EP1663472A1

EP1663472A1 - Microphotoreactor for carrying out photochemical reactions

Info

Publication number: EP1663472A1
Application number: EP04764291A
Authority: EP
Inventors: Wolfgang Ehrfeld; Frank Schael
Original assignee: Ehrfeld Mikrotechnik BTS GmbH
Current assignee: Ehrfeld Mikrotechnik BTS GmbH
Priority date: 2003-09-05
Filing date: 2004-08-19
Publication date: 2006-06-07
Also published as: WO2005028095A1; JP4332180B2; CN1845786A; US20070009403A1; JP2007533422A; DE10341500A1

Abstract

The invention relates to a microphotoreactor (1) used to carry out photochemical reactions with a reaction medium. The reaction medium is liquid, gaseous or a dispersion. The light required to carry out the reaction is supplied from a radiation source (9) located outside the reactor (2). The reaction medium flows through at least one reaction channel (4) of a reaction area. At least one region of said area is light transparent and the direction of flow is inclined at an angle of 10 DEG - 90 DEG counter to the horizontal, such that the reaction mixture is transported in the at least one reaction channel(4) by a pressure differential counter to gravity.

Description

Microphotoreactor for performing photochemical reactions

The invention relates to a microphotoreactor for carrying out photochemical reactions in at least one reaction medium, which is liquid, gaseous or a dispersion.

Photochemical reactions may occur. a. in the technical synthesis of chemical compounds e.g. in the fields of pharmaceuticals, pesticides, fragrances and vitamins. Such reactions are currently mainly carried out in large-format reactors. One problem with this is to uniformly irradiate the reactants with light to carry out the reactions. DE 101 05 427 AI describes a photochemical reactor in which there are glass or quartz hollow bodies in the medium to be converted which are filled with gas. The gas in the hollow bodies is excited by an external electromagnetic field, so that the light is generated directly in the medium.

In order to avoid the formation of a light-absorbing coating on the surface of the lamp cooler, DE 36 25 006 AI describes a photoreactor for photochemical syntheses which, from the inside out, has a concentrically arranged lamp with electrical connections, an annular lamp cooler made of glass and a reaction space which passes through the outer jacket of the lamp cooler and the inner jacket of the reactor with a mirrored inner wall is limited, wherein in the reaction chamber a device equipped with brushes or wipers rotates, which is arranged so that the outer jacket of the lamp cooler is kept free of light-absorbing coating during operation of the photoreactor.

In contrast to conventional reactors, microreactors can offer a more favorable surface to volume ratio. This surface to volume ratio can also be used to transport radiation in a reaction solution to improve significantly compared to conventional photochemical apparatus. The conditions in conventional plants for photochemical conversion often lead to the fact that only low concentrations of starting materials can be used. This is partly due to the fact that the thickness of the irradiated liquid layer cannot be controlled well.

H. Ehrich et al., Application of Microstructured Reactor Technology for the Photochemical Chlorination of Alkylaromatics, Chimia 56 (2002), pp. 647 to 653, describes the use of a microfall film reactor for the selective photochlorination of toluene-2,4-diisocyanate , A corresponding microfall film reactor is also described in DE 101 62 801 AI. This reactor allows radiation to be coupled in through a window, but does not use the full amount of incident radiation, since a part is shadowed due to the construction. Furthermore, this reactor has the disadvantage that the residence and irradiation times cannot be controlled over a wide range, because with the falling film principle there is always the at least latent danger that the film will tear off.

Another microreactor for photochemical reactions is described by Hang Lu et al., Photochemical reactions and on-line UV detection in microfabricated reactors, Lab on a chip, 2001, 1, pp. 22 to 28. In this microreactor, a silicon chip is provided with a channel. The reactor is covered with a Pyrex plate, which allows irradiation with light. A disadvantage of the microreactor disclosed here is that the residence time behavior of the reactants in the channel is not well defined, and that the reactor design with a single channel does not allow a good possibility of adapting flow rates and irradiation times. This is also the case for the Hang Lu et al. The reactor described uses silicon brittle and therefore prone to breakage, difficult to clean and incompatible for many media.

It is therefore an object of the present invention to provide a microphotoreactor which has a defined residence time behavior of the reactants in the reaction spaces and which allows adjustment of flow rates and irradiation times.

The solution according to the invention consists in a microphotoreactor for carrying out photochemical reactions in at least one reaction medium, which is liquid, gaseous or a dispersion, and in which this is for carrying out the reaction required light is supplied from an irradiation source arranged outside the reactor. The reaction medium flows through at least one reaction channel of a reaction zone, at least one area in this zone being transparent to the light and the direction of flow being inclined towards the horizontal, and the inlet and outlet to the at least one reaction channel being arranged such that Reaction medium in the at least one reaction channel is promoted by a pressure difference against gravity.

The angle at which the flow direction is inclined towards the horizontal is preferably in the range from 10 ° to 90 °. This creates a flow resistance in the reaction channels that is greater than edge effects that occur within the individual reaction channels. A narrow residence time distribution in the reaction channels is hereby achieved. The inclination with which the flow direction is inclined towards the horizontal depends on the viscosity of the reaction medium. A lower angle can be selected with increasing viscosity, since the flow resistance also increases with increasing viscosity.

In a preferred embodiment of the invention, the reaction zone is in the form of a plate in which the at least one reaction channel is located and the at least one plate surface of which is transparent. Such a reaction zone plate can also be represented in such a way that the reaction channels are only in one plate part and this is then covered with a transparent plate part, but the reverse arrangement is also possible.

The direction of flow is determined by the inclination of the reaction zone.

A crucial part of the total residence time of the reaction medium in the apparatus is the time during which it passes through the irradiated zone and can be converted photochemically. The irradiation time required to convert a certain number of moles of a substance can be estimated using the following relationship: hcN _L t = n Iλφ (1) t is the irradiation time (in s), / is the radiation power (in watts), h is the Planck 'see quantum of action (in Js), c is the speed of light (in m / s), λ is the wavelength (in m), N _L is the Avogrado number (in mol ^"1 ), n is the mol number of the irradiated molecules, φ is the quantum yield of the reaction.

This relationship shows that the irradiation time essentially depends on the quantum yield, the intensity of the light source and the number of molecules to be converted. The irradiation time of the microphotoreactor according to the invention can be adapted to the requirements by adjusting the flow rate via the applied pressure difference. The exchange of the reaction zone plate additionally allows the adaptation to a required throughput.

In a preferred embodiment there are 10 to 10,000 reaction channels in the reaction zone. The dimensions of the reaction channels are preferably adapted to the photochemical conversion to be carried out. Preferred dimensions of depth and width of the reaction channels are in the range from 10 to 1000 μm.

The reaction channels are preferably produced with the aid of etching processes, laser material processing, microfunk erosion or other methods of microfabrication. The depth of the reaction channels is selected so that, on the one hand, sufficient irradiance is generated up to the edge of the channel in order to achieve a desired conversion even at the edge. On the other hand, the largest possible amount of radiation should be absorbed in the reaction medium in order to be able to use as much of the radiated energy as possible for the implementation. The depth of penetration can be calculated using the Lambert-Beer law, as the thickness of the liquid layer, after which the intensity of the incident radiation has dropped to 90% of the intensity of the originally incident radiation.

", 90% _ -J_ (2) εc Here ε and c are the molar extinction coefficient (in L mol ^"1 cm ^{" 1} ) and the concentration (in mol / L). Alternatively, other depths of penetration (e.g. decrease in intensity to 1/1 of the original intensity) can be applied.

In a preferred embodiment, the reaction channels have a round cross section. This prevents substances contained in the reaction medium from sticking in the corners.

In parallel arrangements, the microchannels can be straight, angled, curved or in other geometries known to the person skilled in the art. To adjust the irradiation time, a longer distance of the reaction channels in the irradiated reaction zone is preferably realized at the same flow rate.

In a further preferred embodiment, the feed to the reaction channels is designed in such a way that mixing of at least two components is made possible.

In a particularly preferred embodiment, the reaction channels are coated. Coatings can be used that act on the surface tension of the reaction medium in order to influence the flow properties. Catalytically active coatings which can have a favorable influence on the chemical reaction in the microphotoreactor are particularly preferred. A coating with a material which has a high reflectivity in the spectral range of the radiation used is also possible. In addition to the coating of the reaction channels, in a further preferred embodiment the lower plate layer can be made of a material which has a catalytically active effect, which influences the surface tension of the reaction medium, or which has a high reflectivity in the spectral range of the radiation used.

In order to enable the reaction medium to be irradiated, the reaction zone plate in a preferred embodiment comprises at least a lower plate part and a transparent cover plate part which lies flush on the lower plate part. In a preferred embodiment, the radiation sources used are, for example, gas discharge lamps, semiconductor light sources or lasers which irradiate the reaction medium to be irradiated through the transparent cover plate. Several radiation sources which emit at different wavelengths or in different spectral ranges can be used simultaneously. The radiation source preferably used for the photochemical reaction irradiates the reaction medium homogeneously and spectrally selectively in the selected range.

The microphotoreactor can be flat, curved or cylindrical. In the case of a curved or cylindrical design, the transparent plate part is preferably arranged on the inside, which points to an irradiation source.

In a preferred embodiment, the transparent plate part is thermally insulating. For this purpose, it can be made from a thermally insulating material or preferably be double-walled with an air gap. This prevents fogging at low temperatures in the reaction medium. In a further preferred embodiment, it is designed as a spectral filter. The spectral filter can be a short pass, long pass, band pass or interference filter. Furthermore, the transparent plate part can contain an IR filter in order to prevent undesired heating of the reaction medium by infrared components from the radiation source.

In a preferred embodiment, the reaction channels are formed in the lower plate part. The reaction channels are covered by the transparent cover plate so that no reaction medium can escape from the reaction channels. The transparent plate part can be smooth or also contain reaction channels formed therein. In a preferred embodiment, the reaction channels are taken up both in the lower plate part and in the transparent plate part and brought congruently one above the other. As a result, the cross-sectional geometry of the reaction channels is determined by the shape of the reaction channels in the lower plate part and the shape of the reaction channels in the transparent plate part.

In order to remove the heat generated during the reaction or to additionally supply heat, the reaction zone can be releasably attached to a heat transfer module. The heat transfer module can be used to temper the Reaction zone plate include an electrical heater or Peltier elements or be designed as a heat exchanger. By including gaps between individual heating or cooling zones in the heat transfer module, a temperature gradient can be set in the reaction zone plate in the direction of flow. Sensors, which are integrated either in the lower plate of the reaction zone plate or in the heat transfer module, can be used, for example, to determine the pressure, the temperature, the viscosity or the flow rate. For example, pressure, temperature, thermal conductivity, viscosity or radiation sensors as well as capacitive, inductive, piezoresistive, dielectric sensors, conductivity or ultrasonic detectors can be used for this purpose.

The invention is described in more detail below with reference to a drawing.

This shows in:

FIG. 1 shows a perspective view of a vertically standing microphotoreactor with an irradiation device,

FIG. 2.1 shows a schematic illustration of a reaction zone plate with straight reaction channels,

FIG. 2.2 shows a schematic illustration of a reaction zone plate with angled reaction channels,

FIG. 2.3 shows a schematic illustration of a reaction zone plate with a channel with a structured wall,

FIG. 3 shows a schematic illustration of a reaction zone plate with integrated mixer structures,

Figure 4 is a microphotoreactor with heat transfer module and reaction zone plate. Figure 5.1 shows a section through a reaction zone plate in a first embodiment

Figure 5.2 shows a section through a reaction zone plate in a second embodiment

FIG. 1 shows a perspective view of a vertically standing microphotoreactor with a radiation source.

A microphotoreactor 1 comprises a reaction zone designed as a reaction zone plate 2, which is accommodated in a housing 3. In the reaction zone plate 2, reaction channels 4 are received, in which the photochemical reaction takes place. Depending on the size of the reaction zone plate 2, between 10 and 10,000 reaction channels 4 can preferably be accommodated in the reaction zone plate 2. In addition to the arrangement shown in FIG. 1 with parallel, straight reaction channels 4, the reaction channels 4 can also be angled or curved or adopt any other arrangement known to the person skilled in the art.

The reaction zone plate 2 can be fastened in the housing 3 in a force-locking or positive manner. In the embodiment shown in Figure 1, the reaction zone plate 2 is non-positively fastened with screws 5 in the housing 3. The reaction zone plate 2 preferably comprises a lower plate part which is closed by a transparent cover plate part 6 which is transparent to light with the wavelength required for the reaction.

The reaction medium is fed to the reaction zone plate 2 via an inlet 7. If a mixture of reactants is only to take place in the reaction zone plate 2, a separate feed 7 must be provided for each reactant.

The product produced by the photochemical reaction is removed from the microphotoreactor 1 through an outlet 8. In order to increase the flow resistance in the reaction channels 4 in addition to the flow resistance impressed by gravity, a valve can be arranged at the outlet 8. The reaction medium is transported in the reaction channels 4 by means of a pressure difference. The light required for the photochemical reaction is emitted by an radiation source 9 emitted. Suitable radiation sources are, for example, gas discharge lamps, semiconductor light sources or lasers. The radiation source 9 is selected so that light is emitted in the wavelength range as is required for the photochemical reaction. The wavelength range of the light can extend from the infrared range over the range of visible light to the ultraviolet range. The radiation source 9 is preferably designed such that the emitted light strikes the reaction zone plate 2 along the direction identified by reference number 10.

Sensors can be integrated in the microphotoreactor to monitor pressure, temperature, viscosity and flow velocity. The voltage supply to the sensors, if such is required, and the data transmission then take place via an electrical connection 11 arranged on the housing 3. The data transmission can take place via cables, optical fibers or radio technology to an external periphery. The task of the periphery is the registration, display, further processing and regulation of temperatures, pressures, flow rates, radiation intensities or radiation wavelengths. The measurement of the radiation intensities or radiation wavelength is preferably carried out on the basis of the measurement of sales. Computers are preferably used as external peripherals.

Figures 2.1, 2.2 and 2.3 show different embodiments of the reaction channels in the reaction zone plate.

In the embodiment shown in FIG. 2.1, the reaction channels 4 are arranged parallel and straight in the reaction zone plate 2. The reaction medium is supplied via inlet openings 12 in the lower region of the reaction channels 4. The reaction medium then flows upward in the individual reaction channels 4, wherein it is irradiated by light from the radiation source 9, not shown here. In the reaction channels 4, the reaction medium is converted into the product. The product collects in a collecting zone 13 arranged above the reaction channels 4. The product is removed from the collecting zone 13 via an outlet 14.

In contrast to this, FIG. 2.2 shows an embodiment with angled reaction channels 4. Here, too, the reaction medium is via inlet openings 12 Reaction channels 4 supplied. The photochemical reaction takes place in the reaction channels 4, in which the reaction medium is converted into product. The product collects in the collecting zone 13 and is discharged from the collecting zone 13 via the outlet 14. The angled arrangement of the reaction channels 4 means that fewer reaction channels 4 can be accommodated on the reaction zone plate 2 than with straight reaction channels. The angled reaction channels 4 extend the flow path and thus the dwell time in the microphotoreactor.

FIG. 2.3 shows a further embodiment with a wide reaction channel 4, into which a structure 15 is stamped. In the embodiment variant shown in FIG. 2.3, the reaction medium is also added via inlet openings 12 in the lower region of the reaction zone plate 2. The product is removed here via the outlet 14, which is arranged in the upper region of the reaction zone plate 2. A collection zone 13 can be omitted in the embodiment as shown in FIG. 2.3, since the entire reaction medium is passed through a reaction channel 4. In addition, in the embodiment variant shown in FIG. 2.3, a further fluid can be supplied via openings 16 which are attached on the side. Due to the structure 15 in the reaction channel 4, the fluid added laterally via the openings 16 mixes with the reaction medium supplied via the inlet opening 12. By adding the fluid through the openings 16, a cross flow is generated with which, for example, solid particles can be removed from the reaction medium. The cross flow with the solid particles contained therein can then be withdrawn from the channel via outlet openings 29.

Figure 3 shows a reaction zone plate with integrated mixer structures.

The embodiment shown in FIG. 3 essentially corresponds to the embodiment shown in FIG. 2.1. In contrast to the embodiment shown in FIG. 2.1, the feed of the reaction medium to the reaction channels 4 does not take place via an inlet opening 12 each, but via a mixing zone 20 in which a first fluid via inlet openings 17 for the first fluid and a second fluid via inlet openings 18 is supplied to the reaction channels 4 via the second fluid. In order to ensure intensive mixing of the first fluid and the second fluid, the inlet openings 17, 18 are arranged alternately. The inlet are openings 17 for the first fluid in the embodiment shown in FIG. 3 each on the right side of the reaction channel 4 and the inlet opening 18 for the second fluid on the left side of the reaction channel 4. The inlet openings 17 for the first fluid are interlocked with the inlet openings 18 for the second fluid. This ensures intensive mixing of the two fluids. In the reaction channel 4, the reaction medium flows in the flow direction of the collecting zone 13 identified by the reference numeral 19. The product is then removed from the collecting zone 13 via the outlet 14. In addition to the alternately arranged toothed inlet openings 17, 18, a profile can also be introduced into the reaction channel 4 for mixing the components of the reaction medium. The irradiation required for the photochemical reaction can then take place either in the region of the mixing zone 20 and / or at the connection to the mixing zone 20.

FIG. 4 shows a microphotoreactor with a heat transfer module and reaction zone plate.

In order to be able to remove heat generated during the photochemical reaction or to be able to supply additional heat, the reaction zone plate 2 can preferably be detachably mounted on a heat transfer module 21. The supply of heat can be supplied either via electrical heating elements 22 or a temperature control medium. For example, water or thermal oils are suitable as the temperature control medium. The temperature control medium is fed to the heat transfer module 21 via an inlet 23 for the temperature control medium and removed again via an outlet 24 for the temperature control medium. When heating or cooling the reaction zone plate 2 with a temperature control medium, fluid channels are arranged in the heat transfer module 21, through which the temperature control medium flows. The arrangement of columns 25 in the heat transfer module 21 arranged transversely to the direction of flow of the reaction medium in the reaction zone plate 2 allows the heat transfer module 21 to be divided into individual temperature control areas 26. With different tempering of the individual tempering areas 26, a temperature gradient can be generated in the reaction zone plate 2. To monitor the temperature of the individual temperature control areas 26, temperature sensors 27 are preferably arranged in the temperature control areas 26. Suitable temperature sensors 27 are, for example, thermocouples or resistance thermometers. The releasable connection of the reaction zone plate 2 to the heat transfer module 21 enables a simple exchange of the reaction zone plate 2 if other reaction conditions are desired or another reaction is to be carried out.

In order to increase the throughput, several microphotoreactors 1 can be connected in parallel in a simple manner. The advantage of connecting individual microreactors 1 in parallel is that the reaction conditions do not change when the reaction rate is increased.

In addition to the parallel arrangement of the reaction channels 4, the reaction channels 4 can also be arranged consecutively.

5.1 shows a section through a reaction zone plate in a first embodiment.

The reaction zone plate 2 comprises a lower plate part 28 and a transparent cover plate part 6. The lower plate part 28 is preferably made of a material which has a favorable influence on the surface tension of the reaction medium, has a catalytic effect or which has a high reflectivity in the spectral range.

The transparent plate part 6 is preferably thermally insulating. For this purpose, it can either be made of a thermally insulating material or have an air gap 32.

In the embodiment shown in FIG. 5.1, the reaction channels 4 are formed in the lower plate part 28. In addition to the semicircular cross section shown here, the reaction channels 4 can also assume a triangular, rectangular, trapezoidal or any other cross section known to the person skilled in the art. The reaction channels 4 are preferably closed by the transparent cover plate part 6. For this purpose, the transparent cover plate part 6 is preferably connected to the lower plate part 28 in a positive or non-positive manner. In contrast to the embodiment in FIG. 5.1, the reaction channels 4 are also formed in the transparent cover plate part 6 in FIG. 5.2. The fact that the reaction channels 4 formed in the lower plate part 28 and the transparent cover plate part 6 are congruent one above the other enables a circular cross section of the reaction channels 4 to be produced. By avoiding corners in the reaction channels 4, it is advantageously avoided that substances from the reaction medium are deposited on the channel walls 30, 31.

LIST OF REFERENCE NUMBERS

Microphotoreactor

Reaction zone plate

casing

reaction channel

screw

Transparent cover plate part

Intake

procedure

radiation source

Direction of light rays

Electrical connection

inlet opening

collection zone

outlet

structure

opening

Inlet opening for the first fluid

Inlet opening for second fluid

flow direction

mixing zone

Heat Transfer Module

heating element

Inlet for temperature control medium

Process for temperature control medium

column

Temperature control

temperature sensor

Lower plate part

outlet openings

First duct wall Second duct wall

Claims

claims

1. Microphotoreactor for carrying out photochemical reactions in at least one reaction medium, the reaction medium being liquid, gaseous or a dispersion, and in which the light required for carrying out the reaction is supplied from an irradiation source (9) arranged outside the reactor, characterized in that the reaction medium flows through at least one reaction channel (4) of a reaction zone (2), at least one area in this zone being transparent to the light and the direction of flow being inclined at an angle of 10 ° to 90 ° to the horizontal that the reaction medium in the at least one reaction channel (4) is promoted by a pressure difference against gravity.

2. Microphotoreactor according to claim 1, characterized in that the reaction zone is in the form of a reaction zone plate (2).

3. Microphotoreactor according to claim 2, characterized in that the reaction zone plate (2) is releasably attached to a heat transfer module (21).

4. Microphotoreactor according to claim 2 or 3, characterized in that the reaction zone plate (2) is flat, curved or cylindrical.

5. Microphotoreactor according to one of claims 2 to 4, characterized in that the reaction zone plate (2) at least a lower plate part (28) and a transparent cover plate part (6) which rests flush on the lower plate part (28) and with this positively or is non-positively connected.

6. Microphotoreactor according to claim 5, characterized in that the at least one reaction channel (4) is accommodated in the lower plate part (28).

7. Microphotoreactor according to claim 5 or 6, characterized in that the at least one reaction channel (4) is received in the transparent cover plate part (6).

5 8. Microphotoreactor according to one of claims 5 to 7, characterized in that the lower plate part (28) is made of a material which has a high reflectivity in the spectral range of the radiation used.

9. Microphotoreactor according to one of claims 5 to 7, characterized in that 10 the lower plate part (28) is made of a material which has a catalytically active effect.

10. Microphotoreactor according to one of claims 1 to 7, characterized in that the at least one reaction channel (4) with a high reflectivity in

I spectral region material or a catalytically active material 15 is coated.

11. Microphotorector according to one of claims 5 to 10, characterized in that the transparent cover plate part (6) is made of a thermally insulating material. 20

12. Microphotoreactor according to one of claims 5 to 11, characterized in that the transparent cover plate part (6) acts as a spectral filter.

13. Microphotoreactor according to claim 3, characterized in that the heat transfer module (21) for temperature control of the reaction zone plate (2) comprises electrical heaters or Peltier elements or is designed as a heat exchanger.

14. Microphotoreactor according to one of claims 3 to 13, characterized in that the heat transfer module (21) is designed such that a temperature gradient can be set along the reaction zone plate (2) in the direction of flow.

15. Microphotoreactor according to one of claims 1 to 14, characterized in that in the lower plate part (28) or in the heat transfer module (21) sensors (27) for monitoring the reaction medium and for regulating reaction parameters are accommodated.

16. Microphotoreactor according to one of claims 1 to 15, characterized in that in the at least one reaction channel (4) a mixing zone (20) for mixing at least two reaction media is added.

17. Microphotoreactor according to claim 16, characterized in that the mixing zone (20) can be irradiated.

18. Microphotoreactor according to claim 16, characterized in that the irradiation with light takes place directly after the mixing zone (20).

19. Microphotoreactor according to one of claims 1 to 18, characterized in that the at least one reaction channel (4) is coated with a material with which the surface tension of the reaction medium is favorably influenced.