Synthesis method and synthesis apparatus for liquid hydrocarbon

Abstract

To provide a method and an apparatus for extremely efficiently generating a liquid hydrocarbon via a photocatalyst with respect to water in which oxygen and carbon dioxide are dissolved.SOLUTION: A liquid hydrocarbon synthesis method and synthesis apparatus for reducing carbon dioxide and water W into carbon monoxide and hydrogen via a photocatalyst in a reaction tank 1 that contains water in which carbon dioxide and oxygen are dissolved and that is in a mixed state with a liquid hydrocarbon HC, and further synthesizing the liquid hydrocarbon HC through a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, achieve the above-mentioned object by bringing air A containing carbon dioxide at an adjustable concentration into contact with an upper interface of a layer of the liquid hydrocarbon HC formed in a region above the water W.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention is directed to a method and apparatus for reducing carbon dioxide and water to carbon monoxide and hydrogen in water via a photocatalyst, and synthesizing liquid hydrocarbons by a chemical reaction of the carbon monoxide and the hydrogen via the photocatalyst. [Background technology]

[0002] The synthesis of liquid hydrocarbons by reducing carbon dioxide in water has already been proposed in the prior art.

[0003] For example, Patent Document 1 proposes a method of producing liquid hydrocarbons by supplying oxygen to water containing carbon dioxide in a photoelectrochemical cell and reducing the carbon dioxide (page 81, lines 4-21).

[0004] That is, the photocatalyst in Patent Document 1 is premised on a photoelectrochemical cell, and on the premise that fuel is produced from liquid hydrocarbons or the like at the cathode (Claims 2, 77, 79).

[0005] Therefore, in Patent Document 1, reduction of carbon dioxide and water by pure photocatalysis is not realized. In fact, in Patent Document 1, activation of oxygen by irradiating water with ultraviolet light is not achieved (in this respect, it is clearly different from Patent Document 2).

[0006] As shown in Patent Document 2, the inventors of the present application have proposed a method and apparatus for producing liquid hydrocarbons, which is based on the premise that oxygen is supplied to water containing dissolved carbon dioxide and oxygen nanobubbles are generated, and the carbon dioxide and water are reduced to carbon monoxide and hydrogen via a photocatalyst in the presence of active oxygen generated from the nanobubbles by irradiation with ultraviolet light.

[0007] However, in the case of Patent Document 2, the configuration is not necessarily simple in that it requires the generation of oxygen nanobubbles and the generation of active oxygen by irradiation with ultraviolet rays.

[0008] In Patent Documents 1 and 2, when liquid hydrocarbons are produced via a photocatalyst, a layer of liquid hydrocarbons is produced in an upper region above water.

[0009] In such a case, contact with the air above containing carbon dioxide is realized, and in this case, the reduction efficiency of carbon dioxide in the water depends on the concentration of carbon dioxide gas contained in the air.

[0010] However, in the conventional techniques such as those disclosed in Patent Documents 1 and 2, the basic idea of ​​efficiently producing liquid hydrocarbons by adjusting the concentration of carbon dioxide gas in the air that comes into contact with the upper interface where liquid hydrocarbons are present is not proposed at all. The inventors of the present application propose the following (1) hydrocarbon synthesis method and (2) hydrocarbon synthesis apparatus configuration in Patent Application No. 2023-132405 (hereinafter referred to as the "Prior Invention") as an improved configuration of the conventional hydrocarbon synthesis method and synthesis apparatus. (1) A method for synthesizing hydrocarbons by reducing carbon dioxide and water to carbon monoxide and hydrogen via a photocatalyst in water containing dissolved carbon dioxide and oxygen, and then chemically reacting the carbon monoxide with the hydrogen via the photocatalyst, characterized in that the upper interface of a hydrocarbon layer produced in an area above the water is contacted with air containing carbon dioxide at an adjustable concentration. (2) A hydrocarbon synthesis apparatus which reduces carbon dioxide and water to carbon monoxide and hydrogen in water via a photocatalyst, and further synthesizes hydrocarbons through a chemical reaction between the carbon monoxide and hydrogen via the photocatalyst, comprising a reaction vessel for storing water in which carbon dioxide and oxygen are dissolved, a photocatalytic means within the reaction vessel, a carbon dioxide supply device above the reaction vessel, and an apparatus for adjusting the amount of carbon dioxide ejected from an outlet of the reaction vessel. However, the prior invention does not specify a synthesis method or synthesis apparatus capable of producing liquid hydrocarbons extremely efficiently. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] WO2010 / 042196 A1 [Patent Document 2] Patent No. 6440742 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention aims to provide a method and apparatus for highly efficient production of liquid hydrocarbons via photocatalysis of water having dissolved therein oxygen and carbon dioxide. [Means for solving the problem]

[0013] In order to solve the above problems, the basic configuration of the present invention is as follows: (1) A method for synthesizing liquid hydrocarbons, comprising reducing carbon dioxide and water to carbon monoxide and hydrogen via a photocatalyst in a reaction vessel containing water in which carbon dioxide and oxygen are dissolved and which is mixed with liquid hydrocarbons, and further synthesizing the liquid hydrocarbons by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, the method being characterized in that an upper interface of a layer of liquid hydrocarbons generated in an area above the water is brought into contact with air containing carbon dioxide at an adjustable concentration; (2) An apparatus for reducing carbon dioxide and water to carbon monoxide and hydrogen via a photocatalyst in a reaction vessel containing water mixed with liquid hydrocarbons, and further synthesizing the liquid hydrocarbons by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, the apparatus being characterized in that it is equipped with a photocatalytic means in the reaction vessel, a carbon dioxide supply device above the reaction vessel, and an apparatus for adjusting the amount of carbon dioxide ejected from an ejection port. It consists of: Effect of the Invention

[0014] By using the method of the basic configuration (1) and the apparatus of the basic configuration (2), it is possible to adjust the concentration of carbon dioxide in the air layer that is in contact with the upper interface of the layer of liquid hydrocarbons produced in the region above the water in the reaction tank, and thus to select an appropriate concentration, thereby making it possible to realize extremely efficient reduction of carbon dioxide and further production of liquid hydrocarbons.

[0015] Moreover, the method of basic configuration (1) and the device of basic configuration (2) are extremely simple compared to the configuration employing electrodes in Patent Document 1, and do not require the application of voltage, and can obtain liquid hydrocarbons as fuel purely through a photocatalytic reaction.

[0016] Furthermore, compared to the configuration of Patent Document 2, the configuration is simpler in that it does not require a mechanism for generating oxygen nanobubbles, such as an ultrasonic vibration device.

[0017] In this way, the present invention, which is based on the method of the basic configuration (1) and the device of the basic configuration (2), can realize extremely efficient production of liquid hydrocarbons, despite its simple configuration. Incidentally, the configuration of Patent Document 2 also includes a configuration in which carbon dioxide is reduced in the presence of active oxygen formed from separately prepared liquid hydrocarbons and oxygen nanobubbles. When such a mixed state is allowed to stand for, for example, 24 hours, the proportion of liquid hydrocarbons further synthesized is usually 10 to 15% (paragraph

[0029] ). In contrast, in the basic configuration (1), when the carbon dioxide concentration of the air in contact with the liquid hydrocarbons is adjusted to within the range of 450 ppm to 5000 ppm, the proportion of liquid hydrocarbons further synthesized can be set to 20 to 30%, as will be described later. Moreover, in comparison with the prior invention, the proportion of further synthesis of liquid hydrocarbons can be increased and the synthesis rate can be improved depending on the mixed state of liquid hydrocarbons and water activated by a photocatalyst. Furthermore, the basic configurations (1) and (2) are considered to be selection inventions in relation to the prior invention in that the essential requirement is that the mixture be in a liquid hydrocarbon state. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram showing the method of the basic configuration (1). [Diagram 2] 1 is a schematic diagram showing the configuration of the device of basic configuration (2), in which the lower reaction tank is shown in cross section, and the upper carbon dioxide supply device and the ejection amount adjustment device are shown in side view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Basic configuration (1), as shown in the block diagram of FIG. 1, is a method for reducing carbon dioxide and water W to carbon monoxide and hydrogen via a photocatalyst in a reaction tank 1 that contains water W in which carbon dioxide and oxygen are dissolved and which is mixed with liquid hydrocarbons HC, and further synthesizing the liquid hydrocarbons HC by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, characterized in that the method for synthesizing liquid hydrocarbons HC is characterized in that air A containing carbon dioxide at an adjustable concentration is brought into contact with the upper interface of a layer of liquid hydrocarbons HC generated in an area above the water W.

[0020] As shown in the schematic diagram of FIG. 2, the apparatus of basic configuration (2) is an apparatus that reduces carbon dioxide and water W to carbon monoxide and hydrogen via a photocatalyst in a reaction tank 1 that contains water W mixed with liquid hydrocarbons HC, and further synthesizes the liquid hydrocarbons HC by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, and is an apparatus for synthesizing liquid hydrocarbons HC that is characterized by comprising a photocatalyst means in the reaction tank 1, a carbon dioxide supply device 2 above the reaction tank 1, and an ejection amount adjustment device 21 at the carbon dioxide ejection port.

[0021] As shown in the basic configurations (1) and (2), the reduction reaction is promoted by the carbon dioxide contained in the air A that comes into contact with the upper interface of the water W in which the liquid hydrocarbons HC are formed, and the efficiency of the reduction reaction is determined by the content of the carbon dioxide. Regarding this, the following technical points can be presumed to be the basis.

[0022] When carbon dioxide dissolved in water is photocatalyst-treated to form radical water, that is, activated water that is prone to chemical reactions, the following reduction reactions caused by the radicalization proceed sequentially. CO2+H2O→CO+H2+O2 (1) That is, in the above formula (1), the reduction reaction proceeds sequentially from left to right. When focusing on each individual reaction, there is a reverse reaction in which carbon monoxide molecules are oxidized to carbon dioxide molecules, but overall, the reaction proceeds in which carbon dioxide molecules are sequentially reduced to carbon monoxide molecules.

[0023] Following the reaction formula (1) above, in the radical water, the following reaction formula proceeds, which further produces liquid hydrocarbons HC due to the radicalization: (2n+1)H2+nCO→C n H 2n+2 +nH2O (2) Therefore, C generated in the upper region of the water Wn H 2n+2 The liquid hydrocarbon layer formed by the above process is derived from reaction (2). Incidentally, the carbon number n is the same as the carbon number of the liquid hydrocarbons HC that are blended in advance and are in a mixed state with the radical water, and therefore the liquid hydrocarbons HC that are blended in advance are called the mold. However, the reason why the carbon number n of the further synthesized liquid hydrocarbons HC is the same as the carbon number of the template liquid hydrocarbons HC has not been fully elucidated.

[0024] In the case of the above reactions (1) and (2), the carbon dioxide contained in the air A above the layer of liquid hydrocarbons HC has an affinity for the liquid hydrocarbons HC, so it permeates the layer of liquid hydrocarbons HC, migrates to the water W in the lower region, and dissolves therein.

[0025] As a result of the dissolution, the reduction reaction of the formula (1) is promoted by the supply of carbon dioxide, and thus the reaction of the formula (2) is also promoted. However, since the degree of dissolution of carbon dioxide in the aqueous solution in which the reactions of the above formulas (1) and (2) take place is uncertain, the appropriate concentration of carbon dioxide to be in contact with the upper interface of the layer of liquid hydrocarbons HC is not necessarily determined.

[0026] Reflecting the above situation, in the basic configurations (1) and (2), the concentration of carbon dioxide contained in the air A at the upper interface is made freely adjustable.

[0027] In the basic configurations (1) and (2) which correspond to the selection invention in relation to the prior invention, it is an essential requirement that the pre-blended liquid hydrocarbons HC and radical water are in a mixed state, and this requirement results in the rapid progress of the reaction formula (2) above. The mixed state of the basic configurations (1) and (2) can be realized by stirring the liquid hydrocarbons HC and the radical water in the reaction vessel 1. However, in the case of an embodiment characterized in that the liquid hydrocarbons HC and the water W in a mixed state flow into the reaction tank 1 in the basic configuration (1), and in the case of an embodiment characterized in that the liquid hydrocarbons HC and the water W flow into the reaction tank 1 by a piston pump or a plunger pump in the basic configuration (2), mechanical vibration of the reaction tank 1 due to stirring can be prevented in either case, and the progress of each of the reaction formulas (1) and (2) can be smoothly promoted. As far as the reaction formulas (1) and (2) are concerned, the higher the concentration of the liquid hydrocarbons HC, which can be freely adjusted above the interface, the more the reactions of the formulas (1) and (2) are promoted.

[0028] However, according to the experience of the inventors, it has been found that the higher the concentration of carbon dioxide, the more the reactions of the above formulas (1) and (2) are not promoted, and when the concentration of carbon dioxide above the interface exceeds a certain level, the production of liquid hydrocarbons HC may actually decrease.

[0029] Specifically, when the concentration of carbon dioxide exceeds 9000 ppm, the efficiency of generating liquid hydrocarbons HC often decreases.

[0030] The exact reason why the efficiency of generating liquid hydrocarbons (HC) decreases when the carbon dioxide concentration exceeds a certain value is not clear at present. However, it can be assumed that the function of the photocatalyst in the reaction formulas (1) and (2) above will be reduced if the carbon dioxide concentration exceeds a certain level.

[0031] The appropriate concentration of carbon dioxide at the upper interface depends on the amount of carbon dioxide contained in the water, but in most cases, the appropriate carbon dioxide concentration can be set within the range of 450 ppm to 5000 ppm. When such a numerical range is selected, about twice as much liquid hydrocarbons HC are synthesized as compared to the case of Patent Document 2, as already explained in the section on effects.

[0032] In the case of the configuration of Patent Document 2, in which oxygen nanobubbles are essential, it was assumed that the temperature in the reaction tank 1 would preferably be room temperature, 40°C, and more preferably 30°C (paragraph

[0028] ). In contrast, in the cases of the basic configurations (1) and (2), as described below, oxygen nanobubbles are not generated. As a result, the water temperature includes the natural state, the case where it is cooled, and the case where it is heated. However, the water temperature does not have a significant effect on the generation efficiency of liquid hydrocarbons HC.

[0033] The basis for this is believed to be that the photocatalyst acting through the reduction reaction of the above formula (1) and the synthesis reaction of liquid hydrocarbons HC of the above formula (2) locally generates molecular vibrations in the water with frequencies orders of magnitude greater than thermal vibrations, and that the thermal vibrations that affect the water temperature have almost no effect on the molecular motion.

[0034] In the configuration of Patent Document 2, as already explained, oxygen nanobubbles are generated, and active oxygen is generated by irradiation with ultraviolet rays.

[0035] However, when nanobubbles are generated by ultrasonic waves, vibrations are inevitably applied to the water W involved in the reaction formula (1) above, which inevitably causes an impediment to the progress of the reduction reaction due to the equilibrium of the reaction formula (1) under calm conditions. However, the fact remains that active oxygen is effective in the reduction reaction of the above formula (1).

[0036] Taking into consideration the effectiveness of such active oxygen, in the basic configuration (1), an embodiment can be adopted in which at least a portion of the dissolved oxygen is activated only by irradiating it with ultraviolet light, and in the basic configuration (2), an embodiment can be adopted in which an ultraviolet irradiation device is provided for activating at least a portion of the oxygen dissolved in the reaction tank 1. Incidentally, when a part of the dissolved oxygen is activated by irradiation with ultraviolet light, the efficiency of carbon dioxide reduction can be significantly improved compared to when the oxygen is not activated.

[0037] The basis for this is that hydrogen peroxide (H2O2) is formed by activation of dissolved oxygen, which results in an efficient reduction of carbon dioxide, as envisaged by the following chemical equation: CO2+H2O2→CO+H2+3O2 / 2 ···(3) The following will explain the present invention based on examples. EXAMPLES

[0038] The first embodiment is characterized in that in the basic configuration (1), the humidity at the interface and in the vicinity above it is set to 50% or less.

[0039] If the humidity at the upper interface is high, the carbon dioxide contained in the air A near the interface will merge with water droplets forming water vapor in the air and drift away, thereby exacerbating the problem of not falling to the interface.

[0040] Considering such adverse effects, in the first embodiment, the humidity at the interface is set to 50% or less.

[0041] By setting an upper humidity limit of 50% or less, the drift of carbon dioxide can be reduced. In order to adjust the humidity in this manner, it is advisable to employ either heat drying above the interface or wind drying, which generates horizontal wind force to suppress an increase in humidity due to water vapor from the water W below the interface. EXAMPLES

[0042] Example 2 is characterized in that in the basic configuration (2), the horizontal area of ​​the interface in the reaction vessel 1 is at least twice as large as the cross-sectional area in the up-down direction perpendicular to the horizontal direction.

[0043] Due to these characteristics, in the device of the basic configuration (2), the area of ​​the interface where liquid hydrocarbons (HC) are generated can be set relatively wide, and as a result, the reduction of the above formula (1) and the liquid hydrocarbon reaction of the above formula (2) can be efficiently promoted. [Industrial Applicability]

[0044] The present invention, which is based on the method of the basic configuration (1) and the apparatus of the basic configuration (2), has a great advantage in that liquid hydrocarbons can be efficiently produced by a simple configuration in which the interface at which liquid hydrocarbons are produced is brought into contact with air containing carbon dioxide, the concentration of which can be adjusted, and thus has enormous industrial value. [Explanation of symbols]

[0045] W water A. Air HC Liquid hydrocarbons (abbreviation of hydrocarbon) 1 Reactor 2 Carbon dioxide supply device 21 Spout amount adjustment device

Claims

1. A method for synthesizing liquid hydrocarbons, comprising the steps of: reducing carbon dioxide and water to carbon monoxide and hydrogen via a photocatalyst in a reaction vessel containing water in which carbon dioxide and oxygen are dissolved and which is mixed with liquid hydrocarbons; and further synthesizing the liquid hydrocarbons by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, said method comprising contacting an upper interface of a layer of liquid hydrocarbons produced in an area above the water with air containing carbon dioxide at an adjustable concentration.

2. 2. The method for synthesizing liquid hydrocarbons according to claim 1, wherein the liquid hydrocarbons and the water in a mixed state flow into a reaction vessel.

3. 2. The method for synthesizing liquid hydrocarbons according to claim 1, wherein the concentration of carbon dioxide is 9,000 ppm or less.

4. 4. The method for synthesizing liquid hydrocarbons according to claim 3, wherein the concentration of carbon dioxide is 450 ppm to 5000 ppm.

5. 3. The method for synthesizing liquid hydrocarbons according to claim 1, wherein the dissolved oxygen is at least partially activated only by irradiation with ultraviolet light.

6. 3. The method for synthesizing liquid hydrocarbons according to claim 1, wherein the humidity at the upper interface is set to 50% or less.

7. An apparatus for reducing carbon dioxide and water to carbon monoxide and hydrogen via a photocatalyst in a reaction tank containing water mixed with liquid hydrocarbons, and further synthesizing the liquid hydrocarbons by a chemical reaction between the carbon monoxide and the hydrogen via the photocatalyst, the apparatus being characterized by comprising a photocatalytic means in the reaction tank, a carbon dioxide supply device above the reaction tank, and an apparatus for adjusting the amount of carbon dioxide ejected at an ejection port.

8. 8. The apparatus for synthesizing liquid hydrocarbons according to claim 7, wherein the liquid hydrocarbons and the water are flowed into the reaction tank by a piston pump or a plunger pump.

9. 9. The apparatus for synthesizing liquid hydrocarbons according to claim 7 or 8, further comprising an ultraviolet ray irradiation device for activating at least a part of the oxygen dissolved in the reaction vessel.

10. 9. The apparatus for synthesizing liquid hydrocarbons according to claim 7, wherein the horizontal area of ​​the interface in the reaction vessel is at least twice as large as the cross-sectional area in the vertical direction perpendicular to the horizontal direction.

Images