HK1096331A - Microphotoreactor for carrying out photochemical reactions - Google Patents

Description

Micro-photo-reactor for carrying out photochemical reactions

The invention relates to a micro-reactor for carrying out photochemical reactions in a reaction medium, wherein the medium is liquid, gaseous or dispersed.

Photochemical reactions are used for the technical synthesis of chemical compounds in the fields of, for example, pharmaceuticals, plant protection agents, odorants and vitamins. These reactions are now first carried out in large-scale reactors. There is a problem that the reactant is uniformly irradiated with light in order to perform the reaction. DE 10105427 a1 describes a photochemical reactor in which a glass or quartz hollow body is located inside the medium to be converted, said hollow body being filled with a gas. The gas in the hollow body is excited by an external electromagnetic field, as a result of which light is generated directly in the medium.

In order to avoid the formation of light-absorbing coatings on the lamp cooler surfaces, a photoreactor for photochemical synthesis is described in DE 3625006 a1, which comprises, from the inside to the outside, a concentrically arranged lamp with electrical connections, a circular ring-shaped lamp cooler made of glass, and a reaction space which is bounded by the outer shell of the lamp cooler and the inner shell of the reactor by mirrored (Verspiegelter) inner walls, wherein a device provided with brushes or wipers is rotated in the reaction space and is arranged such that the outer shell of the lamp cooler is free of light-absorbing coatings during operation of the photoreactor.

Unlike conventional reactors, photoreactors can provide a more favorable surface to volume ratio. This surface to volume ratio can also be used to provide a significant improvement in the transmission of light through the reaction solution as compared to conventional photochemical devices. This ratio in the customary photochemical reaction apparatuses often results in the use of only minute concentrations of educt. This results in part in a poor monitoring of the thickness of the irradiated liquid layer.

The use of a microdialysis reactor for the selective photochlorination of toluene-2, 4-diisocyanate is described in "Application of Microstructured reactor Technology" published by H.Ehrich et al, Chimia 56(2002) pages 647 to 653. A corresponding micro-biofilm reactor is also described in DE 10162801 a 1. This reactor, although allowing the incoming light to pass through a window, does not utilize the entire amount of incident light, since a portion is shielded by the structure. Furthermore, this reactor has the disadvantage that the residence time and the irradiation time cannot be monitored over a wide range, since there is always at least a potential risk of film cracking for the film-dropping principle.

"Photochemical reactions and on-line UVdetection in microbial reactions", Lab on a chip 2001, pages 22 to 28, published by Hang Lu et al, describe another microreactor for Photochemical reactions. In this microreactor a silicon chip is provided with a channel. The reactor was covered by a parylene sheet, so that it allowed for light irradiation. A disadvantage of the microreactors disclosed here is that the residence time behavior of the reactants in the channels cannot be determined well and a reactor concept with one single channel does not allow a good matching of the throughflow rate to the irradiation time. Furthermore, the silicon material used for the reactor described by Hang Lu et al is brittle and therefore easily breaks, is difficult to clean and is incompatible with many media.

It is therefore an object of the present invention to provide a miniature photoreaction reactor which provides a defined residence time behavior of the reactants in the reaction space and which makes it possible to adapt the throughflow rate to the irradiation time.

The solution according to the invention is a microphotoreactor for carrying out photochemical reactions in at least one reaction medium which is liquid, gaseous or dispersed, wherein the light required for carrying out the reaction is supplied by a radiation source arranged outside the reactor. The reaction medium flows through the reaction channels of the at least one reaction zone, wherein at least one point in this reaction zone is transparent to light and the flow direction is inclined with respect to the horizontal, and the supply and discharge with respect to the at least one reaction channel is arranged such that the reaction medium is conveyed in the at least one reaction channel by a pressure difference counter to the force of gravity.

The angle at which the flow direction is inclined relative to the horizontal is preferably in the range from 10 ° to 90 °. This results in a flow resistance in the reaction channels which is greater than the edge effect which occurs in the individual reaction channels. Thereby achieving a narrow residence time distribution in the reaction channel. The inclination of the throughflow direction relative to the horizontal depends on the viscosity of the reaction medium. A smaller angle can be selected with increasing viscosity, since the flow resistance increases with increasing viscosity.

In a preferred embodiment of the invention the reaction zone has the shape of a plate in which at least one reaction channel is located and at least one of its plate planes is transparent. It is also possible to describe a reaction zone plate in which the reaction channel is located only within one plate and which is covered by a transparent plate, but the opposite configuration can also be achieved.

The throughflow direction is determined by the inclination of the reaction zone. One decisive component of the total residence time of the reaction medium in the apparatus is the time during which the reaction medium flows through the irradiated region and can be converted photochemically. The irradiation time required for converting a defined molar mass of a substance can be deduced by the following relation:

t is the irradiation time(s), I is the power of the light (W), h is the Planckian quantum, (Js), c is the speed of light (m/s), λ is the wavelength (m), N_LIs the number (mol) of Frafgardolo^-1) N is the number of moles of irradiated molecules,  is the quantum output of the reaction.

This relationship indicates that the illumination time depends mainly on the quantum output, the intensity of the light source and the number of molecules to be converted. The irradiation time of the inventive micro-photoreaction reactor can be adapted to the requirements by adjusting the throughflow rate by means of the applied pressure difference. The replacement of the reaction zone plates additionally allows adaptation to the flow rate delivered.

In a preferred embodiment there are 10 to 10,000 reaction channels in the reaction zone. The dimensions of the reaction channel are preferably adapted to the photochemical conversion to be carried out. Preferred reaction channel depths and widths are between 10 μm and 1000 μm.

The reaction channel is preferably formed by means of etching, laser material machining, micro-spark erosion or other micro-machining methods. The depth of the reaction channel is selected such that, on the one hand, sufficient radiation intensity is generated up to the channel edge for achieving the desired conversion also at the edge. On the other hand, as large an amount of light as possible is absorbed in the reaction medium, so that as much incident energy as possible can be used for the conversion. The penetration depth can be calculated by means of the lambert-beer law as the thickness of the liquid layer, according to which the incident light intensity is reduced to 90% of the original incident light intensity.

Where ε and c are the molar extinction coefficients (L mol)^-1cm^-1) Or concentration (mol/L). Other penetration depths (e.g., 1/e tel of intensity reduction to initial intensity) may also be selected.

In a preferred embodiment the reaction channel has a circular cross-section. This prevents substances contained in the reaction medium from adhering inside the corners.

The microchannels may be formed linearly, angularly, meanderingly, or in other geometries known to those of ordinary skill in the art in parallel configurations. For adaptation to the irradiation time, a longer reaction channel section is preferably realized in the irradiated reaction zone for the same throughflow rate.

In a further preferred embodiment, the feed to the reaction channel is designed such that at least two components are mixed.

In a particularly preferred embodiment, the reaction channels are coated. Coatings acting on the surface stress of the reaction medium can be used here for influencing the flow behavior. Particularly preferred are catalytically active coatings, which can advantageously influence chemical reactions in the miniature photoreaction reactor. It is also possible to coat with a material which has a high reflectivity for light in the spectral range used.

In addition to the coating of the reaction channels, in a further preferred embodiment the lower plate layer can be made of a catalytically active material, which influences the surface stress of the reaction medium or which has a high reflectivity for light in the spectral range used.

In order to be able to achieve irradiation of the reaction medium, the reaction zone plate comprises in a preferred embodiment at least one lower plate and a transparent covering plate, which rests flush against the lower plate.

In a preferred embodiment, a gas discharge lamp, a semiconductor light source or a laser is used as the radiation source, which irradiates the reaction medium to be irradiated via the transparent cover plate. While multiple illumination sources may be used, they emit at different wavelengths or in different spectral ranges. The radiation source preferably used for the photochemical reaction irradiates the reaction medium homogeneously and spectrally selectively in the selected range.

The microreactor can be designed in a planar, curved or cylindrical manner. The plate, which is transparent for the curved or cylindrical embodiment, is preferably arranged on the inner side directed towards an irradiation source.

In a preferred embodiment, the transparent plate is thermally insulating. For this purpose, the plate can be made of an insulating material or preferably double-walled by means of an air gap. Thereby preventing deposition at low temperatures of the reaction medium. In a further preferred embodiment, the plate forms a spectral filter. The spectral filter may be a short channel, long channel, band channel or interference rejection filter. The transparent plate may furthermore comprise an IR filter for preventing undesired heating of the reaction medium by infrared components from the radiation source.

In a preferred embodiment, the reaction channel is formed in the lower plate. In order to prevent the reaction medium from being discharged from the reaction channels, the reaction channels are covered by a transparent covering plate. The transparent plate can be smooth or likewise comprise reaction channels formed therein. In a preferred embodiment, the reaction channels are accommodated in both the lower plate and the transparent plate and are aligned with one another. Whereby the cross-sectional geometry of the reaction channel is determined by the shape of the reaction channel in the lower plate and the shape of the reaction channel in the transparent plate.

The reaction zone can be detachably fastened to a heat transfer module for removing the heat generated during the reaction or for supplying additional heat. The heat transfer module may comprise an electric heater or peltier element or be formed by a heat exchanger for temperature regulation of the reaction zone plate. The temperature gradient in the reaction zone plates in the flow direction can be set by accommodating gaps between the individual heating or cooling zones in the heat transfer module. The pressure, temperature, viscosity or flow rate can be determined, for example, by sensors which are integrated either in the reaction zone underfloor or in the heat transfer module. For this purpose, for example, pressure sensors, temperature sensors, heat-conducting sensors, viscosity sensors or light sensors, as well as capacitive, inductive, piezoelectric, dielectric sensors, conductivity detectors or ultrasonic detectors can be used.

The invention is described in additional detail below with the aid of the figures. In the drawings:

figure 1 shows in a perspective view a vertical micro-reactor with irradiation means,

FIG. 2.1 shows a schematic representation of a reaction zone plate with linear reaction channels,

figure 2.2 shows in a schematic view a reaction zone plate with corner reaction channels,

figure 2.3 shows in a schematic view a reaction zone plate with structured wall channels,

figure 3 shows in a schematic representation a reaction zone plate with an integrated mixer structure,

figure 4 shows a micro-photo-reactor with heat transfer modules and reaction zone plates,

figure 5.1 shows a first embodiment of a reaction zone plate in a cross-sectional view,

FIG. 5.2 shows a second embodiment of a reaction zone plate in a sectional view.

In fig. 1, a vertical mini-reactor with a radiation source is shown in perspective.

A micro-reactor 1 comprises a reaction zone formed by a reaction zone plate 2, which is accommodated in a housing 3. Within the reaction zone plate 2 is accommodated a reaction channel 4 in which a photochemical reaction is carried out. It is preferable that 10 to 10000 reaction channels 4 are accommodated in the reaction zone plate 2 according to the size of the reaction zone plate 2. In addition to the configuration shown in fig. 1 with parallel, straight reaction channels 4, the reaction channels 4 can also be of a cornered or meandering or any other configuration known to the person skilled in the art.

The fixing of the reaction zone plates 2 in the housing 3 can be effected in a force-fitting or form-fitting manner. In the embodiment shown in fig. 1, the reaction zone plate 2 is fixed in a force-fitting manner in the housing 3 by means of screws 5. The reaction zone plate 2 preferably comprises a lower plate member which is closed by a transparent cover plate member 6 which is transparent to light having the wavelength required for the reaction.

The reaction medium is fed to the reaction zone plate 2 through an inlet 7. If mixing of the reactants is to be effected only in the reaction zone plate 2, there is provided an own inlet 7 for each reactant.

The products produced by the photochemical reaction are discharged from the microphotoreactor 1 through an outlet 8. In order to additionally increase the throughflow resistance for the throughflow resistance which is generated in the reaction channel 4 as a result of gravity compression, a valve can be provided at the outlet 8. The reaction medium is supplied to the reaction channel 4 by a pressure difference. The light required for the photochemical reaction is emitted by an irradiation source 9. Suitable as illumination sources are, for example, gas discharge lamps, semiconductor light sources or lasers. The radiation source 9 is selected such that light is emitted in the wavelength range required for the photochemical reaction. The wavelength range of the light can extend here from the infrared range of the visible range up to the ultraviolet range. The radiation source 9 is preferably designed such that the emitted light is incident on the reaction field plate 2 in a direction indicated by reference numeral 10.

Sensors may be integrated in the micro-photo-reactor for monitoring pressure, temperature, viscosity and flow rate. The power supply of the sensor, if required, and the data transmission are effected via an electrical connection 11 provided on the housing 3. Where the data transfer is to an external device via cable, fiber optic or radio technology. The task of the external device is to record, display, continue processing and adjust the temperature, pressure, flow, irradiation intensity or irradiation wavelength. The measurement of the irradiation intensity or the irradiation wavelength is preferably carried out on the basis of a conversion measurement. A computer is preferably used as the external device.

FIGS. 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 linearly inside the reaction zone plate 2. The reaction medium is fed in through an inlet opening 12 in the lower part of the reaction channel 4. The reaction medium is then caused to flow upward in each reaction channel 4, wherein the reaction medium is caused to be irradiated with light from an irradiation source 9, not shown. The conversion of the reaction medium into product takes place in the reaction channel 4. The product is collected in a collecting zone 13 arranged in the upper part of the reaction channel 4. The product is removed from the collection zone 13 through an outlet 14.

In contrast, FIG. 2.2 shows an embodiment of a reaction channel 4 with corners. Here too, the reaction medium is fed to the reaction channel 4 via the inlet opening 12. A photochemical reaction is effected in the reaction channel 4, in which the reaction medium is converted into the product. The product collects in the collection zone 13 and is discharged from the collection zone 13 through the outlet 14. Fewer reaction channels 4 than straight reaction channels can be arranged on the reaction zone plate 2 by means of the corner structure of the reaction channels 4. The reaction channel 4 through the corner lengthens the throughflow path and thus the residence time in the miniature photoreaction reactor.

Fig. 2.3 shows a further embodiment with wide reaction channels 4, in which a structure 15 is pressed. For the embodiment variant shown in FIG. 2.3, the reaction medium is also fed in via the feed opening 12 in the lower part of the reaction zone plate 2. The product is discharged here through an outlet 14 which is arranged in the upper part of the reaction zone plate 2. For the embodiment shown in FIG. 2.3, one collecting zone 13 can be dispensed with, since all reaction medium heads are guided through one reaction channel 4. In addition, another fluid can be fed through the laterally arranged openings 16 for the embodiment variant shown in fig. 2.3. Owing to the structure 15 in the reaction channel 4, the fluid fed laterally through the opening 16 is mixed with the reaction medium fed through the inlet opening 12. The introduction of fluid through the openings 16 generates a cross flow through which, for example, solid particles in the reaction medium can be removed. The cross flow containing solid particles may be discharged from the channel through the outlet 29.

FIG. 3 shows a reaction zone plate with integrated mixing structure.

The embodiment shown in fig. 3 corresponds substantially to the embodiment shown in fig. 2.1. In contrast to the embodiment shown in fig. 2.1, the supply of the reaction medium to the reaction channel 4 is effected not via the individual supply openings 12, but via the mixing zone 20, a first fluid being supplied to the mixing zone via the supply opening 17 for the first fluid and a second fluid being supplied to the reaction channel 4 via the supply opening 18 for the second fluid. In order to ensure intensive mixing of the first fluid with the second fluid, the inlet openings 17, 18 are arranged alternately. The inlet openings 17 for the first fluid are in this case arranged on the right side of the reaction channel 4 and the inlet openings 18 for the second fluid are arranged on the left side of the reaction channel 4 for the embodiment variant shown in fig. 3. The inlet opening 17 for the first fluid engages with the inlet opening 18 for the second fluid. Thereby ensuring intensive mixing of the second fluid. The reaction medium is flowed through the reaction channel 4 in the flow direction through a collecting zone 13, which is designated by reference numeral 19. From the collection zone 13 the product is withdrawn through an output port 14. In addition to the alternating arrangement of the engaging feed openings 17, 18, a profile can also be provided in the reaction channel 4 for mixing the components of the reaction medium. The irradiation required for the photochemical reaction may be effected either at the mixing zone 20 and/or at a junction of the mixing zone 20.

In fig. 4, a micro photo-reactor with heat transfer modules and reaction zone plates is shown.

In order to be able to remove the heat generated in the photochemical reaction or to supply additional heat, the reaction zone plate 2 can preferably be detachably mounted on a heat transfer module 21. The heat input here is either via the electric heating element 22 or via a temperature control medium (tempiermedium). For example water or heat transfer oil are suitable as temperature regulating medium. The temperature control medium is fed into the heat transfer module 21 via a temperature control medium inlet 23 and is discharged again via a temperature control medium outlet 24. The fluid passages through which the temperature control medium flows are arranged inside the heat transfer modules 21 when the reaction zone plates 2 are heated or cooled by the temperature control medium. The heat transfer module 21 can be divided into individual temperature control zones 26 by the arrangement of slots 25 in the reaction zone plates 2, which are located in the heat transfer module 21, transversely to the flow direction of the reaction medium. Different temperature adjustments for the individual temperature adjustment zones 26 can produce a temperature gradient in the reaction zone plate 2. In order to monitor the temperature of the individual temperature-regulated zones 26, temperature sensors 27 are preferably provided in the temperature-regulated zones 26. For example, a thermocouple or a resistance thermometer is suitable as the temperature sensor 27.

By means of the detachable connection of the reaction zone plates 2 to the heat transfer module 21, the reaction zone plates 2 can be easily replaced when other reaction conditions are desired or other reactions are to be carried out.

A plurality of the micro-bioreactors 1 may be connected in parallel by a simple method in order to increase the yield. The parallel connection of the respective micro photoreactions 1 has an advantage that the reaction conditions are not changed when the reaction amount is increased.

In addition to the parallel arrangement of the reaction channels 4, the reaction channels 4 may also be arranged in series.

A first embodiment of a reaction zone plate is shown in fig. 5.1.

The reaction zone plate 2 comprises a lower plate member 28 and a transparent cover plate member 6. The lower plate 28 is preferably made of a material which advantageously influences the surface stress of the reaction medium, acts catalytically or is highly reflective for the light in the spectral range used.

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

For the embodiment shown in fig. 5.1, the reaction channel 4 is formed in the lower plate 28. Instead of the semi-circular cross-section shown here, it may also be a triangular, rectangular, trapezoidal or any other cross-sectional shape known to the skilled person.

The reaction channels 4 are preferably closed by means of a transparent cover plate 6. For this purpose, the transparent covering plate 6 is preferably connected to the lower plate 28 in a form-fitting or force-fitting manner. In contrast to the exemplary embodiment shown in fig. 5.1, in fig. 5.2 the reaction channels 4 are also formed in a transparent cover plate 6. By aligning the reaction channels 4 formed in the lower plate 28 and the transparent cover plate 6 with one another, a circular cross section of the reaction channels 4 can be produced. The deposition of substances in the reaction medium on the channel walls 30, 31 is advantageously prevented by avoiding corners in the reaction channel 4.

List of reference numerals

1 micro photo-reactor

2 reaction zone plate

3 outer cover

4 reaction channel

5 bolt

6 transparent covering plate

7 inlet

8 outlet

9 irradiation source

10 direction of light

11 electric connector

12 input hole

13 collection zone

14 outlet

15 structure

16 open pores

17 first fluid input aperture

18 second fluid input aperture

19 flow direction

20 mixing zone

21 Heat transfer module

22 heating element

23 inlet for a temperature-regulating medium

24 outlet for temperature-regulating medium

25 gap

26 temperature regulation zone

27 temperature sensor

28 lower plate

29 discharge hole

30 first channel wall

31 second channel wall

Claims (19)

1. A micro-reactor for carrying out photochemical reactions in at least one reaction medium, wherein the reaction medium is liquid, gaseous or dispersed, wherein the light required for the reaction is supplied by a radiation source (9) arranged outside the reactor, characterized in that the reaction medium flows through the reaction channel (4) of at least one reaction zone (2), wherein at least one point in this reaction zone is transparent to light and the direction of flow is inclined at an angle of 10 DEG to 90 DEG relative to the horizontal, and the reaction medium is supplied to the at least one reaction channel (4) by a pressure difference counter to gravity.

2. The microphotoreactor according to claim 1, wherein the reaction region is formed in the shape of a reaction region plate (2).

3. The microphotoreactor according to claim 2, wherein the reaction zone plate (2) is detachably fixed to a heat transfer module (21).

4. The microphotoreactor according to claim 2 or 3, wherein the reaction zone plate (2) is formed planar, curved or cylindrical.

5. The microphotoreactor according to any of claims 2 to 4, wherein the reaction zone plate (2) comprises at least one lower plate element (28) and a transparent cover plate element (6), which rests flush against the lower plate element (28) and is connected to this plate element in a form-fitting or force-fitting manner.

6. The microphotoreactor according to claim 5, wherein the at least one reaction channel (4) is accommodated inside the lower plate member (28).

7. The microphotoreactor according to claim 5 or 6, wherein the at least one reaction channel (4) is accommodated inside a transparent covering plate (6).

8. The microphotoreactor according to any one of claims 5 to 7, wherein the lower plate member (28) is made of a material having a high reflectivity for light in a spectral range of use.

9. The microphotoreactor according to any one of claims 5 to 7, wherein the lower plate member (28) is made of a material that functions as a catalytic activation.

10. The microphotoreactor according to any of claims 1 to 7, wherein the at least one reaction channel (4) is coated with a material having a high reflectivity in the spectral range or a catalytically activated material.

11. The microphotoreactor according to any one of claims 5 to 10, wherein the transparent covering plate (6) is made of a heat insulating material.

12. The microphotoreactor according to any of claims 5 to 11, wherein the transparent covering plate (6) functions as a spectral filter.

13. The microphotoreactor according to claim 3, wherein the heat transfer module (21) comprises an electric heater or a Peltier element for temperature regulation of the reaction zone plate (2) or is constituted by a heat exchanger.

14. The microphotoreactor according to any one of claims 3 to 13, wherein the heat transfer module (21) is configured such that a temperature gradient in the flow direction along the reaction zone plate (2) can be adjusted.

15. The microphotoreactor according to any one of claims 1 to 14, wherein a sensor (27) for monitoring the reaction medium and a sensor (27) for adjusting a reaction parameter are accommodated in the lower plate (28) or in the heat transfer module (21).

16. The microphotoreactor according to any one of claims 1 to 15, wherein a mixing zone (20) for mixing at least two reaction media is accommodated inside the at least one reaction channel (4).

17. The microphotoreactor of claim 16, wherein the mixing region (20) may be irradiated.

18. The microphotoreactor according to claim 16, wherein the irradiation with light is effected immediately after the mixing zone (20).

19. The microphotoreactor according to any of claims 1 to 18, wherein the at least one reaction channel (4) is coated with a material by means of which the surface stress of the reaction medium is favourably influenced.