Formic acid producing apparatus

Abstract

To provide a formic acid producing apparatus that enables efficient irradiation of light to a reaction solution and allows improvement in formic acid generation efficiency.SOLUTION: A formic acid producing apparatus 50 includes a raw material charging part 10 into which a solution containing an organic substance and a metal oxide powder having a photocatalytic function is charged, an artificial photosynthesis reaction part 20 in which the mixed solution of the organic substance and the metal oxide powder is irradiated with sunlight or light to effect reaction, and a formic acid recovery part 30 for recovering formic acid from the mixed solution after the reaction, characterized in that the artificial photosynthesis reaction part 20 is a plate-like container in which at least the surface irradiated with light is made of a light-transmissive member, the container is inclined relative to the ground surface, and the artificial photosynthesis reaction is performed by flowing the mixed solution through the interior of the container.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a formic acid generator that generates formic acid from organic substances using sunlight. [Background technology]

[0002] The idea of a "hydrogen society" that uses hydrogen as fuel has been proposed for some time, but it has yet to become widespread due to the difficulty of storing and transporting hydrogen and the energy conversion efficiency. For example, to transport hydrogen, which has a low energy density, as a vehicle fuel, it must be subjected to high pressures of several hundred atmospheres. While there is a method of producing liquid hydrogen, this is not common because it requires ultra-low temperatures. Therefore, research is being conducted into technologies that produce and store formic acid (HCOOH) as an intermediate hydrogen source. Formic acid is an excellent storage material because it is liquid at room temperature and has a high energy density.

[0003] Utilizing sunlight as a natural energy source to produce highly active organic compounds from relatively stable organic substances is an important technology that humanity should acquire now in many fields, from pharmaceutical manufacturing to transportation fuels and power generation, and there is a desire to establish such artificial photosynthesis methods and to achieve more efficient yields.

[0004] Given this situation, there is a need to provide a low-cost means for using solar energy to produce formic acid, a chemical substance that can be converted relatively easily into hydrogen as chemical energy and is useful to humans.

[0005] The applicants have previously proposed a formic acid generation method and system as described in Patent Document 1. The invention described in Patent Document 1 is a formic acid generation method characterized by mixing a metal oxide powder having photocatalytic function with a solution containing an organic substance to form a mixed solution, and generating formic acid by irradiating the mixed solution with light.

[0006] Even after proposing the invention described in Patent Document 1, the applicants have continued to conduct intensive research with the aim of further improving the amount of formic acid produced. For example, the invention described in Patent Document 1 proposes a light-transmitting tubular or cylindrical member of any shape that is laid on the roof or rooftop of a building and that performs an artificial photosynthesis reaction by circulating a mixed solution within the member. However, it was found that sunlight is almost entirely absorbed near the liquid surface of the solution, and therefore, sufficient sunlight does not reach the interior of the solution, and therefore the formic acid production reaction does not occur sufficiently. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7076113 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a formic acid generator that can efficiently irradiate a reaction solution with light and improve the efficiency of formic acid production. [Means for solving the problem]

[0009] One aspect of the present invention is a formic acid generation device that includes a raw material input section into which a solution containing an organic substance and a metal oxide powder having photocatalytic function are input, an artificial photosynthesis reaction section that irradiates the mixed solution of the organic substance and the metal oxide powder with sunlight or light to cause a reaction, and a formic acid recovery section that recovers formic acid from the mixed solution after the reaction, wherein the artificial photosynthesis reaction section is a plate-shaped container with at least the surface onto which light is irradiated made of a light-transmitting material, the container is inclined with respect to the ground surface, and the artificial photosynthesis reaction is carried out by flowing the mixed solution inside the container.

[0010] According to one aspect of the present invention, by supplying a reaction solution into an inclined plate-shaped container, the reaction solution can be efficiently irradiated with light while flowing at a moderate speed, resulting in a formic acid generator with improved formic acid production efficiency.

[0011] In this case, in one aspect of the present invention, the artificial photosynthesis reaction unit may be equipped with a nozzle that sprays the mixed solution onto the upper surface inside the container located upstream of the slope, and the sprayed mixed solution may be configured to adhere to the upper surface of the container due to surface tension while flowing downstream along the slope.

[0012] By doing this, the reaction solution that adheres to the top surface of the container due to surface tension spreads widely and thinly throughout the container, allowing the reaction solution to be efficiently irradiated with light, thereby improving the efficiency of formic acid production.

[0013] Alternatively, in one aspect of the present invention, the artificial photosynthesis reaction unit may be provided with a nozzle for flowing the mixed solution onto the bottom surface inside a container located upstream of the slope, and the mixed solution may be configured to flow downstream along the slope on the bottom surface of the container.

[0014] By flowing the reaction solution from upstream to the bottom surface, the reaction solution can be spread widely and thinly throughout the entire reaction system, allowing the reaction solution to be efficiently irradiated with light and improving the efficiency of formic acid production.

[0015] Alternatively, in one aspect of the present invention, the artificial photosynthesis reaction unit may be configured to include a nozzle that supplies the mixed solution to the bottom surface inside the container located downstream of the slope, and to send the mixed solution from the downstream side to the upstream side of the slope by the supply pressure of the nozzle.

[0016] By doing so, the time for the solution to pass through the container can be relatively long, so that the reaction solution can be efficiently irradiated with light, and the efficiency of formic acid production can be improved.

[0017] In one aspect of the present invention, the formic acid recovery section may be provided with equipment for recovering and cooling the gas phase of the mixed solution after the reaction, thereby recovering formic acid as a liquid by reflux.

[0018] In this way, it becomes possible to separate formic acid at a high concentration from the mixed solution after the reaction.

[0019] In one aspect of the present invention, the apparatus may further include an air supply means for supplying air to the mixed solution.

[0020] By appropriately supplying air to the mixed solution using the air supply means, oxygen necessary for the reaction of producing formic acid is supplied, and the efficiency of producing formic acid can be improved.

[0021] In addition, one aspect of the present invention may include a control unit that can continuously measure the amount of formic acid produced in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance.

[0022] By providing such a control unit, it becomes possible to remotely operate and control the formic acid generating device.

[0023] In one aspect of the present invention, the light-transmitting member may be embossed glass.

[0024] In one embodiment of the present invention, the angle formed by the inclination with respect to the horizontal plane may be 10° or more and 15° or less.

[0025] In one embodiment of the present invention, the organic substance may include glucose, and the photocatalytic function may include titanium oxide fine particles. [Effects of the Invention]

[0026] As described above, according to the present invention, it is possible to provide a formic acid generator that can efficiently irradiate a reaction solution with light and improve the efficiency of formic acid production. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram illustrating an example of a formic acid generating apparatus according to an embodiment of the present invention. [Figure 2] 1A and 1B are diagrams showing one aspect of an artificial photosynthesis reaction unit in a formic acid production device according to one embodiment of the present invention, in which (A) is a front view of the artificial photosynthesis reaction unit, and (B) is a cross-sectional view taken along line AA in (A). [Figure 3] FIG. 2 is a cross-sectional view showing one mode of supplying a reaction solution in an artificial photosynthesis reaction unit of a formic acid production device according to one embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing another aspect of supplying a reaction solution in the artificial photosynthesis reaction unit of the formic acid producer according to one embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing another aspect of supplying a reaction solution in the artificial photosynthesis reaction unit of the formic acid producer according to one embodiment of the present invention. [Figure 6] 1 is a graph showing the amounts of formic acid produced in an example in which one aspect of the present invention is applied and in a comparative example of the prior art. [Figure 7] 1 is a graph showing the amount of formic acid produced in an example when one embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims, and not all of the configurations described in the embodiments are necessarily essential as means for solving the problems of the present invention.

[0029] 1 is a schematic diagram showing an example of a formic acid generator according to one embodiment of the present invention. One aspect of the present invention is a formic acid generator 50 comprising a raw material input unit 10 into which a solution containing an organic substance and a metal oxide powder having photocatalytic function are input, an artificial photosynthesis reaction unit 20 that irradiates the mixed solution of the organic substance and the metal oxide powder with sunlight or light to cause a reaction, and a formic acid recovery unit 30 that recovers formic acid from the mixed solution after the reaction. The artificial photosynthesis reaction unit 20 is a plate-shaped container with at least the surface irradiated with light made of a light-transmitting material, and the container is inclined with respect to the ground surface ... is carried out by flowing the mixed solution into the container.

[0030] The mixed solution is preferably circulated and supplied to the artificial photosynthesis reaction unit 20 via, for example, a pump 45. While the mixed solution is circulated by the pump 45, formic acid is produced in the artificial photosynthesis reaction unit 20, and the formic acid is recovered in the formic acid recovery unit 30. While the reaction solution is appropriately supplied to the raw material input unit 10, formic acid is repeatedly produced by the artificial photosynthesis reaction. Each configuration of the present invention will be described below.

[0031] The raw material input section 10 is a facility for inputting a solution containing an organic substance and a metal oxide powder having photocatalytic function. The organic substance is not particularly limited as long as it contains carbon atoms. The organic substance is preferably one containing a pigment that aids the photoreaction, but pigment-free organic substances are also applicable. For example, inositol (a type of B vitamin) and glucose (the most abundant monosaccharide in nature) have a formic acid production rate ratio equivalent to that of anthocyanin B (a pigment found in purple cabbage). Furthermore, disaccharides and polysaccharides such as dextrin, cellobiose, and cellulose, which have a lower formic acid production rate than anthocyanin B, are also applicable to the present invention.

[0032] The organic matter may be plants, fallen leaves, vegetables, fruits, etc. If discarded plants such as fallen leaves or discarded food such as food waste are used as raw materials for producing formic acid, an environmentally friendly formic acid generator can be realized.

[0033] The organic substance preferably contains a pigment that aids in the photoreaction. The pigment can be a combination of green pigment, gardenia red, and mercurochrome to improve the rate of formic acid production. Alternatively, carbon powder can be used instead of the pigment. For example, activated carbon powder can be used as the carbon powder. Of course, the present invention can also be applied to organic substances without a pigment.

[0034] The metal oxide powder is not particularly limited as long as it has photocatalytic function. Titanium oxide or zinc oxide is particularly preferred. These metal oxides are preferably in the form of fine particles to increase the contact surface area in the mixed solution. The average particle size of the fine particles is not particularly limited, but an example is 20 to 50 nm. In particular, the average particle size of titanium oxide fine particles is preferably about 25 nm. Furthermore, among titanium oxides, anatase type is preferred because it exhibits activity approximately 10 times higher than rutile type.

[0035] The raw material input unit 10 is, for example, a tank-like facility that appropriately supplies raw materials to the artificial photosynthesis reaction unit 20. The solution containing the organic substance and the metal oxide powder having photocatalytic function may be mixed in advance, or may be stored separately and mixed when the raw materials are supplied and supplied onto the path to the artificial photosynthesis reaction unit 20. Alternatively, instead of a tank-like facility, the raw materials may be sent via piping from a source of generation or production of the organic substance.

[0036] The artificial photosynthesis reaction unit 20 is a facility that irradiates a mixed solution of an organic substance and a metal oxide powder with sunlight or light to cause a reaction. In one aspect of the present invention, the artificial photosynthesis reaction unit 20 is a plate-shaped container in which at least the surface to be irradiated with light is made of a light-transmitting material, and the container is installed at an angle with respect to the ground surface.

[0037] FIG. 2 shows one embodiment of an artificial photosynthesis reaction unit in a formic acid generator according to one embodiment of the present invention. FIG. 2(A) is a front view of the artificial photosynthesis reaction unit, and FIG. 2(B) is a cross-sectional view taken along line AA in FIG. 2(A). As an example, the artificial photosynthesis reaction unit 20 can have a plate-like structure, as shown in FIG. 2(B), in which light-transmitting members 22 are installed at regular intervals on a bottom panel 21. The bottom panel 21 may or may not be light-transmitting and may be, for example, a concrete panel. On the other hand, the surface exposed to sunlight is preferably made of a light-transmitting member such as tempered glass. The distance between the panel surface 21 and the glass surface 22 can be adjusted, for example, by forming a wall surface using a frame material 23 or the like around the edge of the panel and adjusting the height of the frame material 23.

[0038] In one embodiment of the present invention, a nozzle installation hole 24 or the like is provided near the upstream end of the inclined panel. In one embodiment of the present invention, a reaction solution (mixed solution) is supplied from a nozzle provided in the installation hole 24. Although FIG. 2 shows only one nozzle installation hole 24, multiple nozzle installation holes may be provided. Alternatively, a liquid supply pipe may be provided near the upstream end of the inclined panel, and multiple injection ports for the mixed solution may be provided on the liquid supply pipe. In another embodiment of the present invention, a discharge hole (drain hole) 25 for the post-reaction solution is provided near the downstream end of the inclined panel. Therefore, the reaction solution is supplied from a nozzle near the upstream end of the inclined panel, and as it flows along the inclined panel, it receives light such as sunlight from the glass surface and undergoes an artificial photosynthetic reaction, and the post-reaction solution is discharged from the discharge hole 25.

[0039] The inventors discovered that in the formic acid production reaction using sunlight, almost all (99% or more) of the sunlight is absorbed at a depth of the liquid surface (approximately 1 mm) of the mixed solution. In other words, in the method of circulating the sunlight inside a tubular pipe as in Patent Document 1, only the solution near the surface of the tube receives the irradiation energy of sunlight, and sunlight does not sufficiently reach the solution inside, which is thought to be why sufficient formic acid production efficiency was not achieved.

[0040] Therefore, in one embodiment of the present invention, by supplying the reaction solution into an inclined plate-like container, the entire reaction solution can be irradiated with sunlight, resulting in a formic acid generator with improved formic acid production efficiency. The angle of inclination is not particularly limited as long as the mixed solution can flow at an appropriate speed, but as an example, it can be 10 to 15 degrees with respect to the horizontal plane.

[0041] There are several possible modes for the method of supplying the reaction solution in the artificial photosynthesis reaction unit 20. Figure 3 is a cross-sectional view showing one mode of supplying the reaction solution in the artificial photosynthesis reaction unit of a formic acid production device according to one embodiment of the present invention.

[0042] In one embodiment of the present invention, as shown in Figure 3, the artificial photosynthesis reaction unit 20 is equipped with a nozzle 15 that sprays the mixed solution onto the upper surface inside the container located upstream of the slope, and the sprayed mixed solution 55 can be configured to flow downstream along the slope while adhering to the inside of the upper surface 22 of the container due to surface tension. In this way, the reaction solution 55 that adheres to the upper surface 22 of the container due to surface tension spreads widely and thinly throughout the container, allowing the reaction solution 55 to be efficiently irradiated with light and improving the efficiency of formic acid production. Furthermore, the embodiment of Figure 3 can also prevent the upper surface inside the container from becoming cloudy due to water vapor.

[0043] 3, the nozzle 15 is positioned so that the nozzle is directed upward and sprays the solution onto the back surface (the surface facing the inside of the container) of the light-transmitting member (glass, etc.). The surface of the light-transmitting member 22 to which the solution is to be applied may be embossed or otherwise processed so that a large amount of the solution can be attached by surface tension.

[0044] FIG. 4 is a cross-sectional view showing another embodiment of the reaction solution supply in the artificial photosynthesis reaction unit of a formic acid generator according to one embodiment of the present invention. In another embodiment of the present invention, as shown in FIG. 4, the artificial photosynthesis reaction unit 20 may be configured to include a nozzle 15 for flowing the mixed solution onto the bottom surface inside a container located upstream of the slope, and the mixed solution 55 may be configured to flow downstream along the slope on the bottom surface 21 of the container. By flowing the reaction solution from upstream to the bottom, the reaction solution can be spread widely and thinly throughout the entire container, allowing for efficient light irradiation of the reaction solution and improving formic acid production efficiency. Furthermore, in the embodiment of FIG. 4, the liquid delivery pressure of the pump 45 or the like may be relatively small.

[0045] In the case of the embodiment shown in Figure 4, the nozzle outlet only needs to be directed toward the panel at the bottom of the container, and there is no need to spray with any particular force. The mixed solution will fall down the slope of the panel due to gravity, and during this time a photoreaction will occur due to sunlight or other factors.

[0046] 5 is a cross-sectional view showing another aspect of the supply of the reaction solution in the artificial photosynthesis reaction unit of a formic acid generator according to one embodiment of the present invention. In another aspect of the present invention, as shown in FIG. 5, the artificial photosynthesis reaction unit 20 may be configured to include a nozzle 15 that supplies the mixed solution 55 to the bottom surface inside a container located downstream of the slope, and to send the mixed solution 55 from the downstream side to the upstream side of the slope by the supply pressure of the nozzle 15. This allows the solution to pass through the container for a relatively long time, allowing the reaction solution to be efficiently irradiated with light and improving the efficiency of formic acid production.

[0047] In the embodiment shown in Fig. 5, the nozzle 15 has an injection port provided near the downstream end of the slope of the panel 21, and the discharge hole 25 is provided near the upstream end of the slope of the panel 21. The mixed solution supplied from the nozzle 15 flows upstream on the slope of the panel 21 due to the supply pressure of the nozzle 15. In the embodiment shown in Fig. 5, if the gap between the panel 21 and the light-transmitting member 22 is made as small as possible to form a sheet-like artificial photosynthesis reaction unit 20, it is more effective because sunlight can be irradiated onto the entire mixed solution 55.

[0048] The specific reaction process in the formic acid generating device according to one embodiment of the present invention can be considered as follows: First, water is decomposed by the photocatalyst to generate oxygen, hydrogen ions, and electrons, as shown in reaction formula (1). 2H2O→O2+4H + +4e - ···(1)

[0049] Next, through a photoreaction (artificial photosynthesis) process using a photocatalyst or dye, formic acid is produced from hydrogen ions and electrons, and carbon dioxide or organic substances mixed into the solution (reaction formula (2) or (3) below). Carbon dioxide is not essential to this reaction; the hydrogen ions and electrons produced in reaction formula (1) are consumed during this process. Furthermore, while reaction formula (2) allows for the use of carbon dioxide present in the atmosphere and / or exhaust gases from other engines, reaction formula (3) has a significant advantage in that formic acid can also be produced from carbon C in organic substances mixed into the solution. CO2+2H + +2e - →HCOOH (2) Organic matter +2H + +2e - →HCOOH (3)

[0050] At this time, of the irradiated light, mainly ultraviolet light acts on the metal oxide as a photocatalyst, and visible light acts on the dye, so it is thought that in the formic acid generator according to one embodiment of the present invention, this combined action doubles the efficiency of formic acid production. In other words, even in the case of only a metal oxide and a dye, it is thought that the interaction between the metal oxide and the dye makes it possible to directly donate electrons to the formic acid production reaction.

[0051] The formic acid recovery unit 30 is a facility for recovering formic acid from the post-reaction mixed solution. The facility's form is not particularly limited as long as it can recover formic acid. For example, the formic acid recovery unit 30 may include a facility for recovering and cooling the vapor phase of the post-reaction mixed solution, thereby recovering formic acid as a liquid through reflux. Because the vapor pressure of formic acid is greater than that of water below the boiling point, more formic acid vaporizes than water. Therefore, by recovering and cooling the vapor phase of the post-reaction mixed solution, formic acid can be concentrated and recovered. In the formic acid recovery unit 30, an aqueous formic acid solution can be obtained by cooling the vapor phase containing formic acid using a heat exchanger or the like. The formic acid thus produced can be stored, for example, in a storage facility or the like.

[0052] Furthermore, in one aspect of the present invention, it has been confirmed that mixing air into the mixed solution improves the efficiency of formic acid production. Therefore, in one aspect of the present invention, it is preferable to further include an air supply means 40 that supplies air to the mixed solution. Examples of the air supply means 40 include a fan that supplies air and a gas pump that supplies air. The air supply means 40 may be configured to supply air directly into the artificial photosynthesis reaction unit 20, or may be installed around the raw material input unit 10 or the pump to supply air to the mixed solution being fed. The air supply means 40 may, for example, supply air intermittently so as not to affect the formic acid recovery unit 30 described above.

[0053] In one embodiment of the present invention, a control unit may be provided that can continuously measure the amount of formic acid produced by the formic acid generator in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance. This allows the amount of formic acid produced in the formic acid generator to be remotely monitored, enabling remote operation and control.

[0054] The formic acid generating apparatus according to one embodiment of the present invention as described above has the following advantages. 1. By supplying the reaction solution into an inclined plate-like container, the entire reaction solution can be irradiated with sunlight, improving the efficiency of formic acid production. 2. By supplying air from the air supply means, oxygen is supplied during the production of formic acid, and the efficiency of the production of formic acid is further improved. 3. Recovery of generated formic acid and replenishment of artificial photosynthetic materials can all be achieved at specific locations. 4. By simply adding and replenishing all the materials, the artificial photosynthesis device can operate semi-permanently. [Example]

[0055] The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples in any way.

[0056] Example 1 A formic acid generator according to the present invention was created in accordance with the embodiment shown in Fig. 3, and a mixed solution containing glucose, a dye, and a photocatalyst was circulated. The tempered glass on the side exposed to sunlight was 820 mm x 1620 mm x 3 mm, and the mixed solution was 5 to 10 L at a flow rate of 1 m / s.

[0057] (Comparative Example 1) A similar mixed solution was circulated using the method described in Patent Document 1.

[0058] (Comparative Example 2) In the method described in Patent Document 1, a similar mixed solution was circulated while mixing air with a stirrer.

[0059] Figure 6 is a graph showing the amount of formic acid produced in an example in which one embodiment of the present invention is applied and in a comparative example of the prior art, and Figure 7 is a graph showing the amount of formic acid produced in an example in which one embodiment of the present invention is applied. As shown in Figure 6, in Comparative Example 2, the amount of formic acid produced was about 80 mM in 25 days, whereas in the example in which the present invention is applied, as shown in Figures 6 and 7, the amount of formic acid produced was 370 mM in just over 10 days. It was found that the formic acid production rate in the example was more than 10 times faster than in the comparative example.

[0060] Furthermore, when comparing Comparative Example 2, in which a moderate amount of air was mixed in by stirring, with Comparative Example 1, in which no air was mixed in, Comparative Example 2 produced a greater amount of formic acid, and it was also found that mixing air by stirring is effective in improving the amount of formic acid produced.

[0061] Although the embodiments and examples of the present invention have been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0062] For example, a term described at least once in the specification or drawings together with a different term having a broader or similar meaning can be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration of the formic acid generating device is not limited to those described in each embodiment and each example of the present invention, and various modifications are possible. [Explanation of symbols]

[0063] 10 raw material input section, 15 nozzle, 20 artificial photosynthesis reaction section, 21 panel, 22 light-transmitting member, 23 frame material, 24 (nozzle) installation hole, 25 discharge hole, 30 formic acid recovery section, 40 air supply means, 45 pump, 50 formic acid generator, 55 mixed solution (reaction solution)

Claims

1. a raw material input section into which a solution containing an organic substance and a metal oxide powder having a photocatalytic function are input; An artificial photosynthesis reaction unit that irradiates sunlight or light to the mixed solution of the organic substance and the metal oxide powder to cause a reaction; a formic acid recovery section for recovering formic acid from the mixed solution after the reaction; Equipped with The artificial photosynthesis reaction unit is a plate-shaped container in which at least the surface onto which light is irradiated is formed of a light-transmitting material, the container is inclined with respect to the ground surface, and the artificial photosynthesis reaction is carried out by flowing the mixed solution inside the container. A formic acid generation device.

2. The artificial photosynthesis reaction unit is provided with a nozzle that sprays the mixed solution onto the upper surface inside the container located upstream of the slope, and the sprayed mixed solution adheres to the upper surface of the container due to surface tension while flowing downstream along the slope. The formic acid generating apparatus described in claim 1.

3. The artificial photosynthesis reaction unit is provided with a nozzle for flowing the mixed solution into the bottom surface of the container located upstream of the slope, and the mixed solution is configured to flow downstream along the slope on the bottom surface of the container. The formic acid generation apparatus described in claim 1.

4. The artificial photosynthesis reaction unit is provided with a nozzle that supplies the mixed solution to the bottom surface inside the container located downstream of the slope, and is configured to send the mixed solution from the downstream side of the slope to the upstream side by the supply pressure of the nozzle. The formic acid generator described in claim 1.

5. The formic acid generating apparatus according to any one of claims 1 to 4, characterized in that the formic acid recovery section is provided with equipment for recovering and cooling the gas phase of the mixed solution after the reaction, thereby recovering formic acid as a liquid by refluxing.

6. 5. The formic acid generating apparatus according to claim 1, further comprising an air supply means for supplying air to the mixed solution.

7. 5. The formic acid generating apparatus according to claim 1, further comprising a control unit capable of continuously measuring the amount of formic acid generated in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance.

8. 5. The formic acid generating apparatus according to claim 1, wherein the light-transmitting member is embossed glass.

9. 5. The formic acid generating apparatus according to claim 1, wherein the angle of the inclination with respect to the horizontal plane is between 10° and 15°.

10. 5. The formic acid generating apparatus according to claim 1, wherein the organic substance includes glucose, and the photocatalytic function includes titanium oxide fine particles.

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