REACTION APPARATUS

Abstract

An apparatus for carrying out chemical reactions is provided. The apparatus comprises a first reactor/reaction zone for carrying out a first chemical reaction and a second reactor/reaction zone for carrying out a second chemical reaction. Each reactor/reaction zone comprises: a) an inner surface and an outer surface which are spaced apart from each other to define a reaction volume configured such that, in use, a respective chemical reaction takes place in the reaction volume, and wherein the inner surface and outer surface are configured for relative rotation with respect to each other, (b) an inlet for introduction of a reagent to the reaction volume, and (b) an outlet through which a reaction product can leave the reaction volume. The reaction products of the first reactor/reaction zone comprise reagents of the second reactor/reaction zone.

Claims

1. An apparatus for carrying out chemical reactions, the apparatus comprising a first reactor/reaction zone for carrying out a first chemical reaction and a second reactor/reaction zone for carrying out a second chemical reaction, wherein each reactor/reaction zone comprises: a. an inner surface and an outer surface which are spaced apart from each other to define a reaction volume configured such that, in use, a respective chemical reaction takes place in the reaction volume, and wherein the inner surface and outer surface are configured for relative rotation with respect to each other, b. an inlet for introduction of a reagent to the reaction volume, and c. an outlet through which a reaction product can leave the reaction volume, wherein the reaction products of the first reactor/reaction zone comprise reagents of the second reactor/reaction zone.

2. An apparatus according to claim 1, wherein the first and second reactors/reaction zones are provided by first and second reactors respectively, wherein each reaction volume comprises a reaction chamber, and wherein the outlet of the first reactor is coupled to the inlet of the second reactor, optionally via a fluid conduit.

3. An apparatus according to claim 2, wherein first and/or second reactors are configurable such that the speed of relative rotation of the first reactor is the same as or different from the speed of relative rotation of the second reactor; and/or wherein the apparatus is configurable such that a flow rate of fluid from the outlet of the first reactor is equal to the flow rate of fluid into the inlet of the second reactor, for example, the apparatus comprises at least one pump for pumping fluid through the plurality of reactors at a constant flow rate.

4. An apparatus according to claim 1, wherein the first and second reactors/reaction zones are provided by first and second reaction regions of a single reactor, and wherein each reaction volume comprises a portion of a reaction chamber of the single reactor defined by said inner and outer surfaces.

5. An apparatus according to claim 1, wherein the apparatus comprises a third reactor/reaction zone for carrying out a third chemical reaction; optionally wherein the third reactor/reaction zone comprises a third reactor/reaction zone which is provided in series with the first and second reactors; optionally wherein the third reactor/reaction zone comprises a third reactor which is provided in parallel with the first and/or second reactor; optionally wherein the apparatus comprises more than three reactors/reaction zones.

6. An apparatus according to claim 1, wherein one or more of the chemical reactions is a photochemical reaction, an electrochemical reaction and/or a thermal reaction.

7. An apparatus according to claim 1, wherein the inner and/or outer surface of one or more of the reactors/reaction zones is formed of a material which permits electromagnetic radiation of a desired wavelength to be transmitted to the respective reaction chamber; optionally wherein the inner and/or outer surface of at least one reactor/reaction zone permits radiation of a first desired wavelength to be transmitted, and the inner and/or outer surface of at least one other reactor/reaction zone permits radiation of a second desired wavelength to be transmitted, wherein the first and second wavelengths are the same or different; optionally wherein the inner and/or outer surface of at least one reactor/reaction zone permits visible light and/or ultraviolet light and/or infrared radiation to enter the reaction chamber.

8. An apparatus according to claim 1, further comprising an electromagnetic radiation source, e.g. visible light and/or ultraviolet light and/or infrared radiation source.

9. An apparatus according to claim 1, wherein a gap size between the inner surface and the outer surface of one or more of the reactors/reaction zones is up to 6 mm, optionally wherein the gap size is in the range 1-6 mm; optionally wherein one or more of the reactors/reaction zones is configured for carrying out photochemical reactions, and wherein the gap size between the inner surface and the outer surface is about 3 mm.

10. An apparatus according to claim 1, wherein the inner and outer surfaces of at least one reactor/reaction zone are configured as electrodes and wherein the chemical reaction is an electrochemical reaction.

11. A reactor for carrying out chemical reactions, the reactor comprising: a. an inner surface and an outer surface which are spaced apart from each other to define a reaction chamber, wherein the inner surface and outer surface are configured for relative rotation with respect to each other, b. an inlet for introduction of a reagent to the reaction chamber, and c. an outlet through which of a reaction product can leave the reaction chamber, wherein the inner and outer surfaces are configured as electrodes and wherein the chemical reaction is wholly or partly an electrochemical reaction.

12. A reactor according to claim 11, wherein a gap size between the inner surface and the outer surface of the or at least one reactor/reaction zone is 1.5 mm or less, optionally wherein the gap size is in the range 0.1-1.5 mm, optionally wherein the gap size is about 0.5 mm, optionally wherein the gap size is about 1.0 mm.

13. A reactor according to claim 11, comprising a carbon-containing electrode.

14. A reactor according to claim 11, wherein at least one of the inner or the outer surface comprises a porous material, optionally wherein at least one of the inner or outer surface is coated with a porous material.

15. An apparatus according to claim 1, wherein the inner and outer surfaces of at least one reactor/reaction zone define a reaction chamber/reaction volume having an annular cross section, optionally wherein the inner and outer surfaces comprise approximately concentric cylindrical surfaces.

16. An apparatus according to claim 1, wherein at least one reactor/reaction zone comprises a flow path configured such that fluid can flow along the flow path from the input to the output via the reaction chamber/reaction volume, optionally further comprising a pump configured to generate a continuous flow of fluid along the or each flow path.

17. An apparatus according to claim 1, wherein a gap size between the inner and outer surfaces and/or the speed of relative rotation between the surfaces of at least one reactor/reaction zone is configurable such that, in use, Taylor vortices are generated in fluid present in the reaction chamber/reaction volume.

18. An apparatus according to claim 1, wherein at least one reactor/reaction zone comprises a rotor defining the inner surface of the reaction chamber/reaction volume, wherein the rotor is configured to rotate such that the inner surface rotates with respect to the outer surface of the reaction chamber, optionally wherein the or at least one reactor/reaction zone comprises a reaction vessel defining the outer surface of the reaction chamber/reaction volume, wherein the rotor is located, at least partially, in the reaction vessel.

19. An apparatus according to claim 1, wherein at least one reactor/reaction zone comprises a rotor provided with a rotor jacket covering the rotor, and wherein the rotor jacket defines the inner surface of the reaction chamber/reaction volume, wherein the rotor is configured to rotate such that the inner surface rotates with respect to the outer surface of the reaction chamber/reaction volume, optionally wherein the or at least one reactor/reaction zone comprises a reaction vessel defining the outer surface of the reaction chamber/reaction volume, wherein the rotor is located, at least partially, in the reaction vessel.

20. An apparatus according to claim 1, wherein at least one reactor/reaction zone comprises a reaction vessel defining the outer surface of the reaction chamber/reaction volume or wherein the outer surface is provided by a jacket covering the outer wall of the reaction vessel; optionally wherein the reaction vessel comprises a jacketed vessel through which heating or cooling fluid can be circulated for controlling a temperature of fluid flowing through the reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0163] Embodiments disclosed herein will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0164] FIG. 1 shows a schematic illustration of an apparatus according to an embodiment of this disclosure comprising three reactors;

[0165] FIG. 2 shows a schematic illustration of how reactors according to embodiments of this disclosure can be coupled together;

[0166] FIG. 3 shows a schematic illustration of a reactor according to an embodiment of this disclosure configured for a photochemical reaction;

[0167] FIG. 4 shows a perspective view of the reactor of FIG. 3;

[0168] FIG. 5 shows a schematic of an alternative embodiment of a reactor of this disclosure;

[0169] FIG. 6 shows a schematic illustration of a reactor according to an embodiment of this disclosure configured for an electrochemical reaction,

[0170] FIG. 7 shows a schematic illustration of a reactor according to an embodiment of this disclosure and configured for electrochemical and/or photochemical reactions,

[0171] FIG. 7a shows a schematic illustration of a reactor according to an embodiment of this disclosure and configured for electrochemical and/or photochemical reactions,

[0172] FIG. 8 illustrates the reaction mechanism for Example 1,

[0173] FIG. 9 shows a schematic illustration of a reactor according to an embodiment of this disclosure comprising a plurality of reaction zones, and

[0174] FIG. 10 illustrates the permutations of 2, 3 and 4 reactor/reactor zones couple in series.

DETAILED DESCRIPTION

[0175] With reference to FIG. 1, an apparatus for carrying out chemical reactions is generally indicated at reference numeral 2. The apparatus 2 comprises a first reactor 4a for carrying out a first chemical reaction, a second reactor 4b for carrying out a second chemical reaction, and a third reactor 4c for carrying out a third chemical reaction.

[0176] Each reactor includes an inner surface 6 and an outer surface 8 which are spaced apart from each other by a gap distance g to define a reaction chamber 10.

[0177] Each reactor also includes an inlet 12 through which reagents are introduced to the reaction chamber 10. Each reactor also includes an outlet 14 through which reaction products leave the reaction chamber 10.

[0178] As is illustrated in FIG. 1, the outlet 14 of the first reactor 4a is coupled to the inlet 12 of the second reactor 4b via a fluid conduit 16, e.g. a pipe. Similarly, the outlet 14 of the second reactor 4b is coupled to the inlet 12 of the third reactor 4c via a fluid conduit 16, e.g. a second pipe.

[0179] In each of the reactors 4a, 4b, 4c, the inner surface 6 and the outer surface 8 are configured for relative rotation with respect to each other. Each of the first, second and third reactors 4a, 4b, 4c is configurable such that the speed of relative rotation may be tailored to meet a particular reaction requirement. Accordingly the speed of relative rotation of the first reactor 4a, the second reactor 4b and the third reactor 4c may be the same as or different from each other.

[0180] As will be appreciated with reference to FIG. 1, a continuous flow path is provided from the inlet 12 of the first reactor 4a to the outlet 14 of the third reactor 4c, via the reaction chambers 10 of each of the three reactors 4a, 4b, 4c. The apparatus 2 of the embodiment illustrated in FIG. 1 further comprises a pump 18 for pumping fluid through the first, second and third reactors 4a, 4b, 4c at a constant flow rate.

[0181] With reference to FIGS. 1, 3 and 6, the reactors 4a, 4b and 4c are shown in cross section. The inner surface 6 is defined by a rotor 22, which is configured to rotate with respect to the outer surface 8 of the reaction chamber 10. Each reactor also includes a cylindrical reaction vessel 24 which defines the outer surface 8 of the reaction chamber 10. The rotor 22 extends into the reaction vessel 24. The rotor 22 also comprises a cylindrical profile. Accordingly, an annular reaction chamber 10 is defined by the space between the inner and outer surfaces 6, 8.

[0182] In exemplary embodiments, the inner and outer surfaces 6, 8 define concentric cylindrical surfaces. The rotor 22 of each reactor 4a, 4b, 4c is coupled to a motor 26 which controls rotation of the rotor 22 within the reaction vessel 24. As illustrated in FIG. 1, each reactor, hence each rotor 22, is coupled to a separate motor such that the rotation of each rotor 22 in the reactors 4a, 4b, 4c can be controlled independently.

[0183] The reactor may be made of a metallic material, or may be made of a plastics material e.g. PEEK, which is more lightweight.

[0184] In exemplary embodiments, the diameter of the outer surface 8 is approximately 10 cm.

[0185] In exemplary embodiments, the rotor 22 of a given reactor 4a, 4b, 4c may rotate at a speed in the range of 50-5,000 rpm, e.g. 4,000 rpm. The rotor 22 is configured to rotate about a longitudinal axis X of the respective reactor. The rotor 22 also comprises a longitudinal axis which is co-axial with the longitudinal axis X of the reactor.

[0186] In the embodiments illustrated in FIGS. 1, 3 and 6, each reactor includes a gas inlet 28 for introducing gas into the reaction chamber 10.

[0187] In the embodiments illustrated in FIGS. 1, 3 and 6, the inlet 12 is provided towards the bottom end of the reactor 4a, 4b, 4c and the outlet 14 is provided towards the top end. In this way, reaction fluid flows from the bottom of the reactor 4a, b, c to the top. It will be appreciated that the reactor(s) could be arranged to have the inlet 12 at the top of the reactor and the outlet at the bottom.

[0188] In the embodiments illustrated in FIGS. 1, 3 and 6, the reaction vessel 24 comprises upper and lower flanges 36a, b, which project radially from the lower and upper ends, respectively, of the vessel 24 to form a pair of flat rings. Further, the reaction vessel 24 includes an open top and open bottom.

[0189] In this way, the reaction vessels can easily be stacked to create a larger reactor or to perform a series of reactions as the reaction fluid flows directly through the stacked reaction vessels. In such an arrangement, the open top or bottom is the inlet or outlet of the reactor. In such embodiments the reaction vessels may share a common rotor.

[0190] In the embodiments illustrated in FIGS. 1, 3 and 6, it will be appreciated that the top and bottom of the reaction vessel 24 are both sealed to prevent ingress of air from the atmosphere.

[0191] With reference to FIGS. 1, 3 and 6, when apparatus 2 is in use, starting materials SM are introduced to reactor 4a via its inlet 12. These are pumped into the reaction chamber 10 via pump 18. The motor 26 controls the rotor 22 to rotate in the reaction vessel 24. Optionally, gas reagents are introduced to the reaction chamber 10 via gas inlet 28.

[0192] As the rotor 22 rotates, Taylor vortices 32 are generated in the reaction chamber 10. These are toroidal vortices threaded around the central rotor 22. The reaction fluid moves through the reaction chamber 10 from the inlet 12 to the outlet 14. Reaction products leave the reaction chamber 10 via the outlet 14 and flow through the fluid conduit 16 to the inlet 12 of the next reactor 4b. The process is repeated for the second and third reactors 4b, 4c.

[0193] The first, second and third reactors 4a, 4b, 4c may be suitable for an electrochemical reaction, a photochemical reaction and/or a thermal reaction, for example.

[0194] In the illustrated embodiment shown in FIG. 3, the first reactor 4a is configured for carrying out photochemical reactions. With reference to FIG. 1, this is the first reactor in the series, but could be any of the first, second, third or further reactors. One or more of the chemical reactions carried out by the reactors 4a, 4b, 4c of apparatus 2 may be a photochemical reaction, an electrochemical reaction and/or a thermal reaction.

[0195] With reference to FIG. 6, the second reactor 4b is configured for carrying out electrochemical reactions. With reference to FIG. 1, this is the second reactor in the series, but could be any of the first, second or third reactors.

[0196] It will be appreciated that the apparatus may include more than three reactors.

[0197] With reference to FIG. 2, exemplary configurations of reactors are illustrated. In FIG. 2, reactors configured for photochemical reactions are indicated as P1, P2 and P3, reactors configured for carrying out electrochemical reactions are indicated as E1, E2 and E3, and reactors configured for carrying out thermal reactions are indicated as T1, T2 and T3. Three exemplary arrangements are illustrated in FIG. 2. Of course it will be appreciated that any suitable arrangement of reactors will be possible, as desired.

[0198] A reactor pool 20 is provided which includes reactors P1, P2, P3, E1, E2, E3, T1, T2 and T3. In other words three reactors configured for carrying out photochemical reactions, three reactors configured for carrying out electrochemical reactions and three reactors configured for carrying out thermal reactions. It will be appreciated that any number of reactors may be included in the pool.

[0199] To the left of the reactor pool an apparatus comprising three reactors is illustrated. These are P1, E3 and T2. Starting materials SM are input to the first reactor P1 via its inlet 12. Products of the photochemical reaction carried out in P1 pass from the outlet of P1 to the inlet of E3. In E3, an electrochemical reaction is then carried out. The products of the reaction carried out in E3 leave E3 via its outlet 14 and flow to the inlet 12 of reactor T2. A thermal reaction is carried out in reactor T2 and the products of this exit the reactor via its outlet 14. This example illustrates an apparatus having three reactors coupled together in series. To the right of the reactor pool 20 shown in FIG. 2, an exemplary apparatus comprising four reactors is illustrated. These are coupled together in series in a similar manner as previously described.

[0200] Below the reactor pool 20 shown in FIG. 2, a third exemplary configuration is illustrated. This comprises five reactors coupled together, partly in series and partly in parallel. In this arrangement, the reaction products of P1 and the reaction products of P2 are both input as reagents to the reactor E1. An electrochemical reaction is carried out in E1 and the reaction products passed to T1 where a thermal reaction is then carried out. It will be appreciated that any desired configuration of reactors may be used.

[0201] Possible combinations of 2, 3 and 4 reactors are shown in FIG. 10, where “P” or “Photo” denotes a reactor configured for carrying out photochemical reactions, “E” or “Electro” denotes a reactor configured for carrying out electrochemical reactions, and “T” or “Thermal” denotes a reactor configured for carrying out thermal reactions.

[0202] Of course, it will be appreciated that, rather than a plurality of reactors being provided and coupled together in series, a single reactor with a plurality of reaction zones may be provided, as shown in FIG. 9. First, second and third reaction zones are indicated by reference numerals A, B and C respectively. It will be appreciated that zones A, B and C can be configured for any of electrochemical, photochemical and thermal reactions. Each reaction zone comprises a corresponding reaction volume in which the respective reaction takes place. In the illustrated embodiment, the reaction zones A, B and C are provided by discrete portions of a single reactor, and the respective reaction volumes are provided by corresponding discrete portions of the reaction chamber.

[0203] With reference to FIG. 3, a reactor 4b for photochemical reactions is shown. In addition to the reactor features previously described, the outer surface 8 of the reactor 4a is formed of a material which permits visible light to enter the reaction chamber 10. This may be a particular wavelength of visible light or a broader bandwidth.

[0204] In exemplary embodiments, reactors disclosed herein may include an outer surface 8 which is formed of a material which permits electromagnetic radiation, e.g. of a desired wavelength, to be transmitted to the reaction chamber.

[0205] It will be appreciated that, in such embodiments, the reaction vessel, or at least a portion thereof, must also permit electromagnetic radiation e.g. visible light, to enter the reaction chamber.

[0206] In the case where an apparatus includes more than one reactor/reactor zone for photochemical reactions, the outer surface 8 of at least one reactor/reactor zone may permit radiation of a first desired wavelength to be transmitted to the reaction chamber/reaction volume and the outer surface of at least one other reactor/reactor zone may permit radiation of a second desired wavelength to be transmitted to the second reaction chamber/reaction volume, wherein the first and second wavelengths are the same or different.

[0207] With reference to FIG. 3 the reactor 4a (or apparatus 2) also includes a light source 30. In exemplary embodiments this may be an array of white LEDs of 360 watts each. Alternatively any type or power of LED or other light source can be used. Further any number of arrays or any number of light sources may be used, e.g. 1, 2, 3, 4, 5, 6 or more.

[0208] In exemplary embodiments, the reactor or apparatus may include an electromagnetic radiation source.

[0209] The gap size g between the inner surface 6 and the outer surface 8 is typically up to 6 mm, e.g. in the range of 1-6 mm, for a rotor diameter of 20 mm. In the case of photochemical reactions, it has been found that a gap size of approximately 3 mm is optimal.

[0210] As illustrated in FIG. 3, the reactor includes a jacketed reaction vessel 24. This is illustrated in relation to a reactor 4a which is configured for photochemical reactions, but may also be used for other reaction types e.g. thermal reactions. In the embodiment shown in FIG. 3, the reaction vessel 24 is a double walled reaction vessel having a volume 34 through which heating or cooling fluid can be circulated to control the temperature of reaction fluid flowing through the reactor.

[0211] As will be appreciated, this is particularly advantageous for thermal reactions, although can equally apply to other types of reaction.

[0212] In exemplary embodiments, the jacket 34 is configured to permit electromagnetic radiation to be transmitted to the reagents in the reaction chamber/reaction volume (e.g. optically transparent for photochemical reactions). In exemplary embodiments, the jacket 34 is configured to act as an electrode (e.g. for electrochemical reactions—described in more detail below). It will be appreciated that the jacket 34 may be configured to perform all or some of these functions, in any combination.

[0213] FIG. 4 illustrates the embodiment of FIG. 3 in perspective view.

[0214] With reference to FIG. 5 an alternative embodiment of reactor is illustrated. In the illustrated embodiment, the inlet 12 comprises a bore through the centre of the rotor 22 such that reactants are introduced at the bottom of the reaction chamber 10. The rotor 22 is supported at its upper end.

[0215] Further, the reaction vessel 24 is an open topped vessel such that the reaction fluid is in contact with the air. In this way air can be drawn into the reaction fluid as the reaction is carried out. Also reaction products can be drawn from the top of the reaction fluid e.g. using a pump.

[0216] The embodiment shown in FIG. 5 can be adapted for any type of reaction, for example photochemical, electrochemical or thermal, in a similar manner as described herein in relation to FIGS. 3 and 6.

[0217] With reference to FIG. 6, a reactor 4b is shown which is configured for electrochemical reactions. In this embodiment, the inner surface 6 and the outer surface 8 are configured as electrodes.

[0218] In this reactor the inner surface is the cathode and the outer surface the anode and the cathode may be copper and the anode zinc in an electrolyte of sodium chloride solution. The gap size is 1.0 mm±0.1 mm. Alternatively, the gap size is up to 0.5 mm, e.g. 0.5 mm±0.1 mm. The rotor 22 is securely supported at its upper end for rotation about its longitudinal axis. Given the small gap size between the inner and outer surfaces 6,8, the coupling between the motor 26 and the rotor 22 is configured to reduce lateral movement of the rotor 22, e.g. the coupling is machined and manufactured to strict tolerances. In this way, lateral movement between the anode and the cathode is minimised to prevent short circuiting of the system.

[0219] With reference to FIG. 7, an alternative embodiment of reactor is illustrated. This reactor is configured for electrochemical and/or photochemical reactions. In this reactor, the outer wall of the reaction vessel 24 comprises a mesh material 38, which is configured to permit visible light and/or ultraviolet light and/or infrared radiation to enter the reaction chamber 10 via gaps in the mesh 38. The mesh 38 is also configured as an electrode, so that the reactor is configured for electrochemical reactions. In the embodiment of FIG. 7, the mesh 38 is the anode. In alternative embodiments, the mesh is the cathode.

[0220] With reference to FIG. 7a, an alternative embodiment of the reactor is illustrated. This reactor is the same as that shown in FIG. 7, with the exception that the inner surface electrode is provided by a jacket 22a fitted to the rotor 22. The electrode jacket 22a is removable and is configured to cover the outer surface of the rotor 22 when fitted to the rotor 22.

[0221] In this way, the rotor 22 does not need to be made of a particular material required by a given reaction. Instead, an electrode jacket 22a of the required material can be used.

[0222] Examples of the use of reactors and apparatuses disclosed herein will now be detailed.

Example 1a

[0223] An electrochemical reaction was carried out using a reactor disclosed herein. Specifically, the methoxylation of N-formyl pyrrolidine, according to the reaction equation below and mechanism illustrated in FIG. 8:

##STR00001##

[0224] Reaction mixture included 0.1 M N-formyl pyrrolidine. The electrolyte was NEt.sub.4BF.sub.4 in Methanol.

[0225] Flow rate through the reactor was 6.25 mlmin.sup.−1, with a residence time of approximately 2 minutes. Reactor volume was 12.5 ml within this example. A constant current was applied across the electrodes with a voltage of 12 V.

[0226] The results of this reaction are detailed in Table 1 below. “Rotation Speed” is the rotation speed of the rotor. “Conversion” is the consumption of N-formyl pyrrolidine, “Yield” is the amount of N-formyl-2-methoxypyrrolidine produced. Both were measured by 1H NMR using biphenyl as an external standard.

[0227] “Productivity” per hour was calculated by the following equation:

Productivity (gh.sup.−1)=((Flow rate×60×concentration)/1000)×129.16×yield  (2)

[0228] Productivity per day was calculated as productivity per hour multiplied by 24.

[0229] For the reactions with no relative rotation between the inner and outer surfaces of the reactor (entry 4 and 9) a double methoxylated product was observed due to over-oxidation. In entry 4 there was approximately 3% of N-formyl-2,5-dimethoxypyrrollidine, and at entry 9 there was 5% N-formyl-2,5-dimethoxypyrrollidine.

TABLE-US-00001 TABLE 1 Resusts of example 1a Rotation Electrolyte Speed Concentration Current Conversion Yield Productivity Productivity Entry (RPM) (mM) (A) (%) (%) (g h.sup.−1) (g day.sup.−1)  1 4000  50 0.5 32 17 0.8 19.2   2 4000  50 1.0 68 36 1.7 40.8   3 4000  50 2.0 93 73 3.5 84.0   4   0  50 2.1 67 54 2.6 62.4   5 1000  50 2.1 92 77 3.7 88.8   6 2000  50 2.1 93 79 3.8 91.2   7 3000  50 2.1 91 82 4.0 96.0   8 4000  50 2.1 90 84 4.1 98.4   9   0  50 3   90 70 3.4 81.6  10 1000  50 3   >99  90 4.4 105.6  11 2000  50 3   >99  89 4.3 103.2  12 3000  50 3   >99  92 4.5 108.0  13 4000  50 3   >99  96 4.6 110.4  14 4000  25 3   98 90 4.4 105.6  15 4000 100 3   98 96 4.6 110.4 

[0230] From this it can be seen that whilst excellent conversions and yields are observed under all conditions, increasing both current and rotation speed enhance these properties of the reaction.

Example 1b

[0231] Similar to Example 1a, an electrochemical reaction was carried out using a reactor disclosed herein. Specifically, the methoxylation of N-formyl pyrrolidine, according to the reaction equation (1) above and mechanism illustrated in FIG. 8.

[0232] N-formylpyrrolidine (0.992 g, 10 mmol) and tetrabutylammonium tetrafluoroborate (NEt.sub.4BF.sub.4, 1.086 g, 5 mmol) were dissolved in methanol (100 mL), with sonication to aid dissolution.

[0233] An inlet pump was primed with the reaction mixture and the flow rate set at 6.25 mLmin.sup.−1, with a residence time of approximately 2 minutes. An outlet pump, provided at the reactor outlet, was set to a speed greater than the inlet flow rate plus the volume of H.sub.2 generated per minute. Typically the outlet pump was set to a speed of about 600 rpm.

[0234] The power supply was set to constant current mode with a voltage of 12 V. The rotation speed of the reactor was set to the desired speed.

[0235] To begin the reaction, the output of the power supply was turned on and the inlet and outlet pumps were started. Once the solution began to exit the reactor (after approximately 2 min), 3 reactor volumes were passed through the reactor (i.e. over 6 minutes) to reach equilibration before a sample was collected for analysis.

[0236] Once the sample collection was complete, the power supply output was turned off. The inlet pump was primed with methanol and the reactor was flushed for 5 reactor volumes (10 minutes at a flow rate of 6.25 mL min.sup.−1). The reactor was then drained of excess methanol from the inlet port.

[0237] Analysis of the reaction product included NMR analysis, gas chromatography analysis and high resolution mass spectrometry to identify the methoxylated product.

[0238] For NMR analysis, 1 mL of the solution from the reactor was taken and biphenyl (0.5 mL of 0.2 M in MeOH) was added and then then methanol was removed by rotary evaporation. The resulting slurry was then re-dissolved in MeOD (0.7 mL) and put into an NMR tube for analysis.

[0239] For Gas Chromatography analysis, 1 mL of the solution from the reactor was taken and biphenyl (0.5 mL of 0.2 M in MeOH) was added and then methanol removed by rotary evaporation. The resulting slurry was re-dissolved in ethyl acetate (1 mL) and insoluble NEt.sub.4BF.sub.4 was removed by filtration with the remaining solution placed into a sample vial for analysis.

[0240] To isolate the product, 100 mL of the solution from the reactor was taken and evaporated to dryness before re-dissolving in ethyl acetate (30 mL). Insoluble NEt.sub.4BF.sub.4 was removed by filtration and the remaining solution was evaporated to dryness to yield a pale-yellow oil. The crude product was then purified using automated flash chromatography (Teledyne CombiFlash, UV-Vis—254 nm, 40 g RediSep gold cartridge with a gradient system of CH.sub.2Cl.sub.2 increasing to 5% MeOH in CH.sub.2Cl.sub.2 over 45 minutes). The first fraction contained the product, which was isolated as a clear colourless oil.

[0241] Conversion and Yield were both are measured by .sup.1H NMR and Gas Chromatography using biphenyl as an external standard. Productivity was calculated using equation (2) above.

[0242] The results of this reaction are detailed in table 2 below. For the reactions with no relative rotation of the electrodes (entry 4 and 9 in table 2 below) a double methoxylated product was observed from over-oxidation. At 2.1 A (entry 4) there was approximately 3% yield of the double-methoxylated and 54% yield of the mono-methoxylated products and at 3 A (entry 9) there was approximately 5% yield of the double-methoxylated and 70% yield of the mono-methoxylated products.

[0243] For entry 14, the reaction was run with 25 mM of electrolyte (NEt.sub.4BF.sub.4). For entry 15, the reaction was run with 100 mM of electrolyte (NEt.sub.4BF.sub.4).

[0244] In all reactions, the rotor used was made of steel and was covered with an electrode jacket. In reactions 1-15 of the reactions detailed in table 2 below, the rotor electrode jacket, was made of graphite, and in reactions 17-20, the rotor electrode jacket was made of C/PTFE (C/PTFE is PTFE filled with carbon at 25% carbon by weight).

TABLE-US-00002 TABLE 2 Results of example 1b Rotor Electrolyte Rotation Jacket concentration Speed Current Conversion Yield Productivity Productivity Entry Rotor electrode (mM) (RPM) (A) (%) (%) (g h.sup.−1) (g day.sup.−1)  1 Steel Graphite  50 4000 0.5 32 17 0.8 19.2   2 Steel Graphite  50 4000 1.0 68 36 1.7 40.8   3 Steel Graphite  50 4000 2.0 93 73 3.5 84.0   4 Steel Graphite  50   0 2.1 67 54 2.6 62.4   5 Steel Graphite  50 1000 2.1 92 77 3.7 88.8   6 Steel Graphite  50 2000 2.1 93 79 3.8 91.2   7 Steel Graphite  50 3000 2.1 91 82 4.0 96.0   8 Steel Graphite  50 4000 2.1 90 84 4.1 98.4   9 Steel Graphite  50   0 3   90 70 3.4 81.6  10 Steel Graphite  50 1000 3   99 90 4.4 105.6  11 Steel Graphite  50 2000 3   99 89 4.3 103.2  12 Steel Graphite  50 3000 3   99 92 4.5 108.0  13 Steel Graphite  50 4000 3   99 96 4.7 112.8  14 Steel Graphite  25 4000 3   98 90 4.4 105.6  15 Steel Graphite 100 4000 3   98 96 4.7 112.8  16 Steel C/PTFE  50 4000 0.5 32 20 1.0 24.0  17 Steel C/PTFE  50 4000 1   52 39 1.9 45.6  18 Steel C/PTFE  50 4000 2   74 47 2.3 55.2  19 Steel C/PTFE  50 4000 3   57 44 2.1 50.4 

Example 2a

[0245] A two stage reaction for the production of artemisinin was carried out using two reactors as disclosed herein coupled together in series.

[0246] The reaction sequence carried out is illustrated below:

##STR00002##

[0247] The first step of the reaction was carried out in a first reactor, configured for carrying out photochemical reactions, and the second step of the reaction was carried out in a second reactor. The reaction was carried out under 7 different sets of conditions, as detailed by entries 1-7 in table 3 below.

[0248] For entries 1-3 the flow rate through both reactors was at 1 mlmin.sup.−1. The reagents included DHAA, TPP and toluene solution (0.05 M) containing 0.025 M TFA (acid). These reagents were all pre-mixed prior to introduction to the first reactor.

[0249] For entries 4-7 the flow rate through both reactors was 1 mlmin.sup.−1. The reagents included DHAA, TPP and toluene solution, however this time the acid in solution (0.5 M in toluene) and was added to the second reactor using a pump at 0.05 mlmin.sup.−1. In this way, the acid was only added to the second stage of the reaction.

TABLE-US-00003 TABLE 3 two stage reaction conditions and results Temp. 1.sup.st Temp. 2.sup.nd Reactor Reactor Acid Artemisinin Entry (° C.) (° C.) Addition Yield (%) 1 25 25 Pre-mixed at 45 2 10 25 the beginning 44 3 5 25 45 4 25 25 Added at the 56 5 10 25 start of the 55 6 5 25 second 51 7 −15 25 reactor 46

[0250] From this is can be seen that the use of a two-reactor system can be advantageous in multi-step reactions as shown by the increased yields of artemisinin where the acid is present only in the second reactor, and hence only during the second step of the reaction.

Example 2b

[0251] The two stage reaction for the production of artemisinin described in Example 2a was carried out. Instead of using two reactors coupled together in series, as used in Example 2a, the two steps of the reaction were carried out in a single large reactor, comprising two reaction zones, similar to the arrangement illustrated in FIG. 9, which shows three reaction zones.

[0252] The photochemical reaction (i.e. step one) was carried out in a first portion of the reactor. The reaction mixture then migrates to a second portion of the reaction chamber, where the second step of the reaction proceeds. This reactor arrangement is particularly useful in reactions where the flow rates in each step of the reaction do not need to be decoupled.

[0253] The photosensitiser (TPP, DCA or Ru(bpy).sub.3Cl.sub.2), TFA and DHAA were dissolved in solvent (toluene or CH.sub.2Cl.sub.2) to the desired concentration of DHAA (0.05 M). The solution was flowed through the reactor at the flow rate stated in Table 4 below and 660 RPM relative rotation speed.

[0254] The results of this experiment are set out in Table 4 below. In entry 7, high power LED lights were used.

TABLE-US-00004 Flow Rate Solvent Temp. Acid Artemisinin Entry (mL min.sup.−1) (0.05 M) reactor 1 Photosensitiser Addition Yield (%) 1 20 Toluene −10 TPP Pre-mixed 45 (0.5 mol %) at the 2 15 Toluene −10 TPP beginning 51 (0.5 mol %) TFA 3 10 Toluene −10 TPP (0.025 M) 49 (0.5 mol %) 4 20 Toluene −10 DCA  9   (5 mol %) 5 12 CH.sub.2Cl.sub.2 −10 TPP 51 (0.5 mol %) 6 20 CH.sub.2Cl.sub.2 −10 Ru(bPY).sub.3Cl.sub.2 46 (0.5 mol %) 7 20 CH.sub.2Cl.sub.2 −10 Ru(bPY).sub.3Cl.sub.2 23 (0.5 mol %)