EP3419750A1 - Application of ultrasound in a microreactor - Google Patents
Application of ultrasound in a microreactorInfo
- Publication number
- EP3419750A1 EP3419750A1 EP17707331.9A EP17707331A EP3419750A1 EP 3419750 A1 EP3419750 A1 EP 3419750A1 EP 17707331 A EP17707331 A EP 17707331A EP 3419750 A1 EP3419750 A1 EP 3419750A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- manipulation
- channel
- fluids according
- fluid carrier
- fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0093—Microreactors, e.g. miniaturised or microfabricated reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/40—Static mixers
- B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions
- B01F25/43—Mixing tubes, e.g. wherein the material is moved in a radial or partly reversed direction
- B01F25/433—Mixing tubes wherein the shape of the tube influences the mixing, e.g. mixing tubes with varying cross-section or provided with inwardly extending profiles
- B01F25/4331—Mixers with bended, curved, coiled, wounded mixing tubes or comprising elements for bending the flow
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F31/00—Mixers with shaking, oscillating, or vibrating mechanisms
- B01F31/80—Mixing by means of high-frequency vibrations above one kHz, e.g. ultrasonic vibrations
- B01F31/86—Mixing by means of high-frequency vibrations above one kHz, e.g. ultrasonic vibrations with vibration of the receptacle or part of it
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F33/00—Other mixers; Mixing plants; Combinations of mixers
- B01F33/30—Micromixers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
- B01F35/71—Feed mechanisms
- B01F35/717—Feed mechanisms characterised by the means for feeding the components to the mixer
- B01F35/7174—Feed mechanisms characterised by the means for feeding the components to the mixer using pistons, plungers or syringes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00788—Three-dimensional assemblies, i.e. the reactor comprising a form other than a stack of plates
- B01J2219/00792—One or more tube-shaped elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00801—Means to assemble
- B01J2219/0081—Plurality of modules
- B01J2219/00813—Fluidic connections
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00801—Means to assemble
- B01J2219/0081—Plurality of modules
- B01J2219/00817—Support structures
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00851—Additional features
- B01J2219/00858—Aspects relating to the size of the reactor
- B01J2219/0086—Dimensions of the flow channels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00889—Mixing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00781—Aspects relating to microreactors
- B01J2219/00925—Irradiation
- B01J2219/00932—Sonic or ultrasonic vibrations
Definitions
- the invention relates to an ultrasound liquid manipulating system and more specifically a system for manipulation of a liquid-liquid system or a gas-liquid system using an interval-contact reactor.
- Liquid-liquid extractions consist of heterogeneous systems of immiscible liquids.
- Microreactors can provide intensified effects for such systems owing to the different flow patterns that can be generated as a result of the mixing elements used and the flow rate applied.
- the various flow patterns generated can provide very high interfacial areas, shorter diffusion lengths and internal mixing effects, even under laminar flow conditions.
- methodologies such as the numbering up have been developed, which involves introducing identical parallel flow channels.
- Embodiments of the present invention may be directed to liquid- liquid systems or to gas-liquid systems.
- the present invention provides devices for manipulation of fluids, the device comprising:
- the reactor base comprises at least one channel
- a fluid carrier for carrying a fluid stream, said fluid carrier adapted to be positioned in said at least one channel;
- the fluid carrier is intermittently in direct contact with the at least one channel defining at least two distinct contact areas in the channel.
- at least one contact area may be provided.
- a plurality of channels are provided such to enable a residence time to produce significant improvement in the process as compared to the direct contact device.
- the at least one channel is defined by two walls and a longitudinal surface, whereby the fluid carrier is intermittently in direct contact with the longitudinal surface of the channels.
- the channel may have a V- or U-groove cross-section.
- a channel is defined by successive through-holes provided in the reactor base, whereby the fluid carrier is intermittently in direct contact with the through-holes.
- the fluid carrier is not in contact with the reactor base along its entire surface, but only at specific contact points or areas. These contact points will work as a local antenna enabling a maximum and efficient transmission of the vibrations into the fluid carrier by direct contact with the transducer and thereby eliminating the dependence on the far field distance.
- the intermittent direct contact between the fluid carrier and the at least one channel may be obtained by a plurality of distanced supporting protrusions in the channel.
- the number of contact point may be between 2 and 10, and may be for example 5. It is an advantage of embodiments of the present invention that when an emulsified bubble or droplet passes in the fluid carrier over such a contact area or local antenna, the ultrasound causes the emulsified aqueous phase to split up.
- the plurality of antenna's may cause these bubbles to split up repetitively at successive antennas or at each successive antenna. Even though there is an increase in the interfacial area by the emulsification, this change in size of the emulsified aqueous phase due to the repetitive splitting and coalescence, can provide additional interfacial area, thereby increasing the mass transfer between the phases and further improving the yield of the process. It is an advantage of embodiments of the present invention that introduction of intervals along the channels for direct contact transfer of ultrasound to the microchannel was found to be effective in improving the performance of the reactive extraction process.
- the intervals brought two major advantages: in first aspect the points of high intensity became concentrated at the intervals and secondly the intervals caused a repetitive change in the size of the emulsified aqueous phase which contributed to additional improvement in mass transfer between the two immiscible phases.
- the quantity of intervals is preferably determined by considering for example, amongst others the total size of the base plate, the used wavelength of the ultrasonic oscillation source, the design of the transducer and the total length of the channel pass laying on top of the transducer.
- the best configuration in terms of number of intervals was found to be five intervals per x cm of channel and per y cm of wavelength.
- the improvement in yield of the hydrolysis reaction was found to be highest for the five interval design compared to the direct contact design at all the residence times for the operating conditions studied. In some embodiments, the presence of five intervals was found to result in the best design.
- the percentage improvement in the sonicated yield for the interval design over the direct contact design was between 23 to 13% and in terms of the volumetric mass transfer coefficient between 29 to 17 %.
- At least five contact points are provided.
- a plurality of contact points are provided, whereby said plurality of contact points are distributed in a spatial pattern.
- the device further comprises a cover plate, said cover plate adapted to at least partially cover the reactor base.
- the fluid carrier is made of a material adapted to absorb signals generated by the ultrasonic oscillation source.
- the material is an acoustic soft or hard material.
- the material is not chemically reactive with the fluid and/or an optical transparent material.
- the material may be Teflon or perfluoroalkoxy (PFA).
- the reactor base comprising the fluid carrier is attached on the ultrasonic oscillation source.
- the channel may be a volume substantially larger than the fluid carrier.
- the channel may comprise supporting elements such that at different distances from the ultrasonic oscillation source one or more fluid carriers can be positioned.
- the supporting elements may be configured such that a plurality of fluid carriers can be supported, each fluid carrier being positioned at a distinct distance from the ultrasonic oscillation source.
- the supporting elements may be configured for supporting the fluid carriers at predetermined distances from the ultrasonic oscillation source, one of these distances being lambda/2 from the ultrasonic oscillation source, wherein lambda is the wavelength of the ultrasonic oscillation source.
- the supporting elements may be configured for supporting the fluid carriers by through holes in the supporting elements through which the fluid carriers pass.
- the fluid carrier is attached by means of clamping or gluing, for example by using a two part glue or any other glue with good acoustic impedance characteristics.
- the tightness of attaching by means of a screw is important as it is the link between the ultrasonic transducer and the reactor plate. The tightness should be as tight as possible. Currently a 10 mm screw is used at the center of a 80X80 mm plate.
- the ultrasonic oscillation source comprises a waveform generator and an amplifier.
- the device may be a microreactor.
- the reactor base may be metal plate, for example an aluminum metal plate.
- the fluid carrier may be a tube.
- cavities are present and a liquid is provided in said cavities or openings, which stabilizes the temperature of the reaction liquid present in the fluid carrier.
- the liquid provided in said cavities or openings is a heating or cooling liquid.
- devices according to embodiments of the present invention may be used for liquid-liquid extraction.
- the present invention provides methods for manufacturing a device for manipulation of fluids, said method comprising:
- the reactor base comprises at least one channel
- a fluid carrier for carrying a fluid stream, said fluid carrier adapted to be positioned in said at least one channel and said fluid carrier comprising a continuous outer surface; characterized in that the fluid carrier is intermittently in direct contact with at least one channel defining at least two distinct contact areas.
- FIG. 1 (a) illustrates a schematic representation of a reactor according to embodiments of the invention
- (b) illustrates a cross section of single channel direct-contact type reactor known in the art
- (c) illustrates a cross section of a single channel of an interval-contact type reactor according to embodiments of the present invention.
- FIG. 2 schematically illustrates details of a single interval as indicated in Fig. 1 (c).
- FIG. 3(a)-(c) schematically illustrate different arrangements of intervals provided in a channel
- Fig. 3(a) illustrates a cross-section of a specific embodiment where the channel comprises three interval contact arrangement
- Fig. 3 (b) illustrates a cross- section of a specific embodiment where the channel has five interval contacts
- Fig. 3 (c) illustrates a specific embodiment providing a channel having seven contacts.
- FIG. 4 illustrates a microreactor known in the art and its process and electrical connections.
- FIG. 5 illustrates the chemical reaction related to the hydrolysis of p- nitrophenylacetate.
- FIGs. 6 (a)-(b) illustrate thermal imaging of the ultrasound reactor plate of a microreactor of (a) the direct contact type as known in the art and (b) interval contact type according to embodiments of the present invention.
- FIGs. 7 (a)-(e) illustrate behavior of emulsified slug at an interval in embodiments of the present invention.
- FIG. 8 illustrates variation of yield with number of intervals per channel of a reactor plate used in embodiments of the present invention. Error bars calculated on the basis of three replicates. (If no error bars are shown they are smaller than the symbol).
- FIG. 9 illustrates a thermal profile of a plate comprising intervals according to embodiments of the present invention, more specifically comprising seven intervals per channel of the reactor plate.
- FIG. 10 illustrates variation of extraction yield with reactor design type. Error bars calculated on the basis of three replicates. (If no error bars are shown they are smaller than the symbol).
- FIG. 11 illustrates variation of temperature between outlet and inlet with residence time of a microreactor based on direct contact as known in the art and on interval contact according to embodiments of the present invention. Error bars calculated on the basis of three replicates. (If no error bars are shown they are smaller than the symbol).
- FIG. 12 illustrates variation of volumetric mass transfer coefficient with reactor design type. Error bars calculated on the basis of three replicates. (If no error bars are shown they are smaller than the symbol).
- FIG. 13 illustrates an alternative embodiment of a microreactor according to embodiments of the present invention.
- FIG. 14 illustrates a microreactor with multiple layers, according to an embodiment of the present invention.
- FIG. 15 illustrates the variation in yield at different levels of a multiple layer microreactor, illustrating features of embodiments of the present invention.
- FIG. 16 illustrates a thermal image of a multiple layer microreactor, illustrating features of embodiments of the present invention.
- microreactor reference may be made to a reactor comprising channel widths up to 2 mm or larger.
- intermittently indirect contact reference is made to two elements that are not in contact over their whole length but are in direct contact with each other at different distinct points, i.e. at points distanced from each other, also referred to as intervals.
- the present invention relates to a device for manipulation of fluids.
- the latter includes liquid or solvent extraction, but is not limited thereto.
- the device comprising an ultrasonic oscillation source, a reactor base comprising at least one channel, and a fluid carrier for carrying a fluid stream, said fluid carrier adapted to be positioned in said at least one channel.
- the fluid carrier is intermittently in direct contact with the at least one channel defining at least two distinct contact areas in the channel.
- the system under study can be a gas in a liquid (e.g. bubbles) as well as a liquid in a liquid (droplet).
- the system thus may be a gas-liquid system or a liquid-liquid system.
- intervals along the channel(s) for direct contact transfer of ultrasound to the microchannels were found to be effective in improving the performance of the reactive extraction process.
- the intervals brought about two major improvements to the design. Firstly, the points of high temperature became concentrated at the intervals and, secondly, the intervals caused a repetitive change in the size of the emulsified aqueous phase which contributed to additional improvement in mass transfer between the two immiscible phases.
- the best configuration in terms of number of intervals was found to be five intervals per channel for this particular reactor size and geometry, although embodiments of the present invention are not limited thereto.
- the improvement in yield of the hydrolysis reaction was found to be the highest for the five-intervals design compared to the direct-contact design at all residence times for the operating conditions studied.
- Embodiments of the present invention provide novel reactors, preferably microreactors, suitable for ultrasound-assisted action on liquid-liquid systems or gas- liquid systems. Examples of possible action are extraction, emulsification, separation, stripping, absorption, distillation, etc. . Reactors according to embodiments of the present invention are suitable for ultrasound-assisted treatment of a fluid, e.g. a fluid stream.
- Embodiments of the present invention introduce short contact intervals in a microchannel tubing of the microreactor, along the reactor plate channel, in order to advantageously have a more focused transmission of the ultrasound.
- the non-contacted parts of the tubing are still under the influence of the ultrasound as a result of the pseudo-sonicated zone created by the adjacent intervals.
- a device wherein one or more fluid carriers are supported at different distances from the ultrasound oscillation source is provided, such that the overall length of the fluid carriers or the number of fluid carriers wherein ultrasonic treatment can be performed can be increased.
- the system then operates in a stacked mode by providing different layers, levels or planes wherein fluid carriers can be positioned.
- the reactor assembly according to the present invention is similar to the direct- contact type reactors known in the art, which is illustrated in FIG. 1(a).
- the reactor 100 in Fig. 1(a) comprises a reactor plate 102, e.g. a metal like an aluminum plate, of for example 4 mm thickness and dimensions of 80x80 mm, with at least one, e.g. four channels, preferably square shaped in cross-section, cut through the plate 102. These channels preferably have the same dimensions as the outer diameter of the tubing 104 to be placed in them. The four channels account for four passes through the sonicated zone.
- the tubing 104 is preferably PFA (perfluoroalkoxy) tubing with an internal diameter of 0.8 mm and outer diameter of 1.6 mm, which is preferably held in place in the channels, e.g. in the square channels, with a cover plate 106, e.g. a Plexiglas cover plate of 5 mm thickness, fixed to the reactor plate 102, e.g. bolted at the four corners on top of the aluminum plate.
- the entire assembly is bolted onto a transducer 110 whose input parameters are then controlled by a wave form generator and amplifier combination (FIG. 1 (a)).
- a pseudo-sonicated zone is present, which showed sonication activity in a region of the tube that was not embedded in the reactor plate 102. This region existed for a distance of up to 8 cm away from the reactor plate 102, both at the inlet and outlet of the reactor 100. This behavior was also observed in the tubing bends in between the sonicated passes, which are also outside the reactor plate as illustrated in Fig. 1(a).
- the cross section of a part of a single channel of the direct-contact reactor is shown in FIG. 1 (b), where it can be seen that the tube is in contact with the reactor plate along the full length of the channel.
- each interval 120 may have a width as small as possible, whereby at least 1mm of contact length is present.
- the height must be sufficient enough to prevent contact with the non-contact surface even when the ultrasonic vibrations are applied.
- the width may be 1mm and the height may be 2.4mm from the bottom of the plate, although embodiments are not limited to these specific dimensions and other dimensions also can be used. .
- the space between the intervals is in one example at a height of 1.6 mm from the bottom of the plate.
- This arrangement made sure that the tubing is in contact with the bottom part of the channel only at the intervals and this makes only the intervals to be at the same height at which the tubing was in contact in the direct-contact type.
- the individual intervals act as different focused transmission points along the length of the channel. The parts of the tubing that are not in contact with the intervals will still be under the influence of the ultrasound as a result of the pseudo-sonicated zone created by the adjacent intervals.
- Embodiments of the present invention are based on contacting the tubing with the reactor plate at intervals, whereby the number of intervals can be varied.
- the number of interval elements was varied to determine the ideal number required along each channel for an effective transfer of the ultrasound using specific materials.
- FIG. 13 schematically illustrates an alternative embodiment where a channel is defined by successive through-holes provided in the reactor base, whereby the fluid carrier is intermittently in direct contact with the through-holes, as the fluid carrier is positioned inside the through-holes.
- the reactor 1300 and the contact intervals 1302 are shown.
- a water bath may be provided, whereby said liquid, e.g. water bath, is provided in the channel or cavities defined by the space of the fluid carrier not in direct contact with the reactor plate, which are present in between the intervals, and whereby said liquid is adapted to heat/cool the fluid and fluid carrier.
- the liquid may be provided by means of a liquid input or output mechanism, as indicated by "liquid medium in/out” on the figure.
- a gas may be used for heating or cooling the fluid and fluid carrier.
- the fluid or liquid entrance 1304 is shown in FIG. 13.
- the introduction of temperature control by a matching mini-ultrasonic-bath is obtained by providing a supply for the temperature-control medium.
- a temperature-control medium may e.g. be pumped through the channel.
- the medium is pumped through two elbows with push-in fittings provided at both ends of the hollowed-out area, which act as inlet and exit points.
- a watertight sealing may be provided.
- the temperature-control medium can also facilitates transfer of the ultrasound from the transducer to the reaction mass, thus providing an indirect contact between the source and the sonicated system.
- This method of sonication holds an advantage over conventional horn setups as it prevents the reaction mass coming in direct contact with the sonication source, thereby avoiding metal contamination by erosion through ultrasound source surface cavitation.
- Variations of three, five and seven intervals along each channel were studied. They were arranged along the channel as shown in FIG. 3. With this arrangement three plates were manufactured to perform the required experiments. The thermal profile of the plates for different variations in the design and process parameters were also studied with a thermal camera with spatial resolution of 1.36 mrad.
- the device preferably comprises two pumps, e.g. syringe pumps, that pump the fluid, in the present example aqueous and organic phases, through a T-junction with a selected flow rate (between 0.1 and 1.0 ml/min) to form the desired flow pattern.
- a selected flow rate between 0.1 and 1.0 ml/min
- the slug flow persists.
- both the aqueous and the organic streams are pumped at the same flow rate (i.e. phase ratio 1:1).
- the total length of tubing used is 58 cm out of which the first 9 cm constitute the distance from the T-junction to the reactor plate, the next 40 cm the sonicated section and finally 9 cm, being the distance from the reactor plate outlet to the separating flask. From the T-junction the two phase system flows into the designed reactor after which 2 ml of the phases is collected in a separating flask and separated by gravity separation.
- FIG. 4 illustrates syringe pumps 402 for providing an aqueous stream 404 and an organic steam 406. These streams are mixed in a mixing and flow pattern generation zone 412 .
- a pseudo-sonification zone 414 is present.
- a sonification zone 416 is present.
- a high speed camera 408 may be positioned.
- a settling and separation zone 418 is present, ending in a separating flask 422.
- the electrical components comprise a waveform generator 430, an amplifier 432 providing a signal to the transducer 434 of the reactor plate 410, and a cooling fan 436.
- the ultrasound wave characteristics frequency, amplitude and shape of the wave may be controlled by a Picotest G5100A waveform generator.
- the signal is sent to the transducer through an E&l 1020L RF amplifier.
- the transducer is a multi- frequency type which can operate at frequencies of 20, 40 & 60 kHz (Ultrasonics World MPI-7850D-20-40-60 H).
- a cooling fan is used to keep the transducer cool, to avoid variations in power and to avoid overheating of the reactor plate.
- a reaction of interest is the hydrolysis of p-nitrophenyl acetate, as this has been well described in terms of solvent extraction and acoustic enhancement and therefore allows good comparison.
- This is a reactive extraction process which is illustrated in FIG. 5.
- the organic input stream is p-nitrophenyl acetate dissolved in toluene at a concentration of 0.05 M, while the aqueous phase consists of a 0.5 M NaOH solution. This is an instantaneous reaction and hence it is mass transfer controlled. As an excess of NaOH is used, this reaction can be considered as a pseudo- first order reaction.
- the sodium p-nitrophenolate is formed in the water phase, the solution turns yellow, which can be utilized to quantify its concentration in a UV- 1601 Shimadzu spectrophotometer at a wavelength of 400 nm.
- the effect of introducing the intervals along the length of the channel according to embodiments of the present invention was first studied in terms of the thermal profile of the reactor plate when sonicated for a certain amount of time. Both the direct-contact type and the interval-contact type with 5 intervals were subjected to a frequency of 20 kHz, at an amplitude of 590 m.V and net applied electrical power of 20 W. The thermal profile was then observed after a period of 30 min with the thermal camera. The images obtained are shown in FIG. 6.
- the high temperature area in the channel is spread in a non-uniform way along the length of the channel, whereas the introduction of the intervals in the interval-type reactor seems to concentrate the high temperature points at the intervals.
- the high intensity points of the interval-contact type are at a higher temperature (average of 37.1°C - 41°C at the intervals) than the direct-contact type (average of 32.2°C - 35.1°C along the channels).
- the temperature variation is approximately proportional to the ultrasound intensity variation along the plate, we perceive that the objective of focusing the ultrasound at defined points along the channel is met with this design.
- the behavior of the two- phase system was also observed with a high speed camera (Photron Fastcam Mini UX- 100).
- PFA tubing used which is hydrophobic, as a result the organic phase is the continuous phase and the aqueous phase is the dispersed phase.
- a similar initiation mechanism which made use of the vibration of either clusters of small bubble or individual large bubbles formed in the continuous phase was observed in the interval-type reactor as in the direct-type contact reactor.
- the next step is to obtain the ideal number of intervals along each channel according to embodiments of the present invention.
- the sonicated reactive extraction of p-nitrophenyl acetate experiment was carried out in each of these plates at a frequency of 20.3 kHz, amplitude of 590 m.V and the net applied power of 20 W.
- both the aqueous and the organic streams are pumped at the same flow rate (i.e. phase ratio 1:1).
- the extraction yields obtained at different residence times are plotted in (FIG. 8). From the graph it is very evident that irrespective of the number of intervals there is always an improvement in the yield by sonication (e.g. non-silent).
- the infrared image for the five-intervals type was already shown in FIG. 6(b), while that for the seven-intervals design is shown in FIG. 9.
- Form the thermal profile it is seen that there is a clear difference in the temperature distribution along the surface of the plate depending on the number of intervals.
- the five-interval design shows a higher temperature both overall and at the intervals. Higher temperature is considered to represent better power transmission along the channel, and hence the five-interval design provides better transmission of power, resulting in better yield of the extraction process.
- the five-intervals design was compared to the direct-contact type (triangle) known in the art at a frequency of 20.3 kHz, amplitude of 590 m.V and net applied power of 20 W at the same residence times in terms of the yield obtained for the sonicated hydrolysis reaction of p-nitrophenyl acetate.
- the results obtained are shown in FIG. 10. From the results it is evident that the five-interval design according to the present invention advantageously performs better at all the residence times compared to the direct-contact type. The causes of this improvement were investigated. Firstly, the temperature difference between the inlet and outlet of the reactor plate was measured at the same ultrasound parameters and residence times. The results obtained are plotted in FIG. 11.
- Kia volumetric mass transfer coefficient
- Kia -1A In(l-a)
- Kia The variation of Kia with residence time for the two design types is shown in FIG. 12.
- the Kia value seems to exhibit an asymptotic behaviour at higher residence time. With sonication the entire curve shifts upward with the asymptote reached faster.
- the highest values of Kia are observed for the interval- contact type which shows an improvement in the Kia. values in the range of 85 to 58 % (at residence times of 87 s to 9.7 s respectively) with respect to the silent condition.
- the Ki values are similar and that the increase in the Kia value can be attributed to the increase in the interfacial area available for mass transfer due to the splitting and combining of the emulsified aqueous slugs.
- the improvement in the interfacial area is in the range of 29 to 17 % with respect to the direct-contact design.
- the space between the contact points was explored for provision of temperature control.
- a two-step approach was applied whereby firstly temperature control was induced using direct contact method design parameters and whereby direct contact elements were introduced as intervals.
- the step of temperature control was achieved by suspending the tubing in a temperature controlled and sonicated liquid medium, leading to an indirect transfer of ultrasound termed the indirect contact reactor.
- the direct contact elements were introduced at regular intervals along the tubing. Open as well as closed intervals were assessed.
- open interval design the fluid carrier is mainly supported by the supporting elements.
- closed interval design the fluid carrier is in contact at a certain position but substantially along the circumference of the fluid carrier.
- the reactor design which incorporates both the interval and indirect approaches of ultrasound transfer is termed the hybrid contact reactor.
- the hybrid reactors performed better than the indirect contact reactor (20 to 27% higher yield) for lower residence times of ⁇ 45 s and similar for higher residence times. Comparing the two hybrid designs (open and closed intervals), even though their performance was similar the closed interval gave more stable and distinct yields. The design showed a relative performance similar to the interval contact design which gave the highest yields thus far for the same operating conditions. It was found that the device can work as a continuous emulsifier.
- the multilevel interval reactor 1400 has a fixed volume that can be sonicated.
- the volume is dependent on the length of the tubing which in turn is governed by the diameter and hence the bending radius available for this diameter. The dimensions also factor into the number and position of the channels thereby determining the length of the sonicated tube.
- the volume that can be sonicated limits the throughput of a device.
- a solution to increase the throughput for a given plate size is proposed here by providing multiple levels at which the tubing can be placed. These levels can either be used for parallel or series operation. The addition of levels advantageously is done at locations at points of oscillation maximums. These points are determined to be at a height of ⁇ /2 or at half wavelength.
- the reactor comprises a top and bottom plate which act as supports for the intervals.
- the intervals are held in place, e.g. using two screws at the top and bottom of the plates. All the intervals are of similar dimensions except at the entry and exist to facilitate the placement of flat end fittings to hold the tubing in place.
- the thickness of the intervals was selected to be 2.5 mm to facilitate the placement of screws to hold the intervals in place.
- the assembly is connected to a transducer with a 10 mm screw placed at the bottom of the plate.
- the hydrolysis of the p- nitrophenylacetate was tested. The experiments were conducted for similar residence times of 27 s and compared to the silent condition. The results obtained are as shown in FIG. 15.
- FIG. 15 shows an improvement in yield for the levels 0 and ⁇ /2.
- the yield obtained in silent and at level ⁇ /4 are almost similar, showing there is little or no improvement.
- the improvement in level zero is what is expected as it is in the near field of operation.
- the improvement in ⁇ /2 shows that there is an oscillation maximum at this point and it can be exploited for improvement in throughput.
- the improvement is further supported by the thermal image in FIG. 3, which shows a higher heating rate at the zero and ⁇ /2 levels.
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GBGB1603238.5A GB201603238D0 (en) | 2016-02-25 | 2016-02-25 | Ultrasound solvent extractor |
PCT/EP2017/054508 WO2017144720A1 (en) | 2016-02-25 | 2017-02-27 | Application of ultrasound in a microreactor |
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