Patent Grant
7582481
1. Field of the Invention
The present invention relates to a method of multiple reaction in a microreactor and to the microreactor. More particularly, the present invention relates to a method of multiple reaction in a microreactor and the microreactor capable of obtaining a target product in a high yield by multiple reaction.
2. Description of the Related Art
In recent years, the development of a new manufacturing processing using a microspace called a microreactor has been pursued in the chemical industry or the pharmaceutical industry relating to manufacture of medicines, reagents, etc. A very small space (microreactionchannel) connecting to a plurality of microchannels (fluid introduction channels) is provided in a micromixer or a microreactor. A plurality of fluids (e.g., solutions in which raw materials to be reacted with each other are dissolved) are caused to flow together into the small space. Mixing or mixing and reaction between the fluids are caused thereby. Micromixers and microreactors are basically identical in structure. In some particular cases, however, those in which a plurality of fluids are mixed with each other are referred to as “micromixer”, while those in which mixing of a plurality of solutions is accompanied by chemical reaction between the solutions are referred to as “microreactor”. A microreactor in accordance with the present invention is assumed to comprise a micromixer.
Points of difference between reaction in the a microreactor as defined above and batch mixing or reaction using an agitation tank or the like will be described. That is, chemical reaction in liquid phase occurs ordinarily in such a manner that molecules meet each other at the interface between reaction solutions. In the case of chemical reaction in liquid phase in a very small space, therefore, the area of the interface is relatively increased to such an extent that the reaction efficiency is markedly high. Also, diffusion of molecules itself is such that the diffusion time is proportional to the square of the distance. This means that if the scale of the small space is smaller, mixing progresses faster due to diffusion of molecules to facilitate the reaction, even when the reaction solutions are not positively mixed with each other. Also, in the flow caused in the small space, laminar flows are dominant because of the small scale, and the solutions flow as laminar flows and react with each other by diffusing in a direction perpendicular to the laminar flows.
If such a microreactor is used, the reaction time, mixing temperature and reaction temperature in reaction of solutions can be controlled with improved accuracy in comparison with, for example, a conventional batch system using large-capacity tank or the like as a place for reaction.
Therefore, if multiple reaction is performed by using a microreactor, solutions flow continuously through the small space in the microreactor without staying substantially in the space and a non-uniform reaction product is not easily produced. In this case, a comparatively pure primary product can be extracted.
As such a microreactor, one disclosed in PCT International Publication WO No. 00/62913, one disclosed in Japanese National Publication of International Patent Application No. 2003-502144 and one disclosed in Japanese Patent Application Laid-open No. 2002-282682 are known. In each of these microreactors, two kinds of solutions are respectively passed through microchannels to be introduced into a small space as laminar flows in the form of extremely thin laminations, and are mixed and reacted with each other in the small space.
In multiple reaction using various kinds of reaction, there is a need to increase the yield of a primary product or to increase the yield of a secondary product while reducing the yield of the primary product according to the selection of a target product. However, sufficient techniques have not been established for control of the yield, i.e., the selectivity, of a target product in multiple reaction, particularly a primary product obtained as a reaction intermediate product.
In view of the above-described circumstances, an object of the present invention is to provide a method of multiple reaction in a microreactor capable of controlling the yield and selectivity of a target product in multiple reaction and therefore capable of improving the yield of a primary product obtained as a reaction intermediate product in particular, and a microreactor suitable for carrying out the method of multiple reaction.
The inventor of the present invention noticed, from a feature of a microreactor which resides in that a plurality of fluids flowing together into a microreactionchannel flow as laminar flows, the possibility of factors including the number, sectional shape, arrangement, aspect ratio, width (thickness in the direction of arrangement) and concentration of fluid segments in a diametral section of the microreactionchannel at the entrance side being freely controlled, and conceived control of the yield and selectivity of a target product in multiple reaction based on control of these factors.
The plurality of kinds of fluids are, for example, a fluid A and a fluid B if the number of kinds is two, and the fluid segments are fluid sections formed by dividing fluids A and B in the diametral section at the entrance side of the microreactionchannel and reconstructing fluids having the desired numbers of segment, arrangements, sectional shapes, widths and a concentration. “Diffusion distance between fluids” refers the distance between centroids of the shapes of the fluid segments in the diametral section of the microreactionchannel, and “specific surface area” refers to the ratio of the area of contact in the interface between an adjacent pair of fluid segments to a unit length of the fluid segments. These terms refer to the same concepts below.
To achieve the above-described object, according to a first aspect of the present invention, there is provided a method of multiple reaction in a microreactor in which a plurality of kinds of fluids are caused to flow together into a microreactionchannel, and are mixed with each other by molecular diffusion to perform multiple reaction while being caused to flow as laminar flows, comprising the step of: changing the diffusion distance and/or the specific surface area of the plurality of kinds of fluids flowing together into the microreactionchannel by dividing each of the plurality of kinds of fluids into a plurality of fluid segments in a diametral section of the microreactionchannel at the entrance side of the microreactionchannel, and by causing the fluid segments differing in kind to contact each other.
According to the first aspect, when multiple reaction between fluids A and B for example, expressed by reaction formulae:
A+B→R (primary reaction)
B+R→S (secondary reaction)
is performed, the yield of primary product R with respect the rate of reaction of fluid A is increased if the diffusion distance between fluid A and fluid B is reduced or if the specific surface area is increased. Conversely, if the specific surface area is reduced, the yield of primary product R with respect to the rate of reaction of fluid A becomes lower. That is, the yield of the secondary product is increased. Thus, it is possible to control the yield and selectivity of the target product in the multiple reaction by changing the diffusion distance and/or the specific surface area between the plurality of kinds of fluids flowing together into the microreactionchannel.
According to a second aspect of the present invention, each of the plurality of kinds of fluids is divided into a plurality of fluid segments in the diametral section of the microreactionchannel at the entrance side, thereby changing the number of fluid segments. If the number of fluid segments is thereby increased, the diffusion distance is reduced and the specific surface area is increased. Conversely, if the number of fluid segments is reduced, the diffusion distance is increased and the specific surface area is reduced.
According to a third aspect of the present invention, each of the plurality of kinds of fluids is divided into a plurality of fluid segments in the diametral section of the microreactionchannel at the entrance side, thereby changing the sectional shapes of the fluid segments in the diametral section of the microreactionchannel at the entrance side. The sectional shapes are selected from, for example, rectangular shapes such as squares and rectangles, parallelograms, triangles, and concentric circles. The effect of improving the yield of primary product R with respect to the rate of reaction of fluid A by selecting from such shapes increases in order of rectangles, parallelograms, triangles and concentric circles, because the diffusion distance is substantially reduced in correspondence with this order. In a case where a zigzag shape or a convex shape is selected as the sectional shape, the specific surface area is increased if the number of zigzag corners or projecting portions, i.e., the number of times a shape recurs, is increased, thereby increasing the yield of primary product R with respect to the rate of reaction of fluid A. Thus, the diffusion distance and the specific surface area can be changed by changing the shapes of the fluid segments in the diametral section of the microreactionchannel at the entrance side. In this way, the yield and selectivity of the target product in multiple reaction can be controlled. Both the number of fluid segments and the sectional shapes of the fluid segments may be changed.
According to a fourth aspect of the present invention, each of the plurality of kinds of fluids is divided into a plurality of fluid segments in the diametral section of the microreactionchannel at the entrance side, thereby changing the arrangement of the fluid segments differing in kind in the diametral section of the microreactionchannel at the entrance side. The method of arranging the fluid segments comprises a one-row arrangement in which, for example, fluid segments A obtained by dividing fluid and fluid segments B obtained by dividing fluid B are alternately arranged in one horizontal row, a two-row arrangement in which the one-row arrangements are formed one over another in two stages in such a manner that the kinds of fluid segments in each upper and lower adjacent pair of fluid segments are different from each other, and a checkered arrangement in which fluid segments A and fluid segments B are arranged in horizontal and vertical directions in the diametral section of the microreactionchannel at the entrance side so as to form a checkered pattern. The effect of improving the yield of primary product R with respect to the rate of reaction of fluid A increases in order of the one-row arrangement, the two-row arrangement and the checkered arrangement, because the specific surface area is substantially increased in correspondence with this order. The numbers, sectional shapes, arrangement factors of the fluid segments may be changed in combination.
According to a fifth aspect of the present invention, each of the plurality of kinds of fluids is divided into a plurality of fluid segments in the diametral section of the microreactionchannel at the entrance side, thereby forming a plurality of fluid segments having a rectangular sectional shape in the diametral section of the microreactionchannel at the entrance side, and changing the aspect ratio (the ratio of the depth to the width) of the fluid segments.
The aspect ratio is the ratio of the depth of a rectangular segment to the width of the segment (the thickness of the fluid segment in the arrangement direction. This aspect ratio may be changed by changing the depth of the fluid segment while constantly maintaining the width, or by changing the depth while constantly maintaining the area of the rectangle. In the case of changing the depth of the fluid segment while constantly maintaining the width, the yield of primary product R with respect to the rate of reaction of fluid A is reduced if the aspect ratio is lower, that is, the depth is smaller. In other words, the yield of primary product R with respect to the rate of reaction of fluid A is increased if the aspect ratio is higher, that is, the depth is larger. This may be because a rate distribution with a large gradient is also developed in the depth direction with the rate distribution in the widthwise direction due to laminar flows, as the yield and selectivity of the parallel reaction intermediate product become, step by step, lower under laminar flows than under a plug-flow. In the case of changing the depth while constantly maintaining the area of the rectangle, the yield of primary product R with respect to the rate of reaction of fluid A is increased if the aspect ratio is higher, that is, the width is smaller. This is because the diffusion distance becomes shorter if the aspect ratio is increased. In either case, it is possible to change the yield and selectivity of the target product in multiple reaction by changing the aspect ratio. The numbers, sectional shapes, arrangement, and aspect ratio factors of the fluid segments may be changed in combination.
In the second to fifth aspects, the microreactor is arranged so that each of the numbers, sectional shapes, arrangements, and aspect ratios of the fluid segments in the diametral section of the microreactionchannel at the entrance side can be changed. However, a raw material concentration in fluid segments identical in kind to each other may be changed as well as these factors.
To achieve the above-described object, according to a sixth aspect of the present invention, there is provided a method of multiple reaction in a microreactor in which a plurality of kinds of fluids are caused to flow together into one microreactionchannel via respective fluid introduction channels, and are mixed with each other by molecular diffusion to perform multiple reaction while being caused to flow as laminar flows, comprising the steps of: dividing each of the plurality of kinds of fluids into a plurality of fluid segments having a rectangular sectional shape in a diametral section of the microreactionchannel at the entrance side; arranging the fluid segments so that the fluid segments differing in kind contact each other; and changing the width of the arranged fluid segments in the direction of arrangement.
This method has been achieved based on the finding that the yield of primary product R with respect to the rate of reaction of fluid A can be changed according to the way of arranging rectangular fluid segments differing in width. For example, arrangements using combinations of fluid segments A and fluid segments B having two segment widths include an equal-width arrangement in which fluid segments A and B made equal in width to each other are alternately arranged, a large-central-width arrangement in which fluid segments A and B of a smaller width are placed at opposite positions in the arrangement direction while fluid segments A and B of a larger width are placed at central positions, a small-central-width arrangement in which fluid segments A and B of a larger width are placed at opposite positions in the arrangement direction while fluid segments A and B of a smaller width are placed at central positions, and a one-sided arrangement in which fluid segments A and B of a smaller width are placed at positions closer to one end in the arrangement direction while fluid segments A and B of a larger width are placed at positions closer to the other end. By selecting from arrangements using combinations of such different segment widths, the yield of primary product R with respect to the rate of reaction of fluid A can be changed. Thus, the yield and selectivity of the target product in multiple reaction can be controlled.
To achieve the above-described object, according to a seventh aspect of the present invention, there is provided a method of multiple reaction in a microreactor in which a plurality of kinds of fluids are caused to flow together into one microreactionchannel via respective fluid introduction channels, and are mixed with each other by molecular diffusion to perform multiple reaction while being caused to flow as laminar flows, comprising the steps of: dividing each of the plurality of kinds of fluids into a plurality of fluid segments having a rectangular sectional shape in a diametral section of the microreactionchannel at the entrance side of the microreactionchannel; arranging the fluid segments so that the fluid segments differing in kind contact each other with a certain width; and changing a concentration between the fluid segments identical in kind to each other in the arranged fluid segments.
This method has been achieved based on the finding that the yield of primary product R with respect to the rate of reaction of fluid A can be changed in such a manner that rectangular fluid segments are arranged while being made equal in width to each other, and a concentration is changed among fluid segments identical in kind to each other.
For example, arrangements using combinations of concentrations in fluid segments A and fluid segments B include an equal-concentration arrangement in which fluid segments A having equal concentrations and fluid segments B having equal concentrations (which may be different from the concentrations in the fluid segments A) are alternately arranged, a center high-concentration arrangement in which fluid segments A and B having higher concentrations are placed at central positions in the arrangement direction, a center low-concentration arrangement in which fluid segments A and B having lower concentrations are placed at central positions in the arrangement direction, and a one-sided-concentration arrangement in which fluid segments A and B having higher concentrations are placed at positions closer to one end in the arrangement direction while fluid segments A and B having lower concentrations are placed at positions closer to the other end. By selecting from arrangements using such combinations of segments having different concentrations, the yield of primary product R with respect to the rate of reaction of fluid A can be changed. Thus, the yield and selectivity of the target product in multiple reaction can be controlled.
In the sixth aspect, arrangements using combinations of different segment widths are provided. In the seventh aspect, arrangements using combinations of segments having different concentrations are provided. However, arrangements using both a combination of different segment widths and a combination of segments having different concentrations may be provided.
To achieve the above-described object, according to an eighth aspect of the present invention, there is provided a microreactor in which a plurality of kinds of fluids are caused to flow together into a microreactionchannel, and are mixed with each other by molecular diffusion to perform multiple reaction while being caused to flow as laminar flows, comprising: a fluid introduction portion having a multiplicity of fine introduction openings divided in a grid pattern in a diametral section of the microreactionchannel at the entrance side, a multiplicity of fluid introduction channels communicating with the introduction openings being stacked in the fluid introduction portion; and a distribution device which forms a plurality of fluid segments into which the plurality of kinds of fluids are divided in the diametral section of the microreactionchannel at the entrance side by distributing the fluids to the multiplicity of fluid introduction channels and introducing the fluids from the introduction openings into the microreactionchannel.
In the eighth aspect of the present invention, a microreactor is arranged which is capable of freely controlling factors including the numbers, sectional shapes, arrangements, aspect ratios, widths (thickness in the direction of arrangement) and concentrations of fluid segments in a diametral section of a microreactionchannel at the entrance, and a multiplicity of fluid instruction channels divided into fine introduction openings in a grid pattern are formed in the diametral section of the microreactionchannel at the entrance side. A plurality of kinds of fluids are distributed to the multiplicity of fluid introduction channels by the distribution device to form a plurality of fluid segments of each kind of fluid in the diametral section of the microreactionchannel at the entrance side. That is, according to the present invention, the configurations of groups of introduction openings in the grid pattern formed in the diametral section of the microreactionchannel at the entrance side are formed in correspondence with the shapes of rectangles, parallelograms, triangles or the like, thus forming the above-described sectional shapes of the fluid segments corresponding to the shapes of rectangles, parallelograms, triangles or the like. If the sectional shapes are formed as concentric circles, it is preferred that the diametral section of the microreactionchannel be circular. The one-row arrangement, two-row arrangement or checkered arrangement described above can be formed according to the same concept. It is also possible to change the aspect ratio, the width and the number of fluid segments. In this case, the desired shape can be formed with accuracy if the size of one introduction opening is smaller. However, the diameter of one introduction opening is preferably in the range from several microns to 100 μm in terms of equivalent diameter since it is preferred that the microreactionchannel be a fine channel of an equivalent diameter of 2000 μm or less.
According to a ninth aspect, the number of the fluid segments is changed by the distribution device distributing the plurality of kinds of fluids to the multiplicity of fluid introduction channels. According to a tenth aspect, the sectional shape is changed. According to an eleventh aspect, the arrangement is changed. According to a twelfth aspect, the aspect ratio of the rectangular shape is changed.
According to a thirteenth aspect, a concentration control device which changes a raw-material concentration between fluid segments identical in kind to each other is provided, thereby enabling selection from combinations of segments having different concentrations.
According to a fourteenth aspect, a preferable equivalent diameter of the microreactionchannel allowing the plurality of fluids flowing together into the microreactionchannel to flow as laminar flows is defined. The equivalent diameter is preferably 2000 μm or less, more preferably 1000 μm or less, depending on the viscosities of the fluids. If the microreactionchannel is defined in terms of Reynolds number, Re 200 or less is preferred.
Thus, the microreactor of the present invention is capable of freely changing factors including the numbers, sectional shapes, arrangements, aspect ratios, widths and concentrations of fluid segments in the diametral section of the microreactionchannel and is, therefore, extremely useful as a microreactor for multiple reaction. However, the microreactor of the present invention can be applied to various reaction systems without being limited to multiple reaction.
As described above, the method of multiple reaction in a microreactor and the microreactor in accordance with the present invention are capable of controlling the yield and selectivity of a target product in multiple reaction and therefore increase, in particular, the yield of a primary product, which is an intermediate reaction product.
A preferred embodiment of the method and microreactor for multiple reaction in accordance with the present invention will be described below with reference to the accompanying drawings.
The microreactor 10 is constituted mainly by a microreactor main unit 16 and a fluid supply device 18 for supplying fluids A and B to the microreactor main unit 16. Preferably, the fluid supply device 18 is capable of continuously supplying the microreactor main unit 16 with small amounts of fluids A and B at a constant pressure. Syringe pumps 18A will be described as the fluid supply device 18 by way of example. The device for supplying fluids A and B to the microreactor main unit 16 is not limited to syringe pumps 18A and 18B. Any device suffices if it is capable of supplying small amounts of fluids A and B at a constant pressure.
The microreactor main unit 16 is constituted mainly by the microreactionchannel 12 in which a plurality of fluids A and B are passed as laminar flows and are mixed with each other by molecular diffusion to react with each other, and a fluid introduction portion 14 for introducing fluids A and B into the microreactionchannel 12.
The microreactionchannel 12 is a small space in the form of a channel generally rectangular as seen in a diametral section. Since there is a need to cause fluid segments A and B to pass as laminar flows in the microreactionchannel 12, the equivalent diameter of the microreactionchannel 12 is preferably 2000 μm or less, more preferably 1000 μm or less, and most preferably 500 μm or less, depending on the viscosity of fluids A and B and other factors. The Reynolds number of the fluids flowing in the microreactionchannel 12 is preferably 200 or less. The shape of the diametral section of the microreactionchannel 12 at the entrance side is not limited to the rectangular shape. The diametral shape may alternatively be circular for example.
As shown in
The distribution device 24 is connected to the syringe pumps 18A and 18B by tubes 26, and communicates with each of the multiplicity of fluid introduction channels 22 constituting the fluid introduction portion 14 via fine pipes 29. The distribution device 24 is constructed so as to be capable of selectively introducing fluids A and B through each of the multiplicity of fluid introduction channels 22. Fluids A and B are thereby divided into a plurality of fluid segments A and B in the diametral section at the entrance side of the microreactionchannel 12 when caused to flow together from the fluid introduction portion 14 into the microreactionchannel 12. These fluid segments A and B are made to pass as laminar flows and are mixed by molecular diffusion to effect multiple reaction. Reaction products generated by the multiple reaction are discharged through a discharge port 17. Association between fluids A and B and the fluid introduction channels 22 in distribution of fluids A and B to the fluid introduction channels 22 by the distribution device 24 is determined by selecting, for example, settings of the numbers of segments, sectional shapes, arrangements, aspect ratios, widths and concentrations of fluid segments A and B in the diametral section at the entrance side of the microreactionchannel 12. That is, since the multiplicity of fluid segments A and B flowing together into the microreactionchannel 12 flow as laminar flows according to the characteristics of the microreactionchannel 12, factors including the numbers of segments, sectional shapes, arrangements, aspect ratios, widths and concentrations of the fluid segments in the diametral section at the entrance side of the microreactionchannel 12 can be freely controlled.
For example, the fluid introduction portion 14 may be constituted by a multiplicity of fluid introduction channels 22 divided in such a manner that, as shown in
If fluid segments A and B should be arranged in a checkered pattern in the diametral section at the entrance side of the microreactionchannel 12 as shown in
If the aspect ratios of rectangular sectional shapes of fluid segments A and B alternately arranged should be changed as shown in
If the widths of fluid segments A and B (the thicknesses of fluid segments A and B in the arrangement direction) should be changed to obtain, for example, a large-central-width arrangement, such as shown in
As shown in
The microreactor 10 constructed as described above is capable of controlling the numbers of segments, sectional shapes, arrangements and aspect ratios of fluid segments A and B in the diametral section at the entrance side of the microreactionchannel 12, and freely setting the diffusion distance and specific surface area of fluids A and B. Further, the microreactor 10 is capable of controlling the arrangements of fluid segments A and B differing in width and concentration and freely setting even the concentration distribution in the widthwise direction of the microreactionchannel 12.
The microreactor 10 of the present invention is suitable for carrying out multiple reaction of fluids A and B because it is capable of controlling the yield and selectivity of a target product of the multiple reaction by changing the diffusion distance and specific surface area between the plurality of kinds of fluids flowing together into the microreactionchannel 12 and by changing the concentration distribution in the widthwise direction of the microreactionchannel 12. The microreactor 10 of the present invention can be applied not only to carrying out of multiple reaction but also to other systems which need changing the diffusion distance and specific surface area between fluids and changing the concentration distribution in the widthwise direction of the microreactionchannel 12.
Also, the microreactor 10 of the present invention can be effectively used as a microreactor for studying optimum conditions to find optimum conditions for various reaction systems. If an optimum condition for a reaction system is found with the microreactor 10 of the present invention by changing factors including the numbers of segments, sectional shapes, arrangements, aspect ratios, widths and concentrations of fluid segments A and B, a microreactor main unit 16 fixed according to the optimum condition may be additionally prepared. For example, a microreactor 10 may be additionally manufactured and used in which fluid segments have fixed sectional shapes, e.g., rectangular sectional shapes, such as the shape of a square or an oblong, parallelogrammatic shapes, triangular shapes, concentric circular shapes, zigzag shapes, or convex shapes as the sectional shapes in the diametral section at the entrance side of the microreactionchannel 12. Similarly, a microreactor 10 may be additionally manufactured and used which has, as a fixed factor, optimum numbers of segments, sectional shapes, arrangements, aspect ratios, widths or concentrations of fluid segments A and B.
The above-described microreactor 10 is manufactured by a fine processing technique. The following are examples of fine processing techniques for manufacture of the microreactor:
As materials for manufacture of the microreactor 10, materials selected from metals, glass, ceramics, plastics, silicon, Teflon, and other materials according to required characteristics such as heat resistance, pressuretightness, solvent resistance and workability can be suitably used.
In embodiment 1, multiple reaction of fluids A and B shown below was performed and the influence of changes in the number of segments, sectional shape, arrangement and aspect ratio in fluid segments on the yield and selectivity of a target product was checked by using a computational fluid dynamics (CFD) simulation. Fluid A is a solution in which a reaction raw material A is dissolved, and fluid B is a solution in which a reaction raw material B is dissolved. “Sectional shape” of fluid segments A and B denotes the shapes of fluid segments A and B in the diametral section of the microreactionchannel at the entrance side of the microreactionchannel.
Common conditions for this check will first be described.
It is assumed that multiple reaction expressed by a reaction formula and a reaction rate formula shown below is caused under a constant-temperature condition in the microreactionchannel. R represents a target product, and S represents a byproduct.
A+B→R, r1=k1 CA CB (formula 1)
B+R→S, r2=k2 CB CR (formula 2)
In these formulae, ri is the reaction rate in the ith stage [kmol·m−3·S−1]; ki is a reaction rate constant for the reaction rate in the ith stage, where k is 1 m3·kmol·m−1·S−1; and Cj is the molar concentration of component j [kmol·m−3]. The reaction order of each of the first and second stages of reaction is primary with respect to each component and is secondary with respect to the whole. Fluids A and B are supplied at a molar ratio 1:2 at the microreactionchannel entrance. The initial concentration is CA0=13.85 kmol·m−3, CB0=27.70 kmol·m−3. Flows in the microreactionchannel are laminar flows. Fluids A and B flow out of the fluid introduction channels into the microreactionchannel at equal flow rates of 0.0005 m/seconds. The channel length of the microreactionchannel is 1 cm and the average retention time during which fluids A and B stay in the microreactionchannel is 20 seconds. A nondimensional number indicating the influence of axial diffusion in the microreactionchannel (vessel dispersion number) is D/uL=2×10−4, and the influence of axial diffusion on mixing is extremely small. Changes in physical properties due to reaction are not considered and the physical properties of all the components are assumed to be identical to each other. The density is 998.2 kg·m−3, the viscosity 0.001 Pa·s, and the molecular diffusion coefficient 10−9m2·s−1. A momentum preservation equation and a preservation equation for each component are solved by using a secondary-accuracy upwind difference method, and a pressure and rate coupling equation is solved by using a SINPLE method.
(1) Influence of Selection of the Numbers of Fluid Segments A and B on Progress of Multiple Reaction
Of each of fluid segments A and B flowing along channel walls of the microreactionchannel at opposite ends, half on the wall side is not reacted with the reaction row material in the other fluid segment A or B since the raw material comes by diffusing only from the opposite side, as shown in
In the two-dimensional simulation, large numbers of fluid segments A and B in the form of thin layers flow one on another into flat parallel plates for the microreactionchannel to form parallel laminar flows, as shown in
As can be understood from
Thus, selection of the number of fluid segments A and B influences the yield (YR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by changing the number of fluid segments A and B. If R is a target product as in this embodiment, the yield of R can be increased. If S is a target product, the yield of S can be increased.
(2) Influence of the Method of Arranging Fluid Segments A and B on Progress of Multiple Reaction
(2-1) Influence of the Arrangement Method on Progress of Multiple Reaction
Progress of multiple reaction in the microreactionchannel when 100 μm square segments were arranged was calculated with respect to five arrangements such as shown in
(2-2) Correspondence Between Vertical Periodic Arrangement and Horizontal-One-Row Periodic Arrangement
To quantitatively examine a correspondence between arrangements, a correspondence between arrangement 2 (horizontal-one-row periodic arrangement) and arrangement 5 (vertical periodic arrangement) shown in
As can be understood from the above-described results, the method of arranging fluid segments A and B includes the yield (yR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by changing the method of arranging fluid segments A and B. If R is a target product as in this embodiment, the yield of R can be increased. If S is a target product, the yield of S can be increased. Also, if the specific surface area is increased by changing the arrangement, the yield (yR) of R is increased. However, if the length of one of arranged fluid segments A and B is increased while the specific surface area is fixed, that is, diffusion control is approached, the yield of R is changed. This means that there is a need to also consider the length of one side of arranged fluid segments A and B for control of the yield (yR) of R as well as to simply increase the specific surface area.
(3) Influence of the Aspect Ratio of Fluid Segments A and B on Progress of Multiple Reaction.
As the way of changing the aspect ratio, a case (3-1) where only the depth of fluid segments A and B was changed while the width of fluid segments A and B (thickness in the direction of arrangement of fluid segments A and B) was fixed, that is, the influence of the depth when diffusion distance was constant was examined, and a case (3-2) where the aspect ratio was changed so that the area of fluid segments A and B was constant in the diametral section were examined. Further, the length of one side of square fluid segments A and B corresponding in terms of the maximum value of the yield of target product R to rectangular fluid segments A and B changed in aspect ratio in arrangement 5 shown in
(3-1) Case of Changing the Depth While Fixing the Width
Rectangular fluid segments A and B had a fixed width of 100 μm and their aspect ratio was changed as shown in
The calculation region where a CFD simulation was performed has a symmetry in the depth direction and can therefore be reduced to half of its entire size by setting as a symmetry boundary a plane indicated by the dotted line in
(3-2) Case of Changing the Depth While Constantly Maintaining the Segment Area.
In (3-1), the area of each segment was changed with the depth, since the depth was changed while the segment width was constantly maintained. The segment depth and width were then changed so that the area was constant. Fluid segments A and B were changed in width and depth by selecting from three combinations of width and depth values: a width of 200 μm and a depth of 50 μm (an aspect ratio of 0.25), a width of 100 μm and a depth of 100 μm (an aspect ratio of 1), and a width of 50 μm and a depth of 200 μm (an aspect ratio of 4). Calculations were also performed with respect to the case where the number of fluid segments A and B is 2 (a pair of segments A and B) (the number of discretization meshes is 20,000), the case of a one-row periodic arrangement (the number of discretization meshes: 40,000) and the case of a vertical periodic arrangement (the number of discretization meshes: 80,000).
(3-3) Correspondence Between Rectangular Segments and Square Segments
In the case of the vertical periodic arrangement (arrangement 5 in
From the results shown above, it can be said that the aspect ratio of fluid segments A and B having a rectangular shape (the shape of one of rectangles) influences the yield (yR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by changing the aspect ratio of fluid segments A and B. If R is a target product as in this embodiment, the yield of R can be increased. If secondary product S is a target product, the yield of S can be increased.
(4) Influence of the Sectional Shape of Fluid Segments A and B on Progress of Multiple Reaction
The influence of selection of the sectional shape of fluid segments A and B in the diametral section of the microreactionchannel from various shapes other than the square or rectangular shape on the progress of multiple reaction and the concentration distribution in the microreactionchannel was examined. With respect to each shape, the length of one side of square fluid segments A and B capable of setting the maximum yield of the same target product was obtained. Further, the influence of a change in the reaction rate constant with respect to each shape on the progress of reaction was examined.
(4-1) Influence of Selection of the Sectional Shape of Fluid Segments A and B on Progress of Multiple Reaction
As shown in
With respect to the squares, parallelograms and triangles, calculation was performed on a periodic arrangement in one horizontal row and a vertical periodic arrangement. With respect to the segments in the zigzag shapes and the segments in the convex shapes, calculation was performed only on a periodic arrangement in one horizontal row. In the zigzag shapes, a symmetry boundary is used at a center in the depth direction, as indicated by a thick line in
(4-2) Correspondences Between the Shapes of Fluid Segments A and B
It can be understood from the results shown in (4-1) that the progress of reaction changes if the shape is changed while the area of fluid segments A and B is fixed. Correspondences between the shapes of fluid segments A and B were also examined.
(4-3) Arrangement of Expression of the Diffusion and Reaction Rate by Nondimensional Number with Respect to Each Shape
Correspondence in terms of progress of reaction between fluid segments A and B differing in sectional shape and the influence of each shape on the process of reaction with respect to the width were examined by fixing the reaction rate constant and by considering the segment area and the specific surface area per microreactionchannel volume between the segments. The influence of the width of fluid segments A and B and the reaction rate constant on the progress of reaction in each sectional shape was then examined. A check was made as to whether or not there was a correspondence in terms of progress of reaction between a case where the reaction rate constant was quadrupled and the size of fluid segments A and B was reduced to half while the similarity of the shape was maintained and a case where fluid segments A and B were in the original size and the original reaction rate constant was used. More specifically, a check was made as to correspondence in terms of progress of reaction in a case where W was 200 μm, H was 50 μm and the reaction rate constant k was 4, a case where W was 400 μm, H was 100 μm and the reaction rate constant k was 1, a case where W was 25 μm, H was 50 μm and the reaction rate constant k was 4, and a case where W was 50 μm, H was 100 μm and the reaction rate constant k was 1. W and H correspond to the values shown in
where L is a typical length of the shape. It is thought that if a method for expressing the representative length for each sectional shape (the quantity having a length dimension determined for each sectional shape) is provided, the progress of the reaction can be expressed only with a nondimensional number independently of the sectional shape. However, since the concentration distribution varies largely depending on the sectional shape, it is supposed that it is difficult to express the progress of the reaction with respect to all the shape with such a nondimensional number.
According to the results shown above, the shapes of fluid segments A and B in the diametral section of the microreactionchannel influence the yield (yR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by changing the shape of fluid segments A and B. If R is a target product as in this embodiment, the yield of R can be increased. If secondary product S is a target product, the yield of S can be increased. Also, if the specific surface area is increased by changing the shape, the yield (yR) of R is increased. However, if the shape is changed while the specific surface area is fixed, the yield of R is changed. This means that there is a need to also suitably control the shape for control of the yield (yR) of R as well as to simply increase the specific surface area.
(5) As embodiment 2, the results of check by CFD simulation of the influence of a change in the method of arranging fluid segments A and B differing in width or a change in the method of arranging fluid segments A and B differing in raw-material concentration on the yield and selectivity of the target product will be described.
As a common setting for simulation, it is assumed that reaction expressed by formulae 3 and 4 shown below progresses in the microreactionchannel and that k1=k2=1 m3 (kmol·s)
A+B→R, r1=k1 CA CB (formula 3)
B+R→S, r2=k2 CB CR (formula 4)
The channel length of the microreactionchannel is 1 cm, the entrance flow rate is 0.0005 m/seconds, and the average retention time of retention in the mmppp is 20 seconds. The physical properties of the reaction fluids are a density of 998.2 kg·m, a molecular diffusion coefficient D of 10−9m2·S−1, a molecular weight of 1.802×10−2 kg/mol, and a viscosity of 0.001 Pas.
(5-1) Case Where There is a Difference in Width Among Fluid Segments A and B
A case where there is a difference between the widths of segments of each kind in fluid segments A and B will first be considered. The relationship between YR and xA was examined by calculation with respect to cases such as shown in
The total number of rectangular meshes for disretization in arrangement 1 is 8,000, the number of disretization meshes in each of arrangements 2 and 3 is 12,000, and the number of disretization meshes in arrangement 4 is 10,000. The segment width in arrangement 1 is 50 μm, the larger segment width in arrangements 2 to 4 is 75 μm or 90 μm, and the smaller segment width in arrangements 2 to 4 is 25 μm or 10 μm.
In the case where W1=25 μm and W2=75 μm (
In the case where W1=10 μm and W2=90 μm (
Thus, the method of forming fluid segments A and B so that fluid segments of each kind differ in width, and selecting the way of arranging these segments influences the yield (YR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by suitably setting the method of arranging fluid segments A and B differing in width. If R is a target product as in this embodiment, the yield of R can be increased. If secondary product S is a target product, the yield of S can be increased.
Also, as shown in
(5-2) Case Where Different Raw Material Concentrations are Provided in Fluid Segments A and B.
A case where different raw-material concentrations are provided in each kind in fluid segments A and B will next be considered. The relationship between YR and xA was examined by calculation with respect to cases such as shown in
Discretization was performed with rectangular meshes. The total number of meshes is 8,000 in any of the arrangements. The raw material concentrations in arrangement 1 are CA0=6.92 kmol/m3 in fluid segment A and CB0=13.85 kmol/m3 in fluid segment B. In arrangements 2 to 4, the raw material concentration in the lower-concentration fluid segments A and B is expressed by Cj0,1, the raw material concentration in the higher-concentration fluid segments A and B is expressed by Cj0,1 (j=A, B), and a combination of raw material concentrations Cj0,1=0.5Cj0, Cj0,2=1.5Cj0, or Cj0,1=0.2Cj0, Cj0,2=1.8Cj0 are provided. The average raw material concentration corresponds to CA0 or CB0 in all the cases.
The case where fluid segments A and B have the combination of raw material concentrations Cj0,1=0.5Cj0, Cj0,2=1.5Cj0 will first be examined. YR in the case of placement 2 is highest as shown in
A concentration distribution in the microreactionchannel will next be considered.
Thus, the method of forming fluid segments A and B so that fluid segments of each kind have different concentrations, and selecting the way of arranging these segments influences the yield (YR) of target product R. In other words, it is possible either to increase or to reduce the yield of R by suitably selecting the arrangement of fluid segments A and B differing in width. If R is a target product as in this embodiment, the yield of R can be increased. If secondary product S is a target product, the yield of S can be increased.
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