the reaction medium from the reactor.

The deflection trough preferably extends in the horizontal plane in the transverse direction of the reactor over a majority of the heat exchanger tubes, but preferably not over the entire cross section of the heat exchanger tubes. This ensures that the reaction medium in the outer region of the reactor can only reach the outlet for removing the reaction medium from the reactor after it has flowed upwards in the tubes above the deflection trough. Preferably, the reaction medium flows in the tubes above the Umlenkwanne up and a partial flow then in the tubes outside the cross section of the Umlenkwanne back down.

Preferably, the horizontal cross-sectional area of the deflection trough is from 60 to 98% of the area occupied by the lower end of the heat exchanger in the cross section of the reactor, in particular from 70 to 95%, particularly preferably from 75 to 90%.

The height of the border of the deflection trough is from 1 to 30% of the longest diameter of the deflection trough, in particular from 2 to 20%, particularly preferably from 3 to 15%.

The angle of the border relative to the inner surface of the Umlenkwanne is preferably from 90 to 170 °, in particular from 90 to 150 °, particularly preferably from 90 to 120 °. In a preferred embodiment, the deflection trough on emptying openings, which can be at least partially closed in particular. In operation, the openings are at least partially or preferably completely closed, whereas they can be opened at standstill.

In an alternative embodiment, the reactor bottom is the means for deflecting the reaction medium flowing downwardly through the mixing chamber. In this case, the outlet for removing the reaction medium from the reactor is mounted above the bottom of the heat exchanger of the reactor.

In one embodiment of the invention, a heat exchanger is provided in the external circuit, which may also be referred to as external loop flow. Any remaining part of the heat of reaction can thus be removed via a heat exchanger, which is arranged in the external circuit. Preferably, a shell-and-tube heat exchanger is used.

The gas space can also be referred to as Gasabscheideraum. In a preferred embodiment are above the heat exchanger below the liquid level means for gas separation, preferably sheets that do not extend in a horizontal plane to the edge of the reactor, so that the reaction medium can flow undisturbed to the outlet from the reactor in the outer region. In the middle, the means for gas separation have at least one recess so that gas can rise in the area of the propulsion jet nozzles. The gas collects on the sheets, which rises upwards in the reaction space, and is partially sucked back down by the internal circulation flow (suction flow).

The volume of the gas in the reaction medium should be adjusted in operation according to the material properties to 5 to 20 vol .-% based on the volume of the reaction medium.

If the level of the liquid in the reactor is kept constant (for example by using a multi-hole nozzle), the gas content is preferably controlled by adjusting the amount of reaction product discharged. Alternatively, the level of the liquid level in the reactor can also be controlled by adjusting the amount of reaction product discharged, then the gas content can be e.g. be influenced by the amount of metered below the heat exchanger fresh gas.

The reactor can in principle be made of any material that has the necessary mechanical and thermal capacity and product compatibility. The reactor is preferably made of steel (eg 1 .0037 or 1.0565), particularly preferably of stainless steel (eg 1.4541 or 1.4571) and / or of duplex steel (eg 1.4462). Of course possible Also combinations in which eg product contacting parts made of stainless steel and / or duplex and non-product contacting parts are made of unalloyed steel.

method

The device according to the invention is preferably used for the reaction of gases with liquids. The reaction is preferably a hydrogenation, oxidation or acetylation, particularly preferably a hydrogenation. In this case, preferably nitroaromatic compounds are hydrogenated.

In the context of the process according to the invention, preference is given to aromatic nitro compounds having one or more nitro groups and from 6 to 18 carbon atoms, for example. Nitrobenzo- le, such as. As nitrobenzene, 1, 3-dinitrobenzene, nitrotoluenes, such as. B. 2,4-, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, nitroxylols, such as. B. 1, 2-dimethyl-3, 1, 2 dimethyl-4, 1, 4-dimethyl-2-, 1, 3-dimethyl-2-, 2,4-dimethyl-1 - and 1, 3 Dimethyl-5-nitrobenzene, nitronaphthalenes, such as. B. 1-, 2- nitronaphthalene, 1, 5 and 1, 8-dinitronaphthalene, Chlornitrobenzole such. B. 2-chloro-1, 3-, 1-chloro-2,4-dinitrobenzene, o-, m-, p-chloronitrobenzene, 1, 2-dichloro-4-, 1, 4-dichloro-2-, 2 , 4-dichloro-1 - and 1, 2-dichloro-3-nitrobenzene, chloronitrotoluenes, such as. For example, 4-chloro-2, 4-chloro-3, 2-chloro-4-and 2-chloro-6-nitrotoluene, nitroanilines, such as. For example, o-, m-, p-nitroaniline; Nitro alcohols, such as. Tris (hydroxymethyl) nitromethane, 2-nitro-2-methyl, 2-nitro-2-ethyl-1,3-propanediol, 2-nitro-1-butanol and 2-nitro-2-methyl-1 Propanol and any mixtures of two or more of the nitro compounds mentioned.

Preferred by the process according to the invention are aromatic nitro compounds, preferably mononitrobenzene, mononitrotoluene or dinitrotoluene, and in particular 2,4-dinitrotoluene or its technical mixtures with 2,6-dinitrotoluene, these mixtures preferably up to 35% by weight, based on the total mixture, of 2 , 6-Dinitrotoluol and proportions of 1 to 4 percent of vicinal DNT and 0.5 to 1, 5% of 2,5- and 3,5-dinitrotoluene hydrogenated to the corresponding amines. Particularly preferably, the technical DNT mixture is used in the isomer composition in which it is obtained in the two-stage nitration of toluene.

In particular, in the hydrogenation of Dinitrotoluolisomeren to the corresponding Toluylenendi- amine derivatives (TDA), in the hydrogenation of o- or p-mononitrotoluene to o- or p-toluidine and in the hydrogenation of mononitrobenzene to aniline, the inventive method can be used advantageously.

The preferred embodiment of the hydrogenation of dinitrotoluene is explained in more detail below.

Dinitrotoluene is preferably fed at the upper end of the reactor, preferably in the gas space above the liquid level in the reactor. Advantageously, the dinitrotoluene dosed directly into the mixing chamber for the purpose of uniform feeding, particularly preferably in the trombe produced by the jet from the propulsion jet nozzle. In this case, preference is given to a mono- and / or polynitro compound in pure form, as a mixture with the corresponding mono- and / or polyamine, as a mixture with the corresponding mono- and / or polyamine and water or as a mixture with the corresponding mono- and / or polyamine, water and a particular alcoholic solvent used. The aromatic mono- and / or Polynitroverbindung is finely divided into the mixture.

In a preferred embodiment of the method according to the invention, the supply of the nitroaromatic is realized by a supply line and a metering device without geometric possibility of dead space formation. Corresponding units or devices are known per se to the person skilled in the art. It is advantageous in this case that, given the filling level of the reactor, neither in the operating state nor during shutdown, a direct spatial contact between the supply of the nitroaromatic and the liquid phase, preferably containing the aromatic amine, d. H. the corresponding reaction product, water and catalyst, can be carried out in the reactor and / or in the pumped circulation. This is realized in particular in that the distance between the supply of the nitroaromatic and the liquid phase is for example 0.01 to 3 m, preferably 0.05 to 1, 0 m. In a further preferred embodiment of the method according to the invention, the feed of the nitroaromatic is realized via one or more independent pipelines, whose partial or complete blocking can be detected metrologically.

Corresponding pipelines are known per se to those skilled in the art. The preferably used pipelines are made of metal, for example black steel or stainless steel, for example. The pipelines preferably have diameters which are based on the quantities of nitroaromatics which are fed.

In general, the pipes preferably used can have any suitable cross section. Preference is given to using pipelines with DN50 or smaller, particularly preferably DN40 or DN25, since these act as a detonation barrier.

In a preferred embodiment, the outlet cross section of the supply of the nitroaromatic at the ends of the one or more independent pipeline (s) on a constriction or deviating from the rotationally symmetrical shape shape. The exiting nitroaromatic jet may exhibit laminar or turbulent behavior. A corresponding implementation is described, for example, in WO2012 / 123469.

The introduction of the dinitrotoluene into the gas phase above the liquid level prevents the reaction product from flowing back into the dinitrotoluene feed line and thereby causing decomposition or explosion of the dinitrotoluene. Pure dinitrotoluene has a decomposition temperature of about 260 ° C, but the decomposition temperature drops drastically as toluene diamine and catalyst are mixed up to 100 ° C. Therefore, it is also advantageous to flush the supply of dinitrotoluene in case of interruptions in the production or shutdown of the system with hot water. Preferably, the concentration of nitro groups, ie the sum of the products of all contained nitroaromatics, multiplied in each case by the number of their nitro groups per molecule, for example for the hydrogenation of dinitrotoluene (DNT) c (nitroaromatic) = c (DNT) ^■ 2 + c (ANT ) ^■ 1 (ANT = amino-nitro-toluene), or for the hydrogenation of ortho-nitrotoluene (o-NT) c (nitroaromatic) = c (o-NT) ^■ 1, in the liquid phase of the product discharge from the reactor in the range between the reactor and the downstream product separation unit to a value in the range of 0 to 2000 ppm by weight, preferably 0.5 to 1000 ppm by weight, more preferably 1 to 200 ppm by weight and very particularly preferably 1 to 50 wt. ppm, based on the total weight of the liquid phase of the product output from the reactor. As a result, both the by-product formation can be reduced and the catalyst deactivation can be largely avoided. Corresponding methods are described in WO201 1/144481. The above-mentioned concentration ranges can be more easily achieved the faster the mixing of the liquid reactant (for example by means of a highly efficient propulsion jet nozzle with diffuser) takes place and the better short-circuit currents are prevented (in particular by means of a deflection trough). In comparison to reactors without such auxiliaries, these concentrations can therefore be achieved with less catalyst, higher space-time yield or lower temperature (and thus frequently higher selectivity).

It is advantageous to ensure by suitable measures that the concentration of hydrogen in the reaction mixture flowing from the internal circulation flow into the external loop is 1% by volume, preferably 3% by volume, based on the total volume of the reaction mixture, which flows in the external loop, does not fall below. For this purpose, it is possible to design the diameter of the reactor or the outflow velocity of the reaction mixture from the reactor or the possibly existing gas separation plates above the heat exchanger accordingly. In another embodiment, it is possible to ensure the minimum concentration of hydrogen flowing from the internal circulation flow into the external loop by supplying hydrogen into the reaction mixture flowing from the internal circulation flow into the external loop as close to the reactor as possible. The reaction product is preferably taken from the external circuit. In order to be able to drive the external pitch circle, a pump must be installed, which in addition to liquid can also convey gas and suspended solids. In this case, up to 20% by volume of gas and 20% by weight of suspended solids should be pumpable. To avoid Ni deposits in Ni-containing catalysts or to avoid over-crushing of supported catalysts, an arrangement of several (preferably two) pumps in series or the use of a multi-stage pump may be useful. The cooling medium is preferably water. In a preferred embodiment, water is supplied liquid and removed as a vapor. The steam can be utilized within any chemical plant complex for the supply of heat or energy. In addition, the steam can also be fed into an existing steam network at the site of the plant.

From the heat of reaction liberated, steam can be generated in both the internal and a possibly present external heat exchanger in two ways: 1) by evaporating part of the cooling water in the cooling tubes (direct steam generation) or 2) by heating the cooling water to a pressure, which is above the pressure of the steam to be generated, and subsequent expansion to the pressure level of the steam to be generated (flash evaporation). During this relaxation, part of the cooling water evaporates, and the steam / water mixture cools down to the boiling temperature corresponding to the pressure of the steam. Both types of evaporation can be used in both internal and external heat exchangers. Likewise, a combination of both types of evaporation is possible, that is direct evaporation in the internal heat exchanger and flash evaporation in an external heat exchanger or vice versa. In an alternative embodiment, at least partially water from a secondary cooling circuit is used as the cooling medium. In a preferred alternative embodiment, steam is generated in the internal heat exchanger in one of the two types described and an external heat exchanger is cooled with water from a secondary cooling water circuit. Preferably, the reaction is carried out in the process according to the invention in the presence of a suspended or dissolved, more preferably in the presence of a suspended catalyst.

For the hydrogenation of dinitrotoluene to toluenediamine a variety of catalysts have been developed, the improvement of yield and selectivity of the reaction and the stability of the catalysts were also at higher reaction temperatures priority tasks in the development of new catalysts.

According to a first general embodiment of the invention, the method according to the invention, as stated above, in the presence of a catalyst, in particular in the presence of a supported catalyst, as the active component nickel alone or together with at least one metal of I., V., VI. and / or VIII. Subgroup of the Periodic Table performed. The catalysts used can advantageously be prepared by applying nickel and optionally at least one of the abovementioned additional metals to a suitable support. Preferably, as metals of I., II., V., VI. and / or VIII. Subgroup of the Periodic Table used palladium, platinum, rhodium, iron, cobalt, zinc, chromium, vanadium, copper, silver or a mixture of two or more thereof. Catalysts which have proved to be particularly suitable are one or more metals selected from the group consisting of platinum, palladium, rhodium and ruthenium and, in addition, one or more further metals selected from the group consisting of nickel, cobalt, iron and zinc is applied on an inert support. According to a preferred embodiment of the invention, the catalyst has a nickel content of 0.1 to 99 wt .-%, preferably from 1 to 90 wt .-%, particularly preferably from 25 to 85 wt .-% and most preferably from 60 to 80 Wt .-%, based on the total weight of the catalyst. According to a preferred embodiment of the invention, the catalyst contains Ni and platinum. According to another preferred embodiment of the invention, the catalyst contains Ni and Al; According to another particularly preferred embodiment, the catalyst contains nickel, palladium and iron. Particularly advantageous are hydrogenation catalysts containing platinum and nickel on a support in the form of an alloy having an atomic ratio of nickel to platinum, determined by means of EDXS (Energy Dispersive X-Ray Spectroscopy) in the alloy from 30: 70 to 70: 30. The atomic ratio of nickel to platinum, determined by means of EDXS (Energy Dispersive X-Ray

Spectroscopy) is in particular from 45:55 to 55:45.

As support materials are preferably activated carbon, carbon black, graphite, or oxidic carrier components such as silica, silicon carbide, diatomaceous earth, alumina, magnesia, titania, zirconia and / or hafnia or a mixture of two or more thereof, more preferably zirconia, ZrÜ2, HfÜ2 and / or S1O2, ZrÜ2 and / or S1O2, Zr0 ₂ , Hf0 ₂ used.

The carriers used are preferably mesoporous and have an average pore diameter of 35 to 50 nm and a specific surface area of 50 to 250 m ² / g. The surface of the support is determined by the BET method by N 2 adsorption, in particular according to DIN 66131. The average pore diameter and the pore size distribution are determined by Hg porosimetry, in particular according to DIN 66133.

The application of nickel and optionally of the at least one further metal can be achieved by the customary suitable methods known to the person skilled in the art of catalyst technology. The coated with the metal or metal salt coated by co-precipitation or impregnated support are then dried and calcined by known methods. Subsequently, the coated carrier by Treatment thereof in a gas stream containing free hydrogen activated. This activation usually takes place at temperatures in the range from 30 to 600.degree. C., preferably in the range from 80 to 150.degree. C. and particularly preferably at 100.degree. The gas stream preferably consists of 50 to 100% by volume of hydrogen and 0 to 50% by volume of nitrogen. The catalyst prepared for the use according to the invention has a reduction rate of at least 70% after a one-hour reduction at 100 ° C.

The supported catalysts thus obtained generally have a nickel metal surface area of about 10 to about 50 m ² / g, preferably about 20 to about 60 m ² / g. The nickel content of the catalysts used in the process of the invention is generally in the range of 0.1 to 99 wt .-%, preferably in the range of 1 to 90 wt .-%, particularly preferably in the range of 25 to 85 wt .-%, based on the total weight of the catalysts used. Suitable catalysts of this embodiment are described, for example, in the publications EP 1 161 297 A1 and EP 1 165 231 A1.

According to a second embodiment of the invention, activated nickel catalysts, as described, for example, in WO 2008/145179 A1, are used in the context of the process according to the invention. Accordingly, according to a preferred embodiment of the invention, activated nickel catalysts based on a Ni / Al alloy containing one or more metals selected from the group Mg, Ce, Ti, V, Nb, Cr, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Pt, Cu, Ag, Au and Bi can be used. The doping level is in the range of 0.05 wt .-% to 20 wt .-% for each doping element. The average particle size of the catalysts used is <25 μηη.

According to a third embodiment of the invention catalysts are used in the context of the inventive method, which are described for example in WO 2008/138784 A1. The invention thus further provides, according to a preferred embodiment of the invention, the use of hydrogenation catalysts comprising as active component a mixture of nickel, palladium and an additional element selected from the group comprising cobalt, iron, vanadium, manganese, chromium, platinum, Iridium, gold, bismuth, molybdenum, selenium, tellurium, tin and antimony on a support, for the preparation of aromatic amines by catalytic hydrogenation of the corresponding nitro compounds, in particular for the preparation of toluenediamine by hydrogenation of dinitrotoluene. The additional element is preferably selected from the group containing cobalt, iron, vanadium, bismuth and tin.

As supports for the catalysts, the customary and known materials can be used for this purpose. Preferably, activated carbon, carbon black, graphite or metal oxides, preferably hydrothermally stable metal oxides such as ZrÜ2, T1O2, Al2O3 used. For graphite, the HSAG (High Surface Area Graphite) with a surface area of 50 to 300 m ² / g are particularly preferred. Particularly preferred are activated carbons, especially physically or chemically activated carbons, or carbon blacks, such as acetylene black

The catalysts used in the process according to the invention are produced, for example, by initially introducing the support and bringing it together with the additive element using an aqueous solution of the palladium and nickel salts. In this case, the amount of water used to dissolve the salts should be such that a kneadable paste is formed. Preferably, the water is used in an amount of 100 to 200 wt .-% of the carrier mass. As metal salts in particular nitrates or chlorides are used, with nitrates being preferred because of their lower corrosivity. The paste is mixed and then the water is evaporated at low pressure and temperatures in the range between 50 and 100 ° C, for example in a rotary evaporator or an oven. For safety reasons, the evaporation can take place in a stream of nitrogen. The fixation of the metals on the carrier can take place when using chlorides as metal salts by reduction with hydrogen. However, corrosion can occur here. The metals are therefore preferably fixed alkaline. This is done in particular by adding an aqueous solution of alkali metal carbonates and subsequent anion-free washing of the carrier. Alternatively, the metals may also be precipitated alkaline, especially at a pH in the range of 8 to 9, from a supernatant solution onto the support. Thereafter, the support is dried, preferably as described above, and reduced with hydrogen. This can be done for example in a rotary kiln. Before the catalyst is removed, it is passivated, for example under an inert gas such as nitrogen, which contains traces of air, preferably not more than 10% by volume. The preferred hydrogenation catalysts prepared by this process preferably contain 0.5 to 5 wt .-% palladium, 10 to 20 wt .-% nickel and 0.5 to 5 wt .-% of the additional element.

According to a further embodiment of the preparation of the hydrogenation catalysts preferably used, the reduction of the catalysts takes place by addition of reducing salts, such as ammonium carboxylates or alkali metal carboxylates, for example ammonium formate or sodium formate. For this purpose, the carrier is suspended with water and at the same time or after the suspension, the solutions of the metal salts are added. As metal salts in particular nitrates or chlorides are used, with nitrates being preferred because of their lower corrosivity. To this solution, the reducing salts are added and the suspension is heated, for example by boiling under reflux. Subsequently, the catalysts are washed anion-free and filtered, for example by a filter press or a centrifuge, and used as a wet paste. Further examples of the preparation of the catalysts preferably used can be found in WO 2005/037768 A1.

The hydrogenation of dinitrotoluene, mononitrotoluene and mononitrobenzene can be carried out in solution. The solvents used are the customary substances, in particular lower alcohols, preferably ethanol or methanol used. Due to the optimum flow conditions and the immediate removal of the heat of reaction in the reactor used in the invention, it is possible to carry out the hydrogenation without solvent. This has the advantages that the volume of the reaction mixture is lower, which allows smaller dimensioning of the reactor and of the pumps and pipelines, excludes side reactions between the solvent and the starting materials, and reduces the work-up time of the end products.

The majority of the reaction mixture is guided in the internal loop flow, only a small portion of the reaction mixture is pumped externally and thus ensures the drive of the loop flow. The ratio of the volume flows from internal loop flow to external loop flow is 1: 1 to 15: 1, preferably 3: 1 to 10: 1. Due to the small proportion of external loop flow in the entire reaction mixture, significantly smaller amounts of catalyst per unit time are circulated via the circulation pump than in the case of cooling exclusively via an external heat exchanger. This leads to a reduction of the mechanical catalyst stress and thus to a longer life of the catalyst. In addition, this embodiment, in conjunction with the integrated heat exchangers, ensures a high isotherm of the reaction, i. H. a very small temperature gradient across the reactor height (typically between 1 and 10 K), since the hydrogenation proceeds almost completely in the internal loop flow and the heat of reaction is thus already discharged at the place of its formation. At the same time, restrictions on the reaction rate due to mass transfer and heat transfer are virtually completely eliminated. Side reactions that are favored by temperature gradients in the reaction system are almost completely suppressed. The reaction rate is then limited only by the reaction kinetics. In addition, the safety of the process is improved over cooling in the outer circuit, since the reactor cooling still works when the pump for the external circuit fails.

Preferably, the volume flow of the internal loop flow is monitored directly by measuring the pressure difference between the gas space and the cylindrical mixing space. With insufficient loop flow - and thus insufficient mixing in the reactor - the supply of liquid starting material is interrupted to prevent deactivation of the catalyst. The dispersion of the individual reactants, in conjunction with the other reaction parameters, achieves intensive mixing of all components at low substrate concentrations, high mass transfer coefficients and high volume-specific phase boundary surfaces. The arrangement of the cooling tubes in the reactor parallel to the reactor walls has a substantial gradient freedom of the reactor contents with respect to the reaction temperature result. By avoiding local overheating side reactions are clearly suppressed and catalyst deactivation largely avoided. It will be even with it low catalyst concentrations achieved high space-time yields at high selectivity.

Due to the low concentration of the nitroaromatic in the reaction mixture, a catalyst deactivation is largely avoided and thermal decomposition of the nitroaromatic can be reliably prevented.

The hydrogenation of the dinitrotoluene is preferably carried out at temperatures of 80 to 200 ° C, preferably from 1 10 to 190 ° C, and pressures in the range of 10 to 50 bar, preferably from 15 to 35 bar performed.

Preferably, the catalyst is suspended in the reaction medium. In order to remove the reaction product free of catalyst particles, the reaction product is separated from the catalyst in the external circuit. The product or catalyst separation unit is generally a filter (e.g., a membrane filter / crossflow filter), a static decanter (e.g., a settler, often a lamellar clarifier), or a dynamic decanter (e.g., a centrifuge or a jet separator). The catalyst is separated from the product and then returned to the reactor (usually as a thickened suspension). Preferably, the product is discharged while retaining the catalyst. The amine can then be purified by the usual and known methods, for example by distillation or extraction.

The separation of the reaction product from the catalyst is preferably carried out by membrane filtration.

The advantage of membrane filtration is that it enables fast, complete and gentle retention of the catalysts.

The membrane filtration is preferably at a pressure on the suspension side of 5 to 50 bar, preferably 20 to 35 bar, a pressure difference between the suspension side and the permeate side of from 0.3 bar to 5 bar and a flow rate on the suspension side of 1 to 6 m / s is performed. The term "suspension side" refers to the side of the membrane filter on which the mixture containing the catalyst is located, the permeate side being understood to be the side of the membrane filter on which the catalyst-free mixture is located.

The membrane filtration can be carried out continuously or discontinuously.

In the continuous implementation, at least a partial stream of the reaction mixture is constantly driven through a membrane filter. In this embodiment of the method according to the invention, it is preferable to arrange the membrane filter in the external circuit of a circulation reactor. This embodiment of the method according to the invention is preferred. In the discontinuous execution of the filtration, the discharged reaction mixture is passed through a switchable purification stage, consisting of membrane filter and a separate circulation pump. In another embodiment of the discontinuous filtration, the reaction mixture is passed through a membrane filter following the reaction. This embodiment is less preferred, since here the separated catalyst has to be concentrated to a higher degree.

The filter membranes used for the method may for example consist of ceramic (eg 0Al2O3) or stainless steel (eg 1.4404) and have, depending on the particle size of the catalyst used, preferably number-weighted mean pore diameter in the range between 10 nm and 20 microns, in particular in the range between 50 nm and 10 micrometers, and preferably between 100 nm and 1 micrometer.

Suitable embodiments of membrane filtration, in particular cross-flow filtration, are known to the person skilled in the art and are described, for example, in WO2010 / 125025, the content of which is hereby incorporated into this application.

Despite optimal reaction, moderate catalyst deactivation can not be completely prevented. Therefore, the outer loop preferably contains a connection for the supply of fresh catalyst preferably suspended in water and a further outlet for the discharge of catalyst-containing reaction product which is connected to a Katalysatorausschleuseunit. This in turn preferably consists of a collecting container at least one Umpumpkreislauf containing at least one membrane filter. The invention will be explained in more detail with reference to embodiments and drawings. Here, preferred embodiment are described, without wishing to limit the invention thereto.

The figures show a device according to the invention, wherein the areas provided for the reaction medium are marked hatched; the intended areas for the cooling medium are not hatched. In detail, in FIGS. 1 to 2:

1 - vertically extended reactor

2 - heat exchanger, which is arranged inside the reactor,

3 - reaction space

4 - inlet for supplying the cooling medium into the heat exchanger,

5 - outlet for removing the cooling medium from the heat exchanger,

6 - inlet for feeding the gaseous reactant into the reaction space,

7 - inlet for feeding the liquid reactant into the reaction space,

8 - mixing chamber,

9 - downwardly directed jet nozzle for entry of the reaction medium

10 - outlet for removing the reaction medium from the reactor 1 1 - below the heat exchanger (2) and below the mixing chamber (8) arranged means (1 1) for deflecting the downward through the mixing chamber (8) flowing reaction medium

12 - diffuser

13 - cylindrical section

14 - pump

15 - external circuit

16 - internal circulation flow

17 - Product separation unit

18 - product

20 - heat exchanger tubes

21 - the area surrounding the heat exchanger tubes

22 - inner region of the heat exchanger tubes FIG. 1 shows a device according to the invention with an ejector (section in the longitudinal direction).

FIG. 2 shows a device according to the invention with four ejectors (section in transverse direction). The area surrounding the heat exchanger tubes (21) is in fluid communication with the inlet (4) for supplying the cooling medium and the outlet (5) for removing the cooling medium. The inner region of the heat exchanger tubes (22), which forms part of the reaction space, is in fluid communication with the at least one propulsion jet nozzle (9) and the outlet (10) for removing the reaction medium from the reactor.

Examples

Example 1 (according to the invention)

In a reactor according to FIG. 1 and FIG. 2 (an ejector as in FIG. 1) with an external circulation flow of 0.06 m ³ / s, a liquid density of 1000 kg / m ³ , a nozzle diameter of 50 mm, a mixing tube, which forms the mixing chamber, with a diameter of 200 mm and a length of 1 m, with a rounded inlet and a diffuser underneath, with a total opening angle of 5 ° and an outlet diameter of 300 mm and a cylindrical section underneath and a tube length of In a simulation of 0.3 m ³ / s, the viscosity of the liquid was 10 ^-6 m ² / s.

Example 2 (Comparative) As in Example 1, but with a 300 mm diameter insert tube, only 0.25 m ³ / s could be aspirated. ņiguren

Claims

Patent claims

Device for the continuous reaction of liquids with gases, in particular for the production of toluenediamine by hydrogenation of dinitrotoluene, comprising a vertically extended reactor (1) in which there is a reaction space (3),

at least one heat exchanger (2) which is arranged within the reactor (1),

at least one inlet (4) for feeding the cooling medium into the heat exchanger (2),

at least one outlet (5) for removing the cooling medium from the heat exchanger (2),

at least one inlet (6) for feeding the gaseous reactant into the reaction space (3),

at least one inlet (7) for feeding the liquid reactant into the

reaction space (3),

at least one mixing chamber (8),

at least one downward-directed driving jet nozzle (9) for introducing the reaction medium, the outlet of which is arranged above the at least one mixing chamber (8) and which is in fluid communication with the reaction space (3),

at least one outlet (10) for removing the reaction medium from the reactor, and

at least one means (1 1) arranged below the heat exchanger (2) and below the mixing chamber (8) for redirecting the reaction medium flowing downward through the mixing chamber (8) in such a way that the reaction medium flows upward again through the heat exchanger (2), characterized in that the mixing chamber or the mixing chambers (8) are each connected to a diffuser (12) at their lower end.

Device according to claim 1, wherein the heat exchanger

(2) includes heat exchanger tubes (20).

3. Device according to claim 1 or 2, wherein the means (1 1) for deflecting the reaction medium flowing downward through the mixing chamber (8) is a deflection trough.

4. Device according to one or more of claims 1 to 3, wherein above the heat exchanger (2) there is an outlet for removing the reaction medium from the internal circulation flow (16).

5. Device according to one or more of claims 1 to 4, wherein the at least one mixing chamber (8) is each formed by one or more insertion tubes.

6. Device according to one or more of claims 1 to 5, wherein the inlet for supplying the gaseous reactant (6) into the reaction space (3) below the heat exchanger (2) and at the same time above the means (1 1) for deflecting the reaction medium flowing downward through the mixing chamber (8).

7. The device according to claim 6, wherein an additional inlet for supplying the gaseous reactant into the reaction space above the heat exchanger (2) is additionally provided.

8. Device according to one or more of claims 1 to 7, wherein the heat exchanger (2) comprises heat exchanger tubes (20) and the area (21) surrounding the heat exchanger tubes (20) with the inlet (4) for supplying the cooling medium and the outlets ( 5) is in fluid communication for removing the cooling medium, and the inner region (22) of the heat exchanger tubes (20) forms part of the reaction space (3) and with the at least one driving jet nozzle (9) and the outlet (10) for removing the reaction medium is in fluid communication with the reactor.

9. Device according to one or more of claims 1 to 8, wherein each ejector arranged in the longitudinal direction of the reactor from top to bottom is provided by a propulsion jet nozzle (9), a mixing chamber (8), a diffuser (12) and possibly further cylindrical Sections (13) are formed, below the propulsion jet nozzle (9) comprising at least 3 sections, an upper section which has a substantially round cross section with the diameter d1, a diffuser (12) as a middle section, the cross section of which is opposite to the upper section extended from top to bottom, and a lower section which has a substantially round cross section with diameter d2, where d2 > d1.

10. The device according to claim 9, wherein multiple ejectors are used.

1 1 . Device according to one or more of claims 1 to 10, wherein multi-hole nozzles are used as driving jet nozzles (9).

12. Device according to one or more of claims 1 to 1 1, wherein for each driving jet nozzle (9) there is at least one inlet (7) for supplying the liquid reactant into the

Reaction space (3) is provided.

13. Device according to one or more of claims 1 to 12, wherein an external circuit (15) has a fluid connection between the outlet (10) for removing the reaction medium from the reactor and the at least one propulsion jet nozzle (9) for introducing the reaction medium into the reactor (1).

14. The device according to claim 13, wherein a pump (14) is arranged in the external circuit.

15. Process for the continuous reaction of liquid reactants with gaseous reactants in a device according to one or more of claims 1 to 14.

16. The method according to claim 15, wherein a tube bundle heat exchanger is used as the heat exchanger (2) and the reaction medium flows through the heat exchanger tubes (20) and the cooling medium surrounds the heat exchanger tubes (20).

17. The method according to claim 15 or 16, wherein the reaction takes place in the presence of a suspended or dissolved catalyst.

18. The method according to one or more of claims 15 to 17, wherein the liquid reactant is a nitroaromatic and the gaseous reactant is hydrogen.

19. The method according to one or more of claims 15 to 18, wherein the internal circulation flow (16) is driven by the at least one driving jet nozzle (9).