RU2842078C1 - Plant for microreactor synthesis in liquid-gas and liquid-liquid systems - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical, petrochemical, food, pharmaceutical and other industries, can be used for various technological processes in heterogeneous liquid-liquid, liquid-gas systems, such as absorption, gas-liquid reactions, inter-phase transfer, including with a chemical reaction, and is mainly intended for processes that require a long residence time (10 minutes or more, up to several hours), characteristic for synthesis of organic compounds, organometallic compounds and other products. Plant for microreactor synthesis in liquid-gas and liquid-liquid systems comprises tanks with initial media, pumps, microchannels connected to pump discharge branch pipes. Plant represents a cascade of several stages, each of which includes three in-series connected units – a dispersion unit, a contact unit and a phase separation unit. Containers with initial media are connected to the first stage of the cascade. Dispersion unit includes pumps for supply of continuous and disperse phases, distributing chamber for introduction of disperse phase, distributing chamber for introduction of continuous phase and microdispersers installed in it. Phase contact unit comprises one or several microchannels connected in parallel with their inlets connected to microdisperser while microchannel outlets are connected via manifold to phase separation unit. Phase separation unit comprises separator, wherein microdispersers are equipped with nozzles while products are withdrawn from phase separation unit of cascade last stage.

EFFECT: invention ensures continuous synthesis of products which require a long residence time (from tens of minutes to several hours), increases efficiency of the apparatus, provides high uniformity of distribution of phases on the channels (if there is more than one channel) and on the length of the channels.

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Description

The invention relates to the chemical, petrochemical, food, pharmaceutical and other industries, can be used to carry out various technological processes in heterogeneous liquid-liquid, liquid-gas systems, such as absorption, gas-liquid reactions, interphase transfer, including with a chemical reaction, and is primarily intended for carrying out processes that require a long residence time (10 minutes or more, up to several hours), typical for the synthesis of organic compounds, organometallic compounds and other products.

A device for microreactor synthesis (prototype device) is known (RU Patent No. 2559369, MGZ C07D 257/04 (2006.01), B01J 19/24 (2006.01)), comprising a housing with nozzles for feeding reagents and an outlet nozzle for removing products, feed pumps, the discharge nozzles of which are connected to the nozzles for feeding reagents, according to the invention, the housing of the microreactor is made in the form of a cylindrical tube with a hydraulic diameter of 10 to 2000 μm, the nozzle for feeding methylene chloride is made coaxially with the housing, and the nozzle for feeding 5-phenyltetrazoles is connected to the housing from the side at an angle between their axes in the range from 30° to 130° with the possibility of continuously or discretely changing this angle, and a liquid phase separator and a separator of gases and vaporous products, wherein the lower branch pipe of the liquid phase separator is connected to the suction branch pipe of one feed pump, and the lower branch pipe of the gas and vaporous product separator is connected to the suction branch pipe of another feed pump, the upper branch pipe of the liquid phase separator is connected to the lower part of the gas and vaporous product separator, and the upper branch pipe of the gas and vaporous product separator is connected to the atmosphere, wherein methylene chloride with methyl iodide dissolved therein is fed into the axial branch pipe, and an aqueous solution of caustic soda and 5-phenyltetrazoles is fed into the side branch pipe at flow rates that ensure the formation of droplets of the dispersed phase in the slug (Taylor) mode.

The known device allows to exclude expensive catalysts, energy-consuming high-speed mixing devices from the synthesis scheme and to obtain target products with a high yield (at least 80-90%). Thus, the energy and additional reagent costs (including the phase transfer catalyst) for the process are reduced.

However, the known device has the following disadvantages:

1) The length of the microchannels used in the known device (typical values are about 2 meters) is insufficient to ensure the residence time; it is significantly less than the duration of the reaction, which does not allow achieving acceptable values of the useful effect, including the degree of conversion.

However, with a simple increase in the length of the microchannel, the pressure losses increase so much that it is impossible to provide the supply of a two-phase mixture through it with a given flow rate using existing pumps. The flow rate of the mixture decreases so much that the quality of micro-mixing becomes unsatisfactory due to a decrease in the speed and frequency of liquid circulation.

2) In the known device, to increase the residence time in the apparatus, circulation (recirculation) of the flow is carried out by closing the outlet of the microchannel to the inlet of the pump branch pipe. Multiple circulation of a limited amount of the processed medium through the volume of a single microchannel occurs, ensuring mixing throughout the volume of the apparatus and a specified residence time equal to the duration of the process. However, in this case, the volumetric productivity of the apparatus is sharply reduced, since it is determined by the small volume of a relatively short microchannel divided by the duration of the process. The molar and mass productivity are reduced proportionally.

3) Attempts to simply increase the flow rate in one microchannel lead to a significant increase in pressure, i.e. the network curve (including mainly losses in the microchannel) in the coordinates H=f(Q) (where H is the pressure, Q is the flow rate) becomes significantly higher, and the pumps do not provide the necessary increase in productivity.

4) When attempting to simply increase the number of parallel microchannels, there is a problem with the uniform distribution of phases both by channels (if there is more than one) and by the length of the channels. The uneven distribution of phases by channels leads to the fact that some channels do not participate in mass-exchange processes, since one of the two phases (usually dispersed) practically does not enter them.

The uneven distribution of phases along the length of the channels can be caused by a change in the volume of droplets or bubbles during the reaction, as well as their coalescence or disintegration as they move in the microchannel; such unevenness leads to a change in the flow structure, the circulation mode in the continuous and dispersed phase, and therefore to a deterioration in the mass transfer characteristics of the apparatus and the installation as a whole.

The objective of the proposed invention is to ensure continuous synthesis of products requiring a long residence time (from tens of minutes to several hours), to increase the productivity of the installation, to ensure high uniformity of phase distribution both in channels (if there is more than one) and along the length of the channels.

The stated task is achieved in that in the installation for microreactor synthesis in liquid-gas and liquid-liquid systems, including tanks with initial media, pumps, microchannels connected to the outlet pipes of the pumps, according to the invention, the installation is a cascade of several stages, each of which contains three units connected in series - a dispersion unit, a contacting unit and a phase separation unit, wherein the tanks with the initial media are connected to the first stage of the cascade, the dispersion unit includes pumps for feeding the continuous and dispersed phases, a distribution chamber for introducing the dispersed phase, a distribution chamber for introducing the continuous phase and microdispersers installed therein, the phase contacting unit contains one or more microchannels connected in parallel, the inputs of each of which are connected to the microdisperser, and the outputs from the microchannels are connected through a manifold to the phase separation unit, the phase separation unit contains a separation device that ensures the separation of the heavy and light phases, wherein Microdispersers are equipped with nozzles, and the products are collected from the phase separation unit of the last stage of the cascade.

Definitions of terms used in this description:

microchannels - channels with a hydraulic diameter from 10 µm to 4-5 mm; the cross-section can be round, rectangular, hexagonal, triangular, or have another shape;

distribution chamber - a device for distributing a phase (continuous or dispersed) through microchannels or nozzles;

pump - a device for supplying liquid or gas, i.e. for transferring mechanical energy to liquid or gas; thus, here the term pump refers not only to pumps for pumping liquids, but also to compressors and gas blowers.

The claimed technical solution is new, has an inventive level and is industrially applicable.

Fig. 1 shows a block diagram of the installation, Fig. 2 - a detailed diagram of the main units of the installation, with disclosure of information on the composition of each block of the installation. Fig. 3 shows the design options for the microdispersers and their relative positions relative to the distribution chambers and microchannels: in Fig. 3a - with the possibility of axial adjustment of the microdisperser nozzles, in Fig. 3b - with fixation of the microdisperser nozzles in the required axial position. Figs. 4-6 show design options for the microdispersers (view A, designated by a dashed rectangle in Fig. 3, is shown on an enlarged scale). Fig. 4 shows a diagram of the microdispersers equipped with nozzles with the possibility of axial adjustment of their position relative to the expansion zone in the microchannels, Fig. 5 - a diagram of the microdispersers equipped with nozzles with the possibility of axial adjustment of their position relative to the mouth of the microchannels, in Fig. 6 - diagram of microdispersers equipped with nozzles with a fixed axial position of the nozzles: in Fig. 6a - in microchannels without an expansion zone, in Fig. 6b - in microchannels with an expansion zone.

Fig. 1 shows stages I, II, etc. of the cascade. The number of stages is determined by calculation based on the required process time.

Tanks 1 and 2 with the initial media are connected to the first (I) stage of the cascade, which includes phase dispersion unit A, phase contact unit B and phase separation unit B. At the outlet of the last stage, the light and heavy phases are removed, one of which contains the finished product, as shown by the arrows in Fig. 1.

Each of the stages (I, II, etc.) of the cascade contains a dispersion block A, a phase contacting block B, and a phase separation block B.

The phase dispersion unit A contains pumps 3a and 3b, a distribution chamber 4a for introducing the dispersed phase, a distribution chamber 4b for introducing the continuous phase and microdispersers installed in it.

The phase contacting block B contains one or more microchannels 5 connected in parallel, the inputs of each of which are connected to the microdisperser, and the outputs from the microchannels are connected through the collector 6 to the phase separation block B.

The phase separation unit B contains a separation device 7, which ensures the separation of the heavy and light phases. In the upper part of the device 7, a layer 8a of the light phase is formed, and in the lower part of the device 7, a layer 8b of the heavy phase is formed. The separation device 7 can be of the gravitational type (sedimentation tank) or of the inertial type (cyclone, hydrocyclone, centrifugal separator), as well as of another type (for example, using an electric field).

To remove or supply heat to microchannels 5, phase contact block B can be equipped with a heat exchange jacket 9 with pipes 10 for input and output of the coolant.

Microdispersers include a nozzle 11, and their outer contour is formed either by the wall of microchannels 5 (as shown in Fig. 5 and Fig. 6a) or by the surface of the expansion zone 16 (as shown in Fig. 4 and Fig. 6b).

Fig. 3a shows microdispersers, the nozzles 11 of which pass through the distribution chambers 4a and 4b with the possibility of changing their axial position (as shown in Figs. 4 and 5), and Fig. 3b shows nozzles 11 fixed in the required axial position.

Fig. 4 shows a diagram of microdispersers equipped with nozzles with the possibility of axial adjustment of their position relative to the expansion zone in the microchannels, as shown by the arrow, i.e. nozzles 11 shown in Fig. 3a are shown on an enlarged scale. One end of nozzles 11 is plugged (on the left in Fig. 3a and Fig. 4), and the second end of nozzles 11 passes through distribution chambers 4a and 4b, and is located inside the mouth of microchannels 5. Openings 12 are made on the side surface of nozzles 11, and nozzles 11 are installed so that openings 12 are in distribution chamber 4a, where the dispersed phase is introduced. This ensures the flow of the dispersed phase through the openings 12 into the nozzles 11. To ensure the possibility of displacement of the nozzles I relative to the microchannels 5, seals 13 and 14 are installed in the chambers 4a and 4b. The tube grid 15, located between the distribution chambers 4a and 4b, is the boundary on the right for the position of the openings 12. The open end of the nozzles 11 is located in the expansion zone 16 of the microchannels, which ensures the expansion of the range of phase flows, ensuring a stable slug flow regime. At the open end of the nozzles 11 (the exit from the nozzles 11), a bubble or drop 17 of the dispersed phase is formed, which after separation is transferred with the continuous phase 18 at a velocity U _d .

Fig. 5 shows a diagram of microdispersers equipped with nozzles 11, with the possibility of axial adjustment of their position relative to the mouth of the microchannels, as shown by the arrow. In Fig. 5, nozzles 11 of the microdispersers are connected to a tube sheet 15 located between distribution chambers 4a and 4b (nozzles 11 shown in Fig. 3b are shown on an enlarged scale). The difference from the microchannels shown in Fig. 4 consists only in the absence of an expansion zone 16. This somewhat simplifies the design of the microchannels. At the same time, expansion zone 16 shown in Fig. 4 makes it possible to expand the range of phase flows that ensure a stable slug flow regime in the microchannels.

Fig. 6 shows a diagram of microdispersers equipped with nozzles with a fixed axial position of the nozzles: in Fig. 6a - in microchannels without an expansion zone, in Fig. 6b - in microchannels with an expansion zone. Nozzles 11 are attached to the tube sheet 15 (by welding, soldering, flaring or a combination thereof, made from a single blank). This design of nozzles significantly simplifies the process of manufacturing the installation, but in this case the possibility of adjusting the position of the end of nozzles 11 relative to expansion zone 16 or the mouth of microchannel 5 disappears.

The proposed device operates as follows.

Containers 1 and 2 are filled with the initial media (if one of the media is a gas, then a gas cylinder can be used as a container), which are fed by pumps 3a and 3b into distribution chambers 4a and b for introducing the dispersed phase and for introducing the continuous phase, respectively. The dispersed phase is distributed over nozzles 11 through openings 12 (for the embodiments shown in Figs. 4 and 5) or through their open ends connected to the tube sheet 15 (for the embodiments shown in Figs. 6a and 6b), exiting through the open end of nozzles 11 (on the right in Figs. 4-6) in the form of bubbles or drops 17. In this way, the phases are fed into dispersion unit A, in which a two-phase system is formed, primarily in the form of slug (i.e. elongated) drops or bubbles 18 moving in the continuous phase. Next, from the dispersion block A, the two-phase system enters the phase contact block B, which contains one or more microchannels 5, connected in parallel. When a two-phase system moves in microchannels 5, Taylor vortices arise in the continuous and dispersed phases (Wegmann A., von Rohr P.R. Two phase liquid-liquid flows in pipes of small diameters // International Journal of Multiphase Flow, V. 32, 2006, pp.1017-1028; R.Sh.Abiev Mathematical model of two-phase Taylor flow hydrodynamics for four combinations of non-Newtonian and Newtonian fluids in microcharmels. Chem. Eng. Sci., 2022 (247) 116930, https://doi.org/10.1016/j.ces.2021.l 16930), contributing to the intensification of mixing, an increase in the heat transfer and mass transfer coefficients from the walls of the microchannels into the continuous phase, between the continuous and dispersed phases. Along the length of the microchannels, the pressure decreases, reaching minimum values in the zone of connection of the microchannels 5 with the separation unit B. The phase separation unit B contains a separation device 7. In the upper part of the device 7, a layer 8a of the light phase is formed, and in the lower part of the device 7, a layer 86 of the heavy phase is formed.

From the separation device 7, the light phase (for example, dispersed) is removed by pump 3a of the second (II) stage of the cascade, and the heavy phase (for example, continuous) is removed by pump 3b of the second (II) stage of the cascade and fed to the contacting block B of the second stage of the cascade, and then to the phase separation block B, i.e. the process described above for the first stage is repeated for the second and subsequent stages of the cascade.

If necessary (taking into account the consumption of one or more reagents in the previous stages), “fresh” initial media can be supplied to the suction lines of pumps 3a and 3b of the second and subsequent stages, as shown by the arrows in Fig. 2.

Pumps 3a and 3b of each stage serve to restore the pressure at the inlet to distribution chambers 4a and 4b, and then to microchannels 5, necessary to overcome the hydraulic resistance of microchannels 5 with a two-phase system at a given flow rate through the microchannels of each stage. Due to this, a flow of a two-phase system is achieved through an unlimited number of successive stages with the required flow rate, which allows for the required residence time of the phases in the device.

From the phase separation block B of the last stage of the cascade, i.e. from the separation device 7 of the last stage, the final products of the process carried out in the device are selected.

If necessary, intermediate products can be partially removed from the separation devices 7, but the removed amount must be replenished (completely or partially, depending on the process requirements) by introducing “fresh” portions of the initial media, as shown by the arrows in Fig. 2, to ensure the plant’s productivity for the finished product.

The preferred flow regime of a two-phase medium in microchannels is the slug regime (Bauer T. Intensification of heterogeneous catalytic gas-liquid reactions in reactors with a multichannel monolithic catalyst / T. Bauer, M. Schubert, R. Lange, R.Sh. Abiev // Zhurn. Prikl. Chem., 2006, Vol. 79, No. 7, pp. 1057-1066; Kreutzer, M.T. Multiphase monolith reactors: Chemical reaction engineering of segmented flow in microcharmels / M.T. Kreutzer, F. Kapteijn, J.A. Moulijn, J.J. Heiszwolf // Chemical Engineering Science. - 2005. - Vol. 60 - pp. 5895-5916), however, the device can operate with the implementation of film (annular) or bubble regimes, as well as other flow regimes (projectile-bubble, emulsion-ring).

The basic version is illustrated by the following example (example 1)

EXAMPLE 1. Carrying out an alkylation reaction in a known device - in a capacitive reactor with a high-speed disperser and with a phase transfer catalyst in the system of an aqueous solution of reagents - methylene chloride.

In the method for producing N-methyl-5-phenyltetrazoles, which consists of alkylating 5-phenyltetrazole with alkyl iodide in a two-phase system of methylene chloride - aqueous sodium hydroxide solution at room temperature, the process is carried out in a microreactor without the use of phase transfer catalysts and mechanical mixing devices. This process is considered in all examples presented below for the convenience of comparing the advantages and disadvantages of various types of devices.

Alkylation of 5-phenyltetrazole with methyl iodide was carried out in a 50 ml glass reactor with a jacket, equipped with a reflux condenser and a thermometer. The temperature in the reactor was maintained at 24°C using a water thermostat.

A solution of 5-phenyltetrazole in NaOH (aq.) (0.140 mol l ^-1 ) and a solution of methyl iodide in methylene chloride (0.154 mol l ^-1 ) were successively dosed into the reactor, preheated to the experimental temperature. A phase transfer catalyst, tetrabutylammonium bromide, was added to the reaction mixture to intensify the process. The reaction mass was maintained under vigorous stirring for 4 hours. Vigorous stirring of the reaction mass was performed using an IKA ULTRA-TURRAX Package T18 disperser.

To perform a qualitative analysis of the reaction products, the chromatograph mass spectrometry method was chosen as one of the modern and highly accurate physicochemical methods. Mass spectra were recorded for samples of the reaction mass, taken at certain intervals. The formation of alkylation products during the catalyzed process is evidenced by signals at 161 m/z in the mass spectra, which correspond to the molecular ions of 1-methyl- and 2-methyl-5-phenyltetrazole.

The reaction progress was monitored by HPLC (a Shimadzu LC10-AVP liquid chromatograph with a UV detector and a Waters C-18 chromatographic column (4.6 × 250 mm, 5 μm) were used). For quantitative assessment of the content of individual isomers of N-alkyl-5-phenyltetrazoles, calibration curves S(C) were constructed for each isomer in the range (0-1.7) -10 ³ mol l ^-1 .

As a result of the experiment, dependences of the concentrations of alkylation products on the reaction time were obtained, which clearly indicate the successful course of the process under these conditions: in 12000 s (3.33 hours) in the known device, the concentration of 1-methyl-5-phenyltetrazole reached 0.01 mol/l, and the concentration of 2-methyl-5-phenyltetrazole (target product) in the same time was 0.02 mol/l.

Thus, the productivity of the known reactor for the target product was 3⋅10 ^-4 mol/h.

The prototype device variant is illustrated by the following example (example 2)

EXAMPLE 2. Carrying out an alkylation reaction in a prototype device in the system of an aqueous solution of reagents - methylene chloride.

Alkylation of 5-phenyltetrazole with methyl iodide was carried out in a glass microreactor (d=1.5 mm, L=2 m) at 24°C. A solution of 5-phenyltetrazole in NaOH (aq.) (0.140 mol l ^-1 ) and a solution of methyl iodide in methylene chloride (0.154 mol l ^-1 ) were fed into the reactor through a mixer. The system maintained a slug (Taylor) flow regime of a two-phase reaction system. The microreactor operated in the reagent recirculation mode, i.e. not in a flow regime, but essentially in a periodic regime.

According to HPLC data, it was established that when organizing this mode of liquid flow in a microchannel, the corresponding alkylation products of 5-phenyltetrazole are formed. It was shown that in 1.5 hours under these conditions, almost complete conversion of the substrate to the corresponding alkyl derivatives occurred, namely, in 12,000 s (3.33 hours) in the prototype device, the concentration of 1-methyl-5-phenyltetrazole reached 0.04 mol/l, and the concentration of 2-methyl-5-phenyltetrazole (target product) for the same time was 0.13 mol/l.

Thus, the accumulation of alkylation products under Taylor mode conditions in a microreactor occurs approximately 10 times faster than when using a phase transfer catalyst in a “traditional” tank apparatus.

The volume of the prototype device is 3.53 ml, and taking into account the residence time in the microreactor according to the prototype invention, the productivity of the prototype device for the target product was 1.38⋅10 ^-4 mol/h, i.e. it turned out to be lower than in the apparatus with significantly less intensive mixing and mass exchange described in Example 1.

During the time spent in the prototype device (50 minutes), a concentration of 2-methyl-5-phenyltetrazole of 0.1 mol/l is achieved, close to the almost complete conversion of the substrate to the corresponding alkyl derivatives. Taking this fact into account, the nominal productivity of the prototype device is 4.24⋅10 ^-4 mol/h.

The average velocity of the two-phase flow in the microchannel was Utp=0.108 m/s.

The proposed option is illustrated by the following examples (examples 3 and 4)

EXAMPLE 3. Carrying out an alkylation reaction in the proposed device in the system of an aqueous solution of reagents - methylene chloride.

The process described in Example 2 was carried out in the device according to the proposed invention, with the target value of the product concentration (2-methyl-5-phenyltetrazole) at the outlet of the device being C ₁ = 0.1 mol/l, i.e. when a residence time of 50 minutes is required.

Each stage used 12 parallel microchannels with an internal diameter of 1.5 mm and an external diameter of 2.5 mm. When the continuous and dispersed phases are fed into the device by pumps, elongated drops of the dispersed phase are formed in the microchannels, i.e. the flow occurs in the slug (Taylor) mode.

Calculations using the methodology described in a number of works (R. Abiev, Analysis of Segmented Flow in MicroChannel Reactors. In: Yeoh, G.H., Joshi, J.B. (eds) Handbook of Multiphase Flow Science and Technology. Springer, Singapore. 2023. pp 1-58. https://doi.org/10.1007/978-981-4585-86-6_30-l; Print ISBN 978-981-4585-86-6; Online ISBN 978-981-4585-86-6) showed that the pressure gradient in the microchannels under consideration is (Δp/Δx)=1.54 kPa/m.

Gear pumps with a nominal pressure of up to Δр _n = 3 bar = 300 kPa and a capacity of up to 1.5 l/min are used to supply the media.

One such pump is capable of providing operation of microchannels with a length of L = Δр _n / (Δр/Δх) = 300/1.54 = 194.5 m.

For a residence time of T ₁ = 50 minutes, the required total length of microchannels in all stages is equal to L _tot = T ₁ ⋅ Utp = 50 ⋅ 60 ⋅ 0.108 = 325.4 m.

The number of stages in the cascade is Nst=L _tot /L=325.4/194.5=1.673.

Thus, for the case under consideration, two stages in the cascade are sufficient. If Nch=12 parallel microchannels with an internal diameter of d=1.5 mm are used in each stage, then the volumetric productivity of the installation will be

Q ₁ = Nch-7⋅πd ² /4⋅Utp=12⋅π(0.0015) ² /4⋅0.108=138 ml/min.

The molar productivity of the installation according to the proposed invention for the conditions under consideration will be

QM ₁ = Q ₁ - C ₁ = 138 ml/min⋅0.1 mol/l = 2.30⋅10 ^-4 mol/s = 0.828 mol/h,

which is 1952 times higher than the performance of the prototype device under the given conditions (4.24 x ^{10 -4} mol/h).

The existing pumps are capable of providing a capacity of up to 1.5 l/min, from which it is easy to find the maximum number of parallel microchannels in each stage, equal to 130, which allows, if necessary, to increase the productivity of the installation by another 10.87 times.

EXAMPLE 4. Carrying out an alkylation reaction in the proposed device in the system of an aqueous solution of reagents - methylene chloride (with increased conversion).

The process described in Example 2 was carried out in the device according to the proposed invention, with the target value of the product concentration (2-methyl-5-phenyltetrazole) at the outlet of the device being _C2 = 0.13 mol/l, to achieve which a residence time of 12,000 s (3.33 hours or 200 minutes) was required.

In each stage, 24 parallel microchannels with an inner diameter of d = 1.5 mm and an outer diameter of d ₂ = 2.5 mm were used.

Gear pumps with a nominal pressure of up to 7 bar = 700 kPa and a capacity of up to 1.5 l/min are used to supply the media.

One such pump is capable of operating a microchannel with a length of L=700/1.54=453.8 m.

As in example 3, the pressure gradient in the microchannels under consideration is (Δр/Δх)=1.54 kPa/m.

For a residence time of T ₂ = 200 minutes, the required total length of microchannels in all stages is equal to L _tot = T ₂ ⋅ Utp = 200 ⋅ 60 ⋅ 0.108 = 1302 m.

The number of stages in the cascade is Nst=L _tot /L=1302/453.8=2.868.

For the case under consideration, three stages in the cascade are sufficient. If Nch=12 parallel microchannels with an internal diameter of d=1.5 mm are used in each stage, then the volumetric productivity of the installation will be

Q ₂ =Nch⋅πd ² /4⋅Utp=24⋅π(0.0015) ² /4⋅0.108=276 ml/min.

The molar productivity of the installation according to the proposed invention for the conditions under consideration will be

QM ₂ = Q ₂ ⋅ C ₂ = 276 ml/min - 0.13 mol/l = 4.60⋅10 ^-4 mol/s = 1.656 mol/h,

which is 12010 times higher than the performance of the prototype device under the given conditions (1.3⋅10 ^-4 mol/h).

The microchannels in examples 3 and 4 were wound in the form of a helical spiral on a supporting cylinder with a diameter of 200 m.

In example 4, the number of turns of each stage Nvit=L/(πD)=453.8/(π0.2)=722. The height of one microchannel wound on the supporting cylinder is H=Nvit d ₂ =722 0.0025=1.805 m. For the device described in example 3, the dimensions are even more compact. Thus, the entire installation has fairly compact dimensions.

As shown in the presented examples, the proposed device allows for continuous synthesis of products requiring a long residence time (up to several hours), while achieving complete (example 4) or almost complete conversion (example 3), while the productivity of the installation increases by 3-4 orders of magnitude compared to the prototype device (more than 1900 times in example 3 and more than 12000 times in example 4).

Due to the presence of microdispersers with nozzles that have sufficient hydraulic resistance, as well as due to the significant length of the microchannels in the proposed invention (see examples 3 and 4), also having a hydraulic resistance of about 3-7 bar, both phases - continuous and dispersed - are evenly distributed across all microchannels 5, i.e. the leakage of media through one or more channels is excluded.

During the process, the lengths of the droplets or bubbles of the dispersed phase may change, but due to the implementation of each of the stages in the form of three blocks during the redispersion of the phases in the dispersion blocks of each of the stages, the sizes of the droplets or bubbles are restored to the original. Due to this, a sufficiently high uniformity of the phase distribution along the length of the channels in the installation as a whole is achieved, at least in comparison with the implementation of a microchannel with a total length equal to the sum of the lengths of the microchannels at all stages.

Thus, the use of the proposed device allows for continuous synthesis of products requiring a long residence time (from tens of minutes to several hours), increases the productivity of the installation, and ensures high uniformity of phase distribution both in channels (if there is more than one) and along the length of the channels.

Claims (1)

An installation for microreactor synthesis in liquid-gas and liquid-liquid systems, including tanks with initial media, pumps, microchannels connected to the outlet pipes of the pumps, characterized in that the installation is a cascade of several stages, each of which contains three units connected in series - a dispersion unit, a contacting unit and a phase separation unit, wherein the tanks with the initial media are connected to the first stage of the cascade, the dispersion unit includes pumps for feeding the continuous and dispersed phases, a distribution chamber for introducing the dispersed phase, a distribution chamber for introducing the continuous phase and microdispersers installed therein, the phase contacting unit contains one or more microchannels connected in parallel, the inputs of each of which are connected to the microdisperser, and the outputs from the microchannels are connected through a manifold to the phase separation unit, the phase separation unit contains a separation device that ensures the separation of the heavy and light phases, wherein the microdispersers are equipped nozzles, and the products are collected from the phase separation unit of the last stage of the cascade.

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