EP2192975A1

EP2192975A1 - Reactor and method for the production thereof

Info

Publication number: EP2192975A1
Application number: EP08801889A
Authority: EP
Inventors: Ralph Schellen; Evin Hizaler Hoffmann; Leslaw Mleczko; Stephan Schubert
Original assignee: Bayer Technology Services GmbH
Current assignee: Bayer AG
Priority date: 2007-09-20
Filing date: 2008-09-06
Publication date: 2010-06-09
Also published as: CN101801516A; DE102007045123A1; US20100310436A1; WO2009039946A1

Abstract

The present invention relates to a chemical reactor (1) for the conversion of liquid reaction mixtures, comprising at least one adiabatic reaction zone (2), which comprises a catalyst bed (3), and also comprising at least one heat exchanger (4), following the reaction zone (2), wherein the heat exchanger (4) comprises plates (5, 6) stacked one on top of the other and connected to one another, the individual plates (5, 6) have at least two fluid flow channels (7, 8) according to a predetermined pattern, and the plates provided with fluid flow channels (7, 8) are arranged in such a way that the reaction mixture flows through the heat exchanger (4) in a first flow path direction and the heat exchange medium used in the heat exchanger (4) flows through the heat exchanger (4) in a second flow path direction. The plates (5, 6) in the at least one heat exchanger (4) are connected to one another by brazing.

Description

Reactor and process for its production

The present invention relates to a chemical reactor for the reaction of fluid reaction mixtures. It further relates to a process for the preparation of this reactor and its use.

In the majority of chemical processes, either heat must be supplied or removed. As a result, many parts of chemical plants are occupied with harboring or moving fluids that need to be heated or cooled at certain points of the process. Many industrially used chemical processes use reactors in which the starting materials are reacted under certain pressure and temperature conditions in the presence of a catalyst. Almost all of the reactions produce or absorb heat, that is, they are exothermic or endothermic. Cooling due to the endothermic reaction usually affects the reaction rate and related parameters such as conversion and selectivity. Uncontrolled heating by exothermic reactions usually damages the reaction apparatus. In the case of an uncontrolled increase in temperature, ie, when the reaction passes, undesirable by-products can be formed and the catalyst used can be deactivated. Furthermore, while an ideal catalyst is not altered by the reaction process, in reality many catalysts are deactivated or poisoned, so that on an industrial scale the cost of catalyst regeneration or catalyst exchange represents a significant cost.

WO 01/54806 discloses a reactor comprising a reaction zone and plate-type heat exchange means in operative communication with the reaction zone, wherein the heat exchange means is composed of a plurality of metal plates positioned one on top of the other. Fluid flow channels are formed in the metal plates according to a predetermined pattern. The metal plates are aligned, when juxtaposed, to define discrete heat exchange paths for fluids and bonded by diffusion bonding. Disadvantages of diffusion welding, however, are that very high demands are made on the surface quality of the components to be joined with regard to roughness, purity, dimensional accuracy and planarity. Another disadvantage is the production conditions: it is a high vacuum needed, high joining temperatures of up to about 1000 ° C and the associated energy consumption, long standstill and process times and restrictions on the basic materials and material combinations. The resulting costs of such products can drastically reduce their use. With regard to the materials, at higher temperatures, as occur in diffusion welding, the risk that the workpiece warps thermally and that due to structural changes, the strength of the workpiece suffers. Alternative joining methods are discussed in the context of microreactors. For example, DE 102 51 658 A1 discloses that, for the production of microstructure components, at least the joining surfaces of microstructured component layers of aluminum and / or aluminum alloys, copper / copper alloys and / or stainless steels have at least one multifunctional barrier layer and a solder layer applied to the at least one barrier layer, the component layers stacked and then soldered under heat. However, this publication relates to microstructure components.

It will be appreciated from the foregoing that there remains a need for a chemical reactor that is not limited to the microstructure scale that can be designed as a multi-stage adiabatic reactor that can be made more inexpensively and with less thermal stress than previously possible by diffusion welding ,

The object is achieved according to the present invention by a chemical reactor for reacting fluid reaction mixtures, comprising at least one adiabatic reaction zone, which comprises a catalyst bed, and further comprising at least one heat exchanger following the reaction zone, the heat exchanger comprising layers stacked and interconnected with one another, the individual plates having at least two separate fluid flow channels according to a predetermined pattern and the plates provided with fluid flow channels are arranged such that the reaction mixture in a first flow path direction and the heat exchange medium used in the heat exchanger in a second Strömungswegrichtung flow through the heat exchanger, wherein the plates in the at least a heat exchanger are connected by brazing.

The reaction zones contain catalyst beds. Catalyst bed is understood here to mean an arrangement of the catalyst in all known forms, for example a fixed bed, a fluidized bed or a fluidized bed. Preferred is a fixed bed arrangement. This comprises a catalyst bed in the true sense, ie loose, supported or unsupported catalyst in any form and in the form of suitable packings.

The term catalyst bed as used herein also encompasses contiguous areas of suitable packages on a support material or structured catalyst supports. These would be, for example, to be coated ceramic honeycomb carrier with comparatively high geometric surfaces or corrugated layers of metal wire mesh on which, for example, catalyst granules is immobilized.

The heat exchanger is constructed so that it can be described as a succession of stacked and interconnected plates. In the plates are fluid flow incorporated channels through which a fluid from one side of a plate to the other side, for example to the opposite side, can flow. The channels can be linear, thus forming the shortest possible path. However, they can also form a longer path by being laid out according to a wavy, meandering or zigzag pattern. The cross-sectional profile of the channels may, for example, be semicircular, elliptical, square, rectangular, trapezoidal or triangular. Having at least two separate fluid flow channels per plate means that these channels pass over the plate and the fluid flowing therein can not change between the channels.

The flow path direction may be defined by the vector between the plane in which the starting points of the fluid flow channels lie and the plane in which the end points of the fluid flow channels of a plate or plate stack lie. So she gives the general

Direction of the flow of fluid through the heat exchanger. This is the name of a first

Flow path direction is the direction in which the process gas mixture flows through the heat exchanger or, in continuation, through the reaction zone. A second flow path direction designates the path of the heat exchange medium. This can, for example, in direct current,

Countercurrent or crossflow flow to the process gas mixture.

Overall, the heat exchanger works so effectively that the temperature of the process gas mixture on entering the catalyst bed of the next reaction zone, even when the reaction starts, does not lead to a local overheating of the catalyst.

The joining of the plates in the at least one heat exchanger by means of brazing means that, by definition, a solder having a melting temperature of> 450 ^° C. is used. At lower melting temperatures one speaks of soft soldering, which also has a lower mechanical strength of the solder joint result. In the context of the present invention, the solder may also have an upper limit of the melting temperature of <900 ⁰ C, <1 100 ⁰ C or <1200 ⁰ C. Brazing is also known by the term brazing.

By soldering the plates of the heat exchanger, it is possible to provide a heat exchanger and thus a total of a chemical reactor according to the invention with a lower energy input. By a suitable choice of a solder and material combinations of the individual plates can be joined, which are not accessible to a diffusion welding.

In one embodiment, the material of the plates of the heat exchanger is selected from the group comprising stainless steel, 1.4571, nickel and / or nickel-based alloy. These materials Due to their mechanical and chemical resistance they are suitable for use in heat exchangers.

In a further embodiment, the plates of the heat exchanger are interconnected by solder, which is selected from the group comprising Kupferbasislot, silver-containing solder, cadmium- and silver-containing solder and / or nickel-based solder. These solders are suitable for their mechanical and chemical resistance.

In a further embodiment, the catalyst bed is formed as a structured packing in the reactor. In a further embodiment of the present invention, the catalyst is present in the catalyst bed as a monolithic catalyst. The use of structured catalysts such as monoliths, structured packings, as well as coated catalysts has mainly a reduction of the pressure loss to the advantage. In addition to the advantages for the overall process can be realized at a lower specific Druckvεrlust the volume to be introduced into the construction of the reactor for the catalyst and the heat exchanger surface by a smaller flow cross-section at longer reaction and heat exchanger stages. A further advantage of the use of structured catalysts is that shorter diffusion paths of the reactants are necessary in the thinner catalyst layers, which can be accompanied by an increase in the catalyst selectivity.

In the structured catalyst bed channels can be incorporated, wherein the hydraulic diameter of the channels> 0.1 mm to <10 mm, preferably> 0.3 mm to <5 mm, more preferably> 0.5 mm to <2 mm. The specific surface area of the catalyst increases as the hydraulic diameter decreases. If the diameter is too small, too much pressure loss occurs. Furthermore, in the case of an impregnation with a catalyst suspension, a channel can also clog.

In a further embodiment, in the reactor, the hydraulic diameter of the fluid flow channels in the heat exchanger is> 10 μm to <10 mm, preferably> 100 μm to <5 mm, more preferably> 1 mm to <2 mm. With these diameters, an effective heat exchange is particularly ensured.

In a further embodiment, the reactor comprises> 6 to <50, preferably> 10 to <40, more preferably> 20 to <30 sequences of reaction zone and heat exchanger. With such a number of reaction zones, the use of materials can be optimized with regard to the reaction of reactants. A smaller number of reaction zones would result in an unfavorable temperature control. The inlet temperature of the reaction mixture would have to be chosen lower, which would make certain catalysts less active. Farther then the average temperature of the reaction also drops. A higher number would not justify the cost and material costs due to the low increase in sales. Especially the handling of corrosive gases such as HCl, O ₂ and Cl ₂ requires resistant and correspondingly expensive materials for the reactor.

In a further embodiment, in the reactor, the length of at least one reaction zone, measured in the flow path direction of the reaction mixture, is> 0.01 m to <5 m, preferably> 0.03 m to <1 m, more preferably> 0.05 m to <0.5 m. The reaction zones can all be the same length or different in length. For example, the early reaction zones may be short, as there are sufficient starting materials available and excessive heating of the reaction zone should be avoided. The late reaction zones can then be long to increase the overall conversion of the process, with less fear of overheating the reaction zone. The stated lengths themselves have proven to be advantageous because at shorter lengths, the reaction can not proceed with the desired conversion and increases at greater lengths, the flow resistance to the process gas mixture too strong. Furthermore, the catalyst exchange is difficult to carry out at longer lengths.

In a further embodiment, in the reactor, the catalyst in the reaction zones independently of one another comprises substances which are selected from the group comprising copper, potassium, sodium, chromium, cerium, gold, bismuth, iron, ruthenium, osmium, uranium, cobalt, rhodium, Iridium, nickel, palladium and / or platinum and oxides, chlorides and / or oxychlorides of the aforementioned elements. Particularly preferred compounds include: copper (I) chloride, copper (II) chloride, copper (I) oxide, copper (II) oxide, potassium chloride, sodium chloride, chromium (III) oxide, chromium (RV) oxide, chromium (VI) oxide, bismuth oxide, ruthenium oxide, ruthenium chloride, ruthenium oxychloride and / or rhodium oxide.

The catalyst can be applied to a carrier. The carrier fraction may comprise: titanium oxide, tin oxide, aluminum oxide, zirconium oxide, vanadium oxide, chromium oxide, uranium oxide, silicon oxide, silica, carbon nanotubes or a mixture or compound of said substances, in particular mixed oxides, such as silicon-aluminum oxides. Further particularly preferred carrier materials are tin oxide and carbon nanotubes.

The ruthenium-supported catalysts can be obtained, for example, by impregnation of the support material with aqueous solutions of RuC.sub.1 and, if appropriate, of a promoter for doping. The shaping of the catalyst can take place after or preferably before the impregnation of the support material. For doping the catalysts are suitable as promoters alkali metals such as lithium, sodium, rubidium, cesium and especially potassium, alkaline earth metals such as calcium, strontium, barium and especially magnesium, rare earth metals such as scandium, yttrium, praseodymium, neodymium and especially lanthanum and cerium, furthermore cobalt and Manganese and mixtures of the aforementioned promoters.

The moldings can then be dried at a temperature of> 100 ⁰ C to <400 ⁰ C under a nitrogen, argon or air atmosphere and optionally calcined. Preferably, the moldings are first dried at> 100 ⁰ C to <150 ⁰ C and then calcined at> 200 ⁰ C to <400 ⁰ C.

In a further embodiment, in the reactor, the particle size of the catalyst independently of each other> 1 mm to <10 mm, preferably> 1.5 mm to <8 mm, more preferably> 2 mm to <5 mm. The particle size may correspond to the diameter for approximately spherical catalyst particles or, for approximately cylindrical catalyst particles, for expansion in the longitudinal direction. The mentioned particle size ranges have been found to be advantageous since with smaller particle sizes, a high pressure loss occurs and with larger particles, the usable particle surface decreases in proportion to the particle volume and thus the achievable space-time yield is lower. In principle, the catalysts or the supported catalysts can have any desired form, for example spheres, rods, Raschig rings or granules or tablets.

In a further embodiment, in the reactor in different reaction zones, the catalyst has a different activity, wherein preferably the activity of the catalyst in the reaction zones, seen along the flow path direction of the reaction mixtures, increases. As a result, if the concentration of the starting materials in the early reaction stages is high, their reaction and thus also the temperature of the process gas mixture will rise sharply. Therefore, in order not to experience undesirable temperature increase in the early reaction zones, a catalyst having a lower activity can be selected. An effect of this is also that less expensive catalysts can be used. In order to achieve the highest possible conversion of the remaining educts in late reaction zones, more active catalysts can be used there. Overall, it is thus possible by the different activity of the catalysts in the individual reaction zones to keep the temperature of the reaction in a narrower and thus more favorable temperature range.

An example of a change in catalyst activity would be when the activity in the first reaction zone is 30% of the maximum activity and increases per reaction zone in increments of 5%, 10%, 15% or 20% until the activity in the last reaction zone is 100%. is. The activity of the catalyst can be adjusted, for example, by the fact that, given the same base material of the support, the same promoter and the same catalytically active compound, the quantitative proportions of the catalytically active compound are different. Furthermore, in the sense of a macroscopic dilution, particles without activity can also be added.

In a further embodiment, in the reactor, the heat exchange medium which flows through a heat exchanger selected from the group comprising liquids, boiling liquids, gases, organic heat carriers, molten salts and / or ionic liquids, wherein preferably water, partially evaporating water and / or water vapor selected become. Under partially evaporating water is to be understood that in the individual fluid flow channels of the heat exchanger liquid water and water vapor are present side by side. This offers the advantages of a high heat transfer coefficient on the side of the heat exchange medium, a high specific heat absorption by the enthalpy of evaporation of the heat exchange medium and a constant temperature across the channel of the heat exchange medium. Especially in cross-flow to the reactant flow guided heat exchange medium, the constant evaporation temperature is advantageous because it allows a uniform heat removal across all reaction channels. The regulation of the Reaktandentemperatur can be done via the adjustment of the pressure level and thus the temperature for the evaporation of the heat exchange medium.

A further subject of the present invention is a method for producing a reactor according to the present invention, wherein the production of the heat exchanger comprises the following steps:

a) cleaning the surfaces of the webs and backs of the plates of oxides and linings;

b) applying solder to the top of the webs;

c) stacking and aligning the heat exchanger plates to be connected;

d) brazing the plate stack by heat input in an oven.

In one embodiment of the method, a roughness depth of <100 .mu.m, preferably of <25 .mu.m is achieved in step a).

In a further embodiment of the method, a protective compound is introduced into the fluid flow channels in step b) before the solder is applied to the upper side of the webs, the protective compound being suitable for preventing the penetration of solder into the fluid flow channels and the protective composition after application the lot is removed again. The protective mass may line or fill the fluid flow channels. The removal of the protective compound can be done by leaching or by melting out. The protective compound prevents the solder clogging the fluid flow channels.

In a further embodiment of the method, the heat input takes place in an inert and / or reducing protective gas atmosphere in step d). An example of an inert inert gas atmosphere is argon or nitrogen gas. An example of a reducing inert gas atmosphere is hydrogen gas.

The present invention will be further explained with reference to FIGS. 1 to 3, without the figures representing a limitation of the invention. Show it:

FIG. 1 a chemical reactor according to the invention

FIG. 2 two plates of the heat exchanger

FIG. 3 interconnected plates of the heat exchanger

In the figures, the reference numerals denote:

I reactor

2 reaction zone

3 catalyst bed

4 heat exchangers

5 plate of the heat exchanger

6 plate of the heat exchanger

7 fluid flow channel

8 fluid flow channel

9 Surface of a plate of the heat exchanger

10 Surface of a plate of the heat exchanger

I 1 cover plate

12 inlet for reaction mixture 13 outlet for reaction mixture

FIG. 1 shows a chemical reactor 1 according to the invention. The reactor is suitable for reacting fluid reaction mixtures which flow through the reactor. The reaction mixture is introduced via inlet 12 into the reactor. Initially, it flows through a heat exchanger 4. This heat exchanger, like the following heat exchangers, comprises a sequence of two plates 5 and 6. The plates, which are lined up alternately, have fluid flow channels. In the illustration of FIG. 1, 5 fluid flow channels 7 are shown in cross section on the first plates. Through this a heat exchange medium can flow. The fluid flow channels of the second plates 6 run in the direction of the flowing reaction mixtures and are therefore not shown in the illustration of FIG.

After the reaction mixture has passed through the first heat exchanger and has reached the predetermined temperature, it continues to flow into a reaction zone 2. This is designed for adiabatic reaction. A catalyst bed 3 is shown in honeycomb shape. The reaction mixture leaves the reaction zone and enters the next heat exchanger, where it is brought to the desired temperature. This sequence of reaction zone and heat exchanger is repeated until the reaction mixture leaves the reactor through the outlet 13 again.

FIG. 2 shows two plates 5 and 6 of the heat exchanger 4. The representation can be understood as a section of an exploded view of the heat exchanger. The first plate 5 has semicircular, straight running fluid flow channels 7. The flow path direction, which is given by the fluid flow channels 7, is represented by the drawn vector A-> B. Between the fluid flow channels 7 are webs with a surface. 9

The second plate 6 in FIG. 2 likewise has semicircular, straight-running fluid flow channels 8. They are perpendicular to the channels 7 of the first plate 5. The flow path direction, which is given by the fluid flow channels 8, is represented by the drawn vector C- → D. Accordingly, this vector is perpendicular to the vector A → B. Between the fluid flow channels 8 are webs with a surface 10th

FIG. 3 shows plates 5 and 6 of the heat exchanger 4 connected to one another in a stack. The plates 5 and 6 are alternately stacked on one another. The fluid flow channels 7 of the plates 5 define a first flow path direction represented by the vector A- »B. The fluid flow channels 8 of the plates 6 define a second flow path direction represented by the vector C-> D. Thus, for example, the reaction mixture along the first flow path direction and a heat exchange medium along the second Strömungswegrichtung flow through the heat exchanger. The top plate 5 is closed by a cover plate 1 1. This cover plate may also constitute part of the shell of the reactor.

Claims

claims

Anspruch [en] A chemical reactor (1) for reacting fluid reaction mixtures comprising at least one adiabatic reaction zone (2) comprising a catalyst bed (3) and further comprising at least one heat exchanger (4) following the reaction zone (2)

the heat exchanger (4) comprises plates (5, 6) stacked on each other and connected to each other,

the individual plates (5, 6) have at least two separate fluid flow channels (7, 8) according to a predetermined pattern and

the plates provided with fluid flow channels (7, 8) are arranged so that the

Reaction mixture in a first Strömungswegrichtung and the heat exchange medium used in the heat exchanger (4) flow through the heat exchanger (4) in a second Strömungswegrichtung, characterized in that

the plates (5, 6) in the at least one heat exchanger (4) are connected together by brazing.

2. Reactor according to claim 1, wherein the material of the plates (5, 6) of the heat exchanger (4) is selected from the group comprising stainless steel, 1.4571, nickel and / or nickel-based alloy.

3. Reactor according to claims 1 or 2, wherein the plates (5, 6) of the heat exchanger (4) are interconnected by solder, which is selected from the group comprising

Copper-based solder, silver-containing solder, cadmium- and silver-containing solder and / or nickel-based solder.

4. Reactor according to one of the preceding claims, wherein the catalyst bed (3) is formed as a structured packing.

5. Reactor according to one of the preceding claims, wherein the catalyst in the catalyst bed (3) is present as a monolithic catalyst.

6. Reactor according to one of the preceding claims, wherein the hydraulic diameter of the fluid flow channels (7, 8) in the heat exchanger (4)> 10 microns to <10 mm, preferably> 100 microns to <5 mm, more preferably> 1 mm to <2 mm.

7. Reactor according to one of the preceding claims comprising> 6 to <50, preferably

> 10 to <40, more preferably> 20 to <30 sequences of reaction zone (2) and heat exchanger (4).

8. Reactor according to one of the preceding claims, wherein the length of at least one reaction zone (2), measured in the flow path direction of the reaction mixture,

> 0.01 m to <5 m, preferably> 0.03 m to <1 m, more preferably> 0.05 m to <0.5 m.

9. Reactor according to one of the preceding claims, wherein the catalyst in the reaction zones (2) independently comprises substances selected from the group comprising copper, potassium, sodium, chromium, cerium, gold, bismuth, iron,

Ruthenium, osmium, uranium, cobalt, rhodium, iridium, nickel, palladium and / or platinum and oxides, chlorides and / or oxychloridec of the aforementioned elements.

10. Reactor according to one of the preceding claims, wherein the particle size of the catalyst, independently of one another> 1 mm to <10 mm, preferably> 1.5 mm to <8 mm, more preferably> 2 mm to <5 mm.

1 1. A reactor according to any one of the preceding claims, wherein in different reaction zones (2) the catalyst has a different activity, wherein preferably the activity of the catalyst in the reaction zones (2), seen along the Strömungswegrichtung the reaction mixtures, increases.

12. Reactor according to one of the preceding claims, wherein the heat exchange medium which flows through a heat exchanger (4) is selected from the group comprising liquids, boiling liquids, gases, organic heat transfer media, molten salts and / or ionic liquids, preferably water, partially vaporizing Water and / or steam are selected.

13. A process for producing a reactor according to claims 1 to 12, wherein the production of the heat exchanger comprises the following steps:

a) cleaning the surfaces of the webs (9, 10) and the backs of the plates (5, 6) of oxides and coatings;

b) applying solder to the top of the webs (9, 10);

c) stacking and aligning the heat exchanger plates (5, 6) to be connected; d) brazing the plate stack by heat input in an oven.

14. The method of claim 13, wherein in step a) a roughness of <100 microns, preferably of <25 microns is achieved.

15. The method according to claims 13 or 14, wherein in step b) before the application of the solder on the upper side of the webs (9, 10) in the fluid flow channels (7, 8) a protective compound is introduced, wherein the protective composition is suitable, the penetration Lot to prevent in the fluid flow channels (7, 8) and wherein the protective compound is removed after the application of the solder again.

16. The method according to any one of claims 13 to 15, wherein in step d) the heat input takes place in an inert and / or reducing inert gas atmosphere.