JPH0733697A - Methanol synthesizing apparatus - Google Patents

Abstract

PURPOSE:To obtain a methanol synthesizing apparatus capable of efficiently synthesizing methanol from carbon dioxide gas using sunlight, etc., without using an electrical energy and a large-scale apparatus. CONSTITUTION:This synthesizing apparatus is provided with a treating tank having a feeding port 18 and an exhaustion port 22 and capable of holding a treating the object. The top face 12 of the tank is made of a light-transmitting material and at least one face of the inner faces of the treating tank is provided with a thin film 16 exhibiting photo-catalytic function with sunlight 14, e.g. titanium oxide. Preferably, a light-receiving member of a solar battery is placed under the bottom of the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for synthesizing methanol, and more specifically, by using a thin film material having a photocatalytic function, methanol can be efficiently synthesized from carbon dioxide by sunlight without supplying electric energy or the like. The present invention relates to a methanol synthesizer that can be used.

[0002]

2. Description of the Related Art In recent years, the WE of the New Sunshine Project has been proposed as a method for achieving the two purposes of solving the energy problem and controlling the emission of carbon dioxide, which causes global warming.
-NET (World Energy Network) concept is drawing attention. It collects the discharged carbon dioxide, concentrates and liquefies it, transfers it to countries rich in solar energy, and uses the electric power obtained by solar cells to generate hydrogen by electrolysis of water, Using hydrogen and carbon dioxide aqueous solution, hydrogen and carbon dioxide are reacted to synthesize methanol, which is used as an energy source to replace petroleum.

However, in the conventional technique, the solar cell has a low power generation efficiency for converting light energy into electric energy, and further, the electric energy converts water into hydrogen to synthesize methanol. The conversion rate is about 3%, the energy conversion efficiency is low, and additional equipment such as electric power transmission equipment, water electrolysis equipment, hydrogen storage / transfer equipment, and methanol reaction equipment are required. There was a problem of becoming.
Further, the solar cell utilizes only visible light of sunlight having a relatively low energy level, and the ultraviolet portion having a high energy level deteriorates the semiconductor material used for the solar cell, and thus has not been utilized. Further, also in a method of obtaining methanol in one step using a catalyst from a water gas containing hydrogen and carbon monoxide, which is a general methanol synthesis method, a high pressure of 100 to 350 atm and 300 to 4 atm are used.
Since a high temperature condition of 00 ° C. is required, it was hard to say that it is an energy efficient synthesis method.

In recent years, it has been noted that the photocatalytic function of semiconductors is utilized, and it is known that semiconductors such as titanium oxide exhibit a photocatalytic function by light of a specific wavelength and have a strong oxidizing / reducing action. Japanese Patent Publication No. 9850/1990 describes a method for purifying waste using a semiconductor such as titanium oxide carrying a metal or a metal oxide. Utilizing this function, a method of directly synthesizing methanol from an aqueous carbon dioxide solution by an oxidation / reduction action by a photocatalytic function has been attempted. In this method, fine particles of a substance having a photocatalytic function are dispersed in an aqueous carbon dioxide solution. Since the reaction is carried out, the obtained methanol and fine particles must be separated after the reaction, resulting in a large loss and a low work efficiency. As described above, the use of the photocatalytic function is at an experimental stage or a temporary one, and has not yet been practically used effectively.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to efficiently synthesize methanol from carbon dioxide gas using sunlight or the like without requiring large-scale equipment and using electric energy. To provide a device that can.

[0006]

[Means for Solving the Problems] Claim 1 according to the present application
According to the invention described in the above, at least one surface of a treatment tank into which a material to be treated can be introduced is made of a light-transmissive material, and a thin film material having a photocatalytic function is laid on at least one inner surface of the treatment tank. The present invention relates to a synthesizer.

According to a second aspect of the present invention, a pair of opposing surfaces of the processing tank are each made of a light transmissive material, and the thin film material having a photocatalytic function is a light transmissive thin film. The methanol synthesizing apparatus according to claim 1, further comprising a light receiving member for the solar cell located below the surface on which the thin film is laid.

[0008]

[Action] a thin film material having a photocatalytic function of the present invention, when the wavelength hits of about 400nm or less of ultraviolet light, electron (e ^-)
Is excited from a stable ground state to an active excited state, and holes (h ⁺ ) are formed after the electrons are removed. These excited electrons and holes have a very strong reducing power and oxidizing power, respectively, and act on carbon dioxide and water on the surface of the thin film material to cause an oxidation / reduction reaction represented by the following general formula. Therefore, it is considered that methanol is synthesized.

[0009]

## STR00001 ## CO ₂ + 6H ⁺ + 6e ⁻ → CH ₃ OH + H ₂ OH ₂ O + 2h ⁺ → 1 / 2O ₂ + 2H ⁺ The apparatus of the present invention comprises a thin film material having a photocatalytic function on one surface of a light-transmitting treatment tank. Since it is used, methanol can be synthesized in one step only by supplying the energy of sunlight by the reaction mechanism. Further, in the second aspect, ultraviolet rays are absorbed by the light-transmitting thin film material having a photocatalytic function, and sunlight without ultraviolet rays reaches the light receiving portion of the solar cell. It is possible to use the energy of sunlight efficiently without any deterioration and without loss.

[0010]

The present invention will be described in more detail below.

(Embodiment 1) FIG. 1 is a schematic view showing one embodiment of the methanol synthesis apparatus of the present invention.

The upper surface 12, which corresponds to the light-receiving surface of the methanol synthesizing apparatus 10, is made of a light-transmissive material.
4 is irradiated. A thin film 16 of titanium oxide having a thickness of about 1 μm is laid on the inner surface of the bottom surface of the device. The carbon dioxide gas aqueous solution is supplied from the supply port 18, and at the contact portion with the thin film 16 made of titanium oxide in the treatment tank, carbon dioxide in the aqueous solution and the oxidation / reduction reaction by the energy of the ultraviolet rays in the sunlight of the water, Methanol is synthesized. A baffle plate 20 is provided in the treatment tank to improve the contact area between the thin film and the aqueous solution. The aqueous solution moves along the liquid moving path constituted by the baffle plate 20 while continuing the reaction, and the obtained methanol is recovered from the discharge port 22.

By using the methanol synthesizing apparatus of this embodiment, the carbon dioxide aqueous solution can be converted into solar energy using
Since it can be directly converted into methanol without passing through electric energy or an intermediate medium such as hydrogen, the conversion efficiency of solar energy into methanol is significantly increased as compared with the conventional method.

In the methanol synthesizing apparatus 10, at least the light receiving portion for sunlight needs to be made of a light transmissive material, but the whole may be integrally made of the same light transmissive material. . Further, it is preferable in terms of reaction efficiency that the inner surface of the facing surface of the light receiving portion is made of a thin film having a photocatalytic function.

The thin film composed of the thin film 16 made of titanium oxide can be made light transmissive by setting the thickness to about 1 μm. Even if the thickness of the thin film is reduced, the surface condition related to the photocatalytic function does not change. Therefore, it is preferable to reduce the thickness of the thin film in terms of material cost. This is also preferable in terms of relaxing restrictions on installation location.

(Embodiment 2) FIG. 2 is a schematic sectional view showing another embodiment of the methanol synthesizing apparatus of the present invention provided with a light receiving surface of a solar cell.

In the methanol synthesizing device 30, the upper surface 32 and the bottom surface 34, which correspond to the light receiving surface, are made of a light transmissive material. On the inner surface of the bottom surface of the device, a thin film 36 of light-transmitting titanium oxide having a film thickness of about 1 μm is laid, and a solar cell light receiving portion 38 is installed below the thin film 36. The carbon dioxide gas aqueous solution is supplied from the supply port 40. When irradiated with sunlight, the ultraviolet ray 42 portion having a wavelength of about 400 nm or less is absorbed by the thin film 36 made of titanium oxide, and in the treatment tank,
At the contact portion with the titanium oxide thin film 36, methanol is synthesized by the oxidation / reduction reaction by the energy of carbon dioxide in the aqueous solution and the ultraviolet energy of the sunlight in the water, and the obtained methanol is recovered from the outlet 44. To be done. A portion of visible light 46 of sunlight passes through the light-transmitting titanium oxide thin film 36 and reaches the solar cell light receiving portion 38, and the light energy is converted into electric energy by the solar cell.

FIG. 3 is a graph showing the energy density of sunlight. In the conventional solar cell, only the visible light portion of the diagonal line is used.

According to this embodiment, the wavelength of sunlight is about 40.
Ultraviolet rays of 0 nm or less are used for methanol synthesis, and visible light having a wavelength of about 400 to about 900 nm is transmitted through the titanium oxide thin film and the transparent bottom of the processing tank and absorbed by the solar cell light receiving portion to be used for power generation. , Both the lattice portion and the shaded portion shown in FIG. 3 are used, and the total energy conversion efficiency is further improved. Further, since the silicon-based semiconductor used in the light receiving portion of the solar cell is deteriorated by ultraviolet rays, as in this embodiment, by using only visible light after absorbing ultraviolet rays as a light source, the solar cell Shows an excellent effect of improving the life of the.

As the light transmissive material used in the treatment tank of the methanol synthesizing apparatus of the present invention, glass is generally used, but synthetic resins are used as long as they can transmit light having a wavelength in the ultraviolet range. You can As synthetic resins,
Examples thereof include acrylic resins such as polymethylmethacrylate, polycarbonate resins, polystyrene, polyethylene, polyphenylene oxide, polyvinyl chloride, styrene-maleic acid copolymers and the like, and mixtures thereof. Synthetic resins are excellent in moldability and strength and can easily mold any processing tank shape, but it is particularly necessary to select those having excellent weather resistance and durability.

The shape of the methanol synthesizing apparatus of the present invention is generally a rectangular parallelepiped having a wide light receiving area, but any shape is acceptable as long as the light receiving area can be sufficiently obtained.
Further, as in Example 1, it is preferable to provide a baffle plate in the treatment tank to form a liquid transfer path of the carbon dioxide aqueous solution in order to improve the contact area between the aqueous solution and the thin film material having a photocatalytic function.

In each of the above-mentioned embodiments, methanol is continuously synthesized, but the carbon dioxide aqueous solution is held in the treatment tank for a certain period of time to allow the reaction to proceed, and the obtained methanol is discharged from the outlet. It is also possible to synthesize by a batch method taken out from. In this case, it is preferable to provide a means for stirring the aqueous solution in the treatment tank, for example, a stirring blade, a liquid circulation device connected to a pump, or the like.

In Examples 1 and 2, the titanium oxide thin film having a photocatalytic function has a planar shape, but in order to improve the contact area, a curved surface such as a corrugated shape is formed as long as a non-light receiving portion (shadow) is not formed. May be done. Further, a titanium oxide thin film may be formed on the surface of the baffle plate.

Examples of the substance exhibiting a photocatalytic function used in the methanol synthesizer of the present invention include metal oxide semiconductors such as titanium oxide. Specifically, Japanese Patent Fair 2-
9850, and particularly titanium oxide, iron oxide, copper oxide, tungsten oxide, zinc oxide,
Strontium titanate and the like, and silicon carbide and the like are widely known. The semiconductor used in the methanol synthesizer of the present invention may be any of these, but titanium oxide, copper oxide, and silicon carbide are particularly preferable from the viewpoint of reaction efficiency and easy availability.

Metals or other metal oxides which modify the above metal oxides to improve the catalytic function of titanium oxide and the like are also suitably used for further promoting the photocatalytic reaction, and examples thereof include platinum, gold and palladium. , Silver, copper, nickel, cobalt, rhodium, niobium, tin, ruthenium oxide, it is preferable to use a metal selected from the group consisting of nickel oxide in combination, among others, from the viewpoint of effect, platinum,
Gold, palladium, and silver are preferable, and palladium is preferable in terms of easiness of processing and price. The amount of modification is preferably 0.01 to 20% by weight based on the metal oxide in the present invention.

The metal oxide may be prepared by, for example, high temperature firing of metal, electrolytic oxidation, chemical vapor deposition method, vacuum vapor deposition method, coprecipitation method, evaporative oxidation method such as metal halogenation method, or inorganic metal salt. Hydrolysis and hydrolysis, hydrolysis of metal alkoxide,
It can be prepared by a sol-gel method or the like. Moreover, you may use a commercial item. The method of modifying the metal or other metal oxide may be a conventionally used method such as an impregnation method, a precipitation method, an ion exchange method, a photodeposition method or a kneading method.

As a method of coating a thin film on the inner surface of the apparatus, a part or all of the surface of a member having a flat surface, a curved surface or a complex shaped surface is coated with the above metal oxide, for example, a spray coating method, a dip coating method, a spin coating method. Method, a method of fixing by at least one method such as a sputtering method, a method of preparing a metal oxide thin film in advance and adhering it to the surface of a member, and pulverizing a material having a photocatalytic function such as a modified metal oxide, Examples include a method of spraying the powder with an adhesive.

In the present invention, the device is required to be exposed to light, and the light energy has a wavelength corresponding to exciting the photocatalyst and contributes to the photocatalytic reaction. Light energy rich in ultraviolet wavelengths below about 400 nm is preferred. As the light energy source, a natural light source of sunlight is most easily used. Light emitted from a mercury lamp, light emitted from a fluorescent lamp, light emitted from a halogen lamp type filament lamp, short arc xenon light, a laser beam, etc. An artificial light source or the like can also be used. Further, as an auxiliary light source of sunlight, an artificial light source can be used at the same time, but from the viewpoint of efficiently synthesizing methanol without supplying electric energy, which is an object of the present invention, Natural light sources are particularly preferred.

[0029]

EFFECT OF THE INVENTION By using the methanol synthesizing apparatus of the present invention, it is possible to efficiently synthesize methanol from carbon dioxide using sunlight or the like without using large-scale equipment and without using electric energy. And in addition,
When combined with a solar cell, it exhibits an excellent effect that solar energy can be used efficiently and the durability of the solar cell can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of a methanol synthesizer of the present invention.

FIG. 2 is a schematic cross-sectional view showing another embodiment of the methanol synthesizing apparatus of the present invention provided with a light receiving surface of a solar cell.

FIG. 3 is a graph showing the energy density of sunlight.

[Explanation of symbols]

 10, 30 Methanol synthesizer 14 Sunlight 16,36 Thin film made of titanium oxide 38 Photoreceptive surface of solar cell

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Hiromatsu 2-5-14 Minamisuna, Koto-ku, Tokyo Inside the Takenaka Corporation Technical Research Institute (72) Inventor Norio Igawa 2-5, Minamisuna, Koto-ku, Tokyo No. 14 Incorporated Takenaka Corp. Technical Research Institute (72) Inventor Eiyoshi Masaki 2-5-14 Minamisuna, Koto-ku, Tokyo Incorporated Incorporated Takenaka Corp. Technical Research Institute (72) Toshio Saito Koto-ku, Tokyo 2-5-14 Minamisuna Technical Research Institute, Takenaka Corp. (72) Inventor Akira Fujishima 5 of 710 Nakamaruko, Nakahara-ku, Kawasaki City, Kanagawa Prefecture (72) Kazuhito Hashimoto 2000-10, Kosugeya-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture No. 2 Minami Kosugaya House No. 506

Claims (2)

[Claims] 1. Methanol obtained by laying a thin film material having a photocatalytic function on at least one inner surface of a processing tank in which at least one surface of a processing tank into which a material to be processed can be put is made of a light-transmissive material. Synthesizer. 2. A pair of opposing surfaces of the processing tank are each made of a light-transmissive material, the thin film material having a photocatalytic function is a light-transmissive thin film, and the thin film material is located below the surface on which the thin film is laid. The methanol synthesis apparatus according to claim 1, further comprising a light receiving member for a solar cell.