Mesofluidic reactor with pulsing ultrasound frequency

Abstract

A mesofluidic reactor performs a chemical reaction of a starting material. A liquid phase starting material is introduced into a spraying head equipped with an ultrasound generating piezoelectric crystal unit. An inert/reagent gas feeds into the spraying head, connected to a reactor tube arranged within a thermally insulated multi-zone heating unit. For solid phase, an inert/reagent gas is introduced into a solids container connected to a spraying head equipped with an ultrasound generating piezoelectric crystal unit. The spraying head connects to a reactor tube arranged within a thermally insulated multi-zone heating unit. In either case, a reactor tube outlet connects to a cooled product trap to collect conversed substances. The spraying head generates a particle size distribution with nano and micro sized particles for the liquid phase and nano, micro or larger particles for the solid phase. The inert/reagent gas is preheated over the piezoelectric crystal unit's surface.

Claims

1. A mesofluidic reactor to perform a chemical reaction of a starting material, wherein components of the reactor are combined together depending on phase state of the starting material to form said reactor, the mesofluidic reactor comprising: (i) in case of a liquid phase starting material, a container (1) to store said liquid phase starting material, a high-pressure spraying head (4) equipped with an ultrasound generating piezoelectric crystal unit and having a nozzle, a tubing (3) to provide fluid communication between the container (1) and the spraying head (4), a reactor tube (12) with an inlet and an outlet, a heating unit accommodating said reactor tube (12), wherein the spraying head (4) is connected to the inlet of the reactor tube (12), the outlet of the reactor tube (12) is connected to a cooled product trap (13) to collect conversed substances, and the product trap (13) having an outlet connected to a vacuum tap (14) and a vacuum pump (15) to facilitate the use of vacuum, a gas source (6) to provide an inert/reagent gas, a gas conduit (10) to provide gas communication between the gas source (6) and the spraying head (4) to feed inert/reagent gas from said gas source (6) into said spraying head (4), wherein a control valve (7), a mass flowmeter (8) and a pressure gauge (9) are inserted in this order, into said gas conduit (10), or (ii) in case of a solid phase starting material, a solids container (5) to store said solid phase starting material, a high-pressure spraying head (4) equipped with an ultrasound generating piezoelectric crystal unit and having a nozzle, wherein, said solids container (5) is connected essentially from below and at right angle to said spraying head (4), a reactor tube (12) with an inlet and an outlet, a heating unit accommodating said reactor tube (12), an inert/reagent gas is introduced from a gas source (6) through a control valve (7), a mass flowmeter (8) and a pressure gauge (9) into, the spraying head (4) is connected to the inlet of the reactor tube (12), the outlet of the reactor tube (12) is connected to a cooled product trap (13) to collect conversed substances, and the product trap (13) having an outlet connected to a vacuum tap (14) and a vacuum pump (15) to facilitate the use of vacuum, a gas source (6) to provide an inert/reagent gas, a gas conduit (10) to provide gas communication between the gas source (6) and the solids container (5) to feed inert/reagent gas from said gas source (6) into said spraying head (4) through said solids container (5), wherein a control valve (7), a mass flowmeter (8) and a pressure gauge (9) are inserted, in this order, into said gas conduit (10), wherein said heating unit is provided as a thermally insulated multi-zone heating unit (11); said spraying head (4) is configured to generate a particle size distribution with nano and micro sized particles in case of the liquid phase starting material and a particle size distribution with nano, micro or even larger sized particles in case of the solid phase starting material; and wherein the gas conduit (10) is arranged to be heated, in use, by waste heat produced said piezoelectric crystal unit so as to preheat the inert/reagent gas flowing through the gas conduit (10).

2. The reactor according to claim 1, wherein said spraying head (4) is configured to atomize solvents, solutions, and sublimated non-soluble solids under pressure through a spraying tip of the nozzle, said spraying tip having a maximum inner diameter of about 0.5 mm.

3. The reactor according to claim 1, wherein said spraying head (4) further comprises an atomizer (19) as said nozzle and an ultrasonic unit (25) as said ultrasound generating piezoelectric crystal unit combined with the atomizer (19) so as to form a feedstock container (8) between the atomizer (19) and the ultrasonic unit (25), wherein the atomizer (19) comprises a capillary (20) having a first end and a second end, such that the first end of the capillary (20) is formed by the nozzle, said container (8) being in communication with the capillary (20) and the ultrasonic unit (25), wherein the ultrasonic unit (25) comprises a cylindrical envelope with an outer skirt to enclose the piezoelectric crystal unit, wherein a gas-tightly sealed helical groove (4) is formed in the outer skirt of the cylindrical envelope, said helical groove (4) is configured to provide a gas communication between the gas conduit (10) and said second end of the capillary (20) to enable, in use, flowing through of the inert/reagent gas.

4. The reactor according to claim 1, wherein the atomizer is made of a structural material chosen from the group of corrosion-resistant steel, quartz, borosilicate, Pyrex glass, Hastelloy materials, PEEK material, and Teflon.

5. The reactor according to claim 1, wherein said starting material is arranged in said solids container (5) as a solid fine-powdered substance.

6. The reactor according to claim 1, wherein the average diameter of the reactor tube (12) is at least 10 mm.

7. The reactor according to claim 1, wherein the reactor tube comprises more than one reactor tube (12) extending parallel to one another and arranged within said heating unit (11).

8. The reactor according to claim 1, wherein said reactor tube (12) is made of a material selected from the group of borosilicate, quartz, Pyrex glass, corrosion-resistant steel, and Hastelloy materials.

9. The reactor according to claim 1 wherein said reactor tube (12) has a length in a range of 10 mm and 2000 mm.

10. The reactor according to claim 1, wherein said reactor tube (12) is configured to be evacuated by the vacuum pump (15) so as to perform chemical reactions under reduced pressure and to control residence time.

11. The reactor according to claim 1, wherein the reactor is configured to allow variable atomization time for a solution of the starting material.

12. The reactor according to claim 1, wherein the product trap (13) or product condenser is provided as a water cooled chiller or a chiller filled with a mixture of dry ice and acetone, liquid nitrogen, a reflux cooler, a Peltier element, or any other kind of heat-exchanger.

13. The reactor according to claim 1, wherein said heating unit (11) is configured to provide indirect heating of said each reactor tube (12) arranged therein on a zone by zone basis.

14. The reactor according to claim 1, wherein the piezoelectric crystal unit comprises at least one piezoelectric crystal having a form of a replaceable unit to enable operation of the piezoelectric crystal unit at various frequencies as desired.

15. The reactor according to claim 1, wherein an HPLC pump or an other pump (2) for transporting fluids is inserted into the tubing (3) between the container (1) and the spraying head (4).

16. The reactor according to claim 1, wherein said ultrasound generating piezoelectric crystal unit is configured to be driven by a square signal regulated voltage applied to said unit.

17. The reactor according to claim 1, wherein the piezoelectric crystal unit of the spraying head (4) is operated at a frequency freely variable between 500 kHz and 5 MHz.

18. The reactor according to claim 1, wherein the reactor tube (12) is connected to the nozzle of the spraying head (4) or the respective spraying head (4) in an airtight manner.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

(1) In what follows, the present invention is discussed in detail with reference to the accompanying drawings, wherein

(2) FIG. 1 illustrates a preferred exemplary embodiment of a VFP apparatus implemented as a mesofluidic reactor according to the invention in a schematic sectional representation;

(3) FIG. 2 shows a possible exemplary embodiment of the pneumatic spraying module used in the VFP apparatus according to the invention in a schematic sectional representation; and

(4) FIGS. 3A and 3B show graphically and in tabular form, respectively, the isolated yields as the function of liquid flow and ultrasound frequency for a Gould-Jacobs 6 electrocyclization reaction (further details of which are discussed in relation to Example 1) performed by a VFP apparatus implemented as a mesofluidic reactor according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) The VFP apparatus implemented preferably as a high-temperature mesofluidic reactor according to the invention is illustrated in FIG. 1. According to FIG. 1, components of the inventive apparatusin line with its two different operational modes (i) and (ii) (i.e. atomization of a solution and/or a solid material, respectively)are connected as follows.

(6) (i) A (liquid phase) starting material is arranged in a container 1, said container 1, optionally and if required, is connected through a pump 2 suitable for transporting liquids, preferably a HPLC pump and a tubing 3 suitable for transporting liquids to a high-pressure spraying head 4 (see FIG. 2) equipped with a piezoelectric crystal unit (that emits preferably in the ultrasound range) and a nozzle with a spraying tip that has an inner diameter of preferably 0.5 mm, more preferably of 0.2 mm, and most preferably about 0.1 mm. Feeding of the starting material into the spraying head 4 takes place through the tubing 3, optionally by means of operating the pump 2. The spraying head 4 is connected through a conduit 10 to a gas source 6 of inert and other reagent gas, wherein said gas source 6 is provided by e.g. one or more gas cylinders or gas generators (in situ gas generation) or a combination thereof. In the flow path of the inert and other reagent gas defined by the conduit 10 and directed from the gas source 6 towards the spraying head 4 a control valve 7, a mass flowmeter 8 and a pressure gauge 9 are arranged one after the other in the direction of gas flow. The spraying head 4 is connected to the entrance side of the, preferably, tubular reactor tube 12 of the apparatus according to the invention in a sealed manner. To adjust the temperature of the reaction volume defined/surrounded by said reactor tube 12 as desired, said reactor tube 12 is disposed in its entire length inside a heating unit 11. Exhaust side of the reactor tube 12 opens into a cooled product trap 13 that serves for cooling and thus condensing/precipitating the converted substance exiting from the hot reaction volume. Finally, a vacuum tap 14 and a vacuum pump 15 are connected to the outlet of the product trap 13.
(ii) The inert and other reagent gas enters from the gas source 6 through the control valve 7, the mass flowmeter 8 and the pressure gauge 9 via said conduit 10 into a solids container 5 which, in this case, contains a solid phase starting material; here, said solids container 5 is connected directly to the spraying head 4 substantially at a right angle from below. Furthermore, the spraying head 4 is directly connected to the entrance side of the reactor tube 12. Said reactor tube 12 is disposed in its entire length inside the heating unit 11. The exhaust side of the reactor tube 12similarly to operational mode (i)opens into the cooled product trap 13 that serves for cooling and thus condensing/precipitating the converted substance exiting from said reactor tube 12. Again, a vacuum tap 14 and a vacuum pump 15 are connected to the outlet of the product trap 13.

(7) The average diameter of the reactor tube 12, i.e. the reaction volume delimited by said reactor tube 12 is at least 10 mm, preferably is at least 15 mm or more, while its length can be chosen arbitrarily in a range that extends from 10 mm to 2000 mm. An advantage of the relatively large inner diameter of the reaction volume is that, optionally, it can be divided up among several reactor tubes parallel to each other. This means that more than one reactor tubes 12 can be arranged at a time within the heating unit 11. In such a case, naturally, modifications are required at the entrance and exhaust sides of the chemical mesofluidic reactor 100 according to the present invention (as to e.g. the number and arrangement/connections of the spraying units or the product trap). Said reactor tube/reactor tubes 12 are preferably made of a material selected from the group of borosilicate, quartz, Pyrex glass, corrosion-resistant steel and Hastelloy materials.

(8) The product trap 13 for collecting the converted substances is preferably provided in the form of a precooled large surface area condenser or solvent absorber. The inert/reagent gas can be any of hydrogen, nitrogen, oxygen, etc. The mass flowmeter 8, the control valve 7 and the pressure gauge 9 serve for controlling the pressure and the flowing of the inert/reagent gas. To guide the flow of substance and to reduce the residence time, the vacuum pump 15 is applied. Those components of the apparatus which are used to feed the liquid phase starting materials belong to the microfluidic range (in terms of their respective parameters). Feeding of solid phase starting materials is performed by said solids container 5 through suitable and known ways/means.

(9) Construction of the pneumatic spraying module with an ultrasonic spraying head of the VFP apparatus implemented as a mesofluidic reactor according to the invention is shown in FIG. 2.

(10) The ultrasonic spraying head 4 used in the inventive VFP apparatus implemented as a mesofluidic reactor comprises an atomizer 19 and an ultrasonic unit 25 communicating with each other, on the one hand, through a feedstock container 8 and, on the other hand, through a thermally insulated gas pipe 15 that serves for transporting inert/reagent gas.

(11) Liquid and/or solid phase starting materials are provided in said feedstock container 8. The ultrasonic unit 25 includes one (optionally more than one) piezoelectric crystal(s) 1. To receive volumetric changes arising due to mechanical work, the at least one piezoelectric crystal 1 is sheathed with a padding 2. To assure chemical resistance, a surface of the piezoelectric crystal 1 that contacts the starting material is covered with a ceramic plate 3. The ultrasonic unit 25 of the apparatus according to the invention also functions as a heat exchanger. To this end, the piezoelectric crystal 1 sheathed with said padding 2 is enclosed in the form of a cylindrical envelope by an aluminum block having equally spaced grooves 4, wherein the 4 grooves are formed in a side of said block facing away from the piezoelectric crystal 1 (i.e. in the outer side of the block). To provide gas-tightness, the grooves 4 are covered with a polymer/PTFE sealing jacket 5 that thrusts against the surface of the aluminum block. Outer surface of the sealing jacket 5 is enclosed cylindrically and supported by a close fitted aluminum/steel casing 6 that also ensures pressure-tightness of the thus obtained unit serving as a heat exchanger in operation. The inert/reagent gas enters the ultrasonic unit 25 via a gas inlet 7 of said unit and through a gas entrance connection 13 of the unit. This way the inert/reagent gas passes into a groove 4 which is in communication with the gas entrance connection 13. Here preheating of the inert/reagent gas takes place by employing the heat (which is adverse to the reaction in certain cases) generated during the operation of the piezoelectric crystal 1 to preheat the in-flowing inert/reagent gas; the in-flowing inert/reagent gas flows along the groove 4 formed preferably helically, absorbs thereby heat produced by said piezoelectric crystal 1 and gets warm. Next, said inert/reagent gas exits through a gas exhaust connection 14 of the ultrasonic unit 25, passes along the gas pipe 15 and then enters the atomizer 19 through a connecting and thermometer-fitting block 17. Said gas preheating can also be realized by inserting a gas transporting tube of suitable (practically small) diameter made of a suitable structural material into the groove 4. Here, a significant drop in heat transfer efficacy should be also taken into account.

(12) The atomizer 19 is made of a structural material chosen preferably form the group of corrosion-resistant steel, quartz, borosilicate, Pyrex glass, Hastelloy materials, PEEK material and Teflon.

(13) The inert/reagent gas passing through a capillary 20 formed in the atomizer 19 with high velocity creates vacuum. The thus produced vacuum sucks up the small-sized particulate substance broken up into small particles by the ultrasonic unit 25 and/or sublimated by the heat generated on the surface of the piezoelectric crystal 1 and the ceramic plate 3 from the feedstock container 8 via a feedstock tube 9 extending substantially perpendicularly to the capillary 20 and opening into said feedstock container 8. Said vacuum then transports the particulate substance towards the reactor tube 22 by spraying/atomizing it into the flow, wherein the reactor tube 22 is connected to the atomizer 19 along a sealing ring 21 in an airtight manner. To increase nebulization efficacy, in case of a solution, the solution is subjected to dynamical mechanical impacts exerted by the at least one piezoelectric crystal of said ultrasonic unit 25. Due to this, liquid drops leave the surface of the solution, which are brought into motion and then transported towards the capillary 20 and then the reaction tube 22 by the vacuum developing in the feedstock tube 9 due to the flow of the inert/reagent gas.

(14) The feedstock container 8 is connected to the atomizer 19 through a threaded connection 12. To avoid precipitation of the sublimated material on the cold spots, said connection is enclosed by a tempering jacket 23. If the amount of heat dissipated by means of preheating the inert/reagent gas is too small, said tempering jacket 23 can be cooled on its outer side. Thus, evaporation of the solution from the surface of the ceramic plate 3 taking place due to the heat produced when the piezoelectric crystal 1 operates can be simply avoided. The temperature in the feedstock container 8 is measured by a thermometer which is directed through a thermoelement-fitting opening 10 and sealed to the feedstock container 8 by an appropriate sealing ring.

(15) Based on the temperature data measured by a thermometer sealed through a sealing 18 in said connecting and thermometer-fitting block 17, the temperature of the inert/reagent gas is also controlled by means of a thermal insulation/pipe-heating 16 prior to the entry of said inert/reagent gas into the atomizer 19. To ensure that inert/reagent gas of a desired temperature arrives at the atomizer 19, compensation of the heat loss of said gas and additional heating of the gas take place in the gas pipe 15 as a function of the measured temperature data. Thereby, the temperature gradient over the reaction volume can be reduced at an entry point of said reaction volume.

(16) The piezoelectric crystal 1 is energized continuously, or rather periodically through an electric connection 24 by a voltage that is matched with the type of said piezoelectric crystal. When the ultrasonic unit 25 is actuated, it is capable of operating only in a single frequency range at a time. The piezoelectric crystal 1 is formed as a replaceable unit which can thus be changed depending on the frequency to be achieved. Actuation takes place by applying a given voltage to said piezoelectric crystal, wherein the voltage is regulated by a square signal. Depending on the duty cycle of the square signal, the sonic waves will be continuous or dynamic, pulsed.

(17) The VFP apparatus, implemented as a mesofluidic reactor, with an ultrasonic spraying head is susceptible for being used basically in two application fields: (i) to atomize solutions with small particle size distributions in the micron regime in such a way that the waste heat is used to preheat the inert/reagent gas, and (ii) to nebulize/sublimate hardly or non-soluble solids. It is apparent to a person skilled in the art, however, that the present apparatus can also be used in other application fields differing from the ones defined above without significant modifications as to its structural unity and, therefore, without going beyond the scope of protection claimed below.

(18) In operational mode (i), the solution of the starting material enters the ultrasonic spraying head 4 from belowit is transported by the pump 2 or due to Venturi's principle. The solution enters the reactor tube through a tube/capillary with a diameter of about 0.2 mm at a pressure that builds up as a consequence of the resistance of the system. Inert/reagent gas is fed into the system along the entire periphery of said capillary which reduces, disperses the size of the liquid drops entering the reaction volume. To decrease the particle size distribution of said liquid drops further, the ultrasonic spraying head 4 is operated at a (n operational) frequency that can be freely varied between 500 kHz and 5 MHz; this way the degree of atomizing is controlled. The live piezoelectric unit generating ultrasounds produces heat during its operation. This waste heat is used to preheat the introduced inert/reagent gas in order to reduce the temperature gradient due to the inflow gas. To achieve good heat transfer, a mechanical coupling is established between the piezoelectric crystal(s) utilized and the tube/coil of tube by e.g. bringing said elements into direct or indirect contact; said indirect contact is realized e.g. by means of inserting a material with good thermal conductance between said piezoelectric crystal(s) and said tube/coil of tube. This way the desired degree of warming-up of the gas is ensured.

(19) In operational mode (ii), a cushioning pressure of about 0.2-0.3 bars is generated and maintained in the solids container 5 connected to the ultrasonic spraying head 4 from above by means of the inert/reagent gas introduced through the valve 7 and the pressure gauge 9. By exploiting mechanical work of the piezoelectric crystal(s), the particle size distribution is reduced from the millimeter range and/or the range of several hundreds of microns into the range of 100 to 250 m. This way, on the one hand, the substance can be handled as a solid fluid (i.e. a fine powdered material) and, on the other hand, the heat generated on the surface of the piezoelectric crystal(s) induces sublimation of said substance; the thus obtained gaseous substance is then entrained by the inert/reagent gas providing the cushioning pressure and flows into the reaction volume.

(20) Heating of the heated rector tube 12 is provided by indirect heating (by e.g. infrared radiation, heating cartridges, heating filaments, hot air blowing, etc.); thus, any temperature between room temperature (here, about 20 to 25 C.) and at least about 1000 C. can be achieved within the reaction volume. Said heated reaction volume is surrounded by multiple layers of insulation with low heat transmission coefficient. Temperature of the furnace comprising multiple separate reactor zones is measured by at least one temperature sensing means per zone, preferably, by a temperature sensor arranged in the given zone of the furnace chamber.

(21) The reactor tube 12 of mesofluidic size range to be heated to high temperatures is arranged inside the heating unit 11 along its entire length, wherein said ultrasonic spraying head 4 is located at the entrance side, while the pre-cooled large surface area substance-precipitating/-condensing product trap 13 at the exhaust side of said heating unit 11.

(22) Optionally, a vacuum pump 15 is utilized for directing the flow of substance and reducing the residence time further; said vacuum pump 15 can be connected to the outlet of the substance-precipitating/-condensing product trap 13 by means of e.g. a suitable tubing.

(23) A preferable exemplary embodiment of the VFP apparatus, implemented as a mesofluidic reactor, with ultrasonic spraying means according to the invention exhibits the following non-limiting technical parameters: temperature range: between room temperature, i.e. about 20 to 25 C. and 1000 C.; accuracy of temperature control: 3% up to 100 C., and 2% from above 100 C. and up to 1000 C.; nominal pressure: between 10.sup.3 mbar and 3 bar; flow rate of inert/reagent gas: 1 to 10000 ml/min; flow rate of solution: 0.1 to 1000 ml/min; pressure of solution: between about 1 bar (atmospheric pressure) and 400 bar; applied ultrasonic frequency: between 500 kHz and 5 MHz; and reactor size: 50026 mm.

(24) In what follows, some chemical reactions performed in the chemical reactor equipped with an ultrasonic spraying means according to the invention, as well as related measurement results are discussed in more detail. It is obvious to a person skilled in the art that said chemical reactor is also suitable to carry out other chemical reactions as well if appropriately modified (in terms of e.g. pressure, temperature, etc.). Accordingly, the chemical reactions discussed below should only be taken as examples that do not limit the scope of application of the inventive chemical reactor.

EXAMPLES

Example 1: Gould-Jacobs 6 Electrocyclization Reaction

(25) TABLE-US-00001 VFP UVFP Reactor temperature ( C.) 450 450 Preheating temperature ( C.) 150 Reactor length (mm) 500 500 Reactor diameter (mm) 26 26 Pressure 10.sup.3 mbar 3 bar Solution flow rate 0.5 (ml/min) N.sub.2 gas flow (l/min) 2 Ultrasound frequency 1.7 (MHz) Solvent DMA (dimethylacetamide) Conversion (%) >99 >99 Isolated yield (%) 80 91 NMR purity (%) >95 >98
A Gould-Jacobs 6 Electrocyclization Experiment Performed in a Vacuum Flash Pyrolysis (VFP) Device

(26) An amount of 200 mg of the starting material was measured into the distillation flask of the device. Then the temperature-control unit of the preheater was set to 150 C., and that of the reactor to 450 C. After achieving and the stabilization of the values set, a vacuum of 10.sup.3 mbar was created in the system. Due to the temperature and vacuum, the starting material starts to sublimate and a few seconds later a product obtained from the reactor appears in the product trap which is precooled to 78 C. and is disposed at the outlet of the reactor tube of 500 mm in length. The product obtained is dissolved from the trap by alcohol and/or dichloromethane, and then is evaporated. If necessary, the product is subjected to further purification.

(27) A Gould-Jacobs 6 Electrocyclization Experiment Performed in an Ultrasonic Vacuum Flash Pyrolysis (UVFP) Device

(28) An amount of 1390 mg of the starting material was measured into the distillation flask, and is then solved in 50 ml of dimethylacetamide (DMA). This way a solution having a concentration of 0.1M was obtained. The temperature-control unit of the reactor was set to 450 C. The flow rate of the solution WAs set to 0.5 ml/min, the nitrogen gas flow was set to 2 l/min and the frequency of the ultrasonic unit was set to 1.7 MHz. A few seconds after the flow of the solution has been started by the HPLC pump, a product to be collected appears in the large surface area product trap which is precooled to 78 C. As soon as the solution of the starting material has run out at the inlet, the product was drained off said trap and evaporated. If necessary, the product is subjected to further processing.

(29) FIGS. 3A and 3B illustrate graphically and in tabular form, respectively, the isolated yields for a Gould-Jacobs 6 electrocyclization reaction as the function of the applied flow rate and frequency in case of a VFP apparatus implemented as a mesofluidic reactor according to the invention. When optimizing (Simplex method), only the liquid flow rate and the ultrasound frequency have been changed; all other parameters have been kept unchanged. The obtained measurement results clearly show that the application of ultrasounds exerts an optimizing effect on the course of reaction in case of e.g. the aforementioned chemical reaction, that is, the isolated yield can be maximized if ultrasounds are applied.

Example 2: Conrad-Limpach Cyclization Reaction

(30) TABLE-US-00002 VFP UVFP Reactor temperature ( C.) 450 450 Preheating temperature ( C.) 150 Reactor length (mm) 500 500 Reactor diameter (mm) 26 26 Pressure 10.sup.3 mbar 2 bar Solution flow rate (ml/min) 0.4 N.sub.2 gas flow (l/min) 2 Ultrasound frequency (MHz) 2 Solvent DMA (dimethylacetamide) Conversion (%) >99 >99 Isolated yield (%) 60 75 NMR purity (%) >95 >95
A Conrand-Limpach Cyclization Experiment Performed in a Vacuum Flash Pyrolysis (VFP) Device

(31) An amount of 200 mg of the starting material was measured into the distillation flask of the device. Then the temperature-control unit of the preheater was set to 150 C., and that of the reactor to 450 C. After achieving and the stabilization of the values set, a vacuum of 10.sup.3 mbar was created in the system. Due to the temperature and vacuum, the starting material starts to sublimate and a few seconds later a product obtained from the reactor appears in the product trap which is precooled to 78 C. and is disposed at the outlet of the reactor tube of 500 mm in length. The product obtained is dissolved from the trap by alcohol and/or dichloromethane, and then is evaporated. If necessary, the product is subjected to further purification.

(32) A Conrand-Limpach Cyclization Experiment Performed in an Ultrasonic Vacuum Flash Pyrolysis (UVFP) Device

(33) An amount of 1050 mg of the starting material was measured into the distillation flask, and is then solved in 50 ml of dimethylacetamide (DMA). This way a solution having a concentration of 0.1M was obtained. The temperature-control unit of the reactor was set to 450 C. The flow rate of the solution was set to 0.4 ml/min, the nitrogen gas flow was set to 2 l/min and the frequency of the ultrasonic unit was set to 2.0 MHz. A few seconds after the flow of the solution has been started by the HPLC pump, a product to be collected appears in the large surface area product trap which is precooled to 78 C. As soon as the solution of the starting material has run out at the inlet, the product was drained off said trap and evaporated. If necessary, the product is subjected to further processing.

(34) In light of the present teaching, it is apparent to a person skilled in the art that the ultrasonic VFP apparatus implemented preferably as a mesofluidic reactor according to the invention is suitable for performing other chemical reactions than VFP reactions as well.